T-Cell Receptor/CD28-Mediated Activation of Human T Lymphocytes Induces Expression of Functional μ-Opioid Receptors

Abstract

Opiates function as immunomodulators, partly by their effects on T cells. Opioids act via -, ␦-, and -opioid receptors, among which the -type is of particular interest, because morphine-like opioids preferentially bind to it. Here we report that -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 -opioid receptor promoter was transactivated by CD3/28 stimulation. Transcriptional induction of the -opioid receptor gene was mediated by activator protein-1 (AP-1), nuclear factor-B, and nuclear factor of activated T cells (NFAT). NFAT was found to bind to three sequences of the -opioid receptor promoter, located at nucleotides Ϫ1064, Ϫ785, and Ϫ486. Although the Ϫ486 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 -opioid receptors had been induced by CD3/28 monoclonal antibodies (mAbs), and that this effect was blocked by the -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 -opioid receptor mRNA is translated into functional receptor protein. Furthermore, a -opioid receptor-enhanced green fluorescent protein-fusion protein was localized in membranes of Jurkat cells and internalized in response to [D-Ala 2 ,NMe-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.

Regulation of Opioid and Cannabinoid Receptor Genes in Human Neuroblastoma and T Cells by the Epigenetic Modifiers Trichostatin A and 5-Aza-2’-Deoxycytidine

“…Probably, the chromosomes of these genes are already maximally accessible for the transcriptional machinery. An induction of CB1 and -opioid receptors in Jurkat cells was also observed earlier by our group in response to various cytokines and to antigens ( -opioid receptors: interleukin-4 [7][8][9][10][11] , tumor necrosis factor [10,12] and antigens [13] ; CB1: interleukin-4 [21,22] , tumor necrosis factor [unpubl. observation] and antigens [23] ).…”

“…In immune cells, -opioid receptors are typically not expressed constitutively, but their expression is induced by several stimuli, e.g. cytokines like interleukin-4 [7][8][9][10][11] and tumor necrosis factor [10,12] and antigens [13] .…”

Mechanisms of Opioid-Mediated Inhibition of Human T Cell Receptor Signaling

“…In addition, expression of opioid receptors is also induced indirectly by drugs and stimuli, which increase the expression of TNF and IL-4, like cannabinoids (23). As demonstrated recently by our group, also anti-CD3/anti-CD28-mediated activation of human T cells induces the expression of functional opioid receptors (24). Studies in mice have shown that morphine is only effective on mitogen-activated T cells, which may be explained by an induction of opioid receptors after T cell activation (4,5,25).…”

Inducible Expression of Functional Mu Opioid Receptors in Murine Dendritic Cells

“…Other factors, such as human immunodeficiency virus gp120, can transactivate MOR gene expression (Chang et al 2007). A recent study demonstrated that MOR mRNA was induced after CD3/28-mediated activation of primary human T lymphocytes, and transcriptional induction was proceeded by activator protein-1 (AP-1), nuclear factor-κB (NF-κB), and nuclear factor of activated T cells (Borner et al 2008). Most of the knowledge about regulation of MOR expression was established from studies on T lymphocytes.…”