亚低温对体外缺氧缺糖损伤后神经元的保护作用及其对谷氨酸转运体、亲代谢型谷氨酸受体表达的影响

目的通过研究亚低温对体外缺氧缺糖损伤的神经细胞谷氨酸转运体(GLT-1)、亲代谢型谷氨酸受体(mGluR2/3)表达的影响,探讨亚低温的神经保护途径。方法分组培养大鼠大脑皮层细胞,亚低温组在33 C条件、常温组在37 C条件,缺氧缺糖培养2h后,复氧复糖37 C培养,经时(6h、12h、24h、3d)检测LDH释放量、GLT-1和mGluR2/3蛋白表达量。结果在复氧复糖后,两组LDH释放均呈现上升趋势,其中24h和3d亚低温组的LDH上升水平显著降低(P<0.05);两组GLT-1表达均呈现先下降后上升的趋势,其中6h和12h亚低温组的GLT-1下降水平显著降低(P<0.05);两组mGluR2/3表达均呈现上升趋势,其中12h和24h亚低温组的mGluR2/3升高水平显著增加(P<0.05)。结论亚低温能够在体外水平,通过抑制GLT-1蛋白的表达下调,促进mGluR2/3的表达上调,抑制神经元兴奋性损伤。     

亚低温对脑缺血后Smac表达和释放的影响

目的 观察脑缺血模型第2个线粒体源胱天酶激活剂(Smac)在脑缺血后不同时间点的表达和释放情况,探讨亚低温治疗与Smac表达的可能相关机制.方法 将大鼠随机分为常温假手术组、亚低温假手术组、常温缺血组和亚低温缺血组,用线栓法制作局部脑缺血模型.亚低温治疗3 h后,在脑缺血3、6、12、24 h及3、7 d后进行神经功能评分,并用免疫组化法、蛋白免疫印迹法检测Smac表达,实时定量PCR法测定Smac mRNA表达.结果 亚低温各组神经功能评分均较常温组降低(P＜0.05或P＜0.01).常温组Smac释放、蛋白及mRNA表达均表现为随时间延长而增高,约24 h达峰值,经亚低温治疗后各组数值均较相应常温组显著降低(P＜0.05或P＜0.01).结论 亚低温可能通过抑制Smac转录、表达和释放减轻细胞凋亡水平,从而发挥脑保护作用.     

局部亚低温对大鼠脑出血后血肿周围脑组织白介素-1β表达的影响

目的 观察局部亚低温对脑出血大鼠血肿周围脑组织的形态学变化和对白介素(IL)-1β表达的影响.方法 72只Wistar大鼠随机分为假手术组和脑出血后6 h、24 h、48 h、72 h、7 d组,每组再分为常温亚组和亚低温亚组,每个亚组6只大鼠.采用自体不凝血注人大鼠尾状核制备脑出血模型.各亚低温亚组注血后实施亚低温治疗4 h,维持脑温在(33±0.5)℃.观察血肿周围组织的形态学改变和IL-1β表达的变化.结果 亚低温亚组各时间点脑组织水肿明显轻于常温亚组;神经元变性坏死、炎症反应及胶质细胞增生程度明显轻于常温亚组.脑出血后6 h血肿周围脑组织IL-1β开始表达,48 h达高峰,7 d时仍明显高于对照亚组(均P＜0.01).脑出血24 h～7 d亚低温亚组IL-1β表达水平较相应时点常温亚组显著降低(均P＜0.01).结论 亚低温治疗能明显抑制血肿周围IL-1β的过度表达,减轻血肿周围脑组织的炎症反应.     

