The synthetic melanocortin (CKPV)2 exerts broad anti-inflammatory effects in human neutrophils

Natural melanocortin peptides exert broad effects on the host and they have remarkable therapeutic potential. However, successful use of melanocortins as therapeutic agents depends on the design of molecules that have more stable pharmacological profiles. The synthetic peptide (CKPV)₂, based on the C-terminal sequence of α-melanocyte stimulating hormone (α-MSH), has anti-tumor necrosis factor-α (TNF-α) effects in vitro and in vivo and is a promising candidate to treat inflammation. Because neutrophil activity is a major target for anti-inflammatory therapies, we determined whether (CKPV)₂ modulates human neutrophil functions in vitro. Incubation of freshly-separated human neutrophils with 10^-12-10^-6 M (CKPV)₂ significantly inhibited activities relevant to the inflammatory reaction. Neutrophil migration toward the two chemoattractants interleukin 8 (IL-8) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) was significantly inhibited by (CKPV)₂. (CKPV)₂ also inhibited reactive oxygen intermediate (ROI) production induced by phorbol 12-myristate 13-acetate (PMA), but not that induced by fMLP. Because these effects of (CKPV)₂ were abolished by the adenylyl cyclase inhibitor 2′,5′-dideoxyadenosine (ddAdo), they appear to be cAMP-dependent. Finally, the peptide reduced lipopolysaccharide (LPS)-stimulated expression of TNF-α, interleukin-1β (IL-1β), interleukin-8 (IL-8), and intercellular adhesion molecule 1 (ICAM-1), as well as TNF-α protein release in cell supernatants. The data indicate that (CKPV)₂ modulates broad cAMP-dependent, anti-inflammatory pathways in human neutrophils.