Effects of hydrogen rich water on the expression of Nrf 2 and the oxidative stress in rats with traumatic brain injury

Abstract:

Objective: To investigate the effects of hydrogen rich water on the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and oxidative stress in rats with traumatic brain injury (TBI).

Methods: Ninety healthy male Sprague-Dawley (SD) rats were randomly divided into sham operation group, TBI group and hydrogen rich water treatment group (HW group), with 30 rats in each group. TBI model was reproduced by the modified Feeney weight dropping method. The skulls of rats in sham operation group underwent only craniotomy without direct hit. The rats in HW group received brain injury by hitting after craniotomy, followed by injection of hydrogen rich water (5 mL/kg) intraperitoneally once a day for 5 days after successful reproduction of the model. The rats in sham operation group and TBI group were given an equal amount of normal saline in same manner. Six rats from each group were sacrificed at 6, 12, 24, 48 hours and 5 days after evaluating neurological severity scores (NSS). The brain tissue in injured ipsilateral cortex was harvested. The activity of catalase (CAT), glutathione peroxidase (GSH-Px), and content of malondialdehyde (MDA) were determined by spectrophotometry. The expressions of mRNA and nucleoprotein of Nrf2 were determined by quantitative real-time polymerase chain reaction (RT-qPCR) and Western Blot. The pathological changes were observed with microscopy after hematoxylin and cosin (HE) staining.

Results: (1) NSS score: compared with TBI group, NSS in HW group at 12, 24, 48 hours and 5 days were significantly decreased (12 hours: 9.83 ± 2.32 vs. 13.17 ± 2.71, 24 hours: 9.83 ± 2.79 vs. 13.50 ± 2.43, 48 hours: 7.50 ± 2.07 vs. 11.83 ± 2.14, 5 days: 5.50 ± 1.87 vs. 10.50 ± 2.43, all P < 0.05). (2) Compared with sham operation group, the activity of GSH-Px and CAT in TBI group were markedly declined after operation, while the MDA content was elevated significantly, especially at 24 hours [CAT (kU/g): 1.080 ± 0.312 vs. 3.571 ± 0.758, GSH-Px (kU/g): 9.195 ± 3.173 vs. 32.385 ± 10.619; MDA (µmol/g): 12.282 ± 2.896 vs. 4.349 ± 1.511, all P < 0.01]. Compared with TBI group, the parameters in HW group were improved, and they were similar as sham operation group. (3) RT-qPCR: no significant difference was found in the expression of Nrf2 mRNA at each time point in three groups. (4) Western Blot: the expression of Nrf2 nucleoprotein (gray value) in TBI group was apparently higher than that in sham operation group, and peaked at 24 hours (0.703 ± 0.262 vs. 0.238 ± 0.120, P < 0.05), and the expression in HW group was obviously higher than that in TBI group, especially at 24 hours (1.110 ± 0.372 vs. 0.703 ± 0.262, P < 0.05). (5) HE staining: the brain structure in sham operation group was found to be intact. However, there were different degrees of pathological changes at each time in TBI group, especially at 24 hours. The pathological damage of brain tissue in HW group was significantly milder. Conclusions: Hydrogen rich water can up-regulate the expression of Nrf2, and reduce oxidative damage of traumatic brain injury in rats. Nrf2 can up-regulate the expression of its downstream antioxidant enzymes, which may be the mechanism of the upregulation expression of Nrf2 in the study.