线粒体跨膜电位与细胞凋亡

细胞凋亡作为细胞固有的、受机体严密调控的细胞死亡形式,在多细胞生物体清除衰老细胞及无能细胞等方面发挥重要的作用.近年来,细胞凋亡的研究重点已从细胞核转向线粒体.各种死亡信号诱导线粒体膜通透性改变孔（permeability transition pore, PT pore）开放,引起线粒体跨膜电位下降,导致促凋亡物质释放,继而激活caspase,最终使细胞凋亡.Bcl-2和Bcl-X_L通过对线粒体作用而抑制细胞凋亡,而Bax、Bak与Bad通过调节线粒体而诱导细胞凋亡.     

细胞凋亡蛋白酶活化因子（Apafs）的功能研究

细胞凋亡蛋白酶活化因子(Apafs)参与激活程序性细胞死亡(PCD)过程中的胱冬肽酶(caspase或Casp)。Apaf1、细胞色素c(Apaf2)及Casp9(Apaf3)首先形成凋亡体,随后Casp9激活Casp3,进而引发PCD最后阶段的细胞学事件。Apafs的突变或缺失会导致脑和视网膜的异常发育。对Apafs功能的研究将为神经退化性疾病和癌症的治疗开辟新路。     

JNK/Bim/Bax 途径在 TNF-α 诱导分化PC12 细胞凋亡过程中的作用机制

阿尔茨海默病(Alzheimer′s disease,AD)是一种神经系统退行性疾病,近年来许多研究发现AD与细胞凋亡关系密切,有研究证明肿瘤坏死因子(tumor necrosis factor-α,TNF-α)的合成过量会造成神经细胞的凋亡从而导致AD等神经退行性疾病的发生,然而人们对TNF-α造成神经细胞凋亡的分子机制并不了解.采用激光共聚焦扫描成像技术和荧光共振能量转移(fluorescence resonance energy transfer,FRET)技术在活细胞中实时对TNF-α诱导分化PC12细胞凋亡的信号通路进行了细致的研究.实验结果证明,TNF-α诱导的分化PC12细胞凋亡会经过线粒体和非线粒体途径,并通过激活核转录因子(NF-κB)上调Bcl-xL的表达来抑制经过线粒体的凋亡途径.进一步的研究证明,BimL会在线粒体上替换原来被Bcl-xL抑制的Bax,从而让Bax寡聚化,进而引发细胞凋亡,而c-Jun氨基末端激酶(JNK)抑制剂SP600125可以抑制Bax寡聚化.此外,在未分化PC12细胞中共表达GFP-BimL和YFP-Bax质粒,发现BimL可以促进Bax发生聚集,并且它们二者之...     

高糖通过线粒体途径诱导成骨细胞凋亡

线粒体途径是细胞凋亡的重要途径之一. 在特定的刺激下,例如高糖条件,可以通过caspase依赖性和非依赖性两种途径诱导多种细胞凋亡.但线粒体凋亡途径在高糖引起成骨细胞凋亡中所起的作用,目前尚不清楚.本研究证明,高糖可以通过线粒体凋亡途径诱导成骨细胞凋亡.Annexin V-FITC/PI流式细胞学检测显示,高糖可诱导MC3T3-E1细胞凋亡.Western印迹检测发现,不同浓度D-葡萄糖（11,22,33 mmol/L）可以引起线粒体中Bax蛋白表达的增加,使Bax蛋白由细胞质中易位到线粒体,激活了线粒体凋亡途径.JC-1荧光探针检测证实,高糖处理成骨细胞后,线粒体膜电位明显降低,表明线粒体途径被激活.而细胞质中的细胞色素c、凋亡诱导因子（AIF）表达增加,细胞色素c和AIF从线粒体中释放到细胞质中,释放到细胞质中的细胞色素c使caspase-3、caspase-9剪切活化,从而激活了caspase依赖性凋亡途径.因此,线粒体凋亡途径可能是高糖诱导成骨细胞凋亡过程中一个重要的途径.     

