Reactive oxygen radicals and pathogenesis of neuronal death after cerebral ischemia

Astrocytes, but not microglia, rapidly sense H₂O₂via STAT6 phosphorylation, resulting in cyclooxygenase-2 expression and prostaglandin release

Emerging evidence has established that astrocytes, once considered passive supporting cells that maintained extracellular ion levels and served as a component of the blood-brain barrier, play active regulatory roles during neurogenesis and in brain pathology. In the current study, we demonstrated that astrocytes sense H(2)O(2) by rapidly phosphorylating the transcription factor STAT6, a response not observed in microglia. STAT6 phosphorylation was induced by generators of other reactive oxygen species (ROS) and reactive nitrogen species, as well as in the reoxygenation phase of hypoxia/reoxygenation, during which ROS are generated. Src-JAK pathways mediated STAT6 phosphorylation upstream. Experiments using lipid raft disruptors and analyses of detergent-fractionated cells demonstrated that H(2)O(2)-induced STAT6 phosphorylation occurred in lipid rafts. Under experimental conditions in which H(2)O(2) did not affect astrocyte viability, H(2)O(2)-induced STAT6 phosphorylation resulted in STAT6-dependent cyclooxygenase-2 expression and subsequent release of PGE(2) and prostacyclin, an effect also observed in hypoxia/reoxygenation. Finally, PGs released from H(2)O(2)-stimulated astrocytes inhibited microglial TNF-α expression. Accordingly, our results indicate that ROS-induced STAT6 phosphorylation in astrocytes can modulate the functions of neighboring cells, including microglia, through cyclooxygenase-2 induction and subsequent release of PGs. Differences in the sensitivity of STAT6 in astrocytes (highly sensitive) and microglia (insensitive) to phosphorylation following brief exposure to H(2)O(2) suggest that astrocytes can act as sentinels for certain stimuli, including H(2)O(2) and ROS, refining the canonical notion that microglia are the first line of defense against external stimuli.

Astrocytes: targets for neuroprotection in stroke

In the past two decades, over 1000 clinical trials have failed to demonstrate a benefit in treating stroke, with the exception of thrombolytics. Although many targets have been pursued, including antioxidants, calcium channel blockers, glutamate receptor blockers, and neurotrophic factors, often the focus has been on neuronal mechanisms of injury. Broader attention to loss and dysfunction of non-neuronal cell types is now required to increase the chance of success. Of the several glial cell types, this review will focus on astrocytes. Astrocytes are the most abundant cell type in the higher mammalian nervous system, and they play key roles in normal CNS physiology and in central nervous system injury and pathology. In the setting of ischemia astrocytes perform multiple functions, some beneficial and some potentially detrimental, making them excellent candidates as therapeutic targets to improve outcome following stroke and in other central nervous system injuries. The older neurocentric view of the central nervous system has changed radically with the growing understanding of the many essential functions of astrocytes. These include K+ buffering, glutamate clearance, brain antioxidant defense, close metabolic coupling with neurons, and modulation of neuronal excitability. In this review, we will focus on those functions of astrocytes that can both protect and endanger neurons, and discuss how manipulating these functions provides a novel and important strategy to enhance neuronal survival and improve outcome following cerebral ischemia.

Role of the NMDA receptor and iron on free radical production and brain damage following transient middle cerebral artery occlusion

Excess activation of ionotropic glutamate receptors and iron is believed to contribute to free radical production and neuronal death following hypoxic ischemia. We examined the possibility that both NMDA receptor activation and iron overload determine spatial and temporal patterns of free radical production after transient middle cerebral artery occlusion (tMCAO) in male Sprague-Dawley rats. Mitochondrial free radical (MFR) levels were maximally increased in neurons in the core at 1 h and 24 h after tMCAO. Early MFR production was blocked by administration of MK-801, an NMDA receptor antagonist, but not deferoxamine, an iron chelator. Neither MK-801 nor deferoxamine attenuated late MFR production in the core. Increased MFRs were observed in penumbral neurons within 6 h and gradually increased over 24 h after tMCAO. Slowly-evolving MFRs in the core and penumbra were accompanied by iron overload. Deferoxamine blocked iron overload but reduced MFR production only in the penumbra. Combined MK-801/deferoxamine reduced late MFR production in both core and penumbra in an additive manner. Combination therapy significantly ameliorated infarction compared with monotherapy. These findings suggest that the NMDA receptor activation and iron overload mediate late MFR production and infarction after tMCAO.

Inhalation of hydrogen gas attenuates cognitive impairment in transient cerebral ischemia via inhibition of oxidative stress

OBJECTIVE

To investigate the effects of inhalation of hydrogen gas on cognitive impairment induced by transient cerebral ischemia and its potential mechanism.

METHODS

Two-vessel occlusion rat model was used to produce 10-minute transient global cerebral ischemia. One hundred and twenty male Wistar rats were randomly divided into sham, sham+H(2), ischemia, and ischemia+H(2) groups (n = 30 each group). Inhalation of 2% hydrogen gas was performed immediately at the end of operation and lasted for 3 hours. Cognitive function of rats was evaluated via Morris water maze. Neuronal damage in the CA1 region was quantified according to their morphological changes revealed by hematoxylin-eosin staining. The levels of oxidative stress products malondialdehyde (MDA) and 8-iso-prostaglandin F2alpha, and the activities of anti-oxidative enzymes catalase and superoxide dismutase were measured to investigate the effects of inhalation of hydrogen gas on oxidative stress.

RESULTS

Inhalation of hydrogen gas decreased significantly the average latency of the ischemic rats in finding hidden platform and elongated markedly their retention in the target quadrant. The neuronal density 3·3±2·1 cells/mm in CA1 region of the ischemic rats increased to 21·7±2·6 cells/mm after they were treated with hydrogen gas. Moreover, hydrogen gas made higher levels of MDA and 8-iso-PGF2α in the ischemic rats attenuate to 3·2±0·2, 3·5±0·5, 3·4±0·3 and 26·4±2·3, 28·2±2·6, 26·8±2·1 at reperfusion 4, 24, and 72 hours, respectively (P<0·01 versus ischemia group at each indicated time). By contrast, the activities of superoxide dismutase and catalase damaged by ischemia/reperfusion recovered to 129·7±14·8, 100·5±12·2 and 11·4±0·8, 9·6±1·1 at reperfusion 24 and 72 hours, respectively (P<0·01 versus ischemia group at each indicated time).

CONCLUSION

Inhalation of hydrogen gas could attenuate cognitive impairment in the ischemic rats. This protection is associated with decreased neuronal death in CA1 region and inhibition of oxidative stress.

