Study Of The Mechanisms Associated With Pm2.5 Induced Reactive Oxygen Species Production In Alveolar Macrophages

California's central valley is among the regions with the highest rate of air pollution in the United States. Concerns have arisen over the negative health effects caused by exposure to high concentrations of small atmospheric particulate matter (PM) in heavily-polluted areas—innate defense mechanisms in the upper airway fail to capture particles with a diameter less than 2.5 microns (PM2.5), permitting the smallest pollutants to generate an acute inflammatory response at the distal ends of the respiratory tract. We have recently tested the potential of PM2.5 samples collected during the peak pollution periods of two cities in California, Fresno and Claremont, to induce the production of Reactive Oxygen Species (ROS) in alveolar macrophages (AM) using a DCF-based fluorescence assay. Interestingly, the specific PM2.5-induced ROS dose response was significantly different in several sets of samples indicating that the chemical composition of PM2.5 was playing a major role in this process. After chemical analysis,we identified three commonly occurring cyclic diones, specifically quinones 9,10-phenanthrenequinone, 1,2-naphthoquinone, and 1,4-naphthoquinone, and two commonly occurring transition metals, Cu2+ and Fe2+, as potential ROS production triggers. We also observed that the specific ROS production induced by cyclic diones in AM required concentrations that were 2-3 orders of magnitude lower than that required to obtain a similar response with transition metals. Given the oxidative role of quinone derivative Coenzyme-Q in the mitochondrial electron transport chain (ETC), we suggest that quinones contained in PM2.5 may interfere with electron transfer in the ETC; leading to an increased ROS production. This last hypothesis will be tested using flow cytometry-based approach using DCF and mitochondria-specific ROS fluorescent probes (such as MitoSox) to better define the intracellular location of these PM2.5-induced ROS responses.