Opioid peptides endomorphin-1 and endomorphin-2 in the immune system in humans and in a rodent model of inflammation.
Endomorphin (EM)-1 and EM-2 are tetrapeptides with high affinity and selectivity for the micro-opioid receptor. We have utilized specific radioimmunoassays to characterize EM-1 and EM-2 in immune tissues from normal human subjects and from rats with adjuvant arthritis (AA). PBLs from three normal human subjects contained 248, 13, and 303 pg EM-1 per 100 million cells, whereas EM-2 was measured in two subjects at 69 and 588 pg per 100 million cells. In AA rats, EM-1 (but not EM-2) contents in the spleen and thymus were elevated compared with levels in tissues from non-AA controls. EM-1 was detectable in five of eight samples of synovial tissue from inflamed hind paws, whereas EM-2 was detectable in two of eight synovial extracts. Neither EM-1 nor EM-2 were detectable in synovial tissue from non-AA rats. To our knowledge, this is the first report of endomorphins in normal human immune cells. Increased endomorphin expression or uptake in peripheral tissues in a rodent model of chronic inflammation provides potential for endomorphins to selectively modulate chronic inflammation in mammals.
University Research Centre for Neuroendocrinology, University of Bristol, Bristol, United Kingdom. david.jessop@bristol.ac.uk
David S
DS
Jessop
Louise J
LJ
Richards
Michael S
MS
Harbuz
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001169:Arthritis, Experimental / Q000276:immunology* / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D016131:Lymphocyte Subsets / Q000737:chemistry* / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009842:Oligopeptides / Q000032:analysis* / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000737:chemistry; D013582:Synovial Fluid / Q000737:chemistry; D013950:Thymus Gland / Q000737:chemistry
D008070:Lipopolysaccharides; D009842:Oligopeptides; C105293:endomorphin 1; D003208:Concanavalin A; C105294:endomorphin 2; D009020:Morphine