Increased plasma levels of soluble TNF receptor I in patients with bipolar disorder

Assessment of cytokine levels and hs-CRP in bipolar I disorder before and after treatment

We aimed to assess the relationship between cytokine levels and the severity of the manic period in medication free patients. 30 Medication free patients and 28 healthy subjects (HS) were recruited. Plasma levels of pro-inflammatory, anti-inflammatory, inflammatory cytokines, and hs-CRP levels were investigated upon hospital admission, after six weeks follow up in bipolar disease manic episode and the results were compared to HS. The severity of the manic episodes was assessed according to the Young mania rating scale. TNF-α, INF-γ, IL-6 and hs-CRP levels were significantly higher in patients with manic episode of bipolar I disorder before treatment than HS. After treatment the levels of TNF-α, INF-γ, IL-6 and hs-CRP were observed to be significantly decreased. There was no difference between the levels of anti-inflammatory cytokines in patients before or after treatment of bipolar disorder and HS. hs-CRP was observed to be the only parameter correlated with clinical response. The most significant outcome of this study is the correlation between clinical outcome and hs-CRP levels in treatment naive manic episode bipolar type I patients. hs-CRP is the most consistent indicator according to pro-inflammatory, inflammatory and anti-inflammatory cytokines, in predicting treatment outcomes.

Neutrophil-lymphocyte and platelet-lymphocyte ratios as inflammation markers for bipolar disorder

In the present study we investigated the involvement of inflammatory cells and their ratios as inflammation markers in Bipolar Disorder. We have enrolled 61 manic, 55 euthymic patients and 54 control subjects to the study. Neutrophil-lymphocyte and platelet-lymphocyte ratios were found significantly higher in both manic and euthymic patients compared to control group. These findings suggest that the inflammatory cells have a role in the pathophysiology of bipolar disorder manic and even in euthymic state.

Inhibition of tumor necrosis factor improves sleep continuity in patients with treatment resistant depression and high inflammation

Blockade of the inflammatory cytokine tumor necrosis factor (TNF) in depressed patients with increased inflammation has been associated with decreased depressive symptoms. Nevertheless, the impact of TNF blockade on sleep in depressed patients has not been examined. Accordingly, sleep parameters were measured using polysomnography in 36 patients with treatment resistant major depression at baseline and 2weeks after 3 infusions (week 8) of either the TNF antagonist infliximab (n=19) or placebo (n=17). Markers of inflammation including c-reactive protein (CRP) and TNF and its soluble receptors were also assessed along with depression measured by the 17-item Hamilton Depression Rating Scale. No differences in sleep parameters were found as a function of infliximab treatment over time. Nevertheless, wake after sleep onset (WASO), the spontaneous arousal index and sleep period time significantly decreased, and sleep efficiency significantly increased, from baseline to week 8 in infliximab-treated patients with high (CRP>5mg/L) (n=9) versus low inflammation (CRP⩽5mg/L) (n=10), controlling for changes in scores of depression. Stage 2 sleep also significantly decreased in infliximab-treated patients with high versus low inflammation. Decreases in soluble TNF receptor 1 (sTNFR1) significantly correlated with decreases in WASO and increases in sleep efficiency in infliximab-treated subjects with high inflammation. Placebo-treated subjects exhibited no sleep changes as a function of inflammation, and no correlations between inflammatory markers and sleep parameters in placebo-treated patients were found. These data suggest that inhibition of inflammation may be a viable strategy to improve sleep alterations in patients with depression and other disorders associated with increased inflammation.

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.

Comparison of pro-inflammatory cytokines among patients with bipolar disorder and unipolar depression and normal controls

OBJECTIVE

Research evidence has shown that bipolar disorder (BD) and unipolar depression (UD) are both related to inflammatory dysregulation, but few studies have compared the levels of cytokines between these two disorders.

METHODS

Study subjects were age- and gender-matched outpatients with BD or UD and normal controls (NC). Severities of depression and mania symptoms were assessed with the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Young Mania Rating Scale (YMRS). Pro-inflammatory cytokines, including soluble interleukin-6 receptor (sIL-6R), soluble interleukin-2 receptor (sIL-2R), C-reactive protein (CRP), soluble tumor necrosis factor receptor type 1 (sTNF-R1), soluble p-selectin receptor (sP-selectin), and monocyte chemotactic protein-1 (MCP-1), were assessed in all subjects by enzyme-linked immunosorbent assays.

