Effects Of Aldosterone Research Articles

The effect of spironolactone versus eplerenone on blood pressure targets in resistant hypertension patients

Abstract Objective to evaluate different effects on blood pressure (BP) control in two treatment options spironolactone (SPIR) versus eplerenone (EPL) as an add-on therapy in resistant hypertensive (RAH) patients. Design and methods: We studied 208 patients with true RAH confirmed by the office and ambulatory BP monitoring (ABPM) despite the use of 3 antihypertensive medications including a calcium channel blocker, a blocker of the renin-angiotensin system, and a thiazide diuretic with maximally tolerated doses for at least 3 months. Patients were randomized into 2 groups throughout 12 weeks of once-daily treatment with SPIR (25–50 mg) or EPL (25-50 mg) in addition to their baseline triple-combination and then rotated with drugs. BP was measured in the office and by ABPM. Changes in laboratory tests were also studied. The predictive values of plasma aldosterone, active renin concentration (ARC), aldosterone-renin ratio (ARR), and serum potassium were analyzed to determine the antihypertensive response. Results There were no significant differences in the reduction of average office BP, average systolic 24-h, daytime, and nighttime BP by SPIR and EPL. SPIR reduced average diastolic 24-h BP by 7.3 mm Hg, diastolic daytime BP by 7.2 mm Hg, and diastolic nighttime BP by 7.5 mm Hg compared with a reduction of 5.6 mm Hg (P = 0.01), 5.6 mm Hg (P = 0.03) and 4.2 mm Hg (P = 0.0001) with EPL, respectively. Overall, 40.7 % RAH patients achieved targets of clinical BP and 24-h ABPM levels on SPIR and 33.3 % on EPL (Р = 0.002). After 12 weeks of treatment mean plasma potassium concentrations increased by 7.1 (P = 0.0001) on SPIR and by 5.0 % (Р = 0.0001) on EPL, but eGFR did not significantly change on the two drugs. Plasma aldosterone (β = 0.498, Р = 0.02) and ARC (β= -0.374, Р = 0.04) were predictors of the BP-lowering effect of SPIR and plasma aldosterone (β = 0.453, Р = 0.04) was a predictor of reduction BP for EPL in multivariate modeling. Breast pain or tenderness, changes in sex drive, and irregular menstrual cycles or spotting were more often by SPIR than by EPL (5.2 % vs 1.9 %, respectively, P = 0.04). Conclusions The greater antihypertensive effect of SPIR is related to aldosterone status, ARS level in resistant hypertension. EPL may be recommended for RAH patients who have high serum potassium levels that cannot tolerate spironolactone and for people with systolic resistant hypertension.

Transmembrane Serine Protease 2 and Proteolytic Activation of the Epithelial Sodium Channel in Mouse Kidney.

The renal epithelial sodium channel (ENaC) is essential for sodium balance and blood pressure control. ENaC undergoes complex proteolytic activation by not yet clearly identified tubular proteases. Here, we examined a potential role of transmembrane serine protease 2 (TMPRSS2). Murine ENaC and TMPRSS2 were (co-)expressed in Xenopus laevis oocytes. ENaC cleavage and function were studied in TMPRSS2-deficient murine cortical collecting duct (mCCDcl1) cells and TMPRSS2-knockout (Tmprss2-/-) mice. Short-circuit currents (ISC) were measured to assess ENaC-mediated transepithelial sodium transport of mCCDcl1 cells. The mCCDcl1 cell transcriptome was studied using RNA sequencing. The effect of low-sodium diet with or without high potassium were compared in Tmprss2-/- and wildtype mice using metabolic cages. ENaC-mediated whole-cell currents were recorded from microdissected tubules of Tmprss2-/- and wildtype mice. In oocytes, co-expression of murine TMPRSS2 and ENaC resulted in fully cleaved γ-ENaC and ∼2-fold stimulation of ENaC currents. High baseline expression of TMPRSS2 was detected in mCCDcl1 cells without a stimulatory effect of aldosterone on its function or transcription. TMPRSS2 knockout in mCCDcl1 cells compromised γ-ENaC cleavage and reduced baseline and aldosterone-stimulated ISC which could be rescued by chymotrypsin. A compensatory transcriptional upregulation of other proteases was not observed. Tmprss2-/- mice kept on standard diet exhibited no apparent phenotype, but renal γ-ENaC cleavage was altered. In response to a low-salt diet, particularly with high potassium intake, Tmprss2-/- mice increased plasma aldosterone significantly more than wildtype mice to achieve a similar reduction of renal sodium excretion. Importantly, the stimulatory effect of trypsin on renal tubular ENaC currents was much more pronounced in Tmprss2-/- mice than that in wildtype mice. This indicated the presence of incompletely cleaved and less active channels at the cell surface of TMPRSS2-deficient tubular epithelial cells. TMPRSS2 contributes to proteolytic ENaC activation in mouse kidney in vivo.

