Serotonin acts as a radical scavenger and is oxidized to a dimer during the respiratory burst of human mononuclear and polymorphonuclear phagocytes.
Isolated human mononuclear and polymorphonuclear phagocytes were stimulated in the presence and absence of serotonin (5-HT), the major secretory product of activated platelets, and the release of reactive oxygen metabolites during the respiratory burst was assessed by luminol-enhanced chemiluminescence. In the presence of 5-HT, a dose-dependent suppression of the chemiluminescence signal occurred, irrespective of the stimulus used to elicit the respiratory burst. A similar suppression of luminol-enhanced chemiluminescence was also seen in a radical generating cell free system. 5-HT was found to be oxidized by the reactive oxygen species released by stimulated phagocytes. This oxidation is prevented in the presence of other antioxidants. The major 5-HT oxidation product was isolated by gel chromatography and identified by mass-spectrometry as a 5-HT dimer, probably 5,5'-dihydroxy-4,4'-bitryptamine. It is concluded that the 5-HT released from activated thrombocytes at sites of inflammation and endothelial cell damage acts as a true scavenger of reactive oxygen species generated during the respiratory burst of stimulated phagocytes and may thus modulate various aspects of cell-mediated defence reactions.
Schuff-Werner
P
P
University Clinics, Department of Internal Medicine, Goettingen, Germany.
Splettstösser
W
W
Schmidt
F
F
Huether
G
G
D016166:Free Radical Scavengers / Q000097:blood / Q000494:pharmacology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008163:Luminescent Measurements; D008165:Luminol; D013058:Mass Spectrometry; D009000:Monocytes / Q000187:drug effects / Q000502:physiology*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D010084:Oxidation-Reduction; D016897:Respiratory Burst; D012701:Serotonin / Q000097:blood* / Q000494:pharmacology*
D016166:Free Radical Scavengers; D007202:Indicators and Reagents; D012701:Serotonin; D008165:Luminol; D006861:Hydrogen Peroxide