Combination ACE Inhibitor and Angiotensin Receptor Blocker Therapy-Future Considerations

Angiotensin Converting Enzyme Regulates Cell Proliferation and Migration

Background

The angiotensin-I converting enzyme (ACE) plays a central role in the renin-angiotensin system, acting by converting the hormone angiotensin-I to the active peptide angiotensin-II (Ang-II). More recently, ACE was shown to act as a receptor for Ang-II, and its expression level was demonstrated to be higher in melanoma cells compared to their normal counterparts. However, the function that ACE plays as an Ang-II receptor in melanoma cells has not been defined yet.

Aim

Therefore, our aim was to examine the role of ACE in tumor cell proliferation and migration.

Results

We found that upon binding to ACE, Ang-II internalizes with a faster onset compared to the binding of Ang-II to its classical AT1 receptor. We also found that the complex Ang-II/ACE translocates to the nucleus, through a clathrin-mediated process, triggering a transient nuclear Ca²⁺ signal. In silico studies revealed a possible interaction site between ACE and phospholipase C (PLC), and experimental results in CHO cells, demonstrated that the β3 isoform of PLC is the one involved in the Ca²⁺ signals induced by Ang-II/ACE interaction. Further studies in melanoma cells (TM-5) showed that Ang-II induced cell proliferation through ACE activation, an event that could be inhibited either by ACE inhibitor (Lisinopril) or by the silencing of ACE. In addition, we found that stimulation of ACE by Ang-II caused the melanoma cells to migrate, at least in part due to decreased vinculin expression, a focal adhesion structural protein.

Conclusion

ACE activation regulates melanoma cell proliferation and migration.

A guide to the management of blood pressure in the diabetic hypertensive patient

Diabetes mellitus and hypertension frequently coexist in patients with the insulin resistance syndrome (IRS). Patients with both diabetes and hypertension typically have widespread endothelial dysfunction, increased oxidative stress, an activated sympathoadrenal system, and an elevated systemic burden of inflammatory mediators. Patients with diabetes and hypertension also have concomitant mixed dyslipidemia and obesity with significant frequency, and are at high risk for the development of macro- and microvascular disease, congestive heart failure, and nephropathy. Current data suggest that ACE inhibitors or angiotensin receptor blockers with or without a diuretic are important, if not preferred, initial therapies for the patient with diabetes and hypertension. Other drug classes such as combined alpha-/beta-adrenoceptor antagonists, dihydropyridine calcium channel antagonists (CCAs), and peripheral alpha-adrenoceptor antagonists are also useful therapeutic options in these patients. In order to optimally reduce the risk for cardiovascular events in the patient with diabetes and hypertension, optimal BP control should be coupled with comprehensive lifestyle modification and aggressive management of dyslipidemia and hyperglycemia.

Randomized study to compare valsartan +/- HCTZ versus amlodipine +/- HCTZ strategies to maximize blood pressure control

OBJECTIVE

Delays in achieving blood pressure (BP) control may increase morbidity and mortality in patients with hypertension. Thus, deciding which antihypertensive agent to use and at what dosage, in addition to determining when to initiate combination therapy and which agents to combine, is important for achieving BP control.

METHODS

This randomized, double-blind, 14-week study was conducted to compare the efficacy and tolerability of various doses of valsartan +/- hydrochlorothiazide (HCTZ) versus amlodipine +/- HCTZ for maximizing BP control in 1,285 patients with uncontrolled hypertension. Patients with stage 1 hypertension and naïve to antihypertensive therapy (33.9%) started valsartan 160 mg or amlodipine 5 mg. Treatment-naïve patients with stage 2 hypertension (13.5%) or those uncontrolled on current antihypertensive monotherapy (52.6%) started valsartan 160 mg/HCTZ 12.5 mg or amlodipine 10 mg. At weeks 4, 8, and 11, patients not achieving BP control were up-titrated (maximum: valsartan 320 mg/HCTZ 25 mg, amlodipine 10 mg/HCTZ 25 mg).

RESULTS

At study end, 78.8% of patients on valsartan +/- HCTZ were controlled (BP <140/90 mmHg) and still on study medication versus 67.8% on amlodipine +/- HCTZ (P < 0.0001). Amlodipine-treated patients had a higher incidence of peripheral edema (22.4% vs 2.2%) and associated discontinuations (7.3% vs <1%). Initiating therapy earlier with valsartan/HCTZ, rather than titrating monotherapy to its maximum dose before adding a second agent, was superior to amlodipine monotherapy or amlodipine +/- HCTZ for achieving BP control, and avoided excessive treatment adjustments and maintained tolerability.

