高三尖杉酯碱通过激活Caspase-3诱导鼻咽癌细胞凋亡

目的　了解高三尖杉酯碱 (HHT)是否可通过激活Caspase 3诱导鼻咽癌细胞CNE 2Z凋亡。方法　将细胞分为 4组 :对照组、1mg/LHHT处理组 (HHT组 ) ,以及分别用Caspase抑制剂 (z VAD fmk)和Caspase 3抑制剂 (DEVD fmk)预处理 2h后 ,再用 1mg/LHHT处理的z VAD fmk +HHT组和DEVD fmk +HHT组。采用流式细胞术及荧光染色法 ,检测 4组细胞的凋亡率 ,以比色法检测它们中Caspase 3的相对活性。结果　流式细胞术和荧光染色均发现 ,HHT组的凋亡率明显高于其它各组 (P <0 .0 1) ;Caspase 3的活性于 2h开始升高 ,8h达高峰 ,明显高于其它各组 (P <0 .0 1) ,2 4h时同其它各组的差异无显著性 (P >0 .0 5 )。结论　HHT可通过激活Cas pase 3诱导CNE 2Z细胞凋亡 ,Caspase 3的活性升高具有时间依赖性     

β淀粉样肽1-40通过激活caspase-3诱导大鼠皮层神经元凋亡

目的　探讨半胱氨酸蛋白酶caspase 3在 β淀粉样肽1 4 0 (β AP1 4 0 )诱导大鼠皮层神经元凋亡中的可能作用。　方法　用 β AP1 4 0 诱导神经元凋亡 ,同时检测caspase 3活力和caspase 3活性片段及caspase 3mRNA的表达水平。　结果　 4 0mg·L- 1 的凝聚态 β AP1 4 0 诱导大鼠皮层神经元凋亡过程中 ,caspase 3活力和caspase 3mRNA的表达水平均有明显增高 (P <0 0 1) ;特异性的caspase 3抑制剂Ac DEVD CHO对caspase 3的激活和皮层神经元细胞凋亡均有明显的阻断作用。　结论　caspase 3可能是 β AP1 4 0 诱导大鼠皮层神经元凋亡的效应因子     

缺血预处理经抑制p53表达减轻缺血再灌后大鼠海马神经元损伤

目的：观察缺血预处理能否对大鼠缺血再灌注后海马CA1区神经元凋亡起拮抗作用，并探讨p53基因在其中的作用。 方法： 复制全脑缺血再灌注及缺血预处理模型，利用HE染色，流式细胞仪，RT-PCR和免疫组化方法检测海马CA1区锥体细胞形态学变化、神经元凋亡百分率及p53基因表达。 结果：缺血预处理（IPC）组的神经元存活数目［(217±9)/0.72 mm²］明显高于单纯缺血再灌注（IR）组［(29±5)/0.72 mm²］，P＜0.01；IPC组的凋亡百分率(2.07%±0.21%)显著低于IR组(4.26%±0.08%), P＜0.01; IPC组p53基因表达显著弱于IR组。 结论： 缺血预处理可通过抑制p53基因表达，从而抑制大鼠海马神经元凋亡，对缺血神经元起保护作用。     

缺血后处理抑制内质网应激PERK通路减轻大鼠离体心脏缺血/再灌注损伤

目的探讨缺血后处理对大鼠离体心脏缺血再灌注损伤的作用及相关机制。方法 36只Wistar大鼠(257-326g),随机分为3组,对照组(Con组),缺血再灌注组(IR组),缺血后处理组(IPo C组)。采用Langendorff灌流装置建立缺血再灌注损伤模型,TTC染色评价梗死面积,Western blot检测凋亡蛋白及内质网应激相关通路蛋白表达。结果 IR组较Con组梗死面积增加,而Bcl-2表达显著降低,GRP78、CHOP、cleaved caspase12、cleaved caspase3、Bax及p-PERK表达水平显著增加。缺血后处理显著缩小梗死面积,并部分逆转相关蛋白表达的变化。结论缺血后处理减轻大鼠离体心脏缺血再灌注损伤,可能与抑制PERK通路介导的ERS相关凋亡相关。     

