Isoprene-Derived Secondary Organic Aerosol Induces the Expression of MicroRNAs Associated with Inflammatory/Oxidative Stress Response in Lung Cells

Exposure to fine particulate matter (PM_2.5), of which secondary organic aerosol (SOA) is a major constituent, is linked to adverse health outcomes, including cardiovascular disease, lung cancer, and preterm birth. Atmospheric oxidation of isoprene, the most abundant nonmethane hydrocarbon emitted into Earth’s atmosphere primarily from vegetation, contributes to SOA formation. Isoprene-derived SOA has previously been found to alter inflammatory/oxidative stress genes. MicroRNAs (miRNAs) are epigenetic regulators that serve as post-transcriptional modifiers and key mediators of gene expression. To assess whether isoprene-derived SOA alters miRNA expression, BEAS-2B lung cells were exposed to laboratory-generated isoprene-derived SOA constituents derived from the acid-driven multiphase chemistry of authentic methacrylic acid epoxide (MAE) or isomeric isoprene epoxydiols (IEPOX) with acidic sulfate aerosol particles. These IEPOX- and MAE-derived SOA constituents have been shown to be measured in large quantities within PM_2.5 collected from isoprene-rich areas affected by acidic sulfate aerosol particles derived from human activities. A total of 29 miRNAs were identified as differentially expressed when exposed to IEPOX-derived SOA and 2 when exposed to MAE-derived SOA, a number of which are inflammatory/oxidative stress associated. These results suggest that miRNAs may modulate the inflammatory/oxidative stress response to SOA exposure, thereby advancing the understanding of airway cell epigenetic response to SOA.