Characterization of steroidogenic enzyme expression in aldosterone-producing adenoma: a comparison with various human adrenal tumors

Cardiovascular risk assessments in patients with cortisol-producing adenoma: impact of clinical features and genetic characteristics

The causes of adrenal Cushing's syndrome (CS) encompass a wide spectrum of adrenal cortisol proliferations that exhibit clinical and molecular heterogeneity. The aims of our study were to investigate whether clinical and molecular heterogeneity influences endothelial function and metabolic abnormalities in patients with cortisol-producing adenoma (CPA). We retrospectively enrolled 25 patients with CPA and 45 patients with essential hypertension (EH). All CPAs were studied by direct sequencing of PRKACA. Flow-mediated vasodilation (FMD), an index of vascular endothelial function, was significantly lower in CS and subclinical CS (SCS) groups than in the EH group. FMD impairment did not differ significantly between CS and SCS groups. No differences in FMD were seen between PRKACA mutant and wild-type groups. FMD correlated negatively with hemoglobin A1c (HbA1c) in both PRKACA mutant and wild-type groups, as well as in CS and SCS groups. After adrenalectomy, systolic blood pressure (SBP) and HbA1c decreased significantly from baseline in the CS group, and SBP and low-density lipoprotein cholesterol (LDL-C) decreased significantly from baseline in the SCS group. While SBP and LDL-C decreased significantly from baseline in patients with wild-type PRKACA, only HbA1c decreased from baseline in patients harboring PRKACA mutations. Our data showed that patients with CPA have impaired endothelial function compared with EH patients and suggest the need for strict monitoring of atherosclerosis, even in patients with SCS or without PRKACA mutation.

Association of DNA methylation with steroidogenic enzymes in Cushing's adenoma

DNA methylation and demethylation regulate the transcription of genes. DNA methylation-associated gene expression of adrenal steroidogenic enzymes may regulate cortisol production in cortisol-producing adenoma (CPA). We aimed to determine the DNA methylation levels of all genes encoding steroidogenic enzymes involved in CPA. Additionally, the aims were to clarify the DNA methylation-associated gene expression and evaluate the difference of CPA genotype from others using DNA methylation data. Twenty-five adrenal CPA and six nonfunctioning adrenocortical adenoma (NFA) samples were analyzed. RNA sequencing and DNA methylation array were performed. The methylation levels at 118 methylation sites of the genes were investigated, and their methylation and mRNA levels were subsequently integrated. Among all the steroidogenic enzyme genes studied, CYP17A1 gene was mainly found to be hypomethylated in CPA compared to that in NFA, and the Benjamini-Hochberg procedure demonstrated that methylation levels at two sites in the CYP17A1 gene body were statistically significant. PRKACA mutant CPAs predominantly exhibited hypomethylation of CYP17A1 gene compared with the GNAS mutant CPAs. Inverse associations between CYP17A1 methylation in three regions of the gene body and its mRNA levels were observed in the NFAs and CPAs. In applying clustering analysis using CYP17A1 methylation and mRNA levels, CPAs with PRKACA mutation were differentiated from NFAs and CPAs with a GNAS mutation. We demonstrated that CPAs exhibited hypomethylation of the CYP17A1 gene body in CPA, especially in the PRKACA mutant CPAs. Methylation of CYP17A1 gene may influence its transcription levels.

Genotype-specific cortisol production associated with Cushing's syndrome adenoma with PRKACA mutations

The intracellular molecular mechanisms underlying the genotype of cortisol-producing adenoma (CPA) have not been fully determined. We analyzed gene expressions in CPA and the human adrenocortical cell line (HAC15 cells) with PRKACA mutation. Clustering analysis using a gene set associated with responses to cAMP revealed the possible differences between PRKACA mutant CPAs and GNAS and CTNNB1 mutant CPAs. The levels of STAR, CYP11A1, CYP17A1, CYP21A2, and FDX1 transcripts and cortisol levels per unit area in PRKACA mutant CPAs were significantly higher than those in GNAS mutant CPAs. PRKACA mutations led to an increase in steroidogenic enzyme expression and cortisol production in HAC15 cells. Transcriptome analysis revealed differences between PRKACA mutant CPAs and GNAS and CTNNB1 mutant CPAs. Cortisol production in PRKACA mutant CPAs is increased by the cAMP-PKA signaling pathway-mediated upregulation of steroidogenic enzymes transcription. The intracellular molecular mechanisms underlying these processes would be notably important in PRKACA mutant CPAs.

