Effects of kainate-mediated excitotoxicity on the expression of rat counterparts of A170 and MSP23 stress proteins in the brain

Stress proteins play important roles in the protective mechanisms under cri tical conditions for cell survival. We report here the expression of A170 a nd MSP23, oxidative stress-inducible proteins, under kainate-mediated excit otoxicity in the rat brain. A170 mRNA was significantly induced in the brai n 5-8 h after i.p. kainate administration. MSP23 mRNA was observed at quite a low level in the rat brain, and the induction of MSP23 mRNA was not obse rved during the period 24 h after kainate administration. Immunoblot analys is demonstrated that the maximal expression level of A170 protein occurred 8 h after treatment in each part of the brain. MSP23 protein was constituti vely expressed in the brain and the level of this protein was significantly decreased during the period 24 h after kainate administration. In situ hyb ridization and immunohistochemical studies showed that A170 was expressed p redominantly in neurons, especially in pyramidal neurons of the cerebrum an d cerebellar Purkinje cells, while MSP23 was expressed in oligodendrocytes. The induction of A170 was observed in the regions which are affected by ex citotoxicity and this induction was observed in the earlier phase than cell death. Also, the region which shows high vulnerability to excitotoxicity s uch as pyramidal cell layer in the hippocampus, showed lower A170 expressio n than that which shows resistance to excitotoxicity, such as the dentate g yrus in the hippocampus. These results suggest that A170 may play a protect ive role in the brain under kainate-mediated excitotoxicity. (C) 1999 Elsev ier Science B.V. All rights reserved.