More severe type 2 diabetes‐associated ischemic stroke injury is alleviated in aldose reductase‐deficient mice

Aldose reductase (AR), the first enzyme in the polyol pathway, has been implicated in a wide variety of physiological and pathological functions, such as diabetic vascular and neural complications. It is known that diabetes mellitus can exacerbate brain and retina damage after ischemic injuries. However, the underlying mechanisms are not clear. In the present study, we made use of db/db mice with an AR null mutation (AR^?/?db/db) to understand better the role of AR in the pathogenesis of brain and retina ischemic injuries under diabetic conditions. Cerebral and retinal ischemia was induced by transient middle cerebral artery occlusion in control and diabetic mice either with or without an AR null mutation. Mice were evaluated for neurological deficits after 30 min of ischemia and 23.5 hr of reperfusion. Our results showed that the diabetic db/db mice had significantly more severe neurological deficit and larger brain infarct size than the nondiabetic mice. Compared with wild‐type db/db mice, the AR^?/?db/db mice had significantly lower neurological scores, smaller brain infarct areas, and less hemispheric brain swelling. Retinal swelling was also significantly decreased in the AR^?/?db/db mice. Less swelling in the brain and retina of the AR^?/?db/db mice correlated with less expression of the water channel aquaporin 4. Taken together, these data clearly show that deletion of AR leads to less severe brain and retinal ischemic injuries in the diabetic db/db mouse. The present study indicates that inhibition of AR in diabetics may protect against damage in the brain and retina following ischemic reperfusion injury. © 2010 Wiley‐Liss, Inc.     

PI3-K/Akt通路在脑缺血治疗中的调控机制研究

目的观察脑缺血-再灌注损伤后PI3-K/Akt通路的活性变化,并探讨阿利吉仑的调控机制。方法采用改良线栓法制备大脑中动脉缺血-再灌注模型。实验采用Western blot和qR-T PCR观察PI3-K、Akt基因和蛋白变化,比较各组脑梗死体积、患侧脑水肿和神经功能。结果缺血-再灌注后PI3-K、Akt表达明显减少。阿利吉仑通过激活PI3-K/Akt通路,明显改善神经功能缺失,减轻脑水肿,减小梗死体积。结论 PI3-K/Akt通路参与了阿利吉仑的脑保护作用,为其临床应用提供了理论基础。     

槐定碱抑制TLR4/NF-κB通路的激活和机制研究

目的观察脑缺血-再灌注损伤后TLR4/NF-κB通路的活性变化,并探讨槐定碱的调控机制。方法采用改良线栓法制备大脑中动脉缺血-再灌注模型。实验采用Western blot和qR-T PCR观察TLR4、NF-κB基因和蛋白变化,比较各组脑梗死体积、患侧脑水肿和神经功能。结果脑缺血-再灌注后TLR4、NF-κB表达明显上调。槐定碱通过抑制TLR4/NF-κB通路的激活,明显改善神经功能缺失,减轻脑水肿,减小脑梗死体积。结论 TLR4/NF-κB通路参与了槐定碱的脑保护作用,为其临床应用提供了理论基础。     

The Akt/glycogen synthase kinase-3β pathway participates in the neuroprotective effect of interleukin-4 against cerebral ischemia/reperfusion injury

Interleukin-4(IL-4) has a protective effect against cerebral ischemia/reperfusion injury. Animal experiments have shown that IL-4 improves the short-and long-term prognosis of neurological function. The Akt(also called protein kinase B, PKB)/glycogen synthase kinase-3β(Akt/GSK-3β) signaling pathway is involved in oxidative stress, the inflammatory response, apoptosis, and autophagy. However, it is not yet clear whether the Akt/GSK-3β pathway participates in the neuroprotective effect of IL-4 against cerebral ischemia/reperfusion injury. In the present study, we established a cerebral ischemia/reperfusion mouse model by middle cerebral artery occlusion for 60 minutes followed by a 24-hour reperfusion. An IL-4/anti-IL-4 complex(10 μg) was intraperitoneally administered 30 minutes before surgery. We found that administration of IL-4 significantly alleviated the neurological deficits, oxidative stress, cell apoptosis, and autophagy and reduced infarct volume of the mice with cerebral ischemia/reperfusion injury 24 hours after reperfusion. Simultaneously, IL-4 activated Akt/GSK-3β signaling pathway. However, an Akt inhibitor LY294002, which was injected at 15 nmol/kg via the tail vein, attenuated the protective effects of IL-4. These findings indicate that IL-4 has a protective effect on cerebral ischemia/reperfusion injury by mitigating oxidative stress, reducing apoptosis, and inhibiting excessive autophagy, and that this mechanism may be related to activation of the Akt/GSK-3β pathway. This animal study was approved by the Animal Ethics Committee of Renmin Hospital of Wuhan University, China(approval No. WDRY2017-K037) on March 9, 2017.     

