Amlodipine enhances NO production induced by an ACE inhibitor through a kinin-mediated mechanism in canine coronary microvessels

Cardioprotective Effects of Mebudipine in a Rat Model of Doxorubicin-Induced Heart Failure

Background

Mebudipine, a dihydropyridine calcium-channel blocker (CCB), shows greater time- and voltage-dependent inhibitory effects than nifedipine. Its significant negative chronotropic effects without having considerable negative inotropic properties may make it a suitable candidate for the pharmacotherapy of heart failure (HF). This study aimed to investigate the possible beneficial action of mebudipine in a rat model of HF.

Methods

The present study carried out in the Department of Pharmacology at the Iran University of Medical Sciences during the years of 2009-2011. An experimental model of HF was induced in male Wistar rats using doxorubicin (DOX). The rats were divided into five groups with seven animals in each group: normal control group, DOX-induced HF control groups, and treatment groups. The animals were administered DOX for 15 days. A consistent deterioration occurred after a four-week rest period. The animals were then treated with intraperitoneal mebudipine (0.5 mg/kg) and intraperitoneal amlodipine (0.35 mg/kg), as well as an equal volume of distilled water for 15 days. The plasma levels of big endothelin-1 (BET-1), creatine kinase-myocardial band (CK-MB), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), as well as the clinical status (heart rate and blood pressure), were assessed before and after treatment. Statistical analysis was performed with SPSS software using parametric and nonparametric ANOVA.

Results

Mebudipine and amlodipine reversed the increased plasma BET-1 values in the treated animals when compared with the HF control group (0.103 and 0.112 vs 0.231 pg/mL, respectively). The increased plasma levels of AST, ALT, CK-MB, and LDH were also reversed in the HF animals that received mebudipine or amlodipine.

Conclusion

The administration of mebudipine to HF animals, akin to amlodipine, palliated the clinical and biochemical signs of the disease in the present study. The abstract was presented in the Iranian Congress of Physiology and Pharmacology as a poster and published in the Scientific Information Database as a supplement (2015; Vol 22).

Amlodipine/atorvastatin: the first cross risk factor polypill for the prevention and treatment of cardiovascular disease

In 2002, the World Health Organization estimated that over 58% of cardiovascular disease in North America is due to 'both blood pressure and cholesterol higher than optimal'. Unfortunately, less than a third of patients with both conditions are identified, and fewer than one in ten reach the treatment goals for both factors. Adherence to treatment is notably improved when therapy is initiated simultaneously. Combination therapy of amlodipine besylate (Norvasc, Pfizer Ltd) with atorvastatin calcium (Lipitor, Pfizer Ltd), marketed as Caduet (Pfizer Ltd) is the first dual-therapy compound designed to treat hypertension and/or angina and dyslipidemia concurrently with a single daily pill in the full range of dosing combinations. Amlodipine/atorvastatin retains the safety and efficacy of its parent compounds whilst simplifying the management of these comorbid conditions, in what may be considered the first version of a polypill.

Modern views on amlodipine and new S-amlodipine medications

The review presents the latest evidence on the calcium antagonist amlodipine, summarizing its mechanisms of action, its pleiotropic, endothelial function-related effects, and its anti-atherogenic activity. Amlodipine suppresses the proliferation of vascular smooth myocytes and extracellular matrix and improves endothelial vasodilatation, despite the absence of L-type calcium channels in these cells. This mechanism is related to an increase in endothelial nitric oxide (NO) release. The results of experimental studies on the role of S and R amlodipine isomers in its hemodynamic and pleiotropic activity are presented. While S-amlodipine is a pharmacologically active blocker of L-type calcium channels, R-amlodipine increases endothelial NO release. New medications have been developed, based on S-amlodipine. It has been shown that S-amlodipine 5 mg/d is bioequivalent to amlodipine 10 mg/d. The pharmacodynamics analysis demonstrated that S-amlodipine 5 mg/d and amlodipine 10 mg/d did not differ significantly in terms of mean levels of systolic and diastolic blood pressure, or mean heart rate. S-amlodipine was better tolerated and characterised by a lower incidence of peripheral edema than amlodipine. However, the effects of S-amlodipine on hard end-points should be investigated in the long-term prospective studies.

Improving vascular function in hypertension: potential benefits of combination therapy with amlodipine and renin-angiotensin-aldosterone system blockers

Hypertension is characterized by endothelial dysfunction and increased risk for adverse cardiovascular outcomes. In addition to lowering blood pressure, the calcium-channel blocker amlodipine and blockers of the renin-angiotensin-aldosterone system (angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers) may further reduce cardiovascular risk by improving endothelial function when used alone or in combination. In fact, the beneficial effects of the combination of amlodipine and a renin-angiotensin-aldosterone system blocker on endothelial function have been found to be greater than the effect of either drug alone, likely due to additive effects on nitric oxide activity. This review summarizes the observed effects of these agents on endothelial function and the complementary mechanisms by which they act, thus providing rationale (beyond blood pressure benefits) for their use in combination.

