In vitro exposure to isoprene-derived secondary organic aerosol by direct deposition and its effects on <i>COX-2</i> and <i>IL-8</i> gene expression

Abstract

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 acidcatalyzed 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 isoprenederived SOA on inflammation-associated gene expression in human lung cells using a direct deposition exposure method. We assessed altered expression of inflammationrelated 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.

Chemical oxidative potential of secondary organic aerosol (SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds

“…Aerosol mass concentrations were determined using volume concentrations obtained from SMPS and assuming an aerosol density of 1 g cm −3 . While typical SOA density is about 1.4 g cm −3 , it varies with hydrocarbon precursor identity and reaction conditions, and a density between ∼ 1.0 and 1.6 g cm −3 has been reported in previous studies (Ng et al, 2006(Ng et al, , 2007aChan et al, 2009;Tasoglou and Pandis, 2015;Bahreini et al, 2005). The use of a density of 1 g cm −3 is to facilitate easier comparisons with past and future studies.…”

The acidity of atmospheric particles and clouds

“…Cloud pH values have been measured at remote locations in the Luquillo Mountains on the Caribbean island of Puerto Rico since 1967. Mean values reported in several studies up through 2012 (Lazrus et al, 1970;Weathers et al, 1988;Asbury et al, 1994;Gioda et al, , 2011Gioda et al, , 2013Reyes-Rodríguez et al, 2009;Valle-Díaz et al, 2016) fall between 4.6 and 5.8, with no apparent trend. The pH values observed and the lack of a clear trend here are consistent with the fairly clean conditions in the region.…”

Predominance of secondary organic aerosol to particle-bound reactive oxygen species activity in fine ambient aerosol

“…All in all, except for locations affected by strong haze and specific sources of toxic components (e.g., polycyclic aromatic hydrocarbons (PAHs) and coal combustion in winter in China), a stronger association between PM and mortality was observed at different locations during hotter days, when SOA formation is the most active. Various experiments have also shown that pure SOA does induce adverse effects upon exposure of airway epithelial cells (Arashiro et al, , 2018Gaschen et al, 2010;Lin et al, 2016;Chowdury et al, 2018;Jiang et al, 2016). Similarly, cellular-based ROS assays showed a strong connection with pure SOA or its fraction in PM (Tuet et al, 2016(Tuet et al, , 2017aSaffari et al, 2014).…”