PEROXYNITRITE-MEDIATED DNA STRAND BREAKAGE ACTIVATES POLY(ADP-RIBOSE)SYNTHETASE AND CAUSES CELLULAR-ENERGY DEPLETION IN A NONSEPTIC SHOCK MODEL INDUCED BY ZYMOSAN IN THE RAT

The aim of the present study was to investigate the role of poly(ADP-r ibose) synthetase in a nonseptic shock model, wherein oxyradicals, nit ric oxide, and peroxynitrite are known to play a crucial role in the i nflammatory process. DNA single-strand breakage and activation of the nuclear enzyme poly(ADP-ribose) synthetase (PARS) triggers an energy-c onsuming, inefficient repair cycle, which contributes to peroxynitrite -induced cellular injury. Here we investigated whether peroxynitrite p roduction and PARS activation are involved in cytotoxicity in macropha ges collected from rats subjected to zymosan-induced shock. Macrophage s harvested from the peritoneal cavity exhibited a significant product ion of peroxynitrite, as measured by the oxidation of the fluorescent dye dihydrorhodamine 123. Furthermore, zymosan-induced shock caused a suppression of macrophage mitochondrial respiration, DNA strand breaka ge, activation of PARS, and reduction of NAD(+) cellular levels. In vi vo treatment with 3-aminobenzamide (10 mg/kg intraperitoneally, 1 and 6 h after zymosan injection) or nicotinamide (50 mg/kg intraperitoneal ly, 1 and 6 h after zymosan injection) significantly inhibited the dec rease in mitochondrial respiration and the activation of PARS, and par tially restored the cellular level of NAD(+). In a separate group of e xperiments, in vivo pretreatment with N-G-nitro-L-arginine methyl este r, a nonselective inhibitor of nitric oxide synthesis (10 mg/kg intrap eritoneally, 15 min before zymosan administration), reduced peroxynitr ite formation and prevented the appearance of DNA damage, the decrease in mitochondrial respiration, and the loss of cellular levels of NAD( +). Our study suggests that formation of peroxynitrite and subsequent activation of PARS may alter macrophage function in inflammatory proce sses and inhibition of nitric oxide, and that PARS may be a novel phar macological approach to prevent cell injury in inflammation.