Inhibition of sphingosine kinase-2 suppresses inflammation and attenuates graft injury after liver transplantation in rats

PLoS One. 2012;7(7):e41834. doi: 10.1371/journal.pone.0041834. Epub 2012 Jul 25.

Abstract

Inflammation mediates/promotes graft injury after liver transplantation (LT). This study investigated the roles of sphingosine kinase-2 (SK2) in inflammation after LT. Liver grafts were stored in UW solution with and without ABC294640 (100 µM), a selective inhibitor of SK2, before implantation. Hepatic sphingosine-1-phosphate (S1P) levels increased ∼4-fold after LT, which was blunted by 40% by ABC294640. Hepatic toll-like receptor-4 (TLR4) expression and nuclear factor-κB (NF-κB) p65 subunit phosphorylation elevated substantially after transplantation. The pro-inflammatory cytokines/chemokines tumor necrosis factor-α, interleukin-1β and C-X-C motif chemokine 10 mRNAs increased 5.9-fold, 6.1-fold and 16-fold, respectively following transplantation, while intrahepatic adhesion molecule-1 increased 5.7-fold and monocytes/macrophage and neutrophil infiltration and expansion of residential macrophage population increased 7.8-13.4 fold, indicating enhanced inflammation. CD4+ T cell infiltration and interferon-γ production also increased. ABC294640 blunted TLR4 expression by 60%, NF-κB activation by 84%, proinflammatory cytokine/chemokine production by 45-72%, adhesion molecule expression by 54% and infiltration of monocytes/macrophages and neutrophils by 62-67%. ABC294640 also largely blocked CD4+ T cell infiltration and interferon-γ production. Focal necrosis and apoptosis occurred after transplantation with serum alanine aminotransferase (ALT) reaching ∼6000 U/L and serum total bilirubin elevating to ∼1.5 mg/dL. Inhibition of SK2 by ABC294640 blunted necrosis by 57%, apoptosis by 74%, ALT release by ∼68%, and hyperbilirubinemia by 74%. Most importantly, ABC294640 also increased survival from ∼25% to ∼85%. In conclusion, SK2 plays an important role in hepatic inflammation responses and graft injury after cold storage/transplantation and represents a new therapeutic target for liver graft failure.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adamantane / analogs & derivatives*
  • Adamantane / pharmacology
  • Adamantane / therapeutic use
  • Animals
  • Cell Adhesion Molecules / metabolism
  • Chemokines / genetics
  • Enzyme Inhibitors / pharmacology*
  • Enzyme Inhibitors / therapeutic use
  • Inflammation / drug therapy
  • Leukocytes / drug effects
  • Leukocytes / immunology
  • Liver / drug effects*
  • Liver / injuries*
  • Liver / metabolism
  • Liver / physiopathology
  • Liver Transplantation / adverse effects*
  • Lysophospholipids / biosynthesis
  • Male
  • NF-kappa B / metabolism
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors*
  • Pyridines / pharmacology*
  • Pyridines / therapeutic use
  • Rats
  • Rats, Inbred Lew
  • Reactive Oxygen Species / metabolism
  • Reperfusion Injury / drug therapy
  • Reperfusion Injury / immunology
  • Reperfusion Injury / metabolism
  • Reperfusion Injury / physiopathology
  • Sphingosine / analogs & derivatives
  • Sphingosine / biosynthesis
  • Toll-Like Receptor 4 / metabolism
  • Up-Regulation / drug effects

Substances

  • Cell Adhesion Molecules
  • Chemokines
  • Enzyme Inhibitors
  • Lysophospholipids
  • NF-kappa B
  • Pyridines
  • Reactive Oxygen Species
  • Toll-Like Receptor 4
  • sphingosine 1-phosphate
  • 3-(4-chlorophenyl)-adamantane-1-carboxylic acid (pyridin-4-ylmethyl)amide
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • Sphingosine
  • Adamantane