title: Angiotensin preconditioning of the heart: evidence for redox signaling.
abstract: Angiotensin II (Ang II) has been found to exert preconditioning-like effect on mammalian hearts. Diverse mechanisms are known to exist to explain the cardioprotective abilities of Ang II preconditioning. The present study hypothesized, based on the recent report that Ang II generates reactive oxygen species (ROS) through NADPH oxidase, that Ang II preconditioning occurs through redox cycling. To test this hypothesis, a group of rat hearts was treated with Ang II in the absence or presence of an NADPH oxidase inhibitor, apocynin; or a cell-permeable ROS scavenger, N-acetyl cysteine (NAC). Ang II pretreatment improved postischemic ventricular recovery; reduced myocardial infarction; and decreased the number of cardiomyocyte apoptosis, indicating its ability to precondition the heart against ischemic injury. Both apocynin and NAC almost abolished the preconditioning ability of Ang II. Ang II resulted in increase in ROS activity in the heart, which was reduced by either NAC or apocynin. Ang II also increased both the NADPH oxidase subunits gp91 phox and p22phox mRNA expression, which was abolished with apocynin and NAC. Our results thus demonstrate that the Ang II preconditioning was associated with enhanced ROS activities and increased NADPH oxidase subunits p22phox and gp91phox expression. Both NAC and apocynin reduced ROS activities simultaneously abolishing preconditioning ability of Ang II, suggesting that Ang II preconditioning occurs through redox cycling. That both NAC and apocynin reduced ROS activities and abolished Ang II-mediated increase in p22phox and gp91phox activity further suggest that such redox cycling occurs via both NADPH oxidase-dependent and -independent pathways.
authors.affiliation: Cardiovascular Research Center, University of Connecticut School of Medicine, Farmington, CT, USA.
authors.forename: Samarjit
authors.initials: S
authors.lastname: Das
authors.forename: Richard M
authors.initials: RM
authors.lastname: Engelman
authors.forename: Nilanjana
authors.initials: N
authors.lastname: Maulik
authors.forename: Dipak K
authors.initials: DK
authors.lastname: Das
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000111:Acetylcysteine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D006321:Heart / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D009203:Myocardial Infarction / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000150:complications; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics; D010084:Oxidation-Reduction; D010477:Perfusion; D010750:Phosphoproteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D016277:Ventricular Function, Left / Q000187:drug effects; D020257:Ventricular Remodeling / Q000187:drug effects
chemical_list: D000098:Acetophenones; D000975:Antioxidants; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000804:Angiotensin II; C056165:acetovanillone; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C086986:CYBA protein, human; D000111:Acetylcysteine