title: Lack of calmodulin antagonism of melatonin in T-lymphocyte activation.
abstract: Despite various reported effects of the pineal hormone melatonin on the immune system, its mechanism of action on immune cells is still unknown. Since melatonin has been suggested as a physiological antagonist to calmodulin in certain cell types, we investigated effects of melatonin on calmodulin-dependent IL-2 production and proliferation of activated T-lymphocytes. It was found, however, that, in contrast to the calmodulin antagonists trifluoperazine and W7, melatonin neither inhibited the IL-2 production of activated lymphoblastoid Jurkat T-cells nor decreased the mitogen response of peripheral blood mononuclear leukocytes. Preincubation of Jurkat cells with melatonin did not influence trifluoperazine effects on IL-2 production indicating that melatonin does not bind to the same sites of calmodulin as trifluoperazine, as has been postulated. In conclusion, these results did not give any evidence for a calmodulin antagonism of melatonin in T-lymphocyte activation. Thus, melatonin as a calmodulin antagonist appears not to be a universal phenomenon.
authors.affiliation: Institute of General & Experimental Pathology, University of Graz, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Wölfler
authors.forename: K
authors.initials: K
authors.lastname: Schauenstein
authors.forename: P M
authors.initials: PM
authors.lastname: Liebmann
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D019169:Jurkat Cells; D007700:Kinetics; D008213:Lymphocyte Activation / Q000187:drug effects*; D008550:Melatonin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects*; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D018492:Dopamine Antagonists; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D007476:Ionophores; D013449:Sulfonamides; D014268:Trifluoperazine; D015759:Ionomycin; C017967:W 7; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D008550:Melatonin