Aldosterone-receptor antagonism in hypertension

Potential of Modulating Aldosterone Signaling and Mineralocorticoid Receptor with microRNAs to Attenuate Diabetic Kidney Disease

Diabetic Kidney Disease (DKD) is a significant complication of diabetes and primary cause of end-stage renal disease globally. The exact mechanisms underlying DKD remain poorly understood, but multiple factors, including the renin-angiotensin-aldosterone system (RAAS), play a key role in its progression. Aldosterone, a mineralocorticoid steroid hormone, is one of the key components of RAAS and a potential mediator of renal damage and inflammation in DKD. miRNAs, small noncoding RNA molecules, have attracted interest due to their regulatory roles in numerous biological processes. These processes include aldosterone signaling and mineralocorticoid receptor (MR) expression. Numerous miRNAs have been recognized as crucial regulators of aldosterone signaling and MR expression. These miRNAs affect different aspects of the RAAS pathway and subsequent molecular processes, which impact sodium balance, ion transport, and fibrosis regulation. This review investigates the regulatory roles of particular miRNAs in modulating aldosterone signaling and MR activation, focusing on their impact on kidney injury, inflammation, and fibrosis. Understanding the complex interaction between miRNAs and the RAAS could lead to a new strategy to target aldosterone signaling and MR activation using miRNAs. This highlights the potential of miRNA-based interventions for DKD, with the aim of enhancing kidney outcomes in individuals with diabetes.

Non-coding RNAs and the mineralocorticoid receptor in the kidney

The final steps in the Renin-Angiotensin-Aldosterone signaling System (RAAS) involve binding of the corticosteroid hormone, aldosterone to its mineralocorticoid receptor (MR). The bound MR interacts with response elements to induce or repress the transcription of aldosterone-regulated genes. Along with the classic genomic targets of aldosterone that alter mRNA and protein expression, aldosterone also regulates the expression of non-coding RNAs (ncRNAs). Short ncRNAs termed microRNAs (miRs) have been shown to play a role in transducing aldosterone's actions via MR signaling. The role of miRs in homeostatic regulation of aldosterone signaling, and the potential for aldosterone-regulated miRs to act as feedback regulators of MR have been recently reported. In this review, the role of miRs in RAAS signaling and feedback regulation of MR in kidney epithelial cells will be discussed.

Aldosterone-induced microRNAs act as feedback regulators of mineralocorticoid receptor signaling in kidney epithelia

The final steps in the Renin-Angiotensin-Aldosterone signaling System (RAAS) involve binding of the corticosteroid hormone, aldosterone to its mineralocorticoid receptor (MR). The bound MR interacts with response elements to induce or repress the transcription of aldosterone-regulated genes. A well characterized aldosterone-induced gene is the serum and glucocorticoid-induced kinase (SGK1), which acts downstream to increase sodium transport in distal kidney nephron epithelial cells. The role of microRNAs (miRs) induced by extended aldosterone stimulation in regulating MR and SGK1 has not been reported. In these studies, miRs predicted to bind to the 3'-UTR of mouse MR were profiled by qRT-PCR after aldosterone stimulation. The miR-466a/b/c/e family was upregulated in mouse kidney cortical collecting duct epithelial cells. A luciferase reporter assay confirmed miR-466 binding to both MR and SGK1 3'-UTRs. Inhibition of miR-466 increased MR and SGK1 mRNA and protein levels. Inhibiting miR-466b and preventing its upregulation after aldosterone stimulation increased amiloride-sensitive sodium transport and sensitivity to aldosterone stimulation. In vivo upregulation of miR-466 was confirmed in distal nephrons of mice on low Na+ diets. Repression of MR and SGK1 by aldosterone-induced miRs may represent a negative feedback loop that contributes to a form of aldosterone escape in vivo.

Aldosterone receptor antagonists

Blocking the mineralocorticoid receptor (MR) is one of the most effective ways of reducing blood pressure in patients with resistant hypertension and improving cardiovascular prognosis in patients with heart failure with reduced ejection fraction and left ventricular dysfunction after myocardial infarction. Blockade of the biological effects of aldosterone has mostly been achieved with spironolactone and eplerenone, the two steroidal MR antagonists currently on the market. Development of new non-steroidal dihydropyridine-based third- and fourth-generation MR antagonists is ongoing. These antagonists are highly selective for the MR, but have no effect on the glucocorticoid, androgen, progesterone and estrogen receptors, in contrast with spironolactone.

Management of primary aldosteronism and mineralocorticoid receptor-associated hypertension

Resistant hypertension is associated with a poor prognosis due to organ damage caused by prolonged suboptimal blood pressure control. The concomitant use of mineralocorticoid receptor (MR) antagonists with other antihypertensives has been shown to improve blood pressure control in some patients with resistant hypertension, and such patients are considered to have MR-associated hypertension. MR-associated hypertension is classified into two subtypes: one with a high plasma aldosterone level, which includes primary aldosteronism (PA), and the other with a normal aldosterone level. In patients with unilateral PA, adrenalectomy may be the first-choice procedure, while in patients with bilateral PA, MR antagonists are selected. In addition, in patients with other types of MR-associated hypertension with high aldosterone levels, MR antagonists may be selected as a first-line therapy. In patients with normal aldosterone levels, ARBs or ACE inhibitors are used as a first-line therapy, and MR antagonists may be used as an add-on agent. Since MR antagonist therapy may have efficacy as a first-line or add-on agent in these patients, it is important to recognize this type of hypertension. Further studies are needed to elucidate the pathogenesis and management of MR-associated hypertension in more detail to improve the clinical outcomes of patients with MR-associated hypertension.

