Tryptophan consumption and indoleamines production by peritoneal cavity macrophages

Abstract

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.

The Immune-Pineal Axis: A Shuttle between Endocrine and Paracrine Melatonin Sources

“…These enzymes were already activated under basal conditions. A similar picture was observed when studying rodent peritoneal macrophages [13] .…”

“…A wide range of concentrations, which are not attained by pineal-released hormone, exerts these multiple effects. In fact, melatonin is also produced at extrapineal sites, such as immune-competent cells, where it reaches very high local concentrations [12][13][14] . Several studies show that melatonin interferes in several steps of both the pro-and anti-inflammatory phases of the innate immune response; however, the putative effects of inflammatory mediators on the production of melatonin by the pineal gland have been poorly understood [15] .…”

Effects of the blockade of high voltage‐activated calcium channels on in vitro pineal melatonin synthesis

“…AA-NAT activity was measured by radiometric assay (Deguchi and Axelrod, 25 modified by Parfitt et al 26,27 ). Briefly, 100 ml of 0.1 M sodium phosphate buffer, pH 6.8, containing 40 mM tryptamine and [ 3 H]-acetyl coenzyme A (2 mM, final specific activity ¼ 4 mCi/mmol) were added to a microcentrifuge tube containing one gland kept at 4 C. The glands were sonicated and then incubated at 37 C for 20 min.…”

Efeito da estimulação purinérgica sobre a produção de melatonina em macrófagos da linhagem RAW 264.7

“…Em células imunocompetentes, a produção desse hormônio foi verificada em linfócitos humanos (Carrilo-Viccoet al, 2004), macrófagos da cavidade peritoneal (Martins et al, 2004) e células do colostro humano Pontes et al, 2006Pontes et al, , 2007.…”