Expression of Cytokines in Radiation Injured Brain at Acute Phase

Lee, Jang Bo; Kim, Min Ho; Chung, Yong Gu; Park, Jung Yul

Abstract

OBJECTIVE
Radiation therapy is an important treatment for brain tumor. However, serious complications such as radiation necrosis can occur and it may be secondary to the expression of acute phase genes, like cytokines. In particular, inflammatory cytokines (IL-1beta, TNF-alpha) and other immunomodulatory cytokines (TNF-alpha, TGF-beta1) might be changed after irradiation (high single dose irradiation). Although it has been reported that IL-1 level is remarkably elevated within 8 week after the irradiation to the rat brain, the change of cytokines levels at acute phase (within 24 hours) has not been reported. In the present study, we examined TNF-alpha, TGF-beta1, and IL-1beta levels in acute phase to clarify the early effect of cytokines on the radiation-induced brain damage.
METHODS
Fifty Sprague-Dawley rats were used and these were divided into irradiation group and control group. After a burr-hole trephination on the right parietal area using a drill, a single 10 Gy was irradiated at the trephined site. Their forebrains were extirpated at 30 min, 2 hr, 8 hr, 12 hr and 24 hr, respectively and examined for the expression of TNF-alpha, TGF-beta1 and IL-1beta.
RESULTS
The expression of TNF-alpha and TGF-beta1 were decreased until 12 hr after irradiation but elevated thereafter. The expression of IL-1 was peak at 8 hr and then decreased until 12 hr but elevated after this time window. The present study indicated that expression of cytokines (TNF-alpha, TGF-beta1 and IL-1beta) were increased at 24 hr after the irradiation to the rat brain. IL-1beta level, on the other hand, reached peak at 8 hr after radiation injury.
CONCLUSION
These findings indicate that IL-1, among various cytokines, may have a more important role in the inflammatory reaction by radiation injury at acute phase and provide some clues for better understanding of the pathogenesis of radiation injury.