Immunologic variables in acute mania of bipolar disorder

Psychoneuroimmunology of Mood Disorders

Recent research has shed light on the intricate relationship between mood disorders, such as major depressive disorder (MDD) and bipolar disorder (BD), and inflammation. This chapter explores the complex interplay involving immune and metabolic dysfunction in the pathophysiology of these disorders, emphasizing their association with autoimmunity/inflammatory conditions, chronic low-grade systemic inflammation, T cell overactivation, and immunosenescence. This perspective underscores the notion that MDD and BD are not solely brain disorders, highlighting their nature as multi-system conditions.

Sex Differences in Brain Disorders

A remarkable feature of the brain is its sexual dimorphism. Sexual dimorphism in brain structure and function is associated with clinical implications documented previously in healthy individuals but also in those who suffer from various brain disorders. Sex-based differences concerning some features such as the risk, prevalence, age of onset, and symptomatology have been confirmed in a range of neurological and neuropsychiatric diseases. The mechanisms responsible for the establishment of sex-based differences between men and women are not fully understood. The present paper provides up-to-date data on sex-related dissimilarities observed in brain disorders and highlights the most relevant features that differ between males and females. The topic is very important as the recognition of disparities between the sexes might allow for the identification of therapeutic targets and pharmacological approaches for intractable neurological and neuropsychiatric disorders.

Hormonal and inflammatory signatures of different mood episodes in bipolar disorder: a large-scale clinical study

BACKGROUND

Bipolar disorder (BD) is characterized by intensive mood fluctuations. While hormones imbalance plays important role in the mood swings, it is unknown whether peripheral hormones profiles could differentiate the manic and depressive mood episodes in BD. In this study, we investigated the changes of various hormones and inflammatory markers across distinct mood episodes of BD in a large clinical study to provide mood episode-specific peripheral biomarkers for BD.

METHODS

A total of 8332 BD patients (n = 2679 depressive episode; n = 5653 manic episode) were included. All patients were in acute state of mood episodes and need hospitalization. A panel of blood tests were performed for levels of sex hormones (serum levels of testosterone, estradiol, and progesterone), stress hormones (adrenocorticotropic hormone and cortisol), and an inflammation marker (C-reactive protein, CRP). A receiver operating characteristic (ROC) curve was used to analyze the discriminatory potential of the biomarkers for mood episodes.

RESULTS

In overall comparison between mood episodes, the BD patients expressed higher levels of testosterone, estradiol, progesterone, and CRP (P < 0.001) and lower adrenocorticotropic hormone (ACTH) level (P < 0.001) during manic episode. The episode-specific changes of testosterone, ACTH, and CRP levels remained between the two groups (P < 0.001) after correction for the confounding factors including age, sex, BMI, occupation, marital status, tobacco use, alcohol consumption, psychotic symptoms, and age at onset. Furthermore, we found a sex- and age-specific impact of combined biomarkers in mood episodes in male BD patients aged ≥ 45 years (AUC = 0.70, 95% CI, 0.634-0.747), not in females.

CONCLUSIONS

While both hormone and inflammatory change is independently associated with mood episodes, we found that the combination of sex hormones, stress hormones and CRP could be more effective to differentiate the manic and depressive episode. The biological signatures of mood episodes in BD patients may be sex- and age-specific. Our findings not only provide mood episode-related biological markers, but also better support for targeted intervention in BD treatments.

Effects of Cannabidiol on Innate Immunity: Experimental Evidence and Clinical Relevance

Cannabidiol (CBD) is the main non-psychotropic cannabinoid derived from cannabis (Cannabis sativa L., fam. Cannabaceae). CBD has received approval by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of seizures associated with Lennox-Gastaut syndrome or Dravet syndrome. However, CBD also has prominent anti-inflammatory and immunomodulatory effects; evidence exists that it could be beneficial in chronic inflammation, and even in acute inflammatory conditions, such as those due to SARS-CoV-2 infection. In this work, we review available evidence concerning CBD's effects on the modulation of innate immunity. Despite the lack so far of clinical studies, extensive preclinical evidence in different models, including mice, rats, guinea pigs, and even ex vivo experiments on cells from human healthy subjects, shows that CBD exerts a wide range of inhibitory effects by decreasing cytokine production and tissue infiltration, and acting on a variety of other inflammation-related functions in several innate immune cells. Clinical studies are now warranted to establish the therapeutic role of CBD in diseases with a strong inflammatory component, such as multiple sclerosis and other autoimmune diseases, cancer, asthma, and cardiovascular diseases.

Kynurenine pathway abnormalities are state-specific but not diagnosis-specific in schizophrenia and bipolar disorder

Schizophrenia (SCZ) and bipolar disorder (BD) are associated with immunological dysfunctions that have been hypothesized to lead to clinical symptomatology in particular through kynurenine pathway abnormalities. The aim of this study was thus to investigate the impact of serum kynurenine metabolite levels on diagnosis, clinical state, symptom severity and clinical course in a large French transdiagnostic cohort of SCZ and BD patients. Four patient groups (total n = 507) were included in a cross-sectional observational study: 1) hospitalized acute bipolar patients (n = 205); 2) stable bipolar outpatients (n = 116); 3) hospitalized acute schizophrenia patients (n = 111) and 4) stable schizophrenia outpatients (n = 75), in addition to healthy controls (HC) (n = 185). The quantitative determination of serum kynurenine metabolites was performed using liquid chromatography-tandem mass spectrometry. Kynurenine levels were lower in all patients combined compared to HC while ANCOVA analyses did not reveal inter-diagnostic difference between SCZ and BD. Interestingly, hospitalized patients of both diagnostic groups combined displayed significantly lower kynurenine levels than stabilized outpatients. Psychotic symptoms were associated with lower quinaldic acid (F = 9.18, p=<.001), which is KAT-driven, whereas a longer duration of illness contributed to abnormalities in tryptophan (F = 5.41, p = .023), kynurenine (F = 16.93, p=<.001), xanthurenic acid (F = 9.34, p = .002), quinolinic acid (F = 9.18, p = .003) and picolinic acid (F = 4.15, p = .043), metabolized through the KMO-branch. These data confirm illness state rather than diagnosis to drive KP alterations in SCZ and BD. Lower levels of KP metabolites can thus be viewed as a transdiagnostic feature of SCZ and BD, independently associated with acute symptomatology and a longer duration of illness. Quinaldic acid has seldomly been investigated by previous studies and appears an important state marker in SCZ and BD. As serum samples are used in this study, it is not possible to extrapolate these findings to the brain.

Inflammatory markers at baseline correlate with subsequent clinical response to quetiapine in patients with bipolar disorder

OBJECTIVES

Recent studies proposed the existence of a correlation between patients' inflammatory status and therapy response in bipolar disorder (BD). Here we investigated the correlation between levels of inflammatory markers and quetiapine (QUE) effects in BD patients.

METHODS

In 15 hospitalised BD patients, we investigated changes in inflammatory markers such as C-Reactive Protein (CRP), Erythrocyte Sedimentation Rate (ESR) and cytokines after a 6-week treatment with QUE monotherapy.

RESULTS

We found QUE treatment to significantly reduce CRP and IL-6 plasma levels. Moreover, we found higher CRP and IL-6 plasma levels at baseline correlated with better improvement of patients' clinical symptoms.