Srs11-92, a ferrostatin-1 analog,improves oxidative stress and neuroinflammation via Nrf2 signal following cerebral ischemia/reperfusion injury

Aim

Ferroptosis is increasingly becoming to be considered as an important mechanism of pathological cell death during stroke, and specific exogenous ferroptosis inhibitors have the ability to reverse cerebral ischemia/reperfusion injury. However, research on Srs11-92 (AA9), a ferrostatin-1 (Fer-1) analog, in preclinical studies is limited.

Methods

In the middle cerebral artery occlusion-reperfusion (MCAO/R) mice model or oxygen–glucose deprivation/reperfusion (OGD/R) cell model, Fer-1, AA9, and/or ML385 were administered, and brain infarct size, neurological deficits, neuronal damage, oxidative stress, and neuroinflammation were determined after the damage, in vitro and in vivo.

Results

Fer-1 and AA9 improved brain infarct size, neuronal damage, and neurological deficits in mice model of MCAO/R, and inhibited the overloaded iron deposition, ROS accumulation, and neuroinflammation response: it also increased the expression of GPx4, Nrf2, and HO-1 and suppressed the expression of HMGB1 and NF-κB p65 in the epicenter of injured hippocampal formation. However, Nrf2 inhibitor ML385 reversed the neuroprotective effect of AA9, including the oxidative stress and neuroinflammation. In vitro studies showed that AA9 relieved OGD/R-induced neuronal oxidative stress and neuroinflammation via the Nrf2 pathway, which was impaired by ML385 in primary neurons.

Conclusion

The findings imply that Fer-1 analog AA9 may be suitable for further translational studies for the protection of neuronal damage via Nrf2 signal pathway-mediated oxidative stress and neuroinflammation in stroke and others neurological diseases.     

IRAK-4在大鼠缺血性脑损伤早期的表达及意义

目的 探讨白细胞介素-1受体相关激酶-4(interleukin-1 receptor-associated kinases,IRAK-4)在大鼠大脑缺血性损伤早期的表达及意义.方法 应用大脑中动脉线栓法(MCAO)建立大鼠局灶永久性脑梗死模型,随机分为正常对照组、假手术组、缺血组、干预组.采用RT-PCR、Western blot、免疫荧光、神经功能5分评定及TTC染色等方法,检测大鼠额顶叶皮层组织IRAK-4在脑缺血性损伤早期的mRNA及蛋白表达变化、神经功能缺损程度及脑梗死体积变化,并统计各组死亡率.结果 大鼠大脑缺血性损伤早期额顶叶皮层组织IRAK-4 mRNA表达:3 h开始增加,12 h达到高峰,24 h仍维持在较高水平;IRAK-4蛋白表达:3 h开始增加,6 h达到高峰,12 h仍维持在较高水平,24 h下降与正常对照组无统计学意义;IRAK-4抑制能明显缩小脑梗死体积、改善神经功能、降低死亡率.结论 大鼠额顶叶皮层组织IRAK-4在脑缺血性损伤早期表达迅速上调,可能参与了脑缺血后炎性反应的调控,早期抑制其功能可以发挥显著脑保护作用.

