GP120-INDUCED NEUROTOXICITY IN HIPPOCAMPAL PYRAMIDAL NEURON CULTURES - PROTECTIVE ACTION OF TGF-BETA-1

We found that TGF-beta 1, a cytokine that previously has been reported to have neuroprotective effects: was able to prevent the toxicity ind uced by the HIV-1 coat protein gp120 in hippocampal pyramidal neuron c ultures, In the presence of glia, gp120 induced time- and dose-depende nt cell death, which was more pronounced in mature (7-19 d in culture) than in young neurons (2-7 d in culture). Staining with nuclear dyes (propidium iodide and Hoechst 33342), in situ detection of DNA fragmen ts, and DNA analysis on agarose gels indicated that apoptosis was main ly responsible for the death caused by the viral protein. However, aft er several days of treatment, death-displaying necrotic features also occurred, Neurotoxicity induced by gp120 was dependent on the activati on of NMDA receptors and required the presence of glia as well as new protein synthesis. Thus, the effect of gp120 was abolished by the NMDA receptor antagonist APV and partially reduced by cycloheximide. Only modest neurotoxicity was observed in pure neuronal cultures deprived o f the glia feeder layer, Fura-2-based videoimaging showed that treatme nt with gp120 enhanced the ability of NMDA to increase neuronal [Ca2+] (i). The impairment of neuronal Ca2+ homeostasis was prevented complet ely by TGF-beta 1. Therefore, it is likely that the neuroprotective ac tion of the cytokine is attributable to its ability to stabilize neuro nal [Ca2+](i).