cyclic-gmp and Erectile-Dysfunction

Cyclic guanosine monophosphate (cGMP), an important intracellular second messenger, mediates cellular functional responses in all vital organs. Phosphodiesterase 5 (PDE5) is one of the 11 members of the cyclic nucleotide phosphodiesterase (PDE) family that specifically targets cGMP generated by nitric oxide-driven activation of the soluble guanylyl cyclase. PDE5 inhibitors, including sildenafil and tadalafil, are widely used for the treatment of erectile dysfunction, pulmonary arterial hypertension, and certain urological disorders. Preclinical studies have shown promising effects of PDE5 inhibitors in the treatment of myocardial infarction, cardiac hypertrophy, heart failure, cancer and anticancer-drug-associated cardiotoxicity, diabetes, Duchenne muscular dystrophy, Alzheimer's disease, and other aging-related conditions. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular, anticancer, and neurological benefits. In this review, we provide an overview of the current state of knowledge on PDE5 inhibitors and their potential therapeutic indications for various clinical disorders beyond erectile dysfunction.

Topics: Cyclic GMP; Erectile Dysfunction; Humans; Male; Neoplasms; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate

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

We aimed to systematically assess the effect of adipose tissue-derived stem cell (ADSC) therapy and its influential factors on the treatment of erectile dysfunction (ED) in rats.. Two authors independently searched for published studies through PubMed and EMBASE from study inception until August 31, 2016. A meta-analysis was used to combine the effect estimate from the published studies. A subgroup analysis was performed to identify the effect of some influential factors. The pooled standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated by a fixed-effects or random-effects model analysis.. Twenty studies with a total of 248 rats were included in this meta-analysis. The pooled analysis showed that ADSC therapy significantly increased the ratio of intracavernous pressure and mean arterial pressure (ICP/MAP; SMD 3.46, 95% CI 2.85-4.06; P < 0.001) compared to control therapy. The levels of neuronal nitric oxide synthase (nNOS; SMD 6.37, 95% CI 4.35-8.39; P < 0.001), the cavernous smooth muscle content (CSMC; SMD 3.65, 95% CI 2.65-4.65; P < 0.001), the ratio of cavernous smooth muscle and collagen (CSM/collagen; SMD 4.16, 95% CI 2.59-5.72; P < 0.001), and the cyclic guanosine monophosphate (cGMP; SMD 7.12, 95% CI 2.76-11.48; P = 0.001) were higher following ADSC therapy than following control therapy. Subgroup analysis showed that ADSCs modified by growth or neurotrophic factors significantly recovered erectile function (P < 0.001) compared with ADSC therapy.. The adequate data indicated that ADSC therapy recovered erectile function and regenerated cavernous structures in ED rats, and ADSCs modified by some growth and neurotrophic factors accelerated the recovery of erectile function and cavernous structures in ED rats.

Topics: Adipose Tissue; Animals; Arterial Pressure; Collagen; Cyclic GMP; Erectile Dysfunction; Male; Muscle, Smooth; Nitric Oxide Synthase Type I; Penile Erection; Rats; Stem Cell Transplantation

To provide a systematic review of epidemiological data regarding the association between erectile dysfunction (ED) and lower urinary tract symptoms (LUTS) in men.. A research has been conducted on the Medline database using the keywords: ("erectile dysfunction" or "sexual dysfunction") and ("benign prostatic hyperplasia" or "lower urinary tract symptoms"). The eligibility of studies was defined using the PICOS method in accordance with the PRISMA statement. Cross-sectional studies and prospective cohorts assessing the association between LUTS and ED in the primary care setting or in general practice (i.e. exclusion of patients seen in outpatient urology or andrology) were included.. Among 898 reports assessed, seven studies were included in this systematic review (whole cohort: 1,196,393 men). There were five cross-sectional studies and two prospective cohorts. The whole seven studies reported an association between LUTS and ED (range of odds-ratio: 1.52-4.03). Four common pathogenic mechanisms were found in the literature, all of them being somewhat related with metabolic syndrome and cardiovascular risk factors: reduced nitric oxide (NO) pathway signalling, increased RhoA-Rho kinase signalling, autonomic nervous system hyperactivity and pelvic atherosclerosis.. The main limitations of this review were: a possible publication bias, the relatively low number of included studies and the lack of assessment of potential confounders such as factors related to sexual partner.. The close epidemiological and pathogenic links between LUTS and ED have given rise to a new nosological entity: the erectile urogenital dysfunction, which should be assessed globally with special considerations to frequently associated comorbidities such as metabolic syndrome and cardiovascular risk factors.

Topics: Atherosclerosis; Autonomic Nervous System; Cardiovascular Diseases; Comorbidity; Cross-Sectional Studies; Cyclic GMP; Endothelium, Vascular; Erectile Dysfunction; Humans; Impotence, Vasculogenic; Lower Urinary Tract Symptoms; Male; Metabolic Syndrome; Muscle, Smooth; Nitric Acid; Prospective Studies; Prostatic Hyperplasia; rho-Associated Kinases; rhoA GTP-Binding Protein; Risk Factors; Signal Transduction

Phosphodiesterase 5 (PDE5) inhibitors (PDE5i) have been used clinically for the treatment of erectile dysfunction, acting on the nitric oxide/cyclic guanosine monophosphate (NO/cGMP) signaling pathway. Simultaneously, researchers have elucidated the roles that this pathway plays in the regulation of cell proliferation, tumor development, and progression. As a result, our knowledge of PDE5i and cancer biology has expanded and provides an integration that holds great promise for some, but concern for others.. This review evaluates the role of PDE5i and the NO/cGMP signaling pathway in the pathogenesis and prevention of various malignancies.. A literature review was performed with regard to the role of NO/cGMP pathway in tumor formation and prevention in preclinical and clinical studies. Studies that utilized PDE5i to further explore the involvement of this pathway also were included.. To evaluate whether PDE5i provide a potential benefit for treating and/or preventing malignancies; or if they create potential harm leading to the development of these malignancies.. The best available data suggest that the interactions between PDE5i and cancer are tumor- and tissue-specific. Currently, the effect of PDE5i use on melanoma development is being debated. Further clinical controversy lies in PDE5i use for penile rehabilitation after nerve-sparing prostate cancer surgery. Preclinical studies suggest that PDE5 inhibition could lead to a decreased risk of developing colorectal and breast cancer, leukemia, and myeloma. PDE5i also may provide an additional antitumor immune response. Finally, researchers have demonstrated a synergistic effect from combining PDE5i with current chemotherapeutic regimens.. Currently, there are inadequate data to make any conclusive statements regarding the role of PDE5i in cancer pathogenesis and how to alter clinical management. In order to create appropriate clinical guidelines, further experimental and clinical evidence is required.

Topics: Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Male; Neoplasms; Nitric Oxide; Penis; Phosphodiesterase 5 Inhibitors

The ability to get and keep an erection is important to men for several reasons and the inability is known as erectile dysfunction (ED). ED has started to be accepted as an early indicator of systemic endothelial dysfunction and subsequently of cardiovascular diseases. The role of NO in endothelial relaxation and erectile function is well accepted. The discovery of NO as a small signalling gasotransmitter led to the investigation of the role of other endogenously derived gases, carbon monoxide (CO) and hydrogen sulphide (H2 S) in physiological and pathophysiological conditions. The role of NO and CO in sexual function and dysfunction has been investigated more extensively and, recently, the involvement of H2 S in erectile function has also been confirmed. In this review, we focus on the role of these three sister gasotransmitters in the physiology, pharmacology and pathophysiology of sexual function in man, specifically erectile function. We have also reviewed the role of soluble guanylyl cyclase/cGMP pathway as a common target of these gasotransmitters. Several studies have proposed alternative therapies targeting different mechanisms in addition to PDE-5 inhibition for ED treatment, since some patients do not respond to these drugs. This review highlights complementary and possible coordinated roles for these mediators and treatments targeting these gasotransmitters in erectile function/ED.

Topics: Animals; Carbon Monoxide; Cyclic GMP; Drug Design; Erectile Dysfunction; Guanylate Cyclase; Humans; Hydrogen Sulfide; Male; Molecular Targeted Therapy; Nitric Oxide; Penile Erection; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Soluble Guanylyl Cyclase

In recent years, research on penile erection has increasingly been centered on the molecular mechanisms involved. Major progress has been made in the field and at present a whole number of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex process of erection. This knowledge has led to the discovery of several new therapeutic targets and multiple medical approaches for the treatment of erectile dysfunction (ED). This review focuses on the progress made in this field within the last few years.

Topics: Complementary Therapies; Cyclic AMP; Cyclic GMP; Erectile Dysfunction; Humans; Hydrogen Sulfide; Male; Nitric Oxide; Receptors, Adrenergic; Receptors, Angiotensin; Receptors, Endothelin; Regenerative Medicine; rhoA GTP-Binding Protein; Signal Transduction; Stem Cell Transplantation; Tissue Engineering; Urotensins; Vasoconstriction; Vasodilation

Erectile dysfunction (ED) is a common, male sexual disorder that has a negative impact on the quality of life of men and their sexual partners. The prevalence of ED in diabetic men is ≥ 50%. Animal models provide a valuable perspective in the investigation of ED. Most basic science studies have utilized the rodent model of type 1 diabetes. However, an animal model for type 2 diabetes-associated ED requires verification. The streptozotocin (STZ) induced type 1 diabetic model has contributed to significant advancement in the study of ED. A Medline search using the keywords "diabetic animals and ED" was performed, and available peer-reviewed English articles between 2007-2013 were evaluated. The proposed mechanisms for developing ED in diabetics include: hyperglycemia, impaired nitric oxide (NO) synthesis, cyclic guanosine monophosphate (cGMP) pathway dysfunction, increased levels of reactive free-radicals, up-regulation of the RhoA/Rho-kinase pathway, and neuropathic damage. The current treatment regimen of diabetes-induced ED is multimodal. Modification of comorbidities and, specifically, rectifying the underlying hyperglycemia is vital to prevent or halt progression of the disease. Further research on the basic mechanisms of ED and additional studies using better animal models of ED associated with type 1 and 2 diabetes are needed. Preclinical studies using the diabetic animal model will likely provide further insight for intervention and prevention strategies for diabetic ED treatment.

Topics: Animals; Blood Glucose; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Neuropathies; Erectile Dysfunction; Intracellular Signaling Peptides and Proteins; Male; Oxidative Stress; Penis; Rats; rho-Associated Kinases; Smad Proteins; Transforming Growth Factor beta1

Sildenafil and other PDE-5 inhibitors have revolutionized erectile dysfunction (ED) treatment. However, a significant number of patients do not respond or present adverse reactions to these drugs. While genetic polymorphisms may underlie this phenomenon, very little research has been undertaken in this research field. Most of the current knowledge is based on sildenafil, thus almost completely ignoring other important pharmacological therapies. Currently, the most promising genes with pharmacogenetic implications in ED are related to the nitric oxide and cGMP pathway, although other genes are likely to affect the responsiveness to treatment of ED. Nevertheless, the small number of studies available opens the possibility of further exploring other genes and phenotypes related to ED. This article provides a comprehensive overview of the genes being tested for their pharmacogenetic relevance in the therapy of ED.

Topics: Animals; Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Pharmacogenetics; Phosphodiesterase 5 Inhibitors; Piperazines; Polymorphism, Genetic; Purines; Sildenafil Citrate; Sulfonamides

Phosphodiesterase-5 (PDE5) inhibitors, such as sildenafil, tadalafil and vardenafil are first line treatment for erectile dysfunction (ED). These PDE5 inhibitors are known to increase cyclic guanosine monophosphate (cGMP) concentrations in the smooth muscle cells of the corpora cavernosa penis by inhibiting PDE5, leading to smooth muscle relaxation. This mode of action is also believed to result in prostatic smooth muscle relaxation and to improve lower urinary tract symptoms (LUTS). Randomized controlled trials have shown beneficial effects on LUTS and on objective parameters such as maximum urinary flow rate (tadalafil). Based on these data tadalafil was recently approved for treatment of patients with male LUTS; however, the mechanisms leading to improvement of symptoms are still under debate.

Topics: Carbolines; Controlled Clinical Trials as Topic; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Imidazoles; Lower Urinary Tract Symptoms; Male; Phosphodiesterase 5 Inhibitors; Piperazines; Prostatic Hyperplasia; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Urodynamics; Vardenafil Dihydrochloride

Nitric oxide (NO) is the principal mediator of penile erection, and PDE-5 inhibitors are the first-line agents used to treat erectile dysfunction (ED). When NO formation or bioavailability is decreased by oxidative stress and PDE-5 inhibitors are no longer effective, a new class of agents called soluble guanylate cyclase (sGC) stimulators like BAY 41-8543 will induce erection. sGC stimulators bind to the normally reduced, NO-sensitive form of sGC to increase cGMP formation and promote erection. The sGC stimulators produce normal erectile responses when NO formation is inhibited and the nerves innervating the corpora cavernosa are damaged. However, with severe oxidative stress, the heme iron on sGC can be oxidized, rendering the enzyme unresponsive to NO or sGC stimulators. In this pathophysiological situation, another newly developed class of agents called sGC activators can increase the catalytic activity of the oxidized enzyme, increase cGMP formation, and promote erection. The use of newer agents that stimulate or activate sGC to promote erection and treat ED is discussed in this brief review article.

Topics: Cyclic GMP; Erectile Dysfunction; Guanylate Cyclase; Humans; Male; Morpholines; Nitric Oxide; Penile Erection; Phosphodiesterase 5 Inhibitors; Pyrimidines; Treatment Outcome

Great progress has been made in the basic researches on erectile dysfunction (ED) ever since the recognition of the close association of micromolecular nitric oxide (NO) with penile smooth muscle relaxation in 1990. NO-cGMP-PDE5 signaling pathway plays an important role in regulating the relaxation of corpus cavernosum smooth muscle, and its relevant studies have contributed greatly to the clinical treatment of ED. Chinese herbal drugs have long been used in the treatment of ED, and the action mechanisms of some of them clarified through the NO-cGMP-PDE5 signaling pathway. This article presents an overview on the recent advances in the studies of ED treatment with Chinese herbal drugs.

Topics: Animals; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drugs, Chinese Herbal; Erectile Dysfunction; Flavonoids; Male; Nitric Oxide; Phytotherapy; Rabbits; Rats; Signal Transduction

Erectile dysfunction (ED) is strongly linked to cardiovascular disease (CVD), especially in diabetics. ED is associated with deleterious changes in the overall vasculature and is recognized as an indicator of higher risk for adverse cardiovascular events. Endothelial dysfunction, vascular smooth muscle changes and increased fibrosis are indicated as major players in both ED and CVD. ED in diabetics is more refractory to acute treatment with phosphodiesterase-5 (PDE5) inhibitors (Viagra, Cialis, Levitra, Zydena) than in non-diabetics, but recent studies indicate that chronic administration of these drugs improves endothelial function, preserves vascular smooth muscle and decreases fibrotic changes. Use of PDE5 inhibitors in pre-diabetic and diabetic men may protect cardiovascular health, including vascular function in penile tissues.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Type 2; Diabetic Angiopathies; Endothelium, Vascular; Erectile Dysfunction; Fibrosis; Humans; Male; Molecular Targeted Therapy; Muscle, Smooth, Vascular; Penile Erection; Phosphodiesterase 5 Inhibitors

During the last decades it turned out that the NO/cGMP signaling cascade is one of the most prominent regulators of a variety of physiological and pathophysiological processes in a broad range of mammalian tissues. Thus cGMP is a key second messenger and targeting this pathway by increasing intracellular cGMP levels is a very successful approach in pharmacology as shown for nitrates, PDE5 inhibitors and more recently for stimulators of the guanylate cyclase. Besides the beneficial effects of cGMP elevation in cardiac, vascular, pulmonary, renal or liver disorders the launch of PDE5 inhibitors for the treatment of erectile dysfunction 10 years ago, has directed a lot of attention to the NO/cGMP signaling in the lower urinary tract. Triggered by the use of PDE5 inhibitors in ED it turned out that cGMP is a common regulatory mechanism for lower urinary tract function also beyond ED. In recent years intense research and development efforts were undertaken to elucidate the role of the NO/cGMP and to fully exploit the therapeutic implications of cGMP elevation in urological disorders in ED and beyond. Therefore we have summarized the effects of cGMP elevation for treatment of erectile dysfunction in males and in females. We have also reviewed the recent pre-clinical and clinical lines of evidence for treatment options of benign prostatic hyperplasia and lower urinary tract symptoms in male patients and overactive bladder and urinary incontinence in female patients. In addition we also touch more speculative concepts using cGMP elevating drugs for the treatment of premature ejaculation, peyornies disease and stone disease.

Topics: Animals; Cyclic GMP; Erectile Dysfunction; Female; Humans; Male; Nephrolithiasis; Nitric Oxide; Penile Induration; Prostatic Hyperplasia; Sexual Dysfunction, Physiological; Signal Transduction; Urinary Bladder, Overactive; Urinary Incontinence

Penile detumescence depends on the hydrolysis of cyclic guanosine monophosphate (cGMP) by phosphodiesterase type 5 (PDE5). It is hoped that a review of publications relevant to the regulation of PDE5 in the penis will be helpful to both scientists and clinicians who are interested in the sciences of erectile function/dysfunction.. The aim of this article is to comprehensively review the mechanisms by which PDE5 activity and expression in the penis are regulated. All published studies relevant to PDE5 regulation in the penis or penile cells will be reviewed.. Entrez (PubMed) was used to search for publications relevant to the topics of this review. Keywords used in the searches included vascular, cavernous, penis, smooth muscle, signaling molecules, erection, priapism, and PDE5. Articles that are dedicated to the study of erectile function/dysfunction were prioritized for citation.. Regulation of PDE5 can occur at both protein and gene levels. At protein level, PDE5 is activated by phosphorylation and/or allosteric cGMP binding. Deactivation is carried out by protein phosphatase 1 and thus linked to the Rho-kinase signaling pathway. Cleavage of PDE5 into an inactive form has been shown as carried out by caspase-3. At the gene level, PDE5 expression is regulated at two alternative promoters, PDE5A and PDE5A2, both of which are positively regulated by cyclic adenosine monophosphate and cGMP. Downregulation of PDE5 has been observed in the penis of castrated animals; however, proof of androgen regulation of PDE5 gene requires examination of the smooth muscle content. Hyperoxia and hypoxia, respectively, regulate PDE5 expression positively and negatively. Hypoxic downregulation of PDE5 is a possible mechanism for the development of priapism.. PDE5 can be regulated at protein and gene levels. In the penis, changes of PDE5 activity have been linked to its phosphorylation status, and downregulation of PDE5 expression has been associated with hypoxia.

Topics: Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Male; Muscle, Smooth; Nitric Oxide Synthase; Penis; Priapism; rho-Associated Kinases; Up-Regulation

To review the current literature regarding the relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED), and the role of phosphodiesterase-5 (PDE5) inhibitors for the treatment of LUTS. Review of recently published (1990-2009) data regarding epidemiologic and pathophysiologic mechanisms are involved in LUTS-ED, focusing on PDE5 inhibitors particularly evidenced from level 1 clinical trials. Search terms included phosphodiesterase inhibitors, nitric oxide, autonomic hyperactivity, Rho-kinase, atherosclerosis, LUTS, benign prostatic hypertrophy, and ED. Results of several epidemiologic studies show a possible causal relationship between LUTS and ED. Four possible mechanisms have been proposed to explain this association. Multiple large clinical trials have shown a benefit in LUTS after PDE5-inhibitors treatment. PDE5 inhibitors show promise as a future treatment for LUTS, either in conjunction with existing therapies or as a primary treatment.

Topics: Aged; Aging; Animals; Atherosclerosis; Autonomic Nervous System; Clinical Trials as Topic; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Male; Middle Aged; Nitric Oxide; Nitric Oxide Synthase; Phosphodiesterase Inhibitors; Prostate; Prostatic Hyperplasia; Prostatism; rho-Associated Kinases

Topics: Blood Pressure; Carbolines; Cyclic GMP; Erectile Dysfunction; Food-Drug Interactions; Humans; Male; Muscle Relaxation; Muscle, Smooth; Penis; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Randomized Controlled Trials as Topic; Tadalafil

Diabetes and ageing are associated with erectile dysfunction (ED). Under these conditions, increased oxidative stress produces superoxide ions, which in turn suppresses the nitric oxide-cyclic guanosine monophosphate pathway. The phophodiesterase-5 (PDE5) inhibitors still remain ineffective in 15 - 57% of impotent men.. To identify the efficacy of conventional and novel PDE5 inhibitors on oxidative stress involved in diabetes and ageing.. An electronic search of the literature was conducted to review published information relating diabetes and ageing to ED and to cover late-stage developments of novel PDE5 inhibitors.. Safe and more efficacious alternatives that can modulate PDE5 levels in ED regarding oxidative stress conditions are needed. Included in this review are updates on the new PDE5 inhibitors avanafil, udenafil, SLx-2101, and mirodenafil.

Topics: Aging; Animals; Clinical Trials as Topic; Cyclic GMP; Diabetes Complications; Drug Evaluation, Preclinical; Erectile Dysfunction; Humans; Male; Nitric Oxide; Oxidative Stress; Oxygen; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Rabbits; Rats; Reactive Oxygen Species; Vasodilator Agents

In recent years male sexual research has increasingly centered on molecular mechanisms operating from the central nervous system to peripheral end-organ levels involved in the penile erectile response. Major progress has been made in the field, and currently a whole host of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex physiology of erectile function. Foremost among these mediators is nitric oxide (NO), which was initially characterized as a locally released physiologic mediator of the erectile response. Impaired formation and action of NO is closely associated with erectile dysfunction (ED), which may be caused by a variety of pathogenic factors. The impact of this knowledge has been substantial, leading to the development of several NO-based medical approaches for the treatment of ED. This review will focus on recent patents and current clinical trials involving innovative pharmacological and gene therapies in the field of male ED, particularly targeting the NO/intracellular cyclic GMP pathway, which still represents the most promising therapeutic approach to treat patients with ED.

Topics: Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Phosphodiesterase 5 Inhibitors

Erectile dysfunction is a common, multifactorial disorder that is associated with aging and a range of organic and psychogenic conditions, including hypertension, hypercholesterolemia, diabetes mellitus, cardiovascular disease, and depression. Penile erection is a complex process involving psychogenic and hormonal input, and a neurovascular nonadrenergic, noncholinergic mechanism. Nitric oxide (NO) is believed to be the main vasoactive nonadrenergic, noncholinergic neurotransmitter and chemical mediator of penile erection. Released by nerve and endothelial cells in the corpora cavernosa of the penis, NO activates soluble guanylyl cyclase, which increases 3',5'-cyclic guanosine monophosphate (cGMP) levels. Acting as a second messenger molecule, cGMP regulates the activity of calcium channels as well as intracellular contractile proteins that affect the relaxation of corpus cavernosum smooth muscle. Impaired NO bioactivity is a major pathogenic mechanism of erectile dysfunction. Treatment of erectile dysfunction often requires combinations of psychogenic and medical therapies, many of which have been only moderately successful in the past. The advent of oral phosphodiesterase type 5 (PDE-5) inhibitors, however, has greatly enhanced erectile dysfunction treatment; patients have demonstrated high tolerability and success rates for improved erectile function. The efficacy of the PDE-5 inhibitors also serves to illustrate the importance of the NO-cGMP pathway in erectile function since these agents counteract the degradation of NO-generated cGMP. Because not all patients respond to PDE-5 inhibitors, additional therapies are being investigated, such as soluble guanylyl cyclase activators and NO donors, which act on NO-independent and NO-dependent pathways, respectively.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Comorbidity; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus; Erectile Dysfunction; Humans; Male; Nitric Oxide; Nitric Oxide Synthase; Penile Erection; Phosphodiesterase Inhibitors; Risk Factors

During the past decade, several progresses have been made for a deeper understanding of the regulatory factors that mediate normal erectile function, although the mechanisms involved in pathophysiology of erectile dysfunction (ED) remain to be completely elucidated. However, dramatic advances in the management of ED have occurred. Many drugs are now available, with oral pharmacotherapy representing the first-line option for most patients. ED is a common condition associated with aging but not necessarily a consequence of aging. The most important risk factors are associated to the impaired balance between contractant and relaxant mechanisms of penile structures, resulting in arterial insufficiency and defect smooth muscle relaxation. The normal erectile function involves the synthesis of NO, the main neurotransmitter mediating erectile processes, and the subsequent accumulation of cyclic GMP (cGMP). The NO formation, and therefore the erection, is strictly controlled by the activity of NO synthase (NOS) isoenzymes, whereas cGMP degradation is specifically controlled by phosphodiesterase type 5 (PDE5), which promotes smooth muscle tone and terminates erection. The regulation of the activity of these 2 counteracting enzymes allows the penis to be contracted for the majority of the time. Androgens play a pivotal role in these mechanisms by regulating both NOS and PDE5 activity. This peripheral and antithetic role of androgens seems to regulate penile erections synchronizing erectile processes to sexual desire. Moreover, the androgen-dependent activity of PDE5 mirrors the unresponsiveness of certain patients with ED to PDE5 inhibitors (PDE5i), the most widely prescribed oral drugs. In fact, PDE5i cannot work if the target enzyme is lacking. This suggests the importance to test testosterone plasma levels in those patients with ED who do not respond to PDE5i. In conclusion, a better understanding of the pathogenic factors of ED will be useful to appropriately design pharmacotherapy and improve clinical management depending on the unique condition of each patient.

Topics: Administration, Oral; Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Phosphodiesterase Inhibitors

In the last few years, the clinical context of the diagnosis and treatment of erectile dysfunction (ED) has changed radically. In fact, oral drug treatment with phosphodiesterase type-5 inhibitors (PDE5-i), licensed in the past years, appeared to offer advantages over other medical approaches in terms of ease of administration and cost. PDE5-i are now widely advocated as first-line therapy for ED. PDE5-i represent a class of orally active drugs for ED, which inhibit PDE5 enzyme and in turn enhance smooth muscle relaxation via prolongation of cyclic GMP action within the cavernous smooth muscle. Although the various types of PDE5-i differ with respect to selectivity and pharmacokinetic profiles, efficacy and safety of these agents are mostly comparable in broad populations of men with erectile ED, including those with diabetes, cardiovascular disease or those taking multiple antihypertensive agents. Aim of this article will be to review the different efficacy and safety profiles of oral short-acting compounds and to give indication for treatment of special populations of men with ED.

Topics: Administration, Oral; Cardiovascular Diseases; Cyclic GMP; Diabetes Complications; Erectile Dysfunction; Humans; Hypertension; Male; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Penile Erection; Phosphodiesterase Inhibitors; Time Factors; Vasodilator Agents

Erectile function is determined by tight regulation of relaxation or contraction of corpus cavernosal smooth muscle, which is the result of a long and complex chain of molecular events. Control of erectile function resides in signaling pathways of the central and peripheral nervous system, as well as intracellular events in the penile smooth muscle. Vascular events resulting in erection have long been understood, and the role of the signaling pathways of the central and peripheral nervous systems in erectile function and dysfunction has become increasingly clear over the last decade. This knowledge has led to the development and current availability of effective oral treatments for erectile dysfunction, the selective phosphodiesterase type 5 (PDE5) inhibitors-sildenafil, vardenafil and tadalafil. In the past few years we have seen an elucidation of the molecular events involved in erectile function and dysfunction and the detailed mechanisms of action by which the specific PDE5 inhibitors work. A review of those mechanisms helps to explain the success of the currently available PDE5 inhibitors and the differences between them and suggests new approaches for developing potential future novel therapies or refinements to existing structures that may improve their efficacy, selectivity and safety profiles.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Carbolines; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Interactions; Erectile Dysfunction; Humans; Imidazoles; Male; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Vardenafil Dihydrochloride

Penile erection depends on cavernous smooth muscle relaxation that is principally regulated by cyclic nucleotide signaling. It is hoped that a comprehensive review of publications relevant to this subject will be helpful to both scientists and clinicians who are interested in the sciences of erectile function/dysfunction. AIMS. To review the roles of extracellular signaling molecules, their receptors, intracellular effectors, and phosphodiesterases in cyclic nucleotide signaling that leads to cavernous smooth muscle relaxation. The involvement of these molecules in the development of erectile dysfunction and the possibility of using them as therapeutic agents or targets are also discussed.. Entrez, the search engine for life sciences, was used to search for publications relevant to the topics of this review. Keywords used in the searches included vascular, cavernous, penis, smooth muscle, signaling molecules (adenosine, nitric oxide, etc.), and key elements in the cyclic nucleotide signaling pathways (cAMP, cGMP, cyclases, PKG, PKA, etc.). Articles that are dedicated to the study of erectile function/dysfunction were prioritized for citation.. More than 1,000 articles were identified, many of which are studies of the vascular system and are therefore reviewed but not cited. Studies on erectile function have identified both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) signaling pathways in cavernous smooth muscle. Many signaling molecules of these two pathways have been shown capable of inducing erection when administered intracavernously. However, for sexually induced erection, nitric oxide (NO) is the responsible signaling molecule and it passes on the signal through soluble guanyl cyclase (sGC), cGMP, and protein kinase G (PKG).. The NO/sGC/cGMP/PKG pathway is principally responsible for sexually stimulated erection. Detumescence is mainly carried out by the degradation of cGMP by phosphodiesterase 5. Both cAMP and cGMP signaling pathways are susceptible to genetic and biochemical alterations in association with erectile dysfunction. Several key elements along these pathways are potential therapeutic targets.

Topics: Cyclic AMP; Cyclic GMP; Erectile Dysfunction; Humans; Male; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nucleotides, Cyclic; Penile Erection; Signal Transduction

A spinal reflex and the L-arginine-nitric oxide-guanylyl cyclase-cyclic guanosine monophosphate (cGMP) pathway mediate smooth muscle relaxation that results in penile erection. Nerves and endothelial cells directly release nitric oxide in the penis, where it stimulates guanylyl cyclase to produce cGMP and lowers intracellular calcium levels. This triggers relaxation of arterial and trabecular smooth muscle, leading to arterial dilatation, venous constriction, and erection. Phosphodiesterase 5 (PDE5) is the predominant phosphodiesterase in the corpus cavernosum. The catalytic site of PDE5 normally degrades cGMP, and PDE5 inhibitors such as sildenafil potentiate endogenous increases in cGMP by inhibiting its breakdown at the catalytic site. Phosphorylation of PDE5 increases its enzymatic activity as well as the affinity of its allosteric (noncatalytic/GAF domains) sites for cGMP. Binding of cGMP to the allosteric site further stimulates enzymatic activity. Thus phosphorylation of PDE5 and binding of cGMP to the noncatalytic sites mediate negative feedback regulation of the cGMP pathway.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Calcium; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Guanylate Cyclase; Humans; Male; Muscle, Smooth; Penile Erection; Penis; Phosphodiesterase Inhibitors; Phosphorylation; Piperazines; Purines; Sildenafil Citrate; Sulfones

Phosphodiesterase 5 (PDE5) inhibitors prevent the normal hydrolysis of cGMP. As the resulting cGMP accumulation facilitates penile smooth muscle relaxation, PDE5 inhibitors can partially reverse deficiencies in the nitric oxide (NO)/cGMP pathway to treat erectile dysfunction (ED). However, approximately 30-40% of men with ED do not respond to drug therapy. Patients with severe neurologic damage, diabetes mellitus, or severe vascular disease may be resistant to PDE5 inhibitors. Decreased expression or activity of neuronal or endothelial NO synthase (NOS), impaired NO release, or NO destruction will preclude sufficient cGMP formation to permit PDE5 inhibitor efficacy. This article discusses the possible reasons for unresponsiveness and strategies to overcome it. Therapeutic approaches proposed to increase available NO in penile tissue include facilitating NO release by using alpha-2 antagonists, enhancing NO synthesis by providing more substrate for the reaction, and using antioxidants to inhibit NO breakdown by reactive oxygen species.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Antioxidants; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Resistance; Erectile Dysfunction; Humans; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penis; Phosphodiesterase Inhibitors; Reactive Oxygen Species; Treatment Failure

Nitric oxide (NO) is formed from the conversion of L-arginine by nitric oxide synthase (NOS), which exists in three isoforms: neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). nNOS is expressed in penile neurons innervating the corpus cavernosum, and eNOS protein expression has been identified primarily in both cavernosal smooth muscle and endothelium. NO is released from nerve endings and endothelial cells and stimulates the activity of soluble guanylate cyclase (sGC), leading to an increase in cyclic guanosine-3',5'-monophosphate (cGMP) and, finally, to calcium depletion from the cytosolic space and cavernous smooth muscle relaxation. The effects of cGMP are mediated by cGMP dependent protein kinases, cGMP-gated ion channels, and cGMP-regulated phosphodiesterases (PDE). Thus, cGMP effect depends on the expression of a cell-specific cGMP-receptor protein in a given cell type. Numerous systemic vasculature diseases that cause erectile dysfunction (ED) are highly associated with endothelial dysfunction, which has been shown to contribute to decreased erectile function in men and a number of animal models of penile erection. Based on the increasing knowledge of intracellular signal propagation in cavernous smooth muscle tone regulation, selective PDE inhibitors have recently been introduced in the treatment of ED. Phosphodiesterase 5 (PDE5) inactivates cGMP, which terminates NO-cGMP-mediated smooth muscle relaxation. Inhibition of PDE5 is expected to enhance penile erection by preventing cGMP degradation. Development of pharmacologic agents with this effect has closely paralleled the emerging science.

