Neuroprotective effects of erythropoietin in the rat hippocampus after pilocarpine-induced status epilepticus

Neuroprotective functions of erythropoietin (Epo) are thought to involve a heteroreceptor composed of both Epo receptor (Epo-R) and common beta chain (betac). Here, we measured the response of hippocampal Epo system components (Epo, Epo-R and betac) during neurodegenerative processes following pilocarpine-induced status epilepticus (SE), and examined whether recombinant human Epo (rHuEpo) could support neuronal survival. We evidence that Epo is induced in astroglia following SE, in particular within areas displaying delayed neuronal death. In addition, we demonstrate for the first time that rHuEpo reduces considerably hippocampal neurodegeneration following SE. rHuEpo may thus supplement astroglial induction of Epo to promote enhanced hippocampal neuronal survival following SE. We also show that Epo-R is expressed by neurons and astrocytes mainly, while betac is barely detectable in basal conditions and induced in reactive microglia exclusively following SE. Altogether, our results suggest that Epo/rHuEpo exerts neuroprotection, through Epo-R signaling and independently of betac, and, therefore, may be anti-epileptogenic.     

Cerebral blood flow changes during pilocarpine-induced status epilepticus activity in the rat hippocampus

Introduction

There is a known relationship between convulsive status epilepticus (SE) and hippocampal injury. Although the precise causes of this hippocampal vulnerability remains uncertain, potential mechanisms include excitotoxicity and ischaemia. It has been hypothesised that during the early phase of seizures, cerebral blood flow (CBF) increases in the cortex to meet energy demand, but it is unclear whether these compensatory mechanisms occur in the hippocampus. In this study we investigated CBF changes using perfusion MRI during SE in the pilocarpine rat.

Methods

First, we determined whether SE could be induced under anaesthesia. Two anaesthetic protocols were investigated: isoflurane (n = 6) and fentanyl/medetomidine (n = 7). Intrahippocampal EEG electrodes were used to determine seizure activity and reflex behaviours were used to assess anaesthesia. Pilocarpine was administered to induce status epilepticus. For CBF measurements, MRI arterial spin labelling was performed continuously for up to 3 h. Either pilocarpine (375 mg/kg) (n = 7) for induction of SE or saline (n = 6) was administered. Diazepam (10 mg/kg) was administered i.p. 90 min after the onset of SE.

Results and discussion

We demonstrated time-dependent significant (p < 0.05) differences between the CBF responses in the parietal cortex and the hippocampus during SE. This regional response indicates a preferential distribution of flow to certain regions of the brain and may contribute to the selective vulnerability observed in the hippocampus in humans.     

自由基清除剂依达拉奉对大鼠脑出血的治疗作用

目的 探讨自由基清除剂依达拉奉对实验性脑出血的保护作用及其作用机制.方法 240只SD雄性大鼠随机分为4组:假手术组、手术模型组、依达拉奉术前给药(A)组和依达拉奉术后给药(B)组.参考Rosenberg的脑出血模型的制作方法建立大鼠脑出血模型,采用干重法评价脑水肿程度,Bederson评分法评价神经功能缺损,并观察依达拉奉对血肿周围脑组织中超氧化物歧化酶(SOD)活性和丙二醛(MDA)的影响.结果 手术模型组及依达拉奉A、B组脑组织中水的含量高于假手术组,而依达拉奉A、B组低于模型组,其差异有统计学意义(P＜0.01);依达拉奉A、B组大鼠肢体神经功能缺损的恢复明显快于模型组;与假手术组[(70.7±2.7)U/mg]相比,造模后20 min模型组及依达拉奉A、B组大鼠脑组织SOD活性即开始下降[分别为(62.5±2.5)、(65.2±5.3)、(61.6±4.2)U/mg],180 min时降至最低(P＜0.01),而与同时点模型组比较,依达拉奉各组SOD活性有不同程度升高,其差异有统计学意义(P＜0.01).与假手术组[(2.9±0.2)nmol/mg]相比,造模后20min模型组及依达拉奉A、B组大鼠脑组织MDA含量开始增加[分别为(3.4±0.2)、(3.1±0.2)、(3.2±0.5)nmol/mg],与同时点模型组比较,依达拉奉各组MDA含量有不同程度降低,80、110、180min时差异有统计学意义(P＜0.01).结论 依达拉奉可抑制大鼠实验性脑出血脑细胞的过氧化作用,减轻脑水肿,改善神经功能,具有脑保护作用.     

