Hyperaldosteronism, hypervolemia, and increased blood pressure in mice expressing defective APC

Genome-Wide Interaction Study of Late-Onset Asthma With Seven Environmental Factors Using a Structured Linear Mixed Model in Europeans

Asthma is among the most common chronic diseases worldwide, creating a substantial healthcare burden. In late-onset asthma, there are wide global differences in asthma prevalence and low genetic heritability. It has been suggested as evidence for genetic susceptibility to asthma triggered by exposure to multiple environmental factors. Very few genome-wide interaction studies have identified gene-environment (G×E) interaction loci for asthma in adults. We evaluated genetic loci for late-onset asthma showing G×E interactions with multiple environmental factors, including alcohol intake, body mass index, insomnia, physical activity, mental status, sedentary behavior, and socioeconomic status. In gene-by-single environment interactions, we found no genome-wide significant single-nucleotide polymorphisms. However, in the gene-by-multi-environment interaction study, we identified three novel and genome-wide significant single-nucleotide polymorphisms: rs117996675, rs345749, and rs17704680. Bayes factor analysis suggested that for rs117996675 and rs17704680, body mass index is the most relevant environmental factor; for rs345749, insomnia and alcohol intake frequency are the most relevant factors in the G×E interactions of late-onset asthma. Functional annotations implicate the role of these three novel loci in regulating the immune system. In addition, the annotation for rs117996675 supports the body mass index as the most relevant environmental factor, as evidenced by the Bayes factor value. Our findings help to understand the role of the immune system in asthma and the role of environmental factors in late-onset asthma through G×E interactions. Ultimately, the enhanced understanding of asthma would contribute to better precision treatment depending on personal genetic and environmental information.

What Did We Learn from the Molecular Biology of Adrenal Cortical Neoplasia? From Histopathology to Translational Genomics

Approximately one-tenth of the general population exhibit adrenal cortical nodules, and the incidence has increased. Afflicted patients display a multifaceted symptomatology-sometimes with rather spectacular features. Given the general infrequency as well as the specific clinical, histological, and molecular considerations characterizing these lesions, adrenal cortical tumors should be investigated by endocrine pathologists in high-volume tertiary centers. Even so, to distinguish specific forms of benign adrenal cortical lesions as well as to pinpoint malignant cases with the highest risk of poor outcome is often challenging using conventional histology alone, and molecular genetics and translational biomarkers are therefore gaining increased attention as a possible discriminator in this context. In general, our understanding of adrenal cortical tumorigenesis has increased tremendously the last decade, not least due to the development of next-generation sequencing techniques. Comprehensive analyses have helped establish the link between benign aldosterone-producing adrenal cortical proliferations and ion channel mutations, as well as mutations in the protein kinase A (PKA) signaling pathway coupled to cortisol-producing adrenal cortical lesions. Moreover, molecular classifications of adrenal cortical tumors have facilitated the distinction of benign from malignant forms, as well as the prognostication of the individual patients with verified adrenal cortical carcinoma, enabling high-resolution diagnostics that is not entirely possible by histology alone. Therefore, combinations of histology, immunohistochemistry, and next-generation multi-omic analyses are all needed in an integrated fashion to properly distinguish malignancy in some cases. Despite significant progress made in the field, current clinical and pathological challenges include the preoperative distinction of non-metastatic low-grade adrenal cortical carcinoma confined to the adrenal gland, adoption of individualized therapeutic algorithms aligned with molecular and histopathologic risk stratification tools, and histological confirmation of functional adrenal cortical disease in the context of multifocal adrenal cortical proliferations. We herein review the histological, genetic, and epigenetic landscapes of benign and malignant adrenal cortical neoplasia from a modern surgical endocrine pathology perspective and highlight key mechanisms of value for diagnostic and prognostic purposes.

Interplay between the renin-angiotensin system, the canonical WNT/β-catenin pathway and PPARγ in hypertension

PURPOSE OF REVIEW

Heterogeneous causes can determinate hypertension.

RECENT FINDINGS

The renin-angiotensin system (RAS) has a major role in the pathophysiology of blood pressure. Angiotensin II and aldosterone are overexpressed during hypertension and lead to hypertension development and its cardiovascular complications. In several tissues, the overactivation of the canonical WNT/β-catenin pathway leads to inactivation of peroxisome proliferator-activated receptor gamma (PPARγ), while PPARγ stimulation induces a decrease of the canonical WNT/β-catenin pathway. In hypertension, the WNT/β-catenin pathway is upregulated, whereas PPARγ is decreased. The WNT/β-catenin pathway and RAS regulate positively each other during hypertension, whereas PPARγ agonists can decrease the expression of both the WNT/β-catenin pathway and RAS. We focus this review on the hypothesis of an opposite interplay between PPARγ and both the canonical WNT/β-catenin pathway and RAS in regulating the molecular mechanism underlying hypertension. The interactions between PPARγ and the canonical WNT/β-catenin pathway through the regulation of the renin-angiotensin system in hypertension may be an interesting way to better understand the actions and the effects of PPARγ agonists as antihypertensive drugs.

