Mechanism of Endoplasmic Reticulum Stress in Cerebral Ischemia

Smart Hesperidin/Chitosan Nanogel Mitigates Apoptosis and Endoplasmic Reticulum Stress in Fluoride and Aluminum-Induced Testicular Injury

Fluoride and aluminum are ubiquitous toxic metals with adverse reproductive effects. The citrus flavonoid hesperidin has protective activities but poor solubility and bioavailability. Nanoparticulate delivery systems can improve flavonoid effectiveness. We conducted this study to prepare a pH-responsive chitosan-based nanogel for hesperidin delivery and evaluate its effectiveness against sodium fluoride (NaF) and aluminum chloride (AlCl3) induced testicular toxicity in mice. The nanogel was synthesized using 2 kGy gamma irradiation, enabling a size under 200 nm and enhanced hesperidin release at pH 6 matching testicular acidity. Male mice received 200 mg/kg AlCl3 and 10 mg/kg NaF daily for 30 days. Hesperidin nanogel at 20 mg/kg was administered orally either prophylactically (pretreatment) or after intoxication (posttreatment). The results showed that AlCl3 + NaF induced severe oxidative stress, hormonal disturbance, apoptosis, and endoplasmic reticulum stress, evidenced by significant changes in the studied parameters and testicular histological damage. Hesperidin nanogel administration significantly inhibited oxidative stress markers, restored luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone levels, and alleviated tissue damage compared to the intoxicated group. It also downregulated the expression level of pro-apoptotic genes Bax, caspase-3, caspase-9, and P38MAPK, while upregulating the expression level of the anti-apoptotic BCL2 gene. Endoplasmic reticulum stress sensors PERK, ATF6, and IRE-α were also downregulated by the nanogel. The chitosan-based nanogel enhanced the delivery and efficacy of poorly bioavailable hesperidin, exhibiting remarkable protective effects against AlCl3 and NaF reproductive toxicity. This innovative nanosystem represents a promising approach to harnessing bioactive phytochemicals with delivery challenges, enabling protective effects against chemical-induced testicular damage.

Proteolysis of mitochondrial calpain-13 in cerebral ischemia-reperfusion injury

Calpains are calcium-dependent cysteine proteases activated by intracellular Ca2+. Although calpains mainly exist in the cytosol, calpain-13 is present in the mitochondria in mouse brains; however, the enzymatic properties and physiological functions of calpain-13 remain unknown. Hence, in this study, we predicted and evaluated the enzymatic properties of calpain-13. Based on our bioinformatic approaches, calpain-13 possessed a catalytic triad and EF-hand domain, similar to calpain-1, a well-studied calpain. Therefore, we hypothesized that calpain-13 had calpain-1-like enzymatic properties; however, calpain-13 was not proteolyzed in C57BL/6J mouse brains. Subsequently, cerebral ischemia/reperfusion (I/R) injury caused proteolysis of mitochondrial calpain-13. Thus, our study showed that mitochondrial calpain-13 was proteolyzed in the mitochondria of the I/R injured mouse brain. This finding could be valuable in further research elucidating the involvement of calpain-13 in cell survival or death in brain diseases, such as cerebral infarction.

Identification of endoplasmic reticulum stress genes in human stroke based on bioinformatics and machine learning

After ischemic stroke (IS), secondary injury is intimately linked to endoplasmic reticulum (ER) stress and body-brain crosstalk. Nonetheless, the underlying mechanism systemic immune disorder mediated ER stress in human IS remains unknown. In this study, 32 candidate ER stress-related genes (ERSRGs) were identified by overlapping MSigDB ER stress pathway genes and DEGs. Three Key ERSRGs (ATF6, DDIT3 and ERP29) were identified using LASSO, random forest, and SVM-RFE. IS patients with different ERSRGs profile were clustered into two groups using consensus clustering and the difference between 2 group was further explored by GSVA. Through immune cell infiltration deconvolution analysis, and middle cerebral artery occlusion (MCAO) mouse scRNA analysis, we found that the expression of 3 key ERSRGs were closely related with peripheral macrophage cell ER stress in IS and this was further confirmed by RT-qPCR experiment. These ERS genes might be helpful to further accurately regulate the central nervous system and systemic immune response through ER stress and have potential application value in clinical practice in IS.

The role of taurine through endoplasmic reticulum in physiology and pathology

Taurine is a sulfur-containing amino acid found in many cell organelles that plays a wide range of biological roles, including bile salt production, osmoregulation, oxidative stress reduction, and neuromodulation. Taurine treatments have also been shown to ameliorate the onset and development of many diseases, including hypertension, fatty liver, neurodegenerative diseases and ischemia-reperfusion injury, by exerting antioxidant, anti-inflammatory, and antiapoptotic effects. The endoplasmic reticulum (ER) is a dynamic organelle involved in a wide range of cellular functions, including lipid metabolism, calcium storage and protein stabilization. Under stress, the disruption of the ER environment leads to the accumulation of misfolded proteins and a characteristic stress response called the unfolded protein response (UPR). The UPR protects cells from stress and helps to restore cellular homeostasis, but its activation promotes cell death under prolonged ER stress. Recent studies have shown that ER stress is closely related to the onset and development of many diseases. This article reviews the beneficial effects and related mechanisms of taurine by regulating the ER in different physiological and pathological states, with the aim of providing a reference for further research and clinical applications.

Uvaol ameliorates lipid deposition in hyperlipidemic hepatocytes by suppressing protein-tyrosine phosphatase 1B/ER stress signaling

Uvaol (UV), a pentacyclic triterpene found in olives and virgin olive oil, is known for its anti-inflammatory and antioxidant effects in various disease models. While olive oil is reported to reduce obesity and insulin resistance, the specific impact of UV on liver lipid metabolism and its molecular mechanisms are not fully understood. In this study, hepatic lipid accumulation was measured using oil red O staining, and protein expression levels in liver cells were assessed via Western blot analysis. Apoptosis was evaluated through cell viability and caspase 3 activity assays. UV treatment reduced lipid accumulation, fatty acid uptake, apoptosis, and ER stress in palmitate-treated liver cells. Additionally, UV enhanced fatty acid oxidation. Mechanistically, increased SIRT6 expression and autophagy were observed in UV-treated cells. SIRT6-targeted siRNA or 3-methyladenine blocked the effects of UV in hyperlipidemic cells. In conclusion, UV improves SIRT6/autophagy signaling, reducing lipid deposition and apoptosis in liver cells under high lipid conditions. This in vitro study provides strong evidence for potential therapeutic strategies for hepatic steatosis.

Pharmacological inhibition of receptor-interacting protein kinase 2 (RIPK2) elicits neuroprotective effects following experimental ischemic stroke

Ischemic stroke induces a debilitating neurological insult, where inflammatory processes contribute greatly to the expansion and growth of the injury. Receptor-interacting protein kinase 2 (RIPK2) is most well-known for its role as the obligate kinase for NOD1/2 pattern recognition receptor signaling and is implicated in the pathology of various inflammatory conditions. Compared to a sham-operated control, ischemic stroke resulted in a dramatic increase in the active, phosphorylated form of RIPK2, indicating that RIPK2 may be implicated in the response to stroke injury. Here, we assessed the effects of pharmacological inhibition of RIPK2 to improve post-stroke outcomes in mice subjected to experimental ischemic stroke. We found that treatment at the onset of reperfusion with a RIPK2 inhibitor, which inhibits the phosphorylation and activation of RIPK2, resulted in marked improvements in post-stroke behavioral outcomes compared to the vehicle-administered group assessed 24 h after stroke. RIPK2 inhibitor-treated mice exhibited dramatic reductions in infarct volume, concurrent with reduced damage to the blood-brain barrier, as evidenced by reduced levels of active matrix metalloproteinase-9 (MMP-9) and leakage of blood-borne albumin in the ipsilateral cortex. To explore the protective mechanism of RIPK2 inhibition, we next pretreated mice with RIPK2 inhibitor or vehicle and examined transcriptomic alterations occurring in the ischemic brain 6 h after stroke. We observed a dramatic reduction in neuroinflammatory markers in the ipsilateral cortex of the inhibitor-treated group while also attaining a comprehensive view of the vast transcriptomic alterations occurring in the brain with inhibitor treatment through bulk RNA-sequencing of the injured cortex. Overall, we provide significant novel evidence that RIPK2 may represent a viable target for post-stroke pharmacotherapy and potentially other neuroinflammatory conditions.