Adrenal Corticomedullary Mixed Tumor Associated With the FGFR4-G388R Variant

Adrenal corticomedullary mixed tumors (CMMTs) are extremely rare; with only 20 cases being reported to date, the pathogenesis has remained elusive. A 31-year-old woman developed gestational hypertension with psychiatric disturbances persistent to postpartum and was diagnosed with pheochromocytoma, for which adrenalectomy was performed. Histological findings showed mixed adrenocortical adenoma and pheochromocytoma. Double immunostaining of inhibin and INSM1 (insulinoma-associated protein 1) showed that the 2 tumor components had distinct functional properties. Exome analysis of peripheral leukocytes and tumor (singular, as anatomically it is only 1 mass) revealed a homozygous germline FGFR4-G388R variant. As a readout of the variant, serine phosphorylation of signal transducer and activator of transcription 3 (STAT3) was detected only in the nucleus of adrenocortical adenoma component but not in the pheochromocytoma component. No tyrosine phosphorylation of STAT3 was detected. We report a case of CMMT with the germline FGFR4-G388R variant. Although additional studies are required, our immunohistochemical analysis suggests that the variant may play a role in the development of the adrenocortical component within the pheochromocytoma, leading to CMMT.

MiR-193a-3p functions as a tumour suppressor in human aldosterone-producing adrenocortical adenoma by down-regulating CYP11B2

The mechanism of aldosterone-producing adrenocortical adenoma (APA) pathogenesis and the role of microRNAs (miRNAs) in APA pathogenesis have not been completely clarified. We examined the expression and function of miR-140-3p, miR-193a-3p and miR-22-3p, which have binding sites in CYP11B2. Expression of miRNAs and CYP11B2 mRNA was measured by quantitative reverse transcription PCR (qRT-PCR). Cell proliferation was monitored by colorimetric analysis, and cell apoptosis and cell cycle progression were analysed by flow cytometry. ELISA was carried out to detect aldosterone levels in cell culture supernatants. Luciferase reporter assays, qRT-PCR and Western blotting were performed to identify CYP11B2 as a target of miR-193a-3p. Of the three miRNAs examined, miR-193a-3p exhibited a significant decrease and CYP11B2 mRNA exhibited a significant increase in expression in APA compared with adjacent normal adrenal gland tissue. Transfection of miR-193a-3p mimic into the human adrenocortical cell line H295R showed that elevated miR-193a-3p expression inhibits proliferation and aldosterone secretion, induces G1-phase arrest and promotes apoptosis in H295R cells. Furthermore, in luciferase reporter assays, overexpression of miR-193a-3p in H295R cells significantly reduced the luciferase activity of the wild-type CYP11B2 3'-UTR construct, which could be reversed by mutation of the miR-193a-3p-binding site. Moreover, miR-193a-3p overexpression downregulated CYP11B2 mRNA and protein expression. Finally, overexpression of CYP11B2 diminished the effects of miR-193a-3p on H295R cells. Taken together, our results suggest that CYP11B2 levels may be modulated by miR-193a-3p in APA, which could explain, at least partially, why downregulation of miR-193a-3p during APA formation may promote cell growth and suppress apoptosis.

