‘Hit & Run' model of closed-skull traumatic brain injury (TBI) reveals complex patterns of post-traumatic AQP4 dysregulation

Cerebral edema is a major contributor to morbidity associated with traumatic brain injury (TBI). The methods involved in most rodent models of TBI, including head fixation, opening of the skull, and prolonged anesthesia, likely alter TBI development and reduce secondary injury. We report the development of a closed-skull model of murine TBI, which minimizes time of anesthesia, allows the monitoring of intracranial pressure (ICP), and can be modulated to produce mild and moderate grade TBI. In this model, we characterized changes in aquaporin-4 (AQP4) expression and localization after mild and moderate TBI. We found that global AQP4 expression after TBI was generally increased; however, analysis of AQP4 localization revealed that the most prominent effect of TBI on AQP4 was the loss of polarized localization at endfoot processes of reactive astrocytes. This AQP4 dysregulation peaked at 7 days after injury and was largely indistinguishable between mild and moderate grade TBI for the first 2 weeks after injury. Within the same model, blood–brain barrieranalysis of variance permeability, cerebral edema, and ICP largely normalized within 7 days after moderate TBI. These findings suggest that changes in AQP4 expression and localization may not contribute to cerebral edema formation, but rather may represent a compensatory mechanism to facilitate its resolution.     

AQP4-siRNA alleviates traumatic brain edema by altering post-traumatic AQP4 polarity reversal in TBI rats

The spatial and temporal distribution of aquaporin-4 (AQP4) expression in rat brain following brain trauma and AQP4-siRNA treatment, as well as corresponding pathological changes, were studied to explore the mechanism underlying the effect of AQP4-siRNA treatment on traumatic brain injury (TBI). The rats in the sham operation group had normal structure, with AQP4 located in the perivascular end-foot membranes and astrocytic membranes in a polarized pattern. The accelerated polarity reversal was observed in the TBI group in 1–12 h after TBI. During this period, AQP4 abundance on the astrocytic membrane is gradually increased, while AQP4 abundance on the perivascular end-foot membrane declined rapidly. Twelve hours after TBI, AQP4 expression was depolarized, showing a shift from the perivascular end-foot membrane to the astrocytic membrane. Pathological observation showed that vasogenic edema occurred immediately after TBI, at which time the extracellular space was expanded, leading to severe intracellular edema. AQP4-siRNA reduced the polarity reversal index at the early stage of TBI recovery and reduced edema, demonstrating the potential benefit of reduced AQP4 expression during recovery from TBI.     

Gliovascular changes precede white matter damage and long‐term disorders in juvenile mild closed head injury

Traumatic brain injury (TBI) is a leading cause of hospital visits in pediatric patients and often leads to long‐term disorders even in cases of mild severity. White matter (WM) alterations are commonly observed in patients months or years after the injury assessed by magnetic resonance imaging (MRI), but little is known about WM pathophysiology early after mild pediatric TBI. To evaluate the status of the gliovascular unit in this context, mild TBI was induced in postnatal‐day 17 mice using a closed head injury model with two grades of severity (G1, G2). G2 resulted in significant WM edema (increased T2‐signal) and BBB damage (IgG‐extravasation immunostaining) whereas decreased T2 and the increased levels of astrocytic water‐channel AQP4 were observed in G1 mice 1 day post‐injury. Both severities induced astrogliosis (GFAP immunolabeling). No changes in myelin and neurofilament were detected at this acute time point. One month after injury G2 mice exhibited diffusion tensor imaging MRI alterations (decreased fractional anisotropy) accompanied by decreased neurofilament staining in the WM. Both severities induced behavioral impairments at this time point. In conclusion, long‐term deficits and WM changes similar to those found after clinical TBI are preceded by distinct early gliovascular phenotype alterations after juvenile mild TBI, revealing AQP4 as a potential candidate for severity‐based treatments.     

