Angiotensin receptor blockers: evidence for preserving target organs

A Case of Significant Improvement of Heart Failure With Reduced Ejection Fraction With a Small Dose of Candesartan in a Hemodialysis Patient With Hypertensive Heart Disease and Nephrosclerosis

Hypertension induces vascular damage followed by organ damage, including heart failure in hypertensive heart disease (HHD) and nephrosclerosis (the resultant renal pathologic change from long-standing hypertension affecting renal vascular supply), ultimately causing renal failure. Renin-angiotensin-aldosterone system (RAAS) inhibitors are well known as effective drugs for the treatment of hypertension and the anti-remodeling of affected organs. A 52-year-old male was evaluated. Right atrophic kidney and proteinuria were noted in his high school years; however, he had no symptoms for about 35 years. He had pollakiuria in November and oliguria and leg edema in December 2020. The edema deteriorated rapidly, and general fatigue and orthopnea emerged in January 2021. Anasarca, hypertension (198/151 mmHg), tachycardia (115/minute), and hypoxemia (oxygen saturation {SpO2} of 93%) were observed on admission. A bilateral pleural effusion and pulmonary congestion were found on a chest X-ray (CXR) examination. An echocardiogram showed a 22% left ventricle ejection fraction (LVEF). Blood urea nitrogen (BUN) and serum creatinine concentrations were 70 mg/dL and 6.05 mg/dL, respectively. He was diagnosed with nephrosclerosis and HHD-induced cardiac exhaustion. Hemodialysis was started in April 2021. Even though the dry weight was decreased by draining water, cardiomegaly (cardiothoracic ratio {CTR}: 60%), low LVEF (20%-30%), and hypertension, especially diastolic hypertension (140-150/100-120 mmHg), were sustained. After 2 mg of candesartan was added in November 2021, the cardiomegaly, blood pressure (BP), and LVEF were rapidly ameliorated. The CTR and LVEF recovered to 48.5% and 60%, respectively, in April 2022. Statistical analyses showed that the independent factors for CTR were the mean monthly diastolic BP (standard partial regression coefficient {[Formula: see text]}: 0.9058, p<0.0001) and candesartan ([Formula: see text]: -0.7389, p=0.0011) in vital signs and prescribed drugs, respectively. We experienced a case of a significant effect of candesartan treatment against heart failure with reduced ejection fraction (HFrEF) caused by HHD in a hemodialysis patient with nephrosclerosis. Statistical analyses suggested that the improvement of HFrEF resistant to fluid removal by hemodialysis was presumably due to a decrease in diastolic BP caused by a small dose of candesartan.

Non-communicable diseases (NCDs) and vulnerability to COVID-19: The case of adult patients with hypertension or diabetes mellitus in Gamo, Gofa, and South Omo zones in Southern Ethiopia

BACKGROUND

A growing body of evidence demonstrating that individuals with Non-Communicable Disease (NCD) are more likely to have severe forms of COVID-19 and subsequent mortality. Hence, our study aimed to assess the knowledge of vulnerability and preventive practices towards COVID-19 among patients with hypertension or diabetes in Southern Ethiopia.

OBJECTIVE

To assess the knowledge and preventive practices towards COVID-19 among patients with hypertension or diabetes mellitus in three zones of Southern Ethiopia, 2020.

METHODS

A community-based cross-sectional study design was used with a multi-stage random sampling technique to select 682 patients with hypertension or diabetes mellitus from 10th -17th July 2020 at the three zones of Southern Ethiopia. Logistic regression analysis with a 95% confidence interval was fitted to identify independent predictors of knowledge and preventive practices towards COVID-19. The adjusted odds ratio (AOR) was used to determine the magnitude of the association between the outcome and independent variables. P-value <0.05 is considered statistically significant.

RESULTS

The Multi-dimensional knowledge (MDK) analysis of COVID-19 revealed that 63% of study subjects had good knowledge about COVID-19. The overall preventive practice towards COVID -19 was 26.4%. Monthly income (AOR = 1.42; 95% CI: 1.04, 1.94) significantly predicted knowledge towards COVID-19. Ninety-five percent of the study subjects knew that the COVID-19 virus spreads via respiratory droplets of infected individuals. One hundred and ten (16.2%) of study subjects correctly responded to the questions that state whether people with the COVID-19 virus who do not have a fever can infect the other. Knowledge about COVID-19 (AOR = 1.47; 95% CI: 1.03, 2.1) became the independent predictor of preventive practice.

CONCLUSIONS

In this study, the knowledge of the respondents towards the COVID-19 pandemic was good. But the preventive practice was very low. There was a significant gap between knowledge and preventive practices towards the COVID-19 pandemic among the study subjects. Monthly income was significantly associated with knowledge of COVID-19. Knowledge of COVID-19 was found to be an independent predictor of preventive practice towards COVID-19. Community mobilization and improving COVID-19- related knowledge and practice are urgently recommended for those patients with hypertension or diabetes mellitus.

