sildenafil-citrate and Disease-Models--Animal

The FDA approval of Viagra (sildenafil) for the on demand treatment of erectile dysfunction (ED) through relaxation of the corporal and cavernosal vascular smooth muscle that results in an increase in blood flow to the corporal tissues stemmed from 2 decades of research, mainly at academic centers. This culminated in the finding of the nitric oxide/cGMP pathway as the mediator of penile erection, followed by some years of basic studies and clinical validation at Pfizer. Further on, new translational laboratory and animal research from our group initiated a second phase when we proposed an alternative therapeutic schedule and mechanism of action for PDE5 inhibitors (PDE5i) in both corporal veno-occlusive dysfunction (CVOD) and Peyronie's disease (PD), specifically, continuous long-term administration (CLTA) to achieve sustained levels of cGMP within the penis. Due to the extended half-life of the long-acting PDE5i, tadalafil, this new alternative encompasses preferentially daily administration, although shorter half-life PDE5i, like sildenafil and vardenafil work too, depending on the duration, dose, and frequency of their administration This novel use was initially supported by showing the antifibrotic/antioxidant effects of nitric oxide and cGMP, produced by the induction of iNOS, as a mechanism of defense against collagen deposition in the localized fibrotic plaque of PD in an avascular tissue, the tunica albuginea. Our studies on iNOS and the progressive diffuse fibrosis occurring in the smooth muscle in CVOD, led to proposing the CLTA of PDE5i for maintaining sustained cGMP levels both in PD and in CVOD in order to halt or regress the penile fibrosis. In CVOD, we showed that PDE5i protect the corporal smooth muscle and reduce myofibroblast activation and number, counteracting the underlying corporal tissue pathology that causes CVOD, and potentially ameliorating long-term CVOD or even curing it. This review is focused on this novel PDE5i anti-fibrotic therapeutic concept.

Topics: Animals; Arterial Occlusive Diseases; Cyclic GMP; Disease Models, Animal; Drug Evaluation, Preclinical; Erectile Dysfunction; Humans; Male; Muscle, Smooth; Nitric Oxide Synthase Type II; Penile Induration; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Translational Research, Biomedical

Sildenafil citrate is a potent, selective phosphodiesterase type 5 inhibitor approved for the treatment of pulmonary arterial hypertension (PAH) and plays an important role in the management of the disease.. In this review, we focus on the current available information on the pharmacokinetics, pharmacodynamics, clinical efficacy and safety of sildenafil citrate in PAH through a MEDLINE literature search. Comparison of sildenafil citrate with tadalafil, another phosphodiesterase type 5 inhibitor was also performed.. In the last few years, considerable progress has been made in the understanding and treatment of PAH. Sildenafil citrate has multiple advantages and whether it is first-line treatment alone or in combination for the mild form of the disease, it is one of the treatments of choice. In terms of its future use, more studies are still needed to better evaluate the benefit/risk balance of sildenafil citrate in pediatric populations.

Topics: Adult; Animals; Carbolines; Child; Disease Models, Animal; Drug Evaluation, Preclinical; Humans; Hypertension, Pulmonary; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Randomized Controlled Trials as Topic; Sildenafil Citrate; Sulfones; Tadalafil

Stem cells (SCs) have been investigated for the treatment of erectile dysfunction (ED).. This review covers key disease targets and all 33 preclinical studies, including their use of SC types, animal models, transplantation routes, and outcome assessment methods.. In the past one and half years there have been more stem-cell-for-erectile-dysfunction studies than the prior 8 years combined. These new studies tend to use combinatory treatment approaches by modifying or supplementing SCs with angiogenic or neurotrophic genes or proteins. However, when considering all risks and benefits, these combinatory approaches do not seem more advantageous than single-SC approaches. Another trend is the choice of transplantation routes other than the standard intracavernous (IC) injection. However, with the exception of intravenous injection, these new transplantation approaches are more cumbersome than IC injection and yet offer no evidence of producing better outcomes. In contrast to these variations, a consensus among these studies is the suggestion that paracrine action, as opposed to cellular differentiation, is the principal therapeutic mechanism. In conclusion, IC injection of a single SC type should be the choice protocol for initial clinical trials, and this is clearly the case with two clinical trials that are currently recruiting patients.

Topics: Animals; Clinical Trials as Topic; Diabetes Complications; Disease Models, Animal; Erectile Dysfunction; Evaluation Studies as Topic; Humans; Injections, Intravenous; Male; Myocytes, Smooth Muscle; Organ Specificity; Paracrine Communication; Penile Induration; Piperazines; Postoperative Complications; Prevalence; Prostatectomy; Purines; Radiotherapy; Rats; Sildenafil Citrate; Stem Cell Transplantation; Sulfones; Treatment Outcome

Phosphodiesterase-5 inhibitors (PDE5Is) improve erectile function by enhancing nitric oxide availability in the penis and its supplying vasculature, resulting in vasodilation and increased blood flow. PDE5Is might benefit cardiovascular diseases because phosphodiesterase-5 is also located elsewhere in the body, including the pulmonary and systemic vasculature and in hypertrophied myocardium. PDE5Is are approved for pulmonary arterial hypertension, given that they improved several hemodynamic and clinical parameters in large randomized trials. Initial evidence suggests that PDE5Is benefit patients with congestive heart failure and secondary pulmonary hypertension. PDE5Is seem to improve hemodynamic and clinical parameters in patients with high-altitude pulmonary edema (HAPE) and high-altitude pulmonary hypertension. In climbers with prior episodes of HAPE, PDE5Is prevented HAPE in 2 small randomized trials. In small randomized trials of PDE5Is, patients with Raynaud's phenomenon demonstrated improved blood flow, fewer symptoms and frequency of attacks, and resolution of digital ulcers. In addition to enhancing vasodilation, PDE5Is seem to protect the myocardium through complex pathways that involve nitric oxide, cyclic guanosine monophosphate, protein kinase G, extracellular-signal-regulated kinase, B-cell lymphoma protein-2, and Rho kinase inhibition. In animal models of acute myocardial infarction, PDE5Is consistently reduced infarct size indicating cardioprotection and PDE5Is also promote reverse remodeling and reduce myocardial apoptosis, fibrosis, and hypertrophy. PDE5Is might also benefit patients with treatment-resistant hypertension, preeclampsia, or peripheral arterial disease. This review presents the pathophysiology and trial data with regard to the use of PDE5Is for cardiac diseases.

Topics: Animals; Coronary Circulation; Cross-Over Studies; Disease Models, Animal; Female; Heart Failure; Hemodynamics; Humans; Hypertension, Pulmonary; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Prognosis; Purines; Randomized Controlled Trials as Topic; Risk Assessment; Severity of Illness Index; Sildenafil Citrate; Sulfones; Survival Analysis; Treatment Outcome

Persistent pulmonary hypertension of the newborn (PPHN) is a serious and potentially fatal condition, characterized by hypoxemia due to increased pulmonary vascular resistance (PVR) with resultant shunting of pulmonary blood to the systemic circulation. Inhaled nitric oxide (iNO) has been considered a revolutionary treatment of PPHN. Data show that the use of iNO has reduced the need of ECMO in neonates with severe PPHN, while in moderate PPHN, iNO administration has been associated with a significant decrease in ventilatory support and prevented progression to severe PPHN. Not all neonates respond to iNO therapy though, and phosphodiesterase (PDE) inhibitors with their potent vasodilator properties have evolved as an alternative therapy or as an adjunct to the treatment of PPHN with iNO. There are ten families of PDE isoenzymes. PDE 5 is particularly prevalent in vascular smooth muscle (VSM) and PDE 5 inhibitors, such as sildenafil, have been used in clinical practice. This review provides a comprehensive account of existing data in the literature, from animal and clinical studies, on the use of sildenafil for the treatment of PPHN. Sildenafil may also have a role as a single mode of therapy, since in resource-limited settings the cost of iNO is a serious concern.

Topics: Administration, Inhalation; Animals; Disease Models, Animal; Humans; Infant, Newborn; Nitric Oxide; Persistent Fetal Circulation Syndrome; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilator Agents

Sildenafil could be an alternative in the treatment of intrauterine growth retardation (IUGR) and premature delivery. In order to systematically review the reproductive-related effects of sildenafil, a search was made on PubMed and the Science Citation Index for studies evaluating the effects of sildenafil on uterine vessels or myometrium either in vitro or in experimental animal models as well as for any clinical trial or case reporting the outcome of pregnant women treated with sildenafil. The information was obtained from: three in vitro studies, five studies performed in experimental animal models, four studies on women with fertility and sterility disorders receiving 100 mg/day of sildenafil intravaginally, and two case reports of pregnant women who received sildenafil for the treatment of pulmonary hypertension. Incubation with sildenafil of different in vitro preparations resulted in vasodilator and uterine relaxant effects. No evidence of teratogenicity was observed in the studies performed in mice, rats and dogs. Sildenafil increased fetal weight in rats. In women, contradictory results on uterine blood flow and endometrial development were reported after the intravaginal administration of sildenafil. No adverse fetal outcomes were reported in the two pregnant women with pulmonary hypertension receiving sildenafil late in their pregnancy. In conclusion, there is still limited information about the efficacy of sildenafil for the treatment of IUGR and premature delivery. However, studies in experimental animal models and two human case reports have reported no deleterious effects on the mother or offspring.

Topics: Administration, Intravaginal; Animals; Disease Models, Animal; Female; Fetal Growth Retardation; Humans; Obstetric Labor, Premature; Piperazines; Pregnancy; Purines; Sildenafil Citrate; Sulfones; Tocolytic Agents

The prognosis of patients with pulmonary arterial hypertension (PAH) is poor. Available therapies (Ca(++)-channel blockers, epoprostenol, bosentan) have limited efficacy or are expensive and associated with significant complications. PAH is characterized by vasoconstriction, thrombosis in-situ and vascular remodeling. Endothelial-derived nitric oxide (NO) activity is decreased, promoting vasoconstriction and thrombosis. Voltage-gated K+ channels (Kv) are downregulated, causing depolarization, Ca(++)-overload and PA smooth muscle cell (PASMC) contraction and proliferation. Augmenting the NO and Kv pathways should cause pulmonary vasodilatation and regression of PA remodeling. Several inexpensive oral treatments may be able to enhance the NO axis and/or K+ channel expression/function and selectively decrease pulmonary vascular resistance (PVR). Oral L-Arginine, NOS' substrate, improves NO synthesis and functional capacity in humans with PAH. Most of NO's effects are mediated by cyclic guanosine-monophosphate (c-GMP). cGMP causes vasodilatation by activating K+ channels and lowering cytosolic Ca++. Sildenafil elevates c-GMP levels by inhibiting type-5 phosphodiesterase, thereby opening BK(Ca). channels and relaxing PAs. In PAH, sildenafil (50 mg-po) is as effective and selective a pulmonary vasodilator as inhaled NO. These benefits persist after months of therapy leading to improved functional capacity. 3) Oral Dichloroacetate (DCA), a metabolic modulator, increases expression/function of Kv2.1 channels and decreases remodeling and PVR in rats with chronic-hypoxic pulmonary hypertension, partially via a tyrosine-kinase-dependent mechanism. These drugs appear safe in humans and may be useful PAH therapies, alone or in combination.

Topics: Administration, Inhalation; Administration, Oral; Animals; Arginine; Dichloroacetic Acid; Disease Models, Animal; Humans; Hypertension, Pulmonary; Models, Biological; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Potassium Channels; Pulmonary Circulation; Purines; Rats; Sildenafil Citrate; Sulfones

Vascular dysfunction is a common feature in end-organ complications of type 2 diabetes mellitus (T2DM). The endothelium-specific receptor tyrosine kinase Tie2 and its ligand, angiopoietin-1 (Ang1), participate in the processes of vessel repair, renewal, and maturation. However, their dysregulation in T2DM has seldom been investigated.. To examine the relationship between angiogenic Tie2-expressing monocytes (TEMs) and Ang1, and their pharmacological modulation by the phosphodiesterase type 5 inhibitor (PDE5i) sildenafil, in T2DM and in db/db mouse model.. Randomized, double-blind, placebo-controlled study.. db/db male mice were randomly assigned to receive 8 weeks of sildenafil or vehicle. Diabetic men were randomly assigned to receive 4 weeks of sildenafil or placebo.. Peripheral blood cells were investigated by flow cytometry to quantify inflammatory myeloid CD11b+ Gr1+ cells and proangiogenic TEMs in mice and classical CD14++CD16neg monocytes and proangiogenic TEMs in humans at baseline and after treatment. In vitro human tube formation assay was used to test serum angiogenic potential.. We show that TEMs and Ang1 are defective in mouse and human models of diabetes and are normalized by PDE5i treatment. Serum angiogenic properties are impaired in diabetes because they do not support the in vitro formation of capillary-like structures, but they are reestablished by in vivo PDE5i treatment.. Restoring a more physiological Tie2-Ang1 axis with sildenafil reestablishes serum angiogenic properties in diabetes, promoting angiogenic homeostasis.

Topics: Aged; Angiopoietin-1; Animals; Diabetes Mellitus, Type 2; Disease Models, Animal; Double-Blind Method; Humans; Male; Mice; Middle Aged; Monocytes; Neovascularization, Physiologic; Phosphodiesterase 5 Inhibitors; Placebos; Receptor, TIE-2; Sildenafil Citrate; Treatment Outcome

Sepsis is a complex syndrome which comes out after infection, characterized by activation of inflammation and infection and has a high morbidity and mortality. Sildenafil (SLD) is a selective phosphodiesterase Type 5 enzyme inhibitor and is used in the treatment of erectile dysfunction effectively all over the world. In this study, we investigated whether SLD had protective effect or not by studying the effect of SLD on reactive oxygen species and antioxidants in cecal ligation and puncture (CLP) polymicrobial sepsis model in rat liver histopathologically and biochemically.. Rats were divided into four groups: (1) 10 mg/kg SLD given CLP group; (2) 20 mg/kg SLD given CLP group; (3) CLP group; and (4) SHAM operated group. CLP polymicrobial sepsis model was applied to the rats. All rats in our study were sacrificed by overdose general anesthetic after 16 h (thiopental sodium, 50 mg/kg). Specimens of rat liver were analyzed histopathologically and biochemically. In the study, superoxide dismutase (SOD) and glutathione (GSH) parameters were measured to indicate the antioxidant activity in liver during sepsis. To evaluate the oxidant activity, myeloperoxidase (MPO) and lipid peroxidation (LPO) parameters were measured in liver tissue.. SOD and MPO activities and GSH and LPO levels were high in CLP polymicrobial sepsis model when compared to SHAM group (p<0.05). In all SLD groups, GSH levels were high when compared to CLP group. In 20 mg/kg SLD given sepsis group, high GSH levels were observed according to SHAM group. In addition, while all SLD dose groups had a significant decrease versus CLP group in LPO levels (p<0.05), they had a significant increase in MPO activities. In 20 mg/kg SLD administrated rats, an improvement observed in biochemical parameters. In this study, SOD and MPO activities which were low in SHAM group increased in CLP polymicrobial sepsis model. When SLD administrated, MPO activity increased in both SHAM and CLP groups. In this study, GSH and LPO levels also increase in septic liver tissue. When SLD administrated to SHAM group, it increased VI protective GSH level and decreased detrimental LPO level. In histopathological examination, it was observed that 10 mg/kg SLD administration had a curative effect in liver tissue partly.. It was shown that acute SLD administration decreased liver damage in septic rats dose-dependently in this study. In addition, it was observed that it corrected the broken oxidant-antioxidant balance. This might mediate the protective effect of SLD in liver. However, we believe that new experimental and clinical studies should be in the future to understand the protective effect of SLD in liver.

Topics: Animals; Antioxidants; Chemical and Drug Induced Liver Injury, Chronic; Disease Models, Animal; Glutathione; Male; Oxidants; Rats; Rats, Wistar; Sepsis; Sildenafil Citrate; Superoxide Dismutase

Topics: Administration, Inhalation; Administration, Oral; Animals; Collagen; Disease Models, Animal; Epoprostenol; Heart; Hemodynamics; Hypoxia; Indoles; Male; Myocardium; Phosphodiesterase 5 Inhibitors; Pulmonary Arterial Hypertension; Pulmonary Artery; Pyrroles; Rats, Sprague-Dawley; Sildenafil Citrate; Vascular Remodeling; Vasodilator Agents

Background cGMP-hydrolyzing phosphodiesterase type 5 (PDE5) regulates vascular smooth muscle cell (SMC) contraction by antagonizing cGMP-dependent protein kinase I (PKGI)-dependent SMC relaxation. SMC contractile dysfunction is implicated in the pathogenesis of aortic aneurysm. PDE5 inhibitors have been used for treating erectile dysfunction, such as drug Viagra (sildenafil). However, a few clinical cases have reported the association of Viagra usage with aortic dissection, and reduced PDE5A expression was found in human aortic aneurysm tissues. Therefore, we aimed to investigate the effect of sildenafil on experimental abdominal aortic aneurysm (AAA), the most common form of aortic aneurysm in elderly men. Methods and Results AAA was induced in C57BL/6J male mice by periaortic elastase in combination with blocking elastin/collagen formation via 3-aminopropionitrile fumarate salt for 35 days. PDE5A protein levels detected by immunostaining were significantly reduced in mouse AAA. Sildenafil application in drinking water significantly aggravated aortic wall dilation and elastin degradation with pre-existing moderate AAA. The phosphorylation level of myosin light chain 2 at Ser19, a biochemical marker of SMC contraction, was significantly reduced by sildenafil in AAA. Proximity ligation assay further revealed that the interaction between cGMP and PKGI was significantly increased by sildenafil in AAA, suggesting an elevation of PKGI activation in AAA. Conclusions Sildenafil treatment aggravated the degradation of elastin fibers and progression of experimental AAA by dysregulating cGMP and contractile signaling in SMCs. Our findings may raise the caution of clinical usage of Viagra in aneurysmal patients.

Topics: Aged; Animals; Aorta, Abdominal; Aortic Aneurysm, Abdominal; Disease Models, Animal; Elastin; Humans; Male; Mice; Mice, Inbred C57BL; Sildenafil Citrate

Chronic treatment with sildenafil (SILD) is an effective protector on the development of cardiovascular complications of pulmonary hypertension (PH) and diabetes. However, to date, no studies have evaluated the effect of SILD on cardiopulmonary pathophysiology during PH secondary to type 1 diabetes.. The present study aimed to evaluate the beneficial effects of chronic SILD treatment on pulmonary arterial pressure, right ventricular hypertrophy (RVH) and cardiac autonomic dysfunction in rats with PH secondary to diabetes.. Male Sprague Dawley rats were randomly distributed into the control group (saline), diabetic group (60 mg/kg with streptozotocin), SILD-treated control group (20 mg/kg) and SILD-treated diabetic group.. After 8 weeks the type 1 diabetic animals presented PH, endothelial dysfunction of the pulmonary arteries, electrocardiographic alterations, RVH and overexpression of phosphodiesterase type 5 in the heart. In type 1 diabetic animals, SILD treatment prevented the development of PH, endothelial dysfunction and RVH. SILD treatment also prevented alterations in the corrected QT period and heart rate variability and prevented overexpression of phosphodiesterase type 5.. Our results indicate for the first time that SILD treatment prevents pulmonary arterial endothelial dysfunction, pulmonary hypertension, right ventricular hypertrophy and improves heart rate variability in type 1 diabetic rats.

Topics: Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Disease Models, Animal; Heart Rate; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Rats; Rats, Sprague-Dawley; Sildenafil Citrate

Dapagliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), can reduce cardiovascular events and mortality in patients with heart failure. A number of mechanisms have been proposed to explain the beneficial effects of SGLT2 inhibitors. The purpose of this study was to determine whether dapagliflozin can improve pulmonary vascular remodelling and the efficacy of dapagliflozin as an add-on therapy to sildenafil in rats with pulmonary arterial hypertension (PAH).. A monocrotaline (MCT)-induced PAH rat model was used in our study. MCT-injected rats were randomly divided into four groups and treated for 3 weeks with daily per os treatment with vehicle, dapagliflozin (1 mg/kg/day), sildenafil (25 mg/kg/day), or a combination of dapagliflozin (1 mg/kg/day) and sildenafil (25 mg/kg/day). Haemodynamic measurements, histological analysis, enzyme-linked immunosorbent assay and western blotting analysis were employed to detect the changes in PAH rats after treatments.. Dapagliflozin significantly attenuated MCT-induced increases in right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH) in PAH rats. Dapagliflozin effectively decreased the thickening of pulmonary artery media and decreased the muscularization of pulmonary arterioles in PAH rats. Moreover, dapagliflozin attenuated nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome activation in lung tissues and the levels of interleukin-1β (IL-1β) and interleukin-18 (IL-18) in plasma. However, dapagliflozin as an add-on therapy to sildenafil in rats with PAH did not show a more pronounced beneficial effect on right ventricular systolic pressure and pulmonary vascular remodelling in MCT rats than sildenafil alone.. Dapagliflozin reduces right ventricular systolic pressure and pulmonary vascular remodelling in a rat model of PAH. However, combination therapy with dapagliflozin and sildenafil was not more effective than monotherapy with sildenafil in PAH rats.

Topics: Animals; Benzhydryl Compounds; Disease Models, Animal; Familial Primary Pulmonary Hypertension; Glucosides; Humans; Hypertension, Pulmonary; Monocrotaline; Pulmonary Arterial Hypertension; Pulmonary Artery; Rats; Sildenafil Citrate; Vascular Remodeling

Necrotizing enterocolitis (NEC) has a 45% mortality in neonatal intensive care units. This paper aimed to evaluate the isolated and combined effects of sildenafil and L-arginine in the prevention of necrotizing enterocolitis. Neonatal rats were fed formula milk and submitted to hypoxia under a 100% N2 atmosphere for 70 s. Then, animals were subjected to hypothermia (4 °C for 10 min), twice a day for 3 days. Forty neonatal rats were divided into five groups: negative control-not submitted to the protocol (n = 5), sildenafil group-NEC protocol (n = 9), L-arginine group-NEC protocol (n = 9), L-arginine and sildenafil group-NEC protocol (n = 9) and positive control-NEC protocol and intraperitoneal saline solution (n = 8). Jejunum and terminal ileus were removed for histopathologic and immunohistochemical Ki-67 analysis. Kruskal-Wallis test was used to analyze mortality, survival, body weight, intestinal injury score and Ki-67 proliferation index. All animals submitted to the protocol developed enterocolitis. Mortality rate was higher in group that received only L-arginine (p = 0.0293). The Ki-67 analysis showed a higher proliferative index in groups that received interventional drugs (p = 0.017). In conclusion, sildenafil and L-arginine were not effective to reduce intestinal injury.

Topics: Animals; Animals, Newborn; Arginine; Disease Models, Animal; Enterocolitis, Necrotizing; Humans; Infant, Newborn; Infant, Newborn, Diseases; Ki-67 Antigen; Rats; Sildenafil Citrate

Pulmonary hypertension (PAH) is a proliferative disease of pulmonary blood vessels, but the pathogenesis of pulmonary hypertension is still unclear. This article explores the role of tumor necrosis factor-

Topics: Animals; Blood Coagulation; Disease Models, Animal; Drug Carriers; Hypertension, Pulmonary; Monocrotaline; Nanoparticles; Pulmonary Artery; Rats; Sildenafil Citrate; Thromboplastin; Tumor Necrosis Factor-alpha

There is a lack of effective therapeutic interventions for preeclampsia. A central factor in the etiology of the disease is the development of placental hypoxia due to abnormal vascular remodeling. However, methods to assess the impact of potential therapies on placental growth and remodeling are currently lacking. Here, we develop and validate ultrasound-guided photoacoustic imaging methods to monitor the placental response to therapeutic intervention. Establishing non-invasive tools to image placental function opens up previously unachievable understandings of placental therapeutic response.. Studies were performed in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. Preclinical research has identified tempol, a superoxide dismutase mimetic, and the phosphodiesterase inhibitor sildenafil as potential therapeutics for preeclampsia, as both improve in vivo maternal outcomes. PA images of the placental environment were acquired in RUPP rats receiving tempol (n = 8) or sildenafil (n = 8) to assess the longitudinal effects of treatment on placental oxygenation and vascular remodeling. Imaging measurements were validated with ex vivo histological analysis.. Spectral photoacoustic imaging non-invasively measured placental hypoxia and impaired vascular growth two days after the RUPP procedure was implemented. Sildenafil significantly improved (p < 0.05) placental oxygenation and promoted vascular remodeling in RUPP animals, while RUPP animals treated with tempol had a diminished placental therapeutic response.. We demonstrate that photoacoustic imaging provides in vivo measures of placental oxygenation and vascular remodeling, a previously unobtainable assessment of preeclamptic therapeutic response. These imaging tools have tremendous potential to accelerate the search for effective therapies for preeclampsia.

Topics: Animals; Disease Models, Animal; Female; Humans; Hypoxia; Ischemia; Photoacoustic Techniques; Placenta; Pre-Eclampsia; Pregnancy; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Vascular Remodeling

Necrotizing enterocolitis (NEC) is a devastating disease that impacts the intestine of premature infants. Sildenafil has shown benefit in colitis and ischemia/reperfusion models but has not been adequately studied in NEC. Sildenafil's best studied mechanism involves augmenting nitric oxide induced vasodilation. We hypothesized that sildenafil would improve outcomes during experimental NEC in an eNOS dependent manner.. NEC was induced in five-day old mouse pups with gavage formula feeds plus intermittent hypoxia and hypothermia. Using wild type (WT) mice, the route of sildenafil administration was studied in the following groups: (1) breastfed controls, (2) NEC + oral (PO) sildenafil, (3) NEC + PO vehicle, (4) NEC + intraperitoneal (IP) sildenafil, (5) NEC + IP vehicle. The eNOS KO groups studied included: (1) breastfed controls, (2) NEC + PO sildenafil, (3) NEC + PO vehicle. Data were tested for normality and compared using t-tests or Mann-Whitney with a p-value <0.05 considered significant.. In WT mice, oral and IP sildenafil resulted in improved clinical outcomes compared to their respective vehicle group. Only orally administered sildenafil significantly improved perfusion to the intestine and protected it from macroscopic and histologic injury. When repeated in eNOS KO mice, oral sildenafil improved clinical scores and attenuated intestinal injury scores, despite no effect on intestinal perfusion.. Sildenafil, when administered orally, improves clinical outcomes and protects the intestine in a murine model of experimental necrotizing enterocolitis. While sildenafil requires eNOS to impact mesenteric perfusion, it does not appear to be dependent on eNOS to attenuate intestinal injury.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Enterocolitis, Necrotizing; Intestinal Mucosa; Intestines; Mice; Nitric Oxide; Nitric Oxide Synthase Type III; Sildenafil Citrate

To evaluate the effect of combining antenatal sildenafil with fetal tracheal occlusion (TO) in fetal rabbits with surgically induced congenital diaphragmatic hernia (CDH).. Although antenatal sildenafil administration rescues vascular abnormalities in lungs of fetal rabbits with CDH, it only partially improves airway morphometry. We hypothesized that we could additionally stimulate lung growth by combining this medical treatment with fetal TO.. CDH was created on gestational day (GD)23 (n=54). Does were randomized to receive either sildenafil 10 mg/kg/d or placebo by subcutaneous injection from GD24 to GD30. On GD28, fetuses were randomly assigned to TO or sham neck dissection. At term (GD30) fetuses were delivered, ventilated, and finally harvested for histological and molecular analyses. Unoperated littermates served as controls.. The lung-to-body-weight ratio was significantly reduced in sham-CDH fetuses either (1.2 ± 0.3% vs 2.3 ± 0.3% in controls, P=0.0003). Sildenafil had no effect on this parameter, while CDH fetuses undergoing TO had a lung-to-body-weight ratio comparable to that of controls (2.5 ± 0.8%, P<0.0001). Sildenafil alone induced an improvement in the mean terminal bronchiolar density (2.5 ± 0.8 br/mm2 vs 3.5 ± 0.9 br/mm2, P=0.043) and lung mechanics (static elastance 61 ± 36 cmH2O /mL vs 113 ± 40 cmH2O/mL, P=0.008), but both effects were more pronounced in fetuses undergoing additional TO (2.1 ± 0.8 br/mm2, P=0.001 and 31 ± 9 cmH2O/mL, P<0.0001 respectively). Both CDH-sham and CDH-TO fetuses treated with placebo had an increased medial wall thickness of peripheral pulmonary vessels (41.9 ± 2.9% and 41.8 ± 3.2%, vs 24.0 ± 2.9% in controls, P<0.0001). CDH fetuses treated with sildenafil, either with or without TO, had a medial thickness in the normal range (29.4% ± 2.6%). Finally, TO reduced gene expression of vascular endothelial growth factor and surfactant protein A and B, but this effect was counteracted by sildenafil.. In the rabbit model for CDH, the combination of maternal sildenafil and TO has a complementary effect on vascular and parenchymal lung development.

Topics: Animals; Combined Modality Therapy; Disease Models, Animal; Female; Fetus; Hernias, Diaphragmatic, Congenital; Lung; Pregnancy; Rabbits; Random Allocation; Sildenafil Citrate; Trachea

One of the main functions of the sensory system in our body is to maintain somatosensory homeostasis. Recent reports have led to a significant advance in our understanding of pain signaling mechanisms; however, the exact mechanisms of pain transmission have remained unclear. There is an urgent need to reveal the precise signaling mediators of pain to provide alternative therapeutic agents with more efficacy and fewer side effects. Accordingly, although the anti-inflammatory, antioxidative and anti-neuropathic effects of astaxanthin (AST) have been previously highlighted, its peripheral antinociceptive mechanisms are not fully understood. In this line, considering the engagement of l-arginine/nitric oxide (NO)/cyclic GMP (cGMP)/potassium channel (KATP) signaling pathway in the antinociceptive responses, the present study evaluated its associated role in the antinociceptive activity of AST. Male mice were intraperitoneally (i.p.) injected with l-arginine (100 mg/kg), SNAP (1 mg/kg), L-NAME (30 mg/kg), sildenafil (5 mg/kg), and glibenclamide (10 mg/kg) alone and prior to the most effective dose of AST. Following AST administration, intraplantarly (i.pl) injection of formalin was done, and pain responses were evaluated in mice during the primary (acute) and secondary (inflammatory) phases of formalin test. The results highlighted that 10 mg/kg i.p. dose of AST showed the greatest antinociceptive effect. Besides, while L-NAME and glibenclamide reduced the antinociceptive effect of AST, it was significantly increased by l-arginine, SNAP and sildenafil during both the primary and secondary phases of formalin test. These data suggest that the antinociceptive activity of AST is passing through the l-arginine/NO/cGMP/KATP pathway.

Topics: Analgesics; Animals; Arginine; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Glyburide; KATP Channels; Male; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Pain; Signal Transduction; Sildenafil Citrate; Xanthophylls

Right ventricle (RV) dysfunction is a main determinant of morbidity and mortality in postcapillary pulmonary hypertension (PH). However, currently there are not available therapies. Since reduced nitric oxide (NO) availability and cyclic guanylate monophosphate (cGMP) levels are central in this disease, therapies targeting the NO pathway might have a beneficial effect on RV performance. In this regard, sildenafil has shown contradictory results. Our objective was to evaluate the effect of sildenafil on RV performance in an experimental pig model of postcapillary PH induced by a fixed banding of the venous pulmonary confluent. Animals were evaluated by right heart catheterization and cardiac magnetic resonance before randomization and after 8 weeks on sildenafil (n = 8) or placebo (n = 8), and myocardial tissues were analyzed with histology and molecular biology. At the end of the study, animals receiving sildenafil showed better RV performance as compared with those on placebo (improvement in RV ejection fraction of 7.3% ± 5.8% versus -0.6% ± 5.0%, P= 0.021) associated with less apoptotic cells and gene expression related with reduced oxidative stress and increased anti-inflammatory activity in the myocardium. No differences were observed in pulmonary hemodynamics. In conclusion, in a translational large animal model of chronic postcapillary PH, sildenafil improved RV systolic function independently of afterload. Further research with pharmacological approaches able to manipulate the NO-cGMP axis are needed to confirm this potential cardioprotective effect.

Topics: Animals; Disease Models, Animal; Heart Ventricles; Hypertension, Pulmonary; Sildenafil Citrate; Swine; Vasodilator Agents

MiRNA-155 and miRNA-145 have been demonstrated to function as a key regulator in the development of the cardiovascular system. Recent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion (I/R) injury. This study was designed to investigate if administration of sildenafil will attenuate post-resuscitation myocardial dysfunction by regulating miRNA-155 and miR-145 expressions.. Thirty-two male pigs (weighing 30 ± 2 kg) were randomly divided into 4 groups, sildenafil group (n = 8), sildenafil +NG-nitro-l-arginine methyl ester (L-NAME) (20 mg/kg L) group (n = 8), saline (SA group, n = 8); and sham operation group (sham group, n = 8). Eight minutes of untreated VF was followed by defibrillation in anesthetized, closed-chest pigs. Hemodynamic status and blood samples were obtained at 0 min, 0.5, 1, 2, 4 and 6 h after return of spontaneous circulation (ROSC), and the hearts were removed and analyzed under electron microscopy, quantitative real-time polymerase chain reaction and ultra structural analysis were performed to evaluate myocardial injury.. Compared with the sildenafil + L-NAME and saline groups, the sildenafil group had better outcomes in terms of hemodynamic and oxygen metabolism parameters as well as 24-h survival rate, and attenuated myocardial injury; In this study, CA pigs showed evidently increased levels of miR-155-5p and miR-145-5p, while the sildenafil treatment decreased the levels of miR-155-5p and miR-145-5p in CA pigs. In addition, the levels of eNOS was decreased in CA pigs, validating sildenafil attenuating post-resuscitation myocardial dysfunction by regulating miRNA-155 and miR-145 expressions.. Sildenafil group had better outcomes in terms of hemodynamic and oxygen metabolism parameters as well as 24-h survival rate, inhibited the increases in the miR-155-5p and miR-145-5p levels and attenuated myocardial injury in a porcine model of CA and resuscitation.

Topics: Animals; Cardiomyopathies; Cardiopulmonary Resuscitation; Disease Models, Animal; Heart Arrest; Hemodynamics; Male; MicroRNAs; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Swine

To investigate the long-term effects of juvenile sub-chronic sildenafil (SIL) treatment on the depressive-like behaviour and hippocampal brain-derived neurotrophic factor (BDNF) levels of adult Sprague-Dawley (SD) versus Flinders Sensitive Line (FSL) rats.. SD and FSL rats were divided into pre-pubertal and pubertal groups, whereafter 14-day saline or SIL treatment was initiated. Pre-pubertal and pubertal rats were treated from postnatal day 21 (PND21) and PND35, respectively. The open field and forced swim tests (FST) were performed on PND60, followed by hippocampal BDNF level analysis 1 day later.. FSL rats displayed greater immobility in the FST compared to SD rats (p < 0.0001), which was reduced by SIL (p < 0.0001), regardless of treatment period. Hippocampal BDNF levels were unaltered by SIL in all treatment groups (p > 0.05).. Juvenile sub-chronic SIL treatment reduces the risk of depressive-like behaviour manifesting during young adulthood in genetically susceptible rats.

Topics: Animals; Antidepressive Agents; Behavior, Animal; Brain-Derived Neurotrophic Factor; Depression; Disease Models, Animal; Male; Motor Activity; Rats; Rats, Sprague-Dawley; Rats, Transgenic; Sildenafil Citrate

To assess the effect of sildenafil on monocrotaline-induced right ventricular (RV) remodeling and investigate the possible mechanism.. Rats were subcutaneously injected with monocrotaline to establish an RV remodeling model and then administered sildenafil (25 mg/kg) from days 1 to 28. After 28 days of administration, the RV systolic pressure and the RV hypertrophy index (RVHI) were measured. The morphology of the right ventricle was observed by H&E staining. The ultrastructure of the right ventricle was observed using a transmission electron microscope. The myocardial apoptosis of the right ventricle was evaluated by TUNEL staining. The protein expression of apoptosis-related proteins and PPARs were examined by western blotting.. The results indicated that sildenafil decreased the RV systolic pressure and RVHI, and improved the microstructure and ultrastructure of the right ventricle in monocrotaline-induced rats. In addition, sildenafil suppressed myocardial apoptosis and promoted the protein expression of PPARs of the right ventricle in monocrotaline-induced rats.. Sildenafil inhibits RV remodeling in monocrotaline-induced rats, which might be partially mediated by reducing myocardial apoptosis and activating PPARs.

Topics: Animals; Apoptosis; Disease Models, Animal; Heart Ventricles; In Situ Nick-End Labeling; Monocrotaline; Myocardium; Peroxisome Proliferator-Activated Receptors; Phosphodiesterase 5 Inhibitors; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Ventricular Remodeling

Erectile dysfunction (ED) is defined as the inability to achieve and/or maintain penile erection sufficient for satisfactory sexual relations, and aging is one of the main risk factors involved. The D-(+)-Galactose aging model is a consolidated methodology for studies of cardiovascular aging; however, its potential for use with ED remain unexplored. The present study proposed to characterize a new experimental model for ED, using the D-(+)-Galactose aging model. For the experiments, the animals were randomly divided into three groups receiving: vehicle (CTL), D-galactose 150 mg/kg (DGAL), and D-(+)-galactose 150 mg/Kg + sildenafil 1.5 mg/Kg (DGAL+SD1.5) being administered daily for a period of eight weeks. All of the experimental protocols were previously approved by the Ethics Committee on the Use of Animals at the Federal University of Paraíba n° 9706070319. During the treatment, we analyzed physical, molecular, and physiological aspects related to the aging process and implicated in the development of ED. Our findings demonstrate for the first time that D-(+)-Galactose-induced aging represents a suitable experimental model for ED assessment. This was evidenced by an observed hyper-contractility in corpora cavernosa, significant endothelial dysfunction, increased ROS levels, an increase in cavernous tissue senescence, and the loss of essential penile erectile components.

Topics: Aging; Animals; Disease Models, Animal; Electric Stimulation; Erectile Dysfunction; Galactose; Male; Penile Erection; Penis; Rats; Rats, Wistar; Reactive Oxygen Species; Sildenafil Citrate

Impaired angiogenesis function in pulmonary artery endothelial cells (PAEC) contributes to persistent pulmonary hypertension of the newborn (PPHN). Decreased nitric oxide (NO) amounts in PPHN lead to impaired mitochondrial biogenesis and angiogenesis in the lung; the mechanisms remain unclear. We hypothesized that decreased cyclic guanosine monophosphate (cGMP)-PKG (protein kinase G) signaling downstream of NO leads to decreased mitochondrial biogenesis and angiogenesis in PPHN. PPHN was induced by ductus arteriosus constriction from 128-136 days' gestation in fetal lambs. Control animals were gestation-matched lambs that did not undergo ductal constriction. PAEC isolated from PPHN lambs were treated with the sGC (soluble guanylate cyclase) activator cinaciguat, the PKG activator 8-bromo-cGMP, or the PDE-V (PDE type V) inhibitor sildenafil. Lysates were immunoblotted for mitochondrial transcription factors and electron transport chain C-I (complex I), C-II, C-III, C-IV, and C-V proteins. The

Topics: Animals; Animals, Newborn; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Endothelial Cells; Female; Guanosine Monophosphate; Humans; Hypertension, Pulmonary; Infant, Newborn; Mitochondria; Neovascularization, Pathologic; Nitric Oxide Synthase Type III; Pregnancy; Pulmonary Artery; Sheep; Signal Transduction; Sildenafil Citrate

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

The aim of this study was to investigate whether concomitant treatment of dutasteride and sildenafil could prevent structural changes in the penis of a BPH rodent model.. Thirty-two adult male rats were divided into the following groups: Ctrl, untreated control rats; BPH, untreated spontaneously hypertensive rats (SHRs); BPH + D, SHRs treated with dutasteride; and BPH + DS, SHRs treated with dutasteride and sildenafil. All treatments were performed during 40 days, following which the penises were collected for histomorphometrical analysis. The results were compared via one-way ANOVA with Bonferroni's post-test, considering. The smooth muscle density decreased by 28.6% and 21.4% in BPH + D and BPH + DS, respectively, when compared to the BPH group. The sinusoid space density reduced by 32.2% in BPH, when compared to the Ctrl group; this density was also reduced by 22.6% in BPH + D, when compared to the BPH group. The density of the elastic fibers increased 51.6% and 65.6% in BPH + D and BPH + DS, when compared to the BPH group.. Treatment with dutasteride promoted morphological changes in the corpus cavernous of this BPH model. Concomitant treatment with sildenafil did not prevent the morphological changes caused by dutasteride; on the contrary, it also promoted a further increase in elastic fibers.

Topics: 5-alpha Reductase Inhibitors; Animals; Disease Models, Animal; Dutasteride; Humans; Male; Penis; Prostatic Hyperplasia; Rats; Sildenafil Citrate

Acute mesenteric ischemia carries a significant morbidity. Measures to improve blood flow parameters to the intestine may ameliorate the disease. Sildenafil, a phosphodiesterase 5 inhibitor, increases cyclic guanosine monophosphate and has been shown to prevent the effects of ischemia when given before injury. However, its effects as a rescue agent have not been established. We therefore hypothesized that sildenafil, when given as a rescue agent for intestinal ischemia, would improve mesenteric perfusion, limit intestinal epithelial injury, and decrease intestinal leukocyte chemoattractants.. Eight to 12 wk-old-male C57BL/6J mice underwent laparotomy and temporary occlusion of the superior mesenteric artery for 60 min. Following ischemia, reperfusion was permitted, and before closing the abdomen, sildenafil was injected intraperitoneally in a variety of concentrations. After 24 h, reperfusion was reassessed. Animals were euthanized and intestines evaluated for histologic injury and leukocyte chemoattractants.. Postischemic administration of sildenafil did not improve mesenteric perfusion following intestinal ischemia and reperfusion injury. However, sildenafil did improve histologic injury scores in dose ranges of 0.01 to 10 mg/kg. No difference was noted in histological injury with 100 mg/kg dose, and all members of the 1000 mg/kg group died within 24 h of injury. Epithelial protection was not facilitated by the leukocyte chemoattractants Regulated on Activation, Normal T Cell Expressed, and Secreted, macrophage inflammatory protein 1 alpha, monocyte chemoattractant protein, neutrophil activating protein, or granulocyte colony stimulating factor.. Administration of sildenafil following intestinal ischemia may limit intestinal mucosal injury but does not appear to alter mesenteric perfusion or leukocyte chemoattractant influx. TYPE: Basic science.. N/A.

Topics: Animals; Disease Models, Animal; Humans; Injections, Intraperitoneal; Intestinal Mucosa; Male; Mesenteric Artery, Superior; Mesenteric Ischemia; Mesentery; Mice; Phosphodiesterase 5 Inhibitors; Reperfusion Injury; Sildenafil Citrate; Treatment Outcome

Arterial hypertension is a condition associated with endothelial dysfunction, accompanied by an imbalance in the production of reactive oxygen species (ROS) and NO. The aim of this study was to investigate and elucidate the possible mechanisms of sildenafil, a selective phosphodiesterase-5 inhibitor, actions on endothelial function in aortas from spontaneously hypertensive rats (SHR). SHR treated with sildenafil (40 mg/kg/day, p.o., 3 weeks) were compared to untreated SHR and Wistar-Kyoto (WKY) rats. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography and vascular reactivity was determined in isolated rat aortic rings. Circulating endothelial progenitor cells and systemic ROS were measured by flow cytometry. Plasmatic total antioxidant capacity, NO production and aorta lipid peroxidation were determined by spectrophotometry. Scanning electron microscopy was used for structural analysis of the endothelial surface. Sildenafil reduced high SBP and partially restored the vasodilator response to acetylcholine and sodium nitroprusside in SHR aortic rings. Using selective inhibitors, our experiments revealed an augmented participation of NO, with a simultaneous decrease of oxidative stress and of cyclooxygenase-1 (COX-1)-derived prostanoids contribution in the endothelium-dependent vasodilation in sildenafil-treated SHR compared to non-treated SHR. Also, the relaxant responses to sildenafil and 8-Br-cGMP were normalized in sildenafil-treated SHR and sildenafil restored the pro-oxidant/antioxidant balance and the endothelial architecture. In conclusion, sildenafil reverses endothelial dysfunction in SHR by improving vascular relaxation to acetylcholine with increased NO bioavailability, reducing the oxidative stress and COX-1 prostanoids, and improving cGMP/PKG signaling. Also, sildenafil reduces structural endothelial damage. Thus, sildenafil is a promising novel pharmacologic strategy to treat endothelial dysfunction in hypertensive states reinforcing its potential role as adjuvant in the pharmacotherapy of cardiovascular diseases.

Topics: Animals; Antihypertensive Agents; Aorta; Blood Pressure; Cyclic GMP; Cyclooxygenase 1; Disease Models, Animal; Endothelial Progenitor Cells; Endothelium, Vascular; Hypertension; Lipid Peroxidation; Male; Membrane Proteins; NADP; Nitric Oxide; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Rats, Inbred SHR; Rats, Inbred WKY; Signal Transduction; Sildenafil Citrate; Vasodilation; Vasodilator Agents

The aim of the study was to evaluate the potential protective role of sildenafil and tadalafil in contrast-induced nephropathy (CIN) by modulating oxidative stress. Thirty Wistar male rats were equally assigned into five groups: sham, CIN, CIN + sildenafil (10 mg/kg bw/day), CIN + tadalafil (5 mg/kg bw/day) and CIN + N-Acetyl Cysteine (NAC) (100 mg/kg bw/day) as a positive control. CIN was induced by 12 h dehydration and administration of indomethacin (10 mg/kg bw), N-ω- nitro-L-arginine methyl ester (10 mg/kg bw), and iopromide (3 g/kg bw iodine). Blood was drawn prior to and 24 h after CIN induction for evaluating renal function and oxidative stress. In the CIN group, total antioxidant capacity (TAC), reduced glutathione (GSH) and catalase (CAT) levels were significantly decreased; and protein carbonyl (PROTC) and thiobarbituric reactive species (TBARS) were significantly increased compared to the sham group. Pre- Sildenafil and tadalafil pre-treatment reduced CIN risk and reversed oxidative stress almost to the sham group levels. These results suggest that PDE5Is can be good candidates for preventing CIN based on their ability to modulate the oxidant/antioxidant balance.

Topics: Acetylcysteine; Animals; Antioxidants; Catalase; Contrast Media; Disease Models, Animal; Glutathione; Kidney Diseases; Male; Mice; Oxidants; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Rats; Rats, Wistar; Sildenafil Citrate; Tadalafil; Thiobarbituric Acid Reactive Substances

Radiation induced skin wound/dermatitis is one of the common side effects of radiotherapy or interventional radiobiology. In order to combat impaired healing of radiation wounds, alternative therapy to use sildenafil citrate (SC) topical hydrogel as a therapeutic option was proposed that has known to enhance nitric oxide in wounds. Our aim was to develop a radiation induced skin wound model and to investigate the wound healing efficacy of 5% SC hydrogel formulation in Sprague-Dawley rats. In the present study, the radiation wound inducing dose was optimized using a multi-dose localized γ-radiation trail with 10-55Gy range (15Gy interval). Optimal irradiation dose for wound induction was selected based on radiation skin damage assessment criteria followed the relative change from <35Gy or>55Gy showed significant variation and median 45Gy γ-dose was selected for studying acute effects of radiation on wound healing. Significant (p<0.05) higher wound contraction (88±1.02%), skin damage reduction (81±0.82%), tensile strength (45±1.61%), nitric oxide and protein recovery (53±0.72%) at dermal level prove the wound healing efficacy of 5% SC hydrogel formulation as compared to Rad 45Gy control. In addition, the dose modifying factor (DMF) for SC hydrogel treatment was found to be 1.83 and 1.57 with respect to total wound area contraction and skin damage reduction. Skin histopathology in treated tissues showed improved granulation tissue formation, less inflammatory infiltrates and mature collagen fibres in the dermis. Thus, the modality could help to improve delayed wound healing in irradiated skin tissues.

Topics: Animals; Disease Models, Animal; Gamma Rays; Hydrogels; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Radiodermatitis; Rats; Re-Epithelialization; Sildenafil Citrate; Skin

To investigate the effect of sildenafil on an experimental sodium selenite-induced cataract model in rats.. Twenty-six young Wistar rats were separated into four groups. On postpartum day 10, six rats received only selenite (group 1, selenite-induced cataract), seven rats received selenite and high dose oral sildenafil (group 2, high-dose sildenafil-treated), seven rats received selenite and low dose oral sildenafil (group 3, low-dose sildenafil-treated), and six rats received only saline (group 4, controls). On postpartum day 30, cataract formation was graded and recorded using an operating microscope. The rats were sacrificed, lens tissues were isolated, and serum samples were collected. Nitrite oxide metabolites (NOx), advanced oxidative protein products (AOPP), and total sulfhydryl (TSH) levels were assessed in both serum and lenticular samples.. The rats treated with low-dose sildenafil showed lower levels of AOPP and NOx, and the higher levels of TSH than the rats in other experimental groups. Otherwise, the rats treated with high-dose sildenafil, similar to the selenite-induced cataract group, showed higher levels of AOPP and serum NOx than rats in the low-dose sildenafil-treated group. The rats treated with low-dose sildenafil also showed less cataract development than rats in the other experimental groups.. Low doses (0.7 mg/kg) of oral sildenafil might show a protective effect on cataract development by lowering oxidative stress.

Topics: Administration, Oral; Advanced Oxidation Protein Products; Animals; Cataract; Disease Models, Animal; Lens, Crystalline; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Rats; Rats, Wistar; Sildenafil Citrate; Slit Lamp Microscopy; Sodium Selenite; Sulfhydryl Compounds; Trace Elements

Information regarding the pharmacokinetics of oral sildenafil in dogs with pulmonary hypertension is limited. In this study, we examined the pharmacokinetics of oral sildenafil in a canine model of chronic embolic pulmonary hypertension (CEPH). The CEPH model was developed by repeatedly injecting microspheres into the pulmonary arteries. The pharmacokinetics of oral sildenafil at 1, 2 and 4 mg/kg was evaluated using four dogs with pulmonary hypertension in the fasted state. The plasma concentrations of sildenafil were determined using high-performance liquid chromatography, and pharmacokinetic parameters were calculated using a noncompartmental analysis. Sildenafil was well tolerated in this study. Proportional increments in the maximum plasma concentration and area under the curve extrapolated to infinity at drug doses of 1, 2 and 4 mg/kg were detected using a power model analysis. No significant differences were observed among the three doses in the time to maximum plasma concentration. The mean residence time and elimination half-life were slightly but significantly higher at a dose of 4 mg/kg than at a dose of 1 mg/kg.

Topics: Administration, Oral; Animals; Area Under Curve; Disease Models, Animal; Dog Diseases; Dogs; Female; Hypertension, Pulmonary; Microspheres; Sildenafil Citrate

NTP42 is a novel antagonist of the thromboxane prostanoid receptor (TP), currently in development for the treatment of pulmonary arterial hypertension (PAH). PAH is a devastating disease with multiple pathophysiological hallmarks including excessive pulmonary vasoconstriction, vascular remodelling, inflammation, fibrosis, in situ thrombosis and right ventricular hypertrophy. Signalling through the TP, thromboxane (TX) A. PAH was induced by subcutaneous injection of 60 mg/kg MCT in male Wistar-Kyoto rats. Animals were assigned into groups: 1. 'No MCT'; 2. 'MCT Only'; 3. MCT + NTP42 (0.25 mg/kg BID); 4. MCT + Sildenafil (50 mg/kg BID), and 5. MCT + Selexipag (1 mg/kg BID), where 28-day drug treatment was initiated within 24 h post-MCT.. From haemodynamic assessments, NTP42 reduced the MCT-induced PAH, including mean pulmonary arterial pressure (mPAP) and right systolic ventricular pressure (RSVP), being at least comparable to the standard-of-care drugs Sildenafil or Selexipag in bringing about these effects. Moreover, NTP42 was superior to Sildenafil and Selexipag in significantly reducing pulmonary vascular remodelling, inflammatory mast cell infiltration and fibrosis in MCT-treated animals.. These findings suggest that NTP42 and antagonism of the TP signalling pathway have a relevant role in alleviating the pathophysiology of PAH, representing a novel therapeutic target with marked benefits over existing standard-of-care therapies.

Topics: Acetamides; Animals; Antihypertensive Agents; Disease Models, Animal; Heart Ventricles; Hemodynamics; Humans; Hypertrophy, Right Ventricular; Male; Monocrotaline; Pulmonary Arterial Hypertension; Pulmonary Artery; Pyrazines; Rats; Rats, Inbred WKY; Receptors, Thromboxane; Sildenafil Citrate; Vascular Remodeling

Combined pulmonary fibrosis and emphysema (CPFE) is a relatively new entity within the spectrum of cigarette smoke induced lung disorders. Currently there is no consensus about its treatment. We hypothesized that caveolin-1 critically determines the parenchymal and vascular remodeling leading to the development of CPFE. We assessed the effect of therapeutic targeting of caveolin-1 in mesenchymal and endothelial cells by the phosphodiesterase-5 inhibitor, sildenafil.. Male Wistar rats (n = 168) were exposed to; room air (control); bleomycin (7 U/kg), bleomycin+sildenafil (50 mg/kg/day P.O.), cigarette smoke (CS) (4 Gold Flake 69 mm/day), CS + sildenafil, CS + bleomycin, CS + bleomycin+sildenafil. Animals were euthanized at 8, 9, 11, 12 weeks and lung histopathological changes, collagen deposition, ROS, Xanthine oxidase, caveolin-1 determined.. Cigarette smoke causes progressive ROS accumulation, caveolin-1 up-regulation in alveolar epithelial cells, alveolar macrophages, peribronchiolar fibroblasts, endothelial and vascular smooth muscle cells, interstitial inflammation and emphysema. Sildenafil reduces oxidative stress, parenchymal caveolin-1 and attenuates emphysema caused by CS. Bleomycin increases lung ROS and downregulates caveolin-1 leading to fibroblast proliferation and fibrosis. Combined cigarette smoke and bleomycin exposure, results in differential caveolin-1 expression and heterogeneous parenchymal remodeling with alternating areas of emphysema and fibrosis. Increased caveolin-1 induces premature senescence of lung fibroblasts and emphysema. Decreased caveolin-1 is associated with propagation of EMT and fibrosis. Sildenafil attenuates the parenchymal remodeling however it is not effective in reducing VSMC hypertrophy in combined group.. CPFE is characterized by heterogenous parenchymal remodeling and differential caveolin-1 expression. Sildenafil therapy attenuates parenchymal pathologies in CPFE. Additional therapy is however needed for attenuating VSMC remodeling.

Topics: Animals; Bleomycin; Caveolin 1; Cigarette Smoking; Collagen; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Endothelial Cells; Fibroblasts; Gene Expression Regulation; Humans; Lung; Male; Mesenchymal Stem Cells; Phosphodiesterase 5 Inhibitors; Pulmonary Emphysema; Pulmonary Fibrosis; Rats; Rats, Wistar; Reactive Oxygen Species; Sildenafil Citrate; Xanthine Oxidase

Chronic social defeat can inhibit the reproductive system of subordinate males and causes behavioral deficits. Sildenafil treatment increases mice testosterone levels through its effects on Leydig cells of mice and it has been found to work as an antidepressant drug both in humans and in animal models. Since previous findings showed that sildenafil can counteract the inhibitory effects of chronic social defeat on agonistic, reproductive and anxiety-like behaviors of subordinate male mice, we investigated whether these behavioral outcomes can be explained by Sildenafil stimulation of testosterone. CD1 mice underwent an intruder-resident paradigm. After the fifth day of test, subordinate mice were injected with either a 10 mg/kg Sildenafil or a saline solution for 4 weeks. The results of the present study showed that Sildenafil treatment increased counterattacking behaviors and sexual motivation of subordinate males in addition to limiting the increase in body weight often observed in subordinate mice following chronic psychosocial stress. Moreover, sildenafil treated mice showed a pattern of behaviors reflecting lower anxiety. In agreement with previous studies, Sildenafil also increased testosterone levels. These data demonstrate that sildenafil can counteract the effects of chronic stress, possibly through its stimulatory effects on Leydig cells. These data demonstrate that sildenafil might counteract the effects of chronic psychosocial stress through centrally and peripherally mediated mechanisms.

Topics: Aggression; Animals; Anxiety; Disease Models, Animal; Male; Mice; Motivation; Sildenafil Citrate; Social Defeat; Stress, Psychological; Testosterone

Abusive chronic alcohol consumption can cause metabolic and functional derangements in the heart and is a risk factor for development of non-ischemic cardiomyopathy. microRNA 214 (miR-214) is a molecular sensor of stress signals that negatively impacts cell survival. Considering cardioprotective and microRNA modulatory effects of sildenafil, a phosphodiesterase 5 (PDE5) inhibitor, we investigated the impact of chronic alcohol consumption on cardiac expression of miR-214 and its anti-apoptotic protein target, Bcl-2 and whether sildenafil attenuates such changes. Adult male FVB mice received unlimited access to either normal liquid diet (control), alcohol diet (35% daily calories intake), or alcohol + sildenafil (1 mg/kg/day, p.o.) for 14 weeks (n = 6-7/group). The alcohol-fed groups with or without sildenafil had increased total diet consumption and lower body weight as compared with controls. Echocardiography-assessed left ventricular function was unaltered by 14-week alcohol intake. Alcohol-fed group had 2.6-fold increase in miR-214 and significant decrease in Bcl-2 expression, along with enhanced phosphorylation of ERK1/2 and cleavage of PARP (marker of apoptotic DNA damage) in the heart. Co-ingestion with sildenafil blunted the alcohol-induced increase in miR-214, ERK1/2 phosphorylation, and maintained Bcl-2 and decreased PARP cleavage levels. In conclusion, chronic alcohol consumption triggers miR-214-mediated pro-apoptotic signaling in the heart, which was prevented by co-treatment with sildenafil. Thus, PDE5 inhibition may serve as a novel protective strategy against cardiac apoptosis due to chronic alcohol abuse.

Topics: Alcoholism; Animals; Apoptosis; Disease Models, Animal; Heart Diseases; Male; Mice; MicroRNAs; Myocytes, Cardiac; Phosphodiesterase 5 Inhibitors; Phosphorylation; Signal Transduction; Sildenafil Citrate; Up-Regulation

Docetaxel plays an indispensable role in the management of advanced prostate cancer. However, more than half of patients do not respond to docetaxel, and those good responders frequently experience significant cumulative toxicity, which limits its dose duration and intensity. Hence, a second agent that could increase the initial efficacy of docetaxel and maintain tolerability at biologically effective doses may improve outcomes for patients.. We determined phosphodiesterase 5 (PDE5) expression levels in human and genetically engineered mouse (GEM) prostate tissues and tumor-derived cell lines. Furthermore, we investigated the therapeutic benefits and underlying mechanism of PDE5 inhibitor sildenafil in combination with docetaxel using. PDE5 expression was higher in both human and mouse prostate tumors and cancer cell lines compared with normal tissues/cells. In GEM prostate-derived cell lines, PDE5 expression increased from normal prostate (wild-type) epithelial cells to androgen-dependent and castrated prostate-derived cell lines. The addition of physiologically achievable concentrations of sildenafil enhanced docetaxel-induced prostate cancer cell growth inhibition and apoptosis. Our results demonstrate that sildenafil's addition could sensitize docetaxel chemotherapy in prostate cancer cells at much lesser concentration than needed for inducing cell death. Thus, the combinatorial treatment of sildenafil and docetaxel may improve anticancer efficacy and reduce chemotherapy-induced side-effects among patients with advanced prostate cancer.

Topics: Androgens; Animals; Apoptosis; Cell Line, Tumor; Cyclic AMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Docetaxel; Drug Synergism; Epithelial Cells; Gene Expression Regulation, Neoplastic; Heterografts; Humans; Male; Mice; Mice, Knockout; Nitric Oxide; Prostatic Neoplasms, Castration-Resistant; Signal Transduction; Sildenafil Citrate

Ischemic preconditioning and postconditioning are strong measures preserving the heart against ischemia-reperfusion injury in experimental setting but are too invasive and impractical for clinical routine. The cardioprotective effects of ischemic preconditioning and postconditioning can be imitated pharmacologically, for example, with the phosphodiesterase inhibitors sildenafil and milrinone. We hypothesize that sildenafil-induced preconditioning is concentration dependent and further that a combined treatment of "nonprotective" versus "protective" concentrations of sildenafil and milrinone leads to a significant infarct size reduction. Experiments were performed on isolated hearts of male Wistar rats, randomized into 12 groups, mounted onto a Langendorff system, and perfused with Krebs-Henseleit buffer. All hearts underwent 33 minutes ischemia and 60 minutes of reperfusion. For determination of a concentration-dependent effect of sildenafil, hearts were perfused with increasing concentrations of sildenafil (0.1-1 µM) over 10 minutes before ischemia. In a second series of experiments, hearts were treated with 0.3 µM sildenafil or 1 µM milrinone as the "protective" concentrations. A higher concentration of respective drugs did not further reduce infarct size. In addition, a combination of "protective" and "nonprotective" concentrations of sildenafil and milrinone was applied. Sildenafil and milrinone in lower concentrations led to significant infarct size reduction, whereas combining both substances in cardioprotective concentrations did not enhance this effect. Sildenafil in a concentration of 0.3 µM induces myocardial protection. Furthermore, treatment with sildenafil and milrinone in lower concentrations had an equally strong cardioprotective effect regarding infarct size reduction compared with the administration of "protective" concentrations.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Therapy, Combination; Hemodynamics; Isolated Heart Preparation; Male; Milrinone; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Phosphodiesterase 3 Inhibitors; Phosphodiesterase 5 Inhibitors; Rats, Wistar; Sildenafil Citrate; Ventricular Function, Left

Topics: Animals; Antioxidants; Disease Models, Animal; Drug Synergism; Humans; Male; Malondialdehyde; Oxidative Stress; Pregnatrienes; Reperfusion Injury; Sildenafil Citrate; Superficial Back Muscles; Surgical Flaps; Swine; Tumor Necrosis Factor-alpha

To investigate the acute effects of sildenafil citrate in an experimental model of severe head trauma, and to compare it with the efficacy of mannitol, which is an osmotically active agent frequently used in clinical treatment of traumatic brain injury (TBI).. Twenty-eight Wistar-derived albino strain female rats were randomized into four groups comprising seven rats each. These groups were designated as follows: Group I: sham; Group II: TBI; Group III: TBI + mannitol (20% 1 gr/ kg, intraperitoneal); and Group IV: TBI + sildenafil citrate (10 mg/kg, intraperitoneal). Sections prepared following the tissue processing of samples obtained from the right prefrontal cortex and right hippocampal regions of the brains of sacrificed rats were histopathologically evaluated. Fractionator method via the Stereo Investigator software program (Micro Bright Field) was used to count the neurons. Pyknotic neuron count and pyknotic / total neuron count were compared between the groups.. In the comparison of Group II and IV, pyknotic neuron count (prefrontal; group II: 116.00 ± 30.50, group IV: 80.00 ± 19.47) and pyknotic/ total neuron count (prefrontal; group II: 0,30 ± 0.08, group IV: 0.21 ± 0.02) were significantly lower in Group IV in both regions (p < 0.05). Similarly, in the comparison of Group II and III, the values in Group III were lower in both regions (p < 0.05).. Sildenafil citrate decreases neuronal death in the acute phase and produces similar results with mannitol. Therefore, we believe that sildenafil citrate can be a useful adjunct or alternative agent for the clinical treatment of patients with acute TBI.

Topics: Animals; Brain; Brain Injuries, Traumatic; Cell Death; Disease Models, Animal; Female; Mannitol; Neurons; Neuroprotective Agents; Phosphodiesterase 5 Inhibitors; Rats; Rats, Wistar; Sildenafil Citrate

Much evidence indicates that metabolic syndrome is strongly correlated with a decrease in nitric oxide and an increase in oxidative stress leading to cardiovascular alterations. In recent years, gut microbiota has emerged as a new contributor to the metabolic syndrome establishment and associated cardiovascular diseases, but the underlying mechanisms remain unclear. We hypothesized that a positive modulation of cyclic guanosine monophosphate (cGMP) pathway, through phosphodiesterase type 5 (PDE5) inhibition could prevent cardiovascular alterations and gut dysbiosis that may be associated to metabolic syndrome. Spontaneously hypertensive rats (SHR) were randomly divided into 4 groups: control, cafeteria diet (CD) and sildenafil citrate treated groups (5mg/kg per os) were given either a CD or a standard chow diet for 10 weeks. Body weight, arterial blood pressure and glucose tolerance test were monitored. At the 10th week, cardiac inotropy and coronary perfusion pressure were evaluated on isolated heart according to Langendorff method. Cumulative concentration response curves to phenylephrine and acetylcholine were determined on thoracic aorta rings for vascular reactivity evaluation. Faecal samples were collected for the gut microbiota analysis. Compared to the control group, CD-fed rats showed a significant increase in body weight gain, arterial blood pressure and were glucose intolerant. This group showed also a decrease in β-adrenoceptor-induced cardiac inotropy and coronary vasodilation. Gut microbiota analysis revealed a significant reduction in the abundance of Lactobocillus spp in cafeteria diet-fed rats when compared to the control ones. Sildenafil citrate long-term treatment decreased weight gain and arterial blood pressure, improved coronary vasodilation and reduced α1-adrenoceptor-induced vasoconstriction in CD group. However, it did not reverse gut dysbiosis induced by chronic CD feeding. These results suggest that cGMP pathway targeting may be a potential therapeutic strategy for the management of the metabolic syndrome and associated cardiovascular disorders.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Blood Pressure; Cardiovascular Diseases; Cyclic GMP; Diet; Disease Models, Animal; Gastrointestinal Microbiome; Glucose Tolerance Test; Male; Metabolic Syndrome; Phenylephrine; Phosphodiesterase 5 Inhibitors; Rats; Rats, Inbred SHR; Sildenafil Citrate; Vasodilation; Vasodilator Agents

Sildenafil is a potential new treatment for placental insufficiency in human pregnancies as it reduces the breakdown of vasodilator nitric oxide. Pulmonary vasodilatation is observed in normoxemic fetuses following sildenafil administration. Placental insufficiency often leads to fetal hypoxemia that can cause pulmonary vasoconstriction and fetal cardiac dysfunction as evidenced by reduced isovolumic myocardial velocities. We tested the hypotheses that sildenafil, when given directly to the hypoxemic fetus, reverses reactive pulmonary vasoconstriction, increases left ventricular cardiac output by increasing pulmonary venous return, and ameliorates hypoxemic myocardial dysfunction. We used an instrumented sheep model. Fetuses were made hypoxemic over a mean (standard deviation) duration of 41.3 (9.5) minutes and then given intravenous sildenafil or saline infusion. Volume blood flow through ductus arteriosus was measured with an ultrasonic transit-time flow probe. Fetal left and right ventricular outputs and lung volume blood flow were calculated, and ventricular function was examined using echocardiography. Lung volume blood flow decreased and the ductus arteriosus volume blood flow increased with hypoxemia. There was a significant reduction in left ventricular and combined cardiac outputs during hypoxemia in both groups. Hypoxemia led to a reduction in myocardial isovolumic velocities, increased ductus venosus pulsatility, and reduced left ventricular myocardial deformation. Direct administration of sildenafil to hypoxemic fetus did not reverse the redistribution of cardiac output. Furthermore, fetal cardiac systolic and diastolic dysfunction was observed during hypoxemia, which was not improved by fetal sildenafil treatment. In conclusion, sildenafil did not improve pulmonary blood flow or cardiac function in hypoxemic sheep fetuses.

