tranilast and Ventricular-Dysfunction--Left

Tranilast is clinically indicated for the treatment of allergic disorders and is also a nonselective blocker of the transient receptor potential vanilloid 2 (TRPV2) channel. Previous studies have found that it has protective effects in various animal models of cardiac disease. Our laboratory has found that genetic deletion of TRPV2 results in a blunted hypertrophic response to increased afterload; thus, this study tested the hypothesis that tranilast through cardiomyocyte TRPV2 blockade can inhibit the hypertrophic response to pressure overload in vivo through transverse aortic constriction and ex vivo through isolated myocyte studies. The in vivo studies demonstrated that tranilast blunted the fibrotic response to increased afterload and, to a lesser extent, the hypertrophic response. After 4 weeks, this blunting was associated with improved cardiac function, although at 8 weeks, the cardiac function deteriorated similarly to the control group. Finally, the in vitro studies demonstrated that tranilast was not inhibiting these responses at the cardiomyocyte level. In conclusion, we demonstrated that tranilast blunting of the fibrotic and hypertrophic response occurs independently of cardiac TRPV2 channels and may be cardioprotective in the short term but not after prolonged administration.

Topics: Animals; Calcium Channels; Disease Models, Animal; Disease Progression; Fibrosis; Hypertrophy, Left Ventricular; Male; Mice, Knockout; Myocytes, Cardiac; ortho-Aminobenzoates; Recovery of Function; Signal Transduction; Time Factors; Transforming Growth Factor beta1; TRPV Cation Channels; Ventricular Dysfunction, Left; Ventricular Function, Left; Ventricular Remodeling

This study sought to assess the effects of tranilast on atrial remodeling in a canine atrial fibrillation (AF) model.. Tranilast inhibits transforming growth factor (TGF)-β1 and prevents fibrosis in many pathophysiological settings. However, the effects of tranilast on atrial remodeling remain unclear.. Beagles were subjected to atrial tachypacing (400 beats/min) for 4 weeks while treated with placebo (control dogs, n = 8) or tranilast (tranilast dogs, n = 10). Sham dogs (n = 6) did not receive atrial tachypacing. Atrioventricular conduction was preserved. Ventricular dysfunction developed in the control and tranilast dogs due to rapid ventricular responses.. Atrial fibrillation duration (211 ± 57 s) increased, and AF cycle length and atrial effective refractory period shortened in controls, but these changes were suppressed in tranilast dogs (AF duration, 18 ± 10 s, p < 0.01 vs. control). The L-type calcium channel α1c (Cav1.2) micro ribonucleic acid expression decreased in control dogs (sham 1.38 ± 0.24 vs. control 0.65 ± 0.12, p < 0.01), but not in tranilast dogs (0.97 ± 0.14, p = not significant vs. sham). Prominent atrial fibrosis (fibrous tissue area, sham 0.8 ± 0.1 vs. control 9.3 ± 1.3%, p < 0.01) and increased expression of tissue inhibitor of metalloproteinase protein 1 were observed in control dogs but not in tranilast dogs (fibrous tissue area, 1.4 ± 0.2%, p < 0.01 vs. control). The TGF-β1 (sham 1.00 ± 0.07 vs. control 3.06 ± 0.87, p < 0.05) and Rac1 proteins were overexpressed in control dogs, but their overexpression was inhibited in tranilast dogs (TGF-β1, 1.28 ± 0.20, p < 0.05 vs. control).. Tranilast prevented atrial remodeling and suppressed AF development in a canine model. Its inhibition of TGF-β1 and Rac1 overexpression may contribute to its antiremodeling effects.

Topics: Animals; Atrial Fibrillation; Cardiac Pacing, Artificial; Cardiotonic Agents; Disease Models, Animal; Dogs; Heart Atria; ortho-Aminobenzoates; Tachycardia; Ventricular Dysfunction, Left

Diastolic dysfunction is an increasingly recognized complication of diabetes that develops in relatively young patients as a result of diabetic cardiomyopathy (DCM). With recent advances in echocardiographic technology now permitting the reliable assessment of diastolic function in the rat, we examined cardiac function and structure in diabetic rodents and assessed the effects of intervening with tranilast, an antifibrotic compound that has been shown to attenuate the actions of transforming growth factor-beta (TGF-beta) in cardiac fibroblasts. We also sought to examine the mechanism whereby tranilast inhibits the actions of TGF-beta. Six-week-old heterozygous (mRen-2)27 rats were randomized to receive either streptozotocin or citrate buffer and then further randomized to receive either tranilast (400 mg x kg(-1) x day(-1) by twice daily gavage) or vehicle for another 8 wk. Cell signaling was examined in neonatal cardiac fibroblasts. After 8 wk, diabetic rats showed evidence of impaired diastolic function with reduced early-to-late atrial wave ratio and prolonged deceleration time in association with fibrosis, apoptosis, and hypertrophy (all P < 0.05). Treatment with tranilast prevented the development of diastolic dysfunction and the histopathological features of DCM. While tranilast did not affect Smad phosphorylation, it significantly attenuated TGF-beta-induced p44/42 mitogen-activated protein kinase phosphorylation.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Cardiomyopathies; Cytokines; Diabetes Complications; Diastole; Disease Models, Animal; Dose-Response Relationship, Drug; Female; ortho-Aminobenzoates; Rats; Streptozocin; Treatment Outcome; Ultrasonography; Ventricular Dysfunction, Left

Mast cells are believed to be involved in the pathophysiology of heart failure, but their precise role in the process is unknown. This study examined the role of mast cells in the progression of heart failure, using mast cell-deficient (WBB6F1-W/W(v)) mice and their congenic controls (wild-type [WT] mice). Systolic pressure overload was produced by banding of the abdominal aorta, and cardiac function was monitored over 15 wk. At 4 wk after aortic constriction, cardiac hypertrophy with preserved left ventricular performance (compensated hypertrophy) was observed in both W/W(v) and WT mice. Thereafter, left ventricular performance gradually decreased in WT mice, and pulmonary congestion became apparent at 15 wk (decompensated hypertrophy). In contrast, decompensation of cardiac function did not occur in W/W(v) mice; left ventricular performance was preserved throughout, and pulmonary congestion was not observed. Perivascular fibrosis and upregulation of mast cell chymase were all less apparent in W/W(v) mice. Treatment with tranilast, a mast cell-stabilizing agent, also prevented the evolution from compensated hypertrophy to heart failure. These observations suggest that mast cells play a critical role in the progression of heart failure. Stabilization of mast cells may represent a new approach in the management of heart failure.

Topics: Animals; Animals, Congenic; Atrial Natriuretic Factor; Chymases; Disease Models, Animal; Gene Expression; Heart Failure; Hypertrophy, Left Ventricular; Male; Mast Cells; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; ortho-Aminobenzoates; Serine Endopeptidases; Ventricular Dysfunction, Left; Ventricular Function, Left