Control of left ventricular mass by moxonidine involves reduced DNA synthesis and enhanced DNA fragmentation

Place of imidazoline receptor agonists in the treatment of hypertension

The review is devoted to selective I1-imidazoline-receptor agonists. An analysis of Russian and foreign studies is presented, the results of which indicate that this drug class not only provides adequate and long-term control of blood pressure, but also has a number of favorable metabolic effects. Therefore, it contributes to reducing insulin resistance (weight loss) and has organ protective properties (endothelial function improvement, left ventricular hypertrophy regression, microalbuminuria reduction). At the same time, selective I1-imidazoline-receptor agonists are much less likely to cause side effects characteristic of old-generation sympatholytic agents. This class of drugs is invariably included in Russian guidelines for the diagnosis and treatment of hypertension.

Moxonidine modulates cytokine signalling and effects on cardiac cell viability

Regression of left ventricular hypertrophy and improved cardiac function in SHR by the centrally acting imidazoline I1-receptor agonist, moxonidine, are associated with differential actions on circulating and cardiac cytokines. Herein, we investigated cell-type specific I1-receptor (also known as nischarin) signalling and the mechanisms through which moxonidine may interfere with cytokines to affect cardiac cell viability. Studies were performed on neonatal rat cardiomyocytes and fibroblasts incubated with interleukin (IL)-1β (5 ng/ml), tumor necrosis factor (TNF)-α (10 ng/ml), and moxonidine (10(-7) and 10(-5) M), separately and in combination, for 15 min, and 24 and 48 h for the measurement of MAPKs (ERK1/2, JNK, and p38) and Akt activation and inducible NOS (iNOS) expression, by Western blotting, and cardiac cell viability/proliferation and apoptosis by flow cytometry, MTT assay, and Live/Dead assay. Participation of imidazoline I1-receptors and the signalling proteins in the detected effects was identified using imidazoline I1-receptor antagonist and signalling protein inhibitors. The results show that IL-1β, and to a lower extent, TNF-α, causes cell death and that moxonidine protects against starvation- as well as IL-1β -induced mortality, mainly by maintaining membrane integrity, and in part, by improving mitochondrial activity. The protection involves activation of Akt, ERK1/2, p38, JNK, and iNOS. In contrast, moxonidine stimulates basal and IL-1β-induced fibroblast mortality by mechanisms that include inhibition of JNK and iNOS. Thus, apart from their actions on the central nervous system, imidazoline I1-receptors are directly involved in cardiac cell growth and death, and may play an important role in cardiovascular diseases associated with inflammation.

Moxonidine-based combination antihypertensive therapy in patients with metabolic syndrome

Aim.To assess the effects of moxonidine-based combination therapy on clinical status, laboratory parameters, and target organs in patients with metabolic syndrome (MS).Material and methods.In total, 60 MS patients with Stage 1-2 arterial hypertension (AH) were randomised into 3 groups. Group I was administered moxonidine (0,2-0,4 mg/d) and amlodipine (5-10 mg/d); Group II received moxonidine (0,2-0,4 mg/d) and hydrochlorothiazide (12,5 mg/d); Group III was treated with moxonidine (0,2-0,4 mg/d) and enalapril (10-20 mg/d). At baseline and after 24 weeks of treatment, the following characteristics were assessed: waist circumference (WC), body mass index (BMI), 24-hour blood pressure monitoring (BMP) parameters, left ventricular myocardial mass index (LVMMI), E/A ratio, isovolumetric relaxation time (IVRT), deceleration time (DT) of early diastolic velocity, peak Em velocity at interventricular septum and lateral wall levels, E/Em ratio (myocardial tissue Doppler echocardiography), pulse wave velocity (PWV) between descending aorta and aortic bifurcation levels (ultrasound method), and stiffness index β of ascending aorta. In addition, lipid, carbohydrate, and purine metabolism parameters were assessed; glomerular filtration rate (GFR) was calculated (MDRD method); and urine albumin levels were measured.Results.In Group I (moxonidine + amlodipine), target blood pressure (BP) levels were achieved in 70% of the patients. Systolic BP (SBP) levels, LVMMI, and DT decreased by 19,3±11,4 mm Hg, 4,4 g/m2 (p=0,09), and 10,6 ms (p<0,05), respectively. The increase in E/A ratio and Em annular velocity (Em av) reached 0,4 (p<0,05) and 1,4 cm/s (p<0,05), respectively, while E/Em av ratio decreased by 0,8 (p<0,05), and PWV decreased by 1,6 ms (p<0,05). The BMI decrease reached 0,7 kg/m2 (p<0,05). In Group II (moxonidine + hydrochlorothiazide), target BP levels were achieved in 40% of the participants, with a decrease in SBP levels by 14,7 mm Hg (p<0,05). DT was reduced by 9,4 ms (p<0,05), E/A ratio increased by 0,1 (p<0,05), while PWV, BMI, and GFR decreased by 1,3 m/s (p<0,05), 0,8 kg/m2 (p<0,05), and 5,6 ml/min/1,73 m2 (p<0,05), respectively. In Group III (moxonidine + enalapril), 60% of the patients achieved target BP levels, and SBP levels were reduced by 21,1 mm Hg (p<0,05). LVMMI decreased by 5,1 g/m2 (p<0,05), Em av increased by 0,3 cm/s (p<0,05), while the respective reduction in PWV, WC, and BMI reached 1,1 m/s (p<0,05), 1,8 cm (p<0,05), and 0,5 kg/m2 (p<0,05). All three groups demonstrated a significant reduction in urine albumin levels.Conclusion.The moxonidine-based combination therapy effectively reduced the levels of BP and urine albumin. The combination of moxonidine with amlodipine or enalapril improved cardiac structure and function, as well as renal excretory function. The combination of moxonidine and hydrochlorothiazide, however, negatively affected renal excretion. All three variants of combination therapy were metabolically neutral and demonstrated beneficial effects on visceral obesity.

