Association of thalamic serotonin transporter and interleukin-10 in bipolar I disorder: a SPECT study

Disruption of the gut microbiota-inflammation-brain axis in unmedicated bipolar disorder II depression

The relationships of the gut microbiota-inflammation-brain axis in depressive bipolar disorder (BD) remains under-elaborated. Sixty-five unmedicated depressive patients with BD II and 58 controls (HCs) were prospectively enrolled. Resting-state functional MRI data of static and dynamic amplitude of low-frequency fluctuation (ALFF) was measured, and abnormal ALFF masks were subsequently set as regions of interest to calculate whole-brain static functional connectivity (sFC) and dynamic functional connectivity (dFC). Fecal samples were collected to assess gut diversity and enterotypes using 16S amplicon sequencing. Blood samples were also collected, serum was assayed for levels of cytokines (interleukin [IL]-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor [TNF]-α). Patients with BD II exhibited decreased static ALFF values in the left cerebellum Crus II, and decreased cerebellar sFC and dFC to the right inferior parietal lobule and right superior frontal gyrus, respectively. Moreover, higher pro-inflammatory and anti-inflammatory cytokines levels, and increased proinflammatory bacteria and glutamate and gamma-aminobutyric acid metabolism related bacteria were identified in BD II. The interaction of Parabacteroides levels × IL-8 levels was an independent contributor to static ALFF in the left cerebellar Crus II. The findings bridged a gap in the underlying pathophysiological mechanism of the gut microbiota-inflammation-brain axis in BD II depression.

Molecular mechanisms of quetiapine bidirectional regulation of bipolar depression and mania based on network pharmacology and molecular docking: Evidence from computational biology

BACKGROUND

Quetiapine monotherapy is recommended as the first-line option for acute mania and acute bipolar depression. However, the mechanism of action of quetiapine is unclear. Network pharmacology and molecular docking were employed to determine the molecular mechanisms of quetiapine bidirectional regulation of bipolar depression and mania.

METHODS

Putative target genes for quetiapine were collected from the GeneCard, SwissTargetPrediction, and DrugBank databases. Targets for bipolar depression and bipolar mania were identified from the DisGeNET and GeneCards databases. A protein-protein interaction (PPI) network was generated using the String database and imported into Cytoscape. DAVID and the Bioinformatics platform were employed to perform the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of the top 15 core targets. The drug-pathway-target-disease network was constructed using Cytoscape. Finally, molecular docking was performed to evaluate the interactions between quetiapine and potential targets.

RESULTS

Targets for quetiapine actions against bipolar depression (126 targets) and bipolar mania (81 targets) were identified. Based on PPI and KEGG pathway analyses, quetiapine may affect bipolar depression by targeting the MAPK and PI3K/AKT insulin signaling pathways via BDNF, INS, EGFR, IGF1, and NGF, and it may affect bipolar mania by targeting the neuroactive ligand-receptor interaction signaling pathway via HTR1A, HTR1B, HTR2A, DRD2, and GRIN2B. Molecular docking revealed good binding affinity between quetiapine and potential targets.

LIMITATIONS

Pharmacological experiments should be conducted to verify and further explore these results.

CONCLUSIONS

Our findings suggest that quetiapine affects bipolar depression and bipolar mania through distinct biological core targets, and thus through different mechanisms. Furthermore, our results provide a theoretical basis for the clinical use of quetiapine and possible directions for new drug development.

Progress in the application of molecular imaging in psychiatric disorders

Psychiatric disorders have always attracted a lot of attention from researchers due to the difficulties in their diagnoses and treatments. Molecular imaging, as an emerging technology, has played an important role in the researchers of various diseases. In recent years, molecular imaging techniques including magnetic resonance spectroscopy, nuclear medicine imaging, and fluorescence imaging have been widely used in the study of psychiatric disorders. This review will briefly summarize the progression of molecular imaging in psychiatric disorders.

