EPIGALLOCATECHIN GALLATE DIFFERENTIALLY MODULATES INTERLEUKIN SECRETION IN NICOTINE AND TNFΑ-TREATED HUMAN GINGIVAL EPITHELIAL CELLS

Objectives: To determine the effects of Epigallocatechin Gallate (EGCG), a major catechin component of green tea, on cytokine expression in a human oral epithelial cell culture model of nicotine use. Methods: Confluent gingival epithelial cells in wells of a 24-well plate were subjected to one of six treatments. For controls cells received 1) no treatment or 2) were treated with 10 μg /ml EGCG for 1 hour and cultured for 24 hours prior to analysis. A set of cells were pre-treated for 1 hour with 10 μg /ml EGCG and 3) treated for 24 hours with 0.1 mM nicotine prior to challenge with 10 ng/ml TNFα for 1 hour, or 4) not treated with nicotine but challenged with TNFα for 1 hour prior to analysis. A setof cells were not pre-treated with EGCG and 5) treated for 24 hours with 0.1 mM nicotine prior to challenge with 10 ng/ml TNFα for 1 hour, or 6) not treated with nicotine but challenged with TNFα for 1 hour prior to analysis. Culture medium samples were assayed for levels of secreted interleukins IL-1α, IL-1β, IL-4, IL-6, IL-8, and IL-10 by ELISA. Statistical analysis was completed for individual interleukins using ANOVA and Tukey post-test with probability set at p ? 0.05. Results: The levels of IL-4 for all treatments were below the detection limit of the ELISA. EGCG significantly suppressed the secretion of IL-1α, IL-1β, IL-6 and IL-8 in nicotine and TNFα-treated cells (p < 0.01). In contrast, the presence of EGCG resulted in a significant increase in the secretion of IL-10 in nicotine and TNFα-treated cells (p < 0.001). Conclusion: This study suggests that tea catechins such as EGCG may function to suppress pro-inflammatory cytokines and to increase the secretion of the anti-inflammatory cytokine IL-10 in cells challenged by nicotine and TNFα.