Meyer F, Fiala E, Westendorf J
Department of Toxicology, University Medical School of Hamburg, Grindelallee 117, D-20146, Hamburg, Germany.
Toxicology. 2000 May 5;146(2-3):83-92. doi: 10.1016/s0300-483x(00)00140-2.
The pre-mutagen 8-Oxo-2'-deoxyguanosine-5'-triphosphate (8-oxo-dGTP) is formed during normal cellular metabolism and its incorporation into DNA leads to transversion mutations. Human cells possess the hMTH-1 gene encoding the enzyme 8-oxo-dGTPase, which catalyzes the hydrolysis of 8-oxo-dGTP to the corresponding 8-oxo-dGMP, preventing mutations. To elucidate the involvement of 8-oxo-dGTPase in carcinogenesis, we studied hMTH-1 gene expression and enzyme activity in response to oxidative stress to human skin fibroblasts and Jurkat cells. In fibroblasts, ranges from 0 to 100 microM H(2)O(2) caused a 2-fold induction of hMTH-1-mRNA expression and a 3-fold induction of enzyme activity. A 1.7-fold induction of mRNA expression and a 3.5-fold induction of enzyme activity was obtained in Jurkat cells after treatment ranging from 0 to 300 microM H(2)O(2). Cytotoxic concentrations of hydrogen peroxide lead to an almost complete loss of enzyme activity and an inhibition of hMTH-1 mRNA expression. Induction of hMTH-1 gene expression was prevented by addition of actinomycin D and cycloheximide. These data indicate the inducibility of the hMTH-1 gene expression and enzyme activity by prooxidative molecules, such as hydrogen peroxide. These parameters can thus be used as a marker of oxidative stress.
诱变前体8-氧代-2'-脱氧鸟苷-5'-三磷酸（8-氧代-dGTP）在正常细胞代谢过程中形成，其掺入DNA会导致颠换突变。人类细胞拥有编码8-氧代-dGTP酶的hMTH-1基因，该酶催化8-氧代-dGTP水解为相应的8-氧代-dGMP，从而防止突变。为了阐明8-氧代-dGTP酶在致癌过程中的作用，我们研究了人类皮肤成纤维细胞和Jurkat细胞在氧化应激下hMTH-1基因的表达及酶活性。在成纤维细胞中，0至100微摩尔/升的过氧化氢可使hMTH-1 mRNA表达诱导2倍，酶活性诱导3倍。在Jurkat细胞中，0至300微摩尔/升的过氧化氢处理后，mRNA表达诱导1.7倍，酶活性诱导3.5倍。细胞毒性浓度的过氧化氢会导致酶活性几乎完全丧失，并抑制hMTH-1 mRNA表达。放线菌素D和环己酰亚胺的添加可阻止hMTH-1基因表达的诱导。这些数据表明，hMTH-1基因表达和酶活性可被过氧化氢等促氧化分子诱导。因此，这些参数可作为氧化应激的标志物。
