Edema and brain trauma

Brain contusions induce a strong local overexpression of MMP-9. Results of a pilot study

BACKGROUND

Brain contusions are inflammatory evolutive lesions that induce intracranial pressure increase and edema, contributing to neurological outcome. Matrix metalloproteinases (MMPs) 2 and 9 can degrade the majority of the extracellular matrix components, and are implicated in blood-brain barrier disruption and edema formation. The aim of this study was to investigate MMP-2 and MMP-9 profiles in human brain contusions using zymography.

METHODS

A prospective study was conducted in 20 traumatic brain injury patients where contusion brain tissue was resected. Brain tissues from lobectomies were used as controls. Brain homogenates were analysed by gelatin zymography and in situ zimography was performed to confirm results, on one control and one brain contusion tissue sample.

FINDINGS

MMP-2 and MMP-9 levels were higher in brain contusions when compared to controls. MMP-9 was high during the first 24 hours and at 48 to 96 hours, whereas MMP-2 was slightly high at 24 to 96 hours. In situ zymography confirmed gelatin zymography results. A relation between outcome and MMP-9 levels was found; MMP-9 levels were higher in patients with worst outcome.

CONCLUSIONS

Our results indicate strong time-dependent gelatinase expression primarily from MMP-9, suggesting that the inflammatory response induced by focal lesions should be considered as a new therapeutic target.

Propofol and erythropoietin antioxidant properties in rat brain injured tissue

So far, several treatment modalities have been attempted to brain protection in cases such as brain trauma, stroke or brain hemorrhage. However, a treatment method that the effect begins immediately and definitely helpful has not been discovered yet. In this study, we aimed to compare the effects of propofol and erythropoietin (Epo) on brain injury caused by oxidative stress and antioxidant properties of these agents after closed head injury (CHI) in rats. For this study, female Wistar Albino rats were divided into five groups: non-traumatic control group, trauma performed group CHI, trauma with propofol (100 mg/kg) intraperitoneally (i.p.), trauma with Epo (5000 U/kg) i.p. and trauma with propofol and Epo performed study groups. Twenty-four hours after CHI, rats were sacrificed and the brains were removed. Superoxide dismutase (SOD), catalase (CAT), xanthine oxidase (XO), nitric oxide (NO), and malondialdehyde (MDA) levels were measured in brain tissue. MDA and NO levels were decreased significantly in Groups Epo, Propofol and Epo+Propofol than Group CHI (p<0.01). XO activity was significantly lower in Group Epo than Group CHI (p<0.05). Epo and propofol decreased oxidative stress by decreasing MDA and NO level in brain tissue after CHI. However, combination of Epo and propofol has no significant beneficial advantage than Epo or propofol alone.

Regulation of AQP4 protein expression in rat brain astrocytes: role of P2X7 receptor activation

ATP has been recognized as an important extracellular signaling molecule and P2X receptors are membrane ion channels activated by the binding of extracellular ATP. Since both AQP4 and P2X7 receptor (P2X7R) are known to be present in astrocytes, we examined whether P2X7R activation plays a role in the regulation of AQP4 expression in astrocytes. Immunoblotting and immunocytochemistry confirmed the expression of both P2X7R and AQP4 in primary cultured rat astrocytes. Co-immunoprecipitation assays of the HEK293 cells expressing both proteins revealed no protein-protein interaction. An activation of P2X7R in primary cultured astrocytes by a P2X7R agonist significantly decreased the AQP4 protein expression, which was abolished by the pre-treatment of a P2X7R antagonist. In addition, AQP4 expression was not affected by high extracellular copper, zinc, or iron concentrations. In a rat model with anoxia-induced brain injury where extracellular ATP levels could be increased, whole brain AQP4 expression was significantly decreased, whereas P2X7R expression was unchanged. Importantly, pre-treatment of P2X7R antagonist in rats significantly inhibited the AQP4 down-regulation in anoxic brain injury, consistent with the in vitro results observed in astrocytes. In conclusion, P2X7R activation in astrocytes was associated with down-regulation of AQP4 in rat brain astrocytes in vitro and in vivo, and this was prevented by P2X7 receptor blockade. Thus, an activation of P2X7R in astrocytes in response to brain injury is likely to play a role in the protective down-regulation of AQP4, which might inhibit water influx to the cells and attenuate the acute cytotoxic brain edema after acute brain injury.

Perfusional deficit and the dynamics of cerebral edemas in experimental traumatic brain injury using perfusion and diffusion-weighted magnetic resonance imaging

The aim of this work was to characterize edema dynamics, cerebral blood volume, and flow alterations in an experimental model of brain trauma using quantitative diffusion and perfusion magnetic resonance imaging (MRI). Associated with an influx of water in the intracellular space 1-5 h post-trauma as demonstrated by the 40% reduction in apparent diffusion coefficient, a 70-80% reduction in cerebral blood flow was measured within the lesioned region. Transient hypoperfusion (40-50%) was also observed in the non-traumatized contralateral hemisphere, although there was no evidence of edema formation. After the initial cytotoxic edema, a clear evolution toward extracellular water accumulation was observed, demonstrated by an increase in apparent diffusion coefficient.

Aquaporin-4 in hepatic encephalopathy

Brain edema is a critical component of hepatic encephalopathy (HE) associated with acute liver failure and such edema appears to be principally due to astrocyte swelling (cytotoxic edema). Ammonia is believed to represent a major factor responsible for astrocyte swelling, although the mechanisms by which ammonia causes such swelling are not completely understood. Recent studies have implicated potential role of oxidative stress, and the mitochondrial permeability transition (mPT). While it is not known how oxidative stress and the mPT cause astrocyte swelling, it is reasonable to suggest that these events may affect one or more plasma membrane proteins involved in water and ion homeostasis in astrocytes. One such protein strongly implicated in brain edema in other neurological conditions is the water channel protein aquaporin-4 (AQP-4), which is abundantly expressed in astrocytes. This article summarizes the potential role of AQP-4 in brain edema in in vivo models of HE, as well as in ammonia-induced cell swelling in cultured astrocytes. The involvement of AQP-4 in the effects of manganese, another toxin implicated in HE, will also be discussed.

Role of biological modifiers regulating the immune response after trauma

Trauma induces a profound immunological dysfunction. This is characterised by an early state of hyperinflammation, followed by a phase of immunosuppression with increased susceptibility to infection and multiple organ failure. Therapeutic strategies directed at restoring immune homeostasis after traumatic injuries have largely failed in translation from "bench to bedside". The present review illustrates the role of biological modifiers of the posttraumatic immune response by portraying different modalities of therapeutic immune modulation. The emphasis is placed on anti-inflammatory (steroids) and immune-stimulatory (interferon) pharmacological strategies and modified resuscitative strategies, as well as more unconventional immunomodulatory approaches, such as immunonutrition.

Aquaporins in the brain: from aqueduct to "multi-duct"

The aquaporin channel family was first considered as a family of water channels, however it is now clear that some of these channels are also permeable to small solutes such glycerol, urea and monocarboxylates. In this review, we will consider AQP4 and AQP9 expressed in the rodent brain. AQP4 is present on astrocytic end-feet in contact with brain vessels and could be involved in ionic homeostasis. However, AQP4 may also be involved in cell adhesion. AQP4 expression is highly modified in several brain disorders and it can play a key role in the cerebral edema formation. However, the exact role of AQP4 in edema formation is still debated. Recently, AQP4 has been shown to be also involved in astrocyte migration during glial scar formation. AQP9 is expressed in astrocytes and in catecholaminergic neurons. Two isoforms of AQP9 are expressed in brain cells, the shortest isoform is localized in the inner membrane of mitochondria and the longest in the cell membrane. The level of expression of AQP9 is negatively regulated by high concentrations of insulin. Taken together, these results suggest that AQP9 could be involved in brain energy metabolism. The induction of AQP9 in astrocytes is observed with time after stroke onset suggesting participation in the clearance of excess lactate in the extracellular space. These recent exciting results suggest that AQPs may not only be involved in water homeostasis in the brain but could also participate in other important physiological functions.

