title: A quantitative in situ hybridization and polymerase chain reaction study of microglial-macrophage expression of interleukin-1beta mRNA following permanent middle cerebral artery occlusion in mice.
abstract: Interleukin-1beta (IL-1beta) is known to play a central role in ischemia-induced brain damage in rodents. In comparison to the rat, however, the available data on the cellular synthesis of IL-1beta mRNA and protein in the mouse are very limited. Here, we report on the time profile, the topography and the quantitative, cellular expression of IL-1beta mRNA in mice subjected to permanent occlusion of the distal middle cerebral artery (MCA). The in situ hybridization analysis showed that IL-1beta mRNA was expressed during the first post-surgical hour in a small number of high-expressing macrophage-like cells, located in cortical layers I and II of the future infarct. At 2 h, a significant number of faintly labeled IL-1beta mRNA-expressing cells had appeared in the developing peri-infarct, and the number remained constant at 4 h and 6 h, when the hybridization signal began to distribute to the cellular processes. Quantitative PCR performed on whole hemispheres showed a significant 20-fold increase in the relative level of IL-1beta mRNA at 12 h and a highly significant 42-fold increase at 24 h, at which time single IL-1beta mRNA-expressing cells were supplemented by aggregates and perivascular infiltrates of intensely labeled IL-1beta mRNA-expressing cells. Immunohistochemistry and double immunohistochemical stainings in addition to combined in situ hybridization, confirmed that the intensely labeled IL-1beta mRNA-expressing and IL-1beta protein synthesizing cells predominantly were glial fibrillary acidic protein-immunonegative, macrophage associated antigen-1-immunopositive microglia-macrophages. By day 5 there was a dramatic decline in the relative level of IL-1beta mRNA in the ischemic hemisphere. In summary, the data provide evidence that permanent occlusion of the distal MCA in mice results in expression of IL-1beta mRNA and IL-1beta synthesis in spatially and temporally segregated subpopulations of microglia and macrophages.
authors.affiliation: Medical Biotechnology Center, University of Southern Denmark, Odense, Denmark.
authors.forename: B H
authors.initials: BH
authors.lastname: Clausen
authors.forename: K L
authors.initials: KL
authors.lastname: Lambertsen
authors.forename: M
authors.initials: M
authors.lastname: Meldgaard
authors.forename: B
authors.initials: B
authors.lastname: Finsen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D020244:Infarction, Middle Cerebral Artery / Q000378:metabolism* / Q000473:pathology; D007375:Interleukin-1 / Q000096:biosynthesis*; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
chemical_list: D007375:Interleukin-1; D012333:RNA, Messenger