Plasma fibronectin is neuroprotective following traumatic brain injury

Promotion of repair and regeneration following traumatic brain injury remains a challenging clinical problem. While significant efforts have been made to reduce inhibitory extracellular matrix expression following central nervous system injury, much less attention has been given to the role of endogenous reparative matrix proteins, such as fibronectin. Traumatic brain injury leads to increased levels of plasma-derived fibronectin in the brain tissue, though the specific function of this protein following neurotrauma was unknown. In this study, we utilized conditional plasma fibronectin (pFN) knockout mice to examine the role of fibronectin following a traumatic insult. Injured mice deficient in pFN performed significantly worse on both motor and cognitive tasks, had significantly increased lesion volume and apoptotic cell death, and had significantly less phagocytic cells in the injured cortex compared to injured mice with normal pFN levels. Moreover, intravenous injections of fibronectin prior to the injury restored the neural deficits seen in the pFN deficient mice to that of wild type injured mice. These results demonstrate that fibronectin is neuroprotective to the traumatically injured brain and identify a novel target for therapeutic interventions.     

Rapamycin is a neuroprotective treatment for traumatic brain injury

The mammalian target of rapamycin, commonly known as mTOR, is a serine/threonine kinase that regulates translation and cell division. mTOR integrates input from multiple upstream signals, including growth factors and nutrients to regulate protein synthesis. Inhibition of mTOR leads to cell cycle arrest, inhibition of cell proliferation, immunosuppression and induction of autophagy. Autophagy, a bulk degradation of sub-cellular constituents, is a process that keeps the balance between protein synthesis and protein degradation and is induced upon amino acids deprivation. Rapamycin, mTOR signaling inhibitor, mimics amino acid and, to some extent, growth factor deprivation. In the present study we examined the effect of rapamycin, on the outcome of mice after brain injury. Our results demonstrate that rapamycin injection 4 h following closed head injury significantly improved functional recovery as manifested by changes in the Neurological Severity Score, a neurobehavioral testing. To verify the activity of the injected rapamycin, we demonstrated that it inhibits p70S6K phosphorylation, reduces microglia/macrophages activation and increases the number of surviving neurons at the site of injury. We therefore suggest that rapamycin is neuroprotective following traumatic brain injury and as a drug used in the clinic for other indications, we propose that further studies on rapamycin should be conducted in order to consider it as a novel therapy for traumatic brain injury.     

N-arachidonoyl--serine is neuroprotective after traumatic brain injury by reducing apoptosis

N-arachidonoyl--serine (AraS) is a brain component structurally related to the endocannabinoid family. We investigated the neuroprotective effects of AraS following closed head injury induced by weight drop onto the exposed fronto-parietal skull and the mechanisms involved. A single injection of AraS following injury led to a significant improvement in functional outcome, and to reduced edema and lesion volume compared with vehicle. Specific antagonists to CB2 receptors, transient receptor potential vanilloid 1 (TRPV1) or large conductance calcium-activated potassium (BK) channels reversed these effects. Specific binding assays did not indicate binding of AraS to the GPR55 cannabinoid receptor. N-arachidonoyl--serine blocked the attenuation in phosphorylated extracellular-signal-regulated kinase 1/2 (ERK) levels and led to an increase in pAkt in both the ipsilateral and contralateral cortices. Increased levels of the prosurvival factor Bcl-xL were evident 24 hours after injury in AraS-treated mice, followed by a 30% reduction in caspase-3 activity, measured 3 days after injury. Treatment with a CB2 antagonist, but not with a CB1 antagonist, reversed this effect. Our results suggest that administration of AraS leads to neuroprotection via ERK and Akt phosphorylation and induction of their downstream antiapoptotic pathways. These protective effects are related mostly to indirect signaling via the CB2R and TRPV1 channels but not through CB1 or GPR55 receptors.     

