Suppressive Effects of Epigallocatechin Gallate Pretreatment on the Expression of Inflammatory Cytokines in RAW264.7 Cells Activated by Lipopolysaccharide

Abstract

Epigallocatechin gallate (EGCG), the main catechin in green tea, has been shown to have some beneficial effects against various human diseases, including diabetes, neurodegenerative disorders, cancer, cardiovascular disease and obesity. To investigate the mechanism of the suppressive effects of EGCG on inflammatory response in macrophages, alterations on the levels of nitric oxide (NO) regulatory factors and inflammatory cytokines were measured in lipopolysaccharide (LPS)-activated RAW264.7 cells. No significant toxicity was detected in RAW264.7 cells treated with 100-400 μM EGCG. Moreover, the optimal concentration of LPS was determined to be 1 μg/ml based on the results of cell viability assay, NO assay and IL-6 enzyme-linked immunsorbent assay (ELISA). Furthermore, NO levels decreased significantly by 68.2% in the 400 μM EGCG/LPS treated group, while the level of inducible nitric oxide synthase (iNOS) expression decreased by 12-17% in the 200 and 400 μM EGCG/LPS treated group. A significant decrease in transcription of pro-inflammatory cytokines (TNFα and IL-1β) and anti-inflammatory cytokine (IL-10) was also detected in the EGCG/LPS treated group. However, IL-6 transcript and protein was maintained at a constant level when in the LPS treated group relative to the EGCG/LPS treated group. Overall, these results suggest that the differential regulation of inflammatory cytokines is an important factor influencing the suppressive effects of EGCG against LPS-activated inflammatory response in RAW264.7 cells.