大鼠重型颅脑创伤后急性期下丘脑-垂体-肾上腺轴损害和功能改变的意义

The clinical significance of the injury and functional change of hypothalamic-pituitary-adrenal axis after acute severely traumatic brain injury in the rats

目的探讨大鼠重型颅脑创伤（traumatic braininjury，TBI）后急性期下丘脑-垂体-肾上腺（ hypothalamic-pituitary-adrenal, HPA）轴损害和功能改变的意义。方法成年健康封闭群雄性SD大鼠60只，随机（随机数字法）分为假手术组、模型组和治疗组，每组20只。采用Feeney法建立大鼠重型TBI模型。治疗组于伤后10min、24h和48h腹腔注射地塞米松0．6ms／kg，假手术组和模型组给予等容量生理盐水替代。各组大鼠腹腔注射1μg促。肾上腺皮质激素（adrenocorticotropic hormone，ACTH）作刺激试验，分别于伤后第3、12、24、72小时4个时间点进行观察。应用化学发光法测定血清皮质酮（corticosterone，CORT）和ACTH含量。第72小时取大鼠下丘脑、垂体和肾上腺，采用免疫组织化学方法观察白细胞介素6（intedeukin-6，IL-α）和肿瘤坏死因子α（tumor necrosis factor-alpha，TNF-α）表达情况。所得数据采用SPSS17．0统计软件包进行单因素方差分析和SNK-q检验。结果①模型组大鼠伤后第3小时外周血CORT和ACTH达高峰，明显高于假手术组，随后逐渐降低；各时间点ACTH刺激试验后CORT上升的幅度（△max）均低于假手术组（P〈0．05或P〈0．01）。治疗组大鼠伤后所有时间点CORT均高于模型组，ACTH仅伤后第24小时高于模型组；ACTH刺激后CORT的△mmax值均较模型明显升高（P〈0．05或P〈0．01）。②模型组大鼠伤后第72小时下丘脑与垂体IL-6、TNF-α阳性细胞数较假手术组明显升高（P〈0．01）；治疗组则较模型组明显降低（P〈0．01）；肾上腺皮质仅IL-6阳性细胞数差异显著（P〈0．01）。结论重型TBI大鼠早期即可存在肾上腺皮质功能改变，随着时间推移，对ACTH反应程度降低。小剂量短疗程地塞米松可减轻HPA轴炎症反应程度，增强。肾上腺皮质对ACTH的敏感性。

Objective To study the clinical significance of the injury and functional change of hypothalamic-pituitary-adrenal （HPA） axis after acute severe traumatic brain injury （TBI） in the rats. Methods A total of 60 adult healthy male Spraque-Dawley rats were randomly （random number） divided into 3 groups （n = 20 in each group ） ： sham operation group, model group and treatment group. The TBI models of rats were established by Feeney＇ s method. A low dose of dexamethasone （0. 6 mg,/kg） was injected into the abdominal cavity 20 minutes, 24 hours and 48 hours after injury in treatment group, while rats of shamoperation group and model group received equal volume of normal saline instead. All the rats were injected 1 μg adrenocorticotropic hormone （ACTH） into the abdominal cavity. The related parameters were detected at four time points, 3 hours, 12 hours, 24 hours and 72 hours after cerebral contusion. The plasma corticosterone （CORT） and ACTH levels were measured by chemiluminescence. The hypothalamic, pituitary and adrenal of the rats were taken out for observing interleukin-6 （IL-6） and tumor necrosis factor- alpha （TNF-α） expression detecting by immunohistochemical techniques at 72nd hour after TBI. One-way ANOVA and SNK-q test were used to analyze the results with SPSS 17. 0 software package. Results The levels of ACTH and CORT on 3rd hour of model group raised remarkably compared with that of sham operation group, then they reduced gradually. The levels of CORT were lower than that of sham operation group at every time points after ACTH stimulation test （P 〈 0. 05 or P 〈 0. 01 ）. The levels of CORT at all time points of treatment group were changed remarkably compared with that of model group. However, the ACTH levels of treatment group on 24 h increased slightly than that of model group. And the tendency of them was similar to model group （P 〈 0. 05 or P 〈 0. 01 ）. The number of the hypothalamus and pituitary cells which express IL-6 and TNF-α in model group was more significantly increased when compared with that in sham operation group （ P 〈 0. 01 ）, while the number of this kind of cell in treatment group was significantly decreased than that in model group （P 〈 0. 01 ）. The number of the adrenal cortex cells which express IL-6 in treatment group was more significantly decreased when compared with that in model group （ P 〈 0. 01 ）, while the number of this kind of cell in model group was significantly increased than that in sham operation group （ P 〈 0. 01 ）. However, there was no significant difference of the TNF-α between all the groups （P 〉 0. 05）. Conclusions Functional change of adrenal occurs early in the severe acute traumatic brain injury rats, and the response of adrenal to ACTH decreased as time goes by. Low-dose, short-course dexamethasone can delay the pathological changes, reduce the inflammatory response of HPA axis and increase the sensitivity of adrenal response to ACTH.