CONCLUSION

The reported results, although preliminary, could be useful in clinical practice, providing not only markers for QUE response, but also allowing for identification of new targets and new therapies for the treatment of this condition.

Sex differences in the blood-brain barrier: Implications for mental health

Prevalence of mental disorders, including major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ) are increasing at alarming rates in our societies. Growing evidence points toward major sex differences in these conditions, and high rates of treatment resistance support the need to consider novel biological mechanisms outside of neuronal function to gain mechanistic insights that could lead to innovative therapies. Blood-brain barrier alterations have been reported in MDD, BD and SZ. Here, we provide an overview of sex-specific immune, endocrine, vascular and transcriptional-mediated changes that could affect neurovascular integrity and possibly contribute to the pathogenesis of mental disorders. We also identify pitfalls in current literature and highlight promising vascular biomarkers. Better understanding of how these adaptations can contribute to mental health status is essential not only in the context of MDD, BD and SZ but also cardiovascular diseases and stroke which are associated with higher prevalence of these conditions.

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.

Are serum levels of inflammatory markers associated with the severity of symptoms of bipolar disorder?

BACKGROUND

To explore the relationship between serum levels of inflammatory markers and symptomatic severity of bipolar disorder (BD).

MATERIALS AND METHODS

A cross-sectional study was conducted on 126 BD patients with current depressive episode (BDD), 102 BD patients with current mixed or (hypo)manic episode (BDM) and 94 healthy controls (HC). All participants were drug-naïve and had no current active physical illness associated with inflammatory response or history of substance abuse. Fasting serum levels of CRP, leptin (LEP), adiponectin (ADP), visfatin (VIS), TNF-α, IL-2, IL-6, IL-10, IL-17), and monocyte chemoattractant protein-1 (MCP-1) were measured with enzyme-linked immunosorbent assay (ELISA). Symptomatic severity of BD was assessed with HAMD-17 and YMRS. Generalized linear model was used to determine the association between the serum levels of inflammatory markers and symptomatic severity of BD.

RESULTS

The serum levels of IL-6, IL-10 and IL-17, and the IL-6/IL-10 ratio were significantly lower in mild BDD than in HC. In moderate BDD, the serum levels of MCP, IL-6 and IL-17 were significantly lower than in HC. In severe BDD, the serum level of ADP, MCP-1, IL-10 and IL-17and the IL-17/IL-10 ratio were significantly lower than in HC. The serum levels of TNF-α and the IL-6/IL-10 ratio were significantly higher in mild BDM than in HC. In moderate BDM, the serum level of VIS, IL-2, and IL-17 were significantly higher than in HC, but the IL-6/IL-10 ratio was significantly lower than in control. In severe BDM, the serum levels of IL-6 and IL-17 and the ratios of IL-6/IL-10 and IL-17/IL-10 were significantly lower than in HC, but the neutrophil/lymphocyte ratio was significantly higher than in HC.

CONCLUSION

In BDD, immune-inhibition is persistently predominant, while in mild-to-moderate BDM, immune system is activated but inhibited in severe BDM. The dynamic change of serum inflammatory markers suggests that alteration of peripheral inflammatory markers in BD is state-dependent instead of trait-marked.

Anti-TNF-α Compounds as a Treatment for Depression

Millions of people around the world suffer from psychiatric illnesses, causing unbearable burden and immense distress to patients and their families. Accumulating evidence suggests that inflammation may contribute to the pathophysiology of psychiatric disorders such as major depression and bipolar disorder. Copious studies have consistently shown that patients with mood disorders have increased levels of plasma tumor necrosis factor (TNF)-α. Given these findings, selective anti-TNF-α compounds were tested as a potential therapeutic strategy for mood disorders. This mini-review summarizes the results of studies that examined the mood-modulating effects of anti-TNF-α drugs.

Neuroinflammation in Bipolar Depression

Bipolar disorder (BD) is a leading cause of worldwide disability among mood disorders. Pathological mechanisms are still vastly unclear, and current treatments with conventional medications are often unsatisfactory in maintaining symptoms control and an adequate quality of life. Consequently, current research is focusing on shedding new light on disease pathogenesis, to improve therapeutic effectiveness. Recent evidence has suggested a prominent role of inflammation in mood disorders. Elevated levels of peripheral proinflammatory mediators have been reported in BD, as well as in other mood disorders, and people with systemic autoimmune diseases have an increased risk of developing BD. These immunological alterations are stable, and current medications are unable to alter peripheral concentrations even when clinical improvement is evident. These findings have also been replicated in the central nervous system (CNS) milieu, whereas genetic studies have shown that these immune alterations are not due to the disorder itself, being detectable before the illness onset. Moreover, these inflammatory modifications seem to be affected by and linked to other biomarkers of the disorder, such as alterations of white matter (WM) microstructure, metabolism, kynurenine pathway, and circadian rhythmicity. Finally, these immune variations seem to be useful as predictors of therapeutic responsiveness to medications, and in discriminating between clinically different outcomes. The objective of this review is to summarize available evidence on the connection between inflammation and BD, focusing on peripheral inflammatory markers and recent findings on their connection with other typical features of BD, to outline a general overview of the disorder. Moreover, it is meant to analyze the issues with data gathering and interpretation, given the partially contradictory and inconsistent nature of results.

Changes in inflammation with treatment for bipolar II depression: Pilot trial data on differential effects of psychotherapy and medication

OBJECTIVES

Limited prospective data, mostly focused on bipolar I disorder, suggests that pro-inflammatory cytokines are elevated in abnormal mood states. We evaluated whether treatment normalizes peripheral markers of inflammation in bipolar II disorder.

METHODS

Using data from a randomized clinical trial of Interpersonal and Social Rhythm Therapy (IPSRT) + quetiapine vs. IPSRT + placebo for bipolar II depression, we examined whether these treatments for bipolar II depression impact inflammatory cytokines and whether observed changes in cytokines are associated with changes in depressive symptomatology as measured by the Hamilton Rating Scale for Depression (HRSD-17).

RESULTS

Cytokine values were available for 33 participants who completed baseline and 20-week followup visits. After excluding those with CRP values >=10 mg/L, there were 27 patients available for analysis (IPSRT+quetiapine N=10, IPSRT+placebo N=17). Baseline measure of inflammation did not appear to moderate treatment response, nor was change in HRSD-17 score correlated with changes in cytokines. Those who received IPSRT+quetiapine had significantly greater increases in IL-6 (p=0.02) and TNF-α (p=0.04), even after adjusting for changes in body mass index, than the IPSRT alone group. Descriptively, the quetiapine group showed increases in pro-inflammatory and decreases in anti-inflammatory cytokines and the psychotherapy group showed reduced pro-inflammatory cytokines.

CONCLUSIONS

Despite both groups showing depression improvement, this small study suggests a more pro-inflammatory cytokine profile over time with quetiapine plus psychotherapy compared to psychotherapy alone. Elevated risk of cardiovascular morbidity and mortality among those with bipolar II disorder underscores the importance of delivering treatments that do not exacerbate these risk factors.