Astroglial loss and edema formation in the rat piriform cortex and hippocampus following pilocarpine-induced status epilepticus

In the present study we analyzed aquaporin-4 (AQP4) immunoreactivity in the piriform cortex (PC) and the hippocampus of pilocarpine-induced rat epilepsy model to elucidate the roles of AQP4 in brain edema following status epilepticus (SE). In non-SE-induced animals, AQP4 immunoreactivity was diffusely detected in the PC and the hippocampus. AQP4 immunoreactivity was mainly observed in the endfeet of astrocytes. Following SE the AQP4-deleted area was clearly detected in the PC, not in the hippocampus. Decreases in dystrophin and α-syntrophin immunoreactivities were followed by reduction in AQP4 immunoreactivity. These alterations were accompanied by the development of vasogenic edema and the astroglial loss in the PC. In addition, acetazolamide (an AQP4 inhibitor) treatment exacerbated vasogenic edema and astroglial loss both in the PC and in the hippocampus. These findings suggest that SE may induce impairments of astroglial AQP4 functions via disruption of the dystrophin/α-syntrophin complex that worsen vasogenic edema. Subsequently, vasogenic edema results in extensive astroglial loss that may aggravate vasogenic edema.     

匹罗卡品致痫大鼠海马calpain活性变化和其对神经元死亡的影响

目的探讨在匹罗卡品致痫的癫痫持续状态（SE）大鼠模型中,钙蛋白酶在大鼠海马组织中的活性,及钙蛋白酶对神经元坏死、凋亡产生的影响。方法雄性成年wistar大鼠,应用匹罗卡品致痫产生SE后60min后终止发作,24h后取材,行HE染色及tunel染色,观察海马神经元的坏死及凋亡情况,以及western blot检测钙蛋白酶1（μ-calpain）的活性。结果癫痫持续状态后24h,海马组织HE染色神经元数量减少,tunel阳性细胞数增加,钙蛋白酶1出现76ku条带。结论大鼠癫痫持续状态后24h,钙蛋白酶1在海马组织神经元活性增加,海马神经元出现坏死及凋亡。钙蛋白酶1与神经元的死亡存在着正相关。     

Unaltered control of extracellular GABA-concentration through GAT-1 in the hippocampus of rats after pilocarpine-induced status epilepticus

The uptake of the inhibitory transmitter GABA (gamma-aminobutyric acid) limits the efficacy of synaptic and tonic inhibition in brain tissue. It has been reported that GABA-uptake is down-regulated in temporal lobe epilepsy. This down-regulation may increase the inhibitory action of GABA but may also limit the anticonvulsant activity of GABA-uptake blockers. We have directly compared the function of GABA-uptake in hippocampal slices from normal and chronically epileptic rats. We raised the global extracellular concentration of GABA by bath-application of the agonist in the absence and presence of the GABA-uptake blocker tiagabine. GABA-induced currents were measured in dentate granule cells and CA1 pyramidal neurons in hippocampal slices. The potentiation of currents by tiagabine was taken as a measure for the efficacy of GABA-uptake in the hippocampal tissue. There was no difference between cells from control- or pilocarpine-treated animals in the response to GABA or in the conductance increase following application of tiagabine. Our data show that in the chronic phase of the pilocarpine-model GABA-uptake maintains its ability to control the extracellular background concentration of GABA.     

Caffeic acid effects on oxidative stress in rat hippocampus after pilocarpine-induced seizures

The objective of the study was to evaluate the caffeic acid (CA) effects against the oxidative stress (OS) observed during seizures. Wistar rats were intraperitoneally treated with either 0.9% saline (control), CA (4 mg/kg), pilocarpine (400 mg/kg, pilocarpine group), or the association of CA (4 mg/kg) plus pilocarpine (400 mg/kg). The thiobarbituric-acid-reacting substances and the hippocampal nitrite content were significantly increased (89 and 94%, respectively) in pilocarpine group when compared with control. There were marked decreases in lipid peroxidation level (43%) and nitrite content (45%) in CA group when compared with pilocarpine group. There were no marked alterations in superoxide dismutase (SOD) and catalase (CAT) activities in pilocarpine group; however, the SOD and CAT activities were significantly increased (35 and 51%, respectively) after CA pretreatment. Our findings strongly support the hypothesis that OS was indeed generated in hippocampus. CA pretreatment can reduces the OS produced by seizures.     

