title: Phosphorylation of ARC is a critical element in the antiapoptotic effect of anesthetic preconditioning.
abstract: BACKGROUND
  Transient exposure to volatile anesthetics before cardiac ischemia/reperfusion (I/R), termed anesthetic preconditioning, limits myocardial injury and inhibits apoptosis. Apoptosis repressor with caspase recruitment domain (ARC) is a novel protein that has been demonstrated to protect cardiomyocytes from apoptosis induced by I/R and is regulated by phosphorylation. We therefore hypothesized that the antiapoptotic effect of anesthetic preconditioning is, in part, mediated by phosphorylation of ARC.
  
  
  METHODS
  In the experiments we used a perfused rat heart model of sevoflurane anesthetic preconditioning and I/R. In addition to measures of left ventricular function, phosphorylation of ARC was measured with and without anesthetic preconditioning. Because the phosphorylation status of ARC is determined by calcineurin and protein kinase CK2, the role of ARC was defined by measuring calcineurin activity and using the calcineurin inhibitor FK506 and the ARC phosphorylation inhibitor 4,5,6,7-tetrabromobenzotrizole (TBB).
  
  
  RESULTS
  I/R without anesthetic preconditioning increased calcineurin and reduced ARC phosphorylation levels, whereas anesthetic preconditioning significantly improved functional recovery, decreased ischemic injury, limited the increase in calcineurin activity, increased the phosphorylation level of ARC, reduced cytochrome c release, and blocked the increase in caspase-8 after I/R. The effects of anesthetic preconditioning were mirrored by FK506 and abolished by TBB.
  
  
  CONCLUSIONS
  This study has identified a novel cardiac pathway in which anesthetic preconditioning prevents the increase in calcineurin after I/R, resulting in increased phosphorylated ARC and decreased markers of apoptosis.
authors.affiliation: Department of Internal Medicine, Division of Cardiovascular Medicine, University of California, Davis, One Shields Avenue, TB 172, Davis, CA 95616, USA.
authors.forename: Xiyuan
authors.initials: X
authors.lastname: Lu
authors.forename: Peter G
authors.initials: PG
authors.lastname: Moore
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Saul
authors.initials: S
authors.lastname: Schaefer
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D018685:Anesthetics, Inhalation; D051017:Apoptosis Regulatory Proteins; D065095:Calcineurin Inhibitors; D009124:Muscle Proteins; C491788:Nol3 protein, rat; D019703:Calcineurin