猪水肿病毒素Stx2e的致Vero细胞凋亡作用

The apoptosis of Vero cells induced by Shiga toxin 2e

【目的】研究猪水肿病的致病因子志贺毒素2e(Shigatoxin2e,Stx2e)的致病机理。【方法】以AO/EB荧光染色法、琼脂糖凝胶电泳法和Western blotting等方法研究Stx2e对Vero细胞的致凋亡作用及其信号途径。【结果】从细胞形态学和染色质水平证明,Stx2e能诱导Vero细胞凋亡,并表现出时间和浓度依赖性;同时引起caspase-3表达量明显上调,Bax、caspase-9的表达量没有明显变化。【结论】Stx2e对Vero细胞的致凋亡作用主要通过膜受体通路引起,线粒体信号通路所起的作用较小。

[ Objective] Shiga-like toxin-producing Escherichia coli （STEC） causes edema disease in piglets and hemolytic uremic syndrome in human. Shiga-like toxins （Stxs） produced by STEC induce mammalian cells death via either necrosis or apoptosis. However, the ability of stx2e, separated from edema disease （Stx2e）, to trigger apoptosis and the sequence of intracellular signaling events have not yet been completely defined. In this study we investigated the apoptotic effects of Stx2e on Vero cells. [Methods] Vero cells were treated with different concentrations of Stx2e for different time and the apoptotic cells were characterized by acridine orange and ethidium bromide fluorescent dye staining. The fragmentation of chromatin from Vero cells treated with Stx2e were detected by agarose gel electrophoresis. The expression patterns of apoptosis-associated factors were assayed by Western blotting. [Results] Stx2e-treated cells showed characteristic features of apoptosis, including membrane blebbing, DNA fragmentation, chromatin condensation, and the formation of apoptotic bodies, whereas ricin did not induce apoptosis of Vero cells even at a high dose. Fluorescent dye staining showed that Stx2e induced apoptosis of Vero cells in dose- and time-dependent manners. Caspase-3 was activated whereas expression levels of bcl2 associated X protein （Bax） and caspase- 9 had no change compared with the negative control. [ Conclusion] Stx2e induced intensively apoptosis of Vero cells, which was mediated through the mitochondrion-independent pathway and might be throught a receptor-dependent pathway.