凋亡基因Fas系统与心力衰竭

近年的研究表明,细胞凋亡是慢性心力衰竭(心衰)发生、发展的重要机制,而Fas作为凋亡信号传导途径的重要基因,在心衰患者心肌细胞凋亡过程中起着重要的调控作用,故血清sFas与sFasL可以反映心肌细胞凋亡与心衰的严重程度.     

实验性心肌梗死大鼠心肌细胞凋亡及其调控机制

目的心肌梗死过程中存在病理性心肌细胞凋亡增加,心肌细胞的减少可能参与与梗死后充血性心力衰竭的发病.本研究通过观察心肌梗死后不同时相的大鼠左心功能、心室重塑、心肌细胞凋亡、以及Fas受体、Fas配体(FasL)和Bcl-2的表达,探讨心肌细胞凋亡在充血性心力衰竭发生、发展中的作用,以及Bcl-2和Fas及其配体对心肌细胞凋亡的调控.     

Fas/FasL与充血性心力衰竭

Fas在心肌细胞凋亡中的作用日益受到重视，本文对Fas的性质，结构，作用机制及其与心力衰竭中的心肌细胞凋亡的关系进行了综述。     

Fas/FasL系统与心肌细胞凋亡

心肌细胞凋亡是许多心血管疾病发生发展的重要机制。Fas／FasL系统作为细胞凋亡的信号传导系统也参与了心肌细胞凋亡。当表达Fas的靶细胞和活性细胞的FasL交联后，启动Fas／FasL死亡信号传导系统，分别激活神经鞘磷脂途径蛋白酶途径和DAxx途径而引起Fas表达阳性的靶细胞凋亡。大量研究表明，Fas／FasL系统参与了急性心肌梗塞、病毒性心肌炎、扩张型心肌病、风湿性心脏病、心律失常、心脏移植排斥反应和心力衰竭等心肌细胞凋亡。因此对Fas／FasL系统某一环节的干预为心血管疾病的防治开辟一个新的涂释。     

Fas/FasL系统与结核病

Fas/FasL抗原系统是重要的细胞凋亡信号传导系统 ,在抵抗结核分枝杆菌入侵中对维持宿主自身稳定起重要调控作用。近年来 ,人们对Fas/FasL抗原系统及其在结核病的发生、发展中的作用有了进一步的了解 ,对结核病的发病机制有了全新的认识 ,现综述如下。一、Fas/FasL系统自 1972年Kerr提出细胞凋亡 (apoptosis)的概念后 ,1989年Trauth等[1] 才首次报道了死亡因子Fas(APO 1,CD95)的发现。 1991年Itoh等[2 ] 发现了Fas的相应配体FasL(Fasligand ,CD95L)的存在 ,Fas可与FasL组成死亡起始信号复合物 (deathinitiatingsignallingcomplex…     

硝酸甘油对心肌细胞凋亡和Fas基因蛋白及mRNA表达的影响

目的　探讨硝酸甘油对持续缺血和缺血再灌注损伤时心肌细胞凋亡和 Fas基因蛋白及 m RNA表达的影响。方法　将大白鼠随机分为 5组 ,以活结结扎左冠状动脉的前降支 ,分别造成阻断冠脉血流和再灌注。以缺口末端标记法 (TUNEL)标记凋亡细胞 ;以 S- P免疫组化及逆转录聚合酶链反应 (RT- PCR)法分别检测 Fas基因蛋白与 m RNA的表达变化。结果　凋亡细胞原位标记与半定量分析表明 :硝酸甘油处理组与持续缺血组、缺血再灌注组比较心肌细胞凋亡程度明显降低 ,Fas基因蛋白及 m RNA表达明显减少。结论　硝酸甘油预处理能能明显减轻心肌细胞凋亡程度 ;其机制可能与下调 Fas基因蛋白及 m RNA表达有关。     

