Variations in circulating cytokine levels during 52 week course of treatment with SSRI for major depressive disorder

Effect of antidepressant treatment on peripheral inflammation markers - A meta-analysis

INTRODUCTION

Major Depressive Disorder (MDD) in accordance to the inflammatory concept is associated with complex immunological disturbances in the central nervous system (CNS). This is reflected by elevated plasma levels of inflammatory cytokines in depressed subjects. Although numerous studies report significant influence of antidepressants on pro-inflammatory/anti-inflammatory cytokines balance, the available data is often inconsistent regarding specific cytokines and drugs used. We aimed to perform a comprehensive meta-analysis of the effect of antidepressant treatment on a wide array of cytokines.

METHODS

We performed a systematic search of 6 databases, which yielded 32 studies measuring the levels of selected cytokines before and at a second time-point during antidepressant treatment. For meta-analysis of selected studies with a continuous measure we analysed variables containing the number of cases, mean and standard deviation of the level of IL-1ß, IL-2, IL-5, IL-6, IL-8, IL-10, CRP, TNF-α, IFN-γ levels observed in the different studies, in the intervention groups before and after antidepressant treatment.

RESULTS

Statistical analysis revealed significant decreases of IL-4, IL-6, and IL-10 in MDD subjects after antidepressant treatment. In case of IL-1ß the decrease was significant exclusively for SSRI drugs. We did not find any significant effect of antidepressant medication on IL-2, TNF-α IFN-γ and CRP.

CONCLUSIONS

Antidepressant treatment affects the levels of cytokines in depression. The immunological imbalance in MDD is complex and seems to be mediated by other factors yet to be elucidated. The credibility of our results is limited by high heterogeneity among studies and very few studies with a placebo-controlled design. Research with MDD subtypes, response to treatment status and cytokine associations with the kynurenine pathway taken into account pose a promising target for future studies.

Stability of Cellular Immune Parameters over 12 Weeks in Patients with Major Depression or Somatoform Disorder and in Healthy Controls

OBJECTIVE

Cellular immune status in major depression (MD) patients differs from that in somatoform disorder (SFD) patients and healthy controls (HC). It is still questionable whether the patterns of immune parameters remain stable over time. Therefore, we studied lymphocyte and monocyte cell counts and neopterin levels in peripheral blood of MD and SFD patients and HC over 12 weeks and tested for correlations between biochemical and psychometric parameters.

METHODS

Thirty-nine patients with MD, 27 with SFD, and 51 HC were recruited. Peripheral blood was drawn at four visits, at 4-week intervals. We assessed the total cell count of B lymphocytes, natural killer (NK) cells, T lymphocyte subpopu-lations, and monocytes by flow cytometry, and neopterin serum levels by ELISA. Psychometric parameters were measured with questionnaires.

RESULTS

Counts of lymphocytes, monocytes, and neopterin were stable in the SFD and HC groups. In the MD group, total CD3+, CD3+CD8+, NK cells, and CD3+CD25+ T cells showed inhomogeneous variances in Friedman tests, particularly in females. Neopterin correlated with depressed mood in MD patients, and with body mass index in HC.

CONCLUSIONS

Cellular immune parameters are stable in HC and SFD. Our results may indicate influences of MD and gender on some cellular immune parameters. This may need to be considered in future immunological studies.

Differences in immunomodulatory properties between venlafaxine and paroxetine in patients with major depressive disorder

Inflammatory processes play a crucial role in the pathophysiology of depression, and identifying the specific cytokines targeted by different antidepressants is important for personalized treatment. The aims of this study were to examine whether venlafaxine and paroxetine cause different immunomodulatory effects when used to treat patients with major depression and to clarify the relationships between plasma cytokine levels and the therapeutic effectiveness of these drugs. A total of 91 Han Chinese patients with major depression completed the 8-week paroxetine or venlafaxine treatment and 90 healthy controls were recruited. A multiplex assay was used to measure cytokines levels in patients with major depression before and after an 8-week venlafaxine and paroxetine treatment. Cytokine levels were measured in healthy controls at the baseline. The 21-item Hamilton Depression Rating Scale was used to assess the changes in psychopathological symptoms from the baseline to the end point in each patient. Venlafaxine treatment caused greater decreases in the levels of interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), interleukin 4 (IL-4), IL-5, IL-1β, and IL-8 than did paroxetine. Paroxetine treatment increased the levels of proinflammatory cytokines IFN-γ, TNF-α, and IL-6 and decreased Th2 cytokine levels. After paroxetine treatment, IL-6 levels increased more in the non-remitter group than in the remitter group. In the remitter group, IL-4 and IL-5 levels decreased to values seen in the healthy controls. After venlafaxine treatment in both the remitter and non-remitter groups, IL-1β levels decreased to values seen in the healthy controls. Our results suggest that venlafaxine and paroxetine have different immunomodulatory properties and that venlafaxine has greater anti-inflammatory effects than paroxetine.

Serum Markers of Inflammation Mediate the Positive Association Between Neuroticism and Depression

Background: The personality trait neuroticism has been implicated in a poor response to stress, may relate to increased concentrations of cytokines and the development of depression. Inflammatory mechanisms may also be associated with the onset, severity and symptoms of depression. Both are related to poor antidepressant treatment outcome. Therefore, mediators of inflammation may bridge the relationship between neuroticism and depression. Methods: To disentangle these interrelationships, the associations between neuroticism (according to NEO-PIR-N), depressive symptoms (BDI-II scores) and serum levels of hsCRP, TNF-α, IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, GM-CSF were investigated in a group of 212 participants, consisting of 37 depressed and 175 non-depressed subjects. A mediation model was used to investigate whether the impact of neuroticism on depressive symptoms may be mediated by cytokines. Results: Regression analyses revealed that IFN-γ, IL-5, and IL-12-levels, but none of the anti-inflammatory cytokines, were associated with the overall neuroticism score and several of the cytokines were related to the different facets of neuroticism. TNF-α, IFN-γ, IL-5, IL-12, and IL-13 were further related to the severity of depressive symptoms, as well as the somatic-affective and the cognitive dimensions of depression. Pro-inflammatory IFN-γ, IL-5 and IL-12 were identified as mediators of the positive prediction of depression severity by the degree of neuroticism. Conclusions: The current findings demonstrate that conditions related to long-term stress, such as depression and high neuroticism, are related to an up-regulation of inflammatory agents. Neuroticism may increase stress perception and, thus, increase the production of pro-inflammatory messenger molecules which are involved in the development of depression. This evidence may contribute to future anti-inflammatory interventions, particularly in subjects with high neuroticism who are at risk for developing depression. Furthermore, depressed patients with high neuroticism and cytokine levels may require early escalations in the intensity of treatment, along with additional therapeutic elements to increase the rate of treatment success.

Modulating Neuroinflammation to Treat Neuropsychiatric Disorders

Neuroinflammation is recognised as one of the potential mechanisms mediating the onset of a broad range of psychiatric disorders and may contribute to nonresponsiveness to current therapies. Both preclinical and clinical studies have indicated that aberrant inflammatory responses can result in altered behavioral responses and cognitive deficits. In this review, we discuss the role of inflammation in the pathogenesis of neuropsychiatric disorders and ask the question if certain genetic copy-number variants (CNVs) associated with psychiatric disorders might play a role in modulating inflammation. Furthermore, we detail some of the potential treatment strategies for psychiatric disorders that may operate by altering inflammatory responses.

Anti-inflammatory treatment for major depressive disorder: implications for patients with an elevated immune profile and non-responders to standard antidepressant therapy

Major depressive disorder (MDD) is a prevalent and disabling psychiatric disease with rates of non-responsiveness to antidepressants ranging from 30-50%. Historically, the monoamine depletion hypothesis has dominated the view on the pathophysiology of depression. However, the lack of responsiveness to antidepressants and treatment resistance suggests that additional mechanisms might play a role. Evidence has shown that a subgroup of depressive patients may have an underlying immune deregulation that could explain the lack of therapeutic benefit from antidepressants. Stimuli like inflammation and infection can trigger the activation of microglia to release pro-inflammatory cytokines, acting on two main pathways: (1) activation of the hypothalamic-pituitary adrenal axis, generating an imbalance in the serotonergic and noradrenergic circuits; (2) increased activity of the enzyme indoleamine-2,3-dioxygenase, resulting in depletion of serotonin levels and the production of quinolinic acid. If this hypothesis is proven true, the subgroup of MDD patients with increased levels of pro-inflammatory cytokines, mainly IL-6, TNF-α and IL-1β, might benefit from an anti-inflammatory intervention. Here, we discuss the pre-clinical and clinical studies that have provided support for treatment with non-steroidal anti-inflammatory drugs in depressed patients with inflammatory comorbidities or an elevated immune profile, as well as evidences for anti-inflammatory properties of standard antidepressants.

