Model Of Global Cerebral Ischemia Research Articles

Dietary supplementation with sodium nitrite can exert neuroprotective effects on global cerebral ischemia/reperfusion in mice.

Nitrite-derived NO protects against middle cerebral artery occlusion in mice. We developed a new mouse model of global cerebral ischemia and reperfusion (GCI/R) involving reversible occlusion of the major vessels from the aortic arch supplying the brain, and investigated neuroprotection with dietary sodium nitrite supplementation against GCI/R injury. Mice received drinking water with (nitrite group) or without (control group) sodium nitrite (2 mM) for 5 days and underwent 3-min GCI/R by reversible occlusion of major vessels from the aortic arch (i.e., brachiocephalic, left common carotid, and left subclavian artery). Survival rates and neurological function scores were evaluated for up to 5 days after GCI/R. Histopathological studies were performed to detect neurological degeneration and caspase-3 activation in serial hippocampal sections. In the control group, 17/30 mice (57 %) survived 5 days after 3-min GCI/R, whereas in the nitrite group 25/30 mice (83 %) survived (p < 0.05). The neurological score at 5 days after GCI in control group was significantly higher than in the nitrite group. Cerebral blood flow (CBF) during GCI was significantly higher in the nitrite group than in the control group, while MABP did not differ significantly between groups. Degenerative changes and caspase-3 activation in hippocampal sections after GCI were observed in the control group but not in the nitrite group. Pretreatment with the NO scavenger c-PTIO abolished the neuroprotective effects of sodium nitrite. Sodium nitrite supplementation attenuated mortality and neurological impairment after 3-min GCI in mice; an effect likely mediated via vascular mechanisms involving NO.

Effects of total saponins of Panax notoginseng on immature neuroblasts in the adult olfactory bulb following global cerebral ischemia/reperfusion

The main active components extracted from Panax notoginseng are total saponins. They have been shown to inhibit platelet aggregation, increase cerebral blood flow, improve neurological behavior, decrease infarct volume and promote proliferation and differentiation of neural stem cells in the hippocampus and lateral ventricles. However, there is a lack of studies on whether total saponins of Panax notoginseng have potential benefits on immature neuroblasts in the olfactory bulb following ischemia and reperfusion. This study established a rat model of global cerebral ischemia and reperfusion using four-vessel occlusion. Rats were administered total saponins of Panax notoginseng at 75 mg/kg intraperitoneally 30 minutes after ischemia then once a day, for either 7 or 14 days. Total saponins of Panax notoginseng enhanced the number of doublecortin (DCX)+ neural progenitor cells and increased co-localization of DCX with neuronal nuclei and phosphorylated cAMP response element-binding/DCX+ neural progenitor cells in the olfactory bulb at 7 and 14 days post ischemia. These findings indicate that following global brain ischemia/reperfusion, total saponins of Panax notoginseng promote differentiation of DCX+ cells expressing immature neuroblasts in the olfactory bulb and the underlying mechanism is related to the activation of the signaling pathway of cyclic adenosine monophosphate response element binding protein.

Neuroinflammation and neuronal autophagic death were suppressed via Rosiglitazone treatment: New evidence on neuroprotection in a rat model of global cerebral ischemia

Ischemic stroke is one of the leading causes of mortality and disability with documented high incidence and relapse rate. Accumulating evidence indicates that autophagy participated in neuronal cell death and functional loss induced following ischemia/reperfusion (I/R) injury. The peroxisome proliferating activating receptor-γ (PPAR-γ) agonist, Rosiglitazone (RSG), is known for its anti-inflammatory actions. Previous studies have demonstrated that RSG can exert neuroprotection in animal models of both chronic brain injuries and acute brain insults. However, whether RSG treatment is involved in the autophagic neuronal death following I/R injury remains totally unclear. The present study aimed to hypothesize that treatment of RSG could induce neuroprotective properties in a rat model of global cerebral ischemia (GCI), and thereby to investigate the underline mechanisms. We found that a single injection of RSG immediately following GCI significantly reduced cerebral infarct volume and brain edema, as well as increased neuron survival rate and function recovery. These effects correlate with a decrease of inflammatory cytokines and autophagy-associated proteins expression in the hippocampus region. Our results provide in vivo evidence that RSG significantly protected rats against I/R injury induced brain injury, and the mechanism might associate with inhibiting the processes of neuroinflammation and thereby attenuated of neuronal autophagic death. All data suggest that RSG can be further developed as a clinical neuroprotective candidate in ischemic stroke.

