María Teresa Miras Portugal: a pioneer in the study of purinoceptors in chromaffin cells.

María Teresa Miras Portugal devoted most of her scientific life to the study of purinergic signalling. In an important part of her work, she used a model system: the chromaffin cells of the adrenal medulla. It was in these cells that she identified diadenosine polyphosphates, from which she proceeded to the study of adrenomedullary purinome: nucleotide synthesis and degradation, adenosine transport, nucleotide uptake into chromaffin granules, exocytotic release of nucleotides and autocrine regulation of chromaffin cell function via purinoceptors. This short review will focus on the current state of knowledge of the purinoceptors of adrenal chromaffin cells, a subject to which María Teresa made seminal contributions and which she continued to study until the end of her scientific life.

ADP-mediated Modulation of Intracellular Calcium Responses in Chromaffin Cells: The Role of Ectonucleoside Triphosphate Diphosphohydrolase 2 on Rat Adrenal Medulla Function.

The present study investigated the localization and the adenosine 5'-triphosphate (ATP)-degrading function of the plasma membrane-bound ecto-nucleotidase, ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2), in the rat adrenal medulla. The effect of ATP degradation product, adenosine 5'-diphosphate (ADP), on carbachol (CCh)-induced intracellular Ca2+ ([Ca2+]i) responses in adrenal chromaffin cells was examined using calcium imaging. NTPDase2-immunoreactive cells were distributed between chromaffin cells. NTPDase2-immunoreactive cells were immunoreactive for glial fibrillary acidic protein and S100B, suggesting that they were sustentacular cells. NTPDase2-immunoreactive cells surrounded chromaffin cells immunoreactive for vesicular nucleotide transporter and P2Y12 ADP-selective purinoceptors. In ATP bioluminescence assays using adrenal medullary slices, ATP was rapidly degraded and its degradation was attenuated by the NTPDase inhibitors sodium polyoxotungstate (POM-1) and 6-N, N-diethyl-d-ß,γ-dibromomethylene ATP (ARL67156). ADP inhibited CCh-induced [Ca2+]i increases of chromaffin cells in adrenal medullary slices. The inhibition of CCh-induced [Ca2+]i increases by ADP was blocked by the P2Y12 purinoceptor antagonist AZD1283. CCh-induced [Ca2+]i increases were also inhibited by the P2Y1, P2Y12, and P2Y13 purinoceptor agonist 2-methylthioadenosine diphosphate trisodium (2MeSADP), in combination with the P2Y1 purinoceptor antagonist MRS2179. These results suggest that sustentacular cells express NTPDase2 to degrade ATP released from adrenal chromaffin cells, and ADP modulates the excitability of chromaffin cells via P2Y12 purinoceptors to regulate catecholamine release during preganglionic sympathetic stimuli. (J Histochem Cytochem 72: 41-60, 2024).

Dysfunction of calcium-regulated exocytosis at a single-cell level causes catecholamine hypersecretion in patients with pheochromocytoma.

Neuroendocrine tumors constitute a heterogeneous group of tumors arising from hormone-secreting cells and are generally associated with a dysfunction of secretion. Pheochromocytoma (Pheo) is a neuroendocrine tumor that develops from chromaffin cells of the adrenal medulla, and is responsible for an excess of catecholamine secretion leading to severe clinical symptoms such as hypertension, elevated stroke risk and various cardiovascular complications. Surprisingly, while the hypersecretory activity of Pheo is well known to pathologists and clinicians, it has never been carefully explored at the cellular and molecular levels. In the present study, we have combined catecholamine secretion measurement by carbon fiber amperometry on human tumor cells directly cultured from freshly resected Pheos, with the analysis by mass spectrometry of the exocytotic proteins differentially expressed between the tumor and the matched adjacent non-tumor tissue. In most patients, catecholamine secretion recordings from single Pheo cells revealed a higher number of exocytic events per cell associated with faster kinetic parameters. Accordingly, we unravel significant tumor-associated modifications in the expression of key proteins involved in different steps of the calcium-regulated exocytic pathway. Altogether, our findings indicate that dysfunction of the calcium-regulated exocytosis at the level of individual Pheo cell is a cause of the tumor-associated hypersecretion of catecholamines.

HIF2α regulates the synthesis and release of epinephrine in the adrenal medulla.

