Endoplasmic reticulum stress plays critical role in brain damage after cerebral ischemia/reperfusion in rats

A mechanistic exploration of the metabolome of African mango seeds and its potential to alleviate cognitive impairment induced by high-fat/high-carbohydrate diets: Involvement of PI3K/AKT/GSK-3β/CREB, PERK/CHOP/Bcl-2, and AMPK/SIRT-1/mTOR Axes

ETHNOPHARMACOLOGICAL RELEVANCE

Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill., also known as "African mango" or "bush mango", belonging to family Irvingiaceae, has been mostly used as food and traditional medicine for weight loss and to enhance the health.

AIM OF THE STUDY

The overconsumption of high-fat and high-carbohydrate (HFHC) food induces oxidative stress, leading to neurological and cognitive dysfunction. Consequently, there is an immediate need for effective treatment. Hence, this study explored the efficacy of orlistat, metformin, and I. gabonensis seeds' total aqueous extract (IG SAE) in addressing HFHC-induced cognitive impairment by mitigating oxidative stress and their underlying mechanistic pathways.

MATERIALS AND METHODS

Initially, the secondary metabolite profile of IG SAE is determined using high-performance liquid chromatography coupled with a mass detector (UHPLC/MS). The in vivo study involves two phases: an established model phase with control (10 rats on a standard diet) and HFHC diet group (50 rats) for 3 months. In the study phase, HFHC is divided into 5 groups. The first subgroup receives HFHC diet only, while the remaining groups each receive HFHC diet with either Orlistat, metformin, or IG SAE at doses of 100 mg/kg and 200 mg/kg, respectively, for 28 days.

RESULTS

More than 150 phytoconstituents were characterized for the first holistic approach onto IG metabolome. Characterization of IG SAE revealed that tannins dominate metabolites in the plant. Total phenolics and flavonoids were estimated to standardize our extract (77.12 ± 7.09 μg Gallic acid equivalent/mg extract and 8.039 ± 0.53 μg Rutin equivalent/mg extract, respectively). Orlistat, metformin, and IG SAE successfully reduced the body weight, blood glucose level, lipid profile, oxidative stress and neurotransmitters levels leading to improved behavioral functions as well as histological alternation. Also, IG SAE halted inflammation, apoptosis, and endoplasmic reticulum stress, together with promoting autophagy, via modulation of PI3K/AKT/GSK-3β/CREB, PERK/CHOP/Bcl-2 and AMPK/SIRT-1/m-TOR pathways.

CONCLUSION

Metformin, orlistat, and IG SAE offer a promising multi-target therapy to mitigate HFHC diet-induced oxidative stress, addressing cognitive function. This involves diverse molecular mechanisms, particularly the modulation of inflammation, ER stress, and both PI3K/AKT/GSK-3β/CREB and AMPK/SIRT-1/m-TOR pathways. Furthermore, the higher dose of IG SAE demonstrated effects comparable to orlistat and metformin across most studied parameters.

Therapeutic Potential of Targeting the PERK Signaling Pathway in Ischemic Stroke

Many pathologic states can lead to the accumulation of unfolded/misfolded proteins in cells. This causes endoplasmic reticulum (ER) stress and triggers the unfolded protein response (UPR), which encompasses three main adaptive branches. One of these UPR branches is mediated by protein kinase RNA-like ER kinase (PERK), an ER stress sensor. The primary consequence of PERK activation is the suppression of global protein synthesis, which reduces ER workload and facilitates the recovery of ER function. Ischemic stroke induces ER stress and activates the UPR. Studies have demonstrated the involvement of the PERK pathway in stroke pathophysiology; however, its role in stroke outcomes requires further clarification. Importantly, considering mounting evidence that supports the therapeutic potential of the PERK pathway in aging-related cognitive decline and neurodegenerative diseases, this pathway may represent a promising therapeutic target in stroke. Therefore, in this review, our aim is to discuss the current understanding of PERK in ischemic stroke, and to summarize pharmacologic tools for translational stroke research that targets PERK and its associated pathways.

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.

ALKBH5 protects against stroke by reducing endoplasmic reticulum stress-dependent inflammation injury via the STAT5/PERK/EIF2α/CHOP signaling pathway in an m6A-YTHDF1-dependent manner

BACKGROUND

Endoplasmic reticulum (ER) stress causes neuroinflammation and neuronal apoptosis during ischemic stroke progression. This study has investigated the role of ALKBH5 in ER stress during ischemic stroke progression.

METHODS

In vivo and in vitro models of ischemic stroke were established by middle cerebral artery occlusion (MCAO) and OGD/R treatment, respectively. Cerebral infarct size was detected using triphenyltetrazolium chloride staining (TTC), and pathological changes were examined using histological staining. The levels of inflammatory factors were analyzed using Enzyme-linked immunosorbent assay. Cell counting kit-8 assay and flow cytometry were used to measure cell viability and apoptosis, respectively. The global m6A level was detected using the commercial kit, and STAT5 mRNA m6A level was determined using methylated RNA binding protein immunoprecipitation (Me-RIP). ALKBH5, YTHDF1, and STAT5 interactions were analyzed using RIP and RNA pull-down assays.

RESULTS

ALKBH5 was upregulated in MCAO animals and OGD/R cell models. ALKBH5 knockdown exacerbated ER stress, neuroinflammation, and neuronal apoptosis in brain tissues and neuronal cells. ALKBH5 inhibited STAT5 mRNA stability and expression in an m6A-YTHDF1-dependent manner. STAT5 promoted ER stress by activating the PERK/eIF2/CHOP signaling pathway. Furthermore, STAT5 knockdown reversed the effects of ALKBH5 knockdown on OGD/R-induced ER stress and neuroinflammation in HT22 cells.

CONCLUSION

ALKBH5 knockdown exacerbated ischemic stroke by increasing ER stress-dependent neuroinflammation and neuronal apoptosis via the STAT5/PERK/EIF2α/CHOP signaling pathway in an m6A-YTHDF1-dependent manner.

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.

Exploring the molecular mechanism of Yinao Fujian formula on ischemic stroke based on network pharmacology and experimental verification

Background

Ischemic stroke (IS) is a leading cause of long-term disability and even mortality, threatening people's lives. Yinao Fujian (YNFJ) formula is a Traditional Chinese Medicine formula that has been widely used to treat patients with IS. However, the molecular mechanism of YNFJ for the treatment of IS is still elusive. Our study aimed to explore the potential protective effect and the underlying mechanisms of YNFJ on IS using a network pharmacology approach coupled with experimental validation.

Materials and methods

Effective compounds of YNFJ were collected from BATMAN-TCM and TCMSP databases, while IS targets were obtained from GeneCards, OMIM, TTD and DrugBank databases. The protein-protein interaction (PPI) network was constructed to further screen the hub targets of YNFJ in IS treatment. GO and KEGG enrichment analyses were used to identify the critical biological processes and signaling pathways of YNFJ for IS. Moreover, Nissl staining, HE, TTC staining and Tunel staining were used in the MCAO model to prove the neuroprotective effect of YNFJ. Oxidative damage, inflammatory factor release and related pathways were tested in MCAO rat model and hypoxia-induced BV2 cell model, respectively.

Results

We found that YNFJ treatment significantly alleviated MCAO-induced nerve damage and apoptosis. Then, network pharmacology screening combined with literature research revealed IL6, TNF, PTGS2, NFKBIA and NFE2L2 as the critical targets in a PPI network. Moreover, the top 20 signaling pathways and biological processes associated with the protective effects of YNFJ on IS were enriched through GO and KEGG analyses. Further analysis indicated that NF-κB and Nrf2/HO-1 signaling pathways might be highly involved in the protective effects of YNFJ on IS. Finally, in vitro and in vivo experiments confirmed that YNFJ inhibited the release of inflammatory factors (IL-6 and TNF-α) and MDA content, and increased the activity of SOD. In terms of the mechanism, YNFJ inhibited the release of inflammatory factors by suppressing the NF-κB pathway and decreased the expression of iNOS and COX-2 to protect microglia from inflammation damage. In addition, YNFJ initiated the dissociation of Keap-1 and Nrf2, and activated the downstream protein HO-1, NQO1, thus decreasing oxidative stress.

Conclusion

Taken together, the findings in our research showed that the protective effects of YNFJ on IS were mainly achieved by regulating the NF-κB and Nrf2/HO-1 signaling pathways to inhibit oxidative stress damage and inflammatory damage of microglia.

Advancements in Genetic and Biochemical Insights: Unraveling the Etiopathogenesis of Neurodegeneration in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative movement disorder worldwide, which is primarily characterized by motor impairments. Even though multiple hypotheses have been proposed over the decades that explain the pathogenesis of PD, presently, there are no cures or promising preventive therapies for PD. This could be attributed to the intricate pathophysiology of PD and the poorly understood molecular mechanism. To address these challenges comprehensively, a thorough disease model is imperative for a nuanced understanding of PD's underlying pathogenic mechanisms. This review offers a detailed analysis of the current state of knowledge regarding the molecular mechanisms underlying the pathogenesis of PD, with a particular emphasis on the roles played by gene-based factors in the disease's development and progression. This study includes an extensive discussion of the proteins and mutations of primary genes that are linked to PD, including α-synuclein, GBA1, LRRK2, VPS35, PINK1, DJ-1, and Parkin. Further, this review explores plausible mechanisms for DAergic neural loss, non-motor and non-dopaminergic pathologies, and the risk factors associated with PD. The present study will encourage the related research fields to understand better and analyze the current status of the biochemical mechanisms of PD, which might contribute to the design and development of efficacious and safe treatment strategies for PD in future endeavors.