Neuroprotective effects of recombinant human erythropoietin in the developing brain of rat after lithium-pilocarpine induced status epilepticus

Status epilepticus triggers a mixture of apoptotic and necrotic cell death within the hippocampus. This neuronal loss may result in the development of epilepsy and cognitive deficits. Erythropoietin mediates a number of biological actions within the central nervous system and has been shown to be neuroprotective. In the present study, we investigated the effects of recombinant human erythropoietin on hippocampus of rat after lithium-pilocarpine induced status epilepticus. Twenty-one dam reared Wistar male rats, 21-day-old were divided into three groups: control group, lithium-pilocarpine induced status epilepticus and lithium-pilocarpine induced status epilepticus and erythropoietin treated group. Erythropoietin treated group received recombinant human erythropoietin 10 U/g intraperitoneally 40 min after pilocarpine injection for 5 days. Rats were sacrificed and brain tissues were collected at 5th day of experiment. Neuronal cell death and apoptosis were evaluated. Histopathological examination showed that erythropoietin significantly decreased neuronal cell death in CA1, CA2, CA3 and dentate gyrus regions of hippocampus. It also diminished apoptosis in the CA1 and dentate gyrus regions of hippocampus. In conclusion, erythropoietin may preserve the number of neurons and decrease apoptosis in model of status epilepticus induced by lithium-pilocarpine. This experimental study suggests that erythropoietin administration may be neuroprotective in status epilepticus.     

Attenuation of extravasation of tissue plasminogen activator by the free radical scavenger, edaravone: evaluation in a rat thromboembolic stroke model

OBJECTIVES AND METHODS: Deleterious effects of tissue plasminogen activator (tPA) have been described recently in experimental studies. For example, tPA can aggravate ischemic neuronal damage through its proteolytic activity. The present study was undertaken to examine whether or not the free radical scavenger, edaravone, could prevent the extravasation of tPA administered for the purpose of fibrinolysis in a rat model of thromboembolic stroke. RESULTS: Significant amounts of tPA were extravasated through the cerebral vessels even when early recanalization was induced by administering tPA at 30 minutes after the onset of schema. Edaravone significantly attenuated such extravasation of tPA. CONCLUSION: In acute ischemic stroke patients, combination therapy using tPA with edaravone appears to be a reasonable strategy for diminishing the negative effects of tPA.     

Attenuation of extravasation of tissue plasminogen activator by the free radical scavenger,edaravone: evaluation in a rat thromboembolic stroke model

Abstract

Objectives and methods: Deleterious effects of tissue plasminogen activator (tPA) have been described recently in experimental studies. For example, tPA can aggravate ischemic neuronal damage through its proteolytic activity. The present study was undertaken to examine whether or not the free radical scavenger, edaravone, could prevent the extravasation of tPA administered for the purpose of fibrinolysis in a rat model of thromboembolic stroke.

Results: Significant amounts of tPA were extravasated through the cerebral vessels even when early recanalization was induced by administering tPA at 30 minutes after the onset of schema. Edaravone significantly attenuated such extravasation of tPA.

Conclusion: In acute ischemic stroke patients, combination therapy using tPA with edaravone appears to be a reasonable strategy for diminishing the negative effects of tPA.     

Glutamate receptor 1-immunopositive neurons in the gliotic CA1 area of the mouse hippocampus after pilocarpine-induced status epilepticus

