Effects of dynorphin on the PHA-induced lymphocyte proliferation in vitro

Dynorphins in regulation of immune system functions

Dynorphins constitute a family of opioid peptides manifesting the highest affinity for κ-opiate receptors. Immune system cells are known to express a κ-receptor similar to that in the central nervous system, and as a consequence dynorphins are involved in the interaction between cells of the nervous and immune systems. In this review, data on dynorphin structure are analyzed and generalized, the κ-opiate receptor is characterized, and data on the regulation by dynorphins of functioning of the innate and adaptive immunity cells are summarized.

Effect of dynorphin A (1-17) on proliferation and IL-2, IL-4, IFN-γ production by peripheral blood mononuclears

Dynorphin A (1-17) in concentrations of 10(-8)-10(-9) M inhibits phytohemagglutinin (2.5 μg/ml)-induced proliferative response of mononuclear fraction lymphocytes. In mitogen-stimulated cultures, 10(-8) M dynorphin A (1-17) stimulates the production of IL-4, inhibits the production of IL-2, and does not modify the production of IFN-γ. Nonselective κ-receptor antagonist naloxone and selective antagonist binaltorphimine hydrochloride abolish the inhibitory effects of both dynorphin A concentrations on the lymphocyte proliferative response. On the other hand, evaluation of the effect of κ-receptor blockade on the production of IL-2 and IL-4 showed that this effect depends on peptide concentration and antagonist type. Hence, the results attest to an important role of κ-receptors in modulation of functional activity of immune cells.

Substance P and calcitonin gene-related peptide increase IL-1 beta, IL-6 and TNF alpha secretion from human peripheral blood mononuclear cells

We found that substance P (SP) and calcitonin gene-related peptide (CGRP) (0.3-1 microM) increased, in a concentration-dependent manner, the basal secretion of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF alpha) from cultured lymphocyte-enriched mononuclear cells isolated from human peripheral blood. SP and CGRP (0.1 microM) synergistically increased basal TNF alpha secretion. Dynorphin A((1-17)) (0.1-1 microM) did not modify basal cytokine secretion. Lipopolysaccharide (10 ng/ml)-induced cytokine secretion and [(3)H]thymidine uptake were not altered by any neuropeptide (at 0.1 microM). Thus, SP and CGRP stimulate the production of pro-inflammatory cytokines from lymphocytes only at high concentrations, similar to those reached during tissue damage.

Immunomodulating effect of met-enkephalin on different stages of lymphocyte proliferation induced with concanavalin A in vitro

Met-enkephalin (ME) in the range of concentrations 10(-15) M to 10(-9) M has exhibited an immunomodulating effect on concanavalin A (Con A) induced proliferation of mice lymphocytes from lymph nodes in vitro. The effect of ME was shown to vary with the stage of lymphocyte activation and to depend on the mitogen dose. In the case that ME and Con A were injected simultaneously, at the zero time of proliferation, maximum inhibition was observed on the first and fourth days. In an other set of experiments when ME was added at intervals of 4 hours before measuring the proliferation response value, both inhibition (after 24 hours of proliferation) and stimulation (after 28 and 96 hours) were observed. Opioid ligands of various classes were found to act in the same manner as ME. Naloxone was shown to block the immunomodulating effect of opioids.