Shared postulations between bipolar disorder and polycystic ovary syndrome pathologies

INTRODUCTION

Women with bipolar disorder (BD) present a high prevalence of polycystic ovary syndrome (PCOS) and other reproductive disorders even before diagnosis or treatment of the disease. Postulations on the potential molecular mechanisms of comorbid PCOS in women with BD remain limited to influence of medications and need further extension.

OBJECTIVES

This review focuses on evidence suggesting that common metabolic and immune disorders may play an important role in the development of BD and PCOS.

RESULTS

The literature covered in this review suggests that metabolic and immune disorders, including the dysfunction of the hypothalamic-pituitary-adrenal axis, chronic inflammatory state, gut microbial alterations, adipokine alterations and circadian rhythm disturbance, are observed in patients with BD and PCOS. Such disorders may be responsible for the increased prevalence of PCOS in the BD population and indicate a susceptibility gene overlap between the two diseases. Current evidence supports postulations of common metabolic and immune disorders as endophenotype in BD as well as in PCOS.

CONCLUSIONS

Metabolic and immune disorders may be responsible for the comorbid PCOS in the BD population. The identification of hallmark metabolic and immune features common to these two diseases will contribute to the clarification of the effect of BD on the reproductive endocrine function and development of symptomatic treatments targeting the biomarkers of the two diseases.

Inflammatory markers, brain-derived neurotrophic factor, and the symptomatic course of adolescent bipolar disorder: A prospective repeated-measures study

BACKGROUND

Numerous studies have found elevated pro-inflammatory markers and reduced brain-derived neurotrophic factor (BDNF) during symptomatic episodes of bipolar disorder (BD) in adults. There is a paucity of research examining these markers in youth with BD, or longitudinally in any BD age group.

METHODS

79 adolescents, ages 13-19 years, were enrolled, including 43 symptomatic adolescents with BD and 36 age-matched healthy controls (HC). Blood samples were collected from all participants at intake, and repeatedly from BD participants at pre-specified intervals over the course of two years. Serum was assayed for levels of pro-inflammatory markers (c-reactive protein [CRP], interleukin [IL]-6, tumor necrosis factor alpha [TNF-α]), BDNF and the anti-inflammatory marker, IL-10. Week-by-week severity of mood symptoms was assessed using semi-structured interviews.

RESULTS

Adolescents with BD provided an average of 4.6 blood samples, on average every 5.0 months. During the most severe symptomatic interval (i.e., highest sum of mood symptom scores) among BD adolescents, levels of CRP (p = 0.01) and pro- to anti-inflammatory ratios (CRP/IL-10; p < 0.001 and IL-6/IL-10; p = 0.046) were significantly greater, and IL-10 levels (p = 0.004) were significantly lower, vs. HC. There were no differences between BD and HC in IL-6, TNF-α or BDNF. Within BD participants, higher BDNF (p = 0.01) and IL-10 levels (p = 0.001) significantly predicted greater burden of mood symptoms over the subsequent epoch. Moreover, higher CRP levels (p = 0.009) at intake predicted greater time to recovery from the index symptomatic episode.

CONCLUSIONS

In the first repeated-measures study on this topic in adolescents with BD, we found evidence that CRP, an inexpensive and ubiquitous blood test, may be useful in predicting the prospective course of BD symptoms. Future larger studies are warranted.

A study of tryptophan, kynurenine and serotonin transporter in first-episode drug-naïve major depressive disorder