线粒体相关内质网膜在神经退行性疾病中的研究进展

线粒体相关内质网膜(mitochondria-associated endoplasmic reticulum membrane,MAM)是线粒体外膜和内质网膜之间紧密接触的特殊区域,参与调节Ca~(2+)稳态、脂质合成与转移、线粒体分裂和融合、内质网应激、自噬体形成、细胞凋亡以及炎性小体的形成等过程。近年来,越来越多的研究发现,MAM结构和功能异常与神经退行性疾病如阿尔茨海默病、帕金森病、肌萎缩性侧索硬化症和亨廷顿舞蹈症的发病机制密切相关。该文将对MAM的结构组成和功能,以及其在神经退行性疾病中的作用进行综述,为探索神经退行性疾病的药物治疗靶点提供理论依据。     

细胞程序性死亡通路的研究进展

细胞程序性死亡(programmed cell death,PCD)一直被看做是细胞凋亡(apoptosis).随着细胞生物学研究的深入,新的细胞死亡途径逐渐被揭示出来,如胀亡、自噬、副凋亡等.这些通路有些是caspase依赖的,有些不依赖于caspase途径.在细胞程序性死亡过程中,各种通路不是单独起作用的,而是相互交联的,有彼此重叠的机制出现.目前,Clarke形态学分类法是得到大多数学者认可的细胞程序性死亡的分类方式.按照该分类法,可将PCD分为3大类,即:Ⅰ型细胞程序性死亡、Ⅱ型细胞程序性死亡和Ⅲ型细胞程序性死亡.     

线粒体通透性增高过程中新的参与者

 应激时,线粒体通透性增高可导致位于线粒体膜间的致凋亡因子释放入细胞质,胱天蛋白酶 (caspase)激活,以及细胞死亡.但线粒体通透性增高的确切机制尚不清楚.许多研究表明,线粒体通透性增高过程需要Bcl-2家族蛋白中促凋亡Bax亚家族蛋白,主要是Bax和Bak的激活;该家族中其它蛋白可对Bax和Bak进行调节.但最近的研究表明,其它非Bcl-2家庭蛋白的蛋白质包括抑制因子和激活因子,也可对线粒体通透性增高过程进行调节.此外,应激时线粒体脂质重新分布,对于线粒体膜通透性增高过程也起重要作用.     

果蝇蜕皮激素诱导程序性细胞死亡的遗传调控因子

近年来关于果蝇程序性细胞死亡（programmed cell death, PCD）的研究结果表明,在果蝇的变态发育过程中,蜕皮激素与受体结合后诱导转录因子的表达。这些转录因子作为程序性细胞死亡调控网络中的初、次级应答信号,激活凋亡诱导因子Reaper、Hid和Grim的表达。Reaper、Hid和Grim进而阻止凋亡蛋白抑制因子的活性,从而启动半胱氨酸蛋白酶caspase途径,引起细胞凋亡（apoptosis）。该文综述了蜕皮激素诱导的果蝇程序性细胞死亡中各遗传调控因子之间的关系。     

PI3K/Akt与细胞线粒体途径凋亡因子相关性研究进展

线粒体途径细胞凋亡与多种疾病(如肿瘤、心血管疾病、神经退行性疾病等)密切相关,B淋巴细胞瘤-2(B-cell leukemia-2,Bcl-2)家族蛋白的调控在这些疾病的治疗中起着重要作用。磷脂酰肌醇-3-激酶(phosphatidylinositol-3-kinase,PI3K)/丝/苏氨酸蛋白激酶(serine/threonine protein kinase Akt)信号通路作为机体细胞信号转导的重要通路,可通过影响下游效应分子(Bcl-x L、Bcl-w、Mcl-1、A1、Bax、Bak、Bim、Bad、Bid等)的活性调节细胞的凋亡。就PI3K/Akt与线粒体途径凋亡相关因子的关联性进行综述,以期发现此通路中某些关键的分子靶点,为凋亡相关性疾病的治疗及药物研发提供参考。     

