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

Immunity impacts cognitive deficits across neurological disorders

Cognitive deficits are a common comorbidity with neurological disorders and normal aging. Inflammation is associated with multiple diseases including classical neurodegenerative dementias such as Alzheimer's disease (AD) and autoimmune disorders such as multiple sclerosis (MS), in which over half of all patients experience some form of cognitive deficits. Other degenerative diseases of the central nervous system (CNS) including frontotemporal lobe dementia (FTLD), and Parkinson's disease (PD) as well as traumatic brain injury (TBI) and psychological disorders like major depressive disorder (MDD), and even normal aging all have cytokine-associated reductions in cognitive function. Thus, there is likely commonality between these secondary cognitive deficits and inflammation. Neurological disorders are increasingly associated with substantial neuroinflammation, in which CNS-resident cells secrete cytokines and chemokines such as tumor necrosis factor (TNF)α and interleukins (ILs) including IL-1β and IL-6. CNS-resident cells also respond to a wide variety of cytokines and chemokines, which can have both direct effects on neurons by changing the expression of ion channels and perturbing electrical properties, as well as indirect effects through glia-glia and immune-glia cross-talk. There is significant overlap in these cytokine and chemokine expression profiles across diseases, with TNFα and IL-6 strongly associated with cognitive deficits in multiple disorders. Here, we review the involvement of various cytokines and chemokines in AD, MS, FTLD, PD, TBI, MDD, and normal aging in the absence of dementia. We propose that the neuropsychiatric phenotypes observed in these disorders may be at least partially attributable to a dysregulation of immunity resulting in pathological cytokine and chemokine expression from both CNS-resident and non-resident cells.

Pilot Biomarker Analysis and Decision Tree Algorithm Modeling of Patients with Chronic Subdural Hematomas

The elderly population are at high risk for developing chronic subdural hematoma (cSDH). Surgical evacuation of cSDH is one of the most common procedures performed in neurosurgery. The present study aims to identify potential inflammatory biomarkers associated with its development and recurrence. Patients (>65 years of age) who presented with symptomatic cSDH (≥1 cm thickness or ≥5 mm midline shift [MLS]), requiring surgical intervention, were prospectively enrolled. The collected cSDH fluid was analyzed for inflammatory markers. Computed tomography (CT) scan data included pre-operative cSDH thickness and MLS. Outcome data included Glasgow Outcome Scale-Extended (GOS-E) score at 3, 6, and 12 months post-surgery, as well as cSDH recurrence. A decision tree model was used to determine the predictive power of extracted analytes for MLS, cSDH thickness, and recurrence. This pilot study includes 20 enrolled patients (mean age 77.9 ± 7.4 years and 85% falls). Rate of cSDH recurrence was 42%, with 21% requiring reoperation. Chemokine (C-X-C motif) ligand 9 (CXCL9) concentrations correlated with cSDH thickness (r = 0.975, p = 0.040). Interleukin (IL)-6 and vascular endothelial growth factor (VEGF)-A concentrations correlated with MLS (r = 0.974, p = 0.005; r = 0.472, p = 0.036, respectively). IL-5 concentrations correlated with more favorable GOS-E scores at 3, 6, and 12 months (r = 0.639, p = 0.006; r = 0.727, p = 0.003; r = 0.693, p = 0.026, respectively). Regulated on activation, normal T-cell expressed and secreted (RANTES) concentrations correlated with complete cSDH resolution (r = 0.514, p = 0.021). The decision tree model identified that higher concentrations of CXCL9 were predictive of MLS (risk ratio [RR] = 12.0), higher concentrations of IL-5 were predictive of cSDH thickness (RR = 4.5), and lower concentrations of RANTES were predictive of cSDH recurrence (RR = 2.2). CXCL9, IL-6, VEGF, IL-5, and RANTES are associated with recurrence after surgery and may be potential biomarkers for predicting cSDH recurrence and neurological outcomes.

Emerging Targets for Modulation of Immune Response and Inflammation in Stroke

The inflammatory and immunological responses play a significant role after stroke. The innate immune activation stimulated by microglia during stroke results in the migration of macrophages and lymphocytes into the brain and are responsible for tissue damage. The immune response and inflammation following stroke have no defined targets, and the intricacies of the immunological and inflammatory processes are only partially understood. Innate immune cells enter the brain and meninges during the acute phase, which can cause ischemia damage. Activation of systemic immunity is caused by danger signals sent into the bloodstream by injured brain cells, which is followed by a significant immunodepression that encourages life-threatening infections. Neuropsychiatric sequelae, a major source of post-stroke morbidity, may be induced by an adaptive immune response that is initiated by antigen presentation during the chronic period and is directed against the brain. Thus, the current review discusses the role of immune response and inflammation in stroke pathogenesis, their role in the progression of injury during the stroke, and the emerging targets for the modulation of the mechanism of immune response and inflammation that may have possible therapeutic benefits against stroke.

Pathogenesis and management of traumatic brain injury (TBI): role of neuroinflammation and anti-inflammatory drugs

Traumatic brain injury (TBI) is an important global health concern that represents a leading cause of death and disability. It occurs due to direct impact or hit on the head caused by factors such as motor vehicles, crushes, and assaults. During the past decade, an abundance of new evidence highlighted the importance of inflammation in the secondary damage response that contributes to neurodegenerative and neurological deficits after TBI. It results in disruption of the blood-brain barrier (BBB) and initiates the release of macrophages, neutrophils, and lymphocytes at the injury site. A growing number of researchers have discovered various signalling pathways associated with the initiation and progression of inflammation. Targeting different signalling pathways (NF-κB, JAK/STAT, MAPKs, PI3K/Akt/mTOR, GSK-3, Nrf2, RhoGTPase, TGF-β1, and NLRP3) helps in the development of novel anti-inflammatory drugs in the management of TBI. Several synthetic and herbal drugs with both anti-inflammatory and neuroprotective potential showed effective results. This review summarizes different signalling pathways, associated pathologies, inflammatory mediators, pharmacological potential, current status, and challenges with anti-inflammatory drugs.

Cerebrospinal fluid proteomic study of two bipolar disorder cohorts

The pathophysiology of bipolar disorder remains to be elucidated and there are no diagnostic or prognostic biomarkers for the condition. In this explorative proteomic study, we analyzed 201 proteins in cerebrospinal fluid (CSF) from mood stable bipolar disorder patients and control subjects sampled from two independent cohorts, amounting to a total of 204 patients and 144 controls. We used three Olink Multiplex panels, whereof one specifically targets immune biomarkers, to assess a broad set of CSF protein concentrations. After quality control and removal of proteins with a low detection rate, 105 proteins remained for analyses in relation to case-control status and clinical variables. Only case-control differences that replicated across cohorts were considered. Results adjusted for potential confounders showed that CSF concentrations of growth hormone were lower in bipolar disorder compared with controls in both cohorts. The effect size was larger when the analysis was restricted to bipolar disorder type 1 and controls. We found no indications of immune activation or other aberrations. Growth hormone exerts many effects in the central nervous system and our findings suggest that growth hormone might be implicated in the pathophysiology of bipolar disorder.

Transcriptomic Deconvolution of Dorsal Striata Reveals Increased Monocyte Fractions in Bipolar Disorder

Introduction

Accumulating evidence suggests a relationship between the immune system, neuroinflammation, and mood disorders such as bipolar disorder (BD). However, the immunological landscape of critical brain structures implicated with BD, such as the dorsal striatum, has yet to be characterized. This study sought to investigate the immunological composition of dorsal striata in patients with BD.

Methods

CIBERSORTx, an established RNA deconvolution algorithm, was applied on RNA-sequencing data developed from dorsal striata of 18 BD patients and 17 controls. A validated gene signature matrix for 22 human hematopoietic cell subsets was used to infer the relative proportions of immune cells that were present in the original brain tissue.

Results

Deconvolution of the bulk gene expression data showed that dorsal striata from BD subjects had a significantly greater relative abundance of monocytes compared to control samples.

Conclusion

Monocytes may play a role in the pathogenesis of BD in dorsal striata. Further studies are warranted to confirm the computational results presented herein.

