Molecular biology of CNS injury

Neuronal adhesion and synapse organization in recovery after brain injury

Few specific therapeutic targets exist to manage brain injury, despite the prevalence of stroke or traumatic brain injury. With traumatic brain injury, characteristic neuronal changes include axonal swelling and degeneration, and the loss of synapses, the sites of communication between neurons. This is followed by axonal sprouting and alterations in synaptic markers in recovery. The resulting changes in neuronal connectivity are likely to contribute to the effects of traumatic brain injury on cognitive functions and the underlying mechanisms may represent points of therapeutic intervention. In agreement, animal studies implicate adhesion and signaling molecules that organize synapses as molecular players in neuronal recovery. In this article, the authors focus on the role of cell surface interactions in the recovery after brain injury in humans and animals. The authors review cellular and synaptic alterations that occur with injury and how changes in cell adhesion, protein expression and modification may be involved in recovery. The changes in neuronal surface interactions as potential targets and their possible value for the development of therapeutics are also discussed.

Umbilical cord blood-derived CD34⁺ cells improve outcomes of traumatic brain injury in rats by stimulating angiogenesis and neurogenesis

Human umbilical cord blood cells (HUCBCs) have been shown to be beneficial in reducing neurological deficits in rats with brain fluid percussion injury (FPI). This study aimed to assess the basic mechanisms underlying the neuroprotective effects of HUCBC-derived cluster of differentiation 34-positive (CD34⁺) cells. Rats were divided into three major groups: (i) sham-operated controls; (ii) FPI rats treated with phosphate-buffered saline (PBS); (iii) FPI rats treated with 0.2%, 50%, or 95% CD34⁺ cells (in 5 × 10⁵ cord blood lymphocytes and monocytes). Intravenous (IV) administration of 0.3 ml of PBS, 0.2% CD34⁺ cells, 50% CD34⁺ cells, or 95% CD34⁺ cells was conducted immediately after FPI. It was found that 4 days post-FPI, CD34⁺ cells could be detected in the ischemic brain tissues for 50% CD34⁺ cell- or 95% CD34⁺ cell-treated FPI rats, but not for the PBS-treated FPI rats or the 0.2% CD34⁺ cell-treated FPI rats. CD34⁺ cell (0.2%)-treated FPI rats or PBS-treated FPI rats displayed neurological and motor deficits, cerebral contusion and apoptosis [e.g., increased numbers of both TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling)-positive cells and caspase-3-positive cells], and activated inflammation (e.g., increased serum levels of tumor necrosis factor-α). FPI-induced neurological motor dysfunction, cerebral contusion and apoptosis, and activated inflammation could be attenuated by 50% CD34⁺ or 95% CD34⁺ cell therapy. In addition 50% or 95% CD34⁺ cell therapy but not PBS or 0.2% CD34⁺ cell therapy significantly promoted angiogenesis (e.g., increased numbers of both vasculoendothelial growth factor-positive cells and 5-bromodeoxyuridine (BrdU)-endothelial double-positive cells), neurogenesis (e.g., increased numbers of both glial cell line-derived neurotrophic factor-positive cells and BrdU/neuronal nuclei double-positive cells) in the ischemic brain after FPI, and migration of endothelial progenitor cells from the bone marrow. Our data suggest that IV administration of HUCBC-derived CD34⁺ cells may improve outcomes of FPI in rats by stimulating both angiogenesis and neurogenesis.

Etanercept attenuates traumatic brain injury in rats by reducing early microglial expression of tumor necrosis factor-α

Background

Tumor necrosis factor-alpha (TNF-α) is elevated early in injured brain after traumatic brain injury (TBI), in humans and in animals. Etanercept (a TNF-α antagonist with anti-inflammatory effects) attenuates TBI in rats by reducing both microglial and astrocytic activation and increased serum levels of TNF-α. However, it is not known whether etanercept improves outcomes of TBI by attenuating microglia-associated, astrocytes-associated, and/or neurons-associated TNF-α expression in ischemic brain. A well clinically relevant rat model, where a lateral fluid percussion is combined with systemic administration of etanercept immediately after TBI, was used. The neurological severity score and motor function was measured on all rats preinjury and on day 3 after etanercept administration. At the same time, the neuronal and glial production of TNF-α was measured by Immunofluorescence staining. In addition, TNFα contents of ischemic cerebral homogenates was measured using commercial enzyme-linked immunosorbent assay kits.

Results

In addition to inducing brain ischemia as well as neurological and motor deficits, TBI caused significantly higher numbers of microglia-TNF-α double positive cells, but not neurons-TNF-α or astrocytes-TNF-α double positive cells in the injured brain areas than did the sham operated controls, when evaluated 3 days after TBI. The TBI-induced cerebral ischemia, neurological motor deficits, and increased numbers of microglia-TNF-α double positive cells and increased TNF-α levels in the injured brain were all significantly attenuated by etanercept therapy.

Conclusion

This finding indicates that early microglia overproduction of TNF-α in the injured brain region after TBI contributes to cerebral ischemia and neurological motor deficits, which can be attenuated by etanercept therapy. Studies in this model could provide insight into the mechanisms underlying neurological motor disturbance in brain-injured patients.

Biologic and plastic effects of experimental traumatic brain injury treatment paradigms and their relevance to clinical rehabilitation

Neuroplastic changes, whether induced by traumatic brain injury (TBI) or therapeutic interventions, alter neurobehavioral outcome. Here we present several treatment strategies that have been evaluated by using experimental TBI models and discuss potential mechanisms of action (ie, plasticity) and how such changes affect function.

Involvement of the glycogen synthase kinase-3 signaling pathway in TBI pathology and neurocognitive outcome

BACKGROUND

Traumatic brain injury (TBI) sets in motion cascades of biochemical changes that result in delayed cell death and altered neuronal architecture. Studies have demonstrated that inhibition of glycogen synthase kinase-3 (GSK-3) effectively reduces apoptosis following a number of stimuli. The Wnt family of proteins, and growth factors are two major factors that regulate GSK-3 activity. In the absence of stimuli, GSK-3 is constitutively active and is complexed with Axin, adenomatous polyposis coli (APC), and casein kinase Iα (CK1α) and phosphorylates ß-Catenin leading to its degradation. Binding of Wnt to Frizzled receptors causes the translocation of GSK-3 to the plasma membrane, where it phosphorylates and inactivates the Frizzled co-receptor lipoprotein-related protein 6 (LRP6). Furthermore, the translocation of GSK-3 reduces ß-Catenin phosphorylation and degradation, leading to ß-Catenin accumulation and gene expression. Growth factors activate Akt, which in turn inhibits GSK-3 activity by direct phosphorylation, leading to a reduction in apoptosis.

METHODOLOGY/PRINCIPAL FINDINGS

Using a rodent model, we found that TBI caused a rapid, but transient, increase in LRP6 phosphorylation that is followed by a modest decrease in ß-Catenin phosphorylation. Phospho-GSK-3β immunoreactivity was found to increase three days post injury, a time point at which increased Akt activity following TBI has been observed. Lithium influences several neurochemical cascades, including inhibiting GSK-3. When the efficacy of daily lithium was assessed, reduced hippocampal neuronal cell loss and learning and memory improvements were observed. These influences were partially mimicked by administration of the GSK-3-selective inhibitor SB-216763, as this drug resulted in improved motor function, but only a modest improvement in memory retention and no overt neuroprotection.

CONCLUSION/SIGNIFICANCE

Taken together, our findings suggest that selective inhibition of GSK-3 may offer partial cognitive improvement. As a broad spectrum inhibitor of GSK-3, lithium offers neuroprotection and robust cognitive improvement, supporting its clinical testing as a treatment for TBI.