Topics: Cyclic GMP; Endothelium, Vascular; Erectile Dysfunction; Guanylate Cyclase; Humans; Ion Channels; Male; Muscle Contraction; Muscle, Smooth; Nitric Oxide; Nitric Oxide Synthase; Penis; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Protein Kinases

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Adrenergic alpha-Antagonists; Arteriosclerosis; Blood Pressure; Carbolines; Contraindications; Coronary Disease; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Interactions; Endothelium, Vascular; Erectile Dysfunction; Heart Rate; Humans; Hypotension; Imidazoles; Isosorbide Dinitrate; Male; Molecular Structure; Myocardial Infarction; Nitric Oxide Donors; Nitroglycerin; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Randomized Controlled Trials as Topic; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Vardenafil Dihydrochloride; Vasodilation; Vasodilator Agents

The incidence of erectile dysfunction (ED) significantly increases in aging men, which may be associated with the decrease of the serum growth hormone (GH) level. GH may play an important role in the maintenance of penile erectile function, perhaps by promotion of the NO-cGMP pathway, stimulation of the regeneration of NOS-containing nerve fibers and the augmentation of androgenic action.

Topics: Adult; Age Factors; Aged; Animals; Cyclic GMP; Erectile Dysfunction; Growth Hormone; Humans; Male; Middle Aged; Nitric Oxide Synthase; Rats; Signal Transduction

Upon sexual stimulation, penile erection, occurring in response to the activation of pro-erectile autonomic pathways, is greatly dependent on adequate inflow of blood to the erectile tissue and requires coordinated arterial endothelium-dependent vasodilatation and sinusoidal endothelium-dependent corporal smooth muscle relaxation. Nitric oxide (NO) is the principal peripheral pro-erectile neurotransmitter which is released by both non-adrenergic, non-cholinergic neurons and the sinusoidal endothelium to relax corporal smooth muscle through the cGMP pathway. Any factors modifying the basal corporal tone, the arterial inflow of blood to the corpora, the synthesis/release of neurogenic or endothelial NO are prime suspects for being involved in the pathophysiology of erectile dysfunction (ED). In fact, conditions associated with altered endothelial function, such as ageing, hypertension, hypercholesterolemia and diabetes, may, by changing the balance between contractant and relaxant factors, cause circulatory and structural changes in penile tissues, resulting in arterial insufficiency and defect in smooth muscle relaxation and thus, ED. There is increasing evidence to suggest that ED is predominantly a vascular disease and may even be a marker for occult cardiovascular disease. Recent results illustrating the importance of endothelial dysfunction in the pathophysiology of different forms of experimental ED are discussed. These pathways may represent new potential treatment targets.

Topics: Animals; Cardiovascular Diseases; Cyclic GMP; Diabetes Complications; Diabetes Mellitus, Experimental; Endothelium, Vascular; Erectile Dysfunction; Humans; Hypercholesterolemia; Hypertension; Male; Models, Biological; Muscle, Smooth, Vascular; Nitric Oxide; Penile Erection; Rabbits; Rats; Rats, Inbred SHR; Risk Factors; Vasoconstriction; Vasodilation

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Hypertension, Pulmonary; Male; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Pyrimidinones; Structure-Activity Relationship

The prominence of phosphodiesterase-5 (PDE-5) inhibitors in the treatment of male erectile dysfunction and other diseases related to vascular dysfunction mandates a comprehensive understanding of the properties and effects of these compounds. Three potent and selective PDE-5 inhibitors (sildenafil, tadalafil, and vardenafil) have been approved for clinical use. The clinical efficacy and safety profiles of these medications are related to their molecular mode of action, the selectivity for PDE-5, and the pharmacokinetic properties (absorption, bioavailability, time to onset of action, distribution, metabolism, and elimination). These PDE-5 inhibitors share some common properties with regard to mechanisms of action and selectivities for PDE-5. They also have distinctive characteristics that may impact their clinical use. This article focuses on the basic biochemistry of cyclic guanosine monophosphate signaling and the pharmacokinetic parameters that describe characteristics of drug action of these PDE-5 inhibitors in facilitating smooth muscle relaxation, leading to improved penile erectile response or causing side effects.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Dose-Response Relationship, Drug; Drug Evaluation; Erectile Dysfunction; Humans; Male; Metabolic Clearance Rate; Muscle, Smooth; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Sulfones

The scientific rationale of pharmacologically inhibiting phosphodiesterase type 5 (PDE5) in the treatment of erectile dysfunction (ED) is reviewed. Published literature on the nitric oxide-cyclic guanosine monophosphate (cGMP) pathway for penile erection and on PDE5 inhibition using sildenafil as the model for pharmacologic PDE5 inhibition are assessed. The key second messenger in the mediation of penile erection is cGMP. PDE5 is the predominant PDE in the corpus cavernosum, and cGMP is its primary substrate. Therefore, in men with ED, elevation of cGMP in corpus cavernosal tissue via selective inhibition of cGMP-specific PDE5 is a means of improving erectile function at minimal risk of adverse events. This approach is validated by the clinical efficacy and safety of sildenafil, the pioneering drug for selective PDE5 inhibitor therapy for ED. Sildenafil exhibits inhibitory potency against PDE5 and a 10-fold lower dose-related inhibitory potency against rod outer segment PDE6, the predominant PDE in the phototransduction cascade in rods. Thus, its pharmacologic profile is predictable, with close correlation between pharmacodynamic and pharmacokinetic properties. Clinically, sildenafil improves erectile function in a large percentage of men with ED. The most common adverse events are due to PDE5 inhibition in vascular and visceral smooth muscle; similar adverse events are expected during therapeutic use of all PDE5 inhibitors. As free sildenafil plasma concentrations approach concentrations sufficient to inhibit retinal PDE6, usually at higher therapeutic doses, transient, reversible visual adverse events can occur, albeit infrequently. Selective inhibition of PDE5 is a rational therapeutic approach in ED, as proved by the clinical success of sildenafil.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Male; Nitric Oxide; Penile Erection; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilator Agents

Phosphodiesterase type-5 (PDE-5) inhibitors are a new class of vasoactive drugs that have been developed for treatment of erectile dysfunction (ED). The mechanism of action involves active inhibition of the PDE-5 enzyme and resulting increase in cyclic guanosine monophosphate (cGMP) and smooth muscle relaxation in the penis. Sildenafil citrate (Viagra) is a potent and selective PDE-5 inhibitor, which is the first drug in this class to be approved for treatment of ED. More than 10 million men worldwide have been treated with this drug. Sildenafil has been shown to be generally effective in the treatment of ED, although the degree of efficacy varies according to the etiology and severity of the disorder. The drug is well tolerated, with relatively few contraindications (e.g., nitrates) and safety risks. The cardiovascular effects of sildenafil, in particular, have been extensively investigated. The results of recent studies suggest that sildenafil may have an additional role in the treatment of other male and female sexual disorders, such as premature ejaculation and female sexual arousal disorder, although results to date are inconclusive. Two additional agents in this class (tadalafil [Cialis], vardenafil [Levitra]) have been developed recently and are under regulatory review. Tadalafil is a long-acting PDE-5 inhibitor, which is effective for up to 36 hr in the majority of men. Vardenafil has a similar duration of action to sildenafil, but is more potent and selective biochemically. Both drugs appear to be generally safe and well tolerated, with a similar side-effect profile to sildenafil. There are no controlled comparison studies to date. Despite the overall effectiveness of PDE-5 inhibitors in the treatment of ED, significant psychological and interpersonal issues need to be addressed in their clinical use. The potential impact on societal attitudes toward sexuality and sexual dysfunction also warrants consideration.

Topics: Carbolines; Clinical Trials as Topic; Cyclic GMP; Erectile Dysfunction; Female; Humans; Imidazoles; Male; Muscle, Smooth; Penile Erection; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Treatment Outcome; Triazines; Vardenafil Dihydrochloride; Vasodilator Agents

Recent advances in the research on erectile dysfunction (ED) has more clearly explained the mechanism of penile erection, which is a hemodynamic process involving relaxation of corpus cavernosum smooth muscle and related arterials, and NO-cGMP signaling pathway proven to play an important role on modulating the relaxation of corpus cavernosum smooth muscle. Studies on NOS and PDEs not only provide strong evidence for the clinical treatment of ED, but also provide the chance to develop Sildenafil. Although the gene therapy for ED is still in the laboratory stage by now, it may be one of the effective clinical therapies for ED in future.

Topics: Cyclic GMP; Erectile Dysfunction; Genetic Therapy; Humans; Male; Nitric Oxide; Penile Erection; Transforming Growth Factor beta; Transforming Growth Factor beta1

Based on the increasing knowledge of intracellular signal propagation in cavernous smooth muscle tone regulation, which is of major importance to the understanding of both the physiology of erection and the pathophysiology of erectile dysfunction, selective phosphodiesterase (PDE) inhibitors have recently been introduced in the treatment of erectile dysfunction. The first promising clinical data on the use of the orally active PDE5 inhibitor Sildenafil in the treatment of erectile dysfunction were accompanied by boosting research activities on cavernous intracellular signal transduction and phosphodiesterase characterization with the aid of molecular biology and protein chemistry. The presence of mRNA transcripts specific for 14 different human phosphodiesterase isoenzymes and isoforms in human cavernous tissue was shown by RT-PCR: Three isogenes of PDEI, PDE2A and 10A, which hydrolyse cAMP as well as cGMP, the cAMP-specific PDE3A, four isogenes of PDE4, PDE7A and PDE8A, as well as cGMP-specific PDEs PDE5A and PDE9A. Using anion exchange chromatography, the activities of PDE isoenzymes 2, 3, 4, and 5 were detected in cytosolic supernatants of human cavernous smooth muscle. To date, the efficacy and safety of several next generation PDE5 inhibitors for use in the treatment of male erectile dysfunction are under evaluation in vitro and in vivo. Further research will possibly allow identification of diagnostic tools for erectile dysfunction and of even more selective drugs in its therapy.

Topics: Cyclic GMP; Erectile Dysfunction; Humans; Isoenzymes; Male; Penis; Phosphoric Diester Hydrolases

Erectile dysfunction (ED) is defined as the consistent inability to obtain or maintain an erection for satisfactory sexual relations. An estimated 20-30 million men suffer from some degree of sexual dysfunction. The past 20 years of research on erectile physiology have increased our understanding of the biochemical factors and intracellular mechanisms responsible for corpus cavernosal smooth muscle contraction and relaxation, and revealed that ED is predominantly a disease of vascular origin. Since the advent of sildenafil (Viagra), there has been a resurgence of interest in ED, and an increase in patients presenting with this disease. A thorough knowledge of the physiology of erection is essential for future pharmacological innovations in the field of male ED.

Topics: Adrenergic alpha-Antagonists; Cyclic AMP; Cyclic GMP; Dopamine Agonists; Erectile Dysfunction; Genetic Therapy; Humans; Male; Nitric Oxide; Penile Erection; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

Phosphodiesterases are enzymes that catalyze the degradation of the cyclic nucleotides, cyclic AMP and cyclic GMP, to the corresponding 5' nucleotide monophosphates. Ten different phosphodiesterase families have been described to date. These enzymes exist as homodimers and there is structural similarity between the different families. However, they differ in several respects like selectivity for cyclic nucleotides, sensitivity for inhibitors and activators, physiological roles and tissue distribution. Interest in these enzymes has increased tremendously, both within the medical community and in the general public as a consequence of sildenafil (Viagra), the medication recently introduced for the treatment of erectile dysfunction. Sildenafil mediates its effects by inhibiting phosphodiesterase 5. Some biochemical and molecular biological aspects of this enzyme are presented here. To achieve satisfactory erection, normal penile innervation is required. Nitrogen monoxide, the transmitter substance in these nerves, activates guanylyl cyclase, thereby increasing cyclic GMP production. The increased levels of cyclic GMP cause relaxation of smooth muscles in penile vessels and this leads to an erection. Erection is dependent on elevated levels of cyclic GMP and sildenafil mediates its effects by inhibiting the degradation of cyclic GMP. Other functions that are mediated by the phosphodiesterases explain visual disturbances, flushing and decreased blood pressure that are some of the side effects seen with sildenafil treatment. Furthermore, the potentially fatal consequence of combining sildenafil and nitrovasodilators is discussed.

Topics: Cyclic GMP; Erectile Dysfunction; Humans; Male; Nucleotides, Cyclic; Penile Erection; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Sildenafil Citrate; Sulfones

An estimated 20 million to 30 million American men have erectile dysfunction (ED). The past 2 decades of research defining erectile physiology and investigating the pathogenesis of ED have led to the recognition of a predominantly vascular basis for organic male sexual dysfunction. These scientific advances have laid the foundation for the advent of pharmacotherapies. The Food and Drug Administration approval of intracavernosal, intraurethral, and oral pharmacotherapeutics for ED has revolutionized non-surgical management of this condition. The primary care physician is faced with the challenges of diagnosis and treatment of ED, as well as referral of patients to urologists. In this article, erectile physiology and pathophysiology are reviewed, and pharmacotherapeutics are classified and discussed by their mechanisms of action and the means of administration. A thorough understanding of these new therapeutic options is key to the accurate diagnosis and successful treatment of ED and maximal patient satisfaction and care.

Topics: Adrenergic alpha-Antagonists; Cyclic AMP; Cyclic GMP; Erectile Dysfunction; Fibrosis; Humans; Male; Penile Erection; Penis; Phosphodiesterase Inhibitors

The molecular mechanisms of the effects of sildenafil, a specific inhibitor of cyclic guanosine monophosphate (cGMP) phosphodiesterases are briefly reviewed. The second messenger cGMP as well as its molecular targets (with the exception of the photoreceptor signal transduction machinery) have long played an underdog role compared with cyclic adenosine monophosphate and other signalling molecules such as inositoltrisphosphate. The same holds for guanylyl cyclase, which, albeit being the main effector molecule of the gaseous neurotransmitters carbon monoxide and nitric oxide (NO), has received much less attention relative to its activators and their synthases. Stimulation of the arginine --> NO --> cGMP pathway by bypassing NO-synthase is a well-established pharmacological principle in the treatment of cardiovascular disorders. In contrast, local application of NO-donors or oral feeding of excessive amounts of precursor amino acid L-arginine to treat erectile dysfunction were met with variable success or failure. The advent of a new principle, amplification of the NO-signaling cascade by means of target organ selective phosphodiesterase inhibition, has renewed interest in phosphodiesterases and cGMP.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Aged; Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Sulfones; Vasodilation

Penile erection follows relaxation of the corpus cavernosum in which nitric oxide (NO) released during sexual stimulation from non-adrenergic non-cholinergic nerve endings and from endothelial cells of the corpus cavernosum plays a crucial role. Sildenafil (VIAGRA) selectively inhibited phosphodiesterase type 5 (PDE5) activity in the human corpus cavernosum and increased cGMP concentrations in the rabbit cavernosum in the presence of NO. Sildenafil enhanced the NO-dependent relaxation of the isolated human corpus cavernosum and the intracavernosal pressure in the anesthetized dog without affecting systemic blood pressure and heart rate. In the patients with erectile dysfunction, an orally administered sildenafil enhanced the penile rigidity during visual sexual stimulation. Sildenafil did not affect the phenylephrine-induced contraction of the isolated rabbit aorta, but enhanced the relaxant effect of glyceryl trinitrate. The pharmacodynamic interaction with glyceryl trinitrate was also observed in human studies where sildenafil potentiated the hypotensive effect of the nitrate. These results indicate that sildenafil, which enhances the physiological process of penile erection during sexual arousal, is a novel orally effective treatment for erectile dysfunction. It should be noted, however, that sildenafil enhanced the hypotensive effect of glyceryl trinitrate, as a result of inhibition of PDE5 in vascular smooth muscle. Therefore, administration of sildenafil to patients who are using nitrates and NO donors is contraindicated.

Topics: Animals; Blood Pressure; Cyclic GMP; Dogs; Drug Interactions; Erectile Dysfunction; Humans; Male; Nitric Oxide; Nitric Oxide Donors; Nitroglycerin; Penile Erection; Penis; Phosphodiesterase Inhibitors; Piperazines; Purines; Rabbits; Sildenafil Citrate; Sulfones

Topics: Contraindications; Cyclic GMP; Erectile Dysfunction; Humans; Male; Penile Erection; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

Erectile function in man depends upon a complex interaction of psychogenic, neurologic, hormonal and vascular factors, and therefore the management of erectile dysfunction (ED) reflects this complexity of control. Therapeutic options include psychological and non-pharmacological approaches as well as drug treatments. The effectiveness of the type-5 cGMP phosphodiesterase inhibitor sildenafil citrate (Viagra) confirms the pivotal role of the NO-cGMP axis in promoting and maintaining erection. Although widely acclaimed, sildenafil leaves many questions unanswered, especially regarding its susceptibility to pharmacokinetic drug interactions, and its safety in patients with ischaemic heart disease and those taking nitrates. In view of the epidemiological link between erectile dysfunction and cardiovascular disease in the elderly, this limitation might have much broader implications. The presently available scientific documentation, although less extensive, indicates that NO donors, such as topically applied nitroglycerin (GTN; for example, 1-2 puffs of an ordinary GTN spray applied to the shaft of the penis), might be a reasonable alternative. Further larger-scale research on the efficacy and tolerability of topical GTN is needed to establish its full therapeutic potential in the treatment of erectile dysfunction.

Topics: Cyclic GMP; Drug Interactions; Enzyme Inhibitors; Erectile Dysfunction; Humans; Male; Nitric Oxide; Nitric Oxide Donors; Penile Erection; Piperazines; Purines; Sildenafil Citrate; Sulfones

Topics: Administration, Oral; Adrenergic alpha-Antagonists; Antidepressive Agents, Second-Generation; Apomorphine; Cyclic GMP; Dopamine Agonists; Enzyme Inhibitors; Erectile Dysfunction; Humans; Male; Phentolamine; Piperazines; Purines; Sildenafil Citrate; Sulfones; Trazodone; Yohimbine

Nitric oxide has been identified as an Endothelium-Derived Relaxing Factor (EDRF). Non adrenergic-non cholinergic nerves synthesise and release nitric oxide, thus modulating the arterial tone. Nitric oxide synthase exists either as a constitutive enzyme in many cell types and as an inducible form expressed under immunological stimulation. Nitric oxide is also involved in the non adrenergic-non cholinergic neurotransmission that leads to smooth muscle relaxation in the corpus cavernosum. Similarly nitric oxide induces reduction of cytosolic free Ca++ as a result of activation of the soluble form of guanylyl cyclase. VIP and nitric oxide may function as co-transmitters. Relaxation of the corpus cavernosum is blocked by methylene blue which inhibits cyclic GMP synthesis; so, high flow priapism refractory to medical and surgical treatments can be managed successfully by intracavernous methylene blue. Moreover it is suggested that enhanced alpha 1-adrenergic mediated constrictor tone and penile flaccidity in diabetic men may respond to exogenous generators of nitric oxide. We postulate that relaxation of the corpus cavernosum, started by nitric oxide in response to non adrenergic-non cholinergic neurotransmission, could be amplified and maintained by nitric oxide production as a result of platelet trapping in the corpus cavernosum during the first phase of the penile erection.

Topics: Amino Acid Oxidoreductases; Calcium; Cyclic GMP; Endothelium, Vascular; Erectile Dysfunction; Humans; Male; Methylene Blue; Neurotransmitter Agents; Nitric Oxide; Nitric Oxide Synthase; Penile Erection; Penis; Priapism; Signal Transduction; Vasodilation

Evidences have been suggested that phosphodiesterase type 5 (PDE5) inhibition promotes vasculoprotective benefits in patients with cardiovascular diseases.. The aim of this study is to analyze the systemic effect of PDE5 inhibition in type 2 diabetes mellitus patients with erectile dysfunction (ED) determining changes in the expression levels of plasma proteins.. Seventeen patients with controlled type 2 diabetes mellitus and ED were included in the study. Patients received vardenafil hydrochloride 20 mg on demand during 12 weeks. At the beginning and 12 weeks after vardenafil administration, plasma samples were collected and analyzed using proteomics.. International Index of Erectile Function-Erectile Function Domain (IIEF-EFD) and plasma protein expression before and after vardenafil administration. Nitrate/nitrite release, PDE5, and soluble guanylate cyclase (sGC) expression and cyclic guanosine monophosphate (cGMP) content in cultured bovine aortic endothelial cells (BAECs).. The IIEF-EFD score was markedly improved after 12 weeks of vardenafil administration. Plasma levels of alpha 1-antitrypsin isotypes 4 and 6 and β-tropomyosin were decreased, whereas apolipoprotein AI isoype 5 was increased 12 weeks after vardenafil administration. Only β-tropomyosin plasma levels were inversely correlated with IIEF-EFD score. Tropomyosin has been added to cultured BAECs and after 24 hours reduced the protein expression level of sGC-β1 subunit and decreased the cGMP content. Tropomyosin did not modify PDE5 expression and nitric oxide release in BAECs as compared with control BAECs. Vardenafil (10 μg/mL) did not modify sGC-β1 subunit expression in tropomyosin + vardenafil-incubated BAECs; however, vardenafil significantly reversed the reduction of cGMP content induced by tropomyosin.. Vardenafil administration improved erectile functionality in controlled type 2 diabetes mellitus patients with ED, which was associated with reduction of circulating plasma β-tropomyosin levels. Tropomyosin affected by itself the cGMP generating system suggesting a possible new mechanism involved in ED. Vardenafil reversed the reduction effect of cGMP content elicited by tropomyosin in BAECs.

Topics: Animals; Cattle; Cyclic GMP; Diabetes Mellitus, Type 2; Erectile Dysfunction; Guanylate Cyclase; Humans; Imidazoles; Male; Middle Aged; Nitric Oxide; Penile Erection; Phosphodiesterase 5 Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Sulfones; Triazines; Tropomyosin; Vardenafil Dihydrochloride

We investigated changes in serum biomarkers of vascular function after short-term, continuous sildenafil dosing in men with type 2 diabetes with erectile dysfunction.. Men with erectile dysfunction associated with type 2 diabetes mellitus were randomized to receive continuous, daily sildenafil (50 mg for 1 week run-in and 100 mg for 3 weeks) (148), or placebo (144) for 4 weeks (phase I) and then sildenafil (25, 50 or 100 mg) on demand for 12 weeks (phase II). Blood draws at baseline and after phases I and II were analyzed for cyclic guanosine monophosphate (endothelial function marker), 8-isoprostane (oxidative stress marker), and interleukin-6 and interleukin-8 (inflammatory cytokines). Primary and secondary erectile function outcome variables were affirmative responses on Sexual Encounter Profile question 3 (ability to maintain erection sufficient for sexual intercourse) and Erection Hardness Score, respectively.. Serum cyclic guanosine monophosphate levels were increased in the sildenafil group relative to the placebo group at 4 (p <0.01) and 16 (p <0.05) weeks, correlating with affirmative responses to Sexual Encounter Profile question 3 at the 4-week interval only (p <0.05). Serum 8-isoprostane levels were decreased to a nonsignificant degree in the sildenafil group at 4 weeks with no further change at 16 weeks, whereas interleukin-6 and interleukin-8 levels were unchanged at either interval, and these levels were unassociated with erectile function outcomes.. These data suggest that short-term, continuous sildenafil treatment causes systemic endothelial function to be enhanced and remain so for a duration after its discontinuation. However, they do not indicate any influence of this treatment on systemic oxidative stress or inflammation, or an effect on long-term erectile function improvement.

Topics: Adult; Aged; Biomarkers; Cyclic GMP; Diabetes Complications; Diabetes Mellitus, Type 2; Dinoprost; Endothelium, Vascular; Erectile Dysfunction; Humans; Interleukin-6; Interleukin-8; Male; Middle Aged; Oxidative Stress; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Treatment Outcome

Phosphodiesterase 5 inhibitors (PDE5-Is) are a mainstay in the therapy of erectile dysfunction (ED). The primary end point of clinical efficacy, both in clinical studies and normal practice, is represented by the International Index of Erectile Function (IIEF).. To evaluate if platelet cyclic guanosine monophosphate (cGMP) could represent a valuable marker for PDE5-I activity in ED.. The study enrolled 46 patients with psychogenic, organic, and mixed ED (20-71 yr of age; IIEF score<26). Patients were randomized to 6 wk of vardenafil, 5 mg/d at bedtime, or placebo.. All patients donated two blood samples, one before starting the protocol and the second after 6 wk of treatment.. Platelet cGMP was measured in both placebo and vardenafil groups. All the patients completed the IIEF-Erectile Function (EF) domain and the sexual encounter profile (SEP) and underwent visual sexual stimulation (VSS) coupled with Rigiscan. All the measurements were performed prior to starting the protocol and after the 6 wk of treatment.. Platelet cGMP production was significantly (p<0.05) elevated in patients taking 5mg vardenafil versus placebo. Vardenafil was not superior to placebo in improving IIEF-EF and SEP scores. Conversely, VSS-Rigiscan revealed a significant amelioration (p<0.028) in the vardenafil group versus placebo. The changes in platelet cGMP level correlated well with VSS-Rigiscan (p=0.0037) but not with IIEF-EF and SEP.. Platelet cGMP could represent a relatively simple, reliable, and objective biomarker of PDE5-I activity in ED clinical studies. Larger clinical studies are needed to further validate the use, utility, and limits of this assay.

Topics: Adult; Aged; Biomarkers; Blood Platelets; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Drug Monitoring; Erectile Dysfunction; Humans; Imidazoles; Male; Middle Aged; Phosphodiesterase 5 Inhibitors; Piperazines; Placebos; Reproducibility of Results; Sulfones; Triazines; Vardenafil Dihydrochloride; Young Adult

Corpus cavernosum smooth muscle relaxation and hence penile erection are regulated in part by increases in smooth muscle synthesis of the second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). The object of this study was to determine 30-month follow-up results in motivated patients desiring noninvasive medical therapy using sildenafil citrate (Viagra) in combination with intraurethral prostaglandin E(1) (PGE(1)) (Medicated Urethral System for Erection [MUSE]). Twenty-eight patients (mean +/- s.d. age, 59 +/-7.3 y; 17 who had undergone radical prostatectomy and 11 who had a diagnosis of organic erectile dysfunction) were included in this study. Detailed history taking and physical examinations were performed and vascular risk factors noted. In these patients, treatment with either 100 mg of sildenafil citrate and/or 1000 microg of MUSE had failed. None of these patients desired intracavernosal injection. Duplex Doppler ultrasonography after redosing was carried out on all patients. Dynamic infusion corpus cavernosography/cavernosometry was obtained in 17 of 28 patients, and combination therapy was initiated using 100 mg of sildenafil citrate orally 60 min before intercourse and 500 microg of MUSE intraurethrally immediately before intercourse. Independently, either 100 mg of sildenafil citrate or 1000 microg of MUSE was not efficacious in inducing an erection sufficient for vaginal penetration in any of the 28 patients. After initiating a combination therapy, at 30 months, all 28 patients were reporting erections sufficient for vaginal penetration, with 3.6 intercourse episodes per month. None of the patients crossed over to intracavernosal therapy or penile prosthesis. During therapy, eight of 28 patients reduced the dose of sildenafil citrate to 50 mg. Combination therapy with MUSE and sildenafil may be more efficacious in the salvage of patients who desire noninvasive therapy but in whom single-treatment modalities fail. Although both cAMP- and cGMP-mediated vasodilation can lead to penile erection, combining therapies that incorporate both pathways may succeed when single therapies fail.

Topics: Aged; Alprostadil; Cohort Studies; Cyclic AMP; Cyclic GMP; Drug Therapy, Combination; Erectile Dysfunction; Humans; Male; Middle Aged; Muscle, Smooth; Patient Satisfaction; Piperazines; Prostatectomy; Purines; Sildenafil Citrate; Sulfones; Urethra; Vasodilator Agents

Sildenafil (Viagra, UK-92,480) is a novel oral agent under development for the treatment of penile erectile dysfunction. Erection is dependent on nitric oxide and its second messenger, cyclic guanosine monophosphate (cGMP). However, the relative importance of phosphodiesterase (PDE) isozymes is not clear. We have identified both cGMP- and cyclic adenosine monophosphate-specific phosphodiesterases (PDEs) in human corpora cavernosa in vitro. The main PDE activity in this tissue was due to PDE5, with PDE2 and 3 also identified. Sildenafil is a selective inhibitor of PDE5 with a mean IC50 of 0.0039 microM. In human volunteers, we have shown sildenafil to have suitable pharmacokinetic and pharmacodynamic properties (rapid absorption, relatively short half-life, no significant effect on heart rate and blood pressure) for an oral agent to be taken, as required, prior to sexual activity. Moreover, in a clinical study of 12 patients with erectile dysfunction without an established organic cause, we have shown sildenafil to enhance the erectile response (duration and rigidity of erection) to visual sexual stimulation, thus highlighting the important role of PDE5 in human penile erection. Sildenafil holds promise as a new effective oral treatment for penile erectile dysfunction.

Topics: Administration, Oral; Cross-Over Studies; Cyclic GMP; Double-Blind Method; Enzyme Inhibitors; Erectile Dysfunction; Humans; Isoenzymes; Male; Middle Aged; Penis; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Sildenafil Citrate; Sulfones; Treatment Outcome

Intracellular levels of cyclic nucleotides can also be controlled by the action of multidrug resistance protein types 4 (MRP4) and 5 (MRP5). To date, no studies evaluated the role of their inhibition in an animal model of erectile dysfunction (ED).. To evaluate the effect of a 2-week treatment with MK571, an inhibitor of the efflux of cyclic nucleotides in the ED of obese mice.. Mice were divided in three groups: (i) lean, (ii) obese, and (iii) obese + MK571. The corpus cavernosum (CC) were isolated, and concentration-response curves to acetylcholine (ACh), sodium nitroprusside (SNP), and tadalafil in addition to electrical field stimulation (EFS) were carried out in phenylephrine pre-contracted tissues. Expression of ABCC4 and ABCC5, intracellular levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), the protein levels for pVASP. The MRPs inhibition by MK571 favored the accumulation of cGMP in the smooth muscle cells, thus improving the smooth muscle relaxation and the erectile function in obese mice.

