Both estrogen and progesterone attenuate edema formation following diffuse traumatic brain injury in rats

Females have reduced brain edema compared to males after experimental brain trauma, although contradictory reports exist as to whether this is due to either estrogen or progesterone. In the present study, we demonstrate in both male and ovariectomized female rats that a single physiological dose of either hormone at 30 min after diffuse traumatic brain injury reduces both blood brain barrier permeability and edema formation. We conclude that both hormones may contribute to reduce edema in females after brain injury.     

Neurogenesis and glial proliferation are stimulated following diffuse traumatic brain injury in adult rats

Although increased neurogenesis has been described in rodent models of focal traumatic brain injury (TBI), the neurogenic response occurring after diffuse TBI uncomplicated by focal injury has not been examined to date, despite the pervasiveness of this distinct type of brain injury in the TBI patient population. Here we characterize multiple stages of neurogenesis following a traumatic axonal injury (TAI) model of diffuse TBI as well as the proliferative response of glial cells. TAI was induced in adult rats using an impact-acceleration model, and 5-bromo-2'-deoxyuridine (BrdU) was administered on days 1-4 posttrauma or sham operation to label mitotic cells. Using immunohistochemistry for BrdU combined with phenotype-specific markers, we found that proliferation was increased following TAI in the subventricular zone of the lateral ventricles and in the hippocampal subgranular zone, although the ultimate production of new dentate granule neurons at 8 weeks was not significantly enhanced. Also, abundant proliferating and reactive astrocytes, microglia, and polydendrocytes were detected throughout the brain following TAI, indicating that a robust glial response occurs in this model, although very few new cells in the nonneurogenic brain regions became mature neurons. We conclude that diffuse brain injury stimulates early stages of a neurogenic response similar to that described for models of focal TBI.     

Effects of progesterone on neurologic and morphologic outcome following diffuse traumatic brain injury in rats

Previous studies have identified that progesterone may be neuroprotective following traumatic brain injury (TBI). However, most of these have utilized models of TBI that produce a focal lesion or a significant ischemic component, neither of which is necessarily present in diffuse TBI. The current study uses a model of diffuse TBI in rats to examine the effects of progesterone on morphological changes and functional outcome following TBI. Male and ovariectomized female rats were subject to severe impact-acceleration injury under halothane anesthesia. After injury, animals were given a physiological, subcutaneous dose of progesterone (1.67 mg/kg) or equal volume of vehicle (sesame oil) daily throughout a 9-day neurologic assessment period where functional outcome was assessed using the rotarod and Barnes maze tests. There was a similar post-injury performance of male and ovariectomized female animals. Post-injury administration of progesterone improved the motor and cognitive performance of ovariectomized and male animals compared to vehicle-treated controls. Morphological differences between these animals, such as dark cell change, caspase-3 and APP immunoreactivity, were also investigated. Progesterone-treated males showed comparatively less dead or dying neurons, and marked attenuation of caspase-3 immunoreactivity. Both ovariectomized female and male animals treated with progesterone showed a profound reduction in axonal injury (seen via diminished APP immunoreactivity) when compared to controls. We conclude that physiological concentrations of progesterone administered after diffuse TBI confers beneficial effects on morphologic and functional outcome in both ovariectomized female and male animals.     

Glycerol accumulation in edema formation following diffuse traumatic brain injury

Traumatic brain injury (TBI) induces brain edema via water and glycerol transport channels, called aquaporins (AQPs). The passage of glycerol across brain cellular compartments has been shown during edema. Using a modified impact/head acceleration rodent model of diffuse TBI, we assessed the role of hypoxia inducible factor (HIF)-1alpha in regulating AQP9 expression and glycerol accumulation during the edema formation. Adult (400-425 g) male Sprague-Dawley rats received a closed head injury with a weight drop (450 g, 2-m height) and were allowed to survive up to 48 hours. Some rat groups were administered 2-methoxyestradiol (2ME2, a HIF-1alpha inhibitor) 30 minutes after injury and were euthanized at 4 and 24 hours after injury. Brain edema was measured directly by water content, and glycerol concentration was determined by the Cayman Glycerol Assay. HIF-1alpha and AQP9 protein levels were assessed by Western immunoblotting. This study demonstrated a significant (P<0·05) increase in brain water content at 4-48 hours following impact. Cerebral glycerol was significantly (P<0.05) up-regulated at as early as 1 hour and remained at high levels for up to 48 hours. Similarly, significant (P<0.05) increases in HIF-1alpha and AQP9 protein levels were found at 1 hour and up to 48 hours after injury. Compared to untreated but injured rats, inhibition of HIF-1alpha by 2ME2 significantly (P<0.05) reduced the TBI-induced AQP9 up-regulation. This reduction was temporally associated with significant (P<0.05) decreases in both edema and glycerol accumulation. The data suggested an associated induction of HIF-1alpha, AQP9, and extracellular glycerol accumulation in edema formation following diffuse TBI. The implication of HIF-1alpha and AQP9 underlying TBI-induced edema formation offers possibilities for novel TBI therapies.     

