Study on oxidative DNA damage and repair enzyme in acute and chronic renal disease

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We examined the contents of 8-oxo-2'-deoxyguanosine (8-oxo-dG), which is a major type of oxidative damage in DNA, in the rat kidney during I/R injury, and also investigated the expression level of the OGG1gene encoding the 8-oxoguanine DNA glycosylase. High-performance liquid chromatography with an MS/MS analysis of the nuclear DNA revealed an immediate accumulation of 8-oxo-dG in the nuclear DNA prepared from the cortex and OM of the kidney 1 h after I/R, and an immunohistochemical analysis demonstrated the immediate accumulation of 8-oxo-dG in the nuclei of renal tubular cells both in the cortex and OM. A delayed increase of cytoplasmic staining with anti-8-oxo-dG was observed only in the cortico-medulla and OM, where the cytoplasmic staining in the proximal tubular cells is higher than in the distal tubular cells. The level of cytoplasmic staining representing 8-oxo-dG in mitochondrial DNA, peaked at 6 h after I/R and preceded the necrosis of proximal tubular cells in the OM, An Rna … More se protection assy showed a high level of OGG1 mRNA in the normal kidney, and the level decreased within 3 h only in the OM, and increased thereafter 1 to 7 days of I/R both in the cortex and OM. In situ hybridization showed higher levels of OGG1 mRNA expression in the renal tubules in the OM than in the cortex of the normal kidney, which decreased rapidly within 3 h of I/R. Thus, the accumulation of 8-oxo-dG in the mitochondrial DNA rather than in nuclear DNA is likely to be involved in the pathogenic responses such as necrosis of renal tubular cells during I/R injury of the kidney, together with an altered level of OGG1 expression.Furthermore, we examined the involvement of 8-oxo-dG in cisplatin-induced renal tubular cell death, in vivo and in vitro. Cisplatin induced accumulation of 8-oxo-dG in renal tubular cells before cell death, and co-administration of DMTU, a scavenger of hydroxyl radicals, inhibited such accumulation and renal tubular damage.In the kidney of 5/6 nephrectomized rats, obvious accumulation of 8-oxo-dG was not observed. Less