The p75 neurotrophin receptor is essential for neuronal cell survival and improvement of functional recovery after spinal cord injury

The mechanisms initiating post-spinal cord injury (SCI) apoptotic cell death remain incompletely understood. The p75 neurotrophin receptor (p75(NTR)) has been shown to exert both pro-survival and pro-apoptotic effects on neural cells in vitro. While a previous study had shown that there is decreased oligodendrocyte apoptosis distal to a clean partial transection injury of the cord in mice with nonfunctional p75(NTR), most human spinal cord injuries do not involve partial transections but are rather due to compression/contusion injuries with significant perilesional ischemia. Therefore, we sought to examine the role of the p75(NTR) in a clinically relevant clip compression model of SCI in p75 null mice with an exon III mutation. Mice with a functional p75(NTR) had increased caspase-9 activation at 3 days after SCI in comparison to the functionally deficient p75(NTR) mice. However, at 7 days following SCI there was no difference in the activation of the effector caspases (caspase-3 and caspase-6) at the spinal cord lesion. Moreover, at 7 days after injury, there was increased terminal deoxynucleotidyl transferase-mediated dUTP nick-end (TUNEL) positive cell death at the injury site in the functionally deficient p75(NTR) mice. Using double labeling with TUNEL and cell specific markers we showed that the absence of p75(NTR) function increased the extent of neuronal but not oligodendroglial cell death at the injury site. This selective loss of neuronal cells after SCI was confirmed with a decrease in levels of microtubule-associated protein 2 in the p75 null mice. Furthermore, the wild-type animals had dramatically improved survival and enhanced locomotor recovery at 8 weeks after SCI when compared with the p75(NTR) null mice. Also at 8 weeks, there were significantly more neurons present at the injury site of wild-type mice when compared with p75 null mice. We conclude that the p75(NTR) receptor is integral to neuronal cell survival and endogenous reparative mechanisms after compressive/contusive SCI.     

Evidence that Par-4 Participates in the Pathogenesis of HIV Encephalitis

Progressive neuronal degeneration in brain regions involved in learning and memory processes is a common occurrence in patients infected with human immunodeficiency virus type 1 (HIV-1). We now report that levels of Par-4, a protein recently linked to neuronal apoptosis in Alzheimer's disease, are increased in neurons in hippocampus of human patients with HIV encephalitis and in monkeys infected with a chimeric strain of HIV-1 and simian immunodeficiency virus. Par-4 levels increased rapidly in cultured hippocampal neurons following exposure to the neurotoxic HIV-1 protein Tat, and treatment of the cultures with a Par-4 antisense oligonucleotide protected the neurons against Tat-induced apoptosis. Additional findings show that Par-4 participates at an early stage of Tat-induced neuronal apoptosis before caspase activation, oxidative stress, and mitochondrial dysfunction. Our data suggest that Par-4 may be a mediator of neuronal apoptosis in HIV encephalitis and that therapeutic approaches targeting the Par-4 apoptotic cascade may prove beneficial in preventing neuronal degeneration and associated dementia in patients infected with HIV-1.     

Cell-specific DNA fragmentation may be attenuated by a survivin-dependent mechanism after traumatic brain injury in rats

Survivin attenuates apoptosis by inhibiting cleavage of some cell proteins by activated caspase-3. We recently discovered strong up-regulation of survivin, primarily in astrocytes and a sub-set of neurons, after traumatic brain injury (TBI) in rats. In this study we characterized co-expression of survivin with activated caspase-3 and downstream DNA fragmentation (TUNEL) in astrocytes and neurons after TBI. Western blot analysis revealed significant time-dependent increases in active caspase-3 between 5 and 14 days post-injury. No difference was observed between the proportion of survivin-positive and survivin-negative cells labeled with active caspase-3 at 5 or 7 days post-injury, as indicated by dual fluorescent immunostaining. Labeling of survivin-negative cells with TUNEL was, however, significantly greater than for survivin-positive cells, suggesting that expression of survivin may attenuate DNA cleavage and progression of apoptosis. A higher proportion of astrocytes than neurons accumulated active caspase-3. In contrast, co-localization with TUNEL was significantly higher for neurons than for astrocytes. These data suggest that survivin expression may attenuate DNA cleavage and cell death, and that this mechanism operates in a cell type-specific manner after TBI.     

