Journal of the Renin-Angiotensin-Aldosterone System

The aim of this study was to investigate the early changes of cardiac uncoupling protein-2 (UCP2) expression following myocardial ischemia reperfusion in rats chronically treated with ramiprilat and losartan.

Male Wistar rats were assigned into seven groups (six in each): intact (control); sham-operated; nontreated rats subjected to ischemia and reperfusion (IR); ramiprilat-treated rats with (Ram+IR) and without ischemia (Ram); losartan treated with (Los+IR) and without ischemia (Los). Quantitative evaluation of UCP2 mRNA was carried out using real-time reverse transcription-polymerase chain reaction (RT-PCR). Mitochondria were isolated, and protein expression was quantified by Western blotting.

In IR group: UCP2 protein but not mRNA level was increased in the ischemic area of the left ventricle (LV) (172% ± 26.7, p < 0.001 vs. LV of control). Following acute myocardial IR, UCP2 protein levels was increased in the ischemic area of the LV but not in RV, suggesting the local effect of ischemia on UCP2 expression. IR-induced overexpression of UCP2 was suppressed by ramiprilat and losartan.

These findings suggest that losartan and ramiprilat can suppress UCP2 expression following myocardial IR, and by this mechanism may protect the myocardium against IR injury.

This study was performed to address the pathological roles of the skeletal renin-angiotensin system (RAS) in type 1 diabetes-induced osteoporosis and the effects of the angiotensin II type 1 receptor blocker losartan on bones in diabetic mice.

Bone histomorphology was detected by H&E staining, Safranin O staining and X-ray radiography. Micro-CT was performed for the analysis of bone parameters. Gene and protein expression were determined by RT-PCR and immunoblotting.

Type 1 diabetic mice displayed osteopenia phenotype, and losartan treatment had no osteoprotective effects on diabetic mice as shown by the reduction of bone mineral density and microarchitectural parameters at the proximal metaphysis of the tibia. The mRNA expression of AGT, renin receptor and ACE, and protein expression of renin and AT1R were markedly up-regulated in the bones of vehicle-treated diabetic mice compared to those of non-diabetic mice. The treatment with losartan further significantly increased the expression of AGT, renin, angiotensin II and AT1R, and reduced the expression of AT2R receptor as compared to those of diabetic mice.

A low-sodium diet (LSD) was shown to increase both angiotensin II (AngII) and aldosterone levels, and to accelerate atherosclerosis in apolipoprotein E-deficient (E0) mice. The aim of the present study was to examine whether accelerated atherosclerosis in E0 mice fed a LSD is mediated by aldosterone, using the mineralocorticoid receptor blocker, eplerenone (Epl).

Mice were divided into three groups: normal diet (ND), LSD and LSD treated with Epl at 100 mg/kg per day (LSD+Epl) for 10 weeks. LSD significantly enhanced plasma renin and aldosterone levels, which were further increased in mice fed LSD+Epl. The aortic lesion area increased three-fold with LSD, while LSD+Epl significantly reduced the lesion area to values similar to ND. Serum and peritoneal macrophages obtained from LSD-fed mice exhibited pro-atherogenic properties including increased inflammation, oxidation and cholesterol accumulation, which were inhibited in mice fed LSD+Epl. In a J774A.1 macrophage-like cell line stimulated with lipopolysaccharide, Epl was shown to have a direct anti-inflammatory effect.

In E0 mice, Epl inhibited LSD-accelerated atherosclerosis, despite the elevation of renin and aldosterone levels. It is therefore suggested that the atherogenic action of LSD could be mediated, at least in part, by activation of the mineralocorticoid receptor. In addition, eplerenone may have direct anti-inflammatory actions.

All-trans retinoic acid (ATRA) exerts various effects on physiological processes such as cell growth, differentiation, apoptosis and inflammation. Prohibitins (PHB), including prohibitin 1 (PHB1) and prohibitin 2 (PHB2), are evolutionary conserved and pleiotropic proteins implicated in various cellular functions, including proliferation, tumor suppression, apoptosis, transcription, and mitochondrial protein folding. The renin–angiotensin–aldosterone system plays a pivotal role in the regulation of blood pressure and volume homeostasis. All these factors and systems have been implicated in renal interstitial fibrosis. Therefore, the objective of this study was to investigate the effect of ATRA treatment on the renin–angiotensin–aldosterone system and expression of prohibitins to further understand its role in the processes leading to renal interstitial fibrosis.

