Inhibitory effects of spinorphin, a novel endogenous regulator, on chemotaxis, O-2(-) generation, and exocytosis by N-formylmethionyl-leucyl-phenylalanine (FMLP)-stimulated neutrophils

To characterize the inflammatory effect of spinorphin, an endogenous peptide purified from bovine spinal cord, its effects on chemotaxis, O-2(-) generation, and exocytosis by N-formylmethionyl-leucyl-phenylalanine (FMLP) stimulated human neutrophils (PMNs) in vitro were examined. At 10 mu M, spinorphin significantly inhibited chemotaxis by FMLP-stimulated PMNs. Spinorphin at 100 mu M also inhibited both O-2(-) generation and exocytosis of beta-glucuronidase and collagenase by FMLP-stimulated PMNs. The mechanisms by which spinorphin inhibits these PMN functions were examined further. Spinorphin markedly suppressed the binding of FML[H-3]P to its receptor on PMNs, as observed in a binding assay. However, other neuropeptides that were examined (angiotensin III and substance P) had no effect on FML[H-3]P binding, suggesting the possibility that spinorphin plays a specific role in the inhibition of the binding between FMLP and its receptor. The suppression of FMLP binding also caused a decrease of the FMLP-induced intracellular calcium concentration [Ca2+](i), which acts as a second messenger leading to PMN functions. These results suggest that spinorphin may be a new endogenous inflammation-regulatory peptide that modulates the interaction of FMLP with its receptor. (C) 1997 Elsevier Science Inc.