Protective effect of 20-HETE inhibition in a model of oxygen-glucose deprivation in hippocampal slice cultures

Recent studies have indicated that inhibitors of the synthesis of 20-hydroxyeicosatetraenoic acid (20-HETE) may have direct neuroprotective actions since they reduce infarct volume after ischemia reperfusion in the brain without altering blood flow. To explore this possibility, the present study used organotypic hippocampal slice cultures subjected to oxygen-glucose deprivation (OGD) and reoxygenation to examine whether 20-HETE is released by organotypic hippocampal slices after OGD and whether it contributes to neuronal death through the generation of ROS and activation of caspase-3. The production of 20-HETE increased twofold after OGD and reoxygenation. Blockade of the synthesis of 20-HETE with N-hydroxy-N'-(4-butyl-2-methylphenol)formamidine (HET0016) or its actions with a 20-HETE antagonist, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid, reduced cell death, as measured by the release of lactate dehydrogenase and propidium iodide uptake. Administration of a 20-HETE mimetic, 20-hydroxyeicosa-5(Z),14(Z)-dienoic acid (5,14-20-HEDE), had the opposite effect and increased injury after OGD. The death of neurons after OGD was associated with an increase in the production of ROS and activation of caspase-3. These effects were attenuated by HET0016 and potentiated after the administration of 5,14-20-HEDE. These findings indicate that the production of 20-HETE by hippocampal slices is increased after OGD and that inhibitors of the synthesis or actions of 20-HETE protect neurons from ischemic cell death. The protective effect of 20-HETE inhibitors is associated with a decrease in superoxide production and activation of caspase-3.

Anti-inflammatory properties and pharmacological induction of Hsp70 after brain injury

The 70-kDa heat shock protein (Hsp70) is thought to protect the brain from a variety of insults. Although the mechanism has been largely limited to its chaperone functions, recent work indicates that Hsp70 also modulates inflammatory pathways. Brain injury and ischemia are associated with an immune response that is largely innate. Hsp70 appears to suppress this response and lead to improved neurological outcome. However, most of this work has relied on the use of genetic mutant models or Hsp70 overexpression using gene transfer or heat stress, thus limiting its translational utility. A few compounds have been studied by various disciplines which, through their ability to inhibit Hsp90, can cause induction of Hsp70. The investigation of Hsp70-inducing pharmacological compounds has obvious clinical implications in terms of potential therapies to mitigate neuroinflammation and lead to neuroprotection from stroke or traumatic brain injury. This review will focus on the inflammation modulating properties of Hsp70, and the current literature surrounding the pharmacological induction in acute neurological injury models with comments on potential applications at the clinical level.

Antioxidant therapies: a potential role in perinatal medicine

Pregnancies complicated by impaired placentation, acute severe reductions in oxygen supply to the fetus, or intrauterine infection are associated with oxidative stress to the mother and developing baby. Such oxidative stress is characterized as an upregulation in the production of oxidative or nitrative free radicals and a concomitant decrease in the availability of antioxidant species, thereby creating a state of fetoplacental oxidative imbalance. Recently, there has been a good deal of interest in the potential for the use of antioxidant therapies in the perinatal period to protect the fetus, particularly the developing brain, against oxidative stress in complications of pregnancy and birth. This review will examine why the immature brain is particularly susceptible to oxidative imbalance and will provide discussion on antioxidant treatments currently receiving attention in the adult and perinatal literature - allopurinol, melatonin, α-lipoic acid, and vitamins C and E. In addition, we aim to address the interaction between oxidative stress and the fetal inflammatory response, an interaction that may be vital when proposing antioxidant or other neuroprotective strategies.

The Use of Hypothermia Therapy in Traumatic Ischemic / Reperfusional Brain Injury: Review of the Literatures

Therapeutic mild hypothermia has been used widely in brain injury. It has evaluated in numerous clinical trials, and there is strong evidence for the use of hypothermia in treating patients with several types of ischemic / reperfusional (I/R) injuries, examples being cardiac arrest and neonatal hypoxic-ischemic encephalopathy.In spite of many basic research projects demonstrating effectiveness, therapeutic hypothermia has not been proven effective for the heterogeneous group of traumatic brain injury patients in multicenter clinical trials. In the latest clinical trial, however, researchers were able to demonstrate the significant beneficial effects of hypothermia in one specific group; patients with mass evacuated lesions. This suggested that mild therapeutic hypothermia might be effective for I/R related traumatic brain injury.In this article we have reviewed much of the previous literature concerning the mechanisms of I/R injury to the protective effects of mild therapeutic hypothermia.

The C718T polymorphism in the 3'-untranslated region of glutathione peroxidase-4 gene is a predictor of cerebral stroke in patients with essential hypertension

In the present study we have investigated the association of three single nucleotide polymorphisms in glutathione peroxidase (GPx) genes GPX1 rs1050450 (P198L), GPX3 rs2070593 (G930A) and GPX4 rs713041 (T718C) with the risk of cerebral stroke (CS) in patients with essential hypertension (EH). A total of 667 unrelated EH patients of Russian origin, including 306 hypertensives (the EH-CS group) who suffered from CS and 361 people (the EH-CS group) who did not have cerebrovascular accidents, were enrolled in the study. The variant allele 718C of the GPX4 gene was found to be significantly associated with an increased risk of CS in hypertensive patients (odds ratio (OR) 1.53, 95% confidence interval (CI) 1.23-1.90, P(adj) = 0.0003). The prevalence of the 718TC and 718CC genotypes of the GPX4 gene was higher in the EH-CS group than the EH-alone group (OR = 2.12, 95%CI 1.42-3.16, P(adj) = 0.0018). The association of the variant GPX4 genotypes with the increased risk of CS in hypertensives remained statistically significant after adjusting for confounding variables such as sex, body mass index (BMI), blood pressure and antihypertensive medication use (OR = 2.18, 95%CI 1.46-3.27, P = 0.0015). Multiple logistic regression analysis did not reveal any interaction between various combinations of GPX1, GPX3 and GPX4 genotypes regarding the risk of CS in patients with EH. The study demonstrated for the first time that the C718T polymorphism in the 3'-untranslated region of the GPX4 gene could be considered as a genetic marker of susceptibility to CS in patients with EH.

Rapid conditioning with oxygen oscillation: neuroprotection by intermittent normobaric hyperoxia after transient focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

Normobaric hyperoxia (NBO) has been shown to exert neuroprotective effects against cerebral ischemia and to restore penumbral oxygenation. Inspired by recent reports on postconditioning with intermittent occlusions of cerebral artery, we tested the hypothesis that intermittent NBO (iNBO) may cause oscillation of cerebral oxygenation and thereby elicit repetitive interruptions to reperfusion, leading to attenuated ischemia/reperfusion damage after transient focal cerebral ischemia in rats.

METHODS

Rats were subjected to 90 minutes of middle cerebral artery occlusion. During ischemia, animals received air, iNBO (4 cycles of 3 minutes of NBO and 2 minutes of air), continuous NBO (cNBO; 75 minutes), short NBO (18 minutes), or a combination of iNBO and cNBO. Infarct volume and neurological score were evaluated at 24 and 72 hours after ischemia. Production of superoxide was assessed by the hydroethidine method, and the expression of Akt and phosphorylated Akt was examined by Western blot.

