艰难梭菌A毒素诱导SMMC7721细胞和Vero细胞凋亡的比较研究

背景与目的:艰难梭菌是假膜性大肠炎及抗生素诱发性腹泻的主要致病菌之一,它产生的毒素具有不同的生物学活性.本实验拟研究艰难梭菌 A毒素诱导人肝癌细胞株( SMMC7721)和非洲绿猴肾细胞( Vero细胞)凋亡的作用. 方法:由脑心浸液对艰难梭菌 VPI 10463菌株培养产毒 , 经甲状腺球蛋白亲合层析和 Q Sephrose层析提纯得到精制 A毒素.对 SMMC7721细胞的研究以 Vero细胞为对照.抑制细胞增殖的检测采用 MTT法;用荧光显微镜、电子显微镜、流式细胞仪观察细胞形态和细胞周期的改变;采用琼脂糖凝胶电泳法观测 DNA碎片.结果:不同浓度 A毒素 (0.293～ 4.690 mg@ L- 1)明显抑制了 SMMC7721及 Vero细胞的增殖,并且呈时间和浓度依赖性;两种细胞与 A毒素共同培养 48 h,荧光显微镜和透射电镜都观察到典型的凋亡形态变化; SMMC7721细胞与 A毒素共同培养 48 h后,琼脂糖凝胶电泳显示梯形条带.结论: A毒素明显诱导了两种细胞的凋亡 ; A毒素对 SMMC7721细胞具有更强的诱导凋亡作用.

Comparative study on apoptosis induction of SMMC7721 and Vero cells by Clostridium difficile toxin A

BACKGROUND & OBJECTIVE: Clostridium difficile is recognized as a frequent cause of antibiotic-induced diarrhea. This study was designed to investigate whether Clostridium difficile toxin A might induce apoptosis on human hepatoma cell line SMMC7721 and African green monkey kidney Vero cells. METHODS: Highly purified toxin A was obtained by bovine thyroglobulin affinity purification followed by ion exchange chromatography on Q sepharose. The apoptosis induction of toxin A was examined on SMMC7721 cells with Vero cells as a control. Inhibition of proliferation was measured by MTT assay. Morphological assessment of apoptosis was performed with fluorescence and electronic microscopy. DNA fragmentation was observed by agarose gel electrophoresis. Cell cycle distribution was analyzed by flow cytometry. RESULTS: Toxin A (0.293-4.690 mg x L(-1) ) inhibited proliferation of SMMC7721 and Vero cells in a time- and concentration-dependent manner. Morphological changes of typical apoptosis showed that SMMC7721 had a higher percentage of apoptosis than Vero cells. Agarose gel electrophoresis of DNA from SMMC7721 treated with toxin A for 48 hours revealed a "ladder" pattern. CONCLUSION: Clostridium difficile toxin A induced apoptosis of SMMC7721 and Vero cells. The apoptosis induction on SMMC7721 cells was more effective than that on Vero cells.