AIM:To study whether the inflammatory bowel disease(IBD)colon which exhibits varying severity and cytokine levels across its mucosa create varying types of transepithelial leak.METHODS:We examined the effects of tumor necrosis factor-α(TNF-α),interferon-γ(IFN-γ),interleukin-1-β(IL1β)and hydrogen peroxide(H_2O_2)-singly and in combinations-on barrier function of CACO-2 cell layers.Our focus was on the type(not simply the magnitude)of transepithelial leak generated by these agents as measured by transepithelial electrical resistance(TER)and transepithelial flux of ~(14)C-D-mannitol,3H-Lactulose and ~(14)C-Polyethylene glycol as radiolabeled probe molecules.The isoquinoline alkaloid,berberine,was then examined for its ability to reduce specific types of transepithelial leak.RESULTS:Exposure to TNF-α alone(200 ng/mL;48 h)induced a 50% decrease in TER,i.e.,increased leak of Na~+ and Cl--with only a marginal but statistically significant increase in transepithelial leak of ~(14)C-mannitol(Jm).Exposure to TNF-α + IFN-γ(200 ng/mL;48 h)+ IL1β(50 ng/mL;48 h)did not increase the TER change(from TNF-α alone),but there was now a 100% increase in J_m.There however was no increase in transepithelial leak of two larger probe molecules,~3H-lactulose and ~(14)C-polyethylene glycol(PEG).However,exposure to TNF-α + IFN-γ + IL1β followed by a 5 h exposure to2 mmol/L H_2O_2 resulted in a 500% increase in ~(14)C-PEG leak as well as leak to the luminal mitogen,epidermal growth factor.CONCLUSION:This model of graded transepithelial leak is useful in evaluating therapeutic agents reducing IBD morbidity by reducing barrier leak to various luminal substances. AIM: To study whether the inflammatory bowel disease (IBD) colon where exhibits varying severity and cytokine levels across its mucosa create varying types of transepithelial leak. METHODS: We examined the effects of tumor necrosis factor-a (TNF-a), interferon- γ (IFN-γ), interleukin-1-β (IL1β) and hydrogen peroxide (H_2O_2) -singly and in combinations-on barrier function of CACO-2 cell layers. Our focus was on the type (not simply the magnitude) of transepithelial leak generated by these agents as measured by transepithelial electrical resistance (TER) and transepithelial flux of CD-mannitol, 3H-Lactulose and ~ (14) C-Polyethylene glycol as radiolabeled probe molecules. isoquinoline alkaloid, berberine, was then examined for its ability to reduce specific types of transepithelial leaks. RESULTS: Exposure to TNF-α alone (200 ng / mL; 48 h) induced a 50% decrease in TER, ie, increased leak of Na ~ + and Cl- -with only a marginal but marked significant increase in transepithelial leak of ~ (14) C-mann itol (Jm). Post-to TNF-α + IFN-γ (200 ng / mL; 48 h) + IL1β (50 ng / mL; 48 h) did not increase the TER change was now a 100% increase in J_m.There was was no increase in transepithelial leak of two larger probe molecules, ~ 3H-lactulose and ~ (14) C-polyethylene glycol (PEG) .However, exposure to TNF-α + IFN- γ + IL1β followed by a 5 h exposure to 2 mmol / L H_2O_2 resulted in a 500% increase in ~ (14) C-PEG leak as well as leak as the luminal mitogen, epidermal growth factor. CONCLUSION: This model of graded transepithelial leak is useful in evaluating therapeutic agents reducing IBD morbidity by reducing barrier leak to various luminal substances.