脑损伤后水通道蛋白4表达与血脑屏障通透性的关系

目的研究脑损伤后，水通道蛋白4（AQP4）的表达变化与血脑屏障（BBB）通透性之间的关系。方法健康成年Wistar大鼠，随机分成创伤性（TBI）组和假手术（SO）组。自由落体硬膜外撞击方法致重度脑创伤模型。于伤后4h、8h、12h、1d、3d、5d、7d取出大鼠脑组织，进行以下实验：①测创伤脑组织中伊文思蓝（EB）外渗的量，以EB外渗的量反应BBB通透性的变化；②免疫组化（IHC）和原位杂交（ISH）检测AQP4的表达变化。结果脑损伤后，BBB通透性增加，其增加有两个高峰，分别在TBI后12h和3d，后者尤为更明显。IHC和ISH显示，脑损伤后AQP4在脑组织中的表达逐渐上调，1d达高峰，持续至3d后下降，7d接近SO组水平。AQP4的表达变化与脑组织伊文思蓝（EB）含量的变化呈正相关（r=0．894，P〈0．05）。结论脑损伤后BBB通透性的增加与脑水肿的形成密切相关。TBI后BBB通透性增加，可能与AQP4表达上调有关，两者的变化影响TBI后脑水肿的发生、发展。     

Simvastatin therapy prevents brain trauma‐induced increases in β‐amyloid peptide levels

Elevations in β‐amyloid peptide (Aβ) levels after traumatic brain injury (TBI) may confer risk for developing Alzheimer's disease in head trauma patients. We investigated the effects of simvastatin, a 3‐hydroxy‐3‐methylglutaryl‐CoA reductase inhibitor, on hippocampal Aβ burden in a clinically relevant head injury/intervention model using mice expressing human Aβ. Simvastatin therapy blunted TBI‐induced increases in Aβ, reduced hippocampal tissue damage and microglial activation, and improved behavioral outcome. The ability of statins to reduce post‐injury Aβ load and ameliorate pathological sequelae of brain injury makes them potentially effective in reducing the risk of developing Alzheimer's disease in TBI patients. Ann Neurol 2009;66:407–414     

盐酸纳美芬对大鼠颅脑损伤后脑水肿的影响

目的探讨盐酸纳美芬对大鼠颅脑损伤后脑水肿的影响。方法将54只Wistar大鼠按随机数字表法随机分为假手术组、颅脑损伤组及纳美芬治疗组。采用自由落体法建立大鼠颅脑损伤模型,分别于伤后6 h、1 d、3 d、7 d,采用干湿重法检测脑组织含水量,应用免疫组织化学法检测损伤脑组织中水通道蛋白4（AQP4）的表达。结果与假手术组比较,颅脑损伤组和纳美芬治疗组的脑组织含水量及AQP4水平明显升高（P〈0.05）;与颅脑损伤组相比,纳美芬治疗组脑组织含水量及AQP4表达水平明显降低（P〈0.05）。通过相关性分析发现,大鼠颅脑损伤后脑组织AQP4表达水平与脑含水量呈明显正相关性（r=0.676,P〈0.01）。结论盐酸纳美芬可能通过抑制AQP4表达,减轻脑水肿,发挥神经保护作用。     

TLR4, IL‐6, IL‐18, MyD88 and HMGB1 are highly expressed in intracranial inflammatory lesions and the IgG4/IgG ratio correlates with TLR4 and IL‐6

We determined distribution of plasma cells and IgG4/IgG index and factors associated with the index in intracranial inflammatory lesions. Specimens of nine patients were analyzed immunohistochemically using antibodies against CD45, CD68, CD3, CD4, CD8, CD20, CD138, lambda chain, kappa chain, IgG, IgG4, IL‐1α, IL‐6, IL‐18, toll‐like receptor (TLR) 2, TLR4, high‐mobility group box 1 (HMGB1), tumor necrosis factor‐alpha (TNF‐α), myeloid differentiation factor 88 (MyD88), and anaplastic lymphoma kinase (ALK). The relationship between all the factors was assessed using Spearman's rank correlation coefficient (ρ). Negative ALK staining was observed in all the patients. Plasma cells were detected in eight patients with varying degrees. The highest number of neutrophils, but no plasma cells, was observed in a patient with the shortest history of inflammation. IgG4/IgG index was independent of the number of plasma cells. The index was relatively highly correlated with IL‐6 (ρ = 0.7271) and TLR4 expression (ρ = 0.7246). IL‐6 expression was highly correlated with TLR4 expression (ρ = 0.8042). IL‐18 was maximally expressed in all the patients. TLR4 expression was strong, but TRL2 expression was weak. Positive HMGB1 staining was observed in all the patients, predominantly in the nuclei, but also in the cytoplasm in four patients. The cytoplasmic expression strongly correlated with IL‐1α expression (ρ = 0.9583). The cytoplasmic colocalization of HMGB1 and IL‐1α was histologically confirmed in cells with collapsing nuclei by the double‐staining method. The IgG4/IgG indexes varied case by case. IL‐6 and TLR4 expressions may influence IgG4/IgG index. The nuclei of cells with both IL‐1α and HMGB1 expressions in the cytoplasm collapse in the cell death stage. The cooperative high expression of TLR4, IL‐6, IL‐18, MyD88 and HMGB1 suggest their critical roles in the inflammation circuit.     