Microarray analysis of expression of cell death-associated genes in rat spinal cord cells exposed to cyclic tensile stresses in vitro

Background

The application of mechanical insults to the spinal cord results in profound cellular and molecular changes, including the induction of neuronal cell death and altered gene expression profiles. Previous studies have described alterations in gene expression following spinal cord injury, but the specificity of this response to mechanical stimuli is difficult to investigate in vivo. Therefore, we have investigated the effect of cyclic tensile stresses on cultured spinal cord cells from E15 Sprague-Dawley rats, using the FX3000^® Flexercell Strain Unit. We examined cell morphology and viability over a 72 hour time course. Microarray analysis of gene expression was performed using the Affymetrix GeneChip System^®, where categorization of identified genes was performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) systems. Changes in expression of 12 genes were validated with quantitative real-time reverse transcription polymerase chain reaction (RT-PCR).

Results

The application of cyclic tensile stress reduced the viability of cultured spinal cord cells significantly in a dose- and time-dependent manner. Increasing either the strain or the strain rate independently was associated with significant decreases in spinal cord cell survival. There was no clear evidence of additive effects of strain level with strain rate. GO analysis identified 44 candidate genes which were significantly related to "apoptosis" and 17 genes related to "response to stimulus". KEGG analysis identified changes in the expression levels of 12 genes of the mitogen-activated protein kinase (MAPK) signaling pathway, which were confirmed to be upregulated by RT-PCR analysis.

Conclusions

We have demonstrated that spinal cord cells undergo cell death in response to cyclic tensile stresses, which were dose- and time-dependent. In addition, we have identified the up regulation of various genes, in particular of the MAPK pathway, which may be involved in this cellular response. These data may prove useful, as the accurate knowledge of neuronal gene expression in response to cyclic tensile stress will help in the development of molecular-based therapies for spinal cord injury.

Neuronal apoptosis is inhibited by cord blood stem cells after spinal cord injury

Spinal cord injury (SCI) induces a series of endogenous biochemical changes that lead to secondary damage involving apoptosis as one of the major events. To understand the molecular basis of apoptosis after spinal cord injury, we subjected male rats to spinal cord injury using a weight drop device (NYU impactor) and evaluated the therapeutic potential of human umbilical cord blood stem cells (hUCB), which were stereotactically transplanted into the injury epicenter 1 week after SCI. We identified genes that render the adult-injured spinal cord nonconducive and the hUCB-treated spinal cord conducive to regeneration and repair at 3 weeks post-injury using an RT-PCR microarray by analyzing 84 apoptotic genes. Genes involved in inflammation and apoptosis were upregulated in injured spinal cords of rats, whereas genes involved in neuroprotection were upregulated in the hUCB-treated rats. Quantitative RT-PCR verified mRNA changes in the apoptotic genes of TNF-alpha, TNFR1, TNFR2, Fas, Lta, and CD40. Based on these results, we evaluated the role of TNF-alpha and its related apoptotic genes in neuronal death after SCI. Changes in the expression of TNF-alpha, TNFR1, and TNFR2 were observed over a period of 3 weeks post-SCI and after treatment with hUCB. Expression of P50 and P65 on neurons after SCI was efficiently downregulated by hUCB. These results were confirmed by the evaluation of apoptotic proteins of co-cultures of spinal neurons with hUCB under in-vitro conditions. The results of this study suggest that hUCB have therapeutic potential in inhibiting neuronal apoptosis during the repair of injured spinal cord.

Alterations in neuronal gene expression profiles in response to experimental demyelination and axonal transection

The main pathological features of multiple sclerosis, demyelination and axonal transection, are considered to cause reversible and irreversible neurological deficits, respectively. This study aimed to separately analyze the effects of these pathological hallmarks on neuronal gene expression in experimental paradigms. The pontocerebellar pathway was targeted with either lysolecithin-induced chemical demyelination or a complete pathway transection (axonal transection) in rats. Transcriptional changes in the pontocerebellar neurons were investigated with microarrays at days 4, 10 and 37 post-intervention, which was confirmed by immunohistochemistry on protein level. A common as well as unique set of injury-response genes was identified. The increased expression of activating transcription factor 3 (Atf3) and thyrotropin-releasing hormone (Trh) in both injury paradigms was validated by immunohistochemistry. The expression of Atf3 in a patient with Marburg's variant of multiple sclerosis was also detected, also confirming the activation of the Atf3 pathway in a human disease sample. It was concluded that this experimental approach may be useful for the identification of pathways that could be targeted for remyelinative or neuroprotective drug development.

The tumor suppressor protein p53 is required for neurite outgrowth and axon regeneration

Axon regeneration is substantially regulated by gene expression and cytoskeleton remodeling. Here we show that the tumor suppressor protein p53 is required for neurite outgrowth in cultured cells including primary neurons as well as for axonal regeneration in mice. These effects are mediated by two newly identified p53 transcriptional targets, the actin-binding protein Coronin 1b and the GTPase Rab13, both of which associate with the cytoskeleton and regulate neurite outgrowth. We also demonstrate that acetylation of lysine 320 (K320) of p53 is specifically involved in the promotion of neurite outgrowth and in the regulation of the expression of Coronin 1b and Rab13. Thus, in addition to its recognized role in neuronal apoptosis, surprisingly, p53 is required for neurite outgrowth and axonal regeneration, likely through a different post-translational pathway. These observations may suggest a novel therapeutic target for promoting regenerative responses following peripheral or central nervous system injuries.

Regeneration following spinal cord injury, from experimental models to humans: where are we?

Regeneration in the adult CNS following injury is extremely limited. Traumatic spinal cord injury causes a permanent neurological deficit followed by a very limited recovery due to failed regeneration attempts. In fact, it is now clear that the spinal cord intrinsically has the potential to regenerate, but cellular loss and the presence of an inhibitory environment strongly limit tissue regeneration and functional recovery. The molecular mechanisms responsible for failed regeneration are starting to be unveiled. This gain in knowledge led to the design of therapeutic strategies aimed to limit the tissue scar, to enhance the proregeneration versus the inhibitory environment, and to replace tissue loss, including the use of stem cells. They have been very successful in several animal models, although results are still controversial in humans. Nonetheless, novel experimental approaches hold great promise for use in humans.

Incorporation of protein-eluting microspheres into biodegradable nerve guidance channels for controlled release

Nerve guidance channels (NGCs) promote axonal regeneration after transection injury of the peripheral nerve or spinal cord, yet this regeneration is limited. To enhance regeneration further, we hypothesize that localized delivery of therapeutic molecules combined with the NGC is required. In an attempt to achieve such an NGC, we designed and synthesized a novel NGC in which protein-encapsulated microspheres were stably incorporated into the tube wall. Specifically, poly(lactide-co-glycolide) (PLGA 50/50) microspheres were physically entrapped in the annulus between two concentric tubes, consisting of a chitosan inner tube and a chitin outer tube. Taking advantage of the extensive shrinking that the outer chitin tube undergoes with drying, >15 mg of microspheres were loaded within the tube walls. Using BSA-encapsulated microspheres as the model drug delivery system, BSA was released from microsphere loaded tubes (MLTs) for 84 days, and from freely suspended PLGA microspheres for 70 days. An initial burst release was observed for both MLTs and free microspheres, followed by a degradation-controlled release profile that resulted in a higher release rate from MLTs initially, which was then attenuated likely due to the buffering effect of chitin and chitosan tubes. Epidermal growth factor (EGF), co-encapsulated with BSA in PLGA 50/50 microspheres in MLTs, was released for 56 days with a similar profile to that of BSA. Released EGF was found to be bioactive for at least 14 days as assessed by a neurosphere forming bioassay.

