Secondhand smoke-prevalent polycyclic aromatic hydrocarbon binary mixture-induced specific mitogenic and pro-inflammatory cell signaling events in lung epithelial cells

Abstract

Lowmolecular weight polycyclic aromatic hydrocarbons (LMWPAHs; < 206.3 g/mol) are prevalent and ubiquitous environmental contaminants, presenting a human health concern, and have not been as thoroughly studied as the highMW PAHs. LMWPAHs exert their pulmonary effects, in part, through P38-dependent and -independentmechanisms involving cellcell communication and the production of pro-inflammatorymediators known to contribute to lung disease. Specifically, we determined the effects of two representative LMWPAHs, 1-methylanthracene (1-MeA) and fluoranthene (Flthn), individually and as a binary PAHmixture on the dysregulation of gap junctional intercellular communication (GJIC) and connexin 43 (Cx43), activation ofmitogen activated protein kinases (MAPK), and induction of inflammatorymediators in amouse non-tumorigenic alveolar type II cell line (C10). Both 1-MeA, Flthn, and the binary PAHmixture of 1-MeA and Flthn dysregulated GJIC in a dose and time-dependentmanner, reduced Cx43 protein, and activated the following MAPKs: P38, ERK1/2, and JNK. Inhibition of P38 MAPK prevented PAH-induced dysregulation of GJIC, whereas inhibiting ERK and JNK did not prevent these PAHs from dysregulating GJIC indicating a P38-dependentmechanism. A toxicogenomic approach revealed significant P38-dependent and -independent pathways involved in inflammation, steroid synthesis,metabolism, and oxidative responses. Genes in these pathways were significantly altered by the binary PAH mixture when compared with 1-MeA and Flthn alone suggesting interactive effects. Exposure to the binary PAH mixture induced the production and release of cytokines and metalloproteinases from the C10 cells. Our findings with a binary mixture of PAHs suggest that combinations of LMW PAHs may elicit synergistic or additive inflammatory responses which warrant further investigation and confirmation.