Hydrogen Sulfide Protects Against Cerebral Ischemia-Reperfusion Injury in Rats via S-Sulfhydrating NAMPT to Enhance...

Objective: Cerebral ischemia-reperfusion (I/R) injury constitutes a pivotal pathological driver in cerebrovascular disorders such as stroke, yet effective therapeutic interventions remain scarce. This study explored whether hydrogen sulfide (H₂S) mitigates endothelial cell damage in the cerebral vasculature during I/R by modulating nicotinamide phosphoribosyltransferase (NAMPT) activity and its S-sulfhydration status, consequently restoring mitochondrial integrity and energetic homeostasis. Methods: Primary cerebrovascular endothelial cells (ECs) were subjected to hypoxia/reoxygenation (H/R) conditions in vitro, while rats experienced middle cerebral artery occlusion/reperfusion (MCAO/R) in vivo. The H₂S donor sodium hydrosulfide (NaHS) was administered, and outcomes were evaluated through Western blot analysis, S-sulfhydration assays, mitochondrial functional tests, autophagy profiling, and neurobehavioral assessments. The contributions of NAMPT and S-sulfhydration were validated using FK866 and dithiothreitol (DTT), respectively. LC-MS/MS was employed to identify candidate S-sulfhydration sites on NAMPT triggered by H₂S. Results: In cellular models, NaHS substantially boosted NAMPT enzymatic activity, elevated NAD⁺ and ATP levels, and enhanced cell survival. These protective benefits were nullified upon NAMPT inhibition with FK866 or reversal of S-sulfhydration via DTT. In animal studies, NaHS treatment significantly diminished infarct volume and ameliorated neurological deficits in MCAO/R rats; however, pretreatment with FK866 or DTT attenuated these benefits. Mechanistic investigations revealed that NaHS promoted S-sulfhydration of NAMPT, thereby activating autophagy of dysfunctional mitochondria. LC-MS/MS analysis confirmed enhanced S-sulfhydration at Cys39 and Cys397 residues of NAMPT following H₂S exposure. Conclusions: H₂S exerts neuroprotection against cerebral I/R injury in rats through S-sulfhydration-mediated activation of NAMPT, which improves mitochondrial performance and stimulates autophagy in cerebrovascular ECs.