Mitochondrial localization of cellular prion protein (PrPC) invokes neuronal apoptosis in aged transgenic mice overexpressing PrPC

Recent studies suggest that the disease isoform of prion protein (PrPSc) is non-neurotoxic in the absence of cellular isoform of prion protein (PrPC), indicating that PrPC may participate directly in the neurodegenerative damage by itself. Meanwhile, transgenic mice harboring a high-copy-number of wild-type mouse (Mo) PrPC develop a spontaneous neurological dysfunction in an age-dependent manner, even without inoculation of PrPSc and thus, investigations of these aged transgenic mice may lead to the understanding how PrPC participate in the neurotoxic property of PrP. Here we demonstrate mitochondria-mediated neuronal apoptosis in aged transgenic mice overexpressing wild-type MoPrPC (Tg(MoPrP)4053/FVB). The aged mice exhibited an aberrant mitochondrial localization of PrPC concomitant with decreased proteasomal activity, while younger littermates did not. Such aberrant mitochondrial localization was accompanied by decreased mitochondrial manganese superoxide dismutase (Mn-SOD) activity, cytochrome c release into the cytosol, caspase-3 activation, and DNA fragmentation, most predominantly in hippocampal neuronal cells. Following cell culture studies confirmed that decrease in the proteasomal activity is fundamental for the PrPC-related, mitochondria-mediated apoptosis. Hence, the neurotoxic property of PrPC could be explained by the mitochondria-mediated neuronal apoptosis, at least in part.     

Neuronal apoptosis and autophagy cross talk in aging PS/APP mice, a model of Alzheimer's disease

Mechanisms of neuronal loss in Alzheimer’s disease (AD) are poorly understood. Here we show that apoptosis is a major form of neuronal cell death in PS/APP mice modeling AD-like neurodegeneration. Pyknotic neurons in adult PS/APP mice exhibited apoptotic changes, including DNA fragmentation, caspase-3 activation, and caspase-cleaved α-spectrin generation, identical to developmental neuronal apoptosis in wild-type mice. Ultrastructural examination using immunogold cytochemistry confirmed that activated caspase-3-positive neurons also exhibited chromatin margination and condensation, chromatin balls, and nuclear membrane fragmentation. Numbers of apoptotic profiles in both cortex and hippocampus of PS/APP mice compared with age-matched controls were twofold to threefold higher at 6 months of age and eightfold higher at 21 to 26 months of age. Additional neurons undergoing dark cell degeneration exhibited none of these apoptotic features. Activated caspase-3 and caspase-3-cleaved spectrin were abundant in autophagic vacuoles, accumulating in dystrophic neurites of PS/APP mice similar to AD brains. Administration of the cysteine protease inhibitor, leupeptin, promoted accumulation of autophagic vacuoles containing activated caspase-3 in axons of PS/APP mice and, to a lesser extent, in those of wild-type mice, implying that this pro-apoptotic factor is degraded by autophagy. Leupeptin-induced autophagic impairment increased the number of apoptotic neurons in PS/APP mice. Our findings establish apoptosis as a mode of neuronal cell death in aging PS/APP mice and identify the cross talk between autophagy and apoptosis, which influences neuronal survival in AD-related neurodegeneration.     

Inhibition of apoptosis by the intrinsic but not the extrinsic apoptotic pathway in myocardial ischemia-reperfusion

