高压氧治疗对急性脑创伤后血脑屏障损伤大鼠MMP-9mRNA表达的影响

Effects of hyperbaric oxygen on blood-brain barrier and the expression of MMP-9 mRNA followingacute brain injury

目的观察高压氧（hyperbaric oxygen，HBO）治疗对急性脑创伤后血脑屏障损伤大鼠MMPOmRNA表达的影响，探讨高压氧治疗急性脑损伤的机制。方法选取40只sD大鼠，采用自由落体打击法制备急性脑创伤模型。造模成功后采用数字表法随机分为4组，每组10只。分别为正常对照组：动物置于加压舱内，模拟除压力和氧浓度以外的其他实验条件。急性颅脑损伤24h组：动物颅脑打击后1h，置于加压舱内，模拟除压力和氧浓度以外的其他实验条件，于伤后24h断头取材。急性颅脑损伤高压氧治疗24h组：动物颅脑打击后1h和12h，置于高压氧舱内，在0．25MPaHBO下各停留40min，于伤后24h断头取材。急性颅脑损伤常氧高氮治疗24h组：动物颅脑打击后1h和12h，置于高压氧舱内，在0．25MPa常氧高氮环境下各停留40min，于伤后24h6只断头取材行含水量及RT—PCR测定，4只行脑组织伊文蓝（Evansblue，EB）测定。结果急性颅脑损伤伤侧和非伤侧脑组织含水量为77．39nlg和72．25m异，与急性颅脑损伤HBO治疗24h组（70．83mg、70．27mg）比较差异有统计学意义（P〈0．05）。急性颅脑损伤经0．25MPaHBO治疗后，脑组织含水量较未治疗组下降（P〈0．01），高压氧治疗组半球及海马EB均显著增加（P〈0．05，P〈0．01）。急性颅脑损伤经0．25MPaHBO治疗后，损伤侧和非损伤侧半球及海马EB较未治疗组下降（P〈0．0，1），急性颅脑损伤组及0．25MPa常氧高氮组损伤侧半球及海马EB多于非损伤侧（P〈0．05），0．25MPaHBO治疗组损伤侧半球及海马EB高于非损伤侧（P〈0．05）。急性颅脑损伤经0．25MPaHBO治疗后，损伤侧和非损伤侧半球及海马MMPOmRNA较未治疗组下降（P〈0．0，1）。急性颅脑损伤组、0．25MPa常氧高氮组及0．25MPaHBO治疗组损伤侧半球及海马MMP．9mRNA高于非损伤侧（均P〈0．05）。结论HBO治疗急性脑创伤可以保护血脑屏障，从而减轻脑水肿，机制之一是HBO治疗减少了MMPOmRNA表达。

Objective To observe effects of hyperbaric oxygen （HBO） on blood-brain barrier and the expression of MMP-9 mRNA following acute brain injury （ABI） and also to explore the mechanism involved in the treatment of ABI. Methods Forty SD rats were selected for the experiment. Following development of the ABI model by using free-fall hit method, the animals were randomly divided into 4 groups： the normal control group, the 24 h ABI group, the 24 h HBO therapy group and the 24 h normoxic nitrogen rich therapy group, each consisting of 10 animals. （ 1 ） The animals in the normal control group were simply housed in the chamber and received all the same treatments, except for high pressure and high level of oxygen breathing. （2） One hour after ABI, the animals in the 24 h ABI group were put into the hyperbaric chamber and received all the same treatments except for high pressure and high level of oxygen breathing, then they were killed 24 h afterinjury for collection of samples. （3） The animals in the ABI and 24 h HBO therapy groups were also housed in the hyperbaric chamber 1 h and 12 h after brain injury, and stayed at 0.25 MPa for a duration of 40 min, then they were sacrificed 24 h after injury. （4） The animals in the 24 h normoxie nitrogen rich therapy group were exposed to the 0.25 MPa normoxic nitrogen rich environment for a duration of 40 min, 1 h and 12 h after brain injury, then 6 of the animals were killed 24 h after injury for the measurement of water content and RT-PCR, and 4 of the animals were killed for Evans blue detection （EB）. Results Water contents both in the injured side and non-injured side of the brain following acute brain injury were 77.39 mg and 72.25 mg respectively, and statistical significance could be noticed when compared with the 24 h HBO therapy group（ 70.83 mg,70.27 mg） （ P 〈 0.05 ）. Following 0.25 MPa HBO treatment of ABI, water content of the brain tissue decreased when compared with that of the non-treatment group （ water contents of the brain tissue were 70.83 for the injured side and 77.39 for the non-injured side, P 〈0.01 ） . Changes in brain tissue EB after HBO treatment were as follows： EB increased significantly both in the injured side and non-injured side of the hemisphere, and the hippoeampus, following ABI and various treatments （ P 〈 0.05, P 〈 0.01 ）. As shown in the study, EB in the injured side and non-injured side of the hemisphere and the hippocampus decreased, when compared with those of the non-treatment group, following 0.25 MPa HBO therapy （ P 〈 0.01 ）. Changes in the expression of MMP- 9 mRNA were as follows： the expression of MMP-9 mRNA in the injured side and non-injured side of the hemisphere and hippocampus all increased significantly, following ABI and various treatment （ P 〈 0.05, P 〈 O. 01 ）. After 0.25 MPa HBO treatment of ABI, the expression of MMP-9 mRNA in the injured side and non- injured side of the hemisphere and hippocampus decreased, when compared with that of the non-treatlnent group （P 〈 0. 01 ）. Conclusions HBO treatment of ABI could protect the blood-brain barrier, thus alleviating cerebral edema. One of the mechanisms involved might be the reduction in the expression of MMP-9 mRNA through HBO treatment.