Abstract: BACKGROUND AND AIM: To assess the interactions of MutT homologue (MTH1) and 8-oxoguanine-DNA glycosylase1 (OGG1), two important genes of base excision repair. We examined 8-hydroxyguanine(8-oxo-dG) formation and 8-oxo-dG repair enzyme activity in pulmonary type-II-like epithelial cells to determine the association of hOGG1 and hMTH1 under oxidative stress induced by H2O2 . MATERIALS AND METHODS: A549 cells were incubated with H2O2 at concentrations of 0，50,100,200 and 300 μmol/L for 24 h. We then evaluated 8-oxo-dG formation, 8-oxo-dG repair enzyme activity and expressions of hOGG1 and hMTH1 genes. This was done using a high-performance liquid chromatography system equipped with an electrochemical detector, endonuclease nicking assay and reverse transcription polymerase chain reaction, respectively. RESULTS: H2O2 induced the formation of 8-oxo-dG in DNA at concentrations of 100 and 200 μmol/L. 8-oxo-dG levels peaked at 12 h and had declined to near baseline at 24 h, whereas 8-oxo-dG repair enzyme activity peaked at 18 h post-H2O2 exposure. hOGG1 and hMTH1 mRNA levels were also increased by H2O2 exposure, with alternating peaks. CONCLUSION: These data suggested that hOGG1 and hMTH1 displayed alternating effects in the process of oxidized DNA repair.

Key words: MTH1, OGG1, H2O2, 8-oxo-dG, DNA repair