Multi-modal magnetic resonance imaging alterations in two rat models of mild neurotrauma

Magnetic resonance imaging (MRI) is increasingly used in the assessment of the severity and progression of neurotrauma. We evaluated temporal and regional changes after mild fluid percussion (FPI) and controlled cortical impact (CCI) injury using T2-weighted-imaging (T2WI) and diffusion-weighted imaging (DWI) MRI over 7 days. Region of interest analysis of brain areas distant to the injury site (such as the hippocampus, retrosplenial and piriform cortices, and the thalamus) was undertaken. In the hippocampus of CCI animals, we found a slow increase (51%) in apparent diffusion coefficients (ADC) over 72 h, which returned to control values. The hippocampal T2 values in the CCI animals were elevated by 18% over the 7-day time course compared to control, indicative of edema formation. Histological analysis supported the lack of overt cellular loss in most brain regions after mild CCI injury. FPI animals showed a generalized decrease in hippocampal ADC values over the first 72 h, which then returned to sham levels, with decreased T2 values over the same period, which remained depressed at 7 days. Histological assessment of FPI animals revealed numerous shrunken cells in the hippocampus and thalamus, but other regions showed little damage. Increased immunohistochemical staining for microglia and astroglia at 7 days post-injury was greater in FPI animals within the affected brain regions. In summary, traumatic brain injury is less severe in mild CCI than FPI, based on the temporal events assessed with MRI.

Chronic erythropoietin-mediated effects on the expression of astrocyte markers in a rat model of contusive spinal cord injury

Using a standardized rat model of contusive spinal cord injury (SCI; [Gorio A, Gokmen N, Erbayraktar S, Yilmaz O, Madaschi L, Cichetti C, Di Giulio AM, Vardar E, Cerami A, Brines M (2002) Recombinant human erythropoietin counteracts secondary injury and markedly enhances neurological recovery from experimental spinal cord trauma. Proc Natl Acad Sci U S A 99:9450-9455]), we previously showed that the administration of recombinant human erythropoietin (rhEPO) improves both tissue sparing and locomotory outcome. In the present study, to better understand rhEPO-mediated effects on chronic astrocyte response to SCI in rat, we have used immunocytochemical methods combined with confocal and electron microscopy to investigate, 1 month after injury, the effects of a single rhEPO administration on the expression of a) aquaporin 4 (AQP4), the main astrocytic water channel implicated in edema development and resolution, and two molecules (dystrophin and syntrophin) involved in its membrane anchoring; b) glial fibrillary acidic protein (GFAP) and vimentin as markers of astrogliosis; c) chondroitin sulfate proteoglycans of the extracellular matrix which are upregulated after SCI and can inhibit axonal regeneration and influence neuronal and glial properties. Our results show that rhEPO administration after SCI modifies astrocytic response to injury by increasing AQP4 immunoreactivity in the spinal cord, but not in the brain, without apparent modifications of dystrophin and syntrophin distribution. Attenuation of astrogliosis, demonstrated by the semiquantitative analysis of GFAP labeling, was associated with a reduction of phosphacan/RPTP zeta/beta, whereas the levels of lecticans remained unchanged. Finally, the relative volume of a microvessel fraction was significantly increased, indicating a pro-angiogenetic or a vasodilatory effect of rhEPO. These changes were consistently associated with remarkable reduction of lesion size and with improvement in tissue preservation and locomotor recovery, confirming previous observations and underscoring the potentiality of rhEPO for the therapeutic management of SCI.

[The relevance of the inflammatory response in the injured brain]

Research efforts in recent years have defined traumatic brain injury (TBI) as a predominantly immunological and inflammatory disorder. This perception is based on the fact that the overwhelming neuroinflammatory response in the injured brain contributes to the development of posttraumatic edema and to neuropathological sequelae which are, in large part, responsible for the adverse outcome. While the "key" mediators of neuroinflammation, such as the cytokine cascade and the complement system, have been clearly defined by studies in experimental TBI models, their exact pathways of interaction and pathophysiological implications remain to be further elucidated. This lack of knowledge is partially due to the concept of a "dual role" of the neuroinflammatory response after TBI. This notion implies that specific inflammatory molecules may mediate diverse functions depending on their local concentration and kinetics of expression in the injured brain. The inflammation-induced effects range from beneficial aspects of neuroprotection to detrimental neurotoxicity. The lack of success in pushing anti-inflammatory therapeutic concepts from"bench to bedside" for patients with severe TBI strengthens the further need for advances in basic research on the molecular aspects of the neuroinflammatory network in the injured brain. The present review summarizes the current knowledge from experimental studies in this field of research and discusses potential future targets of investigation.

Neuroprotection by erythropoietin administration after experimental traumatic brain injury

A large body of evidence indicates that the hormone erythropoietin (EPO) exerts beneficial effects in the central nervous system (CNS). To date, EPO's effect has been assessed in several experimental models of brain and spinal cord injury. This study was conducted to validate whether treatment with recombinant human EPO (rHuEPO) would limit the extent of injury following experimental TBI. Experimental TBI was induced in rats by a cryogenic injury model. rHuEPO or placebo was injected intraperitoneally immediately after the injury and then every 8 h until 2 or 14 days. Forty-eight hours after injury brain water content, an indicator of brain edema, was measured with the wet-dry method and blood-brain barrier (BBB) breakdown was evaluated by assay of Evans blue extravasation. Furthermore, extent of cerebral damage was assessed. Administration of rHuEPO markedly improved recovery from motor dysfunction compared with placebo group (P<0.05). Brain edema was significantly reduced in the cortex of the EPO-treated group relative to that in the placebo-treated group (80.6+/-0.3% versus 91.8%+/-0.8% respectively, P<0.05). BBB breakdown was significantly lower in EPO-treated group than in the placebo-treated group (66.2+/-18.7 mug/g versus 181.3+/-21 mug/g, respectively, P<0.05). EPO treatment reduced injury volume significantly compared with placebo group (17.4+/-5.4 mm3 versus 37.1+/-5.3 mm3, P<0.05). EPO, administered in its recombinant form, affords significant neuroprotection in experimental TBI model and may hold promise for future clinical applications.

Inhibitory effect on cerebral inflammatory agents that accompany traumatic brain injury in a rat model: a potential neuroprotective mechanism of recombinant human erythropoietin (rhEPO)

Erythropoietin (EPO) has recently been shown to have a neuroprotective effect in animal models of traumatic brain injury (TBI). However, the precise mechanisms remain unclear. Cerebral inflammation plays an important role in the pathogenesis of secondary brain injury after TBI. We, therefore, tried to analyze how recombinant human erythropoietin (rhEPO) might effect the inflammation-related factors common to TBI: nuclear factor kappa B (NF-kappaB), interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and intercellular adhesion molecule-1 (ICAM-1) in a rat TBI model. Male rats were given 0 or 5000 units/kg injections of rhEPO 1h post-injury and on days 1, 2 and 3 after surgery. Brain samples were extracted at 3 days after trauma. We measured NF-kappaB by electrophoretic mobility shift assay (EMSA); IL-1beta, TNF-alpha and IL-6 by enzyme-linked immunosorbent assay (ELISA); ICAM-1 by immunohistochemistry; brain edema by wet/dry method; blood-brain barrier (BBB) permeability by Evans blue extravasation and cortical apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. We found that NF-kappaB, pro-inflammatory cytokines and ICAM-1 were increased in all injured animals. In animals given rhEPO post-TBI, NF-kappaB, IL-1beta, TNF-alpha and ICAM-1 were decreased in comparison to vehicle-treated animals. Measures of IL-6 showed no change after rhEPO treatment. Administration of rhEPO reduced brain edema, BBB permeability and apoptotic cells in the injured brain. In conclusion, post-TBI rhEPO administration may attenuate inflammatory response in the injured rat brain, and this may be one mechanism by which rhEPO improves outcome following TBI.