The adrenal gland and its hormones regulate numerous fundamental biological processes; however, the impact of hypoxia signaling on adrenal function remains poorly understood. Here, we reveal that deficiency of HIF (hypoxia inducible factors) prolyl hydroxylase domain protein-2 (PHD2) in the adrenal medulla of mice results in HIF2α-mediated reduction in phenylethanolamine N-methyltransferase (PNMT) expression, and consequent reduction in epinephrine synthesis. Simultaneous loss of PHD2 in renal erythropoietin (EPO)-producing cells (REPCs) stimulated HIF2α-driven EPO overproduction, excessive RBC formation (erythrocytosis), and systemic hypoglycemia, which is necessary and sufficient to enhance exocytosis of epinephrine from the adrenal medulla. Based on these results, we propose that the PHD2-HIF2α axis in the adrenal medulla regulates the synthesis of epinephrine, whereas in REPCs, it indirectly induces the release of this hormone. Our findings are also highly relevant to the testing of small molecule PHD inhibitors in phase III clinical trials for patients with renal anemia. KEY MESSAGES: HIF2α and not HIF1α modulates PNMT during epinephrine synthesis in chromaffin cells. The PHD2-HIF2α-EPO axis induces erythrocytosis and hypoglycemia. Reduced systemic glucose facilitates exocytosis of epinephrine from adrenal gland.

Partial Agonist Activity of Neonicotinoids on Rat Nicotinic Receptors: Consequences over Epinephrine Secretion and In Vivo Blood Pressure.

Neonicotinoid insecticides are nicotine-derived molecules which exert acute neurotoxic effects over the insect central nervous system by activating nicotinic acetylcholine receptors (nAChRs). However, these receptors are also present in the mammalian central and peripheral nervous system, where the effects of neonicotinoids are faintly known. In mammals, cholinergic synapses are crucial for the control of vascular tone, blood pressure and skeletal muscle contraction. We therefore hypothesized that neonicotinoids could affect cholinergic networks in mammals and sought to highlight functional consequences of acute intoxication in rats with sub-lethal concentrations of the highly used acetamiprid (ACE) and clothianidin (CLO). In this view, we characterized their electrophysiological effects on rat α3ß4 nAChRs, knowing that it is predominantly expressed in ganglia of the vegetative nervous system and the adrenal medulla, which initiates catecholamine secretion. Both molecules exhibited a weak agonist effect on α3ß4 receptors. Accordingly, their influence on epinephrine secretion from rat adrenal glands was also weak at 100 µM, but it was stronger at 500 µM. Challenging ACE or CLO together with nicotine (NIC) ended up with paradoxical effects on secretion. In addition, we measured the rat arterial blood pressure (ABP) in vivo by arterial catheterization. As expected, NIC induced a significant increase in ABP. ACE and CLO did not affect the ABP in the same conditions. However, simultaneous exposure of rats to both NIC and ACE/CLO promoted an increase of ABP and induced a biphasic response. Modeling the interaction of ACE or CLO on α3ß4 nAChR is consistent with a binding site located in the agonist pocket of the receptor. We present a transversal experimental approach of mammal intoxication with neonicotinoids at different scales, including in vitro, ex vivo, in vivo and in silico. It paves the way of the acute and chronic toxicity for this class of insecticides on mammalian organisms.

Adrenal medulla development and medullary-cortical interactions.

The mammalian adrenal gland is composed of two distinct tissue types in a bidirectional connection, the catecholamine-producing medulla derived from the neural crest and the mesoderm-derived cortex producing steroids. The medulla mainly consists of chromaffin cells derived from multipotent nerve-associated descendants of Schwann cell precursors. Already during adrenal organogenesis, close interactions between cortex and medulla are necessary for proper differentiation and morphogenesis of the gland. Moreover, communication between the cortex and the medulla ensures a regular function of the adult adrenal. In tumor development, interfaces between the two parts are also common. Here, we summarize the development of the mammalian adrenal medulla and the current understanding of the cortical-medullary interactions under development and in health and disease.

Stimulation of brain α7-nicotinic acetylcholine receptors suppresses the rat micturition through brain GABAergic receptors.