SummaryThe detailed molecular mechanisms following activation of apoptosis in ischemia-reperfusion injury are unknown. This study using different transgenic mouse models provided first evidence that apoptosis in myocardial ischemia-reperfusion injury is rather linked to the mitochondrial pathway than to death receptor pathway.IntroductionThere is a wealth of evidence for activation of apoptosis in ischemia-reperfusion injury. However, the understanding of detailed molecular mechanism is lacking.MethodsThe extent of myocardial infarction after ligation of the left anterior descending artery in mice carrying different transgenes for inhibition of either the intrinsic or the extrinsic or a combination of both apoptotic cascades was evaluated. The extent of myocardial damage was assessed by echocardiographic determination of left ventricular (LV) ejection fraction, LV hemodynamics, troponin T, and histology. The rate of apoptosis was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and caspase-3 staining.ResultsHighest perioperative rate of death was observed in the dominant-negative form of a truncated Fas-associated death domain (FADD-DN) group. Infarction size by 2,3,5-triphenyltetrazolium chloride (TTC) staining was smaller in the Bcl-2, but not in the other groups as compared to wild-type mice. This was accompanied by lower troponin T values in Bcl-2 transgenic mice as compared to the all other groups. Troponin T correlated well with macroscopic extent of myocardial infarction by TTC staining. A lower decline of LV ejection fraction was seen in the Bcl-2 as compared to wild-type or FADD-DN mice. A smaller number of TUNEL- and caspase-3-positive myocyte nuclei were observed in the Bcl-2 and FADD-DN group as compared to wild-type mice.ConclusionsWe provide first evidence for protective effects on the myocardium in a transgenic mouse model of myocardial ischemia-reperfusion due to inhibition of the Bcl-2, but not the FADD pathway despite that reduced apoptotic cells were observed in both groups as compared to wild-type mice.     

PGC-1α过表达逆转OGD/R诱导的神经元线粒体功能降低和凋亡

目的:探讨过氧化物酶体增殖物激活受体γ辅助活化因子1α(PGC-1α)基因过表达对氧糖剥夺/复氧(OGD/R)诱导的神经元线粒体功能及细胞凋亡的影响。方法:采用RT-PCR的方法从C57BL/6乳鼠大脑皮层获取PGC-1α的全基因序列,并克隆到真核表达载体p EGFP-N1上,经PCR初步鉴定后转染原代皮层神经元,Western blot鉴定PGC-1α的表达情况,成功构建PGC-1α真核表达载体p EGFP-N1-PGC-1α。分别将转染p EGFP-N1和p EGFP-N1-PGC-1α载体的皮层神经元进行OGD/R处理,分别采用Mito Tracker Red染色、流式细胞术、ATP代谢检测试剂盒和TUNEL细胞凋亡检测试剂盒检测线粒体质量分数、活性氧簇(ROS)和ATP生成、细胞凋亡以及caspase-3激活的变化。结果:PGC-1α过表达可抑制OGD/R诱导的神经元线粒体生成能力的降低和ROS的生成(P0.05),增强ATP的合成能力(P0.01),抑制神经元的凋亡(P0.01)并降低caspase-3的激活(P0.05)。结论:PGC-1α过表达可通过促进线粒体生成、抑制ROS的产生和维护线粒体功能而抑制OGD/R诱导的神经元凋亡。PGC-1α可以作为开发脑缺血再灌注损伤药物的靶标之一。     

Caspase-3 activity is reduced after spinal cord injury in mice lacking dynorphin: differential effects on glia and neurons

Dynorphins are endogenous opioid peptide products of the prodynorphin gene. An extensive literature suggests that dynorphins have deleterious effects on CNS injury outcome. We thus examined whether a deficiency of dynorphin would protect against tissue damage after spinal cord injury (SCI), and if individual cell types would be specifically affected. Wild-type and prodynorphin(-/-) mice received a moderate contusion injury at 10th thoracic vertebrae (T10). Caspase-3 activity at the injury site was significantly decreased in tissue homogenates from prodynorphin(-/-) mice after 4 h. We examined frozen sections at 4 h post-injury by immunostaining for active caspase-3. At 3-4 mm rostral or caudal to the injury, >90% of all neurons, astrocytes and oligodendrocytes expressed active caspase-3 in both wild-type and knockout mice. At 6-7 mm, there were fewer caspase-3(+) oligodendrocytes and astrocytes than at 3-4 mm. Importantly, caspase-3 activation was significantly lower in prodynorphin(-/-) oligodendrocytes and astrocytes, as compared with wild-type mice. In contrast, while caspase-3 expression in neurons also declined with further distance from the injury, there was no effect of genotype. Radioimmunoassay showed that dynorphin A(1-17) was regionally increased in wild-type injured versus sham-injured tissues, although levels of the prodynorphin processing product Arg(6)-Leu-enkephalin were unchanged. Our results indicate that dynorphin peptides affect the extent of post-injury caspase-3 activation, and that glia are especially sensitive to these effects. By promoting caspase-3 activation, dynorphin peptides likely increase the probability of glial apoptosis after SCI. While normally beneficial, our findings suggest that prodynorphin or its peptide products become maladaptive following SCI and contribute to secondary injury.     

