Reactive oxygen radicals and pathogenesis of neuronal death after cerebral ischemia

Momordica charantia polysaccharides could protect against cerebral ischemia/reperfusion injury through inhibiting oxidative stress mediated c-Jun N-terminal kinase 3 signaling pathway

Momordica charantia (MC) is a medicinal plant for stroke treatment in Traditional Chinese Medicine, but its active compounds and molecular targets are unknown yet. M. charantia polysaccharide (MCP) is one of the important bioactive components in MC. In the present study, we tested the hypothesis that MCP has neuroprotective effects against cerebral ischemia/reperfusion injury through scavenging superoxide (O2(-)), nitric oxide (NO) and peroxynitrite (ONOO(-)) and inhibiting c-Jun N-terminal protein kinase (JNK3) signaling cascades. We conducted experiments with in vivo global and focal cerebral ischemia/reperfusion rat models and in vitro oxygen glucose deprivation (OGD) neural cells. The effects of MCP on apoptotic cell death and infarction volume, the bioactivities of scavenging O2(-), NO and ONOO(-), inhibiting lipid peroxidation and modulating JNK3 signaling pathway were investigated. Major results are summarized as below: (1) MCP dose-dependently attenuated apoptotic cell death in neural cells under OGD condition in vitro and reduced infarction volume in ischemic brains in vivo; (2) MCP had directing scavenging effects on NO, O2(-) and ONOO(-) and inhibited lipid peroxidation; (3) MCP inhibited the activations of JNK3/c-Jun/Fas-L and JNK3/cytochrome C/caspases-3 signaling cascades in ischemic brains in vivo. Taken together, we conclude that MCP could be a promising neuroprotective ingredient of M. charantia and its mechanisms could be at least in part attributed to its antioxidant activities and inhibiting JNK3 signaling cascades during cerebral ischemia/reperfusion injury.

Protection of Tong-Sai-Mai Decoction against Apoptosis Induced by H2O2 in PC12 Cells: Mechanisms via Bcl-2-Mitochondria-ROS-INOS Pathway

Tong-Sai-Mai decoction (TSM) is a Chinese materia medica polyherbal formulation that has been applied in treating brain ischemia for hundreds of years. Because it could repress the oxidative stress in in vivo studies, now we focus on the in vitro studies to investigate the mechanism by targeting the oxidative stress dependent signaling. The relation between the neurogenesis and the reactive oxygen species (ROS) production remains largely unexamined. PC12 cells are excitable cell types widely used as in vitro model for neuronal cells. Most marker genes that are related to neurotoxicity, apoptosis, and cell cycles are expressed at high levels in these cells. The aim of the present study is to explore the cytoprotection of TSM against hydrogen peroxide- (H₂O₂-) induced apoptosis and the molecular mechanisms underlying PC12 cells. Our findings revealed that TSM cotreatment with H₂O₂ restores the expression of bcl-2, inducible nitric oxide synthase (INOS), and mitochondria membrane potential. Meanwhile, it reduces intracellular [Ca²⁺] concentration, lactate dehydrogenase (LDH) release, and the expression of caspase-3 and bax. The results of the present study suggested that the cytoprotective effects of the TSM might be mediated, at least in part, by the bcl-2-mitochondria-ROS-INOS pathway. Due to its nontoxic characteristics, TSM could be further developed to treat the neurodegenerative diseases which are closely associated with the oxidative stress.

Inductive and Deductive Approaches to Acute Cell Injury

Many clinically relevant forms of acute injury, such as stroke, traumatic brain injury, and myocardial infarction, have resisted treatments to prevent cell death following injury. The clinical failures can be linked to the currently used inductive models based on biological specifics of the injury system. Here we contrast the application of inductive and deductive models of acute cell injury. Using brain ischemia as a case study, we discuss limitations in inductive inferences, including the inability to unambiguously assign cell death causality and the lack of a systematic quantitative framework. These limitations follow from an overemphasis on qualitative molecular pathways specific to the injured system. Our recently developed nonlinear dynamical theory of cell injury provides a generic, systematic approach to cell injury in which attractor states and system parameters are used to quantitatively characterize acute injury systems. The theoretical, empirical, and therapeutic implications of shifting to a deductive framework are discussed. We illustrate how a deductive mathematical framework offers tangible advantages over qualitative inductive models for the development of therapeutics of acutely injured biological systems.

Neuroprotection of antioxidant enzymes against transient global cerebral ischemia in gerbils

Experimentally transient global cerebral ischemia using animal models have been thoroughly studied and numerous reports suggest the involvement of oxidative stress in the pathogenesis of neuronal death in ischemic lesions. In animal models, during the reperfusion period after ischemia, increased oxygen supply results in the overproduction of reactive oxygen species (ROS), which are involved in the process of cell death. ROS, such as superoxide anions, hydroxyl free radicals, hydrogen peroxide and nitric oxide are produced as a consequence of metabolic reactions and central nervous system activity. These reactive species are directly involved in the oxidative damage of cellular macromolecules such as nucleic acids, lipids and proteins in ischemic tissues, which can lead to cell death. Antioxidant enzymes are believed to be among the major mechanisms by which cells counteract the deleterious effect of ROS after cerebral ischemia. Consequently, antioxidant strategies have been long suggested as a therapy for experimental ischemic stroke; however, clinical trials have not yet been able to promote the translation of this concept into patient treatment regimens. This article focuses on the contribution of oxidative stress or antioxidants to the post-ischemic neuronal death following transient global cerebral ischemia by using a gerbil model.

Role of iron in ischemia-induced neurodegeneration: mechanisms and insights

Iron is an important micronutrient for neuronal function and survival. It plays an essential role in DNA and protein synthesis, neurotransmission and electron transport chain due to its dual redox states. On the contrary, iron also catalyses the production of free radicals and hence, causes oxidative stress. Therefore, maintenance of iron homeostasis is very crucial and it involves a number of proteins in iron metabolism and transport that maintain the balance. In ischemic conditions large amount of iron is released and this free iron catalyzes production of more free radicals and hence, causing more damage. In this review we have focused on the iron transport and maintenance of iron homeostasis at large and also the effect of imbalance in iron homeostasis on retinal and brain tissue under ischemic conditions. The understanding of the proteins involved in the homeostasis imbalance will help in developing therapeutic strategies for cerebral as well retinal ischemia.