Long-term antiproteinuric effect of dual renin-angiotensin system blockade

We evaluated the long-term changes on overt proteinuria induced by dual blockade of the renin-angiotensin system (RAS). Dual blockade was produced by adding an angiotensin II receptor blocker (ARB) to treatment with maximal recommended doses of an angiotensin converting enzyme (ACE) inhibitor in proteinuric patients. A total of 28 patients (19 men and 9 women) with proteinuria higher than 1 g/24 h were enrolled in this trial of treatment with the ARB candesartan (from 4 up to 32 mg daily) added to existing treatment with an ACE inhibitor. At 6, 12, 24, and 36 months, we evaluated proteinuria in 24-h urinary collections, office blood pressure (BP), plasmatic creatinine (Cr), serum potassium (K), and 24 h urine collection creatinine clearance (CrC). During monoblockade of the RAS by ACE inhibitor treatment, albuminuria was 2.94 +/- 1.92 mg/24 h; BP was 137/76 mmHg; K+ was 4.8 +/- 0.5 mmol/l, Cr was 1.76 +/- 0.67 mg/dL, and CrC was 62 +/- 31.9 mL/min. After 6 months, dual blockade of the RAS albuminuria was 2.18 +/- 2.29 mg/24 h (P < 0.01 vs. baseline) and BP was 133/75 mmHg (not significant). At 36 months, albuminuria was 2.21 +/- 2.20 mg/24 h (P < 0.05 vs. baseline); BP was 133/73 mmHg (not significant). CrC was not changed along the follow up. A small increment of Cr was detected at 24 months (2.11 +/- 1.06 mg/mL, P < 0.05). The antiproteinuric effect of dual renin-angiotensin system blockade combining candesartan and ACE inhibitors remain after 36 months without losing its initial effect. Blood pressure changes seem not to explain this long-term antiproteinuric effect.

ACE-inhibitor, AT1-receptor-antagonist, or both? A clinical pharmacologist's perspective after publication of the results of ONTARGET

Clinical Pharmacology is commonly accepted to be a bridging discipline between basic science observations and clinical practice. Today, it should be a major task of the clinical pharmacologist in academia to provide support in the interpretation of preclinical and clinical study data, to develop evidence-based treatment guidelines and to serve as drug expert supporting all disciplines of clinical medicine with specific pharmacological and therapeutic knowledge. The results of the ONTARGET-trial confront both researchers and clinicians with the unexpected truth that AT(1)-receptor-blockade with an angiotensin-receptor-blocker (ARB) does not seem to have superior therapeutic benefit compared with an ACE-inhibitor (ACE-I) at reducing fatal and nonfatal cardiovascular events. The combination of the two drugs was associated with more adverse events without an increase in benefit. Therefore, the crucial question 'ACE-I, ARB, or both?' requires a new and critical appraisal depending on the medical indication for which these renin-angiotensin-system (RAS)-inhibitors are used: In a population of high-risk patients suffering from cardiovascular disease or diabetes mellitus, the evidence to favor an ARB over an ACE-I is still limited after ONTARGET and because of the higher costs for ARBs one can rather support the old therapeutic advice that ARBs are equally effective as ACE-Is and therefore therapeutic alternatives for patients with ACE-I intolerance. With respect to a very moderate additive BP-lowering effect of dual therapy with an ACE-I and an ARB seen in metaanalysis which was not even clearly attributable to dual RAS-inhibition and the increased adverse event rate in the combination treatment group of ONTARGET, this regimen seems not to be recommendable for the treatment of hypertension. Dual-RAS-blockade using an ACE-I-ARB-combination is an effective therapy to treat proteinuria and might be of therapeutic benefit especially in diabetic patients without concomitant diseases. There may be a therapeutic rationale to prefer ARBs over ACE-Is in well-selected patients with congestive heart failure (CHF) because a considerable amount of angiotensin II (Ang II) is produced independent of angiotensin-conversion-enzyme (ACE) in the failing heart and is therapeutically unaffected by ACE-I treatment. The results of the Val-HeFt and the CHARM-added-study revealed additive effects of an ARB on heart failure related morbidity and mortality when added to existing therapy with an ACE-I suggesting a role for ACE-I-ARB-combination treatment in well selected heart failure patients. Independent of the medical indication for its use, the concept of dual RAS-blockade with an ARB-ACE-I-combination should clinically be used with caution and a close monitoring of potassium levels and kidney function. Although the results of ONTARGET revealed equity of ramipril and telmisartan at reducing fatal and nonfatal cardiovascular events, we should not forget that pharmacologically not all ARBs are the same and the question if the study results of ONTARGET with telmisartan are transferable to the complete class of ARBs still merits further investigation.