The hypoxic and oxidative stress conditions in obstructive renal disease were simulated in a hypoxia/reoxygenation model with renal tubular epithelial cells (RTEC) as a model system. Subsequently, the effect of ATRA on mRNA and protein expression levels was determined and correlations were established between factors involved in the renin–angiotensin–aldosterone system, the prohibitins, cellular redox status, renal interstitial fibrosis and ATRA treatment.

Correlation analysis showed that both PHB1 and PHB2 protein levels were negatively correlated with angiotensin I, ACE1, angiotensin II, TGF-β1, Col-IV, FN, ROS, and MDA (PHB1: r = −0.792, –0.834, –0.805, –0.795, –0.778, –0.798, –0.751, –0.682; PHB2: r = −0.872, –0.799, –0.838, –0.773, –0.769, –0.841, –0.794, –0.826; each p < 0.05), but positively correlated with ACE2, SOD, and GSH (PHB1: r = 0.796, 0.879, 0.824; PHB2: r = 0.785, 0.914, 0.849; each p < 0.05). ACE1 was positively correlated with angiotensin I, angiotensin II, TGF-β1, Col-IV, FN, ROS, and MDA, and negatively correlated with ACE2, SOD, and GSH (each p < 0.05). ACE2 was negatively correlated with ACE1, angiotensin I, angiotensin II, TGF-β1, Col-IV, FN, ROS, and MDA, and positively correlated with SOD and GSH (each p < 0.05).

The results suggest that ATRA acts as a positive regulator of PHB1, PHB2 and ACE2, and as a negative regulator of ACE1, angiotensin I, and angiotensin II in a RTEC model system under hypoxia/reoxygenation conditions.

Statins, a class of lipid lowering drugs, decrease mortality associated with cardiovascular events. As hypercholesterolemia is often accompanied by hypertension, a large number of patients receive therapy with statins and antihypertensive drugs which act via the renin–angiotensin–aldosterone system (RAAS). New guidelines published by the American Heart Association and American College of Cardiology on the treatment of dyslipidaemia and the reduction of atherosclerotic cardiovascular risk, which use a risk prediction algorithm based on risk factors such as hypertension but not low-density lipoprotein (LDL) level, may even further increase the number of patients receiving such concomitant therapy.

In this paper we review studies on an interaction between statins, the RAAS and antihypertensive drugs acting via the RAAS.

Accumulating evidence suggests that the combination of statins and drugs affecting the RAAS exerts a synergistic effect on the circulatory system. For example, statins may lower arterial blood pressure and augment the effect of antihypertensive drugs acting via the RAAS. Statins may interact with the RAAS in a number of ways i.e. to decrease the expression of receptors for angiotensin II (Ang II), inhibit the Ang II-dependent intracellular signalling, reduce the RAAS-dependent oxidative stress and inflammation as well as inhibit the synthesis of Ang II and aldosterone.

Although statins given either alone or together with antihypertensive drugs acting via the RAAS may lower arterial blood pressure, further research is needed to evaluate the mechanisms and their therapeutic significance.

This study was designed to investigate the underlying mechanisms of synergistic antihypertensive effect produced by combination therapy of losartan and pioglitazone in metabolic syndrome (MS) rats.

An MS model was induced by feeding rats a high-fat, high-sodium diet and 20% sucrose solution. Losartan (20 mg/kg/day), pioglitazone (10 mg/kg/day), and their combination were orally administered for eight consecutive weeks. Systolic blood pressure (SBP) and mean arterial pressure (MAP) were measured using the tail-cuff method and carotid arterial catheterization, respectively. The aortas were isolated and in vitro vascular reactivity studies were performed. The protein expression of angiotensin type 1 receptor (AT₁), endothelial nitric oxide synthase (eNOS), phosphorylated eNOS and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47^phox, level of nitrotyrosine as well as activity of eNOS and NADPH oxidase in aortas of MS rats were detected.

