Sevoflurane post-conditioning alleviated hypoxic-ischemic brain injury in neonatal rats by inhibiting endoplasmic reticulum stress-mediated autophagy via IRE1 signalings

Endoplasmic Reticulum Stress Promotes Neuronal Damage in Neonatal Hypoxic-Ischemic Brain Damage by Inducing Ferroptosis

Hypoxic-ischemic brain damage (HIBD) poses a significant risk of neurological damage in newborns. This study investigates the impact of endoplasmic reticulum stress (ERS) on neuronal damage in neonatal HIBD and its underlying mechanisms. HIBD neonatal rat model was constructed and pre-treated with 4-phenylbutiric acid (4-PBA). Nissl and TUNEL staining were utilised to assess neuronal damage and apoptosis in rat brains. HIBD cell model was established by inducing oxygen-glucose deprivation (OGD) in rat H19-7 neurons, which were then pre-treated with Thapsigargin (TG), Ferrostatin-1 (Fer-1), or both. Cell viability and apoptosis of H19-7 neurons were analysed using cell counting kit-8 assay and TUNEL staining. GRP78-PERK-CHOP pathway activity and glutathione peroxidase-4 (GPX4) expression in rat brains and H19-7 neurons were assessed using Western blot. Ferroptosis-related indicators, including glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA) and iron content, were measured using commercial kits in both rat brains and H19-7 neurons. GRP78-PERK-CHOP pathway was overactivated in HIBD neonatal rats' brains, which was mitigated by 4-PBA treatment. 4-PBA treatment demonstrated a reduction in neuronal damage and apoptosis in HIBD-affected neonatal rat brains. Furthermore, it attenuated ferroptosis in rats by increasing GPX4, GSH and SOD while decreasing MDA and iron content. In the OGD-induced H19-7 neurons, Fer-1 treatment counteracted the suppressive effects of TG on viability, the exacerbation of apoptosis, the promotion of ferroptosis and the activation of the GRP78-PERK-CHOP pathway. Overall, ERS facilitates neuronal damage in neonatal HIBD by inducing ferroptosis. Consequently, the suppression of ERS may represent a promising therapeutic strategy for treating neonatal HIBD.

The role of the ER stress sensor IRE1 in cardiovascular diseases

Despite enormous advances in the treatment of cardiovascular diseases, including I/R injury and heart failure, heart diseases remain a leading cause of mortality worldwide. Inositol-requiring enzyme 1 (IRE1) is an evolutionarily conserved sensor endoplasmic reticulum (ER) transmembrane protein that senses ER stress. It manages ER stress induced by the accumulation of unfolded/misfolded proteins via the unfolded protein response (UPR). However, if the stress still persists, the UPR pathways are activated and induce cell death. Emerging evidence shows that, beyond the UPR, IRE1 participates in the progression of cardiovascular diseases by regulating inflammation levels, immunity, and lipid metabolism. Here, we summarize the recent findings and discuss the potential therapeutic effects of IRE1 in the treatment of cardiovascular diseases.

The IRE1-XBP1 Axis Regulates NLRP3 Inflammasome-Mediated Microglia Activation in Hypoxic Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a perinatal injury caused by cerebral hypoxia and reduced blood perfusion. Microglia activation-induced neuroinflammatory injury is a leading cause of neuron loss and brain injury. Efficient treatment strategies are still required further investigation. Our study is aimed to investigate the role of IRE1-XBP1 inhibitor 4μ8С in HIE. Rat pups (7 d) were used to establish HIE model using unilateral carotid artery ligation and hypoxia. A series of experiments including Western blot, Morris water maze test, TTC staining, RT-qPCR, TUNEL staining, and immunofluorescence staining were operated to evaluate the role of 4μ8С in HIE. 4μ8С treatment effectively reduced phosphorylated IRElα and XBP1 protein levels. 4μ8С treatment improves cognition and learning abilities of HIE rats. 4μ8С treatment alleviated brain infarction and cell apoptosis in HIE rats. 4μ8С treatment inhibited NLRP3 inflammasome activation-mediated microglia activation and inflammatory response. In conclusion, 4μ8С suppressed microglia and NLRP3 inflammasome activation by inactivating IRE1/XBP1 axis during HIE development, which revealed IRE1α inhibition as a novel mechanism for neuron protection.

