zaprinast and Disease-Models--Animal

Herein, we describe the rapid synthesis of a focused library of trisubstituted imidazo[4,5-b]pyridines and imidazo[4,5-c]pyridines from 2,4-dichloro-3-nitropyridine using the combination of solution-phase/solid-phase chemistry as new potential anti-inflammatory agents in the treatment of autoimmune diseases. Structure-activity relationship studies, followed by the structure optimization, provided hit compounds (17 and 28) which inhibited phosphodiesterase 4 (PDE4) with IC

Topics: Animals; Anti-Inflammatory Agents; Autoimmune Diseases; Cyclic Nucleotide Phosphodiesterases, Type 7; Disease Models, Animal; Female; Humans; Imidazoles; Inflammation; Male; Mice, Inbred BALB C; Phosphodiesterase 4 Inhibitors; Phosphodiesterase Inhibitors; Pyridines; Rats, Wistar

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

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

There is a major clinical need for new therapies for the treatment of chronic itch. Many of the molecular components involved in itch neurotransmission are known, including the neuropeptide NPPB, a transmitter required for normal itch responses to multiple pruritogens in mice. Here, we investigated the potential for a novel strategy for the treatment of itch that involves the inhibition of the NPPB receptor NPR1 (natriuretic peptide receptor 1). Because there are no available effective human NPR1 (hNPR1) antagonists, we performed a high-throughput cell-based screen and identified 15 small-molecule hNPR1 inhibitors. Using in vitro assays, we demonstrated that these compounds specifically inhibit hNPR1 and murine NPR1 (mNPR1). In vivo, NPR1 antagonism attenuated behavioral responses to both acute itch- and chronic itch-challenged mice. Together, our results suggest that inhibiting NPR1 might be an effective strategy for treating acute and chronic itch.

Topics: Animals; Behavior, Animal; Cell-Free System; Dermatitis, Contact; Disease Models, Animal; Ganglia, Spinal; Humans; Mice, Inbred C57BL; Mice, Knockout; Neurons; Pruritus; Receptors, Atrial Natriuretic Factor; Reproducibility of Results; Signal Transduction; Small Molecule Libraries

The G protein-coupled receptor 35 (GPR35), is considered important for nociceptive transmission, as suggested by accumulating evidence. This receptor was discovered in 1998; however, a lack of pharmacological tools prevented a complete understanding of its function and how to exploit it therapeutically. We studied the influence of CXCL17, kynurenic acid and zaprinast on nociceptive transmission in naïve and neuropathic mice. Additionally, we investigated the influence of kynurenic acid and zaprinast on morphine effectiveness in neuropathic pain.. The chronic constriction injury (CCI) of the sciatic nerve in Swiss mice was performed. The CXCL17, kynurenic acid, zaprinast and morphine were injected intrathecally into naive and CCI-exposed mice at day 14. To evaluate tactile and thermal hypersensitivity, the von Frey and cold plate tests were used, respectively.. Our results have shown, for the first time, that administration of CXCL17 in naïve mice induced strong pain-related behaviours, as measured by von Frey and cold plate tests. Moreover, we demonstrated that kynurenic acid and zaprinast diminished CXCL17-evoked pain-related behaviours in both tests. Kynurenic acid and zaprinast reduced thermal and tactile hypersensitivity developed by sciatic nerve injury and strongly enhanced the effectiveness of morphine in neuropathy.. Our study highlights the importance of GPR35 as a receptor involved in neuropathic pain development. Therefore, these results suggest that the modulation of GPR35 could become a potential strategy for the treatment of neuropathic pain.

Topics: Analgesics; Analgesics, Opioid; Animals; Behavior, Animal; Chemokines, CXC; Disease Models, Animal; Injections, Spinal; Kynurenic Acid; Male; Mice; Morphine; Pain Perception; Pain Threshold; Purinones; Receptors, G-Protein-Coupled; Sciatica; Spinal Cord

Topics: Animals; Bone Density; Bone Remodeling; Cyclic Nucleotide Phosphodiesterases, Type 5; Dexamethasone; Disease Models, Animal; Dose-Response Relationship, Drug; Glucocorticoids; Male; Osteoporosis; Oxidation-Reduction; Oxidative Stress; Phosphodiesterase 5 Inhibitors; Purinones; Pyrimidines; Rats

