8-Nitro-cGMP (8-nitroguanosine 3′,5′-cyclic monophosphate) is a nitrated derivative of cGMP, which can function as a unique electrophilic second messenger involved in regulation of an antioxidant adaptive response in cells. In the present study, we investigated chemical and biochemical regulatory mechanisms involved in 8-nitro-cGMP formation, with particular focus on the roles of ROS (reactive oxygen species). Chemical analyses demonstrated that peroxynitrite-dependent oxidation and myeloperoxidase-dependent oxidation of nitrite in the presence of H2O2 were two major pathways for guanine nucleotide nitration. Among the guanine nucleotides examined, GTP was the most sensitive to peroxynitrite-mediated nitration. Immunocytochemical and tandem mass spectrometric analyses revealed that formation of 8-nitro-cGMP in rat C6 glioma cells stimulated with lipopolysaccharide plus pro-inflammatory cytokines depended on production of both superoxide and H2O2. Using the mitochondria-targeted chemical probe MitoSOX™ Red, we found that mitochondria-derived superoxide can act as a direct determinant of 8-nitro-cGMP formation. Furthermore, we demonstrated that Nox2 (NADPH oxidase 2)-generated H2O2 regulated mitochondria-derived superoxide production, which suggests the importance of cross-talk between Nox2-dependent H2O2 production and mitochondrial superoxide production. The results of the present study suggest that 8-nitro-cGMP can serve as a unique second messenger that may be implicated in regulating ROS signalling in the presence of NO.
Regulation by mitochondrial superoxide and NADPH oxidase of cellular formation of nitrated cyclic GMP: potential implications for ROS signalling
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Khandaker Ahtesham Ahmed, Tomohiro Sawa, Hideshi Ihara, Shingo Kasamatsu, Jun Yoshitake, Md. Mizanur Rahaman, Tatsuya Okamoto, Shigemoto Fujii, Takaaki Akaike; Regulation by mitochondrial superoxide and NADPH oxidase of cellular formation of nitrated cyclic GMP: potential implications for ROS signalling. Biochem J 15 January 2012; 441 (2): 719–730. doi: https://doi.org/10.1042/BJ20111130
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