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L. Knels, M. Worm, M. Wendel, C. Roehlecke, E. Kniep, R. H. W. Funk; Effects of Age-Inductor Glyoxal and H2O2 As Oxidative Stress Factors on Rat Retinal Organ Cultures and Neuroprotection by Brimonidine. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5624.
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Reactive oxygen species (ROS) and advanced glycation end products (AGEs) seem to be involved in the degeneration of retinal ganglion cells (RGCs) and are linked to the risk of diabetic neuropathy, diabetic retinopathy, and age-related macular degeneration (AMD). In the present study we investigated the effects of the reactive AGE-intermediate glyoxal and of H2O2 on rat retinal organ cultures and tested the neuroprotective effects of the alpha2-adrenergic agonist brimonidine.
Rat retina whole mounts exposed to glyoxal or H2O2 were either treated with brimonidine or with brimonidine and the PI3-kinase inhibitor LY 294002. The accumulation of the glycoxidation product Nε-[carboxymethyl] lysine (CML) was assessed immunohistochemically. Changes in intracellular pH (pHi), mitochondrial transmembrane potential (MTMP) and ROS production in RGCs were studied by intravital fluorescence microscopy and confocal laser scanning microscopy using the fluorescence dyes BCECF, JC-1, and CM-H2DCFDA. Ultrastructural changes of RGC-mitochondria were determined by transmission electron microscopy.
Glyoxal and H2O2 caused CML production which was inhibited by brimonidine treatment. Both glyoxal and H2O2 increased ROS production whereas brimonidine completely prevented this effect (p<0.01). Glyoxal and H2O2 decreased pHi and MTMP in RGCs. Brimonidine partially ameliorated the acidification produced by glyoxal but significantly prevented the H2O2 induced decrease in pHi. MTMP tended to be preserved in group glyoxal/brimonidine and H2O2/brimonidine, respectively. In parallel with these observations, brimonidine attenuated ultrastructural damage of RGC mitochondria. LY 294002 reversed the brimonidine-mediated attenuation of CML and ROS-production induced by glyoxal and H2O2.
Using rat retinal whole mounts, we show that brimonidine prevents oxidative stress and preserves mitochondrial ultrastructure. These protective effects seem, at least in part, to be mediated by PI3 kinase-dependent pathways.
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