Choice of ACE inhibitor combinations in hypertensive patients with type 2 diabetes: update after recent clinical trials

The diabetes epidemic continues to grow unabated, with a staggering toll in micro- and macrovascular complications, disability, and death. Diabetes causes a two- to fourfold increase in the risk of cardiovascular disease, and represents the first cause of dialysis treatment both in the UK and the US. Concomitant hypertension doubles total mortality and stroke risk, triples the risk of coronary heart disease and significantly hastens the progression of microvascular complications, including diabetic nephropathy. Therefore, blood pressure reduction is of particular importance in preventing cardiovascular and renal outcomes. Successful antihypertensive treatment will often require a combination therapy, either with separate drugs or with fixed-dose combinations. Angiotensin converting enzyme (ACE) inhibitor plus diuretic combination therapy improves blood pressure control, counterbalances renin-angiotensin system activation due to diuretic therapy and reduces the risk of electrolyte alterations, obtaining at the same time synergistic antiproteinuric effects. ACE inhibitor plus calcium channel blocker provides a significant additive effect on blood pressure reduction, may have favorable metabolic effects and synergistically reduce proteinuria and the rate of decline in glomerular filtration rate, as evidenced by the GUARD trial. Finally, the recently published ACCOMPLISH trial showed that an ACE inhibitor/calcium channel blocker combination may be particularly useful in reducing cardiovascular outcomes in high-risk patients. The present review will focus on different ACE inhibitor combinations in the treatment of patients with type 2 diabetes mellitus and hypertension, in the light of recent clinical trials, including GUARD and ACCOMPLISH.

Combining RAAS and calcium channel blockade: ACCOMPLISH in perspective

The Avoiding Cardiovascular events through COMbination therapy in Patients LIving with Systolic Hypertension (ACCOMPLISH) trial was the first trial to compare the cardiovascular outcomes of initial fixed-dose combination angiotensin-converting enzyme inhibitor (ACEI)/calcium channel blocker (CCB) and ACEI/diuretic therapy in patients with hypertension and high risk of cardiovascular events. The initial combination therapy was effective in this population, with ACEI/CCB therapy providing the greatest benefit (reduction in risk of cardiovascular events). Whether or not the findings of ACCOMPLISH can be applied to other renin-angiotensin-aldosterone system (RAAS) inhibitor/CCB combinations, such as angiotensin receptor blocker (ARB)/CCB combinations, has yet to be investigated. The present report reviews the results of ACCOMPLISH, data from trials comparing ARB and ACEI therapies, and findings from studies of ARB/CCB combination therapy that support the use and further study of combination therapy with RAAS inhibitors and CCBs.

Risk-based classification of hypertension and the role of combination therapy

The recognition of a continuous relationship between elevated blood pressure (BP) and cardiovascular risk has influenced national and international guidelines for the classification, prevention, and management of hypertension. The most recent report (2003) of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure uses BP thresholds to define categories of normal, prehypertension, and hypertension. A new definition proposed by the Hypertension Writing Group in 2005 offers an approach to diagnosis and management based on global or total risk. Thus, even in the absence of sustained elevations in BP, patients may have a moderate to high risk of vascular events due to the presence of additional cardiovascular risk factors, disease markers, and target organ damage. The 2007 European guidelines continue to classify hypertension based on cutoffs while also placing emphasis on multivariate formulations for cardiovascular risk assessment and goals of therapy. All 3 sets of guidelines acknowledge the necessity of using > or =2 antihypertensive agents to attain BP goals in many patients.

Exceptional early blood pressure control rates: the ACCOMPLISH trial

BACKGROUND

ACCOMPLISH is a "new-generation" hypertension trial assessing single-tablet combination therapy for initial treatment of high-risk hypertension. At baseline, 97% of subjects were treated with anti-hypertensive medication at entry, but only 37% of participants had blood pressure (BP) control (<140/90 mmHg). Single-tablet combination therapy may improve control rates.

METHODS

The mean BP change from baseline at the end of 6 months (the time point when subjects should have had all of the drug titrations to achieve BP control) was examined for 10,704 randomized patients. Within-group changes were examined using t-tests. Comparisons between subgroups were made using analysis of variance (ANOVA) and covariance (ANCOVA).

RESULTS

Mean (+/-SD) BP fell from 145+/-18/80+/-11 mmHg at randomization to 132+/-16/74+/-10 mmHg. The 6-month BP control rate was 73% in the overall trial (78% in the US), 43% in diabetics and 40% in patients with renal disease. Of the patients uncontrolled, 61% were not on maximal medications, suggesting potential increases in control rates. Serious hypotensive events occurred in 1.8% of participants.

CONCLUSION

ACCOMPLISH BP control rates are the highest of any multi-national trial to date. Whereas current guidelines recommend combination therapy only for stage 2 hypertension, in this trial it is expedient and safe for both stage 1 and 2 hypertension.

Combination therapy with renin-angiotensin system blockers: Will amlodipine replace hydrochlorothiazide?

Amlodipine is a highly effective and safe antihypertensive dihydropyridine calcium channel blocker. It is even more effective when used in combination with other antihypertensive medications, including hydrochlorothiazide. When antihypertensive calcium channel blockers were first introduced, evidence in the laboratory that they had some natriuretic properties was adduced to suggest that they would be "the diuretics of the 1990s." This turned out not to be the case. Because of its clinical efficacy, amlodipine is frequently used in fixed-dose combination products, but it is not likely to replace hydrochlorothiazide.

