nitroarginine and peroxynitric-acid

In this study we investigated the effect of immunostimulation on intracellular ATP level in rat glial cells. Rat primary astrocytes or C6 glioma cells were treated for 48 h with IFN-gamma, LPS or IFN-gamma plus LPS. These treatments increased NO production from the cells and a synergistic increase in NO production was observed with IFN-gamma plus LPS. Intracellular ATP level was decreased to about half the control level at the highest concentration of IFN-gamma (100 U/ml) plus LPS (1 microg/ml) without affecting cell viability. The level of intracellular ATP was inversely correlated with the extent of NO production from the glial cells. The increase in NO production is at least 6 h ahead of the initiation of ATP depletion, and NOS inhibitor N(G)-nitro-L-arginine (NNA) or Nomega-nitro-L-arginine methyl ester (L-NAME) inhibited NO production and ATP depletion. Exogenous addition of peroxynitrite generator 3-morpholinosydnonimine (SIN-1) and to a lesser extent NO generator S-nitroso-N-acetylpenicillamine (SNAP) depleted intracellular ATP level in a dose-dependent manner. The results from the present study imply that immunostimulation of rat glial cells decreases the intracellular ATP level without affecting cell viability. Considering the role of astrocytes as an essential regulator of the extracellular environment in the brain, the immunostimulation-induced decrease in intracellular ATP level may participate in the pathogenesis of various neurological diseases.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Astrocytes; Central Nervous System; Dose-Response Relationship, Drug; Encephalitis; Enzyme Inhibitors; Inflammation Mediators; Interferon-gamma; Intracellular Fluid; L-Lactate Dehydrogenase; Lipopolysaccharides; Molsidomine; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Penicillamine; Rats; Rats, Sprague-Dawley; S-Nitroso-N-Acetylpenicillamine; Tumor Cells, Cultured

Oxygen-derived free radicals have been implicated in the pathogenesis of myocardial injury. We therefore investigated the pathophysiology of myocardial injury induced in isolated rat hearts by perfusion with superoxide radical generated by reacting 2.5 mmol/l purine, 0.03 U/ml xanthine oxidase and 300 U/ml catalase. Perfusion with superoxide significantly (P<0.05) increased left ventricular end-diastolic pressure within 15 to 20 min. During the same time period, heart rate and left-ventricular developed pressure significantly declined to 44.6+/-8.2% and 31.0+/-4.9% of control, respectively. Superoxide perfusion also significantly increased production of prostaglandins, nitric oxide (detected as nitrites) and peroxynitrite (detected immunohistochemically as nitrotyrosine). N(G)-nitro-l-arginine (100 micromol/l), a nitric oxide synthase inhibitor, attenuated superoxide-induced generation of peroxynitrite, increased synthesis of prostacyclin, and partially blocked myocardial dysfunction, as did 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (30 micromol/l), a selective inhibitor of soluble guanylate cyclase, and ONO-3708 (10 micromol/l), a selective thromboxane A(2)receptor antagonist. In contrast, nitroglycerin (4 micromol/l) and sodium nitroprusside (1 micromol/l) each exacerbated the superoxide-induced myocardial dysfunction. These results suggest that nitric oxide and related reactive species contribute to myocardial injury induced by superoxide. Moreover, they suggest that oxidative stress can be delayed or inhibited by reducing levels of nitric oxide, by inhibiting soluble guanylate cyclase, and by blocking thromboxane/prostaglandin receptors.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Aspartate Aminotransferases; Colforsin; Enzyme Inhibitors; Heart; Myocardial Contraction; Myocardium; Nitrates; Nitric Acid; Nitroarginine; Nitroglycerin; Nitroprusside; Oxadiazoles; Phosphodiesterase Inhibitors; Platelet Aggregation Inhibitors; Prostaglandins; Quinoxalines; Rats; Superoxides; Thromboxane A2; Vasodilator Agents