Topics: Acetylcholine; Animals; ATP Binding Cassette Transporter, Subfamily B; Cyclic GMP; Erectile Dysfunction; Humans; Male; Mice; Mice, Obese; Nitroprusside; Obesity; Tadalafil

Topics: Aged; Animals; Cyclic GMP; Erectile Dysfunction; Fetal Blood; Humans; Male; Mice; Penis; Scrotum; Testosterone

Oxidative stress has been linked with sleep deprivation (SD)-induced pathological conditions and reproductive dysfunction. On the other hand, glutamine has been established to have antioxidant property. However, the impact of SD, with or without glutamine, on male reproductive function is yet to be elucidated. Thus, this study was designed to investigate the role of SD, with or without glutamine, on male reproductive function and possible associated mechanisms. Ten-week old male Wistar rats weighing 175.6 g± 0.42 were randomly assigned into vehicle that received per os (p.o.) distilled water, glutamine (1 g/kg; po), SD, and SD + glutamine that received treatments as glutamine and SD. Treatment/exposure lasted for 72 h. The results showed that SD led to reduced body weight, seminiferous luminal and epididymal sperm density, low sperm quality, increased testicular and epididymal malondialdehyde, uric acid, DNA fragmentation, and testicular injury markers. In addition, SD caused a reduction in reduced glutathione level and activities of superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, and glutathione-S-transferase. Also, SD increased tumor necrotic factor-α, interleukin-1β, and nuclear factor-kappa B levels. Furthermore SD led to impaired libido and erectile dysfunction, and suppression of circulatory nitric oxide, gonadotropins and testosterone, and penile cGMP. However, glutamine attenuated the effects induced by SD. Taken together, the findings of this study demonstrate that SD induces reproductive dysfunction via glutathione-dependent defense depletion and down-regulation of NO/cGMP signaling, which was abolished by glutamine supplementation.

Topics: Animals; Antioxidants; Cyclic GMP; Epididymis; Erectile Dysfunction; Glutamine; Libido; Male; Nitric Oxide; Oxidative Stress; Random Allocation; Rats; Rats, Wistar; Sexual Dysfunction, Physiological; Sleep Deprivation; Testis

Timely activation of the luteinizing hormone receptor (LHCGR) is critical for fertility. Activating mutations in LHCGR cause familial male-limited precocious puberty (FMPP) due to premature synthesis of testosterone. A mouse model of FMPP (KiLHRD582G), expressing a constitutively activating mutation in LHCGR, was previously developed in our laboratory. KiLHRD582G mice became progressively infertile due to sexual dysfunction and exhibited smooth muscle loss and chondrocyte accumulation in the penis. In this study, we tested the hypothesis that KiLHRD582G mice had erectile dysfunction due to impaired smooth muscle function. Apomorphine-induced erection studies determined that KiLHRD582G mice had erectile dysfunction. Penile smooth muscle and endothelial function were assessed using penile cavernosal strips. Penile endothelial cell content was not changed in KiLHRD582G mice. The maximal relaxation response to acetylcholine and the nitric oxide donor, sodium nitroprusside, was significantly reduced in KiLHRD582G mice indicating an impairment in the nitric oxide (NO)-mediated signaling. Cyclic GMP (cGMP) levels were significantly reduced in KiLHRD582G mice in response to acetylcholine, sodium nitroprusside and the soluble guanylate cyclase stimulator, BAY 41-2272. Expression of NOS1, NOS3 and PKRG1 were unchanged. The Rho-kinase signaling pathway for smooth muscle contraction was not altered. Together, these data indicate that KiLHRD582G mice have erectile dysfunction due to impaired NO-mediated activation of soluble guanylate cyclase resulting in decreased levels of cGMP and penile smooth muscle relaxation. These studies in the KiLHRD582G mice demonstrate that activating mutations in the mouse LHCGR cause erectile dysfunction due to impairment of the NO-mediated signaling pathway in the penile smooth muscle.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Erectile Dysfunction; Extracellular Matrix; Female; Infertility, Male; Male; Mice; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Penis; Receptors, LH

The leech and centipede granules have good curative effects on many diabetic vascular diseases, including diabetes-induced erectile dysfunction (DIED).. To explore the effect of leech and centipede on erectile function in rats with diabetes-induced erectile dysfunction and its possible mechanism.. After 8 weeks, the erectile function of rats in the DG group significantly improved (1.26 ± 0.73). Penis tissue cGMP levels were higher in the DG group (1.48 ± 0.11) than in the M group (0.58 ± 0.15). Protein and mRNA expression levels of NOS were significantly higher (0.77 ± 0.05; 0.61 ± 0.02) but those of PDE5 (0.43 ± 0.05; 0.61 ± 0.03) were lower in the DG group than in the M group (0.37 ± 0.06; 0.51 ± 0.01; 0.78 ± 0.06; 0.81 ± 0.04).. The leech-centipede can improve erectile dysfunction in DIED rats by regulating the expression of cGMP, NOS, and PDE5-related molecules in the PDE5 pathway. This study provides a potential mechanism for the treatment of DIED with leech-centipede.

Topics: Animals; Blood Glucose; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus, Experimental; Erectile Dysfunction; Male; Nitric Oxide Synthase; Penile Erection; Rats; Rats, Sprague-Dawley; Signal Transduction; Streptozocin; Tissue Extracts

To investigate the protective effects and mechanisms of human tissue kallikrein 1 (hKLK1) on type 1 diabetes mellitus- (DM-) induced erectile dysfunction in rats.. The. hKLK1 preserves erectile function of DM rats through its antitissue excessive OS, apoptosis, and fibrosis effects, as well as activation of the PI3K/AKT/eNOS/cGMP pathway in the penis. Moreover, hKLK1 promotes relaxation and prevents high glucose-induced injuries of CSMC mediated by EC-CSMC crosstalk.

Topics: Animals; Apoptosis; Blood Glucose; Body Weight; Calcium; Cyclic GMP; Diabetes Mellitus, Experimental; Electric Stimulation; Erectile Dysfunction; Fasting; Fibrosis; Glucose; Male; Myocytes, Smooth Muscle; Nitric Oxide Synthase Type III; Oxidative Stress; Penis; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats, Sprague-Dawley; Rats, Transgenic; Signal Transduction; Streptozocin; Tissue Kallikreins

In corpus cavernosum (CC), guanosine triphosphate (GTP) is converted into cyclic guanosine monophosphate (cGMP) to induce erection. The action of cGMP is terminated by phosphodiesterases and efflux transporters, which pump cGMP out of the cell. The nucleotides, GTP, and cGMP were detected in the extracellular space, and their hydrolysis lead to the formation of intermediate products, among them guanosine. Therefore, our study aims to pharmacologically characterize the effect of guanosine in isolated CC from mice. The penis was isolated and functional and biochemical analyses were carried out. The guanine-based nucleotides GTP, guanosine diphosphate, guanosine monophosphate, and cGMP relaxed mice corpus cavernosum, but the relaxation (90.7 ± 12.5%) induced by guanosine (0.000001-1 mM) was greater than that of the nucleotides (~ 45%, P < 0.05). Guanosine-induced relaxation was not altered in the presence of adenosine type 2A and 2B receptor antagonists. No augment was observed in the intracellular levels of cyclic adenosine monophosphate in tissues stimulated with guanosine. Inhibitors of nitric oxide synthase (L-NAME, 100 μM) and soluble guanylate cyclase (ODQ, 10 μM) produced a significant reduction in guanosine-induced relaxation in all concentrations studied, while in the presence of tadalafil (300 nM), a significant increase was observed. Pre-incubation of guanosine (100 μM) produced a 6.6-leftward shift in tadalafil-induced relaxation. The intracellular levels of cGMP were greater when CC was stimulated with guanosine. Inhibitors of ecto-nucleotidases and xanthine oxidase did not interfere in the response induced by guanosine. In conclusion, our study shows that guanosine relaxes mice CC and opens the possibility to test its role in models of erectile dysfunction.

Topics: Animals; Cyclic AMP; Cyclic GMP; Erectile Dysfunction; Guanosine; Male; Mice; Mice, Inbred C57BL; Nitric Oxide Synthase; Nucleosides

Testosterone (T) deficiency is associated with erectile dysfunction (ED). The relaxant response of T on the corporal smooth muscle through a non-genomic pathway has been reported; however, the in vitro modulating effects of T on human corpus cavernosum (HCC) have not been studied.. To compare the effects of various concentrations of T on nitric oxide (NO)-dependent and nitric oxide-independent relaxation in organ bath studies and elucidate its mode of action, specifically targeting the cavernous NO/cyclic guanosine monophosphate (cGMP) pathway.. Human corpus cavernosum (HCC) samples were obtained from men undergoing penile prosthesis implantation (n = 9). After phenylephrine (Phe) precontraction, the effects of various relaxant drugs of HCC strips were performed using organ bath at low (150 ng/dL), eugonadal (400 ng/dL), and hypergonadal (600 ng/dL) T concentrations. The penile tissue measurements of endothelial nitric oxide synthase (eNOS), neuronal (n)NOS, and phosphodiesterase type 5 (PDE5) were evaluated via immunostaining, Western blot, cGMP and nitrite/nitrate (NOx) assays.. Relaxation responses to ACh and EFS in isolated HCC strips were significantly increased at all T levels compared with untreated tissues. The sildenafil-induced relaxant response was significantly increased at both eugonadal and hypergonadal T levels. Normal and high levels of T are accompanied by increased eNOS, nNOS, cGMP, and NOx levels, along with reduced PDE5 protein expression.. This study reveals an important role of short-term and modulatory effects of different concentrations of T in HCC. T positively regulates functional activities, inhibition of PDE5 expression, and formation of cGMP and NOx in HCC. These results demonstrate that T indirectly contributes to HCC relaxation via downstream effects on nNOS, eNOS, and cGMP and by inhibiting PDE5. This action provides a rationale for normalizing T levels in hypogonadal men with ED, especially when PDE5 inhibitors are ineffective. T replacement therapy may improve erectile function by modulating endothelial function in hypogonadal men.

Topics: Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Hormone Replacement Therapy; Humans; Male; Middle Aged; Nitric Oxide; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penile Induration; Penis; Sildenafil Citrate; Testosterone

Erectile dysfunction (ED) is a major health issue among men with diabetes, and ED induced by diabetes mellitus (DMED) is particularly difficult to treat. Therefore, novel therapeutic approaches for the treatment of DMED are urgently needed. Exosomes, nanosized particles involved in many physiological and pathological processes, may become a promising tool for DMED treatment. In this study, we investigated the therapeutic effect of exosomes derived from corpus cavernosum smooth muscle cells (CCSMC-EXOs) on erectile function in a rat model of diabetes and compared their effect with that of exosomes derived from mesenchymal stem cells (MSC-EXOs). We incubated labelled CCSMC-EXOs and MSC-EXOs with CCSMCs and then observed uptake of the exosomes at different time points using laser confocal microscopy. CCSMC-EXOs were more easily taken up by CCSMCs. The peak concentration and retention time of labelled CCSMC-EXOs and MSC-EXOs in the corpus cavernosum of DMED rats after intracavernous injection were compared by in vivo imaging techniques. Intracavernous injection of CCSMC-EXOs was associated with a relatively high peak concentration and long retention time. Our data showed that CCSMC-EXOs could improve erectile function in DMED rats. Meanwhile, CCSMC-EXOs could exert antifibrotic effects by increasing the smooth muscle content and reducing collagen deposition. CCSMC-EXOs also increased the expression of eNOS and nNOS, followed by increased levels of NO and cGMP. These findings initially identify the possible role of CCSMC-EXOs in ameliorating DMED through inhibiting corporal fibrosis and modulating the NO/cGMP signalling pathway, providing a theoretical basis for a breakthrough in the treatment of DMED.

Topics: Adipocytes; Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Exosomes; Fibrosis; Male; Microscopy, Confocal; Myocytes, Smooth Muscle; Nitric Oxide; Penile Erection; Penis; Rats; Rats, Sprague-Dawley; Signal Transduction; Stem Cells

To investigate the effect of Xiongcan Yishen Prescription (XYP) on the expressions of eNOS and cGMP in the penile tissue of ED rats with liver depression and kidney deficiency (LDKD).. The model of ED-LDKD was established in 30 eight-week-old SPF-class male SD rats by injecting hydrocortisone intramuscularly and binding the limbs for 14 days, and another 10 rats were taken as blank controls. Then, the model rats were randomized into six groups of equal number and treated intragastrically with distilled water (model control), tadalafil tablets at 0.52 mg/kg/d (tadalafil control), Shugan Yiyang Capsules 0.3125 g/kg/d (SYC control), and XYP at 10.4 g/kg/d (low-dose XYP), 20.8 g/kg/d (medium-dose XYP) and 41.6 g/kg/d (high-dose XYP), bid, for 28 successive days, respectively. Before and after modeling and after 28-day treatment, the animals were subjected to tail suspension and mating tests. The next day after medication, the penile tissues of the rats were harvested for determining the expression levels of eNOS and cGMP proteins by immunohistochemical analysis of the mean optical density.. Compared with the model controls, the rats of the high-, medium- and low-dose XYP and SYC control groups all showed significant decreases in the tail suspension time (［3.17 ± 0.11］ vs ［2.58 ± 0.25］, ［2.52 ± 0.31］, ［2.51 ± 0.3］ and ［2.57 ± 0.29］ min, P < 0.05) and mount latency (ML) (［9.23 ± 0.11］ vs ［1.21 ± 0.12］, ［2.17 ± 0.16］, ［2.26 ± 0.13］, ［1.23 ± 0.15］ and ［2.48 ± 0.18］ min, P < 0.05) but increases in mount frequency (MF) (［0.48 ± 0.18］ vs ［3.29 ± 0.11］, ［3.18 ± 0.11］, ［3.05 ± 0.05］, ［3.23 ± 0.12］ and ［3.2 ± 0.28］ times, P < 0.05) and intromission frequency (IF) (［0.8 ± 0.84］ vs ［11.8 ± 0.84］, ［11.2 ± 1.48］, ［9.4 ± 1.14］, ［11.4 ± 1.14］ and ［10 ± 1.22］ times, P < 0.05). The eNOS and cGMP proteins were mainly expressed in the nucleus and cytoplasm of the arterial and venous endothelial cells and sinusoidal endothelial cells of the cavernous, as brownish yellow particles in a scattered and focal pattern. Both the expressions of eNOS and cGMP in the penile tissue were remarkably upregulated in the high-, medium- and low-dose XYP and SYC control groups as compared with those in the model control (P < 0.05) but exhibited no statistically significant difference between the tadalafil and model control groups (P > 0.05).. Xiongcan Yishen Prescription can relieve the depression symptoms, increase the mount frequency, activate the NO/cGMP pathway, and upregulate the expressions of eNOS and cGMP in the penile tissue of ED rats with liver depression and kidney deficiency.

Topics: Animals; Cyclic GMP; Drugs, Chinese Herbal; Endothelial Cells; Erectile Dysfunction; Kidney; Liver; Male; Nitric Oxide Synthase Type III; Penile Erection; Penis; Random Allocation; Rats; Rats, Sprague-Dawley

Some medicinal mushrooms have effects on sexual dysfunctions. Nitric oxide synthase (NOS)-cyclic gua-nosine monophosphate (cGMP)-phosphodiesterase 5 enzyme (PDE5) pathway is one of the pathophysiological basis of erectile dysfunction (ED). The normal erectile function involves the synthesis of nitric oxide (NO), and the subsequent accumulation of cGMP, whereas cGMP degradation is specifically controlled by PDE5, which promotes corporal smooth muscle cell (SMC) tone and terminates erection. The antioxidant activities of Inonotus obliquus (chaga) water extracts (IO1) and water extraction and alcohol precipitation extracts (IO2) were compared using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay and oxygen radical absorbance capacity (ORAC) method. Three subtypes of NOS (nNOS, iNOS, and eNOS) and PDE5 protein expressions were tested by Western blotting, and cGMP was determined by ELISA on a rat corporal primary SMC. The results revealed that IO2, which had a significantly higher polysaccharide content than IO1, showed a significantly higher ORAC value and a significantly lower half inhibitory concentration for DPPH scavenging activity than IO1. We observed that both IO1 and IO2 increased the expression of eNOS and iNOS significantly compared with the control. Furthermore, when compared with the control, IO1 increased PDE5 expression significantly, while IO2 showed no effect. The different impacts on PDE5 might be the reason that IO2, not IO1, showed significant inducible effect on cGMP compared with the control. This is to our knowledge, the first study exploring the effect of I. obliquus on NOS-cGMP-PDE5 pathway on SMC. The results provide a possible selection of I. obliquus for the treatment of ED.

Topics: Agaricales; Animals; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Inonotus; Male; Myocytes, Smooth Muscle; Nitric Oxide Synthase; Penis; Plant Extracts; Rats

The natural product icariin inhibits human phosphodiesterase-5 (PDE5) and represents a unique pharmacophore for treating erectile dysfunction, pulmonary hypertension, and other diseases. In this study, we explore the available icariin-derived chemical scaffolds through medicinal chemistry to develop novel icariin PDE5 inhibitors with improved potency and specificity. We synthesized six novel semi-synthetic icariin analogs as well as three naturally occurring icariin analogs, and characterized the structure-activity relationship in the context of human PDE5 inhibition using in vitro enzyme inhibition and kinetics assays and molecular modeling. Mammalian-cell-based assays and in vitro enzyme inhibition assays against human PDE6C further helped to identify the most potent and selective icariin analogs. Our results reveal the synergistic contribution of functional groups at the C3 and C7 positions of the icariin backbone towards PDE5 inhibition. Whereas a hydrophobic and flexible alkanol group at the C7 position is sufficient to enhance icariin analog potency, combining this group with a hydrophilic sugar group at the C3 position leads to further enhancement of potency and promotes specificity towards PDE5 versus PDE6C. In particular, compounds 3 and 7 exhibit Ki values of 0.036 ± 0.005 μM and 0.036 ± 0.007 μM towards PDE5 respectively, which are approaching those of commercial PDE5 inhibitors, and can effectively reduce GMP levels in cultured human BJ-hTERT cells. This study identifies novel icariin analogs as potent and selective PDE5 inhibitors poised to become lead compounds for further pharmaceutical development.

Topics: Animals; Biocatalysis; Cell Line; Cell Line, Tumor; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Flavonoids; Humans; Hypertension, Pulmonary; Male; Models, Chemical; Molecular Structure; Phosphodiesterase 5 Inhibitors; Structure-Activity Relationship

With the aim of overcoming the high toxicity of PnTx2-6 (or δ-CNTX-Pn2a), a toxin from the venom of the armed spider (Phoneutria nigriventer), the 19-aminoacid peptide, PnPP-19 (P nigriventer potentiator peptide), was synthesized based on molecular modeling studies of PnTx2-6. PnPP-19 improved the erectile function of normotensive rats and mice, without eliciting side effects, and no signs of toxicity were observed. In addition, PnPP-19 was able to potentiate the effect of sildenafil.. To evaluate the efficacy of PnPP-19 in hypertensive and diabetic mouse/rat models in restoring erectile function, after topical administration; verify the biodistribution of PnPP-19 administration (topical and intravenous), permeation, and cyclic guanosine monophosphate (cGMP)/nitric oxide via implication.. PnPP-19 seems to be an indicated drug to be tested to treat ED in diabetic and hypertensive patients.. PnPP-19, although active by topical application and showing safety to human beings (not shown), has low permeability, about 10% of the applied dose.. Our results showed that PnPP-19 may emerge as a potent new drug that can be topically administered, becoming a promising alternative for erectile dysfunction treatment. Nunes da Silva C, Pedrosa Nunes K, De Marco Almeida F, et al. PnPP-19 Peptide Restores Erectile Function In Hypertensive And Diabetic Animals Through Intravenous And Topical Administration. J Sex Med 2019;16:365-374.

Topics: Administration, Intravenous; Administration, Topical; Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Male; Mice; Mice, Inbred C57BL; Nitric Oxide; Penile Erection; Peptides; Phosphodiesterase 5 Inhibitors; Rats; Rats, Inbred SHR; Rats, Sprague-Dawley; Rats, Wistar; Sildenafil Citrate; Spider Venoms; Streptozocin; Tissue Distribution

Diabetes mellitus is associated with sexual dysfunction, which leads to infertility in animal models. The aim of this study was to evaluate sexual behavior in diabetic rats administered with naringenin. Rats were classified into five groups including healthy controls, those with STZ-induced diabetes, and those with STZ-induced diabetes then treated with 25, 50, or 100 mg kg

Topics: Animals; Cyclic GMP; Diabetes Complications; Diabetes Mellitus, Experimental; Ejaculation; Erectile Dysfunction; Flavanones; Humans; Male; Oxidative Stress; Penile Erection; Rats; Spermatogenesis; Spermatozoa; Streptozocin; Testis; Testosterone

Ginseng has been reported to have diverse pharmacological effects. One of the therapeutic claims for ginseng is to enhance sexual function. Ginsenosides are considered as the major active constituents. A steaming process can alter the ginsenoside profile of ginseng products. The structure-function relationship of ginsenosides in the treatment of erectile dysfunction (ED) has not been investigated yet. In this work, 15 different processed ginsengs are produced by steaming, and 13 major ginsensosides are quantified by liquid chromatography with UV detection, including Rg1, Re, Rf, Rb1, Rc, Rb2, Rf, Rk3, Rh4, 20S-Rg3, 20R-Rg3, Rk1, and Rg5. Their anti-ED activities are screened using hydrocortisone-induced mice model (Kidney Yang Deficiency Syndrome in Chinese Medicine) and primary corpus cavernosum smooth muscle cells (CCSMCs). A processed ginseng with steaming treatment at 120[Formula: see text]C for 4[Formula: see text]h and five times possesses abundant ginsenosides Rk1, Rk3, Rh4 and Rg5 transformed via deglycosylation and dehydroxylation, and produces optimal activity against ED. The number of sugar molecules, structure of hydroxyl groups and stereoselectivity in ginsenosides affect their anti-ED activity. Among the 13 ginsenosides, Rk1, Rk3, Rh4 and Rg5 are the most efficient in decreasing intracellular calcium levels by inhibiting phosphodiesterase 5A (PDE5A) to reduce the degradation of cyclic guanosine monophosphate (cGMP) in CCSMCs. Rg5 also restrain hypoxia inducible factor-1[Formula: see text] (HIF-1[Formula: see text] expression in hypoxia state, and increase endothelial nitric oxide synthase (eNOS) expression in isolated rat cavernous tissue. These observations suggest a role for steamed ginseng containing two pairs of geometric isomers (i.e., Rk1/Rg5 and Rk3/Rh4) in the treatment of ED.

Topics: Animals; Calcium; Cells, Cultured; Cyclic GMP; Disease Models, Animal; Erectile Dysfunction; Ginsenosides; Hypoxia-Inducible Factor 1, alpha Subunit; Isomerism; Male; Mice, Inbred ICR; Myocytes, Smooth Muscle; Nitric Oxide Synthase Type III; Panax; Phosphodiesterase 5 Inhibitors; Rats, Sprague-Dawley; Steam; Structure-Activity Relationship; Temperature

Stimulation of thermogenic pathways appears to be a promising approach to find new ways of tackling metabolic diseases like obesity and diabetes mellitus type 2. Thermogenic, weight reducing and insulin sensitizing effects of phosphodiesterase 5 (PDE 5) inhibitors have recently been postulated, suggesting that modulators of endogenous cGMP signaling have the therapeutic potential to treat metabolic disorders. However, most studies have been performed in vitro or in animals that were not glucose intolerant. We, thus, aimed to test the metabolic effects of the PDE 5 inhibitor sildenafil by treating diet-induced obese (DIO) mice orally for 8 days. Surprisingly, our results revealed no changes in body temperature, brown adipose tissue (BAT) thermogenesis and gene expression in BAT and inguinal white adipose tissue (iWAT), thus excluding a thermogenic or 'browning' effect of sildenafil in preexisting obesity. In contrast, sildenafil-treated DIO mice displayed changes in liver metabolism and glucose homeostasis resulting in impaired glucose tolerance (P < 0.05), demonstrating for the first time an unfavorable metabolic effect of increased hepatic cGMP signaling in obesity. As sildenafil is commonly prescribed to treat pulmonary arterial hypertension and erectile dysfunction in diabetic and/or obese patients, follow up studies are urgently required to re-evaluate the drug safety.

Topics: Adipose Tissue; Adipose Tissue, Brown; Adipose Tissue, White; Animals; Blood Glucose; Cyclic GMP; Erectile Dysfunction; Glucose Intolerance; Homeostasis; Hypertension; Liver; Male; Mice, Inbred C57BL; Mice, Obese; Obesity; Phosphodiesterase 5 Inhibitors; Signal Transduction; Sildenafil Citrate; Thermogenesis

cGMP-independent nitric oxide (NO) signaling occurs via S-nitrosylation. We evaluated whether aberrant S-nitrosylation operates in the penis under conditions of cavernous nerve injury and targets proteins involved in regulating erectile function. Adult male Sprague-Dawley rats underwent bilateral cavernous nerve crush injury (BCNI) or sham surgery. Rats were given a denitrosylation agent N-acetylcysteine (NAC, 300 mg/kg/day) or vehicle in drinking water starting 2 days before BCNI and continuing for 2 weeks following surgery. After assessment of erectile function (intracavernous pressure), penes were collected for measurements of S-nitrosylation by Saville-Griess and TMT-switch assays and PKG-I function by immunoblotting of phospho (P)-VASP-Ser-239. Erectile function was decreased (P < 0.05) after BCNI, and it was preserved (P < 0.05) by NAC treatment. Total S-nitrosothiols and total S-nitrosylated proteins were increased (P < 0.05) after BCNI, and these were partially prevented by NAC treatment. S-nitrosylation of sGC was increased (P < 0.05) after BCNI, and it was prevented (P < 0.05) by NAC treatment. S-nitrosylation of eNOS was increased (P < 0.05) after BCNI, and showed a trend towards decrease by NAC treatment. Protein expression of P-VASP-Ser-239 was decreased (P < 0.05) after BCNI, and showed a trend towards increase by NAC treatment. In conclusion, erectile dysfunction following BCNI is mediated in part by S-nitrosylation of eNOS and its downstream signaling mediator GC, while denitrosylation protects erectile function by preserving the NO/cGMP signaling pathway.

Topics: Acetylcysteine; Animals; Cyclic GMP; Erectile Dysfunction; Male; Nerve Crush; Nitric Oxide; Nitric Oxide Synthase Type III; Penile Erection; Penis; Rats; Rats, Sprague-Dawley; Signal Transduction

Diabetic erectile dysfunction (DMED) is mainly attributed to oxidative stress, and Nrf2 plays an important role in cellular antioxidation and regulates NO production in the vascular endothelium. Probucol maintains endothelial function through its antioxidant activity. This study investigated the efficacy and mechanism of probucol in improving erectile function in streptozotocin-induced diabetic rats.. In our study, thirty 12-week-old Sprague-Dawley male rats were fasted for 12 h. All rats received a 1-time injection of intraperitoneal streptozotocin(60 mg/kg) or vehicle. After 72 h, STZ-treated rats (with random blood glucose concentrations consistently greater than 16.7 mmol/L) were considered diabetic. The diabetic rats were randomly assigned into 2 groups and treated with daily gavage feedings of probucol at doses of 0 and 500 mg/kg for 12 weeks. A positive control group underwent intraperitoneal injection of normal saline followed by daily gavage of saline solution. Erectile function was assessed by electrical stimulation of the cavernous nerves with real-time intracavernous pressure measurement. After euthanasia, penile tissue was investigated using immunohistochemistry, Western blot, and ELISA to assess the proteins of Nrf2/HO-1/DDAH/PPAR-γ/eNOS pathways.. After treatment, the rats in the probucol group presented significantly improved erectile function (P < 0.05) than that of the diabetic group without probucol treatment (DM). Also, protein expression of Nrf2, DDAH, PPAR-γ, HO-1 and eNOS was significantly higher than that of the DM group (P < 0.05). CGMP concentrations and SOD concentrations of probucol-treated rats were higher than those of DM group (P < 0.05). The MDA levels and ADMA levels were significantly lower than those of DM group rats (P < 0.05).. Probucol can improve erectile function via activation of Nrf2, which coordinates the HO-1/DDAH/PPAR-γ/eNOS pathways in streptozotocin-induced diabetic rats.

Topics: Amidohydrolases; Animals; Arginine; Blood Glucose; Body Weight; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Heme Oxygenase-1; Male; Malondialdehyde; NF-E2-Related Factor 2; Nitric Oxide Synthase Type III; PPAR gamma; Probucol; Rats, Sprague-Dawley; Signal Transduction; Streptozocin; Superoxide Dismutase

The study aimed at exploring the effect of microRNA-328 (miR-328) antagomir on erectile dysfunction (ED) in streptozotocin (STZ)-induced diabetic rats. A total of 120 male Sprague-Dawley (SD) rats were selected for this study. Fifteen rats were assigned as the diabetic control group and 75 out of the remaining rats (105 diabetic rat models) were divided into five groups with 15 rats in each group: diabetic ED, diabetic ED+negative control (NC), diabetic ED+miR-328 antagomir, diabetic ED+sildenafil and diabetic ED+miR-328 antagomir+sildenafil groups. The cGMP/AGEs production levels were measured using enzyme-linked immunosorbent assay (ELISA) test. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were conducted for testing the expression level of miR-328, transcription and protein levels of endothelial nitric oxide synthase (eNOS) and dickkopf-3 (DKK3). The diabetic ED+miR-328 antagomir group had better erectile function, lower cGMP production level, transcription and protein levels of eNOS and DKK3 but higher AGEs production level than the diabetic control group. The diabetic control group showed higher cGMP production level transcription and protein levels of eNOS and DKK3 and lower production levels of AGEs and miR-328 than the diabetic ED and diabetic ED+NC groups. Our results indicated that miR-328 antagomir could improve ED in STZ-induced diabetic rats by regulating cGMP and AGEs.

