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Joana M. Galvao, Li Guo, Ana R. Santiago, Antonio F. Ambrosio, M Francesca Cordeiro; Adenosine A3 receptor agonist inhibits retinal ganglion cell apoptosis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6590.
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© ARVO (1962-2015); The Authors (2016-present)
Adenosine receptors have been considered as potential therapeutic targets in neurodegenerative diseases. In the retina, adenosine and three of its four receptors have been identified at the level of retinal ganglion cells (RGCs). Our previous study shows the presence of adenosine A3 receptor on the RGC layer, and a protective effect of an intravitreal injection of an adenosine A3 receptor agonist on retinal ganglion cells in a model of RGC apoptosis in vivo. In this study, we focused on assessing adenosine A3 receptor expression and the potential neuroprotective effects of a selective adenosine A3 agonist, 2-Cl-IB-MECA in an axotomy rat model of ganglion cell death.
Partial optic nerve transection (ONT) was induced in one eye of Dark Agouti rats, with the opposite eye as control (n=6/treatment group). Eyes were intravitreally injected with either 2-Cl-IB-MECA, adenosine A3 agonist (1.2 µM - the optimal dose from our previous study) or PBS (vehicle) immediately before surgery. Animals eyes were imaged to assess RGC apoptosis using DARC (Detection of Apoptosis in Retinal Cells) seven days after transection of the optic nerve, with methods and analysis we have previously described. Immunohistochemical analysis of adenosine A3 receptor expression was performed in 10 µm-thick retinal cryosections.
DARC imaging analysis revealed that the adenosine A3 receptor agonist, 2-Cl-IB-MECA (1.2 µM), significantly (p ≤ 0.01) reduced RGC apoptosis, to approximately 50% compared to vehicle treated control (mean 239±93.65 vs 449±84.58, respectively). Immunohistochemistry confirmed the expression of adenosine A3 receptor in RGC layer, which was down regulated in ONT eyes compared to control.
In accordance with our previous findings, these results suggest that adenosine A3 receptor activation is neuroprotective against RGC apoptosis in vivo. We suggest that targeting A3 receptor and delineation of its relationship with RGC apoptosis could have great potential in the management of retinal neurodegeneration, such as glaucoma. Further work is underway to understand the mechanism behind the protective effect of adenosine A3 receptor on retinal ganglion cells.Acknowledgements to: Prof. Claire Mitchell, University of Pennsylvania, Department of Ophthalmology
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