Neuritin attenuates oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal injury by promoting autophagic flux

Neuritin promotes autophagic flux by inhibiting the cGAS-STING pathway to alleviate brain injury after subarachnoid haemorrhage

BACKGROUND

Early brain injury (EBI) is closely associated with poor prognosis in patients with subarachnoid haemorrhage (SAH), with autophagy playing a pivotal role in EBI. However, research has shown that the stimulator of interferon genes (STING) pathway impacts autophagic flux. While the regulatory impact of neuritin on EBI and autophagic flux has been established previously, the underlying mechanism remains unclear. This study aimed to determine the role of the cGAS-STING pathway in neuritin-mediated regulation of autophagic flux following SAH.

METHODS

A SAH model was established in male Sprague-Dawley rats via intravascular perforation. Neuritin overexpressions using adeno-associated virus, the STING antagonist "C-176," and the activator, "CMA," were determined to investigate the cGAS-STING pathway's influence on autophagic flux and brain injury post-SAH, along with the neuritin's regulatory effect on STING. In this study, SAH grade, neurological score, haematoxylin and eosin (H&E) staining, brain water content (BWC), sandwich enzyme-linked immunosorbent assay, Evans blue staining, immunofluorescence staining, western blot analysis, and transmission electron microscopy (TEM) were examined.

RESULTS

Neuritin overexpression significantly ameliorated neurobehavioural scores, blood-brain barrier injury, brain oedema, and impaired autophagic flux in SAH-induced rats. STING expression remarkably increased post-SAH. C-176 and CMA mitigated and aggravated autophagic flux injury and brain injury, respectively, while inhibiting and enhancing STING, respectively. Particularly, CMA treatment nullified the protective effects of neuritin against autophagic flux and mitigated brain injury.

CONCLUSION

Neuritin alleviated EBI by restoring impaired autophagic flux after SAH through the regulation of the cGAS-STING pathway.

SIRT3 facilitates mitochondrial structural repair and functional recovery in rats after ischemic stroke by promoting OPA1 expression and activity

BACKGROUND

Optical atrophy 1 (OPA1), a protein accountable for mitochondrial fusion, facilitates the restoration of mitochondrial structure and function following cerebral ischemia/reperfusion (I/R) injury. The OPA1-conferred mitochondrial protection involves its expression and activity, which can be improved by SIRT3 in non-cerebral ischemia. Nevertheless, it remains obscure whether SIRT3 enhances the expression and activity of OPA1 after cerebral I/R injury.

METHODS

Mature male Sprague Dawley rats were intracranially injected with adeno-associated viral-Sirtuin-3(AAV-SIRT3) and AAV-sh_OPA1, followed by a 90-min temporary blockage of the middle cerebral artery and subsequent restoration of blood flow. Cultured cortical neurons of rats were transfected with LV-SIRT3 or LV-sh_OPA1 before a 2-h oxygen-glucose deprivation and reoxygenation. The rats and neurons were subsequently treated with a selective OPA1 activity inhibitor (MYLS22). The interaction between SIRT3 and OPA1 was assessed by molecular dynamics simulation technology and co-immunoprecipitation. The expression, function, and specific protective mechanism of SIRT3 were examined by various analyses.

RESULTS

SIRT3 interacted with OPA1 in the rat cerebral cortex before and after cerebral I/R. After cerebral I/R damage, SIRT3 upregulation increased the OPA1 expression, which enhanced deacetylation and OPA1 activity, thus alleviating cerebral infarct volume, neuronal apoptosis, oxidative pressure, and impairment in mitochondrial energy production; SIRT3 upregulation also improved neuromotor performance, repaired mitochondrial ultrastructure and membrane composition, and promoted the mitochondrial biogenesis. These neuroprotective effects were partly reversed by OPA1 expression interference and OPA1 activity inhibitor MYLS22.

CONCLUSION

In rats, SIRT3 enhances the expression and activity of OPA1, facilitating the repair of mitochondrial structure and functional recovery following cerebral I/R injury. These findings highlight that regulating SIRT3 may be a promising therapeutic strategy for ischemic stroke.

Neuritin has a neuroprotective role in the rat model of acute ischemia stroke by inhibiting neuronal apoptosis and NLRP3 inflammasome

OBJECTIVES

This study explored the anti-inflammatory, anti-neuronal apoptosis, and neuroprotective effects of Neuritin in rat models of acute ischemia stroke (AIS).

METHODS

AIS was induced in male Sprague Dawley rats by middle cerebral artery occlusion (MCAO). Rats were divided into sham, MCAO, MCAO+neuritin, MCAO + neuritin + PBS, MCAO + neuritin+MCC950, and MCAO + neuritin + MSU groups. Neurological score assessment, brain water content measurement, HE staining, TTC staining, TUNEL staining, ELISA, and Western blot were performed.

RESULTS

Neuritin significantly improved the neurobehavioral score, infarct size, brain water content, apoptosis, and neuroinflammatory response compared with the MCAO and MCAO + PBS groups within 24 h after AIS. Moreover, Neuritin inhibited the protein expression of NLRP3 inflammasome, and reduced the expression of IL-18 and IL-1B, thereby reducing the inflammatory response. Meanwhile, the neuroprotection, anti-inflammation, and anti-apoptosis effects of Neuritin were enhanced by MCC950 but partly counteracted by MSU.

