Angiotensin receptor blockade improves myocardial beta-adrenergic receptor signaling in postinfarction left ventricular remodeling

Effects of olmesartan therapy on the expression of lung adrenoceptors in rats with chronic heart failure

INTRODUCTION

Adrenergic receptors (AR) play important roles in regulating lung function. However, there are few reports concerning AR expression and the protective effect of angiotensin II receptor blockers (ARB) on the lung in chronic heart failure (CHF). In this study, we aimed to investigate the protective effects of the ARB olmesartan on the lung in CHF.

MATERIALS AND METHODS

Wistar rats were randomly divided into four groups: normal control, sham-operated rats, rats with CHF induced by ligating the left anterior descending coronary arteries, and rats with CHF treated with olmesartan (1 mg/kg) once daily for 8 weeks. Heart function, plasma renin activity (PRA) and angiotensin II (Ang II) levels, lung microscopic structure inspection and mRNA and protein expressions of α1A-, β1- and β2-AR in lung were tested.

RESULTS

Compared with the CHF group, PRA and Ang II levels were decreased while heart function and mRNA and protein expression of α1A-AR, β1-AR and β2-AR were up-regulated in the olmesartan group (p<0.05 or p<0.01). The inflammation and cell proliferation in CHF lung tissue were reduced in the olmesartan group.

CONCLUSION

Olmesartan may play a beneficial role in protecting lung in CHF by up-regulating AR and decreasing levels of PRA and Ang II.

Effects of azilsartan compared to other angiotensin receptor blockers on left ventricular hypertrophy and the sympathetic nervous system in hemodialysis patients

Hypertension is a major risk factor for cardiovascular and cerebrovascular events, and most patients with hypertension are administered antihypertensive drugs. However, not all patients achieve normal blood pressure levels. The new angiotensin receptor blocker azilsartan (Takeda Pharmaceutical Company Limited, Osaka, Japan) has been reported to have a strong hypotensive effect. Our study investigated the efficacy of azilsartan compared with other angiotensin receptor blockers. This study included 17 hypertensive patients on HD, who had been administered angiotensin receptor blockers, except for azilsartan, for more than 6 months before enrolling, and after enrollment, they were switched to azilsartan. Blood tests, Holter electrocardiogram, ambulatory blood pressure monitoring, and echocardiography were performed at baseline and at the 6-month follow-up. The blood pressure from baseline to 6 months had significantly decreased (24-h systolic blood pressure from 150.9 ± 16.2 mm Hg to 131.3 ± 21.7 mm Hg, P = 0.008), awakening time systolic blood pressure from 152.1 ± 16.9 mm Hg to 131.7 ± 23.2 mm Hg, P = 0.01, sleep-time systolic blood pressure from 148.1 ± 19.7 mm Hg to 130.0 ± 20.1 mm Hg, P = 0.005). There was a significant reduction in serum noradrenaline levels as well as left ventricular mass index after switching to azilsartan (from 550.1 ± 282.9 pg/mL, to 351.7 ± 152.3 pg/mL, P = 0.002; from 117.0 ± 26.4 g/m(2) to 111.3 ± 23.9 g/m(2), P = 0.01, respectively). Azilsartan had a significantly stronger hypotensive effect than other angiotensin receptor blockers. Thus, the switch to azilsartan might improve prognosis of hemodialysis patients. We suggest that the strong anti-hypertensive effect of azilsartan originated from a combination of primary angiotensin receptor blocker class-effect and a stronger suppression of sympathetic nervous system.

Telmisartan, a unique ARB, improves left ventricular remodeling of infarcted heart by activating PPAR gamma