Topics: Animals; Cardiac Output; Disease Models, Animal; Female; Hemodynamics; Hypoxia; Placental Insufficiency; Pregnancy; Pulmonary Circulation; Sheep; Sildenafil Citrate; Vasodilator Agents

The current study aimed to investigate the effects of sildenafil and N-acetylcysteine (NAC) on the haemodynamics in a rabbit model of acute pulmonary thromboembolism (APT). We developed an APT model using healthy male China big-ear rabbits (2.7 ± 0.4 kg). The rabbits were divided into five groups subjected to various interventions. We recorded the haemodynamic parameters and assessed the oxidative stress and lipid peroxidation response in the groups. Additionally, we detected apoptosis-associated molecules, FoxO1, Bad and Bcl-2, in the lung tissue. Gelatine zymography was used to detect matrix metalloproteinase (MMP) activity in bronchoalveolar lavage (BLA). Pulmonary artery endothelial cells were isolated, and their apoptosis rates and MMP activity were assayed. N-acetylcysteine potentiated the haemodynamic-improving effect of sildenafil and significantly inhibited the oxidative stress response. N-acetylcysteine combined with sildenafil decreased MMP-2 and MMP-9 activity and NO consumption and inhibited apoptosis of pulmonary arterial endothelial cells. Moreover, NAC combined with sildenafil inhibited the expression of MCP-1 and p-p38 MAPK. Thus, NAC potentiates the haemodynamic-improving effect of sildenafil in a rabbit model of acute pulmonary thromboembolism via the MCP-1 and p38 MAPK signalling pathway. This study may provide a promising treatment method for APT.

Topics: Acetylcysteine; Acute Disease; Animals; Apoptosis; Cell Count; Chemokine CCL2; Disease Models, Animal; Drug Synergism; Endothelial Cells; Hemodynamics; Lipid Peroxidation; Lung; Male; MAP Kinase Signaling System; Matrix Metalloproteinase 9; Neutrophils; Nitric Oxide; Oxidative Stress; p38 Mitogen-Activated Protein Kinases; Pulmonary Embolism; Rabbits; Sildenafil Citrate

and purpose: In this study, we employed a multiple microinfarction (MMI) based vascular dementia (VaD) model in aged rats and tested the therapeutic effects of Sildenafil, a phosphodiesterase type 5 inhibitor, on cognitive decline, white matter damage, autophagy and inflammatory response associated with VaD.. Male, aged (16-18 months) Wistar rats were subjected to MMI (800 ± 100, 70-100 μm cholesterol crystals injected into the internal carotid artery) and treated with or without Sildenafil (2 mg/kg, i.p) starting at 24 h after MMI daily for 28 days. Four experimental groups were employed: Sham control, Sham + Sildenafil, MMI, and MMI + Sildenafil. A battery of cognitive tests were performed and rats were sacrificed at 28 days after MMI for immunohistochemical evaluation and PCR assay.. Sildenafil treatment in aged MMI rats significantly improves short term memory evaluated by the novel object recognition test and improves spatial learning and memory in the Morris water maze test compared to aged control MMI rats. Sildenafil treatment of aged MMI rats significantly increases axon and myelin density in the corpus callosum and white matter bundles in the striatum, increases oligodendrocyte and oligodendrocyte progenitor cell number in the corpus callosum, cortex and striatum, and increases synaptic protein expression in the cortex and striatum compared to aged control MMI rats. In addition, Sildenafil treatment of MMI in aged rats significantly decreases Beclin1 expression and inflammatory factors Monocyte chemoattractant protein-1 and Interleukin-1β expression in brain. Sildenafil treatment in aged rats does not improve cognitive outcome compared to aged sham control rats.. Sildenafil treatment of MMI in aged rats significantly improves cognition and memory at 1 month after MMI. Sildenafil treatment increases axon and myelin density, increases Synaptophysin expression, decreases autophagic activity and exerts anti-inflammatory effects which in concert may contribute to cognitive improvement in aged rats subjected to MMI.

Topics: Aging; Animals; Brain; Cognition; Cognitive Dysfunction; Dementia, Vascular; Disease Models, Animal; Male; Maze Learning; Myelin Sheath; Neuroprotective Agents; Rats, Wistar; Sildenafil Citrate

Pulmonary arterial hypertension is a fatal lung disease caused by the progressive remodeling of small pulmonary arteries (PAs). Sildenafil can prevent the remodeling of PAs, but conventional sildenafil formulations have shown limited treatment efficacy for their poor accumulation in PAs. Here, glucuronic acid (GlcA)-modified liposomes (GlcA-Lips) were developed to improve the delivery of sildenafil to aberrant over-proliferative PA smooth muscle cells via targeting the GLUT-1 (glucose transport-1), and, therefore, inhibiting the remodeling of PAs in a monocrotaline-induced PA hypertension model. GlcA-Lips encapsulating sildenafil (GlcA-sildenafil-Lips) had a size of 90 nm and a pH-sensitive drug release pattern. Immunostaining assay indicated the overexpression of GLUT-1 in PA smooth muscle cells. Cellular uptake studies showed a 1-fold increase of GlcA-Lips uptake by PA smooth muscle cells and pharmacokinetics and biodistribution experiments indicated longer blood circulation time of GlcA-Lips and increased ability to target PAs by 1-fold after 8 hours administration. Two-week treatment indicated GlcA-sildenafil-Lips significantly inhibited the remodeling of PAs, with a 32% reduction in the PA pressure, a 41% decrease in the medial thickening, and a 44% reduction of the right ventricle cardiomyocyte hypertrophy, and improved survival rate. Immunohistochemical analysis showed enhanced expression of caspase-3, after administration of GlcA-sildenafil-Lips, and reduced expression of P-ERK1/2 (phosphorylated ERK1/2) and HK-2 (hexokinase-2), and increased level of eNOS (endothelial nitric oxide synthase) and cyclic GMP (cGMP). In conclusion, targeted delivery of sildenafil to PA smooth muscle cells with GlcA-Lips could effectively inhibit the remodeling of PAs in the monocrotaline-induced PA hypertension.

Topics: Animals; Disease Models, Animal; Hypertension, Pulmonary; Immunohistochemistry; Liposomes; Male; Muscle, Smooth, Vascular; Nitric Oxide Synthase Type III; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Tissue Distribution; Vascular Remodeling; Vasodilator Agents; Ventricular Function, Right

Fetal growth restriction (FGR) is associated with increased risk for cardiovascular and renal disorders in later life. Prenatal sildenafil improves birth weight in FGR animal models. Whether sildenafil treatment protects against long-term cardiovascular and renal disease in these offspring is unknown. The aim of this study is to test the hypothesis that prenatal sildenafil ameliorates cardiovascular and renal function in FGR offspring of Dahl salt-sensitive rats. Sildenafil citrate (60 mg/kg per day) or control gel diet (containing 0.3% salt) was administered from gestational day ten until birth. In male and female offspring, the mean arterial pressure was measured by telemetry in 1 subset from week 5 until week twenty. Echocardiographic parameters, glomerular filtration rate, and fractional electrolyte excretion were determined in another subset at week 9. Aortic and mesenteric artery rings were prepared to assess endothelial-dependent (acetylcholine) and -independent (sodium nitroprusside) vasorelaxation (week 10). The rise in mean arterial pressure per week was attenuated in treated versus untreated male offspring. Mesenteric arteries showed an increased endothelium-dependent relaxation and improved endothelium-independent relaxation in treated versus control male offspring. No differences in aortic relaxation, echocardiographic parameters or renal function were observed between groups. Prenatal sildenafil treatment subtly improves cardiovascular but not renal function in the offspring of this FGR rat model. Translationally, in utero treatment could be beneficial for cardiovascular programming in a sex-specific manner; however, caution is warranted since recent human trials have been halted because of potentially deleterious neonatal side effects when treating pregnancies complicated with severe FGR with sildenafil.

Topics: Animals; Cardiovascular System; Disease Models, Animal; Female; Fetal Development; Fetal Growth Retardation; Pregnancy; Pregnancy, Animal; Prenatal Care; Rats; Rats, Inbred Dahl; Sildenafil Citrate; Vasodilator Agents

Myocardial relaxation and stiffness are influenced by fibrillar collagen content. Cyclic nucleotide signaling regulators have been investigated targeting more effective modulation of collagen deposition during myocardial healing process. To assess the effects of phosphodiesterase type 3 and phosphodiesterase type 5 inhibitors on cardiac function and left ventricular myocardial fibrosis in catecholamine-induced myocardial injury, sildenafil and pimobendan were administered to male Wistar rats 24 hours after isoproterenol injection. Echocardiography and electrocardiogram were performed to assess kinetic and rhythm changes during 45 days of drug administration. At the end of study, type I and type III collagen were measured through immunohistochemistry analysis, and left ventricular pressure was assessed through invasive method. Echocardiography assessment showed increased relative wall thickness at 45 days in pimobendan group with significant diastolic dysfunction and increased collagen I deposition compared with nontreated positive group (3.03 ± 0.31 vs. 2.73 ± 0.28%, P < 0.05). Diastolic pressure correlated positively with type I collagen (r = 0.54, P < 0.05). Type III collagen analysis did not demonstrate difference among the groups. Sildenafil administration attenuated type I collagen deposition (2.15 ± 0.51 vs. positive group, P < 0.05) and suggested to be related to arrhythmic events. Arrhythmic events were not related to the quantity of fibrillar collagen deposition. Although negative modulation of collagen synthesis through cyclic nucleotides signaling have shown promising results, in this study, pimobendan postconditioning resulted in increased collagen type I formation and severe diastolic dysfunction while sildenafil postconditioning reduced collagen type I deposition and attenuated diastolic dysfunction.

Topics: Animals; Arrhythmias, Cardiac; Collagen Type I; Collagen Type III; Disease Models, Animal; Fibrosis; Isoproterenol; Male; Myocardium; Phosphodiesterase 3 Inhibitors; Phosphodiesterase 5 Inhibitors; Pyridazines; Rats, Wistar; Risk Assessment; Sildenafil Citrate; Ventricular Dysfunction, Left; Ventricular Function, Left; Ventricular Remodeling

Cyclic neucleotides are involved in many cellular functions including smooth muscle relaxation, inflammation, and signal transduction. Sildenafil and tadalafil are phosphodiesterase-5 (PDE-5) inhibitors which prevent the degradation of cyclic neucleotide i.e. guanosine 3',5' cyclic monophosphate (cGMP) and increase the levels of cGMP. In this study sildenafil and tadalafil were evaluated for their anti-inflammatory, anti-oxidative and anti-nitrosative stress potential in animal model of bronchial asthma.. Wistar rats were sensitized with 10 mg intraperitoneal (ip) ovalbumin adsorbed to 10 μg of aluminum hydroxide on day 0. Animals were given sildenafil (1 and 3 mg/kg ip) and tadalafil (1 and 3 mg/kg ip) from day 1 to day 14. Also, on day 14 animals were challenged with ovalbumin (1 mg ip). After 24 h, samples were collected to analyze interleukin-4 (IL-4) and tumour necrosis factor-α (TNF-α), in serum and bronchoalveolar lavage fluid (BALF). The oxidative stress markers malondialdehyde (MDA), reduced glutathione (GSH) and nitric oxide metabolites (NO. Pre-treatment with sildenafil (1 and 3 mg/kg ip) and tadalafil (1 and 3 mg/kg ip) significantly reduced the levels of pro-inflammatory cytokines IL-4 and TNF-α in rat serum and BALF. In addition, pre-treatment with both the drugs decreased the levels of MDA and NO. Sildenafil and tadalafil decreased pro-inflammatory cytokines in serum and BALF. Both drugs inhibit oxidative and nitrosative stress in animal model of bronchial asthma and could have a therapeutic potential in bronchial asthma.

Topics: Animals; Asthma; Bronchi; Bronchoalveolar Lavage Fluid; Cytokines; Disease Models, Animal; Female; Glutathione; Inflammation; Lung; Male; Malondialdehyde; Nitric Oxide; Nitrosative Stress; Oxidative Stress; Rats; Rats, Wistar; Sildenafil Citrate; Tadalafil

To investigate the potential neuroprotective effect of sildenafil on the ocular circulation in mice with/without optic nerve crush (ONC).. Male adult mice (n = 63) were treated with intravitreal (IVT) sildenafil 24 μg/3 μL, intraperitoneal (IP) sildenafil 24 μg/300 μL, or IP saline immediately before right ONC induction (ONC group). A second group (n = 123) received the same treatments without ONC induction (naïve group). Evaluations included fluorescein angiography (naïve group; day 0), molecular studies (days 1 and 3), and retinal and optic nerve histology (day 21).. Maximal retinal vessel dilatation and increased choroidal effusion were detected within 30 minutes of sildenafil injection. In the ONC group, moderate retinal ganglion cell (RGC) loss was noted at 21 days. However, molecular studies showed increased stress induced gene expression (IP superoxide dismutase [SOD]-1: 3.1-fold; heme oxygenase [HO]-1: 5.8-fold; IVT SOD-1: 1.47-fold), proapoptotic gene expression (IP BAX/B-cell lymphoma [BCL]-2 10.8-/2.3-fold), and glial gene expression (IP glial fibrillary acidic protein [GFAP]: 2.8- and myelin basic protein [MBP]: 2.5-fold). In the naïve group, IVT sildenafil was not associated with RGC loss or optic nerve stroke on histology, although in two samples, molecular parameters were compatible with stroke, showing increased gene expression of HO-1 (3.8-fold) and BCL-2 (2.5-fold). In the IP sildenafil subgroup, optic neuropathy was observed in 6/120 optic nerves, including 3 cyan fluorescence protein (CFP)-Thy-1 mice. Levels of antiapoptosis and anti-ischemia genes were decreased (<0.5-fold) except for three outliers.. Sildenafil affects retinal and choroidal perfusion in mice. When injected immediately before ONC, molecular parameters showed a preconditioning neuroprotective effect while histologic studies did not. In the absence of ONC, it is associated with neuropathy, possibly dose-dependent.

Topics: Animals; Apoptosis; Disease Models, Animal; Dose-Response Relationship, Drug; Fluorescein Angiography; Fundus Oculi; Intravitreal Injections; Male; Mice; Mice, Inbred C57BL; Optic Nerve; Optic Nerve Injuries; Phosphodiesterase 5 Inhibitors; Retinal Ganglion Cells; Sildenafil Citrate

In comparison to other antidepressant drugs, erectile dysfunction (ED) is more pronounced in paroxetine use. On the other hand, orange (Citrus sinensis) peels commonly consumed in various forms are used in folkloric medicine for ED management. Thus, this study evaluated the effect of orange peels infusion on sexual behaviour, nitric oxide (NO) level and some enzymes (arginase, phosphodiesterase-5 [PDE-5], acetylcholinesterase [AChE] and adenosine deaminase [ADA]) in paroxetine-treated rats. Erectile dysfunction was induced with paroxetine (10 mg/kg body weight). The animals were grouped into five (n = 6): normal rats; paroxetine-induced rats; paroxetine-induced rats treated with sildenafil citrate (5 mg/kg); paroxetine-induced rats treated with orange peels infusion (50 mg/kg); Paroxetine induced rats treated with orange peel infusions (100 mg/kg). The results revealed a significant decrease in sexual behaviour, NO level and the activities of antioxidant enzymes, while there was a significant increase in arginase, PDE-5, AChE and ADA activities in paroxetine-induced rats. However, orange peel infusions ameliorated erectile dysfunction in paroxetine-treated rats. This study showed some possible biochemical basis underlying the use of orange peels infusion in erectile dysfunction management.

Topics: Acetylcholinesterase; Adenosine Deaminase; Animals; Antidepressive Agents, Second-Generation; Antioxidants; Arginase; Citrus sinensis; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Erectile Dysfunction; Female; GPI-Linked Proteins; Humans; Male; Membrane Proteins; Nitric Oxide; Paroxetine; Penile Erection; Penis; Plant Extracts; Rats; Sexual Behavior; Sildenafil Citrate; Treatment Outcome

Sildenafil is an approved drug for the treatment of erectile dysfunction. The drug exerts its action through the relaxation of smooth muscles and the modulation of vascular endothelial permeability. In this work, we tested whether the aforementioned effects of sildenafil on tumour vasculatures could result in an improvement of anticancer drug concentration in tumour tissues and hence improves its anticancer effect. Sildenafil when added to doxorubicin showed synergistic anticancer activity against 4T1 breast cancer cells in vitro. Adding 1, 30 and 100 μM of Viagra to 1 μM of doxorubicin resulted in 1.8-fold, 6.2-fold and 21-fold statistically significant increases in its cytotoxic effect, respectively. As a result, 4T1 tumour-bearing mice showed up to 2.7-fold increase in drug concentrations of the fluorescent Dye DiI and doxorubicin in tumour tissues, as well as their nanoformulations. Animals treated with the combinations of both Sildenafil citrate and doxorubicin showed a statistically significant 4.7-fold reduction in tumour size compared to doxorubicin alone. This work highlights the effect of Sildenafil on tumour vasculatures and provides a rational for further testing the combination on breast cancer patients.

Topics: Animals; Antibiotics, Antineoplastic; Disease Models, Animal; Doxorubicin; Drug Delivery Systems; Drug Synergism; Humans; Mammary Neoplasms, Experimental; Mice; Nanoparticles; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate

Testing of investigational drugs in animal models is a critical step in drug development. Current models of pulmonary hypertension (PH) have limitations. The most relevant outcome parameters such as pulmonary artery pressure (PAP) are measured invasively which requires anesthesia of the animal. We developed a new canine PH model in which pulmonary vasodilators can be characterized in conscious dogs and lung selectivity can be assessed non-invasively.. Telemetry devices were implanted to measure relevant hemodynamic parameters in conscious dogs. A hypoxic chamber was constructed in which the animals were placed in a conscious state. By reducing the inspired oxygen fraction (FiO. The new hypoxic chamber provided a stable hypoxic atmosphere during all experiments. The mean PAP under normoxic conditions was 15.8 ± 1.8 mmHg. Hypoxia caused a reliable increase in mean PAP (+ 12.2 ± 3.2 mmHg, p < 0.0001). Both, sildenafil (- 6.8 ± 4.4 mmHg) and ANP (- 6.4 ± 3.8 mmHg) significantly (p < 0.05) decreased PAP. Furthermore sildenafil and ANP showed similar effects on systemic hemodynamics. In subsequent studies, the in vitro effects and gene expression pattern of the two pathways were exemplified.. By combining the hypoxic environment with the telemetric approach, we could successfully establish a new acute PH model. Sildenafil and ANP demonstrated equal effects regarding pulmonary selectivity. This non-invasive model could help to rapidly screen pulmonary vasodilators with decreased animal burden.

Topics: Animals; Atrial Natriuretic Factor; Disease Models, Animal; Dogs; Drug Evaluation, Preclinical; Hypertension, Pulmonary; Hypoxia; Lung; Male; Pulmonary Artery; Sildenafil Citrate; Telemetry; Vasodilator Agents; Wakefulness

Cardiac arrhythmia is a common cause of mortality, and its progression may be due to abnormal sympathetic nerve activity and catecholamine release. Besides, lactate dehydrogenase (LDH) and creatine kinase (CK) downregulation and adiponectin expression play important roles in promoting coronary artery disease. The study aimed to examine the possible cardioprotective effect of members of phosphodiesterase type 5 (PDE-5) inhibitors in epinephrine-induced arrhythmia in rats. Arrhythmia was induced by cumulative boluses of epinephrine (4, 8, 16, 32, 64, and 128 mg/kg) given at 10-min intervals. Rats were randomly allocated into five groups. Group I: Normal control group received only saline. Group II: Rats injected with epinephrine and served as arrhythmia group. Groups III, IV, and V: Rats received daily oral sildenafil (0.5 mg/kg), vardenafil (3 mg/kg), and tadalafil (10 mg/kg), respectively, for 30 days prior to epinephrine injections. Injection of epinephrine to rats decreased heart rate and QTc interval but increased RR interval and duration of arrhythmia. Epinephrine group had lower serum reduced glutathione (GSH) and adiponectin levels and higher serum malondialdehyde (MDA), nitric oxide (NO), heart LDH, and CK contents. Histopathological investigations of epinephrine group provoked necrotic changes with strong positive immunoreactivity for caspases-3. While pretreatment of rats with PDE-5 inhibitors improved GSH and adiponectin contents, ameliorated serum MDA and NO levels and heart LDH and CK contents and corrected epinephrine-induced histopathological changes. PDE-5 inhibitors may delay epinephrine-induced arrhythmia through expression of adiponectin and downregulation of heart LDH and CK.

Topics: Adiponectin; Animals; Anti-Arrhythmia Agents; Apoptosis; Arrhythmias, Cardiac; Caspase 3; Creatine Kinase; Disease Models, Animal; Electrocardiography; Epinephrine; Glutathione; Heart Rate; L-Lactate Dehydrogenase; Male; Malondialdehyde; Myocardium; Necrosis; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Rats, Wistar; Sildenafil Citrate; Tadalafil; Vardenafil Dihydrochloride

Sickle cell disease (SCD) is associated with intravascular hemolysis and oxidative inhibition of nitric oxide (NO) signaling. BAY 54-6544 is a small-molecule activator of oxidized soluble guanylate cyclase (sGC), which, unlike endogenous NO and the sGC stimulator, BAY 41-8543, preferentially binds and activates heme-free, NO-insensitive sGC to restore enzymatic cGMP production. We tested orally delivered sGC activator, BAY 54-6544 (17 mg/kg/d), sGC stimulator, BAY 41-8543, sildenafil, and placebo for 4-12 weeks in the Berkeley transgenic mouse model of SCD (BERK-SCD) and their hemizygous (Hemi) littermate controls (BERK-Hemi). Right ventricular (RV) maximum systolic pressure (RVmaxSP) was measured using micro right-heart catheterization. RV hypertrophy (RVH) was determined using Fulton's index and RV corrected weight (ratio of RV to tibia). Pulmonary artery vasoreactivity was tested for endothelium-dependent and -independent vessel relaxation. Right-heart catheterization revealed higher RVmaxSP and RVH in BERK-SCD versus BERK-Hemi, which worsened with age. Treatment with the sGC activator more effectively lowered RVmaxSP and RVH, with 90-day treatment delivering superior results, when compared with other treatments and placebo groups. In myography experiments, acetylcholine-induced (endothelium-dependent) and sodium-nitroprusside-induced (endothelium-independent NO donor) relaxation of the pulmonary artery harvested from placebo-treated BERK-SCD was impaired relative to BERK-Hemi but improved after therapy with sGC activator. By contrast, no significant effect for sGC stimulator or sildenafil was observed in BERK-SCD. These findings suggest that sGC is oxidized in the pulmonary arteries of transgenic SCD mice, leading to blunted responses to NO, and that the sGC activator, BAY 54-6544, may represent a novel therapy for SCD-associated pulmonary arterial hypertension and cardiac remodeling.

Topics: Anemia, Sickle Cell; Animals; Arterial Pressure; Disease Models, Animal; Enzyme Activation; Enzyme Activators; Heart Ventricles; Hypertension, Pulmonary; Hypertrophy, Left Ventricular; Mice, Transgenic; Morpholines; Nitric Oxide; Pulmonary Artery; Pyrimidines; Sildenafil Citrate; Soluble Guanylyl Cyclase; Vasodilation; Ventricular Dysfunction, Right; Ventricular Function, Right; Ventricular Pressure; Ventricular Remodeling

Current treatment with vasodilators for pulmonary hypertension associated with respiratory diseases is limited by their inhibitory effect on hypoxic pulmonary vasoconstriction (HPV) and uncoupling effects on ventilation-perfusion (V'/Q'). Hypoxia is also a well-known modulator of the nitric oxide (NO) pathway, and may therefore differentially affect the responses to phosphodiesterase 5 (PDE5) inhibitors and soluble guanylyl cyclase (sGC) stimulators. So far, the effects of the sGC stimulator riociguat on HPV have been poorly characterized.. Contraction was recorded in pulmonary arteries (PA) in a wire myograph. Anesthetized rats were catheterized to record PA pressure. Ventilation and perfusion were analyzed by micro-CT-SPECT images in rats with pulmonary fibrosis induced by bleomycin.. The PDE5 inhibitor sildenafil and the sGC stimulator riociguat similarly inhibited HPV in vitro and in vivo. Riociguat was more effective as vasodilator in isolated rat and human PA than sildenafil. Riociguat was ≈3-fold more potent under hypoxic conditions and it markedly inhibited HPV in vivo at a dose that barely affected the thromboxane A2 (TXA2) mimetic U46619-induced pressor responses. Pulmonary fibrosis was associated with V'/Q' uncoupling and riociguat did not affect the V'/Q' ratio.. PDE5 inhibitors and sGC stimulators show a different vasodilator profile. Riociguat was highly effective and potentiated by hypoxia in rat and human PA. In vivo, riociguat preferentially inhibited hypoxic than non-hypoxic vasoconstriction. However, it did not worsen V'/Q' coupling in a rat model of pulmonary fibrosis.

Topics: Aged; Animals; Disease Models, Animal; Enzyme Activators; Female; Humans; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Male; Middle Aged; Phosphodiesterase 5 Inhibitors; Pulmonary Artery; Pulmonary Fibrosis; Pyrazoles; Pyrimidines; Rats; Rats, Wistar; Sildenafil Citrate; Soluble Guanylyl Cyclase; Vasoconstriction; Vasodilator Agents; Ventilation-Perfusion Ratio

It has been suggested that the nitric oxide-sensitive guanylyl cyclase (NO-GC)/cyclic guanosine monophosphate (cGMP)-dependent signalling pathway affords protection against cardiac damage during acute myocardial infarction (AMI). It is, however, not clear whether the NO-GC/cGMP system confers its favourable effects through a mechanism located in cardiomyocytes (CMs). The aim of this study was to evaluate the infarct-limiting effects of the endogenous NO-GC in CMs in vivo.. Ischemia/reperfusion (I/R) injury was evaluated in mice with a CM-specific deletion of NO-GC (CM NO-GC KO) and in control siblings (CM NO-GC CTR) subjected to an in vivo model of AMI. Lack of CM NO-GC resulted in a mild increase in blood pressure but did not affect basal infarct sizes after I/R. Ischemic postconditioning (iPost), administration of the phosphodiesterase-5 inhibitors sildenafil and tadalafil as well as the NO-GC activator cinaciguat significantly reduced the amount of infarction in control mice but not in CM NO-GC KO littermates. Interestingly, NS11021, an opener of the large-conductance and Ca2+-activated potassium channel (BK), an important downstream effector of cGMP/cGKI in the cardiovascular system, protects I/R-exposed hearts of CM NO-GC proficient and deficient mice.. These findings demonstrate an important role of CM NO-GC for the cardioprotective signalling following AMI in vivo. CM NO-GC function is essential for the beneficial effects on infarct size elicited by iPost and pharmacological elevation of cGMP; however, lack of CM NO-GC does not seem to disrupt the cardioprotection mediated by the BK opener NS11021.

Topics: Animals; Benzoates; Cyclic GMP; Disease Models, Animal; Enzyme Activators; Female; Ischemic Postconditioning; Large-Conductance Calcium-Activated Potassium Channels; Male; Mice, Knockout; Myocardial Infarction; Myocardial Reperfusion Injury; Myocytes, Cardiac; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Signal Transduction; Sildenafil Citrate; Soluble Guanylyl Cyclase; Tadalafil; Tetrazoles; Thiourea; Time Factors; Up-Regulation

The purpose of the present study was to evaluate the effects of sildenafil on mandibular fracture healing in animals treated with zoledronic acid by using histologic, histomorphometric, immunohistochemical, and radiodensitometric methods.. A total of 36 Sprague-Dawley rats (3 months old) were used. All animals were treated intraperitoneally with 0.1 mg/kg zoledronate three times per week, for a total of 8 weeks. Postoperatively, the animals were divided into two groups: zoledronate group (Z), which had no treatment applied (n = 18), and zoledronate + sildenafil (ZS), which were treated daily with 10 mg/kg sildenafil (n = 18). Each group was divided into two subgroups and the animals were sacrificed at the end of week 1 (Z1 and ZS1, n = 9) and week 4 (Z4 and ZS4, n = 9) after the operation. Histologic, histomorphometric, immunohistochemical analysis, and radiodensitometry were performed on the test subjects.. Sildenafil-treated groups showed a significant increase in fracture healing scores. This result was supported by the densitometric, histologic, histomorphometric, and immunohistochemical findings.. Sildenafil may have positive effects on accelerating and improving fracture healing, and it may be used as a supporting factor in bone healing in patients treated with bisphosphonate (BP) to prevent negative effects of BP's.

Topics: Animals; Biopsy; Bone Density Conservation Agents; Diphosphonates; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Therapy, Combination; Female; Fracture Healing; Imidazoles; Mandibular Fractures; Phosphodiesterase 5 Inhibitors; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Zoledronic Acid

Right ventricular (RV) dysfunction following left ventricular (LV) failure is associated with poor prognosis. RV remodeling is thought initiated by the increase in the afterload of RV due to secondary pulmonary hypertension (PH) to impaired LV function; however, RV molecular changes might occur in earlier stages of the disease. cGMP (cyclic guanosine monophosphate)-phosphodiesterase 5 (PDE5) inhibitors, widely used to treat PH through their pulmonary vasorelaxation properties, have shown direct cardiac benefits, but their impacts on the RV in LV diseases are not fully determined. Here we show that RV molecular alterations occur early in the absence of RV hemodynamic changes during LV pressure-overload and are ameliorated by PDE5 inhibition. Two-day moderate LV pressure-overload (transverse aortic constriction) neither altered RV pressure/ function nor RV weight in mice, while it induced only mild LV hypertrophy. Importantly, pathological molecular features were already induced in the RV free wall myocardium, including up-regulation of gene markers for hypertrophy and inflammation, and activation of extracellular signal-regulated kinase (ERK) and calcineurin. Concomitant PDE5 inhibition (sildenafil) prevented induction of such pathological genes and activation of ERK and calcineurin in the RV as well as in the LV. Importantly, dexamethasone also prevented these RV molecular changes, similarly to sildenafil treatment. These results suggest the contributory role of inflammation to the early pathological interventricular interaction between RV and LV. The current study provides the first evidence for the novel early molecular cross-talk between RV and LV, preceding RV hemodynamic changes in LV disease, and supports the therapeutic strategy of enhancing cGMP signaling pathway to treat heart diseases.

Topics: Animals; Calcineurin; Cardiomegaly; Cardiovascular Agents; Dexamethasone; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; Heart Ventricles; Hemodynamics; Macrophages; Male; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Ventricular Dysfunction; Ventricular Function, Left; Ventricular Function, Right; Ventricular Pressure

Cisplatin-induced nephrotoxicity in large proportion of patients. The aim of this work is to clarify the effect of combination of sildenafil and gemfibrozil on cisplatin-induced nephrotoxicity either before or after cisplatin treatment and determination of nephrotoxicity predictors among the measured tissue markers.. Thirty two adult male albino rats were divided into four equal groups (G) GI control, GII received cisplatin, GIII received sildenafil and gemfibrozil before cisplatin, GIV received sildenafil and gemfibrozil after cisplatin. Creatinine and urea were measured and animals were sacrificed and kidney was taken for histopathology. The following tissue markers were measured, heme oxygenase-1 (HO-1) activity, reduced glutathione, quantitative (real-time polymerase chain reaction) RT-PCR for gene expression of tumor necrosis factor alpha (TNF-α) and endothelial nitric oxide synthase (ENOS) level.. GII developed AKI demonstrated by significantly high urea and creatinine and severe diffuse (80-90%) tubular necrosis. TNF-α was highly and significantly elevated while the rest of tissue markers were significantly reduced in GI1 compared to other groups. GIV showed better results compared to GIII. There was a significant positive correlation between creatinine and TNF-α when combining GI and GII while there were significant negative correlation between creatinine and other tissue markers in same groups. Linear regression analysis demonstrated that HO-1 was the independent predictor of AKI demonstrated by elevated creatinine among GI and GII.. Combination of sildenafil and gemfibrozil can be used in treatment of cisplatin-induced nephrotoxicity. HO-1 is a promising target for prevention and/or treatment of cisplatin-induced nephrotoxicity.

Topics: Animals; Antineoplastic Agents; Apoptosis; Biomarkers; Cisplatin; Creatinine; Disease Models, Animal; Drug Therapy, Combination; Gemfibrozil; Glutathione; Heme Oxygenase-1; Humans; Kidney; Male; Neoplasms; Oxidative Stress; Rats; Renal Insufficiency; Sildenafil Citrate; Treatment Outcome; Urea

Investigate the short-term effect of sildenafil on microcirculation, especially the velocity, the pattern of the flow and the recruitment of the leukocyte in postcapillaries.. In male Sprague-Dawley rats, the microcirculatory consequences of 60 min experimental testicular torsion, followed by 240 min of reperfusion, were examined. Using fluorescence intravital microscopy, changes in red blood cell velocity in post-capillary venules and rolling as well as adhesion of leukocytes in the postcapillary venules were examined before the torsion and every hour during the reperfusion period. Sildenafil was given 10 min prior to reperfusion (iv 0.7 mg/kg, n = 6), while control animals received saline vehicle (n = 5).. The characteristic flow motion disappeared in the affected testicular during the torsion. Red blood cell velocity values were dramatically decreased (by > 50%) and both rolling and adhesion of leukocytes increased during the reperfusion phase. Sildenafil treatment resulted in significantly higher red blood cell velocity values during the entire reperfusion period, but exerted only a temporary positive effect on the plost-ischaemic leukocyte-endothelial interactions.. Intraoperative administration of sildenafil during surgical detorsion may provide marked testicular microperfusion benefits, but failed to influence the overall leukocyte-driven microcirculatory inflammatory reactions.

Topics: Animals; Blood Flow Velocity; Cell Adhesion; Disease Models, Animal; Intravital Microscopy; Leukocyte Rolling; Leukocytes; Male; Microcirculation; Microscopy, Fluorescence; Rats; Rats, Sprague-Dawley; Reperfusion; Reperfusion Injury; Sildenafil Citrate; Spermatic Cord Torsion; Testis; Vasodilator Agents

Different adipose tissue (AT) depots are associated with multiple metabolic risks. Phosphodiesterase type 5 (PDE5) is involved in adipocyte physiology and PDE5 inhibition may affect adipogenesis and ameliorate white AT quality. The aim of this study is to investigate the distribution of AT and the composition of the stroma-vascular fraction (SVF) of subcutaneous AT (SAT) in type 2 diabetic mice after prolonged treatment with a PDE5 inhibitor, Sildenafil. 18 db/db mice were treated with Sildenafil or vehicle for 12 weeks. AT distribution was monitored and SAT was processed for isolation of SVF by flow cytometry. Sildenafil induced an overall reduction in AT, mainly in visceral AT (VAT), compared with SAT. In Sildenafil-treated mice, the mean change in body weight from baseline positively correlated with VAT, but not with SAT. Characterization of SVF of SAT showed an increase in the frequency of M2 macrophages and endothelial cells in treated mice. Sildenafil improved the maintenance of SAT homeostasis and distribution.

Topics: Adipocytes; Adipogenesis; Animals; Cell Plasticity; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus, Type 2; Disease Models, Animal; Humans; Intra-Abdominal Fat; Mice; Obesity; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Stromal Cells; Subcutaneous Fat

Topics: Disease Models, Animal; Hypertension, Pulmonary; Pulmonary Artery; Pyrazoles; Pyrimidines; Sildenafil Citrate; Ventricular Function, Right

Topics: Advisory Committees; Animals; Clinical Trials as Topic; Disease Models, Animal; Female; Fetal Growth Retardation; Humans; Infant, Newborn; Pregnancy; Review Literature as Topic; Sildenafil Citrate

This study sought to compare the effects of quercetin and rutin on some enzymes linked to erectile function as well as antioxidant status in penile tissue of paroxetine - induced erectile dysfunction in rats. Animals were randomly divided into twelve groups: normal control (NC), sildenafil (SD), quercetin (QA) (25 and 50 mg/kg), rutin (RU) (25 and 50 mg/kg), PAR (10 mg/kg); PAR + SD; PAR + QA, PAR + RU (25 and 50 mg/kg). After 14 days' treatment, phosphodiesterase-5' (PDE-5'), arginase, adenosine deaminase (ADA), acetylcholinesterase (AChE) and angiotensin-I converting enzyme (ACE) activities as well as malondialdehyde (MDA) and non-protein thiol levels were determined in rat penile tissues. Elevated levels of PDE-5', arginase, AChE, ADA and ACE activities and MDA were observed in PAR-induced rats with concomitant decrease in non-protein thiol levels when compared to the NC group. However, treatment with SD, QA and RU significantly reduced the activities of AChE, PDE-5', arginase, ADA and ACE and MDA levels and elevated non-protein thiol levels in penile tissues of PAR-induced rats. Furthermore, administration of QA and RU in PAR-induced rats modulated the key enzymes relevant to erection, improved antioxidant status and could be potential functional food ingredients and nutraceuticals in the prevention and/or management of erectile dysfunction.

Topics: Animals; Antioxidants; Disease Models, Animal; Enzymes; Erectile Dysfunction; Male; Malondialdehyde; Paroxetine; Penile Erection; Quercetin; Rats; Rutin; Sildenafil Citrate

Sildenafil influences seizure activity in animal seizure models, and its both proconvulsant and anticonvulsant effects were reported. We previously found that this PDE5 inhibitor significantly increased seizure threshold for the 6 Hz-induced psychomotor seizures in mice and therefore we aimed to investigate the influence of some modulators of neurotransmitter receptors, i.e., diazepam (GABA/benzodiazepine receptor agonist), flumazenil (GABA/benzodiazepine receptor antagonist), N-methyl-d-aspartic acid (NMDA glutamate receptor agonist), CGP 37849 (NMDA receptor antagonist), metergoline (serotonin receptor antagonist), 8-cyclopentyl-1,3-dipropylxanthine (adenosine A

Topics: Animals; Anticonvulsants; Disease Models, Animal; Electroshock; Male; Mice; Muscle Strength; Phosphodiesterase 5 Inhibitors; Seizures; Sildenafil Citrate; Synaptic Transmission

The primary goal was to assess the effects of chronic sildenafil treatment over the Achilles tendons in rats.. Animals were divided into two groups, control and sildenafil administration (n = 5). After 60 days, the tendons were subject to biochemical and image analysis to compare tendons between the groups: collagen I and decorin content, polarisation microscopy and birefringence analysis, and tissue zymography.. The animals exposed to sildenafil presented a much less organised tendon matrix, with reduced collagen I and non-collagenous protein content and a much higher decorin content.. The results observed in the animals can be characterised as tendinopathy, a condition not yet described as a sildenafil side effect.

Topics: Achilles Tendon; Animals; Collagen Type I; Disease Models, Animal; Male; Rats; Rats, Wistar; Sildenafil Citrate; Tendinopathy; Vasodilator Agents

Topics: Acetylcysteine; Animals; Contrast Media; Disease Models, Animal; Female; Hypoxia-Inducible Factor 1, alpha Subunit; Kidney Diseases; Phosphodiesterase 5 Inhibitors; Rats; Rats, Wistar; Sildenafil Citrate

Acute lung injury (ALI) is associated with deterioration of alveolar-capillary lining and transmigration and activation of inflammatory cells. Sildenafil, phosphodiesterase 5 (PDE5) inhibitor, inhibits degradation of cyclic guanosine monophosphate (cGMP) by competing with cGMP for binding site of PDE5. Positive effects of sildenafil treatment result from influencing proliferation of regulatory T cells and production of proinflammatory cytokines and autoantibodies as well as from modulation of platelet activation, angiogenesis, and pulmonary vasoreactivity. This study evaluated if intravenous sildenafil can influence inflammation, edema formation, apoptosis, and respiratory parameters in rabbits with a model of ALI induced by repetitive lung lavage by saline (30 ml/kg). animals were divided into 3 groups: ALI without therapy (ALI), ALI treated with sildenafil intravenously (1 mg/kg; ALI + Sil), and healthy ventilated controls (Control) which were oxygen-ventilated for 4 hours following treatment administration. during this period, respiratory parameters (ventilator pressures, lung compliance, blood gases, oxygenation indexes etc.) were regularly measured. at the end of experiment, animals were overdosed by anesthetics. The left lung was saline-lavaged and total and differential cell counts and protein content in the bronchoalveolar lavage fluid (BAL) were estimated. The right lung was used for determination of lung edema formation expressed as wet/dry lung weight ratio, for detection of inflammation and oxidative stress markers by ELISA methods, and for detection of lung epithelial cells apoptosis by TUNEL methods and level of caspase-3. Sildenafil treatment reduced leak of cells (P < 0.05), particularly of neutrophils (P < 0.001) into the lung, release of pro-inflammatory mediators (TNF-α, P < 0.001; IL-8 and IL-6, P < 0.01), level of nitrite/nitrate (P < 0.001), markers of oxidative damage (3-nitrotyrosine and malondialdehyde, both P < 0.01), lung edema formation (P < 0.01), protein content in BAL (P < 0.001), and apoptosis of epithelial cells (P < 0.01), and improved respiratory parameters. Concluding, the results indicate a future potential of PDE5 inhibitors also for the therapy of ALI.

Topics: Acute Lung Injury; Animals; Anti-Inflammatory Agents; Apoptosis; Bronchoalveolar Lavage; Cytokines; Disease Models, Animal; Epithelial Cells; Neutrophils; Nitrates; Nitrites; Phosphodiesterase 5 Inhibitors; Pulmonary Ventilation; Rabbits; Saline Solution; Sildenafil Citrate

Right-sided heart failure-often caused by elevated pulmonary arterial pressure-is a chronic and progressive condition with particularly high mortality rates. Recent studies and our current findings suggest that components of Wild garlic (

Topics: Allium; Animals; Biomarkers; Disease Models, Animal; Echocardiography; Heart Function Tests; Hypertension, Pulmonary; Lung; Male; Mass Spectrometry; Myocardium; Plant Extracts; Pulmonary Artery; Rats; Sildenafil Citrate

The aim of the study were to evaluate the effect of sildenafil against avascular necrosis of femoral head (ANFH) in a rabbit model, and to study the role of protein kinase G (PKG) pathway and vascular endothelial growth factor (VEGF) in ANFH.. Three weeks after inducing ANFH with methylprednisolone injection, 45 female adult New Zealand white rabbits were divided into three groups and treated as follows: group SI received daily intraperitoneal sildenafil with a dose of 10 mg/kg per day; group SD received daily sildenafil identically to group SI plus auricular vein injection DT3 (a specific PKG inhibitor); group NS received only normal saline. The blood perfusion function in the femoral head was measured by perfusion MRI and ink artery infusion. Bilateral femora heads were examined histopathologically for the presence of osteonecrosis; VEGF of tissue was examined by Western blot analysis; cGMP level and PKG activity were also measured.. The incidence of ANFH in SI group was significantly lower than that observed in NS and SD groups (p < 0.05). VEGF in SI group was increased compared to NS group. cGMP level and PKG activity were also significantly different between NS and SI group (p < 0.05). However, these effects of sildenafil in SD group were all markedly inhibited by the administration of DT3 compared to SI group.. Sildenafil appear to increase the perfusion of femoral head by up-regulating VEGF through PKG pathway. The increased perfusion of femoral head could prevent ANFH.

Topics: Animals; Cyclic GMP-Dependent Protein Kinases; Diffusion Magnetic Resonance Imaging; Disease Models, Animal; Female; Femur Head; Femur Head Necrosis; Glucocorticoids; Methylprednisolone; Rabbits; Regional Blood Flow; Sildenafil Citrate; Treatment Outcome; Vascular Endothelial Growth Factor A

Bronchopulmonary dysplasia (BPD), a common complication of preterm birth, is associated with pulmonary hypertension (PH) in 25% of infants with moderate to severe BPD. Neonatal mice exposed to hyperoxia for 14d develop lung disease similar to BPD, with evidence of associated PH. The cyclic guanosine monophosphate (cGMP) signaling pathway has not been well studied in BPD-associated PH. In addition, there is little data about the natural history of hyperoxia-induced PH in mice or the utility of phosphodiesterase-5 (PDE5) inhibition in established disease. C57BL/6 mice were placed in room air or 75% O2 within 24h of birth for 14d, followed by recovery in room air for an additional 7 days (21d). Additional pups were treated with either vehicle or sildenafil for 7d during room air recovery. Mean alveolar area, pulmonary artery (PA) medial wall thickness (MWT), RVH, and vessel density were evaluated at 21d. PA protein from 21d animals was analyzed for soluble guanylate cyclase (sGC) activity, PDE5 activity, and cGMP levels. Neonatal hyperoxia exposure results in persistent alveolar simplification, RVH, decreased vessel density, increased MWT, and disrupted cGMP signaling despite a period of room air recovery. Delayed treatment with sildenafil during room air recovery is associated with improved RVH and decreased PA PDE5 activity, but does not have significant effects on alveolar simplification, PA remodeling, or vessel density. These data are consistent with clinical studies suggesting inconsistent effects of sildenafil treatment in infants with BPD-associated PH.

Topics: Animals; Animals, Newborn; Bronchopulmonary Dysplasia; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Guanylate Cyclase; Hyperoxia; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Lung; Mice; Mice, Inbred C57BL; Oxygen; Phosphodiesterase 5 Inhibitors; Pulmonary Alveoli; Pulmonary Artery; Signal Transduction; Sildenafil Citrate; Vascular Remodeling

The purpose of our investigative work has been to determine whether there can be therapeutic roles in the administration of sildenafil citrate, heparin and several neuropeptides on an animal model where gastric ulcers were induced with acetic acid, and to compare their efficacy.. The animals were divided into 13 groups, with 4 animals in each. Gastric ulcers was induced in the animals of 12 groups with one untreated group being left as the control (Group I - control; given normal saline (NS)). The other groups were: Group II (ulcer+NS); Group III (5mg/kg sildenafil citrate, low dose); Group IV (10mg/kg sildenafil citrate, high dose); Group V (0.6mg/kg heparin, low dose); Group VI (6mg/kg heparin, high dose); Group VII (20nmol/kg des-acyl ghrelin); Group VIII (40nmol/kg des-acyl ghrelin); Group IX (4nmol/kg acyl ghrelin); Group X (8nmol/kg acly ghrelin); Group XI (20pmol/kg Nesfatin-1); Group XII (15nmol/kg Obestatin) and Group XIII (5nmol/kg Neuropeptide Y). Gastric neuropeptide expression was measured using an immunohistochemical method, and the amount in circulation was detected using ELISA. To compare with no treatment, the controls and other treatment groups, we recorded loss of the surface epithelium of the stomach, erosion, bleeding and inflammatory cell infiltration in the upper halves of the gastric glands.. The muscularis and the layers beneath it were, however, apparently normal. The gastric mucosa healed with little or no inflammation when sildenafil citrate, low dose heparin, ghrelin, NUCB2/Nesfatin-1, obestatin, Neuropeptide Y were administered.. Overall the data indicate that low dose heparin, and especially sildenafil citrate and neuropeptides, can be used clinically as an alternative approach in the treatment of the gastric ulcer.

Topics: Acetic Acid; Animals; Anti-Ulcer Agents; Disease Models, Animal; Dose-Response Relationship, Drug; Gastric Mucosa; Heparin; Neuropeptides; Rats, Sprague-Dawley; Sildenafil Citrate; Stomach Ulcer

Pemetrexed is an approved therapeutic in NSCLC and ovarian cancer. Our studies focused on the ability of [pemetrexed + sildenafil] exposure to alter the immunogenicity of lung and ovarian cancer cells. Treatment of lung and ovarian cancer cells with [pemetrexed + sildenafil] in vitro rapidly reduced the expression of PD-L1, PD-L2 and ornithine decarboxylase (ODC), and increased the expression of class I MHCA. In a cell-specific fashion, some cells also released the immunogenic nuclear protein HMGB1 into the extracellular environment. [Pemetrexed + sildenafil] reduced the expression of multiple histone deacetylases that was blocked by knock down of autophagy regulatory proteins. [Pemetrexed + sildenafil] lethality was enhanced by the histone deacetylase inhibitors AR42 and sodium valproate; AR42 and valproate as single agents also rapidly reduced the expression of PD-L1, PD-L2 and ODC, and increased expression of MHCA and CerS6. Nitric oxide and CerS6 signaling was required for drug-induced death receptor activation and tumor cell killing. In vivo, [pemetrexed + sildenafil] lethality against lung cancer cells was enhanced by sodium valproate. Using syngeneic mouse lung cancer cells [pemetrexed + sildenafil] enhanced the anti-tumor effects of antibodies directed to inhibit PD-1 or CTLA4. [Pemetrexed + sildenafil] interacted with the anti-PD-1 antibody to strongly enhance tumor infiltration by M1 macrophages; activated NK cells and activated T cells. Our data demonstrate that treatment of tumor cells with [pemetrexed + sildenafil] results in tumor cell killing and via autophagy-dependent downregulation of HDACs, it opsonizes the remaining tumor cells to anti-tumor immunotherapy antibodies.

Topics: Animals; Antineoplastic Agents; Autophagy; Biomarkers, Tumor; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Disease Models, Animal; Drug Synergism; Female; Histone Deacetylase Inhibitors; Humans; Immunotherapy; Lung Neoplasms; Mice; Pemetrexed; Signal Transduction; Sildenafil Citrate; Xenograft Model Antitumor Assays

Hepatic fibrosis is a potential health problem that may end with life-threatening cirrhosis and primary liver cancer. Recent studies point out to the protective effects of silent information regulator1 (SIRT1), against different models of organs fibrosis. This work aimed to investigate the possible protective effect of sildenafil (SIRT1 activator) against hepatic fibrosis induced by bile duct ligation (BDL). Firstly, three different doses of sildenafil (5, 10, 20mg/kg/day) were investigated; to detect the most protective one against BDL induced liver dysfunction and hepatic fibrosis. The most protective dose is then used; to study its effect on BDL induced SIRT1 downregulation, imbalance of oxidant/antioxidant status, increased inflammatory cytokines and fibrosis. Sildenafil (20mg/kg/day) was the most protective one, it caused upregulation of SIRT1, reduction of hepatic malondialdehyde (MDA) content, increase in expression of nuclear factor erythroid 2-related factor 2 (Nrf2), hemeoxygenease (HO)-1, reduced glutathione (GSH) content and superoxide dismutase (SOD) activity. Hepatic content of tumor necrosis factor-α (TNF-α) and nuclear factor κB (NFκB) expression & content displayed significant reductions with sildenafil treatment, Furthermore, sildenafil caused marked reductions of transforming growth factor (TGF)-β content, expression of plasminogen activator inhibitor-1 (PAI-1), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), α-smooth muscle actin (α-SMA), fibronectin, collagen I (α1) and hydroxyproline content. However, sildenafil protective effects were significantly reduced by co-administration of EX527 (SIRT1 inhibitor). Our work showed, for the first time that, sildenafil has promising protective effects against BDL induced liver dysfunction and hepatic fibrosis. These effects may be, in part, mediated by up regulation of SIRT1.

Topics: Animals; Anti-Inflammatory Agents; Antioxidants; Biomarkers; Carbazoles; Cholestasis; Cytoprotection; Disease Models, Animal; Histone Deacetylase Inhibitors; Inflammation Mediators; Ligation; Liver; Liver Cirrhosis, Biliary; Male; Oxidative Stress; Protective Agents; Rats, Wistar; Signal Transduction; Sildenafil Citrate; Sirtuin 1; Up-Regulation

In our study, sildenafil alone and everolimus or alagebrium in combination with sildenafil were investigated in terms of their additional therapeutic and anti-remodeling activity in monocrotaline-induced pulmonary hypertension (PH) model in rats. In particular, the inter-relationships between PH and matrix metalloproteinases (MMPs) were investigated.. The pulmonary artery responses of male Sprague Dawley rats were recorded using myography, and the quantities and activities of MMPs were analyzed in homogenates of the pulmonary arteries and lungs by enzyme-linked immunosorbent assays, activity assays, and gelatin zymography techniques.. Our results indicated that the therapeutic effects of sildenafil were accompanied by its suppressor effects on MMP activity. It was also shown that everolimus or alagebrium in combination with sildenafil showed additional regulatory effects on MMPs as well as functional responses on pulmonary artery pressure. Therefore, the enzymes in the MMP superfamily are likely to be target molecules for the treatment of PH.. In conclusion, MMPs were involved in the pathogenesis of PH, and our results suggested that the addition of everolimus or alagebrium to sildenafil therapy may be beneficial in PH. Our results indicated that agents that limit pulmonary vascular hypertrophy and inflammation via their anti-remodeling effects significantly ameliorate mortality and morbidity in PH.

Topics: Animals; Disease Models, Animal; Drug Therapy, Combination; Everolimus; Hypertension, Pulmonary; Male; Matrix Metalloproteinases; Monocrotaline; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Thiazoles; Vasodilator Agents

The present study evaluated the effectiveness of sildenafil citrate (SC) to improve placental and fetal growth in a diet-induced rabbit model of intrauterine growth restriction (IUGR). Pregnant rabbits were fed either ad libitum (Group C) or restricted to 50% of dietary requirements (Group R) or restricted and treated with SC (Group SC). The treatment with SC improved placental development by increasing vascularity and vessel hypertrophy in the decidua. The assessment of feto-placental haemodynamics showed higher resistance and pulsatility indices at the middle cerebral artery (MCA) in fetuses treated with SC when compared with Group R, which had increased systolic peak and time-averaged mean velocities at the MCA. Furthermore, fetuses in the SC group had significantly higher biparietal and thoracic diameters and longer crown-rump lengths than fetuses in Group R. Hence, the SC group had a reduced IUGR rate and a higher kit size at birth compared with Group R. In conclusion, SC may provide potential benefits in pregnancies with placental insufficiency and IUGR, partially counteracting the negative effects of food restriction on placental development and fetal growth. However, the present study also found evidence of a possible blood overflow in the brain that warrants further investigation.

Topics: Animals; Caloric Restriction; Cerebrovascular Circulation; Crosses, Genetic; Decidua; Disease Models, Animal; Female; Fetal Development; Fetal Growth Retardation; Maternal Nutritional Physiological Phenomena; Phosphodiesterase 5 Inhibitors; Placenta; Placental Circulation; Placentation; Pregnancy; Pulsatile Flow; Rabbits; Random Allocation; Sildenafil Citrate; Vascular Resistance; Vasodilator Agents

The stem bark of Terminalia arjuna (Roxb.) is widely used in Ayurveda in various cardiovascular diseases. Many animal and clinical studies have validated its anti-ischemic, antihypertensive, antihypertrophic and antioxidant effects. Pulmonary hypertension (PH) is a fatal disease which causes right ventricular hypertrophy and right heart failure. Pulmonary vascular smooth muscle hypertrophy and increased oxidative stress are major pathological features of PH. As available limited therapeutic options fail to reduce the mortality associated with PH, alternative areas of therapy are worth exploring for potential drugs, which might be beneficial in PH.. The effect of a standardised aqueous extract of the stem bark of Terminalia arjuna (Roxb.) in preventing monocrotaline (MCT)-induced PH in rat was investigated.. The study was approved by Institutional Animal Ethics Committe. Male Wistar rats (150-200g) were randomly distributed into five groups; Control, MCT (50mg/kg subcutaneously once), sildenafil (175µg/kg/day three days after MCT for 25 days), and Arjuna extract (TA125 and TA250 mg/kg/day orally after MCT for 25 days). PH was confirmed by right ventricular weight to left ventricular plus septum weight (Fulton index), right ventricular systolic pressure (RVSP), echocardiography, percentage medial wall thickness of pulmonary arteries (%MWT). Oxidative stress in lung was assessed by super oxide dismutase (SOD), catalase, reduced glutathione (GSH) and thiobarbituric acid reactive substance (TBARS). The protein expressions of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX-1) in lung and gene expression of Bcl2 and Bax in heart were analyzed by Western blot and RT PCR respectively.. MCT caused right ventricular hypertrophy (0.58±0.05 vs 0.31±0.05; P<0.001 vs. control) and increase in RVSP (33.5±1.5 vs 22.3±4.7mm of Hg; P<0.001). Both sildenafil and Arjuna prevented hypertrophy and RVSP. Pulmonary artery acceleration time to ejection time ratio in echocardiography was decreased in PH rats (0.49±0.05 vs 0.32±0.06; P<0.001) which was prevented by sildenafil (0.44±0.06; P<0.01) and TA250 (0.45±0.06; P<0.01). % MWT of pulmonary arteries was increased in PH and was prevented by TA250. Increase in TBARS (132.7±18.4 vs 18.8±1.6nmol/mg protein; P<0.001) and decrease in SOD (58.4±14.1 vs 117.4±26.9U/mg protein; P<0.001) and catalase (0.30±0.05 vs 0.75±0.31U/mg protein; P<0.001) were observed in lung tissue of PH rats, which were prevented by sildenafil and both the doses of Arjuna extract. Protein expression of NOX1 was significantly increased in lung and gene expression of Bcl2/Bax ratio was significantly decreased in right ventricle in MCT-induced PH, both were significantly prevented by Arjuna and sildenafil.. Aqueous extract of Terminalia arjuna prevented MCT-induced pulmonary hypertension which may be attributed to its antioxidant as well as its effects on pulmonary arteriolar wall thickening.

Topics: Animals; Antihypertensive Agents; Antioxidants; bcl-2-Associated X Protein; Catalase; Disease Models, Animal; Heart Ventricles; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Lung; Male; Medicine, Ayurvedic; NADH, NADPH Oxidoreductases; NADPH Oxidase 1; Plant Bark; Plant Extracts; Plant Stems; Proto-Oncogene Proteins c-bcl-2; Pulmonary Artery; Rats; Rats, Wistar; Sildenafil Citrate; Terminalia; Water

Retinal ischemia is a common cause of visual impairment and blindness. Sildenafil, a PDE5 inhibitor which inhibits cGMP degradation and in turn prolongs the effect of nitric oxide, has been shown to be protective in a number of ischemia/reperfusion (I/R) injuries, as well as in neuronal damage. We hypothesized that treatment with sildenafil might be neuroprotective in a model of acute retinal I/R injury.. Anterior chamber cannulation was performed to induce unilateral I/R injury in 38 Lewis rats. Animals received intraperitoneal injections of sildenafil (0.5 and 1 mg/kg once a day, for a period of 7 and 18 days, respectively), or saline. Electroretinography recordings, retinal ganglion cell (RGC) counts following retrograde labeling with fluorogold, histopathology, and immunohistochemistry (IHC) using antibodies against PDE5, NOS2, caspase-3, caspase-9, and Bcl-2 were conducted.. No significant differences in electroretinography, RGC counts, or retinal morphometry were observed between experimental eyes of sildenafil- and saline-treated animals. A tendency toward less necrosis in histopathology, and a slight trend toward lower PDE5, NOS2, and caspase-9 and higher Bcl-2 IHC scores were evident in experimental retinas of sildenafil-treated animals.. Electroretinography, RGC counts, and retinal morphometry failed to show any neuroprotective effect of sildenafil in acute retinal I/R injury in rats. A slight positive effect of sildenafil was qualitatively indicated by histopathology and IHC.

Topics: Animals; Caspase 3; Caspase 9; Cell Count; Disease Models, Animal; Electroretinography; Immunohistochemistry; In Situ Nick-End Labeling; Male; Phosphodiesterase 5 Inhibitors; Rats; Rats, Inbred Lew; Reperfusion Injury; Retinal Diseases; Retinal Ganglion Cells; Sildenafil Citrate; Treatment Outcome

Our aim was to investigate the effects of doxazosin, sildenafil, and their combination on bladder tissue contractility and adrenergic receptor (AR) and inducible nitric oxide synthase (iNOS) expression utilizing a male rat model of partial urethral obstruction (PUO).. Thirty male Sprague Dawley rats were divided into five groups. Except the SHAM group, all animals in remaining four groups underwent surgery for PUO. No further treatment was given to the first group (NT group). Remaining three groups received 6 weeks of treatment with 20 mg/kg doxazosin (D group), 20 mg/kg sildenafil (S group), 20 mg/kg doxazosin, and 20 mg/kg sildenafil combination (DS group), respectively via oral gavage. Then, bladder strips were harvested from each animal for isometric tension studies and for real time polymerase chain reaction studies of both AR subtypes and iNOS mRNA.. Contractile responses to carbachol and electrical field stimulation at various concentrations/frequencies showed a significant increase after PUO. Any treatment helped to normalize these increased responses. Alpha 1a and 1d AR subtype expressions were found to be down- and up-regulated, respectively, in every group with PUO, compared to SHAM group. iNOS expression was similar in D and NT groups and significantly increased in S and DS groups.. Contractile changes of rat bladder tissue due to PUO were prevented by sildenafil or doxazosin alone or in combination where combination treatment did not provide any additional advantage. Further studies are needed to clarify the role of phosphodiesterase inhibitors and combination treatment in the treatment of LUTS.

Topics: Adrenergic alpha-1 Receptor Antagonists; Animals; Carbachol; Disease Models, Animal; Doxazosin; Male; Muscle Contraction; Nitric Oxide Synthase Type II; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, alpha; Sildenafil Citrate; Urinary Bladder Neck Obstruction; Urological Agents

Noise exposure has been well characterized as an environmental stressor, and is known to have auditory and non-auditory effects. Phosphodiesterase 5 (PDE5) inhibitors affect memory and hippocampus plasticity through various signaling cascades which are regulated by cGMP. In this study, we investigated the effects of sildenafil on memory deficiency, neuroprotection and oxidative stress in mice caused by chronic noise exposure. Mice were exposed to noise for 4h every day up to 14days at 110dB SPL of noise level. Sildenafil (15mg/kg) was orally administered 30min before noise exposure for 14days. Behavioral assessments were performed using novel object recognition (NOR) test and radial arm maze (RAM) test. Higher levels of memory dysfunction and oxidative stress were observed in noise alone-induced mice compared to control group. Interestingly, sildenafil administration increased memory performance, decreased oxidative stress, and increased neuroprotection in the hippocampus region of noise alone-induced mice likely through affecting memory related pathways such as cGMP/PKG/CREB and p25/CDK5, and induction of free radical scavengers such as SOD1, SOD2, SOD3, Prdx5, and catalase in the brain of stressed mice.

Topics: Animals; Brain-Derived Neurotrophic Factor; CREB-Binding Protein; Cytokines; Disease Models, Animal; Indoles; Male; Maze Learning; Memory Disorders; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Noise; Norepinephrine; Oxidative Stress; Reactive Oxygen Species; Recognition, Psychology; Sildenafil Citrate; Stress, Psychological; Superoxide Dismutase; tau Proteins

Pre-eclampsia (PE), a hypertensive disorder of pregnancy, is detrimental to both mother and foetus. There is currently no effective treatment, but we have shown that Sildenafil Citrate (SC) improve various foetal outcomes in N

Topics: Animals; Biomarkers; Blood Pressure; Disease Models, Animal; Female; Gene Expression Regulation; Inflammation; Interferon-gamma; Neovascularization, Physiologic; NG-Nitroarginine Methyl Ester; Nitric Oxide; Pre-Eclampsia; Pregnancy; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sildenafil Citrate; Time Factors; Transforming Growth Factor beta; Uterus; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-1

The development of novel therapeutic options is imperative in patients with erectile dysfunction, especially those non-responsive to phosphodiesterase type 5 inhibitors. LDD175, a potent BKCa channel opener, has a relaxation effect on the in vitro cavernosal smooth muscle strip.. To investigate the effect of LDD175 on erectile function using in vivo animal disease model.. Male Sprague-Dawley rats were assigned to a normal control group and seven diabetic groups: diabetic control, sildenafil (1 and 5 mg/kg), LDD175 (5 and 10 mg/kg), LDD175 5 mg/kg plus sildenafil 1 mg/kg, and LDD175 10 mg/kg plus tetraethylammonium.. Intracavernosal pressure (ICP), ratio of ICP to mean arterial pressure (MAP), and the area under curve of ICP/MAP of eight groups were compared using in vivo pelvic nerve stimulation.. The ICP, ICP/MAP ratio, and area under curve of the ICP/MAP ratio of the normal control rats increased with an increase in electrical field stimulation voltage. All parameters in the diabetic control group were significantly lower than those in the normal control rats, with an electrical field stimulation ranging from 1 to 5 V (P < .05). LDD175 improved the erectile response in diabetic rats in a dose-dependent manner. The combination of sildenafil (1 mg/kg) and LDD175 (5 mg/kg) showed a significant additive effect (P < .05) on the improvement of erectile function compared with sildenafil (1 mg/kg) alone. The enhancement of erectile function by LDD175 was completely blocked by tetraethylammonium.. The results showed that the BKCa channel opener LDD175 improved erectile function in an in vivo diabetic rat model. Furthermore, combination therapy of LDD175 and sildenafil had an additive effect on the improvement of erectile function in diabetic rats. LDD175 could be a new candidate for the treatment of erectile dysfunction.

Topics: Animals; Benzofurans; Diabetes Mellitus, Experimental; Disease Models, Animal; Erectile Dysfunction; Indoles; Male; Muscle, Smooth; Penile Erection; Phosphodiesterase 5 Inhibitors; Rats; Rats, Sprague-Dawley; Sildenafil Citrate

Topics: Animals; Disease Models, Animal; Female; Gene Expression Regulation; Humans; Intracellular Signaling Peptides and Proteins; Kidney; Membrane Proteins; NG-Nitroarginine Methyl Ester; Pre-Eclampsia; Pregnancy; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sildenafil Citrate

Topics: Angiotensin II; Animals; Antihypertensive Agents; Blood Pressure; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Hypertension; Male; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Renal Artery; Renal Circulation; Sildenafil Citrate; Vasodilation; Vasodilator Agents; Vinca Alkaloids

Sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, has endothelium protective and angiogenic effects.. To test if sildenafil improves tissue perfusion and neovascularization and downregulates proinflammatory molecules following limb ischemia.. 30 ApoE-/- male mice, bred with cholesterol rich diet for 4 weeks, were anesthetized and underwent unilateral hind-limb ischemia with ligation of the left femoral artery. Mice were randomized in 2 groups: sildenafil (1 mg/Kg for 7 days intraperitoneally, i.p.) or normal saline (0.4 ml for 7 days, i.p.). Bilateral hind-limb perfusion was estimated by laser Doppler imaging after surgery on days 0, 7 and 28.. Sildenafil significantly reduced at day 28 compared with day 0 levels of soluble intracellular adhesion molecule-1(sICAM-1) [2.24(1.81-2.41) vs. 1.29(0.87-1.45) ng/ml, p=0,01], soluble E-selectin (sE-Selectin) [5.52 (3.67-6.14) vs 1.71 (1.42-2.86) ng/ml, p=0.02] and tissue plasminogen activator inhibitor- 1 (tPAI-1) [0.13(0.07-0.21) vs 0.08 (0.04-0.10) ng/ml, p=0.01] while normal saline had no effect on the levels of sICAM-1, sE-Selectin and tPAI-1. Treatment with sildenafil was associated with increased perfusion in the ischemic limb compared with controls.. Sildenafil exerts significant beneficial effects on tissue perfusion and inflammatory status after limb ischemia, a finding implying neovascularization and potential vascular protective properties of sildenafil.