Assessing Protein Biomarkers to Detect Lethal Acute Traumatic Brain Injuries in Cerebrospinal Fluid

Diagnosing traumatic brain injury (TBI) from body fluids in cases where there are no obvious external signs of impact would be useful for emergency physicians and forensic pathologists alike. None of the previous attempts has so far succeeded in establishing a single biomarker to reliably detect TBI with regards to the sensitivity: specificity ratio in a post mortem setting. This study investigated a combination of body fluid biomarkers (obtained post mortem), which may be a step towards increasing the accuracy of biochemical TBI detection. In this study, serum and cerebrospinal fluid (CSF) samples from 30 acute lethal TBI cases and 70 controls without a TBI-related cause of death were evaluated for the following eight TBI-related biomarkers: brain-derived neurotrophic factor (BDNF), ferritin, glial fibrillary acidic protein (GFAP), interleukin 6 (IL-6), lactate dehydrogenase, neutrophil gelatinase-associated lipocalin (NGAL), neuron-specific enolase and S100 calcium-binding protein B. Correlations among the individual TBI biomarkers were assessed, and a specificity-accentuated threshold value analysis was conducted for all biomarkers. Based on these values, a decision tree modelling approach was performed to assess the most accurate biomarker combination to detect acute lethal TBIs. The results showed that 92.45% of acute lethal TBIs were able to be diagnosed using a combination of IL-6 and GFAP in CSF. The probability of detecting an acute lethal TBI was moderately increased by GFAP alone and considerably increased by the remaining biomarkers. BDNF and NGAL were almost perfectly correlated (p = 0.002; R2 = 0.944). This study provides evidence that acute lethal TBIs can be detected to a high degree of statistical accuracy using forensic biochemistry. The high inter-individual correlations of biomarkers may help to estimate the CSF concentration of an unknown biomarker, using extrapolation techniques.

An observational study investigating cytokine levels in the cerebrospinal fluid of patients with schizophrenia spectrum disorders

INTRODUCTION

The role of immunological mechanisms in the pathophysiology of mental disorders has been discussed with increasing frequency. In this context, especially schizophrenia has become the focus of attention after the discovery of autoimmune encephalitis, which might present with psychotic symptoms. Furthermore, multiple studies have identified associations between infections or autoimmune diseases and schizophreniform disorders. Cerebrospinal fluid (CSF) analysis plays a central role in identifying potential inflammatory processes in the central nervous system. Therefore, the rationale of this retrospective study was the analysis of different cytokines, including interleukin-8 (IL-8) levels, in the CSF of patients with schizophrenia spectrum disorders.

METHODS

The authors examined the CSF of 40 patients with schizophrenia spectrum disorders, in comparison to the CSF of a mentally healthy control group of 39 patients with idiopathic intracranial hypertension (IIH). Magnetic bead multiplexing immunoassay was used to retrospectively determine different cytokines in the participants' CSF.

RESULTS

Participants with schizophrenia spectrum disorders had significantly higher IL-8 levels in their CSF than controls (mean ± SD: 41.83 ± 17.50 pg/ml versus 21.40 ± 7.96 pg/ml; p < 0.001).

CONCLUSION

The main finding of this study is the presence of significantly higher IL-8 concentrations in the CSF of patients with schizophrenia spectrum disorders when compared to the control group. This supports the hypothesis that immunological processes may be involved in the pathophysiology of a subgroup of patients with schizophrenia spectrum disorders. However, the study's results are limited by the retrospective design, methodological aspects, and the control group with IIH.

Temporal Acute Serum Estradiol and Tumor Necrosis Factor-α Associations and Risk of Death after Severe Traumatic Brain Injury

Severe traumatic brain injury (TBI) activates a robust systemic response that involves inflammatory and other factors, including estradiol (E2), associated with increased deaths. Tumor necrosis factor-alpha (TNFα) is a significant mediator of systemic shock, and it is an extra-gonadal transcription factor for E2 production. The study objectives were to test the hypotheses: (1) a positive feedback relationship exists between acute serum TNFα and E2; and (2) acute concentrations of E2 and TNFα are prognostic indicators of death after severe TBI. This prospective cohort study included N = 157 adults with severe TBI. Serum samples were collected for the first five days post-injury. The TNFα and E2 levels were averaged into two time epochs: first 72 h (T1) and second 72 h post-injury (T2). A cross-lag panel analysis conducted between T1 and T2 TNFα and E2 levels showed significant cross-lag effects: T1 TNFα and T1 E2 were related to T2 E2 and T2 TNFα, respectively. Cox proportional hazards multi variable regression models determined that increases in T1 E2 (hazard ratio [HR] = 1.79, 95% confidence interval [CI]: 1.15, 2.81), but not T2 E2 (HR = 0.91, 95% CI: 0.56, 1.47), were associated with increased risk of death. Increased T2 TNFα (HR = 2.47, 95% CI: 1.35, 4.53), and T1 TNFα (HR = 1.47, 95% CI: 0.99, 2.19), to a lesser degree, were associated with increased risk of death. Relationships of death with T2 TNFα and T1 E2 were mediated partially by cardiovascular, hepatic, and renal dysfunction. Both E2 and TNFα are systemic, reciprocally related biomarkers that may be indicative of systemic compromise and increased risk of death after severe TBI.

Genome-wide study of immune biomarkers in cerebrospinal fluid and serum from patients with bipolar disorder and controls

Bipolar disorder is a common, chronic psychiatric disorder. Despite high heritability, there is a paucity of identified genetic risk factors. Immune biomarkers are under more direct genetic influence than bipolar disorder. To explore the genetic associations with immune biomarker levels in cerebrospinal fluid (CSF) and blood serum which previously showed differences in bipolar disorder, we performed a study involving 291 individuals (184 bipolar disorder patients and 107 controls). The biomarkers assayed in both CSF and serum were: chitinase-3-like protein-1 (YKL-40), monocyte chemoattractant protein-1 (MCP-1), soluble cluster of differentiation (sCD14), tissue inhibitor of metalloproteinases-1 and 2 (TIMP-1 and TIMP-2). C-reactive protein (CRP) was only quantified in serum, and interleukin 8 (IL-8) measures were only available in CSF. Genome-wide association studies were conducted using PLINK for each of three genotyping waves and incorporated covariates for population substructure, age, sex, and body mass index (BMI). Results were combined by meta-analysis. Genome-wide significant associations were detected for all biomarkers except TIMP-1 and TIMP-2 in CSF. The strongest association in CSF was found for markers within the CNTNAP5 gene with YKL-40 (rs150248456, P = 2.84 × 10^-10). The strongest association in serum was also for YKL-40 but localized to the FANCI gene (rs188263039, P = 5.80 × 10^-26). This study revealed numerous biologically plausible genetic associations with immune biomarkers in CSF and blood serum. Importantly, the genetic variants regulating immune biomarker levels in CSF and blood serum differ. These results extend our knowledge of how biomarkers showing alterations in bipolar disorder are genetically regulated.

Cytokine-mediated cellular immune activation in electroconvulsive therapy: A CSF study in patients with treatment-resistant depression

Objectives: Evidence points towards an important relationship between the antidepressant effects of electroconvulsive therapy (ECT) and the modulation of the immune system. To further elucidate this interplay, we performed a study on the effects of the antidepressant treatment by ECT on 25 cytokines in patients with depression.Methods: We measured 25 different cytokines (interleukin (IL)-1β, IL-1RA, Il-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12 (p40/p70), IL-13, IL-15, IL-17, tumor necrosis factor-α, interferon (IFN)-α, IFN-γ, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein (MIP)-1α, MIP-1β, IFN-γ-induced protein 10 (IP-10), monokine induced by IFN-γ, Eotaxin, Rantes and monocyte chemoattractant protein 1) in the cerebrospinal fluid (CSF) and blood of 12 patients with a severe and treatment-resistant depressive episode before and after a course of ECT.Results: CSF levels of IP-10, IL-5 and IL-8 were elevated after ECT and more ECT sessions were associated with the differences of CSF levels before and after ECT of IFN-γ, IL-2RA, Rantes, IL-6 and IL-1β. Responders and/or remitters had a decrease of CSF levels of IL-17, MIP-1α, Rantes and IL-2R during ECT. CSF IP-10 levels increased less during ECT in patients who had a remission.Conclusions: Although the sample size was small, we found different effects of the ECT treatment per se and of the antidepressant action induced by ECT in CSF and blood.

Direct effects of antipsychotic drugs on insulin, energy sensing and inflammatory pathways in hypothalamic mouse neurons

INTRODUCTION

Second-generation antipsychotics cause serious metabolic side effects, but the mechanisms behind these effects remain largely unknown. However, emerging evidence supports that antipsychotics may act upon the hypothalamus, the primary brain region understood to regulate energy homeostasis. We have recently reported that the antipsychotics olanzapine, clozapine, and aripiprazole can directly act on hypothalamic rat neurons (rHypoE-19) to impair insulin, energy sensing, and modulate inflammatory pathways. In the current paper, we sought to replicate these findings to a mouse neuronal model.

