s-nitro-n-acetylpenicillamine and Myocardial-Ischemia

Nitric oxide (NO) has been known to play various functional and pathological roles as an intracellular or intercellular messenger in the heart. In this study, we investigated whether NO produced during ischemia was involved in the coordination of ATP supply and demand, and also in protection from cell death using cultured cardiac myocytes. Unexpectedly, the survival rate of myocytes for 3 h simulated ischemia (SI) was increased as compared with that for 2 h SI at 24 h after reperfusion. The cellular ATP level at 3 h after the start of SI was increased compared with that at 2 h, and was almost the same as that before the start of SI. The cellular ATP level at 3 h SI was significantly reduced by either the inhibition of nitric oxide synthase (NOS) or scavenging of NO. Either the inhibition of NOS or the scavenging of NO during SI for 3 h also resulted in a significant decrease in the survival rate of myocytes. Immunocytochemical and Western blot analyses revealed that the expression of nNOS was most evident in cardiac myocytes, but no significant change was observed in the expression of all three NOS isoforms at 2 h SI and at 3 h SI. The fluorescent intensity of DAF-FM was significantly increased at 3 h SI as compared with that at 2 h SI, and the increase in DAF fluorescence during SI was almost completely suppressed by treatment with vinyl-L-NIO (L-VNIO), a potent specific inhibitor of nNOS. In addition, treatment with L-VNIO decreased the cellular ATP level and survival rate. This study suggested that the enhanced production of NO was critical in balancing ATP supply and demand during ischemia, and also in protecting cells from ischemia/reperfusion injury.

Topics: Adenosine Triphosphate; Animals; Benzoates; Cell Death; Cells, Cultured; Enzyme Inhibitors; Fluoresceins; Fluorescent Dyes; Imidazoles; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; omega-N-Methylarginine; Ornithine; Penicillamine; Rats; Rats, Wistar

Aldose reductase, a member of the aldo-keto reductase family, has been implicated in the development of vascular and neurological complications in diabetes. Despite recent studies from our laboratory demonstrating protection of ischemic hearts by an aldose reductase inhibitor, the presence and influence of aldose reductase in cardiac tissue remain unknown. Our goal in this study was to isolate and characterize the kinetic properties of cardiac aldose reductase, as well as to study the impact of flux via this enzyme on glucose metabolism and contractile function in hearts subjected to ischemia-reperfusion. Results demonstrate that ischemia increases myocardial aldose reductase activity and that these increases are, in part, due to activation by nitric oxide. The kinetic parameter of cardiac aldose reductase (Kcat) was significantly higher in ischemic tissues. Aldose reductase inhibition increased glycolysis and glucose oxidation. Aldose reductase inhibited hearts, when subjected to ischemia/reperfusion, exhibited less ischemic injury and was associated with lower lactate/pyruvate ratios (a measure of cytosolic NADH/NAD+), greater tissue content of adenosine triphosphate, and improved cardiac function. These findings indicate that aldose reductase is a component of ischemic injury and that pharmacological inhibitors of aldose reductase present a novel adjunctive approach for protecting ischemic hearts.

Topics: Aldehyde Reductase; Animals; Benzothiazoles; Enzyme Inhibitors; Glucose; Myocardial Ischemia; Myocardium; Nitric Oxide; Nitric Oxide Donors; Penicillamine; Phthalazines; Rats; Thiazoles

As shown previously, exposure to NO donors initiates protective mechanisms in cardiomyocytes that persist after removal of the donor, a form of pharmacological preconditioning. Because NO also affects mitochondrial respiration, we studied the effect of NO on mitochondrial Ca(2+) uptake.. Neonatal rat ventricular myocytes in primary culture were exposed to 1 hour of simulated ischemia and 1 hour of reoxygenation (sI/R). Pretreatment with the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) (1 mmol/L for 90 minutes), followed by washing and incubation for 10 to 30 minutes, reduced sI/R-induced cell death to 25.4% compared with control (propidium iodide exclusion assay, P<0.001). Short (10-second) exposures to SNAP reversibly suppressed mitochondrial respiration without a detectable change in mitochondrial potential. In contrast, treatment with SNAP for 90 minutes caused a modest but sustained mitochondrial depolarization, as judged by JC-1 fluorescence. SNAP pretreatment limited cellular Ca(2+) overload during ischemia (fura-2 ratio rose to 226+/-40% versus 516+/-170% of baseline, n=5, P<0.05) and prevented loss of cell membrane integrity during reoxygenation. SNAP pretreatment also significantly reduced the ability of mitochondria to accumulate Ca(2+) in the face of a similar cytosolic Ca(2+) load (peak rhod-2 fluorescence 133+/-4% versus 166+/-7% of baseline at similar fluo-3 levels, P=0.0004, n=52 and 25, respectively).. Pretreatment with an NO donor induces a modest, sustained mitochondrial depolarization and protects cardiomyocytes from sI/R injury. The demonstrated reduction in mitochondrial Ca(2+) uptake possibly reduces cytosolic Ca(2+) overload, providing a likely mechanism for NO-induced protection.

