氧化修饰极低密度脂蛋白增强其致动脉粥样硬化作用

Oxidative Modification of Very Low Density Lipoprotein Enhances Its Atherogenicity

研究了氧化修饰极低密度脂蛋白（ｏｘ－ＶＬＤＬ）对小白鼠腹腔巨噬细胞内脂质堆积作用及其机制。经Ｃｕ^（２＋）修饰后ＶＬＤＬ的电泳迁移率及脂质过氧化物含量均显著增加。ｏｘ－ＶＬＤＬ更易导致小鼠腹腔巨噬细胞内脂质堆积。以相同浓度（３００μｇＴＧ／ｍＬ）或不同浓度（２００─５００μｇＴＧ／ｍＬ）的ｏｘ－ＶＬＤＬ及正常ＶＬＤＬ（ｎ－ＶＬＤＬ）与巨噬细胞温育２４ｈ，前者使巨噬细胞内ＴＧ堆积均比后者显著（Ｐ＜０．０１）。同时，随ｏｘ－ＶＬＤＬ的脂质过氧化物含量（ＴＢＡＲＳ水平）增加，巨噬细胞内ＴＧ含量的百分率相应增加。以５０μｇ蛋白／ｍＬ的ｎ－ＬＤＬ，ｏｘ－ＬＤＬ，ｎ－ＶＬＤＬ及ｏｘ－ＶＬＤＬ与巨噬细胞温育６０ｈ。细胞内ＣＥ堆积中氧化组均比正常组高（Ｐ＜０．０１）。巨噬细胞对^（１２５）Ｉ－ｎ－ＶＬＤＬ与^（１２５）Ｉ－ｏｘ－ＶＬＤＬ的结合、降曲线均有饱和趋势。两结合曲线无明显差异，但细胞对后者降解的量比前者多。结合的竞争实验表明，ｎ－ＶＬＤＬ能抑制大部分^（１２５）Ｉ－ｏｘ－ＶＬＤＬ与细胞结合，而Ａｃ－ＬＤＬ只能抑制小部分。结果表明ｏｘ－ＶＬＤＬ主要通过受体途径：大部分经过ｎ－ＶＬＤＬ受体，小部分经过清道夫受体被巨噬细胞摄?

Normolipidemic human very low density lipoprotein(n-VLDL)is susceptible to oxidative modification by Cu￣(2+), resulting in increase of electrophoretic mobility and increase of thiobarbituric acid-reactive substance (TBARS) in the lipoprotein. Oxidized VIDL (ox-VLDL)caused a nearly twe-fold higher increment of cellular TG as compared to n-VLDL after macrophages were incubated with both lipoprotein (300pg TG/mL) for 24h [277. 95± 15.5%, 157. 80±4. 97% of control, respectively]. Incubating cells with increasing concentration of both lipoprotein (200-500μgTG/mL)revealed that TG accumulation stimulated by ox-VLDL were well correlated with the percentage increase of cellular TG. As the cells exposed to n-LDL, ox-LDL , n-VLDL, or ox-VLDL ( 50μg prot. /mL) for 60h , both oxidized lipoprotein caused more striking cellular CE deposition than non-oxidized lipoprotein [19. 24±4. 63 (μg CE/mg prot. )160. 54±8. 32<n-LDL/ox-LDL>; 8. 74±3. 20/31. 56±9. 46<n-VLDL/ox-VLDL>] ￣(125)I-n-VLDL were bound and degraded by macrophages by a saturable mechanism. Binding curve of both lipoprtein was superimposed, but degradation of ￣(125)I-ox-VLDL by macrophages was rapid than that of ￣(125)I-n-VLDL. The results suggested that ox-VLDL may be metabolized by a receptor pathway on marcrophages. The competitive binding experiments demonstrated that ox-VLDL was taken up mainly by n-VLDL receptor and probably a small part by scavenger receptor of macrophages. These evidences suggested that oxidative modification of VLDL enhances its atherogenictiy.