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.