Cerebral Ischemic Stress Research Articles

Mechanism of Endoplasmic Reticulum Stress in Cerebral Ischemia.

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

The Role of Ubiquitin-Proteasome Pathway and Autophagy-Lysosome Pathway in Cerebral Ischemia.

The ubiquitin-proteasome pathway and autophagy-lysosome pathway are two major routes for clearance of aberrant cellular components to maintain protein homeostasis and normal cellular functions. Accumulating evidence shows that these two pathways are impaired during cerebral ischemia, which contributes to ischemic-induced neuronal necrosis and apoptosis. This review aims to critically discuss current knowledge and controversies on these two pathways in response to cerebral ischemic stress. We also discuss molecular mechanisms underlying the impairments of these protein degradation pathways and how such impairments lead to neuronal damage after cerebral ischemia. Further, we review the recent advance on the understanding of the involvement of these two pathways in the pathological process during many therapeutic approaches against cerebral ischemia. Despite recent advances, the exact role and molecular mechanisms of these two pathways following cerebral ischemia are complex and not completely understood, of which better understanding will provide avenues to develop novel therapeutic strategies for ischemic stroke.

Activation of c-Jun N-terminal kinase and p38 after cerebral ischemia upregulates cerebral sodium-glucose transporter type 1

Cerebral ischemic stress increases cerebral sodium-glucose transporter type 1 (SGLT-1). However, the mechanism by which cerebral ischemia leads to the up-regulation of SGLT-1 remains unclear. In peripheral tissue, the activation of mitogen-activated protein kinases (MAPKs) increases SGLT-1. MAPK pathways [c-Jun N-terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated protein kinase (ERK)] are activated by cerebral ischemic stress. Therefore, we confirmed the involvement of MAPKs in the up-regulation of cerebral SGLT-1 after cerebral ischemia. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO). Protein expression was assessed by western blotting. Mice received an intracerebroventricular (i.c.v.) injection of SP600125 (JNK inhibitor), SB203580 (p38 inhibitor), and PD98059 (MEK inhibitor) immediately after reperfusion. The infarction and behavioral abnormalities were assessed on days 1 and 3 after MCAO. The MAPK inhibitors suppressed the activation of JNK, p38, and ERK 3 h after MCAO. SP600125 and SB203580 administration ameliorated cerebral ischemic neuronal damage, whereas PD98059 administration exacerbated cerebral ischemic neuronal damage. SP600125 and SB203580 significantly suppressed the increase in SGLT-1 12 h after MCAO. PD98059 had no effect on SGLT-1 expression after MCAO. Our results indicate that the activation of JNK and p38 participate in the up-regulation of cerebral SGLT-1 after MCAO.

Potential of the Cerebral Sodium-Glucose Transporter as a Novel Therapeutic Target in Cerebral Ischemia

Cerebral ischemic stress often induces a hyperglycemic condition. This postischemic hyperglycemia exacerbates the development of cerebral ischemic neuronal damage, although the mechanism of this exacerbation remains to be clarified. We previously discovered that the cerebral sodium-glucose transporter (SGLT) was closely involved in the development of cerebral ischemic neuronal damage. SGLT is a member of the glucose transporter family and moves glucose together with sodium ions. SGLT-1, -3, -4, and -6 are distributed in the brain. We conducted further experiments to elucidate the detailed mechanism of the exacerbation of cerebral ischemia by cerebral SGLT. The results clarified: 1) the relationship between cerebral SGLT and postischemic hyperglycemia; 2) the involvement of cerebral SGLT-1 (a cerebral SGLT isoform) in cerebral ischemic neuronal damage; and 3) the effects of sodium influx through cerebral SGLT on the development of cerebral ischemic neuronal damage. This paper presents our data on the involvement of cerebral SGLT in the exacerbation of cerebral ischemic neuronal damage.

Alleviation of glutamate mediated neuronal insult by piroxicam in rodent model of focal cerebral ischemia: a possible mechanism of GABA agonism.