Animal models of head trauma

Animal models of traumatic brain injury (TBI) are used to elucidate primary and secondary sequelae underlying human head injury in an effort to identify potential neuroprotective therapies for developing and adult brains. The choice of experimental model depends upon both the research goal and underlying objectives. The intrinsic ability to study injury-induced changes in behavior, physiology, metabolism, the blood/tissue interface, the blood brain barrier, and/or inflammatory- and immune-mediated responses, makes in vivo TBI models essential for neurotrauma research. Whereas human TBI is a highly complex multifactorial disorder, animal trauma models tend to replicate only single factors involved in the pathobiology of head injury using genetically well-defined inbred animals of a single sex. Although such an experimental approach is helpful to delineate key injury mechanisms, the simplicity and hence inability of animal models to reflect the complexity of clinical head injury may underlie the discrepancy between preclinical and clinical trials of neuroprotective therapeutics. Thus, a search continues for new animal models, which would more closely mimic the highly heterogeneous nature of human TBI, and address key factors in treatment optimization.

Chronic alterations in the cellular composition of spinal cord white matter following contusion injury

Spinal cord injury (SCI) involves the loss of neurons and glia due to initial mechanical and secondary biochemical mechanisms. Treatment with the sodium channel blocker tetrodotoxin (TTX) reduces acute white matter pathology and increases both axon density and hindlimb function chronically at 6 weeks after injury. We investigated the cellular composition of residual white matter chronically to determine whether TTX also has a significant effect on the numbers and types of cells present. Rats received an incomplete thoracic contusion injury, in the presence or absence of TTX (0.15 nmole) injected focally, beginning at 15 min prior to injury. Six weeks later, cell density was significantly increased in the residual white matter of the dorsal, lateral, and ventral funiculi, both rostral and caudal to the injury site in both TTX-treated and injury control groups. Oligodendrocyte and astrocyte density was similar to normal but large numbers of cells expressing microglia/macrophage markers were present. Labeling with the progenitor markers nestin and NG2 showed that precursor cell density had also doubled or tripled as compared with uninjured controls. Some of these cells were also labeled for antigens that indicate their possible progression along an oligodendrocyte or astrocyte lineage. Our results support the hypothesis that the beneficial effect of TTX in SCI is related to its preservation of axons per se; no effect on chronic white matter cell composition was detected. They highlight the profound changes in cellular composition in preserved white matter chronically at 6 weeks after injury, including the accumulation of endogenous progenitor cells and the persistence of activated macrophages/microglia. The manipulation of these endogenous cells may be used in the future to enhance recovery after SCI.

Interleukin 1beta and interleukin 6 relationship with paediatric head trauma severity and outcome

BACKGROUND

Based on the known inflammatory role of interleukins (IL), we evaluated IL-1beta and IL-6 expressions and their association with the severity of traumatic brain injury (TBI; Glasgow Coma Scale [GCS]) and the outcome (Glasgow Outcome Score [GOS]) recorded in a paediatric population.

DESIGN

The design was a perspective observational clinical study carried out in the paediatric intensive care unit of the University Hospital.

METHODS

We measured the IL-1beta and IL-6 levels in 14 children with severe TBI (patients) and in 12 children with obstructive hydrocephalus (control group). Cerebrospinal fluid (CSF) and plasma samples were collected 2 h (T1) and 24 h (T2) after TBI. Interleukins were assayed using the immunoenzymatic method.

RESULTS

The IL-1beta mean level was significantly lower than the IL-6 mean level both in the CSF and plasma of TBI children. In the CSF, the IL-1beta level increased from 55.71+/-72.79 pg/ml at T1 to 106.10+/-142.12 pg/ml at T2 and the IL-6 level increased from 405.43+/-280.28 pg/ml at T1 to 631.57+/-385.35 pg/ml at T2; a similar trend was observed in plasma. We found a statistically significant correlation between the increase in CSF and plasma interleukin levels between T1 and T2 and head injury severity (GCS<or=5) as well as poor outcome (GOS<or=3).

CONCLUSIONS

The increases in IL-1beta and IL-6 expression were correlated with head injury severity and were indicative of poor clinical outcome, reflecting an endogenous neuroinflammatory response after TBI.

Neuronal plasticity after spinal cord injury: identification of a gene cluster driving neurite outgrowth

Functional recovery after spinal cord injury (SCI) may result in part from axon outgrowth and related plasticity through coordinated changes at the molecular level. We employed microarray analysis to identify a subset of genes the expression patterns of which were temporally coregulated and correlated to functional recovery after SCI. Steady-state mRNA levels of this synchronously regulated gene cluster were depressed in both ventral and dorsal horn neurons within 24 h after injury, followed by strong re-induction during the following 2 wk, which paralleled functional recovery. The identified cluster includes neuritin, attractin, microtubule-associated protein 1a, and myelin oligodendrocyte protein genes. Transcriptional and protein regulation of this novel gene cluster was also evaluated in spinal cord tissue and in single neurons and was shown to play a role in axonal plasticity. Finally, in vitro transfection experiments in primary dorsal root ganglion cells showed that cluster members act synergistically to drive neurite outgrowth.

Lesional Expression of RhoA and RhoB following Traumatic Brain Injury in Humans

Inhibition of the small GTPase Rho or of its downstream target Rho-associated kinase (ROCK) has been shown to promote axon regeneration and to improve functional recovery following traumatic CNS lesions in the adult rat. In order to determine the expression pattern of RhoA and RhoB following human traumatic brain injury (TBI) and to assess whether Rho is a possible target for pharmacological intervention in humans, we investigated expression patterns of RhoA and RhoB in brain specimens from 25 patients who died after closed TBI in comparison to brain tissue derived from four neuropathologically unaffected control patients by immunohistochemistry. A highly significant lesional upregulation of both RhoA and RhoB was observed beginning several hours after the traumatic event and continuing for months after TBI. The cellular sources of both molecules included polymorphonuclear granulocytes, monocytes/macrophages, and reactive astrocytes. Additionally, expression of RhoA was also detected in neuronal cells in some of the cases. From our data, we conclude that inhibition of Rho is a promising mechanism for the development of new pharmacological interventions in human TBI. As the observed upregulation of RhoA and RhoB was still detectable months after TBI, we speculate that even delayed treatment with Rho inhibitors might be a therapeutic option.

Common patterns of bcl-2 family gene expression in two traumatic brain injury models

Cell death/survival following traumatic brain injury (TBI) may be a result of alterations in the intracellular ratio of death and survival factors. Bcl-2 family genes mediate both cell survival and the initiation of cell death. Using lysate RNase protection assays, mRNA expression of the anti-cell death genes Bcl-2 and Bcl-xL, and the pro-cell death gene Bax, was evaluated following experimental brain injuries in adult male Sprague-Dawley rats. Both the lateral fluid-percussion (LFP) and the lateral controlled cortical impact (LCI) models of TBI showed similar patterns of gene expression. Anti-cell death bcl-2 and bcl-xL mRNAs were attenuated early and tended to remain depressed for at least 3 days after injury in the cortex and hippocampus ipsilateral to injury. Pro-cell death bax mRNA was elevated in these areas, usually following the decrease in anti-cell death genes. These common patterns of gene expression suggest an important role for Bcl-2 genes in cell death and survival in the injured brain. Understanding the regulation of these genes may facilitate the development of new therapeutic strategies for a condition that currently has no proven pharmacologic treatments.

