title: Oxidative stress, mitochondrial damage, and cores in muscle from calsequestrin-1 knockout mice.
abstract: BACKGROUND
  Mutations in the gene encoding ryanodine receptor type-1 (RYR1), the calcium ion (Ca (2+)) release channel in the sarcoplasmic reticulum (SR) of skeletal muscle, are linked to central core disease (CCD) and malignant hyperthermia (MH) susceptibility. We recently reported that mice lacking the skeletal isoform of calsequestrin (CASQ1-null), the primary Ca (2+) buffer in the SR of skeletal muscle and a modulator of RYR1 activity, exhibit lethal heat- and anesthetic-induced hypermetabolic episodes that resemble MH events in humans.
  
  
  METHODS
  We compared ultrastructure, oxidative status, and contractile function in skeletal fibers of extensor digitorum longus (EDL) muscles in wild type (WT) and CASQ1-null mice at different ages (from 4 to 27 months) using structural, biochemical, and functional assays.
  
  
  RESULTS
  About 25% of fibers in EDL muscles from CASQ1-null mice of 14 to 27 months of age exhibited large areas of structural disarray (named core-like regions), which were rarely observed in muscle from age-matched WT mice. To determine early events that may lead to the formation of cores, we analyzed EDL muscles from adult mice: at 4 to 6 months of age, CASQ1-null mice (compared to WT) displayed significantly reduced grip strength (40 ± 1 vs. 86 ± 1 mN/gr) and exhibited an increase in the percentage of damaged mitochondria (15.1% vs. 2.6%) and a decrease in average cross-sectional fiber area (approximately 37%) in EDL fibers. Finally, oxidative stress was also significantly increased (25% reduction in ratio between reduced and oxidized glutathione, or GSH/GSSG, and 35% increase in production of mitochondrial superoxide flashes). Providing ad libitum access to N-acetylcysteine in the drinking water for 2 months normalized GSH/GSSG ratio, reduced mitochondrial damage (down to 8.9%), and improved grip strength (from 46 ± 3 to 59 ± 2 mN/gr) in CASQ1-null mice.
  
  
  CONCLUSIONS
  Our findings: 1) demonstrate that ablation of CASQ1 leads to enhanced oxidative stress, mitochondrial damage, and the formation of structural cores in skeletal muscle; 2) provide new insights in the pathogenic mechanisms that lead to damage/disappearance of mitochondria in cores; and 3) suggest that antioxidants may provide some therapeutic benefit in reducing mitochondrial damage, limiting the development of cores, and improving muscle function.
authors.affiliation: CeSI - Center for Research on Ageing & DNICS - Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio, Via L. Polacchi, 11, I-66013 Chieti, Italy.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Paolini
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, I-35131 Padova, Italy ; Department of Neurology and Neurological Sciences, Stanford University, 450 Serra Mall, Stanford, CA 94305 USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Quarta
authors.affiliation: Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Ave., Rochester, NY 14642 USA.
authors.forename: Lan
authors.initials: L
authors.lastname: Wei-LaPierre
authors.affiliation: CeSI - Center for Research on Ageing & DNICS - Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio, Via L. Polacchi, 11, I-66013 Chieti, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Michelucci
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, I-35131 Padova, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Nori
authors.affiliation: Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, I-35131 Padova, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Reggiani
authors.affiliation: Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Ave., Rochester, NY 14642 USA.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dirksen
authors.affiliation: CeSI - Center for Research on Ageing & DNICS - Department of Neuroscience, Imaging and Clinical Sciences, University G. d'Annunzio, Via L. Polacchi, 11, I-66013 Chieti, Italy.
authors.forename: Feliciano
authors.initials: F
authors.lastname: Protasi
keywords: Excitation-contraction (EC) coupling; Mitochondria; Ryanodine receptor (RYR)