创伤性脑损伤后认知障碍发生机制的研究进展

创伤性脑损伤(traumatic brain injury,TBI)也称为脑外伤,其发生率高、死残率高、后遗症多,给患者及家庭造成极大的痛苦和经济负担也给社会带来沉重的负担.TBI的严重后果包括:运动功能缺陷、知觉障碍、认知缺陷、语言障碍、外伤性癫痫、人格改变等,其中认知障碍为最持久和最严重的症状之一,通常表现在注意力和记忆力两方面.研究表明空间记忆缺失发生于各种程度的TBI之后,而有关TBI之后认知障碍的确切机制至今仍不十分清楚.     

Normobaric oxygen worsens outcome after a moderate traumatic brain injury

Traumatic brain injury (TBI) is a multifaceted injury and a leading cause of death in children, young adults, and increasingly in Veterans. However, there are no neuroprotective agents clinically available to counteract damage or promote repair after brain trauma. This study investigated the neuroprotective effects of normobaric oxygen (NBO) after a controlled cortical impact in rats. The central hypothesis was that NBO treatment would reduce lesion volume and functional deficits compared with air-treated animals after TBI by increasing brain oxygenation thereby minimizing ischemic injury. In a randomized double-blinded design, animals received either NBO (n=8) or normal air (n=8) after TBI. Magnetic resonance imaging (MRI) was performed 0 to 3 hours, and 1, 2, 7, and 14 days after an impact to the primary forelimb somatosensory cortex. Behavioral assessments were performed before injury induction and before MRI scans on days 2, 7, and 14. Nissl staining was performed on day 14 to corroborate the lesion volume detected from MRI. Contrary to our hypothesis, we found that NBO treatment increased lesion volume in a rat model of moderate TBI and had no positive effect on behavioral measures. Our results do not promote the acute use of NBO in patients with moderate TBI.     

Selective activation of protein kinase C∊ in mitochondria is neuroprotective in vitro and reduces focal ischemic brain injury in mice

Activation of protein kinase C? (PKC?) confers protection against neuronal ischemia/reperfusion. Activation of PKC? leads to its translocation to multiple intracellular sites, so a mitochondria‐selective PKC? activator was used to test the importance of mitochondrial activation to the neuroprotective effect of PKC?. PKC? can regulate key cytoprotective mitochondrial functions, including electron transport chain activity, reactive oxygen species (ROS) generation, mitochondrial permeability transition, and detoxification of reactive aldehydes. We tested the ability of mitochondria‐selective activation of PKC? to protect primary brain cell cultures or mice subjected to ischemic stroke. Pretreatment with either general PKC? activator peptide, TAT‐Ψ?RACK, or mitochondrial‐selective PKC? activator, TAT‐Ψ?HSP90, reduced cell death induced by simulated ischemia/reperfusion in neurons, astrocytes, and mixed neuronal cultures. The protective effects of both TAT‐Ψ?RACK and TAT‐Ψ?HSP90 were blocked by the PKC? antagonist ?V_1–2, indicating that protection requires PKC? interaction with its anchoring protein, TAT‐?RACK. Further supporting a mitochondrial mechanism for PKC?, neuroprotection by TAT‐Ψ?HSP90 was associated with a marked delay in mitochondrial membrane depolarization and significantly attenuated ROS generation during ischemia. Importantly, TAT‐Ψ?HSP90 reduced infarct size and reduced neurological deficit in C57/BL6 mice subjected to middle cerebral artery occlusion and 24 hr of reperfusion. Thus selective activation of mitochondrial PKC? preserves mitochondrial function in vitro and improves outcome in vivo, suggesting potential therapeutic value clinically when brain ischemia is anticipated, including neurosurgery and cardiac surgery. © 2013 Wiley Periodicals, Inc.     

