Synergism of atenolol and amlodipine on lowering and stabilizing blood pressure in spontaneously hypertensive rats

Pharmacological characterization of MT-1207, a novel multitarget antihypertensive agent

Hypertension is a serious public health problem worldwide. MT-1207, chemically named 3-(4-(4-(1H-benzotriazole-1-yl)butyl)piperazine-1-yl) benzisothiazole hydrochloride, is a new chemical entity that has entered into clinical trial as antihypertensive agent in China. In this paper we report the pharmacological profile of MT-1207 regarding its acute, subacute, and long-term effects on hypertensive animal models, and its actions on isolated organs in vitro as well as its molecular targets. Blood pressure (BP) was measured in conscious animals; amlodipine was taken as a positive control drug. We showed that both single dose of MT-1207 (1.25-20 mg/kg, ig) in spontaneously hypertensive rats (SHR) and MT-1207 (0.25-6 mg/kg, ig) in two-kidney one-clip (2K1C) dogs dose-dependently decreased BP. MT-1207 quickly decreased BP within 5 min after administration; the hypotensive effect lasted for 8 and 12 h, respectively, in SHR and 2K1C dogs without reflex increase in heart rate. Multiple doses of MT-1207 (5 mg · kg-1 · d-1 in SHR; 2 mg · kg-1 · d-1 in 2K1C dogs, for 7 days) significantly decreased BP, slightly reduced heart rate, and both of them recovered after withdrawal. Long-term administration of MT-1207 (10 mg · kg-1 · d-1 for 4 months or more time) produced a stable BP reduction, improved baroreflex sensitivity, reduced renal and cardiovascular damage in SHR, and delayed stroke occurrence and death in stroke-prone SHR. In isolated rat aortic rings precontracted by adrenaline, KCl, noradrenaline or 5-hydroxytryptamine (5-HT), MT-1207 (10-9-10-4 M) caused concentration-dependent relaxation. In a panel of enzyme activity or radioligand binding assays of 87 molecular targets, MT-1207 potently inhibited adrenergic α1A, α1B, α1D, and 5-HT2A receptors with Ki < 1 nM. The antagonism of MT-1207 against these receptors was confirmed in isolated rabbit arteries. We conclude that MT-1207 is a novel and promising single-molecule multitarget agent for hypertension treatment to reduce hypertensive organ damage and stroke mortality.

Nebivolol is more effective than atenolol for blood pressure variability attenuation and target organ damage prevention in L-NAME hypertensive rats

β-Adrenergic blockers are no longer recommended as first-line therapy due to the reduced cardioprotection of traditional β-blockers compared with other antihypertensive drugs. It is unknown whether third-generation β-blockers share the limitations of traditional β-blockers. The aim of the present study was to compare the effects of nebivolol or atenolol on central and peripheral systolic blood pressure (SBP) and its variability and target organ damage (TOD) in N-nitro-L-arginine methyl ester (L-NAME) hypertensive rats. Male Wistar rats were treated with L-NAME for 8 weeks together with oral administration of nebivolol 30 mg/kg (n = 8), atenolol 90 mg/kg (n = 8), or vehicle (n = 8). The control group was composed of vehicle-treated Wistar rats. SBP and its variability, as well as echocardiographic parameters, were assessed during the last 2 weeks of treatment. Tissue levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and transforming growth factor β (TGF-β), and histopathological parameters were evaluated in the left ventricle and aorta. Nebivolol had a greater ability than atenolol to decrease central SBP and mid-term and short-term blood pressure variability (BPV) in L-NAME rats. Echocardiographic analysis showed that nebivolol was more effective than atenolol on E/A wave ratio normalization. Compared with atenolol treatment, nebivolol had a greater protective effect on different TOD markers, inducing a decrease in collagen deposition and a reduction in the proinflammatory cytokines IL-6 and TNF-α in the left ventricle and aorta. Our findings suggest that the adverse hemodynamic profile and the reduced cardiovascular protection reported with traditional β-blockers must not be carried forward to third-generation β-blockers.