Association of purinergic receptor P2RX7 gene polymorphisms with depression symptoms

INTRODUCTION

The activation of the ATP-gated P2RX7 (purinergic receptor P2X, ligand-gated ion channel, 7) produces microglial activation, a process which has been demonstrated in depression, bipolar disorder, and schizophrenia. Emerging data over the last years highlighted the importance of P2X7 cation channel as a potential drug target for these central nervous system disorders. The Gln460Arg (rs2230912) polymorphism of the P2RX7 gene has been widely studied in mood disorders, however the results are still controversial. Therefore, we aimed to investigate the C-terminal region of this gene in major depressive and bipolar disorders (MDD and BD) by studying possibly functional, non-synonymous polymorphisms within a 7 kb long region around the Gln460Arg, including Ala348Thr (rs1718119), Thr357Ser (rs2230911), and Glu496Ala (rs3751143) variants. Since Gln460Arg is located at the 3' end of the P2RX7 gene, we included additional, potentially functional single nucleotide polymorphisms (SNPs) from the 3' untranslated region (UTR), which can be in linkage with Gln460Arg. Based on in silico search, we chose two SNPs in putative microRNA target sites which are located in consecutive positions: rs1653625 and rs1718106.

METHODS

P2RX7 SNPs from the C-terminal region were selected based on previous functional assays, 3' UTR variants were chosen using PolymiRTS and Patrocles databases. The genotyping of the non-synonymous SNPs was carried out by pre-designed TaqMan^® kits, while the 3' UTR variants were analyzed by PCR-RFLP method. Case-control analyses were carried out between 315 inpatients with acute major depressive episode (195 MDD, 120 BD) and 406 healthy control subjects. The two subscales of the Hospital Anxiety and Depression Scale (HADS) self-report questionnaire were used for quantitative analyses, including an additional, "at-risk" population of 218 patients with diabetes mellitus. The in vitro reporter gene assays were carried out on HEK and SK-N-FI cells transiently transfected with pMIR vector constructs containing the P2RX7 3' UTR downstream of the luciferase gene.

RESULTS

Haplotype analysis indicated a relatively high linkage between the analyzed P2RX7 SNPs. Our case-control study did not yield any association between P2RX7 gene variants and depression. However, dimensional analyses showed significant associations of the HADS depression severity scores with Gln460Arg (rs2230912) and Ala348Thr (rs1718119) in the depressed and diabetic patient groups. In the in vitro experiments, the P2RX7 3' UTR constructs with the lowest predicted binding efficiency to their miRNAs showed the highest expression of the gene. The combination of the depression-associated P2RX7 C-terminal and 3' UTR SNPs contributed to the highest depression severity score in the haplotype analysis.

CONCLUSION

Based on our findings, we propose that a P2RX7 haplotype combination of the Gln460Arg and neighboring SNPs contribute to the observed genetic association with depressive symptoms.

Effects of Aspirin in Rats With Ouabain Intracerebral Treatment-Possible Involvement of Inflammatory Modulation?

Bipolar disorder (BD) is a chronic and refractory disease with high probability of morbidity and mortality. Although epidemiological studies have established a strong association between BD and immune dysfunction, the precise etiology is still debatable, and the underpinning mechanism remains poorly investigated and understood. In the present study, manic-like symptoms of BD were induced in rats after intracerebroventricular administration of ouabain. Aspirin, a commonly used anti-inflammatory agent, was used to treat the induced manic-like symptoms and inflammation. Concentrations of a spectrum of inflammatory cytokines were examined by enzyme-linked immunosorbent assay in both plasma and brain tissues, and expression of Toll-like receptors 3 and 4 were determined in rat brains. Locomotor activity was monitored with open-field test to assess the effects of ouabain challenge and to evaluate the treatment efficacy of aspirin. Ouabain administration recapitulated many mania-like features such as increased stereotypic counts, traveling distance in open-field test, and decreased expression of brain-derived neurotrophic factor, interferon gamma, and Toll-like receptor 3, which were frequently found in patients with BD. These abnormalities could be partially reversed by aspirin. Our findings suggest that aspirin could be used as a promising adjunctive therapy for BD.

Neurotrophins, cytokines, oxidative stress mediators and mood state in bipolar disorder: systematic review and meta-analyses

BACKGROUND

A reliable biomarker signature for bipolar disorder sensitive to illness phase would be of considerable clinical benefit. Among circulating blood-derived markers there has been a significant amount of research into inflammatory markers, neurotrophins and oxidative stress markers.AimsTo synthesise and interpret existing evidence of inflammatory markers, neurotrophins and oxidative stress markers in bipolar disorder focusing on the mood phase of illness.

METHOD

Following PRISMA (Preferred Reporting Items for Systematic reviews and Meta-analyses) guidelines, a systematic review was conducted for studies investigating peripheral biomarkers in bipolar disorder compared with healthy controls. We searched Medline, Embase, PsycINFO, SciELO and Web of Science, and separated studies by bipolar mood phase (mania, depression and euthymia). Extracted data on each biomarker in separate mood phases were synthesised using random-effects model meta-analyses.

RESULTS

In total, 53 studies were included, comprising 2467 cases and 2360 controls. Fourteen biomarkers were identified from meta-analyses of three or more studies. No biomarker differentiated mood phase in bipolar disorder individually. Biomarker meta-analyses suggest a combination of high-sensitivity C-reactive protein/interleukin-6, brain derived neurotrophic factor/tumour necrosis factor (TNF)-α and soluble TNF-α receptor 1 can differentiate specific mood phase in bipolar disorder. Several other biomarkers of interest were identified.

CONCLUSIONS

Combining biomarker results could differentiate individuals with bipolar disorder from healthy controls and indicate a specific mood-phase signature. Future research should seek to test these combinations of biomarkers in longitudinal studies.Declaration of interestNone.

Depressive disorders: Processes leading to neurogeneration and potential novel treatments

Mood disorders are wide spread with estimates that one in seven of the population are affected at some time in their life (Kessler et al., 2012). Many of those affected with severe depressive disorders have cognitive deficits which may progress to frank neurodegeneration. There are several peripheral markers shown by patients who have cognitive deficits that could represent causative factors and could potentially serve as guides to the prevention or even treatment of neurodegeneration. Circadian rhythm misalignment, immune dysfunction and oxidative stress are key pathologic processes implicated in neurodegeneration and cognitive dysfunction in depressive disorders. Novel treatments targeting these pathways may therefore potentially improve patient outcomes whereby the primary mechanism of action is outside of the monoaminergic system. Moreover, targeting immune dysfunction, oxidative stress and circadian rhythm misalignment (rather than primarily the monoaminergic system) may hold promise for truly disease modifying treatments that may prevent neurodegeneration rather than simply alleviating symptoms with no curative intent. Further research is required to more comprehensively understand the contributions of these pathways to the pathophysiology of depressive disorders to allow for disease modifying treatments to be discovered.

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.

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.

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.

Effect of Increased Neutrophil-to-Lymphocyte Ratio (NLR) and Decreased Mean Platelet Volume (MPV) Values on Inflammation in Acute Mania

INTRODUCTION

The neutrophil-to-lymphocyte ratio (NLR) and mean platelet volume (MPV) are simple, low-cost, and useful inflammatory markers detected in routine complete blood count (CBC), and their use has recently become widespread. In this study, we aimed to investigate the presence of an inflammatory state in manic patients on the basis of NLR and MPV values.

METHODS

This retrospective study was performed on 76 patients with acute mania who were admitted to the Inpatients Psychiatry Clinic of Afyon Kocatepe University Hospital in Turkey. Diagnoses were based on Diagnostic and Statistical Manuel of Mental disorder (DSM-IV). The control group consisted of 74 healthy individuals recruited from the community. They were age- and sex-matched with the study group.