Sex differences in the lung ACE/ACE2 balance in hypertensive rats

The angiotensin-converting enzyme (ACE)/Angiotensin II (Ang II) and angiotensin-converting enzyme 2 (ACE2)/angiotensin-(1-7) (Ang-(1-7)) pathways are coexpressed in most tissues. The balance between these pathways determines, at least in part, whether tissue damage will occur in response to pathological stimuli. The present study tested the hypothesis that male sex and high blood pressure are associated with ACE/ACE2 imbalance in the lungs. Experiments were conducted in male and female Wistar rats and spontaneously hypertensive rats (SHRs). Lung ACE and ACE2 gene expression was also evaluated in normotensive and hypertensive humans using the Genotype-Tissue Expression (GTEx) project. Compared with Wistar rats and female SHRs, male SHRs displayed reduced lung ACE2 mRNA, ACE2 protein abundance and ACE2 activity, and increased Ang II concentration. Lung ACE mRNA levels were higher in male SHRs than in Wistar rats, whereas lung ACE protein abundance and activity were similar among the four groups of rats. Lung Ang-(1-7) concentration was higher in female than in male SHRs (89 ± 17 vs. 43 ± 2 pg/g, P<0.05). Lung ACE to ACE2 mRNA expression in hypertensive patients was significantly higher than that in normotensive subjects. Taken together, these results demonstrate that male hypertensive rats display imbalance between the ACE/Ang II and ACE2/Ang-(1-7) pathways in the lungs mainly attributable to ACE2 down-regulation. Further studies should be conducted to investigate whether this imbalance between ACE/ACE2 may promote and accelerate lung injury in respiratory infections, including coronavirus disease 2019 (COVID-19).

Antiproteinuric and Hyperkalemic Mechanisms Activated by Dual Versus Single Blockade of the RAS in Renovascular Hypertensive Rats

This study aimed to investigate the antiproteinuric and hyperkalemic mechanisms activated by dual renin-angiotensin system (RAS) blockade in renovascular hypertensive rats (2-kidney 1-clip model [2K-1C]). Six weeks after clipping the left renal artery or sham operation (2K), rats were treated with losartan, enalapril, or both drugs for two weeks. We found that 2K-1C rats displayed higher tail-cuff blood pressure (BP), increased non-clipped kidney Ang II concentration, and more pronounced urinary albumin excretion than 2K. BP was decreased by the treatment with either enalapril or losartan, and the combination of both drugs promoted an additional antihypertensive effect in 2K-1C rats. Renal Ang II content and albuminuria were reduced by either enalapril or losartan in monotherapy and restored to control levels by dual RAS blockade. Albuminuria in 2K-1C rats was accompanied by downregulation of the glomerular slit protein podocin, reduction of the endocytic receptors megalin and cubilin, and a marked decrease in the expression of the ClC-5 chloride channel, compared to 2K animals. Treatment with losartan and enalapril in monotherapy or combination increased the expression of podocin, cubilin, and ClC-5. However, only the combined therapy normalized podocin, cubilin, and ClC-5 protein abundance in the non-clipped kidney of 2K-1C rats. Renovascular hypertensive 2K-1C rats had a lower concentration of plasma potassium compared to 2K rats. Single RAS blockade normalized potassium plasma concentration, whereas 2K-1C rats treated with dual RAS blockade exhibited hyperkalemia. Hypokalemia in 2K-1C rats was accompanied by an increase in the cleaved activated forms of α-ENaC and γ-ENaC and the expression of β-ENaC. Combined RAS blockade but not monotherapy significantly reduced the expression of these ENaC subunits in 2K-1C rats. Indeed, double RAS blockade reduced the abundance of cleaved-α-ENaC to levels lower than those of 2K rats. Collectively, these results demonstrate that the antiproteinuric effect of dual RAS blockade in 2K-1C rats is associated with the restored abundance of podocin and cubilin, and ClC-5. Moreover, double RAS blockade-induced hyperkalemia may be due, at least partially, to an exaggerated downregulation of cleaved α-ENaC in the non-clipped kidney of renovascular hypertensive rats.

Biological Context Linking Hypertension and Higher Risk for COVID-19 Severity

The coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), represents a public health crisis of major proportions. Advanced age, male gender, and the presence of comorbidities have emerged as risk factors for severe illness or death from COVID-19 in observation studies. Hypertension is one of the most common comorbidities in patients with COVID-19. Indeed, hypertension has been shown to be associated with increased risk for mortality, acute respiratory distress syndrome, need for intensive care unit admission, and disease progression in COVID-19 patients. However, up to the present time, the precise mechanisms of how hypertension may lead to the more severe manifestations of disease in patients with COVID-19 remains unknown. This review aims to present the biological plausibility linking hypertension and higher risk for COVID-19 severity. Emphasis is given to the role of the renin-angiotensin system and its inhibitors, given the crucial role that this system plays in both viral transmissibility and the pathophysiology of arterial hypertension. We also describe the importance of the immune system, which is dysregulated in hypertension and SARS-CoV-2 infection, and the potential involvement of the multifunctional enzyme dipeptidyl peptidase 4 (DPP4), that, in addition to the angiotensin-converting enzyme 2 (ACE2), may contribute to the SARS-CoV-2 entrance into target cells. The role of hemodynamic changes in hypertension that might aggravate myocardial injury in the setting of COVID-19, including endothelial dysfunction, arterial stiffness, and left ventricle hypertrophy, are also discussed.

