NEUROBIOLOGY OF HEAT SHOCK RESPONSE IN NEURONAL CULTURES

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We have recently demonstrated that glutamate excitotoxicity is attenuated by the prior induction of the heat-shock response. A short thermal stress induced a pattern of protein synthesis characteristic of the highly conserved heat-shock response and increase the expression of hear shock protein (HSP) mRNA. Protein synthesis was necessary for the neuroprotective effect. Evidence suggests that both excitotoxicity and the heat-shock response play a significant role in a variety of neurologic disorders. A number of intra-and intercellular processes have been proposed as important mediators of excitotoxicity in vitro. Here we plan to examine how the elements of the heat-shock response act to alter the sequence of events leading to excitotoxic cell death. In many of these studies we intend to utilized neuronal cultures grown in the presence of blockers of neurotransmission. Or previous studies with such cultures show that they have low basal levels of HSP expression and they exhibit robust, seizure-like activity when blockers are removed. The latter feature we plan to study as a form of synaptically mediated excitatory stress, akin to epileptiform activity in vivo. Specifically we proposed to characterized the effect of the heat-shock proteins on calcium homeostasis,electrophysiological responsiveness of neurons to glutamate, glutamate activation of phospholipase A2, and spontaneous excitatory neurotransmission. In addition, using recently available immunologic reagents we plan to carefully characterize the neuroprotective pattern of HSP expression in neurons and glial cells in the cultures. The work is expected to further our understanding of the protective properties of the HSPs and of the important mechanisms they inhibit to confer neuroprotection.