After eight weeks of treatment, the SBP and MAP in the losartan (115 ± 5 and 106 ± 6 mmHg), pioglitazone (130 ± 6 and 118 ± 6 mmHg), and combination therapy (105 ± 6 and 98 ± 5 mmHg) groups were lower than those in the model group (150 ± 8 and 136 ± 9 mmHg). Combination therapy of losartan and pioglitazone reduced BP more than either monotherapy, and showed additive effects on improving endothelial dysfunction and abolishing the increased vascular responsiveness to angiotensin II. These synergistic effects were associated with further reductions in protein expression of p47^phox and AT₁, NADPH oxidase activity, and nitrotyrosine level.

Our data indicate that combined treatment exerts more beneficial effects on lowering BP and improving vascular lesions.

The combination therapy of aliskiren and renin–angiotensin–aldosterone system (RAAS) blocker in chronic kidney disease (CKD) is controversial. Whether such dual blockade can effectively apply to patients with CKD irrespective of stage and amount of proteinuria remains uncertain.

We added aliskiren at a dosage of 150 mg/day for six months in 103 Chinese CKD patients who had been treated with angiotensin converting enzyme inhibitors (ACEis) or angiotensin receptor blockers (ARBs) and still had significant proteinuria or uncontrolled hypertension. Blood pressure, serum creatinine, estimated glomerular filtration rate (eGFR), potassium, and spot urine protein-to-creatinine ratio (UPCR) were measured at three and six months after aliskiren add-on therapy and compared with baseline.

The combination of aliskiren and ACEi or ARB significantly reduced UPCR by 23% (p=0.001) and mean arterial pressure by 7.9 ± 13.8 mmHg (p<0.001) at six months. Twenty-five percent of subjects had a greater than 50% reduction in UPCR. No significant changes in eGFR and serum potassium level were noted at six months.

Adding aliskiren on ACEi or ARB in CKD patients, both in diabetes and non-diabetes, has a favorable effect on reducing residual proteinuria and inadequately controlled blood pressure.

Aldosterone antagonists may mediate their effects on heart failure through parathyroid hormone (PTH) in chronic kidney disease (CKD) patients.

Patients with CKD on spironolactone were selected and matched for age, gender, race, use of a vitamin D analogue, the number of antihypertensive medications, and CKD stage. PTH levels before and after the first prescription of spironolactone were measured. A thorough chart review was conducted to assess for heart failure hospitalizations. An adjusted Cox proportional model was used to calculate the hazard ratio (HR) for heart failure hospitalizations among cases versus controls.

There were a total of 950 (mean age 67±13 years, 40% men) patients with CKD. Of these, there were 48 hospitalizations for heart failure among the cases and 82 among the controls (HR 0.37; 95% confidence interval (CI) 0.19–0.74, p=0.005). We noted a more significant decrease in PTH levels among the cases when compared to the controls (p<0.0001). The adjusted hazard for heart failure hospitalization increased with higher PTH levels (p=0.002) and mediation analysis revealed change in PTH level as a significant mediator of heart failure hospitalization (p=0.04).

Aldosterone antagonists may be helpful in preventing hospitalizations for heart failure exacerbation in CKD patients through a PTH-mediated effect.

The development of left ventricular remodelling after acute myocardial infarction is a predictor of heart failure and mortality. The purpose of the present study was to assess whether the polymorphism of angiotensinogen (AGT) gene with threonine (T) instead of methionine (M) at amino acid 235 in exon 2 (M235T) had effects on cardiac remodelling after acute myocardial infarction.

One hundred and forty-one patients (mean age 56.4±11.1 years) with a first acute myocardial infarction were enrolled. Within 24–72 hours of the onset of the symptoms and at a four month period two-dimensional echocardiography was performed. Remodelling was defined as a 20% increase from the baseline in left ventricular end-diastolic volume. The genotypes of the study group were compared with the reference group (n=1010) genotypes. AGT M235T polymorphism was determined using polymerase chain reaction amplification.

