Tea pigments are oxidized products of polyphenols derived from tea leaves (Camellia sinensis). Theaflavins are constituents of tea pigments with antioxidant, antineoplastic and antiinflammatory properties similar to their parent compounds. The biological properties of polyphenols and theaflavins have been linked to their capacity to inhibit the activation of nuclear factor-kappaB (NF-kappaB), a transcription factor, which is critically involved in the molecular regulation of a number of proinflammatory cytokines. The current study examines the requirement for NF-kappaB in the immunosuppressive effects mediated by tea antioxidants. Specifically, we tested the hypothesis that cytokines produced by type 1 (T(H1)) CD4(+) T cells which require NF-kappaB for gene expression, such as interleukin-2 (IL-2) and interferon gamma (IFN gamma), are selectively inhibited by tea pigments. We found that tea pigments potently suppress IL-2 secretion, IL-2 gene expression and the activation of NF-kappaB in murine spleens enriched for CD4(+) T cells, as expected. Consistent with our hypothesis, tea pigments also inhibited the induction of IFNgamma mRNA. However, the expression of the T(H2) cytokines IL-4 and IL-5, which lack functional NF-kappaB sites within their promoters was unexpectedly suppressed by tea pigments, as well. The results indicate that NF-kappaB may be only one of multiple transcription factors inhibited by tea pigments.
Copyright 2002 John Wiley and Sons, Ltd.