Soluble amyloid precursor protein alpha reduces neuronal injury and improves functional outcome following diffuse traumatic brain injury in rats

Amyloid precursor protein (APP) has previously been shown to increase following traumatic brain injury (TBI). Whereas a number of investigators assume that increased APP may lead to the production of neurotoxic Abeta and be deleterious to outcome, the soluble alpha form of APP (sAPPalpha) is a product of the non-amyloidogenic cleavage of amyloid precursor protein that has previously been shown in vitro to have many neuroprotective and neurotrophic functions. However, no study to date has addressed whether sAPPalpha may be neuroprotective in vivo. The present study examined the effects of in vivo, posttraumatic sAPPalpha administration on functional motor outcome, cellular apoptosis, and axonal injury following severe impact-acceleration TBI in rats. Intracerebroventricular administration of sAPPalpha at 30 min posttrauma significantly improved motor outcome compared to vehicle-treated controls as assessed using the rotarod task. Immunohistochemical analysis using antibodies directed toward caspase-3 showed that posttraumatic treatment with sAPPalpha significantly reduced the number of apoptotic neuronal perikarya within the hippocampal CA3 region and within the cortex 3 days after injury compared to vehicle-treated animals. Similarly, sAPPalpha-treated animals demonstrated a reduction in axonal injury within the corpus callosum at all time points, with the reduction being significant at both 3 and 7 days postinjury. Our results demonstrate that in vivo administration of sAPPalpha improves functional outcome and reduces neuronal cell loss and axonal injury following severe diffuse TBI in rats. Promotion of APP processing toward sAPPalpha may thus be a novel therapeutic strategy in the treatment of TBI.     

Apoptotic and anti-apoptotic mechanisms following spinal cord injury

A number of studies have provided evidence that cell death from moderate traumatic spinal cord injury (SCI) is regulated, in part, by apoptosis that involves the caspase family of cysteine proteases. However, little or no information is available about anti-apoptotic mechanisms mediated by the inhibitors of apoptosis (IAP) family of proteins that inhibit cell death pathways. In the present study, we examined caspase and IAP expression in spinal cords of rats subjected to moderate traumatic injury. Within 6 h after injury, caspase-8 and-9 (2 initiators of apoptosis) were predominantly present in gray matter neurons within the lesion epicenter. By 3 days following spinal cord injury (SCI), caspase-8 and-9 immunoreactivity was localized to gray and white matter cells, and by 7 days following SCI, both upstream caspases were expressed in cells within white matter or within foamy macrophages in gray matter. Caspase-3, an effector caspase, was evident in a few fragmented cells in gray matter at 24 h following injury and then localized to white matter in later stages. Thus, distinct patterns of caspase expression can be found in the spinal cord following injury. XIAP, cIAP-1, and cIAP-2, members of the IAP family, were constitutively expressed in the cord. Immunoblots of spinal cord extracts revealed that the processed forms of caspases-8 and-9 and cleavage of PARP are present as early as 6 h following trauma. The expression of caspases corresponded with the detection of cleavage of XIAP into 2 fragments following injury. cIAP-1 and cIAP-2 expression remained constant during early periods following SCI but demonstrated alterations by 7 days following SCI. Our data are consistent with the idea that XIAP may have a protective role within the spinal cord, and that alteration in cleavage of XIAP may regulate cell death following SCI.     

Reduced sensorimotor reactivity following traumatic brain injury in rats

The present study examined sensorimotor reactivity in rats following traumatic brain injury (TBI). Moderate injury was induced with midline fluid percussion in some of the rats. Others received identical surgery, but were not injured (sham-injured rats), or received neither surgery nor injury (naive rats). All rats were evaluated in acoustic and/or tactile startle procedures. At 8 days post-injury, the sensorimotor reactivity of TBI rats to acoustic stimuli was severely reduced compared to that of sham-injured rats. This TBI-induced deficit was enduring (> 30 days). In a separate experiment, greater sensorimotor reactivity was observed with tactile (vs. acoustic) stimulation in both TBI and naive rats, although startle amplitudes for the TBI rats were lower than control levels for both types of stimuli. These results suggest that sensorimotor reactivity is altered by TBI and that the startle procedure is a promising method for investigation of information processing alterations following TBI.     