Clock genes and salt-sensitive hypertension: a new type of aldosterone-synthesizing enzyme controlled by the circadian clock and angiotensin II

With the current societal norm of shiftwork and long working hours, maintaining a stable daily life is becoming very difficult. An irregular lifestyle disrupts circadian rhythms, resulting in the malfunction of body physiology and ultimately leading to lifestyle-related diseases, including hypertension. By analyzing completely arrhythmic Cry1/Cry2 double-knockout (Cry-null) mice, we found salt-sensitive hypertension accompanied by hyperaldosteronism. On the basis of a DNA microarray analysis of the adrenal gland and subsequent biochemical analyses, we discovered that Hsd3b6/HSD3B1, a subtype of 3β-HSD, is markedly overexpressed in aldosterone-producing cells in the Cry-null adrenal cortex. In addition, we found that Hsd3b6/HSD3B1, which converts pregnenolone to progesterone, is a clock-controlled gene and might also be a key enzyme for the regulation of aldosterone biosynthesis, in addition to the previously established CYP11B2, which synthesizes aldosterone from deoxycorticosterone. Importantly, angiotensin II induces HSD3B1 via the transcription factor NGFIB in human adrenocortical H295R cells, similarly to CYP11B2. As HSD3B1 levels are abnormally high in the adrenal aldosterone-producing cells of idiopathic hyperaldosteronism (IHA), the temporal component of this system in the pathophysiology of IHA is a promising area for future research.

Normoaldosteronemic aldosterone-producing adenoma: immunochemical characterization and diagnostic implications

BACKGROUND

A high aldosterone-renin ratio (ARR) is commonly used to identify primary aldosteronism, but the ARR is high when renin is low, even if plasma aldosterone concentration values are normal, suggesting the existence of 'normoaldosteronemic' primary aldosteronism. However, most such cases did not undergo adrenalectomy; moreover, because of the lack of antibody for the human CYP11B2 (aldosterone synthase), conclusive demonstration of a normoaldosteronemic aldosterone-producing adenoma was not possible thus far.

METHOD

In 2003, a lady presented with severe hypertension a right adrenal nodule, low renin, high ARR, but normal plasma aldosterone concentration. As adrenal vein sampling showed lateralized aldosterone secretion, she underwent left adrenalectomy, which consistently normalized blood pressure (BP) and renin during 11-year follow-up.

RESULT AND CONCLUSION

The development of a novel monoclonal antibody for the human CYP11B2 in 2014 allowed immunochemically identification of a CYP11B2-positive adenoma in the resected adrenal. Moreover, this case unequivocally demonstrates for the first time the existence of normoaldosteronemic aldosterone-producing adenoma, which suggests that many cases of 'low renin-essential hypertension' might instead have a surgically curable form of primary aldosteronism.

Estimation of the Mechanism of Adrenal Action of Endocrine-Disrupting Compounds Using a Computational Model of Adrenal Steroidogenesis in NCI-H295R Cells

Adrenal toxicity is one of the major concerns in drug development. To quantitatively understand the effect of endocrine-active compounds on adrenal steroidogenesis and to assess the human adrenal toxicity of novel pharmaceutical drugs, we developed a mathematical model of steroidogenesis in human adrenocortical carcinoma NCI-H295R cells. The model includes cellular proliferation, intracellular cholesterol translocation, diffusional transport of steroids, and metabolic pathways of adrenal steroidogenesis, which serially involve steroidogenic proteins and enzymes such as StAR, CYP11A1, CYP17A1, HSD3B2, CYP21A2, CYP11B1, CYP11B2, HSD17B3, and CYP19A1. It was reconstructed in an experimental dynamics of cholesterol and 14 steroids from an in vitro steroidogenesis assay using NCI-H295R cells. Results of dynamic sensitivity analysis suggested that HSD3B2 plays the most important role in the metabolic balance of adrenal steroidogenesis. Based on differential metabolic profiling of 12 steroid hormones and 11 adrenal toxic compounds, we could estimate which steroidogenic enzymes were affected in this mathematical model. In terms of adrenal steroidogenic inhibitors, the predicted action sites were approximately matched to reported target enzymes. Thus, our computer-aided system based on systems biological approach may be useful to understand the mechanism of action of endocrine-active compounds and to assess the human adrenal toxicity of novel pharmaceutical drugs.