Punicalagin's Protective Effects on Parkinson's Progression in Socially Isolated and Socialized Rats: Insights into Multifaceted Pathway

Parkinson's disease (PD) is a gradual deterioration of dopaminergic neurons, leading to motor impairments. Social isolation (SI), a recognized stressor, has recently gained attention as a potential influencing factor in the progress of neurodegenerative illnesses. We aimed to investigate the intricate relationship between SI and PD progression, both independently and in the presence of manganese chloride (MnCl2), while evaluating the punicalagin (PUN) therapeutic effects, a natural compound established for its cytoprotective, anti-inflammatory, and anti-apoptotic activities. In this five-week experiment, seven groups of male albino rats were organized: G1 (normal control), G2 (SI), G3 (MnCl2), G4 (SI + MnCl2), G5 (SI + PUN), G6 (MnCl2 + PUN), and G7 (SI + PUN + MnCl2). The results revealed significant changes in behavior, biochemistry, and histopathology in rats exposed to SI and/or MnCl2, with the most pronounced effects detected in the SI rats concurrently exposed to MnCl2. These effects were associated with augmented oxidative stress biomarkers and reduced antioxidant activity of the Nrf2/HO-1 pathway. Additionally, inflammatory pathways (HMGB1/RAGE/TLR4/NF-ᴋB/NLRP3/Caspase-1 and JAK-2/STAT-3) were upregulated, while dysregulation of signaling pathways (PI3K/AKT/GSK-3β/CREB), sustained endoplasmic reticulum stress by activation PERK/CHOP/Bcl-2, and impaired autophagy (AMPK/SIRT-1/Beclin-1 axis) were observed. Apoptosis induction and a decrease in monoamine levels were also noted. Remarkably, treatment with PUN effectively alleviated behaviour, histopathological changes, and biochemical alterations induced by SI and/or MnCl2. These findings emphasize the role of SI in PD progress and propose PUN as a potential therapeutic intervention to mitigate PD. PUN's mechanisms of action involve modulation of pathways such as HMGB1/RAGE/TLR4/NF-ᴋB/NLRP3/Caspase-1, JAK-2/STAT-3, PI3K/AKT/GSK-3β/CREB, AMPK/SIRT-1, Nrf2/HO-1, and PERK/CHOP/Bcl-2.

Role of PERK-mediated pathway in the effect of mild hypothermia after cerebral ischaemia/reperfusion

BACKGROUND

Hypothermia is an effective method of reducing brain injury caused by a variety of neurological insults. It is aimed to elucidate whether a change in the expression of PERK-mediated pathway proteins is an indicator of the neuroprotective effect of mild hypothermia after cerebral ischaemia/reperfusion.

METHODS

One hundred and ninety-two male C57BL/6 mice were randomly divided into three groups: a sham group, a cerebral normothermic ischaemia/reperfusion (I/R) group and a cerebral hypothermic I/R group. A cerebral ischaemia model was established by ligating the bilateral common carotid artery for 15 min. Mice in the hypothermia group stayed in a cage that was set at 33°C, sprayed with a spray of 70% ethanol, and blown with two high-speed fans. The state of neurons was assessed on micropreparations stained with haematoxylin-eosin and TUNEL. The expressions of GRP78, p-perk, p-eif2α, ATF4 and CHOP were measured by western blot analysis 6, 12, 24 and 72 h after reperfusion.

RESULTS

The number of surviving cells was significantly higher in the hypothermia group than in the group without hypothermia (p < .05). The GRP78 expression in the hypothermia group was statistically higher (p < .05) than in the ischaemia/reperfusion group. Optical densities of p-perk, p-eif2α and ATF4 in hippocampus CA1 neurons ischaemia were statistically significantly lower in the hypothermia group than in the ischaemia/reperfusion group (p < .05). The CHOP expression in the hypothermia group was statistically lower (p < .05) than in the ischaemia/reperfusion group.

CONCLUSION

Mild hypothermia for 6 h promoted moderate neuroprotection by mediating the expression of GRP78, p-PERK, p-eIF2α, ATF4 and CHOP.

Proteostasis plays an important role in demyelinating Charcot Marie Tooth disease

Type 1 Charcot-Marie-Tooth disease (CMT1) is the most common demyelinating peripheral neuropathy. Patients suffer from progressive muscle weakness and sensory problems. The underlying disease mechanisms of CMT1 are still unclear and no therapy is currently available, hence patients completely rely on supportive care. Balancing protein levels is a complex multistep process fundamental to maintain cells in their healthy state and a disrupted proteostasis is a hallmark of several neurodegenerative diseases. When protein misfolding occurs, protein quality control systems are activated such as chaperones, the lysosomal-autophagy system and proteasomal degradation to ensure proper degradation. However, in pathological circumstances, these mechanisms are overloaded and thereby become inefficient to clear the load of misfolded proteins. Recent evidence strongly indicates that a disbalance in proteostasis plays an important role in several forms of CMT1. In this review, we present an overview of the protein quality control systems, their role in CMT1, and potential treatment strategies to restore proteostasis.

Endoplasmic reticulum stress in Alzheimer's disease: Molecular mechanisms and therapeutic prospects

Alzheimer's disease (AD) is a progressive neurodegenerative condition that leads to memory loss and cognitive impairment over time. It is characterized by protein misfolding as well as prolonged cellular stress, such as perturbing calcium homeostasis and redox management. Numerous investigations have proven that endoplasmic reticulum failure may exhibit exacerbation of AD pathogenesis in AD patients, in-vivo and in-vitro models. The endoplasmic reticulum (ER) participates in a variety of biological functions including folding of protein, quality control, cholesterol production, and maintenance of calcium balance. A diverse range of physiological, pathological and pharmacological substances can interfere with ER activity and thus lead to exaggeration of ER stress. The unfolded protein response (UPR), an intracellular signaling network is stimulated due to ER stress. Three stress sensors found in the endoplasmic reticulum, the PERK, ATF6, and IRE1 transducers detect protein misfolding in the ER and trigger UPR, a complex system to maintain homeostasis. ER stress is linked to many of the major pathological processes that are seen in AD, including presenilin1 and 2 (PS1 and PS2) gene mutation, tau phosphorylation and β-amyloid formation. The role of ER stress and UPR in the pathophysiology of AD implies that they can be employed as potent therapeutic target. This study shows the relationship between ER and AD and how the pathogenesis of AD is influenced by the impact of ER stress. An effective method for the prevention or treatment of AD may involve therapeutic strategies that modify ER stress pathways.

RGC-specific ATF4 and/or CHOP deletion rescues glaucomatous neurodegeneration and visual function

Endoplasmic reticulum (ER) stress has been linked with various acute and chronic neurodegenerative diseases. We previously found that optic nerve (ON) injury and diseases induce neuronal ER stress in retinal ganglion cells (RGCs). We further demonstrated that germline deletion of CHOP preserves the structure and function of both RGC somata and axons in mouse glaucoma models. Here we report that RGC-specific deletion of CHOP and/or its upstream regulator ATF4 synergistically promotes RGC and ON survival and preserves visual function in mouse ON crush and silicone oil-induced ocular hypertension (SOHU) glaucoma models. Consistently, topical application of the ATF4/CHOP chemical inhibitor ISRIB or RGC-specific CRISPR-mediated knockdown of the ATF4 downstream effector Gadd45a also delivers significant neuroprotection in the SOHU glaucoma model. These studies suggest that blocking the neuronal intrinsic ATF4/CHOP axis of ER stress is a promising neuroprotection strategy for neurodegeneration.

Multi-Drug Cocktail Therapy Improves Survival and Neurological Function after Asphyxial Cardiac Arrest in Rodents

BACKGROUND

Cardiac arrest (CA) can lead to neuronal degeneration and death through various pathways, including oxidative, inflammatory, and metabolic stress. However, current neuroprotective drug therapies will typically target only one of these pathways, and most single drug attempts to correct the multiple dysregulated metabolic pathways elicited following cardiac arrest have failed to demonstrate clear benefit. Many scientists have opined on the need for novel, multidimensional approaches to the multiple metabolic disturbances after cardiac arrest. In the current study, we have developed a therapeutic cocktail that includes ten drugs capable of targeting multiple pathways of ischemia-reperfusion injury after CA. We then evaluated its effectiveness in improving neurologically favorable survival through a randomized, blind, and placebo-controlled study in rats subjected to 12 min of asphyxial CA, a severe injury model.