Topics: Angiogenesis Inducing Agents; Animals; Anti-Inflammatory Agents; Atherosclerosis; Blood Flow Velocity; Disease Models, Animal; E-Selectin; Hindlimb; Inflammation; Inflammation Mediators; Intercellular Adhesion Molecule-1; Ischemia; Male; Mice, Knockout, ApoE; Muscle, Skeletal; Neovascularization, Physiologic; Plasminogen Activator Inhibitor 1; Regional Blood Flow; Sildenafil Citrate; Time Factors

Abnormal vision has been reported by 3% of patients treated with sildenafil citrate (Viagra). Although many men use Viagra for an extended period for treatment of erectile dysfunction, the implications of the long term-daily use of it on the retina and optic nerve are unclear.. To investigate the effect of chronic daily use of sildenafil citrate in a dose equivalent to men preferred therapeutic dose on the histology of the retina and optic nerve of adult male rat.. Eighteen adult male Wistar rats were equally divided into three groups. Group I: control. Group II: treated with sildenafil citrate orally (10mg/kg/day) for 8 weeks. Group III (withdrawal): treated as group II and then left for 4 weeks without treatment. Specimens from the retina and optic nerve were processed for light and electron microscopy.. In sildenafil citrate treated group, the retina and optic nerve revealed vacuolations and congested blood capillaries with apoptotic endothelial and pericytic cells, and thickened basal lamina. Caspase-3 (apoptotic marker) and CD31 (endothelial marker) expression increased. Glial cells revealed morphological changes: Müller cells lost their processes, activated microglia, astrocytic clasmatodendrosis, degenerated oligodendrocytes surrounded by disintegrated myelin sheathes of the optic nerve fibers. The retina and optic nerve of the withdrawal group revealed less vacuolations and congestion, and partial recovery of the glial cells.. Chronic treatment with sildenafil citrate (Viagra) caused toxic effect on the structure of the retina and optic nerve of the rat. Partial recovery was observed after drug withdrawal.

Topics: Animals; Disease Models, Animal; Ependymoglial Cells; Erectile Dysfunction; Humans; Male; Neuroglia; Optic Nerve; Rats; Retina; Sildenafil Citrate; Vision Disorders

The commonly utilized phosphodiesterase type 5 inhibitors do not lead to satisfactory penile erection after radical prostatectomy mainly because of insufficient nitric oxide drive from the damaged cavernous nerves. The aim of this study was to assess the efficacy and mechanisms of icariin in combination with daily sildenafil on neurogenic erectile dysfunction and penile atrophy in a rat model of bilateral cavernous nerves injury. Sixty male Sprague-Dawley rats injected with 5-ethynyl-2-deoxyuridine (50 mg/kg) at postnatal day 1 for the purpose of tracking endogenous stem cells in penis. Forty-eight rats of bilateral cavernous nerves injury were randomized equally into gavage feeding of vehicle, sildenafil (10 mg/kg), icariin (1.5 mg/kg) and sildenafil + icariin, respectively. Twelve sham-operated rats served as control. The intracavernous pressure and mean arterial pressure was measured and mid-penile cross sections were histologically examined 5 weeks after surgery. Western blotting of cavernous tissue protein was also performed. Animals treated with sildenafil + icariin had significantly higher mean intracavernous pressure/mean arterial pressure ratio relative to other rats with bilateral cavernous nerves injury (p < 0.05). The circumference and mean cross-sectional area of the paired corpus cavernosum were effectively preserved in the sildenafil + icariin. Treatment with sildenafil + icariin significantly increased the cavernous cyclic guanosine monophosphate concentration compared with the icariin group (p < 0.05). In addition, the numbers of neuronal nitric oxide synthase-positive nerves and 5-ethynyl-2-deoxyuridine-positive cells co-expressing S100 in the icariin-treated groups were greater compared with the bilateral cavernous nerves injury control group (p < 0.05). These data suggest that the combined use of icariin and daily sildenafil holds promise as a potential therapy for neurogenic erectile dysfunction in the future. The underlying mechanisms appears to involve two aspects: (i) icariin promotes differentiation of endogenous stem cells to Schwann cells, which help to repair the damaged neural pathway for erection; (ii) on this basis, sildenafil can further improve penile engorgement through the cyclic guanosine monophosphate-dependent smooth muscle relaxation.

Topics: Animals; Atrophy; Blotting, Western; Disease Models, Animal; Erectile Dysfunction; Flavonoids; Fluorescent Antibody Technique; Male; Penile Erection; Penis; Prostatectomy; Rats; Rats, Sprague-Dawley; Sildenafil Citrate

Patients with liver disease may develop hepatic encephalopathy (HE), with cognitive impairment and motor in-coordination. Rats with HE due to portacaval shunts (PCS) show motor in-coordination. We hypothesized that in PCS rats: (i) Motor in-coordination would be due to enhanced GABAergic tone in cerebellum; (ii) increased GABAergic tone would be due to neuroinflammation; (iii) increasing cGMP would reduce neuroinflammation and GABAergic tone and restore motor coordination. To assess these hypotheses, we assessed if (i) treatment with sildenafil reduces neuroinflammation; (ii) reduced neuroinflammation is associated with reduced GABAergic tone and restored motor coordination.. Rats were treated with sildenafil to increase cGMP. Microglia and astrocytes activation were analyzed by immunohistochemistry, extracellular GABA by microdialysis, and motor coordination in the beam walking.. PCS rats show neuroinflammation in cerebellum, with microglia and astrocytes activation, increased IL-1b and TNF-a and reduced YM-1 and IL-4. Membrane expression of the GABA transporter GAT1 is reduced, while GAT3 is increased. Extracellular GABA and motor in-coordination are increased. Sildenafil treatment eliminates neuroinflammation, microglia and astrocytes activation; changes in membrane expression of GABA transporters; and restores motor coordination.. This study supports an interplay between cGMP-neuroinflammation and GABAergic neurotransmission in impairing motor coordination in PCS rats.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Astrocytes; Cerebellum; Disease Models, Animal; GABA Plasma Membrane Transport Proteins; gamma-Aminobutyric Acid; Hepatic Encephalopathy; Interleukin-1beta; Interleukin-4; Male; Microglia; Motor Skills; Neuroimmunomodulation; Rats, Wistar; Sildenafil Citrate; Tumor Necrosis Factor-alpha

Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are frequent problems in older men worldwide. We evaluated the effect of short- and long-term sildenafil treatment on erectile function in rats with surgically induced partial bladder outlet obstruction (PBOO).. A total of 60 male Sprague-Dawley rats were randomized in five groups: (1) control (sham-operated); (2) PBOO for 3 weeks; (3) PBOO for 6 weeks; (4) sildenafil (1.5 mg/rat/day) treated PBOO for 3 weeks; and (5) sildenafil treated PBOO for 6 weeks. We assessed erectile function by measuring intracavernous pressures (ICP), mean arterial pressure (MAP) and total ICP after cavernous nerve stimulation. Corpus cavernous smooth muscle (CCSM) strips were isolated and evaluated for relaxation responses using organ-bath preparation. Neuronal nitric oxide synthase (nNOS) expression was determined immunohistochemically.. Experimental PBOO at 3 and 6 weeks showed decreased erectile response based on ICP/MAP ratio, total ICP and decreased expression of nNOS, which returned to normal after prolonged daily treatment with sildenafil. CCSM strips from PBOO rats displayed reduced relaxation responses to both electrical field stimulation (EFS) and acetylcholine (ACh) as well as nNOS enzyme intensity when compared to untreated PBOO group, which was reversed by treatment with sildenafil for 6 weeks.. Daily sildenafil treatment prevents development of ED in PBOO rats in a time dependent manner. Further studies are needed to explore the effectiveness of sildenafil in patients with BPH/LUTS in association with ED.

Topics: Animals; Disease Models, Animal; Erectile Dysfunction; Male; Muscle Relaxation; Muscle, Smooth; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Time Factors; Treatment Outcome; Urinary Bladder Neck Obstruction; Urological Agents

Preeclampsia, a hypertensive disorder of pregnancy, is detrimental to both mother and fetus. There is currently no effective treatment, but sildenafil, a phosphodiesterase-5 inhibitor, has been proposed as a potential therapy to reduce blood pressure and improve uteroplacental perfusion in preeclamptic patients. We hypothesized that sildenafil would improve the maternal syndrome and fetal outcomes in the Dahl S rat model of superimposed preeclampsia. Dahl S rats were mated, and half received sildenafil (50 mg/kg per day, via food) from day 10 through day 20 of pregnancy. The untreated Dahl S rats had a significant rise in blood pressure and a 2-fold increase in urinary protein excretion from baseline to late pregnancy; however, sildenafil-treated Dahl S rats exhibited ≈40 mm Hg drops in blood pressure with no rise in protein excretion. Sildenafil also increased creatinine clearance and reduced nephrinuria and glomerulomegaly. Sildenafil treatment reduced the uterine artery resistance index during late pregnancy in the Dahl S rat and improved fetal outcomes (survival, weight, and litter size). In addition, 19% of all pups were resorbed in untreated rats, with no incidence of resorptions observed in the treated group. Furthermore, tumor necrosis factor-α, endothelin-1, and oxidative stress, which are characteristically increased in women with preeclampsia and in experimental models of the disease, were reduced in treated rats. These data suggest that sildenafil improves the maternal syndrome of preeclampsia and blood flow to the fetoplacental unit, providing preclinical evidence to support the hypothesis that phosphodiesterase type 5 inhibition may be an important therapeutic target for the treatment of preeclampsia.

Topics: Animals; Blood Pressure; Disease Models, Animal; Female; Fetal Development; Pre-Eclampsia; Pregnancy; Pregnancy, Animal; Rats; Rats, Inbred Dahl; Sildenafil Citrate; Syndrome; Vascular Resistance; Vasodilator Agents

An established macaque model to assess HIV interventions against penile transmission is currently not available. Physiological changes during penile erections may affect susceptibility to infection and drug pharmacokinetics (PK). Here, we identify methods to establish erections in macaques to evaluate penile transmission, PK, and efficacy under physiologic conditions.. Penile rigidity and length were evaluated in eight rhesus macaques following rectal electrostimulation (RES), vibratory stimulation (VS), or pharmacological treatment with Sildenafil Citrate (Viagra) or Alprostadil.. Rectal electrostimulation treatment increased penile rigidity (>82%) and length (2.5 ± 0.58 cm), albeit the response was transient. In contrast, VS alone or coupled with Viagra or Alprostadil failed to elicit an erection response.. Rectal electrostimulation treatment elicits transient but consistent penile erections in macaques. High rigidity following RES treatment demonstrates increased blood flow and may provide a functional model for penile PK evaluations and possibly simian immunodeficiency virus (SIV) transmission under erect conditions.

Topics: Alprostadil; Animals; Anti-Retroviral Agents; Disease Models, Animal; Electric Stimulation; Macaca mulatta; Male; Penile Diseases; Penile Erection; Penis; Sildenafil Citrate; Simian Acquired Immunodeficiency Syndrome; Vasodilator Agents; Vibration

Wuling mycelia powder is the dry powder of rare a fungi Xyla ria sp., Carbon species, with a long history of medicinal use in Chinese medicine. Recently it has shown a powerful antidepressant activity in clinic.. The present study explores the antidepressant activity of Wuling mycelia powder in chronic unpredictable mild stress (CUMS) rats and its possible involvement of l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signaling pathway.. Experiments were performed in the rat CUMS model. CUMS rats were treated with Wuling mycelia powder (0.5, 1.0 or 2.0 g/kg, i.g.) to test behavioral changes including the sucrose preference, the crossing number and food consumption. Further, L-arginine (substrate for nitric oxide) (750 mg/kg), 7-nitroindazole (a specific neuronal nitric oxide synthase inhibitor) (25 mg/kg), sildenafil (phosphodiesterase 5 inhibitor) (5 mg/kg) and methylene blue (direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase) (10 mg/kg) were treated for 60 min before each test to detect the possible mechanism of antidepressant-like effect of Wuling mycelia powder.. After 4 weeks of administration, both 1.0 or 2.0 g/kg Wuling mycelia powder suppressed the behavioral changes including the sucrose preference [F(3, 31)=50.87, p<0.001], the crossing number [F(3, 31)=68.98, p<0.05], and food consumption [F(3, 31)=19.04, p<0.05] in the CUMS rats. The antidepressant-like effect of Wuling mycelia powder was prevented by pretreatment with l-arginine and sildenafil. Pretreatment of rats with 7-nitroindazole and methylene blue potentiated the effect of Wulin mycelia powder.. Our findings demonstrate that Wuling mycelia powder has an antidepressant-like effect in the CUMS rats, and possible involvement of L-arginine-nitric oxide-cyclic GMP signaling pathway in its antidepressant effect.

Topics: Animals; Antidepressive Agents; Arginine; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Feeding Behavior; Food Preferences; Hippocampus; Indazoles; Male; Methylene Blue; Mycelium; Nitric Oxide; Powders; Rats, Sprague-Dawley; Signal Transduction; Sildenafil Citrate; Stress, Psychological; Sucrose

We aimed to evaluate the effect of sildenafil on the intestinal adaptation in short bowel syndrome (SBS).. Forty-eight male Wistar-albino rats (weight, 231-390 g) were randomly divided into four groups with 12 rats in each. Group TA had only ileal transection+anastomosis, Group TA+S was given sildenafil after ileal transection+anastomosis, Group RA had a resection of 75% of the small bowel+anastomosis, Group RA+S was given sildenafil after small bowel resection+anastomosis. Sildenafil was injected subcutaneously at 60 mg/kg/day dose throughout 3-21 days postoperatively. Bowel and mucosal weights, villus height, crypt depth, DNA and protein concentrations were determined.. Jejunal bowel weight was lower in TA and TA+S groups than RA and RA+S groups (p < 0.05). RA+S group had higher ileal and jejunal mucosal weights than RA and TA+S groups (p < 0.05). Villus height was highest in RA+S group both in ileum and jejunum (466.1 ± 38.6 μm and 648.1 ± 65.7 μm, respectively). Jejunal crypt depth was highest in RA+S group (255.1 ± 21.9 μm) compared to other groups (p < 0.05). There was no significant difference in ileal and jejunal protein concentration between TA and TA+S groups and in ileal protein concentration between RA ve RA+S groups (p > 0.05). Ileal DNA concentration was higher in TA+S group, and jejunal DNA concentration was higher in RA and RA+S groups than TA and TA+S groups (p < 0.05).. Sildenafil has a positive effect on intestinal adaptation parameters, particularly in jejunum in a rat SBS model. Thus, its role in the treatment of SBS should be further investigated with clinical studies.

Topics: Adaptation, Physiological; Animals; Apoptosis; Disease Models, Animal; DNA; Ileum; Intestine, Small; Jejunum; Male; Rats; Rats, Sprague-Dawley; Rats, Wistar; Short Bowel Syndrome; Sildenafil Citrate

Lipopolysaccharide (LPS) injections during pregnancy are well established as models for pregnancy complications, including fetal growth restriction (FGR), thrombophilia, preterm labor and abortion. Indeed, inflammation, as induced by LPS injection has been described as a pivotal factor in cases of miscarriage related to placental tissue damage. The phosphodiesterase-5 inhibitor sildenafil (Viagra®) is currently used to treat FGR cases in women, while low-molecular weight heparin (Fragmin®) is a standard treatment for recurrent miscarriage (RM). However, the pathways and cellular dynamics involved in RM are not completely understood. The aim of this study was to evaluate the protective effect of sildenafil and dalteparin in a mouse model of LPS-induced abortion. Histopathology, ultrastructural analysis and immunofluorescence for P-selectin were studied in two different placental cell types: trophoblast cells and labyrinth endothelial cells. Treatment with sildenafil either alone or in combination with heparin showed the best response against LPS-induced injury during pregnancy. In conclusion, our results support the use of these drugs as future therapeutic agents that may protect the placenta against inflammatory injury in RM events. Analyses of the ultrastructure and placental immunophysiology are important to understand the mechanism underlying RM. These findings may spark future studies and aid in the development of new therapies in cases of RM.

Topics: Abortion, Habitual; Animals; Anticoagulants; Dalteparin; Disease Models, Animal; Female; Lipopolysaccharides; Male; Mice; Phosphodiesterase 5 Inhibitors; Placenta; Pregnancy; Sildenafil Citrate; Trophoblasts

The management of congenital diaphragmatic hernia (DH) would benefit from an antenatal medical therapy, which addresses both lung hypoplasia and persistent pulmonary hypertension. We aimed at evaluating the pulmonary effects of sildenafil in the fetal rabbit model for DH.. We performed a dose-finding study to achieve therapeutic fetal plasmatic concentrations without toxicity following maternal sildenafil administration. Subsequently, DH fetuses were randomly exposed to transplacental placebo or sildenafil 10 mg/kg/day from gestational day 24 until examination at term (day 30). Efficacy measures were ipsilateral pulmonary vascular and airway morphometry, micro-CT-based branching analysis, Doppler flow in the main pulmonary artery and postnatal lung mechanics.. Fetal sildenafil plasmatic concentration was above the minimal therapeutic level for at least 22 h/day without maternal and fetal side effects. The placebo-exposed DH fetuses had increased wall thickness in peripheral pulmonary vessels and significantly less fifth-order vessels compared with controls (CTR). Sildenafil-exposed DH fetuses, instead, had a medial and adventitial thickness in peripheral pulmonary vessels in the normal range and normal vascular branching. Fetal pulmonary artery Doppler showed a reduction of pulmonary vascular resistances both in DH and in CTR fetuses treated by sildenafil compared with the placebo-treated ones. Sildenafil also reversed the mean terminal bronchiolar density to normal and improved lung mechanics, yet without measurable impact on lung-to-bodyweight ratio.. In the rabbit model for DH, antenatal sildenafil rescues vascular branching and architecture, reduces pulmonary vascular resistances and also improves airway morphometry and respiratory mechanics.

Topics: Animals; Disease Models, Animal; Female; Hernias, Diaphragmatic, Congenital; Lung; Pregnancy; Rabbits; Random Allocation; Respiratory Mechanics; Sildenafil Citrate; Ultrasonography, Doppler; Vascular Resistance; X-Ray Microtomography

Sildenafil improves the 6-min walking distance in patients with idiopathic pulmonary fibrosis (IPF) and right-sided ventricular systolic dysfunction.We analysed the previously unexplored role of sildenafil on vasoconstriction and remodelling of pulmonary arteries from patients with IPF and pulmonary hypertension (PH) ex vivo Pulmonary arteries from 18 donors without lung disease, nine IPF, eight PH+IPF and four PH patients were isolated to measure vasodilator and anti-contractile effects of sildenafil in isometric organ bath. Ventilation/perfusion was explored in an animal model of bleomycin lung fibrosis.Sildenafil relaxed serotonin (5-HT) pre-contracted pulmonary arteries in healthy donors and IPF patients and, to a lesser extent, in PH+IPF and PH. Sildenafil inhibited 5-HT dose-response contraction curve mainly in PH+IPF and PH, but not in healthy donors. Sildenafil did not impair the ventilation/perfusion mismatching induced by bleomycin. Pulmonary arteries from PH+IPF patients showed a marked expression of phosphodiesterse-5 and extracellular matrix components. Sildenafil inhibited pulmonary artery endothelial and smooth muscle cell to mesenchymal transition by inhibition of extracellular regulated kinases 1 and 2 (ERK1/2) and SMAD3 phosphorylation.These results suggest an absence of direct relaxant effect and a prominent anti-contractile and anti-remodelling role of sildenafil in PH+IPF pulmonary arteries that could explain the beneficial effects of sildenafil in IPF with PH phenotype.

Topics: Animals; Bleomycin; Disease Models, Animal; Endothelium, Vascular; Extracellular Matrix; Fibroblasts; Humans; Hypertension, Pulmonary; Lung; Male; Myocytes, Smooth Muscle; Myofibroblasts; Pulmonary Artery; Pulmonary Disease, Chronic Obstructive; Pulmonary Fibrosis; Rats; Rats, Wistar; Serotonin; Signal Transduction; Sildenafil Citrate; Transforming Growth Factor beta1; Vasoconstriction; Vasodilator Agents

No previous studies have examined the effect of sildenafil on fracture healing. This study was designed to investigate the effect of sildenafil on the fracture healing process.. Thirty-six female Sprague-Dawley rats (3-month-old) were used in this study. Animals were randomly divided into 2 groups based on treatment duration (1 week versus 4 weeks) and each group was then divided further into 2 subgroups, control (C) and study (S) groups. Group C (C1, C2) was treated daily with saline solution and group S (S1, S2) was treated daily with 10 mg/kg of sildenafil. Histologic, histomorphometric, radiological, and immunohistochemical analyses were performed at 1 week and 4 weeks after a fracture.. The sildenafil group showed a significant increase in fracture healing scores (P = 0.00). The authors observed a transition from fibrous callus to cartilage tissue and immature bone tissue in group S1; and an increased transition of cartilage tissue to completely immature bone tissue in group S2, both of which were administered sildenafil. The strong expression of bone morphogenetic protein 2 and col-1 was observed in the fibrous matrix and osteoblasts within areas of new bone formation, especially in group S1. This group also showed an increase in bone density measurements at 1 week that was statistically significant (P = 0.03).. Sildenafil accelerates fracture healing and can be used as a supporting factor in the improvement of fracture healing under various conditions.

Topics: Animals; Bone Density; Disease Models, Animal; Female; Fracture Healing; Mandibular Fractures; Phosphodiesterase 5 Inhibitors; Radiography; Rats; Rats, Sprague-Dawley; Sildenafil Citrate

Perinatal ischemic stroke is the most frequent form of cerebral infarction in neonates; however, evidence-based treatments are currently lacking. We have previously demonstrated a beneficial effect of sildenafil citrate, a PDE-5 inhibitor, on stroke lesion size in neonatal rat pups. The present study investigated the effects of sildenafil in a neonatal mouse stroke model on (1) hemodynamic changes and (2) regulation of astrocyte/microglia-mediated neuroinflammation.. Ischemia was induced in C57Bl/6 mice on postnatal (P) day 9 by permanent middle cerebral artery occlusion (pMCAo), and followed by either PBS or sildenafil intraperitoneal (i.p.) injections. Blood flow (BF) velocities were measured by ultrasound imaging with sequential Doppler recordings and laser speckle contrast imaging. Animals were euthanized, and brain tissues were obtained at 72 h or 8 days after pMCAo. Expression of M1- and M2-like microglia/macrophage markers were analyzed.. Although sildenafil (10 mg/kg) treatment potently increased cGMP concentrations, it did not influence early collateral recruitment nor did it reduce mean infarct volumes 72 h after pMCAo. Nevertheless, it provided a significant dose-dependent reduction of mean lesion extent 8 days after pMCAo. Suggesting a mechanism involving modulation of the inflammatory response, sildenafil significantly decreased microglial density at 72 h and 8 days after pMCAo. Gene expression profiles indicated that sildenafil treatment also modulates M1- (ptgs2, CD32 and CD86) and M2-like (CD206, Arg-1 and Lgals3) microglia/macrophages in the late phase after pMCAo. Accordingly, the number of COX-2(+) microglia/macrophages significantly increased in the penumbra at 72 h after pMCAo but was significantly decreased 8 days after ischemia in sildenafil-treated animals.. Our findings argue that anti-inflammatory effects of sildenafil may provide protection against lesion extension in the late phase after pMCAo in neonatal mice. We propose that sildenafil treatment could represent a potential strategy for neonatal ischemic stroke treatment/recovery.

Topics: Animals; Animals, Newborn; Brain Ischemia; Disease Models, Animal; Immunohistochemistry; Mice; Mice, Inbred C57BL; Microglia; Phosphodiesterase Inhibitors; Polymerase Chain Reaction; Sildenafil Citrate

Sildenafil is a selective and potent inhibitor of cyclic guanosine monophosphate specific phosphodiesterase-5 and has anti-inflammatory effects. The aim of the study was to evaluate the effects of sildenafil on smoke-induced lung inflammation.. Twenty-nine Wistar-Albino rats were enrolled into 3 groups as control, smoker and sildenafil groups. Smoker and sildenafil groups were exposed to cigarette smoke for 2 hours per day for 8 weeks. Sildenafil 10 mg/kg/day was administered to the sildenafil group by nasogastric lavage after smoke exposure. The degree of lung inflammation was scored histopathologically for each group.. The inflammation score was 7.25±0.93 in the control group, 8.18±1.21 in the smoker group and 7.08±1.66 in the sildenafil group. There was a non-significant decrease of inflammation score in sildenafil group with respect to control or smoker groups. While there was no significant difference of oedema, hyperemia, hemorrhage and mononuclear cell infiltration scores among the groups, it was found that the thickness of interalveolar septum and alveolar distortion was decreased in sildenafil group. However this decrease was not statistically significant.. This study suggests that sildenafil might reduce smoke-induced inflammation in rat lungs. Future studies are needed in order to investigate the clinical effectiveness of this finding in smoking related lung diseases.

Topics: Animals; Anti-Inflammatory Agents; Cytoprotection; Disease Models, Animal; Inhalation Exposure; Male; Phosphodiesterase 5 Inhibitors; Pneumonia; Pulmonary Alveoli; Rats, Wistar; Sildenafil Citrate; Smoke; Smoking

Presence of pulmonary hypertension (PH) and right ventricular dysfunction worsens prognosis in patients with chronic heart failure (CHF). Preclinical and clinical studies suggest a role for the impaired nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) signaling pathway in both PH and CHF. Hence, we examined the effects of the NO-sGC-cGMP pathway modulation by the PDE5 inhibitor sildenafil or sGC stimulator riociguat on pulmonary hemodynamics and heart function in a murine model of secondary PH induced by transverse aortic constriction.. C57Bl/6N mice were subjected to transverse aortic constriction (TAC) for 6weeks to induce left heart failure and secondary PH and were subsequently treated with either sildenafil (100mg/kg/day) or riociguat (10mg/kg/day) or placebo for 2weeks.. Six weeks after surgery, TAC induced significant left ventricular hypertrophy and dysfunction associated with development of PH. Treatment with riociguat and sildenafil neither reduced left ventricular hypertrophy nor improved its function. However, both sildenafil and riociguat ameliorated PH, reduced pulmonary vascular remodeling and improved right ventricular function.. Thus, modulation of the NO-sGC-cGMP pathway by the PDE5 inhibitor sildenafil or sGC stimulator riociguat exerts direct beneficial effects on pulmonary hemodynamics and right ventricular function in the experimental model of secondary PH due to left heart disease and these drugs may offer a new therapeutic option for therapy of this condition.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Heart Function Tests; Humans; Hypertension, Pulmonary; Hypertrophy, Left Ventricular; Male; Mice; Mice, Inbred C57BL; Nitric Oxide; Pyrazoles; Pyrimidines; Signal Transduction; Sildenafil Citrate; Soluble Guanylyl Cyclase; Treatment Outcome

Sildenafil is a phosphodiesterase type 5 inhibitor mainly used for male erectile dysfunction. One of rare yet serious adverse effects of Sildenafil is its potential to decrease seizure threshold. Ample evidence suggests that Sildenafil exerts central effects through induction of Oxytocin (OT) secretion and CREB phosphorylation. The aim of the present study is to evaluate potential roles of OT and CREB in the proconvulsant effects of Sildenafil. The Pentylenetetrazole-induced seizure was used as a standard convulsion model in this study. OT release and pCREB expression were evaluated in the hippocampus of mice using ELISA and western blot assays, respectively. Our results showed that Sildenafil at the dose of 10mgkg(-1) or higher, significantly decreased seizure threshold. Pretreatment with a non-effective dose of OT, potentiated while OT receptor antagonist, Atosiban, reversed fully the proconvulsant effects of Sildenafil (5mgkg(-1)). At biochemical inspection, Sildenafil markedly increased CREB which was attenuated by coadministration of Atosiban. The present study shows for the first time that OT release and the subsequent CREB phosphorylation are involved in the proconvulsant effects of acute Sildenafil treatment in an experimental model of seizure.

Topics: Animals; CREB-Binding Protein; Disease Models, Animal; Dose-Response Relationship, Drug; Hippocampus; Hormone Antagonists; Male; Mice; Oxytocin; Pentylenetetrazole; Phosphodiesterase 5 Inhibitors; Phosphorylation; Receptors, Oxytocin; Seizures; Signal Transduction; Sildenafil Citrate; Time Factors; Vasotocin

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease in the world. Several signaling pathways are involved in the pathogenesis of DN including elevation in level of angiotensin II, formation of advanced glycation end products (AGE), activation of protein kinase c (PKC), and lipid accumulation. These pathways activate one another mutually leading to oxidative stress, increasing expression of transforming growth factor beta-1(TGF-β 1) and release of interleukins and adhesion molecules, so the aim of this study is to interrupt more than pathogenic pathway to ameliorate the progression of DN. In the present study, white male rats (N=48) were divided into six groups (8 rats each), the first two groups served as normal control and a control vehicle group while the remaining four groups were rendered diabetic by a single intraperitoneal injection of Streptozotocin (STZ) and being left for 4 weeks to develop DN. Thereafter, the rats were divided into DN group, DN group receiving Telmisartan or Sildenafil or Telmisartan Sildenafil combination. After the specified treatment period, urine samples were collected (using metabolic cages) to measure proteinuria, animals were then euthanized, blood and tissue samples were collected for measurement of Blood glucose,BUN, S.Cr, LDL, NO, TGF-β1, IL-1β, AGEPs, and SOD. The combination therapy showed significant decrease in BUN, S.Cr,LDL, TGF-β1, IL-1β, Proteinuria and AGEPs and significant increase in SOD and NO. The findings showed that combination therapy was able to ameliorate DN and that the effects were superior to the single drugs alone.

Topics: Animals; Benzimidazoles; Benzoates; Blood Glucose; Blood Urea Nitrogen; Body Weight; Cholesterol, LDL; Creatinine; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Disease Models, Animal; Disease Progression; Drug Therapy, Combination; Glycation End Products, Advanced; Interleukin-1beta; Kidney; Nitric Oxide; Proteinuria; Rats; Sildenafil Citrate; Streptozocin; Superoxide Dismutase; Telmisartan; Transforming Growth Factor beta1

Preeclampsia is a hypertensive disorder of pregnancy in which patients develop profound sensitivity to vasopressors, such as angiotensin II, and is associated with substantial morbidity for the mother and fetus. Enhanced vasoconstrictor sensitivity and elevations in soluble fms-like tyrosine kinase 1 (sFLT1), a circulating antiangiogenic protein, precede clinical signs and symptoms of preeclampsia. Here, we report that overexpression of sFlt1 in pregnant mice induced angiotensin II sensitivity and hypertension by impairing endothelial nitric oxide synthase (eNOS) phosphorylation and promoting oxidative stress in the vasculature. Administration of the NOS inhibitor l-NAME to pregnant mice recapitulated the angiotensin sensitivity and oxidative stress observed with sFlt1 overexpression. Sildenafil, an FDA-approved phosphodiesterase 5 inhibitor that enhances NO signaling, reversed sFlt1-induced hypertension and angiotensin II sensitivity in the preeclampsia mouse model. Sildenafil treatment also improved uterine blood flow, decreased uterine vascular resistance, and improved fetal weights in comparison with untreated sFlt1-expressing mice. Finally, sFLT1 protein expression inversely correlated with reductions in eNOS phosphorylation in placental tissue of human preeclampsia patients. These data support the concept that endothelial dysfunction due to high circulating sFLT1 may be the primary event leading to enhanced vasoconstrictor sensitivity that is characteristic of preeclampsia and suggest that targeting sFLT1-induced pathways may be an avenue for treating preeclampsia and improving fetal outcomes.

Topics: Angiotensin II; Angiotensins; Animals; Blood Pressure; Disease Models, Animal; Female; Humans; Male; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type III; Oxidative Stress; Phosphorylation; Placenta; Pre-Eclampsia; Pregnancy; Pregnancy, Animal; Signal Transduction; Sildenafil Citrate; Treatment Outcome; Vascular Endothelial Growth Factor Receptor-1

To evaluate the effect of bevacizumab and sildenafil on stroke parameters in a mouse model, middle cerebral artery occlusion was induced in male C57Bl/6 mice using an intra-arterial filament method. The filament was removed after 60 minutes, and the mice were immediately given a single intraperitoneal injection of saline, bevacizumab, or sildenafil. An additional group of mice (n = 7) received bevacizumab 6 h after MCAO induction. The mice were euthanized 24 hours later and evaluated for infarct area and brain edema using triphenyltetrazolium chloride staining and ImageJ. In the saline-treated mice (n = 16), total stroke volume was 19.20 ± 6.38 mm(3), mean penumbra area was 4.5 ± 2.03 mm(3), and hemispheric asymmetry was 106.5%. Corresponding values in the bevacizumab group (n = 19) were 17.79 ± 5.80 mm(3), 7.3 ± 3.5 mm(3), and 108.6%; in the delayed (6 h) bevacizumab injected mice (n = 7) they were 9.80 ± 8.00 mm(3), 2.4 ± 2.0 mm(3), and 98.2%; and in the sildenafil group (n = 16) they were 18.42 ± 5.41 mm(3), 5.7 ± 2.02 mm(3), and 109.9%. The bevacizumab group had a significantly larger mean penumbra area when given immediately and smaller total stroke area in both groups than the saline- (p = 0.03) and sildenafil-treated (p = 0.003) groups. Only delayed bevacizumab group had reduced edema. Bevacizumab, injected immediately or delayed after injury, exerts a neuroprotective/salvage effect, whereas immediate treatment with sildenafil does not. Inflammation may play a role in the neuroprotective effect.

Topics: Angiogenesis Inhibitors; Animals; Bevacizumab; Disease Models, Animal; Dose-Response Relationship, Drug; Male; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Sildenafil Citrate; Stroke; Treatment Outcome; Vasodilator Agents

Cardiovascular dysfunction at birth may underlie poor outcomes after fetal growth restriction (FGR) in neonates. We compared the cardiovascular transition between FGR and appropriately grown (AG) preterm lambs and examined possible mechanisms underlying any cardiovascular dysfunction in FGR lambs.. FGR was induced in ewes bearing twins at 0.7 gestation; the twin was used as an internal control (AG). At 0.8 gestation, lambs were delivered and either euthanized with their arteries isolated for in vitro wire myography, or ventilated for 2 h. At 60 min, inhaled nitric oxide (iNO) was administered in a subgroup for 30 min. Molecular assessment of the nitric oxide (NO) pathway within lung tissue was conducted.. FGR lambs had lower left ventricular output and cerebral blood flow (CBF) and higher systemic vascular resistance compared with AG lambs. INO administration to FGR lambs rapidly improved cardiovascular and systemic hemodynamics but resulted in decreased CBF in AG lambs. Isolated arteries from FGR lambs showed impaired sensitivity to NO donors, but enhanced vasodilation to Sildenafil and Sodium nitroprusside, and altered expression of components of the NO pathway.. Cardiovascular dysfunction at birth may underlie the increased morbidity and mortality observed in preterm FGR newborns. Impaired NO signaling likely underlies the abnormal vascular reactivity.

Topics: Administration, Inhalation; Animals; Animals, Newborn; Cerebrovascular Circulation; Disease Models, Animal; Echocardiography, Doppler; Female; Fetal Growth Retardation; Hemodynamics; Litter Size; Lung; Nitric Oxide; Nitric Oxide Synthase Type III; Nitroprusside; Oxygen; Sheep; Sheep, Domestic; Sildenafil Citrate; Time Factors; Vascular Resistance

Intrauterine growth restriction (IUGR) causes short- and long-term morbidity. Reduced placental perfusion is an important pathogenic component of IUGR; substances that enhance vasodilation in the uterine circulation, such as sildenafil citrate (sildenafil), may improve placental blood flow and fetal growth. This study aimed to examine the effects of sildenafil in the growth-restricted ovine fetus. Ewes carrying singleton pregnancies underwent insertion of vascular catheters, and then, they were randomized to receive uterine artery embolization (IUGR) or to a control group. Ewes in the IUGR group received a daily infusion of sildenafil (IUGR+SC; n=10) or vehicle (IUGR+V; n=8) for 21 days. The control group received no treatment (n=9). Umbilical artery blood flow was measured using Doppler ultrasound and the resistive index (RI) calculated. Fetal weight, biometry, and placental weight were obtained at postmortem after treatment completion. Umbilical artery RI in IUGR+V fell less than in controls; the RI of IUGR+SC was intermediate to that of the other 2 groups (mean±SEM for control versus IUGR+V versus IUGR+SC: ∆RI, 0.09±0.03 versus -0.01±0.02 versus 0.03±0.02; F(2, 22)=4.21; P=0.03). Compared with controls, lamb and placental weights were reduced in IUGR+V but not in IUGR+SC (control versus IUGR+V versus IUGR+SC: fetal weight, 4381±247 versus 3447±235 versus 3687±129 g; F(2, 24)=5.49; P=0.01 and placental weight: 559.7±35.0 versus 376.2±32.5 versus 475.2±42.5 g; F(2, 24)=4.64; P=0.01). Sildenafil may be a useful adjunct in the management of IUGR. An increase in placental weight and fall in fetal-placental resistance suggests that changes to growth are at least partly mediated by changes to placental growth rather than alterations in placental efficiency.

Topics: Animals; Blood Gas Analysis; Disease Models, Animal; Female; Fetal Development; Fetal Growth Retardation; Placental Circulation; Placentation; Pregnancy; Pregnancy, Animal; Random Allocation; Reference Values; Regional Blood Flow; Sheep; Sildenafil Citrate; Uterine Artery; Vascular Resistance

The purpose of this study was to investigate the effects of sildenafil on retinal injury following neonatal hypoxia-ischemia (HI) at term-equivalent age in rat pups.. Hypoxia-ischemia was induced in male Long-Evans rat pups at postnatal day 10 (P10) by a left common carotid ligation followed by a 2-hour exposure to 8% oxygen. Sham-operated rats served as the control group. Both groups were administered vehicle or 2, 10, or 50 mg/kg sildenafil, twice daily for 7 consecutive days. Retinal function was assessed by flash electroretinograms (ERGs) at P29, and retinal structure was assessed by retinal histology at P30.. Hypoxia-ischemia caused significant functional (i.e., attenuation of the ERG a-wave and b-wave amplitudes and photopic negative response) and structural (i.e., thinning of the total retina, especially the inner retinal layers) retinal damage in the left eyes (i.e., ipsilateral to the carotid ligation). Treatment with the different doses of sildenafil led to a dose-dependent increase in the amplitudes of the ERG a- and b-waves and of the photopic negative response in HI animals, with higher doses associated with greater effect sizes. Similarly, a dose response was observed in terms of improvements in the retinal layer thicknesses.. Hypoxia-ischemia at term-equivalent age induced functional and structural damage mainly to the inner retina. Treatment with sildenafil provided a dose-dependent recovery of retinal function and structure.

Topics: Administration, Oral; Animals; Animals, Newborn; Disease Models, Animal; Electroretinography; Female; Follow-Up Studies; Hypoxia; Male; Phosphodiesterase 5 Inhibitors; Rats; Rats, Long-Evans; Reperfusion Injury; Retina; Retinal Diseases; Sildenafil Citrate

Term asphyxiated newborns remain at risk of developing brain injury despite available neuropreventive therapies such as hypothermia. Neurorestorative treatments may be an alternative. This study investigated the effect of sildenafil on brain injury induced by neonatal hypoxia-ischemia (HI) at term-equivalent age. Neonatal HI was induced in male Long-Evans rat pups at postnatal day 10 (P10) by left common carotid ligation followed by a 2-hour exposure to 8% oxygen; sham-operated rat pups served as the control. Both groups were randomized to oral sildenafil or vehicle twice daily for 7 consecutive days. Gait analysis was performed on P27. At P30, the rats were sacrificed, and their brains were extracted. The surfaces of both hemispheres were measured on hematoxylin and eosin-stained brain sections. Mature neurons and endothelial cells were quantified near the infarct boundary zone using immunohistochemistry. HI caused significant gait impairment and a reduction in the size of the left hemisphere. Treatment with sildenafil led to an improvement in the neurological deficits as measured by gait analysis, as well as an improvement in the size of the left hemisphere. Sildenafil, especially at higher doses, also caused a significant increase in the number of neurons near the infarct boundary zone. In conclusion, sildenafil administered after neonatal HI may improve brain injury recovery by promoting neuronal populations.

Topics: Animals; Animals, Newborn; Brain; Brain Injuries; Disease Models, Animal; Hypoxia-Ischemia, Brain; Male; Neurons; Recovery of Function; Sildenafil Citrate

We aimed to examine the effects of sildenafil and n-acetylcystein on ischemia/reperfusion injury in femoral artery endothelium and gastrocnemius muscle.. 32 rats of Sprague-Dawley breed were randomly divided into four groups (n=8). Median laparotomy was performed, then a 120-minute ischemia was created by microvascular clamping of infrarenal aorta, followed by the release of clamping. In sildenafil group, 1 mg/kg of sildenafil infusion and in the n-acetylcystein group, 100 mg/kg of n-acetylcystein infusion was administered after release of clamps. Blood samples and tissue samples of femoral artery and gastrocnemius muscle were extracted for a histopathological evaluation.. Serum levels of malondialdehyde in ischemia/reperfusion group (6.16±0.79) were higher compared to the control group (4.69±0.33), whereas a significant decrease was detected in sildenafil (5.17±0.50) and n-acetylcystein (4.96±0.49) groups. Femoral artery tissue sections of the control group, mean tumor necrosis factor alpha and hypoxy-induced factor-1 alpha immunoreactivity were found to be negative. In the ischemia/reperfusion group, mean tumor necrosis factor α immunoreactivity was intense and mean hypoxy-induced factor-1 alpha immunoreactivity was 51-75%. In the ischemia/reperfusion+Sildenafil and ischemia/reperfusion+NAS groups, mean tumor necrosis factor α immunoreactivity was slight and mean hypoxy-induced factor-1 alpha immunoreactivity was 26-50%.. In conclusion, sildenafil and n-acetylcystein may reduce femoral artery endothelium and gastrocnemius muscle injury following lower extremity ischemia/reperfusion.

Topics: Acetylcysteine; Animals; Antioxidants; Biomarkers; Cytoprotection; Disease Models, Animal; Endothelium, Vascular; Femoral Artery; Hypoxia-Inducible Factor 1, alpha Subunit; Lipid Peroxidation; Malondialdehyde; Muscle, Skeletal; Oxidative Stress; Piperazines; Purines; Rats, Sprague-Dawley; Reperfusion Injury; Sildenafil Citrate; Sulfonamides; Time Factors; Tumor Necrosis Factor-alpha; Vasodilator Agents

Crohn disease is still incurable. Compounds with anti-inflammatory and/or antioxidative effects are tested in various preclinical models of the disease. Our aim was to investigate the effects of sildenafil and lazaroid U-74389G in an experimental rat model of trinitrobenzenesulfonic acid-induced colitis.. Trinitrobenzenesulfonic acid was instilled into the colon of all male Wistar rats except for the rats belonging to the first group. For 6 days, the animals in group 3 were administered daily sildenafil orally, the rats in group 4 were administered daily U-74389G intravenously, and the rats in group 5 were coadministered daily sildenafil orally and intravenous U-74389G. The rats in groups 1 and 2 were not administered any treatment. During the study, the weights were recorded as a marker of clinical condition. The colon damage was evaluated using macroscopic colon mucosal damage index (CMDI), microscopic (Geboes score), and biochemical methods (tissue tumor necrosis factor [TNF]-α and malondialdehyde [MDA]).. Sildenafil reduced TNF-α tissue levels and increased body weight. U-74389G reduced TNF-α, the macroscopic index of mucosal damage score (CMDI) and increased body weight. The combined treatment with sildenafil and U-74389G reduced tissue levels of both TNF-α and MDA, lowered CMDI and microscopic Geboes score, and increased body weight.. U-74389G demonstrated a significant anti-inflammatory activity related to its ability to reduce colonic TNF-α, CMDI score, and improve weight change. We confirmed that sildenafil has anti-inflammatory capacity by reducing colonic TNF-α and by improving body weight. Finally, the combined treatment showed superior effects by reducing colonic TNF-α, colonic MDA, CMDI score, Geboes score, and by improving weight.

Topics: Animals; Antioxidants; Colitis; Colon; Disease Models, Animal; Drug Evaluation, Preclinical; Drug Therapy, Combination; Male; Malondialdehyde; Phosphodiesterase 5 Inhibitors; Piperazines; Pregnatrienes; Purines; Random Allocation; Rats, Wistar; Sildenafil Citrate; Sulfones; Trinitrobenzenesulfonic Acid; Tumor Necrosis Factor-alpha

We previously reported that the phosphodiesterase-5 (PDE5) inhibitor sildenafil prevented neurodegeneration but not learning deficits in middle-aged rats that were subjected to the permanent, three-stage, four-vessel occlusion/internal carotid artery (4-VO/ICA) model of chronic cerebral hypoperfusion (CCH). In the present study, we examined whether the PDE3 inhibitor cilostazol alleviates the loss of long-term memory (i.e., retrograde amnesia) caused by CCH. The effect of sildenafil was then compared to cilostazol. Naive rats (12-15 months old) were trained in a non-food-rewarded eight-arm radial maze and subjected to CCH. One week later, retrograde memory was assessed for 5 weeks. Cilostazol (50mg/kg, p.o.) was administered for 42 days or 15 days, beginning approximately 45 min after the first occlusion stage. Sildenafil (3mg/kg, p.o.) was similarly administered for 15 days only. Histological examination was performed after behavioral testing. Chronic cerebral hypoperfusion caused persistent retrograde amnesia, which was reversed by cilostazol after both short-term and long-term treatment. This antiamnesic effect of cilostazol was sustained throughout the experiment, even after discontinuing treatment (15-day treatment group). This effect occurred in the absence of neuronal rescue. Sildenafil failed to prevent CCH-induced retrograde amnesia, but it reduced hippocampal cell death. Extending previous findings from this laboratory, we conclude that sildenafil does not afford memory recovery after CCH, despite its neuroprotective effect. In contrast, cilostazol abolished CCH-induced retrograde amnesia, an effect that may not depend on histological neuroprotection. The present data suggest that cilostazol but not sildenafil represents a potential strategy for the treatment of cognitive sequelae associated with CCH.

Topics: Aging; Amnesia, Retrograde; Animals; Brain Ischemia; Carotid Artery Diseases; Carotid Artery, Internal; Cell Death; Cilostazol; Disease Models, Animal; Male; Maze Learning; Memory, Long-Term; Neuroprotective Agents; Nootropic Agents; Pyramidal Cells; Rats, Wistar; Sildenafil Citrate; Tetrazoles

Diced cartilage grafts are frequently used, especially in rhinoplasty. The effect of sildenafil on the viability of diced cartilage grafts was investigated in this study.. Animal experiment.. An approximate 2 × 2-cm cartilage graft was taken from the ears of 14 New Zealand rabbits, diced to approximately 1-mm(3) dimensions, then wrapped in muscle fascia taken from the right rear leg. These were then weighed and placed in prepared cavities on the backs of the rabbits. The animals were separated into two groups, and although no procedure was applied to the control group, a daily dose of 10 mg/kg sildenafil was administered orally to the sildenafil group. After 3 months, the rabbits were sacrificed and the grafts were removed, weighed, and examined histopathologically.. No statistically significant difference was observed between groups with respect to graft weight. Histopathologically, graft tissue viability was 85% in the sildenafil group and 41.43% in the control group, which was determined to be statistically significant. A lower resorption rate and higher basophilia rate was observed in the sildenafil group (P < .05) compared with the control group. No statistically significant differences were determined between the groups with respect to calcification, bone metaplasia, inflammation, or fibrosis.. Independent of surgical technique, sildenafil may be clinically useful as a medical agent to enhance graft viability.. NA

Topics: Animals; Disease Models, Animal; Ear Cartilage; Fascia; Follow-Up Studies; Graft Survival; Male; Piperazines; Purines; Rabbits; Rhinoplasty; Sildenafil Citrate; Sulfonamides; Vasodilator Agents

We examined the interaction between OSU-03012 (also called AR-12) with phosphodiesterase 5 (PDE5) inhibitors to determine the role of the chaperone glucose-regulated protein (GRP78)/BiP/HSPA5 in the cellular response. Sildenafil (Viagra) interacted in a greater than additive fashion with OSU-03012 to kill stem-like GBM cells. Treatment of cells with OSU-03012/sildenafil: abolished the expression of multiple oncogenic growth factor receptors and plasma membrane drug efflux pumps and caused a rapid degradation of GRP78 and other HSP70 and HSP90 family chaperone proteins. Decreased expression of plasma membrane receptors and drug efflux pumps was dependent upon enhanced PERK-eIF2α-ATF4-CHOP signaling and was blocked by GRP78 over-expression. In vivo OSU-03012/sildenafil was more efficacious than treatment with celecoxib and sildenafil at killing tumor cells without damaging normal tissues and in parallel reduced expression of ABCB1 and ABCG2 in the normal brain. The combination of OSU-03012/sildenafil synergized with low concentrations of sorafenib to kill tumor cells, and with lapatinib to kill ERBB1 over-expressing tumor cells. In multiplex assays on plasma and human tumor tissue from an OSU-03012/sildenafil treated mouse, we noted a profound reduction in uPA signaling and identified FGF and JAK1/2 as response biomarkers for potentially suppressing the killing response. Inhibition of FGFR signaling and to a lesser extent JAK1/2 signaling profoundly enhanced OSU-03012/sildenafil lethality.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Blood-Brain Barrier; Blotting, Western; Brain Neoplasms; Cell Line, Tumor; Disease Models, Animal; Drug Synergism; Endoplasmic Reticulum Chaperone BiP; Humans; Mice; Molecular Chaperones; Piperazines; Purines; Pyrazoles; RNA, Small Interfering; Signal Transduction; Sildenafil Citrate; Sulfonamides; Transfection; Xenograft Model Antitumor Assays

This study was undertaken to test the effects of sildenafil citrate (SC), a type 5 phosphodiesterase inhibitor, on valproic acid (VPA)-induced teratogenesis. On gestation day (GD) 8, ICR (CD-1) mice were treated by gastric intubation with SC at 0 (vehicle), 1.0, 2.5, 5.0 or 10mg/kg. One hour later, animals received a teratogenic dose of VPA (600mg/kg) or vehicle. Developmental endpoints were evaluated near the end of gestation. Twenty-eighth percent of fetuses exposed to VPA had neural tube defects (exencephaly). Pretreatment with SC at 2.5, 5.0 or 10mg/kg significantly reduced the rate of VPA-induced exencephaly to 15.9%, 13.7%, and 10.0%, respectively. Axial skeletal defects were observed in 75.8% of VPA-exposed fetuses. Pre-treatment with SC at 10mg/kg, but not at lower doses, significantly decreased the rate of skeletally affected fetuses to 61.6%. These results show that SC, which prolongs nitric oxide (NO) signaling action protects from VPA-induced teratogenesis.

Topics: Abnormalities, Drug-Induced; Animals; Bone and Bones; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Mice, Inbred ICR; Neural Tube Defects; Neuroprotective Agents; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Pregnancy; Signal Transduction; Sildenafil Citrate; Valproic Acid

This study was designed to assess the progression of pulmonary arterial hypertension (PAH) and the effectiveness of therapy using recently investigated echocardiographic parameters. PAH is characterized by the progressive elevation of pulmonary artery pressure and right ventricular hypertrophy and dysfunction, which ultimately results in right-sided heart failure and death. Echocardiography results and invasive measurements of right and left ventricular systolic pressures were compared after 3-week administrations of sildenafil (S group), pimobendan (P group), nicorandil (N group), and their combinations (SP and SPN groups) in male rats with monocrotaline (MCT)-induced pulmonary hypertension (M group) and without this condition (C group). The groups that received pimobendan alone and in combinations (SP and SPN groups) showed improvement in their echocardiographic parameters of systolic function. A significant improvement of diastolic function was achieved in the SPN group. Invasive measurements showed the most significant decreases of right ventricular systolic pressure in the N and SPN groups, and the use of pimobendan resulted in a comparatively low risk of adverse hemodynamic effects (left ventricular systolic pressure). Although our results suggested the attenuation of PAH severity in all treatment groups, PAH could not be reversed.

Topics: Animals; Disease Models, Animal; Drug Therapy, Combination; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Monocrotaline; Nicorandil; Phosphodiesterase 3 Inhibitors; Phosphodiesterase 5 Inhibitors; Pyridazines; Rats, Wistar; Recovery of Function; Severity of Illness Index; Sildenafil Citrate; Vasodilator Agents; Ventricular Dysfunction, Right; Ventricular Function, Right

Sildenafil (Viagra), a cGMP-specific phosphodiesterase type 5 inhibitor, is widely used for the treatment of erectile dysfunction and pulmonary hypertension. Clinical studies have reported transient visual impairments in patients after single-dose sildenafil use, suggesting neural involvement in several retinal layers, and also, possibly, retinal ganglion cells (RGCs), which provide the unique output of visual information to the brain. However, the effect of sildenafil on the RGC light responses is poorly understood. We therefore evaluated its effect on RGC spiking activity.. We measured spontaneous and light-induced RGC spiking activity in Long-Evans rat ex vivo retinas by using the multielectrode array technique. Sildenafil citrate (0.3-30 μM) was applied to retinal preparations under continuous perfusion, during 10 to 60 minutes, followed by sildenafil washout.. A high concentration (30 μM) of sildenafil decreased the magnitudes of both ON- and OFF-type RGC light responses, to 26.3% ± 17% and 18.3% ± 7%, respectively, of the initial value, in a reversible and concentration-dependent fashion, while in 50% of RGCs all light responses were completely suppressed. Sildenafil also greatly increased the latency of both types of light responses. In this study, we provided evidence that extended exposure to both sildenafil and repeated light stimulation potentiates drug effects and delays recovery.. We found transient and concentration-dependent alterations of light responses at the RGC level after sildenafil exposure that are relevant for a better understanding of the acute visual effects of administration of this compound in humans.

Topics: Animals; Disease Models, Animal; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Long-Evans; Retinal Ganglion Cells; Sildenafil Citrate; Sulfonamides; Vision Disorders

Stimulators of the soluble guanylate cyclase (sGC) have recently been shown to inhibit transforming growth factor-β signalling. Here, we aimed to demonstrate that riociguat, the drug candidate for clinical trials in systemic sclerosis (SSc), is effective in experimental fibrosis and to compare its efficacy to that of phosphodiesterase V inhibitors that also increase the intracellular levels of cyclic guanosine monophosphate.. The antifibrotic effects of riociguat and sildenafil were compared in the tight-skin 1 model, in bleomycin-induced fibrosis and in a model of sclerodermatous chronic graft-versus-host-disease (cGvHD). Doses of 0.1-3 mg/kg twice a day for riociguat and of 3-10 mg/kg twice a day for sildenafil were used.. Riociguat dose-dependently reduced skin thickening, myofibroblast differentiation and accumulation of collagen with potent antifibrotic effects at 1 and 3 mg/kg. Riociguat also ameliorated fibrosis of the gastrointestinal tract in the cGvHD model. The antifibrotic effects were associated with reduced phosphorylation of extracellular signal-regulated kinases. Sildenafil at doses of 3 and 10 mg/kg exerted mild antifibrotic effects that were significantly less pronounced compared with 1 and 3 mg/kg riociguat.. These data demonstrated potent antifibrotic effects of riociguat on experimental skin and organ fibrosis. These findings suggest a role for riociguat for the treatment of fibrotic diseases, especially for the treatment of SSc. A phase II study with riociguat in patients with SSc is currently starting.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Fibrosis; Guanylate Cyclase; Mice; Mice, Inbred Strains; Phosphodiesterase 5 Inhibitors; Pyrazoles; Pyrimidines; Scleroderma, Systemic; Sildenafil Citrate; Skin

Pulmonary hypertension (PH) and right ventricular hypertrophy (RVH) affect 25-35% of premature infants with significant bronchopulmonary dysplasia (BPD), increasing morbidity and mortality. We sought to determine the role of phosphodiesterase 5 (PDE5) in the right ventricle (RV) and left ventricle (LV) in a hyperoxia-induced neonatal mouse model of PH and RVH. After birth, C57BL/6 mice were placed in room air (RA) or 75% O2 (CH) for 14 days to induce PH and RVH. Mice were euthanized at 14 days or recovered in RA for 14 days or 42 days prior to euthanasia at 28 or 56 days of age. Some pups received sildenafil or vehicle (3 mg·kg(-1)·dose(-1) sc) every other day from P0. RVH was assessed by Fulton's index [RV wt/(LV + septum) wt]. PDE5 protein expression was analyzed via Western blot, PDE5 activity was measured by commercially available assay, and cGMP was measured by enzyme-linked immunoassay. Hyperoxia induced RVH in mice after 14 days, and RVH did not resolve until 56 days of age. Hyperoxia increased PDE5 expression and activity in RV, but not LV + S, after 14 days. PDE5 expression normalized by 28 days of age, but PDE5 activity did not normalize until 56 days of age. Sildenafil given during hyperoxia prevented RVH, decreased RV PDE5 activity, and increased RV cGMP levels. Mice with cardiac-specific overexpression of PDE5 had increased RVH in RA. These findings suggest normal RV PDE5 function is disrupted by hyperoxia, and elevated PDE5 contributes to RVH and remodeling. Therefore, in addition to impacting the pulmonary vasculature, sildenafil also targets PDE5 in the neonatal mouse RV and decreases RVH.

Topics: Animals; Animals, Newborn; Antihypertensive Agents; Cyclic AMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Down-Regulation; Heart Ventricles; Hyperoxia; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Mice, Inbred C57BL; Mice, Transgenic; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Second Messenger Systems; Sildenafil Citrate; Sulfonamides; Time Factors; Ventricular Function, Right; Ventricular Remodeling

Sildenafil, a phosphodiesterase-5 inhibitor used to treat pulmonary hypertension, may have effects on pulmonary vessel structure and function. We evaluated the effects of sildenafil in a cigarette smoke (CS)-exposed model of chronic obstructive pulmonary disease (COPD).42 guinea-pigs were exposed to cigarette smoke or sham-exposed and treated with sildenafil or vehicle for 12 weeks, divided into four groups. Assessments included respiratory resistance, pulmonary artery pressure (PAP), right ventricle (RV) hypertrophy, endothelial function of the pulmonary artery and lung vessel and parenchymal morphometry.CS-exposed animals showed increased PAP, RV hypertrophy, raised respiratory resistance, airspace enlargement and intrapulmonary vessel remodelling. CS exposure also produced wall thickening, increased contractility and endothelial dysfunction in the main pulmonary artery. CS-exposed animals treated with sildenafil showed lower PAP and a trend to less RV hypertrophy than CS-exposed only animals. Furthermore, sildenafil preserved the intrapulmonary vessel density and attenuated the airspace enlargement induced by CS. No differences in gas exchange, respiratory resistance, endothelial function and vessel remodelling were observed.We conclude that in this experimental model of COPD, sildenafil prevents the development of pulmonary hypertension and contributes to preserve the parenchymal and vascular integrity, reinforcing the notion that the nitric oxide-cyclic guanosine monophosphate axis is perturbed by CS exposure.

Topics: Animals; Disease Models, Animal; Guinea Pigs; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Phosphodiesterase 5 Inhibitors; Pulmonary Artery; Pulmonary Disease, Chronic Obstructive; Sildenafil Citrate; Tobacco Smoke Pollution

Impaired nitric oxide (NO), soluble guanylyl cyclase (sGC), and cyclic guanosine monophosphate (cGMP) signaling (NO-sGC-cGMP) has been implicated in the pathogenesis of diabetic vascular dysfunction. Efforts to directly target this signaling have led to the development of sGC agonists that activate the heme group of sGC (stimulators) or preferentially activate sGC when the heme is oxidized (activators). In this study, we hypothesized that resistance arteries from female rats with spontaneous type 2 diabetes (Goto-Kakizaki rats, GK) would have reduced vasodilatory responses to heme-dependent sGC activation and increased responses to heme-independent sGC activation compared with control rats (Wistar). Endothelium-dependent and -independent relaxation was assessed in isolated segments from mesenteric resistance arteries (MA) mounted in a wire myograph. GK MA had reduced responses to acetylcholine (pEC50: 7.96 ± 0.06 vs. 7.66 ± 0.05, P < 0.05) and sodium nitroprusside (pEC50: 8.34 ± 0.05 vs. 7.77 ± 0.04, P < 0.05). There were no group differences in 8-bromoguanosine cGMP-induced relaxation and protein kinase G1 expression (P > 0.05). GK MA had attenuated responses to BAY 41-2272 (heme-dependent sGC stimulator; pEC50: 7.56 ± 0.05 vs. 6.93 ± 0.06, P < 0.05) and BAY 58-2667 (heme-independent sGC activator; pEC50: 10.82 ± 0.07 vs. 10.27 ± 0.08, P < 0.05) and increased sensitivity to sildenafil [phosphodiesterase 5 (PDE5) inhibitor; pEC50: 7.89 ± 0.14 vs. 8.25 ± 0.13, P < 0.05]. Isolated resistance arteries from female rats of reproductive age that spontaneously develop type 2 diabetes have increased sensitivity to PDE5 inhibition and reduced responsiveness to sGC activators and stimulators.

Topics: Animals; Arterial Pressure; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Activators; Female; Guanylate Cyclase; Mesenteric Arteries; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Receptors, Cytoplasmic and Nuclear; Sildenafil Citrate; Soluble Guanylyl Cyclase; Sulfonamides; Vasodilation; Vasodilator Agents

N(omega)-nitro-L-arginine methyl ester (L-NAME) decreases the vasodilator effect of nitric oxide (NO) and induces pre-eclampsia in mouse. Sildenafil inhibits the degradation of nitric oxide and increases vasodilation. This study aimed to determine the effects of sildenafil citrate on angiogenesis and oxidative stress at the maternal foetal interface on pre-eclampsia-like mouse model induced by L-NAME. Twenty pregnant mice were divided into four groups: (i) vehicle control; (ii) L-NAME; (iii) sildenafil; (4) L-NAME+sildenafil. L-NAME was administered from day 7 of pregnancy and sildenafil from day 8 until day 16; animals were euthanized on day 17. Placental and foetal sizes and weights were measured; lipid peroxide levels and catalase activity in placental homogenates were determined, and placental vascular endothelia were identified by lectin-histochemistry using BSA-I lectin. Western blot analysis was used to determine VEGF expression in placental homogenates. No changes were seen in placental and foetal development in mice with normal pregnancies treated with sildenafil. Treatments with L-NAME reduced significantly the placental weight and average height and decreased the percentage of the endothelial surface. These alterations may be mediated by the reduction of NO levels in trophoblastic cells, due to the inhibitory effect of L-NAME on nitric oxide synthase (NOS) synthesis. This effect was offset by the treatment with sildenafil, with an increase in the percentage of the endothelial surface. In conclusion, our results indicate that treatment with sildenafil on pre-eclampsia mouse model can be used without adverse effects on the concept and its use in the treatment of pre-eclampsia is promising.

Topics: Animals; Disease Models, Animal; Female; Fetus; Mice; Mice, Inbred BALB C; Neovascularization, Physiologic; NG-Nitroarginine Methyl Ester; Oxidative Stress; Placenta; Pre-Eclampsia; Pregnancy; Sildenafil Citrate; Vasodilator Agents

In translational medicine, the discovery of new drugs or new potential uses for currently available drugs is crucial for treating the resistant hypertension associated with renal artery stenosis. The phosphodiesterase 5 inhibitor sildenafil has been shown to reduce blood pressure and to improve the endothelium-dependent relaxation in the two kidney, one clip (2K1C) mouse model of renovascular hypertension. In the present study, we evaluated the effects of sildenafil (40 mg/kg/day for two weeks) on the endothelial structure and contractile function in mesenteric resistance arteries 28 days after clipping the renal artery. The data showed an enhanced vascular contractile response to norepinephrine in 2K1C hypertensive mice (56%) when compared with Sham mice, which was associated with increased oxidative stress and with a thinning of endothelial cells. Sildenafil treatment caused a significant amelioration in the enhanced contractile responsiveness (18%), which was associated to the recovery of the endothelial surface and abolishment of the oxidative stress. These data suggest that sildenafil could be considered a promising therapeutic option to manage endothelial dysfunction and hypertension in resistant patients.

Topics: Animals; Disease Models, Animal; Endothelium, Vascular; Hypertension, Renovascular; Male; Mice; Mice, Inbred C57BL; Oxidative Stress; Sildenafil Citrate; Vasodilator Agents

The most important issue in flap surgery is flap viability. This study aimed to compare the effects of most commonly used phosphodiesterase type 5 (PDE5) inhibitors on flap survival.. A 3 × 9 cm flap was elevated from the dorsum of 32 Wistar albino rats. In the control group, saline was administered 2 hours before the flap elevation and continued for 2 days after the surgery. In the sildenafil, tadalafil, and vardenafil groups, the related drug was administered. Blood flow in the flaps was monitored with laser Doppler flowmetry. On postoperative day 7, flaps were photographed and biopsies were obtained.. The ratios of flap necrosis area in the tadalafil, sildenafil, and vardenafil groups were lower than that in the control group, but without significant difference (p = 0.077). Histopathological evaluation revealed no significant difference among the groups.. The ratio of flap necrosis area tended to be lower in the groups receiving oral PDE5 inhibitors than in the control group, although not statistically significant. The role of PDE5 inhibitors needs to be evaluated in larger studies before a conclusion can be made regarding their effects on flap viability.

Topics: Animals; Biopsy, Needle; Blood Flow Velocity; Disease Models, Animal; Female; Graft Rejection; Immunohistochemistry; Infusions, Intravenous; Laser-Doppler Flowmetry; Microcirculation; Random Allocation; Rats; Rats, Wistar; Reference Values; Sildenafil Citrate; Skin Transplantation; Surgical Flaps; Tadalafil; Vardenafil Dihydrochloride; Wound Healing

Olfactory bulbectomy (OB) is an animal model of depression that can mimic symptoms that are characteristic of depressive patients, such as behavioral, neurochemical and neuromorphological changes. Quercetin decreased the immobility time in the forced swimming test and tail suspension test. With the open field test, quercetin did not alter the locomotor activity of mice and in the splash test, quercetin increased the time spent grooming. The repeated treatment with quercetin (25mg/kg, for 14days) reversed the behavioral hyperactivity induced by OB in the open field test and was able to prevent depressant-like effects in the forced swimming test and tail suspension test. Regarding oxidative stress, OB reduced the levels of glutathione and increase the activity of superoxide dismutase and lipid hydroperoxide content (LOOH) in the hippocampus. Only the increase in LOOH levels was reversed by treatment with quercetin. In a further series of experiments with non-bulbectomized mice, the antidepressant effect of quercetin in the tail suspension test was reversed by the pretreatment of mice with NMDA, l-arginine or sildenafil. The administration of methylene blue and 7-nitroindazole, in combination with an underactive dose of quercetin (5mg/kg, p.o.), decreased the immobility time in the tail suspension test compared with the use of drug alone. There was no significant change in locomotor activity in the open field test. Our results suggest that the antidepressant effect of quercetin is dependent on the inhibition of the NMDA receptors and/or synthesis of nitric oxide. In addition, considering the reduction of LOOH levels on the hippocampus, we verify that the antioxidant effects of quercetin also contribute to its antidepressive potential. These data contribute to the understanding of the mechanisms involved in the antidepressant effect of quercetin and reinforce the involvement of the NMDA receptors and the nitric oxide on the pathophysiology of depression.