METHODS

The mouse hypothalamic neuronal cell line, mHypoE-46, was treated with olanzapine, clozapine, or aripiprazole. Western blots were used to measure the energy sensing protein AMPK, components of the insulin signalling pathway (AKT, GSK3β), and components of the MAPK pathway (ERK1/2, JNK, p38), the latter linked to inflammation. RT-qPCR was used to measure mRNA expression of the inflammatory mediators IL-6, IL-10, and BDNF, well as putative receptors in the mHypoE-46 (current) and the rHypoE-19 (previously studied) cell lines.

RESULTS

In the mHypoE-46 neurons, olanzapine and aripiprazole increased AMPK phosphorylation, while clozapine and aripiprazole inhibited insulin-induced phosphorylation of AKT. Clozapine increased JNK and aripiprazole decreased ERK1/2 phosphorylation. Olanzapine also decreased IL-6 mRNA expression, while olanzapine and clozapine increased IL-10 mRNA expression. The rHypoE-19 neurons expressed the H₁, 5 H T_2A, and M₃ receptors, while the mHypoE-46 neurons expressed the 5 H T_2A, D₂, and M₃ receptors. Neither cell line expressed the 5 H T_2C receptor.

CONCLUSION

Similar to observed effects of these agents in rat neurons, induction of AMPK by aripiprazole and olanzapine suggests impaired energy sensing, while suppression of insulin-induced pAKT by clozapine and aripiprazole suggests impaired insulin signalling, seen across both rodent derived hypothalamic cell lines. Conversely, olanzapine-induced suppression of pro-inflammatory IL-6, alongside olanzapine and clozapine-induced IL-10, demonstrate anti-inflammatory effects, which do not corroborate with our prior observations in the rat neuronal line. The different findings between cell lines could be explained by differential expression of neurotransmitters receptors and/or reflect genetic heterogeneity across the rat and mouse lines. However, overall, our findings support direct effects of antipsychotics to impact insulin, energy sensing, and inflammatory pathways in hypothalamic rodent neurons.

The Relationship between Serum Concentrations of Pro- and Anti-Inflammatory Cytokines and Nutritional Status in Patients with Traumatic Head Injury in the Intensive Care Unit

Background and objective: The aim of the present study was to examine the relationship between serum levels of pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α) and anti-inflammatory cytokines (IL-10) measured once at the baseline with changes in nutritional status of patients with traumatic head injury (THI) assessed at three consecutive times (24 h after admission, day 6 and day 13) during hospital stay in the intensive care unit (ICU). Materials and Methods: Sixty-four patients with THI were recruited for the current study (over 10 months). The nutritional status of the patients was determined within 24 h after admission and on days 6 and 13, using actual body weight, body composition analysis, and anthropometric measurements. The APACHE II score and SOFA score were also assessed within 24 h of admission and on days 6 and 13 of patients staying in the ICU. Circulatory serum levels of cytokines (IL-6, IL-1β, TNF-α, and IL-10) were assessed once within 24 h of admission. Results: The current study found a significant reduction in BMI, FBM, LBM, MAUAC, and APM, of THI patients with high serum levels the cytokines, over the course of time from the baseline to day 7 and to day 13 in patients staying in the ICU (p < 0.001). It was also found that patients with low levels of some studied cytokines had significant improvement in their nutritional status and clinical outcomes in term of MAUAC, APM, APACHE II score and SOFA score (p < 0.001 to p < 0.01). Conclusion: THI patients who had high serum levels of studied cytokines were more prone to develop a reduction of nutritional status in terms of BMI, FBM, LBM MAUAC and APM over the course of time from patient admission until day 13 of ICU admission.

Recommendations for cerebrospinal fluid analysis

Diseases of the central nervous system (CNS) mean for the human organism a potentially dangerous situation. An investigation of cerebrospinal fluid (CSF) provides important information about a character of CNS impairment in the decision-making diagnostic and therapeutic algorithm. The authors present a brief overview of available cerebrospinal fluid assays, shortened indication criteria, a recommended algorithm of CSF assessment in different suspected diseases, and a view of the external quality system. The whole portfolio of obtainable CSF methodology is further subdivided according to the adequate choice into the first and inevitable basic routine panel, and following complicated analyses of highly specialized character. The basic panel is considered for standard laboratories, the complete specialized assessment should be provided by a super-consulting laboratory.

Angiogenic Properties of 'Leukocyte- and Platelet-Rich Fibrin'

Leukocyte- and Platelet-Rich Fibrin (L-PRF) is an autologous platelet concentrate, consisting of a fibrin matrix enriched with platelets, leukocytes and a plethora of cytokines and growth factors. Since L-PRF is produced bedside from whole blood without the use of an anti-coagulant, it is becoming a popular adjuvant in regenerative medicine. While other types of platelet concentrates have been described to stimulate blood vessel formation, little is known about the angiogenic capacities of L-PRF. Therefore, this study aimed to fully characterize the angiogenic potential of L-PRF. With an antibody array, the growth factors released by L-PRF were determined and high levels of CXC chemokine receptor 2 (CXCR-2) ligands and epidermal growth factor (EGF) were found. L-PRF induced in vitro key steps of the angiogenic process: endothelial proliferation, migration and tube formation. In addition, we could clearly demonstrate that L-PRF is able to induce blood vessel formation in vivo, the chorioallantoic membrane assay. In conclusion, we could demonstrate the angiogenic capacity of L-PRF both in vitro and in vivo, underlying the clinical potential of this easy-to-use platelet concentrate.

Antidepressant efficacy of electroconvulsive therapy is associated with a reduction of the innate cellular immune activity in the cerebrospinal fluid in patients with depression

OBJECTIVES

A bidirectional link between the antidepressant effects of electroconvulsive therapy (ECT) and the modulation of the immune system has been proposed. To elucidate the interplay between antidepressant treatment and macrophage/microglia activation in humans, we performed a study on the effects of the antidepressant treatment by ECT on markers of macrophage/microglia activation in patients with depression.

METHODS

We measured six different markers (IL-6, neopterin, sCD14, sCD163 MIF and MCP1) of macrophage/microglia activation in the cerebrospinal fluid (CSF) and blood of 12 patients with a severe, treatment-resistant depressive episode before and after a course of ECT.

RESULTS

Some markers in the CSF of remitters were reduced after the ECT course and differed from non-remitters, but no differences were found before and after ECT independently from the antidepressant efficacy. CSF baseline levels of some markers could predict the reduction of depressive psychopathology during ECT. Higher CSF levels indicating increased macrophage/microglia activation at baseline predicted a better treatment response to ECT.

CONCLUSIONS

Although the sample size was small, our data suggest that macrophages/microglia are involved in the pathophysiology of major depression and that antidepressant efficacy by ECT might be partly explained by the modulation of the innate immune system within the brain.

Metabolomics analysis of serum in a rat heroin self-administration model undergoing reinforcement based on 1H-nuclear magnetic resonance spectra

Background

Understanding the process of relapse to abused drugs and ultimately developing treatments that can reduce the incidence of relapse remains the primary goal for the study of substance dependence. Therefore, exploring the metabolite characteristics during the relapse stage is valuable.

Methods

A heroin self-administered rat model was employed, and analysis of the ¹H-nuclear magnetic resonance-based metabolomics was performed to investigate the characteristic metabolite profile upon reintroduction to the drug after abstinence.

Results

Sixteen metabolites in the serum of rats, including phospholipids, intermediates in TCA (Tricarboxylic Acid Cycle) cycle, keto bodies, and precursors for neurotransmitters, underwent a significant change in the reinstatement stage compared with those in the control group. In particular, energy production was greatly disturbed as evidenced by different aspects such as an increase in glucose and decrease in intermediates of glycolysis and the TCA cycle. The finding that the level of 3-hydroxybutyrate and acetoacetate increased significantly suggested that energy production was activated from fatty acids. The concentration of phenylalanine, glutamine, and choline, the precursors of major neurotransmitters, increased during the reinstatement stage which indicated that an alteration in neurotransmitters in the brain might occur along with the disturbance in substrate supply in the circulatory system.

Conclusions

Heroin reinforcement resulted in impaired energy production via different pathways, including glycolysis, the TCA cycle, keto body metabolism, etc. A disturbance in the substrate supply in the circulatory system may partly explain heroin toxicity in the central nervous system. These findings provide new insight into the mechanism underlying the relapse to heroin use.

Electronic supplementary material

The online version of this article (10.1186/s12868-018-0404-5) contains supplementary material, which is available to authorized users.