Identification of new antiviral agents against Kaposi's sarcoma-associated herpesvirus (KSHV) by high-throughput drug screening reveals the role of histamine-related signaling in promoting viral lytic reactivation

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several human cancers, such as Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). Current treatment options for KSHV infection and virus associated diseases are sometimes ineffective, therefore, more effectively antiviral agents are urgently needed. As a herpesvirus, lytic replication is critical for KSHV pathogenesis and oncogenesis. In this study, we have established a high-throughput screening assay by using an inducible KSHV+ cell-line, iSLK.219. After screening a compound library that consisted of 1280 Food and Drug Administration (FDA)-approved drugs, 15 hit compounds that effectively inhibited KSHV virion production were identified, most of which have never been reported with anti-KSHV activities. Interestingly, 3 of these drugs target histamine receptors or signaling. Our data further confirmed that antagonists targeting different histamine receptors (HxRs) displayed excellent inhibitory effects on KSHV lytic replication from induced iSLK.219 or BCBL-1 cells. In contrast, histamine and specific agonists of HxRs promoted viral lytic replication from induced iSLK.219 or KSHV-infected primary cells. Mechanistic studies indicated that downstream MAPK and PI3K/Akt signaling pathways were required for histamine/receptors mediated promotion of KSHV lytic replication. Direct knockdown of HxRs in iSLK.219 cells effectively blocked viral lytic gene expression during induction. Using samples from a cohort of HIV+ patients, we found that the KSHV+ group has much higher levels of histamine in their plasma and saliva than the KSHV- group. Taken together, our data have identified new anti-KSHV agents and provided novel insights into the molecular bases of host factors that contribute to lytic replication and reactivation of this oncogenic herpesvirus.

The renin-angiotensin-aldosterone system and its suppression

Chronic activation of the renin-angiotensin-aldosterone system (RAAS) promotes and perpetuates the syndromes of congestive heart failure, systemic hypertension, and chronic kidney disease. Excessive circulating and tissue angiotensin II (AngII) and aldosterone levels lead to a pro-fibrotic, -inflammatory, and -hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Understanding of the role of the RAAS in this abnormal pathologic remodeling has grown over the past few decades and numerous medical therapies aimed at suppressing the RAAS have been developed. Despite this, morbidity from these diseases remains high. Continued investigation into the complexities of the RAAS should help clinicians modulate (suppress or enhance) components of this system and improve quality of life and survival. This review focuses on updates in our understanding of the RAAS and the pathophysiology of AngII and aldosterone excess, reviewing what is known about its suppression in cardiovascular and renal diseases, especially in the cat and dog.

Managing resistant hypertension: focus on mineralocorticoid-receptor antagonists

Mineralocorticoid-receptor antagonists (MRAs) have proven to be effective in some types of hypertension, especially in resistant hypertension (RHTN). In this phenotype of hypertension, the renin-angiotensin-aldosterone pathway plays an important role, with MRAs being especially effective in reducing blood pressure. In this review, we show the relevance of aldosterone in RHTN, as well as some clinical characteristics of this condition and the main concepts involving its pathophysiology and cardiovascular damage. We analyzed the mechanisms of action and clinical effects of two current MRAs - spironolactone and eplerenone - both of which are useful in RHTN, with special attention to the former. RHTN represents a significant minority (10%-15%) of hypertension cases. However, primary-care physicians, cardiologists, nephrologists, neurologists, and geriatricians face this health problem on a daily basis. MRAs are likely one of the best pharmacological options in RHTN patients; however, they are still underused.

Eplerenone for hypertension

BACKGROUND

Eplerenone is an aldosterone receptor blocker that is chemically derived from spironolactone. In Canada, it is indicated for use as adjunctive therapy to reduce mortality for heart failure patients with New York Heart Association (NYHA) class II systolic chronic heart failure and left ventricular systolic dysfunction. It is also used as adjunctive therapy for patients with heart failure following myocardial infarction. Additionally, it is indicated for the treatment of mild and moderate essential hypertension for patients who cannot be treated adequately with other agents. It is important to determine the clinical impact of all antihypertensive medications, including aldosterone antagonists, to support their continued use in essential hypertension. No previous systematic reviews have evaluated the effect of eplerenone on cardiovascular morbidity, mortality, and magnitude of blood pressure lowering in patients with hypertension.

OBJECTIVES

To assess the effects of eplerenone monotherapy versus placebo for primary hypertension in adults. Outcomes of interest were all-cause mortality, cardiovascular events (fatal or non-fatal myocardial infarction), cerebrovascular events (fatal or non fatal strokes), adverse events or withdrawals due to adverse events, and systolic and diastolic blood pressure.

SEARCH METHODS

We searched the Cochrane Hypertension Specialised Register, CENTRAL, MEDLINE, Embase, and two trials registers up to 3 March 2016. We handsearched references from retrieved studies to identify any studies missed in the initial search. We also searched for unpublished data by contacting the corresponding authors of the included studies and pharmaceutical companies involved in conducting studies on eplerenone monotherapy in primary hypertension. The search had no language restrictions.

SELECTION CRITERIA

We selected randomized placebo-controlled trials studying adult patients with primary hypertension. We excluded studies in people with secondary or gestational hypertension and studies where participants were receiving multiple antihypertensives.

DATA COLLECTION AND ANALYSIS

Three review authors independently reviewed the search results for studies meeting our criteria. Three review authors independently extracted data and assessed trial quality using a standardized data extraction form. A fourth independent review author resolved discrepancies or disagreements. We performed data extraction and synthesis using a standardized format on Covidence. We conducted data analysis using Review Manager 5.

MAIN RESULTS

A total of 1437 adult patients participated in the five randomized parallel group studies, with treatment durations ranging from 8 to 16 weeks. The daily doses of eplerenone ranged from 25 mg to 400 mg daily. Meta-analysis of these studies showed a reduction in systolic blood pressure of 9.21 mmHg (95% CI -11.08 to -7.34; I² = 58%) and a reduction of diastolic pressure of 4.18 mmHg (95% CI -5.03 to -3.33; I² = 0%) (moderate quality evidence).There may be a dose response effect for eplerenone in the reduction in systolic blood pressure at doses of 400 mg/day. However, this finding is uncertain, as it is based on a single included study with low quality evidence. Overall there does not appear to be a clinically important dose response in lowering systolic or diastolic blood pressure at eplerenone doses of 50 mg to 400 mg daily. There did not appear to be any differences in the number of patients who withdrew due to adverse events or the number of patients with at least one adverse event in the eplerenone group compared to placebo. However, only three of the five included studies reported adverse events. Most of the included studies were of moderate quality, as we judged multiple domains as being at unclear risk in the 'Risk of bias' assessment.

