Physicochemical and ultrastructural properties of cholesterol esters bound to elastin

Physicochemical and ultrastructural properties of cholesterol ester complexes of fibrous elastin and of K-elastin were studied using differential scanning calorimetry (DSC) and electron-microscopy. The number of molecules of the different fatty acids retained in these elastin complexes varied between large limits according to the nature of the fatty acid of the cholesterol ester, ranging from 0.1 microgram/200 mg of elastin for cholesterol arachidonate to 48 micrograms/200 mg elastin for cholesterol palmitate. The ultrastructural studies confirmed the association of cholesterol esters with fibrous elastin and soluble K-elastin. The DSC-data showed that the temperature of transition between the crystalline and the liquid crystalline state shifts towards higher temperatures (well above body temperature) when cholesterol esters are bound to elastin: no liquid crystalline mesophase was observed in cholesterol oleate or linoleate-elastin complexes at 37 degrees C; melting of the crystalline structures took place at 51 degrees C and at 42 degrees C for the cholester Holeate and linoleate-elastin complexes respectively. These results indicate that in the elastin-bound form the crystalline-liquid crystalline transition is inhibited. The "stabilization" of the crystalline structure of cholesterol esters by fibrous elastin may be of biological significance and account for the crystalline deposits seen in advanced atherosclerotic lesions at sites of elastic fiber breakdown.