An update on diagnostic and prognostic biomarkers for traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major worldwide neurological disorder of epidemic proportions. To date, there are still no FDA-approved therapies to treat any forms of TBI. Encouragingly, there are emerging data showing that biofluid-based TBI biomarker tests have the potential to diagnose the presence of TBI of different severities including concussion, and to predict outcome. Areas covered: The authors provide an update on the current knowledge of TBI biomarkers, including protein biomarkers for neuronal cell body injury (UCH-L1, NSE), astroglial injury (GFAP, S100B), neuronal cell death (αII-spectrin breakdown products), axonal injury (NF proteins), white matter injury (MBP), post-injury neurodegeneration (total Tau and phospho-Tau), post-injury autoimmune response (brain antigen-targeting autoantibodies), and other emerging non-protein biomarkers. The authors discuss biomarker evidence in TBI diagnosis, outcome prognosis and possible identification of post-TBI neurodegernative diseases (e.g. chronic traumatic encephalopathy and Alzheimer's disease), and as theranostic tools in pre-clinical and clinical settings. Expert commentary: A spectrum of biomarkers is now at or near the stage of formal clinical validation of their diagnostic and prognostic utilities in the management of TBI of varied severities including concussions. TBI biomarkers could serve as a theranostic tool in facilitating drug development and treatment monitoring.

Markers of neuroinflammation and neuronal injury in bipolar disorder: Relation to prospective clinical outcomes

Neuroimmune mechanisms have been linked to the pathophysiology of bipolar disorder based on studies of biomarkers in plasma, cerebrospinal fluid (CSF), and postmortem brain tissue. There are, however, no longitudinal studies investigating if CSF markers of neuroinflammation and neuronal injury predict clinical outcomes in patients with bipolar disorder. We have in previous studies found higher CSF concentrations of interleukin-8 (IL-8), monocyte chemoattractant protein 1 (MCP-1/CCL-2), chitinase-3-like protein 1 (CHI3L1/YKL-40), and neurofilament light chain (NF-L) in euthymic patients with bipolar disorder compared with controls. Here, we investigated the relationship of these CSF markers of neuroinflammation and neuronal injury with clinical outcomes in a prospective study. 77 patients with CSF analyzed at baseline were followed for 6-7years. Associations of baseline biomarkers with clinical outcomes (manic/hypomanic and depressive episodes, suicide attempts, psychotic symptoms, inpatient care, GAF score change) were investigated. Baseline MCP-1 concentrations were positively associated with manic/hypomanic episodes and inpatient care during follow-up. YKL-40 concentrations were negatively associated with manic/hypomanic episodes and with occurrence of psychotic symptoms. The prospective negative association between YKL-40 and manic/hypomanic episodes survived multiple testing correction. Concentrations of IL-8 and NF-L were not associated with clinical outcomes. High concentrations of these selected CSF markers of neuroinflammation and neuronal injury at baseline were not consistently associated with poor clinical outcomes in this prospective study. The assessed proteins may be involved in adaptive immune processes or reflect a state of vulnerability for bipolar disorder rather than being of predictive value for disease progression.

The Role of Astrocytes in Neuroprotection after Brain Stroke: Potential in Cell Therapy

Astrocytes are commonly involved in negative responses through their hyperreactivity and glial scar formation in excitotoxic and/or mechanical injuries. But, astrocytes are also specialized glial cells of the nervous system that perform multiple homeostatic functions for the survival and maintenance of the neurovascular unit. Astrocytes have neuroprotective, angiogenic, immunomodulatory, neurogenic, and antioxidant properties and modulate synaptic function. This makes them excellent candidates as a source of neuroprotection and neurorestoration in tissues affected by ischemia/reperfusion, when some of their deregulated genes can be controlled. Therefore, this review analyzes pro-survival responses of astrocytes that would allow their use in cell therapy strategies.

Cerebrospinal fluid microglia and neurodegenerative markers in twins concordant and discordant for psychotic disorders

Schizophrenia and bipolar disorder are debilitating psychiatric disorders with partially shared symptomatology including psychotic symptoms and cognitive impairment. Aberrant levels of microglia and neurodegenerative cerebrospinal fluid (CSF) markers have previously been found in schizophrenia and bipolar disorder. We aimed to analyze familial and environmental influences on these CSF markers and their relation to psychiatric symptoms and cognitive ability. CSF was collected from 17 complete twin pairs, nine monozygotic and eight dizygotic, and from one twin sibling. Two pairs were concordant for schizophrenia, and 11 pairs discordant for schizophrenia, schizoaffective disorder or bipolar disorder, and four pairs were not affected by psychotic disorders. Markers of microglia activation [monocyte chemoattractant protein-1 (MCP-1), chitinase 3-like protein 1 (YKL-40), and soluble cluster of differentiation 14 (sCD14)], markers of β-amyloid metabolism (AβX-38, AβX-40, AβX-42 and Aβ1-42), soluble amyloid precursor proteins (sAPP-α and sAPP-β), total tau (T-tau), phosphorylated tau (P-tau), and CSF/serum albumin ratio were measured in CSF using immunoassays. Heritability of the CSF markers was estimated, and associations to psychiatric and cognitive measurements were analyzed. Heritability estimates of the microglia markers were moderate, whereas several neurodegenerative markers showed high heritability. In contrast, AβX-42, Aβ1-42, P-tau and CSF/serum albumin ratio were influenced by dominant genetic variation. Higher sCD14 levels were found in twins with schizophrenia or bipolar disorder compared to their not affected co-twins, and higher sCD14-levels were associated with psychotic symptoms. The study provides support for a significant role of sCD14 in psychotic disorders and a possible role of microglia activation in psychosis.

Interleukin-6-mediated signaling in adrenal medullary chromaffin cells

The pro-inflammatory cytokines, tumor necrosis factor-α, and interleukin-1β/α modulate catecholamine secretion, and long-term gene regulation, in chromaffin cells of the adrenal medulla. Since interleukin-6 (IL6) also plays a key integrative role during inflammation, we have examined its ability to affect both tyrosine hydroxylase activity and adrenomedullary gene transcription in cultured bovine chromaffin cells. IL6 caused acute tyrosine/threonine phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), and serine/tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3). Consistent with ERK1/2 activation, IL6 rapidly increased tyrosine hydroxylase phosphorylation (serine-31) and activity, as well as up-regulated genes, encoding secreted proteins including galanin, vasoactive intestinal peptide, gastrin-releasing peptide, and parathyroid hormone-like hormone. The effects of IL6 on the entire bovine chromaffin cell transcriptome were compared to those generated by G-protein-coupled receptor (GPCR) agonists (histamine and pituitary adenylate cyclase-activating polypeptide) and the cytokine receptor agonists (interferon-α and tumor necrosis factor-α). Of 90 genes up-regulated by IL6, only 16 are known targets of IL6 in the immune system. Those remaining likely represent a combination of novel IL6/STAT3 targets, ERK1/2 targets and, potentially, IL6-dependent genes activated by IL6-induced transcription factors, such as hypoxia-inducible factor 1α. Notably, genes induced by IL6 include both neuroendocrine-specific genes activated by GPCR agonists, and transcripts also activated by the cytokines. These results suggest an integrative role for IL6 in the fine-tuning of the chromaffin cell response to a wide range of physiological and paraphysiological stressors, particularly when immune and endocrine stimuli converge.

Time course of cerebrospinal fluid inflammatory biomarkers and relationship to 6-month neurologic outcome in adult severe traumatic brain injury

OBJECTIVE

Activation of the inflammatory cascade is a known pathophysiologic process in severe traumatic brain injury (TBI) with yet non-standardized scientific data regarding relationship to outcome. The understanding of the time course of expression of cerebrospinal fluid (CSF) biomarker levels following severe TBI is an important step toward using these biomarkers to measure injury severity and/or early response to therapeutic interventions. The objective of the current study is to report the time course and values of a battery of CSF inflammatory biomarkers following severe TBI in our reasonably sized patient cohort.

PATIENTS AND METHODS

Our patient cohort consists of 32 consented patients, who met the study's inclusion criteria for data collection from 2000 to 2010. The time course and values of a battery of CSF biomarkers (IL-1β, IL-6, TNF-α, IFN-γ, IL-12p70, IL-10, and IL-8) following severe TBI in this patient cohort was characterized. Additionally, the correlation of biomarker concentration with 6-month neurological outcome was assessed. Serial CSF sampling through an external ventricular drain was performed over the first five days following injury. Concentration of a panel of inflammatory biomarkers (IL-1β, IL-6, TNF-α, IFN-γ, IL-12p70, IL-10, and IL-8) were evaluated using Meso Scale Discovery's Multi-Array technology. Glasgow Outcome Scale (GOS) score at six months following injury was dichotomized into poor outcome (GOS 1-3) and favorable outcome (GOS 4-5). Statistical analyses were performed using Kruskal-Wallis test and linear regression analysis.

