Rufinamide pretreatment attenuates ischemia-reperfusion injury in the gerbil hippocampus

Extremely Low-Frequency Electromagnetic Stimulation (ELF-EMS) Improves Neurological Outcome and Reduces Microglial Reactivity in a Rodent Model of Global Transient Stroke

Extremely low-frequency electromagnetic stimulation (ELF-EMS) was demonstrated to be significantly beneficial in rodent models of permanent stroke. The mechanism involved enhanced cerebrovascular perfusion and endothelial cell nitric oxide production. However, the possible effect on the neuroinflammatory response and its efficacy in reperfusion stroke models remains unclear. To evaluate ELF-EMS effectiveness and possible immunomodulatory response, we studied neurological outcome, behavior, neuronal survival, and glial reactivity in a rodent model of global transient stroke treated with 13.5 mT/60 Hz. Next, we studied microglial cells migration and, in organotypic hippocampal brain slices, we assessed neuronal survival and microglia reactivity. ELF-EMS improved the neurological score and behavior in the ischemia-reperfusion model. It also improved neuronal survival and decreased glia reactivity in the hippocampus, with microglia showing the first signs of treatment effect. In vitro ELF-EMS decreased (Lipopolysaccharide) LPS and ATP-induced microglia migration in both scratch and transwell assay. Additionally, in hippocampal brain slices, reduced microglial reactivity, improved neuronal survival, and modulation of inflammation-related markers was observed. Our study is the first to show that an EMF treatment has a direct impact on microglial migration. Furthermore, ELF-EMS has beneficial effects in an ischemia/reperfusion model, which indicates that this treatment has clinical potential as a new treatment against ischemic stroke.

Neuroprotective Effects of Ethanol Extract of Polyscias fruticosa (EEPF) against Glutamate-Mediated Neuronal Toxicity in HT22 Cells

In traditional herbal medicine, the Polyscias fruticosa has been frequently used for the treatment of ischemia and inflammation. Oxidative stress mediated by elevated glutamate levels cause neuronal cell death in ischemia and various neurodegenerative diseases. However, so far, the neuroprotective effects of this plant extract against glutamate-mediated cell death have not been investigated in cell models. The current study investigates the neuroprotective effects of ethanol extracts of Polyscias fruticosa (EEPF) and elucidates the underlying molecular mechanisms of EEPFs relevant to neuroprotection against glutamate-mediated cell death. The oxidative stress-mediated cell death was induced by 5 mM glutamate treatment in HT22 cells. The cell viability was measured by a tetrazolium-based EZ-Cytox reagent and Calcein-AM fluorescent dye. Intracellular Ca²⁺ and ROS levels were measured by fluorescent dyes, fluo-3 AM and 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA), respectively. Protein expressions of p-AKT, BDNF, p-CREB, Bax, Bcl-2, and apoptosis-inducing factor (AIF) were determined by western blot analysis. The apoptotic cell death was measured by flow cytometry. The in vivo efficacy of EEPF was evaluated using the Mongolian gerbil mouse by surgery-induced brain ischemia. EEPF treatment showed a neuroprotective effect against glutamate-induced cell death. The EEPF co-treatment reduced the intracellular Ca²⁺ and ROS and apoptotic cell death. Furthermore, it recovered the p-AKT, p-CREB, BDNF, and Bcl-2 levels decreased by glutamate. The EEPF co-treatment suppressed the activation of apoptotic Bax, the nuclear translocation of AIF, and mitogen-activated protein kinase (MAPK) pathway proteins (ERK1/2, p38, JNK). Further, EEPF treatment significantly rescued the degenerative neurons in the ischemia-induced Mongolian gerbil in vivo model. EEPF exhibited neuroprotective properties that suppress glutamate-mediated neurotoxicity. The underlying mechanism of EEPF is increasing the level of p-AKT, p-CREB, BDNF, and Bcl-2 associated with cell survival. It has therapeutic potential for the treatment of glutamate-mediated neuropathology.