Neurotransmitter imbalance is an inevitable outcome in cerebral ischemia that leads to neuronal death. In the present study, we evaluated the effects of piroxicam, a nonsteroidal anti-inflammatory drug (NSAID), on extracellular brain glutamate and γ-aminobutyric acid (GABA) release, survival time, and neuronal cell death. Transient focal cerebral ischemia in male Charles Foster rat led to neuronal infarction and compromised intrinsic antioxidant status. Thirty-minute preadministration of piroxicam (10 mg/kg b.w.) showed a significant (P < 0.01) reduction in cerebral infarct volume and potentiation of the intrinsic antioxidant status. High-performance liquid chromatography of brain cortex and striatum revealed changes in extracellular concentrations of neurotransmitters which were found to be 0.519 ± 0.44 pmole/mg (GABA); 1.18 ± 0.28 pmole/mg (glutamate), and 0.63 ± 0.21 pmole/mg (serotonin), respectively. Hydroxyl radical (·OH) adduct of salicylate in the frontal cortex and striatum in control, untreated, and treated groups was found to be 0.261 ± 0.06, 0.68 ± 0.52, and 0.401 ± 0.68 pmole/mg, respectively. After stroke, the extracellular level of glutamate in rat brain increases continuously as compared to that of control group. However, piroxicam administration in stroke rat significantly reduced (P < 0.05) elevated extracellular cerebral glutamate. This indicates that piroxicam attenuates extracellular glutamate release and also reduces neuronal cell death due to reduction in oxidative stress in cerebral ischemia. Our results also indicate a consequent increase of extracellular GABA in brain regions administered with piroxicam, which hints that piroxicam alleviates glutamate excitotoxicity possibly by GABA agonism.

Role of orexin-A-mediated communication system between brain and peripheral tissues on the development of post-ischemic glucose intolerance-induced neuronal damage

I recently found that cerebral ischemic stress per se causes hyperglycemia (i.e., post-ischemic glucose intolerance) and suppression of post-ischemic glucose intolerance might be important to improve prognosis. Here, I analyzed the efficacy of suppression of post-ischemic glucose intolerance using orexin-A (OXA) endogenous neuropeptide as a novel therapeutic strategy against cerebral ischemic neuronal damage. OXA in hypothalamus plays a role in many physiological functions including regulation of glucose metabolism. I previously found that the development of post-ischemic glucose intolerance is suppressed by OXA. Other reports have shown that the communication system between brain and peripheral tissues through the autonomic nervous system is important for maintaining glucose and energy metabolism. The aim of this study was to determine the involvement of the hepatic vagus nerve on hypothalamic OXA-mediated suppression of post-ischemic glucose intolerance and neuronal damage. Intrahypothalamic administration of OXA significantly suppressed the development of post-ischemic glucose intolerance on day 1 and of neuronal damage on day 3 after middle cerebral artery occlusion (MCAO). In the liver, MCAO-induced decrease in insulin receptors and increase in gluconeogenic enzymes on day 1 was recovered to control levels by OXA; these effects were reversed by hepatic vagotomy. In the medulla oblongata, OXA induced co-localization of the cholinergic neuronal marker choline acetyltransferase with orexin-1 receptor and c-Fos. These results suggest that the vagus nerve projecting from the medulla oblongata plays an important role in the recovery of post-ischemic glucose intolerance and mediates neuroprotection by hypothalamic OXA.

