2 DIFFERENT SIGNALING PATHWAYS FOR THE INDUCTION OF IMMUNOREACTIVE BETA-ENDORPHIN SECRETION BY HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS

Lymphocytes are now recognized as an extrapituitary source of neuropeptides, such as the opioid peptide beta-endorphin. In the present paper the intracellular signalling pathways involved in regulation of the secretion of immunoreactive (ir) beta-endorphin by human peripheral blood mononuclear cells are described. Activation of protein kinase-C with a phorbol ester rapidly induces secretion of ir-beta-endorphin by T-cells as well as by the non-T cell fraction. Stimulation of protein kinase-A by the addition of (Bu)2cAMP to T-cells or non-T-cells can also induce the secretion or ir-beta-endorphin by these cells. Investigation of the effect of different mitogens or antigen on ir-beta-endorphin secretion by lymphocytes revealed that the nature of the stimulus determines the kinetics of the response and the responding cell type. Induction of ir-beta-endorphin secretion by T-cells after stimulation with a T-cell mitogen is relatively fast; it can be observed within 3 h. In contrast, the response of the non-T-cell fraction to, for example, stimulation with (Bu)2cAMP can only be observed after 18 h of culture. Evidence will be presented that the fast response is mediated via protein kinase-C activation. The response observed after 18 h can be mediated via protein kinase-C as well protein kinase-A activation.