Neuroprotective effects of salidroside against cerebral ischemia-reperfusion injury involve downregulation of total NAMPT and suppression of microglial inflammation

Objective This study investigated the protective effect of Salidroside (SAL) against cerebral ischemia-reperfusion (I/R) injury and its role in regulating nicotinamide phosphoribosyltransferase (NAMPT)-mediated neuroinflammation and damage. Methods In vivo , a middle cerebral artery occlusion/reperfusion (MCAO/R) model was established in male SD rats. Animals were divided into sham-operated (Sham), I/R (MCAO-NS), MCAO+eNAMPT, and MCAO+eNAMPT+SAL groups. Recombinant NAMPT (5 μg/rat) and/or SAL (10 μg/rat) were administered intracerebroventricularly. Neurological deficit scores (mNSS), infarct volume (TTC), brain levels of IL-1β/TNF-α (ELISA), total NAMPT expression (WB/ELISA), and NAD+ content were assessed. In vitro , primary microglia were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) and divided into control (Ctrl), OGD-NS, OGD+eNAMPT (20 ng/mL), and OGD+eNAMPT+SAL (6 μg/mL) groups. Cytotoxicity (LDH), viability (MTT), and IL-1β/TNF-α secretion (ELISA) were measured. Results Compared to Sham, the I/R group showed worsened neurological deficits, larger infarct volumes, elevated total NAMPT, TNF-α, and IL-1β levels ( P < 0.001), and reduced NAD+ ( P < 0.001). Exogenous eNAMPT further exacerbated these injuries and inflammation ( P < 0.001). SAL treatment significantly reversed eNAMPT-aggravated neurological deficits and infarction ( P < 0.001), downregulated total NAMPT, TNF-α, and IL-1β, and increased NAD+ levels ( P < 0.001). In vitro , eNAMPT stimulation increased OGD/R-induced TNF-α and IL-1β secretion from microglia ( P < 0.001), which SAL effectively inhibited ( P < 0.001). Conclusion This study provides experimental evidence that the neuroprotective effects of SAL against cerebral I/R injury are associated with downregulation of pathologically elevated NAMPT expression (likely reflecting a reduction in pro-inflammatory eNAMPT), restoration of cerebral NAD+ homeostasis (potentially preserving iNAMPT function), and suppression of microglia-mediated neuroinflammation, suggesting that eNAMPT may serve as a potential effector molecule of SAL.