Topics: Animals; Antidepressive Agents; Antioxidants; Arginine; Behavior, Animal; Disease Models, Animal; Drug Synergism; Fluoxetine; Hippocampus; Indazoles; Male; Methylene Blue; Mice; N-Methylaspartate; Olfactory Bulb; Oxidative Stress; Quercetin; Signal Transduction; Sildenafil Citrate

There are contradictory results about the effects of exercise and sildenafil on cognitive functions.. To investigate the effects of sildenafil pretreatment and chronic exercise on anxiety and cognitive functions.. Wistar rats (n=42) were divided as sedentary and exercise groups. A moderate-intensity swimming exercise was performed for 6 weeks, 5 days/week, 1h/day. Some of the rats were administered orogastrically with sildenafil (25mg/kg/day) either acutely or chronically. Exposure to cat odor was used for induction of stress. The level of anxiety was evaluated by elevated plus maze test, while object recognition test was used to determine cognitive functions. Brain tissues were removed for the measurement of myeloperoxidase (MPO), malondialdehyde (MDA), nitric oxide levels, lucigenin-enhanced chemiluminescence, and for histological analysis.. Increased MPO and MDA levels in sedentary-stressed rats were decreased with sildenafil applications. Chronic exercise inhibited the increase in MPO levels. Increased nitric oxide and lucigenin chemiluminescence levels in sedentary-stressed rats, were diminished with chronic sildenafil pretreatment. The time spent in the open arms of the plus maze was declined in sedentary-stressed rats, while chronic sildenafil pretreatment increased the time back to that in non-stressed rats. Acute sildenafil application to exercised rats prolonged the time spent in open arms as compared to non-treated exercise group. The time spent with the novel object, which was decreased in sedentary-stressed rats, was increased with sildenafil pretreatment. Our results suggest that sildenafil pretreatment or exercise exerts a protective effect against acute stress and improves cognitive functions by decreasing oxidative damage.

Topics: Acute Disease; Animals; Anxiety Disorders; Cognition; Disease Models, Animal; Exercise Therapy; Exploratory Behavior; Hippocampus; Male; Malondialdehyde; Nitric Oxide; Peroxidase; Physical Conditioning, Animal; Psychotropic Drugs; Random Allocation; Rats, Wistar; Recognition, Psychology; Sildenafil Citrate; Stress, Psychological; Swimming; Treatment Outcome

Recurrent pregnancy losses (RPL) are common women's health issues. Inflammatory and thrombotic events have been associated with RPL including excessive production of cytokines, in particular TNF-α. However, mechanisms behind gestational losses are not yet fully understood. Sildenafil inhibits phosphodiesterase Type-5 (PDE5). This drug increases intracellular cyclic guanosine monophosphate, having vasodilatory and, more recently described, anti-inflammatory properties. PDE5 is present in murine and human uterus and placenta. Sildenafil is already used clinically for treatment of human fetal growth restriction (FGR). Our objective was to determine if Sildenafil alone or in combination with Heparin had protective effects in pregnant Swiss albino challenged to abort by lipopolysaccharide (LPS).. Treatments (Sildenafil (50 mg/kg/day), Heparin (500 IU/Kg/day) or Sildenafil + Heparin at the same doses) were initiated the morning of copulation plug detection (gestational day (gd0)). On the 15th day of pregnancy, an intra-peritoneal injection of LPS (100 μg/kg) was administered. Untreated, pregnant mice challenged by LPS served as controls.. Assessments at 48 h after LPS revealed that Sildenafil + Heparin prevented fetal loss. Early assessments at 2 h after LPS indicated that the pretreatments prevented induction of inflammatory cytokine production (TNF-α, IL-1β/NF-κβ) and preserved placental histopathology.. Combined Sildenafil + Heparin therapy was superior to either treatment alone in most analyses. The known safety of Sildenafil and Heparin in human pregnancy suggests that usage of these combined agents may be of value for treatment of patients with impending pregnancy loss or prophylactically in women with a history of recurrent miscarriages.

Topics: Abortion, Habitual; Abortion, Spontaneous; Animals; Disease Models, Animal; Drug Evaluation, Preclinical; Female; Lipopolysaccharides; Male; Mice; Phosphodiesterase 5 Inhibitors; Placenta; Pregnancy; Sildenafil Citrate

Imbalanced matrix metalloproteinase (MMP)-2 activity and transforming growth factor expression (TGF-β) are involved in vascular remodeling of hypertension. Atorvastatin and sildenafil exert antioxidant and pleiotropic effects that may result in cardiovascular protection. We hypothesized that atorvastatin and sildenafil alone or in association exert antiproliferative effects by down-regulating MMP-2 and TGF-β, thus reducing the vascular hypertrophy induced by two kidney, one clip (2K1C) hypertension. Sham and 2K1C rats were treated with oral atorvastatin 50 mg/kg, sildenafil 45 mg/kg, or both, daily for 8 weeks. Blood pressure was monitored weekly. Morphologic changes in the aortas were studied. TGF-β levels were determined by immunofluorescence. MMP-2 activity and expression were determined by in situ zymography, gel zymography, Western blotting, and immunofluorescence. The effects of both drugs on proliferative responses of aortic smooth muscle cells to PDGF and on on MMP-2 activity in vitro were determined. Atorvastatin, sildenafil, or both drugs exerted antiproliferative effects in vitro. All treatments attenuated 2K1C-induced hypertension and prevented the increases in the aortic cross-sectional area and media/lumen ratio in 2K1C rats. Aortas from 2K1C rats showed higher collagen deposition, TGF-β levels and MMP-2 activity and expression when compared with Sham-operated animals. Treatment with atorvastatin and/or sildenafil was associated with attenuation of 2K1C hypertension-induced increases in these pro-fibrotic factors. However, these drugs had no in vitro effects on hr-MMP-2 activity. Atorvastatin and sildenafil was associated with decreased vascular TGF-β levels and MMP-2 activity in renovascular hypertensive rats, thus ameliorating the vascular remodeling. These novel pleiotropic effects of both drugs may translate into protective effects in patients.

Topics: Animals; Aorta; Atorvastatin; Cardiovascular Agents; Collagen; Disease Models, Animal; Drug Combinations; Drug Synergism; Endothelium, Vascular; Gene Expression Regulation; Hypertension, Renovascular; Male; Matrix Metalloproteinase 2; Myocytes, Smooth Muscle; Oxidative Stress; Platelet-Derived Growth Factor; Rats; Rats, Wistar; Reactive Oxygen Species; Signal Transduction; Sildenafil Citrate; Transforming Growth Factor beta; Vascular Remodeling

Recent research suggests that priapism in sickle cell disease (SCD) is due to dysregulation of penile erection homeostasis including alteration of nitric oxide synthase (NOS) and phosphodiesterase type 5 (PDE5) activities by excessive levels of reactive oxygen species (ROS) released during hemolysis. It is unknown if subacute exposure to hemolysis is sufficient or if chronic reconditioning of erectile tissues is required for perturbation of homeostatic pathways and whether PDE5 inhibitor (PDE5I) treatment can restore erectile homeostasis in the subacute setting.. The aim of this study was to investigate the effects of subacute hemolysis (3-month exposure) on priapism and NO pathway regulation.. Mice underwent bone marrow transplantation with either SCD (BM-SS) or wild-type (WT) bone marrow. BM-SS mice were treated with sildenafil 100 mg/kg/day. We measured intracavernous pressure (ICP) measurements with or without cavernous nerve stimulation following bone marrow transplantation to assess for priapism.. ICP and frequency of erections were assessed. Penile tissues were analyzed for NOS, protein kinase G (PKG), PDE5, and ROS activities.. BM-SS mice demonstrated a priapism phenotype. PDE5I treatment reduced the frequency of erections in BM-SS mice (1.7 ± 1.1 vs. 5.5 ± 2.8 erections per hour, P < 0.05). Penile tissues from BM-SS mice demonstrated decreased NOS, PKG, PDE5 and elevated ROS activities compared with that of control mice. PDE5I treatment increased NOS (11.6 ± 1.3% vs. 7.8 ± 2.3%, P < 0.05) and PDE5 (76.3 ± 9.8% vs. 52.3 ± 11.1%, P < 0.05) activities and decreased ROS activity (137.8 ± 12.1% vs. 199.1 ± 11.3%, P < 0.05) compared with non-PDE5I treated BM-SS mice. PKG activity was increased beyond control levels with PDE5I treatment (158.4 ± 10.3%, P < 0.05).. Short-term hemolysis is sufficient to establish a priapism phenotype and results in loss of erectile function. PDE5I treatment ameliorates priapism, in part, because of restored NO balance with decreased ROS generation and increased PDE5 activity.

Topics: Acute Disease; Anemia, Sickle Cell; Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Hemolysis; Male; Mice; Mice, Transgenic; Nitric Oxide Synthase; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Priapism; Signal Transduction; Sildenafil Citrate

To study the possible renoprotective effect of sildenafil against renal ischemia/reperfusion (I/R) injury and its effect on the expression of some antioxidant, antiapoptotic gene and proinflammatory cytokine genes in rat model of renal I/R injury.. One hundred and twenty male Sprague Dawley rats were subdivided into three equal groups: sham (underwent right nephrectomy without ischemia), control (underwent right nephrectomy and left ischemia for 45 min) and study [as control with 1 mg/kg sildenafil (per oral) 60 min before anesthesia]. Serum creatinine and BUN were measured at the baseline and the study endpoints (2, 24, 48 h and 7 days), and the left kidney was harvested at study endpoints for histopathological examination as well as for assessment of the expression of antioxidant genes (Nrf-2, HO-1 and NQO-1), antiapoptotic gene (Bcl-2) and inflammatory cytokines, e.g., TNF-a, IL-1β and ICAM-1.. I/R caused significant increase in serum creatinine, BUN, histopathological damage score (p < 0.001) and significant reduction in antioxidant genes (nrf2, HO-1 and NQO-1) and antiapoptotic gene (Bcl2) with significant increase in TNF-a, IL-1β and ICAM-1 genes in kidney tissues. Pretreatment with sildenafil caused significant attenuation of serum creatinine and BUN as well as significant increase in the expression of antioxidant genes and Bcl-2 genes with significant reduction in the expression of proinflammatory cytokine genes (p value < 0.001).. The renoprotective effect of sildenafil against renal I/R might be due to the activation of antioxidant genes (Nrf2, HO-1 and NQO-1) and antiapoptotic gene (Bcl2) and attenuation of proinflammatory cytokines (TNF-a, IL-1β and ICAM-1).

Topics: Animals; Blood Urea Nitrogen; Creatinine; Disease Models, Animal; Gene Expression; Heme Oxygenase-1; Intercellular Adhesion Molecule-1; Interleukin-1beta; Male; NAD(P)H Dehydrogenase (Quinone); Nephrectomy; NF-E2-Related Factor 2; Phosphodiesterase 5 Inhibitors; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sildenafil Citrate; Tumor Necrosis Factor-alpha; Warm Ischemia

Sildenafil (Viagra®) has recently been found to have a neuroprotective effect, which occurs through the inhibition of inflammation and demyelination in the cerebellum. However, the mechanism of action of sildenafil remains unknown. AMPK, the regulatory protein of the lipid and glucose metabolism, plays a protective role by activating the eNOS enzyme. The production of a nanomolar concentration of NO by eNOS has an anti-inflammatory effect through the cGMP signaling pathway and plays an important role in the regulation of the nuclear transcription factor (NFkB), preventing the expression of inflammatory genes. The present study investigated whether AMPK-eNOS-NO-cGMP-IКβα-NFkB is involved in the mechanism of action of sildenafil in a cuprizone-demyelination model. Neuroinflammation and demyelination induced by cuprizone in rodents have been widely used as a model of MS. In the present study, five male C57BL/6 mice (7-10 weeks old) were used. Over a four week period, the groups received: cuprizone (CPZ) 0.2% mixed in feed; CPZ in the diet, combined with the administration of sildenafil (Viagra®, Pfizer, 25mg/kg) orally in drinking water, starting concurrently (sild-T0) or 15 days (sild-T15) after the start of CPZ. Control animals received pure food and water. The cerebella of the mice were dissected and processed for immunohistochemistry, immunofluorescence (frozen), western blotting and dosage of cytokines (Elisa). CPZ induced an increase in the expression of GFAP, IL-1β TNF-α, total NFkB and inactive AMPK, and prompt microglia activation. CPZ also induced a reduction of IKβα. The administration of sildenafil reduced the expression of the pro-inflammatory cytokines IL-1β and TNF-α and increased the expression of the anti-inflammatory cytokine IL-10. In addition, the administration of sildenafil reduced expression of GFAP, NFkB, inactive AMPK and iNOS, and increased IKβα. Interestingly, sildenafil also reduced levels of NGF. In general, the sild-T0 group was more effective than sild-T15 in improving clinical status and promoting the control of neuroinflammation. The present study offers evidence that sildenafil has anti-inflammatory and neuroprotective effects, which are probably achieved through modulation of AMPK-IKβα-NFκB signaling. In addition, eNOS may play a role in the sildenafil neuroprotective mechanism, contributing to the activation of AMPK. However, other pathways such as MAPK-NFkB and the downstream proteins AMPK (AMPK-SIRT1-NFκB) should also be

Topics: AMP-Activated Protein Kinases; Animals; Anti-Inflammatory Agents; Chelating Agents; Cuprizone; Cytokines; Demyelinating Diseases; Disease Models, Animal; Encephalitis; Enzyme Inhibitors; Glial Fibrillary Acidic Protein; Male; Mice; Mice, Inbred C57BL; NF-kappa B; Nitric Oxide Synthase Type III; Sildenafil Citrate

The present study evaluates possible drug interactions between glimepiride (GLIM) and sildenafil citrate (SIL) in streptozotocin (STZ)-induced diabetic nephropathic (DN) animals and also postulates the possible mechanism of interaction based on molecular modeling studies. Diabetic nephropathy was induced by single dose of STZ (60 mg kg(-1), i.p.) and was confirmed by assessing blood and urine biochemical parameters 28 days after induction. Selected DN animals were used to explore the drug interaction between GLIM (0.5 mg kg(-1), p.o.) and SIL (2.5 mg kg(-1), p.o.) on the 29th and 70th day of the protocol. Possible drug interaction was assessed by evaluating the plasma drug concentration using HPLC-UV and changes in biochemical parameters in blood and urine were also determined. The mechanism of the interaction was postulated from the results of a molecular modeling study using the Maestro module of Schrodinger software. DN was confirmed as there was significant alteration in blood and urine biochemical parameters in STZ-treated groups. The concentration of SIL increased significantly (P < 0.001) in rat plasma when co-administered with GLIM on the 70th day of the protocol. Molecular modeling revealed important interactions with rat serum albumin and CYP2C9. GLIM has a strong hydrophobic interaction with binding site residues of rat serum albumin compared to SIL, whereas for CYP2C9, GLIM forms a stronger hydrogen bond than SIL with polar contacts and hydrophobic interactions. The present study concludes that bioavailability of SIL increases when co-administered chronically with GLIM in the management of DN animals, and the mechanism is supported by molecular modeling studies.

Topics: Animals; Blood Glucose; Cytochrome P-450 CYP2C9; Diabetic Nephropathies; Disease Models, Animal; Drug Interactions; Hypoglycemic Agents; Kidney Function Tests; Models, Molecular; Molecular Docking Simulation; Molecular Dynamics Simulation; Molecular Structure; Phosphodiesterase 5 Inhibitors; Protein Conformation; Rats; Serum Albumin; Sildenafil Citrate; Structure-Activity Relationship; Sulfonylurea Compounds

Sildenafil, a phosphodiesterase-5 inhibitor sold as Viagra, is a cardioprotector against myocardial ischemia/reperfusion (I/R) injury. Our study explored whether sildenafil protects against I/R-induced damage in a porcine cardiac arrest and resuscitation (CAR) model via modulating the renin-angiotensin system. Male pigs were randomly divided to three groups: Sham group, Saline group, and sildenafil (0.5 mg/kg) group. Thirty min after drug infusion, ventricular fibrillation (8 min) and cardiopulmonary resuscitation (up to 30 min) was conducted in these animals. We found that sildenafil ameliorated the reduced cardiac function and improved the 24-h survival rate in this model. Sildenafil partly attenuated the increases of plasma angiotensin II (Ang II) and Ang (1-7) levels after CAR. Sildenafil also decreased apoptosis and Ang II expression in myocardium. The increases of expression of angiotensin-converting-enzyme (ACE), ACE2, Ang II type 1 receptor (AT1R), and the Ang (1-7) receptor Mas in myocardial tissue were enhanced after CAR. Sildenafil suppressed AT1R up-regulation, but had no effect on ACE, ACE2, and Mas expression. Sildenafil further boosted the upregulation of endothelial nitric oxide synthase (eNOS), cyclic guanosine monophosphate (cGMP) and inducible nitric oxide synthase(iNOS). Collectively, our results suggest that cardioprotection of sildenafil in CAR model is accompanied by an inhibition of Ang II-AT1R axis activation.

Topics: Angiotensin II; Animals; Apoptosis; Cardiopulmonary Resuscitation; Cardiotonic Agents; Cyclic GMP; Disease Models, Animal; Gene Expression Regulation; Heart Arrest; Hemodynamics; Male; Myocardial Reperfusion Injury; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Peptidyl-Dipeptidase A; Phosphodiesterase 5 Inhibitors; Receptor, Angiotensin, Type 1; Renin-Angiotensin System; Sildenafil Citrate; Swine

Preeclampsia (PE) and fetal growth restriction (FGR) are serious complications of pregnancy, associated with greatly increased risk of maternal and perinatal morbidity and mortality. These complications are difficult to diagnose and no curative treatments are available. We hypothesized that the metabolomic signature of two models of disease, catechol-O-methyl transferase (COMT(-/-)) and endothelial nitric oxide synthase (Nos3(-/-)) knockout mice, would be significantly different from control C57BL/6J mice. Further, we hypothesised that any differences in COMT(-/-) mice would be resolved following treatment with Sildenafil, a treatment which rescues fetal growth. Targeted, quantitative comparisons of serum metabolic profiles of pregnant Nos3(-/-), COMT(-/-) and C57BL/6J mice were made using a kit from BIOCRATES. Significant differences in 4 metabolites were observed between Nos3(-/-) and C57BL/6J mice (p < 0.05) and in 18 metabolites between C57BL/6J and COMT(-/-) mice (p < 0.05). Following treatment with Sildenafil, only 5 of the 18 previously identified differences in metabolites (p < 0.05) remained in COMT(-/-) mice. Metabolomic profiling of mouse models is possible, producing signatures that are clearly different from control animals. A potential new treatment, Sildenafil, is able to normalize the aberrant metabolomic profile in COMT(-/-) mice; as this treatment moves into clinical trials, this information may assist in assessing possible mechanisms of action.

Topics: Animals; Catechol O-Methyltransferase; Disease Models, Animal; Female; Fetal Growth Retardation; Metabolome; Metabolomics; Mice; Mice, Knockout; Pre-Eclampsia; Pregnancy; Sildenafil Citrate

The administration of phosphodiesterase 5 inhibitor commencing at the time of castration might preserve erectile function.. To determine if sildenafil citrate treatment could improve erectile function after castration. To determine if sildenafil citrate treatment reduces collagenisation and apoptosis in erectile tissue after castration.. In all, 60 Sprague-Dawley rats were studied; the rats were divided into the following groups: sham - no orchidectomy (S), control - orchidectomy only (O) and treatment - orchidectomy plus sildenafil treatment (V), with 10 rats per group. Erectile haemodynamics assessment was done at 7 days (S7, O7, V7) and at 28 days (S28, O28, V28) yielding a total of six groupings. Functional assessment measured the mean maximum intracavernosal pressure-mean arterial pressure (ICP/MAP) ratio. TUNEL assay was used to define apoptotic indices (AIs) and Masson's trichrome staining was used to evaluate smooth muscle-collagen (SM-C) ratios.. The S28 group had the highest and the O7 group the lowest ICP/MAP ratio, at a mean (sd) of 70 (6)% and 36 (6)%, respectively. Both treatment groups, V7 [42 (12)%] and V28 [49 (13)%] showed statistically significant improvements over their corresponding control groups: O7 [36 (6)%] and O28 [37 (9)%] (P < 0.05). However, ICP/MAP values for V7 and V28 remained significantly below the S28 group (P < 0.001). There were no significant differences in ICP/MAP values between the 28-day and 7-day ICP/MAP ratios within each group (S, O, V). There were no significant differences in SM-C ratio between the O and V groups (O7 vs V7, P = 0.45; O28 vs V28, P = 0.16). There were no significant differences in AIs between the O and V groups (O7 vs V7, P = 0.54; O28 vs V28, P = 0.8).. Daily treatment with sildenafil improved erectile function in rats after castration. ICP/MAP ratios increased significantly in the treatment groups compared with the control groups with the greatest erectile function occurring 28 days from administration. In this series of experiments the improved erectile function recovery with sildenafil after surgical castration cannot be explained by smooth muscle protection and decreased collagenisation. The improved erectile function with sildenafil after surgical castration cannot be explained by reduced apoptosis in erectile tissue.

Topics: Animals; Disease Models, Animal; Erectile Dysfunction; Hemodynamics; Male; Orchiectomy; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Random Allocation; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones

Age-related cognitive decline is accompanied by an increase of neuronal apoptosis and a dysregulation of neuroplasticity-related molecules such as brain-derived neurotrophic factor and neurotoxic factors including beta amyloid (Aβ) peptide. Because it has been previously demonstrated that phosphodiesterase-5 inhibitors (PDE5-Is) protect against hippocampal synaptic dysfunction and memory deficits in mouse models of Alzheimer's disease and physiological aging, we investigated the effect of a treatment with the PDE5-I, sildenafil, on cell death, pro- and antiapoptotic molecules, and Aβ production. We demonstrated that chronic intraperitoneal injection of sildenafil (3 mg/kg for 3 weeks) decreased terminal deoxyuridine triphosphate nick end labeling-positive cells in the CA1 hippocampal area of 26-30-month-old mice, downregulating the proapoptotic proteins, caspase-3 and B-cell lymphoma 2-associated X, and increasing antiapoptotic molecules such as B-cell lymphoma protein-2 and brain-derived neurotrophic factor. Also, sildenafil reverted the shifting of amyloid precursor protein processing toward Aβ42 production and the increase of the Aβ42:Aβ40 ratio in aged mice. Our data suggest that PDE5-I might be beneficial to treat age-related detrimental features in a physiological mouse model of aging.

Topics: Aging; Alzheimer Disease; Amyloid beta-Peptides; Animals; Apoptosis; bcl-2-Associated X Protein; Brain; Brain-Derived Neurotrophic Factor; CA1 Region, Hippocampal; Caspase 3; Cyclic AMP Response Element-Binding Protein; Cyclic Nucleotide Phosphodiesterases, Type 5; Deoxyuracil Nucleotides; Disease Models, Animal; Humans; Injections, Intraperitoneal; Mice; Mice, Inbred C57BL; Molecular Targeted Therapy; Neuronal Plasticity; Phosphodiesterase 5 Inhibitors; Phosphorylation; Piperazines; Proto-Oncogene Proteins c-bcl-2; Purines; Sildenafil Citrate; Sulfones

In addition to detrimental inflammation, widespread axon degeneration is an important feature of multiple sclerosis (MS) pathology and a major correlate for permanent clinical deficits. Thus, treatments that combine immunomodulatory and neuroprotective effects are beneficial for MS. Using myelin oligodendrocyte glycoprotein peptide 35-55 (MOG)-induced experimental autoimmune encephalomyelitis (EAE) as a model of MS, we recently showed that daily treatment with the phosphodiesterase 5 (PDE5) inhibitor sildenafil at peak disease rapidly ameliorates clinical symptoms and neuropathology (Pifarre et al., 2011). We have now investigated the immunomodulatory and neuroprotective actions of sildenafil treatment from the onset of EAE when the immune response prevails and show that early administration of the drug prevents disease progression. Ultrastructural analysis of spinal cord evidenced that sildenafil treatment preserves axons and myelin and increases the number of remyelinating axons. Immunostaining of oligodendrocytes at different stages of differentiation showed that sildenafil protects immature and mature myelinating oligodendrocytes. Brain-derived neurotrophic factor (BDNF), a recognized neuroprotectant in EAE, was up-regulated by sildenafil in immune and neural cells suggesting its implication in the beneficial effects of the drug. RNA microarray analysis of spinal cord revealed that sildenafil up-regulates YM-1, a marker of the alternative macrophage/microglial M2 phenotype that has neuroprotective and regenerative properties. Immunostaining confirmed up-regulation of YM-1 while the classical macrophage/microglial activation marker Iba-1 was down-regulated. Microarray analysis also showed a notable up-regulation of several members of the granzyme B cluster (GrBs). Immunostaining revealed expression of GrBs in Foxp3+-T regulatory cells (Tregs) suggesting a role for these proteases in sildenafil-induced suppression of T effector cells (Teffs). In vitro analysis of splenocytes from sildenafil-treated animals showed down-regulation of Th1/Th2/Th17 responses while Tregs were up-regulated. Additionally, sildenafil treatment prevented MOG-specific IgG2b accumulation in serum. Taken together these data demonstrates that daily sildenafil treatment from the initiation of EAE symptoms prevents further clinical deterioration by stimulating immunomodulatory and neuroprotective mechanisms. Importantly, we also show here that sildenafil enhances the ability of human

Topics: Animals; Axons; Brain; Cytokines; Disease Models, Animal; Disease Progression; Encephalomyelitis, Autoimmune, Experimental; Female; Freund's Adjuvant; Gene Expression Regulation; Humans; Mice; Mice, Inbred C57BL; Myelin Basic Protein; Myelin-Oligodendrocyte Glycoprotein; Oligodendroglia; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Severity of Illness Index; Sildenafil Citrate; Sulfones; T-Lymphocytes; Time Factors

Duchenne muscular dystrophy (DMD) is caused by a lack of the dystrophin protein and has no effective treatment at present. Zebrafish provide a powerful in vivo tool for high-throughput therapeutic drug screening for the improvement of muscle phenotypes caused by dystrophin deficiency. Using the dystrophin-deficient zebrafish, sapje, we have screened a total of 2640 compounds with known modes of action from three drug libraries to identify modulators of the disease progression. Six compounds that target heme oxygenase signaling were found to rescue the abnormal muscle phenotype in sapje and sapje-like, while upregulating the inducible heme oxygenase 1 (Hmox1) at the protein level. Direct Hmox1 overexpression by injection of zebrafish Hmox1 mRNA into fertilized eggs was found to be sufficient for a dystrophin-independent restoration of normal muscle via an upregulation of cGMP levels. In addition, treatment of mdx(5cv) mice with the PDE5 inhibitor, sildenafil, which was one of the six drugs impacting the Hmox1 pathway in zebrafish, significantly increased the expression of Hmox1 protein, thus making Hmox1 a novel target for the improvement of dystrophic symptoms. These results demonstrate the translational relevance of our zebrafish model to mammalian models and support the use of zebrafish to screen for new drugs to treat human DMD. The discovery of a small molecule and a specific therapeutic pathway that might mitigate DMD disease progression could lead to significant clinical implications.

Topics: Animals; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Drug Evaluation, Preclinical; Dystrophin; Heme Oxygenase-1; Mice; Mice, Inbred C57BL; Mice, Transgenic; Muscular Dystrophy, Duchenne; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; RNA, Messenger; Signal Transduction; Sildenafil Citrate; Sulfones; Up-Regulation; Zebrafish

Sensory neurons mediate diabetic peripheral neuropathy. Using a mouse model of diabetic peripheral neuropathy (BKS.Cg-m+/+Lepr(db)/J (db/db) mice) and cultured dorsal root ganglion (DRG) neurons, the present study showed that hyperglycemia downregulated miR-146a expression and elevated interleukin-1 receptor-activated kinase (IRAK1) and tumor necrosis factor receptor-associated factor 6 (TRAF6) levels in DRG neurons. In vitro, elevation of miR-146a by miR-146a mimics in DRG neurons increased neuronal survival under high-glucose conditions. Downregulation and elevation of miR-146a in DRG neurons, respectively, were inversely related to IRAK1 and TRAF6 levels. Treatment of diabetic peripheral neuropathy with sildenafil, a phosphodiesterase type 5 inhibitor, augmented miR-146a expression and decreased levels of IRAK1 and TRAF6 in the DRG neurons. In vitro, blockage of miR-146a in DRG neurons abolished the effect of sildenafil on DRG neuron protection and downregulation of IRAK1 and TRAF6 proteins under hyperglycemia. Our data provide the first evidence showing that miR-146a plays an important role in mediating DRG neuron apoptosis under hyperglycemic conditions.

Topics: Animals; Cells, Cultured; Diabetic Neuropathies; Disease Models, Animal; Down-Regulation; Ganglia, Spinal; Interleukin-1 Receptor-Associated Kinases; Male; Mice; Mice, Mutant Strains; MicroRNAs; Neurons; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Receptors, Leptin; Sildenafil Citrate; Sulfones; TNF Receptor-Associated Factor 6

We sought to determine the effect of sildenafil on retinal vascular changes in a mouse model of oxygen-induced retinopathy (OIR).. Vascular defects in OIR mice were quantified by measuring vaso-obliteration at postnatal days 12 and 17 (P12 and P17) and neovascularization at P17 to compare sildenafil-treated to dextrose-treated OIR mice. Retinal HIF1α protein expression was quantified by Western blotting and normalized to that of β-actin. Right ventricular hypertrophy was measured by Fulton's index as a surrogate for hyperoxia-induced pulmonary hypertension.. At P12, OIR mice treated with sildenafil demonstrated a 24% reduction in vaso-obliteration (P < 0.05), whereas at P17, treated animals showed a 50% reduction in neovascularization (P < 0.05) compared to dextrose-treated controls. Sildenafil-treated OIR mice had stabilization of retinal HIF1α at P12, immediately after hyperoxia. At P17, sildenafil-treated OIR mice had decreased HIF1α relative to untreated mice. OIR mice developed right ventricle hypertrophy that was significant compared to that in room air controls, which was abrogated by sildenafil.. Sildenafil treatment significantly decreased retinal vaso-obliteration and neovascularization in a mouse OIR model. These effects are likely due to sildenafil-induced HIF1α stabilization during hyperoxia exposure. Furthermore, we confirm disease overlap by showing that OIR mice also develop hyperoxia-induced right ventricular hypertrophy, which is prevented by sildenafil. This study is a first step toward delineating a potential therapeutic role for sildenafil in OIR and further suggests that there may be common pathophysiologic mechanisms underlying hyperoxia-induced retinal and pulmonary vascular disease.

Topics: Animals; Disease Models, Animal; Mice; Mice, Inbred C57BL; Piperazines; Purines; Retinal Neovascularization; Retinal Vessels; Retinopathy of Prematurity; Sildenafil Citrate; Sulfones; Vasoconstriction; Vasodilator Agents

Our previous studies support the protective effect of cGMP and cGMP-dependent protein kinase I (PKG-I) pathway on the development of renal fibrosis. Therefore, in the present studies, we determined whether pharmacologically or genetically increased PKG activity attenuates renal fibrosis in a unilateral ureteral obstruction (UUO) model and also examined the mechanisms involved. To increase PKG activity, we used the phosphodiesterase 5 inhibitor sildenafil and PKG transgenic mice. UUO model was induced in wild-type or PKG-I transgenic mice by ligating the left lateral ureteral and the renal fibrosis was observed after 14 days of ligation. Sildenafil was administered into wild-type UUO mice for 14 days. In vitro, macrophage and proximal tubular cell function was also analyzed. We found that sildenafil treatment or PKG transgenic mice had significantly reduced UUO-induced renal fibrosis, which was associated with reduced TGF-β signaling and reduced macrophage infiltration into kidney interstitial. In vitro data further demonstrated that both macrophages and proximal tubular cells were important sources of UUO-induced renal TGF-β levels. The interaction between macrophages and tubular cells contributes to TGF-β-induced renal fibrosis. Taken together, these data suggest that increasing PKG activity ameliorates renal fibrosis in part through regulation of macrophage and tubular cell function, leading to reduced TGF-β-induced fibrosis.

Topics: Actins; Angiotensin II; Animals; Cadherins; Cells, Cultured; Culture Media, Conditioned; Cyclic GMP-Dependent Protein Kinase Type I; Cytokines; Disease Models, Animal; Fibrosis; Inflammation Mediators; Kidney Diseases; Kidney Tubules, Proximal; Macrophages; Male; Mice; Mice, Transgenic; Phosphodiesterase 5 Inhibitors; Phosphorylation; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Smad2 Protein; Sulfones; Time Factors; Transforming Growth Factor beta1; Up-Regulation; Ureteral Obstruction

Inflammation, oxidative and nitrosative stress underlie depression being assessed in rodents by the systemic administration of lipopolysacharide (LPS). There is an increasing body of evidence of an involvement of nitric oxide (NO) pathway in depression, but this issue was not investigated in LPS-induced model. Thus, herein we evaluated the effects of NO-pathway-modulating drugs, named aminoguanidine, l-NAME, sildenafil and l-arginine, on the behavioral (forced swimming test [FST], sucrose preference [SPT] and prepulse inhibition [PPI] of the startle) and neurochemical (glutathione [GSH], lipid peroxidation, IL-1β) alterations in the prefrontal cortex, hippocampus and striatum as well as in BDNF levels in the hippocampus 24h after LPS (0.5mg/kg, i.p.) administration, a time-point related to depressive-like behavior. Twenty-four hours post LPS there was an increase in immobility time in the FST, decrease in sucrose preference and PPI levels accompanied by a decrease in GSH levels and an increase in lipid peroxidation, IL-1β and hippocampal BDNF levels suggestive of a depressive-like state. The pretreatment with the NOS inhibitors, l-NAME and aminoguanidine as well as sildenafil prevented the behavioral and neurochemical alterations induced by LPS, although sildenafil and l-NAME were not able to prevent the increase in hippocampal BDNF levels induced by LPS. The iNOS inhibitor, aminoguanidine, and imipramine prevented all behavioral and neurochemical alterations induced by LPS. l-arginine did not prevent the alterations in immobility time, sucrose preference and GSH induced by LPS. Taken together our results show that the NO-cGMP pathway is important in the modulation of the depressive-like alterations induced by LPS.

Topics: Animals; Antidepressive Agents; Arginine; Behavior, Animal; Brain; Brain-Derived Neurotrophic Factor; Cyclic GMP; Depressive Disorder; Disease Models, Animal; Enzyme Inhibitors; Guanidines; Imipramine; Interleukin-1beta; Lipopolysaccharides; Male; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Oxidative Stress; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Sulfones

Hypercholesterolaemia promotes erectile dysfunction through increased superoxide formation and decreased nitric oxide bioactivity in cavernosal tissue. The role of nitric oxide on erectile function is well known. Statins have lipid lowering properties and can modulate endothelial nitric oxide bioavailability. Sildenafil, enhances smooth muscle relaxation in corpus cavernosum. We investigated in-vitro effects of sildenafil and rosuvastatin on nonadrenergic, non-cholinergic and nitric oxide mediated cavernosal smooth muscle relaxation in metabolic syndrome rabbits, since alterations in this pathway are recognised in diabetic and hypercholesterolemic erectile dysfunction.. Ten male rabbits were fed a standard diet as control group, fourty male rabbits were fed a hypercholesterolemic diet for 12 weeks. Hypercholesterolemic group were divided for without treatment, rosuvastatin treatment, sildenafil treatment, and rosuvastatin + sildenafil treatment (N = 10 per groups).. Serum levels of cholesterol and glucose were significantly higher in the experimental group than in the control group (p < 0.05). After therapy no differences were found among the groups in relaxation responses to sodium nitroprusside. The relaxation responses to carbachol and EFS were significantly reduced in metabolic syndrome group to control group (p < 0.05), but there were no differences between the other groups and control group. There was a significantly lower in-vitro relaxation response in the metabolic syndrome rabbits than in controls and the others (p < 0.05).. Both agents improve in-vitro relaxation responses of erectile tissue from metabolic syndrome rabbits to endothelial non-adrenergic, non-cholinergic and nitric oxide. This finding supports to the results of other clinical studies with these drugs.

Topics: Animals; Disease Models, Animal; Fluorobenzenes; Hydroxymethylglutaryl-CoA Reductase Inhibitors; In Vitro Techniques; Male; Metabolic Syndrome; Muscle Contraction; Muscle Relaxation; Myocytes, Smooth Muscle; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Pyrimidines; Rabbits; Rosuvastatin Calcium; Sildenafil Citrate; Sulfonamides; Sulfones

Ischemia-reperfusion injury can cause testicular damage and phosphodiesterase inhibitors are reported to regulate antioxidant activity. We investigated the prevention of ipsilateral and contralateral testicular damage using 2 phosphodiesterase inhibitors after testicular detorsion in rats.. A total of 28 adult male rats were randomly divided into 4 groups of 7 each, including group 1-sham operation, group 2-testicular torsion and detorsion, group 3- testicular torsion and detorsion with sildenafil administration before detorsion and group 4- testicular torsion and detorsion with udenafil administration before detorsion. Tissue levels of malondialdehyde, total sulfhydryl and nitrite were evaluated, and histopathological changes in the groups were examined.. Compared to group 1 significantly increased tissue malondialdehyde (p = 0.001), significantly decreased total sulfhydryl (p = 0.038) and insignificantly increased nitrite were found in group 2. Compared to group 2 malondialdehyde decreased significantly and total sulfhydryl increased significantly in groups 3 and 4. The decrease in nitrite was insignificant in the latter 2 groups. Histopathology revealed increased hemorrhage, congestion and edema in group 2 rats. The testicular injury score was lower in groups 3 and 4. In group 2 grades II to IV injury was detected while most specimens in treated groups showed grade II injury.. This study indicates that intraperitoneal administration of sildenafil and udenafil efficiently suppresses radical production while decreasing histological changes after testicular ischemia-reperfusion injury.

Topics: Animals; Disease Models, Animal; Drug Therapy, Combination; Injections, Intraperitoneal; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Pyrimidines; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sildenafil Citrate; Sulfonamides; Sulfones; Testicular Diseases; Testis

This study investigates whether endothelin-1 (ET-1) mediates monocrotaline (MCT)-induced pulmonary artery hypertension (PAH) and right ventricular hypertrophy (RVH), and if so, whether the G-protein coupled receptor antagonist KMUP-1 (7-{2-[4-(2-chlorobenzene)piperazinyl]ethyl}-1,3-dimethylxanthine) inhibits ET-1-mediated PA constriction and the aforementioned pathological changes. In a chronic rat model, intraperitoneal MCT (60 mg/kg) induced PAH and increased PA medial wall thickening and RV/left ventricle + septum weight ratio on Day 21 after MCT injection. Treatment with sublingual KMUP-1 (2.5 mg/kg/day) for 21 days prevented these changes and restored vascular endothelial nitric oxide synthase (eNOS) immunohistochemical staining of lung tissues. Western blotting analysis demonstrated that KMUP-1 enhanced eNOS, soluble guanylate cyclase, and protein kinase G levels, and reduced ET-1 expression and inactivated Rho kinase II (ROCKII) in MCT-treated lung tissue over long-term administration. In MCT-treated rats, KMUP-1 decreased plasma ET-1 on Day 21. KMUP-1 (3.6 mg/kg) maximally appeared at 0.25 hours in the plasma and declined to basal levels within 24 hours after sublingual administration. In isolated PA of MCT-treated rats, compared with control and pretreatment with l-NG-nitroarginine methyl ester (100 μM), KMUP-1 (0.1-100 μM) inhibited ET-1 (0.01 μM)-induced vasoconstriction. Endothelium-denuded PA sustained higher contractility in the presence of KMUP-1. In a 24-hour culture of smooth muscle cells (i.e., PA smooth muscle cells or PASMCs), KMUP-1 (0.1-10 μM) inhibited RhoA- and ET-1-induced RhoA activation. KMUP-1 prevented MCT-induced PAH, PA wall thickening, and RVH by enhancing eNOS and suppressing ET-1/ROCKII expression. In vitro, KMUP-1 inhibited ET-1-induced PA constriction and ET-1-dependent/independent RhoA activation of PASMCs. In summary, KMUP-1 attenuates ET-1-induced/ET-1-mediated PA constriction, and could thus aid in the treatment of PAH caused by MCT.

Topics: Animals; Blood Pressure; Body Weight; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Endothelin-1; Guanylate Cyclase; Heart Rate; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; In Vitro Techniques; Male; Monocrotaline; Nitric Oxide Synthase Type III; Piperazines; Piperidines; Pulmonary Artery; Purines; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Receptors, G-Protein-Coupled; rho-Associated Kinases; rhoA GTP-Binding Protein; Signal Transduction; Sildenafil Citrate; Soluble Guanylyl Cyclase; Sulfonamides; Vasoconstriction; Xanthines

Inhibition of cGMP-specific phosphodiesterase 5 (PDE5) ameliorates pathological cardiac remodeling and has been gaining attention as a potential therapy for heart failure. Despite promising results in males, the efficacy of the PDE5 inhibitor sildenafil in female cardiac pathologies has not been determined and might be affected by estrogen levels, given the hormone's involvement in cGMP synthesis. Here, we determined that the heart-protective effect of sildenafil in female mice depends on the presence of estrogen via a mechanism that involves myocyte eNOS-dependent cGMP synthesis and the cGMP-dependent protein kinase Iα (PKGIα). Sildenafil treatment failed to exert antiremodeling properties in female pathological hearts from Gαq-overexpressing or pressure-overloaded mice after ovary removal; however, estrogen replacement restored the effectiveness of sildenafil in these animals. In females, sildenafil-elicited myocardial PKG activity required estrogen, which stimulated tonic cardiomyocyte cGMP synthesis via an eNOS/soluble guanylate cyclase pathway. In contrast, eNOS activation, cGMP synthesis, and sildenafil efficacy were not estrogen dependent in male hearts. Estrogen and sildenafil had no impact on pressure-overloaded hearts from animals expressing dysfunctional PKGIα, indicating that PKGIα mediates antiremodeling effects. These results support the importance of sex differences in the use of PDE5 inhibitors for treating heart disease and the critical role of estrogen status when these agents are used in females.

Topics: Animals; Cardiotonic Agents; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Disease Models, Animal; Estradiol; Estrogens; Female; GTP-Binding Protein alpha Subunits, Gq-G11; Guanylate Cyclase; Heart Diseases; Heart Failure; Humans; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide Synthase Type III; Ovariectomy; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Receptors, Atrial Natriuretic Factor; Sex Characteristics; Sildenafil Citrate; Sulfones; Treatment Outcome

Right ventricular (RV) function is an important determinant of prognosis in congenital heart diseases, pulmonary hypertension, and heart failure. Preventive sildenafil treatment has been shown to enhance systolic RV function and improve exercise capacity in a model of fixed RV pressure load. However, it is unknown whether sildenafil has beneficial effects when treatment is started in established RV dysfunction, which is clinically more relevant. Our aim was to assess the effects of sildenafil treatment on RV function and fibrosis in a model of established RV dysfunction due to fixed afterload. Rats were subjected to pulmonary artery banding (PAB), which induced RV dysfunction after 4 wk, characterized by reduced exercise capacity, decreased tricuspid annular plane systolic excursion, and RV dilatation. From week 4 onward, 50% of rats were treated with sildenafil (100 mg·kg(-1)·day(-1), n = 9; PAB-SIL group) or vehicle (n = 9; PAB-VEH group). At 8 wk, exercise capacity was assessed using cage wheels, and RV function was assessed using invasive RV pressure-volume measurements under anesthesia. Sildenafil treatment, compared with vehicle, improved RV ejection fraction (44 ± 2% vs. 34 ± 2%, P < 0.05, PAB-SIL vs. PAB-VEH groups), reduced RV end-diastolic pressure (2.3 ± 0.5 vs. 5.1 ± 0.9 mmHg, P < 0.05), and RV dilatation (end-systolic volume: 468 ± 45 vs. 643 ± 71 μl, P = 0.05). Sildenafil treatment also attenuated RV fibrosis (30 ± 6 vs. 17 ± 3‰, P < 0.05) but did not affect end-systolic elastance, exercise capacity, or PKG or PKA activity. In conclusion, sildenafil improves RV diastolic function and attenuates interstitial fibrosis in rats with established RV dysfunction, independent from afterload. These results indicate that sildenafil treatment has therapeutic potential for established RV dysfunction.

Topics: Animals; Cardiotonic Agents; Diastole; Disease Models, Animal; Exercise Tolerance; Fibrosis; Heart Ventricles; Hypertrophy, Right Ventricular; Male; Piperazines; Purines; Rats, Wistar; Recovery of Function; Sildenafil Citrate; Stroke Volume; Sulfones; Time Factors; Ventricular Dysfunction, Right; Ventricular Function, Right; Ventricular Pressure

To evaluate the effects of sildenafil on antioxidant enzyme activities, lipid peroxidation and histopathological changes in ovarian tissue after ischemia-reperfusion (I/R) injury in a rat model.. A total of 18 adult female Wistar albino rats weighing 200-250 g were studied as follows: (1) control group: sham operation, (2) I/R group: 3 h of reperfusion after 3 h of ischemia and (3) I/R + sildenafil group: 3 h of reperfusion after 3 h of ischemia; half an hour before reperfusion, sildenafil (1.4 mg·kg(-1)) was given by oral gavage. At the end of the reperfusion periods, the ovarian tissues were removed for histopathological examination and to determine malondialdehyde (MDA) levels and glutathione peroxidase, myeloperoxidase (MPO) and superoxide dismutase (SOD) activities.. The I/R group had higher ovarian tissue MDA levels than the control group and the IR + sildenafil group (p = 0.016 and p = 0.044, respectively). MPO activity was lower in the IR + sildenafil group compared with the I/R group (p = 0.022). SOD activity was lower in the I/R group compared with the control group and the I/R + sildenafil group (p = 0.030 and p = 0.015, respectively). The I/R + sildenafil group had improved histological appearance which was not different to the control group (p > 0.05).. The biochemical and histopathological results of this experimental study demonstrated that I/R injury in the ovary is ameliorated by sildenafil treatment.

Topics: Animals; Disease Models, Animal; Female; Ovarian Diseases; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Reperfusion Injury; Sildenafil Citrate; Sulfonamides

Fetal growth restriction (FGR) affects 3-8% of human pregnancies. Mouse models have provided important etiological data on FGR; they permit the assessment of treatment strategies on the physiological function of both mother and her developing offspring. Our study aimed to 1) develop a method to assess vascular function in fetal mice and 2) as a proof of principle ascertain whether a high dose of sildenafil citrate (SC; Viagra) administered to the pregnant dam affected fetal vascular reactivity. We developed a wire myography methodology for evaluation of fetal vascular function in vitro using the placenta-specific insulin-like growth factor II (Igf2) knockout mouse (P0; a model of FGR). Vascular function was determined in abdominal aortas isolated from P0 and wild-type (WT) fetuses at embryonic day (E) 18.5 of gestation. A subset of dams received SC 0.8 mg/ml via drinking water from E12.5; data were compared with water-only controls. Using wire myography, we found that fetal aortic rings exhibited significant agonist-induced contraction, and endothelium-dependent and endothelium-independent relaxation. Sex-specific alterations in reactivity were noted in both strains. Maternal treatment with SC significantly attenuated endothelium-dependent and endothelium-independent relaxation of fetal aortic rings. Mouse fetal abdominal aortas reproducibly respond to vasoactive agents. Study of these vessels in mouse genetic models of pregnancy complications may 1) help to delineate early signs of abnormal vascular reactivity and 2) inform whether treatments given to the mother during pregnancy may impact upon fetal vascular function.

Topics: Animals; Aorta, Abdominal; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Fetal Growth Retardation; Gestational Age; Insulin-Like Growth Factor II; Mice; Mice, Knockout; Phenotype; Phosphodiesterase 5 Inhibitors; Piperazines; Pregnancy; Purines; Sildenafil Citrate; Sulfones; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Pulmonary arterial hypertension (PAH) is a cardiovascular disorder associated with enhanced proliferation and suppressed apoptosis of pulmonary arterial smooth muscle cells (PASMCs). The sildenafil can regulate the Connexin (Cx) 43 in the PASMCs and thus inhibit the PASMCs proliferation and the remodeling of pulmonary arterial. However, how sildenafil exert regulation in the Cx40 in the PASMCs in PAH remains unclear.. Using the rat PAH model induced by the monocrotoline, we demonstrated that the Cx40 in the PASMCs is down-regulated in the PAH. The sildenafil promotes the up-regulation of Cx40 in the PASMCs via bone morphogenetic protein (BMP) signaling, accompanied by an anti-proliferative response in PASMCs. Inhibition of the BMP axis reverses the up-regulation of Cx40 and anti-proliferation of the sildenafil in these cells. In monocrotaline-induced PAH rat models, which display reduced levels of BMP signaling, this study further indicates that the BMP-Cx40 axis is activated in lungs following the sildenafil treatment. Furthermore, we also find in vitro that sildenafil increases the Cx40 expression of PASMCs isolated from MCT-PAH rats and inhibit the proliferation of these cells. These phenomenon are reversed by LDN-193189, the antagonist of type II receptor for bone morphogenetic protein (BMPR2) treatment, providing strong evidence for the protect effect of sildenafil and the BMP-Cx40 axis involvement.. Taken together, these data suggest the sildenafil activate BMP-Cx40 signaling in the PAH. This axis may be a potential therapeutic target in PAH.

Topics: Animals; Blotting, Western; Bone Morphogenetic Proteins; Connexins; Disease Models, Animal; Gap Junction alpha-5 Protein; Hypertension, Pulmonary; Male; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Signal Transduction; Sildenafil Citrate; Sulfonamides; Vascular Remodeling; Vasodilator Agents

Sildenafil, the active ingredient in Viagra, has been reported to cause transient visual disturbance from inhibition of phosphodiesterase 6 (PDE6), a key enzyme in the visual phototransduction pathway. This study investigated the effects of sildenafil on the rd1(+/-) mouse, a model for carriers of Retinitis Pigmentosa which exhibit normal vision but may have a lower threshold for cellular stress caused by sildenafil due to a heterozygous mutation in PDE6. Sildenafil caused a dose-dependent decrease in electroretinogram (ERG) responses of normal mice which mostly recovered two days post administration. In contrast, rd1(+/-) mice exhibited a significantly reduced photoreceptor and a supernormal bipolar cell response to sildenafil within 1 h of treatment. Carrier mice retinae took two weeks to return to baseline levels suggesting sildenafil has direct effects on both the inner and outer retina and these effects differ significantly between normal and carrier mice. Anatomically, an increase in expression of the early apoptotic marker, cytochrome C in rd1(+/-) mice indicated that the effects of sildenafil on visual function may lead to degeneration. The results of this study are significant considering approximately 1 in 50 people are likely to be carriers of recessive traits leading to retinal degeneration.

Topics: Animals; Cytochromes c; Disease Models, Animal; Dose-Response Relationship, Drug; Electroretinography; Female; Fluorescent Antibody Technique, Indirect; Glial Fibrillary Acidic Protein; Heterozygote; In Situ Nick-End Labeling; Male; Mice; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Photoreceptor Cells, Vertebrate; Piperazines; Purines; Retina; Retinal Bipolar Cells; Retinitis Pigmentosa; Sildenafil Citrate; Sulfones

In order to address the gap in our understanding of the pathogenesis and pathophysiology of PE, we optimized the NOS inhibition animal model by comparing changes in different parameters at various time frames during pregnancy, in both early and late-onset PE.. 120 nulliparous Sprague-Dawley rats were divided into 5 groups (n=24). A pregnant control, two groups that represented early and late-onset PE and two groups that were treated with sildenafil citrate (SC) to show reversal of the pre-eclamptic-like symptoms.. Our results showed that treatment with L-NAME caused significant changes in physiological parameters for both early and late-onset PE groups. There was a significant increase in systolic blood pressure (SBP) levels in the early-onset PE group (128.5±5.71 mmHg) and late-onset PE group (128.3±6.15 mmHg) on day 19 compared to the SBPs on day 0, (p<0.01). Urine excretion volumes in the early-onset PE group (13.62±3.18 mL) and in the late-onset PE (13.28±2.60 mL), compared to the pregnant control group (11.96±1.9 mL) were also increased (p<0.05). There was also an increase in total urinary protein in the early-onset PE group (0.62±0.08 g/L and the late-onset PE group (0.45±0.05 g/L), when compared to the pregnant control group (0.38±0.07) (p<0.05). We also found a decrease in fetal numbers in the PE group in comparison to the pregnant control and SC treated groups. The remission of these signs was seen after delivery of the fetuses. We also demonstrated that treatment of this syndrome with SC prevented the development of these signs.. The NOS inhibition model can be used for the study of the pathogenesis and pathophysiology of PE, since the pathogenic changes mimic those of early and late-PE.

Topics: Animals; Blood Pressure; Disease Models, Animal; Female; Fetal Weight; Litter Size; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Parturition; Piperazines; Pre-Eclampsia; Pregnancy; Proteinuria; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfonamides; Time Factors; Urine; Vasodilator Agents

Erectile dysfunction is a common complication for patients undergoing surgeries for prostate, bladder, and colorectal cancers, due to damage of the nerves associated with the major pelvic ganglia (MPG). Functional re-innervation of target organs depends on the capacity of the neurons to survive and switch towards a regenerative phenotype. PDE5 inhibitors (PDE5i) have been successfully used in promoting the recovery of erectile function after cavernosal nerve damage (BCNR) by up-regulating the expression of neurotrophic factors in MPG. However, little is known about the effects of PDE5i on markers of neuronal damage and oxidative stress after BCNR. This study aimed to investigate the changes in gene and protein expression profiles of inflammatory, anti-inflammatory cytokines and oxidative stress related-pathways in MPG neurons after BCNR and subsequent treatment with sildenafil. Our results showed that BCNR in Fisher-344 rats promoted up-regulation of cytokines (interleukin- 1 (IL-1) β, IL-6, IL-10, transforming growth factor β 1 (TGFβ1), and oxidative stress factors (Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, Myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS), TNF receptor superfamily member 5 (CD40) that were normalized by sildenafil treatment given in the drinking water. In summary, PDE5i can attenuate the production of damaging factors and can up-regulate the expression of beneficial factors in the MPG that may ameliorate neuropathic pain, promote neuroprotection, and favor nerve regeneration.

Topics: Animals; Cytokines; Disease Models, Animal; Ganglia; Heme Oxygenase-1; Male; NADPH Oxidases; Nerve Tissue; Nitric Oxide Synthase Type II; Oxidative Stress; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Inbred F344; Sildenafil Citrate; Sulfonamides; Transcriptome; Up-Regulation

There is considerable interest in the pleiotropic effects of statins and their potential role in the treatment of pulmonary hypertension. Previous experimental findings indicate that a combination of lipophilic statins with phosphodiesterase type-5 inhibitor, sildenafil, can offer preventive effects on rat monocrotaline-induced pulmonary hypertension. The present study is aimed to assess whether therapeutic regimen provides any benefits. Seven days after pulmonary hypertension induction, hydrophilic rosuvastatin and sildenafil were given for 14 days to male Wistar outbred rats. Right ventricular pressure, right ventricle mass and three biomarkers were evaluated after 21 days: brain natriuretic peptide, high-density lipoprotein cholesterol and vascular endothelial growth factor. The present study demonstrates that administration of hydrophilic statin with sildenafil results in reduction of pulmonary vascular remodeling and right ventricular pressure. The results of biochemical measurements may suggest that statins play a positive role in right ventricle function or the process of angiogenesis in pulmonary hypertension development.

Topics: Animals; Antihypertensive Agents; Arterial Pressure; Biomarkers; Cholesterol, HDL; Disease Models, Animal; Drug Therapy, Combination; Fluorobenzenes; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Monocrotaline; Natriuretic Peptide, Brain; Phosphodiesterase 5 Inhibitors; Piperazines; Pulmonary Artery; Purines; Pyrimidines; Rats, Wistar; Rosuvastatin Calcium; Sildenafil Citrate; Sulfonamides; Time Factors; Vascular Endothelial Growth Factor A; Vascular Remodeling; Vasodilator Agents; Ventricular Function, Right; Ventricular Pressure

To evaluate the effects of bosentan, sildenafil, and combined therapy on the cardiovascular system using impedance cardiography (ICG) in rats with monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH).. Seventy male Wistar-albino rats were randomized into five groups. A single dose of MCT was given to all rats, except to the control group. After 4 weeks, bosentan, sildenafil, and combined treatment was started and lasted for 3 weeks. The last group that developed PAH did not receive any medication. Echocardiographic evaluation was performed to determine the PAH development. Thoracic fluid content index (TFCI), stroke volume index (SI), heart rate (HR), cardiac index (CI), and myocardial contractility index (IC) were determined. All procedures were performed at the baseline and after 4 and 7 weeks.. Echocardiographic parameters showed that the all MCT-injected rats developed PAH. There were no significant inter- and intra-group differences in TFCI, SI, and IC (P>0.05), but at the 7th week, CI value in the sildenafil-treated PAH rats was significantly higher than in other groups and HR of PAH rats with combined therapy was significantly lower than in other groups.. PAH did not have an effect on LV function of rats, or if it did, the effect was compensated by physiological processes. Also, sildenafil treatment deteriorated the LV cardiac index.

Topics: Animals; Blood Pressure; Bosentan; Cardiography, Impedance; Disease Models, Animal; Drug Therapy, Combination; Echocardiography; Endothelin Receptor Antagonists; Heart Ventricles; Hypertension, Pulmonary; Male; Monocrotaline; Phosphodiesterase 5 Inhibitors; Piperazines; Pulmonary Artery; Purines; Rats, Wistar; Sildenafil Citrate; Sulfonamides

Contrast-induced acute kidney injury (CIAKI) is one of the commonest complications associated with contrast media (CM). Although the exact etiology of CIAKI remains unclear, one hypothesis involves vasoconstriction of afferent arterioles resulting in renal ischemia. Increased renal blood flow, therefore, might represent an attractive target for the treatment of CIAKI. In this study we evaluated the protective effects of the phosphodiesterase type 5 (PDE5) inhibitor, sildenafil citrate, in a rabbit model of CIAKI. New Zealand white rabbits were used due to their susceptibility to CIAKI. To evaluate the effects of sildenafil, the drug was administered before CM infusion and repeatedly throughout the remainder of the experiment (6 mg/kg, p.o.). Animals were sacrificed after 48 hours and kidneys were prepared for histological evaluation. Intravenous administration of CM produced marked kidney injury. Serum creatinine concentrations were elevated within two hours of the infusion and remained elevated for the duration of the experiment. Histological evaluation of the kidneys revealed significant tubular necrosis. The effects of the CM were dose dependent. Treatment with sildenafil was associated with lesser degree of histological injury, attenuation in markers of acute kidney injury (48 hour creatinine 1.54±0.21 versus 4.42±1.31 mg/dl, p<0.05) and reduction in electrolyte derangement (percent change in serum K+ at 48 hours 2.55±3.80% versus 15.53±4.47%, p<0.05; serum Na+ at 48 hours -0.14±0.26% versus -1.97±1.29%, p = 0.20). The results suggest a possible role for PDE5 inhibitors in the treatment of CIAKI and warrant further evaluation to determine the exact mechanism of protection.

Topics: Acute Kidney Injury; Animals; Contrast Media; Creatinine; Disease Models, Animal; Glomerular Filtration Rate; Kidney; Male; Phosphodiesterase 5 Inhibitors; Rabbits; Sildenafil Citrate; Urological Agents

Lung hypoplasia, pulmonary persistent hypertension of the newborn and its morphological changes are the main features in congenital diaphragmatic hernia (CDH). This study was undertaken to investigate if antenatal use of sildenafil and/or bosentan attenuates vascular remodeling, promotes branching, and improves alveolarization in experimental nitrofeninduced CDH.. Nitrofen (100 mg) was gavage-fed to pregnant rats at post conception day (PCD) 9 to induce CDH. The rats were randomized to 5 groups: 1) control; 2) nitrofen; 3) nitrofen+sildenafil 100 mg/kg per day at PCD 16-20; 4) nitrofen+bosentan 30 mg/kg per day, at PCD 16-20, and 5) nitrofen+bosentan+sildenafil, same doses and administration days. After cesarean delivery, the offsprings were sacrificed. The diaphragmatic defect and pulmonary hypoplasia were identified, and the lungs were dissected. Arterial wall thickness, bronchiolar density and alveolarization were assessed.. The offsprings with CDH were characterized by severe pulmonary hypoplasia (lung weight-to-body weight ratio: 0.0263 [95% confidence interval (CI) 0.0242-0.0278)] in the nitrofen group versus 0.0385 (95% CI 0.0355-0.0424) in the control group (P=0.0001). Pulmonary arterial wall thickness was decreased to 3.0 (95% CI 2.8-3.7) μm in the nitrofen+sildenafil group versus 5.0 (95% CI 4.1-4.9) μm in the nitrofen group (P=0.02). Terminal bronchioles increased to 13.7 (95% CI 10.7-15.2) μm in the nitrofen+bosentan group in contrast to 8.7 (95% CI 7.2-9.4) μm in the nitrofen group (P=0.002). More significant differences (P=0.0001) were seen in terminal bronchioles in the nitrofen+sildenafil+bosentan group than in the nitrofen group [14.0 (95% CI 12.5-15.4) μm versus 8.5 (95% CI 7.1-9.3) μm]. Pulmonary arterial wall thickness was also decreased in the former group.. In this rat model, antenatal treatment with sildenafil attenuates vascular remodeling. Bosentan promotes the development of terminal bronchioles in nitrofen-induced CDH.

Topics: Animals; Bosentan; Disease Models, Animal; Female; Hernias, Diaphragmatic, Congenital; Lung; Lung Diseases; Phenyl Ethers; Piperazines; Pregnancy; Purines; Random Allocation; Rats; Rats, Wistar; Sildenafil Citrate; Sulfonamides; Vascular Remodeling

Thrombosis of vascular anastomosis in the field of reconstructive microsurgery is a clinical problem of extraordinary importance for the devastating consequences for affected patients. Sildenafil has been shown to be relaxing vascular action on the peripheral vascular system in vivo and have an ability to reduce platelet aggregation. There is no study up to date on the effect of sildenafil on microvascular anastomosis, neither experimental studies nor clinical settings.. A purposeful thrombotic back-wall stitch was performed in the groin flap pedicle to obtain an anastomosis with thrombotic potential where the drug effect was studied.. Data in the experimental group treated with papaverine or sildenafil indicate a considerable decrease in the percentage of necrotic flaps (20% necrotic flaps in papaverine group versus 30% necrotic flaps in sildenafil group) in comparison with control group (60% necrotic flaps). In papaverine group, in 100% cases, flap necrosis was established in the first 24 h, but in sildenafil group, 66% flap necrosis was established between the second and the seventh postoperative days.. The study did not demonstrate significant differences between the groups, but it does suggest a benefit in applying papaverine and sildenafil in the anastomosis with already thrombogenetic disease, compared to the nonapplication of antithrombotic drugs. The establishment of thrombosis in the necrotic flaps in the group treated with sildenafil was later than in the group treated with papaverine, with a statistical trend but without becoming significant.

Topics: Anastomosis, Surgical; Animals; Disease Models, Animal; Free Tissue Flaps; Humans; Male; Microsurgery; Necrosis; Piperazines; Postoperative Complications; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfonamides; Sutures; Thrombosis; Vasodilator Agents

The senescence accelerated mouse-prone 8 (SAMP8) strain of mice is an experimental model of accelerated senescence that also shares several pathological features with Alzheimer's disease. Among them, cognitive impairments and abnormal hyperphosphorylation of tau are ameliorated by the phosphodiesterase 5 inhibitor sildenafil, possibly through the modulation of Cdk5/p25 and Akt/GSK-3β pathways. Here we studied the implication of protein phosphatase 2A (PP2A) and c-Jun N-terminal kinase (JNK) in the therapeutic effects of sildenafil. Results demonstrated that there were no differences in hippocampal PP2A protein levels or activity (measured by its inactive isoform phopho-PP2A Y307) when we compared 6-month old SAMP8 mice and age-matched control, SAMR1 mice, treated with saline or sildenafil (7.5mg/kg i.p. for 4 weeks). However, this same treatment of sildenafil, that had been shown to reverse the cognitive impairment and tau hyperphosphorylation in this animal model, also reversed the increased levels of activated JNK (p-JNK) found in the hippocampus of SAMP8 mice. Moreover, the administration of the JNK inhibitor, D-JNKI-1 (0.2mg/kg i.p. for 3 weeks) also ameliorated the cognitive deficits shown by SAMP8 mice in the Morris water maze and decreased hippocampal levels of phospho-c-Jun(Ser73). When phosphorylated tau (AT8 epitope) was analyzed a significant reduction was observed in the hippocampus of D-JNKI-1 treated SAMP8 mice, providing a plausible explanation for the attenuation of cognitive decline shown by these animals. These findings suggest the involvement of the JNK pathway on tau pathology and cognitive deficits shown by 6-month old SAMP8 mice. They also point to the modulation of this kinase to be among the mechanisms responsible for the beneficial effects shown by sildenafil.

Topics: Aging; Animals; Cognition Disorders; Disease Models, Animal; Hippocampus; Male; MAP Kinase Signaling System; Maze Learning; Mice; Phosphorylation; Piperazines; Purines; Sildenafil Citrate; Space Perception; Sulfones; tau Proteins; Tauopathies; Vasodilator Agents

To investigate the effect of sildenafil citrate (SC) on skeletal muscle ischemia-reperfusion (IR) injury in rats.. Adult male Wistar rats were randomized into three groups: vehicle-treated control (CTG), sildenafil citrate-treated (SCG), and sham group (SG). CTG and SCG had femoral artery occluded for 6 hours. Saline or 1 mg/kg of SC was given 5.5 hours after occlusion. SG had a similar procedure without artery occlusion. Soleus muscle samples were acquired 4 or 24h after the reperfusion. Immunohistochemistry caspase-3 analysis was used to estimate apoptosis using the apoptotic ratio (computed as positive/negative cells). Wilcoxon rank-sum or Kruskal-Wallis tests were used to assess differences among groups.. Eighteen animals were included in the 4h reperfusion groups and 21 animals in the 24h reperfusion groups. The mean apoptotic ratio was 0.18 ± 0.1 for the total cohort; 0.14 ± 0.06 for the 4h reperfusion groups and 0.19 ± 0.08 for the 24h groups (p<0.05). The SCG had lower caspase-3 ratio compared to the control groups at the 24h reperfusion time point (p<0.05).. Sildenafil citrate administration after the onset of the ischemic injury reduces IR-induced cellular damage in skeletal muscle in this rat hindlimb ischemia model.