Major depressive disorder (MDD) is associated with the disharmonic functioning of the serotonin system. The serotonin system is mainly modulated by the serotonin transporter (SERT) which regulates serotonin uptake and the metabolism of its precursor, tryptophan and following kynurenine pathway. Currently, there is a lack of research examining both markers concurrently in MDD. This study evaluated the alterations and inter-relationships of both markers in first-episode drug-naïve MDD patients. Thirty-three MDD patients and 33 age- and sex-matched healthy controls (HC) were recruited. The SERT availability were comparable between two groups in the midbrain, thalamus, caudate, and putamen. The kynurenine/tryptophan ratio which indicates tryptophan metabolism was lower in MDD than HC with no group difference in the tryptophan or kynurenine concentration. A negative correlation between the midbrain SERT availability and kynurenine concentration in HC was found. For the subgroup of HC with high kynurenine/tryptophan ratio, the SERT availability was positively associated with the kynurenine/tryptophan ratio and negatively correlated with tryptophan or kynurenine concentration. This study demonstrated the altered tryptophan metabolism and the relationship between tryptophan metabolism and the SERT availability in first-episode drug-naïve MDD patients, which gave a new insight towards the future investigation of the pathophysiology of MDD.

Evaluating endophenotypes for bipolar disorder

BACKGROUND

Phenotypic heterogeneity is a major impediment to the elucidation of the neurobiology and genetics of bipolar disorder. Endophenotype could help in reducing heterogeneity by defining biological traits that are more direct expressions of gene effects. The aim of this review is to examine the recent literature on clinical, epidemiological, neurobiological, and genetic findings and to select and evaluate candidate endophenotypes for bipolar disorder. Evaluating putative endophenotype could be helpful in better understanding the neurobiology of bipolar disorder by improving the definition of bipolar-related phenotypes in genetic studies. In this manner, research on endophenotypes could be useful to improve psychopathological diagnostics in the long-run by dissecting psychiatric macro phenotypes into biologically valid components.

MAIN BODY

The associations among the psychopathological and biological endophenotypes are discussed with respect to specificity, temporal stability, heritability, familiarity, and clinical and biological plausibility. Numerous findings regarding brain function, brain structure, neuropsychology and altered neurochemical pathways in patients with bipolar disorder and their relatives deserve further investigation. Overall, major findings suggest a developmental origin of this disorder as all the candidate endophenotypes that we have been able to select are present both in the early stages of the disorder as well as in subjects at risk.

CONCLUSIONS

Among the stronger candidate endophenotypes, we suggest circadian rhythm instability, dysmodulation of emotion and reward, altered neuroimmune state, attention and executive dysfunctions, anterior cingulate cortex thickness and early white matter abnormalities. In particular, early white matter abnormalities could be the result of a vulnerable brain on which new stressors are added in young adulthood which favours the onset of the disorder. Possible pathways that lead to a vulnerable brain are discussed starting from the data about molecular and imaging endophenotypes of bipolar disorder.

Interleukin-1 family and serotonin transporter in first-episode, drug-naive major depressive disorder: A pilot study

Abnormalities of neuroinflammatory process and serotonergic system have been reported in major depressive disorder (MDD). However, most previous studies were performed in recurrent MDD and only a few studies explored the interaction of the two systems. This study examined both systems concurrently and their clinical relevance in first-episode drug-naive MDD. Thirty-four MDD patients and 34 age and gender matched healthy controls (HC) were recruited. Plasma concentrations of the cytokines of interleukin-1 (IL-1) family, including IL-1α, IL-1β, IL-1 receptor antagonist (IL-1Ra) and IL-1 receptor type 2 (IL-1R2) were measured using enzyme-linked immune-sorbent assays. The serotonin transporter (SERT) availability in midbrain, thalamus, caudate, and putamen was examined by single-photon emission computed tomography with ¹²³I-ADAM. There were significantly lower concentrations of pro-inflammatory IL-1β and its inhibitor, IL-1R2 in MDD than HC. The SERT availability was at the same level between groups. A negative association between IL-1Ra concentration and the SERT availability in midbrain was observed in MDD but not in HC. Both IL-1β concentration and the SERT availability in caudate negatively correlated with depression severity and the effect of IL-1β was not moderated or mediated by the SERT. In conclusion, this study demonstrated the involvement of IL-1 family in the early stage of MDD, especially for IL-1β. SERT was not the main central target of altered IL-1β and these two systems might contribute to MDD by different mechanisms. The pathophysiology might be varied between early and recurrent MDD and tuning treatment strategies at different clinical stages might be needed.

