Vitamin E isoforms alpha-tocotrienol and gamma-tocopherol prevent cerebral infarction in mice

Alpha-tocopherol and its derivatives have been shown to be effective in reducing cerebral ischemia-induced brain damage. However, the effects of other vitamin E isoforms have not been characterized. In the present study, we investigated the effects of six different isoforms of vitamin E on the ischemic brain damage in the mice middle cerebral artery (MCA) occlusion model. All vitamin E isoforms were injected i.v., twice, immediately before and 3 h after the occlusion. Alpha-tocopherol (2 mM), alpha-tocotrienol (0.2 and 2 mM) and gamma-tocopherol (0.2 and 2 mM) significantly decreased the size of the cerebral infarcts 1 day after the MCA occlusion, while gamma-tocotrienol, delta-tocopherol and delta-tocotrienol showed no effect on the cerebral infarcts. These results suggest that alpha-tocotrienol and gamma-tocopherol are potent and effective agents for preventing cerebral infarction induced by MCA occlusion.     

高压氧预处理通过HIF-1α/VEGF通路减轻大脑缺血再灌注损伤

目的:探讨缺氧诱导因子1α(HIF-1α)/血管内皮生长因子(VEGF)通路在高压氧(HO)预处理减轻缺血再灌注(IR)模型大鼠大脑损伤过程中的作用。方法:选择SPF级健康雄性成年SD大鼠32只,使用随机数字软件将其分为对照组(control组)、IR组、HO-IR组和HO-IR-HIF-1α抑制剂组(HO-IR-I组)。IR模型通过大脑中动脉栓塞法制作,对照组仅分离暴露相应血管。HO-IR组和HO-IR-I组大鼠均在制模前在动物高压舱内进行HO治疗4周(每天1次);HO-IR-I组每天在HO预处理前,经腹腔注射4 mg/kg的HIF-1α抑制剂YC-1[3-(5’-hydroxymethyl-2’-furyl)-1-benzylindazol]。在制作模型第1天和第7天行神经行为学评估,第7天观察结束后麻醉处死大鼠,取脑组织测量梗死体积,Western blot检测HIF-1α/VEGF通路相关蛋白及凋亡相关蛋白Bax和Bcl-2的水平,TUNEL法检测凋亡细胞数。结果:与control组比较,IR组、HO-IR组和HO-IR-I组大鼠的神经功能评分降低,脑梗死体积比例及HIF-1α、VEGF、Bax和Bcl-2的蛋白表达均增加,凋亡细胞数量亦增加(P0.05);与IR组比较;HO-IR组和HO-IR-I组的神经功能评分升高,HIF-1α、VEGF和抑凋亡蛋白Bcl-2表达上调,脑梗死体积比例降低,促凋亡蛋白Bax表达下调,凋亡细胞数量减少(P0.05);与HO-IR组比较,HO-IR-I组的神经功能评分降低,HIF-1α、VEGF和抑凋亡蛋白Bcl-2表达下调,脑梗死体积比例升高,促凋亡蛋白Bax表达上调,凋亡细胞数量增加(P0.05)。结论:HO预处理减轻大脑IR损伤的机制可能与通过诱导HIF-1α/VEGF通路调节凋亡进程有关。     

Delayed treatment of Na+/H+ exchange inhibitor SM-20220 reduces infarct size in both transient and permanent middle cerebral artery occlusion in rats

SM-20220 (N-(aminoiminomethyl)-1-methyl-1H-indole-2-carboxamide methanesulfonate) is a Na+/H+ exchanger (NHE) inhibitor which has been shown to attenuate cerebral edema in the rat transient focal ischemia model. However, to date, the effect of SM-20220 on cerebral infarction has not been examined. The present experiments were designed to investigate these effects, using both transient and permanent middle cerebral artery (MCA) occlusion models in rats. A dose of 1 mg/kg given intravenously 30 min after the onset of transient MCA occlusion reduced the infarcted area. In the permanent MCA occlusion model, SM-20220 reduced the infarcted area when treatment was delayed for 5, 30 or 60 min after the onset of ischemia. The present results show that NHE has a crucial role in the pathogenesis of ischemic brain damage. This NHE inhibitor may be useful for treating stroke because of its effectiveness with both forms of ischemia and because of its postischemic administration.     