The impact of mineralocorticoid and glucocorticoid receptor interaction on corticosteroid transcriptional outcomes

The mineralocorticoid and glucocorticoid receptors (MR and GR, respectively) are members of the steroid receptor subfamily of nuclear receptors. Their main function is to act as ligand-activated transcription factors, transducing the effects of corticosteroid hormones (aldosterone and glucocorticoids) by modulating gene expression. Corticosteroid signaling is essential for homeostasis and adaptation to different forms of stress. GR responds to glucocorticoids by regulating genes involved in development, metabolism, immunomodulation and brain function. MR is best known for mediating the effects of aldosterone, a key hormone controlling electrolyte and water homeostasis. In addition to aldosterone, MR binds glucocorticoids (cortisol and corticosterone) with equally high affinity. This ligand promiscuity has important repercussions to understand MR function, as well as glucocorticoid signaling. MR and GR share significant sequence and structural similarities, regulate overlapping sets of genes and are able to interact forming heteromeric complexes. However, the precise role of these heteromers in regulating corticosteroid-regulated transcriptional outcomes remains an open question. In this review, we examine the evidence supporting MR-GR heteromerization, the molecular determinants of complex formation and their possible role in differential regulation of transcription in different cellular contexts and ligand availability.

Aldosterone Robustly Promotes Atrial Fibrillation in the Presence of Chronic Volume Overload in Rats.

We investigated the modulatory effects of aldosterone on atrial remodeling induced by an abdominal aorto-venocaval shunt (AVS) in rats, as patients with primary hyperaldosteronism are suggested to have a higher risk of developing atrial fibrillation (AF). The rats were divided into four groups based on the basis of whether they underwent AVS surgery, received aldosterone using an intraperitoneally implanted osmotic minipump, or both. Aldosterone was started at 0.5 µg/h during the AVS surgery, and morphological and electrophysiological assessments were performed four weeks after AVS creation. The atrial structural changes induced by AVS, including atrial cell hypertrophy and fibrosis, were not modulated by aldosterone, whereas P-wave duration was longer in aldosterone-treated AVS rats than in non-treated rats. Although the average AF duration induced by burst pacing was 10-25 s in the untreated, aldosterone-treated, and AVS rats, the AF duration was approximately 100 s in the aldosterone-treated AVS rats. Meanwhile, there was no significant difference in the atrial effective refractory period among the four experimental groups. Notably, premature atrial contractions (PAC) were frequently observed in aldosterone-treated sham rats, while paroxysmal AF, in addition to PAC, was detected in aldosterone-treated AVS rats, which was not induced in non-treated AVS rats. These findings suggest that aldosterone robustly promotes AF, particularly in the presence of chronic volume overload.

New ways of mitigating aldosterone in cardiorenal disease.

Steroidal mineralocorticoid receptor antagonists (MRAs) bind to the mineralocorticoid receptor and antagonize the effects of aldosterone, which contributes to the development and progression of cardio- and renovascular diseases. Guidelines recommend steroidal MRAs in patients with heart failure with reduced or mildly reduced ejection fraction, as they reduce morbidity and mortality. In heart failure with preserved ejection fraction, MRAs have not convincingly shown to improve prognosis. Steroidal MRAs delay the progression of chronic kidney disease, reduce proteinuria and lower blood pressure in resistant hypertension but can induce hyperkalaemia. Due to their limited selectivity to the mineralocorticoid receptor, steroidal MRAs can cause significant adverse effects, i.e. libido loss, erectile dysfunction, gynaecomastia, and amenorrhoea, leading to low rates of persistance. Against this background, new avenues for developing non-steroidal, selective (ns)MRAs and aldosterone-synthase inhibitors have been taken. Finerenone has been shown to delay the progression of diabetic nephropathy and lower the incidence of heart failure hospitalizations in patients with chronic kidney disease and diabetes compared with placebo. Finerenone has therefore been recommended by the 2023 European Society of Cardiology Guidelines for the management of diabetes in patients with type 2 diabetes and chronic kidney disease. Further randomized controlled trials assessing the safety and effectiveness of finerenone in patients with heart failure are currently ongoing. Esaxerenone provides antihypertensive effects and has been approved for the treatment of hypertension in Japan. Baxdrostat and lorundostat, novel selective aldosterone-synthase inhibitors, are currently under investigation. In phase II trials, baxdrostat and lorundostat were safe and effective in lowering blood pressure in resistant hypertension. In this review, we summarize and critically discuss the evidence for new drugs mitigating aldosterone in heart failure, hypertension, and chronic kidney disease.

Aldosterone Effect on Cardiac Structure and Function.

