Mineralocorticoid receptor activation causes cerebral vessel remodeling and exacerbates the damage caused by cerebral ischemia

Mineralocorticoid receptor antagonists protect against ischemic cerebrovascular disease; this appears to be caused by changes in cerebral vessel structure that would promote blood flow. Therefore, we hypothesized that mineralocorticoid receptor activation with deoxycorticosterone acetate would cause deleterious remodeling of the cerebral vasculature and exacerbate the damage caused by cerebral ischemia. Six-week-old male Wistar rats were treated with deoxycorticosterone acetate (200 mg/kg) for 6 weeks. At 12 weeks of age, the deoxycorticosterone acetate-treated rats had elevated systolic blood pressure compared with age-matched controls (157+/-5.9 versus 124+/-3.1 mm Hg deoxycorticosterone acetate versus control; P<0.05). The area of ischemic damage resulting from middle cerebral artery occlusion was greater in the deoxycorticosterone acetate-treated rats than control (63.5+/-3.72 versus 46.6+/-5.52% of the hemisphere infarcted, deoxycorticosterone acetate versus control; P<0.05). Middle cerebral artery structure was assessed using a pressurized arteriograph under calcium-free conditions. Over a range of intralumenal pressures, the lumen and ODs of the middle cerebral arteries were smaller in the deoxycorticosterone acetate-treated rats than the control rats (P<0.05). There was also an increase in the wall thickness and wall:lumen ratio in the vessels from deoxycorticosterone acetate-treated rats (P<0.05). The vessels from the deoxycorticosterone acetate-treated rats were stiffer than those from control rats as evidenced by a leftward shift in the stress/strain curve. These novel data suggest that mineralocorticoid receptor activation without salt loading and nephrectomy is sufficient to elicit deleterious effects on the cerebral vasculature that lead to inward hypertrophic remodeling and an increase in the ischemic damage in the event of a stroke.     

Fasting prior to transient cerebral ischemia reduces delayed neuronal necrosis

A transient brain ischemia of 30-min duration was induced by the four-vessel occlusion technique in normally fed and in 48-hr-fasted rats. Evaluation of brain damage 72 hr after ischemia showed that fasting reduced neuronal necrosis in the striatum, the neocortex, and the lateral part of the CA1 sector of hippocampus. Signs of status spongiosis in the pars reticulata of the substantia nigra were seen in 75% of fed rats and in only 19% of fasted rats. The protective effect was associated with reduction in mortality and in postischemic seizure incidence. The metabolic changes induced by fasting were evaluated before and during ischemia. After 30 min of four-vessel occlusion, fasted rats showed a marked decrease in brain lactate level (14.7 vs 22.5 mol/g in fed rats;P < 0.001). The decrease in brain lactate concentration might explain the beneficial effect of fasting by minimizing the neuropathological consequences of lactic acidosis. Several factors may account for lower lactate production during ischemia in fasted rats: hypoglycemia, reduction in preischemic stores of glucose and glycogen, or increased utilization of ketone bodies aiming at reducing the glycolytic rate.     

Melatonin attenuates gray and white matter damage in a mouse model of transient focal cerebral ischemia

We have previously shown that melatonin reduces infarct volumes and enhances neurobehavioral and electrophysiological recoveries following transient middle cerebral artery (MCA) occlusion in rats. In the study, we examined whether melatonin would display neuroprotection against neuronal, axonal and oligodendrocyte pathology after 24 hr of reperfusion following 1 hr of MCA occlusion in mice. Melatonin (5 mg/kg) or vehicle was given intraperitoneally at the commencement of reperfusion. Neurological deficits were assessed 24 hr after ischemia. Gray matter damage was evaluated by quantitative histopathology. Axonal damage was determined with amyloid precursor protein and microtubule-associated protein tau-1 immunohistochemistry to identify postischemic disrupted axonal flow and oligodendrocyte pathology, respectively. Oxidative damage was assessed by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4-hydroxynonenal (4-HNE) immunohistochemistry. Relative to controls, melatonin-treated animals not only had a significantly reduced volume of gray matter infarction by 42% (P<0.001), but also exhibited a decreased score of axonal damage by 42% (P<0.001) and a reduction in the volume of oligodendrocyte pathology by 58% (P<0.005). Melatonin-treated animals also had significantly reduced immunopositive reactions for 8-OHdG and 4-HNE by 53% (P<0.001) and 49% (P<0.001), respectively. In addition, melatonin improved sensory and motor neurobehavioral outcomes by 47 and 30%, respectively (P<0.01). Thus, delayed (1 hr) treatment with melatonin reduced both gray and white matter damage and improved neurobehavioral outcomes following transient focal cerebral ischemia in mice. The finding of reduced oxidative damage observed with melatonin suggests that its major mechanisms of action are mediated through its antioxidant and radical scavenging activity.     