RESULTS

14 rats were given the cocktail and 14 received the vehicle after resuscitation. At 72 h post-resuscitation, the survival rate was 78.6% among cocktail-treated rats, which was significantly higher than the 28.6% survival rate among vehicle-treated rats (log-rank test; p = 0.006). Moreover, in cocktail-treated rats, neurological deficit scores were also improved. These survival and neurological function data suggest that our multi-drug cocktail may be a potential post-CA therapy that deserves clinical translation.

CONCLUSIONS

Our findings demonstrate that, with its ability to target multiple damaging pathways, a multi-drug therapeutic cocktail offers promise both as a conceptual advance and as a specific multi-drug formulation capable of combatting neuronal degeneration and death following cardiac arrest. Clinical implementation of this therapy may improve neurologically favorable survival rates and neurological deficits in patients suffering from cardiac arrest.

Hydroxysafflor Yellow A Exerts Neuroprotective Effect by Reducing Aβ Toxicity Through Inhibiting Endoplasmic Reticulum Stress in Oxygen-Glucose Deprivation/Reperfusion Cell Model

Ischemia stroke is thought to be one of the vascular risks associated with neurodegenerative diseases, such as Alzheimer's disease (AD). Hydroxysafflor yellow A (HSYA) has been reported to protect against stroke and AD, while the underlying mechanism remains unclear. In this study, SH-SY5Y cell model treated with oxygen-glucose deprivation/reperfusion (OGD/R) was used to explore the potential mechanism of HSYA. Results from cell counting kit-8 (CCK-8) showed that 10 μM HSYA restored the cell viability after OGD 2 hours/R 24 hours. HSYA reduced the levels of malondialdehyde and reactive oxygen species, while improved the levels of superoxide dismutase and glutathione peroxidase. Furthermore, apoptosis was inhibited, and the expression of brain-derived neurotrophic factor was improved after HSYA treatment. In addition, the expression levels of amyloid-β peptides (Aβ) and BACE1 were decreased by HSYA, as well as the expression levels of binding immunoglobulin heavy chain protein, PKR-like endoplasmic reticulum (ER) kinase pathway, and activating transcription factor 6 pathway, whereas the expression level of protein disulfide isomerase was increased. Based on these results, HSYA might reduce Aβ toxicity after OGD/R by interfering with apoptosis, oxidation, and neurotrophic factors, as well as relieving ER stress.

Modulation of the endoplasmic reticulum stress and unfolded protein response mitigates the behavioral effects of early-life stress

BACKGROUND

Early-life stress (ELS) affects brain development and increases the risk of mental disorders associated with the dysfunction of the medial prefrontal cortex (mPFC). The mechanisms of ELS action are not well understood. Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) are cellular processes involved in brain maturation through the regulation of pro-survival or proapoptotic processes. We hypothesized that ER stress and the UPR in the mPFC are involved in the neurobiology of ELS.

METHODS

We performed a maternal separation (MS) procedure from postnatal days 1 to 14 in rats. Before each MS, pups were injected with an inhibitor of ER stress, salubrinal or a vehicle. The mRNA and protein expression of UPR and apoptotic markers were evaluated in the mPFC using RT-qPCR and Western blot methods, respectively. We also estimated the numbers of neurons and glial cells using stereological methods. Additionally, we assessed behavioral phenotypes related to fear, anhedonia and response to psychostimulants.

RESULTS

MS slightly enhanced the activation of the UPR in juveniles and modulated the expression of apoptotic markers in juveniles and preadolescents but not in adults. Additionally, MS did not affect the numbers of neurons and glial cells at any age. Both salubrinal and vehicle blunted the expression of UPR markers in juvenile and preadolescent MS rats, often in a treatment-specific manner. Moreover, salubrinal and vehicle generally alleviated the behavioral effects of MS in preadolescent and adult rats.

CONCLUSIONS

Modulation of ER stress and UPR processes may potentially underlie susceptibility or resilience to ELS.

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.

ADP-ribose transferase PARP16 mediated-unfolded protein response contributes to neuronal cell damage in cerebral ischemia/reperfusion

Ischemic stroke is known to cause the accumulation of misfolded proteins and loss of calcium homeostasis, leading to impairment of endoplasmic reticulum (ER) function and activating the unfolded protein response (UPR). PARP16 is an active (ADP-ribosyl)transferase known tail-anchored ER transmembrane protein with a cytosolic catalytic domain. Here, we find PARP16 is highly expressed in ischemic cerebral hemisphere and oxygen-glucose deprivation/reoxygenation (OGD/R)-treated immortalized hippocampal neuronal cell HT22. Using an adeno-associated virus-mediated PARP16 knockdown approach in mice, we find PARP16 knockdown decreases infarct demarcations and has a better neurological outcome after ischemic stroke. Our data indicate PARP16 knockdown decreases ER stress and neuronal death caused by OGD/R, whereas PARP16 overexpression promotes ER stress-mediated cell damage in primary cortical neurons. Furthermore, PARP16 functions mechanistically as ADP-ribosyltransferase to modulate the level of ADP-ribosylation of the corresponding PERK and IRE1α arm of the UPR, and such modifications mediate activation of PERK and IRE1α. Indeed, pharmacological stimulation of the UPR using Brefeldin A partly counteracts PARP16 knockdown-mediated neuronal protection upon OGD/R treatment. In conclusion, PARP16 plays a crucial role in post-ischemic UPR and PARP16 knockdown alleviates brain injury after ischemic stroke. This study demonstrates the potential of the PARP16-PERK/IRE1α axis as a target for neuronal survival in ischemic stroke.

Ketogenic Diet and Ketone Bodies against Ischemic Injury: Targets, Mechanisms, and Therapeutic Potential

The ketogenic diet (KD) has been used as a treatment for epilepsy since the 1920s, and its role in the prevention of many other diseases is now being considered. In recent years, there has been an intensive investigation on using the KD as a therapeutic approach to treat acute pathologies, including ischemic ones. However, contradictory data are observed for the effects of the KD on various organs after ischemic injury. In this review, we provide the first systematic analysis of studies conducted from 1980 to 2022 investigating the effects and main mechanisms of the KD and its mimetics on ischemia-reperfusion injury of the brain, heart, kidneys, liver, gut, and eyes. Our analysis demonstrated a high diversity of both the composition of the used KD and the protocols for the treatment of animals, which could be the reason for contradictory effects in different studies. It can be concluded that a true KD or its mimetics, such as β-hydroxybutyrate, can be considered as positive exposure, protecting the organ from ischemia and its negative consequences, whereas the shift to a rather similar high-calorie or high-fat diet leads to the opposite effect.

Inhibition of the Activating Transcription Factor 6 Branch of Endoplasmic Reticulum Stress Ameliorates Brain Injury after Deep Hypothermic Circulatory Arrest

Neurological dysfunction is a common complication of deep hypothermic circulatory arrest (DHCA). Endoplasmic reticulum (ER) stress plays a role in neuronal ischemia-reperfusion injury; however, it is unknown whether it contributes to DHCA-induced brain injury. Here, we aimed to investigate the role of ER stress in a rat DHCA model and cell hypothermic oxygen-glucose deprivation reoxygenation (OGD/R) model. ER stress and apoptosis-related protein expression were identified using Western blot analysis. Cell counting assay-8 and flow cytometry were used to determine cell viability and apoptosis, respectively. Brain injury was evaluated using modified neurological severity scores, whereas brain injury markers were detected through histological examinations and immunoassays. We observed significant ER stress molecule upregulation in the DHCA rat hippocampus and in hypothermic OGD/R PC-12 cells. In vivo and in vitro experiments showed that ER stress or activating transcription factor 6 (ATF6) inhibition alleviated rat DHCA-induced brain injury, increased cell viability, and decreased apoptosis accompanied by C/EBP homologous protein (CHOP). ER stress is involved in DHCA-induced brain injury, and the inhibition of the ATF6 branch of ER stress may ameliorate this injury by inhibiting CHOP-mediated apoptosis. This study establishes a scientific foundation for identifying new therapeutic targets for perioperative brain protection in clinical DHCA.

Investigating a Genetic Link Between Alzheimer's Disease and CADASIL-Related Cerebral Small Vessel Disease

Monogenic forms of Alzheimer's disease (AD) have been identified through mutations in genes such as APP, PSEN1, and PSEN2, whilst other genetic markers such as the APOE ε carrier allele status have been shown to increase the likelihood of having the disease. Mutations in these genes are not limited to AD, as APP mutations can also cause an amyloid form of cerebral small vessel disease (CSVD) known as cerebral amyloid angiopathy, whilst PSEN1 and PSEN2 are involved in NOTCH3 signalling, a process known to be dysregulated in the monogenic CSVD, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). The overlap between AD genes and causes of CSVD led to the hypothesis that mutations in other genes within the PANTHER AD-presenilin pathway may be novel causes of CSVD in a cohort of clinically suspicious CADASIL patients without a pathogenic NOTCH3 mutation. To investigate this, whole exome sequencing was performed on 50 suspected CADASIL patients with no NOTCH3 mutations, and a targeted gene analysis was completed on the PANTHER. ERN1 was identified as a novel candidate CSVD gene following predicted pathogenic gene mutation analysis. Rare variant burden testing failed to identify an association with any gene; however, it did show a nominally significant link with ERN1 and TRPC3. This study provides evidence to support a genetic overlap between CSVD and Alzheimer's disease.

