PEDF-derived peptide protects against Amyloid-β toxicity in vitro and prevents retinal dysfunction in rats

Amanda Qarawani ^1,2 Efrat Naaman ^1,3 Rony Ben-Zvi Elimelech ^1,2 Michal Harel ^1,2 Chen Itzkovich ¹ Shadi Safuri ^1,3 Jack Henkin ⁴ Shiri Soudry ^1,2,3

¹Clinical Research Institute, Rambam Health Care Campus, Israel
²Ruth and Bruce Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Israel
³Department of Ophthalmology, Rambam Health Care Campus, Israel
⁴Center for Developmental Therapeutics, Northwestern University, USA

Amyloid-beta (Aβ) is implicated in the pathophysiology of age-related macular degeneration. We have shown that Aβ possess differential neurotoxicity in the retina, where oligomeric and fibrillar Aβ42 assemblies mediated the primary retinotoxic effects. In neuronal cells, the 67kDa laminin receptor (67LR) mediates the internalization of oligomeric Aβ42 and related cell death. The peptide PEDF335, developed from pigment epithelium-derived factor (PEDF), can bind to 67LR. Here, we hypothesized that 67LR mediates intracellular uptake of Aβ42 in the retina, and that PEDF335 may limit Aβ42 internalization, thereby inhibiting its toxicity.

ARPE-19 cells were cultured with PEDF335 for 6h before treatment with Aβ42 for 24h. XTT assay determined cell viability, and intracellular Aβ42 uptake was assessed using immunostaining. Sprague-Dawley rats were treated with intravitreal injection (10μl) of PEDF335 (3mM) in the right eye two days prior to administration of Aβ42 to both eyes. Retinal function was assessed at baseline and through 6 weeks post injection. Retinal presence of 67LR was determined ex vivo by immunostaining and western blotting.

PEDF335 diminished amyloid internalization into ARPE-19 cells and maintained their viability in the presence of oligomeric and fibrillar Aβ42. Electroretinography responses in rat eyes treated with the Aβ42 assemblies were near-normal in eyes treated with PEDF335, whereas eyes treated with Aβ42 alone showed pathologic attenuation through 6 weeks. Immunostaining and western blot demonstrated the expression of 67LR.

PEDF335 protects against oligomeric and fibrillar Aβ42 retinal toxicity, at least partially via inhibition of Aβ42 internalization. Such insights may promote the mechanistic understanding of Aβ-related retinal pathogenicity.