Increased oxidative stress is associated with chronic intermittent hypoxia-mediated brain cortical neuronal cell apoptosis in a mouse model of sleep apnea

Chronic intermittent hypoxia (CIH), as occurs in obstructive sleep apnea (SA), is associated with substantial cortico-hippocampal damage leading to impairments of neurocognitive, respiratory and cardiovascular functions. Previous studies in a rat model have shown that CIH increases brain cortical neuronal cell death. However, the molecular events leading to CIH-mediated neuronal cell death remain largely undefined. The oscillation of O2 concentrations during CIH remarkably mimics the processes of ischemia/re-oxygenation and could therefore increase cellular production of reactive oxygen species (ROS). We extended the CIH paradigm to a mouse model of SA to identify the molecular mechanisms underlying cortical neuronal cell death. A significant increase of ROS production in mouse brain cortex and cortical neuronal cells was detected by fluorescent oxidation assays upon exposure of mice to CIH, followed by increased expression of oxidative stress response markers, c-Fos, c-Jun and NF-kappaB in mouse brain cortex, as revealed by immunohistochemical and LacZ reporter assays respectively. Long-term exposure of mice to CIH increased the levels of protein oxidation, lipid peroxidation and nucleic acid oxidation in mouse brain cortex. Furthermore, exposure of mice to CIH induced caspase-3 activation and increased some cortical neuronal cell apoptosis. On the other hand, transgenic mice overexpressing Cu,Zn-superoxide dismutase exposed to CIH conditions had a lower level of steady-state ROS production and reduced neuronal apoptosis in brain cortex compared with that of normal control mice. Taken together, these findings suggest that the increased ROS production and oxidative stress propagation contribute, at least partially, to CIH-mediated cortical neuronal apoptosis and neurocognitive dysfunction.     

Differential activation of caspase-3 at two maturational stages during okadaic acid-induced rat neuronal death

Okadaic acid (OA), a protein phosphatase inhibitor, is used as a research model of Alzheimer's disease to induce tau phosphorylation and neuronal death. We reported previously that OA induces neuronal apoptosis of immature neurons (in vitro days (IVD) 3-5), which is inhibited by cycloheximide (CHX). In this study, we demonstrate that CHX fails to prevent OA-induced neuronal death in mature neurons (IVD 14-15). Upon comparison of both types of dying cells, the immature neurons displayed characteristic features of apoptosis, such as nuclear fragmentation, phosphatidylserine externalization and prominent caspase-3 activation, while the mature neurons showed few characteristic features of apoptosis. Lack of the beneficial effects of CHX and the lesser activation of caspase-3 in the mature neurons argue against typical apoptotic neuronal death in the OA-induced neurodegeneration model.     

Thalamic neuron apoptosis emerges rapidly after cortical damage in immature mice

In adults and children, head trauma can have long-term neuropathological and functional consequences. The thalamus is a major site of remote neurodegeneration after cortical damage in adult humans and experimental animals, but less is known about thalamic responses to cortical injury in the immature brain. This study introduces an in vivo model of axotomy/target deprivation-induced neuronal apoptosis in the dorsal lateral geniculate nucleus of the thalamus produced by unilateral ablation of the occipital cortex in the immature mouse. We specifically examined whether occipital cortex ablation in the immature brain causes apoptotic death of projection neurons in the dorsal lateral geniculate nucleus. After unilateral occipital cortex aspiration, 10-day-old C57BL/6 mice were recovered for up to 28 days. Fluorogold-prelabeled thalamocortical projection neurons were apoptotic at 36-48 h after ablation. The structural progression of apoptosis in the immature lateral geniculate nucleus reveals typical chromatolytic morphology by 18-24 h, followed by cytoplasmic shrinkage and chromatin condensation characteristic of end-stage apoptosis after 36-48 h. Electron microscopy confirmed the presence of apoptosis. This study shows internucleosomal DNA fragmentation and expression of cleaved caspase-3 occurs rapidly, being noted first at 18 h, well before the peak of apoptotic cell death occurring at 36 h after cortical damage in the immature brain.From these data we suggest that axotomy/target deprivation-induced cell death in the immature brain may: (1) differ from that previously reported in adult mice with respect to the time required for progression to cell death; (2) be mediated by caspase-3 activation.     