RESULTS

The result shows that CSF concentrations of inflammatory biomarkers had a significant association with 6-month neurological outcome (p-values≤0.05 for each marker), with the favorable outcome group having lower concentrations of these biomarkers on average, in comparison to the poor neurologic outcome group over the first five days after TBI. All inflammatory biomarkers decreased to normal levels by post-trauma day 5, except for IL-6 and IL-8. Upregulation and increased expression of key inflammatory markers following severe TBI were significant predictors of worse 6-month neurologic outcome. Additionally, post-trauma day 5 concentrations of IL-6 and IL-8 remained elevated over normal CSF values.

CONCLUSION

The study shows that inflammatory biomarkers in CSF are potential biomarkers of injury severity and progression and/or recovery; they could prove beneficial in the future assessment of injury severity and response to therapy after severe TBI.

Comparison and relationship of thyroid hormones, IL-6, IL-10 and albumin as mortality predictors in case-mix critically ill patients

OBJECTIVE

To compare the ability of thyroid hormones, IL-6, IL-10, and albumin to predict mortality, and to assess their relationship in case-mix acute critically ill patients.

METHODS

APACHE II scores and serum thyroid hormones (FT3, FT4, and TSH), IL-6, IL-10, and albumin were obtained at EICU admission for 79 cases of mix acute critically ill patients without previous history of thyroid disease. Patients were followed for 28 days with patient's death as the primary outcome. All mean values were compared, correlations assessed with Pearson' test, and mortality prediction assessed by multivariate logistic regression and ROC.

RESULTS

Non survivors were older, with higher APACHE II score (p=0.000), IL-6 (p<0.05), IL-10 (p=0.000) levels, and lower albumin (p=0.000) levels compared to survivors at 28 days. IL-6 and IL-10 had significant negative correlation with albumin (p=0.001) and FT3 (p ⩽ 0.05) respectively, while low albumin had a direct correlation with FT3 (p<0.05). In the mortality prediction assessment, IL-10, albumin and APACHE II were independent morality predictors and showed to have a good (0.70-0.79) AUC-ROC (p<0.05). Despite that the entire cohort showed low FT3 serum levels (p=0.000), there was not statistical difference between survivors and non-survivors; neither showed any significance as mortality predictor.

CONCLUSIONS

IL-6 and IL-10 are correlated with Low FT3 and hypoalbuminemia. Thyroid hormones assessed at EICU admission did not have any predictive value in our study. And finally, high levels of IL-6 and IL-10 in conjunction with albumin could improve our ability to evaluate disease's severity and predict mortality in the critically ill patients. When use in combination with APACHE II scores, our model showed improved mortality prediction.

Assessing brain immune activation in psychiatric disorders: clinical and preclinical PET imaging studies of the 18-kDa translocator protein

Accumulating evidence from different lines of research suggests an involvement of the immune system in the pathophysiology of several psychiatric disorders. During recent years, a series of positron emission tomography (PET) studies have been published using radioligands for the translocator protein (TSPO) to study microglia activation in schizophrenia, bipolar I disorder, major depression, autism spectrum disorder, and drug abuse. The results have been somewhat conflicting, which could be due to differences both in patient sample characteristics and in PET methods. In particular, further work is needed to address both methodological and biological sources of variability in TSPO levels, a process in which the use of animal models and small animal PET systems can be a valuable tool. Given this development, PET studies of immune activation have the potential to further increase our understanding of disease mechanisms in psychiatric disorders, which is a requisite in the search for new treatment approaches. Furthermore, molecular imaging could become an important clinical tool for identifying specific subgroups of patients or disease stages that would benefit from treatment targeting the immune system.

CSF neuroinflammatory biomarkers in bipolar disorder are associated with cognitive impairment

Persistent cognitive impairment in the euthymic state of bipolar disorder is increasingly recognized. Mounting evidence also suggests an association between neuroinflammation and cognitive dysfunction. The purpose of this study was to test if cerebrospinal fluid (CSF) markers of neuroinflammation could account for cognitive impairment in bipolar disorder. Hierarchical linear regression models were applied to account for performance in five cognitive domains using CSF neuroinflammatory biomarkers as predictors in patients with bipolar disorder type I and II (N=78). The associations between these biomarkers and cognition were further tested in healthy age- and sex-matched controls (N=86). In patients with bipolar disorder, the CSF biomarkers accounted for a significant proportion of the variance in executive functions (42.8%, p=<.0005) independently of age, medication, disease status, and bipolar subtype. The microglial marker YKL-40 had a high impact (beta=-.99), and was the only biomarker that contributed individually. CSF biomarkers were not associated with cognitive performance in healthy controls. The CSF neuroinflammation biomarker YKL-40 is associated with executive performance in euthymic bipolar disorder, but not in healthy controls.

Monocyte and microglial activation in patients with mood-stabilized bipolar disorder

BACKGROUND

Bipolar disorder is associated with medical comorbidities that have been linked to systemic inflammatory mechanisms. There is, however, limited evidence supporting a role of neuroinflammation in bipolar disorder. Here we tested whether microglial activation and associated tissue remodelling processes are related to bipolar disorder by analyzing markers in cerebrospinal fluid (CSF) and serum from patients and healthy controls.

METHODS

Serum was sampled from euthymic patients with bipolar disorder and healthy controls, and CSF was sampled from a large subset of these individuals. The levels of monocyte chemoattractant protein-1 (MCP-1), YKL-40, soluble cluster of differentiation 14 (sCD14), tissue inhibitor of metalloproteinases-1 (TIMP-1) and tissue inhibitor of metalloproteinases-2 (TIMP-2), were measured, and we adjusted comparisons between patients and controls for confounding factors.

RESULTS

We obtained serum samples from 221 patients and 112 controls and CSF samples from 125 patients and 87 controls. We found increased CSF levels of MCP-1 and YKL-40 and increased serum levels of sCD14 and YKL-40 in patients compared with controls; these differences remained after controlling for confounding factors, such as age, sex, smoking, blood-CSF barrier function, acute-phase proteins and body mass index. The CSF levels of MCP-1 and YKL-40 correlated with the serum levels, whereas the differences between patients and controls in CSF levels of MCP-1 and YKL-40 were independent of serum levels.

LIMITATIONS

The cross-sectional study design precludes conclusions about causality.

CONCLUSION

Our results suggest that both neuroinflammatory and systemic inflammatory processes are involved in the pathophysiology of bipolar disorder. Importantly, markers of immunological processes in the brain were independent of peripheral immunological activity.

Impact of cytokine in type 1 narcolepsy: Role of pandemic H1N1 vaccination ?

Recent advances in the identification of susceptibility genes and environmental exposures (pandemic influenza 2009 vaccination) provide strong support that narcolepsy type 1 is an immune-mediated disease. Considering the limited knowledge regarding the immune mechanisms involved in narcolepsy whether related to flu vaccination or not and the recent progresses in cytokine measurement technology, we assessed 30 cytokines, chemokines and growth factors using the Luminex technology in either peripheral (serum) or central (CSF) compartments in a large population of 90 children and adult patients with narcolepsy type 1 in comparison to 58 non-hypocretin deficient hypersomniacs and 41 healthy controls. Furthermore, we compared their levels in patients with narcolepsy whether exposed to pandemic flu vaccine or not, and analyzed the effect of age, duration of disease and symptom severity. Comparison for sera biomarkers between narcolepsy (n = 84, 54 males, median age: 15.5 years old) and healthy controls (n = 41, 13 males, median age: 20 years old) revealed an increased stimulation of the immune system with high release of several pro- and anti-inflammatory serum cytokines and growth factors with interferon-γ, CCL11, epidermal growth factor, and interleukin-2 receptor being independently associated with narcolepsy. Increased levels of interferon-γ, CCL11, and interleukin-12 were found when close to narcolepsy onset. After several adjustments, only one CSF biomarker differed between narcolepsy (n = 44, 26 males, median age: 15 years old) and non-hypocretin deficient hypersomnias (n = 57, 24 males, median age: 36 years old) with higher CCL 3 levels found in narcolepsy. Comparison for sera biomarkers between patients with narcolepsy who developed the disease post-pandemic flu vaccination (n = 36) to those without vaccination (n = 48) revealed an increased stimulation of the immune system with high release of three cytokines, regulated upon activation normal T-cell expressed and secreted, CXCL10, and CXCL9, being independently and significantly increased in the group exposed to the vaccine. No significant differences were found between narcoleptics whether exposed to flu vaccination or not for CSF biomarkers except for a lower CXCL10 level found in the exposed group. To conclude, we highlighted the role of sera cytokine with pro-inflammatory properties and especially interferon-γ being independently associated with narcolepsy close to disease onset. The activity of the interferon-γ network was also increased in the context of narcolepsy after the pandemic flu vaccination being a potential key player in the immune mechanism that triggers narcolepsy and that coordinates the immune response necessary for resolving vaccination assaults.