Pathophysiology of traumatic brain injury

The knowledge of the pathophysiology after traumatic head injury is necessary for adequate and patient-oriented treatment. As the primary insult, which represents the direct mechanical damage, cannot be therapeutically influenced, target of the treatment is the limitation of the secondary damage (delayed non-mechanical damage). It is influenced by changes in cerebral blood flow (hypo- and hyperperfusion), impairment of cerebrovascular autoregulation, cerebral metabolic dysfunction and inadequate cerebral oxygenation. Furthermore, excitotoxic cell damage and inflammation may lead to apoptotic and necrotic cell death. Understanding the multidimensional cascade of secondary brain injury offers differentiated therapeutic options.

Deletion of aldose reductase leads to protection against cerebral ischemic injury

Previously, we reported that transgenic mice overexpressing endothelin-1 in astrocytes showed more severe neurological deficits and increased infarct after transient focal ischemia. In those studies, we also observed increased level of aldose reductase (AR), the first and rate-limiting enzyme of the polyol pathway, which has been implicated in osmotic and oxidative stress. To further understand the involvement of the polyol pathway, the mice with deletion of enzymes in the polyol pathway, AR, and sorbitol dehydrogenase (SD), which is the second enzyme in this pathway, were challenged with similar cerebral ischemic injury. Deletion of AR-protected animals from severe neurological deficits and large infarct, whereas similar protection was not observed in mice with SD deficiency. Most interestingly, AR(-/-) brains showed lowered expression of transferrin and transferrin receptor with less iron deposition and nitrotyrosine accumulation. The protection against oxidative stress in AR(-/-) brain was also associated with less poly(adenosine diphosphate-ribose) polymerase (PARP) and caspase-3 activation. Pharmacological inhibition of AR by Fidarestat also protected animals against cerebral ischemic injury. These findings are the first to show that AR contributes to iron- and transferrin-related oxidative stress associated with cerebral ischemic injury, suggesting that inhibition of AR but not SD may have therapeutic potential against cerebral ischemic injury.

Longitudinal changes in global brain volume between 79 and 409 days after traumatic brain injury: relationship with duration of coma

Neuropathological and experimental animal studies indicate that traumatic brain injury (TBI) results in long-term, neurodegenerative changes. Structural image evaluation using normalization of atrophy (SIENA) offers an automated analysis of the subtle changes in percent brain volume change (%BVC) associated with TBI. In the present study, SIENA was used to evaluate %BVC in individuals who had sustained a mild to severe TBI. We obtained three-dimensional (3D) T1-weighted anatomical magnetic resonance imaging (MRI) scans approximately 79 days and again 409 days post-injury. TBI patients (n = 37) displayed significantly greater decline in %BVC (-1.43%) relative to a normal comparison group (+0.1%, n = 30). Greater %BVC was associated with longer duration of post-injury coma. These results confirm previous findings from cross-sectional studies and argue that the brain undergoes continued structural change for several months post-injury.

Erythropoietin protects from post-traumatic edema in the rat brain

Erythropoietin (Epo) is gaining interest in various neurological insults as a possible neuroprotective agent. We determined the effects of recombinant human Epo (rhEpo, 5000 IU per kg bw) on brain edema induced in rats by traumatic brain injury (TBI; impact-acceleration model; rhEpo administration 30 mins after injury). Magnetic resonance imaging (MRI) and a gravimetric technique were applied. In the MRI experiments, the apparent diffusion coefficient (ADC) and the tissue T(1) relaxation time were measured hourly in the neocortex and caudoputamen, during a 6 h time span after TBI. In the gravimetric experiments, brain water content (BWC) was determined in these two regions, 6 h after TBI. Apparent diffusion coefficient measurements showed that rhEpo decreased brain edema early and durably. Gravimetric measurements showed that rhEpo decreased BWC at H(6) in the neocortex as well as in the caudoputamen. No significant differences in ADC, in T(1), or in BWC were found between rhEpo treated-TBI rats and sham-operated rats. Our findings show that post-traumatic administration of rhEpo can significantly reduce the development of brain edema in a model of diffuse TBI. Further studies should be conducted to identify the biochemical mechanisms involved in these immediate effects and to assess the use of rhEpo as a possible therapy for post-traumatic brain edema.

Effects of l-arginine on cerebral blood flow, microvascular permeability, number of perfused capillaries, and brain water content in the traumatized mouse brain

It is has been suggested that decreased production of the vasodilatory and anti-aggregative substance NO (nitric oxide) may result in lower cerebral blood flow (CBF) in injured areas of the traumatized brain. The NO-precursor L-arginine has been shown to counteract CBF decreases early after trauma, but microcirculatory and more long-term effects on CBF of L-arginine have not been investigated. In an attempt to analyze effects of L-arginine on the microcirculation in the traumatized brain, the present study was designed to evaluate the effects of L-arginine compared to vehicle (0.9% saline) following a standardized controlled cortical-impact brain trauma in mice. Cerebral blood flow (autoradiography [(14)C]-iodoantipyrine), number of perfused capillaries (FITC-dextran fluorescence technique), brain water content (wet vs. dry weight) and the blood to brain transfer constant K(i) for [(51)Cr]-EDTA were analyzed in the injured and the contralateral cortex. Cortical blood flow in the injured cortex was 0.43+/-0.3 mL/g/min and 0.81+/-0.3 mL/g/min 3 h after trauma in the vehicle and L-arginine groups, respectively (p<0.05), and no treatment effect was seen 24 h after trauma. The number of perfused capillaries decreased following trauma and was unaffected by L-arginine. K(i) increased following trauma and was unaffected by L-arginine. Brain water content was lower in the L-arginine group than in the vehicle group 3 h after trauma and there was no difference between the groups 24 h after trauma. We conclude that L-arginine reduces brain edema formation and improves cortical blood flow in the early phase after a brain trauma, whereas no circulatory effects can be seen after prolonged treatment.

Multimodal monitoring in traumatic brain injury: current status and future directions

Traumatic brain injury (TBI) remains a major cause of morbidity and mortality, particularly in young people. Despite encouraging animal studies, human trials assessing the use of pharmacological agents after TBI have all failed to show efficacy. Current management strategies are therefore directed towards providing an optimal physiological environment in order to minimize secondary insults and maximize the body's own regenerative processes. Modern neurocritical care management utilizes a host of monitoring techniques to identify or predict the occurrence of secondary insults and guide subsequent therapeutic interventions in an attempt to minimize the resulting secondary injury. Recent data suggest that the use of protocolized management strategies, informed by multimodality monitoring, can improve patient outcome after TBI. Developments in multimodality monitoring have allowed a movement away from rigid physiological target setting towards an individually tailored, patient-specific, approach. The wealth of monitoring information available provides a challenge in terms of data integration and accessibility and modern software applications may aid this process.

Traumatic brain injury: intensive care management

Traumatic brain injury (TBI) is a major cause of morbidity and mortality worldwide. The modern management of severe TBI has fallen into the domain of a multidisciplinary team led by neurointensivists, neuroanaesthetists, and neurosurgeons and is based on the avoidance of secondary injury, maintenance of cerebral perfusion pressure (CPP), and optimization of cerebral oxygenation. In this review, we will discuss the intensive care management of severe TBI with emphasis on the specific measures directed at the control of intracranial pressure and CPP.

Expression of the Water Channel Protein Aquaporin-9 in Malignant Brain Tumors

Recently, many studies seen concerning the expression and distribution of aquaporins and K channels in the central nervous system, and their physiological and pathophysiologic roles in water and ion homeostasis. Whereas most data were collected on aquaporin-4 (AQP4) in astrocytes, only little attention was paid to AQP9 which is a water channel transporting glycerol, mannitol, and urea as well. This is the first study describing AQP9 in human brain and human brain tumors. For comparison, we also investigated the immunohistochemical distribution of AQP9 in the rat glioma RG2. Whereas in the normal rat brain AQP9 is only weakly expressed by astrocytes, the anti-AQP9 immunoreactivity was found to be increased at the tumor border, but not within the tumor. In contrast, in human glioblastoma, most glioma cells throughout the tumor revealed a strong anti-AQP9 immunoreactivity across the whole surface of the cell. In the discussion, the increase of the anti-AQP9 immunoreactivity in glioma cells is suggested to reflect an upregulation and to counteract the glioma-associated lactic acidosis by clearance of glycerol and lactate from the extracellular space. In addition, the increased level of AQP9 immunoreactivity could be involved in the energy metabolism of the glioma and/or surrounding neuronal cells.