Brain nicotinic acetylcholine receptors (nAChRs) reportedly suppress the micturition, but the mechanisms responsible for this suppression remain unclear. We previously reported that intracerebroventricularly administered (±)-epibatidine (non-selective nAChR agonist) activated the sympatho-adrenomedullary system, which can affect the micturition. Therefore, we investigated (1) whether intracerebroventricularly administered (±)-epibatidine-induced effects on the micturition were dependent on the sympatho-adrenomedullary system, and (2) brain nAChR subtypes involved in the (±)-epibatidine-induced effects in urethane-anesthetized male Wistar rats. Plasma noradrenaline and adrenaline (catecholamines) were measured just before and 5 min after (±)-epibatidine administration. Evaluation of urodynamic parameters, intercontraction intervals (ICI) and maximal voiding pressure (MVP) by cystometry was started 1 h before (±)-epibatidine administration or intracerebroventricular pretreatment with other drugs and continued 1 h after (±)-epibatidine administration. Intracerebroventricularly administered (±)-epibatidine elevated plasma catecholamines and prolonged ICI without affecting MVP, and these changes were suppressed by intracerebroventricularly pretreated mecamylamine (non-selective nAChR antagonist). Acute bilateral adrenalectomy abolished the (±)-epibatidine-induced elevation of plasma catecholamines, but had no effect on the (±)-epibatidine-induced ICI prolongation. The latter was suppressed by intracerebroventricularly pretreated methyllycaconitine (selective α7-nAChR antagonist), SR95531 (GABAA antagonist), and SCH50911 (GABAB antagonist), but not by dihydro-ß-erythroidine (selective α4ß2-nAChR antagonist). Intracerebroventricularly administered PHA568487 (selective α7-nAChR agonist) prolonged ICI without affecting MVP, similar to (±)-epibatidine. These results suggest that stimulation of brain α7-nAChRs suppresses the rat micturition through brain GABAA/GABAB receptors, independently of the sympatho-adrenomedullary outflow modulation.

Thyroid Hormone Deficiency Suppresses Fetal Pituitary-Adrenal Function Near Term: Implications for the Control of Fetal Maturation and Parturition.

Background: The fetal hypothalamic-pituitary-adrenal (HPA) axis plays a key role in the control of parturition and maturation of organ systems in preparation for birth. In hypothyroid fetuses, gestational length may be prolonged and maturational processes delayed. The extent to which the effects of thyroid hormone deficiency in utero on the timing of fetal maturation and parturition are mediated by changes to the structure and function of the fetal HPA axis is unknown. Methods: In twin sheep pregnancies where one fetus was thyroidectomized and the other sham-operated, this study investigated the effect of hypothyroidism on circulating concentrations of adrenocorticotrophic hormone (ACTH) and cortisol, and the structure and secretory capacity of the anterior pituitary and adrenal glands. The relative population of pituitary corticotrophs and the masses of the adrenal zones were assessed by immunohistochemical and stereological techniques. Adrenal mRNA abundances of key steroidogenic enzymes and growth factors were examined by quantitative polymerase chain reaction. Results: Hypothyroidism in utero reduced plasma concentrations of ACTH and cortisol. In thyroid-deficient fetuses, the mass of corticotrophs in the anterior pituitary gland was unexpectedly increased, while the mass of the zona fasciculata and its proportion of the adrenal gland were decreased. These structural changes were associated with lower adrenocortical mRNA abundances of insulin-like growth factor (IGF)-I and its receptor, and key steroidogenic enzymes responsible for glucocorticoid synthesis. The relative mass of the adrenal medulla and its proportion of the adrenal gland were increased by thyroid hormone deficiency in utero, without any change in expression of phenylethanolamine N-methyltransferase or the IGF system. Conclusions: Thyroid hormones are important regulators of the structure and secretory capacity of the pituitary-adrenal axis before birth. In hypothyroid fetuses, low plasma cortisol may be due to impaired adrenocortical growth and steroidogenic enzyme expression, secondary to low circulating ACTH concentration. Greater corticotroph population in the anterior pituitary gland of the hypothyroid fetus indicates compensatory cell proliferation and that there may be abnormal corticotroph capacity for ACTH synthesis and/or impaired hypothalamic input. Suppression of the development of the fetal HPA axis by thyroid hormone deficiency may contribute to the delay in fetal maturation and delivery observed in hypothyroid offspring.

Mechanisms for pituitary adenylate cyclase-activating polypeptide-induced increase in excitability in guinea-pig and mouse adrenal medullary cells.

