Induction of acute phase gene expression by brain irradiation.
OBJECTIVE
To investigate the in vivo acute phase molecular response of the brain to ionizing radiation.


METHODS
C3Hf/Sed/Kam mice were given midbrain or whole-body irradiation. Cerebral expression of interleukins (IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6), interferon (IFN-gamma), tumor necrosis factors (TNF-alpha and TNF-beta), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthetase (iNOS), von Willebrand factor (vWF), alpha 1-antichymotrypsin (EB22/5.3), and glial fibrillary acidic protein (GFAP) was measured at various times after various radiation doses by ribonuclease (RNase) protection assay. The effects of dexamethasone or pentoxifylline treatment of mice on radiation-induced gene expression were also examined.


RESULTS
Levels of TNF-alpha, IL-1 beta, ICAM-1, EB22/5.3 and to a lesser extent IL-1 alpha and GFAP, messenger RNA were increased in the brain after irradiation, whether the dose was delivered to the whole body or only to the midbrain. Responses were radiation dose dependent, but were not found below 7 Gy; the exception being ICAM-1, which was increased by doses as low as 2 Gy. Most responses were rapid, peaking within 4-8 h, but antichymotrypsin and GFAP responses were delayed and still elevated at 24 h, by which time the others had subsided. Pretreatment of mice with dexamethasone or pentoxifylline suppressed radiation-induced gene expression, either partially or completely. Dexamethasone was more inhibitory than pentoxifylline at the doses chosen.


CONCLUSIONS
The initial response of the brain to irradiation involves expression of inflammatory gene products, which are probably responsible for clinically observed early symptoms of brain radiotherapy. This mechanism explains the beneficial effects of the clinical use of steroids in such circumstances.
Hong
J H
JH
Department of Radiation Oncology, UCLA School of Medicine 90095, USA.
Chiang
C S
CS
Campbell
I L
IL
Sun
J R
JR
Withers
H R
HR
McBride
W H
WH
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D016371:Cranial Irradiation; D016207:Cytokines / Q000096:biosynthesis / Q000187:drug effects / Q000528:radiation effects*; D003907:Dexamethasone / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects*; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis / Q000187:drug effects / Q000528:radiation effects; D007375:Interleukin-1 / Q000096:biosynthesis / Q000528:radiation effects; D008233:Lymphotoxin-alpha / Q000096:biosynthesis / Q000528:radiation effects; D051379:Mice; D008809:Mice, Inbred C3H; D010431:Pentoxifylline / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects / Q000528:radiation effects*; D011879:Radiotherapy Dosage; D013997:Time Factors; D014158:Transcription, Genetic / Q000528:radiation effects; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000187:drug effects / Q000528:radiation effects; D014665:Vasodilator Agents / Q000494:pharmacology
D000893:Anti-Inflammatory Agents; D016207:Cytokines; D007375:Interleukin-1; D008233:Lymphotoxin-alpha; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D014665:Vasodilator Agents; D018799:Intercellular Adhesion Molecule-1; D003907:Dexamethasone; D010431:Pentoxifylline