The functions of IRE1α in neurodegenerative diseases: Beyond ER stress

Inositol-requiring enzyme 1 α (IRE1α) is a type I transmembrane protein that resides in the endoplasmic reticulum (ER). IRE1α, which is the primary sensor of ER stress, has been proven to maintain intracellular protein homeostasis by activating X-box binding protein 1 (XBP1). Further studies have revealed novel physiological functions of the IRE1α, such as its roles in mRNA and protein degradation, inflammation, immunity, cell proliferation and cell death. Therefore, the function of IRE1α is not limited to its role in ER stress; IRE1α is also important for regulating other processes related to cellular physiology. Furthermore, IRE1α plays a key role in neurodegenerative diseases that are caused by the phosphorylation of Tau protein, the accumulation of α-synuclein (α-syn) and the toxic effects of mutant Huntingtin (mHtt). Therefore, targeting IRE1α is a valuable approach for treating neurodegenerative diseases and regulating cell functions. This review discusses the role of IRE1α in different cellular processes, and emphasizes the importance of IRE1α in neurodegenerative diseases.

Increased serum concentrations of Mesencephalic astrocyte-derived neurotrophic factor in patients and rats with ischemic stroke

OBJECTIVES

Although Mesencephalic astrocyte-derived neurotrophic factor (MANF) shows protection in multiple cells, the role of circulating MANF in patients with acute ischemic stroke (AIS) and transient ischemic attack (TIA) remains unclear. Here, we aimed to explore the value of circulating MANF levels in cerebral ischemic events.

MATERIALS AND METHODS

Using a rat cerebral ischemic model, MANF expression in ischemic brains and serum was detected. 50 AIS patients, 56 TIA patients and 48 controls were enrolled, and MANF mRNA, inflammatory cytokines and MANF concentrations in serum and different blood cell types were detected. The National Institutes of Health Stroke Scale (NIHSS) score and Alberta Stroke Program Early CT Score (ASPECTS) were used to evaluate stroke severity. Cerebrovascular recurrence within 90 d was documented during TIA follow-up.

RESULTS

MANF expression increased at 2h, peaking at 24h and decreased to baseline at 7d in rat ischemic brains and serum. Serum MANF concentrations increased at 24h and 7d in AIS patients compared to controls and were correlated with NIHSS score, ASPECTS and inflammatory cytokines. MANF protein was present in blood cells, while MANF mRNA levels did not differ between AIS patients and controls. MANF levels revealed a good value to diagnose TIA with area under the curve (AUC) of 0.949 (95% CI: 0.9093-0.9892). MANF levels were lower in TIA patients with recurrence compared to non-recurrence patients. The AUC for MANF to predict a re-event was 0.80 (95% CI: 0.6746-0.9282).

CONCLUSIONS

Serum MANF levels correlate with neuroprotection, stroke severity, inflammation, and TIA recurrence.

UPR Responsive Genes Manf and Xbp1 in Stroke

Stroke is a devastating medical condition with no treatment to hasten recovery. Its abrupt nature results in cataclysmic changes in the affected tissues. Resident cells fail to cope with the cellular stress resulting in massive cell death, which cannot be endogenously repaired. A potential strategy to improve stroke outcomes is to boost endogenous pro-survival pathways. The unfolded protein response (UPR), an evolutionarily conserved stress response, provides a promising opportunity to ameliorate the survival of stressed cells. Recent studies from us and others have pointed toward mesencephalic astrocyte-derived neurotrophic factor (MANF) being a UPR responsive gene with an active role in maintaining proteostasis. Its pro-survival effects have been demonstrated in several disease models such as diabetes, neurodegeneration, and stroke. MANF has an ER-signal peptide and an ER-retention signal; it is secreted by ER calcium depletion and exits cells upon cell death. Although its functions remain elusive, conducted experiments suggest that the endogenous MANF in the ER lumen and exogenously administered MANF protein have different mechanisms of action. Here, we will revisit recent and older bodies of literature aiming to delineate the expression profile of MANF. We will focus on its neuroprotective roles in regulating neurogenesis and inflammation upon post-stroke administration. At the same time, we will investigate commonalities and differences with another UPR responsive gene, X-box binding protein 1 (XBP1), which has recently been associated with MANF’s function. This will be the first systematic comparison of these two UPR responsive genes aiming at revealing previously uncovered associations between them. Overall, understanding the mode of action of these UPR responsive genes could provide novel approaches to promote cell survival.

Eleutheroside E alleviates cerebral ischemia-reperfusion injury in a 5-hydroxytryptamine receptor 2C (Htr2c)-dependent manner in rats

Stroke is the central disorder underlined by ischemia-reperfusion (I/R) injury. Eleutheroside E (EE) is administered as the shield in some ischemia tissues with anti-inflammatory action. However, whether EE defends I/R-induced damage in the brain remains unknown. Here, we demonstrated that EE significantly alleviated the cerebral I/R injury and reduced the apoptosis of hippocampal neuron cells in rats. During the anti-apoptosis process, EE significantly upregulated the expression of 5-hydroxytryptamine receptor 2C (Htr2c) gene. Silencing Htr2c expression dramatically weakened the protective effect of EE on I/R-induced apoptosis of rat hippocampal neuron. EE-regulated Htr2c also remarkably inhibited the expression of caspase-3, −6 and −7, thereby suggesting a plausible anti-apoptosis mechanism associated with Htr2c/caspase axis. These findings elicit the potentially clinical strategy that targets Htr2c to improve outcome of ischemia brain.

Endoplasmic Reticulum Stress and the Unfolded Protein Response in Cerebral Ischemia/Reperfusion Injury

Ischemic stroke is an acute cerebrovascular disease characterized by sudden interruption of blood flow in a certain part of the brain, leading to serious disability and death. At present, treatment methods for ischemic stroke are limited to thrombolysis or thrombus removal, but the treatment window is very narrow. However, recovery of cerebral blood circulation further causes cerebral ischemia/reperfusion injury (CIRI). The endoplasmic reticulum (ER) plays an important role in protein secretion, membrane protein folding, transportation, and maintenance of intracellular calcium homeostasis. Endoplasmic reticulum stress (ERS) plays a crucial role in cerebral ischemia pathophysiology. Mild ERS helps improve cell tolerance and restore cell homeostasis; however, excessive or long-term ERS causes apoptotic pathway activation. Specifically, the protein kinase R-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1 (IRE1) pathways are significantly activated following initiation of the unfolded protein response (UPR). CIRI-induced apoptosis leads to nerve cell death, which ultimately aggravates neurological deficits in patients. Therefore, it is necessary and important to comprehensively explore the mechanism of ERS in CIRI to identify methods for preserving brain cells and neuronal function after ischemia.

Downregulated XBP-1 Rescues Cerebral Ischemia/Reperfusion Injury-Induced Pyroptosis via the NLRP3/Caspase-1/GSDMD Axis

Ischemic stroke is a major condition that remains extremely problematic to treat. A cerebral reperfusion injury becomes apparent after an ischemic accident when reoxygenation of the afflicted area produces pathological side effects that are different than those induced by the initial oxygen and nutrient deprivation insult. Pyroptosis is a form of lytic programmed cell death that is distinct from apoptosis, which is initiated by inflammasomes and depends on the activation of Caspase-1. Then, Caspase-1 mobilizes the N-domain of gasdermin D (GSDMD), resulting in the release of cytokines, such as interleukin-1β (IL-1β) and interleukin-18 (IL-18). X-box binding protein l (XBP-1) is activated under endoplasmic reticulum (ER) stress to form an important transcription factor XBP-1 splicing (XBP-1s). The cerebral ischemia/reperfusion (CI/R) causes cytotoxicity, which correlates with the activation of splicing XBP-1 mRNA and NLRP3 (NOD-, LRR-, and pyrin domain-containing 3) inflammasomes, along with increases in the expression and secretion of proinflammatory cytokines and upregulation of pyroptosis-related genes in HT22 cells and in the middle cerebral artery occlusion (MCAO) rat model. However, whether XBP-1 plays a role in regulating pyroptosis involved in CI/R is still unknown. Our present study showed that behavior deficits, cerebral ischemic lesions, and neuronal death resulted from CI/R. CI/R increased the mRNA level of XBP-1s, NLRP3, IL-1β, and IL-18 and the expressions of XBP-1s, NLRP3, Caspase-1, GSDMD-N, IL-1β, and IL-18. We further repeated this process in HT22 cells and C8-B4 cells and found that OGD/R decreased cell viability and increased LDH release, XBP-1s, NLRP3, Caspase-1, GSDMD-N, IL-1β, IL-18, and especially the ratio of pyroptosis, which were reversed by Z-YVAD-FMK and downregulated XBP-1. Our results suggest that downregulated XBP-1 inhibited pyroptosis through the classical NLRP3/Caspase-1/GSDMD pathway to protect the neurons.

