The Structural Characteristics of Green Tea Polyphenols on Lipopolysaccharide-Stimulated RAW Cells
The inflammatory response of macrophages is involved in pathogenesis of lifestyle-related diseases. Green tea consumption reduces the incidence of lifestyle-related diseases. This study investigated the anti-inflammatory effect of polyphenols of green tea including gallic acid, (+)-catechin, (-)-catechin, (-)-epicatechin and (-) epigallocatechin-3-gallate (EGCG) in vitro. The macrophage cell line RAW264 cells were pre-treated with different concentrations of polyphenols (gallic acid, (+)-catechin, (-)-catechin, (-)-epicatechin and EGCG) for 4 h, and were stimulated with LPS for 45 min, 2 h and 24 h. After 24 h LPS challenge, cell lysates and supernatants were harvested. The protein concentration of whole cell lysate was used for determination of cell growth/viability by the BCA assay. The production of TNF-? and IL-6 was measured by ELISA. The total expression and phosphorylation of p38 MAPK was detected by Western blotting. Our results showed that the total protein content of cells was decreased after LPS challenge, while this effect was attenuated when cells were pre-treated with 10 ?M gallic acid and EGCG. Pre-treatment with 1 and 10 ?M EGCG and (-)-catechin significantly decreased the production of TNF-? and IL-6. Furthermore, pre-treatment with 10 ?M gallic acid significantly reduced the production of TNF-? and IL-6. Pre-treatment with 10 ?M (+)-catechin, (-)-catechin, (-) epicatechin, and EGCG enhanced the expression and phosphorylation of p38 MAPK after stimulation with LPS for 45 min and 2 h. By contrast, pre-treatment with gallic acid did not affect the production and phosphorylation of p38 MAPK. These results demonstrated that polyphenols with pyrogallol-type structures in green tea attenuate the activation of macrophages.