| In the published experimental results of our research group showed that focal moderate hypothermia was prove to have effect on the formation of brain edema, reduction in metabolic rate of injured brain tissue, preservation of the activity of ATPase,inhibition of acidosis and oxidative stress, attenuation of the infiltration of inflammatory of cells and their cytokines, medulating the activity of NOS, protection from the death and apoptosis of neurons. It also has the benefit of less side effects.To date, we have know some about the protective mechanism of focal moderate hypothermia, but wether it has effect on the expression of cerebral ischemia association factor is unknow. On the basis of above-mentioned findings, we first use focal irrigation therapy with artificial cerebral-spinal fluid. The aim of this experiment was to study the effect of focal moderate hypothermia, focal irrigation with artificial cerebral-spinal fluid on brain edema, the expression of AQP4, HIF-1αand VEGF after severe TBI, From the molecular mechanism of brain edema and cerebral ischemia, we further explore the protective mechanism about focal moderate hypothermia and focal irrigation with artificial cerebral-spinal fluid.OBJECTIVE: We investigated the effect of focal hypothermic artificial cerebral spinal fluid on brain edema and the ion content and the expression of AQP4, also the cerebral ischemia association factor HIF-1α, VEGF following severe traumatic brain injury (TBI) in rats.METHODS: Four hundred and twenty healthy adult male Sprague- Dawley rats were randomly divided into five groups: Sham operation group (SO group), traumatic brain injury group (TBI group), focal moderate hypothermia group (FH group), focal irrigation group (FI group), focal hypothermic irrigation group (FHI group). The subjects were sacrificed at 4, 8hrs, and 1, 3, 5, 7days. Groups were divided into six subgroups according to the six time points (n=14 in each subgroups).The samples of injury brain tissue were collected to detect the content of water, sodium (Na~+), potassium (K~+), and the expression of HIF-1αand VEGF mRNA by RT-PCR, also the expression of AQP4, HIF-1αand VEGF protein by immunohischemistry respectively. In addition, histological and ultrastructural studies were made. Rats were underwent severe parasagital control cortical impact brain injury. After thirty minutes, the traumatic rats were differently received focal moderate hypothermia, focal irrigation treatment with 37.0℃artificial cerebral spinal fluid, and focal hypothermic irrigation treatment with 25℃artificial cerebral spinal fluid for 3 hours. The injured rats were put to death according to corresponding.RESULTS: 1.Water and ion content: Water content was increased at the 4h, the peak value appeared at 1～3d after TBI, and began to decline at 5d, went back to normal levels at 7d compared with SO group (P＞0.05). The change of sodium content was in parallel with the content of water, but the change of potassium content was reverse. The rise in brain edema and sodium content were significantly reduced with posttraumatic focal moderate hypothermia, focal irrigation, and focal hypothermic irrigation therapy, and the decline in Potassium ion was significantly reduced in the 4h, 8h, 1d, 3d, and 5d subgroups compared with TBI (P＜0.05). 2.The expression of AQP4: After TBI, the expression of AQP4 protein were significantly increased at 4h, peaked at 1～3d, and maintain high at 5d compared with SO group (P＜0.05). The expression of AQP4 was significantly reduced at 4h, 8h, ld, 3d, and 5d after treated with focal moderate hypothermia, focal irrigation, and focal hypothermic irrigation respectively compared with TBI (P＜0.05). The most significant reduction was in Fill group. 3.The expression of HIF-1αmRNA and protein: The expression of HIF-1αmRNA and protein were significantly increased within the injured cerebral cortex at 4h, 8h, ld, 3d, and 5d after TBI compared with the SO group (P＜0.05). The rise of HIF-1αmRNA and protein expression were significantly reduced after treated with focal moderate hypothermia, focal irrigation, and focal hypothermic irrigation respectively (P＜0.05). 4.The expression of VEGF mRNA and protein:After TBI, the expression of VEGF mRNA and protein were increased at 4h, 8h, 1d, 3d, and 5d, compared with SO group(P＜0.05). The protein was in parallel with the expression of mRNA. Both the rise of expression of VEGF mRNA and protein were significantly decreased posttraumatic treated with focal moderate hypothermia, focal irrigation, and focal hypothermic irrigation compared with SO group (P＜0.05). 5. Pathological changes: In terms of damaged neurons and destroyed BBB,TBI group was more obvious than FH, FI, and FHI group.CONCLUSION:1. These data indicated that the fastigium of brain edema is at 1～3 days after experimental severe brain injury in rats. The change of Natrium ion is consistent with brain edema. The change of Potassium ion is inverse correlation to brain edema. The expression of AQP4 is increased after TBI, and is consistent with brain edema.2. The expression of HIF-1αand VEGF mRNA and protein are increased after TBI. The expression of protein is correlation with mRNA. Both HIF-1αand VEGF are expressed in a time-dependent manner after severe traumatic brain injury, and are correlated with brain edema.3. Focal moderate hypothermia could significantly reduce brain edema and the expression of AQP4 protein, and the expression of HIF-1αand VEGF mRNA and protein.4. Focal irrigation could significantly reduce brain, maintain the homeostasis of ion, and decrease the expression of AQP4 protein.5. Focal irrigation could significantly decrease the expression of cerebral ischemia association factor HIF-1αand VEGF mRNA and protein.6. Focal hypothermia irrigation could significantly reduce brain edema after TBI, and decrease the expression of AQP4 protein, and the expression of HIF-1αand VEGF mRNA and protein. FHI is the better than FH and FI.TO our knowledge, this is the first report about the above-mentioned 3, 4, 5 and 6 conclusions.
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