MODERN METHODS OF PERINATAL HYPOXIC-ISCHEMIC BRAIN INJURY MODELING IN VIVO

Review describes modern approaches to the study of pathogenic mechanisms of perinatal hypoxic-ischemic brain injury. The classification of modeling methods hypoxic-ischemic brain injury in vivo reflects the basic approaches to disease modeling. Given the nature of the brain pathology in the perinatal period, the article details the characteristic of global cerebral ischemia models, which are currently in use. It should be remembered that there is still no single ideal experimental model of hypoxia-ischemia in vivo, which completely mimics the human pathology, and that must be considered when planning experiments.

Pre- and posttreatment with edaravone protects CA1 hippocampus and enhances neurogenesis in the subgranular zone of dentate gyrus after transient global cerebral ischemia in rats.

Edaravone is clinically used for treatment of patients with acute cerebral infarction. However, the effect of double application of edaravone on neurogenesis in the hippocampus following ischemia remains unknown. In the present study, we explored whether pre- and posttreatment of edaravone had any effect on neural stem/progenitor cells (NSPCs) in the subgranular zone of hippocampus in a rat model of transient global cerebral ischemia and elucidated the potential mechanism of its effects. Male Sprague-Dawley rats were divided into three groups: sham-operated (n = 15), control (n = 15), and edaravone-treated (n = 15) groups. Newly generated cells were labeled by 5-bromo-2-deoxyuridine. Immunohistochemistry was used to detect neurogenesis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling was used to detect cell apoptosis. Reactive oxygen species (ROS) were detected by 2,7-dichlorofluorescien diacetate assay in NSPCs in vitro. Hypoxia-inducible factor-1α (HIF-1α) and cleaved caspase-3 proteins were quantified by western blot analysis. Treatment with edaravone significantly increased the number of NSPCs and newly generated neurons in the subgranular zone (p < .05). Treatment with edaravone also decreased apoptosis of NSPCs (p < .01). Furthermore, treatment with edaravone significantly decreased ROS generation and inhibited HIF-1α and cleaved caspase-3 protein expressions. These findings indicate that pre- and posttreatment with edaravone enhances neurogenesis by protecting NSPCs from apoptosis in the hippocampus, which is probably mediated by decreasing ROS generation and inhibiting protein expressions of HIF-1α and cleaved caspase-3 after cerebral ischemia.

Harmine mediated neuroprotection via evaluation of glutamate transporter 1 in a rat model of global cerebral ischemia

Global cerebral ischemia (GCI) causes energy deficiency results in excessive release of glutamate from neurons. Astrocytic glutamate transporters play a predominant role in keeping extracellular glutamate concentrations below excitotoxic levels. Glutamate transporter 1 (GLT-1) may account for more than 90% of glutamate uptake in adult forebrain. Preclinical findings implicate that Harmine present neuroprotection effects in a rat model of amyotrophic lateral sclerosis disease, and the beneficial effects were specifically due to up-regulation of GLT-1. However, no experiments have explored the potential of Harmine to provide neuroprotection in the setting of GCI. The current study was designed to determine whether Harmine could attenuate cerebral infarction as well as improve neuronal survival after GCI. Furthermore, to test whether the mechanisms were associated with up-regulating of GLT-1, we used a GLT-1 specific inhibitor dihydrokainate (DHK) and analysis the expression of GLT-1 mRNA and protein in cortex of brain. We also examined whether Harmine treatment affected astrocytes activation via immunofluorescence. Our results showed that post-GCI administration of Harmine could attenuate cerebral infarct volume and decrease neurons death. It also caused significantly elevation of GLT-1 mRNA and protein and remarkably attenuation of astrocyte activation. We provide novel clues in understanding the mechanisms of which Harmine exerts its neuroprotective activity in neurological disorders.

The protective effect of ginko bilboa leaves injection on the brain dopamine in the rat model of cerebral ischemia/reperfusion injury.

