title: Structure, activity and uptake mechanism of siRNA-lipid nanoparticles with an asymmetric ionizable lipid.
abstract: Lipid nanoparticles (LNPs) represent the most advanced platform for the systemic delivery of siRNA. We have previously reported the discovery of novel ionizable lipids with asymmetric lipid tails, enabling potent gene-silencing activity in hepatocytes in vivo; however, the structure and delivery mechanism had not been elucidated. Here, we report the structure, activity and uptake mechanism of LNPs with an asymmetric ionizable lipid. Zeta potential and hemolytic activity of LNPs showed that LNPs were neutral at the pH of the blood compartment but become increasingly charged and fusogenic in the acidic endosomal compartment. (31)P NMR experiments indicated that the siRNA was less mobile inside particles, presumably because of an electrostatic interaction with an ionizable lipid. The role of Apolipoprotein E (apoE) was studied using recombinant human apoE both in vitro and in vivo. A comparative study in wild-type and apoE-deficient mice revealed that apoE significantly influenced the in vivo biodistribution of LNPs and enhanced the cellular uptake. Pretreatment of mice with siRNA targeting low-density lipoprotein receptor (LDLR) impaired gene-silencing of the following siRNA treatment, demonstrating that in vivo activity of LNPs is dependent on LDLR. Our studies on the detailed mechanism should lead to the creation of more sophisticated LNP-based RNAi therapeutics.
authors.affiliation: DDS Research Group, Formulation Research Laboratory, Pharmaceutical Science and Technology, Medicine Development Center, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan. Electronic address: y14-suzuki@hhc.eisai.co.jp.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: DDS Research Group, Formulation Research Laboratory, Pharmaceutical Science and Technology, Medicine Development Center, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishihara
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008055:Lipids / Q000737:chemistry* / Q000493:pharmacokinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008813:Mice, Inbred ICR; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014018:Tissue Distribution / Q000187:drug effects / Q000502:physiology
chemical_list: D008055:Lipids; D034741:RNA, Small Interfering; D011994:Recombinant Proteins
keywords: Drug delivery; Gene silencing; Lipid nanoparticles; Nanomedicines; siRNA