s-nitrosocysteine and 1-1-diethyl-2-hydroxy-2-nitrosohydrazine

Nitric oxide (NO) is an excitatory agent within the isolated respiratory network of immature rats (Pierrefiche et al., 2002) and modulates bursting discharge of rhythmic respiratory neurone in juvenile rats (Pierrefiche et al., 2007). However, whether NO is acting directly via a specific cellular mechanism or by increasing NMDA receptor activity is unknown. Our present aim was to study NO modulation of NMDA-induced excitation within the isolated neonatal respiratory network. The NO-scavenger, haemoglobin, and the NOS inhibitor L-NO-Arg, reduced spontaneous activity and were more effective during NMDA-induced excitation. Both diethylamine-NO (DEA-NO) and S-nitroprussiate (SNP), two NO-donors not related chemically, increased spontaneous activity in a dose-dependent manner. However, when co-applied with NMDA only DEA-NO facilitated NMDA-induced excitation whereas SNP partially reversed or prevented NMDA-induced excitation. Similar reversion of NMDA-induced excitation were obtained with K₃-(FeCN)₆ (Fe III) or inactivated SNP. On the contrary, FeSO₄ did not have any effect on either spontaneous activity or NMDA-induced excitation. These data suggest that activation of NMDA receptors increase endogenous NO production which participates in endogenous NMDA-induced excitation during spontaneous XII bursting activity. It also demonstrated that the type of NO-donors used during pharmacological study implicating NMDA receptors should be carefully chosen.

Topics: Action Potentials; Animals; Animals, Newborn; Brain Stem; Cysteine; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Ferricyanides; Ferrous Compounds; Hemoglobins; Hydrazines; In Vitro Techniques; N-Methylaspartate; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Rats; S-Nitrosothiols

The aim of the present study was to investigate the role of nitric oxide (NO) in the regulation of hemoglobin oxygen affinity (HOA) in the presence of different oxygen partial pressure. In this research the effect of NO donors on gas-transport, acid-base balance, HOA indexes, metHb, iron-nitrosylhemoglobin amounts, and total nitrite/nitrate concentration was estimated in vitro. Experimentally, positive correlation was found between NO-dependent shift of HOA and hemoglobin oxygen saturation level. In conclusion, NO is a component of autonomous intraerythrocytic system of HOA regulation, which action is determined by oxygen in the blood. We assume that the physiological significance of such NO action is to maintain aerobic metabolism through optimal blood oxygenation in the pulmonary circulation, on the one hand, and, on the other hand, its compensation under low oxygen tension in the working tissues.

Topics: Acid-Base Equilibrium; Animals; Cysteine; Electron Spin Resonance Spectroscopy; Hemoglobins; Hydrazines; Hydrogen-Ion Concentration; Male; Methemoglobin; Nitrates; Nitric Oxide; Nitric Oxide Donors; Nitrites; Oxygen; Oxyhemoglobins; Rabbits; S-Nitroso-N-Acetylpenicillamine; S-Nitrosothiols

The ability of various nitric oxide (NO) donors to induce long-lasting inhibition of contraction in isolated arteries was compared. All the studied compounds elicited a relaxant effect in rat aortic rings precontracted with norepinephrine (NE). Almost maximal relaxation was obtained with 1 microM of each compound. The S-nitrosating agents S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine, S-nitroso-N-acetylcysteine, and sodium nitroprusside (1 microM) produced a decrease of the maximal effect of NE that persisted after removal of the drug. This hyporesponsiveness to NE was associated with a relaxant effect of N-acetylcysteine, a low-molecular weight thiol that can displace NO from cysteine-NO bonds. Such modifications of contraction were not observed in aortic rings previously exposed to 1 microM S-nitrosocysteine, glyceryl trinitrate, 3-morpholinosydnonimine, or 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA-NO). The same differential effects of GSNO and DEA-NO on contraction were also observed in porcine coronary arteries. Rat aortic rings previously exposed to 100 microM GSNO, but not to 100 microM DEA-NO, displayed a persistent increase in NO content (determined by NO spin trapping) and cysteine-NO residues (determined by immunostaining with an anti-cysteine-NO antiserum). The GSNO-induced increase in cysteine-NO residues in aortic tissue was prevented by the thiolmodifying agent p-hydroxymercuribenzoic acid. This study shows that in isolated arteries, the effects of S-nitrosating agents differed from those of other NO-donating agents. S- Nitrosating agents induced a persistent inhibition of contraction, which was attributed to the formation of releasable NO stores by S-nitrosation of tissue thiols. These differential effects of NO donors may be important for orientating their therapeutic indications.

