title: Involvement of lipid rafts in macrophage apoptosis induced by cationic liposomes.
abstract: We have demonstrated that protein kinase Cδ (PKCδ) could be involved in macrophage apoptosis induced by cationic liposomes composed of stearylamine (SA-liposomes), but the detailed mechanism of how SA-liposomes activate PKCδ has remained unclear. In this paper, we clarified whether lipid rafts are involved in the PKCδ activation induced by SA-liposomes. Co-localization of SA-liposomes and Cholera toxin B subunit (CBT), which specifically binds to ganglioside GM1 on lipid rafts, was found by microscopic observation. The incorporation of SA-liposomes into lipid rafts was clearly inhibited by the pretreatment of cells with an agent, 2,6-di-O-methyl-α-cyclodextrin (DM-α-CD) which disrupts lipid rafts. Activation of PKCδ and externalization of phosphatidylserine induced by SA-liposomes were also suppressed by DM-α-CD, which extracts sphingolipids and proteins from lipid rafts. Reactive oxygen species (ROS) generation, which could be involved in the macrophage apoptosis, was also inhibited by DM-α-CD. Furthermore, apoptosis induced by SA-liposomes was clearly inhibited when the cells were pre-treated with DM-α-CD, but not nystatin, a cholesterol-sequestering agent that disrupt lipid rafts. These findings suggest that sphingolipids in lipid rafts are involved in the activation of PKCδ which leads to apoptosis induced by cationic liposomes, SA-liposomes.
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Arisaka
authors.forename: Katsuki
authors.initials: K
authors.lastname: Takano
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Negishi
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Arima
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Aramaki
mesh_terms: D000588:Amines / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D008081:Liposomes / Q000737:chemistry* / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D051745:Protein Kinase C-delta / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000588:Amines; D008081:Liposomes; D017382:Reactive Oxygen Species; D051745:Protein Kinase C-delta; C009317:stearylamine