3-nitrotyrosine and 2-mercaptoethylguanidine

The aim of this study was to test whether peroxynitrite neutralizers would reduce peroxynitrite accumulation and improve myocardial contractile dysfunction and inflammation in endotoxin-treated rats.. Release of endogenous proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha in response to endotoxin is responsible for the production of large amounts of nitric oxide (NO), which may exert detrimental effects on the myocardium in animal models, isolated hearts, and isolated cardiac myocytes. Recent studies have indicated that many of the deleterious effects of NO are mediated by peroxynitrite, a powerful oxidant generated from a fast diffusion-limited reaction of NO and superoxide anion.. We studied the effects of peroxynitrite neutralizers, such as mercaptoethylguanidine (MEG) sodium succinate (10 mg/kg) and 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrinato iron (III) (FeTPPS) (30 mg/kg) on peroxynitrite accumulation, in vivo endothelial cell-leukocyte activation on the mesenteric venule, and myocardial contractile dysfunction and inflammation in a model of sepsis induced by injection of endotoxin (10 mg/kg) in rats.. Mercaptoethylguanidine sodium succinate and FeTPPS largely prevented the accumulation of peroxynitrite as measured by plasma rhodamine fluorescence and heart nitrotyrosine staining. Interestingly, MEG sodium succinate and FeTPPS improved endotoxin-induced myocardial contractile dysfunction, which was associated with reduced degradation of nuclear factor kappa B inhibitory protein I-kappa-B, plasma TNF-alpha levels, and microvascular endothelial cell-leukocyte activation.. These observations suggest that the beneficial effects of MEG and FeTPPS on endotoxin-induced myocardial contractile dysfunction could be related to the unique effects of these compounds on cardiovascular inflammation processes.

Topics: Animals; Biomarkers; Catalysis; Disease Models, Animal; Endothelium, Vascular; Endotoxemia; Enzyme Inhibitors; Fluorescent Dyes; Guanidines; I-kappa B Proteins; Leukocytes; Metalloporphyrins; Models, Cardiovascular; Myocarditis; NF-kappa B; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Peroxynitrous Acid; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha; Tyrosine; Xanthenes

In previous studies of transgenic sickle cell mice, increased renal expression of inducible nitric oxide synthase (iNOS) and endothelial cell isoform of NOS (EcNOS) was found by Western blot and immunohistochemistry. In addition, putative evidence of peroxynitrite (ONOO-) formation was found in the form of positive immunostaining and immunoblot for nitrotyrosine. Apoptosis was also detected by DNA strand breakage and TUNEL assay. The present study was carried out to examine the role of NO/ONOO- in mediating renal tubular cell apoptosis in sickle cell mouse kidneys.. Mercaptoethylguanidine (MEG), a compound that selectively inhibits iNOS and also is a scavenger of ONOO-, was administered intraperitoneally over a five-day period to control and betas mice. Immunohistochemistry of iNOS and nitrotyrosine, DNA electrophoresis, ApoTACS assay for apoptosis, and Western blot of poly(ADP-ribose) polymerase (PARP) were carried out.. MEG administration virtually eliminated renal immunostaining of iNOS and nitrotyrosine and prevented DNA strand breakage. In addition, Western blot analysis of PARP, a nuclear DNA-reparative enzyme activated in response to DNA strand breakage, was found to be cleavaged in hypoxic betas mice, but was partially protected in MEG-treated betas hypoxic mice. Finally, apoptosis was markedly reduced by MEG in betas hypoxic mice.. These observations provide evidence that NO and/or ONOO- are responsible for initiating cell damage, which leads to apoptosis in sickle cell mouse kidneys.

Topics: Alanine Transaminase; Anemia, Sickle Cell; Animals; Apoptosis; Aspartate Aminotransferases; Blotting, Western; Cell Hypoxia; DNA Fragmentation; Electrophoresis, Agar Gel; Enzyme Inhibitors; Guanidines; Immunohistochemistry; In Situ Nick-End Labeling; Kidney Diseases; Kidney Tubules; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nitrates; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Poly(ADP-ribose) Polymerases; Tyrosine

Reactive oxygen and nitrogen species participate in the inflammatory process during meningitis. Among them, superoxide, nitric oxide (NO), and their reaction product peroxynitrite exert cytotoxic effects. Mercaptoethylguanidine (MEG) exerts beneficial effects in in vivo inflammatory conditions by scavenging peroxynitrite and inhibiting the inducible NO synthase. This study was designed to investigate whether MEG may attenuate inflammation and brain injury in experimental meningitis. Meningitis increased nitrite/nitrate, and protein content in the cerebrospinal fluid (CSF). In the brain tissue high levels of malondialdehyde and formation of nitrotyrosine indicated lipid peroxidation and nitrosative stress, respectively. Myeloperoxidase activity was increased indicating accumulation of neutrophils into the brain parenchyma. Treatment with MEG decreased nitrite/nitrate levels whereas it did not affect the bacterial clearance from the CSF. Furthermore, treatment with MEG markedly reduced brain tissue levels of myeloperoxidase and malondialdehyde. These data demonstrate that MEG could have a therapeutic role in meningitis.

Topics: Animals; Brain; Enzyme Inhibitors; Guanidines; Immunoenzyme Techniques; Male; Malondialdehyde; Meningitis, Bacterial; Meningitis, Meningococcal; Nitrates; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Peroxidase; Proteins; Rabbits; Streptococcal Infections; Streptococcus agalactiae; Tyrosine

The effect of mercaptoethylguanidine (MEG), a selective inhibitor of the inducible nitric oxide synthase and peroxynitrite scavenger, was evaluated in a rat model of colonic injury. A single intracolonic administration of trinitrobenzene sulfonic acid (TNBS, 20 mg/kg) dissolved in ethanol induced a severe colitis in male rats. Rats experienced bloody diarrhea and a significant loss of body weight. At 4 days after TNBS administration, the colon damage was characterized by areas of mucosal necrosis. Activity of myeloperoxidase, a marker of neutrophil infiltration, and levels of the 6-keto-prostaglandin F1alpha, were also markedly increased, whereas colonic ATP levels were reduced into the damaged tissue. Immunohistochemistry for the inducible nitric oxide synthase and nitrotyrosine, an index of nitrosative stress, showed an intense staining in the inflamed colon. Treatment with MEG (10 mg/kg i.v. b. i.d.) significantly reduced the appearance of diarrhea and the loss of body weight. This was associated with a remarkable amelioration of the disruption of the colonic architecture and suppression of the energetic failure, as well as a significant reduction of colonic myeloperoxidase activity and 6-keto-prostaglandin F1alpha levels. MEG also reduced the appearance of iNOS and nitrotyrosine immunoreactivity in the colon. The results of this study suggested that administration of MEG may be beneficial for the treatment of inflammatory bowel diseases.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Body Weight; Colitis; Enzyme Inhibitors; Free Radical Scavengers; Guanidines; Immunohistochemistry; Male; Nitrates; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Rats; Rats, Wistar; Trinitrobenzenesulfonic Acid; Tyrosine