Interleukin-8 released into the cerebrospinal fluid after brain injury is associated with blood-brain barrier dysfunction and nerve growth factor production

Role of chemokines in CNS health and pathology: a focus on the CCL2/CCR2 and CXCL8/CXCR2 networks

Chemokines and their receptors have crucial roles in the trafficking of leukocytes, and are of particular interest in the context of the unique immune responses elicited in the central nervous system (CNS). The chemokine system CC ligand 2 (CCL2) with its receptor CC receptor 2 (CCR2), as well as the receptor CXCR2 and its multiple ligands CXCL1, CXCL2 and CXCL8, have been implicated in a wide range of neuropathologies, including trauma, ischemic injury and multiple sclerosis. This review aims to overview the current understanding of chemokines as mediators of leukocyte migration into the CNS under neuroinflammatory conditions. We will specifically focus on the involvement of two chemokine networks, namely CCL2/CCR2 and CXCL8/CXCR2, in promoting macrophage and neutrophil infiltration, respectively, into the lesioned parenchyma after focal traumatic brain injury. The constitutive brain expression of these chemokines and their receptors, including their recently identified roles in the modulation of neuroprotection, neurogenesis, and neurotransmission, will be discussed. In conclusion, the value of evidence obtained from the use of Ccl2- and Cxcr2-deficient mice will be reported, in the context of potential therapeutics inhibiting chemokine activity which are currently in clinical trial for various inflammatory diseases.

Pediatric brain trauma outcome prediction using paired serum levels of inflammatory mediators and brain-specific proteins

Many potential brain trauma biomarkers have been reported, but no previous study has described outcome prediction using combinations of biomarker levels. We aimed to investigate the outcome predictive values of multiple biomarkers from different mediator families and to determine whether combinations of two serum biomarkers may achieve higher outcome predictive values than individual biomarker levels. A prospective observational study was conducted involving 28 children requiring intensive care management following brain trauma. Day 1 post-injury serum concentrations of eight different biomarkers--S100b protein (S100b), neuron-specific enolase (NSE), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), soluble intracellular adhesion molecule (SICAM), L-selectin, and endothelin--were quantified using enzyme-linked immunosorbent assay (ELISA). Global outcome was assessed at 6 months post-injury using the Glasgow Outcome Score (GOS). Receiver operator characteristic curve (ROC) analysis and its multivariate extension, Multivariate ROC (MultiROC), were used to assess the outcome predictive values of the individual and the paired biomarkers. None of the eight biomarkers assessed individually achieved an area under the ROC curve (AUC) of more than 0.95 for predicting unfavorable outcome, but five of the 20 biomarker pairs assessed had this high degree of outcome predictability. Two combinations using S100b as the "screening marker" and either L-selectin or IL-6 as the "varying marker" achieved an AUC of 0.98, and their specificity and sensitivity for unfavorable outcome prediction were 96% and 100%, respectively. Prognostic pairs combining serum levels of two biomarkers (inflammatory mediators and brain-specific proteins) offer better outcome predictive values for unfavorable outcome after childhood brain trauma than may be achieved using individual marker levels.

The temporal expression, cellular localization, and inhibition of the chemokines MIP-2 and MCP-1 after traumatic brain injury in the rat

The expression of the neutrophil chemokine macrophage inflammatory protein-2 (MIP-2/CXCL2) and the monocyte chemokine monocyte chemotactic protein-1 (MCP-1/CCL2) have been described in glial cells in vitro but their origin following TBI has not been established. Furthermore, little is known of the modulation of these chemokines. Chemokine expression was investigated in male Sprague-Dawley rats following moderate lateral fluid percussion injury (LFPI). At 0, 4, 8, 12, and 24 h after injury, brains were harvested and MIP-2/CXCL2 and MCP-1/CCL2 levels measured by ELISA. To investigate the inhibition of chemokine expression a second cohort of animals received dexamethasone (1-15mg/kg), FK506 (1mg/kg), or vehicle, systemically, immediately after injury. These animals were sacrificed at the time of peak chemokine expression. A third cohort of animals was also sacrificed at the time of peak chemokine expression and immunohistochemistry performed for MIP-2/CXCL2 and MCP-1/CCL2. Following LFPI, chemokines were increased in the ipsilateral hemisphere, MIP-2/CXCL2 peaking at 4 h and MCP-1/CCL2 peaking at 8-12 h post-injury. Dexamethasone significantly reduced cortical MCP-1/CCL2, but not MIP-2/CXCL2 concentrations. FK506 did not inhibit chemokine expression. In undamaged brain, chemokine expression was localized to cells with a neuronal morphology. For MIP-2/CXCL2 this was supported by double staining for the neuronal antigen NeuN. In contused tissue, increased MIP-2/CXCL2 and MCP-1/CCL2 staining was visible in cells with the morphology of degenerating neurons. MIP-2/CXCL2 and MCP-1/CCL2 are increased after injury, and neurons appear to be the source of this expression. Chemokine expression was selectively inhibited by dexamethasone. The implications of this are discussed.

Serum IL-8 and MCP-1 concentration do not identify patients with enlarging contusions after traumatic brain injury

BACKGROUND

Cerebral contusions contain numerous leukocytes, and a temporal relationship exists among cerebral chemokine expression, leukocyte recruitment, and contusion enlargement. This would suggest a role for chemokines in contusion development. However, it has not been established if serum concentrations of chemokines such as interleukin-8 (IL-8) or monocyte chemoattractant protein-1 (MCP-1) change with contusion enlargement.

METHODS

Eighteen adult patients with severe contusional traumatic brain injury, on computerized tomography, were identified. Patients with diffuse injuries or extradural and subdural hematomas associated with mass effect were not included in the study. Daily serum samples were taken for the measurement of IL-8 and MCP-1 concentrations for up to 11 days postinjury.

RESULTS

In the patients who died while in intensive care, IL-8 and MCP-1 were significantly greater than in those patients discharged (18 [0-202] vs. 0 [0-156] pg/mL and 498 [339-1,063] vs. 368 [86-11,289] pg/mL for IL-8 and MCP-1, respectively). No difference was seen in serum chemokine levels in patients who deteriorated with contusion enlargement compared with those that did not. The IL-8 and MCP-1 concentrations did not change significantly over time either in the group as a whole or in the subgroup of patients who deteriorated.

CONCLUSIONS

These inflammatory mediators may be predictive of a poor outcome in patients with traumatic brain injury in which contusions are the predominant abnormality. However, they do not distinguish those patients who will deteriorate because of contusion enlargement.

Interleukin-6 and nerve growth factor upregulation correlates with improved outcome in children with severe traumatic brain injury

Secondary brain damage after traumatic brain injury (TBI) involves neuro-inflammatory mechanisms that are mainly dependent on the intracerebral production of cytokines. Interleukin-6 (IL-6) may have a role both in the pathogenesis of neuronal damage and in the recovery mechanisms of injured neurons through the modulation of nerve growth factor (NGF) biosynthesis. However, the relationship between IL-6 and NGF expression and the severity and outcome of TBI remains controversial. We have conducted a prospective observational clinical study to determine whether the concentration of IL-6 and NGF in the cerebrospinal fluid (CSF) of children with TBI correlates with the severity of the injury and neurologic outcome of patients. CSF samples were collected from 29 children at 2 h (time T1) and 48 h (time T2) after severe TBI, and from 31 matched controls. TBI severity was evaluated by Glasgow Coma Scale (GCS) and neurologic outcome by Glasgow Outcome Score (GOS). CSF concentrations of IL-6 and NGF were measured by immunoenzymatic assays. Early NGF concentrations (T1) correlated significantly with head injury severity, whereas no correlation was found between GCS and IL-6. Furthermore, IL-6 and NGF upregulation after injury was associated with better neurologic outcomes. Based on these findings, we posit that NGF expression is a useful marker of brain damage following severe TBI. Moreover, the early upregulation of both IL-6 and NGF, which correlates with a favorable neurologic outcome, may reflect an endogenous attempt at neuroprotection in response to the damaging biochemical and molecular cascades triggered by traumatic insult.

