Mechano-inflammatory sensitivity of ACE2: Implications for the regional distribution of SARS-CoV-2 injury in the lung

The coronavirus disease (COVID-19) caused by SARS-CoV-2 can result in severe injury to the lung. Computed tomography images have revealed that the virus preferentially affects the base of the lung, which experiences larger tidal stretches than the apex. We hypothesize that the expression of both the angiotensin converting enzyme-2 (ACE2) receptor for SARS-CoV-2 and the transmembrane serine protease 2 (TMPRSS2) are sensitive to regional cell stretch in the lung. To test this hypothesis, we stretched precision cut lung slices (PCLS) for 12 h with one of the following protocols: 1) unstretched (US); 2) low-stretch (LS), 5% peak-to-peak area strain mimicking the lung base; or 3) high-stretch (HS), the same peak-to-peak area strain superimposed on 10% static area stretch mimicking the lung apex. PCLS were additionally stretched in cigarette smoke extract (CSE) to mimic an acute inflammatory exposure. The expression of ACE2 was higher whereas that of TMPRSS2 was lower in the control samples following LS than HS. CSE-induced inflammation substantially altered the expression of ACE2 with higher levels following HS than LS. These results suggest that ACE2 and TMPRSS2 expression in lung cells is mechanosensitive, which could have implications for the spatial distribution of COVID-19-mediated lung injury and the increased risk for more severe disease in active smokers and patients with COPD.