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

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_1-42-injured N2a and PC12 cells.

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_1-42-injured cells.

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_1-42-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_1-42-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.

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.