Relationship of elevated neural cell adhesion molecule 1 with interleukin-10 and disease severity in bipolar disorder

Neural plasticity and inflammation are known to play a role in the pathogenesis of Bipolar disorder. The data related to markers of neural plasticity in bipolar disorder are limited. The objective of the study was to assess the levels of neural cell adhesion molecule 1 (NCAM 1) and interleukin-10 and their association with disease severity in bipolar disorder. 40 bipolar disorder I patients with acute manic symptoms and 40 age matched controls were enrolled in the study. Neural cell adhesion molecule 1 and interleukin-10 (IL-10) levels were assessed in both the groups. NCAM 1 and interleukin-10 levels were significantly increased in bipolar disorder when compared with controls. There was significant positive correlation of Young Mania Rating score with NCAM 1 (r = 0.538, p = < 0.001) in patients with BD. Multi variate analysis revealed that IL-10 (p = 0.021) was lower in controls by 0.012 ng/L and NCAM 1(p = 0.048) was lower in controls by 0.002 ng/L compared to BD cases and this difference was statistically significant. Based on the findings we conclude that neural cell adhesion molecule 1 is increased and associated with disease severity in bipolar disorder.

The Relationship Between Neuroimmunity and Bipolar Disorder: Mechanism and Translational Application

Neuroimmune system may be involved in the pathological process of bipolar disorder (BD), but the essential association is not fully understood. Accumulating evidence has shown that BD involves the activation of immune cells and the release of inflammatory substances in the central nerve system (CNS). Meanwhile, neuroimmune responses also interact with other hypothesis of the etiology of BD that are widely recognized, such as neurotransmitter systems, neuroendocrine systems, neurotrophic factors, and oxidative stress. Simultaneously, related genes and immune changes in peripheral blood vary with it. Overall, neuroimmunity may play an important role in the pathogenesis of BD, and the inflammatory cytokines, especially interleukin-6 and tumor necrosis factor-alpha, have potential value for the clinical diagnosis and prognosis of BD, as well as predicting the therapeutic effects of drugs. Large-scale studies are needed to extend the evidence on neuroimmunity in BD, and to examine its clinical value for applications such as early prediction and treatment.

Potential Mechanism for HIV-Associated Depression: Upregulation of Serotonin Transporters in SIV-Infected Macaques Detected by 11C-DASB PET

Purpose: Increased incidence of depression in HIV+ patients is associated with lower adherence to treatment and increased morbidity/mortality. One possible underlying pathophysiology is serotonergic dysfunction. In this study, we used an animal model of HIV, the SIV-infected macaque, to longitudinally image serotonin transporter (SERT) expression before and after inoculation, using 11C-DASB (SERT ligand) PET imaging. Methods: We infected seven rhesus macaques with a neurovirulent SIV strain and imaged them at baseline and multiple time points after inoculation (group A). Pyrosequencing methylation analysis of the SERT promoter region was performed. We also measured SERT mRNA/protein in brain single-cell suspensions from another group (group B) of SIV-infected animals (n = 13). Results: Despite some animals showing early fluctuations, 86% of our group A animals eventually showed a net increase in midbrain/thalamus binding potential (BP_ND) over the course of their disease (mean increased binding between last time point and baseline = 30.2% and 32.2%, respectively). Repeated-measures mixed-model analysis showed infection duration to be predictive of midbrain BP_ND (p = 0.039). Thalamic BP_ND was statistically significantly associated with multiple CSF cytokines (P < 0.05). There was higher SERT protein levels in the second group (group B) of SIV-infected animals with SIV encephalitis (SIVE) compared to those without SIVE (p = 0.014). There were no longitudinal changes in SERT gene promoter region percentage methylation between baselines and last time points in group A animals. Conclusion: Upregulated SERT leading to lower synaptic levels of serotonin is a possible mechanism of depression in HIV+ patients, and extrapolating our conclusions from SIV to HIV should be sought using translational human studies.