AUTHORS' CONCLUSIONS

Eplerenone 50 to 200 mg/day lowers blood pressure in people with primary hypertension by 9.21 mmHg systolic and 4.18 mmHg diastolic compared to placebo, with no difference of effect between doses of 50 mg/day to 200 mg/day. A dose of 25 mg/day did not produce a statistically significant reduction in systolic or diastolic blood pressure and there is insufficient evidence for doses above 200 mg/day. There is currently no available evidence to determine the effect of eplerenone on clinically meaningful outcomes such as mortality or morbidity in hypertensive patients. The evidence available on side effects is insufficient and of low quality, which makes it impossible to draw conclusions about potential harm associated with eplerenone treatment in hypertensive patients.

Eplerenone improves carotid intima-media thickness (IMT) in patients with primary aldosteronism

Primary aldosteronism (PA) is associated with a higher rate of cardiovascular events than essential hypertension. Although adrenalectomy has been reported to reduce carotid intima-media thickness (IMT) in patients with PA, the effects of the selective aldosterone blocker, eplerenone, on vascular damage in these patients remains unclear. To evaluate the effects of eplerenone on vascular status in PA patients, we sequentially measured carotid IMT (using computer software to calculate an average IMT for accurate and reproducible evaluation) in 22 patients including 8 patients treated by unilateral adrenalectomy and 14 patients treated with eplerenone for 12 months. Patients who underwent adrenalectomy showed significant reductions in aldosterone concentration (from 345 ± 176 pg/mL to 67 ± 34 pg/mL; P<0.01) and IMT (from 0.67 ± 0.07 mm to 0.63 ± 0.09 mm; P<0.05) 6 months after surgery. Patients treated with eplerenone showed significant reductions in IMT from baseline (0.75 ± 0.10 mm) to 6 (0.71 ± 0.11 mm; P<0.05) and 12 (0.65 ± 0.09 mm; P<0.01) months, although plasma aldosterone level increased significantly, from 141 ± 105 pg/mL to 207 ± 98 pg/mL (P<0.05). Eplerenone treatment of patients with PA reduces blood pressure, increases serum potassium level, and improves vascular status. Carotid IMT may be a useful marker for evaluating the effectiveness of eplerenone in patients with PA.

Relationship of Genetic Polymorphisms of Aldosterone Synthase Gene Cytochrome P450 11B2 and Mineralocorticoid Receptors with Coronary Artery Disease in Taiwan

The aldosterone synthase gene, cytochrome P450 11B2 (CYP11B2), and mineralocorticoid receptor (MR) genes have been reported to be associated with coronary artery disease (CAD). In this study, we investigated the association of single nucleotide polymorphisms (SNPs) of CYP11B2 (CYP11B2 T-344C) and MR (MR C3514G and MR C4582A) with CAD in Taiwanese. Six hundred and nine unrelated male and female subjects who received elective coronary angiography were recruited from Chung Shan Medical University Hospital. The enrolled subjects were those who had a positive noninvasive test. CYP11B2 T-344C, MR C3514G and MR C4582A were determined by polymerase chain reaction-restriction fragment length polymorphism. We found that women with CYP11B2 C/C had a higher risk of developing CAD. However, there were no significant differences in the genotype distributions of MR C3514G and MR C4582A between the women with and without CAD. In multivariate analysis, CYP11B2 T-344C was most significantly associated with CAD in Taiwanese women. In conclusions, CYP11B2 C/C was more significantly associated with the development of CAD than diabetes mellitus or hypertension. This implies that CYP11B2 C/C plays a more important role than some conventional risk factors in the development of CAD in Taiwanese women.

Drug therapy of apparent treatment-resistant hypertension: focus on mineralocorticoid receptor antagonists

Apparent treatment-resistant hypertension (aTRH) is defined as blood pressure (BP) >140/90 mmHg despite three different antihypertensive drugs including a diuretic. aTRH is associated with an increased risk of cardiovascular events, including stroke, chronic renal failure, myocardial infarction, congestive heart failure, aortic aneurysm, atrial fibrillation, and sudden death. Preliminary studies of renal nerve ablation as a therapy to control aTRH were encouraging. However, these results were not confirmed by the Symplicity 3 trial. Therefore, attention has refocused on drug therapy. Secondary forms of hypertension and associated conditions such as obesity, sleep apnea, and primary aldosteronism are common in patients with aTRH. The pivotal role of aldosterone in the pathogenesis of aTRH in many cases is well recognized. For patients with aTRH, the Joint National Committee-8, the European Society of Hypertension, and a recent consensus conference recommend that a diuretic, ACE inhibitor, or angiotensin receptor blocker and calcium channel blocker combination be used to maximally tolerated doses before starting a 'fourth-line' drug such as a mineralocorticoid receptor (MR) antagonist. Although the best fourth-line drug for aTRH has not been extensively investigated, a number of studies summarized here show that an MR antagonist is effective in reducing BP when added to the standard multi-drug regimen.

Hypertension: renin-angiotensin-aldosterone system alterations

Blockers of the renin-angiotensin-aldosterone system (RAAS), that is, renin inhibitors, angiotensin (Ang)-converting enzyme (ACE) inhibitors, Ang II type 1 receptor antagonists, and mineralocorticoid receptor antagonists, are a cornerstone in the treatment of hypertension. How exactly they exert their effect, in particular in patients with low circulating RAAS activity, also taking into consideration the so-called Ang II/aldosterone escape that often occurs after initial blockade, is still incompletely understood. Multiple studies have tried to find parameters that predict the response to RAAS blockade, allowing a personalized treatment approach. Consequently, the question should now be answered on what basis (eg, sex, ethnicity, age, salt intake, baseline renin, ACE or aldosterone, and genetic variance) a RAAS blocker can be chosen to treat an individual patient. Are all blockers equal? Does optimal blockade imply maximum RAAS blockade, for example, by combining ≥2 RAAS blockers or by simply increasing the dose of 1 blocker? Exciting recent investigations reveal a range of unanticipated extrarenal effects of aldosterone, as well as a detailed insight in the genetic causes of primary aldosteronism, and mineralocorticoid receptor blockers have now become an important treatment option for resistant hypertension. Finally, apart from the deleterious ACE-Ang II-Ang II type 1 receptor arm, animal studies support the existence of protective aminopeptidase A-Ang III-Ang II type 2 receptor and ACE2-Ang-(1 to 7)-Mas receptor arms, paving the way for multiple new treatment options. This review provides an update about all these aspects, critically discussing the many controversies and allowing the reader to obtain a full understanding of what we currently know about RAAS alterations in hypertension.