三七总皂甙降低兔肺缺血再灌注损伤和抑制细胞凋亡

 目的: 探讨细胞凋亡与肺缺血再灌注损伤的关系以及三七总皂甙的作用及机制。方法: 健康日本大耳白兔84只,随机分为对照组、肺缺血再灌注1、3、5h组和相应三七总皂甙干预组。复制肺缺血再灌注损伤模型。用原位缺口末端标记(TUNEL)法、聚丙烯酰胺凝胶电泳观测肺组织细胞凋亡,原位杂交技术检测肺组织细胞Fas/FasL系统和Caspase-3基因表达。结果: 肺缺血再灌注组肺组织细胞凋亡指数(肺缺血再灌注5h组:22.08±1.93;对照组:2.04±0.67)、Fas/FasL和Caspase-3基因表达(肺缺血再灌注5h组:0.241±0.029;对照组:0.121±0.015)均显著高于对照组(P<0.01),并出现电泳梯形条带结构;三七总皂甙干预组Fas/FasL mRNA及其Caspase-3的表达(三七总皂甙干预5h组:0.199±0.020;肺缺血再灌注5h组:0.241±0.029)显著低于缺血再灌注组(P<0.01),肺组织细胞凋亡指数(三七总皂甙干预5h组:12.58±1.82;肺缺血再灌注5h组:22.08±1.93)也显著低于缺血再灌注组(P<0.01),梯形条带结构基本消失。肺组织细胞凋亡指数分别与Caspase-3 mRNA及Fas/FasL mRNA之间均呈显著正相关(P<0.01)。结论:三七总皂甙可能通过抑制Fas/FasL系统的激活,阻遏肺组织细胞凋亡,从而减轻肺缺血再灌注损伤。     

雌二醇对缺血性脑损伤的保护作用

目的　观察雌二醇对大鼠海马神经元缺血性损伤的保护作用。方法　 3月龄SD雌性大鼠 2 9只 ,应用Pulsinelli Brierley脑缺血模型 ,分为脑缺血性损伤雌二醇组 (n =9,10 0 μg·kg-1·d-1)肌肉注射 ;尼莫地平组 (n =8,1μg·kg-1·d-1)腹腔注射 ;以及缺血损伤对照组和假手术组。再灌流 6天后 ,观察海马各区神经元变化。结果　雌二醇治疗组海马CA1和CA2区神经元死亡的数量 (CA1、CA2分别为 9 8± 2 4和 7 7± 2 1)明显少于对照组 (CA1、CA2分别为 4 7± 2 2和 5 0± 3 0 ) ,P <0 0 1,脑缺血性癫痫的发生率和大鼠的死亡率均较对照组低。结论　雌二醇对大鼠全脑缺血 /再灌流损伤具有保护作用。     

丙泊酚对大鼠肾缺血/再灌注损伤细胞凋亡信号通路的影响

目的探讨丙泊酚对大鼠肾缺血/再灌注损伤细胞凋亡通路的影响及可能的作用机制。方法建立大鼠肾缺血/再灌注损伤模型,将动物分为对照(Con)组、缺血再灌注(IR)组、缺血再灌注 丙泊酚(IR P)组。观察损伤肾的形态学改变,用免疫组织化学观察细胞凋亡相关蛋白BCL-2、BAX、caspase3和细胞色素C(cytochrome C)的表达情况。结果光镜可观察到肾缺血/再灌注引起的肾损害,损害程度依次为近曲小管、远曲小管、集合管、肾小球;免疫组化图像分析观察到IR组与Con组相比,BAX、caspase3,细胞色素C表达增加,BCL-2表达未见明显变化;IR P组与IR组比较,前者BAX、caspase3和细胞色素C表达下降,BCL-2表达增高(P<0·05)。结论丙泊酚对肾缺血/再灌注损伤引起的细胞凋亡可能具有保护作用,可能机制是抑制促凋亡蛋白BAX、caspase3和细胞色素C的表达,对BCL-2的表达无影响,与细胞凋亡的线粒体通路途径有关。     