Topics: Animals; Animals, Newborn; Calcium; Cell Death; Cells, Cultured; Heart Ventricles; Ischemic Preconditioning; Microscopy, Fluorescence; Mitochondria; Myocardial Ischemia; Myocardial Reperfusion Injury; Nitric Oxide; Nitric Oxide Donors; Oxygen; Penicillamine; Rats; Rats, Sprague-Dawley; Time Factors

The endothelial layer of the myocardial vasculature serves as an important protective barrier between blood and myocardium. Ischemic reperfusion (I/R) of the endothelium has been shown to initiate a series of events that leads to ischemic reperfusion injury in the heart. At the onset of ischemic reperfusion, endothelial cells initiate apoptosis, a process whereby the cells self-destruct. Ischemic reperfusion was simulated to study its effects on the induction of apoptosis in cultured human endothelial cells (ECV 304). In addition, the cells were treated with nitric oxide (NO) to test its effect on induction of apoptosis. To mimic hypoxia, four ECV 304 cultures were placed in a medium that had been bubbled with pure nitrogen gas for 24 hours. A continuous flow of nitrogen gas was applied to the culture flasks during the course of the 2-hour ischemic period. After 2 hours, the nitrogen was removed from the hypoxic cultures to simulate reperfusion. Exposure to NO was achieved through the NO-donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP) at 100 microM, Cell cultures were exposed to hypoxia only, hypoxia and SNAP, and SNAP only. One positive control was established by exposure to staurosporine. A second positive control was established by exposure to a 30-min heat treatment at 43 degrees C. Two cultures were left untreated to serve as negative controls. All cell cultures were incubated for 4 hours. Apoptosis was detected by the binding of annexin V-fluorescein isothiocyanate (annexin V-FITC). In addition, morphologic changes detected by electron microscopy were used. Apoptosis increased in all treated cultures, excluding SNAP only treated cells. It was concluded that I/R may lead to induction of apoptosis.

Topics: Apoptosis; Cells, Cultured; Endothelium, Vascular; Humans; In Vitro Techniques; Myocardial Ischemia; Myocardial Reperfusion Injury; Nitric Oxide; Penicillamine; United States

Nitric oxide (NO) has been shown to induce apoptosis in cardiomyocytes under normoxic conditions. The ability of NO to induce apoptosis after ischemia-reperfusion, a situation of increased NO release in vivo, has not been investigated. The present study was undertaken to characterize the pathway of induction of apoptosis by NO and the influence of ischemia on this pathway in cardiomyocytes.. The study was performed on isolated adult cardiomyocytes of the rat. Ischemia was simulated by anoxia in a glucose free medium, pH 6.4. Induction of apoptosis was detected (1) by annexinV-fluorescein isothiocyanate (annexinV-FITC) binding to cells under exclusion of propidium iodide and (2) by laddering of genomic DNA.. Incubation of cardiomyocytes with the NO-donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP, 100 microM) induced apoptosis in 14.1 +/- 1.9% of the cells and necrosis in 24.4 +/- 4.6%. The induction of apoptosis but not necrosis could be blocked by inhibition of soluble guanylyl cyclase or of protein kinase G. Apoptosis induction was mimicked by incubation of cardiomyocytes with 8-pCPT-cGMP (100 microM, 9.6 +/- 0.6% apoptotic cells) or YC-1 (75 microM, 14.6 +/- 2.8% apoptotic cells), a direct activator of soluble guanylyl cyclase. After 3 h of anoxia, cardiomyocytes were transiently protected against apoptosis induced by NO, but not by 8-pCPT-cGMP or YC-1 (8.9 +/- 0.7% or 13.4 +/- 2.4% apoptotic cells). A correlation of the apoptotic response to SNAP or YC-1 with an increased activity of soluble guanylyl cyclase, determined by measurements of intracellular cGMP contents, was found.. NO induces apoptosis in a cGMP dependent manner in isolated adult cardiomyocytes whereas induction of necrosis seems cGMP-independent. After simulated in vitro ischemia the activation of soluble guanylyl cyclase by NO is transiently inhibited resulting in a transient anti-apoptotic protection.