Dietary composition influences sperm quality and testis damage via endoplasmic reticulum stress in lambs

BACKGROUND

The metabolic impacts of including soya meal, wheat gluten and corn gluten in the diet of male lambs could influence their reproductive performance.

OBJECTIVES

An experiment was carried out to assess the effects of corn gluten, wheat gluten and soya meal on the reproductive system of male lambs.

METHODS

Twenty-four male Morkaraman lambs, aged 9 months, were utilized in this study and were fed experimental diets for 56 days. The lambs were divided into a control group (soybean meal + safflower meal), a corn group (corn gluten) and a wheat group (wheat gluten).

RESULTS

The serum follicle-stimulating hormone level of the control group was significantly higher and tumour necrosis factor-alpha (TNF-α) level was lower than the wheat and corn gluten groups (p < 0.05). The lowest malondialdehyde level in testicular tissue was observed in the control group, whereas the highest was in the wheat gluten group (p < 0.05). The glutathione level in the control group was significantly higher than in the other groups (p < 0.05). The corn gluten group showed the highest CHOP and IRE1 levels; the lowest Bcl-2 levels and the highest IL-1B and P2 × 7R levels were found in the wheat group; and the lowest TNF-α levels were in the control group (p < 0.05). Additionally, the study revealed that diet had a significant impact on spermatological parameters of the testis such as diameter, volume and weight (p < 0.05).

CONCLUSIONS

These results concluded that the inclusion of different protein sources in the diet of reproductive male lambs affects the metabolism of testicular tissue.

Exploring the intricacies of calcium dysregulation in ischemic stroke: Insights into neuronal cell death and therapeutic strategies

Calcium ion (Ca2+) dysregulation is one of the main causes of neuronal cell death and brain damage after cerebral ischemia. During ischemic stroke, the ability of neurons to maintain Ca2+ homeostasis is compromised. Ca2+ regulates various functions of the nervous system, including neuronal activity and adenosine triphosphate (ATP) production. Disruptions in Ca2+ homeostasis can trigger a cascade of events, including activation of the unfolded protein response (UPR) pathway, which is associated with endoplasmic reticulum (ER) stress and mitochondrial dysfunction. This response occurs when the cell is unable to manage protein folding within the ER due to various stressors, such as a high influx of Ca2+. Consequently, the UPR is initiated to restore ER function and alleviate stress, but prolonged activation can lead to mitochondrial dysfunction and, ultimately, cell death. Hence, precise regulation of Ca2+ within the cell is mandatory. The ER and mitochondria are two such organelles that maintain intracellular Ca2+ homeostasis through various calcium-operating channels, including ryanodine receptors (RyRs), inositol trisphosphate receptors (IP3Rs), sarco/endoplasmic reticulum calcium ATPases (SERCAs), the mitochondrial Na+/Ca2+ exchanger (NCLX), the mitochondrial calcium uniporter (MCU) and voltage-dependent anion channels (VDACs). These channels utilize Ca2+ sequestering and release mechanisms to maintain intracellular Ca2+ homeostasis and ensure proper cellular function and survival. The present review critically evaluates the significance of Ca2+ and its physiological role in cerebral ischemia. We have compiled recent findings on calcium's role and emerging treatment strategies, particularly targeting mitochondria and the endoplasmic reticulum, to address Ca2+ overload in cerebral ischemia.

Microglia-neuron-vascular interactions in ischemia

Cerebral ischemia is a devastating condition that results in impaired blood flow in the brain leading to acute brain injury. As the most common form of stroke, occlusion of cerebral arteries leads to a characteristic sequence of pathophysiological changes in the brain tissue. The mechanisms involved, and comorbidities that determine outcome after an ischemic event appear to be highly heterogeneous. On their own, the processes leading to neuronal injury in the absence of sufficient blood supply to meet the metabolic demand of the cells are complex and manifest at different temporal and spatial scales. While the contribution of non-neuronal cells to stroke pathophysiology is increasingly recognized, recent data show that microglia, the main immune cells of the central nervous system parenchyma, play previously unrecognized roles in basic physiological processes beyond their inflammatory functions, which markedly change during ischemic conditions. In this review, we aim to discuss some of the known microglia-neuron-vascular interactions assumed to contribute to the acute and delayed pathologies after cerebral ischemia. Because the mechanisms of neuronal injury have been extensively discussed in several excellent previous reviews, here we focus on some recently explored pathways that may directly or indirectly shape neuronal injury through microglia-related actions. These discoveries suggest that modulating gliovascular processes in different forms of stroke and other neurological disorders might have presently unexplored therapeutic potential in combination with neuroprotective and flow restoration strategies.

Hypoxia and its effect on the cellular system

Eukaryotic cells utilize oxygen for different functions of cell organelles owing to cellular survival. A balanced oxygen homeostasis is an essential requirement to maintain the regulation of normal cellular systems. Any changes in the oxygen level are stressful and can alter the expression of different homeostasis regulatory genes and proteins. Lack of oxygen or hypoxia results in oxidative stress and formation of hypoxia inducible factors (HIF) and reactive oxygen species (ROS). Substantial cellular damages due to hypoxia have been reported to play a major role in various pathological conditions. There are different studies which demonstrated that the functions of cellular system are disrupted by hypoxia. Currently, study on cellular effects following hypoxia is an important field of research as it not only helps to decipher different signaling pathway modulation, but also helps to explore novel therapeutic strategies. On the basis of the beneficial effect of hypoxia preconditioning of cellular organelles, many therapeutic investigations are ongoing as a promising disease management strategy in near future. Hence, the present review discusses about the effects of hypoxia on different cellular organelles, mechanisms and their involvement in the progression of different diseases.

Xingnaojing injection alleviates cerebral ischemia/reperfusion injury through regulating endoplasmic reticulum stress in Vivo and in Vitro

Background

Xingnaojing (XNJ) injection, an extract derived from traditional Chinese medicine, is commonly used to treat ischemic stroke (IS). Previous studies have shown that XNJ has the ability to alleviate apoptosis in cerebral ischemia-reperfusion injury. However, the potential mechanisms have not been clarified.

Objective

To identify the neuroprotective effect of XNJ and explore whether XNJ inhibits cell apoptosis associated with endoplasmic reticulum stress (ERS) after IS.

Methods

In this study, cultured hippocampal neurons from mouse embryos and Sprague-Dawley rats were assigned randomly to four groups: sham, model, XNJ, and edaravone. The treatment groups were administered 2 h after modelling. Neurological deficit scores and motor performance tests were performed after 24 h of modelling. Additionally, pathomorphology, cell apoptosis and calcium content were evaluated. To ascertain the expression of ERS proteins, western blotting and polymerase chain reaction were employed.

Results

The results indicated that XNJ treatment resulted in a notable decrease in infarct volume, apoptosis and missteps compared with the model group. XNJ also exhibited improvements in neurological function, grip strength and motor time. The calcium content significantly reduced in XNJ group. The XNJ administration resulted in a reduction in the levels of proteins associated with ERS including CHOP, GRP78, Bax, caspase-12, caspase-9, and cleaved-caspase-3, but an increase of the Bcl-2/Bax ratio. Furthermore, the downregulation of mRNA expression of CHOP, GRP78, caspase-12, caspase-9, and caspase-3 was confirmed in both cultured neurons and rat model.

Conclusion

These findings suggest that XNJ may alleviate apoptosis by modulating the ERS-induced apoptosis pathway, making it a potential novel therapeutic approach for ischemic stroke.