风疹病毒诱导细胞凋亡分子机制的研究进展

风疹病毒是披膜病毒科风疹病毒属的唯一成员,能够诱导细胞发生细胞凋亡。Ras-Raf-MEK-ERK和PI3KAkt信号通路是病毒增殖与细胞生存的必要通路,在细胞凋亡过程中起着必不可少的作用。p53蛋白和TAp63蛋白能够进入细胞核与DNA特异结合,抑制Bcl-2的表达,促进Bax的表达,导致线粒体内外膜间的物质(细胞色素C等)释放,进而引起caspase级联反应,最终导致细胞凋亡。本文从风疹病毒感染的细胞系,病毒感染导致的细胞病理改变和病毒诱导的细胞凋亡信号通路及其相关因子等方面对风疹病毒诱导细胞凋亡的分子机制进行了综述。     

Neuroprotective Effects of Tetramethylpyrazine against Dopaminergic Neuron Injury in a Rat Model of Parkinson's Disease Induced by MPTP

Parkinson''s disease (PD) is the second most prevalent progressive neurodegenerative disease. Although several hypotheses have been proposed to explain the pathogenesis of PD, apoptotic cell death and oxidative stress are the most prevalent mechanisms. Tetramethylpyrazine (TMP) is a biological component that has been extracted from Ligusticum wallichii Franchat (ChuanXiong), which exhibits anti-apoptotic and antioxidant roles. In the current study, we aimed to investigate the possible protective effect of TMP against dopaminergic neuron injury in a rat model of Parkinson''s disease induced by MPTP and to elucidate probable molecular mechanisms. The results showed that TMP could notably prevent MPTP-induced dopaminergic neurons damage, reflected by improvement of motor deficits, enhancement of TH expression and the content of dopamine and its metabolite, DOPAC. We observed MPTP-induced activation of mitochondrial apoptotic death pathway, evidenced by up-regulation of Bax, down-regulation of Bcl-2, release of cytochrome c and cleavage of caspase 3, which was significantly inhibited by TMP. Moreover, TMP could prevent MPTP-increased TBARS level and MPTP-decreased GSH level, indicating the antioxidant role of TMP in PD model. And the antioxidant role of TMP attributes to the prevention of MPTP-induced reduction of Nrf2 and GCLc expression. In conclusion, in MPTP-induced PD model, TMP prevents the down-regulation of Nrf2 and GCLc, maintaining redox balance and inhibiting apoptosis, leading to the attenuation of dopaminergic neuron damage. The effectiveness of TMP in treating PD potentially leads to interesting therapeutic perspectives.     

Programmed cell death and new discoveries in the genetics of parkinsonism

The concept that activation of cellular pathways of programmed cell death (PCD) may lead to the death of neurons has been an important hypothesis for adult neurodegenerative diseases. For Parkinson's disease (PD), up until now, the evidence for this hypothesis has largely been of two types: clear evidence of a role for PCD in neurotoxin models of the disease, and somewhat controversial evidence from human postmortem studies. With the rapid pace of discoveries in recent years of the genetic basis of PD, a new form of evidence has emerged. The prevailing concept of the role for PCD in PD has been that its mediators are 'downstream' effectors of more proximate and specific causes related to genetic or environmental factors. However, recent studies of three genes which cause autosomal recessive forms of parkinsonism, parkin, PTEN-induced kinase, and DJ-1, suggest that they may have more intimate relationships with the mediators of PCD and that loss-of-function mutations may result in an increased propensity for neurons to die. Intriguingly, independent studies of the function of these genes have suggested that they may share roles in regulating survival signaling pathways, such as those mediated by the survival signaling kinase Akt. Further elucidation of these relationships will have implications for the pathogenesis and neuroprotective treatment of PD.     

Caspase requirement for neuronal apoptosis and neurodegeneration

The execution of the apoptotic programme involves a relatively few pathways that converge on activation of the caspase family of proteases. However, increasing evidence indicates that apoptotic-like features can be found also when cells are treated with inhibitors of caspases. This has posed questions as to whether death with apoptotic features can still occur in a caspase-independent way, and whether caspase inhibitors may then be used to prevent excess apoptosis in disease. Metabolic defects, loss of neuronal connectivity and cell loss characterise several neurodegenerative diseases. Targeting excessive cell demise may be one therapeutic strategy. However, loss of connectivity and neurite regression may not be part of the apoptotic programme, and degenerating neurons might use multiple execution pathways. In addition, metabolic defects leading to ATP depletion can preclude caspase activation and consequently switch execution of cell death towards necrosis. The possibility of inhibiting apoptosis as strategy to treat neurodegenerative disease is discussed in this review.     