RESULTS

In all, 130 patients with BD, 149 patients with UD, and 130 NC were enrolled in the study; 67.6% were female and the average age was mean ± standard deviation (SD) 43.5 ± 11.8 years. The BD group had a significantly higher smoking rate, more medical comorbidity, higher body mass index (BMI), and higher levels of sIL-2R, sIL-6R, CRP, sTNF-R1, and MCP-1 (all p < 0.01) than the UD and NC groups. When the remitted patients with BD (YMRS scores ≤ 12) were compared with the patients with UD, controlling for age, MADRS score, smoking, medical comorbidity, and BMI in the regression model, the results showed that the BD group had significantly higher levels of sIL-6R (p < 0.001), CRP (p = 0.045), sTNF-R1 (p = 0.036), and MCP-1 (p = 0.001) than the UD group.

CONCLUSIONS

Higher levels of sIL-6R, CRP, sTNF-R1, and MCP-1 were noted in BD than in UD. These results may suggest a more severe inflammatory dysregulation in BD. Further studies are required to investigate whether these cytokines could be biomarkers for affective disorders.

IL-23 and TGF-β1 levels as potential predictive biomarkers in treatment of bipolar I disorder with acute manic episode

BACKGROUND

Growing evidence suggests that immune dysfunction may be involved in the physiopathology of bipolar disorders, with typical first-line treatment using lithium and quetiapine serving to restore pro-inflammation status. This study aimed to explore the relationship between inflammatory cytokines-especially regulatory factors and the effect of combination treatment-with quetiapine and lithium in manic patients.

METHODS

41 patients of bipolar I disorder with manic episode were enrolled and received combination treatment with quetiapine and lithium. Blood sampling and assessments were performed at baseline and after 8-week treatment. YMRS was used to evaluate the severity of manic symptoms at the same time of detecting plasma levels. A control group comprised of 36 age and gender matched healthy volunteers were enrolled, and their blood samples were assessed at the time of enrollment.

RESULTS

TGF-β1 and IL-23 plasma levels in patients were significantly higher than healthy controls at baseline (P<0.05). When comparing remitted patients with non-remitted patients, initial plasma level TGF-β1 was higher (P=0.029) while IL-23 was lower (P=0.035). The plasma levels of TNF-α, TGF-β1, IL-23 and IL-17 significantly decreased after treatment among the patients who achieved response (P<0.05).

LIMITATIONS

The relatively small sample size in patients and control groups should be considered as a limitation of the study.

CONCLUSIONS

The high initial plasma level of TGF-β1 and low initial plasma level of IL-23 indicated better prognosis during combination treatment with quetiapine and lithium in manic patients. The trend of decreasing plasma levels of TNF-α, TGF-β1, IL-23 and IL-17 indicated therapeutic effect.

Increased plasma levels of soluble TNF receptors 1 and 2 in bipolar depression and impact of lithium treatment

OBJECTIVE

TNF system (TNF and its soluble receptors sTNFR1 and 2) has been investigated as a potential molecular target in bipolar disorder. The aim of the study was to compare plasma levels of these receptors in unmedicated bipolar depressed patients compared with healthy controls, and to evaluate the effects of a 6-week lithium treatment on sTNFR1 and sTNFR2 levels.

METHODS

The study enrolled 29 patients with unmedicated bipolar disorder in a major depressive episode and 27 matched controls. Patients had blood collected at baseline and after 6 weeks of lithium treatment. The concentration of sTNFRs was measured by ELISA.

RESULTS

sTNFR1 and sTNFR2 levels were significantly increased in bipolar depression in comparison with healthy subjects. Lithium treatment did not significantly change sTNFR1 and sTNFR2 levels from baseline to endpoint. There was no correlation between improvement in depressive symptoms and the change in sTNFR1 or sTNFR1 levels.

CONCLUSION

These results reinforce the involvement of an activated immune response system in the pathophysiology of bipolar disorder, with no impact of lithium treatment on the related biomarkers.

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

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

Monocyte and lymphocyte activation in bipolar disorder: a new piece in the puzzle of immune dysfunction in mood disorders

BACKGROUND

This study tested the hypothesis that the low-grade inflammation presented in patients with bipolar disorder (BD) is associated with expansion of activated T cells, and this activated state may be due to a lack of peripheral regulatory cells.

METHODS

Specifically, we investigated the distribution of monocytes and lymphocyte subsets, and investigated Th1/Th2/Th17 cytokines in plasma by flow cytometry. Twenty-one BD type I patients and 21 age- and sex-matched controls were recruited for this study.

RESULTS

BD patients had increased proportions of monocytes (CD14+). Regarding lymphocyte populations, BD patients presented reduced proportions of T cells (CD3+) and cytotoxic T cells (CD3+CD8+). BD patients also exhibited a higher percentage of activated T CD4+CD25+ cells, and a lower percentage of IL-10 expressing Treg cells.

CONCLUSIONS

Our data shed some light into the underlying mechanisms involved with the chronic low-grade inflammatory profile described in BD patients.