Temporal alterations in cellular Bax:Bcl-2 ratio following traumatic brain injury in the rat

Cell death/survival following CNS injury may be a result of alterations in the intracellular ratio of death and survival factors. Using immunohistochemistry, Western analysis and in situ hybridization, the expression of the anti-cell death protein, Bcl-2, and the pro-cell death protein, Bax, was evaluated following lateral fluid-percussion (FP) brain injury of moderate severity (2.3-2.6 atm) in adult male Sprague-Dawley rats. By 2 h post-injury, a marked reduction of cellular Bcl-2-immunoreactivity (IR) and a mild decrease in cellular Bax IR were observed in the temporal and occipital cortices, and in the hippocampal CA3 ipsilateral to the site of impact. These decreases in Bcl-2 and Bax IR appeared to precede the overt cell loss in these regions that was evident at 24 h. Immunoblot analysis supported the immunohistochemical data, with a modest but significant reduction in the intensities of both the Bcl-2 and Bax protein bands at 2 h (p < 0.05 compared to sham levels). However, the Bax:Bcl-2 ratio increased significantly at 2 h (2.28 +/- 0.13) and remained elevated up to 7 days (2.05 +/- 0.13) post-injury compared to sham-injured control tissue (1.62 +/- 0.10, p < 0.05). Furthermore, cortical, but not hippocampal, levels of Bax protein increased by 25% (p < 0.05 compared to sham-injured controls) at 24 h post-injury, and returned to control levels by 7 days. In situ hybridization analysis of Bax mRNA revealed increased cellular grain density in the injured cortex (p < 0.05 compared to sham-injured brains), but not in the CA3 region of the injured hippocampus. No injury-induced changes in the expression of Bcl-2 mRNA were observed in any brain region. Taken together, these data suggest that the association between regional post-traumatic cell death and alterations in the cellular ratio of Bcl-2 and Bax may be, in part, due to alterations in mRNA and/or protein expression of the Bcl-2 family of proteins.

Gene profiling in spinal cord injury shows role of cell cycle in neuronal death

Spinal cord injury causes secondary biochemical changes leading to neuronal cell death. To clarify the molecular basis of this delayed injury, we subjected rats to spinal cord injury and identified gene expression patterns by high-density oligonucleotide arrays (8,800 genes studied) at 30 minutes, 4 hours, 24 hours, or 7 days after injury (total of 26 U34A profiles). Detailed analyses were limited to 4,300 genes consistently expressed above background. Temporal clustering showed rapid expression of immediate early genes (30 minutes), followed by genes associated with inflammation, oxidative stress, DNA damage, and cell cycle (4 and 24 hours). Functional clustering showed a novel pattern of cell cycle mRNAs at 4 and 24 hours after trauma. Quantitative reverse transcription polymerase chain reaction verified mRNA changes in this group, which included gadd45a, c-myc, cyclin D1 and cdk4, pcna, cyclin G, Rb, and E2F5. Changes in their protein products were quantified by Western blot, and cell-specific expression was determined by immunocytochemistry. Cell cycle proteins showed an increased expression 24 hours after injury and were, in part, colocalized in neurons showing morphological evidence of apoptosis. These findings suggest that cell cycle-related genes, induced after spinal cord injury, are involved in neuronal damage and subsequent cell death.

Acute systemic administration of interleukin-10 suppresses the beneficial effects of moderate hypothermia following traumatic brain injury in rats

Traumatic injury to the central nervous system initiates inflammatory processes such as the synthesis of proinflammatory mediators that contribute to secondary tissue damage. Hence, administration of anti-inflammatory cytokines, such as interleukin-10 (IL-10) may be neuroprotective. Moderate hypothermia (30-32 degrees C) also decreases the pro-inflammatory response to traumatic brain injury (TBI). Thus, we hypothesized that the combination of IL-10 and hypothermia would provide synergistic neuroprotective effects after TBI. To test this hypothesis, fifty isoflurane-anesthetized rats underwent a controlled cortical impact (2.7 mm tissue deformation at 4 m/s) or sham injury and then were randomly assigned to one of five conditions (TBI/VEH Normothermia (37 degrees C), TBI/VEH Hypothermia (32 degrees C for 3 h), TBI/IL-10 Normothermia, TBI/IL-10 Hypothermia, and Sham/VEH Normothermia). Human IL-10 (5 microg) or VEH was administered (i.p.) 30 min after surgery. Function was assessed by established motor and cognitive tests on post-operative days 1-5 and 14-18, respectively. Cortical lesion volume and hippocampal CA(1)/CA(3) cell survival were quantified at 4 weeks. Brain sections from 15 additional rats were immunohistochemically assessed (MoAB RP-3) to determine neutrophil accumulation at 5 h after TBI. The administration of IL-10 after TBI produced an approximately 75% reduction in the number of RP-3-positive cells in both the normothermic and hypothermic groups vs. the normothermic vehicle-treated group (P<0.05), but did not improve functional outcome. In contrast, hypothermia alone enhanced both motor and cognitive function and increased CA(3) neuronal survival after TBI. Contrary to our hypothesis, systemic administration of IL-10 combined with hypothermia did not provide synergistic neuroprotective effects after TBI. Rather, IL-10 administration suppressed the beneficial effects produced by hypothermia alone after TBI. The mechanism(s) for the negative effects of IL-10 combined with hypothermia after TBI remain to be determined.

Pharmacological treatment of traumatic brain injury: a review of agents in development

Successful treatment strategies for patients with traumatic brain injury (TBI) remain elusive despite standardised clinical treatment guidelines, improved understanding of mechanisms of cellular response to trauma, and a decade of clinical trials aimed at identifying therapeutic agents targeted at mediators of secondary injury. The information explosion relative to mechanisms of secondary injury has identified several potential targets for intervention. Depending on the type of injury to the brain and the intensity and the success of resuscitation, necrosis, apoptosis, inflammatory and excitotoxic cellular damage can be seen. These same processes may continue postinjury, depending on the adequacy of clinical care. Each of these mechanisms of cellular damage can initiate a cascade of events mediated by endogenous signals that lead to secondary neurological injury. Several factors contributed to the failure of earlier clinical trials. Now that these have been recognised, a positive impact on future drug development in TBI has been realised. Both the US and Europe have organised brain injury consortiums where experts in the treatment of TBI provide insight into study design, implementation, conduct and oversight in conjunction with the pharmaceutical industry. Consequently, future clinical trials of new investigational treatments have greater potential for identifying therapies of merit in specific populations of patients with TBI. Pharmacological strategies under investigation are targeting sites involved in the secondary cascade that contribute to overall poor outcome following the primary injury. These treatments include ion channel antagonists including calcium channel antagonists, growth factors, antioxidants, stem cells, apoptosis inhibitors, and inhibitors of other signal modulators. In conclusion, the complexity of TBI pathology and the mechanisms contributing to secondary injury present unique therapeutic challenges. Appropriate research targets for intervention continue to be investigated, however, the likelihood of improving outcomes with a single approach is extremely small. There is a need for collaborative efforts to investigate the optimal time for drug administration and the logical sequence or combination of treatments that will ultimately lead to improved neurological outcomes in this population.

A model of acute subdural hematoma in the mouse

The availability of genetically modified mice has allowed the study of genetic influences on acute brain injury. An animal model of acute subdural hematoma (ASDH) has been previously described in the rat but not the mouse. We describe a method for producing ASDH in the mouse. Subdural injections of 50 and 30 microL of nonheparinized autologous blood were associated with excessive mortality. Injections of 10 and 20 microL were associated with mean percentage volumes of damage of 1.804% and 4.019%, respectively. Sham subdural injections of saline were associated with minimal hemisphere damage (0.152%). This mouse model provides a means of investigating the effects of genotype on the brain's response to ASDH.

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.

Neuroprotective agents in traumatic brain injury

The role of neuroprotection in traumatic brain injury (TBI) is reviewed. Basic research and experimental investigations have identified many different compounds with potential neuroprotective effect. However, none of the Phase III trials performed in TBI have been successful in convincingly demonstrating efficacy in the overall population. A common misconception is that consequently these agents are ineffective. The negative results as reported in the overall population may in part be caused by specific aspects of the head injury population as well as by aspects of clinical trial design and analysis. The heterogeneity of the TBI population causes specific problems, such as a risk of imbalances between placebo and treated groups but also causes problems when a possible treatment effect is evaluated in relation to the prognostic effect present. Trials of neuroprotective agents should be targeted first of all to a population in which the mechanism at which the agent is directed is likely to be present and secondly to a population in which the chances of demonstrating efficacy are realistic, e.g., to patients with an intermediate prognosis. The possibilities for concomitant or sequential administration of different neuroprotective agents at different times deserve consideration. The potential for neuroprotection in TBI remains high and we should not be discouraged by recent failures obtained up until now. Rather, prior to initiating new trials, careful consideration of experimental evidence is required in order to optimise chances for mechanistic targeting and lessons learned from previous experience need to be taken to heart in the design of future studies.