Blood Pressure Variability: Prognostic Value and Therapeutic Implications

Blood pressure variability (BPV) is considered nowadays a novel risk factor for cardiovascular disease. Early findings in sinoaortic denervated rats have clearly shown that enhanced fluctuation of blood pressure induced left ventricular hypertrophy, vascular stiffness, and renal lesion. A large number of clinical trials confirm that short-term and long-term blood pressure variability independently contributes to target organ damage, cardiovascular events, and mortality not only in hypertensive patients but also in subjects with diabetes mellitus and chronic kidney disease. Therefore, amelioration of BPV has been suggested as an additional target of the treatment of cardiovascular diseases. Preliminary evidence obtained from meta-analysis and controlled clinical trials has shown that antihypertensive classes differ in their ability to control excessive BP fluctuations with an impact in the prevention of cardiovascular events. Calcium channel blockers seem to be more effective than other blood pressure lowering drugs for the reduction of short-term and long-term BPV. In order to increase actual knowledge regarding the prognostic value and therapeutic significance of BPV in cardiovascular disease, there is a need for additional clinical studies specifically designed for the study of the relevance of short-term and long-term BPV control by antihypertensive drugs.

Beneficial effect of calcium channel blockers on home blood pressure variability in the morning in patients with type 2 diabetes

Aims/Introduction

Recent studies have shown the association between blood pressure variability and cardiovascular events. The present study was designed to investigate the relationship between antihypertensive drug class and home blood pressure variability in patients with type 2 diabetes.

Materials and Methods

We compared home blood pressure variability among patients treated with calcium channel blockers (n = 44), with angiotensin II receptor blockers and/or angiotensin‐converting enzyme inhibitors (n = 159), and with calcium channel blockers combined with angiotensin II receptor blockers and/or angiotensin‐converting enzyme inhibitors (n = 183). Next, we analyzed the effect of calcium channel blockers on morning blood pressure variability using multiple linear regression analysis.

Results

Coefficient variation of morning systolic blood pressure in patients treated with calcium channel blockers was significantly lower than that in patients treated with angiotensin II receptor blockers and/or angiotensin‐converting enzyme inhibitors (P = 0.036). Multivariate linear regression analyses showed that treatment with calcium channel blockers was significantly correlated with coefficient variation of morning systolic blood pressure (β = −0.264, P = 0.001).

Conclusions

The present study implies a possibility for validity on selecting calcium channel blockers in hypertensive patients with type 2 diabetes to reduce home blood pressure variability.

Synergic effects of levamlodipine and bisoprolol on blood pressure reduction and organ protection in spontaneously hypertensive rats

AIMS

Stroke is a major cause of disability and death worldwide. Hypertension is one of the most important risk factors for stroke. The objective of this work was to study the synergic effects of levamlodipine and bisoprolol on blood pressure reduction and organ protection in spontaneously hypertensive rats (SHR).

METHODS

Blood pressure was continuously monitored in conscious SHR. For acute study, a single dose of drugs was administrated via an intragastric catheter. For chronic study (4 months), drugs were delivered via rat chow.

RESULTS

A single dose of levamlodipine (from 1 mg/kg), bisoprolol (from 0.125 mg/kg), and their combinations significantly decreased blood pressure. The levamlodipine-induced tachycardia and the bisoprolol-induced bradycardia were temporized by the combination of these two drugs. Upon chronic treatment, this combination also decreased blood pressure variability and reduced organ damage.

CONCLUSION

Levamlodipine and bisoprolol produce synergic effects on blood pressure reduction and organ protection in SHR.

The combination of atenolol and amlodipine is better than their monotherapy for preventing end-organ damage in different types of hypertension in rats

