Amyloid precursor protein, Aβ and amyloid-associated proteins involved in chloroquine retinopathy in rats – immunopathological studies

To understand the retinal changes in Alzheimer disease (AD) patients, pathological and immunocytochemical studies were performed on retinal cells in the chloroquine-treated rats at 0, 4, 8, 12, 16, 20, and 24 weeks after the initial injection, using anti-amyloid precursor protein (APP), -amyloid beta protein (A beta), -apolipoprotein E (apoE), -ubiquitin, and -cathepsin D antibodies. Pathological alterations consistent with chloroquine retinopathy were recognized in the ganglion cells of the ganglion cell layer (GCL) and the inner plexiform layer (IPL) 4 weeks after initial chloroquine injection. Rat retinal changes appear to have a direct relationship to the duration of chloroquine administration. Intense immunoreactivities for anti-APP, A beta, apoE (an associated protein), and ubiquitin co-localized in the swollen ganglion cells and Muller cells by 20-24 weeks together with the lysosomal enzyme cathepsin D. The present data indicate that the endosomal/lysosomal pathway plays an important role in the processing of APP in rat retina. This experimental model is considered to be a suitable neural model to understand retinal pathology and the processing of APP in terms of the pathogenesis of AD, whereas chloroquine-induced myopathy is a useful extra neuronal model.