DETECTION OF LOW-DENSITY-LIPOPROTEIN PARTICLE FUSION BY PROTON NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

Recent evidence suggests that fusion of low density lipoprotein (LDL) particles is a key process in the initial accumulation of lipid in the arterial intima, In order to gain a better understanding of this earl y event in the development of atherosclerosis, it would thus be necess ary to characterize: the process of LDL fusion in detail, Such studies , however, pose severe methodological difficulties, such as differenti ation of particle fusion from aggregation, In this paper we describe t he use of novel methodology, based on H-1 NMR spectroscopy, to study l ipoprotein particle fusion, To test the methodology, we chose proteoly tic fusion of LDL particles, an in vitro model that has been well char acterized in our laboratory, The spectroscopic data suggested that pro teolysis of LDL with alpha-chymotrypsin induced slow initiation of fus ion, which was followed by particle fusion at an increased rate, Moreo ver, H-1 NMR spectroscopic data on different kinds of LDL interactions , for example, when LDL formed aggregates with antibodies against huma n apolipoprotein B-100, were obtained and compared with the electron m icroscopic characteristics of these preparations, An important finding was that limited aggregation of LDL particles did not disturb the H-1 NMR spectroscopic parameters used for the detection of particle fusio n and preserved the physicochemical information on the particles. The H-1 NMR methodology developed is sensitive to and specific for low den sity lipoprotein (LDL) fusion and may also allow for studies of the fa te of LDL particles in other in vitro preparations that mimic the arte rial interactions in vivo.