Cardiac remodelling could be a key mechanism in aldosteronemediated cardiovascular morbidity and mortality. Experimental and clinical evidence has demonstrated that aldosterone causes cardiac structural remodelling and dysfunction by its profibrotic and pro-hypertrophic effects, which result mainly from the direct effects on myocardial collagen deposition, inflammation, and oxidative stress. Clinical studies have investigated the aldosterone effects on the heart in different clinical conditions, including general population, essential hypertension, primary aldosteronism, heart failure, and atrial fibrillation. Robust findings indicate that aldosterone or the activation of the cardiac mineralocorticoid receptor can cause damage to myocardial tissue by mechanisms independent of the blood pressure, leading to tissue hypertrophy, fibrosis, and dysfunction. Aldosterone-mediated cardiovascular morbidity and mortality mainly result from cardiac structural and functional alterations. In different clinical settings, aldosterone can induce cardiac structural remodelling and dysfunction via several pathological mechanisms, including cardiac fibrosis, inflammation, and oxidative stress. Aldosterone antagonists could effectively decrease or reverse the detrimental aldosterone-mediated changes in the heart.

Dietary potassium effects on renal calcium transport at single nucleus resolution

Calcium homeostasis is maintained by the coordination of the intestines, bones, and kidneys. Dietary calcium is absorbed in the intestines, enters the bloodstream, and eventually finds its place in the bone reservoir or undergoes filtration by the glomerulus before being reabsorbed throughout the nephron. The late distal convoluted tubule (DCT2) and connecting tubule (CNT) determine the final rate of urinary calcium excretion, since no calcium reabsorption takes place beyond the connecting tubule (CNT). When excess calcium is excreted in the urine, also known as hypercalciuria, it contributes to the development of osteoporosis and the formation of kidney stones. High dietary potassium intake is strongly associated with a lower risk of kidney stone formation. Yet, the precise mechanism by which potassium intake modulates calcium excretion is not clear. To examine the transcriptional changes linking high dietary potassium intake and calcium transport, we applied single-nucleus RNA-sequencing (snRNA-Seq) in enriched distal nephron cells. To achieve the enrichment, we crossed a Calbindin 1 (Calb1)-driven Cre mouse line with the INTACT (for Isolation of Nuclei TAgged in Specific Cell Types) reporter line, which allows the GFP reporter to be expressed at the nuclear envelope of all calbindin 1-expressing cells. As the Calb1-Cre is constitutively expressed, all cells that have calbindin 1 expression at any time point during development will express the reporter. We examined the GFP expression by immunofluorescence, and found that it is expressed along the entire distal nephron from the distal convoluted tubule (DCT), CNT, to the collecting duct (CD). Male Calb1-Cre-INTACT mice were provided either a normal (NK, 1.05%) or a high (HK, 2%) potassium diet for 4 days and kidneys were snap-frozen for targeted snRNA-Seq using 10X Chromium (n=3 mice per group, targeting 10,000 nuclei per mouse). Our snRNA-seq dataset showed 6 major clusters, including DCT (DCT1 and DCT2), CNT (3 subclusters), CD principal cells (3 subclusters), ɑ-intercalated cells (2 subclusters), β-intercalated cells (2 subclusters), and proliferating cells. We curated a calcium score from the expression of known calciotropic genes ( Slc8a1, Vdr, Trpv5, Calb1, S100g, Ryr2, Trpv6) and used it as an index of calcium handling capacity. The calcium score is the highest in DCT2 and CNT along the distal nephron. In all CNT subclusters of the HK-treated animals, the calcium score is higher compared to the NK-treated animals, suggesting more calcium transport in CNT. Given that HK stimulates aldosterone and causes CNT hypertrophy, we compared the results with mice subjected to low dietary potassium (LK) treatment and metolazone (thiazide) treatment. The aim was to delineate the effects of dietary potassium and aldosterone A comprehensive summary of plasma potassium levels, urinary calcium excretion, aldosterone levels, calcium scores, and CNT morphology has been presented in the table below. Notably, the comparative analysis reveals a significant correlation between aldosterone levels and CNT size, both of which exhibit an inverse relationship with urinary calcium excretion: [Formula: see text] Our results suggest that DCT2 and CNT are the major sites for calcium transport. Yet, CNT exhibit more heightened adaptability in response to physiological or pharmacological perturbations at both transcriptional and morphological levels. Calcium homeostasis coincides with the regulation of aldosterone levels and CNT remodeling. DK51496 and DK133220 to DHE; K01DK121737 and AHA 20CDA35320169 to JWN. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

SODIUM RESTRICTION CONCOMITANT WITH SUFFICIENT ALDOSTERONE SUPPRESSION MAY BE ASSOCIATED WITH RENOPROTECTIVE EFFECTS IN THE PATIENTS WITH PRIMARY ALDOSTERONISM

