NLRP3 Inflammasome Expression Is Driven by NF-κB in Cultured Hepatocytes

Biochem Biophys Res Commun. 2015 Mar 13;458(3):700-706. doi: 10.1016/j.bbrc.2015.02.029. Epub 2015 Feb 14.

Abstract

The inflammasomes are cytoplasmic multiprotein complexes that are responsible for activation of inflammatory reactions. In principle, there are four individual inflammasome branches (NLRP1, NLRP3, NLRC4/NALP4, and AIM2) that mediate the cleavage and activation of Caspase-1 and IL-1β that in turn lead to a complex network of cellular reactions initiating local and systemic inflammatory reactions. We have recently shown that NLRP3 expression is virtually absent in primary cultured hepatocytes and that in vitro the stimulation of hepatocytes with lipopolysaccharides results in strong activation of NLRP3 expression. We here demonstrate that this activation can be blocked by the NF-κB activation inhibitor QNZ or by infection with an adenoviral expression vector constitutively expressing a superrepressor of NF-κB. We show that QNZ blocks NF-κB-dependent expression of TNF-α, IL-1β and NLRP3. Likewise, the superrepressor of NF-κB prevents expression of NLRP3 and significantly reduces expression of inflammatory marker genes in liver cells. In a primary murine hepatoma cells, the concomitant depletion of NEMO and Caspase-8 resulted in a significant suppression of NLRP3 expression after Lipopolysaccharide challenge. Moreover, we demonstrate that a 1.3-kbp fragment located in close proximity of the most upstream transcriptional start site of the human NLRP3 gene that harbours one putative octamer NF-κB binding site renders LPS sensitivity in reporter gene assay. We conclude that NF-κB signalling is a necessary prerequisite for proper activation of the NLRP3 inflammasome in primary hepatocytes.

Keywords: Inflammasome; Inflammation; Lipopolysaccharides; Liver; NF-κB signalling; QNZ.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / genetics*
  • Carrier Proteins / immunology
  • Caspase 8 / immunology
  • Cells, Cultured
  • Gene Expression Regulation / drug effects
  • Hepatocytes / drug effects
  • Hepatocytes / immunology*
  • Hepatocytes / metabolism
  • Humans
  • Inflammasomes / genetics*
  • Inflammasomes / immunology
  • Intracellular Signaling Peptides and Proteins / immunology
  • Lipopolysaccharides / immunology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / immunology*
  • NLR Family, Pyrin Domain-Containing 3 Protein

Substances

  • Carrier Proteins
  • Inflammasomes
  • Intracellular Signaling Peptides and Proteins
  • Lipopolysaccharides
  • NEMO protein, mouse
  • NF-kappa B
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • NLRP3 protein, human
  • Nlrp3 protein, mouse
  • Caspase 8