title: Activation of adenosine A2A receptor protects sympathetic neurons against nerve growth factor withdrawal.
abstract: Adenosine mediates a range of effects in the central nervous system (CNS), including the promotion of neuronal survival, but its actions on sympathetic neurons are less well characterized. We therefore sought to understand the role of endogenous adenosine in contributing to the survival of neurotrophin-dependent sympathetic neurons. Rat superior cervical ganglion (SCG) cultures were maintained in the continuous presence of nerve growth factor (NGF) and then exposed to adenosine deaminase (ADA), to deplete endogenous adenosine. This resulted in a marked increase in cellular apoptosis, to a level that approximated the effect of NGF withdrawal. Furthermore, the addition of exogenous adenosine to NGF-deprived SCG neurons resulted in enhanced cell survival. Analysis of adenosine receptor (AR) subtypes on these neurons, using real-time RT-PCR and receptor binding analyses, revealed that the A2A receptor was the major subtype present. Accordingly, the A2A receptor agonist CGS21680 significantly reduced both ADA-induced and NGF-withdrawal-induced neuronal apoptosis, whereas the A1 receptor agonist R-PIA had no such effect. The survival-promoting effect of CGS21680 was eliminated when cells were coincubated with a molar excess of an A2A receptor antagonist. Finally, follow-up experiments revealed that CGS21680 prevented the induction of early apoptotic events, such as changes in mitochondrial integrity and caspase activation, and that it also triggered an increase in ERK activation, which was essential for neurotrophin-independent cell survival. Taken together, these findings provide evidence that endogenous adenosine may be important in mediating protection of sympathetic neurons and that it may act via the A2A receptor subtype.
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
authors.forename: Servio H
authors.initials: SH
authors.lastname: Ramirez
authors.forename: Shongshan
authors.initials: S
authors.lastname: Fan
authors.forename: Casey A
authors.initials: CA
authors.lastname: Maguire
authors.forename: Seth
authors.initials: S
authors.lastname: Perry
authors.forename: Kathy
authors.initials: K
authors.lastname: Hardiek
authors.forename: Vickram
authors.initials: V
authors.lastname: Ramkumar
authors.forename: Harris A
authors.initials: HA
authors.lastname: Gelbard
authors.forename: Stephen
authors.initials: S
authors.lastname: Dewhurst
authors.forename: Sanjay B
authors.initials: SB
authors.lastname: Maggirwar
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000494:pharmacology; D058907:Adenosine A1 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D000243:Adenosine Deaminase / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D020169:Caspases / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D005728:Ganglia, Sympathetic / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects; D020932:Nerve Growth Factor / Q000172:deficiency / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010627:Phenethylamines / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D043682:Receptor, Adenosine A1 / Q000378:metabolism; D043705:Receptor, Adenosine A2A / Q000235:genetics / Q000378:metabolism*
chemical_list: D058907:Adenosine A1 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D018696:Neuroprotective Agents; D010627:Phenethylamines; D012333:RNA, Messenger; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C047235:N-(1-methyl-2-phenylethyl)adenosine; D020932:Nerve Growth Factor; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases; D000243:Adenosine Deaminase; D000241:Adenosine