Identification of genes related to heart failure using global gene expression profiling of human failing myocardium.

Although various management methods have been developed for heart failure, it is necessary to investigate the diagnostic or therapeutic targets of heart failure. Accordingly, we have developed different approaches for managing heart failure by using conventional microarray analyses. We analyzed gene expression profiles of myocardial samples from 12 patients with heart failure and constructed datasets of heart failure-associated genes using clinical parameters such as pulmonary artery pressure (PAP) and ejection fraction (EF). From these 12 genes, we selected four genes with high expression levels in the heart, and examined their novelty by performing a literature-based search. In addition, we included four G-protein-coupled receptor (GPCR)-encoding genes, three enzyme-encoding genes, and one ion-channel protein-encoding gene to identify a drug target for heart failure using in silico microarray database. After the in vitro functional screening using adenovirus transfections of 12 genes into rat cardiomyocytes, we generated gene-targeting mice of five candidate genes, namely, MYLK3, GPR37L1, GPR35, MMP23, and NBC1. The results revealed that systolic blood pressure differed significantly between GPR35-KO and GPR35-WT mice as well as between GPR37L1-Tg and GPR37L1-KO mice. Further, the heart weight/body weight ratio between MYLK3-Tg and MYLK3-WT mice and between GPR37L1-Tg and GPR37L1-KO mice differed significantly. Hence, microarray analysis combined with clinical parameters can be an effective method to identify novel therapeutic targets for the prevention or management of heart failure.

Natriuretic peptides enhance the production of adiponectin in human adipocytes and in patients with chronic heart failure.

OBJECTIVES: We investigated the functional relationship between natriuretic peptides and adiponectin by performing both experimental and clinical studies. BACKGROUND: Natriuretic peptides are promising candidates for the treatment of congestive heart failure (CHF) because of their wide range of beneficial effects on the cardiovascular system. Adiponectin is a cytokine derived from adipose tissue with various cardiovascular-protective effects that has been reported to show a positive association with plasma brain natriuretic peptide (BNP) levels in patients with heart failure. METHODS: The expression of adiponectin messenger ribonucleic acid (mRNA) and its secretion were examined after atrial natriuretic peptide (ANP) or BNP was added to primary cultures of human adipocytes in the presence or absence of HS142-1 (a functional type A guanylyl cyclase receptor antagonist). Changes of the plasma adiponectin level were determined in 30 patients with CHF who were randomized to receive intravenous ANP (0.025 microg/kg/min human ANP for 3 days, n = 15) or saline (n = 15). RESULTS: Both ANP and BNP dose-dependently enhanced the expression of adiponectin mRNA and its secretion, whereas such enhancement was inhibited by pre-treatment with HS142-1. The plasma adiponectin level was increased at 4 days after administration of human ANP compared with the baseline value (from 6.56 +/- 0.40 microg/ml to 7.34 +/- 0.47 microg/ml, p < 0.05), whereas there was no change of adiponectin in the saline group (from 6.53 +/- 0.57 microg/ml to 6.55 +/- 0.56 microg/ml). CONCLUSIONS: Natriuretic peptides enhance adiponectin production by human adipocytes in vitro and even in patients with CHF, which might have a beneficial effect on cardiomyocytes in patients receiving recombinant natriuretic peptide therapy for heart failure.

Long-term stimulation of adenosine A2b receptors begun after myocardial infarction prevents cardiac remodeling in rats.

BACKGROUND: Adenosine inhibits proliferation of cardiac fibroblasts and hypertrophy of cardiomyocytes, both of which may play crucial roles in cardiac remodeling. In the present study, we investigated whether chronic stimulation of adenosine receptors begun after myocardial infarction (MI) prevents cardiac remodeling. METHODS AND RESULTS: MI was produced in Wistar rats by permanent ligation of the left anterior descending coronary artery. One week after the onset of MI, animals were randomized into 8 groups: vehicle, dipyridamole (DIP; the adenosine uptake inhibitor, 50 mg/kg), 2-chroloadenosine (CADO; the stable analogue of adenosine, 2 mg/kg), and CADO in the presence of the nonselective adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT) or the selective antagonist for adenosine A1, A2a, A2b, or A3 receptor. Three weeks after treatment, hemodynamic and echocardiographic parameters in the DIP and CADO groups were significantly improved compared with the vehicle group. These hemodynamic and echocardiographic improvements were blunted by either 8-SPT or the selective adenosine A2b antagonist MRS1754 but not by the selective antagonists for other subtypes of adenosine receptors. The collagen volume fraction was smaller, and gene expression of the molecules associated with cardiac remodeling such as matrix metalloproteinase in noninfarcted areas was reduced in the DIP and CADO groups compared with the vehicle group, both of which were attenuated by either 8-SPT or MRS1754. CONCLUSIONS: Long-term stimulation of adenosine A2b receptors begun after MI attenuates cardiac fibrosis in the noninfarcted myocardium and improves cardiac function. Drugs that stimulate adenosine A2b receptors or increase adenosine levels are new candidates for preventing cardiac remodeling after MI.