Increased levels of IL-6 in the cerebrospinal fluid of patients with chronic schizophrenia--significance for activation of the kynurenine pathway

BACKGROUND

Accumulating evidence indicates that schizophrenia is associated with brain immune activation. While a number of reports suggest increased cytokine levels in patients with schizophrenia, many of these studies have been limited by their focus on peripheral cytokines or confounded by various antipsychotic treatments. Here, well-characterized patients with schizophrenia, all receiving olanzapine treatment, and healthy volunteers were analyzed with regard to cerebrospinal fluid (CSF) levels of cytokines. We correlated the CSF cytokine levels to previously analyzed metabolites of the kynurenine (KYN) pathway.

METHODS

We analyzed the CSF from patients and controls using electrochemiluminescence detection with regard to cytokines. Cell culture media from human cortical astrocytes were analyzed for KYN and kynurenic acid (KYNA) using high-pressure liquid chromatography or liquid chromatography/mass spectrometry.

RESULTS

We included 23 patients and 37 controls in our study. Patients with schizophrenia had increased CSF levels of interleukin (IL)-6 compared with healthy volunteers. In patients, we also observed a positive correlation between IL-6 and the tryptophan:KYNA ratio, indicating that IL-6 activates the KYN pathway. In line with this, application of IL-6 to cultured human astrocytes increased cell medium concentration of KYNA.

LIMITATIONS

The CSF samples had been frozen and thawed twice before analysis of cytokines. Median age differed between patients and controls. When appropriate, all present analyses were adjusted for age.

CONCLUSION

We have shown that IL-6, KYN and KYNA are elevated in patients with chronic schizophrenia, strengthening the idea of brain immune activation in patients with this disease. Our concurrent cell culture and clinical findings suggest that IL-6 induces the KYN pathway, leading to increased production of the N-methyl-D-aspartate receptor antagonist KYNA in patients with schizophrenia.

Acute CSF interleukin-6 trajectories after TBI: associations with neuroinflammation, polytrauma, and outcome

Traumatic brain injury (TBI) results in a significant inflammatory burden that perpetuates the production of inflammatory mediators and biomarkers. Interleukin-6 (IL-6) is a pro-inflammatory cytokine known to be elevated after trauma, and a major contributor to the inflammatory response following TBI. Previous studies have investigated associations between IL-6 and outcome following TBI, but to date, studies have been inconsistent in their conclusions. We hypothesized that cohort heterogeneity, temporal inflammatory profiles, and concurrent inflammatory marker associations are critical to characterize when targeting subpopulations for anti-inflammatory therapies. Toward this objective, we used serial cerebrospinal fluid (CSF) samples to generate temporal acute IL-6 trajectory (TRAJ) profiles in a prospective cohort of adults with severe TBI (n=114). We examined the impact of injury type on IL-6 profiles, and how IL-6 profiles impact sub-acute (2weeks-3months) serum inflammatory marker load and long-term global outcome 6-12months post-injury. There were two distinct acute CSF IL-6 profiles, a high and low TRAJ group. Individuals in the high TRAJ had increased odds of unfavorable Glasgow Outcome Scale (GOS) scores at 6months (adjusted OR=3.436, 95% CI: 1.259, 9.380). Individuals in the high TRAJ also had higher mean acute CSF inflammatory load compared to individuals in the low TRAJ (p⩽0.05). The two groups did not differ with respect acute serum profiles; however, individuals in the high CSF IL-6 TRAJ also had higher mean sub-acute serum IL-1β and IL-6 levels compared with the low TRAJ group (p⩽0.05). Lastly, injury type (isolated TBI vs. TBI+polytrauma) was associated with IL-6 TRAJ group (χ(2)=5.31, p=0.02). Specifically, there was 70% concordance between those with TBI+polytrauma and the low TRAJ; in contrast, isolated TBI was similarly distributed between TRAJ groups. These data provide evidence that sustained, elevated levels of CSF IL-6 are associated with an increased inflammatory load, and these increases are associated with increased odds for unfavorable global outcomes in the first year following TBI. Future studies should explore additional factors contributing to IL-6 elevations, and therapies to mitigate its detrimental effects on outcome.

Elevated levels of IL-6 and IL-18 in manic and hypomanic states in rapid cycling bipolar disorder patients

Inflammatory system dysregulation may be involved in the pathophysiology of bipolar disorder with peripheral cytokine levels varying between affective states; however, the evidence is based primarily on case-control studies and limited by methodological issues. The objectives of the present study were to assess alterations of peripheral cytokine levels between affective states in rapid cycling bipolar disorder patients and to compare these with levels in healthy control subjects. In a longitudinal design, repeated measurements of plasma levels of IL-6, IL-10, IL-18, IL-1β and TNF-α were obtained in affective states of varying polarity during 6-12 months in 37 rapid cycling bipolar disorder patients and compared with repeated measurements in 40 age- and gender matched healthy control subjects, using rigorous laboratory-, clinical- and statistical methodology. Adjusting for demographical, clinical- and lifestyle factors, levels of IL-6 (p<0.05) and IL-18 (p<0.005) were significantly elevated in rapid cycling bipolar disorder patients in a manic/hypomanic state, compared with a depressed and a euthymic state. Compared with healthy control subjects, unadjusted levels of IL-6 (p<0.05) and IL-18 (p<0.05) were elevated in manic/hypomanic bipolar disorder patients. Levels of IL-10 and IL-1β were undetectable in the majority of samples; high TNF-α assay variability was found. The results support a role for altered peripheral immune response signaling in rapid cycling bipolar disorder and suggest that IL-6 and IL-18 could be markers of manic episodes.

Increased cerebrospinal fluid interleukin-8 in bipolar disorder patients associated with lithium and antipsychotic treatment

Inflammation has been linked to the pathophysiology of bipolar disorder based on studies of inflammation markers, such as cytokine concentrations, in plasma and serum samples from cases and controls. However, peripheral measurements of cytokines do not readily translate to immunological activity in the brain. The aim of the present study was to study brain immune and inflammatory activity. To this end, we analyzed cytokines in cerebrospinal fluid from 121 euthymic bipolar disorder patients and 71 age and sex matched control subjects. Concentrations of 11 different cytokines were determined using immunoassays. Cerebrospinal fluid IL-8 concentrations were significantly higher in patients as compared to controls. The other cytokines measured were only detectable in part of the sample. IL-8 concentrations were positively associated to lithium- and antipsychotic treatment. The findings might reflect immune aberrations in bipolar disorder, or be due to the effects of medication.

IL-6 regulation of synaptic function in the CNS

A growing body of evidence supports a role for glial-produced neuroimmune factors, including the cytokine IL-6, in CNS physiology and pathology. CNS expression of IL-6 has been documented in the normal CNS at low levels and at elevated levels in several neurodegenerative or psychiatric disease states as well as in CNS infection and injury. The altered CNS function associated with these conditions raises the possibility that IL-6 has neuronal or synaptic actions. Studies in in vitro and in vivo models confirmed this possibility and showed that IL-6 can regulate a number of important neuronal and synaptic functions including synaptic transmission and synaptic plasticity, an important cellular mechanism of memory and learning. Behavioral studies in animal models provided further evidence of an important role for IL-6 as a regulator of CNS pathways that are critical to cognitive function. This review summarizes studies that have lead to our current state of knowledge. In spite of the progress that has been made, there is a need for a greater understanding of the physiological and pathophysiological actions of IL-6 in the CNS, the mechanisms underlying these actions, conditions that induce production of IL-6 in the CNS and therapeutic strategies that could ameliorate or promote IL-6 actions. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Circadian rhythmicity, variability and correlation of interleukin-6 levels in plasma and cerebrospinal fluid of healthy men

BACKGROUND

Interleukin-6 (IL-6) is a cytokine with pleiotropic actions in both the periphery of the body and the central nervous system (CNS). Altered IL-6 secretion has been associated with inflammatory dysregulation and several adverse health consequences. However, little is known about the physiological circadian characteristics and dynamic inter-correlation between circulating and CNS IL-6 levels in humans, or their significance.

METHODS

Simultaneous assessment of plasma and cerebrospinal fluid (CSF) IL-6 levels was performed hourly in 11 healthy male volunteers over 24h, to characterize physiological IL-6 secretion levels in both compartments.

RESULTS

IL-6 levels showed considerable within- and between-subject variability in both plasma and CSF, with plasma/CSF ratios revealing consistently higher levels in the CSF. Both CSF and plasma IL-6 levels showed a distinctive circadian variation, with CSF IL-6 levels exhibiting a main 24h, and plasma a biphasic 12h, circadian component. Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was at around 7 p.m. There was no correlation between coincident CSF and plasma IL-6 values, but evidence for significant correlations at a negative 7-8h time lag.

