Abstract 409: Ambient Fine Particulate Matter Impairs Endothelial Progenitor Cells Through Card9-mediated Innate Immune Response

Background/Aims: Endothelial progenitor cells (EPCs) play a critical role in angiogenesis and vascular repair. Some environmental insults, like fine particulate matter (PM) exposure, significantly impair EPCs through inflammation and ROS production. Cytosolic adaptor caspase recruitment domain 9 (CARD9) is important to the function of macrophages and involved in the innate immune response. The present study was to determine the role of macrophage-mediated immune response in PM-induced adverse effects on EPCs. Methods: PM was intranasal-distilled into male C57BL/6 mice for 1, 2, 7, 14 and 28 days. The level of EPCs (CD34 + /Flk-1 + , Sca-1 + /Flk-1 + , c-Kit + /CD31 + and CD34 + /CD133 + ) in the bone marrow (BM) and circulation was determined using flow cytometry along with the proliferation and apoptotic level of EPCs as well as intracellular reactive oxygen species (ROS) formation. Serum TNF-α, IL-1β, IL-6 and IL-10 were measured using ELISA. To determine the role of CARD9-mediated signaling in PM-induced detrimental effects on EPCs, CARD9 knock out (CARD9 -/- ) mice were used to repeat the experiment. The population of total macrophages as well as M1 and M2 subpopulations in both BM and blood were analyzed in the mice with and without PM exposure. To study the function of macrophages after PM exposure, the peritoneal macrophages were isolated and cultured for 48 hours to measure the production of TNF- α, IL-1β, IL-6 and IL-10 in the media. Results: PM exposure significantly decreased BM and circulating CD34 + /FLk-1 + as well as BM Scal-1 + /Flk-1 + population, promoted apoptosis and inhibited proliferation of EPCs in association with increased ROS production, serum TNF-α, IL-1β, IL-6 and decreased serum IL-10 level. These PM-induced effects on EPC population and cytokine production were largely prevented in CARD9 -/- mice along with increased M2 population in both BM and blood. The production of TNF-α, IL-1β and IL-6 was significantly decreased, while the IL-10 level increased, from cultured macrophage of CARD9 -/- mice compared with WT control. Conclusion: PM exposure significantly decreased BM and circulating EPCs population due to CARD9-mediated innate immune response.