亚低温对大鼠缺血性脑损伤后JAK1-STAT1通路的作用

目的 观察大鼠局灶性脑缺血再灌注后不同时间点JAK1和STAT1的表达情况及实施亚低温后两者的变化,进一步探讨亚低温的脑保护作用.方法 用线栓法制做大鼠大脑中动脉栓塞(middle cerebral artery occlusion, MCAO)局灶性脑缺血再灌注模型,同时给予亚低温治疗.免疫组化检测JAK1和STAT1的表达,Western blot检测STAT1蛋白的表达.结果 与假手术组相比,常温缺血再灌注后6 h JAK1和STAT1的表达开始增强,至24 h达高峰;亚低温缺血组各时间点表达均明显少于常温缺血组(P<0.05).结论 脑缺血再灌注损伤激活了具有促凋亡作用的JAK1-STAT1通路,亚低温可能通过抑制JAK1和STAT1的表达发挥缺血后抗神经元凋亡的作用.     

亚低温对脑缺血再灌注后大鼠海马齿状回MAP-2表达的影响

目的:观察大鼠脑缺血再灌注损伤后海马齿状回微管相关蛋白(MAP-2)变化规律及其意义;探讨亚低温对大鼠脑缺血再灌注损伤的保护作用.方法:制备大鼠缺血再灌注动物模型,将大鼠分为亚低温组、常温组、假手术对照组,分别在不同时间点断头取脑,取材前应用神经功能等级评分观察脑缺血再灌注后行为功能的恢复,连续切片作MAP-2的免疫组化染色和HE染色,应用透射电镜观察大鼠海马齿状回超微结构的改变.结果:亚低温组于4d、6d、8d神经功能评分减低与常温组相应时间点比较有显著性差异(P＜0.05);常温组缺血侧海马齿状回再灌注12h MAP-2的光密度值较假手术组明显减低(P＜0.01),4d时逐渐增强,8d达高峰,14d恢复至假手术组水平.亚低温组MAP-2各时间点(1d～6d)其光密度值较常温组明显增强(P＜0.05);亚低温组神经元超微结构损伤较常温组相应时间点明显减轻.结论:脑缺血再灌注后早期MAP-2表达减弱,后持续上升.缺血早期应用亚低温可减轻脑组织损伤,促进脑缺血后神经功能恢复,其机理可能与增强脑组织中MAP-2表达有关.     

亚低温对大鼠缺血性脑损伤后SOCS3表达的影响

目的观察大鼠局灶性脑缺血再灌注后不同时间点细胞因子信号转导抑制因子-3(supressor of cytokine signaling 3,SOCS3)的表达情况及实施亚低温后的变化,进一步探讨亚低温的脑保护作用。方法线栓法制作大鼠大脑中动脉栓塞局灶性脑缺血再灌注模型,同时给予亚低温治疗。HE染色观察病理形态改变,免疫组化法检测SOCS3的表达,TUNEL法检测凋亡细胞。结果与假手术组相比,常温缺血组于再灌注3 h后SOCS3的表达开始增强,至24 h达高峰,7天时仍有表达;亚低温缺血组各时间点表达均明显高于常温缺血组(P<0.05);常温缺血组凋亡阳性细胞数随再灌注时间的延长而逐渐增多,至72h达高峰;亚低温缺血组各时间点的表达均明显少于常温缺血组(P<0.05)。结论脑缺血再灌注损伤后SOCS3的表达增强,亚低温可能通过促进SOCS3的表达发挥缺血后抗神经元凋亡的作用。     