Objective: Primary aldosteronism (PA) is an independent risk factor for various cardiovascular diseases and chronic kidney disease, which makes it important to treat this condition at an early phase. Currently, the use of mineralocorticoid receptor antagonists (MRAs) is recommended for the treatment of bilateral type, mainly idiopathic hyperaldosteronism. However, recent reports suggest that the benefit of the treatment with MRAs is only obtained in the patients with enough aldosterone suppression, which is indicated as post-treatment plasma renin activity (PRA) >=1.0 ng/mL/h. Since PRA is affected by the amount of sodium intake, PRA elevation after MRAs treatment might partially reflect an adherence to strict sodium restriction, thereby leads to organ protective effects in PA patients. Design and method: A total of 91 patients who received eplerenone or esaxerenone for PA treatment were included. The patients with PRA>=1.0 ng/mL/h at one year after the initiation of MRAs were determined as responders, and others were determined as non-responders. The differences between responders and non-responders were analyzed. In addition, these patients were followed for another two years (total three years), and the transitions of estimated glomerular filtration (eGFR) among responders and non-responders were also compared. Results: The doses of MRAs were equivalent between responders and non-responders. Estimated sodium intake was significantly lower in responders (responders: non-responders; 156.2±42.3 mmol/day: 124.7±41.8 mmol/day P<0.05). Multivariate logistic regression analysis has shown that estimated sodium intake was an independent predictor for responders. During three years’ period, eGFR was significantly decreased in non-responders (pre-treatment: post-treatment; 73.0±14.7 ml/min: 69.5±14.1 ml/min P<0.05), whereas it was comparatively preserved in responders (pre-treatment: post-treatment; 68.3±17.9 ml/min: 68.0±19.0 ml/min P=0.84). Conclusions: The present study have shown that responders in PA patients may partially benefit from an adherence to sodium restriction. Sodium restriction concomitant with sufficient suppression of aldosterone effect may exert renoprotective effects for PA patients.

Adverse Effects of Aldosterone: Beyond Blood Pressure.

Aldosterone is a steroid hormone that primarily acts through activation of the mineralocorticoid receptor (MR), a nuclear receptor responsible for downstream genomic regulation. Classically, activation of the MR in the renal tubular epithelium is responsible for sodium retention and volume expansion, raising systemic blood pressure. However, activation of the MR across a wide distribution of tissue types has been implicated in multiple adverse consequences for cardiovascular, cerebrovascular, renal, and metabolic disease, independent of blood pressure alone. Primary aldosteronism, heart failure, and chronic kidney disease are states of excessive aldosterone production and MR activity where targeting MR activation has had clinical benefits out of proportion to blood pressure lowering. The growing list of established and emerging therapies that target aldosterone and MR activation may provide new opportunities to improve clinical outcomes and enhance cardiovascular and renal health.

Dietary sodium alters aldosterone's effect on renal sodium transporter expression and distal convoluted tubule remodelling.

Aldosterone is responsible for maintaining volume and potassium homeostasis. Although high salt consumption should suppress aldosterone production, individuals with hyperaldosteronism lose this regulation, leading to a state of high aldosterone despite dietary sodium consumption. The present study examines the effects of elevated aldosterone, with or without high salt consumption, on the expression of key Na+ transporters and remodelling in the distal nephron. Epithelial sodium channel (ENaC) α-subunit expression was increased with aldosterone regardless of Na+ intake. However, ENaC β- and γ-subunits unexpectedly increased at both a transcript and protein level with aldosterone when high salt was present. Expression of total and phosphorylated Na+ Cl- cotransporter (NCC) significantly increased with aldosterone, in association with decreased blood [K+ ], but the addition of high salt markedly attenuated the aldosterone-dependent NCC increase, despite equally severe hypokalaemia. We hypothesized this was a result of differences in distal convoluted tubule length when salt was given with aldosterone. Imaging and measurement of the entire pNCC-positive tubule revealed that aldosterone alone caused a shortening of this segment, although the tubule had a larger cross-sectional diameter. This was not true when salt was given with aldosterone because the combination was associated with a lengthening of the tubule in addition to increased diameter, suggesting that differences in the pNCC-positive area are not responsible for differences in NCC expression. Together, our results suggest the actions of aldosterone, and the subsequent changes related to hypokalaemia, are altered in the presence of high dietary Na+ . KEY POINTS: Aldosterone regulates volume and potassium homeostasis through effects on transporters in the kidney; its production can be dysregulated, preventing its suppression by high dietary sodium intake. Here, we examined how chronic high sodium consumption affects aldosterone's regulation of sodium transporters in the distal nephron. Our results suggest that high sodium consumption with aldosterone is associated with increased expression of all three epithelial sodium channel subunits, rather than just the alpha subunit. Aldosterone and its associated decrease in blood [K+ ] lead to an increased expression of Na-Cl cotransporter (NCC); the addition of high sodium consumption with aldosterone partially attenuates this NCC expression, despite similarly low blood [K+ ]. Upstream kinase regulators and tubule remodelling do not explain these results.

