PEDF exerts neuroprotective effects on retinal ganglion cells via PEDF receptors

Abstract

Purpose : The aim of this study was to investigate expression and regulation of two of several receptors for PEDF, patatin-like phospholipase 2 gene product/PEDF-R and laminin receptor (LR), in serum-starved RGCs under hypoxia, which is a relevant pathological condition in retinal neurodegenerative diseases such as glaucoma or ischemic retinopathies, and explore their involvement in the survival of retinal neuronal cells. Changes in the expression of some neuroprotective factors (PEDF, VEGF, BDNF) and anti-apoptotic Bcl-2 family members (Bcl-2, Bcl-x_L), when reducing the expression of PEDF receptors. In addition, we have also evaluated whether ERK1/2 signaling pathway was involved in the process which PEDF exerts pro-survival effects on retinal ganglion cells.

Methods : Using RGCs isolated from mice eyeballs and the immortalized retinal cell line R28 as the main research objects. Immunocytochemical Staining, RNA Interference, qPCR, and western blot techniques, were used to detect the expression levels of PEDF-R and Laminin-R under different stimulations. After knocking out PEDF-R and LR genes with interfering RNA, the expression level of neuroprotective factors and anti-apoptotic Bcl-2 family-related factors were detected. Western blot technology was also used to explore the phosphorylation level of ERK1/2 signaling pathway.

Results : RGCs and R28 cells express both PEDF-R and LR. PEDF and VEGF exposure, as well as the presence of Müller cells, enhance the expression of both receptors. These expression trends were the same under hypoxic conditions. After knocking down PEDF-R and LR, the anti-apoptotic Bcl-2 family members’ (Bcl-2, Bcl-x_L) and neuroprotective mediators’ (PEDF, VEGF, BDNF) expression was significantly reduced. PEDF treatment enhanced the phosphorylation level of ERK1/2 in R28 cells.

Conclusions : The enhancement of PEDF-R and Laminin R under hypoxia sensitizes retinal neurons to interaction with PEDF, which leads to increased cell viability through induction of anti-apoptotic Bcl-2 family members, expression of secretable pro-survival factors, and suppression of apoptosis. ERK1/2 signaling pathway might be involved in the PEDF’s action. Elucidating PEDF-R, Laminin R function and signaling pathways regulating receptor-promoted RGC survival may be helpful in developing more efficient treatment options for retinal neurodegenerative diseases.

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