Personalizing the diuretic treatment of hypertension: the need for more clinical and research attention

Neither randomized controlled trials nor efforts to identify genetic markers have been helpful with regard to the goal of individualizing diuretic therapy in the treatment of hypertension, a goal that receives little clinical or research attention. This review will examine, and bring attention to, the considerable yet overlooked information relevant to individualizing diuretic therapy. It will bring attention to clinical, biochemical, and pharmacological clues that can be helpful in identifying who is likely to respond to a diuretic, who needs a stronger diuretic regimen, which diuretic to prescribe, and how to minimize adverse effects. New directions for clinical research aimed at individualizing use in hypertension will be explored. Research and clinical attention to the goal of individualizing diuretic treatment in hypertension need to be renewed, to help us achieve greater hypertension control with fewer adverse effects and lower costs.

Effect of spironolactone in resistant arterial hypertension: a randomized, double-blind, placebo-controlled trial (ASPIRANT-EXT)

This study was designed to assess the effect of the addition of low-dose spironolactone on blood pressure (BP) in patients with resistant arterial hypertension. Patients with office systolic blood pressure (SBP) >140 mm Hg or diastolic blood pressure (DBP) >90 mm Hg despite treatment with at least 3 antihypertensive drugs, including a diuretic, were enrolled in this double-blind, placebo-controlled, multicentre trial. One hundred sixty-one patients in outpatient internal medicine departments of 6 hospitals in the Czech Republic were randomly assigned to receive 25 mg of spironolactone (N = 81) or a placebo (N = 80) once daily as an add-on to their antihypertensive medication, using simple randomization. This study was registered with ClinicalTrials.gov, number NCT00524615. A nalyses were done with 150 patients who finished the follow-up (74 in the spironolactone and 76 in the placebo group). At 8 weeks, BP values were decreased more by spironolactone, with differences in mean fall of SBP of -9.8, -13.0, -10.5, and -9.9 mm Hg (P < 0.001 for all) in daytime, nighttime, and 24-hour ambulatory BP monitoring and in the office. The respective DBP differences were -3.2, -6.4, -3.5, and -3.0 mm Hg (P = 0.013, P < 0.001, P = 0.005, and P = 0.003). Adverse events in both groups were comparable. The office SBP goal <14 mm Hg at 8 weeks was reached in 73% of patients using spironolactone and 41% using placebo (P = 0.001). Spironolactone in patients with resistant arterial hypertension leads to a significant decrease of both SBP and DBP and markedly improves BP control.

Efficacy and safety of mineralocorticoid receptors in mild to moderate arterial hypertension

The mineralocorticoid receptor antagonists have been shown to have favourable safety and cost-effectiveness profiles across a broad range of clinical indications, including heart failure, primary aldosteronism and resistant hypertension. The clinical biology of the first aldosterone blocker, i.e. spironolactone, and its effects in several organ systems has been well elucidated from multiple studies. The range of adverse effects experienced with spironolactone has led to its modification and the consequent synthesis of eplerenone. Scientific evidence accumulated so far supports the role of eplerenone as first-choice drug in heart failure, with lower prevalence rates of sex-related adverse effects associated with eplerenone as compared to spironolactone. In Europe, eplerenone is currently marketed only in some countries and only with the indication of heart failure, whereas its clinical efficacy and safety in mild to moderate hypertension is said to be uncertain. A review of available scientific evidence, however, discloses that 11 randomized clinical trials assessing eplerenone in >3500 hypertensives have been reported so far. The results of these studies clearly show that eplerenone is an effective antihypertensive agent when used alone or in combination with other medications. In doses ranging from 25 to 100mg daily, eplerenone monotherapy results in a dose-dependent reduction in clinic blood pressure. As compared to placebo, eplerenone reduces significantly blood pressure from baseline. In general, 100mg daily eplerenone has a blood pressure lowering that is 50 to 75% that of spironolactone. Eplerenone results in a greater reduction in blood pressure as compared with losartan, and comparison between eplerenone and amlodipine shows that both treatments decrease systolic blood pressure to a similar extent but eplerenone is better tolerated. In conclusion, there is now evidence that eplerenone can play an important role in the treatment of mild to moderate arterial hypertension and therefore scientific experts and regulatory authorities should support its wider use in clinical practice worldwide.

Blood pressure and neurohormonal responses to renal nerve ablation in treatment-resistant hypertension

OBJECTIVE

Catheter-based renal nerve ablation is a novel therapy for treatment-resistant hypertension. Although the precise mechanism is unknown, a reduction in global sympathetic tone and renal sympathetic tone, potentially resulting in a decrease in renin, may account for the antihypertensive effect.

DESIGN AND METHODS

In 17 patients (mean age 51.2 ± 9.4 years) with treatment-resistant hypertension (antihypertensive drugs 4.7 ± 1.3), office and ambulatory blood pressure (BP) measurements and circulating concentrations of catecholamines, renin, aldosterone and endothelin-1 were measured at baseline and 6 and 12 months after ablation. Office BP was measured for 1 h at 5-min intervals using an automatic device.

RESULTS

Office BP (164.7 ± 27.7/102.3 ± 19.3  mmHg) decreased by 5.7 ± 18.8  mmHg (P = 0.11) systolic and by 2.6 ± 10.7 (P = 0.33) mmHg diastolic after 6 months, whereas after 12 months decreases were 12.7 ± 16.0  mmHg (P = 0.007) and 7.3 ± 11.9  mmHg (P = 0.02). Heart rate, 24-h (151.8 ± 12.6/94.2 ± 10.3  mmHg) and day and night ambulatory BP did not change, after either 6 or 12 months. Of the neurohormones, only plasma noradrenaline (397  pg/ml, interquartile range 268-461  pg/ml) decreased by 128 ± 167  pg/ml (P = 0.008) after 6 months, whereas other neurohormones remained unchanged. Forty-seven percent of patients had at least 10  mmHg decrease in 24-h ambulatory SBP. In these responders, office and ambulatory BP tended to be higher than in nonresponders, but neurohormones or changes after ablation between responders and nonresponders did not differ.

CONCLUSION

Renal nerve ablation in treatment-resistant hypertensive patients had a moderate effect on office BP and is associated with a decrease in plasma noradrenaline but not in renin. The absent decrease in renin may imply that the intensity of efferent renal denervation achieved with the number of ablations applied was insufficient.