Early versus late onset of multiple organ failure is associated with differing patterns of plasma cytokine biomarker expression and outcome after severe trauma

Although multiple organ failure (MOF) remains the leading cause of death after trauma, the pathogenic cellular and molecular mechanisms underlying MOF are poorly understood. In addition to proinflammatory and anti-inflammatory mediator cascades, the temporal onset of MOF has generated recent interest because the organ systems involved into MOF seem to deteriorate in a time-dependent fashion after trauma. We therefore investigated the temporal course of MOF in traumatized human patients and evaluated and compared the distribution patterns of cytokine expression, including interleukin (IL) 6, IL-8, IL-10, and the soluble tumor necrosis factor-[alpha] receptors sTNF-R p55 and sTNF-R p75 in early-onset versus late-onset MOF. In addition, we analyzed the predictive value of cytokine biomarkers of MOF and lethal outcome. In a prospective observational cohort study conducted at three trauma centers, all patients (n = 352) admitted to two level 1 trauma centers in Germany were enrolled in the study based on the following inclusion criteria: severe traumatic brain injury (TBI) with a Glasgow Coma Scale (GCS) score of 8 or lower and/or distinct changes in cranial computed tomography and/or multiple injuries (MT) to the body (at least two regions had Abbreviated Injury Scale score of 3 or higher). The incidence of MOF was evaluated using the modified Goris-MOF score. The temporal onset of MOF was divided into early-onset MOF (EMOF, developing on days 0-3), late-onset MOF (LMOF, developing on days 4-10), combined early-onset and late-onset MOF (CMOF), and patients never showing signs of MOF during the observation period. In addition, the levels of the serum cytokine markers IL-6, IL-8, IL-10, sTNF-R p55, and sTNF-R p75 were analyzed at specific posttraumatic time points using established enzyme-linked immunosorbent assay techniques. A total of 352 patients (274 men and 78 women; TBI, 101; TBI + MT, 125; MT, 126) were enrolled into the study. Patients assigned to the EMOF group showed specific disruption of pulmonary and cardiocirculatory function, whereas LMOF was significantly associated with hepatic failure. The patients without signs of MOF and the EMOF patients had the same risk of lethal outcome (8.2% vs. 7.5%); LMOF and CMOF were found to be associated with a 3- to 4-fold increase in mortality (38.5% vs. 30.6%, respectively). Analysis of cytokine serum biomarkers revealed that patients with LMOF showed a biphasic elevation of IL-6 and significantly higher sTNF-R concentrations than did all other subgroups (P < 0.001). In addition, the initial values (days 0-1) of sTNF-R p55 and sTNF-R p75 expression levels had a good predictive capacity for the development of LMOF (p55, 0.75; p75, 0.72); values greater than 0.65 were accepted to have a predictive capacity. These results demonstrate that mortality differs significantly between the development of EMOF and LMOF after traumatic injury. Our results also suggest that serum cytokine measurements may be important early biochemical markers for predicting the development of delayed MOF.

Nerve growth factor expression correlates with severity and outcome of traumatic brain injury in children

BACKGROUND

Secondary brain damage after traumatic brain injury (TBI) involves neuro-inflammatory mechanisms, mainly dependent on the intracerebral production of cytokines. In particular, interleukin 1beta (IL-1beta) is associated with neuronal damage, while interleukin 6 (IL-6) exerts a neuroprotective role due to its ability to modulate neurotrophins biosynthesis. However, the relationship between these cytokines and neurotrophins with the severity and outcome of TBI remains still controversial.

AIMS

To determine whether the concentration of IL-1beta and IL-6 and neurotrophins (nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF)) in the cerebrospinal fluid (CSF) of children with TBI correlates with the severity of the injury and its neurologic outcome.

METHODS

Prospective observational clinical study in a university hospital. CSF samples were collected from 27 children at 2h (Time T1) and 48 h (Time T2) after severe TBI, and from 21 matched controls. Severity of TBI was evaluated by GCS and neurologic outcome by GOS. CSF concentrations of cytokines and neurotrophins were measured by immunoenzymatic assays.

RESULTS

Early NGF and IL-1beta concentrations (T1) correlated significantly with the severity of head injury, whereas no correlation was found for IL-6, BDNF, and GDNF. Furthermore, higher NGF and IL-6 and lower IL-1beta expression at T2 were associated with better neurologic outcomes. No significant association was found between BDNF or GDNF expression and neurologic outcome.

CONCLUSIONS

NGF concentration in CSF is a useful marker of brain damage following severe TBI and its up-regulation, in the first 48 h after head injury together with lower IL-1beta expression, correlates with a favorable neurologic outcome. Clinical and prognostic information may also be obtained from IL-6 expression.

Multiplex assessment of cytokine and chemokine levels in cerebrospinal fluid following severe pediatric traumatic brain injury: effects of moderate hypothermia

This study performed a comprehensive analysis of cerebrospinal fluid (CSF) cytokine levels after severe traumatic brain injury (TBI) in children using a multiplex bead array assay and to evaluate the effects of moderate hypothermia on cytokine levels. To this end, samples were collected during two prospective randomized controlled trials of therapeutic moderate hypothermia in pediatric TBI. Thirty-six children with severe TBI (Glasgow Coma Scale [GCS] score of <or=8) and 10 children with negative diagnostic lumbar punctures. All children with TBI had continuous monitoring of intracranial pressure and CSF drainage via an intraventricular catheter. Moderate hypothermia (32-33 degrees C) was maintained for 48 h in 17 patients, and they were slowly re-warmed at 48-72 h. A multiplex bead array assay was used to analyze serial CSF samples (<18 h, 24 +/- 6 h, 48 +/- 6 h, and 72 +/- 6 h) for 21 pro-and anti-inflammatory cytokines and chemokines. Interleukin (IL)-8 and transforming growth factor beta were measured by enzyme-linked immunosorbant assay (ELISA). There was a strong correlation (Spearman correlation coefficient = 0.92, p < 0.001) between multiplex assay and ELISA for IL-8. Pro-inflammatory IL-1beta, -6 and -12p70, anti-inflammatory IL-10 and chemokines IL-8 and MIP-1alpha were increased after TBI compared to controls, p < 0.05; however, there was no association between cytokines and age, gender, initial GCS, or outcome. Hypothermia did not attenuate the increases in CSF cytokine levels after TBI versus normothermia. This investigation confirmed that the multiplex bead array assay is a useful method to measure CSF cytokine levels. Severe TBI in infants and children induces increases in pro- and anti-inflammatory cytokines and chemokines. It is the first clinical report of increased levels of MIP-1alpha after TBI in any patient population and the most comprehensive assessment of cytokines after TBI to date. Moderate therapeutic hypothermia did not attenuate the increase in CSF cytokine levels in children after TBI.

Modulation of immune response by head injury

Despite the fact that traumatic brain injury (TBI) is a silently growing epidemic, we are yet to understand its multifaceted pathogenesis, where various cellular pathways are initiated in response to both the primary mechanical insult and secondary physiologically mediated injury. Although the brain has traditionally been considered an immunologically privileged site, evidence to the contrary exists in studies of central nervous system (CNS) pathology, in particular TBI. Transmigration of leukocytes following blood brain barrier (BBB) disruption results in activation of resident cells of the CNS, such as microglia and astrocytes, to possess immunological function. Both infiltrating peripheral immune cells and activated resident cells subsequently engage in the intrathecal production of cytokines, important indicators of the presence of neuroinflammation. Cytokines can either promote this neurotoxicity, by encouraging excitotoxicity and propagating the inflammatory response, or attenuate the damage through neuroprotective and neurotrophic mechanisms, including the induction of cell growth factors. Certain cytokines perform both functions, for example, interleukin-6 (IL-6). This review article discusses the notion that the inflammatory response to TBI is no longer a peripherally mediated phenomenon, and that the CNS significantly influences the immunological sequence of events in the aftermath of injury.

Reliability of S100B in predicting severity of central nervous system injury

S100B is a protein biomarker that reflects CNS injury. It can be measured in the CSF or serum with readily available immunoassay kits. The excellent sensitivity of S100B has enabled it to confirm the existence of subtle brain injury in patients with mild head trauma, strokes, and after successful resuscitation from cardiopulmonary arrest. The extent of S100B elevation has been found to be useful in predicting clinical outcome after brain injury. Elevations of S100B above certain threshold levels might be able to reliably predict brain death or mortality. A normal S100B level reliably predicts the absence of significant CNS injury. The specificity of S100B levels as a reflection of CNS injury is compromised by the findings that extra-cranial injuries can lead to elevations in the absence of brain injury. This potential problem can most likely be avoided by measuring serial S100B levels along with other biomarkers and carefully noting peripheral injuries. Serum markers GFAP and NSE are both more specific for CNS injury and have little to no extra-cranial sources. Sustained elevations of S100B over 24 h along with elevations of GFAP and NSE can more reliably predict the extent of brain injury and clinical outcomes. In the future, S100B measurements might reliably predict secondary brain injury and enable physicians to initiate therapeutic interventions in a timelier manner. S100B levels have been shown to rise hours to days before changes in ICP, neurological examinations, and neuroimaging tests. S100B levels may also be used to monitor the efficacy of treatments.

[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.