Persistent inflammation and its relationship to leptin and insulin in phases of bipolar disorder from acute depression to full remission

OBJECTIVE

A proinflammatory phase with various immunomodulatory mechanisms has been noted in bipolar mania and major depression. Weight gain and increased production of leptin may be associated with immunomodulation and insulin resistance in bipolar disorder. However, immunomodulation and its linkage with leptin and insulin in the depressive episode of bipolar disorder remain unclear. We investigated alterations in inflammatory markers and their relationship with leptin and insulin levels in patients with phases of bipolar disorder from acute depression to full remission.

METHODS

Thirty-two physically healthy bipolar I depressed patients aged <45 years and age- and sex-matched healthy controls participated in this study. We measured their circulating levels of leptin, insulin, high-sensitivity C-reactive protein (hs-CRP), soluble interleukin-2 receptor (sIL-2R), soluble interleukin-6 receptor (sIL-6R), soluble tumor necrosis factor receptor 1 (sTNF-R1), and interleukin-1 receptor antagonist (IL-1Ra) in three phases, i.e., acute depression, subsequent partial remission, and full remission.

RESULTS

In acute depression, subsequent partial remission, and full remission, patients with bipolar disorder had significantly higher mean levels of hs-CRP, IL-1Ra, sTNF-R1, and sIL-2R compared with control subjects. The IL-1Ra and sTNF-R1 levels in various affective phases were significantly correlated to body mass index, leptin level, circulating lipids, and medication status. The sIL-2R levels in the three affective phases were all independent of other inflammatory markers and clinical and laboratory variables. Patients showed no alteration of sIL-6R levels through the depressive episode.

CONCLUSIONS

Patients with bipolar disorder in depressive episodes may exhibit persistent inflammation with elevated levels of hs-CRP, IL-1Ra, sTNF-R1, and sIL-2R but not sIL-6R from the acute phases to full remission. Only sIL-2R production seems to be tightly linked with the pathophysiology of bipolar depression and is independent of insulin and leptin levels.

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.

Comparison of inflammatory cytokine levels among type I/type II and manic/hypomanic/euthymic/depressive states of bipolar disorder

OBJECTIVE

Inflammatory cytokines have been suggested to be the trait or state markers of bipolar disorder, but with inconsistent results. This may be related to small sample sizes and poor control of some important confounding factors.

METHODS

Gender/age-matched outpatients with bipolar disorder and normal controls were enrolled. The clinical symptoms were rated using the Montgomery Åsberg Depression Rating Scale and Young Mania Rating Scale. Inflammatory cytokines, including soluble interleukin-6 receptor (sIL-6R), soluble interleukin-2 receptor (sIL-2R), C-reactive protein (CRP), soluble tumor necrosis factor receptor type 1 (sTNF-R1), soluble P-selectin receptor (sP-selectin), and monocyte chemotactic protein-1 (MCP-1), were assessed by enzyme-linked immunosorbent assays.

RESULTS

In total, 130 patients with bipolar disorder and 130 normal subjects were enrolled. Among the patients with bipolar disorder, 77 (59.2%) had bipolar I disorder, 53 (40.8%) had bipolar II disorder; 75 (57.7%) were in a euthymic state, 14 (10.8%) were in a manic/hypomanic state, and 41 (31.5%) were in a depressive state. The 130 bipolar patients had significantly higher levels of all cytokines than the normal controls (all p<0.0001). Using multivariate regression analysis with controlling of age, gender, BMI, smoking, duration of illness, and medication grouping, the patients with bipolar II disorder had significantly lower levels of sTNF-R1 than the patients with bipolar I disorder (p=0.038); the patients in a depressive state had significantly lower levels of sTNF-R1 than the patients in manic/hypomanic and euthymic states (p=0.009).

CONCLUSION

The study supported the association of bipolar disorder with inflammatory dysregulation, and sTNF-R1 may be a potential biomarker for staging bipolar disorder.

Mild cognitive impairment. Part 2: Biological markers for diagnosis and prediction of dementia in Alzheimer's disease

OBJECTIVE

To present a critical review of publications reporting on the rationale and clinical implications of the use of biomarkers for the early diagnosis of Alzheimer's disease (AD).

METHODS

We conducted a systematic search of the PubMed and Web of Science electronic databases, limited to articles published in English between 1999 and 2012, and based on the following terms: mild cognitive impairment, Alzheimer's disease OR dementia, biomarkers. We retrieved 1,130 articles, of which 175 were reviews. Overall, 955 original articles were eligible.

RESULTS

The following points were considered relevant for the present review: a) rationale for biomarkers research in AD and mild cognitive impairment (MCI); b) usefulness of distinct biomarkers for the diagnosis and prediction of AD; c) the role of multimodality biomarkers for the diagnosis and prediction of AD; d) the role of biomarkers in clinical trials of patients with AD and MCI; and e) current limitations to the widespread use of biomarkers in research and clinical settings.

