ABSTRACT
OBJECTIVE: To understand the mechanism by which (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol of green tea, exerts its anti-inflammatory action. METHODS: To check our hypothesis that the anti-inflammatory properties of EGCG could be related to its antifolate action and whether adenosine and its receptors are involved in EGCG action, we investigated the EGCG-induced suppression of NF-kappaB in Caco-2 cell monolayer, which acted as a model of the human intestinal epithelium. RESULTS: We demonstrate that the anti-inflammatory properties of EGCG are associated with its antifolate activity. By using a natural stable folate we were able to reverse the EGCG suppression of TNF-alpha-induced NF-kappaB activation, the phosphorylation and degradation of IkappaBalpha and the phosphorylation of Akt in this human colon carcinoma cell line. These suppressions were mediated by the release of adenosine following disruption of the folate cycle by EGCG. By binding to its specific receptors, adenosine can modulate the Akt and NF-kappaB pathway. Moreover, EGCG produces a significant increase in a specific adenosine receptor, which could explain the suppression of the constitutive activation of NF-kappaB in colon cancer cells. CONCLUSIONS: The data suggest that by modulating NF-kappaB activation, EGCG might not only combat inflammation, but also cancer.
