Are there differences in lipid peroxidation and immune biomarkers between major depression and bipolar disorder: Effects of melancholia, atypical depression, severity of illness, episode number, suicidal ideation and prior suicide attempts

A Scoping Review of Digital-Based Intervention for Reducing Risk of Suicide Among Adults

Suicide is a serious public health problem, especially among adults. Risk factors for suicide include the presence of mental health disorders, history of previous suicide attempts; substance or alcohol use and lack of social support. The impact of suicide risk includes psychological loss, as well as the trauma and emotional stress that can be felt by the families and communities left behind. Digital interventions have emerged as a promising alternative for suicide risk prevention. Previous research has focused on the findings of various designs, which did not provide clear intervention information to inform the implementation of the intervention. This study aims to describe a digital intervention to reduce the risk of suicidal behavior in adults. The design used in this study was a scoping review. The authors conducted a literature search from the Scopus, PubMed, and CINAHL databases. Inclusion criteria in this study were articles discussing digital interventions aimed at preventing suicide risk in adult populations, English language, full-text, RCT or quasi-experiment design, and publication period of the last 10 years (2014-2024). The major keywords used in the article search were suicide prevention, digital intervention, and adults. Data extraction used manual table and data analysis used descriptive qualitative with a content approach. The results showed that there were 9 articles that discussed digital-based interventions to reduce suicide risk in adults. The various types of digital interventions used were smartphone apps, online learning modules, and game-based interventions. These interventions offer significant potential in reducing the risk of suicidal behavior in adults. Digital interventions have an important role in reducing the risk of suicidal behavior in adults by considering aspects of suitability to individual needs and understanding digital literacy. Then, the development of mental health services and public health policies presented needs to be done with collaboration between stakeholders in suicide prevention efforts.

The recurrence of illness (ROI) index is a key factor in major depression that indicates increasing immune-linked neurotoxicity and vulnerability to suicidal behaviors

In this study, we aimed to investigate the associations between the recurrence of illness (ROI) and biomarkers related to an activated immune network, immune-linked neurotoxicity (INT), and a combined INT and atherogenicity index (METAMMUNE). The study involved 67 healthy controls and 66 outpatient MDD (OMDD) participants. We utilized a Multiplex method to measure 48 cytokines and examined INT and METAMMUNE composite scores in association with different ROI indices. Our findings revealed that a ROI index was successfully created by extracting a validated principal component, from the physician-rated or self-declared number of depressive episodes, the frequency of lifetime suicidal ideation and attempts. ROI was significantly associated with INT and METAMMUNE indices, neuroticism, lifetime and current suicidal behaviors, and the phenome. Our analysis also revealed that a significant portion of the variance in the OMDD phenome, which includes current suicidal behaviors, anxiety, and depression, can be accounted for by the regression on INT, ROI, and emotional neglect and abuse. A validated latent construct was successfully extracted from the three ROI components, INT and METAMMUNE indices. The results indicate that increasing ROI indicates heightened immune-metabolic abnormalities, increased risk of suicidal behaviors, and elevated severity of lifetime and current phenome features.

Association between inflammatory joint disease and severe or treatment-resistant depression: population-based cohort and case-control studies in Sweden

OBJECTIVE

To investigate whether the association between depression and inflammatory joint disease (IJD; rheumatoid arthritis [RA], psoriatic arthritis [PsA], ankylosing spondylitis/spondyloarthropathies [AS], and juvenile idiopathic arthritis [JIA]) is affected by the severity or treatment-resistance of depression.

METHOD

Parallel cohort studies and case-control studies among 600,404 patients with a depressive episode identified in Swedish nationwide administrative registers. Prospective and retrospective risk for IJD in patients with depression was compared to matched population comparators, and the same associations were investigated in severe or treatment-resistant depression. Analyses were adjusted for comorbidities and sociodemographic covariates.

RESULTS

Patients with depression had an increased risk for later IJD compared to population comparators (adjusted hazard ratio (aHR) for any IJD 1.34 [95% CI 1.30-1.39]; for RA 1.27 [1.15-1.41]; PsA 1.45 [1.29-1.63]; AS 1.32 [1.15-1.52]). In case-control studies, patients with depression more frequently had a history of IJD compared to population controls (adjusted odds ratio (aOR) for any IJD 1.43 [1.37-1.50]; RA 1.39 [1.29-1.49]; PsA 1.59 [1.46-1.73]; AS 1.49 [1.36-1.64]; JIA 1.52 [1.35-1.71]). These associations were not significantly different for severe depression or TRD.

CONCLUSION

IJD and depression are bidirectionally associated, but this association does not seem to be influenced by the severity or treatment resistance of depression.

T cell activation and lowered T regulatory cell numbers are key processes in severe major depressive disorder: Effects of recurrence of illness and adverse childhood experiences

BACKGROUND

Major depressive disorder (MDD) is characterized by increased T helper (Th)1 polarization, T cell activation (e.g., CD71+ and CD40L+), and cannabinoid receptor type 2 bearing CD20+ B cells; and lower T regulatory (Treg) numbers.

AIMS

To delineate the effects of adverse childhood experiences (ACEs) and recurrence of illness (ROI) on activated T and CB2-bearing B populations, and Tregs, including FoxP3 + CD152+, FoxP3 + GARP+, and FoxP3 + CB1+ cells.

METHODS

We measured ROI, ACEs, the number of activated T cells, Tregs, and CD20 + CB2+ B cells, in 30 MDD patients and 20 healthy controls.

RESULTS

A larger part of the variance in the depression phenome (40.8 %) was explained by increased CD20 + CB2+ and activated T cells, and lowered Tregs. ROI and lifetime suicidal behaviors were significantly and positively associated with CD20 + CB2+, CD3 + CD71+, CD3 + CD40L+, CD4 + CD71+, CD4 + CD40L+, and CD4HLADR+ numbers. ROI was significantly correlated with CD8 + CD40L+ numbers. The sum of ACEs was significantly associated with CD20 + CB2+, CD3 + CD40L+, CD4 + 40 L+ numbers, T cell activation (positively) and Treg (inversely) indices. One replicable latent vector could be extracted from activated T cells, lifetime and current suicidal behaviors, number of depressive episodes, and severity of depression, and 48.8 % of its variance was explained by ACEs.

CONCLUSIONS

ACE-induced activation of T effector and cytotoxic cells and B cells with autoimmune potential, coupled with lowered Treg numbers are a key component of depression. The findings indicate that increasing ROI, the phenome of depression and suicidal behaviors, are caused by autoimmune processes, which are the consequence of ACEs and increasing sensitization of immune responses.

Repeated Sulforaphane Treatment Reverses Depressive-like Behavior and Exerts Antioxidant Effects in the Olfactory Bulbectomy Model in Mice

Growing evidence suggests that activators of nuclear factor erythroid-derived 2-like 2 (Nrf2), such as sulforaphane, may represent promising novel pharmacological targets for conditions related to oxidative stress, including depressive disorder. Therefore, we conducted a study to explore the behavioral and biochemical effects of repeated (14 days) sulforaphane (SFN) treatment in the olfactory bulbectomy (OB) animal model of depression. An open field test (OFT), splash test (ST), and spontaneous locomotor activity test (LA) were used to assess changes in depressive-like behavior and the potential antidepressant-like activity of SFN. The OB model induced hyperactivity in mice during the OFT and LA as well as a temporary loss of self-care and motivation in the ST. The repeated administration of SFN (10 mg/kg) effectively reversed these behavioral changes in OB mice across all tests. Additionally, a biochemical analysis revealed that SFN (10 mg/kg) increased the total antioxidant capacity in the frontal cortex and serum of the OB model. Furthermore, SFN (10 mg/kg) significantly enhanced superoxide dismutase activity in the serum of OB mice. Overall, the present study is the first to demonstrate the antidepressant-like effects of repeated SFN (10 mg/kg) treatment in the OB model and indicates that these benefits may be linked to improved oxidative status.

Role of Inflammatory Mechanisms in Major Depressive Disorder: From Etiology to Potential Pharmacological Targets

The involvement of central and peripheral inflammation in the pathogenesis and prognosis of major depressive disorder (MDD) has been demonstrated. The increase of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, IL-18, and TNF-α) in individuals with depression may elicit neuroinflammatory processes and peripheral inflammation, mechanisms that, in turn, can contribute to gut microbiota dysbiosis. Together, neuroinflammation and gut dysbiosis induce alterations in tryptophan metabolism, culminating in decreased serotonin synthesis, impairments in neuroplasticity-related mechanisms, and glutamate-mediated excitotoxicity. This review aims to highlight the inflammatory mechanisms (neuroinflammation, peripheral inflammation, and gut dysbiosis) involved in the pathophysiology of MDD and to explore novel anti-inflammatory therapeutic approaches for this psychiatric disturbance. Several lines of evidence have indicated that in addition to antidepressants, physical exercise, probiotics, and nutraceuticals (agmatine, ascorbic acid, and vitamin D) possess anti-inflammatory effects that may contribute to their antidepressant properties. Further studies are necessary to explore the therapeutic benefits of these alternative therapies for MDD.

