Acute organ failure following the loss of anti-apoptotic cellular FLICE-inhibitory protein involves activation of innate immune receptors

Cell Death Differ. 2015 May;22(5):826-37. doi: 10.1038/cdd.2014.178. Epub 2014 Oct 24.

Abstract

Apoptosis signaling is involved in both physiological tissue homeostasis and acute and chronic diseases. The role of regulatory apoptosis signaling molecules and their organ-specific functions are less defined. Therefore, we investigated the loss of the anti-apoptotic cellular FLICE-inhibitory protein (cFLIP) and the mechanisms of the resulting lethal organ failure in vivo using inducible knockout mice. These were generated by crossing floxed cFLIP mice to a tamoxifen inducible Rosa26-creERT2 mouse strain. Death following global loss of cFLIP resulted from liver failure, accumulation of M1-polarized macrophages and accompanying hepatic cell death and inflammation. Apoptosis was also prominent in immune cells, the kidney and intestinal epithelial cells (IECs) but not in cardiomyocytes. Cellular injury led to the release of damage-associated molecular patterns (DAMPs) and the induction of innate immune receptors including toll-like receptors (TLRs) 4 and 9, and stimulator of interferon genes (STING). Transplantation of bone marrow with intact cFLIP or depletion of macrophages prevented the phenotype of acute liver failure. Interestingly, compound deletion of cFLIP in bone marrow-derived cells and hepatocytes did not promote organ failure. Thus, cFLIP exerts a critical role in tissue homeostasis by preventing the activation of monocytic cells and innate immunity, which causes cell death and inflammation in susceptible tissues. These results encourage the development of organ-specific anti-apoptotic and anti-inflammatory therapies in acute organ failure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CASP8 and FADD-Like Apoptosis Regulating Protein / genetics
  • CASP8 and FADD-Like Apoptosis Regulating Protein / immunology*
  • Hepatocytes / immunology
  • Hepatocytes / pathology
  • Immunity, Innate*
  • Liver Failure, Acute / genetics
  • Liver Failure, Acute / immunology*
  • Liver Failure, Acute / pathology
  • Macrophages / immunology*
  • Macrophages / pathology
  • Membrane Proteins / genetics
  • Membrane Proteins / immunology
  • Mice
  • Mice, Transgenic
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / immunology*
  • Toll-Like Receptor 9 / genetics
  • Toll-Like Receptor 9 / immunology*

Substances

  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • Cflar protein, mouse
  • Membrane Proteins
  • Sting1 protein, mouse
  • Tlr4 protein, mouse
  • Tlr9 protein, mouse
  • Toll-Like Receptor 4
  • Toll-Like Receptor 9