Genetic Causes of Functional Adrenocortical Adenomas

Aldosterone and cortisol, the main mineralocorticoid and glucocorticoid hormones in humans, are produced in the adrenal cortex, which is composed of three concentric zones with specific functional characteristics. Adrenocortical adenomas (ACAs) can lead to the autonomous secretion of aldosterone responsible for primary aldosteronism, the most frequent form of secondary arterial hypertension. In the case of cortisol production, ACAs lead to overt or subclinical Cushing syndrome. Genetic analysis driven by next-generation sequencing technology has enabled the discovery, during the past 7 years, of the genetic causes of a large subset of ACAs. In particular, somatic mutations in genes regulating intracellular ionic homeostasis and membrane potential have been identified in aldosterone-producing adenomas. These mutations all promote increased intracellular calcium concentrations, with activation of calcium signaling, the main trigger for aldosterone production. In cortisol-producing adenomas, recurrent somatic mutations in PRKACA (coding for the cyclic adenosine monophosphate-dependent protein kinase catalytic subunit α) affect cyclic adenosine monophosphate-dependent protein kinase A signaling, leading to activation of cortisol biosynthesis. In addition to these specific pathways, the Wnt/β-catenin pathway appears to play an important role in adrenal tumorigenesis, because β-catenin mutations have been identified in both aldosterone- and cortisol-producing adenomas. This, together with different intermediate states of aldosterone and cortisol cosecretion, raises the possibility that the two conditions share a certain degree of genetic susceptibility. Alternatively, different hits might be responsible for the diseases, with one hit leading to adrenocortical cell proliferation and nodule formation and the second specifying the hormonal secretory pattern.

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.

Somatic and inherited mutations in primary aldosteronism

Primary aldosteronism (PA), the most common form of secondary hypertension, is caused in the majority of cases by unilateral aldosterone-producing adenoma (APA) or bilateral adrenal hyperplasia. Over the past few years, somatic mutations in KCNJ5, CACNA1D, ATP1A1 and ATP2B3 have been proven to be associated with APA development, representing more than 50% of sporadic APA. The identification of these mutations has allowed the development of a model for APA involving modification on the intracellular ionic equilibrium and regulation of cell membrane potential, leading to autonomous aldosterone overproduction. Furthermore, somatic CTNNB1 mutations have also been identified in APA, but the link between these mutations and APA development remains unknown. The sequence of events responsible for APA formation is not completely understood, in particular, whether a single hit or a double hit is responsible for both aldosterone overproduction and cell proliferation. Germline mutations identified in patients with early-onset PA have expanded the classification of familial forms (FH) of PA. The description of germline KCNJ5 and CACNA1H mutations has identified FH-III and FH-IV based on genetic findings; germline CACNA1D mutations have been identified in patients with very early-onset PA and severe neurological abnormalities. This review summarizes current knowledge on the genetic basis of PA, the association of driver gene mutations and clinical findings and in the contribution to patient care, plus the current understanding on the mechanisms of APA development.

Wnt signaling, a novel pathway regulating blood pressure? State of the art review

Recent antihypertensive trials show conflicting results on blood pressure (BP) targets in patient populations with different metabolic profiles, with lowest benefit from tight BP control observed in patients with type 2 diabetes mellitus. This paradox could arise from the heterogeneity of study populations and underscores the importance of precision medicine initiatives towards understanding and treating hypertension. Wnt signaling pathways and genetic variations in its signaling peptides have been recently associated with metabolic syndrome, hypertension and diabetes, generating a breakthrough for advancement of precision medicine in the field of hypertension. We performed a review of PubMed for publications addressing the contributions of Wnt to BP regulation and hypertension. In addition, we performed a manual search of the reference lists for relevant articles, and included unpublished observations from our laboratory. There is emerging evidence for Wnt's role in BP regulation and its involvement in the pathogenesis of hypertension. Wnt signaling has pleiotropic effects on distinct pathways that involve vascular smooth muscle plasticity, and cardiac, renal, and neural physiology. Hypertension is a heterogeneous disease with unique molecular pathways regulating its response to therapy. Recognition of these pathways is a prerequisite to identify novel targets for drug development and personalizing medicine. A review of Wnt signaling reveals its emerging role in BP regulation and as a target for novel drug development that has the potential to transform the therapy of hypertension in specific populations.