Purpurogallin improves neurological functions of cerebral ischemia and reperfusion mice by inhibiting endoplasmic reticulum stress and neuroinflammation

BACKGROUND

Purpurogallin (PPG) has been testified to have neuroprotective effects. This study intends to probe the neuroprotection of PPG on cerebral ischemia/reperfusion (I/R) injury and its potential mechanism.

METHODS

C57/B6 mice, BV2 microglia and HT22 hippocampal neurons were used for in-vivo and in-vitro experiments. I/R injury models were constructed using middle cerebral artery occlusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R), respectively. The expression of apoptosis and inflammatory proteins, and endoplasmic reticulum (ER) stress proteins were gauged by Western blotting (WB). The contents of inflammatory cytokines in OGD/R-induced BV2 microglia were testified by enzyme-linked immunosorbent assay (ELISA). Cell counting kit-8 (CCK-8), TUNEL assay and flow cytometry (FCM) were utilized to examine the viability and apoptosis of cells. The neurological, learning and memory functions were evaluated by the modified neurological severity score (mNSS) and water maze experiment. 2, 3, 5-triphenyltetrazole chloride (TTC) staining was utilized to calculate the volume of cerebral infarction and cerebral edema in the peri-infarct area. Apoptosis-related proteins, inflammation-related proteins and ER stress proteins were gauged by WB. ELISA was conducted to verify inflammatory cytokines.

RESULTS

PPG treatment notably abated the expression of ER stress proteins and inflammatory factors in OGD/R-induced BV2 microglia and boosted HT22 neuron's viability and eased their apoptosis in comparison to the control group. In vivo, PPG treatment signally lessened cerebral infarct area, cerebral edema, and neurological deficit scores in MCAO/R mice. Additionally, PPG caused a dramatic decline in neuronal apoptosis and levels of ER stress proteins and inflammatory factors in the brain's peri-infarct region of MCAO/R mice. Mechanically, PPG blocked the TLR4/NF-κB pathway in OGD/R-induced BV2, HT22 neurons, and the MCAO/R mice.

CONCLUSION

PPG attenuates brain I/R damage probably by suppressing ER stress and neuroinflammation via inactivation of the TLR4/NF-κB pathway, suggesting that PPG may be a candidate drug for treating cerebral I/R injury.

Hypothermia Induced by Oxcarbazepine after Transient Forebrain Ischemia Exerts Therapeutic Neuroprotection through Transient Receptor Potential Vanilloid Type 1 and 4 in Gerbils

In the present study, we investigated the neuroprotective effect of post-ischemic treatment with oxcarbazepine (OXC; an anticonvulsant compound) against ischemic injury induced by transient forebrain ischemia and its mechanisms in gerbils. Transient ischemia was induced in the forebrain by occlusion of both common carotid arteries for 5 min under normothermic conditions (37 ± 0.2 °C). The ischemic gerbils were treated with vehicle, hypothermia (whole-body cooling; 33.0 ± 0.2 °C), or 200 mg/kg OXC. Post-ischemic treatments with vehicle and hypothermia failed to attenuate and improve, respectively, ischemia-induced hyperactivity and cognitive impairment (decline in spatial and short-term memory). However, post-ischemic treatment with OXC significantly attenuated the hyperactivity and the cognitive impairment, showing that OXC treatment significantly reduced body temperature (to about 33 °C). When the hippocampus was histopathologically examined, pyramidal cells (principal neurons) were dead (lost) in the subfield Cornu Ammonis 1 (CA1) of the gerbils treated with vehicle and hypothermia on Day 4 after ischemia, but these cells were saved in the gerbils treated with OXC. In the gerbils treated with OXC after ischemia, the expression of transient receptor potential vanilloid type 1 (TRPV1; one of the transient receptor potential cation channels) was significantly increased in the CA1 region compared with that in the gerbils treated with vehicle and hypothermia. In brief, our results showed that OXC-induced hypothermia after transient forebrain ischemia effectively protected against ischemia–reperfusion injury through an increase in TRPV1 expression in the gerbil hippocampal CA1 region, indicating that TRPV1 is involved in OXC-induced hypothermia.

