Quantification of Axonal Damage in Traumatic Brain Injury

Abstract : Diffuse axonal injury is a primary feature of head trauma and is one of the most frequent causes of mortality and morbidity. Diffuse axonal injury is microscopic in nature and difficult or impossible to detect with imaging techniques. The objective of the present study was to determine whether axonal injury in head trauma patients could be quantified by measuring levels of CSF tau proteins. Tau proteins are structural microtubule binding proteins primarily localized in the axonal compartment of neurons. Monoclonal antibodies recognizing the form of tau found in the CSF of head trauma patients were developed by differential CSF hybridoma screening using CSF from head trauma and control patients. Clones positive for head trauma CSF tau proteins were used to characterize this form of tau and for ELISA development. Using the developed ELISA, CSF tau levels were elevated >1,000-fold in head trauma patients (mean, 1,519 ng/ml of CSF) when compared with patients with multiple sclerosis (mean, 0.014 ng/ml of CSF ; p < 0.001), normal pressure hydrocephalus (nondetectable CSF tau), neurologic controls (mean, 0.031 ng/ml of CSF ; p < 0.001), or nonneurologic controls (nondetectable CSF tau ; p < 0.001). In head trauma, a relationship between clinical improvement and decreased CSF tau levels was observed. These data suggest that CSF tau levels may prove a clinically useful assay for quantifying the axonal injury associated with head trauma and monitoring efficacy of neuroprotective agents. Affinity purification of CSF tau from head trauma patients indicated a uniform cleavage of ~ 18 kDa from all six tau isoforms, reducing their apparent molecular sizes to 30-50 kDa. These cleaved forms of CSF tau consisted of the interior portion of the tau sequence, including the microtubule binding domain, as judged by cyanogen bromide digestion. Consistent with these data, CSF cleaved tau bound taxolpolymerized microtubules, indicating a functionally intact microtubule binding domain. Furthermore, epitope mapping studies suggested that CSF cleaved tau proteins consist of the interior portion of the tau sequence with cleavage at both N and C terminals.     

Toll-Like Receptor 4 Knockdown Attenuates Brain Damage and Neuroinflammation After Traumatic Brain Injury via Inhibiting Neuronal Autophagy and Astrocyte Activation

Toll-like receptor 4 (TLR4) has been linked to various pathophysiological conditions, such as traumatic brain injury (TBI). It is reported that posttraumatic neuroinflammation is an essential event in the progression of brain injury after TBI. Recent evidences indicate that TLR4 mediates glial phagocytic activity and inflammatory cytokines production. Thus, TLR4 may be an important therapeutic target for neuroinflammatory injury post-TBI. This study was designed to explore potential effects and underlying mechanisms of TLR4 in rats suffered from TBI. TBI model was induced using a controlled cortical impact in rats, and application of TLR4 shRNA silenced TLR4 expression in brain prior to TBI induction. Elevated TLR4 was specifically observed in the hippocampal astrocytes and neurons posttrauma. Interestingly, TLR4 shRNA decreased the concentrations of interleukin (IL)-1β, IL-6, and tissue necrosis factor-α; alleviated hippocampal neuronal damage; reduced brain edema formation; and improved neurological deficits after TBI. Meanwhile, to further explore underlying molecular mechanisms of this neuroprotective effects of TLR4 knockdown, our results showed that TLR4 knockdown significantly inhibited the upregulation of autophagy-associated proteins caused by TBI. More importantly, an autophagy inducer, rapamycin pretreated, could partially abolish neuroprotective effects of TLR4 knockdown on TBI rats. Furthermore, TLR4 silencing markedly suppressed GFAP upregulation and improved cell hypertrophy to attenuate TBI-induced astrocyte activation. Taken together, these findings suggested that TLR4 knockdown ameliorated neuroinflammatory response and brain injury after TBI through suppressing autophagy induction and astrocyte activation.     

Naloxone for Severe Traumatic Brain Injury: A Meta-Analysis

Objective

The efficiency of naloxone for the management of secondary brain injury after severe traumatic brain injury (sTBI) remains undefined. The aim of this study is to evaluate the current evidence regarding the clinical efficiency and safety of naloxone as a treatment for sTBI in mainland China.