Sestrin2 attenuates depressive-like behaviors and neuroinflammation in CUMS mice through inhibiting ferroptosis

Sestrin2 (SESN2) is a stress-inducible protein and acts as a neuroprotective regulator. The present study aimed to explore the antidepressant activity of SESN2 and its relevant mechanism. Depression mouse model was established by chronic unpredictable mild stress (CUMS) for a successive 5 weeks. Behaviors tests were conducted to examine depressive-like behaviors including sugar preference test, tail suspension test and open field test. The expression of SESN2 and ferroptosis-related proteins was examined by western blot. The production of cytokines was measured by ELISA. Iron deposition was assessed using Prussian blue staining and Fe 2+ content was measured using commercial kits. Lipid peroxidation was evaluated by thiobarbituric acid reactive substances assay. BV-2 cells were treated with LPS to induce microglial activation, which was evaluated by the iba-1 level adopting immunofluorescence assay. The ferroptosis inducer Erastin was adopted for the pretreatment in BV-2 cells to conduct a rescue experiment. SESN2 was downregulated in CUMS-induced mice, and SESN2 overexpression dramatically ameliorated CUMS-induced depression-like behaviors. Meanwhile, SESN2 reduced the production of pro-inflammatory cytokines and iba-1 level in hippocampus of CUMS mice, as well as reducing iron deposition and lipid peroxidation, demonstrating that SESN2 reduced microglial activation, neuroinflammation and ferroptosis in CUMS mice. Similarly, SESN2 also restricted iba-1 level, pro-inflammatory cytokines production, and ferroptosis in LPS-induced BV-2 cells, which was partly reversed by additional treatment of Erastin. These findings suggest that SESN2 possesses potent antidepressant property through inhibiting ferroptosis and neuroinflammation.

Investigation of mechanisms of action involved in the antidepressant-like effect of Trans,trans-farnesol in mice

This study aimed to investigate, through in vivo and biochemical methodologies, the effect of trans,trans-farnesol (12.5, 25, 50 or 100 mg/kg, p.o.) acute administration, adopting different behavioral and neurochemical parameters associated with an acute induced-depression model in mice. The initial results showed that, the oral treatment with trans,trans-farnesol, at the dose of 100 mg/kg induced a possible antidepressant-like effect in animals subjected to forced swim test (FST) and reserpine-induced akinesia. In addition, it was observed that the compound in question has an effect size and properties similar to imipramine (prototype of tricyclic antidepressants), but devoid of proconvulsant adverse effect. In biochemical assays, the pretreatment with trans,trans-farnesol, at a dose of 100 mg/kg (p.o.), decreased the hippocampal concentration of thiobarbituric acid reactive substances (TBARS) and restored striatal levels of noradrenaline and serotonin in mice subjected to FST. Altogether, these results suggest that trans,trans-farnesol showed a significant antidepressant-like effect, which seems to be mediated by the antagonism of muscarinic cholinergic receptors, reduction of oxidative stress and the modulation of noradrenaline and serotonin content in the central nervous system.

T helper-1 activation via interleukin-16 is a key phenomenon in the acute phase of severe, first-episode major depressive disorder and suicidal behaviors

BACKGROUND

Immune-inflammatory pathways in major depressive disorder are confined to the major dysmood disorder (MDMD) phenotype (Maes et al., 2022). No studies have addressed the immune profile of first episode MDMD (FE-MDMD).

METHODS

This study investigated the immune profiles of 71 patients with the acute phase of first-episode major depressive disorder (FE-MDMD) and 40 healthy controls. We measured 48 cytokines/chemokines/growth factors, classical M1, alternative M2, T helper (Th)-1, Th-2, and Th-17 phenotypes, immune-inflammatory response system (IRS), compensatory immunoregulatory system (CIRS), and neuro-immunotoxicity profiles.

RESULTS

FE-MDMD patients show significantly activated M1, M2, Th-1, IRS, CIRS, and neurotoxicity, but not Th-2 or Th-17, profiles compared to controls. FE-MDMD is accompanied by Th-1 polarization, while there are no changes in M1/M2 or IRS/CIRS ratios. The top single indicator of FE-MDMD was by far interleukin (IL)-16, followed at a distance by TRAIL, IL-2R, tumor necrosis factor (TNF)-β. The severity of depression and anxiety was strongly associated with IRS (positively) and Th-2 (inversely) profiles, whereas suicidal behavior was associated with M1 activation. Around 56-60% of the variance in depression, anxiety, and suicidal behavior scores was explained by IL-16, platelet-derived growth factor (PDGF) (both positively), and IL-1 receptor antagonist (inversely). Increased neurotoxicity is mainly driven by IL-16, TNF-α, TRAIL, IL-6, and chemokine (CCL2, CCL11, CXCL1, CXCL10) signaling. Antidepressant-treated patients show an increased IRS/CIRS ratio as compared with drug-naïve FE-MDMD patients.

CONCLUSIONS

FE-MDMD is accompanied by positive regulation of the IRS mainly driven by Th-1 polarization and T cell activation (via binding of IL-16 to CD4), and TNF, chemokine, and growth factor signaling.

The Importance of α-Klotho in Depression and Cognitive Impairment and Its Connection to Glutamate Neurotransmission-An Up-to-Date Review

Depression is a serious neuropsychiatric disease affecting an increasing number of people worldwide. Cognitive deficits (including inattention, poor memory, and decision-making difficulties) are common in the clinical picture of depression. Cognitive impairment has been hypothesized to be one of the most important components of major depressive disorder (MDD; referred to as clinical depression), although typical cognitive symptoms are less frequent in people with depression than in people with schizophrenia or bipolar disorder (BD; sometimes referred to as manic-depressive disorder). The importance of α-Klotho in the aging process has been well-documented. Growing evidence points to the role of α-Klotho in regulating other biological functions, including responses to oxidative stress and the modulation of synaptic plasticity. It has been proven that a Klotho deficit may contribute to the development of various nervous system pathologies, such as behavioral disorders or neurodegeneration. Given the growing evidence of the role of α-Klotho in depression and cognitive impairment, it is assumed that this protein may be a molecular link between them. Here, we provide a research review of the role of α-Klotho in depression and cognitive impairment. Furthermore, we propose potential mechanisms (related to oxidative stress and glutamatergic transmission) that may be important in α-Klotho-mediated regulation of mental and cognitive function.

Putative role of glial cells in treatment resistance depression: An updated critical literation review and evaluation of single-nuclei transcriptomics data

AIMS

Major depressive disorder (MDD) is a prevalent global mental illness with diverse underlying causes. Despite the availability of first-line antidepressants, approximately 10-30 % of MDD patients do not respond to these medications, falling into the category of treatment-resistant depression (TRD). Our study aimed to elucidate the precise molecular mechanisms through which glial cells contribute to depression-like episodes in TRD.

MATERIALS AND METHODS

We conducted a comprehensive literature search using the PubMed and Scopus electronic databases with search terms carefully selected to be specific to our topic. We strictly followed inclusion and exclusion criteria during the article selection process, adhering to PRISMA guidelines. Additionally, we carried out an in-depth analysis of postmortem brain tissue obtained from patients with TRD using single-nucleus transcriptomics (sn-RNAseq).

KEY FINDINGS

Our data confirmed the involvement of multiple glia-specific markers (25 genes) associated with TRD. These differentially expressed genes (DEGs) primarily regulate cytokine signaling, and they are enriched in important pathways such as NFκB and TNF-α. Notably, DEGs showed significant interactions with the transcription factor CREB1. sn-RNAseq analysis confirmed dysregulation of nearly all designated DEGs; however, only Cx30/43, AQP4, S100β, and TNF-αR1 were significantly downregulated in oligodendrocytes (OLGs) of TRD patients. With further exploration, we identified the GLT-1 in OLGs as a hub gene involved in TRD.

SIGNIFICANCE

Our findings suggest that glial dysregulation may hinder the effectiveness of existing therapies for TRD. By targeting specific glial-based genes, we could develop novel interventions with minimal adverse side effects, providing new hope for TRD patients who currently experience limited benefits from invasive treatments.

Examining the Relationships between the Incidence of Infectious Diseases and Mood Disorders: An Analysis of Data from the Global Burden of Disease Studies, 1990-2019

Mood disorders are among the commonest mental disorders worldwide. Epidemiological and clinical evidence suggests that there are close links between infectious diseases and mood disorders, but the strength and direction of these association remain largely unknown. Theoretical models have attempted to explain this link based on evolutionary or immune-related factors, but these have not been empirically verified. The current study examined cross-sectional and longitudinal associations between the incidence of infectious diseases and mood disorders, while correcting for climate and economic factors, based on data from the Global Burden of Disease Studies, 1990-2019. It was found that major depressive disorder was positively associated with lower respiratory infections, while bipolar disorder was positively associated with upper respiratory infections and negatively associated with enteric and tropical infections, both cross-sectionally and over a period of 30 years. These results suggest that a complex, bidirectional relationship exists between these disorders. This relationship may be mediated through the immune system as well as through the gut-brain and lung-brain axes. Understanding the mechanisms that link these groups of disorders could lead to advances in the prevention and treatment of both.

Meta-analysis of soluble tumour necrosis factor receptors in severe mental illnesses

Tumour necrosis factor (TNF), as an innate immune defense molecule, functions through binding to TNF receptor 1 (TNFR1) or TNF receptor 2 (TNFR2). Peripheral levels of soluble TNFR1 (sTNFR1) and soluble TNFR2 (sTNFR2) were widely measured in severe mental illnesses (SMIs) including schizophrenia (SCZ), bipolar disorder (BD) and major depressive disorder (MDD) but inconsistencies existed. Hence, the present meta-analysis was conducted to identify the overall association between plasma/serum sTNFR1 and sTNFR2 levels and SMIs. Published studies were searched using Pubmed and Scopus. Data were analysed using Comprehensive Meta-Analysis version 2. Hedges's g effect sizes and 95% confidence intervals were pooled using fixed-effect or random-effects models. Heterogeneity, publication bias and study quality were assessed. Sensitivity analysis and subgroup analysis were performed. Our findings revealed that sTNFR1 level was significantly higher in SMI, particularly in BD. The sTNFR2 level significantly elevated in SMI but with smaller effect size. These findings further support the association between altered immune system and inflammatory abnormalities in SMI, especially in patients with BD. Subgroup analysis showed that younger age of onset, longer illness duration and psychotropic medication raised both sTNFR levels, especially sTNFR1, as these factors may contribute to the activation of inflammation. Future studies were suggested to identify the causality between TNFR pathway and SCZ, BD and MDD respectively using homogenous group of each SMI, and to determine the longitudinal effect of each psychotropic medication on TNFR pathway.