RESULTS

NLR values of the manic patient group were 2.2±1.4 and those of the control group were 1.6±0.5. NLR values were significantly higher (p=0.004) and MPV values were significantly lower in the manic patient group than in the control group (10.0±1.2 vs. 10.9±2.3, p=0.027).

CONCLUSION

Increased NLR and decreased MPV levels may reflect inflammation in manic patients, and inflammation may play a role in the complex pathophysiology of acute mania.

Circadian preferences, oxidative stress and inflammatory cytokines in bipolar disorder: A community study

OBJECTIVE

To assess circadian preference among a community sample of people with bipolar disorder, major depression and without any mood disorders. Secondly, we investigated the association of circadian preference with cytokines interleukin-6 (IL-6), interleukin-10 (IL-10) and, tumor necrosis factor alpha (TNF-α) and oxidative stress assessed by thiobarbituric acid reactive substances (TBARS), uric acid and Protein Carbonyl Content (PCC).

METHOD

A cross-sectional study nested in a population-based sample. Caseness was confirmed with the Structured Clinical Interview for DSM-IV. A sample of 215 participants, in whom we measured circadian preferences, IL-6, IL-10, TNF-α, TBARS, uric acid, PCC. Biological rhythms were evaluated using the Biological Interview of Assessment in Neuropsychiatry.

RESULTS

Bipolar group presented a higher alteration in biological rhythms (40.40±9.78) when compared with the major depression group (36.35±9.18) and control group (27.61±6.89) p<0.001. Subjects with bipolar disorder who were active at night and had a day/night cycle reverse showed decreased levels of IL-6 (t, 44=2.096; p=0.042), (t, 44=2.213; p=0.032), respectively. In the bipolar disorder group subjects who presented day/night cycle reverse had lower TBARS levels (t, 41=2.612; p=0.013). TNF-α were decreased in subjects more active at night with bipolar disorder.

CONCLUSION

Lower serum levels of IL-6, TNF-α and TBARS were associated with evening preference in bipolar disorder group. These findings suggest that chronotype may alter the levels of interleukins and oxidative stress levels in bipolar and healthy subjects. A better understanding of the role of circadian preferences in levels of interleukins and oxidative stress are needed.

Risk of developing major depression and bipolar disorder among adolescents with atopic diseases: A nationwide longitudinal study in Taiwan

BACKGROUNDS

Previous studies have found an increased prevalence of atopic diseases among patients with major depression and bipolar disorder. But the temporal association between atopic diseases in adolescence and the subsequent risk of developing mood disorders has been rarely investigated.

METHODS

Using the Taiwan National Health Insurance Research Databases, 5075 adolescents with atopic diseases (atopic cohort) and 44,729 without (non-atopic cohort) aged between 10 and 17 in 2000 were enrolled into our study and followed to the end of 2010. Subjects who developed major depression or bipolar disorder during the follow-up were identified.

RESULTS

The atopic cohort had an increased risk of developing major depression (HR: 2.45, 95% CI: 1.93~3.11) and bipolar disorder (HR: 2.51, 95% CI: 1.71~3.67) compared to the non-atopic cohort, with a dose-dependent relationship between having a greater number of atopic comorbidities and a greater likelihood of major depression (1 atopic disease: HR: 1.80, 95% CI: 1.29~2.50; 2 atopic comorbidities: HR: 2.42, 95% CI: 1.93~3.04;≥3 atopic comorbidities: HR: 3.79, 95% CI: 3.05~4.72) and bipolar disorder (HR: 1.40, 95% CI: 0.57~3.44; HR: 2.81, 95% CI: 1.68~4.68; HR: 3.02, 95% CI: 1.69~5.38).

DISCUSSION

Having atopic diseases in adolescence increased the risk of developing major depression and bipolar disorder in later life. Further studies may be required to clarify the underlying mechanism between atopy and mood disorders, and to investigate whether prompt intervention may decrease the risk of subsequent mood disorders.

The effect of mood-stabilizing drugs on cytokine levels in bipolar disorder: A systematic review

OBJECTIVES

Cytokine level alterations suggest a role for the immune system in the pathophysiology of bipolar disorder (BD). Pharmacotherapy is an important confounding factor in clinical research on cytokine levels. In this systematic review we collate the evidence on blood cytokine levels in medication-free BD and the effects of single mood-stabilizing drugs on these levels.

METHODS

A systematic review was conducted according to the PRISMA statement. We searched the Pubmed and Embase databases for clinical studies reporting either on cytokine levels in medication-free BD or on the effects of single mood-stabilizing drugs on cytokine levels in BD.

RESULTS

Of the 564 articles screened, 17 were included. Fourteen articles report on medication-free patients with BD and indicate state-related cytokine alterations. Six articles discuss the effect of lithium. Whereas no data on short-term effects of lithium were found, ≥2 months lithium use in euthymic populations is associated with normal cytokine levels. Two studies report no effect of valproate and no studies were found on carbamazepine, lamotrigine or antipsychotics.

LIMITATIONS

The available studies are characterized by a broad methodological heterogeneity and limited replication between studies.

CONCLUSIONS

This systematic review suggests the presence of state-related cytokine level alterations in medication-free BD with most evidence pointing to a proinflammatory cytokine response in mania. Euthymia and long-term lithium use are associated with normal cytokine levels. To improve our understanding of the impact of mood-stabilizing drugs on cytokine levels, longitudinal studies with medication-free baseline, randomized controlled single-drug treatment protocols and close mood state monitoring are needed.

Chemokine and Chemokine Receptor Polymorphisms in Bipolar Disorder

OBJECTIVE

Bipolar disorder (BD) is a debilitating psychiatric disease with unknown etiology. Recent studies have shown inflammation as a potential contributing factor of BD pathogenesis. However, potential associations between chemokine and chemokine receptor polymorphisms and BD have been fundamentally understudied. To identify participation of chemokines in BD pathogenesis, we examined genetic variants of several chemokine and chemokine receptor genes.

METHODS

The study population comprised 200 patients with BD and 195 age- and sex-matched healthy controls. Genotyping of monocyte chemotactic protein 1 (MCP-1) A2518G, CCR2 V64I, CCR5 Δ32, CCR5 A55029G, stromal cell-derived factor 1 (SDF-1) 3'A, and CXCR4 C138T polymorphisms was performed using polymerase chain reaction and restriction enzyme digestion.

RESULTS

We found that CCR5-Δ32 II and CXCR4-C138T C+ genotype frequencies contributed to an increased risk for BD. However, no statistical significance could be obtained with these genotypes after Bonferroni correction. A significant asssociation was only found with MCP-1 GG and G+ genotypes, which were markedly more prevalent in patients with BD and these genotypes seemed to significantly increase the risk for BD even after Bonferroni correction.

CONCLUSION

Our findings indicate an association between genetic variants of certain chemokine and chemokine receptor (especially MCP-1) genes and BD. The exact mechanisms by which these variants contribute to BD pathogenesis and their clinical implications need to be further investigated.

Does CRP predict outcome in bipolar disorder in regular outpatient care?

