Variable expression of the V1 vasopressin receptor modulates the phenotypic response of steroid-secreting adrenocortical tumors

Metabolic effects of vasopressin in pathophysiology of diabetic kidney disease

The diabetic kidney disease (DKD) is the major cause of the chronic kidney disease (CKD). Enhanced plasma vasopressin (VP) levels have been associated with the pathophysiology of DKD and CKD. Stimulation of VP release in DKD is caused by glucose-dependent reset of the osmostat leading to secondary pathophysiologic effects mediated by distinct VP receptor types. VP is a stress hormone exhibiting the antidiuretic action in the kidney along with broad adaptive effects in other organs. Excessive activation of the vasopressin type 2 (V2) receptor in the kidney leads to glomerular hyperfiltration and nephron loss, whereas stimulation of vasopressin V1a or V1b receptors in the liver, pancreas, and adrenal glands promotes catabolic metabolism for energy mobilization, enhancing glucose production and aggravating DKD. Increasing availability of selective VP receptor antagonists opens new therapeutic windows separating the renal and extra-renal VP effects for the concrete applications. Improved understanding of these paradigms is mandatory for further drug design and translational implementation. The present concise review focuses on metabolic effects of VP affecting DKD pathophysiology.

Aldosterone is Aberrantly Regulated by Various Stimuli in a High Proportion of Patients with Primary Aldosteronism

CONTEXT

In primary aldosteronism (PA), aldosterone secretion is relatively independent of the renin-angiotensin system, but can be regulated by several other stimuli.

OBJECTIVE

To evaluate aldosterone response to several stimuli in a series of patients with PA secondary either to bilateral adrenal hyperplasia (BAH) or unilateral aldosterone-producing adenoma (APA).

DESIGN AND SETTING

Prospective cohort study conducted in a university teaching hospital research center.

PATIENTS

Forty-three patients with confirmed PA and subtyped by adrenal vein sampling (n = 39) were studied, including 11 with BAH, 28 with APA, and 4 with undefined etiology. We also studied 4 other patients with aldosterone and cortisol cosecretion.

INTERVENTIONS

We systematically explored aberrant regulation of aldosterone using an in vivo protocol that included the following stimulation tests performed over 3 days under dexamethasone suppression: upright posture, mixed meal, adrenocorticotropin (ACTH) 1-24, gonadotropin-releasing hormone (GnRH), vasopressin, and serotonin R4 agonist.

MAIN OUTCOME MEASURES

Positive response was defined as >50% renin or ACTH-independent increase in plasma aldosterone/cortisol concentration following the various stimulation tests.

RESULTS

Renin-independent aldosterone secretion increased in response to several aberrant stimuli (upright posture, GnRH) in up to 83% of patients with APA or BAH in whom ACTH 1-24 and HT4R agonists also produced aldosterone oversecretion in all patients. The mean significant aberrant responses per patient was similar in BAH (4.6) and in APA (4.0).

CONCLUSIONS

Aldosterone secretion in PA is relatively autonomous from the renin-angiotensin system, but is highly regulated by several other stimuli, which contributes to the large variability of aldosterone levels in PA patients.

A case of Adrenocoricotrophic hormone -independent bilateral adrenocortical macronodular hyperplasia concomitant with primary aldosteronism

Background

Adrenocoricotrophic hormone (ACTH) – independent bilateral adrenocortical macronodular hyperplasia (AIMAH) is a rare cause of Cushing’s syndrome, and is characterized by bilateral adrenal hyperplasia. However, Primary aldosteronism (PA) is a relatively common adrenal disease.

Case presentation

A 56-year-old man who has been treated hypertension and diabetes mellitus was detected low plasma potassium level with an elevated level of plasma aldosterone concentration and bilateral adrenal swelling. Endocrinological examinations showed autonomous secretion of cortisol and aldosterone, with suppression of plasma ACTH level and renin activity. A selective adrenal venous sampling demonstrated that left adrenal gland was responsible for aldosterone hypersecretion. He was diagnosed preclinical Cushing’s syndrome due to ACTH – independent bilateral adrenocortical macronodular hyperplasia (AIMAH) associated with aldosterone producing adenoma of the left adrenal gland. A laparoscopic left adrenalectomy was performed.

Conclusion

The resected adrenal specimen histologically consisted with a diagnosis of AIMAH. Moreover, tiny cell clusters positive immunostaining for aldosterone synthase was revealed. This is a rare case of AIMAH accompanied by preclinical Cushing’s syndrome and primary aldosteronism.

Cell-to-cell communication in bilateral macronodular adrenal hyperplasia causing hypercortisolism

It has been well established that, in the human adrenal gland, cortisol secretion is not only controlled by circulating corticotropin but is also influenced by a wide variety of bioactive signals, including conventional neurotransmitters and neuropeptides, released within the cortex by various cell types such as chromaffin cells, neurons, cells of the immune system, adipocytes, and endothelial cells. These different types of cells are present in bilateral macronodular adrenal hyperplasia (BMAH), a rare etiology of primary adrenal Cushing's syndrome, where they appear intermingled with adrenocortical cells in the hyperplastic cortex. In addition, the genetic events, which cause the disease, favor abnormal adrenal differentiation that results in illicit expression of paracrine regulatory factors and their receptors in adrenocortical cells. All these defects constitute the molecular basis for aberrant autocrine/paracrine regulatory mechanisms, which are likely to play a role in the pathophysiology of BMAH-associated hypercortisolism. The present review summarizes the current knowledge on this topic as well as the therapeutic perspectives offered by this new pathophysiological concept.

