Fig. 2.

Nicotine vapor inhalation increases ACE2 mRNA and protein expression in male, but not female, lung. (a-b) After five consecutive days of vapor exposure, lung tissue was analyzed for the expression of ACE2 mRNA. (a) Increased ACE2 mRNA expression was found in lung tissue of male mice exposed to nicotine vapor, as compared to control (no vapor exposure) and vehicle vapor exposure. (b) In females, no significant differences were found in ACE2 mRNA expression among exposure conditions. (c-d) Lung tissue was also examined for ACE2 protein expression. (c) Quantification of the number of ACE2-positive cells in lung tissue revealed that nicotine vapor significantly increased ACE2 protein expression in male mice, as compared to the control and vehicle vapor groups. (d) The number of ACE2-positive cells did not differ among groups in female lung tissue. Individual data points are represented on each graph, and graph bars express as the mean ± SEM. ^##p < 0.01 vs vehicle vapor, ^###p < 0.001 vs vehicle, **p < 0.01 vs control, ***p < 0.001 vs control. (e-j) Representative images of ACE2 immunoreactivity (red) in lung tissue following exposure. In males, high levels of ACE2 immunoreactivity can be evidenced in lungs exposed to nicotine vapor (i), as compared to control (e) and vehicle vapor (g). For females, representative images demonstrate similar levels of lung ACE2 protein expression for the control (f), vehicle vapor (h) and nicotine vapor (j) groups. DAPI: Blue. Scale bar =50 μm.