The benefit of angiotensin AT1 receptor blockers for early treatment of hypertensive patients

ESC guidelines for management of arterial hypertension allow one to choose among five classes of antihypertensive drugs indiscriminately. They are based on the principle that in the management of hypertensive patients, it is fundamental to reduce blood pressure (BP), independently of the utilized drug. However, it has been demonstrated that the renin-angiotensin system (RAS) plays a relevant role in the hypertensive-derived development and progression of organ damage. Thus, antihypertensive drugs interfering with the RAS should be preferred in preventing and reducing target organ damage. The availability of two classes of drugs, ACE-inhibitors and angiotensin AT1 receptor blockers (ARBs), both interfering with the RAS, makes the choice between them difficult. Both pharmacological strategies offer an effective BP control, and a substantial improvement of prognosis in different associated pathologies. Regarding cardiovascular prevention, ACE-inhibitors have an extensive scientific literature regarding utility in high-risk patients. Nevertheless, there is evidence to support the concept that in the early phases of organ tissue damage, the RAS is activated, but the ACE pathway producing angiotensin II is not always employed. Accordingly, ACE-inhibitors appear to be less effective, whereas ARBs have a greater beneficial action in the initial stages of atherosclerotic disease. Moreover, patients undergoing ARBs therapy show a substantially lower risk of therapy discontinuation when compared to those treated with ACE-inhibitors, because of a better tolerability. In conclusion, ACE-inhibitors should be used in patients who have already developed organ damage, but tolerate this drug well, while ARBs should be the first choice in naïve hypertensive patients without organ damage or at the initial stages of disease.

Sub-chronic lead exposure produces β1-adrenoceptor downregulation decreasing arterial pressure reactivity in rats

Lead is considered a causative factor for hypertension and other cardiovascular diseases.

AIMS

To investigate the effects of sub-chronic lead exposure on blood pressure reactivity and cardiac β₁-adrenoceptor activity and to evaluate whether the effects found in vitro are similar to those found in vivo.

MAIN METHODS

Male Wistar rats were randomly distributed into two groups: control rats (Ct) and rats administered drinking water containing 100ppm lead (Pb) for 30days.

KEY FINDINGS

Blood pressure in the Pb rats increased starting from the first week of treatment until the end of the study [systolic blood pressure, Ct: 122±4 vs. Pb: 143±3mmHg; diastolic blood pressure, Ct: 63±4 vs. Pb: 84±4mmHg]. The heart rate was also increased (Ct: 299±11 vs. Pb: 365±11bpm), but the pressure reactivity to phenylephrine was decreased. Losartan and hexamethonium exhibited a greater reduction in blood pressure of Pb rats than in the Ct rats. Isoproterenol increased the left ventricular systolic and end-diastolic pressure, and heart rate only in Ct rats, suggesting that lead induced β₁-adrenoceptor downregulation. Indomethacin reduced the blood pressure and heart rate in the Pb rats, suggesting the involvement of cyclooxygenase-derived products (which are associated with reduced nitric oxide bioavailability) in this process.

SIGNIFICANCE

These findings offer further evidence that the effects of sub-chronic lead exposure in vitro can be reproduced in vivo-even at low concentrations-thus triggering mechanisms for the development of hypertension. Therefore, lead should be considered an environmental risk factor for cardiovascular disease.

Erythropoietin Regulation by Angiotensin II

The renin-angiotensin system (RAS) is a key regulator of blood pressure and blood volume homeostasis. The RAS is primarily comprised of the precursor protein angiotensinogen and the two proteases, renin and angiotensin-converting enzyme (ACE). Angiotensin I (Ang I) is derived from angiotensinogen by renin, but appears to have no biological activity. In contrast, angiotensin II (Ang II) that has a variety of biological functions in the cells is converted from Ang I through removal of two-C-terminal residues by ACE. The physiological effects of Ang II are due to Ang II signaling through specific receptor binding, resulting in muscle contraction leading to increased blood pressure and volume. To modulate RAS, three classes of drugs have been developed: (1) renin inhibitors to prevent angiotensinogen conversion to Ang I, (2) ACE inhibitors, to prevent Ang I processing to Ang II and (3) angiotensin receptor blockers, to inhibit Ang II signaling through its receptor. Studies using the RAS inhibitors and Ang II demonstrated that RAS signaling mediates actions of Ang II in the regulation of proliferation and differentiation of specific hematopoietic cell types, especially in the red blood cell lineage. Accumulating evidence indicates that RAS regulates EPO, an essential mediator of red cell production, for human anemia and erythropoiesis in vivo and in vitro. The regulation of EPO expression by Ang II may be responsible for maintaining red blood cell homeostasis. This review highlights the biological roles of RAS for blood cell and EPO homeostasis through Ang II signaling. The molecular mechanism for Ang II-induced EPO production of the cell or tissue type-specific expression is discussed.

