The susceptibility of elastin-fatty acid complexes to elastolytic enzymes

Elastin in vivo is likely to be complexed with amphipathic ligands such as lipids. The susceptibility of stable [3H] elastin-fatty acid complexes to the action of porcine pancreatic elastase (PPE) and to human neutrophil lysates over time was assessed. Elastolysis by PPE of substrates prepared with oleic or linoleic acids was initially higher (for up to 2 hours) than that of uncomplexed elastin. Stearic acid and elaidic acid (the trans isomer of oleic acid) did not enhance the elastolytic rate above control. The stimulatory effect of oleic and linoleic acids appeared to derive from increased adsorption of PPE onto elastin; the loss of stimulatory activity over time occurred in parallel with a progressive decrease in adsorption. All fatty acids tested inhibited elastolysis by neutrophil lysates, the effect being particularly marked with oleic and elaidic acids. These results indicate that 1). Complexed fatty acids can modulate the rate of elastin breakdown by elastases; 2). The effects observed with PPE are due to differences in adsorption of enzyme onto substrate, possibly as a result of steric considerations; 3). Since elastolysis by neutrophil lysates is inhibited by all fatty acids, the properties of different elastolytic enzymes should be considered in in vitro model systems of connective tissue breakdown.