Free radical scavenging activity and neuroprotective potentials of D138, one Cu(II)/Zn(II) Schiff-base complex derived from N,N'-bis(2-hydroxynaphthylmethylidene)-1,3-propanediamine

There is increasing evidence that free radicals play an important role in neuronal damages induced by diabetes mellitus or cerebral ischemia insults. Antioxidants with free radical scavenging activities have been shown to be beneficial and neuroprotective for these pathological conditions. Here, we report free radical scavenging activity and neuroprotective potential of D138, one copper(II)/zinc(II) Schiff-base complex derived from N,N'-2(2-hydroxynaphthylmethylidene)-1,3-propanediamine. The data from three in vitro assays, 2,2-diphenyl-1-picrylhydrazyl assay, nitro blue tetrazolium assay and hydroxyl radical scavenging assay, indicated that D138 presented a potent free radical scavenging activity. The neuroprotective and antioxidative effects of D138 were further evaluated in vivo using bilateral common carotid artery occlusion (BCCAO) mouse model and streptozotocin (STZ) diabetic mouse model. Our results indicated that treatment of D138 significantly ameliorated the hippocampal neuronal damage and the oxidative stress levels in these animal models. Moreover, D138 also reversed the behavioral deficiencies induced by BCCAO or STZ, as assessed by Y-maze test and fear conditioning test. In conclusion, all these findings support that D138 exerts free radical scavenging and neuroprotective activities and has the potentials to be a potent therapeutic candidate for brain oxidative damage induced by cerebral ischemia or diabetes mellitus.

The beneficial effect of melatonin in brain endothelial cells against oxygen-glucose deprivation followed by reperfusion-induced injury

Melatonin has a cellular protective effect in cerebrovascular and neurodegenerative diseases. Protection of brain endothelial cells against hypoxia and oxidative stress is important for treatment of central nervous system (CNS) diseases, since brain endothelial cells constitute the blood brain barrier (BBB). In the present study, we investigated the protective effect of melatonin against oxygen-glucose deprivation, followed by reperfusion- (OGD/R-) induced injury, in bEnd.3 cells. The effect of melatonin was examined by western blot analysis, cell viability assays, measurement of intracellular reactive oxygen species (ROS), and immunocytochemistry (ICC). Our results showed that treatment with melatonin prevents cell death and degradation of tight junction protein in the setting of OGD/R-induced injury. In response to OGD/R injury of bEnd.3 cells, melatonin activates Akt, which promotes cell survival, and attenuates phosphorylation of JNK, which triggers apoptosis. Thus, melatonin protects bEnd.3 cells against OGD/R-induced injury.

Acupuncture mechanism and redox equilibrium

Oxidative stress participates in the pathological process of various diseases. Acupuncture is a component of the health care system in China that can be traced back for at least 3000 years. Recently, increased evidences indicate that acupuncture stimulation could reduce oxidative damage in organisms under pathological state, but the exact mechanism remains unclear. This review focuses on the emerging links between acupuncture and redox modulation in various disorders, such as vascular dementia, Parkinson's disease, and hypertension, ranging from redox system, antioxidant system, anti-inflammatory system, and nervous system to signaling pathway. Although the molecular and cellular pathways studies of acupuncture effect on oxidative stress are preliminary, they represent an important step forward in the research of acupuncture antioxidative effect.

Pre-treatment with the synthetic antioxidant T-butyl bisphenol protects cerebral tissues from experimental ischemia reperfusion injury

Treatments to inhibit or repair neuronal cell damage sustained during focal ischemia/reperfusion injury in stroke are largely unavailable. We demonstrate that dietary supplementation with the antioxidant di-tert-butyl-bisphenol (BP) before injury decreases infarction and vascular complications in experimental stroke in an animal model. We confirm that BP, a synthetic polyphenol with superior radical-scavenging activity than vitamin E, crosses the blood-brain barrier and accumulates in rat brain. Supplementation with BP did not affect blood pressure or endogenous vitamin E levels in plasma or cerebral tissue. Pre-treatment with BP significantly lowered lipid, protein and thiol oxidation and decreased infarct size in animals subjected to middle cerebral artery occlusion (2 h) and reperfusion (24 h) injury. This neuroprotective action was accompanied by down-regulation of hypoxia inducible factor-1α and glucose transporter-1 mRNA levels, maintenance of neuronal tissue ATP concentration and inhibition of pro-apoptotic factors that together enhanced cerebral tissue viability after injury. That pre-treatment with BP ameliorates oxidative damage and preserves cerebral tissue during focal ischemic insult indicates that oxidative stress plays at least some causal role in promoting tissue damage in experimental stroke. The data strongly suggest that inhibition of oxidative stress through BP scavenging free radicals in vivo contributes significantly to neuroprotection. We demonstrate that pre-treatment with ditert-butyl bisphenol(Di-t-Bu-BP) inhibits lipid, protein, and total thiol oxidation and decreases caspase activation and infarct size in rats subjected to middle cerebral artery occlusion (2 h) and reperfusion (24 h) injury. These data suggest that inhibition of oxidative stress contributes significantly to neuroprotection.

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

BACKGROUND

Hydrogen, 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 METHODS

We 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.

RESULTS

Hydrogen-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).

CONCLUSIONS

Our study showed that hydrogen-rich saline was able to attenuate neuronal I/R injury, probably by protecting mitochondrial function in rats.

MSTMP, a Stilbene Derivative, Protects SH-SY5Y Cells Against Oxidative Stress

OBJECTIVE

the protective effects of a novel stilbene derivative, (e)-2-(3,4,5- trimethoxystyryl)-3,5,6-trimethylpyrazine (MStMp), on hydrogen peroxide (h2o2)-induced human derived neuroblastoma cell (Sh-Sy5y) damage and its molecular mechanisms were investigated.

METHODS

Sh-Sy5y cells were exposed to 200 μmol.l-1 h2o2 for 12 h. the effect of MStMp on cell viability and apoptosis was assessed by 3-(4,5-dimethyl- thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (Mtt) assay and flow cytometry method. the activities of lactate dehydrogenase (ldh), superoxide dismutase (Sod) and nitric oxide synthetase (noS) and the content of malondialdehyde (Mda), reduced glutathione (gSh) and nitric oxide (no) in cells were determined by commercial kits. the expressions of pro-apoptotic factor caspase-3, caspase-9 and inducible noS (inoS) were detected by Western blotting. intracellular formation of reactive oxygen species (roS) was assessed using 6-carboxy-2’,7’-dichlorofluorescin diacetate (dCfh-da) fluorescent probe.

RESULTS

MStMp increased the Sh-Sy5y cell viability by inhibition of cell apoptosis induced by h2o2. these effects were accompanied by an increase of Sod activity, gSh level, and a decrease of Mda content. Moreover, MStMp showed stronger effects on inhibition of ldh leakage, apoptotic cells, intracellular roS level and the expression of caspase-3 and caspase-9 than tMp. furthermore, MStMp induced a decrease of no level and the activity of inoS, tnoS in a time-dependent manner.

CONCLUSIONS

MStMp prevents h2o2-induced cell injury through anti-oxidation and anti-apoptosis via roS-no pathway.

The role of Nox2-derived ROS in the development of cognitive impairment after sepsis

Background

Sepsis- associated encephalopathy (SAE) is an early and common feature of severe infections. Oxidative stress is one of the mechanisms associated with the pathophysiology of SAE. The goal of this study was to investigate the involvement of NADPH oxidase in neuroinflammation and in the long-term cognitive impairment of sepsis survivors.

