Induction of vascular endothelial growth factor expression and hypoxia-inducible factor 1α protein by the oxidative stressor arsenite

Recent evidence suggests that vascular endothelial growth factor (VEGF) expression is up-regulated by oxidative stressors through activation of hypoxia-inducible Factor I (HIF-1). To investigate whether this is a general phenomenon, we studied the effects of the sulfhydryl reagent arsenite on VEGF expression in human ovarian cancer cells. Arsenite potently induces the production of reactive oxygen species (ROS) in several cell systems and directly interacts with sulfhydryl groups of cellular thiols. We report that arsenite induces VEGF mRNA and protein levels in normoxic H134 and OVCAR-3 cells. Arsenite also increases HIF-1 alpha protein levels, suggesting a role for HIF-1 in the induction of VEGF expression. Pretreatment with the ROS inhibitors catalase and mannitol attenuated arsenite-induced ROS production, but did not affect induction of VEGF mRNA and HIF-1 alpha protein. In contrast, pretreatment with the thiol antioxidants glutathione or N-acetylcysteine completely abrogated both effects, whereas a potentiation was observed by depletion of intracellular glutathione. These results demonstrate that arsenite-induced VEGF mRNA and HIF-1 alpha protein expression is independent of increased ROS production but critically regulated by the cellular reduced glutathione content. In addition, these data suggest the involvement of a thiol-sensitive mechanism in the regulation of VEGF mRNA expression and HIF-1 alpha protein in human ovarian cancer cells.