Regulation of zonation and homeostasis in the adrenal cortex

The adult adrenal cortex is organized into concentric zones, each specialized to produce distinct steroid hormones. Cellular composition of the cortex is highly dynamic and subject to diverse signaling controls. Cortical homeostasis and regeneration rely on centripetal migration of steroidogenic cells from the outer to the inner cortex, which is accompanied by direct conversion of zona glomerulosa (zG) into zona fasciculata (zF) cells. Given the important impact of tissue structure and growth on steroidogenic function, it is essential to understand the mechanisms governing adrenal zonation and homeostasis. Towards this end, we review the distinctions between each zone by highlighting their morphological and ultra-structural features, discuss key signaling pathways influencing zonal identity, and evaluate current evidence for long-term self-renewing stem cells in the adult cortex. Finally, we review data supporting zG-to-zF transdifferentiation/direct conversion as a major mechanism of adult cortical renewal.

Aldosterone-Producing Adenoma With a Somatic KCNJ5 Mutation Revealing APC-Dependent Familial Adenomatous Polyposis

CONTEXT

Recurrent somatic mutations in KCNJ5, CACNA1D, ATP1A1, and ATP2B3 have been identified in aldosterone-producing adenomas (APAs). The question as to whether they are responsible for both nodulation and aldosterone production is not solved.

CASE DESCRIPTION

We describe the case of a young patient who was diagnosed with severe arterial hypertension due to primary aldosteronism at age 26 years, followed by hemorrhagic stroke 4 years later. Abdominal computed tomography showed bilateral macronodular adrenal hyperplasia. Identification of lateralized aldosterone secretion led to right adrenalectomy, followed by normalization of biochemical and hormonal parameters and amelioration of blood pressure. The resected adrenal showed three nodules, one of them expressing aldosterone synthase and harboring a somatic KNCJ5 mutation. A Weiss revisited index of 3 of the APA prompted us to perform a second 18F-2-fluoro-2-deoxy-D-glucose-positron emission tomography after surgery, which revealed abnormal rectal activity despite the absence of clinical symptoms. Gastrointestinal exploration showed multiple polyps with severe dysplasia, and the diagnosis of familial adenomatous polyposis was established in the presence of a germline heterozygous APC gene mutation. Sequencing of somatic DNA from the APA and a second adrenal nodule revealed biallelic APC inactivation due to loss of heterozygosity in both nodules.

CONCLUSIONS

This case report underlines the need for establishing the frequency of germline APC variants in patients with primary aldosteronism and bilateral macronodular adrenal hyperplasia because their presence may predispose to APA development and severe hypertension well before the first familial adenomatous polyposis symptoms appear. From a mechanistic point of view, it supports a two-hit model for APA development, whereby the first hit drives increased cell proliferation whereas the second hit specifies the pattern of hormonal secretion.

Molecular and Cellular Mechanisms of Aldosterone Producing Adenoma Development

Primary aldosteronism (PA) is the most common form of secondary hypertension with an estimated prevalence of ~10% in referred patients. PA occurs as a result of a dysregulation of the normal mechanisms controlling adrenal aldosterone production. It is characterized by hypertension with low plasma renin and elevated aldosterone and often associated with hypokalemia. The two major causes of PA are unilateral aldosterone producing adenoma (APA) and bilateral adrenal hyperplasia, accounting together for ~95% of cases. In addition to the well-characterized effect of excess mineralocorticoids on blood pressure, high levels of aldosterone also have cardiovascular, renal, and metabolic consequences. Hence, long-term consequences of PA include increased risk of coronary artery disease, myocardial infarction, heart failure, and atrial fibrillation. Despite recent progress in the management of patients with PA, critical issues related to diagnosis, subtype differentiation, and treatment of non-surgically correctable forms still persist. A better understanding of the pathogenic mechanisms of the disease should lead to the identification of more reliable diagnostic and prognostic biomarkers for a more sensitive and specific screening and new therapeutic options. In this review, we will summarize our current knowledge on the molecular and cellular mechanisms of APA development. On one hand, we will discuss how various animal models have improved our understanding of the pathophysiology of excess aldosterone production. On the other hand, we will summarize the major advances made during the last few years in the genetics of APA due to transcriptomic studies and whole exome sequencing. The identification of recurrent and somatic mutations in genes coding for ion channels (KCNJ5 and CACNA1D) and ATPases (ATP1A1 and ATP2B3) allowed highlighting the central role of calcium signaling in autonomous aldosterone production by the adrenal.