Antidepressant-like effect of a new selenium-containing compound is accompanied by a reduction of neuroinflammation and oxidative stress in lipopolysaccharide-challenged mice

Organoselenium compounds and indoles have gained attention due to their wide range of pharmacological properties. Depression is a recurrent and disabling psychiatric illness and current evidences support that oxidative stress and neuroinflammation are mechanisms underlying the pathophysiology of this psychiatric condition. Here, we evaluated the effect of 3-((4-chlorophenyl)selanyl)-1-methyl-1H-indole (CMI) in lipopolysaccharide (LPS)-induced depressive-like behaviour, neuroinflammation and oxidative stress in male mice. CMI pre-treatment (20 and 50 mg/kg, intragastrically) significantly attenuated LPS (0.83 mg/kg, intraperitoneally)-induced depressive-like behaviour in mice by reducing the immobility time in the tail suspension test (TST) and forced swimming test (FST). CMI pre-treatment ameliorated LPS-induced neuroinflammation by reducing the levels of interleukin (IL)-1β, IL-4 and IL-6 in the hippocampus and prefrontal cortex, as well as markers of oxidative damage. Additionally, we investigated the toxicological effects of CMI (200 mg/kg, i.g.) in the liver, kidney and brain through determination of the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), δ-aminolevulinate dehydratase (δ-ALA-D) and creatinine levels. These biomarkers were not modified, indicating the possible absence of neuro-, hepato- and nephrotoxic effects. Our results suggest that CMI could be a therapeutic approach for the treatment of depression and other neuropsychiatric disorders associated with inflammation and oxidative stress.

Inflammation and internalizing disorders in adolescents

Serum inflammatory markers have been studied in adults with anxiety and depression, but little is known about cytokine levels in young adolescents with emotional disorders. The objective of this study is to compare serum levels of interleukin-6 (IL-6) and interleukin-10 (IL-10) between adolescents with internalizing disorders and adolescents from the same community without internalizing disorders. A total of 134 non-medicated subjects (n=76 with internalizing disorders) were recruited from a larger sample of 2457 individuals. Serum levels of IL-6 and IL-10 were quantified and psychiatric diagnosis was evaluated using structured clinical interviews. Adolescents with internalizing disorders presented significantly higher levels of IL-6 as compared to youngsters without internalizing disorders. Differences between groups in IL-10 levels were not statistically significant. This study points out that IL-6 levels may be associated with internalizing disorders in youths and suggests that inflammation might be an early biomarker of emotional distress. High levels of cytokines may adversely affect general health in the long-term, which raise broader issues in terms of public health if results are replicated.

Peripheral Alterations in Cytokine and Chemokine Levels After Antidepressant Drug Treatment for Major Depressive Disorder: Systematic Review and Meta-Analysis

Mounting evidence suggests that aberrations in immune-inflammatory pathways contribute to the pathophysiology of major depressive disorder (MDD), and individuals with MDD may have elevated levels of predominantly pro-inflammatory cytokines and C-reactive protein. In addition, previous meta-analyses suggest that antidepressant drug treatment may decrease peripheral levels of interleukin-1 beta (IL-1β) and IL-6. Recently, several new studies examining the effect of antidepressants on these cytokines have been published, and so we performed an updated meta-analysis of studies that measured peripheral levels of cytokines and chemokines during antidepressant treatment in patients with MDD. The PubMed/MEDLINE, EMBASE, and PsycInfo databases were searched from inception through March 9, 2017. Forty-five studies met inclusion criteria (N = 1517). Peripheral levels of IL-6, tumor necrosis factor-alpha (TNF-α), IL-1β, IL-10, IL-2, IL-4, interferon-γ, IL-8, the C-C motif ligand 2 chemokine (CCL-2), CCL-3, IL-1 receptor antagonist, IL-13, IL-17, IL-5, IL-7, and the soluble IL-2 receptor were measured in at least three datasets and thus were meta-analyzed. Antidepressant treatment significantly decreased peripheral levels of IL-6 (Hedges g = -0.454, P <0.001), TNF-α (g = -0.202, P = 0.015), IL-10 (g = -0.566, P = 0.012), and CCL-2 (g = -1.502, P = 0.006). These findings indicate that antidepressants decrease several markers of peripheral inflammation. However, this meta-analysis did not provide evidence that reductions in peripheral inflammation are associated with antidepressant treatment response although few studies provided separate data for treatment responders and non-responders.

Immune System Activation and Depression: Roles of Serotonin in the Central Nervous System and Periphery

Serotonin (5-hydroxytryptamine, 5-HT) has long been recognized as a key contributor to the regulation of mood and anxiety and is strongly associated with the etiology of major depressive disorder (MDD). Although more known for its roles within the central nervous system (CNS), 5-HT is recognized to modulate several key aspects of immune system function that may contribute to the development of MDD. Copious amounts of research have outlined a connection between alterations in immune system function, inflammation status, and MDD. Supporting this connection, peripheral immune activation results in changes in the function and/or expression of many components of 5-HT signaling that are associated with depressive-like phenotypes. How 5-HT is utilized by the immune system to effect CNS function and ultimately behaviors related to depression is still not well understood. This Review summarizes the evidence that immune system alterations related to depression affect CNS 5-HT signaling that can alter MDD-relevant behaviors and that 5-HT regulates immune system signaling within the CNS and periphery. We suggest that targeting the interrelationships between immune and 5-HT signaling may provide more effective treatments for subsets of those suffering from inflammation-associated MDD.

Biomarkers for depression: recent insights, current challenges and future prospects

A plethora of research has implicated hundreds of putative biomarkers for depression, but has not yet fully elucidated their roles in depressive illness or established what is abnormal in which patients and how biologic information can be used to enhance diagnosis, treatment and prognosis. This lack of progress is partially due to the nature and heterogeneity of depression, in conjunction with methodological heterogeneity within the research literature and the large array of biomarkers with potential, the expression of which often varies according to many factors. We review the available literature, which indicates that markers involved in inflammatory, neurotrophic and metabolic processes, as well as neurotransmitter and neuroendocrine system components, represent highly promising candidates. These may be measured through genetic and epigenetic, transcriptomic and proteomic, metabolomic and neuroimaging assessments. The use of novel approaches and systematic research programs is now required to determine whether, and which, biomarkers can be used to predict response to treatment, stratify patients to specific treatments and develop targets for new interventions. We conclude that there is much promise for reducing the burden of depression through further developing and expanding these research avenues.

Immune and Neuroendocrine Mechanisms of Stress Vulnerability and Resilience

Diagnostic criteria for mood disorders including major depressive disorder (MDD) largely ignore biological factors in favor of behavioral symptoms. Compounding this paucity of psychiatric biomarkers is a need for therapeutics to adequately treat the 30-50% of MDD patients who are unresponsive to traditional antidepressant medications. Interestingly, MDD is highly prevalent in patients suffering from chronic inflammatory conditions, and MDD patients exhibit higher levels of circulating pro-inflammatory cytokines. Together, these clinical findings suggest a role for the immune system in vulnerability to stress-related psychiatric illness. A growing body of literature also implicates the immune system in stress resilience and coping. In this review, we discuss the mechanisms by which peripheral and central immune cells act on the brain to affect stress-related neurobiological and neuroendocrine responses. We specifically focus on the roles of pro-inflammatory cytokine signaling, peripheral monocyte infiltration, microglial activation, and hypothalamic-pituitary-adrenal axis hyperactivity in stress vulnerability. We also highlight recent evidence suggesting that adaptive immune responses and treatment with immune modulators (exogenous glucocorticoids, humanized antibodies against cytokines) may decrease depressive symptoms and thus represent an attractive alternative to the current antidepressant treatments.