Memory deficits and oxidative stress in cerebral ischemia–reperfusion: Neuroprotective role of physical exercise and green tea supplementation

Ischemic stroke is a major cause of morbidity and mortality all over the world. Among impairments observed in survivors there is a significant cognitive learning and memory deficit. Neuroprotective strategies are being investigated to minimize such deficits after an ischemia event. Here we investigated the neuroprotective potential of physical exercise and green tea in an animal model of ischemia–reperfusion. Eighty male rats were divided in 8 groups and submitted to either transient brain ischemia–reperfusion or a sham surgery after 8weeks of physical exercise and/or green tea supplementation. Ischemia–reperfusion was performed by bilateral occlusion of the common carotid arteries during 30min. Later, their memory was evaluated in an aversive and in a non-aversive task, and hippocampus and prefrontal cortex were removed for biochemical analyses of possible oxidative stress effects. Ischemia–reperfusion impaired learning and memory. Reactive oxygen species were increased in the hippocampus and prefrontal cortex. Eight weeks of physical exercise and/or green tea supplementation before the ischemia–reperfusion event showed a neuroprotective effect; both treatments in separate or together reduced the cognitive deficits and were able to maintain the functional levels of antioxidant enzymes and glutathione.

ARRB1/β-arrestin-1 mediates neuroprotection through coordination of BECN1-dependent autophagy in cerebral ischemia

Autophagy, a highly conserved process conferring cytoprotection against stress, contributes to the progression of cerebral ischemia. β-arrestins are multifunctional proteins that mediate receptor desensitization and serve as important signaling scaffolds involved in numerous physiopathological processes. Here, we show that both ARRB1 (arrestin, β 1) and ARRB2 (arrestin, β 2) were upregulated by cerebral ischemic stress. Knockout of Arrb1, but not Arrb2, aggravated the mortality, brain infarction, and neurological deficit in a mouse model of cerebral ischemia. Accordingly, Arrb1-deficient neurons exhibited enhanced cell injury upon oxygen-glucose deprivation (OGD), an in vitro model of ischemia. Deletion of Arrb1 did not affect the cerebral ischemia-induced inflammation, oxidative stress, and nicotinamide phosphoribosyltransferase upregulation, but markedly suppressed autophagy and induced neuronal apoptosis/necrosis in vivo and in vitro. Additionally, we found that ARRB1 interacted with BECN1/Beclin 1 and PIK3C3/Vps34, 2 major components of the BECN1 autophagic core complex, under the OGD condition but not normal conditions in neurons. Finally, deletion of Arrb1 impaired the interaction between BECN1 and PIK3C3, which is a critical event for autophagosome formation upon ischemic stress, and markedly reduced the kinase activity of PIK3C3. These findings reveal a neuroprotective role for ARRB1, in the context of cerebral ischemia, centered on the regulation of BECN1-dependent autophagosome formation.

Sulindac for stroke treatment: neuroprotective mechanism and therapy.

Sulindac, a widely used nonsteroidal anti-inflammatory drug (NSAID) is a prodrug that is reduced by methionine sulfoxide reductase to its active form as an inhibitor of cyclooxygenase 1 and 2. The drug has been shown to elicit tissue protection by processes that may include at least three functions: antioxidant, preconditioning and anti-inflammatory. Sulindac demonstrates neuroprotection that involves inhibition of mitochondrial calcium overload or a decrease in protein oxidation. We have demonstrated the induction by sulindac treatment of pro-survival proteins Hsp27, Akt and Bcl-2 in the ischemic penumbra and core of the central nervous system (CNS) infarct in a rat model of ischemic stroke. Our findings point to sulindac acting on the endoplasmic reticulum (ER) to decrease ATF-6 and on the mitochondrion to increase Bcl-2 as well as decrease pro-apoptotic components BAK and PUMA. The resulting decrease in ER stress and reduction in apoptosis underlies the protective effect of sulindac in reducing infarct size following transient focal brain ischemia. The potent neuroprotective effect of sulindac in the stroke model is obtained with low-dose administration of the drug pointing to the potential of sulindac as a valuable neuroprotective agent against oxidative stress in cerebral ischemia.

