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.