不同剂量卡维地洛干预对心肌梗死后心力衰竭大鼠心肌细胞凋亡和凋亡相关基因表达的影响

目的 :探讨不同剂量卡维地洛 (CAR)对心肌梗死 (MI)后大鼠心肌细胞凋亡的影响及CAR治疗充血性心力衰竭 (CHF)的作用机制。方法 :将雄性Waistar大鼠前降支结扎 ,于术后 1周开始分别予大剂量CAR[HCAR组 ,6 0mg/ (kg·d) ]和小剂量CAR[LCAR组 ,6mg/ (kg·d) ]干预 7周 ,观察不同剂量CAR对大鼠血流动力学参数、心肌细胞凋亡、Fas、Fas配体 (FasL)和Bcl 2mRNA表达的影响。结果 :CAR可改善心功能指标 ,降低心肌细胞凋亡指数、Fas及FasL的mRNA水平 ,上调Bcl 2表达 ,其中对心肌细胞凋亡指数、Fas及Bcl 2mRNA表达的影响以HCAR组明显。结论 :CAR可有效地减少MI后心肌细胞凋亡 ,防治CHF ,效果以大剂量明显 ,这可能与其对凋亡相关基因表达影响的差异有关     

小鼠病毒性心肌炎中Fas/FasL异常表达的研究

目的探讨柯萨奇病毒B3(CVB3)所致小鼠病毒性心肌炎(VM)心肌细胞损伤的变化,观察Fas/FasL介导的细胞凋亡在心肌损伤中的作用.方法采用CVB3制备小鼠病毒性心肌炎动物模型,心肌组织切片HE染色了解心肌损伤情况;电镜检测观察心肌组织中的细胞凋亡;同时采用免疫组化、逆转录-聚合酶链反应(RT-PCR)两种方法检测心肌炎小鼠不同时期心肌组织中Fas与FasL基因转录与蛋白的表达.结果光镜观察见对照组小鼠心肌组织无异常改变,实验组病鼠可见心肌细胞坏死和单核、淋巴细胞浸润,后期可见纤维化;电镜观察对照组心肌中未检出凋亡细胞,而病鼠心肌凋亡细胞检出率较高58.33%(7/12例),且细胞凋亡多存在于炎症病灶周围的心肌细胞及病灶处炎性浸润细胞;感染后第7～14天的病鼠心肌组织中,主要表达于心肌细胞的Fas mRNA及蛋白和主要表达于浸润淋巴细胞的FasL mRNA及蛋白均明显增强;FasL蛋白表达水平与心肌病变积分呈正相关(r=0.9082,P＜0.001).结论小鼠病毒性心肌炎中心肌损伤坏死与心肌细胞凋亡共存,通过Fas/FasL基因路径介导的心肌细胞凋亡与病毒性心肌炎的发病过程有关.     

人参皂甙Re对大鼠缺血再灌注心肌细胞凋亡及Fas基因表达的影响

目的 :观察人参皂甙Re(以下简称Re)对缺血再灌注心肌细胞凋亡及Fas基因表达的影响 ,探讨Re抑制心肌细胞凋亡的可能机制。方法 :结扎Wistar大鼠左冠状动脉前降支 ,建立大鼠缺血再灌注动物模型 ;采用透射电镜、缺口末端标记法检测心肌凋亡细胞 ,利用光学显微镜进行细胞计数 ;原位杂交及免疫组化分别检测Fas基因mRNA及蛋白的表达 ,并利用图像分析系统测量阳性表达区域平均光密度值 ,进行定量分析。结果 :①透射电镜发现缺血再灌注组缺血区出现心肌凋亡细胞 ,假手术组未发现心肌凋亡细胞 ;②缺血再灌注组心肌细胞凋亡数为 (134.4 5± 4 5 .6 1)个 /视野 ,Re治疗组细胞凋亡数 (90 .6 6± 19.2 2 )个 /视野 ,两组间差异有非常显著性意义 (P<0 .0 1) ;③原位杂交及免疫组化检测均发现Fas基因的表达缺血再灌注组较假手术组明显增加 (P <0 .0 1) ,Re治疗组较缺血再灌注组明显下降 (P <0 .0 5 )。结论 :心肌缺血再灌注诱导心肌细胞凋亡 ,Re治疗则可以显著减少缺血再灌注心肌细胞的凋亡。Re通过抑制Fas基因的表达而抑制心肌细胞凋亡     

一个新的凋亡分子--Trail

细胞凋亡是生物体最重要的生理和病理现象之一,其在癌变机制和维持宿主免疫系统的内稳定方面有着重要的意义和不可缺的调节作用[1].在细胞凋亡的调控系统中,Fas/Fas配体(FasL)已被广泛的研究.新近,肿瘤坏死因子(TNF)家族中的另一个重要分子Trail(TNF-related apoptosis-inducing ligand),或称Apo-2配体在细胞凋亡中的调控作用引起了学者们的极大兴趣和重视[2].本文就Trail的生物学特点,尤其是在T细胞的表达和诱导T细胞凋亡方面的研究近况作一简介.     

