Schouten D, van der Kooij M, Muller J, Pieters M N, Bijsterbosch M K, van Berkel T J
Division of Biopharmaceutics, University of Leiden, The Netherlands.
Mol Pharmacol. 1993 Aug;44(2):486-92.
The possibility was explored of synthesizing, from commercially available lipids, high density lipoprotein (HDL)-like particles (neo-HDL) with the same physico-chemical and biological properties as native HDL. A preparation method involving egg yolk phosphatidylcholine, cholesterol, and apoproteins from HDL led to the formation of particles with a composition, size, electrophoretic mobility, and density similar to those of discoidal HDL. In vitro experiments with isolated parenchymal liver cells showed that unlabeled HDL and neo-HDL competed for the same high affinity binding sites as did radiolabeled neo-HDL, whereas an excess of unlabeled low density lipoprotein was ineffective. In vivo experiments with radio-labeled neo-HDL indicated that neo-HDL showed a slow decay upon injection into rats, whereas the liver uptake did not exceed > 10% of the injected dose. The small additional liver uptake of radioactivity from neo-HDL, compared with HDL, was due to enhanced uptake by endothelial and Kupffer cells. Lactosylation of neo-HDL led to a markedly increased decay rate and a rapid uptake by rat liver (80% in 10 min). Parenchymal cells accounted for > 90% of the total liver uptake of radiolabeled lactosylated neo-HDL. Because the liver uptake of lactosylated 125I-neo-HDL could be blocked by preinjection of N-acetylgalactosamine, we conclude that the asialoglycoprotein receptor, which is specifically localized on parenchymal liver cells, is responsible for the avid liver uptake. With a fibroblast cell line transfected with the human asialoglycoprotein receptor, it was found that lactosylated neo-HDL binds with high affinity (Kd, 40 nM), in a galactose-specific way. It can be concluded that, with commercially available lipid components, HDL-like particles (neo-HDL) with virtually the same characteristics as found for native apolipoprotein E-free HDL can be reconstituted. Lactosylated neo-HDL, which is rapidly taken up by galactose-specific receptors on parenchymal liver cells, might be used to transport antiviral drugs specifically to parenchymal liver cells.
探讨了用市售脂质合成具有与天然高密度脂蛋白（HDL）相同物理化学和生物学特性的高密度脂蛋白样颗粒（新HDL）的可能性。一种涉及蛋黄磷脂酰胆碱、胆固醇和HDL载脂蛋白的制备方法导致形成了组成、大小、电泳迁移率和密度与盘状HDL相似的颗粒。对分离的肝实质细胞进行的体外实验表明，未标记的HDL和新HDL与放射性标记的新HDL竞争相同的高亲和力结合位点，而过量的未标记低密度脂蛋白则无效。用放射性标记的新HDL进行的体内实验表明，新HDL注射到大鼠体内后显示出缓慢的衰减，而肝脏摄取量不超过注射剂量的10%。与HDL相比，新HDL放射性的少量额外肝脏摄取是由于内皮细胞和库普弗细胞摄取增加所致。新HDL的乳糖基化导致衰减率显著增加，大鼠肝脏快速摄取（10分钟内摄取80%）。实质细胞占放射性标记的乳糖基化新HDL肝脏总摄取量的90%以上。由于预先注射N-乙酰半乳糖胺可阻断乳糖基化125I-新HDL的肝脏摄取，我们得出结论，特异性定位于肝实质细胞的去唾液酸糖蛋白受体是肝脏大量摄取的原因。在用转染了人去唾液酸糖蛋白受体的成纤维细胞系进行的实验中发现，乳糖基化新HDL以半乳糖特异性方式高亲和力结合（解离常数，40 nM）。可以得出结论，利用市售脂质成分，可以重构出与天然无载脂蛋白E的HDL几乎具有相同特征的HDL样颗粒（新HDL）。乳糖基化新HDL可被肝实质细胞上的半乳糖特异性受体快速摄取，可用于将抗病毒药物特异性转运至肝实质细胞。