Bedside invasive monitoring techniques in severe brain-injured patients

In patients with severe brain injury, brain edema, elevated intracranial pressure, and cerebral ischemia are accountable for a significant morbidity and mortality. New invasive methods of monitoring attempt to foresee the physiopathological mechanisms responsible for the production of secondary brain injuries. The available methods for monitoring severely brain-injured patients, their potential usefulness, advantages, and disadvantages are reviewed.

Head injury: recent past, present, and future

There is no question that substantial progress has been made over the last 30 years, since the pioneering multinational studies of Jennett and colleagues, in our understanding of the mechanisms involved in the production, progression, and amelioration of brain damage. The introduction of computed tomography and simple but elegant classifications of the severity of injury (e.g., the Glasgow Coma Scale and the Glasgow Outcome Scale) were seminal milestones in neurotraumatology. When neurosurgeons such as Langfitt, Becker, and Miller took advantage of the pioneering investigations of intracranial hypertension by Janny and Lundberg and combined them with imaging, classification of brain damage, and improvements in emergency medical services, substantial gains were soon made. However, given the perspective of the beginning of the 21 st century, one can see those gains as relatively straightforward, as they have required the consolidation of concepts and ideas that fit together relatively easily. Better attention to easily delineated abnormalities, such as shock, hypoxia, and hypercarbia, and the early evacuation of mass lesions coupled with the concurrent development of modern principles of critical care account for substantial reductions in mortality and a reduction in the number of vegetative, contracted, spastic survivors. Future improvement in the care of patients with head injuries will increasingly be dependent on advances in molecular neurobiology and psychology, our ability to successfully modulate genetic expression, and progress in the treatment of related illnesses, such as stroke, subarachnoid hemorrhage, depression, and Alzheimer's disease.

Dynamic mechanical stretch of organotypic brain slice cultures induces differential genomic expression: relationship to mechanical parameters

Although the material properties of biological tissues are reasonably well established, recent studies have suggested that the biological response of brain tissue and its constituent cells may also be viscoelastic and sensitive to both the magnitude and rate of a mechanical stimulus. Given the potential involvement of changes in gene expression in the pathogenic sequelae after head trauma, we analyzed the expression of 22 genes related to cell death and survival and found that a number of these genes were differentially regulated after mechanical stretch of an organotypic brain slice culture. Twenty-four hours after stretch, the expression of BDNF, NGF, and TrkA was significantly increased, whereas that of bcl-2, CREB, and GAD65 was significantly decreased (MANOVA followed by ANOVA, p < 0.05). Expression of CREB and GAD65 was negatively correlated with strain, whereas expression of APP695 was negatively correlated with strain rate (all p < 0.05). This study demonstrates that a subset of genes involved in cell death and survival are differentially regulated after dynamic stretch in vitro and that the expression of specific genes is correlated with mechanical parameters of that stretch.

Interleukin-8 is increased in cerebrospinal fluid of children with severe head injury

OBJECTIVE

To determine interleukin (IL)-8 concentrations in ventricular cerebrospinal fluid from children with severe traumatic brain injury (TBI).

DESIGN

Prospective study.

SETTING

University children's hospital.

PATIENTS

Twenty-seven children hospitalized with severe TBI (Glasgow Coma Scale score < or =8), seven children with cerebrospinal fluid culture-positive bacterial meningitis, and twenty-four age-equivalent controls.

INTERVENTIONS

Placement of an intraventricular catheter and continuous drainage of cerebrospinal fluid.

MEASUREMENTS AND MAIN RESULTS

Median [range] cerebrospinal fluid IL-8 concentration in children with TBI (0-12 hrs) (4,452.5 [0-20,000] pg/mL) was markedly greater than that in controls (14.5 [0-250]) (p < .0001) and equivalent to concentrations in children with meningitis (5,300 [1,510-22,000] pg/mL) (p = .33). Cerebrospinal fluid IL-8 remained increased in children with severe TBI for up to 108 hrs after injury. Univariate logistic regression analysis demonstrated an association between cerebrospinal fluid IL-8 and child abuse (p = .07) and mortality (p = .01). Multivariate analysis demonstrated a strong, independent association between cerebrospinal fluid IL-8 and mortality (p = .01).

CONCLUSIONS

The data are consistent with an acute inflammatory component of TBI in children and suggest an association between cerebrospinal fluid IL-8 and outcome after TBI. IL-8 may represent a potential target for anti-inflammatory therapy.

Traumatic injury induces differential expression of cell death genes in organotypic brain slice cultures determined by complementary DNA array hybridization

The expression of a large panel of selected genes hypothesized to play a central role in post-traumatic cell death was shown to be differentially altered in response to a precisely controlled, mechanical injury applied to an organotypic slice culture of the rat brain. Within 48 h of injury, the expression of nerve growth factor messenger RNA was significantly increased whereas the levels of bcl-2, alpha-subunit of calcium/calmodulin-dependent protein kinase II, cAMP response element binding protein, 65,000 mol. wt isoform of glutamate decarboxylase, 1beta isoform of protein kinase C, and ubiquitin messenger RNA were significantly decreased. Because the expression levels of a number of other messenger RNAs such as the neuron-specific amyloid precursor protein, beta(2) microglobulin, bax, bcl(xl), brain-derived neurotrophic factor, cyclooxygenase-2, interleukin-1beta, interleukin-6, tumor necrosis factor-alpha, receptor tyrosine kinase A, and receptor tyrosine kinase B were unaffected, these selective changes may represent components of an active and directed response of the brain initiated by mechanical trauma. Interpretation of these co-ordinated alterations suggests that mechanical injury to the central nervous system may lead to disruption of calcium homeostasis resulting in altered gene expression, an impairment of intracellular cascades responsible for trophic factor signaling, and initiation of apoptosis via multiple pathways. An understanding of these transcriptional changes may contribute to the development of novel therapeutic strategies to enhance beneficial and blunt detrimental, endogenous, post-injury response mechanisms.

[Understanding of molecular biology]

OBJECTIVES

To display theorical and methodological basis of the molecular biology. To point out its main medical applications.

DATA SOURCES

For this review, we analysed the English and French literature concerning the research and clinical aspects of the molecular biology, especially in anaesthesiology and intensive care, using the Medline database. The current textbooks were also used.

STUDY SELECTION

We selected: 1) the original articles corresponding to the main advances that resulted in the present state of this discipline; 2) the reviews; 3) some chapters of textbooks.

DATA EXTRACTION

In this review, we report: 1) the current knowledge concerning the conservation and the expression of the genome; 2) the principles of the most widely used experimental techniques; 3) the medical applications of this knowledge in anaesthesiology and intensive care; 4) the more recent developments of this research field.

DATA SYNTHESIS

Within medical biology, molecular biology essentially corresponds to the study of nucleic acids. In this review, the general principles governing the organization and expression of the genome are discussed. The expansion of molecular biology has been a consequence of the widespread use of enzymatic tools, of which bacterial restriction enzymes were the first. Numerous enzymes are now available, permitting DNA strands to be cut, linked, synthesized and sequenced. Several of the most representative molecular biology techniques are described. Some of them, such as PCR, are commonly used in clinical situations. Animal experimental models have also been generated by genome altering methods, in order to analyse the phenotypic consequences of these modifications. Recently, a viable mammal, deriving from a differentiated cell, has been cloned. Human embryonic totipotent stem cells are now available in cultures. These advances have important ethical implications whilst, at the same time, offering new opportunities for medical applications. The state of gene therapy and human genome sequencing programmes is discussed.