CONCLUSION

Neuritin may reduce brain injury after AIS by inhibiting the expression of NLRP3 inflammasome and then inhibiting the inflammatory response.

The Pathological Mechanism of Neuronal Autophagy-Lysosome Dysfunction After Ischemic Stroke

The abnormal initiation of autophagy flux in neurons after ischemic stroke caused dysfunction of autophagy-lysosome, which not only led to autophagy flux blockage, but also resulted in autophagic death of neurons. However, the pathological mechanism of neuronal autophagy-lysosome dysfunction did not form a unified viewpoint until now. In this review, taking the autophagy lysosomal dysfunction of neurons as a starting point, we summarized the molecular mechanisms that led to neuronal autophagy lysosomal dysfunction after ischemic stroke, which would provide theoretical basis for the clinical treatment of ischemic stroke.

Tregs depletion aggravates activation of astrocytes by modulating IL-10/GXP4 following cerebral infarction

Background

Tregs plays a critical role in the development of secondary injuries in diseases. Accumulating evidence suggests an association between ischemic stroke and renal dysfunction; however, the underlying mechanisms remain unclear. This study aimed to investigate the potential of Tregs in inhibiting the activation of astrocytes after focal cerebral infarction.

Methods

This study aimed to investigate the renal consequences of focal cerebral ischemia by subjecting a mouse model to transient middle cerebral artery occlusion (tMCAO). Subsequently, we assessed renal fibrosis, renal ferroptosis, Treg infiltration, astrocyte activation, as well as the expression levels of active GPX4, FSP1, IL-10, IL-6, and IL-2 after a 2-week period.

Results

In the tMCAO mouse model, depletion of tregs protected against activation of astrocyte and significantly decreased FSP1, IL-6, IL-2, and NLRP3 expression levels, while partially reversing the changes in Tregs. Mechanistically, tregs depletion attenuates renal fibrosis by modulating IL-10/GPX4 following cerebral infarction.

Conclusion

Tregs depletion attenuates renal fibrosis by modulating IL-10/GPX4 following cerebral infarction.

Fluoride-Induced Cortical Toxicity in Rats: the Role of Excessive Endoplasmic Reticulum Stress and Its Mediated Defective Autophagy

The cerebral cortex is closely associated with learning and memory, and fluoride is capable of inducing cortical toxicity, but its mechanism is unclear. This study aimed to investigate the role of endoplasmic reticulum stress and autophagy in fluoride-induced cortical toxicity. Rats exposed to sodium fluoride (NaF) were used as an in vivo model. The results showed that NaF exposure impaired the learning and memory capacities and increased urinary fluoride levels in rats. In addition, NaF exposure induced excessive endoplasmic reticulum stress and associated apoptosis, as evidenced by elevated IRE1α, GRP78, cleaved caspase-12, and cleaved caspase-3, as well as defective autophagy, as evidenced by increased expression of Beclin1, LC3-II, and p62 in cortical areas. Importantly, the endoplasmic reticulum stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated endoplasmic reticulum stress as well as defective autophagy, thus confirming the critical role of endoplasmic reticulum stress and autophagy in fluoride-induced cortical toxicity. Taken together, these results suggest that excessive endoplasmic reticulum stress and its mediated defective autophagy lead to fluoride-induced cortical toxicity. This provides new insights into the mechanisms of fluoride-induced neurotoxicity and a new theoretical basis for the prevention and treatment of fluoride-induced neurotoxicity.

Reverse relationship between autophagy and apoptosis in an in vitro model of cortical neuronal injury

Autophagy and apoptosis are intertwined, and their relationship involves complex cross-talk. Whether the activation and inhibition of autophagy protect or damage neurons in the central nervous system has been a matter of longstanding controversy. We investigated the effect of autophagy on the apoptosis of cortical neurons after oxygen- and glucose-deprivation/reoxygenation (OGD/R) injury in vitro and found that protective mechanism activation was the predominant response to enhanced autophagy activation and increased autophagic flux. After successful establishment of an OGD/R model with cortical neurons, the autophagy activator rapamycin (Rap) or the late-autophagy inhibitor bafilomycin A1 (BafA1) was added to cell groups according to the experimental design. Cell viability was determined by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays, and the apoptosis rate was measured by analysing Annexin V-FITC/PI-stained cells. The protein and mRNA expression levels of the apoptosis factors Caspase8 and Caspase3 and autophagy-associated proteins LC3 and p62 were measured by Western blotting and RT-qPCR. The extent of autophagic flux was determined by measuring the intensity of double immunofluorescence labelled protein after cells were transfected with RFP-GFP-LC3-expressing virus, and the ultrastructures of autophagosomes were observed by transmission electron microscopy (TEM). The results showed that cell viability decreased and that cells underwent autophagy and apoptosis after OGD/R. After the addition of Rap, cell viability was increased, and the apoptosis rate was decreased significantly. In addition, the level of the autophagic flux protein LC3II was increased, and the level of p62 was decreased. The number of autophagosomes and the ratio of autophagosomes to lysosomes were increased significantly. After BafA1 intervention, however, these results were reversed, with decreased cell viability, a significantly increased apoptosis rate, and disrupted autophagic flux. In conclusion, enhanced autophagy activation or autophagic flux exerted a significant protective effect on neurons after OGD/R injury in vitro.