Neuroprotective effect of herniarin following transient focal cerebral ischemia in rats

Metabolic Brain Disease - Ischemic stroke is a devastating central nervous disease. Despite extensive research in to this area, few innovative neuroprotective treatments have been presented....     

MEK1 protein kinase inhibition protects against damage resulting from focal cerebral ischemia.

The MEK1 (MAP kinase/ERK kinase)/ERK (extracellular-signal-responsive kinase) pathway has been implicated in cell growth and differentiation [Seger, R. & Krebs, E. G. (1995) FASEB J. 9, 726-735]. Here we show that the MEK/ERK pathway is activated during focal cerebral ischemia and may play a role in inducing damage. Treatment of mice 30 min before ischemia with the MEK1-specific inhibitor PD98059 [Alessi, D. R., Cuenda, A., Cohen, P. , Dudley, D. T. & Saltiel, A. R. (1995) J. Biol. Chem. 270, 27489-27494] reduces focal infarct volume at 22 hr after ischemia by 55% after transient occlusion of the middle cerebral artery. This is accompanied by a reduction in phospho-ERK1/2 immunohistochemical staining. MEK1 inhibition also results in reduced brain damage 72 hr after ischemia, with focal infarct volume reduced by 36%. This study indicates that the MEK1/ERK pathway contributes to brain injury during focal cerebral ischemia and that PD98059, a MEK1-specific antagonist, is a potent neuroprotective agent.     

细胞间粘附分子-1和E-选择素在局部脑缺血中的作用

目的　探讨细胞间粘附分子 1(ICAM 1)和E 选择素 (E selectin)在局部脑缺血炎性反应过程中的作用。方法　采用尼龙线栓堵大鼠大脑中动脉 ,造成局部持续脑缺血模型 ,用RT PCR方法检测缺血侧脑组织持续缺血后不同时间点ICAM 1和E selectinmRNA的表达。结果　假手术组及手术组非缺血侧大脑皮层未见ICAM 1和E selectinmRNA的表达。持续脑缺血后 1h ,手术组缺血侧大脑皮层ICAM 1和E selectinmRNA的表达量开始升高 ;缺血后 6h ,ICAM 1mRNA的上调达高峰 ,且持续至缺血后 48h。而E selectinmRNA的上调在缺血后 12h达高峰。结论　ICAM 1和E selectin参与了持续局部脑缺血后脑组织损伤的病理过程。两者协同发挥作用 ,在白细胞进入缺血区脑组织的病理过程中起重要作用。     

尼莫通对脑缺血后迟发性神经元损伤保护作用的实验研究

目的　研究脑缺血再灌注后迟发性神经元坏死（ Ｄ Ｎ Ｄ ）的病理学改变及测定病灶区 Ｃａ２ ＋ 含量的变化,并观察尼莫通对 Ｄ Ｎ Ｄ 的保护作用。方法　制作大鼠一侧大脑中动脉缺血再灌注模型。结果　当脑缺血 ６ ｈ 以上再灌流时 Ｄ Ｎ Ｄ 现象明显。结论　早期应用尼莫通治疗可使 Ｄ Ｎ Ｄ 减轻,起到神经元保护作用。     

慢性脑缺血导致脑损害的实验研究进展

慢性脑缺血被认为是多种疾病如血管性痴呆（vascular dementia,VD）、Alzheimer病（AD）和Binswanger病等发展过程中的一个共同的病理学过程。高血脂引起的脑内动脉粥样硬化、高血压引起的脑小动脉硬化、高血糖引起的脑微循环障碍等都可造成慢性脑供血不足。慢性脑缺血的发生、发展使脑组织产生不同程度的病理损伤,引起认知功能下降从而导致痴呆的产生。     

