Age-related sensitivity to lung oxidative stress during ozone exposure

Abstract

As immature and aged rats could be more sensitive to ozone (O3)-linked lung oxidative stress we have attempted to shed more light on age-related susceptibility to O3 with focusing our interest on lung mitochondrial respiration, reactive oxygen species (ROS) production and lung pro/antioxidant status. For this purpose, we exposed to fresh air or O3 (500 ppb 12 h per day, for 7 days) 3 week- (immature), 6 month- (adult) and 20 month-old rats (aged). We determined, in lung, H2O2 release by mitochondria, activities of major antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)], heat shock protein (HSP72) content and 8-oxodG and dG-HNE nDNA contents, as DNA oxidative damage markers. In adult rats we did not observe alteration of pro/antioxidant status. In contrast to adults, immature rats exposed to O3 higher nDNA 8-oxodG content and HSP72 and without antioxidant enzymes modification. Aged rats displayed mild uncoupled lung mitochondria, increased SOD and GPx activities, and higher 8-oxodG content after O3 exposure. Thus, in contrast to adults, immature and aged rats displayed lung oxidative stress after O3 exposure. Higher sensitivity of immature to O3 was partly related to ventilatory parameters and to the absence of antioxidant enzyme response. In aged rats, the increase in cytosolic SOD and GPx activities during O3 exposure was not sufficient to prevent the impairment in mitochondrial function and accumulation in lung 8- oxodG. Finally, we showed that mitochondria seem not to be a major source of ROS under O3 exposure.