title: Increased retinal toxicity of intravitreal tissue plasminogen activator in a central retinal vein occlusion model.
abstract: BACKGROUND
  Intravitreal injection of tissue plasminogen activator (tPA) is used to treat several ocular conditions, although excessive doses of intravitreal tPA cause retinal toxicity. Toxicity may increase in the ischemic retina, such as in central retinal vein occlusion (CRVO), because tPA toxicity to neural tissues increases under ischemic conditions. We investigated tPA toxicity to the retina in a CRVO rat model.
  
  
  METHODS
  CRVO was induced in pigmented rats with rose Bengal-assisted laser photothrombosis. One hour after CRVO induction, 3 microl of tPA (0.075, 0.75, 3, or 7.5 microg) was injected intravitreally. Eyes that did not receive laser treatment, which served as non-CRVO controls, received tPA (0.75, 3, or 7.5 microg). The same amount of balanced salt solution (BSS) was injected as a nondrug control. Eyes were enucleated at 12 hours after injection, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining was performed to evaluate retinal cell apoptosis.
  
  
  RESULTS
  The number of TUNEL-positive cells increased in a dose-dependent manner in both non-CRVO and CRVO group and significantly (P = 0.002) increased when 0.75, 3, or 7.5 microg of tPA was injected into the CRVO eyes. When comparing the number of TUNEL-positive cells between the eyes with and without CRVO that received the same treatment, apoptosis significantly increased in CRVO eyes.
  
  
  CONCLUSIONS
  Retinal toxicity associated with intravitreally injected tPA can increase in a dose-dependent manner and be exacerbated in CRVO eyes, suggesting that the dose of tPA should be reduced when tPA is used to treat eyes with CRVO.
authors.affiliation: Department of Ophthalmology, E7, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita 565-0871, Japan.
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Motohiro
authors.initials: M
authors.lastname: Kamei
authors.forename: Paradee
authors.initials: P
authors.lastname: Kunavisarut
authors.forename: Mihoko
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Tano
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002452:Cell Count; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005343:Fibrinolytic Agents / Q000008:administration & dosage / Q000633:toxicity*; D005451:Fluorescein Angiography; D020287:In Situ Nick-End Labeling; D007267:Injections; D051381:Rats; D012160:Retina / Q000187:drug effects* / Q000473:pathology; D012164:Retinal Diseases / Q000139:chemically induced / Q000473:pathology; D012170:Retinal Vein Occlusion / Q000188:drug therapy*; D012395:Rose Bengal; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage / Q000633:toxicity*; D014822:Vitreous Body
chemical_list: D005343:Fibrinolytic Agents; D012395:Rose Bengal; D010959:Tissue Plasminogen Activator