title: NADPH oxidase-2 inhibition restores contractility and intracellular calcium handling and reduces arrhythmogenicity in dystrophic cardiomyopathy.
abstract: Duchenne muscular dystrophy may affect cardiac muscle, producing a dystrophic cardiomyopathy in humans and the mdx mouse. We tested the hypothesis that oxidative stress participates in disrupting calcium handling and contractility in the mdx mouse with established cardiomyopathy. We found increased expression (fivefold) of the NADPH oxidase (NOX) 2 in the mdx hearts compared with wild type, along with increased superoxide production. Next, we tested the impact of NOX2 inhibition on contractility and calcium handling in isolated cardiomyocytes. Contractility was decreased in mdx myocytes compared with wild type, and this was restored toward normal by pretreating with apocynin. In addition, the amplitude of evoked intracellular Ca(2+) concentration transients that was diminished in mdx myocytes was also restored with NOX2 inhibition. Total sarcoplasmic reticulum (SR) Ca(2+) content was reduced in mdx hearts and normalized by apocynin treatment. Additionally, NOX2 inhibition decreased the production of spontaneous diastolic calcium release events and decreased the SR calcium leak in mdx myocytes. In addition, nitric oxide (NO) synthase 1 (NOS-1) expression was increased eightfold in mdx hearts compared with wild type. Nevertheless, cardiac NO production was reduced. To test whether this paradox implied NOS-1 uncoupling, we treated cardiac myocytes with exogenous tetrahydrobioterin, along with the NOX inhibitor VAS2870. These agents restored NO production and phospholamban phosphorylation in mdx toward normal. Together, these results demonstrate that, in mdx hearts, NOX2 inhibition improves the SR calcium handling and contractility, partially by recoupling NOS-1. These findings reveal a new layer of nitroso-redox imbalance in dystrophic cardiomyopathy.
authors.affiliation: Departamento de Ciencias Basicas Biomedicas, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile; and.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Gonzalez
authors.affiliation: Departamento de Ciencias Basicas Biomedicas, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile; and.
authors.forename: Adriana V
authors.initials: AV
authors.lastname: Treuer
authors.affiliation: Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lamirault
authors.affiliation: Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Vera
authors.initials: V
authors.lastname: Mayo
authors.affiliation: Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Yenong
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Raul A
authors.initials: RA
authors.lastname: Dulce
authors.affiliation: Interdisciplinary Stem Cell Institute, Miller School of Medicine, University of Miami, Miami, Florida jhare@med.miami.edu.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Hare
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism*; D001583:Benzoxazoles / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D009202:Cardiomyopathies / Q000378:metabolism* / Q000503:physiopathology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018101:Mice, Inbred mdx; D009200:Myocardial Contraction; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D014230:Triazoles / Q000494:pharmacology
chemical_list: C511179:3-benzyl-7-(2-benzoxazolyl)thio-1,2,3-triazolo(4,5-d)pyrimidine; D001583:Benzoxazoles; D008562:Membrane Glycoproteins; D014230:Triazoles; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D002118:Calcium
keywords: BH4; Duchenne; NADPH oxidase; NOS-1 uncoupling; mdx; phospholamban; ryanodine receptor; superoxide