Methodology/Principal Findings

A systematic search of the China Biology Medicine disc (CBM), China Science and Technology Journal Database (VIP), China National Knowledge Internet (CNKI), and Wan Fang Database was performed to identify randomized controlled trials (RCTs) of naloxone treatment for patients with sTBI in mainland China. The quality of the included trials was assessed, and the RevMan 5.1 software was employed to conduct this meta-analysis. Nineteen RCTs including 2332 patients were included in this study. The odds ratio (OR) showed statistically significant differences between the naloxone group and the control group (placebo) in terms of mortality at 18 months after treatment (OR, 0.51, 95%CI: 0.38–0.67; p<0.00001), prevalence of abnormal heart rates (OR, 0.30, 95%CI: 0.21–0.43; p<0.00001), abnormal breathing rate (OR, 0.25, 95%CI: 0.17–0.36; p<0.00001) at discharge, the level of intracranial pressure at discharge (OR, 2.00, 95%CI: 1.41–2.83; p = 0.0001), verbal or physical dysfunction rate (OR, 0.65, 95%CI: 0.43–0.98; p = 0.04), and severe disability rate (OR, 0.47, 95%CI: 0.30–0.73; p = 0.0001) at 18 months after the treatment. The mean difference (MD) showed statistically significant differences in awakening time at discharge (MD, −4.81, 95%CI: −5.49 to −4.12; p<0.00001), and GCS at 3 days (MD, 1.00, 95%CI: 0.70–1.30; p<0.00001) and 10 days (MD, 1.76, 95%CI: 1.55–1.97; p<0.00001) after treatment comparing naloxone with placebo group.

Conclusions/Significance

This study indicated that applying naloxone in the early stage for sTBI patients might effectively reduce mortality, control intracranial pressure (ICP), and significantly improve the prognosis.     

Association between Serum Tissue Inhibitor of Matrix Metalloproteinase-1 Levels and Mortality in Patients with Severe Brain Trauma Injury

Objective

Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) play a role in neuroinflammation after brain trauma injury (TBI). Previous studies with small sample size have reported higher circulating MMP-2 and MMP-9 levels in patients with TBI, but no association between those levels and mortality. Thus, the aim of this study was to determine whether serum TIMP-1 and MMP-9 levels are associated with mortality in patients with severe TBI.

Methods

This was a multicenter, observational and prospective study carried out in six Spanish Intensive Care Units. Patients with severe TBI defined as Glasgow Coma Scale (GCS) lower than 9 were included, while those with Injury Severity Score (ISS) in non-cranial aspects higher than 9 were excluded. Serum levels of TIMP-1, MMP-9 and tumor necrosis factor (TNF)-alpha, and plasma levels of tissue factor (TF) and plasminogen activator inhibitor (PAI)-1 plasma were measured in 100 patients with severe TBI at admission. Endpoint was 30-day mortality.

Results

Non-surviving TBI patients (n = 27) showed higher serum TIMP-1 levels than survivor ones (n = 73). We did not find differences in MMP-9 serum levels. Logistic regression analysis showed that serum TIMP-1 levels were associated 30-day mortality (OR = 1.01; 95% CI = 1.001–1.013; P = 0.03). Survival analysis showed that patients with serum TIMP-1 higher than 220 ng/mL presented increased 30-day mortality than patients with lower levels (Chi-square = 5.50; P = 0.02). The area under the curve (AUC) for TIMP-1 as predictor of 30-day mortality was 0.73 (95% CI = 0.624–0.844; P<0.001). An association between TIMP-1 levels and APACHE-II score, TNF- alpha and TF was found.

Conclusions

The most relevant and new findings of our study, the largest series reporting data on TIMP-1 and MMP-9 levels in patients with severe TBI, were that serum TIMP-1 levels were associated with TBI mortality and could be used as a prognostic biomarker of mortality in TBI patients.     