Significant reduction in glutamate receptor 1 (GluR1)- and GluR2/3-immunopositive neurons was demonstrated in the hilus of the dentate gyrus in mice killed on days 1, 7 and 60 after pilocarpine-induced status epilepticus (PISE). In addition, GluR1 and GluR2/3 immunostaining in the strata oriens, radiatum and lacunosum moleculare of areas CA1-3 decreased drastically on days 7 and 60 after PISE. Neuronal loss observed in the above regions may account, at least in part, for a decrease in GluR immunoreactivity. By contrast, many GluR1-immunopositive neurons were observed in the gliotic area of CA1. Of these, about 42.8% were immunopositive for markers for hippocampal interneurons, namely calretinin (7.6%), calbindin (12.8%) and parvalbumin (22.4%). GluR1 or GluR2/3 and BrdU double-labelling showed that the GluR1- and GluR2/3-immunopositive neurons at 60 days after PISE were neurons that had survived rather than newly generated neurons. Furthermore, anterograde tracer and double-labelling studies performed on animals at 60 days after PISE indicated a projection from the hilus of the dentate gyrus to gliotic areas in both CA3 and CA1, where the projecting fibres apparently established connections with GluR1-immunopositive neurons. The projection to CA1 was unexpected. These novel findings suggest that the intrinsic hippocampal neuronal network is altered after PISE. We speculate that GluR1-immunopositive neurons in gliotic CA1 act as a bridge between dentate gyrus and subiculum contributing towards epileptogenesis.     

Opioid peptide release in the rat hippocampus after kainic acid-induced status epilepticus

It has been suggested that kainic acid enhances opioid peptide release. However, no direct evidence exists to support this hypothesis. The main aim of the present study was to determine whether such release occurs in the hippocampus of the rat after status epilepticus induced by kainic acid. Microdialysis experiments revealed significant opioid peptide release in the hippocampus 90-150 min (100%) and 270-300 min (50%) after kainic acid-induced status epilepticus. The peptides released were identified by high-performance liquid chromatography linked to radioimmunoassay as Met-enkephalin, Leu-enkephalin, Dynorphin-A (1-6), and Dynorphin-A (1-8). Reduced extracellular opioid peptide immunoreactivity was detected 28 days after status epilepticus (38% compared with control situation). The present results indicate an important activation of opioid peptide systems by kainic acid-induced status epilepticus. In addition, the reduced hippocampal extracellular opioid peptide levels long-term after kainic acid administration could have important implications for the progressive nature of epileptogenesis.     

Effect of the free radical scavenger edaravone on peripheral nerve ischemia–reperfusion injury

We investigated the effects of edaravone, a free radical scavenger, on peripheral nerve ischemia–reperfusion injury caused by ligation of vessels supplying the sciatic and tibial nerves in rats. The control group was administered a placebo, the standard‐dose group was given 3 mg/kg of edaravone intraperitoneally every 24 hours, and the low‐dose group was given 1 mg/kg of edaravone. At 7 days after reperfusion, neurological and electrophysiological parameters were improved in the standard‐dose group as compared with the control group. After 14 days, however, these differences were no longer observed. After 21 days, persistent edema and nerve fiber degeneration were noted in the standard‐dose group, but not in the control or low‐dose groups. Edaravone was effective during the early reperfusion period, but chronic inhibition of reactive oxygen species may be detrimental for nerve regeneration after ischemia–reperfusion injury. Further studies are necessary to confirm the long‐term influence of edaravone. Muscle Nerve, 2009     

Nitric oxide-induced apoptosis in cultured rat astrocytes: protection by edaravone, a radical scavenger

Nitric oxide induces apoptosis-like cell death in cultured astrocytes, but the exact mechanism is not known. This study further characterized the mechanism of nitric oxide-induced cytotoxicity, and examined the effect of edaravone, a radical scavenger, on cytotoxicity. Treatment of cultured rat astrocytes with sodium nitroprusside (SNP), a nitric oxide donor, for 72 h, decreased cell viability by causing apoptosis-like cell death. The injury was accompanied by increases in the production of reactive oxygen species and in the level of nuclear apoptosis-inducing factor, but not in caspase activity. SNP-induced cytotoxicity was blocked by the c-jun N-terminal protein kinase (JNK) inhibitor SP600125 (20 microM), the p38 mitogen-activated protein (MAP) kinase inhibitor SB203580 (20 microM), and the extracellular signal-regulating kinase (ERK) inhibitor U0126 (10 microM), and the nitric oxide donor stimulated the phosphorylation of p38 MAP kinase, JNK, and ERK. Edaravone (10 microM) protected astrocytes against SNP-induced cell injury and it inhibited SNP-induced phosphorylation of p38 MAP kinase, JNK, and ERK, and the production of reactive oxygen species. Edaravone also attenuated SNP-induced increase in nuclear apoptosis-inducing factor levels. These results suggest that MAP kinase pathways play a key role in nitric oxide-induced apoptosis and that edaravone protects against nitric oxide-induced cytotoxicity by inhibiting nitric oxide-induced MAP kinase activation in astrocytes.     

