The dynamic changes of nuclear factor-κB during brain injury of irradiated rats

Objective To investigate the dynamic changes of nuclear factor-κB(NF-κB) during brain injury of irradiated rats. Methods According to the random number table method, 82 healthy Sprague-Dawley rats were divided into two groups: 50 rats in the irradiation group and the other 32 rats in the control group given sham-irradiation. The whole brains of rats in the irradiation group were irradiated with a single dose of 20 Gy electron beam to establish an animal model of radiation-induced brain injury. All brain tissues were respectively taken out 1, 3, 7, 14 and 28 d after irradiation. The quantificational real-time-polymerase chain reaction (QRT-PCR) was used to detect the expressions of the NF-κB mRNA while the expression of NF-κB protein was analyzed by ELISA and Western blot. The positioning expression of NF-κB protein in the hippocampus was measured with immunohistochemical staining. Results In the irradiation group, the expression of NF-κB mRNA significantly increased at 3 and 7 d following irradiation (t=37.79, 35.30, P<0.05) and it approached a peak value on the third day following irradiation. The expression of NF-κB protein in whole brain tissues after irradiation was up-regulated and reached a peak on the first day post-irradiation and it was significantly higher than controls at 1, 3, 7, 14 d after irradiation (t=30.94, 14.87, 27.17, 13.27, P<0.05) then declined and dropped to the normal level by 28 d. The results of immunohistochemical staining showed that the number of NF-κB positive cells in the hippocampus increased at 1, 3 and 7 d following irradiation (t=-8.49, -4.47, -3.46, P<0.05). Conclusions After irradiation, the expressions of NF-κB mRNA and corresponding protein first increase and then later decrease, which promotes the development of brain injury. Key words: Nuclear factor-κB; Radiation-induced brain injury; Animal model