B Lymphocytes Express Pomc mRNA, Processing Enzymes and β-Endorphin in Painful Inflammation

Immune cell-derived beta-endorphin (end) and other opioid peptides elicit potent and clinically relevant inhibition of pain (analgesia) in inflamed tissue by activation of peripheral opioid receptors. pro-opiomelanocortin (pomc) is the polypeptide precursor of end and is processed by prohormone convertases (pcs). this study aims to decipher the processing of pomc in lymphocyte subsets in a rat model of unilateral painful hindpaw inflammation. lymphocytes, isolated from popliteal lymph nodes, were separated into b-cells, t-cells, t-helper cells and cytotoxic t-cells using magnetic cell sorting, and were examined by polymerase chain reaction, immunofluorescence and radioimmunoassay. at 2 h of inflammation, pomc exon 2–3 mrna was mostly expressed in b- but not in t-cells. prohormone convertase 1 (pc1) mrna and protein were upregulated in b-cells and t-helper cells. prohormone convertase 2 (pc2) was expressed in t- and b-cells, both in inflamed and non-inflamed lymph nodes. end was expressed in b- but not in t-cells. we conclude that pomc, its processing enzymes and end are predominantly expressed in b-lymphocytes at 2 h of paw inflammation.