Rufinamide (RUF) suppresses inflammation and maintains the integrity of the blood-brain barrier during kainic acid-induced brain damage

Rufinamide (RUF) is a structurally unique anti-epileptic drug, but its protective mechanism against brain injury remains unclear. In the present study, we validated how the RUF protected mice with kainic acid (KA)-induced neuronal damage. To achieve that, a mouse epilepsy model was established by KA intraperitoneal injection. After Nissl staining, although there was a significant reduction in Nissl bodies in mice treated with KA, 40, 80, and 120 mg/kg, RUF significantly reduced KA-induced neuronal damage, in a dose-dependent manner. Among them, 120 mg/kg RUF was most pronounced. Immunohistochemistry (IHC) and western blot analysis showed that RUF inhibited the IBA-1 overexpression caused by KA to block microglia cell overactivation. Further, RUF treatment partially reversed neuroinflammatory cytokine (IL-1β, TNFα, HMGB1, and NLRP3) overexpression in mRNA and protein levels in KA mice. Moreover, although KA stimulation inhibited the expression of tight junctions, RUF treatment significantly upregulated expression of tight junction proteins (occludin and claudin 5) in both mRNA and protein levels in the brain tissues of KA mice. RUF inhibited the overactivation of microglia, suppressed the neuroinflammatory response, and reduced the destruction of blood-brain barrier, thereby alleviating the excitatory nerve damage of the KA-mice.

Sevoflurane protects against ischemia-reperfusion injury in mice after total knee arthroplasty via facilitating RASD1-mediated protein kinase A pathway activation

This study aimed to explore effects of Sevoflurane on ischemia-reperfusion (I/R) injury after total knee arthroplasty (TKA). To explore potential molecular mechanism, Ras related dexamethasone induced 1 (RASD1), a Protein kinase A (PKA) activator, frequently associated with various models of I/R injury, was also investigated. In vivo mouse models with I/R injury after TKA and in vitro cell models with I/R injury were induced. Contents of creatinine kinase (CK), lactic dehydrogenase (LDH), superoxide dismutase (SOD), and malondialdehyde (MDA), serum levels of inflammatory factors, expression of PKA pathway-related genes and cell proliferation and apoptosis were measured. RASD1 was altered and PKA pathway was inhibited in mice and cells to elucidate the involvement of RASD1 and PKA pathway in Sevoflurane treatment on I/R injury. RASD1 was upregulated in I/R injury after TKA. Sevoflurane treatment or silencing RASD1 reduced RASD1 expression, CK, LDH and MDA contents, inflammation, apoptosis, but increased proliferation, SOD content, cAMP expression, and extents of PKA and cAMP responsive element binding protein (CREB) phosphorylation in skeletal muscle cells of I/R injury. Additionally, PKA pathway activation potentiated the therapeutic effect of Sevoflurane on I/R injury after TKA. Altogether, Sevoflurane treatment confines I/R injury after TKA via RASD1-mediated PKA pathway activation.

Ion channels and transporters in microglial function in physiology and brain diseases

Microglial cells interact with all components of the central nervous system (CNS) and are increasingly recognized to play essential roles during brain development, homeostasis and disease pathologies. Functions of microglia include maintaining tissue integrity, clearing cellular debris and dead neurons through the process of phagocytosis, and providing tissue repair by releasing anti-inflammatory cytokines and neurotrophic factors. Changes of microglial ionic homeostasis (Na⁺, Ca²⁺, K⁺, H⁺, Cl^-) are important for microglial activation, including proliferation, migration, cytokine release and reactive oxygen species production, etc. These are mediated by ion channels and ion transporters in microglial cells. Here, we review the current knowledge about the role of major microglial ion channels and transporters, including several types of Ca²⁺ channels (store-operated Ca²⁺ entry (SOCE) channels, transient receptor potential (TRP) channels and voltage-gated Ca²⁺ channels (VGCCs)) and Na⁺ channels (voltage-gated Na⁺ channels (Nav) and acid-sensing ion channels (ASICs)), K⁺ channels (inward rectifier K⁺ channels (K_ir), voltage-gated K⁺ channels (K_V) and calcium-activated K⁺ channels (K_Ca)), proton channels (voltage-gated proton channel (Hv1)), and Cl^- channels (volume (or swelling)-regulated Cl^- channels (VRCCs) and chloride intracellular channels (CLICs)). In addition, ion transporter proteins such as Na⁺/Ca²⁺ exchanger (NCX), Na⁺-K⁺-Cl^- cotransporter (NKCC1), and Na⁺/H⁺ exchanger (NHE1) are also involved in microglial function in physiology and brain diseases. We discussed microglial activation and neuroinflammation in relation to the ion channel/transporter stimulation under brain disease conditions and therapeutic aspects of targeting microglial ion channels/transporters for neurodegenerative disease, ischemic stroke, traumatic brain injury and neuropathic pain.