Differential effects of traumatic brain injury on vesicular acetylcholine transporter and M2 muscarinic receptor mRNA and protein in rat

Experimental traumatic brain injury (TBI) produces cholinergic neurotransmission deficits that may contribute to chronic spatial memory deficits. Cholinergic neurotransmission deficits may result from presynaptic alterations in the storage and release of acetylcholine (ACh) or from changes in the receptors for ACh. The vesicular ACh transporter (VAChT) mediates accumulation of ACh into secretory vesicles, and the M2 muscarinic receptor subtype can modulate cholinergic neurotransmission via a presynaptic inhibitory feedback mechanism. We examined the effects of controlled cortical impact (CCI) injury on hippocampal VAChT and M2 muscarinic receptor subtype protein and medial septal mRNA levels at 4 weeks following injury. Rats were anesthetized and surgically prepared for CCI injury (4 m/sec, 2.5 to 2.9 mm in depth) and sham surgery. Animals were sacrificed, and coronal sections (35 microm thick) were cut through the dorsal hippocampus for VAChT and M2 immunohistochemistry. Semiquantitative measurements of VAChT and M2 protein in hippocampal homogenates from injured and sham rats were assessed with Western blot analysis. Changes in VAChT and M2 mRNA levels were evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). At 4 weeks after injury, both immunohistochemical and Western blot methods demonstrated an increase in hippocampal VAChT protein. An increase in VAChT mRNA was also observed. Immunohistochemistry demonstrated a loss of M2; however, there was no significant change in M2 mRNA levels in comparison with sham controls. These changes may represent a compensatory response of cholinergic neurons to increase the efficiency of ACh neurotransmission chronically after TBI through differential transcriptional regulation.

Increased calpain I-mediated proteolysis, and preferential loss of dephosphorylated NF200, following traumatic spinal cord injury

We investigated the hypothesis that the Ca2+-activated protease calpain is involved in the pathophysiology of spinal cord injury, and is linked to the proteolytic degradation of cytoskeletal proteins. We report here that levels of calpain I (mu-calpain)-mediated spectrin breakdown products are increased by 15 min post-injury, with peak levels reached by 2 h post-injury. The dephosphorylated form of the neurofilament protein NF200 is substantially lost over the same time-period. A 35-g compressive injury was applied to the midthoracic rat spinal cord for 1 min, and animals were killed at 15 min, 1, 2, 4, 8, 16, and 24 h post-injury. Calpain I-mediated spectrin breakdown products accumulated post-injury, with peak levels reached at 2 h. Secondly, we have demonstrated a progressive loss of the 200,000 mol. wt neurofilament protein NF200, a cytoskeletal calpain substrate, which began within 1-2 h post-injury. Densitometric analyses confirmed that loss of NF200 is a substrate-specific phenomenon, since (i) dephosphorylated NF200 was preferentially lost while phosphorylated NF200 was relatively spared, and (ii) actin, which is not a substrate for calpain, was relatively spared following spinal cord injury. Finally, we demonstrated calpain I-mediated spectrin breakdown within NF200-positive neuronal processes post-injury. We conclude that the accumulation of spectrin breakdown products is temporally and spatially correlated with loss of dephosphorylated NF200 after spinal cord injury.

Expression of brain-derived neurotrophic factor, nerve growth factor, and heat shock protein HSP70 following fluid percussion brain injury in rats

Traumatic brain injury can induce the expression of stress-related and neurotrophic genes both within the injury site and in distant regions. These genes may affect severity of damage and/or be neuroprotective. We used in situ hybridization to assess the alterations in expression of the heat shock protein HSP70, nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF) genes in rat brain following moderate fluid-percussion (F-P) injury at various survival times. HSP70 gene expression was induced at and surrounding the injury site as early as 30 min after trauma. This elevated signal spread ventrally and laterally through the ipsilateral cortex and into the underlying white matter over the next few hours. In addition, there was elevated expression in the temporal hippocampus. BDNF was strongly upregulated in the granular cells of the dentate gyrus and in the CA3 hippocampus 2-6 h after injury. Cortical regions at and near the injury site showed no response at the mRNA level. NGF mRNA increased over the granular cells of the dentate gyrus at early time points. There was also a weaker secondary induction of the NGF gene in the contralateral dentate gyrus of some animals. Cortical response was observed in the entorhinal cortex, bilaterally, but not at the injury site. All three of the studied genes responded quickly to injury, as early as 30 min. The induction of gene expression for neurotrophins in regions remote from areas with histopathology may reflect coupling of gene expression to neuronal excitation, which may be associated with neuroprotection and plasticity.

Site-specific cleavage of 28S rRNA as a marker of traumatic brain injury

A cleavage product of 28S rRNA was isolated from ipsilateral hippocampus of rat brain subjected to lateral fluid percussion induced traumatic brain injury (TBI). Northern blot analysis demonstrated that the corresponding cDNA fragment hybridized to 28S rRNA and three cleavage products. Two of the cleaved rRNA fragments (1.3 kb and 0.9 kb) were also observed in differentiated PC12 cells undergoing apoptosis induced by NGF withdrawal. The third fragment (0.6 kb) was detected only in rat brain tissue subjected to trauma, suggesting specific cleavage of 28S following TBI. The 0.6-kb fragment was found only in cortex and hippocampus ipsilateral to the trauma site, but not in brain stem, contralateral cortex or contralateral hippocampus. 28S rRNA cleavage was detected beginning 2 h after trauma and reflected injury severity. Although cleavage of 28S rRNA has been reported in association with apoptosis in white blood cells and apoptosis occurs in the experimental head injury model used, the pattern of 28S rRNA cleavage observed with TBI differs from those observed in apoptotic PC12 cells or those reported for white blood cells. Thus, whereas 28S rRNA fragmentation appears to be a marker of posttraumatic brain injury, its precise role in the secondary injury process remains to be established.

Early neuronal expression of tumor necrosis factor-alpha after experimental brain injury contributes to neurological impairment

Tumor necrosis factor-alpha (TNF alpha) is a pleiotropic cytokine involved in inflammatory cascades associated with CNS injury. To examine the role of TNF alpha in the acute pathophysiology of traumatic brain injury (TBI), we studied its expression, localization and modulation in a clinically relevant rat model of non-penetrating head trauma. TNF alpha levels increased significantly in the injured cortex at 1 and 4, but not at 12, 24 or 72 h after severe lateral fluid-percussion trauma (2.6-2.7 atm). TNF alpha was not elevated after mild injury. At 1 and 4 h after severe TBI, marked increases of TNF alpha were localized immunocytochemically to neurons of the injured cerebral cortex. A small population of astrocytes, ventricular cells and microvessels, also showed positive TNF alpha staining, but this expression was not injury-dependent. Macrophages that were present in a hemorrhagic zone along the external capsule, corpus callosum and alveus hippocampus at 4 h after TBI did not express TNF alpha. Intracerebroventricular administration of a selective TNF alpha antagonist--soluble TNF alpha receptor fusion protein (sTNFR:Fc) (37.5 microg)--at 15 min before and 1 h after TBI, improved performance in a series of standardized motor tasks after injury. In contrast, intravenous administration of sTNFR:Fc (0.2, 1 or 5 mg/kg) at 15 min after trauma did not improve motor outcome. Collectively, this evidence suggests that enhanced early neuronal expression of TNF alpha after TBI contributes to subsequent neurological dysfunction.

Craniocerebral trauma: protection and retrieval of the neuronal population after injury

OBJECTIVE

To review the consequences of mechanical injury to the brain with an emphasis on factors that may explain the variability of outcomes and how this might be influenced.