Topics: Animals; Aorta; Arteries; Cysteine; Hydrazines; Male; Nitric Oxide Donors; Nitrogen Oxides; Rats; Rats, Wistar; S-Nitroso-N-Acetylpenicillamine; S-Nitrosoglutathione; S-Nitrosothiols; Swine; Vasoconstriction; Vasodilator Agents

Conduction in rat peripheral nerve has been monitored following the stimulated release of nitric oxide (NO) from diethylamine-NONOate (DEA-NONOate). Branches of the sciatic nerve were dissected, but left otherwise intact, and propagating signals recorded externally. At levels consistent with inflammation, NO exposure resulted in a complete loss of the compound action potential. Conduction was fully restored on removal of the drug. Most notably, this loss of excitability was dependent on the axonal environment. Removal of the connective tissue sheaths surrounding the nerve bundle, a process that normally enhances drug action, prevented block of signal propagation by nitric oxide. The epineurium seemed not to be required, and the decreased susceptibility to NO appeared to be correlated with a gradual loss of a component of the endoneurium that surrounds individual fibers. Tested on the rat vagus nerve, NO eliminated action potentials in both myelinated and unmyelinated fibers. One chemical mechanism that is consistent with the reversibility of block and the observed lack of effect of 8-Br-cGMP on conduction is the formation of a nitrosothiol through reaction of NO with a sulfhydryl group. In contrast to DEA-NONOate, S-nitrosocysteine, which can both transfer nitrosonium cation (NO+) to another thiol and also release nitric oxide, was effective on both intact and desheathed preparations. It has previously been demonstrated that chemical modification of invertebrate axons by sulfhydryl-reactive compounds induces a slow inactivation of Na+ channels. Nitric oxide block of axonal conduction may contribute to clinical deficits in inflammatory diseases of the nervous system.

Topics: Action Potentials; Animals; Axons; Cyclic GMP; Cysteine; Depression, Chemical; Female; Hydrazines; Myelin Sheath; Neural Conduction; Nitric Oxide; Nitrogen Oxides; Nitroso Compounds; Oxidation-Reduction; Rats; Rats, Inbred Lew; S-Nitrosothiols; Sciatic Nerve; Sodium Channels; Sulfhydryl Compounds; Tetrodotoxin; Vagus Nerve

Intracellular killing of Leishmania parasites within activated murine macrophages is thought to result from the toxic activities of nitrogen oxidation products (referred to as NO) released by the activated cells. In order to determine possible mechanisms of NO toxicity for these microorganisms, promastigotes of Leishmania major and Leishmania enriettii were exposed to NO generated chemically from acidified nitrite, S-nitrosocysteine, diethylamine NONOate, or nitroprusside. Treatment with these agents led to loss of viability (as determined from decreased motility and inhibition of [3H]TdR uptake upon reincubation in NO-free medium) with kinetics characteristic for each compound L. major was less sensitive to these effects than L. enriettii, and amastigotes displayed the same sensitivity as promastigotes of the same species. The early effects of NO toxicity could be detected within minutes of exposure to the NO donors; they included decreased respiration rate and inhibition of glucose, proline, and adenine incorporation. Inhibition of the activities of glyceraldehyde 3-phosphate dehydrogenase and of aconitase were also evidenced. In order to determine whether these phenomena reflected the mechanisms of toxicity of bona fide NO generated by macrophages, promastigotes were exposed to IFN-gamma + LPS-activated macrophages across permeable membranes. This resulted in marked inhibition of proline and adenine uptake in the parasites, which was restored, however, to control levels when macrophages were activated in the presence of the nitric oxide synthase inhibitor NGMMA. These results indicate that several cellular targets may be subject to NO toxicity in Leishmania parasites, including enzymes of glycolysis and respiratory metabolism as well as trans-membrane transport systems.

Topics: Aconitate Hydratase; Adenine; Animals; Cysteine; Dose-Response Relationship, Drug; Female; Glucose; Glyceraldehyde-3-Phosphate Dehydrogenases; Guinea Pigs; Hydrazines; Hydrogen-Ion Concentration; Leishmania; Leishmania enriettii; Leishmania major; Macrophages; Mice; Mice, Inbred CBA; Mutagens; Nitrogen; Nitrogen Oxides; Oxidation-Reduction; Oxygen Consumption; Proline; S-Nitrosothiols; Sodium Nitrite

Nitric oxide (NO.) does not react significantly with thiol groups under physiological conditions, whereas a variety of endogenous NO donor molecules facilitate rapid transfer to thiol of nitrosonium ion (NO+, with one less electron than NO.). Here, nitrosonium donors are shown to decrease the efficacy of evoked neurotransmission while increasing the frequency of spontaneous miniature excitatory postsynaptic currents (mEPSCs). In contrast, pure NO donors have little effect (displaying at most only a slight increase) on the amplitude of evoked EPSCs and frequency of spontaneous mEPSCs in our preparations. These findings may help explain heretofore paradoxical observations that the NO moiety can either increase, decrease, or have no net effect on synaptic activity in various preparations.

Topics: Animals; Aplysia; Cells, Cultured; Cerebral Cortex; Cyclic GMP; Cysteine; Ethylmaleimide; Fetus; Hippocampus; Hydrazines; Kinetics; Neuroglia; Neurons; Nitric Oxide; Nitrogen Oxides; Nitroglycerin; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; S-Nitrosothiols; Synapses; Synaptic Transmission