RESULTS

iNBO and cNBO had similar effects in reducing infarct volume and neurological deficit at 24 hours after ischemia, whereas at 72 hours the neuroprotection exerted by iNBO was greater than cNBO. Combining iNBO and cNBO produced no greater protection, and short NBO failed to provide neuroprotection. Both iNBO and cNBO attenuated superoxide production. Importantly, prolonged activation of Akt was observed in the iNBO group, and neuroprotection by iNBO was partly eliminated by inhibition of Akt activation.

CONCLUSIONS

iNBO may represent a novel form of postconditioning, and this neuroprotection is likely mediated by attenuating superoxide generation and activation of the Akt pathway.

Vitamin E renders protection to PC12 cells against oxidative damage and apoptosis induced by single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are potential candidates in many biomedical applications. However, many reports demonstrated its potential toxicity to human and other biological systems. Our study has demonstrated that SWCNTs can induce apoptosis and oxidative damage on PC12 cells, an in vitro model of neuronal cells. In the present study, we for the first time investigated the neuroprotective effects of vitamin E (VE) on SWCNT-induced neurotoxicity in cultured PC12 cells. Vitamin E (0.01-2mM) increased PC12 cells viability and significantly attenuated SWCNTs-induced apoptotic cell death in a time and dose-dependent manner, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) release and morphological observation. The presence of VE inhibited the formation of reactive oxygen species (ROS), decreased the level of lipid peroxide, elevated the level of glutathione (GSH) and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). Additionally, VE blocked the reduction in the mitochondrial membrane potential and the activation of caspase-3. VE prevented the down-regulation of Bcl-2 expression and up-regulation of Bax expression induced by SWCNTs in PC12 cells. In summary, VE might protect PC12 cells from the injury induced by SWCNTs through the down-regulation of oxidative stress and prevention of mitochondrial-mediated apoptosis.

Increases of antioxidants are related to more delayed neuronal death in the hippocampal CA1 region of the young gerbil induced by transient cerebral ischemia

In age-related studies, young animals are resistant to ischemic damage. In present study, we investigated the neuronal death of pyramidal neurons and compared changes in the immunoreactivities and levels of antioxidants, Cu/Zn-SOD (SOD1), Mn-SOD (SOD2), catalase (CAT) and glutathione peroxidase (Gpx), in the hippocampal CA1 region between adult and young gerbils after 5 min of transient cerebral ischemia. In the adult ischemia-group, only a few (12%) of CA1 pyramidal neurons survived 4 days after ischemia-reperfusion (I-R); however, in the 4 days after I-R the young group, most of CA1 pyramidal neurons survived. Seven days after I-R, many (about 39%) of CA1 pyramidal neurons survived, thereafter, the neuronal death in the CA1 pyramidal neurons was not significantly changed. The immunoreactivities of all the antioxidants were well detected in CA1 pyramidal neurons in the adult sham-groups; in the young sham-groups, they were distinctively low compared to those in the adult sham-group. Four days after I-R in the adult group, all the immunoreactivities in the pyramidal neurons were dramatically deceased. However, at this time after I-R in the young groups, they were dramatically increased in the pyramidal neurons. From 7 days after I-R, all the immunoreactivities in the pyramidal neurons in the young ischemia-groups were distinctively decreased. In addition, the levels of all the antioxidants in the CA1 region of the young sham-groups were lower than those in the adult sham-group. Four days after I-R in the adult groups, the levels of all the antioxidants were dramatically deceased; however, at this time in the young ischemia-groups, they were distinctively increased in the CA1 region. Seven days after I-R, all the antioxidants levels in the CA1 region were distinctively decreased. In brief, we conclude that the increased antioxidants levels were related to a less and much delayed neuronal death in the CA1 pyramidal neurons in the young group following I-R injury.

The neuroprotection of oxymatrine in cerebral ischemia/reperfusion is related to nuclear factor erythroid 2-related factor 2 (nrf2)-mediated antioxidant response: role of nrf2 and hemeoxygenase-1 expression

Cerebral ischemia-reperfusion (CI/R) injury remains a major medical problem due to the lack of effective therapies. Previous studies have shown that increasing the activity of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and gene targets in cell culture and stroke animal models is highly neuroprotective. Oxymatrine is the major quinolizidine alkaloid extracted from the root of Sophora flavescens AIT, and has been proved to be protective after ischemia in recent studies. The present study was designed to investigate the potential effect of oxymatrine in ischemia-reperfusion injury in rat's brain and to explore the possible role of oxymatrine in Nrf2 pathway. The results indicated that the ischemic infarct and edema were significantly reduced in rats that received oxymatrine, with a corresponding improvement in neurological function after CI/R. In immunohistochemistry and Western blotting analyses, Nrf2 and hemeoxygenase-1 (HO-1) were up-regulated in ischemic cortex, beginning at 6 h, peaking at 48 h and declining at 72 h after CI/R. Intraperitoneal injection of oxymatrine inhibited the production of lipid peroxidation and increased the activities of Nrf2 and HO-1 in rats brain after CI/R. Taken together, these results suggest that oxymatrine administered systemically protected brain against focal ischemia-reperfusion damage at the early stage of stroke, and that activating Nrf2/HO-1 pathway may contribute to the neuroprotective action of oxymatrine in rat focal brain ischemia-reperfusion model. Thus, treatment of stroke with oxymatrine may prevent severe consequences after brain attack.

Iron mediates endothelial cell damage and blood-brain barrier opening in the hippocampus after transient forebrain ischemia in rats

Blood cells are transported into the brain and are thought to participate in neurodegenerative processes following hypoxic ischemic injury. We examined the possibility that transient forebrain ischemia (TFI) causes the blood-brain barrier (BBB) to become permeable to blood cells, possibly via dysfunction and degeneration of endothelial cells in rats. Extravasation of Evans blue and immunoglobulin G (IgG) was observed in the hippocampal CA1-2 areas within 8 h after TFI, and peaked at 48 h. This extravasation was accompanied by loss of tight junction proteins, occludin, and zonula occludens-1, and degeneration of endothelial cells in the CA1-2 areas. Iron overload and mitochondrial free radical production were evident in the microvessel endothelium of the hippocampus before endothelial cell damage occurred. Administration of deferoxamine (DFO), an iron chelator, or Neu2000, an antioxidant, blocked free radical production and endothelial cell degeneration. Our findings suggest that iron overload and iron-mediated free radical production cause loss of tight junction proteins and degeneration of endothelial cells, opening of the BBB after TFI.

