Tumor necrosis factor-α upregulates 11β-hydroxysteroid dehydrogenase type 1 expression by CCAAT/enhancer binding protein-β in HepG2 cells

Abstract

The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the conversion of inactive to active glucocorticoids. 11β-HSD1 plays a crucial role in the pathogenesis of obesity and controls glucocorticoid actions in inflammation. Several studies have demonstrated that TNF-α increases 11β-HSD1 mRNA and activity in various cell models. Here, we demonstrate that mRNA and activity of 11β-HSD1 is increased in liver tissue from transgenic mice overexpressing TNF-α, indicating that this effect also occurs in vivo. To dissect the molecular mechanism of this increase, we investigated basal and TNF-α-induced transcription of the 11β-HSD1 gene ( HSD11B1) in HepG2 cells. We found that TNF-α acts via p38 MAPK pathway. Transient transfections with variable lengths of human HSD11B1 promoter revealed highest activity with or without TNF-α in the proximal promoter region (−180 to +74). Cotransfection with human CCAAT/enhancer binding protein-α (C/EBPα) and C/EBPβ-LAP expression vectors activated the HSD11B1 promoter with the strongest effect within the same region. Gel shift and RNA interference assays revealed the involvement of mainly C/EBPα, but also C/EBPβ, in basal and only of C/EBPβ in the TNF-α-induced HSD11B1 expression. Chromatin immunoprecipitation assay confirmed in vivo the increased abundance of C/EBPβ on the proximal HSD11B1 promoter upon TNF-α treatment. In conclusion, C/EBPα and C/EBPβ control basal transcription, and TNF-α upregulates 11β-HSD1, most likely by p38 MAPK-mediated increased binding of C/EBPβ to the human HSD11B1 promoter. To our knowledge, this is the first study showing involvement of p38 MAPK in the TNF-α-mediated 11β-HSD1 regulation, and that TNF-α stimulates enzyme activity in vivo.