Therapeutic Sesamol Attenuates Monocrotaline-Induced Sinusoidal Obstruction Syndrome in Rats by Inhibiting Matrix Metalloproteinase-9

We investigated the therapeutic effect of sesamol against monocrotaline-induced sinusoidal obstruction syndrome (SOS) in rats. Male Sprague–Dawley rats were gavaged with a single dose of monocrotaline (90 mg/kg) to induce SOS. Sesamol (5, 10, 20, and 40 mg/kg) was subcutaneously injected 24 h after monocrotaline treatment. Control rats were given saline only. Aspartate transaminase, alanine transaminase, mast cells, CD 68⁺ Kupffer cells, neutrophils, myeloperoxidase, matrix metalloproteinase-9 (MMP-9), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), laminin, and collagen were assessed 48 h after monocrotaline treatment. All tested parameters, except for TIMP-1, laminin, and collagen, were significantly higher in monocrotaline-treated rats than in control rats, and, except for TIMP-1, laminin, and collagen, significantly lower in sesamol-treated rats than in monocrotaline-treated rats. In addition, liver pathology revealed that sesamol offered significant protection against SOS. We conclude that a single dose of sesamol therapeutically attenuated SOS by decreasing the recruitment of inflammatory cells, downregulating MMP-9, and upregulating TIMP-1 expression.     

Matrix Metalloproteinase-9 Protects Islets from Amyloid-induced Toxicity

Deposition of human islet amyloid polypeptide (hIAPP, also known as amylin) as islet amyloid is a characteristic feature of the pancreas in type 2 diabetes, contributing to increased β-cell apoptosis and reduced β-cell mass. Matrix metalloproteinase-9 (MMP-9) is active in islets and cleaves hIAPP. We investigated whether hIAPP fragments arising from MMP-9 cleavage retain the potential to aggregate and cause toxicity, and whether overexpressing MMP-9 in amyloid-prone islets reduces amyloid burden and the resulting β-cell toxicity. Synthetic hIAPP was incubated with MMP-9 and the major hIAPP fragments observed by MS comprised residues 1–15, 1–25, 16–37, 16–25, and 26–37. The fragments 1–15, 1–25, and 26–37 did not form amyloid fibrils in vitro and they were not cytotoxic when incubated with β cells. Mixtures of these fragments with full-length hIAPP did not modulate the kinetics of fibril formation by full-length hIAPP. In contrast, the 16–37 fragment formed fibrils more rapidly than full-length hIAPP but was less cytotoxic. Co-incubation of MMP-9 and fragment 16–37 ablated amyloidogenicity, suggesting that MMP-9 cleaves hIAPP 16–37 into non-amyloidogenic fragments. Consistent with MMP-9 cleavage resulting in largely non-amyloidogenic degradation products, adenoviral overexpression of MMP-9 in amyloid-prone islets reduced amyloid deposition and β-cell apoptosis. These findings suggest that increasing islet MMP-9 activity might be a strategy to limit β-cell loss in type 2 diabetes.     

The AMPAR Antagonist Perampanel Attenuates Traumatic Brain Injury Through Anti-Oxidative and Anti-Inflammatory Activity

Perampanel is a novel α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor (AMPAR) antagonist, approved in over 35 countries as an adjunctive therapy for the treatment of seizures. Recently, it was found to exert protective effects against ischemic neuronal injury in vitro. In the present study, we investigated the potential protective effects of perampanel in a traumatic brain injury (TBI) model in rats. Oral administration with perampanel at a dose of 5 mg/kg exerted no major organ-related toxicities. We found that perampanel significantly attenuated TBI-induced brain edema, brain contusion volume, and gross motor dysfunction. The results of Morris water maze test demonstrated that perampanel treatment also improved cognitive function after TBI. These neuroprotective effects were accompanied by reduced neuronal apoptosis, as evidenced by decreased TUNEL-positive cells in brain sections. Moreover, perampanel markedly inhibited lipid peroxidation and obviously preserved the endogenous antioxidant system after TBI. In addition, enzyme-linked immunosorbent assay (ELISA) was performed at 4 and 24 h after TBI to evaluate the expression of inflammatory cytokines. The results showed that perampanel suppressed the expression of pro-inflammatory cytokines TNF-α and IL-1β, whereas increased the levels of anti-inflammatory cytokines IL-10 and TGF-β1. These data show that the orally active AMPAR antagonist perampanel affords protection against TBI-induced neuronal damage and neurological dysfunction through anti-oxidative and anti-inflammatory activity.     

