Blocking the renin-angiotensin system: dual- versus mono-therapy

Calcium channel blocker enhances beneficial effects of an angiotensin II AT1 receptor blocker against cerebrovascular-renal injury in type 2 diabetic mice

Recent clinical trials have demonstrated that combination therapy with renin-angiotensin system inhibitors plus calcium channel blockers (CCBs) elicits beneficial effects on cardiovascular and renal events in hypertensive patients with high cardiovascular risks. In the present study, we hypothesized that CCB enhances the protective effects of an angiotensin II type 1 receptor blocker (ARB) against diabetic cerebrovascular-renal injury. Saline-drinking type 2 diabetic KK-A^y mice developed hypertension and exhibited impaired cognitive function, blood-brain barrier (BBB) disruption, albuminuria, glomerular sclerosis and podocyte injury. These brain and renal injuries were associated with increased gene expression of NADPH oxidase components, NADPH oxidase activity and oxidative stress in brain and kidney tissues as well as systemic oxidative stress. Treatment with the ARB, olmesartan (10 mg/kg/day) reduced blood pressure in saline-drinking KK-A^y mice and attenuated cognitive decline, BBB disruption, glomerular injury and albuminuria, which were associated with a reduction of NADPH oxidase activity and oxidative stress in brain and kidney tissues as well as systemic oxidative stress. Furthermore, a suppressive dose of azelnidipine (3 mg/kg/day) exaggerated these beneficial effects of olmesartan. These data support the hypothesis that a CCB enhances ARB-associated cerebrovascular-renal protective effects through suppression of NADPH oxidase-dependent oxidative stress in type 2 diabetes.

Effects of an angiotensin 2 receptor blocker plus diuretic combination drug in chronic heart failure complicated by hypertension

The effects of 24 weeks' treatment with an angiotensin 2 receptor blocker (ARB)/diuretic combination drug were investigated in an open-label study of 61 patients with stabilized chronic heart failure. Renin-angiotensin-aldosterone system inhibitors were replaced with a tablet containing hydrochlorothiazide 6.25 mg plus candesartan 8 mg, administered orally, once daily, in patients with systolic blood pressure (SBP) ≥ 140 mmHg or diastolic blood pressure (DBP) ≥ 90 mmHg while under optimal treatment. Both SBP and DBP declined significantly during the ARB/diuretic combination treatment. Diuretics administered previously were discontinued during the study period in 15 patients, decreasing the number of drugs being taken. During ARB/diuretic combination treatment, the blood urea nitrogen level worsened but no significant changes were noted in potassium or estimated glomerular filtration rate, which had been a matter of concern. Additionally, the level of brain natriuretic peptide, an indicator of the severity of heart failure, was improved, indicating effectiveness and safety of the ARB/diuretic combination drug.

Trends in co-prescribing of angiotensin converting enzyme inhibitors and angiotensin receptor blockers in Ireland

AIMS

(i) To examine the trends in co-prescribing of angiotensin converting enzyme inhibitor (ACEI) and angiotensin-II receptor blocker (ARB) therapy and (ii) to examine the influence of major clinical trials (CALM, COOPERATE, VALIANT and ONTARGET) on co-prescribing.

METHODS

The Irish HSE-Primary Care Reimbursement Services database was used to identify patients ≥16 years old co-prescribed ACEIs and ARBs between January 2000 and April 2009 (n= 266 554 prescriptions). The rate of prescribing per 1000 general medical services (GMS) scheme population was calculated for each month. Patients with diabetes, hypertension, heart failure and ischaemic heart disease were also identified by prescribing of certain medications. A linear trend test was used to examine prescribing trends. Logistic regression was used to examine prescribing according to patient characteristics. The effects of the major trials on prescribing were examined using segmented regression analysis for 12 months pre- and post-trials.

