Laboratory of Biophysical Chemistry, Kobe Pharmaceutical University.
Laboratory of Functional Molecular Chemistry, Kobe Pharmaceutical University.
Biol Pharm Bull. 2019;42(8):1376-1383. doi: 10.1248/bpb.b19-00287.
High-density lipoprotein (HDL) particles that are formed in vivo adopt a disk-shaped structure, in which the periphery of the discoidal phospholipid bilayer is surrounded by apolipoprotein. Such discoidal nanoparticles can be reconstituted with certain apolipoproteins and phospholipids and are commonly called lipid nanodisks. Apolipoprotein E (apoE), one of the HDL constituent proteins, serves as a ligand for the low-density lipoprotein (LDL) receptor. Thus, it is considered that biocompatible delivery vehicles targeting LDL receptors could be prepared by incorporating apoE as the protein component of lipid nanodisks. To enhance targeting efficiency, we designed lipid nanodisks with a large number of ligands using a peptide with the LDL receptor-binding region of apoE combined with a high lipid affinity sequence (LpA peptide). In our study, the LpA peptide spontaneously formed discoidal complexes (LpA nanodisks) of approximately 10 nm in size, equivalent to native HDL. LpA peptides on nanodisks adopted highly α-helical structures, a competent conformation capable of interacting with LDL receptors. As anticipated, the uptake of LpA nanodisks into LDL receptor-expressing cells (HepG2) was higher than that of apoE nanodisks, suggesting an enhanced targeting efficiency via the enrichment of LDL receptor-binding regions on the particle. Biodistribution studies using In-labeled LpA nanodisks showed little splenic accumulation and prolonged retention in blood circulation, reflecting the biocompatibility of LpA nanodisks. High accumulation of In-labeled LpA nanodisks was observed in the liver as well as in implanted tumors, which abundantly express LDL receptors. Thus, LpA nanodisks are potential biocompatible delivery vehicles targeting LDL receptors.
高密度脂蛋白（HDL）颗粒在体内形成时采用盘状结构，其中盘状磷脂双层的外周被载脂蛋白包围。这种盘状纳米颗粒可以用某些载脂蛋白和磷脂重新构成，通常称为脂质纳米盘。载脂蛋白 E（apoE）是 HDL 组成蛋白之一，作为 LDL 受体的配体。因此，人们认为可以通过将 apoE 作为脂质纳米盘的蛋白质成分来制备靶向 LDL 受体的生物相容性递送载体。为了提高靶向效率，我们设计了具有大量配体的脂质纳米盘，使用载脂蛋白 E 的 LDL 受体结合区域与高脂质亲和力序列（LpA 肽）结合的肽作为蛋白质成分。在我们的研究中，LpA 肽自发形成大小约为 10nm 的盘状复合物（LpA 纳米盘），相当于天然 HDL。纳米盘上的 LpA 肽采用高度α-螺旋结构，是一种能够与 LDL 受体相互作用的有效构象。正如预期的那样，LpA 纳米盘进入 LDL 受体表达细胞（HepG2）的摄取量高于 apoE 纳米盘，表明通过在颗粒上富集 LDL 受体结合区域，靶向效率得到了提高。使用 In 标记的 LpA 纳米盘进行的生物分布研究表明，脾脏积累较少，血液循环中保留时间延长，反映了 LpA 纳米盘的生物相容性。在肝脏以及大量表达 LDL 受体的植入肿瘤中观察到 In 标记的 LpA 纳米盘的高积累。因此，LpA 纳米盘是潜在的生物相容性靶向 LDL 受体的递送载体。