Time Course of Early Metabolic Changes following Diffuse Traumatic Brain Injury in Rats as Detected by1H NMR Spectroscopy

Experimental models of traumatic brain injury (TBI) provide a useful tool for understanding the cerebral metabolic changes induced by this pathological condition. Here, we report on the time course of changes in cerebral metabolites after TBI and its correlation with early brain morphological changes using a combination of high-resolution proton magnetic resonance spectroscopy ((1)H MRS) and magnetic resonance imaging (MRI). Adult male Sprague-Dawley rats were subjected to closed head impact and examined by MRI at 1, 9, 24, 48, and and 72 h after the injury. Extracts from funnel frozen rat brains were then obtained and analyzed quantitatively by high-resolution (1)H MRS. Finally, statistical multivariate analysis was carried out to identify the combination of cerebral metabolites that best described the time evolution of diffuse TBI. The temporal changes observed in the concentration of cerebral metabolites followed three different patterns. The first pattern included taurine, threonine, and glycine, with concentrations peaking 24 h after the injury. The second pattern included glutamate, GABA, and alanine, with concentrations remaining elevated between 24 and 48 h post-injury. The third one involved creatine-phosphocreatine, N-acetylaspartate, and myo-inositol, with concentrations peaking 48 h after the injury. A multivariate stepwise discriminant analysis revealed that the combination of the organic osmolytes taurine and myo-inositol allowed optimal discrimination among the different time groups. Our findings suggest that the profile of some specific brain molecules that play a role as organic osmolytes can be used to follow-up the progression of the early diffuse brain edema response induced by TBI.

Cortical edema in moderate fluid percussion brain injury is attenuated by vagus nerve stimulation

Development of cerebral edema (intracellular and/or extracellular water accumulation) following traumatic brain injury contributes to mortality and morbidity that accompanies brain injury. Chronic intermittent vagus nerve stimulation (VNS) initiated at either 2 h or 24 h (VNS: 30 s train of 0.5 mA, 20 Hz, biphasic pulses every 30 min) following traumatic brain injury enhances recovery of motor and cognitive function in rats in the weeks following brain injury; however, the mechanisms of facilitated recovery are unknown. The present study examines the effects of VNS on development of acute cerebral edema following unilateral fluid percussion brain injury (FPI) in rats, concomitant with assessment of their behavioral recovery. Two hours following FPI, VNS was initiated. Behavioral testing, using both beam walk and locomotor placing tasks, was conducted at 1 and 2 days following FPI. Edema was measured 48 h post-FPI by the customary method of region-specific brain weights before and after complete dehydration. Results of this study replicated that VNS initiated at 2 h after FPI: 1) effectively facilitated the recovery of vestibulomotor function at 2 days after FPI assessed by beam walk performance (P<0.01); and 2) tended to improve locomotor placing performance at the same time point (P=0.18). Most interestingly, results of this study showed that development of edema within the cerebral cortex ipsilateral to FPI was significantly attenuated at 48 h in FPI rats receiving VNS compared with non-VNS FPI rats (P<0.04). Finally, a correlation analysis between beam walk performance and cerebral edema following FPI revealed a significant inverse correlation between behavior performance and cerebral edema. Together, these results suggest that VNS facilitation of motor recovery following experimental brain injury in rats is associated with VNS-mediated attenuation of cerebral edema.

Tissue hyperosmolality and brain edema in cerebral contusion

Severe cerebral contusion is often associated with nonhemorrhagic mass effect that progresses rapidly within 12 to 48 hours posttrauma. The mechanisms underlying such a rapid progression of mass effect cannot be fully explained by classic concepts of vasogenic and cytotoxic brain edema. Data from previous clinical trials, including diffusion-weighted magnetic resonance imaging studies, have indicated that cells in the central (core) area of the contusion undergo shrinkage, disintegration, and homogenization, whereas cellular swelling is located predominately in the peripheral (rim) area during this period. The authors hypothesized that high osmolality within the contused brain tissue generates an osmotic potential across the central and peripheral areas or causes blood to accumulate a large amount of water. To elucidate the role of tissue osmolality in contusion edema, they investigated changes in tissue osmolality, specific gravity, and ion concentration in contused brain in both experimental and clinical settings. Their results demonstrated that cerebral contusion induced a rapid increase in tissue osmolality from a baseline level of 311.4 ± 11.3 to 402.8 ± 15.1 mOsm at 12 hours posttrauma (p < 0.0001). Specific gravity in tissue significantly decreased from 1.0425 ± 0.0026 to 1.0308 ± 0.0028 (p < 0.01), reflecting water accumulation in contused tissue. The total ionic concentration [Na+] + [K+] + [Cl−] did not change significantly at any time point. Inorganic ions do not primarily contribute to this elevation in osmolality, suggesting that the increase in colloid osmotic pressure through the metabolic production of osmoles or the release of idiogenic osmoles can be a main cause of contusion edema.

A review of progress in understanding the pathophysiology and treatment of brain edema

Object

Brain edema resulting from traumatic brain injury (TBI) or ischemia if uncontrolled exhausts volume reserve and leads to raised intracranial pressure and brain herniation. The basic types of edema—vasogenic and cytotoxic—were classified 50 years ago, and their definitions remain intact.

Methods

In this paper the author provides a review of progress over the past several decades in understanding the pathophysiology of the edematous process and the success and failures of treatment. Recent progress focused on those manuscripts that were published within the past 5 years.

Results

Perhaps the most exciting new findings that speak to both the control of production and resolution of edema in both trauma and ischemia are the recent studies that have focused on the newly described “water channels” or aquaporins. Other important findings relate to the predominance of cellular edema in TBI.

Conclusions

Significant new findings have been made in understanding the pathophysiology of brain edema; however, less progress has been made in treatment. Aquaporin water channels offer hope for modulating and abating the devastating effects of fulminating brain edema in trauma and stroke.

Cerebral edema induced in mice by a convulsive dose of soman. Evaluation through diffusion-weighted magnetic resonance imaging and histology

PURPOSE

In the present study, diffusion-weighted magnetic resonance imaging (DW-MRI) and histology were used to assess cerebral edema and lesions in mice intoxicated by a convulsive dose of soman, an organophosphate compound acting as an irreversible cholinesterase inhibitor.

METHODS

Three hours and 24 h after the intoxication with soman (172 microg/kg), the mice were anesthetized with an isoflurane/N(2)O mixture and their brain examined with DW-MRI. After the imaging sessions, the mice were sacrificed for histological analysis of their brain.

RESULTS

A decrease in the apparent diffusion coefficient (ADC) was detected as soon as 3 h after the intoxication and was found strongly enhanced at 24 h. A correlation was obtained between the ADC change and the severity of the overall brain damage (edema and cellular degeneration): the more severe the damage, the stronger the ADC drop. Anesthesia was shown to interrupt soman-induced seizures and to attenuate edema and cell change in certain sensitive brain areas. Finally, brain water content was assessed using the traditional dry/wet weight method. A significant increase of brain water was observed following the intoxication.

CONCLUSIONS

The ADC decrease observed in the present study suggests that brain edema in soman poisoning is mainly intracellular and cytotoxic. Since entry of water into the brain was also evidenced, this type of edema is certainly mixed with others (vasogenic, hydrostatic, osmotic). The present study confirms the potential of DW-MRI as a non-invasive tool for monitoring the acute neuropathological consequences (edema and neurodegeneration) of soman-induced seizures.

