title: Reduced photoreceptor damage after photodynamic therapy through blockade of nitric oxide synthase in a model of choroidal neovascularization.
abstract: OBJECTIVE
  To investigate the role of nitric oxide synthase (NOS) in photoreceptor degeneration associated with photodynamic therapy (PDT) in a laser-induced model of choroidal neovascularization (CNV).
  
  
  METHODS
  PDT was performed in monkey and Brown Norway rats with laser-induced CNV. L-NAME, a NOS inhibitor, or saline was injected intraperitoneally in rats with CNV. An NO donor, or saline, was injected intravitreously into normal rats. Photoreceptor apoptosis was evaluated by TUNEL and electron microscopy. NOS, ED-1, and cleaved-caspase-3 (c-casp-3) expression were determined by immunohistochemistry. CNV lesions were examined by fluorescence angiography and choroidal flat mount.
  
  
  RESULTS
  TUNEL and electron microscopy showed photoreceptor apoptosis after PDT. In rats, there were significantly more TUNEL-positive cells in the photoreceptors 24 hours after PDT, whereas in the CNV lesions there were more TUNEL-positive cells 6 hours after PDT. C-casp-3 was detected in the CNV lesions but not in the photoreceptors after PDT. There was no difference in the numbers of ED-1-positive macrophages before and after PDT. However, inducible NOS (iNOS) was increased after PDT in macrophages. Intravitreous injection of the NO donor without PDT also induced substantial photoreceptor apoptosis. L-NAME-treated animals had significantly fewer TUNEL-positive cells in the photoreceptors than saline-treated animals after PDT (P < 0.05). There were no differences in CNV size and leakage between L-NAME- and saline-treated groups.
  
  
  CONCLUSIONS
  iNOS expression in macrophages contributes to PDT-induced photoreceptor degeneration. NOS inhibition reduces PDT-induced photoreceptor degeneration without compromising the treatment effect of PDT in an experimental model of CNV.
authors: Angiogenesis and Laser Laboratories, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors: Haicheng
authors: H
authors: She
authors: Toru
authors: T
authors: Nakazawa
authors: Akihisa
authors: A
authors: Matsubara
authors: Toshio
authors: T
authors: Hisatomi
authors: Tara A
authors: TA
authors: Young
authors: Norman
authors: N
authors: Michaud
authors: Edward
authors: E
authors: Connolly
authors: Ali
authors: A
authors: Hafezi-Moghadam
authors: Evangelos S
authors: ES
authors: Gragoudas
authors: Joan W
authors: JW
authors: Miller
mesh_terms: D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D020256:Choroidal Neovascularization / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005451:Fluorescein Angiography; D019084:Fluorescent Antibody Technique, Indirect; D020287:In Situ Nick-End Labeling; D007274:Injections, Intraperitoneal; D008252:Macaca fascicularis; D008264:Macrophages / Q000201:enzymology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors*; D010778:Photochemotherapy; D020419:Photoreceptor Cells, Vertebrate / Q000201:enzymology / Q000648:ultrastructure*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011166:Porphyrins / Q000627:therapeutic use; D051381:Rats; D011914:Rats, Inbred BN; D012162:Retinal Degeneration / Q000139:chemically induced / Q000201:enzymology / Q000473:pathology / Q000517:prevention & control*; D000077362:Verteporfin
chemical_list: D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D017319:Photosensitizing Agents; D011166:Porphyrins; D000077362:Verteporfin; D052247:Nitric Oxide Synthase Type II; D053148:Caspase 3; D019331:NG-Nitroarginine Methyl Ester