Bosentan inhibits cigarette smoke-induced endothelin receptor expression in pulmonary arteries

The endothelin (ET) system contributes to lung vascular tension and remodelling in smokers and chronic obstructive pulmonary disease (COPD) patients. This study examined the effect of cigarette smoke (CS) on ET receptor A (ET A ) and B (ET B ) expression in human pulmonary artery smooth muscle cells (HPASMCs) and human small intrapulmonary arteries, as well as their functional consequences. CS extract (CSE) increased ET A and ET B expression in HPASMCs and small intrapulmonary arteries, which was attenuated by bosentan, the ET A antagonist BQ123 and the ET B antagonist BQ788, and by blocking ET-1 with a monoclonal antibody against ET-1, suggesting a feed-forward mechanism mediated by ET-1 release. ET receptor (ETR) antagonism attenuated the CSE-induced HPASMC proliferation. Furthermore, CSE exposure increased the acute ET-1-induced small intrapulmonary artery contraction, which was attenuated by bosentan, BQ123 and BQ788. Pulmonary arteries from smokers and COPD patients showed a higher expression of ET A and ET B than those of nonsmoker patients. These results show a novel mechanism by which ETR blockade attenuates CS-induced ETR overexpression and, subsequently, small intrapulmonary artery tension. These data may be of potential value to explain therapeutic effects of bosentan in some forms of disproportionate pulmonary hypertension in COPD patients.