Moxonidine improves cardiac structure and performance in SHR through inhibition of cytokines, p38 MAPK and Akt

BACKGROUND AND PURPOSE

Regression of left ventricular hypertrophy by moxonidine, a centrally acting sympatholytic imidazoline compound, results from a sustained reduction of DNA synthesis and transient stimulation of DNA fragmentation. Because apoptosis of cardiomyocytes may lead to contractile dysfunction, we investigated in spontaneously hypertensive rats (SHR), time- and dose-dependent effects of in vivo moxonidine treatment on cardiac structure and function as well as on the inflammatory process and signalling proteins involved in cardiac cell survival/death.

EXPERIMENTAL APPROACH

12 week old SHR received moxonidine at 0, 100 and 400 µg·kg(-1)·h(-1) , s.c., for 1 and 4 weeks. Cardiac function was evaluated by echocardiography; plasma cytokines were measured by elisa and hearts were collected for histological assessment of fibrosis and measurement of cardiac proteins by Western blotting. Direct effects of moxonidine on cardiac cell death and underlying mechanisms were investigated in vitro by flow cytometry and Western blotting.

KEY RESULTS

After 4 weeks, the sub-hypotensive dose of moxonidine (100 µg) reduced heart rate and improved global cardiac performance, reduced collagen deposition, regressed left ventricular hypertrophy, inhibited Akt and p38 MAPK phosphorylation, and attenuated circulating and cardiac cytokines. The 400 µg dose resulted in similar effects but of a greater magnitude, associated with blood pressure reduction. In vitro, moxonidine inhibited norepinephrine-induced neonatal cardiomyocyte mortality but increased fibroblast mortality, through I(1)-receptor activation and differential effects on downstream Akt and p38 MAPK.

CONCLUSIONS AND IMPLICATIONS

While the antihypertensive action of centrally acting imidazoline compounds is appreciated, new cardiac-selective I(1)-receptor agonists may confer additional benefit.

A Western-type diet attenuates pulmonary hypertension with heart failure and cardiac cachexia in rats

Western-type diets (WD) constitute risk factors for disease but may have distinct effects in heart failure (HF) with cardiac cachexia (CC). We evaluated hemodynamic, metabolic, and inflammatory effects of short-term WD intake in pulmonary hypertension (PH) with CC. Male Wistar rats randomly received 60 mg · kg(-1) monocrotaline (M) or vehicle (C) and consumed either a 5.4-kcal · g(-1) WD (35% animal fat, 35% simple carbohydrate, 20% protein, 0.4% Na(+)) or a 2.9-kcal · g(-1) (3% vegetable fat, 60% complex carbohydrate, 16% protein, 0.25% Na(+)) normal diet (ND) for 5 wk. Mortality, energy intake, body weight (BW), metabolism, hemodynamics, histology, apoptosis, gene expression, transcription factors, and plasma cytokines were evaluated. Compared with the C-ND group, the M-ND group had PH, HF, and mortality that were significantly attenuated in M-WD. The extent of myocardial remodeling and apoptosis was higher in M-ND than in C-ND but lower in M-WD than in M-ND, while conversely, energy intake, BW, cholesterol, and TG plasma concentrations were lower in M-ND than in C-ND but higher in M-WD than in M-ND. M-ND had increased myocardial NF-κB transcription factor activity, endothelin-1, and cytokine overexpression and higher circulating cytokine concentrations than C-ND, which were lower in M-WD than in M-ND. PPARα activity, however, was lower in M-ND, but not in M-WD, compared with the respective C groups. WD attenuated PH and CC, ameliorating survival, myocardial function, metabolism, and inflammation, through transcription factor modulation, suggesting a beneficial role in CC.

