title: PKCζ mediates breakdown of outer blood-retinal barriers in diabetic retinopathy.
abstract: OBJECTIVE
  Diabetic macular edema represents the main cause of visual loss in diabetic retinopathy. Besides inner blood retinal barrier breakdown, the role of the outer blood retinal barrier breakdown has been poorly analyzed. We characterized the structural and molecular alterations of the outer blood retinal barrier during the time course of diabetes, focusing on PKCζ, a critical protein for tight junction assembly, known to be overactivated by hyperglycemia.
  
  
  METHODS
  Studies were conducted on a type2 diabetes Goto-Kakizaki rat model. PKCζ level and subcellular localization were assessed by immunoblotting and immunohistochemistry. Cell death was detected by TUNEL assays. PKCζ level on specific layers was assessed by laser microdissection followed by Western blotting. The functional role of PKCζ was then evaluated in vivo, using intraocular administration of its specific inhibitor.
  
  
  RESULTS
  PKCζ was localized in tight junction protein complexes of the retinal pigment epithelium and in photoreceptors inner segments. Strikingly, in outer segment PKCζ staining was restricted to cone photoreceptors. Short-term hyperglycemia induced activation and delocalization of PKCζ from both retinal pigment epithelium junctions and cone outer segment. Outer blood retinal barrier disruption and photoreceptor cone degeneration characterized long-term hyperglycemia. In vivo, reduction of PKCζ overactivation using a specific inhibitor, restored its tight-junction localization and not only improved the outer blood retinal barrier, but also reduced photoreceptor cell-death.
  
  
  CONCLUSIONS
  In the retina, hyperglycemia induced overactivation of PKCζ is associated with outer blood retinal barrier breakdown and photoreceptor degeneration. In vivo, short-term inhibition of PKCζ restores the outer barrier structure and reduces photoreceptor cell death, identifying PKCζ as a potential target for early and underestimated diabetes-induced retinal pathology.
authors: Institut National de la Santé et de la Recherche Médicale, U872, Paris, France ; Université Paris Descartes, UMRS 872, Paris, France ; Centre de Recherche des Cordeliers, UPMC-Paris6, UMRS 872, Paris, France.
authors: Samy
authors: S
authors: Omri
authors: Francine
authors: F
authors: Behar-Cohen
authors: Pierre-Raphaël
authors: PR
authors: Rothschild
authors: Emmanuelle
authors: E
authors: Gélizé
authors: Laurent
authors: L
authors: Jonet
authors: Jean Claude
authors: JC
authors: Jeanny
authors: Boubaker
authors: B
authors: Omri
authors: Patricia
authors: P
authors: Crisanti
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001813:Blood-Retinal Barrier / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003930:Diabetic Retinopathy / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D006943:Hyperglycemia / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D009419:Nerve Tissue Proteins; D020419:Photoreceptor Cells, Vertebrate / Q000187:drug effects / Q000473:pathology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D055213:Retinal Pigment Epithelium / Q000187:drug effects / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D000099221:Protein Kinase C zeta; C472451:Pard3 protein, rat; C504908:Pard6a protein, rat