Disordered CYP11B2 Expression in Primary Aldosteronism

Primary aldosteronism is the most common type of secondary hypertension affecting 6-10% of patients with primary hypertension. PA is mainly caused by unilateral hyperaldosteronism due to an aldosterone-producing adenoma, unilateral hyperplasia with or without micronodules or bilateral zona glomerulosa hyperplasias with or without macro or micronodules. The development of antibodies against the terminal enzyme of aldosterone biosynthesis (CYP11B2) has permitted the further characterization of normal adrenals and resected adrenals from patients with primary aldosteronism. Normal adrenals exhibit two different patterns of cellular expression of CYP11B2: young individuals display a relatively uniform expression of the enzyme throughout the zona glomerulosa while the adrenals of older individuals have dispersed CYP11B2-expressing cells but have more groups of cells called aldosterone-producing cell clusters (APCC). APAs exhibit different patterns of CYP11B2 staining that vary from uniform to homogeneous. There are also a proportion of cells within the APA that co-express different enzymes that are not normally co-expressed in normal individuals. Approximately 30% of patients with unilateral hyperaldosteronism do not have an APA, but either have an increased number of CYP11B2 expressing micronodules or hyperplasia of the zona glomerulosa. In summary, the studies reported in this review are shedding new light on the pathophysiology of primary aldosteronism. The wide variation in histopathological features of the adenomas and concurrent presence of APCCs raises the possibility that most cases of unilateral production of aldosterone actually might represent bilateral asymmetric hyperplasia with nodules frequently due to the development of somatic aldosterone-driving mutations

Mouse models of primary aldosteronism: from physiology to pathophysiology

Primary aldosteronism (PA) is a common form of endocrine hypertension that is characterized by the excessive production of aldosterone relative to suppressed plasma renin levels. PA is usually caused by either a unilateral aldosterone-producing adenoma or bilateral adrenal hyperplasia. Somatic mutations have been identified in several genes that encode ion pumps and channels that may explain the aldosterone excess in over half of aldosterone-producing adenomas, whereas the pathophysiology of bilateral adrenal hyperplasia is largely unknown. A number of mouse models of hyperaldosteronism have been described that recreate some features of the human disorder although none replicate the genetic basis of human PA. Animal models that reproduce the genotype-phenotype associations of human PA are required to establish the functional mechanisms that underlie the endocrine autonomy and deregulated cell growth of the affected adrenal and for preclinical studies of novel therapeutics. Herein, we discuss the differences in adrenal physiology across species and describe the genetically-modified mouse models of PA that have been developed to date

Role of osmolality in blood pressure stability after dialysis and ultrafiltration

Role of osmolality in blood pressure stability after dialysis and ultrafiltration. To clarify the mechanisms involved in the stability of blood pressure during ultrafiltration (UF) alone versus regular dialysis, this study systematically examined the importance of changes in serum potassium, osmolality, and plasma norepinephrine during several dialysis maneuvers. Six stable, normotensive chronic dialysis patients were subjected to a uniform 2 to 3% decrease in body weight during the 2 hours of each dialysis maneuver. Supine to upright mean blood pressure (MBP) decreased (90 to 75 mm Hg, P < 0.05), and three patients became symptomatic after weight loss during regular dialysis, but orthostatic blood pressure was stable (89 to 86 mm Hg, NS) and the patients were asymptomatic after UF and weight loss. Isokalemic regular dialysis did not afford hemodynamic stability, as orthostatic MBP declined (85 to 56 mm Hg, P < 0.02), and four of the patients again were symptomatic after standing. A continuous hypertonic mannitol (25%) infusion during the 2-hour dialysis, however, kept osmolality from decreasing and was associated with a stable orthostatic MBP (89 to 83 mm Hg, NS). A continuous infusion of isotonic mannitol (5%) given in a volume five times that of the hypertonic mannitol failed to prevent orthostatic hypotension (89 to 60 mm Hg, P < 0.005). Plasma norepinephrine concentrations were high in these patients and increased only modestly after weight loss. These results implicate constant plasma osmolality as a critical protective factor of blood pressure during UF and further demonstrate that changes in blood pressure may be dissociated from changes in both serum potassium and plasma norepinephrine concentration.Rôle de l'osmolalité dans la stabilité de la pression artérielle après dialyse et ultrafiltration. Afin de clarifier les mécanismes impliqués dans la stabilité de la pression artérielle au cours de l'ultrafiltration (UF) seule par comparaison avec la dialyse habituelle ce travail évalue systématiquement l'importance des modifications de la kaliémie, de l'osmolalité et de la norépinéphrine plasmatique au cours de plusieurs tactiques de dialyse. Six sujets stables, normotendus, en hémodialyse chronique ont subi une diminution de poids corporel de 2 à 3% au cours des 2 heures de chaque tactique de dialyse. La pression artérielle moyenne a diminué de la position couchée à la position debout (de 90 à 75 mm Hg, P < 0,05) et trois patients sont devenus symptomatiques après la perte de poids au cours de la dialyse habituelle. Par contre la pression artérielle orthostatique a été stable (89 à 86 mm Hg, NS) et les malades ont été asymptomatiques après UF. La dialyse habituelle isokaliémique n'a pas déterminé de stabilité hémodynamique, la pression artérielle moyenne orthostatique a diminué (85 à 56 mm Hg, P < 0,02) et quatre malades ont été à nouveau symptomatiques quand ils se sont levés. Cependant quand une perfusion continue de mannitol hypertonique (25%) pendant les deux heures de la dialyse a empêché la baisse de l'osmolalité la pression artérielle moyenne orthostatique a été stable (89 à 83 mm Hg, NS). Une perfusion continue de mannitol isotonique (5%) apportant un volume cinq fois celui du mannitol hypertonique n'a pas empêché l'hypotention orthostatique (89 à 60 mm Hg, P < 0,005). Les concentrations plasmatiques de norépinéphrine étaient élevées chez ces malades et n'ont que peu augmenté après la perte de poids. Ces résultats impliquent qu'une osmolalité plasmatique constante est un facteur protecteur critique pour la pression artérielle au cours de UF et ils démontrent, de plus, que les modifications de la pression artérielle peuvent être dissociées des modifications du potassium plasmatique et de la concentration de norépinéphrine

