Activation of microglial cells triggers a release of brain-derived neurotrophic factor (BDNF) inducing their proliferation in an adenosine A2A receptor-dependent manner: A2A receptor blockade prevents BDNF release and proliferation of microglia.
BACKGROUND
Brain-derived neurotrophic factor (BDNF) has been shown to control microglial responses in neuropathic pain. Since adenosine A2A receptors (A2ARs) control neuroinflammation, as well as the production and function of BDNF, we tested to see if A2AR controls the microglia-dependent secretion of BDNF and the proliferation of microglial cells, a crucial event in neuroinflammation.


METHODS
Murine N9 microglial cells were challenged with lipopolysaccharide (LPS, 100 ng/mL) in the absence or in the presence of the A2AR antagonist, SCH58261 (50 nM), as well as other modulators of A2AR signaling. The BDNF cellular content and secretion were quantified by Western blotting and ELISA, A2AR density was probed by Western blotting and immunocytochemistry and cell proliferation was assessed by BrdU incorporation. Additionally, the A2AR modulation of LPS-driven cell proliferation was also tested in primary cultures of mouse microglia.


RESULTS
LPS induced time-dependent changes of the intra- and extracellular levels of BDNF and increased microglial proliferation. The maximal LPS-induced BDNF release was time-coincident with an LPS-induced increase of the A2AR density. Notably, removing endogenous extracellular adenosine or blocking A2AR prevented the LPS-mediated increase of both BDNF secretion and proliferation, as well as exogenous BDNF-induced proliferation.


CONCLUSIONS
We conclude that A2AR activation plays a mandatory role controlling the release of BDNF from activated microglia, as well as the autocrine/paracrine proliferative role of BDNF.
Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, Coimbra 3004-517, Portugal. catarinareisvalegomes@gmail.com
Catarina
C
Gomes
Raquel
R
Ferreira
Jimmy
J
George
Rui
R
Sanches
Diana I
DI
Rodrigues
Nélio
N
Gonçalves
Rodrigo A
RA
Cunha
D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000378:metabolism*; D043705:Receptor, Adenosine A2A / Q000502:physiology*
D058917:Adenosine A2 Receptor Antagonists; D019208:Brain-Derived Neurotrophic Factor; D008070:Lipopolysaccharides; D043705:Receptor, Adenosine A2A