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Mediators of Inflammation
Volume 2015, Article ID 148367, 16 pages
http://dx.doi.org/10.1155/2015/148367
Research Article

Lung Epithelial TRPA1 Transduces the Extracellular ROS into Transcriptional Regulation of Lung Inflammation Induced by Cigarette Smoke: The Role of Influxed Ca2+

1Department of Physiology, School of Medicine, National Yang-Ming University, Taipei 11221, Taiwan
2Department of Chest Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan

Received 13 February 2015; Accepted 2 April 2015

Academic Editor: Mauricio Retamal

Copyright © 2015 An-Hsuan Lin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The mechanism underlying the inflammatory role of TRPA1 in lung epithelial cells (LECs) remains unclear. Here, we show that cigarette smoke extract (CSE) sequentially induced several events in LECs. The Ca2+ influx was prevented by decreasing extracellular reactive oxygen species (ROS) with the scavenger N-acetyl-cysteine, removing extracellular Ca2+ with the chelator EGTA, or treating with the TRPA1 antagonist HC030031. NADPH oxidase activation was abolished by its inhibitor apocynin, EGTA, or HC030031. The increased intracellular ROS was halted by apocynin, N-acetyl-cysteine, or HC030031. The activation of the MAPKs/NF-κB signaling was suppressed by EGTA, N-acetyl-cysteine, or HC030031. IL-8 induction was inhibited by HC030031 or TRPA1 siRNA. Additionally, chronic cigarette smoke (CS) exposure in wild-type mice induced TRPA1 expression in LECs and lung tissues. In CS-exposure trpa1−/− mice, the increased BALF level of ROS was similar to that of CS-exposure wild-type mice; yet lung inflammation was lessened. Thus, in LECs, CSE may initially increase extracellular ROS, which activate TRPA1 leading to an increase in Ca2+ influx. The increased intracellular Ca2+ contributes to activation of NADPH oxidase, resulting in increased intracellular ROS, which activate the MAPKs/NF-κB signaling leading to IL-8 induction. This mechanism may possibly be at work in mice chronically exposed to CS.