Glucocorticoid remediable aldosteronism: low morbidity and mortality in a four-generation italian pedigree.

Glucocorticoid remediable hyperaldosteronism (GRA) is a monogenic form of inherited hypertension caused by a chimeric gene originating from an unequal cross-over between the 11 beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes. GRA is characterized by high plasma levels of aldosterone (regulated by ACTH) with suppressed plasma renin activity and the production of two rare steroids, 18hydroxycortisol and 18oxocortisol. Affected patients usually show severe hypertension and an elevated frequency of stroke at a young age. Affected women have a high risk of developing preeclampsia during pregnancy. Here, we describe a 5-generation pedigree from Sardinia in which the presence of the chimeric gene is demonstrated in 4 generations. This family displays a mild phenotype with average blood pressure levels of 131/86 mm Hg for GRA+ patients. The occurrence of stroke is very low, and preeclampsia was not observed in 29 pregnancies from 8 GRA+ mothers. We investigated whether the cross-over site (between the CYP11B1 and CYP11B2 genes) or biochemical characteristics could explain this phenotype. The cross-over site was located at the end of intron 3, in the same region as described in other families. We found a significant correlation between blood pressure and 18hydroxycortisol, 18oxocortisol, and plasma aldosterone levels, but not with kallikrein. However, none of the biochemical or genetic parameters investigated could explain the mild phenotype of the family

Primary Aldosteronism: KCNJ5 Mutations and Adrenocortical Cell Growth

Aldosterone-producing adenomas with somatic mutations in the KCNJ5 G-protein-coupled inwardly rectifying potassium channel are a cause of primary aldosteronism. These mutations drive aldosterone excess, but their role in cell growth is undefined. Our objective was to determine the role of KCNJ5 mutations in adrenal cell proliferation and apoptosis. The Ki67 proliferative index was positively correlated with adenoma diameter in aldosterone-producing adenomas with a KCNJ5 mutation (r=0.435, P=0.007), a negative correlation was noted in adenomas with no mutation detected (r=-0.548, P=0.023). Human adrenocortical cell lines were established with stable expression of cumate-inducible wild-type or mutated KCNJ5. Increased cell proliferation was induced by low-level induction of KCNJ5-T158A expression compared with control cells (P=0.009), but increased induction ablated this difference. KCNJ5-G151R displayed no apparent proliferative effect, but KCNJ5-G151E and L168R mutations each resulted in decreased cell proliferation (difference P<0.0001 from control cells, both comparisons). Under conditions tested, T158A had no effect on apoptosis, but apoptosis increased with expression of G151R (P<0.0001), G151E (P=0.008), and L168R (P<0.0001). We generated a specific KCNJ5 monoclonal antibody which was used in immunohistochemistry to demonstrate strong KCNJ5 expression in adenomas without a KCNJ5 mutation and in the zona glomerulosa adjacent to adenomas irrespective of genotype as well as in aldosterone-producing cell clusters. Double immunofluorescence staining for KCNJ5 and CYP11B2 (aldosterone synthase) showed markedly decreased KCNJ5 immunostaining in CYP11B2-positive cells compared with CYP11B2-negative cells in aldosterone-producing adenomas with a KCNJ5 mutation. Together, these findings support the concept that cell growth effects of KCNJ5 mutations are determined by the expression level of the mutated channel

Cardiomyocyte glucocorticoid and mineralocorticoid receptors directly and antagonistically regulate heart disease in mice

