Induction of low density lipoprotein receptor and a transcription factor SP-1 by tumor necrosis factor in human microvascular endothelial cells.
We have previously reported that tumor necrosis factor-alpha (TNF-alpha) enhances expression of interleukin-6, collagenase, plasminogen activator inhibitor-1, and basic fibroblast growth factor genes in human omental microvascular endothelial (HOME) cells in culture. In this study, we found that treatment of HOME cells with TNF-alpha or interleukin-1 (IL-1) caused enhanced expression of low density lipoprotein (LDL) receptor. A few-fold increase in both LDL binding activity and the receptor mRNA levels was observed when HOME cells were treated with either TNF-alpha or IL-1. Northern blot analysis showed that cellular expression of LDL receptor gene was significantly increased 12-24 h after exposure to TNF-alpha. No significant changes in the life-span of LDL receptor mRNA were observed in untreated and TNF-alpha-treated cells. Scatchard analysis showed an increased receptor number for LDL in TNF-alpha-treated cells. Parallel to increased LDL binding activity, internalization and degradation of LDL were also increased in HOME cells treated with TNF-alpha or IL-1. TNF-alpha-induced enhancement of LDL receptor gene expression was not observed when cycloheximide was present. Cellular mRNA level of SP-1 gene was increased about 3-4-fold at 12 h after treatment with TNF-alpha. Nuclear run-on assays showed increased transcription of LDL receptor gene as well as SP-1 gene by TNF-alpha. Gel retardation assay with the SP-1 consensus fragment showed that SP-1 binding activity was increased about 4-5-fold 12-24 h after treatment with TNF-alpha. NF-kB binding activity was also dramatically increased, but there is no NF-kB motif on the promoter for LDL receptor gene. The induction of LDL receptor by TNF might be mediated through a transcription factor, SP-1.
Hamanaka
R
R
Department of Biochemistry, Oita Medical University, Japan.
Kohno
K
K
Seguchi
T
T
Okamura
K
K
Morimoto
A
A
Ono
M
M
Ogata
J
J
Kuwano
M
M
D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D011973:Receptors, LDL / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D011973:Receptors, LDL; D016329:Sp1 Transcription Factor; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide