title: Sphingosine kinase 2 mediates cerebral preconditioning and protects the mouse brain against ischemic injury.
abstract: OBJECTIVE
  Cerebral preconditioning provides insights into endogenous mechanisms that protect the brain from ischemic injury. Hypoxia and the anesthetic isoflurane are powerful preconditioning agents. Recent data show that sphingosine 1-phosphate receptor stimulation improves outcome in rodent models of stroke. Endogenous sphingosine 1-phosphate levels are controlled by the expression and activity of sphingosine kinases (SPK). We hypothesize that SPK upregulation mediates preconditioning induced by isoflurane and hypoxia and reduces ischemic injury.
  
  
  METHODS
  Male wild-type C57BL/J, SPK1(-/-) and SPK2(-/-) mice were exposed to isoflurane or hypoxia preconditioning before transient middle cerebral artery occlusion. Infarct volume and neurological outcome were measured 24 hours later. SPK inhibitors (SKI-II and ABC294640) were used to test the involvement of SPK2. Expressions of SPK1, SPK2, and hypoxia-inducible factor 1α were determined. Primary cultures of mouse cortical neurons were exposed to isoflurane before glutamate- or hydrogen peroxide-induced cell death.
  
  
  RESULTS
  Isoflurane preconditioning and hypoxia preconditioning significantly reduced infarct volume and improved neurological outcome in wild-type and SPK1(-/-) mice but not in SPK2(-/-) mice. Pretreatment with SKI-II or ABC294640 abolished the isoflurane preconditioning-induced tolerance. Western blot showed a rapid and sustained increase in SPK2 level, whereas SPK1 level was similar between preconditioned mice and controls. Hypoxia-inducible factor 1α was upregulated in wild-type isoflurane-preconditioned mice but not in SPK2(-/-). Isoflurane preconditioning protected primary neurons against cell death, which was abolished in ABC294640-treated cells.
  
  
  CONCLUSIONS
  Applying genetic and pharmacological approaches, we demonstrate that neuronal SPK2 isoform plays an important role in cerebral preconditioning.
authors: Stroke and Neurovascular Regulation Laboratory, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA.
authors: Lai Ming
authors: LM
authors: Yung
authors: Ying
authors: Y
authors: Wei
authors: Tao
authors: T
authors: Qin
authors: Yumei
authors: Y
authors: Wang
authors: Charles D
authors: CD
authors: Smith
authors: Christian
authors: C
authors: Waeber
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D002545:Brain Ischemia / Q000378:metabolism* / Q000473:pathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D019194:Ischemic Preconditioning / Q000379:methods*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D000099157:Sphingosine Kinase
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017853:Phosphotransferases (Alcohol Group Acceptor); D000099157:Sphingosine Kinase; C497443:Hif1a protein, mouse