Neuroprotective effects of sinomenine and metformin in diabetic stroke: Role of NLRP3/caspase‐1 and mitophagy

Type 2 diabetes mellitus (T2DM) significantly increases the risk and severity of cerebral ischaemia-reperfusion (IR) injury, yet effective neuroprotective treatments for diabetic stroke remain limited. This study explored whether a combination of sinomenine and metformin could offer enhanced neuroprotection in diabetic rats subjected to cerebral IR injury, and investigated the molecular pathways involved. Male rats were rendered diabetic using a high-fat diet and low-dose streptozotocin. After establishing diabetes, rats underwent transient middle cerebral artery occlusion followed by 24 h of reperfusion. Animals received sinomenine, metformin, or their combination for 7 days prior to IR induction. Neurological function was assessed using standardized behavioural tests. Molecular analyses measured markers of pyroptosis (NLRP3, cleaved caspase-1, gasdermin D N-terminal fragment), mitophagy (PTEN-induced kinase 1 (PINK-1), Parkin), inflammation (interleukin (IL)-1β, IL-18) and oxidative stress (malondialdehyde, superoxide dismutase, glutathione peroxidase). To determine the role of mitophagy, a subset of animals was pretreated with the mitophagy inhibitor mitochondrial division inhibitor 1 (Mdv-1). Combination therapy led to significant improvements in neurological performance, accompanied by downregulation of pyroptosis-associated proteins and pro-inflammatory cytokines, as well as enhanced activation of the PINK-1/Parkin mitophagy pathway and improved antioxidant status. The neuroprotective effects of the combined treatment were abolished by Mdv-1, indicating a critical role for mitophagy in mediating these benefits. The combination of sinomenine and metformin confers additive neuroprotection against cerebral IR injury in diabetic rats, primarily through inhibition of NLRP3-mediated pyroptosis and activation of the PINK-1/Parkin mitophagy pathway. These findings highlight a promising therapeutic strategy for diabetic stroke and warrant further preclinical and clinical investigation.