Topics: Analysis of Variance; Animals; Annexin A5; Apoptosis; Cells, Cultured; Cyclic GMP; DNA Fragmentation; Male; Myocardial Ischemia; Myocardium; Nitric Oxide; Nitric Oxide Donors; Penicillamine; Rats; Rats, Wistar; Signal Transduction

The aim of this study was to investigate the role of nitric oxide (NO) in a cellular model of early preconditioning (PC) in cultured neonatal rat ventricular myocytes. Cardiomyocytes "preconditioned" with 90 min of stimulated ischemia (SI) followed by 30 min reoxygenation in normal culture conditions were protected against subsequent 6 h of SI. PC was blocked by N(G)-monomethyl-L-arginine monoacetate but not by dexamethasone pretreatment. Inducible nitric oxide synthase (NOS) protein expression was not detected during PC ischemia. Pretreatment (90 min) with the NO donor S-nitroso-N-acetyl-L,L-penicillamine (SNAP) mimicked PC, resulting in significant protection. SNAP-triggered protection was completely abolished by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) but was unaffected by chelerythrine or the presence of glibenclamide and 5-hydroxydecanoate. With the use of RIA, SNAP treatment increased cGMP levels, which were blocked by ODQ. Hence, NO is implicated as a trigger in this model of early PC via activation of a constitutive NOS isoform. After exposure to SNAP, the mechanism of cardioprotection is cGMP dependent but independent of protein kinase C or ATP-sensitive K(+) channels. This differs from the proposed mechanism of NO-induced cardioprotection in late PC.

Topics: Alkaloids; Animals; Animals, Newborn; Anti-Infective Agents; Benzophenanthridines; Cells, Cultured; Cyclic GMP; Dexamethasone; Enzyme Inhibitors; Fatty Acids, Monounsaturated; Glucocorticoids; Glyburide; Heart Ventricles; Hypoglycemic Agents; Ischemic Preconditioning; Muscle Fibers, Skeletal; Myocardial Ischemia; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; omega-N-Methylarginine; Oxadiazoles; Penicillamine; Phenanthridines; Potassium Channels; Protein Kinase C; Quinoxalines; Rats; Rats, Sprague-Dawley

Nitric oxide (NO) has been implicated as a mediator in myocardial ischemia/reperfusion (I/R) injury, but its functional properties have been conflicting. We investigated whether NO has a protective role against I/R injury.. Using endothelial NO synthase knockout (eNOS KO) mice, inducible NOS KO mice, the NO donor S-nitroso-N-acetylpenicillamine (SNAP), and the NOS inhibitor N-iminoethyl-L-ornithine (L-NIO), we performed studies of isolated perfused hearts subjected to 30 minutes of global ischemia followed by reperfusion. After 60 minutes of reperfusion, nitrite levels in the coronary effluent in the SNAP and eNOS KO groups were significantly elevated compared with other groups. Immunoblot and immunohistochemistry showed that iNOS was markedly induced in the eNOS KO hearts. Under spontaneous beating conditions during reperfusion, increased NO activity was correlated with a prevention of the hyperdynamic contractile response and enhanced myocardial protection, as evidenced by a reduction in myocardial injury and infarct size. During prolonged reperfusion, SNAP-treated hearts were able to preserve contractile functions for 180 minutes, whereas L-NIO-treated hearts showed a sustained deterioration in contractility.. NO protects against I/R injury by preventing the hyperdynamic response of isolated perfused hearts during early reperfusion. In the eNOS KO hearts, a paradoxical increase in NO production was seen, accompanied by a superinduction of iNOS, possibly due to an adaptive mechanism.

Topics: Animals; Creatine Kinase; Gene Expression Regulation, Enzymologic; Heart; Hemodynamics; In Vitro Techniques; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocardial Contraction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Ornithine; Penicillamine

Myocardial ischaemia followed by reperfusion (I/R) is associated with impaired endothelial function including diminished release and/or effects of nitric oxide (NO) which may contribute to the development of I/R injury. The aim of the present study was to investigate the role of the L-arginine/NO pathway in myocardial I/R injury. In isolated rat hearts subjected to global ischaemia followed by reperfusion L-arginine and the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP), but not D-arginine, significantly enhanced the recoveries of mycardial performance and coronary flow, and reduced the area of no-reflow and creatine kinase outflow. The NO synthase inhibitor NG-nitro-L-arginine (L-NNA) abolished the protective effects of L-arginine. Endothelium-dependent vasodilatation after I/R was preserved in L-arginine treated but not in vehicle hearts. Following I/R Ca2+-dependent NO synthase activity was reduced by 90% in comparison with non-ischaemic hearts. L-arginine but not D-arginine significantly increased NO synthase activity. In anaesthetized pigs, L-arginine given by local coronary venous retroinfusion reduced myocardial infarct size induced by 45 min of coronary artery ligation and 4 h of reperfusion to 35% of the area at risk from 76% in controls. The protective effect of L-arginine was blocked by L-NNA. Acetylcholine-induced coronary vasodilatation following I/R was attenuated in controls but not in L-arginine treated pigs. It is concluded that L-arginine or the NO donor SNAP reduces I/R-induced myocardial and endothelial injury. The protective effect of L-arginine seems to be mediated through maintained production of NO by preserving the function of Ca2+-dependent NO synthase in the heart.

Topics: Animals; Arginine; Coronary Circulation; Creatine Kinase; Enzyme Inhibitors; Heart; Hemodynamics; In Vitro Techniques; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Penicillamine; Perfusion; Rats; Rats, Sprague-Dawley; Swine