Therapeutic potential of serum and glucocorticoid inducible kinase inhibition

INTRODUCTION

Expression of serum-and-glucocorticoid-inducible kinase-1 (SGK1) is low in most cells, but dramatically increases under certain pathophysiological conditions, such as glucocorticoid or mineralocorticoid excess, inflammation with TGFβ release, hyperglycemia, cell shrinkage and ischemia. SGK1 is activated by insulin and growth factors via phosphatidylinositide-3-kinase, 3-phosphoinositide-dependent kinase and mammalian target of rapamycin. SGK1 sensitive functions include activation of ion channels (including epithelial Na(+) channel ENaC, voltage gated Na(+) channel SCN5A transient receptor potential channels TRPV4 - 6, Ca(2+) release activated Ca(2+) channel Orai1/STIM1, renal outer medullary K(+) channel ROMK, voltage gated K(+) channels KCNE1/KCNQ1, kainate receptor GluR6, cystic fibrosis transmembrane regulator CFTR), carriers (including Na(+),Cl(-) symport NCC, Na(+),K(+),2Cl(-) symport NKCC, Na(+)/H(+) exchangers NHE1 and NHE3, Na(+), glucose symport SGLT1, several amino acid transporters), and Na(+)/K(+)-ATPase. SGK1 regulates several enzymes (e.g., glycogen synthase kinase-3, ubiquitin-ligase Nedd4-2) and transcription factors (e.g., forkhead transcription factor 3a, β-catenin, nuclear factor kappa B).

AREAS COVERED

The phenotype of SGK1 knockout mice is mild and SGK1 is apparently dispensible for basic functions. Excessive SGK1 expression and activity, however, contributes to the pathophysiology of several disorders, including hypertension, obesity, diabetes, thrombosis, stroke, fibrosing disease, infertility and tumor growth. A SGK1 gene variant (prevalence ∼ 3 - 5% in Caucasians and ∼ 10% in Africans) is associated with hypertension, stroke, obesity and type 2 diabetes. SGK1 inhibitors have been developed and shown to reduce blood pressure of hyperinsulinemic mice and to counteract tumor cell survival.

EXPERT OPINION

Targeting SGK1 may be a therapeutic option in several clinical conditions, including metabolic syndrome and tumor growth.

Loss of adenomatous poliposis coli-α3 integrin interaction promotes endothelial apoptosis in mice and humans

RATIONALE

Pulmonary hypertension (PH) is characterized by progressive elevation in pulmonary pressure and loss of small pulmonary arteries. As bone morphogenetic proteins promote pulmonary angiogenesis by recruiting the Wnt/β-catenin pathway, we proposed that β-catenin activation could reduce loss and induce regeneration of small pulmonary arteries (PAs) and attenuate PH.

OBJECTIVE

This study aims to establish the role of β-catenin in protecting the pulmonary endothelium and stimulating compensatory angiogenesis after injury.

METHODS AND RESULTS

To assess the impact of β-catenin activation on chronic hypoxia-induced PH, we used the adenomatous polyposis coli (Apc(Min/+)) mouse, where reduced APC causes constitutive β-catenin elevation. Surprisingly, hypoxic Apc(Min/+) mice displayed greater PH and small PA loss compared with control C57Bl6J littermates. PA endothelial cells isolated from Apc(Min/+) demonstrated reduced survival and angiogenic responses along with a profound reduction in adhesion to laminin. The mechanism involved failure of APC to interact with the cytoplasmic domain of the α3 integrin, to stabilize focal adhesions and activate integrin-linked kinase-1 and phospho Akt. We found that PA endothelial cells from lungs of patients with idiopathic PH have reduced APC expression, decreased adhesion to laminin, and impaired vascular tube formation. These defects were corrected in the cultured cells by transfection of APC.

CONCLUSIONS

We show that APC is integral to PA endothelial cells adhesion and survival and is reduced in PA endothelial cells from PH patient lungs. The data suggest that decreased APC may be a cause of increased risk or severity of PH in genetically susceptible individuals.

