Binary polycyclic aromatic hydrocarbon exposure alters the transcriptome inducing inflammation and inhibiting cell communication through p38 MAPK in lung cells

Low molecular weight polycyclic aromatic hydrocarbons (LMW PAHs) are generated by the incomplete combustion of organic material and are prevalent and ubiquitous in the environment, presenting a human health concern. While much is known about the high molecular weight genotoxic species of PAHs, there are insufficient studies for LMW PAHs and their impact on pulmonary health. Secondhand smoke, or environmental tobacco smoke (ETS), is a mixture of many PAHs, among other constituents. To study the effect of more than one PAH, we examined single PAH and a binary mixture on the dysregulation of gap junctional intercellular communication (GJIC), activation of mitogen activated protein kinases (MAPK), and induction of inflammation with a focus on the p38 MAPK pathway through transcriptomic analysis. A mouse non-tumorigenic alveolar type II cell line, C10, along with two normal, non-tumorigenic human bronchial epithelial cell lines, Beas2b and HBE1 cells, for human comparisons. Our findings in all cell lines indicate that 1-methylanthracene (1-MeA) and fluoranthene (Flthn), can dysregulated GJIC in a dose dependent manner and combining these two compounds lead to a similar effect on GJIC. MAPKs, particularly P38, are rapidly activated and the inhibition of this MAPK leads to a reversal of PAH dysregulation of GJIC. A toxicogenomic approach conducted using the C10 cells revealed inflammatory, metabolic, steroid synthesis, and oxidative pathways altered synergistically by a mixture of PAHs (1-MeA and Flthn), followed by qRT-PCR, ELISAs, and immunoblots validation. Our findings indicated LMW PAHs potential to induce pulmonary inflammation and emphasize the need for mixture exposure research to accurately estimate human exposure risk.

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