Neuroprotective effect through the cerebral sodium–glucose transporter on the development of ischemic damage in global ischemia

Diabetes mellitus and impaired glucose metabolism are the most important risk factors for stroke. We recently demonstrated that cerebral ischemic stress causes hyperglycemia (i.e., post-ischemic hyperglycemia) and may worsen ischemic neuronal damage in a mouse model of focal ischemia. However, the detailed mechanisms are still unknown. The sodium–glucose transporter (SGLT) generates inward currents in the process of transporting glucose into cells, resulting in depolarization and increased excitability, which is well known to be caused by cerebral ischemia. Hence, we focused on the role of SGLT on the development of neuronal damage using a global ischemic model.Male ddY mice were subjected to 30min of bilateral carotid artery occlusion (BCAO). The neuronal damage was estimated by histological analysis using HE staining on day 3 after BCAO.Intraperitoneal (i.p.) administration of phlorizin (a specific and competitive inhibitor of SGLT, 200mg/kg immediately after reperfusion) suppressed the development of post-ischemic hyperglycemia on day 1 after BCAO. In contrast, intracerebroventricular (i.c.v.) administration of phlorizin (40μg/mouse immediately and 6h after reperfusion) had no effect on day 1 after BCAO. Interestingly, the development of ischemic neuronal damage was significantly suppressed by i.p. and i.c.v. administration of phlorizin on day 3 after BCAO. In addition, BCAO-induced spasticity was significantly suppressed by PHZ (40μg/mouse, i.c.v.) from using gait analysis.Our results indicated that cerebral SGLT was involved in the development of ischemic neuronal damage in global ischemia.

Brain-derived neurotrophic factor inhibits glucose intolerance after cerebral ischemia.

Brain-derived neurotrophic factor is associated with the insulin signaling pathway and glucose tabolism. We hypothesized that expression of brain-derived neurotrophic factor and its receptor may be involved in glucose intolerance following ischemic stress. To verify this hypothesis, this study aimed to observe the changes in brain-derived neurotrophic factor and tyrosine kinase B receptor expression in glucose metabolism-associated regions following cerebral ischemic stress in mice. At day 1 after middle cerebral artery occlusion, the expression levels of brain-derived neurotrophic factor were significantly decreased in the ischemic cortex, hypothalamus, liver, skeletal muscle, and pancreas. The expression levels of tyrosine kinase B receptor were decreased in the hypothalamus and liver, and increased in the skeletal muscle and pancreas, but remained unchanged in the cortex. Intrahypothalamic administration of brain-derived neurotrophic factor (40 ng) suppressed the decrease in insulin receptor and tyrosine-phosphorylated insulin receptor expression in the liver and skeletal muscle, and inhibited the overexpression of gluconeogenesis-associated phosphoenolpyruvate carboxykinase and glucose-6-phosphatase in the liver of cerebral ischemic mice. However, serum insulin levels remained unchanged. Our experimental findings indicate that brain-derived neurotrophic factor can promote glucose metabolism, reduce gluconeogenesis, and decrease blood glucose levels after cerebral ischemic stress. The low expression of brain-derived neurotrophic factor following cerebral ischemia may be involved in the development of glucose intolerance.

Orexin-A Suppresses Postischemic Glucose Intolerance and Neuronal Damage through Hypothalamic Brain-Derived Neurotrophic Factor

