Signaling pathway involved in the pro-apoptotic effect of dopamine in the GH3 pituitary cell line.
Besides its physiological role as a neurotransmitter, dopamine (DA) induces apoptosis in the central nervous system. This effect is mediated partly by the DA transporter (DAT) and involves reactive oxygen species (ROS) formation as well as oxidative stress. In the pituitary, the inhibitory control by DA of prolactin release and synthesis and lactotrope cell proliferation is well known, while the pro-apoptotic effect of DA remains unclear. Our aim was to study the pro-apoptotic effect of DA in the GH3 mammosomatotrope cell line and determine the DA mechanism that leads to apoptosis in these cells. Using flow cytometry, Western blot, and confocal microscopy, we showed for the first time that DA induced: (1) loss of mitochondrial potential; (2) relocation of Bax to the mitochondria; (3) cytochrome c release; (4) caspase-3 activation, and (5) nuclear fragmentation, resulting in apoptosis. We observed that DAT was expressed in GH3 cells and participated in the DA effect, as apoptosis was significantly reversed in the presence of DAT inhibitors. Direct measurement showed that DA rapidly increased the formation of intracellular ROS. The antioxidant N-acetyl-L-cysteine (NAC) effectively blocked DA-induced ROS formation and apoptosis. Neither JNK nor p38 were involved in this process, so we suggest that the mitochondrial pore of transition is the likely target of the ROS generated by DA. These data provide the first evidence that DA triggers apoptosis in pituitary cells via a mechanism involving DAT and oxidative stress. These findings may be particularly relevant in understanding lactotrope apoptosis during postnatal life.
Jaubert
Arnaud
A
Laboratoire de Signalisation et Mécanismes Moléculaires de l'Apoptose, INSERM E347, Institut Européen de Chimie et de Biologie, IECB, Université de Bordeaux 2, Pessac, France.
Ichas
François
F
Bresson-Bepoldin
Laurence
L
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002452:Cell Count / Q000379:methods; D002460:Cell Line; D003580:Cytochromes / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry / Q000379:methods; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020287:In Situ Nick-End Labeling / Q000379:methods; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal / Q000379:methods; D008928:Mitochondria / Q000187:drug effects; D010902:Pituitary Gland / Q000166:cytology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection / Q000379:methods; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D003580:Cytochromes; D050483:Dopamine Plasma Membrane Transport Proteins; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D049452:Green Fluorescent Proteins; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D004298:Dopamine