低压缺氧延迟预适应小鼠海马差异表达基因的筛选及鉴定研究

目的：探索低压缺氧延迟预适应小鼠海马差异表达基因。 方法： 将近交系Babl/c小鼠放入减压舱，模拟海拔 7 000 m高度减压2.5 h/d，连续3 d。第3次减压毕36 h后，提取海马总RNA，SMART PCR合成cDNA，经抑制消减杂交，建立消减cDNA文库。随机挑取文库单克隆，用反向Northern杂交，分别对来自于正、反向文库的452个和74个克隆进行了筛选。 结果： 用消减探针筛选时，217个基因片段的杂交信号在延迟预适应海马增加2倍以上，85个基因片段的杂交信号则降低66%以下。用未消减探针筛选时，135个基因片段的杂交信号在延迟预适应海马增加2倍以上，44个基因片段的杂交信号则降低66%以下。对部分基因片段测序显示，小鼠线粒体细胞色素C氧化酶亚单位1、线粒体NADH脱氢酶亚单位1和6、小鼠DSS1和克隆号为IMAGE:3582855的基因在延迟预适应海马表达增加。克隆号为IMAGE: 3593193的基因、与成年雄性小鼠嗅脑的一个cDNA高度相似的基因及与小鼠bladder RCB-0544 MBT-2 cDNA高度相似的基因在延迟预适应海马表达降低。 结论： 小鼠海马低压缺氧延迟预适应多种基因表达发生改变，它们可能是产生低压缺氧延迟预适应的重要机制之一。     

低氧预处理对大鼠海马神经元缺氧耐受性和bcl-2表达的影响

采用免疫组织化学方法观察了低氧预处理对大鼠海马神经元缺氧耐受性和 bcl-2表达的影响。结果显示 ,经低氧预处理的海马神经元缺氧 -复氧后 bcl-2表达较对照组明显增强 ,神经元损伤程度减轻 ,神经元存活数明显高于对照组。本结果表明 ,低氧预处理可使海马培养神经元对缺氧产生耐受 ,增加缺氧 -复氧后神经元 bcl-2的表达。提高神经元存活数     

低氧预适应可减少缺氧—复氧后大鼠海马培养神经元凋亡

用原位末端标记 ( TUNEL )法观察低氧预适应对大鼠海马培养神经元缺氧 -复氧后神经元凋亡的影响。结果显示 ,经低氧预适应的海马神经元缺氧 -复氧后凋亡神经元百分率明显低于对照组。本结果表明 ,低氧预适应可使体外培养的海马神经元对缺氧产生耐受 ,减少缺氧 -复氧后的海马神经元凋亡     

间歇性低压缺氧预处理对大鼠全脑缺血/再灌注海马CA1区Ngb和Bcl-2蛋白表达的影响

 目的：探讨间歇性低压缺氧预处理对大鼠全脑缺血/再灌注海马CA1区脑红蛋白（Ngb）和Bcl-2蛋白表达的影响。方法：将Wistar大鼠随机分为假手术组、低压缺氧预处理对照组、全脑缺血/再灌注组、低压缺氧预处理+全脑缺血/再灌注组4组,将间歇暴露于低压缺氧环境的大鼠作为低压缺氧预处理对照组。采用Pulsinelli四血管闭塞法复制大鼠全脑缺血/再灌注模型,夹闭颈总动脉造成全脑缺血8 min后再灌注。用硫堇染色法和免疫组织化学方法分别观察大鼠海马组织学改变和海马组织Ngb、Bcl-2蛋白表达变化。结果：低压缺氧预处理+全脑缺血/再灌注组大鼠海马CA1区存活细胞数较全脑缺血/再灌注组明显增加,其海马组织Ngb和Bcl-2蛋白表达量较全脑缺血/再灌注组显著升高。结论：间歇性低压缺氧预处理可能通过上调海马组织Ngb和Bcl-2蛋白的表达,减少全脑缺血再灌注后海马神经元的死亡而发挥神经保护作用。     

缺氧对大鼠海马神经元生物学功能的影响

为进一步探讨缺氧缺血如何诱导海马神经元损伤直至凋亡,明确缺氧对海马神经元生物学功能的影响及其相关机制,从而为缺血缺氧性脑病的防治提供实验依据,本研究以19d的SD胎鼠脑作为取材对象,经过条件培养基纯化建立海马神经元原代培养体系,通过MTT法、TUNEL法、免疫荧光、化学发光等方法检测海马神经元生长增殖活力、凋亡、Caspase-3活性等指标。结果显示缺氧可抑制SD大鼠海马神经元的生长增殖活力,并伴随着神经元凋亡和Caspase-3活性增高,且随着缺氧时间的增长程度加重。以上结果说明,缺氧通过诱导细胞凋亡导致SD大鼠海马神经元的损害,Caspase-3活性的激活可能是其重要的通路之一。     