Beta amyloid (Abeta) is implicated in Alzheimer's disease (AD). Abeta(1 - 42) (5, 10, or 20 microM) was able to increase NO release and decrease cellular viability in primary rat cortical mixed cultures. L-NOARG and SMTC (both at 10 or 100 microM) - type I NOS inhibitors - reduced cellular NO release in the absence of Abeta(1 - 42). At 100 microM, both drugs decreased cell viability. L-NIL (10 or 100 microM), and 1400W (1 or 5 microM) - type II NOS inhibitors - reduced NO release and improved viability when either drug was administered up to 4 h post Abeta(1 - 42) (10 microM) treatment. L-NOARG and SMTC (both at 10 or 100 microM) were only able to decrease NO release. Carboxy-PTIO or Trolox (both at 10 or 100 microM) - a NO scavenger and an antioxidant, respectively - increased viability when administered up to 1 h post Abeta(1 - 42) treatment. Either L-NIL (50 microM) or 1400W (3 microM) and Trolox (50 microM) showed synergistic actions. Peroxynitrite (100 or 200 microM) reduced cell viability. Viabilities were improved by L-NIL (100 microM), 1400W (5 microM), carboxy-PTIO (10 or 100 microM), and Trolox (10 or 100 microM). Hence, the data show that Abeta(1 - 42) induced NO release in neurons and glial cells, and that Abeta neurotoxicity is, at least in part, mediated by NO. NO concentration modulating compounds and antioxidant may have therapeutic importance in neurological disorders where oxidative stress is likely involved such as in AD.

Topics: Amyloid beta-Peptides; Animals; Antioxidants; Benzoates; Cell Survival; Cells, Cultured; Cerebral Cortex; Chromans; Citrulline; Dose-Response Relationship, Drug; Enzyme Inhibitors; Imidazoles; Isoenzymes; Lysine; Neuroprotective Agents; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidants; Peptide Fragments; Rats; Rats, Sprague-Dawley; Thiourea; Time Factors

Reactive oxygen species have been shown to be involved in the mutagenicity, clastogenicity, and apoptosis of mammalian cells treated with arsenic or cadmium. As these endpoints require several hours of cellular processing, it is not clear that reactive oxygen species damage DNA directly or interfere with DNA replication and repair. Using single-cell alkaline electrophoresis, we have detected DNA strand breaks (DSBs) in bovine aortic endothelial cells by a 4-h treatment with sodium arsenite (As) and cadmium chloride (Cd) in sublethal concentrations. As-induced DSBs could be decreased by nitric oxide (NO) synthase inhibitors, superoxide scavengers, and peroxynitrite scavengers and could be increased by superoxide generators and NO generators. Treatment with As also increased nitrite production. These results suggest that As-increased NO may react with O2*- to produce peroxynitrite and cause DNA damage. The results showing that Cd increased cellular H2O2 levels and that Cd-induced DSBs could be modulated by various oxidant modulators suggest that Cd may induce DSBs via O2*-, H2O2, and *OH. Nevertheless, the DSBs in both As- and Cd-treated cells seem to come from the excision of oxidized bases such as formamidopyrimidine and 8-oxoguanine, as the Escherichia coli enzyme formamidopyrimidine-DNA glycosylase (Fpg) increased DSBs in cells treated with As, 3-morpholinosydnonimine (a peroxynitrite-generating agent), Cd, or H2O2.

Topics: Amitrole; Animals; Antioxidants; Aorta; Arsenites; Bacterial Proteins; Cadmium Chloride; Catalase; Cattle; Cells, Cultured; Chromans; Citrulline; Ditiocarb; DNA Damage; DNA-Formamidopyrimidine Glycosylase; Endothelium, Vascular; Enzyme Inhibitors; Escherichia coli Proteins; Free Radical Scavengers; Hydrogen Peroxide; Molsidomine; Mutagens; N-Glycosyl Hydrolases; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Onium Compounds; Phenanthrolines; Reactive Oxygen Species; Sodium Compounds; Sodium Selenite; Superoxide Dismutase; Superoxides; Thiomalates; Thiourea; Uric Acid

