Opioid peptides endomorphin-1 and endomorphin-2 in the immune system in humans and in a rodent model of inflammation

Opioid peptides endomorphin-1 and endomorphin-2 in the immune system in humans and in a rodent model of inflammation

Jessop DS; Richards LJ; Harbuz MS

Annals Of The New York Academy Of Sciences

2002

Humans; Male; Animals; Rats; Non-U.S. Gov't; Research Support; Arthritis; Radioimmunoassay; Concanavalin A/pharmacology; Wistar; Spleen/chemistry; Thymus Gland/chemistry; Morphine/pharmacology; Apoptosis/drug effects; Experimental/immunology/metabolism; Lipopolysaccharides/pharmacology; Lymphocyte Activation/drug effects; Lymphocyte Subsets/chemistry/drug effects; Oligopeptides/analysis/pharmacology; Synovial Fluid/chemistry

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.

2002

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