title: Exercise and tachycardia increase NADPH oxidase and ryanodine receptor-2 activity: possible role in cardioprotection.
abstract: OBJECTIVE
  Our objective was to investigate in cardiac muscle the contribution of NADPH oxidase to (a) ryanodine receptor-2 (RyR2) S-glutathionylation and (b) the preconditioning effects of exercise and tachycardia on infarct size following coronary artery occlusion.
  
  
  RESULTS
  We measured NADPH oxidase activity, RyR2 S-glutathionylation, and calcium release kinetics in sarcoplasmic reticulum (SR) vesicles isolated from dog ventricular muscle after exercise and tachycardia, plus or minus prior administration of the NADPH oxidase inhibitor apocynin. In ventricular muscle sections, we studied the colocalization of NADPH oxidase and RyR2 by confocal microscopy using fluorescent antibodies. We determined the effect of apocynin on the infarct size produced by occlusion of the descendent anterior coronary artery in animals preconditioned by exercise or tachycardia. Exercise and tachycardia increased NADPH oxidase activity, RyR2 S-glutathionylation, and calcium release rates in isolated SR vesicles. Cardiac muscle sections displayed significant colocalization of NADPH oxidase and RyR2, suggesting direct and specific effects of reactive oxygen species (ROS) produced by NADPH oxidase on RyR2 activation. The NADPH oxidase inhibitor apocynin prevented the increase in RyR2 S-glutathionylation, reduced calcium release activity, and completely prevented the protective effects of exercise and tachycardia on infarct size.
  
  
  CONCLUSIONS
  The loss of cardioprotection induced by the NADPH oxidase inhibitor suggests that ROS generated by this enzyme are important mediators of the preconditioning response, which presumably involves NADPH oxidase-induced RyR2 S-glutathionylation.
authors.affiliation: Programa de Fisiopatología, Instituto de Ciencias Biomédicas y Centro FONDAP de Estudios Moleculares de la Célula, Facultad de Medicina, Universidad de Chile, Chile.
authors.forename: Gina
authors.initials: G
authors.lastname: Sánchez
authors.forename: Matías
authors.initials: M
authors.lastname: Escobar
authors.forename: Zully
authors.initials: Z
authors.lastname: Pedrozo
authors.forename: Pilar
authors.initials: P
authors.lastname: Macho
authors.forename: Raúl
authors.initials: R
authors.lastname: Domenech
authors.forename: Steffen
authors.initials: S
authors.lastname: Härtel
authors.forename: Cecilia
authors.initials: C
authors.lastname: Hidalgo
authors.forename: Paulina
authors.initials: P
authors.lastname: Donoso
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004285:Dogs; D005260:Female; D005978:Glutathione / Q000378:metabolism; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D019255:NADPH Oxidases / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D017382:Reactive Oxygen Species / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013610:Tachycardia / Q000378:metabolism*
chemical_list: D000098:Acetophenones; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel; C056165:acetovanillone; D019255:NADPH Oxidases; D005978:Glutathione; D002118:Calcium