Methods

Sepsis was induced in WT and gp91^phox knockout mice (gp91^phox-/-) by cecal ligation and puncture (CLP) to induce fecal peritonitis. We measured oxidative stress, Nox2 and Nox4 gene expression and neuroinflammation in the hippocampus at six hours, twenty-four hours and five days post-sepsis. Mice were also treated with apocynin, a NADPH oxidase inhibitor. Behavioral outcomes were evaluated 15 days after sepsis with the inhibitory avoidance test and the Morris water maze in control and apocynin-treated WT mice.

Results

Acute oxidative damage to the hippocampus was identified by increased 4-HNE expression in parallel with an increase in Nox2 gene expression after sepsis. Pharmacological inhibition of Nox2 with apocynin completely inhibited hippocampal oxidative stress in septic animals. Pharmacologic inhibition or the absence of Nox2 in gp91^phox-/- mice prevented glial cell activation, one of the central mechanisms associated with SAE. Finally, treatment with apocynin and inhibition of hippocampal oxidative stress in the acute phase of sepsis prevented the development of long-term cognitive impairment.

Conclusions

Our results demonstrate that Nox2 is the main source of reactive oxygen species (ROS) involved in the oxidative damage to the hippocampus in SAE and that Nox2-derived ROS are determining factors for cognitive impairments after sepsis. These findings highlight the importance of Nox2-derived ROS as a central mechanism in the development of neuroinflammation associated with SAE.

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 7^th (immediate effect of ELF-MF) and 14^th day after reperfusion (delayed effect of ELF-MF). Ischemia per se increased oxidative stress in the brain on the 7^th and 14^th 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 7^th day after reperfusion, but to a lesser extent than ischemic or ELF-MF-exposed animals. On the 14^th 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.

s-Methyl cysteine enhanced survival of nerve growth factor differentiated PC12 cells under hypoxic conditions

A nerve growth factor-differentiated PC12 cell line was used to investigate the protective effects ofs-methyl cysteine (SMC) at 1, 2, 4, and 8 μM under oxygen–glucose deprivation (OGD) conditions.

Glutathione prevents free fatty acids-induced oxidative stress and apoptosis in human brain vascular endothelial cells through Akt pathway

AIMS

The damage of human brain vascular endothelial cells (HBVECs) is the key pathogenesis of diabetes-associated cerebral vascular complications. The aim of this study was to elucidate the effects of glutathione (GSH) on free fatty acids (FFAs)-induced HBVECs apoptosis, oxidative stress, and the involved possible signaling pathway.

METHODS

After culturing HBVECs for 72 h with GSH and FFAs, we determined cell proliferation by CCK8, detected apoptosis by caspase-3 and Annexin V-FITC/PI staining, and judged oxygen stress by determining the reactive oxygen species (ROS) and the mitochondrial membrane potential (MMP). We investigated whether the Akt pathway was involved in FFAs-induced signaling pathway alteration and whether GSH influenced the above effects.

RESULTS

After being cultured in 200 μM FFAs for 72 h, the HBVECs proliferation significantly decreased; HBVECs apoptosis increased; the ROS levels increased; and the HBVECs MMP subsequently decreased. FFAs induced a significant decrease in phosphorylated active Akt. These alterations were obviously prevented when 1 mM GSH was added to culture medium containing FFAs, and the above effects of GSH were blocked by Akt inhibitor.

CONCLUSION

GSH may prevent FFAs-induced HBVECs damage, oxidative stress, and apoptosis through activating the Akt pathway.

A tetramethylpyrazine piperazine derivate CXC137 prevents cell injury in SH-SY5Y cells and improves memory dysfunction of rats with vascular Dementia

We investigated the effects of CXC137, a tetramethylpyrazine piperazine derivate, on cell damage induced by N-methyl-D-aspartate (NMDA) in human derived neuroblastoma cells (SH-SY5Y) and its effect on memory dysfunction of rats with vascular dementia. It was found that the presence of CXC137 increased SH-SY5Y cells viability by inhibition of cell apoptosis induced by NMDA. These effects of CXC137 were accompanied by increases of the antioxidant superoxide dismutase activity and the level of reduced glutathione, and a decrease of lipid peroxidation product, malondialdehyde. The presence of CXC137 also showed to produce strong inhibition of cellular lactate dehydrogenase leakage, cell apoptosis and intracellular calcium overload. In a vascular dementia rat model established by bilateral common carotid arteries occlusion, treatment with CXC137 from 2 to 35 day of post-operation significantly improves the motor performance, spatial learning and memory capability of rats in both the prehensile traction test and Morris water maze test, an effect that was companied by reductions of the animal glutamic acid levels and the degree of brain mitochondrial swelling. These results suggest that CXC137 can improve the memory dysfunction in dementia and thus has important therapeutic potential for the treatment of dementia.

Effects of acupuncture on declined cerebral blood flow, impaired mitochondrial respiratory function and oxidative stress in multi-infarct dementia rats

Brain energy disorders and oxidative stress due to chronic hypoperfusion were considered to be the major risk factors in the pathogenesis of dementia. In previous studies, we have demonstrated that acupuncture treatment improved cognitive function of VaD patients and multi-infarct dementia (MID) rats. Acupuncture therapy also increased the activities of glycometabolic enzymes in the brain. But it is not clear whether acupuncture treatment compensates neuronal energy deficit after cerebral ischemic through enhancing the activities of glucose metabolic enzymes and preserving mitochondrial function, and whether acupuncture neuroprotective effect is associated with activations of mitochondrial antioxidative defense system. So, the effect of acupuncture therapy on cognitive function, cerebral blood flow (CBF), mitochondrial respiratory function and oxidative stress in the brain of MID rats was investigated in this study. The results showed that acupuncture treatment significantly improved cognitive abilities and increased regional CBF of MID rats. Acupuncture elevated the activities of total SOD, CuZnSOD and MnSOD, decreased the level of malondialdehyde (MDA) and superoxide anion, regulated the ratio of reduced glutathione (GSH) and oxidized glutathione (GSSG) in mitochondria, and raised the level of the respiratory control index (RCI) and P/O ratio and the activities of mitochondrial respiratory enzymes of MID rats. These results indicated that acupuncture treatment improved cognitive function of MID rats; and this improvement might be due to increased CBF, which ameliorated mitochondrial dysfunction induced by ischemia and endogenous oxidative stress system of brain.

Daphnetin, a natural coumarin derivative, provides the neuroprotection against glutamate-induced toxicity in HT22 cells and ischemic brain injury

Daphnetin (DAP), a coumarin derivative, has been reported to have multiple pharmacological actions including analgesia, antimalarial, anti-arthritic, and anti-pyretic properties. It is unclear whether DAP has neuroprotective effects on ischemic brain injury. In this study, we found that DAP treatment (i.c.v.) reduced the infarct volume at 24 h after ischemia/reperfusion injury and improved neurological behaviors in a middle cerebral artery occlusion mouse model. Moreover, we provided evidences that DAP had protective effects on infarct volume in neonate rats even it was administrated at 4 h after cerebral hypoxia/ischemia injury. To explore its neuroprotective mechanisms of DAP, we examined the protection of DAP on glutamate toxicity-induced cell death in hippocampal HT-22 cells. Our results demonstrated that DAP protected against glutamate toxicity in HT-22 cells in a concentration-dependent manner. Further, we found that DAP maintained the cellular levels of glutathione and superoxide dismutase activity, suggesting the anti-oxidatant activity of DAP. Since DAP has been used for the treatment of coagulation disorder and rheumatoid arthritis for long time with a safety profile, DAP will be a promising agent for the treatment of stroke.

