PEDF-derived peptide inhibits Amyloid-β internalization and ameliorates retinal toxicity

Abstract

Purpose : Amyloid-beta (Aβ) has been implicated in the pathophysiology of age-related macular degeneration. We have shown that Aβ species possess differential retinal neurotoxicity, where oligomeric and fibrillar assemblies of Aβ42 mediated the primary retinotoxic effects. The mechanism of internalization of extracellular Aβ42 species in the retina is not well defined. In the brain, Aβ binding to the 67kDa laminin receptor (67LR) mediated the internalization of oligomeric Aβ42 and related neuronal cell death. We have found that PEDF335, a pigment epithelium-derived factor derived peptide, can bind to 67LR. Here, we hypothesized that 67LR mediates Aβ42 uptake in the retina, and PEDF335 may limit extracellular Aβ internalization, thereby inhibit Aβ42 retinal toxicity.

Methods : ARPE-19 cells were cultured with PEDF335 for 6h before treatment with oligomeric or fibrillar Aβ42 for 24 h. Cell viability was determined by XTT assay. The uptake of Aβ42 was assessed using immunostaining. Wild type rats were treated with intravitreal injection (10μl) of PEDF335 (3mM) in each eye two days prior to administration of oligomeric or fibrillar Aβ42 to the right eye. Retinal function was assessed at baseline and thereafter through 6 weeks after the injection. At each time point, electroretinography (ERG) measures were compared between eyes. The presence of 67LR in ex-vivo retina was determined using immunostaining.

Results : PEDF335 treatment blocked amyloid internalization into ARPE-19 cells and maintained their viability in the presence of oligomeric and fibrillar Aβ42. ERG responses in rat eyes treated with oligomeric or fibrillar Aβ42 assemblies were near-normal in eyes previously treated with PEDF335, whereas those measured in eyes treated with Aβ42 alone showed pathologic attenuation through 14 days. No adverse effects were noted in response to PEDF335. Retinal immunostaining demonstrated the expression of 67LR in rats’ retina.

Conclusions : Our results show that PEDF335 protects against oligomeric and fibrillar Aβ42 retinal toxicity, at least in part, via binding to 67LR and inhibition of Aβ42 internalization. These observations provide evidence on the importance of extracellular versus intracellular Aβ42 in the retina and suggest that the mechanism of toxicity of fibrils possibly involves secondary release of oligomers. Such insights may promote the mechanistic understanding of the retinal pathogenicity of Aβ.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.