BACKGROUND

The association between inflammation and the course of mood disorders is receiving increased attention. This study aims to investigate whether a sub-group of patients with BD can be identified for which a higher CRP (C-reactive protein) level at baseline is associated with an unfavorable prognosis.

METHODS

This is a historic cohort study using CRP at baseline, with 15-month follow-up of mood status and medication. Cross-sectional analyses include boxplots, one-way ANOVA, receiver operating characteristics (ROC) curve and Chi square test, and the longitudinal analysis using multivariate Cox-regression.

RESULTS

Eighty-four bipolar disorder patients were included in the analyses. Cross-sectionally, no statistically significant difference was found in CRP distribution across mood states (p = 0.372) or rapid cycling state (p = 0.656). Also, no CRP cut-off level was distinguished between euthymic and non-euthymic patients according to the ROC curve (p = 0.449, AUC = 0.452, 95 % CI 0.327, 0.576), and a literature-derived cut-off value (3 mg/L) again demonstrated no difference (p = 0.530). Longitudinally, no association was found between CRP and prognosis of disease neither in euthymic [-2 log likelihood = 120.460; CRP: p = 0.866, B = -0.011, OR = 0.989 (95 % CI 0.874-1.120)] nor non-euthymic patients [(-2 log likelihood = 275.028; CRP: p = 0.802, B = 0.010, OR = 1.010 (95 % CI 0.937-1.088)]. Medication use did not affect these associations.

CONCLUSIONS

We found no statistically significant association between CRP and a more unfavorable BD prognosis, suggesting that the application of CRP as a practical biomarker to predict outcome in a naturalistic outpatient care setting is not as straightforward as it may seem.

Bipolar Disorder and Inflammation

The pathophysiology of bipolar disorder (BD) remains poorly understood. Current psychopharmacologic treatments are often poorly tolerated and carry high rates of treatment resistance. Mounting evidence has suggested that innate immune system dysfunction may play a role in the pathophysiology of BD. Elevated proinflammatory cytokine levels have been identified. The innate immune system is a novel therapeutic target in BD. Lithium has been shown to have antiinflammatory properties. Further research is needed to establish the role of antiinflammatory agents in the treatment of BD; however, evidence from several clinical trials indicates that antiinflammatory agents may be incorporated into clinical practice soon.

Inflammation as a neurobiological substrate of cognitive impairment in bipolar disorder: Evidence, pathophysiology and treatment implications

BACKGROUND

Bipolar disorder (BD) has been associated with cognitive impairment during depressed, manic and euthymic periods. Inflammation has been shown to be involved in the pathophysiology of BD and cognitive impairment.

METHODS

For this systematic review, the MEDLINE/PubMed, Embase, Google Scholar and ClinicalTrials.gov databases were searched for relevant articles assessing the association between cognitive function and inflammatory markers in BD subjects. A discussion of potential mechanisms and therapeutic implications is also included to provide further context to the subject matter.

RESULTS

Eight studies, including a total of 555 BD subjects, assessing the association between cognitive function and inflammatory markers were identified. Cognitive dysfunction was associated with elevated levels of pro-inflammatory markers YKL40, IL-6, sCD40L, IL-1Ra, hsCRP and TNF-α. Mechanistically, elevation in inflammatory cytokines alters monoamine levels leading to cognitive and affective dysfunction. Neuro-inflammation, manifesting as microglial activation, leads to increased oxidative stress, pathologic synaptic pruning and impaired neuroplasticity in key brain regions sub-serving mood and cognition. Immune dysfunction also activates the hypothalamic-pituitary-adrenal (HPA) axis leading to hypercortisolemia and metabolic dysfunction, further promoting neuronal dysfunction. Anti-inflammatory agents are therefore currently being investigated in the treatment of BD and appear to exert an antidepressant effect; however, cognitive outcomes have yet to be reported.

CONCLUSION

Several studies suggest that immune dysfunction is associated with cognitive impairment in BD. Several neurobiological pathways have been identified whereby immune dysfunction may promote cognitive impairment in BD. Future investigations of anti-inflammatory agents targeting cognitive function as a treatment outcome are merited.

Risk of bipolar disorder among adolescents with allergic rhinitis: A nationwide longitudinal study

BACKGROUND

Previous studies have suggested an immunological dysfunction in bipolar disorder, but none has investigated the temporal association between allergic rhinitis (AR) and bipolar disorder.

METHODS

Using Taiwan National Health Insurance Research Database, 9506 adolescents aged 12-18 years with allergic rhinitis were enrolled between 2000 and 2008 and compared to 38,024 age-and gender-matched (1:4) control groups. Subjects of bipolar disorder that occurred up to the end of follow-up (December 31, 2011) were identified.

RESULTS

Adolescents with AR had a significantly higher incidence of developing bipolar disorder (0.77 vs. 0.18 per 1000 person-years, p<0.001) during the follow-up period than the controls. Adolescents with AR had an increased risk (hazard ratio [HR]: 4.62, 95% confidence interval [CI]: 3.17-6.75) of developing bipolar disorder in their later life compared to the control group after adjusting for demographic data and comorbid allergic diseases.

DISCUSSION

This is the first study showing a temporal association between AR and bipolar disorder, in that patients who had AR in adolescence exhibited an increased risk of developing bipolar disorder in later life. Further study would be required to investigate the underlying mechanism about this association.

Peripheral inflammation during abnormal mood states in bipolar I disorder

BACKGROUND

Bipolar disorder carries a substantive morbidity and mortality burden, particularly related to cardiovascular disease. Abnormalities in peripheral inflammatory markers, which have been commonly reported in case-control studies, potentially link these co-morbidities. However, it is not clear whether inflammatory markers change episodically in response to mood states or are indicative of chronic pro-inflammatory activity, regardless of mood, in bipolar disorder.

METHODS

Investigations focused on comparing concentrations of specific inflammatory cytokines associated with immune activation status (primary outcome=tumor necrosis factor alpha (TNF-α)) in 37 participants with bipolar disorder across 3 mood states (mania N=15, depression N=9, normal mood N=13) and 29 controls without a psychiatric disorder (total N=66). Cytokine levels were also compared to T1ρ, a potential neuroimaging marker for inflammation, in select brain regions in a subsample (N=39).

RESULTS

Participants with bipolar disorder and healthy controls did not differ significantly in inflammatory cytokine concentrations. However, compared to cases with normal mood, cases with abnormal mood states (mania and depression) had significantly elevated levels of TNF-α, its soluble receptors (sTNFR1/sTNFR2), other macrophage-derived cytokines (interleukin 1β (IL-1β), IL-6, IL-10, and IL-18) in addition to IL-4, interferon-γ, monocyte chemotactic protein-1, fibroblast growth factor β, and vascular endothelial growth factor. Cytokine levels were not correlated with signals from T1ρ imaging in selected structures (amygdalae, hippocampi, hypothalamus, anterior cingulate gyrus, and middle frontal gyrus).

LIMITATIONS

Participants were not followed prospectively across mood states.

CONCLUSION

Activation of inflammatory markers was found in abnormal mood states of bipolar disorder. Longitudinal study of individuals with mood disorders is needed to confirm these findings and to elucidate the time course of any such changes.

Are medical comorbid conditions of bipolar disorder due to immune dysfunction?

OBJECTIVE

Epidemiological data have shown a clear association between bipolar disorder (BD) and medical comorbidities. The aim of this article was to assess the evidence of immune dysfunction as a key mediator of this observed association.