亚低温对急性脑缺血再灌注大鼠TNF-α表达的影响

目的：探讨亚低温对大鼠急性脑缺血／再灌注损伤后神经功能及缺血脑组织中TNF—α表达的影响。方法：取健康成年雄性SD大鼠150只。随机均分为假手术组、脑缺血再灌注常温组、脑缺血再灌注亚低温组；根据再灌注时间不同，每组分别于再灌注8h，24h，3d，7d，30d各处死10只大鼠，并取其缺血脑组织，其中5只用于免疫组化染色，另外5只用于RT—PCR检测TNF—αmRNA。结果：脑缺血再灌注后，TNF—α阳性细胞数在再灌注1d时即达高峰，3d后迅速下降，再灌注7d时即降到较低水平，组间比较差异有统计学意义（P〈0．05）。TNF—α及其mRNA表达假手术组很弱，缺血再灌注后TNF—α及其mRNA在8h表达为顶峰，随后有所下降，但直到再灌注7d仍然保持相对高的表达水平，一个月基本恢复正常；其表达在亚低温组较常温脑缺血组有显著地下降（P〈0．05），但仍较假手术组高（P〈0．05）。结论：脑缺血再灌注损伤后TNF—α明显升高，应用亚低温可以降低TNF—α升高的程度；亚低温可以明显减少缺血再灌注后脑梗死的区域，并能明显改善缺血再灌注大鼠的神经功能。提示亚低温治疗对脑的保护作用有可能通过降低TNF—α水平来实现的。     

亚低温对局灶性脑缺血再灌注大鼠过氧化物酶体增殖物激活受体γ表达的影响

目的:研究亚低温对局灶性脑缺血再灌注大鼠过氧化物酶体增殖物激活受体(PPARγ)表达的影响,进一步探讨亚低温对局灶性脑缺血再灌注损伤脑保护作用的机制.方法:线拴法建立大鼠大脑中动脉阻塞再灌注模型,分为假手术组、假手术+亚低温组、模型组及模型+亚低温组.应用Western blotting和免疫组化技术分别检测再灌注后不同时相缺血侧皮层PPARγ蛋白的含量和空间分布.结果:假手术组、假手术+亚低温组PPARγ蛋白有少量表达.脑缺血2h再灌注3h,PPARγ蛋白表达开始增加,随再灌注时间的延长表达量逐渐增加,至再灌注24h达高峰,然后明显减少,再灌注72h时仍高于假手术组的水平.每一相同再灌注时间点,模型+亚低温组PPARγ蛋白表达量均明显低于模型组.结论:亚低温可通过抑制PPARγ的表达上调而发挥一定程度的脑保护作用.     

亚低温联合尼莫地平对兔全脑缺血再灌注损伤的保护

目的 探讨亚低温及尼莫地平对脑缺血再灌注损伤的保护作用及机制.方法 健康新西兰大耳白兔24只,随机分为健康对照组(Ⅰ组)、常温缺血再灌注损伤组(Ⅱ组)、亚低温缺血再灌注损伤组(Ⅲ组)、亚低温+尼萸地平组(Ⅳ组),每组6只.采用双侧颈总动脉夹闭低血压脑缺血模型,除健康对照组外,各组均行脑缺血30 min,再灌注3 h;Ⅲ组在双侧颈总动脉夹闭的同时行局部脑组织亚低温处理,Ⅳ组在夹闭的同时行局部脑组织亚低温+尼萸地平10μg·kg-1·h-1静脉输注并维持至再灌注后3 h.常规监测鼓膜温度、创伤性平均动脉压(MAP)和中心静脉压(CVP).分别于缺血前、缺血30 min、再灌注30、60、120、180 min采血标本,血气分析仪检测颈静脉血氧饱和度(SjvO2).再灌注3 h后处死动物,取脑称干湿重比计算脑含水量.ELISA方法检测血清烯醇化酶(NSE)含量.结果 脑含水量Ⅱ组>Ⅲ组>Ⅳ组.Ⅱ组全脑缺血冉灌注后60 min,血清NSE含量明显升高至(14.07±0.67)μg/L,120 min达高峰(18.53±0.85)μg/L,而SjvO2降低至(66±7.6)%.Ⅲ组冉灌注60min时血清NSE含量下降至(7.27±0.25)μg/L;180 min时至(9.17±0.57)μg/L,SjvO2升高至(91±4.5)%,与Ⅱ组比较差异有统计学意义(P均<0.01).Ⅳ组的血清NSE含量显著低于Ⅲ组,差异具有统计学意义.再灌注30 min,颈静脉血氧饱和度升高,Ⅲ组与Ⅳ组差异无统计学意义(P>0.05).结论 局部脑组织亚低温联合尼莫地平静脉输注能显著减少兔全脑缺血再灌注后血清NSE表达,升高SjvO2,减轻缺血再灌注损伤所致的脑水肿.     