Growing evidence indicates that reactive oxygen species (ROS) as well as nitric oxide (NO) have a profound influence on contractile function of skeletal muscle possibly through modulation of excitation-contraction coupling. We hypothesized that if NO and xanthine oxidase (XO) interact at key sites in excitation-contraction coupling, the effects of XO with nitric oxide synthase (NOS) inhibitors and NO donors on contractile function of the unfatigued diaphragm would not be additive. Diaphragm fibre bundles were extracted from 4-month Fischer-344 rats and placed in Krebs solution bubbled with 95% O2, 5% CO2. Baseline twitch tension, tension at 20 Hz (low-frequency), and maximal tetanic tension (Po) at 120 Hz were then measured (PRE). In Experiment 1 diaphragm fibre bundles were exposed to Krebs with 200 microM hypoxanthine as a control (CON); 0.02 U mL-1 XO + 200 microM hypoxanthine; 1 mM of the NOS inhibitor N-nitro-L-arginine (L-NNA) or L-NNA + XO. Five minutes were allowed for equilibration, and a second set of contractile measures was taken (POST). In Experiment 2 we exposed diaphragm fibre bundles to one of the following four solutions: CON, XO, 100 microM of the NO donor sodium nitroprusside (SNP) and XO + SNP, and evaluated contractile function as described above. In Experiment 3 we tested to determine if peroxynitrite production from the reaction of superoxide anion and NO affected the above results for SNP using 30 microM ebselen as a peroxynitrite quencher. Xanthine oxidase resulted in a significant potentiation of diaphragm twitch tension and tension at 20 Hz (+29%) without affecting Po. L-NNA also significantly increased 20 Hz tension but did not alter Po. However, the combination of XO + L-NNA did not further increase low-frequency contractility. Sodium nitroprusside alone did not affect diaphragm contractility, but did attenuate XO-induced potentiation in the XO + SNP group. Ebselen did not alter the impact of SNP on XO in the diaphragm. These data support the hypothesis that XO and NO interact or compete at similar sites of action that modulate contractility of the unfatigued diaphragm.

Topics: Analysis of Variance; Animals; Antioxidants; Azoles; Diaphragm; Enzyme Inhibitors; Hypoxanthine; In Vitro Techniques; Isoindoles; Muscle Contraction; Nitrates; Nitric Oxide; Nitroarginine; Nitroprusside; Organoselenium Compounds; Rats; Rats, Inbred F344; Reactive Oxygen Species; Vasodilator Agents; Xanthine Oxidase

Proinflammatory cytokines depress myocardial contractile function by enhancing the expression of inducible NO synthase (iNOS), yet the mechanism of iNOS-mediated myocardial injury is not clear. As the reaction of NO with superoxide to form peroxynitrite markedly enhances the toxicity of NO, we hypothesized that peroxynitrite itself is responsible for cytokine-induced cardiac depression. Isolated working rat hearts were perfused for 120 minutes with buffer containing interleukin-1 beta, interferon-gamma, and tumor necrosis factor-alpha. Cardiac mechanical function and myocardial iNOS, xanthine oxidoreductase (XOR), and NAD(P)H oxidase activities (sources of superoxide) were measured during the perfusion. Cytokines induced a marked decline in myocardial contractile function accompanied by enhanced activity of myocardial XOR, NADH oxidase, and iNOS. Cardiac NO content, myocardial superoxide production, and perfusate nitrotyrosine and dityrosine levels, markers of peroxynitrite, were increased in cytokine-treated hearts. The peroxynitrite decomposition catalyst FeTPPS (5,10,15, 20-tetrakis-[4-sulfonatophenyl]-porphyrinato-iron[III]), the NO synthase inhibitor N(G)-nitro-L-arginine, and the superoxide scavenger tiron each inhibited the decline in myocardial function and decreased perfusate nitrotyrosine levels. Proinflammatory cytokines stimulate the concerted enhancement in superoxide and NO-generating activities in the heart, thereby enhancing peroxynitrite generation, which causes myocardial contractile failure.