Angiotensin II type 1 receptor blocker prevents atrial structural remodeling in rats with hypertension induced by chronic nitric oxide inhibition.

The prevalence of atrial fibrillation (AF) increases in patients with hypertension. Angiotensin II is involved in structural atrial remodeling, which contributes to the onset and maintenance of AF in paced animal models. We investigated the role of angiotensin II in atrial structural remodeling in rats with hypertension. Ten-week-old male Wistar-Kyoto rats were randomly divided into 4 groups: a control group (no treatment), an Nomega-nitro-L-arginine methyl ester (L-NAME) group (administered L-NAME, an inhibitor of nitric oxide synthase, 1 g/l in drinking water), an L-NAME+candesartan group (L-NAME plus candesartan-an angiotensin II receptor blocker (ARB)-at 0.1 mg/kg/day), and an L-NAME + hydralazine group (L-NAME plus hydralazine at 120 mg/l in drinking water). Eight weeks after treatment, the L-NAME group showed significantly higher systolic blood pressure than the control group (197 +/- 12 vs.138 +/- 5 mmHg, p < 0.05). Candesartan or hydralazine with L-NAME reduced systolic blood pressure to baseline. Chronic inhibition of NO synthesis increased the extent of fibrosis and transforming growth factor-beta expression in atrial tissue, and both of these effects were prevented by candesartan, but not by hydralazine. Cardiac hypertrophy and dysfunction were induced in the L-NAME group, and these effects were also prevented by candesartan, but not by hydralazine. In contrast, the decrease in thrombomodulin expression in the atrial endocardium in hypertensive rats was restored by candesartan and hydralazine. The ARB prevented atrial structural remodeling, a possible contributing factor for the development of AF, in the hearts of rats with hypertension induced by long-term inhibition of NO synthesis.

Unusual appearance of mitral annular calcification mimicking intracardiac tumor prompting early surgery.

Although mitral annular calcification (MAC) is usually easy to diagnose by transthoracic echocardiography, we experienced a rare case with MAC which looked like an intracardiac tumor. The patient who had been on chronic hemodialysis for 20 years was admitted to our hospital because of dyspnea. Transthoracic echocardiography showed a mass with severe calcification on the anterior mitral annulus and mean mitral gradient of 20 mm Hg. Because of the suspicion of the intracardiac calcified tumor that restricted mitral valve motion causing mitral obstruction, she underwent resection of the mass and mitral valve replacement. Pathological findings showed that the mass had a calcified envelope containing liquefied necrotic eosinophilic material with lympocytic infiltrate inside consistent with MAC. We should consider a possibility of MAC when we see a severe calcified mass attached to the mitral annulus in a patient on long-term hemodialysis.

Depression of proteasome activities during the progression of cardiac dysfunction in pressure-overloaded heart of mice.

The ubiquitin-proteasome system contributes to regulation of apoptosis degrading apoptosis-regulatory proteins. Marked accumulation of ubiquitinated proteins in cardiomyocytes of human failing hearts suggested impaired ubiquitin-proteasome system in heart failure. Since cardiomyocyte apoptosis contributes to the progression of cardiac dysfunction in pressure-overloaded hearts, we investigated the role of ubiquitin-proteasome system in such conditions. We found that proteasome activities already depressed before the onset of cardiac dysfunction in pressure-overloaded hearts of mice. Cardiomyocyte apoptosis was observed along with depression of proteasome activities and elevation of proapoptotic/antiapoptotic protein ratio in failing hearts. In cultured cardiomyocytes, pharmacological inhibition of proteasome accumulated proapoptotic proteins such as p53 and Bax. Gene silencing of these proapoptotic proteins by RNA interference prevented the accumulation of respective proteins and attenuated cardiomyocyte apoptosis induced by proteasome inhibition. We conclude that depression of proteasome activities contributes to cardiac dysfunction resulting from cardiomyocyte apoptosis through accumulation of proapoptotic proteins by impaired degradation.