Hakamata H, Miyazaki A, Sakai M, Matsuda H, Suzuki H, Kodama T, Horiuchi S
Department of Biochemistry, Kumamoto University School of Medicine, Japan.
J Lipid Res. 1998 Mar;39(3):482-94.
A high concentration of oxidized low density lipoprotein (Ox-LDL) showed a cytotoxic effect on mouse macrophage-derived J774 cells. Mutant cells were selected from these cells that were resistant to the cytotoxic effect of Ox-LDL. One mutant form, named JO21b cells, was characterized in the present study. In spite of a marked resistance to the cytotoxic effect of Ox-LDL, JO21b cells were apparently as sensitive as the parent cells not only to toxic moieties of Ox-LDL, such as 7-ketocholesterol and lysophosphatidylcholine, but also to t-butyl hydroperoxide, an artificial lipid hydroperoxide analog. However, the cellular association of 125I-labeled Ox-LDL with, and subsequent endocytic degradation by JO21b cells was reduced by 70-80% compared with J774 cells. Similarly, accumulation of cholesteryl esters in JO21b cell by Ox-LDL was also reduced by 70%. Northern blot analyses of type I and type II macrophage scavenger receptors (type I and type II MSR) demonstrated that the mRNA levels of JO21b cells were lower than those of J774 cells. Moreover, peritoneal macrophages obtained from MSR-knockout mice showed a higher resistance to the cytotoxic effect of Ox-LDL than those from their wild-type littermates. Our results suggest, therefore, that macrophage scavenger receptor-mediated endocytic uptake of oxidized low density lipoproteins (Ox-LDL) may play an enhancing role in Ox-LDL cytotoxicity to macrophages or macrophage-derived cells.
高浓度的氧化型低密度脂蛋白（Ox-LDL）对小鼠巨噬细胞来源的J774细胞具有细胞毒性作用。从这些对Ox-LDL的细胞毒性作用具有抗性的细胞中筛选出突变细胞。在本研究中对一种名为JO21b细胞的突变形式进行了表征。尽管JO21b细胞对Ox-LDL的细胞毒性作用具有明显抗性，但它们不仅对Ox-LDL的毒性部分（如7-酮胆固醇和溶血磷脂酰胆碱），而且对人工脂质过氧化氢类似物叔丁基过氧化氢，显然与亲本细胞一样敏感。然而，与J774细胞相比，JO21b细胞对125I标记的Ox-LDL的细胞结合以及随后的内吞降解减少了70-80％。同样，Ox-LDL在JO21b细胞中导致的胆固醇酯积累也减少了70％。对I型和II型巨噬细胞清道夫受体（I型和II型MSR）的Northern印迹分析表明，JO21b细胞的mRNA水平低于J774细胞。此外，从MSR基因敲除小鼠获得的腹腔巨噬细胞对Ox-LDL的细胞毒性作用的抗性高于其野生型同窝小鼠。因此，我们的结果表明，巨噬细胞清道夫受体介导的氧化型低密度脂蛋白（Ox-LDL）的内吞摄取可能在Ox-LDL对巨噬细胞或巨噬细胞来源细胞的细胞毒性中起增强作用。