Manganese superoxide dismutase deficiency exacerbates ischemic brain damage under hyperglycemic conditions by altering autophagy

Both preischemic hyperglycemia and suppression of SOD2 activity aggravate ischemic brain damage. This study was undertaken to assess the effect of SOD2 mutation on ischemic brain damage and its relation to the factors involved in autophagy regulation in hyperglycemic wild-type (WT) and heterozygous SOD2 knockout (SOD2(-/+)) mice subjected to 30-min transient focal ischemia. The brain samples were analyzed at 5 and 24 h after recirculation for ischemic lesion volume, superoxide production, and oxidative DNA damage and protein levels of Beclin 1, damage-regulated autophagy modulator (DRAM), and microtubule-associated protein 1 light chain 3 (LC3). The results revealed a significant increase in infarct volume in hyperglycemic SOD2(-/+) mice, and this was accompanied with an early (5 h) significant rise in superoxide production and reduced SOD2 activity in SOD2(-/+) mice as compared to WT mice. The superoxide production is associated with oxidative DNA damage as indicated by colocalization of the dihydroethidium (DHE) signal with 8-OHdG fluorescence in SOD2(-/+) mice. In addition, while ischemia in WT hyperglycemics increased the levels of autophagy markers Beclin 1, DRAM, and LC3, ischemia in hyperglycemic, SOD2-deficient mice suppressed the levels of autophagy stimulators. These results suggest that SOD2 knockdown exacerbates ischemic brain damage under hyperglycemic conditions via increased oxidative stress and DNA oxidation. Such effect is associated with suppression of autophagy regulators.

Intravenous administration of tetramethylpyrazine reduces intestinal ischemia-reperfusion injury in rats

Intestinal ischemia-reperfusion injury (IIRI) is a life-threatening condition requiring prompt medical intervention. Tetramethylpyrazine (TMP) is a biologically active alkaloid isolated from Ligusticum wallichii. Previously, it was shown that TMP causes vasodilatation and inhibition of platelet aggregation as well as exhibits significant antioxidant effects. Therefore, the aim of the present study was to evaluate possible therapeutic effects of TMP in the prevention of IIRI. Wistar rats (n = 80) were randomly divided into eight experimental groups and subjected to a 1 h occlusion of cranial mesenteric artery followed by 0, 1, 12, and 24 h period of reperfusion. Thirty minutes before the IIRI animals received either TMP (30 mg/kg, i.v.) or identical volume of saline. In addition, a control group of 10 animals was not exposed to IIRI. Intestine morphology was evaluated by using histopathological injury index examination (HII), goblet and Paneth cells quantification as well as by applying immunofluorescent methods such as InSitu TUNEL and caspase-3 positivity assessment. Here we showed that preconditioning with TMP prior IIRI decreases the grade of injury. Significant reduction of HII was detected in TMP pretreated groups after 0, 1, and 12 h of reperfusion where injury reduction up to 75% was found. Lower histopathological damage in preconditioned groups was accompanied with increased number of secretory epithelial cells and decreased number of apoptotic cells. These results demonstrate the protective effect of TMP on the small intestine mucosa, suggesting administration of TMP as a molecule for pharmacological intervention against IIRI.

Link between oxidative stress and acute brain ischemia

The pathogenesis of acute brain ischemia (ABI) is highly complex and involves multiple mechanisms including free radical generation. Imbalance between the cellular production of free radicals and the ability of cells to defend against them is referred to as oxidative stress. Oxidative stress is one of the mechanisms contributing to neuronal damage, potentially induced through the ABI. Through interactions with a large number of molecules, reactive oxygen species may irreversibly destroy or alter the function of the cellular lipids, proteins, and nucleic acids and initiate cell signaling pathways after cerebral ischemia. Future investigations should focus on the understanding of oxidative stress mechanisms and neuroprotection in order to discover new treatment targets.

Impairment of autophagic flux promotes glucose reperfusion-induced neuro2A cell death after glucose deprivation

Hypoglycemia-induced brain injury is a common and serious complication of intensive insulin therapy experienced by Type 1 diabetic patients. We previously reported that hypoglycemic neuronal death is triggered by glucose reperfusion after hypoglycemia rather than as a simple result of glucose deprivation. However, the precise mechanism of neuronal death initiated by glucose reperfusion is still unclear. Autophagy is a self-degradation process that acts through a lysosome-mediated trafficking pathway to degrade and recycle intracellular components, thereby regulating metabolism and energy production. Recent studies suggest that autophagic and lysosomal dysfunction leads to abnormal protein degradation and deposition that may contribute to neuronal death. Here, we focused on the relationship between autophagy and lysosomal dysfunction in hypoglycemia-induced neuronal death. In neuronal cells, glucose reperfusion after glucose deprivation resulted in inhibition of autophagy, which may promote cell death. This cell death was accompanied with activation of caspase3 and the lysosomal proteases cathepsin B and D, which indicated impairment of autophagic flux. Taken together, these results suggest that interplay of autophagy, caspase3 activation and lysosomal proteases serve as a basis for neuronal death after hypoglycemia. Thus, we provide the molecular mechanism of neuronal death by glucose reperfusion and suggest some clues for therapeutic strategies to prevent hypoglycemia-induced neuronal death.

Glutathione metabolism and Parkinson's disease

It has been established that oxidative stress, defined as the condition in which the sum of free radicals in a cell exceeds the antioxidant capacity of the cell, contributes to the pathogenesis of Parkinson disease. Glutathione is a ubiquitous thiol tripeptide that acts alone or in concert with enzymes within cells to reduce superoxide radicals, hydroxyl radicals, and peroxynitrites. In this review, we examine the synthesis, metabolism, and functional interactions of glutathione and discuss how these relate to the protection of dopaminergic neurons from oxidative damage and its therapeutic potential in Parkinson disease.

Screening of radical-scavenging natural neuroprotective antioxidants from Swertia chirayita

To detect and identify natural antioxidants in Swertia chirayita with protective effect against cerebral infarction, a screening method, using column chromatography and cerebral ischemia-reperfusion injury in rat, was developed. Seventeen compounds were purposefully separated and identified by Nuclear Magnetic Resonance, Fourier Transform Infrared Spectroscopy, Ultraviolet Spectrum, and Mass Spectrometry. The purified compounds were further screened by radical scavenging activity and cerebral ischemia-reperfusion injury in rats. Two compounds showed apparent radical scavenging activity and neuroprotective activity. The two compounds were identified as 1-hydroxy-2,3,4,6-tetramethoxyxanthone and 1,5,8-trihydroxy-3-methoxy xanthone, and were preliminarily considered as primary natural neuroprotective antioxidants in Swertia chirayita. These two compounds (20 mg kg-1) markedly decreased infarct size to below 5%, and also caused a significant improvement of activities of superoxide dismutase (SOD) (92.90 ± 11.19 U ml-1), glutathione peroxidase (GSH-Px) (122.58 ± 12.31 μmol mg-1) and a decrease in the content of malondialdehyde (MDA) (3.98 ± 2.00 nmol ml-1) in serum. The two compounds showed strong capability for protective effects against cerebral damages induced by ischemia-reperfusion, and the protective effect may be related to the inhibition of lipid peroxidation. The use of the screening method based on tracing separation and ischemia reperfusion would provide a new way for detection of radical-scavenging and natural neuroprotective compounds from Swertia chirayita or complex matrices.

