Neuritin Attenuates Neuronal Apoptosis Mediated by Endoplasmic Reticulum Stress In Vitro

TIGAR Suppresses ER Stress-Induced Neuronal Injury through Targeting ATF4 Signaling in Cerebral Ischemia/Reperfusion

Endoplasmic reticulum (ER) stress is crucial in cerebral ischemia/reperfusion injury by triggering cellular apoptosis and exacerbating neuronal damage. This study elucidates the dynamics of TP53-induced glycolysis and apoptosis regulator (TIGAR) translocation and its role in regulating neural fate during cerebral ischemia-induced ER stress, specifically in male mice. We found enhanced nuclear localization of TIGAR in neurons after transient middle cerebral artery occlusion/reperfusion (tMCAO/R) in male mice, as well as oxygen glucose deprivation/reperfusion (OGD/R) and treatment with ER stress inducer (tunicamycin and thapsigargin) in neuronal cells. Conditional neuronal knockdown of Tigar aggravated the injury following ischemia-reperfusion, whereas overexpression of Tigar attenuated cerebral ischemic injury and ameliorated intraneuronal ER stress. Additionally, TIGAR overexpression reduced the elevation of ATF4 target genes and attenuated ER stress-induced cell death. Notably, TIGAR colocalized and interacted with ATF4 in the nucleus, inhibiting its downstream proapoptotic gene transcription, consequently protecting against ischemic injury. In vitro and in vivo experiments revealed that ATF4 overexpression reversed the protective effects of TIGAR against cerebral ischemic injury. Intriguingly, our study identified the Q141/K145 residues of TIGAR, crucial for its nuclear translocation and interaction with ATF4, highlighting a novel aspect of TIGAR's function distinct from its known phosphatase activity or mitochondrial localization domains. These findings reveal a novel neuroprotective mechanism of TIGAR in regulating ER stress through ATF4-mediated signaling pathways. These insights may guide targeted therapeutic strategies to protect neuronal function and alleviate the deleterious effects of cerebral ischemic injury.

Neuritin attenuates neuroinflammation and apoptosis in early brain injury after subarachnoid hemorrhage via endoplasmic reticulum stress-related inflammatory pathways

Neuroinflammation is a key destructive pathophysiological process in early brain injury (EBI) following subarachnoid hemorrhage (SAH). Recent studies have discovered that endoplasmic reticulum stress-related inflammatory pathways include the IRE1α-TRAF2-NF-κB pathway, PERK-eIF2α-NF-κB pathway, and ATF6-AKT -NF-κB pathway leading to neuroinflammatory response. Neuritin is a neurotrophin that is involved in neuronal plasticity and regeneration. Studies have suggested that Neuritin has a vital role in reducing neuroinflammation, and can also decrease the expression of proteins related to endoplasmic reticulum stress following SAH. This suggests that Neuritin could be a potential therapeutic target for SAH and other neurological conditions. However, the regulatory mechanisms of Neuritin in ER stress-related inflammatory pathways after SAH are not yet fully understood. In this work, we discovered that the activation of ER stress-related inflammatory pathways leads to neuroinflammation, which further aggravates neuronal apoptosis after SAH. Our findings indicate that Neuritin overexpression play a neuroprotective role by inhibiting IRE1α-TRAF2-NF-κB pathway, PERK-eIF2α-NF-κB pathway, and ATF6-AKT-NF-κB pathway associated with endoplasmic reticulum stress. These inhibitory effects on neuroinflammation ultimately reduce nerve cell apoptosis.

Oxysophocarpine Prevents the Glutamate-Induced Apoptosis of HT-22 Cells via the Nrf2/HO-1 Signaling Pathway

Oxysophocarpine (OSC), a quinolizidine alkaloid, shows neuroprotective potential, though its mechanisms are unclear. The aim of the present study was to investigate the neuroprotective effects of OSC through the nuclear factor erythroid 2-related factor 2 (Nrf2)/ heme oxygenase-1 (HO-1) signaling pathway using the HT-22 cell line. Assessments of cell viability were conducted utilizing the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Assessments of oxidative stress (OS) were conducted through the quantification of reactive oxygen species (ROS). The integrity of the mitochondrial membrane potential (MMP) was scrutinized using fluorescent probe technology. Apoptosis levels were quantified using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. The trafficking of Nrf2 within the cell nucleus was examined through immunofluorescence analysis. Furthermore, Western blotting (WB) was applied to evaluate the expression levels of proteins implicated in apoptosis and the Nrf2/HO-1 pathway. To further probe the influence of OSC on the overexpression of antioxidant enzymes, cells were subjected to transfection with HO-1 siRNA. The results showed that OSC inhibited glutamate-induced OS, as evidenced by reduced cell viability and ROS levels. Furthermore, the apoptotic condition induced by glutamate in HT-22 cells was significantly reduced following OSC treatment. More interestingly, the Nrf2/HO-1 signaling pathway was upregulated following OSC treatment. These results suggest that OSC can exert neuroprotective effects by regulating the Nrf2/HO-1 pathway to inhibit neuronal cell apoptosis, potentially aiding in the treatment of neurodegenerative diseases.