Sevoflurane postconditioning alleviates hypoxic-ischemic brain damage in rats by inhibiting the endoplasmic reticulum stress PERK/ATF4/CHOP pathway

Hypoxic-ischemic brain damage (HIBD) frequently induces cognitive impairments. Investigating the role of sevoflurane postconditioning (SPC) in HIBD, we conducted experiments involving HIBD modeling, SPC treatment, and interventions with the PERK inhibitor GSK2656157 or the PERK activator CCT020312, administered 30 min before modeling, followed by SPC treatment. Behavioral testing using the Morris water maze test and Neurological Deficiency Scale (NDS) was conducted. Additionally, Nissl staining assessed hippocampal CA1 area neuronal density, TUNEL staining evaluated hippocampal CA1 area neuronal apoptosis, and Western blot determined hippocampal CA1 area protein levels, including Bax, Bcl-2, p-PERK/PERK, p-eIF2/eIF2, ATF4, CHOP, GRP78, Bax, and Bcl-2 protein levels. Following SPC treatment, HIBD rats exhibited improved spatial learning and memory abilities, reduced neuronal apoptosis, increased neuronal density in the hippocampal CA1 area, elevated Bcl-2 protein level, decreased Bax protein levels, and decreased levels of endoplasmic reticulum stress pathway related proteins (p-PERK/PERK, p-eIF2/eIF2, ATF4, CHOP and GRP78). Pre-modeling treatment with the PERK inhibitor treatment improved outcomes in HIBD rats. However, pre-modeling treatment with the PERK activator CCT020312 counteracted the protective effects of SPC against HIBD in rats. In conclusion, SPC alleviates neuronal apoptosis in the hippocampus CA1 area of HIBD rats by inhibiting the endoplasmic reticulum stress pathway PERK/ATF4/CHOP, thereby mitigating HIBD in rats.

Linarin ameliorates ischemia-reperfusion injury by the inhibition of endoplasmic reticulum stress targeting AKR1B1

Due to various factors, there is still a lack of effective neuroprotective agents for ischemic stroke in clinical practice. Neuroinflammation and neuronal apoptosis mediated by endoplasmic reticulum stress are some of the important pathological mechanisms in ischemic stroke. Linarin has been reported to have anti-inflammation, antioxidant, and anti-apoptotic effects in myocardial ischemia, osteoarthritis, and kidney disease. Whether it exerts neuroprotective functions in ischemic stroke has not been investigated. The results showed that linarin could reduce the infarct volume in cerebral ischemia animal models, improve the neurological function scores and suppress the expression of inflammatory factors mediating the NF-κB. Meanwhile, it could protect the neurons from OGD/R-induced-apoptosis, which was related to the PERK-eIF2α pathway. Our results suggested linarin could inhibit neuronal inflammation and apoptosis induced by endoplasmic reticulum stress. Furthermore, the neuroprotective effect of linarin may be related to the inhibition of AKR1B1. Our study offers new insight into protecting against ischemia-reperfusion injury by linarin treatment in stroke.

Alleviating CB2-Dependent ER Stress and Mitochondrial Dysfunction Improves Chronic Cerebral Hypoperfusion-Induced Cognitive Impairment

Augmentation of endoplasmic reticulum (ER) stress may trigger excessive oxidative stress, which induces mitochondrial dysfunction. The fatty acid amide hydrolase inhibitor, URB597, shows anti-oxidation characteristics in multiple neurological disorders. The present study aimed to determine whether inhibition of ER stress was involved in the protective effects of URB597 against chronic cerebral hypoperfusion (CCH)-induced cognitive impairment. Hippocampal HT-22 cells were exposed to oxygen-glucose deprivation. The cell viability, apoptosis, ER stress, mitochondrial ATP, and oxidative stress levels were assessed following treatment with URB597, benzenebutyric acid (4-PBA), and thapsigargin (TG). Furthermore, the effects of URB597 on ER stress and related pathways were investigated in the CCH animal model, including Morris water maze testing of cognition, western blotting analysis of ER stress signaling, and transmission electron microscopy of mitochondrial and ER ultrastructure changes. The results suggested that cerebral ischemia caused ER stress with upregulation of ER stress signaling-related proteins, mitochondrial dysfunction, neuronal apoptosis, ultrastructural injuries of mitochondria-associated ER membranes, and cognitive decline. Co-immunoprecipitation experiments confirmed the interaction between CB2 and β-Arrestin1. Inhibiting ER stress by URB597 improved these changes by activating CB2/β-Arrestin1 signaling, which was reversed by the CB2 antagonist, AM630. Together, the results identified a novel mechanism of URB597, involving CCH-induced cognitive impairment alleviation of CB2-dependent ER stress and mitochondrial dysfunction. Furthermore, this study identified CB2 as a potential target for therapy of ischemic cerebrovascular diseases.

Selenium Nanoparticles in Protecting the Brain from Stroke: Possible Signaling and Metabolic Mechanisms

Strokes rank as the second most common cause of mortality and disability in the human population across the world. Currently, available methods of treating or preventing strokes have significant limitations, primarily the need to use high doses of drugs due to the presence of the blood-brain barrier. In the last decade, increasing attention has been paid to the capabilities of nanotechnology. However, the vast majority of research in this area is focused on the mechanisms of anticancer and antiviral effects of nanoparticles. In our opinion, not enough attention is paid to the neuroprotective mechanisms of nanomaterials. In this review, we attempted to summarize the key molecular mechanisms of brain cell damage during ischemia. We discussed the current literature regarding the use of various nanomaterials for the treatment of strokes. In this review, we examined the features of all known nanomaterials, the possibility of which are currently being studied for the treatment of strokes. In this regard, the positive and negative properties of nanomaterials for the treatment of strokes have been identified. Particular attention in the review was paid to nanoselenium since selenium is a vital microelement and is part of very important and little-studied proteins, e.g., selenoproteins and selenium-containing proteins. An analysis of modern studies of the cytoprotective effects of nanoselenium made it possible to establish the mechanisms of acute and chronic protective effects of selenium nanoparticles. In this review, we aimed to combine all the available information regarding the neuroprotective properties and mechanisms of action of nanoparticles in neurodegenerative processes, especially in cerebral ischemia.

Biomimetic nanoparticles in ischemic stroke therapy

Abstract

Ischemic stroke is one of the most severe neurological disorders with limited therapeutic strategies. The utilization of nanoparticle drug delivery systems is a burgeoning field and has been widely investigated. Among these, biomimetic drug delivery systems composed of biogenic membrane components and synthetic nanoparticles have been extensively highlighted in recent years. Biomimetic membrane camouflage presents an effective strategy to prolong circulation, reduce immunogenicity and enhance targeting. For one thing, biomimetic nanoparticles reserve the physical and chemical properties of intrinsic nanoparticle. For another, the biological functions of original source cells are completely inherited. Compared to conventional surface modification methods, this approach is more convenient and biocompatible. In this review, membrane-based nanoparticles derived from different donor cells were exemplified. The prospect of future biomimetic nanoparticles in ischemic stroke therapy was discussed.

Graphic abstract

Melissa officinalis extract suppresses endoplasmic reticulum stress-induced apoptosis in the brain of hypothyroidism-induced rats exposed to γ-radiation

The purpose of this study was to demonstrate the neuroprotective effect of Melissa officinalis extract (MEE) against brain damage associated with hypothyroidism induced by propylthiouracil (PTU) and/or γ-radiation (IR) in rats. Hypothyroidism induction and/or exposure to IR resulted in a significant decrease in the serum levels of T3 and T4 associated with increased levels of lipid peroxidation end product, malondialdehyde (MDA), and nitrites (NO) in the brain tissue homogenate. Also, hypothyroidism and /or exposure to IR markedly enhance the endoplasmic reticulum stress by upregulating the gene expressions of the protein kinase RNA-like endoplasmic reticulum kinase (PERK), activated transcription factor 6 (ATF6), endoplasmic reticulum-associated degradation (ERAD), and CCAAT/enhancer-binding protein homologous protein (CHOP) in the brain tissue homogenate associated with a proapoptotic state which indicated by the overexpression of Bax, BCl2, and caspase-12 that culminates in brain damage. Meanwhile, the PTU and /or IR-exposed rats treated with MEE reduced oxidative stress and ERAD through ATF6. Also, the MEE treatment prevented the Bax and caspase-12 gene expression from increasing. This treatment in hypothyroid animals was associated with neuronal protection as indicated by the downregulation in the gene expressions of the microtubule-associated protein tau (MAPT) and amyloid precursor protein (APP) in the brain tissue. Furthermore, the administration of MEE ameliorates the histological structure of brain tissue. In conclusion, MEE might prevent hypothyroidism-induced brain damage associated with oxidative stress and endoplasmic reticulum stress.

