Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Int J Pharm. 2010 Feb 15;386(1-2):122-30. doi: 10.1016/j.ijpharm.2009.11.005. Epub 2009 Nov 13.
Octaarginine (R8)-modified liposomes have been used to deliver therapeutic substances into cells owing to the efficient cellular uptake via macropinocytosis. Recent analyses revealed that R8-modified liposomes are mainly taken up via macropinocytosis, and escape from endosomes efficiently to avoid lysosomal degradation in non-polarized NIH-3T3 cells. In the present study, we evaluated the intracellular fate of R8-modified liposomes in polarized MDCK cells, comparing their trafficking with that of conventional cationic liposomes by confocal laser scanning microscopy (CLSM). In contrast to what occurs in NIH-3T3 cells, R8-modified liposomes are internalized by MDCK cells equally well via clathrin-mediated endocytosis and macropinocytosis. The most salient characteristic in subsequent intracellular trafficking in MDCK cells is that R8-modified liposomes become trapped in the endosomal compartment and subsequently, a portion of them colocalizes with the Golgi apparatus. Similar colocalization with the Golgi apparatus was observed for octalysine (K8)-modified liposomes. In contrast, cationic liposomes were found to colocalize predominantly with lysosomes stained with lysotracker. Collectively, in polarized MDCK cells, cationic peptide-modified liposomes may be subjected to a different sorting pathway from that used for liposomes composed of cationic lipids.
八聚精氨酸(R8)修饰的脂质体由于通过巨胞饮作用有效地摄取细胞内的治疗物质而被用于将治疗物质递送到细胞内。最近的分析表明,R8 修饰的脂质体主要通过巨胞饮作用被摄取,并有效地从内涵体中逃逸以避免在非极化 NIH-3T3 细胞中的溶酶体降解。在本研究中,我们通过共聚焦激光扫描显微镜(CLSM)评估了 R8 修饰的脂质体在极化的 MDCK 细胞中的细胞内命运,比较了它们与常规阳离子脂质体的转运。与在 NIH-3T3 细胞中发生的情况相反,R8 修饰的脂质体通过网格蛋白介导的内吞作用和巨胞饮作用同样被 MDCK 细胞内化。在随后的细胞内转运中最显著的特征是 R8 修饰的脂质体被困在内体区室中,随后一部分与高尔基体共定位。类似的与高尔基体的共定位也观察到了八赖氨酸(K8)修饰的脂质体。相比之下,阳离子脂质体被发现与用溶酶体追踪剂染色的溶酶体主要共定位。总的来说,在极化的 MDCK 细胞中,阳离子肽修饰的脂质体可能经历不同于由阳离子脂质组成的脂质体的不同分选途径。