Aldosterone synthase inhibition in hypertension

Hypertension is an established risk factor for stroke, premature coronary artery disease and heart failure. Control of elevated blood pressure has been shown to result in significant reduction of cardiovascular risk. Aldosterone, the final product of the renin-angiotensin-aldosterone system (RAAS), not only causes salt and water reabsorbtion in the kidneys through its effect on the mineralocorticoid hormone receptor (MR), but also an MR-independent effect, not regulated by conventional MR blockade. Although many pharmacological agents target different levels of the RAAS cascade, these generally result in elevated renin concentration and plasma renin activity. This upstream feedback response subsequently results in elevated levels of angiotensin II, a potent vasoconstrictor and stimulus to aldosterone release. This aldosterone breakthrough counteracts the long-term blood pressure-lowering effect of these agents. Therefore the development of a new class of pharmacologic agents that directly inhibit the production of aldosterone may prove clinically useful in reducing aldosterone and thereby controlling elevated blood pressure.

A global approach to hypertension

Hypertension is an extremely common condition and quantitatively the most important risk factor for cardiovascular disease and mortality. Cardiovascular risk factors other than hypertension occur more frequently in hypertensive subjects and contribute to the elevated cardiovascular risk. Management of hypertensive subjects includes lifestyle modification and, usually, treatment with antihypertensive agents. Due to the limited blood pressure lowering effect of a single antihypertensive agent, more than 2/3 of hypertensive patients require at least two or more antihypertensive agents to achieve target blood pressure. For combination therapy combining an agent that interferes with the renin-angiotensin system with an agent that does not is recommended. Treatment adherence and persistence can be improved by using fixed-dose combinations instead of single agents.

Sequential comparison of aldosterone synthase inhibition and mineralocorticoid blockade in patients with primary aldosteronism

OBJECTIVE

We compared the effects of aldosterone synthase inhibition with LCI699 with those of mineralocorticoid receptor blockade in patients with primary aldosteronism.

METHODS

After a 2-week placebo run-in, 14 patients with primary aldosteronism received oral LCI699 (0.5 mg b.i.d.) from day 1 to 14, LCI699 (1 mg b.i.d.) from day 15 to 29, and placebo from day 29 to 36. From day 36 to day 66, patients were treated with eplerenone (50 mg b.i.d., up-titrated to 100 mg b.i.d. in 12/14 patients), in addition to their previous antihypertensive treatment, which was maintained unchanged.

RESULTS

Eplerenone significantly decreased more 24-h ambulatory SBP on day 66 than LCI699 on day 29 and the difference between the two treatment was -5.34 [95% confidence interval (CI) -10.30; -0.38)] mmHg (P = 0.027). Plasma potassium concentration achieved on eplerenone (4.30 ± 0.45 mmol/l) was significantly greater than on LCI699 (3.89 ± 0.35 mmol/l; P = 0.009). The increase in plasma renin concentration was significantly greater after eplerenone [+131% (range 61; 231)] than on LCI699 on day 29 [+39% (range 5; 86); P = 0.023]. LCI699 markedly decreased plasma aldosterone concentration by 75% (range -84;-63), whereas eplerenone markedly increased this concentration, from day 36, by 89% (range 40;154; P < 0.0001 vs. day 29).

CONCLUSION

In patients with primary aldosteronism, the effects on blood pressure and plasma potassium and renin concentrations of 4 weeks of eplerenone treatment (50-100 mg b.i.d.) were more marked than those of 4 weeks of LCI699 treatment (0.5-1 mg b.i.d.). These two drugs had opposite effects on plasma aldosterone concentration.

Spironolactone, eplerenone and the new aldosterone blockers in endocrine and primary hypertension

Mineralocorticoid receptor antagonists (MRAs) are commonly used to reduce blood pressure, left-ventricular hypertrophy, and urinary albumin excretion in patients with essential hypertension or primary aldosteronism. Effects of MRAs on hypertensive organ damage seem to occur beyond what is expected from the mere reduction of blood pressure. This suggests that activation of the mineralocorticoid receptor plays a central role in the development of cardiac and renal abnormalities in hypertensive patients. However, broad use of classic MRAs such as spironolactone has been limited by significant incidence of gynecomastia and other sex-related adverse effects. To overcome these problems, new aldosterone blockers have been developed with different strategies that include use of nonsteroidal MRAs and inhibition of aldosterone synthesis. Both strategies have been designed to avoid the steroid receptor cross-reactivity of classic MRAs that accounts for most adverse effects. Moreover, inhibition of aldosterone synthesis could have an additional benefit due to blockade of the mineralocorticoid receptor-independent pathways that might account for some of the untoward effects of aldosterone. The new aldosterone blockers are currently having extensive preclinical evaluation, and one of these compounds has passed phase 2 trials showing promising results in patients with primary hypertension and primary aldosteronism. This narrative review summarizes the knowledge on the use of classic MRAs in hypertension and covers the evidence currently available on new aldosterone blockers.

Determinants of blood pressure reduction by eplerenone in uncontrolled hypertension

BACKGROUND

Add-on therapy with aldosterone receptor antagonists has been reported to lower blood pressure (BP) in patients with uncontrolled hypertension. We assessed potential predictors of this response.

METHODS

In essential hypertensive patients with uncontrolled BP, despite the use of at least two antihypertensives, plasma renin and aldosterone concentrations and the transtubular potassium gradient (TTKG) were measured. Patients were treated with eplerenone 50 mg daily on top of their own medication. The office and ambulatory BP response and biochemical changes were evaluated after 1 week and 3 months of treatment and 6 weeks after discontinuation. Potential predictors for the change in 24-h ambulatory BP were tested in a multivariate regression model.

RESULTS

One hundred and seventeen patients with a mean age of 50.5 ± 6.6 years were included. Office BP decreased from 149/91 to 142/87 mmHg (P < 0.001) and ambulatory BP from 141/87 to 132/83 mmHg after 3 months of treatment (P < 0.001). Six weeks after discontinuation of eplerenone, office and ambulatory BP measurements returned to baseline values. Treatment resulted in a small rise in serum potassium and creatinine, and a small decrease in the TTKG. In a multivariate model, neither renin, aldosterone, or their ratio, nor the TTKG predicted the BP response. Only baseline ambulatory SBP predicted the BP response, whereas the presence of left ventricular hypertrophy was associated with a smaller BP reduction.

