Tumor necrosis factor alpha down-regulates expression of the alpha1(I) collagen gene in rat hepatic stellate cells through a p20C/EBPbeta- and C/EBPdelta-dependent mechanism.
Tumor necrosis factor alpha (TNF-alpha) is one of the key cytokines of the acute phase response and of many inflammatory processes. This cytokine has several antifibrogenic actions and down-regulates the expression of the type I collagen genes and induces the expression of metalloproteinases. Because TNF-alpha directly antagonizes some fibrogenic actions of transforming growth factor beta(1) (TGF-beta(1)), we considered it important to map the cis-acting regulatory element of the alpha1(I) collagen (col1a1) promoter involved in TNF-alpha responsiveness in hepatic stellate cells (HSC), to investigate the transcription factors that bind to it, and to establish possible mechanisms by which TNF-alpha down-regulates its expression. In this article, we show the presence of a functional TNF-alpha-responsive element (TaRE) in the -378 to -345 region of the col1a1 promoter. This element colocalizes with a previously reported TGF-beta(1)-responsive element. We further demonstrate that TNF-alpha induces nuclear translocation and binding of transcriptional complexes containing p20C/EBPbeta, p35C/EBPbeta, and C/EBPdelta to this sequence of the promoter. Transient overexpression of C/EBPdelta or p20C/EBPbeta, the natural dominant negative form of C/EBPbeta in HSC, down-regulated activity of a CAT reporter vector driven by -412 to +110 of the col1a1 promoter. Taken together, these data suggest that the -378 to -340 region of the col1a1 promoter is the site of convergence of different stimuli that ultimately modulate col1a1 gene transcription.
Iraburu
M J
MJ
Division of Gastroenterology, Hepatology, and Nutrition, Marion Bessin Liver Research Center, and Departments of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Domínguez-Rosales
J A
JA
Fontana
L
L
Auster
A
A
García-Trevijano
E R
ER
Covarrubias-Pinedo
A
A
Rivas-Estilla
A M
AM
Greenwel
P
P
Rojkind
M
M
D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins; D002460:Cell Line; D003094:Collagen / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000502:physiology*; D015536:Down-Regulation; D005786:Gene Expression Regulation / Q000187:drug effects*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D009687:Nuclear Proteins / Q000502:physiology*; D011347:Procollagen / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020218:Response Elements; D014157:Transcription Factors / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011347:Procollagen; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D003094:Collagen