Cytochrome c oxidase isoform IV‐2 is involved in 3‐nitropropionic acid‐induced toxicity in striatal astrocytes

Astrocyte mitochondria play an important role for energy supply and neuronal survival in the brain. Toxic and degenerative processes are largely associated with mitochondrial dysfunction. We, therefore, investigated the effect of 3‐nitropropionic acid (NPA), a mitochondrial toxin and in vitro model of Huntington's disease (HD), on mitochondrial function and viability of primary striatal astrocytes. Although NPA is known as an irreversible inhibitor of succinate dehydrogenase, we observed an increase of astrocyte ATP levels after NPA treatment. This effect could be explained by NPA‐mediated alterations of cytochrome c oxidase subunit IV isoform (COX IV) expression. The up‐regulation of COX isoform IV‐2 caused an increased enzyme activity at the expense of elevated mitochondrial peroxide production causing increased cell death. The application of a small interfering RNA against COX IV‐2 revealed the causal implication of COX isoform IV‐2 in NPA‐mediated elevation of oxidative stress and necrotic cell death. Thus, we propose a novel, additional mechanism of NPA‐induced cell stress and death which is based on structural and functional changes of astrocyte COX and which could indirectly impair neuronal survival. © 2009 Wiley‐Liss, Inc.     

Naltrexone is neuroprotective against traumatic brain injury in mu opioid receptor knockout mice

AimsNaltrexone is a mu opioid receptor (MOR) antagonist used to treat drug dependence in patients. Previous reports indicated that MOR antagonists reduced neurodegeneration and inflammation after brain injury. The purpose of this study was to evaluate the neuroprotective effect of naltrexone in cell culture and a mouse model of traumatic brain injury (TBI).MethodsThe neuroprotective effect of naltrexone was examined in primary cortical neurons co‐cultured with BV2 microglia. Controlled cortical impact (CCI) was delivered to the left cerebral cortex of adult male MOR wild‐type (WT) and knockout (KO) mice. Naltrexone was given daily for 4 days, starting from day 2 after lesioning. Locomotor activity was evaluated on day 5 after the CCI. Brain tissues were collected for immunostaining, Western, and qPCR analysis.ResultsGlutamate reduced MAP2 immunoreactivity (‐ir), while increased IBA1‐ir in neuron/BV2 co‐culture; both responses were antagonized by naltrexone. TBI significantly reduced locomotor activity and increased the expression of IBA1, iNOS, and CD4 in the lesioned cortex. Naltrexone significantly and equally antagonized the motor deficits and expression of IBA1 and iNOS in WT and KO mice. TBI‐mediated CD4 protein production was attenuated by naltrexone in WT mice, but not in KO mice.ConclusionNaltrexone reduced TBI‐mediated neurodegeneration and inflammation in MOR WT and KO mice. The protective effect of naltrexone involves non‐MOR and MOR mechanisms.     

Association between cognitive impairments and anxiety disorders following traumatic brain injury

This study examined the association between cognitive impairment and anxiety disorders following traumatic brain injury (TBI). Sixty-six participants recruited from a rehabilitation hospital completed the Structured Clinical Interview for the DSM–IV (Diagnostic and Statistical Manual of Mental Disorders–Fourth Edition) and cognitive tests at one year post injury. Prevalence of anxiety disorder was 27.3%. Logistic regression analyses revealed that the attention/working memory, information processing, and executive functions models were significantly associated with anxiety disorder. The memory model was not significant. Processing speed emerged as the strongest model associated with anxiety disorder. The role of cognitive impairment in the etiology of anxiety disorders after TBI is discussed, and treatment implications are explored.     

Normalization of coagulopathy is associated with improved outcome after isolated traumatic brain injury

Acute traumatic coagulopathy (ATC) has been reported in the setting of isolated traumatic brain injury (iTBI) and is associated with poor outcomes. We aimed to evaluate the effectiveness of procoagulant agents administered to patients with ATC and iTBI during resuscitation, hypothesizing that timely normalization of coagulopathy may be associated with a decrease in mortality. A retrospective review of the Alfred Hospital trauma registry, Australia, was conducted and patients with iTBI (head Abbreviated Injury Score [AIS] ⩾3 and all other body AIS <3) and coagulopathy (international normalized ratio ⩾1.3) were selected for analysis. Data on procoagulant agents used (fresh frozen plasma, platelets, cryoprecipitate, prothrombin complex concentrates, tranexamic acid, vitamin K) were extracted. Among patients who had achieved normalization of INR or survived beyond 24 hours and were not taking oral anticoagulants, the association of normalization of INR and death at hospital discharge was analyzed using multivariable logistic regression analysis. There were 157 patients with ATC of whom 68 (43.3%) received procoagulant products within 24 hours of presentation. The median time to delivery of first products was 182.5 (interquartile range [IQR] 115–375) minutes, and following administration of coagulants, time to normalization of INR was 605 (IQR 274–1146) minutes. Normalization of INR was independently associated with significantly lower mortality (adjusted odds ratio 0.10; 95% confidence interval 0.03–0.38). Normalization of INR was associated with improved mortality in patients with ATC in the setting of iTBI. As there was a substantial time lag between delivery of products and eventual normalization of coagulation, specific management of coagulopathy should be implemented as early as possible.     