代谢型谷氨酸受体1α在大鼠脑缺血再灌注损伤中的基因表达变化

目的　观察大鼠大脑中动脉闭塞 (MCAO)后再灌注不同时点代谢型谷氨酸受体 1α(mGluR1α)的蛋白与基因表达的变化 ,以探讨其在脑缺血再灌注损伤中的意义。方法　 4 8只SD大鼠随机分为假手术组及缺血 2h再灌注 1、3、6、12、2 4、4 8及 72h组 ,用免疫组织化学、逆转录 聚合酶链反应 (RT PCR)技术和HE染色检测各组mGluR1α的蛋白表达、mRNA转录水平及坏死神经元的计数。结果　各缺血再灌注组mGluR1α表达均高于假手术组 ,再灌注 1hmGluR1α的mRNA转录即有升高 ,6h达到高峰 ,mGluR1α蛋白表达从 3h开始增加 ,12h达高峰 ,与神经元损伤程度一致。结论　脑缺血再灌注可引起mGluR1α表达上调 ,且与神经元损伤程度平行 ,提示mGluR1α参与介导了局灶性脑缺血再灌注损伤。     

Neuroprotection by melatonin against ischemic neuronal injury associated with modulation of DNA damage and repair in the rat following a transient cerebral ischemia

In the present study, double fluorescence staining combined with confocal laser scanning microscopy analysis were used to examine the effects of melatonin on ischemia-induced neuronal DNA strand breaks and its possible mechanisms in a transient middle cerebral artery (MCA) occlusion model. Results showed that melatonin dose-dependently reduced infarct areas and decreased both DNA double and single strand breaks (DSB and SSB) and enhanced cell viability in the peri-ischemic brain regions. Furthermore, Bcl-2 induction in the ischemic brain was further enhanced by melatonin treatment. Double staining analysis indicated that the cells costained for Bcl-2 and TdT-mediated-deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL), a DSB marker, displayed a relative regular morphology compared with the cells only stained with TUNEL. Transient ischemia induced an expression of excision repair cross-complementing factor 6 (ERCC6) mRNA, a gene essential for the preferential repair of nuclear excision repair, in the injured neurons. Double labeling showed that ERCC6 only co-localized with proliferating cell nuclear antigen (PCNA), a member of the nuclear excision repair complex, but not with TUNEL. Melatonin further and statistical significantly up-regulated ERCC6 mRNA expression in the peri-ischemic region of rat brains. The results suggest that neuroprotection by melatonin against ischemic injury may be related to modulation of apoptosis and DNA repair capacity.     

脂联素受体在短暂性脑缺血小鼠模型脑组织中的表达

目的观察脂联素受体(APNR)在小鼠脑缺血模型中的表达,有助于对脂联素作用机制的研究。方法 60只健康雄性CD-1小鼠行短暂性大脑中动脉栓塞术,分别于缺血前、再灌注后1、4h、1、3及7d时处死取脑,每个时间点12只。用PT-PCR、Western blot和免疫组织化学的方法观察小鼠脑缺血再灌注后各时间点脑内APNR蛋白和mRNA表达。结果与缺血前比较,再灌注后4h、1、3、7d缺血侧脑组织中APNR1蛋白和mRNA表达量增高(P<0.05,P<0.01),缺血中心区和缺血周边区APNR1蛋白表达量相似;脑血管内皮细胞、星形胶质细胞和神经元细胞中均有APNR1的表达。各时间点小鼠缺血前后的脑组织均未见APNR2蛋白和mRNA表达。结论缺血再灌注损伤后,APNR1在缺血脑组织中表达上调,脂联素可能通过APNR1的介导发挥脑保护作用。     

强制性运动疗法对脑缺血后大鼠神经功能重塑的影响及机制探讨

目的 观察强制性运动疗法对脑缺血后大鼠神经功能重塑的影响,并探讨其机制.方法 将90只健康SD大鼠随机分为假手术组、模型组、运动疗法组各30只,3组大鼠均用3.5％水合氯醛1 mL/kg腹腔麻醉,取左侧颈部直切口,分离左颈总动脉、颈内动脉、颈外动脉（ECA）,电凝ECA分支,离断ECA.假手术组到此步为止,模型组、运动疗法组制备左侧大脑中动脉闭塞模型;脑缺血模型成功后7d,运动疗法组建立强制性运动疗法模型.参照改良的Bederson氏6级评分标准对各组大鼠进行神经功能缺损评分,采用原位杂交检测缺血侧大脑皮质及梗塞灶边缘区Nogo受体（NgR）及轴突再生脑源性神经营养因子（BDNF） mRNA,免疫印迹检测NgR、BDNF蛋白.结果 与模型组比较,运动疗法组在制模后2、4、8周神经功能缺损评分明显降低,NgR mRNA及蛋白表达降低,BDNFmRNA及蛋白表达升高（P均＜0.01）.结论 强制性运动疗法可以明显改善大鼠脑缺血后神经功能,其机制可能与下调NgR的表达、上调BDNF表达,从而促进神经功能重塑有关.     