Pituitary adenylate cyclase-activating polypeptide (PACAP) acts on adrenal medullary (AM) cells as a neurotransmitter of the sympathetic preganglionic nerve. In guinea-pig AM cells, PACAP induces little catecholamine secretion, but enhances secretion evoked by stimulants, whereas in other animals, such as mouse, PACAP itself induces depolarization and/or catecholamine secretion. The present studies aim to explore the physiological implication of these species differences in PACAP actions, the ion channel mechanism for PACAP-induced depolarization, and the mechanism for facilitation of muscarinic receptor-mediated cation currents in mouse and guinea-pig AM cells. The perforated patch clamp technique was used to record the whole-cell current in isolated AM cells. The amplitudes of 3 nM PACAP-induced inward currents were significantly larger in mouse AM cells than guinea-pig, whereas 1 µM muscarine-induced currents were larger in guinea-pig AM cells than mouse. Exposure to PACAP consistently resulted in enhancement of muscarine-induced currents in guinea-pig AM cells and facilitation of cell membrane insertion of heteromeric TRPC1-TRPC4 channels in response to muscarine in PC12 cells. The PACAP-induced current was inhibited by 30 µM 9-phenanthrol, a specific TRPM4 channel inhibitor, and abolished by replacement of external Na+ with N-methyl D-glucamine. TRPM4-like immunoreactivity was located at the cell periphery in AM cells. The present results indicate that PACAP and muscarinic receptors are major metabotropic receptors mediating generation of depolarizing inward currents in mouse and guinea-pig AM cells, respectively. We conclude that PACAP activates TRPM4-like channels and enhance the muscarinic current through facilitating the membrane insertion of TRPC1-TRPC4 channels in AM cells.

Cholinergic and peptidergic neurotransmission in the adrenal medulla: A dynamic control of stimulus-secretion coupling.

Synaptic neurotransmission at the splanchnic nerve-chromaffin cell synapse is a chief element of the stimulus-secretion coupling in the adrenal medullary tissue, managing and regulating the secretion of catecholamines. Making the state of play more intricate than initially envisioned, the synaptic vesicles of nerve terminals innervating the medulla contain various compounds, including various neurotransmitters and neuropeptides. Under basal conditions associated with a low splanchnic nerve discharge rate, neurotransmission is ensured by the synaptic release of the primary neurotransmitter acetylcholine (ACh). Under sustained and repetitive stimulations of the splanchnic nerve, as triggered in response to stressors, the synaptic release of neuropeptides, such as the pituitary adenylate cyclase-activating polypeptide PACAP, supplants ACh release. The anatomical and functional changes that occur presynaptically at the preganglionic splanchnic nerve, combined with changes occurring postsynaptically at nicotinic acetylcholine receptors (nAChRs), confer the adrenomedullary synapses a solid and persistent aptitude to functional remodeling, from birth to aging. The present review focuses on the composite cholinergic and noncholinergic nature of neurotransmission occurring at the splanchnic nerve-chromaffin cell synapse and its remodeling in response to physiological or pathological stimuli.

A rare case of takotsubo syndrome within the first day after heart transplantation.

A 39-year-old woman underwent heart transplantation (HTx) for advanced heart failure. The donor was a 36-year-old young woman without past medical history. The first day after HTx, T-waves changes were noted. Echocardiography revealed akinesia/dyskinesia of all basal segments of the two ventricles. Coronary catheterization plus biopsy were done 7 days later showing no coronary obstruction, no rejection and complete recovery of wall motion abnormalities on echocardiogram, suggesting biventricular inverted takotsubo syndrome (TTS). This is a case of TTS during the first day after HTx, with completely denervated heart but because of the inotropic drug support it still represents a target for catecholamine-induced cardiac dysfunction.

Regulation of catecholamine release from the adrenal medulla is altered in deer mice (Peromyscus maniculatus) native to high altitudes.