Combinations therapy is often used in hypertensive patients whether combination therapy is necessary for preventing end-organ damage is not known. The objective of this study was to determine in four different hypertensive animal models the necessity of adding the calcium channel blocker amlodipine to therapy with the ß-blocker atenolol to modulate end-organ damage. Spontaneously hypertensive rats, DOCA-salt hypertensive rats, two-kidney, one-clip renovascular hypertensive rats and Lyon genetically hypertensive rats were used to study this objective. These animal models have different sensitivities to atenolol and amlodipine. The dosages of therapy employed were 10 mg/kg atenolol alone, 1 mg/kg amlodipine, 10 mg atenolol + 1 mg/kg amlodipine and 5 mg/kg atenolol+0.5 mg/kg amlodipine. BP was continuously recorded in all animals. After determination of baroreflex sensitivity, rats were sacrificed for end-organ damage evaluation. The combination of amlodipine and atenolol had a synergistic inhibitory effect on blood pressure and blood pressure variability, and end-organ damage as compared with monotherapy with atenolol or amlodipine in all animal models. Baroreflex sensitivity also improved with the combination therapy more than with monotherapy. In conclusion, atenolol and amlodipine combination exerts a superior effect on blood pressure, blood pressure variability, baroreflex sensitivity and end-organ damage. The superior effect of the combination was observed in all four models of hypertension.

Stability of amlodipine besylate and atenolol in multi-component tablets of mono-layer and bi-layer types

Multi-drug tablets of amlodipine besylate and atenolol were prepared as either mono-layer (mixed matrix) or bilayer tablets containing each drug in a separate layer by using similar excipients and processing. Each tablet batch was packed in strip and blister packs and kept under accelerated temperature and humidity conditions. The stability of two tablet and packaging types was compared by HPLC analysis after 0, 1, 3 and 4.5 months and expressed as the content of intact amlodipine and atenolol. The content of atenolol did not decline regardless of tablet and packaging type. Amlodipine content in bi-layer tablets decreased to about 95 and 88% when packed in strips and blisters, respectively. When prepared as mono-layer tablets, the content decreased to 72 and 32%, respectively.The study revealed that the bi-layer tablet formulation was more stable than the mono-layer type. Further, the stability was increased when the tablets were packed in aluminium strips as compared to PVC blisters.

Influence of atenolol and nifedipine on nitric-oxide deficient cardiomyocyte hypertrophy and expression of the cardio-endocrine peptide intermedin and its receptor components

BACKGROUND/AIMS

Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial ischemia, oxidative stress and hypertrophy; expression of adrenomedullin (AM) and intermedin (IMD) and their receptor activity modifying proteins (RAMPs 1-3) is augmented in cardiomyocytes, indicating that the myocardial AM/ IMD system may be activated in response to pressure loading and ischemic insult. The aim was to examine effects on (i) parameters of cardiomyocyte hypertrophy and on (ii) expression of AM and IMD and their receptor components in NO-deficient cardiomyocytes of an intervention chosen specifically for ability to alleviate pressure loading and ischemic injury concurrently.

METHODS

The NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 35 mg.kg(-1).day(-1)) was given to rats for 8 weeks, with/ without concurrent administration of beta-adrenoceptor antagonist, atenolol (25 mg.kg(-1).day(-1)) / calcium channel blocker, nifedipine (20mg.kg(-1).day(-1)).

RESULTS

In L-NAME treated rats, atenolol / nifedipine abolished increases in systolic blood pressure and plasma AM and IMD levels and in left ventricular cardiomyocytes: (i) normalized increased cell width and mRNA expression of hypertrophic (sk-alpha-actin) and cardio-endocrine (ANP, BNP, ET) genes; (ii) normalized augmented membrane protein oxidation; (iii) normalized mRNA expression of AM, IMD, RAMP1, RAMP2 and RAMP3.

CONCLUSIONS

normalization of blood pressure and membrane oxidant status together with prevention of hypertrophy and normalization of the augmented expression of AM, IMD and their receptor components in NO-deficient cardiomyocytes by atenolol / nifedipine supports involvement of both pressure loading and ischemic insult in stimulating cardiomyocyte hypertrophy and induction of these counter-regulatory peptides and their receptor components. Attenuation of augmented expression of IMD in this model cannot however be explained simply by prevention of cardiomyocyte hypertrophy.

Effects of combination therapy with atenolol and amlodipine on blood pressure control and stroke prevention in stroke-prone spontaneously hypertensive rats

AIM

To test the effects of atenolol and amlodipine, either alone or in combination, on blood pressure, blood pressure variability (BPV), baroreflex sensitivity (BRS), and the prevalence of stroke in stroke-prone spontaneously hypertensive rats (SHR-SP).

