N-acetylcysteine protects against chorioretinal damage induced by photodynamic therapy for experimental choroidal neovascularization in a rat model.

Purpose: We explored the protective effects of N-acetylcysteine (NAC) on chorioretinal damage induced by photodynamic therapy (PDT) in an experimental rat model of choroidal neovascularization (CNV).

Methods: Experimental CNV was induced by an argon laser in 24 Brown Norway rats 7 days prior to PDT. Commencing 1 day after CNV induction, 0.5 mL of NAC was orally administered daily to the NAC + group (12 rats), and 0.5 mL of normal saline to the NAC- group (12 rats). Diode laser treatment was delivered for 42 s (total energy, 25 J/cm2) to the left eye prior to verteporfin infusion (PDT-) and to the right eye 15-20 min after such infusion (PDT+). Fluorescein angiography was performed just prior to PDT and enucleation to evaluate fluorescein leakage and CNV closure. We compared the CNV thickness, PDT-induced apoptosis [evaluated via terminal dUTP nick-end labeling (TUNEL)], fluorescein angiographic data, and extents of immunohistofluorescent staining for cleaved caspase-3 and superoxide dismutase (SOD) between the two groups.

Results: Fourteen days after diode laser treatment, the CNV closure rate was significantly higher in the PDT-treated than the control group. However, the CNV closure rates did not differ significantly between the NAC- and NAC + groups. The TUNEL activity (a measure of PDT-induced apoptosis) of retinal cells was higher in the NAC-/PDT + than the NAC+/PDT + group at 1, 3, 7, and 14 days. The cleaved caspase-3 and SOD levels were higher in the NAC-/PDT + than the NAC+/PDT + group at 3 and 7 days.

Conclusions: PDT triggers oxygen radical-induced injury to, and apoptosis in, the retina. NAC may reduce PDT-induced damage to the retina without compromising the therapeutic efficacy of CNV.