Preferential neuron loss in the rat piriform cortex following pilocarpine-induced status epilepticus

Structures within the piriform cortex (PC) including the endopiriform nucleus (DEN) and pre-endopiriform nucleus (pEn) have been implicated to be involved in seizure genesis in models of temporal lobe epilepsy. We used stereological methods to examine the specificity and extent of neuron loss in the PC of pilocarpine-treated rats. Both 7 days and 2 months post-status epilepticus rats showed significant neuron loss in the pEn and DEN, layer III of the intermediate PC, and layers II and III of the caudal PC. Total losses in the PC were 40 and 46% in 7 days and 2 months post-status epilepticus rats, respectively (p<0.01). The numbers of parvalbumin (PV)- and cholecystokinin (CCK)-immunopositive neuron profiles significantly decreased, and somatostatin (SS)-immunopositive neuron profiles tended to decrease. A large decrease in the number of PV-immunopositive neuron profiles occurred in the pEn, adjoining parts of the DEN and deep layer III of the PC, portions of the DEN bordering the claustrum and agranular insular cortex, and layer III of the caudal PC. The regions with decreased numbers of PV-, CCK-, and SS-immunopositive neuron profiles overlapped with those where many Nissl-stained neurons were lost and many degenerating cell bodies were detected. These results suggest that the decreases in the numbers of PV/SS/CCK-immunopositive neurons are related to neuron loss rather than to a low rate of synthesis of their peptides or proteins.     

新型自由基清除剂依达拉奉治疗肌萎缩侧索硬化的随机开放临床试验

目的观察新型自由基清除剂依达拉奉治疗肌萎缩侧索硬化的疗效和安全性。方法采用随机数字表分组方法将50例肌萎缩侧索硬化患者随机分为依达拉奉组和对照组，对照组常规给予维生素E和肌生注射液：依达拉奉组在常规药物治疗基础之上加用依达拉奉30mg静脉滴注，1次／d，连续治疗14d。分别于治疗前及治疗后第3、6、9、12、15和18个月进行肌萎缩侧索硬化功能等级评分（ALS-FRS）评价，并观察依达拉奉治疗期间的不良反应。结果两组患者在治疗第3、6、9、12、15和18个月时ALS-FRS变化值的绝对值均不同程度增加（病情加重），且治疗后不同时限ALS-FRS变化值组内差异有统计学意义（P〈0．05），但两组治疗后第3、6、9、12、15和18个月时ALS-FRS变化值组问差异无统计学意义（P=0．081）。生存分析显示，依达拉奉组患者平均生存时间为14．80个月。对照组15．60个月；依达拉奉组患者在第3、6、9、12、15和18个月时的累积生存率分别为96％、96％、80％、76％、60％和60％，对照组为92％、88％、84％、80％、80％和80％，两组Log-rank检验累积生存率差异无统计学意义（P=0．178）。依达拉奉治疗期间未发生明显的不良反应。结论依达拉奉治疗肌萎缩侧索硬化安全．疗效有待于增加样本量或增加剂量进一步证实．     

全蝎醇提物对Li-Pilo癫痫持续状态大鼠海马神经细胞凋亡的影响

目的 探讨全蝎醇提物(Ethanol Extracts of Scorpion,EES)对大鼠癫痫持续状态(SE)后海马神经元凋亡的影响.方法 建立氯化锂.匹罗卡品癫痫持续状态(Lithium-Pilocarpine induced status epilepticus,Li-Pilo SE)模型.使用TUNEL技术观察正常对照组、Li-Piio SE模型组、丙戊酸钠组(VPA)和EES低(L)、中(M)、高(H)剂量组大鼠SE后6h、24h、48h、72h和7d海马CA_1区和CA_3区TUNEL阳性细胞的动态变化,并进行组间比较.结果 正常对照组未见TUNEL阳性细胞.造模各组大鼠SE后6h海马可见部分TUNEL阳性细胞,主要分布在CA_1、CA_3区,其中模型组和EES(L)组72h达高峰,而VPA、EES(M)和EES(H)组高峰提前到SE后48h,以后各组逐渐下降.VPA、EES(M)和EES(H)组SE后各观察时间点TUNEL阳性细胞数较模型组极显著减少(P<0.01),而EES(L)组除个别时间点外,与模型组比较无统计学差异(P>0.05),其中VPA和EES(H)组各时间点TUNEL阳性细胞数减少较EES(M)组(P<0.01,和P<0.05)及EES(L)组(P<0.01,和P<0.05)更显著,EES(M)组各时间点减少又较EES(L)组更显著(P<0.01),而VPA与EES(H)组TUNEL阳性细胞数在各时间点无统计学差异(P>0.05).结论 EES能防止Li-Pilo SE大鼠海马神经元凋亡,并呈明显的量-效关系,高剂量EES抗凋亡作用与VPA相近.     