CONCLUSIONS

This study provides evidence in humans for a circadian IL-6 rhythm in CSF and confirms prior observations reporting a plasma biphasic circadian pattern. Our results indicate differential IL-6 regulation across the two compartments and are consistent with local production of IL-6 in the CNS. Possible physiological significance is discussed and implications for further research are highlighted.

Cerebrospinal fluid and serum cytokine profiles in narcolepsy with cataplexy: a case-control study

Recent advances in the identification of susceptibility genes and environmental exposures provide strong support that narcolepsy-cataplexy is an immune-mediated disease. Only few serum cytokine studies with controversial results were performed in narcolepsy and none in the cerebrospinal fluid. We measured a panel of 12 cytokines by a proteomic approach in the serum of 35 patients with narcolepsy-cataplexy compared to 156 healthy controls, and in the cerebrospinal fluid of 34 patients with narcolepsy-cataplexy compared to 17 non-narcoleptic patients; and analyzed the effect of age, duration and severity of disease on the cytokine levels. After multiple adjustments we reported lower serum IL-2, IL-8, TNF-α, MCP-1 and EGF levels, and a tendency for higher IL-4 level in narcolepsy compared to controls. Significant differences were only found for IL-4 in cerebrospinal fluid, being higher in narcolepsy. Positive correlations were found in serum between IL-4, daytime sleepiness, and cataplexy frequency. The expression of some pro-inflammatory cytokines (MCP-1, VEGF, EGF, IL2, IL-1β, IFN-γ) in either serum or CSF was negatively correlated with disease severity and duration. No correlation was found for any specific cytokine in 18 of the patients with narcolepsy with peripheral and central samples collected the same day. Significant decreased pro/anti-inflammatory cytokine profiles were found at peripheral and central levels in narcolepsy, together with a T helper 2/Th1 serum cytokine secretion imbalance. To conclude, we showed some evidence for alterations in the cytokine profile in patients with narcolepsy-cataplexy compared to controls at peripheral and central levels, with the potential role of IL-4 and significant Th1/2 imbalance in the pathophysiology of narcolepsy.

Cytokines in bipolar disorder vs. healthy control subjects: a systematic review and meta-analysis

BACKGROUND

Bipolar disorder may be associated with peripheral immune system dysfunction; however, results in individual studies are conflicting. Our aim was to systematically review evidence of peripheral cytokine alterations in bipolar disorder integrating findings from various affective states.

METHODS

We conducted a meta-analysis of studies comparing peripheral cytokine concentrations in patients with bipolar disorder with healthy control subjects. Results were reported according to the PRISMA statement.

RESULTS

Eighteen studies with a total of 761 bipolar disorder patients and 919 healthy controls were included. Overall, concentrations of soluble Interleukin (IL)-2 receptor (sIL-2R), tumor necrosis factor-α (TNF-α), soluble tumor necrosis factor receptor type 1 (sTNFR1) (p < 0.001 each), sIL-6R (p = 0.01) and IL-4 (p = 0.04) were significantly higher in bipolar patients compared with healthy controls. There were no significant differences between bipolar disorder patients and healthy control subjects for IL-1, IL-2, IL-5, IL-6, IL-8, IL-10, IL-12, IL-1β, IL-1 receptor antagonist (IL-1RA), interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1) and sTNFR2.

CONCLUSIONS

Employing a global approach, incorporating evidence across affective states, this meta-analysis found some support for peripheral inflammatory alterations in bipolar disorder. Results were limited by heterogeneity between studies, insufficient standardization and lacking control for confounders in individual studies. Further research exploring the role of the peripheral inflammatory system in relation to neuroinflammation is warranted.

The role of markers of inflammation in traumatic brain injury

Within minutes of a traumatic impact, a robust inflammatory response is elicited in the injured brain. The complexity of this post-traumatic squeal involves a cellular component, comprising the activation of resident glial cells, microglia, and astrocytes, and the infiltration of blood leukocytes. The second component regards the secretion immune mediators, which can be divided into the following sub-groups: the archetypal pro-inflammatory cytokines (Interleukin-1, Tumor Necrosis Factor, Interleukin-6), the anti-inflammatory cytokines (IL-4, Interleukin-10, and TGF-beta), and the chemotactic cytokines or chemokines, which specifically drive the accumulation of parenchymal and peripheral immune cells in the injured brain region. Such mechanisms have been demonstrated in animal models, mostly in rodents, as well as in human brain. Whilst the humoral immune response is particularly pronounced in the acute phase following Traumatic brain injury (TBI), the activation of glial cells seems to be a rather prolonged effect lasting for several months. The complex interaction of cytokines and cell types installs a network of events, which subsequently intersect with adjacent pathological cascades including oxidative stress, excitotoxicity, or reparative events including angiogenesis, scarring, and neurogenesis. It is well accepted that neuroinflammation is responsible of beneficial and detrimental effects, contributing to secondary brain damage but also facilitating neurorepair. Although such mediators are clear markers of immune activation, to what extent cytokines can be defined as diagnostic factors reflecting brain injury or as predictors of long term outcome needs to be further substantiated. In clinical studies some groups reported a proportional cytokine production in either the cerebrospinal fluid or intraparenchymal tissue with initial brain damage, mortality, or poor outcome scores. However, the validity of cytokines as biomarkers is not broadly accepted. This review article will discuss the evidence from both clinical and laboratory studies exploring the validity of immune markers as a correlate to classification and outcome following TBI.

The role of markers of inflammation in traumatic brain injury

Within minutes of a traumatic impact, a robust inflammatory response is elicited in the injured brain. The complexity of this post-traumatic squeal involves a cellular component, comprising the activation of resident glial cells, microglia, and astrocytes, and the infiltration of blood leukocytes. The second component regards the secretion immune mediators, which can be divided into the following sub-groups: the archetypal pro-inflammatory cytokines (Interleukin-1, Tumor Necrosis Factor, Interleukin-6), the anti-inflammatory cytokines (IL-4, Interleukin-10, and TGF-beta), and the chemotactic cytokines or chemokines, which specifically drive the accumulation of parenchymal and peripheral immune cells in the injured brain region. Such mechanisms have been demonstrated in animal models, mostly in rodents, as well as in human brain. Whilst the humoral immune response is particularly pronounced in the acute phase following Traumatic brain injury (TBI), the activation of glial cells seems to be a rather prolonged effect lasting for several months. The complex interaction of cytokines and cell types installs a network of events, which subsequently intersect with adjacent pathological cascades including oxidative stress, excitotoxicity, or reparative events including angiogenesis, scarring, and neurogenesis. It is well accepted that neuroinflammation is responsible of beneficial and detrimental effects, contributing to secondary brain damage but also facilitating neurorepair. Although such mediators are clear markers of immune activation, to what extent cytokines can be defined as diagnostic factors reflecting brain injury or as predictors of long term outcome needs to be further substantiated. In clinical studies some groups reported a proportional cytokine production in either the cerebrospinal fluid or intraparenchymal tissue with initial brain damage, mortality, or poor outcome scores. However, the validity of cytokines as biomarkers is not broadly accepted. This review article will discuss the evidence from both clinical and laboratory studies exploring the validity of immune markers as a correlate to classification and outcome following TBI.

Understanding the neuroinflammatory response following concussion to develop treatment strategies

Mild traumatic brain injuries (mTBI) have been associated with long-term cognitive deficits relating to trauma-induced neurodegeneration. These long-term deficits include impaired memory and attention, changes in executive function, emotional instability, and sensorimotor deficits. Furthermore, individuals with concussions show a high co-morbidity with a host of psychiatric illnesses (e.g., depression, anxiety, addiction) and dementia. The neurological damage seen in mTBI patients is the result of the impact forces and mechanical injury, followed by a delayed neuroimmune response that can last hours, days, and even months after the injury. As part of the neuroimmune response, a cascade of pro- and anti-inflammatory cytokines are released and can be detected at the site of injury as well as subcortical, and often contralateral, regions. It has been suggested that the delayed neuroinflammatory response to concussions is more damaging then the initial impact itself. However, evidence exists for favorable consequences of cytokine production following traumatic brain injuries as well. In some cases, treatments that reduce the inflammatory response will also hinder the brain's intrinsic repair mechanisms. At present, there is no evidence-based pharmacological treatment for concussions in humans. The ability to treat concussions with drug therapy requires an in-depth understanding of the pathophysiological and neuroinflammatory changes that accompany concussive injuries. The use of neurotrophic factors [e.g., nerve growth factor (NGF)] and anti-inflammatory agents as an adjunct for the management of post-concussion symptomology will be explored in this review.