骨形态发生蛋白-7对大鼠脑缺血再灌注后Caspase-3表达的影响

目的 观察骨形态发生蛋白-7（BMP-7）对大鼠局灶性脑缺血再灌注损伤神经细胞凋亡的影响及其机制。方法 将40只SD雄性大鼠随机分为实验组、对照组和假手术组,采用改良线栓法制作大脑中动脉栓塞缺血再灌注（MCAO/R）模型,实验组在缺血2h再灌注后尾静脉注射BMP-7（0.1mg/kg）250μl,对照组和假手术组尾静脉注射等量生理盐水,运用Bederson评分法进行神经功能缺失评分。再灌注24h后将大鼠处死,采用2,3,5-氯化三苯基四氮唑（TTC）染色法观察梗死灶范围,并计算梗死灶体积占半球体积的百分比;HE染色观察脑组织病理变化,原位缺口末端标记法（TUNEL）计数神经元凋亡数量,免疫组织化学染色观察缺血脑组织内Caspase-3表达。结果 BMP-7组大鼠Bederson评分（1.7±0.5）比对照组（2.7±0.5）明显降低（t =4.66,P ＜0.01）,脑梗死体积百分比（7.6±1.4）比对照组（22.3±4.5）明显降低（t =6.98,P ＜0.01）。与对照组相比,HE染色显示BMP-7组大鼠缺血侧大脑皮质脑组织损伤明显减轻。BMP-7组缺血侧大脑皮质、纹状体及海马TUNEL阳性细胞数（分别为3.6±0.6、7.4 ±1.1、5.0±0.7）明显低于对照组同一区域（分别为13.4±1.1、17.8±1.5、15.4±1.1,P ＜0.01）。BMP-7组缺血侧大脑皮质、纹状体及海马Caspase-3阳性细胞数（分别为7.6±0.9、5.8±0.8、10.6±1.1）明显低于对照组同一区域（分别为15.4±0.6、14.0±1.2、17.2±0.8,P ＜0.01）。结论 BMP-7可通过下调Caspase-3表达而抑制大鼠脑缺血再灌注损伤引起的细胞凋亡,起到神经保护作用。     

锌指蛋白A20在内毒素所致人脐静脉内皮细胞损伤中的作用

目的　探讨外源性锌指蛋白A2 0对内毒素 (LPS)诱导的内皮细胞同型半胱氨酸蛋白酶caspase 3表达和凋亡的影响。　方法　RT PCR检测A2 0基因在内毒素诱导内皮细胞中的表达。DOTAP脂质体转染pCDNA3 1EHA2 0于脐静脉内皮细胞 ,经G4 18筛选 ,A2 0表达经免疫荧光鉴定。Tunnel原位末端标记法、原位杂交检测转染前后内毒素诱导内皮细胞凋亡情况及caspase 3的表达情况。　结果　A2 0基因在内毒素诱导的内皮细胞中能表达。正常对照组及转染A2 0基因组人脐静脉内皮细胞 (HUVEC)凋亡为 (5± 1) %、(6± 1) % ,LPS作用后对照组与转染A2 0基因组凋亡分别为 (36± 3) %、(10± 1) % ,两者相差显著 (P <0 0 5 )。A2 0基因能显著抑制内毒素诱导的内皮细胞caspase 3的表达。　结论　A2 0基因在创伤的治疗中可能有一定作用。     

