Cyclophilin D is a component of mitochondrial permeability transition and mediates neuronal cell death after focal cerebral ischemia

Mitochondrial permeability transition (PT) is a phenomenon induced by high levels of matrix calcium and is characterized by the opening of the PT pore (PTP). Activation of the PTP results in loss of mitochondrial membrane potential, expansion of the matrix, and rupture of the mitochondrial outer membrane. Consequently, PT has been implicated in both apoptotic and necrotic cell death. Cyclophilin D (CypD) appears to be a critical component of the PTP. To investigate the role of CypD in cell death, we created a CypD-deficient mouse. In vitro, CypD-deficient mitochondria showed an increased capacity to retain calcium and were no longer susceptible to PT induced by the addition of calcium. CypD-deficient primary mouse embryonic fibroblasts (MEFs) were as susceptible to classical apoptotic stimuli as the WT, suggesting that CypD is not a central component of cell death in response to these specific death stimuli. However, CypD-deficient MEFs were significantly less susceptible than their WT counterparts to cell death induced by hydrogen peroxide, implicating CypD in oxidative stress-induced cell death. Importantly, CypD-deficient mice displayed a dramatic reduction in brain infarct size after acute middle cerebral artery occlusion and reperfusion, strongly supporting an essential role for CypD in an ischemic injury model in which calcium overload and oxidative stress have been implicated.     

Phagocytosis executes delayed neuronal death after focal brain ischemia

Delayed neuronal loss and brain atrophy after cerebral ischemia contribute to stroke and dementia pathology, but the mechanisms are poorly understood. Phagocytic removal of neurons is generally assumed to be beneficial and to occur only after neuronal death. However, we report herein that inhibition of phagocytosis can prevent delayed loss and death of functional neurons after transient brain ischemia. Two phagocytic proteins, Mer receptor tyrosine kinase (MerTK) and Milk fat globule EGF-like factor 8 (MFG-E8), were transiently up-regulated by macrophages/microglia after focal brain ischemia in vivo. Strikingly, deficiency in either protein completely prevented long-term functional motor deficits after cerebral ischemia and strongly reduced brain atrophy as a result of inhibiting phagocytosis of neurons. Correspondingly, in vitro glutamate-stressed neurons reversibly exposed the “eat-me” signal phosphatidylserine, leading to their phagocytosis by microglia; this neuronal loss was prevented in the absence of microglia and reduced if microglia were genetically deficient in MerTK or MFG-E8, both of which mediate phosphatidylserine-recognition. Thus, phagocytosis of viable neurons contributes to brain pathology and, surprisingly, blocking this process is strongly beneficial. Therefore, inhibition of specific phagocytic pathways may present therapeutic targets for preventing delayed neuronal loss after transient cerebral ischemia.Cerebral ischemia is one of the most common causes of death and disability worldwide and occurs as a result of interrupted blood supply to the brain, resulting in neurodegeneration during stroke and vascular dementia. In the ischemic area where the reduction of blood flow is most pronounced (the core), neuronal death follows rapidly as a result of energy depletion. However, in areas of partial ischemia (the penumbra) and in areas around the infarct (peri-infarct), neurons stressed by ischemia or its consequences are lost only after some delay, providing an opportunity for therapeutic interference hours or days after stroke (1, 2).In addition to the directly neurotoxic effects of ischemia, damage-associated ligands released from dying cells induce a strong inflammatory response, which can cause further neuronal damage. However, inflammation is a self-limiting process and after ischemia and reperfusion, microglia and recruited macrophages clear cell debris and dying cells through phagocytosis (3, 4).Phagocytosis is generally considered to be a beneficial process that leads to clearance of potentially harmful cellular components and may also contribute to the resolution of inflammation (5). It has been assumed that cells are only phagocytosed after they are committed to die (6); therefore, a potential contribution of phagocytosis to pathology has not been investigated. However, it has recently become clear that viable cells exposed to sublethal stimuli may expose the “eat-me” signal phosphatidylserine (PS), leading to their phagocytosis and thus death (7–11).The recognition of cells exposing PS can be mediated by a variety of proteins and is dependent on the inflammatory state of the macrophage (for review, see ref. 12). For example, two phagocytic proteins that have been shown to be up-regulated by inflammatory activation are: (i) Milk fat globule EGF-like factor-8 (MFG-E8), which binds PS on the phagocytic target cell and the vitronectin receptor on macrophages (13); and (ii) Mer receptor tyrosine kinase (MerTK), which detects PS-exposing target cells with the help of PS-binding bridging proteins, such as Gas6 and Protein S (14, 15). However, MerTK can also initiate engulfment because of phosphorylation by focal adhesion kinase downstream of the MFG-E8 receptor, the vitronectin receptor (16).Interestingly, it has been shown that viable neurons in the ischemic penumbra and surrounding brain are labeled by annexin V, indicating PS exposure peaking 3 d after transient ischemia but reversing thereafter (17), and large numbers of stressed neurons and phagocytic microglia are found together in brain regions during and after ischemia (1, 3). We therefore hypothesized that phagocytosis may contribute to delayed neuronal loss after cerebral ischemia. Our data show that phagocytosis executes neuronal death after transient brain ischemia, because blocking phagocytic signaling prevents both the delayed neuronal loss and long-term functional deficits.     