Orexin-A (a glucose-sensing neuropeptide in the hypothalamus) and brain-derived neurotrophic factor (BDNF; a member of the neurotrophin family) play roles in many physiologic functions, including regulation of glucose metabolism. We previously showed that the development of postischemic glucose intolerance is one of the triggers of ischemic neuronal damage. The aim of this study was to determine whether there was an interaction between orexin-A and BDNF functions in the hypothalamus after cerebral ischemic stress. Male ddY mice were subjected to 2 hours of middle cerebral artery occlusion (MCAO). Neuronal damage was estimated by histologic and behavioral analyses. Expression of protein levels was analyzed by Western blot. Small interfering RNA directed BDNF, orexin-A, and SB334867 [N-(2-methyl-6-benzoxazolyl)-N'-1,5-naphthyridin-4-yl urea; a specific orexin-1 receptor antagonist] were administered directly into the hypothalamus. The level of hypothalamic orexin-A, detected by immunohistochemistry, was decreased on day 1 after MCAO. Intrahypothalamic administration of orexin-A (1 or 5 pmol/mouse) significantly and dose-dependently suppressed the development of postischemic glucose intolerance on day 1 and development of neuronal damage on day 3. The MCAO-induced decrease in insulin receptor levels in the liver and skeletal muscle on day 1 was recovered to control levels by orexin-A, and this effect of orexin-A was reversed by the administration of SB334867 as well as by hypothalamic BDNF knockdown. These results suggest that suppression of postischemic glucose intolerance by orexin-A assists in the prevention of cerebral ischemic neuronal damage. In addition, hypothalamic BDNF may play an important role in this effect of orexin-A.

Neuron‐specific non‐classical release of prothymosin alpha: a novel neuroprotective damage‐associated molecular patterns

Prothymosin alpha (ProTα), a nuclear protein devoid of signal sequence, has been shown to possess a number of cellular functions including cell survival. Most recently, we demonstrated that ProTα is localized in the nuclei of neurons, while it is found in both nuclei and cytoplasm in the astrocytes and microglia of adult brain. However, the cell type-specific non-classical release of ProTα under cerebral ischemia is yet unknown. In this study, we report that ProTα is non-classically released along with S100A13 from neurons in the hippocampus, striatum and somatosensory cortex at 3h after cerebral ischemia, but amlexanox (an anti-allergic compound) reversibly blocks this neuronal ProTα release. We found that none of ProTα is released from astrocytes and microglia under ischemic stress. Indeed, ProTα intensity is increased gradually in astrocytes and microglia through 24h after the cerebral ischemia. Interestingly, Z-Val-Ala-Asp fluoromethyl ketone, a caspase 3 inhibitor, pre-treatment induces ProTα release from astrocytes in the ischemic brain, but this release is reversibly blocked by amlexanox. However, Z-Val-Ala-Asp fluoromethyl ketone as well as amlexanox has no effect on ProTα distribution in microglia upon cerebral ischemia. Taken together, these results suggest that only neurons have machineries to release ProTα upon cerebral ischemic stress in vivo.

RETRACTED: Ameliorating Effect of Hypothalamic Brain-Derived Neurotrophic Factor Against Impaired Glucose Metabolism After Cerebral Ischemic Stress in Mice

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. In Figure1C some of the numbers of the original raw data were changed. Hence, the Figures were different from real Figures obtained from original raw data and the significant difference in Figure 1C was not obtained.

Ischemic Stroke and Glucose Intolerance: a Review of the Evidence and Exploration of Novel Therapeutic Targets

Stroke is one of the leading causes of death and disability worldwide. It is well known that hyperglycemia and/or diabetes potentially exacerbate the neuronal damage observed following ischemic stroke. Recent reports have shown that hyperglycemia/glucose intolerance may be induced by cerebral ischemic stress, and that normalization of blood glucose levels during the first 48 h of hospitalization appears to confer greater survival outcomes in stroke patients. However, the mechanisms underlying post-ischemic glucose intolerance remain unclear. Here, we review research to date on the mechanisms through which ischemic neuronal damage develops and on the role of post-ischemic glucose intolerance focusing on insulin and adiponectin signaling and communication between the brain and peripheral tissues. The relationship between ischemic neuronal damage and post-ischemic glucose intolerance is also discussed. With respect to therapeutic options, in addition to traditional post-stroke therapies, we also discuss the effect of anti-diabetic drugs and glucose-sensing neuropeptides on the development of the post-ischemic glucose intolerance and neuronal damage. In conclusion, we support the idea for focusing research on the development of post-ischemic glucose intolerance as a new therapeutic target for the stroke patients.

