Abstract
Abstract: :
Purpose: Pigment epithelium–derived factor (PEDF) has been shown to protect against ischemia–induced loss of retinal ganglion cells (RGC). We tested if PEDF can exert a direct protective effect on cultured RGC. Methods: Cytotoxicity was induced in primary culture of adult rat RGC by glutamate treatment or by trophic factor withdrawal. The protective effect of PEDF was evaluated by including the peptide during cell insults. RGC survival was assessed by counting Thy–1–positive cells. Results: The primary culture of retinal cells used in these studies contained mainly retinal neurons enriched with RGC. By immunocytochemistry, 30–50% of all cells expressed Thy–1 and neurofilament–L; both are RGC–specific markers. In contrast, cells in culture did not express markers for several other retinal cell types: arrestin (photoreceptor), GFAP (astroglia), glutamine synthetase (Müller cell), or ED1 (microglia). Less than 10% of the cells were labeled by the anti–protein kinase Cα antibody (rod bipolar cells). After a 3–day treatment, glutamate induced a concentration–dependent loss of RGC with an EC50 of approximately 10 µM. In the presence of 100 µM glutamate, RGC survival decreased by 40%–60%. The glutamate toxicity was completely eliminated by 100 nM MK801, an NMDA receptor antagonist. Similarly, trophic factor withdrawal for 3 days also induced a 50% loss of RGC in culture. PEDF protected against both insults. Its effect was dose–dependent with an EC50 ≈ 3 ng/mL. At 100 ng/mL, it completely protected the cells from injuries. Conclusions: An adult rat RGC–enriched culture was established and used successfully to evaluate cytotoxic and cytoprotective agents. In this culture, both glutamate treatment and trophic factor withdrawal induced RGC loss. PEDF potently and efficaciously protected against both insults. The neuroprotective effect of PEDF represents a novel approach for potential treatment of various retinopathies.
Keywords: neuroprotection • ganglion cells • pharmacology