How to: Measuring blood cytokines in biological psychiatry using commercially available multiplex immunoassays

Cytokines produced by both immune and non-immune cells are likely to play roles in the development and/or progression of psychiatric disorders. Indeed, many investigators have compared the blood cytokine levels in psychiatric patients with those of healthy controls or monitored their levels in patients during disease progression to identify biomarkers. Nevertheless, very few studies have confirmed that such cytokines remain stable in healthy individuals through periods of weeks and months. This is an important issue to consider before using blood cytokine levels as biomarkers of disease traits, disease state, or treatment response. Although multiplex assay technology represents an advance in identifying biomarkers because it allows simultaneous examination of large panels of analytes from a small volume of sample, it is necessary to verify whether these assays yield enough sensitivity and reproducibility when applied to the blood from neuropsychiatric patients. Therefore, we compared two multiplex immunoassays, the bead-based Luminex^® (Bio-Rad) and the electro-chemiluminescence-based V-plex^® (MesoScaleDiscovery), for the detection and quantification of 31 cytokines, chemokines and growth factors in both the sera and plasma of patients with major depressive episodes (MDE) and age- and sex-matched healthy control subjects during a 30-week period. Although both platforms exhibited low coefficients of variability (CV) between the duplicates in the calibration curves, the linearity was better in general for the V-PLEX^® platform. However, neither platform was able to detect the absolute values for all of the tested analytes. Among the 16 analytes that were detected by both assays, the intra-assay reproducibility was in general better with the V-PLEX^® platform. Although it is not a general rule that the results from sera and plasma will be correlated, consistent results were more frequent with the V-PLEX^® platform. Furthermore, the V-PLEX^® results were more consistent with the gold standard ELISA simplex assay for IL-6 in both sera and plasma. The intra-individual variability of the measurements, among the sera and plasma for the 4 samples harvested from each healthy individual, was low for Eotaxin, G-CSF, IL-4, IL-7, IL-9, IL-12p40, IL-12p70, IL-15, MIP-1β, PDGF-BB, TNF, TNF-β and VEGF, but intermediate or high for IFN-γ, IL-6, IL-8, IL-10, and IP10. Together, these data suggest that extreme caution is needed in translating the results of multiplex cytokine profiling into biomarker discovery in psychiatry.

Interleukin-1 β-targeted treatment strategies in inflammatory depression: toward personalized care

OBJECTIVES

It is unknown whether a cytokine signature may help the identification of subgroup of patient who would respond to personalized treatment. As interleukin-1 beta (Il-1β) seems to play a major role in mood disorder, a systematic review and meta-analysis of its potential role in major depressive disorder (MDD) was carried out.

METHODS

A systematic search was performed to identify appropriate MDD vs. control studies pertaining to Il-1β. Methodological quality and possible moderators were also assessed.

RESULTS

A total of 1922 studies were identified, and 53 articles were selected. Results showed an association between increased blood IL-1β and MDD in high-quality studies only. No association with age was found. No IL-1β gene-related polymorphisms has been associated with MDD. No effect of antidepressant on IL-1β level has been found, although the antidepressants investigated were various. Qualitative analyses indicate that MDD coupled to a history of childhood trauma may be a subgroup for IL-1β -targeted therapies. No difference in studies utilizing a stimulation method has been identified to date.

CONCLUSIONS

The present work has confirmed IL-1β as a biological marker of interest for innovative MDD treatments. However, further studies are needed to clarify the patients with MDD who may benefit from these therapies.

A meta-analysis of blood cytokine network alterations in psychiatric patients: comparisons between schizophrenia, bipolar disorder and depression

Schizophrenia, bipolar disorder and major depressive disorder (MDD) have all been associated with aberrant blood cytokine levels; however, neither the pattern of cytokine alterations nor the impact of clinical status have been compared across disorders. We performed a meta-analysis of blood cytokines in acutely and chronically ill patients with these major psychiatric disorders. Articles were identified by searching the PubMed, PsycInfo and Web of Science, and the reference lists of these studies. Sixty-eight studies met the inclusion criteria (40 schizophrenia, 10 bipolar disorder and 18 MDD) for acutely ill patients. Forty-six studies met the inclusion criteria (18 schizophrenia, 16 bipolar disorder and 12 MDD) for chronically ill patients. Levels of two cytokines (interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α)), one soluble cytokine receptor (sIL-2R), and one cytokine receptor antagonist (IL-1RA) were significantly increased in acutely ill patients with schizophrenia, bipolar mania and MDD compared with controls (P<0.01). Following treatment of the acute illness, IL-6 levels significantly decreased in both schizophrenia and MDD (P<0.01); sIL-2R levels increased in schizophrenia; and IL-1RA levels in bipolar mania decreased. In chronically ill patients, the levels of IL-6 were significantly increased in schizophrenia, euthymic (but not depressed) bipolar disorder and MDD compared with controls (P<0.01). The levels of IL-1β and sIL-2R were significantly increased in both chronic schizophrenia and euthymic bipolar disorder. Overall, there were similarities in the pattern of cytokine alterations in schizophrenia, bipolar disorder and MDD during acute and chronic phases of illness, raising the possibility of common underlying pathways for immune dysfunction. Effects of treatment on cytokines were more robust for schizophrenia and MDD, but were more frequently studied than for acute mania. These findings have important implications for our understanding of the pathophysiology and treatment of major psychiatric disorders.

TSPAN5, ERICH3 and selective serotonin reuptake inhibitors in major depressive disorder: pharmacometabolomics-informed pharmacogenomics

Millions of patients suffer from major depressive disorder (MDD), but many do not respond to selective serotonin reuptake inhibitor (SSRI) therapy. We used a pharmacometabolomics-informed pharmacogenomics research strategy to identify genes associated with metabolites that were related to SSRI response. Specifically, 306 MDD patients were treated with citalopram or escitalopram and blood was drawn at baseline, 4 and 8 weeks for blood drug levels, genome-wide single nucleotide polymorphism (SNP) genotyping and metabolomic analyses. SSRI treatment decreased plasma serotonin concentrations (P<0.0001). Baseline and plasma serotonin concentration changes were associated with clinical outcomes (P<0.05). Therefore, baseline and serotonin concentration changes were used as phenotypes for genome-wide association studies (GWAS). GWAS for baseline plasma serotonin concentrations revealed a genome-wide significant (P=7.84E-09) SNP cluster on chromosome four 5' of TSPAN5 and a cluster across ERICH3 on chromosome one (P=9.28E-08) that were also observed during GWAS for change in serotonin at 4 (P=5.6E-08 and P=7.54E-07, respectively) and 8 weeks (P=1.25E-06 and P=3.99E-07, respectively). The SNPs on chromosome four were expression quantitative trait loci for TSPAN5. Knockdown (KD) and overexpression (OE) of TSPAN5 in a neuroblastoma cell line significantly altered the expression of serotonin pathway genes (TPH1, TPH2, DDC and MAOA). Chromosome one SNPs included two ERICH3 nonsynonymous SNPs that resulted in accelerated proteasome-mediated degradation. In addition, ERICH3 and TSPAN5 KD and OE altered media serotonin concentrations. Application of a pharmacometabolomics-informed pharmacogenomic research strategy, followed by functional validation, indicated that TSPAN5 and ERICH3 are associated with plasma serotonin concentrations and may have a role in SSRI treatment outcomes.

Microglia Transcriptome Changes in a Model of Depressive Behavior after Immune Challenge

Depression symptoms following immune response to a challenge have been reported after the recovery from sickness. A RNA-Seq study of the dysregulation of the microglia transcriptome in a model of inflammation-associated depressive behavior was undertaken. The transcriptome of microglia from mice at day 7 after Bacille Calmette Guérin (BCG) challenge was compared to that from unchallenged Control mice and to the transcriptome from peripheral macrophages from the same mice. Among the 562 and 3,851 genes differentially expressed between BCG-challenged and Control mice in microglia and macrophages respectively, 353 genes overlapped between these cells types. Among the most differentially expressed genes in the microglia, serum amyloid A3 (Saa3) and cell adhesion molecule 3 (Cadm3) were over-expressed and coiled-coil domain containing 162 (Ccdc162) and titin-cap (Tcap) were under-expressed in BCG-challenged relative to Control. Many of the differentially expressed genes between BCG-challenged and Control mice were associated with neurological disorders encompassing depression symptoms. Across cell types, S100 calcium binding protein A9 (S100A9), interleukin 1 beta (Il1b) and kynurenine 3-monooxygenase (Kmo) were differentially expressed between challenged and control mice. Immune response, chemotaxis, and chemokine activity were among the functional categories enriched by the differentially expressed genes. Functional categories enriched among the 9,117 genes differentially expressed between cell types included leukocyte regulation and activation, chemokine and cytokine activities, MAP kinase activity, and apoptosis. More than 200 genes exhibited alternative splicing events between cell types including WNK lysine deficient protein kinase 1 (Wnk1) and microtubule-actin crosslinking factor 1(Macf1). Network visualization revealed the capability of microglia to exhibit transcriptome dysregulation in response to immune challenge still after resolution of sickness symptoms, albeit lower than that observed in macrophages. The persistent transcriptome dysregulation in the microglia shared patterns with neurological disorders indicating that the associated persistent depressive symptoms share a common transcriptome basis.

Modulatory Effects of Antidepressant Classes on the Innate and Adaptive Immune System in Depression

Current reviews exploring for unique immune-modulatory profiles of antidepressant classes are limited by focusing mainly on cytokine modulation only and neglecting other aspects of the innate and adaptive immune system. These reviews also do not include recent comparative clinical trials, immune-genetic studies and therapeutics with unique neurotransmitter profiles (e. g., agomelatine). This systematic review extends the established literature by comprehensively reviewing the effects of antidepressants classes on both the innate and adaptive immune system. Antidepressants appear, in general, to reduce pro-inflammatory factor levels, particularly C-reactive protein (CRP), tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6. We caution against conclusions as to which antidepressant possesses the greater anti-inflammatory effect, given the methodological heterogeneity among studies and the small number of comparative studies. The effects of antidepressant classes on adaptive immune factors are complex and poorly understood, and few studies have been conducted. Methodological heterogeneity is high among these studies (e. g., length of study, cohort characteristics, dosage used and immune marker analysis). We recommend larger, comparative studies - in clinical and pre-clinical populations.