Unfavorable left ventricular (LV) remodeling after myocardial infarction (MI) leads to cardiac dysfunction. We examined whether Telmisartan, an angiotensin (Ang) II type I receptor blocker (ARB), could improve the recovery of LV function in a rat model of MI. The effect of Telmisartan as a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist was also investigated. After 28 days of MI, a significant improvement of survival was observed in the Telmisartan-treated rat group compared with the vehicle control rat group, non-PPAR-γ agonistic ARB (Losartan)-treated rat group, and Telmisartan plus specific PPAR-γ antagonist (GW9662)-treated rat group. Although no significant differences of blood pressure or infarct size were observed among these four groups, the Telmisartan group had better systolic and diastolic LV function. There was a significant reduction of the plasma brain natriuretic peptide level, cardiac fibrosis area, infiltration of macrophages, size of cardiomyocytes, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive myocytes, activation of matrix metalloproteinases-2 and -9 (MMPs-2/9), and expression of transforming growth factor β-1 (TGF-β1), connective tissue growth factor (CTGF), and osteopontin (OPN), while expression of PPAR-γ and activation of tissue inhibitor of metalloproteinase-1 (TIMP-1) was enhanced, in the noninfarcted myocardium of rats from the Telmisartan group compared with the other three groups. To mimic ischemic conditions in vitro, neonatal rat cardiomyocytes and cardiac fibroblasts were incubated in hypoxic condition for 24 h. Increased transcriptional activation of PPAR-γ and TIMP-1, and inhibition of TGF-β1 expression were observed in cardiomyocytes, while decreased activation of MMPs-2/9 and decrease in CTGF and OPN expression was seen in cardiac fibroblasts cultured with Telmisartan. In conclusion, Telmisartan prevented unfavorable cardiac remodeling through a reduction of cardiac hypertrophy and fibrosis. An anti-inflammatory effect and PPAR-γ activation were suggested to be important in addition to suppression of Ang II activity.

Role of vascular endothelial growth factor-A in development of abdominal aortic aneurysm

AIMS

Increased angiogenesis, chronic inflammation, and extracellular matrix degradation are the major pathological features of abdominal aortic aneurysm (AAA). We sought to elucidate the role of vascular endothelial growth factor (VEGF)-A, a potent angiogenic and proinflammatory factor, in the development of AAA.

METHODS AND RESULTS

Human AAA samples showed increased VEGF-A expression, neovascularization, and macrophage infiltration compared with normal aortic walls. AAA was induced in mice by periaortic application of CaCl(2). AAA mice were treated with soluble VEGF-A receptor (sFlt)-1 or phosphate-buffered saline and sacrificed 6 weeks after the operation. Treatment with sFlt-1 resulted in reduced aneurysm size, restored wavy structure of the elastic lamellae, reduced Mac-2(+) monocytes/macrophages, CD3(+) T-lymphocytes, and CD31(+) vessels, and attenuated matrix metalloproteinase (MMP)-2 and 9 activity in periaortic tissue of AAA. Increased aortic mRNA expression of monocyte chemotactic protein-1, tumour necrosis factor-α, and intercellular adhesion molecule-1 in AAA was attenuated by sFlt-1 treatment.

CONCLUSION

VEGF-A was overexpressed in the aortic wall of human and experimental AAA. Treatment with sFlt-1 inhibited AAA development in mice, in association with reduced neoangiogenesis, infiltration of inflammatory cells, MMP activity, and extracellular matrix degradation. These findings suggest a crucial role of VEGF-A in the development of AAA.

Disruption of adenylyl cyclase type V does not rescue the phenotype of cardiac-specific overexpression of Galphaq protein-induced cardiomyopathy

Adenylyl cyclase (AC) is the principal effector molecule in the β-adrenergic receptor pathway. AC(V) and AC(VI) are the two predominant isoforms in mammalian cardiac myocytes. The disparate roles among AC isoforms in cardiac hypertrophy and progression to heart failure have been under intense investigation. Specifically, the salutary effects resulting from the disruption of AC(V) have been established in multiple models of cardiomyopathy. It has been proposed that a continual activation of AC(V) through elevated levels of protein kinase C could play an integral role in mediating a hypertrophic response leading to progressive heart failure. Elevated protein kinase C is a common finding in heart failure and was demonstrated in murine cardiomyopathy from cardiac-specific overexpression of G(αq) protein. Here we assessed whether the disruption of AC(V) expression can improve cardiac function, limit electrophysiological remodeling, or improve survival in the G(αq) mouse model of heart failure. We directly tested the effects of gene-targeted disruption of AC(V) in transgenic mice with cardiac-specific overexpression of G(αq) protein using multiple techniques to assess the survival, cardiac function, as well as structural and electrical remodeling. Surprisingly, in contrast to other models of cardiomyopathy, AC(V) disruption did not improve survival or cardiac function, limit cardiac chamber dilation, halt hypertrophy, or prevent electrical remodeling in G(αq) transgenic mice. In conclusion, unlike other established models of cardiomyopathy, disrupting AC(V) expression in the G(αq) mouse model is insufficient to overcome several parallel pathophysiological processes leading to progressive heart failure.

