title: Ranolazine antagonizes catecholamine-induced dysfunction in isolated cardiomyocytes, but lacks long-term therapeutic effects in vivo in a mouse model of hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  Hypertrophic cardiomyopathy (HCM) is often accompanied by increased myofilament Ca(2+) sensitivity and diastolic dysfunction. Recent findings indicate increased late Na(+) current density in human HCM cardiomyocytes. Since ranolazine has the potential to decrease myofilament Ca(2+) sensitivity and late Na(+) current, we investigated its effects in an Mybpc3-targeted knock-in (KI) mouse model of HCM.
  
  
  RESULTS
  Unloaded sarcomere shortening and Ca(2+) transients were measured in KI and wild-type (WT) cardiomyocytes. Measurements were performed at baseline (1 Hz) and under increased workload (30 nM isoprenaline (ISO), 5 Hz) in the absence or presence of 10 µM ranolazine. KI myocytes showed shorter diastolic sarcomere length at baseline, stronger inotropic response to ISO, and drastic drop of diastolic sarcomere length under increased workload. Ranolazine attenuated ISO responses in WT and KI cells and prevented workload-induced diastolic failure in KI. Late Na(+) current density was diminished and insensitive to ranolazine in KI cardiomyocytes. Ca(2+) sensitivity of skinned KI trabeculae was slightly decreased by ranolazine. Phosphorylation analysis of cAMP-dependent protein kinase A-target proteins and ISO concentration-response measurements on muscle strips indicated antagonism at β-adrenoceptors with 10 µM ranolazine shifting the ISO response by 0.6 log units. Six-month treatment with ranolazine (plasma level >20 µM) demonstrated a β-blocking effect, but did not reverse cardiac hypertrophy or dysfunction in KI mice.
  
  
  CONCLUSIONS
  Ranolazine improved tolerance to high workload in mouse HCM cardiomyocytes, not by blocking late Na(+) current, but by antagonizing β-adrenergic stimulation and slightly desensitizing myofilaments to Ca(2+). This effect did not translate in therapeutic efficacy in vivo.
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Frederik
authors.initials: F
authors.lastname: Flenner
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Felix W
authors.initials: FW
authors.lastname: Friedrich
authors.affiliation: Clinic for Cardiology and Pneumology, Georg-August-University Göttingen, Göttingen, Germany.
authors.forename: Nele
authors.initials: N
authors.lastname: Ungeheuer
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Christ
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Geertz
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Reischmann
authors.affiliation: Clinic for Cardiology and Pneumology, Georg-August-University Göttingen, Göttingen, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany Department for Internal Medicine II, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wagner
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Konstantina
authors.initials: K
authors.lastname: Stathopoulou
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany.
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Söhren
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Weinberger
authors.affiliation: DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany Department of Clinical Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Edzard
authors.initials: E
authors.lastname: Schwedhelm
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Cuello
authors.affiliation: Clinic for Cardiology and Pneumology, Georg-August-University Göttingen, Göttingen, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany Department for Internal Medicine II, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Lars S
authors.initials: LS
authors.lastname: Maier
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany l.carrier@uke.de t.eschenhagen@uke.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Eschenhagen
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße 52, D-20246 Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Hamburg, Germany l.carrier@uke.de t.eschenhagen@uke.de.
authors.forename: Lucie
authors.initials: L
authors.lastname: Carrier
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002312:Cardiomyopathy, Hypertrophic / Q000188:drug therapy* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000502:physiology; D010766:Phosphorylation; D000069458:Ranolazine / Q000494:pharmacology*; D026941:Sodium Channel Blockers / Q000494:pharmacology*
chemical_list: D000319:Adrenergic beta-Antagonists; D026941:Sodium Channel Blockers; D000069458:Ranolazine; D007545:Isoproterenol; D002118:Calcium
keywords: Ca2+ sensitivity; Cardiac myosin-binding protein C; Hypertrophic cardiomyopathy; Ranolazine; β-Adrenergic signalling