Cigarette smoke extract (CSE) induces transient receptor potential ankyrin 1(TRPA1) expression via activation of HIF1αin A549 cells

We previously found that transient receptor potential ankyrin 1 (TRPA1) in guinea pig tracheal epithelial cells was elevated after 14 days of cigarette smoke (CS) exposure. However, the mechanism underlying CS-induced TRPA1 expression remains unknown. Here, we explored whether cigarette smoke extract (CSE)-induced TRPA1 expression is related with modulation of HIF1α in A549 cells. Our results showed that CSE increased TRPA1 expression in A549 cells, decreased Iκ B, PHD2, and HDAC2, and increased ROS release and nuclear translocation of NF-κ B and HIF1α. Moreover, HIF1α siRNA and/or MG132 (a proteasome inhibitor) pretreatment significantly inhibited CSE-induced TRPA1 expression and HIF1α nuclear translocation in A549 cells. However, HIF1α siRNA pretreatment did not affect CSE-induced NF-κ B nuclear translocation, suggesting that CSE-induced TRPA1 expression in A549 cells is directly mediated by HIF1α, but not by NF-κ B. Similar to CSE treatment, treatment of A549 cells with LPS caused significant increases in nuclear translocation of NF-κ B and HIF1α mRNA expression, but did not alter TRPA1 mRNA expression. However, pretreatment with PHD2 siRNA did result in increased TRPA1 mRNA expression in LPS-treated A549 cells; an effect that was inhibited by SN50 (a NF-κ B inhibitor). It suggests a role for NF-κ B to indirectly regulate TRPA1 mRNA expression via modulating HIF1α mRNA transcription. In addition, treatment cells with HDAC2 siRNA plus 2%CSE resulted in increased HIF1α nuclear translocation and TRPA1 expression, which was significantly inhibited by MG132 and HIF1α siRNA. These results suggest that HDAC2 indirectly modulates TRPA1 expression by promoting the DNA-binding activity of HIF1α. These findings show that CSE increases TRPA1 expression in airway epithelial cells by directly activating HIF1α, and that this increase in TRPA1 expression is indirectly regulated via NF-κ B, PHD2 and HDAC2 modulation of HIF1α activity.