METHODS

Information regarding the pathophysiology of traumatic brain damage contained in original scientific reports and in review articles published in recent years was reviewed from the perspective of a clinical neurosurgeon and a neuropathologist, each with major research interests in traumatic brain damage. The information was compiled on the basis of the knowledge of and personal selection of articles that were identified through selective literature searches and current awareness profiles. A systematic literature review was not conducted.

RESULTS

Mechanical input affects neuronal and vascular elements and is translated into biological effects on the brain through a complex series of interacting cellular and molecular events. Whether these lead to permanent structural damage or to resolution and recovery is determined by the balance between processes that, on the one hand, mediate the effects of initial injury and subsequent secondary insults and, on the other, are manifestations of the brain's protective, reparative response. Experimental and clinical research has identified opportunities for altering the balance in a way that might promote recovery, but data demonstrating that this can lead to substantial clinical benefit are lacking. Recent evidence of genetically determined, individual susceptibility to the effects of injury may explain some of the puzzling variability in outcome after apparently similar insults and may also provide new opportunities for treatment.

CONCLUSION

The understanding of traumatic brain damage that is being gained from recent research is widening and broadening perspectives from the traditional focus on mechanical, vascular, and metabolic effects to encompass wider, neurobiological issues, drawn from the fields of neurodevelopment, neuroplasticity, neurodegeneration, and neurogenetics. Neurotrauma is a fascinating area of neuroscience research, with promise for the translation of knowledge to improved clinical management and outcome.

Soluble adhesion molecules in CSF are increased in children with severe head injury

Leukocyte-endothelial adhesion molecules, critical to the development of acute inflammation, are expressed in brain as part of the acute inflammatory response to traumatic brain injury (TBI). We measured the concentrations of the adhesion molecules P-selectin, ICAM-1, E-selectin, L-selectin, and VCAM-1 in ventricular cerebrospinal fluid (CSF) from children with severe TBI (Glasgow coma score < 8) and compared these findings with those from children with bacterial meningitis. P-selectin, an adhesion molecule associated with ischemia/reperfusion, was increased in children with TBI versus meningitis and control. Univariate and multivariate regression analyses demonstrated associations between CSF P-selectin and child abuse and age of < 4 years, and a significant, independent association between CSF intercellular adhesion molecule-1 (ICAM-1) and child abuse. These results are consistent with a specific acute inflammatory component to TBI in children. Future studies of secondary injury mechanisms and therapy after TBI should assess on the roles of P-selectin and ICAM-1 in injury and repair processes in brain after TBI.

Anaesthetic considerations for acute spinal cord injury

The recently published research data on the possible pathophysiology of acute spinal cord injury provide the basis of a number of exciting possibilities for its treatment. The present article reviews these lines of investigation. It focusses on methylprednisolone, which is the only effective proven therapy to limit secondary spinal cord injury known to date. In addition, the initial evaluation of patients with possible spinal cord trauma and airway management in patients with cervical spine injury are also discussed. Finally, the anaesthetic regimen in patients with these injuries is reviewed, showing that no anaesthetic agent or technique is superior to other anaesthetic methods.

Interleukin-10 improves outcome and alters proinflammatory cytokine expression after experimental traumatic brain injury

Traumatic injury to the central nervous system initiates inflammatory processes that are implicated in secondary tissue damage. These processes include the synthesis of proinflammatory cytokines, leukocyte extravasation, vasogenic edema, and blood-brain barrier breakdown. Interleukin-10 (IL-10), a cytokine with antiinflammatory properties, negatively modulates proinflammatory cascades at multiple levels. We examined the hypothesis that IL-10 treatment can improve outcome in a clinically relevant model of traumatic brain injury (TBI). IL-10 was administered via different routes and dosing schedules in a lateral fluid-percussion model of TBI in rats. Intravenous administration of IL-10 (100 micrograms) at 30 min before and 1 h after TBI improved neurological recovery and significantly reduced TNF expression in the traumatized cortex at 4 h after injury. Such treatment was associated with lower IL-1 expression in the injured hippocampus, and to a lesser extent, in the injured cortex. Subcutaneous IL-10 administration (100 micrograms) at 10 min, 1, 3, 6, 9, and 12 h after TBI also enhanced neurological recovery. In contrast, intracerebroventricular administration of IL-10 (1 or 6 micrograms) at 15 min, 2, 4, 6, and 8 h after TBI was not beneficial. These results indicate that IL-10 treatment improves outcome after TBI and suggest that this improvement may relate, in part, to reductions in proinflammatory cytokine synthesis.

Degeneration of spared axons following partial white matter lesion: implications for optic nerve neuropathies

Neuroprotective therapy is a relatively new development in the approach to the treatment of acute and chronic brain damage. Though initially viewed in the framework of acute CNS injuries, the concept was recently extended to include chronic injuries, in which at any given time there are some neurons in an acute phase of degeneration coexisting with others that are healthy, marginally damaged, or dead. The healthy neurons and those that are only marginally damaged are the potential targets for neuroprotection. For the development of neuroprotective therapies, it is essential to employ an animal model in which the damage resulting from secondary degeneration can be quantitatively distinguished from primary degeneration. This is of particular relevance when the site of the damage is in the white matter (nerve fibers) rather than in the gray matter (cell bodies). In the present work we reexamine the concepts of secondary degeneration and neuroprotection in white matter lesions. Using a partial crush injury of the adult rat optic nerve as a model, we were able to assess both primary and secondary nerve damage. We show that neurons whose axons were not damaged or only marginally damaged after an acute insult will eventually degenerate as a consequence of their existence in the degenerative environment produced by the injury. This secondary degeneration does not occur in all of the neurons at once, but affects them in a stepwise fashion related to the severity of the damage inflicted. These findings, which may be applicable to the progression of acute or chronic neuropathy, imply that neuroprotective therapy may have a beneficial effect even if there is a time lag between injury and treatment.

Chronic effects of traumatic brain injury on hippocampal vesicular acetylcholine transporter and M2 muscarinic receptor protein in rats

Experimental traumatic brain injury (TBI) produces cholinergic neurotransmission deficits that may contribute to chronic spatial memory deficits. Cholinergic neurotransmission deficits may be due to presynaptic alterations in the storage and release of acetylcholine (ACh) or from changes in the receptors for ACh. The vesicular ACh transporter (VAChT) mediates accumulation of ACh into secretory vesicles, and M2 receptors can modulate cholinergic neurotransmission via a presynaptic inhibitory feedback mechanism. We examined the effects of controlled cortical impact (CCI) injury on hippocampal VAChT and M2 muscarinic subtype receptor protein levels at four time points: 1 day, 1 week, 2 weeks, and 4 weeks following injury. Rats were anesthetized and surgically prepared for controlled cortical impact injury (4 m/s, 2.5- to 2.9-mm depth) and sham surgery. Animals were sacrificed and coronal sections (35 micro(m) thick) were cut through the dorsal hippocampus for VAChT and M2 immunohistochemistry. Semiquantitative measurements of VAChT and M2 protein in hippocampal homogenates from injured and sham rats were assessed using Western blot analysis. Immunohistochemistry showed no obvious changes in VAChT and M2 immunoreactivity at 1 day and 1 week postinjury. At 2 and 4 weeks postinjury, an increase in hippocampal VAChT protein and a corresponding loss of hippocampal M2 protein was observed compared to sham controls. Consistent with these results, Western blot analyses at 4 weeks postinjury demonstrated a 40-50% increase in VAChT and a 25-30% decrease in M2. These changes may represent a compensatory response of cholinergic neurons to increase the efficiency of ACh neurotransmission chronically after TBI, by upregulating the storage capacity and subsequent release of ACh and downregulating presynaptic inhibitory receptors.