Herpes simplex virus 1 inhibits apoptosis through a caspase-3-dependent pathway in primary cultures of cortical neuronal cells of fetal mice

We could induce apoptosis in primary cultures of cortical neurons of fetal mice with ceramide or sorbitol. The induction was accompanied by an increase in caspase-3 (CAS-3) activity and depolarization of the inner mitochondrial membrane of neuronal cells which both could be reversed by Herpes simplex virus 1 (HSV-1) infection. We conclude tha HSV-1 infection inhibited the apoptosis, induced in neuronal cells by sorbitol or ceramide, via a CAS-dependent pathway.     

Dynamic change of SGK expression and its role in neuron apoptosis after traumatic brain injury

Aims: Activation of specific signaling pathways in response to mechanical trauma causes delayed neuronal apoptosis; GSK-3β/β-catenin signaling plays a critical role in the apoptosis of neurons in CNS diseases, SGK was discovered as a regulator of GSK-3β/β-catenin pathway, The goal of this study was to determine if the mechanism of cell death or survival mediated by the SGK/GSK-3β/β-catenin pathway is involved in a rat model of TBI. Main methods: Here, an acute traumatic brain injury model was applied to investigate the expression change and possible roles of SGK, Expression of SGK, and total-GSK-3β, phospho-GSK3β on ser-9, beta-catenin, and caspase-3 were examined by immunohistochemistry and Western blot analysis. Double immunofluorescent staining was used to observe the SGK localizations. Si-RNA was performed to identify whether SGK regulates neuron apoptosis via GSK-3β/β-catenin pathway, ultimately inhibit caspase-3 activation. Key findings: Temporally, SGK expression showed an increase pattern after TBI and reached a peak at day 3. Spatially, SGK was widely expressed in the neuron, rarely in astrocytes and oligodendrocytes; in addition, the expression patterns of active caspase-3 and phospho-GSK3β were parallel with that of SGK, at the same time, the expression of β-catenin shows similarity with SGK. In vitro, to further investigate the function of SGK, a neuronal cell line PC12 was employed to establish an apoptosis model. We analyzed the association of SGK with apoptosis on PC12 cells by western blot, immunofluorescent labeling and siRNA. Significance: the results implied that SGK plays an important role in neuron apoptosis via the regulation of GSK3β/β-catenin signaling pathway; ultimately inhibit caspase-3 activation. Taken together, we inferred traumatic brain injury induced an upregulation of SGK in the central nervous system, which show a protective role in neuron apoptosis.     

碱性成纤维细胞生长因子对小鼠创伤性脑损伤后神经元凋亡及星形胶质细胞活化的影响

目的 观察碱性成纤维细胞生长因子(bFGF)对小鼠脑损伤后伤侧皮质和海马神经元凋亡及星形胶质细胞活化的影响. 方法 36只小鼠随机分为对照组、生理盐水组、bFGF组,每组各12只.采用自由落体打击装置建立脑损伤模型,分别于建模后3d和7d取脑(每时相点6只),应用免疫荧光双标和免疫印迹法检测大脑皮质、海马神经细胞凋亡因子caspase-3的变化,以及大脑皮质中胶质纤维酸性蛋白(GFAP)的表达. 结果 bFGF组皮质和海马中caspase-3的表达比生理盐水组和对照组减少(P<0.05);bFGF组皮质中GFAP表达比生理盐水组和对照组增加(P<0.05);生理盐水组与对照组的caspase-3及GFAP表达差异无统计学意义(P>0.05). 结论 bFGF能降低小鼠脑损伤后大脑皮质和海马caspase-3表达并增高大脑皮质GFAP表达,从而促进大脑皮质星形胶质细胞活化和抑制神经细胞凋亡.     

