s-nitro-n-acetylpenicillamine and zaprinast

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

We previously reported that several nitric oxide (NO) donors, guanylate cyclase activators, and cyclic GMP lower intraocular pressure (IOP) in rabbits.. This study evaluated a novel method for studying cGMP production in the iris-ciliary body after the administration of different NO donors and guanylate cyclase activators. Tissue samples of porcine iris-ciliary body were incubated for 30 or 60 minutes with the test compounds and with or without the phosphodiesterase inhibitor zaprinast. The concentration of cGMP in the iris-ciliary body as an indicator of soluble guanylate cyclase activation was measured by radioimmunoassay.. The tested NO donors - SNOG, NONOate, NOR-3, and SNAP - were shown to release NO in incubation medium, and clearly increase cGMP concentration in the iris-ciliary body. Cyclic GMP production was 2-5 times higher with nitrosocaptopril and about 10 times higher with SNP than in the unstimulated control tissue incubation. Captopril, the reference for nitrosocaptopril, did not induce cGMP production in the porcine iris-ciliary body. ODQ, a guanylate cyclase inhibitor, shut down the production of cGMP after the administration of nitrosocaptopril and SNP. The guanylate cyclase activators YC-1 and atriopeptin III increased cGMP dose-dependently.. In this novel tissue incubation method, several NO donors and guanylate cyclase activators increased cGMP production in the porcine iris-ciliary body. This method can be used to screen new molecules in terms of cGMP production, since the ciliary body is important in lowering intraocular pressure.

Topics: Animals; Captopril; Ciliary Body; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanylate Cyclase; Intraocular Pressure; Iris; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitrites; Nitro Compounds; Nitrogen Oxides; Oxadiazoles; Penicillamine; Phosphodiesterase Inhibitors; Purinones; Quinoxalines; Rabbits; S-Nitrosothiols; Spermine; Swine; Time Factors

Nitric oxide (NO) donors are believed to exert their vasodilatory action through the activation of soluble guanylate cyclase (sGC), the heme site of which can be specifically inhibited by 1H-[1,2, 4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). We examined the vascular relaxation of the rat aorta mediated by eight different NO donors in the presence of ODQ (0.1, 1, or 10 microM), and demonstrated that these NO donors displayed different sensitivities toward ODQ inhibition (ANOVA, P <.05). Among the NO donors studied, S-nitrosothiols such as S-nitroso-N-acetylpenicillamine (SNAP) and S-nitrosoglutathione exhibited partial resistance toward ODQ inhibition at 0.1 microM ODQ, whereas nitroglycerin (NTG) showed nearly complete inhibition at this concentration of ODQ. Three NO donors representing increasing sensitivity toward ODQ inhibition, SNAP < sodium nitroprusside (SNP) < NTG, were chosen for additional mechanistic studies. ODQ (1 microM) inhibition of vascular relaxation by SNAP and SNP, but not that by NTG, was partially reversed by a sulfhydryl donor, N-acetylpenicillamine (100 microM), and by a phosphodiesterase inhibitor, zaprinast (10 microM), specific for cGMP. Our results strongly indicate that the vascular relaxation mechanism(s) of NO donors is not identical for each. In the rat aorta, NTG appeared to exhibit its vasodilatory effect exclusively through activation of the heme site of sGC. On the other hand, in the intact vascular tissue, SNAP and SNP could bring about vasodilation through a secondary pathway. These results are consistent with the view that SNAP and SNP, but not NTG, can induce vascular relaxation additionally through the activation of the sulfhydryl site of sGC.

