Green tea polyphenols block endotoxin-induced tumor necrosis factor-production and lethality in a murine model.
Green tea polyphenols are potent antioxidants. They have both anti-cancer and anti-inflammatory effects. However, their mechanisms of actions remain unclear. In inflammation, tumor necrosis factor-alpha(TNFalpha) plays a pivotal role. NF-KB, an oxidative stress -sensitive nuclear transcription factor, controls the expression of many genes including the TNFalpha gene. We postulated that green tea polyphenols regulate TNFalpha gene expression by modulating NF-KB activation through their antioxidant properties. In the macrophage cell line, RAW264.7, (-)epigallocatechin gallate (EGCG), the major green tea polyphenol, decreased lipopolysaccharide (LPS)-induced TNFalpha production in a dose-dependent fashion (50% inhibition at 100 mmol/L). EGCG also inhibited LPS-induced TNFalpha mRNA expression and nuclear NF-KB-binding activity in RAW264.7 cells (30-40% inhibition at 100 mmol/L). Similarly, EGCG inhibited LPS-induced TNFalpha production in elicited mouse peritoneal macrophages. In male BALB/c mice, green tea polyphenols (given by oral gavage 2 h prior to an i.p. injection of 40 mg LPS/kg body wt) decreased LPS-induced TNFalpha production in serum in a dose-responsive fashion. At a dose of 0.5 g green tea polyphenols/kg body wt, serum TNFalpha was reduced by 80% of control. Moreover, 0.5 g green tea polyphenols/kg body wt completely inhibited LPS-induced lethality in male BALB/c mice. We conclude that the anti-inflammatory mechanism of green tea polyphenols is mediated at least in part through down-regulation of TNFalpha gene expression by blocking NF-KB activation. These findings suggest that green tea polyphenols may be effective therapy for a variety of inflammatory processes.