Abstract：

Objective To investigate the expression and significance of Interleukin - 1 ReceptorAssociated Kinases 4( IRAK -4) in rat ischemic brain injury. Method Models of focal cerebral infarct were established by occlusion of middle cerebral artery ( MCAO ). Rats were randomly divided into normal control group, sham surgery group, ischemic group, treated group. The mRNA and protein expressions of IRAK-4 in cerebral cortex were detected by RT- PCR method, Western blot analysis and laser scanning confocal microscope(LSCM). The neurological deficits were evaluated in 0 ～ 4 scales. The infarct size was measured by TTC staining. The mortality of each group was also calculated. Results The mRNA and protein expressions of IRAK -4 in cerebral cortex increased after ischemic injury 3 hours and decreased gradually after reaching the highest level at 12 h or 6 h( P ＜0.01 ) ,after 24 h the concentration of protein showed no significant differences compared with normal control group ( P ＞ 0.05 ), but mRNA is still at a high level ( P ＜ 0.05 ) ;the inhibition of IRAK -4 could induce the cerebral infarct, neurological deficits and mortality rate. Conclusions Brain ischemic injury increased the expression of IRAK - 4 in cerebral cortex,and inhibition of neuronal IRAK-4 by IRAK- 1/4 inhibitor at the early stage could effectively protect the neuron against death. The mechanism may be related with down - regulation of the inflammation response resulted from stroke.     

Neuroprotective effects of salidroside on focal cerebral ischemia/reperfusion injury involve the nuclear erythroid 2-related factor 2 pathway

Salidroside,the main active ingredient extracted from Rhodiola crenulata,has been shown to be neuroprotective in ischemic cerebral injury,but the underlying mechanism for this neuroprotection is poorly understood.In the current study,the neuroprotective effect of salidroside on cerebral ischemia-induced oxidative stress and the role of the nuclear factor erythroid 2-related factor 2(Nrf2)pathway was investigated in a rat model of middle cerebral artery occlusion.Salidroside(30 mg/kg)reduced infarct size,improved neurological function and histological changes,increased activity of superoxide dismutase and glutathione-S-transferase,and reduced malon-dialdehyde levels after cerebral ischemia and reperfusion.Furthermore,salidroside apparently increased Nrf2 and heme oxygenase-1 expression.These results suggest that salidroside exerts its neuroprotective effect against cerebral ischemia through anti-oxidant mechanisms and that activation of the Nrf2 pathway is involved.The Nrf2/antioxidant response element pathway may become a new therapeutic target for the treatment of ischemic stroke.     

低氧预适应对小鼠急性脑缺血性损伤保护作用的研究

目的 探讨低氧预适应对小鼠急性脑梗死致脑缺血性损伤的保护作用.方法 将Blb/c近交系小鼠按照随机数字表法分为正常对照组(N组),不做任何处理;假手术组(C组),仅行冷光源照射,不注射玫瑰红;急性脑梗死组(CI组),光化学法诱导制作小鼠脑皮层梗死模型;低氧预适应+急性脑梗死组(HP+CI组),低氧预适应后光化学法诱导制作小鼠脑皮层梗死模型.利用行为学、免疫荧光和激光共聚焦等实验方法.分别行神经功能评定、脑梗死体积测定、细胞凋亡检测.结果 (1)脑梗死体积比较:N组、C组未发现梗死灶,CI和HP+CI组均见明显缺血梗死灶,其中HP+CI组脑梗死体积较CI组明显减小,差异有统计学意义(P<0.05);(2)神经功能评分比较:N组、C组无神经功能缺损症状,CI组和HP+CI组出现明显神经功能缺损症状,神经功能评分明显降低,其中HP+CI组神经功能评分比CI组明显增加,差异有统计学意义(P<0.05);(3)细胞凋亡比较:N组、C组小鼠大脑皮层偶见TUNEL阳性细胞,CI组和HP+CI组TUNEL阳性细胞数明显增多,其中HP+CI组TUNEL阴性细胞数较CI组减少,差异有统计学意义(P<0.05).结论 低氧预适应可能通过减小小鼠急性脑梗死体积、减少细胞凋亡两个方面发挥脑缺血性损伤的保护作用.     