The use of phosphodiesterase 5 (PDE5) inhibitors to treat newborns with pulmonary hypertension is increasing. The effect of PDE5 inhibitors on the neonatal cerebral circulation remains unknown. The neonatal piglet model of chronic hypoxia-induced pulmonary hypertension allows the study of the effects of PDE5 inhibitors on both the pulmonary and cerebral circulations.. To determine whether the PDE5 inhibitor, zaprinast, causes dilation in pulmonary and middle cerebral arteries (MCA) of normoxic newborn piglets and those with chronic hypoxia-induced pulmonary hypertension, and to evaluate whether zaprinast alters responses to increased pressure (autoregulatory ability) of the MCA.. Two-day-old piglets were raised in normoxia or hypoxia for 3 or 10 days. Pulmonary arteries and MCA were isolated and pressurized, after which changes in diameter to zaprinast were measured. MCA pressure-diameter relationships were determined.. Dilation to zaprinast was similar in pulmonary arteries from normoxic and hypoxic piglets. Zaprinast dilated MCA from all groups but the response was diminished in MCA from piglets raised in hypoxia for 10 days. MCA pressure-diameter relationships (autoregulation) did not differ between the groups.. Pulmonary artery dilation to zaprinast supports the use of PDE5 inhibitors to treat pulmonary hypertension in neonates. PDE5 inhibitors function as MCA dilators but do not impair the pressure-diameter behavior of the cerebral circulation of either normoxic newborn piglets or those with chronic hypoxia-induced pulmonary hypertension. These findings suggest that cerebral autoregulation is likely to be intact with acute PDE5 inhibitor treatment in infants with pulmonary hypertension in conditions associated with chronic hypoxia.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Animals, Newborn; Chronic Disease; Disease Models, Animal; Hypertension, Pulmonary; Hypoxia; Middle Cerebral Artery; Phosphodiesterase Inhibitors; Pulmonary Artery; Purinones; Swine; Vasodilation

Recent evidence obtained in cultured glial cells indicates that cGMP-mediated pathways regulate cytoskeleton dynamics, glial fibrillary acidic protein expression and motility in astrocytes, as well as inflammatory gene expression in microglia, suggesting a role in the regulation of the glial reactive phenotype. The aim of this work was to examine if cGMP regulates the glial inflammatory response in vivo following CNS damage caused by a focal cryolesion onto the cortex in rats. Results show that treatment with the cGMP phosphodiesterase inhibitor zaprinast (10 mg/kg i.p.) 2 h before and 24 and 48 h after the lesion results 3 days post-lesion in notably enhanced astrogliosis manifested by increased glial fibrillary acidic protein immunoreactivity and protein levels around the lesion. In contrast, zaprinast decreased the number of round/ameboid lectin-positive cells and the expression of the activated microglia/macrophage markers Iba-1 and CD11b indicating decreased recruitment and activation of these cells. This altered inflammatory response is accompanied by a decrease in protein oxidative stress, apoptotic cell death and neuronal degeneration. In addition, zaprinast enhanced angiogenesis in the lesioned cortex probably as a result of vascular endothelial growth factor expression in reactive astrocytes. These results suggest that regulation of the glial inflammatory response may contribute to the reported neuroprotective effects of cGMP-phosphodiesterase inhibitors in brain injury.

Topics: Animals; Brain Injuries; Calcium-Binding Proteins; CD11b Antigen; Cell Count; Cell Death; Cerebral Cortex; Cryosurgery; Disease Models, Animal; Drug Administration Schedule; In Situ Nick-End Labeling; Lectins; Male; Microfilament Proteins; Neovascularization, Physiologic; Nerve Degeneration; Neuroglia; Oxidative Stress; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Sprague-Dawley; Time Factors; Vascular Endothelial Growth Factor A

Guanosine-specific cyclic nucleotide signaling is suggested to serve protective actions in the vasculature; however, the influence of selective pharmacologic modulation of cyclic guanosine monophosphate- synthesizing soluble guanylate cyclase or cyclic guanosine monophosphate-degrading phosphodiesterase on vessel remodeling has not been thoroughly examined. In this study, rat carotid artery balloon injury was performed and the growth-modulating effects of the soluble guanylate cyclase stimulator YC-1 or the cyclic guanosine monophosphate-dependent phosphodiesterase-V inhibitor zaprinast were examined. YC-1 or zaprinast elevated vessel cyclic guanosine monophosphate content, reduced medial wall and neointimal cell proliferation, stimulated medial and neointimal cellular apoptosis, and markedly attenuated neointimal remodeling in comparable fashion. Interestingly, soluble guanylate cyclase inhibition by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one failed to noticeably alter neointimal growth, and concomitant zaprinast with YC-1 did not modify any parameter compared to individual treatments. These results provide novel in vivo evidence that YC-1 and zaprinast inhibit injury-induced vascular remodeling through antimitogenic and proapoptotic actions and may offer promising therapeutic approaches against vasoproliferative disorders.

