Intestinal epithelial cells (IECs) have been known to produce galactose-alpha1,4-galactose-beta1,4-glucose ceramide (Gb3) that play an important role in the mucosal immune response. The regulation of Gb3 is important to prevent tissue damage causing shiga like toxin. Epigallocatechin-3-gallate (EGCG) has been studied as anti-carcinogenic, anti-oxidant, anti-angiogenic, and anti-viral activities, and anti-diabetic. However, little is known between the expressions of Gb3 on IECs. The aim of this study was to examine the inhibitory effect of EGCG, a major ingredient of green tea, on Gb3 production via mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-kappa B) in the TNF-alpha stimulated human colon epithelial cells, HT29. To investigate how Gb3 is regulated, ceramide glucosyltransferase (CGT), lactosylceramide synthase (GalT2), and Gb3 synthase (GalT6) were analyzed by RT-PCR in HT 29 cells exposed to TNF-alpha in the presence or absence of EGCG. EGCG dose-dependently manner, inhibits TNF-alpha induced Gb3 expression by blocking in both the MAPKs and NF-kappaB pathways in HT29 cells. TNF-alpha enhanced CGT, GalT2 and GalT6 mRNA levels and EGCG suppressed the level of these enzymes enhanced by TNF-alpha treatment.
Apoptosis/drug effects ; Blotting, Western ; Catechin/*analogs & derivatives/pharmacology ; Cell Nucleus/drug effects/metabolism ; Cell Proliferation/drug effects ; Dose-Response Relationship, Drug ; Epithelial Cells/drug effects/metabolism/pathology ; Flow Cytometry ; Galactosyltransferases/genetics ; Gene Expression Regulation, Enzymologic/drug effects ; Glucosyltransferases/genetics ; HT29 Cells ; Humans ; Intestinal Mucosa/drug effects/metabolism/pathology ; Mitogen-Activated Protein Kinases/antagonists & inhibitors/*metabolism ; NF-kappa B/antagonists & inhibitors/*metabolism ; Phosphorylation/drug effects ; Protein Transport/drug effects ; RNA, Messenger/genetics/metabolism ; Research Support, Non-U.S. Gov't ; Reverse Transcriptase Polymerase Chain Reaction ; Trihexosylceramides/*biosynthesis ; Tumor Necrosis Factor-alpha/*pharmacology