枸杞多糖对小鼠脑缺血再灌注损伤的保护作用及其抗氧化应激的机制研究

目的探讨枸杞多糖(lycium barbarum polysaccharides,LBP)对缺血再灌脑损伤小鼠的保护作用及其可能的机制。方法通过颈总动脉栓线造成大脑中动脉缺血,缺血2 h后将栓线拔出以实现大脑中动脉血流再灌注,形成小鼠短暂性大脑中动脉阻塞(transient middle cerebral artery occlusion,t MCAO)模型,观察LBP(25 mg/kg,50 mg/kg和100 mg/kg)对小鼠脑梗死范围,脑含水量,神经症状的影响,采用Westernblot法检测缺血大脑皮质NOX4蛋白的表达,采用DHE染色法检测脑组织中ROS的生成,采用分光光度计检测缺血侧脑组织匀浆SOD活力,GSH-Px活力,及MDA含量。结果 LBP对缺血再灌注小鼠神经症状有明显的改善作用,能明显降低脑梗死范围和脑含水量。Westernblot结果显示:小鼠缺血再灌后,缺血侧大脑皮质NOX4蛋白水平明显增高,LBP能显著降低NOX4蛋白水平。DHE染色显示,LBP能显著降低缺血再灌后ROS的生成。LBP能升高SOD和GSH-Px活力,降低MDA含量。结论 LBP对缺血再灌注小鼠脑损伤有明显保护作用,该作用可能与其抑制脑缺血再灌注引起的氧化应激损伤有关。     

Protective effect of oxysophoridine on cerebral ischemia/reperfusion injury in mice

Oxysophoridine, a new alkaloid extracted from Sophora alopecuroides L., has been shown to have a protective effect against ischemic brain damage. In this study, a focal cerebral ischemia/reperfusion injury model was established using middle cerebral artery occlusion in mice. Both 62.5, 125, and 250 mg/kg oxysophoridine, via intraperitoneal injection, and 6 mg/kg nimodipine, via intragastric administration, were administered daily for 7 days before modeling. After 24 hours of reperfusion, mice were tested for neurological deficit, cerebral infarct size was assessed and brain tissue was collected. Results showed that oxysophoridine at 125, 250 mg/kg and 6 mg/kg nimodipine could reduce neurological deficit scores, cerebral infarct size and brain water content in mice. These results provided evidence that oxysophoridine plays a protective role in cerebral ischemia/reperfusion injury. In addition, oxysophoridine at 62.5, 125, and 250 mg/kg and 6 mg/kg nimodipine increased adenosine-triphosphate content, and decreased malondialdehyde and nitric oxide content. These compounds enhanced the activities of glutathione-peroxidase, superoxide dismutase, catalase, and lactate dehydrogenase, and decreased the activity of nitric oxide synthase. Protein and mRNA expression levels of N-methyl-D-aspartate receptor subunit NR1 were markedly inhibited in the presence of 250 mg/kg oxysophoridine and 6 mg/kg nimodipine. Our experimental findings indicated that oxysophoridine has a neuroprotective effect against cerebral ischemia/reperfusion injury in mice, and that the effect may be due to its ability to inhibit oxidative stress and expression of the N-methyl-D-aspartate receptor subunit NR1.     

Endogenous level of TIGAR in brain is associated with vulnerability of neurons to ischemic injury

In previous studies,we showed that TP53-induced glycolysis and apoptosis regulator(TIGAR) protects neurons against ischemic brain injury.In the present study,we investigated the developmental changes of TIGAR level in mouse brain and the correlation of TIGAR expression with the vulnerability of neurons to ischemic injury.We found that the TIGAR level was high in the embryonic stage,dropped at birth,partially recovered in the early postnatal period,and then continued to decline to a lower level in early adult and aged mice.The TIGAR expression was higher after ischemia/reperfusion in mouse brain 8and 12 weeks after birth.Four-week-old mice had smaller infarct volumes,lower neurological scores,and lower mortality rates after ischemia than 8- and12-week-old mice.TIGAR expression also increased in response to oxygen glucose deprivation(OGD)/reoxygenation insult or H_2O_2 treatment in cultured primary neurons from different embryonic stages(E16 and E20).The neurons cultured from the early embryonic period had a greater resistance to OGD and oxidative insult.Higher TIGAR levels correlated with higher pentose phosphate pathway activity and less oxidative stress.Older mice and more mature neurons had more severe DNA and mitochondrial damage than younger mice and less mature neurons in response to ischemia/reperfusion or OGD/reoxygenation insult.Supplementation of cultured neurons with nicotinamide adenine dinuclectide phosphate(NADPH) significantly reduced ischemic injury.These results suggest that TIGAR expression changes during development and its expression level may be correlated with the vulnerability of neurons to ischemic injury.     

