Accuri C6 Flow Cytometer System
Originally published online as doi:10.1189/jlb.1203614 on February 24, 2004

Published online before print February 24, 2004
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(Journal of Leukocyte Biology. 2004;75:1116-1121.)
© 2004 by Society for Leukocyte Biology

Tryptophan consumption and indoleamines production by peritoneal cavity macrophages

E. Martins, Jr.*, A. C. F. Ferreira*, A. L. Skorupa{dagger}, S. C. Afeche{ddagger}, J. Cipolla-Neto{dagger} and L. F. B. P. Costa Rosa*,1

Departments of
* Histology and Embryology and
{dagger} Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil; and
{ddagger} Butantan Institute, São Paulo, Brazil

1Correspondence: Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas I, Universidade de São Paulo, Av. Lineu Prestes, 1524, sala 302, 05508-900, Butantan, São Paulo, Brasil. E-mail: ggrosa{at}icb.usp.br

Melatonin has been shown to regulate several immune functions, and some authors showed that leukocytes are also able to produce the indolamine. In fact, it seems to take part in some immunoregulatory axis, including that related to interferon (IFN) production. So, we evaluated the rate of tryptophan consumption and melatonin and serotonin production in peritoneal cavity-isolated macrophages and the effect of IFN-{alpha} and -{gamma}, lipopolysaccharide (LPS), and phorbol myristate acetate (PMA) on such parameters. Our results indicate that macrophages obtained from the peritoneal cavity of normal rats when incubated with tryptophan show an increase in arylalkylamine N-acetyltransferase activity that corresponds to an increased melatonin production, as determined in the incubation medium. This process is regulated by IFN-{alpha} and -{gamma}, PMA, LPS, and the serum from tumor-bearing rats, opening the possibility of speculation about different immunoregulatory loops acting through the balance of melatonin/serotonin production by such cells.

Key Words: melatonin production • serotonin • interferon