Evaluation of PM2.5-induced Antioxidant Consumption and ROS Generation as a Proxy for the Aerosol Toxicity

SUDHEER SALANA, Yixiang Wang, Vishal Verma, University of Illinois at Urbana-Champaign

     Abstract Number: 173
     Working Group: Health-Related Aerosols

Abstract
It is widely believed that antioxidants are primarily reactive oxygen species (ROS) scavenging molecules. Consequently, a number of assays have been developed to measure the rate of depletion of key cellular antioxidants such as glutathione and ascorbate, as a proxy for the ambient PM_2.5 oxidative stress and subsequent toxicity. However, depletion of some of these antioxidants such as reduced glutathione (GSH) is not limited to its reaction with ROS. So far, very few studies have explored the relationship between antioxidants consumption, ROS generation and cytotoxicity induced by ambient PM_2.5. We evaluated this relationship using a large number of ambient PM_2.5 samples (N=230) collected in Mid-West USA. We investigated the association between cell viability, GSH consumption and ROS response for A549 cells, by exposing the cells to the water extracts of PM_2.5 samples. Our results show that there is a good correlation between cell viability and ROS response (r >0.5). However, both ROS response and cell viability were poorly correlated (0.11<r<0.41) with the GSH consumption (measured via both cellular as well as acellular methods). Finally, we pre-treated the cells with GSH and measured the intracellular GSH depletion, cellular ROS generation and cytotoxicity, caused by PM_2.5 extracts. Interestingly, pre-treating the cells with GSH resulted in a substantial decrease (>50 %) in both ROS response and cell death. These results indicate that although GSH is involved in eliminating ROS and protecting the cells from PM_2.5 toxicity, measuring GSH consumption alone cannot be considered a surrogate for the PM_2.5 induced cytotoxicity and cellular oxidative stress. This is probably because PM_2.5 might induce glutathione depletion through other mechanisms beside ROS generation. Nevertheless, our results show that PM_2.5-induced cellular ROS measurement is still a biologically relevant parameter to represent cellular oxidative stress and cytotoxicity.