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A possible immunoregulatory function for [Met]-enkephalin-Arg6-Phe7 involving human and invertebrate granulocytes
G B Stefano1, M A Shipp, B Scharrer
1Multidisciplinary Center for the Study of Aging, SUNY, Old Westbury 11568.
Abstract:
Opioid peptides and their analogs have been shown to stimulate adherence, conformational changes and locomotory activity in human as well as invertebrate granulocytes. The present study demonstrates that [Met]-enkephalin-Arg6-Phe7, an opioid substance thus far not included in these immunological tests, exhibits stimulatory effects comparable to those of [Met]-enkephalin in this regard. Furthermore, since neutral endopeptidase 24.11 (enkephalinase; CD10/NEP) exists in invertebrate immunocyte membranes, we demonstrate that its specific inhibitor, phosphoramidon, potentiates the effects of the heptapeptide in inducing conformational change in both human and invertebrate granulocytes. Additionally, the major metabolic products of NEP activity, Phe-Met-Arg-Phe and Tyr-Gly-Gly, appear to be potent antagonists of this enzyme activity, especially the tetrapeptide. The effects of heptapeptide stimulation showed a major difference between vertebrate and invertebrate immunocytes with respect to their time course, namely, the speed of their onset. [Met]-enkephalin-Arg6-Phe7 markedly stimulated the locomotory activity of these cells which becomes most noticeable within 15-45 min for Mytilus cells and in a 5-15 min period for human cells. It also enhanced the mobility and velocity of the responsive human (5 microns/min) and invertebrate cells (2.1 microns/min).
Insights
This study shows that the opioid peptide [Met]-enkephalin-Arg6-Phe7 stimulates immune cells in both humans and invertebrates. Its effects are enhanced by inhibiting neutral endopeptidase 24.11 (NEP), revealing insights into immune cell responses.
Area of Science:
- Immunology
- Neuroendocrinology
- Comparative Biology
Background:
- Opioid peptides modulate immune cell functions like adherence and motility.
- The role of specific opioid analogs, such as [Met]-enkephalin-Arg6-Phe7, in immune responses is not fully understood.
- Neutral endopeptidase 24.11 (NEP) is involved in opioid peptide metabolism and is present in invertebrate immune cells.
Purpose of the Study:
- To investigate the immunomodulatory effects of [Met]-enkephalin-Arg6-Phe7 on human and invertebrate granulocytes.
- To explore the role of NEP in mediating the effects of [Met]-enkephalin-Arg6-Phe7.
- To compare the time course of immune cell stimulation between vertebrate and invertebrate species.
Main Methods:
- Treatment of human and invertebrate granulocytes with [Met]-enkephalin-Arg6-Phe7.
- Assessment of cell adherence, conformational changes, and locomotory activity.
- Use of phosphoramidon, a specific NEP inhibitor, to evaluate its effect on peptide-induced responses.
- Analysis of metabolic products of NEP activity.
Main Results:
- [Met]-enkephalin-Arg6-Phe7 stimulated conformational changes and locomotory activity in both human and invertebrate granulocytes, comparable to [Met]-enkephalin.
- Phosphoramidon potentiated the effects of [Met]-enkephalin-Arg6-Phe7, indicating NEP's role in its action.
- The major NEP metabolic products, Phe-Met-Arg-Phe and Tyr-Gly-Gly, acted as antagonists, particularly the tetrapeptide.
- Significant differences in the onset time of stimulation were observed: 15-45 min for Mytilus cells versus 5-15 min for human cells.
- [Met]-enkephalin-Arg6-Phe7 enhanced cell mobility and velocity in both cell types.
Conclusions:
- [Met]-enkephalin-Arg6-Phe7 is a potent immunomodulator for both vertebrate and invertebrate granulocytes.
- NEP plays a crucial role in the action of [Met]-enkephalin-Arg6-Phe7, with its inhibition leading to potentiated effects.
- The differential time course of stimulation highlights species-specific differences in immune cell signaling pathways.
- This study expands the understanding of opioid peptide signaling in innate immunity across diverse species.