METHODS

In the first set of the study, 24 8-month-old, female SHR-SP rats were randomly divided into 3 groups. Blood pressure, heart period, and BRS were determined before and after the intragastric administration of atenolol (10 mg/kg) and amlodipine (1.0 mg/kg), either alone or in combination. In the second set of the study, 40 male and 40 female rats were randomly assigned to 1 of the following 4 groups: control, atenolol (10 mg.kg(-1).d(-1)), amlodipine (1.0 mg.kg(-1).d(-1)), and both (10 male and 10 female in each group). The stroke incident and survival time were recorded.

RESULTS

Atenolol and amlodipine, either alone or in combination, significantly decreased blood pressure, with the exception of the amlodipine-induced effect on diastolic blood pressure. Meanwhile, only the combination treatment significantly decreased the BPV levels for the same period. The q-values calculated by the probability sum analysis were 1.17 and 2.67 for systolic and diastolic blood pressure, respectively, and were 2.48 and 2.10 for systolic and diastolic BPV, respectively, following administration. Neither drug exhibited any significant effect on BRS. Atenolol and amlodipine, either alone or in combination, significantly increased the lifespan of SHR-SP, with the best effect elicited by the combination therapy.

CONCLUSION

A significant synergism exists between atenolol and amlodipine in lowering and stabilizing blood pressure in SHR-SP. Combination therapy may be an optimal strategy for the prevention of stroke in hypertension.

Treatment of hypertension based on measurement of blood pressure variability: lessons from animal studies

PURPOSE OF REVIEW

Blood pressure variability, a quantitative index for the spontaneous variation in blood pressure, has been proposed as a risk factor for end-organ damage and to determine the efficacy of hypertension treatment.

RECENT FINDINGS

Animal studies indicate that blood pressure variability is as important as blood pressure level in determining end-organ damage, and that high blood pressure variability is associated with end-organ damage, including myocardial lesions, aortic hypertrophy, vascular remodeling and renal damage. Although the organ damage induced by high blood pressure variability was similar to that induced by hypertension, comparative studies in sinoaortic-denervated and spontaneously hypertensive rats revealed that aortic hypertrophy is a sensitive index of high blood pressure variability, and left ventricular hypertrophy is a sensitive index of high blood pressure level. The possible mechanisms for high blood pressure variability-induced end-organ damage include: direct endothelial lesions, renin-angiotensin system activation, inflammation initiation and cardiomyocyte apoptosis augmentation. Blood pressure variability reduction contributes importantly to the organ-protective effect of some antihypertensive drugs.

SUMMARY

Although animal studies suggest some advantages in blood pressure variability measurements, clinical trials are necessary before the widespread use of blood pressure variability as a predictor of hypertensive organ damage and a new strategy for the treatment of hypertension.

Functional Arterial Baroreflex Attenuates the Effects of Antihypertensive Drugs in Conscious Rats

The present work was designed to observe the influences of arterial baroreflex (ABR) function on cardiovascular effects produced by four routinely used antihypertensive drugs in conscious rats. A low ABR model was obtained by the performance of sinoaortic denervation (SAD). The doses of the four drugs were as follows: nifedipine (1.5, 3.0 mg/kg), captopril (50, 100 mg/kg), atenolol (10, 20 mg/kg), and hydrochlorothiazide (20, 40 mg/kg). They were administered via an intra-gastric catheter. Compared with sham-operated rats, SAD significantly increased blood pressure variability about 2 times without modification of blood pressure level. The decrease in blood pressure level induced by the four tested drugs was larger in SAD rats than in sham-operated rats, which decreased to about 10 mmHg. Pulse interval was not changed by the treatment of captopril, but prolonged by atenolol in both sham-operated and SAD rats. In sham-operated groups, treatment of both nifedipine and hydrochlorothiazide decreased pulse interval. Whereas in sinoaortic denervated ones, this tachycardia was prevented. Among the four tested drugs, it was found that only nifedipine and atenolol significantly decreased blood pressure variability in SAD rats. It can be concluded that arterial baroreflex function was able to attenuate the hypotensive effects produced by antihypertensive drugs in conscious rats.

