Fig. 2

ACE2 expression in bronchial and alveolar epithelium from mice exposed to room air and acutely or chronically to cigarette smoke (CS). WT C57BL6 mice were exposed to air or cigarette smoke (CS) for up to 6 months (n = 3/4 group). In A, the number of ACE2+ cells in the bronchial epithelium were decreased in 6-month CS-exposed mice versus 1-, 3-, and 6- month air-exposed mice. The number of ACE2+ cells in the bronchial epithelium was decreased in 3-month CS-exposed mice versus 3- and 6-month air-exposed mice. The number of ACE2+ cells in the bronchial epithelium was decreased in 6-month CS-exposed mice versus 1-month CS-exposed mice. Also, the number of ACE2+ cells in the alveolar epithelium was decreased in 6- and 3-month CS-exposed mice versus 1- and 6- month air-exposed mice. The number of ACE2+ cells in the alveolar epithelium was decreased in 6-month CS-exposed mice versus 1-month CS-exposed mice. In B, representative images of air-exposed (upper 3 panels) and CS-exposed (lower 3 panels) murine small airways where bronchial epithelial cells are identified by staining with a red fluorophore, mucin-producing cells by a cyan fluorochrome, and ACE2+ cells by a green fluorophore. In C, representative images of air-exposed (upper three panels) and CS-exposed (lower three panels) murine alveolar cells where the epithelial cells are identified by staining with a red fluorophore, and ACE2+ cells by a green fluorophore. The staining isotype control for each staining is also shown. In D, the ACE2 protein levels measured by ELISA in total lung homogenates were decreased in mice exposed to CS for one month versus air (n = 10–15/group). * = P < 0.05; ** = P < 0.01; *** = P < 0.001. CS cigarette smoke