Topics: Animals; Antagomirs; Base Sequence; Blood Glucose; Blood Pressure; Body Weight; Cyclic GMP; Diabetes Mellitus, Experimental; Disease Models, Animal; Erectile Dysfunction; Gene Expression Regulation; Genes, Reporter; Glycation End Products, Advanced; Intercellular Signaling Peptides and Proteins; Luciferases; Male; MicroRNAs; Nitric Oxide Synthase Type III; Penis; Rats; Rats, Sprague-Dawley; Streptozocin

The pathophysiology of increased severity of erectile dysfunction in men with diabetes and their poor response to oral pharmacotherapy are unclear. Defective vascular endothelium and consequent impairment in the formation and action of nitric oxide (NO) are implicated as potential mechanisms. Endothelial NO synthase, critical for NO generation, is localized to caveolae, plasma membrane lipid rafts enriched in structural proteins, and caveolins. Type 2 diabetes mellitus (T2DM)-induced changes in caveolin expression are recognized to play a role in cardiovascular dysfunction.. To evaluate DM-related changes to male erectile tissue in a mouse model that closely resembles human T2DM and study the specific role of caveolins in penile blood flow and microvascular perfusion using mice lacking caveolin (Cav)-1 or Cav-3.. We used wild-type C57BL6 (control) and Cav-1 and Cav-3 knockout (KO) male mice. T2DM was induced by streptozotocin followed by a high-fat diet for 4 months. Penile expressions of Cav-1, Cav-3, and endothelial NO synthase were determined by western blot, and phosphodiesterase type 5 activity was measured using [. Penile erectile tissues were harvested for histologic studies to assess Cav-1, Cav-3, and endothelial NO synthase expression, phosphodiesterase type 5 activity, and blood flow, and perfusion measurements were assessed for hemodynamic studies before and after an intracavernosal injection of prostaglandin E. Our findings provide novel mechanistic insights into erectile dysfunction severity and poor pharmacotherapy that could have potential application to patients with T2DM.. Use of KO mice and novel hemodynamic techniques are the strengths. A limitation is the lack of direct evaluation of penile hemodynamics in T2DM mice.. Altered penile Cav-1 expression in T2DM mice and impaired penile hemodynamics in Cav-1 KO mice suggests a regulatory role for Cav-1 in DM-related erectile dysfunction. Parikh J, Zemljic-Harpf A, Fu J, et al. Altered Penile Caveolin Expression in Diabetes: Potential Role in Erectile Dysfunction. J Sex Med 2017;14:1177-1186.

Topics: Animals; Caveolin 1; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Erectile Dysfunction; Male; Mice; Mice, Knockout; Microcirculation; Nitric Oxide Synthase Type III; Penile Erection; Penis

Metabolic syndrome (MetS) is a risk factor for erectile dysfunction (ED), but the underlying mechanisms are unclear. The aims of this study were to determine the underlying mechanisms of metabolic syndrome-related ED (MED). Sprague Dawley (SD) rats were fed a high-fat diet for 6 months, and metabolic parameters were then assessed. An apomorphine test was conducted to confirm MED. Only rats with MED were administered an intracavernosal injection of either epidermal growth factor (EGF) or vehicle for 4 weeks. Erectile responses were evaluated by determining the mean arterial blood pressure (MAP) and intracavernosal pressure (ICP). Levels of protein expression were examined by western blotting and immunohistochemistry. Body weight, fasting blood glucose, plasma insulin and plasma total cholesterol were increased in the MetS rats compared with those in control rats (each p < 0.05). The  maximum ICP/MAP, total ICP/MAP and concentration of cyclic guanosine mono-phosphate (cGMP) were significantly decreased in MED rats (each p < 0.05). The expression levels of p110α, p-Akt1 (Tyr308)/Akt1 and p-eNOS (Ser1177)/eNOS were reduced in MED rats (each p < 0.05). Activation of the PI3K/Akt/eNOS signaling cascade (intracavernosal injection of EGF) reversed these changes (each p < 0.05). The present study demonstrates that downregulation of the PI3K/Akt/eNOS signaling pathway is involved in MED.

Topics: Animals; Biomarkers; Cyclic GMP; Diet, High-Fat; Disease Models, Animal; Enzyme Activation; Epidermal Growth Factor; Erectile Dysfunction; Fluorescent Antibody Technique; Immunohistochemistry; Male; Metabolic Syndrome; Nitric Oxide Synthase Type III; Penile Erection; Phosphatidylinositol 3-Kinases; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats; Signal Transduction

Phosphodiesterase 5 (PDE5) inhibitors can be used for the treatment of erectile dysfunction and pulmonary hypertension. In order to search for new leads of PDE5 inhibitors, we investigated the chemical constituents of the tubers of Eulophia macrobulbon (E.C. Parish & Rchb. f.) Hook. f. A new phenanthrene, 9,10-dihydro-4-(4'-hydroxybenzyl)-2,5-dimethoxyphenanthrene-1,7-dio (1) and three known phenanthrenes i.e., 1-(4'-hydroxybenzyl)-4,8- dimethoxyphenanthrene-2,7-diol (2), (9,10-dihydro-2,5-dimethoxyphenanthrene-1,7-diol (3) and 1,5,7-trimethoxyphenanthrene-2,6-diol). (4) were isolated Among these, 2 was the most potent PDE5 inhibitor (IC₅₀ =1.67±0.54 μM) evaluated by the [3H]cGMP radioassay method, whereas 1 showed mild activity (IC₅₀ = 62.3±3.3 μM). Their inhibitory selectivities against PDE5 over PDE6 were also studied. This study suggests phenanthrenes as a new class of PDE5 inhibitors.

Topics: Animals; Cyclic GMP; Erectile Dysfunction; Lung; Male; Molecular Structure; Orchidaceae; Phenanthrenes; Phosphodiesterase 5 Inhibitors; Plant Extracts; Plant Roots; Rats; Substrate Specificity

The present study aimed to investigate effects of rutin on diabetic-induced impairments of sexual behaviour, spermatogenesis and oxidative testicular damage. Diabetes was induced by a single injection of STZ (65 mg/kg) in male adult Wistar rats. Two weeks later, rutin (50 and 100 mg kg

Topics: Animals; Antioxidants; Cell Survival; Cyclic GMP; Diabetes Mellitus, Experimental; Disease Models, Animal; Erectile Dysfunction; Lipid Peroxidation; Male; Oxidative Stress; Penis; Rats; Rats, Wistar; Rutin; Sexual Behavior, Animal; Sperm Count; Sperm Motility; Spermatozoa; Testis; Testosterone

Our previous studies had reported that Human Tissue Kallikrein 1 (hKLK1) preserved erectile function in aged transgenic rats, while the detailed mechanism of hKLK1 protecting erectile function in aged rats through activation of cGMP and cAMP was not mentioned. To explore the latent mechanism, male wild-type Sprague-Dawley rats (WTR) and transgenic rats harboring the hKLK1 gene (TGR) were fed to 4 and 18 months old and divided into four groups: young WTR (yWTR) as the control, aged WTR (aWTR), aged TGR (aTGR) and aged TGRs with HOE140 (aTGRH). Erectile function of all rats was evaluated by cavernous nerve electrostimulation method and measured by the ratio of intracavernous pressure/ mean arterial pressure (ICP/MAP) in rats. Expression levels of cAMP and cGMP were assessed, and related signaling pathways were detected by western blot, immunohistochemistry and RT-PCR. Our experiment results showed erectile function of the aWTR group and aTGRH group was lower compared with those of other two groups. Also, expression levels of cAMP and cGMP were significantly lower than those of other two groups. Moreover, expressions of related signaling pathways including DDAH/ADMA/NOS/cGMP and COX-2/PTGIS/cAMP were also downregulated in the corpus cavernosum of rats in aWTR group. Our finding revealed hKLK1 played a protective role in age-related ED. The DDAH/ADMA/NOS/cGMP and COX-2/PTGIS/cAMP pathways that were linked to the mechanism hKLK1 could increase the levels of cGMP and cAMP, which might provide novel therapy targets for age-related ED.

Topics: Aging; Amidohydrolases; Animals; Arginine; Cyclic AMP; Cyclic GMP; Cyclooxygenase 2; Cytochrome P-450 Enzyme System; Erectile Dysfunction; Humans; Intramolecular Oxidoreductases; Male; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penile Erection; Penis; Rats; Rats, Sprague-Dawley; Rats, Transgenic; Recombinant Proteins; RNA, Messenger; Signal Transduction; Tissue Kallikreins

This study was aimed to analyze the potential role of Corin in the procession of diabetic ED and to explore the underlying mechanism. Diabetic ED rat model was constructed and the characteristics of diabetic ED and control rats were recorded at 4, 8, 12, and 16 weeks. qRT-PCR and Western bloting were used to detected the mRNA and protein levels. Intracellular cGMP detection was accomplished using a commercial radioimmunoassay method. Vascular endothelial cell from rat corpus cavernosum spiral artery was isolated and transfected with si- Corin to analyzed the potential role of Corin. Cell viability was assessed using crystal violet. The results showed that diabetic ED rats showed significantly higher glucose level, and lower body weight, ICP level, and ICP/MAP ratio at 12 and 16 weeks in diabetic ED rats compared with control rats. The protein levels of Corin, atrial natriuretic peptide (ANP) and eNOS, and the level of cGMP were significantly down-regulated in corpus cavernosum in diabetic ED rats, revealing the potential role of Corin in NO-associated diabetic ED. Further, studies proved that defect of Corin not only inhibited the vascular endothelial cell viability in high-glucose condition, but also suppressed ANP, eNOS, and cGMP expression in vascular endothelial cells. To sum up, Corin contributes to the progression of diabetic ED and the underlying mechanism is associated with the down-regulation of ANP /NO/cGMP signal pathway. J. Cell. Biochem. 118: 2325-2332, 2017. © 2017 Wiley Periodicals, Inc.

Topics: Animals; Arterial Pressure; Atrial Natriuretic Factor; Blood Pressure; Cell Survival; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Male; Nitrogen Oxides; Rats; Rats, Sprague-Dawley; Serine Endopeptidases

The nitric oxide (NO), soluble guanylate cyclase (sGC), and cyclic guanosine monophosphate (cGMP) pathway is the leading pathway in penile erection.. To assess erectile function in a mouse model in which sGC is deficient in heme (apo-sGC) and unresponsive to NO.. Mutant mice (sGCβ. In vitro and in vivo recordings of erectile responses in sGCβ. NO-induced responses were abolished in sGCβ. Our results suggest that sGC is the sole target of NO in erectile physiology. Furthermore, this study provides indirect evidence that, in addition to sGCα

Topics: Animals; Cyclic GMP; Disease Models, Animal; Erectile Dysfunction; Guanylate Cyclase; Heme; Humans; Male; Mice; Nitric Oxide; Penile Erection; Penis; Soluble Guanylyl Cyclase

Intracellular cyclic guanosine monophosphate (cGMP) concentrations are regulated by degradation enzymes (phosphodiesterases) and by active transport across the plasma membrane by multidrug resistance proteins (MRPs) 4 and 5.. To evaluate the functional effect of MRP-4 inhibition and the role of MRP-4-mediated cGMP export in mouse corpora cavernosa.. Isometric tension of mouse corpora cavernosa was measured after cumulative addition of MK-571, an inhibitor of MRP-4, or sildenafil, a phosphodiesterase type 5 inhibitor. In addition, the effect of MRP-4 inhibition on cGMP-independent and cGMP-dependent relaxations was studied. In vivo intracavernosal pressure and mean arterial pressure measurements were performed after intracavernosal injection of MK-571. The effect of MRP-4 inhibition on cGMP content was determined using an enzyme immunoassay kit.. Measurement of the effect of MK-571 on cGMP content, relaxant responses of mouse corpora cavernosa to cGMP-independent and cGMP-dependent vasodilating substances, and determination of the ratio of intracavernosal pressure to mean arterial pressure after intracavernosal injection of MK-571.. MK-571 and sildenafil relaxed the corpora cavernosa concentration dependently, with sildenafil being the more potent relaxing compound. Furthermore, MK-571 enhanced relaxing responses to cGMP-dependent substances, such as sodium nitroprusside, sildenafil, acetylcholine, and electrical field stimulation, with the latter even under in vitro diabetic conditions. In contrast, cGMP-independent relaxations were not altered by MRP-4 inhibition. Intracavernosal administration of MK-571 significantly increased intracavernosal pressure, with minimal effect on mean arterial pressure. The cGMP analysis showed that MRP-4 inhibition was accompanied by increased cGMP levels.. MRP-4, at least when targeted locally in the penis or when combined with a phosphodiesterase type 5 inhibitor, might be a valuable alternative strategy for the treatment of (diabetic) erectile dysfunction.. This study is the first to demonstrate an in vitro direct relaxant and an in vivo pro-erectile effect of the MRP-4 inhibitor, MK-571, on mouse corpora cavernosa. However, the functional effect of MRP-5-mediated export in mouse corpora cavernosa was not explored, which has been suggested to play the predominant role in cGMP export.. Inhibition of MRP-4 increases basal and stimulated levels of cGMP, leading to corpora cavernosa relaxation and penile erection. Therefore, in addition to degradation of cGMP, export of cGMP by MRP-4 could contribute substantially to regulating cGMP levels in mouse corpora cavernosa. Boydens C, Pauwels B, Vanden Daele L, Van de Voorde J. Inhibition of Cyclic GMP Export by Multidrug Resistance Protein 4: A New Strategy to Treat Erectile Dysfunction? J Sex Med 2017;14:502-509.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B; Cyclic GMP; Dose-Response Relationship, Drug; Erectile Dysfunction; Male; Mice; Multidrug Resistance-Associated Proteins; Nitric Oxide; Nitroprusside; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Phosphoric Diester Hydrolases; Sildenafil Citrate

Molecular mechanisms of the beneficial effects of angiotensin-(1-7), Ang-(1-7), in diabetes-related complications, including erectile dysfunction, remain unclear. We examined the effect of diabetes and/or Ang-(1-7) treatment on vascular reactivity and cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE) in corpus cavernosum. Male Wistar rats were grouped as (1) control, (2) diabetic (streptozotocin, STZ, treated), (3) control + Ang-(1-7), and (4) diabetic + Ang-(1-7). Following 3 weeks of Ang-(1-7) treatment subsequent to induction of diabetes, rats were sacrificed. Penile cavernosal tissue was isolated to measure vascular reactivity, PDE gene expression and activity, and levels of p38MAP kinase, nitrites, and cGMP. Carbachol-induced vasorelaxant response after preincubation of corpus cavernosum with PE was significantly attenuated in diabetic rats, and Ang-(1-7) markedly corrected the diabetes-induced impairment. Gene expression and activity of PDE and p38MAP kinase were significantly increased in cavernosal tissue of diabetic rats, and Ang-(1-7) markedly attenuated STZ-induced effects. Ang-(1-7) significantly increased the levels of nitrite and cGMP in cavernosal tissue of control and diabetic rats. Cavernosal tissue of diabetic rats had significantly reduced cGMP levels and Ang-(1-7) markedly prevented the STZ-induced cGMP depletion. This study demonstrates that attenuation of diabetes-induced PDE activity might be one of the key mechanisms in the beneficial effects of Ang-(1-7).

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Angiotensin I; Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Down-Regulation; Erectile Dysfunction; Gene Expression Regulation, Enzymologic; Male; Nitrites; p38 Mitogen-Activated Protein Kinases; Penis; Peptide Fragments; Rats; Rats, Wistar; Risk Factors

To explore aging-related changes in erectile function and the expressions of SIRT1 and other relevant factors in rats.. We divided 40 male SD rats into four age groups of equal number: 2-month-old (2 mo), 8-month-old (8 mo), 14-month-old (14 mo), and 20-month-old (20 mo), measured the intracavernous pressure (ICP), mean arterial pressure (MAP), and ICP/MAP ratio by electrostimulation of the cavernous nerve, evaluated fibrosis in the corpus cavernosum by Masson's trichrome staining, detected the expressions of SIRT1, P53, and FOXO3a by Western blot, and determined the levels of NO and cGMP using the NO/cGMP kit.. Both the ICP/MAP ratio and the cGMP level were elevated with aging, reaching the peak at 8 months and then gradually decreased. Masson staining showed an aging-related increase of collagen fibers in the corpus cavernosum.The expression of SIRT1 was reduced while those of P53 and FOXO3a increased with aging.. Aging-related erectile dysfunction may be attributed to the reduced activity of the NO/cGMP pathway, apoptosis and oxidative stress, and SIRT1 may play a role in aging-related erectile dysfunction.. 目的： 研究衰老过程中大鼠勃起功能变化、抗衰老蛋白SIRT1表达及其相关因子改变，探索SIRT1与老年性勃起功能障碍(ED)发生的关系。方法: SD大鼠按不同月龄分组，利用电刺激大鼠盆腔星状神经节法测定阴茎海绵体内压（ICP）,颈动脉穿刺测定平均动脉压（MAP），ICP/MAP作为勃起功能的评价指标；马松染色观察胶原纤维变化；Western印迹测定不同月龄大鼠阴茎海绵体中SIRT1、P53及FOXO3a的表达变化；NO、cGMP检测试剂盒测定阴茎海绵体中NO、cGMP含量。结果： 随月龄增长，大鼠勃起功能（ICP/MAP）在8月龄达到峰值，其后随月龄增长降低。cGMP含量变化与勃起功能一致。随月龄增加，大鼠阴茎海绵体中胶原纤维增多。SIRT1的表达随月龄增加不断降低；而凋亡因子P53、氧化应激因子FOXO3a的表达随月龄增加不断上升。结论： NO/cGMP通路活性降低、凋亡及氧化应激可能是衰老导致ED的原因。抗衰老蛋白SIRT1与其调控的凋亡、氧化应激因子改变与勃起功能一致，推测SIRT1与老年性ED的发病有关。.

Topics: Aging; Animals; Apoptosis; Cyclic GMP; Erectile Dysfunction; Fibrosis; Forkhead Box Protein O3; Male; Nitric Oxide; Oxidative Stress; Penile Erection; Penis; Rats; Rats, Sprague-Dawley; Sirtuin 1; Tumor Suppressor Protein p53

It was investigated whether short hairpin ribonucleic acid constructs targeting insulin-like growth factor binding protein-3 (IGFBP-3 shRNA) can rehabilitate dyslipidaemia in streptozotocin-induced diabetic rats. After 12 weeks of intracavernous administration of IGFBP-3 shRNA, intracavernous pressure responses to electrical stimulation of cavernous nerves were evaluated. The concentrations of serum low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride and cavernous cyclic guanosine monophosphate were all detected by enzyme-linked immunosorbent assay. The per cent of smooth muscle in corpus cavernous tissue was also evaluated. It was found that the cavernosal pressure was significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic control group after 12 weeks of intracavernous administration of IGFBP-3 shRNA (P < 0.01). The concentrations of serum low-density lipoprotein cholesterol and triglyceride were significantly decreased in the IGFBP-3 shRNA treatment group compared to the diabetic control group, while no significant changes of serum high-density lipoprotein cholesterol concentration were found (P < 0.01). At the same time, cavernous cyclic guanosine monophosphate concentrations and the percentage of cavernosal smooth muscle were both significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic control group (P < 0.01). This study indicated that IGFBP-3 shRNA might rehabilitate erectile function via a decrease in concentrations of serum low-density lipoprotein and triglyceride, an increase in the percentage of cavernosal smooth muscle and an improvement in the nitric oxide-cyclic guanosine monophosphate signalling activities in streptozotocin-induced diabetic rats.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Dyslipidemias; Enzyme-Linked Immunosorbent Assay; Erectile Dysfunction; Gene Knockdown Techniques; Insulin-Like Growth Factor Binding Protein 3; Lipoproteins, HDL; Lipoproteins, LDL; Male; Muscle, Smooth; Nitric Oxide; Penile Erection; Penis; Rats; RNA, Small Interfering; Triglycerides

Topics: Animals; Arteries; Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Phosphodiesterase 5 Inhibitors

We investigated the role of insulin-like growth factor-1 (IGF-1) in spontaneously hypertensive rats with erectile dysfunction. Firstly, we evaluated intracavernous pressure. The bioavailability of IGF-1 at both mRNA and protein levels were measured by quantitative real-time PCR and Western blot respectively. Then, cavernous cyclic guanosine monophosphate concentrations were detected by enzyme-linked immunosorbent assay. The cavernosal pressure was significantly decreased in the hypertensive and the propranolol treatment groups compared to the normal control group (P < 0.01). Cavernous IGF-1 bioavailability and the concentrations of cavernous cyclic guanosine monophosphate were both significantly decreased in the hypertensive and the propranolol treatment groups compared to the normal control group (P < 0.01). This study suggests that an obvious decrease in cavernous IGF-1 levels might play an important role in spontaneously hypertensive rats with erectile dysfunction.

Topics: Animals; Antihypertensive Agents; Blotting, Western; Cyclic GMP; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Erectile Dysfunction; Humans; Hypertension; Insulin-Like Growth Factor I; Male; Penis; Propranolol; Rats; Rats, Inbred SHR; Real-Time Polymerase Chain Reaction; RNA, Messenger

Erectile dysfunction is highly prevalent in type II diabetes mellitus. Low intensity extracorporeal shock wave therapy improves erectile function in patients with erectile dysfunction of vasculogenic origin, including diabetes. However, its mode of action remains unknown. We investigated the effects of low intensity extracorporeal shock wave therapy compared to or combined with sildenafil on erectile dysfunction in a type II diabetes mellitus model. Our purpose was to test our hypothesis of a mode of action targeting the cavernous nitric oxide/cyclic guanosine monophosphate pathway.. GK rats, a validated model of type II diabetes mellitus, and age matched Wistar rats were treated with low intensity extracorporeal shock wave therapy twice weekly for 3 weeks. Treatment was repeated after a 3-week no-treatment interval. The penis was stretched and dipped in a specifically designed water-filled cage. Shock waves were delivered by a calibrated probe yielding a controlled energy flux density (0.09 mJ/mm(2)). The probe was attached to an electrohydraulic unit with a focused shock wave source, allowing for accurate extrapolation to humans. Following a 4-week washout period erectile function was assessed as well as endothelium dependent and independent, and nitrergic relaxations of the corpus cavernosum of GK rats.. Low intensity extracorporeal shock wave therapy significantly improved erectile function in GK rats to the same extent as sildenafil. Treatment effects were potentiated when combined with sildenafil. Shock wave effects were not associated with improved cavernous endothelium dependent or independent, or nitrergic reactivity.. Low intensity extracorporeal shock wave therapy improved erectile function in GK rats. Unexpectedly, this was not mediated by a nitric oxide/cyclic guanosine monophosphate dependent mechanism. Sildenafil increased shock wave efficacy. This preclinical paradigm to deliver low intensity extracorporeal shock wave therapy to the rat penis should help further exploration of the mode of action of this therapy on erectile tissue.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Disease Models, Animal; Erectile Dysfunction; Extracorporeal Shockwave Therapy; Male; Nitric Oxide; Penile Erection; Rats, Wistar; Signal Transduction

To evaluate the effect of Schisandrol A on rabbit corpus cavernosum smooth muscle and elucidate the potential mechanism. Penises were obtained from healthy male New Zealand White rabbits (2.5-3.0 kg). The pre-contracted penis with phenylephrine (Phe, 10 µM) was treated with accumulative concentrations of Schisandrol A (10-7, 10-6, 10-5 and 10-4 M). The change in intracavernosum pressure (ICP) and tension was recorded, cyclic nucleotides in the cavernosum tissue were measured by radioimmunoassay, mRNA level and expression of endothelial nitric oxide synthase (eNOS) and neuronal NOS (nNOS) were measured by real time PCR and western blot respectively. The corpus cavernosum smooth muscle relaxation induced by Schisandrol A was in a dose-dependent manner. Pre-treatment with NOS inhibitor (Nω nitro-L-arginine-methyl ester, L-NAME) or guanylyl cyclase inhibitor (1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one, ODQ) significantly diminished the relaxation. The cyclic guanosine monophosphate (cGMP) level was significantly increased in the cavernosum tissue. Real time PCR and western blot showed the mRNA level and expression of eNOS and nNOS was also upregulated. Schisandrol A relaxes the cavernosum smooth muscle by activating NO-cGMP signaling pathway. It may be a new promising treatment for erectile dysfunction and cardiovascular disease.

Topics: Animals; Cyclic GMP; Cyclooctanes; Erectile Dysfunction; Gene Expression Regulation; Lignans; Male; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penis; Rabbits; Schisandra; Signal Transduction

Human tissue kallikrein 1 (hKLK1) has enormous potential for the protection of vasodilation and endothelial function in the cardiovascular system. Our previous study proved the decreased expression of kallikrein 1 in the corpus cavernosum (CC) of aged rats, but the role of kallikrein 1 in age-related erectile dysfunction remains unknown.. To explore the effect and underlying mechanisms of hKLK1 on age-related erectile dysfunction.. Male wild-type Sprague-Dawley rats (WTR) and transgenic rats harboring the hKLK1 gene (TGR) were fed to 4 and 27 months of age, respectively, and divided into four groups: young WTR (yWTR) as the control, young TGR (yTGR), aged WTR (aWTR), and aged TGR (aTGR). Rats' erectile function was evaluated by the cavernous nerve electrostimulation method. Then, CCs were collected for verification of hKLK1 followed by measurement of nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) and RhoA-Rho-kinase (ROCK) signaling activities. Masson trichrome staining and terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick end labeling assay were conducted to evaluate penile fibrosis and apoptosis.. Erectile response, NO-cGMP and RhoA-ROCK pathway-related indices, ratio of smooth muscle to collagen, and apoptosis index.. The hKLK1 alleviated the decrease of erectile function in the aWTR group. Endothelial NO synthase (eNOS) and phospho-eNOS(Ser1177) expressions, NO synthase activity, and NO and cGMP levels were decreased, whereas phospho-eNOS(Thr495), L-type Ca(2+) channel, RhoA, ROCK1, ROCK2, and transforming growth factor β1 proteins were increased in the CCs of the aWTR group compared with the control yWTR group. These changes were obviously mitigated in the aTGR group. Moreover, hKLK1 prevented the sharp decrease of the ratio of smooth muscle to collagen and the increase of the apoptosis index in the CCs of the aWTR group.. These results suggest that hKLK1 could play a preventive role in age-related erectile dysfunction by activation of the NO-cGMP pathway and inhibition of the RhoA-ROCK pathway and by antitissue fibrotic and apoptotic effects.

Topics: Animals; Cyclic GMP; Erectile Dysfunction; In Situ Nick-End Labeling; Lim Kinases; Male; Nitric Oxide Synthase Type III; Penile Erection; Penis; Rats; Rats, Sprague-Dawley; Rats, Transgenic; rho-Associated Kinases; Tissue Kallikreins; Transforming Growth Factor beta1

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is an independent risk factor for the development of erectile dysfunction (ED). But the molecular mechanisms underlying the relationship between CP/CPPS and ED are still unclear. The aim of this study was to investigate the effect of CP/CPPS on erectile function in a rat model and the possible mechanisms. A rat model of experimental autoimmune prostatitis (EAP) was established to mimic human CP⁄CPPS. Then twenty 2-month-old male Sprague-Dawley rats were divided into EAP group and control group. Intracavernosal pressure (ICP) and mean arterial pressure (MAP) were measured during cavernous nerve electrostimulation, the ratio of max ICP/MAP was calculated. Blood was collected to measure the levels of serum C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and testosterone, respectively. The expression of endothelial nitric oxide synthase (eNOS), cyclic guanosine monophosphate (cGMP) levels, superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels in corpus cavernosum were detected. We also evaluated the smooth muscle/collagen ratio and apoptotic index (AI). The ratio of max ICP/MAP in EAP group were significantly lower than that in control group. The levels of serum CRP, TNF-α, IL-1β, and IL-6 in EAP group were all significantly higher than these in control group. The expression of eNOS and cGMP levels in corpus cavernosum of EAP rats were significantly downregulated. Furthermore, decreased SOD activity and smooth muscle/collagen ratio, increased MDA levels and AI were found in corpus cavernosum of EAP rats. In conclusion, CP/CPPS impaired penile erectile function in a rat model. The declines of eNOS expression and cGMP levels in corpus cavernosum may be an important mechanism of CP/CPPS-induced ED. CP/CPPS also increased oxidative stress, cell apoptosis and decreased smooth muscle/collagen ratio in corpus cavernosum of rats, which were all important for erectile function.

Topics: Animals; Apoptosis; C-Reactive Protein; Cyclic GMP; Disease Models, Animal; Endothelium, Vascular; Erectile Dysfunction; Fibrosis; Interleukin-1beta; Interleukin-6; Male; Malondialdehyde; Muscle, Smooth, Vascular; Nitric Oxide Synthase Type III; Oxidative Stress; Pelvic Pain; Penile Erection; Penis; Prostatitis; Rats; Rats, Sprague-Dawley; Superoxide Dismutase; Testosterone; Tumor Necrosis Factor-alpha

There is no consensus on the best oral phosphodiesterase type 5 inhibitor (PDE5I) for patients undergoing penile rehabilitation after surgical nerve injury.. To determine the mechanism of PDE5I on cultured neuronal cells and the effectiveness of local drug delivery using nanospheres (NSPs) to sites of nerve injury in a rat model of bilateral cavernous nerve injury (BCNI).. The effects of sildenafil, tadalafil, and vardenafil on cyclic adenosine monophosphate, cyclic guanosine monophosphate, and cell survival after exposure to hypoxia and H. Viability of neuronal cells was measured. Intracavernous pressure changes after cavernous nerve electrostimulation and expression of neurofilament, nitric oxide synthase, and actin in mid-shaft of penis were analyzed 14 days after injury.. Sildenafil and rolipram significantly decreased cell death after exposure to H. Sildenafil showed the most profound neuroprotective effect compared with tadalafil and vardenafil. Sildenafil- or rolipram-loaded NSP delivery to the site of nerve injury prevented erectile dysfunction and led to increased neurofilament, nitric oxide synthase, smooth muscle content in rat penile tissue after BCNI.

Topics: Animals; Cyclic GMP; Erectile Dysfunction; Humans; Hydrogen Peroxide; Male; Muscle, Smooth; Nitric Oxide Synthase; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Prostatectomy; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Trauma, Nervous System

The efficacy of a novel curcumin derivative (NCD) versus tadalafil in erectile signalling was assessed. Ten control male rats and 50 diabetic male rats were used and divided into the following: diabetic (DM), curcumin (CURC), NCD, tadalafil and NCD combined with tadalafil rat groups. Cavernous tissue gene expression of heme oxygenase-1 (HO-1), Nrf2, NF-B and p38, enzyme activities of heme oxygenase (HO) and nitric oxide synthase (NOS), cGMP and intracavernosal pressure (ICP)/mean arterial pressure (MAP) were assessed. Results showed that 12 weeks after induction of diabetes, erectile dysfunction (ED) was confirmed by the significant decrease in ICP/MAP, a significant decrease in cGMP, NOS, HO enzyme activities, a significant decrease in HO-1 gene and a significant increase in NF-Ҡβ, p38 genes. Administration of all therapeutic interventions led to a significant increase in ICP/MAP, cGMP levels, a significant increase in HO-1 and NOS enzymes, a significant increase in HO-1, and Nrf2 gene expression, and a significant decrease in NF-Ҡβ, p38 gene expression. NCD or its combination with tadalafil showed significant superiority and more prolonged duration of action. In conclusion, a tendency was observed that CURC and NCD have high efficacy and more prolonged duration of action in enhancing erectile function.

Topics: Animals; Curcumin; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Heme Oxygenase-1; Male; NF-E2-Related Factor 2; NF-kappa B; Nitric Oxide Synthase; p38 Mitogen-Activated Protein Kinases; Penis; Phosphodiesterase 5 Inhibitors; Rats; Tadalafil

To investigate the effect of sildenafil on platelet function and cyclic guanosine monophosphate (cGMP) levels in patients with erectile dysfunction, we evaluated the association between erectile function and platelet responses after administration of 100 mg sildenafil. Erectile responses were monitored after 8 daily doses of the drug. Adenosine diphosphate (ADP) and collagen-induced platelet aggregation and simultaneous adenosine triphosphate (ATP) release and cGMP levels were determined before and after sildenafil therapy. Basal levels for platelet aggregation, ATP release and cGMP were compared with age-matched controls. There was no difference among basal levels of platelet responses between patients and controls, except for ADP-induced platelet aggregation (P = 0.04). It was significantly higher in the patient group. Analysis of the responses to sildenafil revealed that for the patients who showed a positive erectile response, there was a significant increase in platelet cGMP (P = 0.028) and a decrease in ADP-induced platelet aggregation (P = 0.04). However, for those who showed a negative or poor erectile response, there was no change in platelet cGMP levels and platelet functions. Sildenafil did not affect collagen-induced platelet responses although cGMP levels of the responders increased. It is concluded that sildenafil increases platelet cGMP in the patients with positive erectile response. Therefore, it has been speculated that platelet cGMP may be used as an index for erectile response.