NOX activation in reactive astrocytes regulates astrocytic LCN2 expression and neurodegeneration

Reactive astrocytes (RA) secrete lipocalin-2 (LCN2) glycoprotein that regulates diverse cellular processes including cell death/survival, inflammation, iron delivery and cell differentiation. Elevated levels of LCN2 are considered as a biomarker of brain injury, however, the underlying regulatory mechanisms of its expression and release are not well understood. In this study, we investigated the role of astrocytic Na+/H+ exchanger 1 (NHE1) in regulating reactive astrocyte LCN2 secretion and neurodegeneration after stroke. Astrocyte specific deletion of Nhe1 in Gfap-CreER+/-;Nhe1f/f mice reduced astrogliosis and astrocytic LCN2 and GFAP expression, which was associated with reduced loss of NeuN+ and GRP78+ neurons in stroke brains. In vitro ischemia in astrocyte cultures triggered a significant increase of secreted LCN2 in astrocytic exosomes, which caused neuronal cell death and neurodegeneration. Inhibition of NHE1 activity during in vitro ischemia with its potent inhibitor HOE642 significantly reduced astrocytic LCN2+ exosome secretion. In elucidating the cellular mechanisms, we found that stroke triggered activation of NADPH oxidase (NOX)-NF-κB signaling and ROS-mediated LCN2 expression. Inhibition of astrocytic NHE1 activity attenuated NOX signaling and LCN2-mediated neuronal apoptosis and neurite degeneration. Our findings demonstrate for the first time that RA use NOX signaling to stimulate LCN2 expression and secretion. Blocking astrocytic NHE1 activity is beneficial to reduce LCN2-mediated neurotoxicity after stroke.

Omarigliptin attenuates rotenone-induced Parkinson's disease in rats: Possible role of oxidative stress, endoplasmic reticulum stress and immune modulation

The current study aimed to explore the potential neuroprotective effect of omarigliptin (OG), an antidiabetic drug that crosses the blood-brain barrier (BBB), in a Parkinson's disease (PD) rotenone-based rat-model. Results showed that OG attenuated motor impairment, histological aberrations, α-synuclein accumulation, and rescued the dopaminergic neurons in rotenone-administered rats. Furthermore, OG halted rotenone-induced oxidative stress; as shown by reduced lipid peroxidation, decline in the oxidative stress sensor (nuclear factor erythroid 2-related factor 2) and its downstream heme oxygenase-1. In addition, OG abrogated neuroinflammation and apoptosis in rotenone-treated rats. Moreover, OG ameliorated endoplasmic reticulum (ER) stress in rotenone-administered rats; as evidenced by reduced levels of ER resident proteins such as glucose-regulated protein 78, C/EBP homologous protein and apoptotic caspase-12. In conclusion, this study implies repurposing of OG, as a novel neuroprotective agent due to its antioxidant properties, its effects on ER stress in addition to its anti-inflammatory and anti-apoptotic activities.

The integrated stress response in ischemic diseases

Ischemic disease is among the deadliest and most disabling illnesses. Prominent examples include myocardial infarction and stroke. Most, if not all, underlying pathological changes, including oxidative stress, inflammation, and nutrient deprivation, are potent inducers of the integrated stress response (ISR). Four upstream kinases are involved in ISR signaling that sense a myriad of input stress signals and converge on the phosphorylation of serine 51 of eukaryotic translation initiation factor 2α (eIF2α). As a result, translation initiation is halted, creating a window of opportunity for the cell to repair itself and restore homeostasis. A growing number of studies show strong induction of the ISR in ischemic disease. Genetic and pharmacological evidence suggests that the ISR plays critical roles in disease initiation and progression. Here, we review the basic regulation of the ISR, particularly in response to ischemia, and summarize recent findings relevant to the actions of the ISR in ischemic disease. We then discuss therapeutic opportunities by modulating the ISR to treat ischemic heart disease, brain ischemia, ischemic liver disease, and ischemic kidney disease. Finally, we propose that the ISR represents a promising therapeutic target for alleviating symptoms of ischemic disease and improving clinical outcomes.

Early Aerobic Exercise Promotes Neurological Function Recovery of Rats after Cerebral Ischemia/Reperfusion by Upregulating the Expression of Heat Shock Protein A5

OBJECTIVE

The neuroprotective function of heat shock protein A5 (HSPA5) in ischemic stroke has been confirmed. This study aimed to investigate the effects of early aerobic exercise on neurological function recovery from cerebral ischemia/reperfusion and to determine whether these effects are associated with the expression level of HSPA5 in the ischemic penumbra.

METHODS

A total of 72 male Sprague-Dawley rats were randomly assigned to the ischemia and exercise group [middle cerebral artery occlusion (MCAO)-Ex, n=18], ischemia and sedentary group (MCAO-St, n=18), sham-surgery and exercise group (Sham-Ex, n=18), or sham-surgery and sedentary group (Sham-St, n=18). The MCAO-Ex and MCAO-St groups were subjected to MCAO for 60 min, whereas the Sham-Ex and Sham-St groups were subjected to an identical operation without MCAO. Rats in the MCAO-Ex and Sham-Ex groups then ran on a treadmill for 30 min once a day for 5 consecutive days. After reperfusion, the motor function of the rats was scored by the Bederson neurological function test, balance beam test, and screen test. Nissl staining was conducted to assess morphological and structural change of nerve cells in the ischemic penumbra. The reverse transcription-quantitative polymerase chain reaction was applied to detect the mRNA expression of HSPA5. Western blot analysis was conducted to determine the protein expression of HSPA5. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining was carried out in the ischemic penumbra after MCAO.

RESULTS

Rats receiving early treadmill exercise had lower Bederson neurological function, balance beam, and screen test scores on the 3rd, 7th, and 14th days after MCAO; in addition, more neurons survived in the ischemic penumbra after MCAO, and higher mRNA and protein expression of HSPA5 and fewer TUNEL-positive stained cells were observed.

CONCLUSION

Our study demonstrated that early aerobic exercise can improve neurological function recovery after ischemia/reperfusion. Furthermore, the increased level of HSPA5 in the ischemic penumbra might be one of the mechanisms of enhanced neurological function recovery.

Long-Lasting Exendin-4-Loaded PLGA Nanoparticles Ameliorate Cerebral Ischemia/Reperfusion Damage in Diabetic Rats

Exendin-4 (Ex-4) is an incretin mimetic agent approved for diabetes treatment and neuronal protection. However, the required frequent injections restrict its clinical application. We prepared Ex-4-loaded poly(d,l-lactide-co-glycolide) nanoparticles (PEx-4) and investigated their effect on cerebral ischemia/reperfusion (IR) injury associated with micturition center damage-induced cystopathy in diabetic rats. Using ten minutes of bilateral carotid artery occlusion combined with hemorrhage-induced hypotension of the IR model in streptozotocin-induced type 1 diabetic (T1DM) Wistar rats, we compared the effects of Ex-4 and PEx-4 on prefrontal cortex edema, voiding function and oxidative stress including cerebral spinal fluid (CSF) reference H₂O₂ (RH₂O₂) and HOCl (RHOCl) levels, endoplasmic reticulum (ER) stress, apoptosis, autophagy and pyroptosis signaling in brain and bladder by Western blot and immunohistochemistry. Single injection of PEx-4 displayed higher CSF antioxidant activity and a long-lasting hypoglycemic effect compared to Ex-4 in rats. T1DM and IR primarily enhanced CSF RH₂O₂, and pIRE-1/caspase-12/pJNK/CHOP-mediated ER stress, caspase-3/PARP-mediated apoptosis, Beclin-1/LC3B-mediated autophagy and caspase-1/IL-1β-mediated pyroptosis signaling in the damaged brains. Our data further evidenced that PEx-4 were more efficient than Ex-4 in attenuating IR-evoked prefrontal cortex edema, the impairment in micturition center and the enhanced level of CSF RH₂O₂ and HOCl, ER stress, apoptosis, autophagy and pyroptosis parameters in the damaged brains, but had less of an effect on IR-induced voiding dysfunction in bladders of T1DM rats. In summary, PEx-4 with stronger antioxidant activity and long-lasting bioavailability may efficiently confer therapeutic efficacy to ameliorate IR-evoked brain damage through the inhibitory action on oxidative stress, ER stress, apoptosis, autophagy and pyroptosis signaling in diabetic rats.