亚低温对大鼠局灶性脑缺血再灌注后HIF-1α及凋亡相关蛋白变化的影响

目的观察病变侧亚低温对大鼠局灶性脑缺血再灌注后HIF-1α和Bcl-2蛋白变化的影响。方法用线栓法制作大鼠大脑中动脉闭塞(MCAO)局灶脑缺血再灌注模型,随机分为正常组、假手术组、常温缺血组和亚低温缺血组,于缺血2h再灌注3h、6h、12h、24h、72h、7d后处死,其中亚低温组于缺血后30min实施病灶侧脑亚低温并持续4h。处死前进行神经功能缺陷评分、HE染色、免疫组化检测HIF-1α和Bcl-2的表达。结果 (1)神经功能缺陷评分:亚低温缺血组大鼠各时间点均明显低于常温缺血组(P0.05);(2)HIF-1α的表达:再灌注3h表达显著增高,至24h左右达高峰,其后又随之下降,亚低温缺血组各时间点表达与常温缺血组无显著性差异(P0.05);(3)Bcl-2的表达:再灌注3h增多,随再灌注时间的延长,其表达逐渐增多(P0.05),6h达高峰,其后又随之下降,亚低温缺血组各时间点表达明显高于常温缺血组(P0.05)。结论 HIF-1α在脑缺血早期就发挥重要的保护作用。Bcl-2在脑缺血再灌注损伤过程中主要起抑制细胞凋亡的作用。亚低温能增加Bcl-2的表达;能明显减轻缺血所致的损伤,并能明显抑制细胞调亡;对大鼠缺血后神经功能的恢复有确切的疗效。     

头孢曲松钠对脑缺血再灌注大鼠脑损伤和谷氨酸转运体-1表达的影响

目的 研究头抱曲松钠对脑缺血再灌注损伤大鼠的神经损害程度、脑组织水肿以及谷氨酸转运体-1(GLT-1)表达的影响.方法 线栓法阻塞大鼠大脑中动脉,并于缺血后2h进行再灌注,造成脑缺血再灌注损伤,大鼠分为假手术组(S组)、脑缺血再灌注组(M组)、头孢曲松钠组(C组)3组,C组于造模后6h给予头孢曲松钠200mg/(kg·d),共5d.脑缺血再灌注ld、3d、5d时进行大鼠神经行为学评分和脑组织含水量测定,RT-PCR检测GLT-1 mRNA表达.结果 M组、C组较S组大鼠神经行为学评分降低,脑组织含水量增加,GLT-1 mRNA表达相对量减少;M组上述改变在缺血再灌注3d时最明显,5d时有所减轻.在同一实验时间点,C组较M组大鼠神经行为学评分明显升高,脑组织含水量明显减少,GLT-1 mRNA表达量明显增加(P<0.01),且C组GLT-1 mRNA表达相对量随时间延长逐渐增加(P<0.05).结论 脑缺血再灌注损伤中,头孢曲松钠可能通过上调GLT-1 mRNA的表达来减轻脑缺血损伤和再灌注后脑水肿,从而发挥神经保护作用.     

大鼠脑梗死后脑水肿MRI动态变化及亚低温的干预效应

目的 探讨亚低温对大鼠脑梗死后脑水肿的干预作用.方法 12只雄性SD大鼠按随机数字表法分为对照组(r=6)及亚低温组(n=6).2组均采用线栓法阻塞大脑中动脉以制作局灶性脑梗死模型,亚低温组在造模后亚低温干预3h.在造模后6h、1d、3d、5d、7d时对2组大鼠行MRI扫描,测量计算梗死体积、水肿吸收率,梗死区T1WI、T2WI、FLAIR、DWI序列的信号强度比(SIR)及信号强度比相对变化率(△SIR).结果 亚低温组大鼠在造模后3d、5d、7d时梗死体积均明显小于对照组,差异有统计学意义(P＜0.05).亚低温组大鼠造模后7d相对于3d时水肿吸收率明显高于对照组,差异有统计学意义(P＜0.05).亚低温组大鼠在造模后3d、5d、7d时T1Wl序列SIR均明显高于对照组,T2WI及FLAIR序列SIR均明显低于对照组,差异有统计学意义(P＜0.05);亚低温组大鼠在造模后7d时DWI序列SIR明显低于对照组,差异有统计学意义(P＜0.05).亚低温组大鼠T2WI 、FLAIR及DWI序列△SIR均明显高于对照组,差异有统计学意义(P＜0.05).结论 亚低温对大鼠脑梗死后脑水肿有明显的抑制作用.     