Topics: Adult; Aged; Blood Platelets; Case-Control Studies; Cyclic GMP; Erectile Dysfunction; Humans; Male; Middle Aged; Phosphodiesterase 5 Inhibitors; Platelet Aggregation; Sildenafil Citrate

The aim of this study was to determine if shRNA constructs targeting insulin-like growth factor binding protein-3 can rehabilitate decreased serum testosterone concentrations in streptozotocin-induced diabetic rats.. After 12 weeks of intracavernous administration of IGFBP-3 shRNA, intracavernous pressure responses to electrical stimulation of cavernous nerves were evaluated. The expression of IGFBP-3 at mRNA and protein levels was detected by quantitative real-time PCR analysis and Western blot, respectively. The concentrations of serum testosterone and cavernous cyclic guanosine monophosphate were detected by enzyme-linked immunosorbent assay.. After 12 weeks of intracavernous administration of IGFBP-3 shRNA, the cavernosal pressure was significantly increased in response to the cavernous nerves stimulation compared to the diabetic control group (p<0.01). Cavernous IGFBP-3 expression at both mRNA and protein levels was significantly inhibited. Both serum testosterone and cavernous cyclic guanosine monophosphate concentrations were significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic control group (p<0.01).. These results suggest that IGFBP-3 shRNA may rehabilitate erectile function via increases of concentrations of serum testosterone and cavernous cyclic guanosine monophosphate in streptozotocin-induced diabetic rats.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Electric Stimulation; Enzyme-Linked Immunosorbent Assay; Erectile Dysfunction; Insulin-Like Growth Factor Binding Protein 3; Male; Methyltestosterone; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Testosterone

To characterise the relaxation induced by the soluble guanylate cyclase (sGC) activator, BAY 60-2770 (4-({(4-carboxybutyl) [2- (5-fluoro-2-{[4'-(trifluoromethyl) biphenyl-4-yl]methoxy}phenyl)ethyl] amino}methyl)benzoic acid) in rabbit corpus cavernosum (CC).. The penis from male New Zealand rabbits was removed and fours strips of CC were obtained. Concentration-response curves to BAY 60-2770 were constructed in the absence and presence of inhibitors of nitric oxide synthase, N (G)-nitro-L- arginine methyl ester (L-NAME, 100 μm), sGC, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 μm) and phosphodiesterase type 5 (PDE-5), tadalafil (0.1 μm). The potency (pEC50 ) and maximal response (Emax ) values were determined. Then, electrical-field stimulation (EFS)-induced contraction or relaxation was tested in the absence and presence of BAY 60-2770 (0.1 or 1 μm) alone or combined with ODQ (10 μm). For EFS-induced relaxation two protocols were used: (i) ODQ (10 μm) was first incubated for 20 min and then BAY 60-2770 (1 μm) was added for another 20 min (ODQ + BAY 60-2770); (ii) in different CC strips, BAY 60-2770 was incubated for 20 min followed by another 20 min with ODQ (BAY 60-2770 + ODQ). The intracellular levels of cyclic guanosine monophosphate (cGMP) were also determined.. BAY 60-2770 potently relaxed rabbit CC with mean (sem) pEC50 and Emax values of 7.58 (0.19) and 81 (4)%, respectively. The inhibitors ODQ (n = 7) or tadalafil (n = 7) produced 4.2- and 6.3-leftward shifts, respectively in BAY 60-2770-induced relaxation without interfering with the Emax values. The intracellular levels of cGMP were augmented after stimulation with BAY 60-2770 (1 μm) alone, whereas its co-incubation with ODQ produced even higher levels of cGMP. The EFS-induced contraction was reduced in the presence of BAY 60-2770 (1 μm) and this inhibition was even greater when BAY 60-2770 was co-incubated with ODQ. The nitrergic stimulation induced CC relaxation, which was abolished in the presence of ODQ. BAY 60-2770 alone increased the amplitude of relaxation. Co-incubation of ODQ and BAY 60-2770 did not alter the relaxation in comparison with ODQ alone. Interestingly, when BAY 60-2770 was incubated before ODQ, EFS-induced relaxation was partly restored in comparison with ODQ alone or ODQ + BAY 60-2770.. The relaxation induced by the sGC activator, BAY 60-2770 was increased after sGC oxidation and unaltered in the absence of nitric oxide. Thus, this class of substances may have advantages over sGC stimulators or PDE-5 inhibitors for treating patients with erectile dysfunction and extensive endothelial damage.

Topics: Animals; Benzoates; Biphenyl Compounds; Cyclic GMP; Erectile Dysfunction; Guanylate Cyclase; Hydrocarbons, Fluorinated; Male; Muscle Contraction; Muscle Relaxation; Penis; Rabbits; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase

To establish a feasible rat model of radiation-induced erectile dysfunction after targeted prostate irradiation using an image-guided irradiation unit specially designed for small-animal radiation research.. The X-RAD 225Cx research platform was used in the present study. We first performed quality assurance testing using a rat cadaver. After confirming dosimetry, 24 age-matched, young, adult, male rats were assigned to sham radiation or radiation to the prostate with doses of 15, 20, or 25 Gy. To confirm appropriate prostate irradiation, physiological erectile function was evaluated using intracavernous pressure (ICP) measurements with cavernous nerve electrical stimulation at 9 weeks after radiotherapy. Each animal was weighed at the time of ICP measurement. In addition, we investigated the cyclic guanosine monophosphate level in the penile cavernosa using a commercial enzyme-linked immunosorbent assay kit.. Quality assurance results confirmed the accuracy of the irradiation technique. Dose-dependent decreases in ICP in irradiated rats were observed without major toxicity. No difference in body weight was noted among the experimental groups. Cyclic guanosine monophosphate levels were significantly decreased in the group that received 25 Gy compared with the age-matched sham-irradiated group.. High-precision imaging and targeting capabilities provided by the micro-IGRT platform enable us to develop a reproducible animal model of radiation-induced erectile dysfunction in prostate cancer research.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Erectile Dysfunction; Male; Penis; Pilot Projects; Prostate; Radiation Dosage; Radiation Injuries; Rats; Rats, Sprague-Dawley

Precise spatiotemporal control of physiological processes by optogenetic devices inspired by synthetic biology may provide novel treatment opportunities for gene- and cell-based therapies. An erectile optogenetic stimulator (EROS), a synthetic designer guanylate cyclase producing a blue-light-inducible surge of the second messenger cyclic guanosine monophosphate (cGMP) in mammalian cells, enabled blue-light-dependent penile erection associated with occasional ejaculation after illumination of EROS-transfected corpus cavernosum in male rats. Photostimulated short-circuiting of complex psychological, neural, vascular, and endocrine factors to stimulate penile erection in the absence of sexual arousal may foster novel advances in the treatment of erectile dysfunction.

Topics: Animals; Cyclic GMP; Erectile Dysfunction; Guanylate Cyclase; Light; Male; Optogenetics; Penile Erection; Rats

Despite effective control of blood glucose levels in diabetic patients, complaints of diabetes-associated erectile dysfunction (ED) persist. Resveratrol has been indicated to possess anti-diabetic effects and therapeutic potential for ED. This study was conducted to observe the effect of resveratrol alone or in combination with sildenafil on ED in streptozotocin (STZ)-induced diabetic rats.. Among 58 adult male STZ-induced (60 mg/kg) diabetic Sprague-Dawley rats, 48 STZ-induced diabetic rats were randomized equally to four groups: untreated diabetic rats, resveratrol (25mg/kg), sildenafil (5mg/kg) or resveratrol (25mg/kg) plus sildenafil (5mg/kg) through oral gavage for 8 weeks. Additionally, 12 age-matched rats were chosen as controls. Intracavernous pressure (ICP) and mean arterial blood pressure (MAP) were used to measure erectile function. The cavernous level of cyclic guanosine monophosphate (cGMP), protein and mRNA of endothelial NO synthase (eNOS), neuronal NOS (nNOS), and phosphodiesterase-5 (PDE5) was measured.. Treatment with either resveratrol or sildenafil improved ICP/MAP compared to the untreated diabetic rats (P<0.05). Treatment with resveratrol increased nNOS and eNOS expression, inhibited PDE5 expression, and increased the cavernous cGMP level compared to the untreated diabetic rats. Resveratrol significantly decreased superoxide anion and ROS production. Two-way ANOVA indicated that resveratrol in combination with sildenafil therapy had a significant synergistic effect in improving ICP/MAP and cavernous cGMP levels.. Resveratrol improves diabetes-associated ED in rats. Combination therapies with resveratrol and sildenafil have a synergistic effect in improving ED. The mechanisms might be attributed to its anti-oxidative properties and NO-cGMP signaling pathway upregulation.

Topics: Animals; Antioxidants; Blood Pressure; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Complications; Diabetes Mellitus, Experimental; Erectile Dysfunction; Male; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Resveratrol; Second Messenger Systems; Sildenafil Citrate; Stilbenes; Sulfonamides

We designed a peptide, PnPP-19, comprising the potential active core of the Phoneutria nigriventer native toxin PnTx2-6. We investigated its role on erectile function, and its toxicity and immunogenicity.. Erectile function was evaluated by the intracavernous pressure-to-mean arterial pressure ratio during electrical field stimulation on rat pelvic ganglia. Cavernous strips were contracted with phenylephrine and relaxation was induced by electrical field stimulation with or without PnPP-19 (10(-8) M). Activity on sodium channels was evaluated by electrophysiological screening of transfected channels on Xenopus oocytes and dorsal root ganglion cells. Antibodies were detected by indirect enzyme-linked immunosorbent assay in mice previously treated with the peptide. Histopathological studies were performed with mouse organs treated with different doses of PnPP-19.. PnPP-19 was able to potentiate erection at 4 and 8 Hz in vivo and ex vivo. It showed no toxicity and low immunogenicity in mice, and did not affect sodium channels or rat hearts. PnPP-19 increased cyclic guanosine monophosphate levels at 8 Hz. This effect was inhibited by L-NAME (10(-4) M). Erectile function was partially inhibited by 7-nitroindazole (10(-5) M), a selective inhibitor of neuronal nitric oxide synthase.. PnPP-19 potentiates erection in vivo and ex vivo via the nitric oxide/cyclic guanosine monophosphate pathway. It does not affect sodium channels or rat hearts and shows no toxicity and low immunogenicity. These findings make it a promising candidate as a novel drug in the therapy of erectile dysfunction.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Erectile Dysfunction; Male; Mice; Neuropeptides; Neurotoxins; Nitric Oxide Synthase Type I; Patch-Clamp Techniques; Penile Erection; Rats; Rats, Sprague-Dawley

Erectile dysfunction (ED) is very prevalent in the older population, although the ageing-related mechanisms involved in the development of ED are poorly understood. We propose that age-induced differences in nerve- and endothelium-mediated smooth muscle contractility in the corpus cavernosum (CC) could be found between a senescent-accelerated mouse prone (SAMP8) and senescent-accelerated mouse resistant (SAMR1) strains. We analysed the changes in muscle tension induced by electrical field stimulation (EFS) or agonist addition 'in vitro', assessing nerve density (adrenergic, cholinergic and nitrergic), the expression of endothelial nitric oxide synthase (eNOS), cGMP accumulation and the distribution of interstitial cells (ICs) by immunofluorescence. We observed no change in both the nerve-dependent adrenergic excitatory contractility at physiological levels of stimulation and in the nitrergic inhibitory response in SAMP8 animals. Unlike cholinergic innervation, the density of adrenergic and nitrergic nerves increased in SAMP8 mice. In contrast, smooth muscle sensitivity to exogenous noradrenaline (NA) was slightly reduced, whereas cGMP accumulation in response to EFS and DEA/NO, and relaxations to DEA/NO and sildenafil, were not modified. No changes in the expression of eNOS and in the distribution of vimentin-positive ICs were detected in the aged animals. The ACh induced atropine-sensitive biphasic endothelium-dependent responses involved relaxation at low concentrations that turned into contractions at the highest doses. CC relaxation was mainly because of the production of NO together with some relaxant prostanoid, which did not change in SAMP8 animals. In contrast, the contractile component was considerably higher in the aged animals and it was completely inhibited by indomethacin. In conclusion, a clear imbalance towards enhanced production of contractile prostanoids from the endothelium may contribute to ED in the elderly. On the basis of these data, we propose the senescence-accelerated mouse model as a reliable tool to analyse the basic ageing mechanisms of the CC.

Topics: Aging; Animals; Cyclic GMP; Electric Stimulation; Erectile Dysfunction; Male; Mice; Models, Animal; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Nitric Oxide Synthase Type III; Piperazines; Purines; Sildenafil Citrate; Sulfones

The efficacy of oral pharmacotherapy for erectile dysfunction (ED) (i.e., type 5 phosphodiesterase[PDE5] inhibitors) is significantly reduced in diabetic patients. Nebivolol is a selective β1-blocker used for treatinghy pertension that has been shown to increase the efficacy of sildenafil to reverse ED in diabetic rats.. To evaluate the effects of nebivolol on the efficacy of the PDE5 inhibitors, sildenafil, tadalafil, and vardenafil to relax human corpus cavernosum (HCC) and vasodilate human penile resistance arteries (HPRA) from diabetic patients with ED (DMED). The influence of nebivolol on the capacity of these three PDE5 inhibitors to stimulate cyclic guanosine monophosphate (cGMP) production in HCC was also evaluated.. HCC and HPRA were obtained from organ donors without ED (NEND; n = 18) or patients with diabetes undergoing penile prosthesis implantation (DMED; n = 19). Relaxations of HCC strips and HPRA to sildenafil,tadalafil, and vardenafil were evaluated in organ chambers and wire myographs. cGMP content in HCC was determined by ether extraction and quantification by ELISA.. Effects of nebivolol on PDE5 inhibitor-induced relaxation of HCC, vasodilation ofHPRA and cGMP accumulation in HCC.. Treatment with nebivolol (1 μM) significantly potentiated sildenafil-, tadalafil- and vardenafil-induced relaxations of HCC and vasodilations of HPRA from both NEND and DMED. Enhancement of relaxant capacity by nebivolol resulted in reversion of the impairment of PDE5 inhibition-induced responses in DMED and it was accompanied by enhancing the ability of PDE5 inhibitors to increase cGMP in HCC restoring reduced cGMP levelsin HCC from DMED.. Nebivolol potentiated the capacity of PDE5 inhibitors to relax vascular structures of erectile tissue from diabetic patients by enhancing the nitric oxide (NO)/cGMP pathway in these tissues. These effects suggest a potential therapeutic utility of nebivolol as an adjunct to PDE5 inhibitors for the treatment of ED associated with diabetes.

Topics: Arteries; Benzopyrans; Carbolines; Cyclic GMP; Diabetes Mellitus, Type 2; Drug Synergism; Erectile Dysfunction; Ethanolamines; Humans; Imidazoles; Male; Middle Aged; Muscle Relaxation; Muscle, Smooth, Vascular; Nebivolol; Nitric Oxide; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Vardenafil Dihydrochloride; Vasodilator Agents

Possible effect of olmesartan, an angiotensin II receptor blocker (ARB), or nifedipine, an L-type calcium channel blocker, on penile dysfunction in the spontaneously hypertensive rat (SHR) was investigated in this study. Twelve-week-old male SHRs were treated with olmesartan (1 or 3 mg/kg, per orally (p.o.)) or nifedipine (30 mg/kg, p.o.) once a day for 6 weeks. Wistar rats and SHRs with vehicle treatment were used as controls. Penile cGMP and malondialdehyde concentrations, and mRNA levels of endothelial and neuronal NO synthase (eNOS and nNOS) were measured. Penile function was evaluated by organ bath studies with norepinephrine-induced contractions and acetylcholine-induced relaxations. The SHR showed significantly increased blood pressure, decreased cGMP concentrations, increased malondialdehyde concentrations, decreased eNOS and nNOS mRNA levels, norepinephrine-induced hyper-contractions, and acetylcholine-induced hypo-relaxations in the penile tissue compared to the Wistar rat. Both nifedipine and olmesartan significantly decreased blood pressure, increased cGMP and normalized the hyper-contractions and hypo-relaxations observed in the SHR group. However, not nifedipine but olmesartan improved the malondialdehyde concentrations and increased mRNA levels of eNOS and nNOS in the penis. Our results indicate that the hypertension-associated penile dysfunction might be treated with ARBs such as olmesartan better than calcium channel blockers, such as nifedipine.

Topics: Angiotensin Receptor Antagonists; Animals; Calcium Channel Blockers; Cyclic GMP; Disease Models, Animal; Erectile Dysfunction; Gene Expression; Hypertension; Male; Malondialdehyde; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Rats

To explore the therapeutic potential of PnTx2-6 injected 3 times a week for 4 weeks into the intracavernosal tissue in a rat model of bilateral cavernous nerve crush injury (BCNI).. Eight-week-old male Sprague-Dawley rats were randomly divided into the following 6 groups (n = 5 per group): age-matched control (normal group), BCNI (injury group), post-BCNI phosphate-buffered saline injection (PBS group), post-BCNI Sf9 cell-lysate injection (N/C group), post-BCNI injection of cell lysate from S9 cells infected with wild-type recombinant baculovirus (W/T group), and post-BCNI injection of cell lysate from S9 cells infected with recombinant baculovirus containing PnTx2-6 (PnTx2-6 group). Injections were delivered 3 times a week for 4 weeks. After 4 weeks, intracavernosal pressure-to-mean arterial pressure ratio, smooth muscle and collagen content via the Masson trichrome staining, levels of neural nitric oxide synthase, phosphoendothelial nitric oxide synthase, and cyclic guanosine monophosphate were all measured.. The PnTx2-6 group showed significantly higher intracavernosal pressure-to-mean arterial pressure ratio (P <.05), smooth muscle-to-collagen ratio (P <.01), expression levels of neural nitric oxide synthase, phosphoendothelial nitric oxide synthase (P <.05), and cyclic guanosine monophosphate (P <.05) than all other experimental groups.. We conclude that PnTx2-6 improved erectile function and prevented muscle atrophy in a rat model of BCNI via increased synthesis of nitric oxide and cyclic guanosine monophosphate.

Topics: Animals; Baculoviridae; Cyclic GMP; Disease Models, Animal; Endothelium; Erectile Dysfunction; Insecta; Male; Nerve Crush; Neuropeptides; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Penile Erection; Penis; Rats; Rats, Sprague-Dawley; Spider Venoms; Spiders

Cardiovascular and endocrine-metabolic diseases associated with increased oxidative stress such as obesity lead to erectile dysfunction (ED). Activators of soluble guanylyl cyclase (sGC) such as BAY 60-2770 reactivate the heme-oxidized sGC in vascular diseases.. This study aimed to evaluate the effects of 2-week oral intake with BAY 60-2270 on a murine model of obesity-associated ED.. C57BL/6 male mice were fed for 12 weeks with standard chow or high-fat diet. Lean and obese mice were treated with BAY 60-2770 (1 mg/kg/day, 2 weeks).. Measurements of intracavernosal pressure (ICP), along with acetylcholine (10(-9) to 10(-5)  M) and electrical field stimulation (EFS; 4-10 Hz)-induced corpus cavernosum relaxations in vitro, were obtained. Levels of cyclic guanosine monophosphate (cGMP), reactive oxygen species (ROS), and sGC protein expressions in cavernosal tissues were measured.. Cavernous nerve stimulation caused frequency-dependent ICP increases, which were significantly lower in obese compared with lean mice (P < 0.05). Two-week therapy with BAY 60-2770 fully reversed the decreased ICP in obese group. Acetylcholine-induced cavernosal relaxations were 45% lower (P < 0.001) in obese mice, which were fully restored by BAY 60-2770 treatment. Likewise, the EFS-induced relaxations in obese mice were restored by BAY 60-2770. Basal cGMP content in erectile tissue was 68% lower (P < 0.05) in obese mice, an effect normalized by BAY 60-2770. Levels of ROS were 52% higher (P < 0.05) whereas protein expression of α1 sGC subunit was reduced in cavernosal tissue of obese mice, both of which were normalized by BAY 60-2770. In lean group, BAY 60-2770 did not significantly affect any functional, biochemical, or molecular parameter analyzed.. Two-week therapy with BAY 60-2770 restores the erectile function in obese mice that is associated with reduced ROS levels, up-regulation of α1 sGC subunit, and increased cGMP levels in the erectile tissue.

Topics: Animals; Benzoates; Biphenyl Compounds; Cyclic GMP; Diet, High-Fat; Enzyme Activators; Erectile Dysfunction; Guanylate Cyclase; Humans; Hydrocarbons, Fluorinated; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Obesity; Penile Erection; Penis; Reactive Oxygen Species; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Up-Regulation

To examine the effect of pioglitazone on erectile function in a rat model of postprostatectomy erectile dysfunction.. Twenty adult rats were divided into 4 groups: (a) sham, (b) control--bilateral cavernosal nerve crush injury (BCNI), (c) BCNI + low-dose pioglitazone (PioL), and (d) BCNI + high-dose pioglitazone (PioH). Sham and control rats were administered phosphate-buffered saline, whereas PioL and PioH rats received 0.65 and 6.5 mg/kg of pioglitazone, respectively. All treatments were administered by oral gavage for 14 days. After treatment, animals underwent surgery for endpoint cavernosal response to define hemodynamic parameters of erectile function, reported as the ratio of intracavernosal pressure to mean arterial pressure. Corporal tissue was retrieved for histologic and molecular analysis.. Animals treated with pioglitazone experienced dose-dependent improvements in the ratio of intracavernosal pressure to mean arterial pressure, with the PioH group achieving results similar to the sham group: sham, 0.774; BCNI, 0.421; PioL, 0.616; PioH, 0.758 (P = .0006). PioH animals demonstrated increased expression of endothelial nitric oxide (eNOS) and neuronal nitric oxide (nNOS), whereas both PioL and PioH animals had increased staining for anti--smooth muscle actin antibody and nonsignificant increases in cyclic guanosine monophosphate (cGMP).. Pioglitazone improves erectile function in rats undergoing BCNI via a nitric oxide--mediated pathway.

Topics: Animals; Arterial Pressure; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Erectile Dysfunction; Hemodynamics; Hypoglycemic Agents; Male; Microscopy, Fluorescence; Muscle, Smooth; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penile Erection; Penis; Peripheral Nerve Injuries; Pioglitazone; Rats; Thiazolidinediones; Treatment Outcome

To compare the effects of subcutaneous penile injection of basic fibroblast growth factor (bFGF)-hydrogel and intracavernous injection of human adipose-derived stem cells (h-ADSCs) on improving erectile function in a rat model of cavernous nerve injury.. Adult male Sprague-Dawley rats were randomly divided into 5 groups (n = 10 per group): age-matched control (normal group), bilateral cavernous nerve injury (BCNI group), penile subcutaneous injection of hydrogel after BCNI (hydrogel group), penile subcutaneous injection of bFGF-hydrogel after BCNI (bFGF-hydrogel group) and intracavernous injection of h-ADSCs after BCNI (ADSC group). Four weeks after the treatment, all rats underwent an erectile function test. Then, penile tissue was harvested for immunohistological analysis of bFGF, phalloidin, and cluster of differentiation (CD) 31. The cyclic guanosine monophosphate (cGMP) level of the corpus cavernosum was quantified by cGMP assay.. From the functional test and immunohistological result, we observed that bFGF-hydrogel and h-ADSCs injection significantly elevated intracavernous pressure. The evaluation of filamentous actin content, CD31 expression, and cGMP concentration in the corpus cavernosum were meaningfully increased in the bFGF-hydrogel and ADSC groups compared with BCNI group. The bFGF released from bFGF-hydrogel prevented smooth muscle atrophy. Moreover, bFGF expression was significantly increased in bFGF-hydrogel group.. The subcutaneous injection of bFGF-hydrogel prevented smooth muscle atrophy, increased the intracavernous pressure, and improved erectile function like an intracavernous injection of h-ADSCs.

Topics: Actins; Adipose Tissue; Animals; Cyclic GMP; Erectile Dysfunction; Fibroblast Growth Factor 2; Humans; Hydrogels; Male; Penile Erection; Penis; Platelet Endothelial Cell Adhesion Molecule-1; Prostatectomy; Rats; Rats, Sprague-Dawley; Stem Cells

Overall efficacy rates of phosphodiesterase type 5 inhibitors (PDE5-i) for erectile dysfunction (ED) are 60-70%. PDE5-i treatment failures currently have to resort to invasive treatment options for restoration of erectile function. AIMS.: To assess changes in the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/protein kinase (PKG) pathway in human corpus cavernosum (HCC) of PDE5-i nonresponders compared with healthy controls. To evaluate the effects of BAY 60-4552, a stimulator of soluble guanylate cyclase (sGC), and vardenafil on relaxation of HCC strips from PDE5-i nonresponders.. mRNA expression, morphological localization of the NO/cGMP/PKG pathway, and relaxant capacity of both compounds alone or combined. Analysis of variance, t-test or Mann-Whitney test based upon number of groups and normality of data.. HCC tissues were harvested after consent from individuals undergoing penile prosthesis implantation (patients) and potent patients undergoing transurethral surgery (healthy controls, needle biopsy). HCC tissues of patients were compared with those of healthy controls for the expression of mRNA coding for PDE5A, eNOS, PKGα1, PKG2, sGCα1, sGCα2, sGCβ1, sGCβ2, α-smooth muscle actin (aSMA) and β-actin by quantitative polymerase chain reaction (qPCR). The respective proteins were localized using immunofluorescence. Tissue strips of patients were precontracted with phenylepinephrine followed by incubation with 1 μM of either vardenafil or BAY 60-4552, or both simultaneously.. The main targets in the NO/cGMP/sGC pathway were downregulated in PDE5-i nonresponders. The pathway was morphologically located to HCC smooth muscle, of which the overall content was preserved in ED patients based on aSMA expression. BAY 60-4552 and vardenafil have synergistic effects on relaxation of HCC of PDE5-i nonresponders. The main limitation is the small amount of control tissue precluding functional testing on these samples.. Despite downregulation of the NO/cGMP/PKG pathway, combining BAY 60-4552 with vardenafil significantly enhanced relaxation HCC strips of PDE5-i nonresponders.

Topics: Actins; Cyclic GMP; Drug Synergism; Erectile Dysfunction; Guanylate Cyclase; Humans; Imidazoles; Male; Middle Aged; Muscle, Smooth; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Pyrazoles; Pyrimidines; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase; Sulfones; Triazines; Vardenafil Dihydrochloride

We have evaluated the influence of calcium-activated potassium channels (KCa ) activation on cGMP-mediated relaxation in human penile tissues from non-diabetic and diabetic patients, and on the effects of PDE5 inhibitors on erectile responses in control and diabetic rats.. Cavernosal tissues were collected from organ donors and from patients with erectile dysfunction (ED). Relaxations of corpus cavernosum strips (HCC) and penile resistance arteries (HPRA) obtained from these specimens were evaluated. Intracavernosal pressure (ICP) increases to cavernosal nerve electrical stimulation were determined in anaesthetized diabetic and non-diabetic rats.. Concentration-dependent vasodilation to the PDE5 inhibitor, sildenafil, in HPRA was sensitive to endothelium removal, NO/cGMP pathway inhibition and KCa blockade. Accordingly, activation of KCa with NS-8 (10 μM) significantly potentiated sildenafil-induced relaxations in HPRA (EC50 0.49 ± 0.22 vs. 5.21 ± 0.63 μM). In HCC, sildenafil-induced relaxation was unaffected by KCa blockade or activation. Potentiating effects in HPRA were reproduced with an alternative PDE5 inhibitor (tadalafil) and KCa activator (NS1619) and prevented by removing the endothelium. Large-conductance KCa (BK) and intermediate-conductance KCa (IK) contribute to NS-8-induced effects and were immunodetected in human and rat penile arteries. NS-8 potentiated sildenafil-induced enhancement of erectile responses in rats. Activation of KCa recovered the impaired relaxation to sildenafil in diabetic HPRA while sildenafil completely reversed diabetes-induced ED in rats only when combined with KCa activation.. Activation of KCa improves vasodilatory capacity of PDE5 inhibitors in diabetic and non-diabetic HPRA, resulting in the recovery of erectile function in diabetic rats. These results suggest a therapeutic potential for KCa activation in diabetic ED.

Topics: Adult; Aged; Animals; Benzimidazoles; Carbolines; Cyclic GMP; Diabetes Mellitus, Experimental; Dose-Response Relationship, Drug; Electric Stimulation Therapy; Erectile Dysfunction; Humans; Male; Middle Aged; Nitric Oxide; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Potassium Channels, Calcium-Activated; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Tadalafil; Vasodilation; Vasodilator Agents

Despite the fact that metal toxicity has been widely reported in industrial toxicological studies, very little has been reported about the effect of lead exposure on erectile function. This study investigated the effect of lead on erectile function in rats and aimed to preliminarily test the mechanisms by which it might affect erection. Rats were injected with lead acetate (0.25-2 mg/kg) intraperitoneally for 21 days. Intracavernosal pressure/mean arterial pressure (ICP/MAP) next to nerve stimulation; nitrite/nitrate; malonaldehyde; and reduced glutathione levels and superoxide dismutase activity in the corpus cavernosum, kidney, and brain were measured in addition to creatinine, urea, and testosterone. For acute studies, rats were injected intravenously with lead acetate, and then ICP/MAP was recorded for 45 min. Subacute treatment significantly reduced erection with significant elevation of malonaldehyde and reduction of nitrite/nitrate levels in the corpus cavernosum. In acute studies, lead (2 and 5 mg/kg) reduced neurogenic erections by 28.42 ± 3.76 and 96.84 ± 8.52%, respectively, an effect that was masked in the presence of NG-nitro-L-arginine, tetraethyl ammonium, or methylene blue, but not zinc protoporphyrine, and reversed by vitamin C and partially by sildenafil. Lead acetate may inhibit the erectile process in rats. Besides its prooxidant effect and consequent inactivation of nitric oxide, lead may negatively modulate the action of nitric oxide on guanylate cyclase and potassium channels.

Topics: Animals; Ascorbic Acid; Cyclic GMP; Environmental Pollutants; Erectile Dysfunction; Kidney; Male; Malondialdehyde; Nitric Oxide; Organometallic Compounds; Oxidative Stress; Piperazines; Purines; Rats; Rats, Wistar; Signal Transduction; Sildenafil Citrate; Sulfones; Urological Agents

Sildenafil citrate (Viagra), a phosphodiesterase 5 inhibitor (PDE5i), is a commonly prescribed drug for erectile dysfunction. Since the introduction of Viagra in 1997, several case reports have linked Viagra to sudden sensorineural hearing loss. However, these studies are not well controlled for confounding factors, such as age and noise-induced hearing loss and none of these reports are based on prospective double-blind studies. Further, animal studies report contradictory data. For example, one study (2008) reported hearing loss in rats after long-term and high-dose exposure to sildenafil citrate. The other study (2012) showed vardenafil, another formulation of PDE5i, to be protective against noise-induced hearing loss in mice and rats. Whether or not clinically relevant doses of sildenafil citrate cause hearing loss in normal subjects (animals or humans) is controversial. One possibility is that PDE5i exacerbates age-related susceptibility to hearing loss in adults. Therefore, we tested sildenafil citrate in C57BL/6J, a strain of mice that displays increased susceptibility to age-related hearing loss, and compared the results to those obtained from the FVB/N, a strain of mice with no predisposition to hearing loss. Six-week-old mice were injected with the maximum tolerated dose of sildenafil citrate (10 mg/kg/day) or saline for 30 days. Auditory brainstem responses (ABRs) were recorded pre- and post injection time points to assess hearing loss. Entry of sildenafil citrate in the mouse cochlea was confirmed by qRT-PCR analysis of a downstream target of the cGMP-PKG cascade. ABR data indicated no statistically significant difference in hearing between treated and untreated mice in both backgrounds. Results show that the maximum tolerated dose of sildenafil citrate administered daily for 4 weeks does not affect hearing in the mouse. Our study gives no indication that Viagra will negatively impact hearing and it emphasizes the need to revisit the issue of Viagra related ototoxicity in humans.