AIF-Mediated Programmed Necrosis: A Highly Orchestrated Way to Die

Historically, two main forms of cell death have been distinguished: apoptosis and necrosis. Apoptosis was initially considered as the only physiological and programmed form of cell death. This type of death is recurrently associated with caspases, a family of cysteine proteases activated in apoptotic conditions. However, it is now widely recognized that programmed cell death (PCD) can also occur in the complete absence of caspase activation. The existence of non-caspase PCD pathways was corroborated by the discovery of caspase-independent executioners, such as the mitochondrial protein Apoptosis-Inducing Factor (AIF). Necrosis has often been viewed as an accidental and uncontrolled cell death process. Nevertheless, increasing evidence shows that, like apoptosis, necrosis could be a highly regulated type of PCD. Indeed, apoptosis and necrosis present more similarities than it has been originally thought. Here, we summarize the different classifications of PCD and the current knowledge of a necrotic PCD pathway mediated by AIF: alkylating DNA-damage mediated death. We also outline the molecular mechanisms controlling this form of PCD and discuss their potential relevance in physiological and pathological settings. These emerging data on the molecular mechanisms regulating programmed necrosis may certainly have potent therapeutic consequences in treating both apoptotic-resistant tumors and degenerating adult neurons.     

Application of proteasomal inhibitors to mouse sympathetic neurons activates the intrinsic apoptotic pathway

Proteasomal dysfunction may play a role in a number of neurodegenerative conditions, and in particular Parkinson's disease (PD) and related Lewy body (LB) diseases. Application of proteasomal inhibitors to neuronal cell culture systems is associated with survival-promoting effects or with cell death depending on the model system. We have applied pharmacological proteasomal inhibitors to cultured neonatal mouse sympathetic neurons in order to investigate whether these catecholaminergic neurons, which are affected in PD, are sensitive to proteasomal inhibition and, if so, which cell death pathway is activated. We report here that proteasomal inhibition leads to apoptotic death of mouse sympathetic neurons. This death is accompanied by caspase 3 activation and cytochrome c release from the mitochondria and is abrogated by caspase inhibition. Bax deletion prevented both cytochrome c release and caspase 3 activation, and also provided complete protection against proteasomal inhibition-induced death. Bcl-2 overexpression achieved a similar survival-promoting effect. There was no change in Bax levels following proteasomal inhibition, suggesting that Bax itself is not regulated by the proteasome in this cell culture system, and that a primary increase in Bax is unlikely to account for death. In contrast, levels of the BH3-only protein, Bim, increased with proteasomal inhibition. We conclude that proteasomal inhibition of mouse sympathetic neurons activates the intrinsic apoptotic pathway involving bcl-2 family members and the mitochondria.     

Over‐expression of HSP70 attenuates caspase‐dependent and caspase‐independent pathways and inhibits neuronal apoptosis

HSP70 is a member of the family of heat‐shock proteins that are known to be up‐regulated in neurons following injury and/or stress. HSP70 over‐expression has been linked to neuroprotection in multiple models, including neurodegenerative disorders. In contrast, less is known about the neuroprotective effects of HSP70 in neuronal apoptosis and with regard to modulation of programmed cell death (PCD) mechanisms in neurons. We examined the effects of HSP70 over‐expression by transfection with HSP70‐expression plasmids in primary cortical neurons and the SH‐SY5Y neuronal cell line using four independent models of apoptosis: etoposide, staurosporine, C2‐ceramide, and β‐Amyloid. In these apoptotic models, neurons transfected with the HSP70 construct showed significantly reduced induction of nuclear apoptotic markers and/or cell death. Furthermore, we demonstrated that HSP70 binds and potentially inactivates Apoptotic protease‐activating factor 1, as well as apoptosis‐inducing factor, key molecules involved in development of caspase‐dependent and caspase‐independent PCD, respectively. Markers of caspase‐dependent PCD, including active caspase‐3, caspase‐9, and cleaved PARP were attenuated in neurons over‐expressing HSP70. These data indicate that HSP70 protects against neuronal apoptosis and suggest that these effects reflect, at least in part, to inhibition of both caspase‐dependent and caspase‐independent PCD pathways.     