A systematic review of evidence for the role of inflammatory biomarkers in bipolar patients

Bipolar disorder (BD) is a neuropsychiatric disorder that is characterized by a phasic course of affective episodes interspersed with a euthymic state. Epidemiological, clinical, genetic, post-mortem and preclinical studies have shown that inflammatory reactions and immune modulation play a pivotal role in the pathophysiology of BD. It is conceptualized that biomarkers of inflammation and immune responses should be employed to monitor the disease process in bipolar patients. The objective of this systematic review is to analyse the inflammatory markers involved in human studies and to explore each individual marker for its potential clinical application and summarize evidence regarding their role in BD. A systematic review of human studies to measure inflammatory markers was conducted, and the studies were identified by searching PubMed/MEDLINE, PsycINFO, EMBASE, and Web of Science databases for peer-reviewed journals that were published until September 2015. In this review, we included peripheral markers, genetic, post-mortem and cell studies with inflammatory biomarker analysis in BD. One hundred and two (102) papers met the inclusion criteria. The pro-inflammatory cytokines were elevated and the anti-inflammatory cytokines were reduced in BD patients, particularly during manic and depressive phases when compared to the controls. These changes tend to disappear in euthymia, indicating that inflammation may be associated with acute phases of BD. Even though there are promising findings in this field, further clinical studies using more established detection techniques are needed to clearly show the benefit of using inflammatory markers in the diagnosis, follow-up and prognosis of patients with BD.

Clinical staging and serum cytokines in bipolar patients during euthymia

AIMS

Changes in serum cytokines and altered neutrophin concentration have been associated with bipolar disorder (BD). Our aim here was to analyze peripheral blood biomarkers according to the clinical stages of BD.

METHOD

Euthymic BD-I patients were grouped according to their level of functioning in early-stage (n=25) and late-stage (n=23), and compared to healthy siblings (n=23) and genetically unrelated healthy controls (n=21). Neurotrophin (neurotrophin-3 and BDNF) concentration and biomarkers of inflammation, including cytokines (IL-6, IL-10 and TNF-α), leukocytes count and acute phase proteins, were measured.

RESULTS

IL-10 concentration was significantly increased in early-stage patients compared to late-stage patients, healthy siblings and controls whereas TNF-α concentration was significantly increased in late-stage patients compared to controls. Total leukocytes, neutrophil and monocyte count were significantly increased in late-stage patients compared to healthy siblings and controls. The concentration of IL-6, neurotrophin-3 and BDNF was unchanged in euthymia. Healthy siblings did not show significant changes in any biomarker.

CONCLUSIONS

The concentration of IL-10, TNF-α, neutrophil and monocytes subtype count in blood is altered in patients with BD during euthymic state. The link between peripheral inflammation and different stages in BD deserves further studies.

Inflammation-Associated Co-morbidity Between Depression and Cardiovascular Disease

