The stress protein response in cultured neurons: characterization and evidence for a protective role in excitotoxicity.

We used purified cultures of cerebellar granule cells to investigate the possible protective role of stress proteins in an in vitro model of excitotoxicity. Initial experiments used one- and two-dimensional polyacrylamide gel electrophoresis to confirm the induction of typical stress protein size classes by heat shock, sodium arsenite, and the calcium ionophore A23187. Immunoblot analysis and immunocytochemistry verified the expression of the highly inducible 72 kd heat shock protein (HSP72). Granule cell cultures exposed to glutamate showed evidence of cellular injury that was prevented by the noncompetitive NMDA antagonist MK-801, yet glutamate did not induce a detectable stress protein response. Nonetheless, preinduction of heat shock proteins was associated with protection from toxic concentrations of glutamate. These results imply that the HSP72 expression observed in in vivo models of excitotoxicity may not be directly related to the effects of excitatory amino acids. However, the ability of stress protein induction to protect against injury from glutamate may offer a novel approach toward ameliorating damage from excitotoxins.