Multimodality comparison of neuroimaging in pediatric traumatic brain injury

Traumatic brain injury is a common cause of death and disability in children; early neuroimaging has assumed an increasingly important role in evaluating the extent and severity of injury. Several imaging methods were assessed in a study of 40 children with traumatic brain injury: computed tomography (CT), T(2)-weighted magnetic resonance imaging (MRI), fluid-attenuated inversion recovery (FLAIR) MRI, and susceptibility-weighted imaging (SWI) MRI to determine which were most valuable in predicting 6-12 month outcomes as classified by the Pediatric Cerebral Performance Category Scale score. Patients were subdivided into three groups: (1) normal, (2) mild disability, and (3) moderate/severe disability/persistent vegetative state. T(2), FLAIR, and SWI showed no significant difference in lesion volume between normal and mild outcome groups, but did indicate significant differences between normal and poor and between mild and poor outcome groups. Computed tomography revealed no significant differences in lesion volume between any groups. The findings suggest that T(2), FLAIR, and SWI MRI sequences provide a more accurate assessment of injury severity and detection of outcome-influencing lesions than does CT in pediatric traumatic brain injury patients. Although CT was inconsistent at lesion detection/outcome prediction, it remains an essential part of the acute traumatic brain injury work-up to assess the need for neurosurgic intervention.

Plasma proteins in edematous white matter after intracerebral hemorrhage confound immunoblots: an ELISA to quantify contamination

Intracerebral hemorrhage (ICH) and traumatic brain injury can induce brain tissue edema (i.e., interstitial and/or vasogenic), containing high concentrations of plasma proteins. To understand biochemical processes in edema development following these insults, it would be useful to examine alterations in various proteins (e.g., transcription factors, signaling). However, determining altered protein responses in edematous brain tissue using standard immunoblotting techniques is problematic due to contaminating plasma proteins. To solve this problem, we developed an enzyme-linked immunosorbent assay (ELISA) method to quantify the two major plasma proteins, albumin and immunoglobulin G (IgG), that comprise about 80% of the total plasma proteins. We tested our method on edematous white matter samples from our porcine ICH model. To induce ICH, we infused autologous arterial whole blood (3 mL) into frontal hemispheric white matter of pentobarbital- anesthetized pigs ( approximately 20 kg) over 15 min. We froze brains in situ at various times up to 24 h post- ICH and sampled white matter adjacent and contralateral to hematomas. We prepared cytoplasmic extracts that we subjected to ELISA and immunoblotting analyses. Our results demonstrate that this ELISA method is accurate, reproducible, and enables the concentrations of albumin and IgG in edematous brain tissue samples to be accurately determined. By using this correction method, equal amounts of cellular protein can be loaded onto gels during immunoblotting procedures. This method is applicable to edematous tissue samples in brain injury models in which high plasma protein concentrations result from interstitial or vasogenic edema development.

Dexamethasone treatment modulates aquaporin-4 expression after intracerebral hemorrhage in rats

This study investigated whether dexamethasone (DEX) treatment could regulate the expression of aquaporin-4 (AQP4) in rats with intracerebral hemorrhage (ICH). The results demonstrated that DEX significantly reduced AQP4 mRNA level in the perihematomal area compared with control group, but it increased the level in the brain area surrounding the third ventricle at day 1 post-ICH. There was no difference in AQP4 protein levels between DEX group and control group at the two above-mentioned brain regions at day 1 after ICH. The changes in AQP4 protein induced by DEX were marked at day 3 following surgery and still lasted at day 5 post-ICH, which were accompanied by a reduction of brain edema. Our results demonstrated that the expression of AQP4 protein after ICH was region-specific, time-dependent, and also indicated that DEX-induced cerebral edema clearance was correlated with the regulation of AQP4 expression in different brain regions.

Cilostazol, a phosphodiesterase 3 inhibitor, protects mice against acute and late ischemic brain injuries

Cilostazol, a selective inhibitor of phosphodiesterase 3, exerts neuroprotective effects on acute brain injury after cerebral ischemia in rats. However, it is unknown whether cilostazol affects the subacute or chronic ischemic injury. In the present study, we evaluated the dose- and time-dependent effects of cilostazol on acute ischemic brain injury and the long-lasting effect on the late (subacute/chronic) injury in mice with focal cerebral ischemia induced by transient middle cerebral artery occlusion. We found that pre-treatment of cilostazol (injected i.p. at 30 min before ischemia) significantly ameliorated the acute injury 24 h after ischemia, and the effective doses were 3-10 mg/kg. The post-treatment of cilostazol (10 mg/kg) was effective on the acute injury when it was injected 1 and 2 h after ischemia. In addition, for the late injury, post-treatment of cilostazol (10 mg/kg, i.p., for 7 consecutive days after ischemia) attenuated neurological dysfunctions, brain atrophy and infarct volume. It also inhibited astrocyte proliferation/glial scar formation and accelerated the angiogenesis in the ischemic boundary zone 7 and 28 days after ischemia. Thus, we conclude that cilostazol protects against not only the acute injury, but also the late injury in mice with focal cerebral ischemia; especially it can modify brain remodeling, astrogliosis and angiogenesis.

Bilobalide prevents ischemia-induced edema formation in vitro and in vivo

EGb761, a standardized extract of Ginkgo biloba, has neuroprotective properties in animal models of ischemia, an activity that is partially attributed to its constituent, bilobalide. EGb761 has also been reported to inhibit edema formation induced by toxins such as triethyltin. The goal of this study was to test the activity of pure bilobalide to prevent edema formation in models of ischemia. Oxygen-glucose deprivation (OGD) in rat hippocampal slices served as a model of in vitro-ischemia. OGD caused cellular edema formation as indicated by an increase of slice water contents in 30 min. Bilobalide (1-10 microM) reduced slice water contents in ischemic slices in a concentration-dependent manner. As a model of in vivo-ischemia, we performed middle cerebral artery occlusion (MCAO) in mice. Permanent MCAO caused cell death and swelling of the ischemic hemisphere within 24 h. Pretreatment of the mice with bilobalide (10 mg/kg i.p.) reduced infarct area by 43% (as judged by 2,3,5-triphenyl-tetrazolium chloride (TTC) staining) and edema formation by 70% (as judged by hemispheric enlargement). In parallel experiments, pretreatment with bilobalide also reduced forebrain water contents in the ischemic hemisphere by 57%. As an alternative model of brain edema formation, we used water intoxication to increase brain water content; bilobalide, was, however, inactive in this model. We conclude that bilobalide strongly and specifically attenuates edema formation in models of brain ischemia in vitro and in vivo. Bilobalide may be therapeutically effective in brain edema which occurs secondarily to large hemispheric stroke and traumatic brain injury in humans.

The molecular basis of paediatric malarial disease

Severe falciparum malaria is an acute systemic disease that can affect multiple organs, including those in which few parasites are found. The acute disease bears many similarities both clinically and, potentially, mechanistically, to the systemic diseases caused by bacteria, rickettsia, and viruses. Traditionally the morbidity and mortality associated with severe malarial disease has been explained in terms of mechanical obstruction to vascular flow by adherence to endothelium (termed sequestration) of erythrocytes containing mature-stage parasites. However, over the past few decades an alternative ‘cytokine theory of disease’ has also evolved, where malarial pathology is explained in terms of a balance between the pro- and anti-inflammatory cytokines. The final common pathway for this pro-inflammatory imbalance is believed to be a limitation in the supply and mitochondrial utilisation of energy to cells. Different patterns of ensuing energy depletion (both temporal and spatial) throughout the cells in the body present as different clinical syndromes. This chapter draws attention to the over-arching position that inflammatory cytokines are beginning to occupy in the pathogenesis of acute malaria and other acute infections. The influence of inflammatory cytokines on cellular function offers a molecular framework to explain the multiple clinical syndromes that are observed during acute malarial illness, and provides a fresh avenue of investigation for adjunct therapies to ameliorate the malarial disease process.