Topics: 1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; Animals; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Heart; Heart Failure; Inflammation; Interferon-gamma; Interleukin-1; Male; Muscle Proteins; Myocardial Contraction; Myocardium; NADPH Oxidases; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Oxidation-Reduction; Oxidative Stress; Perfusion; Porphyrins; Rats; Rats, Sprague-Dawley; Superoxides; Tumor Necrosis Factor-alpha; Xanthine Oxidase

Reperfusion injury is one of the factors that unfavorably affects stroke outcome and shortens the window of opportunity for thrombolysis. Surges of nitric oxide (NO) and superoxide generation on reperfusion have been demonstrated. Concomitant generation of these radicals can lead to formation of the strong oxidant peroxynitrite during reperfusion.. We have examined the role of NO generation and peroxynitrite formation on reperfusion injury in a mouse model of middle cerebral artery occlusion (2 hours) and reperfusion (22 hours). The infarct volume was assessed by 2,3,5-triphenyl tetrazolium chloride staining; blood-brain barrier permeability was evaluated by Evans blue extravasation. Nitrotyrosine formation and matrix metalloproteinase-9 expression were detected by immunohistochemistry.. Infarct volume was significantly decreased (47%) in animals treated with the nonselective nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine (L-NA) at reperfusion. The specific inhibitor of neuronal NOS, 7-nitroindazole (7-NI), given at reperfusion, showed no protection, although preischemic treatment with 7-NI decreased infarct volume by 40%. Interestingly, prereperfusion administration of both NOS inhibitors decreased tyrosine nitration (a marker of peroxynitrite toxicity) in the ischemic area. L-NA treatment also significantly reduced vascular damage, as indicated by decreased Evans blue extravasation and matrix metalloproteinase-9 expression.. These data support the hypothesis that in addition to the detrimental action of NO formed by neuronal NOS during ischemia, NO generation at reperfusion plays a significant role in reperfusion injury, possibly through peroxynitrite formation. Contrary to L-NA, failure of 7-NI to protect against reperfusion injury suggests that the source of NO is the cerebrovascular compartment.

Topics: Animals; Biomarkers; Blood-Brain Barrier; Coloring Agents; Endothelium, Vascular; Enzyme Inhibitors; Evans Blue; Indazoles; Infarction, Middle Cerebral Artery; Matrix Metalloproteinase 9; Mice; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidants; Permeability; Reperfusion Injury; Tyrosine

To determine whether reactive nitrogen species contribute to secondary damage in CNS injury, the time courses of nitric oxide, peroxynitrite, and nitrotyrosine production were measured following impact injury to the rat spinal cord. The concentration of nitric oxide measured by a nitric oxide-selective electrode dramatically increased immediately following injury and then quickly declined. Nitro-L-arginine reduced nitric oxide production. The extracellular concentration of peroxynitrite, measured by perfusing tyrosine through a microdialysis fiber into the cord and quantifying nitrotyrosine in the microdialysates, significantly increased after injury to 3.5 times the basal level, and superoxide dismutase and nitro-L-arginine completely blocked peroxynitrite production. Tyrosine nitration examined immunohistochemically significantly increased at 12 and 24 h postinjury, but not in sham-control sections. Mn(III) tetrakis(4-benzoic acid)-porphyrin (a novel cell-permeable superoxide dismutase mimetic) and nitro-L-arginine significantly reduced the numbers of nitrotyrosine-positive cells. Protein-bound nitrotyrosine was significantly higher in the injured tissue than in the sham-operated controls. These results demonstrate that traumatic injury increases nitric oxide and peroxynitrite production, thereby nitrating tyrosine, including protein-bound tyrosine. Together with our previous report that trauma increases superoxide, our results suggest that reactive nitrogen species cause secondary damage by nitrating protein through the pathway superoxide + nitric oxide peroxynitrite protein nitration.

