title: Extracellular adenosine production by ecto-5'-nucleotidase protects during murine hepatic ischemic preconditioning.
abstract: OBJECTIVE
  The liver tolerates ischemia/reperfusion (IR) poorly. The discovery of ischemic preconditioning (IP) has raised hopes that natural pathways could be activated to increase hepatic resistance to ischemia. However, mechanisms of hepatic IP remain largely unknown. Extracellular adenosine has been implicated as an innate anti-inflammatory metabolite, particularly during ischemia. We investigated whether ecto-5'-nucleotidase (CD73), the "pacemaker" enzyme of extracellular adenosine production, is critical for hepatic protection by IP.
  
  
  METHODS
  Mice were subjected to 4 cycles of portal triad occlusion and reperfusion (3 minutes of ischemia/3 minutes of reperfusion) prior to IR or IR alone.
  
  
  RESULTS
  Hepatic IP was associated with a significant induction of CD73 transcript and protein. Targeted gene deletion or pharmacologic inhibition of CD73 abolished hepatic protection by IP as measured by lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase serum levels or histologic injury. Increases in extracellular adenosine with IP were significantly attenuated in cd73-deficient (cd73(-/-)) mice. Reconstitution of cd73(-/-) mice with soluble 5'-nucleotidase resulted in complete restoration of hepatoprotection by IP, and hepatic injury following ischemia was attenuated by treatment of WT mice with soluble 5'-nucleotidase. Mice deficient in CD73 did not demonstrate the same degree of IP-dependent inhibition of acute phase complement gene expression/activation as did wild-type mice suggesting that extracellular adenosine attenuates hepatic IR via complement regulation.
  
  
  CONCLUSIONS
  Extracellular adenosine production by CD73 mediates protection during murine hepatic IP. Use of soluble 5'-nucleotidase may be a potential therapeutic for hepatic ischemia.
authors.affiliation: Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Hart
authors.forename: Chressen
authors.initials: C
authors.lastname: Much
authors.forename: Iris C
authors.initials: IC
authors.lastname: Gorzolla
authors.forename: Jens
authors.initials: J
authors.lastname: Schittenhelm
authors.forename: Doris
authors.initials: D
authors.lastname: Kloor
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Stahl
authors.forename: Holger K
authors.initials: HK
authors.lastname: Eltzschig
mesh_terms: D015720:5'-Nucleotidase / Q000235:genetics* / Q000378:metabolism; D000241:Adenosine / Q000096:biosynthesis*; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D045604:Extracellular Fluid / Q000201:enzymology; D019194:Ischemic Preconditioning / Q000379:methods*; D008099:Liver / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D012313:RNA / Q000235:genetics*; D015427:Reperfusion Injury / Q000150:complications / Q000201:enzymology / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D012313:RNA; D015720:5'-Nucleotidase; D000241:Adenosine