Phenothiazines reduced autophagy in ischemic stroke through endoplasmic reticulum (ER) stress-associated PERK-eIF2α pathway

BACKGROUND

Neuroprotective effects have been the main focus of new treatment modalities for ischemic stroke. Phenothiazines, or chlorpromazine plus promethazine (C + P), are known to prevent the generation of free radicals and uptake of Ca2+ by plasma membrane; they have a potential as a treatment for acute ischemic stroke (AIS). This study aims to investigate the role of endoplasmic reticulum (ER) stress-associated PERK-eIF2α pathway underlying the phenothiazine-induced neuroprotective effects after cerebral ischemia/reperfusion (I/R) injury.

METHODS

A total of 49 male Sprague Dawley rats (280-320 g) were randomly divided into 4 groups (n = 7 per group): (1) sham, (2) I/R that received 2 h of middle cerebral artery occlusion (MCAO), followed by 6 or 24 h of reperfusion, (3) MCAO treated by C + P without temperature control and (4) MCAO treated by C + P with temperature control. Human neuroblastoma (SH-SY5Y) cells were used in 5 groups: (1) control, (2) oxygen-glucose deprivation (OGD) for 2 h followed by reoxygenation (OGD/R), (3) OGD/R with C + P; (4) OGD/R with PERK inhibitor, GSK2656157, and (5) OGD/R with C + P and GSK2656157. The molecules of ER stress, unfolded protein response (UPR) (Bip, PERK, p-PERK, p-PERK/PERK, eIF2α, p-eIF2α, p-eIF2α/eIF2α), autophagy (ATG12, LC3II/I), and apoptosis (BAX, Bcl-XL) were measured at mRNA levels by real time PCR and protein levels by Western blotting.

RESULTS

In ischemic rats followed by reperfusion, expression of Bip, p-PERK/PERK, p-eIF2α/eIF2α, ATG12, and LC3II/I, as well as BAX were all significantly increased. These markers were significantly reduced by C + P at both 6 and 24 h of reperfusion. Anti-apoptotic Bcl-XL expression was increased, while pro-apoptotic BAX expression was decreased by C + P. In SH-SY5Y cell lines, both C + P and GSK2656157 significantly reduced the level of autophagy and apoptosis after I/R, respectively. The combination of GSK2656157 and C + P did not promote the same effect, suggesting that C + P did not induce any neuroprotective effect by inhibiting autophagy and apoptosis through the PERK-eIF2α pathway when this pathway was already blocked by GSK2656157. In general, the reduction in body temperature by phenothiazines was associated with better neuroprotection but it did not reach significant levels.

CONCLUSION

The combined treatment of C + P plays a crucial role in stroke therapy by inhibiting ER stress-mediated autophagy, thereby leading to reduced apoptosis and increased neuroprotection. Our findings highlight the PERK-eIF2α pathway as a central mechanism through which C + P exerts its beneficial effects. The results from this study may pave the way for the development of more targeted and effective treatments for stroke patients.

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.

Cross-talk between bioactive lipid mediators and the unfolded protein response in ischemic stroke

Ischemic cerebral stroke is a severe medical condition that affects about 15 million people every year and is the second leading cause of death and disability globally. Ischemic stroke results in neuronal cell death and neurological impairment. Current therapies may not adequately address the deleterious metabolic changes and may increase neurological damage. Oxygen and nutrient depletion along with the tissue damage result in endoplasmic reticulum (ER) stress, including the Unfolded Protein Response (UPR), and neuroinflammation in the affected area and cause cell death in the lesion core. The spatio-temporal production of lipid mediators, either pro-inflammatory or pro-resolving, decides the course and outcome of stroke. The modulation of the UPR as well as the resolution of inflammation promotes post-stroke cellular viability and neuroprotection. However, studies about the interplay between the UPR and bioactive lipid mediators remain elusive and this review gives insights about the crosstalk between lipid mediators and the UPR in ischemic stroke. Overall, the treatment of ischemic stroke is often inadequate due to lack of effective drugs, thus, this review will provide novel therapeutical strategies that could promote the functional recovery from ischemic stroke.

Modulation of the autophagy-lysosomal pathway and endoplasmic reticulum stress by ketone bodies in experimental models of stroke

Ischemic stroke is a leading cause of disability worldwide. There is no simple treatment to alleviate ischemic brain injury, as thrombolytic therapy is applicable within a narrow time window. During the last years, the ketogenic diet (KD) and the exogenous administration of the ketone body β-hydroxybutyrate (BHB) have been proposed as therapeutic tools for acute neurological disorders and both can reduce ischemic brain injury. However, the mechanisms involved are not completely clear. We have previously shown that the D enantiomer of BHB stimulates the autophagic flux in cultured neurons exposed to glucose deprivation (GD) and in the brain of hypoglycemic rats. Here, we have investigated the effect of the systemic administration of D-BHB, followed by its continuous infusion after middle cerebral artery occlusion (MCAO), on the autophagy-lysosomal pathway and the activation of the unfolded protein response (UPR). Results show for the first time that the protective effect of BHB against MCAO injury is enantiomer selective as only D-BHB, the physiologic enantiomer of BHB, significantly reduced brain injury. D-BHB treatment prevented the cleavage of the lysosomal membrane protein LAMP2 and stimulated the autophagic flux in the ischemic core and the penumbra. In addition, D-BHB notably reduced the activation of the PERK/eIF2α/ATF4 pathway of the UPR and inhibited IRE1α phosphorylation. L-BHB showed no significant effect relative to ischemic animals. In cortical cultures under GD, D-BHB prevented LAMP2 cleavage and decreased lysosomal number. It also abated the activation of the PERK/eIF2α/ATF4 pathway, partially sustained protein synthesis, and reduced pIRE1α. In contrast, L-BHB showed no significant effects. Results suggest that protection elicited by D-BHB treatment post-ischemia prevents lysosomal rupture allowing functional autophagy, preventing the loss of proteostasis and UPR activation.

Metal-Binding Proteins Cross-Linking with Endoplasmic Reticulum Stress in Cardiovascular Diseases

The endoplasmic reticulum (ER), an essential organelle in eukaryotic cells, is widely distributed in myocardial cells. The ER is where secreted protein synthesis, folding, post-translational modification, and transport are all carried out. It is also where calcium homeostasis, lipid synthesis, and other processes that are crucial for normal biological cell functioning are regulated. We are concerned that ER stress (ERS) is widespread in various damaged cells. To protect cells' function, ERS reduces the accumulation of misfolded proteins by activating the unfolded protein response (UPR) pathway in response to numerous stimulating factors, such as ischemia or hypoxia, metabolic disorders, and inflammation. If these stimulatory factors are not eliminated for a long time, resulting in the persistence of the UPR, it will aggravate cell damage through a series of mechanisms. In the cardiovascular system, it will cause related cardiovascular diseases and seriously endanger human health. Furthermore, there has been a growing number of studies on the antioxidative stress role of metal-binding proteins. We observed that a variety of metal-binding proteins can inhibit ERS and, hence, mitigate myocardial damage.

Mitochondria associated ER membrane and cerebral ischemia: molecular mechanisms and therapeutic strategies

Endoplasmic reticulum (ER) and mitochondria are two important organelles that are highly dynamic in mammalian cells. The physical connection between them is mitochondria associated ER membranes (MAM). In recent years, studies on endoplasmic reticulum and mitochondria have shifted from independent division to association and comparison, especially MAM has gradually become a research hotspot. MAM connects the two organelles, not only to maintain their independent structure and function, but also to promote metabolism and signal transduction between them. This paper reviews the morphological structure and protein localization of MAM, and briefly analyzes the functions of MAM in regulating Ca²⁺ transport, lipid synthesis, mitochondrial fusion and fission, endoplasmic reticulum stress and oxidative stress, autophagy and inflammation. Since ER stress and mitochondrial dysfunction are important pathological events in neurological diseases including ischemic stroke, MAM is likely to play an important role in cerebral ischemia by regulating the signaling of the two organelles and the crosstalk of the two pathological events.

