(-)- Epigallocatechin- 3- gallate improves cognitive impairment and oxidative stress after traumatic brain injury in mice

Objective To investigate the influence of (-)- epigallocatechin- 3- gallate (EGCG) on brain cognitive function and oxidative stress in traumatic brain injury (TBI) mouse model. Methods The animal model was established by the improved weight drop method. Experimental mice were randomly divided into Veh and EGCG groups. After 3 days, enzyme linked immunosorbent assay (ELISA) kit was used to detect the expression of superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione (GSH). Hydroethidine (HEt) staining was done to detect reactive oxygen species (ROS) production. The number of apoptosis cells was detected by TdT-mediated dUTP nick end labeling (TUNEL) kit. After 28 days, Morris water maze was used to evaluate the spatial learning and memory ability. Novel object recognition was used to evaluate non- spatial memory and cognitive ability of mice. Results (1) The results of Morris water maze showed that the escape latency in EGCG group [24 d (49.862±7.449) s, 25 d (43.446±8.207) s, 26 d (34.381±7.668) s and 27 d (23.742±6.527) s] was significantly higher than that in Veh group [24 d (55.120±6.236) s, 25 d (50.834±7.993) s, 26 d (44.832±8.971) s and 27 d (38.948±8.127) s] (F=9.890, P=0.010). The number of mice passing through the platform at the 28th day in EGCG group (4.673±0.803) times was significantly more than that in the Veh group (1.667±0.558) times (t=2.728, P=0.021). The residence time in the target quadrant of EGCG mice [(41.305±3.643) s] was significantly longer than that in Veh group [(23.198±3.516) s] (t=3.577, P=0.005). (2) The results of Novel object recognition experiments showed that as compared with Veh group [(49.209±4.008)%], the discrimination index in the EGCG group [(65.284±4.572)%] was significantly increased (t=2.644, P=0.025). (3) The levels of SOD (180.442±11.817) U/ml, MDA (587.518±59.306) nmol/L and GSH (71.071±5.763) ng/L in the EGCG group were significantly lower than those in Veh group [SOD: (120.840±9.095) U/ml, MDA: (966.613±70.115) nmol/L and GSH: (49.731±5.218) ng/L] (SOD: t=3.997, P=0.004; MDA: t=4.128, P=0.003; GSH: t=2.745, P=0.025). (4) The expression of ROS in the EGCG group (1 265.542±100.780) was significantly lower than that in the Veh group (1 631.329±126.300) (t=2.264, P=0.047). (5) The number of apoptotic cells in the EGCG group [(21.667±3.602) cells] was significantly less than that in the Veh group [(39.167±4.078) cells] (t=3.216, P=0.009). Conclusion EGCG improved the cognitive impairment and oxidative stress in traumatic brain injured mice. Key words: (-)- Epigallocatechin- 3- gallate; Traumatic brain injury; Cognition; Oxidative stress