脑缺血及后适应对树鼩海马内质网应激信号分子PERK及GRP78的影响

目的:探讨脑缺血及后适应对树鼩海马内质网应激信号分子蛋白激酶R样内质网激酶(PERK)及葡萄糖调节蛋白78(GRP78)的影响及后适应的脑保护机制。方法:光化学反应诱导树鼩局部血栓性脑缺血,于脑缺血后3.5 h夹闭、打开缺血侧颈总动脉交替3个循环(每次5 min)以复制缺血后适应模型。HE染色观察缺血侧海马神经元损伤及超微结构变化,RT-PCR检测脑缺血及后适应不同时间海马组织PERK及GRP78 mRNA表达的变化,免疫组织化学法与Western blot法检测PERK及GRP78的蛋白定位及表达变化。结果:海马神经元随脑缺血时间延长而损伤加重,缺血24 h损伤最为严重,后适应可减轻损伤。脑缺血4 h、24 h及72 h PERK的mRNA及蛋白表达较假手术组增高(P0.05),后适应组与相应的缺血组相比,PERK的mRNA及蛋白表达减少,4 h、24 h差异显著(P0.05);脑缺血4 h、24 h及72 h GRP78的mRNA及蛋白表达与假手术组无明显差异,后适应24 h组较缺血24 h组表达增高(P0.05)。结论:树鼩局部血栓性脑缺血可激活缺血侧海马内质网应激反应,引起PERK/e IF2α信号转导通路中相关分子PERK的mRNA及蛋白表达增高。缺血后适应处理通过下调PERK、上调GRP78的表达,减轻内质网应激反应,减少神经元损伤,具有一定的脑保护作用。     

缺血、缺氧对小鼠海马DNA甲基化的影响

目的建立缺血、缺氧脑片模型,探讨缺血、缺氧对小鼠海马的损伤及其机制。方法利用C57BL/6J小鼠建立海马脑片缺血、缺氧性脑损伤(HIBD)模型,采用免疫组织化学染色法和Western blotting法分析正常对照组海马脑片与HIBD实验组海马脑片炎症损伤、DNA甲基化相关酶的表达情况。结果 HIBD实验组海马脑片氧化应激、炎症损伤细胞明显多于对照组(P0.01),诱发海马应激损伤;同时HIBD实验组海马脑片DNA甲基化水平高于对照组(P0.01)。结论脑片缺血、缺氧可促发炎症反应对海马组织造成损伤,DNA甲基化水平升高,提示DNA甲基化可能参与缺血、缺氧组织损伤过程;机制可能是HIBD影响DNA代谢活动,诱导DNA甲基化水平升高,DNA甲基化调控相关基因表达产生氧化应激,促发炎症反应,对海马造成损伤。     

低氧预处理对缺氧-复氧后体外培养大鼠海马神经元Fos、Jun表达和神经元凋亡的影响

目的　观察低氧预处理对体外培养大鼠海马神经元缺氧 复氧后Fos、Jun表达和神经元凋亡的变化。方法　取培养 12d的两组 (对照组和低氧预处理组 )神经元 ,同时置于缺氧环境 (0 90l LN2 、0 10l LCO2 )中培养 4h后取出 ,置含 0 10l LCO2 和空气的培养箱内复氧培养 2 4和 72h。于不同时间取出 ,观察神经元存活数 ,并分别用抗Fos和Jun抗血清进行免疫组织化学染色 ,观察Fos、Jun表达阳性和阴性神经元数目 ,计数Fos和Jun表达神经元所占百分率。并用原位末端标记 (TUNEL)法和流式细胞术分别检测缺氧 复氧对体外培养海马神经元凋亡的影响。　结果　缺氧 复氧后大鼠海马培养神经元中Fos、Jun表达阳性神经元百分率和凋亡神经元百分率均较缺氧前显著增加。经低氧预处理的海马神经元缺氧 复氧后Fos、Jun表达神经元和凋亡神经元百分率均较对照组明显减少。神经元损伤程度减轻 ,神经元存活数明显高于对照组。　结论　低氧预处理可使培养中海马神经元对缺氧产生耐受 ,减少缺氧 复氧后神经元Fos和Jun表达 ,减少缺氧 复氧后神经元凋亡。     