Topics: Animals; Apoptosis; Carotid Artery Injuries; Cell Proliferation; Cyclic GMP; Disease Models, Animal; Enzyme Activators; Guanylate Cyclase; Indazoles; Male; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Sprague-Dawley

BKCa channels regulate pulmonary arterial pressure, and protein kinase C (PKC) inhibits BK(Ca) channels, but little is known about PKC-mediated modulation of BKCa channel activity in pulmonary arterial smooth muscle. Studies were carried out to determine mechanisms of PKC modulation of BKCa channel activity in pulmonary arterial smooth muscle cells (PASMC) of the fawn-hooded rat (FHR), an animal model of pulmonary hypertension. Forskolin opened BKCa channels in FHR PASMC, which was blocked by PKC activation, and reversed by the phosphodiesterase (PDE) inhibitors IBMX, milrinone, and zaprinast. PDE inhibition also blocked the vasoconstrictor response to PKC activation in FHR pulmonary arteries. These results indicate that PKC inhibits cAMP-induced activation of BKCa channels and causes pulmonary vasoconstriction in hypertensive pulmonary arterial smooth muscle via PDE, which further suggests PDE inhibitors for treatment of pulmonary hypertension.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Colforsin; Cyclic AMP; Disease Models, Animal; Hypertension, Pulmonary; Milrinone; Muscle, Smooth, Vascular; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Potassium Channels, Calcium-Activated; Protein Kinase C; Pulmonary Artery; Purinones; Rats; Vasoconstriction

The liver has the remarkable ability to regenerate following damage or surgical resection. Although this feature of the liver has been studied for over 100 years, the trigger of the liver regeneration cascade remains controversial. Recent experimental evidence supports the hypothesis that nitric oxide (NO) and prostaglandins (PGs), released secondary to an increase in the blood flow-to-liver mass ratio following two-thirds partial hepatectomy (PHx), work synergistically to trigger liver regeneration. To extend this research, the hypothesis that NO and PGs are potential therapeutic targets to potentiate the liver regeneration cascade is tested. The NO donor s-nitroso-n-acetylpenicillamine, the phosphodiesterase V antagonist zaprinast (ZAP) and PGI2 each potentiated c-fos messenger RNA expression, an index of initiation of the liver regeneration cascade, following PHx. Also, the triple combination of s-nitroso-n-acetylpenicillamine, ZAP and PGI2 potentiated c-fos messenger RNA expression. These results support the hypothesis that NO and PGs can potentiate initiation of the regeneration cascade. An additional index of liver weight restoration 48 h after PHx was also used to test the hypothesis, because this index encompasses the entire liver regeneration cascade. ZAP and 6-keto-PGF1alpha, a stable metabolite of PGI2, and the combination of ZAP and 6-keto-PGF1alpha, each potentiated liver weight restoration 48 h after PHx. These results also provide support for the hypothesis that NO and PGs are possible therapeutic targets to potentiate liver regeneration following surgical resection.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Blotting, Northern; Disease Models, Animal; Epoprostenol; Gene Expression; Genes, fos; Hepatectomy; Liver; Liver Regeneration; Male; Nitric Oxide; Organ Size; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Sprague-Dawley; RNA, Messenger

Intellectual function is impaired in patients with hyperammonemia and hepatic encephalopathy. Chronic hyperammonemia with or without liver failure impairs the glutamate-nitric oxide-cGMP pathway function in brain in vivo and reduces extracellular cGMP in brain as well as the ability of rats to learn a Y maze conditional discrimination task. We hypothesized that the decrease in extracellular cGMP may be responsible for the impairment in learning ability and intellectual function and that pharmacological modulation of the levels of cGMP may restore learning ability. The aim of this work was to try to reverse the impairment in learning ability of hyperammonemic rats by pharmacologically increasing extracellular cGMP in brain. We assessed whether learning ability may be restored by increasing extracellular cGMP in brain by continuous intracerebral administration of: (1) zaprinast, an inhibitor of the phosphodiesterase that degrades cGMP or (2) cGMP. We carried out tests of conditional discrimination learning in a Y maze with control and hyperammonemic rats treated or not with zaprinast or cGMP. Learning ability was reduced in hyperammonemic rats, which needed more trials than control rats to learn the task. Continuous intracerebral administration of zaprinast or cGMP restored the ability of hyperammonemic rats to learn this task. Pharmacological modulation of extracellular cGMP levels in brain may be a useful therapeutic approach to improve learning and memory performance in individuals in whom cognitive abilities are impaired by different reasons, for example in patients with liver disease who present hyperammonemia and decreased intellectual function.