Simvastatin reduced ischemic brain injury and perfusion deficits in an embolic model of stroke

Simvastatin is cholesterol lowering agent and also a modulator of cytokine in the nervous system. The functional significance and neuroprotectiove mechanism of simvastatins in ischemic brain injury is controversial. The purpose of study is to evaluate the effect of simvastatin on ischemic brain injury and to investigate the perfusion capability of brain microvessels in the ischemic injury. This study included two series of experiments. In the first series, we studied if simvastatin is neuroprotective in an embolic model of stroke. The treatments began 2 weeks before middle cerebral artery (MCA) occlusion. Infarct volume was measured at 48 h post stroke. Neurological deficits were assessed at 2 h, 24 h and 48 h post stroke. Results showed that infarct volume in rats which received saline and simvastatin was 32.5 +/- 9.3% (mean +/- SD) and 18.7 +/- 6.5%, respectively. The infarct volume in the simvastatin group was significantly smaller than in the controls (P < 0.002). Treatment with simvastatin also improved neurological deficits and reduced brain edema significantly (P < 0.05). In the second series, we studied if simvastatin can improve microvascular reperfusions after ischemia. Perfusion deficits were detected at 8 h post stroke using Evens blue dye. Neurological deficits were assessed at 2 h and 8 h post stroke. Results showed that perfusion deficit in saline and simvastatin-treated groups were 58.7 +/- 8.7% and 23.4 +/- 7.5%, respectively. The perfusion deficit in simvastatin-treated group was decreased 61% (P < 0.01). These studies thus suggest that simvastatin is a protective agent in ischemic brain injury and this protective effect may be partially due to its action in the improvement of microvascular reperfusion.     

Neuroprotection of Everolimus Against Focal Cerebral Ischemia-Reperfusion Injury in Rats

BackgroundMammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates cell growth and metabolism and integrates various signals under physiological and pathological conditions. Altered signaling of mTOR has been shown to play pathogenic roles in ischemic stroke. In the present study, the protective effect of everolimus, the selective mTOR inhibitor, in the middle cerebral artery occlusion (MCAO) model of ischemic stroke was evaluated.MethodsWistar rats were exposed to MCAO (30 min) followed by reperfusion for 24 h. Everolimus (100, and 500 µg/kg) was administered at the time of reperfusion, intraperitoneally. 24 h post operation, the neurological function, infarct volume, histopathological alterations and the markers of oxidative stress including superoxide dismutase (SOD) activity, malondialdehyde (MDA), and total thiol levels were analyzed in the peri-infarct region.ResultsIn the rats subjected to MCAO, everolimus ameliorated neurological deficits, neuronal cell loss, and infarct volume, as compared to the stroke group. Also, everolimus significantly increased SOD activity and total thiol content, while markedly decreased the MDA level, as compared to MCAO group.ConclusionSingle-dose administration of everolimus significantly improved neurological deficits and inhibited cortical cell loss by enhancing redox status, subsequently protected cerebral ischemia-reperfusion injury in rats.     

Sevoflurane postconditioning attenuates cerebral ischemia-reperfusion injury via protein kinase B/nuclear factor-erythroid 2-related factor 2 pathway activation