亚低温对大鼠局灶性脑缺血后细胞凋亡及Caspase-3的影响

目的 探讨亚低温对脑缺血损伤的保护作用。方法 用原位末端标记（TUNEL）和原位杂交技术分别观察亚低温组、常温组脑缺血不同时间点神经细胞凋亡的变化及Caspase-3的表达。结果 （1）常温组脑缺血后凋亡神经细胞主要分布于缺血周围区，随着时间的延长凋亡细胞数逐渐增加，至12h达高峰，24h后开始下降，7d时仍高于假手术组；（2）亚低温组脑缺血后，凋亡神经细胞也主要位于缺血周围区，数量相对较少，其变化规律与常温组相似，同一时间点相比较，亚低温组均显著低于常温组；（3）常温组脑缺血2h后，神经细胞Caspase-3开始表达，并随着时间的延长而增强，24h达高峰，其后逐渐下降，至7d略高于假手术组；（4）亚低温组脑缺血后，神经细胞Caspase-3的表达也主要位于缺血周围区，其变化规律与常温组相似，同一时间点相比较，亚低温组均显著低于常温组。结论 脑缺血后，缺血周围区神经细胞的凋亡是一个动态的渐进过程，Caspase-3基因在介导脑缺血损伤神经元凋亡过程中起关键作用。亚低温对短暂性脑缺血后的神经元凋亡有明显的抑制作用，亚低温可能通过Caspase-3途径抵抗脑缺血损伤。     

亚低温对大鼠急性脑缺血再灌注损伤后脑组织半胱氨酸蛋白酶-12表达及神经元凋亡的影响

目的 观察亚低温对大鼠急性脑缺血再灌注损伤后脑组织半胱氨酸蛋白酶( caspase) - 12表达及神经元凋亡的影响.方法 56只大鼠随机分为正常组、假手术组、缺血组和亚低温组;后两组再分为再灌注3h、6h、12h、24h、72 h及7d6个亚组.应用线栓法制作大鼠大脑中动脉栓塞局灶性脑缺血(2 h)再灌注模型;亚低温组于缺血30 min实施病灶侧头部亚低温4h.各组大鼠在相应时点处死前行神经功能缺损评分(NDS);脑组织切片行HE、免疫组化及原位末端标记法(TUNEL)染色观察病理改变、caspase-12表达及神经元凋亡.结果 正常组及假手术组脑组织均未见明显病理改变及caspase-12和TUNEL阳性细胞.缺血组可见明显的脑梗死灶,大量神经元坏死及消失;亚低温组梗死灶较小,可见神经元固缩.与缺血组比较,亚低温组各时间点亚组NDS明显降低,脑组织caspase-12及TUNEL阳性细胞数明显减少(均P＜0.05).结论 急性脑缺血再灌注损伤后亚低温治疗可抑制脑组织caspase-12表达,减少神经元凋亡及神经功能的损害.     

亚低温对局灶性脑缺血再灌注大鼠脑皮质神经元凋亡及存活素、脑源性神经营养因子表达的影响

目的观察亚低温干预对局灶性脑缺血再灌注大鼠脑皮质神经元凋亡及存活累(Survivin)、脑源性神经营养因子(BDNF)表达的影响,探讨Survivin、BDNF在亚低温脑保护机制中的作用。方法采用线栓法制备成年雄性SD大鼠大脑中动脉闭塞(MCAO)局灶性脑缺血再灌注改良模型,将90只大鼠随机分为假手术组、常温缺血组和亚低温缺血组,缺血组分别于缺血3h再灌注3h、6h、12h、24h、48h、72h、7d处死,亚低温缺血组于缺血后10min实施全身亚低温持续3h。进行TUNEL染色及免疫组化染色,检测梗死灶周围皮质神经元凋亡数量和Sur-vivin、BDNF的表达水平。结果 (1)亚低温缺血组和常温缺血组于再灌注6h皮质区均出现TUNEL染色阳性细胞,72h达高峰,随后逐渐减少,两组内相邻时间点比较差异均有统计学意义(P<0.05);在相同时间点亚低温缺血组凋亡细胞数明显少于常温缺血组,两组间比较差异有统计学意义(P<0.05)。(2)亚低温缺血组于再灌注3hSurvivin、BDNF表达有所增加,BDNF于24h达高峰,Survivin于48h达高峰,随后表达逐渐降低,但7d时仍高于假手术组,常温缺血组表达趋势与之相似,两组各时间点Survivin、BDNF表达均高于假手术组,差异有统计学意义(P<0.05);除再灌注3h Survivin表达在亚低温缺血组与常温缺血组间无明显差异外,其余各时间点亚低温缺血组Sur-vivin、BDNF表达均高于常温缺血组,差异有统计学意义(P<0.05)。结论亚低温干预可抑制梗死灶周围脑皮质神经细胞凋亡,促进存活素及脑源性神经营养因子的表达,发挥脑保护作用。     