Angiotensin Receptor Blockers Decrease the Risk of Major Adverse Cardiovascular Events in Patients with End-Stage Renal Disease on Maintenance Dialysis: A Nationwide Matched-Cohort Study

Background

Major adverse cardiovascular events (MACE) cause the leading cause of morbidity and mortality in patients with end-stage renal disease (ESRD) on maintenance Hemodialysis (HD) or peritoneal dialysis (PD). Many randomized-controlled trials (RCTs) have proved that angiotensin receptor blockers (ARBs) can reduce the risk of MACE in the people with normal or impaired kidney function without dialysis. This study seeks to clarify whether ARBs therapy could also attenuate this risk in patients with ESRD on maintenance dialysis.

Materials and Methods

The National Health Research Institute provided a database of one million random subjects for the study. A random sample was taken of 1800 patients ≥18 years y/o with ESRD on dialysis without a history of MACE and use of ARBs within 6-months prior to enrollment. Cox proportional hazard regression analysis was used to identify the risk factors and compute the hazard ratios accompanying 95% confidence intervals.

Results

In these 1800 patients, 1061 had never used ARBs, while 224 had used them for 1–90 days, and 515 had used them for more than 90 days. We found that ARBs significantly decrease the incidences of acute myocardial infarctions (AMI), coronary artery diseases (CAD) requiring coronary stent or percutaneous transluminal coronary angioplasty (PTCA), peripheral artery disease (PAD) requiring percutaneous transluminal angioplasty (PTA), and acute stroke. Cumulative prescription days of ARBs beyond 365–760 days or more were found to be negatively correlated with incidence of MACEs. For patients with dual comorbidity (i.e., mellitus and hyperlipidemia), 91–365 cumulative prescription days might also attenuate the risk.

Conclusions

For patients on maintenance dialysis, the use of ARBs could significantly attenuate the risk of major cardiovascular events: AMI, acute stroke, and PAD requiring PTA.

The role of sulfur dioxide in the regulation of mitochondrion-related cardiomyocyte apoptosis in rats with isopropylarterenol-induced myocardial injury

The authors investigated the regulatory effects of sulfur dioxide (SO₂) on myocardial injury induced by isopropylarterenol (ISO) hydrochloride and its mechanisms. Wistar rats were divided into four groups: control group, ISO group, ISO plus SO₂ group, and SO₂ only group. Cardiac function was measured and cardiomyocyte apoptosis was detected. Bcl-2, bax and cytochrome c (cytc) expressions, and caspase-9 and caspase-3 activities in the left ventricular tissues were examined in the rats. The opening status of myocardial mitochondrial permeability transition pore (MPTP) and membrane potential were analyzed. The results showed that ISO-treated rats developed heart dysfunction and cardiac injury. Furthermore, cardiomyocyte apoptosis in the left ventricular tissues was augmented, left ventricular tissue bcl-2 expression was down-regulated, bax expression was up-regulated, mitochondrial membrane potential was significantly reduced, MPTP opened, cytc release from mitochondrion into cytoplasm was significantly increased, and both caspase-9 and caspase-3 activities were increased. Administration of an SO₂ donor, however, markedly improved heart function and relieved myocardial injury of the ISO-treated rats; it lessened cardiomyocyte apoptosis, up-regulated myocardial bcl-2, down-regulated bax expression, stimulated mitochondrial membrane potential, closed MPTP, and reduced cytc release as well as caspase-9 and caspase-3 activities in the left ventricular tissue. Hence, SO₂ attenuated myocardial injury in association with the inhibition of apoptosis in myocardial tissues, and the bcl-2/cytc/caspase-9/caspase-3 pathway was possibly involved in this process.

Telmisartan: from lowering blood pressure to end-organ protection

The principal aim in the treatment of patients with high blood pressure is to ensure a maximum reduction in the total risk of cardiovascular morbidity and mortality. The renin-angiotensin system plays an important role in volume homeostasis and blood pressure regulation. The angiotensin receptor blockers control high blood pressure by preventing the binding of angiotensin II to the subtype 1 receptor, which is believed to mediate most of the physiologic actions of angiotensin II relevant to the regulation of blood pressure. Telmisartan is a widely used angiotensin receptor blocker with distinct pharmacokinetic and pharmacodynamic properties. Due to its long duration of action, it compares favorably with other angiotensin receptor blockers. Latest data from clinical trials and newest research regarding telmisartan will be reviewed in this article.

