The DNA Binding Protein BTEB Mediates Acetaldehyde-Induced, Jun N-Terminal Kinase-Dependent αI(I) Collagen Gene Expression in Rat Hepatic Stellate Cells

Abstract

Alcohol-induced cirrhosis results partially from the excessive production of collagen matrix proteins, which, predominantly ␣I(I) collagen, are produced and secreted by activated hepatic stellate cells (HSC). The accumulation of ␣I(I) collagen in HSC during cirrhosis is largely due to an increase in ␣I(I) collagen gene expression. Acetaldehyde, the major active metabolite of alcohol, is known to stimulate ␣I(I) collagen production in HSC. However, the mechanisms responsible for it remain unknown. The aim of this study was to elucidate the mechanisms by which ␣I(I) collagen gene expression is induced by acetaldehyde in rat HSC. In the present study, the acetaldehyde response element was located in a distal GC box, previously described as the UV response element, in the promoter of the ␣I(I) collagen gene (؊1484 to ؊1476). The GC box was predominantly bound by the DNA binding transcription factor BTEB (basic transcription element binding protein), expression of which was acetaldehyde and UV inducible. Blocking BTEB protein expression significantly reduced the steady-state levels of the acetaldehyde-induced ␣I(I) collagen mRNA, suggesting that BTEB is required for this gene expression. Further studies found that acetaldehyde activated Jun N-terminal kinase (JNK) 1 and 2 and activator protein 1 (AP-1) transactivating activity. Inhibition of JNK activation resulted in the reduction of the acetaldehyde-induced BTEB protein abundance and ␣I(I) collagen mRNA levels, indicating that the expression of both genes is JNK dependent in HSC. Taken together, these studies demonstrate that BTEB mediates acetaldehyde-induced, JNK-dependent ␣I(I) collagen gene expression in HSC.

Pathogenesis of alcoholic liver disease: Role of oxidative metabolism

“…In human HSCs, acetaldehyde directly induces the transcription of the α1(I) and α2(I) procollagen genes by a PKC-dependent pathway, which is involved in rapid activation of activator protein (AP)-1 transcription factors [111] (Figure 3). In human HSCs, PKC phosphorylates p70s6k by a mechanism that involves extracellular signal-regulated kinase (ERK)1/2 and PI3K, and all these pathways lead to collagen α2(I) gene expression [112] . Both collagen α1(I) and α2(I) promoters have an acetaldehyde-responsive element (AcRE) that includes binding sites for different transcription factors including AP-1 and specificity protein (SP)-1.…”

Interspecies comparison of neuroglobin, cytoglobin and myoglobin: Sequence evolution and candidate regulatory elements

“…Many of these sites are conserved in position and sequence in the human and mouse sequence. From the collection of transcription factors and binding sites thought to be involved in the regulation of gene expression in activated hepatic stellate cells (Eng and Friedman, 2001), only the multiple conserved GC boxes as potential binding sites for transcription factor Sp1, for NFÎB (Rippe et al, 1999) and for Kruppel-like zinc finger proteins (Chen and Davis, 2000) are notable.…”

Activation of peroxisome proliferator-activated receptor-γ by curcumin blocks the signaling pathways for PDGF and EGF in hepatic stellate cells

“…23 Proteins were separated by SDS-PAGE with 10% of resolving gel and transferred to a PVDF membrane. The target proteins were respectively recognized by primary antibodies against phosphorylated types of PDGF-bR, EGFR, ERK1/2, or JNK1/2 and the corresponding non-phosphorylated proteins, and subsequently detected by horseradish peroxidase-conjugated secondary antibodies (Santa Cruz Biotechnology, Santa Cruz, CA, USA).…”

“…23 Primary cells were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with 20% fetal bovine serum (FBS). The passaged cells were grown in DMEM with 10% of FBS.…”