Influence of chondroitin sulfate charge density, sulfate group position, and molecular mass on Cu2+-mediated oxidation of human low-density lipoproteins: Effect of normal human plasma-derived chondroitin sulfate
N. Volpi et P. Tarugi, Influence of chondroitin sulfate charge density, sulfate group position, and molecular mass on Cu2+-mediated oxidation of human low-density lipoproteins: Effect of normal human plasma-derived chondroitin sulfate, J BIOCHEM, 125(2), 1999, pp. 297-304
The effects of chondroitin sulfate samples with decreasing charge densities
, different 4-sulfate/6-sulfate ratios, and various molecular masses on Cu2
+-induced oxidation of human low-density lipoprotein (LDL) were evaluated b
y monitoring conjugated diene formation and the tryptophan fluorescence kin
etics. Low-sulfated chondroitin sulfate (CS) from beef trachea had a very s
trong protective antioxidant effect. Quite similar behavior was observed fo
r CS from pig trachea, and a fructose-containing polysaccharide with a chon
droitin backbone from Escherichia coli was also strongly protective as to L
DL oxidation, CS samples with decreasing charge densities proved effective
in inhibiting LDL oxidation, A totally desulfated sample still exhibited a
great capacity to protect LDL against oxidation, CS-4-sulfate samples (sulf
ate to carboxyl ratio of 0.62, about 65% 4-sulfate groups and 5% g-sulfate
groups) retained great ability to inhibit the Cu2+-mediated human LDL oxida
tion, CS fractions with different molecular masses were examined as possibl
e inhibitors of LDL oxidation, Samples with molecular masses lower than abo
ut 8,570 (13-15 disaccharide units) were unable to protect human LDL from C
u2+-induced oxidation, Similar results were obtained on studying the degrad
ation of tryptophan residues of the LDL protein moiety resulting from Cu2complexation through amino acid residues. A low-sulfated CS (sulfate to car
boxyl ratio of 0.41, a molecular mass of about 15,600) having effective ant
i-oxidant properties as to metal-induced LDL oxidation was isolated from no
rmal human plasma. The protective capacity as to Cu2+-mediated LDL oxidatio
n of CS is discussed in relation to its structure, also considering the phy
siological role of plasma CS in relation to factors that can alter its prop
erties.