METHOD

For this narrative clinical overview, the MEDLINE/PubMed, EMBASE, Google Scholar, and ClinicalTrials.gov databases were searched for relevant articles.

RESULTS

Bipolar disorder has been shown to have an increased prevalence in patients with autoimmune disorders, cardiovascular disease, and metabolic dysfunction. Further, an elevation in proinflammatory cytokines in BD has been repeatedly demonstrated. Several mechanisms have been proposed to explain the effect of immune dysfunction on mood and cognition. Anti-inflammatory agents including TNF-α inhibitors, non-steroidal anti-inflammatory drugs (NSAIDs), minocycline and omega-3 polyunsaturated fatty acids (O3PUFA) are being investigated for their use as novel treatment of BD in patients with immune dysfunction.

CONCLUSION

Immune dysfunction appears to be an important mediator of the association observed between BD and medical comorbidities. It therefore serves as a potential novel target for treatment of BD. Further, the observed bidirectional interaction merits screening for psychiatric disorders in patients with immune dysfunction and vice versa to allow for early detection and treatment of this at risk population.

The Potential Role of the NLRP3 Inflammasome as a Link between Mitochondrial Complex I Dysfunction and Inflammation in Bipolar Disorder

Mitochondrial dysfunction and activation of the inflammatory system are two of the most consistently reported findings in bipolar disorder (BD). More specifically, altered levels of inflammatory cytokines and decreased levels of mitochondrial complex I subunits have been found in the brain and periphery of patients with BD, which could lead to increased production of mitochondrial reactive oxygen species (ROS). Recent studies have shown that mitochondrial production of ROS and inflammation may be closely linked through a redox sensor known as nod-like receptor pyrin domain-containing 3 (NLRP3). Upon sensing mitochondrial release of ROS, NLRP3 assembles the NLRP3 inflammasome, which releases caspase 1 to begin the inflammatory cascade. In this review, we discuss the potential role of the NLRP3 inflammasome as a link between complex I dysfunction and inflammation in BD and its therapeutic implications.

The effect of deficient muscarinic signaling on commonly reported biochemical effects in schizophrenia and convergence with genetic susceptibility loci in explaining symptom dimensions of psychosis

With the advent of DSM 5 criticism has generally centered on a lack of biological validity of the diagnostic criteria. Part of the problem in describing a nosology of psychosis is the tacit assumption of multiple genetic causes each with an incremental loading on the clinical picture that fails to differentiate a clear underlying pathophysiology of high impact. The aim of this paper is to consolidate a primary theory of deficient muscarinic signaling underlying key clinical features of schizophrenia and its regulation by several important genetic associations including neuregulin, DISC and dysbindin. Secondary reductions in markers for GABAergic function and changes in the levels of interneuron calcium binding proteins parvalbumin and calbindin can be attributed to dysfunctional muscarinic transduction. A parallel association exists for cytokine production. The convergent pathway hypothesis is likewise used to model dopaminergic and glutamatergic theories of schizophrenia. The negative symptom dimension is correlated with dysfunction of Akt and ERK transduction, a major point of convergence. The present paradigm predicts the importance of a recent finding of a deletion in a copy number variant of PLCB1 and its potential use if replicated, as one of the first testable biological markers differentiating schizophrenia from bipolar disorder and further subtyping of schizophrenia into deficit and non-deficit. Potential limitations of PLCB1 as a prospective marker are also discussed.

Common biological mechanisms between bipolar disorder and type 2 diabetes: Focus on inflammation

INTRODUCTION

Bipolar disorder (BD) patients present a 3-5 fold greater risk of developing type 2 diabetes (T2D) compared to general population. The underlying mechanisms for the increased prevalence of T2D in BD population are poorly understood.

OBJECTIVES

The purpose of this review is to critically review evidence suggesting that inflammation may have an important role in the development of both BD and T2D.

RESULTS

The literature covered in this review suggests that inflammatory dysregulation take place among many BD patients. Such dysregulated and low grade chronic inflammatory process may also increase the prevalence of T2D in BD population. Current evidence supports the hypothesis of dysregulated inflammatory processes as a critical upstream event in BD as well as in T2D.

CONCLUSIONS

Inflammation may be a factor for the development of T2D in BD population. The identification of inflammatory markers common to these two medical conditions will enable researchers and clinicians to better understand the etiology of BD and develop treatments that simultaneously target all aspects of this multi-system condition.

Depression and cardiovascular disease: an update on how course of illness may influence risk

Depression constitutes a novel and independent risk factor for cardiovascular disease, which despite extensive support in the literature has been underappreciated. While much of the evidence for depression as a risk factor for cardiovascular disease is based on studies following myocardial infarction, the elevated vascular risk conveyed by depression is not confined to periods following acute coronary syndromes. For that matter, the risk appears across mood disorders with evidence for even greater risk in bipolar disorder. This review summarizes the literature linking depressive disorders to cardiovascular mortality with a focus on how the course of illness of mood disorders may influence this risk. Mood disorders may influence risk over decades of illness in a dose-response to symptom burden, or the persistence of affective symptomatology. This may be mediated through changes in the activity of the autonomic nervous system, the hypothalamic-pituitary-adrenal axis, and inflammatory cytokines. Whether treatment of depression can mitigate this risk is not established although there are suggestions to support this contention, which could be better studied with more effective treatments of depression and larger standardized samples. Directions for future study of mechanisms and treatment are discussed. Regardless of causal mechanisms, persons with depressive disorders and other risk factors for vascular disease represent a neglected, high-risk group for cardiovascular events. In addition to the appropriate treatment for depression, screening and optimized management of traditional risk factors for cardiovascular diseases is necessary.

Effects of ouabain on cytokine/chemokine levels in an animal model of mania

Bipolar disorder (BD) is a chronic and severe psychiatric disorder and despite its importance, little is known about the precise pathophysiology of this disorder. Several studies have reported that inflammation plays a role in the pathogenesis of BD and that cytokines are altered in these patients. Intracerebroventricular (ICV) injection of ouabain (a potent Na(+)/K(+)-ATPase inhibitor) in rats resulted in manic-like effects and it has been widely used as an animal model of bipolar mania. In this study, we assessed the cytokine levels (IL-1β, IL-6, IL-10, TNF-α, CINC-1) in the brain structures (hippocampus, striatum, frontal cortex, amygdala), serum and cerebrospinal fluid (CSF) of rats submitted to an animal model of mania induced by ouabain. Our findings demonstrated that ouabain induced hyperlocomotion in rats. However, the only cytokine that showed alteration was IL-6, which was decreased in the striatum after ouabain administration. In conclusion, despite the ouabain administration in rats be a valid model to study the physiopathology of bipolar mania, it seems that this model was not able to mimic the changes in cytokines observed in bipolar patients.

Rheumatoid arthritis and the risk of bipolar disorder: a nationwide population-based study

BACKGROUND

Studies have suggested that chronic inflammation plays an essential role in the pathophysiology of both rheumatoid arthritis (RA) and bipolar disorder. The most common clinical features associated with RA are anxiety and depression. The risk of bipolar disorder among patients with RA has not been characterized adequately.

OBJECTIVE

To determine the association between RA and the subsequent development of bipolar disorder and examine the risk factors for bipolar disorder among patients with RA.

