PROTECTIVE EFFECT OF OLEOYL PEPTIDE CONJUGATES AGAINST ELASTOLYSIS BY NEUTROPHIL ELASTASE AND KAPPA-ELASTIN-INDUCED MONOCYTE CHEMOTAXIS

Elastin can impair the human neutrophil elastase (HNE) inhibitory capacity of elastase inhibitors. We synthesized oleoyl-alanyl-alanyl-prolyl-valine (Ol-Ala-Ala-Pro-Val-OH) (oleoyl peptide) and the amides (NH2 and NH-C3H7) of this peptide and studied their HNE-inhibitory potencies using succinyl-alanyl-alanyl-alanine-p-nitroanilide (Suc-Ala-Ala-Ala-pNA) or H-3-labeled elastin as substrates, as well as cryostat sections of rabbit skin as an ex vivo substrate. Using Suc-Ala-Ala-Ala-pNA, Ol-Ala-Ala-Pro-Val-OH had an IC50 of 3 muM. When the COOH terminal of the oleoyl peptide was derivatized to amide forms, the compound lost its ability to interact with HNE while keeping its elastin-protecting function: IC50 values for NH2 and NH-C3H7 derivatives were 22 and 17 muM, respectively. Also, the HNE-inhibitory capacity of 01-Ala-Ala-Pro-Val-OH was only reduced 2-fold by using elastin as a substrate. This decrease was much lower than those determined with other HNE inhibitors of similar potency and could be accounted for by the ability of oleoyl peptide to bind to elastin. Cryostat sections of rabbit skin were also used as an ex vivo substrate for assessing the elastin-protecting property of 01-Ala-Ala-Pro-Val-OH. Preincubating HNE and oleoyl peptide before application to tissue sections led to an IC50 of 8 muM, close to the value determined with elastin as a substrate. Treatment of sections with oleoyl peptide before adding HNE gave a lower IC50 (4 muM). Ol-Ala-Ala-Pro-Val-OH could suppress kappa elastin (kE)-induced chemotaxis of human monocytes. Optimal kE chemotactic effect occurred at 13 nM, and 50% inhibition of chemotaxis was observed in presence of 75 muM of this oleoyl peptide. In contrast, oleoyl peptide had no influence on formylmethionylleucylphenylalanine-induced chemotaxis of either human monocytes or rat polymorphonuclear neutrophils. Lipophilic substances such as oleoyl peptide, which simultaneously behave as HNE inhibitors, elastin-protecting agents, and modulators of monocytes chemotaxis induced by elastin fragments, may thus present several advantages in the treatment of human lung diseases.