Improved Neuronal Survival of Focal Ischemia After Delipid Extracorporeal Lipoprotein Treatment in Hyperlipidemic Rabbits

A delipid extracorporeal lipoprotein filter (DELP) system has been used to treat patients with stroke and has shown favorable prognosis. However, the mechanism for the neuronal functional recovery remains unclear. This study aimed to investigate the neuronal histological assessment, and the levels of C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), and oxidized low-density lipoprotein (oxLDL) after ischemic stroke following DELP treatment. Hyperlipidemic rabbits underwent middle cerebral artery occlusion. After 30 min, the animals received an extracorporeal apheresis treatment with a DELP filter. Total cholesterol (TC), triglyceride, and low-density lipoprotein (LDL) of the plasma were measured. The levels of CRP, TNF-α, and oxLDL in brain tissue were also measured by enzyme-linked immunosorbent assay. Hematoxylin and eosin staining, cresyl violet staining, neuron-specific enolase (NSE) and glial fibrillary acidic protein immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay were performed. DELP apheresis reduced TC and LDL by >30%. The number of neurons at day 7 (P < 0.01) and the integrated optical density of NSE at day 1 (P < 0.05) and day 7 (P < 0.01) were significantly increased in the DELP group. TUNEL-positive cells were significantly decreased (P < 0.05). Astrocytes were moderately activated, and this activation persisted up to 7 days. Gliosis was not found in the DELP group. After treatment, the level of CRP declined at day 1 (P < 0.05); TNF-α and oxLDL declined at day 7 (P < 0.05). DELP apheresis decreased neuronal apoptosis, reduced inflammatory markers and oxidative stress in cerebral ischemia, and improved neuronal survival.

The antioxidant effects of Joongpoongtang 05 on brain injury after transient focal cerebral ischemia in rats

Traditional Korean medicines with antioxidant properties are believed to have potential therapeutic effects against oxidative stress in cerebral ischemia. In this study, the antioxidant effects of Joongpoongtang 05 (JP05) were evaluated in rat middle cerebral artery occlusion (MCAO). Male Sprague-Dawley rats treated with JP05 (100 and 200 mg/kg body weight, p.o.) for 5 days showed a reduction in infarct sizes and a decrease in oxidants after MCAO. Furthermore, a significant inhibition of enzymatic antioxidants in the ischemic cerebral cortex was observed. Treatment with JP05 reversed the inhibition to normal levels. In the glutathione system, the reduced glutathione (GSH) level was decreased while oxidized glutathione (GSSG) was increased in MCAO rats. Treatment with JP05 increased the GSH/GSSG ratio and redox index by enhancing the synthesis of GSH from GSSG. Moreover, in vitro studies showed that JP05 has strong antioxidant activity in the Trolox equivalent antioxidant capacity, oxygen radical absorbance capacity and 1,1-diphenyl-2-picrylhydrazyl radical assays. The present findings suggest that JP05 treatment can contribute to a protective effect on brain ischemia through antioxidant mechanisms.

Oxidative Stress and NAD+ in Ischemic Brain Injury: Current Advances and Future Perspectives

Numerous studies have indicated oxidative stress as a key pathological factor in ischemic brain injury. One of the key links between oxidative stress and cell death is excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1), which plays an important role in the ischemic brain damage in male animals. Multiple studies have also suggested that NAD+ depletion mediates PARP-1 cytotoxicity, and NAD+ administration can decrease ischemic brain injury. A number of recent studies have provided novel information regarding the mechanisms underlying the roles of oxidative stress and NAD+-dependent enzymes in ischemic brain injury. Of particular interest, there have been exciting progresses regarding the mechanisms underlying the roles of NADPH oxidase and PARP-1 in cerebral ischemia. For examples, it has been suggested that androgen signaling and binding of PARP-1 onto estrogen receptors could account for the intriguing findings that PARP-1 plays remarkably differential roles in the ischemic brain damage of male and female animals; and some studies have suggested casein kinase 2, copper-zinc superoxide dismutase, and estrogen signaling can modulate the expression and activity of NADPH oxidase. This review summarizes these important current advances, and proposes future perspectives for the studies on the roles of oxidative stress and NAD+ in cerebral ischemia. It is increasingly likely that future studies on NAD- and NADP-dependent enzymes, such as NADPH oxidase, PARP-1, and sirtuins, would expose novel mechanisms underlying the roles of oxidative stress in cerebral ischemia, and suggest new therapeutic strategies for treating the debilitating disease.

