ACE2 and chronic obstructive pulmonary disease: Expression patterns for ACE2 suggest current smoking status is associated with increased ACE2 levels, consistent with previous observations (Brake et al., 2020; Cai et al., 2020; Leung et al., 2020a, 2020b), and that this also accounts for the increased ACE2 in patients with COPD (Figure 3A).