Immunohistochemical localization of endomorphin-1 and endomorphin-2 in immune cells and spinal cord in a model of inflammatory pain
Male; Animals; Rats; Biomarkers of Pain; Immunohistochemistry; Freund's Adjuvant; Hindlimb; Wistar; Lymph Nodes/cytology; Lymphocytes/chemistry; Macrophages/chemistry; Monocytes/chemistry; Oligopeptides/analysis; Pain/chemically induced/immunology; Posterior Horn Cells/chemistry; Skin/chemistry/immunology/innervation
Recently, two novel highly selective mu-opioid receptor (MOR) agonists, endomorphin-1 and endomorphin-2, have been isolated from bovine as well as human brains and were proposed to be the endogenous ligand for MOR. Later, endomorphin-1 and endomorphin-2 have been detected in the immune system of rats and humans using radioimmunoassay in combination with reverse-high-phase-liquid chromatography. In the present study, we analyzed the expression of endomorphin-1, endomorphin-2 and MOR by immunohistochemistry in a model of Freund's complete adjuvant (FCA)-induced painful inflammation. While MOR was upregulated on peripheral and central nerve terminals, inflammation did not alter endomorphin-2 expression in nerve fibers either in the dorsal horn of the spinal cord or in subcutaneous tissue. Endomorphin-1 and endomorphin-2 were expressed in immune cells (macrophage/monocytes) in the medullary region of the popliteal lymph nodes. The proportion of immunocytes (macrophage/monocytes, lymphocytes) containing endomorphin-1 and endomorphin-2 was increased in inflamed lymph nodes and subcutaneous paw tissue of animals with local inflammatory pain. Taken together, the upregulation of MOR and of its endogenous ligands endomorphin-1 and endomorphin-2 in immunocytes suggests an involvement of these opioid peptides in the peripheral control of inflammatory pain.
2002
Mousa SA; Machelska H; Schafer M; Stein C
Journal Of Neuroimmunology
2002
Article information provided for research and reference use only. PedPalASCNET does not hold any rights over the resource listed here. All rights are retained by the journal listed under publisher and/or the creator(s).
Journal Article
<a href="http://doi.org/10.1016/s0165-5728(02)00049-8" target="_blank" rel="noreferrer">10.1016/s0165-5728(02)00049-8</a>
Novel opioid peptides endomorphin-1 and endomorphin-2 are present in mammalian immune tissues
Female; Humans; Male; Adult; Middle Aged; Animals; Rats; Non-U.S. Gov't; Research Support; Wistar; Radioimmunoassay/methods; Chromatography; High Pressure Liquid; Oligopeptides/analysis; Cross Reactions; Immune Sera/immunology; Immune System/chemistry; Spleen/chemistry; Thymus Gland/chemistry; Tissue Extracts/chemistry
Endomorphin (EM)-1 and EM-2 are opioid tetrapeptides, reported within the central nervous system, which have very high specificity and affinity for the mu-opioid receptor. We have used newly developed and well-characterised radioimmunoassays (RIAs) in combination with reversed-phase high-performance liquid chromatography (HPLC) to detect EM-1 and EM-2 immunoreactivity (ir) in rat immune tissues. Endomorphins were detectable in extracts of rat spleen (total EM-1-ir/spleen: 440+/-73 pg, mean+/-SEM, a=group of eight rats; EM-2-ir: 150+/-12 pg) and thymus (EM-1-ir: 152+/-18 pg, mean+/-SEM n=8; EM-2-ir: 156+/-28 pg). EM-2-ir was detectable in extracts of human spleen (338+/-196 pg/g tissue, n=3). Multiple peaks of EM-1-ir and EM-2-ir were observed in rat spleen and thymus extracts, and multiple peaks of EM-2-ir were observed in extracts of human spleen, following reversed-phase HPLC and RIAs. This is the first report of endomorphin immunoreactivity in tissues of the rat and human immune systems.
2000
Jessop DS; Major GN; Coventry TL; Kaye SJ; Fulford AJ; Harbuz MS; De Bree FM
Journal Of Neuroimmunology
2000
Article information provided for research and reference use only. PedPalASCNET does not hold any rights over the resource listed here. All rights are retained by the journal listed under publisher and/or the creator(s).
Journal Article
<a href="http://doi.org/10.1016/s0165-5728(99)00216-7" target="_blank" rel="noreferrer">10.1016/s0165-5728(99)00216-7</a>