CONCLUSION

Different biomarkers are useful for the early diagnosis and prediction of AD in at-risk subjects. Nonetheless, important methodological limitations need to be overcome for widespread use of biomarkers in research and clinical settings.

A preliminary report of increased plasma levels of IL-33 in bipolar disorder: further evidence of pro-inflammatory status

BACKGROUND

Recent findings suggest an important role for inflammation in the neurobiology of bipolar disorder (BD). Interleukin 33 (IL-33) is a cytokine with multiple functions and may act as a nuclear factor regulating transcription and as an "alarmin". IL-33 exerts part of its function through the receptor ST2 that also exists in a soluble form (sST2). This study was performed to evaluate IL-33 and sST2 plasma levels in BD patients.

METHODS

We evaluated IL33 and sST2 plasma levels of 46 BD patients (23 in euthymia and 23 in mania) and 23 healthy controls using enzyme-linked immunosorbent assay (ELISA). BD patients were age and gender matched healthy controls.

RESULTS

IL-33 levels were higher in BD patients (p=0.02) but there was no difference in sST2 (p=0.55). IL33 and sST2 plasma levels were not correlated with age, neither was influenced by clinical comorbidities nor medications in use.

CONCLUSION

These findings corroborate the view of BD as a multisystem condition with a proinflammatory profile.

Serial measurement of the circulating levels of tumour necrosis factor and its soluble receptors 1 and 2 for monitoring leprosy patients during multidrug treatment

Leprosy is an infectious and contagious spectral disease accompanied by a series of immunological events triggered by the host response to the aetiologic agent, Mycobacterium leprae . The induction and maintenance of the immune/inflammatory response in leprosy are linked to multiple cell interactions and soluble factors, primarily through the action of cytokines. The purpose of the present study was to evaluate the serum levels of tumour necrosis factor (TNF)-α and its soluble receptors (sTNF-R1 and sTNF-R2) in leprosy patients at different stages of multidrug treatment (MDT) in comparison with non-infected individuals and to determine their role as putative biomarkers of the severity of leprosy or the treatment response. ELISA was used to measure the levels of these molecules in 30 healthy controls and 37 leprosy patients at the time of diagnosis and during and after MDT. Our results showed increases in the serum levels of TNF-α and sTNF-R2 in infected individuals in comparison with controls. The levels of TNF-α, but not sTNF-R2, decreased with treatment. The current results corroborate previous reports of elevated serum levels of TNF-α in leprosy and suggest a role for sTNF-R2 in the control of this cytokine during MDT.

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.

Altered intracellular signaling cascades in peripheral blood mononuclear cells from BD patients

Bipolar disorder (BD) is a severe psychiatric disorder of complex physiopathology that has been associated with a pro-inflammatory state. The aim of the present study was to investigate intracellular pathways associated with inflammatory signaling, assessing the phosphorylation levels of transcription factor nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPKs) in peripheral blood mononuclear cells of euthymic BD patients and healthy controls. Fifteen BD euthymic type I patients, and 12 healthy controls matched by age and gender were enrolled in this study. All subjects were assessed by the Mini-International Neuropsychiatry Interview and the patients also by the Young Mania Rating Scale and the Hamilton Depression Rating Scale. Phosphorylation levels of p65 NF-κB subunit, and MAPK ERK1/2, and p38 were assessed by Western blot and flow cytometry. Plasma cytokines (IL-2, IL-4, IL6, IL-10, IFN-γ, TNF-α, and IL-17A) were measured using cytometric bead arrays. Western blot and flow cytometry analyses showed increased phosphorylation levels of p65 NF-κB subunit, and MAPKs ERK1/2, and p38 in BD patients in euthymia in comparison with controls. BD patients presented increased pro-inflammatory cytokines levels in comparison with controls, and TNF-α correlated with the levels of phosphorylated p65 NF-κB. The present study found increased activation of MAPK and NF-κB pathways in BD patients, which is in line with a pro-inflammatory status.

Differential neuroendocrine and immune responses to acute psychosocial stress in women with type 1 bipolar disorder