Evidence of an IFN-γ by early life stress interaction in the regulation of amygdala reactivity to emotional stimuli

INTRODUCTION

Since numerous studies have found that exposure to early life stress leads to increased peripheral inflammation and psychiatric disease, it is thought that peripheral immune activation precedes and possibly mediates the onset of stress-associated psychiatric disease. Despite early studies, IFNγ has received little attention relative to other inflammatory cytokines in the context of the pathophysiology of affective disorders. Neuroimaging endophenotypes have emerged recently as a promising means of elucidating these types of complex relationships including the modeling of the interaction between environmental factors and genetic predisposition. Here we investigate the GxE relationship between early-life stress and genetic variants of IFNγ on emotion processing.

METHODS

To investigate the impact of the relationship between genetic variants of IFNγ (rs1861494, rs2069718, rs2430561) and early life stress on emotion processing, a sample of healthy adults (n=409) undergoing an emotional faces paradigm in an fMRI study were genotyped and analysed. Information on early life stress was obtained via Childhood Trauma Questionnaire (CTQ).

RESULTS

A positive association between early life stress and amygdala reactivity was found. Specifically, the main effect of genotype of rs1861494 on amygdala reactivity indicates a higher neural response in C allele carriers compared to T homozygotes, while we did not find main effects of rs2069718 and rs2430561. Importantly, interaction analyses revealed a specific interaction between IFNγ genotype (rs1861494) and early life stress affecting amygdala reactivity to emotional faces, resulting from a positive association between CTQ scores and amygdala reactivity in C allele carriers while this association was absent in T homozygotes.

CONCLUSIONS

Our findings indicate that firstly the genetic variant of IFNγ (rs1861494) is involved with the regulation of amygdala reactivity to emotional stimuli and secondly, that this genetic variant moderates effects of early life stress on emotion processing. These findings reiterate the importance that inflammatory genes play in the interaction with early life stress and the regulation of emotion processing.

Cumulative meta-analysis of interleukins 6 and 1β, tumour necrosis factor α and C-reactive protein in patients with major depressive disorder

Cumulative meta-analyses are used to evaluate the extent to which further studies are needed to confirm or refute a hypothesis. We used this approach to assess observational evidence on systemic inflammation in individuals with major depressive disorder. We identified 58 studies of four common inflammatory markers in a literature search of PubMed, Embase and PsychInfo databases in May 2014. Pooled data from the earliest eight studies already showed an association between interleukin-6 concentrations and major depression; 23 more recent studies confirmed this finding (d=0.54, p<0.0001). A significant association between C-reactive protein levels and major depression was noted after 14 studies and this did not change after addition of six more studies (d=0.47, p<0.0001). For these two inflammatory markers, there was moderate heterogeneity in study-specific estimates, subgroup differences were small, and publication bias appeared to be an unlikely explanation for the findings. Sensitivity analyses including only high-quality studies and subjects free of antidepressant medication further verified the associations. While there was a link between tumour necrosis factor-α levels and major depression (d=0.40, p=0.002), the cumulative effect remained uncertain due to the extensive heterogeneity in study-specific estimates and inconsistencies between subgroups. No evidence was found for the association between interleukin-1β levels and major depression (d=-0.05, p=0.86). In conclusion, this cumulative meta-analysis confirmed higher mean levels of interleukin-6 and C-reactive protein in patients with major depression compared to non-depressed controls. No consistent association between tumour necrosis factor-α, interleukin-1β and major depression was observed. Future studies should clarify the specific immune mechanisms involved as well as continue testing anti-inflammatory therapies in patients suffering from major depression.

Inflammation and clinical response to treatment in depression: A meta-analysis

The depressive state has been characterised as one of elevated inflammation, which holds promise for better understanding treatment-resistance in affective disorders as well as for future developments in treatment stratification. Aiming to investigate alterations in the inflammatory profiles of individuals with depression as putative biomarkers for clinical response, we conducted meta-analyses examining data from 35 studies that investigated inflammation before and after treatment in depressed patients together with a measure of clinical response. There were sufficient data to analyse IL-6, TNFα and CRP. Levels of IL-6 decreased with antidepressant treatment regardless of outcome, whereas persistently elevated TNFα was associated with prospectively determined treatment resistance. Treatment non-responders tended to have higher baseline inflammation, using a composite measure of inflammatory markers. Our findings suggest that elevated levels of inflammation are contributory to treatment resistance. Combining inflammatory biomarkers might prove a useful tool to improve diagnosis and detection of treatment refractoriness, and targeting persistent inflammation in treatment-resistant depression may offer a potential target for the development of novel intervention strategies.

IL-1β and BDNF are associated with improvement in hypersomnia but not insomnia following exercise in major depressive disorder

Given the role of sleep in the development and treatment of major depressive disorder (MDD), it is becoming increasingly clear that elucidation of the biological mechanisms underlying sleep disturbances in MDD is crucial to improve treatment outcomes. Sleep disturbances are varied and can present as insomnia and/or hypersomnia. Though research has examined the biological underpinnings of insomnia in MDD, little is known about the role of biomarkers in hypersomnia associated with MDD. This paper examines biomarkers associated with changes in hypersomnia and insomnia and as predictors of improvements in sleep quality following exercise augmentation in persons with MDD. Subjects with non-remitted MDD were randomized to augmentation with one of two doses of aerobic exercise: 16 kilocalories per kilogram of body weight per week (KKW) or 4 KKW for 12 weeks. The four sleep-related items on the clinician-rated Inventory of Depressive Symptomatology (sleep onset insomnia, mid-nocturnal insomnia, early morning insomnia and hypersomnia) assessed self-reported sleep quality. Inflammatory cytokines (tumor necrosis factor-alpha, interleukin (IL)-1β, IL-6) and brain-derived neurotrophic factor (BDNF) were assessed in blood samples collected before and following the 12-week intervention. Reduction in hypersomnia was correlated with reductions in BDNF (ρ = 0.26, P = 0.029) and IL-1β (ρ = 0.37, P = 0.002). Changes in these biomarkers were not associated with changes in insomnia; however, lower baseline levels of IL-1β were predictive of greater improvements in insomnia (F = 3.87, P = 0.050). In conclusion, improvement in hypersomnia is related to reductions in inflammatory markers and BDNF in persons with non-remitted MDD. Distinct biological mechanisms may explain reductions in insomnia.

Cortisol and α-Amylase Secretion Patterns between and within Depressed and Non-Depressed Individuals

OBJECTIVES

Associations between biological stress markers and depression are inconsistent across studies. We assessed whether inter- and intra-individual variability explain these inconsistencies.

METHODS

Pair-matched depressed and non-depressed participants (N = 30) collected saliva thrice a day for 30 days, resulting in 90 measurements per individual. The relationships between measures of stress-system function and depression were examined at the group level by means of mixed model analyses, and at the individual level by means of pair-matched comparisons. The analyses were repeated after adjusting for time-varying lifestyle factors by means of time-series regression analyses.

RESULTS

Cortisol and α-amylase levels were higher, the α-amylase/cortisol ratio larger, and the daily cortisol slope steeper in the depressed compared to the non-depressed group. Adjusting for lifestyle factors and antidepressant use reduced the associations under study. In 40%-60% of the matched comparisons, depressed individuals had higher cortisol and α-amylase levels, a larger α-amylase/cortisol ratio, and a steeper daily slope than their non-depressed match, regardless of adjustment.

CONCLUSIONS

Our group-level findings were mostly in line with the literature but generalization to individuals appeared troublesome. Findings of studies on this topic should be interpreted with care, because in clinical practice the focus is on individuals instead of groups.