脑缺血后细胞死亡的形式及其分子机制

脑缺血后神经细胞的死亡形式有多种,包括缺血核心区立即发生的细胞坏死,以及随后再灌注过程中由氧化应激和炎症反应等机制引起的细胞凋亡和自噬.脑缺血后,各种不同分子机制最终导致细胞死亡,其过程涉及多条信号通路.通过对细胞死亡的不同形式及其机制进行干预,能减少脑缺血后细胞死亡.     

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.     

Recovery of neuronal transmission after prolonged cerebral ischemia

The potentials of postischemic functional recovery were studied in cats submitted to 1 h of complete cerebrocirculatory arrest in normothermia. Neuronal activity was estimated by recording the electroencephalogram (EEG), the pyramidal response following stimulation of the motor cortex and the somatosensorily evoked cortical potentials. During ischemia EEG was suppressed within 12-15 s, evoked potentials within 2 min, and the pyramidal response within 5 min. After recirculation following ischemia, the electrically evoked D wave of the pyramidal response began to reappear between 7 and 9 min and the synaptically evoked I wave between 25 and 60 min. The evoked cortical potentials returned in parallel with the I wave of the pyramidal response but control amplitude was not reached before 3 h. The peak latencies of the evoked potentials were consistently prolonged for at least 24 h but normalized after a few days, provided secondary postischemic circulatory disturbances could be prevented. EEG began to recover after the beginning appearance of the somatosensorily evoked cortical potentials; initially it exhibited a burst-suppression pattern but it gradually progressed to continuous activity. The frequency pattern of the EEG normalized within 24 h and the amplitude after a few days. After recovery, the behavior of the pyramidal response and of evoked potentials to repetitive stimulation was the same as under control conditions.     

The PIDDosome mediates delayed death of hippocampal CA1 neurons after transient global cerebral ischemia in rats

A brief period of global brain ischemia, such as that induced by cardiac arrest or cardiopulmonary bypass surgery, causes cell death in vulnerable hippocampal CA1 pyramidal neurons days after reperfusion. Although numerous factors have been suggested to account for this phenomenon, the mechanisms underlying it are poorly understood. We describe a cell death signal called the PIDDosome, a protein complex of p53-induced protein with a death domain (PIDD), receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (RAIDD), and procaspase-2. We induced 5 min of transient global cerebral ischemia (tGCI) using bilateral common carotid artery occlusion with hypotension. Western blot analysis showed that expression of twice-cleaved fragment of PIDD (PIDD-CC) increased in the cytosolic fraction of the hippocampal CA1 subregion and preceded procaspase-2 activation after tGCI. Caspase-2 cleaved Bid in brain homogenates. Co-immunoprecipitation and immunofluorescent studies demonstrated that PIDD-CC, RAIDD, and procaspase-2 were co-localized and bound directly, which indicates the formation of the PIDD death domain complex. Furthermore, we tested inhibition of PIDD expression by using small interfering RNA (siRNA) treatment that was initiated 48 h before tGCI. Administration of siRNA against PIDD decreased not only expression of PIDD-CC, but also activation of procaspase-2 and Bid, resulting in a decrease in histological neuronal damage and DNA fragmentation in the hippocampal CA1 subregion after tGCI. These results imply that PIDD plays an important role in procaspase-2 activation and delayed CA1 neuronal death after tGCI. We propose that PIDD is a hypothetical molecular target for therapy against neuronal death after tGCI.     

