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1: Eur J Pharmacol. 1999 Feb 19;367(2-3):379-88.
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Theaflavin-3,3'-digallate from black tea blocks the nitric oxide synthase by down-regulating the activation of NF-kappaB in macrophages.

Lin YL, Tsai SH, Lin-Shiau SY, Ho CT, Lin JK.

Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei.

Nitric oxide (NO) plays an important role in inflammation and also in multiple stages of carcinogenesis. We investigated the effects of various tea polyphenols, including theaflavin, a mixture of theaflavin-3-gallate and theaflavin-3'-gallate, theaflavin-3,3'-digallate, thearubigin, and (-)-epigallocatechin-3-gallate on the induction of NO synthase in lipopolysaccharide-activated murine macrophages, RAW 264.7 cells. Theaflavin-3,3'-digallate was found to be stronger than (-)-epigallocatechin-3-gallate in inhibiting NO generation and inducible NO synthase protein in activated macrophages, while theaflavin, a mixture of theaflavin-3-gallate and theaflavin-3'-gallate and thearubigin were less effective. Inhibition of NO production was observed when cells were cotreated with theaflavin-3,3'-digallate and lipopolysaccharide. Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analyses demonstrated that significantly reduced 130-kDa protein and mRNA levels of inducible NO synthase were expressed in lipopolysacchride-activated macrophages with theaflavin-3,3'-digallate, compared to those without theaflavin-3,3'-digallate. Electrophoretic mobility shift assay (EMSA) indicated that theaflavin-3,3'-digallate blocked the activation of nuclear factor kappaB (NF-kappaB), a transcription factor necessary for inducible NO synthase induction. Theaflavin-3,3'-digallate also blocked phosphorylation of IkappaB from cytosolic fraction and reduced lipopolysacchride-induced nuclear accumulation of transcription factor NF-kappaB p65 and p50 subunits. These results suggest that theaflavin-3,3'-digallate decreases the protein levels of inducible NO synthase by reducing the expression of inducible NO synthase mRNA, and the reduction could be via preventing the activation of NF-kappaB, thereby inhibiting the induction of inducible NO synthase transcription. It was also demonstrated that the gallic acid moiety of theaflavin-3,3'-digallate is essential for their potent anti-inflammation activity.

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PMID: 10079014 [PubMed - indexed for MEDLINE]