Induction of Mdr1b expression by tumor necrosis factor-alpha in rat liver cells is independent of p53 but requires NF-kappaB signaling

Hepatology. 2001 Jun;33(6):1425-31. doi: 10.1053/jhep.2001.24667.

Abstract

The multidrug resistance protein Mdr1b in rats is up-regulated during liver regeneration after partial hepatectomy or after endotoxin treatment. We hypothesize that up-regulation of Mdr1b in these models is TNF-alpha-dependent. The mechanism of Mdr1b activation by TNF-alpha is unknown as TNF-alpha can signal through various pathways, including NF-kappaB and p53, transcription factors for which binding sites in the Mdr1b promoter have been identified. We aimed to elucidate the mechanism of up-regulation of Mdr1b by TNF-alpha. We selectively used constructs expressing dominant negative Fas-associated death domain protein (FADD), TNF receptor associated factor-2 (TRAF2) or IkappaB to inhibit pathways downstream of the TNF receptor. Further, the proteasome inhibitor MG-132 was used, which prevents the breakdown of IkappaB. We show a critical role for NF-kappaB in activation of Mdr1b gene expression both in primary rat hepatocytes and in rat hepatoma H-4-II-E cells. Because p53 is up-regulated by TNF-alpha in an NF-kappaB-dependent manner and the Mdr1b promoter contains a p53 binding site, we used liver cells expressing a dominant negative p53 to show that TNF-alpha up-regulation of Mdr1b is independent of functional p53. Using transient transfection assays, we show that Mdr1b up-regulation correlates with activation of the promoter. Mutation of the NF-kappaB site in the Mdr1b promoter prevents its induction by TNF-alpha. In conclusion our results show that activation of the rat Mdr1b gene by TNF-alpha is a result of NF-kappaB signaling and independent of p53.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / genetics*
  • Animals
  • Binding Sites / physiology
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / pathology
  • Gene Expression Regulation / physiology*
  • Hepatocytes / physiology
  • I-kappa B Proteins / pharmacology
  • Liver / physiology*
  • Liver Neoplasms / genetics
  • Liver Neoplasms / pathology
  • NF-kappa B / physiology*
  • Promoter Regions, Genetic / physiology
  • Rats
  • Signal Transduction / physiology*
  • Transfection
  • Tumor Cells, Cultured
  • Tumor Necrosis Factor-alpha / physiology*
  • Tumor Suppressor Protein p53 / physiology*

Substances

  • ATP Binding Cassette Transporter, Subfamily B
  • I-kappa B Proteins
  • NF-kappa B
  • P-glycoprotein 2
  • Tumor Necrosis Factor-alpha
  • Tumor Suppressor Protein p53