Regulation of glutathione by oxidative stress in bovine pulmonary artery endothelial cells

Glutathione plays important roles as an intracellular antioxidant and in the maintenance of cellular thiol-disulfide balance. In addition, glutathione may regulate cell growth signaling induced by oxidative stress. We previously reported that cellular glutathione is up-regulated by bleomycin in bovine pulmonary artery endothelial cells. The present study examined effects of hydrogen peroxide (H2O2) on cell growth and glutathione levels. Exogenous addition of H2O2 induced biphasic effects on cell growth; 1 muM was stimulatory and >10 muM was inhibitory. However, both growth-promoting and inhibitory levels of H2O2 increased cellular glutathione levels. Whereas 1 muM H2O2 moderately but significantly increased glutathione, 30 muM caused a more substantial increase. Like bleomycin, both concentrations of H2O2 activated DNA binding of antioxidant response element (ARE), a regulatory element in the promoter of the gamma-glutamylcysteine synthetase heavy chain subunit, a key regulator of glutathione synthesis. However, only high concentrations of H2O2 activated p44/42 mitogen-activated protein (MAP) kinase. Thus, cellular glutathione is up-regulated by H2O2, perhaps via activating ARE-binding factors in a mechanism independent of MAP kinase. H2O2-mediated increase in glutathione and activation of ARE binding may play important roles in growth and death of pulmonary artery endothelial cells.