A new method of inducing selective brain hypothermia with saline perfusion into the subdural space: effects on transient cerebral ischemia in cats

In this study, we tested brain surface cooling as a new method of inducing selective brain hypothermia, and evaluated its effects on focal cerebral ischemia using a cat model of transient middle cerebral artery (MCA) occlusion. Cats underwent 1 h of MCA occlusion followed by 5 h of reperfusion. Brain surface cooling was induced for 4 h during and after MCA occlusion in the hypothermia group, but not in the normothermia group. Brain surface cooling was performed using saline perfusion into the subdural space. Rectal temperature, brain surface temperature, and deep brain temperature were monitored, and regional cerebral blood flow (rCBF) and somatosensory evoked potential (SEP) were serially measured. After 5 h of reperfusion, water content was also measured. Although the rectal temperature was maintained at about 37 degrees C, the brain surface temperature decreased rapidly to 33 degrees C and was maintained at that temperature. For 3 h following reperfusion, the rCBF was lower in the hypothermia group than in the normothermia group. At 4 and 5 h after reperfusion, the recovery of SEP amplitude was significantly more enhanced in the hypothermia group than in the normothermia group. In the gray matter, the water content was significantly more diminished in the hypothermia group than in the normothermia group. These results demonstrate that our method is useful for protecting the ischemic brain from a transient MCA occlusion. This method may be adapted for neurological surgery.     

黄芩茎叶黄酮对慢性脑缺血大鼠脑内NMDA受体和VEGF表达的影响

目的: 探讨黄芩茎叶黄酮(SSF)对慢性永久性脑缺血大鼠脑内N-甲基-D-天门冬氨酸受体(NMDAR)和血管内皮生长因子(VEGF)表达的影响。方法: 雌性Sprague-Dawley(SD)大鼠双侧颈总动脉结扎2个月制备慢性脑缺血记忆障碍模型,通过RT-PCR测定海马细胞中NMDAR mRNA和皮层细胞中VEGF mRNA的含量。结果: 与假手术组相比,模型组大鼠海马细胞中NMDAR1 mRNA、NMDAR2A mRNA和NMDAR2B mRNA 的含量显著增加(P<0.01),皮层细胞中VEGF mRNA的含量明显增加(P<0.01);而 SSF 17.5 mg·kg^-1·d^-1、35 mg·kg^-1·d^-1和70 mg·kg^-1·d^-1灌胃给药38 d,能明显降低海马细胞中NMDAR1 mRNA、NMDAR2A mRNA和NMDAR2B mRNA 的含量,显著增加皮层细胞中VEGF mRNA的含量。结论: SSF 能够明显降低脑缺血大鼠海马细胞中NMDAR 的表达,明显增加皮层细胞中VEGF 的表达,提示SSF可能通过影响NMDAR和VEGF的生成发挥神经保护作用。     

Neuronal vulnerability of stroke-prone spontaneously hypertensive rats to ischemia and its prevention with antioxidants such as vitamin E

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) develop severe hypertension, and more than 95% of them die of cerebral stroke. Hypoxic stimulation followed by oxygen reperfusion induces neuronal damage in both normotensive Wistar Kyoto/Izm (WKY/Izm) and SHRSP/Izm rats, and the percentage of neurons that undergo apoptosis during hypoxia-reperfusion is markedly higher in SHRSP/Izm rats than in WKY/Izm rats. The biochemical characteristics of the SHRSP/Izm rats, unlike those of WKY/Izm rats, might act as a factor in the stroke proneness of SHRSP/Izm rats. In the hippocampus, the formation of hydroxyl radicals and the cerebral blood flow-independent formation of nitric oxide (NO) were strongly increased after reperfusion in SHRSP/Izm rats, and the neuronal expression of the thioredoxin and Bcl-2 genes was significantly decreased in the SHRSP/Izm rats compared with the WKY/Izm rats. On the other hand, the effects of antioxidants against neuronal death associated with cerebral ischemia-reperfusion were stronger in the SHRSP/Izm rats, in which the addition of vitamin E or ebselen almost completely inhibited neuronal death. Namely, the addition of 100 μg/ml of vitamin E under hypoxia/reoxygenation (H/R) conditions completely inhibited WKY and SHRSP/Izm neuronal death. Vitamin E exerts a marked inhibitory effect against neuronal damage via its incorporation into mitochondrial membranes, where it captures reactive oxygen and free radicals. The susceptibility of neurons to apoptosis in SHRSP/Izm rats is partly due to an insufficiency of mitochondrial redox regulation and apoptosis-inhibitory proteins. In this review, we describe the neuronal vulnerability of SHRSP/Izm rats induced by cerebral ischemia and the effects of antioxidants such as vitamin E.     