Hydroxysafflor yellow A protects against cerebral ischemia-reperfusion injury by anti-apoptotic effect through PI3K/Akt/GSK3β pathway in rat

Hydroxysafflor yellow A (HSYA) is the major active chemical component of the flower of the safflower plant, Carthamus tinctorius L. Previously, its neuroprotection against cerebral ischemia-reperfusion (I/R) injury was reported by anti-oxidant action and suppression of thrombin generation. Here, we investigate the role of HSYA in cerebral I/R-mediated apoptosis and possible signaling pathways. Male Wistar rats were subjected to transient middle cerebral artery occlusion for 2 h, followed by 24 h reperfusion. HSYA was administered via tail-vein injection just 15 min after occlusion. The number of apoptotic cells was measured by TUNEL assay, apoptosis-related proteins Bcl-2, Bax and the phosphorylation levels of Akt and GSK3β in ischemic penumbra were assayed by western blot. The results showed that administration of HSYA at the doses of 4 and 8 mg/kg significantly inhibited the apoptosis by decreasing the number of apoptotic cells and increasing the Bcl-2/Bax ratio in rats subjected to I/R injury. Simultaneously, HSYA treatment markedly increased the phosphorylations of Akt and GSK3β. Blockade of PI3K activity by wortmannin dramatically abolished its anti-apoptotic effect and lowered both Akt and GSK3β phosphorylation levels. Taken together, these results suggest that HSYA protects against cerebral I/R injury partly by reducing apoptosis via PI3K/Akt/GSK3β signaling pathway.

Neuroprotective activity of Stereospermum suaveolens against global cerebral ischemia rat model

CONTEXT

Stereospermum suaveolens DC. (Bignoniaceae) is a medicinal tree species native to India. Traditionally, the whole plant is used for various diseases including neuronal disorders.

OBJECTIVE

The present study evaluated the neuroprotective activity of Stereospermum suaveolens against global cerebral ischemia in a rat model.

MATERIALS AND METHODS

Neuroprotective activity was carried out by global cerebral ischemia on Sprague-Dawley rats and divided into five groups of eight rats each; sham and control groups received normal saline (10 ml/kg) and treated groups received methanol extract of Stereospermum suaveolens (MES) orally (125, 250, and 500 mg/kg) for 10 days prior to the experiment. Global cerebral ischemia was induced by bilateral carotid artery (BCA) occlusion for 30 min followed by 4-h reperfusion. The antioxidant enzymatic and non-enzymatic levels were estimated by UV spectroscopic method along with cerebral infarction area; histopathological studies were carried out.

RESULTS

LD₅₀ of MES was found to be 5000 mg/kg of body weight. The entire test was performed at dose levels 125, 250, and 500 mg/kg of body weight. The results of the study indicate that the Stereospermum suaveolens methanol extract showed neuroprotective activity by a significant decrease in lipid peroxidation (p < 0.001) and an increase in superoxide dismutase (p < 0.01), catalase (p < 0.01), glutathione (p < 0.001), and total thiol (p < 0.001) levels in extract-treated groups as compared to control group. Measurement of cerebral infarction area and histopathological studies further supported the protective effect of the extract.

DISCUSSION AND CONCLUSION

These findings suggest a potential protective role of Stereospermum suaveolens against global cerebral ischemia/reperfusion-induced brain injury.

Transient neurological deficit following midthoracic decompression for severe stenosis: a series of three cases

PURPOSE

To report three cases of transient perioperative neurological deficit in the absence of direct cord insult following decompression of the severely stenotic thoracic spine.

METHODS

The clinical and radiographic electronic medical records of three patients who underwent decompression for severe midthoracic stenosis with transient neurological deficits perioperatively were reviewed. The cases are presented with consideration of possible underlying mechanisms and multimodality intraoperative monitoring (IOM) findings.

RESULTS

Two patients had neurologic changes on IOM and Stagnara wake-up test, the remaining patient had absent motor and sensory potentials at baseline and throughout the case. IOM changes were observed immediately following decompression in the absence of direct cord insult or displacement. Postoperatively all patients experienced neurological motor deficits which presented as complete paralysis of the right lower extremity in two of the patients and the left lower extremity in one patient. The deficit was transient-improvement of motor strength occurred between 1 and 13 months of follow-up in all patients.

CONCLUSION

Decompression of a severely stenotic region of the thoracic spinal cord may lead to a complete yet transient motor deficit in the perioperative period in the absence of direct mechanical cord insult. Potential etiologies include ischemia-reperfusion injury, microthrombi, and altered perfusion due to internal recoil of spinal cord architecture following decompression. IOM may show conspicuous findings in such events, however, may not be relied upon when baseline potentials are sub-optimal. Recognition of this short-lived neurological deficit following decompression of the severely stenotic thoracic spine will improve preoperative patient counseling and merits further study for determination of the precise pathophysiology.

Interference of apoptosis in the pathophysiology of subarachnoid hemorrhage

Programmed cell death is crucial for the correct development of the organism and the clearance of harmful cells like tumor cells or autoreactive immune cells. Apoptosis is initiated by the activation of cell death receptors and in most cases it is associated with the activation of the cysteine proteases, which lead to apoptotic cell death. Cells shrink, chromatin clumps and forms a large, sharply demarcated, crescent-shaped or round mass; the nucleus condenses, apoptotic bodies are formed and eventually dead cells are engulfed by a neighboring cell or cleared by phagocytosis. The authors have summarized the most important data concerning apoptosis in subarachnoid hemorrhage that have been issued in the medical literature in the last 20 years.

The immune modulating properties of the heat shock proteins after brain injury

Inflammation within the central nervous system often accompanies ischemia, trauma, infection, and other neuronal injuries. The immune system is now recognized to play a major role in neuronal cell death due to microglial activation, leukocyte recruitment, and cytokine secretion. The participation of heat shock proteins (Hsps) in the immune response following in brain injury can be seen as an attempt to correct the inflammatory condition. The Hsps comprise various families on the basis of molecular size. One of the most studied is Hsp70. Hsp70 is thought to act as a molecular chaperone that is present in almost intracellular compartments, and function by refolding misfolded or aggregated proteins. Hsps have recently been studied in inflammatory conditions. Hsp70 can both induce and arrest inflammatory reactions and lead to improved neurological outcome in experimental brain injury and ischemia. In this review, we will focus on underlying inflammatory mechanisms and Hsp70 in acute neurological injury.