Ginkgo Bilboa injection has had been clinically applied to restore the damaged cells and tissues due to the ischemia through improving the cerebral blood supply and decreasing the oxygen consumption. To evaluate the Ginkgo Bilboa injection's therapeutic role towards ischemia/ reperfusion (I/R) injury through determination of monoamine neurotransmitter dopamine (DA) in corpus striatum. After the incomplete global cerebral ischemia and reperfusion models were prepared, rats were randomly assigned into four groups: sham-operated group, ischemia-reperfusion group, nimodipine injection group, and Ginkgo Biloba injection group. The cerebrospinal fluid in the rat brain striatum at different time points was collected with microdialysis, and the level of monoamine neurotransmitters dopamineDA was determined by high performance liquid chromatography (HPLC) with electrochemical detector (ECD). The dopamineDA content in cerebral ischemia model group was significantly higher than that in the sham-operated group (P < 0.05) at the 30 min. However, the DA level in nimodipine injection group and Ginkgo Biloba injection group were lower than the model group (P < 0.05). The dopamineDA level in Ginkgo Biloba injection group gradually decreased, and was significantly different from the model group (P < 0.05). Ginkgo Biloba injection can could significantly inhibit brain I/R injury, as demonstrated by prevention of excessive release of dopamineDA in striatum.

Age-dependent modifications in vascular adhesion molecules and apoptosis after 48-h reperfusion in a rat global cerebral ischemia model.

Stroke is one of the leading causes of death and permanent disability in the elderly. However, most of the experimental studies on stroke are based on young animals, and we hypothesised that age can substantially affect the stroke response. The two-vessel occlusion model of global ischemia by occluding the common carotid arteries for 15min at 40mmHg of blood pressure was carried out in 3- and 18-month-old male Sprague-Dawley rats. The adhesion molecules E- and P-selectin, cell adhesion molecules (CAMs), both intercellular (ICAM-1) and vascular (VCAM-1), as well as glial fibrillary acidic protein (GFAP), and cleaved caspase-3 were measured at 48h after ischemia in the cerebral cortex and hippocampus using Western blot, qPCR and immunofluorescence techniques. Diametric expression of GFAP and a different morphological pattern of caspase-3 labelling, although no changes in the cell number, were observed in the neurons of young and old animals. Expression of E-selectin and CAMs was also modified in an age- and ischemia/reperfusion-dependent manner. The hippocampus and cerebral cortex had similar response patterns for most of the markers studied. Our data suggest that old and young animals present different time-courses of neuroinflammation and apoptosis after ischemic damage. On the other hand, these results suggest that neuroinflammation is dependent on age rather than on the different vulnerability described for the hippocampus and cerebral cortex. These differences should be taken into account in searching for therapeutic targets.

Pinocembrin alleviates memory impairment in transient global cerebral ischemic rats.

The aim of the present study was to investigate the effect of pinocembrin on cognitive ability impairment in a rat model of transient global cerebral ischemia (TGCI). The TGCI model was established by inducing global cerebral ischemia for 20 min, followed by reperfusion for two weeks. The rats were divided into five experimental groups, including the sham group that were not subjected to ischemia, and four ischemic groups where the rats were exposed to TGCI. The sham and control TGCI groups were administered a vehicle intravenously immediately after reperfusion, while the other three groups were intravenously treated with 1, 5 and 10 mg/kg pinocembrin, respectively. In the present study, neurological scores were analyzed at 0 and 24 h after reperfusion, and the effect of pinocembrin on cognitive ability impairment in the TGCI rat model was investigated using a Morris water maze test. Neuronal loss was observed under an optical microscope with the assistance of Nissl staining. In addition, glial fibrillary acidic protein (GFAP)-positive cells were observed under an optical microscope by an immunohistochemistry assay. Pinocembrin treatment was found to alleviate the cognitive impairments, decrease the neurological scores, diminish neuronal loss in the hippocampus and reduce the number of GFAP-positive cells in the hippocampal CA1 region of the TGCI rats. Therefore, pinocembrin alleviated memory impairment in the TGCI rats.

Hydrogen-rich saline attenuates neuronal ischemia–reperfusion injury by protecting mitochondrial function in rats