Extraordinarily high aldosterone, 901.0 ng/dL, in a patient with primary aldosteronism: an insight into the underlying mechanism

A 43-yr-old hypertensive male was admitted due to hypokalemia (1.8 mEq/L) and renal dysfunction (eGFR, 20.0 mL/min/1.73 m2). His plasma aldosterone was 901.0 ng/dL, plasma renin activity 5.7 ng/mL/hr, and aldosterone/renin activity ratio 158. Angiotensin II (AII) was 0.7 pg/mL, ACTH <1.0 pg/mL, and cortisol 21.6 μg/dL. Liquid chromatography-tandem mass spectrometry analysis showed that aldosterone (104 times the control) as well as its precursors were significantly elevated in the patient's plasma. A left adrenal (4-cm-diameter) tumor with 131I-Adosterol uptake was found and removed. Four days later, plasma aldosterone and renin activity had dropped to 7.73 ng/dL and 1.6 ng/mL/hr, respectively. However, they rose to 24.0 ng/dL and 10.9 ng/mL/hr, respectively, by Day 102. Nevertheless, magnetic resonance angiography found no evidence of a renovascular lesion. The tumor was a benign adrenocortical adenoma composed predominantly of clear cells positive for 17α-hydroxylase, [hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerases], and aldosterone synthase. A quantitative real-time polymerase chain reaction analysis of the tumor cells revealed that expression of the gene encoding aldosterone synthase was 85 times the control level. In addition, the tumor cells harbored G151R mutation of the inward rectifying potassium channel subfamily j, member 5 gene. The striking overexpression of aldosterone synthase by the tumor cells was considered the primary mechanism for the extravagant overproduction of aldosterone in this case. This overexpression may have resulted from integration of signals from AII and forced membrane depolarization due to the potassium channel mutation.

Steroid Hormone Production in Patients with Aldosterone Producing Adenomas

Primary aldosteronism encompasses 2 major underlying causes: (1) aldosterone producing adenoma and (2) bilateral adrenal hyperplasia. In addition to the aldosterone excess, increased production of other compounds of the steroidogenic pathways may be involved. Until recently, most studies examined the production of steroids other than aldosterone in tumor tissue, urine, or peripheral plasma samples, but several new studies have also addressed steroid levels in adrenal venous blood samples using liquid chromatography tandem mass spectrometry. Plasma and tissue levels of several precursors of aldosterone with mineralocorticoid activity are higher in patients with aldosterone producing adenomas than in those with bilateral hyperplasia. These include corticosterone, deoxycorticosterone, and their 18-hydroxylated metabolites. Similarly, urinary, peripheral, and adrenal venous concentrations of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol are higher in patients with aldosterone producing adenomas than in bilateral hyperplasia. Differences in the pathophysiology and in clinical and biochemical phenotypes caused by aldosterone producing adenomas and bilateral adrenal hyperplasia may be related to the differential expression of steroidogenic enzymes, and associated to specific underlying somatic mutations. Correct appreciation of differences in steroid profiling between aldosterone producing adenomas and bilateral adrenal hyperplasia may not only contribute to a better understanding of the pathogenesis of primary aldosteronism but may also be helpful for future subtyping of primary aldosteronism.

An update on novel mechanisms of primary aldosteronism

Primary aldosteronism (PA) is the most common and curable form of secondary hypertension. It is caused in the majority of cases by either unilateral aldosterone overproduction due to an aldosterone-producing adenoma (APA) or by bilateral adrenal hyperplasia. Recent advances in genome technology have allowed researchers to unravel part of the genetic abnormalities underlying the development of APA and familial hyperaldosteronism. Recurrent somatic mutations in genes coding for ion channels (KCNJ5 and CACNA1D) and ATPases (ATP1A1 and ATP2B3) regulating intracellular ionic homeostasis and cell membrane potential have been identified in APA. Similar germline mutations of KCNJ5 were identified in a severe familial form of PA, familial hyperaldosteronism type 3 (FH3), whereas de novo germline CACNA1D mutations were found in two cases of hyperaldosteronism associated with a complex neurological disorder. These results have allowed a pathophysiological model of APA development to be established. This model involves modifications in intracellular ionic homeostasis and membrane potential, accounting for ∼50% of all tumors, associated with specific gender differences and severity of PA. In this review, we describe the different genetic abnormalities associated with PA and discuss the mechanisms whereby they lead to increased aldosterone production and cell proliferation. We also address some of the foreseeable consequences that genetic knowledge may contribute to improve diagnosis and patient care.

