Scavenging free radicals by low-dose carvedilol prevents redox-dependent Ca2+ leak via stabilization of ryanodine receptor in heart failure.
OBJECTIVE
We investigated whether defective intracellular Ca2+ handling is corrected by carvedilol in heart failure.


BACKGROUND
In heart failure, the interaction between the N-terminal and central domains of the ryanodine receptor (RyR), the domains where many mutations have been found in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), is defective, as shown in our recent report.


METHODS
Sarcoplasmic reticulum vesicles were isolated from canine left ventricular muscle (normal or 4-weeks rapid ventricular pacing). The RyR was labeled with the fluorescent conformational probe methylcoumarin acetate (MCA) with DPc10 (a synthetic peptide corresponding to Gly2460-Pro2495 of RyR, one of the mutable domains in CPVT) as a site-direction carrier.


RESULTS
Normal cardiac function was well preserved in carvedilol-treated/paced dogs (CV+) but not in the untreated/paced dogs (CV-). In CV-, the interdomain interaction within RyR was defective (i.e., in an unzipped state), as determined by the fluorescence quenching technique. However, in CV+, the domain interaction remained normal (i.e., in a zipped state). In CV-, oxidative stress of RyR (reduction in the number of free thiols) was severe, but it was negligible in CV+. In (CV-) failing cardiomyocytes, incubation with low-dose CV (30 nmol/l), which eliminated intracellular reactive oxygen species with no acute effect on cell shortening, markedly improved the contractile function and Ca2+ transient. However, after domain unzipping by DPc10, CV was without effect.


CONCLUSIONS
Carvedilol, at a concentration that is sufficient to produce antioxidant effect, improves the intracellular Ca2+ handling and contractile dysfunction by correcting defective interdomain interaction within the RyR in the failing heart.
Mochizuki
Mamoru
M
Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, Ube, Japan.
Yano
Masafumi
M
Oda
Tetsuro
T
Tateishi
Hiroki
H
Kobayashi
Shigeki
S
Yamamoto
Takeshi
T
Ikeda
Yasuhiro
Y
Ohkusa
Tomoko
T
Ikemoto
Noriaki
N
Matsuzaki
Masunori
M
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology*; D002303:Cardiac Output, Low / Q000188:drug therapy / Q000503:physiopathology*; D000077261:Carvedilol; D004285:Dogs; D005609:Free Radicals / Q000378:metabolism*; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011412:Propanolamines / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects* / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D005609:Free Radicals; D011412:Propanolamines; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel; D000077261:Carvedilol; D002118:Calcium