High-altitude natives have evolved to overcome environmental hypoxia and provide a compelling system to understand physiological function during reductions in oxygen availability. The sympathoadrenal system plays a key role in responses to acute hypoxia, but prolonged activation of this system in chronic hypoxia may be maladaptive. Here, we examined how chronic hypoxia exposure alters adrenal catecholamine secretion and how adrenal function is altered further in high-altitude natives. Populations of deer mice (Peromyscus maniculatus) native to low and high altitudes were each born and raised in captivity at sea level, and adults from each population were exposed to normoxia or hypobaric hypoxia for 5 mo. Using carbon fiber amperometry on adrenal slices, catecholamine secretion evoked by low doses of nicotine (10 µM) or acute hypoxia (Po2 ∼15-20 mmHg) was reduced in lowlanders exposed to hypobaric hypoxia, which was attributable mainly to a decrease in quantal charge rather than event frequency. However, secretion evoked by high doses of nicotine (50 µM) was unaffected. Hypobaric hypoxia also reduced plasma epinephrine and protein expression of 3,4-dihydroxyphenylalanine (DOPA) decarboxylase in the adrenal medulla of lowlanders. In contrast, highlanders were unresponsive to hypobaric hypoxia, exhibiting typically low adrenal catecholamine secretion, plasma epinephrine, and DOPA decarboxylase. Highlanders also had consistently lower catecholamine secretion evoked by high nicotine, smaller adrenal medullae with fewer chromaffin cells, and a larger adrenal cortex compared with lowlanders across both acclimation environments. Our results suggest that plastic responses to chronic hypoxia along with evolved changes in adrenal function attenuate catecholamine release in deer mice at high altitude.

STIM1-dependent membrane insertion of heteromeric TRPC1-TRPC4 channels in response to muscarinic receptor stimulation.

Muscarinic receptor stimulation results in activation of nonselective cation (NSC) channels in guinea pig adrenal medullary (AM) cells. The biophysical and pharmacological properties of the NSC channel suggest the involvement of heteromeric channels of TRPC1 with TRPC4 or TRPC5. This possibility was explored in PC12 cells and guinea pig AM cells. Proximity ligation assay (PLA) revealed that when exogenously expressed in PC12 cells, TRPC1 forms a heteromeric channel with TRPC4, but not with TRPC5, in a STIM1-dependent manner. The heteromeric TRPC1-TRPC4 channel was also observed in AM cells and trafficked to the cell periphery in response to muscarine stimulation. To explore whether heteromeric channels are inserted into the cell membrane, tags were attached to the extracellular domains of TRPC1 and TRPC4. PLA products developed between the tags in cells stimulated by muscarine, but not in resting cells, indicating that muscarinic stimulation results in the membrane insertion of channels. This membrane insertion required expression of full-length STIM1. We conclude that muscarinic receptor stimulation results in the insertion of heteromeric TRPC1-TRPC4 channels into the cell membrane in PC12 cells and guinea pig AM cells.

Overexpression of P2X3 and P2X7 Receptors and TRPV1 Channels in Adrenomedullary Chromaffin Cells in a Rat Model of Neuropathic Pain.

We have tested the hypothesis that neuropathic pain acting as a stressor drives functional plasticity in the sympathoadrenal system. The relation between neuropathic pain and adrenal medulla function was studied with behavioral, immunohistochemical and electrophysiological techniques in rats subjected to chronic constriction injury of the sciatic nerve. In slices of the adrenal gland from neuropathic animals, we have evidenced increased cholinergic innervation and spontaneous synaptic activity at the splanchnic nerve⁻chromaffin cell junction. Likewise, adrenomedullary chromaffin cells displayed enlarged acetylcholine-evoked currents with greater sensitivity to α-conotoxin RgIA, a selective blocker of α9 subunit-containing nicotinic acetylcholine receptors, as well as increased exocytosis triggered by voltage-activated Ca2+ entry. Altogether, these adaptations are expected to facilitate catecholamine output into the bloodstream. Last, but most intriguing, functional and immunohistochemical data indicate that P2X3 and P2X7 purinergic receptors and transient receptor potential vanilloid-1 (TRPV1) channels are overexpressed in chromaffin cells from neuropathic animals. These latter observations are reminiscent of molecular changes characteristic of peripheral sensitization of nociceptors following the lesion of a peripheral nerve, and suggest that similar phenomena can occur in other tissues, potentially contributing to behavioral manifestations of neuropathic pain.

Stimulation of brain nicotinic acetylcholine receptors activates adrenomedullary outflow via brain inducible NO synthase-mediated S-nitrosylation.

