Assessing susceptibility for polycyclic aromatic hydrocarbon toxicity in an in vitro 3D respiratory model for asthma
There is increased emphasis on understanding cumulative risk from the combined effects of chemical and non-chemical stressors as it relates to public health.  Recent animal studies have identified pulmonary inflammation as a possible modifier and risk factor for chemical toxicity in the lung after exposure to inhaled pollutants; however, little is known about specific interactions and potential mechanisms of action.  In this study, primary human bronchial epithelial cells (HBEC) cultured in 3D at the air-liquid interface (ALI) are utilized as a physiologically relevant model to evaluate the effects of inflammation on toxicity of polycyclic aromatic hydrocarbons (PAHs), a class of contaminants generated from incomplete combustion of fossil fuels. Normal HBEC were differentiated in the presence of IL-13 for 14 days to induce a profibrotic phenotype similar to asthma. Fully differentiated normal and asthmatic phenotype HBEC were treated with benzo[a]pyrene (BAP; 1 – 40 ug/mL) or 1% DMSO/PBS vehicle at the ALI for 48 hrs. Cells were evaluated for cytotoxicity, barrier integrity, and transcriptional biomarkers of chemical metabolism and inflammation by quantitative PCR.  Cells with the asthmatic phenotype treated with BAP show some significant (p<0.05) increase in cytotoxicity and significantly (p<0.05) decreased barrier integrity compared to normal cells.  Asthmatic phenotype cells also showed increase sensitivity to BAP metabolism compared to cells with the normal phenotype.  Additionally, RNA sequencing data showed that a large number of genes were uniquely significantly expressed in cells with the induced asthmatic phenotype exposed to BAP.  Future studies will further explore mechanisms of toxicity from global transcriptomics and investigate the role of microRNA in mediating mechanisms of toxicity and inflammation.  These data are the first to evaluate the role of combined environmental factors associated with inflammation from pre-existing disease and PAH exposure on pulmonary toxicity in a physiologically relevant human in vitro model. Overall design: Fully differentiated bronchial epithelial cells (n=4 replicates) were treated with 40 µg/ml benzo[a]pyrene (BAP) or vehicle control (PBS with 1% DMSO) for 48 hrs.   In addition bronchial epithelial cells differentiated in the presence of 10 ug/mL interluekin-13 were treated with 40 µg/ml benzo[a]pyrene (BAP) or vehicle control (PBS with 1% DMSO) for 48 hrs.  Isolated mRNA were sequenced on BGISEQ-500 platform