Protective Effect Of Acute Splenic Irradiation On Rats With Traumatic Brain Injury

Objective: To explore the protective effect of acute splenic irradiation on traumatic brain injury(TBI)rats.Methods: 96 healthy adult male Sprague-Dawley rats were randomly assigned to Sham+ Nonirradiated group(n=16),Sham + Irradiated group(n=16),TBI + Nonirradiated group(n=16)and TBI + Irradiated group(n=48).The TBI + Irradiated group was randomly divided into 3 subgroups according to the time of starting spleen irradiation after modeling,namely,4-h irradiation group(n=16),6-h irradiation group(n=16)and 8-h irradiation group(n=16).All the above groups were randomly assigned to 3 days sampling group and 7 days sampling group.The rat's model of TBI was established by referring to Feeney method,and the sham groups were opened bone windows without striking;The spleen irradiation group was treated with inverse intensity modulated radiotherapy(IMRT)source axis distance(SAD)irradiation technique at 4 h?6 h and 8 h after TBI,and the spleen sham-irradiation groups were placed under the light source for the same time without irradiation.Blood samples were collected from rats in the 3 days sampling group for detection of tuftsin.Then the brain was taken after heart perfusion,part of which was tested for brain water content,and part of which was reserved for immunofluorescence staining.Spleen was taken,weighed and recorded to the calculate spleen index.Lung,liver,kidney and small intestine were retained for HE staining.Rats in the 7 days sampling group were measured at the same time point from 1 days to 7 days after modeling.Behavioral scores of rats were performed on the 1 days,3 days,5 days,7 days after modeling,and blood was taken for IL-6 and IL-10 detection.Seven days after modeling,blood was taken for tuftsin detection,brain was taken for brain water content detection and immunofluorescence.Results:(1)Compared with the sham group,the behavioral scores of rats in the TBI group on 1 days?3 days?5 days and 7 days after TBI were significantly reduced(P<0.05).Compared with the TBI+ nonirradiated group,the 4-h group had the highest behavioral score,but it was significantly higher than the 6-h and 8-h groups only on the 3 days after TBI(P<0.05);After TBI,there was no significant change in body weight of each group(P>0.05).(2)Compared with the sham group,the water content of the damaged side and the contralateral side of the brain tissues of rats in each group were increased on 3 days after TBI(P<0.05).Compared with the TBI + nonirradiated group,the water content in the damaged side of the brain tissue of rats in the 4-h irradiated group at 3 days after TBI was the least,which was significantly lower than that in the 6-h and 8-h irradiation group(P<0.05).(3)The spleen index of the 4-h irradiated group was significantly lower than that of the TBI+ nonirradiated group(P< 0.05).And the spleen index measured 7 days after 4-h irradiation group was significantly higher than that measured 3 days after TBI(P<0.05).(4)Compared with the nonirradiated group,HE staining of the lung,liver,kidney and small intestine of rats in each irradiation group showed no obvious signs of radiation ingury.(5)At 7 days after TBI,the number of microglia infiltrated around the lesion was significantly smaller in the 4-h irradiation group than in the TBI+ nonirradiated group(P<0.05).(6)Compared with the TBI+ nonirradiated group,the serum IL-6 content of each subgroup of the TBI + irradiated group showed a gradually decreasing trend.Moreover,the serum IL-6 content in each subgroup of TBI+ irradiated group was the lowest in 4-h irradiation group at each measured time point,but it was significantly lower than that in 6-h and 8-h irradiation group only on the 3 days after TBI(P<0.05).(7)Compared with the TBI+ nonirradiated group,the serum IL-10 content of each subgroup in the TBI+ irradiated group increased after 3 days,and the highest level was found in the 4-h irradiation group,but it was significantly higher than that in the 6-h and 8-h irradiation group only on 3 days and 5 days after TBI(P<0.05).(8)The content of tuftsin in serum of each subgroup of TBI + irradiated group on 3 days and 7 days after TBI was significantly lower than that of the TBI+ nonirradiated group(P<0.05).The content of tuftsin in 8-h irradiation group was the lowest and significantly lower than that in 4-h and 6-h irradiation group(P<0.05).Conclusion: Acute splenic irradiation had a protective effect on rats with traumatic brain injury.