Design, Synthesis, Molecular Docking, Antiapoptotic and Caspase-3 Inhibition of New 1,2,3-Triazole/Bis-2(1H)-Quinolinone Hybrids

A series of novel 1,2,3-triazoles hybridized with two quinolin-2-ones, was designed and synthesized through click reactions. The structures of the synthesized compounds were elucidated by NMR, IR, and mass spectra in addition to elemental analysis. The synthesized compounds were assessed for their antiapoptotic activity in testis, as testicular torsion is the main cause of male infertility. This effect was studied in light of decreasing tissue damage induced by I/R in the testis of rats using N-acetylcysteine (NAC) as an antiapoptotic reference. Compounds 6a-c were the most active antiapoptotic hybrids with significant measurements for malondialdehyde (MDA) and total antioxidant capacity (TAC) and the apoptotic biomarkers (testicular testosterone, TNFα, and caspase-3) in comparison to the reference. A preliminary mechanistic study was performed to improve the antiapoptotic activity through caspase-3 inhibition. A compound assigned as 6-methoxy-4-(4-(((2-oxo-1,2-dihydroquinolin-4-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)quinolin-2(1H)-one (6c) was selected as a representative of the most active hybrids in comparison to NAC. Assay of cytochrome C for 6c revealed an attenuation of cytochrome C level about 3.54 fold, comparable to NAC (4.13 fold). In caspases-3,8,9 assays, 6c was found to exhibit more potency and selectivity toward caspase-3 than other caspases. The testicular histopathological investigation was carried out on all targeted compounds 6a-g, indicating a significant improvement in the spermatogenesis process for compounds 6a-c if compared to the reference relative to the control. Finally, molecular docking studies were done at the caspase-3 active site to suggest possible binding modes. Hence, it could conceivably be hypothesized that compounds 6a-c could be considered good lead candidate compounds as antiapoptotic agents.

Cepharanthine attenuates cerebral ischemia/reperfusion injury by reducing NLRP3 inflammasome-induced inflammation and oxidative stress via inhibiting 12/15-LOX signaling

Cepharanthine (CEP) is a potential candidate for treatment of cerebral ischemia/reperfusion (I/R) injury, due to its anti-inflammatory and anti-oxidative properties. To investigate the effect of CEP on cerebral I/R injury, we established a mouse model of transient middle cerebral artery occlusion (tMCAO) and a microglia cell model of oxygen and glucose deprivation/reoxygenation (OGD/R). Administration of CEP attenuated neurological deficits, reduced infarct volume and edema, and decreased microglia activation in MCAO mice. Immunofluorescence staining showed an up-regulation in NLR Family Pyrin Domain Containing 3 (NLRP3) immunoreactivity in Iba1-labled microglia together with total Iba1 and NLRP3 expression in the brain following tMCAO, while down-regulated by CEP treatment. In both tMCAO-induced mice and OGD/R-treated BV-2 cells, CEP exhibited dose-dependent inhibition on the expression of NLRP3, ASC and cleaved caspase-1. Importantly, CEP attenuated tMCAO or OGD/R-induced overproduction of M1 microglia-regulated pro-inflammation cytokines IL-1β and IL-18, suggesting that CEP might involve in suppressing microglia polarization to M1 phenotype in vivo and in vitro. Moreover, CEP dose-dependently inhibited tMCAO-induced arachidonate 15 lipoxygenase (ALOX15) together with Iba1-labled microglia. The subsequent ALOX15-mediated oxidative stress was decreased by CEP treatment in vivo and in vitro, as evidenced by reduced ROS generation and MDA level, and increased SOD activity. Taken together, we demonstrate that CEP attenuates cerebral I/R injury probably by inhibiting microglia activation and NLRP3 inflammasome-induced inflammation and reducing oxidative stress via suppressing 12/15-LOX signaling.

