Green tea polyphenol epigallocatechin-3-gallate improves epithelial barrier function by inducing the production of antimicrobial peptide pBD-1 and pBD-2 in monolayers of porcine intestinal epithelial IPEC-J2 cells

Scope: Green tea has been known to confer numerous health benefits such as the prevention of cardiovascular disease, cancers, and obesity. Epigallocatechin-3-gallate (EGCG) is the major polyphenol present in green tea. Since EGCG is a food-derived component, intestinal epithelial cells lining the gastrointestinal tract are constantly and directly exposed to EGCG. It is anticipated that EGCG can exert beneficial effects in the intestine. The aim of this study was to explore the protective effects of EGCG on intestinal barrier functions against bacterial translocation by using a porcine jejunal epithelial cell line, IPEC-J2. Methods and results: EGCG reduced bacterial translocation across IPEC-J2 cell monolayers through the enhancement of the intestinal epithelial immunological barrier function by inducing secretion of antimicrobial peptides, porcine beta-defensins 1 and 2 (pBD-1 and 2), which possessed higher antimicrobial activity against Escherichia coli. Further mechanistic studies demonstrated that EGCG upregulated pBD-2 but not pBD-1 via the p38 mitogen-activated protein kinase dependent pathway. Such effects were not an artifact of hydrogen peroxide, catechin dimers, or other auto-oxidation products generated from EGCG in cell culture media. Conclusion: Our results imply that EGCG may be useful for prevention of intestinal disorders or bacterial infection in animals/humans.