Major Depressive Disorder and Oxidative Stress: A Review of Peripheral and Genetic Biomarkers According to Clinical Characteristics and Disease Stages

Major depressive disorder (MDD) is currently the main cause of disability worldwide, but its pathophysiology remains largely unknown, especially given its high heterogeneity in terms of clinical phenotypes and biological characteristics. Accordingly, its management is still poor. Increasing evidence suggests that oxidative stress, measured on various matrices such as serum, plasma or erythrocytes, has a critical role in MDD. The aim of this narrative review is to identify serum, plasma and erythrocyte biomarkers of oxidative stress in MDD patients according to disease stage and clinical features. Sixty-three articles referenced on PubMed and Embase between 1 January 1991, and 31 December 2022, were included. Modifications to antioxidant enzymes (mainly glutathione peroxidase and superoxide dismutase) in MDD were highlighted. Non-enzymatic antioxidants (mainly uric acid) were decreased in depressed patients compared to healthy controls. These changes were associated with an increase in reactive oxygen species. Therefore, increased oxidative damage products (principally malondialdehyde, protein carbonyl content and 8-hydroxy-2'-deoxyguanosine) were present in MDD patients. Specific modifications could be identified according to disease stages and clinical features. Interestingly, antidepressant treatment corrected these changes. Accordingly, in patients in remission from depression, oxidative stress markers were globally normalized. This narrative review suggests the particular interest of oxidative stress biomarkers for MDD care that may contribute to the heterogeneity of the disease and provide the opportunity to find new therapeutic targets.

Research and Diagnostic Algorithmic Rules (RADAR) for mood disorders, recurrence of illness, suicidal behaviours, and the patient's lifetime trajectory

The top-down Diagnostic and Statistical Manual/International Statistical Classification of Diseases categories of mood disorders are inaccurate, and their dogmatic nature precludes both deductive (as indisputable) and inductive (as top-down) remodelling of case definitions. In trials, psychiatric rating scale scores employed as outcome variables are invalid and rely on folk psychology-like narratives. Using machine learning techniques, we developed a new precision nomothetic model of mood disorders with a recurrence of illness (ROI) index, a new endophenotype class, namely Major Dysmood Disorder (MDMD), characterised by increased ROI, a more severe phenome, and more disabilities. Nonetheless, our previous studies did not compute Research and Diagnostic Algorithmic Rules (RADAR) to diagnose MDMD and score ROI, lifetime (LT), and current suicidal behaviours, as well as the phenome of mood disorders. Here, we provide rules to compute bottom-up RADAR scores for MDMD, ROI, LT and current suicidal ideation and attempts, the phenome of mood disorders, and the lifetime trajectory of mood disorder patients from a family history of mood disorders and substance abuse to adverse childhood experiences, ROI, and the phenome. We also demonstrate how to plot the 12 major scores in a single RADAR graph, which displays all features in a two-dimensional plot. These graphs allow the characteristics of a patient to be displayed as an idiomatic fingerprint, allowing one to estimate the key traits and severity of the illness at a glance. Consequently, biomarker research into mood disorders should use our RADAR scores to examine pan-omics data, which should be used to enlarge our precision models and RADAR graph.

Inflammatory cytokines in and cognitive function of adolescents with first-episode schizophrenia, bipolar disorder, or major depressive disorder

BACKGROUND

Few studies have explored the complex relationship of pro- and anti-inflammatory cytokines with cognitive function in adolescents with first-episode schizophrenia, bipolar disorder, or major depressive disorder.

METHODS

In total, 26, 35, and 29 adolescents with first-episode schizophrenia, bipolar disorder, and major depressive disorder, respectively, and 22 age- and sex-matched controls were included in the current study. Cytokines, namely interleukin (IL)-2, IL-6, tumor necrosis factor (TNF)-α, and C-reactive protein (CRP), were assessed. The Wisconsin Card Sorting Test (WCST) and the working memory task were administered to assess cognitive function.

RESULTS

Using generalized linear models with adjustment for demographic data and clinical symptoms, patients with bipolar disorder were found to exhibit the highest levels of CRP (P = .023), IL-6 (P = .022), and TNF-α (P = .011), and had the lowest IL-2 levels (P = .034) among the four groups. According to the results of the WCST and working memory task, adolescents with schizophrenia exhibited the lowest performance in cognitive function. In addition, among the assessed cytokines, only CRP levels (P = .027) were negatively associated with WCST scores.

DISCUSSION

Dysregulated pro- and anti-inflammatory cytokines and impaired cognitive functioning were observed in first-episode adolescent-onset schizophrenia, bipolar disorder, and major depressive disorder. The altered cytokine profiles may play important roles in the pathophysiology of schizophrenia, bipolar disorder, and major depressive disorder.

The Role of Inflammation in the Pathophysiology of Depression and Suicidal Behavior: Implications for Treatment

Depression and suicidal behavior are 2 complex psychiatric conditions of significant public health concerns due to their debilitating nature. The need to enhance contemporary treatments and preventative approaches for these illnesses not only calls for distillation of current views on their pathogenesis but also provides an impetus for further elucidation of their novel etiological determinants. In this regard, inflammation has recently been recognized as a potentially important contributor to the development of depression and suicidal behavior. This review highlights key evidence that supports the presence of dysregulated neurometabolic and immunologic signaling and abnormal interaction with microbial species as putative etiological hallmarks of inflammation in depression as well as their contribution to the development of suicidal behavior. Furthermore, therapeutic insights addressing candidate mechanisms of pathological inflammation in these disorders are proposed.

Evaluation of Inflammatory Response System (IRS) and Compensatory Immune Response System (CIRS) in Adolescent Major Depression

Purpose

Nowadays, the role of two tightly interconnected systems, the inflammatory response system (IRS) and the compensatory immune response system (CIRS) in depression, is increasingly discussed. Various studies indicate pro-inflammatory activity in adolescent depression; however, there is an almost complete lack of findings about IRS and CIRS balance. Thus, we aimed to assess different IRS and CIRS indices, profiles, and IRS/CIRS ratios in drug-naïve MDD patients at adolescent age, with respect to sex.

Patients and Methods

One hundred MDD adolescents (40 boys, average age: 15.4±1.2 yrs.) and 60 controls (28 boys, average age: 15.3±1.5 yrs.) were examined. Evaluated parameters were 1. plasma levels of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, interferon gamma, tumor necrosis factor alpha (TNF-α), soluble receptor of IL-6 (sIL-6R), soluble receptors of TNF-α (sTNF-R1, sTNF-R2); 2. profiles: IL-6 trans-signaling, M1 macrophage signaling, helper T lymphocytes (Th) 1 profile, regulatory T lymphocytes (Treg)+Th2, allIRS, and allCIRS; 3. IRS vs CIRS activity ratios: TNF-α/TNF-R1, TNF-α/TNF-R2, TNF-α/sTNF-Rs (ie sTNF-R1+sTNF-R2), Th1/Th2, Th1/Treg, Th1/Th2+Treg, M1/Th2, M1/Treg, M1/Treg+Th2, allIRS/allCIRS.

Results

MDD patients showed increased IL-4, IL-10, TNF-α, sIL-6R, Treg+Th2, allIRS, allCIRS, and TNF-α/sTNF-Rs, and decreased Th1/Th2+Treg. MDD females showed increased IL-10 and TNF-α compared to control females. MDD males showed increased IL-4, IL-10, sIL-6R, Treg+Th2, and TNF-α/TNF-R1 compared to control males. Increased sTNF-R1 was found in MDD males compared to MDD females. Positive correlations were found between CDI score and sIL-6R and IL-10 in the total group and between CDI score and IL-10 in adolescent males.

Conclusion

Our study for the first time extensively evaluated IRS and CIRS interactions revealing enhanced pro-inflammatory TNF-α signaling and IL-6 trans-signaling in association with increased IL-10- and IL-4-mediated anti-inflammatory activity in first-episode depression at the adolescent age. Moreover, results reflect the sex-specific simultaneous activation of IRS and CIRS pathways in adolescent depression.

The Tryptophan Catabolite or Kynurenine Pathway in a Major Depressive Episode with Melancholia, Psychotic Features and Suicidal Behaviors: A Systematic Review and Meta-Analysis

Major depressive disorder (MDD) and bipolar disorder (BD) with melancholia and psychotic features and suicidal behaviors are accompanied by activated immune-inflammatory and oxidative pathways, which may stimulate indoleamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme of the tryptophan catabolite (TRYCAT) pathway resulting in increased tryptophan degradation and elevated tryptophan catabolites (TRYCTAs). The purpose of the current study is to systematically review and meta-analyze levels of TRP, its competing amino acids (CAAs) and TRYCATs in patients with severe affective disorders. Methods: PubMed, Google Scholar and SciFinder were searched in the present study and we recruited 35 studies to examine 4647 participants including 2332 unipolar (MDD) and bipolar (BD) depressed patients and 2315 healthy controls. Severe patients showed significant lower (p < 0.0001) TRP (standardized mean difference, SMD = −0.517, 95% confidence interval, CI: −0.735; −0.299) and TRP/CAAs (SMD = −0.617, CI: −0.957; −0.277) levels with moderate effect sizes, while no significant difference in CAAs were found. Kynurenine (KYN) levels were unaltered in severe MDD/BD phenotypes, while the KYN/TRP ratio showed a significant increase only in patients with psychotic features (SMD = 0.224, CI: 0.012; 0.436). Quinolinic acid (QA) was significantly increased (SMD = 0.358, CI: 0.015; 0.701) and kynurenic acid (KA) significantly decreased (SMD = −0.260, CI: −0.487; −0.034) in severe MDD/BD. Patients with affective disorders with melancholic and psychotic features and suicidal behaviors showed normal IDO enzyme activity but a lowered availability of plasma/serum TRP to the brain, which is probably due to other processes such as low albumin levels.