Continuous infusion of cyclosporin A postinjury significantly ameliorates cortical damage following traumatic brain injury

Traumatic brain injury (TBI) results in the rapid necrosis of cortical tissue at the site of injury. In the ensuing hours and days, secondary injury exacerbates the original damage resulting in significant neurological dysfunction. Recent reports from our lab demonstrate that a bolus injection of the immunosuppressant cyclosporin A (CsA) is neuroprotective following TBI. CsA transiently inhibits the opening of the mitochondrial permeability transition pore and maintains calcium homeostasis in isolated mitochondria. The present study utilized a unilateral controlled cortical impact model of TBI to assess whether the neuroprotective effects of CsA could be extended by chronic infusion. Adult rats were subjected to a moderate (2 mm) cortical deformation and the extent of cortical damage was assessed using modern stereological techniques. Animals were administrated a 20 mg/kg intraperitoneal bolus of CsA or vehicle 15 min postinjury and osmotic minipumps were implanted subcutaneously to deliver CsA (4.5 or 10 mg/kg/day) or vehicle. All animals receiving CsA demonstrated a significant reduction in lesion volume, with the highest dose offering the most neuroprotection (74% reduction in lesion volume). These results extend our previous findings and demonstrate that chronic infusion of CsA is neuroprotective following TBI. These findings also suggest that the mechanisms responsible for tissue necrosis following TBI are amenable to manipulation.     

Acute depletion of reduced glutathione causes extensive carbonylation of rat brain proteins

This study was aimed at establishing whether oxidative stress induced by acute depletion of brain glutathione (GSH) is sufficient to generate protein carbonyls (PCOs). To this end, rat brain slices were incubated separately with the GSH depletors 1,3-bis[2-chloroethyl]-1-nitrosourea (BCNU) and diethyl maleate (DEM), and protein carbonylation was assessed on Western blots after derivatization with dinitrophenyl hydrazine. Incubation with 1 mM BCNU or 10 mM DEM for 2 hr decreased GSH levels by > 70%. Under these conditions the carbonylation of several proteins (40-120 kDa) increased by 2-3 fold. Isolation of carbonylated proteins showed that augmented PCOs represents a rise in the amount of oxidized protein. The iron chelator deferoxamine, the superoxide scavenger rutin and the H2O2 quencher dimethylthiourea all prevented DEM-induced protein carbonylation and lipid peroxidation (TBARS), indicating that the underlying mechanism involves the iron-catalyzed generation of hydroxyl radicals from H(2)O(2) (Fenton reaction). Inhibition of catalase activity with sodium azide and aminotriazole, and glutathione peroxidase activity with mercaptosuccinic acid did not increase PCOs or TBARS, suggesting that increased production of reactive oxygen species (ROS) rather than compromised cellular antioxidant defenses is the cause for the accumulation of H2O2 after GSH depletion. PCO formation was not affected by the xanthine oxidase inhibitor oxypurinol but it was reduced by SKF-525A and carbonyl cyanide 3-chlorophenylhydrazone, indicating that the microsomal monooxygenase system and the mitochondrial electron transport system are the major sources of ROS. Consistent with these findings, subcellular fractionation studies showed that mitochondria and synaptosomes are the major PCO-containing organelles. These results were also supported by the anatomic distribution of PCOs in brain. Our observations may be important in the context of multiple sclerosis where decreased GSH, mitochondrial dysfunction, excessive production of ROS, and increased protein carbonylation have all been reported.     