Post-treatment with oxcarbazepine confers potent neuroprotection against transient global cerebral ischemic injury by activating Nrf2 defense pathway

Oxcarbazepine (OXC), a voltage-gated sodium channel blocker, is an antiepileptic medication and used for the bipolar disorders treatment. Some voltage-gated sodium channel blockers have been demonstrated to display strong neuroprotective properties in models of cerebral ischemia. However, neuroprotective effects and mechanisms of OXC have not yet been reported. Here, we investigated the protective effect of OXC and its mechanisms in the cornu ammonis 1 subfield (CA1) of gerbils subjected to 5 min of transient global cerebral ischemia (tGCI). tGCI led to death of most pyramidal neurons in CA1 at 5 days after ischemia. OXC (100 and 200 mg/kg) was intraperitoneally administered once at 30 min after tGCI. Treatment with 200 mg/kg, not 100 mg/kg OXC, significantly protected CA1 pyramidal neurons from tGCI-induced injury. OXC treatment significantly decreased superoxide anion production, 4-hydroxy-2-nonenal and 8-hydroxyguanine levels in ischemic CA1 pyramidal neurons. In addition, the treatment restored levels of superoxide dismutases, catalase, and glutathione peroxidase. Furthermore, the treatment distinctly inhibited tGCI-induced microglia activation and significantly reduced levels of pro-inflammatory cytokines (interleukin-1β and tumor necrosis factor-α). In particular, OXC treatment significantly enhanced expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream protein heme oxygenase-1 in ischemic CA1. The neuroprotective effects of OXC were abolished by brusatol (an inhibitor of Nrf2). Taken together, these results indicate that post-treatment of OXC can display neuroprotection against brain injuries following ischemic insults. This neuroprotection may be displayed by attenuation of oxidative stress and neuroinflammation, which can be mediated by activation of Nrf2 pathway.

Pre-Treatment with Laminarin Protects Hippocampal CA1 Pyramidal Neurons and Attenuates Reactive Gliosis Following Transient Forebrain Ischemia in Gerbils

Transient brain ischemia triggers selective neuronal death/loss, especially in vulnerable regions of the brain including the hippocampus. Laminarin, a polysaccharide originating from brown seaweed, has various pharmaceutical properties including an antioxidant function. To the best of our knowledge, few studies have been conducted on the protective effects of laminarin against ischemic injury induced by ischemic insults. In this study, we histopathologically investigated the neuroprotective effects of laminarin in the Cornu Ammonis 1 (CA1) field of the hippocampus, which is very vulnerable to ischemia-reperfusion injury, following transient forebrain ischemia (TFI) for five minutes in gerbils. The neuroprotective effect was examined by cresyl violet staining, Fluoro-Jade B histofluorescence staining and immunohistochemistry for neuronal-specific nuclear protein. Additionally, to study gliosis (glial changes), we performed immunohistochemistry for glial fibrillary acidic protein to examine astrocytes, and ionized calcium-binding adaptor molecule 1 to examine microglia. Furthermore, we examined alterations in pro-inflammatory M1 microglia by using double immunofluorescence. Pretreatment with 10 mg/kg laminarin failed to protect neurons in the hippocampal CA1 field and did not attenuate reactive gliosis in the field following TFI. In contrast, pretreatment with 50 or 100 mg/kg laminarin protected neurons, attenuated reactive gliosis and reduced pro-inflammatory M1 microglia in the CA1 field following TFI. Based on these results, we firmly propose that 50 mg/kg laminarin can be strategically applied to develop a preventative against injuries following cerebral ischemic insults.