Effects of metabolic syndrome and obesity on suicidality in individuals with bipolar disorder

BACKGROUND

The prevalence of metabolic syndrome and overweight/obesity is increased in bipolar disorder (BD) compared to the general population and is related to suicidality. The aim of this study was to examine the association between both the rate of suicidal ideation and suicide attempts and metabolic variables in individuals with BD.

METHODS

Anthropometric measures, socio-demographic data, suicide history and serum lipid levels were measured in 215 individuals with BD. Individuals were divided into normal weight, overweight and obese according to their body mass index (BMI), and metabolic syndrome was assessed using "The International Diabetes Federation"-criteria.

RESULTS

Of the 215 individuals studied, 80.9% reported suicidal ideation, 35.3% reported at least one suicide attempt and 30.7% were diagnosed with metabolic syndrome. Both metabolic syndrome and BMI were not related to suicide attempts. However, individuals with normal weight had more suicidal ideation than overweight individuals, while obese individuals did not differ from either group. Furthermore, there was no association between suicide attempts or suicidal ideation and serum lipid levels.

LIMITATIONS

The cross-sectional design of the study, a non-standardized questionnaire for suicidality, and not controlling the medication intake are limiting factors.

CONCLUSION

Contrary to expectations, a difference was found in the BMI categories and suicidal ideation, but not suicide attempts. Serum lipid levels were found to be unsuitable as possible biomarkers for suicidality in individuals with BD. Special attention should be paid to suicidal ideation and BMI rather than metabolic syndrome or lipid values when treating suicidal individuals with BD.

The microbiota-gut-brain axis and its modulation in the therapy of depression: comparison of efficacy of conventional drugs and traditional Chinese medicine approaches

Depression is a common and severe mental disease that places a heavy burden on human society, which can lead to decreased cognitive function, energy loss, insomnia, and even suicide. Although medication plays an important role in improving the symptoms of depression, approximately one third of people with depression do not significantly benefit from medication and experience various adverse reactions. Recently, increasing evidence has shown that gut microbes play an important role in the occurrence and development of depression. There have been illuminating studies previously conducted on the relationship between antidepressant chemicals, traditional Chinese medicine, and the microbiota-gut-brain axis (MGBA). Therefore, in this review, we summarize the role of the MGBA in the occurrence and development of depression, especially the important role of the MGBA in the mechanism of action of antidepressants. Modulation of the MGBA is proposed to enhance the efficacy of antidepressant drugs and reduce their side effects and disease recurrence, so as to provide a new method for the treatment of depression.

Pro-inflammatory cytokines and suicidal behavior among patients with bipolar I disorder

OBJECTIVE

Suicidal behavior and different mood states of bipolar I disorder (BD) have been shown to be associated with dysregulated proinflammatory cytokines. Only a few studies have examined the association between inflammation and SB in BD, and the association between proinflammatory cytokines, SB, and cognitive deficits in patients with BD remains unclear.

METHODS

77 patients with BD and 61 age-/sex-matched healthy controls were recruited. Patients were divided into two groups: with suicidal ideation (SI; n = 21) and no SI (n = 56). SI was defined by a score of ≥1 in item 10 of Montgomery Åsberg Depression Rating Scale. Levels of proinflammatory cytokines, including soluble interleukin-6 receptor (sIL-6R), soluble tumor necrosis factor-α receptor type 1 (sTNF-αR1), and C-reactive protein (CRP), were measured, and cognitive function was assessed using 2-back task and Go/No-Go task.

RESULTS

Patients with SI had higher levels of sTNF-αR1 than those without SI and the controls (p = .004). BD patients with or without a history of suicide attempt had higher levels of CRP than the controls. SI was associated with serum levels of sTNF-αR1 and IL-6sR, even after additionally controlling for working memory and inhibitory control (p < .05).

CONCLUSION

This study indicates that serum levels of sTNF-αR1 have distinct differences between BD patients with or without SI, and our findings strengthen the hypothesis of a link between suicidal behavior and neuro-inflammation pathophysiology in BD.

False dogmas in mood disorders research: Towards a nomothetic network approach

The current understanding of major depressive disorder (MDD) and bipolar disorder (BD) is plagued by a cacophony of controversies as evidenced by competing schools to understand MDD/BD. The DSM/ICD taxonomies have cemented their status as the gold standard for diagnosing MDD/BD. The aim of this review is to discuss the false dogmas that reign in current MDD/BD research with respect to the new, data-driven, machine learning method to model psychiatric illness, namely nomothetic network psychiatry (NNP). This review discusses many false dogmas including: MDD/BD are mind-brain disorders that are best conceptualized using a bio-psycho-social model or mind-brain interactions; mood disorders due to medical disease are attributable to psychosocial stress or chemical imbalances; DSM/ICD are the gold standards to make the MDD/BD diagnosis; severity of illness should be measured using rating scales; clinical remission should be defined using threshold values on rating scale scores; existing diagnostic BD boundaries are too restrictive; and mood disorder spectra are the rule. In contrast, our NNP models show that MDD/BD are not mind-brain or psycho-social but systemic medical disorders; the DSM/ICD taxonomies are counterproductive; a shared core, namely the reoccurrence of illness (ROI), underpins the intertwined recurrence of depressive and manic episodes and suicidal behaviors; mood disorders should be ROI-defined; ROI mediates the effects of nitro-oxidative stress pathways and early lifetime trauma on the phenome of mood disorders; severity of illness and treatment response should be delineated using the NNP-derived causome, pathway, ROI and integrated phenome scores; and MDD and BD are the same illness.

Zhi-Zi-Chi Decoction Reverses Depressive Behaviors in CUMS Rats by Reducing Oxidative Stress Injury Via Regulating GSH/GSSG Pathway

Depression is one of the main diseases that lead to disability and loss of ability to work. As a traditional Chinese medicine, Zhi-zi-chi decoction is utilized to regulate and improve depression. However, the research on the antidepressant mechanism and efficacy material basis of Zhi-zi-chi decoction has not been reported yet. Our previous research has found that Zhi-Zi-chi decoction can reduce glutamate-induced oxidative stress damage to PC 12 cells, which can exert a neuroprotective effect, and the antidepressant effect of Zhi-Zi-chi decoction was verified in CUMS rat models. In this study, the animal model of depression was established by chronic unpredictable mild stimulation combined with feeding alone. The brain metabolic profile of depressed rats was analyzed by the method of metabolomics based on ultra-performance liquid chromatography-quadrupole/time-of-flight mass. 26 differential metabolites and six metabolic pathways related to the antidepressant of Zhi-zi-chi decoction were screened and analyzed. The targeted metabolism of the glutathione metabolic pathway was analyzed. At the same time, the levels of reactive oxygen species, superoxide dismutase, glutathione reductase, glutathione peroxidase in the brain of depressed rats were measured. Combined with our previous study, the antioxidant effect of the glutathione pathway in the antidepressant effect of Zhi-zi-chi decoction was verified from the cellular and animal levels respectively. These results indicated that Zhi-zi-chi decoction exerted a potential antidepressive effect associated with reversing the imbalance of glutathione and oxidative stress in the brain of depressed rats.

The Immune Profile of Major Dysmood Disorder: Proof of Concept and Mechanism Using the Precision Nomothetic Psychiatry Approach

Major depressive disorder and a major depressive episode (MDD/MDE) are characterized by activation of the immune-inflammatory response system (IRS) and the compensatory immune-regulatory system (CIRS). In MDD/MDE, recent precision nomothetic psychiatry studies discovered a new endophenotype class, namely major dysmood disorder (MDMD), a new pathway phenotype, namely reoccurrence of illness (ROI), and a new model of the phenome of depression. The aim of the present study is to examine the association between ROI, the phenome of depression, and MDMD’s features and IRS, CIRS, macrophages (M1), T helper (Th)1, Th2, Th17, T regulatory, and growth factor (GF) profiles. Culture supernatants of unstimulated and stimulated (5 μg/mL of PHA and 25 μg/mL of LPS) diluted whole blood of 30 MDD/MDE patients and 20 controls were assayed for cytokines/GF using the LUMINEX assay. MDMD was characterized by increased M1, Th1, Th2, Th17, Treg, IRS, CIRS, neurotoxicity, and GF profiles. Factor analysis shows that ROI features and immune-GF profiles may be combined into a new pathway phenotype (an extracted latent vector). ROI, lifetime and recent suicidal behaviors, and severity of depression are significantly associated with immunotoxicity and GF profiles. Around 80.0% of the variance in the phenome is predicted by ROI and neurotoxicity or the IRS/CIRS ratio. The molecular pathways underpinning ROI-associated sensitization of immune/growth networks are transmembrane receptor protein kinase-triggered STAT protein phosphorylation, TLR/NF-κB, JAK-STAT, and the main proliferation/survival PI3K/Akt/RAS/MAPK pathway. In conclusion, MDMD’s heightened immune responses are the consequence of ROI-associated sensitization combined with immunostimulatory triggers.

