Calpaine mediated cell death in naive and NGF treated PC12 cells after glutamate induced exitotoxicity

Augmented calcium influx can cause biochemical alterations that involve degradative enzymes (proteases and endonucleases) leeding to neurodegeneration by excitotoxicity. PC12 cells (chromaffinergic rat pheochromocytoma cell line) are a useful model for investigating cell death by glutamate induced excitotoxicity in neurons. Upon treatment with nerve growth factor (NGF), PC12 cells culture shift their phenotype to a post-mitotic, differentiated, neurite-bearing NGF-dependent neuron. The purpose of the present study was to investigate the molecular response of central nervous system to glutamate induced excitotoxicity using PC12 cell cultures, after calpain inhibition treatment in different concentrations. These chromaffinergic transformed cells upon treatment with nerve growth factor (NGF), differentiate to a sympathetic phenotype expressing neurites and excitability. PC12-cells were cultured in full medium DMEM at 37° C with 5% CO2. To cause excitotoxicity from glutamate, undifferentiated and NGF-treated PC12 cultures in DMEM with low glucose concentrations have been exposed for 3h to glutamate in two concentrations (0,5 μM and 10 μM). We investigated the involvement of proteolysis in cell death induced by glutamate toxicity, using a calpain inhibitor MDL28170. Cell viability was estimated by a colorimetric method using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. According to our results MDL28170 appears to have neuroprotective effects in excitotoxic injury caused by glutamate treatment. However, calpain inhibition is effective only in low glutamate concentrations. Our results indicate that the mechanisms implicated in cell death by glutamate excitotoxicity seem to differentially engage calpain dependent and independent pathways.