Erythropoietin prevents neuronal apoptosis after cerebral ischemia and metabolic stress

Erythropoietin (EPO) promotes neuronal survival after hypoxia and other metabolic insults by largely unknown mechanisms. Apoptosis and necrosis have been proposed as mechanisms of cellular demise, and either could be the target of actions of EPO. This study evaluates whether antiapoptotic mechanisms can account for the neuroprotective actions of EPO. Systemic administration of EPO (5,000 units/kg of body weight, i.p.) after middle-cerebral artery occlusion in rats dramatically reduces the volume of infarction 24 h later, in concert with an almost complete reduction in the number of terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling of neurons within the ischemic penumbra. In both pure and mixed neuronal cultures, EPO (0.1--10 units/ml) also inhibits apoptosis induced by serum deprivation or kainic acid exposure. Protection requires pretreatment, consistent with the induction of a gene expression program, and is sustained for 3 days without the continued presence of EPO. EPO (0.3 units/ml) also protects hippocampal neurons against hypoxia-induced neuronal death through activation of extracellular signal-regulated kinases and protein kinase Akt-1/protein kinase B. The action of EPO is not limited to directly promoting cell survival, as EPO is trophic but not mitogenic in cultured neuronal cells. These data suggest that inhibition of neuronal apoptosis underlies short latency protective effects of EPO after cerebral ischemia and other brain injuries. The neurotrophic actions suggest there may be longer-latency effects as well. Evaluation of EPO, a compound established as clinically safe, as neuroprotective therapy in acute brain injury is further supported.     

预处理对老年鼠脑缺血bcl-2表达及细胞凋亡的影响

目的观察缺血预处理对脑缺血再灌注损伤的保护作用。方法将SD老年大鼠分为2组缺血预处理10min再灌注24h再次缺血24h组(PI)及单纯缺血对照组(CI),采用尼龙线栓法制作大鼠局灶性脑缺血模型,通过免疫组化染色技术及原位末端标记技术(TUNEL)检测大鼠大脑皮质bcl-2蛋白的表达和细胞凋亡情况。结果PI组较CI组缺血皮层bcl-2蛋白表达明显增强(P<0.01)。PI组缺血皮层凋亡细胞较CI组明显减少(P<0.05)。结论缺血预处理使缺血脑组织bcl-2蛋白表达增强,抑制凋亡细胞产生,说明缺血预处理对再次脑缺血有保护作用。     

全脑缺血再灌注后迟发性神经元坏死与细胞因子bFGF的相关性研究

目的　探讨细胞因子 b FGF在迟发性神经元坏死时表达的动态变化及对中枢神经系统起到的保护与修复作用。方法　采用了 HE染色、尼氏染色、透射电镜、免疫组化及 RT- PCR等技术。结果　常规光镜及电镜观察均显示再灌注 1～ 7d额叶皮层及海马有不同程度的神经元变性、坏死。免疫组化学结果及 RT- PCR检测均显示皮层与海马区缺血组织 b FGF在缺血再灌注后呈明显阳性表达。结论　在脑缺血损伤 ,尤其是在发生迟发性神经元坏死时 b FGF可呈现明显强于正常脑组织的表达且贯穿于缺血再灌注全过程中。 b FGF在发生迟发性神经元坏死时 ,对中枢神经系统均有保护和修复作用     

