title: St. John's wort (Hypericum perforatum) counteracts cytokine-induced tryptophan catabolism in vitro.
abstract: St. John's wort (Hypericum perforatum) is an ancient folk remedy that has antiviral and antibacterial properties. Anti-inflammatory effects of the plant have been described and the application of H. perforatum extract as an effective antidepressant is well established. In this study we assayed the effect of H. perforatum extract on cytokine-induced tryptophan degradation in human peripheral blood mononuclear cells. Simultaneously, changes in the production of the immune activation marker neopterin were monitored. Both these biochemical pathways are triggered by interferon-gamma. Our results show that extracts of H. perforatum strongly down-regulate mitogen-mediated tryptophan degradation in a dose-dependent manner. This effect seems to be based on a suppressive activity of H. perforatum on activated immunocompetent cells, resulting in a diminished production of interferon-gamma. In line with this finding, neopterin synthesis was strongly down-regulated by the plant extract. Our results suggest that the reduction of tryptophan degradation by H. perforatum might be important in the action of the plant as an antidepressant.
authors.affiliation: Institute of Medical Chemistry and Biochemistry, Innsbruck Medical University, A-6020 Innsbruck, Austria.
authors.forename: Christiana
authors.initials: C
authors.lastname: Winkler
authors.forename: Barbara
authors.initials: B
authors.lastname: Wirleitner
authors.forename: Katharina
authors.initials: K
authors.lastname: Schroecksnadel
authors.forename: Harald
authors.initials: H
authors.lastname: Schennach
authors.forename: Dietmar
authors.initials: D
authors.lastname: Fuchs
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003208:Concanavalin A / Q000494:pharmacology; D016207:Cytokines / Q000037:antagonists & inhibitors*; D006801:Humans; D020902:Hypericum; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007371:Interferon-gamma / Q000096:biosynthesis; D007737:Kynurenine / Q000378:metabolism; D008934:Mitogens / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D019798:Neopterin / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D016207:Cytokines; D007202:Indicators and Reagents; D008934:Mitogens; D010835:Phytohemagglutinins; D010936:Plant Extracts; D003208:Concanavalin A; D007737:Kynurenine; D019798:Neopterin; D007371:Interferon-gamma; D014364:Tryptophan