Post-treatment with apocynin at a lower dose regulates the UPR branch of eIF2α and XBP-1 pathways after stroke

Stroke leads to disturbance in the physiology of the ER (Endoplasmic Reticulum) that triggers UPR (Unfolded Protein Response) pathways aimed to compensate neuronal cell damage. However, sustained UPR causes stressful conditions in the ER lumen forming abnormal protein aggregates. Stroke-induced oxidative stress also amalgamates with UPR to safeguard and ensure the proper functioning of brain cells. Thus we tested the effect of apocynin (a potent antioxidant) post-treatment in experimental stroke on the outcome of ER stress and UPR branch pathways. We administered a low dose of apocynin at 1 mg/kg (intraperitoneal) to adult Sprague-Dawley rats subjected to Middle Cerebral Artery Occlusion (MCAO) for two-time points. The first dose immediately after re-establishing the blood flow and another at 6 h of reperfusion. Apocynin post-treatment significantly reduced ROS (Reactive Oxygen Species) generation at an early reperfusion time point of 4 h. It preserved neuronal morphology, dendritic spine density, reduced protein aggregation, and brain damage after 24 h of reperfusion. Apocynin post-treatment regulates the two UPR branch pathways in our experimental paradigm. 1) Down-regulation of eIF2α (Eukaryotic Initiation Factor 2α) phosphorylation, and CHOP (C/EBP homologous protein) 2) by reducing the XBP-1 (X-Box binding Protein-1) mRNA splicing downstream to PERK (Protein Kinase RNA-Like ER Kinase) and IRE1α (Inositol Requiring Enzyme 1alpha) UPR pathways, respectively. Bioinformatics prediction showed that apocynin has binding sites for PERK (Protein Kinase RNA-Like ER Kinase) and IRE1α proteins. The amino acid residues interacting with apocynin were Cys891 and Gln889 (for PERK), and the amino acids Ser726, Arg722, and Ala719 (for IRE1α) lying within their activation loop. Overall, these studies indicate that apocynin post-treatment might regulate ER stress/UPR pathways and minimize stroke brain damage, thus having implications for developing newer strategies for stroke treatment.

Zinc Accumulation Aggravates Cerebral Ischemia/Reperfusion Injury Through Inducing Endoplasmic Reticulum Stress

Zinc is highly enriched in the central nervous system. Numerous evidences suggest that high concentration of zinc acts as a critical mediator of neuronal death in the ischemic brain, however, the possible mechanisms of neurotoxicity of zinc during cerebral ischemia/reperfusion (I/R) remain elusive. Endoplasmic reticulum (ER) is a storage location of intracellular zinc. ER stress related genes were up-regulated during zinc-induced neuronal death in vascular-type senile dementia. In the present study, we investigated whether intracellular accumulated zinc aggravates I/R injury through ER stress and ER stress-associated apoptosis. Male Sprague-Dawley rats were subjected to 90 min middle cerebral artery occlusion (MCAO) and received either vehicle or zinc chelator TPEN 15 mg/kg. The expression of ER stress related factors glucose-regulated protein 78 (GRP78) and phosphorylated eukaryotic initiation factor 2α (p-eIF2α), ER stress related apoptotic proteins CCAAT-enhancer-binding protein homologous protein (CHOP) and caspase-12, as well as anti-apoptotic factor B-cell lymphoma-2 (Bcl-2) were assessed 24 h after reperfusion. Our results showed that the levels of GRP78 and p-eIF2α, as well as CHOP and caspase-12, were increased in ischemic brain, indicating that cerebral I/R triggers ER stress. Furthermore, GRP78, CHOP and caspase-12 were all colocalized with the zinc-specific dyes NG, suggesting that there is certain relationship between cytosolic labile zinc and ER stress following cerebral ischemia. Chelating zinc with TPEN reversed the expression of GRP78, p-eIF2α in ischemic rats. Moreover, CHOP and NeuN double staining positive cells, as well as caspase-12 and TUNEL double staining positive cells were also decreased after TPEN treatment, indicating that chelating zinc might inhibit ER stress and decreased ER stress associated neuronal apoptosis. In addition, TPEN treatment reversed the downregulated level of Bcl-2, which localized in the ER membrane and involved in the dysfunction of ER, confirming that the anti-apoptosis effects of chelating zinc following I/R are exerted via inhibition of the ER stress. Taken together, this study demonstrated that excessive zinc activates ER stress and zinc induced neuronal cell death is at least partially due to ER stress specific neuronal apoptosis in ischemic penumbra, which may provide an important mechanism of cerebral I/R injury.

Comprehensive Assessment of the STIMs and Orais Expression in Polycystic Ovary Syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a heterogeneous endocrine disease characterized by irregular menstrual, hyperandrogenism, and polycystic ovaries. The definitive mechanism of the disorder is not fully elucidated. Store-operated Ca2+ entry (SOCE) plays a role in glucose and lipid metabolism, inflammation, hormone secretion, and cell proliferation. STIMs and Orais are the main elements of SOCE. The potential role of SOCE in PCOS pathogenesis remains unclear.

METHODS

The expression of STIMs and Orais in granulosa cells (GCs) derived from 83 patients with PCOS and 83 controls were analyzed, respectively, by using quantitative reverse transcription polymerase chain reaction. Binary regression analysis was used to identify the factors affecting PCOS after adjusted by body mass index and age. Pearson correlation analysis was used to determine the association between PCOS phenotypes and SOCE genes expression.

RESULTS

Significantly increased expression of STIM1, STIM2, Orai1, and Orai2 were observed in patients with PCOS compared with controls (P = 0.037, P = 0.004, P ≤ 0.001, and P = 0.013, respectively), whereas the expression of Orai3 was decreased (P = 0.003). In addition, the expression levels of STIMs and Orais were identified as the factors affecting PCOS (P < 0.05). The expressions of these genes were correlated with hormone level and antral follicle count (P < 0.05).

CONCLUSIONS

For the first time, our findings indicated that the elements of SOCE were differently expressed, where STIM1, STIM2, Orai1, and Orai2 significantly increased, whereas Orai3 decreased in PCOS GCs, which might be dominantly involved in dysfunction of ovarian GCs and hormonal changes in PCOS.

Exacerbated VEGF up-regulation accompanies diabetes-aggravated hemorrhage in mice after experimental cerebral ischemia and delayed reperfusion

Reperfusion therapy is the preferred treatment for ischemic stroke, but is hindered by its short treatment window, especially in patients with diabetes whose reperfusion after prolonged ischemia is often accompanied by exacerbated hemorrhage. The mechanisms underlying exacerbated hemorrhage are not fully understood. This study aimed to identify this mechanism by inducing prolonged 2-hour transient intraluminal middle cerebral artery occlusion in diabetic Ins2^Akita/+ mice to mimic patients with diabetes undergoing delayed mechanical thrombectomy. The results showed that at as early as 2 hours after reperfusion, Ins2^Akita/+ mice exhibited rapid development of neurological deficits, increased infarct and hemorrhagic transformation, together with exacerbated down-regulation of tight-junction protein ZO-1 and up-regulation of blood-brain barrier-disrupting matrix metallopeptidase 2 and matrix metallopeptidase 9 when compared with normoglycemic Ins2^+/+ mice. This indicated that diabetes led to the rapid compromise of vessel integrity immediately after reperfusion, and consequently earlier death and further aggravation of hemorrhagic transformation 22 hours after reperfusion. This observation was associated with earlier and stronger up-regulation of pro-angiogenic vascular endothelial growth factor (VEGF) and its downstream phospho-Erk1/2 at 2 hours after reperfusion, which was suggestive of premature angiogenesis induced by early VEGF up-regulation, resulting in rapid vessel disintegration in diabetic stroke. Endoplasmic reticulum stress-related pro-apoptotic C/EBP homologous protein was overexpressed in challenged Ins2^Akita/+ mice, which suggests that the exacerbated VEGF up-regulation may be caused by overwhelming endoplasmic reticulum stress under diabetic conditions. In conclusion, the results mimicked complications in patients with diabetes undergoing delayed mechanical thrombectomy, and diabetes-induced accelerated VEGF up-regulation is likely to underlie exacerbated hemorrhagic transformation. Thus, suppression of the VEGF pathway could be a potential approach to allow reperfusion therapy in patients with diabetic stroke beyond the current treatment window. Experiments were approved by the Committee on the Use of Live Animals in Teaching and Research of the University of Hong Kong [CULATR 3834-15 (approval date January 5, 2016); 3977-16 (approval date April 13, 2016); and 4666-18 (approval date March 29, 2018)].

Isoginkgetin attenuates endoplasmic reticulum stress-induced autophagy of brain after ischemic reperfusion injury

Isoginkgetin is characterized by properties of potent anticancer and anti-inflammation. To explore its effect on ischemic stroke, a rat model of ischemia/reperfusion (I/R) injury was established and induced by transient middle cerebral artery occlusion/reperfusion (MCAO/R). Different doses of isoginkgetin were intraperitoneally injected into each rat. Expressions of ER stress activation-related makers including phosphorylated inositol-requiring enzyme 1 (IRE1), phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), activating transcription factor-6 (ATF6), and two autophagy markers (ratio of LC3II/I and Beclin-1) were detected by western blot. Infarct volume, neurological deficits, and brain water content were detected. The results showed that ER stress and autophagy were activated by cerebral (I/R) injury, which could be effectively attenuated following pre-ischemia isoginkgetin administration. Moreover, autophagy induced by ER stress was triggered by the activation of PERK and IRE1 pathways. ER stress inhibitor (4-PBA) and ER related signaling inhibitors including PERK, GSK, IRE1, and DBSA markedly inhibited ER stress and autophagy induced by I/R. In addition, isoginkgetin markedly mitigated cerebral infarction, edema, neuronal apoptosis as well as neurological impairment induced by I/R injury, while tunicamycin (ER stress activator TM) and rapamycin (autophagy activator RAPA) could eliminate these lesions. This research identified a novel therapeutic agent isoginkgetin, which could effectively attenuate I/R injury by blocking autophagy induced by ER stress.

