Nitric oxide promotes recycling of 8-nitro-cGMP, a cytoprotectivemediator, into intact cGMP in cells
Nitric oxide promotes recycling of 8-nitro-cGMP, a cytoprotectivemediator, into intact cGMP in cells
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一氧化氮促进 8-硝基-cGMP（一种细胞保护介质）再循环为细胞内完整的 cGMP
DOI：
10.1039/c2mb25189b
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Takaaki Akaike and Hirokazu Arimoto
中科院分区：
文献类型：
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作者：
Yohei Saito;Tomohiro Sawa;Jun Yoshitake;Chiaki Ito;Shigemoto Fujii;Takaaki Akaike and Hirokazu Arimoto
8-Nitro-cGMP是在炎症条件下发现的一种内源性核苷酸，是一氧化氮(NO)信号转导的重要介质。除了cGMP的行为外，8-硝基-cGMP还对氧化应激具有独特的细胞保护作用。虽然8-硝基-GTP合成8-硝基-cGMP已被提出，但从细胞中去除多余或未使用的8-硝基-cGMP的机制仍不清楚。在这项研究中，我们报道了在RAW 264.7巨噬细胞中，8-硝基-cGMP在一氧化氮依赖的细胞内转化为完整的cGMP。在我们的实验中，我们合成了同位素标记的8-硝基-cGMP作为代谢物分析的工具，并利用LC-MS/MS技术鉴定了8-氨基-cGMP是8-硝基-cGMP的初始代谢物。我们还证明了内源性8-硝基-cGMP可以通过特异性识别8-氨基-cGMP的抗体免疫细胞化学染色而转化为8-氨基-cGMP。此外，我们还发现，在炎症条件下，同位素标记的8-氨基-cGMP可被代谢成cGMP。我们认为，在胁迫条件下，8-氨基-cGMP亚硝化生成NO，生成8-重氮-cGMP，然后分解为cGMP。据我们所知，这项研究是第一次报道C-8位氨基鸟嘌呤核苷酸的还原脱氨基。这项研究的结果共同表明，NO不仅在8-硝基-cGMP的产生中起着关键作用，而且在氧化应激或炎症条件下对其清除也起着关键作用。
8-Nitro-cGMP is an endogenous nucleotide discovered under inflammation conditions as an important mediator of nitric oxide (NO) signaling. Besides cGMP-like behaviour, 8-nitro-cGMP exerts unique cytoprotective effects against oxidative stress. Although the formation of 8-nitro-cGMP from 8-nitro-GTP has previously been proposed, the mechanism by which excess or unused 8-nitro-cGMP is removed from cells remains unknown. In this study, we report a nitric oxide-dependent cellular conversion of 8-nitro-cGMP to intact cGMP in RAW 264.7 macrophage cells. In our experiments, we synthesized isotopically labeled 8-nitro-cGMP as a tool for metabolites analysis and identified 8-amino-cGMP as an initial metabolite of 8-nitro-cGMP using a LC-MS/MS technique. We also proved that endogenous 8-nitro-cGMP can be converted into 8-amino-cGMP by immunocytochemical staining with an antibody that specifically recognizes 8-amino-cGMP. Moreover, we showed that isotopically labeled 8-amino-cGMP is metabolized into cGMP under inflammation conditions. We propose that nitrosylation of 8-amino-cGMP occurs by NO formation under stress conditions and gives putative 8-diazonium-cGMP, which subsequently decomposes into cGMP. To the best of our knowledge, this study is the first to report reductive deamination of aminoguanine nucleotide at the C-8 position. The findings of this study collectively indicate that NO plays a crucial role not only in the production of 8-nitro-cGMP but also in its elimination under oxidative stress or inflammation.