亚低温对脑缺血再灌注后大鼠海马齿状回S100β蛋白表达的影响及临床意义

目的:研究大鼠脑缺血再灌注损伤后海马齿状回S100β蛋白的变化规律,探讨亚低温对脑缺血再灌注损伤的保护作用.方法:采用线栓法制备大鼠缺血再灌注动物模型,将大鼠分为亚低温组、常温组,假手术对照组.分别在不同时间点断头取脑,取材前应用神经功能等级评分观察脑缺血再灌注后行为功能的恢复,连续切片作S100β的免疫组化染色,行S100β阳性细胞计数,应用透射电镜观察大鼠海马齿状回超微结构的改变.结果:常温组再灌注4d开始、亚低温组于再灌注2d开始神经功能等级评分逐渐减低,亚低温组于6d、8d、10d评分减低与常温组相应时间点比较有显著性差异(P＜0.05);常温组缺血侧再灌注1d～4d S100β阳性细胞数明显增多,4d时达高峰,此后逐渐减少,10d时降至假手术组水平.亚低温组缺血侧S100β蛋白其阳性细胞数在2d、4d、6d、8d均显著高于常温组的相应时间点(P＜0.01);亚低温组脑组织超微结构损伤较常温组相应时间点明显减轻.结论:脑缺血过程中早期应用亚低温可减轻脑组织损伤,促进脑缺血后神经功能恢复,其机理可能与增加脑组织中S100β表达有关.     

L-精氨酸、氨基胍和胍丁胺在大鼠局灶性脑缺血再灌注损伤中的作用

目的: 观察L-精氨酸 (L-Arg)、氨基胍 (AG) 和胍丁胺 (AGM) 对大鼠局灶性脑缺血组织中一氧化氮 (NO) 含量的影响,探讨3种药对脑缺血再灌注损伤大鼠是否具有保护作用和NO在脑缺血再灌注损伤的作用及机制。方法: 线栓法建立大鼠局灶性脑缺血 (MCAO) 模型,大鼠行为学改变用Longa评分标准来评价,血清NO浓度用酶标仪检测,脑内诱导型一氧化氮合酶 (iNOS)用免疫组织化学方法测定。结果: 与假手术组相比,模型组、L-Arg组、AG组和AGM组在缺血再灌注12、24、72 h的NO含量均显著增加(P<0.05);与模型组相比,在缺血再灌注12 h,L-Arg组行为学评分显著降低(P<0.05),NO含量显著升高(P<0.05);在缺血再灌注24 h,AG组和AGM组行为学评分显著降低(P<0.05),NO含量也显著降低(P<0.05)。在缺血再灌注12、24、72 h,L-Arg组的iNOS阳性细胞数与模型组相比无显著差异(P>0.05);而AG组和AGM组则均显著低于模型组(P<0.05)和L-Arg组(P<0.05)。结论: 脑缺血再灌注损伤后血清NO和海马内iNOS的表达随时间有动态变化。L-Arg在术后12 h、AG和AGM在术后24h对局灶性脑缺血再灌注损伤大鼠有保护作用。     

局部亚低温对大鼠局灶性脑缺血-再灌注模型NKCC1 mRNA水平的影响

目的:观察局部亚低温对大鼠局灶性脑缺血-再灌注模型NKCC1 mRNA表达水平的影响,探索局部亚低温的脑保护机制.方法:雄性Wistar大鼠50只,随机分成常温组和亚低温组.应用"线栓法"实现大鼠右侧大脑中动脉阻塞,2h后拔出线栓进行再灌注,于再灌注3h、12h、24h和72h处死大鼠.应用RT-PCR方法观察NKCC1 mRNA水平的变化.结果:与假手术亚组相比,缺血-再灌注亚组大鼠缺血区皮质NKCC1 mRNA水平明显升高,开始于再灌注3h,12h～24h达到高峰,72h开始下降,亚低温组各再灌注时间点NKCC1 mRNA水平均低于常温组中相应亚组的水平.结论:局部亚低温通过抑制缺血-再灌注过程中NKCC1 mRNA水平的上调发挥脑保护作用.     