Antioxidant Biomolecules and Their Potential for the Treatment of Difficult-to-Treat Depression and Conventional Treatment-Resistant Depression

Major depression is a devastating disease affecting an increasing number of people from a young age worldwide, a situation that is expected to be worsened by the COVID-19 pandemic. New approaches for the treatment of this disease are urgently needed since available treatments are not effective for all patients, take a long time to produce an effect, and are not well-tolerated in many cases; moreover, they are not safe for all patients. There is solid evidence showing that the antioxidant capacity is lower and the oxidative damage is higher in the brains of depressed patients as compared with healthy controls. Mitochondrial disfunction is associated with depression and other neuropsychiatric disorders, and this dysfunction can be an important source of oxidative damage. Additionally, neuroinflammation that is commonly present in the brain of depressive patients highly contributes to the generation of reactive oxygen species (ROS). There is evidence showing that pro-inflammatory diets can increase depression risk; on the contrary, an anti-inflammatory diet such as the Mediterranean diet can decrease it. Therefore, it is interesting to evaluate the possible role of plant-derived antioxidants in depression treatment and prevention as well as other biomolecules with high antioxidant and anti-inflammatory potential such as the molecules paracrinely secreted by mesenchymal stem cells. In this review, we evaluated the preclinical and clinical evidence showing the potential effects of different antioxidant and anti-inflammatory biomolecules as antidepressants, with a focus on difficult-to-treat depression and conventional treatment-resistant depression.

Inflammation and nitro-oxidative stress in current suicidal attempts and current suicidal ideation: a systematic review and meta-analysis

A meta-analysis showed a significant association between activated immune-inflammatory and nitro-oxidative (IO&NS) pathways and suicide attempts (SA). There is no data on whether recent suicidal ideation (SI) is accompanied by activated IO&NS pathways and whether there are differences between recent SA and SI. The current study searched PubMed, Google Scholar, and Web of Science, for articles published from inception until May 10, 2021, and systematically reviewed and meta-analysed the association between recent SA/SI (<3 months) and IO&NS biomarkers. We included studies which compared psychiatric patients with and without SA and SI and controls (either healthy controls or patients without SA/SI) and used meta-analysis (random-effect model with restricted maximum-likelihood) to delineate effect sizes with 95% confidence intervals (CI). Our search included 59 studies comprising 4.034 SA/SI cases and 12.377 controls. Patients with SA/SI showed activated IO&NS pathways (SMD: 0.299; CI: 0.200; 0.397) when compared to controls. The immune profiles were more strongly associated with SA than with SI, particularly when compared to healthy controls, as evidenced by activated IO&NS (SMD: 0.796; CI: 0.503; 1.089), immune (SMD: 1.409; CI: 0.637; 1.462), inflammatory (SMD: 1.200; CI: 0.584; 1.816), and neurotoxic (SMD: 0.904; CI: 0.431; 1.378) pathways. The effects sizes of the IO&NS, immune and inflammatory profiles were significantly greater in SA than in SI. In conclusion: activated IO&NS pathways are associated with recent SA and SI, and inflammation, T helper-1 activation, nitro-oxidative stress, lowered neuroprotection, and increased neurotoxicity explain at least in part why psychiatric patients show increased suicidal behaviours, especially SA.

Therapeutic Interventions to Mitigate Mitochondrial Dysfunction and Oxidative Stress–Induced Damage in Patients with Bipolar Disorder

Bipolar disorder (BD) is characterized by mood changes, including recurrent manic, hypomanic, and depressive episodes, which may involve mixed symptoms. Despite the progress in neurobiological research, the pathophysiology of BD has not been extensively described to date. Progress in the understanding of the neurobiology driving BD could help facilitate the discovery of therapeutic targets and biomarkers for its early detection. Oxidative stress (OS), which damages biomolecules and causes mitochondrial and dopamine system dysfunctions, is a persistent finding in patients with BD. Inflammation and immune dysfunction might also play a role in BD pathophysiology. Specific nutrient supplements (nutraceuticals) may target neurobiological pathways suggested to be perturbed in BD, such as inflammation, mitochondrial dysfunction, and OS. Consequently, nutraceuticals may be used in the adjunctive treatment of BD. This paper summarizes the possible roles of OS, mitochondrial dysfunction, and immune system dysregulation in the onset of BD. It then discusses OS-mitigating strategies that may serve as therapeutic interventions for BD. It also analyzes the relationship between diet and BD as well as the use of nutritional interventions in the treatment of BD. In addition, it addresses the use of lithium therapy; novel antipsychotic agents, including clozapine, olanzapine, risperidone, cariprazine, and quetiapine; and anti-inflammatory agents to treat BD. Furthermore, it reviews the efficacy of the most used therapies for BD, such as cognitive–behavioral therapy, bright light therapy, imagery-focused cognitive therapy, and electroconvulsive therapy. A better understanding of the roles of OS, mitochondrial dysfunction, and inflammation in the pathogenesis of bipolar disorder, along with a stronger elucidation of the therapeutic functions of antioxidants, antipsychotics, anti-inflammatory agents, lithium therapy, and light therapies, may lead to improved strategies for the treatment and prevention of bipolar disorder.

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.

Antidepressant-like Effects of Combined Fluoxetine and Zinc Treatment in Mice Exposed to Chronic Restraint Stress Are Related to Modulation of Histone Deacetylase

Chronic stress is the key factor contributing to the development of depressive symptoms. Chronic restraint stress (CRS) is well validated and is one of the most commonly used models to induce depressive-like behavior in rodents. The present study aimed to evaluate whether fluoxetine (FLU 5 mg/kg) and zinc (Zn 10mg/kg) given simultaneously induce a more pronounced antidepressant-like effect in the CRS model than both those compounds given alone. Behavioral assessment was performed using the tail suspension and splash tests (TST and ST, respectively). Furthermore, the effects of CRS, FLU and Zn given alone and combined treatment with FLU + Zn on the expression of proteins involved in the apoptotic, inflammatory, and epigenetic processes were evaluated in selected brain structures (prefrontal cortex, PFC; and hippocampus, Hp) using Western blot analysis or enzyme-linked immunosorbent assays (ELISA). The results obtained indicated that three hours (per day) of immobilization for 4 weeks induced prominent depressive symptoms that manifested as increased immobility time in the TST, as well as decreased number and grooming time in the ST. Behavioral changes induced by CRS were reversed by both FLU (5 and 10 mg/kg) or Zn (10 mg/kg). Zinc supplementation (10 mg/kg) slightly increases the effectiveness of FLU (5 mg/kg) in the TST. However, it significantly increased the activity of FLU in the ST compared to the effect induced by FLU and Zn alone. Biochemical studies revealed that neither CRS nor FLU and Zn given alone or in combined treatment alter the expression of proteins involved in apoptotic or inflammatory processes. CRS induced major alterations in histone deacetylase (HDAC) levels by increasing the level of HADC1 and decreasing the level of HADC4 in the PFC and Hp, decreasing the level of HADC6 in the PFC but increasing it in Hp. Interestingly, FLU + Zn treatment reversed CRS-induced changes in HDAC levels in the Hp, indicating that HDAC modulation is linked to FLU + Zn treatment and this effect is structure-specific.

Suicide attempts are associated with activated immune-inflammatory, nitro-oxidative, and neurotoxic pathways: A systematic review and meta-analysis

BACKGROUND

Suicide attempts (SA) frequently occur in patients with mood disorders and schizophrenia, which are both accompanied by activated immune-inflammatory and nitro-oxidative (IO&NS) pathways.

METHODS

We searched PubMed, Google Scholar, and Web of Science, for articles published from inception until February 1, 2021. We included studies that compared blood biomarkers in psychiatric patients with (SA+) and without SA (SA-) and heathy controls and we combined different IO&NS biomarkers into immune, inflammatory, and neurotoxic profiles and used meta-analysis (random-effect model with restricted maximum-likelihood) to delineate effect sizes with 95% confidence interval (CI).

FINDINGS

Our search included 51 studies comprising 4.945 SA+ patients and 24.148 controls. We stratified the control group into healthy controls and SA- patients. SA+ patients showed significantly (p<0.001) increased immune activation (SMD: 1.044; CI: 0.599, 1.489), inflammation (SMD: 1.109; CI: 0.505, 1.714), neurotoxicity (SMD: 0.879; CI: 0.465, 1.293), and lowered neuroprotection (SMD: 0.648; CI: 0.354, 0.941) as compared with healthy controls. When compared with SA- patients, those with SA+ showed significant (p<0.001) immune activation (SMD: 0.290; CI: 0.183, 0.397), inflammation (SMD: 0.311; CI: 0.191, 0.432), and neurotoxicity (SMD: 0.315; CI: 0.198, 0.432), and lowered neuroprotection (SMD: 0.341; CI: 0.167, 0.515). Patients with current, but not lifetime, SA showed significant (p<0.001) levels of inflammation and neurotoxicity as compared with controls.

CONCLUSIONS

Patients with immune activation are at a higher risk of SA which may be explained by increased neurotoxicity due to inflammation and nitro-oxidative stress. This meta-analysis discovered new biomarkers of SA and therapeutic targets to treat individuals with SA.

The Neurometabolic Basis of Mood Instability: The Parvalbumin Interneuron Link-A Systematic Review and Meta-Analysis

The neurobiological bases of mood instability are poorly understood. Neuronal network alterations and neurometabolic abnormalities have been implicated in the pathophysiology of mood and anxiety conditions associated with mood instability and hence are candidate mechanisms underlying its neurobiology. Fast-spiking parvalbumin GABAergic interneurons modulate the activity of principal excitatory neurons through their inhibitory action determining precise neuronal excitation balance. These interneurons are directly involved in generating neuronal networks activities responsible for sustaining higher cerebral functions and are especially vulnerable to metabolic stress associated with deficiency of energy substrates or mitochondrial dysfunction. Parvalbumin interneurons are therefore candidate key players involved in mechanisms underlying the pathogenesis of brain disorders associated with both neuronal networks' dysfunction and brain metabolism dysregulation. To provide empirical support to this hypothesis, we hereby report meta-analytical evidence of parvalbumin interneurons loss or dysfunction in the brain of patients with Bipolar Affective Disorder (BPAD), a condition primarily characterized by mood instability for which the pathophysiological role of mitochondrial dysfunction has recently emerged as critically important. We then present a comprehensive review of evidence from the literature illustrating the bidirectional relationship between deficiency in mitochondrial-dependent energy production and parvalbumin interneuron abnormalities. We propose a mechanistic explanation of how alterations in neuronal excitability, resulting from parvalbumin interneurons loss or dysfunction, might manifest clinically as mood instability, a poorly understood clinical phenotype typical of the most severe forms of affective disorders. The evidence we report provides insights on the broader therapeutic potential of pharmacologically targeting parvalbumin interneurons in psychiatric and neurological conditions characterized by both neurometabolic and neuroexcitability abnormalities.