Evaluation of cerebroprotective effect of Ricinus communis leaves against ischemia reperfusion injury in rats

Background

Ricinus communis (RC) has been used for a long time as natural origin medicine in the treatment of central nervous system ailments. This present study was designed to identify the possible role of Ricinus communis leaves extract against ischemia-reperfusion induced-neurobehavioral changes, oxidative stress, histopathological and cellular modifications in the brain.

Methods

Sprague Dawley (SD) rats (200–250 g) were induced to bilateral common carotid artery occlusion (BCCAO) for around 30 min later subjected to reperfusion for 24 h to induce cerebral injury by reperfusion. Ricinus communis leaves extract (250 and 500 mg/kg, p.o) was administered continuously for 14 days and on the 15th-day animals were subjected to ischemia-reperfusion injury. Different behavioral tests and biochemical parameters were assessed subsequently.

Results

Fourteen days Ricinus communis leaves extract (250 and 500 mg/kg, p.o.) treatment very significantly improved neurobehavioral alterations when compared to control ischemia-reperfusion. Ricinus communis leaves extract (250 and 500 mg/kg, p.o.) kg, i.p. treatment significantly attenuated oxidative damage when compared to ischemia-reperfusion (I/R) group animals. In addition, Ricinus communis leaves extract treatment was well supported histopathologically when compared to the ischemia-reperfusion (I/R) group.

Conclusion

The data from this study recommend that treatment with Ricinus communis leaves extract increases the antioxidant protection against BCCAO-induced global cerebral ischemia and demonstrates neuroprotective activity.

How cytosolic compartments play safeguard functions against neuroinflammation and cell death in cerebral ischemia

Ischemic stroke is the second leading cause of mortality and disability globally. Neuronal damage following ischemic stroke is rapid and irreversible, and eventually results in neuronal death. In addition to activation of cell death signaling, neuroinflammation is also considered as another pathogenesis that can occur within hours after cerebral ischemia. Under physiological conditions, subcellular organelles play a substantial role in neuronal functionality and viability. However, their functions can be remarkably perturbed under neurological disorders, particularly cerebral ischemia. Therefore, their biochemical and structural response has a determining role in the sequel of neuronal cells and the progression of disease. However, their effects on cell death and neuroinflammation, as major underlying mechanisms of ischemic stroke, are still not understood. This review aims to provide a comprehensive overview of the contribution of each organelle on these pathological processes after ischemic stroke.

Rosuvastatin protects PC12 cells from hypoxia/reoxygenation-induced injury by inhibiting endoplasmic reticulum stress-induced apoptosis

The endoplasmic reticulum stress (ERS) response serves an important role in cerebral ischemia-reperfusion injury (CIRI). However, to the best of the our knowledge, the effect of rosuvastatin on the ERS response in CIRI has not yet been studied. In the present study, the effect of rosuvastatin on cell damage in CIRI was investigated; furthermore, the effect of rosuvastatin on the ERS response was explored. Firstly, a hypoxia/reoxygenation (H/R)-induced cell damage model was established in PC12 cells. Cell viability was subsequently detected by a Cell Counting Kit-8 assay. A lactate dehydrogenase kit was used to detect cytotoxicity. TUNEL assay was then used to measure the extent of cell apoptosis, and western blotting was used to analyze the expression levels of the apoptosis-associated proteins Bax, Bcl-2, cleaved caspase-3 and cleaved caspase-9. In addition, western blotting was used to detect the expression levels of ERS-associated proteins, including phosphorylated (p)-protein kinase R-like endoplasmic reticulum kinase (PERK), p-eukaryotic initiation factor 2α and other proteins. Treatment with rosuvastatin led to an increased activity of H/R-induced PC12 cells and a decrease in their cytotoxicity. Rosuvastatin also led to an inhibition in apoptosis and ERS in H/R-induced PC12 cells. After administration of the ERS response activator thapsigargin (TG), TG was found to reverse the protective effect of rosuvastatin on injury of H/R-induced PC12 cells. Taken together, these findings have shown that rosuvastatin is able to protect PC12 cells from H/R-induced injury via inhibiting ERS-induced apoptosis, providing a strong theoretical basis for the use of rosuvastatin in the clinical treatment of CIRI.

Electroacupuncture Regulates Endoplasmic Reticulum Stress and Ameliorates Neuronal Injury in Rats with Acute Ischemic Stroke

Ischemic stroke is a common cause of morbidity, mortality, and disability worldwide. Electroacupuncture (EA) is an effective method for alleviating brain damage after ischemic stroke. However, the underlying mechanism has not been fully elucidated. This study aimed to determine whether endoplasmic reticulum stress (ERS) could contribute to the protective effects of EA in cerebral ischemia/reperfusion injury (CIRI) to provide a rationale for the widespread clinical use of EA. Rats were divided into the sham-operated (sham) group, the CIRI (model) group, and the EA group. Rats in the model group were subjected to middle cerebral artery occlusion (MCAO) for 2 h followed by 72 h of reperfusion. Rats with CIRI were treated daily with EA at GV20 and ST36 for a total of 3 days. The Longa scoring system and adhesive removal somatosensory test were applied to evaluate neurological deficits. Then, 2,3,5-triphenyltetrazolium chloride (TTC) staining was performed to measure the infarct volume. Immunofluorescence staining for NeuN and GFAP and terminal deoxynucleotidyl transferase- (TdT-) mediated dUTP nick-end labeling (TUNEL) staining were performed to detect apoptotic cells in brain tissue. Immunohistochemistry, quantitative real-time polymerase chain reaction (qPCR), and western blotting were used to measure the levels of ERS indicators (GRP78, CHOP/GADD153, p-eIF2α, and caspase 12). The results showed that EA significantly reduced the cerebral infarct volume, improved neurological function, and inhibited neuronal apoptosis. In the EA group compared with the model group, the mRNA expression levels of GRP78 were significantly increased, and the expression levels of proapoptotic proteins (CHOP/GADD153, p-eIF2α, and caspase 12) were significantly decreased. These results suggest that the possible mechanism by which EA protects cells against neuronal injury in CIRI may involve inhibiting endoplasmic reticulum stress.

CTRP1 Attenuates Cerebral Ischemia/Reperfusion Injury via the PERK Signaling Pathway

Cerebral ischemic stroke is one of the leading causes of death worldwide. Previous studies have shown that circulating levels of CTRP1 are upregulated in patients with acute ischemic stroke. However, the function of CTRP1 in neurons remains unclear. The purpose of this study was to explore the role of CTRP1 in cerebral ischemia reperfusion injury (CIRI) and to elucidate the underlying mechanism. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral ischemic stroke in vivo and in vitro, respectively. CTRP1 overexpression lentivirus and CTRP1 siRNA were used to observe the effect of CTRP1 expression, and the PERK selective activator CCT020312 was used to activate the PERK signaling pathway. We found the decreased expression of CTRP1 in the cortex of MCAO/R-treated rats and OGD/R-treated primary cortical neurons. CTRP1 overexpression attenuated CIRI, accompanied by the reduction of apoptosis and suppression of the PERK signaling pathway. Interference with CTRP1 expression in vitro aggravated apoptotic activity and increased the expression of proteins involved in the PERK signaling pathway. Moreover, activating the PERK signaling pathway abolished the protective effects of CTRP1 on neuron injury induced by CIRI in vivo and in vitro. In conclusion, CTRP1 protects against CIRI by reducing apoptosis and endoplasmic reticulum stress (ERS) through inhibiting the PERK-dependent signaling pathway, suggesting that CTRP1 plays a crucial role in the pathogenesis of CIRI.

Mechanism of Endoplasmic Reticulum Stress in Cerebral Ischemia

Endoplasmic reticulum (ER) is the main organelle for protein synthesis, trafficking and maintaining intracellular Ca²⁺ homeostasis. The stress response of ER results from the disruption of ER homeostasis in neurological disorders. Among these disorders, cerebral ischemia is a prevalent reason of death and disability in the world. ER stress stemed from ischemic injury initiates unfolded protein response (UPR) regarded as a protection mechanism. Important, disruption of Ca²⁺ homeostasis resulted from cytosolic Ca²⁺ overload and depletion of Ca²⁺ in the lumen of the ER could be a trigger of ER stress and the misfolded protein synthesis. Brain cells including neurons, glial cells and endothelial cells are involved in the complex pathophysiology of ischemic stroke. This is generally important for protein underfolding, but even more for cytosolic Ca²⁺ overload. Mild ER stress promotes cells to break away from danger signals and enter the adaptive procedure with the activation of pro-survival mechanism to rescue ischemic injury, while chronic ER stress generally serves as a detrimental role on nerve cells via triggering diverse pro-apoptotic mechanism. What’s more, the determination of some proteins in UPR during cerebral ischemia to cell fate may have two diametrically opposed results which involves in a specialized set of inflammatory and apoptotic signaling pathways. A reasonable understanding and exploration of the underlying molecular mechanism related to ER stress and cerebral ischemia is a prerequisite for a major breakthrough in stroke treatment in the future. This review focuses on recent findings of the ER stress as well as the progress research of mechanism in ischemic stroke prognosis provide a new treatment idea for recovery of cerebral ischemia.

