Enhanced DNA binding and activation of transcription factors NF-kappa B and AP-1 by acetaldehyde in HEPG2 cells.
Because transcription factors NF-kappaB and activator protein-1 (AP-1) are known to regulate gene expression, we have analyzed the role of acetaldehyde in the activation of NF-kappaB and AP-1 in HepG2 cells. Binding activity and transactivation of NF-kappaB and AP-1 were determined by gel retardation assays and transfection of a luciferase reporter construct controlled by kappaB and AP-1 binding sites, respectively. Acetaldehyde enhanced the DNA binding of NF-kappaB and AP-1 by 1 and 4 h, respectively, increasing the kappaB- and AP-1-dependent luciferase expression. Supershift assays revealed the presence of NF-kappaB heterodimers p65/p50 and p50/p52, whereas nuclear c-Jun levels correlated with the DNA binding of AP-1. The enhanced binding of NF-kappaB to DNA by acetaldehyde in intact cells was accompanied by the proteolytic degradation of IkappaB-alpha. However, the addition of acetaldehyde to cytostolic extracts from untreated Hep G2 cells did not affect the DNA binding of AP-1 but activated the NF-kappaB heterodimer p65/p50 in the absence of IkappaB-alpha degradation. Preincubation of HepG2 cells with protein kinase C inhibitors abolished the enhanced DNA binding of NF-kappaB and AP-1 caused by acetaldehyde. Hence, these findings uncover a previously unrecognized role for acetaldehyde in the activation of NF-kappaB and AP-1, which may be of relevance in the alcohol-induced liver disease.
Román
J
J
Liver Unit, Institut Malalties Digestives and Instituto de Investigaciones Biomedicas August Pi Suñer, Consejo Superior de Investigaciones Cientificas, Barcelona 08036, Spain.
Giménez
A
A
Lluis
J M
JM
Gassó
M
M
Rubio
M
M
Caballeria
J
J
Parés
A
A
Rodés
J
J
Fernández-Checa
J C
JC
D000079:Acetaldehyde / Q000494:pharmacology*; D001483:Base Sequence; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D016328:NF-kappa B; D018808:Transcription Factor AP-1; D004247:DNA; D011493:Protein Kinase C; D000079:Acetaldehyde