Sphingosine kinase-2 inhibition improves mitochondrial function and survival after hepatic ischemia-reperfusion

J Hepatol. 2012 Jan;56(1):137-45. doi: 10.1016/j.jhep.2011.05.025. Epub 2011 Jul 12.

Abstract

Background & aims: The mitochondrial permeability transition (MPT) and inflammation play important roles in liver injury caused by ischemia-reperfusion (IR). This study investigated the roles of sphingosine kinase-2 (SK2) in mitochondrial dysfunction and inflammation after hepatic IR.

Methods: Mice were gavaged with vehicle or ABC294640 (50 mg/kg), a selective inhibitor of SK2, 1 h before surgery and subjected to 1 h-warm ischemia to ~70% of the liver followed by reperfusion.

Results: Following IR, hepatic SK2 mRNA and sphingosine-1-phosphate (S1P) levels increased ~25- and 3-fold, respectively. SK2 inhibition blunted S1P production and liver injury by 54-91%, and increased mouse survival from 28% to 100%. At 2 h after reperfusion, mitochondrial depolarization was observed in 74% of viable hepatocytes, and mitochondrial voids excluding calcein disappeared, indicating MPT onset in vivo. SK2 inhibition decreased mitochondrial depolarization and prevented MPT onset. Inducible nitric oxide synthase, phosphorylated NFκB-p65, TNFα mRNA, and neutrophil infiltration, all increased markedly after hepatic IR, and these increases were blunted by SK2 inhibition. In cultured hepatocytes, anoxia/re-oxygenation resulted in increases of SK2 mRNA, S1P levels, and cell death. SK2 siRNA and ABC294640 each substantially decreased S1P production and cell death in cultured hepatocytes.

Conclusions: SK2 plays an important role in mitochondrial dysfunction, inflammation responses, hepatocyte death, and survival after hepatic IR and represents a new target for the treatment of IR injury.

Publication types

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

MeSH terms

  • Adamantane / analogs & derivatives
  • Adamantane / pharmacology
  • Animals
  • Cell Death / drug effects
  • Enzyme Inhibitors / pharmacology
  • Gene Knockdown Techniques
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • In Vitro Techniques
  • Inflammation / enzymology
  • Inflammation / genetics
  • Liver / drug effects
  • Liver / enzymology*
  • Liver / injuries*
  • Lysophospholipids / metabolism
  • Lysophospholipids / pharmacology
  • Male
  • Mice
  • Mitochondria, Liver / drug effects
  • Mitochondria, Liver / enzymology
  • Mitochondrial Membrane Transport Proteins / drug effects
  • Mitochondrial Membrane Transport Proteins / metabolism
  • Mitochondrial Permeability Transition Pore
  • Nitric Oxide Synthase Type II / metabolism
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors*
  • Pyridines / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / genetics
  • Reperfusion Injury / drug therapy
  • Reperfusion Injury / enzymology*
  • Reperfusion Injury / genetics
  • Sphingosine / analogs & derivatives
  • Sphingosine / metabolism
  • Sphingosine / pharmacology

Substances

  • Enzyme Inhibitors
  • Lysophospholipids
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Permeability Transition Pore
  • Pyridines
  • RNA, Messenger
  • RNA, Small Interfering
  • sphingosine 1-phosphate
  • 3-(4-chlorophenyl)-adamantane-1-carboxylic acid (pyridin-4-ylmethyl)amide
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • Sphingosine
  • Adamantane