Targeting mechanisms of hypertensive vascular disease with dual calcium channel and renin-angiotensin system blockade

Patients with hypertension, particularly those with diabetes mellitus, are at heightened risk for cardiovascular and renal disease. Accumulated evidence indicates that the majority of hypertensive patients at high risk will require more than one antihypertensive agent to reach their blood pressure (BP) target. A reasonable strategy is to use agents with complementary mechanisms of action to enhance BP-lowering efficacy and prevent target organ damage. In experimental models, the combination of a calcium channel blocker (CCB) with an agent that blocks the renin-angiotensin system (RAS), an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker, improves measures of endothelial function, inflammation, ventricular remodelling and renal function to a greater degree than these classes given as monotherapy. In clinical trials, calcium channel/RAS blockade combination therapy has been shown to provide greater BP reductions and improve renal function in patients with diabetic and nondiabetic renal disease earlier and to a greater extent than monotherapy. In addition, dual calcium channel/RAS blockade increases arterial compliance, arterial distensibility and flow-mediated vasodilation. Expanding upon extensive research on the benefits of calcium channel blockade and RAS blockade for the prevention of vascular events and preclinical and clinical trial evidence suggests added effects of combination therapy by targeting the underlying mechanisms of hypertensive vascular disease.

Add-on Amlodipine Improves Arterial Function and Structure in Hypertensive Patients Treated With an Angiotensin Receptor Blocker

The present study was designed to determine whether adding amlodipine further improved functional and structural cardiovascular damage in hypertensive patients whose blood pressure was already well controlled with an angiotensin II type 1 receptor blocker (ARB). The cardiothoracic ratio on chest radiographs, level of urinary albumin excretion, pulse wave velocity (PWV), intima-media thickness (IMT) of the carotid arteries, and 24 hour ambulatory blood pressure (BP) were evaluated before and 12 months after the start of add-on of amlodipine or placebo in 50 hypertensive patients being treated with an ARB. The add-on amlodipine therapy significantly improved the PWV from 1689 +/- 61 to 1447 +/- 47 cm/s and the IMT from 0.88 +/- 0.08 to 0.75 +/- 0.06 mm in the hypertensive patients treated with an ARB without altering their mean 24 hour ambulatory BP values, but did not alter the cardiothoracic ratio or urinary albumin excretion. Amlodipine also significantly decreased the variability of ambulatory BP, but the decrease did not significantly contribute to the changes in PWV or IMT. Thus, the add-on low-dose amlodipine therapy had benefits in terms of the vascular function and vascular structure of hypertensive patients treated with an ARB that were independent of its depressor effects. The antiatherogenic pleiotropic properties of amlodipine have a preventive effect on the progression of arterial stiffness in hypertensive patients treated with an ARB.

Interaction of Endothelial Nitric Oxide and Angiotensin in the Circulation

Discovery of the unexpected intercellular messenger and transmitter nitric oxide (NO) was the highlight of highly competitive investigations to identify the nature of endothelium-derived relaxing factor. This labile, gaseous molecule plays obligatory roles as one of the most promising physiological regulators in cardiovascular function. Its biological effects include vasodilatation, increased regional blood perfusion, lowering of systemic blood pressure, and antithrombosis and anti-atherosclerosis effects, which counteract the vascular actions of endogenous angiotensin (ANG) II. Interactions of these vasodilator and vasoconstrictor substances in the circulation have been a topic that has drawn the special interest of both cardiovascular researchers and clinicians. Therapeutic agents that inhibit the synthesis and action of ANG II are widely accepted to be essential in treating circulatory and metabolic dysfunctions, including hypertension and diabetes mellitus, and increased availability of NO is one of the most important pharmacological mechanisms underlying their beneficial actions. ANG II provokes vascular actions through various receptor subtypes (AT1, AT2, and AT4), which are differently involved in NO synthesis and actions. ANG II and its derivatives, ANG III, ANG IV, and ANG-(1-7), alter vascular contractility with different mechanisms of action in relation to NO. This review article summarizes information concerning advances in research on interactions between NO and ANG in reference to ANG receptor subtypes, radical oxygen species, particularly superoxide anions, ANG-converting enzyme inhibitors, and ANG receptor blockers in patients with cardiovascular disease, healthy individuals, and experimental animals. Interactions of ANG and endothelium-derived relaxing factor other than NO, such as prostaglandin I2 and endothelium-derived hyperpolarizing factor, are also described.

Calcium channel blockers in the spectrum of antihypertensive agents

Calcium channel blockers (CCBs) are widely used in the treatment of hypertension. Through blood pressure reduction, and possibly other mechanisms such as antioxidative effects, they may play a role in diminishing the risk for a variety of cardiovascular outcomes. The combination of CCBs with other newer antihypertensive agents such, as ACE inhibitors and angiotensin receptor blockers, may provide complementary effects on risk reduction in cardiovascular adverse events and renal disease. Although the efficacy of CCBs as antihypertensive agents has been adequately demonstrated, there have been concerns regarding the use of short acting dihydropyridines after acute myocardial infarction. There have also been questions about the role of CCBs with regards to other antihypertensive agents in renal disease. For example, differential effects of dihydropyridine and non-dihydropyridine CCBs may affect progression of renal disease and risk for diabetes. Certain precautions involving drug interactions are needed because of the effects of CCBs on the CYP450 enzyme systems.