Various irrigation fluids affect postoperative brain edema and cellular damage during experimental neurosurgery in rats

BACKGROUND

This study was conducted to investigate how various irrigation fluids used during neurosurgical procedures affect the degree of postoperative brain edema and cellular damage during experimental neurosurgery in rats.

METHODS

The cerebral cortex was exposed and incised crosswise with a surgical knife under irrigation with an artificial CSF, lactated Ringer's solution, or normal saline. Four hours after injury, irrigation was stopped and brain tissue samples were obtained from injured and uninjured sites. Specific gravity, cerebrovascular permeability, and TTC staining of the samples were evaluated. Incision and irrigation of the brain were not performed on the control group.

RESULTS

At the injured site, specific gravities of the samples in the normal saline group and the lactated Ringer's solution group were significantly lower than the specific gravity in the artificial CSF group. The EB concentration was significantly higher in the lactated Ringer's solution group and relatively high in the normal saline group as compared with the artificial CSF group. TTC staining did not differ significantly between the artificial CSF group and the control group. It was significantly lower in the lactated Ringer's solution group and the normal saline group than in the control group and the artificial CSF group.

CONCLUSIONS

As compared with normal saline and lactated Ringer's solution, artificial CSF reduced postoperative brain edema, cerebrovascular permeability, and cellular damage in sites injured by experimental neurosurgery in rats.

(Peri)vascular production and action of pro-inflammatory cytokines in brain pathology

In response to tissue injury or infection, the peripheral tissue macrophage induces an inflammatory response through the release of IL-1β (interleukin-1β) and TNFα (tumour necrosis factor α). These cytokines stimulate macrophages and endothelial cells to express chemokines and adhesion molecules that attract leucocytes into the peripheral site of injury or infection. The aims of the present review are to (i) discuss the relevance of brain (peri)vascular cells and compartments to bacterial meningitis, HIV-1-associated dementia, multiple sclerosis, ischaemic and traumatic brain injury, and Alzheimer's disease, and (ii) to provide an overview of the production and action of pro-inflammatory cytokines by (peri)vascular cells in these pathologies of the CNS (central nervous system). The brain (peri)vascular compartments are highly relevant to pathologies affecting the CNS, as infections are almost exclusively blood-borne. Insults disrupt blood and energy flow to neurons, and active brain-to-blood transport mechanisms, which are the bottleneck in the clearance of unwanted molecules from the brain. Perivascular macrophages are the most reactive cell type and produce IL-1β and TNFα after infection or injury to the CNS. The main cellular target for IL-1β and TNFα produced in the brain (peri)vascular compartment is the endothelium, where these cytokines induce the expression of adhesion molecules and promote leucocyte infiltration. Whether this and other effects of IL-1 and TNF in the brain (peri)vascular compartments are detrimental or beneficial in neuropathology remains to be shown and requires a clear understanding of the role of these cytokines in both damaging and repair processes in the CNS.

Outcome after surgical decompression of severe traumatic brain injury

One of the factors that affects outcome following severe traumatic brain injury is development and progression of cerebral oedema with associated increase in intracranial pressure (ICP). Uncontrolled elevations of ICP may compromise energy metabolism of the injured brain and lead to secondary injury, affecting neurological outcome of the patient. Decompressive craniectomy has been used for over a century as a treatment of refractory brain swelling in a variety of neurological conditions. However, conclusive evidence of whether it has a beneficial or adverse affect on outcome is lacking. This article reviews the existing evidence on the role of decompressive craniectomy in management of patients with traumatic brain injury and stresses the need for randomised controlled trials.

Spatiotemporal pH dynamics following insertion of neural microelectrode arrays

Insertion trauma is a critical issue when assessing intracortical electrophysiological and neurochemical recordings. Previous reports document a wide variety of insertion techniques with speeds ranging from 10 microm/s to 10 m/s. We hypothesize that insertion speed has an effect on tissue trauma induced by implantation of a neural probe. In order to monitor the neural interface during and after probe insertion, we have developed a silicon-substrate array with hydrous iridium oxide microelectrodes for potentiometric recording of extracellular pH (pH(e)), a measure of brain homeostasis. Microelectrode sites were sensitive to pH in the super-Nernstian range (-85.9 mV/pH unit) and selective over other analytes including ascorbic acid, Na(+), K(+), Ca(2+), and Mg(2+). Following insertion, arrays recorded either triphasic or biphasic pH(e) responses, with a greater degree of prolonged acidosis for insertions at 50 microm/s than at 0.5 mm/s or 1.0 mm/s (p<0.05). Spatiotemporal analysis of the recordings also revealed micro-scale variability in the pH(e) response along the array, even when using the same insertion technique. Implants with more intense acidosis were often associated histologically with blood along the probe tract. The potentiometric microsensor array has implications not only as a useful tool to measure extracellular pH, but also as a feedback tool for delivery of pharmacological agents to treat surgical brain trauma.

The enantiomer of progesterone acts as a molecular neuroprotectant after traumatic brain injury

Previous work shows that neurosteroid enantiomers activate specific molecular receptors that relay neuroprotection. However, the actions of the enantiomer of progesterone (ent-PROG) at the PROG receptor (PR) are unknown. PR binding and transcriptional assays were performed to determine the actions of ent-PROG at the classical PR. Additionally, the neuroprotective effects of ent-PROG in traumatic brain injury (TBI) were investigated and compared to the actions of PROG and its metabolite allopregnanolone (ALLO), both of which have been shown to have neuroprotective properties when given after TBI. Binding studies performed in COS cells over-expressing the PR showed that ent-PROG inhibited PROG binding to the PR. In contrast, ent-PROG did not activate PR-mediated transcription. Rats received bilateral medial frontal cortex injury followed by treatments at 1, 6, 24 and 48h with PROG, ALLO or ent-PROG. Brains were processed for edema, protein and enzyme activity. ent-PROG treatment in vivo decreased cerebral edema, cell death mediators, inflammatory cytokines, and reactive gliosis, and increased antioxidant activity. These findings suggest that the progestin-mediated pro-survival response seen with TBI is regulated either independently of the classical PR or via nongenomic PR-regulated actions.

Acute and chronic changes in aquaporin 4 expression after spinal cord injury

The effect of spinal cord injury (SCI) on the expression levels and distribution of water channel aquaporin 4 (AQP4) has not been studied. We have found AQP4 in gray and white matter astrocytes in both uninjured and injured rat spinal cords. AQP4 was detected in astrocytic processes that were tightly surrounding neurons and blood vessels, but more robustly in glia limitans externa and interna, which were forming an interface between spinal cord parenchyma and cerebrospinal fluid (CSF). Such spatial distribution of AQP4 suggests a critical role that astrocytes expressing AQP4 play in the transport of water from blood/CSF to spinal cord parenchyma and vice versa. SCI induced biphasic changes in astrocytic AQP4 levels, including its early down-regulation and subsequent persistent up-regulation. However, changes in AQP4 expression did not correlate well with the onset and magnitude of astrocytic activation, when measured as changes in GFAP expression levels. It appears that reactive astrocytes began expressing increased levels of AQP4 after migrating to the wound area (thoracic region) two weeks after SCI, and AQP4 remained significantly elevated for months after SCI. We also showed that increased levels of AQP4 spread away from the lesion site to cervical and lumbar segments, but only in chronically injured spinal cords. Although overall AQP4 expression levels increased in chronically-injured spinal cords, AQP4 immunolabeling in astrocytic processes forming glia limitans externa was decreased, which may indicate impaired water transport through glia limitans externa. Finally, we also showed that SCI-induced changes in AQP4 protein levels correlate, both temporally and spatially, with persistent increases in water content in acutely and chronically injured spinal cords. Although correlative, this finding suggests a possible link between AQP4 and impaired water transport/edema/syringomyelia in contused spinal cords.