Effects of enoxaparin in the rat hippocampus following traumatic brain injury

Purpose of this study was to investigate the effects of low molecular weight heparin, enoxaparin, on different parameters of the hippocampal damage following traumatic brain injury (TBI) in the rat. TBI of moderate severity was performed over the left parietal cortex using the lateral fluid percussion brain injury model. Animals were s.c. injected with either enoxaparin (1 mg/kg) or vehicle 1, 7, 13, 19, 25, 31, 37, and 43 h after the TBI induction. Sham-operated, vehicle-treated animals were used as the control group. Rats were sacrificed 48 h after the induction of TBI. Hippocampi were processed for spectrophotometric measurements of the products of oxidative lipid damage, thiobarbituric acid-reactive substances (TBARS) levels, as well as the activities of antioxidant enzymes, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). Moreover, the Western blotting analyses of the oxidized protein levels, expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), pro- and mature-interleukin-1β (pro-, and mature-IL-1β), and active caspase-3 were performed. COX-2 expressions were also explored by using immunohistochemistry. Glial fibrillary acidic protein immunochistochemistry was performed with the aim to assess the level of astrocytic activity. Fluoro-Jade B staining was used to identify the level and extent of hippocampal neuronal injury. TBI caused statistically significant increases of the hippocampal TBARS and oxidized protein levels as well as COX-2, pro-IL-1β, and active caspase-3 overexpressions, but it did not significantly affect the SOD and GSH-Px activities, the iNOS, and mature-IL-1β expression levels. TBI also induced hippocampal reactive astrocytosis and neurodegeneration. Enoxaparin significantly decreased the hippocampal TBARS and oxidized protein levels, COX-2 overexpression and reactive gliosis, but it did not influence the SOD and GSH-Px activities, pro-IL-1β and active caspase-3 overexpressions as well as neurodegeneration following TBI. These findings demonstrate that enoxaparin may reduce oxidative damage, inflammation and astrocytosis following TBI in the rat and could be a candidate drug for neuroprotective treatment of this injury.     

颅脑外伤后继发性脑损害发病机制的研究进展

颅脑外伤(TBI)对脑组织造成的损伤包括原发性和继发性的，后者存很大程度上决定了TBI的最终结果，继发性脑损害的机制尚未完全明了，最近的研究发现颅脑外伤后的继发性脑损害最值得继续关注的病理机制有：(1)兴奋性氨基酸(EAAs)大量释放引起Ca^2 通道开放；(2)自由基生成和脂质过氧化；(3)炎性介质释放；(4)细胞凋亡等，这些机制既同时发生作用又互相关联构成连锁反应，最终导致神经细胞的死亡。针对上述损伤机制的脑保护措施仍有待于进一步研究。     

Recovered neuronal viability revealed by Iodine-123-iomazenil SPECT following traumatic brain injury

We evaluated cortical damages following traumatic brain injury (TBI) in the acute phase with [¹²³I] iomazenil (IMZ) single photon emission computed tomography (SPECT). In all, 12 patients with cerebral contusion following TBI were recruited. All patients underwent IMZ SPECT within 1 week after TBI. To investigate the changes in distribution of IMZ in the cortex in the chronic phase, after conventional treatment, patients underwent IMZ SPECT again. A decrease in the accumulation of radioligand for the central benzodiazepine receptor in the cortex corresponding to the contusion revealed with computed tomography (CT) scans and magnetic resonance imaging (MRI) were shown on IMZ SPECT in the acute phase in all patients. In 9 of 12 patients (75%), images of IMZ SPECT obtained in the chronic phase of TBI showed that areas with a decreased distribution of IMZ were remarkably reduced in comparison with those obtained in the acute phase. Both CT scans and MRI showed a normal appearance of the cortex morphologically, where the binding potential of IMZ recovered in the chronic phase. Reduced binding potential of radioligand for the central benzodiazepine receptor is considered to be an irreversible reaction; however, in this study, IMZ accumulation in the cortex following TBI was recovered in the chronic phase in several patients. [¹²³I] iomazenil SPECT may have a potential to disclose a reversible vulnerability of neurons following TBI.     

