Low density lipoprotein binding affinity of arterial wall isomeric chondroitin sulfate proteoglycans

Although the selective interaction of low density lipoproteins (LDL) with arterial proteoglycans is known, information is lacking on LDL-binding affinity of different subspecies occurring within a proteoglycan family. Isomeric chondroitin sulfate proteoglycan preparations sedimenting at densities of 1.54 g/ml (D1), 1.50 g/ml (D2) and 1.46 g/ml (D3) were isolated from bovine aorta intima-media under dissociative conditions and subjected to equilibrium binding to LDL-agarose gel. D1, D2 and D3 contained 36%, 37% and 11% dermatan sulfate, respectively. Sulfate to hexosamine ratio was low (0.73) in D1 when compared to D2 and D3 (0.94 and 1.04). Of the total proteoglycans contained in D1, D2 and D3, 41%, 52% and 66% interacted with LDL, respectively. LDL-bound proteoglycans dissociated over a wide range of ionic strengths (0.15-1.0); in comparison, LDL-bound heparin dissociated within a narrow range (0.5-0.75). Unlike other preparations, 30% of bound D3 dissociated at an ionic strength of 1.0. In D1 and D2 the proportion of dermatan sulfate increased in proteoglycan fractions that were bound firmly to LDL, whereas a high affinity fraction in D3 contained no dermatan sulfate. Thus, isomeric chondroitin sulfate proteoglycans display considerable divergence with respect to LDL binding. This may depend not only on the degree of sulfation but on other characteristics of the chondroitin sulfate isomers as well.