Introduction:
Abnormal intracellular Ca2+ handling seems to be involved in the pathogenesis of idiopathic dilated cardiomyopathy (DCM). We have found up-regulation of the expression of transient receptor potential vanilloid 2 (TRPV2), a calcium-permeable cation channel, in the sarcolemma of myocardium of animal and human DCM.
Hypothesis:
We hypothesized an orally active TRPV2 antagonist, tranilast, ameliorated heart failure symptoms of DCM mice.
Methods:
We used 4C30 mice (created by National Institute of Biomedical Innovation, Japan), which has abnormal myocardial calcium handling, as a model of DCM. Sixteen 4C30 mice of 25 weeks old with end-stage heart failure were given no drug (control) or 20 mg/kg/day of carvediol (group C) or 400 mg/kg/day of tranilast (group T) or both of them (group B) for 2 weeks.
Results:
Blood pressure and heart rate were similar among the 4 groups. Echocardiography demonstrated tranilast improved fractional shortening (in %). Control: 6.2±2.5; Group C: 14.2±5.6, NS; Group T: 16.6±2.3, p<0.05; Group B: 17.2±3.2, p<0.05. Tranilast also improved cardiac hypertrophy measured with heart-to-body weight ratio (HW/BW in mg/g). Control: 12.4±2.5; Group C: 11.5±3.4, NS; Group T: 8.6±0.9, p<0.05; Group B: 5.9±1.1, p<0.01. Sarcolemmal expression of TRPV2 measured with immunostaining in 4C30 mice increased twice as much as syngeneic C57BL/6J. Tranilast, not carvedilol, halved the expression of TRPV2, corresponding to reduction in [Ca2+]i of isolated cardiomyocytes. Consistent with those changes, CaMKII phosphorylation reduced in the 4C30 mice after treatment of tranilast.
Conclusions:
Tranilast ameliorated heart failure symptoms of 4C30 mice, possibly due to the inhibition of Ca2+ influx through TRPV2.
1108-112 An embolic event to death in more than 50 percent of patients with idiopathic dilated cardiomyopathy in end-stage heart failure
