Bolton E J, Jessup W, Stanley K K, Dean R T
Heart Research Institute, Sydney NSW, Australia.
Biochim Biophys Acta. 1997 Mar 27;1356(1):12-22. doi: 10.1016/s0167-4889(96)00157-7.
Lipid-loaded macrophages were produced in vitro by incubation with acetylated or copper-oxidized LDL. In order to establish whether cellular membrane traffic is generally perturbed by such loading, we assessed endocytosis of fluid; cell surface binding, internalisation and degradation of a soluble ligand and of a particulate preparation; and exocytosis of lysosmal enzymes. Fluid-phase pinocytosis of sucrose was unaffected by either form of loading. Binding, uptake and degradation of soluble (mannosylated-BSA) and particulate (zymosan) ligands by these lipid-loaded and by non-loaded cells were compared. Loading with oxidized LDL decreased the processing of both ligands, while loading with acetylated LDL had little effect. Loading with oxidized LDL (Ox-LDL) also decreased zymosan binding at 4 degrees C; and the internalisation and degradation of ligands in Ox-LDL loaded and non-loaded cells reflected the extent of surface binding. Changes in binding and uptake of mannosylated-BSA and zymosan were not due to changes in viability or cell number. Zymosan stimulated release of lysosomal beta-N-acetyl-D-glucosaminidase from the cells. Loading with Ox- but not Ac-LDL decreased beta-N-acetyl-D-glucosaminidase secretion. After incubation with zymosan, intracellular levels of the enzyme were increased in the Ox-LDL loaded cells. Zymosan uptake and beta-N-acetyl-D-glucosaminidase secretion were correlated, but enzyme activity per culture rose more in the absence than in the presence of zymosan. We conclude that membrane traffic is perturbed in model foam cells, particularly those loaded with Ox-LDL.
通过与乙酰化或铜氧化的低密度脂蛋白（LDL）孵育，在体外产生了脂质负载的巨噬细胞。为了确定细胞膜运输是否普遍受到这种负载的干扰，我们评估了液体的内吞作用；可溶性配体和颗粒制剂的细胞表面结合、内化和降解；以及溶酶体酶的胞吐作用。蔗糖的液相胞饮作用不受任何一种负载形式的影响。比较了这些脂质负载细胞和未负载细胞对可溶性（甘露糖基化牛血清白蛋白）和颗粒性（酵母聚糖）配体的结合、摄取和降解。用氧化型LDL负载会降低两种配体的处理过程，而用乙酰化LDL负载则影响不大。用氧化型LDL（Ox-LDL）负载还会降低4℃时酵母聚糖的结合；Ox-LDL负载细胞和未负载细胞中配体的内化和降解反映了表面结合的程度。甘露糖基化牛血清白蛋白和酵母聚糖结合与摄取的变化并非由于活力或细胞数量的改变。酵母聚糖刺激细胞释放溶酶体β-N-乙酰-D-氨基葡萄糖苷酶。用Ox-LDL而非Ac-LDL负载会降低β-N-乙酰-D-氨基葡萄糖苷酶的分泌。与酵母聚糖孵育后，Ox-LDL负载细胞中该酶的细胞内水平升高。酵母聚糖摄取与β-N-乙酰-D-氨基葡萄糖苷酶分泌相关，但在无酵母聚糖时，每培养物中的酶活性升高幅度大于有酵母聚糖时。我们得出结论，在模型泡沫细胞中，尤其是那些负载Ox-LDL的细胞，膜运输受到了干扰。