肾缺血预处理减少心肌缺血—再灌注所致的心肌细胞凋亡

在麻醉家兔心肌缺血 /再灌注 (myocardialischemia/reperfusion ,MIR)模型上 ,观察MIR和肾脏缺血预处理 (renalischemicpreconditioning ,RIP)对血流动力学、心外膜电图、心肌梗死范围、心肌细胞凋亡和凋亡相关调控基因蛋白(Fas、Bcl 2和Bax)的影响。所得结果如下 :(1)在MIR过程中 ,动脉血压、心率和心肌耗氧量呈进行性下降 ;心外膜电图ST段在缺血期明显抬高 ,再灌注时逐渐恢复至基础对照值。 (2 )MIR组的坏死心肌占缺血心肌的 (5 5 80±3 5 3) % ,RIP后心肌梗死范围降至 (36 5 1± 6 6 1) %。 (3)凝胶电泳显示 ,MIR组的缺血组织DNA呈云梯状 ,RIP +MIR组则无 ;原位末端标记表明 ,RIP中缺血未坏死心肌的凋亡细胞较MIR组稀少 ;流式细胞术测得MIR和RIP +MIR组中缺血心肌的细胞凋亡率分别为 (10 70± 1 80 ) %和 (5 86± 1 79) %。 (4 )在MIR和RIP +MIR组的缺血心肌中 ,Fas和Bax蛋白表达均明显增高 ,Bcl 2蛋白表达无明显变化。MIR组的Fas和Bax蛋白表达较RIP +MIR组的明显 ,MIR组中Bcl 2 /Bax较非缺血心肌组织和RIP +MIR组中的明显减小。以上结果表明 ,RIP减少MIR引发的心肌细胞凋亡 ,并可能通过减少MIR心肌组织中Fas和Bax蛋白的表达而起作用。     

Bax cleavage implicates caspase-dependent H2O2-induced apoptosis of hepatocytes

Oxidative stress plays an important role in the development of ischemia/reperfusion (I/R)-induced apoptosis of hepatocytes. We aimed to examine the involvement of caspases and calpains in H2O2-induced hepatic cell apoptosis. TUNEL-positive apoptotic cells appeared in parallel with poly(ADP-ribose) polymerase (PARP) cleavage and procaspase-3 proteolysis by H2O2 treatment in a dose-dependent manner (250-1,000 micro M). Bcl-xL and intact Bax expression levels decreased when H2O2 was >250 micro M. The cleaved form of Bax appeared prior to caspase-3 activation, increasing in a dose-dependent manner. A pan-caspase inhibitor, Z-VAD-fmk, completely blocked H2O2-induced procaspase-3 proteolysis and PARP cleavage without changing Bax cleavage, but partially attenuated H2O2-induced apoptosis. Calpeptin, a calpain inhibitor, did not inhibit caspase-3 activation, Bax cleavage or apoptosis. Our results indicate that Bax cleavage is upstream signal of caspase-dependent apoptosis in hepatocytes exposed to H2O2, but not independent upon calpain. Molecular targeting of Bax cleavage may allow the development of strategies to prevent hepatic I/R injury.     

A comparison of the signal pathways between the TNF alpha- and oridonin-induced murine L929 fibrosarcoma cell death

Oridonin, an active component isolated from Rabdosia rubescences, has been reported to have antitumor effects. In this study, we compared the signal transduction pathways between TNFalpha-and oridonin-induced L929 cell death. Oridonin and TNFalpha initiated apoptotic morphologic changes, but DNA fragmentation was found in TNFalpha-treated L929 cells but not in oridonin-treated ones. The pan-caspase inhibitor (z-VAD-fmk), caspase-8 inhibitor (z-IETD-fmk) and caspase-3 inhibitor (z-DEVD-fmk) augmented oridonin-and TNFalpha-induced cell death. However, the caspase-9 inhibitor (z-LEHD-fmk) only increased oridonin-induced L929 cell death. Moreover, poly (ADPribose) polymerase (PARP) was cleaved in oridonin-treated L929 cells but not in the TNFalpha-treated groups, and the caspase-3 inhibitor (z-DEVD-fmk) failed to inhibit PARP cleavage. These results showed that only oridonin-induced L929 cell death required PARP degradation in a caspase-3 independent manner. In addition, oridonin increased the ratio of Bax/Bcl-2 protein expression, but TNFalpha did not. TNFalpha induced p38 and ERK activation, whereas oridonin triggered only ERK activation. We also investigated the effect of oridonin on intracellular TNFalpha expression, and found that oridonin augmented endogenous pro-TNFalpha expression and its upstream protein IkB phosphorylation. These results indicated that although oridonin promoted endogenous pro-TNFalpha expression, a great difference existed between the signal pathways through which TNFalpha-and oridonin-induced cell death.     

