Inhibition of inducible nitric oxide synthase gene expression and enzyme activity by epigallocatechin gallate, a natural product from green tea

Marion Man Ying Chan, Dunne Fong, Chi Tang Ho, Hsing I. Huang

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224 Scopus citations

Abstract

Chronic inflammation has been implicated as the underlying factor in the pathogenesis of many disorders. In the past decade, inflammation related endogenous production of reactive nitrogen species, similar to oxygen free radicals, has also been suggested as a risk factor for cancer, in addition to the well-studied exogenous nitroso compounds. Epidemiological, in vitro, and animal model studies have implicated green tea to be protective against nitroso compound-induced and inflammation-related cancer. Therefore, we investigated the effect of epigallocatechin-3 gallate (EGCG), one of the known biologically active catechins contained in green tea, on the production of nitric oxide (NO.). We have shown previously that EGCG reduces NO. production as measured by nitrite accumulation in the culture medium. Expanding on this finding, in this report we show that EGCG may do so by two mechanisms: reduction of inducible nitric oxide synthase (iNOS) gene expression and inhibition of enzyme activity. Addition of 1-10 μM EGCG to lipopolysaccharide- and interferon-γ-activated mouse peritoneal cells reduced iNOS mRNA expression concentration dependently, to 82-14%, as measured by relative reverse transcription-polymerase chain reaction. Addition of 50-750 μM EGCG, in a concentration-dependent manner, inhibited the enzyme activity of iNOS, to 85-14%, and neuronal nitric oxide synthase (nNOS), to 93-56%, as measured by citrulline formation. EGCG competitively inhibited binding of arginine and tetrahydrobiopterin, and the gallate structure is important for this action.

Original languageEnglish (US)
Pages (from-to)1281-1286
Number of pages6
JournalBiochemical Pharmacology
Volume54
Issue number12
DOIs
StatePublished - Dec 15 1997

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Pharmacology

Keywords

  • Carcinogenesis
  • Catechin
  • Competitive inhibitor
  • Dietary phytochemical
  • Enzyme activity
  • Gene expression
  • Green tea
  • Inflammation
  • Nitric oxide synthase

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