Isolation of macrophage-like cell mutants resistant to the cytotoxic effect of oxidized low density lipoprotein.
A high concentration of oxidized low density lipoprotein (Ox-LDL) showed a cytotoxic effect on mouse macrophage-derived J774 cells. Mutant cells were selected from these cells that were resistant to the cytotoxic effect of Ox-LDL. One mutant form, named JO21b cells, was characterized in the present study. In spite of a marked resistance to the cytotoxic effect of Ox-LDL, JO21b cells were apparently as sensitive as the parent cells not only to toxic moieties of Ox-LDL, such as 7-ketocholesterol and lysophosphatidylcholine, but also to t-butyl hydroperoxide, an artificial lipid hydroperoxide analog. However, the cellular association of 125I-labeled Ox-LDL with, and subsequent endocytic degradation by JO21b cells was reduced by 70-80% compared with J774 cells. Similarly, accumulation of cholesteryl esters in JO21b cell by Ox-LDL was also reduced by 70%. Northern blot analyses of type I and type II macrophage scavenger receptors (type I and type II MSR) demonstrated that the mRNA levels of JO21b cells were lower than those of J774 cells. Moreover, peritoneal macrophages obtained from MSR-knockout mice showed a higher resistance to the cytotoxic effect of Ox-LDL than those from their wild-type littermates. Our results suggest, therefore, that macrophage scavenger receptor-mediated endocytic uptake of oxidized low density lipoproteins (Ox-LDL) may play an enhancing role in Ox-LDL cytotoxicity to macrophages or macrophage-derived cells.
Hakamata
H
H
Department of Biochemistry, Kumamoto University School of Medicine, Japan.
Miyazaki
A
A
Sakai
M
M
Matsuda
H
H
Suzuki
H
H
Kodama
T
T
Horiuchi
S
S
D000818:Animals; D015152:Blotting, Northern; D016923:Cell Death; D002460:Cell Line; D004351:Drug Resistance; D004705:Endocytosis; D007653:Ketocholesterols / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects*; D017737:Macrophages, Peritoneal / Q000187:drug effects; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010545:Peroxides / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011971:Receptors, Immunologic / Q000235:genetics; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D020122:tert-Butylhydroperoxide
D007653:Ketocholesterols; D008077:Lipoproteins, LDL; D008244:Lysophosphatidylcholines; D008565:Membrane Proteins; D010545:Peroxides; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C032629:acetyl-LDL; C099252:oxidized low density lipoprotein; D020122:tert-Butylhydroperoxide; C003001:7-ketocholesterol