血必净注射液对重型颅脑损伤患者的神经保护及其机制研究

目的:探讨血必净注射液对重型颅脑损伤患者的神经保护作用及其机制。方法:将2012年1月至2014年12月我院收治的200例重型颅脑损伤患者分为研究组(100例)和对照组(100例),另选取100例同期在我院体检的健康者为正常组。对照组给予常规治疗,研究组在对照组基础上静脉滴注血必净注射液,治疗后第1天、第3天、第5天、第7天时观察各组TNF-α及IL-6水平变化。结果:对照组、研究组各时间点TNF-α及IL-6水平均高于正常组(均P0.05),且研究组的TNF-α及IL-6水平均低于对照组(均P0.05)。结论:血必净注射液对重型颅脑损伤患者的神经具有保护作用,其作用机制可能跟降低炎症反应有关。     

利用RNAi抑制PARs防治脑缺血性损伤的实验研究

目的:利用RNA干扰技术,通过重组腺病毒导入,抑制脑组织中PARs基因的表达,观察神经功能缺陷评分、缺血脑组织梗死体积的变化,为缺血性脑血管疾病的基因治疗提供实验依据。方法:雄性Wistar大鼠随机分组,以重组腺病毒介导的无序PARs基因shRNA片段、生理盐水进行干预,干预3天后以线栓法建立Wistar大鼠大脑中动脉永久闭塞模型,各组分别于线栓后24h、72h进行神经功能缺陷评分并断头取脑,应用4%TTC染色测脑梗死体积。结果:1.缺血后24h、72h同一时间点:①实验组分别与对照组、生理盐水组对比,神经功能缺陷评分明显降低(P<0.05),脑梗死体积明显减小(P<0.05);②对照组与生理盐水组对比,神经功能缺陷评分、脑梗死体积无明显差异(P>0.05)。2.各组组内缺血后24h、72h对比,神经功能缺陷评分、脑梗死体积各组均有明显差异(P<0.05)。结论:重组腺病毒介导的RNAi能有效抑制脑组织中PARs基因的表达,缩小脑梗死体积,改善神经功能缺陷评分。     

高压氧治疗重型颅脑损伤的临床疗效观察

目的:观察高压氧辅助治疗重型颅脑损伤的临床疗效。方法:68例重型颅脑损伤患者随机分为观察组和对照组各34例,所有患者均根据病情选择手术或保守治疗,观察组在患者病情稳定后加用高压氧辅助治疗,治疗结束后比较两组患者的临床疗效。结果:观察组治疗有效率为91.2%,显著高于对照组的76.5%(P<0.05);治疗后1周和2周观察组的GCS评分均显著高于对照组(P<0.05),治疗后6个月观察组的GOS评分显著高于对照组(P<0.05);治疗后两组患者脑动脉血流速度均较治疗前有明显的改善(P<0.05),且观察的的改善情况优于对照组。结论:选择高压氧辅助治疗重型颅脑损伤的临床疗效好,可改善患者的临床情况和预后,值得临床应用。     

利用RNAi抑制PARs防治脑缺血性损伤的实验研究

目的：利用RNA干扰技术,通过重组腺病毒导入,抑制脑组织中PARs基因的表达,观察神经功能缺陷评分、缺血脑组织梗死体积的变化,为缺血性脑血管疾病的基因治疗提供实验依据。方法：雄性Wistar大鼠随机分组。以重组腺病毒介导的无序PARs基因shRNA片段、生理盐水进行干预,干预3天后以线栓法建立Wistar大鼠大脑中动脉永久闭塞模型,各组分别于线栓后24h、72h进行神经功能缺陷评分并断头取脑,应用4％TTC染色测脑梗死体积。结果：1．缺血后24h、72h同一时间点：①实验组分别与对照组、生理盐水组对比,神经功能缺陷评分明显降低（P〈0．05）,脑梗死体积明显减小（P〈0．05）;②对照组与生理盐水组对比,神经功能缺陷评分、脑梗死体积无明显差异（P〉0．05）。2．各组组内缺血后24h、72h对比,神经功能缺陷评分、脑梗死体积各组均有明显差异（P〈0．05）。结论：重组腺病毒介导的RNAi能有效抑制脑组织中PARs基因的表达,缩小脑梗死体积,改善神经功能缺陷评分。     