Metabolic effects of aldosterone

Currently, increasing evidence shows the mutual influence of aldosterone and adipose tissue. Aldosterone excess has been reported in patients with obesity and metabolic syndrome. Aldosterone has a direct effect on adipose tissue increasing anabolic activity and expression of mineralocorticoid receptors. In turn, excessive activation of MCR leads to stimulation of adipogenesis and an increase in the volume of adipose tissue. Aldosterone excess can be considered an independent cardiovascular risk factor that affects such processes as cardiac fibrosis, nephrosclerosis, and arteriosclerosis. There is convincing evidence of higher prevalence and severity of impaired glucose homeostasis and lipid metabolism disorders among patients with primary hyperaldosteronism. Similar pathological changes are also observed in patients with obesity and metabolic syndrome. This review presents scientific data on the metabolic effects of aldosterone, in particular its effect on adipose tissue function, glucose and lipid metabolism. Treatment with mineralocorticoid receptor antagonists may provide substantial benefit in the management of metabolic syndrome, contribute to the stabilisation of glucose and lipid metabolism, improve clinical status of patients with cardiovascular diseases and reduce the risk of complications. However, available evidence from the conducted studies is not sufficient to justify introduction of such therapy into clinical practice.

Aldosterone and aldosterone synthase inhibitors in cardiorenal disease.

Modulation of the renin-angiotensin-aldosterone system is a foundation of therapy for cardiovascular and kidney diseases. Excess aldosterone plays an important role in cardiovascular disease, contributing to inflammation, fibrosis, and dysfunction in the heart, kidneys, and vasculature through both genomic and mineralocorticoid receptor (MR)-mediated as well as nongenomic mechanisms. MR antagonists have been a key therapy for attenuating the pathologic effects of aldosterone but are associated with some side effects and may not always adequately attenuate the nongenomic effects of aldosterone. Aldosterone is primarily synthesized by the CYP11B2 aldosterone synthase enzyme, which is very similar in structure to other enzymes involved in steroid biosynthesis including CYP11B1, a key enzyme involved in glucocorticoid production. Lack of specificity for CYP11B2, off-target effects on the hypothalamic-pituitary-adrenal axis, and counterproductive increased levels of bioactive steroid intermediates such as 11-deoxycorticosterone have posed challenges in the development of early aldosterone synthase inhibitors such as osilodrostat. In early-phase clinical trials, newer aldosterone synthase inhibitors demonstrated promise in lowering blood pressure in patients with treatment-resistant and uncontrolled hypertension. It is therefore plausible that these agents offer protection in other disease states including heart failure or chronic kidney disease. Further clinical evaluation will be needed to clarify the role of aldosterone synthase inhibitors, a promising class of agents that represent a potentially major therapeutic advance.

Expression of functional mineralocorticoid receptor (MR) and G-protein coupled estrogen receptor (GPER) in human T lymphocytes

Aldosterone plays a key role in controlling blood pressure (BP) values by maintaining body salt, water, and fluid homeostasis. Excess aldosterone production is associated with arterial hypertension, cardiovascular and metabolic diseases, partly via generation of an inflammatory state followed by fibrotic changes in the organs that are target of hypertension. Aldosterone exerts genomic effects that are known to involve activation of the mineralocorticoid receptor (MR). Other aldosterone effects, including those usually defined as ‘rapid’ or ‘non genomic’, involve additional receptors as the G-protein coupled estrogen receptor (GPER). To date, the receptor(s) implicated in the inflammatory action of aldosterone in cells of the innate and adaptive immunity are unknown. Considering the potential role of T-lymphocytes in adaptive immunity in arterial hypertension and related hypertension-mediated organ damage (HMOD), we herein investigated and quantified the expression of the MR and GPER in human CD4+ and CD8+ T-cells. Results provided compelling evidence for the presence at the mRNA and protein level and suggest a functional role of these receptors in the two T-lymphocyte subtypes, thus indicating that they can represent a potential target for modulation of steroid hormone-induced inflammation and ensuing HMOD.

