title: T-cell receptor/CD28-mediated activation of human T lymphocytes induces expression of functional mu-opioid receptors.
abstract: Opiates function as immunomodulators, partly by their effects on T cells. Opioids act via mu-, delta-, and kappa-opioid receptors, among which the mu-type is of particular interest, because morphine-like opioids preferentially bind to it. Here we report that mu-opioid receptor mRNA was induced after CD3/28-mediated activation of primary human T lymphocytes and Jurkat T cells, neither of which expresses the gene constitutively. Moreover, a reporter gene construct containing 2624 base pairs of the mu-opioid receptor promoter was transactivated by CD3/28 stimulation. Transcriptional induction of the mu-opioid receptor gene was mediated by activator protein-1 (AP-1), nuclear factor-kappaB, and nuclear factor of activated T cells (NFAT). NFAT was found to bind to three sequences of the mu-opioid receptor promoter, located at nucleotides -1064, -785, and -486. Although the -486 element is in close proximity to a putative AP-1 site, there was no evidence for a combined AP-1/NFAT site. Furthermore, we demonstrated that the induction of interleukin-2 mRNA and protein in activated T cells was inhibited by morphine in cells, in which mu-opioid receptors had been induced by CD3/28 monoclonal antibodies (mAbs), and that this effect was blocked by the mu-opioid receptor-specific antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2). CD3/28 mAb-induced interleukin-2 transcription was also inhibited by the opioids fentanyl and loperamide. This indicates that the induced mu-opioid receptor mRNA is translated into functional receptor protein. Furthermore, a mu-opioid receptor-enhanced green fluorescent protein-fusion protein was localized in membranes of Jurkat cells and internalized in response to [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin but not morphine. In conclusion, these data emphasize the role of opioids in the modulation of T lymphocyte signaling.
authors.affiliation: Department of Pharmacology and Toxicology, University of Magdeburg, Magdeburg, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Börner
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kraus
authors.forename: Andrea
authors.initials: A
authors.lastname: Bedini
authors.forename: Burkhart
authors.initials: B
authors.lastname: Schraven
authors.forename: Volker
authors.initials: V
authors.lastname: Höllt
mesh_terms: D018106:CD28 Antigens / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*
chemical_list: D018106:CD28 Antigens; D011948:Receptors, Antigen, T-Cell; D017450:Receptors, Opioid, mu