Topics: Animals; Brain; Cyclic GMP; Disease Models, Animal; Extracellular Fluid; Hepatic Encephalopathy; Hyperammonemia; Learning Disabilities; Male; Maze Learning; Memory Disorders; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Wistar; Recovery of Function; Treatment Outcome; Up-Regulation

Guanosine 3', 5'-cyclic monophosphate (cGMP) acts as a relaxant second messenger in the cerebral vessels. cGMP-specific phosphodiesterase type 5 (PDE5) inhibitor increases intracellular cGMP levels. This study investigated the effect of the PDE5 inhibitor on the ischemic brain.. Regional cerebral blood flow (rCBF), cGMP concentration, and infarction volume were measured in the rat middle cerebral artery occlusion model. Ten minutes after ischemia, the animals received an intravenous (i.v.) infusion of vehicle (phosphate-buffered saline), PDE5 inhibitor, zaprinast (10 mg/kg), or nitric oxide donor, S-nitroso-N-acetyl-penicillamine (SNAP, 100 microg/kg). rCBF was measured continuously by laser-Doppler flowmetry in the ischemic penumbra of the ischemic and contralateral sides under continuous blood pressure monitoring. cGMP concentrations were determined using the enzyme immunoassay and infarct volumes were estimated by 2,3,5-triphenyltetrazolium chloride staining.. The administration of zaprinast significantly increased rCBF in the ischemic brain compared with the pre-drug control value despite the decreased mean blood pressure, whereas it did not affect rCBF in the contralateral side. The cGMP concentration was significantly higher in the ischemic cortex compared with the contralateral side. SNAP infusion increased the cGMP concentration in the bilateral cortices to a similar extent. The volume of cerebral infarction was significantly decreased by zaprinast administration.. The PDE5 inhibitor zaprinast may selectively increase CBF in the ischemic brain via increased cGMP levels, thus providing a new strategy against acute cerebral infarction.

Topics: Analysis of Variance; Animals; Blood Circulation Time; Blood Pressure; Brain Ischemia; Cerebrovascular Circulation; Cyclic GMP; Disease Models, Animal; Functional Laterality; Immunoenzyme Techniques; Infarction, Middle Cerebral Artery; Laser-Doppler Flowmetry; Male; Nitric Oxide Donors; Penicillamine; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Wistar; Regional Blood Flow; Tetrazolium Salts; Time Factors

In different animal models, photoreceptor degeneration was correlated to an abnormal increase in cGMP concentration. The cGMP-induced photoreceptor toxicity was demonstrated by applying the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine on retinal explants. To assess the role of cGMP-gated channels in this cGMP toxicity, the Ca(2+) channel blockers verapamil and L- and D-diltiazem, which block cGMP-gated channels with different efficacies, were applied to in vitro animal models of photoreceptor degeneration. These models included: (i) adult rat retinal explants incubated with zaprinast, a more specific inhibitor of the rod phosphodiesterase than 3-isobutyl-1-methylxanthine and (ii) rd mouse retinal explants. Photoreceptor apoptosis was assessed by terminal dUTP nick end labelling and caspase 3 activation. Effects of the blockers on the synaptic rod Ca(2+) channels were measured by patch-clamp recording. In the zaprinast-induced photoreceptor degeneration model, both diltiazem isomers rescued photoreceptors whereas verapamil had no influence. Their neuroprotective efficacy was correlated to their inhibition of cGMP-gated channels (l-diltiazem>d-diltiazem>verapamil=0). In contrast, all three Ca(2+) channel blockers suppressed rod Ca(2+) channel currents similarly. This suppression of the currents by the diltiazem isomers was very weak (16.5%) at the neuroprotective concentration (10 microm). In rd retinal explants, both diltiazem isomers also slowed down rod degeneration in contrast to verapamil. L-diltiazem exhibited this effect at concentrations ranging from 1 to 20 microm. This study further supports the photoreceptor neuroprotection by diltiazem particularly in the rd mouse retina, whereas the absence of neuroprotection by verapamil further suggests the role of cGMP-gated channel activation in the induction of photoreceptor degeneration.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Animals, Newborn; Blotting, Western; Cadmium Chloride; Calcium Channel Blockers; Cell Death; Cells, Cultured; Cyclic Nucleotide-Gated Cation Channels; Diltiazem; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; In Situ Nick-End Labeling; In Vitro Techniques; Ion Channels; Mice; Mice, Mutant Strains; Nerve Degeneration; Neuroglia; Phosphodiesterase Inhibitors; Photoreceptor Cells; Purinones; Rats; Rats, Wistar; Swine; Verapamil