Glycyrrhetinic acid triggers a protective autophagy by inhibiting the JAK2/STAT3 pathway in cerebral ischemia/reperfusion injury

Cerebral ischemia/reperfusion injury (CIRI) is a common feature of ischemic stroke leading to a poor prognosis. Effective treatments targeting I/R injury are still insufficient. The study aimed to investigate the mechanisms, by which glycyrrhizic acid (18β-GA) in ameliorates CIRI. Our results showed that 18β-GA significantly decreased the infarct volume, neurological deficit scores, and pathological changes in the brain tissue of rats after middle cerebral artery occlusion. Western blotting showed that 18β-GA inhibited the expression levels of phosphorylated JAK2 and phosphorylated STAT3. Meanwhile, 18β-GA increased LC3-II protein levels in a reperfusion duration-dependent manner, which was accompanied by an increase in the Bcl-2/Bax ratio. Inhibition of 18β-GA-induced autophagy by 3-methyladenine (3-MA) enhanced apoptotic cell death. In addition, 18β-GA inhibited the JAK2/STAT3 pathway, which was largely activated in response to oxygen-glucose deprivation/reoxygenation. However, the JAK2/STAT3 activator colivelin TFA abolished the inhibitory effect of 18β-GA, suppressed autophagy, and significantly decreased the Bcl-2/Bax ratio. Taken together, these findings suggested that 18β-GA pretreatment ameliorated CIRI partly by triggering a protective autophagy via the JAK2/STAT3 pathway. Therefore might be a potential drug candidate for treating ischemic stroke.

Stem cells alleviate OGD/R mediated stress response in PC12 cells following a co-culture: modulation of the apoptotic cascade through BDNF-TrkB signaling

Apoptosis mediated by endoplasmic reticulum (ER) stress plays a crucial role in several neurovascular disorders, including ischemia/reperfusion injury (I/R injury). Previous in vitro and in vivo studies have suggested that following I/R injury, ER stress is vital for mediating CCAT-enhancer-binding protein homologous protein (CHOP) and caspase-12-dependent apoptosis. However, its modulation in the presence of stem cells and the underlying mechanism of cytoprotection remains elusive. In vivo studies from our lab have reported that post-stroke endovascular administration of stem cells renders neuroprotection and regulates apoptosis mediated by ER stress. In the current study, a more robust in vitro validation has been undertaken to decipher the mechanism of stem cell-mediated cytoprotection. Results from our study have shown that oxygen-glucose deprivation/reoxygenation (OGD/R) potentiated ER stress and apoptosis in the pheochromocytoma 12 (PC12) cell line as evident by the increase of protein kinase R (PKR)-like ER kinase (p-PERK), p-Eukaryotic initiation factor 2α subunit (EIF2α), activation transcription factor 4 (ATF4), CHOP, and caspase 12 expressions. Following the co-culture of PC12 cells with MSCs, ER stress was significantly reduced, possibly via modulating the brain-derived neurotrophic factor (BDNF) signaling. Furthermore, inhibition of BDNF by inhibitor K252a abolished the protective effects of BDNF secreted by MSCs following OGD/R. Our study suggests that inhibition of ER stress-associated apoptotic pathway with MSCs co-culture following OGD/R may help to alleviate cellular injury and further substantiate the use of stem cells as a therapeutic modality toward neuroprotection following hypoxic injury or stroke in clinical settings.

Protective effect of food derived nutrients on cisplatin nephrotoxicity and its mechanism

Platinum-based metal complexes, especially cisplatin (cis-diamminedichloroplatinum II, CDDP), possess strong anticancer properties and a broad anticancer spectrum. However, the clinical application of CDDP has been limited by its side effects including nephrotoxicity, ototoxicity, and neurotoxicity. Furthermore, the therapeutic effects of current clinical protocols are imperfect. Accordingly, it is essential to identify key targets and effective clinical protocols to restrict CDDP-induced nephrotoxicity. Herein, we first analyzed the relevant molecular mechanisms during the process of CDDP-induced nephrotoxicity including oxidative stress, apoptosis, and inflammation. Evidence from current studies was collected and potential targets and clinical protocols are summarized. The evidence indicates an efficacious role of nutrition-based substances in CDDP-induced renal injury.

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.

