Remote ischemic preconditioning protects against cerebral ischemia/reperfusion injury through lactate-dependent AMPK/ULK1 signaling and autophagy

Cerebral ischemia-reperfusion (I/R) injury is a major contributor to ischemic cerebral damage and poor functional outcomes following ischemic stroke, and effective neuroprotective strategies remain limited. Remote ischemic preconditioning (RIPC) has emerged as a promising, noninvasive approach; however, its underlying mechanisms are incompletely understood. Here, we investigated whether lactate serves as a key metabolic mediator linking RIPC to neuroprotection through regulation of autophagy. Using an oxygen-glucose deprivation/reoxygenation (OGD/R) model in PC12 cells and a middle cerebral artery occlusion (MCAO) model in rats, we demonstrate that I/R impairs autophagic flux, as evidenced by p62 accumulation and reduced LC3-II and Beclin-1 expression, leading to increased cellular apoptosis and injury. Lactate supplementation restored autophagic flux, enhanced cell viability, and suppressed apoptosis under OGD/R conditions. Mechanistically, lactate activated the AMPK/ULK1 signaling pathway, whereas pharmacological inhibition of AMPK or ULK1 attenuated lactate-induced autophagy and cytoprotection. In vivo, RIPC elevated plasma and cerebral lactate levels, activated AMPK/ULK1 signaling, promoted autophagy, reduced infarct volume, and improved acute neurological outcomes. Notably, blockade of lactate transport or inhibition of AMPK/ULK1 signaling attenuated these protective effects. Collectively, our findings suggest that lactate serves as an important mediator of RIPC-induced neuroprotection and reveal a novel lactate-AMPK/ULK1-autophagy axis that mitigates cerebral I/R injury. These results provide mechanistic insight into RIPC and suggest potential therapeutic targets for ischemic stroke.