Activation of Fas by FasL induces apoptosis by a mechanism that cannot be blocked by Bcl-2 or Bcl-x(L)

Fas activation triggers apoptosis in many cell types. Studies with anti-Fas antibodies have produced conflicting results on Fas signaling, particularly the role of the Bcl-2 family in this process. Comparison between physiological ligand and anti-Fas antibodies revealed that only extensive Fas aggregation, by membrane bound FasL or aggregated soluble FasL consistently triggered apoptosis, whereas antibodies could act as death agonists or antagonists. Studies on Fas signaling in cell lines and primary cells from transgenic mice revealed that FADD/MORT1 and caspase-8 were required for apoptosis. In contrast, Bcl-2 or Bcl-x(L) did not block FasL-induced apoptosis in lymphocytes or hepatocytes, demonstrating that signaling for cell death induced by Fas and the pathways to apoptosis regulated by the Bcl-2 family are distinct.     

The Fas antigen is detected on immature B cells and the representative cell lines show Fas-mediated apoptosis

The expression and functions of Fas antigen, a major regulator of apoptosis, in T-cell selection have been intensively investigated, but little is known about its expression in immature B cells which are also selected in the bone marrow, and plasma cells which are at the terminal stage of B-cell differentiation and are designed to die. We examined bone marrow cells and found Fas antigen on these cells at low levels. Next, we analysed Fas expression and susceptibility to anti-Fas antibody-mediated apoptosis on B-cell lines representing various stages of differentiation. We also examined the expression of Bcl-2 and Bax on these lines, which were intimately related to apoptosis. Fas antigen was almost negative on pre-pre-B cell lines and was detected on pre-B-cell lines at low levels. All plasma cell lines expressed Fas at a low to moderate level. Some cell lines with peripheral B-cell phenotype expressed Fas antigen. Except for the Burkitt cell lines and one plasma cell line, susceptibility to Fas-mediated apoptosis depended on Fas expression. Bcl-2 protein was detected on all but one cell line and Bax was detected on 15/23 lines, but neither were related to cellular differentiation or Fas expression.     

Apoptose hépatique

Apoptosis or programmed cell death occurs in the liver as well as in other organs. In the normal state it is not a frequent event of hepatic cell destruction. Nevertheless morphological and biochemical characteristics of liver apoptosis do not differ from that it is observed in other cells. Between the various hepatic apoptotic pathways the Fas receptor pathway is frequently involved and its intra-cellular signal is amplified by mitochondria. Although hepatic apoptosis may occur through several others pathways, Fas which is abundantly expressed on the plasma membrane of hepatocytes and biliary cells, is very often involved in cell destruction during B or C viral hepatitis, whatever their clinical form, alcoholic hepatitis, primary biliary cirrhosis, cholestasis due to hepatic biliary salt accumulation, or drug hepatitis. In contrast, one of the causes for the resistance of hepatic cancerous cells to apoptosis could be due to an alteration of the Fas receptor. It is the reason why many experimental works are presently performed to inhibit the Fas receptor either at the level of its mRNA or at the level of caspases which are Fas-inductible proteolytic enzymes.     

