title: Effects of heat shock protein 72 (Hsp72) on evolution of astrocyte activation following stroke in the mouse.
abstract: Astrocyte activation is a hallmark of the response to brain ischemia consisting of changes in gene expression and morphology. Heat shock protein 72 (Hsp72) protects from cerebral ischemia, and although several protective mechanisms have been investigated, effects on astrocyte activation have not been studied. To identify potential mechanisms of protection, microarray analysis was used to assess gene expression in the ischemic hemispheres of wild-type (WT) and Hsp72-overexpressing (Hsp72Tg) mice 24 h after middle cerebral artery occlusion or sham surgery. After stroke both genotypes exhibited changes in genes related to apoptosis, inflammation, and stress, with more downregulated genes in Hsp72Tg and more inflammation-related genes increased in WT mice. Genes indicative of astrocyte activation were also upregulated in both genotypes. To measure the extent and time course of astrocyte activation after stroke, detailed histological and morphological analyses were performed in the cortical penumbra. We observed a marked and persistent increase in glial fibrillary acidic protein (GFAP) and a transient increase in vimentin. No change in overall astrocyte number was observed based on glutamine synthetase immunoreactivity. Hsp72Tg and WT mice were compared for density of astrocytes expressing activation markers and astrocytic morphology. In animals with comparable infarct size, overexpression of Hsp72 reduced the density of GFAP- and vimentin-expressing cells, and decreased astrocyte morphological complexity 72 h following stroke. However, by 30 days astrocyte activation was similar between genotypes. These data indicate that early modulation of astrocyte activation provides an additional novel mechanism associated with Hsp72 overexpression in the setting of ischemia.
authors.affiliation: Department of Anesthesia, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, USA.
authors.forename: George E
authors.initials: GE
authors.lastname: Barreto
authors.forename: Robin E
authors.initials: RE
authors.lastname: White
authors.forename: Lijun
authors.initials: L
authors.lastname: Xu
authors.forename: Curtis J
authors.initials: CJ
authors.lastname: Palm
authors.forename: Rona G
authors.initials: RG
authors.lastname: Giffard
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D005075:Biological Evolution; D002544:Cerebral Infarction / Q000209:etiology; D004195:Disease Models, Animal; D005163:Factor Analysis, Statistical; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D020244:Infarction, Middle Cerebral Artery / Q000150:complications; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D046228:Microarray Analysis; D009419:Nerve Tissue Proteins / Q000378:metabolism; D020521:Stroke / Q000209:etiology / Q000473:pathology*; D013997:Time Factors
chemical_list: C086936:Fabp7 protein, mouse; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005904:Glial Fibrillary Acidic Protein; D050884:HSP72 Heat-Shock Proteins; D009419:Nerve Tissue Proteins