Effects of hydrogen-rich water on expression of aquaporin 4 in brain tissue of rats after traumatic brain injury / 中国中西医结合急救杂志

ABSTRACT

Objective To investigate the effects of hydrogen-rich water (HRW) on brain edema and the expression of aquaporin 4 (AQP4) in brain tissue of rats after acute traumatic brain injury (TBI) and explor the mechanism of its action. Methods Ninety male adult Sprague-Dawley (SD) rats were randomly divided into three groups Sham group, TBI model group (TBI group) and HRW intervention group (HRW group), each group n = 30 rats. The TBI rat models were replicated by craniocerebral collision, while the Sham group rats underwent only craniotomy without collision and the cranial opening was closed by suturing and bone wax. After successful modeling, in HRW group the rats received intraperitoneal injection of HRW 5 mL/kg, and in the TBI group and Sham group, equal amount of 5 mL/kg 0.9% normal saline was given by the same method, once a day for 5 days in all the groups. The neurological severity scores (NSS) and brain water contents were detected at postoperative 6, 12, 24, 48 hours and 5 days in the three groups;the cerebral cortex expression levels of AQP4 mRNA, positive expression levels of AQP4, the cerebral cortex AQP4 protein expression, protein kinase C (PKC) activity were detected in each group. Results ① The NSS of each time point in Sham group was 0; in TBI group, the rats levels of NSS and brain water contents showed a tendency of firstly rising and then decreasing, and after postoperative 24 hours, the levels reached the peak values and then gradually decreased; in HRW group, the levels of NSS and brain water contents were reduced significantly and at postoperative 24 hours when compared with those in TBI group, the levels of decreasing amplitude in HRW group were more significant [NSS score 5.50±1.87 vs. 10.50±2.42, brain water content (78.78±0.65)% vs. (79.98±0.61)% , all P ＜ 0.05].② The AQP4 mRNA expression levels of sham group at all time points were 1; compared with the Sham group, the AQP4 mRNA levels of TBI group and HRW group at the time points showed a tendency of firstly decreasing and then rising and reaching the valley level at 24 hours (2-ΔΔCt 0.33±0.06, 0.36±0.12 vs. 1, both P ＞ 0.05). ③ The immunohistochemistry detection showed that the brain AQP4 mainly expressed in astrocytes in Sham group at various time points. However, in TBI group, the positive expression of AQP4 in astrocytes in injury area at each time point was decreased, at postoperative 24 hours being the most significant; the positive expression of AQP4 in HRW group was significantly higher than that in the TBI group at each time point and since postoperative 12 hours the statistical significant difference appeared in the comparison between the two groups [Absorbance (A) value 0.206±0.010 vs. 0.170±0.014, P ＜ 0.05]. ④ The expressions of AQP4 protein at various time points were significantly lower in TBI group compared with those of Sham group, and reached the minimum at postoperative 24 hours (gray value 0.282±0.100 vs. 1.281±0.115, P ＜ 0.05); but in HRW group, the expressions of AQP4 protein at various time points showed significantly higher than those of TBI group, and since postoperative 12 hours the statistical significant difference occurred (gray value0.681±0.096 vs. 0.420±0.090, P ＜ 0.05). ⑤ The activity of PKC in TBI group at each time point was significantly decreased compared with that in Sham group, but it was significantly increased in HRW group at each time point and reached the maximum at postoperative 24 hours (A value 2.67±0.52 vs. 1.51±0.42, P ＜ 0.05). ⑥ Correlation analysis:there was an obvious negative correlation between the brain activity of PKC and brain water content (r2= 0.209, P ＜ 0.001);but there was a significant positive correlation between the activity of PKC and the expression of AQP4 protein (r2= 0.406, P ＜0.001). Conclusion HRW can improve the brain edema in rats following TBI, and the mechanism may be associated with the up-regulation of expression of AQP4 protein and PKC activity in brain tissue.