pO₂-dependent NO production determines OPPC activity in macrophages

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• 作者：Mary A. Robinson ; Stephen W. Tuttle ; Cynthia M. Otto ; Cameron J. Koch
• 关键词：NADPH ; Reactive nitrogen-mediated stress ; Oxidative stress ; Inflammation
• 刊名：Free Radical Biology and Medicine
• 出版年：2010
• 出版时间：15 January 2010
• 年：2010
• 卷：48
• 期：2
• 页码：189-195
• 全文大小：507 K

文摘

Stimulated macrophages produce nitric oxide (NO) via inducible nitric oxide synthase (iNOS) using molecular O₂, L-arginine, and NADPH. Exposure of macrophages to hypoxia decreases NO production within seconds, suggesting substrate limitation as the mechanism. Conflicting data exist regarding the effect of pO₂ on NADPH production via the oxidative pentose phosphate cycle (OPPC). Therefore, the present studies were developed to determine whether NADPH could be limiting for NO production under hypoxia. Production of NO metabolites (NOx) and OPPC activity by RAW 264.7 cells was significantly increased by stimulation with lipopolysaccharide (LPS) and interferon γ (IFNγ) at pO₂ ranging from 0.07 to 50 % . OPPC activity correlated linearly with NOx production at pO₂ > 0.13 % . Increased OPPC activity by stimulated RAW 264.7 cells was significantly reduced by 1400 W, an iNOS inhibitor. OPPC activity was significantly increased by concomitant treatment of stimulated RAW 264.7 cells with chemical oxidants such as hydroxyethyldisulfide or pimonidazole, at 0.07 and 50 % O₂, without decreasing NOx production. These results are the first to investigate the effect of pO₂ on the relationship between NO production and OPPC activity, and to rule out limitations in OPPC activity as a mechanism by which NO production is decreased under hypoxia.