LDL INTERACTION WITH PROTEOGLYCANS ISOLATED FROM HUMAN AORTAS WITH DIFFERENT ATHEROSCLEROTIC INVOLVEMENT

Background. Proteoglycan (PG) - LDL interaction is likely to be involv ed in lipid deposition in arterial wall. The relative content and the structural properties of different PG populations change in human aort a with atherosclerotic degeneration. Therefore, we extracted and separ ated these PGs from human aorta samples with increasing severity of at herosclerotic involvement and studied their interactions with human LD L. Materials and Methods. PGs were extracted with 6 M urea, purified b y ion-exchange chromatography and separated into two different populat ions (PGI and PGII) on the basis of hydrodynamic size and glycosaminog lycan composition. The interaction of both PGI and PGII with LDL was s tudied separately by precipitation assay. Results. The ratio PGI/PGII decreased markedly with increasing severity of the disease. Both PGI a nd PGII formed insoluble complexes with LDL. However, the shape of sat uration curves was markedly different. An excess of PGI from normal or intermediately affected aorta inhibited insoluble complex formation w ith LDL. On the contrary, an excess either of PGII or of PGI from seve rely affected aorta did not inhibit insoluble complex formation. In th e case of PGII, the maximum of percentage cholesterol precipitated was higher when PGII from severely affected aorta was used. Conclusions. The different interactions of LDL with either PGI or PGII are likely t o depend on the different structural properties of PGs. The decrease o f PGI/PGII ratio following atherosclerotic degeneration could play an important role in lipid deposition in arterial wall.