Age-related sensitivity to lung oxidative stress during ozone exposure

As immature and aged rats could be more sensitive to ozone (O-3)-linked lung oxidative stress we have attempted to shed more light on age-related susceptibility to O-3 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 O-3 (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 O-3 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 O-3 exposure. Thus, in contrast to adults, immature and aged rats displayed lung oxidative stress after O-3 exposure. Higher sensitivity of immature to O-3 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 O-3 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 O-3 exposure.