A Randomized, Double-Blind Trial Comparing the Effects of Amlodipine Besylate/Benazepril HCl vs Amlodipine on Endothelial Function and Blood Pressure

Evidence suggests that renin-angiotensin-aldosterone system inhibition ameliorates endothelial dysfunction. The authors examined the effect of amlodipine besylate/benazepril HCl combination treatment compared with amlodipine besylate monotherapy in modulating endothelial dysfunction. This multicenter, double-blind, 12-week study randomized 70 hypertensive subjects with at least one other endothelial dysfunction risk factor to amlodipine besylate/benazepril HCl (5/20 mg/d force-titrated to 5/40 mg/d) or amlodipine besylate monotherapy (5 mg/d force-titrated to 10 mg/d). Both the combination and monotherapy produced significant median increases from baseline in percentage flow-mediated vasodilation (2.0% and 1.2%, respectively) and percentage change in percent flow-mediated vasodilation (25% and 16%, respectively). These improvements were numerically larger with combination treatment, but between-group differences did not achieve statistical significance. Reductions in systolic and diastolic blood pressure were significantly greater (P=.0452/P=.0297) with combination treatment (-18.6/-12.3 mm Hg) than with monotherapy (-14.8/-9.1 mm Hg). A highly positive correlation between change in systolic blood pressure and change in percent of flow-mediated vasodilation was demonstrated only for combination treatment.

Insulin resistance in hypertension and cardiovascular disease

Insulin resistance is not simply a problem of decreased glucose uptake in response to insulin, but a multifaceted syndrome that significantly increases the risk for cardiovascular disease. Insulin resistance is strongly associated with arterial hypertension and a pathogenetic role in the development of arterial hypertension has been suggested. One question that remains open concerns the clinical approach to insulin-resistant patients. Observational and clinical trial data suggest that lifestyle changes including weight reduction and regular physical activity can improve insulin sensitivity and reduce the incidence and mortality of cardiovascular disease. Daily physical activity of moderate intensity for 30 min has a cardioprotective effect and reduces insulin resistance, independent of the effect on body weight. A pharmacological therapy for insulin resistance reducing cardiovascular disease remains to be defined. Concerning the antihypertensive therapy of insulin-resistant hypertensive patients, most hypertensive guidelines fail to provide specific advice.

Optimal Vascular Protection: A Case for Combination Antihypertensive Therapy

Endothelial dysfunction is an important factor in the pathogenesis of atherosclerosis, hypertension, and heart failure. The endothelium mediates vascular tone, structure, and function by the release and regulation of multiple vasoactive substances that promote or inhibit vasodilation, vasoconstriction, cell growth, and other mechanisms. The effect of antihypertensive drugs on endothelial function may be an important indicator of their ability to reduce risks for cardiovascular morbidity and mortality. Endothelium-dependent vasodilation induced by various antihypertensive drugs is accurately measured with high-resolution ultrasound of flow-mediated dilation of the brachial artery. Calcium channel blockers and angiotensin-converting enzyme inhibitors have been shown to reverse endothelial dysfunction. The benefits of angiotensin-converting enzyme inhibitors and calcium channel blockers on the endothelium are believed to derive from their effects on nitric oxide production and antioxidant effects, possibly independent of blood pressure reduction. Due to their complementary mechanisms of action, it has been hypothesized that the combination of an angiotensin-converting enzyme inhibitor and a calcium channel blocker will provide superior cardiovascular protection, in part by producing an additive effect of increased nitric oxide availability, when compared with either agent alone.

Endothelial antioxidant actions of dihydropyridines and angiotensin converting enzyme inhibitors

Dihydropyridines and angiotensin converting enzyme inhibitor effects on superoxide and nitric oxide (NO) were compared in high glucose (20 mM, 24 h)-treated human Ea.hy 926 endothelial cells. High glucose stimulated superoxide both extracellularly (lucigenin chemiluminescence, cytochrome c reduction) and intracellularly (dihydrorhodamine 123 fluorescence). The dihydropyridines amlodipine, nisoldipine, BayK 8644 or the angiotensin converting enzyme inhibitors captopril and enalaprilat attenuated extra- and intracellular superoxide formation; nifedipine blocked extracellular increases only, ramiprilat was without antioxidant effect. Dihydropyridines and captopril also prevented NADPH-driven superoxide release. Antioxidant actions were blunted by a bradykinin B(2) receptor antagonist or an inhibitor of p38 mitogen activated protein kinase (MAPK), and were accompanied by improved NO release (amperometric sensor). p38MAPK inhibition prevented the NO-sparing actions of dihydropyridines but not angiotensin converting enzyme inhibitors. Thus, dihydropyridines and angiotensin converting enzyme inhibitors limit high glucose-induced superoxide formation and improve NO bioavailability in human endothelial cells, in part via bradykinin and p38MAPK.

