Takano Shuhei, Aramaki Yukihiko, Tsuchiya Seishi
School of Pharmacy, Tokyo University of Pharmacy and Life Science, Tokyo 192-0392, Japan.
Pharm Res. 2003 Jul;20(7):962-8. doi: 10.1023/a:1024441702398.
Cationic liposomes are expected to be useful as nonviral vectors for gene delivery. Cationic liposomes showed cytotoxicity, and we proposed that the cytotoxicity is through apoptosis. In this study, we examined the effects of liposomal properties, such as liposomal charge, size, membrane fluidity, and PEG coating, on the induction of apoptosis in the macrophage-like cell line RAW264.7.
RAW264.7 cells were treated with liposomes, and the induction of apoptosis was evaluated by monitoring the changes in DNA content by flow cytometry. The association of liposomes with cells and the generation of reactive oxygen species (ROS) were also measured by flow cytometry.
The induction of apoptosis of RAW264.7 cells was dependent on the concentrations of stearylamine or cholesterol, a component of cationic liposomes. A significant correlation was observed between the degree of apoptosis and association of cationic liposomes with the cells. Coating the liposomal surface with polyethylene glycol (PEG) decreased the association of cationic liposomes with RAW264.7 cells and reduced the induction of apoptosis. Liposomal size also affected the induction of apoptosis, and larger liposomes showed a higher degree of apoptosis induction. Furthermore, ROS, which were required for the induction of apoptosis by cationic liposomes, were generated in a cholesterol content-dependent manner, and ROS generation was also decreased by PEG coating as the association and the induction of apoptosis were reduced.
The degree of apoptosis is related to the extent of association of cationic liposomes with cells and is related to the generation of ROS.
阳离子脂质体有望成为基因递送的非病毒载体。阳离子脂质体具有细胞毒性，我们推测其细胞毒性是通过凋亡实现的。在本研究中，我们检测了脂质体特性，如脂质体电荷、大小、膜流动性和聚乙二醇（PEG）包被，对巨噬细胞样细胞系RAW264.7凋亡诱导的影响。
用脂质体处理RAW264.7细胞，通过流式细胞术监测DNA含量变化来评估凋亡诱导情况。还通过流式细胞术检测脂质体与细胞的结合以及活性氧（ROS）的产生。
RAW264.7细胞的凋亡诱导取决于阳离子脂质体成分硬脂胺或胆固醇的浓度。凋亡程度与阳离子脂质体和细胞的结合之间存在显著相关性。用聚乙二醇（PEG）包被脂质体表面可降低阳离子脂质体与RAW264.7细胞的结合，并减少凋亡诱导。脂质体大小也影响凋亡诱导，较大的脂质体显示出更高程度的凋亡诱导。此外，阳离子脂质体诱导凋亡所需的ROS以胆固醇含量依赖的方式产生，并且随着结合和凋亡诱导的减少，PEG包被也降低了ROS的产生。
凋亡程度与阳离子脂质体和细胞的结合程度相关，且与ROS的产生有关。