Interleukin-8 production from human umbilical vein endothelial cells during brief hyperglycemia: the effect of tumor necrotic factor-alpha

BACKGROUND

This study evaluated the changes in chemokine interleukin (IL)-8 production from endothelial cells under various hyperglycemic conditions and investigated whether the hyperglycemia associated with the acute inflammatory response could enhance the IL-8 production from the endothelial cells.

MATERIALS AND METHODS

Human umbilical endothelial cells (HUVECs) were seeded at a concentration of 1 x 10(5) cells/well and cultured. The culture medium was replaced with Medium 199 containing various concentrations of glucose (final glucose concentration of culture medium was 100, 200, 300, 400, 500 mg/dL; n = 7 each) with or without 100 ng of tumor necrosis factor-alpha (TNF-alpha). After 12 or 24 h at 37 degrees C, the supernatants were collected from the cultures and stored at -80 degrees C until cytokine assay. IL-8 levels of the samples from the supernatants were quantified using a commercially available enzyme-linked immunosorbent assay kit.

RESULTS

The IL-8 production by the HUVECs was significantly higher in the high glucose culture than in the control culture (glucose concentration of 100 mg/dL) (P < 0.05). Moreover, the hyperglycemia associated with elevated TNF-alpha was found to enhance the level of IL-8 production by the HUVECs cultured at all glucose concentrations and over both time courses, compared to the control (P < 0.05).

CONCLUSIONS

In this study we observed a significant augmentation of IL-8 production by endothelial cells during short-term hyperglycemia, and a similar but significantly stronger augmentation was obtained through TNF treatment. These findings suggest that the hyperglycemia associated with acute inflammatory response after trauma may put the patients at high risk for secondary tissue damage.

Biphasic elevation in cerebrospinal fluid and plasma concentrations of endothelin 1 after traumatic brain injury in human patients

Severe traumatic brain injury (TBI) is characterized by a high mortality and poor outcome. The pathomechanisms involved are cytokine-mediated proinflammatory and anti-inflammatory reactions and significant cerebral microcirculatory disorders. The role of endothelin 1 (ET-1), a very potent vasoconstrictive peptide, in the deterioration of cerebral perfusion after trauma is still unclear. The presented study investigated the changes in ET-1 in the cerebrospinal fluid (CSF) and plasma after TBI in humans, with special regard to the presence of subarachnoid hemorrhage (SAH) and clinical outcome. Twenty patients with TBI were consecutively enrolled into the study, 10 patients without SAH (TBI group) and 10 patients with SAH (TBI-H group). Paired samples of plasma and CSF were collected for 10 days after trauma. Analysis of the ET-1 concentrations showed that TBI is associated with initially increased ET-1 values in plasma (TBI, day 1; TBI-H, days 2-3) and significantly increased (P < 0.05, vs. control) CSF concentrations (TBI, days 1-2; TBI-H, days 1-3) in the first days after trauma. In the further time course, ET-1 values declined in both groups, reaching reference values in plasma. The CSF values remained significantly (P < 0.05 vs. control) elevated. Both groups showed a second peak on the beginning of the second week after trauma in plasma and CSF. Whereas plasma concentrations failed to reach significance, CSF values showed a significant peak on day 7 in both groups. The TBI-H patients had significantly (P < 0.05) higher values in the secondary peak compared with patients of the TBI group. The kinetics of traumatic SAH-dependent ET-1 needs to be assessed in further investigations.

Effect of time, injury, age and ethanol on interpatient variability in valproic acid pharmacokinetics after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) results in an increase in hepatic metabolism. The increased metabolism is in significant contrast to a large body of in vitro and in vivo data demonstrating that activation of the host-defence response downregulates hepatic metabolism. Theoretically, this occurs because of activation of the pro-inflammatory cytokines tumour necrosis factor-alpha, interferon-gamma, interleukin (IL)-1 and IL-6. As part of a large double-blind, placebo-controlled clinical trial evaluating the use of valproic acid for prophylaxis of post-traumatic seizures, we obtained extensive valproic acid concentration-time data. Valproic acid is a hepatically metabolised, low extraction-ratio drug. Therefore, unbound clearance (CL(u)) is equal to intrinsic or metabolic clearance.

OBJECTIVE

The objective of this study was to evaluate the time-dependent effects of TBI on the pharmacokinetics of total and unbound valproic acid with the goal of identifying patient factors that may predict changes in total clearance (CL) and CL(u). In addition, by determining the factors that influence the magnitude and time course of induction of hepatic metabolism and understanding their interaction with the host-defence mediators, we can further our insight into the mechanism(s) responsible for the changes in CL and CL(u).

STUDY DESIGN

Valproic acid plasma concentration data were obtained from 158 TBI patients. Unbound valproic acid plasma concentrations were estimated using total valproic acid plasma and albumin concentrations following a Scatchard equation binding model previously developed in a subset of TBI patients. The effect of 13 patient factors on CL and CL(u) was evaluated initially in a univariate analysis. The significant factors were then included in a multiple linear regression analysis by use of step-wise selection and forward selection procedures.

RESULTS

CL and CL(u) were significantly increased after TBI in a time-dependent manner. The average increase was >75% by weeks 2 and 3 post-injury. The magnitude of the induction of CL was increased with decreased albumin concentrations, in addition to the presence of ethanol on admission, increased severity of head injury, tube feeding and total parenteral nutrition (TPN). The magnitude of induction of CL(u) was increased by older age, presence of ethanol on admission, increased severity of head injury, tube feeding, TPN, and if the patient had a post-injury neurosurgical procedure. The time to normalisation of CL(u) was significantly longer in patients with head injury plus other injuries compared with those with head injury alone.

CONCLUSIONS

As has been reported with other drugs, TBI results in a significant increase in the metabolism of valproic acid. The patient factors identified in this study that resulted in an increase in the magnitude and time course of the induction of CL(u) (ethanol, older age, presence of a neurosurgical procedure, severity of TBI and presence of multiple non-TBI injuries) have all been reported to cause a shift to the anti-inflammatory mediators IL-4 and IL-10. This suggests that the increase in hepatic metabolism after TBI may be due to the increased presence of anti-inflammatory mediators in contrast to the inhibition effect of the pro-inflammatory mediators in non-TBI inflammation and infection.

Trauma-associated inflammatory response impairs embryonic stem cell survival and integration after implantation into injured rat brain

Pluripotent embryonic stem cells were shown to survive and differentiate into mature neuronal cells after implantation in experimental models of Parkinson disease and cerebral ischemia. Embryonic stem cell transplantation has also been proposed as a potential therapy for cerebral trauma, characteristic of massive loss of multiple cell types due to primary insult and secondary sequelae. Green fluorescent protein (GFP)-transfected murine embryonic stem cells were implanted into the ipsi or contralateral cortex of male Sprague-Dawley rats 72 h after fluid-percussion injury. Animals were sacrificed at day 5 or week 7 postimplantation. Brain sections were examined using conventional and fluorescent double-labelling immunohistochemistry. Five days after implantation, clusters of GFP-positive cells undergoing partial differentiation along neuronal pathway, were detected at the implantation site. However, after 7 weeks, only a few GFP-positive cells were found, indicating an extensive loss of stem cells during this time period. For the first time, we proved the observed cell loss to be mediated via phagocytosis of implanted cells by activated macrophages. Cerebral trauma, induced 3 days prior to implantation, has activated the inflammatory potential of otherwise immunologically privileged tissue. Subsequent cell implantation was accompanied by reactive astrogliosis, activation of microglia, as well as a massive invasion of macrophages into transplantation sites even if the grafts were placed into contralateral healthy hemispheres, remote from the traumatic lesion. Our results demonstrate a significant post-traumatic inflammatory response, which impairs survival and integration of implanted stem cells and has generally not been taken into account in designs of previous transplantation studies.

Plasma interleukin-8 as a potential predictor of mortality in adult patients with severe traumatic brain injury

Because of complex pathophysiology and severe consequences, traumatic brain injuries (TBI) are an important medical problem. Pathophysiology of TBI includes local and systemic stress response, in which interleukin-8 (IL-8) is considered as a key mediator of neuroinflammation. However, prognostic relevance of IL-8 measurement in adult patients with severe TBI is not certain. Therefore, IL-8 was determined in blood samples from central venous and jugular bulb catheter and in cerebrospinal fluid of twenty patients with isolated TBI at admission to Intensive Care Unit. None of the patients had history of stroke, dementia, autoimmune diseases, acute infection or medication with anti-inflammatory drugs. Ten patients died due to traumatic brain injury, while the other ten recovered well. While there was no significant difference of IL-8 levels in cerebrospinal fluid between survivors and nonsurvivors, central venous plasma level of IL-8 was significantly lower in survivors (71.00 +/- 14.17 pg/ml), than in nonsurvivors (111.26 +/- 16.9 pg/ml). Receiver Operating Characteristic (ROC) analysis revealed significant prognostic value for IL-8 in the blood as well as for the age of patients, Glasgow Coma Scale (GCS) and Acute Physiologic and Chronic Health Evaluation (APACHE II). These findings suggest that the central venous plasma values of IL-8 at admission might be an early predictive marker in patients with severe TBI, comparative to standard clinical prognostic markers such as APACHE II and GCS.

