Signaling through delta opioid receptors on murine splenic T cells and stably transfected Jurkat cells.
beta-Endorphin (beta-EP) and delta opioid receptor (DOR) agonists affect immune functions such as lymphocyte chemotaxis, proliferation, and cytokine production. Recent studies indicate that both neuronal DOR and novel G-protein-coupled receptors with high affinity for beta-EP and DOR agonists are expressed by mononuclear cells. In addition, proenkephalin A mRNA and enkephalin-related peptides are expressed by lymphocytes. These investigations were conducted to identify signal transduction pathways that mediate the effects of beta-EP and DOR agonists on T cells. Calcium mobilization was studied because it is central to T-cell activation initiated by antigen presentation to the T-cell receptor (TCR). Using the calcium-sensitive dye Fluo-3 and flow cytofluorometry to determine the concentration of free intracellular calcium, physiological concentrations of beta-EP were shown to enhance concanvalin. A (con A)-stimulated calcium mobilization by murine splenic T cells (p < 0.01). The DOR antagonist, naltrindole, inhibited this, whereas CTAP, a selective mu OR antagonist, was ineffective. In addition, N-Ac-beta-EP and the mu OR agonist DAMGO, failed to mimic the effects of beta-EP. Although it was less potent than beta-EP, DADLE, a DOR agonist, also enhanced Con-A-induced calcium mobilization (p < 0.01). A DOR-transfected human T-cell line (DOR-Jul.1) was developed to study signal transduction. Both DADLE and the selective DOR agonist, deltorphin, rapidly increased intracellular free calcium concentrations; ED50s were 10(-9) M. Pertussis toxin prevented the response, and EGTA significantly reduced it. In addition, DADLE inhibited forskolin-stimulated cAMP production (ED50: 10(-11) M). These findings with normal splenic T cells and DOR-transfected T-cell line indicate that beta-EP and DOR agonists affect calcium mobilization. This is likely to modulate downstream pathways that regulate T-cell activation and function.
Sharp
B M
BM
Endocrine-Neuroscience Laboratory, Minneapolis Medical Research Foundation, Minnesota 55404, USA. Sharp002@maroon.tc.umn.edu
McKean
D J
DJ
McAllen
K
K
Shahabi
N A
NA
D000818:Animals; D006801:Humans; D019169:Jurkat Cells / Q000502:physiology*; D051379:Mice; D017465:Receptors, Opioid, delta / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013154:Spleen / Q000166:cytology / Q000502:physiology*; D013601:T-Lymphocytes / Q000502:physiology*; D014162:Transfection
D017465:Receptors, Opioid, delta