亚低温治疗对大鼠脑梗死后Bax和Bcl-2表达的影响

目的探讨亚低温对大鼠急性脑梗死Bax、Bcl-2表达的影响。方法清洁级（SPF）雄性健康SD大鼠,采用线栓法建立局灶性脑梗死模型,分别于缺血3、6、12 h给予亚低温治疗,缺血24 h取材观察。实验分常温组（大鼠10只）、亚低温3、6、12 h组（每组大鼠各10只）,假手术组（大鼠6只）,用TTC染色测定脑梗死体积,用免疫组化的方法检测Bax、Bcl-2的表达水平。结果与常温组比较,亚低温组脑梗死体积明显减少（P〈0.01）、Bcl-2表达上调、Bax表达下调（P〈0.05）。亚低温组脑梗死体积3 h〈6 h〈12 h组,Bcl-2表达3 h〉6 h〉12 h、Bax表达3 h〈6 h〈12 h（P〈0.05）。结论亚低温治疗可能通过抑制Bax和Bcl-2表达,从而抑制神经元凋亡、降低脑梗死体积,脑缺血后越早期给予亚低温治疗效果越好。     

Dual regulation of Ca2+‐dependent glutamate release from astrocytes: Vesicular glutamate transporters and cytosolic glutamate levels

Vesicular glutamate transporters (VGLUTs) are responsible for vesicular glutamate storage and exocytotic glutamate release in neurons and astrocytes. Here, we selectively and efficiently overexpressed individual VGLUT proteins (VGLUT1, 2, or 3) in solitary astrocytes and studied their effects on mechanical stimulation‐induced Ca²⁺‐dependent glutamate release. Neither VGLUT1 nor VGLUT2 overexpression changed the amount of glutamate release, whereas overexpression of VGLUT3 significantly enhanced Ca²⁺‐dependent glutamate release from astrocytes. None of the VGLUT overexpression affected mechanically induced intracellular Ca²⁺ increase. Inhibition of glutamine synthetase activity by L ‐methionine sulfoximine in astrocytes, which leads to increased cytosolic glutamate concentration, greatly increased their mechanically induced Ca²⁺‐dependent glutamate release, without affecting intracellular Ca²⁺ dynamics. Taken together, these data indicate that both VGLUT3 and the cytosolic concentration of glutamate are key limiting factors in regulating the Ca²⁺‐dependent release of glutamate from astrocytes. © 2009 Wiley‐Liss, Inc.     

Activation of Group II/III metabotropic glutamate receptors attenuates LPS-induced astroglial neurotoxicity via promoting glutamate uptake

Altered glial function that leads to oxidative stress and excitotoxicity may contribute to the initiation or progression of neuronal death in neurodegenerative diseases. We report the pivotal role of astroglial Group II and III metabotropic glutamate receptors (mGluR) against neurotoxicity. Activation of Group II or III mGluR on astrocytes with selective agonists DCG-IV or L-AP4 respectively inhibited astroglial lipopolysaccharide (LPS)-conditioned medium induced apoptosis of primary cultured mesencephalic neurons. Specific Group II or III mGluR antagonists APICA or MSOP completely abolished the neuroprotective effects of DCG-IV and L-AP4. Morphologic analysis showed that DCG-IV or L-AP4 could also attenuate the astroglial neurotoxicity to dopaminergic neurons. Measurement of extracellular glutamate concentration and [(3)H]-glutamate uptake showed that the restoration of glutamate uptake capability in LPS-treated astrocytes might be involved in the neuroprotective effects of activating astroglial Group II or III mGluR. Furthermore, we found that the repression of astroglial uptake function could be revived by GSH, and both Group II and III mGluR agonists could recover the endogenous reduced glutathione (GSH) level in LPS-treated astrocytes. These results suggested that the possible mechanisms of neuroprotection by either Type II or Type III mGluR activation may involve restoration of endogenous GSH, in turn affording recovery of astroglial capability to take up glutamate.     