Causal role of apoptosis-inducing factor for neuronal cell death following traumatic brain injury

Traumatic brain injury (TBI) consists of two phases: an immediate phase in which damage is caused as a direct result of the mechanical impact; and a late phase of altered biochemical events that results in delayed tissue damage and is therefore amenable to therapeutic treatment. Because the molecular mechanisms of delayed post-traumatic neuronal cell death are still poorly understood, we investigated whether apoptosis-inducing factor (AIF), a pro-apoptotic mitochondrial molecule and the key factor in the caspase-independent, cell death signaling pathway, plays a causal role in neuronal death following TBI. Using an in vitro model of neuronal stretch injury, we demonstrated that AIF translocated from mitochondria to the nucleus of neurons displaying axonal disruption, chromatin condensation, and nuclear pyknosis in a caspase-independent manner, whereas astrocytes remained unaffected. Similar findings were observed following experimental TBI in mice, where AIF translocation to the nucleus coincided with delayed neuronal cell death in both cortical and hippocampal neurons. Down-regulation of AIF in vitro by siRNA significantly reduced stretch-induced neuronal cell death by 67%, a finding corroborated in vivo using AIF-deficient harlequin mutant mice, where secondary contusion expansion was significantly reduced by 44%. Hence, our current findings demonstrate that caspase-independent, AIF-mediated signaling pathways significantly contribute to post-traumatic neuronal cell death and may therefore represent novel therapeutic targets for the treatment of TBI.     

N-乙酰-L-色氨酸减轻H2O2诱导小鼠海马神经元细胞凋亡

 目的 探讨N-乙酰-L-色氨酸(L-NAT)对海马神经元（PHN）缺血低氧损伤的影响。方法 用600μmol/L H2O2诱导PHN制备海马神经元细胞凋亡模型,采用免疫荧光染色检测caspase-3的表达,Rhodamine 123染色检测线粒体膜势能（ΔΨm）的改变,台盼蓝染色检测细胞存活率,比色法检测caspase-3、乳酸脱氢酶（LDH）的活性,Western blot检测caspase-3及凋亡诱导因子（AIF）和细胞色素C（CytC）等线粒体促凋亡因子在胞质蛋白和线粒体蛋白中的表达。结果 L-NAT可减轻H2O2所引起的细胞形态的死亡、存活率的降低、LDH的释放、caspase-3的激活、线粒体膜势能的丧失及AIF和CytC等线粒体促凋亡因子的释放。 结论 L-NAT能通过抑制caspase依赖性和非依赖性的细胞凋亡途径,减轻H2O2诱导的小鼠海马神经元的细胞损伤。     

CD8+ T cell apoptosis induced by Escherichia coli heat-labile enterotoxin B subunit occurs via a novel pathway involving NF-kappaB-dependent caspase activation

The B subunit of Escherichia coli heat-labile enterotoxin (EtxB) is a potent immunomodulatory molecule capable of treating and preventing autoimmune disease. These properties result from its ability to bind to glycolipid receptors, principally G(M1) ganglioside, and modulate immune cell function. EtxB receptor binding causes B cell activation, modulates monocyte cytokine secretion and triggers apoptosis of CD8+ T cells. These wide-ranging effects suggest that B subunit receptor interaction triggers signaling events affecting cellular differentiation. We have investigated the processes by which EtxB induces CD8+ T cell apoptosis. We show that receptor interaction by EtxB activates caspase-3 in CD8+ but not in CD4+ T cells. Inhibition of caspase-3 blocks the apoptotic process. EtxB induces the activation of NF-kappaB in both CD8+ and CD4+ T cells. The findings that (i) SN50, a peptide inhibitor of NF-kappaB nuclear translocation, prevents caspase-3 activation and subsequent apoptosis, and (ii) CD8+CD4- thymocytes from transgenic mice expressing a dominant-negative form of the IkappaBalpha protein were markedly less susceptible to EtxB-induced apoptosis than cells from wild-type mice, indicate that NF-kappaB is important in the induction of the apoptotic pathway. Further investigations revealed that while caspase-8 activity is detected concomitant to caspase-3, caspase-9 activation, following mitochondrial cytochrome c release, is detectable later on. These observations are consistent with death receptor-mediated signaling, however, experiments using lpr/lpr and p55 TNFR -/- mice rule out the involvement of Fas and the p55 TNF receptor, respectively. The data therefore indicate that EtxB-mediated apoptosis occurs via a novel pathway involving NF-kappaB.     