Neuro-endocrine regulation of blood pressure

As our understanding of the underlying aetiology of hypertension is far from adequate, over 90% of patients with hypertension receive a diagnosis of essential hypertension. This non-specific diagnosis leads to suboptimal therapeutics and a major problem with non-compliance. Understanding the normal control of blood pressure (BP) is, hence, important for a better understanding of the disease.This review attempts to unravel the present understanding of BP control. The local mechanisms of BP control, the neural mechanisms, renal-endocrine mechanisms, and a variety of other hormones that have a bearing in normal BP control are discussed and the possible role in the pathophysiology is alluded to.

Choosing an angiotensin-receptor blocker: blood pressure lowering, cardiovascular protection or both?

Angiotensin-receptor blockers (ARBs) offer superior tolerability to angiotensin-converting enzyme inhibitors, and are increasingly used in patient management. ARBs vary in their pharmacological profiles, which results in efficacy differences. Therefore, deciding between ARBs should be evidence-based and related to the specific requirements of the individual patient. For patients with hypertension but at low additional risk, an ARB that provides sustained, powerful 24-h reductions in blood pressure is suitable. For patients at very high additional risk (with heart failure), an ARB with demonstrated efficacy in this patient population is the preferred option. For patients at increased risk, telmisartan should be the ARB of choice based on the results from the Ongoing Telmisartan Alone and in Combination with Ramipril Global End Point Trial (ONTARGET), which demonstrated for the first time that an ARB has equivalent protection to the reference angiotensin-converting enzyme inhibitor in a broad cross-section of at-risk patients but a better side-effect profile.

Choosing among renin-angiotensin system blockers for the management of hypertension: from pharmacology to clinical efficacy

BACKGROUND

Hypertension is an important healthcare challenge, yet despite initiatives to improve detection and advances in therapy, the majority of patients do not achieve recommended blood pressure targets and remain at high cardiovascular risk. Physicians are confronted with an array of antihypertensive agents, accompanied by increasingly complex and often conflicting evidence regarding their efficacy and tolerability.

SCOPE

An extensive PubMed and Cochrane database search was conducted to identify clinical literature (published 1990-2009) on the blood pressure lowering efficacy, tolerability and target organ protection of angiotensin converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs). While not a systematic review, this article reviews the best available evidence in an attempt to clarify current uncertainty within medical practice regarding treatment options in patients with hypertension.

FINDINGS

ACEIs have been at the forefront of hypertension therapy for several years, especially in hypertensive at-risk patients. However, their use is restricted by burdensome side-effects and their limited ability to reach target blood pressure. Newer ARBs, such as telmisartan, have more sustained blood pressure control throughout the 24-h dosing period compared with ACEIs and other ARBs. For uncomplicated hypertension, ARBs are preferred to ACEIs because of their superior tolerability and adherence. In specific patient populations, namely heart failure patients, ARBs have previously shown equal cardiovascular protection to ACEIs. ONTARGET showed that an ARB, in this case telmisartan, was as effective as ramipril in reducing cardiovascular events in a wide cross-section of at-risk cardiovascular patients, but was better tolerated even though patients were screened for ACEI tolerance.

CONCLUSION

Telmisartan is currently the only ARB to have demonstrated equivalence to ramipril in reducing cardiovascular events in a broad patient population. In practical terms, telmisartan is superior to the reference standard ramipril because of more powerful blood pressure lowering and superior tolerability. However, in many countries, guidance to physicians prioritizes ACEIs. In these countries, telmisartan should be the first choice ARB for hypertensive at-risk patients who do not achieve adequate blood pressure control with an ACEI, or for whom tolerability is a concern.

[Ca2+]i and PKC-alpha are involved in the inhibitory effects of Ib, a novel nonpeptide AngiotensinII subtype AT1 receptor antagonist, on AngiotensinII-induced vascular contraction in vitro

The vasoactive peptide AngiotensinII (AngII) is an important factor in the cardiovascular system, exerting most of its effects through AngII receptor type 1 (AT1). Ib, a new nonpeptide AT1 receptor antagonist, has been observed to play a positive role in the treatment of hypertension in preclinical tests. In this study, the inhibitory effects of Ib on AngII-induced vascular contraction in vitro were investigated, and its molecular mechanisms were further explored. In endothelium-denuded aortic rings from rabbits, Ib produced a rightward shift in the concentration-response curve for AngII with a decrease in the maximal contractile response and the pD2' was 7.29. In vascular smooth muscle cells (VSMCs), the specific binding of [125I]AngII to AT1 receptors was inhibited by Ib in a concentration-dependent manner with IC50 value of 0.96nM. Ib could inhibit both AngII-induced Ca2+ mobilization from internal stores and Ca2+ influx. Moreover, the translocation of PKC-alpha stimulated by AngII was inhibited by Ib. Thus, the inhibitory effects of Ib might be related with the depression on AngII-induced increase in [Ca2+]i and translocation of PKC-alpha through blocking AT1 receptors.