Immunomodulatory effects mediated by serotonin

Serotonin (5-HT) induces concentration-dependent metabolic effects in diverse cell types, including neurons, entherochromaffin cells, adipocytes, pancreatic beta-cells, fibroblasts, smooth muscle cells, epithelial cells, and leukocytes. Three classes of genes regulating 5-HT function are constitutively expressed or induced in these cells: (a) membrane proteins that regulate the response to 5-HT, such as SERT, 5HTR-GPCR, and the 5HT₃-ion channels; (b) downstream signaling transduction proteins; and (c) enzymes controlling 5-HT metabolism, such as IDO and MAO, which can generate biologically active catabolites, including melatonin, kynurenines, and kynurenamines. This review covers the clinical and experimental mechanisms involved in 5-HT-induced immunomodulation. These mechanisms are cell-specific and depend on the expression of serotonergic components in immune cells. Consequently, 5-HT can modulate several immunological events, such as chemotaxis, leukocyte activation, proliferation, cytokine secretion, anergy, and apoptosis. The effects of 5-HT on immune cells may be relevant in the clinical outcome of pathologies with an inflammatory component. Major depression, fibromyalgia, Alzheimer disease, psoriasis, arthritis, allergies, and asthma are all associated with changes in the serotonergic system associated with leukocytes. Thus, pharmacological regulation of the serotonergic system may modulate immune function and provide therapeutic alternatives for these diseases.

Cellular and Molecular Inflammatory Profile of the Choroid Plexus in Depression and Suicide

The inflammatory hypothesis of depression is one of the main theories that endeavors to explain and describe the underlying biological mechanisms of depression and suicide. While mounting evidence indicates altered peripheral and central inflammatory profiles in depressed patients and suicide completers, little is known about how peripheral and central inflammation might be linked in these contexts. The choroid plexus (ChP), a highly vascularized tissue that produces cerebrospinal fluid (CSF) and lacks a blood-brain-barrier, is an interface between peripheral and central immune responses. In the present study, we investigated the cellular and molecular inflammatory profile of the ChP of the lateral ventricle in depressed suicides and psychiatrically healthy controls. Gene expression of macrophages, pro- and anti-inflammatory cytokines, and various factors implicated in immune cell trafficking were measured; and density of ionized calcium-binding adaptor molecule 1-positive (Iba1+) macrophages associated with the ChP epithelial cell layer (ECL) was examined. Significant downregulations of the genes encoding interleukin 1ß (IL1ß), a pro-inflammatory acute-phase protein; intercellular cell adhesion molecule 1 (ICAM1), a protein implicated in immune cell trafficking in the ChP; and IBA1, a monocyte/macrophage marker; were detected in depressed suicides as compared to controls. No difference in the density of Iba1+ macrophages associated with the ChP ECL was observed. While interpretation of these findings is challenging in the absence of corroborating data from the CSF, peripheral blood, or brain parenchyma of the present cohort, we hypothesize that the present findings reflect a ChP compensatory mechanism that attenuates the detrimental effects of chronically altered pro-inflammatory signaling caused by elevated levels of pro-inflammatory cytokines, such as IL-1ß, peripherally and/or centrally. Together, these findings further implicate neuroimmune processes in the etiology of depression and suicide.

Vagal pathways for microbiome-brain-gut axis communication

There is now strong evidence from animal studies that gut microorganism can activate the vagus nerve and that such activation plays a critical role in mediating effects on the brain and behaviour. The vagus appears to differentiate between non-pathogenic and potentially pathogenic bacteria even in the absence of overt inflammation and vagal pathways mediate signals that can induce both anxiogenic and anxiolytic effects, depending on the nature of the stimulus. Certain vagal signals from the gut can instigate an anti-inflammatory reflex with afferent signals to the brain activating an efferent response, releasing mediators including acetylcholine that, through an interaction with immune cells, attenuates inflammation. This immunomodulatory role of the vagus nerve may also have consequences for modulation of brain function and mood.What is currently lacking are relevant data on the electrophysiology of the system. Certainly, important advances in our understanding of the gut-brain and microbiome- gut-brain axis will come from studies of how distinct microbial and nutritional stimuli activate the vagus and the nature of the signals transmitted to the brain that lead to differential changes in the neurochemistry of the brain and behaviour.Understanding the induction and transmission of signals in the vagus nerve may have important implications for the development of microbial-or nutrition based therapeutic strategies for mood disorders.

A phase-specific neuroimmune model of clinical depression

Immune dysfunction and pro-inflammatory states in particular have been implicated in the aetiology and pathogenesis of depression. Whilst the onset of an episode and certain symptoms of depression appear well explained by this inflammatory model, the underpinnings of the episodic and progressive nature, as well as relapse and remission status in depression require attention. In this review it is suggested that additional immune factors beyond pro- and anti-inflammatory cytokines may effectively contribute to the understanding of the neurobiology of clinical depression. Considering neurobiological effects of immunomodulatory factors such as T cells, macrophages, microglia and astrocytes relevant to depression, we suggest a neuroimmune model of depression underpinned by dynamic immunomodulatory processes. This perspective paper then outlines a neuroimmune model of clinical phases of depression in an attempt to more adequately explain depression-like behaviours in pre-clinical models and the dynamic nature of depression in clinical populations. Finally, the implications for immunomodulatory treatments of depression are considered.

Comorbidity between depression and asthma via immune-inflammatory pathways: a meta-analysis

BACKGROUND

Depression is often present in patients with asthma and vice versa. In this review, we aimed to summarize reports on the comorbidity of depression and asthma, and to seek evidence that the biological mechanisms of allergy may have an important role linking asthma and depression.

METHOD

To explore the relationship and pathway underpinning this comorbidity, we reviewed medical articles and undertook a meta-analysis of epidemiological studies on (i) incidence of asthma in patients with depression; (ii) morbidity of depression in patients with asthma; (iii) concentration of cytokines in depressed subjects.

RESULTS

High level of comorbidity of asthma and depression was consistently demonstrated in 10 studies of patients with asthma and four studies of patients with depression. In search of biological connection of the two illnesses, thirty-eight studies were included for Meta-analyses examining differences in allergy related cytokines between patients with depression and non-depressive subjects. In people with depression, concentration of monocytes related cytokines such as IL-1 (1.56ng/mL, 95% CI: 0.00-3.12, p=0.05) was significantly higher than that in non-depressive control subjects. At the same time, some other inflammatory factors including IL-4 (5.77pg/mL, 95% CI: 2.34-9.21, p=0.00010), IL-6 (1.44ng/mL, 95% CI: 1.05-1.82, p<0.00001) and TNF-α(3.01ng/mL, 95% CI: 1.76-4.26, p<0.00001) were extremely significantly higher in depressed people compared with the controls. There was no significant differences of the T cell related cytokine levels, IFN-γ (-0.16ng/mL, 95% CI: -0.85-7.73, p=0.97), accompanied with IL-10 (0.67ng/mL, 95% CI: -0.84-2.18, p=0.38) between depressive and non-depressive groups.

CONCLUSIONS

The varying levels of certain cytokines play an important role in arousing and remitting asthma and depression. That suggests inflammatory response could be a common pathway adjusting both depression and asthma.

Cytokine levels in depressed and non-depressed subjects, and masking effects of obesity

In major depressive disorder, changes in cytokine levels have been reported to play a role in pathogenesis. Therefore, we sought to investigate a broad range of cytokines in depression. We compared serum levels of interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12, IL-13, granulocyte macrophage colony-stimulating factor (GM-CSF), interferon (INF-γ) and tumor necrosis factor (TNF)-α in 64 subjects with current depression and 206 non-depressed subjects. Depressed patients had higher levels of IL-2, IL-5, IL-12, IL-13, GM-CSF, INF-γ and TNF-α, compared to non-depressed subjects. Splitting groups into non-obese (BMI < 30) and obese (BMI ≥ 30), the non-obese depressed patients (n = 40) showed elevated IL-5, IL-12, IL-13, GM-CSF, INF-γ and TNF-α levels compared to non-obese and non-depressed subjects (n = 85). The obese and depressed patients (n = 24) showed elevated levels of IL-5, IL-12 and INF-γ compared to obese but not depressed subjects (n = 121). Levels of several cytokines were found to be associated with physical activity, employment status and presence of daily naps. The results support over-expression of pro-inflammatory cytokines in depression and extend the range of cytokines potentially associated with depression to include GM-CSF, IL-5 and IL-13. Changes in these cytokines may contribute to co-morbidity between depression and allergic and asthmatic diseases. The results also suggest inflammatory processes associated with obesity, and support an interaction between cytokine serum concentrations and behavioral aspects of both obesity and depression.

The plasma levels of various cytokines are increased during ongoing depression and are reduced to normal levels after recovery

BACKGROUND

Cytokines are implicated in the pathophysiology of major depressive disorder (MDD). However, the pattern of alterations in cytokine levels is still unclear. The current study investigated the plasma levels of a range of cytokines in a follow-up design, with the aim of determining their involvement in depression.

METHODS

Fifty medication-free MDD patients with a depressive episode and 34 healthy controls were included at baseline; the patients were followed up after 12 weeks. Before initiating treatment, the patients were diagnosed and assessed for depressive symptoms and blood for cytokine analysis was obtained. The same clinical assessments and cytokine measurements were performed after 12 weeks of "treatment as usual."