METHODS

We identified patients who were diagnosed with RA in the Taiwan National Health Insurance Research Database. A comparison cohort was created by matching patients without RA with those with RA according to age, sex, and comorbidities. The occurrence of bipolar disorder was evaluated in both cohorts.

RESULTS

The RA cohort consisted of 2,570 patients, and the comparison cohort consisted of 2,570 matched control patients without RA. The incidence of bipolar disorder (incidence rate ratio  = 2.13, 95% confidence interval [CI]  = 1.12-4.24, P =  .013) was higher among patients with RA than among control patients. Multivariate, matched regression models revealed that asthma (hazard ratio [HR]  = 2.76, 95% CI 1.27-5.96, P =  .010), liver cirrhosis (HR  = 3.81, 95% CI  = 1.04-14.02, P =  .044), and alcohol use disorders (HR  = 5.29, 95% CI  = 1.71-16.37, P =  .004) were independent risk factors for the development of bipolar disorder among patients with RA.

CONCLUSION

RA might increase the incidence of bipolar disorder development. Based on our data, we suggest that, following RA diagnosis, greater attention be focused on women with asthma, liver cirrhosis, and alcohol use disorder. Prospective clinical studies of the relationship between RA and bipolar disorder are warranted.

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.

Applications of blood-based protein biomarker strategies in the study of psychiatric disorders

Major psychiatric disorders such as schizophrenia, major depressive and bipolar disorders are severe, chronic and debilitating, and are associated with high disease burden and healthcare costs. Currently, diagnoses of these disorders rely on interview-based assessments of subjective self-reported symptoms. Early diagnosis is difficult, misdiagnosis is a frequent occurrence and there are no objective tests that aid in the prediction of individual responses to treatment. Consequently, validated biomarkers are urgently needed to help address these unmet clinical needs. Historically, psychiatric disorders are viewed as brain disorders and consequently only a few researchers have as yet evaluated systemic changes in psychiatric patients. However, promising research has begun to challenge this concept and there is an increasing awareness that disease-related changes can be traced in the peripheral system which may even be involved in the precipitation of disease onset and course. Converging evidence from molecular profiling analysis of blood serum/plasma have revealed robust molecular changes in psychiatric patients, suggesting that these disorders may be detectable in other systems of the body such as the circulating blood. In this review, we discuss the current clinical needs in psychiatry, highlight the importance of biomarkers in the field, and review a representative selection of biomarker studies to highlight opportunities for the implementation of personalized medicine approaches in the field of psychiatry. It is anticipated that the implementation of validated biomarker tests will not only improve the diagnosis and more effective treatment of psychiatric patients, but also improve prognosis and disease outcome.

Increased M1/decreased M2 signature and signs of Th1/Th2 shift in chronic patients with bipolar disorder, but not in those with schizophrenia

We here present data on immune gene expression of chemokines, chemokine receptors, cytokines and regulatory T-cell (T-reg) markers in chronic patients suffering from either schizophrenia (SCZ, N=20) or bipolar disorder (BD=20) compared with healthy controls (HCs, N=20). We extracted RNA from peripheral blood mononuclear cells and performed real-time (RT)-PCR to measure mRNA levels of chemokines, chemokine receptors, cytokines and T-reg markers. All the analyses were Bonferroni-corrected. The classical monocyte activation (M1) markers il6, ccl3 were significantly increased in BD as compared with both HC and SCZ patients (P=0.03 and P=0.002; P=0.024 and P=0.021, respectively), whereas markers of alternative (M2) monocyte activation ccl1, ccl22 and il10 were coherently decreased (controls: P=0.01, P=0.001 and P=0.09; SCZ subjects: P=0.02, P=0.05 and P=0.011, respectively). Concerning T-cell markers, BD patients had compared with HC downregulated ccr5 (P=0.02) and upregulated il4 (P=0.04) and compared with both healthy and SCZ individuals downregulated ccl2 (P=0.006 and P=0.003) and tgfβ (P=0.004 and P=0.007, respectively). No significant associations were found between any immune gene expression and clinical variables (prior hospitalizations, Brief Psychiatric Rating Scale, medications' dosages and lifetime administration). Although some markers are expressed by different immune cell types, these findings suggest a coherent increased M1/decrease M2 signature in the peripheral blood of BD patients with potential Th1/Th2 shift. In contrast, all the explored immune marker levels were preserved in SCZ. Further larger studies are needed to investigate the relevance of inflammatory response in BD, trying to correlate it to psychopathology, treatment and outcome measures and, possibly, to brain connectivity.

The relationship between interleukin-1 receptor antagonist and cognitive function in older adults with bipolar disorder

OBJECTIVE

Cognitive impairments are a feature of bipolar disorder (BD) and could be worsened by inflammatory cytokines. We determined whether (i) serum interleukin-1 receptor antagonist (IL-1RA) was increased in elderly BD subjects; (ii) whether IL-1RA was associated with worse neurocognitive function; and (iii) whether IL-1RA was associated with white matter integrity.

METHODS

Twenty-one euthymic BD patients (65 +/- 9 years) with serum available for IL-1RA measures by enzyme-linked immunoassays were compared with 26 similarly aged control participants. Four factor analysis-derived z-scores and a global z-score were obtained from a battery of 21 neurocognitive tests. Diffusion tensor images were used to obtain fractional anisotropy (FA), and an automated labeling pathway algorithm was used to obtain white matter hyperintensity burden.

RESULTS

Interleukin-1 receptor antagonist was elevated in BD subjects compared with controls (439+/-326 pg/mL vs. 269+/-109 pg/mL; p = 0.004). Moreover, IL-1RA was inversely correlated with three cognitive function factors and global cognition (r = -0.37; p = 0.01). IL-1RA continued to correlate with global cognitive function even when covarying for either IL-6 or brain-derived neurotrophic factor. Although FA was lower in BD subjects (0.368 +/- 0.02 vs. 0.381 +/- 0.01; p = 0.02), IL-1RA was not associated with FA or white matter hyperintensity burden.

CONCLUSION

Elevated serum levels of IL-1RA in BD subjects, even during euthymic states, were associated with worse cognitive function. This association was not explained by co-occurring increases in IL-6, by decreased brain-derived neurotrophic factor, nor by measures of white matter integrity. These cross-sectional findings support the possibility that the IL-1 family may contribute to cognitive impairments in BD.

Antibodies to Toxoplasma gondii in individuals with mania

OBJECTIVES

Increased rates of infection with Toxoplasma gondii have been found in individuals with schizophrenia as compared to control groups but this issue has not been studied in mania.

METHODS

We measured immunoglobulin G (IgG) and IgM class antibodies to T. gondii in 57 individuals with mania who were assessed at up to three time-points. We also measured these antibodies in 743 individuals in other psychiatric groups and in 314 non-psychiatric controls. T. gondii antibody levels were compared among groups by multivariate analyses. IgG class and IgM class antibodies to cytomegalovirus were also measured in the same samples. T. gondii antibody levels were also compared over time in the mania group.

RESULTS

The mania group had a significantly elevated level of IgM antibodies to T. gondii as compared to the control individuals without a psychiatric diagnosis [odds ratio (OR) = 2.33, p < 0.04 at hospital admission; and OR = 2.32, p < 0.02 at study entry during the hospital stay]. Elevated IgM class antibodies to T. gondii were not found in individuals with the other psychiatric diagnoses. We also did not find an increased level of IgG class antibodies to T. gondii or IgG or IgM class antibodies to CMV in the individuals with mania. Within the mania group, there was a significant difference between the prevalences of increased levels of T. gondii IgM at the baseline and the follow-up time-point (t = 2.97, p < 0.003).