Evaluation of cerebral autoregulation following diffuse brain injury in rats

Abstract

The normal cerebral circulation has the ability to maintain a stable cerebral blood flow over a wide range of cerebral perfusion p(essures and this is known as cerebral autoregulation. This autoregulation may be impaired in the injured brain. Closed head injury was induced in 28 Sprague-Dawley rats weighing 400-450 g. Four groups were studied: control group, head injured rat from meter height using 350 g, 400 g and 450 g respectively. CBF, volume velocity was monitored using laser-Doppler flowmetry together with monitoring of ICP and arterial blood pressure. Correlation to assess the relationship between CBF and CPP was done in each animal every hour. If correlation coefficient was> 0.85 and CPP was within normal range, loss of autoregulation was hypothesized. Chi square test, ANOVA test and unpaired Studen(s t-test were done and significant level of p < 0.05 was established. Mean CBF in injured rats was significantly lower than controls (p = 0.028) at the fifth hour. CBV was lower in the group of 450 g 1 m impact than in controls at 3 h (p = 0.04). Velocity in the group ofall injured rats, was significantly lower than in controls at 3 h (p = 0.032) and at 4 h (p = 0.027). Loss ofautoregulation was seen during first four hours after trauma in all groups of rats who sustained injury. Statistical significant difference (p = 0.041) in loss of autoregulation between injured and control animals was seen. No loss of autoregulation was observed in the control group. In conclusion CBF and CPP provide information about loss of autoregulation in diffuse brain injury. Decrease in CBF and increase of ICP is observed as a result ofloss of cerebral autoregulation. Knowledge of loss of autoregulation could give important information and help in the management of head injured patients. [Neural Res 1997; 19: 393-402]     

大鼠颅脑损伤后钠通道α亚单位1.3(Navl.3)在海马中的表达

目的 研究颅脑损伤(TBI)后钠通道α亚单位1.3(Navl.3)的mRNA和蛋白在海马中的表达情况.方法 对成年SD大鼠实施脑液压伤后,在伤后2 h、12 h、24 h和72 h处死,取伤侧海马行荧光定量PCR和Western blot检测Navl.3的mRNA和蛋白表达情况,通过免疫荧光染色检测Navl.3在海马的表达特点.结果 大鼠脑液压伤后Nayl.3的mRNA表达显著上调(P＜0.01).伤后12 h其上调达最高水平,而Navl.3蛋白的表达也在相同时间段出现显著上调(P＜0.01).免疫荧光染色显示Nayl.3在海马主要表达于神经元细胞.结论 TBI可导致Nayl.3的mRNA和蛋白表达显著上调,这可能是TBI后神经元细胞膜上钠通道功能异常及其诱发兴奋性毒性作用的分子学基础之一.     

Serum extravasation and cytoskeletal alterations following traumatic brain injury in rats

Disruption of the blood-brain barrier (BBB) and neuronal cytoskeletal damage were evaluated in two commonly used rat models of traumatic brain injury. Adult rats received a lateral cortical impact (CI) or lateral fluid percussion (FP) injury of mild or moderate severity or a sham procedure. Six hours after trauma, the brains were removed and analyzed with immunocytochemical techniques for alterations in the serum protein, IgG, and the cytoskeletal protein, microtubule-associated protein 2 (MAP2). Both models induced profound alterations in these proteins in the ipsilateral cortex and hippocampus compared to sham-injured controls. Following an injury of moderate severity, the CI injury resulted in greater IgG extravasation in the cortex and hippocampus than the FP injury. Conversely, after a mild injury, IgG extravasation in the hippocampus was greater for FP than CI. All of the animals in the CI group and most of the FP group showed a loss of MAP2 in the hippocampus. The specific subregions within the cortex and hippocampus that were affected by the injury varied between models, despite having identical impact sites. These data demonstrate that there are both similarities and differences between a CI and FP injury on vascular and neuronal cystoskeletal integrity, which should be considered when utilizing these animal models to study selected features of human head injury.     

Two-point discrimination following traumatic brain injury.