Topics: Amino Acids; Animals; Immunohistochemistry; Male; Models, Biological; Nitrates; Nitric Oxide; Nitroarginine; Proteins; Rats; Rats, Sprague-Dawley; Spinal Cord; Spinal Cord Injuries; Superoxide Dismutase; Tyrosine; Wounds, Nonpenetrating

It has been suggested that free radicals are involved in esophagitis. To study the role and potential interaction of superoxide anion and nitric oxide (NO) in low-grade esophagitis, we perfused acidified pepsin (30 min every 12 hr) for seven days in rabbits treated with different agents to modulate the generation of these radicals. Measurements included macroscopic and microscopic damage, superoxide anion generation, mucosal nitric oxide synthase activity, and peroxynitrite formation. Low-grade esophagitis was associated with increased nitric oxide synthase mucosal activity and mucosal damage was dose-dependently increased by treatment with the NO synthase inhibitor NG-nitro-L-arginine. Superoxide anion was scarcely generated in the mucosa, but this was not accompanied by any change in the activity of mucosal superoxide dismutase. Treatment with superoxide dismutase did not improve mucosal damage. Generation of peroxynitrites was not detected. In conclusion, nitric oxide is involved in the mucosal defense of the esophagus against acid- and pepsin-induced damage. Superoxide anion generation seems irrelevant in the induction of low-grade esophagitis and not sufficient to interact with nitric oxide to generate measurable mucosal peroxynitrite radicals.

Topics: Animals; Enzyme Inhibitors; Esophagitis; Esophagus; Free Radicals; Mucous Membrane; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Oxidants; Pepsin A; Rabbits; Superoxide Dismutase; Superoxides

Nitric oxide (NO*) is an inhibitory neurotransmitter that induces sphincter of Oddi relaxation. Superoxide (O*-2)-scavenging enzymes are present in enteric plexuses of the sphincter of Oddi and O*-2 alters sphincter of Oddi motor function. O*-2 rapidly oxidizes nitric oxide (NO*) to form peroxynitrite (ONOO-), thus terminating the biological activity of NO*. The aim of our study was to determine the effects of ONOO- on sphincter of Oddi motility in vitro.. Adult opossums were sacrificed and the sphincter of Oddi was removed and placed in a tissue bath containing oxygenated Krebs solution at 37 degreesC. In the first series of experiments, force transducers recorded tension in a transverse orientation at two sites along the spontaneously contracting sphincter of Oddi. In a second series of experiments, circular muscle strips were precontracted with carbachol and stimulated by an electrical field.. ONOO-, superoxide dismutase (SOD), Nomega-nitro-l-arginine (l-NNA), or oxyhemoglobin were added to the tissue baths. ONOO- decreased the frequency of contractions in the spontaneously contracting sphincter of Oddi. Adding hemoglobin increased the frequency of contractions. ONOO- also increased the stimulation-induced relaxation compared to controls. The increase in relaxation induced by ONOO- was inhibited by oxyhemoglobin and l-NNA but not SOD. Pretreatment with oxyhemoglobin prevented the increase in the stimulation-induced relaxation caused by ONOO-.. These results suggest that hemoglobin binds ONOO- or that ONOO- generates NO.

Topics: Animals; Carbachol; Catalase; Electric Stimulation; Enzyme Inhibitors; Female; Gastrointestinal Motility; In Vitro Techniques; Male; Muscle Contraction; Muscle Relaxation; Nitrates; Nitric Oxide Synthase; Nitroarginine; Opossums; Oxyhemoglobins; Sphincter of Oddi; Superoxide Dismutase