Neuroprotective and antioxidant potential of terpenoid fraction from Hygrophila auriculata against transient global cerebral ischemia in rats

CONTEXT

The plant Hygrophila auriculata (K. Schum) Heine. (Acanthaceae) is widely used in the Indian System of Medicine as "Rasayana" for treating brain and liver diseases.

OBJECTIVES

The present study evaluated the in vivo antioxidant and neuroprotective effect of aterpenoid rich fraction (TF) from Hygrophila auriculata in a rat model of transient global cerebral ischemia (tGCI).

MATERIALS AND METHODS

Male Wistar rats were grouped as sham control, tGCI control, vitamin E (500 mg/kg) and TF (100 & 200 mg/kg) treated groups. Following 7 days of drug administration, animals were subjected to tGCI by permanent occlusion of both vertebral and transient occlusion of carotid arteries for 10 min followed by reperfusion. The neuroprotective effect was assessed by tGCI induced neurological, sensory motor deficit in rats. Brain antioxidants such as superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were investigated. Further, a histopathological examination was done in CA1 hippocampus.

RESULTS

tGCI induction resulted in an increase in beam balance score (5.1), number of entries in open field (131) and a decrease in time spent in rotorod (47 s). In contrast, TF treatment resulted in a significant decrease in (p < 0.01) beam balance score (2.9), number of entries (67) and increased time spent in rotorod (63.25 s). There was also a significant (p < 0.001) decrease in brain SOD and GSH with an increase in MDA. TF treatment resulted in restoration of antioxidants and protection of hippocampal CA1 neurons against tGCI insult.

CONCLUSION

It is concluded that TF from Hygrophila auriculata shows neuroprotective potential against tGCI induced oxidative stress.

Ischaemic postconditioning rescues brain injury caused by focal ischaemia/reperfusion via attenuation of protein oxidization

OBJECTIVE

To investigate the effects of ischaemic postconditioning on brain injury and protein oxidization in focal ischaemia/reperfusion.

METHODS

Adult male Wistar rats (n = 30) were randomly divided into sham-operated, ischaemia, and ischaemic postconditioning groups. Ischaemia was produced by middle cerebral artery occlusion and ischaemic postconditioning was performed using three cycles of 30-s/30-s reperfusion/reocclusion after 2 h of ischaemia. Brain infarction size, hydrogen peroxide concentration, superoxide dismutase (SOD), catalase (CAT) and proteasome activities, protein carbonyl derivatives and advanced oxidized protein products (AOPPs) were evaluated.

RESULTS

The size of brain infarction after ischaemic postconditioning was significantly smaller compared with the ischaemia group, and was concomitant with significant reduction in protein carbonyl derivatives and AOPPs. The activities of SOD, CAT and proteasomes were elevated by ischaemic postconditioning compared with the ischaemia group.

CONCLUSIONS

Ischaemic postconditioning is an effective way of reducing the size and effects of brain infarction caused by focal ischaemia/reperfusion, possibly due to a decrease in oxidized protein levels. Decreasing protein oxidization may, therefore, be a useful target for preventing cerebral injury.

Ginger pharmacopuncture improves cognitive impairment and oxidative stress following cerebral ischemia

Recent findings have demonstrated that acupuncture and ginger can each improve memory impairment following cerebral ischemia. We hypothesized that ginger pharmacopuncture, a combination of these two treatments, could increase the beneficial effects. Due to the limitation of supporting evidence, we aimed to determine whether ginger pharmacopuncture could improve cognitive function and oxidative stress following cerebral ischemia. Male Wistar rats were induced by right middle cerebral artery occlusion (Rt. MCAO) and subjected to either acupuncture or ginger pharmacopuncture once daily over a period of 14 days after Rt. MCAO. Cognitive function was determined every 7 days, using escape latency and retention time as indices, and the oxidative stress status of the rats was determined at the end of the study. Rats subjected either to acupuncture or to ginger pharmacopuncture at GV20 demonstrated enhanced spatial memory, and the activities of catalase and glutathione peroxidase in both cerebral cortex and hippocampus were improved. Elevation of superoxide dismutase activity was observed only in the hippocampus. Cognitive enhancement was observed sooner with ginger pharmacopuncture than with acupuncture. The cognitive enhancing effect of acupuncture and ginger pharmacopuncture is likely to be at least partially attributable to decreased oxidative stress. However, other mechanisms may also be involved, and this requires further study.

Preconditioning for traumatic brain injury

Traumatic brain injury (TBI) treatment is now focused on the prevention of primary injury and reduction of secondary injury. However, no single effective treatment is available as yet for the mitigation of traumatic brain damage in humans. Both chemical and environmental stresses applied before injury have been shown to induce consequent protection against post-TBI neuronal death. This concept termed "preconditioning" is achieved by exposure to different pre-injury stressors to achieve the induction of "tolerance" to the effect of the TBI. However, the precise mechanisms underlying this "tolerance" phenomenon are not fully understood in TBI, and therefore even less information is available about possible indications in clinical TBI patients. In this review, we will summarize TBI pathophysiology, and discuss existing animal studies demonstrating the efficacy of preconditioning in diffuse and focal type of TBI. We will also review other non-TBI preconditioning studies, including ischemic, environmental, and chemical preconditioning, which maybe relevant to TBI. To date, no clinical studies exist in this field, and we speculate on possible future clinical situations, in which pre-TBI preconditioning could be considered.

Guanosine protects against reperfusion injury in rat brains after ischemic stroke

After ischemic stroke, early thrombolytic therapy to reestablish tissue perfusion improves outcome but triggers a cascade of deleterious cellular and molecular events. Using a collaborative approach, our groups examined the effects of guanosine (Guo) in response to ischemic reperfusion injury in vitro and in vivo. In a transient middle cerebral artery occlusion (MCAO) in rats, Guo significantly reduced infarct volume in a dose-dependent manner when given systemically either immediately before or 30 min, but not 60 min, after the onset of the 5.5-hr reperfusion period. In a separate experiment, Guo significantly reduced infarct volume after 24 hr of reperfusion when administered 5 min before reperfusion. Western blot analysis did not reveal any significant changes either in endoplasmic reticulum (ER) stress proteins (GRP 78 and 94) or HSP 70 or in levels of m-calpain. In vitro oxygen and glucose deprivation (OGD) significantly increased production of both reactive oxygen species (ROS) and interleukin-8 (IL-8) in the primary astrocytes. Guo did not alter ROS or IL-8 production when given to the astrocytes before OGD. However, Guo when added to the cells prior to or 30 min after reperfusion significantly reduced IL-8 release but not ROS formation. Our study revealed a dose- and time-dependent protective effect of Guo on reperfusion injury in vitro and vivo. The mechanisms by which Guo exerts its effect are independent of unfolded proteins in ER or the level of intracellular calcium or ROS formation. However, the effect may be induced, at least partially, by inhibiting IL-8, a marker of reperfusion-triggered proinflammatory events.

