Effect of NO 2 exposure on antioxidant defense of endothelial cells

Abstract

Nitrogen dioxide (NO 2), an environmental oxidant pollutant, is toxic to lung cells. We evaluated the changes in antioxidant enzyme activities in porcine pulmonary artery (PA) and aortic (AO) endothelial cells in monolayer cultures. Confluent PA or AO endothelial cells were exposed to 3 or 5 ppm NO 2 or air (control) for 3–24 h and assayed for GSH-reductase (GSH-red), GSH-peroxidase (GSH-per), and glucose-6-phosphate dehydrogenase (G6PDH) activities as well as for intracellular GSH content. After 3, 6, or 12 h exposure to 3 or 5 ppm, GSH-red and G6PDH activities were not different from those of controls in both PA and AO endothelial cells. Exposure to 3 or 5 ppm NO 2 for 24 h resulted in significant increases in GSH-red ( P < 0.05) and G6PDH ( P < 0.001) activities in both cell types. GSH-per activity and GSH content in NO 2-exposed PA and AO endothelial cells were not different from those of controls, irrespective of NO 2 concentration and exposure time. These results indicate that enzyme activities of G6PDH and GSH-red are increased in PA and AO endothelial cells exposed to NO 2, and this response is comparable, in part, to that in the lungs from animals exposed to NO 2.