Study of the effect of exercise training on ozone toxicity in mice

Background: Ozone is a highly toxic oxidant found in urban environment. Chronic exposure causes an increase in oxidative stress and has been associated with an increase in pulmonary diseases, reduced pulmonary function and an increase in mortality. Previous studies from our group have shown the antioxidant properties of exercise training. Aim: The aim of this study was (i) to determine the effect of 8 months of aerobic exercise training on the pulse oximeter SaO2 and in different performance tests (grip strength, VO2max and tightrope test) in mice treated with high doses of ozone. Methods: Twenty C57BL/6J mice were divided into four experimental groups: Rest Air [RA] (n=4), Rest Ozone [RO] (n=6), Trained Air [TA] (n=4) and Trained Ozone [TO] (n=6). Endurance-trained animals were exercised 5 d/wk during 8 months on an animal treadmill at an intensity of 75%VO2max. After the training period the animals (rest and ozone) were exposed 4h/day to 4ppm ozone for 7 weeks. SaO2 and body weight were determined daily in all the experimental groups. The performance tests were run before and after the ozone exposure. Results: We found a significant decrease in the pulse oximeter SaO2 in the animals exposed to ozono. However, there was a higher decrease 14.7% [RO] vs 13.2% [TO] in the SaO2 in the group of animals maintained in resting conditions when compared with those trained and exposed to ozone. We also found a significant decrease in the neuromuscular competence, grip strength and maximal oxygen consumption in the rest mice exposed to ozone. Exercise training prevented the negative effects of ozone on the performance tests. Conclusions: Our results show that aerobic exercise training partially protects against ozone-induced toxicity. More research is needed to determine whether this protective effect is related to the training-induced increase in the antioxidant defences. Acknowledgements: Work supported by grants SAF2009-08334; BFU2007-65803/BFI, ISCIII2006-RED13-027 (RETICEF), PROMETEO2010/074 and EU Funded COSTB35. Co-financed by FEDER funds from the EU.