Rosmarinic acid alleviates ischemic stroke by targeting BAG3 to modulate autophagy via the P62-Keap1-Nrf2 pathway.

Ischemic stroke remains a major clinical challenge due to limited treatment options and the lack of effective neuroprotectants. Here, we identified a novel neuroprotective mechanism of rosmarinic acid (RosA), a natural phenolic compound, through precision targeting of the autophagy regulator BAG3. Using activity-based protein profiling, we demonstrated that RosA covalently bound to the Cys378 residue of BAG3, disrupting its interaction with the selective autophagy receptor P62. This disruption activated the P62/Keap1/Nrf2 signaling axis, attenuating excessive autophagic flux and reducing neuronal injury. Both in vitro oxygen-glucose deprivation/reoxygenation (OGD/R) and in vivo middle cerebral artery occlusion/reperfusion (MCAO/R) models confirmed that RosA significantly reduced autophagosome accumulation, infarct volume, and neurological deficits in a BAG3-dependent manner. BAG3 knockdown mimicked RosA's effects and abolished RosA-induced autophagy regulation, highlighting BAG3 as the functional target. These findings not only elucidated the molecular mechanism of RosA but also proposed BAG3 as a promising therapeutic target for ischemic stroke intervention.