Aquaporins in brain: distribution, physiology, and pathophysiology.

Water homeostasis in the brain is of central physiologic and clinical importance. Neuronal activity and ion water homeostasis are inextricably coupled. For example, the clearance of K+ from areas of high neuronal activity is associated with a concomitant water flux. Furthermore, cerebral edema, a final common pathway of numerous neurologic diseases, including stroke, may rapidly become life threatening because of the rigid encasement of the brain. A water channel family, the aquaporins, facilitates water flux through the plasma membrane of many cell types. In rodent brain, several recent studies have demonstrated the presence of different types of aquaporins. Aquaporin 1 (AQP1) was detected on epithelial cells in the choroid plexus whereas AQP4, AQP5 and AQP9 were localized on astrocytes and ependymal cells. In rodent brain, AQP4 is present on astrocytic end-feet in contact with brain vessels, and AQP9 is found on astrocytic processes and cell bodies. In basal physiologic conditions, AQP4 and AQP9 appear to be implicated in brain homeostasis and in central plasma osmolarity regulation. Aquaporin 4 may also play a role in pathophysiologic conditions, as shown by the reduced edema formation observed after water intoxication and focal cerebral ischemia in AQP4-knockout mice. Furthermore, pathophysiologic conditions may modulate AQP4 and AQP9 expression. For example, AQP4 and AQP9 were shown to be upregulated after ischemia or after traumatic injuries. Taken together, these recent reports suggest that water homeostasis in the brain is maintained by regulatory processes that, by control of aquaporin expression and distribution, induce and organize water movements. Facilitation of these movements may contribute to the development of edema formation after acute cerebral insults such as ischemia or traumatic injury.     

Role for mammalian chitinase 3‐like protein 1 in traumatic brain injury

Traumatic brain injury (TBI) is accompanied by inflammatory infiltrates and CNS tissue response. The astrocytosis associated with TBI has been proposed to have both beneficial and detrimental effects on surviving neural tissue. We recently observed prominent astrocytic expression of YKL‐40/chitinase 3‐like protein 1 (CHI3L1) associated with severity of brain injury. The physiological role of CHI3L1 in the CNS is unknown; however, its distribution at the perimeter of contusions and temporal course of expression suggested that in TBI it might be an important component of the astrocytic response to modulate CNS inflammation. To address this hypothesis, we used serially sectioned brains to quantitatively compare the neuropathological outcomes of TBI produced by controlled cortical impact in wild type (WT) and chi3l1 knockout (KO) mice where the murine YKL‐40 homologue, breast regression protein 39 (BRP‐39/CHI3l1), had been homozygously disrupted. At 21 days post‐injury, chi3l1 KO mice displayed greater astrocytosis (increased GFAP staining) in the hemispheres ipsilateral and contralateral to impact compared with WT mice. Similarly, Iba1 expression as a measure of microglial/macrophage response was significantly increased in chi3l1 KO compared with WT in the hemisphere contralateral to impact. We conclude that astrocytic expression of CHI3L1 limits the extent of both astrocytic and microglial/macrophage facets of neuroinflammation and suggests a novel potential therapeutic target for modulating neuroinflammation.     

Serum ceruloplasmin and copper are early biomarkers for traumatic brain injury‐associated elevated intracranial pressure

High intracranial pressure (ICP) is a prominent secondary pathology after traumatic brain injury (TBI) and is a major contributor to morbidity and mortality. Currently, there are no clinically proven methods for predicting which TBI patients will develop high ICP. In the present study, we examined whether the serum levels of the copper‐binding protein ceruloplasmin are differentially altered in patients with elevated ICP (≥25 mmHg) vs. those whose ICP remained below 20 mmHg throughout the study period. Consistent with its role as an acute‐phase reactant, we found that ceruloplasmin levels were significantly increased by 3 days post‐TBI compared with healthy volunteers. However, prior to this delayed increase, ceruloplasmin levels during the first 24 hr following injury were found to be significantly reduced in patients who subsequently developed high ICP. This decrease was found to have prognostic accuracy in delineating TBI patients based on their ICP status (cutoff of 140 μg/ml; sensitivity: 87%, specificity: 73%), Likewise, low total serum copper (below 1.32 μg/ml) was also found to be predictive of high ICP (sensitivity 86%, specificity 73%). These results suggest that initial serum ceruloplasmin/copper levels may have diagnostic value in predicting patients at risk for developing high intracranial pressure. © 2010 Wiley‐Liss, Inc.     