This study investigated two point discrimination (TPD) perception in survivors of traumatic brain injury (TBI). Inpatient and outpatient survivors of severe TBI and age-matched healthy controls aged between 16 and 65 years were included in the study with a mean TPD of 3.61, 3.41 and 2.61 mm respectively. Significant group effects were seen in TPD between subjects with TBI and controls. TPD deficits did not appear to be influenced by GCS or PTA duration, nor did they show evidence of improvement over time. Similarly, CT scan data did not explain the observed TPD differences in TBI survivors. Admission functional independence measure (FIM), a global measure of functional independence, had a strong negative correlation with TPD. The lack of change in TPD over time mirrors other basic markers of neurological recovery but is at odds with TBI outcome literature reporting continuing improvements in function for at least 5 years post injury.     

Vigilance and fatigue following traumatic brain injury.

Research findings have suggested that individuals with traumatic brain injury (TBI) show greater psychophysiological and subjective costs associated with performing vigilance tasks, but have not examined relationships with fatigue. The present study aimed to investigate vigilance and its relationship with subjective and objective fatigue measures. Forty-six TBI participants and 46 controls completed a 45-minute vigilance task. They also completed a subjective fatigue scale (the VAS-F) and a selective attention task before and after the vigilance task, and had their blood pressure (BP) monitored. TBI participants performed at a lower level on the vigilance task, but performed at a similar level across the duration of the task. Higher subjective fatigue ratings on the VAS-F were associated with more misses on the vigilance task for TBI participants. TBI participants showed greater increases in diastolic BP, and these were associated with greater increases in subjective fatigue ratings on the VAS-F. A subgroup of TBI participants showed a decline in performance on the vigilance task and also showed disproportionate increases in subjective fatigue. Findings provide support for the coping hypothesis, suggesting that TBI individuals expend greater psychophysiological costs in order to maintain stable performance over time, and that these costs are also associated with subjective increases in fatigue.     

Nuclear magnetic resonance characterization of secondary mechanisms following traumatic brain injury

Much of the injury that occurs following a traumatic insult to the central nervous system is the result of physiological, and biochemical processes initiated by the primary traumatic event. These processes occur over a period of hours to days following the insult, and although a number of factors have been identified as being associated with this secondary injury process, their role and interrelationship with one another is unclear. Nuclear magnetic resonance spectroscopy has been utilized to characterize many of these secondary factors and their relationship to eventual neurological outcome. In particular, the role of high energy phosphates, pH, lactic acid excitatory amino acids, and magnesium has been investigated, along with pharmacotherapies directed toward altering the status of these factors following traumatic injury. This review critically examines the role that each of these factors may play in the secondary injury process, and proposes a scheme which theoretically accounts for the interrelationships among the various factors.     

Temporal and egional profiles of cytoskeletal protein accumulation in the rat brain following traumatic brain injury

Abstract To characterize the cytoskeletal aberration due to traumatic injury, temporal and regional profiles of changes in immunoreactivity of microtubule-associated protein 2 (MAP2), neurofilament heavy subunit protein (NFH) and heat shock protein 72 (HSP72) were investigated after different magnitudes of traumatic brain injury by fluid percussion. The experimental rat brain was perfusion-fixed at 1, 6 and 24 hours after traumatic brain injury. Conventional histological staining has demonstrated that the mildest traumatic brain injury (1.0 atm) induced no neuronal loss at the impact site and that neuron loss was apparent when traumatic brain injury was increased to 4.3 atm. The mildest traumatic brain injury, however, caused a significant increase in HSP72 immunoreactivity in the superficial cortical layers at the impact site as early as 1 hour after the injury. In the case of severe traumatic brain injury (4.3 atm), neuron loss was apparent in the area at the impact site, but the increase in HSP72 immunoreactivity was moderate, and it was observed only after 6 hours in the deep cortical layers under the necrotic area. The increased immunostaining of MAP2 was demonstrated in damaged axons and neuronal perikarya in the wider area surrounding the impact site at 6 and 24 hours after the injury. Six and 24 hours after the injury, perikaryal accumulation of neurofilament was observed, and the accumulated neurofilament was mostly phosphorylated. These results indicate that the severe traumatic brain injury of 4.3 atm triggers the abnormal accumulation of cytoskeletal proteins in neuronal perikarya, most probably due to an impairment of axonal transport. It is implied that the increased expression of HSP72 may be involved in the protective process of neurons after traumatic brain injury.     

Apoptotic and antiapoptotic mechanisms after traumatic brain injury.

