Figure 2.
Regulation of epithelial cell proliferation and apoptosis by inflammatory cytokines is associated with inhibition of Wnt signaling. (A) Proliferation of T84 intestinal epithelial cells was determined by EdU incorporation for 2 hours. IFN-γ elicited a biphasic response after extended treatment, which was potentiated by TNF-α. (B) Apoptosis of T84 cells was determined by TUNEL staining. IFN-γ and TNF-α synergistically enhanced cell death over the observation period. (C) Dkk1 protein expression in T84 cells was induced by IFN-γ treatment for 72 hours. (D) Recombinant Dkk1 dose-dependently induced Caspase-3 activation in T84 cells after 72 hours. (E) Mice were treated with recombinant Dkk1 (rDkk1) or PBS for 16 hours, and apoptosis was determined by active Caspase-3 staining. The graph shows results from >1000 crypts of two mice per group. (F) IFN-γ-induced apoptosis in T84 cells after 72 hours was inhibited by co-treatment with GSK-3β inhibitor AR-A014418, or a functional Dkk1 antibody. Apoptosis was assessed by M30 staining. Scale bar, 100μm. Data in all graphs in this figure are represented as mean ± s.e.m. * P < 0.001 vs control (Student’s t-test); † P < 0.01 vs IFN-γ (ANOVA with Dunnett’s post-test).