Apelin-13 enhances neurofunctional recovery and suppresses neuroinflammation via the SIRT1/NF-κB axis in ischemic stroke.

BACKGROUND: Ischemic stroke is a major cause of mortality and disability, with neuroinflammation driving secondary brain injury. Microglial activation contributes to neuronal apoptosis, BBB disruption, and prolonged neurological deficits. Apelin-13, an endogenous peptide, has demonstrated neuroprotective potential, but its precise mechanisms remain unclear. This study investigates how Apelin-13 modulates neuroinflammation and the molecular pathways involved in ischemic stroke.

METHODS: Mice underwent middle cerebral artery occlusion-reperfusion (MCAO/R) to model ischemic stroke, followed by Apelin-13 administration. Neurological function was assessed using Garcia scoring, adhesive removal, rotarod, and grid-walking tests. Infarct volume was quantified via TTC staining, and MRI evaluated cerebral edema. Immunofluorescence staining and Western blotting were used to assess neuronal apoptosis and BBB integrity. Microglial activation and polarization were analyzed via Iba1 co-immunostaining with CD16 (pro-inflammatory) and Arg1 (anti-inflammatory) markers. In vitro, primary microglia and BV2 cells were exposed to oxygen-glucose deprivation (OGD) to mimic ischemia, and Apelin-13's effects on inflammatory signaling were examined. The role of the SIRT1/NF-κB axis was evaluated using the SIRT1 inhibitor EX-527.

RESULTS: Apelin-13 significantly improved post-stroke neurological function, reduced infarct volume, and alleviated cerebral edema. It preserved BBB integrity by reducing vascular leakage and albumin extravasation and suppressed neuronal apoptosis by downregulating cleaved caspase-3. Apelin-13 also mitigated neuroinflammation by decreasing microglial activation and shifting polarization toward an anti-inflammatory phenotype, as evidenced by reduced CD16+ and increased Arg1+ microglia. In vitro, Apelin-13 suppressed OGD-induced pro-inflammatory cytokine release while promoting anti-inflammatory responses. Mechanistically, Apelin-13 upregulated SIRT1, inhibiting NF-κB signaling and reducing inflammatory mediator expression. SIRT1 inhibition with EX-527 reversed these effects, restoring NF-κB activation and pro-inflammatory microglial polarization.

CONCLUSIONS: Apelin-13 exerts neuroprotective effects in ischemic stroke by preserving BBB integrity, reducing neuronal apoptosis, and suppressing neuroinflammation. These effects are mediated through SIRT1 activation and NF-κB inhibition. Targeting the Apelin-13/SIRT1/NF-κB axis may offer a promising therapeutic strategy for mitigating neuroinflammation and improving stroke recovery.