Orexins stimulate glucocorticoid secretion from cultured rat and human adrenocortical cells, exclusively acting via the OX1 receptor.
Orexins A and B are hypothalamic peptides, that act via two subtypes of receptors, named OX1-R and OX2-R. Rat and human adrenal cortexes are provided with both OX1-R and OX2-R, and we have previously shown that orexin-A, but not orexin-B, enhances glucocorticoid secretion from dispersed adrenocortical cells. Since OX1-Rs preferentially bind orexin-A and OX2-Rs are non-selective for both orexins, the hypothesis has been advanced that the secretagogue effect of orexin-A is exclusively mediated by the OX1-R. Here, we aimed to verify this contention and to gain insight into the signaling mechanism(s) underlying the secretagogue effect of orexins using primary cultures of rat and human adrenocortical cells. Reverse transcription-polymerase chain reaction showed that cultured cells, as freshly dispersed cells, expressed both OX1-R and OX2-R mRNAs. Orexin-A, but not orexin-B, concentration-dependently increased corticosterone and cortisol secretion from cultured rat and human adrenocortical cells, respectively. The blockade of OX1-Rs by selective antibodies abrogated the secretagogue effect of orexin-A, while the immuno-blockade of OX2-Rs was ineffective. The glucocorticoid response of cultured cells to orexin-A was annulled by the adenylate cyclase and protein kinase (PK) A inhibitors SQ-22536 and H-89, and unaffected by the phospholipase C and PKC inhibitors U-73122 and calphostin-C. Orexin-A, but not orexin-B, enhanced cyclic-AMP production from cultured cells, and did not alter inositol-3-phosphate release. Collectively, our present results allow us to conclude that orexins stimulate glucocorticoid secretion from rat and human adrenocortical cells, exclusively acting through OX1-Rs coupled to the adenylate cyclase/PKA-dependent signaling cascade.
Ziolkowska
Agnieszka
A
Department of Histology and Embryology, Poznan School of Medicine, PL-60781 Poznan, Poland.
Spinazzi
Raffaella
R
Albertin
Giovanna
G
Nowak
Magdalena
M
Malendowicz
Ludwik K
LK
Tortorella
Cinzia
C
Nussdorfer
Gastone G
GG
D000302:Adrenal Cortex / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009479:Neuropeptides / Q000502:physiology*; D064446:Orexin Receptors; D000068797:Orexins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
D005938:Glucocorticoids; C000596229:HCRT protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide