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 μM was stimulatory and >10 μM was inhibitory. However, both growth-promoting and inhibitory levels of H₂O ₂ increased cellular glutathione levels. Whereas 1 μM H ₂O₂ moderately but significantly increased glutathione, 30 μM 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 γ-glutamylcysteine synthetase heavy chain subunit, a key regulator of glutathione synthesis. However, only high concentrations of H₂O ₂ 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. H ₂O₂-mediated increase in glutathione and activation of ARE binding may play important roles in growth and death of pulmonary artery endothelial cells.