脑缺血对昆明小鼠大脑动脉环结构的影响

目的　探讨昆明小鼠是否具有大脑动脉环 (Willis环 )结构。方法　结扎昆明小鼠双侧颈总动脉 ,经升主动脉灌注甲苯胺蓝 ,观察脑染色区域。结扎双侧颈总动脉 4、7和 10min ,存活 4 8h后观察海马CA1区神经元Caspase 3的表达。结果　双侧颈总动脉结扎后 ,双侧大脑半球未染色 ,而小脑、脑干染色 ,双侧海马冠状切面均未染色 ,而对照组全脑染色。结扎双侧颈总动脉 10min组 ,小鼠于术中或术后短时间内死亡。结扎双侧颈总动脉 4、7min存活 4 8h海马CA1区神经元Caspase 3免疫染色阳性 ,且 7min组阳性神经元数明显多于 4min组 ,差异有显著性 (P <0 0 1)。对照组未见阳性神经元。结论　昆明小鼠Willis环不完善 ,双侧颈总动脉结扎能引起严重的大脑皮质和海马缺血 ,这为脑缺血的研究提供了一种新的动物模型。     

低氧预适应后小鼠海马神经肽Y及突触的变化

目的 探讨低氧预适应产生神经保护作用的机制。方法 将小鼠随机分为对照组（H0组）和低氧组（H4组）,H4组为通过整体重复低氧建立的小鼠低氧预适应动物模型,H0组不进行低氧处理。用免疫组织化学方法检测小鼠海马神经肽Y(NPY)及突触体素（SYP）的表达,电镜观察海马CA1区的不对称突触和穿通型不对称突触形态及数量。结果 与H0组相比较,H4组海马NPY阳性细胞数量有中等量增多(n=30),SYP阳性细胞数量有明显增多(n=30),而海马CA1区的不对称突触和穿通型不对称突触数量减少(n=6)。结论 低氧预适应后海马的这些变化可能降低了神经元的兴奋性,从而增强了脑抵抗低氧/缺血的能力而产生神经保护作用。     

慢性低压低氧暴露对小鼠海马CA1区神经元树突棘形态及细丝蛋白A表达的影响

目的:探讨低压低氧暴露对小鼠海马CA1区神经元树突棘形态及细丝蛋白A表达的影响。方法:6～8周龄C57BL/6雄性小鼠分为常氧暴露7 d组、常氧暴露14 d组、低压低氧暴露7 d组和低压低氧暴露14 d组。低压低氧暴露组置于低压舱模拟6 000 m海拔高原进行低压低氧暴露。Golgi染色法观察小鼠海马CA1区树突的分支数,以及基树突棘和顶树突棘长度和密度的变化; Western blot方法检测小鼠海马细丝蛋白A表达水平的变化;免疫组织荧光染色法检测小鼠海马CA1区细丝蛋白A的表达及分布变化。结果:与常氧暴露组相比,低压低氧暴露后,小鼠海马CA1区树突分支数的差异无统计学显著性,但基树突棘和顶树突棘的长度显著增加(P 0. 05),密度显著降低(P 0. 01)。低压低氧暴露后,小鼠海马细丝蛋白A表达水平低于常氧暴露组(P 0. 01或P0. 05)。免疫组织荧光染色显示细丝蛋白A在小鼠海马CA1区表达,低压低氧暴露后,海马CA1区细丝蛋白A表达水平降低(P 0. 05)。结论:慢性低压低氧暴露可影响小鼠海马CA1区细丝蛋白A表达,并导致海马CA1区神经元树突棘形态发生改变。     

Hypobaric hypoxia-induced dendritic atrophy of hippocampal neurons is associated with cognitive impairment in adult rats

Simulated hypobaric hypoxia (HBH), resembling high altitude hypoxia severely affects the CNS and results in several physiological changes. The hippocampus is closely associated with learning and memory and an insult to this region affects cognition. Previous studies suggest that rapid or prolonged exposures to HBH are associated with psychomotor and cognitive impairments. The defense personnel, mountain climbers and rescue teams are exposed to such harsh environment and thus it demands a systematic study emphasizing the subtle effects of such extreme environments on cognitive function. Accordingly, this study evaluated the effect of hypobaric hypoxia on structural changes in the principal neurons of the hippocampus and learning in eight-arm radial maze. Adult male Wistar rats, subjected to simulated hypobaric hypoxia equivalent to an altitude of 6000 m for a period of 2 or 7 days, in a hypoxic chamber served as hypoxic group (HY). Rats housed in a similar chamber for the same period of time, without hypoxic exposure served as sham control (SC), while normal control (NC) group of rats were housed in standard laboratory conditions. The dendritic morphology of neurons in cornu ammonis region 1 (CA1) and cornu ammonis region 3 (CA3) was studied in Golgi-impregnated hippocampal sections. Exposure for 2 days to hypobaric hypoxia had minimal deleterious effects on the CA1 pyramidal neurons, while exposure for 7 days resulted in a significant decrease in the number of branching points, intersections and dendritic length. Unlike the CA1 pyramidal neurons, the CA3 neurons exhibited dendritic atrophy following both 2 and 7 days of hypoxic exposure. Further, hippocampal-dependent spatial learning was affected marginally following 2 day exposure, while 7 day exposure severely affected learning of the partially baited radial arm maze task. Our study suggests that dendritic atrophy in the hippocampus on exposure to HBH could be one of the bases for the cognitive deficits exhibited under such conditions.     

