Neuroprotective effect of Urolithin A via downregulating VDAC1-mediated autophagy in Alzheimer's disease.

Background: Amyloid β (Aβ) accumulation in the brains of patients with Alzheimer's disease (AD) contributes to cognitive impairment and neuronal damage. Urolithin A (UA), a gut microbiota-derived metabolite of ellagic acid, has been reported to cross the blood-brain barrier to exert anti-inflammatory and anti-oxidation effects in the brain. However, the molecular mechanisms of UA in AD were still unclear. This study aims to explore the neuroprotective effect and mechanism of UA on APP/PS1 mice and Aβ-injured N2a and PC12 cells.

Methods: In this study, Morris water maze was used to detect the cognitive function. Immunofluorescence was used to detect the deposition of Aβ and the expression of voltage-dependent anion channel 1 (VDAC1) in the brains of APP/PS1 mice. Western blotting was used to detect the expression of VDAC1, AMPK pathway, PI3K pathway and autophagy-related proteins. CCK8 was used to detect the viability of Aβ-injured cells.

Results: In this research, we found that UA improved cognitive dysfunction and reduced Aβ deposition in APP/PS1 mice. Furthermore, UA activated autophagy and upregulated the levels of autophagy-related proteins in both APP/PS1 mice and Aβ-injured N2a and PC12 cells. At the same time, UA down-regulated the phosphorylation level of PI3K/AKT/mTOR and up-regulated the phosphorylation level of AMPK in APP/PS1 mice and Aβ-injured N2a cells and PC12 cells. In addition, UA down-regulated VDAC1, consistent with the effect of VDAC1 antagonist DIDS (4'-diisothiocyano-2,2'-disulfonic acid stilbene). Importantly, the UA-induced activation of autophagy and modulation of the PI3K and AMPK pathways were reversed by VDAC1 overexpression.

Conclusion: These findings demonstrated that UA down-regulated VDAC1 played a key neuroprotective role on AD by inhibiting the PI3K/AKT/mTOR pathway and activating the AMPK pathway to promote autophagy.