BackgroundHydrogen, a popular antioxidant gas, can selectively reduce cytotoxic oxygen radicals and has been found to protect against ischemia–reperfusion (I/R) injury of multiple organs. Acute neuronal death during I/R has been attributed to loss of mitochondrial permeability transition coupled with mitochondrial dysfunction. This study was designed to investigate the potential therapeutic effect of hydrogen-rich saline on neuronal mitochondrial injury from global cerebral I/R in rats. Materials and methodsWe used a four-vessel occlusion model of global cerebral ischemia and reperfusion, with Sprague–Dawley rats. The rats were divided randomly into six groups (n = 90): sham (group S), I/R (group I/R), normal saline (group NS), atractyloside (group A), hydrogen-rich saline (group H), and hydrogen-rich saline + atractyloside (group HA). In groups H and HA, intraperitoneal hydrogen-rich saline (5 mL/kg) was injected immediately after reperfusion, whereas the equal volume of NS was injected in the other four groups. In groups A and HA, atractyloside (15 μL) was intracerebroventricularly injected 10 min before reperfusion, whereas groups NS and H received equal NS. The mitochondrial permeability transition pore opening and mitochondrial membrane potential were measured by spectrophotometry. Cytochrome c protein expression in the mitochondria and cytoplasm was detected by western blot. The hippocampus mitochondria ultrastructure was examined with transmission electron microscope. The histologic damage in hippocampus was assessed by hematoxylin and eosin staining. ResultsHydrogen-rich saline treatment significantly improved the amount of surviving cells (P < 0.05). Furthermore, hydrogen-rich saline not only reduced tissue damage, the degree of mitochondrial swelling, and the loss of mitochondrial membrane potential but also preserved the mitochondrial cytochrome c content (P < 0.05). ConclusionsOur study showed that hydrogen-rich saline was able to attenuate neuronal I/R injury, probably by protecting mitochondrial function in rats.

Treatment with Actovegin improves spatial learning and memory in rats following transient forebrain ischaemia.

This study aimed to investigate whether Actovegin, which is a deproteinized ultrafiltrate derived from calf blood, demonstrates neuroprotective effects in a rat model of transient global cerebral ischaemia. Forty Sprague Dawley rats were subjected to four-vessel occlusion to induce transient global cerebral ischaemia followed by either saline or Actovegin treatment. Sham operations were performed on 15 rats. Actovegin (200 mg/kg) or saline was administered 6 hrs after carotid artery occlusion and then daily until Day 40. Learning and memory were evaluated using the Morris water maze test over two different 5-day periods, and grip strength testing was also performed to control for potential motor impairments. Rat brains were harvested for histological analysis on Day 68. In comparison to controls, Actovegin-treated rats exhibited a decreased latency to reach the hidden platform on the second learning trial of water maze testing (46.82 ± 6.18 versus 27.64 ± 4.53 sec., P < 0.05; 38.3 ± 8.23 versus 13.37 ± 2.73 sec., P < 0.01 for the first and second 5-day testing periods, respectively). In addition, Actovegin-treated rats spent more time in the platform quadrant than saline-treated rats during memory trials (P < 0.05). No differences in grip strength were detected. Histological analyses demonstrated increased cell survival in the CA1 region of the hippocampus following Actovegin treatment (left hemisphere, 166 ± 50 versus 332 ± 27 cells, P < 0.05; right hemisphere, 170 ± 45 versus 307 ± 28 cells, P < 0.05, in saline- versus Actovegin-treated rats, respectively). In rats, Actovegin treatment improves spatial learning and memory following cerebral ischaemia, which may be related to hippocampal CA1 neuroprotection.

Sarcosine preconditioning induces ischemic tolerance against global cerebral ischemia

Brain ischemic tolerance is an endogenous protective mechanism activated by a preconditioning stimulus that is closely related to N-methyl-d-aspartate receptor (NMDAR). Glycine transporter type 1 (GlyT-1) inhibitors potentiate NMDAR and suggest an alternative strategy for brain preconditioning. The aim of this work was to evaluate the effects of brain preconditioning induced by sarcosine, a GlyT-1 inhibitor, against global cerebral ischemia and its relation to NMDAR. Sarcosine was administered over 7days (300 or 500mg/kg/day, ip) before the induction of a global cerebral ischemia model in Wistar rats (male, 8-week-old). It was observed that sarcosine preconditioning reduced cell death in rat hippocampi submitted to cerebral ischemia. Hippocampal levels of glycine were decreased in sarcosine-treated animals, which was associated with a reduction of [3H] glycine uptake and a decrease in glycine transporter expression (GlyT-1 and GlyT-2). The expression of glycine receptors and the NR1 and NR2A subunits of NMDAR were not affected by sarcosine preconditioning. However, sarcosine preconditioning reduced the expression of the NR2B subunits of NMDAR. In conclusion, these data demonstrate that sarcosine preconditioning induces ischemic tolerance against global cerebral ischemia and this neuroprotective state is associated with changes in glycine transport and reduction of NR2B-containing NMDAR expression.

