Figure 2. The role of ACE2 in neurodegenerative diseases. Reduction of ACE2 and ACE levels has been found in many neurodegenerative diseases, such as AD, PD and MS. The over-activation of ACE/Ang2/AT1 pathway and the imbalance of ACE2/Ang(1-7)/Mas pathway have been found to be closely related to the occurrence of AD. In addition, ACE2/Ang(1-7)/Mas pathway can alleviate the symptoms of AD by regulating the PI3K/Akt signaling pathway. ACE and ACE2 are also involved in the transformation of Aβ protein in AD patients. ACE: angiotensin converting enzyme; Ang: angiotensin; AT1R: Ang II type 1 receptor; Aβ: amyloid-β; MASR: MAS receptor.