BACKGROUND AND PURPOSE: We have demonstrated that i.c.v.-administered (±)-epibatidine, a nicotinic ACh receptor (nAChR) agonist, induced secretion of noradrenaline and adrenaline (catecholamines) from the rat adrenal medulla with dihydro-ß-erythroidin (an α4ß2 nAChR antagonist)-sensitive brain mechanisms. Here, we examined central mechanisms for the (±)-epibatidine-induced responses, focusing on brain NOS and NO-mediated mechanisms, soluble GC (sGC) and protein S-nitrosylation (a posttranslational modification of protein cysteine thiol groups), in urethane-anaesthetized (1.0 g·kg-1 , i.p.) male Wistar rats. EXPERIMENTAL APPROACH: (±)-Epibatidine was i.c.v. treated after i.c.v. pretreatment with each inhibitor described below. Then, plasma catecholamines were measured electrochemically after HPLC. Immunoreactivity of S-nitrosylated cysteine (SNO-Cys) in α4 nAChR subunit (α4)-positive spinally projecting neurones in the rat hypothalamic paraventricular nucleus (PVN, a regulatory centre of adrenomedullary outflow) after i.c.v. (±)-epibatidine administration was also investigated. KEY RESULTS: (±)-Epibatidine-induced elevation of plasma catecholamines was significantly attenuated by L-NAME (non-selective NOS inhibitor), carboxy-PTIO (NO scavenger), BYK191023 [selective inducible NOS (iNOS) inhibitor] and dithiothreitol (thiol-reducing reagent), but not by 3-bromo-7-nitroindazole (selective neuronal NOS inhibitor) or ODQ (sGC inhibitor). (±)-Epibatidine increased the number of spinally projecting PVN neurones with α4- and SNO-Cys-immunoreactivities, and this increment was reduced by BYK191023. CONCLUSIONS AND IMPLICATIONS: Stimulation of brain nAChRs can induce elevation of plasma catecholamines through brain iNOS-derived NO-mediated protein S-nitrosylation in rats. Therefore, brain nAChRs (at least α4ß2 subtype) and NO might be useful targets for alleviation of catecholamines overflow induced by smoking.

Acute Hypoxia Induces Enkephalin Production and Release in an Adrenergic Cell Line Model of Neonatal Chromaffin Cell Responses to Hypoxic Stress.

OBJECTIVE: Prior to maturation of the human sympathetic nervous system, the neonatal adrenal medulla senses and responds to hypoxia. In addition to catecholamine release, the adrenal medulla synthesizes and stores opioid peptides, notably enkephalin (ENK). However, it is not known whether acute hypoxia evokes adrenal ENK production and release, as seen in the central nervous system (CNS). We hypothesize that acute hypoxia stimulates synthesis and release of ENK in chromaffin cells. STUDY DESIGN: Cultures of adrenergic mouse pheochromocytoma cells (MPC) 10/9/96CR were incubated in 10% oxygen (O2) at intervals of up to 60 minutes. ENK content and release were measured by Met-ENK enzyme-linked immunosorbent assay (ELISA). ENK messenger ribonucleic acid (mRNA) was analyzed by quantitative reverse-transcriptase polymerase chain reaction (PCR). RESULTS: Incubation of MPC 10/9 cells in 10% O2 evoked rapid release of epinephrine and of Met-ENK which increased approximately twofold in 15 minutes. Reduced [O2] also induced an overall increase (14%) in cellular ENK peptide content within 60 minutes. Acute hypoxia-stimulated release of Met-ENK was accompanied by increased mRNAENK expression in MPC 10/9s, a cell culture model of adrenergic chromaffin cells. CONCLUSION: We speculate that the ability of reduced [O2] to evoke ENK release from chromaffin cells may influence blood pressure regulation and heart contractility, thereby providing an adaptive survival advantage during neonatal asphyxia.

Expression and regulation of M-type K+ channel in PC12 cells and rat adrenal medullary cells.