Topics: Aging; Animals; Cochlea; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Erectile Dysfunction; Evoked Potentials, Auditory, Brain Stem; Hearing Loss; Humans; Male; Mice; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Rats; Reverse Transcriptase Polymerase Chain Reaction; Sildenafil Citrate; Sulfones

Erectile dysfunction (ED) is a major complication of diabetes mellitus. Icariin has been shown to enhance erectile function through its bioactive form, icarisid II. This study investigates the effects of icarisid II on diabetic rats with ED and its potential mechanism via the assessment of advanced glycosylation end products (AGEs), autophagy, mTOR and the NO-cGMP pathway. Icarisid II was extracted from icariin by an enzymatic method. In the control and diabetic ED groups, rats were administered normal saline; in the icarisid II group, rats were administered icarisid II intragastrically. Erectile function was evaluated by measuring intracavernosal pressure/mean arterial pressure (ICP/MAP). AGE concentrations, nitric oxide synthase (NOS) activity and cGMP concentration were assessed by enzyme immunoassay. Cell proliferation was analysed using methyl thiazolyl tetrazolium assay and flow cytometry. Autophagosomes were observed by transmission electron microscopy, monodansylcadaverine staining and GFP-LC3 localisation. The expression of NOS isoforms and key proteins in autophagy were examined by western blot. Our results have shown that Icarisid II increased ICP/MAP values, the smooth muscle cell (SMC) growth curve, S phase and SMC/collagen fibril (SMC/CF) proportions and decreased Beclin 1 (P<0.05). Icarisid II significantly increased the proliferative index and p-p70S6K(Thr389) levels and decreased the numbers of autophagosomes and the levels of LC3-II (P<0.01). Icarisid II decreased AGE concentrations and increased cGMP concentration, NOS activity (P<0.05) and cNOS levels (P<0.01) in the diabetic ED group. Therefore, Icarisid II constitutes a promising compound for diabetic ED and might be involved in the upregulation of SMC proliferation and the NO-cGMP pathway and the downregulation of AGEs, autophagy and the mTOR pathway.

Topics: Animals; Autophagy; Cell Proliferation; Cyclic GMP; Diabetes Mellitus, Experimental; Down-Regulation; Erectile Dysfunction; Flavonoids; Glycation End Products, Advanced; Male; Muscle, Smooth; Nitric Oxide Synthase; Rats; Rats, Wistar; TOR Serine-Threonine Kinases; Up-Regulation

Nitric oxide (NO) and cGMP have been shown to be important mediators of penile erection. Erectile dysfunction may result from reduced or non-functional signal transduction within this cascade. There is, however, some inconsistency in the available data as mice lacking NO synthases (endothelial and neuronal nitric oxide synthase, or both) appear to be fertile whereas mice deficient in cGMP-dependent protein kinase I (PKGI) suffer from erectile dysfunction. To clarify this discrepancy we performed studies on mice lacking the NO receptor NO-sensitive guanylyl cyclase (NO-GC). In addition, we generated cell-specific NO-GC knockout (KO) lines to investigate the function of NO in individual cell types. NO-GC was specifically deleted in smooth muscle or endothelial cells (SM-guanylyl cyclase knockout (SM-GCKO) and EC-GCKO, respectively) and these KO lines were compared with total knockouts (GCKO) and wild-type animals. We investigated expression of NO-GC, NO-induced relaxation of corpus cavernosum smooth muscle and their ability to generate offspring. NO-GC-positive immunostaining was detected in smooth muscle and endothelial cells of murine corpus cavernosum but not in interstitial cells of Cajal. NO released from NO donors as well as from nitrergic neurons failed to relax precontracted corpus cavernosum from GCKO mice in organ bath experiments. Similar results were obtained in corpus cavernosum from SM-GCKO mice whereas deletion of NO-GC in endothelial cells did not affect relaxation. The lack of NO-induced relaxation in GCKO animals was not compensated for by guanosine 3,5-cyclic monophosphate (cGMP) signalling. To our surprise, GCKO males were fertile although their ability to produce offspring was decreased. Our data show that deletion of NO-GC specifically in smooth muscle cells abolishes NO-induced corpus cavernosum relaxation but does not lead to infertility.

Topics: Animals; Cyclic GMP; Endothelial Cells; Erectile Dysfunction; Fertility; Gene Deletion; Guanylate Cyclase; Interstitial Cells of Cajal; Male; Mice; Mice, Knockout; Muscle Relaxation; Muscle, Smooth; Neurons; Nitric Oxide; Penis; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase

The effect of Cuscuta chinensis extract on the rabbit penile corpus cavernosum (PCC) was evaluated in the present study. Penises obtained from healthy male New Zealand white rabbits (2.5-3.0 kg) were precontracted with phenylephrine (Phe, 10 µmol l(-1)) and then treated with various concentrations of Cuscuta chinensis extract (1, 2, 3, 4 and 5 mg ml(-1)). The change in penile tension was recorded, and cyclic nucleotides in the PCC were measured by radioimmunoassay (RIA). The interaction between Cuscuta chinensis and sildenafil was also evaluated. The result indicated that the PCC relaxation induced by Cuscuta chinensis extract was concentration-dependent. Pre-treatment with an nitric oxide synthase (NOS) inhibitor (Nω nitro-L-arginine-methyl ester, L-NAME), a guanylyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ), or a protein kinase A inhibitor (KT 5720) did not completely inhibit the relaxation. Incubation of penile cavernous tissue with the Cuscuta chinensis extract significantly increased cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) in the PCC. Moreover, the Cuscuta chinensis extract significantly enhanced sildenafil-induced PCC relaxation. In conclusion, the Cuscuta chinensis extract exerts a relaxing effect on penile cavernous tissue in part by activating the NO-cGMP pathway, and it may improve erectile dysfunction (ED), which does not completely respond to sildenafil citrate.

Topics: Animals; Cuscuta; Cyclic GMP; Enzyme Inhibitors; Erectile Dysfunction; Herb-Drug Interactions; Male; Muscle Relaxation; Muscle, Smooth; NG-Nitroarginine Methyl Ester; Penile Erection; Penis; Phytotherapy; Piperazines; Plant Extracts; Purines; Rabbits; Sildenafil Citrate; Sulfones

INTRODUCTION.: Prevalence of erectile dysfunction (ED) increases progressively with aging, but the ED pathophysiology at its early stages is still poorly investigated. AIM.: This study aimed to evaluate the functional and molecular alterations of erectile function at middle age, focusing on the contribution of oxidative stress in erectile tissue for the ED. METHODS.: Young (3.5-month) and middle-aged (10-month) male Wistar rats were used. Rat corpus cavernosum (RCC) was dissected free and mounted in 10-mL organ baths containing Krebs solution. Intracavernosal pressure (ICP) in anesthetized rats was evaluated. MAIN OUTCOME MEASURES.: Concentration-response curves to endothelium-dependent and endothelium-independent agents, as well as to electrical field stimulation (EFS), were obtained in RCC strips. Measurement of cyclic guanosine monophosphate (cGMP) and expressions of neuronal nitric oxide synthase (nNOS) and endothelial NOS (eNOS), gp91(phox) and superoxide dismutase-1 (SOD-1) expressions in RCC were evaluated. RESULTS.: ICP was significantly reduced in middle-aged compared with young rats. RCC relaxations to acetylcholine (10(-8) to 10(-2)  M), sodium nitroprusside (10(-8) to 10(-2)  M), sildenafil (10(-9) to 10(-5)  M), BAY 41-2272 (10(-9) to 10(-5)  M), and EFS (4-32 Hz) were decreased in middle-aged group, which were nearly normalized by apocynin (NADPH oxidase inhibitor; 10(-4)  M) or SOD (75 U/mL). Prolonged treatment with apocynin (85 mg/rat/day, 4 weeks) also restored the impaired relaxations in middle-aged rats. Relaxations to 8-bromoguanosine 3',5'-cyclic monophosphate sodium salt (8-Br-cGMP; 10(-8) to 3 × 10(-4)  M) remained unchanged between groups. Basal and stimulated cGMP production were lower in middle-aged group, an effect fully restored by apocynin and SOD. Protein expression of nNOS and phosphorylated eNOS (p-eNOS) (Ser-1177) reduced, whereas gp(91phox) mRNA expression increased in RCC from middle-aged rats. CONCLUSIONS.: ED in middle-aged rats is associated with decreased NO bioavailability in erectile tissue due to upregulation of NADPH oxidase subunit gp91(phox) and downregulation of nNOS/p-eNOS. Antioxidant therapies may be a good pharmacological approach to prevent ED at its early stages.

Topics: Acetophenones; Acetylcholine; Aging; Animals; Blood Pressure; Cyclic GMP; Down-Regulation; Electric Stimulation; Endothelium, Vascular; Enzyme Inhibitors; Erectile Dysfunction; Free Radical Scavengers; Male; Membrane Glycoproteins; Muscle Relaxation; NADPH Oxidase 2; NADPH Oxidases; Nitric Oxide Synthase; Nitroprusside; Penile Erection; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Pyrazoles; Pyridines; Rats; RNA, Messenger; Sildenafil Citrate; Sulfones; Superoxide Dismutase; Superoxide Dismutase-1; Up-Regulation; Vasodilator Agents

To investigate the expression of insulin-like growth factor binding protein-3 (IGFBP-3) in penile cavernous of streptozotocin (STZ)-induced DM rats and whether downregulation of IGFBP-3 by intracavernosal injection of short hairpin ribonucleic acid (shRNA) targeting IGFBP-3 could improve the erectile function in DM rats.. Diabetes was induced in rats by intraperitoneal injection of STZ, and the expression of IGFBP-3 in the penile tissue of adult normal and DM male rats was assayed using reverse transcriptase-polymerase chain reaction and Western blot. Next, shRNA-targeting IGFBP-3 and a scramble sequence were injected into the penile corpora cavernosa of DM rats. At 12 weeks after shRNA-IGFBP-3 administration, the intracavernous pressure in response to electrical stimulation of the cavernous nerves was evaluated. The expression of IGFBP-3 was assayed by Western blot. The concentration of cyclic guanosine monophosphate in the corpus cavernosum was assayed by enzyme-linked immunosorbent assay.. At 12 week after intraperitoneal administration of STZ, IGFBP-3 expression had increased in the penis of the DM rat (P <.05) compared with that of the normal control rats. Among the DM rats, IGFBP-3 expression at the messenger RNA and protein level was significantly inhibited 12 weeks after intracavernous administration of IGFBP-3 shRNA (P <.01). At 12 weeks after shRNA-IGFBP-3 injection, intracavernosal pressure was significantly increased in response to cavernous nerve stimulation (P <.05), and an increase in the concentration of cyclic guanosine monophosphate in the corpus cavernous tissue (P <.01) was detected compared with the "randomer" shRNA treatment group.. Gene transfer of shRNA-IGFBP-3 could improve erectile function in STZ-induced DM rats by an increase in the cyclic guanosine monophosphate concentration in cavernous tissue.

Topics: Animals; Blood Pressure; Cyclic GMP; Diabetes Mellitus, Experimental; Down-Regulation; Erectile Dysfunction; Insulin-Like Growth Factor Binding Protein 3; Male; Penis; Rats; Rats, Wistar; RNA, Messenger; RNA, Small Interfering; Statistics, Nonparametric; Streptozocin

The seriousness of metabolic syndrome is not due to the disease itself but its promotion of other diseases, such as erectile dysfunction and cardiovascular and cerebrovascular diseases. We investigated the effects of Korean red ginseng (KRG, Panax ginseng) extract on erectile function in a rat model of metabolic syndrome. We divided the rats into three groups: control, metabolic syndrome+normal saline (N/S) and metabolic syndrome+KRG. To determine the occurrence of metabolic syndrome in all groups, body weight and various biochemical parameters (e.g., blood glucose, insulin, cholesterol) were measured, and the intra-abdominal glucose tolerance test was performed. To investigate penile erection, the peak intracavernosal pressure (ICP), mean arterial pressure (MAP) and Masson's trichrome stain were evaluated. Erectile function was also investigated by measuring the cyclic guanosine monophosphate (cGMP) levels of the corpus cavernosum. We found that the various biochemical parameters and body weight were similar in the metabolic syndrome+KRG group and the control group, although the values were slightly higher. The peak ICP/MAP ratio of the metabolic syndrome+N/S group was markedly decreased compared to the other groups. The cGMP level of the corpus cavernosum in the metabolic syndrome+N/S group was significantly lower than that of the other groups. As demonstrated in this model of metabolic syndrome with erectile dysfunction, KRG may improve erectile function.

Topics: Animals; Arterial Pressure; Cyclic GMP; Disease Models, Animal; Erectile Dysfunction; Male; Metabolic Syndrome; Panax; Penile Erection; Penis; Phytotherapy; Plant Extracts; Rats; Rats, Inbred WKY; Transforming Growth Factor beta

The aim of this study was to explore the effects and mechanisms of Icarisid II (ICA-II) on enhancing the cellular cGMP in rat corpus cavernosum tissue (RCCT). Diabetes mellitus Wistar rats were induced by streptozotocin, and diabetic ED rats were selected for the RCCT culture by apomorphine. ICA-II was extracted and purified from Icariin (ICA) by enzymatic method. The RCCT was treated with ICA-II, ICA and Sildenafil at different concentrations. cGMP and nitric oxide synthase (NOS) activities were checked respectively by enzyme immunoassay. Meanwhile, nNOS, iNOS and eNOS in RCCT were checked by western blot. ICA-II evaluated the intracellular cGMP to 8.01 ± 1.02 pmol mg(-1) min(-1), which is much weaker than that from Sildenafil (12.4 ± 1.16 pmol mg(-1) min(-1)) (P < 0.05). There is no significant difference between ICA-II and ICA. With the treatment of 10 μm ICA-II for 24 and 48 h, nNOS expression was significantly increased in RCCT (P < 0.05), while the eNOS expression level was very low without any change. Notably, ICA-II increased the intracellular NOS activity significantly in vitro in RCCT. Except the PDE5 inhibitory effect, ICA-II increases the intracellular cGMP through the enhancement of nNOS expression and NOS activity in RCCT in vitro. ICA-II implies a potential compound for neurogenic erectile dysfunction by NO-cGMP pathway.

Topics: Animals; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Complications; Epimedium; Erectile Dysfunction; Flavonoids; Male; Nitric Oxide Synthase; Phosphodiesterase Inhibitors; Rats; Rats, Wistar

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

The nitric-oxide (NO)-cyclic-guanosine-monophosphate (cGMP) pathway plays a key role in penile erection. Erectile dysfunction (ED) is a complication in male diabetic patients that impacts their quality of 1ife. Recently, Yidiyin, a Chinese herbal decoction, is used to treat diabetic ED, but convincing evidence is lacking, and the potential mechanisms remain uncertain. In the study, diabetic ED patients had low scores on international index of erectile function-5 (IIEF-5), and administration of Yidiyin and hypoglycemic drugs for 16 weeks ameliorated patients' scores on IIEF-5 more than the hypoglycemic drug alone. Moreover, streptozotocin-induced diabetes severely impaired rats' erectile function and the activity of the NO-cGMP pathway in the corpora cavernosum, and treatment with Yidiyin for 4 weeks obviously increased the rats' erectile function, remarkably enhanced the activity of nitric oxide synthase (NOS), and elevated the contents of NO and cGMP. Our findings indicate that Yidiyin improves diabetic ED probably by enhancing the NO-cGMP pathway.

Topics: Animals; Cyclic GMP; Diabetes Complications; Diabetes Mellitus; Drugs, Chinese Herbal; Erectile Dysfunction; Humans; Hypoglycemic Agents; Male; Nitric Oxide; Rats; Treatment Outcome

This study aimed to assess the effect of testosterone (T) administration and chronic low-dose sildenafil/tadalafil on cavernous tissue oxidative stress (OS) of aged diabetic rats. In all, 140 Sprague-Dawley aged rats were subdivided into the following: controls; streptozotocin (STZ)-induced diabetic rats; diabetic rats injected with T every 4 weeks; diabetic rats on sildenafil orally daily; diabetic rats on T and daily sildenafil; diabetic rats on tadalafil orally every other day; diabetic rats on T and tadalafil; diabetic rats on alternate sildenafil/tadalafil; and diabetic rats on alternate sildenafil/tadalafil with T. After 12 weeks, the rats were euthanised where in dissected cavernous tissues malondialdehyde (MAD), glutathione peroxidase (GPx) and cGMP (cyclic guanosine monophosphate) were estimated. Compared with controls, aged diabetic rats demonstrated significant increase in cavernous tissue MDA and significant decrease in GPx and cGMP where diabetic rats injected with T had marked improvement of these parameters. Diabetic rats on sildenafil, tadalafil or alternate sildenafil/tadalafil demonstrated significant increased cavernous tissue GPx, cGMP and decreased cavernous MDA that was further improved when supplemented with T. It is concluded that frequent low-dose use of sildenafil and/or tadalafil supplemented with T has a marked impact on ameliorating cavernous OS in aged diabetic rats.

Topics: Aging; Animals; Carbolines; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Glutathione Peroxidase; Male; Malondialdehyde; Oxidative Stress; Penile Erection; Penis; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Sildenafil Citrate; Sulfones; Tadalafil; Testosterone; Vasodilator Agents

Cavernous nerve injury is the main reason for post-prostatectomy erectile dysfunction (ED). Stem cell and neuroprotection therapy are promising therapeutic strategy for ED.. To evaluate the therapeutic efficacy of adipose-derived stem cells (ADSCs) and brain-derived neurotrophic factor (BDNF) immobilized Poly-Lactic-Co-Glycolic (PLGA) membrane on the cavernous nerve in a rat model of post-prostatectomy ED. Methods.  Rats were randomly divided into five groups: normal group, bilateral cavernous nerve crush injury (BCNI) group, ADSC (BCNI group with ADSCs on cavernous nerve) group, BDNF-membrane (BCNI group with BDNF/PLGA membrane on cavernous nerve) group, and ADSC/BDNF-membrane (BCNI group with ADSCs covered with BDNF/PLGA membrane on cavernous nerve) group. BDNF was controlled-released for a period of 4 weeks in a BDNF/PLGA porous membrane system.. Four weeks after the operation, erectile function was assessed by detecting the ratio of intra-cavernous pressure (ICP)/mean arterial pressure (MAP). Smooth muscle and collagen content were determined by Masson's trichrome staining. Neuronal nitric oxide synthase (nNOS) expression in the dorsal penile nerve was detected by immunostaining. Phospho-endothelial nitric oxide synthase (eNOS) protein expression and cyclic guanosine monophosphate (cGMP) level of the corpus cavernosum were quantified by Western blotting and cGMP assay, respectively.. In the ADSC/BDNF-membrane group, erectile function was significantly elevated, compared with the BCNI and other treated groups. ADSC/BDNF-membrane treatment significantly increased smooth muscle/collagen ratio, nNOS content, phospho-eNOS protein expression, and cGMP level, compared with the BCNI and other treated groups.. ADSCs with BDNF-membrane on the cavernous nerve can improve erectile function in a rat model of post-prostatectomy ED, which may be used as a novel therapy for post-prostatectomy ED.

Topics: Adipocytes; Animals; Brain-Derived Neurotrophic Factor; Cyclic GMP; Erectile Dysfunction; Humans; Immobilized Proteins; Lactic Acid; Male; Membranes, Artificial; Nerve Crush; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penis; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Prostatectomy; Pudendal Nerve; Random Allocation; Rats; Rats, Sprague-Dawley; Stem Cell Transplantation

Hypertension represents a major risk factor for erectile dysfunction. Although the etiology of hypertension-induced erectile dysfunction is multifactorial and still unknown, Rho-Rho kinase pathway is one of the key factors. To investigate whether administration of hydroxyfasudil, a Rho kinase inhibitor could prevent dysfunction of NO-induced relaxation in corpus cavernosum smooth muscle in the SHR (spontaneously hypertensive rat), twelve-week-old male SHRs were treated with hydroxyfasudil (3 or 10 mg/kg, i.p.) once a day for 6 weeks. Wistar rats and SHRs treatment with vehicle were used as age-matched controls. Penile cGMP concentrations and Rho kinase activities were determined, and penile function was estimated by organ bath studies with norepinephrine-induced contractions and acetylcholine-induced relaxations. The participation mRNA levels of eNOS and participation protein levels of eNOS and phosphorylated eNOS were investigated by quantitative real-time PCR methods and immunoblot analysis, respectively. The SHR showed significantly decreased cGMP concentrations, increased Rho kinase activities, norepinephrine-induced hyper-contractions, and acetylcholine-induced hypo-relaxations in the penile tissue. Treatment with hydroxyfasudil significantly improved the decreased penile cGMP concentrations, the increased Rho kinase activities, the increased norepinephrine-induced contractions, and the decreased acetylcholine-induced relaxation in a dose-dependent manner. Although there were no significant differences in expression protein levels of eNOS among any of the groups, down-regulation of eNOS mRNAs as well as phosphorylated eNOS were significantly ameliorated after treatment with hydroxyfasudil. Our data suggest that hydroxyfasudil ameliorates hypertension-associated dysfunction of NO-induced relaxation in corpus cavernosum smooth muscle possibly via inhibition of the Rho-Rho kinase pathway and activation of NO-eNOS pathway in the SHR.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Cyclic GMP; Erectile Dysfunction; Gene Expression Regulation; Hypertension; Male; Nitric Oxide Synthase Type III; Penis; Phosphorylation; Rats; Rats, Inbred SHR; Rats, Wistar; rho-Associated Kinases; RNA, Messenger

Age-associated erectile dysfunction (ED) involves a decrease in nitric oxide (NO) availability and impaired relaxation. PnTx2-6, a toxin from the Phoneutria nigriventer spider, has been demonstrated to improve erectile function via NO/cyclic guanosine monophosphate (cGMP) pathway. This spider's venom is characterized by several symptoms, including erection. PnTx2-6 has been implicated in this phenomenon. Animal venoms have been postulated as potential drugs to treat ED.. PnTx2-6 toxin improves erectile function in aged rats via NO/cGMP. We investigated the effect of PnTx2-6 in the erectile function of aged rats.. ED was evaluated through changes in intracavernosal pressure/mean arterial pressure ratio during electrical field stimulation (EFS) of the pelvic ganglion of aged and adult rats (70 vs. 14 weeks). In functional studies, EFS-induced relaxation of corpus cavernosum (CC) strips were performed with or without PnTx2-6 (10-8M).. The decrease in erectile function associated with age was partially restored 15-20 minutes after injection of PnTx2-6 and further improved by sildenafil. PnTx2-6 enhanced EFS-induced relaxation, as well as cGMP levels in CC, from young and aged rats. Relaxation due to PnTx2-6 was further increased after 30 minutes incubation with Y-27632, a Rho-kinase inhibitor (10-6 M), in aging CC. Nitric oxide synthase (NOS) activity in aged and young cavernosal tissue was increased by incubation with PnTx2-6 (10 minutes). However, this toxin did not modify NOS expression.. PnTx2-6 improves penile relaxation in aged rats, via increased NOS activity and NO release, resulting in enhanced cGMP levels.

Topics: Animals; Blood Pressure; Cyclic GMP; Erectile Dysfunction; Male; Nitric Oxide; Penile Erection; Peptides; Rats; Rats, Wistar; Spider Venoms

• To investigate the potential beneficial effects of 4-week oral treatment with 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1Hpyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine (BAY 41-2272), a nitric oxide (NO)-independent soluble guanylate cyclase activator, on impaired rat corpus cavernosum relaxations in NO-deficient rats.. • Male Wistar rats were divided into four groups: Control, N (G)-nitro-L- arginine methyl ester (L-NAME; 20 mg/rat/day), BAY 41-2272 (20 mg/kg/day) and L-NAME + BAY 41-2272. • Rats were treated with L-NAME concomitantly with BAY 41-2272 for 4 weeks. • Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP), along with the nitrergic relaxations (1-32 Hz) were obtained in rat corpus cavernosum (RaCC). • The RaCC contractile responses to the α₁ -adrenoceptor agonist phenylephrine (PE) were obtained.. • Acetylcholine (0.01-1000 µmol/L) produced concentration-dependent relaxing responses in RaCC that were significantly enhanced (P < 0.05) in BAY 41-2272-treated rats. • The ACh-induced relaxations were largely reduced in L-NAME-treated rats, and co-treatment with BAY 41-2272 failed to significantly modify these impaired relaxations. • The SNP-induced relaxations were modified neither by L-NAME nor by co-treatment with BAY 41-2272. • The nitrergic relaxations were significantly amplified in BAY 41-2272-treated rats (at 16 and 32 Hz). A significant reduction in the nitrergic relaxations was observed in L-NAME-treated rats, an effect largely restored by co-treatment with BAY 41-2272. • The contractile RaCC responses produced by PE (0.001-100 µmol/L) were significantly higher (P < 0.05) in L-NAME-treated rats, and co-treatment of L-NAME with BAY 41-2272 nearly restored these enhanced contractile responses.. • Four-week therapy with BAY 41-2272 prevents the impaired corpus cavernosum relaxations of rats treated chronically with L-NAME, indicating that accumulation of cyclic guanosine monophosphate into erectile tissue counteracts the NO deficiency.

Topics: Animals; Cyclic GMP; Enzyme Inhibitors; Erectile Dysfunction; Guanylate Cyclase; Male; Muscle Relaxants, Central; NG-Nitroarginine Methyl Ester; Nitric Oxide; Penile Erection; Pyrazoles; Pyridines; Rats; Rats, Wistar

Phosphodiesterase type 5 (PDE5) inhibitors are very effective agents for erectile dysfunction; however, specific patient populations are hard to treat. The efficacy of PDE5 inhibitors is limited because a minimum amount of nitric oxide (NO) is necessary. Resveratrol, a plant polyphenol, is reported to activate endothelial NO synthase (eNOS) through activation of sirtuin 1. We previously reported that human corpus cavernosal smooth muscle cells (CCSMCs) express eNOS and synthesize cyclic guanosine monophosphate (cGMP) via the NO/cGMP pathway.. To investigate the ability of resveratrol and/or vardenafil to increase cGMP in an in vitro model using CCSMCs and to improve erectile function in an in vivo rat model of streptozotocin (STZ)-induced diabetes.. CCSMCs were treated with resveratrol and/or vardenafil. Twenty male Sprague-Dawley rats were randomly divided into five groups (N = 4 in each group): age-matched controls, diabetic controls, and diabetic rats treated with resveratrol, vardenafil, or both in combination for the last 4 weeks of an 8-week period of diabetes induction.. Intracellular cGMP measurement, intracovernous pressure (ICP)/mean arterial pressure (MAP) ratio, and smooth muscle/collagen ratio.. Intracellular cGMP level was elevated by resveratrol treatment in CCSMCs. The combination treatment of resveratrol and vardenafil had a synergistic effect. Diabetic rats showed impairment of erectile function. Treatment with either resveratrol or vardenafil improved ICP/MAP ratio, and combination therapy with resveratrol and vardenafil had a synergistic effect in improvement of ICP/MAP.. Treatment with either resveratrol or vardenafil elevated cGMP level in CCSMCs and improved erectile function in STZ-induced diabetic rats. Furthermore, a synergistic effect was observed in vitro and in vivo. Resveratrol or combination therapy of resveratrol and vardenafil can improve erectile function in which NO release is impaired, although further study is needed to confirm the results.

Topics: Animals; Antioxidants; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Imidazoles; Male; Muscle, Smooth; Nitric Oxide; Nitric Oxide Synthase Type III; Penis; Phosphodiesterase 5 Inhibitors; Piperazines; Rats; Rats, Sprague-Dawley; Resveratrol; Stilbenes; Sulfones; Triazines; Vardenafil Dihydrochloride

It is of great importance to investigate an effective and reliable medication against chronic renal failure (CRF)-related erectile dysfunction (ED), which aims to improve patients' life qualities. The concentrations of cyclic guanosine monophosphate (cGMP) in the corpus cavernosal smooth muscle of both CRF and control rabbits were measured. The effects of various concentrations of tadalafil, papaverine, and sodium nitroprusside on the relaxation responses of corpus cavernosal smooth muscle pre-contracted with phenylephrine in CRF rabbits were observed. There was significant difference in the concentration of cGMP between CRF and control rabbits (P<0.01). Tadalafil had the greatest impacts on CRF rabbits when given the same concentration of papaverine or sodium nitroprusside and particularly significant differences were identified under the concentration levels of 10⁻⁵ and 10⁻⁴ mol/L (P<0.01). The results suggest that the cGMP concentrations of the corpus cavernosum had been greatly reduced in CRF rabbits compared with control rabbits and that tadalafil may be an ideal medication for use in the treatment of CRF-related ED.

Topics: Animals; Carbolines; Cyclic GMP; Erectile Dysfunction; Kidney Failure, Chronic; Male; Nitroprusside; Phosphodiesterase 5 Inhibitors; Rabbits; Tadalafil; Vasodilator Agents

Periodontitis is one of the important risk factors resulting in cardiovascular diseases. Erectile dysfunction (ED) is strongly correlated with cardiovascular diseases. The expression of endothelial nitric oxide synthase (eNOS) in penile tissue has an important role in the mechanism of erection.. To investigate the effect of periodontitis on erectile function and the possible mechanism.. After induction of periodontitis in rat, the ratio of maximum intracavernosal pressure/mean arterial pressure (ICPmax /MAP)×100, the expression of eNOS in penile tissue, the level of serum C-reactive protein (CRP) and tumor necrosis factor-α (TNF-α), and the ultrastructural changes of the cavernous tissue were examined and compared between periodontitis rats (group A) and control rats (group B).. Periodontitis significantly decrease not only the ICPmax/MAP×100 and the expression of eNOS but also the activity of NOS and the level of cyclic guanosine monophosphate (cGMP) in cavernous tissue of rat.. After electrostimulation by 3 and 5 voltage, the ratio of ICPmax /MAP×100 in group A was significantly less than that in group B (19.54±6.16 vs. 30.45±3.12; 30.91±5.61 vs. 50.52±9.52, respectively; P<0.05).The level of serum CRP and TNF-α in group A is significantly higher in group B (P<0.05).The quantitative real-time reverse transcription polymerase chain reaction study demonstrated no statistically significant difference in the expression of mRNA of eNOS in cavernous tissue between the two groups (P>0.05). But there was significant decrease in eNOS protein of the cavernous tissue in group A than in group B (P<0.05). Total NOS activity and cGMP level in cavernosal tissue were significantly lower in group A than in group B (P<0.05). There was no significant alternation occurred in the ultrastructures of penile cavernous tissue.. The function of penile erection is impaired by periodontitis. The decreased in the expression of eNOS and NOS activity in penile cavernous tissue caused by mild systemic inflammatory status in periodontitis may be one of the important risk factors of ED.