Plasma inflammatory cytokines and treatment-resistant depression with comorbid pain: improvement by ketamine

Background

Treatment-resistant depression (TRD) and pain frequently coexist clinically. Ketamine has analgesic and antidepressant effects, but few studies have evaluated individual differences in antidepressant outcomes to repeated ketamine in TRD patients with comorbid pain. Our aims were to determine the difference in ketamine’s antidepressant effects in TRD patients with or without pain and then to examine whether inflammatory cytokines might contribute to ketamine’s effect.

Methods

Sixty-six patients with TRD received six infusions of ketamine. Plasma levels of 19 inflammatory cytokines were assessed at baseline and post-infusion (day 13 and day 26) using the Luminex assay. Plasma inflammatory cytokines of sixty healthy controls (HCs) were also examined.

Results

TRD patients with pain had a higher antidepressant response rate (χ² = 4.062, P = 0.044) and remission rate (χ² = 4.062, P = 0.044) than patients without pain. Before ketamine treatment, GM-CSF and IL-6 levels were higher in the pain group than in the non-pain and HC groups. In the pain group, levels of TNF-α and IL-6 at day 13 and GM-CSF, fractalkine, IFN-γ, IL-10, MIP-3α, IL-12P70, IL-17α, IL-1β, IL-2, IL-4, IL-23, IL-5, IL-6, IL-7, MIP-1β, and TNF-α at day 26 were lower than those at baseline; in the non-pain group, TNF-α levels at day 13 and day 26 were lower than those at baseline. In the pain group, the changes of IL-6 were associated with improvement in pain intensity (β = 0.333, P = 0.001) and depressive symptoms (β = 0.478, P = 0.005) at day 13. Path analysis showed the direct (β = 2.995, P = 0.028) and indirect (β = 0.867, P = 0.042) effects of changes of IL-6 on improvement in depressive symptoms both were statistically significant.

Conclusion

This study suggested that an elevated inflammatory response plays a critical role in individual differences in TRD patients with or without pain. Ketamine showed great antidepressant and analgesic effects in TRD patients with pain, which may be related to its effects on modulating inflammation.

Trial registration

ChiCTR, ChiCTR-OOC-17012239. Registered on 26 May 2017

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02245-5.

Andrographolide blocks 50-kHz ultrasonic vocalizations, hyperlocomotion and oxidative stress in an animal model of mania

In rats, lisdexamfetamine (LDX) induces manic-like behaviors such as hyperlocomotion and increases in appetitive 50-kHz ultrasonic vocalizations (USV), which are prevented by antimanic drugs, such as lithium. Inhibition of glycogen synthase kinase 3 beta (GSK3β) and antioxidant activity have been associated with antimanic effects. Thus, the aim of the present study was to evaluate the possible antimanic-like effects of andrographolide (ANDRO), a GSK3β inhibitor, on LDX-induced hyperlocomotion and 50-kHz USV increases. In addition, the effect of ANDRO was studied on LDX-induced oxidative stress. Lithium was used as positive control. Adult Wistar rats were treated with vehicle, lithium (100 mg/kg i.p., daily) or ANDRO (2 mg/kg i.p., 3 times a week) for 21 days. On the test day, either 10 mg/kg LDX or saline was administered i.p. and USV and locomotor activity were recorded. LDX administration increased the number of 50-kHz calls, as well as locomotor activity. Repeated treatment with lithium or ANDRO prevented these effects of LDX on 50-kHz USV and locomotor activity. LDX increased lipid peroxidation (LPO) levels in rat striatum and both lithium and ANDRO prevented this effect. LPO levels in rat striatum were positively correlated with increases in 50-kHz USV emission as well as hyperlocomotion. In conclusion, the present results indicate that ANDRO has antimanic-like effects, which may be mediated by its antioxidant properties.

Dendritic Cells: Neglected Modulators of Peripheral Immune Responses and Neuroinflammation in Mood Disorders?

Affective disorders (AD) including major depressive disorder (MDD) and bipolar disorder (BD) are common mood disorders associated with increased disability and poor health outcomes. Altered immune responses characterized by increased serum levels of pro-inflammatory cytokines and neuroinflammation are common findings in patients with AD and in corresponding animal models. Dendritic cells (DCs) represent a heterogeneous population of myeloid cells that orchestrate innate and adaptive immune responses and self-tolerance. Upon sensing exogenous and endogenous danger signals, mature DCs secrete proinflammatory factors, acquire migratory and antigen presenting capacities and thus contribute to neuroinflammation in trauma, autoimmunity, and neurodegenerative diseases. However, little is known about the involvement of DCs in the pathogenesis of AD. In this review, we summarize the current knowledge on DCs in peripheral immune responses and neuroinflammation in MDD and BD. In addition, we consider the impact of DCs on neuroinflammation and behavior in animal models of AD. Finally, we will discuss therapeutic perspectives targeting DCs and their effector molecules in mood disorders.

Hippocampal proteomic analysis reveals activation of necroptosis and ferroptosis in a mouse model of chronic unpredictable mild stress-induced depression

Neuronal loss has been identified in depression, but its mechanisms are not fully understood. Proteomic analyses provide a novel insight to explore the potential mechanisms of such pathological alterations. In this study, mice were treated with chronic unpredictable mild stress (CUMS) for 2 months to establish depression models. The hippocampus was analyzed for proteomic patterns by mass spectrometry followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Behavioral tests showed that mice receiving CUMS showed depression-like symptoms such as anhedonia in the sucrose preference test (SPT) and behavioral despair in the forced swimming test (FST). CUMS induced anxiety-like behaviors in the open field test (OFT), but did not impair spatial learning and memory ability in the Morris water maze (MWM) test. Out of 4046 quantified proteins, 47 differentially expressed proteins were obtained between the CUMS and control groups. These proteins were functionally enriched in a series of biological processes. Among the notably enriched pathways, necroptosis and ferroptosis were significantly activated. Western blot and biochemical assay analyses identified changes in receptor-interacting protein kinase 3 (RIP3), phosphorylated mixed lineage kinase domain-like protein (p-MLKL), ferritin light chain 1 (Ftl1) and lipid peroxidation that were related to necroptosis and ferroptosis. Further, we found reduced levels of alpha-crystallin B (Cryab) and brain-derived neurotrophic factor (BDNF), which were also associated with neuronal survival. Our study highlighted that necroptosis and ferroptosis were involved in depression and partially account for neuronal loss, thereby providing potentially novel targets for the treatment of depression.

Behavior and oxidative stress parameters in rats subjected to the animal's models induced by chronic mild stress and 6-hydroxydopamine

Major depressive disorder (MDD) is one of the most prevalent forms of mental illness also affecting older adults. Recent evidence suggests a relationship between MDD and neurodegenerative diseases, including Parkinson's disease (PD). Individuals with PD have a predisposition to developing MDD, and both neurobiological conditions are associated with oxidative stress. Thus, we conducted this study to investigate depressive-like behavior and oxidative stress parameters using both animal models of PD and stress. Adult Wistar rats were subjected to chronic mild stress (CMS) protocol by 40 days and then it was used 6-hydroxydopamine (6-OHDA) as a model of PD, into the striatum. The experimental groups were: Control + Sham, Stress + Sham, Control+6-OHDA, and Stress+6-OHDA. Depressive like-behavior was evaluated by the forced swimming test (FST) and spontaneous locomotor activity by open-field test. Oxidative stress parameters were measured in the striatum, hippocampus, and prefrontal cortex (PFC). The results showed effects to increase immobility and decrease climbing times in the FST in Stress + Sham, Control+6-OHDA, and Stress+6-OHDA groups. The number of crossings and rearings were decreased in the Stress+6-OHDA group. The lipid peroxidation was increased in the PFC of Stress + Sham, and the hippocampus and striatum of Stress + Sham and Control+6-OHDA groups. Carbonyl protein levels increased in the PFC of Stress + Sham and striatum in Control+6-OHDA. Nitrite/Nitrate concentration was elevated in the PFC of Stress + Sham, in the hippocampus of Control+6-OHDA, the striatum of Stress + Sham, and Control+6-OHDA groups. Myeloperoxidase (MPO) activity was increased in the PFC and hippocampus of Stress + Sham and Control+6-OHDA groups. The activity of catalase decreased in the PFC of the Stress + Sham group. The activity of the superoxide dismutase (SOD) was decreased in the PFC of the Stress + Sham group, in the hippocampus of Stress + Sham and Control+6-OHDA groups, and the striatum of Control+6-OHDA group. These findings suggest that both stress and 6-OHDA induce depressive-like behavior and oxidative stress in the brain. The joining models have little evidence of the effects. Thus these findings suggest that other pathways are involved in the common point of the pathophysiology of PD and MDD.

