Published online May 15, 2016. doi: 10.4291/wjgp.v7.i2.223
Peer-review started: January 2, 2016
First decision: February 2, 2016
Revised: March 1, 2016
Accepted: March 17, 2016
Article in press: March 18, 2016
Published online: May 15, 2016
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 (H2O2) - 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 14C-D-mannitol, 3H-Lactulose and 14C-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 14C-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 Jm. There however was no increase in transepithelial leak of two larger probe molecules, 3H-lactulose and 14C-polyethylene glycol (PEG). However, exposure to TNF-α + IFN-γ + IL1β followed by a 5 h exposure to 2 mmol/L H2O2 resulted in a 500% increase in 14C-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.
Core tip: A cell culture model of graded transepithelial leak can be very valuable in evaluating the various types and magnitudes of leak that can exhibit across the inflammatory bowel disease mucosa. This graded leak can be achieved through various combinations of proinflammatory cytokines and peroxide. Berberine provides an example of a micronutrient that can be more effective against one type of induced leak than another.