Topics: Animals; Caspase 3; Disease Models, Animal; Extremities; Male; Muscle, Skeletal; Phosphodiesterase 5 Inhibitors; Piperazines; Protective Agents; Purines; Random Allocation; Rats; Rats, Wistar; Reperfusion Injury; Sildenafil Citrate; Sulfones; Time Factors

We investigated if soluble guanylate cyclase stimulation either alone or in combination with phosphodiesterase-5 (PDE5) inhibition could prevent pressure overload-induced right ventricular (RV) hypertrophy and failure.. The soluble guanylate cyclase stimulator BAY 41-2272 (BAY, 10 mg · kg⁻¹ · d⁻¹) either alone or in combination (BAY + SIL) with a PDE5 inhibitor sildenafil (SIL, 100 mg · kg⁻¹ · d⁻¹) was examined for prevention of RV hypertrophy and failure in Wistar rats (n = 73) operated by pulmonary trunk banding.. All treatments failed to inhibit the development of RV hypertrophy and failure. In the BAY and BAY + SIL groups, there was an increased mortality. Mean arterial blood pressure was lowered and cardiac output increased in the BAY + SIL group. Systolic RV pressure was increased in the BAY and BAY + SIL groups possibly because of an inotropic response and/or increased venous return.. Stimulation of soluble guanylate cyclase by BAY 41-2272 alone or in combination with sildenafil failed to prevent the development of RV hypertrophy and failure in rats subjected to pulmonary trunk banding. An increased mortality was observed in animals treated by BAY 41-2272 alone and in combination with sildenafil.

Topics: Animals; Blood Pressure; Cardiac Output; Cyclic GMP; Disease Models, Animal; Disease Progression; Enzyme Activators; Guanylate Cyclase; Heart Failure; Heart Ventricles; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Pyrazoles; Pyridines; Random Allocation; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Sildenafil Citrate; Soluble Guanylyl Cyclase; Sulfones; Survival Analysis

Vascular bubble formation after decompression contributes to endothelial injuries which form the basis for the development of decompression sickness (DCS). Nitric oxide (NO) is a powerful vasodilator that contributes to vessel homeostasis. It has been shown that NO-releasing agent may reduce bubble formation and prevent serious decompression sickness. The use of sildenafil, a well-known, phosphodiesterase-5 blocker, which act by potentiating the vasodilatory effect on smooth muscle relaxation, has never been studied in DCS. The purpose of the present study was to evaluate the clinical effects of sildenafil pre-treatment on DCS in a rat model. 67 rats were subjected to a simulated dive at 90 msw for 45 min before staged decompression. The experimental group received 10 mg/kg of sildenafil one hour before exposure (n = 35) while controls were not treated (n = 32). Clinical assessment took place over a period of 30 min after surfacing. At the end, blood samples were collected for blood cells counts and the level of circulating bubbles in the right cavities was quantified. There were significantly more manifestations of DCS in the sildenafil group than in the controls (34.3% vs 6.25%, respectively, p = 0.012). Platelet count was more reduced in treated rats than in controls (-21.7% vs -7%, respectively, p = 0.029), whereas bubble grades did not differ between groups. We concluded that pre-treatment with sildenafil promotes the onset and severity of neurological DCS. When considering the use of phosphodiesterase-5 blockers in the context of diving, careful discussion with physician should be recommended.

Topics: Animals; Blood Cell Count; Decompression Sickness; Disease Models, Animal; Male; Piperazines; Purines; Rats; Sildenafil Citrate; Sulfones; Vasodilator Agents

Shortening tuberculosis treatment could significantly improve patient adherence and decrease the development of drug resistance. Phosphodiesterase inhibitors (PDE-Is) have been shown to be beneficial in animal models of tuberculosis. We assessed the impact of PDE-Is on the duration of treatment in tuberculous mice.. We analyzed the time to death in Mycobacterium tuberculosis-infected mice receiving type 4 PDE-Is (rolipram and cilomilast) and the impact on bacterial burden, time to clearance, and relapse when types 3 and 5 PDE-Is (cilostazol and sildenafil, respectively) and rolipram were added to the standard treatment. We investigated pharmacokinetic interactions between PDE-Is (cilostazol and sildenafil) and rifampin.. The type 4 PDE-Is rolipram and cilomilast accelerated the time to death in tuberculous mice. The addition of rolipram to standard tuberculosis treatment increased bacterial burden and did not decrease the time to bacterial clearance in the lung, while the addition of the cilostazol and sildenafil reduced the time to clearance by 1 month. Cilostazol and sildenafil did not have negative pharmacokinetic interactions with rifampin.. Type 4 PDE-Is may increase the severity of tuberculosis and should be carefully investigated for use in patients with latent or active tuberculosis. Cilostazol and sildenafil may benefit tuberculosis patients by shortening the duration of therapy.

Topics: Animals; Antitubercular Agents; Bacterial Load; Cilostazol; Disease Models, Animal; Drug Interactions; Humans; Mice; Mice, Inbred BALB C; Mycobacterium tuberculosis; Phosphodiesterase Inhibitors; Piperazines; Purines; Rifampin; Rolipram; Sildenafil Citrate; Sulfones; Survival Analysis; Tetrazoles; Treatment Outcome; Tuberculosis

Memory deficit is a marker of Alzheimer's disease (AD) that has been highly associated with the dysfunction of cyclic GMP (cGMP) signaling and an ongoing inflammatory process. Phosphodiesterase-5 (PDE5) inhibitors prevent the breakdown of cGMP and are currently studied as a possible target for cognitive enhancement. However, it is still unknown whether inhibition of PDE5 reversed β-amyloid peptide (Aβ)-induced neuroinflammation in APP/PS1 transgenic (Tg APP/PS1) mice. The present study evaluated the cognitive behaviors, inflammatory mediators, and cGMP/PKG/pCREB signaling in 15-month-old Tg APP/PS1 mice and age-matched wild-type (WT) mice that were treated with PDE5 inhibitor sildenafil and the inhibitor of cGMP-dependent protein kinase Rp-8-Br-PET-cGMPS. In comparison with WT mice, Tg APP/PS1 mice were characterized by impaired cognitive ability, neuroinflammatory response, and down-regulated cGMP signaling. Sildenafil reversed these memory deficits and cGMP/PKG/pCREB signaling dysfunction; it also reduced both the soluble Aβ1-40 and Aβ1-42 levels in the hippocampus. These effects of sildenafil were prevented by intra-hippocampal infusion of the Rp-8-Br-PET-cGMPS. These results suggest that sildenafil could restore cognitive deficits in Tg APP/PS1 mice by the regulation of PKG/pCREB signaling, anti-inflammatory response and reduction of Aβ levels.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Analysis of Variance; Animals; Cognition Disorders; Cyclic GMP; Cytokines; Disease Models, Animal; Dose-Response Relationship, Drug; Encephalitis; Exploratory Behavior; Humans; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Phosphodiesterase 5 Inhibitors; Piperazines; Presenilin-1; Purines; Recognition, Psychology; RNA, Messenger; Sildenafil Citrate; Sulfones; Thionucleotides

Preeclampsia is a complication of pregnancy that is marked by hypertension, proteinuria, and maternal endothelial dysfunction. A central factor in the etiology of the disease is the development of placental hypoxia/ischemia, which releases pathogenic soluble factors. There is currently no effective treatment for preeclampsia, but the phosphodiesterase-5 (PDE-5) inhibitor sildenafil has been suggested, as PDE-5 is enriched in the uterus, and its antagonism could improve uteroplacental function. Here, we report in the reduced uterine perfusion pressure (RUPP) rat model that administration of oral sildenafil is effective in attenuating placental ischemia-induced hypertension during gestation. RUPP animals have significantly elevated arterial pressure compared with control animals (132 ± 3 vs. 100 ± 2 mmHg; P < 0.05). Administration of oral sildenafil (45 mg·kg⁻¹·day⁻¹) had no effect on blood pressure in control rats but decreased pressure in RUPP rats (115 ± 1 mmHg; P < 0.05). RUPP induced changes in placental sFlt-1, and vascular endothelial growth factor (VEGF) was unaffected by sildenafil administration, as was the decrease in free plasma VEGF. RUPP animals had a significant increase in medullary PDE-5/β-actin ratio (1 ± 0.14 vs. 1.63 ± 0.18; P < 0.05) expression with a resulting reduction in renal medullary cGMP (1.5 ± 0.15 vs. 0.99 ± 0.1 pmol/μg protein, P < 0.05) compared with controls. Although sildenafil had no effect on renal medullary cGMP in control animals, it significantly increased cGMP in RUPP animals (1.3 ± 0.1 pmol/μg protein; P < 0.05). These data suggest that sildenafil might provide an effective therapeutic option for the management of hypertension during preeclampsia.

Topics: Actins; Administration, Oral; Animals; Antihypertensive Agents; Arterial Pressure; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Female; Ischemia; Kidney Medulla; Phosphodiesterase 5 Inhibitors; Piperazines; Placenta; Placental Circulation; Pre-Eclampsia; Pregnancy; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-1; Vasodilator Agents

Neurogenic bladder is a common complication of several central nervous system injuries. Statins and phosphodiesterase-5 (PDE-5) inhibitors are reportedly beneficial in neural injuries and urinary system dysfunction. The effect of simvastatin, sildenafil and tadalafil on several renal function indices of an animal model of neurogenic bladder was investigated.. Forty male rats were assessed in five equal groups. Dura mater and the cord were injured with an aneurysmal clamp at the level of T9-T10 in all rats except in sham group. The sham and control groups (treated by normal saline), simvastatin (4 mg/kg), sildenafil (5 mg/kg), and tadalafil (2 mg/kg) groups received treatment (i.p.) for seven consecutive days following injury. Renal system and motor functions were assessed at day 28 following injury. Data were analyzed by analysis of variance followed by the Student-Newman-Keuls post hoc test.. Simvastatin improved both the renal and the motor function compared with the control group. However, sildenafil and tadalafil could only improve the motor function but could not make any significant differences in renal indices in comparison with the control group.. Statins can effectively improve the motor and renal functions in a condition of renal dysfunction in a rat model of neurogenic bladder. PDE-5 inhibitors could help to improve motor function, but are not helpful in renal function, at least in short time.

Topics: Analysis of Variance; Animals; Carbolines; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Kidney; Male; Organ Size; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Simvastatin; Sulfones; Tadalafil; Urinary Bladder; Urinary Bladder, Neurogenic; Urine

Lung ischemia-reperfusion (I/R) injury plays an important role in lung transplantation. Less well known is the role of sildenafil in lung I/R injury; therefore, we attempted to determine whether sildenafil could alleviate lung apoptosis and tissue injury in a rat model.. Forty male Sprague-Dawley rats were randomized into four groups: saline + sham, saline + I/R, sildenafil + sham, and sildenafil + I/R groups. Three hours before the operation, each rat received normal saline or sildenafil (10 mg/kg) by lavage. The animals designed to I/R injury were subjected to 2 h of ischemia induced by occlusion of left pulmonary artery, veins, and bronchus, followed by reperfusion for 2 h. The lung tissue was harvested for the analysis of the expression of Bax, Bcl-2, p53, caspase 3, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and wet/dry (W/D) weight ratio.. Compared with the saline + sham group, the saline + I/R group had significant increases in Bax, p53, Bax/Bcl-2 ratio, caspase 3, IL-6, TNF-α, and W/D weight ratio but a decrease in Bcl-2 (P < 0.05). Compared with the saline + I/R group, sildenafil + I/R group had significant decreases in Bax, p53, Bax/Bcl-2 ratio, caspase 3, IL-6, TNF-α level, and W/D weight ratio but an increase in Bcl-2 expression (P < 0.05). Compared with the sildenafil + sham group, there were significant increases in p53 and TNF-α expression in the sildenafil + I/R group (P < 0.05).. Pretreatment with sildenafil alleviates lung apoptosis and tissue injury in a rat model.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Caspase 3; Disease Models, Animal; Interleukin-6; Lung; Lung Transplantation; Male; Piperazines; Proto-Oncogene Proteins c-bcl-2; Pulmonary Circulation; Purines; Random Allocation; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sildenafil Citrate; Sulfones; Tumor Necrosis Factor-alpha; Tumor Suppressor Protein p53; Vasodilator Agents

It is well known that enhanced production of reactive oxygen species (ROS) leads to oxidative stress observed in atherosclerosis and that ROS can also cause damage in cellular macromolecules, including DNA. Considering previous report that sildenafil, an inhibitor of phosphodiesterase 5 (PDE5), has antioxidant effects, in the present study we evaluated the effect of this drug on genotoxicity of blood mononuclear cells (MNC) and liver cells from atherosclerotic apolipoprotein E knockout mice (apoE(-/-)).. ROS production in MNC was evaluated by flow cytometry with the fluorescent dye dihydroethidium (DHE), a method that has been used to quantify the production of superoxide anion, and DNA damage was evaluated in both MNC and liver cells using the alkaline comet assay. Sildenafil-administered apoE(-/-) mice were compared with strain-matched mice administered with vehicle and with C57BL/6 wild-type (WT) mice.. MNC from apoE(-/-) vehicle exhibited a 2-fold increase in production of superoxide anion in comparison with WT. In contrast, sildenafil-administered apoE(-/-) mice showed superoxide anion levels similar to those observed in WT mice. Similarly, MNC and liver cells from apoE(-/-) vehicle mice showed a 4-fold and 2-fold augmented DNA fragmentation compared with WT, respectively, and sildenafil-administered apoE(-/-) mice exhibited minimal DNA damage in those cells similar to WT mice.. ApoE(-/-) mice chronically administered with sildenafil exhibited reduced levels of superoxide anion in MNC and less DNA fragmentation in MNC and liver cells, which are biomarkers of genotoxicity. Therefore, sildenafil may offer a new perspective to the use of PDE5 inhibitors to protect against DNA damage, in cells involved in the inflammatory and dyslipidemic processes that accompany atherosclerosis.

Topics: Animals; Apolipoproteins E; Atherosclerosis; Comet Assay; Disease Models, Animal; DNA Fragmentation; Leukocytes, Mononuclear; Lipoproteins; Liver; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Superoxides; Triglycerides

Sildenafil, a selective phosphodiesterase 5 inhibitor (PDE5), has been recently reported to have both pro- and anticonvulsant action in various experimental models of seizures and epilepsy. Furthermore, it affects anticonvulsant action of some antiepileptic drugs (AEDs) in mice seizure tests and both pharmacodynamic and pharmacokinetic interactions were noted. The present study was carried out to investigate influence of sildenafil on the threshold for 6 Hz-induced psychomotor seizures in mice. Effect of sildenafil on activity of some AEDs, i.e., phenobarbital (PB), clonazepam (CZP), ethosuximide (ETS), valproic acid (VPA), tiagabine (TGB), oxcarbazepine (OXC) and levetiracetam (LEV), in 6 Hz test was also examined. Moreover, combination of sildenafil with LEV was investigated in terms of influence on motor coordination (determined by the chimney test), muscular strength (evaluated in the grip-strength test) and long-term memory (assessed in the passive avoidance task) in mice. To determine the type of pharmacological interaction between sildenafil and LEV, free plasma and total brain concentrations of this AED were determined by LC-MS/MS method. Sildenafil at a dose ranging from 10 to 40 mg/kg statistically increased psychomotor seizure threshold in mice. Moreover, sildenafil enhanced the anticonvulsant action of all the studied AEDs in this test. Interactions between this PDE5 inhibitor and PB, CZP, ETS, TGB and OXC seem to be pharmacodynamic. Since sildenafil increased free plasma and total brain concentration of LEV, interactions between these drugs have pharmacokinetic nature. This kind of interaction was also noted between sildenafil and VPA. Neither LEV (2.32 mg/kg) nor its co-administration with sildenafil (40 mg/kg) produced any significant changes in motor coordination, muscular strength and long-term memory in mice.

Topics: Analysis of Variance; Animals; Antiemetics; Avoidance Learning; Disease Models, Animal; Dose-Response Relationship, Drug; Electroshock; Hand Strength; Male; Mice; Phosphodiesterase 5 Inhibitors; Piperazines; Psychomotor Performance; Purines; Seizures; Sildenafil Citrate; Sulfones

Inhibition of the cGMP-specific phosphodiesterase 5 (PDE5) exerts profound beneficial effects on failing hearts. However, the mechanisms underlying the therapeutic effects of PDE5 inhibition on heart failure are unclear. The purpose of this study was to investigate whether PDE5 inhibition decreases endoplasmic reticulum (ER) stress, a key event in heart failure.. Heart failure was induced by isoprenaline s.c. injection in Sprague-Dawley rats and transverse aortic constriction (TAC) in mice. PDE5 was inhibited with sildenafil. Heart function was detected by invasive pressure-volume analysis and echocardiography. ER stress markers were analysed by Western blotting. Apoptosis was measured by flow cytometric analysis.. PDE5 inhibition markedly attenuated isoprenaline-induced and TAC-induced cardiac hypertrophy and dysfunction, and reduced ER stress and apoptosis. Further, PDE5 inhibition with sildenafil largely prevented ER stress and reduced apoptosis in isoprenaline- or thapsigargin-treated cardiomyocytes. PKG inhibition markedly prevented the protective effects of sildenafil in vivo and in vitro. To further understand the mechanism of the effect of PDE5 inhibition on ER stress, we demonstrated that PDE5 inhibitor increased sarco-(endo)-plasmic reticulum Ca(2+) -ATPase activity via phosphorylation of phospholamban at Ser(16) . This may contribute to the attenuation of ER stress induced by PDE5 inhibition.. These results suggest that PDE5 inhibition can attenuate ER stress and improve cardiac function in vivo and in vitro. Suppression of ER stress by inhibiting PDE5 may contribute to the therapeutic effects on heart failure.

Topics: Animals; Aorta; Apoptosis; Calcium-Binding Proteins; Cardiomegaly; Constriction; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Heart Failure; Humans; Isoproterenol; Male; Mice; Mice, Inbred C57BL; Myocardial Contraction; Myocytes, Cardiac; Phosphodiesterase 5 Inhibitors; Phosphorylation; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Signal Transduction; Sildenafil Citrate; Stroke Volume; Sulfones; Ventricular Function, Left

Fetal growth restriction (FGR) is defined as the inability of a fetus to achieve its genetic growth potential and is associated with a significantly increased risk of morbidity and mortality. Clinically, FGR is diagnosed as a fetus falling below the 5(th) centile of customised growth charts. Sildenafil citrate (SC, Viagra™), a potent and selective phosphodiesterase-5 inhibitor, corrects ex vivo placental vascular dysfunction in FGR, demonstrating potential as a therapy for this condition. However, many FGR cases present without an abnormal vascular phenotype, as assessed by Doppler measures of uterine/umbilical artery blood flow velocity. Thus, we hypothesized that SC would not increase fetal growth in a mouse model of FGR, the placental-specific Igf2 knockout mouse, which has altered placental exchange capacity but normal placental blood flow. Fetal weights were increased (by 8%) in P0 mice following maternal SC treatment (0.4 mg/ml) via drinking water. There was also a trend towards increased placental weight in treated P0 mice (P = 0.056). Additionally, 75% of the P0 fetal weights were below the 5(th) centile, the criterion used to define human FGR, of the non-treated WT fetal weights; this was reduced to 51% when dams were treated with SC. Umbilical artery and vein blood flow velocity measures confirmed the lack of an abnormal vascular phenotype in the P0 mouse; and were unaffected by SC treatment. (14)C-methylaminoisobutyric acid transfer (measured to assess effects on placental nutrient transporter activity) per g placenta was unaffected by SC, versus untreated, though total transfer was increased, commensurate with the trend towards larger placentas in this group. These data suggest that SC may improve fetal growth even in the absence of an abnormal placental blood flow, potentially affording use in multiple sub-populations of individuals presenting with FGR.

Topics: Animals; Blood Flow Velocity; Disease Models, Animal; Female; Fetal Development; Fetal Growth Retardation; Fetal Weight; Fetus; Humans; Insulin-Like Growth Factor II; Mice; Mice, Knockout; Phenotype; Phosphodiesterase Inhibitors; Piperazines; Placenta; Pregnancy; Purines; Sildenafil Citrate; Sulfones; Umbilical Arteries; Uterine Artery

NO/cGMP signaling plays an important role in vascular relaxation and regulation of blood pressure. The key enzyme in the cascade, the NO-stimulated cGMP-forming guanylyl cyclase exists in two enzymatically indistinguishable isoforms (NO-GC1, NO-GC2) with NO-GC1 being the major NO-GC in the vasculature. Here, we studied the NO/cGMP pathway in renal resistance arteries of NO-GC1 KO mice and its role in renovascular hypertension induced by the 2-kidney-1-clip-operation (2K1C). In the NO-GC1 KOs, relaxation of renal vasculature as determined in isolated perfused kidneys was reduced in accordance with the marked reduction of cGMP-forming activity (80%). Noteworthy, increased eNOS-catalyzed NO formation was detected in kidneys of NO-GC1 KOs. Upon the 2K1C operation, NO-GC1 KO mice developed hypertension but the increase in blood pressures was not any higher than in WT. Conversely, operated WT mice showed a reduction of cGMP-dependent relaxation of renal vessels, which was not found in the NO-GC1 KOs. The reduced relaxation in operated WT mice was restored by sildenafil indicating that enhanced PDE5-catalyzed cGMP degradation most likely accounts for the attenuated vascular responsiveness. PDE5 activation depends on allosteric binding of cGMP. Because cGMP levels are lower, the 2K1C-induced vascular changes do not occur in the NO-GC1 KOs. In support of a higher PDE5 activity, sildenafil reduced blood pressure more efficiently in operated WT than NO-GC1 KO mice. All together our data suggest that within renovascular hypertension, cGMP-based PDE5 activation terminates NO/cGMP signaling thereby providing a new molecular basis for further pharmacological interventions.

Topics: Animals; Blood Pressure; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Hypertension, Renovascular; Kidney; Mice; Mice, Knockout; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilation; Vasodilator Agents

Nitric oxide (NO)-derived metabolites including the anion nitrite can recycle back to NO and thus complement NO formation independent of NO synthases. While nitrite is as a major vascular storage pool and source of NO, little is known about drugs that increase tissue nitrite concentrations. This study examined the effects of atorvastatin or sildenafil, or the combination, on vascular nitrite concentrations and on endothelial dysfunction in the 2 kidney-1 clip (2K1C) hypertension model. Sham-operated or 2K1C hypertensive rats were treated with vehicle, atorvastatin (50 mg/Kg), sildenafil (45 mg/Kg), or both for 8 weeks. Systolic blood pressure (SBP) was monitored weekly. Nitrite concentrations were assessed in the aortas and in plasma samples by ozone-based reductive chemiluminescence assay. Aortic rings were isolated to assess endothelium-dependent and independent relaxation. Aortic NADPH activity and ROS production were evaluated by luminescence and dihydroethidium, respectively, and plasma TBARS levels were measured. Aortic nitrotyrosine staining was evaluated to assess peroxynitrite formation. Atorvastatin and sildenafil, alone or combined, significantly lowered SBP by approximately 40 mmHg. Atorvastatin significantly increased vascular nitrite levels by 70% in hypertensive rats, whereas sildenafil had no effects. Both drugs significantly improved the vascular function, and decreased vascular NADPH activity, ROS, and nitrotyrosine levels. Lower plasma TBARS concentrations were found with both treatments. The combination of drugs showed no improved responses compared to each drug alone. These findings show evidence that atorvastatin, but not sildenafil, increases vascular NO stores, although both drugs exert antioxidant effects, improve endothelial function, and lower blood pressure in 2K1C hypertension.

Topics: Animals; Aorta; Atorvastatin; Blood Pressure; Body Weight; Disease Models, Animal; Drug Therapy, Combination; Heptanoic Acids; Hypertension, Renovascular; Male; Nitric Oxide; Piperazines; Purines; Pyrroles; Rats; Rats, Wistar; Sildenafil Citrate; Sulfonamides

Previous studies have demonstrated that cognitive function can be restored in mouse models of Alzheimer's disease (AD) following administration of sildenafil, a specific PDE5 inhibitor (Puzzo et al., 2009; Cuadrado-Tejedor et al.). Another very potent PDE5 inhibitor with a longer half-life and safe in chronic treatments, tadalafil, may represent a better alternative candidate for AD therapy. However, tadalafil was proven unable to achieve similar benefits than those of sildenafil in AD animal models (Puzzo et al., 2009). The lack of efficacy was attributed to inability to cross the blood-brain barrier (BBB). In this paper we first measured the blood and brain levels of tadalafil to prove that the compound crosses BBB and that chronic treatment leads to accumulation in the brain of the J20 transgenic mouse model of AD. We demonstrated the presence of PDE5 mRNA in the brain of the mice and also in the human brain. After a 10 week treatment with either of these PDE5 inhibitors, the performance of the J20 mice in the Morris water maze test improved when compared with the transgenic mice that received vehicle. Biochemical analysis revealed that neither sildenafil nor tadalafil altered the amyloid burden, although both compounds reduced Tau phosphorylation in the mouse hippocampus. This study provides evidence of the potential benefits of a chronic tadalafil treatment in AD therapy. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Topics: Alzheimer Disease; Animals; Blood-Brain Barrier; Brain; Carbolines; Cognition Disorders; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Female; Gene Expression Regulation, Enzymologic; Half-Life; Humans; Macaca fascicularis; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nootropic Agents; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Species Specificity; Sulfones; Tadalafil; Tissue Distribution

Pulmonary hypertension (PH) is a life-threatening disease that causes endothelial dysfunction in the pulmonary vascular bed. Systemic endothelial dysfunction has also been reported in PH. This study compared the systemic and pulmonary vascular responses and some blood biomarkers of endothelial function in monocrotaline (MCT)-induced PH of rats. It also investigated the effect of sildenafil and iloprost treatment. MCT application induced elevation in the right ventricular pressures of the rat heart that had been reversed by sildenafil and iloprost treatment. Acetylcholine-induced endothelium-dependent relaxations of the isolated pulmonary artery were decreased in the PH group and this failure was reversed by sildenafil and iloprost treatment. Acetylcholine-induced endothelium-dependent relaxations of the isolated thoracic aorta were similar in all groups. Serotonin-induced contractions of the pulmonary artery were augmented by PH. In the isolated aorta, serotonin-stimulated contraction was not different in the control and MCT groups, but sildenafil and iloprost treatment decreased serotonin responses. The nitric oxide (NO) level in systemic circulation was not significantly changed by PH. However, sildenafil and iloprost treatments caused a decrease in the plasma level of NO. Asymmetric dimethylarginine levels in plasma were significantly decreased after MCT application and were not recovered by sildenafil and iloprost treatment. Total antioxidant capacity and H2S level of plasma were similar in all groups. Results of this study showed that MCT-induced PH caused specific toxic effects on pulmonary vasculature without any functional effects on the aorta. In addition, it was also demonstrated that sildenafil and iloprost treatments were effective in the MCT-induced PH.

Topics: Animals; Aorta, Thoracic; Arginine; Disease Models, Animal; Endothelium, Vascular; Hydrogen Sulfide; Hypertension, Pulmonary; Iloprost; Male; Monocrotaline; Nitric Oxide; Piperazines; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Vasodilation; Vasodilator Agents

In this study, we tested whether the phosphodiesterase-5 inhibitor sildenafil protects against neurodegeneration and facilitates recovery from learning deficits examined long after chronic cerebral hypoperfusion (CCH) induced by the 4-vessel occlusion/internal carotid artery (4-VO/ICA) model in middle-aged rats. Male Wistar rats (12-15 months of age) were subjected to permanent 3-stage 4-VO/ICA with an interstage interval of 4 days. Sildenafil (3 mg/kg, p.o.) was administered at one dose per day for 10 days, beginning soon after the first occlusion stage. Three months later, learning in a non-food-rewarded, eight-arm radial maze task was tested. Learning performance is expressed as the latency to find a goal box and the number of reference or working memory errors. Histological examination was performed 1-3 days after behavioral testing. In the vehicle-treated group, permanent 4-VO/ICA markedly disrupted learning performance and caused moderate-to-severe neurodegeneration in the CA1-CA4 subfields of the hippocampus (56.2%), dentate gyrus (DG; 19.2%), retrosplenial cortex (RS cortex; 47.4%), and parietal association cortex (PtA cortex; 38.2%). Sildenafil treatment did not prevent 4-VO/ICA-induced learning deficits, whereas neurodegeneration was significantly reduced in the CA1-CA4 subfields (30.5%), DG (7.2%), RS cortex (11.8%), and PtA cortex (6.5%). Advancing previous findings from our laboratory, this study suggests that while sildenafil can provide important neuroprotection in different brain regions of middle-aged rats subjected to CCH, such histological effect does not translate into cognitive recovery.

Topics: Animals; Arterial Occlusive Diseases; Brain; Carotid Artery, Internal; Cell Count; Disease Models, Animal; Learning Disabilities; Male; Maze Learning; Neuroprotective Agents; Piperazines; Purines; Rats; Rats, Wistar; Reaction Time; Sildenafil Citrate; Sulfones; Time Factors

Resuscitation after cardiac arrest may lead to ischemia-reperfusion injury and infarction. We evaluated whether sildenafil, a phosphodiesterase-5 inhibitor, has an impact on recovery after cardiac arrest in a rat cardiac transplantation model.. Sixty-one Fischer344 rats underwent syngeneic heterotopic cardiac transplantation after ischemia and ligation of the left anterior coronary artery of the heart to yield myocardial infarction (IRI + MI). Of these, 22 rats received subcutaneously injected sildenafil (1 mg/kg/day) (IRI +MI + S). Twenty-three additional grafted animals with transplantation only served as controls with ischemia reperfusion injury (IRI). After 2 days, immunohistochemistry for eNOS, and RT-PCR for iNOS and Aquaporin-7 were performed after graft harvesting and histology.. Two days after transplantation, remote intramyocardial arteries were more preserved in IRI + MI + S as compared with IRI +MI and IRI (0.74 ± 0.14, 0.56 ± 0.23 and 0.55 ± 0.22, PSU, p < 0.05, respectively). Decreased eNOS staining confirmed the presence of developing infarction in IRI + MI and IRI + MI + S. The expression of iNOS was significantly lower during IRI + MI +S as compared with IRI + MI (0.02 ± 0.01 and 1.02 ± 0.02, FC, p < 0.05).. Administered at the onset of reperfusion and developing infarction, sildenafil has an impact on myocardial recovery after cardiac arrest and ischemia.

Topics: Animals; Aquaporins; Coronary Vessels; Disease Models, Animal; Drug Administration Schedule; Heart Arrest; Heart Transplantation; Immunohistochemistry; Injections, Subcutaneous; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Inbred F344; Reverse Transcriptase Polymerase Chain Reaction; Sildenafil Citrate; Sulfones; Time Factors; Vasodilator Agents

Bronchopulmonary dysplasia (BPD) is a major cause of morbidity in premature infants receiving oxygen therapy. Currently, sildenafil is being examined clinically to improve pulmonary function in patients with BPD. Based on the pharmacological action of sildenafil, the elevation of cyclic guanosine 3',5'-monophosphate (cGMP) in lung tissue is considered to underlie its beneficial effects, but this mechanism is not understood at the molecular level. Here, we examined the possibility that sildenafil helps the pulmonary system adapt to hyperoxic stress. To induce BPD, fetal rats were exposed to LPS before delivery, and neonates were exposed to hyperoxia, followed by intraperitoneal injections of sildenafil. Alveolarization was impaired in rats exposed to hyperoxia, and alveolarization significantly recovered with sildenafil. An immunohistochemical examination revealed that sildenafil effectively increased vascular distribution in lung tissue. Furthermore, the oxygen sensor hypoxia-inducible factor (HIF)-1/2α and the angiogenic factor vascular endothelial growth factor (VEGF) were highly expressed in the lungs of sildenafil-treated rats. In human small-airway epithelial cells, HIF-1/2α and its downstream genes, including VEGF, were confirmed to be induced by sildenafil at both the protein and mRNA levels. Mechanistically, cGMP in airway cells accumulated after sildenafil treatment because of interfering phosphodiesterase Type 5, and subsequently cGMP activated HIF-mediated hypoxic signaling by stimulating the phosphoinositide 3-kinase (PI3K)-v-akt murine thymoma viral oncogene homolog 1 (AKT)-mammalian target of rapamycin (mTOR) pathway. This study provides a better understanding about the mode of action for sildenafil, and suggests that HIF can be a potential target for treating patients with BPD.

Topics: Animals; Animals, Newborn; Basic Helix-Loop-Helix Transcription Factors; Bronchopulmonary Dysplasia; Cells, Cultured; Cyclic GMP; Disease Models, Animal; Female; Humans; Hypoxia-Inducible Factor 1; Infant, Newborn; Lung; Neovascularization, Physiologic; Phosphatidylinositol 3-Kinases; Piperazines; Pregnancy; Proto-Oncogene Proteins c-akt; Purines; Rats; Rats, Sprague-Dawley; RNA, Messenger; Signal Transduction; Sildenafil Citrate; Sulfones; TOR Serine-Threonine Kinases; Up-Regulation; Vascular Endothelial Growth Factor A

Mutations in the bone morphogenetic protein type II receptor (BMPR-II) are responsible for the majority of cases of heritable pulmonary arterial hypertension (PAH), and BMPR-II deficiency contributes to idiopathic and experimental forms of PAH. Sildenafil, a potent type-5 nucleotide-dependent phosphodiesterase inhibitor, is an established treatment for PAH, but whether sildenafil affects bone morphogenetic protein (BMP) signaling in the pulmonary circulation remains unknown.. Studies were undertaken in human pulmonary arterial smooth muscle cells (PASMCs) and in vivo in the monocrotaline rat model of PAH. In PASMCs, sildenafil enhanced BMP4-induced phosphorylation of Smad1/5, Smad nuclear localization, and Inhibitor of DNA binding protein 1 gene and protein expression. This effect was mimicked by 8-bromo-cyclic GMP. Pharmacological inhibition or small interfering RNA knockdown of cyclic GMP-dependent protein kinase I inhibited the effect of sildenafil on BMP signaling. In functional studies, we observed that sildenafil potentiated the antiproliferative effects of BMP4 on PASMC proliferation. Furthermore, sildenafil restored the antiproliferative response to BMP4 in PASMCs harboring mutations in BMPR-II. In the monocrotaline rat model of PAH, which is characterized by BMPR-II deficiency, sildenafil prevented the development of pulmonary hypertension and vascular remodeling, and partly restored Smad1/5 phosphorylation and Inhibitor of DNA binding protein 1 gene expression in vivo in monocrotaline exposed rat lungs.. Sildenafil enhances canonical BMP signaling via cyclic GMP and cyclic GMP-dependent protein kinase I in vitro and in vivo, and partly restores deficient BMP signaling in BMPR-II mutant PASMCs. Our findings demonstrate a novel mechanism of action of sildenafil in the treatment of PAH and suggest that targeting BMP signaling may be beneficial in this disease.

Topics: Animals; Antihypertensive Agents; Binding Sites; Bone Morphogenetic Protein 4; Bone Morphogenetic Protein Receptors, Type II; Bone Morphogenetic Proteins; Cell Proliferation; Cells, Cultured; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Disease Models, Animal; Dose-Response Relationship, Drug; Familial Primary Pulmonary Hypertension; Humans; Hypertension, Pulmonary; Inhibitor of Differentiation Protein 1; Male; Monocrotaline; Muscle, Smooth, Vascular; Mutation; Myocytes, Smooth Muscle; Phosphodiesterase 5 Inhibitors; Phosphorylation; Piperazines; Promoter Regions, Genetic; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; RNA Interference; Signal Transduction; Sildenafil Citrate; Smad1 Protein; Smad5 Protein; Sulfones; Transfection; Vasodilator Agents

Severe burn induces biochemical mediators such as reactive oxygen species that leads to lipid peroxidation which may have a key role in formation of acute lung injury (ALI). Sildenafil is a selective and potent inhibitor of cyclic guanosine monophosphate specific phosphodiesterase-5. Sildenafil preserves alveolar growth, angiogenesis, reduces inflammation and airway reactivity. The purpose of the present study was to evaluate the effects of different dosages of sildenafil in ALI due to severe scald burn in rats. Twenty-four rats were subjected to 30% total body surface area severe scald injury and were randomly divided into three equal groups as follow: control, 10 and 20mg/kg sildenafil groups. Levels of malondialdehyde (MDA), activities of glutathione peroxidase (Gpx), catalase (Cat), total oxidative stress (TOS), and total antioxidative capacity (TAC) were measured in both tissues and serums. Oxidative stress index (OSI) was calculated. A semi-quantitative scoring system was used for the evaluation of histopatological findings. Sildenafil increased Gpx, Cat, TAC and decreased MDA, TOS and OSI. Sildenafil decreased inflammation scores in lungs. Our results reveal that sildenafil is protective against scald burn related ALI by decreasing oxidative stress and inflammation and the dosage of 10mg/kg could be apparently better than 20mg/kg.

Topics: Acute Lung Injury; Animals; Biomarkers; Burns; Catalase; Disease Models, Animal; Female; Glutathione Peroxidase; Malondialdehyde; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones

Aging is associated with a deterioration of cognitive performance and with increased risk of neurodegenerative disorders. In the present study we tested whether the specific phosphodiesterase 5 inhibitor sildenafil could ameliorate the age-dependent cognitive impairments shown by the senescence-accelerated mouse prone-8 (SAMP8). Sildenafil administration (7.5 mg/kg for 4 weeks) to 5-month-old SAMP8 mice attenuated spatial learning and memory impairments shown by these mice in the Morris Water Maze. Tau hyperphosphorylation (AT8 but not PHF-1 epitope) shown by SAMP8 mice at this age was also decreased in the hippocampus of sildenafil-treated mice, an effect probably related to a decrease in cyclin-dependent kinase 5 protein expression and activity (p25/p35 ratio). Interestingly, sildenafil also phosphorylated Akt, which was associated with an increase of glycogen synthase kinase-3β phosphorylation, providing a plausible explanation for the reductions in tau hyperphosphorylation (AT8 and PHF-1 epitopes) and attenuation of cognitive deficits shown by 9-month-old SAMP8 mice. Overall, sildenafil might be beneficial in age-related brain dysfunction and could be an emerging candidate for the treatment of other neurodegenerative diseases.

Topics: Aging; Animals; Cognition Disorders; Disease Models, Animal; Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); Male; Mice; Mice, Neurologic Mutants; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tauopathies

The involvement of cGMP/KATP pathway in effects of sildenafil on experimental colitis was investigated. Sildenafil significantly attenuated colonic injury markers. These effects were reversed by the addition of glibenclamide or ODQ, indicating the involvement of ATP-sensitive potassium channels (KATP) and cGMP, respectively.

Topics: Animals; Colitis; Cyclic GMP; Disease Models, Animal; Glyburide; KATP Channels; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Trinitrobenzenesulfonic Acid

Cerebral vasospasm is an independent predictor of poor outcome after subarachnoid hemorrhage (SAH). The nitric oxide-cyclic guanosine monophosphate (NO-cGMP) vasodilatory pathway is strongly implicated in its pathophysiology. Preliminary studies suggest that phosphodiesterase 5 (PDE5), an enzyme that degrades cGMP, may play a role because the PDE5 inhibitor sildenafil was found to reduce vasospasm after SAH. However, several questions that are critical when considering translational studies remain unanswered.. To elucidate the mechanism of action of sildenafil against vasospasm and to assess whether sildenafil attenuates SAH-induced neuronal cell death, improves functional outcome after SAH, or causes significant physiological side effects when administered at therapeutically relevant doses.. SAH was induced via endovascular perforation in male C57BL6 mice. Beginning 2 hours later, mice received sildenafil citrate (0.7, 2 or 5 mg/kg orally twice daily) or vehicle. Neurological outcome was assessed daily. Vasospasm was determined on post-SAH day 3. Brain PDE5 expression and activity, cGMP content, neuronal cell death, arterial blood pressure, and intracranial pressure were examined.. We found that PDE5 activity (but not expression) is increased after SAH, leading to decreased cGMP levels. Sildenafil attenuates this increase in PDE5 activity and restores cGMP levels after SAH. Post-SAH initiation of sildenafil was found to decrease vasospasm and neuronal cell death and markedly improve neurological outcome without causing significant physiological side effects.. Sildenafil, a US Food and Drug Administration-approved drug with a proven track record of safety in humans, is a promising new therapy for vasospasm and neurological deficits after SAH.

Topics: Animals; Blood Pressure; Cell Death; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Enzyme-Linked Immunosorbent Assay; Extremities; In Situ Nick-End Labeling; Intracranial Pressure; Male; Mice; Mice, Inbred C57BL; Motor Activity; Movement; Neurons; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Recovery of Function; Severity of Illness Index; Sildenafil Citrate; Subarachnoid Hemorrhage; Sulfones; Vasospasm, Intracranial

To evaluate the effects of the Chinese herbal formula Shuganyiyang (SGYY) capsule on arteriogenic erectile dysfunction (ED) in a rat model and to investigate the underlying molecular mechanism.. Forty male Sprague-Dawley rats were subjected to bilateral ligation of the internal iliac artery and then divided into 4 groups (n=10 per group). They were treated daily with either sildenafil (10.5 mg/kg), or SGYY at 1 of 2 dosages (1 g/kg and 0.5 g/kg) for 30 days. Erectile function was evaluated using cavernous nerve electrical stimulation after treatment, and the cavernous tissue specimens of all animals were harvested for gene and protein examination using real-time reverse transcriptase polymerase chain reaction, Western blot analysis, and cyclic guanosine monophosphate (cGMP) measurement.. The ratio of the maximal intracavernous pressure to the mean arterial pressure was significantly higher in the SGYY (1 g/kg and 0.5 g/kg) rats than that in the models (P<.01). The gene and protein expression of 3 subtypes of nitric oxide synthase (NOS)--neuropathic (nNOS), inducible (iNOS), and endothelial (eNOS)--and cGMP concentrations in cavernous tissue in SGYY-treated rats were significantly higher than in the models. However, phosphodiesterase type 5 (PDE5) expression in the SGYY rats was lower than those in models (P<.01 or P<.05).. SGYY significantly improves the maximal intracavernous pressure in arteriogenic ED in a rat model. The underlying mechanism of action of SGYY involves increasing the expression of some main factors in the NOS-cGMP pathway and reducing the expression of PDE5.

Topics: Analysis of Variance; Animals; Blotting, Western; Cyclic GMP; Disease Models, Animal; Drugs, Chinese Herbal; Erectile Dysfunction; Gene Expression Regulation; Male; Nitric Oxide Synthase; Penile Erection; Piperazines; Purines; Random Allocation; Rats; Rats, Sprague-Dawley; Reference Values; Sensitivity and Specificity; Sildenafil Citrate; Sulfones

Oxytocin (OT) levels in plasma increase during sexual response and are significantly lower in patients with depression. A drug for the treatment of sexual dysfunction, sildenafil, enhances the electrically evoked release of OT from the posterior pituitary. In this study, we showed that sildenafil had an antidepressant-like effect through activation of an OT signaling pathway. Application of sildenafil reduced depression-related behavior in male mice. The antidepressant-like effect was blocked by an OT receptor (OTR) antagonist and was absent in OTR knockout (KO) mice. Sildenafil increased the phosphorylation of cAMP response element-binding protein (CREB) in the hippocampus. The OTR antagonist inhibited sildenafil-induced CREB phosphorylation and sildenafil had no effect on CREB phosphorylation in OTR KO mice. These results suggest sildenafil to have an antidepressant-like effect through the activation of OT signaling and to be a promising drug for the treatment of depression.

Topics: Aniline Compounds; Animals; Antidepressive Agents; Benzamides; Cyclic AMP Response Element-Binding Protein; Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Exploratory Behavior; Female; Gene Expression Regulation; Immobility Response, Tonic; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Oxytocin; Phosphorylation; Piperazines; Purines; Receptors, Oxytocin; Sex Factors; Sexual Behavior, Animal; Sildenafil Citrate; Sulfones; Swimming

Right ventricular (RV) failure (RVF) is the main cause of death in patients with pulmonary artery hypertension (PAH). Sildenafil, a phosphodiesterase type 5 inhibitor, was approved recently for treatment of PAH patients. However, the mechanisms underlying RV contractile malfunction and the benefits of sildenafil on RV function are not well understood. We aimed to investigate the following: (1) the ultrastructural and excitation-contraction coupling alterations underlying PAH-induced RVF; (2) whether the ultrastructural changes are reversible; and (3) the mechanisms underlying the therapeutic benefits of sildenafil in PAH-RVF. We used a single injection of monocrotaline in Wistar rats to induce pulmonary vascular proliferation, which led to PAH and RVF. RV myocytes displayed severe transverse (T)-tubule loss and disorganization, as well as blunted and dys-synchronous sarcoplasmic reticulum Ca(2+) release. Sildenafil prevented and reversed the monocrotaline-induced PAH and LV filling impairment. Early intervention with sildenafil prevented RV hypertrophy and the development of RVF, T-tubule remodeling, and Ca(2+) handling dysfunction. Although late treatment with sildenafil did not reverse RV hypertrophy in animals with established RVF, RV systolic function was improved. Furthermore, late intervention partially reversed both the impairment of myocyte T-tubule integrity and Ca(2+) handling protein and sarcoplasmic reticulum Ca(2+) release function in monocrotaline-treated rats. In conclusion, PAH-induced increase in RV afterload causes severe T-tubule remodeling and Ca(2+) handling dysfunction in RV myocytes, leading to RV contractile failure. Sildenafil prevents and partially reverses ultrastructural, molecular, and functional remodeling of failing RV myocytes. Reversal of pathological T-tubule remodeling, although incomplete, is achievable without the regression of RV hypertrophy.

Topics: Animals; Calcium; Disease Models, Animal; Excitation Contraction Coupling; Heart Failure; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Microscopy, Confocal; Monocrotaline; Myocardial Contraction; Myocytes, Cardiac; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones; Treatment Outcome; Ventricular Dysfunction, Right; Ventricular Remodeling

Sildenafil increases ocular blood flow. Thus, the authors investigated if it also increases anterior chamber (AC) refilling after paracentesis.. Corriedale sheep and albino rabbits were used as animal models. Intraocular pressure (IOP) was measured, paracentesis performed on one eye, and AC refilling followed by observation using oblique illumination. IOP measurements continued as the AC formed. After IOP stabilization, sildenafil (100 mg) was orally administered. Forty to 60 minutes later, AH was withdrawn from the contralateral eye. The point at which IOP recovered was used to determine refilling time. Paracentesis volumes were either 60, 120, or 300 μL in sheep, and 50 or 100 μL in rabbits.. IOP recovered in approximately 49, 56, and 50 minutes after the 60, 120, and 300 μL withdrawals in sheep. The refilling times of the contralateral eye after sildenafil ingestion were approximately 19, 26, and 37 minutes for the respective AH withdrawals. With rabbits, IOP recovered in approximately 13 minutes after the 50 and 100 μL AH withdrawals. After sildenafil, the IOP recovery times of the fellow eye were approximately 6 minutes. AH refilling rates were estimated by dividing the paracentesis volume by IOP recovery time. After sildenafil, such rates were larger than the AH formation rate attributed to secretion by the ciliary epithelium.. Sildenafil accelerates the rate of AC refilling and might have beneficial utility as an agent enhancing fluid entry into the AC of patients who experienced AH loss during eye surgery, as well as in some cases of ocular hypotony.

Topics: Animals; Anterior Chamber; Aqueous Humor; Disease Models, Animal; Female; Intraocular Pressure; Male; Ocular Hypotension; Paracentesis; Piperazines; Purines; Rabbits; Recovery of Function; Regional Blood Flow; Sheep; Sildenafil Citrate; Sulfones; Tonometry, Ocular; Vasodilator Agents

Phosphodiesterase type 5 inhibitors are potent in relieving erectile dysfunction (ED), however, they are less satisfactory in diabetic patients, probably due to the pro-inflammatory biomarkers caused by diabetes. Therefore, it was interesting to compare the effects of sildenafil with strontium fructose 1,6-diphosphate (FDP-Sr) on cavernosal vascular activity and expressions of pro-inflammatory biomarkers in diabetic rats.. Male Sprague-Dawley rats were injected with streptozocin (60 mg/kg, i.p.) to develop diabetes. The animals were diabetic for eight weeks with sildenafil (12 mg/kg per day) or FDP-Sr (200 mg/kg per day) being administered for the last four of those eight weeks.. Sildenafil was more effective in relieving reduced vascular dilatation (relevant to ED), but less in attenuating over-expressions of NADPH oxidase p22, p47 and p67 subunits, and ET(A/B) R (endothelin receptor type A and type B) in the diabetic cavernosum. In contrast, FDP-Sr was less effective in improving ED, but more effective in normalizing the abnormal NADPH oxidase and ET(A/B) R.. The activated NADPH oxidase and upregulated ET(A) R and ET(B) R due to diabetic lesions played a minor or moderate role in ED. By offering extra ATP, FPD-Sr suppressed these abnormalities, however, sildenafil did not. A combined therapy of sildenafil with FDP-Sr may be more effective in relieving ED in diabetic patients through normalizing pro-inflammatory cytokines and improving the nitric oxide/cGMP pathway in the cavernosum.

Topics: Animals; Blood Glucose; Blotting, Western; Diabetes Mellitus, Experimental; Disease Models, Animal; Endothelin-1; Erectile Dysfunction; Fructosediphosphates; Male; Malondialdehyde; NADPH Oxidases; Piperazines; Protein Kinase C-epsilon; Purines; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sildenafil Citrate; Sulfones; Superoxide Dismutase; Up-Regulation; Vasodilator Agents

We tested the hypothesis that chronic treatment with sildenafil attenuates left ventricular (LV) remodeling and prevents exercise intolerance in chronic mitral regurgitation (MR).. MR was created in Sprague-Dawley rats by making a hole on the mitral leaflet. Two weeks after MR creation, MR and LV dilatation were confirmed by echocardiography, and rats were randomly assigned to sildenafil treatment (MR+sildenafil group; 50 mg/kg PO twice a day; n=16) or normal saline only (MR group; n=16) and continued for 4 months. Sixteen sham rats were compared with MR rats. After 4 months, LV size was smaller in the MR+sildenafil compared with the MR group (LV end-systolic dimension, 4.7±0.3 for sham versus 5.9±0.3 for MR+sildenafil versus 7.4±0.5 mm for MR; P<0.05; LV end-diastolic dimension, 8.3±0.4 versus 10.5±0.2 versus 11.7±0.61 mm, respectively; P<0.05). LV ejection fraction was greater in the MR+sildenafil group than in the MR group (70.2±2.2 for sham versus 67.0±4.2 for MR+sildenafil versus 58.9±2.5 for MR; P=0.01). Serial treadmill test revealed that exercise capacity was reduced in the MR but not in the MR+sildenafil group. Transcriptional profiling of cardiac apical tissues revealed that gene sets related to inflammatory response, DNA damage response, cell cycle checkpoint, and cellular signaling pathways were significantly enriched by genes with reciprocal changes. Pathological analysis showed that perivascular fibrosis was more prominent in the MR than in the MR+sildenafil group and that the percentage of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells was 2-fold greater in the MR compared with the MR+sildenafil group.. Sildenafil significantly attenuates LV remodeling and prevents exercise intolerance in a rat model of chronic MR. This benefit may be associated with the antiapoptotic, anti-inflammatory effects of sildenafil.

Topics: Animals; Chronic Disease; Disease Models, Animal; Male; Mitral Valve Insufficiency; Physical Conditioning, Animal; Physical Endurance; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Survival Analysis; Time Factors; Ventricular Remodeling

Topics: Animals; Disease Models, Animal; Male; Mitral Valve Insufficiency; Physical Conditioning, Animal; Physical Endurance; Piperazines; Purines; Sildenafil Citrate; Sulfones; Ventricular Remodeling

Global control of tuberculosis (TB), an infectious disease that claims nearly 2 million lives annually, is hindered by the long duration of chemotherapy required for curative treatment. Lack of adherence to this intense treatment regimen leads to poor patient outcomes, development of new or additional drug resistance, and continued spread of M.tb. within communities. Hence, shortening the duration of TB therapy could increase drug adherence and cure in TB patients. Here, we report that addition of the United Stated Food and Drug Administration-approved phosphodiesterase inhibitors (PDE-Is) cilostazol and sildenafil to the standard TB treatment regimen reduces tissue pathology, leads to faster bacterial clearance and shortens the time to lung sterilization by one month, compared to standard treatment alone, in a murine model of TB. Our data suggest that these PDE-Is could be repurposed for use as adjunctive drugs to shorten TB treatment in humans.

Topics: Animals; Antitubercular Agents; Cilostazol; Disease Models, Animal; Mice; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tetrazoles; Time Factors; Treatment Outcome; Tuberculosis; United States; United States Food and Drug Administration

There are conflicting results from behavioural studies regarding whether the activation or inhibition of the cGMP-nitric oxide (NO) pathway induces anxiolytic-like behaviour. Sildenafil, an inhibitor of cGMP-selective phosphodiesterase-5, increases anxiety acutely, but previous evidence suggests that its chronic administration may be anxiolytic, and could involve a cholinergic interaction. We used the Flinders Sensitive Line (FSL) rat, a genetic model of depression that presents with increased anxiety- and depression-like behaviour, to investigate the action of chronic treatment with the PDE5 inhibitors sildenafil or tadalafil, with/without atropine on social interaction behaviour, a correlate for anxiety. Fluoxetine was used as positive control, with validation performed using Flinders Resistant Line (FRL) rats. In order to relate behavioural changes to brain penetration, we determined the concentration of sildenafil in cortex and hippocampus of rats following the schedule above using LC-MS/MS. FSL rats displayed significantly reduced social interactive behaviour than FRL rats, while sildenafil, tadalafil, and fluoxetine significantly reversed these deficits. Atropine did not exert effects on social interactive behaviour, nor did it modulate the effects of sildenafil or tadalafil. Sildenafil was present in cortex and hippocampus regions in lower nanomolar concentrations after chronic treatment, in agreement with the binding to PDE5 required for pharmacological effects. This study emphasizes the complicated regulation of anxiety by the cGMP-NO system, and provides supporting evidence for an anxiolytic action after the chronic activation of this pathway. As far as we know this is also the first report to formally demonstrate that sildenafil effectively crosses the blood-brain barrier to elicit central effects.

Topics: Animals; Anti-Anxiety Agents; Anxiety Disorders; Carbolines; Disease Models, Animal; Drug Administration Schedule; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Rats, Inbred Strains; Sildenafil Citrate; Sulfones; Tadalafil

Preeclampsia and fetal growth restriction are responsible for the majority of maternal and perinatal morbidity and mortality associated with complicated pregnancies. Although their etiologies are complex and multifactorial, both are associated with increased uterine artery resistance. Sildenafil citrate is able to rescue the dysfunction observed ex vivo in uterine arteries of women with preeclampsia. The ability of sildenafil citrate to increase uterine artery vasodilation, thereby decreasing uterine artery resistance and, hence, ameliorated preeclampsia and fetal growth restriction, was tested in a mouse model of preeclampsia, the catechol-O-methyl transferase knockout mouse (COMT(-/-)). COMT(-/-) and C57BL/6J mice were treated (0.2 mg/mL in drinking water, n=6-12) from gestational day 12.5 to 18.5. Measures of pup growth, including body weight, crown/rump length, and abdominal circumference, were reduced in COMT(-/-) mice; this was normalized after treatment with Sildenafil. COMT(-/-) mice also demonstrated abnormal umbilical Doppler waveforms, including reverse arterial blood flow velocity. This was normalized after treatment with Sildenafil. Abnormal uterine artery Doppler waveforms were not demonstrated in COMT(-/-) mice, although ex vivo responses of uterine arteries to phenylephrine were increased; moreover, treatment with Sildenafil did improve ex vivo sensitivity to an endothelium-dependent vasodilator. The data presented here demonstrate that Sildenafil can rescue pup growth and improve abnormal umbilical Doppler waveforms, providing support for a potential new therapeutic strategy targeting fetal growth restriction.

Topics: Animals; Blood Flow Velocity; Catechol O-Methyltransferase; Disease Models, Animal; Female; Fetal Growth Retardation; Hypertension; Mice; Mice, Inbred C57BL; Mice, Knockout; Myometrium; Piperazines; Pre-Eclampsia; Pregnancy; Proteinuria; Purines; Sildenafil Citrate; Sulfones; Ultrasonography, Doppler; Umbilical Arteries; Vasodilation; Vasodilator Agents

To assess the effect of sildenafil citrate in a rat model of Nω-nitro-l-arginine methyl ester (L-NAME)-induced intrauterine growth restriction (IUGR).. An in vivo experimental study was conducted where 40 pregnant Sprague-Dawley rats were randomly assigned to receive either: (1) control, (2) L-NAME 50 mg/kg/d by gavage (days 14 to 19), (3) L-NAME and sildenafil 15 mg/kg/d by gavage, or (4) sildenafil (days 14 to 21). On day 21, a hysterotomy was performed and all fetuses (live and dead) were counted, examined, and weighed. The primary outcome measure was the difference in pup birth weight.. The median number of live pups per dam was 11.5 (range: 1 to 15), 13.5 (2 to 17), 13.5 (7 to 16), and 11.5 (4 to 17) in controls, L-NAME, sildenafil, and combined drug groups, respectively (p = 0.02). Rats treated with L-NAME had a significantly higher number of stillbirths compared with control (p = 0.013) and sildenafil (p = 0.008) groups. L-NAME reduced pup birth weight compared with controls (4.53 ± 1.49 versus 5.65 ± 1.63 g, p < 0.001); this effect was more pronounced in the L-NAME and sildenafil groups (3.37 ± 1.25 g, p < 0.001).. Our data indicate that sildenafil citrate does not ameliorate L-NAME-induced IUGR, and in the doses utilized in this study might even have a synergistic negative effect on pup birth weight.

Topics: Animals; Birth Weight; Disease Models, Animal; Female; Fetal Growth Retardation; NG-Nitroarginine Methyl Ester; Piperazines; Pre-Eclampsia; Pregnancy; Proteinuria; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Vasodilator Agents

Topics: Animals; Carbolines; Disease Models, Animal; Familial Primary Pulmonary Hypertension; Female; Humans; Hypertension, Pulmonary; Male; Penile Erection; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Vascular Diseases; Vasodilator Agents

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy caused by mutations in the dystrophin gene. Loss of dystrophin initiates a progressive decline in skeletal muscle integrity and contractile capacity which weakens respiratory muscles including the diaphragm, culminating in respiratory failure, the leading cause of morbidity and mortality in DMD patients. At present, corticosteroid treatment is the primary pharmacological intervention in DMD, but has limited efficacy and adverse side effects. Thus, there is an urgent need for new safe, cost-effective, and rapidly implementable treatments that slow disease progression. One promising new approach is the amplification of nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signalling pathways with phosphodiesterase 5 (PDE5) inhibitors. PDE5 inhibitors serve to amplify NO signalling that is attenuated in many neuromuscular diseases including DMD. We report here that a 14-week treatment of the mdx mouse model of DMD with the PDE5 inhibitor sildenafil (Viagra(®), Revatio(®)) significantly reduced mdx diaphragm muscle weakness without impacting fatigue resistance. In addition to enhancing respiratory muscle contractility, sildenafil also promoted normal extracellular matrix organization. PDE5 inhibition slowed the establishment of mdx diaphragm fibrosis and reduced matrix metalloproteinase-13 (MMP-13) expression. Sildenafil also normalized the expression of the pro-fibrotic (and pro-inflammatory) cytokine tumour necrosis factor α (TNFα). Sildenafil-treated mdx diaphragms accumulated significantly less Evans Blue tracer dye than untreated controls, which is also indicative of improved diaphragm muscle health. We conclude that sildenafil-mediated PDE5 inhibition significantly reduces diaphragm respiratory muscle dysfunction and pathology in the mdx mouse model of Duchenne muscular dystrophy. This study provides new insights into the therapeutic utility of targeting defects in NO-cGMP signalling with PDE5 inhibitors in dystrophin-deficient muscle.

Topics: Animals; Creatine Kinase; Cyclic GMP; Diaphragm; Disease Models, Animal; Evans Blue; Fibrosis; Male; Mice; Mice, Inbred C57BL; Mice, Inbred mdx; Muscle Contraction; Muscle Fatigue; Muscle Weakness; Muscular Dystrophy, Duchenne; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

Sildenafil, a selective phosphodiesterase 5 (PDE5) inhibitor, has recently been reported to affect convulsant activity in some animal models of seizures and epilepsy. Moreover, its influence on the protective activity of some antiepileptic drugs (AEDs) was also noted. The aim of the present study was to investigate the effect of sildenafil on the anticonvulsant potential of gabapentin (GBP) and vigabatrin (VGB) in the timed intravenous (i.v.) pentylenetetrazole (PTZ) test in mice. The chimney test, the passive avoidance task and the grip strength test were used to estimate some possible side effects caused by the studied AEDs and their combinations with sildenafil. Total brain and free plasma concentrations of GBP and VGB were determined to evaluate the characteristics of interactions. Our studies revealed that GBP (25-100 mg/kg) increases the threshold for the forelimb tonic extension, whereas VGB raises thresholds both, for myoclonic (200-600 mg/kg) and generalized clonic (400-600 mg/kg) seizures in the used model of seizures. GBP at sub-effective dose of 12.5 mg/kg co-administered with sildenafil at doses of 10 and 20 mg/kg significantly increases the threshold for tonic seizures in the i.v. PTZ test in mice. Combination of sub-effective dose of VGB (200 mg/kg) with sildenafil at a dose of 5mg/kg also showed significant anticonvulsant activity against clonic seizures. The studied AEDs and their combinations with sildenafil did not produce any changes in the motor coordination, long-term memory and muscular strength in mice. Sildenafil did not influence total brain and free plasma concentrations of GBP and VGB. Interactions between the studied AEDs and sildenafil were pharmacodynamic in nature and for that reason they are worthy of consideration in the clinical practice.

Topics: Amines; Animals; Anticonvulsants; Avoidance Learning; Cyclohexanecarboxylic Acids; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Gabapentin; gamma-Aminobutyric Acid; Hand Strength; Male; Mice; Motor Skills; Pentylenetetrazole; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Seizures; Sildenafil Citrate; Sulfones; Vigabatrin

Sildenafil induces cGMP accumulation through phosphodiesterase-5 (PDE5) inhibition. cGMP-pathways protect oligodendrocytes and modulate astroglial and microglial reactions. Microglia and astrocytes play an important role in perpetuating multiple sclerosis (MS), a chronic inflammatory disease characterized by demyelination. Therefore, sildenafil can be a potential tool for MS treatment. The present study investigated the effects of sildenafil on the myelin structure and astrocyte/microglia-mediated neuroinflammation in an animal model of MS. Cuprizone-induced demyelination and neuroinflammation in rodents has been widely used as a model for MS. Herein, five male C57BL/6 mice (7-10 weeks old) were used per group. Over a 4-week period, the different groups received the following: (1) cuprizone (0.2%) mixed into the chow; (2) cuprizone in the chow and sildenafil (Viagra®; 3, 25 or 50mg/kg) in the drinking water; or (3) pure chow and water (control group). Cerebella were analyzed using transmission electron microscopy, western blotting, immunohistochemistry and luxol fast blue staining. Cuprizone induced tissue damage, with an increase in GFAP, Iba-1 and COX-2 and demyelination in comparison to the control group. However, cuprizone did not affect the expression of cytokines (TNF-α, IFN-γ, IL-1β and IL-2). Sildenafil reduced GFAP (25 and 50mg/kg) and Iba-1 expression (25mg/kg) in comparison to the cuprizone group, indicating the modulation of astrocytes and microglia, respectively. Sildenafil preserved myelin and axons ultrastructure and strongly reduced IFN-γ, TNF-α, IL-1β, IL-2 and COX-2 expression in comparison to the control and/or cuprizone groups. The results demonstrate a protective effect of sildenafil in the cerebellum. Thus, well-designed clinical trials may demonstrate that the oral administration of sildenafil can be suitable for individuals with MS and other neuroinflammatory/neurodegenerative diseases, providing additional benefits to current treatments.

Topics: Animals; Cerebellum; Cuprizone; Cyclooxygenase 2; Cytokines; Demyelinating Diseases; Disease Models, Animal; Down-Regulation; Fluorescent Antibody Technique; Glial Fibrillary Acidic Protein; Immunoblotting; Male; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Piperazines; Purines; Sildenafil Citrate; Sulfones

Sildenafil, the first selective phosphodiesterase-5 (PDE5) inhibitor to be widely used for treating erectile dysfunction, has been investigated with regard to its cardioand renoprotective effects in animal models. This study further investigated the renoprotective effects of sildenafil and their molecular mechanisms in deoxycorticosterone acetate (DOCA)-salt hypertensive (DSH) rats.. DOCA strips (200 mg/kg) were implanted in rats 1 week after unilateral nephrectomy. These rats were fed on a control diet, with or without sildenafil (50 mg·kg(-1)day(-1)), for 2 weeks. Systolic blood pressure (SBP) was measured by the tail cuff method, and the urinary albumin-to-creatinine ratio (ACR) was calculated. The extent of glomerulosclerosis and tubulointerstitial fibrosis was determined by Masson's trichrome stain. Renal expression of ED-1, transforming growth factor-β1 (TGF-β1), Bax, and Bcl-2 were determined by semiquantitative immunoblotting, polymerase chain reaction (PCR), and immunohistochemistry. TUNEL staining was used for detecting apoptotic cells.. The increased SBP in DSH rats was not attenuated by sildenafil treatment. The decreased creatinine clearance and increased ACR in DSH rats, compared with control animals, were attenuated by sildenafil treatment. Further, sildenafil treatment attenuated glomerulosclerosis and tubulointerstitial fibrosis in DSH rats and counteracted the increased expression of ED-1, TGF-β1, and Bax and the decreased expression of Bcl-2 in the kidneys of these rats. The increase in the number of apoptotic cells in DSH rats was attenuated by sildenafil treatment.. Sildenafil effectively prevented the progression of renal injury in DSH rats via its anti-inflammatory, antifibrotic, and antiapoptotic effects.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Blood Pressure; Desoxycorticosterone; Disease Models, Animal; Disease Progression; Hypertension; Kidney; Kidney Diseases; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Proto-Oncogene Proteins c-bcl-2; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Transforming Growth Factor beta1

To explore the effects of sildenafil on bladder compliance and endothelin-1 in the rabbit model of partial bladder outlet obstruction.. A total of 24 adult male New Zealand white rabbits were randomly divided into group A, group B, group C and group D (n = 6 each). The rabbit model of partial bladder outlet obstruction was established in groups C and D while groups A and B underwent a sham operation. Daily sildenafil (10 mg/kg) was dosed to groups B and C by lavage. Daily normal saline was dosed similarly to groups A and D. Bladder urodynamic examinations were conducted in each group at Week 16. Then bladder was isolated and weighed from each group. And ET-1 in bladder tissue was measured by ELISA.. Pressure thresholds for voiding (PT) in A-D groups were (10.6 ± 2.0), (11.6 ± 2.7), (14.0 ± 4.2) and (20.4 ± 6.1) cm H2O respectively. Compared with groups A, B and C, PT in group D was significantly higher (all P < 0.01). Bladder compliance in 4 groups were (2.75 ± 0.51), (2.78 ± 0.46), (4.98 ± 2.15) and (1.22 ± 0.25) ml/cm H2O respectively. Compared with groups A, B and C, bladder compliance was significantly lower in group D (all P < 0.01). Bladder compliance in group C was higher than that in groups A and B (both P < 0.01). The weights of bladder specimens in 4 groups were (5.0 ± 0.4), (4.6 ± 0.4), (8.2 ± 1.3) and (17.9 ± 2.3) g respectively. Compared with groups A and B, the weights of groups C and D were significantly heavier (all P < 0.01). And the weight of group D was much greater than that of group C (P < 0.01). The contents of ET-1 in bladder tissue of 4 groups were (72 ± 19), (69 ± 18), (76 ± 21) and (106 ± 29) pg/g respectively. Compared with groups A, B and C, ET-1 in bladder tissue was significantly higher in group D (all P < 0.05).. Daily sildenafil can effectively alleviate the damage of rabbit bladder compliance from partial bladder outlet obstruction and protect bladder functions. Its mechanism may be related with the down-regulation of ET-1 in bladder tissue of partial bladder outlet obstruction.

