Differential expression of egr1 and activation of microglia following irradiation in the rat brain.
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.
Vollmann
Henning
H
Institute of Brain Research, University of Tübingen, Germany.
Wölfel
Sarah
S
Ohneseit
Petra
P
Stransky
Elke
E
Vonthein
Reinhard
R
Wick
Wolfgang
W
Meyermann
Richard
R
Simon
Perikles
P
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
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