title: Vagal nerve stimulation reduces infarct size via a mechanism involving the alpha-7 nicotinic acetylcholine receptor and downregulation of cardiac and vascular arginase.
abstract: OBJECTIVE
  Vagal nerve stimulation (VNS) protects from myocardial and vascular injury following myocardial ischaemia and reperfusion (IR) via a mechanism involving activation of alpha-7 nicotinic acetylcholine receptor (α7 nAChR) and reduced inflammation. Arginase is involved in development of myocardial IR injury driven by inflammatory mediators. The aim of the study was to clarify whether VNS downregulates myocardial and vascular arginase via a mechanism involving activation of α7 nAChR following myocardial IR.
  
  
  METHODS
  Anaesthetized rats were randomized to (i) sham-operated, (ii) control IR (30-min ischaemia and 2-h reperfusion, (iii) VNS throughout IR, (iv) the arginase inhibitor nor-NOHA+IR, (v) nor-NOHA+VNS+IR, (vi) selective α7 nAChR blockade by methyllycaconitine (MLA) followed by VNS throughout IR and (vii) MLA+IR.
  
  
  RESULTS
  Infarct size was reduced by VNS compared to control IR (41 ± 3% vs. 67 ± 2% of the myocardium at risk, P < 0.001). Myocardial IR increased myocardial and aortic arginase activity 1.7- and 3.1-fold respectively (P < 0.05). VNS attenuated the increase in arginase activity compared to control IR both in the myocardium and aorta (P < 0.05). MLA partially abolished the cardioprotective effect of VNS and completely abrogated the effect of VNS on arginase activity. Arginase inhibition combined with VNS did not further reduce infarct size.
  
  
  CONCLUSIONS
  Vagal nerve stimulation reduced infarct size and reversed the upregulation of arginase induced by IR both in the myocardium and aorta via a mechanism depending on α7 nAChR activation. The data suggest that the cardioprotective effect of VNS is mediated via reduction in arginase activity.
authors.affiliation: Department of Medicine, Unit of Cardiology, Karolinska Institutet, Heart and Vascular Theme, Karolinska University Hospital, Stockholm, Sweden.|Ludwig Boltzmann Cluster for Cardiovascular Research at the Center for Biomedical Research, Medical University of Vienna, Vienna, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Kiss
authors.affiliation: Department of Medicine, Unit of Cardiology, Karolinska Institutet, Heart and Vascular Theme, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Y
authors.initials: Y
authors.lastname: Tratsiakovich
authors.affiliation: Department of Medicine, Unit of Cardiology, Karolinska Institutet, Heart and Vascular Theme, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Mahdi
authors.affiliation: Department of Medicine, Unit of Cardiology, Karolinska Institutet, Heart and Vascular Theme, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Medicine, Unit of Cardiology, Karolinska Institutet, Heart and Vascular Theme, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: A T
authors.initials: AT
authors.lastname: Gonon
authors.affiliation: Ludwig Boltzmann Cluster for Cardiovascular Research at the Center for Biomedical Research, Medical University of Vienna, Vienna, Austria.
authors.forename: B K
authors.initials: BK
authors.lastname: Podesser
authors.affiliation: Department of Medicine, Unit of Cardiology, Karolinska Institutet, Heart and Vascular Theme, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Pernow
mesh_terms: D000157:Aconitine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001119:Arginase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D015536:Down-Regulation; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology*; D017202:Myocardial Ischemia; D015428:Myocardial Reperfusion Injury; D009206:Myocardium / Q000378:metabolism; D018733:Nicotinic Antagonists / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D055536:Vagus Nerve Stimulation; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000502:physiology*
chemical_list: C404735:N(omega)-hydroxynorarginine; D018733:Nicotinic Antagonists; D064569:alpha7 Nicotinic Acetylcholine Receptor; C054634:methyllycaconitine; D001120:Arginine; D001119:Arginase; D000157:Aconitine
keywords: alpha-7 nicotinic acetylcholine receptor; arginase; ischaemia/reperfusion; vagal nerve stimulation