Expression of c-Fos protein in the spinal cord after brachial plexus injury: comparison of root avulsion and distal nerve transection

OBJECTIVE

Clinical reports indicate poor outcomes for avulsion injuries, compared with more peripheral nerve damage. These two different injuries may both affect gene expression in spinal neurons, and the changes in gene expression may be related to the types of injuries.

METHODS

The brachial plexus of 48 adult male rats was lesioned by either root avulsion close to the spinal cord or distal nerve transection. The rats were quickly revived and remained awake until death at 30, 60, or 120 min after surgery. In rats with avulsive injuries, traumatic sites on the dorsal and ventral horns of the spinal cord were microscopically detected. Immunocytochemical analysis of the c-fos product was performed for the two experimental groups and for sham-treated control animals at the same survival times.

RESULTS

An increase in Fos-like immunoreactivity (FLI) in cells of the spinal cord, at levels C4-T1, was detected at 30 min after nerve transection or root avulsion. The number of FLI-positive cells continued to increase at 60 and 120 min after the nerve injury (P=0.001). FLI-positive cells were compared at the C7 level, in laminae 1 and 2, 3 and 4, and 5 to 10, after the two injuries and were found to be more abundant after the avulsive injury (P=0.0001); furthermore, the number of FLI-positive cells increased with time (P=0.001). In a comparison of all levels, both experimental groups demonstrated significantly greater numbers of FLI-positive cells than did controls, and the group with nerve root avulsion showed significantly (P=0.0001) more FLI-positive cells than did the group with distal nerve transection.

CONCLUSION

These results suggest that nerve root avulsion from the spinal cord leads to increased and prolonged expression of c-fos and, potentially, greatly increased transcription of new messages for recovery, survival, or cell death.

Structural alterations and changes in cytoskeletal proteins and proteoglycans after focal cortical ischemia

In order to study structural alterations which occur after a defined unilateral cortical infarct, the hindlimb region of the rat cortex was photochemically lesioned. The infarcts caused edema restricted to the perilesional cortex which affected allocortical and isocortical areas differently. Postlesional changes in cytoskeletal marker proteins such as microtubule-associated protein 2, non-phosphorylated (SMI32) and phosphorylated (SMI35, SMI31 and 200,000 mol. wt) neurofilaments and 146,000 mol. wt glycoprotein Py as well as changes in proteoglycans visualized with Wisteria floribunda lectin binding (WFA) were studied at various time points and related to glial scar formation. The results obtained by the combination of these markers revealed six distinct regions in which transient, epitope-specific changes occurred: the core, demarcation zone, rim, perilesional cortex, ipsilateral thalamus and contralateral homotopic cortical area. Within the core immunoreactivity for microtubule-associated protein 2 and SMI32 decreased and the cellular components showed structural disintegration 4 h post lesion, but partial recovery of somatodendritic staining was seen after 24 h. Microtubule-associated protein 2 and SMI32 persisted up to days 7 and 5 respectively in the core, whereas the number of glial fibrillary acidic protein- and WFA-positive cells decreased between days 7 and 14. The demarcation zone showed a dramatic loss of immunoreactivity for all epitopes 4 h post lesion which was not followed by a phase of recovery. In the inner region of the demarcation zone there was an invasion and accumulation of non-neuronal WFA-positive cells which formed a tight capsule around the core. Neuronal immunoreactivities for microtubule-associated protein 2, SMI31 and Py as well as astrocytic glial fibrillary acidic protein increased strongly within an approximately 0.4-1.0 mm-wide rim region directly bordering the demarcation zone. Py immunoreactivity increased significantly in the perilesional cortex, whereas glial fibrillary acidic protein-positive astrocytes became transiently more numerous in the entire lesioned hemisphere including strongly enhanced immunoreactivity in the thalamus by days 5-7 post lesion. Glial fibrillary acidic protein immunoreactivity increased in the corpus callosum and the homotopic cortical area of the unlesioned hemisphere by days 5-7. In this homotopic area additional changes in SMI31 immunoreactivity occurred. Our results showed that a cortical infarct is not only a locally restricted lesion, but leads to a variety of cytoskeletal and other structural changes in widely-distributed functionally-related areas of the brain.

72-kDa heat shock protein and mRNA expression after controlled cortical impact injury with hypoxemia in rats

As part of the stress response, the 72 kDa heat shock protein (hsp72) is induced in neurons after ischemic and traumatic brain injury (TBI). To examine the stress response after TBI with secondary insult, we examined the regional and cellular expression of hsp72 mRNA and protein after controlled cortical impact (CCI) injury with secondary hypoxemia and mild hypotension in rats. Rats were killed at 6, 8, 24, 72, or 168 h after trauma. Naive and sham-operated rats were used as controls. Brains were removed, and in situ hybridization (n = 2/group), immunocytochemistry (n = 4/group), and Western blot analysis (n = 3 to 5/group) for hsp72 was performed. Hsp72 mRNA was expressed in neurons in the ipsilateral cortex, CA3 region of the hippocampus, hilus, and dentate gyrus at 6 h. Hsp72 mRNA was expressed primarily in the ipsilateral cortex, at 24 h, and by 72 h hsp72 mRNA expression returned to near basal levels. Hsp72 protein was seen in ipsilateral cortical neurons, hilar neurons, and neurons in the medial aspect of the CA3 region of the hippocampus (CA3-c) at 24 h. At 72 h, hsp72 immunoreactivity was reduced versus 24 h in these same regions, but it was increased versus baseline. Western blot analysis confirmed an increase in hsp72 protein in the ipsilateral cortex. The regional pattern of hsp72 mRNA induction in neurons was similar to the pattern of protein expression after CCI, with the exceptions that hsp72 mRNA, but not protein, was expressed in the dentate gyrus and the lateral aspect of the CA3 region of the hippocampus (CA3-a). The stress response, as detected by hsp72 expression, is induced in some neurons in some regions that are selectively vulnerable to delayed neuronal death in this model of TBI. The failure to translate some proteins including hsp72 may be associated with delayed neuronal death in certain hippocampal regions after TBI.

Neuroprotective effects of group III mGluR in traumatic neuronal injury

We have used an in vitro trauma model to examine the effects of modulation of group III metabotropic glutamate receptors (mGluR) on post-traumatic neuronal cell death. Rat cortical neuronal/glial cultures were subjected to standardized mechanical injury using a punch that delivers 28 parallel cuts to 96-well culture plates, resulting in approximately 50% neuronal cell loss in untreated cultures. RT-PCR demonstrated expression of mRNA for mGluR4, mGluR6, mGluR7, and mGluR8 in uninjured cultures as well as in adult rat brain. Treatment with the group III agonists L-(+)-2-amino-4-phosphonobutyric acid (L-AP4) or L-serine-O-phosphate (L-SOP) resulted in dose-dependent neuroprotection. In contrast, treatment with the group III antagonists alpha-methyl-AP4 (MAP4) or (RS)-alpha-methylserine-O-phosphate (MSOP) caused dose-dependent exacerbation of injury, which was significantly attenuated by L-AP4 or L-SOP. The neuroprotective actions of L-AP4 or L-SOP were markedly reduced by the cyclic AMP analog 8-CPT-cAMP (500 microm), which by itself had no effects at this concentration. Moreover, treatment with L-AP4 or L-SOP reduced basal cyclic AMP levels. Treatment with the NMDA antagonist MK 801 decreased post-traumatic cell death by 45% at optimal concentrations; combined treatment with MK 801 and group III agonists showed a significant enhancement of neuroprotection as compared to treatment with the NMDA antagonist alone. Our findings indicate a clear neuroprotective action for group III agonists in this model and suggest that group III mGluR are endogenously activated in response to trauma. The neuroprotective effects of group III agonists appear to result in part from modulation of adenylyl cyclase activity and are additive to those of an NMDA receptor antagonist.