Fig. 1

Sensitivity of human colonic epithelial cell to TcdA-induced cell apoptosis. The human colonic epithelial cells were exposed to 5 ng/ml, 10 ng/ml, 20 ng/ml TcdA for 24 h. a The viability of cells was detected by WST-1 assay (n = 3 individual experiments). b Apoptotic death of NCM 460 cells was assessed by flow cytometric analysis (n = 3). Q2_LL represents normal cells, and the early and late apoptotic cells are located in the Q2_LR and Q2_UR regions. The necrotic cells are distributed in the Q2_UL region. The relative ratio of early and lately apoptotic cells was chosen for further comparison. c TUNNEL staining of human colonic epithelial cells. Cells with shrunken brown stained nuclei were considered positive (Red arrows). ***p < 0.001, **p < 0.01, *p < 0.05, ^#p > 0.05 versus Mock group (Control group)