Exercise pre-conditioning reduces brain damage in ischemic rats that may be associated with regional angiogenesis and cellular overexpression of neurotrophin

There is increasing evidence that physical activity is associated with a decreased stroke risk. The purpose of this study was to determine if exercise could also reduce brain damage in rats subjected to transient middle cerebral artery (MCA) occlusion, and if the reduced brain injury is associated with angiogenesis as well as cellular expression of the nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in regions supplied by the MCA. Adult male Sprague Dawley rats (n=36) exercised 30 min each day for 3 weeks on a treadmill on which repetitive locomotor movement was required. Then, stroke was induced by a 2-h MCA occlusion using an intraluminal filament, followed by 48 h of reperfusion. In addition to the two exercised groups of animals with or without MCA occlusion, there were two other groups of animals, with or without MCA occlusion, housed for the same duration and used as non-exercised controls. Brain damage in ischemic rats was evaluated by neurologic deficits and infarct volume. Exercise preconditioned and non-exercised brains were processed for immunocytochemistry to quantify the number of microvessels or NGF- and BDNF-labeled cells. Pre-ischemic motor activity significantly (P<0.01) reduced neurologic deficits and infarct volume in the frontoparietal cortex and dorsolateral striatum. Cellular expressions of NGF and BDNF were significantly (P<0.01) increased in cortex (neuron) and striatum (glia) of rats under the exercise condition. Significant (P<0.01) increases in microvessel density were found in striatum. Physical activity reduced stroke damage. The reduced brain damage may be attributable to angiogenesis and neurotrophin overexpression in brain regions supplied by the MCA following exercise.     

大鼠实验性MCA区缺血再灌流模型的改进和可靠性探讨

局灶性脑缺血模型是研究缺血性脑血管病的重要模型.目前国外用血管内栓线技术建立的局灶性脑缺血大鼠模型存在两方面的不足:(1)栓线所用4-0外科缝线较软,手术前需经专门处理,使实验程序繁琐;(2)由于大鼠存在年龄、体重以及种族的差异,使用统一栓线往往造成受累脑组织缺血程度不一.我们采用不同直径(1.2号、1.5号、2.0号)和不同长度(1.5—2. 5cm)的市售单股尼龙线与不同年龄、体重的成年SD大鼠匹配使用,建立了恒定的大脑中动脉梗塞(MCAO)模型,实验证明该模型可靠性和重复性好.     

P>灵芝孢子防止妊娠高血压大鼠的胎鼠及其生后幼鼠海马细胞增殖下降和神经元存活减少/P>

目的 探讨灵芝孢子对妊娠高血压大鼠的胎鼠及幼鼠海马细胞增殖下降和神经元存活减少的干预作用.方法 40只SD妊娠大鼠分为正常对照组、N硝基左旋精氨酸甲酯(L-NAME) 蒸馏水组、L-NAME 精氨酸组、L-NAME 灵芝孢子组.采用免疫组织化学、Western blottin、RT-PCR、流式细胞计数和电镜等技术对海马组织进行检测.结果 应用L-NAME后,E21海马低氧诱导因子-1α(HIF-1α)和血管内皮生长因子(VEGF)的表达增加,直到P30时仍有表达.E21海马微血管密度增高,P30海马毛细血管结构异常.E21海马细胞的增殖下降,P30海马神经元减少.应用灵芝孢子后,E21海马HIF-1α和VEGF低水平表达,在P30时则未见表达.E21海马微血管密度达到正常水平,P30海马毛细血管结构正常.E21海马细胞增殖上升,P30海马神经元恢复性增多.结论 灵芝孢子能防止妊娠高血压大鼠的胎鼠及幼鼠海马细胞增殖下降和神经元存活减少.     

