Abstract
Purpose: :
PAF is a mediator of the inflammatory/immune response to several pathologies (N. Bazan, Nature, 374:501, 1995), including protection of photoreceptor apoptosis (S. Cortina et al, Exp Eye Res, 146:4292, 2005). Because phospholipase A2 is activated and PAF synthesis enhanced in neural injury, we reasoned that a novel PAF receptor antagonist, systematically applied, may suppress experimental CNV.
Methods: :
Mouse eyes were dilated and laser-induced choroidal neovascularization was performed; 3 lesions were made on each retina at 4, 8, and 12 o’clock around the optic nerve. Each pulse (Lumenis Novus-Spectra ophthalmic laser on a Topcon SLD7 slitlamp; 50 µm dia, 200 mW , 100 mS) produced a retinal bubble as Bruch’s was breached. The Paf receptor antagonist LAU-0901 (60 mg/kg bw, 45% [2-hydroxypropyl]-β-cyclodextrin) was delivered on day 1 and 2, and on day 7 and 14 FITC leakage was analyzed for each lesion. Images were captured with the Topcon IMAGEnet 2000 LITE digital imaging system, and ranked as strong, moderate, slight, or none; only strong is considered clinically relevant in human. 1 day later choroidal flat-mounts labeled with FITC-conjugated isolectin B4 (specific for endothelial cells) were analyzed. Diameters of choroidal lesions (laser + 15 days) were plotted to determine degree of neovascularization for each drug treatment. The incorporation of LAU into retina following ip delivery was obtained by mass spectrometry from a time course at 0.5, 1, 2, 4, 6, and 9 hours.
Results: :
LAU peaked in retina 2 h after ip delivery, but declined to negligible amounts by 9 h. 76% of the laser-induced lesions in control (cyclodextrin vehicle alone) retinas demonstrated strong FITC leakage after 7 days, and 55% of control lesions remained strong after 14 days. However, in animals treated with LAU, only 37% of the lesions showed strong leakage after 7 days, with an additional decline to 9% by day 14. Endothelial cell labeling at the site of each lesion demonstrated that the lesion sites of LAU-treated retinas increased to about 67 µm in diameter, while control retinal lesions increased from 50 µm to 105 µm.
Conclusions: :
The protective effect of LAU results in a reduction of the amount of leakage (neovascularization) by 50-80%. This is supported by a reduced lesion site diameter in LAU treatments. We suggest that this novel PAF receptor antagonist may be of therapeutic use in CNV.
Keywords: age-related macular degeneration • choroid: neovascularization • second messengers