The Neuroprotective Role of Ginsenoside Rg1 Against Cerebral Ischemia–Reperfusion Damage Through Inhibition of Mitophagy via Blocking Mitophagosome‐Lysosome Fusion

Ginsenoside Rg1 has shown promise in ameliorating cerebral ischemia-reperfusion injury (CIRI). However, its precise molecular mechanisms remain unclear. In this study, an in vitro CIRI model was established using SH-SY5Y and SK-N-AS neuronal cell lines subjected to oxygen-glucose deprivation followed by reoxygenation (OGD/R). For the in vivo model, C57BL/6J mice underwent middle cerebral artery occlusion and subsequent reperfusion (MCAO/R). The protective effects of Rg1 against OGD/R injury were analysed using the CCK-8 assay and the PI exclusion method. The in vivo neuroprotective effects of Rg1 against CIRI were evaluated using various assessments, including brain blood flow, neurological deficits, behavioural tests, TTC, H&E, Nissl and TUNEL staining. Mitophagy was assessed by detecting mitophagy-initiating proteins via Western blotting, transmission electron microscopy, immunohistochemistry and immunofluorescence staining. Additionally, mitochondrial function was assessed by ATP measurement, the JC-1 assay and MitoSOX-based flow cytometry. Our results show that Rg1 significantly mitigated cell death caused by OGD/R and substantially enhanced cell viability in vitro. Moreover, Rg1 alleviated OGD/R-induced mitochondrial dysfunction, as indicated by preserved mitochondrial membrane potential and decreased mitochondrial ROS levels. Mitophagy was induced after OGD treatment, which was subsequently inhibited by Rg1 during reperfusion. Mechanistically, Rg1 disrupted the fusion of mitophagosomes with lysosomes rather than inhibiting mitophagy initiation, leading to an accumulation of mitochondrial proteins and mitophagy-initiating proteins. Notably, prolonged inhibition of mitophagy by Rg1 did not induce cytotoxicity or exacerbate mitochondrial dysfunction. Furthermore, administration of Rg1 in MCAO/R mice significantly improved brain blood reperfusion, reduced infarct volume, improved neurological deficits, preserved brain tissue integrity and decreased neuronal apoptosis. Consistent with the in vitro observations, Rg1 upregulated mitophagy-related protein expression in MCAO/R mouse brain tissues, indicating potential inhibition of mitophagy. In conclusion, our study reveals that Rg1 significantly alleviates CIRI at least partially by suppressing mitophagy, specifically by impeding the fusion of mitophagosomes with lysosomes.