Vasoactive intestinal peptide in rats with focal cerebral ischemia enhances angiogenesis

We studied the effect of vasoactive intestinal peptide (VIP) on angiogenesis in the ischemic boundary area after focal cerebral ischemia. Adult male Sprague–Dawley rats underwent middle cerebral artery occlusion for 2 h. A single dose of VIP was given via i.c.v. injection at the beginning of reperfusion. Immunohistochemistry and Western blotting were performed to assay angiogenesis and brain levels of vascular endothelial growth factor (VEGF) protein, respectively. In addition, the expression of VEGF and its receptors (flt-1 and flk-1), as well as endothelial proliferation, was measured using rat brain microvascular endothelial cells. Immunohistochemical analyses revealed significant (P<0.05) increases in the numbers of bromodeoxyuridine (BrdU) positive endothelial cells and microvessels at the boundary of the ischemic lesion in rats treated with VIP compared with rats treated with saline. Western blotting analysis showed that treatment with VIP significantly (P<0.05) raised VEGF levels in the ischemic hemisphere. In addition, treatment with VIP increased flt-1 and flk-1 immunoreactivity in endothelial cells. In vitro, incubation with VIP significantly (P<0.01) increased the proliferation of endothelial cells and induced the expression of VEGF, flt-1 and flk-1 in endothelial cells. The stimulatory effect of VIP on the proliferation of endothelial cells was significantly (P<0.01) inhibited by SU5416, a selective inhibitor of VEGF receptor tyrosine kinase. Our data suggest that treatment with VIP enhances angiogenesis in the ischemic brain, and this effect may be mediated by increases in levels of VEGF and its receptors.     

Expression of Fos-like immunoreactivity in the brain and spinal cord of rats following middle cerebral artery occlusion

 This study examined c-fos protein expression in the brain and spinal cord of rats following permanent occlusion of the middle cerebral artery (MCA) above the rhinal fissure. At 1 h after right-sided MCA occlusion, Fos-like immunoreactivity (Fos-LI) was detected in neurons not only in the ipsilateral cerebral cortex but also in the spinal cord. In the latter, Fos-LI was localized in the nucleus and perikarya of neurons in the grey matter, notably the large motor neurons in the ventral horn. Fos-LI was most intense at 2–4 h, but became undetectable after 48 h in the cerebral cortex and 72 h in the spinal cord. In sham-operated animals, Fos-LI was almost undetectable or virtually absent. It was also not detected in the core territory supplied by the MCA at any time points after arterial occlusion. When the ischaemia-induced neuronal damage in both the cerebral cortex and spinal cord was evaluated by Nissl staining, some neurons appeared atrophic. We conclude that the induction of Fos-LI in neurons of the cerebral cortex and spinal cord is linked respectively to early onset–short stimulation and persistent excitatory or disinhibition phenomenon as a result of focal ischaemic brain injury. Received: 16 September 1996 / Accepted: 29 November 1996     

丰富环境对大鼠局灶性脑梗死后海马区微血管新生的影响

目的研究丰富环境对局灶性脑梗死后大鼠海马区微血管新生的影响。方法采用开颅电凝法制作SD大鼠右侧大脑中动脉缺血（MCAO）模型,术后24h随机分为丰富环境组（EE组）和标准环境组（SE组）。另设假手术组（Sham组）。免疫组织化学法检测大鼠缺血侧海马区血管内皮生长因子（VEGF）、Ⅷ因子表达,测定微血管密度。结果EE组和SE组大鼠缺血侧海马区术后1d VEGF开始表达,3d达高峰,EE组大鼠经干预后后期VEGF和微血管数目高于SE组大鼠。结论丰富环境可促进脑梗死大鼠海马区VEGF、Ⅵ因子表达,促进微血管新生,有利于脑损伤修复。     

mTOR activates hypoxia-inducible factor-1α and inhibits neuronal apoptosis in the developing rat brain during the early phase after hypoxia-ischemia

The mammalian target of rapamycin (mTOR) exerts neuroprotective effects under hypoxic or ischemic conditions. To explore whether mTOR participates in neuroprotective signaling through regulation of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and neuronal apoptosis in developing rat brain with hypoxia-ischemia (HI), we operated on postnatal day 10 rats by ligating the common carotid artery followed by exposure to systemic hypoxia. Brains were collected at various intervals to detect the expression of mTOR, phosphorylated mTOR (p-mTOR), HIF-1α, VEGF and cleaved caspase 3 (CC3), using immunohistochemistry and Western blot analysis. We also used terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) to detect neuronal apoptosis. The p-mTOR protein expression increased at 2 h after HI, peaked at 8 h, lasted 24 h, and then dropped to the basal level. Also, the expression of HIF-1α and VEGF was significantly enhanced and peaked at 8 h after HI. Up-regulated expression of CC3 was observed at 2 h, peaked at 24 h, and lasted 72 h after HI. Increased neuronal apoptosis is associated with reduced HIF-1α and VEGF expression. Furthermore, pretreatment with rapamycin, a mTOR specific inhibitor, significantly inhibited HIF-1α and VEGF protein after HI. The expression of CC3 and the number of TUNEL-positive cells were up-regulated at 8 h and down-regulated at 24 h after HI in the rapamycin-treated group. Our findings suggest that mTOR may participate in the regulation of HIF-1α, VEGF and neuronal apoptosis, serving neuroprotective functions after HI in developing rat brain.     

