In vitro exposure to isoprene-derived secondary organic aerosol by direct deposition and its effects on COX-2 and IL-8 gene expression
Maiko Arashiro1,Ying-Hsuan Lin1,6,Kenneth G. Sexton1,Zhenfa Zhang1,Ilona Jaspers1,2,3,4,5,Rebecca C. Fry1,3,William G. Vizuete1,Avram Gold1,and Jason D. Surratt1Maiko Arashiro et al. Maiko Arashiro1,Ying-Hsuan Lin1,6,Kenneth G. Sexton1,Zhenfa Zhang1,Ilona Jaspers1,2,3,4,5,Rebecca C. Fry1,3,William G. Vizuete1,Avram Gold1,and Jason D. Surratt1
1Department of Environmental Sciences and Engineering, Gillings School
of Global Public Health, University of North Carolina at Chapel Hill, Chapel
Hill, NC 27599, USA
2Center for Environmental Medicine, Asthma, and Lung Biology, School
of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
27599, USA
3Curriculum in Toxicology, University of North Carolina at Chapel
Hill, Chapel Hill, NC 27599, USA
4Department of Pediatrics, School of Medicine, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
5Department of Microbiology and Immunology, School of Medicine,
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
6Michigan Society of Fellows, Department of Chemistry, University of
Michigan, Ann Arbor, MI 48109, USA
1Department of Environmental Sciences and Engineering, Gillings School
of Global Public Health, University of North Carolina at Chapel Hill, Chapel
Hill, NC 27599, USA
2Center for Environmental Medicine, Asthma, and Lung Biology, School
of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
27599, USA
3Curriculum in Toxicology, University of North Carolina at Chapel
Hill, Chapel Hill, NC 27599, USA
4Department of Pediatrics, School of Medicine, University of North
Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
5Department of Microbiology and Immunology, School of Medicine,
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
6Michigan Society of Fellows, Department of Chemistry, University of
Michigan, Ann Arbor, MI 48109, USA
Correspondence: Jason D. Surratt (surratt@unc.edu)
Received: 13 May 2016 – Discussion started: 17 May 2016 – Revised: 04 Oct 2016 – Accepted: 18 Oct 2016 – Published: 15 Nov 2016
Abstract. Atmospheric oxidation of isoprene, the most abundant non-methane hydrocarbon emitted into Earth's atmosphere primarily from terrestrial vegetation, is now recognized as a major contributor to the global secondary organic aerosol (SOA) burden. Anthropogenic pollutants significantly enhance isoprene SOA formation through acid-catalyzed heterogeneous chemistry of epoxide products. Since isoprene SOA formation as a source of fine aerosol is a relatively recent discovery, research is lacking on evaluating its potential adverse effects on human health. The objective of this study was to examine the effect of isoprene-derived SOA on inflammation-associated gene expression in human lung cells using a direct deposition exposure method. We assessed altered expression of inflammation-related genes in human bronchial epithelial cells (BEAS-2B) exposed to isoprene-derived SOA generated in an outdoor chamber facility. Measurements of gene expression of known inflammatory biomarkers interleukin 8 (IL-8) and cyclooxygenase 2 (COX-2) in exposed cells, together with complementary chemical measurements, showed that a dose of 0.067 µg cm−2 of SOA from isoprene photooxidation leads to statistically significant increases in IL-8 and COX-2 mRNA levels. Resuspension exposures using aerosol filter extracts corroborated these findings, supporting the conclusion that isoprene-derived SOA constituents induce the observed changes in mRNA levels. The present study is an attempt to examine the early biological responses of isoprene SOA exposure in human lung cells.
Atmospheric oxidation of isoprene in the presence of acidic sulfate aerosol yields substantial SOA. Potential adverse health effects resulting from exposure to this aerosol type are largely unknown. Measurements of gene expression of known inflammatory biomarkers interleukin 8 (IL-8) and cyclooxygenase 2 (COX-2) in exposed human lung cells at the air–liquid interface showed that a dose of 0.067 μg cm−2 of isoprene SOA leads to statistically significant increases in IL-8 and COX-2 mRNA levels.
Atmospheric oxidation of isoprene in the presence of acidic sulfate aerosol yields substantial...