Beyond apoptosis: nonapoptotic cell death in physiology and disease.

Apoptosis is a morphologically defined form of programmed cell death (PCD) that is mediated by the activation of members of the caspase family. Analysis of death-receptor signaling in lymphocytes has revealed that caspase-dependent signaling pathways are also linked to cell death by nonapoptotic mechanisms, indicating that apoptosis is not the only form of PCD. Under physiological and pathological conditions, cells demonstrate a high degree of flexibility in cell-death responses, as is reflected in the existence of a variety of mechanisms, including necrosis-like PCD, autophagy (or type II PCD), and accidental necrosis. In this review, we discuss recent data suggesting that canonical apoptotic pathways, including death-receptor signaling, control caspase-dependent and -independent cell-death pathways.     

Caspases and neuronal development

Recent developments have shown that inappropriate activation of apoptotic pathways contributes to many neurodegenerative diseases. The basic mechanisms that underlie apoptosis in neurodegenerative diseases are uncertain, although they likely represent the subversion of normal developmental programs. Several types of neuronal cell death have been reported, including autophagic and caspase-independent cell death. In this review we consider evidence for the participation of apoptotic caspases in neuronal development, and examine the hypothesis that differentiating neurons undergo stage-specific alterations in apoptosis sensitivity that may be due to caspase regulation. In addition, we present data supporting this hypothesis.     

Systems biology of yeast cell death

Programmed cell death (PCD) (including apoptosis) is an essential process, and many human diseases of high prevalence such as neurodegenerative diseases and cancer are associated with deregulations in the cell death pathways. Yeast Saccharomyces cerevisiae, a unicellular eukaryotic organism, shares with multicellular organisms (including humans) key components and regulators of the PCD machinery. In this article, we review the current state of knowledge about cell death networks, including the modeling approaches and experimental strategies commonly used to study yeast cell death. We argue that the systems biology approach will bring valuable contributions to our understanding of regulations and mechanisms of the complex cell death pathways.     

Involvement of activation of PI3K/Akt pathway in the protective effects of puerarin against MPP+-induced human neuroblastoma SH-SY5Y cell death

In an attempt to clarify the protective effect of puerarin on toxin-insulted dopaminergic neuronal death, this present study was carried out by using a typical Parkinson's disease (PD) model - 1-methyl-4-phenylpyridinium iodide (MPP(+))-induced dopaminergic SH-SY5Y cellular model. Data are presented, which showed that puerarin up-regulated Akt phosphorylation in both of MPP(+)-treated and non-MPP(+)-treated cells. The presence of PI3K inhibitor LY294002 completely blocked puerarin-induced activation of Akt phosphorylation. Moreover, puerarin decreased MPP(+)-induced cell death, which was blocked by phosphoinositide 3-kinase (PI3K) inhibitor LY294002. We further demonstrated that puerarin protected against MPP(+)-induced p53 nuclear accumulation, Puma (p53-upregulated mediator of apoptosis) and Bax expression and caspase-3-dependent programmed cell death (PCD). This protection was blocked by applying a PI3K/Akt inhibitor. Additionally, it was Pifithrin-α, but not Pifithrin-μ, which blocked MPP(+)-induced Puma and Bax expression, caspase-3 activation and cell death. Collectively, these data suggest that the activation of PI3K/Akt pathway is involved in the protective effect of puerarin against MPP(+)-induced neuroblastoma SH-SY5Y cell death through inhibiting nuclear p53 accumulation and subsequently caspase-3-dependent PCD. Puerarin might be a potential therapeutic agent for PD.