Cannabinoids transduction signal pathway in GT1-7 immortalized hypothalamic and AtT-20 cell lines
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1
University abdelmalek Essaadi, Faculty of Science, Morocco
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2
Centre of Excellence, Department of Neurosciences, Italy
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3
Max Planck Institute of Psychiatry, ISB, Germany
Cannabinoids chemistry and pharmacology have been the object of thousands of publications over the last 40 years. The mechanism behind the effect of cannabinoïds on brain was investigated by our laboratories using two cell line models: GT1-7 immortalized hypothalamic cells and corticotroph-derived AtT-20 cells transfected with rat cannabinoïd receptors (CB1R).
In GT1-7 cells, we found that the CB1R /CB2R agonist, WIN55,212-2, inhibited the voltage-gated Ca2+ currents by about 35%. The inhibition by WIN55,212-2 (10 µM) was reversible and prevented by nifedipine (3 µM), suggesting a selective action on L-type Ca2+ channels (LTCCs). At variance with WIN55,212-2, the CB1R inverse-agonist AM251 (10 µM) caused 20% increase of Ca2+ currents. The inhibition of LTCCs by WIN55,212-2 was prevented by overnight incubation in pertuxis toxin (PTX) and by intracellular perfusion with Guanosine-5'-O-2- thiodiphosphate (GDP-β-S). The latter caused also a 20% Ca2+current up-regulation. WIN55,212-2 action was also prevented by application of the protein kinase A blocker, H89, or by loading neurons with the cAMP analogue, 8-CPT-cAMP. Our results suggest that L-type Ca2+ channels in GT1-7 neurons are partially inhibited at rest due to a constitutive CB1R activity removed by AM-251 and GDP-β-S.
In the AtT-20 cells, the cannabinoïds agonist WIN55,212-2 (1µM) increased proopiomelanocortin (POMC) transcription by affecting several transcriptional factors which control POMC gene promoter. WIN 55,212-2 (1µM) increased the transcriptional activity of the Nur family transcription factors (Nurr1 and Nur77), and also increased the cAMP responsive binding element (CREB) transcriptional activity, while the cannabinoïd receptor inverse agonist AM251 had the opposite effect. The signal transducer and activator of transcription 3 (STAT3) was not affected by CB1 activation.
WIN 55,212-2 (1µM) increased CREB phosphorylation without affecting basal CREB protein levels and this effect was not blocked by PTX. This study suggests a new mechanism of action for CB1 on the regulation of signal transduction pathways at POMC level.
Acknowledgment: This work was supported by the Marie Curie Research Training Network “CavNET”, the MIUR (grant COFIN no. 2005054435 to E.C.) and Max planck institute, Munich, Germany. H. Hoddah was supported by an IMAGEEN European project and CNRST fellowships. L. Bakkali was supported by a DAAD, EMBO and CNRST fellowships.
Conference:
2nd NEUROMED Workshop, Fez, Morocco, 10 Jun - 12 Jun, 2010.
Presentation Type:
Oral Presentation
Topic:
Oral Session 1: Brain diseases and their treatment
Citation:
Errami
M,
Hoddah
H,
Bakkali
L,
Carbone
E and
Errami
M
(2010). Cannabinoids transduction signal pathway in GT1-7 immortalized hypothalamic and AtT-20 cell lines.
Front. Neurosci.
Conference Abstract:
2nd NEUROMED Workshop.
doi: 10.3389/conf.fnins.2010.12.00012
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Received:
03 Jun 2010;
Published Online:
03 Jun 2010.
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Correspondence:
Mohamed Errami, University abdelmalek Essaadi, Faculty of Science, Tetouan, Morocco, errami.mohammed@gmail.com