title: Differential expression of egr1 and activation of microglia following irradiation in the rat brain.
abstract: BACKGROUND
  Little is known about the immediate effects of whole-brain gamma-irradiation. The authors hypothesize that Egr1 as an immediate early gene and microglia both participate in early reactions.
  
  
  METHODS
  Both, expression of Egr1 and cellular distribution were studied in a temporal sequence in different brain regions of rats subjected to irradiation with 10 Gy. Brain tissue was examined using immunohistochemistry, real-time RT-PCR (reverse transcription-polymerase chain reaction), and Western blotting.
  
  
  RESULTS
  Astroglia and oligodendroglia showed increased Egr1 immunoreactivity within the first hours following irradiation. This was accompanied by a strong peak in CD68 immunoreactivity histologically attributable to activated microglia. A high constitutive expression of Egr1 protein in the nuclei of activated neurons was reduced following irradiation and RT-PCR demonstrated significantly reduced levels of egr1-lv as a neuronal activity-related mRNA variant.
  
  
  CONCLUSIONS
  The induction of Egr1 in glial cells, as well as the activation of microglia take place earlier than histological changes reported so far. The authors revealed a temporal sequence of reactions that point toward the initiation of an immediate inflammatory response including reduced neuronal activity.
authors.affiliation: Institute of Brain Research, University of Tübingen, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Vollmann
authors.forename: Sarah
authors.initials: S
authors.lastname: Wölfel
authors.forename: Petra
authors.initials: P
authors.lastname: Ohneseit
authors.forename: Elke
authors.initials: E
authors.lastname: Stransky
authors.forename: Reinhard
authors.initials: R
authors.lastname: Vonthein
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wick
authors.forename: Richard
authors.initials: R
authors.lastname: Meyermann
authors.forename: Perikles
authors.initials: P
authors.lastname: Simon
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics; D015214:Antigens, Differentiation, Myelomonocytic / Q000235:genetics; D001253:Astrocytes / Q000473:pathology / Q000528:radiation effects; D001921:Brain / Q000473:pathology / Q000528:radiation effects*; D002467:Cell Nucleus / Q000473:pathology / Q000528:radiation effects; D002531:Cerebellum / Q000473:pathology / Q000528:radiation effects; D016371:Cranial Irradiation / Q000009:adverse effects*; D003593:Cytoplasm / Q000473:pathology / Q000528:radiation effects; D018891:Dentate Gyrus / Q000473:pathology / Q000528:radiation effects; D051766:Early Growth Response Protein 1 / Q000235:genetics*; D005625:Frontal Lobe / Q000473:pathology / Q000528:radiation effects; D015870:Gene Expression / Q000528:radiation effects; D006624:Hippocampus / Q000473:pathology / Q000528:radiation effects; D008297:Male; D017628:Microglia / Q000528:radiation effects*; D009474:Neurons / Q000473:pathology / Q000528:radiation effects; D010296:Parietal Lobe / Q000473:pathology / Q000528:radiation effects; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics*; D011833:Radiation Injuries, Experimental / Q000235:genetics* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D051766:Early Growth Response Protein 1; D012333:RNA, Messenger; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C486110:Egr1 protein, rat