Neuroprotective effect of ginkgolide K against acute ischemic stroke on middle cerebral ischemia occlusion in rats

Ginkgolide K, a natural platelet-activating factor receptor antagonist, was isolated from the leaves of Ginkgo biloba. However, little is known about its neuroprotective effect in ischemia-reperfusion (I/R)-induced cerebral injury. Hence, the present study was carried out to investigate the effect of ginkgolide K on neuroprotection and the potential mechanisms in the rat I/R model induced by middle cerebral artery occlusion (MCAO). The rats were pretreated with ginkgolide K 2, 4 and 8 mg/kg (i.v.) once a day for 5 days before MCAO. Neurological deficit score (NDS), brain water content, 2,3,5-triphenyltetrazolium chloride (TTC) staining and pathology of brain tissue, as well as indexes of oxidative stress [superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide (NO) and nitric oxide synthase (NOS)] were measured at 24 h after ischemia. The results indicated that pretreatment with ginkgolide K significantly diminished the volume of infarction and brain water content, and improved NDS. Moreover, ginkgolide K markedly reversed the level of MDA, NO, NOS and SOD to their normal state in serum or cerebral ischemic section. In addition, hematoxylin and eosin staining showed the neuronal injury was significantly improved after being pretreated with ginkgolide K. These findings demonstrate that ginkgolide K exhibits neuroprotective properties through its antioxidative action in MCAO rats.

Phosphatidylinositol-3-kinase gamma plays a central role in blood-brain barrier dysfunction in acute experimental stroke

BACKGROUND AND PURPOSE

Phosphoinositide 3-kinase (PI3K)-γ is linked to inflammation and oxidative stress. This study was conducted to investigate the role of the PI3Kγ in the blood-brain barrier dysfunction and brain damage induced by focal cerebral ischemia/reperfusion.

METHODS

Wild-type and PI3Kγ knockout mice were subjected to middle cerebral artery occlusion (60 minutes) followed by reperfusion. Evans blue leakage, brain edema, infarct volumes, and neurological deficits were examined. Oxidative stress, neutrophil infiltration, and matrix metallopeptidase-9 were assessed. Activation of nuclear factor-κB and expression of proinflammatory and pro-oxidative genes were studied.

RESULTS

PI3Kγ deficiency significantly reduced blood-brain barrier permeability and brain edema formation, which were time-dependently correlated with preventing the degradation of the tight junction protein, claudin-5, and the basal lamina protein, collagen IV, and the phosphorylation of myosin light chain in brain microvessels. PI3Kγ deficiency suppressed ischemia/reperfusion-induced nuclear factor-κB p65 (Ser536) phosphorylation and the expression of the pro-oxidant enzyme NADPH oxidase (Nox1, Nox2, and Nox4) and proinflammatory adhesion molecules (E- and P-selectin, intercellular adhesion molecule-1) at different time points. These molecular changes were associated with significant inhibition of oxidative stress (superoxide production and malondialdehyde content), neutrophil infiltration, and matrix metallopeptidase-9 expression/activity in PI3Kγ knockout mice. Eventually, PI3Kγ deficiency significantly reduced infarct volumes and neurological scores at 24 hours after ischemia/reperfusion.

CONCLUSIONS

Our results provide the first direct demonstration that PI3Kγ plays a significant role in ischemia/reperfusion-induced blood-brain barrier disruption and brain damage. Future studies need to explore PI3Kγ as a potential target for stroke therapy.

Moderately delayed post-insult treatment with normobaric hyperoxia reduces excitotoxin-induced neuronal degeneration but increases ischemia-induced brain damage

Background

The use and benefits of normobaric oxygen (NBO) in patients suffering acute ischemic stroke is still controversial.

Results

Here we show for the first time to the best of our knowledge that NBO reduces both NMDA-induced calcium influxes in vitro and NMDA-induced neuronal degeneration in vivo, but increases oxygen and glucose deprivation-induced cell injury in vitro and ischemia-induced brain damage produced by middle cerebral artery occlusion in vivo.

Conclusions

Taken together, these results indicate that NBO reduces excitotoxin-induced calcium influx and subsequent neuronal degeneration but favors ischemia-induced brain damage and neuronal death. These findings highlight the complexity of the mechanisms involved by the use of NBO in patients suffering acute ischemic stroke.

Isoflurane enhanced hemorrhagic transformation by impairing antioxidant enzymes in hyperglycemic rats with middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Because the potential neuroprotective effect of isoflurane is controversial, we attempted to study whether isoflurane after treatment provides neuroprotection in a rat model of hyperglycemia-induced ischemic hemorrhagic transformation.

METHODS

Rats received an injection of 50% dextrose (6 mL/kg intraperitoneally) and had a middle cerebral artery occlusion 30 minutes later. Four groups were included: sham-operated, ischemia/reperfusion, isoflurane treatment, and vehicle groups. In the treatment group, after 2 hours of ischemia, 2% isoflurane was administered at the onset of reperfusion. We measured the level of blood glucose at 0, 2.5, 4.5, and 6.5 hours after dextrose injection. Infarct and hemorrhagic volumes, neurological scores, oxidative stress (malondialdehyde, 4-hydroxy-2-nonenal, and nitrotyrosine) and the activities of superoxide dismutase and catalase were measured at 24 hours after ischemia.

RESULTS

Isoflurane had no effects on blood glucose, it failed to reduce infarct, hemorrhage volume, and brain edema, and it enhanced neurobehavioral deficits when compared with the ischemia/reperfusion group at 24 hours after middle cerebral artery occlusion. On the contrary, isoflurane exacerbated these parameters compared with the vehicle group. In addition, it increased the expressions of malondialdehyde, 4-hydroxy-2-nonenal, and nitrotyrosine, and it decreased the activities of superoxide dismutase and catalase compared to the vehicle group.

CONCLUSIONS

Isoflurane after treatment worsened physiological and neurological outcomes in this ischemia hyperglycemia-induced hemorrhagic transformation possibly by impairing the antioxidant defense system.

Maternal docosahexaenoic acid-enriched diet prevents neonatal brain injury

Hypoxic-ischemic encephalopathy due to neonatal asphyxia is one of the most important causes of delayed neurological development. Prolonged neuronal apoptosis plays an important role in the processes contributing to neuronal degeneration. Docosahexaenoic acid (DHA), a major component of brain membrane phospholipids, prevents neuronal cell apoptosis and plays an important role as an anti-oxidant agent. We investigated the neuroprotective and anti-oxidant effects of maternal DHA supplementation during pregnancy in a model of neonatal hypoxic-ischemic encephalopathy. Pregnant rats were randomly assigned to two experimental groups: a control group or a DHA-enriched diet group. Hypoxic-ischemic encephalopathy was produced by left common carotid artery occlusion and exposure to 8% oxygen for 1.5 h. TUNEL assay, immunohistochemistry for caspase-3 and 8-hydroxy-deoxyguanosine (8-OHdG), and Western blot for caspase-3 were performed at postnatal days 8, 10 and 14. Fatty acid composition of brain was estimated on postnatal day 7. Maternal diet clearly influenced brain fatty acid composition in pups. Numbers of apoptotic neuronal cells and 8-OHdG immunoreactivity were significantly decreased in the DHA-enriched group. Our findings indicate that maternal DHA-enriched diet during pregnancy provides neuroprotection by inhibiting oxidative stress and apoptotic neuronal death. Dietary supplementation of DHA during pregnancy may thus be beneficial in preventing neonatal brain injury.