Stress is increasingly associated with heart dysfunction and is linked to higher mortality rates in patients with cardiometabolic disease. Glucocorticoids are primary stress hormones that regulate homeostasis through two nuclear receptors, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR), both of which are present in cardiomyocytes. To examine the specific and coordinated roles that these receptors play in mediating the direct effects of stress on the heart, we generated mice with cardiomyocyte-specific deletion of GR (cardioGRKO), MR (cardioMRKO), or both GR and MR (cardioGRMRdKO). The cardioGRKO mice spontaneously developed cardiac hypertrophy and left ventricular systolic dysfunction and died prematurely from heart failure. In contrast, the cardioMRKO mice exhibited normal heart morphology and function. Surprisingly, despite the presence of myocardial stress, the cardioGRMRdKO mice were resistant to the cardiac remodeling, left ventricular dysfunction, and early death observed in the cardioGRKO mice. Gene expression analysis revealed the loss of gene changes associated with impaired Ca2+ handling, increased oxidative stress, and enhanced cell death and the presence of gene changes that limited the hypertrophic response and promoted cardiomyocyte survival in the double knockout hearts. Re-expression of MR in cardioGRMRdKO hearts reversed many of the cardioprotective gene changes and resulted in cardiac failure. These findings reveal a critical role for balanced cardiomyocyte GR and MR stress signaling in cardiovascular health. Therapies that shift stress signaling in the heart to favor more GR and less MR activity may provide an improved approach for treating heart disease

International Histopathology Consensus for Unilateral Primary Aldosteronism

Objective: Develop a consensus for the nomenclature and definition of adrenal histopathologic features in unilateral primary aldosteronism (PA). Context: Unilateral PA is the most common surgically treated form of hypertension. Morphologic examination combined with CYP11B2 (aldosterone synthase) immunostaining reveals diverse histopathologic features of lesions in the resected adrenals. Patients and methods: Surgically removed adrenals (n = 37) from 90 patients operated from 2015 to 2018 in Munich, Germany, were selected to represent the broad histologic spectrum of unilateral PA. Five pathologists (Group 1 from Germany, Italy, and Japan) evaluated the histopathology of hematoxylin-eosin (HE) and CYP11B2 immunostained sections, and a consensus was established to define the identifiable features. The consensus was subsequently used by 6 additional pathologists (Group 2 from Australia, Brazil, Canada, Japan, United Kingdom, United States) for the assessment of all adrenals with disagreement for histopathologic diagnoses among group 1 pathologists. Results: Consensus was achieved to define histopathologic features associated with PA. Use of CYP11B2 immunostaining resulted in a change of the original HE morphology-driven diagnosis in 5 (14%) of 37 cases. Using the consensus criteria, group 2 pathologists agreed for the evaluation of 11 of the 12 cases of disagreement among group 1 pathologists. Conclusion: The HISTALDO (histopathology of primary aldosteronism) consensus is useful to standardize nomenclature and achieve consistency among pathologists for the histopathologic diagnosis of unilateral PA. CYP11B2 immunohistochemistry should be incorporated into the routine clinical diagnostic workup to localize the likely source of aldosterone production

Targeting CXCR4 (CXC Chemokine Receptor Type 4) for Molecular Imaging of Aldosterone-Producing Adenoma

Primary aldosteronism is the most frequent cause of secondary hypertension and is associated with increased morbidity and mortality compared with hypertensive controls. The central diagnostic challenge is the differentiation between bilateral and unilateral disease, which determines treatment options. Bilateral adrenal venous sampling, currently recommended for differential diagnosis, is an invasive procedure with several drawbacks, making it desirable to develop novel noninvasive diagnostic tools. When investigating the expression pattern of chemokine receptors by quantitative real-time polymerase chain reaction and immunohistochemistry, we observed high expression of CXCR4 (CXC chemokine receptor type 4) in aldosterone-producing tissue in normal adrenals, adjacent adrenal cortex from adrenocortical adenomas, and in aldosterone-producing adenomas (APA), correlating strongly with the expression of CYP11B2 (aldosterone synthase). In contrast, CXCR4 was not detected in the majority of nonfunctioning adenomas that are frequently found coincidently. The specific CXCR4 ligand 68Ga-pentixafor has recently been established as radiotracer for molecular imaging of CXCR4 expression and showed strong and specific binding to cryosections of APAs in our study. We further investigated 9 patients with primary aldosteronism because of APA by 68Ga-pentixafor-positron emission tomography. The tracer uptake was significantly higher on the side of increased adrenocortical aldosterone secretion in patients with APAs compared with patients investigated by 68Ga-pentixafor-positron emission tomography for other causes. Molecular imaging of aldosterone-producing tissue by a CXCR4-specific ligand may, therefore, be a highly promising tool for noninvasive characterization of patients with APAs