Many infants with congenital diaphragmatic hernias (CDHs) experience persistent pulmonary hypertension that is refractory to treatment with inhaled nitric oxide (NO). We have examined the responses of isolated pulmonary arterioles from prenatal and postnatal rats with and without nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether)-induced CDH to a variety of activators of the NO-cyclic guanosine monophosphate (cGMP) pathway.. Right-sided CDH was induced in fetal rats by feeding nitrofen to pregnant rats on day 12 of gestation. Control rats were fed olive oil (vehicle). Third-generation pulmonary arterioles were isolated from the right lung of prenatal rats at term and from newborn rats within 8 hours after birth. Responses to increasing concentrations of sodium nitroprusside (SNP), atrial natriuretic peptide, or 8-bromo-cGMP were measured in pulmonary arterioles from control rats and from rats with nitrofen-induced CDH. Postnatal responses to 8-bromo-cGMP were also recorded in the presence of zaprinast, a type V phosphodiesterase inhibitor.. Pulmonary arterioles from prenatal rats did not dilate in response to SNP, atrial natriuretic peptide, or 8-bromo-cGMP. Vasodilatory responses of postnatal pulmonary arterioles from control rats to SNP and 8-bromo-cGMP were significantly greater than for arterioles from rats with CDH. Zaprinast pretreatment resulted in similar responses for postnatal CDH and control arterioles to 8-bromo-cGMP.. Postnatal pulmonary arterioles from CDH rats exhibit altered nitrovasodilator responsiveness, which may be due to rapid degradation of cGMP.

Topics: Animals; Arterioles; Atrial Natriuretic Factor; Cyclic GMP; Disease Models, Animal; Hernia, Diaphragmatic; Hernias, Diaphragmatic, Congenital; Hypertension, Pulmonary; Lung; Nitric Oxide; Nitroprusside; Pesticides; Phenyl Ethers; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Sprague-Dawley; Vasodilation; Vasodilator Agents

To compare the direct pulmonary vasodilating activity and specificity of phosphodiesterase-5 (zaprinast) and phosphodiesterase-3 (milrinone) inhibitors on the pulmonary vascular (PV) bed of the spontaneously breathing cat with an intact chest.. Prospective, randomized animal study.. Laboratory of university hospital.. Experiments were performed in vivo in intact-chest, spontaneously breathing cats with controlled pulmonary blood flow and constant left atrial pressure.. The responses to intralobar injections of zaprinast and milrinone were investigated at low PV tone. PV tone was then increased by intralobar arterial infusion of a thromboxane A(2) mimic, U46619. Animals received intralobar bolus injections of zaprinast or milrinone, followed by continuous IV infusion of the drug, which was administered in incremental doses titrated to produce a 20% reduction in mean systemic arterial pressure.. At low PV tone, zaprinast, but not milrinone, decreased lobar arterial pressure (LoAP). At elevated PV tone, both drugs caused dose-dependent decreases in LoAP; however, milrinone caused significantly less pulmonary vasodilation. Dose-related decreases in mean systemic arterial pressure were observed with milrinone, but not with zaprinast. When the continuous IV infusion was titrated to produce a 20% reduction in mean systemic arterial pressure, the decreases in lobar arterial pressure with zaprinast infusion were significantly greater than those produced by milrinone.. These data show that zaprinast and milrinone exert a direct in vivo vasodilator effect on the PV bed at low (zaprinast) and elevated (zaprinast and milrinone) PV tone; however, at elevated PV tone, the pulmonary vasodilator effect was greater with zaprinast then with milrinone. This suggests that phosphodiesterase-5 inhibitors may potentially offer a therapeutic alternative in the management of acute pulmonary hypertension.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 3',5'-Cyclic-AMP Phosphodiesterases; 3',5'-Cyclic-GMP Phosphodiesterases; Analysis of Variance; Animals; Cats; Cyclic Nucleotide Phosphodiesterases, Type 3; Cyclic Nucleotide Phosphodiesterases, Type 5; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Hypertension, Pulmonary; Infusions, Intravenous; Injections, Intralesional; Male; Milrinone; Phosphoric Diester Hydrolases; Probability; Pulmonary Circulation; Purinones; Random Allocation; Risk Factors; Sensitivity and Specificity; Vascular Resistance

Cyclic GMP plays an important role in maintaining homeostasis in the gastric mucosa. NSAIDs damage the mucosa by mechanisms that may be mediated by alterations in the intragastric concentration of cyclic GMP. To test this hypothesis we studied the effects of the oral administration of acetylsalicylic acid (100, 300, and 500 mg/kg), piroxicam (5, 10, and 20 mg/kg) and sodium diclofenac (10, 25, 50, and 100 mg/kg), and of their interaction with zaprinast (5 mg/kg) and IBMX (10 mg/kg), on intragastric concentrations of cyclic GMP and the gastric erosive index in rats. All determinations were done 3 hr after the NSAID was given. All NSAIDs induced dose-dependent decreases in mucosal concentrations of cyclic GMP, which correlated inversely with the surface area showing mucosal injury. In contrast, cyclic GMP concentrations remained normal, and no intragastric damage was seen in rats given zaprinast (cyclic GMP-specific phosphodiesterase inhibitor) or IBMX (non-specific phosphodiesterase inhibitor) or in combination with NSAIDs. These findings are in line with the hypothesis that cyclic GMP is involved in the biochemical mechanisms of NSAID-induced gastric injury.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cyclic GMP; Disease Models, Animal; Drug Interactions; Gastric Mucosa; Gastritis; Male; Phosphodiesterase Inhibitors; Primary Prevention; Purinones; Random Allocation; Rats; Rats, Wistar; Sensitivity and Specificity