Morbidity and mortality of cardiovascular disease (CVD) is exceedingly high worldwide. Depressive illness is a serious psychiatric illness that afflicts a significant portion of the world population. Epidemiological studies have confirmed the high co-morbidity between these two disease entities. The co-morbidity is bidirectional and the mechanisms responsible for it are complex and multifaceted. In addition to genetic, biological systems, psychosocial, and behavioral factors that are involved include the central and autonomic nervous systems, the neuroendocrine, immune, and the vascular and hematologic systems. Specific pathophysiologic factors across these systems include homeostatic imbalance between the sympathetic and the parasympathetic systems with loss of heart rate variability (HRV) in depression, sympathoadrenal activation, hypothalamic-pituitary-adrenal (HPA) axis activation, immune system dysregulation resulting in a pro-inflammatory status, platelet activation, and endothelial dysfunction. These abnormalities have been demonstrated in most individuals diagnosed with major depressive disorder (MDD), bipolar disorder (BPD), and probably in other psychiatric disorders. A likely common instigator underlying the co-morbidity between cardiovascular pathology and depression is mental stress. Chronic stress shifts the homeostatic balance in the autonomic nervous system with sustained sympathetic overdrive and diminished vagal tone. Diminished vagal tone contributes to a pro-inflammatory status with associated sequelae. Stress hormones and certain pro-inflammatory substances released by macrophages and microglia upregulate the rate-limiting enzymes in the metabolic pathway of tryptophan (TRP). This enzymatic upregulation stimulates the kynurenine (KYN) pathway resulting in the formation of neurotoxic metabolites. Inflammation occurs in cardiac, cardiovascular, and cerebrovascular pathology independent of the presence or absence of depression. Inflammation is closely associated with endothelial dysfunction, a preamble to atherosclerosis and atherothrombosis. Endothelial dysfunction has been detected in depression and may prove to be a trait marker for this illness. Thus understanding vascular biology in conjunction with psychiatric co-morbidity will be of critical importance. Antidepressant drug therapy is of definite benefit to patients with medical and psychiatric co-morbidity and may reverse the pro-inflammatory status associated with depression. There is, however, an urgent need to develop novel pharmacotherapeutic approaches to benefit a much larger proportion of patients suffering from these disease entities.

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.

Evaluation of Paraoxonase, Arylesterase and Malondialdehyde Levels in Schizophrenia Patients Taking Typical, Atypical and Combined Antipsychotic Treatment

Objective

Human serum paraoxonase (PON1) prevents lipids from peroxidation and functions as an antioxidant mechanism. Malonyldialdehyde (MDA) is the final product of lipid peroxidation and can be used as an indicator of oxidative stress. The aim of this study was to investigate PON1, MDA, and arylesterase (ARY) levels in schizophrenic patients who are taking typical, atypical, or combined (typical and atypical) antipsychotic drug treatment, with respect to those of healthy controls.

Methods

We evaluated 41 patients (11 taking typical antipsychotics, 19 taking atypical antipsychotics, 11 taking combined anti-psychotics) and 43 healthy controls.

Results

MDA levels were higher in schizophrenic patients taking typical antipsychotics compared with healthy controls (p=0.001). ARY levels were higher in patients taking atypical antipsychotics compared with healthy controls (p=0.005). PON1 activity was similar in all groups.

Conclusion

Our results indicate that treatment with typical antipsychotic drugs could be related to increased MDA levels; and antipsychotic medication may increase PON1 levels in schizophrenic patients.

Association between the serotonin transporter and cytokines: Implications for the pathophysiology of bipolar disorder

BACKGROUND

Reduced brain serotonin transporter (SERT) has been demonstrated in bipolar disorder (BD). The aim of this study was to explore the potential role of cytokines on reduced SERT in BD.

METHODS

Twenty-eight BD type I patients and 28 age- and gender-matched healthy controls (HCs) were recruited. Single photon emission computed tomography with the radiotracer 123I ADAM was used for SERT imaging. Regions of interest included the midbrain, thalamus, putamen and caudate. Seven cytokines, including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1α (IL-1α), IL-1β, IL-4, IL-6 and IL-10, were measured using an enzyme linked immune-sorbent assay.

RESULTS

SERT availability in the midbrain and caudate was significantly lower in BD compared to HCs. IL-1β was significantly lower, whereas IL-10 was significantly higher in BD compared to HCs. Multiple linear regression analyses revealed that there were associations between cytokines, IL-1α, IL-1β, IL-6 and SERT availability in the midbrain but not in the thalamus, putamen and caudate. Furthermore, linear mixed effect analyses demonstrated that these associations were not different between HCs and BD.

