Objective To determine the effect of apoptosis in different host cells induced by L. in- terrogans and the associated intracellular signaling pathway. Methods L. interrogans serogroup Icterohaem- orrhagiae serovar icterohaemorrhagiae strain Lai infected cell models in mouse mono-macrophage like cell J774A. 1, human EVC304 cells and A549 cells were established, respectively. Flow cytometry with fluores- cein labeling of FITC-Annexin V/PI was performed to examine the apoptosis or necrosis of the infected cells. Fluorometry as well as Western blot assay was applied to measure the activity of caspase-3, -8, -9 and the expression levels of apoptotic associated protein FADD in the infected cells , respectively . Results 36.70%-63.70% of the L. interrogans strain Lai infected J774A. 1 cells displayed obvious early apoptosis during the infection for 1-6 h, and then altered to later apoptosis / necrosis (53.68%) as the major injury pattern when infected for 12 h. 78.52% of the L. interrogans strain Lai infected A549 cells only showed later apoptosis / necrosis. However, no obvious apoptosis and / or necrosis could be found in the L. interrogans strain Lai infected EVC304 cells. The maximal activities of caspase-3 and -8 in the infected J774A. 1 cells were (1453.41±36.07) and (1402.15± 59.09) FU, respectively, which were the 16.38-fold and 29.99- fold of those the non-infected cells. The caspase-9 activity of the infected J774A. 1 cells slightly increased [(89.42±5.08) FU ], which significantly lower than those of caspase-3 and -8 (P <0.001). The FADD expression level of the infected J774A. 1 cells was gradually increased in an infection time-dependent man- ner. Conclusion There is a distinct diversity of apoptosis in different cells induced by L. interrogans, and FADD→caspase-8→caspase-3 is the major signaling pathway to mediate L. interrogans infection associated cell apoptosis.%目的 了解问号钩端螺旋体诱导不同宿主细胞凋亡的作用及相关胞内信号传导通路.方法 建立问号钩体黄疸出血群赖型赖株小鼠单核-巨噬样细胞J774A.1、人脐静脉内皮细胞EVC304和人Ⅱ型肺泡上皮细胞A549感染模型.采用FITC-Annexin V/PI荧光标记流式细胞术检测细胞凋亡或坏死情况.分别采用荧光比色法和Western blot检测感染的J774A.1细胞caspase-3,-8,-9活性和凋亡相关蛋白FADD(Fas-associated death domain)表达水平.结果 问号钩体赖株感染1～6 h后,36.70%～63.70%的J774A.1细胞可H{现明显的早期凋亡,感染12 h时转变为晚期凋亡或坏死为主(53.68%).78.52%问号钩体赖株感染的A549细胞仪出现晚期凋亡或坏死.问号钩体赖株感染的EVC304细胞无细胞凋亡或坏死现象.感染的J774A.1细胞caspase-3和-8最大活性分别为(1453.41±36.07)和(1402.15±59.09)Fu,是未感染细胞的16.38和29.99倍.感染的J774A.1细胞caspase-9虽略有升高为(89.42±5.08)Fu,但明显低于caspase-3和-8(P<0.001).随着感染时间的延长,感染的J774A.1细胞FADD蛋白表达量逐步增加.结论 问号钩体诱导宿主细胞凋亡的效应町因细胞种类不同而有明显差异,FADD→caspase-8→caspase-3是介导问号钩体感染J774A.1细胞凋亡的主要信号通路.
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