Analysis of intraretinal neuro-glial interaction in glaucoma

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1.In an attempt to elucidate the causal effect of diabetes on development of glaucomatous optic neuropathy, male Sprague-Dawley rats were made diabetic by streptozotocin injection, in which unilateral eyes were treated with episcleral vein cauterization to produce chronically elevated intraocular pressure (IOP). Terminal dUTP nick end-labeling (TUNEL) staining was performed on the flat-mount retina dissected at several time points of sacrifice. The number of TUNEL positive cells in the inner retina was significantly higher in diabetic retina with episcleral vein 'cauterization than in control retina with same operation. Thus, diabetes has an additive effect on neuronal apoptosis induced by glaucoma in rats.2.In order to identify whether the pro-survival Akt pathway is activated in retina with chronically elevated IOP, immunohistochmeistry in the crysosection and in the whole mount retina as well as immunoblotting with retinal homogenates were conducted for rat retina with episcleral ve … More in cauterization. Akt phorphorylated at Ser 437 was specifically expressed in the retinal ganglion cells in the retina with cauterization, but not in the contralateral retina. Phosphorylated relative to total Akt was significantly increased in retina with cauterization. Thus, Akt activation may counteract against increased IOP stress in retina.3.Finally, to test whether glial reactivity was altered in glaucomatous retina, immunostaining and immunoblotting for glial fibrially acidic protein (GFAP) was conducted in the same experimental glaucoma model as in 2. Astrocytes lost and Muller cells gained GFAP imunoreactivity as early as at 3 days after episcleral vein cauterization, which was partially reversed overtime but last up to 6 months. GFAP molecular mobility and acidity were also changed by the cauterization. Similar observations were also occurred in the contrallateral retina at 1 month and thereafter. Thus, epicsleral vein cauterization altered glial reactivity not only in the ipsilateral but also in the contralateral eyes in rats. Less