HNF-1α plays an important role in IL-6-induced expression of the human angiotensinogen gene

Angiotensinogen (AGT) is the precursor of one of the most important vasoactive hormone angiotensin II and this gene locus is associated with human essential hypertension. AGT is an acute phase protein and its gene expression is regulated by IL-6. Previous studies have identified three potential STAT-3 binding sites (APREs) located between −160 and −280 of the hAGT gene promoter but only APRE-1 (located between −271 and −279) was shown to be a bonafide enhancer for IL-6-induced promoter activity. We show here that APRE-2, located between −236 and −247, is indeed an HNF-1α-binding site and plays an important role in basal and IL-6 induced promoter activity of this gene. Our chromatin immunoprecipitation (ChIP) assay shows that HNF-1α binds to this region of the hAGT gene promoter and its recruitment is increased in the presence of IL-6 in Hep3B cells. We also show that the promoter activity of a deletion construct containing only 223 bp of the hAGT gene promoter (that contains only APRE-3) is increased after IL-6 treatment. Our ChIP assay shows that IL-6 treatment recruits STAT-3 to APRE-3 and suggests that this is also an IL6 responsive element. We have previously shown that GR binds to the proximal promoter of the hAGT gene. Since GR physically interacts with STAT-3, we propose that transcription factors GR, STAT-3, and HNF-1α that bind to the nucleotide sequence located between −160 and −280 of the hAGT gene promoter are responsible for IL-6 induced promoter activity of this gene.

Blood Pressure Goal Attainment: Meeting the Challenge of the JNC 7's Blood Pressure Goals and the Role of Renin‐Angiotensin‐Aldosterone System Blockade

This roundtable discussion, held in December 2003, was convened to discuss the impact of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure's (JNC 7) challenging blood pressure goal objectives for the clinical management of hypertensive patients. The discussion was moderated by Michael Weber, MD, of the State University of New York Downstate College of Medicine in New York City. Participants included leading experts in the field Joseph Izzo, Jr., MD, of the School of Medicine and Biomedical Sciences at the State University of New York at Buffalo; Suzanne Oparil, MD, of the Vascular Biology and Hypertension Program, Division of Cardiovascular Disease, University of Alabama at Birmingham; and Jan Basile, MD, of the Ralph H. Johnson VA Medical Center and Department of General Internal Medicine/Geriatrics, Medical University of South Carolina in Charleston. The primary intention of this roundtable is to educate physicians about the importance of achieving the blood pressure goals agreed upon by the JNC 7 Committee and to present practical ways for the attainment of such goals in clinical practice.

Sanguinarine Downregulates AT1a Gene Expression in a Hypertensive Rat Model

We studied the in vivo effects of sanguinarine in a hypertensive rat model and its effects on AT1a mRNA expression in kidney tissues. Rats received daily for 14 d sanguinarine 0.1 mg/kg (SangL) and 0.3 mg/kg (SangH), losartan 1 mg/kg by weight (Los), or DMSO (Con). Blood pressures were monitored regularly and urine volume and sodium concentration was measured on days 0, 7, and 14. On day 15, animals were anesthetized (sodium thiopentane, 50 mg/kg), blood samples for aldosterone levels were taken, and kidneys were removed for AT1a mRNA expression. Los and SangH groups showed reduced AT1a mRNA expressions by 4.22- and 5.9-fold, respectively. In the SangL group it was reduced by 2.7-fold. Decreases in systolic blood pressures mirrored decreases in AT1a mRNA expressions in all groups. Los and SangH groups showed reductions in systolic blood pressure of 12.3% and 19.3%, respectively, whereas in the SangL group, it was reduced by 8.07%. Urine output in the Los group increased (228% mean increase from days 0-14), whereas sodium excretion decreased by 69.6% (mean decrease from days 0-14). In the SangL and SangH groups, urine volumes increased significantly by 108.3% and 115% (mean increase from days 0-14), respectively. Urinary sodium excretion increased significantly by 60.9% in the SangH group. We concluded that sanguinarine reduces blood pressure in the Dahl rat because of decreased AT1 receptor expression and reduced aldosterone levels. The action of losartan on increased urinary volume and decreased sodium excretion may be attributed to reduced vasopressin secretion.

