Changes in Gene Expression After Brief Ischemic Insults as Potential Mediators of Induced Tolerance: Postischemic Temperature as a Variable Affecting the Stress Response
Recent studies have described the induction of tolerance to otherwise damaging ischemic insults following short priming challenges that do not themselves cause severe injury. This effect has been most convincingly demonstrated following brief 2-min ischemic insults in the gerbil [7, 8] after which vulnerability of CA1 neurons to a standard 5-min insult was reduced. Increased expression of the inducible 70-kDa heat shock/stress protein hsp72 in the protected neuron population correlated reasonably well with the time course of observed tolerance during 1 – 4 days of recirculation after the initial insult . Parallel results have been obtained in vitro demonstrating reduced sensitivity of cultured neurons to glutamate toxicity following prior heat shock sufficient to induce hsp72 expression [11, 21]. Induced ischemic tolerance in vivo following hyperthermic stress has also been described [4, 9], although hsp72 expression in CA1 neurons after such insults has not been convincingly demonstrated . Taken together the above studies suggest that the induced expression of hsp72 in otherwise vulnerable neurons may contribute to induced ishemic tolerance.
KeywordsIschemic Insult Cereb Blood Flow Hsp70 mRNA Ischemic Tolerance Gerbil Brain
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