Chymase inhibition reduces the progression to heart failure after autoimmune myocarditis in rats.

Chymase has been known as a local angiotensin II-generating enzyme in the cardiovascular system in dogs, monkeys, hamsters, and humans; however, recently it was reported that chymase also has various other functions. Therefore, we decided to examine whether the inhibition of chymase improves disease conditions associated with the pathophysiology of dilated cardiomyopathy in rats and its possible mechanism of action as rat chymase is unable to produce angiotensin II. We examined the effect of TY-51469, a novel chymase inhibitor (0.1 mg/kg/day [group CYI-0.1, n = 15] and 1 mg/kg/day [group CYI-1, n = 15]), in myosin-immunized postmyocarditis rats. Another group of myosin-immunized rats was treated with vehicle (group V, n = 15). Age-matched normal rats without immunization (group N, n = 10) were also included in the study. After 4 weeks of treatment, we evaluated cardiac function; area of fibrosis; fibrogenesis; levels of transforming growth factor (TGF)-beta1 and collagen III; hypertrophy and its marker, atrial natriuretic peptide (ANP); and mast cell activity. Survival rate and myocardial functions improved dose-dependently with chymase inhibitor treatment after myosin immunization. A reduction in the percent area of myocardial fibrosis, fibrogenesis, myocardial hypertrophy, and mast cell activity along with a reduction in TGF-beta1, collagen III, and ANP levels in the myocardium were noted in postmyocarditis rats that received chymase inhibitor treatment. The treatment also decreased myocardial aldosterone synthase levels in those animals. Inhibition of chymase reduces the pathogenesis of postmyocarditis dilated cardiomyopathy and progression to heart failure by preventing the pathological remodeling and residual inflammation in rats.

Swimming stress in DN 14-3-3 mice triggers maladaptive cardiac remodeling: role of p38 MAPK.

It is generally believed that a mechanical signal initiates a cascade of biological events leading to coordinated cardiac remodeling. 14-3-3 family members are dimeric phosphoserine-binding proteins that regulate signal transduction, apoptotic, and checkpoint control pathways. To evaluate the molecular mechanism underlying swimming stress-induced cardiac remodeling, we examined the role of 14-3-3 protein and MAPK pathway by pharmacological and genetic means using transgenic mice with cardiac-specific expression of dominant-negative (DN) mutants of 14-3-3 (DN 14-3-3/TG) and p38alpha/beta MAPK (DNp38alpha and DNp38beta) mice. p38 MAPK activation was earlier, more marked, and longer in the myocardium of the TG group compared with that of the nontransgenic (NTG) group after swimming stress, whereas JNK activation was detected on day 5 and decreased afterward. In contrast, ERK1/2 was not activated after swimming stress in either group. Cardiomyocyte apoptosis, cardiac hypertrophy, and fibrosis were greatly increased in the TG group compared with those in the NTG group. Moreover, we found a significant correlation between p38 MAPK activation and apoptosis in the TG group. Furthermore, DN 14-3-3 hearts showed enhanced atrial natriuretic peptide expression. In contrast, DNp38alpha and DNp38beta mice exhibited reduced mortality and increased resistance to cardiac remodeling after 28 days of swimming stress compared with TG and NTG mice. Besides, treatment with a p38 MAPK inhibitor, FR-167653, resulted in regression of cardiac hypertrophy and fibrosis and improvement in the survival rate in the TG group. These results indicate for the first time that 14-3-3 protein along with p38 MAPK plays a crucial role in left ventricular remodeling associated with swimming stress.

Glycogen synthase kinase 3beta together with 14-3-3 protein regulates diabetic cardiomyopathy: effect of losartan and tempol.

