Activation of Hippocampal ACE2 Prevents the Dysbiosis-induced Depression-like Behavior in Mice by Enhanced Neurogenesis and Neuroprotection via Mas Receptor.

The association between gut microbiota imbalance and depression is well known; however, its underlying mechanisms remain unclear. Angiotensin (Ang)-converting enzyme 2 (ACE2) transforms Ang II into Ang (1-7), which exerts antidepressant effects via the Mas receptor (MasR). However, the role of ACE2 in dysbiosis-related depression in the brain remains unclear. In this study, we assessed changes in brain ACE2 expression and whether diminazene aceturate (DIZE), an ACE2 activator, alleviates depression-like behavior in an antibiotic-induced (ABX) dysbiosis mouse model. The tail suspension test revealed depression-like behavior in ABX mice. Western blotting and immunohistochemistry revealed decreased expression levels of ACE2, Ang (1-7), p-CAMKII, p-CREB, BDNF, synaptophysin, p-PPARγ, CD206, TREM2, and IL-10 and reduced neurogenesis in the dentate gyrus of the hippocampus. Iba1, CD86, iNOS, IL-1β, TNF-α, and cleaved caspase-3 levels were increased, indicating microglial activation in the hippocampus. MasR staining was observed in neurons and microglia in the hippocampus of ABX mice. Furthermore, p-CAMKII and p-CREB staining was observed in neurons, while p-PPARγ staining was observed in microglia in the hippocampus of ABX mice treated with DIZE. DIZE administration prevented ABX-induced changes, whereas the effects of DIZE were abolished by co-administration with A779, a MasR inhibitor. These findings suggest that hippocampal ACE2 expression plays a crucial role in dysbiosis-related depression associated with gut microbiota imbalance, potentially offering a target for therapeutic interventions.