Adenovirus expressing p27KIP1 induces apoptosis against cholangiocarcinoma cells by triggering Fas ligand on the cell surface

BACKGROUND/AIMS: The prognosis of patients with cholangiocarcinoma is poor because of the difficulty of surgical curative resection. Therefore, other effective treatments must be developed especially those involving gene therapy. p27kip1, one of the cyclin-dependent kinase inhibitors, is known to limit proliferation of the cells. Our previous reports have shown that the overexpression of p27kip1 by a recombinant adenoviral vector expressing p27kip1 (Adp27) induces apoptosis. However, the mechanism of the Adp27-mediated apoptosis is not still resolved. Activation of the Fas pathway is one of the important gates for apoptosis. In this report, we examined whether p27kip1-induced apoptosis is closely related to the Fas/Fas ligand (FasL) system. RESULTS: After infection of Adp27, flow cytometric analysis showed that Fas ligand was expressed on the cell surface of cholangiocarcinoma cell lines (TFK-1). In spite of detecting the cell surface expression of Fas ligand, overexpression of p27kip1 increased no amount of Fas ligand in mRNA by quantitative RT-PCR and protein level by Western blot. In addition, the immunocytochemical analysis showed that Fas ligand was adequately stored within the cytosol of TFK-1 cells. More interestingly, Adp27-induced apoptosis was completely inhibited by the neutralizing antibody of Fas ligand (NOK-1). This result suggests that overexpression of p27kip1 may deliver Fas ligand to the cell surface and mainly utilizes the Fas pathway as a gate of apoptosis. CONCLUSIONS: This is the first report to prove that Adp27-mediated apoptosis utilizes the Fas pathway by delivering Fas ligand to the cell surface.     

Contribution of Fas to diabetes development

Fas (Tnfrsf6, Apo-1, CD95) is a death receptor involved in apoptosis induced in many cell types. Fas have been shown to be expressed by insulin-producing beta cells in mice and humans. However, the importance of Fas in the development of autoimmune diabetes remains controversial. To further evaluate the importance of Fas in pathogenesis of diabetes, we generated NOD mice (nonobese diabetic mice developing spontaneous autoimmune diabetes) with beta cell-specific expression of a dominant-negative point mutation in a death domain of Fas, known as lpr(cg) or Fas(cg). Spontaneous diabetes was significantly delayed in NOD mice expressing Fas(cg), and the effect depended on the expression level of the transgene. However, Fas(cg)-bearing mice were still sensitive to diabetes transferred by splenocytes from overtly diabetic NOD mice. At the same time, Fas(cg) expression did neutralize the accelerating effect of transgenic Fas-ligand expressed by the same beta cells. Thus, both Fas-dependent and -independent mechanisms are involved in beta cell destruction, but interference with the Fas pathway early in disease development may retard or prevent diabetes progression.     

Liver and apoptosis

Apoptosis is an energy-requiring mechanism of cell death which is a physiological event in organ morphogenesis, clone selection of lymphoid cells and cell turnover, but also occurs in many pathological conditions. It is under genetic control, bcl-2 being the major apoptosis suppressing gene, while p53 and c-myc are apoptosis promoting genes. Other factors, such as the Fas/Fas1 system, the caspases cascade, cytokines and enzymes also play a role in determining apoptosis. The term apoptosis was introduced by Kerr to describe this type of death in ischaemic rat liver, and the same Councilman bodies are now considered an example of apoptotic death. Virus-infected hepatocytes bear Fas receptors and apoptosis is induced by binding to the Fas ligand which is expressed by activated T cells; this action is probably mediated by enzymes of the caspase family and/or by granzyme B. The Fas/Fas1 system is also involved in apoptosis occurring in chronic non suppurative destructive cholangitis, in transplant rejection and in other liver diseases, including neoplasms; in the latter Bcl-2 protein and mutations of p53 also seem to play an important role. Cytokines are also frequently involved. Toxins like alcohol probably induce apoptosis by producing active oxidants. Whether aging enhances apopstosis in liver is still controversial. Although many molecular mechanisms have been suggested to be involved the switch on/off of apoptosis is still poorly understood and will be a matter of further investigations.     

cMet and Fas receptor interaction inhibits death-inducing signaling complex formation in endothelial cells