Topics: Animals; Blood Pressure; Blotting, Western; C-Reactive Protein; Cyclic GMP; Erectile Dysfunction; Male; Microscopy, Electron, Transmission; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Penis; Periodontitis; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Tumor Necrosis Factor-alpha

Receptors for natriuretic peptides have been demonstrated as potential targets for the treatment of male erectile dysfunction.. This study investigates the relaxant effects of the atrial natriuretic peptide (ANP) and uroguanylin (UGN), and expression of natriuretic peptide receptors on strips of human corpora cavernosa (HCC).. Quantitative analysis of natriuretic receptor expression and relaxation of precontracted strips were used to assess the membrane-bound guanylate cyclase-cyclic guanosine monophosphate (cGMP) pathway in HCC strips.. HCC was obtained from a cadaver donor at the time of collection of organs for transplantation (14-47 years) and strips were mounted in organ baths for isometric studies.. ANP and UGN both induced concentration-dependent relaxation on HCC strips with a maximal response attained at 300 nM, corresponding to 45.4±4.0% and 49±4.8%, respectively. The relaxation is not affected by 30 µM 1H-[1,2,4]oxaolodiazolo[4,3-a]quinoxalin-1-one (ODQ) (a soluble guanylate cyclase inhibitor), but it is significantly blocked by 10 µM isatin, a nonspecific particulate guanylate cyclase (pGC) inhibitor. UGN was unable to potentiate electrical field stimulation (EFS) or acetylcholine-induced relaxations. The potential role of pGC activation and cGMP generation in this effect is reinforced by the potentiation of this effect by phosphodiesterase-5 inhibitor vardenafil (55.0±7.5-UGN vs. 98.6±1.4%-UGN+vardenafil; P<0.05). The relaxant effect was also partially (37.6%) blocked by the combination iberitoxin-apamin but was insensitive to glybenclamide. The expression of guanylate cyclase receptors (GC-A, GC-B, GC-C) and the expression of the natriuretic peptide "clearance" receptor (NPR-C) were confirmed by real-time polymerase chain reaction. The exposure of HCC strips to ANP (1 µM) and UGN (10 µM) significantly increased cGMP, but not cyclic adenosine monophosphate (cAMP) levels.. UGN relaxes HCC strips by a guanylate cyclase and K(ca)-channel-dependent mechanism. These findings obtained in HCC reveal that the natriuretic peptide receptors are potential targets for the development of new drugs for the treatment of erectile dysfunction.

Topics: Adolescent; Adult; Atrial Natriuretic Factor; Cadaver; Cyclic AMP; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Guanylate Cyclase; Humans; Male; Middle Aged; Muscle Relaxation; Muscle, Smooth; Natriuretic Peptides; Penis; Receptors, Atrial Natriuretic Factor; Receptors, Cytoplasmic and Nuclear; Receptors, Peptide; Soluble Guanylyl Cyclase; Young Adult

Traditional beta-blockers have sometimes been associated with erectile dysfunction (ED). Nebivolol is a cardioselective β(1)-adrenoceptor antagonist that promotes vasodilation through a nitric oxide (NO)-dependent mechanism.. We evaluated the effects of nebivolol on the NO/cyclic guanosine monophosphate (cGMP) signaling pathway, on erectile function and dysfunction, and in human penile vascular tissues.. Erectile response to cavernosal nerve electrical stimulation in control and diabetes-induced ED rats were evaluated, along with serum nitrite/nitrate (NOx) concentration and plasma/tissue cGMP levels. Endothelium-dependent and sildenafil-induced relaxation of isolated human corpus cavernosum (HCC) and human penile resistance arteries (HPRA) were also determined.. The effects of nebivolol on erectile function and dysfunction and on NO/cGMP-mediated responses.. Treatment with nebivolol significantly potentiated erectile response in control rats, regardless of its effects on blood pressure. Nebivolol increased NOx and plasma cGMP by 3-fold and 2.75-fold, respectively, and significantly augmented the elevation of plasma cGMP produced by sildenafil. Nebivolol enhanced endothelium-dependent and sildenafil-induced relaxations of HCC tissue, and produced endothelium-dependent vasodilation of HPRA. Nebivolol, but not atenolol, significantly improved erectile response in diabetic rats (51.6%, 53.2%, and 87.1% of response at 3 Hz in nondiabetic rats, for vehicle-treated, atenolol-treated, and nebivolol-treated diabetic rats, respectively); after sildenafil administration, ED was completely reversed in nebivolol-treated diabetic rats (69.6% and 112% for diabetic rats treated with sildenafil and nebivolol plus sildenafil, respectively). Accordingly, nebivolol restored systemic NOx levels and cGMP content in penile tissue from these animals.. Nebivolol in vivo activated the NO/cGMP pathway, enhanced erectile response and reversed ED in diabetic rats. Moreover, nebivolol in vitro potentiated NO/cGMP-mediated relaxation of human erectile tissues. These effects may account for the low incidence of ED in nebivolol-treated hypertensive patients. Nebivolol therefore may have utility in the treatment of ED, particularly ED associated with diabetes.

Topics: Animals; Atenolol; Benzopyrans; Blood Glucose; Blood Pressure; Cyclic GMP; Diabetes Mellitus, Experimental; Dose-Response Relationship, Drug; Endothelium, Vascular; Erectile Dysfunction; Ethanolamines; Heart Rate; Humans; In Vitro Techniques; Injections, Intravenous; Male; Nebivolol; Nitric Oxide; Penis; Piperazines; Purines; Rats; Rats, Sprague-Dawley; Signal Transduction; Sildenafil Citrate; Sulfones; Sympatholytics; Vascular Resistance; Vasodilator Agents

Activation of endothelial cells and platelets is an initial step toward the development of cardiovascular disease. Erectile dysfunction (ED) may be an early manifestation of endotheliopathy. We evaluated the effects of tadalafil on cyclic nucleotides (cGMP and cAMP) and soluble adhesion molecules (E- and P-selectin [ES and PS]). The patients were divided into 2 groups on the basis of the presence (10 patients) or absence (9 patients) of cardiovascular risk factors (dyslipidemia, hypertension, and smoking). Nitric oxide (NO) was unmeasurable in all the patients. Tadalafil administration induced a significant increase in cGMP levels in both groups (P < .01). In contrast, cAMP significantly increased (P < .05) and PS decreased (P < .01) only in patients without cardiovascular risk factors. Tadalafil induced a beneficial effect on platelet activation in patients with ED without cardiovascular risk factors; this effect was not mediated by NO.

Topics: Analysis of Variance; Blood Platelets; Carbolines; Cyclic AMP; Cyclic GMP; Dyslipidemias; E-Selectin; Endothelium, Vascular; Erectile Dysfunction; Humans; Hypertension; Male; Middle Aged; Nitric Oxide; P-Selectin; Phosphodiesterase Inhibitors; Pilot Projects; Risk Factors; Smoking; Tadalafil

Patients with erectile dysfunction (ED) associated with type II diabetes often have impaired endothelial function and tend to respond poorly to oral phosphodiesterase type 5 inhibitors. Therefore, neovascularization is a promising strategy for curing diabetic ED.. To determine the effectiveness of a soluble, stable, and potent angiopoietin-1 (Ang1) variant, cartilage oligomeric matrix protein (COMP)-Ang1, in promoting cavernous angiogenesis and erectile function in a mouse model of type II diabetic ED. Methods.  Sixteen-week-old male db/db mice (in which obesity and type II diabetes are caused by a mutation in the leptin receptor) and control C57BL/6J mice were used and divided into four groups (N=14 per group): age-matched controls; db/db mice receiving two successive intracavernous injections of phosphate-buffered saline (PBS) (days -3 and 0; 20 µL); db/db mice receiving a single intracavernous injection of COMP-Ang1 protein (day 0; 5.8 µg/20 µL); and db/db mice receiving two successive intracavernous injections of COMP-Ang1 protein (days -3 and 0; 5.8 µg/20 µL).. Two weeks later, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was then harvested and stained with antibodies to platelet/endothelial cell adhesion molecule-1 (PECAM-1) (endothelial cell marker), phosphohistone H3 (PH3, a nuclear protein indicative of cell proliferation), phospho-endothelial nitric oxide synthase (eNOS), and eNOS. Penis specimens from a separate group of animals were used for cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) quantification.. Local delivery of COMP-Ang1 protein significantly increased eNOS phosphorylation and cGMP and cAMP expression compared with that in the group treated with PBS. Repeated intracavernous injections of COMP-Ang1 protein completely restored erectile function and cavernous endothelial content through enhanced cavernous neoangiogenesis as evaluated by PECAM-1 and PH3 immunohistochemistry and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay, whereas a single injection of COMP-Ang1 protein elicited partial improvement.. Cavernous neovascularization using recombinant Ang1 protein is a novel therapeutic strategy for the treatment of ED resulting from type II diabetes.

Topics: Angiopoietin-1; Animals; Apoptosis; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Type 2; Endothelium, Vascular; Erectile Dysfunction; Male; Mice; Nitric Oxide Synthase Type III; Penile Erection; Penis; Phosphodiesterase 5 Inhibitors; Platelet Endothelial Cell Adhesion Molecule-1; Recombinant Proteins

Mondia whitei root was evaluated to validate its anecdotal use and determine its possible mode of action in the management of erectile dysfunction. Rabbits were administered with daily oral doses of 100-400 mg kg(-1) crude ethanolic extract of M. whitei and sildenafil (50 mg kg(-1)) as positive control for 6 weeks. Cavernosal tissue NOS activity and levels of NO and cGMP, and NOS and PDE protein expressions were investigated. The effect of the crude extract, chloroform and petroleum ether fractions in vitro on cavernosal tissue NOS activity and levels of NO and cGMP at 0.01 and 0.10 mg g(-1) tissue were also investigated. Results indicate that the crude extract increased NOS activity by 7% at 200 mg kg(-1) with corresponding increases in NO (88%) and cGMP (480%) levels. No significant changes in these measurements were observed with the 100 and 400 mg kg(-1) doses whilst sildenafil slightly reduced them (15.9-37.5%). NOS and PDE protein expressions in test animals were not different from controls. Pre-incubation of cavernosal tissue in vitro with the crude extract of M. whitei and its chloroform fraction markedly increased NOS activity (26-132%) and levels of NO (25%) and cGMP (50-400%) at 0.01 mg g(-1) tissue but these were reduced to near control levels when their concentrations were increased to 0.10 mg g(-1) tissue whilst the petroleum ether fraction had no effect. These findings suggest that M. whitei may influence erectile function through activation/stimulation of NOS with corresponding increases in tissue NO and cGMP levels and that certain chemical constituents present in the chloroform fraction may be responsible for biological activity.

Topics: Animals; Chloroform; Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Penile Erection; Phytotherapy; Plant Extracts; Plant Roots; Rabbits; Zingiber officinale

Topics: Cells, Cultured; Cyclic GMP; Endothelial Cells; Erectile Dysfunction; Humans; Hydrogen Peroxide; Hypochlorous Acid; Intracellular Fluid; Lipoproteins, LDL; Male; Peroxidase

To investigate the impact of daily sildenafil on levels of soluble molecular markers of endothelial function in men with erectile dysfunction.. Patients aged >18 years with erectile dysfunction of vascular etiology for >6 months, either alone or in combination with disease states strongly associated with endothelial dysfunction such as diabetes/metabolic syndrome, hypertension and coronary artery disease, received sildenafil 25 mg orally for 4 weeks. Markers of endothelial function were measured in plasma at baseline and at end of treatment using standard methods and commercially available kits.. Altogether, 112 men with mean (SD) age of 60.6 (7.3) years completed the protocol. Sildenafil 25 mg daily for 4 weeks significantly reduced endothelin-1 levels compared with baseline (2.83+/-1.63 vs 3.24+/-1.90 pg/ml, p<0.001). Significant changes were also observed for nitric oxide (35.12+/-21.14 vs 31.91+/-16.28 pmol/lt, p=0.01) and cyclic guanosine monophosphate (3.79+/-2.37 vs 2.70+/-1.34 pmol/ml, p<0.001) levels, but not for any of the other biomarkers measured. Erectile function was significantly improved.. Daily sildenafil ameliorates endothelial function as assessed by levels of biomarkers of endothelial function in patients with erectile dysfunction. This is in agreement with other studies showing similar benefits with phosphodiesterase-5 inhibitor treatment. The clinical implications of this finding warrant further investigation.

Topics: Administration, Oral; Biomarkers; Cyclic GMP; Drug Administration Schedule; Endothelin-1; Endothelium, Vascular; Erectile Dysfunction; Humans; Male; Middle Aged; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

To investigate the effect of phosphodiesterase type 5 (PDE5) small interfering RNA (siRNA) on cyclic guanosine monophosphatethe (cGMP) in the smooth muscle cells of human corpus cavernosum, and to provide laboratory evidence for the application of the RNA interference (RNAi) technique for the treatment of erectile dysfunction.. The recombinant adenovirus rAd5-shRNA-PDE5A3 expressing three pairs of specific shRNA was constructed successfully. The smooth muscle cells of human corpus cavernosum were divided into an experimental, a negative control and a blank control group, and transfected respectively with rAd5-shRNA-PDE5A3, adenovirus rAd5-mock and phosphate buffered saline. The concentration of cGMP was measured by radioimmunoassay at 24, 48 and 72 hours after transfection, and the effect of rAd5-shRNA-PDE5A3 was detected on the cGMP in the smooth muscle cells of the corpus cavernosum.. The cGMP level in the smooth muscle cells of the corpus cavernosum was significantly higher in the rAd5-shRNA-PDE5A3 group than in the rAd5-mock control and blank control groups (P < 0.05), most significantly at 72 hours after transfection.. The rAd5-shRNA-PDE5A3 can obviously increase the cGMP level in the smooth muscle cells of human corpus cavernosum, and enhance the inhibition of the PDE5 gene.

Topics: Adenoviridae; Cells, Cultured; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Genetic Vectors; Humans; Male; Myocytes, Smooth Muscle; Penis; RNA, Small Interfering

Nitrergic nerves and endothelial cells release nitric oxide (NO) in the corpus cavernosum, a key mediator that stimulates soluble guanylyl cyclase to increase cGMP levels causing penile erection. Phosphodiesterase 5 (PDE5) inhibitors, such as sildenafil, prolong the NO effects by inhibiting cGMP breakdown. Here, we report a novel PDE5 inhibitor, lodenafil carbonate, (Bis-(2-{4-[4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-benzenesulfonyl]piperazin-1-yl}-ethyl)carbonate) that is a dimer of lodenafil. We therefore aimed to compare the effects of sildenafil, lodenafil and lodenafil carbonate on in vitro human and rabbit cavernosal relaxations, activity of crude PDE extracts from human platelets, as well as stability and metabolic studies in rat, dog and human plasma. Pharmacokinetic evaluations after intravenous and oral administration were performed in male beagles. Functional experiments were conducted using organ bath techniques. Pharmacokinetics was studied in beagles by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), following oral or intravascular administration. All PDE5 inhibitors tested concentration-dependently relaxed (0.001-100 microM) phenylephrine-precontracted rabbit and human corpus cavernosum. The cavernosal relaxations evoked by either acetylcholine (0.01-100 microM) or electrical field stimulation (EFS, 1-20 Hz) were markedly potentiated by sildenafil, lodenafil and lodenafil carbonate. Lodenafil carbonate was more potent to inhibit the cGMP hydrolysis in PDE extracts compared with lodenafil and sildenafil. Following intravascular and single oral administration of lodenafil carbonate, only lodenafil and norlodenafil were detected in vivo. These results indicate that lodenafil carbonate works as a prodrug, being lodenafil the active moiety of lodenafil carbonate.

Topics: Administration, Oral; Adult; Animals; Carbonates; Chromatography, Liquid; Cyclic GMP; Dogs; Dose-Response Relationship, Drug; Drug Stability; Electric Stimulation; Erectile Dysfunction; Humans; Injections, Intravenous; Male; Penis; Phosphodiesterase Inhibitors; Piperazines; Prodrugs; Purines; Pyrimidines; Rabbits; Rats; Sildenafil Citrate; Sulfones; Tandem Mass Spectrometry

To further investigate the relaxation mechanism of neferine (Nef), a bis-benzylisoquinoline alkaloid extracted (isolated) from the green seed embryo of Nelumbo nucifera Gaertn in China, on rabbit corpus cavernosum tissue in vitro.. The effects of Nef on the concentrations of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in isolated and incubated rabbit corpus cavernosum tissue were recorded using 125I radioimmunoassay.. The basal concentration of cAMP in corpus cavernosum tissue was 5.67 +/- 0.97 pmol/mg. Nef increased the cAMP concentration in a dose-dependent manner (P < 0.05), but this effect was not inhibited by an adenylate cyclase inhibitor (cis-N-[2-phenylcyclopentyl]azacyclotridec-1-en-2-amine, MDL-12, 330A) (P > 0.05). The accumulation of cAMP induced by prostaglandin E1 (PGE1, a stimulator of cAMP production) was also augmented by Nef in a dose-dependent manner (P < 0.05). The basal concentration of cGMP in corpus cavernosum tissue is 0.44 +/- 0.09 pmol/mg. Nef did not affect this concentration of cGMP, either in the presence or in the absence of a guanyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) (P > 0.05). Also, sodium nitroprusside (SNP, a stimulator of cGMP production)-induced cGMP production was not enhanced by Nef (P > 0.05).. Nef, with its relaxation mechanism, can enhance the concentration of cAMP in rabbit corpus cavernosum tissue, probably by inhibiting phosphodiesterase activity.

Topics: Animals; Benzylisoquinolines; Cyclic AMP; Cyclic GMP; Drugs, Chinese Herbal; Erectile Dysfunction; In Vitro Techniques; Male; Muscle Relaxation; Muscle, Smooth; Nelumbo; Penile Erection; Penis; Phytotherapy; Plant Extracts; Rabbits; Radioimmunoassay; Seeds; Vasodilator Agents

Insulin-like growth factor-1 (IGF-1) is one of the growth factors that have a wide range of biologic effects. We have confirmed that gene transfer of IGF-1 to the penis could improve erectile capacity. However, there are some limitations in gene therapies, such as toxicity or a risk of insertional mutagenesis. Protein treatment may be another choice for decreasing these risks.. To investigate whether intracavernosal injection of IGF-1 protein can restore erectile function in the aging rat.. Erectile responses, morphological changes, and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signaling pathways-related marker were determined.. Ten young (4 months) and 30 old (24 months) Sprague-Dawley male rats were enrolled in this study. The old rats were divided into three groups: vehicle-only (N = 10), IGF-1 1 microg/kg (N = 10) and IGF-1 10 microg/kg treatment group (N = 10). After 4 and 8 weeks of single IGF-1 injection treatment, intracavernous pressure (ICP) responses with electrical stimulation to the cavernous nerve were evaluated. The percent of smooth muscle in corpus cavernosum tissue, the expression of mRNA and protein of endothelial nitric oxide synthase (eNOS) were also evaluated. The activity of nitric oxide synthase (NOS) and concentration of guanosine 3',5'-cyclic-monophosphate (cGMP) that act upon the major NO-cGMP signaling pathways in penile tissue were also analyzed.. After IGF-1 treatment, the ICP responses was significantly increased as the young control group in both the IGF-1 1 microg/kg and the IGF-1 10 microg/kg group compared with the vehicle-only group at 4 and 8 weeks (P < 0.05). Masson's trichrom staining showed the percentage of cavernosal smooth muscle was increased in IGF-1 treatment group. IGF-1 increased e-NOS expression. NOS activities and cGMP concentrations were also significantly increased in IGF-1 treatment rats.. IGF-1 improved erectile function in aged rats via restoration the integrity of smooth muscle of corpus cavernosum and modulation of NO-cGMP pathways.

Topics: Aging; Animals; Blood Pressure; Cyclic GMP; Electric Stimulation; Erectile Dysfunction; Immunohistochemistry; Injections; Insulin-Like Growth Factor I; Male; Muscle, Smooth, Vascular; Nitric Oxide; Penis; Rats; Rats, Sprague-Dawley; RNA, Messenger; Signal Transduction

Erectile dysfunction (ED) can be elicited by a variety of pathogenic factors, particularly impaired formation of and responsiveness to nitric oxide (NO) and the downstream effectors soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase I (PKGI). One important target of PKGI in smooth muscle is the large-conductance, Ca2+ -activated potassium (BKCa) channel. In our previous report (42), we demonstrated that deletion of the BKCa channel in mice induced force oscillations and led to reduced nerve-evoked relaxations and ED. In the current study, we used this ED model to explore the role of the BKCa channel in the NO/sGC/PKGI pathway. Electrical field stimulation (EFS)-induced contractions of corpus cavernosum smooth muscle strips were significantly enhanced in the absence of BKCa channel function. In strips precontracted with phenylephrine, EFS-induced relaxations were converted to contractions by inhibition of sGC, and this was further enhanced by loss of BK channel function. Sildenafil-induced relaxations were decreased to a similar extent by inhibition of sGC or BKCa channels. At concentrations >1 microM, sildenafil caused relaxations independent of inhibition of sGC or BKCa channels. Sildenafil did not affect the enhanced force oscillations that were induced by the loss of BKCa channel function. Yet, these oscillations could be completely eliminated by blocking L-type voltage-dependent Ca2+ channels (VDCCs). These results suggest that therapeutically relevant concentrations of sildenafil act through cGMP and BKCa channels, and loss of BKCa channel function leads to hypercontractility, which depends on VDCCs and cannot be modified by the cGMP pathway.

Topics: Animals; Calcium Channels; Cyclic GMP; Erectile Dysfunction; Gene Deletion; Gene Expression Regulation; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Male; Mice; Muscle, Smooth; Phosphodiesterase 5 Inhibitors; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasoconstriction; Vasodilator Agents

Nitrergic neurons are important for erectile responses in the corpus cavernosum and impaired signalling results in erectile dysfunction, today treated successfully by oral administration of the selective phosphodiesterase 5 (PDE 5) inhibitors sildenafil, tadalafil and vardenafil. Although the importance of nitrergic neurons in urogenital function has become evident, it has not been investigated if the PDE 5 inhibitors affect the nerve-induced release of nitric oxide (NO). In a previous study we found that the soluble guanylate cyclase (sGC)/cyclic guanosine 3',5'-monophosphate (cGMP) pathway might modulate nerve-induced release of NO in isolated cavernous tissue.. Electrical field stimulation (EFS 5 Hz, 40 V, 0.3 ms pulse duration, 25 pulses at intervals of 2 min) of rabbit isolated cavernous tissue elicited reproducible, nerve-mediated relaxations in the presence of scopolamine (10(-5) M), guanethidine (10(-5) M) and phenylephrine (3 x 10(-6) M). In superfusion experiments, nerve stimulation (20 Hz, 40 V, 1 ms) of the cavernous tissue evoked release of NO/NO2-, measured by chemiluminescence.. Sildenafil, tadalafil and vardenafil decreased the muscular tone and prolonged the relaxations to nerve stimulation. The evoked release of NO decreased to 72+/-11%, 55+/-16% and 61+/-14% of control, respectively after addition of sildenafil, tadalafil or vardenafil (all 10(-4) M, n=6-8, p<0.05).. Selective PDE 5 inhibitors influence the nerve-induced release of NO, probably via cGMP-mediated negative feedback. This negative feedback might explain why priapism is not seen during monotherapy with the PDE inhibitors.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Carbolines; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Imidazoles; In Vitro Techniques; Male; Muscle, Smooth; Nitrergic Neurons; Nitric Oxide; Penis; Phosphodiesterase Inhibitors; Piperazines; Priapism; Purines; Rabbits; Sildenafil Citrate; Sulfones; Tadalafil; Triazines; Vardenafil Dihydrochloride

To investigate whether changes in neuronal nitric oxide synthase (nNOS) protein expression and arginase activity are implicated in impairing the neurogenic cavernosal relaxation in aged rabbits, as NO is important in the neurogenic relaxation of corpus cavernosum during the erectile state.. Cavernosal specimens of young adult (3-6 months old) and aged (36-48 months old) rabbits were used for isometric tension experiments, Western blot analysis, cGMP determination and measurements of NOS and arginase activities.. The neurogenic relaxation and cGMP production in response to electrical-field stimulation were significantly impaired in aged cavernosal specimens. Western blot analysis showed that nNOS protein was highly expressed in cavernosal specimens from young rabbits, but was undetectable or greatly decreased in old rabbits, with no change in overall NOS activity. Arginase activity in aged cavernosal specimens was significantly higher than in young rabbits. Supplementing with excess l-arginine, or giving S-(2-boronoethyl)-l-cysteine as an arginase inhibitor, significantly increased the neurogenic relaxation at lower frequencies only in the younger rabbits.. These results suggest that impairment of neurogenic and NO-mediated relaxation in the aged corpus cavernosum possibly results from the down-regulation of nNOS protein. The reduced l-arginine bioavailability to nNOS due to accelerated arginase activity would lead to further impairment of neurogenic NO production, in concert with decreased nNOS protein expression.

Topics: Aging; Animals; Arginase; Blotting, Western; Cyclic GMP; Erectile Dysfunction; Male; Muscle Relaxation; Muscle, Smooth; Nitric Oxide Synthase Type I; Penile Erection; Rabbits

Hypercholesterolemia is one of the most important risk factors for the development of erectile dysfunction (ED) in men.. We employed an established mouse model of hypercholesterolemia.. We test for abnormalities in vasoreactivity in corporal tissue and temporally correlated changes in vasoreactivity with alterations in histology and protein expression.. A total of 150 mice were studied. A total of 100 apolipoprotein-E knockout (ApoE(-/-)) mice were fed a 1.25% cholesterol diet for 2, 4, 8, and 12 weeks (N = 25/group), while a group of ApoE(-/-) and wild-type Bl-6 mice were fed a normal diet. The study was terminated, and all mice were harvested at 22 weeks of age for vasoreactivity, histology, and protein studies from corporal tissues. Dose-response curves were generated to evaluate endothelium-dependent and endothelium-independent vasoreactivity, ex vivo. The contents of endothelial cells, smooth muscle cells, and smooth muscle/collagen ratio were assessed by immunohistochemistry staining or Masson staining. Level of cyclic guanosine monophosphate (cGMP) was detected by enzyme immunoassay assay. Levels of phosphorylated endothelial nitric oxide synthase (p-eNOS)/total eNOS, neuronal nitric oxide synthase (nNOS), and cyclic GMP-dependent kinase (cGK-1) protein were assessed by Western analysis.. Abnormalities in endothelium-dependent and endothelium-independent vasoreactivities, endothelial content, smooth muscle/collagen ratio, p-eNOS phosphorylation at Ser1177 only, nNOS, cGMP, and cGK-1 changed with the different durations of the high-cholesterol diet.. These data demonstrate that this mouse model is suitable for investigating aspects of hypercholesterolemic ED.

Topics: Animals; Blotting, Western; Cholesterol; Cyclic AMP; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Disease Models, Animal; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Erectile Dysfunction; Guanosine Monophosphate; Hypercholesterolemia; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penis

To explore the effect and the mechanism of moxibustion for treatment of diabetic erectile dysfunction (ED).. Diabetes mellitus (DM) rat model was induced by streptozotozin (STZ) and then penis erectile experiment of apomorphine (APO) was used to select diabetic ED rats model, which were divided into 2 groups: a model group and a moxibustion group, with another normal control group set up. The moxibustion group were treated with moxibustion at "Shenshu" (BL 23) and "Sanyinjiao" (SP 6) with small moxa cone about the size of a wheat grain. The effects on penis erectile, blood sugar and total NOS, cNOS, iNOS, and cGMP were investigated.. Moxibustion had a certain improving action on blood sugar, improved significantly erectile function, and more significantly increased NOS, cNOS, iNOS activities and cGMP contents in the penis.. Moxibustion has a certain action on the erectile function in the diabetic ED rats, which is related with improvement of blood sugar and promoting NO-cGMP pathway.

Topics: Animals; Blood Glucose; Cyclic GMP; Diabetes Complications; Diabetes Mellitus, Experimental; Erectile Dysfunction; Male; Moxibustion; Nitric Oxide; Rats; Rats, Sprague-Dawley; Signal Transduction

We previously reported a series of potent and selective pyrimidinyl pyrroloquinolone PDE5 inhibitors such as 2a for potential use in male erectile dysfunction (MED) (Sui, Z.; Guan, J.; Macielag, M. J.; Jiang, W.; Zhang, S.; Qiu, Y.; Kraft, P., Bhattacharjee, S.; John, T. M.; Craig, E.; Haynes-Johnson, D.; Clancy, J. J. Med. Chem. 2002, 45, 4094-4096). Unfortunately, the low aqueous solubility and poor oral bioavailability rendered them undesirable development candidates. To address this issue, we designed a series of analogues using two approaches: increasing the overall basicity and reducing molecular weight of the lead. Through earlier SAR studies, we discovered that the PDE5 potency of the pyrroloquinolones is insensitive to substitution on the pyrrole nitrogen. Basic functional groups such as pyridines and benzimidazoles were appended via the aromatic ring connected to the pyrrole nitrogen. Several truncated analogues were also designed and synthesized to improve oral absorption. These modifications allowed us to identify analogues with good oral bioavailability in rats, dogs, and monkeys while the high potency against PDE5 and desirable selectivity versus other PDE isozymes were maintained. Compounds R-11e and R-11l were selected as development candidates for MED and other indications.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Biological Availability; Blood Pressure; Cell Line; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Dogs; Electric Stimulation; Erectile Dysfunction; Macaca mulatta; Male; Penis; Pyrroles; Quinolones; Rats; Rats, Sprague-Dawley; Solubility; Stereoisomerism; Structure-Activity Relationship

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Down-Regulation; Erectile Dysfunction; Gene Expression Regulation; Gene Transfer Techniques; Genetic Therapy; Humans; Male; Penis; RNA, Small Interfering; Transgenes

Topics: Adult; Arginine; Chronic Disease; Citrulline; Cyclic GMP; Endothelium, Vascular; Erectile Dysfunction; Humans; Hypertension, Pulmonary; Infant; Male; Marketing; Nitric Oxide; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilator Agents

Erectile dysfunction associated with diabetes mellitus is caused in part by disordered endothelial smooth muscle relaxation, neuropathy, and a decrease in cavernosal nitric oxide synthase (NOS) activity. The purpose of this study was to determine whether a combination of sildenafil and adenoviral gene transfer of endothelial NOS (eNOS) could enhance the erectile response in diabetic rats. Five groups of animals were utilized: (1) age-matched control rats, (2) streptozotocin (STZ)-induced diabetic rats (60 mg/kg i.p.), (3) STZ-rats + sildenafil (2 mg/kg i.v.), (4) STZ-rats transfected with AdCMVbetagal or AdCMVeNOS, and (5) STZ-rats transfected with AdCMVeNOS +sildenafil (2 mg/kg i.v.). At 2 months after i.p. injection of STZ, groups 4 and 5 were transfected with the adenoviruses and 1-2 days after transfection, all animals underwent cavernosal nerve stimulation (CNS) to assess erectile function. Cyclic 3',5'-guanosine monophosphate (cGMP) levels were assessed in the cavernosal tissue. STZ-diabetic rats had a significant decrease in erectile function as determined by the peak intracavernosal pressure (ICP) and total ICP (area under the erectile curve; AUC) after CNS when compared to control rats. STZ-diabetic rats+AdCMVeNOS had a peak ICP and AUC, which were similar to control animals. STZ-diabetic rats administered sildenafil demonstrated a significant increase in peak ICP at the 5 and 7.5 V settings, while the AUC was significantly increased at all voltage (V) settings. The increase in both ICP and AUC of STZ-diabetic rats transfected with AdCMVeNOS at all V settings was greater than STZ-diabetic rats transfected with AdCMVbetagal. STZ-diabetic rats transfected with AdCMVeNOS and administered sildenafil had a significant increase in total ICP that was greater than eNOS gene therapy alone. Cavernosal cGMP levels were significantly decreased in STZ-diabetic rats, but were increased after transfection with AdCMVeNOS to values greater than control animals. In conclusion, overexpression of eNOS and cGMP in combination with sildenafil significantly increased both the peak ICP and total ICP to CNS in the STZ-diabetic rat, which was similar to the response observed in control rats. Moreover, the total erectile response was greater in STZ-diabetic rats receiving eNOS gene therapy plus sildenafil than STZ-rats receiving sildenafil or eNOS gene therapy alone.

