Systematic analysis of G protein-coupled receptor gene expression in adrenocorticotropin-independent macronodular adrenocortical hyperplasia identifies novel targets for pharmacological control of adrenal Cushing's syndrome.
BACKGROUND
Stimulation of cortisol secretion through abnormally expressed G protein-coupled receptors (GPCRs) is a frequent feature of ACTH-independent macronodular adrenal hyperplasia (AIMAH). This has opened a pharmacological strategy that targets GPCRs for the treatment of Cushing's syndrome in AIMAH. However, only few drugs are available for the presently described GPCRs.


OBJECTIVE
The objective of the study was to identify new GPCR targets for the pharmacological treatment of adrenal Cushing's syndrome.


METHODS
We designed a cDNA chip containing 865 nucleotidic sequences of GPCRs. mRNAs were extracted from three normal adrenals, 18 AIMAHs, four adrenals from Cushing's disease patients, and 13 cortisol-secreting adenomas. A set of GPCR mRNAs that showed significantly higher or lower expression in AIMAH than in normal adrenal were studied by quantitative RT-PCR analysis. Analysis of protein expression and function were performed on selected GPCRs.


METHODS
The study was conducted at a tertiary care center and basic research laboratories.


RESULTS
The ACTH MC2 receptor showed a low expression in 15 of 18 AIMAHs samples, whereas several previously undescribed GPCR genes were found highly expressed in a subset of AIMAH, such as the receptors for motilin (MLNR; three of 18 AIMAHs) and γ-aminobutyric acid (GABBR1; five of 18 AIMAHs), and the α2A adrenergic receptor (ADRA2A; 13 of 18 AIMAHs), on which we focused our attention. Western blot and immunochemistry analyses showed expression of ADRA2A protein in AIMAH but not in normal adrenal cortex. The ADRA2A agonist clonidine enhanced both basal and stimulated cortisol production. Clonidine-induced increase in basal cortisol levels was blocked by the ADRA2A antagonist yohimbine.


CONCLUSIONS
ADRA2A is a potential target for pharmacological treatment of Cushing's syndrome linked to AIMAH.
Assie
Guillaume
G
Université Paris Descartes, Institut National de la Santé et de la Recherche Médicale Unité 567, Assistance Publique Hôpitaux de Paris, Hôpital Cochin, Paris, France.
Louiset
Estelle
E
Sturm
Nathalie
N
René-Corail
Fernande
F
Groussin
Lionel
L
Bertherat
Jérôme
J
Thomas
Michaël
M
Lefebvre
Hervé
H
Feige
Jean-Jacques
JJ
Clauser
Eric
E
Chabre
Olivier
O
Cherradi
Nadia
N
D049913:ACTH-Secreting Pituitary Adenoma / Q000235:genetics / Q000473:pathology; D000302:Adrenal Cortex / Q000378:metabolism / Q000473:pathology*; D058647:Adrenergic alpha-2 Receptor Agonists; D000324:Adrenocorticotropic Hormone / Q000378:metabolism / Q000502:physiology; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology; D002478:Cells, Cultured; D003000:Clonidine / Q000008:administration & dosage / Q000494:pharmacology; D003480:Cushing Syndrome / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D016503:Drug Delivery Systems; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D006965:Hyperplasia / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010911:Pituitary Neoplasms / Q000235:genetics / Q000473:pathology; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism
C547768:ADRA2A protein, human; D058647:Adrenergic alpha-2 Receptor Agonists; D000959:Antihypertensive Agents; D018341:Receptors, Adrenergic, alpha-2; D043562:Receptors, G-Protein-Coupled; D000324:Adrenocorticotropic Hormone; D003000:Clonidine