黄芪对脑缺血再灌注损伤c-fos表达和细胞凋亡的影响

目的探讨黄芪注射液对大鼠局灶性脑缺血再灌注损伤后的保护作用。方法采用线栓法阻断大鼠一侧大脑中动脉(MCA)血流2h,再灌注24h制成局灶性脑缺血再灌注损伤模型。将24只Wistar雄性大鼠随机分成假手术组、缺血再灌注组、黄芪组。造模前1h时黄芪组给与黄芪200mg/kg腹腔注射。假手术组、缺血再灌注组给予等剂量生理盐水。再灌注24h后断头取脑、切片,进行HE染色、c-fos免疫组化染色和细胞凋亡检测。结果缺血2h再灌注24h后,黄芪组和缺血再灌注组大鼠缺血侧皮层可检测到细胞凋亡细胞,黄芪组凋亡细胞数明显少于缺血再灌注组,假手术组未见凋亡细胞;黄芪组和缺血再灌注组大鼠缺血侧皮层c-fos阳性细胞数均高于假手术组,与缺血再灌注组相比,黄芪组大鼠缺血侧皮层c-fos表达降低。结论黄芪可抑制缺血再灌注损伤后缺血侧皮质的细胞凋亡。     

局部亚低温对大鼠局灶脑缺血再灌注后神经营养因子-3表达的影响

目的：观察病变侧缺血至再灌期亚低温(32～33 ℃)对局灶脑缺血再灌注后梗死体积和神经营养因子-3(neurotrophin-3,NT-3)表达的影响。方法：采用改良线栓法建立大鼠大脑中动脉缺血再灌注模型,随机分为假手术组、常温缺血组和亚低温缺血组,缺血30 min后应用负反馈控温半导体制冷块对大鼠病变侧给予亚低温治疗并持续至再灌期。处死大鼠前进行神经功能缺陷评分,氯化三苯四氮唑染色及计算机图像分析技术观察脑梗死体积,采用免疫组织化学方法检测NT-3表达,末端脱核苷酸转移酶介导的dUTP缺口标记技术观察神经细胞凋亡情况。结果：同常温缺血组相比,亚低温缺血组梗死体积明显减少,NT-3阳性细胞数量增加,凋亡的神经细胞明显减少(均P<0.05)。神经功能缺陷评分亚低温缺血组明显低于相应时间点常温缺血组(P<0.05或P<0.01)。结论：病变侧亚低温可通过增加脑缺血后NT-3的表达水平,抑制细胞凋亡而发挥脑保护作用。     

浅低温对沙土鼠脑缺血再灌后能量代谢及羟自由基产生的影响

目的:研究浅低温对沙土鼠脑缺血再灌后海马三磷酸腺苷(ATP)、二磷酸腺苷(ADP)、腺苷酸(AMP)含量和羟自由基(OH·)产生以及延迟性神经元死亡(DND)的影响。方法:沙土鼠前脑缺血再灌注模型,脑缺血10min。应用高效液相结合电化学检测器测定海马OH·含量,高效液相及紫外检测器测定ATP、ADP、AMP含量,组织学检查判断DND。结果:缺血再灌96h,浅低温+缺血再灌组DND数目明显少于缺血再灌组。缺血再灌6h,浅低温+缺血再灌组海马2,3-二羟基苯甲酸(2,3-DHBA)含量明显低于缺血再灌组(P＜0.01),但在缺血再灌48和96h,3组间2,3-DHBA含量相比差异无显著性。脑缺血再灌6h,3组间ATP、ADP、AMP含量相比差异无显著性。在再灌48和96h,浅低温+缺血再灌组海马ATP、ADP、AMP含量明显高于缺血再灌组。结论:浅低温可能通过改善脑缺血后细胞能量代谢而减少DND。     

