Abstract
Stimulated macrophages produce nitric oxide (NO) via inducible nitric oxide synthase (iNOS) using molecular O 2, 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 pO 2 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 pO 2 ranging from 0.07 to 50%. OPPC activity correlated linearly with NOx production at pO 2 > 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% O 2, without decreasing NOx production. These results are the first to investigate the effect of pO 2 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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.