FIG 3.

C. difficile TcdA promotes TGF-β1 secretion and signaling activation in IEC-6 cells. Treatment of IEC-6 cells with TcdA (10 ng/ml) for 24 h enhanced TGF-β1 mRNA expression (A), followed by induction of SMAD2/3 phosphorylation and nuclear translocation (E and H) compared to control (B), increased TGFRII labeling intensity in IEC-6 cells (F and I) compared to control (C) in a concentration-dependent manner, and decreased number of cells (G) compared to control (D) as observed by DAPI stain. *, P < 0.05; ***, P < 0.0001 by analysis of variance (ANOVA) and Bonferroni’s test. Scale bar: 20 mm.