Effect of propofol on hypoxia re-oxygenation induced neuronal cell damage in vitro*

Propofol may protect neuronal cells from hypoxia re-oxygenation injury, possibly via an antioxidant actions under hypoxic conditions. This study investigated the molecular effects of propofol on hypoxia-induced cell damage using a neuronal cell line. Cultured human IMR-32 cells were exposed to propofol (30 μm) and biochemical and molecular approaches were used to assess cellular effects. Propofol significantly reduced hypoxia-mediated increases in lactate dehydrogenase, a marker of cell damage (mean (SD) for normoxia: 0.39 (0.07) a.u.; hypoxia: 0.78 (0.21) a.u.; hypoxia+propofol: 0.44 (0.17) a.u.; normoxia vs hypoxia, p<0.05; hypoxia vs hypoxia+propofol, p<0.05), reactive oxygen species and hydrogen peroxide. Propofol also diminished the morphological signs of cell damage. Increased amounts of catalase, which degrades hydrogen peroxide, were detected under hypoxic conditions. Propofol decreased the amount of catalase produced, but increased its enzymatic activity. Propofol protects neuronal cells from hypoxia re-oxygenation injury, possibly via a combined direct antioxidant effect along with induced cellular antioxidant mechanisms.

Ischemic postconditioning alleviates neuronal injury caused by relief of carotid stenosis in a rat model of cerebral hypoperfusion

The effects of early relief of heavy bilateral carotid stenosis and ischemic postconditioning on hippocampus CA1 neurons are still unclear. In this study, we used a rat model to imitate severe bilateral carotid stenosis in humans. The rats were divided into sham group, carotid stenosis group, stenosis relief group and ischemic postconditioning group. Ischemic postconditioning consisted of three cycles of 30 s ischemia and 30 s reperfusion. The cerebral blood flow was measured with a laser Doppler flowmeter. Neuronal death in the CA1 region was observed by hematoxylin-eosin staining, and the number of live neurons was assessed by cell counting under a light microscope. The levels of oxidative products MDA and 8-iso-PGF2α, inflammatory factors IL-1β and TNF-α, and the activities of anti-oxidative enzymes SOD and CAT were assayed by specific enzyme-linked immunosorbent assay (ELISA) kits, respectively. We found that relief of carotid stenosis and ischemic postconditioning could increase cerebral blood flow. When stenosis was relieved, the percentage of live neurons was 66.6% ± 6.2% on day 3 and 62.3% ± 9.8% on day 27, which was significantly higher than 55.5% ± 4.8% in stenosis group. Ischemic postconditioning markedly improved the live neurons to 92.5% ± 6.7% on day 3 and 88.6% ± 9.1% on day 27. Further study showed that, neuronal death caused by relief of stenosis is associated with increased oxidative stress and enhanced inflammatory response, and the protection of ischemic postconditioning is related to inhibition of oxidative stress and suppression of inflammatory response.

SOD1 aggregation in astrocytes following ischemia/reperfusion injury: a role of NO-mediated S-nitrosylation of protein disulfide isomerase (PDI)

Background

Ubiquitinated-protein aggregates are implicated in cerebral ischemia/reperfusion injury. The very presence of these ubiquitinated-protein aggregates is abnormal and seems to be disease-related. However, it is not clear what leads to aggregate formation and whether the aggregations represent a reaction to aggregate-mediated neurodegeneration.

Methods

To study the nitrosative stress-induced protein aggregation in cerebral ischemia/reperfusion injury, we used primary astrocyte cultures as a cell model, and systematically examined their iNOS expression and consequent NO generation following oxygen glucose deprivation and reperfusion. The expression of protein disulfide isomerase (PDI) and copper-zinc superoxide dismutase (SOD1) were also examined, and the biochemical interaction between PDI and SOD1 was determined by immunoprecipitation. In addition, the levels of S-nitrosylated PDI in cultured astrocytes after oxygen glucose deprivation and reperfusion treatment were measured using the biotin-switch assay. The formation of ubiquitinated-protein aggregates was detected by immunoblot and immunofluorescence staining.

Results

Our data showed that the up-regulation of iNOS expression after oxygen glucose deprivation and reperfusion treatment led to excessive NO generation. Up-regulation of PDI and SOD1 was also identified in cultured astrocytes following oxygen glucose deprivation and reperfusion, and these two proteins were found to bind to each other. Furthermore, the increased nitrosative stress due to ischemia/reperfusion injury was highly associated with NO-induced S-nitrosylation of PDI, and this S-nitrosylation of PDI was correlated with the formation of ubiquitinated-protein aggregates; the levels of S-nitrosylated PDI increased in parallel with the formation of aggregates. When NO generation was pharmacologically inhibited by iNOS specific inhibitor 1400W, S-nitrosylation of PDI was significantly blocked. In addition, the formation of ubiquitinated-protein aggregates in cultured astrocytes following oxygen glucose deprivation and reperfusion was also suppressed by 1400W. Interestingly, these aggregates were colocalized with SOD1, which was found to co-immunoprecipitate with PDI.

Conclusions

NO-mediated S-nitrosylation of PDI may be involved in the formation of the SOD1-linked ubiquitinated-protein aggregates in cerebral ischemia/reperfusion injury.

Molecular mechanisms of ischemia-reperfusion injury in brain: pivotal role of the mitochondrial membrane potential in reactive oxygen species generation

Stroke and circulatory arrest cause interferences in blood flow to the brain that result in considerable tissue damage. The primary method to reduce or prevent neurologic damage to patients suffering from brain ischemia is prompt restoration of blood flow to the ischemic tissue. However, paradoxically, restoration of blood flow causes additional damage and exacerbates neurocognitive deficits among patients who suffer a brain ischemic event. Mitochondria play a critical role in reperfusion injury by producing excessive reactive oxygen species (ROS) thereby damaging cellular components, and initiating cell death. In this review, we summarize our current understanding of the mechanisms of mitochondrial ROS generation during reperfusion, and specifically, the role the mitochondrial membrane potential plays in the pathology of cerebral ischemia/reperfusion. Additionally, we propose a temporal model of ROS generation in which posttranslational modifications of key oxidative phosphorylation (OxPhos) proteins caused by ischemia induce a hyperactive state upon reintroduction of oxygen. Hyperactive OxPhos generates high mitochondrial membrane potentials, a condition known to generate excessive ROS. Such a state would lead to a "burst" of ROS upon reperfusion, thereby causing structural and functional damage to the mitochondria and inducing cell death signaling that eventually culminate in tissue damage. Finally, we propose that strategies aimed at modulating this maladaptive hyperpolarization of the mitochondrial membrane potential may be a novel therapeutic intervention and present specific studies demonstrating the cytoprotective effect of this treatment modality.