Time-dependent changes in donor brain death related processes

Donor brain death (BD) affects kidney function and survival after transplantation. Studies on brain dead kidney donors indicate that, besides inflammation and coagulation, cytoprotective gene expression is activated as well. Here, we evaluated in a time-course experiment progression of these renal BD-related processes. Animals were sacrificed 0.5, 1, 2 or 4 h after BD and compared to sham-operated controls. Proinflammatory genes (E-selectin, MCP-1, II-6) were massively up-regulated (p < 0.05) already 0.5 h after BD. Inducers of proinflammatory gene expression were either activated (NF-kappaB) or induced in expression (Egr-1) after 0.5 h of BD. Increased numbers of infiltrating granulocytes were seen in the interstitium from 0.5 h on. Also, expression of protective genes HO-1 and HSP70 were increased within 0.5 h. Remarkably, reactive oxygen species formation was detectable only in the later phase of BD. Among 14 measured serum cytokines, MCP-1 and KC-protein were significantly elevated from 0.5 h on. In conclusion, a fast induction of proinflammatory and stress-induced protective processes in brain dead donor kidneys was demonstrated, probably triggered by changes occurring during BD induction. Importantly, hypoxia appeared not to be one of the initial triggers, and early increased systemic levels of chemokines MCP-1 and KC may be regarded as the starting point for the inflammatory cascade in brain dead donor kidneys.

Systemic effects of severe trauma on the function and apoptosis of human skeletal cells

Systemic factors are believed to be pivotal for the development of heterotopic ossification in severely-injured patients. In this study, cell cultures of putative target cells (human fibroblastic cells, osteoblastic cells (MG-63), and bone-marrow stromal cells (hBM)) were incubated with serum from ten consecutive polytraumatised patients taken from post-traumatic day 1 to day 21 and with serum from 12 healthy control subjects.

The serum from the polytraumatised patients significantly stimulated the proliferation of fibroblasts, MG-63 and of hBM cells. The activity of alkaline phosphatase in MG-63 and hBM cells was significantly decreased when exposed to the serum of the severely-injured patient. After three weeks in 3D cell cultures, matrix production and osteogenic gene expression of hBM cells were equal in the patient and control groups. However, the serum from the polytraumatised patients significantly decreased apoptosis of hBM cells compared with the control serum (4.3% vs 19.1%, p = 0.031).

Increased proliferation of osteoblastic cells and reduced apoptosis of osteoprogenitors may be responsible for increased osteogenesis in severely-injured patients.

Hippocampal vulnerability following traumatic brain injury: a potential role for neurotrophin-4/5 in pyramidal cell neuroprotection

Traumatic brain injury (TBI) causes selective hippocampal cell death, which is believed to be associated with cognitive impairment observed both in clinical and experimental settings. Although neurotrophin administration has been tested as a strategy to prevent cell death following TBI, the potential neuroprotective role of neurotrophin-4/5 (NT-4/5) in TBI remains unknown. We hypothesized that NT-4/5 would offer neuroprotection for selectively vulnerable hippocampal neurons following TBI. Measurements of NT-4/5 in rats subjected to lateral fluid percussion (LFP) TBI revealed two-threefold increases in the injured cortex and hippocampus in the acute period (1-3 days) following brain injury. Subsequently, the response of NT-4/5 knockout (NT-4/5(-/-)) mice to controlled-cortical impact TBI was investigated. NT-4/5(-/-) mice were more susceptible to selective pyramidal cell loss in Ahmon's corn (CA) subfields of the hippocampus following TBI, and showed impaired motor recovery when compared with their brain-injured wild-type controls (NT-4/5(wt)). Additionally, we show that acute, prolonged administration of recombinant NT-4/5 (5 microg/kg/day) prevented up to 50% of the hippocampal CA pyramidal cell death following LFP TBI in rats. These results suggest that post-traumatic increases in endogenous NT-4/5 may be part of an adaptive neuroprotective response in the injured brain, and that administration of this neurotrophic factor may be useful as a therapeutic strategy following TBI.

Apoptosis of neuronal cells induced by serum of patients with acute brain injury: a new in vitro prognostic model

OBJECTIVE

To investigate whether serum draining from the jugular bulb of patients with traumatic or haemorrhagic brain injury induced apoptosis of neuronal PC12 cells in vitro and whether the apoptotic rate correlated with patients' outcome at 6 months.

DESIGN AND SETTING

Prospective clinical investigation in a 21-bed intensive care unit (ICU) in a university hospital.

PATIENTS

Seventy patients who had suffered from acute brain injury requiring intensive care.

INTERVENTIONS

Jugular bulb vein and systemic samples were obtained on admission to the ICU and after 48 h. PC12 cells were incubated in the presence of 10% of heat-inactivated patient's sera and apoptotic rate was determined by flow cytometry using annexin V and 7-aminoactinomycin D.

RESULTS

Regional serum draining from the lesions induced higher early apoptosis of PC12 cells than systemic serum. Early apoptotic rate, Glasgow coma score, APACHE II score and the presence of pupil abnormalities were associated with mortality at 6 months in univariate statistical analyses. In logistic regression analysis only early apoptotic rate was an independent factor associated with mortality at 6 months (odds ratio: 1.502, 95% CI 1.2-1.9; p<0.001). The final model has a sensitivity of 82.4% and a specificity of 84.8% for predicting death within 6 months.

CONCLUSIONS

We developed a simple and reproducible in vitro model for predicting outcome in patients with traumatic or haemorrhagic brain injury that survived in the early phase. Our in vitro model combined with clinical and radiological measurements might improve the value of prognostic models to predict acute brain injury patients' outcome.

Physiological Levels of Pro- and Anti-Inflammatory Mediators in Cerebrospinal Fluid and Plasma: A Normative Study

Numerous recent studies have reported a significant inflammatory reaction in the brain and the systemic circulation following traumatic brain injury (TBI), infection, or neoplasm of the brain with a sequential release of pro- and anti-inflammatory mediators. Although there is growing knowledge and understanding of the mechanisms leading to the often poor outcome of these patients, only a limited database exists on the physiological expression of pro- and anti-inflammatory cytokines and molecules in plasma and particularly in cerebrospinal fluid (CSF). Therefore, we analyzed paired plasma/CSF samples of healthy human volunteers for the physiological concentrations of Interleukin (IL)-6, IL-8, IL-10, soluble TNF-receptors (sTNF-R) p55 and p75, soluble ICAM (sICAM), and soluble E-selectin (sE-selectin). A physiological release of IL-6, IL-8, IL-10, and sTNF-R p55 and p75 was detected in plasma and CSF. In contrast, sICAM and sE-selectin were only detectable in plasma. Pro- and anti-inflammatory mediators exhibited different concentration patterns in plasma and CSF, suggesting a pro-inflammatory predisposition in the central nervous system.

Pathophysiology of polytrauma

Immediate and early trauma deaths are determined by primary brain injuries, or significant blood loss (haemorrhagic shock), while late mortality is caused by secondary brain injuries and host defence failure. First hits (hypoxia, hypotension, organ and soft tissue injuries, fractures), as well as second hits (e.g. ischaemia/reperfusion injuries, compartment syndromes, operative interventions, infections), induce a host defence response. This is characterized by local and systemic release of pro-inflammatory cytokines, arachidonic acid metabolites, proteins of the contact phase and coagulation systems, complement factors and acute phase proteins, as well as hormonal mediators: it is defined as systemic inflammatory response syndrome (SIRS), according to clinical parameters. However, in parallel, anti-inflammatory mediators are produced (compensatory anti-inflammatory response syndrome (CARS). An imbalance of these dual immune responses seems to be responsible for organ dysfunction and increased susceptibility to infections. Endothelial cell damage, accumulation of leukocytes, disseminated intravascular coagulation (DIC) and microcirculatory disturbances lead finally to apoptosis and necrosis of parenchymal cells, with the development of multiple organ dysfunction syndrome (MODS), or multiple organ failure (MOF). Whereas most clinical trials with anti-inflammatory, anti-coagulant, or antioxidant strategies failed, the implementation of pre- and in-hospital trauma protocols and the principle of damage control procedures have reduced post-traumatic complications. However, the development of immunomonitoring will help in the selection of patients at risk of post-traumatic complications and, thereby, the choice of the most appropriate treatment protocols for severely injured patients.