MicroRNA-579-3p Exerts Neuroprotective Effects Against Ischemic Stroke via Anti-Inflammation and Anti-Apoptosis

BACKGROUND/AIMS

Multiple studies have found that microRNAs (miRNAs) are involved in the development of cerebral ischemia. MiR-579-3p can inhibit inflammatory responses and apoptosis, leading to ischemia/reperfusion (I/R) damage. However, the mechanism of how miR-579-3p actions in brain I/R injury remains unclear. This study aimed to investigate the mechanism of the role of miR-579-3p in brain I/R injury.

METHODS

A rat model of cerebral ischemia-reperfusion injury was established by suture method. The effects of miR-579-3p on cerebral infarction size, brain water content, and neurological symptoms were evaluated. Flow cytometry was used to detect apoptosis. ELISA was used to detect the level of inflammatory factors. Western blot was used to detect the expression of P65, NCOA1, Bcl-2 and Bax. The relationship between miR-579-3p and NCOA1 was analyzed by bioinformatics analysis and luciferase assay.

RESULTS

Overexpression of miR-579-3p reduced infarct volume, brain water content and neurological deficits. Overexpression of miR-579-3p inhibited the expression level of the inflammatory cytokines, such as TNF-α, IL-6, COX-2 and iNOS, and increased the expression level of IL-10. MiR-579-3p overexpression inhibited NF-кB activity by reducing NRIP1. In addition, miR-579-3p could reduce the apoptotic rate of cortical neurons. Overexpression of miR-579-3p inhibited the activity of caspase-3, increased the expression level of anti-apoptotic gene Bcl-2 in neurons, and decreased the expression level of apoptotic gene Bax.

CONCLUSION

miR-579-3p can be used to treat brain I/R injury, and its neuroprotective effect may be ascribed to the reduction of inflammation and apoptosis.

Analysis of knowledge bases and research focuses of cerebral ischemia-reperfusion from the perspective of mapping knowledge domain

Cerebral ischemia-reperfusion (IR) has attracted wide attention as a serious clinical problem. So far, the field has accumulated a large amount of scientific research literature. To clarify the temporal and spatial distribution characteristics of research resources, knowledge bases and research focuses, a visual analysis was performed on 5814 articles cited in the WoS databases from 2004 to 2019. This analysis was based on bibliometrics and mapping knowledge domain (MKD) analysis with VOSviewer, and CiteSpace 5.4.R4. The results can be elaborated from four aspects. First, the volume of publications in this area is on the rise. Second, the United States and China are the active regions. The USA is the central region of cerebral ischemia-reperfusion research. Third, the knowledge bases of IR have focused on five major areas of "Suitable small-animal models", "A framework with further study", "Molecular signaling targets by oxidative stress", "Finding new potential targets for therapy" and "Protective effect of multiple transient ischemia". Fourth, the research focuses consist of three representative areas: "Oxidative stress closelyd with cerebral ischemia-reperfusion", "Neuronal apoptosis and neuronal protection", and "Neuroprotective effect of the blood-brain barrier".

Time-course pattern of neuronal loss and gliosis in gerbil hippocampi following mild, severe, or lethal transient global cerebral ischemia

