Analysis of mRNA expression for steroidogenic enzymes in the remaining adrenal cortices attached to adrenocortical adenomas

Chronic activation of adrenal Gq signaling induces Cyp11b2 expression in the zona fasciculata and hyperaldosteronism

Hyperaldosteronism is often associated with inappropriate aldosterone production and aldosterone synthase (Cyp11b2) expression. Normally, Cyp11b2 expression is limited to the adrenal zona glomerulosa (ZG) and regulated by angiotensin II which signals through Gq protein-coupled receptors. As cells migrate inwards, they differentiate into 11β-hydroxylase-expressing zona fasciculata (ZF) cells lacking Cyp11b2. The mechanism causing ZG-specific aldosterone biosynthesis is still unclear. We investigated the effect of chronic Gq signaling using transgenic mice with a clozapine N-oxide (CNO)-activated human M3 muscarinic receptor (DREADD) coupled to Gq (hM3Dq) that was expressed throughout the adrenal cortex. CNO raised circulating aldosterone in the presence of a high sodium diet with greater response seen in females compared to males. Immunohistochemistry and transcriptomics indicated disrupted zonal Cyp11b2 expression while Wnt signaling remained unchanged. Chronic Gq-DREADD signaling also induced an intra-adrenal RAAS in CNO-treated mice. Chronic Gq signaling disrupted adrenal cortex zonal aldosterone production associated with ZF expression of Cyp11b2.

CYP17A1 exhibits 17αhydroxylase/17,20-lyase activity towards 11β-hydroxyprogesterone and 11-ketoprogesterone metabolites in the C11-oxy backdoor pathway

Cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1) plays a pivotal role in the regulation of adrenal and gonadal steroid hormone biosynthesis. More recent studies highlighted the enzyme's role in the backdoor pathway leading to androgen production. Increased CYP17A1 activity in endocrine disorders and diseases are associated with elevated C₂₁ and C₁₉ steroids which include 17α-hydroxyprogesterone and androgens, as well as C11-oxy C₂₁ and C11-oxy C₁₉ steroids. We previously reported that 11β-hydroxyprogesterone (11OHP4), 21-deoxycortisol (21dF) and their keto derivatives are converted by 5α-reductases and hydroxysteroid dehydrogenases yielding C₁₉ steroids in the backdoor pathway. In this study the 17α-hydroxylase and 17,20-lyase activity of CYP17A1 towards the unconventional C11-oxy C₂₁ steroid substrates and their 5α- and 3α,5α-reduced metabolites was investigated in transfected HEK-293 cells. CYP17A1 catalysed the 17α-hydroxylation of 11OHP4 to 21dF and 11-ketoprogesterone (11KP4) to 21-deoxycortisone (21dE) with negligible hydroxylation of their 5α-reduced metabolites while no lyase activity was detected. The 3α,5α-reduced C11-oxy C₂₁ steroids-5α-pregnan-3α,11β-diol-20-one (3,11diOH-DHP4) and 5α-pregnan-3α-ol-11,20-dione (alfaxalone) were rapidly hydroxylated to 5α-pregnan-3α,11β,17α-triol-20-one (11OH-Pdiol) and 5α-pregnan-3α,17α-diol-11,20-dione (11K-Pdiol), with the lyase activity subsequently catalysing to conversion to the C11-oxy C₁₉ steroids, 11β-hydroxyandrosterone and 11-ketoandrosterone, respectively. Docking of 11OHP4, 11KP4 and the 5α-reduced metabolites, 5α-pregnan-11β-ol-3,20-dione (11OH-DHP4) and 5α-pregnan-3,11,20-trione (11K-DHP4) with human CYP17A1 showed minimal changes in the orientation of these C11-oxy C₂₁ steroids in the active pocket when compared with the binding of progesterone suggesting the 17,20-lyase is impaired by the C11-hydroxyl and keto moieties. The structurally similar 3,11diOH-DHP4 and alfaxalone showed a greater distance between C17 and the heme group compared to the natural substrate, 17α-hydroxypregnenolone potentially allowing more orientational freedom and facilitating the conversion of the C11-oxy C₂₁ to C11-oxy C₁₉ steroids. In summary, our in vitro assays showed that while CYP17A1 readily hydroxylated 11OHP4 and 11KP4, the enzyme was unable to catalyse the 17,20-lyase reaction of these C11-oxy C₂₁ steroid products. Although CYP17A1 exhibited no catalytic activity towards the 5α-reduced intermediates, once the C4-C5 double bond and the keto group at C3 were reduced, both the hydroxylation and lyase reactions proceeded efficiently. These findings show that the C11-oxy C₂₁ steroids could potentially contribute to the androgen pool in tissue expressing steroidogenic enzymes in the backdoor pathway.