Innate immune response induced by Theiler's murine encephalomyelitis virus infection

Although the causative agents of human multiple sclerosis (MS) are not known, it is suspected that a viral infection may be associated with the initiation of the disease. Several viral disease models in mice have been studied to understand the pathogenesis of demeylination. In particular, Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) has been extensively studied as a relevant model. Various cytokines and chemokines are produced upon viral infection by different cell types, including antigen-presenting cells (APCs) such as macrophages; dendritic cells (DCs); and glial cells, such as astrocytes, microglia, and oligoden-drocytes. The upregulation of the corresponding molecules are also found in MS and are likely to play an important role in the protection and/or pathogenesis of chronic inflammatory demyelinating disease. In this review, the type of cells and molecules, gene-activation mechanisms as well as their potential roles in protection and pathogenesis will be discussed.

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.

The effects of traumatic brain injury on cerebral blood flow and brain tissue nitric oxide levels and cytokine expression

Adult, male, Sprague-Dawley rats were anesthetized, intubated, and mechanically ventilated with 1.5-2.0% isoflurane in oxygen (30%) and air. Rats were prepared for fluid percussion traumatic brain injury (TBI), laser Doppler flowmetry, and measurement of brain tissue nitric oxide (NO) levels using an ISO-NO electrode system. After preparation, isoflurane was reduced to 1.5%, and the rats were randomly assigned to receive sham (n = 6), moderate (1.9 atm, n = 6), or severe (2.8 atm, n = 6) parasagittal fluid percussion TBI. CBF and brain tissue NO levels were measured for 4 h, and then isoflurane levels were increased to 4.0% and the rats were decapitated and the brains were removed. Total RNA was isolated from rat brains and cytokine expression was determined. Laser Doppler flow velocity remained constant in the sham-injured rats but decreased significantly in rats subjected to moderate (p < 0.05) or severe (p < 0.05) TBI. Brain tissue NO levels remained constant in the sham-injured rats but decreased significantly (p < 0.01) after moderate TBI. Severe TBI produced slight, insignificant reductions in NO levels. Cytokine expression was very low in the shaminjured rats. TBI-induced expression of mRNAs for interleukin-1 alpha (IL-1alpha), IL-1beta, IL-6, and tumor necrosis factor-alpha (TNFa). IL-1alpha and IL-1beta mRNA expression increased significantly (p < 0.05 vs. sham-injury) after severe TBI and IL-6 and TNFa mRNA expression increased significant (p < 0.05 vs. sham-injury) after both moderate and severe TBI. Other cytokine mRNA expression was unchanged after TBI.

Closed head injury--an inflammatory disease?

Closed head injury (CHI) remains the leading cause of death and persisting neurological impairment in young individuals in industrialized nations. Research efforts in the past years have brought evidence that the intracranial inflammatory response in the injured brain contributes to the neuropathological sequelae which are, in large part, responsible for the adverse outcome after head injury. The presence of hypoxia and hypotension in the early resuscitative period of brain-injured patients further aggravates the inflammatory response in the brain due to ischemia/reperfusion-mediated injuries. The profound endogenous neuroinflammatory response after CHI, which is phylogenetically aimed at defending the intrathecal compartment from invading pathogens and repairing lesioned brain tissue, contributes to the development of cerebral edema, breakdown of the blood-brain barrier, and ultimately to delayed neuronal cell death. However, aside from these deleterious effects, neuroinflammation has been recently shown to mediate neuroreparative mechanisms after brain injury as well. This "dual effect" of neuroinflammation was the focus of extensive experimental and clinical research in the past years and has lead to an expanded basic knowledge on the cellular and molecular mechanisms which regulate the intracranial inflammatory response after CHI. Thus, head injury has recently evolved as an inflammatory and immunological disease much more than a pure traumatological, neurological, or neurosurgical entity. The present review will summarize the so far known mechanisms of posttraumatic neuroinflammation after CHI, based on data from clinical and experimental studies, with a special focus on the role of pro-inflammatory cytokines, chemokines, and the complement system.

Cerebrospinal fluid and neutrophil respiratory burst after subarachnoid hemorrhage

OBJECTIVES

To investigate the effect of cerebrospinal fluid (CSF) from patients with subarachnoid hemorrhage (SAH) on the activation of polymorphonuclear neutrophils (PMN) in response to receptor-dependent stimulation with N-formyl-l-methionyl-l-leucyl-l-phenylalanine and TNFalpha or non-receptor-dependent stimulation with phorbol 12-myristate 13-acetate.

METHODS

CSF from 12 patients with SAH due to ruptured cerebral aneurysm was collected. Samples of CSF were drawn at different time points. CSF from 6 healthy subjects receiving spinal anesthesia served as the control group. After stimulation of PMN the generation of reactive oxygen intermediates was analyzed on a flow cytometer.

RESULTS

In the presence of CSF, PMN showed a significant suppression of the oxidative burst following stimulation compared to stimulation without CSF. The reduction of the oxidative burst following stimulation was higher in the presence of CSF from patients with SAH. After pretreatment at 56 degrees C, the extent of the suppression observed following receptor-dependent stimulation and CSF from patients with SAH was similar to that seen after stimulation with CSF from healthy individuals.

CONCLUSIONS

These data show that the presence of CSF resulted in a suppression of neutrophil oxidative function. A more distinct depression was seen in the presence of CSF from patients with SAH. We suggest a complex physiological inhibitory and protective mechanism against unfavorable activation of PMN by CSF.

Endothelial cell activation in the presence of African trypanosomes

During human African trypanosomiasis, trypanosomes (Trypanosoma brucei gambiense or T. b. rhodesiense) invade the central nervous system (CNS). Mechanisms of blood-brain barrier and blood-cerebrospinal fluid barrier leakage remain unknown. To better understand the relationships between trypanosomes and endothelial cells, the principal cell population of those barriers, we cultured a human bone marrow endothelial cell (HBMEC) line in the presence or absence of T. b. gambiense, to study cell activation. As indicated by NF-kappaB translocation to the nucleus, cells were activated in the presence of trypanosomes. The expression of the adhesion molecules ICAM-1, E-selectin and VCAM-1 increased in co-culture. The parasites induced the synthesis of the pro-inflammatory cytokines TNF-alpha, IL-6 and IL-8, and of nitric oxide (NO) by HBMEC. Cells were also cultured in the presence of parasite variant surface glycoproteins (VSGs), and an increase in TNF-alpha, IL-6, IL-8, and NO synthesis was also observed. Soluble VSGs induced NF-kappaB translocation, and the expression of adhesion molecules, indicating that they could possibly be the molecular soluble factor responsible for endothelial cell activation. The permeability coefficient of HBMEC layer increased when cells were cultured in the presence of trypanosomes, parasite culture supernatant, or VSGs. Thus, T. b. gambiense can activate endothelial cells in vitro, through the release of soluble activating factors. Consequences of endothelial cell activation by parasite products may include a potentiation of the inflammatory reaction, leukocyte recruitment, passage of trypanosomes into the CNS, and barrier dysfunction observed during CNS involvement of HAT.

The chemokine fractalkine in patients with severe traumatic brain injury and a mouse model of closed head injury

The potential role of the chemokine Fractalkine (CX3CL1) in the pathophysiology of traumatic brain injury (TBI) was investigated in patients with head trauma and in mice after experimental cortical contusion. In control individuals, soluble (s)Fractalkine was present at low concentrations in cerebrospinal fluid (CSF) (12.6 to 57.3 pg/mL) but at much higher levels in serum (21,288 to 74,548 pg/mL). Elevation of sFractalkine in CSF of TBI patients was observed during the whole study period (means: 29.92 to 535.33 pg/mL), whereas serum levels remained within normal ranges (means: 3,100 to 59,159 pg/mL). Based on these differences, a possible passage of sFractalkine from blood to CSF was supported by the strong correlation between blood-brain barrier dysfunction (according to the CSF-/serum-albumin quotient) and sFractalkine concentrations in CSF (R = 0.706; P < 0.01). In the brain of mice subjected to closed head injury, neither Fractalkine protein nor mRNA were found to be augmented; however, Fractalkine receptor (CX3CR1) mRNA steadily increased peaking at 1 week postinjury (P < 0.05, one-way analysis of variance). This possibly implies the receptor to be the key factor determining the action of constitutively expressed Fractalkine. Altogether, these data suggest that the Fractalkine-CX3CR1 protein system may be involved in the inflammatory response to TBI, particularly for the accumulation of leukocytes in the injured parenchyma.