THU474 Primary Hyperaldosteronism As A Cause Of PTH Elevation After Parathyroid Surgery

Abstract Disclosure: W. Thi: None. A. Rao: None. Background: Primary hyperaldosteronism can cause hypercalciuria, parathyroid hormone (PTH) elevation due to secondary hyperparathyroidism, and reduce bone mineral density. Screening for primary hyperaldosteronism can be done with serum aldosterone-renin ratio (ARR). We report a case of recurrent hyperparathyroidism after parathyroid surgery. Workup identified primary hyperaldosteronism as the cause of recurrent hyperparathyroidism. Treatment with spironolactone normalized PTH levels. Case Presentation: A 59-year-old African-American female in the Columbia VA Health Care System presented with hypertension, hypokalemia, bone density loss, and elevated PTH with normal calcium, one year after resection of a right inferior parathyroid adenoma to treat primary hyperparathyroidism. The patient had uncontrolled hypertension with hypokalemia while on losartan and amlodipine. Serum calcium was 9.4mg/dl(8.4-10.2mg/dl), PTH 89.4 pg/ml(29.2-79.9pg/ml), albumin 3.8g/dl(3.5-5G/dl), vitamin D 34 ng/ml(>28.9ng/ml), aldosterone 9ng/dl(</=28ng/dl), plasma renin activity 0.28ng/ml/h(0.25-5.82ng/ml/h), ARR 32. Treatment of the patient with potassium supplements corrected the hypokalemia to 3.7mmol/L (5-5.1mm/l), and ARR was 94 with aldosterone 17 ng/dl and PRA 0.18 ng/ml/h and 24-hour urine calcium 304mg/24h(35-250mg/24h). Based on the laboratory values, and the absence of adrenal nodules during a CT scan, a diagnosis of primary hyperaldosteronism due to idiopathic hyperplasia of the adrenal was made. Spironolactone was started and PTH levels dropped down to 64.8pg/ml and serum calcium remained normal 5 months after treatment was initiated. Discussion: Primary Hyperaldosteronism causes extravascular fluid volume expansion with a reduction in proximal tubular sodium and calcium reabsorption. Increased calcium and sodium delivery to distal segments of the nephron leads to sodium reabsorption by mineralocorticoids without reabsorbing calcium, resulting in hypocalcemia with concomitant secondary hyperparathyroidism. Bone loss results from direct mineralocorticoid receptor-mediated effects of aldosterone on osteoblasts and osteoclasts and indirectly from high PTH levels to promote bone resorption. Treatment of primary hyperaldosteronism can reverse bone loss and reduce fracture risk rate within 18-36 months. This case suggests that primary hyperaldosteronism be considered a cause of secondary hyperparathyroidism and successfully treated with mineralocorticoid receptor antagonists. Presentation: Thursday, June 15, 2023

FRI126 Autoreactive T Cells To Angiotensin II Type 1 Receptor In Salt-dependent Hypertension Due To Primary Aldosteronism

Abstract Disclosure: R. Scarpa: None. M. Piazza: None. B. Caroccia: None. S. Carraro: None. F. Vianello: None. F. Cinetto: None. C. Agostini: None. T.M. Seccia: None. G. Rossi: None. Compelling evidence suggested a role of acquired immunity in hypertension and hypertension-mediated organ damage (HMOD), but the pathogenic role of this acquired immunity is still unknown. Primary Aldosteronism, the paradigm of salt-dependent hypertension, is characterised by a more prominent HMOD than primary (‘essential’) hypertension and by high titer of autoantibodies against the type 1 angiotensin receptor (AT1R). As T cells are broadly recognised as HMOD-mediators, we aim to investigate: 1) the presence of AT1R-autoreactive T cells in PA; 2) aldosterone rapid and chronic effect on AT1R-autoreactive T lymphocytes; 3) the presence and functional role of know aldosterone receptors on T lymphocytes. The presence of AT1R-autoreactive T cells in 11 PA patients was investigated by flow cytometry after stimulation with pool of peptides spanning the full length of AT1R. The expression of mineralocorticoid receptor (MR) and G Protein-Coupled Estrogen Receptor (GPER) on T cells was tested by measuring mRNA copy number by droplet digital PCR and immunoblotting from healthy donors (HD) subjects and PA patients. Peripheral blood mononuclear cells (PBMCs) from PA patients were exposed to aldosterone 10-10 M with or without MR antagonist (canrenone) and GPER agonist (G1) and antagonist (G36). We evaluated the effect of aldosterone on CD8+ T cells by measuring IFNɣ release with flow cytometry. PA patients were found to have CD8+ AT1R-autoreactive T cells after activation of PBMC with AT1R peptides. MR and GPER were detected both at mRNA and protein level in CD4+ and CD8+ T cells with the following rank of expression GR>MR>>GPER. Aldosterone significantly increased IFNɣ release in CD8+ T-cell both under chronic and acute stimulation. Chronic exposure to aldosterone increased IFN-γ production by CD8+ T cells by acting via the MR, as it was prevented (p < 0.004) by canrenone, while the rapid aldosterone action was MR and GPER mediated, as it was reduced by canrenone (p < 0.003), but also by G36 (p < 0.02), and mimicked by G1. These results showed the presence of AT1R-autoreactive T cells in patients with PA. Moreover, upon of MR and GPER receptor stimulation with aldosterone, AT1-R specific CD8+ T cells undergo profound changes that mediated a strong cytotoxic response towards AT1-R-expressing organs. Presentation: Friday, June 16, 2023

Treating Primary Aldosteronism-Induced Hypertension: Novel Approaches and Future Outlooks.

