The effect of berberine on cytokine-induced leak of CACO-2 cell layers. A: Seven-day post-confluent CACO-2 cell layers on Millipore polycarbonate filters were refed in control medium or medium containing 100 μmol/L berberine. After 24 h treatment with berberine alone, the cell layers were given either control or berberine medium in addition to being exposed to no cytokines, TNF-α alone, or cytomix (apical and basal-lateral compartments) for 48 h prior to electrical measurements. Data shown represent the mean ± SE of 8 cell layers per condition. Data represent the percent of control resistance normalized across experiments; B: After electrical measurements, the same CACO-2 cell layers represented in A were used to perform radiotracer flux studies with 0.1 mmol/L, 0.1 μCi/mL 14C-D-mannitol, as described in Materials and Methods. Data represent the percent of control flux rate normalized across experiments and is expressed as the mean ± SE of 8 cell layers per condition. bP < 0.001 vs cytomix alone (one-way ANOVA followed by Tukey’s post hoc testing). TNF-α: Tumor necrosis factor-α.