Sildenafil citrate increases myocardial cGMP content in rat heart, decreases its hypertrophic response to isoproterenol and decreases myocardial leak of creatine kinase and troponin T

BACKGROUND

Cardiac hypertrophy is a major risk factor for morbidity and mortality in a number of cardiovascular diseases. Consequently, the signaling pathways that inhibit cardiac hypertrophy are currently receiving much interest. Among them, nitric oxide (NO), signaling via cGMP and cGMP-dependent protein kinase I, has been recognized as a negative regulator of cardiac hypertrophy. The present study investigated the in-vivo effect of sildenafil as a phosphodiestrase-5A (PDE-5A) inhibitor on the hypertrophic response of rat heart to isoproterenol and the relation of this effect to the level of myocardial cGMP and integrity of the constitutive nitric oxide synthase (cNOS) activity.

RESULTS

The results showed that daily intraperitoneal administration of sildenafil per se for 10 days was without noticeable adverse effects on survival or myocardium. Conversely, daily subcutaneous administration of isoproterenol for 10 days caused significant myocardial hypertrophy, cell injury and decline in survival. When sildenafil was injected daily, one hour before isoproterenol, survival was significantly improved and the myocardium didn't show significant hypertrophy or cell injury. Interestingly, sildenafil was accompanied by significant rise in myocardial cGMP level, a parameter which was found in the present study to possess a significant negative correlation with cardiac hypertrophy and leak of cardiac troponin T into serum. At the same time, cGMP was found to possess a positive correlation with myocardial creatine kinase activity that reflects the efficiency of the energy utilization processes in the myocardium. However, in rats given Nomega-nitro-L-arginine (L-NNA) as a competitive inhibitor of cNOS, sildenafil failed to show any favorable effect on survival or the myocardial injury parameters used to assess isoproterenol-induced injury.

CONCLUSION

The present study suggests that increased cardiac cGMP level by sildenafil have a cardioprotective effect probably through acting as a post-receptor negative regulator of cardiac sympathetic responsiveness. Integrity of NOS function was an essential prerequisite for sildenafil's mediated cardioprotection encountered in the present study.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure; production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells; as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Angiotensin II Receptor Blockers in Older Patients

Older patients with hypertension are often inadequately treated due to misconceptions regarding reasonable goal blood pressures or concerns about treatment side effects. Adequately treating hypertension can yield impressive benefits in terms of improved morbidity and enhanced quality of life in persons of any age. Antagonists of the renin-angiotensin-aldosterone system are especially effective in older persons, many of whom have concomitant conditions such as diabetes mellitus, renal dysfunction, and other cardiovascular risk factors. Treatment with angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers has been shown to improve many of the complications of hypertension, including left ventricular hypertrophy and renal disease. Results of recent key studies such as Losartan Intervention For Endpoint Reduction in Hypertension (LIFE), Valsartan in Heart Failure Trial (Val-HeFT), Candesartan in Heart Failure Assessment of Reduction in Mortality and Morbidity (CHARM), and Valsartan in Acute Myocardial Infarction (VALIANT) add to the evidence that angiotensin II receptor blockers are well suited for the treatment of hypertension in older patients. These trials also indicate that they are appropriate therapy for heart failure patients and for patients who have experienced acute myocardial infarction, particularly those who are unable to tolerate an angiotensin-converting enzyme inhibitor.

Marinobufagenin may mediate the impact of salty diets on left ventricular hypertrophy by disrupting the protective function of coronary microvascular endothelium

Individuals who eat salty diets and who are "salt-sensitive" tend to have increased left ventricular mass, independent of blood pressure; this phenomenon awaits an explanation. It is clear that local up-regulation of angiotensin II (AngII) production and activity play a key role in the induction of left ventricular hypertrophy (LVH). Recent evidence suggests that a healthy coronary microvascular endothelium opposes this effect by serving as a paracrine source of nitric oxide (NO), a natural antagonist of AngII activity, and that up-regulation of this mechanism can account for the protective role of bradykinin with respect to LVH. The coronary microvasculature also possesses NAD(P)H oxidase activity that can generate superoxide, inimical to the bioactivity of endothelial NO. There is now good reason to believe that the triterpenoid marinobufagenin (MBG), a selective inhibitor of the alpha-1 isoform of the sodium pump, mediates the impact of salty diets on blood pressure;production of MBG by the adrenal cortex is boosted when salt-sensitive animals are fed salty diets. It is hypothesized that coronary microvascular endothelium expresses the alpha-1 isoform of the sodium pump, and that MBG thus can target this endothelium. If that is the case, MBG would be expected to decrease membrane potential in these cells;as a consequence, superoxide production would be up-regulated, NO synthase activity would be down-regulated, and myocardial NO bioactivity would thus be suppressed. This would offer a satisfying explanation for the impact of salt and salt-sensitivity on risk for LVH. If expression of the alpha-1 isoform of the sodium pump is a more general property of vascular endothelium, MBG may suppress NO bioactivity in other regions of the vascular tree, thereby contributing to other adverse effects elicited by salty diets: reduced arterial compliance, medial hypertrophy, impaired endothelium-dependent vasodilation, hypertensive/diabetic glomerulopathy, increased risk for stroke, and hypertension.

