title: Hierarchical accumulation of RyR post-translational modifications drives disease progression in dystrophic cardiomyopathy.
abstract: OBJECTIVE
  Duchenne muscular dystrophy (DMD) is a muscle disease with serious cardiac complications. Changes in Ca(2+) homeostasis and oxidative stress were recently associated with cardiac deterioration, but the cellular pathophysiological mechanisms remain elusive. We investigated whether the activity of ryanodine receptor (RyR) Ca(2+) release channels is affected, whether changes in function are cause or consequence and which post-translational modifications drive disease progression.
  
  
  RESULTS
  Electrophysiological, imaging, and biochemical techniques were used to study RyRs in cardiomyocytes from mdx mice, an animal model of DMD. Young mdx mice show no changes in cardiac performance, but do so after ∼8 months. Nevertheless, myocytes from mdx pups exhibited exaggerated Ca(2+) responses to mechanical stress and 'hypersensitive' excitation-contraction coupling, hallmarks of increased RyR Ca(2+) sensitivity. Both were normalized by antioxidants, inhibitors of NAD(P)H oxidase and CaMKII, but not by NO synthases and PKA antagonists. Sarcoplasmic reticulum Ca(2+) load and leak were unchanged in young mdx mice. However, by the age of 4-5 months and in senescence, leak was increased and load was reduced, indicating disease progression. By this age, all pharmacological interventions listed above normalized Ca(2+) signals and corrected changes in ECC, Ca(2+) load, and leak.
  
  
  CONCLUSIONS
  Our findings suggest that increased RyR Ca(2+) sensitivity precedes and presumably drives the progression of dystrophic cardiomyopathy, with oxidative stress initiating its development. RyR oxidation followed by phosphorylation, first by CaMKII and later by PKA, synergistically contributes to cardiac deterioration.
authors.affiliation: Department of Pharmacology and Physiology, New Jersey Medical School, 185 S. Orange Ave., Newark, NJ 07103, USA.
authors.forename: Sergii
authors.initials: S
authors.lastname: Kyrychenko
authors.forename: Eva
authors.initials: E
authors.lastname: Poláková
authors.forename: Chifei
authors.initials: C
authors.lastname: Kang
authors.forename: Krisztina
authors.initials: K
authors.lastname: Pocsai
authors.forename: Nina D
authors.initials: ND
authors.lastname: Ullrich
authors.forename: Ernst
authors.initials: E
authors.lastname: Niggli
authors.forename: Natalia
authors.initials: N
authors.lastname: Shirokova
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000502:physiology; D009202:Cardiomyopathies / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D018450:Disease Progression; D016189:Dystrophin / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D020388:Muscular Dystrophy, Duchenne / Q000150:complications*; D009206:Myocardium / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism; D019255:NADPH Oxidases / Q000502:physiology; D010084:Oxidation-Reduction; D011499:Protein Processing, Post-Translational; D017382:Reactive Oxygen Species / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D016189:Dystrophin; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel; D019255:NADPH Oxidases; D017868:Cyclic AMP-Dependent Protein Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D002118:Calcium