A1 receptor changes throughout light induced retinal degeneration.

SOLIÑO, M.; LÓPEZ, EM.; VACOTTO, M.; GIRARDI, E.; LOPEZ, JJ.

Washington

Congreso; 44th Annual Meetinf of the Society for Neuroscience.; 2014

Society for Neuroscience

Continuous illumination (CI) of rat retina produces photoreceptor degeneration. This model of light induced retinal degeneration (LIRD) resembles many of the characteristics of human retinal degenerative diseases such as Age-related Macular Degeneration (AMD), the first cause of acquired blindness in the developed countries, and Retinitis Pigmentosa (RP). The presence of A1 adenosine receptor has been reported mainly in ganglion cell layer of the retina by in situ hybridizaton, autoradiography and immunocytochemistry (ICC). In addition, A1 receptor agonists have been reported to be neuroprotective in animal models of inflammatory, hypoxic and degenerative diseases of CNS and retina. In order to shed some light on the processes underlying retinal degenerations and to asses a new potential therapeutic  target, we studied the changes of A1 receptor in the retina in the model of LIRD by using ICC and Western Blot (WB) techniques. Sprague Dawley rats were submitted to CI (12000 lux) during 1, 2, 5 and 7 days.  The eyes of the animals were removed and processed either by ICC or by WB. Both techniques were performed using an A1 receptor primary antibody (Santa Cruz). ICC and WB results were quantified by image analysis using the software Image J and Image Light Studio respectively. ICC data were statistically analysed using a one way ANOVA test. Immunocytochemical results showed immunoreactivity in nerve fiber layer, ganglion cell layer, inner plexiform layer, the inner portion of the inner nuclear layer and photoreceptor cell layer. Quantification showed an increase of the reactivity in all layers after 24 hs of CI. This first increase of optical density (OD) at day 1 was maintained steady during days 2 and 5 of CI. A second higher increase of OD was found at day 7. A one way ANOVA  test of the results showed that all the observed OD increments throughout all retinal layers at days 1 to 7 were significant compared with controls (P<0,0001). The WB studies also showed an increase of A1 receptor levels compared to control levels from days 1 to 7 when the maximum relative density was also obtained. Our results showed an increase of A1 receptors in the retina starting at 24 hs which is the moment of maximal oxidative stress in coincidence with the peak of nitric oxide (NO) production. The observed increase of A1 receptor immunoreactivity may be the demonstration of an upregulation of adenosine receptors probably due to the lack of adenosine production during the retinal degeneration process. Knowing the beneficial effects of A1 receptor agonist in animal models of CNS diseases, A1R seems a likely target for future therapies of retinal degeneration.