GPER-1 and estrogen receptor-β ligands modulate aldosterone synthesis

Fertile women have lower blood pressure and cardiovascular risk than age-matched men, which suggests that estrogens exert cardiovascular protective effects. However, whether 17 β-estradiol (E2) blunts aldosterone secretion, and thereby affects the gender dimorphism of blood pressure, is unknown. We therefore sought for the estrogen receptor (ER) subtypes in human adrenocortical tissues ex vivo by performing gene and protein expression studies. We also investigated the effect of E2 on aldosterone synthesis and the involved receptors through in vitro functional experiments in the adrenocortical cells HAC15. We found that in the human adrenal cortex and aldosterone-producing adenoma cells, the most expressed ERs were the ERβ and the G protein-coupled receptor-1 (GPER-1), respectively. After selective ERβ blockade, E2 (10 nmol/L) markedly increased both the expression of aldosterone synthase and the production of aldosterone (+5- to 7-fold vs baseline, P < .001). Under the same condition, the GPER-1 receptor agonist 1-[4-(6-bromo-benzo (1, 3)dioxol-5-yl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c] quinolin-8-yl]-ethanone (G-1) (10 nmol/L) mimicked this effect, which was abrogated by cotreatment with either the GPER-1 receptor antagonist (3aS*,4R*,9bR*)-4-(6-Bro-mo-1,3-benzodioxol-5-yl)-3a,4,5,9b-3H-cyclopenta[c]quinoline (G-15), or a selective protein kinase A inhibitor 8-Bromo-2-monobutyryladenosine-3,5-cyclic mono-phosphorothioate, Rp-isomer. Silencing of the ERβ significantly raised aldosterone synthase expression and aldosterone production. Conversely, silencing of the GPER-1 lowered aldosterone synthase gene and protein expression. Moreover, it blunted the stimulatory effect of E2 on aldosterone synthase that was seen during ERβ blockade. These results support the conclusion that in humans, E2 inhibits aldosterone synthesis by acting via ERβ. Pharmacologic disinhibition of ERβ unmasks a potent secretagogue effect of E2 that involves GPER-1 and protein kinase A signaling.

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.

[Function-preserving adrenalectomy for adrenal tumors]

Organ preserving resection (subtotal adrenalectomy) or adrenocortical autotransplantation can preserve adrenocortical stress capacity in bilateral adrenal surgery. After adrenocortical autotransplantation approximately 30% of patients do not need exogenous steroids. Organ preserving surgery avoids steroid supplementation in more than 80% of cases. After organ preserving resections in secondary or familial diseases, however, there is a relevant risk of recurrent disease: the rate of ipsilateral recurrence in familial pheochromocytoma is approximately 20% during a follow-up of 20 years. Routine administration of exogenous steroids should be avoided after subtotal adrenalectomy as functional restitution of the residual tissue might be disturbed. Approximately 80% of patients, however, present with impaired adrenocortical stress capacity directly after surgery. Within a few weeks some 80% of patients show a sufficient functional restitution of the adrenocortical stress capacity. Organ preserving adrenal surgery should be performed endoscopically. The adrenal remnant should not be devascularized; the adrenal vein, however, can be divided without functional consequences. About one third of a normal adrenal gland usually provides sufficient adrenocortical function.

Clinical characteristics of primary hyperaldosteronism due to adrenal microadenoma

An increasing number of patients are being diagnosed with primary aldosteronism (PA) due to aldosterone-producing macroadenoma (APA). However, there are only limited data available on the clinical characteristics of PA that are associated with adrenal microadenoma. Of the 55 patients that were diagnosed with PA in our study, 22 patients showed a unilateral adrenal over-production of aldosterone. The histopathology of the surgically removed adrenal tissues led to six patients being diagnosed with microadenoma, and the clinical features of microadenoma, macroadenoma and idiopathic hyperaldosteronism (IHA) were studied. The expression levels of CYP11B2, CYP17, CYP21 and 3β-hydroxysteroid dehydrogenase 2 (HSD3B2) mRNA in the adrenal cortices (n=5 and 6, respectively) that remained attached to the adrenal microadenomas or macroadenomas were examined by real time-PCR and then compared to the expression levels in the adrenal cortices (n=5) of non-functioning adrenal adenomas (NF). The patients with microadenoma (n=6) had significantly higher diastolic blood pressure than the patients with macroadenoma (n=16) or IHA (n=33) (p<0.05). The systolic blood pressure, plasma aldosterone concentration, serum potassium level and renal function did not differ between the PA sub-groups. The levels of CYP11B2 and CYP17 mRNA were significantly increased in the adjacent tissues of microadenomas, as compared with macroadenomas or NF (p<0.05), whereas no significant differences in the CYP21 and HSD3B2 mRNA levels were found between the PA sub-groups. The tumor size did not influence the clinical characteristics of APA. The non-tumor portions of the microadenomas showed marked and sustained CYP11B2 mRNA expression under the suppressed renin-angiotensin system. We suggest that an increased number of microadenomas should be sampled, and the immunohistochemistry for steoridogenic enzymes should be investigated to clarify the etiology of microadenoma.

