NADH oxidase activation is involved in arsenite-induced oxidative DNA damage in human vascular smooth muscle cells

Arsenic is atherogenic, carcinogenic, and genotoxic. Because atheroscleroti c plaque has been considered a benign smooth muscle cell tumor, we have stu died the effects of arsenite on DNA integrity of human vascular smooth musc le cells. By using single-cell alkaline electrophoresis, apparent DNA stran d breaks were detected in a 4-hour treatment with arsenite at a concentrati on above 1 mu mol/L. DNA strand breaks of arsenite-treated cells were incre ased by Escherichia coli formamidopyrimidine-DNA glycosylase and decreased by diphenylene iodinium, superoxide dismutase, catalase, pyruvate, DMSO, or D-mannitol. Extract from arsenite-treated cells showed increased capacity for producing superoxide when NADH was included in the reaction mixture; ho wever, addition of arsenite to extract from untreated cells did not increas e superoxide production. The superoxide-producing ability of arsenite-treat ed cells was also suppressed by diphenylene iodinium, 4,5-dihydroxy-1,2-ben zenedisulfonic acid disodium salt (Tiron), or superoxide dismutase. Superox ide production and DNA strand breaks in arsenite-treated cells were also su ppressed by transfecting antisense oligonucleotides of p22phox, an essentia l component of NADH oxidase. Treatment with arsenite also increased the mRN A level of p22phox. These results suggest that arsenite activates NADH oxid ase to produce superoxide, which then causes oxidative DNA damage. The resu lt that arsenite at low concentrations increases oxidant levels,and causes oxidative DNA damage in vascular smooth muscle cells may be important in ar senic-induced atherosclerosis.