Effects Of Mild Hypothermia On The Expression Of Calmoduli, Aquaporin-4 And Cerebral Edema In Brain Tissue Of Rats With Traumatic Brain Injury

Objective: Traumatic brain injury(TBI)is a traumatic disease with a high incidence,and secondary brain injuries such as calcium signal system activation,neuronal apoptosis,and cerebral edema are important factors that make the disease worse.Its comprehensive treatment measures have been an important direction of neurosurgery research.Mild hypothermia treatment is an effective brain protection measure against TBI.This experiment investigated the effects of mild hypothermia treatment on the expression of calmodulin(CAM),aquaporin-4(AQP-4)and cerebral edema in rats with TBI to explore the related mechanisms of TBI and mild hypothermia treatment,and provide further theoretical support for the treatment of mild hypothermia.Methods: Seventy-two healthy adult SD(Sprague-Dawley)rats were selected,male or female,weighing 270-300 g,all provided by the Animal Experiment Center of Southwest Medical University under standard conditions.Rats were randomly divided into sham operation group(open bone window only,no hit,37℃),normal temperature group(make TBI model,37℃)and mild hypothermia group [make TBI model,(32 ± 0.5)℃ for 6h],24 in each group.Controlled cortical impact(CCI)brain injury instrument was used to establish a rat TBI model,and mildhypothermia treatment model was made by ice bed,ice water bath,and ethanol wiping.In each group,four time points were taken at 6,12,24,and 48 hours after brain injury.Six rats at each time point were killed after examination by brain MRI to examine the degree and extent of cerebral edema.Fluorescence quantitative PCR,immunohistochemistry and western-blot were used to detect the expression of CAM mRNA and protein in brain tissue of rats in each group,and immunocytochemistry was used to detect the expression of AQP-4 in brain tissue in 24 h normal temperature group and mild hypothermia group.Results: 1.Fluorescence quantitative PCR show that the expression of CAM mRNA at each time point in the mild hypothermia group and the normal temperature group increased compared with the sham operation group at the same time point,and the difference was statistically significant(P <0.001);the expression of CAM mRNA in the hypothermia group at 6,12,and 24 hours were reduced compared with the normal temperature group at the same time point,and the difference was statistically significant(P <0.001),there was no significant difference in CAM mRNA expression between 48 h mild hypothermia group and 48 h normal temperature group(P> 0.05).2.Western-blot show taht the CAM expression at each time point in the mild hypothermia group and the normal temperature group increased compared with the sham operation group at the same time point,and the difference was statistically significant(P <0.001);the expression of CAM at each time point in themild hypothermia group was reduced compared with the normal temperature group at the same time point,and the differences was statistically significant(P <0.001).3.Immunocytochemistry show taht the expression of CAM in the mild hypothermia group and the normal temperature group increased compared with the sham operation group,and the difference was statistically significant(P <0.001);the expression of CAM in the mild hypothermia group was reduced compared with the normal temperature group,and the difference was statistically significant(P <0.001).The expression of AQP-4 in the 24 h mild hypothermia group was reduced compared with the 24 h normal temperature group,and the difference was statistically significant(P <0.05).4.MRI show that the brain edema was more significant in the hypothermia group and the normal temperature group compared with the sham operation group,and the volume of brain edema was significantly increased in the hypothermia group and the normal temperature group compared with the sham operation group;the volume of brain edema in mild hypothermia group was reduced compared with the normal temperature group,and the difference was statistically significant(P <0.05).Conclusion: 1.CAM expression in rat brain tissue increased after TBI,and may be related to the mechanism of secondary brain injury.2.Mild hypothermia can reduce the expression of CAM and AQP-4 in brain tissues after brain injury in rats.Mild hypothermia may inhibit secondary brain injury mechanisms such as calcium signal system activation andbrain edema by inhibiting CAM and AQP-4,and finally exert brain protection.3.Mild hypothermia treatment can reduce brain edema in rats after TBI.