Inhibition of interleukin-8 secretion by a green tea special extract in the intestinal cell line Caco-2

The intestinal mucosa represents a site of active immunologic activity. Accordingly, intestinal epithelial cells, e.g. Caco-2, secrete a wide array of inflammatory mediators including chemokines, e.g. IL-8, that are able to induce an inflammatory state in intestinal cells or to attract inflammatory immune cells [1, 2]. The chemokine interleukin (IL)-8 is involved in neutrophil attraction and activation and elevated levels have been observed in intestinal inflammation. Natural compounds including green tea have been shown to modulate inflammation in vitro and in vivo [3, 4].

We investigated the influence of the green tea extract EFLA®942 (GTE) on the secretion of IL-8 protein and on the mRNA expression levels of IL-8 in the human gastrointestinal cell line Caco-2 in an inflammatory state. Therefore, extracellular IL-8 concentrations were determined by ELISA and mRNA expression levels of IL-8 were analyzed by quantitative RT-PCR. Characteristic components in 0.01mg/mL GTE are 4.02µM EGCG, 2.27µM EGC, 4.36µM caffeine, and 0.99µM theanine.

GTE did significantly inhibit the IL-1β-induced IL-8 secretion in a dose-dependent manner. At highest concentration the GTE-mediated inhibition was comparable to brefeldin A, a fungal inhibitor of vesicular transport. This was not related to a significant down-regulation of IL-1β-induced IL-8 mRNA expression by GTE. These results suggest that GTE may exert an anti-inflammatory activity in enterocytes, which may be useful for the treatment of intestinal inflammation.

References: 1. Yang, S.K. et al. (1997), Gastroenterology 113: 1214–1223. 2. Eckmann, L. et al. (1993), Gastroenterology 105: 1689–1697. 3. Porath, D. et al. (2005), J. Pharmacol. Exp. Ther. 315: 1172–1180. 4. Varilek, G.W. et al. (2001), J. Nutr. 131: 2034–2039.