Arbutin abrogates testicular ischemia/reperfusion injury in rats through repression of inflammation and ER stress

The aim of this study was to investigate the effects of arbutin (ARB) administration on oxidative stress, inflammation, endoplasmic reticulum (ER) stress and apoptosis in an experimental testicular torsion/detorsion (T/D)-induced testicular injury model for the first time. A total of 24 male Sprague-Dawley rats were divided into four groups with six rats in each group: sham control, T/D, T/D+ARB (50 mg/kg) and T/D+ARB (100 mg/kg). Torsion and detorsion times were applied as 4 h and 2 h, respectively. The levels of lipid peroxidation [malondialdehyde (MDA)] and oxidative stress [total oxidant status (TOS) and total antioxidant status (TAS)] in testicular tissues were determined using colorimetric methods. The levels of DNA damage [8-hydroxy-2'-deoxyguanosine (8-OHdG)], antioxidant system [superoxide dismutase (SOD) and catalase (CAT)], pro-inflammatory cytokines [high mobility group box 1 (HMGB1), nuclear factor kappa B protein 65 (NF-κB p65), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and myeloperoxidase (MPO)], ER stress [78-kDa glucose-regulated protein (GRP78), activating transcription factor 6 (ATF6) and CCAAT-enhancer-binding protein homologous protein (CHOP)] and apoptosis (caspase-3) markers in testicular tissues were determined using commercial enzyme-linked immunosorbent assay (ELISA) kits. Johnsen's testicle scoring system was used for histological evaluation. In the T/D group, it was determined that statistically significant increasing in the levels of oxidative stress, inflammation, ER stress and apoptosis compared with sham control group (p < 0.05). ARB administrations statistically significantly restored testicular I/R damage in a dose dependent manner (p < 0.05). In addition, it was determined that the data of histological examinations supported the biochemical results. Our findings support the hypothesis that ARB may be used as a protective agent against T/D-induced testicular damage.

Pre-ischaemic Treatment with Enriched Environment Alleviates Acute Neuronal Injury by Inhibiting Endoplasmic Reticulum Stress-dependent Autophagy and Apoptosis

Enriched environment (EE) is effective in preventing cerebral ischemia-reperfusion (I/R) injury. However, little is known about the mechanism underlying the neuroprotection of EE preprocessing. Endoplasmic reticulum (ER) stress has been demonstrated to be extensively involved in I/R injury. We aimed to investigate the potential regulatory mechanism of ER stress in the neuroprotection of pre-ischemic EE. Rats were subjected to middle cerebral artery occlusion (MCAO) or sham surgery after 4 weeks of exposure in standard or enriched environments. We found that EE pretreatment alleviates acute neuronal injury after MCAO, as shown by reduced infarct volume and neurological deficit score. The expression of ER stress-related proteins, markers of autophagy, and apoptosis were detected to investigate the underlying mechanism. Our results showed that pre-ischemic EE inhibited the ER stress, as evidenced by the inactivation of activating transcription factor 6 (ATF6), protein kinase RNA (PKR)-like ER kinase (PERK), and inositol-requiring enzyme 1 (IRE1) pathways. Moreover, the rats reared in EE were detected with lower autophagic activity and apoptosis levels. The decrease in activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), and phospho-c-Jun N-terminal kinases (p-JNK) expression suggested EE pretreatment might inhibit autophagy and apoptosis via modulating ER stress-mediated PERK-ATF4-CHOP and IRE1-JNK signal pathways, which provides a new idea for the prevention of the deleterious cerebral and functional consequences of ischemic stroke.

PHLDA1 knockdown alleviates mitochondrial dysfunction and endoplasmic reticulum stress-induced neuronal apoptosis via activating PPARγ in cerebral ischemia-reperfusion injury

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress occur in ischemic stroke. The disruption of these two organelles can directly lead to cell death through various signaling pathways. Thus, investigation of the associated molecular mechanisms in cerebral ischemia is a prerequisite for stroke treatment. Pleckstrin homology-like domain family A member 1 (PHLDA1) is a multifunctional protein that can modulate mitochondrial function and ER stress in cardiomyocyte and cancer cells. This work studied the role of PHLDA1 in cerebral ischemic/reperfusion (I/R) injury and explored the underlying mechanisms associated with mitochondrial functions and ER stress. Middle cerebral artery occlusion/reperfusion (MCAO/R)-treated mice and oxygen-glucose deprivation/reoxygenation (OGD/R)-stimulated neurons were used as I/R models in vivo and in vitro, respectively. PHLDA1 was upregulated in ischemic penumbra of MCAO/R-induced mice and OGD/R-exposed neurons. In vitro, PHLDA1 knockdown protected neurons from OGD/R-induced apoptosis. In vivo, PHLDA1 silencing facilitated functional recovery and reduced cerebral infarct volume. Mechanistically, PHLDA1 knockdown promoted PPARγ nuclear translocation, which may mediate the effects on reversion of mitochondrial functions and alleviation of ER stress. In summary, PHLDA1 knockdown alleviates neuronal ischemic injuries in mice. PPARγ activation and mitochondrial dysfunction and endoplasmic reticulum stress attenuation are involved in the underlying mechanisms.

PERK inhibitor, GSK2606414, ameliorates neuropathological damage, memory and motor functional impairments in cerebral ischemia via PERK/p-eIF2ɑ/ATF4/CHOP signaling

The protein kinase R-like endoplasmic reticulum kinase/eukaryotic initiation factor 2ɑ (PERK/eIF2α), the branch of unfolded protein response (UPR), is responsible for transient arrest in translation to counter the enhanced levels of misfolded or unfolded proteins in the endoplasmic reticulum (ER) following any acute condition. In neurological disorders, overactivation of PERK-P/eIF2-P signaling, leads to a prolonged decline in global protein synthesis resulting in synaptic failure and neuronal death. Our study has shown, PERK/ATF4/CHOP pathway gets activated following cerebral ischemia in rats. We have further demonstrated, PERK inhibitor, GSK2606414 ameliorates ischemia induced neuronal damage by preventing additional neuronal loss, minimizing brain infarct, reducing brain edema, and preventing neurological symptoms from appearing. GSK2606414 was found to improve the neurobehavioral deficits and reduce the pyknotic neurons in ischemic rats. Also, it decreased glial activation and apoptotic protein mRNA expression while enhanced the synaptic protein mRNA expression in rat brain following cerebral ischemia. In conclusion, our findings suggest that PERK/ATF4/CHOP activation play a vital role in cerebral ischemia. Thus, PERK inhibitor, GSK2606414 might be a potential neuroprotective agent in cerebral ischemia.

Salubrinal Ameliorates Inflammation and Neovascularization via the Caspase 3/Enos Signaling in an Alkaline-Induced Rat Corneal Neovascularization Model

Background and Objectives: Ocular alkaline burn is a clinical emergency that can cause permanent vision loss due to limbal stem cell deficiency and corneal neovascularization (CNV). Although the basic pathogenetic mechanisms are considered to be acute oxidative stress and corneal neovascularization triggered by inflammation, the underlying intracellular mechanisms have not been clearly elucidated. The aim of this study was to investigate the role of endoplasmic reticulum (ER) stress on inflammation and neovascularization, and the effect of the ER stress inhibitor salubrinal (SLB), as a novel treatment in a corneal alkaline burn model in rats. Methods: Chemical burns were created by cautery for 4 s using a rod coated with 75% silver nitrate and 25% potassium nitrate in the corneal center for the corneal neovascularization (CNV) model. Twenty-eight Wistar albino rats were divided into four groups: SHAM, CNV, CNV + SLB, and CNV + bevacizumab (BVC). After the CNV model was applied to the right eye, a single subconjunctival dose (0.05 mL) of 1 mg/kg salubrinal was injected into both eyes in the CNV + SLB group. A total of 1.25 mg/mL of subconjunctival BVC was administered to the CNV + BVC group. Fourteen days after experimental modeling and drug administration, half of the globes were placed in liquid nitrogen and stored at -20 °C until biochemical analysis. The remaining tissues were collected and fixed in 10% buffered formalin for histopathological and immunohistochemical analysis. Three qualitative agents from three different pathways were chosen: TNFR for inflammation, endothelial nitric oxide synthase (e-NOS) for vascular endothelial growth factor (VEGF)-mediated vascular permeability, and caspase-3 for cellular apoptosis. Results: Significantly lower caspase-3 and eNOS levels were detected in the CNV + SLB and CNV + BVC groups than in the CNV group. Additionally, histopathological evaluation revealed a significant decrease in neovascularization, inflammatory cell infiltration, and fibroblast activity in the CNV + SLB and CNV + BVC groups. The endoplasmic reticulum stress inhibitor, salubrinal, administered to the treatment group, attenuated apoptosis (caspase-3) and inflammation (e-NOS). In the control group (left eyes of the SLB group), salubrinal did not have a toxic effect on the healthy corneas. Conclusion: The ER stress pathway plays an important role in angiogenesis after alkaline corneal burns, and treatment with SLB modulates this pathway, reducing caspase-3 and eNOS levels. Further studies are needed to understand the molecular mechanisms altered by SLB-mediated therapy. The fact that more than one mechanism plays a role in the pathogenesis of CNV may require the use of more than one molecule in treatment. SLB has the potential to affect multiple steps in CNV pathogenesis, both in terms of reducing ER stress and regulating cellular homeostasis by inhibiting the core event of integrated stress response (ISR). Therefore, it can be used as a new treatment option and as a strengthening agent for existing treatments. Although blockade of intracellular organelle stress pathways has shown promising results in experimental studies, more in-depth research is needed before it can be used in routine practice. To the best of our knowledge, this study is the first to report the role of ER stress in corneal injury.

