The Role of MAPK and Nrf2 Pathways in Ketanserin-Elicited Attenuation of Cigarette Smoke-Induced IL-8 Production in Human Bronchial Epithelial Cells

Cigarette smoking is a major risk factor in chronic obstructive pulmonary disease (COPD) with chronic airway inflammation as a key feature. Blockade of serotonin receptor 2A (5-HTR(2A)) with ketanserin has been found to improve lung function in COPD patients. Furthermore, ketanserin has been shown to possess anti-inflammatory properties in vivo. In this study, we investigated the antioxidative and anti-inflammatory properties of ketanserin and its underlying mechanism of action on cigarette smoke-induced interleukin (IL)-8 release in vitro. Primary normal human bronchial epithelial cells and human bronchial epithelial cell line (BEAS-2B) were treated with or without ketanserin prior to exposure to cigarette smoke medium (CSM). Exposure to CSM caused elevation of both mRNA and release of IL-8 with increased phosphorylation of p38 and extracellular signal-regulated kinases 1 and 2 (ERK1/2). Consistently, CSM-induced IL-8 release was blocked by SB203580, U0126, or MEK1 small interfering RNA (siRNA) but not SP600125. On the other hand, CSM caused a dose-dependent decrease in the ratio of reduced glutathione to oxidized glutathione (rGSH/GSSG) together with an increased translocation of Nrf2 to the nucleus demonstrated by Western blot analysis. Knock down of Nrf2 by siRNA completely blocked CSM-induced IL-8 release. Ketanserin suppressed CSM-induced IL-8 release by inhibiting p38, ERK1/2 MAPK, and Nrf2 signaling pathways and partially inhibited CSM-induced reduction of rGSH/GSSG ratio. Our data demonstrated the novel antioxidative and anti-inflammatory role of ketanserin via the Nrf2 signaling pathway in CSM-exposed human bronchial epithelial cells. This may open up new perspectives in the development of novel therapeutic targets in the treatment of cigarette smoke-related COPD.