Topics: Adenoviridae; Animals; Combined Modality Therapy; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Genetic Therapy; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Penile Erection; Piperazines; Purines; Rats; Rats, Inbred Strains; Sildenafil Citrate; Sulfones; Transfection; Vasodilator Agents

Erectile dysfunction (ED) with aging and diabetes mellitus is caused by impairment of the relaxation evoked by nitric oxide (NO) of penile cavernous smooth muscles and arterioles. However, the mechanism of ED in hypertension is unknown. Carbon monoxide (CO), which is produced by heme oxygenase (HO)-2 in the neuronal system is a neurotransmitter and a vasodilator. We examined the neurogenic role of CO in penile erection and the neurogenic mechanisms of ED in hypertension, using spontaneously hypertensive rats (SHR) or Wistar-Kyoto rats (WKY). The isometric tension of corpus cavernosum tissues from both strains was recorded after guanethidine and atropine treatment. Relaxation in response to electrical field stimulation (EFS) in WKY was suppressed dose-dependently by HO inhibitors both in the absence and presence of an NO synthase (NOS) inhibitor. Reverse transcription-polymerase chain reaction (RT-PCR) showed that the HO-2 gene was expressed in the corpus cavernosum. CO-saturated solution induced a concentration-dependent relaxation in WKY. The neurogenic relaxation to EFS in SHR was impaired as compared with that in WKY after the age of 5 weeks, when blood pressure began to be elevated, due to the attenuated relaxation in response to neurogenic NO and CO. In the corpus cavernosum of SHR, expression of the HO-2 and nNOS genes was similar, and NOx levels after EFS were similar to those of WKY. cGMP levels after EFS and the relaxation evoked by the NO donor was lower in SHR than WKY. Thiobarbituric acid-reacting substance (TBARS) levels were increased, and superoxide dismutase (SOD) activity was suppressed in SHR, as compared with those in WKY, suggesting that the increasing oxidative stress partially causes the impairment of NO-dependent relaxation. These findings suggest that CO regulates the relaxation evoked by EFS in the rat corpus cavernosum, and that ED in hypertension in rats results from an impairment of the relaxation induced by neurogenic CO and NO.

Topics: Animals; Carbon Monoxide; Cyclic GMP; Enzyme Inhibitors; Erectile Dysfunction; Gene Expression Regulation, Enzymologic; Heme Oxygenase (Decyclizing); Hypertension; Male; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oxidative Stress; Penile Erection; Penis; Protoporphyrins; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Vasodilation

Significant impairment in endothelial-derived nitric oxide is present in the diabetic corpus cavernosum. RhoA/Rho-kinase may suppress endothelial nitric oxide synthase (eNOS). Here, we tested the hypothesis that RhoA/Rho-kinase contributes to diabetes-related erectile dysfunction and down-regulation of eNOS in the streptozotocin (STZ)-diabetic rat penis. Colocalization of Rho-kinase and eNOS protein was present in the endothelium of the corpus cavernosum. RhoA/Rho-kinase protein abundance and MYPT-1 phosphorylation at Thr-696 were elevated in the STZ-diabetic rat penis. In addition, eNOS protein expression, cavernosal constitutive NOS activity, and cGMP levels were reduced in the STZ-diabetic penis. To assess the functional role of RhoA/Rho-kinase in the penis, we evaluated the effects of an adeno-associated virus encoding the dominant-negative RhoA mutant (AAVTCMV19NRhoA) on RhoA/Rho-kinase and eNOS and erectile function in vivo in the STZ-diabetic rat. STZ-diabetic rats transfected with AAVCMVT19NRhoA had a reduction in RhoA/Rho-kinase and MYPT-1 phosphorylation at a time when cavernosal eNOS protein, constitutive NOS activity, and cGMP levels were restored to levels found in the control rats. There was a significant decrease in erectile response to cavernosal nerve stimulation in the STZ-diabetic rat. AAVT19NRhoA gene transfer improved erectile responses in the STZ-diabetic rat to values similar to control. These data demonstrate a previously undescribed mechanism for the down-regulation of penile eNOS in diabetes mediated by activation of the RhoA/Rho-kinase pathway. Importantly, these data imply that inhibition of RhoA/Rho-kinase improves eNOS protein content and activity thus restoring erectile function in diabetes.

Topics: Adenoviridae; Amides; Animals; Blood Glucose; Body Weight; Cyclic GMP; Diabetes Mellitus, Experimental; Enzyme Inhibitors; Erectile Dysfunction; Gene Expression; Intracellular Signaling Peptides and Proteins; Male; Muscle Relaxants, Central; Myosin-Light-Chain Phosphatase; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Penis; Protein Serine-Threonine Kinases; Pyridines; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; Transfection

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cyclic Nucleotide Phosphodiesterases, Type 5; Erectile Dysfunction; Humans; Male; Phosphodiesterase Inhibitors

We investigated the mechanisms underlying the effects of an herbal formula (HF) in improving erectile dysfunction (ED), particularly in terms of nitric oxide (NO)-cGMP pathways. Two different rat models, 24-month-old rats (aging) and 10-month-old rats maintained chronically high plasma glucose levels (328 +/- 89 mg/dL) diabetes mellitus (DM), were treated with HF (100 mg/kg per day) for 10 days. We examined the electrostimulated penile responses, expression and activity of three enzymes: neuronal NO synthase (nNOS), endothelial NO synthase (eNOS) and caveolin-1 (CaV-1), and cGMP concentration that act upon the major NO-cGMP signaling pathways in penile tissue. Effect of HF on cGMP degradation was also examined using bovine vascular smooth-muscle cells pretreated with an NO donor, S-nitroso-N-acetylpenicillamine (SNAP). In aging and DM rats, the severely reduced peak intracavernous pressures (ICPs) in penile tissues were restored completely after HF treatment, and HF treatment significantly made the latency period earlier. Furthermore, the penile expression levels of nNOS, eNOS and CaV-1, Ca2+ -dependent NOS activities and cGMP concentrations were increased significantly in the HF-treated rats. Particularly, inhibitory effect of HF on cGMP degradation was confirmed also in cell system. These results indicate that new HF originated from a Korean traditional medicine (Ojayounjonghwon described in 'Dong Ui Bo Gam') can ameliorate the ED impaired by peripheral neuropathy and/or angiopathy, via the activation of NO-cGMP pathways.

Topics: Aging; Animals; Caveolin 1; Caveolins; Cyclic GMP; Diabetes Mellitus, Experimental; Erectile Dysfunction; Male; Muscle, Smooth; Nerve Tissue Proteins; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Penis; Plant Preparations; Pressure; Rats; Rats, Sprague-Dawley

Synthesis of furoyl and benzofuroyl pyrroloquinolones as potent and selective PDE5 inhibitors was reported. Their in vitro potencies in inhibiting PDE5 and selectivity in inhibiting other PDE isozymes (PDE1-4 and PDE6) were evaluated. Some of these compounds are more potent than sildenafil with better selectivity toward PDE1 and PDE6. Incorporation of solublizing groups resulted in bioavailable analogues. Selected compounds showed in vivo efficacy in anesthetized dog model for penile erection.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Biological Availability; Cell Line; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Dogs; Erectile Dysfunction; Furans; Isoenzymes; Male; Penile Erection; Quinolones; Rats; Structure-Activity Relationship

To evaluate the effects of the nitric oxide (NO)-donating compounds sodium nitroprusside (SNP), S-nitroso-glutathione (GSNO), S-nitroso-N-acetylcysteine (SNAC), S-nitroso-N-acetylcysteine-ethylester (SNACET), and linsidomine (SIN-1) on the adrenergic tension of isolated human seminal vesicle strip preparations. The significance of the NO-cyclic guanosine monophosphate (cGMP) pathway in the regulation of smooth muscle tone in the human genitourinary tract has been well established. However, information on the significance of NO-mediated signal transduction in the functional control of the mammalian seminal vesicles is still sparse.. Seminal vesicle strip preparations were applied to an organ bath system under standard conditions. Tension was induced by the addition of 10 microM norepinephrine. After stable tension plateaus had been reached, the drugs were added in a cumulative manner (0.01 to 100 microM) and the isometric responses of the tissue registered. The effects of the compounds on the phasic contractility of the tissue preparations were also evaluated. The adenylyl cyclase-stimulating agent forskolin was used as a reference compound known to interfere with the cyclic adenosine monophosphate pathway.. Adrenergic tension was dose dependently attenuated by the drugs. The rank order of potency, from greater to lesser, was GSNO, SNAC, SNP, SIN-1, forskolin, and SNACET. The rank order (from greater to lesser) with regard to the inhibitory effects of the compounds on the frequency of phasic contractions of the tissue induced by the addition of norepinephrine was GSNO, SNAC, SNP, and SIN-1; the effects of SIN-1, forskolin, and SNACET on the frequency of contractions were nearly equipotent.. Our results strongly support the hypothesis that the contractility of the human seminal vesicle is under the control of the NO-cGMP pathway. This finding may give a rationale for the use of S-nitrosothiols, such as GSNO and SNAC, in the pharmacotherapy of hyperexcitatory disturbances of ejaculation (premature ejaculation).

Topics: Adrenergic alpha-Agonists; Aged; Colforsin; Cyclic GMP; Ejaculation; Erectile Dysfunction; Humans; In Vitro Techniques; Isometric Contraction; Male; Middle Aged; Molsidomine; Muscle Contraction; Muscle, Smooth; Nitric Oxide Donors; Nitroprusside; Norepinephrine; S-Nitroso-N-Acetylpenicillamine; S-Nitrosoglutathione; Seminal Vesicles; Sexual Dysfunction, Physiological; Signal Transduction

To examine a potential association between the response to the phosphodiesterase-5 inhibitor sildenafil and angiotensin-converting enzyme (ACE), as well as NOS3 G894T genotypes in patients with erectile dysfunction (ED). An insertion/deletion (I/D) polymorphism in the gene encoding the ACE and a single nucleotide exchange polymorphism (G894T) in the gene NOS3 encoding endothelial nitric oxide synthase have been associated with cardiovascular disorders.. The response to sildenafil in 113 men with ED was monitored according to the patients' diaries. ACE and NOS3 genotypes were determined in patients with ED and in 108 healthy male blood donors.. Genotype distributions of ACE and NOS3 polymorphisms in the patient group were similar to those of the healthy control group. Analysis of the response to sildenafil revealed that 15 of 20 individuals homozygous for the ACE II genotype showed a positive erectile response after sildenafil use and only 46 of 93 D allele (combined DD and DI genotypes) carriers had a positive response (positive erectile response, odds ratio 3.07, 95% confidence interval 1.03 to 9.13, P = 0.04; chi-square test). Analysis of NOS3 genotypes revealed that 30 of 52 individuals homozygous for the G894 allele had a sufficient response to sildenafil and only 4 of 12 patients homozygous for the 894T allele had a sufficient erection.. It appears that patients with elevated ACE serum concentrations, as associated with the D allele of the ACE I/D polymorphism, are less likely to respond to sildenafil.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Adult; Aged; Alleles; Amino Acid Substitution; Cross-Sectional Studies; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Resistance; Erectile Dysfunction; Genotype; Humans; Male; Middle Aged; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Penis; Peptidyl-Dipeptidase A; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Polymorphism, Genetic; Purines; Retrospective Studies; Sildenafil Citrate; Sulfones; Vasodilation

Erectile dysfunction (ED) management in the following 3-5 years will be dominated by substances targeting the L-arginine-NO-guanylate cyclase-cGMP-PDE-5 pathway, resulting in an intracellular elevation of the cGMP concentrations. Promising alternatives to the PDE-5 inhibitors, such as guanylate cyclase activators and Rho-kinase inhibitors, may also effectively compliment a PDE-5 inhibitor. Intranasal application of the melanocortin agonist PT 141 (Melanotan II) seems to be promising. As scheduled sexual activities are not preferred by the majority of couples, the future of ED-therapy will focus on drugs with a 1-2 day long efficacy window, or a daily bedtime application of low dosage agents which result in nocturnal reoxygenation of the cavernous bodies and in turn in functional improvement. Elevation of the cGMP levels and improvement of endothelial function as a result of this approach also promises benefits in cardiovascular diseases and in LUTS.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Arginine; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drugs, Investigational; Enzyme Activation; Erectile Dysfunction; Forecasting; Guanylate Cyclase; Humans; Intracellular Signaling Peptides and Proteins; Male; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Protein Serine-Threonine Kinases; rho-Associated Kinases

The imbalance between vasoconstrictors and vasodilators may play an important role in the pathogenesis of erectile dysfunction (ED). A total of 36 patients with ED, organogenic [diabetic (n=12) and nondiabetic (n=12)] and psychogenic (n=12) etiology, and 12 healthy adult men as controls were included. The levels of endothelin-1 (ET-1), growth hormone (GH), angiotensin-converting enzyme activity (ACE), nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were determined in the flaccid penis cavernosal blood of patients and in cubital blood of patients and controls. In psychogenic ED, systemic ACE activity was elevated compared to controls (P<0.05). In diabetic and nondiabetic ED patients, systemic levels of ET-1 (P<0.0001 for both) and ACE activity (P<0.01 and <0.05) were higher while GH (P<0.0001 and <0.001), NO (P<0.0001 for both) and cGMP (P<0.01 for both) levels were lower compared to controls. In diabetic patients, systemic and cavernosal ET-1 levels (P<0.0001 for both) and cavernosal ACE activity levels (P<0.05) were significantly elevated while systemic and cavernosal NO (P<0.0001 for both) and GH (<0.001 and <0.05) levels were declined compared to psychogenic. In nondiabetic patients, systemic and cavernosal ET-1 levels (P<0.0001 for both) were significantly elevated while systemic and cavernosal NO (P<0.0001 for both) and systemic GH levels (P<0.05) were declined compared to psychogenic. Systemic NO was positively correlated with GH in psychogenic (r=0.616, P<0.05), diabetic (r=0.583, P<0.05) and nondiabetic (r=0.615, P<0.05) patients and correlated positively with cGMP (r=0.605, P<0.05) but negatively with ACE activities (r=-0.585, P<0.05) in diabetic patients. In conclusion, plasma levels of ET-1, ACE activities are elevated and associated with reduction of GH, NO and cGMP levels in the systemic and cavernous blood of ED patients. This disturbance may indicate endothelial dysfunction that may hind at their significance in the pathophysiology of ED.

Topics: Adult; Cyclic GMP; Diabetic Angiopathies; Endothelin-1; Endothelium, Vascular; Erectile Dysfunction; Human Growth Hormone; Humans; Male; Middle Aged; Nitric Oxide; Penis; Peptidyl-Dipeptidase A; Sexual Dysfunctions, Psychological; Vasoconstriction; Vasodilation

A Rho-kinase inhibitor increases corpus cavernosum (CC) pressure in an in vivo rat model (Chitaley, K., Wingard, C. J., Webb, R. C., Branam, H., Stopper, V. S., Lewis, R. W., and Mills, T. M. (2001) Nat. Med. 7, 119-122) suggesting that Rho-mediated Ca(2+) sensitization of CC smooth muscle maintains the flaccid (contracted) state. We directly demonstrate Ca(2+) sensitization of permeabilized rabbit and human CC and identify a highly expressed molecular component of this pathway. Ca(2+) sensitization of force induced by endothelin or GTPgammaS was significantly greater in CC than in rabbit ileum smooth muscle and was accompanied by a 17-fold higher RhoA content. Pull-down assays with the RhoA binding domain of mDia showed the high RhoA content of CC to be available for activation by GTPgammaS. Ca(2+) sensitization induced by endothelin, phenylephrine, or GTPgammaS was completely relaxed by the Rho kinase inhibitor Y-27632. Human and rabbit CC both express the phosphatase inhibitor CPI-17, the myosin phosphatase regulatory (MYPT-1) and catalytic (PP1delta) subunits, and two isoforms of Rho kinase. We suggest that high expression of RhoA contributes, through RhoA-mediated Ca(2+) sensitization, to the flaccid state of CC that can be reversed by a water-soluble, orally active Rho kinase inhibitor suitable for therapy of erectile dysfunction.

Topics: Animals; Calcium; Cyclic GMP; Endothelins; Erectile Dysfunction; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Male; Penile Erection; Rabbits; rhoA GTP-Binding Protein

Erectile dysfunction in the aging male is caused, in part, by inadequate relaxation of the corpora cavernosal smooth musculature. Calcitonin gene-related peptide (CGRP), a peptide neurotrasmitter localized in the corpora cavernosa, is down-regulated in the aging rat penis. We examined the hypothesis that this reduction in CGRP may contribute to decreased cavernosal smooth muscle relaxation. Therefore, we sought to determine whether adenoviral-mediated gene transfer of prepro-CGRP (AdRSVCGRP) could enhance erectile responses in aged rats. We found a significant decrease in CGRP concentrations and in cAMP and cGMP levels in aged rat cavernosal tissue compared to younger rats. Aged rats also had significantly lower erectile function as determined by cavernosal nerve stimulation compared to younger rats. Five days after transfection with AdRSVCGRP, these aged rats had an approximately threefold increase in cavernosal CGRP levels compared to animals transfected with adenoviruses encoding nuclear-targeted beta-galactosidase (AdRSV beta gal). The AdRSVCGRP-transfected animals also demonstrated an increase in CGRP mRNA and immunohistochemical localization of CGRP in the smooth muscle of the corpora cavernosa. In addition, cAMP levels in the corpora cavernosa were significantly increased, whereas cGMP levels remained unchanged. Adenoviral transduction efficiency of beta-galactosidase reporter gene was measured by chemiluminescence and was observed in cavernosal tissue 5 days after transfection with AdRSV beta gal. More importantly, 5 days after administration of AdRSVCGRP, a significant increase was observed in the erectile response to cavernosal nerve stimulation in the aged rat, similar to the response observed in younger rats. These data suggest that in vivo adenoviral gene transfer of CGRP can physiologically improve erectile function in the aged rat.

Topics: Adenoviridae; Aging; Animals; beta-Galactosidase; Calcitonin; Calcitonin Gene-Related Peptide; Cyclic AMP; Cyclic GMP; Erectile Dysfunction; Genetic Therapy; Immunohistochemistry; Luminescent Measurements; Male; Muscle, Smooth; Penile Erection; Penis; Protein Precursors; Rats; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transfection

We have reported that adrenomedullin (AM)-induced vasodilation is at least in part nitric oxide (NO)-cGMP-dependent in the rat. Although it is well known that NO is much involved in the erectile function, it is controversial as to whether AM influences the erectile function. Thus, we examined the effects of AM on intracavernous pressure (ICP) during penile erection. The left carotid artery of rats was cannulated to monitor of mean arterial pressure (MAP). Bipolar electrodes were positioned on the cavernous nerve. The right cavernous body was cannulated with a needle connected to a pressure transducer to monitor ICP. Electrical stimulation (ES) increased ICP in a voltage-dependent manner. Elevation of ICP continued during ES. The intracavernous injection of 0.5 nmol AM significantly potentiated ES-induced increases in both maximal developed ICP/MAP and area under the curve (ICP trace; AUC). Since AM slightly lowered MAP, ICP was normalized by MAP. i.v. administration of N(omega)-nitro-L-arginine, a NO synthase inhibitor, markedly decreased AM/ES-induced ICP elevation. However, in the presence of E-4021, a cGMP-specific phosphodiesterase inhibitor, AM further increased both ICP/MAP and AUC. These results suggest that a NO-cGMP pathway is involved in the regulation of AM-induced rat cavernous vasorelaxation.

Topics: Adrenomedullin; Animals; Arginine; Cyclic GMP; Disease Models, Animal; Enzyme Inhibitors; Erectile Dysfunction; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Penile Erection; Peptides; Phosphodiesterase Inhibitors; Piperidines; Quinazolines; Rats; Rats, Wistar

The primate model has been used for investigations on the physiology and pharmacology of erection. Recent in vitro investigations indicate that nitric oxide (NO)-donor act as the mediator of penile erection, but it is unclear whether NO-donor could enhance the relaxation effect of sildenafil on diabetic penile smooth muscle. To determine the relaxation effect of NO-donor on diabetic penile smooth muscle, we studied strips of corpus cavernosum tissue obtained from 15 diabetic cynomolgus monkey (Macaca fascicularis). Contraction was induced on isolated strips of corporal smooth muscle by norepinephrine; then relaxation was assessed with the administration of two agents: selective phosphodiesterase type 5 (PDE5) inhibitor (sildenafil citrate) and S-nitroso-N-acetylpenicillamine (SNAP), an NO-donor, and combination of both agents. Analysis of variance was used to compare the responses to the different agents under various treatments. It was concluded that NO-donor could not enhance the relaxation effect of sildenafil on corpus cavernosum of diabetic monkey.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Alloxan; Animals; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Diabetes Mellitus, Experimental; Drug Evaluation, Preclinical; Drug Interactions; Erectile Dysfunction; Macaca fascicularis; Male; Muscle, Smooth; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Norepinephrine; Penicillamine; Penis; Phenylephrine; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilator Agents

We designed and evaluated a new class of molecules, nitrosylated alpha-adrenergic receptor antagonists, as potential agents for the treatment of impotence. In in vitro studies with human and rabbit corpus cavernosum strips in organ chambers, the alpha-adrenergic receptor antagonists (alpha-ARAs) moxisylyte and yohimbine and their corresponding nitrosylated compounds, SNO-moxisylyte (NMI-221) and SNO-yohimbine (NMI-187), concentration-dependently relaxed endothelin-induced contraction. The nitrosylated compounds were significantly more potent than the parent alpha-ARA. In human tissues, the specific phosphodiesterase type 5 inhibitor zaprinast potentiated the relaxing effects of the nitrosylated compounds. Only nitrosylated compounds induced accumulation of cyclic GMP in rabbit corpus cavernosum strips. Yohimbine and NMI-187 demonstrated a potent alpha2-blocking activity, with no significant differences in pA2 values (8.9 versus 8.2, respectively). Moxisylyte and NMI-221 showed moderate potency in antagonizing phenylephrine contraction, with comparable pA2 values for both molecules (6.5 versus 6.6, respectively). alpha-Adrenergic receptor-binding studies showed similar binding affinities for the alpha-ARA and their corresponding nitrosylated compounds. In vivo, intracavernosal injection of nitrosylated molecules caused greater increases in intracavernosal pressure (NMI-221 versus moxisylyte) that were more long lasting than those of moxisylyte or yohimbine. There were no significant differences between nitrosylated and non-nitrosylated compounds in the magnitude of systemic mean arterial pressure decrease after intracavernosal injection. alpha-ARA and the nitrosylated compounds showed no pain-inducing activity as evaluated with the paw-lick model in mice. In summary, nitrosylated alpha-ARA have the dual functionalities of nitric oxide donors and alpha-ARA. These drugs induced penile erection in animals, suggesting their possible therapeutic value as agents for the local pharmacological treatment of impotence.

Topics: Adrenergic alpha-Antagonists; Animals; Cyclic GMP; Drug Design; Endothelins; Erectile Dysfunction; Humans; In Vitro Techniques; Male; Membranes; Mice; Moxisylyte; Muscle Contraction; Muscle, Smooth, Vascular; Nitroso Compounds; Penis; Phenylephrine; Rabbits; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, alpha-1; Vasodilator Agents; Yohimbine

Nitric oxide (NO), a mediator involved in penile erection, is synthesized by the nitric oxide synthase (NOS) family of enzymes. It has been shown that NOS activity decreases with age. To determine whether adenoviral-mediated overexpression of endothelial NOS (eNOS) could enhance erectile responses, we administered a recombinant adenovirus containing the eNOS gene (AdCMVeNOS) into the corpora cavernosum of the aged rat. Adenoviral expression of the beta-galactosidase reporter gene was observed in cavernosal tissue 1 day after intracavernosal administration of AdCMVbetagal; 1 day after administration of AdCMVeNOS, transgene expression was confirmed by immunoblot staining of eNOS protein, and cGMP levels were increased. The increase in cavernosal pressure in response to cavernosal nerve stimulation was enhanced in animals transfected with eNOS, and erectile responses to acetylcholine and zaprinast were enhanced at a time when the erectile response to the NO donor sodium 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate was not altered. These results suggest that in vivo gene transfer of eNOS, alone or in combination with a type V phosphodiesterase inhibitor, may constitute a new therapeutic intervention for the treatment of erectile dysfunction.

Topics: Acetylcholine; Adenoviridae; Aging; Animals; Cyclic GMP; Electric Stimulation; Erectile Dysfunction; Gene Transfer Techniques; Genetic Therapy; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Penis; Purinones; Rats; Rats, Sprague-Dawley

Topics: Combined Modality Therapy; Cyclic GMP; Dopamine Agonists; Erectile Dysfunction; Humans; Male; Penile Erection; Phosphodiesterase Inhibitors; Physician's Role; Prostaglandins; Psychiatry

Topics: Cyclic GMP; Drug Industry; Erectile Dysfunction; History, 19th Century; History, Ancient; Humans; Male; Medicine in the Arts; Paintings; Penile Erection; Piperazines; Sculpture; United States

Topics: Cyclic GMP; Drug Interactions; Erectile Dysfunction; Female; Humans; Hypotension; Male; Nitric Oxide; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones

Topics: Cyclic GMP; Drug Interactions; Erectile Dysfunction; Humans; Hypotension; Male; Nitrates; Phosphodiesterase Inhibitors; Piperazines; Purines; Risk Factors; Sildenafil Citrate; Sulfones

To investigate the effect of alloxan-induced diabetes mellitus (DM, a major risk factor for erectile dysfunction and associated with impaired endothelial function) on the formation of nitric oxide (NO), prostacyclin (PGI2), cGMP and cAMP in the corpus cavernosum of rabbits.. Rabbits were rendered diabetic (hyperglycaemic, nonketotic) with alloxan; after 3 and 6 months, the penises were excised and the corpus cavernosum processed for the study of PGI2, NO, cAMP and cGMP formation, using a range of stimulators and radioimmunoassays.. PGI2 formation in response to acetylcholine and phorbol ester, but not arachidonate, and cGMP formation in response to A23187 (NO-release dependent), was significantly diminished in diabetic rabbit corpus cavernosum compared with controls at both 3 and 6 months after the induction of DM. cAMP formation in response to forskolin and prostaglandin E1 was reduced after 6 but not 3 months, although nitroprusside-stimulated cGMP (activates guanylyl cyclase directly) was unaffected in cavernosal tissue from diabetic rabbits.. These results show that the formation of NO and PGI2, and adenylyl cyclase activity but not guanylyl cyclase, are impaired in the corpus cavernosum of diabetic rabbits. As NO and PGI2 are produced by the endothelium, these studies consolidate the view that endothelial dysfunction is a major contributor to erectile dysfunction in diabetes mellitus.

Topics: Alloxan; Animals; Cyclic AMP; Cyclic GMP; Diabetes Mellitus, Experimental; Epoprostenol; Erectile Dysfunction; Male; Nitric Oxide; Penis; Rabbits

To investigate further the role of the nitric oxide (NO)-cyclic GMP pathway as the mediator of relaxant neurotransmission in human corpus cavernosum and to establish whether impaired activity of this pathway contributes to the pathophysiology of impotence.. Samples of cavernosal tissue were obtained from 59 men undergoing penile operations. The controls comprised four men with penile carcinoma and 17 with Peyronie's disease. Of the impotent men, 35 had clinical evidence of penile vascular disease on pre-operative investigation, whilst three had non-vascular impotence. Each biopsy was divided into two strips which were then suspended under tension in organ bath chambers. The relaxant innervation of one strip of each pair was stimulated electrically whilst the other strip was left unstimulated. The formation of NO and cyclic GMP was calculated by comparing their respective tissue content in the stimulated and unstimulated strips.. Overall, stimulation of the relaxant innervation produced significant increases in the tissue content of both NO and cyclic GMP. Incubation with an inhibitor of NO biosynthesis abolished the mechanical relaxant response and the formation of both NO and cyclic GMP. The magnitude of relaxant response and the formation of NO was diminished in tissue from men with vascular impotence compared to controls. The increase in cyclic GMP content was similar in both these groups. Relaxant response, NO formation and cyclic GMP formation in tissue from men with non-vascular impotence was similar to controls.. This study provides further evidence that the NO-cyclic GMP pathway acts as the mediator of nerve-evoked smooth muscle relaxation in human corpus cavernosum. Diminished NO formation following relaxant nerve stimulation may account for impaired relaxant responses found in tissue from men with vascular impotence and may contribute to the cause of their erectile dysfunction.

Topics: Adult; Aged; Corpus Luteum; Cyclic GMP; Electric Stimulation; Erectile Dysfunction; Female; Humans; Impotence, Vasculogenic; Male; Middle Aged; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Penile Erection

Topics: Cyclic GMP; Erectile Dysfunction; Humans; Male; Nitric Oxide; Penile Erection

Nitric oxide has been identified as an endothelium-derived relaxing factor in blood vessels. We tried to determine whether it is involved in the relaxation of the corpus cavernosum that allows penile erection. The relaxation of this smooth muscle is known to occur in response to stimulation by nonadrenergic, noncholinergic neurons.. We studied strips of corpus cavernosum tissue obtained from 21 men in whom penile prostheses were inserted because of impotence. The mounted smooth-muscle specimens were pretreated with guanethidine and atropine and submaximally contracted with phenylephrine. We then studied the smooth-muscle relaxant responses to stimulation by an electrical field and to nitric oxide.. Electrical-field stimulation caused a marked, transient, frequency-dependent relaxation of the corpus cavernosum that was inhibited in the presence of N-nitro-L-arginine and N-amino-L-arginine, which selectively inhibit the biosynthesis of nitric oxide from L-arginine. The addition of excess L-arginine, but not D-arginine, largely reversed these inhibitory effects. The specific liberation of nitric oxide (by S-nitroso-N-acetylpenicillamine) caused rapid, complete, and concentration-dependent relaxation of the corpus cavernosum. The relaxation caused by either electrical stimulation or nitric oxide was enhanced by a selective inhibitor of cyclic guanosine monophosphate (GMP) phosphodiesterase (M&B 22,948). Relaxation was inhibited by methylene blue, which inhibits cyclic GMP synthesis.. Our findings support the hypothesis that nitric oxide is involved in the nonadrenergic, noncholinergic neurotransmission that leads to the smooth-muscle relaxation in the corpus cavernosum that permits penile erection. Defects in this pathway may cause some forms of impotence.

Topics: Adult; Aged; Arginine; Cyclic GMP; Electric Stimulation; Erectile Dysfunction; Humans; Male; Methylene Blue; Middle Aged; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitroarginine; Organ Culture Techniques; Penile Erection; Penis; Purinones; Synaptic Transmission