Inhibition of Extracellular Calcium Influx Results in Enhanced IL-12 Production in LPS-Treated Murine Macrophages by Downregulation of the CaMKKβ-AMPK-SIRT1 Signaling Pathway

Mediators Inflamm. 2016:2016:6152713. doi: 10.1155/2016/6152713. Epub 2016 May 30.

Abstract

Activated macrophages are the primary sources of IL-12, a key cytokine bridging innate and adaptive immunity. However, macrophages produce low amounts of IL-12 upon stimulation and the underlying regulatory mechanism remains unclear. In this study, we found a new calcium-dependent mechanism that controlled IL-12 production in LPS-treated murine macrophages. First, LPS was demonstrated to induce extracellular calcium entry in murine peritoneal macrophages and inhibition of calcium influx resulted in marked enhancement in IL-12 production. Then, withdrawal of extracellular calcium was found to suppress CaMKKβ and AMPK activation triggered by LPS while chemical inhibition or genetic knockdown of these two kinases augmented LPS induced IL-12 production. AMPK activation increased the NAD(+)/NADH ratio and activated Sirtuin 1 (SIRT1), a NAD(+)-dependent deacetylating enzyme and negative regulator of inflammation. Chemical inhibitor or siRNA of SIRT1 enhanced IL-12 release while its agonist suppressed IL-12 production. Finally, it was found that SIRT1 selectively affected the transcriptional activity of NF-κB which thereby inhibited IL-12 production. Overall, our study demonstrates a new role of transmembrane calcium mobilization in immunity modulation such that inhibition of calcium influx leads to impaired activation of CaMKKβ-AMPK-SIRT1 signaling pathway which lifts restriction on NF-κB activation and results in enhanced IL-12 production.

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Animals
  • Biological Transport / drug effects
  • Calcium / metabolism*
  • Cells, Cultured
  • Interleukin-10 / metabolism
  • Interleukin-12 / metabolism*
  • Interleukin-6 / metabolism
  • Lipopolysaccharides / pharmacology*
  • Macrophages, Peritoneal / drug effects*
  • Macrophages, Peritoneal / metabolism*
  • Male
  • Methyltransferases / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • NF-kappa B / metabolism
  • Signal Transduction / drug effects
  • Sirtuin 1 / metabolism*
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Interleukin-6
  • Lipopolysaccharides
  • NF-kappa B
  • Tumor Necrosis Factor-alpha
  • Interleukin-10
  • Interleukin-12
  • Methyltransferases
  • calmodulin-lysine methyltransferase
  • AMP-Activated Protein Kinases
  • Sirt1 protein, mouse
  • Sirtuin 1
  • Calcium