Primary aldosteronism (PA) is the most common cause of secondary hypertension and is associated with increased morbidity and mortality when compared with blood pressure-matched cases of primary hypertension. Current limitations in patient care stem from delayed recognition of the condition, limited access to key diagnostic procedures, and lack of a definitive therapy option for nonsurgical candidates. However, several recent advances have the potential to address these barriers to optimal care. From a diagnostic perspective, machine-learning algorithms have shown promise in the prediction of PA subtypes, while the development of noninvasive alternatives to adrenal vein sampling (including molecular positron emission tomography imaging) has made accurate localization of functioning adrenal nodules possible. In parallel, more selective approaches to targeting the causative aldosterone-producing adrenal adenoma/nodule (APA/APN) have emerged with the advent of partial adrenalectomy or precision ablation. Additionally, the development of novel pharmacological agents may help to mitigate off-target effects of aldosterone and improve clinical efficacy and outcomes. Here, we consider how each of these innovations might change our approach to the patient with PA, to allow more tailored investigation and treatment plans, with corresponding improvement in clinical outcomes and resource utilization, for this highly prevalent disorder.

AUTOREACTIVE T CELLS TO ANGIOTENSIN II TYPE 1 RECEPTOR IN SALT-DEPENDENT HYPERTENSION DUE TO PRIMARY ALDOSTERONISM

Objective: Compelling evidence suggested a role of acquired immunity in hypertension and hypertension-mediated organ damage (HMOD), but its pathogenic role is still unknown. Primary Aldosteronism (PA), the paradigm of salt-dependent hypertension, is characterised by a more prominent HMOD than primary hypertension and by high titer of autoantibodies against the angiotensin type-1 receptor (AT1R). As T cells are broadly recognised as HMOD-mediators we investigated: 1) the presence of AT1R-autoreactive T cells in PA; 2) aldosterone rapid and chronic effect on AT1R-autoreactive T lymphocytes; 3) the presence and functional role of aldosterone receptors on T lymphocytes. Design and Methods: The presence of AT1R-autoreactive T cells in 11 PA patients was investigated by flow cytometry after stimulation with pool of peptides spanning the full length of AT1R. The expression of mineralocorticoid receptor (MR) and G Protein-Coupled Estrogen Receptor (GPER) on T cells was tested by measuring mRNA copy number and immunoblotting from healthy donors and PA patients. PBMCs from PA patients were exposed to aldosterone 10-10 M with or without MR antagonist (canrenone) and GPER agonist (G1) and antagonist (G36). We evaluated the effect of aldosterone on CD8+ T cells by measuring IFN? release with flow cytometry. Results: PA patients were found to have CD8+ AT1R-autoreactive T cells after activation of PBMC with AT1R peptides. MR and GPER were detected both at mRNA and protein level in CD4+ and CD8+ T cells with the following rank of expression GR>MR>>GPER. Aldosterone significantly increased IFN? release in CD8+ T-cell both under chronic and acute stimulation. Chronic exposure to aldosterone increased IFN-? production by CD8+ T cells by acting via the MR, as it was prevented (p<0.004) by canrenone, while the rapid aldosterone action was MR and GPER mediated, as it was reduced by canrenone (p<0.003), but also by G36 (p<0.02), and mimicked by G1. Conclusion: These results showed the presence of AT1R-autoreactive T cells in patients with PA and demonstrates that, upon of MR and GPER receptor stimulation with aldosterone, AT1-R specific CD8+ T cells undergo profound changes that mediated a strong cytotoxic response towards AT1-R-expressing organs.

Resistant hypertension: cardiorenal protection with mineralocorticoid receptor blockade.

Effects of hypertension, aldosterone, and/or mineralocorticoid receptor activation on inflammatory and fibrotic effects in the vasculature of the heart, kidney, and brain in patients with treatment-resistant hypertension. Abbreviations: Ang I, angiotensin I; Ang II, angiotensin II; CCBs, calcium channel blockers; ACEIs, angiotensin-converting enzyme inhibitors; ARBs, angiotensin receptor blockers; TT, thiazide-type (indapamide and chlorthalidone); MRAs, mineralocorticoid receptor antagonists.

