Blocking of melatonin synthesis and MT1 receptor impairs the activation of Jurkat T cells

Abstract

Melatonin has been proposed as regulating the immune system by affecting cytokine production in immunocompetent cells, enhancing the production of several T helper (Th)1 cytokines. To further investigate the melatonin's role in IL-2/IL-2R system, we established an inducible T-REx expression system in Jurkat cells in which the protein levels of HIOMT enzyme or MT(1) receptor were significantly down-regulated upon tetracycline incubation. We found that T-REx Jurkat cells with lower levels of HIOMT activity, and consequently lower content of endogenous melatonin, showed IL-2 production decrease after activation with lectin. Likewise, tetracycline-inducible stable cell line expressing MT(1) antisense produced decreased amounts of IL-2 (mRNA and protein levels) after stimulation. Moreover, in T-Rex-MT(1) cells incubated with tetracycline, a sub-optimal PHA dose failed to induce the early activation marker CD25 on the cell surface. The results shown here support the relevance of endogenous melatonin and its signaling in T cell activation.

Melatonin: Buffering the Immune System

“…To further investigate the role of immune-derived melatonin in the IL-2/IL-2R system, HIOMT and MT 1 knock-down Jurkat cells were used. Both low levels of HIOMT activity and MT 1 expression diminished IL-2 production after phytohaemagglutinin (PHA) activation [52]. Colostrum immunocompetent cells produced a transient surge of melatonin after in vitro stimulation by enteropathogenic Escherichia coli or zymosan, suggesting the involvement of local melatonin in modulating the phagocytic capacity of the cells [26].…”

Dietary Sources and Bioactivities of Melatonin

“…With MT1 and MT2 receptors, melatonin was found to inhibit the production of forskolin-stimulated cyclic AMP (cAMP), cyclic GMP (cGMP) and diacylglycerol (DAG), leading to the improved immunity [183,184]. Besides, the specific nuclear melatonin receptors have been identified in Jurkat cells [185], lymphocytes [186], thymus [175] and spleen [187], which belong to the RZR/ROR subfamily of nuclear receptors.…”

Melatonin signaling in T cells: Functions and applications

“…In vivo evidence from a study using broiler chickens showed that proliferation of T cells in their thymus is positively correlated with concentrations of melatonin in the plasma, while pinealectomy, which reduces melatonin levels in the blood, or the use of antagonists to MT1 decreases the proliferation of T cells . Direct evidence that melatonin activates T cells was provided by a study which demonstrated that inhibiting HIOMT in PHA‐activated Jurkat cells reduces production of melatonin and IL‐2 . Similarly, exogenous melatonin promotes the proliferative activity of T cells, while antagonists of MT1 limit their proliferation .…”

“…The administration of luzindole (a high‐affinity antagonist for MT1/MT2) to mice inhibited the ability of melatonin to stimulate proliferation of splenic lymphocyte in response to the T‐cell mitogen concanavalin A . Furthermore, inhibition of MT1 decreased the production of IL‐2 by PHA‐activated Jurkat cells and their expression of the early activation marker CD25 . Both luzindole and CGP 55644 significantly inhibit IL‐2 production by Jurkat cells .…”