The selective mGluR5 agonist CHPG protects against traumatic brain injury in vitro and in vivo via ERK and Akt pathway

Group I metabotropic glutamate receptors (mGluRs) have been implicated in the pathophysiology of central nervous system injury, but the role of mGluR5 in traumatic brain injury (TBI) remains unclear. In the present study, we investigated the neuroprotective potency of (R,S)-2-chloro-5-hydroxyphenylglycine (CHPG), a selective mGluR5 agonist, for protecting against TBI in both in vitro and in vivo models. Primary cortical neurons were treated with 1 mM CHPG in an in vitro preparation 30 min before TBI, and 250 nM CHPG was injected into the right lateral ventricle of rats 30 min before TBI was induced in in vivo studies. The results showed that CHPG significantly attenuated lactate dehydrogenase (LDH) release and neuronal apoptosis and reduced lesion volume. Compared to the control or vehicle group, the phosphorylation levels of extracellular signal-regulated kinase (ERK) and Akt were increased in the presence of CHPG, even following the induction of TBI. Furthermore, treatment with either the ERK inhibitor PD98059 or Akt inhibitor LY294002 partially reversed the CHPG's neuroprotective effects. These data suggest that CHPG minimizes brain damage after induction of TBI both in vitro and in vivo, and that these protective effects were possibly mediated by activation of the ERK and Akt signaling pathways. Thus, potentiating mGluR5 activity with selective agonists such as CHPG may be useful for the treatment of traumatic brain injury.     

Role of CD44 in activation-induced cell death: CD44-deficient mice exhibit enhanced T cell response to conventional and superantigens

T cells upon activation are known to up-regulate CD44 expression. However, the precise function of CD44 on activated T cells is not clear. In this report, we demonstrate that signaling through CD44 plays an important role in activation-induced cell death (AICD). CD44 knockout (KO) mice had an elevated in vivo primary and in vitro secondary response to challenge with conalbumin, anti-CD3 mAb and staphylococcal enterotoxin A (SEA), which correlated with reduced AICD when compared to CD44 wild-type mice. In addition, CD44 KO mice exhibited increased delayed-type hypersensitivity response to dinitrofluorobenzene. In a model examining in vitro AICD, splenocytes from CD44 KO mice showed resistance to TCR-mediated apoptosis when compared to splenocytes from CD44 wild-type mice. In addition, signaling through CD44 led to increased apoptosis in TCR-activated but not resting T cells from CD44 wild-type mice without affecting Fas expression. Injection of SEA into mice deficient in CD44 and Fas (CD44 KO/lpr) led to an increased primary response when compared to mice that expressed CD44 but not Fas (CD44 WT/lpr), suggesting that the enhanced response to SEA was dependent on CD44 but not Fas expression. Administration of anti-CD44 mAb into CD44 wild-type mice caused a significant decrease in antigen-specific T cell response. Together, these data implicate CD44 as an important regulator of AICD in T cells. Furthermore, targeting CD44 in vivo may constitute a novel approach to induce apoptosis in activated T cells, and therefore to treat autoimmune diseases, allograft rejection and graft versus host disease.     

HIV-1包膜蛋白gp120在神经元损伤诱发认知障碍中的作用

目的探索HIV-1包膜蛋白gp120在神经元损伤引起认知障碍中的作用。方法免疫印迹和免疫荧光检测gp120处理后的小胶质细胞活化、炎症因子表达和神经元损伤情况;免疫组化分析gp120转基因小鼠的神经元损伤情况;行为学分析转基因小鼠的神经认知状况。结果体内和体外试验结果表明HIV-1 gp120可显著诱导caspase-1与IL-1β表达,并间接引起神经元突触变短和神经元损伤(P<0.05);与野生型小鼠相比,gp120转基因小鼠出现明显的皮层和海马回小胶质细胞激活、神经元丢失与树突损伤以及神经认知紊乱现象。结论HIV-1 gp120可能通过激活小胶质细胞炎症因子释放导致神经元损伤并可能与神经认知障碍发生相关。