罗格列酮对大鼠局灶性脑缺血葡萄糖再灌注性损伤的影响

目的探讨血糖水平和胰岛素反应状态在局灶性脑缺血大鼠再灌注性脑损伤中的作用。方法将雄性SD大鼠随机分为局灶性脑缺血/再灌注模型生理盐水对照组、罗格列酮(RSG)高、中、低剂量预处理组(4、2、1 mg·kg~(-1)·d~(-1))、假手术组,每组8只。线栓法制备大鼠大脑中动脉闭塞2 h再灌注22 h模型(MCAO)。测定空腹血糖(FPG)、甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、血压、血清胰岛素水平,计算胰岛素敏感指数(IAI)。观察RSG对大鼠脑梗死体积和神经功能评分的影响。结果 IAI与梗死体积和神经功能评分存在相关性。与生理盐水对照组比较,RSG各剂量组脑梗死体积显著缩小,神经功能评分显著改善(P<0.05或P<0.01),胰岛素敏感性显著增高(P<0.05或P<0.01),脑缺血后高血糖显著减轻(P<0.05),并呈剂量依赖性。结论高血糖和胰岛素抵抗共同作用加重局灶性脑缺血葡萄糖再灌注性脑损伤,且胰岛素抵抗更持久;RSG对脑缺血葡萄糖再灌注性脑损伤的神经保护,单纯降低血糖是不够的,改善胰岛素抵抗更重要。     

Stress signaling through Ca2+/calmodulin-dependent protein phosphatase calcineurin mediates salt adaptation in plants

Calcineurin (CaN) is a Ca²⁺- and calmodulin-dependent protein phosphatase (PP2B) that, in yeast, is an integral intermediate of a salt-stress signal transduction pathway that effects NaCl tolerance through the regulation of Na⁺ influx and efflux. A truncated form of the catalytic subunit and the regulatory subunit of yeast CaN were coexpressed in transgenic tobacco plants to reconstitute a constitutively activated phosphatase in vivo. Several different transgenic lines that expressed activated CaN also exhibited substantial NaCl tolerance, and this trait was linked to the genetic inheritance of the CaN transgenes. Enhanced capacity of plants expressing CaN to survive NaCl shock was similar when evaluation was conducted on seedlings in tissue culture raft vessels or plants in hydroponic culture that were transpiring actively. Root growth was less perturbed than shoot growth by NaCl in plants expressing CaN. Also, NaCl stress survival of control shoots was enhanced substantially when grafted onto roots of plants expressing CaN, further implicating a significant function of the phosphatase in the preservation of root integrity during salt shock. Together, these results indicate that in plants, like in yeast, a Ca²⁺- and calmodulin-dependent CaN signal pathway regulates determinants of salt tolerance required for stress adaptation. Furthermore, modulation of this pathway by expression of an activated regulatory intermediate substantially enhanced salt tolerance.     

局灶性脑缺血后神经干细胞增殖及GDNF表达变化的实验研究

目的研究局灶性脑缺血后大鼠脑内神经干细胞(NSCs)增殖情况及与胶质细胞源性神经营养因子(GDNF)表达变化的关系。方法将24只SD大鼠随机分为假手术组和模型1组、模型2组、模型3组各6只,后三组用大脑中动脉栓塞法(MCAO)制备局灶性脑缺血模型,分别于术后3、7、14 d处死;假手术组除不以尼龙线阻塞大脑中动脉起始部外,其他操作与模型1组相同。采用免疫组化染色法观察5-溴脱氧尿嘧啶核苷(BrdU)标记的细胞及巢蛋白(Nestin)、GDNF阳性细胞表达,BrdU/Nestin免疫荧光双标法观察NSCs变化。结果模型2组损伤侧脑室下层(SVZ)BrdU阳性细胞显著多于假手术组(P<0.05),模型3组与假手术组相似;模型2、3组皮层梗死灶周围BrdU阳性细胞均显著多于假手术组(P<0.01、0.05);模型1、2组皮层梗死灶周围Nestin阳性细胞均显著多于假手术组(P均<0.01),BrdU/Nestin免疫荧光双标显示BrdU阳性细胞几乎均为Nestin阳性;模型2、3组皮层梗死灶周围GDNF阳性细胞均显著多于假手术组(P均<0.05)。结论大鼠局灶性脑缺血后3～14 d内源性NSCs增殖加快,GDNF表达增加可能对其起促进作用。     

