Neuroprotection by pigment epithelial-derived factor against glutamate toxicity in developing primary hippocampal neurons

Abstract

Pigment epithelial-derived factor (PEDF) has been shown to be a survival factor for cerebellar granule neurons. Here we investigated the ability of PEDF to enhance the survival of hippocampal neurons in culture, and to protect these neurons against acute glutamate toxicity. Hippocampal neurons prepared from 1- to 3-day postnatal rat brain were cultured for either 7 or 14 days in vitro (DIV). At 14 DIV, neurons were only slightly protected (13% +/- 4%) against 50 microM glutamate toxicity when treated with 1 microg/ml of PEDF for 3 successive days before glutamate exposure as measured by lactate dehydrogenase (LDH) release. In comparison, basic fibroblast growth factor (bFGF) at 10 ng/ml for the same treatment period protected 58% +/- 8% of the neurons against glutamate. Using quantitative image analysis of digitized micrographs, we found that the average size of neurons in young, developing hippocampal cultures (7 DIV), was greatly decreased by treatment with 50 microM glutamate. Treatment for up to 5 successive days with 1 microg/ml of PEDF before glutamate addition dramatically increased the average hippocampal neuron soma size, compared to cells treated with glutamate alone. Thus, PEDF may promote the growth of hippocampal neurons, and, if added to developing hippocampal neurons, can also protect these cells from subsequent injury, such as the excitotoxicity of glutamate.

Putative role for EPC‐1/PEDF in the G0 growth arrest of human diploid fibroblasts

“…Interestingly, secretion of the mouse homolog of EPC‐1/PEDF, named caspin, was found to be inversely related to metastasis by a murine colon adenocarcinoma cell line (Kozaki et al, 1998). As a survival factor, EPC‐1/PEDF has been shown to protect photoreceptors from light damage and from death in murine models of retinal degeneration, as well as to promote survival of cerebellar granule, spinal motor, retinal, and primary hippocampal neurons (Taniwaki et al, 1995, 1997; Araki et al, 1998; Bilak et al, 1999; Cao et al, 1999, 2001; Cayouette et al, 1999; DeCoster et al, 1999; Houenou et al, 1999; Nomura et al, 2001; Ogata et al, 2001). It is unclear what functional relationship, if any, exists between the growth inhibitory effects of EPC‐1/PEDF and its role as a survival factor in neuronal cells.…”

“…EPC‐1 is identical to a secreted, retinal pigmented epithelium (RPE)‐derived factor (PEDF) which has been characterized as both an inhibitor of endothelial cell growth and migration as well as a survival factor for neuronal‐like cells (Taniwaki et al, 1995, 1997; Sugita et al, 1997; Araki et al, 1998; Bilak et al, 1999; Cao et al, 1999; Cayouette et al, 1999; Dawson et al, 1999; DeCoster et al, 1999; Houenou et al, 1999; Cohen et al, 2000; Crawford et al, 2001; Mori et al, 2001; Nomura et al, 2001; Ogata et al, 2001; Stellmach et al, 2001). There is a general diminution of EPC‐1 expression with senescence in vitro in all cell types studied thus far including HDF cells from a variety of tissue types and RPE cells (Pignolo et al, 1993; DiPaolo et al, 1995; Tombran‐Tink et al, 1995; Hjelmeland et al, 1999; Tresini et al, 1999).…”

Identification of the Neuroprotective Molecular Region of Pigment Epithelium-Derived Factor and Its Binding Sites on Motor Neurons

“…PEDF has neurotrophic and neuroprotective functions in the CNS beyond the retina. For example, PEDF supports the survival of immature cerebellar granule (CG) neurons (Taniwaki et al, 1995) and protects them from induced apoptosis (Araki et al, 1998;Nomura et al, 2001), protects older CG neurons from glutamate injury (Taniwaki et al, 1997), and protects embryonic hippocampal neurons from glutamate injury (DeCoster et al, 1999). We and others have shown that fulllength and properly folded native PEDF protects postnatal rat motor neurons from chronic glutamate injury and embryonic chick motor neurons from apoptosis (Bilak et al, 1999a;Houenou et al, 1999).…”

Endogenic Regulation of Proliferation and Zinc Transporters by Pigment Epithelial Cells Nonvirally Transfected with PEDF

“…The goal of transfecting pigment epithelial cells with the gene for human PEDF is to transplant PEDF-transfected cells in the subretinal space as a treatment modality for retinal degenerative diseases. Because PEDF is a multifunctional molecule that has been shown to have neuroprotective 40,41 and antiangiogenic 42,43 effects, protect against AGE-mediated effects, 44,45 and suppress metalloproteinase-9, 46 it is critical to verify that the PEDF-transfected cells are able to secrete a functional PEDF protein. To define the biologic activity of the rPEDF secreted into the media by the transfected ARPE-19 cells, we have examined their ability to autoregulate their proliferation and zinc transporter gene expression and the anti-angiogenic activity of rPEDF using an in vitro HUVEC sprouting assay.…”