Bradycardic therapy improves left ventricular function and remodeling in dogs with coronary embolization-induced chronic heart failure.
Both beta-adrenergic blockade and bradycardia may contribute to the therapeutic effect of beta-blockers in chronic heart failure (CHF). This study tested the relative importance of bradycardia by comparing cilobradine (Cilo), a sinus node inhibitor, with a beta-blocker, metoprolol (Meto), in an established canine model of CHF. Dogs were chronically instrumented for hemodynamic and left ventricular (LV) volume measurements. CHF was created by daily coronary embolization via a chronically implanted coronary (left anterior descending coronary artery) catheter. After establishment of CHF, control (n=6), Meto (30 mg/day, n=5), Cilo (low) (1 mg/kg/day, n=5), or Cilo (high) (3 mg/kg/day, n=5) was given orally for 12 weeks. Systemic hemodynamics, echocardiography, and pressure volume analysis were measured at baseline, at CHF, and 3 months after treatment in an awake state. Protein levels of cardiac sarcoplasmic reticulum calcium-ATPase (SERCA2a), ryanodine receptor (RyR2), and Na+-Ca2+ exchanger (NCX1) were measured by Western blot. RyR2 protein kinase A (PKA) phosphorylation was determined by back-phosphorylation. After 12 weeks, Meto and Cilo (high and low) produced similar bradycardic effects, accompanied by a significantly improved LV dP/dt versus control [Meto, 2602+/-70; Cilo (low), 2517+/-45; Cilo (high), 2579+/-78; control, 1922+/-115 mm Hg/s; p<0.05]. Both Meto and Cilo (high) normalized protein levels of SERCA2a and NCX1 and reversed PKA hyperphosphorylation of RyR2, in contrast to controls. High-dose cilobradine effectively produced bradycardia and improved cardiac function after CHF, comparable with metoprolol. Restored protein levels of SERCA2a and improved function of RyR2 may be important mechanisms associated with cilobradine therapy.
Cheng
Yanping
Y
The Institute of Molecular and Experimental Therapeutics, East China Normal University, Shanghai, and Department of Cardiac-Nephrology, Chinese PLA General Hospital, Beijing, People's Republic of China.
George
Isaac
I
Yi
Geng-Hua
GH
Reiken
Steven
S
Gu
Anguo
A
Tao
Yuankai Kenny
YK
Muraskin
Jordan
J
Qin
Siyi
S
He
Kun-Lun
KL
Hay
Ilan
I
Yu
Kenward
K
Oz
Mehmet C
MC
Burkhoff
Daniel
D
Holmes
Jeffrey
J
Wang
Jie
J
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000818:Animals; D001552:Benzazepines / Q000627:therapeutic use*; D002118:Calcium / Q000378:metabolism; D023921:Coronary Stenosis / Q000150:complications; D004285:Dogs; D004452:Echocardiography; D005260:Female; D006333:Heart Failure / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use; D010880:Piperidines / Q000627:therapeutic use*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000032:analysis; D019831:Sodium-Calcium Exchanger / Q000502:physiology; D016277:Ventricular Function, Left / Q000187:drug effects*; D020257:Ventricular Remodeling / Q000187:drug effects*
D000319:Adrenergic beta-Antagonists; D001552:Benzazepines; D010880:Piperidines; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; C490484:cilobradine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D008790:Metoprolol; D002118:Calcium