Evaluation of Antioxidant and Cerebroprotective Effect of Medicago sativa Linn. against Ischemia and Reperfusion Insult

Antioxidants have been the focus of studies for developing neuroprotective agents to be used in the therapy for stroke, which is an acute and progressive neurodegenerative disorder. Medicago sativa (MS) has a long tradition of use as ayurvedic and homoeopathic medicine in central nervous system disorders. The plant has been reported to have antioxidant, anti-inflammatory and antidiabetic effects. Therefore, the present study was designed to investigate the neuroprotective effect of methanol extract of MS on ischemia and reperfusion-induced cerebral injury in mice. Bilateral carotid artery occlusion (BCAO) for 15 min followed by 24-h reperfusion, resulted in significant elevation in infarct size, xanthine oxidase (XO) activity, superoxide anion (O^•−₂) production and thiobarbituric acid-reactive substance (TBARS) levels, and significant depletion in endogenous antioxidant [reduced glutathione (GSH), superoxide dismutase (SOD) and total tissue sulfhydryl (T-SH) groups] systems in mice brain. Further, BCAO led to impairment in short-term memory and motor coordination. Pre-treatment with MS (100 or 200 mg kg⁻¹, p.o.) markedly reduced cerebral infarct size, XO, O^•−₂ and TBARS levels, significantly restored GSH, SOD and T-SH levels and attenuated impairment in short-term memory and motor coordination. In addition, MS directly scavenged free radicals generated against a stable radical 1,1-diphenyl-2-picrylhydrazyl and O^•−₂ generated in phenazine methosulphate-nicotinamide adenine dinucleotide systems, and also inhibited XD/XO conversion and resultant O^•−₂ production. The data from this study suggest that treatment with MS enhances the antioxidant defense against BCAO-induced global cerebral ischemia and exhibits neuroprotective activity.

Normoxic versus hyperoxic resuscitation in pediatric asphyxial cardiac arrest: effects on oxidative stress

OBJECTIVE

To determine the effects of normoxic vs. hyperoxic resuscitation on oxidative stress in a model of pediatric asphyxial cardiac arrest.

DESIGN

Prospective, interventional study.

SETTING

University research laboratory.

SUBJECTS

Postnatal day 16-18 rats (n = 5 per group).

INTERVENTIONS

Rats underwent asphyxial cardiac arrest for 9 min. Rats were randomized to receive 100% oxygen, room air, or 100% oxygen with polynitroxyl albumin (10 mL·kg⁻¹ intravenously, 0 and 30 min after resuscitation) for 1 hr from the start of cardiopulmonary resuscitation. Shams recovered in 100% oxygen or room air after surgery.

MEASUREMENTS AND MAIN RESULTS

Physiological variables were recorded at baseline to 1 hr after resuscitation. At 6 hrs after asphyxial cardiac arrest, levels of reduced glutathione and protein-thiols (fluorescent assay), activities of total superoxide dismutase and mitochondrial manganese superoxide dismutase (cytochrome c reduction method), manganese superoxide dismutase expression (Western blot), and lipid peroxidation (4-hydroxynonenal Michael adducts) were evaluated in brain tissue homogenates. Hippocampal 3-nitrotyrosine levels were determined by immunohistochemistry 72 hrs after asphyxial cardiac arrest. Survival did not differ among groups. At 1 hr after resuscitation, Pao2, pH, and mean arterial pressure were decreased in room air vs. 100% oxygen rats (59 ± 3 vs. 465 ± 46 mm Hg, 7.36 ± 0.05 vs. 7.42 ± 0.03, 35 ± 4 vs. 45 ± 5 mm Hg; p < .05). Rats resuscitated with 100% oxygen had decreased hippocampal reduced glutathione levels vs. sham (15.3 ± 0.4 vs. 20.9 ± 4.1 nmol·mg protein⁻¹; p < .01). Hippocampal manganese superoxide dismutase activity was significantly increased in 100% oxygen rats vs. sham (14 ± 2.4 vs. 9.5 ± 1.6 units·mg protein⁻¹, p < .01), with no difference in protein expression of manganese superoxide dismutase. Room air and 100% oxygen plus polynitroxyl albumin groups had hippocampal reduced glutathione and manganese superoxide dismutase activity levels comparable with sham. Protein thiol levels were unchanged across groups. Compared with all other groups, rats receiving 100% oxygen had increased immunopositivity for 3-nitrotyrosine in the hippocampus and increased lipid peroxidation in the cortex.

CONCLUSIONS

Resuscitation with 100% oxygen leads to increased oxidative stress in a model that mimics pediatric cardiac arrest. This may be prevented by using room air or giving an antioxidant with 100% oxygen resuscitation.

An antioxidant phytotherapy to rescue neuronal oxidative stress

Oxidative stress is involved in the pathogenesis of ischemic neuronal injury. A Chinese herbal formula composed of Poria cocos (Chinese name: Fu Ling), Atractylodes macrocephala (Chinese name: Bai Zhu) and Angelica sinensis (Chinese names: Danggui, Dong quai, Donggui; Korean name: Danggwi) (FBD), has been proved to be beneficial in the treatment of cerebral ischemia/reperfusion (I/R).This study was carried out to evaluate the protective effect of FBD against neuronal oxidative stress in vivo and in vitro. Rat I/R were established by middle cerebral artery occlusion (MCAO) for 1 h, followed by 24 h reperfusion. MCAO led to significant depletion in superoxide dismutase and glutathione and rise in lipid peroxidation (LPO) and nitric oxide in brain. The neurological deficit and brain infarction were also significantly elevated by MCAO as compared with sham-operated group. All the brain oxidative stress and damage were significantly attenuated by 7 days pretreatment with the aqueous extract of FBD (250 mg kg(-1), p.o.). Moreover, cerebrospinal fluid sampled from FBD-pretreated rats protected PC12 cells against oxidative insult induced by 0.2 mM hydrogen peroxide, in a concentration and time-dependent manner (IC(50) 10.6%, ET(50) 1.2 h). However, aqueous extract of FBD just slightly scavenged superoxide anion radical generated in xanthine-xanthine oxidase system (IC(50) 2.4 mg ml(-1)) and hydroxyl radical generated in Fenton reaction system (IC(50) 3.6 mg ml(-1)). In conclusion, FBD was a distinct antioxidant phytotherapy to rescue neuronal oxidative stress, through blocking LPO, restoring endogenous antioxidant system, but not scavenging free radicals.

