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Interferon‐gamma independent oxidation of melatonin by macrophages
Author(s) -
Rodrigues Maria R.,
Rodriguez Dunia,
Henrique Catalani Luiz,
Russo Momtchilo,
Campa Ana
Publication year - 2003
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1034/j.1600-079x.2003.02944.x
Subject(s) - melatonin , myeloperoxidase , interferon gamma , kynurenine , indoleamine 2,3 dioxygenase , concanavalin a , biology , interferon , chemistry , biochemistry , immune system , immunology , inflammation , endocrinology , tryptophan , in vitro , amino acid
Mononuclear phagocytes appear to synthesize kynurenine‐like products from the oxidation of biologically active indole compounds including melatonin, catalyzed by interferon (IFN)‐ γ ‐inducible enzyme indoleamine 2,3‐dioxygenase (IDO). Concanavalin A (Con A) is a plant lectin that induces interferon‐gamma (IFN‐ γ ) production by T cells. In this study we investigated whether Con A‐primed peritoneal macrophages are able to oxidize melatonin to N 1 ‐acetyl‐ N 2 ‐formyl‐5‐methoxykynuramine (AFMK). The AFMK production was accompanied by chemiluminescence. It was found that Con A‐primed but not resident macrophages produce AFMK. Surprisingly, Con A‐primed macrophages from IFN‐ γ ‐deficient mice were as effective as macrophages from IFN‐ γ ‐sufficient mice in oxidizing melatonin. Moreover, addition of an inhibitor of IDO (1‐methyltryptophan) did not affect melatonin oxidation. Con A‐primed but not resident macrophages have a significant content of myeloperoxidase (MPO) and inhibition of MPO by azide completely blocked chemiluminescence and AFMK production. Thus, our findings provide evidence that melatonin oxidation by macrophages may occur through a mechanism dependent of MPO and independent of IFN‐ γ and IDO activity.