Effects of chloride flux modulators in an in vitro model of brain edema formation

Brain edema is a serious consequence of hemispheric stroke and traumatic brain injury and contributes significantly to patient mortality. In the present study, we measured water contents in hippocampal slices as an in vitro model of edema formation. Excitotoxic conditions induced by N-methyl-D-aspartate (NMDA, 300 microM), as well as ischemia induced by oxygen-glucose deprivation (OGD), caused cellular edema formation as indicated by an increase of slice water contents. In the presence of furosemide, an inhibitor of the Na,K,Cl-cotransporter, NMDA-induced edema were reduced by 64% while OGD-induced edema were unaffected. The same observation, i.e., reduction of excitotoxic edema formation but no effect on ischemia-induced edema, was made with chloride transport inhibitors such as DIDS and niflumic acid. Under ischemic conditions, modulation of GABAA receptors by bicuculline, a GABA antagonist, or by diazepam, a GABAergic agonist, did not significantly affect edema formation. Further experiments demonstrated that low chloride conditions prevented NMDA-induced, but not OGD-induced, water influx. Omission of calcium ions had no effect. Our results show that NMDA-induced edema formation is highly dependent on chloride influx as it was prevented by low-chloride conditions and by various compounds that interfere with chloride influx. In contrast, OGD-induced edema observed in brain slices was not affected by modulators of chloride fluxes. The results are discussed with reference to ionic changes occurring during tissue ischemia.

Drug Insight: adjunctive therapies in adults with bacterial meningitis

Despite the availability of effective antibiotics, mortality and morbidity rates associated with bacterial meningitis are high. Studies in animals have shown that bacterial lysis, induced by treatment with antibiotics, leads to inflammation in the subarachnoid space, which might contribute to an unfavorable outcome. The management of adults with bacterial meningitis can be complex, and common complications include meningoencephalitis, systemic compromise, stroke and raised intracranial pressure. Various adjunctive therapies have been described to improve outcome in such patients, including anti-inflammatory agents, anticoagulant therapies, and strategies to reduce intracranial pressure. Although a recent randomized trial provided evidence in favor of dexamethasone treatment, few randomized clinical studies are available for other adjunctive therapies in adults with bacterial meningitis. This review briefly summarizes the pathogenesis and pathophysiology of bacterial meningitis, and focuses on the evidence for and against use of the available adjunctive therapies in clinical practice.

Oxygen treatment after experimental hypoxia-ischemia in neonatal rats alters the expression of HIF-1alpha and its downstream target genes

Recently, mounting evidence has emerged to suggest that hyperbaric oxygenation (HBOT)-induced neuroprotection after experimental global ischemia and subarachnoid hemorrhage entails a decrease in the expression of hypoxia-inducible factor-1alpha (HIF-1alpha). Therefore, the purpose of this study was to test the hypothesis that oxygen-induced neuroprotection after neonatal hypoxia-ischemia involves alterations in the expression of HIF-1alpha. Seven-day-old rat pups were subjected to unilateral carotid artery ligation followed by 2 h of hypoxia (8% O(2) at 37 degrees C). Pups were then treated with HBOT (2.5 ATA) or normobaric oxygenation treatment (NBOT) for 2 h. The expression and phosphorylation status of HIF-1alpha was evaluated at intervals up to 24 h after the insult, as was the expression of glucose transporter (GLUT)-1, GLUT-3, lactate dehydrogenase (LDH), aldolase (Ald), and p53. The protein-protein interaction of HIF-1alpha and p53 was also examined. An elevated expression of HIF-1alpha, GLUT-1, GLUT-3, Ald, and LDH was observed after the insult. An increase in the dephosphorylated form of HIF-1alpha was followed by an increase in the association of HIF-1alpha with p53 and an increase in p53 levels. Both HBOT and NBOT reduced the elevated expression of HIF-1alpha and decreased its dephosphorylated form. Furthermore, both treatments promoted a transient increase in the expression of GLUT-1, GLUT-3, LDH, and Ald, while decreasing the HIF-1alpha-p53 interaction and decreasing the expression of p53. Therefore, the alteration of the HIF-1alpha phenotype by a single oxygen treatment may be one of the underlying mechanisms for the observed oxygen-induced neuroprotection seen when oxygen is administered after a neonatal hypoxic-ischemic insult.

The “Lund Concept” for the treatment of severe head trauma – physiological principles and clinical application

The Lund Concept is an approach to the treatment of severe brain trauma that is mainly based on hypotheses originating from basic physiological principles regarding brain volume and cerebral perfusion regulation. Its main attributes have found support in experimental and clinical studies. This review explains the principles of the Lund Concept and is intended to serve as the current guide for its clinical application. The therapy has two main goals: (1) to reduce or prevent an increase in ICP (ICP-targeted goal) and (2) to improve perfusion and oxygenation around contusions (perfusion-targeted goal). The Lund therapy considers the consequences of a disrupted blood-brain barrier for development of brain oedema and the specific consequences of a rigid dura/cranium for general cerebral haemodynamics. It calls attention to the importance of improving perfusion and oxygenation of the injured areas of the brain. This is achieved by normal blood oxygenation, by maintaining normovolaemia with normal haematocrit and plasma protein concentrations, and by antagonizing vasoconstriction through reduction of catecholamine concentration in plasma and sympathetic discharge (minimizing stress and by refraining from vasoconstrictors and active cooling). The therapeutic measures mean normalization of all essential haemodynamic parameters (blood pressure, plasma oncotic pressure, plasma and erythrocyte volumes, PaO(2), PaCO(2)) the use of enteral nutrition, and avoidance of overnutrition. To date, clinical outcome studies using the Lund Concept have shown favourable results.

Acute infantile encephalopathy predominantly affecting the frontal lobes (AIEF): A novel clinical category and its tentative diagnostic criteria

Acute infantile encephalopathy predominantly affecting the frontal lobes (AIEF) is proposed as a novel form of acute encephalopathy in infancy. To establish the diagnostic criteria for AIEF, we reviewed the clinical data of 10 patients who were seen by us and diagnosed as having AIEF, and those of 7 patients in the literature compatible with the diagnosis of AIEF. The mean age of onset was 1 year and 7 months. Boys and girls were equally affected. There is always an association with hyperpyrexia due to viral illness. Manifestations at the onset were convulsive status epilepticus and prolonged coma followed by signs of frontal lobe dysfunction such as a lack of spontaneity and regression of verbal functions. Imaging studies demonstrated edematous changes of the bilateral frontal lobes, which showed increased cerebral perfusion initially but attenuated perfusion several weeks later. The recovery of intellectual deficit was generally slower than that of motor disability. Based on these findings, we propose tentative diagnostic criteria of AIEF.

Head injury and Parkinson's disease risk in twins

OBJECTIVE

Head injury is an inconsistently reported risk factor for Parkinson's disease (PD). Many related variables might confound this association, such as differences in childhood and adolescent lifestyles or genetically determined risk-taking behaviors. Twin studies circumvent some of these problems, because twins are genetically and environmentally much more similar than typical cases and control subjects.

METHODS

We conducted a case-control study in 93 twin pairs discordant for PD ascertained from the National Academy of Sciences/National Research Council World War II Veteran Twins Cohort.

RESULTS

A prior head injury with amnesia or loss of consciousness was associated with an increased risk for PD (odds ratio, 3.8; 95% confidence interval, 1.3-11; p = 0.014). Truncating observations 10 years before PD onset enhanced the association. Though less precise, the association was somewhat stronger in monozygotic than in dizygotic pairs. Risk increased further with a subsequent head injury (p trend = 0.022) and with head injuries requiring hospitalization. Duration of unconsciousness was not associated. In a subanalysis of 18 pairs concordant for PD, the twin with younger onset PD was more likely to have sustained a head injury, although numbers were small.

INTERPRETATION

Our results suggest that mild-to-moderate closed head injury may increase PD risk decades later.