Reprint of ”GPR30 mediates estrogen rapid signaling and neuroprotection”

G-protein-coupled estrogen receptor-30 (GPR30), also known as G-protein estrogen receptor-1 (GPER1), is a putative extranuclear estrogen receptor whose precise functions in the brain are poorly understood. Studies using exogenous administration of the GPR30 agonist, G1 suggests that GPR30 may have a neuroprotective role in cerebral ischemia. However, the physiological role of GPR30 in mediating estrogen (E2)-induced neuroprotection in cerebral ischemia remains unclear. Also unclear is whether GPR30 has a role in mediating rapid signaling by E2 after cerebral ischemia, which is thought to underlie its neuroprotective actions. To address these deficits in our knowledge, the current study examined the effect of antisense oligonucleotide (AS) knockdown of GPR30 in the hippocampal CA1 region upon E2-BSA-induced neuroprotection and rapid kinase signaling in a rat model of global cerebral ischemia (GCI). Immunohistochemistry demonstrated that GPR30 is strongly expressed in the hippocampal CA1 region and dentate gyrus, with less expression in the CA3 region. E2-BSA exerted robust neuroprotection of hippocampal CA1 neurons against GCI, an effect abrogated by AS knockdown of GPR30. Missense control oligonucleotides had no effect upon E2-BSA-induced neuroprotection, indicating specificity of the effect. The GPR30 agonist, G1 also exerted significant neuroprotection against GCI. E2-BSA and G1 also rapidly enhanced activation of the prosurvival kinases, Akt and ERK, while decreasing proapototic JNK activation. Importantly, AS knockdown of GPR30 markedly attenuated these rapid kinase signaling effects of E2-BSA. As a whole, the studies provide evidence of an important role of GPR30 in mediating the rapid signaling and neuroprotective actions of E2 in the hippocampus.

Long-term fate of grafted hippocampal neural progenitor cells following ischemic injury.

The adult CNS has a very limited capacity to regenerate neurons after insult. To overcome this limitation, the transplantation of neural progenitor cells (NPCs) has developed into a key strategy for neuronal replacement. This study assesses the long-term survival, migration, differentiation, and functional outcome of NPCs transplanted into the ischemic murine brain. Hippocampal neural progenitors were isolated from FVB-Cg-Tg(GFPU)5Nagy/J transgenic mice expressing green fluorescent protein (GFP). Syngeneic GFP-positive NPCs were stereotactically transplanted into the hippocampus of FVB mice following a transient global cerebral ischemia model. Behavioral tests revealed that ischemia/reperfusion induced spatial learning disturbances in the experimental animals. The NPC transplantation promoted cognitive function recovery after ischemic injury. To study the long-term fate of grafted GFP-positive NPCs in a host brain, immunohistochemical approaches were applied. Confocal microscopy revealed that grafted cells survived in the recipient tissue for 90 days following transplantation and differentiated into mature neurons with extensive dendritic trees and apparent spines. Immunoelectron microscopy confirmed the formation of synapses between the transplanted GFP-positive cells and host neurons that may be one of the factors underlying cognitive function recovery. Repair and functional recovery following brain damage represent a major challenge for current clinical and basic research. Our results provide insight into the therapeutic potential of transplanted hippocampal progenitor cells following ischemic brain injury.

Ischemic insults induce necroptotic cell death in hippocampal neurons through the up-regulation of endogenous RIP3

Global cerebral ischemia induces selective acute neuronal injury of the CA1 region of the hippocampus. The type of cell death that ensues may include different programmed cell death mechanisms namely apoptosis and necroptosis, a recently described type of programmed necrosis. We investigated whether necroptosis contributes to hippocampal neuronal death following oxygen-glucose deprivation (OGD), an in vitro model of global ischemia. We observed that OGD induced a death receptor (DR)-dependent component of necroptotic cell death in primary cultures of hippocampal neurons. Additionally, we found that this ischemic challenge upregulated the receptor-interacting protein kinase 3 (RIP3) mRNA and protein levels, with a concomitant increase of the RIP1 protein. Together, these two related proteins form the necrosome, the complex responsible for induction of necroptotic cell death. Interestingly, we found that caspase-8 mRNA, a known negative regulator of necroptosis, was transiently decreased following OGD. Importantly, we observed that the OGD-induced increase in the RIP3 protein was paralleled in an in vivo model of transient global cerebral ischemia, specifically in the CA1 area of the hippocampus. Moreover, we show that the induction of endogenous RIP3 protein levels influenced neuronal toxicity since we found that RIP3 knock-down (KD) abrogated the component of OGD-induced necrotic neuronal death while RIP3 overexpression exacerbated neuronal death following OGD. Overexpression of RIP1 also had deleterious effects following the OGD challenge. Taken together, our results highlight that cerebral ischemia activates transcriptional changes that lead to an increase in the endogenous RIP3 protein level which might contribute to the formation of the necrosome complex and to the subsequent component of necroptotic neuronal death that follows ischemic injury.