谷氨酸受体脱敏机制及神经保护作用

谷氨酸受体在脊椎动物中枢神经系统中介导大多数的兴奋性传递，但是，谷氨酸受体的过度兴奋会引起导致神经元死亡的兴奋毒性过程。受体的脱敏可以阻断这一过度兴奋的过程。本文根据近年来的文献报道，对谷氨酸受体的脱敏机制以及受体脱敏所具有的神经保护作用作一简要论述。     

Influence of serum-free medium on the expression of glutamate transporters and the susceptibility to glutamate toxicity in cultured cortical neurons

The presence of glia and glial glutamate transporters seems to modify glutamate-mediated toxicity in neuronal cultures. In this work we cultured cortical cells in serum-containing medium and in a serum-free medium (Neurobasal medium + B27 supplement) and studied the expression of the glutamate transporters GLAST, GLT, and EAAC by immunocytochemistry and RT-PCR. The proportion of glial cells was below 10% in the Neurobasal medium and 46% in the serum-containing medium. Semiquantitative evaluation of the mRNA for the glutamate transporters showed similar amounts in cells grown in serum-free and serum-containing media. We detected immunoreactivity for the three transporters in both media, but EAAC was coexpressed with the neuronal marker MAP2, whereas GLAST and GLT predominated in nonneuronal cells. When the cultures were treated with glutamate for 15 min, the cultures in serum-containing medium showed a clear concentration-dependent neuronal death, whereas cells primed in this medium and switched to Neurobasal medium, as well as cells grown only in the latter, were less sensitive to glutamate concentrations up to 1 mM. A similar difference in the sensitivity to excitotoxicity was observed when the glutamate uptake inhibitor L-trans-2,4-pyrrolidine-dicarboxylate was applied during 6 hr, although the accumulation of extracellular glutamate was similar in the two media. We conclude that glutamate transporters with the culture conditions studied are sensitive to glutamate uptake inhibition and that Neurobasal/B27 medium protects cells against excitotoxicity.     

The role of glutamate and its receptors in central nervous system in stress-induced hyperalgesia

Purpose: To explore the potential mechanisms of glutamate and its receptors in stress-induced hyperalgesia.

Materials and methods: The stress-induced hyperalgesia, glutamate and its receptors are listed as key items in the pubmed database and the related articles are searched.

Results: Glutamate level is increased under stress and associated with stress-induced hyperalgesia. Moreover, the role of glutamate in stress-induced hyperalgesia depends on its subtypes of its receptors.

Conclusions: Increased glutamate during stress connect with ionotropic glutamate receptors can prompt hyperalgesia, but connect with metabotropic glutamate receptors can inhibit hyperalgesia.     

Activation of group III metabotropic glutamate receptors by endogenous glutamate protects against glutamate-mediated excitotoxicity in the hippocampus in vivo

Perfusion of 4-aminopyridine (4-AP) by microdialysis in the hippocampus produces intense epileptiform behavioral and electrical activity and neurodegeneration, resulting from a stimulated release of glutamate from nerve endings. In contrast, accumulation of extracellular glutamate by blockade of its transport in vivo in anesthetized rats is innocuous, and studies in vitro in brain slices suggest that under these conditions glutamate may activate presynaptic group III metabotropic glutamate receptors (mGluRs) and inhibit its own release. Therefore, using microdialysis, EEG recording, and histological evaluation, we studied the effect of increased endogenous extracellular glutamate by blockade of its transport with pyrrolidine dicarboxylic acid (PDC) on the excitotoxic action of 4-AP in the hippocampus of awake rats. We found that up to a 20-fold increase in extracellular glutamate during >90 min with PDC does not induce any sign of excitotoxicity. On the contrary, this glutamate increase notably protected against the 4-AP-induced seizures and neurodegeneration, and, remarkably, this protection was dependent on the time of perfusion with PDC and thus on the duration of extracellular glutamate accumulation. To test whether this protective action was mediated by the activation of group III mGluRs, we used specific antagonists of these receptors and found that they clearly prevented the protective effect of PDC, without affecting the accumulation of extracellular glutamate. We conclude that the spillover of the excess extracellular glutamate activates presynaptic group III mGluRs and inhibits the stimulatory effect of 4-AP on its release, thus preventing the activation of postsynaptic N-methyl-D-aspartate receptors and its deleterious consequences.     

