INDUCTION OF C-FOS AND JUNB MESSENGER-RNA FOLLOWING IN-VIVO BRAIN IRRADIATION

Although radiotherapy is a front line treatment for brain tumors, litt le is known about the in vivo molecular responses of brain to irradiat ion. In this study, expression of c-fos, c-jun and junB immediate-earl y genes were followed in mouse brain after irradiation. C-fos and junB , but not c-jun, mRNA was induced within 15 min in unanesthetized irra diated mice. Induction was transient and lasted < 4 h. The response wa s dose-dependent with increases in c-Sos and junB mRNA levels after do se of greater than or equal to 2 and 7 Gy, respectively. Anesthesia of mice with pentobarbitol delayed the increases in mRNA expression and the response was attenuated. Pre-treatment of mice with dexamethasone, in a schedule which suppressed acute-phase gene expression after brai n irradiation, did not significantly change c-fas and junB induction. Our results show that c-fos and junB responses occur in the brain in r esponse to irradiation and that they can be modified by pentobarbital treatment but suggest that there is no direct correlation between the level of mRNA expression and later expression of cytokines or other ac ute-phase response genes.