Inflammatory response after neurosurgery

Investigation into the inflammatory response in the central nervous system (CNS) is a rapidly growing field, and a vast amount of information on this topic has accumulated over the past two decades. Inflammation is a particularly interesting issue in the (traditionally non-regenerating) CNS, owing to its dual role in worsening or improving regeneration and functional outcome in certain circumstances. This paper reviews the current literature on the interactions between the immune system and the CNS in physiological and pathological states. The first part will provide an overview of the cellular and molecular components of CNS inflammation, this being followed by a discussion of the concept of systemic immunodepression after neurotrauma and neurosurgery. Finally, the delicate balance of immune responses in the CNS, with an emphasis on the beneficial effects of inflammation and possible therapeutic options, will be discussed.

Glial and neuronal proteins in serum predict outcome after severe traumatic brain injury

OBJECTIVE

To study the ability of glial (glial fibrillary acidic protein [GFAP] and S100b) and neuronal (neuron specific enolase [NSE]) protein levels in peripheral blood to predict outcome after severe traumatic brain injury.

METHODS

Eighty-five patients with severe traumatic brain injury (admission Glasgow Coma Score [GCS] < or = 8) were included. Blood samples taken at the time of hospital admission were analyzed for S100b, GFAP, and NSE. Data collected included demographic and clinical variables. Outcome was assessed using the Glasgow Outcome Scale (GOS) at 6 months post injury.

RESULTS

The median serum levels of S100b, GFAP, and NSE were raised 18.3 fold (S100b), 4.6 fold (GFAP), and twofold (NSE) compared to normal reference values. S100b, GFAP, and NSE serum levels correlated significantly with the injury severity score and CT findings but not with age, sex, or GCS. S100b, GFAP, and NSE levels were significantly higher in patients who died or had a poor outcome 6 months post injury than in those who were alive or had good outcome. S100b level >1.13 microg/L was the strongest predictor of death with 100% discrimination, but GFAP (>1.5 microg/L) and NSE (>21.7 microg/L) levels also strongly predicted death (adjusted odds ratios 5.82 [for GFAP] and 3.91 [for NSE]). S100b, GFAP, and NSE all strongly predicted poor outcome (adjusted odds ratios 5.12 [S100b], 8.82 [GFAP], and 3.95 [NSE]).

CONCLUSIONS

These results suggest that determination of serum levels of glial and neuronal proteins may add to the clinical assessment of the primary damage and prediction of outcome after severe traumatic brain injury.

CHANGES IN CSF S100B AND CYTOKINE CONCENTRATIONS IN EARLY-PHASE SEVERE TRAUMATIC BRAIN INJURY

S100B protein (S100B) has been described as a marker of brain injury. Various cytokines also increase in the cerebrospinal fluid (CSF) of patients with severe traumatic brain injury (TBI). Thus, we investigated early changes in the concentrations of CSF S100B and various cytokines after TBI and evaluated the relations of both S100B and cytokines to intracranial pressure (ICP) and prognosis. Twenty-three patients with severe TBI and a Glasgow Coma Scale score of 8 or less on admission were included in this study. CSF and serum samples were obtained on admission and at 6, 12, 24, 48, 72, and 96 h after injury. CSF concentrations of S100B and CSF and serum concentrations of five cytokines (IL-1beta, TNF-alpha, IL-6, IL-8, and IL-10) were measured and compared. The CSF S100B concentration was increased for 6 h after injury and decreased thereafter. The CSF concentrations of IL-6 and IL-8 peaked within 6 h after injury; other cytokines (IL-1beta, TNF-alpha, and IL-10) were elevated for 24 h after injury and gradually decreased thereafter. Peak CSF S100B concentrations correlated significantly with ICP determined at the time CSF samples were taken (r = 0.729, P < 0.0001). For the cytokines investigated, only the peak CSF IL-1beta concentration correlated significantly and positively with the peak CSF S100B concentration (r = 0.397, P < 0.005). Peak CSF concentrations of S100B (1649 +/- 415 microg/L, mean +/- SEM) and IL-1beta (16.5 +/- 3.3 pg/mL) in the 6 patients with high ICP were significantly higher than those (233 +/- 67 microg/L, 7.6 +/- 1.7 pg/mL, respectively) in the 17 patients with low ICP (P < 0.05). The CSF S100B concentration (1231 +/- 378 microg/L) in eight patients with an unfavorable outcome was significantly higher than that (267 +/- 108 microg/L) in 15 patients with a favorable outcome (P < 0.05). The CSF IL-1beta concentration (14.8 +/- 3.4 pg/mL) in eight patients with an unfavorable outcome tended to be higher than that (7.3 +/- 1.5 pg/mL) in 15 patients with a favorable outcome (P = 0.057). CSF concentrations of S100B and cytokines peak within 24 h after severe TBI and decrease gradually thereafter. CSF S100B and IL-1beta may be useful as predictors of outcome in cases of severe TBI.

Sialylated complex-type N-glycans enhance the signaling activity of soluble intercellular adhesion molecule-1 in mouse astrocytes

Intercellular adhesion molecule-1 (ICAM-1) occurs as both a membrane and a soluble, secreted glycoprotein (sICAM-1). ICAM-1 on endothelial cells mediates leukocyte adhesion by binding to leukocyte function associated antigen-1 (LFA-1) and macrophage antigen-1 (Mac-1). Recombinant mouse sICAM-1 induces the production of macrophage inflammatory protein-2 (MIP-2) in mouse astrocytes by a novel LFA-1- and Mac-1-independent mechanism. Here we showed that N-glycan structures of sICAM-1 influence its ability to induce MIP-2 production. sICAM-1 expressed in Chinese hamster ovary (CHO) cells was a more potent inducer of MIP-2 production than sICAM-1 expressed in HEK 293 cells, suggesting that posttranslational modification of sICAM-1 could influence its signaling activity. To explore the roles of glycosylation in sICAM-1 activity, we expressed sICAM-1 in mutant CHO cell lines differing in glycosylation, including Lec2, Lec8, and Lec1 as well as in CHO cells cultured in the presence of the alpha-mannosidase-I inhibitor kifunensine. Signaling activity of sICAM-1 lacking sialic acid was reduced 3-fold compared with sICAM-1 from CHO cells. The activity of sICAM-1 lacking both sialic acid and galactose was reduced 12-fold, whereas the activity of sICAM-1 carrying only high mannose-type N-glycans was reduced 12-26-fold. sICAM-1 glycoforms carrying truncated glycans retained full ability to bind to LFA-1 on leukocytes. Thus, sialylated and galactosylated complex-type N-glycans strongly enhanced the ability of sICAM-1 to induce MIP-2 production in astrocytes but did not alter its binding to LFA-1 on leukocytes. Glycosylation could therefore serve as a means to regulate specifically the signaling function of sICAM-1 in vivo.

Induction of chemokines in human astrocytes by picornavirus infection requires activation of both AP-1 and NF-kappa B

Infection with different picornaviruses can cause meningitis/encephalitis in humans and experimental animals. To investigate the mechanisms of such inflammatory diseases, potential chemokine gene activation in human astrocytes was investigated following infection with Theiler's murine encephalomyelitis virus (TMEV), coxsackievirus B3 (CVB3), or coxsackievirus B4 (CVB4). We report that all these viruses are potent inducers for the expression of interleukin‐8 (IL‐8) and monocyte chemoattractant protein‐1 (MCP‐1) genes in primary human astrocytes, as well as in an established astrocyte cell line (U‐373MG). Further studies indicated that both activator protein‐1 (AP‐1) and NF‐κB transcription factors are required in the activation of chemokine genes in human astrocytes infected with various picornaviruses. Interestingly, the pattern of activated chemokine genes in human astrocytes is quite restricted compared to that in mouse astrocytes infected with the same viruses, suggesting species differences in gene activation. This may result in potential differences in the pathogenic outcome in each species. © 2003 Wiley‐Liss, Inc.