大豆异黄酮对脑缺血/再灌注诱导的线粒体损伤和脑细胞凋亡的影响

 目的:研究大豆异黄酮（SI）对全脑缺血/再灌注大鼠脑组织线粒体超微结构、细胞凋亡和细胞色素C（Cyt-C）、caspase-3及caspase-9表达的影响,探讨大豆异黄酮对脑缺血/再灌注损伤的作用及机制。方法: 60只健康成年SD 大鼠随机分为假手术组（sham）、缺血再灌注组（I/R）和大豆异黄酮预处理组（SI）。SI组给予SI 120 mg·kg-1·d-1连续灌胃21 d,其余2组用等体积生理盐水灌胃,每天1次,第22天I/R组和SI组行手术阻断三血管制备全脑缺血/再灌注模型。缺血1 h,再灌1 h后处死,取大脑皮层,光镜观察脑细胞形态学变化,透射电镜观察线粒体超微结构变化,流式细胞术检测细胞凋亡率,半定量RT-PCR法和免疫组织化学法测定脑组织中Cyt-C、caspase-9及caspase-3的表达。结果: I/R组线粒体膜崩解、嵴消失,脑细胞大量凋亡。与I/R组相比,大豆异黄酮预处理能明显改善线粒体超微结构的损伤,减少脑细胞凋亡率（P<0.01）。I/R组Cyt-C、caspase-9和caspase-3 mRNA的表达和蛋白的含量高于sham 组（P<0.01）,与I/R组相比,SI组Cyt-C、 caspase-9及caspase-3 mRNA 和蛋白的表达显著降低（P<0.01）。结论: 大豆异黄酮可能通过稳定线粒体结构,减少线粒体释放Cyt-C,降低caspase-9和caspase-3的表达,抑制细胞凋亡,从而减轻脑缺血/再灌注损伤。     

大鼠脑缺血再灌流后神经细胞凋亡与caspase-3和caspase-9基因表达

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caspase-3和caspase-9基因表达的关系。方法：应用原位末端标记和原位杂交技术分别观察细胞凋亡与caspase-3mRNA和caspase-9mRNA表达。结果：脑缺血再灌流后，凋亡神经细胞主要分布于缺血半影区，随着时间的延长凋亡细胞数逐渐增加，至24h达高峰。在缺血半影区，再灌流后神经细胞caspase-3mRNA和caspase-9mRNA表达逐渐增强，到24h阳性细胞数目最多，COD值最高，而缺血中心区两基因均弱表达。结论：脑缺血再灌流后神经细胞凋亡是一个动态的渐进过程。caspase-3和caspase-9基因表达在介导细胞凋亡过程中起重要作用。     

Cocaine exposure in vitro induces apoptosis in fetal locus coeruleus neurons by altering the Bax/Bcl-2 ratio and through caspase-3 apoptotic signaling

Cocaine inhibits survival and growth of rat locus coeruleus (LC) neurons, which may mediate alterations in attention, following in utero exposure to cocaine. These effects are most severe in early gestation during peak neuritogenesis. Prenatal cocaine exposure may specifically decrease LC survival through an apoptotic pathway involving caspases. Dissociated fetal LC neurons or substantia nigra (SN) neurons (control) were exposed in vitro to a pharmacologically active dose of cocaine hydrochloride (500 ng/ml) and assayed for apoptosis using terminal deoxynucleotidyl transferase mediated DNA nick end labeling and Hoechst methodologies. Cocaine exposure decreased survival and induced apoptosis in LC neurons, with no changes in survival of SN neurons. Activation of apoptotic signal transduction proteins was determined using enzyme assays and immunoblotting at 30 min, 1 h, 4 h and 24 h. In LC neurons, Bax levels were induced at 30 min and 1 h, following cocaine treatment, and Bcl-2 levels remained unchanged at all time points, altering the Bax/Bcl-2 ratio. The ratio was reversed for SN neurons (elevated Bcl-2 levels and transient reduction of Bax levels). Further, cocaine exposure significantly increased caspase-9 and caspase-3 activities at all time points, without changes in caspase-8 activity in LC neurons. In addition, cleavage of caspase-3 target proteins, alpha-fodrin and poly (ADP-ribose) polymerase (PARP) were observed following cocaine treatment. In contrast, SN neurons showed either significant reductions, or no significant changes, in caspase-3, -8 or -9 activities or caspase-3 target proteins, alpha-fodrin and PARP. Thus, cocaine exposure in vitro may preferentially induce apoptosis in fetal LC neurons putatively regulated by Bax, via activation of caspases and their downstream target proteins.     