At follow-up, 49 patients (34.7%) were classified as having left ventricular remodelling. Anterior localization of the infarct (p=0.008), leucocyte count at admission (p=0.040), global left ventricular longitudinal strain (p=0.021) and MM genotype of AGT (p=0.024) were independent predictors of ventricular remodelling after myocardial infarction.

Anterior wall infarction, increased leucocyte count, decreased longitudinal strain of left ventricular and polymorphism of AGT M235T may predict remodelling after myocardial infarction.

The angiotensinogen (AGT) gene M235T polymorphism has been reported to be associated with myocardial infarction (MI), but previous studies have been inconsistent. The present study aimed at assessing the association of M235T polymorphism in the AGT gene with MI using a meta-analysis.

We retrieved literature in Google Scholar, PubMed, Cochrane Library and the China National Knowledge Infrastructure database (January 1990–December 2011) for the relevant studies on the AGT polymorphism M235T and risk of MI. Statistical analyses were carried out using Stata 10.0 for combining all the relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association. Begg’s test was used to measure publication bias.

A total of 21 case-control studies containing 5887 patients and 6164 controls were enrolled into this meta-analysis. Overall, significant association was found between the AGT gene M235T polymorphism and risk of MI in the subgroup analysis for TT vs MT in Asians (OR 1.47, 95% CI: 1.01–2.12; p = 0.04). No associations were detected between AGT M235T and the risk of MI in total population and Caucasians.

This meta-analysis demonstrated that the AGT M235T polymorphism could be a prediction marker for risk of MI in Asians. Conclusive evidence on the effects of the variants in MI should be addressed in further studies.

Aldosterone participates in the pathogenesis of calcineurin inhibitor nephrotoxicity (CIN), producing renal vasoconstriction and transforming growth factor beta (TGFß) expression. The objective of this study was to assess aldosterone polymorphisms and relationships to plasma aldosterone levels and the development of renal histological lesions in kidney transplant patients.

Patients with kidney graft biopsy were divided according to the presence or absence of CIN. We determined aldosterone synthase (AS) -344 T/C and int 2 W/C gene polymorphisms and plasma aldosterone levels. Histological, biochemical and clinical variables were measured.

Calcineurin inhibitor (CI) levels were significantly higher in patients with the int 2 WW genotype than in patients with WC or CC genotypes. There was a greater degree of interstitial fibrosis in patients with int 2 CC genotype. No relationship was found between the different polymorphisms and a higher degree and/or frequency of CIN. There was also no relationship with plasma aldosterone levels.

The frequency of the different polymorphisms studied was not related to plasma aldosterone levels or the development of CIN; however, the int 2 CC genotype was related to a greater degree of interstitial fibrosis, whereas the WW genotype was related to higher CI serum levels.

Many reported studies have been conducted to investigate the association of angiotensin II type 1 receptor (AT1R) A1166C gene polymorphism with myocardial infarction (MI) susceptibility. However, the results from those reports are still conflicting. This meta-analysis was performed to study the relationship between AT1R A1166C gene polymorphism and MI risk.

The databases of PubMed, Embase, and Cochrane Library were searched as of 1 March 2012, and eligible investigations were recruited into this meta-analysis.

Eighteen investigations were identified for the analysis of association between AT1R A1166C gene polymorphism and MI risk, 11 in Caucasians, three in Asians, two in Africans, one in the population of Brazil and one in the population of Durban, South Africa . There was a marked association between AT1R C allele and MI susceptibility for overall populations (odds ratio (OR)=1.12, 95% confidence interval (CI): 1.01–1.25, p=0.03), and AT1R AA genotype was associated with a lower risk of MI in overall populations (OR=0.87, 95% CI: 0.78–0.98, p=0.02). However, AT1R A1166C gene polymorphism was not associated with MI risk in the sub-groups of Caucasians, Asians, Africans, Brazil and Durban populations.

C allele is a risk factor for the MI susceptibility in overall populations, and AA genotype might be a protective factor against the MI risk in overall populations. However, more case-control association investigations on larger, stratified populations are required in the future.