弥散富氧对高原颅脑损伤小鼠行为学及海马CA1区的影响

目的:探索低压低氧环境下弥散富氧对颅脑损伤小鼠的行为学以及海马CA1区的影响。方法:利用低压低氧舱模 拟海拔6 000 m环境,利用便携式膜法氧气机与IVC笼构建弥散富氧笼。将21只雄性C57小鼠随机分为颅脑损伤（TBI） 平原组（Sham组）、TBI低氧组（TLO组）和TBI富氧组（THO组）。TLO组与THO组置于模拟舱内饲养1周（24 h/d）,THO 组每天24 h富氧30%±3%（V/V）,Sham组置于当地海拔约400 m同时饲养。1周后,对小鼠体质量、行为学指标进行测量, 并观察海马体结构。结果:实验前各组小鼠体质量无统计学差异（P>0.05）;实验后TLO组与THO组体质量显著降低（P< 0.05）,且THO组较TLO组小鼠体质量显著上升（P<0.05）。与Sham组相比,TLO组垂直活跃度显著降低（P<0.05）;与 TLO组相比,THO组水平活跃度及垂直活跃度显著增强（P<0.05）。TLO组海马锥体细胞胞核体积缩小,染色加深;THO 组海马锥体细胞结构损伤显著减轻,排列相对整齐。结论:模拟海拔6 000 m进行弥散富氧干预可有效减轻高原TBI小鼠 海马损伤,降低其烦躁和焦虑程度,提高空间探索能力。     

Effect of hypoxia on the morphology of mouse striatal neurons

Symptoms of high altitude sickness including headache and neuropsychological dysfunction are thought to result from prolonged exposure to hypoxia. In order to explain how the brain adapts to lower oxygen pressure at high altitude, CD1 mice were exposed to 3 weeks of hypobaric hypoxic conditions. Analyses of the neuronal morphology of striatal medium spiny neurons (MSNs) revealed a significant decrease in dendritic length, yet no change in dendritic volume, in hypoxic mice relative to normoxic mice. Vascular data indicated an increase in blood vessel area in the striatum of mice exposed to prolonged hypoxia. A mouse model of high altitude exposure may assist in elucidating the mechanisms of cerebral adaptation to high altitudes in humans, and therefore aid in developing successful prevention techniques and treatment of problems associated with high altitude disease.     

Sevoflurane immediate preconditioning alters hypoxic membrane potential changes in rat hippocampal slices and improves recovery of CA1 pyramidal cells after hypoxia and global cerebral ischemia

Pretreatment with anesthetics before but not during hypoxia or ischemia can improve neuronal recovery after the insult. Sevoflurane, a volatile anesthetic agent, improved neuronal recovery subsequent to 10 min of global cerebral ischemia when it was present for 1 h before the ischemia. The mean number of intact hippocampal cornus ammonis 1 (CA1) pyramidal neurons in rats subjected to cerebral ischemia without any pretreatment was 17+/-5 (neurons/mm+/-S.D.) 6 weeks after the ischemia; na?ve, non-ischemic rats had 177+/-5 neurons/mm. Rats pretreated with either 2% or 4% sevoflurane had 112+/-57 or 150+/-15 CA1 pyramidal neurons/mm respectively (P<0.01) 6 weeks after global cerebral ischemia. In order to examine the mechanisms of protection we used hypoxia to generate energy deprivation. Intracellular recordings were made from CA1 pyramidal neurons in rat hippocampal slices; the recovery of resting and action potentials after hypoxia was used as an indicator of neuronal survival. Pretreatment with 4% sevoflurane for 15 min improved neuronal recovery 1 h after the hypoxia; 90% of the sevoflurane-pretreated neurons recovered while none (0%) of the untreated neurons recovered. Pretreatment with sevoflurane enhanced the hypoxic hyperpolarization(-6.4+/-0.6 vs. -3.3+/-0.3 mV) and reduced the final level of the hypoxic depolarization (-39+/-6 vs. -0.3+/-2 mV) during hypoxia. Chelerythrine (5 muM), a protein kinase C/protein kinase M inhibitor, blocked both the improved recovery (10%) and the electrophysiological changes with 4% sevoflurane preconditioning. Two percent sevoflurane for 15 min before hypoxia did not improve recovery (0% recovery both groups) and did not enhance the hypoxic hyperpolarization or reduce the final depolarization during hypoxia. However if 2% sevoflurane was present for 1 h before the hypoxia then there was significantly improved recovery, enhanced hypoxic hyperpolarization, and reduced final depolarization. Thus we conclude that sevoflurane preconditioning improves recovery in both in vivo and in vitro models of energy deprivation and that preconditioning enhances the hypoxic hyperpolarization and reduces the hypoxic depolarization. Anesthetic preconditioning may protect neurons from ischemia by altering the electrophysiological changes a neuron undergoes during energy deprivation.     

