Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Sapporo, Hokkaido 060-0812, Japan.
J Control Release. 2011 Aug 25;154(1):77-83. doi: 10.1016/j.jconrel.2011.05.012. Epub 2011 May 17.
The targeted delivery of genes to endothelial cells is a potential strategy for curing certain types of disorders including cancer, inflammation and obesity. We previously reported that a liposome (IRQ-LP) modified with the IRQ peptide (IRQRRRR) was taken up by cells via a unique pathway, namely caveolar endocytosis, a cellular uptake pathway that is involved in the blood-to-tissue uptake of macromolecules in vascular endothelial cells. In the present study, we initally investigated the effect of IRQ peptide-modification on the biodistribution of poly(ethyleneglycol) (PEG)-coated liposomes (PEG-LP) after i.v. administration. The IRQ peptide-modified PEG-LP (IRQ-PEG-LP), as well as the PEG-LP were found to be mainly accumulated in the liver. Nevertheless, the fold increase in the lung accumulation of IRQ-PEG-LP, compared to the PEG-LP (approximately 20-folds) was substantially higher than other tissues (<5-fold). Thus, IRQ could function as a target ligand for lungs. We then used the IRQ peptide as a model for a ligand for targeting normal tissue endothelial cells, and then applied it to a gene delivery system. We previously developed a multifunctional envelope-type nano device (MEND), in which plasmid DNA is condensed using a polycation to form a core particle that is encapsulated in a lipid envelope. We modified the IRQ-modified PEG to the MEND (IRQ-PEG-MEND) and marker gene expression was evaluated after i.v. administration. However the transgene expression of the IRQ-PEG-MEND in lungs was low. This is most likely due to the inhibitory effect of the PEG spacer on intracellular trafficking (especially endosomal escape) of the IRQ-PEG-MEND. To overcome the dilemma associated with PEGylation, we improved the MEND system from the point of view of PEG length, lipid chain of the PEG derivative, the polycation and cationic lipid. As a result, transgene expression in lungs was enhanced in stepwise manner, and was finally improved by 5 orders of magnitude compared with the original IRQ-PEG-MEND. Overcoming the dilemma of PEGylation is critical issue for in vivo applications of gene delivery targeting endothelial cells.
靶向递送至内皮细胞的基因是治疗某些类型疾病的一种潜在策略，这些疾病包括癌症、炎症和肥胖症。我们之前曾报道，一种经过 IRQ 肽（IRQRRRR）修饰的脂质体（IRQ-LP）可通过一种独特的途径，即胞饮作用，被细胞摄取，胞饮作用是一种细胞摄取途径，参与血管内皮细胞中大分子从血液到组织的摄取。在本研究中，我们首先研究了 IRQ 肽修饰对静脉注射后聚乙二醇（PEG）包被脂质体（PEG-LP）的生物分布的影响。IRQ 肽修饰的 PEG-LP（IRQ-PEG-LP）与 PEG-LP 一样，主要积聚在肝脏中。然而，与 PEG-LP 相比（约 20 倍），IRQ-PEG-LP 在肺部的积聚增加了约 20 倍，而其他组织的增加幅度则小于 5 倍。因此，IRQ 可作为肺部的靶标配体。然后，我们将 IRQ 肽用作靶向正常组织内皮细胞的配体模型，并将其应用于基因传递系统。我们之前开发了一种多功能包膜型纳米装置（MEND），其中使用聚阳离子使质粒 DNA 浓缩形成核心颗粒，然后将其包裹在脂质包膜中。我们将 IRQ 修饰的 PEG 修饰到 MEND（IRQ-PEG-MEND）上，并在静脉给药后评估标记基因的表达。然而，IRQ-PEG-MEND 在肺部的转基因表达水平较低。这很可能是由于 PEG 间隔物对内质网逃逸等细胞内运输的抑制作用。为了克服与 PEG 化相关的困境，我们从 PEG 长度、PEG 衍生物的脂质链、聚阳离子和阳离子脂质的角度改进了 MEND 系统。结果，肺部的转基因表达呈逐步增强，最终比原始的 IRQ-PEG-MEND 提高了 5 个数量级。克服 PEG 化的困境对于靶向内皮细胞的基因传递的体内应用是一个关键问题。