CONCLUSION

While many cytokines have been proposed to be important in the pathophysiology of BD, our results demonstrated that significant associations between cytokines and SERT availability may explain the role of cytokines in mood regulation. However, these associations were not different between HCs and BD, which imply the role of these cytokines is not specific for BD.

Bipolar disorder: role of immune-inflammatory cytokines, oxidative and nitrosative stress and tryptophan catabolites

Bipolar disorder (BD) is a complex disorder with a range of presentations. BD is defined by the presentation of symptoms of mania or depression, with classification dependent on patient/family reports and behavioural observations. Recent work has investigated the biological underpinnings of BD, highlighting the role played by increased immune-inflammatory activity, which is readily indicated by changes in pro-inflammatory cytokines or signalling, both centrally and systemically, e.g. increased interleukin-6 trans-signalling. Here, we review the recent data on immune-inflammatory pathways and cytokine changes in BD. Such changes are intimately linked to changes in oxidative and nitrosative stress (O&NS) and neuroregulatory tryptophan catabolites (TRYCATs), both centrally and peripherally. TRYCATs take tryptophan away from serotonin, N-acetylserotonin and melatonin synthesis, driving it down the TRYCAT pathway, predominantly as a result of the pro-inflammatory cytokine induction of indoleamine 2,3-dioxygenase. This has led to an emerging biological perspective on the aetiology, course and treatment of BD. Such data also better integrates the numerous comorbidities associated with BD, including addiction, cardiovascular disorders and increased reporting of pain. Immune-inflammatory, O&NS and TRYCAT pathways are also likely to be relevant biological underpinnings to the significant decrease in life expectancy in BD.

Cytokines in bipolar disorder: paving the way for neuroprogression

Bipolar disorder (BD) is a severe, chronic, and recurrent psychiatric illness. It has been associated with high prevalence of medical comorbidities and cognitive impairment. Its neurobiology is not completely understood, but recent evidence has shown a wide range of immune changes. Cytokines are proteins involved in the regulation and the orchestration of the immune response. We performed a review on the involvement of cytokines in BD. We also discuss the cytokines involvement in the neuroprogression of BD. It has been demonstrated that increased expression of cytokines in the central nervous system in postmortem studies is in line with the elevated circulating levels of proinflammatory cytokines in BD patients. The proinflammatory profile and the immune imbalance in BD might be regarded as potential targets to the development of new therapeutic strategies.

Long-lasting recognition memory impairment and alterations in brain levels of cytokines and BDNF induced by maternal deprivation: effects of valproic acid and topiramate

Exposure to stressful events early in life may have permanent deleterious consequences on nervous system function and increase the susceptibility to psychiatric conditions later in life. Maternal deprivation, commonly used as a source of neonatal stress, impairs memory in adult rats and reduces hippocampal brain-derived neurotrophic factor (BDNF) levels. Inflammatory cytokines, such as interleukins (IL) and tumor necrosis factor-α (TNF-α) have been shown to be increased in the peripheral blood of patients with psychiatric disorders. The aim of the present study was to investigate the effects of maternal separation on the levels of IL-10 and TNF-α, and BDNF in the hippocampus and prefrontal cortex of adult rats. We also evaluated the potential ameliorating properties of topiramate and valproic acid on memory deficits and cytokine and BDNF changes associated with maternal deprivation. The results indicated that, in addition to inducing memory deficits, maternal deprivation increased the levels of IL-10 in the hippocampus, and TNF-α in the hippocampus and in the cortex, and decreased hippocampal levels of BDNF, in adult life. Neither valproic acid nor topiramate were able to ameliorate memory deficits or the reduction in BDNF induced by maternal separation. The highest dose of topiramate was able to reduce IL-10 in the hippocampus and TNF-α in the prefrontal cortex, while valproate only reduced IL-10 levels in the hippocampus. These findings may have implications for a better understanding of the mechanisms associated with alterations observed in adult life induced by early stressful events, and for the proposal of novel therapeutic strategies.