Apoptotic mechanisms for neuronal cells in early brain injury after subarachnoid hemorrhage

OBJECTS

The major causes of death and disability in subarachnoid hemorrhage (SAH) may be early brain injury (EBI) and cerebral vasospasm. Although cerebral vasospasm has been studied and treated by a lot of drugs, the outcome is not improved even if vasospasm is reversed. Based on these data, EBI is considered a primary target for future research, and apoptosis may be involved in EBI after experimental SAH.

METHODS

We reviewed the published literature about the relationship between SAH induced EBI and apoptosis in PubMed.

RESULT

Most available information can be obtained from the endovascular filament perforation animal model. After onset of SAH, intracranial pressure is increased and then cerebral blood flow is reduced. Many factors are involved in the mechanism of apoptotic cell death in EBI after SAH. In the neuronal cells, both intrinsic and extrinsic pathways of apoptosis can occur. Some antiapoptotic drugs were studied and demonstrated a protective effect against EBI after SAH. However, apoptosis in EBI after SAH has been little studied and further studies will provide us more beneficial findings.

CONCLUSIONS

The study of apoptosis in EBI after experimental SAH may give us new therapies for SAH.

Neuroglobin protects neurons against oxidative stress in global ischemia

Neuroglobin (Ngb) is a recently discovered globin that affords protection against hypoxic/ischemic-induced cell injury in brain. Hypoxic/ischemic injury is associated with accumulation of reactive oxygen species (ROS) and/or reactive nitrogen species (RNS). In previous studies, we found that Ngb has antioxidative properties, and protects PC-12 cells against hypoxia- and β-amyloid-induced cell death. To further delineate the potential role of Ngb in protection against cerebral ischemia-reperfusion injury in vivo, we developed a transgenic mouse line that overexpresses Ngb. Hippocampal ischemia-reperfusion injury was induced by a 10-minute bilateral occlusion of the common carotid arteries, and the animal brains were assessed 3 days later. CA1 neural injury was determined by cresyl violet staining. Lipid peroxidation was assessed using a malonyldialdehyde assay kit, whereas ROS/RNS accumulation was determined by Het staining in the CA1 hippocampal region. Hippocampal Ngb mRNA and protein expressions were assessed by reverse transcriptase-PCR and western blotting, respectively. Neuroglobin was successfully overexpressed in the hippocampus of Ngb transgenic mice. After ischemia-reperfusion, CA1 ROS/RNS production and lipid peroxidation were markedly decreased in Ngb transgenic mice compared with wild-type mice. Furthermore, CA1 neuronal injury was also markedly reduced. Thus, Ngb may confer protection against ischemia-reperfusion injury in the brain through its intrinsic antioxidant properties.

Neuroprotective effect of astaxanthin on H(2)O(2)-induced neurotoxicity in vitro and on focal cerebral ischemia in vivo

Astaxanthin (AST) is a powerful antioxidant that occurs naturally in a wide variety of living organisms. Much experimental evidence has proved that AST has the function of eliminating oxygen free radicals and can protect organisms from oxidative damage. The present study was carried out to further investigate the neuroprotective effect of AST on oxidative stress induced toxicity in primary culture of cortical neurons and on focal cerebral ischemia-reperfusion induced brain damage in rats. AST, over a concentration range of 250-1000nM, attenuated 50μM H(2)O(2)-induced cell viability loss. 500nM AST pretreatment significantly inhibited H(2)O(2)-induced apoptosis measured by Hoechst 33342 staining and restored the mitochondrial membrane potential (MMP) measured by a fluorescent dye, Rhodamine 123. In vivo, AST prevented cerebral ischemic injury induced by 2h middle cerebral artery occlusion (MCAO) and 24h reperfusion in rats. Pretreatment of AST intragastrically twice at 5h and 1h prior to ischemia dramatically diminished infarct volume and improved neurological deficit in a dose-dependent manner. Nissl staining showed that the neuronal injury was significantly improved by pretreatment of AST at 80mg/kg. Taken together, these results suggest that pretreatment with AST exhibits noticeable neuroprotection against brain damage induced by ischemia-reperfusion and the antioxidant activity of AST maybe partly responsible for it.

Inhibition of TRPC6 degradation suppresses ischemic brain damage in rats

Brain injury after focal cerebral ischemia, the most common cause of stroke, develops from a series of pathological processes, including excitotoxicity, inflammation, and apoptosis. While NMDA receptors have been implicated in excitotoxicity, attempts to prevent ischemic brain damage by blocking NMDA receptors have been disappointing. Disruption of neuroprotective pathways may be another avenue responsible for ischemic damage, and thus preservation of neuronal survival may be important for prevention of ischemic brain injury. Here, we report that suppression of proteolytic degradation of transient receptor potential canonical 6 (TRPC6) prevented ischemic neuronal cell death in a rat model of stroke. The TRPC6 protein level in neurons was greatly reduced in ischemia via NMDA receptor-dependent calpain proteolysis of the N-terminal domain of TRPC6 at Lys¹⁶. This downregulation was specific for TRPC6 and preceded neuronal death. In a rat model of ischemia, activating TRPC6 prevented neuronal death, while blocking TRPC6 increased sensitivity to ischemia. A fusion peptide derived from the calpain cleavage site in TRPC6 inhibited degradation of TRPC6, reduced infarct size, and improved behavioral performance measures via the cAMP response element-binding protein (CREB) signaling pathway. Thus, TRPC6 proteolysis contributed to ischemic neuronal cell death, and suppression of its degradation preserved neuronal survival and prevented ischemic brain damage.

Neuroprotective effect of Artemisia absinthium L. on focal ischemia and reperfusion-induced cerebral injury

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia absinthium L. has long been used as traditional herbal medicine in China, Europe and Pakistan for the treatment of gastric pain, cardiac stimulation, to improve memory and for the restoration of declining mental function.

AIM OF THE STUDY

The present study was designed to investigate the potential protective effects of Artemisia absinthium on cerebral oxidative stress and damage as well as behavioral disturbances induced by cerebral ischemia and reperfusion injury in rats.

MATERIALS AND METHODS

Focal ischemia and reperfusion were induced by middle cerebral artery occlusion (MCAO) for 90 min, followed by 24 h reperfusion. MCAO led to significant rise in infarct size and lipid peroxidation, and depletion in glutathione content, superoxide dismutase and catalase activity in brain. Further, behavioral deficits like motor incoordination and impairment of short-term memory were also significantly impaired by MCAO as compared with sham group.

RESULTS

The brain oxidative stress and damage, and behavioral deficits were significantly attenuated by pre-treatment with the methanol extract of Artemisia absinthium (100 mg/kg and 200 mg/kg, p.o.).

CONCLUSION

These findings suggested that Artemisia absinthium is neuroprotective and may prove to be useful adjunct in the treatment of stroke.

