Marcel Y L, Jewer D, Leblond L, Weech P K, Milne R W
Laboratory of Lipoprotein Metabolism, Clinical Research Institute, Montreal, Quebec, Canada.
J Biol Chem. 1989 Nov 25;264(33):19942-50.
Incubation of human serum or high density lipoprotein (HDL) at 37 degrees C in the presence of Fe2+, Fe2+/Fe3+, or Mn2+ results in the increased immunoreactivity (up to 12-, 40-, and 80-fold, respectively) of specific apoA-I epitopes identified as 3D4 and 6B8, while Mg2+, Ca2+, or Cu2+ have minimal or nonsignificant effects. The effect of Mn2+ on the 3D4 epitope requires a specific association with lipids since it can be observed with HDL but not with apoHDL, even in the presence of other lipoproteins. The increase in immunoreactivity noted with Fe2+/Fe3+ or Mn2+ can be blocked with either EDTA or antioxidants (GSH and ascorbic acid), suggesting that it takes place during a peroxidative reaction of the lipids. The peroxidation of lipids which accompanies the increase in immunoreactivity does cross-link apoA-I both with itself and with apoA-II but does not cleave the molecule. The apoA-I-containing lipoproteins which float between 1.18 and 1.22 g/ml and have a pre B-electrophoretic migration are characterized by a very low immunoreactivity with monoclonal antibody 3D4 but are 10-fold or more responsive to Mn2+ treatment than other lipoprotein subfractions, thus demonstrating heterogeneity under oxidative conditions. Proteoliposomes containing apoA-I, cholesterol, and dilinoleyl-lecithin are sensitive to Mn2+ treatment, but not those made with dioleyl- or dimyristoyl-lecithins. However, the increase in 3D4 immunoreactivity is weak and transient and is followed by the disappearance of the epitope caused by cross-linking. We conclude that lipid peroxidation can specifically cross-link apoA-I and change its conformation and antigenicity.
在37℃下，于Fe2 +、Fe2 + / Fe3 +或Mn2 +存在的情况下孵育人血清或高密度脂蛋白（HDL），会导致被鉴定为3D4和6B8的特定载脂蛋白A - I表位的免疫反应性增加（分别高达12倍、40倍和80倍），而Mg2 +、Ca2 +或Cu2 +的影响极小或不显著。Mn2 +对3D4表位的影响需要与脂质有特定的结合，因为即使存在其他脂蛋白，在HDL中能观察到这种影响，而在载脂蛋白HDL（apoHDL）中则观察不到。Fe2 + / Fe3 +或Mn2 +引起的免疫反应性增加可被EDTA或抗氧化剂（谷胱甘肽和抗坏血酸）阻断，这表明其发生在脂质的过氧化反应过程中。伴随免疫反应性增加的脂质过氧化确实使载脂蛋白A - I自身以及与载脂蛋白A - II发生交联，但不会裂解该分子。漂浮在1.18至1.22 g/ml之间且具有前β电泳迁移率的含载脂蛋白A - I的脂蛋白，其与单克隆抗体3D4的免疫反应性非常低，但比其他脂蛋白亚组分对Mn2 +处理的反应性高10倍或更多，从而证明在氧化条件下存在异质性。含有载脂蛋白A - I、胆固醇和二油酰卵磷脂的蛋白脂质体对Mn2 +处理敏感，但由二油酰或二肉豆蔻酰卵磷脂制成的蛋白脂质体则不敏感。然而，3D4免疫反应性的增加微弱且短暂，随后因交联导致表位消失。我们得出结论，脂质过氧化可特异性地使载脂蛋白A - I交联并改变其构象和抗原性。
