Orexins modulate the growth of cultured rat adrenocortical cells, acting through type 1 and type 2 receptors coupled to the MAPK p42/p44- and p38-dependent cascades.
Orexin A and B are hypothalamic peptides that act through two subtypes of receptors named OX1-R and OX2-R. The OX1-R almost exclusively binds orexin-A, whereas OX2-R is non-selective for both orexins. We previously found that rat adrenocortical cells express both orexin-receptor subtypes, and orexin-A stimulates corticosterone secretion from dispersed adrenocortical cells acting via the OX1-R. Here, we examined the possibility that orexins, acting through both their receptor subtypes, modulate the growth of adrenocortical cells. Reverse transcription-polymerase chain reaction showed that rat adrenocortical cells cultured in vitro for four days expressed OX1-R and OX2-R mRNAs. Orexin-A increased the proliferation rate (PR) of cultured cells, while orexin-B lowered it. Using selective antibodies, we demonstrated that OX1-R immuno-blockade reversed the proliferogenic action of orexin-A, causing a sizeable decrease in PR. In contrast, OX2-R immuno-blockade magnified the proliferogenic effect of orexin-A and annulled the antiproliferogenic action of orexin-B. The proliferogenic effect of orexin-A in the presence of OX2-R immuno-blockade was abrogated by the MAPK p42/p44 inhibitor PD-98059, while the antiproliferogenic effect of orexin-A in the presence of OX1-R immuno-blockade was annulled by the MAPK p38 inhibitor SB-203580. Neither inhibitor altered per se the basal PR of cultured cells. Taken together, our present findings allow us to conclude that i) orexins modulate the growth of rat adrenocortical cells cultured in vitro, by exerting both proliferogenic and antiproliferogenic effects, which are mediated by OX1-Rs and OX2-Rs, respectively; and ii) OX1-R and OX2-R growth effects involve the activation of the MAPK p42/p44 and p38 signaling cascades, respectively.
Spinazzi
Raffaella
R
Department of Human Anatomy and Physiology, Section of Anatomy, Padova I-35121, Italy.
Ziolkowska
Agnieszka
A
Neri
Giuliano
G
Nowak
Magdalena
M
Rebuffat
Piera
P
Nussdorfer
Gatone G
GG
Andreis
Paola G
PG
Malendowicz
Ludwik K
LK
D000302:Adrenal Cortex / Q000166:cytology*; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D064446:Orexin Receptors; D000068797:Orexins; D009930:Organic Chemicals / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000096:biosynthesis / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
C000596229:HCRT protein, human; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D009930:Organic Chemicals; C466090:PD 98058; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580