Endothelin-A receptor antagonist BQ-610 blocks cigarette smoke-induced mitogenesis in rat airways and vessels

To ascertain whether endothelin may play a role in cigarette smoke-induced cell proliferation in the airways and arterial vasculature of the lung, we exposed groups of seven Sprague-Dawley rats to either room air (control) plus saline infusion, an intravenous infusion of the selective endothelin A antagonist BQ-610 (control BQ-610), the smoke of 10 cigarettes (smoke only), or the smoke of 10 cigarettes after intravenous BQ-610 infusion (smoke + BQ-610). Cell proliferation was quantified by determining the percentage of cell nuclei labeled by 5-bromo-2'-deoxyuridine. We separately evaluated the cells in the epithelium and wall components of the bronchioles, and endothelium and wall components of the peribronchiolar and perialveolar ductular arteries. We found that cigarette smoke produced significant cell proliferation in the airway epithelium and wall, in the peribronchiolar arterial endothelial compartment, and in both the endothelial and wall compartments of the perialveolar ductular arteries. Pretreatment with BQ-610 reduced the peribronchiolar arterial endothelial and the perialveolar ductular arterial wall proliferation to control lev- els and reduced but did not totally abrogate the smoke-in- duced proliferation of the airway epithelial, airway wall, and perialveolar ductular arterial endothelial compartments. We conclude that cigarette smoke-induced cell proliferation of the airways and pulmonary arterial vessels is at least partially mediated through stimulation of the endothelin-A receptors.