Fig. 4.

Renin-angiotensin-aldosterone system (RAAS) in SARS-CoV-2 infection. AngI is converted to AngII by the action of the angiotensin-converting enzyme (ACE). AngII acts angiotensin receptor type 1(AT1R), leads to vasoconstriction, inflammation, fibrosis, lung damage, and oedema. However, the action of AngII on the AT2R produces a reverse effect. ACE2 converts AngII to Ang1-7, which acts on the Mas receptor leading to vasodilation and lung protection. SARS-CoV-2 causes down-regulation of ACE2 with subsequent activation of RAAS, which causes dual effects.