Neuroprotective effect of aquaporin-4 deficiency in a mouse model of severe global cerebral ischemia produced by transient 4-vessel occlusion

Astrocyte water channel aquaporin-4 (AQP4) facilitates water movement across the blood–brain barrier and into injured astrocytes. We previously showed reduced cytotoxic brain edema with improved neurological outcome in AQP4 knockout mice in water intoxication, infection and cerebral ischemia. Here, we established a 4-vessel transient occlusion model to test the hypothesis that AQP4 deficiency in mice could improve neurological outcome following severe global cerebral ischemia as occurs in cardiac arrest/resuscitation. Mice were subjected to 10-min transient bilateral carotid artery occlusion at 24h after bilateral vertebral artery cauterization. Cerebral blood flow was reduced during occlusion by >94% in both AQP4+/+ and AQP4−/− mice. The primary outcome, neurological score, was remarkably better at 3 and 5 days after occlusion in AQP4−/− than in AQP4+/+ mice, and survival was significantly improved as well. Brain water content was increased by 2.8±0.4% in occluded AQP4+/+ mice, significantly greater than that of 0.3±0.6% in AQP4−/− mice. Histological examination and immunofluorescence of hippocampal sections at 5 days showed significantly greater neuronal loss in the CA1 region of hippocampus in AQP4+/+ than AQP4−/− mice. The neuroprotection in mice conferred by AQP4 deletion following severe global cerebral ischemia provides proof-of-concept for therapeutic AQP4 inhibition to improve neurological outcome in cardiac arrest.

Effects of Lithium and Lamotrigine on Oxidative–Nitrosative Stress and Spatial Learning Deficit After Global Cerebral Ischemia

Lithium (Li) and lamotrigine (LTG) have neuroprotective properties. However, the exact therapeutic mechanisms of these drugs have not been well understood. We investigated the antioxidant properties of Li (40 and 80 mg/kg/day) and LTG (20 and 40 mg/kg/day) in a rat model of global cerebral ischemia based on permanent bilateral occlusion of the common carotid arteries (BCAO). Nitric oxide (NO), malondialdehyde (MDA), glutathione (GSH), glutathione reductase (GSH-R), catalase (CAT) and superoxide dismutase (SOD) levels were measured as an indicator of oxidative-nitrosative stress in both prefrontal cortex (PFC) and hippocampus after 28 days of treatment. The spatial learning disability was also assessed at the end of the study by Morris water maze (MWM) test. All oxidative-nitrosative parameters were found to be higher in the groups under treatment than in sham. Both drugs caused a decrease in PFC NO and MDA elevation, meanwhile the increase in GSH, GSH-R, CAT and SOD levels was significantly more evident in treated groups. We also found higher PFC GSH-R and hippocampal SOD levels in BCAO + Li (80 mg/day) treated group when compared with BCAO + LTG 40 mg/day. MWM test data showed a similar increase in spatial learning ability in all groups under treatment. We found no other statistical difference in comparison of treated groups with different dosages. Our findings suggested that Li and LTG treatments may decrease spatial learning memory deficits accompanied by lower oxidative-nitrosative stress in global cerebral ischemia. Both drugs may have potential benefits for the treatment of vascular dementia in clinical practice.