Glycogen synthase kinase (GSK) 3beta is a multifunctional protein that positively regulates myocardial apoptosis and negatively regulates hypertrophy. However, the role of GSK3beta in the diabetic myocardium is largely unknown. We found that GSK3beta became more active (less phosphorylated at serine 9) via decreased Akt phosphorylation, in parallel to c-Jun NH2 terminal kinase activation, which correlated with increased activated caspase 3 and myocardial apoptosis 3 days after streptozotocin (STZ) injection in mice. However, 28 days after STZ injection, GSK3beta became inactive, which correlated with the enhanced protein kinase C beta2 and p38 mitogen activated protein kinase expression, nuclear translocation of nuclear factor of activated T cells c3, cardiac hypertrophy and fibrosis. All of the above parameters were exacerbated in dominant-negative 14-3-3 transgenic mice. Our results suggest that GSK3beta together with 14-3-3 protein plays essential roles in the signaling of diabetic cardiomyopathy, and treatment with either losartan or tempol prevents these changes.

Comparative effects of pranidipine with amlodipine in rats with heart failure.

The aim of the present study was to compare the cardioprotective properties of long-acting calcium channel antagonist pranidipine with amlodipine in rat model of heart failure induced by autoimmune myocarditis. Twenty-eight days after immunization the surviving rats were randomized for the oral administration of low-dose amlodipine (1 mg/kg/day), high-dose amlodipine (5 mg/kg/day), pranidipine (0.3 mg/kg/day) or vehicle (0.5% methylcellulose). After oral administration for 1 month, the animals underwent echocardiography and hemodynamic analysis. Histopathology, immunohistochemistry, and Western immunoblotting were carried out in the heart samples. Both pranidipine and high-dose amlodipine increased survival rate. Although the heart rate did not differ among the four groups, left ventricular end-diastolic pressure was significantly decreased and +/-dP/dt was increased in the pranidipine- and high-dose amlodipine-treated rats, but not in low-dose amlodipine-treated rats. In comparison to amlodipine treatment, pranidipine treatment significantly reduced myocyte size and central venous pressure. Furthermore, both pranidipine and high-dose amlodipine treatment significantly reduced myocardial protein levels of atrial natriuretic peptide and inducible nitric oxide synthase, whereas pranidipine only significantly decreased tumor necrosis factor-alpha, and improved sarcoplasmic reticulum Ca2+ ATPase2 protein levels. We conclude that pranidipine ameliorates the progression of left ventricular dysfunction and cardiac remodeling in rats with heart failure after autoimmune myocarditis in a lower dose when compared to amlodipine and which may be a clinically potential therapeutic agent for the treatment of heart failure.

Effects of angiotensin II receptor blocker (candesartan) in daunorubicin-induced cardiomyopathic rats.

BACKGROUND: Daunorubicin is an anthracycline anti-tumor agent; anthracycline chemotherapy in cancer can cause severe cardiomyopathy leading to a frequently fatal congestive heart failure; the first-line treatment is diuretics and digoxin. Recently, angiotensin-converting enzyme inhibitors have been shown to be effective in the treatment of such toxicity. The purpose of this study was to investigate the effects of angiotensin II type-1 receptor antagonist (candesartan) in a rat model of daunorubicin-induced cardiomyopathy. METHODS: Rats were treated with a cumulative dose of 9 mg/kg body weight daunorubicin (i.v.). 28 days later, after the development of cardiomyopathy, animals were randomly assigned to candesartan-treated (5 mg/kg/day, p.o.) or vehicle-treated groups; age-matched normal rats were used as the control group. Candesartan treatment was continued for 28 days. Hemodynamic and echocardiographic parameters were measured, cardiac protein and mRNA were analyzed, and histopathological analyses of myocardial fibrosis, cell size and apoptosis were conducted. RESULTS: Following cardiomyopathy, left ventricular end diastolic pressure and left ventricular systolic dimension were significantly elevated; while % fractional shortening and Doppler E/A ratio were significantly reduced. Cardiomyopathic hearts showed significant increases in % fibrosis, % apoptosis, and myocyte diameter/body weight ratio; candesartan treatment reversed these changes. Fas-L protein overexpression in myopathic hearts was significantly suppressed by treatment with candesartan. Moreover, SERCA2 mRNA and protein expression were both down-regulated in myopathic hearts and restored to normal by candesartan treatment, significantly. CONCLUSIONS: Our findings suggest that candesartan treatment significantly improved the left ventricular function and reversed the myocardial pathological changes investigated in this model of daunorubicin-induced cardiomyopathy; suggesting its potentials in limiting daunorubicin cardiotoxicity.