Neuroprotection by GDNF in the ischemic brain

The glial cell line-derived neurotrophic factor (GDNF) was first identified as a survival factor for midbrain dopaminergic neurons, but additional studies provided evidences for a role as a trophic factor for other neurons of the central and peripheral nervous systems. GDNF regulates cellular activity through interaction with glycosyl-phosphatidylinositol-anchored cell surface receptors, GDNF family receptor-α1, which might signal through the transmembrane Ret tyrosine receptors or the neural cell adhesion molecule, to promote cell survival, neurite outgrowth, and synaptogenesis. The neuroprotective effect of exogenous GDNF has been shown in different experimental models of focal and global brain ischemia, by local administration of the trophic factor, using viral vectors carrying the GDNF gene and by transplantation of GDNF-expressing cells. These different strategies and the mechanisms contributing to neuroprotection by GDNF are discussed in this review. Importantly, neuroprotection by GDNF was observed even when administered after the ischemic injury.

Cerebralcare Granule® attenuates blood-brain barrier disruption after middle cerebral artery occlusion in rats

Disruption of blood-brain barrier (BBB) and subsequent edema are major contributors to the pathogenesis of ischemic stroke, for which the current clinical therapy remains unsatisfied. Cerebralcare Granule® (CG) is a compound Chinese medicine widely used in China for treatment of cerebrovascular diseases. CG has been demonstrated efficacy in attenuating the cerebral microcirculatory disturbance and hippocampal neuron injury following global cerebral ischemia. However, the effects of CG on BBB disruption following cerebral ischemia have not been investigated. In this study, we examined the therapeutic effect of CG on the BBB disruption in a focal cerebral ischemia/reperfusion (I/R) rat model. Male Sprague-Dawley rats (250 to 300 g) were subjected to 1h middle cerebral artery occlusion (MCAO). CG (0.4 g/kg or 0.8 g/kg) was administrated orally 3h after reperfusion for the first time and then once daily up to 6 days. The results showed that Evans blue extravasation, brain water content, albumin leakage, infarction volume and neurological deficits increased in MCAO model rats, and were attenuated significantly by CG treatment. T2-weighted MRI and electron microscopy further confirmed the brain edema reduction in CG-treated rats. Treatment with CG improved cerebral blood flow (CBF). Western blot analysis and confocal microscopy showed that the tight junction proteins claudin-5, JAM-1, occludin and zonula occluden-1 between endothelial cells were significantly degradated, but the protein expression of caveolin-1, the principal marker of caveolae in endothelial cells, increased after ischemia, all of which were alleviated by CG treatment. In conclusion, the post-treatment with CG significantly reduced BBB permeability and brain edema, which were correlated with preventing the degradation of the tight junction proteins and inhibiting the expression of caveolin-1 in the endothelial cells. These findings provide a novel approach to the treatment of ischemic stroke.

Leonurine protects brain injury by increased activities of UCP4, SOD, CAT and Bcl-2, decreased levels of MDA and Bax, and ameliorated ultrastructure of mitochondria in experimental stroke

BACKGROUND

It has been proved that pre-treatment with leonurine could protect brain tissue against ischemic injury by exerting antioxidant effects and regulating mitochondrial function. Whether this protective effect applies to acute phase after cerebral ischemia, we therefore investigate the potential neuroprotective role of leonurine and the underlying mechanisms in cerebral ischemia.

METHODS

Focal cerebral ischemia was induced in adult male Sprague-Dawley rats by permanent middle cerebral artery occlusion (MCAO). Leonurine was administered intraperitoneally at 7.5 or 15 mg/kg/d at 2h after surgery, then once daily thereafter. Neurological deficit, brain water content, and infarct volume were measured at 24h, 72 h, and 7d after stroke. Superoxide dismutase (SOD), catalase (CAT) activities, and malondialdehyde (MDA) content were also measured by spectrophotometer to evaluate oxidative reactions, and the expression of uncoupling protein 4 (UCP4), Bcl-2, and Bax were detected by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemical staining (IHC), and western blot, while the ultrastructure of the mitochondria were observed under transmission electron microscope.

RESULTS

Leonurine significantly alleviated neurological deficit, decreased brain water content and infarct volume after ischemic stroke, which was accompanied by decreased levels of MDA and Bax, increased activities of SOD, CAT, UCP4, and Bcl-2, and restored ultrastructure of mitochondria.

CONCLUSIONS

The results showed that leonurine protected brain injury by increased activities of UCP4, SOD, CAT and Bcl-2, decreased levels of MDA and Bax, and ameliorated ultrastructure of mitochondria in experimental stroke.

Changes in carotid blood flow after unilateral perinatal arterial ischemic stroke

INTRODUCTION

Little is known about changes in carotid blood flow after perinatal arterial ischemic stroke (PAIS). The aim of this study was to assess the blood flow in the internal carotid arteries (ICAs) after unilateral PAIS.

METHODS

The carotid flow (ml/min) was measured noninvasively by means of two-dimensional phase-contrast magnetic resonance angiography (2D PC-MRA) in 25 full-term infants who had unilateral PAIS within 10 d after birth. In 17 infants a second 2D PC-MRA was carried out at the age of 3 mo. Asymmetry of carotid blood flow was calculated at both time points, and the circle of Willis (CoW) was assessed with a three-dimensional (3D) time-of-flight MRA.

RESULTS

On the early magnetic resonance imaging (MRI), a significant increase in ipsilateral blood flow was observed (7.7%, 95% confidence interval (CI) 3.0-14.9%), which persisted after correcting for CoW configuration. At 3 mo, this asymmetry was no longer observed. No relationship was found between the asymmetry in blood flow and either stroke size or postnatal age at scan.

DISCUSSION

A higher blood flow in the ipsilateral ICA was observed during the acute phase after unilateral PAIS, and this disappeared after 3 mo. Further research into the role of hyperperfusion after PAIS may suggest new approaches to neuroprotection.

Neuroprotective activityof Cymbopogon martinii against cerebral ischemia/reperfusion-induced oxidative stress in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cymbopogon martinii (Roxb.) Watson (Family: Graminae), commonly known as Palmarosa, is traditionally prescribed for central nervous system (CNS) disorders such as neuralgia, epileptic fits and anorexia. Although the plant possesses diverse pharmacological actions, the neuroprotective action has got little attention.

AIM OF THE STUDY

The present study evaluated neuroprotective effect of essential oil of Cymbopogon martinii (EOCM) against global cerebral ischemia/reperfusion (I/R)-induced oxidative stress in rats.

MATERIALS AND METHODS

Global ischemic brain damage was induced by bilateral common carotid artery (BCCA) occlusion for 30 min, followed by 60 min reperfusion on Wistar albino rats. The biochemical levels of lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT), total thiols and glutathione (GSH) were estimated and brain coronal sections and histopathological studies were performed.

RESULTS

BCCA occlusion, followed by reperfusion caused varied biochemical/enzymatic alterations viz. increase in LPO and decrease in SOD, CAT, total thiols and GSH. The prior treatment of EOCM (50 mg/kg and 100 mg/kg, p.o. for 10 days) markedly reversed these changes and restored to normal levels as compared to I/R groups. Moreover, brain coronal sections and histopathological studies revealed protection against ischemic brain damage in the EOCM-treated groups.

CONCLUSION

This study, for the first time, shows potent neuroprotective effect of EOCM against global cerebral I/R-induced oxidative stress in rats, suggesting its therapeutic potential in cerebrovascular diseases (CVD) including stroke.