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

J.E. Ros, JD Schuetz, M Geuken, K Streetz, H Moshage, F Kuipers, MP Manns, PLM Jansen, C Trautwein, M Muller

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59 Citations (Scopus)

Abstract

The multidrug resistance protein Mdr1b in rats is upregulated 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 I kappaB to inhibit pathways downstream of the TNF receptor. Further, the proteasome inhibitor MG-132 was used, which prevents the breakdown of I kappaB, 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.

Original languageEnglish
Pages (from-to)1425-1431
Number of pages7
JournalHepatology
Volume33
Issue number6
Publication statusPublished - Jun-2001

Keywords

  • INTESTINAL EPITHELIAL-CELLS
  • P-GLYCOPROTEIN EXPRESSION
  • MULTIDRUG-RESISTANCE
  • GENE-EXPRESSION
  • UP-REGULATION
  • HEPATOCYTE CULTURES
  • INDUCED APOPTOSIS
  • SUPER-REPRESSOR
  • DOWN-REGULATION
  • MESSENGER-RNA

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