Nitric oxide (NO) is a well-documented effector molecule in rodent phagocytes but its synthesis in human neutrophils has been controversial. In this study, NO production in human neutrophils activated by chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) was measured in the presence of L-arginine (L-Arg) and N(G)-hydroxy-L-arginine (OH-L-Arg), the precursor and intermediate amino acids in NO synthesis, respectively. Incubation of fMLP-activated neutrophils with OH-L-Arg resulted in a production of nitrite, nitrate, and citrulline that was greater than with unstimulated neutrophils but was not inhibited by the NOS inhibitors L-NMMA and L-NIO or the cytochrome P450 inhibitor troleandomycin and was not seen when OH-L-Arg was replaced with L-Arg. This nitrite, nitrate, and citrulline production was not associated with any detectable NO synthesis because no increases in cyclic GMP were observed in the presence of phosphodiesterase inhibitors and in the presence or absence of superoxide dismutase. Moreover, no increases in the formation of the reaction product of NO with superoxide, peroxynitrite, were observed on addition of either OH-L-Arg or L-Arg to activated neutrophils, as assessed either by dihydrorhodamine oxidation or protein nitration. This suggests that, in spite of the production of nitrite, nitrate, and citrulline, commonly used indicators of NO formation, normal human blood neutrophils, are not producing detectable amounts of either NO or peroxynitrite when stimulated with fMLP in the presence of OH-L-Arg.

Topics: Arginine; Cells, Cultured; Citrulline; Cyclic GMP; Humans; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Nitrates; Nitric Oxide; Nitrites; Nitroarginine

Exposure to high glucose causes characteristic dysfunction and morphologic changes of the endothelium. To study the underlying mechanisms of glucotoxicity, human endothelial cells (HUVECs) were isolated from umbilical veins and cultivated under hyperglycemic conditions (10-30 mM) for up to 72 h. The generation of reactive oxygen intermediates (ROIs) was determined by histochemical staining of the cells by dichlorodihydrofluorescein. Activation of the transcription factor nuclear factor-kappa B (NF-KB) family was analyzed by the electromobility shift assay and by histochemical staining of the cells with rhodamine-labelled consensus sequences of activated NF-KB. Apoptotic cells were identified by morphologic analysis and DNA fragmentation. Incubation of HUVECs with high glucose led to rapid increase in the generation of ROIs. After an incubation of 2 to 6 h, NF-KB became activated, with the maximum at 4 h. Exposure of HUVECs to high glucose for up to 72 h caused a significant induction of apoptosis in HUVECs. The increased generation of ROIs, activation of apoptosis, and induction of apoptosis were also observed in cells incubated with 3-O-methyl-D-glucose, a glucose derivative that is taken up by the cells but not metabolized. Generation of ROIs, activation of NF-kappaB, and induction of apoptosis were not only prevented by antioxidants (thioctic acid, tocopherol, superoxide dysmutase-mimetic), but also by L-nitroarginine. These observations indicate that high glucose leads to an increase in generation of ROIs, an activation of NF-KB, and an induction of apoptosis by a glucose-specific and NO synthase-dependent mechanism. Our data suggest that peroxynitrite, which is rapidly formed from nitric oxide and superoxide anions, is the mediator of the cytotoxic effects of high glucose on endothelial cells. Because the induction of apoptosis by glucose was prevented by an antisense nucleotide to the p65NF-kappaB binding site, we assume that the ROI-mediated activation of NF-kappaB plays an important role for induction of apoptosis by glucose.

Topics: 3-O-Methylglucose; Antioxidants; Apoptosis; Binding Sites; Cells, Cultured; DNA Fragmentation; DNA-Binding Proteins; Endothelium, Vascular; Fluorescent Dyes; Glucose; Humans; Microscopy, Fluorescence; NF-kappa B; Nitrates; Nitroarginine; Oligodeoxyribonucleotides, Antisense; Reactive Oxygen Species