M-type K+ channels contribute to the resting membrane potential in the sympathetic ganglion neurons of various animals, whereas their expression in adrenal medullary (AM) cells has been controversial. The present experiment aims to explore the expression of M channels comprising the KCNQ2 subunit in the rat AM cell and its immortalized cell line PC12 cells at the protein level and how its expression in PC12 cells is regulated. The KCNQ2 isoform was recognized in homogenates of PC12 cells but not the rat adrenal medullae by immunoblotting and KCNQ2-like immunoreactivity (IR) was detected in PC12 cells but not in rat AM cells. When the PC12 cells were maintained in a dexamethasone-containing medium, KCNQ2-like IR in the cells was suppressed, whereas the removal of fetal bovine serum from the culture medium for 1 day resulted in an increase in KCNQ2-like IR. A similar enhancement occurred when PC12 cells were cultured under conditions where glucocorticoid receptor (GR) and/or mineralocorticoid receptor (MR) activities were suppressed. These morphological findings were confirmed in functional analysis. The cells cultured in the presence of an inhibitor of either GR or MR exhibited larger amplitudes of Ca2+ signal in response to an M channel inhibitor than did the cells in its absence, whereas the resting Ca2+ level in the former was lower than that in the latter. These results indicate that the M channel is not expressed in rat AM cells and this absence of expression may be ascribed to the suppression by glucocorticoid activity.

Biology of the Adrenal Gland Cortex Obviates Effective Use of Adeno-Associated Virus Vectors to Treat Hereditary Adrenal Disorders.

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder occurring in 1:10,000 to 1:20,000 live births. In >95% of the cases, CAH results from mutations in the CYP21A2 gene, encoding the adrenal steroid enzyme 21-hydroxylase (21OH). Cardinal phenotypic features of CAH include genital ambiguity and sexual precocity, and in severe cases, neonatal salt loss and death. Current standard of care consists of lifelong oral steroid replacement to reverse the cortisol deficiency. Although significant advances in the treatment of CAH have been made, the burden of a lifelong therapeutic intervention is not ideal for quality of life. Gene therapy for CAH by adeno-associated virus (AAV) vectors has been shown to efficiently transduce the adrenal cortex, restoring normal steroidogenesis in the short term. However, adrenocortical cells are continuously renewed by stem cells located at the adrenal capsule, which differentiate as they centripetally migrate towards the adrenal medulla where they undergo apoptosis. In this context, we hypothesized that AAV-mediated genetic correction of the adrenal cortex will work short term but will eventually lead to a loss of correction. To test this hypothesis, we administered intravenously an AAV serotype rh.10 gene transfer vector (AAVrh.10-21OH-HA) to 21-hydroxylase deficient mice (21OH-/-). The data demonstrates that a single intravenous administration efficiently transduces adrenocortical cells leading to 21OH-HA expression and restoration of normal steroidogenesis. However, the duration of therapeutic efficacy lasted for only 8 weeks, accompanied by loss of 21OH-HA expression in the adrenal gland. Analysis in immunodeficient mice confirmed that the disappearance of transgene expression was not due to an antiviral/transgene immune response. Taken together, these results demonstrate that a single treatment with an adeno-associated viral vector expressing a functional copy of the mutated gene can only transiently treat adrenocortical hereditary disorders and that strategies to genetically modify the adrenocortical stem cells population will likely be required.

La chirurgie d'épargne surrénalienne : du cortex à la médulla: Cortical sparing surgery: from cortex to medulla.

The 2017 Endocrine Society annual meeting included several communications and debates on the conservative adrenal surgery in bilateral hereditary pheochromocytomas (BHP), bilateral adrenal macronodular hyperplasia (BAMH) and primary hyperaldosteronism (PHA). The general principle is to preserve a part of the adrenal cortex to prevent the occurrence of a definitive adrenal insufficiency. In BHP, cortical sparing surgery allows more than 50% of patients to maintain normal corticotropic function at 10 years with a low recurrence rate (~ 10%). Since the adrenal medulla cannot be removed entirely, recurrence seems inevitable and long-term follow-up is essential. Individual risk of malignancy must be taken into account. In BAMH responsible for Cushing syndrome, unilateral adrenalectomy induces a normalization of urinary free cortisol in 92 to 100% of cases and even corticotropic insufficiency in 40 to 100% of cases. This is most often transient. Late recurrences of Cushing's syndrome may occur in 13 to 60% of cases. Prolonged patient monitoring is therefore essential. In PAH with lateralized aldosterone production, minimally invasive partial adrenal surgery, which consists of removing only the adrenal adenoma visualized at TDM, allows an improvement blood pressure in about 94% of patients. However, failure or recurrence may occur. Its place therefore remains marginal in the treatment of the lateralized PAHs.