Interleukin-8 promotes non-rapid eye movement sleep in rabbits and rats

Interleukin-8 (IL-8) is a cytokine found in the brain. In this study, the ability of IL-8 to induce sleep in rabbits and rats was investigated. Twenty-seven Sprague-Dawley rats and 16 male New Zealand White rabbits were provided electroencephalographic (EEG) electrodes, a brain thermistor, and a lateral intracerebroventricular cannula. The animals were injected intracerebroventricularly (i.c.v.) with pyrogen-free saline and, one of the following doses of IL-8 on a separate day: 1.25 or 12.5 ng in rabbits and 10, 50, or 100 ng in rats. EEG, brain temperature, and motor activity were recorded for 23 h after the i.c.v. injections. IL-8 increased time spent in non-rapid eye movement sleep (NREMS) without affecting rapid eye movement sleep (REMS). In rabbits, both doses of IL-8 promoted NREMS. In rats, the 10 and 50 ng doses of IL-8 failed to affect sleep, but the 100 ng dose of IL-8 enhanced NREMS. EEG slow-wave activity during NREMS was increased after the high dose of IL-8 in rabbits. IL-8 also induced fever in rabbits but not rats. Heat inactivated IL-8 did not alter any of the parameters measured. Current results support the notion that the brain cytokine network plays a role in sleep regulation.

Cerebrospinal fluid interleukin 8 concentrations and the subsequent development of postherpetic neuralgia

PURPOSE

Other than age, the risk factors for postherpetic neuralgia are not well established. We studied whether the concentration of interleukin 8 in the cerebrospinal fluid is associated with the risk of postherpetic neuralgia.

METHODS

We enrolled 170 patients more than 50 years old who had a typical painful and nontrigeminal herpetic rash. Patients were treated with acyclovir; no corticosteroids were given. Cerebrospinal fluid was taken for analysis of interleukin 8 during and at full crusting of the herpetic rash. Age, sex, comorbid conditions, prodromal pain, localization and severity of herpetic rash, number of skin lesions, and degree of pain were recorded. We used multivariate logistic regression modeling to identify significant predictive factors. Receiver operating characteristic (ROC) curves were evaluated to determine the contribution of each factor.

RESULTS

Six months after healing, 31 patients (18%) had postherpetic neuralgia; 27 patients still had it after 1 year. Only three variables-age (odds ratio [OR] = 2.7 per 10-year increase; 95% confidence interval [CI]: 1.2 to 6.2), acute pain (OR = 1.8 per unit increase in visual analog scale; 95% CI: 1.2 to 2.8), and interleukin 8 concentration in the cerebrospinal fluid at full crusting of the herpetic rash (OR = 1.6 per 20-microg/L increase; 95% CI: 1.3 to 2.0)-were significant predictors of postherpetic neuralgia at 1 year. Interleukin 8 concentration also had the highest area under the ROC curve at these evaluation points (P <0.001).

CONCLUSION

Our results suggest that interleukin 8 concentration in the cerebrospinal fluid at full crusting of herpetic rash may be useful for identifying patients who are likely to develop intractable postherpetic neuralgia.

Neuronal damage in pericontusional edema zone

In this study, we investigated the molecular biological and histopathological aspects of the etiological mechanisms for pericontusional edema zone (PEZ). The subjects were 5 patients with traumatic brain injury who underwent surgery to evacuate the resulting hematoma. The average age of the subjects was 52 +/- 27.5 years. The GCS at the time of admission was 5-9. At operation apart from evacuating the hematoma, the PEZ was also excised and then examined histopathologically. Cerebrospinal fluid (CSF) levels of IL-6, IL-8, and IL-10 were measured at the time of admission and at 24 and 72 hours. Histological examination revealed large numbers of neutrophils accumulating within blood vessels in the PEZ, with some focal migration. IL-6: CSF levels at the time of admission and at 24, 72, and 72 hours were 550, 4350, and 878000 pg/ml, respectively (median values). IL-8: CSF levels were 715, 804, and 24900 pg/ml, respectively. IL-10: CSF levels were 15, 4, and 5 pg/ml, respectively. High levels of IL-6 and IL-8 were seen from an early stage, and became markedly higher with enlargement of the PEZ. The PEZ is thought to be due to microvascular disturbance by neutrophils stimulated by inflammatory cytokines, and neuronal damage from migrated neutrophils.

Traumatic Cerebral Vascular Injury: The Effects of Concussive Brain Injury on the Cerebral Vasculature

In terms of human suffering, medical expenses, and lost productivity, head injury is one of the major health care problems in the United States, and inadequate cerebral blood flow is an important contributor to mortality and morbidity after traumatic brain injury. Despite the importance of cerebral vascular dysfunction in the pathophysiology of traumatic brain injury, the effects of trauma on the cerebral circulation have been less well studied than the effects of trauma on the brain. Recent research has led to a better understanding of the physiologic, cellular, and molecular components and causes of traumatic cerebral vascular injury. A more thorough understanding of the direct and indirect effects of trauma on the cerebral vasculature will lead to improvements in current treatments of brain trauma as well as to the development of novel and, hopefully, more effective therapeutic strategies.

Interferon-beta prevents cytokine-induced neutrophil infiltration and attenuates blood-brain barrier disruption

Inflammation can contribute to brain injury, such as that resulting from ischemia or trauma. The authors have previously shown that the cytokine interferon-beta (IFN-beta) affords protection against ischemic brain injury, which was associated with a diminished infiltration of neutrophils and a reduction in blood-brain barrier (BBB) disruption. The goal of the current study was to directly assess the effects of IFN-beta on neutrophil infiltration, with the use of an in vivo assay of neutrophil infiltration with relevance to ischemic brain injury. Intrastriatal injection of recombinant rat cytokine-induced neutrophil chemoattractant-1, a member of the interleukin-8 family (1 microg in 1 microl), triggered massive infiltration of neutrophils and extensive BBB disruption 6 hours later, as measured using immunofluorescence microscopy and magnetic resonance imaging in the rat, respectively. Depleting the animals of neutrophils before interleukin-8 injection prevented BBB disruption. Treatment with IFN-beta (5 x 106 U/kg) almost completely prevented neutrophil infiltration and attenuated BBB damage. Gelatinase zymography showed matrix metalloproteinase-9 expression in the ipsilateral striatum after interleukin-8 injection. Both neutrophil depletion and IFN-beta treatment downregulated matrix metalloproteinase-9. IFN-beta has already been approved for human use as a treatment for the chronic inflammatory disorder multiple sclerosis. The potential value of IFN-beta as a treatment that can attenuate acute brain inflammation is considered.

Dobutamine modulates lipopolysaccharide-induced macrophage inflammatory protein-1alpha and interleukin-8 production in human monocytes

Chemokines mediate the migration of leukocytes to sites of inflammation. The CC chemokine macrophage inflammatory protein (MIP)-1alpha and the CXC chemokine interleukin (IL)-8 are reported to play an important role in early inflammatory stages, wound healing, sepsis, and some cardiovascular diseases, including acute coronary syndromes and congestive heart failure. We conducted this study to investigate the effect of dobutamine on lipopolysaccharide (LPS)-induced MIP-1alpha and IL-8 production by human monocytic THP-1 cells. Monocytes were incubated in vitro with LPS for 4 or 16 h at 37 degrees C in the presence or absence of dobutamine. The effect of dobutamine on MIP-1alpha and IL-8 synthesis was examined by using an enzyme-linked immunosorbent assay, and MIP-1alpha and IL-8 messenger RNA (mRNA) were examined by using reverse transcriptase-polymerase chain reaction. Dobutamine significantly inhibited LPS-induced MIP-1alpha and IL-8 production by THP-1 cells in a dose-dependent manner. Salbutamol had a similar suppressive effect on LPS-stimulated MIP-1alpha and IL-8 production. MIP-1alpha mRNA was also suppressed by 10 micro M dobutamine, whereas, at the same concentration, dobutamine had no significant effect on the IL-8 mRNA level. Moreover, we found that dobutamine suppressed the MIP-1alpha-induced chemotaxis in THP-1 differentiated macrophages. These findings suggest that dobutamine may inhibit macrophage chemotaxis, as well as MIP-1alpha and IL-8 production by monocytes. The site of chemokine regulation is at the transcriptional level for MIP-1alpha and might be at the posttranscriptional level for IL-8.

IMPLICATIONS

Macrophage inflammatory protein (MIP)-1alpha and interleukin (IL)-8 are reported to play an important role in early inflammatory stages, wound healing, sepsis, and some cardiovascular diseases. Our study suggests that dobutamine may inhibit macrophage chemotaxis, as well as lipopolysaccharide-induced MIP-1alpha and IL-8 production by human monocytes.