Congenital heart disease associated with increased pulmonary blood flow produces pulmonary hypertension. To characterize vascular alterations in the nitric oxide (NO)-cGMP cascade induced by increased pulmonary blood flow and pulmonary hypertension, 10 fetal lambs underwent in utero placement of an aortopulmonary vascular graft (shunt). When the lambs were 4-6 wk of age, we assessed responses of pulmonary arteries (PAs) and pulmonary veins (PVs) isolated from lungs of control and shunted lambs. PVs from control and shunted lambs relaxed similarly to exogenous NO (S-nitrosyl-acetyl-penicillamine), to NO produced endogenously (zaprinast and A-23187), and to cGMP (atrial natriuretic peptide). In contrast, relaxations to A-23187 and zaprinast were blunted in PAs isolated from shunted lambs relative to controls. Inhibitors of NO synthase (NOS) and soluble guanylate cyclase constricted control but not shunt PAs, indicating reduced basal NOS activity in shunt PAs. Pretreatment of shunt PAs with the substrates L-arginine and sepiapterin, a precursor for tetrahydrobiopterin synthesis, did not augment A-23187 relaxations. However, pretreatment with superoxide dismutase and catalase significantly enhanced A-23187 relaxations in shunt PAs. We conclude that increased pulmonary blood flow induces an impairment of endothelium-dependent relaxation that is selective to PAs. The impaired relaxation may be mediated in part by excess superoxide production.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Atrial Natriuretic Factor; Calcimycin; Disease Models, Animal; Endothelium, Vascular; Enzyme Inhibitors; Fetus; Guanylate Cyclase; Hypertension, Pulmonary; In Vitro Techniques; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Phosphodiesterase Inhibitors; Pulmonary Artery; Pulmonary Circulation; Pulmonary Veins; Purinones; Sheep

To determine the effect of combining inhaled nitric oxide (NO) with an inhibitor of guanosine 3',5'-cyclic monophosphate-specific phosphodiesterase on total and segmental lung resistances.. A controlled laboratory study in isolated blood-perfused lungs prepared from lambs.. Animal research facility affiliated with a university teaching hospital.. Five newborn lambs at <48 hrs of life.. Isolated blood-perfused lungs were prepared and treated with indomethacin (40 microg/mL) to inhibit prostaglandin synthesis. After a baseline period of normoxia (28% oxygen), pulmonary hypertension was induced with the thromboxane mimetic U46619 (0.1-0.4 microg/kg/min). During pulmonary hypertension, lungs were studied with inhaled NO only, with infusion of zaprinast only (0.25 mg/kg bolus and 0.05 mg/kg/min infusion), and with a combination of the two. For each study condition, the total pressure decrease across the lung was measured, and the inflow-outflow occlusion technique was used to partition the total pressure gradient measured at constant flow (100 mL/kg/min) into gradients across relatively noncompliant large arteries and veins and more compliant small arteries and veins.. U46619 infusion produced significant pulmonary vasoconstriction. The combination of inhaled NO and zaprinast decreased the total pressure decrease across the lung significantly more than NO alone. This effect was primarily attributable to a significantly greater decrease in gradient across the small artery segment after inhaled NO and zaprinast compared with NO alone.. Guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition with zaprinast enhances the effect of inhaled NO, particularly in conditions in which small arteries represent the site of resistance. Phosphodiesterase inhibition may be a promising adjunct to inhaled NO for the treatment of persistent pulmonary hypertension.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Administration, Inhalation; Animals; Animals, Newborn; Cyclic GMP; Cyclooxygenase Inhibitors; Disease Models, Animal; Drug Evaluation, Preclinical; Drug Synergism; Drug Therapy, Combination; Hypertension, Pulmonary; In Vitro Techniques; Indomethacin; Nitric Oxide; Phosphodiesterase Inhibitors; Purinones; Time Factors; Vascular Resistance; Vasodilator Agents