Transient ischemia in the whole brain leads to neuronal loss/death in vulnerable brain regions. The striatum, neocortex and hippocampus selectively loose specific neurons after transient ischemia. Just 5 minutes of transient ischemia can cause pyramidal neuronal death in the hippocampal cornu ammonis (CA) 1 field at 4 days after transient ischemia. In this study, we investigated the effects of 5-minute (mild), 15-minute (severe), and 20-minute (lethal) transient ischemia by bilateral common carotid artery occlusion (BCCAO) on behavioral change and neuronal death and gliosis (astrocytosis and microgliosis) in gerbil hippocampal subregions (CA1–3 region and dentate gyrus). We performed spontaneous motor activity test to evaluate gerbil locomotor activity, cresyl violet staining to detect cellular distribution, neuronal nuclei immunohistochemistry to detect neuronal distribution, and Fluoro-Jade B histofluorescence to evaluate neuronal death. We also conducted immunohistochemical staining for glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 (Iba1) to evaluate astrocytosis and microgliosis, respectively. Animals subjected to 20-minute BCCAO died in at least 2 days. BCCAO for 15 minutes led to pyramidal cell death in hippocampal CA1–3 region 2 days later and granule cell death in hippocampal dentate gyrus 5 days later. Similar results were not found in animals subjected to 5-minute BCCAO. Gliosis was much more rapidly and severely progressed in animals subjected to 15-minute BCCAO than in those subjected to 5-minute BCCAO. Our results indicate that neuronal loss in the hippocampal formation following transient ischemia is significantly different according to regions and severity of transient ischemia. The experimental protocol was approved by Institutional Animal Care and Use Committee (AICUC) of Kangwon National University (approval No. KW-180124-1) on May 22, 2018.

Intermittent fasting increases SOD2 and catalase immunoreactivities in the hippocampus but does not protect from neuronal death following transient ischemia in gerbils

Intermittent fasting has been shown to have neuroprotective effects against transient focal cerebral ischemic insults. However, the effects of intermittent fasting on transient global ischemic insult has not been studied much yet. The present study examined effects of intermittent fasting on endogenous antioxidant enzyme expression levels in the hippocampus and investigated whether the fasting protects neurons 5 days after 5 min of transient global cerebral ischemia. Gerbils were randomly subjected to either ad libitum or alternate-day intermittent fasting for two months and assigned to sham surgery or transient ischemia. Changes of antioxidant enzymes were examined using immunohistochemistry for cytoplasmic superoxide dismutase 1 (SOD1), mitochondrial (SOD2), catalase (CAT), and glutathione peroxidase (GPX). The effects of intermittent fasting on ischemia-induced antioxidant changes, neuronal damage/degeneration and glial activation were examined. The weight of fasting gerbils was not different from that of control gerbils. In controls, SOD1 and GPX immunoreactivities were strong in pyramidal neurons of filed cornu ammonis 1 (CA1). Transient ischemia in controls significantly decreased expressions of SOD1 and GPX in CA1 pyramidal neurons. Intermittent fasting resulted in increased expressions of SOD2 and CAT, not of SOD1 and GPX, in CA1 pyramidal neurons. Nevertheless, CA1 pyramidal neurons were not protected in gerbils subjected to fasting after transient ischemia, and inhibition of glial-cell activation was not observed in the gerbils. In summary, intermittent fasting for two months increased SOD2 and CAT immunoreactivities in hippocampal CA1 pyramidal neurons. However, fasting did not protect the CA1 pyramidal neurons from transient cerebral ischemia. The results of the present study indicate that intermittent fasting may increase certain antioxidants, but not protect neurons from transient global ischemic insult.

Role of microglia under cardiac and cerebral ischemia/reperfusion (I/R) injury

Both cerebral and cardiac ischemia causes loss of cerebral blood flow, which may lead to neuronal cell damage, neurocognitive impairment, learning and memory difficulties, neurological deficits, and brain death. Although reperfusion is required immediately to restore the blood supply to the brain, it could lead to several detrimental effects on the brain. Several studies demonstrate that microglia activity increases following cerebral and cardiac ischemic/reperfusion (I/R) injury. However, the effects of microglial activation in the brain following I/R remains unclear. Some reports demonstrated that microglia were involved in neurodegeneration and oxidative stress generation, whilst others showed that microglia did not respond to I/R injury. Moreover, microglia are activated in a time-dependent manner, and in a specific brain region following I/R. Recently, several therapeutic approaches including pharmacological interventions and electroacupuncture showed the beneficial effects, while some interventions such as hyperthermia and hyperoxic resuscitation, demonstrated the deteriorated effects on the microglial activity after I/R. Therefore, the present review summarized and discussed those studies regarding the effects of global and focal cerebral as well as cardiac I/R injury on microglia activation, and the therapeutic interventions.