Topics: Animals; Compliance; Disease Models, Animal; Endothelin-1; Male; Piperazines; Purines; Rabbits; Sildenafil Citrate; Sulfones; Urinary Bladder; Urinary Bladder Neck Obstruction

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Disease Models, Animal; Drug Therapy, Combination; Myocardial Infarction; Perindopril; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Swine

Pulmonary hypertension as a frequent complication of left heart disease (PH-LHD) is characterized by lung endothelial dysfunction and vascular remodeling. Although PH-LHD contributes to morbidity and mortality in heart failure, established therapies for PH-LHD are lacking. We tested the effect of chronic sildenafil treatment in an experimental model of PH-LHD.. In Sprague-Dawley rats, PH-LHD was induced by supracoronary aortic banding. Oral sildenafil treatment (60 mg/kg daily) was initiated after 7 days, and lung endothelial function (n=5), vascular remodeling, and right ventricular function (n=11 each) were analyzed 9 weeks after banding. As compared with sham-operated controls, aortic banding induced pulmonary hypertension and lung endothelial dysfunction evident as lack of endothelial nitric oxide production and endothelium-dependent vasodilation. These changes were associated with an increased pulmonary vascular resistance, medial thickening, and biventricular cardiac hypertrophy. Sildenafil treatment largely attenuated these pathological changes and was not associated with detectable adverse effects pertinent to lung vascular barrier function, edema formation, or systemic hemodynamics.. Our data identify sildenafil as a promising therapy for PH-LHD. In light of its documented protective effects at the myocardial level in heart failure, sildenafil presents a particularly attractive strategy in that it simultaneously targets cardiac remodeling and secondary PH-LHD.

Topics: Administration, Oral; Animals; Antihypertensive Agents; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Endothelium, Vascular; Heart Failure, Diastolic; Hypertension, Pulmonary; Hypertrophy, Left Ventricular; Hypertrophy, Right Ventricular; Lung; Male; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Piperazines; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Time Factors; Vascular Resistance; Vasodilation; Ventricular Function, Left; Ventricular Function, Right

Cyclic GMP (cGMP)-mediated pathways regulate inflammatory responses in immune and CNS cells. Recently, cGMP phosphodiesterase inhibitors such as sildenafil, commonly used to treat sexual dysfunction in humans including multiple sclerosis (MS) patients, have been reported to be neuroprotective in animal models of stroke, Alzheimer's disease, and focal brain lesion. In this work, we have examined if sildenafil ameliorates myelin oligodendrocyte glycoprotein peptide (MOG₃₅₋₅₅)-induced experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. We show for the first time that treatment with sildenafil after disease onset markedly reduces the clinical signs of EAE by preventing axonal loss and promoting remyelination. Furthermore, sildenafil decreases CD3+ leukocyte infiltration and microglial/macrophage activation in the spinal cord, while increasing forkhead box transcription factor 3-expressing T regulatory cells (Foxp3 Tregs). However, sildenafil treatment did not significantly affect MOG₃₅₋₅₅-stimulated proliferation or release of Th1/Th2 cytokines in splenocytes but decreased ICAM-1 in spinal cord infiltrated cells. The presence of reactive astrocytes forming scar-like structures around infiltrates was enhanced by sildenafil suggesting a possible mechanism for restriction of leukocyte spread into healthy parenchyma. These results highlight novel actions of sildenafil that may contribute to its beneficial effects in EAE and suggest that treatment with this widely used and well-tolerated drug may be a useful therapeutic intervention to ameliorate MS neuropathology.

Topics: Animals; CD3 Complex; Demyelinating Diseases; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental; Female; Forkhead Transcription Factors; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Gliosis; Glycoproteins; Intercellular Adhesion Molecule-1; Mice; Mice, Inbred C57BL; Myelin-Oligodendrocyte Glycoprotein; Neurofilament Proteins; Peptide Fragments; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Spinal Cord; Sulfones; Time Factors

It has been shown that phosphodiesterase type 5 (PDE5) inhibitors preserve smooth muscle (SM) content and ameliorate the fibrotic degeneration normally seen in the corpora cavernosa after bilateral cavernosal nerve resection (BCNR). However, the downstream mechanisms by which these drugs protect the corpora cavernosa remain poorly understood.. To provide insight into the mechanism, we aimed to determine the gene expression profile of angiogenesis-related pathways within the penile tissue after BCNR with or without continuous sildenafil (SIL) treatment.. Five-month-old Fisher rats were subjected to BCNR or sham operation and treated with or without SIL (20 mg/kg/BW drinking water) for 3 days or 45 days (N = 8 rats per group). Total RNAs isolated from the denuded penile shaft and prostate were subjected to reverse transcription and to angiogenesis real-time-polymerase chain reaction arrays (84 genes). Changes in protein expression of selected genes such as epiregulin (EREG) and connective tissue growth factor (CTGF) were corroborated by Western blot and immunohistochemistry.. Genes modulated by BCNR and SIL treatment.. A decreased expression of genes related to SM growth factors such as EREG, platelet-derived growth factor (PDGF), extracellular matrix regulators such as metalloproteinases 3 and 9, endothelial growth factors, together with an upregulation of pro-fibrotic genes such as CTGF and transforming growth factor beta 2 were found at both time points after BCNR. SIL treatment reversed this process by upregulating endothelial and SM growth factors and downregulating pro-fibrotic factors. SIL did not affect the expression of EREG, VEGF, and PDGF in the ventral prostate of BCNR animals.. SIL treatment after BCNR activates genes related to SM preservation and downregulates genes related to fibrosis in the corpora cavernosa. These results provide a mechanistic justification for the use of SIL and other PDE5 inhibitors as protective therapy against corporal SM loss and fibrosis after radical prostatectomy.

Topics: Animals; Disease Models, Animal; Endothelium, Vascular; Epidermal Growth Factor; Epiregulin; Extracellular Matrix; Fibrosis; Gene Expression; Intercellular Signaling Peptides and Proteins; Male; Matrix Metalloproteinase 1; Matrix Metalloproteinase 3; Nerve Tissue; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Sildenafil Citrate; Sulfones; Transforming Growth Factor beta2

The development of bronchial hyperreactivity (BHR) subsequent to precapillary pulmonary hypertension (PHT) was prevented by acting on the major signalling pathways (endothelin, nitric oxide, vasoactive intestine peptide (VIP) and prostacyclin) involved in the control of the pulmonary vascular and bronchial tones.. Five groups of rats underwent surgery to prepare an aorta-caval shunt (ACS) to induce sustained precapillary PHT for 4 weeks. During this period, no treatment was applied in one group (ACS controls), while the other groups were pretreated with VIP, iloprost, tezosentan via an intraperitoneally implemented osmotic pump, or by orally administered sildenafil. An additional group underwent sham surgery. Four weeks later, the lung responsiveness to increasing doses of an intravenous infusion of methacholine (2, 4, 8 12 and 24 μg/kg/min) was determined by using the forced oscillation technique to assess the airway resistance (Raw).. BHR developed in the untreated rats, as reflected by a significant decrease in ED50, the equivalent dose of methacholine required to cause a 50% increase in Raw. All drugs tested prevented the development of BHR, iloprost being the most effective in reducing both the systolic pulmonary arterial pressure (Ppa; 28%, p = 0.035) and BHR (ED50 = 9.9 ± 1.7 vs. 43 ± 11 μg/kg in ACS control and iloprost-treated rats, respectively, p = 0.008). Significant correlations were found between the levels of Ppa and ED50 (R = -0.59, p = 0.016), indicating that mechanical interdependence is primarily responsible for the development of BHR.. The efficiency of such treatment demonstrates that re-establishment of the balance of constrictor/dilator mediators via various signalling pathways involved in PHT is of potential benefit for the avoidance of the development of BHR.

Topics: Administration, Oral; Airway Resistance; Analysis of Variance; Animals; Antihypertensive Agents; Blood Pressure; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoconstriction; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelins; Hypertension, Pulmonary; Iloprost; Infusion Pumps, Implantable; Infusions, Parenteral; Lung; Lung Volume Measurements; Male; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Piperazines; Prostaglandins I; Purines; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, Endothelin; Signal Transduction; Sildenafil Citrate; Sulfones; Tetrazoles; Time Factors; Vasoactive Intestinal Peptide; Vasodilator Agents

Lung hypoplasia and persistent pulmonary hypertension of the newborn limit survival in congenital diaphragmatic hernia (CDH). Unlike other diseases resulting in persistent pulmonary hypertension of the newborn, infants with CDH are refractory to inhaled nitric oxide (NO). Nitric oxide mediates pulmonary vasodilatation at birth in part via cyclic GMP production. Phosphodiesterase type 5 (PDE5) limits the effects of NO by inactivation of cyclic GMP. Because of the limited success in postnatal management of CDH, we hypothesized that antenatal PDE5 inhibition would attenuate pulmonary artery remodeling in experimental nitrofen-induced CDH.. Nitrofen administered at embryonic day 9.5 to pregnant rats resulted in a 60% incidence of CDH in the offspring and recapitulated features seen in human CDH, including structural abnormalities (lung hypoplasia, decreased pulmonary vascular density, pulmonary artery remodeling, right ventricular hypertrophy), and functional abnormalities (decreased pulmonary artery relaxation in response to the NO donor 2-(N,N-diethylamino)-diazenolate-2-oxide). Antenatal sildenafil administered to the pregnant rat from embryonic day 11.5 to embryonic day 20.5 crossed the placenta, increased fetal lung cyclic GMP and decreased active PDE5 expression. Antenatal sildenafil improved lung structure, increased pulmonary vessel density, reduced right ventricular hypertrophy, and improved postnatal NO donor 2-(N,N-diethylamino)-diazenolate-2-oxide-induced pulmonary artery relaxation. This was associated with increased lung endothelial NO synthase and vascular endothelial growth factor protein expression. Antenatal sildenafil had no adverse effect on retinal structure/function and brain development.. Antenatal sildenafil improves pathological features of persistent pulmonary hypertension of the newborn in experimental CDH and does not alter the development of other PDE5-expressing organs. Given the high mortality/morbidity of CDH, the potential benefit of prenatal PDE5 inhibition in improving the outcome for infants with CDH warrants further studies.

Topics: Animals; Body Weight; Brain; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Female; Hernia, Diaphragmatic; Hernias, Diaphragmatic, Congenital; Hypertension, Pulmonary; Lung; Nitric Oxide; Phenyl Ethers; Phosphodiesterase 5 Inhibitors; Piperazines; Pregnancy; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones

Sildenafil, the first drug for erectile dysfunction, has cardiopulmonary protective actions. A recent study has reported that sildenafil given intraperitoneally (i.p.) attenuated cisplatin (CP)-induced nephrotoxicity. Here, we evaluated whether sildenafil, given by two different routes and at two different doses, can attenuate CP-induced nephrotoxicity and would also affect renal haemodynamics in CP-treated rats. Six groups of rats were treated with saline (controls), CP [5 mg/kg, intraperitoneally (i.p.) once], sildenafil (0.4 mg/kg/day, i.p. for 5 days), sildenafil (0.4 mg/kg/day i.p. for 5 days) plus CP (5 mg/kg, i.p., once), sildenafil [10 mg/kg/day, subcutaneous (s.c.) for 5 days] or sildenafil (10 mg/kg/day, s.c. for 5 days) plus CP (5 mg/kg, i.p. once). Five days after the end of the treatments, urine was collected from all rats, which were then anaesthetized for blood pressure and renal blood flow monitoring. This was followed by intravenous (i.v.) injection of norepinephrine for the measurement of renal vasoconstrictor responses. Thereafter, blood and kidneys were collected for measurement of several biochemical, functional and structural parameters. CP reduced body-weight and renal blood flow but did not affect norepinephrine-induced renal vasoconstriction. It increased the plasma concentrations of urea and creatinine, and reduced creatinine clearance. CP caused extensive renal tubular necrosis, increased urine volume and N-acetyl-β-D-glucosaminidase activity. When sildenafil (0.4 mg/kg/day, i.p. for 5 days) was combined with cisplatin, there was a dramatic improvement in renal histopathology, reduction in N-acetyl-β-D-glucosaminidase and increase in renal blood flow. However, sildenafil (10 mg/kg/day, s.c. for 5 days) did not affect CP nephrotoxicity, suggesting the importance of dose and route selection of sildenafil as a nephroprotectant.

Topics: Animals; Antineoplastic Agents; Cisplatin; Disease Models, Animal; Hemodynamics; Injections, Subcutaneous; Kidney; Kidney Diseases; Kidney Tubules; Male; Necrosis; Piperazines; Purines; Rats; Rats, Wistar; Renal Circulation; Sildenafil Citrate; Sulfones; Vasoconstriction; Vasodilator Agents

Meconium aspiration syndrome causes respiratory failure after birth and in vivo monitoring of pulmonary edema is difficult. The objective of the present study was to assess hemodynamic changes and edema measured by transcardiopulmonary thermodilution in low weight newborn piglets. Additionally, the effect of early administration of sildenafil (2 mg/kg vo, 30 min after meconium aspiration) on this critical parameter was determined in the meconium aspiration syndrome model. Thirty-eight mechanically ventilated anesthetized male piglets (Sus scrofa domestica) aged 12 to 72 h (1660 ± 192 g) received diluted fresh human meconium in the airway in order to evoke pulmonary hypertension (PHT). Extravascular lung water was measured in vivo with a PiCCO monitor and ex vivo by the gravimetric method, resulting in an overestimate of 3.5 ± 2.3 mL compared to the first measurement. A significant PHT of 15 Torr above basal pressure was observed, similar to that of severely affected humans, leading to an increase in ventilatory support. The vascular permeability index increased 57%, suggesting altered alveolocapillary membrane permeability. Histology revealed tissue vessel congestion and nonspecific chemical pneumonitis. A group of animals received sildenafil, which prevented the development of PHT and lung edema, as evaluated by in vivo monitoring. In summary, the transcardiopulmonary thermodilution method is a reliable tool for monitoring critical newborn changes, offering the opportunity to experimentally explore putative therapeutics in vivo. Sildenafil could be employed to prevent PHT and edema if used in the first stages of development of the disease.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Extravascular Lung Water; Humans; Hypertension, Pulmonary; Infant, Newborn; Lung; Male; Meconium Aspiration Syndrome; Piperazines; Purines; Sildenafil Citrate; Sulfones; Sus scrofa; Thermodilution; Time Factors; Vasodilator Agents

According to Indian Systems of Medicine, Spilanthes acmella (L.) Murr. (Family - Asteraceae), is considered effective in the treatment of sexual deficiencies especially due to ageing. In the present study, characterization of ethanolic extracts of the Spilanthes acmella flower and its effect on general mating pattern, penile erection and serum hormone levels of normal male Wistar albino rats were investigated and compared with sildenafil citrate. In vitro nitric oxide release was also investigated in human corpus cavernosum cell line. As N-alkylamides are a promising group, their profiling was performed using a gradient reversed phase high performance liquid chromatography/electrospray ionization ion trap mass spectrometry (HPLC/ESI-MS) method on an embedded polar column. MS(1) and MS(2) fragmentation data were used for identification purposes. For assessment of sexual behavior, animals were divided into five groups of eight male rats. The extracts (50, 100 and 150mg/kgbodyweight/day) and sildenafil citrate (5mg/kgbodyweight/day) (positive control) were administered orally for 28 days. The behavioral and sexual parameters were observed at days 0, 15, 28 and after a lapse of 7 and 14 days of discontinuance of drug treatment. Five N-isobutylamides, one 2-methylbutylamide and one 2-phenylethylamide were identified. The orally administered extract had a dose dependent positive effect on mounting frequency, intromission frequency and ejaculation frequency and the most significant effects (p<0.05) were observed at 150mg/kg treatment, even after a lapse of 7 and 14 days of discontinuance of drug treatment. A dose dependent effect was also observed on the FSH, LH and testosterone serum levels. With 150mg/kg of ethanolic extract the values for FSH, LH and testosterone were 3.10±0.25mlU/ml, 6.87±0.18mlU/ml and 3.72±0.12ng/ml, respectively. In vitro nitric oxide release was 21.7±2.9μM, which was significantly higher compared to the control group (p<0.01). Sildenafil citrate exhibited also a significant effect on NO release, but no effect on hormone levels of rats was observed. The aphrodisiac potential of an ethanolic Spilanthes acmella extract was demonstrated in vitro and in vivo. N-Alkylamides might attribute to the improved sexual potential. Study lends support to the traditional utilization of S. acmella as a sexual stimulating agent.

Topics: Animals; Asteraceae; Cell Line; Chromatography, Liquid; Disease Models, Animal; Erectile Dysfunction; Female; Flowers; Follicle Stimulating Hormone; Humans; Luteinizing Hormone; Male; Piperazines; Plant Extracts; Plants, Medicinal; Purines; Rats; Rats, Wistar; Sexual Behavior, Animal; Sildenafil Citrate; Sulfones; Tandem Mass Spectrometry; Testosterone; Vasodilator Agents

Clinical and preclinical data reported that ascorbic acid has antidepressant properties. The present study was designed to investigate the participation of l-arginine-NO-cGMP pathway in the antidepressant-like effect of ascorbic acid in the tail suspension test (TST) in mice. The antidepressant-like effect of ascorbic acid (1mg/kg, p.o.) in the TST was prevented by the pre-treatment of mice with NMDA (0.1pmol/site, i.c.v.), l-arginine (750mg/kg, i.p., a substrate for nitric oxide synthase) or sildenafil (5mg/kg, i.p., a phosphodiesterase 5 inhibitor). The administration of MK-801 (0.001mg/kg, i.p), 7-nitroindazole (25mg/kg, i.p., a neuronal nitric oxide synthase inhibitor) or ODQ (30pmol/site i.c.v., a soluble guanylate cyclase inhibitor) in combination with a sub-effective dose of ascorbic acid (0.1mg/kg, p.o.) reduced the immobility time in the TST test when compared with either drug alone. None of the results in the TST appears to be due to a nonspecific locomotor effect. Our findings provide evidence that the effect of ascorbic acid in the TST involve an interaction with NMDA receptors and l-arginine-NO-cGMP pathway, contributing to the understanding of the mechanisms underlying the antidepressant-like effect of this vitamin.

Topics: Animals; Antidepressive Agents; Arginine; Ascorbic Acid; Cyclic GMP; Depression; Disease Models, Animal; Dizocilpine Maleate; Enzyme Inhibitors; Exploratory Behavior; Female; Hindlimb Suspension; Indazoles; Mice; N-Methylaspartate; Nitric Oxide; Oxadiazoles; Piperazines; Purines; Quinoxalines; Signal Transduction; Sildenafil Citrate; Sulfones

Peripheral neuropathy is a common and major complication of diabetes, the underlying mechanisms of which are not fully understood. Using a mouse model of type II diabetes, the present study investigated the role of phosphodiesterase-5 (PDE5) in peripheral neuropathy. BKS.Cg-m+/+Leprdb/J (db/db) mice were treated with sildenafil, a specific inhibitor of PDE5, at doses of 2 and 10 mg/kg or saline. Levels of PDE5 and morphometric parameters in sciatic nerve tissue as well as the motor and sensory function were measured in these mice. In diabetic mice, PDE5 expression in sciatic nerve tissue was significantly upregulated, whereas the myelin sheath thickness, myelin basic protein (MBP), and subcutaneous nerve fibers were significantly reduced. Treatment with sildenafil significantly improved neurological function, assayed by motor and sensory conducting velocities and thermal and mechanical noxious stimuli, concomitantly with increases in myelin sheath thickness, MBP levels, and subcutaneous nerve fibers. In vitro, hyperglycemia upregulated PDE5 in Schwann cells and reduced Schwann cell proliferation, migration, and expression of brain-derived neurotrophic factor (BDNF). Blockage of PDE5 with sildenafil increased cyclic guanosine monophosphate (cGMP) and completely abolished the effect of hyperglycemia on Schwann cells. Sildenafil upregulated cGMP-dependent protein kinase G I (PKGI), whereas inhibition of PKGI with a PKG inhibitor, KT5823, suppressed the inhibitory effect of sildenafil on Schwann cells. These data indicate that hyperglycemia substantially upregulates PDE5 expression and that the cGMP/PKG signaling pathway activated by sildenafil mediates the beneficial effects of sildenafil on diabetic peripheral neuropathy.

Topics: Analysis of Variance; Animals; Animals, Newborn; Brain-Derived Neurotrophic Factor; Bromodeoxyuridine; Cells, Cultured; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Complications; Diabetic Neuropathies; Disease Models, Animal; Dose-Response Relationship, Drug; Gene Expression Regulation; Hyperalgesia; Male; Mice; Mice, Inbred C57BL; Mice, Neurologic Mutants; Nerve Tissue Proteins; Neural Conduction; Pain Measurement; Pain Threshold; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Receptors, Leptin; RNA, Small Interfering; Schwann Cells; Sciatic Neuropathy; Sildenafil Citrate; Sulfones; Time Factors; Transfection

Obesity is characterized by chronic inflammation of adipose tissue, which contributes to insulin resistance and diabetes. Although nitric oxide (NO) signaling has antiinflammatory effects in the vasculature, whether reduced NO contributes to adipose tissue inflammation is unknown. We sought to determine whether (1) obesity induced by high-fat (HF) diet reduces endothelial nitric oxide signaling in adipose tissue, (2) reduced endothelial nitric oxide synthase (eNOS) signaling is sufficient to induce adipose tissue inflammation independent of diet, and (3) increased cGMP signaling can block adipose tissue inflammation induced by HF feeding.. Relative to mice fed a low-fat diet, an HF diet markedly reduced phospho-eNOS and phospho-vasodilator-stimulated phosphoprotein (phospho-VASP), markers of vascular NO signaling. Expression of proinflammatory cytokines was increased in adipose tissue of eNOS-/- mice. Conversely, enhancement of signaling downstream of NO by phosphodiesterase-5 inhibition using sildenafil attenuated HF-induced proinflammatory cytokine expression and the recruitment of macrophages into adipose tissue. Finally, we implicate a role for VASP, a downstream mediator of NO-cGMP signaling in mediating eNOS-induced antiinflammatory effects because VASP-/- mice recapitulated the proinflammatory phenotype displayed by eNOS-/- mice.. These results imply a physiological role for endothelial NO to limit obesity-associated inflammation in adipose tissue and hence identify the NO-cGMP-VASP pathway as a potential therapeutic target in the treatment of diabetes.

Topics: Adipose Tissue; Animals; Cell Adhesion Molecules; Cyclic GMP; Dietary Fats; Disease Models, Animal; Endothelium, Vascular; Inflammation; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Microfilament Proteins; Nitric Oxide; Nitric Oxide Synthase Type III; Obesity; Phosphodiesterase 5 Inhibitors; Phosphoproteins; Phosphorylation; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Sulfones

Sildenafil, a selective and potent inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase (PDE)5, has a relaxant effect on the smooth muscle cells of the arterioles supplying the human corpus cavernosum acting via nitric oxide (NO)-dependent mechanism. This study aimed to investigate the possible protective effect of sildenafil citrate on the extent of tissue integrity, oxidant-antioxidant status and neutrophil infiltration to the inflamed organ in a rat model of bleomycin-induced lung fibrosis. Lung fibrosis was induced by intratracheal administration of 0.1 ml of bleomycin hydrochloride (5 mg/kg in 0.9% NaCl) under anesthesia to Sprague-Dawley rats (200-250 g; n = 7-8 per group). Control rats received an equal volume of saline intratracheally. In the treatment groups, the rats were treated with either sildenafil citrate (10 mg/kg per day; subcutaneously) or saline for 14 days. Another group of rats were administered subcutaneously with N(G)-nitro-l-arginine methyl ester (l-NAME; 20 mg/kg in 0.9% NaCl) 5 min after sildenafil injections. After decapitation, the lungs were excised and taken for microscopic evaluation or stored for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, and myeloperoxidase (MPO) activity, and for the assessment of apoptosis. Trunk blood was collected for the assessment of serum tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta levels. In the group with lung fibrosis, the lung tissue was characterized by microscopic lesions, increased lipid peroxidation with a concomitant reduction in GSH content, increased MPO activity and apoptosis. Serum TNF-alpha and IL-1beta levels were higher in the lung fibrosis group compared to control values. Sildenafil reversed tissue MDA levels, MPO activity and serum pro-inflammatory cytokine levels, and preserved GSH content although its effect on the extent of tissue lesion and apoptosis was not statistically significant. Treatment with l-NAME reversed the effect of sildenafil on GSH content. In conclusion, sildenafil citrate administration to rats with bleomycin-induced lung fibrosis seems to be beneficial via prevention of lipid peroxidation, cytokine production and/or release and neutrophil accumulation.

Topics: Animals; Apoptosis; Bleomycin; Disease Models, Animal; Female; Glutathione; Interleukin-1beta; Lung; Male; Malondialdehyde; Neutrophils; NG-Nitroarginine Methyl Ester; Peroxidase; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Pulmonary Fibrosis; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Tumor Necrosis Factor-alpha

Adequate placental blood flow is essential for the optimal delivery of nutrients from mother to fetus for conceptus growth. Restricted fetal development results from pathophysiological and environmental factors that alter utero-placental blood flow, placental function, and, therefore, nutrient availability in the fetus. To test this hypothesis, 0, 75, or 150 mg/d sildenafil citrate (Viagra) was administered subcutaneously from d 28 to 115 of gestation to either nutrient-restricted [50% of NRC requirements) or adequately-fed ewes (100% of NRC requirements). On d 115, maternal, fetal, and placental tissues and fluids were collected. Concentrations of total amino acids and polyamines in uterine venous and arterial sera, amniotic and allantoic fluids, and fetal umbilical venous serum were lower (P < 0.05) in nutrient-restricted ewes than in adequately fed ewes, as were the ratios of total amino acids in fetal umbilical venous serum to uterine arterial serum. Sildenafil citrate dose-dependently increased (P < 0.05) total amino acids and polyamines in amniotic fluid, allantoic fluid, and fetal serum without affecting values in maternal serum. Fetal weight was lower (P < 0.05) in nutrient-restricted ewes on d 115. Sildenafil citrate treatment dose-dependently increased (P < 0.05) fetal weight in both nutrient-restricted and adequately fed ewes. This study supports the hypothesis that long-term sildenafil citrate treatment enhances fetal growth, at least in part, by increasing the availability of amino acids in the conceptus. These findings may lead to the clinical use of sildenafil citrate in human pregnancies suspected to be at risk for intrauterine fetal growth retardation.

Topics: Amino Acids; Amniotic Fluid; Animal Nutritional Physiological Phenomena; Animals; Dietary Proteins; Disease Models, Animal; Dose-Response Relationship, Drug; Embryonic Development; Female; Fetal Growth Retardation; Fetal Weight; Fetus; Maternal Nutritional Physiological Phenomena; Piperazines; Placenta; Polyamines; Pregnancy; Prenatal Nutritional Physiological Phenomena; Purines; Sheep; Sildenafil Citrate; Sulfones; Umbilical Veins; Uterine Artery; Vasodilator Agents

We determined the metabolic changes that precede cell death in the dystrophic proline-23-histidine (P23H) line 3 (P23H-3) rat retina compared with the normal Sprague-Dawley (SD) rat retina. Metabolite levels and metabolic enzymes were analyzed early in development and during the early stages of degeneration in the P23H-3 retina. Control and degenerating retinas showed an age-dependent change in metabolite levels and enzymatic activity, particularly around the time when phototransduction was activated. However, lactate dehydrogenase (LDH) activity was significantly higher in P23H-3 than SD retina before the onset of photoreceptor death. The creatine/phosphocreatine system did not contribute to the increase in ATP, because phosphocreatine levels, creatine kinase, and expression of the creatine transporter remained constant. However, Na(+)-K(+)-ATPase and Mg(2+)-Ca(2+)-ATPase activities were increased in the developing P23H-3 retina. Therefore, photoreceptor apoptosis in the P23H-3 retina occurs in an environment of increased LDH, ATPase activity, and higher-than-normal ATP levels. We tested the effect of metabolic challenge to the retina by inhibiting monocarboxylate transport with alpha-cyano-4-hydroxycinnamic acid or systemically administering the phosphodiesterase inhibitor sildenafil. Secondary to monocarboxylate transport inhibition, the P23H-3 retina did not demonstrate alterations in metabolic activity. However, administration of sildenafil significantly reduced LDH activity in the P23H-3 retina and increased the number of terminal deoxynucleotidyl transferase biotin-dUPT nick end-labeled photoreceptor cells. Photoreceptor cells with a rhodopsin mutation display an increase in apoptotic markers secondary to inhibition of a phototransduction enzyme (phosphodiesterase), suggesting increased susceptibility to altered cation entry.

Topics: Adenosine Triphosphate; Age Factors; Animals; Apoptosis; Ca(2+) Mg(2+)-ATPase; Coumaric Acids; Creatine; Creatine Kinase; Disease Models, Animal; Disease Progression; Energy Metabolism; Histidine; L-Lactate Dehydrogenase; Membrane Transport Proteins; Monocarboxylic Acid Transporters; Mutation; Phosphocreatine; Phosphodiesterase Inhibitors; Piperazines; Proline; Purines; Rats; Rats, Sprague-Dawley; Rats, Transgenic; Retina; Retinitis Pigmentosa; Sensory Rhodopsins; Sildenafil Citrate; Sodium-Potassium-Exchanging ATPase; Sulfones

This study aimed to investigate the effects of sildenafil citrate on various fetal and physiological parameters, including fetal mortality, number of pups, placental weights and micro-albuminuria in pregnant, L-NAME treated Sprague-Dawley rats.. Twenty-four pregnant female Sprague-Dawley rats were divided into 3 groups (n=8). In the L-NAME treated group (PRE), l-NAME (0.3 g/l, drinking water) was used to induce pre-eclampsia-like symptoms on day 1 of the experiment. The experimental group (SCT) also received L-NAME (0.3 g/l, drinking water) on day 1 of the experiment. However, sildenafil citrate (10 mg/kg, s.c., daily) was administered as the test compound from day 7 until day 19. The experimental control (CON) did not receive either L-NAME or sildenafil citrate. L-NAME administration was discontinued in both the PRE and the SCT groups on day 19 of the experiment and the animals were given access to normal drinking water ad libitum. All the animals were sacrificed on day 20, at which time a laparotomy was performed and the various fetal parameters measured. On day 0 and day 20, blood pressure measurements were recorded non-invasively and protein estimations in 24h urine samples were conducted.. Sildenafil citrate decreased fetal mortality and protein excretion and further demonstrated a trend toward increasing birth and placental weights in pregnant, L-NAME treated, Sprague-Dawley rats. In addition, sildenafil citrate administration ameliorated the amplification of the L-NAME induced hypertension in the SCT group.. We speculate that sildenafil citrate by potentiating the effects of nitric oxide in vivo improves uterine artery blood flow resulting in improved fetal outcomes in pregnant, L-NAME treated, Sprague-Dawley rats.

Topics: Analysis of Variance; Animals; Blood Pressure; Disease Models, Animal; Female; Fetal Death; NG-Nitroarginine Methyl Ester; Piperazines; Pre-Eclampsia; Pregnancy; Pregnancy Outcome; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Vasodilator Agents

The present study evaluated the effects of sildenafil using the 4-vessel occlusion (VO)/internal carotid artery (ICA) model of chronic cerebral hypoperfusion (HCC). We previously found that permanent, three-stage occlusion of the vertebral arteries (VA) and ICA, four-VO/ICA, with an interstage interval (ISI) of 7 days was innocuous and caused no structural or functional outcomes in rats. Therefore, before testing sildenafil, we evaluated how a reduction in the number of occlusion stages (from three stages to two) and a shortening of the ISI might impact the survival rate, capacity for learning and memory, and histomorphological integrity of the hippocampus. Survival decreased from 100% to 70%, 62%, and 0% as the ISI was shortened from 7 to 5, 4, or 3 days, respectively. Using the two shortest ISIs, sildenafil (0.75-3.0 mg/kg, p.o.) abolished the mortality rate by approximately 95%. Profound neurodegeneration occurred in the CA1, CA2, CA3, and CA4 hippocampal subfields after an ISI of 4 days. Despite this, however, memory performance was unaffected. Subsequently, sildenafil treatment reduced 4-VO/ICA-induced hippocampal damage. The present results suggest that sildenafil may be potentially beneficial in the treatment of chronic cerebral hypoperfusion. Further studies should examine the manner by which the chronic 4-VO/ICA model may effectively cause cognitive impairment, thus improving its applicability in testing the effects of drugs against structural and/or functional outcomes of chronic cerebral hypoperfusion.

Topics: Animals; Carotid Artery Diseases; Cell Death; Cerebrovascular Disorders; Chronic Disease; Disease Models, Animal; Dose-Response Relationship, Drug; Hippocampus; Male; Maze Learning; Memory; Piperazines; Purines; Pyramidal Cells; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones; Time Factors; Vasodilator Agents; Vertebrobasilar Insufficiency

Arterial hypertension is one of the major diseases in industrial countries and a major cause of mortality. One of the main vascular factors responsible for the relaxation of blood vessels and regulation of blood pressure is nitric oxide (NO). NO acts predominantly via NO-sensitive guanylyl cyclase (NO-GC), which is made up of 2 different subunits (alpha and beta). Deletion of the beta(1) subunit leads to a global NO-GC knockout, and these mice are hypertensive. However, global deletion of NO-GC in mice does not allow identification of the cell/tissue type responsible for the elevated blood pressure.. To determine the relative contribution of smooth muscle cells to the hypertension seen in NO-GC knockout mice, we generated smooth muscle-specific knockout mice for the beta(1) subunit of NO-GC using a tamoxifen-inducible system. Male mice were investigated because the Cre transgene used is located on the Y chromosome. Tamoxifen injection led to a rapid reduction of NO-GC expression in smooth muscle but did not affect that in other tissues. Parallel to a reduction in NO-induced cGMP accumulation, NO-induced relaxation of aortic smooth muscle was gradually lost after induction by tamoxifen. Concomitantly, these animals developed hypertension within 3 to 4 weeks.. We generated a model in which the development of hypertension can be visualized over time by deletion of a single gene in smooth muscle cells. In sum, our data provide evidence that deletion of NO-GC solely in smooth muscle is sufficient to cause hypertension.

Topics: Animals; Blood Platelets; Blood Pressure; Brain; Cyclic GMP; Disease Models, Animal; Endothelium-Dependent Relaxing Factors; Gene Expression; Guanylate Cyclase; Hypertension; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Protein Subunits; Purines; Receptors, Cytoplasmic and Nuclear; Sildenafil Citrate; Soluble Guanylyl Cyclase; Sulfones; Tamoxifen; Transgenes; Vasodilation

Pulmonary hypertension is a group of diseases comprising vascular constriction and obstructive changes of the pulmonary vasculature. Phosphodiesterase type 5 inhibitors, for example, sildenafil, can alleviate vascular remodeling in the monocrotaline pulmonary hypertension model in rats. We investigate the mechanisms of sildenafil on the pulmonary vascular remodeling of pulmonary hypertension induced by monocrotaline (MCT) in rats. Thirty Sprague-Dawley rats (weighing 200-220 g) were administered with MCT abdominal cavity injection or equivalent volume of normal saline (NS) (which were treated as C group n = 10) to induce pulmonary hypertension model. Fourteen days later, 20 MCT treated rats were randomly fed with sildenafil (25mg/kg/day) or placebo as S, P group (10 rats for each group), respectively. Another 6 weeks later, mean pulmonary artery pressure (mPAP), index of right ventricular hypertrophy (RV/LV+S) of all animals were measured under general anesthesia. Pulmonary tissue was collected to investigate pathological features of pulmonary arteries and to measure protein expression of ERK(1)/ERK(2) and MKP1. After 6 weeks, there were significant elevated mPAP and RV/LV+S in both P and S groups. The ratio of wall thickness to vessel diameter in pulmonary arteries with diameters <200 microm were increased in both P and S groups. But the ratio of wall thickness to vessel diameter was smaller in S group than that in P group. The phosphorylation level of ERK(1)/ERK(2) were elevated in both P and S groups, but the level of phosphorlation ERK(1)/ERK(2) were lower in S group than that in P group. Intriguingly, the expression level of MKP1 was significantly increased in both S and P groups, while it was higher in S group than that in P group. The sildenafil can decrease mPAP and inhibit the progress of pulmonary vascular remodeling in pulmonary hypertension rats. The ERK-MAP kinase signaling pathway might play a role during this process.

Topics: Actins; Animals; Antihypertensive Agents; Blood Pressure; Disease Models, Animal; Dual Specificity Phosphatase 1; Fluorescent Antibody Technique; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Monocrotaline; Phosphorylation; Piperazines; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; Signal Transduction; Sildenafil Citrate; Sulfones; Vasodilator Agents

Diet-induced obesity (DIO) in mice causes vascular inflammation and insulin resistance that are accompanied by decreased endothelial-derived NO production. We sought to determine whether reduced NO-cGMP signaling contributes to the deleterious effects of DIO on the vasculature and, if so, whether these effects can be blocked by increased vascular NO-cGMP signaling.. By using an established endothelial cell culture model of insulin resistance, exposure to palmitate, 100 micromol/L, for 3 hours induced both cellular inflammation (activation of IKK beta-nuclear factor-kappaB) and impaired insulin signaling via the insulin receptor substrate-phosphatidylinositol 3-kinase pathway. Sensitivity to palmitate-induced endothelial inflammation and insulin resistance was increased when NO signaling was reduced using an endothelial NO synthase inhibitor, whereas endothelial responses to palmitate were blocked by pretreatment with either an NO donor or a cGMP analogue. To investigate whether endogenous NO-cGMP signaling protects against vascular responses to nutrient excess in vivo, adult male mice lacking endothelial NO synthase were studied. As predicted, both vascular inflammation (phosphorylated I kappaB alpha and intercellular adhesion molecule levels) and insulin resistance (phosphorylated Akt [pAkt] and phosphorylated eNOS [peNOS] levels) were increased in endothelial NO synthase(-/-) (eNOS(-/-)) mice, reminiscent of the effect of DIO in wild-type controls. Next, we asked whether the vascular response to DIO in wild-type mice can be reversed by a pharmacological increase of cGMP signaling. C57BL6 mice were either fed a high-fat diet or remained on a low-fat diet for 8 weeks. During the final 2 weeks of the study, mice on each diet received either placebo or the phosphodiesterase-5 inhibitor sildenafil, 10 mg/kg per day orally. In high-fat diet-fed mice, vascular inflammation and insulin resistance were completely prevented by sildenafil administration at a dose that had no effect in mice fed the low-fat diet.. Reduced signaling via the NO-cGMP pathway is a mediator of vascular inflammation and insulin resistance during overnutrition induced by high-fat feeding. Therefore, phosphodiesterase-5, soluble guanylyl cyclase, and other molecules in the NO-cGMP pathway (eg, protein kinase G) constitute potential targets for the treatment of vascular dysfunction in the setting of obesity.

Topics: Animals; Aorta, Thoracic; Aortic Diseases; Cell Adhesion Molecules; Cells, Cultured; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Dietary Fats; Disease Models, Animal; Down-Regulation; Endothelial Cells; Enzyme Inhibitors; Humans; I-kappa B Kinase; Inflammation; Inflammation Mediators; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; NF-kappa B; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase Type III; Palmitic Acid; Phosphatidylinositol 3-Kinases; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Proto-Oncogene Proteins c-akt; Purines; Signal Transduction; Sildenafil Citrate; Sulfones

The cGMP/PK-G pathway plays a crucial role in neuroprotection and neurotrophin support, and is possibly involved in antidepressant action. Recently we reported on a novel antidepressant-like response following simultaneous administration of sildenafil (phosphodiesterase 5 (PDE5) inhibitor, thereby increasing cGMP levels), and atropine (muscarinic acetylcholine receptor antagonist) in the rat forced swim test (FST). However, it is unclear whether the antidepressant-like activity of sildenafil+atropine is mediated via the activation of PK-G, an important down-stream effector for cGMP, and whether this may target known pathways in antidepressant action. We investigated whether the antidepressant-like response of sildenafil+/-atropine could be reversed by Rp-8-Br-PET-cGMP, a PK-G inhibitor, and also whether a combination of 8-Br-cGMP (PK-G activator)+/-atropine would likewise be active in the FST, and whether this combination could be attenuated by a PK-G inhibitor. 8-Br-cGMP alone, but not sildenafil alone, reduced immobility and selectively increased swimming in the FST. The antidepressant-like action of sildenafil was only evident following co-administration of atropine, and selectively increased climbing behaviour. Importantly, PK-G inhibition prevented the antidepressant-like effects of both 8-Br-cGMP and the sildenafil/atropine combination. These results confirm cholinergic-cGMP-PK-G interactions in the antidepressant-like effects of sildenafil, putatively acting via noradrenergic mechanisms, whereas direct PK-G activation induces antidepressant-like effects that are associated with enhancement of serotonergic neurotransmission.

Topics: Animals; Atropine; Behavior, Animal; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Depression; Disease Models, Animal; Drug Administration Routes; Drug Interactions; Drug Therapy, Combination; Freezing Reaction, Cataleptic; Male; Muscarinic Antagonists; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Statistics, Nonparametric; Sulfones; Swimming; Thionucleotides

Sildenafil, a phosphodiesterase-5 inhibitor, and simvastatin, a cholesterol lowering drug, both have therapeutic effects on PAH; however, the combination of these drugs has not been tested in the treatment of PAH. The purpose of this study was to determine whether the combination of sildenafil and simvastatin is superior to each drug alone in the prevention of MCT-induced PAH. Phosphorylated Smad levels were decreased in lung tissue in MCT-injected rats, whereas ERK protein levels were increased. This indicates a possible role for an increase in mitogenic ERK activity in addition to decreased proapoptotic Smad signaling in the MCT model of PAH. Combination sildenafil and simvastatin treatment prevented the MCT-induced increases in right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH), exerted an anti-proliferative effect on pulmonary artery smooth muscle cells (PASMC). Our results indicate that combination therapy with sildenafil and simvastatin attenuated the development of pulmonary hypertension more than either treatment alone.

Topics: Animals; Anticholesteremic Agents; Disease Models, Animal; Drug Therapy, Combination; Hypertension, Pulmonary; Male; Monocrotaline; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Simvastatin; Sulfones

Lithium is still the mainstay in the treatment of affective disorders as a mood stabilizer. Lithium also shows some anticonvulsant properties. While the underlying mechanisms of action of lithium are not yet exactly understood, we used a model of clonic seizure induced by pentylenetetrazole (PTZ) in male NMRI mice to investigate whether the anticonvulsant effect of lithium is mediated via NO-cGMP pathway. Injection of a single effective dose of lithium chloride (25 mg/kg) intraperitoneally (i.p.) increased significantly the seizure threshold (P<0.01). The anticonvulsant properties of the effective dose of lithium were prevented by pre-treatment with the per se non-effective doses of L-ARG [the substrate for nitric oxide synthase; NOS] (30 and 50 mg/kg) or sildenafil [a phosphodiesterase 5 inhibitor] (10 and 20 mg/kg). L-NAME [a non-specific NOS inhibitor] (5, 15 and 30 mg/kg), 7-NI [a specific neural NOS inhibitor] (30 and 60 mg/kg) or MB [a guanylyl cyclase inhibitor] (0.5 and 1 mg/kg) augmented the anticonvulsant effect of a sub-effective dose of lithium (10 mg/kg, i.p.). Whereas several doses of aminoguanidine [an inducible NOS inhibitor] (20, 50 and 100 mg/kg) failed to alter the anticonvulsant effect of lithium. Our findings demonstrated that nitric oxide-cyclic GMP pathway could be involved in the anticonvulsant properties of the lithium chloride. In addition, the role of constitutive NOS versus inducible NOS is prominent in this phenomenon.

Topics: Animals; Anticonvulsants; Arginine; Convulsants; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Indazoles; Injections, Intraperitoneal; Lithium Chloride; Male; Methylene Blue; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Pentylenetetrazole; Phosphodiesterase Inhibitors; Piperazines; Purines; Seizures; Sildenafil Citrate; Sulfones; Treatment Outcome

Phosphodiesterase type 5 (PDE5) inhibition has been shown to exert profound beneficial effects in the failing heart, suggesting a significant role for PDE5 in the development of congestive heart failure (CHF). The purpose of this study is to test the hypothesis that oxidative stress causes increased PDE5 expression in cardiac myocytes and that increased PDE5 contributes to the development of CHF.. Myocardial PDE5 expression and cellular distribution were determined in left ventricular samples from patients with end-stage CHF and normal donors and from mice after transverse aortic constriction (TAC)-induced CHF. Compared with donor human hearts, myocardial PDE5 protein was increased approximately equal 4.5-fold in CHF samples, and the increase of myocardial PDE5 expression was significantly correlated with myocardial oxidative stress markers 3'-nitrotyrosine or 4-hydroxynonenal expression (P<0.05). Histological examination demonstrated that PDE5 was mainly expressed in vascular smooth muscle in normal donor hearts, but its expression was increased in both cardiac myocytes and vascular smooth muscle of CHF hearts. Myocardial PDE5 protein content and activity also increased in mice after TAC-induced CHF (P<0.05). When the superoxide dismutase (SOD) mimetic M40401 was administered to attenuate oxidative stress, the increased PDE5 protein and activity caused by TAC was blunted, and the hearts were protected against left ventricular hypertrophy and CHF. Conversely, increased myocardial oxidative stress in superoxide dismutase 3 knockout mice caused a greater increase of PDE5 expression and CHF after TAC. In addition, administration of sildenafil to inhibit PDE5 attenuated TAC-induced myocardial oxidative stress, PDE5 expression, and CHF.. Myocardial oxidative stress increases PDE5 expression in the failing heart. Reducing oxidative stress by treatment with M40401 attenuated cardiomyocyte PDE5 expression. This and selective inhibition of PDE5 protected the heart against pressure overload-induced left ventricular hypertrophy and CHF.

Topics: Animals; Antioxidants; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; Heart Failure; Humans; Hypertrophy, Left Ventricular; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocytes, Cardiac; Nitric Oxide Synthase Type II; Organometallic Compounds; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Proto-Oncogene Proteins c-akt; Purines; Signal Transduction; Sildenafil Citrate; Sulfones; Superoxide Dismutase

The therapeutic effect of sildenafil citrate on cerebral vasospasm after experimental subarachnoid hemorrhage (SAH) was studied in a rat model.. We used four groups of seven rats were as follows: no SAH, no treatment; SAH only; SAH plus 2 days of peroral sildenafil citrate 5mg/kg treatment and SAH plus 2 days of peroral sildenafil citrate 15 mg/kg treatment. Three different parameters were evaluated including the diameter of the basilar artery, the level of lipid peroxidation and the degree of the apoptosis 48 hours following SAH.. The results showed that sildenafil citrate attenuated SAH-induced cerebral vasospasm in the treatment groups in terms of the diameter of the basilar artery and lipid peroxidation in the two treatment groups, but there was no difference in terms of the level of apoptosis.. This study indicates that further research on the therapeutic effect of sildenafil citrate can be combined with the use of any apoptosis-blocking agent for the treatment of cerebral vasospasm following experimental subarachnoid hemorrhage.

Topics: Animals; Apoptosis; Disease Models, Animal; Immunohistochemistry; In Situ Nick-End Labeling; Lipid Peroxidation; Male; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Subarachnoid Hemorrhage; Sulfones; Vasodilator Agents; Vasospasm, Intracranial; Vertebrobasilar Insufficiency

We explored the antidepressant-like properties of two phosphodiesterase type 5 (PDE5) inhibitors in a genetic animal model of depression, namely Flinders sensitive line rats. We investigated the dose-dependency of the antidepressant-like action of sildenafil, and its interaction with the cholinergic system and behavioural correlates of monoaminergic neurotransmission, in the forced swim test. Antidepressant-like properties of tadalafil (a structurally distinct PDE5 inhibitor) were also evaluated. Flinders sensitive line rats were treated for 14 days with vehicle, fluoxetine, atropine or PDE5 inhibitors+/-atropine. Immobility, swimming and climbing behaviours were assessed in the forced swim test. In combination with atropine (1 mg/kg), both sildenafil (10, 20 mg/kg) and tadalafil (10 mg/kg) decreased immobility while increasing swimming (serotonergic) and climbing (noradrenergic) behaviours. Interestingly, sildenafil (3 mg/kg) decreased immobility while selectively increasing climbing behaviour in the absence of atropine. These results suggest that the antidepressant-like activity of PDE5 inhibitors involve alterations in monoaminergic neurotransmission, but involve a dependence on inherent cholinergic tone so that the final response is determined by the relative extent of activation of these systems. Furthermore, the behavioural profile of sildenafil alone, and its observed antidepressant-like properties, shows strict dose-dependency, with only higher doses showing an interaction with the cholinergic system.

Topics: Animals; Antidepressive Agents; Atropine; Behavior, Animal; Carbolines; Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Fluoxetine; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Sildenafil Citrate; Sulfones; Swimming; Tadalafil

Experimental left-to-right shunt-induced pulmonary arterial hypertension (PAH) can be partially prevented by the endothelin-A receptor blocker sitaxsentan or by the phosphodiesterase-5 inhibitor sildenafil. We hypothesized that the combined administration of these drugs would completely prevent shunt-induced PAH, arguing in favor of a major role of endothelial dysfunction in the initiation of the disease. Twenty-four 3-wk-old piglets were randomized to a sham operation or to placebo, sitaxsentan therapy, or sitaxsentan combined with sildenafil after the anastomosis of the left subclavian artery to the pulmonary arterial trunk. Three months later, the animals underwent a hemodynamic evaluation, followed by pulmonary tissue sampling for morphometry and quantitative real-time PCR for endothelin-1, angiopoietin-1, and bone morphogenetic protein receptor (BMPR) signaling molecules. Three months of left-to-right shunting induced an increase in pulmonary vascular resistance (PVR) and medial thickness, an overexpression of endothelin-1, and angiopoietin-1 and decreased expressions of BMPR-2 and BMPR-1A. Sitaxsentan partially prevented a shunt-induced increase in PVR, medial thickness, and associated biological disturbances. Sildenafil combined with sitaxsentan normalized PVR, medial thickness, and the expression of endothelin-1. However, the expression of angiopoietin-1 remained increased, and the expressions of BMPR-1A and BMPR-2 were incompletely returned to normal. The coupling of right ventricular end-systolic to arterial elastances was maintained in all circumstances. Sitaxsentan combined with sildenafil prevents shunt-induced PAH more effectively than sitaxsentan alone, suggesting a major role for the targeted signaling pathways in the initiation of the disease. Sitaxsentan alone or combined with sildenafil did not affect right ventricular function.

Topics: Angiopoietin-1; Animals; Bone Morphogenetic Protein Receptors, Type II; Disease Models, Animal; Drug Therapy, Combination; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Isoxazoles; Phosphodiesterase 5 Inhibitors; Piperazines; Pulmonary Artery; Pulmonary Circulation; Purines; Sildenafil Citrate; Subclavian Artery; Sulfones; Thiophenes; Treatment Outcome

Duchenne muscular dystrophy (DMD) is a progressive and fatal genetic disorder of muscle degeneration. Patients with DMD lack expression of the protein dystrophin as a result of mutations in the X-linked dystrophin gene. The loss of dystrophin leads to severe skeletal muscle pathologies as well as cardiomyopathy, which manifests as congestive heart failure and arrhythmias. Like humans, dystrophin-deficient mice (mdx mice) show cardiac dysfunction as evidenced by a decrease in diastolic function followed by systolic dysfunction later in life. We have investigated whether sildenafil citrate (Viagra), a phosphodiesterase 5 (PDE5) inhibitor, can be used to ameliorate the age-related cardiac dysfunction present in the mdx mice. By using echocardiography, we show that chronic sildenafil treatment reduces functional deficits in the cardiac performance of aged mdx mice, with no effect on normal cardiac function in WT controls. More importantly, when sildenafil treatment was started after cardiomyopathy had developed, the established symptoms were rapidly reversed within a few days. It is recognized that PDE5 inhibitors can have cardioprotective effects in other models of cardiac damage, but the present study reports a prevention and reversal of pathological cardiac dysfunction as measured by functional analysis in a mouse model of DMD. Overall, the data suggest that PDE5 inhibitors may be a useful treatment for the cardiomyopathy affecting patients with DMD at early and late stages of the disease.

Topics: Animals; Cardiomyopathies; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dystrophin; Mice; Mice, Inbred mdx; Muscular Dystrophy, Duchenne; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

To evaluate the effect of sildenafil, administered prior to renal ischemia/reperfusion (I/R), by scintigraphy and histopathological evaluation in rats.. Twenty-four rats were divided randomly into two groups. They received 0.1 ml of 99mTechnetium-etilenodicisteine intravenous, and a baseline (initial) renal scintigraphy was performed. The rats underwent 60 minutes of ischemia by left renal artery clamping. The right kidney was not manipulated. The sildenafil group (n=12) received orally 1 mg/kg of sildenafil suspension 60 minutes before ischemia. Treatment with saline 0.9% in the control group (n=12). Half of the rats was assessed after 24 hours and half after seven days I/R, with new renal scintigraphy to study differential function. After euthanasia, kidneys were removed and subjected to histopathological examination. For statistical evaluation, Student t and Mann-Whitney tests were used.. In the control group rats, the left kidneys had significant functional deficit, seven days after I/R, whose scintigraphic pattern was consistent with acute tubular necrosis, compared with the initial scintigraphy (p<0.05). Sildenafil treatment resulted in better differential function of the left kidneys 24h after reperfusion, compared with controls. Histopathologically, the left kidney of control rats (24 hours after I/R) showed a higher degree of cellular necrosis when compared with the sildenafil treated rats (p<0.05).. Sildenafil had a protective effect in rat kidneys subjected to normothermic I/R, demonstrated by scintigraphy and histomorphometry.

Topics: Animals; Disease Models, Animal; Kidney; Piperazines; Purines; Radionuclide Imaging; Random Allocation; Rats; Rats, Wistar; Reperfusion Injury; Sildenafil Citrate; Statistics, Nonparametric; Sulfones; Vasodilator Agents

We determined the effect of passive secondhand cigarette smoke on 1) erectile function in vivo, 2) molecular mechanisms involved in penile vascular function, and 3) erectile function and penile molecular signaling in the presence of phosphodiesterase type 5 inhibitor therapy.. Four groups of mice were used, including group 1--controls, group 2--mice exposed to 3 weeks of secondhand smoke (5 hours per day for 5 days per week), group 3--control plus sildenafil (100 mg/kg per day) and group 4--smoke exposed plus sildenafil (100 mg/kg per day). Cavernous nerve electrical stimulation and intracavernous injection of acetylcholine were done to assess erectile function. Constitutive and inducible nitric oxide synthase activity, reactive oxygen species generation, nitrotyrosine formation and superoxide anion levels were assessed.. Decreased erectile responses to cavernous nerve electrical stimulation and impaired endothelium dependent erectile responses to ACh in mice exposed to secondhand smoke were observed. Superoxide anion was increased in endothelial and corporeal smooth muscle cells of smoking mouse penises. In mice exposed to secondhand smoke constitutive nitric oxide synthase activity was decreased, and inducible nitric oxide synthase activity, reactive oxygen species generation and nitrotyrosine formation increased. Sildenafil therapy restored constitutive nitric oxide synthase activity in the penis of smoking mice, decreased inducible nitric oxide synthase activity, reactive oxygen species generation and nitrotyrosine formation, and improved erectile responses to cavernous nerve electrical stimulation and acetylcholine.. Short-term exposure to secondhand smoke impairs erectile function through excessive penile reactive oxygen species signaling and inducible nitric oxide synthase activity. Decreased penile constitutive nitric oxide synthase activity may be attributable to the decreased endothelial nitric oxide synthase activity resulting from increased oxidative stress. Sildenafil therapy restored nitric oxide synthase activity and decreased reactive oxygen species signaling, resulting in improved erectile function.

Topics: Administration, Oral; Animals; Disease Models, Animal; Endothelium, Vascular; Erectile Dysfunction; Male; Mice; Mice, Inbred C57BL; Nitric Oxide Synthase; Penile Erection; Phosphodiesterase Inhibitors; Piperazines; Purines; Random Allocation; Reactive Oxygen Species; Reference Values; Sensitivity and Specificity; Signal Transduction; Sildenafil Citrate; Sulfones; Superoxides; Tobacco Smoke Pollution

Topics: Animals; Calcium; Disease Models, Animal; Gene Expression; Heart; Humans; Myocardium; Phosphodiesterase Inhibitors; Piperazines; Purines; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Sildenafil Citrate; Sulfones; Ventricular Remodeling

Inhibition of phosphodiesterase 5 (PDE5) decreases pulmonary pressure and improves symptoms in patients with pulmonary arterial hypertension. It is unclear however, whether inhibition of PDE5 can prevent myocardial remodelling during right-ventricular pressure overload.. Right-ventricular pressure overload was produced in male rats in a pulmonary hypertension model (monocrotaline 60 mg/kg s.c.) or by surgical pulmonary artery banding. PDE5 inhibition using oral sildenafil (50 mg/kg/day in drinking water) or placebo was initiated 14 days after monocrotaline treatment and continued for 14 days until final examination. In the pulmonary artery banding groups, rats were treated with sildenafil (50 mg/kg/day) or placebo for 21 days following surgical pulmonary artery banding. At the final experiments, right-ventricular haemodynamics were measured and remodelling was analysed using histological, biochemical, and gene expression markers. Both monocrotaline and pulmonary artery banding increased right-ventricular systolic pressure to approximately 80 mmHg. In parallel, both interventions induced markers of hypertrophy (upregulation of natriuretic peptides, increase in myocyte diameter) and fibrosis (upregulation of collagen types 1A2 and 3A1) as well as mRNA expression of the tissue inhibitor of matrix metalloproteases 1 and osteopontin in the right ventricle. In monocrotaline model, sildenafil decreased pulmonary pressure, reduced right-ventricular hypertrophy, and prevented fibrosis marker gene upregulation. After pulmonary artery banding, in contrast, sildenafil increased markers of myocardial remodelling and right-ventricular myocyte diameter.. Sildenafil prevents myocardial remodelling in pulmonary hypertension through an indirect action via right-ventricular unloading.

Topics: Administration, Oral; Animals; Blood Pressure; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Fibrillar Collagens; Fibrosis; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Monocrotaline; Myocardium; Natriuretic Peptides; Osteopontin; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; Rats, Wistar; RNA, Messenger; Sildenafil Citrate; Stroke Volume; Sulfones; Time Factors; Tissue Inhibitor of Metalloproteinase-1; Ventricular Pressure; Ventricular Remodeling

Inhibition of matrix metalloproteinases (MMPs) improves the hemodynamics during acute pulmonary embolism (APE) and oxidative stress upregulates MMPs. We compared the effects of different NO-cGMP pathway activators on APE-induced increases in MMPs.. Hemodynamic and biochemical evaluations were performed in non-embolized dogs treated with saline (N=5), and in microspheres embolized dogs receiving saline (n=9), or nitrite (6.75 micromol/kg i.v. over 15 min followed by 0.28 micromol/kg/min; n=5), or sildenafil (0.25 mg/kg; n=5), or BAY 41-2272 (0.03, 0.1, 0.3, and 1 mg/kg/h; n=5). Plasma thiobarbituric acid reactive substances (TBARS) concentrations were determined. Zymograms of plasma samples were performed, and in vitro antioxidant effects or inhibition of MMPs by these drugs were examined.. APE increased mean pulmonary artery pressure by ~25 mmHg. Nitrite, BAY 41-2272, or sildenafil reversed this increase by ~40% (P<0.05). Similar effects were seen on the pulmonary vascular resistance. While both nitrite and sildenafil produced no systemic effects, the highest dose of BAY 41-2272 produced systemic hypotension (P<0.05). While nitrite and sildenafil blunted the increases in plasma pro-MMP-9 levels and TBARS (all P<0.05), BAY 41-2272 produced no such effects. Nitrite and sildenafil produced in vitro antioxidant effects and inhibited MMPs only at high concentrations. BAY 41-2272 produced no such effects.. Activation of the NO-cGMP pathway with nitrite or sildenafil, but not with BAY 41-2272, attenuates APE-induced oxidative stress and increased MMP-9 levels. These findings are consistent with the idea that NO-cGMP pathway activators with antioxidant effects prevent the release of MMP-9 during APE.

Topics: Acute Disease; Animals; Disease Models, Animal; Dogs; Female; Humans; Male; Matrix Metalloproteinase 9; Matrix Metalloproteinase Inhibitors; Nitrites; Oxidative Stress; Phosphodiesterase Inhibitors; Piperazines; Pulmonary Embolism; Purines; Pyrazoles; Pyridines; Sildenafil Citrate; Sulfones

One of the proposed mechanisms responsible for diabetes-related erectile dysfunction (ED) is overactivity of RhoA/ROCK signaling, as seen in experimental models of chemical diabetes.. Because statins may interfere with RhoA/Rho-kinase (ROCK) signaling through the reduction of geranyl-geranyl pyrophosphate (GGPP), required for RhoA activation, we investigated whether atorvastatin ameliorated diabetes-related ED.. Streptozotocin-induced (8 weeks) diabetic rats and alloxan-induced (8 weeks) diabetic rabbits received atorvastatin (5 mg/kg daily) for the last 2 weeks. In vitro contractility studies were conducted in the rabbit model. In the rat model, sildenafil effect on electrical stimulation (ES)-induced erection was investigated. Atorvastatin action was also analyzed using human fetal penile smooth muscle cells (hfPSMCs) exposed to low (5 mM), high (22 mM), and very high (40 mM) glucose.. Atorvastatin effect on hyperglycemia-induced RhoA/ROCK signaling was evaluated using the ROCK inhibitor Y-27632 in both animal models and by analyzing functional effects downstream to RhoA activation in hfPSMCs.. In both diabetic models, atorvastatin did not affect glycemia, lipid plasma levels, and the hypogonadal state. In diabetic rats, atorvastatin ameliorated the erectile response to the ES of the cavernous nerve and normalized sildenafil effect on erectile function, strongly decreased by diabetes. In penile tissue from diabetic animals, atorvastatin completely restored the diabetes-induced hypersensitivity to Y-27632 and prevented RhoA membrane translocation/activation. In hfPSMCs, high glucose significantly increased not only membrane RhoA expression, but also ROCK activity (increased phosphorylation of the ROCK substrate myosin phosphatase target subunit 1) and several RhoA-dependent functions such as proliferation, migration, and smooth muscle-related gene expression. Atorvastatin restored all the high-glucose-induced effects, an action specifically reverted by GGPP.. Atorvastatin improves diabetes-related ED and restores sildenafil responsiveness, most probably by inhibiting RhoA/ROCK signaling, which underlies several high-glucose-induced derangements in penile smooth muscle cell commitment.

Topics: Animals; Atorvastatin; Diabetes Mellitus, Experimental; Disease Models, Animal; Electric Stimulation; Heptanoic Acids; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Male; Penile Erection; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Purines; Pyrroles; Rabbits; rho-Associated Kinases; Signal Transduction; Sildenafil Citrate; Sulfones

Sildenafil, a selective inhibitor of phosphodiesterase type 5, induces powerful protection against myocardial ischemia-reperfusion injury through activation of cGMP-dependent protein kinase (PKG). We further hypothesized that PKG-dependent activation of survival kinase ERK may play a causative role in sildenafil-induced cardioprotection via induction of endothelial nitric oxide synthase (eNOS)/inducible nitric oxide synthase (iNOS) and Bcl-2. Our results show that acute intracoronary infusion of sildenafil in Langendorff isolated mouse hearts before global ischemia-reperfusion significantly reduced myocardial infarct size (from 29.4 +/- 2.4% to 15.9 +/- 3.0%; P < 0.05). Cotreatment with ERK inhibitor PD98059 abrogated sildenafil-induced protection (31.8 +/- 4.4%). To further evaluate the role of ERK in delayed cardioprotection, mice were treated with sildenafil (ip) 24 h before global ischemia-reperfusion. PD98059 was administered (ip) 30 min before sildenafil treatment. Infarct size was reduced from 27.6 +/- 3.3% in controls to 7.1 +/- 1.5% in sildenafil-treated mice (P < 0.05). The delayed protective effect of sildenafil was also abolished by PD98059 (22.5 +/- 2.3%). Western blots revealed that sildenafil significantly increased phosphorylation of ERK1/2 and GSK-3beta and induced iNOS, eNOS, Bcl-2, and PKG activity in the heart 24 h after treatment. PD98059 inhibited the enhanced expression of iNOS, eNOS, and Bcl-2 and the phosphorylation of GSK-3beta. PD98059 had no effect on the sildenafil-induced activation of PKG. We conclude that these studies provide first direct evidence that PKG-dependent ERK phosphorylation is indispensable for the induction of eNOS/iNOS and Bcl-2 and the resulting cardioprotection by sildenafil.