The aim of this study was to assess the role of nitric oxide (NO) and endothelin (ET)-1 in the pathophysiology of persistent pulmonary hypertension of the newborn in fetal lambs with a surgically created congenital diaphragmatic hernia (CDH). The pulmonary vascular response to various agonists and antagonists was assessed in vivo between 128 and 132 days gestation. Age-matched fetal lambs served as control animals. Control and CDH lambs had similar pulmonary vasodilator responses to acetylcholine, sodium nitroprusside, zaprinast, and dipyridamole. The ET(A)-receptor antagonist BQ-123 caused a significantly greater pulmonary vasodilatation in CDH than in control animals. The ET(B)-receptor agonist sarafotoxin 6c induced a biphasic response, with a sustained pulmonary vasoconstriction after a transient pulmonary vasodilatation that was not seen in CDH animals. We conclude that the NO signaling pathway in vivo is intact in experimental CDH. In contrast, ET(A)-receptor blockade and ET(B)-receptor stimulation significantly differed in CDH animals compared with control animals. Imbalance of ET-1-receptor activation favoring pulmonary vasoconstriction rather than altered NO-mediated pulmonary vasodilatation is likely to account for persistent pulmonary hypertension of the newborn in fetal lambs with a surgically created CDH.

Topics: Acetylcholine; Animals; Antihypertensive Agents; Cyclic GMP; Dipyridamole; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Female; Hernia, Diaphragmatic; Hernias, Diaphragmatic, Congenital; Hypertension, Pulmonary; Nitric Oxide; Nitroprusside; Peptides, Cyclic; Phosphodiesterase Inhibitors; Pregnancy; Pulmonary Circulation; Purinones; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Sheep; Vasoconstrictor Agents; Vasodilator Agents; Viper Venoms

Pulmonary hypertension plays a significant role in the pathophysiology of congenital diaphragmatic hernia (CDH). Although there has been an intensive research effort directed at mediators that may cause pulmonary vasoconstriction, no single agent has been identified. The authors hypothesize that there may be an alteration in the cGMP-nitric oxide (NO) pathway of vasodilatation contributing to the pulmonary hypertension observed in CDH. The purpose of these studies is to begin to elucidate vasoactive properties of pulmonary vessels with particular attention to the cGMP-NO pathway of vasodilatation in fetal lambs with CDH.. Fourth-generation pulmonary arteries and pulmonary veins were dissected from both right and left lungs of eight, 139-day gestational fetuses with surgically created CDH. Vessels were studied with standard isolated tissue bath techniques. Experiments examined basal release of NO in endothelium-intact PVs and PAs of both right and left lungs by measuring the contractile force of vessels constricted with norepinephrine (NE) in the presence and absence of the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine (L-NA). Concentration-response curves to the vasodilating agents zaprinast and A23187 were also obtained in vessels contracted by NE.. Left and right pulmonary artery responses to NE are enhanced over those of historic controls. Pretreatment of left pulmonary arteries with L-NA enhances the vasoconstrictor response to NE, whereas right PAs show no increased response. Relaxation responses to A23187 and zaprinast, in both left and right pulmonary arteries were not different from control lambs. Relaxation responses of both left and right pulmonary veins to A23187 and zaprinast are blunted compared with controls. This blunting is significantly more in left pulmonary veins than right. Further, right but not left pulmonary veins display enhanced vasoconstrictive response to NE after L-NA pretreatment.. The NO-cGMP pathway of vasodilatation is abnormal in the near term, fetal lamb with CDH. These abnormalities were most apparent in pulmonary veins and may reflect abnormal NOS activity or content between left and right lungs of the fetal lamb with CDH. Pulmonary arteries from CDH lambs have basal and stimulated NO release equal to that of historic controls but appear to be hypersensitive to exogenous vasoconstrictors.

Topics: Animals; Calcimycin; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Fetus; Hernia, Diaphragmatic; Ionophores; Nitric Oxide; Phosphodiesterase Inhibitors; Pulmonary Artery; Pulmonary Veins; Purinones; Sheep; Vasoconstriction; Vasodilation