老龄大鼠局灶性脑缺血周围区DNA损伤的研究

目的　探讨老龄大鼠局灶性脑缺血周围DNA损伤特点。方法　应用HE染色、原位末端标记法 (TUNEL)标记、原位分子杂交、免疫组织化学等方法 ,分别对缺血 4、2 4h和 5d组大鼠脑组织中坏死细胞、凋亡细胞、p5 3mR NA、p5 3蛋白阳性细胞密度及空间分布进行观察和比较。结果　不同时间点病灶周围每高倍视野TUNEL、p5 3蛋白、p5 3mRNA的阳性细胞数分别为 4h :8.0± 1.5、2 5 .1± 2 .6、10 .3± 1.9;2 4h :2 0 .5± 2 .4、6 0 .0± 4.8、2 2 .0± 1.8;5d :2 .1± 0 .4、3.6± 1.4、3.5± 0 .8。p5 3基因主要在形态完整和可逆性损伤细胞中表达、分布范围较TUNEL细胞广泛。结论　局灶性脑缺血后 ,缺血周围DNA损伤区大于凋亡区 ,p5 3基因表达范围可能代表病理意义上的半暗带 ;p5 3主要发挥DNA修复作用     

槐果碱拮抗酸敏感离子通道及其在大鼠缺血性脑损伤中的保护作用

目的 探讨槐果碱对酸敏感离子通道(acid-sensing ion channel,ASIC)的影响及其在缺血性脑损伤大鼠中的神经保护作用.方法 25只SD大鼠随机分为假手术组、脑缺血再灌注组以及槐果碱5、10和20 mg/kg预处理组,每组5只.采用线栓法建立局灶性大鼠缺血模型,5、10和20 mg/kg槐果碱腹腔注...     

Delayed treatment with melatonin enhances electrophysiological recovery following transient focal cerebral ischemia in rats

Melatonin has been reported to reduce infarct volumes induced by transient middle cerebral artery (MCA) occlusion. We examined whether melatonin could improve electrophysiological and neurobehavioral recoveries in rats after 72 hr of reperfusion following 1.5 hr of MCA occlusion. Melatonin (5 mg/kg) or vehicle was given intravenously at the commencement of reperfusion. Neurobehavioral outcome was serially examined, and somatosensory evoked potentials (SSEP) were recorded prior to ischemia and at 72 hr after the onset of reperfusion. Brain infarction was assessed upon killing. Before ischemia-reperfusion, stable SSEP waveforms were consistently recorded after individual fore- or hindpaw stimulation. The amplitude between the first positive (P1) and the first negative (N1) peaks and the P1 latency did not differ significantly between controls and melatonin-treated animals. At 72 hr of reperfusion, controls had severely depressant SSEPs recorded from ischemic fore- and hindpaw cortical fields, and the amplitudes decreased to 36 and 35% of baselines, respectively (P < 0.001). These animals also had transcallosal electrophysiological diaschisis in the SSEPs recorded at the contralateral hindpaw cortical field (P < 0.01). Relative to controls, melatonin-treated animals not only had significantly improved amplitudes of the SSEPs recorded from both ischemic fore- and hindpaw cortical fields, by 33 and 37% of baselines, respectively (P < 0.001), but also exhibited diminished transcallosal electrophysiological diaschisis following ischemia-reperfusion. In addition, melatonin improved sensory and motor neurobehavioral outcomes by 40 and 28%, respectively (P < 0.001), and reduced cortical and striatal infarct sizes by 32 and 40%, respectively (P < 0.05). Thus, delayed intravenous administration with melatonin both enhances electrophysiological and neurobehavioral recoveries and reduces cortical and striatal infarct sizes after cerebral ischemia and reperfusion injury.     

p75神经营养因子受体在脑缺血后神经元凋亡中的作用

p75神经营养因子受体(p75 neurotrophin receptor, p75 NTR)为肿瘤坏死因子受体超家族成员,通过与原肌球蛋白受体激酶(tropomyosin receptor kinase, Trk)受体相互作用或与神经营养因子结合,介导多种复杂的信号转导通路,诱导突触生长和影响细胞存亡。急性...