CONCLUSION

Add-on therapy with eplerenone effectively lowers BP in patients with difficult-to-treat primary hypertension. This effect is unrelated to circulating renin-angiotensin-aldosterone system activity and renal mineralocorticoid receptor activity as assessed by the TTKG.

Is there benefit in dual renin-angiotensin-aldosterone system blockade? No, yes and maybe: a guide for the perplexed

Since the initial discovery of Angiotensin converting enzyme inhibitors (ACEI) in the 1960s and the launch of Captopril as the first available for clinical use in the 1970s, there now exist three other classes of drugs that block the renin angiotensin aldosterone system (RAAS): the angiotensin II receptor blockers (ARB), aldosterone antagonists (AA) and direct renin inhibitors (DRI). With the proven efficacy of RAAS blockers as monotherapy in many arenas there has been considerable interest in the use of dual therapy combinations of these medications that target different points in the pathway. By potentially offering a more complete RAAS blockade with a commensurate enhanced clinical effect, the strong biological rationale for dual therapy has led to it being embraced by clinicians as a treatment option, for hypertension and nephroprotection in particular. However, the initial enthusiasm for this treatment has been tempered by the recent results from several large trials such as ONTARGET and ALTITUDE, which do not support a specific dual therapy approach. In contrast, there is supportive evidence for dual blockade of specific combinations in selected patient groups and data are lacking for others. In the wake of this complex contemporary evidence, the conundrum now faced by clinicians committed to individualised care is, for which patients dual therapy could still be of benefit. This review examines for the practising clinician the current 'state of play' for dual blockade of various combinations and a perspective on its use in cardio-renal disease and diabetic complications.

Sequential nephron blockade versus sequential renin-angiotensin system blockade in resistant hypertension: a prospective, randomized, open blinded endpoint study

OBJECTIVE

To compare two drug regimens to treat resistant hypertension.

METHODS

In a prospective, randomized, open blinded endpoint study, 167 patients with mean baseline daytime ambulatory blood pressure 135 mmHg or more and/or 85 mmHg or more, despite 4 weeks' treatment with irbesartan 300 mg/day, hydrochlorothiazide 12.5 mg/day and amlodipine 5 mg/day, were randomized to sequential nephron blockade (group 1, n = 85) or sequential renin-angiotensin system blockade (group 2, n = 82). First, spironolactone 25 mg/day in group 1 or ramipril 5 mg/day in group 2 were added for 4 weeks. Treatment was increased at weeks 4, 8 or 10 if home blood pressure was 135 mmHg or more and/or 85 mmHg or more by sequentially administering furosemide 20 mg/day, furosemide 40 mg/day and amiloride 5 mg/day in group 1, or ramipril 10 mg/day, bisoprolol 5 mg/day and bisoprolol 10 mg/day in group 2. The primary endpoint was change in systolic daytime ambulatory blood pressure at week 12.

RESULTS

At week 12, the mean between-group difference in daytime ambulatory blood pressure was 10/4 mmHg (95% confidence interval: 7-14/2-7; P < 0.001/P = 0.0014) in favour of the group 1. The blood pressure goal (daytime ambulatory blood pressure <135/85 mmHg) was achieved in 58% in the group 1 and 20% in the group 2 (P < 0.0001). Discontinuation for drug-related adverse events was low (group 1, n = 7; group 2, n = 6).

CONCLUSION

In patients with resistant hypertension, sequential nephron blockade induces a large and well tolerated reduction in blood pressure via a progressive increase in sodium depletion, and is more effective than sequential renin-angiotensin system blockade.

Aldosterone synthase inhibition in humans

Aldosterone synthase (CYP11B2) inhibition has emerged as a new option for the treatment of hypertension, heart failure and renal disorders, in addition to mineralocorticoid receptor (MR) blockade. The aim is to decrease aldosterone concentrations in both plasma and tissues, thereby decreasing MR-dependent and MR-independent effects in the cardiac, vascular and renal target organs. LCI699 was the first orally active aldosterone-synthase inhibitor to be developed for human use. Its structure is similar to that of FAD286, the dextroenantiomer of the aromatase inhibitor, fadrozole. It dose-dependently decreases plasma and urine aldosterone concentrations by up to 70 or 80% and increases plasma renin activity in healthy male subjects on a low-sodium diet. LCI699 does not decrease basal plasma cortisol concentrations at doses of 0.5-3 mg q.d., but it blocks the cortisol response to adrenocorticotropic hormone (ACTH) at doses ≥ 3 mg q.d. In a proof-of-concept study in patients with primary aldosteronism (PA), LCI699 (0.5-1 mg b.i.d.) induced a dose-dependent and reversible 70-80% decrease in plasma and urinary aldosterone concentration accompanied by a massive dose-dependent accumulation of deoxycorticosterone (>+700%), the aldosterone precursor, in the plasma, thereby confirming the inhibition of the CYP11B2 gene product. This effect was associated with a rapid correction of hypokalaemia, a modest decrease in blood pressure (BP) and a mild increase in plasma renin concentration in patients with PA. LCI699 administration induced biological signs of partial inhibition of the glucocorticoid axis, such as dose-dependent increases in both plasma ACTH and 11-deoxycortisol (the precursor of cortisol) concentrations, consistent with the inhibition of the CYP11B1 gene product. An 8-week placebo-controlled dose-response study on patients with Stage 1 and 2 essential hypertension reported an optimal decrease in BP with a dose of 1 mg LCI699 q.d., which had an antihypertensive effect similar to that of 50 mg b.i.d. eplerenone. A blunted cortisol response to ACTH was observed in 20% of patients, but the clinical and biological safety and tolerability of LCI699 were similar to those of placebo and eplerenone. The discovery of this first orally active aldosterone synthase inhibitor, LCI699, has provided new opportunities to assess the feasibility and the haemodynamic, biological and safety consequences as well as the limitations of this new approach to block the aldosterone pathway in hypertensive patients. However, as the effects of LCI699 on the glucocorticoid axis limit the use of higher doses range because of the loss of selectivity for CYP11B2, this aldosterone synthase inhibitor cannot replace the MR blockade in patients with hypertension, other cardiovascular or renal disorders. The development of second-generation aldosterone synthase inhibitors with a higher selectivity index for CYP11B2 than LCI699 should make it possible to test this approach at much higher doses in these patients, after the necessary toxicology and Phase I studies.