Prefrontal cortex glutamate and extraversion

Extraversion is considered one of the core traits of personality. Low extraversion has been associated with increased vulnerability to affective and anxiety disorders. Brain imaging studies have linked extraversion, approach behaviour and the production of positive emotional states to the dorsolateral prefrontal cortex (DLPFC) and glutamatergic neurotransmission. However, the relationship between extraversion and glutamate in the DLPFC has not been investigated so far. In order to address this issue, absolute glutamate concentrations in the DLPFC and the visual cortex as a control region were measured by 3-Tesla proton magnetic resonance spectroscopy (1H-MRS) in 29 subjects with high and low extraversion. We found increased glutamate levels in the DLPFC of introverts as compared with extraverts. The increased glutamate concentration was specific for the DLPFC and negatively associated with state anxiety. Although preliminary, results indicate altered top-down control of DLPFC due to reduced glutamate concentration as a function of extraversion. Glutamate measurement with 1H-MRS may facilitate the understanding of biological underpinnings of personality traits and psychiatric diseases associated with dysfunctions in approach behaviour and the production of positive emotional states.     

Block of locust muscle glutamate receptors by delta-philanthotoxin occurs after receptor activations

One component (delta-philanthotoxin (delta-PTX) of the venom from the wasp Philanthus triangulum blocks transmission postsynaptically at excitatory synapses on locust muscle. delta-PTX depresses both the iontophoretic glutamate potential and the excitatory junctional current (e.j.c.) in a glutamate receptor activation-dependent manner. The rate of recovery from the effects of the toxin is reduced following either prolonged application of L-glutamate or repetitive iontophoretic application of this amino acid or high frequency neural stimulation of the muscle in the presence of delta-PTX. The decay phase of the e.j.c. is shortened by delta-PTX. The effects of delta-PTX on the e.j.c. are not voltage dependent. The open-close kinetics of glutamate channels in extrajunctional muscle membrane are modified by delta-PTX as shown by patch clamp analysis. The mean life time of the glutamate channel is reduced, whilst the mean interval between single opening events is increased with the events often occurring in bursts. These data are consistent with glutamate channel blocking by this toxin. It is proposed that the toxin blocks open channels gated by both junctional and extrajunctional glutamate receptors on locust muscle. It is further proposed that delta-PTX enters a compartment of the muscle through the glutamate open channels and that it can also block the open channels from this site.     

Transmembrane topology of the glutamate receptors

The glutamate receptor subunits were first thought to cross the cell membrane four times in a manner analogous to the neuronal nicotinic acetylcholine, GABA_A, and glycine receptors. This model led the field for nearly five years, although it was frequently in conflict with the data. Recently, comparisons with bacterial proteins, epitope tagging experiments, and the construction of chimeras has produced a new model of glutamate receptor topology that is novel and quite unlike any of the other receptors.     

Functional glutamate transport in rodent optic nerve axons and glia

Recent findings suggest that synaptic-type glutamate signaling operates between axons and their supporting glial cells. Glutamate reuptake will be a necessary component of such a system. Evidence for glutamate-mediated damage of oligodendroglia somata and processes in white matter suggests that glutamate regulation in white matter structures is also of clinical importance. The expression of glutamate transporters was examined in postnatal Day 14-17 (P14-17) mouse and in mature mouse and rat optic nerve using immuno-histochemistry and immuno-electron microscopy. EAAC1 was the major glutamate transporter detected in oligodendroglia cell membranes in both developing and mature optic nerve, while GLT-1 was the most heavily expressed transporter in the membranes of astrocytes. Both EAAC1 and GLAST were also seen in adult astrocytes, but there was little membrane expression of either at P14-17. GLAST, EAAC1, and GLT-1 were expressed in P14-17 axons with marked GLT-1 expression in the axolemma, while in mature axons EAAC1 was abundant at the node of Ranvier. Functional glutamate transport was probed in P14-17 mouse optic nerve revealing Na+-dependent, TBOA-blockable uptake of D-aspartate in astrocytes, axons, and oligodendrocytes. The data show that in addition to oligodendroglia and astrocytes, axons represent a potential source for extracellular glutamate in white matter during ischaemic conditions, and have the capacity for Na(+)-dependent glutamate uptake. The findings support the possibility of functional synaptic-type glutamate release from central axons, an event that will require axonal glutamate reuptake.