title: Activated protein C rescues the retina from ischemia-induced cell death.
abstract: OBJECTIVE
  Ischemia causes severe and persistent visual loss in many eye diseases, including central retinal vein occlusion (CRVO) and diabetic retinopathy. Activated protein C (APC) has been demonstrated to reduce the cell death associated with ischemia in the brain and kidney. This study was performed to examine the ability of APC to rescue hypoxia-induced retinal cell death in vitro and in vivo.
  
  
  METHODS
  Retinal pigment epithelium (RPE) and photoreceptor cells were placed in either a normoxic or a hypoxic chamber. Immediately before they were subjected to ischemia, the cultures were treated with APC (3-240 μg/mL). Incubation was followed by an MTT assay to determine the number of viable cells. The activity of caspase-3, -8, and -9 in RPE cells was also analyzed. Various concentrations of APC were intravitreally injected in a rat CRVO model, followed by TUNEL staining to detect the in vivo effects of APC.
  
  
  RESULTS
  Lower concentrations of APC (0.3-30 μg/mL) showed a cell-protective effect against hypoxia in vitro, whereas higher concentrations (≥120 μg/mL) demonstrated cytotoxicity in both RPE and photoreceptor cells. Caspase-3, -8, and -9 were activated when the cells were exposed to hypoxia, but this activation was significantly inhibited by APC. Experimental CRVO-induced retinal cell apoptosis was reduced dramatically by intravitreal injection of APC.
  
  
  CONCLUSIONS
  APC can reduce ischemia-induced cytotoxicity both in vitro and in vivo via blocking the activation of caspase-3, -8, and -9. APC may be a promising candidate for protecting the retina from ischemia.
authors.affiliation: Department of Ophthalmology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
authors.forename: Zhao-Jiang
authors.initials: ZJ
authors.lastname: Du
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ueda
authors.forename: Mihoko
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Tano
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kamei
mesh_terms: D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D006801:Humans; D000860:Hypoxia; D020287:In Situ Nick-End Labeling; D058449:Intravitreal Injections; D051379:Mice; D008822:Mice, Transgenic; D011486:Protein C / Q000494:pharmacology*; D051381:Rats; D015427:Reperfusion Injury / Q000201:enzymology / Q000473:pathology / Q000517:prevention & control*; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D012170:Retinal Vein Occlusion / Q000201:enzymology / Q000473:pathology / Q000517:prevention & control*
chemical_list: D005343:Fibrinolytic Agents; D011486:Protein C; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9