EGCG Inhibits Inflammatory Effects of Nicotine in Gingival Epithelium

Shango, Jennifer, Awara Kokoiy, and Michelle Wheater

Gingival tissues are exposed to nicotine as a result of tobacco use. It is known that nicotine can upregulate secretion of cytokines including IL-6 and IL-8 in gingival epithelial cells and fibroblasts. Objective: To determine if epigallocatechin gallate (EGCG), a major catechin component of green tea, will suppress nicotine-induced cytokine expression in cultured gingival epithelial cells. Methods: Primary human gingival epithelial cells were purchased from Zen-Bio (Research Triangle Park, NC). Confluent cells were treated for 24 hours with 0.1 mM nicotine with or without 10 mg/ml LPS or 10 mg/ml TNF-a, in the presence or absence of 10 mg/ml EGCG. After 24 hours of treatment, culture medium samples were assayed for IL-6, IL-8, or IL-10 concentrations using ELISA. Results were standardized to total cell number using crystal violet blue staining. In separate experiments cells were treated for 24 hours as described and assayed for cytotoxicity using a colorimetric LDH protocol. Statistical analysis was completed using ANOVA with probability set at p < 0.05. Results: EGCG significantly inhibited cytotoxicity induced by nicotine, nicotine/LPS, and nicotine/LPS/TNF-a (p < 0.05 for all comparisons). EGCG significantly suppressed IL-8 secretion, but significantly increased IL-6 and IL-10 secretion, in gingival epithelial cells treated with combinations of nicotine, LPS, and TNF-a (p < 0.05 for all comparisons). Conclusions: In tobacco users, a combination of nicotine and bacterial infection (LPS) or inflammatory reactions (TNF-a) result in increased cytokine production. This in turn may contribute to increased breakdown of periodontal tissues. This study suggests that tea catechins such as EGCG function as effective natural anti-inflammatory compounds in the oral cavity, functioning to suppress pro-inflammatory cytokines and/or TNF-a. This information could be used to support the use of tea as a natural anti-inflammatory agent to potentially suppress the progression of gingivitis and peridontitis in tobacco users.