Rg. Salomon et al., OXIDATION OF LOW-DENSITY LIPOPROTEINS PRODUCES LEVUGLANDIN-PROTEIN ADDUCTS, Chemical research in toxicology, 10(7), 1997, pp. 750-759
Free-radical oxidation of human low-density lipoprotein (LDL) produces
levuglandin (LG)protein adducts that were detected with an enzyme-lin
ked immunosorbent assay using LGE(2)-KLH antibodies which recognize LG
E(2)-derived pyrroles. The level of immunoreactivity increases with ti
me of oxidation and reaches a maximum by 8 h. The yield of pyrrole var
ies nonlinearly with the level of LG adduction to LDL. At low LG:LDL r
atios, such as those detected in oxidized LDL, the reaction of primary
amino groups with LGE(2) produces mostly non-pyrrole adducts that are
not immunoreactive. Concommitant phospholipolysis must occur if the g
eneration of immunoreactive epitopes in LDL involves oxidation of arac
hidonyl phospholipids. Thus, since a protein adduct prepared from synt
hetic LGE(2)-2-lysophosphatidylcholine ester showed, at most, only 0.5
% cross-reactivity with the LGE(2)-KLH antibodies, the epitopes detect
ed in oxidized LDL are almost certainly not protein adducts of LG-phos
pholipid esters. As expected, hydrolysis of the carboxylic ester in th
e protein adduct of LGE(2)-2-lysophosphatidylcholine ester by treatmen
t with phospholipase A:! produced a fully immunoreactive LGE(2)-protei
n adduct.