DIFFERENTIAL INDUCTION OF MESSENGER-RNA SPECIES ENCODING SEVERAL CLASSES OF STRESS PROTEINS FOLLOWING FOCAL CEREBRAL-ISCHEMIA IN RATS

We report here the time-dependent expression of several classes of HSP mRNAs following focal cerebral ischemia in rats. HSP70, GRP78, HSP27, HSP90 and HSP47 have been reported to possess distinct functions unde r normal and/or stress conditions. These different classes of HSP mRNA s were differentially induced by ischemia, as determined by Northern b lot analysis. Messenger RNAs of the HSP70 family proteins were induced within 4 h after ischemia and then rapidly decreased, whereas HSP27 a nd HSP47 mRNAs reached a maximum level of expression at 24 h and 48 h after ischemic treatment, respectively. In situ hybridization showed t hat the expression of inducible HSP70 mRNA was observed predominantly in regions adjacent to the ischemic core except during the early perio ds of ischemia. HSP27 mRNA was expressed over a broad area of the ipsi lateral cerebral neocortex except for the ischemic center 24 h after i schemia. The unique induction kinetics for each HSP mRNA species may r eflect their distinct roles in the brain during various physiological stresses. We will also discuss that stress proteins may be involved in the central nervous system after ischemia in two important aspects: e arly protection against stress and restoration of damaged lesions in t he brain at later stages after ischemia.