脂肪来源的干细胞移植对大鼠脑缺血后TGF-β1表达的影响

目的:探讨脂肪来源的干细胞(ADSC)移植促进大鼠脑缺血后微血管生成作用的可能机制。方法:108只成年雄性Sprague-Darley大鼠,随机分为假手术组(Sham组)、局灶性脑缺血组(MCAO组)、溶剂对照组(vehicle组)和ADSC治疗组(ADSC组),采用改良的Longa线栓法制作大脑中动脉栓塞(MCAO)模型,ADSC移植前用CFSE标记,ADSC组于造模成功1 d后经侧脑室注射入30μL的ADSC细胞悬液,内含1×106细胞,vehicle组则注射同等剂量的PBS。术后4d、7 d和14 d分批断头取脑,检测缺血区脑组织TGF-β1表达的变化。结果:ADSC组术后4 d、7 d和14 d脑组织中TGF-β1的mRNA和蛋白表达水平均较MCAO组和vehicle组明显增高,同时显示脑缺血后经侧脑室移植的ADSC能够存活并分泌生长因子TGF-β1。结论:ADSC移植促进脑缺血大鼠缺血区微血管生成的机制可能与促进TGF-β1的表达有关。     

In vivo effects of vitamin E deficiency on the intracellular monovalent electrolyte concentrations in brain and liver of rat. An energy dispersive X-ray microanalytic study

Vitamin E is known to play a protective role for cell membranes against free-radical attacks. Vitamin E deficiency causes a rapid macroscopic ageing of rats. On the other hand, during normal ageing, cell membranes undergo functional alterations resulting in an increased intracellular potassium concentration in brain and liver cells. Therefore, it was of interest to study whether vitamin E deficientcy produces similar alterations in young rats. Female Wistar rats were fed with a vitamin E deficiency diet from 1 month of age for 10 months. The parietal brain cortex and the liver were analyzed by means of a quantitative energy dispersive X-ray microanalytic method using a JEOL JSM-35C-EDAX-711-NOVA-3 system. Monovalent electrolyte contents as well as the water content of the cells were determined in 5 treated and 5 control animals. Water content was measured by analyzing the potassium content in aqueous, frozen state, and again in the dry mass of the cells. On the basis of these data, a computer program calculated the water proportions. Average values for 200 or more cells of each organ per group revealed a significant increase in the intracellular potassium content of the brain cells, whereas the sodium and chloride contents increased to a much lower extent. There was a 2.6% loss of intracellular water in the brain cells in the vitamin E deficient group. The liver monovalent ions and water content remained unchanged. The results obtained are discussed in terms of the membrane hypothesis of ageing.     

Candesartan pretreatment is cerebroprotective in a rat model of endothelin-1-induced middle cerebral artery occlusion

Endogenous levels of angiotensin II (Ang II) are increased in the cortex and hypothalamus following stroke, and Ang II type 1 receptor blockers (ARBs) have been shown to attenuate the deleterious effects in animal stroke models using middle cerebral artery (MCA) intraluminal occlusion procedures. However, the endothelin-1 (ET-1)-induced middle cerebral artery occlusion (MCAO) model of cerebral ischaemia is thought to more closely mimic the temporal events of an embolic stroke. This method provides rapid occlusion of the MCA and a gradual reperfusion that lasts for 16–22 h. The aim of the present study was to evaluate whether systemic administration of an ARB prior to ET-1-induced MCAO would provide cerebroprotection during this model of ischaemic stroke. Injection of 3 μl of 80 μ m ET-1 adjacent to the MCA resulted in complete occlusion of the vessel that resolved over a period of 30–40 min. Following ET-1-induced MCAO, rats had significant neurological impairment, as well as an infarct that consisted of 30% of the ipsilateral grey matter. Systemic pretreatment with 0.2 mg kg⁻¹ day⁻¹ candesartan for 7 days attenuated both the infarct size and the neurological deficits caused by ET-1-induced MCAO without altering blood pressure. This study confirms the cerebroprotective properties of ARBs during ischaemic stroke and validates the ET-1-induced MCAO model for examination of the role of the brain renin–angiotensin system in ischaemic stroke.