Regional Expression of Heat Shock Protein-70 mRNA and c-Fos mRNA following Focal Ischemia in Rat Brain

Abstract

Summary: In situ hybridization was used to estimate re gional levels of heat shock protein-70 (HSP-70) mRNA and c-fos mRNA in two related models of focal cerebral ischemia. In the first model, permanent occlusion of the distal middle cerebral artery (MCA) alone caused a patchy increase in HSP-70 mRNA by 1 h in the central zone of the MCA territory of the ipsilateral neocortex. Tissue levels of HSP-70 mRNA continued to increase for several hours and remained elevated at 24 h. In contrast to the focal expression of HSP-70, c-fos mRNA was in creased throughout the ipsilateral cerebral cortex by 15 min and remained elevated for least 3 h. The wide distri bution of c-fos expression suggests it may have been caused by spreading depression. In the second model, severe focal ischemia was produced with a combination of transient (l-h) bilateral carotid artery occlusion and permanent MCA occlusion. Combined occlusion for 1 h Cerebral ischemia induces increased synthesis of a number of specific proteins, despite an overall reduction in the rate of protein synthesis (Kleihues and Hossmann, 1971; Dienel et aI., 1980 Dienel et aI., , 1986Nowak, 1985). Several of the induced proteins are members of a group of "heat shock" or "stress" proteins that are expressed in the central nervous system following a number of stresses, including heat shock (Brown and Rush, 1990), trauma (Gower et aI., 1989), as well as ischemia. Although the func tion of the stress proteins is not well understood, their induction has been correlated with increased resistance to injury in many cell types (for review, see Lindquist and Craig, 1988). In brain, induction of stress proteins prior to an episode of cerebral 204without reperfusion caused expression of HSP-70 mRNA only in regions adjacent to the central zone of the MCA territory of the neocortex. However, reperfusion of the carotids for 2 h generated intense expression of HSP-70 mRNA throughout most of the ipsilateral cerebral cortex, white matter, striatum, and hippocampus. The wide spread increase in HSP-70 mRNA suggests that reperfu sion triggered expression in all previously ischemic re gions. However, at 24 h of reperfusion, increased levels of HSP-70 mRNA were restricted primarily to the isch emic core of the neocortex. These results suggest that expression of HSP-70 mRNA is prolonged in regions un dergoing injury, but is transient in surrounding regions that recover. Key Words: Heat shock protein-70--c-fos Focal ischemia-In situ hybridization-Messenger ribo nucleic acid-Middle cerebral artery.

Suppression of ischemia‐induced fos expression and AP‐1 activity by an antisense oligodeoxynucleotide to c‐fos mRNA

“…The contralateral (left MCA) cortex and ipsilateral and contralateral hippocampi and subcortical structures sustained little or only mild ischemia (blood flow reduction of 0-20%) with no morphological evidence of ischemic injury. In this model, consistent expression of c-fos mRNA by Northern blot or in situ hybridization, and of Fos antigen by immunohistochemistry and increase in AP-1 binding activity have been reported [6,8,9].…”

“…The discrepancy in immunohistochemical findings between the hippocampus and the ischemic cortex is not clear. It should be noted that in this stroke model, the ipsilateral hippocampus sustains little or no ischemia but does show an intense regional expression of c-fos [8,9], presumably due to a probable secondary neurotransmitter mechanism [5,12]. A consistent coagulation necrosis develops in the right MCA cortex.…”

“…The contralateral (left MCA) cortex and ipsilateral and contralateral hippocampi and subcortical structures sustained little or only mild ischemia (blood flow reduction of 0-20%) with no morphological evidence of ischemic injury. In this model, consistent expression of c-fos mRNA by Northern blot or in situ hybridization, and of Fos antigen by immunohistochemistry and increase in AP-1 binding activity have been reported [6,8,9].The rectal temperature was monitored and maintained at 37 ± 0.5°C via an electronic temperature controller (Versa-Therm 2156, Cole-Pharmer, Chicago, IL) connected to a heating lamp. Physiological parameters including arterial blood pressure and pulse rate were monitored and maintained within normal ranges during surgery and up to 60 minutes after ischemia.…”

“…Recent observations of altered gene expression in ischemic brain using animal stroke models have opened new avenues for exploration of the biochemical cascades after stroke [1][2][3][4][5][6][7][8][9][10][11]. These postischemic events include an increase in extracellular excitatory amino acid neurotransmitters such as glutamate.…”

“…Although the cellular uptake of antisense oligodeoxynucleotides can be mediated via carrier-mediated endocytosis [39,40], phosphorothioated oligodeoxynucleotide-lipofectin uptake by cells does not appear to involve endosomes or lysosomes [41,42]. The present study of an in vivo antisense strategy utilizes a focal cerebral ischemia model in rats, in which the expression of c-fos and Fos protein and the enhanced AP-1 binding activity have been established and characterized [6,8,9]. …”