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

The autophagy/apoptosis interaction has always been a focus of study in pathogenicity models. Neuritin is a neurotrophic factor that is highly expressed primarily in the central nervous system. Our previous study revealed that it protects against apoptosis in cortical neurons subjected to oxygen-glucose deprivation (OGD)/reoxygenation (OGD/R), and later animal experiments revealed that it can increase the expression of the autophagy-related protein LC3. Whether this neuroprotective effect is closely related to autophagy is still unclear. In this study, we hypothesized that neuritin can promote autophagic flux to protect nerve cells after OGD/R. To verify this hypothesis, we induced OGD/R in primary cortical neurons and assessed cell viability by the CCK8 and LDH assays. Cell apoptosis was assessed by Annexin V-FITC/PI, staining, and the contents and mRNA abundances of the autophagy-related proteins LC3 and p62, the apoptotic protein Caspase3 were quantified by Western blotting and RT-PCR. Autophagic flux was assessed by immunofluorescence after RFP-GFP-LC3 virus transfection, and ultrastructural changes in autophagosomes were observed by transmission electron microscopy (TEM). The results showed that cell viability was decreased, apoptosis was increased and autophagy was enhanced after OGD/R. Neuritin significantly increased cell viability, decreased apoptosis, further increased the expression of the autophagic flux-related protein LC3, further decreased p62 expression, and significantly increased the autophagosome number and autophagosome to lysosome ratio. Bafilomycin A1 (BafA1) is a late autophagy inhibitor, aggravated cell damage and apoptosis and counteracted the enhancement of autophagy activation and protective effects of neuritin. In conclusion, neuritin may promote the completion of autophagic flux by ameliorating neuronal damage after OGD/R.

Detection of autophagic flux in primary cerebral cortical neurons after oxygen glucose deprivation/reperfusion (OGD/R) using various methods

The current research hot spot in the field of autophagic flux is to explain and alleviate disease from the perspective of autophagy. A highly sophisticated, sensitive, quantifiable and comprehensive method is required to accurately determine the dynamic process of autophagic flux. There are very few methods in neuroscience that specifically examine autophagic flux. Therefore, primary cortical neurons were divided into oxygen glucose deprivation/reperfusion (OGD/R) (group A) and OGD/R plus bafilomycin A1 (BafA1) (group B) groups. ① Transfection of the LC3 gene with the RFP-GFP tandem fluorescent label was performed. ② Direct quantification was performed using transmission electron microscopy (TEM). ③ Autophagy-related tools were used to detect the transformation of LC3I/II. ④ SQSTM1/P62 combined with the LC3 protein flip test was performed to comprehensively evaluate autophagic flux. Using method one, the ratio of autophagolysosomes to autophagosomes in group A was significantly increased based on fluorescence microscopy analysis. Using method two, the autophagy process in group A was more continuous and unobstructed based on TEM analysis, while only some partial processes were observed in group B, and the number of autophagosomes and autophagy lysosomes in group A was significantly greater more than that in group B. The LC3II/I ratio measured in method three was analysed in detail to explain the autophagic flux. The ratio of soluble p62 combined with the ratio of LC3II/I detected using method four reflected the activation of autophagy. In summary, each method has its own advantages, and different methods and indicators can be used to monitor different stages of autophagy. An understanding of these advantages and mastery of these methods, is a very promising strategy to systematically and objectively study central nervous system diseases, facilitate the rational use of drugs, and formulate effective treatment plans from the perspective of autophagy.

Genome-Wide DNA Methylation and Gene Expression Profiles in Cows Subjected to Different Stress Level as Assessed by Cortisol in Milk

Dairy cattle health, wellbeing and productivity are deeply affected by stress. Its influence on metabolism and immune response is well known, but the underlying epigenetic mechanisms require further investigation. In this study, we compared DNA methylation and gene expression signatures between two dairy cattle populations falling in the high- and low-variant tails of the distribution of milk cortisol concentration (MC), a neuroendocrine marker of stress in dairy cows. Reduced Representation Bisulfite Sequencing was used to obtain a methylation map from blood samples of these animals. The high and low groups exhibited similar amounts of methylated CpGs, while we found differences among non-CpG sites. Significant methylation changes were detected in 248 genes. We also identified significant fold differences in the expression of 324 genes. KEGG and Gene Ontology (GO) analysis showed that genes of both groups act together in several pathways, such as nervous system activity, immune regulatory functions and glucocorticoid metabolism. These preliminary results suggest that, in livestock, cortisol secretion could act as a trigger for epigenetic regulation and that peripheral changes in methylation can provide an insight into central nervous system functions.

Endoplasmic reticulum stress in autoimmune diseases

If the body's immune system is disordered and begins to attack "self" and therefore, its own tissues this is considered to be an autoimmune pathology. The specific mechanisms vary between the different diseases and have not always been elucidated but chronic, non-resolving inflammation is a common theme in the pathogenesis of autoimmune diseases. Interestingly, it has been shown that development and occurrence of various inflammatory responses are closely correlated to endoplasmic reticulum stress. Therefore, this review discusses the current progress of research about the relationship between autoimmune diseases and endoplasmic reticulum stress, specifically the unfolded protein response (UPR).