Ascorbic acid and α-tocopherol supplement starting prenatally enhances the resistance of nucleus tractus solitarius neurons to hypobaric hypoxic challenge

Hypobaric hypoxia, encountered at high altitude, could result in severe consequences. Ascorbic acid (AA) and α-tocopherol (αTC), the two readily available over-the-counter antioxidants, are known to protect nervous tissue against oxidative stress. Here we study whether AA or αTC supplement starting prenatally protects animals against hypobaric hypoxic challenge at adulthood. Expressions of c-fos and the NR1 subunit of the N-methyl-d-aspartate receptors in the nucleus tractus solitarius (NTS) subserving cardiorespiratory functions were investigated. AA and αTC supplement reduced the number of c-fos immunoreactive neurons and intensity of NR1 expression in young and adult animals under normoxia. The treatment, in addition, attenuated the activation of NTS neurons, in terms of c-fos and NR1 expressions, and reduced the anxiety behaviors of adult rats subjected to hypobaric hypoxic challenge. Reduction of c-fos immunoreactive neurons was found concentrated in the chemoreceptor, baroreceptor, and tracheobronchial tree NTS subnuclei that receive corresponding afferents. The protective effect was not found in normal adult animals supplemented with AA or αTC a week before hypobaric hypoxic challenge. In short, prenatal and sustained AA or αTC supplement altered NTS substrate and ameliorated animals’ reactions to hypobaric hypoxic insult, suggesting that this may be considered to protect animals from hypoxic insults from young to adult.     

Exercise at simulated high altitude facilitates the increase in capillarity in skeletal muscle of rats

Exercise at simulated high altitude facilitates the increase in capillarity in skeletal muscle of rats     

Iptakalim protects against hypoxic brain injury through multiple pathways associated with ATP-sensitive potassium channels

The rapid and irreversible brain injury produced by anoxia when stroke occurs is well known. Cumulative evidence suggests that the activation of neuronal ATP-sensitive potassium (KATP) channels may have inherent protective effects during cerebral hypoxia, yet little information regarding the therapeutic effects of KATP channel openers is available. We hypothesized that pretreatment with a KATP channel opener might protect against brain injury induced by cerebral hypoxia. In this study, adult Wistar rats were treated with iptakalim, a new KATP channel opener, which is selective for SUR2 type KATP channels, by intragastric administration at doses of 2, 4, or 8 mg/kg/day for 7 days before being exposed to simulated high altitude equivalent to 8000 m in a decompression chamber for 8 h leading to hypoxic brain injury. By light and electron microscopic images, we observed that hypobaric hypoxia-induced brain injury could be prevented by pretreatment with iptakalim. It was also observed that the permeability of the blood-brain barrier, water content, Na+ and Ca2+ concentration, and activities of Na+,K+-ATPase, Ca2+-ATPase and Mg2+-ATPase in rat cerebral cortex were increased and the gene expression of the occludin or aquaporin-4 was down- or upregulated respectively, which could also be prevented by the pretreatment with iptakalim at doses of 2, 4, or 8 mg/kg in a dose-dependent manner. Furthermore, we found that in an oxygen-and-glucose-deprived model in ECV304 cells and rat cortical astrocytes, pretreatment with iptakalim significantly increased survived cell rates and decreased lactate dehydrogenate release, which were significantly antagonized by glibenclamide, a K(ATP) channel blocker. We conclude that iptakalim is a promising drug that may protect against brain injury induced by acute hypobaric hypoxia through multiple pathways associated with SUR2-type K(ATP) channels, suggesting a new therapeutic strategy for stroke treatment.