Heat acclimation provides sustained improvement in functional recovery and attenuates apoptosis after traumatic brain injury

Heat acclimation (HA) offers functional neuroprotection in mice after traumatic brain injury (TBI). This study further characterizes endogenous neuroprotection acquired by HA (34+/-1 degrees C, 30 d) after TBI. We establish here the ability of HA to induce sustained functional benefits and to reduce activation of apoptotic pathways. Neurobehavioral recovery, assessed by the Neurological Severity Score, was greater in HA mice up to 8 days after injury as compared with normothermic controls (P<0.05) and lesion volume was also smaller in the HA group (P<0.05). Reduced apoptotic cell death in HA mice was confirmed using caspase-3 activity measurements and immunohistochemistry. To investigate the underlying molecular pathways, expression levels of intrinsic apoptotic pathway-related proteins were examined. HA mice displayed higher mitochondrial levels of antiapoptotic Bcl-xL, accompanied by lower proapoptotic Bad levels and decreased cytochrome c release, suggesting a higher apoptotic threshold. Taken together with our previous reports, indicating increased Akt phosphorylation and antioxidative capacity, alongside with reduced tumor necrosis alpha levels after TBI in HA animals, the current results support the involvement of an antiapoptotic effect in HA-induced neuroprotection. Current results warrant further study as TBI-induced apoptosis may persist over weeks after injury, possibly providing a target for belated therapeutic intervention.

Reperfusion and neurovascular dysfunction in stroke: from basic mechanisms to potential strategies for neuroprotection

Effective stroke therapies require recanalization of occluded cerebral blood vessels. However, reperfusion can cause neurovascular injury, leading to cerebral edema, brain hemorrhage, and neuronal death by apoptosis/necrosis. These complications, which result from excess production of reactive oxygen species in mitochondria, significantly limit the benefits of stroke therapies. We have developed a focal stroke model using mice deficient in mitochondrial manganese-superoxide dismutase (SOD2-/+) to investigate neurovascular endothelial damage that occurs during reperfusion. Following focal stroke and reperfusion, SOD2-/+ mice had delayed blood-brain barrier breakdown, associated with activation of matrix metalloproteinase and high brain hemorrhage rates, whereas a decrease in apoptosis and hemorrhage was observed in SOD2 overexpressors. Thus, induction and activation of SOD2 is a novel strategy for neurovascular protection after ischemia/reperfusion. Our recent study identified the signal transducer and activator of transcription 3 (STAT3) as a transcription factor of the mouse SOD2 gene. During reperfusion, activation of STAT3 and its recruitment into the SOD2 gene were blocked, resulting in increased oxidative stress and neuronal apoptosis. In contrast, pharmacological activation of STAT3 induced SOD2 expression, which limits ischemic neuronal death. Our studies point to antioxidant-based neurovascular protective strategies as potential treatments to expand the therapeutic window of currently approved therapies.

Acetaminophen reduces mitochondrial dysfunction during early cerebral postischemic reperfusion in rats

Acetaminophen, a popular analgesic and antipyretic, has been found to be effective against neuronal cell death in in vivo and in vitro models of neurological disorders. Acute neuronal death has been attributed to loss of mitochondrial permeability transition coupled with mitochondrial dysfunction. The potential impact of acetaminophen on acute injury from cerebral ischemia-reperfusion has not been studied. We investigated the effects of acetaminophen on cerebral ischemia-reperfusion-induced injury using a transient global forebrain ischemia model. Male Sprague-Dawley rats received 15mg/kg of acetaminophen intravenously during ischemia induced by hypovolemic hypotension and bilateral common carotid arterial occlusion, which was followed by reperfusion. Acetaminophen reduced tissue damage, degree of mitochondrial swelling, and loss of mitochondrial membrane potential. Acetaminophen maintained mitochondrial cytochrome c content and reduced activation of caspase-9 and incidence of apoptosis. Our data show that acetaminophen reduces apoptosis via a mitochondrial-mediated mechanism in an in vivo model of cerebral ischemia-reperfusion. These findings suggest a novel role for acetaminophen as a potential stroke therapeutic.

Catalpol inhibits apoptosis in hydrogen peroxide-induced endothelium by activating the PI3K/Akt signaling pathway and modulating expression of Bcl-2 and Bax

Catalpol, an iridoid glucoside found in the root of Rehmannia glutinosa Libosch, has been demonstrated to reduce apoptosis in neuronal cell lines. Recent data suggests that catalpol also exerts anti-apoptotic effects on other cell types. The aim of the present study was to investigate whether catalpol protects against hydrogen peroxide (H(2)O(2)) induced apoptosis in human umbilical vein endothelial cells (HUVECs). Apoptotic cells were detected by terminal deoxyribonucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling, Annexin V-fluorescein isothiocyanate binding assay and by assessment of caspase-3 activity. The level of intracellular reactive oxygen species was quantified by 2', 7'-dichlorofluorescein diacetate assay. Expression of Akt, Bad, Bcl-2 and Bax mRNA and protein was determined by real-time semiquantitative reverse transcription-polymerase chain reaction and Western blotting. Apoptosis in HUVECs was associated with increased Bax, decreased Bcl-2 activity and inactivated phosphorylation of Akt and Bad after 24h of H(2)O(2) exposure. Pre-treatment of HUVECs with catalpol significantly reduced H(2)O(2)-induced intracellular reactive oxygen species release. Catalpol not only increased the expression of Bcl-2, while decreasing Bax expression, but also induced Akt activation and Bad phosphorylation, and ultimately reduced H(2)O(2)-induced apoptosis. The protective effects of catalpol were partially inhibited by the phosphatidylinositol 3-kinase (PI3K) antagonist wortmannin or 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002). Taken together, these results suggest that pre-treatment of HUVECs with catalpol can block H(2)O(2)-induced apoptosis, and that the underlying mechanism involves reactive oxygen species scavenging, activation of the PI3K/Akt-Bad signaling pathway and increased Bcl-2 and decreased Bax expression.

Oxidative Stress and Apoptosis of Human Brain Microvascular Endothelial Cells Induced by Free Fatty Acids

Damage to endothelial cells is a key event in the pathogenesis of atherosclerosis and vascular disease. This study aimed to determine whether free fatty acids (FFAs) induced oxidative stress and apoptosis in human brain microvascular endothelial cells (HBMVECs) in vitro and, if so, which signalling pathway mediated these effects. After culture in different concentrations of FFAs for 24-72 h, cell viability/proliferation was determined using a cell counting kit, apoptosis was detected by measuring caspase-3 activity and by using annexin V-conjugated fluorescein isothiocyanate/propidium iodide staining, and oxidative stress was evaluated by measuring the levels of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). The HBMVECs exposed to FFAs showed significantly decreased cell proliferation, increased apoptosis and ROS levels, and decreased MMP. In conclusion, the results showed that high levels of FFAs induced oxidative stress, which damaged HBMVECs and resulted in apoptosis.

Protective effect of tetrahydroxystilbene glucoside on cardiotoxicity induced by doxorubicin in vitro and in vivo

AIM

To test the effect of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside (THSG) on doxorubicin (DOX)-induced cardiotoxicity.

