Developmental regulation of neuronal survival by adenosine in the in vitro and in vivo avian retina depends on a shift of signaling pathways leading to CREB phosphorylation or dephosphorylation.
Previous studies have shown a cAMP/protein kinase A-dependent neuroprotective effect of adenosine on glutamate or re-feeding-induced apoptosis in chick retina neuronal cultures. In the present work, we have studied the effect of adenosine on the survival of retinal progenitor cells. Cultures obtained from 6-day-old (E6) or from 8-day-old (E8) chick embryos were challenged 2 h (C0) or 1 day (C1) after seeding and analyzed after 3-4 days in vitro. Surprisingly, treatment with the selective A2a adenosine receptor agonists N(6) -[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)-ethyl]adenosine (DPMA) or 3-[4-[2-[[6-amino-9-[(2R,3R,4S,5S)-5-(ethylcarbamoyl)-3,4-dihydroxy-oxolan-2-yl]purin-2-yl]amino]ethyl]phenyl]propanoic acid (CGS21680) promoted cell death when added at E6C0 but not at E6C1 or E8C0. DPMA-induced cell death involved activation of A2a receptors and the phospholipase C/protein kinase C but not the cAMP/protein kinase A pathway, and was not correlated with early modulation of precursor cells proliferation. Regarding cyclic nucleotide responsive element binding protein (CREB) phosphorylation, cultures from E6 embryos behave in an opposite manner from that from E8 embryos, both in vitro and in vivo. While the phospho-CREB level was high at E6C0 cultures and could be diminished by DPMA, it was lower at E8C0 and could be increased by DPMA. Similar to what was observed in cell survival studies, CREB dephosphorylation induced by DPMA in E6C0 cultures was dependent on the Phospholipase C/protein kinase C pathway. Accordingly, cell death induced by DPMA was inhibited by okadaic acid, a phosphatase blocker. Moreover, DPMA as well as the adenosine uptake blocker nitrobenzyl mercaptopurine riboside (NBMPR) modulate cell survival and CREB phosphorylation in a population of cells in the ganglion cell layer in vivo. These data suggest that A2a adenosine receptors as well as CREB may display a novel and important function by controlling the repertoire of developing retinal neurons.
Laboratories of Cellular Neurobiology and Neurobiology of Retina, Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, RJ, Brazil.
Renato
R
Socodato
Rafael
R
Brito
Karin C
KC
Calaza
Roberto
R
Paes-de-Carvalho
D000241:Adenosine / Q000008:administration & dosage / Q000502:physiology; D058908:Adenosine A2 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D043705:Receptor, Adenosine A2A / Q000502:physiology*; D012160:Retina / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D058908:Adenosine A2 Receptor Agonists; D017362:Cyclic AMP Response Element-Binding Protein; D043705:Receptor, Adenosine A2A; D000241:Adenosine