Heat shock protein 27 shows a distinctive widespread spatial and temporal pattern of induction in CNS glial and neuronal cells compared to heat shockprotein 70 and caspase 3 following kainate administration

Kainate-induced status epilepticus is associated with both apoptotic and ne crotic cell death and induction of heat shock proteins (HSPs) in hippocampa l and cortical regions of the rodent brain. In the present study we have ex amined the temporal, spatial and cellular expression patterns of mRNAs for the highly inducible HSPs, HSP70 and HSP27, together with the apoptotic mar ker, caspase 3 (CPP32) in rat brain after systemic administration of kainat e. HSP70 mRNA was transiently induced in the forebrain by kainate, principa lly in the CA1, CA3 and hilar cells of the hippocampal formation, in pirifo rm cortex and discrete thalamic nuclei. Maximal expression was seen at 8 h after kainate which then declined to background levels by 7 days. Labelling was predominantly neuronal. In contrast, HSP27 mRNA expression was more wi despread. Intense labelling was observed in CAI, CA3 and the hilar region a t 8 h after kainate but the expression profile for HSP27 mRNA expanded cons iderably with intense signals seen in corpus callosum, cortex and thalamus at 24 h post kainate. Emulsion autoradiographs indicated a predominantly gl ial localisation for HSP27 mRNA. In the hilus, a distinct subpopulation of interneurones were found to express HSP27 mRNA. CPP32 mRNA was upregulated in CAI. CA3 and hilus of the hippocampal formation and in piriform cortex. CPP32 mRNA expression was more restricted and similar in distribution to HS P70 mRNA being localised to neurones. The present study demonstrates the un ique early expression of HSP27 mRNA by glial cells and distinct populations of neurones which extends beyond those in which HSP70 and CPP32 induction occurs with subsequent cell loss. (C) 2001 Elsevier Science BY. All rights reserved.