Functional and molecular effects of imidazoline receptor activation in heart failure

AIMS

Heart failure is a progressive deterioration in heart function associated with overactivity of the sympathetic nervous system. The benefit of inhibition of sympathetic activity by moxonidine, a centrally acting imidazoline receptor agonist, was questioned based on the outcome of a failing clinical trial. The following studies measured cardiac structure and hemodynamics and mechanisms underlying moxonidine-induced changes, in cardiomyopathic hamsters, where the stage of the disease, dose, and compliance were controlled.

MAIN METHODS

Male BIO 14.6 hamsters (6 and 10 months old, with moderate and advanced heart failure, respectively) received moxonidine at 2 concentrations: low (2.4 mg/kg/day) and high (9.6 mg/kg/day), or vehicle, subcutaneously, for 1month. Cardiac function was measured by echocardiography, plasma and hearts were collected for histological determination of fibrosis and apoptosis, as well as for measurement cytokines by Elisa and cardiac proteins by Western blotting.

KEY FINDINGS

Compared to age-matched vehicle-treated BIO 14.6, moxonidine did not reduce blood pressure but significantly reduced heart rate and improved cardiac performance. Moxonidine exerted anti-apoptotic effect with differential inflammatory/anti-inflammatory responses that culminate in attenuated cardiac apoptosis and fibrosis and altered protein expression of collagen types. Some effects were observed regardless of treatment onset, although the changes were more significant in the younger group. Interestingly, moxonidine resulted in upregulation of cardiac imidazoline receptors.

SIGNIFICANCE

These studies imply that in addition to centrally mediated sympathetic inhibition, the effects of moxonidine may, at least in part, be mediated by direct actions on the heart. Further investigation of imidazolines/imidazoline receptors in cardiovascular diseases is warranted.

Anti-hypertensive drugs and left ventricular hypertrophy: a clinical update

Structural remodelling of the heart, known as left ventricular hypertrophy (LVH), is a consequence of systemic hypertension, and is associated with an increased risk of cardiovascular morbidity and mortality. Therefore, particular attention should be paid to the identification, prevention and treatment of this condition in hypertensive patients. LVH seems to benefit from all classes of anti-hypertensive drugs; however, antagonists of the renin-angiotensin-aldosterone system (RAAS) have demonstrated an additional benefit in the inhibition and reversal of myocardial interstitial fibrosis. Nevertheless, in evaluating the degree of arterial hypertension and organ damage, many neuro-hormonal systems are involved, primarily the sympathetic nervous system, thereby explaining the use of different classes of anti-hypertensive drugs to prevent or reduce LVH. The RAAS antagonists are actually the recommended anti-hypertensive agents to prevent organ damage in hypertensive subjects or in hypertensives with evidence of LVH to reduce cardiovascular mortality and morbidity.

Hemodynamic and cardiac effects of chronic eprosartan and moxonidine therapy in stroke-prone spontaneously hypertensive rats

The renin-angiotensin and sympathetic nervous systems play critical interlinked roles in the development of left ventricular hypertrophy, fibrosis, and dysfunction. These studies investigated the hemodynamic and cardiac effects of monoblockade and coblockade of renin-angiotensin and sympathetic nervous systems. Stroke-prone spontaneously hypertensive rats (16 weeks old; male; n=12 per group) received the sympatholytic imidazoline compound, moxonidine (2.4 mg/kg per day); the angiotensin-receptor blocker eprosartan (30 mg/kg per day), separately or in combination; or saline vehicle for 8 weeks, SC, via osmotic minipumps. Blood pressure and heart rate were continuously measured by radiotelemetry. After 8 weeks, in vivo cardiac function and structure were measured by transthoracic echocardiography and a Millar conductance catheter, and the rats were then euthanized and blood and heart ventricles collected for various determinations. Compared with vehicle, the subhypotensive dose of moxonidine resulted in lower (P<0.01) heart rate, left ventricular hypertrophy, cardiomyocyte cross-sectional area, interleukin 1 beta, tumor necrosis factor-alpha, and mRNA for natriuretic peptides. Eprosartan reduced pressure (P<0.01), as well as extracellular signal-regulated kinase (ERK) 44 phosphorylation, Bax/Bcl-2, and collagen I/III, and improved left ventricular diastolic function (P<0.03). Combined treatment resulted in greater reductions in blood pressure, heart rate, left ventricular hypertrophy, collagen I/III, and inhibited inducible NO synthase and increased endothelial NO synthase phosphorylation, as well as reduced left ventricular anterior wall thickness, without altering the other parameters. Thus, in advanced hypertension complicated with cardiac fibrosis, sympathetic inhibition and angiotensin II blockade resulted in greater reduction in blood pressure and heart rate, inhibition of inflammation, and improved left ventricular pathology but did not add to the benefits of angiotensin II blockade on cardiac function.