Effect of amiloride and spironolactone on renal tubular function and central blood pressure in patients with arterial hypertension during baseline conditions and after furosemide: a double-blinded, randomized, placebo-controlled crossover trial

This study demonstrates that the increased potassium content in the body seems to change both the blood pressure and renal tubular function. We wanted to test the hypotheses that amiloride and spironolactone induced potassium retention reduces ambulatory blood pressure (ABP) and central blood pressure (CBP) during baseline conditions and after furosemide and that the tubular transport via the epithelial sodium channels (ENaCs) and aquaporin-2 (AQP2) water channels was increased by furosemide in arterial hypertension. Each of three 28-day treatment periods (placebo, amiloride, and spironolactone) was completed by a 4-day period with standardized diet regarding calories and sodium and water intake. At the end of each period, we measured pulse wave velocity (PWV), central systolic blood pressure (CSBP), central diastolic blood pressure (CDBP), glomerular filtration rate (GFR), free water clearance (CH2O), fractional excretion of sodium (FENa) and potassium (FEK), urinary excretion of AQP2 (u-AQP2), urinary excretion of γ-fraction of the ENaC (u-ENaCγ), and plasma concentrations of renin (PRC), angiotensin II (p-Ang II), and aldosterone (p-Aldo) at baseline conditions and after furosemide bolus. Ambulatory blood pressure and CBP were significantly lowered by amiloride and spironolactone. During 24-hour urine collection and at baseline, GFR, CH2O, FENa, FEK, u-AQP2 and u-ENaCγ were the same. After furosemide, CH2O, FENa, FEK, u-AQP2, u-ENaCγ, PRC, p-Ang II, p-Aldo, PWV and CDBP increased after all treatments. However, during amiloride treatment, FEK increased to a larger extent than after spironolactone and during placebo after furosemide, and CSBP was not significantly reduced. The increases in water and sodium absorption via AQP2 and ENaC after furosemide most likely are compensatory phenomena to antagonize water and sodium depletion. Amiloride is less effective than spironolactone to reduce renal potassium excretion.

Inhibition of the renin-angiotensin-aldosterone system: is there room for dual blockade in the cardiorenal continuum?

Antagonism of renin-angiotensin-aldosterone system is exerted through angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, renin inhibitors and mineralocorticoid receptor antagonists. These drugs have been successfully tested in numerous trials and in different clinical settings. The original indications of renin-angiotensin-aldosterone system blockers have progressively expanded from the advanced stages to the earlier stages of cardiorenal continuum. To optimize the degree of blockade of renin-angiotensin-aldosterone system, dose uptitrations of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists or the use of a dual blockade, initially identified with the combination of angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists, have been proposed. The data from the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET) study do not support this specific dual blockade approach. However, the dual blockade of angiotensin-converting enzyme inhibitors/angiotensin receptor antagonists with direct renin inhibitors is currently under investigation while that based on an aldosterone blocker with any of the previous three drugs requires more evidence beyond heart failure. In this review, we revisited potential advantages of dual blockade of renin-angiotensin-aldosterone system in arterial hypertension and diabetes.

Safety of mineralocorticoid receptor antagonists in patients receiving hemodialysis

OBJECTIVE

To evaluate the literature supporting the safe use of mineralocorticoid antagonists (MRAs) in patients with end-stage renal disease who are receiving hemodialysis.

DATA SOURCES

A review of the literature was performed using MEDLINE (1950 through week 2 of February 2012) using the key words and MeSH terms mineralocorticoid antagonists, aldosterone antagonists, spironolactone, or eplerenone combined with dialysis, renal disease, or kidney disease.

STUDY SELECTION AND DATA EXTRACTION

Studies eligible for inclusion evaluated the impact of MRAs on serum potassium levels in patients with end-stage renal disease receiving hemodialysis. Data related to the patient populations and outcomes of interest were extracted from each publication.

DATA SYNTHESIS

Ten studies were included in this review (spironolactone, 9; eplerenone, 1) and reported on the impact of MRAs on potassium levels in this population. In aggregate, the studies, with spironolactone doses ranging from 25 mg 3 times/week after dialysis to 300 mg/day and eplerenone doses of 25 mg twice daily, have shown little increases in serum potassium, particularly with the lower doses. The overall incidence of severe hyperkalemia was low. The literature base is limited by significant methodologic weaknesses of the studies, including low patient numbers, short follow-up periods, and lack of a blinded control group.

CONCLUSIONS

The current literature suggests that MRAs may be used safely in patients with end-stage renal disease receiving hemodialysis, although additional large controlled trials are needed before definitive treatment recommendations can be made.

Mineralocorticoid receptor-associated hypertension and its organ damage: clinical relevance for resistant hypertension

The role of aldosterone in the pathogenesis of hypertension and cardiovascular diseases has been clearly shown in congestive heart failure and endocrine hypertension due to primary aldosteronism. In resistant hypertension, defined as a failure of concomitant use of three or more different classes of antihypertensive agents to control blood pressure (BP), add-on therapy with mineralocorticoid receptor (MR) antagonists is frequently effective, which we designate as "MR-associated hypertension". The MR-associated hypertension is classified into two subtypes, that with elevated plasma aldosterone levels and that with normal plasma aldosterone levels. The former subtype includes primary aldosteronism (PA), aldosterone-associated hypertension which exhibited elevated aldosterone-to-renin ratio and plasma aldosterone levels, but no PA, aldosterone breakthrough phenomenon elicited when angiotensin-converting enzyme inhibitor (ACE-I) or angiotensin II receptor blocker (ARB) is continued to be given, and obstructive sleep apnea. In contrast, the latter subtype includes obesity, diabetes mellitus, chronic kidney disease (CKD), and polycystic ovary syndrome (PCOS). The pathogenesis of MR-associated hypertension with normal plasma aldosterone levels is considered to be mediated by MR activation by pathways other than high aldosterone levels, such as increased MR levels, increased MR sensitivity, and MR overstimulation by other factors such as Rac1. For resistant hypertension with high plasma aldosterone levels, MR antagonist should be given as a first-line therapy, whereas for resistant hypertension with normal aldosterone levels, ARB or ACE-I should be given as a first-line therapy and MR antagonist would be given as an add-on agent.

