title: Cytotoxicity of lipid-free apolipoprotein B.
abstract: To investigate the effect of apolipoprotein B (apoB) on cell viability, we used lipid-free apoB as a model for denatured apoB. Lipid-free apoB had cytotoxicity to J774 macrophages, CHO cells and HepG2 cells, whereas apoB bound to low density lipoprotein (LDL) and lipid-free apolipoprotein A-I had no effect on cell viability. Lipid-free apoB induced apoptosis in J774 macrophages assessed by caspase-3 activation and annexin V binding. LDL receptor, heparan sulfate proteoglycans, and class A scavenger receptor were involved in the binding/uptake of lipid-free apoB, but lipid-free apoB binding/uptake by the cells did not correlate with cytotoxicity. Lipid-free apoB disrupted the lipid bilayer of large unilamellar vesicles containing calcein. We evaluated the interaction between apoB and cellular membrane by monitoring the change in intracellular Ca(2+) concentration using Fura-2, and found that lipid-free apoB rapidly disrupted the cellular membrane in the absence or presence of the inhibitors for cellular binding/uptake mediated by the receptors. Therefore, it is suggested that lipid-free apoB induces cell death by disturbance of the plasma membrane. In addition to other lipid component in modified LDL, apoB itself has an ability to induce apoptosis and plays a crucial role in the development of atherosclerotic lesions.
authors.affiliation: Laboratory of Pharmaceutical Technology, Kobe Pharmaceutical University, Motoyamakita-machi, Higashinada-ku, Kobe 658-8558, Japan.
authors.forename: Shin-ya
authors.initials: SY
authors.lastname: Morita
authors.forename: Yuko
authors.initials: Y
authors.lastname: Deharu
authors.forename: Eriko
authors.initials: E
authors.lastname: Takata
authors.forename: Minoru
authors.initials: M
authors.lastname: Nakano
authors.forename: Tetsurou
authors.initials: T
authors.lastname: Handa
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D000906:Antibodies / Q000494:pharmacology; D001055:Apolipoproteins B / Q000737:chemistry / Q000494:pharmacology*; D020013:Calcium Signaling / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002942:Circular Dichroism; D004789:Enzyme Activation / Q000187:drug effects; D005452:Fluoresceins / Q000378:metabolism; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D017433:Protein Structure, Secondary; D051117:Scavenger Receptors, Class A / Q000378:metabolism
chemical_list: D017304:Annexin A5; D000906:Antibodies; D001055:Apolipoproteins B; D005452:Fluoresceins; D019812:Heparan Sulfate Proteoglycans; D051117:Scavenger Receptors, Class A; D006493:Heparin; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; C007740:fluorexon