大鼠脑缺血再灌注后脑源性神经营养因子的表达及意义

目的　研究脑局灶缺血再灌注后脑源性神经营养因子 (BDNF)的表达规律及其意义。方法　健康雄性Wistar大鼠 30只 ,随机分为正常对照组、假手术组和缺血再灌注组 ,按照改良的栓线法建立大脑中动脉缺血再灌注大鼠模型。用免疫组织化学方法检测BDNF在脑组织中的表达情况。结果　BDNF免疫阳性表达在缺血再灌注组的梗死中心区梗死灶边缘带有显著增强的阳性表达。再灌注 15min开始增多 ,再灌注 1h明显增多 ,2h达到高峰 ,4h开始下降 ,2 4h恢复至正常对照组水平。结论　缺血再灌注损伤可诱导BDNF极早表达 ,并迅速升高 ,有利于缺血再灌注损伤后神经细胞的存活及后期神经功能恢复     

四逆汤对局部脑缺血大鼠的保护作用及其神经酰胺机制

目的：研究四逆汤对大鼠局部脑缺血后脑组织神经酰胺含量的影响。方法：采用大鼠大脑中动脉局部阻塞模型（MCAO），观察四逆汤对脑缺血大鼠丙二醛（MDA）和神经酰胺含量、以及超氧化物歧化酶（SOD）活性的影响。结果：与正常组比较，缺血模型组MDA含量和脑组织神经酰胺含量均显著升高；与缺血模型组比较，四逆汤组能提高SOD的活性，减少MDA的产生（P〈0．05），降低神经酰胺含量（P〈0．001）。结论：四逆汤能对局部脑缺血大鼠产生保护作用，其可能机制是减轻氧化损伤，减少神经酰胺的生成量。     

The importin/karyopherin Kap114 mediates the nuclear import of TATA-binding protein

Two high copy suppressors of temperature-sensitive TATA-binding protein (TBP) mutants were isolated. One suppressor was TIF51A, which encodes eukaryotic translation initiation factor 5A. The other high copy suppressor, YGL241W, also known as KAP114, is one of 14 importin/karyopherin proteins in yeast. These proteins mediate the transport of specific macromolecules into and out of the nucleus. Cells lacking Kap114 partially mislocalize TBP to the cytoplasm. Kap114 binds TBP in vitro, and binding is disrupted in the presence of GTPgammaS. Therefore, Kap114 is an importer of TBP into the nucleus, but alternative import pathways must also exist.     

Caspase activation and neuroprotection in caspase-3- deficient mice after in vivo cerebral ischemia and in vitro oxygen glucose deprivation

Caspase-3 is a major cell death effector protease in the adult and neonatal nervous system. We found a greater number and higher density of cells in the cortex of caspase-3(-/-) adult mice, consistent with a defect in developmental cell death. Caspase-3(-/-) mice were also more resistant to ischemic stress both in vivo and in vitro. After 2 h of ischemia and 48 h of reperfusion, cortical infarct volume was reduced by 55%, and the density of terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling-positive cells was decreased by 36% compared with wild type. When subjected to oxygen-glucose deprivation (2 h), cortical neurons cultured from mice deficient in caspase-3 expression were also more resistant to cell death by 59%. Mutant brains showed caspase-specific poly(ADP-ribose) polymerase cleavage product (85-kDa fragment) in vivo and in vitro, suggesting redundant mechanisms and persistence of caspase-mediated cell death. In the present study, we found that caspase-8 mediated poly(ADP-ribose) polymerase cleavage in caspase-3(-/-) neurons in vivo and in vitro. In addition, mutant neurons showed no evidence of compensatory activation by caspase-6 or caspase-7 after ischemia. Taken together, these data extend the pharmacological evidence supporting an important role for caspase-3 and caspase-8 as cell death mediators in mammalian cortex and indicate the potential advantages of targeting more than a single caspase family member to treat ischemic cell injury.     

