Rutin alleviates preoperative anxiety stress-induced persistent postoperative pain by inhibiting microglia-mediated abnormal synaptic engulfment in the spinal cord dorsal horn

Persistent postoperative pain (PPP) is associated with neuroinflammation and excitatory/inhibitory(E/I) imbalance in the spinal cord. Notably, trained immunity enhances the immune reactivity of microglia to secondary stimuli, exacerbating neuroinflammation and synaptic engulfment of microglia. Here, we investigated whether preoperative anxiety stress promotes trained immunity in microglia and how this phenomenon influences microglia-mediated synaptic engulfment. Given the role of glycolysis in trained immunity, we focused on microglial glucose metabolism. Rutin inhibits microglial glycolysis and reduces neuroinflammation, prompting further investigation into its therapeutic potential for PPP. Preoperative anxiety was modeled in male Sprague-Dawley (SD) rats using single prolonged stress (SPS). We found that SPS aggravated and prolonged incision pain in SD rats. Mechanistically, SPS promoted trained immunity in microglia via mammalian target of rapamycin (mTOR)/hypoxia-inducible factor-1α (HIF-1α) signaling. This amplified inflammatory responses to surgical stimuli and enhanced microglial engulfment of inhibitory synapses. Rutin inhibited microglial activation and inhibitory synaptic engulfment via mTOR/HIF-1α signaling, relieving SPS-induced PPP. These findings suggest preoperative anxiety induces trained immunity in microglia, amplifying neuroinflammation and E/I imbalance in the spinal cord after surgery. Rutin attenuates this process by suppressing mTOR/HIF-1α-driven glycolysis, thereby alleviating PPP.