Mechanism of cis-Nerolidol-Induced Bladder Carcinoma Cell Death

Nerolidol is a naturally occurring sesquiterpene alcohol with multiple properties, including antioxidant, antibacterial, and antiparasitic activities. A few studies investigating the antitumor properties of nerolidol have shown positive results in both cell culture and mouse models. In this study, we investigated the antitumor mechanism of cis-nerolidol in bladder carcinoma cell lines. The results of our experiments on two bladder carcinoma cell lines revealed that nerolidol inhibited cell proliferation and induced two distinct cell death pathways. We confirmed that cis-nerolidol induces DNA damage and ER stress. A mechanistic study identified a common cAMP, Ca²⁺, and MAPK axis involved in signal propagation and amplification, leading to ER stress. Inhibition of any part of this signaling cascade prevented both cell death pathways. The two cell death mechanisms can be distinguished by the involvement of caspases. The early occurring cell death pathway is characterized by membrane blebbing and cell swelling followed by membrane rupture, which can be prevented by the inhibition of caspase activation. In the late cell death pathway, which was found to be caspase-independent, cytoplasmic vacuolization and changes in cell shape were observed. cis-Nerolidol shows promising antitumor activity through an unorthodox mechanism of action that could help target resistant forms of malignancies, such as bladder cancer.

Targeted Brain Delivery of Dendrimer-4-Phenylbutyrate Ameliorates Neurological Deficits in a Long-Term ABCD1-Deficient Mouse Model of X-Linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a genetic disorder that presents neurologically as either a rapid and fatal cerebral demyelinating disease in childhood (childhood cerebral adrenoleukodystrophy; ccALD) or slow degeneration of the spinal cord in adulthood (adrenomyeloneuropathy; AMN). All forms of ALD result from mutations in the ATP Binding Cassette Subfamily D Member (ABCD) 1 gene, encoding a peroxisomal transporter responsible for the import of very long chain fatty acids (VLCFA) and results mechanistically in a complex array of dysfunction, including endoplasmic reticulum stress, oxidative stress, mitochondrial dysfunction, and inflammation. Few therapeutic options exist for these patients; however, an additional peroxisomal transport protein (ABCD2) has been successfully targeted previously for compensation of dysfunctional ABCD1. 4-Phenylbutyrate (4PBA), a potent activator of the ABCD1 homolog ABCD2, is FDA approved, but use for ALD has been stymied by a short half-life and thus a need for unfeasibly high doses. We conjugated 4PBA to hydroxyl polyamidoamine (PAMAM) dendrimers (D-4PBA) to a create a long-lasting and intracellularly targeted approach which crosses the blood-brain barrier to upregulate Abcd2 and its downstream pathways. Across two studies, Abcd1 knockout mice administered D-4PBA long term showed neurobehavioral improvement and increased Abcd2 expression. Furthermore, when the conjugate was administered early, significant reduction of VLCFA and improved survival of spinal cord neurons was observed. Taken together, these data show improved efficacy of D-4PBA compared to previous studies of free 4PBA alone, and promise for D-4PBA in the treatment of complex and chronic neurodegenerative diseases using a dendrimer delivery platform that has shown successes in recent clinical trials. While recovery in our studies was partial, combined therapies on the dendrimer platform may offer a safe and complete strategy for treatment of ALD.

Vanillic acid attenuates testicular ischemia/reperfusion injury in rats

Background

Testicular torsion is an important pediatric problem and ischemia/reperfusion injury (IRI) is involved in its etiopathogenesis. Vanillic acid (VA) is a phenolic acid has strong antioxidant properties. To our knowledge, the ability of VA to reduce testicular IRI has not been previously investigated. It was therefore aimed to evaluate whether VA had a beneficial effect against testicular IRI model in rats for the first time. Twenty-four rats were segregated into four groups: sham control, torsion/detorsion (T/D), T/D + VA (50 mg/kg and 100 mg/kg). The levels of testicular oxidative stress, inflammation, endoplasmic reticulum (ER) stress and apoptosis markers were determined using colorimetric methods. Hematoxylin–eosin staining method was used in the histopathological evaluation.

Results

Oxidative stress, inflammation, ER stress and apoptosis levels were significantly higher in testicular tissues of rats with only IRI model (p < 0.05). VA applications improved these injuries in a dose-dependent manner (p < 0.05). Moreover, it was found that the results of histological examinations supported the biochemical results to a statistically significant extent.

Conclusions

It was revealed that VA application can remove testicular IRI for the first time. This testicular protective efficacy of VA needs to be supported by more extensive preclinical studies.

Gut microbiota in ischemic stroke: Where we stand and challenges ahead

Gut microbiota is increasingly recognized to affect host health and disease, including ischemic stroke (IS). Here, we systematically review the current understanding linking gut microbiota as well as the associated metabolites to the pathogenesis of IS (e.g., oxidative stress, apoptosis, and neuroinflammation). Of relevance, we highlight that the implications of gut microbiota-dependent intervention could be harnessed in orchestrating IS.

AA147 ameliorates post-cardiac arrest cerebral ischemia/reperfusion injury through the co-regulation of the ATF6 and Nrf2 signaling pathways

Ischemia/reperfusion caused by cardiac arrest (CA) disturbs endoplasmic reticulum (ER) homeostasis and redox balance in neurons. AA147, originally developed as a pharmacologic activator of the activating transcription factor 6 (ATF6), can protect multiple tissues from ischemia/reperfusion injury (IRI) by decreasing reactive oxygen species (ROS) and restoring ER function. However, it is unclear whether pharmacologic treatment of AA147 could ameliorate post-CA cerebral IRI and whether it is associated with proteostasis regulation and anti-oxidative stress mechanism. In the present study, mice were subjected to 9 min-CA surgery followed by cardiopulmonary resuscitation (CPR). AA147 or vehicle was administered 1 day before the operation and 15 min after the return of spontaneous circulation. We found that AA147 restored neurological function and reduced dead neurons in mice suffering from CA. Moreover, AA147 inhibited CA/CPR-caused neuronal apoptosis and ER stress, indicated by reduced TUNEL-positive neurons, surged expression of Bcl-2/Bax, and down expression of cleaved caspase-3, caspase-12, C/EBP homologous protein (CHOP). The expression of ATF6 and its regulated gene glucose-regulated protein 78 (GRP78) increased significantly after the administration of AA147, suggesting the activation of the ATF6 pathway. In addition, AA147 also alleviated the upsurge of the ROS generation and MDA levels as well as increased SOD activity, accompanied by enhancement of the nuclear factor E2-related factor 2 (Nrf2) and its modulated heme-oxygenase-1 (HO-1) expressions. Cotreatment of AA147 with inhibitors of the ATF6 or Nrf2 significantly suppressed AA147-dependent reductions in ROS scavenging and neuronal death after CA/CPR. The results suggested that AA147 could confer neuroprotection against post-CA cerebral IRI through inhibition of oxidative stress along with ER stress-associated apoptosis, which is attributed to the coregulation of both ATF6 and Nrf2 signaling pathways activity. Our findings support the potential for AA147 as a therapeutic approach to improve post-CA brain injury.