Comparison of telmisartan versus losartan: meta-analysis of titration-to-response studies

OBJECTIVES

To compare the ability of telmisartan and losartan to reduce mean diastolic blood pressure (DBP) during the last 6 h of the 24-h dosing interval in a prospectively planned meta-analysis of ambulatory blood pressure monitoring (ABPM) data from two independent studies.

METHODS

Data were from two independent randomized, double-blind, double-dummy, titration-to-response studies conducted in patients with mild-to-moderate hypertension (seated cuff DBP 95-109 mmHg, 24-h mean ambulatory DBP >or=85 mmHg). After a 4-week placebo run-in period, patients received once-daily telmisartan 40 mg or losartan 50 mg, with up-titration after 4 weeks to telmisartan 80 mg or losartan 100 mg, respectively, if seated trough cuff DBP >or=90 mmHg. Blood pressures were recorded using ABPM immediately before randomization and after 8 weeks of active treatment. In addition, seated trough cuff blood pressures were measured at baseline and after 4 and 8 weeks of active treatment.

RESULTS

Titration to the higher dose was required in 60.1% of telmisartan patients and 69.5% of losartan patients (P=0.01). Reductions from baseline in the last 6 h mean ambulatory DBP with telmisartan and losartan were 6.6+/-0.4 and 5.1+/-0.4 mmHg, respectively (P<0.01, adjusted for baseline and study); the effects were homogeneous across the two studies. During the last 6 h of the 24-h dosing interval, telmisartan produced greater reductions in each of the observed hourly mean ambulatory DBP values. Telmisartan-induced reductions were also greater for the majority of the observed hourly mean ambulatory DBP values over the entire 24-h dosing interval. Reductions from baseline in the last 6 h adjusted mean ambulatory systolic blood pressure (SBP) for telmisartan and losartan were 9.9+/-0.6 and 7.8+/-0.6 mmHg, respectively (P=0.01). The 24-h profiles of ambulatory SBP hourly mean reductions were similar to those for DBP. Both telmisartan and losartan were found to be safe and well tolerated.

CONCLUSIONS

Telmisartan 40/80 mg is superior to losartan 50/100 mg in controlling DBP and SBP during the last 6 h of the 24-h dosing interval.

Angiotensin II receptor blockers and cardiovascular outcomes: what does the future hold?

The ability of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) to lower blood pressure (BP) is well established. ACE inhibitors (ACE-Is) have also been shown to improve the prognosis of a broad range of patients at high cardiovascular risk, including those with heart failure, post-myocardial infarction (MI), and nephropathy. These benefits suggest that interrupting the renin-angiotensin-aldosterone system (RAAS) with ACE-Is has a widespread vasculoprotective effect, provided that BP is also adequately controlled. Evidence that RAAS blockade by ARBs also improves long-term clinical outcomes in patients with cardiovascular disease has started to accumulate, and will be tested further during the coming years as a number of large-scale, prospective trials are completed. These trials are investigating the long-term protective effects of ARBs on morbidity and mortality in patients with hypertension, heart failure, diabetes mellitus, acute MI, or established vascular disease. The results should establish the extent to which ARBs exhibit the vasculoprotective properties demonstrated by ACE-Is in patients at high cardiovascular risk. If ARBs are found to provide benefits that are similar to, or even greater than ACE-Is, it may have important implications for drug selection, given the excellent tolerability of ARBs. Some studies are also investigating whether more extensive RAAS blockade using a combination of an ARB and an ACE-I will offer even greater protection than either agent alone.

Angiotensinogen gene polymorphism at -217 affects basal promoter activity and is associated with hypertension in African-Americans

Hypertension is a serious health problem in Western society, in particular for the African-American population. Although previous studies have suggested that the angiotensinogen (AGT) gene locus is involved in human essential hypertension, the molecular mechanisms involved in hypertension in African-Americans remain unknown. We show that an A/G polymorphism at -217 in the promoter of the AGT gene plays a significant role in hypertension in African-Americans. The frequency of the -217A allele was increased significantly in African-American hypertensive subjects compared with normotensive controls. We also show that the nucleotide sequence of this region of the AGT gene promoter bound strongly to CAAT/enhancer-binding protein (C/EBP) family transcription factors when nucleoside A was present at -217. In addition, we show that reporter constructs containing the human AGT gene promoter with nucleoside A at -217 had increased basal transcriptional activity upon transient transfection in HepG2 cells compared with reporter constructs with nucleoside G at -217. Finally, we show that interleukin-6 treatment in the presence or absence of overexpressed C/EBPbeta increased the promoter activities of reporter constructs containing nucleoside A at -217 compared with reporter constructs containing nucleoside G at -217. Because the AGT gene is expressed primarily in liver and adipose tissue, and C/EBP family transcription factors play an important role in gene expression in these tissues, we propose that increased transcriptional activity of the -217A allele of the human AGT gene is associated with hypertension in African-Americans.