亚低温下脑缺血大鼠骨髓间充质干细胞迁移和梗死体积的变化

背景：关于亚低温运用到神经损伤修复领域的研究已有一些报道,但亚低温对神经干细胞在脑内移植迁移的影响还不太清楚。 目的：观察亚低温对移植入脑缺血大鼠侧脑室的骨髓间充质干细胞迁移及脑梗死体积的影响。 方法：采用Longa法永久性闭塞SD大鼠大脑中动脉制作局灶性脑缺血损伤模型,50只大鼠随机摸球法分为亚低温组、对照组、假手术组。亚低温组于移植前应用亚低温处理大鼠急性脑缺血损伤,对照组于移植前应用常温处理大鼠急性脑缺血损伤;假手术组大鼠麻醉后分离结扎右侧颈内总动脉。亚低温组和对照组在造模后24 h,在脑立体定向下经侧脑室注射移植用5-BrdU标记的骨髓间充质干细胞。经过5,14,21 d后用免疫组织化学方法检测各组大鼠脑组织BrdU阳性细胞数。 结果与结论：骨髓间充质干细胞移植第14天多数标记的骨髓间充质干细胞已经迁移至梗死灶周围,移植后亚低温组各时间点梗死灶周边皮质的BrdU阳性细胞数明显多于对照组(P < 0.05)。与对照组比较,亚低温组在移植前后各个时间点脑梗死体积均显著减小(P < 0.05)。提示移植前宿主亚低温处理可以促进骨髓间充质细胞的定向迁移,且脑梗死体积显著减小。     

亚低温对构建脑梗死模型大鼠梗死区神经再生微环境的影响

BACKGROUND: Numerous studies have demonstrated that mild hypothermia has a better protective effect on neurons after cerebral infarction. OBJECTIVE:To investigate the effect of mild hypothermia on nerve regeneration microenvironment of infarcted area in rat models of cerebral infarction and analyze its possible effects on neural functional recovery after cerebral infarction. METHODS:Twenty out of 65 adult female Sprague-Dawley rats were randomly selected as the sham group. The remaining 45 rats were subjected to carotid artery ligation to establish rat models of cerebral infarction. Five rats were rejected because of modeling failure or death, the remaining 40 rats were randomly and evenly divided into cerebral infarction and mild hypothermia groups. The head temperature of rats in the cerebral infarction group was downregulated to (37±1) ℃ using a semiconductor refrigeration instrument. The rats were transferred to the room with the temperature of 25 ℃ after the operation. Brain hypothermia was also induced in rats from the mild hypothermia group. At 13.0-14.0 minutes after establishing rat models of cerebral ischemia, the head on the side of cerebral ischemia was tightly connected with the probe of the semiconductor refrigeration instrument. The refrigerator temperature was adjusted to 6-8 ℃, so as to make the temperature of brain tissue on the lesion side at 32.0-33.0 ℃ for 4 hours. RESULTS AND CONCLUSION:Compared with the cerebral infarction group, the BBB scores of rats in the mild hypothermia group were distinctly increased, and the volume of infarcted area decreased. At 1 day after modeling, the expression level of growth associated protein 43 mRNA in brain tissue of rats in the mild hypothermia group was close to that in the cerebral infarction group. At 2 weeks after modeling, the expression level of growth associated protein 43 mRNA in brain tissue of rats in the mild hypothermia group was significantly increased compared with that in the cerebral infarction group. These results suggest that mild hypothermia therapy can protect nerve cells against injury caused by cerebral infarction and promote the recovery of neurological function. Its underlying mechanism may be related to the up-regulation of the expression of growth associated protein 43 in ischemic penumbra.     

Effect of mild hypothermia on energy state recovery following transient forebrain ischemia in the gerbil

A transient (lasting for 15 min) bilateral carotid artery occlusion model was created by using male Mongolian gerbils ( n=20, weight 50-60 g). The animals were divided into a group with mild hypothermia (34 degrees C, n=10) and a normothermic group (37 degrees C, n=10). High-energy phosphate metabolism (ATP, PCr, Pi) and intracellular pH were sequentially measured using (31)P-MRS during ischemia and after reperfusion for 1 week. The same animals were also subjected to a histopathological evaluation. During ischemia, there were no statistically significant differences between the two groups in the quantities of the metabolites. However, after reperfusion the rate of metabolic recovery by the mildly hypothermic (MH) group was significantly higher (by 10-20%) than the normothermic (NT) group. The intracellular pH decreased about 0.4 in both groups after ischemia; and after reperfusion the intracellular pH of the MH group returned to baseline levels faster than in the NT group. One week after ischemia, energy metabolism gradually decreased about 10-20% in both groups. In the histopathological evaluation, pyramidal cell damage in the hippocampus was 33% on average in the MH group and 79% in the NT group. The neuronal damage to the cerebral cortex was 26% in the MH group and 61% in the NT group. Astrocyte reactivity in the hippocampus and cerebral cortex was 2.9% and 1.1% in the MH group and 9.7% and 5.2% in the NT group. The results of this experiment indicate that the protective effect of mild hypothermia is due to the high recovery rate of ATP and PCr and the prevention of a secondary decline in high phosphate energy.     

