title: Early inner retinal astrocyte dysfunction during diabetes and development of hypoxia, retinal stress, and neuronal functional loss.
abstract: OBJECTIVE
  Neuronal and glial alterations precede the overt vascular change that characterizes diabetic retinopathy. Because retinal astrocytes modulate neuronal and vascular function, this study investigated the time course of astrocyte, Müller cell, and neuronal change during diabetes to determine whether astrocytes may play an early role in diabetic retinopathy.
  
  
  METHODS
  Sprague-Dawley rats were rendered diabetic via streptozotocin and neuronal and glial changes were assessed after 2-10 weeks. Astrocyte change was investigated using connexin-26 immunolabeling, whereas connexin-26 and -43 gene expressions were quantified using real-time PCR. Hypoxia was measured by pimonidazole labeling and the expression of hypoxia-inducible factor-1 alpha (HIF-1α) was quantified using Western blot. Müller cell gliosis was assessed by glial fibrillary acidic protein immunolabeling and retinal function assessed using the electroretinogram.
  
  
  RESULTS
  Astrocyte connexin-26 and -43 gene and protein expression decreased after 4 weeks of diabetes, before significant astrocyte loss. At the same time, the retina became hypoxic, with increased HIF-1α expression and pimonidazole labeling in the ganglion cell layer. This coincided with a decrease in ganglion cell function. After 6 weeks of diabetes, Müller cell gliosis became more evident and there were additional functional deficits in photoreceptoral and amacrine cell responses.
  
  
  CONCLUSIONS
  These findings suggest that early changes in astrocytes are coincident with inner retinal hypoxia and ganglion cell functional deficits, whereas Müller cell gliosis and more extensive decreases in neuronal function occur later. Astrocytes may play an early and key role in changes in retinal vasculature and inner retinal dysfunction in diabetes.
authors: Department of Anatomy and Cell Biology, University of Melbourne, Melbourne, Victoria, Australia.
authors: Alice
authors: A
authors: Ly
authors: Peter
authors: P
authors: Yee
authors: Kirstan A
authors: KA
authors: Vessey
authors: Joanna A
authors: JA
authors: Phipps
authors: Andrew I
authors: AI
authors: Jobling
authors: Erica L
authors: EL
authors: Fletcher
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology*; D015153:Blotting, Western; D000072259:Connexin 26; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000378:metabolism / Q000503:physiopathology*; D004596:Electroretinography; D015870:Gene Expression; D005911:Gliosis / Q000378:metabolism / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D018613:Microscopy, Confocal; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*; D055351:Retinal Neurons / Q000378:metabolism / Q000473:pathology*
chemical_list: D018031:Connexin 43; D017630:Connexins; C000607044:Gjb2 protein, rat; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D000072259:Connexin 26