What is the role of aldosterone excess in resistant hypertension and how should it be investigated and treated?

Resistant hypertension has evolved as an important global health care problem. Primary aldosteronism is one of several potentially reversible causes of resistant hypertension. Primary aldosteronism can be effectively treated, when recognized, with a mineralocorticoid receptor antagonist, such as spironolactone and eplerenone. Each of these compounds can reduce blood pressure as monotherapy or when given with a range of other antihypertensive drug classes. These compounds have distinctive pharmacokinetic and pharmacodynamic patterns that require some forethought in their use before they are prescribed. However, as the use of mineralocorticoid-blocking agents has gradually increased, the hazards inherent to use of such drugs has become more apparent. Whereas the endocrine side effects of spironolactone are in most cases little more than a cosmetic annoyance, the potassium-sparing effects of both spironolactone and eplerenone can prove fatal if sufficient degrees of hyperkalemia develop. However, for most patients the risk of developing hyperkalemia in and of itself should not discourage the prudent clinician from bringing these compounds into play. Hyperkalemia should always be considered as a likelihood in any patient receiving one or the other of these medications. As such, steps should be taken to lessen the likelihood of it occurring if therapy is being contemplated with agents in this class.

Management of hypertension in the young: role of antihypertensive medications

Traditionally, antihypertensive medications were used in few children or adolescents, usually just those with underlying renal or other organ system disease. However, with recent data suggesting that the incidence of primary hypertension may be increasing in the young, it is possible that more children and adolescents will be prescribed antihypertensive agents. This article will review currently available pediatric data on the use of calcium channel blockers, agents affecting the renin-angiotensin-aldosterone system and other classes of antihypertensive medications in children, highlighting appropriate indications and safety considerations. Guidelines for use of antihypertensive medications, including choice of initial agent and how to prescribe appropriately, will be presented.

Sympathetic mechanisms, organ damage, and antihypertensive treatment

Sympathetic activation characterizes essential hypertension, contributing to the development and progression of the high blood pressure state. Throughout the years, evidence has been accumulated to show that adrenergic overdrive also participates in the pathogenesis of the end-organ damage associated with hypertension, including cardiac hypertrophy, left ventricular diastolic dysfunction, and heart failure, as well as the vascular structural and functional alterations that frequently can be detected in large, medium-size, and small arteries. Adrenergic overdrive also participates in the renal insufficiency and failure that may accompany the clinical course of the hypertensive state. This paper reviews evidence collected over the past few years documenting the importance of neurogenic factors in the development and progression of end-organ damage. The therapeutic implications of this evidence are also highlighted.

Drug mechanisms to help in managing resistant hypertension in obesity

Obesity is a major risk factor for the development of hypertension. Because the prevalence of obesity is increasing worldwide, the prevalence of obesity hypertension is also increasing. Importantly, hypertension in obesity is commonly complicated by dyslipidemia and type 2 diabetes mellitus and hence imposes a high cardiovascular disease risk. Furthermore, obesity is strongly associated with resistant hypertension. Activation of the sympathetic nervous system and the renin-angiotensin system, leading to renal sodium and water retention, links obesity with hypertension. There is also evidence for the release of factors by visceral adipose tissue promoting excessive aldosterone production, and a more central role of aldosterone in obesity hypertension is emerging. Randomized studies evaluating the effect of different classes of antihypertensive agents in obesity hypertension are scarce, short-lasting, and small. Considering the emerging role of aldosterone in the pathogenesis of obesity hypertension, mineralocorticoid receptor antagonism may play a more central role in the pharmacologic treatment of obesity hypertension in the near future.

Apparent mineralocorticoid excess: time of manifestation and complications despite treatment

Here we describe the case of a patient followed from birth because of a positive family history for apparent mineralocorticoid excess (AME) in an older brother. The patient, a girl, had normal serum electrolyte and blood pressure measurements in the first months after birth. Not until the age of 11 months did she develop anorexia and failure to thrive in combination with hypertension, hypokalemia, and metabolic alkalosis, which are consistent with the diagnosis of AME. This diagnosis was confirmed by mutation analysis of the HSD11B2 gene (C1228T). Treatment with amiloride and furosemide electrolyte disturbances normalized her blood pressure. At the age of 19 years she unexpectedly suffered a stroke. Additional investigations revealed no accepted risk factor for stroke. We discuss the possible underlying mechanisms for the delayed manifestation of hypertension and electrolyte disturbances in AME, propose an additional explanation for the stroke in this patient, and advise treatment with a mineralocorticoid receptor antagonist to reduce stroke risk in patients with AME.

Addition of spironolactone in patients with resistant arterial hypertension (ASPIRANT): a randomized, double-blind, placebo-controlled trial

There is currently limited data on which drug should be used to improve blood pressure (BP) control in patients with resistant hypertension. This study was designed to assess the effect of the addition of 25 mg of spironolactone on BP in patients with resistant arterial hypertension. Patients with office systolic BP >140 mm Hg or diastolic BP >90 mm Hg despite treatment with at least 3 antihypertensive drugs, including a diuretic, were enrolled in this double-blind, placebo-controlled, multicenter trial. One hundred seventeen patients were randomly assigned to receive spironolactone (n=59) or a placebo (n=58) as an add-on to their antihypertensive medication, by the method of simple randomization. Analyses were done with 111 patients (55 in the spironolactone and 56 in the placebo groups). At 8 weeks, the primary end points, a difference in mean fall of BP on daytime ambulatory BP monitoring (ABPM), between the groups was -5.4 mm Hg (95%CI -10.0; -0.8) for systolic BP (P=0.024) and -1.0 mm Hg (95% CI -4.0; 2.0) for diastolic BP (P=0.358). The APBM nighttime systolic, 24-hour ABPM systolic, and office systolic BP values were significantly decreased by spironolactone (difference of -8.6, -6.6, and -6.5 mm Hg; P=0=0.011, 0.004, and 0.011 [corrected]), whereas the fall of the respective diastolic BP values was not significant (-3.0, -1.0, and -2.5 mm Hg; P=0.079, 0.405, and 0.079). The adverse events in both groups were comparable. In conclusion, spironolactone is an effective drug for lowering systolic BP in patients with resistant arterial hypertension.