SRGN aggravates cerebral ischemia/reperfusion injury by inducing SLC7A11 depletion and excessive mitophagy-dependent neuronal death
SRGN appears to worsen neuronal injury in cerebral ischemia/reperfusion, and targeting it may offer a new avenue for research, though its clinical relevance is yet to be established.
Where it sits
this study against the rest of the glutathione (gsh) corpusSummary and findings
This study investigated the role of Serglycin (SRGN) in cerebral ischemia/reperfusion injury (CI/RI) and its potential as a therapeutic target. SRGN expression was assessed in patients and animal models, with in vitro experiments measuring neuronal injury through various biochemical markers. The findings suggest that SRGN aggravates neuronal damage by promoting SLC7A11 degradation and excessive mitophagy.
Abstract
<title>Abstract</title> <p>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.</p>
Background
Cerebral ischemia/reperfusion injury (CI/RI) is a significant complication following recanalization therapy for acute ischemic stroke, leading to neuronal loss and dysfunction. Previous research has indicated that aberrant mitophagy may contribute to neuronal injury in this context. However, the specific role of Serglycin (SRGN) in CI/RI remains unclear, making this study relevant for understanding potential therapeutic targets.
Methods
The study employed both in vitro and in vivo approaches. SRGN expression was measured in serum from patients and in brain tissues from MCAO/R mice. Loss- and gain-of-function experiments were conducted using SRGN knockdown and overexpression, with neuronal injury assessed through LDH release, ROS accumulation, and glutathione content. In vivo, RBC-EVs@siSRGN were evaluated for their ability to cross the blood-brain barrier and silence SRGN in MCAO/R mice.
Results
SRGN was found to be elevated in serum and brain tissues. The primary endpoint showed that SRGN knockdown led to decreased LDH release and increased glutathione content, with statistical significance noted (p<0.01). In vivo results indicated that RBC-EVs@siSRGN effectively reduced infarct volume, p<0.05, and improved neurological deficits.
Interpretation
The findings suggest that SRGN plays a detrimental role in CI/RI by promoting SLC7A11 degradation and excessive mitophagy, aligning with previous literature on the importance of mitophagy in neuronal injury. However, the clinical significance of these findings remains uncertain due to the use of rodent models and the lack of long-term follow-up data. This study highlights the potential for SRGN as a biomarker but requires further validation in human populations.
Key findings
- SRGN was elevated in serum samples of acute cerebral infarction patients.
- In MCAO/R mice, RBC-EVs@siSRGN resulted in reduced infarct volume, p<0.05.
- SRGN knockdown decreased LDH release, ROS accumulation, and pro-inflammatory cytokines.
- Increased glutathione content was observed with SRGN knockdown, p<0.01.
- SRGN overexpression aggravated neuronal injury, evidenced by increased LDH release.
Limitations
- primarily rodent models, limited human data
- specifics on sample size not reported
- short follow-up duration not detailed
- potential confounding factors not addressed