Topics: Animals; Aorta, Thoracic; Dose-Response Relationship, Drug; Drug Interactions; Guanylate Cyclase; Male; Nitric Oxide Donors; Nitroglycerin; Nitroprusside; Oxadiazoles; Penicillamine; Phosphodiesterase Inhibitors; Purinones; Quinoxalines; Rats; Rats, Sprague-Dawley; Vasodilator Agents

Nitric oxide (NO), which is known to inhibit systemic vascular smooth muscle cell proliferation, is used in the management of neonatal pulmonary hypertension. Our objectives were to determine: (1) if endogenous NO production by neonatal porcine pulmonary artery smooth muscle cells (PASMCs) varied with oxygen tension in vitro, and (2) the effect of exogenous NO and inducible NO synthase (iNOS) stimulators and inhibitors on PASMC proliferation and apoptosis. PASMCs were exposed to different conditions (varying PO(2), NO donors and scavengers, iNOS stimulators and inhibitors) and proliferation, apoptosis, and cyclic guanosine 5(')-monophosphate (cGMP) assessed. PASMCs proliferated best between 5 and 10% O(2) but cGMP levels were similar at all oxygen levels. NO donors (S-nitroso-N-acetyl-penicillamine, NOC-12, NOC-18) inhibited PASMC proliferation in a dose-dependent manner with associated cGMP increases, while NO scavengers (carboxy-PTIO), iNOS stimulators (interleukin-1beta, lipopolysaccharide), and iNOS inhibitors (aminoethylisothiourea) did not affect proliferation or cGMP. No changes in apoptosis were found at the concentrations of NO donors or iNOS stimulators used. These results suggest that while exogenous NO inhibits PASMC proliferation, endogenous NO may not regulate proliferation during changes in oxygen tension or cytokine levels. Endothelial derived and inhaled NO may attenuate smooth muscle hyperplasia and vascular remodeling. Inducible NOS in porcine PASMCs appears resistant to stimulation with interleukin-1beta or lipopolysaccharide. The mechanisms underlying hypoxia-mediated changes in PASMC proliferation require investigation.

Topics: Animals; Animals, Newborn; Apoptosis; Cell Division; Cells, Cultured; Cyclic GMP; DNA Damage; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation, Developmental; Immunohistochemistry; Interleukin-1; Lipopolysaccharides; Muscle, Smooth, Vascular; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroso Compounds; Oxygen; Penicillamine; Phosphodiesterase Inhibitors; Pulmonary Artery; Purinones; Swine

Airway smooth muscle (ASM) hypertrophy and hyperplasia are important determinants of bronchial responsiveness in asthma, and agents that interfere with these processes may prevent airway remodeling. We tested the hypothesis that activators of soluble and particulate guanylyl cyclases would inhibit human ASM cell (HASMC) proliferation. We report that the nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP; 10(-6) to 10(-4) M) and sodium nitroprusside (10(-5) to 10(-3) M) and human atrial natriuretic peptide [ANP-(1-28); 10(-8) to 10(-6) M], which activate soluble and particulate guanylyl cyclases, respectively, inhibited serum- and thrombin-induced proliferation of cultured HASMCs. The antimitogenic effect of SNAP was reversed by hemoglobin (10(-5) M), an NO scavenger, suggesting that NO donation was involved. The antiproliferative effects of SNAP and ANP-(1-28) were potentiated by the cGMP-specific phosphodiesterase zaprinast and mimicked by 8-bromo-cGMP (10(-6) to 10(-3) M), suggesting that cGMP-dependent mechanisms were involved. However, first, ANP-(1-28) produced a smaller antiproliferative effect than SNAP in contrast to their abilities to elevate cGMP, and second, rat ANP-(104-126), which binds selectively to ANP clearance receptors without elevating cGMP, had a small antiproliferative effect, suggesting that cGMP-independent mechanisms were also involved. These results provide evidence for a novel antiproliferative effect of NO and ANP in HASMCs mediated through cGMP-dependent and cGMP-independent mechanisms.

Topics: Asthma; Atrial Natriuretic Factor; Blood Proteins; Cell Division; Cells, Cultured; Coloring Agents; Cyclic GMP; Diuretics; Hemoglobins; Hemostatics; Humans; Hyperplasia; Lung; Mitogens; Muscle, Smooth; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Penicillamine; Peptide Fragments; Phosphodiesterase Inhibitors; Purinones; Tetrazolium Salts; Thiazoles; Thrombin; Vasodilator Agents