GPR30 mediates estrogen rapid signaling and neuroprotection

G-protein-coupled estrogen receptor-30 (GPR30), also known as G-protein estrogen receptor-1 (GPER1), is a putative extranuclear estrogen receptor whose precise functions in the brain are poorly understood. Studies using exogenous administration of the GPR30 agonist, G1 suggests that GPR30 may have a neuroprotective role in cerebral ischemia. However, the physiological role of GPR30 in mediating estrogen (E2)-induced neuroprotection in cerebral ischemia remains unclear. Also unclear is whether GPR30 has a role in mediating rapid signaling by E2 after cerebral ischemia, which is thought to underlie its neuroprotective actions. To address these deficits in our knowledge, the current study examined the effect of antisense oligonucleotide (AS) knockdown of GPR30 in the hippocampal CA1 region upon E2-BSA-induced neuroprotection and rapid kinase signaling in a rat model of global cerebral ischemia (GCI). Immunohistochemistry demonstrated that GPR30 is strongly expressed in the hippocampal CA1 region and dentate gyrus, with less expression in the CA3 region. E2-BSA exerted robust neuroprotection of hippocampal CA1 neurons against GCI, an effect abrogated by AS knockdown of GPR30. Missense control oligonucleotides had no effect upon E2-BSA-induced neuroprotection, indicating specificity of the effect. The GPR30 agonist, G1 also exerted significant neuroprotection against GCI. E2-BSA and G1 also rapidly enhanced activation of the prosurvival kinases, Akt and ERK, while decreasing proapototic JNK activation. Importantly, AS knockdown of GPR30 markedly attenuated these rapid kinase signaling effects of E2-BSA. As a whole, the studies provide evidence of an important role of GPR30 in mediating the rapid signaling and neuroprotective actions of E2 in the hippocampus.

Extremely Low Frequency Magnetic Field (50 Hz, 0.5 mT) Reduces Oxidative Stress in the Brain of Gerbils Submitted to Global Cerebral Ischemia

Magnetic field as ecological factor has influence on all living beings. The aim of this study was to determine if extremely low frequency magnetic field (ELF-MF, 50 Hz, 0.5 mT) affects oxidative stress in the brain of gerbils submitted to 10-min global cerebral ischemia. After occlusion of both carotid arteries, 3-month-old gerbils were continuously exposed to ELF-MF for 7 days. Nitric oxide and superoxide anion production, superoxide dismutase activity and index of lipid peroxidation were examined in the forebrain cortex, striatum and hippocampus on the 7th (immediate effect of ELF-MF) and 14th day after reperfusion (delayed effect of ELF-MF). Ischemia per se increased oxidative stress in the brain on the 7th and 14th day after reperfusion. ELF-MF also increased oxidative stress, but to a greater extent than ischemia, only immediately after cessation of exposure. Ischemic gerbils exposed to ELF-MF had increased oxidative stress parameters on the 7th day after reperfusion, but to a lesser extent than ischemic or ELF-MF-exposed animals. On the 14th day after reperfusion, oxidative stress parameters in the brain of these gerbils were mostly at the control levels. Applied ELF-MF decreases oxidative stress induced by global cerebral ischemia and thereby reduces possible negative consequences which free radical species could have in the brain. The results presented here indicate a beneficial effect of ELF-MF (50 Hz, 0.5 mT) in the model of global cerebral ischemia.

Activation of AMP-activated protein kinase by metformin protects against global cerebral ischemia in male rats: Interference of AMPK/PGC-1α pathway

Here, we have investigated the effect of metformin pretreatment in the rat models of global cerebral ischemia. Cerebral ischemia which leads to brain dysfunction is one of the main causes of neurodegeneration and death worldwide. Metformin is used in clinical drug therapy protocols of diabetes. It is suggested that metformin protects cells under hypoxia and ischemia in non-neuronal contexts. Protective effects of metformin may be modulated via activating the AMP activated protein kinase (AMPK). Our results showed that induction of 30 min global cerebral I/R injury using 4-vesseles occlusion model led to significant cell death in the rat brain. Metformin pretreatment (200 mg kg/once/day, p.o., 2 weeks) attenuated apoptotic cell death and induced mitochondrial biogenesis proteins in the ischemic rats, analyzed using histological and Western blot assays. Besides, inhibition of AMPK by compound c showed that metformin resulted in apoptosis attenuation via AMPK activation. Interestingly, AMPK activation was also involved in the induction of mitochondrial biogenesis proteins using metformin, inhibition of AMPK by compound c reversed such effect, further supporting the role of AMPK upstream of mitochondrial biogenesis proteins. In summary, Metformin pretreatment is able to modulate mitochondrial biogenesis and apoptotic cell death pathways through AMPK activation in the context of global cerebral ischemia, conducting the outcome towards neuroprotection.