Primary cultures of rat embryonic motor neurons deprived of brain-derived neurotrophic factor (BDNF) induce neuronal nitric oxide synthase (NOS) within 18 hr. Subsequently, >60% of the neurons undergo apoptosis between 18 and 24 hr after plating. Nitro-L-arginine and nitro-L-arginine methyl ester (L-NAME) prevented motor neuron death induced by trophic factor deprivation. Exogenous generation of nitric oxide at concentrations lower than 100 nM overcame the protection by L-NAME. Manganese tetrakis (4-benzoyl acid) porphyrin, a cell-permeant superoxide scavenger, also prevented nitric oxide-dependent motor neuron death. Motor neurons cultured without trophic support rapidly became immunoreactive for nitrotyrosine when compared with motor neurons incubated with BDNF, L-NAME, or manganese TBAP. Our results suggest that peroxynitrite, a strong oxidant formed by the reaction of NO and superoxide, plays an important role in the induction of apoptosis in motor neurons deprived of trophic factors and that BDNF supports motor neuron survival in part by preventing neuronal NOS expression.

Topics: Animals; Apoptosis; Brain-Derived Neurotrophic Factor; Cells, Cultured; Enzyme Inhibitors; Fetus; Free Radical Scavengers; Motor Neurons; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxidants; Rats; Spinal Cord; Superoxides; Tyrosine

This study was designed to investigate the potential role of endogenous peroxynitrite (ONOO-) formation in the inhibition of cardiac muscle contractility and mitochondrial respiration during posthypoxic reoxygenation. Isometric contraction of isolated rat left ventricular posterior papillary muscle was virtually eliminated at the end of an exposure to 15 minutes of hypoxia and remained 40+/-5% depressed an hour after the reintroduction of O2. O2 uptake by rat left ventricular cardiac muscle, measured by a Clark-type O2 electrode, was also inhibited by 24+/-2% at 10 minutes after reoxygenation. The inhibition of contractility and respiration during posthypoxic reoxygenation was markedly attenuated by the NO synthase inhibitor nitro-L-arginine, exogenous superoxide dismutase, and the ONOO- scavenger urate but not by the hydroxyl radical scavenger mannitol. Generation of ONOO- with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) plus the superoxide-releasing agent pyrogallol caused an irreversible inhibition of cardiac contractile and respiratory function. Unlike ONOO-, exogenous (SNAP) and endogenous (bradykinin) sources of NO inhibited contractility in a reversible manner. Under conditions of comparable amounts of respiratory inhibition in unstimulated incubated muscle, the NO-dependent agents and the mitochondrial antagonist NaCN produced a smaller degree of suppression of contractility compared with ONOO- and posthypoxic reoxygenation. These results are consistent with a contributing role for endogenous ONOO- formation in the inhibition of cardiac muscle contractility and mitochondrial respiration during posthypoxic reoxygenation.

Topics: Animals; Bradykinin; Cyclic GMP; Free Radical Scavengers; Hydroxyl Radical; Hypoxia; In Vitro Techniques; Kinetics; Mannitol; Mitochondria, Heart; Myocardial Contraction; Nitrates; Nitric Oxide; Nitroarginine; Oxidants; Oxygen Consumption; Penicillamine; Rats; S-Nitroso-N-Acetylpenicillamine; Sodium Cyanide; Superoxide Dismutase

Microglia have been shown to be immunostimulated by inflammatory cytokines and produce a number of toxic mediators. Here we report that immunostimulated microglia can synergistically enhance the N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity in rat cerebellar granule cells (CGC) in culture. Neurotoxicity was assessed by morphological examination and by measuring the release of lactate dehydrogenase and DNA fragmentation. Cultured microglia were immunostimulated by interferon-gamma (200 U/ml) and lipopolysaccharides (10 microg/ml) and one or two days later they were used for co-culture with CGC. Co-culture of CGC with immunostimulated microglia resulted in a remarkable enhancement of the NMDA receptor-mediated death of CGC. This enhanced neurotoxicity was mimicked by the nitric oxide releaser 3-morpholinosydnonimine (SIN-1) or S-nitroso-N-acetylpenicillamine (SNAP). Superoxide dismutase and catalase, which stabilise NO by removing superoxide anion, ameliorated the potentiation of the NMDA-mediated death of CGC in co-culture with immunostimulated microglia, implying that reactions of NO with superoxide to form peroxynitrite can be implicated in the potentiated neurotoxicity. Our data indicate that immunostimulated microglia, which may involve in various neuropathologies, potentiate the NMDA receptor-mediated excitotoxicity in part through the expression of inducible nitric oxide synthase.