JNK通路促进大鼠脑缺血再灌注海马神经元凋亡

目的:探讨c-JunN端激酶(JNK)通路在大鼠脑缺血再灌注后海马神经元凋亡中的作用。方法:雄性SD大鼠90只,随机分为假手术组、全脑缺血再灌注组、全脑缺血再灌注+JNK抑制剂(SP600125)组、全脑缺血再灌注+JNK激动剂(茴香霉素)组和全脑缺血再灌注+溶剂对照组,每组再灌注后24h取材。分别采用免疫组化、Westernblotting和实时荧光定量PCR检测海马神经元caspase-3蛋白和mRNA的表达;采用TUNEL染色检测海马神经元凋亡情况。结果:全脑缺血再灌注组caspase-3蛋白和mRNA表达较假手术组增加(P<0.05);与全脑缺血再灌注组相比,全脑缺血再灌注+JNK抑制剂组caspase-3蛋白和mRNA表达均降低(P<0.05),而全脑缺血再灌注+JNK激动剂组caspase-3蛋白和mRNA表达均增加(P<0.05),全脑缺血再灌注+溶剂对照组则无明显变化(P>0.05)。各组海马神经元凋亡趋势与caspase-3蛋白和mRNA变化趋势一致。结论:JNK通路的激活可增加大鼠脑缺血再灌注后海马神经元caspase-3的表达,促进海马神经元凋亡。     

多聚(ADP-核糖)聚合酶和半胱天冬蛋白酶-3在过氧亚硝基阴离子致气道上皮细胞损伤中的作用

目的:探讨过氧亚硝基阴离子(ONOO^-)介导气道上皮细胞损伤的作用机制。方法: 在培养的大鼠气道上皮细胞(RTE), 观察应用多聚(ADP-核糖)聚合酶(PARP)抑制剂3-氨基苯甲酰胺(3-AB)和半胱天冬氨酸蛋白酶-3(caspase-3)抑制剂Ac-DEVD-CHO后, 外源性给予ONOO^-对RTE细胞乳酸脱氢酶(LDH)释放、凋亡百分率的影响, 用Westernblot分析PARP裂解片段。结果:3-AB不能完全抑制ONOO^-引起的RTE细胞LDH释放率的增高。3-AB对ONOO^-引起的RTE细胞凋亡无明显影响。Ac-DEVD-CHO呈剂量依赖性抑制ONOO^-诱导的RTE细胞凋亡。ONOO^-致RTE细胞凋亡过程中有PARP的裂解。结论:PARP活化是ONOO^-介导RTE细胞损伤的途径之一, 过度的PARP活化参与了ONOO^-所致的RTE细胞坏死;caspase-3活化裂解PARP在ONOO^-致RTE细胞凋亡过程中起重要作用。     