RESULTS

The cytokines interleukin (IL)-1β, IL-1 receptor antagonist (IL-1Ra), IL-5, IL-6, IL-7, IL-8, IL-10, granulocyte colony-stimulating factor (G-CSF), and interferon gamma (IFNγ) were significantly elevated (p=0.01-0.047) in depressed patients at baseline compared to healthy controls. After 12 weeks of treatment, the plasma levels of seven of these nine cytokines (IL-1Ra, IL-6, IL-7, IL-8, IL-10, G-CSF, and IFNγ had decreased significantly compared to baseline and did not differ from those in the healthy controls. The depressive symptoms were simultaneously significantly reduced. In addition, the reduction to normal cytokines levels occurred only in those who met the recovery criteria.

CONCLUSION

A more general pattern of elevated cytokine levels is described herein relative to what has been described previously shown in MDD. Furthermore, recovery from depression was associated with reduction to normal levels of the majority of the measured cytokines. These results strongly support the notion that a complex network of cytokines is involved in the pathophysiology of MDD.

Leukocyte Gene Expression in Patients with Medication Refractory Depression before and after Treatment with ECT or Isoflurane Anesthesia: A Pilot Study

Objective. To evaluate leukocyte gene expression for 9 selected genes (mRNAs) as biological markers in patients with medication refractory depression before and after treatment with ECT or isoflurane anesthesia (ISO). Methods. In a substudy of a nonrandomized open-label trial comparing effects of ECT to ISO therapy, blood samples were obtained before and after treatment from 22 patients with refractory depression, and leukocyte mRNA was assessed by quantitative PCR. Patients' mRNAs were also compared to 17 healthy controls. Results. Relative to controls, patients before treatment showed significantly higher IL10 and DBI and lower ADRA2A and ASIC3 mRNA (P < 0.025). Both ECT and ISO induced significant decreases after treatment in 4 genes: IL10, NR3C1, DRD4, and Sult1A1. After treatment, patients' DBI, ASIC3, and ADRA2A mRNA remained dysregulated. Conclusion. Significant differences from controls and/or significant changes after ECT or ISO treatment were observed for 7 of the 9 mRNAs studied. Decreased expression of 4 genes after effective treatment with either ECT or ISO suggests possible overlap of underlying mechanisms. Three genes showing dysregulation before and after treatment may be trait-like biomarkers of medication refractory depression. Gene expression for these patients has the potential to facilitate diagnosis, clarify pathophysiology, and identify potential biomarkers for treatment effects.

Biological differences between melancholic and nonmelancholic depression subtyped by the CORE measure

BACKGROUND

The purpose of this study was to compare melancholic patients rated by the CORE measure of observable psychomotor disturbance with nonmelancholic and control subjects across a set of biomarkers.

METHODS

Depressed patients were classified as melancholic or nonmelancholic by using the CORE measure. Both groups of patients, as well as control subjects, were compared for a set of clinical and laboratory measures. Serum levels of brain-derived neurotrophic factor, of two markers of oxidative stress (protein carbonyl content [PCC] and thiobarbituric acid reactive substances [TBARS]), and of several immunity markers (interleukin [IL]-2, IL-4, IL-6, IL-10, IL-17, tumor necrosis factor-alpha, and interferon-gamma) were analyzed.

RESULTS

Thirty-three depressed patients and 54 healthy controls were studied. Depressive patients showed higher IL-4, IL-6, and PCC values than healthy controls. Thirteen (39%) of the depressed patients were assigned as melancholic by the CORE measure. They generated lower interferon-gamma (compared with nonmelancholic depressed patients) and TBARS (compared with both the nonmelancholic subset and controls) and returned higher IL-6 levels than controls. Both depressive groups generated higher PCC scores than controls, with no difference between melancholic and nonmelancholic subsets.

CONCLUSION

A sign-based measure to rate melancholia was able to replicate and extend biological findings discriminating melancholic depression. Signs of psychomotor disturbance may be a useful diagnostic measure of melancholia.

Effect of selective serotonin reuptake inhibitors and immunomodulator on cytokines levels: an alternative therapy for patients with major depressive disorder

Major depressive disorder (MDD) is a psychiatric illness that presents as a deficit of serotonergic neurotransmission in the central nervous system. MDD patients also experience alterations in cortisol and cytokines levels. Treatment with selective serotonin reuptake inhibitors (SSRIs) is the first-line antidepressant regimen for MDD. The aim of this study was to determine the effect of a combination of SSRIs and an immunomodulator-human dialyzable leukocyte extract (hDLE)-on cortisol and cytokines levels. Patients received SSRIs or SSRIs plus hDLE. The proinflammatory cytokines IL-1 β , IL-2, and IFN- γ ; anti-inflammatory cytokines IL-13 and IL-10; and 24-h urine cortisol were measured at weeks (W) 0, 5, 20, 36, and 52 of treatment. The reduction in cortisol levels in the SSRI-treated group was 30% until W52, in contrast, the combined treatment induced a 54% decrease at W36. The decline in cortisol in patients who were treated with SSRI plus hDLE correlated with reduction of anti-inflammatory cytokines and increases levels of proinflammatory cytokines at the study conclusion. These results suggest that the immune-stimulating activity of hDLE, in combination with SSRIs, restored the pro- and anti-inflammatory cytokine balance and cortisol levels in depressed patients versus those who were given SSRIs alone.

Acute phase protein and cytokine levels in serum and saliva: a comparison of detectable levels and correlations in a depressed and healthy adolescent sample

Recent research has examined associations between inflammation and mental health, and has increasingly focused on utilising younger samples to characterise the temporal relationship between inflammatory responses and the emergence of other symptoms. These studies have typically used blood to measure inflammation, although rates of detection for many inflammatory markers appear to be low. Saliva is a safe and low-cost alternative, and adult research has shown that levels of some salivary markers correlate well with those in serum. However, no research has examined this association in young people. This study examined 16 inflammatory markers in serum and saliva in 17 depressed adolescents and 18 healthy controls, aged 13-18 years. In general, detection rates were higher in saliva compared to in serum. When non-detectable levels were excluded, serum levels of C-reactive protein (CRP) correlated with salivary CRP (r=0.424, p=0.015), and this correlation appeared to only exist for those individuals with high levels of serum CRP (r=0.599, p=0.014). However, when non-detectable levels were included as zero, salivary levels of CRP, interleukin (IL)-2, IL-12p70, and interferon (IFN)-γ correlated with their serum counterparts. No significant clinical group differences in any acute phase proteins or cytokines were present. This study suggests that saliva can be used to measure inflammation in studies with adolescent participants, especially CRP, as it appears to correlate with systemic inflammation for those individuals who are expected to have high levels of inflammation. Implications for future directions in research on salivary inflammatory markers are discussed.

Dysregulation of leukocyte gene expression in women with medication-refractory depression versus healthy non-depressed controls

BACKGROUND

Depressive Disorders (DD) are a great financial and social burden. Females display 70% higher rate of depression than males and more than 30% of these patients do not respond to conventional medications. Thus medication-refractory female patients are a large, under-served, group where new biological targets for intervention are greatly needed.

METHODS

We used real-time quantitative polymerase chain reaction (qPCR) to evaluate mRNA gene expression from peripheral blood leukocytes for 27 genes, including immune, HPA-axis, ion channels, and growth and transcription factors. Our sample included 23 females with medication refractory DD: 13 with major depressive disorder (MDD), 10 with bipolar disorder (BPD). Our comparison group was 19 healthy, non-depressed female controls. We examined differences in mRNA expression in DD vs. controls, in MDD vs. BPD, and in patients with greater vs. lesser depression severity.

RESULTS

DD patients showed increased expression for IL-10, IL-6, OXTR, P2RX7, P2RY1, and TRPV1. BPD patients showed increased APP, CREB1, NFKB1, NR3C1, and SPARC and decreased TNF expression. Depression severity was related to increased IL-10, P2RY1, P2RX1, and TRPV4 expression.

CONCLUSIONS

These results support prior findings of dysregulation in immune genes, and provide preliminary evidence of dysregulation in purinergic and other ion channels in females with medication-refractory depression, and in transcription and growth factors in those with BPD. If replicated in future research examining protein levels as well as mRNA, these pathways could potentially be used to explore biological mechanisms of depression and to develop new drug targets.

Melancholic and atypical major depression--connection between cytokines, psychopathology and treatment

BACKGROUND AND PURPOSE

Growing scientific evidence indicates that there is a correlation between depression and alternations in the immune system. The main aim of the study was to investigate serum levels of Interleukin-6 (IL-6) and Tumour Necrosis Factor-alpha (TNF-α) in melancholic and atypical depressive patients during acute exacerbations of illness, compared to healthy subjects. The secondary aim was to explore a possible association between cytokine levels and clinical characteristics, as well as total duration of prior antidepressant treatment.

