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SJ McKinnon, NL Ransom, NG Tahzib, DM Lehman, HA Reitsamer; A Monoclonal Antibody to Amyloid Precursor Protein Induces Apoptosis in Rat Retinal Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4031.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Evidence suggests that altered metabolism of amyloid precursor protein (APP) plays a role in the pathophysiology of retinal ganglion cell (RGC) death in glaucoma. Studies in hippocampal cultures have shown that mouse monoclonal antibody 22c11 cross-links APP at the N-terminal extracellular domain and induces apoptosis in a dose-dependent manner. We sought to determine the apoptotic effects of intravitreal administration of 22c11 on rat RGCs. Methods: 22c11 (Boerhinger Mannheim, Indianapolis, IN) and control IgG1 (ICN, Aurora, OH) antibodies were desalted using Bio-Gel P-6 spin columns (BioRad, Hercules, CA). 16 adult brown Norway rats (225-250 gm) were placed into two groups, receiving a unilateral intravitreal injection of 2 µl of a 10 µg/ml (in PBS) solution of either 22c11 or IgG1. Two animals from each group were sacrificed at four time points: days 1, 2, 5, and 12. Injected eyes were enucleated and processed into paraffin. Retinal cross-sections were examined for evidence of apoptosis using the terminal deoxynucleotidyl transferase(TdT)-mediated biotinylated-dUTP nick end labeling (TUNEL) assay. Labeled cells were imaged with streptavidin-HRP using light microscopy (Zeiss Axioscope, Thornberry, NY). Positive controls included DNase and negative controls excluded TdT. Results: TUNEL positivity was assessed in treated rat RGCs for each of the four time points. In 22c11-treated retinas, no TUNEL positive cells were noted at days 1 and 2 post-injection. Scattered TUNEL-labeled RGCs were noted at day 5 post-injection. Widespread TUNEL labeling of RGCs was seen at 12 days post-injection. IgG1-treated retinas showed no TUNEL labeling at any of the four time points post-injection. DNase-treated retinas displayed TUNEL-positive RGCs, and TdT-excluded control retinas showed no labeling. Conclusion: Disruption of the homeostatic properties of secreted APP is capable of producing apoptotic cell death in rat RGCs. Axonal transport blockade in glaucoma may also induce caspase activation and apoptosis through APP dysregulation, contributing to the pathophysiology of glaucoma.
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