二苯乙烯苷对沙鼠脑缺血/再灌注引发海马损伤的保护作用

目的　研究二苯乙烯苷（tetrahydroxy stilbene glucoside, TSG）对脑缺血/再灌注（ischemia/reperfusion, I/R）沙鼠脑海马损伤的保护作用及可能机制。 方法 采用结扎沙鼠双侧颈动脉缺血30 min,再灌注5 d复制沙鼠全脑I/R模型。沙鼠随机分为6组,假手术组、模型对照组、TSG大、中、小剂量（6、3、1.5 mg/kg）组和阳性对照药依达拉奉注射组（3 mg/kg）。5 d后通过Morris水迷宫测定沙鼠学习记忆功能;Nissl染色观察沙鼠大脑海马CA1区神经元结构和数量的变化;TUNEL染色法观察沙鼠大脑海马CA1区神经元凋亡的变化;Western blot法检测脑组织active-caspase-3的表达。 结果　与假手术组相比,I/R组沙鼠学习记忆能力明显降低,海马CA1区神经元大量丢失,结构紊乱。同时,I/R组沙鼠CA1区神经元凋亡数量明显增加,脑组织中caspase-3显著活化。TSG中、高（3、6 mg/kg）剂量组和依达拉奉阳性对照组均可以显著改善I/R引发的沙鼠学习记忆能力的降低,抑制海马CA1区神经元的丢失,改善神经元结构;抑制CA1区神经元的凋亡以及caspase-3的活化。而TSG低剂量组对上述变化均没有明显的治疗作用。 结论　TSG对于I/R引发的脑损伤,尤其是海马区神经元迟发性凋亡具有明显的治疗作用,这种作用与其抑制caspase-3的活化相关。     

Leptospira interrogans Induces Apoptosis in Macrophages via Caspase-8- and Caspase-3-Dependent Pathways

Apoptosis of host cells plays an important role in modulating the pathogenesis of many infectious diseases. It has been reported that Leptospira interrogans, the causal agent of leptospirosis, induces apoptosis in macrophages and hepatocytes. However, the molecular mechanisms responsible for host cell death remained largely unknown. Here we demonstrate that L. interrogans induced apoptosis in a macrophage-like cell line, J774A.1, and primary murine macrophages in a time- and dose-dependent manner. Apoptosis was associated with the activation of cysteine aspartic acid-specific proteases (caspase-3, caspase-6, and caspase-8), the increased expression of Fas-associated death domain (FADD), and the cleavage of the caspase substrates poly(ADP-ribose) polymerase (PARP) and nuclear lamina protein (lamin A and lamin C). Caspase-9 was activated to a lesser extent, whereas no release of cytochrome c from mitochondria was detectable. Inhibition of caspase-8 impaired L. interrogans-induced caspase-3 and -6 activation, as well as PARP and lamin A/C cleavage and apoptosis, suggesting that apoptosis is initiated via caspase-8 activation. Furthermore, caspase-3 was required for the activation of caspase-6 and seemed to be involved in caspase-9 activation through a feedback amplification loop. These data indicate that L. interrogans-induced apoptosis in macrophages is mediated by caspase-3 and -6 activation through a FADD-caspase-8-dependent pathway, independently of mitochondrial cytochrome c-caspase-9-dependent signaling.     

Requirement of caspase-3 for efficient apoptosis induction and caspase-7 activation but not viral replication or cell rounding in cells infected with vesicular stomatitis virus

Infection with vesicular stomatitis virus (VSV), a rhabdovirus and economically significant animal pathogen, was previously demonstrated to induce apoptosis. The mechanism of induction and the role of apoptosis in the VSV-host response have not been completely elucidated. Previous data from our laboratory have suggested that caspase-3 is required for the induction of apoptosis but not viral replication in VSV-infected cells. However, these studies used inhibitors that are selective but not specific for caspase-3. To circumvent this difficulty, we infected both MCF-7 cells which do not express caspases-3 (null), and stable transfectants which express caspase-3 (C3+). When caspase-3 null cells were infected, significant PARP cleavage did not occur, but when C3+ cells were infected, PARP cleavage did occur efficiently. Studies in null and C3+ also suggest that: (1) caspases-3 and -7 are activated sequentially after VSV infection; (2) cell shrinkage and detachment are caspase-3 dependent, but cell rounding is not; and (3) the viral titers were similar between caspase-3 null and C3+ cells suggesting that activation of caspases-3 and -7 are not required for viral replication. Taken together, these results strongly support that the activation of caspase-3 by VSV infection is required for efficient apoptosis induction but not viral replication in vitro. Apoptosis mediated by caspase-3, then, is likely either a host cell response to viral replication or perhaps may be required for in vivo viral replication and spread.