Fas receptor is constitutively expressed on endothelial cells; however, these cells are highly resistant to Fas-mediated apoptosis. In this study, we examined death-inducing signaling complex (DISC) formation in endothelial cells after Fas receptor stimulation. Nonfunctional DISC formation was observed in human umbilical vein endothelial cells (HUVECs). Fas-associated death domain (FADD) and large amounts of FADD-like interleukin-1--converting enzyme--inhibitory protein-L were recruited to the receptor; however, no caspase 8 recruitment was observed. A role for the cell surface molecule cMet in controlling Fas sensitivity in endothelial cells was observed. Here, we report that Fas is associated with cMet in HUVECs. Such an interaction may inhibit self-association of Fas in these cells, as suggested by the fact that monomeric Fas is expressed in these cells. Endothelial cells undergoing cell matrix detachment, anoikis, are sensitive to Fas-mediated apoptosis. Despite upregulating the level of Fas receptor, endothelial cells undergoing anoikis have reduced cMet/Fas interaction, in part because of cMet being cleaved in these cells. Dimeric Fas was observed on anoikis cells. These data suggest that cMet/Fas interaction may inhibit self-association of Fas receptor such that reduced DISC formation occurs in these cells after Fas receptor ligation. cMet/Fas interaction may help explain why endothelial cells are resistant to Fas-mediated apoptosis.     

Resistance to Fas (APO-1/CD95)-mediated apoptosis and expression of Fas ligand in esophageal cancer: the Fas counterattack

The mechanisms by which esophageal tumors escape immunologic recognition and clearance are only partly understood at the molecular level. Esophageal cancers have been shown to evade host recognition by down-regulation of antigen presentation and production of immunosuppressive factors. Recently, two independent reports have shown that esophageal tumor cells abundantly express Fas ligand (FasL) in vivo. As the triggering agonist for Fas receptor (Fas or APO-1/CD95)-mediated apoptosis of lymphocytes, FasL normally plays immune down-regulatory roles, including activation-induced cell death of T and B cells, as well as maintaining immune privilege in certain organs. Fas ligand expressed by esophageal cell lines has been shown to induce apoptosis of cocultured Fas-sensitive lymphoid cells in vitro. FasL expression by esophageal carcinomas in vivo has been associated with significantly reduced tumor-infiltrating lymphocytes (TILs) in FasL-positive tumor nests, concomitant with significantly increased TIL apoptosis in these nests. These studies support a 'Fas counterattack' mechanism of immune escape in esophageal cancer. By expressing functional Fas ligand, esophageal cancer cells can deplete antitumor lymphocytes by inducing apoptosis. To express functional FasL, esophageal carcinomas also acquire molecular mechanisms to resist autocrine Fas-mediated apoptosis of tumor cells.     

Expression and function of Fas (APO-1/CD95) in patient myeloma cells and myeloma cell lines

Cross-linkage of the Fas antigen induces programmed cell death in many normal and malignant lymphoid cells by a process known as apoptosis. In this study, we examined the sensitivity of myeloma cell lines and patient plasma cells to a cytolytic anti-Fas monoclonal antibody (MoAb). Eight of 10 myeloma cell lines were induced to undergo programmed cell death by anti-Fas MoAb as determined by DNA fragmentation and morphologic changes. Of the two myeloma cell lines that were resistant to anti-Fas treatment, one did not express the Fas antigen. Only the U266 cell line expressed Fas, but was not killed by the anti0Fas MoAb. To extend these studies, we have examined the expression and function of Fas in freshly isolated CD38hiCD45neg-int plasma cells from patients with multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS), and primary amyloidosis (AL). By three-color flow cytometry, we found Fas expression in CD38hiCD45neg-int plasma cells from all patient groups to be variable, as Fas was expressed in 15 of 28 MM, 3 of 6 MGUS, and 2 of 7 AL patients. In morphologic studies of apoptosis, Fas-positive myeloma cells in patient bone marrow mononuclear cell (MNC) cultures appeared to be resistant to anti-Fas-mediated apoptosis. By contrast, purified myeloma cells from the same patient were sensitive to anti-Fas treatment, suggesting the presence of a protective factor(s) in unseparated MNC cultures that may inhibit Fas-induced apoptosis of plasma cells. Of interest, serum from normal individuals and myeloma patients also protected myeloma cell lines from undergoing Fas-mediated apoptosis. These studies show that Fas expression in myeloma cell lines and CD38hiCD45neg-int patient plasma cells is variable and may reflect a variance in the maturation status of the various plasma cell populations. Moreover, Fas-mediated killing of patient cells and myeloma cell lines was also variable, which may be influenced, in part, by the presence of a soluble protective factor.