Oxygen resuscitation does not ameliorate neonatal hypoxia/ischemia‐induced cerebral edema

Neonatal hypoxia/ischemia (HI) is a common cause of cognitive and behavioral deficits in children with hyperoxia treatment (HHI) being the current therapy for newborn resuscitation. HI induces cerebral edema that is associated with poor neurological outcomes. Our objective was to characterize cerebral edema after HI and determine the consequences of HHI (40% or 100% O₂). Dry weight analyses showed cerebral edema 1 to 21 days after HI in the ipsilateral cortex; and 3 to 21 days after HI in the contralateral cortex. Furthermore, HI increased blood‐brain barrier (BBB) permeability 1 to 7 days after HI, leading to bilateral cortical vasogenic edema. HHI failed to prevent HI‐induced increase in BBB permeability and edema development. At the molecular level, HI increased ipsilateral, but not contralateral, AQP4 cortical levels at 3 and up to 21 days after HI. HHI treatment did not further affect HI‐induced changes in AQP4. In addition, we observed developmental increases of AQP4 accompanied by significant reduction in water content and increase permeability of the BBB. Our results suggest that the ipsilateral HI‐induced increase in AQP4 may be beneficial and that its absence in the contralateral cortex may account for edema formation after HI. Finally, we showed that HI induced impaired motor coordination 21 days after the insult and HHI did not ameliorate this behavioral outcome. We conclude that HHI treatment is effective as a resuscitating therapy, but does not ameliorate HI‐induced cerebral edema and impaired motor coordination. © 2010 Wiley‐Liss, Inc.     

Human and mouse cortical astrocytes differ in aquaporin‐4 polarization toward microvessels

Aquaporin‐4 (AQP4), the predominant water channel in the brain, is expressed in astrocytes and ependymal cells. In rodents AQP4 is highly polarized to perivascular astrocytic endfeet and loss of AQP4 polarization is associated with disease. The present study was undertaken to compare the expression pattern of AQP4 in human and mouse cortical astrocytes. Cortical tissue specimens were sampled from 11 individuals undergoing neurosurgery wherein brain tissue was removed as part of the procedure, and compared with cortical tissue from 5 adult wild‐type mice processed similarly. The tissue samples were immersion‐fixed and prepared for AQP4 immunogold electron microscopy, allowing quantitative assessment of AQP4's subcellular distribution. In mouse we found that AQP4 water channels were prominently clustered around vessels, being 5 to 10‐fold more abundant in astrocytic endfoot membranes facing the capillary endothelium than in parenchymal astrocytic membranes. In contrast, AQP4 was markedly less polarized in human astrocytes, being only two to three‐fold enriched in astrocytic endfoot membranes adjacent to capillaries. The lower degree of AQP4 polarization in human subjects (1/3 of that in mice) was mainly due to higher AQP4 expression in parenchymal astrocytic membranes. We conclude that there are hitherto unrecognized species differences in AQP4 polarization toward microvessels in the cerebral cortex.     

Posttraumatic reduction of edema with aquaporin-4 RNA interference improves acute and chronic functional recovery

Traumatic brain injury (TBI) is common in young children and adolescents and is associated with long-term disability and mortality. The neuropathologic sequelae that result from juvenile TBI are a complex cascade of events that include edema formation and brain swelling. Brain aquaporin-4 (AQP4) has a key role in edema formation. Thus, development of novel treatments targeting AQP4 to reduce edema could lessen the neuropathologic sequelae. We hypothesized that inhibiting AQP4 expression by injection of small-interfering RNA (siRNA) targeting AQP4 (siAQP4) after juvenile TBI would decrease edema formation, neuroinflammation, neuronal cell death, and improve neurologic outcomes. The siAQP4 or a RNA-induced silencing complex (RISC)-free control siRNA (siGLO) was injected lateral to the trauma site after controlled cortical impact in postnatal day 17 rats. Magnetic resonance imaging, neurologic testing, and immunohistochemistry were performed to assess outcomes. Pups treated with siAQP4 showed acute (3 days after injury) improvements in motor function and in spatial memory at long term (60 days after injury) compared with siGLO-treated animals. These improvements were associated with decreased edema formation, increased microglial activation, decreased blood–brain barrier disruption, reduced astrogliosis and neuronal cell death. The effectiveness of our treatment paradigm was associated with a 30% decrease in AQP4 expression at the injection site.     

