Shimizu K, Maitani Y, Takahashi N, Takayama K, Nagai T
Department of Pharmaceutics, Hoshi University, Tokyo, Japan.
Biol Pharm Bull. 1998 Aug;21(8):818-22. doi: 10.1248/bpb.21.818.
Dipalmitoylphosphatidylcholine (DPPC) and cholesterol (Ch) liposomes containing a soybean-derived sterylglucoside mixture (SG) (SG-liposomes) are effective for targeting hepatocytes in mice. We investigated uptake of SG-liposomes to hepatocytes compared with that via the galactose receptor. The association of SG-liposomes entrapping calcein was examined at 4 degrees C or 37 degrees C, changing incubation time and the SG concentration of the liposomes, and using the inhibitor on the galactose receptor in rat primary cultured hepatocytes. The amount of liposomes recovered with hepatocytes was determined by measuring the concentration of calcein and imaged with confocal laser scanning microscopy in the cultured cells. The association of SG-liposomes at 4 degrees C was significantly decreased compared with that at 37 degrees C as that of liposomes containing lactosylceramide (LC) (LC-liposomes) that were already known to be taken up by hepatocytes via the asialoglycoprotein receptor. While the association of SG-liposomes at both 4 degrees C and 37 degrees C increased with the increase of incubation time, the association of SG-liposomes at 37 degrees C was almost saturated after 1 h. The association of SG-liposomes pretreated with concanavalin A was significantly decreased (to about 40% of that without pretreatment at 37 degrees C) and was at the same level as the association of SG-liposomes and non-SG-liposomes at 4 degrees C. The association of the SG-liposomes by hepatocytes incubated for I h at 37 degrees C was almost saturated at about 2.0 nmol SG/mg protein. The association of the SG-liposomes with hepatocytes was not inhibited in the presence of LC-liposomes. The affinity of the galactose residue for hepatocytes appeared to be similar to that of the glucose residue in the liposomes, because the amount of sugar residue and the association of SG-liposomes and LC-liposomes were almost the same values. These results suggest that SG-liposomes may be associated with hepatocytes not by a galactose receptor-mediated endocytosis.
含有大豆衍生的甾醇糖苷混合物（SG）的二棕榈酰磷脂酰胆碱（DPPC）和胆固醇（Ch）脂质体（SG-脂质体）对靶向小鼠肝细胞有效。我们研究了SG-脂质体与通过半乳糖受体摄取到肝细胞的情况相比的摄取情况。在4℃或37℃下，改变孵育时间和脂质体的SG浓度，并在大鼠原代培养肝细胞中使用半乳糖受体抑制剂，检测包载钙黄绿素的SG-脂质体的结合情况。通过测量钙黄绿素的浓度来确定肝细胞回收的脂质体数量，并在培养细胞中用共聚焦激光扫描显微镜成像。与已知通过去唾液酸糖蛋白受体被肝细胞摄取的含有乳糖神经酰胺（LC）的脂质体（LC-脂质体）相比，4℃时SG-脂质体的结合显著减少。虽然4℃和37℃时SG-脂质体的结合都随孵育时间的增加而增加，但37℃时SG-脂质体的结合在1小时后几乎饱和。用伴刀豆球蛋白A预处理的SG-脂质体的结合显著减少（在37℃下降至未预处理时的约40%），且与4℃时SG-脂质体和非SG-脂质体的结合水平相同。在37℃下孵育1小时的肝细胞对SG-脂质体的结合在约2.0 nmol SG/毫克蛋白质时几乎饱和。在存在LC-脂质体的情况下，SG-脂质体与肝细胞的结合未受抑制。半乳糖残基对肝细胞的亲和力似乎与脂质体中葡萄糖残基的亲和力相似，因为糖残基的量以及SG-脂质体和LC-脂质体的结合几乎是相同的值。这些结果表明，SG-脂质体可能不是通过半乳糖受体介导的内吞作用与肝细胞结合。
