Expression and antioxidation of Nrf2/ARE pathway in traumatic brain injury

To explore the expression of Nrf2/ARE pathway in hindbrain tissue after the traumatic brain injury (TBI) and its anti-oxidative stress effect in the secondary nerve injury.

The mice with Nrf2 gene knockout were used for the establishment of brain injury model. The experimental animals were divided into four groups: (Nrf2(+)/(+)) sham-operation group, (Nrf2(+)/(+)) brain injury group, (Nrf2(-)/(-)) sham-operation group and (Nrf2(-)/(-)) brain injury group. The specimen 24 h after cerebral trauma was selected. Then RT-PCR method was adopted to detect the expression of Nrf2 mRNA in brain; Western blotting method was adopted to detect the levels of Nrf2, HO-1 and NQO1 proteins in brain; ELISA method was adopted to detect the oxidative stress indicators: protein carbonyls, 4-hydroxy-2-nonenal (4-HNE) and 8-hydroxy-2'-deoxyguanosine (8-OHdG).

The Nrf2 mRNA and protein of Nrf2(-)/(-) mice were not expressed, and the difference of the relative amount of Nrf2 mRNA between Nrf2(+)/(+) TBI group and Nrf2(+)/(+) sham-operation group was not statistically significant (P>0.05); the level of Nrf2 protein in Nrf2(+)/(+) TBI group increased significantly compared with the Nrf2(+)/(+) sham-operation group (P<0.01); in the sham-operation groups, the levels of HO-1 and NQO1 proteins of Nrf2(-)/(-) mice decreased obviously compared with the Nrf2(+)/(+) mice (P<0.01); after brain injury, the levels of HO-1 and NQO1 proteins of Nrf2(+)/(+) mice increased obviously compared with the corresponding sham-operation group (P<0.01); the levels of HO-1 and NQO1 proteins of Nrf2(-)/(-) mice in TBI group had no obvious change compared with the corresponding sham-operation group (P>0.05); there was only a little amount of expression of protein carbonyls, 4-HNE and 8-OHdG proteins in brain tissues in the Nrf2(+)/(+) and Nrf2(-)/(-) sham-operation groups, and the difference was not statistically significant (P>0.05); after brain injury, the three oxidative stress indicators were significantly up-regulated in the Nrf2(+)/(+) and Nrf2(-)/(-) groups, and the up-regulation of the latter group was more significant (P<0.01).

After TBI the Nrf2/ARE pathway is activated and the activity of Nrf2 transcription regulation increases. However, the regulation dose not occur in the gene transcription level and only could increase the Nrf2 protein level, while the mRNA expression level has no obvious change. The nerve cell protective effect of Nrf2/ARE pathway in TBI achieves through inhibiting the oxidative stress injuries.