RESULTS

There was a significant linear trend in overall ACEI and ARB co-prescribing over the study period (P < 0.001). Rate of co-prescribing in January 2000 and April 2009 was 0.16 and 5.72, per 1000 eligible population, respectively. Those 45-64 years old (OR = 2.88, 95% confidence interval (CI) 2.71, 3.06) and ≥65 years (OR = 2.52, 95% CI 2.36, 2.68) were more likely to receive dual therapy compared with those <45 years old. Those with hypertension (OR = 8.85, 95% CI 8.45, 9.27), diabetes (OR = 4.10, 95% CI 3.97, 4.23) and heart failure (OR = 1.78, 95% CI 1.72, 1.84) were more likely to receive dual therapy compared with the general population. Significant increases in prescribing were observed only after the CALM (P= 0.03) and VALIANT (P= 0.007) trials.

CONCLUSION

Increased co-prescribing of ACEIs and ARBs was observed in Ireland during 2000-09. Prescribing patterns did not appear to be affected by results from major trials.

Local angiotensin II aggravates cardiac remodeling in hypertension

Angiotensin II (ANG II) contributes to hypertension, cardiac hypertrophy, fibrosis, and dysfunction; however, it is difficult to separate the cardiac effect of ANG II from its hemodynamic action in vivo. To overcome the limitations, we used transgenic mice with cardiac-specific expression of a transgene fusion protein that releases ANG II from cardiomyocytes (Tg-ANG II) and treated them with deoxycorticosterone acetate (DOCA)-salt to suppress their systemic renin-angiotensin system. Using this unique model, we tested the hypothesis that cardiac ANG II, acting on the angiotensin type 1 receptor (AT(1)R), increases inflammation, oxidative stress, and apoptosis, accelerating cardiac hypertrophy and fibrosis. Male Tg-ANG II mice and their nontransgenic littermates (n-Tg) were uninephrectomized and divided into the following three groups: 1) vehicle-treated normotensive controls; 2) DOCA-salt; and 3) DOCA-salt + valsartan (AT(1)R blocker).Under basal conditions, systolic blood pressure (SBP) and cardiac phenotypes were similar between strains. In DOCA-salt hypertension, SBP increased similarly in both n-Tg and Tg-ANG II, and cardiac function did not differ between strains; however, Tg-ANG II had 1) greater ventricular hypertrophy as well as interstitial and perivascular fibrosis; 2) a higher number of deoxynucleotidyl-transferase-mediated dUTP nick end labeling-positive cells and infiltrating macrophages; 3) increased protein expression of NADPH oxidase 2 and transforming growth factor-β(1); and 4) downregulation of phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B (Akt) phosphorylation. Valsartan partially reversed these effects in Tg-ANG II but not in n-Tg. We conclude that, when hemodynamic loading conditions remain unchanged, cardiac ANG II does not alter heart size or cardiac functions. However, in animals with hypertension, cardiac ANG II, acting via AT(1)R, enhances inflammation, oxidative stress, and cell death (most likely via downregulation of PI 3-kinase and Akt), contributing to cardiac hypertrophy and fibrosis.

Blocking the RAAS at different levels: an update on the use of the direct renin inhibitors alone and in combination

The renin–angiotensin–aldosterone system (RAAS), an important regulator of blood pressure and mediator of hypertension-related complications, is a prime target for cardiovascular drug therapy. Angiotensin-converting enzyme inhibitors (ACEIs) were the first drugs to be used to block the RAAS. Angiotensin II receptor blockers (ARBs) have also been shown to be equally effective for treatment. Although these drugs are highly effective and are widely used in the management of hypertension, current treatment regimens with ACEIs and ARBs are unable to completely suppress the RAAS. Combinations of ACEIs and ARBs have been shown to be superior than to either agent alone for some, but certainly not all, composite cardiovascular and kidney outcomes, but dual RAAS blockade with the combination of an ACEI and an ARB is sometimes associated with an increase in the risk for adverse events, primarily hyperkalemia and worsening renal function. The recent introduction of the direct renin inhibitor, aliskiren, has made available new combination strategies to obtain a more complete blockade of the RAAS with fewer adverse events. Renin system blockade with aliskiren and another RAAS agent has been, and still is, the subject of many large-scale clinical trials and furthermore, is already available in some countries as a fixed combination.