ACTH-independent macronodular adrenocortical hyperplasia reveals prevalent aberrant in vivo and in vitro responses to hormonal stimuli and coupling of arginine-vasopressin type 1a receptor to 11β-hydroxylase

Background

Adrenal Cushing’s syndrome caused by ACTH-independent macronodular adrenocortical hyperplasia (AIMAH) can be accompanied by aberrant responses to hormonal stimuli. We investigated the prevalence of adrenocortical reactions to these stimuli in a large cohort of AIMAH patients, both in vivo and in vitro.

Methods

In vivo cortisol responses to hormonal stimuli were studied in 35 patients with ACTH-independent bilateral adrenal enlargement and (sub-)clinical hypercortisolism. In vitro, the effects of these stimuli on cortisol secretion and steroidogenic enzyme mRNA expression were evaluated in cultured AIMAH and other adrenocortical cells. Arginine-vasopressin (AVP) receptor mRNA levels were determined in the adrenal tissues.

Results

Positive serum cortisol responses to stimuli were detected in 27/35 AIMAH patients tested, with multiple responses within individual patients occurring for up to four stimuli. AVP and metoclopramide were the most prevalent hormonal stimuli triggering positive responses in vivo. Catecholamines induced short-term cortisol production more often in AIMAH cultures compared to other adrenal cells. Short- and long-term incubation with AVP increased cortisol secretion in cultures of AIMAH cells. AVP also increased steroidogenic enzyme mRNA expression, among which an aberrant induction of CYP11B1. AVP type 1a receptor was the only AVPR expressed and levels were high in the AIMAH tissues. AVPR1A expression was related to the AVP-induced stimulation of CYP11B1.

Conclusions

Multiple hormonal signals can simultaneously induce hypercortisolism in AIMAH. AVP is the most prevalent eutopic signal and expression of its type 1a receptor was aberrantly linked to CYP11B1 expression.

Oxytocin induces the migration of prostate cancer cells: involvement of the Gi-coupled signaling pathway

Expression of genes that encode oxytocin (OXT) and vasopressin (AVP) and their cognate receptors in normal and diseased prostates are only partially characterized. Reverse transcription and PCR were used to examine the expression of these genes in normal prostate epithelial and stromal cell lines, k-ras-transformed prostate epithelial cell lines, and in four prostate cancer cell lines. Secreted and cell-associated OXT peptide was measured by an enzyme immunoassay. OXT and its receptor (OXTR) were expressed in all eight prostate cell lines. Cell-associated OXT peptide was also found in all prostate epithelial cell lines except in DU145 cells. Neither AVP nor its cognate receptors (V1a receptor and V2 receptor) were expressed in any prostate cell line examined. These data point to the OXTR as the primary target of OXT and AVP, and suggest that OXT might be an autocrine/paracrine regulator in human prostate. We found that OXT induces the migration of PC3 and PC3M, but not DU145 prostate cancer cells. The effect of OXT is distinct from the epidermal growth factor (EGF)-induced migration of prostate cancer cells, in which ERK1/2 and EGF receptor kinase activities were required. When cells were pretreated with pertussis toxin, the effect of OXT, but not EGF, on cell migration was abolished. Pretreatment with the cyclic AMP analogue, 8-Br-cAMP, did not affect OXT-induced cell migration, which eliminated the nonspecific effect of pertussis toxin. We conclude that a Gi-dependent mechanism is involved in OXTR-mediated migration of prostate cancer cells, and indicates a role for OXTR in prostate cancer metastasis.

Clinical and genetic heterogeneity, overlap with other tumor syndromes, and atypical glucocorticoid hormone secretion in adrenocorticotropin-independent macronodular adrenal hyperplasia compared with other adrenocortical tumors

OBJECTIVE

ACTH-independent macronodular adrenal hyperplasia (AIMAH) is often associated with subclinical cortisol secretion or atypical Cushing's syndrome (CS). We characterized a large series of patients of AIMAH and compared them with patients with other adrenocortical tumors.

DESIGN AND PATIENTS

We recruited 82 subjects with: 1) AIMAH (n = 16); 2) adrenocortical cortisol-producing adenoma with CS (n = 15); 3) aldosterone-producing adenoma (n = 19); and 4) single adenomas with clinically nonsignificant cortisol secretion (n = 32).

METHODS

Urinary free cortisol (UFC) and 17-hydroxycorticosteroid (17OHS) were collected at baseline and during dexamethasone testing; aberrant receptor responses was also sought by clinical testing and confirmed molecularly. Peripheral and/or tumor DNA was sequenced for candidate genes.

RESULTS

AIMAH patients had the highest 17OHS excretion, even when UFCs were within or close to the normal range. Aberrant receptor expression was highly prevalent. Histology showed at least two subtypes of AIMAH. For three patients with AIMAH, there was family history of CS; germline mutations were identified in three other patients in the genes for menin (one), fumarate hydratase (one), and adenomatosis polyposis coli (APC) (one); a PDE11A gene variant was found in another. One patient had a GNAS mutation in adrenal nodules only. There were no mutations in any of the tested genes in the patients of the other groups.

CONCLUSIONS

AIMAH is a clinically and genetically heterogeneous disorder that can be associated with various genetic defects and aberrant hormone receptors. It is frequently associated with atypical CS and increased 17OHS; UFCs and other measures of adrenocortical activity can be misleadingly normal.