Mercaptoethylguanidine and Guanidine Inhibitors of Nitric-oxide Synthase React with Peroxynitrite and Protect against Peroxynitrite-induced Oxidative Damage

Abstract

Nitric oxide (NO) produced by the inducible nitricoxide synthase (iNOS) is responsible for some of the pathophysiological alterations during inflammation. Part of NO-related cytotoxicity is mediated by peroxynitrite, an oxidant species produced from NO and superoxide. Aminoguanidine and mercaptoethylguanidine (MEG) are inhibitors of iNOS and have anti-inflammatory properties. Here we demonstrate that MEG and related compounds are scavengers of peroxynitrite. MEG caused a dose-dependent inhibition of the peroxynitrite-induced oxidation of cytochrome c 2؉ , hydroxylation of benzoate, and nitration of 4-hydroxyphenylacetic acid. MEG reacts with peroxynitrite with a second-order rate constant of 1900 ؎ 64 M ؊1 s ؊1 at 37°C. In cultured macrophages, MEG reduced the suppression of mitochondrial respiration and DNA single strand breakage in response to peroxynitrite. MEG also reduced the degree of vascular hyporeactivity in rat thoracic aortic rings exposed to peroxynitrite. The free thiol plays an important role in the scavenging effect of MEG. Aminoguanidine neither affected the oxidation of cytochrome c 2؉ nor reacted with ground state peroxynitrite, but inhibited the peroxynitrite-induced benzoate hydroxylation and 4-hydroxyphenylacetic acid nitration, indicating that it reacts with activated peroxynitrous acid or nitrogen dioxide. Compounds that act both as iNOS inhibitors and peroxynitrite scavengers may be useful anti-inflammatory agents.Nitric oxide (NO), 1,2 a free radical produced by a family of isoenzymes termed nitric-oxide synthases (NOS), has been implicated in a variety of physiological and pathophysiological processes. The cytotoxic effects of NO are mediated in part by peroxynitrite (ONOO Ϫ ), 3 a reactive oxidant species formed from NO and superoxide at an almost diffusion-controlled rate (1-4). Although the biological activity and decomposition of peroxynitrite are very much dependent on cellular or chemical environment (concentration of proteins, thiols, glucose, and carbon dioxide and the ratio of NO to superoxide) (1-11), peroxynitrite is now generally considered a more toxic species than either NO or superoxide anion alone (12-19). The cytotoxic processes triggered by peroxynitrite include initiation of lipid peroxidation (5, 15, 16), inhibition of mitochondrial respiration (5,12,(17)(18)(19), inhibition of membrane pumps (20), depletion of glutathione (21), and damage to DNA (22-25) with subsequent activation of poly(ADP-ribose) synthetase and concomitant cellular energy depletion (25)(26)(27).Under certain conditions, NO produced by each of the three major isoforms of NOS can react with superoxide to form peroxynitrite. The constitutive, endothelial NOS isoform mainly serves physiological functions and is necessary for maintaining normal vascular functions, but under conditions of hypoxia/ reoxygenation and ischemia/reperfusion injury and in atherosclerosis, peroxynitrite formed from endothelial NOS-derived NO can initiate cytotoxic processes (28 -33). Similarly, during neuroinjury in response ...

Protein 3-nitrotyrosine formation during Trypanosoma cruzi infection in mice

“…Thus, since in the present study we evaluated the formation of • NO and nitrotyrosine as a marker of nitro-oxidative stress during T. cruzi infection, we chose to work with the C3H and BALB/c strains. The animals were infected with a sublethal dose of parasites and treated with the NOS inhibitors L-NAME or GED or with MEG, the latter an iNOS inhibitor and peroxynitrite scavenger (23). L-NAME is a general NOS inhibitor which has already been used to inhibit • NO production during T. cruzi infection (3,4,30).…”

Активность Глутатионовой Системы В Тканях Крыс При Действии Фенилэтилбигуанида На Фоне Развития Экспериментальной Ишемии/Реперфузии Головного Мозга

“…Èìåþòñÿ äàííûå î ñïîñîáíîñòè íåêîòîðûõ èç íèõ òîðìîçèòü êëåòî÷íûå îêèñëèòåëüíûå ðåàêöèè, â òîì ÷èñëå è îêèñëèòåëüíîãî ãëèêîçèëèðîâàíèÿ áåëêîâ [14]. Êðîìå ýòîãî, ãóàíèäè-íîâûå ïðîèçâîäíûå, íàïðèìåð, ìåðêàïòîýòèëãóàíè-äèí, ìåòôîðìèí è äð., ñïîñîáíû âûñòóïàòü êàê â êà÷å-ñòâå ëîâóøåê ñâîáîäíûõ ðàäèêàëîâ, òàê è èíãèáèðî-âàòü ïðîöåññû èõ îáðàçîâàíèÿ, â ÷àñòíîñòè, ðåàêöèè, êàòàëèçèðóåìûå NADPH-îêñèäàçîé è NO-ñèíòàçîé [13].…”

“… ãðóïïå aeèâîòíûõ, êîòîðûì íà ôîíå ïîñòèøåìè÷åñêîé ðåïåðôóçèè ââîäèëè ÔÝÁ, ñîäåðaeàíèå ÄÊ ñíèaeàëîñü êàê â ãîëîâíîì ìîçãå, òàê è â ñûâîðîòêå êðîâè â 1,3 ðàçà (ð < 0,05) ïî ñðàâíåíèþ ñî çíà÷åíèÿìè ïðè ÈÐÃÌ (ðèñ. 1-I), ÷òî, î÷åâèäíî, ñâèäåòåëüñòâóåò î íàëè÷èè àíòèîêñèäàíòíûõ ñâîéñòâ ó äàííîãî ñîåäèíåíèÿ è ñî-ãëàñóåòñÿ ñ ëèòåðàòóðíûìè äàííûìè î òîì, ÷òî íåêî-òîðûå ïðîèçâîäíûå ãóàíèäèíà ìîãóò âûñòóïàòü â êà-÷åñòâå ñóïðåññîðîâ ÏÎË è èíãèáèòîðîâ îáðàçîâàíèÿ ñâîáîäíûõ ðàäèêàëîâ [13,14].…”

The dose-dependent influence of 3,5-dicarbometoxyphenilbiguanide on activity of the glutathione antioxidant system in heart and blood serum of rats with the experimental myocardial infarction

“…При этом содержание ДК уменьшалось в 2,4 раза в сердце и в 6,4 раза в сыворотке. Известно, что гуанидиновые производные, например меркаптоэтилгуанидин, метформин и другие способны непосредственно перехватывать свободные радикалы или опосредованно уменьшать их содержание за счёт торможения внутриклеточного формирования [6]. Необходимо отметить, что введение 3,5-ДКМФБ в дозе 50 мг/кг сопровождалось снижением уровня ДК ниже показателей контрольной группы животных.…”