SRGN aggravates cerebral ischemia/reperfusion injury by inducing SLC7A11 depletion and excessive mitophagy-dependent neuronal death

Abstract Background Cerebral ischemia/reperfusion injury (CI/RI) is a critical secondary injury that occurs after recanalization therapy for acute ischemic stroke, in which aberrant mitophagy triggers neuronal loss and neurological dysfunction. Serglycin (SRGN) is a secretory proteoglycan that regulates inflammation and protein stability, and it is implicated in multiple inflammatory diseases and tumors. However, its role in CI/RI-induced neuronal injury remains unknown. This study aimed to investigate the function and underlying mechanism of SRGN in CI/RI, and to explore a targeted therapeutic strategy based on SRGN silencing. Methods SRGN expression was measured in serum samples from patients with acute cerebral infarction, in brain tissues of middle cerebral artery occlusion/reperfusion (MCAO/R) mice, and in oxygen glucose deprivation/reoxygenation (OGD/R)-exposed neurons. Loss- and gain-of-function experiments were performed in vitro using SRGN knockdown and overexpression, with neuronal injury assessed by LDH release, ROS accumulation, glutathione content, and pro-inflammatory cytokine levels. The interaction between SRGN and SLC7A11 was evaluated by molecular docking, and the involvement of ubiquitin–proteasomal degradation and mitophagy was examined. HG106-mediated SLC7A11 inhibition was used to validate the mechanistic axis. In vivo, red blood cell-derived extracellular vesicles loaded with siRNA targeting SRGN (RBC-EVs@siSRGN) were evaluated in MCAO/R mice for blood-brain barrier penetration, gene silencing efficiency, and therapeutic efficacy by measuring infarct volume, neuroinflammation, autophagy balance, and neurological deficits. Results SRGN was elevated in the serum of acute cerebral infarction patients, as well as in brain tissues of MCAO/R mice and OGD/R-exposed neurons. In vitro, SRGN knockdown alleviated OGD/R-induced neuronal damage, evidenced by decreased LDH release, ROS accumulation, and pro-inflammatory cytokines, together with increased glutathione content, whereas SRGN overexpression aggravated neuronal injury. Mechanistically, SRGN directly interacted with SLC7A11 and promoted its ubiquitin–proteasomal degradation, leading to mitochondrial dysfunction and excessive mitophagy; HG106-mediated SLC7A11 inhibition abolished the neuroprotective effects of SRGN silencing, confirming the SRGN/SLC7A11/mitophagy axis in CI/RI. In MCAO/R mice, RBC-EVs@siSRGN efficiently crossed the blood–brain barrier, and effectively silenced cerebral SRGN in vivo, resulting in reduced infarct volume, relieved neuroinflammation, restored mitophagy balance, and improved neurological deficits. Conclusions SRGN exacerbates CI/RI by promoting SLC7A11 degradation and pathological mitophagy. Circulating SRGN may serve as a promising non-invasive biomarker for acute cerebral infarction, and RBC-EVs@siSRGN represents an effective targeted therapy for ischemic stroke.