重型颅脑损伤后颅内高压的治疗研究进展

重型颅脑损伤后颅内压增高预示着不良的神经功能预后和极高的死亡率,一直是临床治疗中的研究热点,可采取高渗性脱水,亚低温疗法,巴比妥昏迷治疗及外科手术干预等治疗措施控制颅内压。由于亚低温治疗会增加患者发生肺炎的风险,巴比妥类药物副作用较大,现均已少用。近来研究发现,监测颅内压、脑灌注压、脑组织氧分压并指导临床治疗,可降低死亡率与改善预后。也有研究发现去骨瓣减压术治疗顽固性颅内高压与神经功能预后较差有关。目前关于颅内高压治疗的最佳方案仍存在争议,未来还需根据患者病情,为其制定规范化与个体化的治疗方案,预防继发性颅脑损伤,降低颅内压。本文就近年来重型颅脑损伤后颅内高压的治疗进展进行阐述。     

亚低温治疗对重型颅脑损伤患者颅内压、脑血流及氧代谢的影响

目的:探讨亚低温治疗对重症颅脑损伤(sTBI)患者颅内压(ICP)、脑血流及氧代谢的影响。方法:收集50例sTBI患者随机分为实验组和对照组,每组25例,均给予常规治疗,观察组在常规治疗基础上给予亚低温辅助治疗,检测患者治疗前、治疗第3、5、7天ICP动态变化以及治疗前和治疗7天后脑血流和氧代谢等指标变化。结果:治疗第3、5、7天ICP组间差异均具有统计学意义(P0.05),随着治疗时间增加两组ICP均逐渐降低,差异具有统计学意义(P0.05);治疗前Qmean、Vmean、Wv、DR等组间差异无统计学意义(P0.05),治疗7天后Qmean、Vmean均升高,Wv、DR均降低,差异具有统计学意义(P0.05);治疗前SjvO_2、CjvO_2、CaO_2、CERO_2组间差异无统计学意义(P0.05),治疗7天后SjvO_2、CjvO_2、CERO_2均升高,CaO_2降低,差异具有统计学意义(P0.05)。结论:亚低温治疗可以显著降低患者颅内压,改善脑血流和氧代谢水平。     

Risk Taking in Hospitalized Patients with Acute and Severe Traumatic Brain Injury

Rehabilitation can improve cognitive deficits observed in patients with traumatic brain injury (TBI). However, despite rehabilitation, the ability of making a choice often remains impaired. Risk taking is a daily activity involving numerous cognitive processes subserved by a complex neural network. In this work we investigated risk taking using the Balloon Analogue Risk Task (BART) in patients with acute TBI and healthy controls. We hypothesized that individuals with TBI will take less risk at the BART as compared to healthy individuals. We also predicted that within the TBI group factors such as the number of days since the injury, severity of the injury, and sites of the lesion will play a role in risk taking as assessed with the BART. Main findings revealed that participants with TBI displayed abnormally cautious risk taking at the BART as compared to healthy subjects. Moreover, healthy individuals showed increased risk taking throughout the task which is in line with previous work. However, individuals with TBI did not show this increased risk taking during the task. We also investigated the influence of three patients’ characteristics on their performance at the BART: Number of days post injury, Severity of the head injury, and Status of the frontal lobe. Results indicate that performance at the BART was influenced by the number of days post injury and the status of the frontal lobe, but not by the severity of the head injury. Reported findings are encouraging for risk taking seems to naturally improve with time postinjury. They support the need of conducting longitudinal prospective studies to ultimately identify impaired and intact cognitive skills that should be trained postinjury.     

