ACE2 and severe acute respiratory syndrome: Therefore, during the occurrence of ARDS, the high expression of ACE, Ang II and AT1R aggravated the symptoms of lung injury, while ACE2 and AT2R improved the symptoms.24 Based on the mechanism of action of ACE2 in ARDS and the enlightenment of SARS, it can be considered that ACE2 has a protective effect on lung injury, and the downregulation of ACE2 is associated with more severe lung injury.