title: Rapid ventricular pacing-induced postconditioning attenuates reperfusion injury: effects on peroxynitrite, RISK and SAFE pathways.
abstract: OBJECTIVE
  Rapid ventricular pacing (RVP) applied before an index ischaemia has anti-ischaemic effects. Here, we investigated whether RVP applied after index ischaemia attenuates reperfusion injury and whether peroxynitrite, reperfusion injury salvage kinase (RISK) and survival activating factor enhancement (SAFE) pathways as well as haem oxygenase 1 (HO1) are involved in the mechanism of RVP-induced postconditioning.
  
  
  METHODS
  Langendorff perfused rat hearts were subjected to 30 min regional ischaemia and 120 min reperfusion with or without ischaemic postconditioning (6 × 10/10 s reperfusion/ischaemia; IPost) or RVP (6 × 10/10 s non-pacing/rapid pacing at 600 bpm) applied at the onset of reperfusion.
  
  
  RESULTS
  Meta-analysis of our previous studies revealed an association between longer reperfusion-induced ventricular tachycardia/fibrillation with decreased infarct size. In the present experiments, we tested whether RVP is cardioprotective and found that both IPost and RVP significantly decreased infarct size; however, only RVP attenuated the incidence of reperfusion-induced ventricular tachycardia. Both postconditioning methods increased the formation of cardiac 3-nitrotyrosine and superoxide, and non-significantly enhanced Akt phosphorylation at the beginning of reperfusion without affecting ERK1/2 and STAT3, while IPost alone induced HO1. Application of brief ischaemia/reperfusion cycles or RVP without preceding index ischaemia also facilitated peroxynitrite formation; nevertheless, only brief RVP increased STAT3 phosphorylation.
  
  
  CONCLUSIONS
  Short periods of RVP at the onset of reperfusion are cardioprotective and increase peroxynitrite formation similarly to IPost and thus may serve as an alternative postconditioning method. However, downstream mechanisms of the protection elicited by IPost and RVP seem to be partially different.
  
  
  BACKGROUND
  This article is part of a themed section on Conditioning the Heart - Pathways to Translation. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-8.
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.
authors.forename: Márton
authors.initials: M
authors.lastname: Pipicz
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.|Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.
authors.forename: Zoltán V
authors.initials: ZV
authors.lastname: Varga
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Kupai
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.
authors.forename: Renáta
authors.initials: R
authors.lastname: Gáspár
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.
authors.forename: Gabriella F
authors.initials: GF
authors.lastname: Kocsis
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Csonka
authors.affiliation: Department of Biochemistry, University of Szeged, Szeged, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Csont
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D006352:Heart Ventricles / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000378:metabolism; D057775:Ischemic Postconditioning; D020935:MAP Kinase Signaling System; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000517:prevention & control*; D030421:Peroxynitrous Acid / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D030421:Peroxynitrous Acid; D051547:Heme Oxygenase-1
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