Topics: Animals; Apoptosis; Catalase; Cerebellum; Coculture Techniques; DNA Fragmentation; In Situ Nick-End Labeling; Interferon-gamma; L-Lactate Dehydrogenase; Lipopolysaccharides; Mice; Microglia; Molsidomine; N-Methylaspartate; Neurons; Nitrates; Nitric Oxide; Nitroarginine; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Superoxide Dismutase

In this study, we analysed the implication of superoxide (O2-.) and nitric oxide (NO.) free radicals and their resulting product peroxynitrite (ONOO-) in the neuronal death induced by the activation of the glutamatergic receptor of the N-methyl-D-aspartate (NMDA) subtype using cultured cerebellar granule cells. The NOl donor SIN-1 (3-morpholinosydnonimine N-ethylcarbamide), at concentrations which produced a much higher guanylate cyclase activation (i.e. NO. concentration) than NMDA, was not neurotoxic and did not increase the NMDA-induced neuronal death. The absence of involvement of NO. in NMDA-induced neuronal death was confirmed by the ineffectiveness of L-NG-nitroarginine (L-Narg) as a neuroprotective compound. Electron paramagnetic resonance (EPR) experiments, using 5,5-dimethyl pyrroline 1-oxide (DMPO) as a spin trap, indicated that NMDA receptor stimulation led to the generation of O2-. from at least 15-30 min. The generation of O2-. by xanthine (XA)-xanthine oxidase (XO) induced a neuronal death similar to that of NMDA. XA-XO-induced neuronal death was suppressed by addition of either superoxide dismutase (SOD) plus catalase (CAT), or DMPO in the incubation medium. In contrast, NMDA-induced neuronal death was widely blocked by DMPO and other spin trap compounds, but not by SOD +/- CAT. XA-XO-induced neuronal death was not potentiated by SIN-1 indicating that ONOO- is not more toxic than O2-. in our neuronal model.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Catalase; Cell Death; Cells, Cultured; Cerebellum; Cyclic GMP; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Mice; Molsidomine; N-Methylaspartate; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Receptors, N-Methyl-D-Aspartate; Superoxide Dismutase; Superoxides; Xanthine Oxidase

The potential role of nitric oxide (NO) and its reaction product with superoxide, peroxynitrite, was investigated in a model of hepatic ischemia-reperfusion injury in male Fischer rats in vivo. Pretreatment with the NO synthase inhibitor nitro-L-arginine (10 mg/kg) did neither affect the post-ischemic oxidant stress and liver injury during the initial reperfusion phase nor the subsequent infiltration of neutrophils into the liver and the later, neutrophil-induced injury phase. Furthermore, no evidence was found for a postischemic increase of the urinary excretion of nitrite, a stable oxidation metabolite of NO. In contrast, the administration of Salmonella enteritidis endotoxin (1 mg/kg) induced a significant diuresis in Fischer rats and an 800-fold enhancement of the urinary nitrite excretion. Nitro-L-arginine pretreatment inhibited the endotoxin-induced nitrite formation by 97%. Hepatic cGMP levels, as index of NO formation in the liver, were only increased significantly after endotoxin administration but not after ischemia and reperfusion. Our results provide no evidence for any enhanced generation of NO or peroxynitrite either systemically or locally during reperfusion and therefore it is unlikely that any of these metabolites are involved in the oxidant stress and liver injury during reperfusion after hepatic ischemia.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Kupffer Cells; Liver; Male; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Nitroarginine; Oxidants; Rats; Rats, Inbred F344; Reperfusion Injury; Stress, Physiological; Superoxides