The Protective Effect of Liquiritin in Hypoxia/Reoxygenation-Induced Disruption on Blood Brain Barrier

Background: Stroke is the second leading cause of death in human life health, but current treatment strategies are limited to thrombolytic therapy, and because of the tight time window, many contraindications, and only a very small number of people can benefit from it, new therapeutic strategies are needed to solve this problem. As a physical barrier between the central nervous system and blood, the blood-brain barrier (BBB) maintains the homeostasis of the central nervous system. Maintaining the integrity of the BBB may emerge as a new therapeutic strategy. Liquiritin (LQ) is a flavonoid isolated from the medicinal plant Glycyrrhiza uralensis Fisch. ex DC. (Fabaceae), and this study aims to investigate the protective effects of LQ on brain microvascular endothelial cells (BMECs), to provide a new therapeutic strategy for stroke treatment, and also to provide research ideas for the development of traditional Chinese medicine (TCM).

Methods: The protective effects of LQ on HBMECs under the treatment of hypoxia reoxygenation (H/R) were investigated from different aspects by establishing a model of H/R injury to mimic ischemia-reperfusion in vivo while administrating different concentrations of LQ, which includes: cell proliferation, migration, angiogenesis, mitochondrial membrane potential as well as apoptosis. Meanwhile, the mechanism of LQ to protect the integrity of BBB by antioxidation and inhibiting endoplasmic reticulum (ER) stress was also investigated. Finally, to search for possible targets of LQ, a proteomic analysis approach was employed.

Results: LQ can promote cell proliferation, migration as well as angiogenesis and reduce mitochondrial membrane potential damage and apoptosis. Meanwhile, LQ can also reduce the expression of related adhesion molecules, and decrease the production of reactive oxygen species. In terms of mechanism study, we demonstrated that LQ could activate Keap1/Nrf2 antioxidant pathway, inhibit ER stress, and maintain the integrity of BBB. Through differential protein analysis, 5 disease associated proteins were found.

Conclusions: Studies have shown that LQ can promote cell proliferation, migration as well as angiogenesis, and reduce cell apoptosis, which may be related to its inhibition of oxidative and ER stress, and then maintain the integrity of BBB. Given that five differential proteins were found by protein analysis, future studies will revolve around the five differential proteins.

Lipid droplets in the nervous system

Lipid droplets are dynamic intracellular lipid storage organelles that respond to the physiological state of cells. In addition to controlling cell metabolism, they play a protective role for many cellular stressors, including oxidative stress. Despite prior descriptions of lipid droplets appearing in the brain as early as a century ago, only recently has the role of lipid droplets in cells found in the brain begun to be understood. Lipid droplet functions have now been described for cells of the nervous system in the context of development, aging, and an increasing number of neuropathologies. Here, we review the basic mechanisms of lipid droplet formation, turnover, and function and discuss how these mechanisms enable lipid droplets to function in different cell types of the nervous system under healthy and pathological conditions.

Nao-Fu-Cong ameliorates diabetic cognitive dysfunction by inhibition of JNK/CHOP/Bcl2-mediated apoptosis in vivo and in vitro

Chinese herbal compound Nao-Fu-Cong (NFC) has been mainly used to treat cognitive disorders in Traditional Chinese Medicine (TCM). The present study aimed to investigate whether its neuroprotective effects might be related to the inhibition of JNK/CHOP/Bcl2-mediated apoptosis pathway or not. We randomly assigned STZ (60 mg·kg^-1)-induced diabetic rats into control group, diabetic model group and NFC groups (low-dose, medium-dose and high-dose). The primary culture of hippocampal neurons were transferred into different culture media on the third day. The cells were then divided into control group, high-glucose group, NFC (low-dose, medium-dose and high-dose) groups, CHOP si-RNA intervention group, JNK pathway inhibitor SP600125 group and oxidative stress inhibitor N-acetylcysteine (NAC) group. NFC significantly improved the cognitive function of diabetic rats, and had neuroprotective effect on hippocampal neurons cultured in high glucose. Further research results showed that NFC could reduce the apoptosis of hippocampal neurons in rats with diabetic cognitive dysfunction. NFC had inhibitory effects on CHOP/JNK apoptosis pathway induced by high glucose, and also decreased the levels of ROS and increased the mitochondrial membrane potential. These suggested that the neuroprotective effect of NFC might be related to the inhibition of CHOP and JNK apoptotic signaling pathways, and the cross pathway between oxidative stress and mitochondrial damage pathway.

Pharmacological Approach for Neuroprotection After Cardiac Arrest-A Narrative Review of Current Therapies and Future Neuroprotective Cocktail

Cardiac arrest (CA) results in global ischemia-reperfusion injury damaging tissues in the whole body. The landscape of therapeutic interventions in resuscitation medicine has evolved from focusing solely on achieving return of circulation to now exploring options to mitigate brain injury and preserve brain function after CA. CA pathology includes mitochondrial damage and endoplasmic reticulum stress response, increased generation of reactive oxygen species, neuroinflammation, and neuronal excitotoxic death. Current non-pharmacologic therapies, such as therapeutic hypothermia and extracorporeal cardiopulmonary resuscitation, have shown benefits in protecting against ischemic brain injury and improving neurological outcomes post-CA, yet their application is difficult to institute ubiquitously. The current preclinical pharmacopeia to address CA and the resulting brain injury utilizes drugs that often target singular pathways and have been difficult to translate from the bench to the clinic. Furthermore, the limited combination therapies that have been attempted have shown mixed effects in conferring neuroprotection and improving survival post-CA. The global scale of CA damage and its resultant brain injury necessitates the future of CA interventions to simultaneously target multiple pathways and alleviate the hemodynamic, mitochondrial, metabolic, oxidative, and inflammatory processes in the brain. This narrative review seeks to highlight the current field of post-CA neuroprotective pharmaceutical therapies, both singular and combination, and discuss the use of an extensive multi-drug cocktail therapy as a novel approach to treat CA-mediated dysregulation of multiple pathways, enhancing survival, and neuroprotection.

Protective Effect of Hydrogen Gas on Mouse Hind Limb Ischemia-Reperfusion Injury

BACKGROUND

The aim of this study was to investigate the mechanism of hydrogen gas on hind limb IR injury.

METHODS

Male C57BL/6 mice were randomly divided into three groups: sham group (Sham), ischemia-reperfusion group (IR), IR plus H₂ inhalation group (IR + H₂). IR was induced by interrupting hind limb blood flow for 3h, followed by 4h of reperfusion, and H₂ was administered by inhalation throughout the reperfusion process. Our data show that H₂ inhalation could significantly decrease the infarct-affected tissue volume (P < 0.05), attenuate the degree of morphological injury (P < 0.05), and suppress the level of oxidative stress damage (P < 0.05), compared with the IR group. In exploring the underlying mechanisms, we found that hydrogen could markedly mitigate the degree of IR-induced ER stress and apoptosis (P < 0.05). Additionally, hydrogen could markedly inhibit the IR injury by modulating the phosphorylated c-Jun N-terminal kinase (JNK) signaling pathway (P < 0.05).

CONCLUSIONS

Taken together, these results revealed the protective effect of hydrogen gas on hind limb ischemia reperfusion injury on mice by attenuating oxidative stress, impairing ER stress and apoptosis, and its ability to modulate JNK signaling pathway.

Insight into the effects of melatonin on endoplasmic reticulum, mitochondrial function, and their cross-talk in the stroke

Ischemic stroke has remained a principal cause of mortality and neurological disabilities worldwide. Blood flow resumption, reperfusion, in the cerebral ischemia prompts a cascade in the brain characterized by various cellular mechanisms like mitochondrial dysfunction, oxidative stresses, endoplasmic reticulum (ER) stress, and excitotoxicity, finally resulting in programmed cell death. Any changes in the ER-mitochondria axis are probably responsible for both the onset and progression of central nervous system diseases. Melatonin, a neurohormone secreted by the pineal gland, has antioxidative, anti-inflammatory, and anti-apoptotic properties. Most studies have shown that it exerts neuroprotective effects against ischemic stroke. It was observed that melatonin therapy after the stroke not only leads to reduce mitochondrial dysfunction but also cause to alleviate ER stress and inflammation. This review discusses the impact of melatonin on mitochondrial, ER function, and on the crosstalk between two organelles as a therapeutic target for stroke. Given that the influences of melatonin on each organelle separately, its effects on mechanisms of crosstalk between ER and mitochondria are discussed.