Diffuse traumatic axonal injury in mice induces complex behavioural alterations that are normalized by neutralization of interleukin‐1β

Widespread traumatic axonal injury (TAI) results in brain network dysfunction, which commonly leads to persisting cognitive and behavioural impairments following traumatic brain injury (TBI). TBI induces a complex neuroinflammatory response, frequently located at sites of axonal pathology. The role of the pro‐inflammatory cytokine interleukin (IL)‐1β has not been established in TAI. An IL‐1β‐neutralizing or a control antibody was administered intraperitoneally at 30 min following central fluid percussion injury (cFPI), a mouse model of widespread TAI. Mice subjected to moderate cFPI (n = 41) were compared with sham‐injured controls (n = 20) and untreated, naive mice (n = 9). The anti‐IL‐1β antibody reached the target brain regions in adequate therapeutic concentrations (up to ~30 μg/brain tissue) at 24 h post‐injury in both cFPI (n = 5) and sham‐injured (n = 3) mice, with lower concentrations at 72 h post‐injury (up to ~18 μg/g brain tissue in three cFPI mice). Functional outcome was analysed with the multivariate concentric square field (MCSF) test at 2 and 9 days post‐injury, and the Morris water maze (MWM) at 14–21 days post‐injury. Following TAI, the IL‐1β‐neutralizing antibody resulted in an improved behavioural outcome, including normalized behavioural profiles in the MCSF test. The performance in the MWM probe (memory) trial was improved, although not in the learning trials. The IL‐1β‐neutralizing treatment did not influence cerebral ventricle size or the number of microglia/macrophages. These findings support the hypothesis that IL‐1β is an important contributor to the processes causing complex cognitive and behavioural disturbances following TAI.     

Loss of astrocyte polarization upon transient focal brain ischemia as a possible mechanism to counteract early edema formation

Brain edema is the main cause of death from brain infarction. The polarized expression of the water channel protein aquaporin‐4 (AQP4) on astroglial endfeet surrounding brain microvessels suggests a role in brain water balance. Loss of astrocyte foot process anchoring to the basement membrane (BM) accompanied by the loss of polarized localization of AQP4 to astrocytic endfeet has been shown to be associated with vasogenic/extracellular edema in neuroinflammation. Here, we asked if loss of astrocyte polarity is also observed in cytotoxic/intracellular edema following focal brain ischemia after transient middle cerebral artery occlusion (tMCAO). Upon mild focal brain ischemia, we observed diminished immunostaining for the BM components laminin α4, laminin α2, and the proteoglycan agrin, in the core of the lesion, but not in BMs in the surrounding penumbra. Staining for the astrocyte endfoot anchorage protein β‐dystroglycan (DG) was dramatically reduced in both the lesion core and the penumbra, and AQP4 and Kir4.1 showed a loss of polarized localization to astrocytic endfeet. Interestingly, we observed that mice deficient for agrin expression in the brain lack polarized localization of β‐DG and AQP4 at astrocytic endfeet and do not develop early cytotoxic/intracellular edema following tMCAO. Taken together, these data indicate that the binding of DG to agrin embedded in the subjacent BM promotes polarized localization of AQP4 to astrocyte endfeet. Reduced DG protein levels and redistribution of AQP4 as observed upon tMCAO might therefore counteract early edema formation and reflect a beneficial mechanism operating in the brain to minimize damage upon ischemia. © 2012 Wiley Periodicals, Inc.     

A Precision Medicine Approach to Cerebral Edema and Intracranial Hypertension after Severe Traumatic Brain Injury: Quo Vadis?