Research progress on astrocyte autophagy in ischemic stroke

Ischemic stroke is a highly disabling and potentially fatal disease. After ischemic stroke, autophagy plays a key regulatory role as an intracellular catabolic pathway for misfolded proteins and damaged organelles. Mounting evidence indicates that astrocytes are strongly linked to the occurrence and development of cerebral ischemia. In recent years, great progress has been made in the investigation of astrocyte autophagy during ischemic stroke. This article summarizes the roles and potential mechanisms of astrocyte autophagy in ischemic stroke, briefly expounds on the crosstalk of astrocyte autophagy with pathological mechanisms and its potential protective effect on neurons, and reviews astrocytic autophagy-targeted therapeutic methods for cerebral ischemia. The broader aim of the report is to provide new perspectives and strategies for the treatment of cerebral ischemia and a reference for future research on cerebral ischemia.

Integrative Analyses of Biomarkers Associated with Endoplasmic Reticulum Stress in Ischemic Stroke

Background. Neuronal apoptosis, which is the primary pathological transform of cerebral injury following ischemic stroke (IS), is considered to be induced by endoplasmic reticulum stress (ERS) by numerous reports. However, ERS biomarkers in IS have not been fully identified yet. Consequently, the present study is aimed at exploring potential blood biomarkers by investigating the molecular mechanisms of ERS promoting neuronal apoptosis following IS development. Methods. A comprehensive analysis was performed with two free-accessible whole-blood datasets (GSE16561 and GSE37587) from the Gene Expression Omnibus database. Genetic information from 107 IS and 24 healthy controls was employed to analyze the differentially expressed genes (DEGs). Genes related to ERS (ERS-DEGs) were identified from the analysis. Enrichment analyses were performed to explore the biofunction and correlated signal pathways of ERS-DEGs. Protein-protein interaction (PPI) network and immune correlation analyses were performed to identify the hub genes along with their correspondent expressions and functions, all of which contributed to incremental diagnostic values. Results. A total of 60 IS-related DEGs were identified, of which 27 genes were confirmed as ERS-DEGs. GO and KEGG enrichment analysis corroborated that upregulated ERS-DEGs were principally enriched in pathways related to immunity, including neutrophil activation and Th17 cell differentiation. Moreover, the GSEA and GSVA indicated that T cell-related signal pathways were the most considerably immune pathways for ERS-DEG enrichment. A total of 10 hub genes were filtered out via the PPI network analysis. Immune correlation analysis confirmed that the expression of hub genes is associated with immune cell infiltration. Conclusions. By integrating and analyzing the two gene expression data profiles, it can be inferred that ERS may be involved in the development of neuronal apoptosis following IS via immune homeostasis. The identified hub genes, which are associated with immune cell infiltration, may serve as potential biomarkers for relative diagnosis and therapy.

Protein disulfide isomerase A6 promotes the repair of injured nerve through interactions with spastin

The maintenance of appropriate endoplasmic reticulum (ER) homeostasis is critical to effective spinal cord injury (SCI) repair. In previous reports, protein disulfide isomerase A6 (PDIA6) demonstrated to serve as a reversible functional modulator of ER stress responses, while spastin can coordinate ER organization through the modulation of the dynamic microtubule network surrounding this organelle. While both PDIA6 and spastin are thus important regulators of the ER, whether they interact with one another for SCI repair still needs to be determined. Here a proteomics analysis identified PDIA6 as being related to SCI repair, and protein interaction mass spectrometry further confirmed the ability of PDIA6 and spastin to interact with one another. Pull-down and co-immunoprecipitation assays were further performed to validate and characterize the interactions between these two proteins. The RNAi-based knockdown of PDIA6 in COS-7 cells inhibited the activity of spastin-dependent microtubule severing. PDIA6 was also found to promote injured neuron repair, while spastin knockdown reversed this reparative activity. Together, these results thus confirm that PDIA6 and spastin function together as critical mediators of nerve repair, highlighting their potential value as validated targets for efforts to promote SCI repair.

GANAB and N-Glycans Substrates Are Relevant in Human Physiology, Polycystic Pathology and Multiple Sclerosis: A Review

Glycans are one of the four fundamental macromolecular components of living matter, and they are highly regulated in the cell. Their functions are metabolic, structural and modulatory. In particular, ER resident N-glycans participate with the Glc3Man9GlcNAc2 highly conserved sequence, in protein folding process, where the physiological balance between glycosylation/deglycosylation on the innermost glucose residue takes place, according GANAB/UGGT concentration ratio. However, under abnormal conditions, the cell adapts to the glucose availability by adopting an aerobic or anaerobic regimen of glycolysis, or to external stimuli through internal or external recognition patterns, so it responds to pathogenic noxa with unfolded protein response (UPR). UPR can affect Multiple Sclerosis (MS) and several neurological and metabolic diseases via the BiP stress sensor, resulting in ATF6, PERK and IRE1 activation. Furthermore, the abnormal GANAB expression has been observed in MS, systemic lupus erythematous, male germinal epithelium and predisposed highly replicating cells of the kidney tubules and bile ducts. The latter is the case of Polycystic Liver Disease (PCLD) and Polycystic Kidney Disease (PCKD), where genetically induced GANAB loss affects polycystin-1 (PC1) and polycystin-2 (PC2), resulting in altered protein quality control and cyst formation phenomenon. Our topics resume the role of glycans in cell physiology, highlighting the N-glycans one, as a substrate of GANAB, which is an emerging key molecule in MS and other human pathologies.

Intertwined Relation between the Endoplasmic Reticulum and Mitochondria in Ischemic Stroke

In ischemic stroke (IS), accumulation of the misfolded proteins in the endoplasmic reticulum (ER) and mitochondria-induced oxidative stress (OS) has been identified as the indispensable inducers of secondary brain injury. With the increasing recognition of an association between ER stress and OS with ischemic stroke and with the improved understanding of the underlying molecular mechanism, novel targets for drug therapy and new strategies for therapeutic interventions are surfacing. This review discusses the molecular mechanism underlying ER stress and OS response as both causes and consequences of ischemic stroke. We also summarize the latest advances in understanding the importance of ER stress and OS in the pathogenesis of ischemic stroke and discuss potential strategies and clinical trials explicitly aiming to restore mitochondria and ER dynamics after IS.

The Impact of Genetic Polymorphisms in Glutamate-Cysteine Ligase, a Key Enzyme of Glutathione Biosynthesis, on Ischemic Stroke Risk and Brain Infarct Size

The purpose of this pilot study was to explore whether polymorphisms in genes encoding the catalytic (GCLC) and modifier (GCLM) subunits of glutamate-cysteine ligase, a rate-limiting enzyme in glutathione synthesis, play a role in the development of ischemic stroke (IS) and the extent of brain damage. A total of 1288 unrelated Russians, including 600 IS patients and 688 age- and sex-matched healthy subjects, were enrolled for the study. Nine common single nucleotide polymorphisms (SNPs) of the GCLC and GCLM genes were genotyped using the MassArray-4 system. SNP rs2301022 of GCLM was strongly associated with a decreased risk of ischemic stroke regardless of sex and age (OR = 0.39, 95%CI 0.24−0.62, p < 0.0001). Two common haplotypes of GCLM possessed protective effects against ischemic stroke risk (p < 0.01), but exclusively in nonsmoker patients. Infarct size was increased by polymorphisms rs636933 and rs761142 of GCLC. The mbmdr method enabled identifying epistatic interactions of GCLC and GCLM gene polymorphisms with known IS susceptibility genes that, along with environmental risk factors, jointly contribute to the disease risk and brain infarct size. Understanding the impact of genes and environmental factors on glutathione metabolism will allow the development of effective strategies for the treatment of ischemic stroke and disease prevention.

Stress Granules and Acute Ischemic Stroke: Beyond mRNA Translation

Ischemic stroke is a leading cause of death and disability worldwide. Following an ischemic insult, cells undergo endoplasmic reticulum (ER) stress, which increases the ER’s protein-folding and degradative capacities and blocks the global synthesis of proteins by phosphorylating the eukaryotic translation initiation factor 2-alpha (eIF2α). Phosphorylation of eIF2α is directly related to the dynamics of stress granules (SGs), which are membraneless organelles composed of RNA-binding proteins and mRNA. SGs play a critical role in mRNA metabolism and translational control. Other translation factors are also linked to cellular pathways, including SG dynamics following a stroke. Because the formation of SGs is closely connected to mRNA translation, it is interesting to study the relationship between SG dynamics and cellular outcome in cases of ischemic damage. Therefore, in this review, we focus on the role of SG dynamics during cerebral ischemia.