CONCLUSIONS

Infection with T. gondii may confer risk for mania.

Higher risk of developing major depression and bipolar disorder in later life among adolescents with asthma: a nationwide prospective study

OBJECTIVE

Previous studies have suggested an immunological dysfunction in mood disorders, but rarely have investigated the temporal association between allergic diseases and mood disorders. Using the Taiwan National Health Insurance Research Database, we attempted to investigate the association between asthma in early adolescence and the risk of unipolar depression and bipolar disorder in later life.

METHODS

In all, 1453 adolescents with asthma aged between 10 and 15 years and 5812 age-/gender-matched controls were selected in 1998-2000. Subjects with unipolar depression and bipolar disorder that occurred up to the end of follow-up (December 31 2010) were identified.

RESULTS

Adolescents with asthma had a higher incidence of major depression (2.8% vs. 1.1%, p < 0.001), any depressive disorder (6.1% vs. 2.6%, p < 0.001), and bipolar disorder (1.0% vs. 0.3%, p < 0.001) than the control group. Cox regression analysis showed that asthma in early adolescence was associated with an increased risk of developing major depression (hazard ratio [HR]: 1.81, 95% confidence interval [CI]: 1.14-2.89), any depressive disorder (HR: 1.74, 95% CI: 1.27-2.37), and bipolar disorder (HR: 2.27, 95% CI: 1.01-5.07), after adjusting for demographic data and comorbid allergic diseases.

DISCUSSION

Adolescents with asthma had an elevated risk of developing mood disorders in later life. Further studies would be required to investigate the underlying mechanisms for this comorbid association and elucidate whether prompt intervention for asthma would decrease the risk of developing mood disorders.

The immunology of bipolar disorder

Bipolar disorder (BD) is a psychiatric condition associated with elevated frequency of clinical comorbidities and cognitive impairment. The neurobiology of BD is not completely understood. Recent evidence has implicated immune dysfunction in its physiopathology. Here, we review several data supporting the presence of immunological dysfunction in BD: (i) increased frequency of autoimmune diseases; (ii) distinct immune cell profile; (iii) release of/altered cytokines by stimulated mononuclear cells; (iv) elevated levels of circulating immune markers, and (v) inflammatory changes in the central nervous system. We also discuss the interplay between immunological dysfunction and neuroprogression in BD.

Toward clinically applicable biomarkers in bipolar disorder: focus on BDNF, inflammatory markers, and endothelial function

The importance of biomarkers to many branches of medicine is illustrated by their utility in diagnosis and monitoring treatment response and outcome. There is much enthusiasm in the field of mood disorders on the emergence of clinically relevant biomarkers with several potential targets. While there are generally accepted criteria to establish a biomarker, such approaches are premature for our field as we acquire evidence on the most relevant candidates. A number of components of the inflammatory pathway are supported by published data together with an increasing focus on brain-derived neurotrophic factor. These markers may have measurable impacts on endothelial function, which may be particularly amenable to study in clinical samples. The adolescent population is a key focus as identifying biomarkers before the onset of comorbid medical conditions and which may help direct early intervention seem especially promising. A systematic approach to biomarker development in mood disorders is clearly warranted.

Allostatic load as a tool for monitoring physiological dysregulations and comorbidities in patients with severe mental illnesses

Severe mental illnesses like schizophrenia and bipolar disorder are disabling, chronic conditions that are often accompanied by medical comorbidities. In this theoretical article, we review the allostatic load model representing the "wear and tear" that chronic stress exacts on the brain and body. We propose an innovative way of monitoring physical and psychiatric comorbidities by integrating the allostatic load model into clinical practice. By interpreting peripheral biomarkers differently, medical professionals can calculate a simple, count-based, allostatic load index known to predict diverse stress-related pathologies. In addition to screening for comorbidities, allostatic load indices can be used to monitor the effects of pharmacological and psychosocial interventions. This framework can also be used to generate a dialogue between patient and practitioner to promote preventive and proactive approaches to health care.

Association between C-reactive protein and homocysteine with the subcomponents of metabolic syndrome in stable patients with bipolar disorder and schizophrenia

BACKGROUND

Previous studies revealed high prevalence of metabolic syndrome (MetS) in patients with bipolar disorder and schizophrenia. C-Reactive protein (CRP) and homocysteine have also both emerged as independent risk factors for the development of cardiovascular disease (CVD) but are less investigated in psychiatric disorders.

AIMS

The aim of this study was to ascertain which specific subcomponents of MetS are associated with levels of CRP and homocysteine in patients with bipolar disorder and schizophrenia.

METHODS

Our sample consisted of patient group (n = 122) (60 bipolar and 62 schizophrenic patients) treated with second-generation antipsychotics (SGA) and healthy controls (n = 59). MetS was defined according to NCEP ATP-III criteria; the cut-off point for elevated CRP was set up at 5 mg/l and for hyperhomocysteinemia at 15 μmol/l.

RESULTS

In the patient group, homocysteine was correlated with waist circumference, systolic and diastolic blood pressure, triglycerides and blood glucose, while CRP was correlated with waist circumference and diastolic blood pressure. Patients with hyperhomocysteinemia had an 8.442 times higher chance to have met the criteria for MetS while elevated CRP was not a significant predictor of MetS.

CONCLUSIONS

There is a complex association between CRP and homocysteine with specific subcomponents of MetS in patients with bipolar disorder and schizophrenia. Given the high risk of cardiovascular disorders in psychiatric patients, these relationships deserve further investigation. Clinically, it could be useful to include the measurement of homocysteine and CRP levels in routine psychiatric diagnostic procedures.

A combined marker of inflammation in individuals with mania

Background

Markers of immune activation have been associated with mania but have not been examined in combination. We studied the association between mania and an inflammation score based on four immune markers.

Methods

A total of 57 individuals with mania were assessed at up to three time points: the day of hospital admission, evaluation several days later, and six-month follow-up. Also assessed were 207 non-psychiatric controls and 330 individuals with recent onset psychosis, multi-episode schizophrenia, or bipolar disorder depression. A combined inflammation score was calculated by factor analysis of the levels of class-specific antibodies to the NR peptide of the NMDA receptor; gliadin; Mason-Pfizer monkey virus protein 24; and Toxoplasma gondii. Inflammation scores among groups were compared by multivariate analyses. The inflammation score of the mania group at evaluation was studied as a predictor of re-hospitalization in the follow-up period.

Results

The combined inflammation score of the mania group at hospital admission and at evaluation differed significantly from that of the non-psychiatric controls (t = 3.95, 4.10, p<.001). The inflammation score was significantly decreased at six month follow-up (F = 5.85, p = 0.004). There were not any significant differences in the inflammation scores of any of the other psychiatric groups and that of the controls. Within the mania group, an elevated inflammation score at evaluation predicted re-hospitalization (Hazard ratio = 7.12, p = .005).

Conclusions

Hospitalization for mania is associated with immune activation. The level of this activation is predictive of subsequent re-hospitalization. Interventions for the modulation of inflammation should be evaluated for the therapy of individuals with mania.