Progress in primary aldosteronism: present challenges and perspectives

Primary Aldosteronism (PA) is a disorder of the adrenal zona glomerulosa (ZG) in which aldosterone secretion is increased and is relatively autonomous of normal regulatory mechanisms. A recent conference in Munich organized by Prof. Reincke addressed advances and challenges related to the screening, diagnosis, and identification of uni- and bilateral involvement of the diseased adrenal of PA. Some infrequently addressed issues are described herein. We postulate that most cases of PA are due to the activation by unknown mechanisms of subset of cells resulting in the formation of a multiple foci or nodules of hyperactive zona glomerulosa cells. This implies that one or several yet unidentified stimuli can drive aldosterone overproduction, as well as the proliferation of aldosterone-producing cells. Current diagnostic procedures allow to determine whether inappropriate aldosterone production is driven by one or both adrenal glands and thus to establish optimal treatment.

Cushing's syndrome by left adrenocortical adenoma synchronously associated with primary aldosteronism by right adrenocortical adenoma: report of a case

Synchronous associations of Cushing's syndrome (CS) and primary aldosteronism (PA) with multiple adrenocortical adenomas secreting each hormone independently have rarely been reported. Herein, we describe a unique case of PA associated with CS with detailed clinical and pathological investigations. Bilateral adrenal masses with clinical symptoms of CS and PA were found in a 43-year-old woman. Venous sampling demonstrated excess secretion of cortisol, and aldosterone from right, and left tumor, respectively. A bilateral laparoscopic partial adrenalectomy was undergone. The right adrenal tumor (3 cm) was yellow in color with abundant lipofuscin granules, and was composed of both eosinophilic compact cells and clear cells. In situ hybridization showed that both mRNAs for HSD3B2 and CYP17A1 were strongly expressed in the tumor, suggesting cortisol synthesis. Left adrenal tumor (2.4 cm) was golden-yellow in color, and composed of clear cells only. Expression of HSD3B2 and CYP11B mRNAs were observed in the tumor compatible with the aldosterone synthesis. Furthermore, minute nodules were found at the surface of normal-appearing cortex on both sides of the adrenal glands, and the expression of HSD3B2 and CYP11B mRNAs was clearly demonstrated within the nodules, indicating aldosterone synthesis. We diagnosed that the present case had 1) cortisol-producing right adrenocortical adenoma, 2) aldosterone producing left adrenocortical adenoma, and 3) cortical minute nodules with aldosterone production in both adrenal glands compatible with idiopathic adrenal hyperplasia. We reviewed the cases reported, and discussed the significance of the minute nodules in the adrenal cortex, often found in association with the adrenocortical adenoma.

Primary aldosteronism with aldosterone-producing adenoma consisting of pure zona glomerulosa-type cells in a pregnant woman

Aldosterone-producing adenoma (APA) consisting of pure zona glomerulosa (ZG)-type cells is extremely rare, and primary aldosteronism complicated by pregnancy is also rare. We report a case of APA discovered in a 32-year-old pregnant woman who visited our hospital for hypertension and hypokalemia at 26 weeks gestation. Elevated plasma aldosterone concentration and hypokalemia were observed, and an magnetic resonance imaging scan demonstrated a right adrenal mass. A laparoscopic adrenalectomy was performed because of refractory hypokalemia. Pathologically, the adrenal mass was diagnosed as APA, and in addition to the cytological features, in situ hybridization and real-time polymerase chain reaction proved that all the component cells were ZG-type cells. The cells also showed estrogen receptor beta immunoreactivity and melanocortin 2 receptor mRNA expression, suggesting that estrogen and/or ACTH might be related to the proliferation of APA cells during pregnancy. Our case is the first report of APA consisting of ZG-type cells discovered during pregnancy.