Transcriptional activation of the macrophage-colony stimulating factor gene by minimally modified LDL. Involvement of nuclear factor-kappa B.
Minimally modified LDL (MM-LDL), obtained by mild iron oxidation or prolonged storage at 4 degrees C, has been shown to induce the expression of macrophage-colony stimulating factor (M-CSF) in cultured aortic endothelial cells. To examine whether other cell types also respond to MM-LDL, we investigated its effect on the expression of M-CSF mRNA in mouse L-cells and human aortic smooth muscle cells. Both L-cells and human aortic smooth muscle cells showed increased levels of M-CSF mRNA in response to 10 to 200 micrograms/mL MM-LDL in a dose-dependent manner. This allowed us to use mouse L-cells as a model to study the mechanism involved in MM-LDL-mediated increase in M-CSF mRNA. Nuclear runon assays showed that M-CSF gene transcription was activated by MM-LDL. In the present study, we identified specific elements that conferred MM-LDL-mediated transcriptional activation of the human M-CSF gene. Chimeric constructs containing sequential deletions in the 5'-promoter region of the M-CSF gene linked to a reporter chloramphenicol acetyltransferase (CAT) gene were transfected into mouse L-cells. The human M-CSF promoter region extending upstream from the transcription start site to nucleotide -406 showed maximum induction of CAT activity by MM-LDL. Induction of CAT activity was drastically reduced, with a deletion plasmid lacking the promoter region -406 to -344. A functional nuclear factor (NF)-kappa B binding site present in this critical region was required for MM-LDL-mediated induction of CAT activity since an internal deletion construct lacking this element showed significant loss of transcriptional activation.(ABSTRACT TRUNCATED AT 250 WORDS)
Rajavashisth
T B
TB
Department of Medicine, Harbor-UCLA Medical Center, Torrance 90502-2064, USA.
Yamada
H
H
Mishra
N K
NK
D000818:Animals; D001483:Base Sequence; D006801:Humans; D007739:L Cells; D015227:Lipid Peroxidation; D008077:Lipoproteins, LDL / Q000378:metabolism / Q000494:pharmacology*; D016173:Macrophage Colony-Stimulating Factor / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D015533:Transcriptional Activation
D008077:Lipoproteins, LDL; D016328:NF-kappa B; D012333:RNA, Messenger; D016173:Macrophage Colony-Stimulating Factor