Modulation of endogenous antioxidant enzymes by nitric oxide in rat C6 glial cells.
To understand the possible mechanism of nitric oxide (NO)-mediated cytotoxicity, we investigated the effect of NO on the endogenous antioxidant enzymes (AOEs) catalase, glutathione peroxidase (GPX), and CuZn- and Mn-superoxide dismutases (SODs) in rat C6 glial cells under conditions in which these cells expressed oligodendrocyte-like properties as evidenced by the expression of 2',3'-cyclic-nucleotide 3'-phosphohydrolase. The 24-h treatment with S-nitroso-N-acetylpenicillamine (SNAP), a NO donor, decreased the activities and the protein levels of catalase, GPX, and Mn-SOD in a dose-dependent manner. Alternatively, the activity and the protein level of CuZn-SOD were increased. 2-Phenyl-4,4, 5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), a NO scavenger, blocked the effect of SNAP. Moreover, the treatment of C6 cells with sodium nitroprusside, another NO donor, or with a combination of lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), which induce excessive production of NO, also significantly modulated the AOE activities in a manner similar to that seen with SNAP treatment. The compounds/enzymes that inhibit the production of NO (e.g., N-nitro-L-arginine methyl ester hydrochloride, arginase, and PTIO) blocked the effects of LPS and IFN-gamma on the activities of AOEs. Treatment with SNAP and a combination of LPS and IFN-gamma also modulated the mRNA levels of AOEs, parallel to the changes in their protein levels and activities, except for Mn-SOD where the combination of LPS and IFN-gamma markedly stimulated the mRNA expression. In spite of the stimulation of mRNA level, LPS and IFN-gamma significantly inhibited the activity of Mn-SOD within the first 24 h of incubation; however, Mn-SOD activity gradually increased with the increase in time of incubation. These results suggest that alterations in the status of AOEs by NO may be the basis of NO-induced cytotoxicity in disease states associated with excessive NO production.
Dobashi
K
K
Department of Pediatrics, Medical University of South Carolina, Charleston 29425, U.S.A.
Pahan
K
K
Chahal
A
A
Singh
I
I
D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009457:Neuroglia / Q000187:drug effects / Q000201:enzymology*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000494:pharmacology*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D026423:S-Nitroso-N-Acetylpenicillamine; D013482:Superoxide Dismutase / Q000378:metabolism
D004338:Drug Combinations; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D007371:Interferon-gamma; D010088:Oxidoreductases; D013482:Superoxide Dismutase; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D010396:Penicillamine