AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Assessing the Biological Effects of Various Components of Isoprene-Derived Secondary Organic Aerosol
MAIKO ARASHIRO, Ying-Hsuan Lin, Kenneth Sexton, Avram Gold, Ilona Jaspers, Rebecca Fry, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 465 Working Group: Health Related Aerosols
Abstract Isoprene (2-methyl-1,3-butadiene), a volatile organic compound released primarily by terrestrial vegetation, is an important precursor to the formation of secondary organic aerosol (SOA). Isoprene-derived SOA, which comprises a large mass fraction of global fine particulate matter (PM2.5), results from the atmospheric chemical transformations of isoprene with controllable anthropogenic emissions such as oxides of nitrogen (NOx) and sulfur dioxide. Through a series of in vitro exposure studies, we explored the effects of isoprene-derived SOA on oxidative stress-related gene expression levels in human bronchial epithelial cells (BEAS-2B). We generated atmospherically-relevant compositions of isoprene-derived SOA under light conditions in an outdoor smog chamber to expose BEAS-2B cells to the total isoprene SOA mixture. We then systematically explored the effects of three known composition types of isoprene-derived SOA by generating SOA through dark reactive uptake experiments by starting with key gaseous intermediates, including trans-β-isoprene epoxydiol (trans-β-IEPOX), methacrylic acid epoxide (MAE), or isoprene hydroxyhydroperoxides (ISOPOOH).
Chemical characterization coupled with biological analyses showed that atmospherically-relevant compositions of isoprene-derived SOA altered the levels of 41 oxidative stress-related genes. Of the different composition types of isoprene-derived SOA, MAE-derived SOA altered the greatest number of genes on the same mass basis. Together, the different composition types accounted for 34 of the genes altered by the total isoprene SOA mixture while 7 remained unique to the mixture indicating that there is either a synergistic effect between the different isoprene-derived SOA components or an unknown active component in the total mixture. Finally, this work reveals an enrichment for altered expression of genes associated with Nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a key transcription factor protecting against oxidative stress, in cells exposed to all types of isoprene-derived SOA.