Neuroprotective effects of VCE-004.8 in a rat model of neonatal stroke

BACKGROUND

Currently there is no effective treatment for neonatal stroke, an acute neurologic syndrome with sequelae, due to focal ischemic, thrombotic, or hemorrhagic event occurring in the perinatal period. VCE-004.8, an aminoquinone exhibiting activity on CB2 and PPARγ receptors, is neuroprotective in adult mice models of acute and chronic brain damaging conditions. We hereby aimed to study VCE-004.8 neuroprotection in a rat model of neonatal stroke.

METHODS

7-day-old (P7) Wistar rats of both sexes were submitted to Middle Cerebral Artery Occlusion (MCAO), receiving i.p. 30 min after vehicle (MCAO + VEH) or VCE-004.8 5 mg/kg (MCAO + VCE). Non-occluded rats served as controls (SHAM). MCAO consequences were assessed at P14 by MRI, histological (TUNEL staining), biochemical (lactate/n-acetyl aspartate ratio by 1H-NMR spectroscopy) and motor studies (grasp test), and at P37 assessing myelination (MBP signal), hemiparesis and hyperlocomotion. Effects of VCE-004.8 on excitotoxicity (glutamate/n-acetyl aspartate, 1H-NMR), oxidative stress (protein nitrosylation, Oxyblot) and neuroinflammation (Toll-like receptor 4 and TNFa expression, Western blot) were assessed at P14. Therapeutic window was assessed by delaying drug administration for 12 or 18 h.

RESULTS

Post-MCAO administration of VCE-004.8 reduced the volume of infarct and histological and biochemical brain damage, reducing hyperlocomotion, restoring motor performance and preserving myelination, in a manner linked to the modulation of excitotoxicity, oxidative stress and neuroinflammation. VCE-004.8 was still effective being administered 12-18 h post-insult.

CONCLUSIONS

These data suggest that this drug could be effective for the treatment of stroke in newborns.

Sevoflurane postconditioning ameliorates cerebral ischemia-reperfusion injury in rats via TLR4/MyD88/TRAF6 signaling pathway

To determine whether sevoflurane postconditioning protects against cerebral ischemia reperfusion (I/R) injury and its potential mechanism, we employed bioinformatic analysis, neurological assessments, and western blot analysis, as well as triphenyl tetrazolium chloride, hematoxylin and eosin, Nissl, and immunofluorescence staining. We identified 103 differentially expressed genes induced by cerebral I/R, including 75 upregulated genes and 28 downregulated genes enriched for certain biological processes (involving regulation of inflammatory responses, cellular responses to interleukin 1, and chemokine activity) and signaling pathways (such as transcriptional misregulation in cancer, interleukin-17 signaling, rheumatoid arthritis, MAPK signaling, and Toll-like receptor signaling). As a typical path in Toll-like receptor signaling pathway, in the current study, we investigated the protective effect of sevoflurane postconditioning in cerebral I/R rats and further explore the role of TLR4/MyD88/TRAF6 signaling pathway in it. The results showed cerebral I/R-induced neurological deficits were comparatively less severe following sevoflurane postconditioning. In addition, TLR4/MyD88/TRAF6 signaling pathway-related proteins and neuropathic damage were ameliorated in aged rats following sevoflurane postconditioning, while the TLR4 agonist lipopolysaccharide aggravated these changes. Together, these findings suggest that sevoflurane postconditioning ameliorates cerebral I/R injury by a mechanism involving inhibition of the TLR4/MyD88/TRAF6 signaling pathway to suppress neuroinflammatory responses.

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.