Clinical Pharmacology of Antihypertensive Therapy

Adequate control of blood pressure poses challenges for hypertensive patients and their physicians. Success rates of greater than 80% in reducing blood pressure to target values among high-risk hypertensive patients reported by several recent clinical trials argue that effective medications currently are available. Yet, only 34% of hypertensive patients in the United States are at their goal blood pressure according to the most recent national survey. Rational selection of antihypertensive drugs that target both the patient's blood pressure and comorbid conditions coupled with more frequent use of low-dose drug combinations that have additive efficacy and low adverse-effect profiles could improve significantly US blood pressure control rates and have a positive impact on hypertension-related cardiovascular and renal mortality and morbidity. This article reviews the pharmacokinetic and pharmacodynamic principles that underlie the actions of drugs in each of the classes of antihypertensive agents when used alone and in combination, provides practical pharmacologic information about the drugs most frequently prescribed for treatment of hypertension in the outpatient setting, and summarizes the current data influencing the selection of drugs that might be used most effectively in combination for the majority of hypertensive patients whose blood pressures are not controlled adequately by single-drug therapy.

Addressing the Global Cardiovascular Risk of Hypertension, Dyslipidemia, Diabetes Mellitus, and the Metabolic Syndrome in the Southeastern United States, Part II: Treatment Recommendations for Management of the Global Cardiovascular Risk of Hypertension, Dyslipidemia, Diabetes Mellitus, and the Metabolic Syndrome

An aggressive global approach to screening and to the management of the metabolic syndrome is recommended to slow the growth of the syndrome throughout the United States. Prevention should begin in childhood with healthy nutrition, daily physical activity, and annual measurement of weight, height, and blood pressure beginning at 3 years of age. Such screenings will identify cardiovascular risk factors early, allow the health care provider to define global cardiovascular risk with the COSEHC Cardiovascular Risk Assessment Tool, and allow treatment of each risk factor. Lifelong lifestyle modifications and pharmacologic therapy will be required in most patients. Antihypertensive therapy for these patients should begin with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker unless a compelling indication for another drug is present. Metformin should be considered the first drug for glucose control in the patient with type 2 diabetes. A statin should be used initially for hyperlipidemia unless contraindicated. Combinations of antihypertensive, antiglycemic, and lipid-lowering agents will often be required.

Doxorubicine-congestive heart failure-increased big endothelin-1 plasma concentration: reversal by amlodipine, losartan, and gastric pentadecapeptide BPC157 in rat and mouse

Overall, doxorubicine-congestive heart failure (CHF) (male Wistar rats and NMRI mice; 6 challenges with doxorubicine (2.5 mg/kg, i.p.) throughout 15 days and then a 4-week-rest period) is consistently deteriorating throughout next 14 days, if not reversed or ameliorated by therapy (/kg per day): a stable gastric pentadecapeptide BPC157 (GEPPPGKPADDAGLV, MW 1419, promisingly studied for inflammatory bowel disease (Pliva; PL 10, PLD-116, PL 14736)) (10 microg, 10 ng), losartan (0.7 mg), amlodipine (0.07 mg), given intragastrically (i.g.) (once daily, rats) or in drinking water (mice). Assessed were big endothelin-1 (BET-1) and plasma enzyme levels (CK, MBCK, LDH, AST, ALT) before and after 14 days of therapy and clinical status (hypotension, increased heart rate and respiratory rate, and ascites) every 2 days. Controls (distilled water (5 ml/kg, i.g., once daily) or drinking water (2 ml/mouse per day) given throughout 14 days) exhibited additionally increased BET-1 and aggravated clinical status, while enzyme values maintained their initial increase. BPC157 (10 microg/kg) and amlodipine treatment reversed the increased BET-1 (rats, mice), AST, ALT, CK (rats, mice), and LDH (mice) values. BPC157 (10 ng/kg) and losartan opposed further increase of BET-1 (rats, mice). Losartan reduces AST, ALT, CK, and LDH serum values. BPC157 (10 ng/kg) reduces AST and ALT serum values. Clinical status of CHF-rats and -mice is accordingly improved by the BPC157 regimens and amlodipine.

Systolic Hypertension in the Elderly: Pushing the Frontiers of Therapy—A Suggested New Approach

In elderly patients with systolic hypertension resistant to treatment with conventional therapy, increased aortic pulse wave reflection and a high augmentation index are often present. These findings are indicative of endothelial dysfunction and deficient generation of nitric oxide, a potent vasodilator in the arterial tree. In such patients, treatment with the nitric oxide donor extended-release isosorbide mononitrate characteristically produces prompt and sustained falls in both pulse wave reflection and systolic blood pressure. The adjunct use of this nitrate produces useful additional decreases in systolic blood pressure ranging from 10 to 45 mm Hg, often achieving target blood pressure goals in isolated systolic hypertension. By combining this endothelium-independent nitric oxide donor with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, the potential exists to address both the nitric oxide deficiency and endothelial dysfunction of the vascular endothelium in these patients. Other possibilities for synergism with this combination include complementary hemodynamic, circadian, and metabolic actions together with prevention of nitrate tolerance. Isosorbide mononitrate may also be used successfully with calcium channel blockers, beta blockers, and diuretics.

Preservation of NO production by statins in the treatment of heart failure

OBJECTIVE

Because statins promote endogenous nitric oxide (NO) production in vessels by increasing endothelial nitric oxide synthase (eNOS), we evaluated the clinical benefit and efficiency of simvastatin in preventing the decrease in NO control of coronary blood flow (CBF), NO regulation of myocardial oxygen consumption (MVO(2)) and decreased nitrite production in coronary microvessels, associated with pacing-induced heart failure (HF).

