title: Tempol protects against intravitreous indocyanine green-induced retinal damage in rats.
abstract: OBJECTIVE
  Indocyanine green (ICG) has been widely used as a vital dye for macular surgery. However, ICG can be toxic to retinal cells. Here we evaluate whether tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a free radical scavenger, can protect against ICG-induced retinal damage in rats.
  
  
  METHODS
  Brown Norway rats received intravitreal injections of ICG 0.5 % or BSS as controls. Tempol (20 mg/kg BW) or PBS as a control was administered intraperitoneally 24 h and 30 min before ICG and once daily for 7 consecutive days. Tempol was detected in the retina using electron paramagnetic resonance (EPR) spectroscopy. One week after ICG injections, the effects of tempol on retinal toxicity were assessed by retinal ganglion cell (RGC) back-labeling and by light microscopy. Electroretinography (ERG) was performed after 1 and 2 weeks.
  
  
  RESULTS
  ICG administration reduced RGC numbers by 17 % (1,943 ± 45 vs. 2,342 ± 31 RGCs/mm(2)). Tempol treatment rescued RGCs in a significant manner (2,258 ± 36, p < 0.01) and diminished morphological changes detected by light microscopy. ICG-injected eyes showed a significant reduction of ERG potentials only in PBS-treated animals (V(max) 530 ± 145 µV vs. 779 ± 179 µV, p = 0.0052), but not in the tempol-treated group.
  
  
  CONCLUSIONS
  Tempol significantly attenuates ICG-induced toxicity in rat retinas and may therefore be considered for further evaluation as accompanying treatment in ICG-assisted chromovitrectomy.
authors.affiliation: Centre for Ophthalmology, University of Tübingen, Röntgenweg 11, 72076, Tübingen, Germany. sebastian.thaler@uni-tuebingen.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Thaler
authors.forename: Bogomil
authors.initials: B
authors.lastname: Voykov
authors.forename: Gabriel
authors.initials: G
authors.lastname: Willmann
authors.forename: Michal
authors.initials: M
authors.lastname: Fiedorowicz
authors.forename: Robert
authors.initials: R
authors.lastname: Rejdak
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.forename: C Albrecht
authors.initials: CA
authors.lastname: May
authors.forename: Andreas
authors.initials: A
authors.lastname: Schatz
authors.forename: Frank
authors.initials: F
authors.lastname: Schuettauf
mesh_terms: D000818:Animals; D002452:Cell Count; D002470:Cell Survival; D004396:Coloring Agents / Q000633:toxicity*; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D003623:Dark Adaptation; D004578:Electron Spin Resonance Spectroscopy; D004596:Electroretinography; D005260:Female; D016166:Free Radical Scavengers / Q000494:pharmacology*; D007208:Indocyanine Green / Q000633:toxicity*; D058449:Intravitreal Injections; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010775:Photic Stimulation; D051381:Rats; D011914:Rats, Inbred BN; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D012164:Retinal Diseases / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000473:pathology; D013113:Spin Labels
chemical_list: D004396:Coloring Agents; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D018696:Neuroprotective Agents; D013113:Spin Labels; D007208:Indocyanine Green; C001803:tempol