Enhanced suicidal erythrocyte death in mice carrying a loss-of-function mutation of the adenomatous polyposis coli gene

Loss-of-function mutations in human adenomatous polyposis coli (APC) lead to multiple colonic adenomatous polyps eventually resulting in colonic carcinoma. Similarly, heterozygous mice carrying defective APC (apc^Min/+) suffer from intestinal tumours. The animals further suffer from anaemia, which in theory could result from accelerated eryptosis, a suicidal erythrocyte death triggered by enhanced cytosolic Ca²⁺ activity and characterized by cell membrane scrambling and cell shrinkage. To explore, whether APC-deficiency enhances eryptosis, we estimated cell membrane scrambling from annexin V binding, cell size from forward scatter and cytosolic ATP utilizing luciferin–luciferase in isolated erythrocytes from apc^Min/+ mice and wild-type mice (apc^+/+). Clearance of circulating erythrocytes was estimated by carboxyfluorescein-diacetate-succinimidyl-ester labelling. As a result, apc^Min/+ mice were anaemic despite reticulocytosis. Cytosolic ATP was significantly lower and annexin V binding significantly higher in apc^Min/+ erythrocytes than in apc^+/+ erythrocytes. Glucose depletion enhanced annexin V binding, an effect significantly more pronounced in apc^Min/+ erythrocytes than in apc^+/+ erythrocytes. Extracellular Ca²⁺ removal or inhibition of Ca²⁺ entry with amiloride (1 mM) blunted the increase but did not abrogate the genotype differences of annexin V binding following glucose depletion. Stimulation of Ca²⁺-entry by treatment with Ca²⁺-ionophore ionomycin (10 μM) increased annexin V binding, an effect again significantly more pronounced in apc^Min/+ erythrocytes than in apc^+/+ erythrocytes. Following retrieval and injection into the circulation of the same mice, apc^Min/+ erythrocytes were more rapidly cleared from circulating blood than apc^+/+ erythrocytes. Most labelled erythrocytes were trapped in the spleen, which was significantly enlarged in apc^Min/+ mice. The observations point to accelerated eryptosis and subsequent clearance of apc^Min/+ erythrocytes, which contributes to or even accounts for the enhanced erythrocyte turnover, anaemia and splenomegaly in those mice.

Familial or genetic primary aldosteronism and Gordon syndrome

Salt-sensitive forms of hypertension have received considerable renewed attention in recent years. This article focuses on 2 main forms of salt-sensitive hypertension (familial or genetic primary aldosteronism [PA] and Gordon syndrome) and the current state of knowledge regarding their genetic bases. The glucocorticoid-remediable form of familial PA (familial hyperaldosteronism type I) is dealt with only briefly because it is covered in depth elsewhere.

Wnt/beta-catenin signaling: a novel target for therapeutic intervention of fibrotic kidney disease

Fibrosis of epithelial parenchymal organs and end-stage organ failure, the final common pathway of many progressive chronic diseases including chronic kidney disease, continue to increase worldwide and are a major determinant of morbidity and mortality. Fibrosis is an active biosynthetic healing response initiated to protect the tissue from injury through the timed release of proteins but leads to serious tissue damage when it becomes independent from the initiating stimulus. Massive deposition of extracellular matrix by accumulation of myofibroblasts and disruption of the normal tissue architecture are characteristic of tissue fibrosis. The highly conserved Wnt/beta-catenin signaling pathway is essential to embryonic development in general and kidney morphogenesis in particular by regulating the expression of target genes, most often through the transcription factor T cell factor (TCF) and/or lymphoid enhancer factor (LEF). Emerging evidence from studies of renal fibrosis suggests that altered Wnt/beta-catenin signaling is linked to the pathogenesis of renal fibrosis. The renoprotective properties of some currently available drugs might be attributable in part to inhibition of Wnt signaling. The development of orally active Wnt modulators will provide a potentially important pharmacological tool for further investigating the role of Wnt/beta-catenin signaling and might offer a novel therapeutic strategy in renal fibrosis.

Constitutive beta-catenin activation induces adrenal hyperplasia and promotes adrenal cancer development

Adrenocortical carcinoma is a rare but aggressive cancer with unknown aetiology. Constitutive activation of beta-catenin is the most frequent alteration in benign and malignant adrenocortical tumours in patients. Here, we show that constitutive activation of beta-catenin in the adrenal cortex of transgenic mice resulted in progressive steroidogenic and undifferentiated spindle-shaped cells hyperplasia as well as dysplasia of the cortex and medulla. Over a 17 months time course, transgenic adrenals developed malignant characteristics such as uncontrolled neovascularization and loco-regional metastatic invasion. These oncogenic events were accompanied by ectopic differentiation of glomerulosa at the expense of fasciculata cells, which caused primary hyperaldosteronism. Altogether these observations demonstrate that constitutively active beta-catenin is an adrenal oncogene which triggers benign aldosterone-secreting tumour development and promotes malignancy.