Angiotensin-converting enzyme-2 (ACE2) receptor is the known receptor for SARS-CoV-2 as well as coronavirus NL63

ACE2 receptor is expressed on the surface of type 2 pneumocytes in the lungs

In samples taken from patients who smoke, an upregulation of ACE2 receptor could be seen in the airway epithelium

In particular, ACE2 receptor was expressed at a higher concentration in the pneumocytes, alveolar macrophages, and the apical end of the small airway epithelium in smoking patients compared to non-smoking patients

Previous observations show that SARS-COV-2 adhesion downmodulates ACE2 enzyme expression, increasing production and activation of other ACE enzymes leading to severe acute respiratory failure

Overall, it was observed that smoking upregulates ACE2 receptor and this could be true for electronic cigarette users as well

This upregulation is dangerous as SARS-CoV-2 utilizes this receptor to infect the airway epithelium, leading to severe acute respiratory failure