An experimental ovine fetal model for perinatal pulmonary hypertension of the neonate (PPHN) was characterized by altered pulmonary vasoreactivity and structure. Because past studies had suggested impaired nitric oxide-cGMP cascade in this experimental model, we hypothesized that elevated phosphodiesterase (PDE) activity may contribute to altered vascular reactivity and structure in experimental PPHN. Therefore, we studied the effects of the PDE inhibitors zaprinast and dipyridamole on fetal pulmonary vascular resistance and PDE5 activity, protein, mRNA, and localization in normal and pulmonary hypertensive fetal lambs. Infusion of dipyridamole and zaprinast lowered pulmonary vascular resistance by 55 and 35%, respectively, in hypertensive animals. In comparison with control animals, lung cGMP PDE activity was elevated in hypertensive fetal lambs (150%). Increased PDE5 activity was not associated with either an increased PDE5 protein or mRNA level. Immunocytochemistry demonstrated that PDE5 was localized to vascular smooth muscle. We concluded that PDE5 activity was increased in experimental PPHN, possibly by posttranslational phosphorylation. We speculated that these increases in cGMP PDE activity contributed to altered pulmonary vasoreactivity in experimental perinatal pulmonary hypertension.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Animals, Newborn; Blood Pressure; Chronic Disease; Cyclic Nucleotide Phosphodiesterases, Type 5; Dipyridamole; Disease Models, Animal; Female; Gestational Age; Hypertension, Pulmonary; Lung; Phosphodiesterase Inhibitors; Pregnancy; Pulmonary Circulation; Purinones; Sheep; Vascular Resistance

We investigated the effect of zaprinast (M&B 22948), a specific cGMP phosphodiesterase inhibitor, on pulmonary arteries isolated from lambs with persistent pulmonary hypertension following prenatal ligation of the ductus arteriosus. Relaxations to sodium nitroprusside, which donates nitric oxide inside the smooth muscle cell, were significantly decreased in pulmonary arteries from ligated lambs. Pretreatment with 3 x 10(-5) M zaprinast restored them to levels close to those observed in untreated arteries from control animals. Further studies in intact newborn lambs were then conducted under three experimental conditions: (1) NO inhalation at 6 ppm, (2) zaprinast infusion at 0.05 mg/kg/min, and (3) combination therapy of zaprinast infusion in addition to inhaled NO at 6 ppm. Combined therapy with NO and zaprinast decreased the pulmonary artery pressure (34.3 +/- 3%) and pulmonary vascular resistance (64 +/- 7%) and increased pulmonary blood flow (88 +/- 34%) and postductal PaO2 (287 +/- 34%) to a significantly greater extent than NO alone, zaprinast alone, or the sum of these two responses, indicating a true synergistic effect. Zaprinast pretreatment also markedly increased the duration of pulmonary vasodilation to nitric oxide. There was no effect on systemic blood pressure with the combined therapy. We conclude that zaprinast pretreatment significantly enhances the effect of sodium nitroprusside on isolated pulmonary arteries, as well the effect of inhaled NO at 6 ppm in newborn lambs with persistent pulmonary hypertension. We speculate that phosphodiesterase inhibition may increase the response rate to NO or allow the use of much lower inhaled concentrations of NO.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Animals, Newborn; Disease Models, Animal; Drug Evaluation, Preclinical; Drug Synergism; Drug Therapy, Combination; Hemodynamics; Hypertension, Pulmonary; In Vitro Techniques; Nitric Oxide; Nitroprusside; Phosphodiesterase Inhibitors; Pulmonary Artery; Purinones; Random Allocation; Sheep; Vasodilation

The effect of pharmacological manipulation of atriopeptin (AP) activity on sodium excretion and blood pressure was examined in the rat aortovenocaval (A-V) fistula model of cardiac failure. Introduction of an A-V shunt led to a marked and sustained elevation of plasma AP immunoreactivity and urinary cGMP levels. Further elevation of plasma AP levels by infusion of exogenous peptide induced modest increases in urinary sodium and cGMP excretion and a decrease in blood pressure but these responses were significantly attenuated compared to sham-operated animals. In contrast, low-dose infusion of M + B 22948 (a cGMP phosphodiesterase inhibitor) or thiorphan [a neutral endopeptidase (membrane metallo-endopeptidase, EC 3.4.24.11) inhibitor] induced a natriuresis in A-V fistula rats, which exceeded that seen in control animals given these compounds and matched the peak natriuresis produced in sham-operated animals by high doses of AP. In the doses used, these compounds had little effect on blood pressure. The greater renal efficacy of M + B 22948 in A-V fistula rats is consistent with postreceptor facilitation of AP activity. The effect of thiorphan on sodium excretion was accompanied by a pronounced increase in urinary cGMP and AP immunoreactivity excretion (and was attenuated by anti-AP monoclonal antibody) but could not be explained solely in terms of an increase in circulating AP levels. It is proposed that thiorphan allows filtered AP to reach renal tubule sites that are normally inaccessible to the peptide and are thus protected from down-regulation by high circulating AP levels. The implication of these observations for patients in cardiac failure is the potential for using pharmacological agents to maximize the response to endogenous AP without compromising cardiac function.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Antibodies, Monoclonal; Atrial Natriuretic Factor; Blood Pressure; Cyclic GMP; Disease Models, Animal; Heart Failure; Male; Purinones; Rats; Rats, Inbred Strains; Reference Values; Sodium; Thiorphan