Towards a new model and classification of mood disorders based on risk resilience, neuro-affective toxicity, staging, and phenome features using the nomothetic network psychiatry approach

Current diagnoses of mood disorders are not cross validated. The aim of the current paper is to explain how machine learning techniques can be used to a) construct a model which ensembles risk/resilience (R/R), adverse outcome pathways (AOPs), staging, and the phenome of mood disorders, and b) disclose new classes based on these feature sets. This study was conducted using data of 67 healthy controls and 105 mood disordered patients. The R/R ratio, assessed as a combination of the paraoxonase 1 (PON1) gene, PON1 enzymatic activity, and early life time trauma (ELT), predicted the high-density lipoprotein cholesterol - paraoxonase 1 complex (HDL-PON1), reactive oxygen and nitrogen species (RONS), nitro-oxidative stress toxicity (NOSTOX), staging (number of depression and hypomanic episodes and suicidal attempts), and phenome (the Hamilton Depression and Anxiety scores and the Clinical Global Impression; current suicidal ideation; quality of life and disability measurements) scores. Partial Least Squares pathway analysis showed that 44.2% of the variance in the phenome was explained by ELT, RONS/NOSTOX, and staging scores. Cluster analysis conducted on all those feature sets discovered two distinct patient clusters, namely 69.5% of the patients were allocated to a class with high R/R, RONS/NOSTOX, staging, and phenome scores, and 30.5% to a class with increased staging and phenome scores. This classification cut across the bipolar (BP1/BP2) and major depression disorder classification and was more distinctive than the latter classifications. We constructed a nomothetic network model which reunited all features of mood disorders into a mechanistically transdiagnostic model.

Using classification and regression tree modeling to investigate appetite hormones and proinflammatory cytokines as biomarkers to differentiate bipolar I depression from major depressive disorder

BACKGROUND

Altered immunity and metabolic profiles have been compared between bipolar depression (BD) and major depressive disorder (MDD). This study aimed at developing a composite predictor of appetite hormones and proinflammatory cytokines to differentiate BD from MDD.

METHODS

This cross-sectional study enrolled patients with BD and those with MDD aged 20 to 59 years and displaying depressive episodes. Clinical characteristics (age, sex, body mass index, and depression severity), cytokines (C-reactive protein, interleukin [IL]-2, IL-6, tumor necrosis factor [TNF]-α, P-selectin, and monocyte chemoattractant protein), and appetite hormones (leptin, adiponectin, ghrelin, and insulin) were assessed as potential predictors using a classification and regression tree (CRT) model for differentiating BD from MDD.

RESULTS

The predicted probability of a composite predictor of ghrelin and TNF-α was significantly greater (for BD: area under curve = 0.877; for MDD: area under curve = 0.914) than that of any one marker (all P > .05) to distinguish BD from MDD. The most powerful predictors for diagnosing BD were high ghrelin and TNF-α levels, whereas those for MDD were low ghrelin and TNF-α levels.

CONCLUSION

A composite predictor of ghrelin and TNF-α driven by CRT could assist in the differential diagnosis of BD from MDD with high specificity. Further clinical studies are warranted to validate our results and to explore underlying mechanisms.

The role of gene polymorphisms, and analysis of peripheral and central levels of interleukins in suicidal behavior: A systematic review

In terms of the physiological characteristics of suicidal behavior (SB) disorder, an increase inflammation response has been reported in these individuals. Therefore, the pro-inflammatory and anti-inflammatory activities of interleukins are adequate markers to research in order to understand the pathogenesis of SB. For that reason, the aim of this systematic review was to evaluate the role of interleukins in individuals with suicidal behavior disorder. A systematic search was performed in PubMed, Scopus and EBSCO databases up to July 2019. We used the words "interleukin" AND "suicide", "interleukin" AND "suicidal", and "IL-". Articles where interleukins concentrations were measured in individuals with SB and/or genetic studies addressing interleukins genes variants as possible markers to SB were included. A total of 54 articles were included. Articles that measured interleukin levels comprised 1111 cases and 1588 controls; whereas the genetic studies comprised 3082 cases and 5148 controls. These studies evaluated the concentrations of IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, sIL-2R in serum, plasma. The pro-inflammatory interleukins concentrations were higher in cases than in controls; however, we observed heterogeneity in the measurements and sample sources. Whereas, 9 polymorphisms of IL-1α, IL-1β, IL-6, IL-1β-8 genes were analyzed in association with suicide behavior disorder, though no conclusive outcomes were attained. Our results suggest that individuals with suicide risk undergo continuous stress that could trigger the release and circulation of pro-inflammatory interleukins and therefore their concentration in plasma. However, more studies are necessary in order to reach conclusively outcomes.

Peripheral Markers of Depression

Major Depressive Disorder (MDD) is a leading cause of disability worldwide, creating a high medical and socioeconomic burden. There is a growing interest in the biological underpinnings of depression, which are reflected by altered levels of biological markers. Among others, enhanced inflammation has been reported in MDD, as reflected by increased concentrations of inflammatory markers-C-reactive protein, interleukin-6, tumor necrosis factor-α and soluble interleukin-2 receptor. Oxidative and nitrosative stress also plays a role in the pathophysiology of MDD. Notably, increased levels of lipid peroxidation markers are characteristic of MDD. Dysregulation of the stress axis, along with increased cortisol levels, have also been reported in MDD. Alterations in growth factors, with a significant decrease in brain-derived neurotrophic factor and an increase in fibroblast growth factor-2 and insulin-like growth factor-1 concentrations have also been found in MDD. Finally, kynurenine metabolites, increased glutamate and decreased total cholesterol also hold promise as reliable biomarkers for MDD. Research in the field of MDD biomarkers is hindered by insufficient understanding of MDD etiopathogenesis, substantial heterogeneity of the disorder, common co-morbidities and low specificity of biomarkers. The construction of biomarker panels and their evaluation with use of new technologies may have the potential to overcome the above mentioned obstacles.

Construction of a nitro-oxidative stress-driven, mechanistic model of mood disorders: A nomothetic network approach

Major depression is accompanied by increased IgM-mediated autoimmune responses to oxidative specific epitopes (OSEs) and nitric oxide (NO)-adducts. These responses were not examined in bipolar disorder type 1 (BP1) and BP2. IgM responses to malondialdehyde (MDA), phosphatidinylinositol, oleic acid, azelaic acid, and NO-adducts were determined in 35 healthy controls, and 47 major depressed (MDD), 29 BP1, and 25 BP2 patients. We also measured serum peroxides, IgG to oxidized LDL (oxLDL), and IgM/IgA directed to lipopolysaccharides (LPS). IgM responses to OSEs and NO-adducts (OSENO) were significantly higher in MDD and BP1 as compared with controls, and IgM to OSEs higher in MDD than in BP2. Partial Least Squares (PLS) analysis showed that 57.7% of the variance in the clinical phenome of mood disorders was explained by number of episodes, a latent vector extracted from IgM to OSENO, IgG to oxLDL, and peroxides. There were significant specific indirect effects of IgA/IgM to LPS on the clinical phenome, which were mediated by peroxides, IgM OSENO, and IgG oxLDL. Using PLS we have constructed a data-driven nomothetic network which ensembled causome (increased plasma LPS load), adverse outcome pathways (namely neuro-affective toxicity), and clinical phenome features of mood disorders in a data-driven model. Based on those feature sets, cluster analysis discovered a new diagnostic class characterized by increased plasma LPS load, peroxides, autoimmune responses to OSENO, and increased phenome scores. Using the new nomothetic network approach, we constructed a mechanistically transdiagnostic diagnostic class indicating neuro-affective toxicity in 74.3% of the mood disorder patients.

Molecular correlates of mitochondrial dysfunctions in major depression: Evidence from clinical and rodent studies

Major depressive disorder (MDD) is one of the most prevalent stress-related mental disorders worldwide. Several biological mechanisms underlying the pathophysiology of MDD have been proposed, including endocrine disturbances, neurotransmitter deficits, impaired neuronal plasticity, and more recently, mitochondrial dysfunctions. In this review, we provide an overview of relevant molecular correlates of mitochondrial dysfunction in MDD, based on findings from clinical studies and stress-induced rodent models. We also compare differences and similarities between the phenotypes of MDD patients and animal models. Our analysis of the literature reveals that both MDD and stress are associated, in humans and animals, with changes in mitochondrial biogenesis, redox imbalance, increased oxidative damages of cellular macromolecules, and apoptosis. Yet, a considerable amount of conflicting data exist and therefore, the translation of findings from clinical and preclinical research to novel therapies for MDD remains complex. Further studies are needed to advance our understanding of the molecular networks and biological mechanisms involving mitochondria in the pathophysiology of MDD.

Impairments in Peripheral Blood T Effector and T Regulatory Lymphocytes in Bipolar Disorder Are Associated with Staging of Illness and Anti-cytomegalovirus IgG Levels

There is now evidence that, based on cytokine profiles, bipolar disorder (BD) is accompanied by simultaneous activation of the immune-inflammatory response system (IRS) and the compensatory immune-regulatory system (CIRS), and that both components may be associated with the staging of illness. Nevertheless, no BD studies have evaluated the IRS/CIRS ratio using CD (cluster of differentiation) molecules expressed by peripheral blood activated T effector (Teff) and T regulatory (Treg) subpopulations. This study examined Teff/Treg subsets both before and after ex vivo anti-CD3/CD28 stimulation using flow cytometric immunophenotyping in 25 symptomatic remitted BD patients and 21 healthy controls and assessed human cytomegalovirus (HCMV)-specific IgG antibodies. BD is associated with a significantly lowered frequency of unstimulated CD3 + CD8 + CD71+ and CD4 + CD25 + FOXP3 and increased CD4 + CD25 + FOXP3 + CD152+ frequencies and with lowered stimulated frequencies of CD3 + CD8 + CD71+, CD4 + CD25 + FOXP3 + CD152+, and CD4 + CD25 + FOXP3 + GARP cells and, consequently, by an increased stimulated Teff/Treg ratio. Moreover, the number of manic, but not hypomanic or depressive episodes, is significantly and negatively associated with the stimulated proportions of CD3 + CD4 + CD154+, and CD69+ and CD71+ expression on CD4+ and CD8+ cells, while duration of illness (≥ 10 years) is accompanied by a depleted frequency of stimulated CD152+ Treg, and CD154+ and CD71+ CD4+ T cells. BD and anti-human cytomegalovirus (HCMV) IgG levels significantly interact to decrease the expression of CD4 + CD25 + FOXP+GARP T phenotypes. In conclusion, in BD patients, immune injuries, staging, and HCMV seropositivity interact and cause CIRS dysfunctions and exaggerated IRS responses, which play a key role in parainflammation and neuroaffective toxicity. HCMV seropositivity contributes to an immune-risk phenotype in BD.

