Fig. 1.

The SARS-CoV-2 depends on protease cleavage by TMPRSS2 of the ACE2 receptor and the spike protein of the virus for efficient cell invasion. The infection results in downregulation (endocytosis) of the ACE2 diminishing its anti-inflammatory and anti-fibrotic arm in the renin-angiotensin-system resulting in increased inflammation and subsequently fibrosis. ACE (angiotensin converting enzyme), TNF (tumor necrosis factor), IL (interleukin), CXCL, CCL (chemokines), TMPRSS2 (transmembrane protease serine 2), MMP (matrix metalloprotease).