细胞内丝裂原活化蛋白激酶信号通路与脑缺血后神经元凋亡

脑缺血可导致梗死核心区细胞坏死和缺血半暗带细胞凋亡。脑缺血后,丝裂原活化蛋白激酶（mitogen－activated protein kinases, MAPKs）信号通路被激活,引起程序性细胞死亡,包括细胞凋亡。文章就M APKs信号家族与脑缺血后神经元凋亡的关系进行了综述。     

The contribution of protease-activated receptor 1 to neuronal damage caused by transient focal cerebral ischemia

The serine proteases tissue plasminogen activator, plasmin, and thrombin and their receptors have previously been suggested to contribute to neuronal damage in certain pathological situations. Here we demonstrate that mice lacking protease-activated receptor 1 (PAR1) have a 3.1-fold reduction in infarct volume after transient focal cerebral ischemia. Intracerebroventricular injection of PAR1 antagonist BMS-200261 reduced infarct volume 2.7-fold. There are no detectable differences between PAR1-/- and WT mice in cerebrovascular anatomy, capillary density, or capillary diameter, demonstrating that the neuroprotective phenotype is not likely related to congenital abnormalities in vascular development. We also show that the exogenously applied serine proteases thrombin, plasmin, and tissue plasminogen activator can activate PAR1 signaling in brain tissue. These data together suggest that if blood-derived serine proteases that enter brain tissue in ischemic situations can activate PAR1, this sequence of events may contribute to the harmful effects observed. Furthermore, PAR1 immunoreactivity is present in human brain, suggesting that inhibition of PAR1 may provide a novel potential therapeutic strategy for decreasing neuronal damage associated with ischemia and blood-brain barrier breakdown.     

脑缺血再灌流损伤神经细胞凋亡与Bcl-2和caspase-3的关系

目的 探讨大鼠局灶性脑缺血再灌流后神经细胞凋亡及其与Bcl-2和caspase-3基因表达的关系。方法应用原位末端标记(TUNEL)和原位杂交技术分别观察脑缺血再灌流不同时间点神经细胞凋亡的变化与Bcl-2mRNA和caspase-3 mRNA的表达。结果(1)脑缺血再灌流后凋亡神经细胞主要分布于缺血周围区，随着再灌流时间的延长凋亡细胞数逐渐增加，至24h达高峰，2d开始下降，14d时仍高于假手术组。(2)脑缺血再灌注2h后，神经细胞Bel-2 mRNA开始表达，并随着再灌流时间的延长而增强，12～24h达高峰，2d后逐渐下降，至14d略高于假手术组。(3)脑缺血再灌流后，神经细胞caspase-3 mRNA的表达与Bcl-2m RNA的表达规律相似，但于再灌流24h达高峰。结论脑缺血再灌流后，缺血周围区神经细胞的凋亡是-个动态的渐进过程，Bel-2基因表达可能抑制细胞凋亡，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。     

Neuroprotective role of estradiol against neuronal death induced by glucose deprivation in cultured rat hippocampal neurons

Studies have reported the protective effect of estradiol (E(2)) against neuronal death induced by several insults including oxygen deprivation, mitochondrial toxins and activation of glutamate receptors. Glucose deprivation (GD) is associated with ischemia and hypoglycemia, and to date there is no effective therapeutic agent able to prevent neuronal damage induced by these conditions. In this study, we have investigated the effects of 17β-E(2) and the selective agonists of the alpha (ERα) and beta (ERβ) estrogen receptors, propyl pyrazole triol (PPT) and diarylpropionitrile (DPN), respectively, on neuronal death induced by GD in cultured rat hippocampal neurons. We have also analyzed the expression of both ER isoforms after GD. Results show that GD for 2 and 4 h reduces cell survival by 42 and 55%, respectively. Treatment with 17β-E(2) (10 nM to 10 μM) induces a dose-dependent protective effect that is blocked by ICI 182,780, an ER antagonist, and by 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(-piperidinylethoxy)phenol]-1H'pyrazole dihydrochloride (MPP) and 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP), selective ERα and ERβ antagonists, respectively. The ERα and ERβ agonists PPT and DPN show a similar neuroprotective effect to that of 17β-E(2), but DPN is more efficient. In addition, hippocampal neurons under normal conditions show a higher expression of the ERβ isoform. When exposed to GD during 4 h, the expression of both ER isoforms is increased, while only that of the ERβ isoform significantly increases after 2 h of GD. Results demonstrate that E(2) prevents neuronal death induced by GD through its interaction with ER, although the ERβ isoform might have a predominant role. Results also suggest that GD differentially alters the expression of ERα and ERβ in hippocampal neurons.