Cytokines and innate inflammation in the pathogenesis of human traumatic brain injury

There is an increasing recognition that following traumatic brain injury, a cascade of inflammatory mediators is produced, and contributes to the pathological consequences of central nervous system injury. This review summarises the key literature from pre-clinical models that underlies our understanding of innate inflammation following traumatic brain injury before focussing on the growing evidence from human studies. In addition, the underlying molecular mediators responsible for blood brain barrier dysfunction have been discussed. In particular, we have highlighted the different sampling methodologies available and the difficulties in interpreting human data of this sort. Ultimately, understanding the innate inflammatory response to traumatic brain injury may provide a therapeutic avenue in the treatment of central nervous system disease.

Elevation of cerebrospinal fluid interleukin-1ß in bipolar disorder

BACKGROUND

In recent years, a role for the immune system in the pathogenesis of psychiatric diseases has gained increased attention. Although bipolar disorder appears to be associated with altered serum cytokine levels, a putative immunological contribution to its pathophysiology remains to be established. Hitherto, no direct analyses of cerebrospinal fluid (CSF) cytokines in patients with bipolar disorder have been performed.

METHODS

We analyzed CSF cytokine concentrations in euthymic patients with diagnosed bipolar disorder type I (n = 15) or type II (n = 15) and healthy volunteers (n = 30) using an immunoassay-based protein array multiplex system.

RESULTS

The mean interleukin (IL)-1ß level (4.2 pg/mL, standard error of the mean [SEM] 0.5) was higher and the IL-6 level (1.5 pg/mL, SEM 0.2) was lower in euthymic bipolar patients than in healthy volunteers (0.8 pg/mL, SEM 0.04, and 2.6 pg/mL, SEM 0.2, respectively). Patients with 1 or more manic/hypomanic episodes during the last year showed significantly higher levels of IL-1ß (6.2 pg/mL, SEM 0.8; n = 9) than patients without a recent manic/hypomanic episode (3.1 pg/mL, SEM 1.0; n = 10).

LIMITATIONS

All patients were in an euthymic state at the time of sampling. Owing to the large variety of drugs prescribed to patients in the present study, influence of medication on the cytokine profile cannot be ruled out.

CONCLUSION

Our findings show an altered brain cytokine profile associated with the manifestation of recent manic/hypomanic episodes in patients with bipolar disorder. Although the causality remains to be established, these findings may suggest a pathophysiological role for IL-1ß in bipolar disorder.

Blunted affect is associated with hypothalamic--pituitary--adrenal axis (HPA) hypoactivity and elevated CSF-interleukin-1 beta (IL-1β) in response to lumbar puncture

OBJECTIVE

Proinflammatory activity has been suggested as one of the psychophysiological mechanisms responsible for the health risks associated with stress and mood disorders. There have been limited studies evaluating central immune and hypothalamic- pituitary-adrenal (HPA) axis responses to experimental stress in healthy women. The current study compared, under a controlled condition, the baseline measures and biological and psychological responses to a physical stressor (lumbar puncture [LP]) of healthy women who exhibited an abnormal serum cortisol response (nonresponders [NRs]) to the LP to those of normal controls (responders [Rs]), allowing assessment of stress responsivity and the functional integrity of the feedback system of the HPA axis, sympathetic nervous system (SNS), and neuroimmune axis.

METHOD

Serum adrenocorticotropic hormone (ACTH), cortisol, interleukin (IL)-6, IL-1sR, and central IL-1β, IL-6, norepineprhine (NE), corticotropin-releasing factor (CRF), and affective states (using the Stress Symptom Rating Questionnaire) were measured in five NRs and seven Rs.

RESULTS

Compared with NR subjects, Rs had significantly higher levels of ACTH and central IL-1β, higher ratings of attention, and lower perceived stress and anxiety. There were no differences between the groups in serum cortisol, IL-6, or IL-1sR or in central IL-6, NE, and CRF.

CONCLUSIONS

Women with significantly elevated IL-1β (NRs) responded to an extreme physical stressor with an attenuated HPA system and abnormal subjective ratings compared to healthy women with lower values of central IL-1β. These findings support the suppression of the effects of HPA-axis cortisol on proinflammatory cytokine production. It is possible that these differences in the psychoneuroimmunological profiles of NRs will lead to increased psychobiological vulnerability and predict future health risk.

Is cell salvage safe in liver resection? A pilot study

STUDY OBJECTIVE

To investigate the quality of cell salvaged (CS) blood in patients undergoing hemihepatectomy (study group) and compare it with CS-blood from aortic surgery (control group).

DESIGN

Observational study.

SETTING

Operating room in a university hospital.

MEASUREMENTS

6 patients undergoing hemihepatectomy or aortobifemoral bypass with intraoperative blood loss of more than 800 mL. Samples were drawn from the central venous catheter, from the reservoir of a CS recovery system, and from the processed blood in each patient to determine interleukin (IL)-6, IL-8, IL-10, tumor necrosis factor (TNF), complement C3a, and the terminal complement complex C5b-9. Microbiological analysis included colony count after cultivation in aerobic and anaerobic medium as well as enrichment culture for 6 days.

MAIN RESULTS

In the hemihepatectomy group, levels of IL-6, C3a, and C5b-9 were significantly higher in the reservoir than in samples obtained from the central venous catheter. After the washing procedure, levels of IL-6, C3a, and C5b-9 were lower in the liver resection group than in each patient's own plasma levels. In all patients undergoing aortobifemoral bypass and in 5 patients undergoing hemihepatectomy, blood samples were sterile or showed growth of commensal skin microflora in low numbers (coagulase-negative staphylococci or propionibacteria). In one patient in the liver resection group, we could not exclude contamination with intestinal flora.

CONCLUSION

Cell salvaged blood in liver resection seems to be safe for retransfusion with respect to cytokine release and complement activation, but requires further investigation in regard to bacterial contamination.

Involvement of pro- and anti-inflammatory cytokines and chemokines in the pathophysiology of traumatic brain injury

Despite dramatic improvements in the management of traumatic brain injury (TBI), to date there is no effective treatment available to patients, and morbidity and mortality remain high. The damage to the brain occurs in two phases, the initial primary phase being the injury itself, which is irreversible and amenable only to preventive measures to minimize the extent of damage, followed by an ongoing secondary phase, which begins at the time of injury and continues in the ensuing days to weeks. This delayed phase leads to a variety of physiological, cellular, and molecular responses aimed at restoring the homeostasis of the damaged tissue, which, if not controlled, will lead to secondary insults. The development of secondary brain injury represents a window of opportunity in which pharmaceutical compounds with neuroprotective properties could be administered. To establish effective treatments for TBI victims, it is imperative that the complex molecular cascades contributing to secondary injury be fully elucidated. One pathway known to be activated in response to TBI is cellular and humoral inflammation. Neuroinflammation within the injured brain has long been considered to intensify the damage sustained following TBI. However, the accumulated findings from years of clinical and experimental research support the notion that the action of inflammation may differ in the acute and delayed phase after TBI, and that maintaining limited inflammation is essential for repair. This review addresses the role of several cytokines and chemokines following focal and diffuse TBI, as well as the controversies around the use of therapeutic anti-inflammatory treatments versus genetic deletion of cytokine expression.

Metabolomics tools for identifying biomarkers for neuropsychiatric diseases

The repertoire of biochemicals (or small molecules) present in cells, tissue, and body fluids is known as the metabolome. Today, clinicians utilize only a very small part of the information contained in the metabolome, as revealed by the quantification of a limited set of analytes to gain information on human health. Examples include measuring glucose or cholesterol to monitor diabetes and cardiovascular health, respectively. With a focus on comprehensively studying the metabolome, the rapidly growing field of metabolomics captures the metabolic state of organisms at the global or "-omics" level. Given that the overall health status of an individual is captured by his or her metabolic state, which is a reflection of what has been encoded by the genome and modified by environmental factors, metabolomics has the potential to have a great impact upon medical practice by providing a wealth of relevant biochemical data. Metabolomics promises to improve current, single metabolites-based clinical assessments by identifying metabolic signatures (biomarkers) that embody global biochemical changes in disease, predict responses to treatment or medication side effects (pharmachometabolomics). State of the art metabolomic analytical platforms and informatics tools are being used to map potential biomarkers for a multitude of disorders including those of the central nervous system (CNS). Indeed, CNS disorders are linked to disturbances in metabolic pathways related to neurotransmitter systems (dopamine, serotonin, GABA and glutamate); fatty acids such as arachidonic acid-cascade; oxidative stress and mitochondrial function. Metabolomics tools are enabling us to map in greater detail perturbations in many biochemical pathways and links among these pathways this information is key for development of biomarkers that are disease-specific. In this review, we elaborate on some of the concepts and technologies used in metabolomics and its promise for biomarker discovery. We also highlight early findings from metabolomic studies in CNS disorders such as schizophrenia, Major Depressive Disorder (MDD), Bipolar Disorder (BD), Amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD).