title: Nifedipine treatment reduces resting calcium concentration, oxidative and apoptotic gene expression, and improves muscle function in dystrophic mdx mice.
abstract: Duchenne Muscular Dystrophy (DMD) is a recessive X-linked genetic disease, caused by mutations in the gene encoding dystrophin. DMD is characterized in humans and in mdx mice by a severe and progressive destruction of muscle fibers, inflammation, oxidative/nitrosative stress, and cell death. In mdx muscle fibers, we have shown that basal ATP release is increased and that extracellular ATP stimulation is pro-apoptotic. In normal fibers, depolarization-induced ATP release is blocked by nifedipine, leading us to study the potential therapeutic effect of nifedipine in mdx muscles and its relation with extracellular ATP signaling. Acute exposure to nifedipine (10 µM) decreased [Ca(2+)]r, NF-κB activity and iNOS expression in mdx myotubes. In addition, 6-week-old mdx mice were treated with daily intraperitoneal injections of nifedipine, 1 mg/Kg for 1 week. This treatment lowered the [Ca(2+)]r measured in vivo in the mdx vastus lateralis. We demonstrated that extracellular ATP levels were higher in adult mdx flexor digitorum brevis (FDB) fibers and can be significantly reduced after 1 week of treatment with nifedipine. Interestingly, acute treatment of mdx FDB fibers with apyrase, an enzyme that completely degrades extracellular ATP to AMP, reduced [Ca(2+)]r to a similar extent as was seen in FDB fibers after 1-week of nifedipine treatment. Moreover, we demonstrated that nifedipine treatment reduced mRNA levels of pro-oxidative/nitrosative (iNOS and gp91(phox)/p47(phox) NOX2 subunits) and pro-apoptotic (Bax) genes in mdx diaphragm muscles and lowered serum creatine kinase (CK) levels. In addition, nifedipine treatment increased muscle strength assessed by the inverted grip-hanging test and exercise tolerance measured with forced swimming test in mdx mice. We hypothesize that nifedipine reduces basal ATP release, thereby decreasing purinergic receptor activation, which in turn reduces [Ca(2+)]r in mdx skeletal muscle cells. The results in this work open new perspectives towards possible targets for pharmacological approaches to treat DMD.
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile ; Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.
authors.forename: Francisco
authors.initials: F
authors.lastname: Altamirano
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Denisse
authors.initials: D
authors.lastname: Valladares
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Henríquez-Olguín
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile ; Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Mariana
authors.initials: M
authors.lastname: Casas
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America ; Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Jose R
authors.initials: JR
authors.lastname: López
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America ; Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Allen
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003402:Creatine Kinase / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D018101:Mice, Inbred mdx; D053580:Muscle Strength / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D020388:Muscular Dystrophy, Duchenne / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009543:Nifedipine / Q000627:therapeutic use*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism
chemical_list: D016328:NF-kappa B; D052247:Nitric Oxide Synthase Type II; D003402:Creatine Kinase; D009543:Nifedipine; D002118:Calcium