Mild hypothermia reduces ICAM-1 expression,neutrophil infiltration and microglia/monocyte accumulation following experimental stroke

Mild hypothermia is an established neuroprotectant against cerebral ischemic injury. Studies have shown that inflammation potentiates cerebral ischemic injury, particularly in the setting of reperfusion. To further elucidate the mechanism by which mild hypothermia attenuates the inflammatory response, we assessed endothelial intercellular adhesion molecule-1 (ICAM-1) expression, neutrophil and monocyte infiltration, and microglial activation following 2 h of transient focal cerebral ischemia under normothermic and mildly hypothermic conditions. Ischemia was induced using the intraluminal suture method in Sprague-Dawley rats. Immunohistochemistry was used to detect endothelial ICAM-1, infiltrating neutrophils and monocytes, and microglia at 1, 3, and 7 days post-ischemia. Immunopositive cell and vessel densities were measured in the peri-infarct region. Mild hypothermia was associated with decreased neutrophils at 1 and 3 days post-ischemia, decreased ICAM-1-positive vessels at 1, 3, and 7 days, and decreased monocytes/activated microglia at 3 and 7 days, but not at 1 day. These data demonstrate that mild hypothermia significantly reduces endothelial adhesion molecule expression, acute (neutrophil) and subacute (monocyte) leukocyte infiltration, and microglial activation up to 7 days following insult in a rodent model of transient focal cerebral ischemia.     

Hypothermia differentially increases extracellular signal-regulated kinase and stress-activated protein kinase/c-Jun terminal kinase activation in the hippocampus during reperfusion after asphyxial cardiac arrest

Mitogen-activated protein kinases are signal transduction mediators that have been implicated in cell survival and cell death. This study characterized the activation of pathways in the hippocampus during reperfusion after global cerebral ischemia, as well as the influence of a regimen of hypothermia that reduces ischemic cell death in the hippocampus. Circulatory arrest was induced in rats by 8 min of asphyxia. Relative levels of phosphorylated and total extracellular signal-regulated kinase, stress-activated protein kinase/c-Jun N-terminal kinase and p38 mitogen-activated protein kinase were measured in the hippocampus after 6, 12 or 24h of reperfusion using immunoblotting. Asphyxia induced a progressive increase in phosphorylated extracellular signal-regulated kinase and stress-activated protein kinase/c-Jun N-terminal kinase, but no change in phosphorylated p38 mitogen-activated protein kinase. Induction of mild hypothermia (33 degrees C) during reperfusion increased extracellular signal-regulated kinase phosphorylation and produced a smaller increase in stress-activated protein kinase/c-Jun N-terminal kinase phosphorylation at 24h. Hypothermia did not alter extracellular signal-regulated kinase activation in rats not subjected to ischemia. Extracellular signal-regulated kinase activation was associated with an increase in phosphorylation of the mitogen-activated protein kinase kinase 1/2, and was inhibited by administration of the specific mitogen-activated protein kinase kinase 1/2 inhibitor SL327. Immunohistochemical staining showed an increase in active extracellular signal-regulated kinase in the CA1, CA2, CA3 and dentate gyrus regions of the hippocampus after ischemia and reperfusion. In contrast, active stress-activated protein kinase/c-Jun N-terminal kinase immunoreactivity was most intense in the CA3 and dentate gyrus regions.These data demonstrate that both extracellular signal-regulated kinase and stress-activated protein kinase/c-Jun N-terminal kinase pathways are activated during the first 24h of reperfusion after global cerebral ischemia, and that hypothermia increases the activation of extracellular signal-regulated kinase relative to stress-activated protein kinase/c-Jun N-terminal kinase. Thus, an increase in extracellular signal-regulated kinase activation may be associated with improved neuronal survival after ischemic injury.