A novel dehydroepiandrosterone analog improves functional recovery in a rat traumatic brain injury model

The purpose of this study was to investigate the efficacy of a novel steroid, fluasterone (DHEF, a dehydroepiandrosterone (DHEA) analog), at improving functional recovery in a rat model of traumatic brain injury (TBI). The lateral cortical impact model was utilized in two studies of efficacy and therapeutic window. DHEF was given (25 mg/kg, intraperitoneally) at the initial time point and once a day for 2 more days. Study A included four groups: sham injury, vehicle treated (n = 22); injured, vehicle treated (n = 30); injured, pretreated (5-10 min prior to injury, n = 24); and injured, posttreated (initial dose 30 min postinjury, n = 15). Study B (therapeutic window) included five groups: sham injury, vehicle treated (n = 17); injured, vehicle treated (n = 26); and three posttreatment groups: initial dose at 30 min (n = 18), 2 h (n = 23), or 12 h (n = 16) postinjury. Three criteria were used to grade functional recovery. In study A, DHEF improved beam walk performance both with pretreatment (79%) and 30-min posttreatment group (54%; p < 0.01, Dunnett vs. injured vehicle). In study B, the 12-h posttreatment group showed a 97% improvement in beam walk performance (p < 0.01, Dunnett). The 30-min and 12-h posttreatment groups showed a decreased incidence of falls from the beam, which reached statistical significance (p < 0.05, Dunnett). Tests of memory (Morris water maze) and neurological reflexes both revealed significant improvements in all DHEF treatment groups. In cultured rat mesangial cells, DHEF (and DHEA) potently inhibited interleukin-1beta-induced cyclooxygenase-2 (COX2) mRNA and prostaglandin (PGE2) production. In contrast, DHEF treatment did not alter injury-induced COX2 mRNA levels in the cortex or hippocampus. However, DHEF (and DHEA) relaxed ex vivo bovine middle cerebral artery preparations by about 30%, with an IC(50) approximately 40 microM. This was a direct effect on the vascular smooth muscle, independent of the endothelial cell layer. Fluasterone (DHEF) treatments improved functional recovery in a rat TBI model. Possible mechanisms of action for this novel DHEA analog are discussed. These findings suggest an exciting potential use for this agent in the clinical treatment of traumatic brain injury.

Death receptors on reactive astrocytes: a key role in the fine tuning of brain inflammation?

Immune responses protect the CNS against pathogens. However, the fact that there is little dispensable tissue in the brain makes regulation necessary to avoid disastrous immune-mediated damage. Astrocytes respond vigorously to any brain injury (e.g., tumor, stroke, AD, MS, HIV) and are postulated to play an important role in the fine tuning of brain inflammation. The authors propose that astrocytes use death receptors to modulate pro- and anti-inflammatory effects.

Inhibition of long-term potentiation by interleukin-8: implications for human immunodeficiency virus-1-associated dementia

Human immunodeficiency virus type 1 (HIV-1)-infected mononuclear phagocytes (MP; brain macrophages and microglia) secrete a number of toxic factors that affect the pathogenesis of HIV-1-associated dementia (HAD). The identification and relative role of each MP toxin for neuronal dysfunction during HAD are not well understood. Interleukin-8 (IL-8), a CXC chemokine involved in leukocyte activation and chemotaxis, is constitutively produced by MP, and elevated levels of IL-8 mRNA were detected in the brains of patients with HIV-1 encephalitis (HIVE) by both ribonuclease protection assays and real-time PCR. To determine the role that IL-8 might play in the neuronal dysfunction in HAD, we studied its effect on synaptic transmission and plasticity in the CA1 region of hippocampus, the seat of learning and memory. Bath application of IL-8 (50 ng/ml) to rat hippocampal slices had no effect on basal synaptic transmission. However, IL-8 was shown to inhibit long-term potentiation (LTP) in a concentration-dependent manner. In control and IL-8-treated slices, the LTP magnitudes were 167.8% +/- 11.9% (mean +/- SE; n = 17) and 122.2% +/- 16.2% of basal levels (n = 13), respectively. These differences were statistically significant (P < 0.05). Preincubation of hippocampal slices with a monoclonal CXCR2 antibody (2 microg/ml) but not control IgG (2 microg/ml) blocked IL-8-induced inhibition of LTP. The expression of CXCR2 receptors in the CA1 region was shown by Western blot assays. The induction of IL-8 in HAD, its inhibition of LTP, and the expression of its receptor, CXCR2, in the hippocampus all suggest that it plays a role in the cognitive dysfunction associated with HAD.

Brain-immune interactions in sleep

This chapter discusses various levels of interactions between the brain and the immune system in sleep. Sleep-wake behavior and the architecture of sleep are influenced by microbial products and cytokines. On the other hand, sleep processes, and perhaps also specific sleep states, appear to promote the production and/or release of certain cytokines. The effects of immune factors such as endotoxin and cytokines on sleep reveal species specificity and usually strong dependence on parameters such as substance concentration, time relative to administration or infection with microbial products, and phase relation to sleep and/or the light-dark cycle. For instance, endotoxin increased SWS and EEG SWA in humans only at very low concentrations, whereas higher concentrations increased sleep stage 2 only, but not SWS. In animals, increases in NREM sleep and SWA were more consistent over a wide range of endotoxin doses. Also, administration of pro-inflammatory cytokines such as IL-6 and IFN-alpha in humans acutely disturbed sleep while in rats such cytokines enhanced SWS and sleep. Overall, the findings in humans indicate that strong nonspecific immune responses are acutely linked to an arousing effect. Although subjects feel subjectively tired, their sleep flattens. However, some observations indicate a delayed enhancing effect on sleep which could be related to the induction of secondary, perhaps T-cell-related factors. This would also fit with results in animals in which the T-cell-derived cytokine IL-2 enhanced sleep while cytokines with immunosuppressive functions like IL-4 and L-10 suppressed sleep. The most straightforward similarity in the cascade of events inducing sleep in both animals and humans is the enhancing effect of GHRH on SWS, and possibly the involvement of the pro-inflammatory cytokine systems of IL-1 beta and TNF-alpha. The precise mechanisms through which administered cytokines influence the central nervous system sleep processes are still unclear, although extensive research has identified the involvement of various molecular intermediates, neuropeptides, and neurotransmitters (cp. Fig. 5, Section III.B). Cytokines are not only released and found in peripheral blood mononuclear cells, but also in peripheral nerves and the brain (e.g., Hansen and Krueger, 1997; März et al., 1998). Cytokines are thereby able to influence the central nervous system sleep processes through different routes. In addition, neuronal and glial sources have been reported for various cytokines as well as for their soluble receptors (e.g., Kubota et al., 2001a). Links between the immune and endocrine systems represent a further important route through which cytokines influence sleep and, vice versa, sleep-associated processes, including variations in neurotransmitter and neuronal activity may influence cytokine levels. The ability of sleep to enhance the release and/or production of certain cytokines was also discussed. Most consistent results were found for IL-2, which may indicate a sleep-associated increase in activity of the specific immune system. Furthermore, in humans the primary response to antigens following viral challenge is enhanced by sleep. In animals results are less consistent and have focused on the secondary response. The sleep-associated modulation in cytokine levels may be mediated by endocrine parameters. Patterns of endocrine activity during sleep are probably essential for the enhancement of IL-2 and T-cell diurnal functions seen in humans: Whereas prolactin and GH release stimulate Th1-derived cytokines such as IL-2, cortisol which is decreased during the beginning of nocturnal sleep inhibits Th1-derived cytokines. The immunological function of neurotrophins, in particular NGF and BDNF, has received great interest. Effects of sleep and sleep deprivation on this cytokine family are particularly relevant in view of the effects these endogenous neurotrophins can have not only on specific immune functions and the development of immunological memories, but also on synaptic reorganization and neuronal memory formation.

IL-8 is a key mediator of neuroinflammation in severe traumatic brain injuries

The subjects were 22 patients with severe head injury. The average age was 45 +/- 18.3 years. There were 13 survivors and 9 fatalities. Samples of peripheral blood and cerebrospinal fluid (CSF) were taken four times, at the time of admission and at 24, 72, and 168 hours later. IL-6: For the survivor group, peripheral blood levels were 181, 105, 37, and 26 pg/ml, respectively (median values). CSF levels were 5376, 3565, 328, and 764 pg/ml, respectively. For the fatality group, peripheral blood levels were 102, 176, 873, and 3059 pg/ml, respectively, whereas CSF levels were 15241, 97384, 548225, and 366500 pg/ml, respectively. IL-8: For the survivor group, peripheral blood levels were 36, 15, 15, and 15 pg/ml, respectively, whereas CSF levels were 23736, 4074, 355, and 1509 pg/ml, respectively. For the fatality group, peripheral blood levels were 21, 28, 43, and 77 pg/mL, respectively, whereas CSF levels were 29003, 8906, 5852, and 8220 pg/ml, respectively. IL-6 and IL-8 levels were significantly higher after 72 hours in the fatality group. The fact that CSF IL-8 was 1000 times that in the peripheral blood at the time of admission, and decreased thereafter, indicates that IL-8 is a key mediator of neuroinflammation.