Green Tea Extract Induces Interleukin-8 (IL-8) MRNA and Protein Expression but Specifically Inhibits IL-8 Secretion in Caco-2 Cells

The chemokine interleukin (IL)-8 is a cytokine involved in neutrophil attraction and activation and elevated levels have been observed in intestinal inflammation. Anti-inflammatory activities have been attributed to green tea or its major constituent (-)-epigallocatechin gallate (EGCG). In this study, we investigated the effects of a defined green tea extract (GTE) or EGCG on basal or IL-1beta-induced IL-8 expression and secretion in the human gastrointestinal epithelial cell line Caco-2. mRNA expression levels were determined by quantitative RT-PCR. GTE significantly induced IL-8 mRNA expression, which was not mediated indirectly via an induction of IL-1beta mRNA expression. EGCG only exerted a weak although significant induction of IL-8 mRNA expression at the highest concentration. Intracellular and extracellular protein levels were analyzed by an enzyme-linked immunosorbent assay. GTE and EGCG significantly decreased secreted IL-8 concentrations. Determination of intracellular and secreted IL-8 concentrations after 24 h, 48 h, and 72 h of incubation suggested that GTE specifically inhibited IL-8 secretion while inducing DE NOVO synthesis of IL-8. The IL-1beta-mediated increase of IL-8 secretion was significantly inhibited by GTE in a dose-dependent manner. At the highest concentration, GTE inhibited IL-1beta-induced IL-8 secretion to a similar extent as found for brefeldin A, an inhibitor of vesicular transport. These results suggest that GTE may exert an anti-inflammatory activity in enterocytes, which may be useful for the treatment of intestinal inflammation.