Bipolar disorder (BD) has been associated with immune imbalance, including lymphocyte activation and increased pro-inflammatory cytokines. Immune activation is part of stress response, and psychosocial stress has been implicated in the pathogenesis of psychiatric disorders. Here, we investigated the neuroendocrine and immune responses to acute psychosocial stress challenge in BD. Thirteen euthymic participants with type 1 BD and 15 healthy controls underwent the Trier Social Stress Test protocol (TSST). Blood samples were collected before and after TSST. Lymphocytes were isolated and stimulated in vitro to assess lymphocyte activation profile, lymphocyte sensitivity to dexamethasone, mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling by flow cytometry. Heart rate and salivary cortisol levels were monitored across the task. BD participants exhibited blunted stress responses as shown by reduced heart rate and salivary cortisol levels in comparison to healthy controls. BD was also associated with reduction in the percentage of regulatory T cells, but with expansion of activated T cells. When compared to controls, patients showed increased lymphocyte MAPK p-ERK and p-NF-κB signaling after the stress challenge, but exhibited a relative lymphocyte resistance to dexamethasone. In conclusion, stress-related neuroendocrine responses are blunted, associated with increased immune activation and lower sensitivity to glucocorticoids in BD. An inability in reducing NF-κB and MAPK signaling following TSST could be underlying the immune imbalance observed in BD.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cytokine alterations in bipolar disorder: a meta-analysis of 30 studies

BACKGROUND

We conducted a meta-analysis of studies comparing cytokine concentrations between patients with bipolar disorder (BD) and healthy control subjects (HCs).

METHODS

We searched ISI Web of Science, MEDLINE, BIOSIS Previews, Scopus, Current Contents Connect, and Biological Abstracts for relevant studies. Based on heterogeneity status, we used fixed-effect or restricted maximal likelihood model to perform meta-analysis.

RESULTS

Thirty studies with a total of 2599 participants (1351 BD and 1248 HCs) were eligible for the analysis. Concentrations of interleukin (IL)-4 (p = .008), IL-6 (p = .073), IL-10 (p = .013), soluble IL-2 receptor (sIL-2R; p < .001), sIL-6R (p = .021), tumor necrosis factor (TNF)-α (p = .010), soluble TNF receptor-1 (sTNFR1; p < .001), and IL-1 receptor antagonist (p value in mania < .001 and euthymia = .021) were significantly elevated in patients compared with HCs. Moreover, IL-1β (p = .059), and IL-6 (p = .073) tended to show higher values in patients. Levels of IL-2 (p = .156), interferon (INF)-γ (p = .741), C-C motif ligand 2 (p = .624), and IL-8 (p = .952) did not significantly differ between patients and HCs. Subgroup analysis based on mitogen stimulation status partially or completely resolved heterogeneity for most of the cytokines. Concentrations of IL-2, IL-4, sIL-6R, and INF-γ were unrelated to medication status. Phasic difference was present for TNF-α, sTNFR1, sIL-2R, IL-6, and IL-1RA, whereas it was absent for IL-4 and IL-10.

CONCLUSIONS

This meta-analysis provides evidence for significant elevation of proinflammatory, anti-inflammatory, and regulatory cytokines in BD.

Reduced regulatory T cells are associated with higher levels of Th1/TH17 cytokines and activated MAPK in type 1 bipolar disorder

Bipolar disorder (BD) has been associated with an immunologic imbalance shown by increased peripheral inflammatory markers. The underlying mechanisms of this phenomenon may include changes in circulating cells and differential activation of mitogen-activated protein kinases (MAPKs). Twenty-seven euthymic female subjects with BD type I (all medicated) and 24 age- and sex-matched controls were recruited in this study. Lymphocytes were isolated and stimulated in vitro to assess Th1/Th17/Th2 cytokines (IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ and TNF-α) and MAPK phosphorylation. The expression of phospho-MAPKs, a large panel of lymphocyte subsets and cytokines were assessed by multi-color flow cytometry. BD patients had reduced proportions of natural T regulatory cells (CD4+ CD25+ FoxP3+) (p<0.01) in parallel to higher cytokine production (all p<0.01) than healthy controls. In particular, BD was associated with a strong bias to Th1 rather than Th2 profile. There was an expansion of senescence-associated cells (CD8+ CD28-) in BD (p<0.0001). T cells of BD patients had an increased p-ERK signaling (p<0.0001), indicating lymphocyte activation. Our data suggest that multiple molecular and cellular mechanisms may contribute to the immunologic imbalance observed in BD. In addition, our data concur to an early senescence process in these patients.

Levels of TNF-α, soluble TNF receptors (sTNFR1, sTNFR2), and cognition in bipolar disorder

OBJECTIVE

Tumor necrosis factor-alpha (TNF-α) may play an important role in bipolar disorder (BD) pathogenesis. There is only one study about a relationship between TNF-α levels and cognitive impairments in BD. The aim of the present study was to see whether TNF-α, soluble P55 TNF receptor (sTNFR1), and soluble P75 TNF receptor (sTNFR2) levels in BD patients are different from controls and to investigate the relationships between the levels of TNF-α, sTNFR1, and sTNFR2 and the cognitive functions in euthymic BD patients and controls.

