title: Sphingosine kinase-2 inhibition improves mitochondrial function and survival after hepatic ischemia-reperfusion.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Shi
authors.forename: Hasibur
authors.initials: H
authors.lastname: Rehman
authors.forename: Venkat K
authors.initials: VK
authors.lastname: Ramshesh
authors.forename: Justin
authors.initials: J
authors.lastname: Schwartz
authors.forename: Qinlong
authors.initials: Q
authors.lastname: Liu
authors.forename: Yasodha
authors.initials: Y
authors.lastname: Krishnasamy
authors.forename: Xun
authors.initials: X
authors.lastname: Zhang
authors.forename: John J
authors.initials: JJ
authors.lastname: Lemasters
authors.forename: Charles D
authors.initials: CD
authors.lastname: Smith
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhong
mesh_terms: D000218:Adamantane / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007249:Inflammation / Q000201:enzymology / Q000235:genetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000293:injuries*; D008246:Lysophospholipids / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D051379:Mice; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D015427:Reperfusion Injury / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000099157:Sphingosine Kinase
chemical_list: D000218:Adamantane; D004791:Enzyme Inhibitors; D008246:Lysophospholipids; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D052247:Nitric Oxide Synthase Type II; D017853:Phosphotransferases (Alcohol Group Acceptor); D011725:Pyridines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate; C548780:3-(4-chlorophenyl)-adamantane-1-carboxylic acid (pyridin-4-ylmethyl)amide; C496317:Nos2 protein, mouse