Topics: Animals; bcl-2-Associated X Protein; Cardiovascular Agents; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Enzyme Activation; Flavonoids; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Hemodynamics; Male; Mice; Mice, Inbred ICR; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-bcl-2; Purines; Signal Transduction; Sildenafil Citrate; Sulfones; Time Factors

Phosphodiesterase-5 inhibition with sildenafil has been used to treat severe pulmonary hypertension and bronchopulmonary dysplasia (BPD), a chronic lung disease in very preterm infants who were mechanically ventilated for respiratory distress syndrome.. Sildenafil treatment was investigated in 2 models of experimental BPD: a lethal neonatal model, in which rat pups were continuously exposed to hyperoxia and treated daily with sildenafil (50-150 mg/kg body weight/day; injected subcutaneously) and a neonatal lung injury-recovery model in which rat pups were exposed to hyperoxia for 9 days, followed by 9 days of recovery in room air and started sildenafil treatment on day 6 of hyperoxia exposure. Parameters investigated include survival, histopathology, fibrin deposition, alveolar vascular leakage, right ventricular hypertrophy, and differential mRNA expression in lung and heart tissue.. Prophylactic treatment with an optimal dose of sildenafil (2 x 50 mg/kg/day) significantly increased lung cGMP levels, prolonged median survival, reduced fibrin deposition, total protein content in bronchoalveolar lavage fluid, inflammation and septum thickness. Treatment with sildenafil partially corrected the differential mRNA expression of amphiregulin, plasminogen activator inhibitor-1, fibroblast growth factor receptor-4 and vascular endothelial growth factor receptor-2 in the lung and of brain and c-type natriuretic peptides and the natriuretic peptide receptors NPR-A, -B, and -C in the right ventricle. In the lethal and injury-recovery model we demonstrated improved alveolarization and angiogenesis by attenuating mean linear intercept and arteriolar wall thickness and increasing pulmonary blood vessel density, and right ventricular hypertrophy (RVH).. Sildenafil treatment, started simultaneously with exposure to hyperoxia after birth, prolongs survival, increases pulmonary cGMP levels, reduces the pulmonary inflammatory response, fibrin deposition and RVH, and stimulates alveolarization. Initiation of sildenafil treatment after hyperoxic lung injury and continued during room air recovery improves alveolarization and restores pulmonary angiogenesis and RVH in experimental BPD.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Fibrin; Humans; Hyperoxia; Hypertrophy, Right Ventricular; Lung Injury; Phosphodiesterase Inhibitors; Piperazines; Pneumonia; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones; Survival Analysis; Survival Rate; Treatment Outcome

Sildenafil was the first selective inhibitor of phosphodiesterase-5 (PDE5) to be widely used for treating erectile dysfunction. Many recent studies have investigated the cardioprotective role of sildenafil in animal models. We evaluated the protective effects of sildenafil in experimental renal ischemia-reperfusion (IR) injury in two studies. In study 1, male Sprague-Dawley rats were divided into four groups: sham, sildenafil-treated sham, vehicle-treated IR, and sildenafil-treated IR groups. In study 2, we divided the rats into two groups: sildenafil-treated IR rats and PD98059 (ERK inhibitor)+sildenafil-treated IR rats. Functional parameters of the kidney were evaluated at the molecular and structural levels. Blood urea nitrogen (BUN) and serum creatinine levels were lower in sildenafil-treated IR rats than in vehicle-treated IR rats. The expression of inducible (iNOS) and endothelial nitric oxide synthase (eNOS) proteins in sildenafil-treated IR rats was significantly higher than in vehicle-treated IR rats. Pretreatment with sildenafil in IR rats increased ERK phosphorylation and reduced the renal Bax/Bcl-2 ratio, renal caspase-3 activity, and terminal dUTP nick end-labeling-positive apoptotic cells. In contrast, PD98059 treatment increased BUN and serum creatinine levels and attenuated the sildenafil-induced expression of pERK, iNOS, eNOS, and Bcl-2. PD98059 also increased caspase-3 activity but did not decrease the sildenafil-induced accumulation of cGMP. In conclusion, this study suggests that sildenafil has antiapoptotic effects in experimental IR renal injury via ERK phosphorylation, induction of iNOS and eNOS production, and a decrease in the Bax/Bcl-2 ratio.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Blood Urea Nitrogen; Caspase 3; Creatinine; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Drug Administration Schedule; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Kidney Diseases; Male; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-bcl-2; Purines; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sildenafil Citrate; Sulfones; Time Factors

The aim of the present study was to evaluate the effects of sildenafil on endothelium-dependent mesenteric artery vasorelaxation and nonadrenergic noncholinergic (NANC) ileal responses in an experimental rat intestinal ischemia-reperfusion (I/R) model. The superior mesenteric artery was occluded for 45 min of ischemia and then the clamp was removed for 60 min of reperfusion. Sildenafil (1 mg/kg, i.v.) or saline was administered prior to surgery in the I/R and sham-operated groups. Acetylcholine-induced relaxation of the mesenteric arteries, which were precontracted via submaximal phenylephrine, decreased markedly after I/R. Sildenafil pretreatment reversed the acetylcholine-induced relaxation. In the ileum, NANC responses were significantly attenuated following I/R, which were increased by sildenafil pretreatment. These results indicate that pretreatment with sildenafil prevented both endothelial dysfunction in the mesenteric artery and impairment of ileal NANC responses in a rat intestinal I/R model.

Topics: Acetylcholine; Animals; Disease Models, Animal; Endothelium, Vascular; Ileum; Intestinal Mucosa; Male; Mesenteric Artery, Superior; Phenylephrine; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sildenafil Citrate; Sulfones; Vasodilator Agents

Memory loss, synaptic dysfunction, and accumulation of amyloid beta-peptides (A beta) are major hallmarks of Alzheimer's disease (AD). Downregulation of the nitric oxide/cGMP/cGMP-dependent protein kinase/c-AMP responsive element-binding protein (CREB) cascade has been linked to the synaptic deficits after A beta elevation. Here, we report that the phosphodiesterase 5 inhibitor (PDE5) sildenafil (Viagra), a molecule that enhances phosphorylation of CREB, a molecule involved in memory, through elevation of cGMP levels, is beneficial against the AD phenotype in a mouse model of amyloid deposition. We demonstrate that the inhibitor produces an immediate and long-lasting amelioration of synaptic function, CREB phosphorylation, and memory. This effect is also associated with a long-lasting reduction of A beta levels. Given that side effects of PDE5 inhibitors are widely known and do not preclude their administration to a senile population, these drugs have potential for the treatment of AD and other diseases associated with elevated A beta levels.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Analysis of Variance; Animals; Conditioning, Classical; Cyclic AMP Response Element-Binding Protein; Cyclic GMP; Disease Models, Animal; Immunohistochemistry; Injections, Intraperitoneal; Memory; Mice; Mice, Transgenic; Mutation; Neuropsychological Tests; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Polymerase Chain Reaction; Psychomotor Performance; Purines; Sildenafil Citrate; Spatial Behavior; Sulfones; Synaptic Transmission; Time Factors; Treatment Outcome

In an experimental model we studied the protective effects of the phosphodiesterase-5 inhibitor sildenafil on kidney grafts autotransplanted after 45 minutes of warm ischemia by vascular clamping, nephrectomy and 60 minutes of isolated hypothermic pump perfusion.. A total of 14 laboratory minipigs were divided into group 1-7 administered 100 mg sildenafil orally 1.5 hours preoperatively and group 2-7 in which no sildenafil was given. Right single nephrectomy was completed after 45 minutes of warm ischemia by complete vascular clamping. Before autotransplantation all kidneys underwent 60 minutes of hypothermic pulsatile perfusion. Renal flow, arterial pressure and renal vascular resistance were recorded in real time for 60 minutes after autotransplantation. Nitric oxide levels were determined in blood samples from the renal vein at predefined intervals. Optical and electronic microscopy was done in all organs at the end of the procedure.. In group 1 vs 2 renal vascular flow was significantly higher (155.30 vs 29.04 ml per minute per 100 gm) and renal vascular resistance was significantly lower (0.59 vs 3.10 mm Hg/ml per minute, each p <0.01). No significant differences were observed in systemic arterial pressure between groups 1 and 2 (84.08 and 84.65 mm Hg, respectively, p >0.05). Nitric oxide levels were significantly higher for all periods in group 1 (49.94 vs 16.85 muM, p <0.01). No significant differences were observed in histological studies, although endothelial cell structure was better preserved in the sildenafil group.. To our knowledge our study suggests for the first time in the literature a positive effect of sildenafil in the immediate posttransplantation outcome of warm ischemic kidneys without secondary systemic effects.

Topics: Animals; Disease Models, Animal; Kidney; Kidney Transplantation; Organ Preservation; Piperazines; Purines; Reperfusion Injury; Sildenafil Citrate; Sulfones; Swine; Transplants; Vasodilator Agents; Warm Ischemia

Metabolic syndrome (MetS) is a clustering of cardio-metabolic risk factors (hyperglycemia, hypertension, dyslipidemia, visceral fat accumulation) that is also associated with hypogonadism and erectile dysfunction (ED).. To clarify the relationships among MetS, hypogonadism, and ED, we developed an animal model of MetS.. Male rabbits fed a high-fat diet (HFD), with or without testosterone (T) supplementation, were compared with control rabbits (fed a standard chow) and with rabbits made hypogonadal by a single injection of a long-acting GnRH-analog, triptorelin.. Evaluation of metabolic disturbances (plasma glucose, cholesterol, triglycerides, testosterone, LH, FSH level, glucose tolerance, mean arterial pressure, visceral fat accumulation), and corpora cavernosa (CC) relaxant capacity (in vitro contractility study) in HFD animals as compared with control, GnRH analog-treated rabbits, and T-supplemented HFD rabbits.. HFD rabbits showed all the features of MetS. HFD induced hypogonadotropic hypogonadism is characterized by a reduction of plasma T, FSH, LH levels, testis and seminal vesicles weight, and testicular steroidogenic enzymes. Such a phenotype is similar to that induced by triptorelin administration. A reduced GnRH immunopositivity in hypothalamus suggests a central origin of HFD-related hypogonadism. HFD also induced penile alterations, as demonstrated by a reduction of acetylcholine-and electrical field stimulation-induced CC relaxation, hyper-responsiveness to the NO donor, SNP, and unresponsiveness to PDE5 inhibitors. Similar penile alterations were observed in triptorelin treated rabbit. In HFD, as well as in triptorelin treated rabbits, PDE5 and eNOS mRNA expression quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) were significantly decreased. T administration prevented almost all penile alterations observed in HFD rabbits. T treatment dramatically reduced HFD-induced visceral obesity, partially ameliorating also the metabolic profile.. We have developed an animal model of MetS associated with hypogonadotropic hypogonadism and penile alterations including unresponsiveness to PDE5 inhibitors. T supplementation was able to partially revert HFD-induced phenotype.

Topics: Animals; Blood Glucose; Disease Models, Animal; Drug Synergism; Erectile Dysfunction; Glucose Tolerance Test; Hypogonadism; Male; Metabolic Syndrome; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Rabbits; Sildenafil Citrate; Sulfones; Testosterone

In the present study, effect of aminoguanidine (12.5, 25 and 50mg/kg, i.p.), a selective inhibitor of inducible nitric oxide synthase, was evaluated for its anti-anxiety activity in stressed mice employing elevated plus maze, open field test, light/dark test and social interaction test. Restraint stress induced by immobilizing for 6h enhanced an anxiety-like behavior and increased plasma nitrite levels in mice. Only the highest dose (50mg/kg) employed of aminoguanidine attenuated the stress-induced anxiety-like behavior and decreased plasma nitrite levels. There was no significant anxiolytic effect of aminoguanidine in unstressed mice. Sildenafil (1mg/kg i.p.), was used to explore the probable mechanism of anti-anxiety activity of aminoguanidine through NO-cGMP signaling. Aminoguanidine (50mg/kg) attenuated the anxiogenic effect of sildenafil. Aminoguanidine and sildenafil per se and in combination did not affect the locomotor activity of stressed and unstressed mice as compared to their respective control groups. Thus, aminoguanidine produced anti-anxiety activity in stressed mice through iNOS-NO-cGMP pathway.

Topics: Adaptation, Ocular; Analysis of Variance; Animals; Anti-Asthmatic Agents; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Exploratory Behavior; Female; Guanidines; Interpersonal Relations; Male; Maze Learning; Mice; Nitric Oxide; Nitrites; Piperazines; Purines; Restraint, Physical; Signal Transduction; Sildenafil Citrate; Stress, Psychological; Sulfones

Hypercholesterolemia is associated with impaired neovascularization in response to ischemia. Potential mechanisms include defective NO bioactivity and a reduction in the number/function of endothelial progenitor cells (EPCs). Here we tested the hypothesis that sildenafil, a phosphodiesterase 5 inhibitor that increases NO-driven cGMP levels, could stimulate EPC function and improve ischemia-induced neovascularization in hypercholesterolemic conditions. Apolipoprotein E-deficient (ApoE(-/-)) mice were treated (or not treated) with sildenafil (40 mg/kg per day in water), and hindlimb ischemia was surgically induced by femoral artery removal. Sildenafil treatment led to an improved blood flow recovery, an increased capillary density, and a reduction of oxidative stress levels in ischemic muscles at day 7 after surgery. Sildenafil therapy is associated with an increased activation of angiogenic transduction pathways, including Akt, p44/42 mitogen-activated protein kinase, and p38. In vitro, sildenafil increases cellular migration and tubule formation of mature endothelial cells (human umbilical vascular endothelial cells) in a cGMP-dependent manner. In vivo, ApoE(-/-) mice treated with sildenafil exhibit a significant increase in the number of bone marrow-derived EPCs. Moreover, the angiogenic activities of EPCs (migration and adhesion) are significantly improved in ApoE(-/-) mice treated with sildenafil. In summary, this study demonstrates that sildenafil treatment is associated with improved ischemia-induced neovascularization in hypercholesterolemic ApoE(-/-) mice. The mechanisms involve beneficial effects on angiogenic transduction pathways together with an increase in the number and the functional activity of EPCs. Sildenafil could constitute a novel therapeutic strategy to reduce tissue ischemia in atherosclerotic diseases.

Topics: Analysis of Variance; Animals; Apolipoproteins E; Blotting, Western; C-Reactive Protein; Cell Movement; Cells, Cultured; Disease Models, Animal; Endothelial Cells; Hindlimb; Hypercholesterolemia; Immunohistochemistry; Ischemia; Mice; Mice, Inbred C57BL; Neovascularization, Physiologic; Piperazines; Probability; Purines; Random Allocation; Sildenafil Citrate; Stem Cells; Sulfones

Statins have been proposed to be a potential treatment for pulmonary arterial hypertension. If introduced into clinical practice, the statin would have to be used in conjunction with established therapy. We investigated the effects of combining simvastatin with a phosphodiesterase type-5 inhibitor, sildenafil, in the rat model of hypoxia-induced pulmonary hypertension. Rats were allocated to either: 1) a prevention protocol, to receive simvastatin 20 mg x kg(-1) x day(-1) by intraperitoneal injection or sildenafil 75 mg x kg(-1) x day(-1) orally or the combination (or vehicle) for 2 weeks beginning at the start of exposure to hypoxia (10% inspired oxygen); or 2) a treatment protocol, where the same agents were administered in the last 2 weeks of a 4-week period of hypoxia. In both protocols, the combination of sildenafil and simvastatin lowered pulmonary artery pressure and produced a significantly greater reduction in right ventricular hypertrophy and pulmonary vascular muscularisation than either drug alone. Moreover, the combination augmented significantly endothelial nitric oxide synthase expression and cGMP levels in the lung and right ventricle above that produced by either drug independently and resulted in greater inhibition of RhoA activity. These data suggest that simvastatin can be usefully combined with sildenafil in the treatment of pulmonary arterial hypertension to achieve greater therapeutic benefit.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Drug Therapy, Combination; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Nitric Oxide Synthase Type III; Phosphodiesterase Inhibitors; Piperazines; Pulmonary Circulation; Purines; Rats; Rats, Sprague-Dawley; rhoA GTP-Binding Protein; Signal Transduction; Sildenafil Citrate; Simvastatin; Sulfones

The pathophysiology of pre-eclampsia is still unknown thus effective primary prevention is not possible at the stage. The present study was conducted to research the smooth muscle responses in the pre-eclampsia model with suramin treated rats and the effect of phosphodiesterase-5 (PDE5) inhibitor on these responses. Rats of three groups; control, suramin and suramin+sildenafil were given intraperitoneal injections of saline, suramin or sildenafil citrate. Suramin injections caused increased blood pressure, protein in urine and caused fetal growth retardation. The use of sildenafil citrate straightened significantly both blood pressure and average fetus weight, but did not reach to control values. At the end of pregnancy, thoracic aorta rings were exposed to contractile and relaxant agents. KCl contraction responses, sodium nitroprusside and papaverine relaxation responses were similar in three groups. Contraction responses of phenylephrine, increased significantly in suramin group. Relaxation responses of acethylcholine and bradykinin decreased in suramin group. The use of sildenafil citrate partially straightened both relaxation and contraction responses, but did not reach to control values. In all groups in the presence of L-nitromonomethylarginine (L-NAME), 1H-(1, 2, 4) oxadiazole (4, 3-a) guinoxalin-1-one (ODQ) and indomethacin decreased the relaxation responses of acetylcholine and bradykinin. The cyclic guanosine monophosphate (cGMP) content of thoracic aorta tissue was determined by radioimmunoassay technique. The content of cGMP in suramin group decreased and use of sildenafil citrate increased the cGMP content but did not reach to control values. We conclude that in pre-eclampsia, the increase of contraction responses, the decrease of relaxation responses and the decrease of cGMP content can depend on insufficiency about synthesis or release of relaxant factors which was released from the vessel endothelium. The results in this study show that in pre-eclampsia; PDE5 inhibitors enhance endothelial function and may be used for protection. Further studies are needed to clear the efficiency and safety of PDE5 inhibitors.

Topics: Animals; Aorta, Thoracic; Blood Pressure; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Female; Fetal Development; Fetal Growth Retardation; Muscle, Smooth, Vascular; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Pre-Eclampsia; Pregnancy; Proteinuria; Purines; Radioimmunoassay; Rats; Sildenafil Citrate; Sulfones; Suramin; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Topics: Animals; Carotid Artery Injuries; Carotid Stenosis; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Mice; Mice, Knockout; Muscle, Smooth, Vascular; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Recurrence; Signal Transduction; Sildenafil Citrate; Sulfones; Vasodilation

The objective of this pilot study was to establish an animal model for intra-abdominal infection and to examine the effect of sildenafil on anastomotic healing of the left colon and intra-abdominal adhesion formation.. Fourteen Winstar rats underwent colonic transsection and primary anastomosis after performing intra-abdominal infection. Rats were divided into two groups: Group 1 (n = 7): intra-abdominal infection, resection, and anastomoses; Group 2 (n = 7): intra-abdominal infection, resection, anastomoses, and sildenafil. Anastomotic bursting pressures, hydroxyproline levels, histopathologic grading, and abdominal adhesions were accessed on the postoperative Day 7.. Anastomotic healing was found to be improved in terms of a bursting pressure (P = 0.02). Histopathological examination revealed an increase in angiogenesis (P = 0.007). Moreover, intra-abdominal adhesions were significantly less in rats given sildenafil (P = 0.03).. Sildenafil may improve anastomotic healing of the left colon and diminishes peritoneal adhesion formation in the presense of abdominal infection.

Topics: Anastomosis, Surgical; Animals; Colon; Disease Models, Animal; Hydroxyproline; Injections, Intraperitoneal; Peritonitis; Phosphodiesterase Inhibitors; Pilot Projects; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones; Tissue Adhesions; Wound Healing

Phosphodiesterase 5 (PDE5) inhibitors (e.g., sildenafil) are selective pulmonary vasodilators in patients with pulmonary arterial hypertension. The mechanism(s) underlying this specificity remains unclear, but studies in genetically modified animals suggest it might be dependent on natriuretic peptide bioactivity.. We explored the interaction between PDE5 inhibitors and the natriuretic peptide system to elucidate the (patho)physiological relationship between these two cyclic GMP (cGMP)-regulating systems and potential of a combination therapy exploiting these cooperative pathways.. Pharmacological evaluation of vascular reactivity was conducted in rat isolated conduit and resistance vessels from the pulmonary and systemic circulation in vitro, and in anesthetized mice in vivo. Parallel studies were undertaken in an animal model of hypoxia-induced pulmonary hypertension (PH).. Sildenafil augments vasodilatation to nitric oxide (NO) in pulmonary and systemic conduit and resistance arteries, whereas identical vasorelaxant responses to atrial natriuretic peptide (ANP) are enhanced only in pulmonary vessels. This differential activity is mirrored in vivo where sildenafil increases the hypotensive actions of ANP in the pulmonary, but not systemic, vasculature. In hypoxia-induced PH, combination of sildenafil plus the neutral endopeptidase (NEP) inhibitor ecadotril (which increases endogenous natriuretic peptide levels) acts synergistically, in a cGMP-dependent manner, to reduce many indices of disease severity without significantly affecting systemic blood pressure.. These data demonstrate that PDE5 is a key regulator of cGMP-mediated vasodilation by ANP in the pulmonary, but not systemic, vasculature, thereby explaining the pulmonary selectivity of PDE5 inhibitors. Exploitation of this mechanism (i.e., PDE5 and neutral endopeptidase inhibition) represents a novel, orally active combination therapy for pulmonary arterial hypertension.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Atrial Natriuretic Factor; Disease Models, Animal; Drug Synergism; Drug Therapy, Combination; Hypertension, Pulmonary; Male; Neprilysin; Piperazines; Protease Inhibitors; Pulmonary Artery; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Thiorphan; Treatment Outcome; Vascular Resistance; Vasodilation; Vasodilator Agents

The objective of this study was to determine if the phosphodiesterase 5 (PDE-5) inhibitor, sildenafil, could be used as a neuroprotective agent in a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) murine model of Parkinson's disease. The underlying hypothesis of these studies is that blockade of PDE-5 catabolism of cGMP will attenuate the loss of nigrostriatal dopamine (NSDA) neurons following chronic neurotoxin exposure. Chronic MPTP-treated mice were administered sildenafil using three different regimens. Animals were: 1) treated with sildenafil and then exposed to chronic MPTP; 2) treated concurrently with sildenafil and MPTP; and 3) first exposed to MPTP and subsequently treated with sildenafil. End points of neurotoxicity included dopamine (DA) and tyrosine hydroxylase (TH) concentrations in NSDA axon terminals in the striatum, and stereological cell counts of TH immunoreactive neurons in the substantia nigra. Results reveal that sildenafil did not prevent neurotoxicity produced by chronic MPTP exposure regardless of the treatment paradigms employed. On the other hand, sildenafil did not produce any deleterious effect on NSDA neuron function nor did it potentiate the neurotoxic effects of MPTP. These results suggest that sildenafil would not accelerate DA cell loss when used as a treatment for erectile dysfunction in men diagnosed with Parkinson's disease.

Topics: Animals; Axons; Blotting, Western; Corpus Striatum; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Dopamine; Mice; Mice, Inbred C57BL; Neurons; Parkinsonian Disorders; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Substantia Nigra; Sulfones; Tyrosine 3-Monooxygenase

Insulin resistance constitutes a risk factor for endothelial dysfunction and subsequent cardiovascular diseases including hypertension. Daily treatment with phosphodiesterase type 5 (PDE5) inhibitors has beneficial effects on endothelial function in men with increased cardiovascular risk. Endothelium-dependent vasomotor function is ultimately linked to blood pressure (BP) regulation. We postulated that sildenafil would ameliorate BP and biological markers of endothelial function in fructose-fed rats (FFRs).. Wistar rats were fed a standard chow or a 60% fructose-enriched diet containing 12% fat for 8 weeks (FFR). From week 6 through 8, sildenafil (twice a day subcutaneously, 20 mg/kg) was administered followed by a 1-week washout period. At the end of the washout period, BP was recorded using radiotelemetry following cumulative infusion of norepinephrine (from 50 to 400 ng/kg/min).. FFR displayed both an impaired glucose tolerance and elevated triglyceridemia. The latter was corrected by sildenafil treatment. Resting BP was similar in all rats, whereas pressor responses were significantly enhanced in FFR (maximal increase in mean BP to norepinephrine: 25.6 +/- 3.8 vs. 40.8 +/- 4.0 mm Hg, P < 0.05) and normalized by sildenafil treatment (24.9 +/- 5.3 mm Hg, not significant vs. control). Urinary levels of 8-isoprostanes and thromboxane B(2) were increased in FFR and corrected by sildenafil treatment.. Thus, chronic treatment with sildenafil normalized BP regulation in an experimental model of insulin resistance and hypertriglyceridemia while restoring normal excretion of urinary biological markers of oxidative stress and cyclooxygenase-derived vasoconstrictors. The modulation of ROS and cyclooxygenase-derived vasoconstrictors generation by a chronic treatment with sildenafil may represent an added benefit beyond PDE5 inhibition.

Topics: Animals; Blood Pressure; Consciousness; Disease Models, Animal; Dose-Response Relationship, Drug; Fructose; Heart Rate; Hypertriglyceridemia; Injections, Subcutaneous; Insulin Resistance; Male; Piperazines; Prostaglandin-Endoperoxide Synthases; Purines; Rats; Rats, Wistar; Reactive Oxygen Species; Sildenafil Citrate; Sulfones; Vasodilator Agents

Acute pulmonary embolism produces acute pulmonary hypertension, which can be counteracted by activating the nitric oxide-cyclic guanosine 3',5'-monophosphate (cGMP) pathway. While previous studies have shown that sildenafil (an inhibitor of cGMP-specific phosphodiesterase type 5) or nitrite (a storage molecule for nitric oxide) produces beneficial effects during acute pulmonary embolism, no previous study has examined whether the combination of these drugs can produce additive effects. Here, we expand previous findings and examine whether sildenafil enhances the beneficial haemodynamic effects produced by a low-dose infusion of nitrite in a dog model of acute pulmonary embolism. Haemodynamic and arterial blood gas evaluations were performed in non-embolized dogs treated with saline (n = 4), and in embolized dogs (intravenous injections of microspheres) that received nitrite (6.75 micromol/kg intravenously over 15 min. followed by 0.28 micromol/kg/min.) and sildenafil (0.25 mg/kg over 30 min.; n = 8), or nitrite followed by saline (n = 8), or saline followed by sildenafil (n = 7), or only saline (n = 8). Plasma thiobarbituric acid-reactive substances (TBARS) concentrations were determined using a fluorometric method. Acute pulmonary embolism increased pulmonary artery pressure by approximately 24 mmHg. While the infusion of nitrite or sildenafil infusions reversed this increase by approximately 42% (both P < 0.05), the combined infusion of both drugs reversed this increase by approximately 58% (P < 0.05). Similar effects were seen on the pulmonary vascular resistance index. Nitrite or sildenafil alone produced no significant hypotension. However, the combined infusion of both drugs caused transient hypotension (P < 0.05). Both drugs, either alone or combined, blunted the increase in TBARS concentrations caused by acute pulmonary embolism (all P < 0.05). These results suggest that sildenafil improves the beneficial haemodynamic effects of nitrite during acute pulmonary embolism.

Topics: Acute Disease; Animals; Blood Pressure; Disease Models, Animal; Dogs; Drug Synergism; Drug Therapy, Combination; Female; Hemodynamics; Hypertension, Pulmonary; Infusions, Intravenous; Lipid Peroxides; Male; Phosphodiesterase Inhibitors; Piperazines; Pulmonary Artery; Pulmonary Embolism; Purines; Respiration; Sildenafil Citrate; Sodium Nitrite; Sulfones; Vascular Resistance

Sexual dysfunction is associated with antidepressant discontinuation. Therefore, there is a need for models that predict antidepressant-induced sexual dysfunction.. To develop a predictive method for evaluating antidepressant-induced sexual dysfunction.. Male Sprague-Dawley rats were allowed access to sexually receptive females during a single overnight mating session and then treated with antidepressants known to produce differing levels of sexual dysfunction in the clinic. Two to three weeks later, following either acute, subchronic (7-day), or chronic (14-day) antidepressant treatment, rats were observed for penile erections (PE) in the presence of sexually receptive females that were not accessible for contact but served as visual, auditory, and olfactory stimuli in the testing area.. Chronic treatment of fluoxetine (10 mg/kg), desipramine (10 mg/kg), and bupropion (20 mg/kg) reduced the number of PE 71, 53, and 8%, respectively, relative to vehicle-treated rats. This rank order of the compounds' propensity for reducing PE is comparable to the rank order of the compounds' ability to produce sexual dysfunction during antidepressant treatment in the clinic. Additionally, drugs used to treat antidepressant-induced sexual dysfunction in the clinic, such as sildenafil, yohimbine, and dopamine agonists, were also effective in attenuating the deficits in the number of noncontact PE produced by chronic fluoxetine treatment.. Taken together, this model represents a novel approach for predicting antidepressant-induced sexual dysfunction in rats, which parallels the pattern of reports of sexual dysfunction in the clinic associated with different antidepressant treatments and the ability of adjunct treatment to reverse the sexual impairments produced by antidepressants.

Topics: Animals; Antidepressive Agents; Bupropion; Desipramine; Disease Models, Animal; Dopamine Agonists; Fluoxetine; Long-Term Care; Male; Penile Erection; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Vasodilator Agents; Yohimbine

Sildenafil both enhances vasodilatation by relaxing the smooth muscle in the vessels and inhibits platelet aggregation. We have therefore examined the potential benefits of sildenafil on an animal model for ischemic colitis (IC).. Twenty-eight female Wistar albino rats weighing 250-300 g were randomized into three experimental groups as follows: in Group 1, animals were sham operated (n = 8) and received tap water; in Groups 2 and 3, the rats underwent a standardized surgical procedure to induce IC (n = 10 in each group). Group 2 animals served as the controls, receiving only tap water, while Group 3 animals received 10 mg/kg sildenafil per day as a single dose for a 3-day period. All animals were sacrificed 72 h after devascularization. To determine the severity of the ischemia, we scored the macroscopically visible damage, measured the ischemic area and scored the histopathology. Tissue malondialdehyde levels were also evaluated.. The mean area of ischemic changes were 116.80 +/- 189.93 and 0.55 +/- 1.01 mm2 in Group 2 and 3 animals, respectively (p = 0.0001), while the macroscopically mean visible damage score decreased to 0.66 +/- 0.70 (p = 0.0001) for Group 3 animals. The Chiu scores were 0.00, 3.80 +/- 0.91 and 2.66 +/- 1.00 in Group 1, 2 and 3 animals, respectively. There was a statistically significant difference between Group 2 and 3 animals (p = 0.017).. Our findings support the view that sildenafil leads to a improvement in IC due to its well-known effects on the vascular smooth muscle and on the microcirculatory hemodynamics.

Topics: Animals; Chromatography, High Pressure Liquid; Colitis, Ischemic; Disease Models, Animal; Female; Hemodynamics; Malondialdehyde; Microcirculation; Phosphodiesterase Inhibitors; Piperazines; Purines; Random Allocation; Rats; Rats, Wistar; Sildenafil Citrate; Statistics, Nonparametric; Sulfones

Our goal was to determine whether sildenafil increased fetal weight and favored fetal tolerance to induced asphyxia at birth in guinea pigs.. Twenty guinea pigs were randomly allocated to placebo (n = 10) or sildenafil 50 microg/kg (n = 5) or 500 microg/kg (n = 5), starting from day 35 of gestation to delivery. Fetuses were delivered by cesarean section. Fetal asphyxia was induced by clamping the umbilical cord at birth for 5 minutes.. Sildenafil protected the pups against induced asphyxia at birth in a dose-dependent manner (eg, partial pressure (tension) of carbon dioxide levels were 75.9 +/- 19.3, 66.9 +/- 18.8, and 54.8 +/- 13.0 in the control and low- and high-dose sildenafil groups, respectively). The high-dose sildenafil group of piglets gained 1.5 times more body weight.. In guinea pigs, low doses of sildenafil administered from day 35 to the end of gestation favored fetal tolerability to induced intrapartum asphyxia. High doses of sildenafil increased fetal weight.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Fetal Development; Fetal Hypoxia; Fetal Organ Maturity; Fetal Weight; Guinea Pigs; Piperazines; Pregnancy; Probability; Purines; Random Allocation; Risk Factors; Sensitivity and Specificity; Sildenafil Citrate; Sulfones

Sildenafil has been implicated in the activation of cystic fibrosis transmembrane conductance regulator (CFTR) protein. The effect was observed in vitro and in the presence of doses roughly 300 times larger than those commonly used for treating erectile dysfunction.. To evaluate in vivo the therapeutic efficacy of clinical doses of sildenafil and vardenafil, two clinically approved phosphodiesterase 5 inhibitors, for activating ion transport in cystic fibrosis.. We used transepithelial potential difference in vivo across the nasal mucosa as a measure of sodium and chloride transport. The effect of a single intraperitoneal injection of sildenafil (0.7 mg/kg) or vardenafil (0.14 mg/kg) was investigated in F508del, cftr knockout and normal homozygous mice.. In F508del mice, but not in cftr knockout mice, the chloride conductance, evaluated by perfusing the nasal mucosa with a chloride-free solution in the presence of amiloride and with forskolin, was corrected 1 hour after sildenafil administration. A more prolonged effect, persisting for at least 24 hours, was observed with vardenafil. The forskolin response was increased after sildenafil and vardenafil in both normal and F508del mutant animals. In F508del mice, the chloride conductance in the presence of 200 microM 4-4'-diisothiocyanostilbene-2,2'-disulphonic acid, an inhibitor of alternative chloride channels, was much higher after sildenafil injection than after placebo treatment. No effect on the sodium conductance was detected in any group of animals.. Our results provide preclinical evidence that both drugs stimulate chloride transport activity of F508del-CFTR protein.

Topics: Animals; Chlorides; Colforsin; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Models, Animal; Imidazoles; Injections, Intraperitoneal; Ion Transport; Membrane Potentials; Mice; Mice, Inbred CFTR; Nasal Mucosa; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Protein Modification, Translational; Purines; Sildenafil Citrate; Sulfones; Triazines; Vardenafil Dihydrochloride

Topics: Animals; Disease Models, Animal; Drug Administration Schedule; Endothelium; Insulin Resistance; Male; Oxidative Stress; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones

Patients with insulin resistance exhibit endothelial dysfunction with decreased nitric oxide (NO) production and increased oxidative stress. We postulated that daily sildenafil improved endothelial function in fructose-fed rats.. Wistar rats were fed a standard or fructose-enriched diet (FFR) for 9 wk. From weeks 6-8, sildenafil was administered twice daily (sc, 20 m g/kg), followed by a 1-wk washout. Concentration-response curves (CRCs) to endothelium-dependent (acetylcholine [Ach] and A23187) and -independent (sodium nitroprusside [SNP]) relaxing agents were performed on isolated precontracted aortas and superior mesenteric arteries (SMAs). Vascular cyclic guanosine monophosphate (cGMP) content, urinary excretion of nitrates/nitrites (NOx) and 8-isoprostanes (IPT), and plasma levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were evaluated. Relaxations to ACh were significantly reduced in aortas and SMAs of FFR. Sildenafil restored ACh-induced relaxations in aortas and provoked a significant leftward shift of the CRC to ACh in SMAs, whereas it did not modify the enhanced relaxations to SNP in FFR. IL-6, TNF-alpha, vascular cGMP, and urinary NOx levels were not modified by the fructose or sildenafil treatment. Urinary IPT levels were significantly elevated in FFR and normalized by sildenafil.. Endothelial dysfunction and oxidative stress associated with insulin resistance can be reversed by daily sildenafil, even 1 wk after treatment cessation.

Topics: Animals; Disease Models, Animal; Drug Administration Schedule; Endothelium; Insulin Resistance; Male; Oxidative Stress; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones

Sildenafil is a selective inhibitor of cGMP-specific phosphodiesterase. Sildenafil, acting via NO-dependent mechanisms, prevents indomethacin-induced gastropathy. Activation of ATP-sensitive potassium channels (K(ATP)) is involved in gastric defence. Our objective was to evaluate the role of the NO/cGMP/K(ATP) pathway in the protective effects of sildenafil against ethanol-induced gastric damage.. Rats were treated with L-NAME (1 or 3 mg kg(-1), i.p.) or with L-arginine (200 mg kg(-1), i.p.) + L-NAME (3 mg kg(-1), i.p.), the guanylate cyclase inhibitor, ODQ (10 mg kg(-1), i.p.), glibenclamide (0.1, 0.3, 1 or 3 mg kg(-1), i.p.) or with glibenclamide (1 mg kg(-1), i.p.) + diazoxide (3 mg kg(-1), i.p.). After thirty minutes, the rats received sildenafil (1 mg kg(-1), by gavage), followed by intragastric instillation of absolute ethanol (4 ml kg(-1)) to induce gastric damage. One hour later, gastric damage (haemorrhagic or ulcerative lesions) was measured with a planimetry programme. Samples of stomach were also taken for histopathological assessment and for assays of tissue glutathione and haemoglobin.. Sildenafil significantly reduced ethanol-induced gastric damage in rats. L-NAME alone, without L-arginine, significantly reversed the protection afforded by sildenafil. Inhibition of guanylate cyclase by ODQ completely abolished the gastric protective effect of sildenafil against ethanol-induced gastric damage. Glibenclamide alone reversed sildenafil's gastric protective effect. However, glibenclamide plus diazoxide did not alter the effects of sildenafil.. Sildenafil had a protective effect against ethanol-induced gastric damage through the activation of the NO/cGMP/K(ATP) pathway.

Topics: Animals; Arginine; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diazoxide; Disease Models, Animal; Enzyme Inhibitors; Ethanol; Gastric Mucosa; Glutathione; Glyburide; Guanylate Cyclase; Hemoglobins; KATP Channels; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Oxadiazoles; Peptic Ulcer Hemorrhage; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Potassium Channel Blockers; Purines; Quinoxalines; Rats; Rats, Wistar; Signal Transduction; Sildenafil Citrate; Stomach Ulcer; Sulfones

Although sildenafil (Viagra) and other phosphodiesterase V (PDE V) inhibitors are increasingly recognized for their use in the treatment of male erectile dysfunction and perhaps more recently pulmonary artery hypertension, less is known of their potential beneficial effects in other situations. Medeiros et al., in the current issue of the British Journal of Pharmacology, report that sildenafil dramatically reduces alcohol-induced gastric damage in rats. The authors provide convincing evidence that such protection not only occurs via the nitric oxide (NO)/cGMP pathway, but also involves regulation of ATP-sensitive potassium channels. Therefore, in addition to exerting anti-impotence efficacy, PDE V inhibitors may provide significant beneficial effects from mucosal injury induced by alcohol.

Topics: Animals; Arginine; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Ethanol; Gastric Mucosa; Glutathione; Guanylate Cyclase; Hemoglobins; KATP Channels; Nitric Oxide; Nitric Oxide Synthase; Peptic Ulcer Hemorrhage; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Signal Transduction; Sildenafil Citrate; Stomach Ulcer; Sulfones

Sildenafil slows down the gastric emptying of a liquid test meal in awake rats and inhibits the contractility of intestinal tissue strips. We studied the acute effects of sildenafil on in vivo intestinal transit in rats. Fasted, male albino rats (180-220 g, N = 44) were treated (0.2 mL, iv) with sildenafil (4 mg/kg) or vehicle (0.01 N HCl). Ten minutes later they were fed a liquid test meal (99m technetium-labeled saline) injected directly into the duodenum. Twenty, 30 or 40 min after feeding, the rats were killed and transit throughout the gastrointestinal tract was evaluated by progression of the radiotracer using the geometric center method. The effect of sildenafil on mean arterial pressure (MAP) was monitored in a separate group of rats (N = 14). Data (medians within interquartile ranges) were compared by the Mann-Whitney U-test. The location of the geometric center was significantly more distal in vehicle-treated than in sildenafil-treated rats at 20, 30, and 40 min after test meal instillation (3.3 (3.0-3.6) vs 2.9 (2.7-3.1); 3.8 (3.4-4.0) vs 2.9 (2.5-3.1), and 4.3 (3.9-4.5) vs 3.4 (3.2-3.7), respectively; P < 0.05). MAP was unchanged in vehicle-treated rats but decreased by 25% (P < 0.05) within 10 min after sildenafil injection. In conclusion, besides transiently decreasing MAP, sildenafil delays the intestinal transit of a liquid test meal in awake rats.

Topics: Animals; Blood Pressure; Disease Models, Animal; Gastric Emptying; Gastrointestinal Transit; Intestinal Mucosa; Intestines; Male; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Sildenafil Citrate; Sulfones; Technetium

We assessed the effectiveness of sildenafil administration during ischemic period in a rat model of testicular torsion/detorsion (T/D).. Sprague-Dawley rats were divided into four groups (n = 10). In those animals that underwent T/D, right testes were rotated 720 degrees for 1 h. Base line group was for basal normal values. Sham operated group was served as a control group. T/D group underwent 1 h testicular torsion. Sildenafil group received sildenafil (0.7 mg/kg) intraperitoneally 30 min after initiation of ischemic period. For measurement of lipid peroxidation and antioxidant enzyme activities, right testes of five animals in each group were excised after 4-h reperfusion. Germ cell apoptosis indices were determined 24 h following detorsion in right testes of remaining five animals in each group.. Malondialdehyde (MDA) levels in T/D group were significantly higher versus control and base line groups. Moreover, testicular MDA values in sildenafil group were significantly lower than T/D. There were also significant decreases in catalase and superxide dismutase activities in T/D group compared with control and base line groups. These values were significantly higher in sildenafil group versus T/D. Germ cell apoptosis indices were significantly higher in both groups that experienced T/D in comparison to control and base line groups; however, sildenafil treatment significantly reduced the apoptosis in sildenafil group compared with T/D group.. Sildenafil administration during testicular torsion decreased ischemia/reperfusion cellular damage. The results of biochemical studies suggest that, reduction of oxidative stress by sildenafil may have a major role in its cytoprotective effects.

Topics: Animals; Apoptosis; Catalase; Disease Models, Animal; Male; Malondialdehyde; Oxidative Stress; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Reperfusion Injury; Sildenafil Citrate; Spermatic Cord Torsion; Spermatozoa; Sulfones; Superoxide Dismutase; Testis; Vasodilator Agents

Morphine can inhibit inflammatory edema in experimental animals. The mechanisms and sites by which opioids exert this effect are still under debate. Since the spinal level is a site for modulation of the neurogenic component of inflammation, we investigated the effect of intrathecal (i.t.) administration of morphine, and the involvement of spinal nitric oxide (NO)/cyclic-guanosine monophosphate-GMP pathway in carrageenan (CG)-induced paw edema.. Male Wistar rats received i.t. injections of drugs (20 microL) 30 min before paw stimulation with CG (150 microg). Edema was measured as paw volume increase (mL), and neutrophil migration was evaluated indirectly by myeloperoxidase (MPO) assay.. Morphine (37, 75, and 150 nmol) inhibited inflammatory edema, but had no effect on MPO activity. Coinjection with naloxone (64 nmol) reversed the effect of morphine. The corticosteroid synthesis inhibitor, aminoglutethimide (50 mg/kg, v.o.), administered 90 min before morphine injection did not modify its antiedematogenic effect. Low doses of the NO synthase inhibitor, N(omega)-nitro-L-arginine (L-NNA; 10 and 30 pmol) increased, while higher doses (3 and 30 nmol) inhibited edema. The guanylate cyclase inhibitor 1H-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 21 and 42 nmol) increased, while the phosphodiesterase type 5 inhibitor sildenafil (0.15 and 1.5 nmol) inhibited paw edema. Coadministration of a subeffective dose of L-NNA (3 pmol) or ODQ (10 nmol) with morphine prevented its antiedematogenic effect, but sildenafil (0.15 nmol) rendered a subeffective dose of morphine effective (18 nmol). ODQ also prevented the antiedematogenic effect of the NO donor S-nitroso-N-acetyl-penicilamine.. These results support the idea that morphine can act on opioid receptors at the spinal level to produce antiedematogenic, and that the NO/cGMP pathway seems to be an important mediator in this effect.

Topics: Analgesics, Opioid; Animals; Anti-Inflammatory Agents, Non-Steroidal; Carrageenan; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Edema; Enzyme Inhibitors; Guanylate Cyclase; Inflammation; Injections, Spinal; Male; Morphine; Naloxone; Narcotic Antagonists; Neutrophil Infiltration; Neutrophils; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Oxadiazoles; Peroxidase; Phosphodiesterase Inhibitors; Piperazines; Purines; Quinoxalines; Rats; Rats, Wistar; S-Nitroso-N-Acetylpenicillamine; Signal Transduction; Sildenafil Citrate; Spinal Cord; Sulfones; Time Factors

Topics: Animals; Chlorides; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Models, Animal; Imidazoles; Membrane Potentials; Mice; Mice, Inbred CFTR; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Protein Modification, Translational; Purines; Sildenafil Citrate; Sulfones; Triazines; Vardenafil Dihydrochloride

This study uses T(2)* weighted imaging (T2*WI) to measure the temporal evolution of cerebral angiogenesis in rats subjected to embolic stroke up to 6 weeks after stroke onset with or without sildenafil treatment. Method- Male Wistar rats were subjected to embolic stroke and treated with saline (n=10) or with sildenafil (n=11), with treatment initiated at 24 hours and continued daily for 7 days after onset of ischemia. T2*WI measurements were performed at 24 hours after embolization and weekly up to 6 weeks using a 7-Tesla system. Histological measurements were obtained at 6 weeks after MRI scans.. Using T2*WI, cerebral angiogenesis was detected starting from 4 weeks and from 2 weeks after onset of embolic stroke in saline and sildenafil treated rats, respectively. Significant differences in the temporal and spatial features of angiogenesis after embolic stroke up to 6 weeks after onset of stroke were found between saline and sildenafil treated rats and were identified with T2*WI. MRI permeability parameter, K(i), complementarily detected angiogenesis after ischemia in embolic stroke rats. Sildenafil treatment of stroke rats significantly enhanced the angiogenesis, as confirmed histologically.. T2*WI can quantitatively measure the temporal evolution of angiogenesis in rats subjected to embolic stroke. Compared to control rats, sildenafil treatment significantly increased angiogenesis in treated animals up to 6 weeks after stroke.

Topics: Animals; Brain; Brain Mapping; Cerebral Arteries; Diffusion Magnetic Resonance Imaging; Disease Models, Animal; Intracranial Embolism; Male; Microcirculation; Neovascularization, Physiologic; Piperazines; Predictive Value of Tests; Purines; Rats; Rats, Wistar; Recovery of Function; Sildenafil Citrate; Stroke; Sulfones; Time Factors; Treatment Outcome; Vasodilator Agents

Nitric oxide (NO) is of crucial importance for smooth muscle cell (SMC) function and exerts numerous, and sometimes opposing, effects on vascular restenosis. Although cGMP-dependent protein kinase type I (cGKI) is a principal effector of NO, the molecular pathway of vascular NO signaling in restenosis is unclear. The purpose of this study was to examine the functional role of the smooth muscle cGMP/cGKI signaling cascade in restenosis of vessels.. Tissue-specific mouse mutants were generated in which the cGKI protein was ablated in SMCs. We investigated whether the absence of cGKI in SMCs would affect vascular remodeling after carotid ligation or removal of the endothelium. No differences were detected between the tissue-specific cGKI mutants and control mice at different time points after vascular injury on a normolipidemic or apoE-deficient background. In line with these results, chronic drug treatment of injured control mice with the phosphodiesterase-5 inhibitor sildenafil elevated cGMP levels but had no influence on the ligation-induced remodeling.. The genetic and pharmacological manipulation of the cGMP/cGKI signaling indicates that this pathway is not involved in the protective effects of NO, suggesting that NO affects vascular remodeling during restenosis via alternative mechanisms.

Topics: Animals; Apolipoproteins E; Carotid Artery Injuries; Carotid Artery, Common; Carotid Stenosis; Cyclic GMP; Cyclic GMP-Dependent Protein Kinase Type I; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Ligation; Mice; Mice, Knockout; Muscle, Smooth, Vascular; Nitric Oxide; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Recurrence; Signal Transduction; Sildenafil Citrate; Sulfones; Time Factors

Sildenafil is a pulmonary vasodilator shown to be effective in neonates, but conflicting data exist regarding its effect on arterial oxygenation. To address this issue, we tested the sildenafil effect on the piglet's hypoxic pulmonary vasoconstriction (HPV) response. A segmental lung atelectasis was created by obstructing the corresponding bronchus. Total pulmonary and specific flows to the atelectatic and contra-lateral lobes were measured by magnetic resonance (MR) before and 30-min post sildenafil (0.2 and 1 mg/kg i.v.) or saline administration. Flow was reduced (p < 0.01) in the atelectatic and increased in the contra-lateral lobe indicating an effective HPV response. Sildenafil at both doses significantly (p < 0.01) increased flow solely to the atelectatic lobe. At a dose of 1 mg/kg, sildenafil induced a decrease in Pao2 from 285 +/- 37 to 161 +/- 22 mm Hg (p < 0.01). We conclude that the HPV response in the newborn is capable of almost completely reducing blood flow to nonventilated lung units and is reversed following sildenafil i.v. administration in a dose-dependent manner. In the presence of lung parenchymal disease, the use of i.v. sildenafil as a pulmonary vasodilator may worsen arterial oxygenation by reversing the HPV response in nonventilated lung units.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Dose-Response Relationship, Drug; Hypoxia; Infusions, Intravenous; Lung; Magnetic Resonance Imaging; Piperazines; Pulmonary Atelectasis; Pulmonary Circulation; Pulmonary Ventilation; Purines; Regional Blood Flow; Sildenafil Citrate; Sulfones; Swine; Vasoconstriction; Vasodilator Agents

During the past 18 years, sildenafil has evolved from a potential anti-angina drug to an on-demand treatment for erectile dysfunction and more recently to a new orally active treatment for pulmonary hypertension. Recent studies suggest that the drug has powerful cardioprotective effect against ischemia/reperfusion injury, doxorubicin-induced cardiomyopathy and anti-hypertensive effect induced by chronic inhibition of nitric oxide synthase in animals. Based on several recent basic and clinical studies, it is clear that sildenafil and other clinically approved type-5 phosphodiesterase-5 inhibitors including vardenafil and tadalafil will eventually be developed for several cardiovascular indications including essential hypertension, endothelial dysfunction, ischemia/reperfusion injury, myocardial infarction, ventricular remodeling and heart failure.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Antihypertensive Agents; Carbolines; Cardiomyopathies; Cardiovascular Agents; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Doxorubicin; Endothelium, Vascular; Enzyme Inhibitors; Erectile Dysfunction; Heart Failure; Humans; Hypertension; Hypertension, Pulmonary; Imidazoles; Male; Myocardial Infarction; Myocardial Reperfusion Injury; NG-Nitroarginine Methyl Ester; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Vardenafil Dihydrochloride; Vasodilator Agents; Ventricular Remodeling

Phosphodiesterase-5 inhibitors are beneficial in pulmonary hypertension and congestive heart failure, the two conditions associated with coronary heart disease and ischaemia. We investigated whether sildenafil counteracts the cardiovascular alterations induced by N -nitro-L-arginine methyl ester (L-NAME) in the rat.. Sildenafil was given orally to rats at doses of 0.37, 0.75 or 1.5 mg kg-1day-1 for four weeks, either alone or with L-NAME (35-40 mg kg-1 day-1 in the drinking water). Systolic blood pressure and urinary parameters (6-keto-prostaglandin F1alpha, thromboxane B2, 8-isoprostane-prostaglandin F2 and nitrite/nitrate) were measured in conscious rats. Isolated hearts were subjected to low flow ischaemia-reperfusion, and myocardial levels of guanosine 3', 5'cyclic monophosphate (cGMP) were determined. Endothelial vascular dysfunction was examined in aortic rings.. Sildenafil dose-dependently prevented the rise in systolic blood pressure in L-NAME-treated rats. This activity was associated with a normalization of urinary 8-isoprostane-prostaglandin F2alpha and other biochemical parameters. In perfused hearts, the post-ischaemic ventricular dysfunction was worse in preparations from L-NAME-treated rats than in controls. Sildenafil dose-dependently reduced this effect, and creatine kinase and lactate dehydrogenase release were lower too. cGMP levels, which were low in myocardial tissue from L-NAME-treated rats, were restored by sildenafil. In noradrenaline-precontracted aortic rings from L-NAME-treated rats acetylcholine lost its vasorelaxant effect, and sildenafil restored it.. In a rat model of chronic nitric oxide deprivation, where hypertension and aggravation of post-ischaemic ventricular dysfunction are associated with loss of vascular endothelium-relaxant function, sildenafil provided significant cardiovascular protection, primarily by maintaining tissue cGMP levels.

Topics: Animals; Antihypertensive Agents; Biomarkers; Blood Pressure; Cardiovascular Agents; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Heart Rate; Hypertension; Male; Myocardial Reperfusion Injury; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Severity of Illness Index; Sildenafil Citrate; Sulfones; Time Factors; Vasodilation; Vasodilator Agents; Ventricular Function

The aim of this work was to test whether acute phosphodiesterase 5 (PDE5) inhibition via sildenafil (SIL) mimics and/or potentiates cardiorenal effects of exogenous natriuretic peptide (NP) infusion.. Heart failure (HF) is often accompanied by elevated NP secretion yet blunted responsiveness. Such NP resistance may, in part, relate to increased cyclic guanosine monophosphate (cGMP) catabolism by PDE5.. Dogs (n = 7) were studied before and after tachypacing-induced HF. Animals received 30-min infusion of B-type natriuretic peptide (BNP) (2 mug/kg bolus, 0.02 mug/kg/min), and on a separate day SIL (1 mg/kg, intravenous), followed by BNP (SIL + BNP). Phosphodiesterase 5 activity was measured in lung, vasculature, and kidney.. At baseline (non-failing), BNP lowered central venous, pulmonary capillary wedge, diastolic, mean pulmonary artery, and mean arterial pressure. Sildenafil had no effects, and SIL + BNP was similar to BNP alone. In contrast, SIL lowered these pressures similarly to BNP in dogs with HF, and SIL + BNP was additive in further reducing pulmonary pressures over BNP alone. Plasma cGMP/plasma BNP ratio was markedly reduced with HF, indicating NP resistance. Sildenafil plus BNP increased this ratio in HF, but had no effect in non-failing animals. Sildenafil had no independent diuretic/natriuretic effects nor did it enhance BNP effects under baseline or HF conditions. In HF, PDE5 activity was significantly increased in the systemic and pulmonary vasculature and in the kidney.. The PDE5 activity in systemic and pulmonary vasculature increases in HF rendering hemodynamic responses to PDE5 inhibition identical to those from BNP infusion. Natriuretic peptide desensitization in HF relates, in part, to increased PDE5 activity, supporting a therapeutic role for PDE5 inhibition.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Synergism; Female; Heart Failure; Infusions, Intravenous; Male; Multivariate Analysis; Natriuretic Peptide, Brain; Piperazines; Probability; Purines; Random Allocation; Reference Values; Risk Factors; Sensitivity and Specificity; Sildenafil Citrate; Sulfones

We evaluated the long-term effect of NO-donor, pentaerythrityl tetranitrate (Petn), and sildenafil citrate (sildenafil) on the cardiovascular system of the spontaneously hypertensive rat (SHR). Petn (100 mg/kg/day) and sildenafil (10 mg/kg/day) were administered to SHR individually or together from week 4 (pre-hypertensive period) to week 9 of age. Blood pressure (BP) was measured using a plethysmographic method. The animals were perfused with a glutaraldehyde fixative (120 mmHg). Carotid (AC) and coronary artery (RS) were processed according to electron microscopy procedure. Geometry of the arteries was measured on semi-thin sections using light microscopy. Administration of Petn and sildenafil to SHR individually or together did not prevent an increase of BP, but evoked a decrease of cardiac hypertrophy. Petn and sildenafil affected the geometry of RS and AC differently. In the RS, an increase of inner diameter (ID) without an increase of wall thickness (WT) resulted in increased WT/ID and circumferential stress. In the AC, changes in ID were accompanied by changes in WT and, thereby, WT/ID and circumferential stress remained unchanged. The arterial wall mass of both arteries was increased. The data suggest that administration of the NO donor, Petn, and/or sildenafil does not result in a beneficial effect on the myocardium or on the geometry of the carotid and coronary arteries.

Topics: Animals; Antihypertensive Agents; Blood Pressure; Cardiomegaly; Cardiovascular System; Carotid Arteries; Coronary Vessels; Disease Models, Animal; Disease Progression; Drug Administration Schedule; Drug Therapy, Combination; Hypertension; Nitric Oxide Donors; Pentaerythritol Tetranitrate; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Inbred SHR; Rats, Wistar; Sildenafil Citrate; Sulfones; Time Factors; Vasodilator Agents

Peripheral artery disease (PAD) is a prevalent cardiovascular disorder that results in tissue ischemia which can progress to critical limb ischemia. Restoration of tissue perfusion in the setting of chronic ischemia through stimulation of arteriogenesis and angiogenesis remains a key therapeutic target for PAD. However, experimental therapeutics, including growth factor and gene therapy, have had little clinical success indicating the need for a better understanding of molecular pathways required for therapeutic angiogenesis.. Here we report that phosphodiesterase-5 inhibition by sildenafil significantly increases vascular perfusion, tissue blood flow, and vascular density during chronic ischemia of the mouse hind limb. Importantly, sildenafil therapy did not alter any of these parameters in nonischemic limbs. Sildenafil increased tissue cGMP levels independently of increases in nitric oxide production, and sildenafil therapy stimulated angiogenesis in ischemic limbs of eNOS-/- and iNOS-/- mice. Lastly, sildenafil-mediated angiogenic activity was blocked by inhibition of protein kinase G using the PKG antagonist DT-3.. These data demonstrate that sildenafil therapy results in increased angiogenic activity through a PKG-dependent pathway that is independent of nitric oxide production or NOS activity and identify the angiogenic therapeutic potential of sildenafil for critical limb ischemia.

Topics: Animals; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Hindlimb; Ischemia; Male; Mice; Neovascularization, Physiologic; Peripheral Vascular Diseases; Phosphodiesterase Inhibitors; Piperazines; Purines; Regional Blood Flow; Signal Transduction; Sildenafil Citrate; Sulfones

Immunophilin ligands and phosphodiesterase type 5 (PDE5) inhibitors are touted to promote erectile function recovery after cavernous nerve (CN) injury. However, the mechanisms for their effects remain unclear.. To compare the erection recovery effects of the immunophilin ligand FK506 and the PDE5 inhibitor sildenafil after CN injury and determine whether they involve antioxidative and/or antiapoptotic mechanisms.. Initial experiments established conditions of our CN injury model in adult male Sprague-Dawley rats. Subsequently, we evaluated treatment effects 14 days after: (i) unilateral CN injury (UNI) + saline (vehicle control); (ii) UNI + FK506 (5 mg/kg once daily, subcutaneous x 5 days); (iii) UNI + sildenafil (20 mg/kg every 8 hours, subcutaneous x 7 days); (iv) UNI + FK506/sildenafil; and (v) sham surgery.. Intracavernous pressure (ICP) measurement after CN electrical stimulation to assess erectile function and Western blot analysis of expressions of glutathione peroxidase (GPX; antioxidant enzyme), nitrotyrosine (NT; oxidative stress marker), and phosphorylated and total Akt (antiapoptotic factor) in penes.. In the UNI model, GPX expression was increased at Days 1 and 7, while p-Akt expression decreased at Day 1 and returned to baseline at Day 7. GPX expression was significantly higher in the UNI + FK506 group compared with the saline-treated group (P < 0.05). ICP increased in all treatment groups compared with that of the saline-treated group (P < 0.05). NT levels were increased after saline treatment (P < 0.05) but not after FK506 and sildenafil treatment, alone or in combination. GPX was localized to nerves coursing through the penis and to smooth muscle and endothelium of the dorsal vein and arteries.. Both FK506 and sildenafil protect erectile function after CN injury by decreasing oxidative stress-associated tissue damage. FK506 may act through increased GPX activity. Further research is required to elucidate mechanisms associated with the beneficial effect of sildenafil.

Topics: Animals; Blotting, Western; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Therapy, Combination; Glutathione Peroxidase; Immunohistochemistry; Male; Nerve Regeneration; Nitric Oxide Synthase; Penile Erection; Penis; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Tacrolimus; Tyrosine; Vasodilator Agents

The endothelin system plays an important role in the development of pulmonary hypertension. Several studies have suggested that interfering with the function of the endothelin system will be helpful in pulmonary hypertension treatment. In the present study, we investigated the preventive and therapeutic effects of sildenafil on pulmonary hypertension in monocrotaline-treated rats. In the preventive study, the level of mean pulmonary arterial pressure, right ventricular divide, left ventricular and septum, small pulmonary arterial morphologic and elastic fiber changes were highly improved in the treated group (P<0.05). The expressions of endothelin-1 A type receptors on small pulmonary arterial hypertension were significantly reduced in the sildenafil-treated group (P<0.05). The ET-1 level in plasma was increased in the sildenafil-treated group, but did not reach significance. Emphysema, interstitial pneumonia were significantly improved in the sildenafil-treated group. The same findings were also observed in the therapeutic study. The present results suggest that sildenafil can prevent and reverse the development of pulmonary hypertension in monocrotaline-treated rats by improving the function of endothelin system in pulmonary arteries.

Topics: Administration, Oral; Animals; Antihypertensive Agents; Blood Pressure; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Lung; Lung Diseases, Interstitial; Male; Monocrotaline; Piperazines; Pulmonary Artery; Pulmonary Emphysema; Purines; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Sildenafil Citrate; Sulfones; Time Factors; Vasodilator Agents

Erectile dysfunction (ED) is highly associated to cardiovascular disease, especially arterial hypertension. Phosphodiesterase type 5 (PDE5) inhibitors and angiotensin II receptor blockers (ARB) are both common and efficient therapy in patients with ED and arterial hypertension, respectively.. To evaluate the effect of PDE5 inhibitor, sildenafil (S), and of ARB Losartan (L) in a continuous combined therapy for a long term on penile structures in a hypertensive rat model.. During 6 months, four groups of male spontaneously hypertensive rats (SHR) and one of Wistar-Kyoto (WKY) rats, as control group, were studied: no-treatment SHR, SHR with L, SHR with S, SHR with S + L, and no-treatment WKY. Cavernous smooth muscle (CSM) and vascular smooth muscle (VSM) from cavernous arteries, collagen type III (COL-III), and endothelial nitric oxide synthase (eNOS) expression in cavernous space were evaluated.. Functional and morphological differences between S and L in a continuous combined therapy vs. either drug as monotherapy on penile structures.. After 6 months, SHR that received L, S, or combined therapy showed a similar reduction in blood pressure compared with untreated SHR. Nevertheless, SHR + L + S and control WKY showed significantly lower values of (i) CSM (P < 0.01), (ii) VSM (P < 0.01), and (iii) COL-III (P < 0.01) when compared with the untreated SHR and also with the SHR with monotherapy. Additionally, SHR + L + S, presented a higher eNOS expression in sinusoidal endothelium in comparison with the untreated SHR and the SHR with monotherapy (P < 0.01). In vitro studies revealed that SHR + L + S displayed a better relaxation response to acetylcholine than the untreated SHR and the SHR with monotherapy (P < 0.01).. These results suggest that a long-term combined therapy using L and S is a useful tool for functional and structural modification in cavernous tissue from SHR.

Topics: Animals; Antihypertensive Agents; Blood Pressure; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Therapy, Combination; Hypertension; Impotence, Vasculogenic; Longitudinal Studies; Losartan; Male; Muscle, Smooth, Vascular; Penis; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Inbred SHR; Rats, Wistar; Sildenafil Citrate; Sulfones; Treatment Outcome; Vasodilator Agents

To investigate the protective effects of sildenafil citrate (SC) on indomethacin-induced gastric ulcer in a rat model.. Gastric ulcers were induced by oral ingestion of indomethacin. Thirty rats were used in the study. The rats were divided into 3 groups, and given either SC (n=10) at a dose of 50 mg/kg or omeprazole (n=10), or no treatment (n=10, the control group). In addition to the measurements of ulceration areas, the sum of gastric tissue nitrite (NO2-) and nitrate (NO3-) were evaluated as an indicator of gastric tissue NO level. All the measurements were done at 6th hour of oral administration of indomethacin.. The mean values of ulceration areas were 4.0+/-2.31, 3.0+/-2.00, and 21.4+/-8.43 in the SC, omeprazole and control groups, respectively. The mean values of ulceration areas in the SC-treated group was lower than that of the control group. The contents of NO were 32.2+/-3.05, 24.8+/-3.23 and 21.0+/-0.82 (micromol/g protein) in gastric tissue in indomethacin, SC, omeprazole and control groups, respectively, The content of NO in the SC-treated groups was significantly higher than control group (p<0.001).. Sildenafil citrate may have a role in protecting gastric mucosa from the damage caused by indomethacin. This effect may be associated with the increased level of NO in gastric tissue.