A novel KCNJ5-insT149 somatic mutation close to, but outside, the selectivity filter causes resistant hypertension by loss of selectivity for potassium

CONTEXT

Understanding the function of the KCNJ5 potassium channel through characterization of naturally occurring novel mutations is key for dissecting the mechanism(s) of autonomous aldosterone secretion in primary aldosteronism.

OBJECTIVE

We sought for such novel KCNJ5 channel mutations in a large database of patients with aldosterone-producing adenomas (APAs).

METHODS

We discovered a novel somatic c.446insAAC insertion, resulting in the mutant protein KCNJ5-insT149, in a patient with severe drug-resistant hypertension among 195 consecutive patients with a conclusive diagnosis of APA, 24.6% of whom showed somatic KCNJ5 mutations. By site-directed mutagenesis, we created the mutated cDNA that was transfected, along with KCNJ3 cDNA, in mammalian cells. We also localized CYP11B2 in the excised adrenal gland with immunohistochemistry and immunofluorescence using an antibody specific to human CYP11B2. Whole-cell patch clamp recordings, CYP11B2 mRNA, aldosterone measurement, and molecular modeling were performed to characterize the novel KCNJ5-insT149 mutation.

RESULTS

Compared with wild-type and mock-transfected adrenocortical cells, HAC15 cells expressing the mutant KCNJ5 showed increased CYP11B2 expression and aldosterone secretion. Mammalian cells expressing the mutated KCNJ5-insT149 channel exhibited a strong Na(+) inward current and, in parallel, a substantial rise in intracellular Ca(2+), caused by activation of voltage-gated Ca(2+) channels and reduced Ca(2+) elimination by Na(+)/Ca(2+) exchangers, as well as an increased production of aldosterone.

CONCLUSIONS

This novel mutation shows pathological Na(+) permeability, membrane depolarization, raised cytosolic Ca(2+), and increased aldosterone synthesis. Hence, a novel KCNJ5 channelopathy located after the pore α-helix preceding the selectivity filter causes constitutive secretion of aldosterone with ensuing resistant hypertension in a patient with a small APA.

Adrenal CYP11B1/2 expression in primary aldosteronism: immunohistochemical analysis using novel monoclonal antibodies

CYP11B1 and CYP11B2 play pivotal roles in adrenocorticosteroids synthesis. We performed semi-quantitative immunohistochemical analysis of these proteins in adrenals from patients with primary aldosteronism using novel monoclonal antibodies. Clusters of cortical cells positive for CYP11B2 were detected in the zona glomerulosa (ZG) of normal adrenal gland (NA), idiopathic hyperaldosteronism (IHA) and the adjacent adrenal of aldosterone-producing adenoma (APA). In APA, heterogenous immunolocalization of CYP11B2 and diffuse immunoreactivity of CYP11B1 were detected in tumor cells, respectively. The relative immunoreactivity of CYP11B2 in the ZG of adjacent adrenal of APA was significantly lower than that of NA, IHA and APA tumor cells, suggestive of suppressed aldosterone biosynthesis in these cells. These findings did indicate the regulatory mechanisms of aldosterone biosynthesis were different between normal/hyperplastic and neoplastic aldosterone-producing cells in human adrenals. CYP11B2 immunoreactivity in the ZG could also serve as a potential immunohistochemical marker differentiating morphologically hyperplastic ZG of IHA and APA adjacent adrenal.