Reduction of blood pressure variability: a new strategy for the treatment of hypertension

The main aims of the treatment of hypertension are to prevent end-organ damage (EOD) and to avoid consequent lethal complications associated with hypertension. Blood pressure level is a well-known determinant of EOD. However, recent studies suggest that blood pressure variability (BPV) is as important as blood pressure level in determining EOD. The reduction of BPV is an important contributory factor of the organ protection provided by some antihypertensive drugs. Thus, reduction of BPV might represent a new strategy for the treatment of hypertension.

Synergism of atenolol and nitrendipine on hemodynamic amelioration and organ protection in hypertensive rats

OBJECTIVE

This study was designed to investigate the possible synergism of atenolol and nitrendipine on blood pressure (BP) and blood pressure variability (BPV) reductions, baroreflex sensitivity (BRS) amelioration, and organ protection in hypertensive rats.

METHOD

The dose was 20 mg/kg for atenolol, 10 mg/kg for nitrendipine and 20 + 10 mg/kg for the combination of these two drugs. In an acute study, a single dose was given via a catheter previously inserted into the stomach in spontaneously hypertensive rats (SHR). In a subacute study, SHR, deoxycorticosterone acetate (DOCA)-salt rats, and two-kidney, one-clip (2K1C) rats were used. They received the same dose by gavage daily for 10 days. BP was measured 24 h after drug administration. In chronic studies, these drugs at the aforementioned dose were mixed into rat chow. SHR were treated for 4 months. BP was then continuously recorded for 24 h. After the determination of BRS, rats were killed for organ-damage evaluation.

RESULTS

In the acute study, it was found that the combination of atenolol and nitrendipine had an obviously greater and longer BP reduction than treatment with each of these two drugs separately. In the subacute study, an effective decrease in BP 24 h after administration was found only in the rats treated with the combination. In chronic studies, it was found that the combination possessed the obvious synergism on BP and BPV reduction, BRS amelioration and organ protection in SHR. Multiple-regression analysis showed that the decrease in left ventricular hypertrophy was most significantly related to the decrease in systolic BPV and BP, the decrease in aortic hypertrophy was most significantly related to the increase in BRS and the decrease in systolic BPV, and amelioration in the renal lesion was most significantly associated with the restoration of BRS.

CONCLUSION

Treatment with a combination of atenolol and nitrendipine exhibited a rapid and persistent antihypertensive effect and possessed an obvious synergism on BP and BPV reduction, BRS restoration and organ protection in hypertensive rats. The decrease in BPV and the restoration of BRS may importantly contribute to organ protection in SHR with chronic treatment.

Inhibition of Inflammation Contributes to Organ Protection of Atenolol in Sinoaortic-Denervated Rats

The present study was designed to test the hypothesis that inhibition of inflammation contributes to the protective effects of atenolol on the organ damage induced by sinoaortic denervation (SAD) in rats. SAD was performed in male Sprague-Dawley rats at the age of 10 weeks. Atenolol (20 mg/kg/d, po) was administered for 12 weeks beginning from 4 weeks after SAD. Organ damage evaluation and the determination of plasma TXB2, serum IL-1, TNF-alpha and tissue reactive oxygen species (ROS) were performed at 16 weeks after SAD. It was found that there existed obvious organ damage including increased cardiac and aortic collagen, and glomerular injury, in SAD rats. Plasma TXB2, serum TNF-alpha IL-1, and tissue ROS increased significantly after SAD. Long-term treatment with atenolol significantly prevented the organ damage with a decrease in left ventricular weight, cardiac and aortic collagen contents, and glomerular injury score in SAD rats. Plasma TXB2, serum IL-1, and tissue ROS were found to be significantly decreased by the long-term treatment with atenolol. Furthermore, it was found that the levels of inflammation-related factors were significantly related to all the organ-damage parameters studied in this experiment. These results suggest that inhibition of inflammation and oxygen stress contributes to the organ-protective effects of atenolol in SAD rats.