Purpose of Review

Standard clinical protocols for treating cerebral edema and intracranial hypertension after severe TBI have remained remarkably similar over decades. Cerebral edema and intracranial hypertension are treated interchangeably when in fact intracranial pressure (ICP) is a proxy for cerebral edema but also other processes such as extent of mass lesions, hydrocephalus, or cerebral blood volume. A complex interplay of multiple molecular mechanisms results in cerebral edema after severe TBI, and these are not measured or targeted by current clinically available tools. Addressing these underpinnings may be key to preventing or treating cerebral edema and improving outcome after severe TBI.

Recent Findings

This review begins by outlining basic principles underlying the relationship between edema and ICP including the Monro-Kellie doctrine and concepts of intracranial compliance/elastance. There is a subsequent brief discussion of current guidelines for ICP monitoring/management. We then focus most of the review on an evolving precision medicine approach towards cerebral edema and intracranial hypertension after TBI. Personalization of invasive neuromonitoring parameters including ICP waveform analysis, pulse amplitude, pressure reactivity, and longitudinal trajectories are presented. This is followed by a discussion of cerebral edema subtypes (continuum of ionic/cytotoxic/vasogenic edema and progressive secondary hemorrhage). Mechanisms of potential molecular contributors to cerebral edema after TBI are reviewed. For each target, we present findings from preclinical models, and evaluate their clinical utility as biomarkers and therapeutic targets for cerebral edema reduction. This selection represents promising candidates with evidence from different research groups, overlap/inter-relatedness with other pathways, and clinical/translational potential.

Summary

We outline an evolving precision medicine and translational approach towards cerebral edema and intracranial hypertension after severe TBI.

     

IL-8单抗对颅脑损伤后继发性脑损害的保护作用

目的　观察抗IL 8单抗对兔脑损伤后脑内炎症反应的抑制作用 ,以及对血脑屏障通透性和创伤性脑水肿的影响 ,探讨颅脑损伤后继发性脑损害新的治疗方法。方法　采用自由落体兔脑损伤模型 ,观察家兔抗IL 8单抗治疗前后脑组织中IL 8表达、中性粒细胞 (PMNL)浸润有无变化 ,同时检测脑组织含水量的变化 ,并用胶体金示踪 ,电镜观察抗IL 8单抗使用前后血脑屏障通透性有无改善。结果　抗IL 8单抗治疗组与对照组相比 ,伤后脑组织中IL 8无表达 ,PMNL浸润也明显减少 (P <0 .0 1 ) ,血脑屏障通透性降低 ,脑含水量下降 (P <0 .0 5)。结论　颅脑损伤后早期给予抗IL 8单抗治疗 ,可抑制IL 8的表达 ,抑制IL 8趋化PMNL的作用 ,减少组织中PMNL的浸润 ,减轻脑损伤后脑内炎症反应 ,降低血脑屏障通透性 ,减轻创伤性脑水肿 ,从而改善继发性脑损害。     

局灶性脑低温处理对大鼠创伤性脑损伤模型的保护作用

目的探讨局灶性低温处理对SD大鼠创伤性脑损伤（TBI）模型的保护作用并探讨其相关机制。 方法将15只雄性SD大鼠随机平均分成假手术组（sham）,非冷却组（non-cooling）和冷却组（cooling）。Non-cooling组和cooling组制作TBI模型,3组实验同步进行,创伤后低温处理3 h,复温3 h,过程中检测大鼠血气、皮层脑电。复温结束处死大鼠后,对脑组织进行TTC和HE染色以评价脑死亡和脑水肿情况,Western blot检测相关机制蛋白表达情况。 结果Sham组和non-cooling组受外部刺激脑组织代谢升高,cooling组较其他组脑组织代谢低,TTC和HE染色显示cooling组脑死亡的面积和细胞死亡数量均少于non-cooling组,差异均具有统计学意义（P<0.05）。大鼠TBI后局灶性低温处理能显著降低大脑皮层的癫痫样棘波,在回温时这种不完全抑制持续存在,且低温处理降低了GABA_B1R蛋白的表达,差异均具有统计学意义（P<0.05）。Cooling组的脑水肿情况较non-cooling组轻,且cooling组AQP4蛋白表达降低,差异均具有统计学意义（P<0.05）。 结论局灶性低温处理对TBI大鼠具有保护作用,能显著减轻TBI引起的脑水肿,抑制大脑皮层的癫痫样棘波,具体机制可能分别与GABA_B1R和AQP4相关。为临床治疗TBI提供了一种更加安全、简单有效的方法。