METHODS

We used neonate rat cardiomyocytes and an acute mouse model of DOX-induced cardiotoxicity to examine the protective effect of THSG.

RESULTS

In the mouse model, administration of THSG significantly reduced DOX-induced cardiotoxicity, including animal mortality, histopathological changes, and levels of serum creatine kinase (CK) and lactate dehydrogenase (LDH). Moreover, THSG was able to attenuate the increased malondialdehyde (MDA) and decreased reduced glutathione (GSH) caused by DOX. In in vitro studies, THSG 10-300 micromol/L ameliorated DOX-induced cardiomyocyte apoptosis in a concentration-dependent manner. Further studies showed that THSG inhibited reactive oxygen species (ROS) generation and prevented DOX-induced loss of mitochondrial membrane potential, caspase-3 activation and upregulation of Bax protein expression. We observed a protective response against damage after DOX treatment. The level of Bcl-2 protein was increased. Additionally, THSG inhibited a DOX-induced [Ca(2+)] increase.

CONCLUSION

These results showed that THSG protected against DOX-induced cardiotoxicity by decreasing ROS generation and intracellular [Ca(2+)] and by inhibiting apoptotic signaling pathways.

The protective effect of early hypothermia on PTEN phosphorylation correlates with free radical inhibition in rat stroke

We recently showed that intraischemic moderate hypothermia (30 degrees C) reduces ischemic damage through the Akt pathway after permanent distal middle cerebral artery occlusion in rats. The only Akt pathway component preserved by hypothermia is phosphorylated phosphatase and tensin homolog deleted on chromosome 10 (p-PTEN), which suggests that p-PTEN may have a central role in neuroprotection. Reactive oxygen species (ROS) are critically involved in mediating ischemic damage after stroke by interacting with signaling molecules, including Akt, PTEN, and delta-protein kinase C (PKC). We investigated the protective mechanisms of moderate hypothermia on these signaling proteins after transient focal ischemia in rats. Early moderate hypothermia (3 h) was administered 15 mins before reperfusion, and delayed moderate hypothermia (3 h) was applied 15 mins after reperfusion. Our results indicate that early hypothermia reduced infarction, whereas delayed hypothermia did not. However, both early and delayed hypothermia maintained levels of Mn-SOD (superoxide dismutase) and phosphorylated Akt and blocked delta-PKC cleavage, suggesting that these factors may not be critical to the protection of hypothermia. Nevertheless, early hypothermia preserved p-PTEN levels after reperfusion, whereas delayed hypothermia did not. Furthermore, ROS inhibition maintained levels of p-PTEN after stroke. Together, these findings suggest that phosphorylation levels of PTEN are closely associated with the protective effect of early hypothermia against stroke.

Protection by tetrahydroxystilbene glucoside against cerebral ischemia: involvement of JNK, SIRT1, and NF-kappaB pathways and inhibition of intracellular ROS/RNS generation

Many natural polyphenolic compounds have been shown to attenuate reactive oxygen/nitrogen species (ROS/RNS) formation and protect against ischemia/reperfusion injury both in vitro and in vivo. 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside (TSG), an active component of the rhizome extract from Polygonum multiflorum, exhibits antioxidative and anti-inflammatory effects. Here, we used an in vitro ischemic model of oxygen-glucose deprivation followed by reperfusion (OGD-R) and an in vivo ischemic model of middle cerebral artery occlusion (MCAO) to investigate the neuroprotective effects of TSG on ischemia/reperfusion brain injury and the related mechanisms. We demonstrated that OGD-R-induced neuronal injury, intracellular ROS generation, and mitochondrial membrane potential dissipation were reversed by TSG. The elevation of H2O2-induced [Ca2+]i was also attenuated by TSG. Inhibition of the c-Jun N-terminal kinase (JNK) and Bcl-2 family-related apoptotic signaling pathway was involved in the neuroprotection afforded by TSG. Meanwhile, TSG inhibited iNOS mRNA expression induced by OGD-R, which may be mediated by the activation of SIRT1 and inhibition of NF-kappaB activation. In vivo studies further demonstrated that TSG significantly reduced the brain infarct volume and the number of positive cells by TUNEL staining in the cerebral cortex compared to the MCAO group. Our study indicates that TSG protects against cerebral ischemia/reperfusion injury through multifunctional cytoprotective pathways.

An analysis of methylenetetrahydrofolate reductase and glutathione S-transferase omega-1 genes as modifiers of the cerebral response to ischemia

Background

Cerebral ischemia involves a series of reactions which ultimately influence the final volume of a brain infarction. We hypothesize that polymorphisms in genes encoding proteins involved in these reactions could act as modifiers of the cerebral response to ischemia and impact the resultant stroke volume. The final volume of a cerebral infarct is important as it correlates with the morbidity and mortality associated with non-lacunar ischemic strokes.

Methods

The proteins encoded by the methylenetetrahydrofolate reductase (MTHFR) and glutathione S-transferase omega-1 (GSTO-1) genes are, through oxidative mechanisms, key participants in the cerebral response to ischemia. On the basis of these biological activities, they were selected as candidate genes for further investigation. We analyzed the C677T polymorphism in the MTHFR gene and the C419A polymorphism in the GSTO-1 gene in 128 patients with non-lacunar ischemic strokes.

Results

We found no significant association of either the MTHFR (p = 0.72) or GSTO-1 (p = 0.58) polymorphisms with cerebral infarct volume.

Conclusion

Our study shows no major gene effect of either the MTHFR or GSTO-1 genes as a modifier of ischemic stroke volume. However, given the relatively small sample size, a minor gene effect is not excluded by this investigation.

Doxycycline treatment decreases morbidity and mortality of murine neurocysticercosis: evidence for reduction of apoptosis and matrix metalloproteinase activity

Murine neurocysticercosis is a parasitic infection transmitted through the direct ingestion of Taenia solium eggs, which differentially disrupts the barriers that protect the microenvironment of the central nervous system. Among the host factors that are involved in this response, matrix metalloproteinases (MMPs) have been recently described as important players. Doxycycline is a commonly prescribed antimicrobial drug that acts as an anti-inflammatory agent with broad inhibitory properties against MMPs. In this study, we examined the effects of doxycycline treatment in a murine model of neurocysticercosis. Animals treated with doxycycline exhibited reduced morbidity and mortality throughout the course of infection. Although similar levels of leukocyte infiltration were observed with both treatment regimens, doxycycline appeared to provide improved conditions for host survival, as reduced levels of apoptosis were detected among infiltrates as well as in neurons. As an established MMP blocker, doxycycline reduced the degradation of junctional complex proteins in parenchymal vessels. In addition, doxycycline treatment was associated with an overall reduction in the expression and activity of MMPs, particularly in areas of leukocyte infiltration. These results indicate that a broad-range inhibitor of MMPs promotes host survival and suggest the potential of doxycycline as a therapeutic agent for the control of inflammatory responses associated with neurocysticercosis.