Substrate oxidation by isolated rat brain mitochondria and synaptosomes

The rates of [6-14C]-glucose oxidation by reconstituted systems of cytosol and mitochondria or cytosol and synaptosomes were essentially the same as the rate of oxidation of [3-14C]-3-hydroxybutyrate. However, the rate of [U-14C]-glutamine oxidation by mitochondria was 2.5 times that by synaptosomes. The addition of glutamine (5 mM) caused a reduction in the rates of oxidation [6-14C]-glucose of 20% and 40% by mitochondria and synaptosomes, respectively. Conversely, the addition of glucose (5 mM) had little or no effect on the rate of [U-14C]-glutamine oxidation by either organelle. Amino-oxyacetate decreased [U-14C]-glutamine oxidation by mitochondria more than 35% but had little or no effect on the rate of glutamine oxidation by synaptosomes. When glucose (5 mM) was added to [3-14C]-3-hydroxybutyrate, the rates of oxidation by the mitochondria and synaptosomes were increased by 65% and 77%, respectively. However, in the reverse situation the addition of 3-hydroxybutyrate decreased [6-14C]-glucose oxidation by synaptosomes (35%) but did not decrease the rate by mitochondria. These results suggest that differences in the rates of substrate utilization by mitochondria and synaptosomes and differences in substrate interactions in these two subcellular organelles may contribute to metabolic compartmentation in the brain.     

神经元特异性烯醇化酶与外伤性脑损伤

神经元特异性烯醇化酶（NSE）是一种参与糖代谢功能酶，特异性位于神经元细胞。当神经元坏死时会释放入血液和脑脊液中，通过测定这一生化指标。可以了解外伤性脑损伤（TBI）的严重程度和预后，章综述了NSE和TBI近年来的研究现状。认为NSE可能作为一项生化指标。为TBI诊断提供新的手段。     

Dose-dependent neuroprotective effect of enoxaparin on cold-induced traumatic brain injury

Recent evidence exists that enoxaparin can reduce brain injury because of its anticoagulant activity. To investigate the potential therapeutic effect of enoxaparin on cold-induced traumatic brain injury, at 20 minutes after modeling, male BALB/c mouse models of cold-induced traumatic brain injury were intra-peritoneally administered 3 and 10 mg/kg enoxaparin or isotonic saline solution. Twenty-four hours later, enoxaparin at 10 mg/kg greatly reduced infarct volume, decreased cell apoptosis in the cortex and obviously increased serum level of total antioxidant status. By contrast, administration of enoxaparin at 3 mg/kg did not lead to these changes.These findings suggest that enoxaparin exhibits neuroprotective effect on cold-in-duced traumatic brain injury in a dose-dependent manner.     

Sulforaphane enhances aquaporin-4 expression and decreases cerebral edema following traumatic brain injury

Brain edema, the infiltration and accumulation of excess fluid causing an increase in brain tissue volume, often leads to a rise in intracranial pressure and is a key contributor to the morbidity and mortality associated with traumatic brain injury (TBI). The cellular and molecular mechanisms contributing to the development/resolution of TBI-associated brain edema are poorly understood. Aquaporin-4 (AQP4) water channel is expressed at high levels in brain astrocytes, and the bidirectional transport of water through these channels is critical for the maintenance of brain water homeostasis. By using a rodent injury model, we show that TBI decreased AQP4 level in the injury core and modestly increased it in the penumbra region surrounding the core. Postinjury administration of sulforaphane (SUL), an isothiocyanate present in abundance in cruciferous vegetables such as broccoli, attenuated AQP4 loss in the injury core and further increased AQP4 levels in the penumbra region compared with injured animals receiving vehicle. These increases in AQP4 levels were accompanied by a significant reduction in brain edema (assessed by percentage water content) at 3 days postinjury. These findings suggest that the reduction of brain edema in response to SUL administration could be due, in part, to water clearance by AQP4 from the injured brain.