METHODS

Dogs (n=17) were instrumented for measurement of coronary blood flow and left ventricular end diastolic pressure (LVEDP). HF was induced by pacing. Ten dogs were given simvastatin 20 mg/kg/day orally (HF+SIMVA) from the 10th day of pacing.

RESULTS

HF+SIMVA had a lower LVEDP at 4 weeks of pacing (18+/-1 vs. 25+/-1 mm Hg, p<0.05), and the NO-dependent coronary vasodilation to veratrine was preserved compared to HF (p<0.05). In coronary microvessels, SIMVA potentiated nitrite production compared to HF (p<0.05) and enhanced the NO-dependent decrease in MVO(2) in cardiac tissue in response to 10(-4) mol/l bradykinin, which was markedly blunted in HF (p<0.05). Using Western blotting, there was a reduction in eNOS protein during HF that was preserved at 4-5 weeks of pacing during treatment with SIMVA.

CONCLUSIONS

Simvastatin maintained NO production by coronary vessels and NO bioactivity during pacing-induced dilated cardiomyopathy. Targeting the endothelium, which participates in the control of myocardial metabolism by NO, may be an important mechanism of action of statins in the treatment of heart failure.

Novel Vascular Biology of Third-Generation L-Type Calcium Channel Antagonists

Calcium channel blockers (CCBs) were developed as vasodilators, and their use in cardiovascular disease treatment remains largely based on that mechanism of action. More recently, with the evolution of second- and third-generation CCBs, pleiotropic effects have been observed, and at least some of CCBs’ benefit is attributable to these mechanisms. Understanding these effects has contributed greatly to elucidating disease mechanisms and the rationale for CCB use. Furthermore, this knowledge might clarify why drugs are useful in some disease states, such as atherosclerosis, but not in others, such as heart failure. Although numerous drugs used in the treatment of vascular disease, including statins and angiotensin-converting–enzyme inhibitors, have well-described pleiotropic effects universally accepted to contribute to their benefit, little attention has been paid to CCBs’ potentially similar effects. Accumulating evidence that at least 1 CCB, amlodipine, has pharmacologic actions distinct from L-type calcium channel blockade prompted us to investigate the pleiotropic actions of amlodipine and CCBs in general. There are several areas of research; foci here are (1) the physicochemical properties of amlodipine and its interaction with cholesterol and oxidants; (2) the mechanism by which amlodipine regulates NO production and implications; and (3) amlodipine’s role in controlling smooth muscle cell proliferation and matrix formation.

The first hypertension trial comparing the effects of two fixed-dose combination therapy regimens on cardiovascular events: Avoiding Cardiovascular events through Combination therapy in Patients Living with Systolic Hypertension (ACCOMPLISH)

Current recommendations for the treatment of hypertension clarify the need to achieve lower blood pressure levels in the general population (<140/90 mm Hg) and in specific high-risk patient groups such as patients with diabetes or chronic renal disease (<130/80 mm Hg). Further, it is evident that to reach appropriate blood pressure control, most patients with high blood pressure will require two or more antihypertensive agents. There is scarce clinical trial outcome evidence to guide clinicians in the selection of optimal combinations of antihypertensive classes for high-risk hypertensive patients. A new clinical trial, Avoiding Cardiovascular Events through Combination Therapy in Patients Living with Systolic Hypertension (ACCOMPLISH), is the first large clinical trial to directly compare cardiovascular mortality and morbidity rates for two fixed-dose combination therapies. Results from ACCOMPLISH should provide much-needed guidance for selecting optimal combination therapy for high-risk hypertensive patients.

Effects of the calcium channel blocker amlodipine on serum and aortic cholesterol, lipid peroxidation, antioxidant status and aortic histology in cholesterol-fed rabbits

Reactive oxygen metabolites and oxidized fatty acids are proinflammatory and are involved in the pathophysiology of atherosclerosis. Amlodipine, a unique third-generation dihydropyridine-type calcium channel blocker, seems to exert atheroprotective effects through its antioxidant properties related to its chemical structure and independent of its calcium channel-blocking effect. In this study, the interactions of amlodipine with major cellular antioxidants were investigated in order to elucidate the mechanisms underlying its atheroprotective effects. New Zealand white male rabbits were fed regular chow (group 1), chow with 1% cholesterol (group 2), regular chow plus 5 mg/kg/day amlodipine per os (group 3) and 1% cholesterol plus amlodipine (group 4) for 8 weeks. Total cholesterol, malondialdehyde (MDA) and vitamin E concentrations and catalase and superoxide dismutase (SOD) activities were determined in blood drawn before and after the experimental period. Aortic tissue was examined for atherosclerotic changes and aortic total cholesterol, MDA, catalase and SOD were determined. At the end of the 8-week treatment period, serum total cholesterol and plasma MDA were elevated in groups 2 and 4. In group 2, serum vitamin E and plasma SOD diminished (p < 0.05) and catalase increased (p < 0.05). In group 4, SOD activity increased at the end of treatment. MDA levels were lower and plasma SOD activities were higher in group 4 than in group 2. Aortic tissue investigations revealed higher total cholesterol and MDA concentrations and catalase activities in group 2 than in group 4, and the highest tissue SOD activity was recorded in group 4 (p < 0.05 for all comparisons). Morphological examination of aortic tissues exhibited endothelial disarrangement and lipid deposition in group 2. Histopathological alterations related to atherogenesis were less in group 4 than in group 2. Amlodipine seems to exert atheroprotective effects by reducing aortic cholesterol accumulation and blood and aortic lipid peroxidation, enhancing SOD activity both in blood and aortic tissue and suppressing the consumption of vitamin E. On the other hand, the suppression of catalase activity in blood and the aorta interferes with the drug's well-known antioxidant effects.