Endoplasmic Reticulum Stress-Associated Neuronal Death and Innate Immune Response in Neurological Diseases

Neuronal death and inflammatory response are two common pathological hallmarks of acute central nervous system injury and chronic degenerative disorders, both of which are closely related to cognitive and motor dysfunction associated with various neurological diseases. Neurological diseases are highly heterogeneous; however, they share a common pathogenesis, that is, the aberrant accumulation of misfolded/unfolded proteins within the endoplasmic reticulum (ER). Fortunately, the cell has intrinsic quality control mechanisms to maintain the proteostasis network, such as chaperone-mediated folding and ER-associated degradation. However, when these control mechanisms fail, misfolded/unfolded proteins accumulate in the ER lumen and contribute to ER stress. ER stress has been implicated in nearly all neurological diseases. ER stress initiates the unfolded protein response to restore proteostasis, and if the damage is irreversible, it elicits intracellular cascades of death and inflammation. With the growing appreciation of a functional association between ER stress and neurological diseases and with the improved understanding of the multiple underlying molecular mechanisms, pharmacological and genetic targeting of ER stress are beginning to emerge as therapeutic approaches for neurological diseases.

N-Acetyl-Aspartyl-Glutamate in Brain Health and Disease

N-acetyl-aspartyl-glutamate (NAAG) is the most abundant dipeptide in the brain, where it acts as a neuromodulator of glutamatergic synapses by activating presynaptic metabotropic glutamate receptor 3 (mGluR3). Recent data suggest that NAAG is selectively localized to postsynaptic dendrites in glutamatergic synapses and that it works as a retrograde neurotransmitter. NAAG is released in response to glutamate and provides the postsynaptic neuron with a feedback mechanisms to inhibit excessive glutamate signaling. A key regulator of synaptically available NAAG is rapid degradation by the extracellular enzyme glutamate carboxypeptidase II (GCPII). Increasing endogenous NAAG—for instance by inhibiting GCPII—is a promising treatment option for many brain disorders where glutamatergic excitotoxicity plays a role. The main effect of NAAG occurs through increased mGluR3 activation and thereby reduced glutamate release. In the present review, we summarize the transmitter role of NAAG and discuss the involvement of NAAG in normal brain physiology. We further present the suggested roles of NAAG in various neurological and psychiatric diseases and discuss the therapeutic potential of strategies aiming to enhance NAAG levels.

Cerebral Glucose Metabolism and Potential Effects on Endoplasmic Reticulum Stress in Stroke

Ischemic stroke is an extremely common pathology with strikingly high morbidity and mortality rates. The endoplasmic reticulum (ER) is the primary organelle responsible for conducting protein synthesis and trafficking as well as preserving intracellular Ca2⁺ homeostasis. Mounting evidence shows that ER stress contributes to stroke pathophysiology. Moreover, insufficient circulation to the brain after stroke causes suppression of ATP production. Glucose metabolism disorder is an important pathological process after stroke. Here, we discuss the relationship between ER stress and stroke and treatment and intervention of ER stress after stroke. We also discuss the role of glucose metabolism, particularly glycolysis and gluconeogenesis, post-stroke. Based on recent studies, we speculate about the potential relationship and crosstalk between glucose metabolism and ER stress. In conclusion, we describe ER stress, glycolysis, and gluconeogenesis in the context of stroke and explore how the interplay between ER stress and glucose metabolism contributes to the pathophysiology of stroke.

Evaluation of Endothelial Dysfunction and Autophagy in Fibromyalgia-Related Vascular and Cerebral Cortical Changes and the Ameliorative Effect of Fisetin

Fibromyalgia (FM) is a common chronic pain syndrome that affects 1% to 5% of the population. We aimed to investigate the role of endothelial dysfunction and autophagy in fibromyalgia-related vascular and cerebral cortical changes in a reserpine-induced rat model of fibromyalgia at the histological and molecular levels and to study the ameliorative effect of fisetin. Forty adult female albino rats were divided into four groups (10 each): two control groups, the reserpine-induced fibromyalgia group, and the fisetin-treated group. The carotid arteries and brains of the animals were dissected. Frozen tissue samples were used for total RNA extraction and qPCR analysis of eNOS, caspase-3, Bcl-2, LC-3, BECN-1, CHOP, and TNF-α expression. Histological, immunohistochemical (eNOS), and ultrastructure studies were conducted. The carotid arteries revealed excessive autophagy and endothelial, vascular, and apoptotic changes. The cerebral cortex showed similar findings apart from endoplasmic reticulum stress. Additionally, there was decreased gene expression of eNOS and Bcl-2 and increased expression of caspase-3, LC-3, BECN-1, CHOP, and TNF-α. In the fisetin-treated rats, improvements in the histological and molecular results were detected. In conclusion, oxidative stress, enhanced apoptosis, and excessive autophagy are fundamental pathophysiologic mechanisms of reserpine-induced fibromyalgia. Moreover, fisetin has an ameliorative effect against fibromyalgia.

Mechanism of cell death of endothelial cells regulated by mechanical forces

Cell death of endothelial cells (ECs) is a common devastating consequence of various vascular-related diseases. Atherosclerosis, hypertension, sepsis, diabetes, cerebral ischemia and cardiac ischemia/reperfusion injury, and chronic kidney disease remain major causes of morbidity and mortality worldwide, in which ECs are constantly subjected to a great amount of dynamic changed mechanical forces including shear stress, extracellular matrix stiffness, mechanical stretch and microgravity. A thorough understanding of the regulatory mechanisms by which the mechanical forces controlled the cell deaths including apoptosis, autophagy, and pyroptosis is crucial for the development of new therapeutic strategies. In the present review, experimental and clinical data highlight that nutrient depletion, oxidative stress, tumor necrosis factor-α, high glucose, lipopolysaccharide, and homocysteine possess cytotoxic effects in many tissues and induce apoptosis of ECs, and that sphingosine-1-phosphate protects ECs. Nevertheless, EC apoptosis in the context of those artificial microenvironments could be enhanced, reduced or even reversed along with the alteration of patterns of shear stress. An appropriate level of autophagy diminishes EC apoptosis to some extent, in addition to supporting cell survival upon microenvironment challenges. The intervention of pyroptosis showed a profound effect on atherosclerosis. Further cell and animal studies are required to ascertain whether the alterations in the levels of cell deaths and their associated regulatory mechanisms happen at local lesion sites with considerable mechanical force changes, for preventing senescence and cell deaths in the vascular-related diseases.

The Mechanisms Underlying the Protective Action of Selenium Nanoparticles against Ischemia/Reoxygenation Are Mediated by the Activation of the Ca2+ Signaling System of Astrocytes and Reactive Astrogliosis

In recent years, much attention has been paid to the study of the therapeutic effect of the microelement selenium, its compounds, especially selenium nanoparticles, with a large number of works devoted to their anticancer effects. Studies proving the neuroprotective properties of selenium nanoparticles in various neurodegenerative diseases began to appear only in the last 5 years. Nevertheless, the mechanisms of the neuroprotective action of selenium nanoparticles under conditions of ischemia and reoxygenation remain unexplored, especially for intracellular Ca²⁺ signaling and neuroglial interactions. This work is devoted to the study of the cytoprotective mechanisms of selenium nanoparticles in the neuroglial networks of the cerebral cortex under conditions of ischemia/reoxygenation. It was shown for the first time that selenium nanoparticles dose-dependently induce the generation of Ca²⁺ signals selectively in astrocytes obtained from different parts of the brain. The generation of these Ca²⁺ signals by astrocytes occurs through the release of Ca²⁺ ions from the endoplasmic reticulum through the IP3 receptor upon activation of the phosphoinositide signaling pathway. An increase in the concentration of cytosolic Ca²⁺ in astrocytes leads to the opening of connexin Cx43 hemichannels and the release of ATP and lactate into the extracellular medium, which trigger paracrine activation of the astrocytic network through purinergic receptors. Incubation of cerebral cortex cells with selenium nanoparticles suppresses ischemia-induced increase in cytosolic Ca²⁺ and necrotic cell death. Activation of A2 reactive astrocytes exclusively after ischemia/reoxygenation, a decrease in the expression level of a number of proapoptotic and proinflammatory genes, an increase in lactate release by astrocytes, and suppression of the hyperexcitation of neuronal networks formed the basis of the cytoprotective effect of selenium nanoparticles in our studies.