METHODS

We assessed 54 BD type I patients and 18 controls by using a battery of neuropsychological tests. Serum TNF-α levels were measured using a commercially available enzyme-linked immunosorbent assay, whereas serum sTNFR1 and sTNFR2 levels were measured using a commercially enzyme-amplified sensitivity immunoassay kit.

RESULTS

We found that levels of sTNFR1 and sTNFR2 in BD patients were different from controls. No difference was detected between the BD group and the control group for levels of TNF-α. TNF-α level was found to have a negative correlation with the delayed recall in RAVLT.

CONCLUSIONS

High levels of sTNFR1 and sTNFR2 in euthymic patients showed that it may support that proinflammatory process continues in euthymic period. This is the first study which showed increased sTNFR2 levels in euthymic period, which could be interpreted as a compensatory mechanism and again the first which deals with verbal memory.

Chemokines in bipolar disorder: trait or state?

Recent evidence has suggested that inflammatory and immune mechanisms may play a role in the pathophysiology of bipolar disorder (BD). Only a few studies have assessed the profile of chemokines, a family of chemotactic cytokines related to the recruitment of leukocytes, in BD. The objective of our study was to evaluate the plasma levels of chemokines in BD patients in different mood states in comparison with healthy controls. Seventy BD type I patients (35 in euthymia and 35 in mania), and 50 healthy controls matched by age, gender, and education level were enrolled in this study. All subjects were assessed by the Mini-International Neuropsychiatry Interview and the patients by the Young Mania Rating Scale and the Hamilton Depression Rating Scale. The plasma levels of CCL2, CCL3, CCL11, CCL24, CXCL8, and CXCL10 were measured by enzyme-linked immunosorbent assay. BD patients presented higher plasma levels of CCL11 (1.69-fold increase; p < 0.001), CCL24 (1.40-fold increase; p = 0.02), CXCL10 (1.45-fold increase; p < 0.001) and decreased plasma levels of CXCL8 (8.68-fold decrease p < 0.001). Logistic regression stressed the main effect of increased plasma levels of CXCL10 (OR = 1.009, 95 % CI = 1.000-1.018, p = 0.042) and CCL11 (OR = 1.002, 95 % CI = 1.001-1.003, p = 0.003) and decreased plasma levels of CXCL8 (OR = 0.995, 95 % CI = 0.990-0.999, p = 0.013) to BD. This study reinforces the view that BD is associated with an immune dysfunction.

Cytokines in bipolar disorder: a systematic review and meta-analysis

BACKGROUND

Current research and hypothesis regarding the pathophysiology of bipolar disorder suggests the involvement of immune system dysfunction that is possibly related to disease activity. Our objective was to systematically review evidence of cytokine alterations in bipolar disorder according to affective state.

METHODS

We conducted a systemtic review of studies measuring endogenous cytokine concentrations in patients with bipolar disorder and a meta-analysis, reporting results according to the PRISMA statement.

RESULTS

Thirteen studies were included, comprising 556 bipolar disorder patients and 767 healthy controls, evaluating 15 different cytokines-, cytokine receptors- or cytokine antagonists. The levels of tumor necrosis factor-α (TNF-α), the soluble tumor necrosis factor receptor type 1 (sTNF-R1) and the soluble inlerleukin-2 receptor (sIL-2R) were elevated in manic patients compared with healthy control subjects (p<0.01 for each). Levels of sTNF-R1 and TNF-α were elevated in manic patients compared to euthymic patients (p=0.01 and p=0.04, respectively). sTNF-R1 levels were elevated in euthymic patients compared with healthy control subjects (p<0.01). There were no significant findings for other comparisons, including intra-individual alterations of cytokine levels.

LIMITATIONS

Stratification according to mood state resulted in small study numbers for some cytokines. Findings were limited by heterogeneity, small sample sizes and a lack of control for confounding factors in individual studies.

CONCLUSIONS

This meta-analysis found some support for immune dysregulation in bipolar disorder. Future research is warranted to elucidate the role of endogenous cytokine alterations in bipolar disorder. Clinical studies examining longitudinal changes within individuals are recommended.

Staging and neuroprogression in bipolar disorder

The apparently progressive nature of a considerable proportion of cases of bipolar disorder (BD) has been acknowledged in recently proposed clinical staging models. This has been part of an attempt to facilitate and refine diagnosis, treatment selection, and establish a prognosis. The study of the progressive nature of some cases of BD has given raise to the hypothesis of neuroprogression, which postulates that different stages of BD are associated with distinct neurobiological underpinnings. Given that BD may be intimately associated with chronic stress response and coping mechanisms over the course of illness, we propose that cellular resilience mechanisms may play a key role in the neuroprogression in BD. In the present study, we review neuroanatomical evidence of the progression that occurs in many cases of BD, as well as cellular resilience mechanisms and peripheral biomarkers associated with distinct stages of this disorder. In summary, cellular resilience mechanisms seem to be less efficient at later stages of BD, especially mitochondrial and endoplasmic reticulum-related responses to stress. These insights may help in developing staging models of BD, with a special emphasis on the search for biomarkers associated with illness progression.