Oxidative damage plays a critical role in many diseases of the central nervous system. This study was conducted to determine the molecular mechanisms involved in the putative anti-oxidative effects of sevoflurane against experimental stroke. Focal cerebral ischemia was performed via 1 h of middle cerebral artery occlusion followed by reperfusion. At the onset of reperfusion, rats were subjected to postconditioning with sevoflurane or without sevoflurane for 1 h. Neurological deficit score was assessed at different time points after reperfusion. Cerebral infarct volume, oxidative stress level and the binding activity of Nrf2 to antioxidant response element were assessed, meanwhile the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2), quinine oxidoreductase 1 (NQO1), protein kinase B (Akt) and phosphor-Akt was examined by Western blot at 72 h after reperfusion. Sevoflurane postconditioning administration significantly reduced neurological deficit score, infarct volume and oxidative stress levels, while increased the expression of phosphorylation Akt, NQO1, Nrf2 and the binding activity of Nrf2 to ARE in middle cerebral artery occlusion rats. These neuroprotective effects were all suppressed by LY294002, a selective PI3K blocker. Taken together, these findings provided evidence that sevoflurane postconditioning protects brain against ischemic/reperfusion injury, and this neuroprotective effect involves the Akt/Nrf2 pathway.     

Therapeutic time window of tacrolimus (FK506) in a nonhuman primate stroke model: comparison with tissue plasminogen activator

Tacrolimus (FK506), an immunosuppressive drug, has been shown to exert a potent neuroprotective activity when administered immediately after occlusion of the middle cerebral artery (MCA) in a nonhuman primate model of stroke. Here, we assessed the neuroprotective efficacy of tacrolimus with delayed treatment using the same model and compared with that of recombinant tissue plasminogen activator (rt-PA). Ischemic insult was induced by photochemically induced thrombotic occlusion of MCA in cynomolgus monkeys, and tacrolimus (0.2 mg/kg) and/or rt-PA (1.0 mg/kg) was intravenously administered 2 h after MCA occlusion. In another experiment, tacrolimus (0.1 mg/kg) was administered 4 h after MCA occlusion. Neurological deficits were monitored for 28 days after the ischemic insult and cerebral infarct volumes were measured with brain slices. With drug administration 2 h after the ischemic insult, tacrolimus significantly reduced neurological deficits and infarct volumes in the cerebral cortex without affecting the recanalization pattern in the MCA, however, rt-PA did not significantly improve neurological deficits or infarct volumes, even though it increased the recanalization rate of the occluded MCA. Combined treatment with tacrolimus and rt-PA exerted additional protection. Administration of tacrolimus 4 h after the ischemic insult still showed significant amelioration of neurological deficits. These results suggested that tacrolimus had a wider therapeutic time window than rt-PA in the nonhuman primate stroke model.     

局灶性脑缺血耐受和星形胶质细胞反应

目的　研究短暂性局灶性脑缺血预处理对永久性局灶性脑缺血的保护作用 ,及最佳预处理时间剂量 ,并探讨星形胶质细胞在脑缺血耐受中的反应。方法　采用开颅方法阻断大鼠大脑中动脉 ,通过观察大鼠脑梗死后神经功能损伤状况、脑梗死体积分析及病理形态学变化 ,评价不同的缺血预处理时间剂量 (10分钟、2 0分钟、30分钟 )对永久性局灶性脑缺血的保护作用。采用胶质纤维酸性蛋白 (GFAP)免疫组化法观察星形胶质细胞在脑缺血耐受中的反应。结果　与对照组相比 ,缺血预处理 2 0分钟未引起明显的神经元损伤 ,但使永久性局灶性脑缺血后神经功能损伤减轻 ,梗死体积明显减小 (P <0 .0 1)。免疫组化显示 ,2 0分钟缺血预处理组及重复缺血组星形胶质细胞在损伤预处理侧广泛激活。结论　 2 0分钟局灶性脑缺血预处理能够有效诱导脑缺血耐受。星形胶质细胞的激活可能与脑缺血耐受中神经元的存活相关。     

Sex differences in neuroprotection provided by inhibition of TRPM2 channels following experimental stroke

