Beta-endorphin enhances Concanavalin-A-stimulated calcium mobilization by murine splenic T cells.
Intracellular calcium mobilization is an important early event involved in T cell activation. The endogenous opioid peptide beta-endorphin is known to modulate immune functions that depend on T cell activation, therefore its effect on intracellular calcium mobilization was investigated. The intracellular calcium concentration ([Ca2+]i) of T cell-enriched splenocytes was measured by flow cytofluorometric analysis using the calcium-sensitive dye, Fluo-3. By gating on the T cell marker, Thy-1, a 95%-pure population of T cells was identified for study. Cells preincubated with beta-endorphin showed significantly enhanced [Ca2+]i responses to the mitogen, Concanavalin A (Con A). This was detectable with concentrations of beta-endorphin as low as 10(-13) M; maximal enhancement required 10(-10) to 10(-9) M doses. The efficacy of beta-endorphin was dependent on the duration of pretreatment. beta-Endorphin amplified the Con A-induced increase in [Ca2+]i by reducing the lag time for the response to Con A and by increasing the mean [Ca2+]i of the cells. N-Ac-beta-endorphin, which shows minimal potency at neuronal opiate receptors, was unable to substitute for beta-endorphin. Naltrindole, a highly selective delta opiate receptor antagonist, inhibited the action of beta-endorphin, whereas a selective mu opiate receptor antagonist was ineffective. Although less potent than beta-endorphin, the delta opiate receptor agonist D-Ala2-D-Leu5-enkephalin also significantly enhanced [Ca2+]i responses. In summary, concentrations of beta-endorphin, within the physiological range found in the systemic circulation, modulate the increase in T cell [Ca2+]i induced by Con A. Both the efficacy of D-Ala2-D-Leu5-enkephalin alone and the antagonism of beta-endorphin by naltrindole suggest that a delta-type opiate receptor may mediate these effects.
Shahabi
N A
NA
Endocrine-Neuroscience and Neuroimmunomodulation Research Laboratories, Minneapolis Medical Research Foundation, Minnesota, USA.
Heagy
W
W
Sharp
B M
BM
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D003208:Concanavalin A / Q000494:pharmacology*; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D017465:Receptors, Opioid, delta / Q000819:agonists / Q000037:antagonists & inhibitors; D013154:Spleen / Q000166:cytology / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D001615:beta-Endorphin / Q000494:pharmacology*
D017465:Receptors, Opioid, delta; D003208:Concanavalin A; D009271:Naltrexone; D001615:beta-Endorphin; D016308:Enkephalin, Leucine-2-Alanine; C055382:naltrindole; D002118:Calcium