Antiatherosclerotic effects of calcium channel blockers

Over the past 30 years, a considerable body of experimental and clinical evidence has accumulated to support the suggestion that calcium channel blockers (CCBs) have significant antiatherosclerotic effects that are independent of their hypotensive effects. Early research using animal models of atherosclerosis and CCBs in concentrations that exceeded the normal therapeutic dose range showed definite antiatherosclerotic effects, especially in the development of new lesions. Investigations of these effects in humans have used quantitative coronary angiography and B-mode ultrasonography and have demonstrated some antiatherosclerotic effects. This article reviews the currently available evidence of antiatherosclerotic effects of CCBs in animal models and in clinical trials.

Amlodipine, but not verapamil or nifedipine, dilates rabbit femoral artery largely through a nitric oxide- and kinin-dependent mechanism

1. We investigated the nitric oxide (NO) dependence of vasorelaxation in response to different calcium channel blockers (CCB), in rabbit femoral artery in vivo. 2. Anaesthetized rabbits underwent femoral artery ligation, and blood from the proximal artery was returned distal to the ligature through a constant infusion pump. The effects of local injection of CCB on perfusion pressure and plasma nitrite+nitrate (NO(x), which reflects local NO biosynthesis) concentration in this system were determined. 3. Intra-arterial verapamil, nifedipine or amlodipine 10 micromol x kg(-1) each reduced perfusion pressure. Pre-treatment with intra-arterial N(G)-nitro-L-arginine methyl ester (L-NAME, a NO synthase inhibitor) 1 micromol x kg(-1) did not affect responses to verapamil or nifedipine, but attenuated the reduction in perfusion pressure to amlodipine, from 33.2+/-2.1% to 22.5+/-1.6% (P=0.002). 4. Intra-arterial amlodipine--unlike verapamil or nifedipine--increased femoral venous NO(x), from 9.1+/-0.4 microM to 14.1+/-0.5 microM (P=0.005). 5. The bradykinin B2 receptor antagonist HOE 140, 30 mg x kg(-1), attenuated the reduction in perfusion pressure and abolished the rise in venous NO(x) concentration, following intra-arterial amlodipine. 6. Amlodipine potently inhibited serum angiotensin converting-enzyme (ACE) activity in vitro, as effectively as enalapril at similar concentrations. 7. These results suggest that the vasorelaxant effects of nifedipine and verapamil are NO-independent, whereas those of amlodipine are partly NO-dependent, in rabbit femoral artery in vivo. This effect of amlodipine occurs through B2 receptor activation, and may be related to an increase in local bradykinin through inhibition of ACE.

Paradoxical release of nitric oxide by an L-type calcium channel antagonist, the R+ enantiomer of amlodipine

Amlodipine is a mixture of two enantiomers, one having L-type channel blocking activity (S-) and the other about 1,000-fold weaker activity and of little known other activity (R+). To determine whether the R+ enantiomer releases nitric oxide, the ability of amlodipine, its enantiomers, and nitrendipine to release nitric oxide in isolated coronary microvessels and to regulate cardiac tissue oxygen consumption via nitric oxide release was studied in vitro. Amlodipine and the R+ enantiomer released nitric oxide in a concentration-dependent fashion, increasing nitrite release from coronary microvessels by 57 +/- 12 and 45 +/- 5 pmol/mg/20 min at 10(-6) M (p < 0.05 from control). Nitrite release was entirely blocked by N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, and HOE-140, a B2-kinin receptor antagonist. The S- enantiomer had no effect on nitrite release at any concentration. Amlodipine and the R+ enantiomer also reduced oxygen consumption in canine cardiac tissue in vitro and this was in an L-NAME-blockable manner. The S- enantiomer of amlodipine had no effect. This study shows that the R+ enantiomer of amlodipine is responsible for the release of nitric oxide and not the S- enantiomer (the L-type calcium channel blocking portion of amlodipine). Interestingly, nitric oxide release is dependent on the production of kinins because it is blocked by HOE-140. This study defines a potentially important property by which calcium channel blockers may release nitric oxide and may contribute to their use in the treatment of cardiovascular disease.

Novel mechanisms of the antiproliferative effects of amlodipine in vascular smooth muscle cells from spontaneously hypertensive rats

The calcium channel blocker amlodipine continues to be of interest due to its potential proven ability to hinder the progression of atherosclerosis and reduce the number of clinical ischemic events. Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) are useful in the study of atherosclerosis because they show exaggerated growth with production of angiotensin II (Ang II) by conversion to the synthetic phenotype. To clarify mechanisms of the antiproliferative effects of amlodipine, we evaluated effects of the expression of growth factors, the changes in phenotype, and the proliferation of VSMC from SHR. Amlodipine significantly inhibited basal DNA synthesis and proliferation of VSMC from SHR. Amlodipine also inhibited expression of platelet-derived growth factor (PDGF) A-chain, transforming growth factor beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF) mRNAs in VSMC from SHR. Decreases in levels of PDGF A-chain and bFGF mRNAs in VSMC from SHR were greater with amlodipine than with nifedipine. Amlodipine significantly inhibited expression of the synthetic phenotype markers osteopontin and matrix Gla mRNAs, indicating that it inhibited the exaggerated growth of VSMC from SHR and suppressed the change from the contractile phenotype to the synthetic phenotype. Thus, amlodipine may be a beneficial therapeutic agent for patients with hypertensive vascular diseases.

