Coffee extracts suppress tryptophan breakdown in mitogen-stimulated peripheral blood mononuclear cells.
OBJECTIVE
Coffee consumption is considered to exert an influence on mood, the immune system, cardiovascular disease, and cancer development, but the mechanisms of action of coffee and its compounds are only partly known and understood.


METHODS
Immunomodulatory effects of filtered extracts of coffee and decaffeinated coffee as well as coffee compounds were investigated in human peripheral blood mononuclear cells (PBMCs) stimulated with mitogen phytohemagglutinin (PHA). The activation of PBMCs was monitored by the breakdown of tryptophan to kynurenine via enzyme indoleamine 2,3-dioxygenase (IDO) and the production of the immune activation marker neopterin by GTP-cyclohydrolase I (GCH1). Both of these biochemical pathways are induced during cellular immune activation in response to the Th1-type cytokine interferon-γ (IFN-γ).


RESULTS
Filtered extracts of coffee and decaffeinated coffee both suppressed tryptophan breakdown and neopterin formation in mitogen-stimulated PBMCs efficiently and in a dose-dependent manner. Of 4 coffee compounds tested individually, only gallic acid and less strong also caffeic acid had a consistent suppressive influence but also affected cell viability, whereas pure caffeine and chlorogenic acid exerted no relevant effect in the PBMC assay.


CONCLUSIONS
The parallel influence of extracts on tryptophan breakdown and neopterin production shows an anti-inflammatory and immunosuppressive property of coffee extracts and some of its compounds. When extrapolating the in vitro results to in vivo, IFN-γ-mediated breakdown of tryptophan could be counteracted by the consumption of coffee or decaffeinated coffee. This may increase tryptophan availability for the biosynthesis of the neurotransmitter 5-hydroxytryptamine (serotonin) and thereby improve mood and quality of life.
a Division of Biological Chemistry , Biocenter , Medical University of Innsbruck , Innsbruck , AUSTRIA.
Johanna M
JM
Gostner
Sebastian
S
Schroecksnadel
Marcel
M
Jenny
Angela
A
Klein
Florian
F
Ueberall
Harald
H
Schennach
Dietmar
D
Fuchs
D000893:Anti-Inflammatory Agents; D002109:Caffeic Acids / Q000494:pharmacology; D002478:Cells, Cultured; D002726:Chlorogenic Acid / Q000494:pharmacology; D040503:Coffea / Q000737:chemistry*; D005707:Gallic Acid / Q000494:pharmacology; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology; D007166:Immunosuppressive Agents; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D008934:Mitogens / Q000494:pharmacology*; D019798:Neopterin / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D012701:Serotonin / Q000096:biosynthesis; D014364:Tryptophan / Q000378:metabolism*
D000893:Anti-Inflammatory Agents; D002109:Caffeic Acids; D007155:Immunologic Factors; D007166:Immunosuppressive Agents; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D008934:Mitogens; D010835:Phytohemagglutinins; D010936:Plant Extracts; D002726:Chlorogenic Acid; D012701:Serotonin; D005707:Gallic Acid; D019798:Neopterin; D007371:Interferon-gamma; D014364:Tryptophan; C040048:caffeic acid
3-dioxygenase; Abbreviations: CTB = cell titer blue; FCS = fetal calf serum; GCH1 = GTP-cyclohydrolase I; IDO = indoleamine 2,3-dioxygenase; IFN = interferon; Kyn = kynurenine; Kyn/Trp = kynurenine to tryptophan ratio; ORAC = oxygen radical absorbance capacity assay; PBMC = peripheral blood mononuclear cells; PHA = phytohaemagglutinin; TE = trolox equivalent; Trp = tryptophan; coffee; indoleamine 2; neopterin; peripheral blood mononuclear cells; tryptophan