METHOD

We measured serum levels of IL-6 and TNF-α in 47 patients suffering from major depressive disorder (MDD) (29 melancholic and 18 atypical) in exacerbation of illness, compared to 39 healthy controls, matched by sex, body mass index (BMI) and smoking habits. Serum levels of IL-6 and TNF-α were measured by enzyme-linked immunosorbent assay (ELISA). The severity of psychopathology was assessed using the Hamilton Depression Rating Scale (HDRS).

RESULTS

IL-6 was significantly elevated in melancholic depressive patients (MDD-M) compared to healthy controls, while no difference was found between the patients with atypical depression (MDD-A) and the healthy group. Lower TNF-α serum level was found both in melancholic and in patients with atypical depression, compared with healthy subjects. We detected a positive correlation between cytokine levels in atypical, but not in melancholic subjects. Sex, age, smoking habits and BMI were not associated to cytokine levels in neither group. Clinical parameters (duration of illness, current episode, age of onset) were related to cytokine levels in atypical depression, while the duration of lifetime exposure to antidepressant treatment correlated to IL-6 serum levels in both melancholic and atypical depression.

CONCLUSION

Our results suggest that the difference in pro-inflammatory cytokine levels could reflect a biological difference between melancholic and atypical depression. A positive correlation between the cytokines (TNF-α and IL-6) observed in depressive patients with atypical features, might be influenced by chronic course of illness, while IL-6 elevation could represent a state indicator for acute exacerbation, especially in melancholic patients. Total duration of antidepressant treatment could be a relevant factor influencing the immune status of patients who suffer either from melancholic or atypical depression.

Lack of clinical therapeutic benefit of antidepressants is associated overall activation of the inflammatory system

Despite the evidence of an association between depression and increased inflammatory markers, still little is known in relation to the most severe cases of the disorder i.e., those who fail to respond to antidepressants. We have assessed the cytokine profile and cortisol levels in 21 healthy controls (HC) and 19 medicated patients with depression with treatment-resistance (TRD) moderately ill. As an initial exploratory analysis, we have also related cytokine profile to the patient's clinical treatment outcome after an inpatient admission. Cytokine profile was measured in the serum by the Cytokine Array I kit (Randox). Plasma cortisol was carried out using a commercially available for the IMMULITE system. When compared to healthy controls, depressed patients had higher levels of cortisol, IL-6, IL-10, but lower levels of IL-4 and VEGF. Our exploratory analysis showed subjects who did not go on to respond to the inpatient admission treatment package had lower levels of MCP-1, and a trend toward lower levels of VEGF. Taking together, these data suggest that lack of clinical therapeutic benefit of antidepressants is associated with overall activation of the inflammatory system.

Comparison of the neurobiological effects of attribution retraining group therapy with those of selective serotonin reuptake inhibitors

The aim of this study was to compare the effectiveness of attribution retraining group therapy (ARGT) with selective serotonin reuptake inhibitors (SSRIs) in the treatment of major depressive disorder (MDD), generalized anxiety disorder (GAD), and obsessive-compulsive disorder (OCD). Subjects were sequentially recruited and randomized into two groups, one receiving ARGT (n = 63) and the other SSRIs (n = 66) for 8 weeks. Fifty-four ARGT outpatients with MDD (n = 19), GAD (n = 19), and OCD (n = 16) and 55 SSRI outpatients with MDD (n = 19), GAD (n = 19), and OCD (n = 17) completed the study. All subjects were assessed using the Hamilton Depression Scale and Hamilton Anxiety Scale before and after treatment. The 10-item Yale-Brown Obsessive Compulsive Scale was employed only for OCD subjects. Plasma levels of serotonin, norepinephrine, cortisol, and adrenocorticotropic hormone were also measured at baseline and 8 weeks after completion of treatment. Symptom scores were significantly reduced (P < 0.001) in both the ARGT and SSRI groups at the end of treatment. However, MDD, GAD and OCD patients in the ARGT group had significantly lower plasma cortisol concentrations compared to baseline (P < 0.05), whereas MDD and OCD patients receiving SSRIs showed significantly increased plasma levels of serotonin (P < 0.05). These findings suggest that ARGT may modulate plasma cortisol levels and affect the hypothalamus-pituitary-adrenal axis as opposed to SSRIs, which may up-regulate plasma serotonin levels via a different pathway to produce an overall improvement in the clinical condition of the patients.

Might different cytokine trends in depressed patients receiving duloxetine indicate differential biological backgrounds

BACKGROUND

Correlational studies investigating neurohormonal-cytokine modulation by antidepressants suggest, among others, variations in cytokines balances as state markers of different biological subtypes of major depressive disorder (MDD) and response predictors to specific treatments. Objective of the study was to investigate cytokines modulation by duloxetine, a relatively newer SNRI with "clean" dual serotonin/norepinephrine mechanism.

METHODS

30 MDD patients and 32 healthy controls were assessed using Hamilton Depression Scale (HAM-D) and monitored for levels of IL-1β, IL-2, IL-4, IL-10, IL-12, IFN-γ and TNF-α, at baseline, week 6 and week 12 of duloxetine treatment (60mg/day) and at baseline, respectively.

RESULTS

Early responders (ER: defined at week 6 by reduction >50% of baseline HAM-D score) and early non-responders (ENR) showed opposite trends in cytokine levels during duloxetine treatment: ENR were characterized by baseline Th2 shift compared to controls (lower IL-1β, IFN-γ and TNF-α) with increase in Th1 cytokines levels during treatment (increase of IL-1β, IL-12, IFN-γ, IL-1β/IL-10 and TNF-α/IL-10, decrease of IL-10), achieving clinical response at week 12; ER were characterized by baseline Th2-to-Th1 relative switch compared to ENR (higher IL-1β, IL-1β/IL-10 and TNF-α/IL-10) with reduction in Th1 cytokines levels during treatment (decrease of TNF-α and TNF-α/IL-10), achieving clinical response at week 6.

LIMITATIONS

Small sample size.

CONCLUSIONS

In accordance to early clinical response, duloxetine treatment could divide depressed patients into at least 2 subgroups characterized by clinical and laboratory differentiated behavior, suggesting different neurobiological background within depressive syndrome differentially sensitive to different drug components: pro-serotonergic effect and increase in Th1 cytokines in ENR vs. pro-noradrenergic effect and decrease in Th1 cytokines in ER.

Chronic stress induces structural alterations in splenic lymphoid tissue that are associated with changes in corticosterone levels in wistar-kyoto rats

Major depressive disorder patients present chronic stress and decreased immunity. The Wistar-Kyoto rat (WKY) is a strain in which the hypothalamic-pituitary-adrenal axis is overactivated. To determine whether chronic stress induces changes in corticosterone levels and splenic lymphoid tissue, 9-week-old male rats were subject to restraint stress (3 h daily), chemical stress (hydrocortisone treatment, 50 mg/Kg weight), mixed stress (restraint plus hydrocortisone), or control treatment (without stress) for 1, 4, and 7 weeks. The serum corticosterone levels by RIA and spleens morphology were analyzed. Corticosterone levels as did the structure, size of the follicles and morphology of the parenchyma (increase in red pulp) in the spleen, varied depending on time and type of stressor. These changes indicate that chronic stress alters the immune response in the spleen in WKY rats by inducing morphological changes, explaining in part the impaired immunity that develops in organisms that are exposed to chronic stress.

The role of the innate immune system in psychiatric disorders

There is by now substantial clinical evidence for an association between specific mood disorders and altered immune function. More recently, a number of hypotheses have been forwarded to explain how components of the innate immune system can regulate brain function at the cellular and systems levels and how these may underlie the pathology of disorders such as depression, PTSD and bipolar disorder. In this review we draw reference to biochemical, cellular and animal disease models, as well as clinical observations to elucidate the role of the innate immune system in psychiatric disorders. Proinflammatory cytokines, such as IL-1β IL-6 and TNFα, which feature prominently in the immune response to pathogen in the periphery, have unique and specific actions on neurons and circuits within the central nervous system. Effects of these signaling molecules on neurotransmission, memory, and glucocorticoid function, as well as animal behaviors such as social withdrawal and fear conditioning relevant to psychiatric disorders are elucidated. Finally, we highlight future directions for studies, including the use of peripheral biomarkers, relevant for developing new therapeutic approaches for treating psychiatric illnesses. This article is part of Special Issue entitled 'neuroinflammation in neurodegeneration and neurodysfunction'.

Interleukin-6, C-reactive protein and interleukin-10 after antidepressant treatment in people with depression: a meta-analysis

BACKGROUND

Cross-sectional studies support an association between depression and inflammatory markers. However, little is known of their relationship in the context of antidepressant treatment. Our aim was to explore via meta-analysis whether antidepressant treatment is associated with a reduction in three inflammatory markers associated with depression.