Histamine receptors influence blood-spinal cord barrier permeability, edema formation, and spinal cord blood flow following trauma to the rat spinal cord

The role of histamine in edema formation, blood-spinal cord barrier (BSCB) permeability, and spinal cord blood flow (SCBF) following spinal cord injury (SCI) was examined using modulation of histamine H1, H2, and H3 receptors in the rat. Focal trauma to the spinal cord at the T10-11 level significantly increased spinal cord edema formation, BSCB permeability to protein tracers and SCBF reduction in the T9 and T12 segments. Pretreatment with histamine H1 receptor antagonist mepyramine (1 mg, 5 mg, and 10 mg/kg, i.p.) did not attenuate spinal pathophysiology following SCI. Blockade of histamine H2 receptors with cimetidine or ranitidine (1 mg, 5 mg, or 10 mg/kg 30 minutes before injury) significantly reduced early pathophysiological events in a dose dependent manner. The effects of ranitidine were far superior to cimetidine in identical doses. Pretreatment with a histamine H3 receptor agonist alpha-methylhistamine (1 mg and 2 mg/kg/i.p.), that inhibits histamine synthesis and release in the CNS, thwarted edema formation, BSCB breakdown, and SCBF disturbances after SCI. The lowest dose of histamine H3 agonist was most effective. Blockade of histamine H3 receptors with thioperamide (1 mg, 5 mg/kg, i.p.) exacerbated spinal cord pathology. These observations suggest that stimulation of histamine H3 receptors and blockade of histamine H2 receptors is neuroprotective in SCI.

Progesterone administration modulates AQP4 expression and edema after traumatic brain injury in male rats

This study investigates whether progesterone administration regulates AQP4 and GFAP expression in rats with bilateral contusion injuries of the medial frontal cortex. Male rats were given 0 or 16 mg/kg injections of progesterone at 1, 6, 24, and 48 h post-injury. Brains were extracted at 24 h or 72 h post-injury and assayed for cerebral edema and AQP4 and GFAP expression using Western blot analysis. Progesterone treatments reduced brain water content significantly in the brain-injured groups. There was no significant change in AQP4 expression 24 h after progesterone treatment compared to lesion + vehicle animals. However, progesterone significantly reduced AQP4 expression at 72 h post-injury in the tissue bounded by the lateral ventricles and the peri-contusion areas compared to lesion+ vehicle rats, but increased AQP4 expression in the tissue surrounding the third ventricle. Also progesterone effects on GFAP expression varied according to brain region. Our results can be taken to show that the expression of AQP4 protein after TBI is time-dependent, region-specific, and possibly implicated in the formation and resolution of TBI-induced cerebral edema.

Hyperthermia influences excitatory and inhibitory amino acid neurotransmitters in the central nervous system. An experimental study in the rat using behavioural, biochemical, pharmacological, and morphological approaches

Role of excitatory amino acids, glutamate, aspartate, and inhibitory amino acids, gamma aminobutyric acid (GABA) and glycine in brain damage caused by heat stress was examined in a rat model. Subjection of rats to 4 h heat stress at 38 degrees C in a biological oxygen demand (BOD) incubator resulted in a marked increase in glutamate and aspartate in some brain regions, whereas a significant decline in GABA and glycine was observed in several brain areas. Profound behavioural alterations and impairment of motor and cognitive functions were seen at this time. Breakdown of the blood-brain barrier (BBB), reduction in regional cerebral blood flow (CBF), edema formation and cell injuries are prominent in several parts of the brain. Pretreatment with multiple opioid receptor antagonist, naloxone (10 mg/kg, i.p.) significantly restored the heat stress induced decline in GABA and glycine and thwarted the elevation of glutamate and aspartate in various brain areas. The motor or cognitive deficits were also attenuated. A significant reduction in BBB permeability, cerebral blood flow abnormalities, edema formation and cell injuries was evident. These novel observations suggest that (i) glutamate, aspartate, GABA and glycine are involved in the pathophysiology of heat stress, and (ii) a balance between excitatory and inhibitory amino acids in brain is crucial in hyperthermia induced brain injuries or repair.

Pharmacological complement inhibition at the C3 convertase level promotes neuronal survival, neuroprotective intracerebral gene expression, and neurological outcome after traumatic brain injury

The complement system represents an important mediator of neuroinflammation in traumatic brain injury. We have previously shown that transgenic mice with central nervous system-targeted overexpression of Crry, a potent murine complement inhibitor at the level of C3 convertases, are protected from complement-mediated neuropathological sequelae in brain-injured mice. This knowledge was expanded in the present study to a pharmacological approach by the use of a recombinant Crry molecule (termed Crry-Ig) which was recently made available in a chimeric form fused to the non-complement fixing mouse IgG1 Fc region. In a standardized model of closed head injury in mice, the systemic injection of 1 mg Crry-Ig at 1 h and 24 h after trauma resulted in a significant neurological improvement for up to 7 days, as compared to vehicle-injected control mice (P < 0.05, repeated measures ANOVA). Furthermore, the extensive neuronal destruction seen in the hippocampal CA3/CA4 sublayers in head-injured mice with vehicle injection only was shown to be preserved - to a similar extent as in "sham"-operated mice - by the posttraumatic injection of Crry-Ig. Real-time RT-PCR analysis revealed that the post-treatment with Crry-Ig resulted in a significant up-regulation of candidate neuroprotective genes in the injured hemisphere (Bcl-2, C1-Inh, CD55, CD59), as compared to the vehicle control group (P < 0.01, unpaired Student's t test). Increased intracerebral Bcl-2 expression by Crry-Ig treatment was furthermore confirmed at the protein level by Western blot analysis. These data suggest that pharmacological complement inhibition represents a promising approach for attenuation of neuroinflammation and secondary neurodegeneration after head injury.

Roles of two types of anion channels in glutamate release from mouse astrocytes under ischemic or osmotic stress

Astrocytes release glutamate upon hyperexcitation in the normal brain, and in response to pathologic insults such as ischemia and trauma. In our experiments, both hypotonic and ischemic stimuli caused the release of glutamate from cultured mouse astrocytes, which occurred with little or no contribution of gap junction hemichannels, vesicle-mediated exocytosis, or reversed operation of the Na-dependent glutamate transporter. Cell swelling and chemical ischemia activated, in cell-attached membrane patches, anionic channels with large unitary conductance (approximately 400 pS) and inactivation kinetics at potentials more positive than +20 mV or more negative than -20 mV. These properties are different from those of volume-sensitive outwardly rectifying (VSOR) Cl- channels, which were also expressed in these cells and exhibited intermediate unitary conductance (approximately 80 pS) and inactivation kinetics at large positive potentials of more than +40 mV. Both maxi-anion channels and VSOR Cl- channels were permeable to glutamate with permeability ratios of glutamate to chloride of 0.21 +/- 0.07 and 0.15 +/- 0.01, respectively. However, the release of glutamate was significantly more sensitive to Gd3+, a blocker of maxi-anion channels, than to phloretin, a blocker of VSOR Cl- channels. We conclude that these two channels jointly represent a major conductive pathway for the release of glutamate from swollen and ischemia-challenged astrocytes, with the contribution of maxi-anion channels being predominant.

Inflammation and brain edema: new insights into the role of chemokines and their receptors

Brain edema is associated with a variety of neuropathological conditions such as brain trauma, ischemic and hypoxic brain injury, central nervous system infection, acute attacks of multiple sclerosis, and brain tumors. A common finding is an inflammatory response, which may have a significant impact on brain edema formation. One critical event in the development of brain edema is blood-brain barrier (BBB) breakdown, which may be initiated and regulated by several proinflammatory mediators (oxidative mediators, adhesion molecules, cytokines, chemokines). These mediators not only regulate the magnitude of leukocyte extravasation into brain parenchyma, but also act directly on brain endothelial cells causing the loosening of junction complexes between endothelial cells, increasing brain endothelial barrier permeability, and causing vasogenic edema. Here we review junction structure at the BBB, the effects of pro-inflammatory mediators on that structure, and focus on the effects of chemokines at the BBB. New evidence indicates that chemokines (chemoattractant cytokines) do not merely direct leukocytes to areas of injury. They also have direct and indirect effects on the BBB leading to BBB disruption, facilitating entry of leukocytes into brain, and inducing vasogenic brain edema formation. Chemokine inhibition may be a new therapeutic target to reduce vasogenic brain edema.