AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Aerosol Oxidative Potential and Altered Oxidative Stress-Associated Gene Expression in BEAS-2B Cells Exposed to Major Isoprene Secondary Organic Aerosol Precursors and Constituents
YING-HSUAN LIN, Zhenfa Zhang, Avram Gold, Ilona Jaspers, Rebecca Fry, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 507 Working Group: Linking Aerosol Oxidative Potential with Chemical Composition and Biological Endpoints
Abstract Isoprene (2-methyl-1,3-butadiene)-derived secondary organic aerosol (SOA) contributes a substantial mass fraction of ambient fine particulate matter (PM2.5) in many isoprene-rich regions. Recent studies have revealed that the OH-radical initiated oxidation of isoprene leads to the production of reactive gas-phase SOA precursors, such as epoxides (IEPOX and MAE) and hydroperoxides (ISOPOOH), and further promotes SOA formation through reactive uptake and multiphase chemistry. With synthesis of authentic standards, we have evaluated the oxidative potential (i.e., thiol reactivity) of major isoprene SOA precursors and the resultant SOA constituents with the acellular dithiothreitol (DTT) assay. We have also assessed the exposure-induced differential gene expression of heme oxygenase 1 (HMOX-1) using human airway epithelial cells (BEAS-2B) as an in vitro model. The dose-dependence of HMOX-1 gene expression was examined to evaluate the relative potency of the test compounds. Our findings suggest that ISOPOOH has remarkable DTT activity, but it induces a multiphasic non-monotonic response in HMOX-1 gene expression. Exposures to IEPOX, MAE and the 3-sulfate ester derivative of 2-methylglyceric acid result in significant cytotocxicity and upregulated HMOX-1 gene expression as concentrations increase, while the measured DTT activity of these compounds is insignificant. 2-Methylterols induce significant HMOX-1 gene expression at high dose levels, potentially through metabolic activation. The results indicate that both chemical characteristics and biotransformation (e.g., metabolic activation) of individual chemical components may be responsible for the observed cellular responses.