The calcium-permeable transient receptor potential M2 (TRPM2) ion channel is activated following oxidative stress and has been implicated in ischemic damage; however, little experimental evidence exists linking TRPM2 channel activation to damage following cerebral ischemia. We directly assessed the involvement of TRPM2 channels in ischemic brain injury using pharmacological inhibitors and short-hairpin RNA (shRNA)-mediated knockdown of TRPM2 expression. Each of the four TRPM2 inhibitors tested provided significant protection to male neurons following in vitro ischemia (oxygen–glucose deprivation, OGD), while having no effect in female neurons. Similarly, TRPM2 knockdown by TRPM2 shRNA resulted in significantly reduced neuronal cell death following OGD only in male neurons. The TRPM2 inhibitor clotrimazole reduced infarct volume in male mice, while having no effect on female infarct volume. Finally, intrastriatal injection of lentivirus expressing shRNA against TRPM2 resulted in significantly smaller striatal infarcts only in male mice following middle cerebral artery occlusion, having no significant effect in female mice. Data presented in the current study demonstrate that TRPM2 inhibition and knockdown preferentially protects male neurons and brain against ischemia in vitro and in vivo, indicating that TRPM2 inhibitors may provide a new therapeutic approach to the treatment of stroke in men.     

MiR-34b Protects Against Focal Cerebral Ischemia-Reperfusion (I/R) Injury in Rat by Targeting Keap1

Ischemic stroke is one of the leading causes of death and disability globally and has been regarded as a major public health problem. Understanding the mechanism of ischemia/reperfusion (I/R)-induced oxidative stress injury may provide new treatment for ischemic stroke. Kelch-like ECH-associated protein 1 (Keap1)/ NF-E2-related factor 2 (Nrf2)/ antioxidant response elements (ARE) signaling pathway has been considered to be the major cellular defense against oxidative stress. In the present study, our objective is to evaluate the molecular mechanism of miR-34b/Keap1 in modulating focal cerebral I/R induced oxidative injury. miR-34b was predicted to target the 3′-UTR of the rat Keap1. After focal cerebral I/R, miR-34b expression was downregulated in a time-dependent manner; miR-34b overexpression ameliorated I/R-induced oxidative stress injury in middle cerebral artery occlusion (MCAO) rats by reducing the infarction volume, the neurological severity scores, the levels of nitric oxide (NO) and (3-nitrotyrosine) 3-NT while increasing total (superoxide dismutases) SOD and manganese SOD (MnSOD). Through direct targeting, miR-34b could suppress the protein levels of Keap1 and increase the protein levels of Nrf2 and heme oxygenase (HO-1). Regarding the molecular mechanism, Keap1 overexpression exacerbated, while miR-34b improved H2O2-induced oxidative stress injury; the effect of miR-34b could be partially attenuated by Keap1 overexpression, suggesting that miR-34b modulated oxidative stress injury in vitro and in vivo through targeting Keap1. Taken together, we demonstrate that miR-34b protects against focal cerebral I/R-induced oxidative stress injury in MCAO rats and H2O2-induced oxidative stress injury in rat neuroblast B35 cells through targeting Keap1 and downstream Keap1/Nrf2 signaling pathway. We provided a novel mechanism of focal cerebral I/R injury from the perspective of miRNA regulation.     

Neuroprotective effects of 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), an antioxidant in middle cerebral artery occlusion induced focal cerebral ischemia in rats

OBJECTIVES: In the present study, we have investigated the neuroprotective potential of 6hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), in middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia. METHODS: Sprague-Dawley rats were subjected to 2 hours of MCAO followed by 22 or 70 hours of reperfusion. After reperfusion, rats were evaluated for neurological deficits and cerebral infarction. Brain malondialdehyde (MDA) level and in situ terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) were also estimated. RESULTS: Focal cerebral ischemia produced a significant infarct volume and neurological scores as compared with sham-operated animals. Cerebral ischemia reperfusion injury was associated with an increase in lipid peroxidation in ipsilateral and contralateral hemisphere of brain along with an increase in TUNEL positive cells in ipsilateral hemisphere of brain sections indicating oxidative stress and DNA fragmentation, respectively. Trolox (10 and 30 mg/kg, i.p.) treatment significantly decreased neurological damage which was evident from the reduction in infarct volume and neurological score. Trolox (30 mg/kg) also attenuated oxidative stress and DNA fragmentation. DISCUSSION: Oxidative stress-induced neuronal damage is implicated in the pathophysiology of cerebral ischemia. Our study suggests that Trolox is a potent neuroprotective agent in focal cerebral ischemia and its neuroprotective effects may be attributed to the reduction of lipid peroxidation and DNA fragmentation.