Nitric oxide: does it play a role in the heart of the critically ill?

Nitric oxide regulates many aspects of myocardial function, not only in the normal heart but also in ischemic and nonischemic heart failure, septic cardiomyopathy, cardiac allograft rejection, and myocarditis. Accumulating evidence implicates the endogenous production of nitric oxide in the regulation of myocardial contractility, distensibility, heart rate, coronary vasodilation, myocardial oxygen consumption, mitochondrial respiration, and apoptosis. The effects of nitric oxide promote left ventricular mechanical efficiency, ie, appropriate matching between cardiac work and myocardial oxygen consumption. Most of these beneficial effects are attributed to the low physiologic concentrations generated by the constitutive endothelial or neuronal nitric oxide synthase. By contrast, inducible nitric oxide synthase generates larger concentrations of nitric oxide over longer periods of time, leading to mostly detrimental effects. In addition, the recently identified beta3-adrenoceptor mediates a negative inotropic effect through coupling to endothelial nitric oxide synthase and is overexpressed in heart failure. An imbalance between beta 1 and beta2-adrenoceptor and beta3-adrenoceptor, with a prevailing influence of beta3-adrenoceptor, may play a causal role in the pathogenesis of cardiac diseases such as terminal heart failure. Likewise, changes in the expression of endothelial nitric oxide synthase or inducible nitric oxide synthase within the myocardium may alter the delicate balance between the effects of nitric oxide produced by either of these isoforms. New treatments such as selective inducible nitric oxide synthase blockade, endothelial nitric oxide synthase promoting therapies, and selective beta3-adrenoceptor modulators may offer promising new therapeutic approaches to optimize the care of critically ill patients according to their stage and specific underlying disease process.

Pranidipine, a 1,4-dihydropyridine calcium channel blocker that enhances nitric oxide-induced vascular relaxation

Pranidipine, a long acting 1,4-dihydropyridine calcium channel blocker, prolongs nitric oxide (NO)-mediated relaxation of rat aorta; it prolongs acetylcholine-induced relaxation in presence of endothelium as well as nitroglycerin-induced relaxation in absence of endothelium. In rat aorta the effect of pranidipine on NO-mediated relaxation is cyclic guanosine monophosphate (cGMP)-independent, but in guinea pig carotid artery the same effect of pranidipine is cGMP-dependent. It has been reported that in co-cultured human endothelial and smooth muscle cells pranidipine, at a higher concentration (10(-6) M), enhances vasorelaxant effect of NO by blocking NO decomposition. The enhancement of NO action by pranidipine differs from the direct NO-releasing action of other 1,4-dihydropyridines. It is expected that enhancement of NO-induced vasodilatation will lead to a venodilator action in vivo and less peripheral edema. The target organ protective effects of pranidipine are also reviewed in this article.

Interstitial fibrosis of unilateral ureteral obstruction is exacerbated in kidneys of mice lacking the gene for inducible nitric oxide synthase

Unilateral ureteral obstruction (UUO) is characterized by decreases in renal function and increases in interstitial fibrosis. Previous studies have indicated that pharmacologic manipulations that increase nitric oxide (NO) are beneficial to the obstructed kidneys. NO is produced from arginine by nitric oxide synthase (NOS), an enzyme that exists in both constitutive and inducible (iNOS) forms. To determine the role of the inducible form of NOS in UUO, we used mice with a targeted deletion of iNOS (iNOS -/- mice) and compared them with wild-type (WT) mice. Kidneys were obstructed for 2 weeks in both WT and iNOS -/- mice, and were then removed and bisected. Half of the kidney was embedded in paraffin and tissue sections were examined for interstitial volume or the presence of macrophages. The remainder was flash-frozen and samples were used to measure tissue collagen (hydroxyproline) or transforming growth factor-beta (TGF-beta). This study demonstrates that both cortex and medulla of obstructed kidneys of iNOS -/- mice exhibit significantly increased interstitial volume and interstitial macrophages as compared with their WT counterparts. Furthermore tissue collagen was increased to 9.2+/-1.3 microg/mg tissue in WT obstructed kidneys, whereas in iNOS -/- kidneys, collagen was increased to 13.2+/-0.8 microg/mg tissue. The profibrotic cytokine TGF-beta was also significantly increased in obstructed kidneys of iNOS -/- mice, as compared with WT mice. No differences were noted between the unobstructed kidneys of iNOS -/- mice compared with WT mice in any of the parameters examined. These results demonstrate that targeted deletion of the iNOS results in exacerbation of fibrotic events in the obstructed kidney. These results confirm previous pharmacologic studies, and suggest that NO produced via the inducible NOS normally serves a protective function in UUO.