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

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 μM glutamate toxicity when treated with 1 μg/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 μM glutamate. Treatment for up to 5 successive days with 1 μg/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.