Hydromorphone preconditioning suppresses `NLRP3`-mediated pyroptosis, reducing cerebral ischemia/reperfusion injury in mice.

Cerebral ischemia/reperfusion injury (CIRI) is a critical challenge in stroke management, leading to severe neurological deficits. A key pathological driver is neuroinflammation, particularly pyroptosis, a highly inflammatory form of programmed cell death mediated by the Nod-like receptor protein 3 (NLRP3) inflammasome. Current therapeutic strategies often fall short in effectively mitigating this inflammatory cascade. Understanding novel mechanisms to suppress NLRP3-mediated pyroptosis is crucial for developing improved neuroprotective interventions. This study investigates the molecular pathways by which hydromorphone preconditioning exerts its protective effects in CIRI.

Researchers established an animal model of CIRI in male C57BL/6J mice via middle cerebral artery occlusion/reperfusion. An in vitro I/R cell model was also induced using oxygen-glucose deprivation/reperfusion. Brain tissue and cell injury were assessed using hematoxylin and eosin staining, 2,3,5-triphenyltetrazolium chloride staining, lactate dehydrogenase testing, and a Cell Counting Kit-8 assay. NLRP3-positive expression and caspase-1 activity were quantified by immunostaining and specific activity assays. Expression levels of miR-195-5p, RNA-binding motif protein 15 (RBM15), and upstream stimulatory factor 2 (USF2) were measured via reverse transcription-quantitative PCR or western blotting. RNA immunoprecipitation (RIP) and dual-luciferase assays verified molecular interactions.

Hydromorphone preconditioning significantly inhibited NLRP3-mediated pyroptosis, leading to a notable alleviation of neurological deficits and a reduction in inflammatory injury within brain tissue. > Mechanistically, hydromorphone preconditioning upregulated miR-195-5p expression, which subsequently targeted RBM15. This interaction reduced IGF2BP3-mediated N6-methyladenosine (m6A) modification on USF2, thereby decreasing USF2 expression. The diminished USF2 expression then reduced its enrichment on the NLRP3 promoter, effectively inhibiting the activation of NLRP3-mediated pyroptosis. These findings elucidate a novel miR-195-5p/RBM15/USF2 axis through which hydromorphone confers neuroprotection against CIRI.