Effect of inflammatory cytokines on swine tracheal epithelial barrier damage. A, B Cytokines present in the supernatant decreased TEER and increased paracellular permeability respectively, promoting barrier damage. The supernatant of HPS4-YC-infected and mock-infected STEC was added to the upper chambers of transwells, and TEER and FITC-conjugated dextran crossing the transwell chamber were measured at 12 h and 24 h. C, D TNF-α damaged the epithelial barrier integrity. Different concentrations of TNF-α were added to the medium in the apical compartment for 24 h, and TEER and paracellular permeability were measured to determine their effect on epithelial barrier integrity. Data are shown as the mean ± SD of triplicate assays. Significant differences in A and B were determined using Student t test. Significant differences in C and D were determined using one-way ANOVA. ns: not significant; *, P < 0.05; **, P < 0.01; ***P < 0.001.