Plasma concentrations of soluble cytokine receptors in euthymic bipolar patients with and without subsyndromal symptoms

BACKGROUND

Current evidence suggests that high concentrations of pro-inflammatory markers are associated with bipolar disorder characterized by severe impairment during inter-episodic periods, reduced treatment response and persistent subsyndromal symptoms. We tested whether persistent subsyndromal symptoms in euthymic bipolar patients were associated with markers of an ongoing chronic pro-inflammatory process.

METHODS

Forty-five euthymic bipolar patients (22 with subsyndromal symptoms (BD+) and 23 without subsyndromal symptoms (BD-) and 23 well controls (WC) were recruited for assessment of soluble tumor necrosis factor receptor-1 (sTNF-R1), soluble interleukin-6 receptor (sIL-6R) and soluble interleukin-2 receptor (sIL-2R) concentrations. Soluble cytokine receptor concentrations were assessed using enzyme-linked immunosorbent assay.

RESULTS

In comparison to WC, sTNF-R1 concentration was higher in both BD- and BD+ (age and sex adjusted standardized β, respectively: β = 0.34, p = 0.012 and β = 0.41, p = 0.003). Similarly, compared to WC, sIL-6R concentration was higher in both BD- and BD+ (age and sex adjusted standardized β, respectively: β = 0.44, p = 0.001 and β = 0.37, p = 0.008). There was no difference between BD- and BD+ in the concentration of either sTNF-R1 or sIL-6R; plasma concentration of sIL-2R was not analyzed as 75% percent of the samples were non-detectable.

CONCLUSIONS

Although bipolar patients present with a pro-inflammatory shift compared to well controls, subsyndromal symptoms are not associated with additive increasing effects. Longitudinal studies with larger samples are required to clarify the relationship between illness course and inflammatory markers in bipolar disorder.

Mood stabilizers commonly restore staurosporine-induced increase of p53 expression and following decrease of Bcl-2 expression in SH-SY5Y cells

Adult neurogenesis in dentate gyrus (DG) is involved in the action mechanism of mood stabilizers. However, it is poorly understood how mood stabilizers affect adult neurogenesis in DG. Neurogenesis consists of proliferation, survival (anti-apoptosis) and differentiation of neural precursor cells in adult DG. Using in vitro culture of adult rat DG-derived neural precursor cells (ADP), we have already shown that four mood stabilizers, such as lithium (Li), valproate (VPA), carbamazepine (CBZ) and lamotrigine (LTG), commonly decrease staurosporine (STS)-induced apoptosis of ADP. These suggest that the common anti-apoptotic effect of mood stabilizers could be involved in mood-stabilizing effects. Past studies have shown that Li and VPA increase the expression of Bcl-2, an anti-apoptotic gene. In addition, it has been shown that Li decreases the expression of p53, which plays a prominent role in apoptosis and regulates the expression of Bcl-2. Therefore, p53 and Bcl-2 can be considered to mediate the common anti-apoptotic effects of Li, VPA, CBZ and LTG. To elucidate the molecular mechanism underlying the common anti-apoptotic effects of mood stabilizers, we investigated the effects of Li, VPA, CBZ and LTG on STS-induced expression changes of p53, Bcl-2 and other p53-related molecules using SH-SY5Y cells as a model of neural precursor-like cells. STS increased the expression of p53 and decreased that of Bcl-2. These effects of STS on p53 and Bcl-2 are restored by all of Li, VPA, CBZ and LTG. In addition, p53 overexpression decreased the expression of Bcl-2. Taken together, these results suggest that p53 and Bcl-2 may be involved in a part of mood-stabilizing effects.

A cytokine study of adult patients with obsessive-compulsive disorder

OBJECTIVES

We aimed to determine the plasma levels of cytokines in patients with obsessive-compulsive disorder (OCD) as compared with healthy controls and to investigate whether there is any association between their concentrations and OCD clinical and therapeutic features.

METHODS

Forty patients with OCD and 40 healthy controls had their plasmas assessed for a range of cytokines (tumor necrosis factor-α, or TNF-α), chemokines (CCL2, CCL3, CCL11, CCL24, CXCL8, CXCL9, CXCL10), and other mediators (TNF soluble receptors sTNFR1 and sTNFR2 and interleukin-1 receptor antagonist) by enzyme-linked immunosorbent assay. Patients with OCD were further examined with the Mini-International Neuropsychiatric Interview, the Obsessive-Compulsive Inventory-Revised, and the Beck Depression Inventory.