In mouse kidney endogenous transmembrane serine protease 2 (TMPRSS2) contributes to proteolytic processing and activation of the epithelial sodium channel (ENaC)

Regulation of ENaC in the distal nephron is essential for sodium homeostasis and blood pressure control. A unique feature of ENaC is its complex proteolytic processing leading to channel activation due to release of inhibitory tracts from its α- and γ-subunits. In particular, fully cleaved γ-ENaC is critical for high channel activity. However, the physiologically relevant proteases involved remain elusive. Using Xenopus laevis oocytes and H441 airway epithelial cells, we recently demonstrated that TMPRSS2 proteolytically activates ENaC by cleaving the channel’s γ-subunit ( J Biol Chem 2022 Jun;298(6):102004). Here we investigate whether TMPRSS2 also contributes to proteolytic ENaC regulation in the kidney. Using mRNA sequencing, we demonstrated that mouse cortical collecting duct (mCCD cl1 ) cells express TMPRSS2 at a high level unaffected by aldosterone, an important ENaC stimulating hormone. TMPRSS2 knockdown by CRISPR/Cas9 technology significantly reduced fully cleaved γ-ENaC in membrane-enriched fractions of mCCD cl1 cell lysates (n=5). Apical application of chymotrypsin significantly stimulated ENaC-mediated short circuit current ( I SC ) in TMPRSS2-knockdown cells, but not in control cells (2.0 ± 1.1 μA/cm² vs. 0.2 ± 0.6 μA/cm²; n=13-14; p<0.001; mean ± SD). Moreover, the stimulatory effect of aldosterone on I SC was impaired in TMPRSS2-knockdown cells compared to control cells (9.1 ± 4.0 μA/cm² vs. 18.3 ± 4.0 μA/cm²; n=7-8; p<0.01). After aldosterone treatment I SC stimulation by chymotrypsin was enhanced in TMPRSS2-knockdown cells (5.3 ± 1.9 μA/cm²; n=7) but undetectable in control cells (−0.8 ± 1.6 μA/cm²; n=8). These findings indicate that TMPRSS2 deficiency impairs proteolytic ENaC activation in mCCD cl1 cells. To confirm this in an in vivo model, we used constitutive TMPRSS2 knockout mice ( Tmprss2 -/- ). Using a combination of RNAscope technology and immunofluorescence, we demonstrated high expression of Tmprss2 mRNA in renal tubular cells, including cells with β-ENaC protein staining. Importantly, the ratio of fully to partially cleaved γ-ENaC was significantly reduced in membrane-enriched fractions of whole-kidney lysates from Tmprss2 -/- mice (n=10). Maintained on a standard diet, Tmprss2 -/- mice had no apparent renal phenotype with plasma aldosterone levels similar to those of Tmprss2 +/+ mice (120 ± 43 pg/ml in Tmprss2 -/- vs. 92 ± 17 pg/mL in Tmprss2 +/+ ; n=7-10). Moreover, the ability of Tmprss2 -/- mice to reduce urinary sodium excretion in response to four days of low sodium diet was fully preserved. However, under low sodium diet plasma aldosterone increased to significantly higher levels in Tmprss2 -/- mice compared to controls (752 ± 146 pg/ml in Tmprss2 -/- vs. 268 ± 55 pg/ml in Tmprss2 +/+ ; n=7-11; p<0.01). This is most likely a compensatory response to compromised proteolytic ENaC activation due to TMPRSS2 deficiency. We conclude that TMPRSS2 plays a physiological role in proteolytic ENaC processing and activation in the kidney. This study was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 509149993, TRR 374 (subproject A4 to A.I. and C.K.) and the Bayerisches Staatsministerium für Wissenschaft und Kunst (Bavarian Ministry of Art and Science), project VI-Corona-Forschung (subproject 07 to M.B. and T.G). A.K. was supported by the Interdisziplinäres Zentrum für klinische Forschung (IZKF) Erlangen. S.W. was supported by the Bundesministerium für Bildung und Forschung (BMBF, Federal Ministry of Education and Research, Germany), project SENSE-CoV2, 01KI20172A. P.S. and F.A. were funded by the IZKF Tübingen. The authors declare no conflicts of interest. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The role of aldosterone in the pathogenesis of diabetic retinopathy.

Aldosterone, as a mineralocorticoid of adrenal origin, has effects that are not limited to the urinary tract. As an important regulator in Vasoactive hormone pathways, aldosterone may play an effect in the pathogenesis of diabetic retinopathy (DR) through the regulation of oxidative stress, vascular regulation, and inflammatory mechanisms. This implies that mineralocorticoids, including aldosterone, have great potential and value for the diagnosis and treatment of DR. Because early studies did not focus on the intrinsic association between mineralocorticoids and DR, targeted research is still in its infancy and there are still many obstacles to its application in the clinical setting. Recent studies have improved the understanding of the effects of aldosterone on DR, and we review them with the aim of exploring possible mechanisms for the treatment and prevention of DR.