Angiotensin-receptor blockade reduces border zone myocardial monocyte chemoattractant protein-1 expression and macrophage infiltration in post-infarction ventricular remodeling

BACKGROUND

Monocyte chemoattractant protein-1 (MCP-1) is a key mediator of left ventricular (LV) remodeling during the early phase of myocardial infarction (MI). The hypothesis tested was that myocardial MCP-1 expression would increase during the chronic phase of MI and an angiotensin-II type 1 receptor blocker (ARB) would attenuate macrophage infiltration through decreased myocardial MCP-1 expression.

METHODS AND RESULTS

MI was produced by ligation of the left coronary artery in Wistar rats, which were then randomized to treatment with vehicle (MI/C), candesartan (10 mg.kg(-1).day(-1)) for 6 weeks (MI/ARB0-6W), or candesartan for 2 weeks, starting 4 weeks after MI (MI/ARB4-6W). LV systolic and end-diastolic pressures 6 weeks after MI were decreased in MI/ARB0-6W compared with MI/C or MI/ARB4-6W, however, there were no differences in other hemodynamic or echocardiographic parameters among infarcted rat groups. Both long- and short-term treatments with ARB similarly reduced mRNA expressions of MCP-1, transforming growth factor-beta1, and procollagen type I and III, macrophage infiltration, and myocardial fibrosis in the border zone.

CONCLUSIONS

In post-MI heart failure, ARB attenuated MCP-1 expression and macrophage infiltration in the border zone, resulting in less myocardial fibrosis. ARB may exert its beneficial effect, at least in part, by inhibiting myocardial macrophage-related inflammation.

Role of AT1 receptor in isoproterenol-induced cardiac hypertrophy and oxidative stress in mice

Elevated activities of the sympathetic nerve and renin-angiotensin systems are common features of heart failure. This study was designed to investigate the roles of the AT1 receptor in cardiac hypertrophy and oxidative stress during excessive beta-adrenoceptor stimulation using an AT1 receptor antagonist (ARB) and AT1a receptor-deficient (AT1aR(-/-)) mice. Isoproterenol (ISO) was given to C57BL mice with or without ARB (olmesartan) treatment and to AT1aR(-/-) mice by a subcutaneously implanted osmotic mini-pump for 11 days at a rate of 15 mg/kg/day. Chronic ISO infusion to C57BL mice caused concentric cardiac hypertrophy (sham; 4.1+/-0.1, ISO; 5.2+/-0.2 mg/g heart to body weight ratio), accompanied by enhancement of cardiac collagen accumulation, lipid peroxidation, superoxide generation and NADPH oxidase activity. The AT1a and beta-1,2 receptor mRNA expressions were down-regulated in the heart of ISO-infused mice. Olmesartan markedly suppressed cardiac mass enlargement as well as increases of oxidative indicators without any effects on heart rate. Olmesartan did not affect the cardiac angiotensin and beta-adrenergic receptor mRNA expression patterns. The AT1a receptor contribution to ISO-induced cardiac hypertrophy was reproduced in AT1aR(-/-) mice. These data suggest that the AT1 receptor plays a crucial role in the development of cardiac hypertrophy and oxidative stress under excessive beta-adrenergic stimulation, and that ARB treatment is beneficial for sympatho-excitatory cardiac hypertrophy and failure in mice.

Candesartan

Candesartan cilexetil is the prodrug of candesartan, an angiotensin II receptor antagonist. Candesartan binds selectively and non-competitively to the angiotensin II receptor type 1, thus preventing the actions of angiotensin II. Clinical trials have demonstrated its efficacy at a dose range of 2 to 32 mg once daily in hypertension of all grades, heart failure, in reducing urinary albumin excretion in diabetes mellitus and in coexisting hypertension and renal failure. Pharmacokinetic properties of candesartan cilexetil in elderly patients are not significantly different from those in younger individuals. Hepatic impairment does not change pharmacokinetics of candesartan cilexetil at doses up to 12 mg/day. No dose adjustment is necessary in patients with mild or moderate renal impairment. Tolerability of candesartan cilexetil is not much different from that of placebo. All adverse events are usually of mild to moderate severity and not dose-related. The most common adverse events were headache, upper respiratory tract infection, back pain, and dizziness. The incidence of these adverse effects, as well as of cough, was similar in patients treated with candesartan cilexetil or placebo. The incidence of adverse events in long-term trials was not different from that in short-term trials. Tolerability of candesartan cilexetil does not differ with either age or gender.