Withdrawal: Preventive Effect of &lt;i&gt;Morinda citrifolia&lt;/i&gt; Fruit Juice on Neuronal Damage Induced by Focal Ischemia

It is known that the fruit juice of Morinda citrifolia (M. citrifolia, Noni, Rubiaceae) has various pharmacological effects such as antioxidant or anti-inflammatory activities, which may help the inhibition of ischemic neuronal damage. Here, we examined the effect of the fruit juice of M. citrifolia (Noni juice) on the brain damage caused by ischemic stress in mice. Noni juice was obtained from the mature fruit grown in Okinawa (about 1.5 l/4 kg of fruit; 100% Okinawa Noni juice (ONJ). Male ddY mice were supplied with 3% or 10% juice in the drinking water for 7 d, and compared to the control group. On the 7th day, mice were subjected to 2 h of middle cerebral artery occlusion (MCAO). Interestingly, the intake of juice reduced the infarct volume as analyzed by 2,3,5-triphenyltetrazolium chloride (TTC) staining on the 3rd day of MCAO when compared to the control group. Furthermore, we found that the neurological deficit scores (NDS) were decreased after the reperfusion in the juice-supplied mice. On the other hand, the intake of juice did not affect the expression levels of antioxidant such as Cu/Zn superoxide dismutase. The present study suggests that Noni juice may have a preventive effect against cerebral ischemic stress, while further studies are needed to explain the detailed mechanism.

Hydroxyl Radical Production in the Cortex and Striatum in a Rat Model of Focal Cerebral Ischemia

Increases in hydroxyl radical production have been used as evidence of oxidative stress in cerebral ischemia/ reperfusion. Ischemia can also induce increased dopamine release from the striatum that may contribute to hydroxyl radical formation. We have compared hydroxyl radical production in the cortex and striatum as an index of oxidative stress in a rat model of focal cerebral ischemia with cortical infarction. Using a three vessel occlusion model of focal cerebral ischemia combined with bilateral microdialysis, hydroxylation of 4-hydroxybenzoate (4HB) was continuously monitored in both hemispheres in either the lateral striatum or frontoparietal cortex. The ischemia protocol consisted of one hour equilibration, 30 min of three vessel occlusion, then release of the contralateral common carotid artery (CCA) for 2.5 h. Induction of ischemia resulted in a 30-fold increase in dopamine release in the lateral striatum. Compared to the nonischemic striatum, the ratio of the hydroxylation product 3,4-dihydroxybenzoate (34DHB) to 4HB (trapping agent) in the ipsilateral striatum increased significantly 30 min after ischemia induction. In contrast, during the 30 min of three vessel occlusion there was no increase in the ratio in the cortex. Following the release of the contralateral CCA, the ratio from the ischemic cortex increased significantly compared to sham-operated animals. However, under all circumstances, the 34DHB/4HB ratio was greater in the striatum than in the cortex. The increase in the 34DHB/4HB ratio in the lateral striatum coincides with the increased dopamine release suggesting a role for dopamine oxidation in the increased production of hydroxyl radicals. The significant increase in the ratio from the ischemic cortex compared to that from the sham-operated animals is consistent with increased oxidative stress induced by ischemia. However, the lower 34DHB/4HB ratio in the cortex which does not receive dopaminergic innervation compared to the striatum suggests a different mechanism for hydroxyl radical production. Such an alternate mechanism may represent a more toxic oxidative insult that contributes to infarction.