Neuroprotective effects of the free radical scavenger Edaravone (MCI-186) in mice permanent focal brain ischemia

The present study was aimed to evaluate the effect of the free radical scavenger Edaravone on infarct volume due to permanent MCA occlusion in mice and, if so, to elucidate the mechanism of its neuroprotective effects. Male Balb/c mice were subjected to permanent middle cerebral artery occlusion and were treated with 3.0 mg/kg of Edaravone or vehicle 30 min before ischemia. Infarct volume was assessed by 2,3,5-triphenyltetrazolium chloride (TTC) method after 24 h. Furthermore, in situ detection of superoxide in the ipsilateral neocortex was carried out using the superoxide-sensitive dye dihydroethidium (DHE) staining technique. Pretreatment with 3.0 mg/kg of Edaravone ameliorated the tissue damage in the infarct rim and significantly reduced infarct volume to about 77% of the control (p<0.05). Semi-quantitative measurement of red fluorescence emitted from DHE revealed that the superoxide increased in the ischemic core at 1 h after the onset of ischemia and extended towards the infarct rim at 3 and 6 h, and that pretreatment with 3.0 mg/kg of Edaravone significantly inhibited the increase of superoxide in the infarct rim at 3 and 6 h (p<0.01). Double staining with DHE and monoclonal antibody against NeuN showed that the majority of the nuclei positive for DHE were also positive for NeuN. These findings suggest that Edaravone salvages the boundary zone of infarct by scavenging reactive oxygen species especially in the neurons during permanent focal cerebral ischemia.     

Brain metabolism and diffusion in the rat cerebral cortex during pilocarpine-induced status epilepticus

The real-time iontophoretic method using tetramethylammonium-selective microelectrodes and diffusion-weighted magnetic resonance imaging were used to measure the extracellular space volume fraction alpha, tortuosity lambda and apparent diffusion coefficient of water (ADC(W)) 240 min after the administration of pilocarpine in urethane-anaesthetized rats. The obtained data were correlated with extracellular lactate, glucose, and glutamate concentrations and the lactate/pyruvate-ratio, determined by intracerebral microdialysis. The control values of alpha and lambda were 0.19+/-0.004 and 1.58+/-0.01, respectively. Following pilocarpine application, alpha decreased to 0.134+/-0.012 100 min later. Thereafter alpha increased, reaching 0.176+/-0.009 140 min later. No significant changes in lambda were observed during the entire time course of the experiment. ADC(W) was significantly decreased 100 min after pilocarpine application (549+/-8 microm(2) s(-1)) compared to controls (603+/-11 microm(2) s(-1)); by the end of the experiments, ADC(W) had returned to control values. The basal cortical levels of lactate, the lactate/pyruvate ratio, glucose and glutamate were 0.61+/-0.05 mmol/l, 33.16+/-4.26, 2.42+/-0.13 mmol/l and 6.55+/-1.31 micromol/l. Pilocarpine application led to a rise in lactate, the lactate/pyruvate ratio and glutamate levels, reaching 2.92+/-0.60 mmol/l, 84.80+/-11.72 and 22.39+/-5.85 micromol/l within about 100 min, with a subsequent decrease to control values 140 min later. The time course of changes in glucose levels was different, with maximal levels of 3.49+/-0.24 mmol/l reached 40 min after pilocarpine injection and a subsequent decrease to 1.25+/-0.40 mmol/l observed 200 min later. Pathologically increased neuronal activity induced by pilocarpine causes cell swelling followed by a reduction in the ECS volume fraction, which can contribute to the accumulation of toxic metabolites and lead to the start of epileptic discharges.