Development of monoclonal antibodies against human CYP11B1 and CYP11B2

1. The final enzymes in the biosynthesis of aldosterone and cortisol are by the cytochrome P450 CYP11B2 and CYP11B1, respectively. The enzymes are 93% homologous at the amino acid level and specific antibodies have been difficult to generate. 2. Mice and rats were immunized with multiple peptides conjugated to various immunogenic proteins and monoclonal antibodies were generated. The only peptide sequences that generated specific antibodies were amino acids 41-52 for the CYP11B2 and amino acids 80-90 for the CYP11B1 enzyme. 3. The mouse monoclonal CYP11B2-41 was specific and sensitive for use in western blots and produced specific staining of the zona glomerulosa of normal adrenal glands. The rat monoclonal CYP11B1-80 also detected a single band by western blot and detected only the zona fasciculata. Triple immunofluorescence of the adrenal demonstrated that the CYP11B1 and the CYP11B2 did not co-localize, while as expected the CYP11B1 co-localized with the 17α-hydroxylase.

GATA6, SF1, NGFIB and DAX1 in the remodeled subcapsular zones in primary aldosteronism

The majority of the cases diagnosed as primary aldosteronism (PA) are caused by aldosterone-producing adenoma (APA) or idiopathic hyperaldosteronism (IHA). Histopathologically, both IHA and adjacent adrenal glands of APA demonstrate remodeled subcapsular zone (RSZ) but these zones in two disorders are markedly different in terms of steroidogenesis. 3β-Hydroxysteroid dehydrogenase/Δ⁵-Δ⁴ isomerase (3β-HSD) expression has been known to be activated synergistically by GATA6 and SF1, and repressed by DAX1 through abolishing the activation. Nerve growth factor-induced clone B (NGFIB) is also known as one of the transcription factors to bind to and activate 3β-HSD promoter. The results of our immunohistochemical analysis demonstrated the expression levels of 3β-HSD in RSZ of IHA were higher than in RSZ of adjacent adrenals of APA, while those in the zona glomerulosa (ZG) of normal adrenal gland (NA) were in between these two RSZs. The expression levels of GATA6, SF1 and DAX1 did not prominently differ among these three types of adrenals, especially between in RSZs of IHA and APA cases, indicating the marked difference of 3β-HSD expression was unlikely to be explained by the levels of these three factors. However, the levels of NGFIB expression were significantly higher in RSZ of IHA than in RSZ of adjacent adrenals of APA and the ZG of NA (P<0.05), which may partly account for the expression levels of 3β-HSD among the three groups of adrenals. These results may imply NGFIB plays important roles in the marked differences in steroidogenic functions in the two distinct types of RSZ of PA cases.

Vitamin D receptor, an important transcription factor associated with aldosterone-producing adenoma

OBJECTIVE

To explore the endocrine mechanisms of aldosterone-producing adenoma (APA) by using the microarray expression profiles of normal and APA samples.

METHODS

The gene expression profile GSE8514 was downloaded from Gene Expression Omnibus database, including samples from normal adrenals (n = 5) and APAs (n = 10). The differentially expressed genes (DEGs) were identified by samr package and endocrine DEGs were obtained according to Clinical Genome Database. Then, functional enrichment analysis of screened DEGs was performed by DAVID (Database for Annotation, Visualization and Integrated Discovery). Finally, a regulatory network was constructed to screen endocrine genes related with adrenal dysfunction and pathway enrichment analysis for the constructed network was performed.

RESULTS

A total of 2149 DEGs were identified including 379 up- and 1770 down-regulated genes. And 26 endocrine genes were filtered from the DEGs. Furthermore, the down-regulated DEGs are mainly related to protein kinase cascade, response to molecule of bacterial origin, response to lipopolysaccharide, cellular macromolecule catabolic process and macromolecule catabolic process, while the up-regulated DEGs are related with regulation of ion transport. The target genes of VDR (vitamin D receptor), one of the three endocrine genes differentially expressed in the regulatory network, were endocrine genes including CYP24A1 (25-hydroxyvitamin D-24-hydroxylase) and PTH (parathyroid hormone). Three pathways may be associated with APA pathogenesis including cytokine-cytokine receptor interaction, pathways in cancer and autoimmune thyroid disease.

CONCLUSION

The VDR is the most significant transcription factor and related endocrine genes might play important roles in the endocrine mechanisms of APA.