Transcriptomic Analysis of Human Primary Bronchial Epithelial Cells after Chloropicrin Treatment

Chloropicrin is a vaporizing toxic irritant that poses a risk to human health if inhaled, but the mechanism of its toxicity in the respiratory tract is poorly understood. Here, we exposed human primary bronchial epithelial cells (HBEpC) to two concentrations of chloropicrin (10-50 μM) for 6 or 48 h and used genomic microarray, flow cytometry, and TEM-analysis to monitor cellular responses to the exposures. The overall number of differentially expressed transcripts with a fold-change > ± 2 compared to controls increased with longer exposure times. The initial response was activation of genes with a higher number of up- (512 by 10 μM and 408 by 40 μM chloropicrin) rather than down-regulated transcripts (40 by 10 μM and 215 by 40 μM chloropicrin) at 6 h seen with both exposure concentrations. The number of down-regulated transcripts, however, increased with the exposure time. The differentially regulated transcripts were further examined for enriched Gene Ontology Terms (GO) and KEGG-pathways. According to this analysis, the "ribosome" and "oxidative phosphorylation" were the KEGG-pathways predominantly affected by the exposure. The predominantly affected (GO) biological processes were "protein metabolic process" including "translation," "cellular protein complex assembly," and "response to unfolded protein." Furthermore, the top pathways, "NRF2-activated oxidative stress" and "Ah-receptor signaling," were enriched in our data sets by IPA-analysis. Real time qPCR assay of six selected genes agreed with the microarray analysis. In addition, chloropicrin exposure increased the numbers of late S and/or G2/M-phase cells as analyzed by flow cytometry and induced autophagy as revealed by electron microscopy. The targets identified are critical for vital cellular functions reflecting acute toxic responses and are potential causes for the reduced viability of epithelial cells after chloropicrin exposure.