Caspase and inhibitor of apoptosis (IAP) expression was examined in rats subjected to moderate traumatic brain injury (TBI) using a parasagittal fluid-percussion brain insult (1.7 to 2.2 atm). Within 1 hour after injury, caspase-8 and -9, two initiators of apoptosis, were predominantly expressed in superficial cortical areas adjacent to the impact site and in the thalamus. Caspase-3, an effector caspase, was evident at 6 hours throughout the traumatized cerebral cortex and hippocampus. Moreover, the authors observed that XIAP, cIAP-1, and cIAP-2, members of the IAP family, were constitutively expressed in the brain. Colocalization of XIAP-immunolabled cells with cell-specific markers indicated that XIAP is expressed within neurons and a subpopulation of oligodendrocytes. Immunoblots of brain extracts revealed that the processed forms of caspase-8, -9, and -3 are present as early as 1 hour after trauma. The appearance of activated caspases corresponded with the detection of cleavage of XIAP into fragments after injury and a concomitant increase in the levels of cIAP-1 and cIAP-2 in the traumatized hemispheres. The current data are consistent with the hypotheses that caspases in both the extrinsic and intrinsic apoptotic pathways are activated after moderate TBI and that IAPs may have a protective role within the brain with alterations in levels and cleavage of IAPs that contribute to cell death in this setting.     

Irritability following traumatic brain injury

This study was undertaken to identify the clinical and pathoanatomical correlates of irritability in patients with closed head injuries. A consecutive series of 66 patients was assessed in hospital and at 3, 6, 9, and 12-month follow-ups. Patients fulfilling criteria for irritability were divided into 2 groups based on the immediate or delayed onset of their irritability and compared with patients without irritability for background characteristics, impairment variables, and lesion characteristics. There were 12 patients (18.2%) with acute onset irritability and 10 (15.1%) with delayed onset irritability. Acute onset irritability patients had a higher frequency of left cortical lesions. Delayed onset irritability patients showed a strong association with poor social functioning and greater impairment in activities of daily living. The findings suggest that post-brain injury irritability may have different causes and treatment in the acute and chronic stages.     

Psychosis following traumatic brain injury

Psychosis is a relatively infrequent but potentially serious and debilitating consequence of traumatic brain injury (TBI), and one about which there is considerable scientific uncertainty and disagreement. There are several substantial clinical, epidemiological, and neurobiological differences between the post-traumatic psychoses and the primary psychotic disorders. The recognition of these differences may facilitate identification and treatment of patients whose psychosis is most appropriately regarded as post-traumatic. In the service of assisting psychiatrists and other mental health clinicians in the diagnosis and treatment of persons with post-traumatic psychoses, this article will review post-traumatic psychosis, including definitions relevant to describing the clinical syndrome, as well as epidemiologic, neurobiological, and neurogenetic factors attendant to it. An approach to evaluation and treatment will then be offered, emphasizing identification of the syndrome of post-traumatic psychosis, consideration of the differential diagnosis of this condition, and careful selection and administration of treatment interventions.     

Assessing connectivity related injury burden in diffuse traumatic brain injury

Many of the clinical and behavioral manifestations of traumatic brain injury (TBI) are thought to arise from disruption to the structural network of the brain due to diffuse axonal injury (DAI). However, a principled way of summarizing diffuse connectivity alterations to quantify injury burden is lacking. In this study, we developed a connectome injury score, Disruption Index of the Structural Connectome (DISC), which summarizes the cumulative effects of TBI‐induced connectivity abnormalities across the entire brain. Forty patients with moderate‐to‐severe TBI examined at 3 months postinjury and 35 uninjured healthy controls underwent magnetic resonance imaging with diffusion tensor imaging, and completed behavioral assessment including global clinical outcome measures and neuropsychological tests. TBI patients were selected to maximize the likelihood of DAI in the absence of large focal brain lesions. We found that hub‐like regions, with high betweenness centrality, were most likely to be impaired as a result of diffuse TBI. Clustering of participants revealed a subgroup of TBI patients with similar connectivity abnormality profiles who exhibited relatively poor cognitive performance. Among TBI patients, DISC was significantly correlated with post‐traumatic amnesia, verbal learning, executive function, and processing speed. Our experiments jointly demonstrated that assessing structural connectivity alterations may be useful in development of patient‐oriented diagnostic and prognostic tools. Hum Brain Mapp 38:2913–2922, 2017. © 2017 Wiley Periodicals, Inc.