METHOD

A computerized search of EMBASE, Medline, PsycINFO and Cochrane Library databases was completed using subject headings for depression and either interleukin-6, C-reactive protein or interleukin-10, selecting studies which reported circulating levels of inflammatory markers before and after antidepressant treatment for people with depression. Outcome and moderator variables were coded for analysis, including inflammatory marker change, depression severity change, age, gender ratio, assay brand, treatment response and weight change.

RESULTS

Pooled effect sizes showed a significant decrease in interleukin-6 (n=14, d=-0.42, p=0.02), marginally significant decrease in C-reactive protein (n=8, d=-0.57, p=0.05) and a non-significant decrease in interleukin-10 (n=3, d=-0.45, p=0.14) after treatment. High levels of heterogeneity were observed, which may be associated with clinical variations between the studies such as weight gain, anxiety, incomplete remission and other individual differences and co-morbidities.

CONCLUSIONS

The findings of this meta-analysis indicate that there may be a normalization of overactive inflammatory processes following antidepressant treatment.

Interleukin (IL)-6, tumour necrosis factor alpha (TNF-α) and soluble interleukin-2 receptors (sIL-2R) are elevated in patients with major depressive disorder: a meta-analysis and meta-regression

BACKGROUND

Many studies have explored the association between soluble interleukin-2 receptor (sIL-2R), cytokines and major depressive disorder (MDD). However, the results of these studies were not consistent. The aim of our study is to compare the levels of sIL-2R and cytokines in the blood between MDD patients and controls by a meta-analysis and to identify moderators accounting for potential heterogeneity in the levels of sIL-2R and cytokines in MDD patients versus controls by meta-regression analyses.

METHODS

A comprehensive literature search was performed to identify studies comparing the levels of sIL-2R and cytokines between MDD patients and controls. We pooled the effect sizes for standardized mean differences (SMD) of the levels of sIL-2R and cytokines. We also performed meta-regression and sensitivity analyses to investigate the roles of age, gender, sample type, ethnic origin and selected studies' quality in explaining potential heterogeneity and differences in results respectively.

RESULTS

Twenty-nine studies were selected for this analysis. The levels of sIL-2R, TNF-α and IL-6 in MDD patients were significantly higher than those of healthy controls (SMD=0.555, p<0.001, SMD=0.567, p=0.010; SMD=0.680, p<0.001). Mean age of all subjects was a significant moderator to explain the high heterogeneity of IL-6. Sensitivity analysis found that European but not non-European subjects have higher levels difference of sIL-2R, TNF-α and IL-1β between MDD patients and controls.

LIMITATION

The severity of MDD was not considered.

CONCLUSION

The blood levels of sIL-2R, TNF-α and IL-6 were significantly higher in MDD patients than controls. Age, samples source and ethnic origins may play a potential role in heterogeneity.

Circulating cytokine concentrations are not associated with major depressive disorder in a community-based cohort

OBJECTIVE

The objective was to test the hypotheses that cytokine levels are elevated in community-residing persons at high risk for obstructive sleep apnea with major depressive disorder (MDD) compared to nondepressive persons and that cytokine levels show stronger correlations with somatic than psychological symptoms of depression.

METHOD

A case-control study within the cross-sectional Akershus Sleep Apnea Project was performed. Two controls matched for age, gender, metabolic syndrome and obstructive sleep apnea were drawn for each case of MDD.

RESULTS

Group comparisons revealed no significant difference in the levels of 17 cytokines [interleukin-1β, -2,-4, -5, -6, -7, -8, -10, -12(p70), -13 and -17; tumor necrosis factor-α; interferon-γ; granulocyte colony-stimulating factor; granulocyte-monocyte colony-stimulating factor; macrophage chemoattractant protein-1 and monocyte inhibitory protein-1β] between persons with (n=34) and without MDD (n=68). There was no association between cytokines levels and MDD in multivariate regression analyses. The concentration of interleukin-4 was significantly more positively correlated with psychological than somatic symptoms (r=0.046 vs. -0.143, respectively, P=0.024), while no different correlations were observed for other cytokines.

CONCLUSION

The cytokine levels were not elevated in MDD, and cytokine levels were not more strongly associated with somatic than psychological symptoms of depression. The depression-specific effect on inflammation may be weak in community-based samples with prevalent somatic comorbidity.

Elevated levels of serum IL-5 are associated with an increased likelihood of major depressive disorder

BACKGROUND

Inflammatory mediators in both the peripheral circulation and central nervous system (CNS) are dysregulated in major depressive disorder (MDD). Nevertheless, relatively little is known about the role of the T-helper (Th)-2 effector cytokines interleukin (IL)-5 and IL-13 in MDD.

METHODS

We examined the serum levels of these cytokines and a Th-1 comparison cytokine, interferon (IFN)-γ, in 116 individuals (MDD, n = 58; controls, n = 58).

RESULTS

In our basic multivariate model controlling for the effects of potential confounders on the associations between MDD and the examined cytokines, each 1-unit increase in the serum IL-5 level increased the likelihood of belonging to the MDD group by 76% (OR 1.76, 95% CI 1.03-2.99, p = 0.04; model covariates: age, gender, marital status, daily smoking and alcohol use). The likelihood further increased in models additionally controlling for the effects of the use of antidepressants and NSAIDS, and a diagnosis of asthma. No such associations were detected with regard to IL-13 (OR 1.08, 95% CI 0.96-1.22, p = 0.22) or IFN-γ (OR 1.02, 95% CI 0.99-1.05, p = 0.23).

CONCLUSIONS

Elevated levels of IL-5, which uses the neural plasticity-related RAS GTPase-extracellular signal-regulated kinase (Ras-ERK) pathway to mediate its actions in the central nervous system (CNS), could be one of the factors underlying the depression-related changes in CNS plasticity.

Promoter variants in IL18 are associated with onset of depression in patients previously exposed to stressful-life events

BACKGROUND

Depression is accompanied by an inflammatory reaction and activation of cell mediated immunity (CMI) and stressors may induce the cytokine network in humans. The proinflammatory cytokine interleukin-18 (IL-18) is less investigated in depression but highly relevant since it is produced by activated macrophages and expressed in the brain.

METHODS

The distribution of six polymorphisms in IL10, IL18 and NF was compared between patients with a single episode of depression either preceded by a stressful life event (n=182), or occurring without a prior stressful life event (n=106) and a group of healthy control individuals (n=335).

RESULTS

The major C allele of the IL18 rs187238 and the major G allele of rs1946518 had a significantly higher prevalence among the patients with a stressful life event prior to onset of disease than both patients without a stressful life event and compared with the healthy controls individuals. None of the examined IL10 or NF alleles were differently distributed among these groups.

LIMITATIONS

Data are nominally significant and not resistant to correction for multiple testing.

CONCLUSION

The major C allele of the IL18 rs187238 and the major G allele rs1946518 have previously been associated with higher expression of IL-18 mRNA. Our data suggest that this genetic trend towards higher IL-18 production may increase the susceptibility to depression in response to stressful life events.

Affective symptoms are associated with markers of inflammation and immune activation in bipolar disorders but not in schizophrenia

OBJECTIVE

Elevated levels of inflammation are reported in bipolar disorders (BP), but how this relates to affective symptoms is unclear. We aimed to determine if immune markers that consistently have been reported elevated in BP were associated with depressive and manic symptoms, and if this was specific for BP.

METHODS

From a catchment area, 112 BP patients were included together with 153 schizophrenia (SCZ) patients and 239 healthy controls. Depression and mania were assessed and the patients were grouped into depressed, neutral, and elevated mood. We measured the immune markers tumor necrosis factor receptor 1 (sTNF-R1), interleukin 1 receptor antagonist (IL-1Ra), interleukin 6 (IL-6), high sensitive C-reactive protein (hsCRP), osteoprotegerin (OPG) and von Willebrand factor (vWf) which have been found increased in severe mental disorders.

RESULTS

In BP all inflammatory markers were lowest in depressed state, with significant group differences after control for confounders with respect to TNF-R1 (p = 0.04), IL-1Ra (p = 0.02), OPG (p = 0.004) and IL-6 (p = 0.005). STNF-R1 was positively correlated with the item elevated mood (p = 0.02) whereas sad mood was negatively correlated with OPG (p = 0.0003), IL-1Ra (p = 0.001) and IL-6 (p = 0.006). Compared to controls the neutral mood group had significantly higher levels of OPG (p = 0.0003) and IL-6 (p = 0.005), and the elevated mood group had higher levels of TNF-R1 (p = 0.000005) and vWf (p = 0.002). There were no significant associations between affective states orsymptoms in SCZ.

CONCLUSIONS

The current associations between inflammatory markers and affective symptomatology in BP and not SCZ suggest that immune related mechanisms are associated with core psychopathology of BP.