Malondialdehyde and bipolar disorder: A short comprehensive review of available literature

BACKGROUND

The pathogenetic mechanisms of Bipolar Disorder (BD) have not been totally clarified. Oxidative stress seems to be involved in the etiology of BD, and malondialdehyde (MDA) represents a candidate biomarker for monitoring this aspect in different medical conditions including mood disorders. This article has the objective to critically summarize the available data about the association between MDA and BD.

METHODS

A research in Pubmed, PsycINFO and Isi Web of Knowledge was fulfilled to identify studies in which MDA levels were measured in BD patients for the purpose of securing a comprehensive review concerning the issue.

RESULTS

We detected 20 articles that satisfied the inclusion criteria: most of them observed higher MDA levels (or Thiobarbituric acid-reactive substances-TBARS) in BD patients compared to healthy controls (HC), although there are some contrasting results, depending in particular on the phase of illness or the inclusion criteria or the methodological differences.

LIMITATIONS

We included studies, exclusively in English, that used different laboratory methods to measure MDA.

CONCLUSIONS

The analysed articles suggest that MDA or TBARS are increased in BD patients with respect to HC, thus supporting the hypothesis that MDA may be a promising and potential biomarker to monitor the course of BD, although further studies are needed to confirm this hypothesis.

Alterations of multiple peripheral inflammatory cytokine levels after repeated ketamine infusions in major depressive disorder

Increasing evidence has demonstrated that inflammatory cytokines play an important role in major depressive disorder (MDD) and are associated with treatment outcomes. Few studies have explored the trajectories of multiple inflammatory cytokines after repeated ketamine infusions in MDD. In this study, we conducted a secondary analysis to investigate the impact of ketamine on the modulation of the inflammatory pathway in depression and whether this pathway contributes to the antidepressant properties of ketamine. A total of 60 patients with depression received six ketamine infusions (0.5 mg/kg) during a 12-day period. The Montgomery-Asberg Scale (MADRS) was administered, and blood samples were collected at baseline and 24 h and 14 days after the sixth infusion (days 0, 13, and 26). Plasma levels of the 19 cytokines were measured using the Luminex assay. At baseline, inflammatory cytokines were associated with the severity of depression. The concentrations of pro- and anti-inflammatory factors, including granulocyte macrophage colony-stimulating factor (GM-CSF), fractalkine, interferon gamma (IFN-γ), interleukin (IL)-10, IL-12p70, IL-17A, IL-1β, IL-2, IL-4, IL-23, IL-5, IL-6, IL-7, and tumor necrosis factor alpha (TNF-α), were downregulated after repeated ketamine administration (all p < 0.05). In addition, alterations in the levels of IL-17A (r = -0.259, p = 0.046) and IL-6 (r = -0.262, p = 0.043) were correlated with symptom improvement. A lower level of interferon-inducible T cell alpha chemoattractant (ITAC) at baseline was predictive of ketamine treatment response on day 13 according to a stepwise linear regression analysis (β = -0.296, p = 0.040). Our results suggest that the inflammatory pathway may be involved in the antidepressant effects of ketamine, which may be conducive to future treatment strategy optimization.

Inflammatory markers in depression: A meta-analysis of mean differences and variability in 5,166 patients and 5,083 controls

IMPORTANCE

The magnitude and variability of cytokine alterations in depression are not clear.

OBJECTIVE

To perform an up to date meta-analysis of mean differences of immune markers in depression, and to quantify and test for evidence of heterogeneity in immune markers in depression by conducting a meta-analysis of variability to ascertain whether only a sub-group of patients with depression show evidence of inflammation.

DATA SOURCES

Studies that reported immune marker levels in peripheral blood in patients with depression and matched healthy controls in the MEDLINE database from inception to August 29th 2018 were examined.

STUDY SELECTION

Case-control studies that reported immune marker levels in peripheral blood in patients with depression and healthy controls were selected.

DATA EXTRACTION AND SYNTHESIS

Means and variances (SDs) were extracted for each measure to calculate effect sizes, which were combined using multivariate meta-analysis.

MAIN OUTCOMES AND MEASURES

Hedges g was used to quantify mean differences. Relative variability of immune marker measurements in patients compared with control groups as indexed by the coefficient of variation ratio (CVR).

RESULTS

A total of 107 studies that reported measurements from 5,166 patients with depression and 5,083 controls were included in the analyses. Levels of CRP (g = 0.71; 95%CI: 0.50-0.92; p < 0.0001); IL-3 (g = 0.60; 95%CI: 0.31-0.89; p < 0.0001); IL-6 (g = 0.61; 95%CI: 0.39-0.82; p < 0.0001); IL-12 (g = 1.18; 95%CI: 0.74-1.62; p < 0.0001); IL-18 (g = 1.97; 95%CI: 1.00-2.95; p < 0.0001); sIL-2R (g = 0.71; 95%CI: 0.44-0.98; p < 0.0001); and TNFα (g = 0.54; 95%CI: 0.32-0.76; p < 0.0001) were significantly higher in patients with depression. These findings were robust to a range of potential confounds and moderators. Mean-scaled variability, measured as CVR, was significantly lower in patients with depression for CRP (CVR = 0.85; 95%CI: 0.75-0.98; p = 0.02); IL-12 (CVR = 0.61; 95%CI: 0.46-0.80; p < 0.01); and sIL-2R (CVR = 0.85; 95%CI: 0.73-0.99; p = 0.04), while it was unchanged for IL-3, IL-6, IL-18, and TNF α.

CONCLUSIONS AND RELEVANCE

Depression is confirmed as a pro-inflammatory state. Some of the inflammatory markers elevated in depression, including CRP and IL-12, show reduced variability in patients with depression, therefore supporting greater homogeneity in terms of an inflammatory phenotype in depression. Some inflammatory marker elevations in depression do not appear due to an inflamed sub-group, but rather to a right shift of the immune marker distribution.

Targeting Inflammatory-Mitochondrial Response in Major Depression: Current Evidence and Further Challenges

The prevalence of psychiatric disorders has increased in recent years. Among existing mental disorders, major depressive disorder (MDD) has emerged as one of the leading causes of disability worldwide, affecting individuals throughout their lives. Currently, MDD affects 15% of adults in the Americas. Over the past 50 years, pharmacotherapy, psychotherapy, and brain stimulation have been used to treat MDD. The most common approach is still pharmacotherapy; however, studies show that about 40% of patients are refractory to existing treatments. Although the monoamine hypothesis has been widely accepted as a molecular mechanism to explain the etiology of depression, its relationship with other biochemical phenomena remains only partially understood. This is the case of the link between MDD and inflammation, mitochondrial dysfunction, and oxidative stress. Studies have found that depressive patients usually exhibit altered inflammatory markers, mitochondrial membrane depolarization, oxidized mitochondrial DNA, and thus high levels of both central and peripheral reactive oxygen species (ROS). The effect of antidepressants on these events remains unclear. Nevertheless, the effects of ROS on the brain are well known, including lipid peroxidation of neuronal membranes, accumulation of peroxidation products in neurons, protein and DNA damage, reduced antioxidant defenses, apoptosis induction, and neuroinflammation. Antioxidants such as ascorbic acid, tocopherols, and coenzyme Q have shown promise in some depressive patients, but without consensus on their efficacy. Hence, this paper provides a review of MDD and its association with inflammation, mitochondrial dysfunction, and oxidative stress and is aimed at thoroughly discussing the putative links between these events, which may contribute to the design and development of new therapeutic approaches for patients.

Differential biomarker signatures in unipolar and bipolar depression: A machine learning approach

OBJECTIVE

This study used machine learning techniques combined with peripheral biomarker measurements to build signatures to help differentiating (1) patients with bipolar depression from patients with unipolar depression, and (2) patients with bipolar depression or unipolar depression from healthy controls.

METHODS

We assessed serum levels of interleukin-2, interleukin-4, interleukin-6, interleukin-10, tumor necrosis factor-α, interferon-γ, interleukin-17A, brain-derived neurotrophic factor, lipid peroxidation and oxidative protein damage in 54 outpatients with bipolar depression, 54 outpatients with unipolar depression and 54 healthy controls, matched by sex and age. Depressive symptoms were assessed using the Hamilton Depression Rating Scale. Variable selection was performed with recursive feature elimination with a linear support vector machine kernel, and the leave-one-out cross-validation method was used to test and validate our model.

RESULTS

Bipolar vs unipolar depression classification achieved an area under the receiver operating characteristics (ROC) curve (AUC) of 0.69, with 0.62 sensitivity and 0.66 specificity using three selected biomarkers (interleukin-4, thiobarbituric acid reactive substances and interleukin-10). For the comparison of bipolar depression vs healthy controls, the model retained five variables (interleukin-6, interleukin-4, thiobarbituric acid reactive substances, carbonyl and interleukin-17A), with an AUC of 0.70, 0.62 sensitivity and 0.7 specificity. Finally, unipolar depression vs healthy controls comparison retained seven variables (interleukin-6, Carbonyl, brain-derived neurotrophic factor, interleukin-10, interleukin-17A, interleukin-4 and tumor necrosis factor-α), with an AUC of 0.74, a sensitivity of 0.68 and 0.70 specificity.

CONCLUSION

Our findings show the potential of machine learning models to aid in clinical practice, leading to more objective assessment. Future studies will examine the possibility of combining peripheral blood biomarker data with other biological data to develop more accurate signatures.