Depletion of Brain Docosahexaenoic Acid Impairs Recovery from Traumatic Brain Injury

Omega-3 fatty acids are crucial for proper development and function of the brain where docosahexaenoic acid (DHA), the primary omega-3 fatty acid in the brain, is retained avidly by the neuronal membranes. We investigated the effect of DHA depletion in the brain on the outcome of traumatic brain injury (TBI). Pregnant mice were put on an omega-3 fatty acid adequate or deficient diet from gestation day 14 and the pups were raised on the respective diets. Continuation of this dietary regime for three generations resulted in approximately 70% loss of DHA in the brain. Controlled cortical impact was delivered to both groups of mice to produce severe TBI and the functional recovery was compared. Compared to the omega-3 adequate mice, the DHA depleted mice exhibited significantly slower recovery from motor deficits evaluated by the rotarod and the beam walk tests. Furthermore, the DHA deficient mice showed greater anxiety-like behavior tested in the open field test as well as cognitive deficits evaluated by the novel object recognition test. The level of alpha spectrin II breakdown products, the markers of TBI, was significantly elevated in the deficient mouse cortices, indicating that the injury is greater in the deficient brains. This observation was further supported by the reduction of NeuN positive cells around the site of injury in the deficient mice, indicating exacerbated neuronal death after injury. These results suggest an important influence of the brain DHA status on TBI outcome.     

Berberine Protects Secondary Injury in Mice with Traumatic Brain Injury Through Anti-oxidative and Anti-inflammatory Modulation

Traumatic brain injury (TBI) is one of the major causes of death and disability worldwide. Novel and effective therapy is needed to prevent the secondary spread of damage beyond the initial injury. The aim of this study was to investigate whether berberine has a neuroprotective effect on secondary injury post-TBI, and to explore its potential mechanism in this protection. The mice were randomly divided into Sham-saline, TBI-saline and TBI-Berberine (50 mg/kg). TBI was induced by Feeney’s weight-drop technique. Saline or berberine was administered via oral gavage starting 1 h post-TBI and continuously for 21 days. Motor coordination, spatial learning and memory were assessed using beam-walking test and Morris water maze test, respectively. Brain sections were processed for lesion volume assessment, and expression of neuronal nuclei (NeuN), cyclooxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS), 8-hydroxy-2-deoxyguanosine (8-OHdG), ionized calcium-binding adapter molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) were detected via immunohistochemistry and immunofluorescence. There were statistically significant improvement in motor coordination, spatial learning and memory in the TBI-Berberine group, compared to the TBI-saline group. Treatment with berberine significantly reduced cortical lesion volume, neuronal loss, COX-2, iNOS and 8-OHdG expression in both the cortical lesion border zone (LBZ) and ipsilateral hippocampal CA1 region (CA1), compared to TBI-saline. Berberine treatment also significantly decreased Iba1- and GFAP-positive cell number in both the cortical LBZ and ipsilateral CA1, relative to saline controls. These results indicated that berberine exerted neuroprotective effects on secondary injury in mice with TBI probably through anti-oxidative and anti-inflammatory properties.     

Inhibition of Epidermal Growth Factor Receptor Improves Myelination and Attenuates Tissue Damage of Spinal Cord Injury

Preventing demyelination and promoting remyelination of denuded axons are promising therapeutic strategies for spinal cord injury (SCI). Epidermal growth factor receptor (EGFR) inhibition was reported to benefit the neural functional recovery and the axon regeneration after SCI. However, its role in de- and remyelination of axons in injured spinal cord is unclear. In the present study, we evaluated the effects of EGFR inhibitor, PD168393 (PD), on the myelination in mouse contusive SCI model. We found that expression of myelin basic protein (MBP) in the injured spinal cords of PD treated mice was remarkably elevated. The density of glial precursor cells and oligodendrocytes (OLs) was increased and the cell apoptosis in lesions was attenuated after PD168393 treatment. Moreover, PD168393 treatment reduced both the numbers of OX42 + microglial cells and glial fibrillary acidic protein + astrocytes in damaged area of spinal cords. We thus conclude that the therapeutic effects of EGFR inhibition after SCI involves facilitating remyelination of the injured spinal cord, increasing of oligodendrocyte precursor cells and OLs, as well as suppressing the activation of astrocytes and microglia/macrophages.