RESULTS

Compared with healthy controls, patients with OCD exhibited significantly increased plasma levels of CCL3, CXCL8, sTNFR1, and sTNFR2. Among patients with OCD, there was a positive correlation between relative antidepressant dose and sTNFr2 levels. Furthermore, although the levels of sTNFR1 correlated positively with the severity of washing symptoms, CCL24 levels correlated negatively with the severity of hoarding.

CONCLUSIONS

The levels of certain immune markers are increased in adult patients with OCD and seem to vary according to predominant symptoms dimensions. Other studies are required to establish whether our findings truly reflect immunologic dysfunction in OCD or are the result of other hidden confounding factors.

The relationship between subtypes of depression and cardiovascular disease: a systematic review of biological models

A compelling association has been observed between cardiovascular disease (CVD) and depression, suggesting individuals with depression to be at significantly higher risk for CVD and CVD-related mortality. Systemic immune activation, hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, arterial stiffness and endothelial dysfunction have been frequently implicated in this relationship. Although a differential epidemiological association between CVD and depression subtypes is evident, it has not been determined if this indicates subtype specific biological mechanisms. A comprehensive systematic literature search was conducted using PubMed and PsycINFO databases yielding 147 articles for this review. A complex pattern of systemic immune activation, endothelial dysfunction and HPA axis hyperactivity is suggestive of the biological relationship between CVD and depression subtypes. The findings of this review suggest that diagnostic subtypes rather than a unifying model of depression should be considered when investigating the bidirectional biological relationship between CVD and depression. The suggested model of a subtype-specific biological relationship between depression and CVDs has implications for future research and possibly for diagnostic and therapeutic processes.

Increased levels of adipokines in bipolar disorder

Bipolar disorder (BD) is associated with considerable higher chronic medical comorbidities, overweight and obesity. Adipokines are adipocyte-derived secretory factors which have functions in immune response and seem to be associated with both BD and overweight. The aim of this study was to evaluate the plasma levels of adipokines (adiponectin, resistin and leptin) and TNF-α and its receptors (sTNFR1 and sTNFR2) in BD overweight patients in comparison with overweight controls. Thirty euthymic BD type-I patients and thirty controls matched by age, gender and body-mass index (BMI) were assessed by Mini-International Neuropsychiatric Interview, Young Mania and Hamilton Depression rating scales (YMRS and HDRS, respectively). Plasma levels of adiponectin, resistin, leptin, TNF-α and its soluble receptors were measured by ELISA. BD patients presented increased plasma levels of adiponectin (p < 0.001), leptin (p < 0.001) and sTNFR1 (p = 0.01). Plasma levels of adipokines were not correlated neither with clinical parameters nor TNF-α, sTNFR1 and sTNFR2 plasma levels. This study provides further support to the hypothesis of the immune/inflammatory imbalance in BD.

Inflammatory markers and their relationships with leptin and insulin from acute mania to full remission in bipolar disorder

BACKGROUND

Weight gain and increased production of leptin may be associated with immuno-modulation and insulin resistance in bipolar disorder. The links among inflammatory markers, leptin, and insulin of bipolar patients from acute mania to full remission remain unclear.

METHODS

Thirty-three healthy, bipolar I patients under 45 years of age were enrolled. We measured the circulating levels of high-sensitivity C-reactive protein (hs-CRP), anti-inflammatory mediators (interleukin-1 receptor antagonist [IL-1Ra] and soluble tumor necrosis factor receptor 1 [sTNF-R1]), leptin, and insulin during acute mania and subsequent partial and full remission. The results were compared with 33 age- and gender-matched healthy subjects.

RESULTS

The levels of IL-1Ra and hs-CRP of bipolar patients in both acute mania and partial remission were significantly higher than their levels of control subjects. The hs-CRP level of bipolar patients was also elevated in full remission. The elevation of IL-1Ra and hs-CRP levels in acute mania was independent of each other. They were also independent of the body mass index (BMI) and levels of leptin and insulin measurements. The levels of leptin were all positively associated with insulin levels in the normal subjects and bipolar patients in three phases. However, a significant relationship between leptin and immunoparameter was only seen in full remission with sTNF-R1 (r=0.51). Furthermore, IL-1Ra was inversely correlated with sTNF-R1 (r=-0.37, p<0.05) during partly remission, and while levels of IL-1Ra tended to normalize when patients remitted, levels of hs-CRP and sTNF-R1 showed the opposite trend.

CONCLUSIONS

Activated inflammation was found in acute mania, as evidenced by high levels of IL-1Ra, hs-CRP, and sTNF-R1. The production of leptin may be more tightly linked to insulin than the immunomodulators. Chronic inflammation may exist in bipolar patients and is reflected by elevations of IL-1Ra and hs-CRP levels in acute mania and persistent higher hs-CRP in full remission.