Topics: Administration, Oral; Animals; Anti-Inflammatory Agents, Non-Steroidal; Anti-Ulcer Agents; Disease Models, Animal; Female; Indomethacin; Nitric Oxide; Omeprazole; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Stomach Ulcer; Sulfones

This study investigated the involvement of the L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway in the antidepressant-like effect of an acute administration of memantine in the forced swimming test (FST) in mice, since this signaling pathway is supposed to play a significant role in depression. The antidepressant-like effect of memantine (3 mg/kg, i.p.) was prevented by pretreatment with L-arginine (750 mg/kg, i.p.) or S-nitroso-N-acetyl-penicillamine (SNAP, 25 microg/site, i.c.v.), but not with d-arginine (750 mg/kg, i.p.).The treatment of mice with NG-nitro-L-arginine (L-NNA, 0.03 and 0.3 mg/kg, i.p.) potentiated the effect of a subeffective dose of memantine (0.3 mg/kg, i.p.) in the FST. Moreover, the pretreatment of mice with (1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one) (ODQ, 30 pmol/site, i.c.v.) produced a synergistic antidepressant-like effect with subeffective doses of memantine (0.3 and 1 mg/kg, i.p.) in the FST. Furthermore, the reduction in the immobility time elicited by memantine (3 mg/kg, i.p.) in the FST was prevented by pretreatment with sildenafil (5 mg/kg, i.p.). Taken together, the results demonstrate that memantine produced an antidepressant-like effect in the FST that seems to be mediated through an interaction with the L-arginine-NO-cGMP pathway.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Arginine; Cyclic GMP; Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Female; Immobility Response, Tonic; Male; Memantine; Mice; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Penicillamine; Piperazines; Purines; Sildenafil Citrate; Sulfones; Swimming

Restoring intracellular cGMP and inducing NO-synthesis attenuates ischemia-associated early pulmonary allograft dysfunction. Phosphodiesterase-5 (PDE), predominantly expressed in lung tissue, plays a pivotal role in modulating the cGMP/NO-synthase pathway in endothelial and epithelial cells. In this study, we evaluate the effect of employing sildenafil (Viagra), a specific inhibitor of PDE-5, to counteract ischemia/reperfusion (I/R) injury in a single lung transplantation model of extended ischemia.. Donor animals (weight matched outbred pigs, 28-35 kg) in the treatment group (I) (n=5) were injected with 0.7 mg sildenafil/kg into the pulmonary artery (PA) prior to inflow occlusion. For perfusion, Perfadex, containing 0.7 mg sildenafil/l was used, and the graft stored at 1 degrees C in the perfusion solution. After 24h ischemia, unilateral left lung transplantation was performed. Starting at reperfusion, group I received continuous sildenafil (0.7 mg sildenafil/kg), over 6h. Except for the sildenafil application, the control group (II) (n=4) was treated identically (PGE1 was injected into the PA). One hour after reperfusion, the right main bronchus (MB) and right PA were occluded. Over the next 5h, cardiopulmonary parameters (systemic atrial, PA, central venous, left atrial pressure, pCO(2), pO(2)) were measured, including extravascular lung water (EVLW). Thiobarbituric acid-reactive substance assay (TBARS) and myeloperoxidase (MPO) analysis from lung tissue were run.. All recipients of group I survived the 6-h reperfusion period; in contrast, all control animals died within 1-2h after occlusion of the right side. In comparison to a marked rise in pulmonary vascular resistance (PVR) in group II (>1000 dynescm(-5)), PVR in group I remained stable, moderately elevated from baseline (baseline: 150-180 dynescm(-5) vs endpoint: 1000 dynescm(-5)). EVLW in group I did not increase during reperfusion (baseline: 6.75+/-1.4 mg/kg vs endpoint: 6.7+/-1.0mg/kg), in contrast to group II, where pulmonary edema at 2-h reperfusion preceded terminal graft failure (group I: 9.7+/-0.1mg/kg vs group II: 6.48+/-1.8 mg/kg). Tissue reactive free radicals at endpoint measurement in group I did not differ significantly from native tissue. Yet, when compared to specimen taken from group II at time of terminal graft failure, a significant increase in free radicals was noted (group I: 13.8+/-1.6 pmol/g vs group II: 18.5+/-3.0 pmol/g, p<0.05).. Sildenafil treatment prevents terminal early graft failure, allowing lung transplantation after 24-h ischemia time. Reperfusion edema was strikingly diminished, preserving pulmonary structural and functional integrity while prolonging graft ischemia time. Employing the established PDE-5 inhibitor sildenafil during lung perfusion, storage, and implantation, ischemic tolerance may be extended and early graft function improved.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Drug Evaluation, Preclinical; Extravascular Lung Water; Graft Survival; Lipid Peroxidation; Lung Transplantation; Peroxidase; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Pulmonary Circulation; Purines; Reperfusion Injury; Sildenafil Citrate; Sulfones; Swine; Vascular Resistance

To evaluate the effects of phosphodiesterase type III and V (PDEIII and PDEV) inhibition on pulmonary and systemic haemodynamics in a porcine model of acute pulmonary hypertension.. Twenty-four adult swine were anaesthetized with 1 MAC isoflurane and mechanically ventilated with an FI(O(2)) of 100%. Micromanometer-tipped catheters were placed in the ascending aorta, pulmonary artery and right ventricle. Pulmonary flow was measured with a perivascular probe using transit time ultrasound. Pulmonary hypertension was induced with a continuous infusion of the thromboxane analogue, U46619. The animals were then randomized to four groups: Group 1 (n=6) received 50 mg of sildenafil (PDEV inhibitor) diluted in water via an orogastric tube; Group 2 (n=6) received 50 microg kg(-1) of i.v. milrinone (PDEIII inhibitor); Group 3 (n=6) received sildenafil followed by milrinone; and Group 4 (n=6) received placebo via an orogastric tube.. Pulmonary hypertension was achieved in all animals. Calculated pulmonary vascular resistance decreased by an average of 36% after sildenafil (P<0.05), 41% after milrinone (P<0.05), and 61% with both drugs combined (P<0.05). Systemic vascular resistance decreased by 37% (P<0.05) with milrinone alone, and 36% (P<0.05) with milrinone and sildenafil combined but it was preserved in the sildenafil group. Cardiac output and right ventricular dP/dT were significantly improved after milrinone or both drugs combined, but not with sildenafil.. Milrinone and sildenafil are effective pulmonary vasodilators, with independent action and additive effect. Both drugs combined achieved a better haemodynamic profile, with greater pulmonary vasodilatation and increased contractility but without additional systemic vasodilatation. The systemic haemodynamic profile (systemic vasodilation, cardiac output, right ventricular dP/dT) is improved with milrinone but not with sildenafil.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 3',5'-Cyclic-AMP Phosphodiesterases; Acute Disease; Animals; Cyclic Nucleotide Phosphodiesterases, Type 3; Cyclic Nucleotide Phosphodiesterases, Type 4; Disease Models, Animal; Drug Evaluation; Drug Therapy, Combination; Hemodynamics; Hypertension, Pulmonary; Milrinone; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Swine; Vascular Resistance; Vasoconstrictor Agents; Vasodilator Agents

Hypogonadism is often associated with diabetes and both conditions represent major risk factors for erectile dysfunction (ED).. To investigate the role of hypogonadism on phosphodiesterase type 5 (PDE5) expression and sildenafil responsiveness in diabetes.. Two different models of experimental diabetes were used: (i) alloxan-induced diabetic rabbit; and (ii) streptozotocin (STZ)-induced diabetic rat. In both experimental models, animals were separated into three groups: control, diabetic, diabetic supplemented with testosterone (T) enanthate. Rabbits were used for "in vitro" experiments. Conversely, each rats group was further subdivided: no further treatment or acute sildenafil dosing (25 mg/kg, 1 hour before "in vivo" electrical stimulation [ES]).. Erectile capacity was evaluated either by "in vitro" contractility study (alloxan-induced diabetic rabbit) and "in vivo" evaluation of erectile response elicited by ES of cavernous nerve (STZ-induced diabetic rats). Also endothelial nitric oxide synthase, neural nitric oxide synthase (nNOS), and PDE5 protein (Western blot) and mRNA (quantitative real-time reverse transcriptase polymerase chain reaction [RT-PCR]) expression were measured in rat penile samples of each group.. In both models, hypogonadism was observed, characterized by reduced T and atrophy of androgen-dependent accessory glands. T substitution completely reverted hypogonadism and diabetes-induced penile hyposensitivity to "in vitro" (acetylcholine, rabbit) or "in vivo" (ES, rat) relaxant stimuli, along with nNOS expression, which was reduced (P < 0.05) in STZ rats. In diabetic animals, T substitution reinstated sildenafil-induced enhancement of both "in vitro" nitric oxide donor (NCX 4040) relaxant effect (rabbit) and "in vivo" ES-induced erection (rat). PDE5 was reduced in diabetic STZ rats (P < 0.05) and normalized by T. In STZ rats, sodium nitroprusside (SNP) intracavernous injection induced a more sustained erection than in control rats, which was no further enhanced by sildenafil. T substitution normalized both hyper-responsiveness to SNP and sildenafil efficacy.. In two models of diabetes T deficiency underlies biochemical alterations leading to ED. Normalizing T in diabetes restores nNOS and PDE5, and reinstates sensitivity to relaxant stimuli and responsiveness to sildenafil.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Alloxan; Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus, Experimental; Disease Models, Animal; Endothelium, Vascular; Erectile Dysfunction; Hypogonadism; Male; Nitric Oxide Synthase; Penile Erection; Phosphoric Diester Hydrolases; Piperazines; Purines; Rabbits; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; Sildenafil Citrate; Streptozocin; Sulfones; Testosterone

Sildenafil attenuates acute pulmonary embolism (APE)-induced pulmonary hypertension. However, the hemodynamic effects of sildenafil in combination with other vasodilators during APE have not been examined yet. In the present study, we examined the hemodynamic effects of combined diethylenetriamine/nonoate (DETA-NO, 1microMol kg(-1), i.v.) and sildenafil (0.25mg/kg, i.v.) in an anesthetized dog model of APE. Plasma nitrite/nitrate (NO(x)) and cyclic GMP concentrations were determined using an ozone-based chemiluminescence assay and a commercial enzyme immunoassay, respectively. We found that this dose of DETA-NO did not attenuate APE-induced pulmonary hypertension. However, significant decreases in mean pulmonary artery pressure were observed 15, 30 and 45min after the administration of sildenafil alone or after the combined administration of DETA-NO and sildenafil (all P<0.05). No significant differences among groups were observed in the respiratory parameters. While DETA-NO significantly increased NO(x) concentrations by approximately 4microM, cyclic GMP concentrations increased only when sildenafil was administered (all P<0.05). These results show that the combined administration of 1microMol kg(-1) of DETA-NO and sildenafil is not advantageous compared with sildenafil alone, thus suggesting that sildenafil alone produced maximum attenuation of APE-induced pulmonary hypertension, as far as the NO-cGMP pathway is concerned.

Topics: Animals; Blood Pressure; Cyclic GMP; Disease Models, Animal; Dogs; Drug Interactions; Female; Heart Rate; Hemodynamics; Male; Nitrates; Nitric Oxide Donors; Nitrites; Piperazines; Pulmonary Artery; Pulmonary Embolism; Purines; Respiration; Sildenafil Citrate; Sulfones; Time Factors; Vascular Resistance

Increasing age decreases the number of new neurons in the dentate gyrus and the subventricular zone (SVZ). Sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, enhances neurogenesis in young rats. The present study tested the hypothesis that sildenafil augments neurogenesis in aged rats after focal cerebral ischemia. Nonischemic aged (18 months, n = 6) Wistar rats exhibited a significant reduction of actively proliferating and relatively quiescent cells in the SVZ measured by the number of minichromosome maintenance protein-2-positive (MCM-2+) cells, a marker of the proliferating cells, compared with nonischemic young (3-4 months, n = 8) rats. Occlusion of the middle cerebral artery did not increase the number of MCM-2+ cells in the SVZ of aged rats at 3 months after focal ischemia. However, treatment with sildenafil at a dose of 3 mg/kg (n = 8) daily for 7 consecutive days starting 7 days after focal ischemia significantly increased the number of MCM-2+ cells in the SVZ of aged rats compared with aged rats treated with saline (n = 8). Double immunostaining revealed that substantially more Ki67+ cells (a marker of proliferating cells) were doublecortin+ (a marker of migrating neuroblasts) in sildenafil-treated than in saline-treated aged animals. In addition, treatment with sildenafil significantly improved functional recovery compared with saline-treated rats. These data suggest that inhibition of PDE5 activity by sildenafil augments neurogenesis in the SVZ of aged ischemic rats, although these rats have reduced numbers of neural progenitor and stem cells in the SVZ.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Aging; Animals; Brain Ischemia; Cell Division; Cell Proliferation; Cerebral Cortex; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Doublecortin Domain Proteins; Doublecortin Protein; Ki-67 Antigen; Male; Microtubule-Associated Proteins; Minichromosome Maintenance 1 Protein; Neuronal Plasticity; Neuropeptides; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Recovery of Function; Sildenafil Citrate; Stem Cells; Sulfones; Up-Regulation

Distal ischemic necrosis of the flap remains an unsolved, challenging problem. Phosphodiesterase (PDE) inhibitors, which include the drug sildenafil, are a relatively new class of U.S. Food and Drug Administration-approved medications whose effect on tissue viability has not been widely explored. The vasodilatory effects of these drugs have the potential to enhance blood flow to flaps and increase their survivability. The purpose of this study was to examine the short- and long-term effects of sildenafil, administered intraperitoneally at a dose of 9 mg/kg per day, on the survival of surgical skin flaps in rats.. A McFarlane-type random pattern skin (3 x 10-cm) flap model was used to evaluate the effect of sildenafil on necrosis at multiple time points. Rats were assigned to sildenafil-treated (9 mg/kg per day intraperitoneally; n = 34), vehicle control (n = 35), or sham (no injection; n = 40) groups. In each group, caudally based, dorsal, rectangular (3 x 10-cm) flaps were created. Flap necrosis was determined using orthogonal polarization spectral imaging and digital photography analysis on days 1, 3, 5, and 7 postsurgery.. Orthogonal polarization spectral imaging results showed a significant decrease in necrosis and stasis in rats treated with sildenafil on days 1 and 3. Although reductions observed at days 5 and 7 were not as dramatic as days 1 and 3, digital photography analysis confirmed a decrease in the area of necrosis at all time points evaluated.. These results suggest that PDE 5 inhibitors may play a more important role in early postoperative skin flap viability rather than at later time points and may be beneficial for skin flap viability as shown in the rat model. PDE 5 inhibitors may reduce the extent of necrosis after reconstructive surgeries.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Blood Flow Velocity; Dermatologic Surgical Procedures; Disease Models, Animal; Follow-Up Studies; Male; Microcirculation; Necrosis; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Surgical Flaps; Time Factors; Treatment Outcome

Previous studies have shown that sildenafil inhibits the esophageal motility in both humans and animals. The aim of this study was to investigate the effects of sildenafil on intestinal myoelectrical activity and motility. The study was composed of 2 experiments and performed in 7 healthy female dogs with a duodenal cannula 20 cm beyond pylorus (19-26 kg). The first experiment was designed to study the effects of sildenafil on intestinal myoelectrical activity and it included 2 sessions each consisting of 30-minute baseline, 15-minute posttreatment (placebo or 100 mg sildenafil) and 90 minutes after a liquid meal. Intestinal myoelectrical activity was recorded during the entire experiment period. The second experiment was aimed to investigate the effect of sildenafil on intestinal motility and was performed immediately after a solid meal. Intestinal motility was measured by a manometric catheter inserted into the small intestine via the duodenum cannula for 30 minutes at baseline and 60 minutes after sildenafil. Sildenafil significantly reduced the amplitude but had no effect on the frequency and regularity of the intestinal myoelectrical activity. Sildenafil significantly inhibited postprandial intestinal contractions. Although the frequency of the contractions was not altered, the mean area under the curve was significantly reduced during the first 30 minutes (P < .03) and second 30 minutes after sildenafil (P < .03); the power of intestinal contractile activities was also significantly reduced during the first 30 minutes (P < .0004) and second 30 minutes after sildenafil (P < .0003) in comparison with baseline. In conclusion, sildenafil inhibits the amplitude of both intestinal contractile activity and intestinal slow waves.

Topics: Animals; Area Under Curve; Disease Models, Animal; Dogs; Female; Gastrointestinal Motility; Intestine, Small; Myoelectric Complex, Migrating; Piperazines; Probability; Purines; Random Allocation; Reference Values; Sensitivity and Specificity; Sildenafil Citrate; Sulfones

To determine sildenafil citrate (SC) genotoxicity and cytotoxicity in the Callithrix jacchus.. Fifteen organisms were assigned to one of three groups as follows: experimental (25 mg/kg of SC); negative control (glucose solution 5%); and positive control (3 mg/kg of cytocine arabinoside). Systemic hemodynamic changes were monitored in each animal before and after each treatment. A drop of blood was obtained before and after the treatment at 24-120 h. Smears were made and the frequency of micronucleated erythrocytes (MNE), micronucleated polychromatic erythrocytes (MNPCE) and polychromatic erythrocytes (PCE) was counted.. No significant differences in MNE, MNPCE and PCE were found in the group that received sildenafil and negative control. A significant increase in genotoxicity and cytotoxicity was observed in the positive control group. No changes were observed in systemic hemodynamic changes.. The macro-dose of SC lacks genotoxic, cytotoxic or systemic hemodynamic changes effects in this species.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Administration, Oral; Animals; Blood Pressure; Callithrix; Chromosome Aberrations; Disease Models, Animal; Erythrocytes; Heart Rate; Micronuclei, Chromosome-Defective; Mutagenicity Tests; Piperazines; Purines; Random Allocation; Sildenafil Citrate; Sulfones; Vasodilator Agents

Sildenafil, an oral phosphodiesterase Type 5 inhibitor, has vasodilatory effects through a cGMP-dependent mechanism. We previously showed that aortic banding could result in left ventricular overloading and pulmonary hypertension (PH). In this study, we investigated whether early administration of sildenafil, either immediately after or 2 weeks after aortic banding, could ameliorate the development of PH and alter gene expression of endothelin (ET)-1 and endothelial nitric oxide synthase (eNOS), and alter the levels of cGMP in rats undergoing an ascending aortic banding. Rats (n = 32) were divided into sham-operated and banding groups with or without treatment. The banded rats were further divided into three groups: (i) receiving saline on Days 1-28 (AOB28; n = 8), (ii) receiving saline on Days 1-14 followed by treatment with 50 mg/kg/day sildenafil on Days 15-28 (AOB28/Sil(15-28); n = 8), and (iii) receiving 50 mg/kg/day sildenafil on days 1-28 (AOB28/Sil(1-28); n = 8). The sham-operated rats were administrated saline on Days 1-28 (n = 8). Four weeks after banding, there was a significant development of PH with pulmonary vascular remodeling. Although both sildenafil-treatment groups had significant increases in cGMP and had reductions in the thickening in the medial layer of pulmonary arteriole, notable attenuation of PH occurred only in the AOB28/Sil(1-28) group. PreproET-1 and eNOS messenger RNA (mRNA) expressions were measured by competitive reverse transcription polymerase chain reaction, and eNOS protein was determined by Western blotting. Sildenafil did not alter the elevated ET-1 or preproET-1 mRNA in banded rats. Interestingly, pulmonary eNOS increased in the AOB28/Sil(1-28) group. In conclusion, early treatment with sildenafil inhibited the rise in pulmonary arterial pressure and pulmonary vascular remodeling in PH secondary to heart failure, and cGMP, but not ET-1, might be involved. Clinically, early repeated administration of sildenafil may offer an alternative in protecting against PH in heart failure.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Male; Nitric Oxide Synthase Type III; Phosphodiesterase Inhibitors; Piperazines; Purines; Random Allocation; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones

The dual endothelin receptor antagonist, bosentan, and the phosphodiesterase inhibitor, sildenafil, are efficacious in experimental and clinical pulmonary hypertension (PHT). The effects of bosentan, sildenafil, and their combination were evaluated in rats with monocrotaline (MCT)-induced PHT. A first group consisted of control rats with no MCT injection. Four other groups of rats received MCT subcutaneously and were assigned to receive no treatment, 300 mg/kg/day bosentan as food admix, 100 mg/kg/day sildenafil in drinking water, or their combination for 4 weeks. The doses of bosentan and sildenafil were the maximally effective doses based on a dose-range-finding study. Mortality was 0%, 53%, 11%, 11%, and 0%, respectively, in the five different groups. Bosentan and sildenafil significantly attenuated the increase in mean pulmonary arterial pressure, and the combination had an additional effect. Similarly, bosentan, sildenafil, and, to a greater extent, their combination significantly reduced right ventricular (RV) hypertrophy. Bosentan, but not sildenafil, decreased norepinephrine and BNP plasma concentrations, reduced kidney weight, and normalized systemic hemodynamics. In conclusion, bosentan and sildenafil are efficacious in rats with chronic PHT, and their combination shows an additional effect for decreasing pulmonary arterial pressure, reducing plasma catecholamines, maintaining body weight, and reducing mortality.

Topics: Animals; Bosentan; Disease Models, Animal; Drug Therapy, Combination; Endothelin Receptor Antagonists; Hypertension, Pulmonary; Male; Monocrotaline; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfonamides; Sulfones

Topics: Animals; Disease Models, Animal; Graft Survival; Lung Transplantation; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

Persistent stimulation of nociceptors and C-fibers by tissue injury causes hyperalgesia and allodynia by sensitization of nociceptors and facilitation of synaptic transmission in the spinal cord. The important participant in the inflammatory response of injured peripheral nerve may be nitric oxide (NO). The aim of the present study was to test the sensitivity of PDE5 inhibitor sildenafil in chronic constriction injury (CCI) model a rat model of neuropathic pain. Sciatic nerve injury is associated with development of hyperalgesia 14 days after the nerve ligation. Sildenafil (100 and 200 microg/rat, i.t.) produced a significant decrease in pain threshold, which in lower dose did not alter the nociceptive threshold. The hyperalgesic effect of sildenafil was blocked by L-NAME and methylene blue (MB), which on per se treatment showed antinociceptive effect in nerve ligated rats. The results from the present study indicated that the major activation of NO-cGMP pathway in the chronic constriction injury model of neuropathic pain. The aggravation of hyperalgesic response might be due to the increased cGMP levels resulting in PKG-I activation and its upregulation.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Chronic Disease; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Hyperalgesia; Injections, Spinal; Male; Methylene Blue; NG-Nitroarginine Methyl Ester; Nitric Oxide; Pain; Pain Threshold; Piperazines; Purines; Rats; Rats, Wistar; Sciatic Neuropathy; Signal Transduction; Sildenafil Citrate; Sulfones

One of the phosphodiesterase isoenzymes, Type V (PDE V), specifically hydrolyzes cyclic guanosine monophosphate to cause vasoconstriction. This study analyses the effect of PDE V inhibition with sildenafil citrate (SC) on cerebral vasospasm and its effect on apoptotic changes of the vascular endothelium.. Twenty-four rabbits were divided into four groups. The first group was composed of sham-surgery animals. The second group was the subarachnoid hemorrhage (SAH) group, in which cerebral vasospasm was induced. In the third group, sham-surgery rabbits were treated with SC. In the fourth group, animals were treated with SC after SAH. SC was administered for 48 hours, 0.7 mg/kg, three times per day in Groups 3 and 4. Basilar artery lumen circumferences were measured in all groups by computerized image analysis. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) method was used to evaluate the rate of apoptosis between SAH and SC-treated SAH groups. Results were compared by analysis of variance and paired t tests, and P values less than 0.05 were considered significant.. Basilar artery circumferences between groups were significantly different (P < 0.001). SC (0.7 mg/kg, three times per d) significantly dilated the basilar arteries in both the sham-surgery group (2370 +/- 233 microm; P = 0.039) and the SAH group (2142 +/- 195 microm; P = 0.006) after 48 hours of treatment. The TUNEL method for apoptosis revealed that actual numbers of the apoptotic endothelial cells per cross section after SAH in the control (no treatment) (73 +/- 2) and SC-treated (0.7 mg/kg) groups(76 +/- 3) were not significantly different (P > 0.05).. The vasodilatory effect of SC was observed to be significant on normal cerebral vessels and after SAH-induced vasospasm. SC did not prevent apoptosis of the endothelium in our study, which suggests that prevention of apoptosis is not necessary in the treatment of cerebral vasospasm.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Administration, Oral; Animals; Basilar Artery; Blood Flow Velocity; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dose-Response Relationship, Drug; Male; Phosphodiesterase Inhibitors; Piperazines; Purines; Rabbits; Sildenafil Citrate; Subarachnoid Hemorrhage; Sulfones; Treatment Outcome; Vasodilation; Vasodilator Agents; Vasospasm, Intracranial

Advanced age is associated with a decrease in brain plasticity compared with the young adult. Sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor promotes brain plasticity and improves functional outcome after stroke in the young animal. Here, we test the hypothesis that sildenafil provides restorative therapeutic benefit to the aged animal.. Male Wistar rats (aged, 18-month old; young, 3-month old) were subjected to embolic stroke. Saline or sildenafil was administered daily at a dose of 2 mg/kg orally or 10 mg/kg subcutaneously for 7 consecutive days starting 24 hour after stroke onset.. Aged rats exhibited significant impairment of functional recovery and reductions of vascular density, and endothelial cell proliferation compared with young rats. Aged rats treated with sildenafil at a dose of 10 mg/kg but not 2 mg/kg, showed significant improvements of functional recovery and concomitant increases in cortical cyclic guanosine 3',5'-cyclic monophosphate (cGMP) level, vascular density, endothelial cell proliferation, and synaptogenesis compared with aged rats treated with saline. In young rats, treatment with sildenafil at a dose of 2 or 10 mg/kg significantly enhanced functional recovery and amplified brain plasticity compared with young rats treated with saline.. Age is associated with reduction of angiogenesis, and poor neurological functional recovery after stroke. However, treatment of aged stroke rats with sildenafil improves functional recovery that is likely fostered by enhancement of angiogenesis and synaptogenesis.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Aging; Animals; Bromodeoxyuridine; Cell Proliferation; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Endothelium, Vascular; Immunohistochemistry; Male; Neovascularization, Pathologic; Neuronal Plasticity; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sodium Chloride; Stroke; Sulfones; Synapses; Synaptophysin; Time Factors; Treatment Outcome

Devising therapies that might prevent the onset or progression of pulmonary hypertension in newborns has received little attention. Our major objective was to determine whether sildenafil, a selective phosphodiesterase inhibitor, prevents the development of an early stage of chronic hypoxia-induced pulmonary hypertension in newborn pigs. Another objective was to determine whether sildenafil causes pulmonary vasodilation without systemic vasodilation in piglets with chronic pulmonary hypertension. Piglets were raised in room air (control, n = 5) or 10-11% O(2) (hypoxic, n = 17) for 3 days. Some piglets (n = 4) received oral sildenafil, 12 mg/kg/day, throughout exposure to hypoxia. All piglets were anesthetized and catheterized, and pulmonary arterial pressure (Ppa), pulmonary wedge pressure (Pw), aortic pressure (Ao), and cardiac output (CO) were measured. Then for some piglets raised in hypoxia for 3 days, a single oral sildenafil dose (3 mg/kg, n = 6) or placebo (n = 5) was given, and hemodynamic measurements were repeated. For piglets raised in hypoxia for 3 days, mean Ppa and calculated PVR were elevated above respective values in control piglets. Mean Ppa and PVR did not differ between piglets that received sildenafil throughout exposure to hypoxia and those that did not. For piglets with chronic hypoxia-induced pulmonary hypertension that received a single oral dose of sildenafil, mean Ppa and PVR decreased, while mean Pw, CO, mean Ao, and systemic vascular resistance remained the same. All hemodynamic measurements were unchanged after placebo. Oral sildenafil did not influence the early stage of chronic hypoxia-induced pulmonary hypertension in newborn piglets. However, a single oral dose of sildenafil caused pulmonary vasodilation, without systemic vasodilation, in piglets with chronic hypoxia-induced pulmonary hypertension, which may have therapeutic implications.

Topics: Administration, Oral; Animals; Animals, Newborn; Chronic Disease; Cyclic GMP; Disease Models, Animal; Disease Progression; Dose-Response Relationship, Drug; Hemodynamics; Humans; Hypertension, Pulmonary; Hypoxia; Infant, Newborn; Infant, Newborn, Diseases; Lung; Piperazines; Pulmonary Artery; Purines; Reference Values; Sildenafil Citrate; Sulfones; Swine; Treatment Outcome; Vasodilator Agents

We have previously shown that NO-donor induced elevation in myocardial cGMP levels is associated with improved reperfusion function of the isolated rat heart. The phosphodiesterase 5 (PDE 5) inhibitor, sildenafil could potentially increase myocardial cGMP levels and thus protect the heart against ischaemic/reperfusion injury.. To test our hypothesis we treated the isolated working rat heart with vehicle, OR sildenafil (10, 20, 50, 100, 200 nM), OR sildenafil (50 nM) plus a sarcolemmal (HMR 1098) or a mitochondrial (5-Hydroxydecanoate (5-HD)) K(ATP) channel blocker. Hearts were then subjected to 20 min global, or 35 min regional ischaemia at 37( composite function)C before reperfusion function (aortic output, coronary flow and aortic pressure) and infarct size were documented. Pre-ischaemic, ischaemic and reperfusion myocardial cAMP and cGMP concentrations were determined.. Low concentrations of sildenafil (10, 20 and 50 nM) improved reperfusion aortic output (AO) recovery (61.4+/- 4.5%, 64.8 +/- 5.2% and 62.3 +/- 5.0% vs. 45.4 +/- 3.8% for controls (p < 0.05)) and infarct size, while high concentrations (200 nM) worsened AO recovery (24.9 +/- 4.9.0%, p < 0.05). Myocardial cGMP levels of ischaemic tissue were elevated (34.7 +/- 2.4 vs. 27.3 +/- 2.2 pmol/g ww) and cAMP levels were suppressed (0.59 +/- 0.03 vs. 0.87 +/- 0.06 nmol/g ww) in the sildenafil (50 nM) treated hearts. Co-perfusion with sildenafil plus HMR 1098 decreased AO recovery (21.7 +/- 7.6% vs. 62.3 +/- 5.0% for sildenafil alone, p < 0.05) and increased infarct size (29.7 +/- 2.04% vs. 8.6 +/- 2.39% for sildenafil alone, p < 0.05).Similarly, sildenafil plus 5-HD decreased reperfusion AO recovery (44.4 +/- 6.0% vs. 62.3 +/- 5.0% for sildenafil alone, p < 0.05) and increased infarct size (33.8 +/- 1.62% vs. 8.6 +/- 2.39% for sildenafil alone, p < 0.05).. (1) Pretreatment with low concentrations of sildenafil (20-50 nM) improves, while higher concentrations (200 nM) worsen reperfusion function in this model. (2) Low concentrations of sildenafil (20-50 nM) decrease infarct size while the higher concentrations had no effect. (3) These protective properties of low concentrations of sildenafil may be related to its cGMP elevating and cAMP suppressing effects in the ischaemic heart. (4) Possible end-effectors for sildenafil in the ischaemic heart include the mitochondrial and sarcolemmal K(ATP) channel.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Heart; Hemodynamics; In Vitro Techniques; Male; Myocardial Infarction; Myocardial Reperfusion; Myocardium; Nucleotides, Cyclic; Piperazines; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones

Post-traumatic stress disorder (PTSD) may be associated with shrinkage of the hippocampus, with glutamate release causally related to these events. Recent animal studies strongly implicate activation of the nitric oxide (NO)-cascade in anxiety and stress. Using an animal model of repeated trauma, the effect of stress was investigated on the hippocampal NO-cGMP signalling pathway, specifically the release of nitrogen oxides (NOx) and its modulation by NMDA receptor-, NO-, cGMP- and nuclear factor K-beta (NFK-beta)-selective drugs. Immediately after stress, rats received the glutamate NMDA receptor antagonist, memantine (MEM; 5 mg/kg i.p./d), the NO synthase inhibitor, 7-nitroindazole sodium salt (7-NINA; 20 mg/kg i.p./d), the cGMP-specific PDE inhibitor, sildenafil (SIL; 10 mg/kg i.p./d) or the NFkappa-beta antagonist, pyrollidine dithiocarbamate (PDTC; 70 mg/kg i.p./d), for 7 days. Stress significantly increased hippocampal NOx on day 7 post-stress, which was blocked by either 7-NINA or PDTC, while MEM was without effect. SIL, however, significantly augmented stress-induced NOx accumulation. Increased cGMP therefore acts as a protagonist in driving stress-related events, while both nNOS (neuronal NOS) and iNOS (inducible/immunological NOS) may represent a therapeutic target in preventing the effects of severe stress. The value of NMDA receptor antagonism, however, appears limited in this model.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Hippocampus; Indazoles; Male; NF-kappa B; Nitric Oxide; Piperazines; Proline; Purines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Sildenafil Citrate; Stress Disorders, Post-Traumatic; Sulfones; Thiocarbamates

Persistent pulmonary hypertension of the newborn (PPHN) is partly due to impaired nitric oxide (NO)-cGMP signaling. BAY 41-2272 is a novel direct activator of soluble guanylate cyclase, but whether this drug may be an effective therapy for PPHN is unknown. We hypothesized that BAY 41-2272 would cause pulmonary vasodilation in a model of severe PPHN. To test this hypothesis, we compared the hemodynamic response of BAY 41-2272 to acetylcholine, an endothelium-dependent vasodilator, and sildenafil, a selective inhibitor of PDE5 in chronically instrumented fetal lambs at 1 and 5 days after partial ligation of the ductus arteriosus. After 9 days, we delivered the animals by cesarean section to measure their hemodynamic responses to inhaled NO (iNO), sildenafil, and BAY 41-2272 alone or combined with iNO. BAY 41-2272 caused marked pulmonary vasodilation, as characterized by a twofold increase in blood flow and a nearly 60% fall in PVR at day 1. Effectiveness of BAY 41-2272-induced pulmonary vasodilation increased during the development of pulmonary hypertension. Despite a similar effect at day 1, the pulmonary vasodilator response to BAY 41-2272 was greater than sildenafil at day 5. At birth, BAY 41-2272 dramatically reduced PVR and augmented the pulmonary vasodilation induced by iNO. We concluded that BAY 41-2272 causes potent pulmonary vasodilation in fetal and neonatal sheep with severe pulmonary hypertension. We speculate that BAY 41-2272 may provide a novel treatment for severe PPHN, especially in newborns with partial response to iNO therapy.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Acetylcholine; Animals; Animals, Newborn; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Enzyme Activation; Female; Fetus; Guanylate Cyclase; Hypertension, Pulmonary; Nitric Oxide; Piperazines; Pregnancy; Pulmonary Circulation; Purines; Pyrazoles; Pyridines; Sheep; Signal Transduction; Sildenafil Citrate; Sulfones; Vasodilation

The effects of inhibitors of different subtypes of potassium (K+) channels were investigated in the mouse forced swimming test (FST). The treatment of animals with tetraethylammonium (TEA, a non-specific inhibitor of potassium channels, 0.25-2.5 ng/site, intracerebroventricular, i.c.v.), glibenclamide (an ATP-sensitive potassium channels (K(ATP) inhibitor, 0.05-5 ng/site, i.c.v.), apamine (a small conductance calcium-activated potassium channels inhibitor (SKCa), 0.1-1 ng/site, i.c.v.), charybdotoxin (a large- (big, BK) and intermediate- (IK) conductance calcium-activated potassium channels inhibitor, 2.5-25 ng/site, i.c.v.) produced an anti-depressant-like effect in the FST. At the highest effective doses, none of the drugs affected the locomotor activity in an open-field. Besides that, the pre-treatment of animals with l-arginine (a nitric oxide (NO) precursor, 750 mg/kg, intraperitoneal, i.p.) or sildenafil (a specific phosphodiesterase type 5 (PDE5) inhibitor, 5 mg/kg, i.p.) prevented the anti-depressant-like effect of all K+ channel inhibitors. The present results demonstrate that the decrease in the immobility time in the FST elicited by the inhibition of several subtypes of K+ channels is also dependent on the inhibition of NO-cGMP synthesis.

Topics: Analysis of Variance; Animals; Arginine; Depression; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Escape Reaction; Exploratory Behavior; Female; Guanylate Cyclase; Immobility Response, Tonic; Injections, Intraventricular; Mice; Motor Activity; Nitric Oxide; Nitric Oxide Donors; Piperazines; Potassium Channel Blockers; Potassium Channels; Purines; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Sildenafil Citrate; Soluble Guanylyl Cyclase; Statistics, Nonparametric; Stress, Psychological; Sulfones; Swimming

Sildenafil, a phosphodiesterase 5 inhibitor, is currently under investigation for therapy of pulmonary hypertension. This study was designed to investigate chronic effects of sildenafil in monocrotaline (MCT)-induced pulmonary hypertension in rats. Four weeks after a single subcutaneous injection of MCT, the animals displayed nearly threefold elevated pulmonary artery pressure and vascular resistance values, with a concomitant decline in central venous oxygen saturation and arterial oxygenation. Marked right heart hypertrophy was evident, and massive thickening of the precapillary artery smooth muscle layer was histologically apparent. Further deterioration of pulmonary hypertension occurred 6 weeks after MCT injection, with some animals dying during this period because of right heart failure. When chronically administered from Days 14-28, sildenafil significantly increased plasma cyclic guanosine monophosphate and inhibited the development of pulmonary hypertension and right heart hypertrophy, with preservation of gas exchange and systemic arterial pressure. A corresponding efficacy profile was also noted for long-term feeding with sildenafil from Days 28-42. Moreover, the death rate significantly decreased in those animals treated with sildenafil. We conclude that sildenafil attenuates MCT-induced pulmonary hypertension and cor pulmonale in rats.

Topics: Administration, Oral; Animals; Biopsy, Needle; Disease Models, Animal; Drug Administration Schedule; Drug Interactions; Hemodynamics; Hypertension, Pulmonary; Immunohistochemistry; Male; Monocrotaline; Phosphodiesterase Inhibitors; Piperazines; Probability; Pulmonary Heart Disease; Purines; Random Allocation; Rats; Rats, Sprague-Dawley; Sensitivity and Specificity; Sildenafil Citrate; Sulfones; Survival Rate; Time Factors

Sildenafil, an oral phosphodiesterase type-5 inhibitor, has vasodilatory effects through a cyclic guanosine 3', 5'-monophosphate-dependent mechanism, whereas beraprost, an oral prostacyclin analog, induces vasorelaxation through a cAMP-dependent mechanism. We investigated whether the combination of oral sildenafil and beraprost is superior to each drug alone in the treatment of pulmonary hypertension. Rats were randomized to receive repeated administration of saline, sildenafil, beraprost, or both of these drugs twice a day for 3 weeks. Three weeks after monocrotaline (MCT) injection, there was significant development of pulmonary hypertension. The increases in right ventricular systolic pressure and ratio of right ventricular weight to body weight were significantly attenuated in the Sildenafil and Beraprost groups. Combination therapy with sildenafil and beraprost had additive effects on increases in plasma cAMP and cyclic guanosine 3', 5'-monophosphate levels, resulting in further improvement in pulmonary hemodynamics compared with treatment with each drug alone. Unlike MCT rats given saline, sildenafil, or beraprost alone, all rats treated with both drugs remained alive during 6-week follow-up. These results suggest that combination therapy with oral sildenafil and beraprost attenuates the development of MCT-induced pulmonary hypertension compared with treatment with each drug alone.

Topics: Administration, Oral; Analysis of Variance; Animals; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Therapy, Combination; Epoprostenol; Hemodynamics; Hypertension, Pulmonary; Male; Piperazines; Probability; Purines; Random Allocation; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones; Survival Rate; Vascular Patency; Vasodilator Agents

Topics: Animals; Disease Models, Animal; Drug Therapy, Combination; Epoprostenol; Hypertension, Pulmonary; Male; Piperazines; Purines; Random Allocation; Rats; Rats, Wistar; Reference Values; Sensitivity and Specificity; Sildenafil Citrate; Sulfones; Treatment Outcome

Topics: Animals; Disease Models, Animal; Hypertension, Pulmonary; Lung; Male; Piperazines; Purines; Random Allocation; Rats; Rats, Sprague-Dawley; Reference Values; Sensitivity and Specificity; Sildenafil Citrate; Sulfones; Vasodilator Agents

There has been recent interest in the use of the phosphodiesterase-5 inhibitor sildenafil for treating pulmonary hypertension. We examined the interaction between inhaled nitric oxide (iNO) and i.v. sildenafil in 12 piglets with acute pulmonary hypertension and lung injury secondary to meconium aspiration. Six animals (controls) received no intervention after meconium instillation, and six received iNO (20 ppm) from 120 min, with the addition at 240 min of an i.v. sildenafil infusion (2 mg/kg over 2 h). Meconium instillation increased mean pulmonary artery (PA) pressure from 16.0 +/- 3.1 to 24.8 +/- 4.6 mm Hg (p < 0.01) and pulmonary vascular resistance (PVR) from 0.047 +/- 0.008 to 0.089 +/- 0.027 mm Hg. ml(-1). min(-1). kg(-1) (p < 0.01). Oxygenation index increased from 3 +/- 0.8 to 8.3 +/- 3.0 (p < 0.01). There were no further changes beyond 120 min in controls. iNO reduced PA pressure and PVR to baseline values, without influencing oxygenation. The addition of sildenafil further reduced PA pressure, tended to increase the cardiac output, and reduced PVR from 0.049 +/- 0.02 to 0.028 +/- 0.01 mm Hg. ml(-1). min(-1). kg(-1) (p < 0.05). Sildenafil lowered the systemic blood pressure and systemic vascular resistance and produced profound arterial hypoxemia, reducing arterial Po(2) from 69 +/- 23 mm Hg to 49 +/- 15 mm Hg, despite substantial increases first in inspired oxygen fraction and subsequently in mean airway pressures. Consequently, the oxygenation index increased by 13.9 +/- 4.8 (p = 0.01). When given in addition to iNO, sildenafil at a dose of >0.5 mg/kg produced profound pulmonary vasodilation, but this was coupled with an unacceptable deterioration in oxygenation and systemic vasodilation in this model of pulmonary hypertension with acute parenchymal lung disease.

Topics: Administration, Inhalation; Animals; Disease Models, Animal; Drug Interactions; Humans; Infant, Newborn; Infusions, Intravenous; Meconium Aspiration Syndrome; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Swine

Sildenafil (Pfizer Pharmaceuticals, Sandwich, Kent, UK) has been associated with pulmonary vasorelaxation. A more potent Sildenafil analogue (UK 343-664 [Pfizer Pharmaceuticals]) has been developed, but its effects in vivo have not been studied. This study evaluated the effects of UK 343-664 (Pfizer) during acute pulmonary hypertension.. Fourteen adult swine were anesthetized with 1 minimum alveolar concentration isoflurane and were mechanically ventilated with an FIO(2) of 50%. End tidal CO(2) was maintained between 32 and 36 mm Hg. Micromanometer tipped catheters were placed in the ascending aorta, pulmonary artery, and right ventricle. Pulmonary flow was measured with a perivascular probe using transit time ultrasound.. Pulmonary hypertension was induced with a continuous infusion of the thromboxane analogue U46619. Animals were randomized into two groups. Group 1 (n = 9) received 500 microg of UK 343-664 (Pfizer) intravenously for more than 2 minutes. Group 2 (n = 5) served as the control group. Data were recorded continuously for 60 minutes. Statistical analyses were performed with the analysis of variance and t tests. A p less than 0.05 was considered significant.Pulmonary hypertension was achieved in all animals. The administration of UK 343-664 (Pfizer) was associated with a significant decrease in pulmonary artery pressure (30.3%; p < 0.05) and pulmonary vascular resistance (42%; p < 0.05) with mild systemic vasodilatation. These effects were partially maintained at 30 minutes (a 17.3% and 39% decrease, respectively; p < 0.05).. The administration of UK 343-664 (Pfizer) was associated with predominant pulmonary vasodilatation without systemic hypotension. This may represent a significant advance in the treatment of acute pulmonary hypertension. Potential clinical implications for this new phosphodiesterase enzyme type V (PDEV) inhibitor merit further study.

Topics: Acute Disease; Animals; Disease Models, Animal; Hypertension, Pulmonary; Piperazines; Purines; Pyrimidinones; Random Allocation; Sildenafil Citrate; Sulfones; Swine; Vasodilator Agents

Beta2-adrenoceptor agonists are widely used in the treatment of pulmonary diseases. We have investigated the relaxant and anti-inflammatory activities of NCX-950 (alpha'-[[(1,1-dimethylethy)amino]methyl]-4-hydroxy-1,3-benzenedimethanol nitrate) (a nitric oxide-releasing salbutamol) in human isolated bronchi and on lipopolysaccharide (LPS)-induced acute airway inflammation in mice. NCX-950 (10(-8)-10(-5) M) elicited a relaxation of human isolated bronchi moderately higher than salbutamol, which was reduced by a beta-adrenergic blocking drug, propranolol, but not by an inhibitor of guanylate cyclase, ODQ (1H-[1,2,4]oxadiazolo[4,3-] quinolaxin-1-one). The treatment of mice with NCX-950 (1, 10, and 100 microM aerosol) markedly inhibited the neutrophil influx induced by LPS aerosol in bronchoalveolar lavage (BAL) fluid, whereas salbutamol at equimolar doses elicited a moderate inhibition. Pretreatment of mice with NCX-950 (100 microM) also significantly reduced tumor necrosis factor-alpha, interleukin-6 (IL-6), transforming growth factor-beta, and matrix metalloproteinase-9 release in BAL fluid, whereas salbutamol was ineffective. Propranolol, but not ODQ, suppressed the inhibitory activity of NCX-950 on neutrophil influx and IL-6 release in BAL fluids. A nitric oxide-releasing sildenafil NCX-911 [(5-[2-ethoxy-5-(4-methylpiperidinylsulfonyl)phenyl]-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one nitrate)], but not sildenafil (100 microM) also reduced the neutrophil influx following LPS exposure in mice. This study reported that NCX-950 elicits potent relaxant and anti-inflammatory activities compared with salbutamol, and these effects may be mainly due to the activation of the beta2-adrenoceptor rather than the cGMP pathway.

Topics: Albuterol; Animals; Anti-Inflammatory Agents; Bronchoalveolar Lavage; Bronchodilator Agents; Cell Movement; Cytokines; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Humans; Interleukin-6; Lipopolysaccharides; Male; Metalloproteases; Mice; Mice, Inbred BALB C; Nitric Oxide; Nitric Oxide Donors; Piperazines; Propranolol; Pulmonary Disease, Chronic Obstructive; Purines; Sildenafil Citrate; Sulfones

Sildenafil, a potent type 5 nucleotide-dependent phosphodiesterase (PDE) inhibitor, has been recently proposed as a therapeutic tool to treat or prevent pulmonary artery hypertension (PAHT). We thus studied the effect of sildenafil on both the calcium signaling of isolated pulmonary artery smooth muscle cells (PASMCs) and the reactivity of pulmonary artery (PA) obtained from chronic hypoxia (CH)-induced pulmonary hypertensive rats compared with control (normoxic) rats. CH rats were maintained in an hypobaric chamber (50.5 kPa) for 3 wk leading to full development of PAHT. Intracellular calcium concentration ([Ca2+]i) was measured in PASMCs loaded with the calcium fluorophore indo 1. Unlike in control rats, sildenafil (10-100 nM) decreased the resting [Ca2+]i value in PASMCs obtained from CH rats. In PASMCs from both control and CH rats, sildenafil concentration dependently inhibited the [Ca2+]i response induced by G-coupled membrane receptor agonists such as angiotensin II and phenylephrine but had no effect on the amplitude of the [Ca2+]i response induced by caffeine. Sildenafil (0.1 nM-1 microM) concentration dependently reduced basal PA tone that is present in CH rats and relaxed PA rings precontracted with phenylephrine in both control and CH rats. These data show that sildenafil is a potent pulmonary artery relaxant in CH rats and that it normalizes CH-induced increases in resting [Ca2+]i and basal tone. Consequently, pharmacological inhibition of sildenafil-sensitive PDE5 downregulates the Ca2+ signaling pathway involved in this model of pulmonary hypertension.

Topics: Angiotensin II; Animals; Caffeine; Calcium; Calcium Signaling; Chronic Disease; Disease Models, Animal; Hypertension, Pulmonary; Hypoxia; Male; Muscle, Smooth, Vascular; Phenylephrine; Phosphodiesterase Inhibitors; Piperazines; Pulmonary Artery; Purines; Rats; Rats, Wistar; Sildenafil Citrate; Sulfones; Vasoconstriction; Vasoconstrictor Agents

This study was undertaken to determine whether Viagra (Pfizer, New York, NY), a type 5 phosphodiesterase (PDE-5) inhibitor, increases baseline coronary and uterine blood flow or potentiates estrogen-induced increases in blood flow.. Seven nonpregnant ovariectomized ewes were chronically instrumented to measure blood pressure, heart rate, cardiac output, and coronary and uterine blood flow. Estradiol-17beta (E2, 0.3 microg/kg) (Sigma Chemical Co, St Louis, Mo) and Viagra (50 mg) were intravenously administered separately or together and hemodynamic responses monitored.. Viagra alone rapidly decreased mean arterial pressure and cardiac output while increasing heart rate and uterine blood flow. Viagra tended to decrease coronary blood flow but not significantly. E2 by itself increased coronary and uterine blood flow over a 2-hour time course, whereas mean arterial pressure, cardiac output, and heart rate remained unchanged. Administration of E2 to animals pretreated with Viagra reversed Viagra-related decrease in cardiac output and coronary blood flow, resulting in a time-related increase in both parameters over baseline values. Viagra significantly augmented estradiol-related increases in uterine blood flow.. In our surgically menopausal ovine model, Viagra alone has a tendency to decrease baseline coronary blood flow, but the reduction does not reach statistical significance. The presence of estradiol reverses this Viagra-related negative trend and results in a net increase in coronary blood flow and cardiac output. Furthermore, Viagra significantly augments baseline and estrogen-induced increases in uterine blood flow suggesting the presence of PDE-5 in the ovine uterine vasculature.

Topics: Animals; Blood Flow Velocity; Blood Pressure Determination; Cardiac Output; Coronary Circulation; Disease Models, Animal; Drug Therapy, Combination; Estradiol; Female; Heart Rate; Hemodynamics; Injections, Intravenous; Piperazines; Probability; Purines; Sensitivity and Specificity; Sheep, Domestic; Sildenafil Citrate; Sulfones; Uterus

Phosphodiesterase type 5 (PDE5) inhibitors (eg, sildenafil) are a novel, orally active approach to the treatment of pulmonary arterial hypertension. The role of natriuretic peptides in the response to sildenafil was examined in mice lacking NPR-A, a guanylyl cyclase-linked natriuretic peptide receptor, in which pulmonary hypertension was induced by hypoxia.. Mice homozygous for NPR-A (NPR-A+/+) and null mutants (NPR-A-/-) were studied. Sildenafil inhibited the pressor response to acute hypoxia in the isolated perfused lungs of both genotypes. This effect was greater in the presence of atrial natriuretic peptide in the perfusate in NPR-A+/+ mice but not NPR-A-/- animals. In vivo, NPR-A mutants had higher basal right ventricular (RV) systolic pressures (RVSPs) than did NPR-A+/+ mice, and this was not affected by 3 weeks of treatment with sildenafil (25 mg x kg(-1) x d(-1)). Both genotypes exhibited a rise in RVSP and RV weight with chronic hypoxia (10% O2 for 21 days); RVSP and RV weight were reduced by continuous sildenafil administration in NPR-A+/+ mice, but only RVSP showed evidence of a response to the drug in NPR-A-/- mice. The effect of sildenafil on hypoxia-induced pulmonary vascular muscularization and cyclic GMP levels was also blunted in NPR-A-/- mice.. The natriuretic peptide pathway influences the response to PDE5 inhibition in hypoxia-induced pulmonary hypertension, particularly its effects on RV hypertrophy and vascular remodeling.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Atrial Natriuretic Factor; Blood Pressure; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Guanylate Cyclase; Homozygote; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Lung; Mice; Mice, Mutant Strains; Perfusion; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Receptors, Atrial Natriuretic Factor; Respiration, Artificial; Sildenafil Citrate; Sulfones; Ventricular Function, Right

We investigated the effects of NO on angiogenesis and the synthesis of vascular endothelial growth factor (VEGF) in a model of focal embolic cerebral ischemia in the rat. Compared with control rats, systemic administration of an NO donor, DETANONOate, to rats 24 hours after stroke significantly enlarged vascular perimeters and increased the number of proliferated cerebral endothelial cells and the numbers of newly generated vessels in the ischemic boundary regions, as evaluated by 3-dimensional laser scanning confocal microscopy. Treatment with DETANONOate significantly increased VEGF levels in the ischemic boundary regions as measured by ELISA. A capillary-like tube formation assay was used to investigate whether DETANONOate increases angiogenesis in ischemic brain via activation of soluble guanylate cyclase. DETANONOate-induced capillary-like tube formation was completely inhibited by a soluble guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ). Blocking VEGF activity by a neutralized antibody against VEGF receptor 2 significantly attenuated DETANONOate-induced capillary-like tube formation. Moreover, systemic administration of a phosphodiesterase type 5 inhibitor (Sildenafil) to rats 24 hours after stroke significantly increased angiogenesis in the ischemic boundary regions. Sildenafil and an analog of cyclic guanosine monophosphate (cGMP) also induced capillary-like tube formation. These findings suggest that exogenous NO enhances angiogenesis in ischemic brain, which is mediated by the NO/cGMP pathway. Furthermore, our data suggest that NO, in part via VEGF, may enhance angiogenesis in ischemic brain.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Brain; Bromodeoxyuridine; Cell Division; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Endothelial Growth Factors; Endothelium, Vascular; Enzyme Inhibitors; Guanylate Cyclase; Intercellular Signaling Peptides and Proteins; Lymphokines; Male; Neovascularization, Physiologic; Nitric Oxide; Nitric Oxide Donors; Nitroso Compounds; Piperazines; Purines; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Sildenafil Citrate; Soluble Guanylyl Cyclase; Stroke; Sulfones; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2; Vascular Endothelial Growth Factors

Phosphodiesterase type 5 (PDE5) is a novel therapeutic target for the treatment of pulmonary hypertension. This study examined the distribution of PDE5 in normal and hypoxic lung and the effect of chronic PDE5 inhibition with sildenafil, initiated before and during exposure to hypoxia, on pulmonary artery pressure (PAP) and structure.. Sprague-Dawley rats were exposed to hypoxia (10% O2) for up to 42 days. PAP, measured continuously by telemetry, increased gradually by 20 to 40 mm Hg, reaching a plateau between 10 and 14 days, and declined to normal levels on return to normoxia. PDE5 immunoreactivity was localized to smooth muscle cells in the medial layer of pulmonary arteries and veins in the normal lung and in distal muscularized arteries (<25 microm diameter) after hypoxia-induced pulmonary hypertension. Sildenafil (25 or 75 mg x kg(-1) x d(-1)) given before hypoxia produced marked dose-dependent inhibition in the rise of PAP (60% to 90% reduction; P<0.0001) and vascular muscularization (28.4+/-5.0% reduction; P<0.001). When begun after 14 days of hypoxia, sildenafil significantly reduced PAP (30% reduction; P<0.0001) and partially reversed pulmonary artery muscularization (39.9+/-4.9% reduction; P<0.001).. PDE5 is found throughout the muscularized pulmonary vascular tree, including in newly muscularized distal pulmonary arteries exposed to hypoxia. PDE5 inhibition attenuates the rise in PAP and vascular remodeling when given before chronic exposure to hypoxia and when administered as a treatment during ongoing hypoxia-induced pulmonary hypertension.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Blood Pressure; Blood Pressure Monitoring, Ambulatory; Blotting, Western; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Hypertension, Pulmonary; Hypoxia; Immunohistochemistry; Lung; Male; Muscle, Smooth, Vascular; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Pulmonary Artery; Pulmonary Circulation; Pulmonary Veins; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Telemetry; Vasodilator Agents

We characterized the effects of sildenafil citrate on the growth and metastasis of human prostate cancer cells in nude mice.. The androgen independent human prostate cancer cell line PC-3 was inoculated into the prostate of nude mice to produce orthotopic primary prostate cancers and metastases. Sildenafil citrate gavage was started on day 31 after tumor cell inoculation and given every other day 15 times (30 days). The 7 mice in the low dose group received 25 mg/kg body weight sildenafil citrate per gavage, while the 7 in the high dose group received 50 mg/kg body weight sildenafil citrate and the 9 in the control group received water. Autopsy was performed on day 75 to evaluate primary tumor growth and metastasis. Plasma cyclic guanosine monophosphate concentrations were measured after the single dose of 50 mg/kg sildenafil citrate in the mice.. Plasma cyclic guanosine monophosphate concentration increased 4-fold 1 hour after sildenafil citrate administration. The plasma concentration decreased rapidly and returned to normal after 8 hours. There was no significant difference in tumor weight between any of the 3 groups. The number of metastatic lymph nodes correlated significantly with primary tumor weight (p = 0.03) with a correlation coefficient of 0.454 but there was no significant correlation between the number of involved lymph nodes and sildenafil administration. Distant metastases were not significantly promoted by sildenafil administration.. Incontinuous oral administration of sildenafil citrate did not promote primary tumor growth and metastasis in an orthotopic prostate cancer model.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Lymphatic Metastasis; Male; Mice; Mice, Inbred BALB C; Phosphodiesterase Inhibitors; Piperazines; Prostatic Neoplasms; Purines; Sildenafil Citrate; Sulfones; Tumor Cells, Cultured; Vasodilator Agents

Phosphodiesterase (PDE) inhibitors represent an important advance in the treatment of erectile dysfunction (ED). In spite of widespread use and generally good efficacy, as a class they remain ineffective in 15-57% of men. Specific cohorts of patients with severe vascular or neurogenic basis to their ED, such as diabetic men or those who have undergone radical pelvic surgery, demonstrate lower response rates with PDE inhibition treatment. We believe that circulating levels of nitric oxide (NO) may be enhanced through delivery of adequate concentrations of free oxygen radical scavenger molecules such as vitamin E. Higher levels of NO, theoretically, should produce increased penile blood flow with the potential for a synergistic effect when combined with a PDE5 inhibitor. With this hypothesis in mind, 20 adult male Sprague-Dawley streptozotocin-induced (60 mg/kg i.p.) diabetic rats were divided into four therapeutic groups (n=5). Group I--control animals received peanut oil, group II--vitamin E 20 IU/day, group III--sildenafil 5 mg/kg/day and group IV--vitamin E 20 IU/day plus sildenafil 5 mg/kg/day, by oral gavage daily for 3 weeks. Erectile function was assessed as a rise in intracavernous pressure following cavernous nerve electrostimulation. Penile tissue was harvested to determine the changes in tissue morphology including neuronal nitric oxide synthase, smooth muscle alpha-actin and endothelial cell integrity. PDE5 protein content and activity were measured. Significant increases in intracavernous pressure were measured in the animals receiving combined vitamin E plus sildenafil treatment. Immunohistochemical staining showed increases of neuronal nitric oxide synthase, endothelial cell and smooth muscle cell staining. Western blot analysis did not show significant differences of PDE5 protein between the groups. However, higher PDE5 activity was measured in the sildenafil group and lower activity of PDE5 was recorded in the cohort receiving vitamin E with sildenafil. Vitamin E enhanced the therapeutic effect of the PDE5 inhibitor in a meaningful way in this animal model of diabetes. This study indicates a potential means of salvaging erectile function among patients who are refractory to sildenafil.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Complications; Disease Models, Animal; Drug Therapy, Combination; Erectile Dysfunction; Free Radical Scavengers; Male; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Vitamin E

To assess pro-erectile responses to vardenafil, a new selective PDE5 inhibitor, in vitro in isolated rabbit corpora cavernosa, and in vivo in anaesthetized rats.. Rabbit cavernosal strips were precontracted with 10 microM phenylephrine. Dose-response relaxation curves to cumulative dosings of vardenafil (1 nM-10 microM) were constructed alone and in the presence of 10 mM L-NAME. Relaxation responses to electrical field stimulation (EFS) (2 Hz, 2 ms, 10 V) were compared in control preparations and in the presence of vardenafil (1-10 nM). Male Sprague-Dawley rats were anaesthetized with urethane and prepared for measurement of blood pressure and intracavernous pressure. Erectile responses (ICPmax/dBP x 100) to cavernous nerve submaximal stimulation (10 Hz, 1 ms, 0.45-1.6 V) were determined before, and 3, 10 and 23 min after i.v. administration of saline, vardenafil or sildenafil (0.1, 1 mg/kg).. Vardenafil was effective in relaxing precontracted rabbit cavernosal strips (IC50 54 +/- 18 nM). This relaxing activity was partially antagonized with 10 mM L-NAME, increasing the IC50 to 620 +/- 81 nM. Vardenafil significantly increased (more than 4 times) relaxation of precontracted rabbit cavernosal strips to EFS at 10 nM. In anaesthetized rats, erectile responses were significantly facilitated 3 and 13 min after 0.1 and 1 mg/kg vardenafil was administered. In contrast, 1 mg/kg sildenafil only significantly increased erectile responses at 3 min post-injection.. Vardenafil relaxes rabbit corpus cavernosum in vitro and is effective at a lower dose than sildenafil in facilitating erectile responses to cavernous nerve stimulation in anaesthetized rats.

Topics: Animals; Culture Techniques; Disease Models, Animal; Dose-Response Relationship, Drug; Imidazoles; Male; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Penile Erection; Piperazines; Probability; Purines; Rabbits; Rats; Rats, Sprague-Dawley; Sensitivity and Specificity; Sildenafil Citrate; Sulfones; Triazines; Vardenafil Dihydrochloride

Several studies have reported the anxiolytic-like effects of various nitric oxide synthase inhibitors in distinct animal models. However, in the context of anxiety, the possible involvement of cyclic GMP, believed to be one of the main targets of NO, remains obscure. Cyclic GMP is degraded by the specific phosphodiesterases in the brain. Therefore, we studied the effect of the selective phosphodiesterase type 5 inhibitor sildenafil in the mouse elevated plus-maze test of anxiety and in the open field test of locomotion. We found that sildenafil (0.05-10 mg/kg i.p.) alone did not affect the behavior of animals in the plus-maze or open field tests, but the anxiogenic beta-carboline DMCM given in a subconvulsive dose (2 mg/kg i.p.) decreased the time spent on open arms in the elevated plus-maze. Treatment with the NO precursor L-arginine (200 mg/kg i.p.) did not modify the behavior of animals in the plus-maze, however, when sildenafil (1 mg/kg i.p.) was administered in combination with L-arginine (200 mg/kg i.p.), both the time spent on the open arms and the percentage of open arm visits were significantly decreased. We conclude that augmentation of the NO-cGMP cascade induces anxiogenic-like effect in mice.

Topics: Animals; Anxiety; Arginine; Behavior, Animal; Carbolines; Cyclic GMP; Disease Models, Animal; Drug Therapy, Combination; Injections, Intraperitoneal; Male; Maze Learning; Mice; Motor Activity; Nitric Oxide; Piperazines; Purines; Sildenafil Citrate; Sulfones; Time Factors

Cyclic GMP (cGMP) mediates smooth muscle relaxation in the central nervous system. In subarachnoid hemorrhage (SAH), decreases in intrinsic nitric oxide (NO) cause cerebral vasospasms due to the regulation of cGMP formation by NO-mediated pathways. As phosphodiesterase type V (PDE V) selectively hydrolyzes cGMP, we hypothesized that PDE V may function in the initiation of vasospasm. This study sought to identify the altered PDE V expression and activity in the vasospastic artery in a canine SAH model. We also used this system to examine possible therapeutic strategies to prevent vasospasm. Using a canine model of SAH, we induced cerebral vasospasm in the basilar artery (BA). Following angiographic confirmation of vasospasm on day 7, PDE V expression was immunohistochemically identified in smooth muscle cells of the vasospastic BA but not in cells of a control artery. The isolation of PDE enzymes using a sepharose column confirmed increased PDE V activity in the vasospastic artery only through both inhibition studies, using the highly selective PDE V inhibitor, sildenafil citrate, and Western blotting. Preliminary in vivo experiment using an oral PDE V inhibitor at 0.83 mg kg(-1) demonstrated partial relaxation of the spastic BA. PDE V activity was increased from control levels within the BA seven days after SAH. PDE V expression was most prominent in smooth muscle cells following SAH. These results suggest that clinical administration of a PDE V inhibitor may be a useful therapeutic tool in the prevention of vasospasm following SAH.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Blotting, Western; Cerebral Angiography; Cerebral Arteries; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dogs; Immunohistochemistry; Male; Myocytes, Smooth Muscle; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Sildenafil Citrate; Subarachnoid Hemorrhage; Sulfones; Time Factors; Vasospasm, Intracranial

We tested the hypothesis that sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, promotes functional recovery and neurogenesis after stroke.. Male Wistar rats were subjected to embolic middle cerebral artery occlusion. Sildenafil (Viagra) was administered orally for 7 consecutive days starting 2 or 24 hours after stroke onset at doses of 2 or 5 mg/kg per day. Ischemic rats administered the same volume of tap water were used as a control group. Functional outcome tests (foot-fault, adhesive removal) were performed. Rats were killed 28 days after stroke for analysis of infarct volume and newly generated cells within the subventricular zone and the dentate gyrus. Brain cGMP levels, expression of PDE5, and localized cerebral blood flow were measured in additional rats.. Treatment with sildenafil significantly (P<0.05) enhanced neurological recovery in all tests performed. There was no significant difference of infarct volume among the experimental groups. Treatment with sildenafil significantly (P<0.05) increased numbers of bromodeoxyuridine-immunoreactive cells in the subventricular zone and the dentate gyrus and numbers of immature neurons, as indicated by betaIII-tubulin (TuJ1) immunoreactivity in the ipsilateral subventricular zone and striatum. The cortical levels of cGMP significantly increased after administration of sildenafil, and PDE5 mRNA was present in both nonischemic and ischemic brain.. Sildenafil increases brain levels of cGMP, evokes neurogenesis, and reduces neurological deficits when given to rats 2 or 24 hours after stroke. These data suggest that this drug that is presently in the clinic for sexual dysfunction may have a role in promoting recovery from stroke.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Behavior, Animal; Brain; Bromodeoxyuridine; Cell Count; Cell Division; Cerebrovascular Circulation; Corpus Striatum; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Dentate Gyrus; Disease Models, Animal; Lateral Ventricles; Male; Nerve Regeneration; Neurons; Phosphodiesterase Inhibitors; Piperazines; Purines; Rats; Rats, Wistar; Recovery of Function; RNA, Messenger; Sildenafil Citrate; Stroke; Sulfones; Treatment Outcome

The effects of sildenafil (Viagra), a specific inhibitor of phosphodiesterase 5, on ischemic myocardium was examined using an isolated rat heart model. Rats were pretreated with sildenafil at doses ranging from 0.001 mg to 0.5 mg/kg body weight. After 60 min, isolated hearts were subjected to ischemia for 30 min followed by 2 h of reperfusion. The results demonstrated that at 0.05 mg/kg (and to some extent at 0.01 mg/kg), sildenafil provided significant cardioprotection as evidenced by improved ventricular recovery, a reduced incidence of ventricular fibrillation and decreased myocardial infarction. At higher doses, it caused a significant increase in the incidence of ventricular fibrillation while at very low doses it had no effect on cardiac function. As expected, sildenafil increased cyclic 3',5'-monophosphate (cGMP) content in the heart. The results demonstrate for the first time that within a narrow dose range, sildenafil can protect the heart from ischemia/reperfusion injury, probably through a cGMP-signaling pathway.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Cardiotonic Agents; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Electrocardiography; In Vitro Techniques; Male; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Ventricular Fibrillation; Ventricular Function

Our aim was to determine whether sildenafil citrate (Viagra) unfavorably alters coronary perfusion in canine models of coronary artery stenosis.. Concern has been raised that sildenafil may exacerbate ischemia in patients with coronary artery disease. However, the effects of sildenafil on coronary perfusion are largely unexplored.. Using anesthetized dogs, a micromanometer constrictor was applied to either an intact coronary artery (model of stable hypoperfusion: Protocol 1) or a site of arterial injury (model of recurrent platelet-mediated thrombosis: Protocol 2). After monitoring coronary flow for 1 h, dogs received two escalating, clinically relevant doses of sildenafil or placebo. Perfusion was assessed during the initial hour pretreatment, for 1 h following dose 1 and 1 h following dose 2 by measuring the area of the flow-time profile, normalized to baseline flow x 60 min. Interaction between sildenafil and adenosine-mediated inhibition of platelet aggregation was evaluated by in vitro platelet aggregometry (Protocol 3).. In Protocol 1, flow-time area was maintained at 50% to 60% of baseline in both placebo- and sildenafil-treated groups. In Protocol 2, controls exhibited an expected modest, temporal adenosine-mediated improvement in flow-time area (from 40 +/- 5% to 61 +/- 7%; p < .05) while in contrast, perfusion in sildenafil-treated dogs remained unchanged (37 +/- 6% vs. 33% to 35% before vs. after treatment). In vitro aggregometry confirmed that sildenafil rendered platelets refractory to the inhibitory effects of adenosine receptor stimulation.. Sildenafil did not exacerbate ischemia in canine models of coronary stenosis. However, in the setting of recurrent thrombosis, sildenafil-treated dogs were apparently unresponsive to the platelet inhibitory effects of endogenous adenosine.

Topics: Adenosine; Animals; Blood Flow Velocity; Coronary Circulation; Coronary Disease; Disease Models, Animal; Dogs; Piperazines; Platelet Aggregation; Purines; Sildenafil Citrate; Sulfones

Topics: Animals; Diabetes Mellitus, Experimental; Disease Models, Animal; Gastroparesis; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

Cyclic nucleotide phosphodiesterases (PDEs) are important regulators of cAMP/cGMP secondary messenger systems. Fluctuations in the level of cyclic nucleotides control the smooth muscle tone of corpus cavernosum. It had been shown that milrinone, a PDE3 inhibitor, was as potent as sildenafil, a PDE5 inhibitor, in relaxing human corpus cavernosum. However, milrinone is much less effective in relaxing rabbit corpus cavernosum than sildenafil. PDEs in rabbit corpus cavernosum were characterized and organ bath experiments were carried out in an attempt to search for the biochemical basis of this species difference.. In a biochemical study, PDE isozymes from rabbit corpus cavernosum were isolated by FPLC and characterized by PDE assay. In organ bath experiments, rabbit corpus cavernous tissue strips were precontracted and increasing doses of various inhibitors were added.. The major PDE in rabbit corpus cavernosum is PDE5. There are small amounts of PDE2 and PDE1. PDE3, which contributes significantly to the total PDE activity in human corpus cavernosum, is apparently lacking in rabbit corpus cavernosum. Organ bath experiments with isotype-specific inhibitors confirm this conclusion.. The distribution of PDE isozymes in corpus cavernosum is different in human and in rabbit. This could be the biochemical basis for the differential effects of milrinone in relaxing rabbit and human corpus cavernosum. Our study emphasizes the importance of a more complete understanding of the tissue distribution of targeted proteins in an animal model before applying the results to humans.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 1; Cyclic Nucleotide Phosphodiesterases, Type 3; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Exonucleases; Humans; Isoenzymes; Male; Milrinone; Muscle Tonus; Muscle, Smooth; Penis; Phosphodiesterase I; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Rabbits; Second Messenger Systems; Sildenafil Citrate; Species Specificity; Sulfones