Nitric oxide inhibited peroxyl and alkoxyl radical formation with concomitant protection against oxidant injury in intestinal epithelial cells.
A model compound of lipid peroxidation, tert-butyl hydroperoxide (tBOOH), was used in vitro to investigate (i) the generation of tBOOH-derived peroxyl and alkoxyl radicals by rat intestinal epithelial cells or enterocytes and (ii) the role of nitric oxide (NO) on cell-generated free radical formation and cellular cytotoxicity. Peroxyl, alkoxyl, and methyl radicals were detected and characterized by direct and spin-trapping electron paramagnetic resonance spectroscopy in incubations containing tBOOH and hematin, enterocytes, or intestinal epithelial cell line-6 cells. The direct interactions of tBOOH-derived radicals and NO from nitrosoglutathione (GSNO), nitrosoacetyl penicillamine (SNAP), or 1-¿b3-aminopropy-4-(3-aminopropylammonio)¿ butylamino-diazeniumdiolate (SpNONOate) were demonstrated as their levels were depleted in these incubations. SNAP, not GSNO or SpNONOate, was capable of trapping methyl radical produced during hematin-catalyzed decomposition of tBOOH. Cellular cytotoxicity expressed by percentage of dead cells and lactate dehydrogenase was increased with tBOOH treatment. Addition of GSNO, SNAP, or SpNONOate suppressed tBOOH-induced elevation of cell cytotoxicity. The NO donor precursor glutathione, acetylpenicillamine, or spermine did not have any effects on tBOOH-derived radical generation or cell cytotoxicity. These findings demonstrated free radical-free radical reactions between NO- and tBOOH-derived alkoxyl and peroxyl radicals generated by enterocytes. These reactions, at least in part, describe the protective role of NO from hydroperoxide-induced injury in intestinal epithelial cells.
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Department of Physiology, Louisiana State University Medical Center, 1901 Perdido Street, New Orleans, Louisiana, 70112-1393, USA.
D000438:Alcohols / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D004578:Electron Spin Resonance Spectroscopy; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005609:Free Radicals / Q000378:metabolism; D006427:Hemin / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018384:Oxidative Stress; D010545:Peroxides / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020122:tert-Butylhydroperoxide
D000438:Alcohols; D000975:Antioxidants; D005609:Free Radicals; D010545:Peroxides; C059688:alkoxyl radical; C049375:perhydroxyl radical; D009569:Nitric Oxide; D006427:Hemin; D020122:tert-Butylhydroperoxide