Targeting classical IL-6 signalling or IL-6 trans-signalling in depression?

Interleukin 6 as a pathogenic factor mediating clinical manifestations and a therapeutic target for rheumatic diseases and depressive disorders

The review summarizes current idea on the key role of interleukin 6 (IL-6) in the pathogenesis of rheumatic diseases (RDs) and depressive disorders. It considers in detail the mechanisms by which IL6 induces the clinical and laboratory manifestations of RDs and depression; the influence of precipitating and predisposing stress factors, including childhood mental traumas, which increase the risk of RDs and depression, on IL-6 production. Particular attention is paid to the consideration of prospects for using IL-6 inhibitors in the therapy of depression.

Interaction of the immune-inflammatory and the kynurenine pathways in rats resistant to antidepressant treatment in model of depression

The kynurenine pathway (KP), a major route of tryptophan catabolism, may be associated with the pathophysiology of depressive disorders. KP is responsible for ca. 99% of brain tryptophan metabolism via its degradation to kynurenine (KYN) catalyzed by indoleamine 2,3-dioxygenase (IDO). Some cytokines, such as interferon-γ (IFN-γ) and interleukin (IL)-6 are potent inducers of IDO. KYN is further converted by kynurenine aminotransferase (KAT) to the more neuroprotective kynurenic acid or by kynurenine 3-monooxygenase (KMO) to neurotoxic 3-hydroxykynurenine. The aim of the present study was to delineate whether the administration of imipramine (IMI) to rats subjected to chronic mild stress (CMS) may reverse behavioral changes induced by CMS in association with changes in immune-inflammatory markers and KP. We confirmed that the CMS procedure modeled one of the main symptoms of depression, i.e. anhedonia, and administration of IMI for 5 weeks resulted in a significant reduction in anhedonia in a majority of animals (CMS IMI-R animals), whereas 20% of animals did not respond to IMI treatment (CMS IMI-NR animals). We established that CMS procedure increased IFN-γ and IDO mRNA and decreased KAT II mRNA expression in the rat cortex. In the cortex and hippocampus, IMI treatment and non-responsiveness to IMI (in CMS IMI-NR animals) were associated with increased IL-6 mRNA expression. In the spleen, CMS increased production of IFN-γ and IL-6 proteins, while these cytokines were decreased by IMI in CMS IMI-R animals. Chronic IMI administration to CMS rats decreased IDO and KMO mRNA and protein expression and increased KAT II/KMO mRNA and protein ratio in IMI responders (CMS IMI-R) in comparison to CMS rats. In CMS IMI-NR rats, a significant increase in IDO mRNA expression and protein level in comparison with IMI responders was observed. Our findings indicate that resistance to therapeutic action of IMI could be explained by a deficiency of the inhibitory properties of IMI on IDO, KMO and KYN synthesis in the cortex. We conclude that the antidepressant activity of IMI may, at least in part, be explained by modulatory activities on the KAT II/KMO ratio in brain areas.

Immune-inflammatory, oxidative stress and biochemical biomarkers predict short-term acute ischemic stroke death

The aim of the study was to define new immune-inflammatory, oxidative stress and biochemical biomarkers, which predict mortality within a period of 3 months after acute ischemic stroke (AIS). We recruited 176 healthy volunteers and 145 AIS patients, categorized as AIS survivors and non-survivors, and measured interleukin (IL)-6, high sensitivity C-reactive protein (hsCRP), ferritin, iron, total serum protein (TSP), erythrocyte sedimentation rate (ESR), white blood cells (WBC), 25 hydroxyvitamin D [25(OH)D], lipid hydroperoxides (CL-LOOH), insulin, glucose and high-density lipoprotein (HDL)-cholesterol. In patients, these biomarkers were measured within 24 h after AIS onset. We also computed two composite scores reflecting inflammatory indices, namely INFLAM index1 (sum of z scores of hsCRP+IL-6 + ferritin+ESR + WBC) and INFLAM index2 (z INFLAM index1 - z 25(OH)D - z iron + z TSP). Three months after AIS, non-survivors (n = 54) showed higher baseline levels of IL-6, hsCRP, ferritin and glucose and lower levels of HDL-cholesterol and 25(OH)D than survivors (n = 91). Non-survivors showed higher baseline ESR and lowered TSP than controls, while survivors occupied an intermediate position. Death after AIS was best predicted by increased IL-6, glucose, ferritin and CL-LOOH and lowered 25(OH)D levels. The area under the receiver operating curves computed on the INFLAM index1 and 2 scores were 0.851 and 0.870, respectively. In conclusion, activation of peripheral immune-inflammatory, oxidative and biochemical pathways is critically associated with mortality after AIS. Our results may contribute to identify new biomarker sets, which may predict post-stroke death, as well as suggest that IL-6 trans-signaling coupled with redox imbalances may be possible new targets in the prevention of short-term outcome AIS death.

Chronic pain and central sensitization in immuno-inflammatory rheumatic diseases: pathogenesis, clinical manifestations, the possibility of using targeted disease modifying antirheumatic drugs

Chronic pain is one of the main manifestations of immuno-inflammatory rheumatic diseases (IIRD), such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA), which determines the severity of suffering, reduced quality of life and disability of patients. Unfortunately, the use of synthetic and biological disease modifying antirheumatic drugs, as well as non-steroidal anti-inflammatory drugs does not always provide sufficient control of pain in IIRD, even when it is possible to achieve a significant reduction in inflammatory activity. The reason for this is the complex mechanism of chronic pain. It includes not onlystimulation of pain receptors caused by damage of the elements of the musculoskeletal system, but also a change in the perception of pain associated with the phenomenon of central sensitization (CS). CS is characterized by a significant and persistent increase in the sensitivity of nociceptive neurons to pain and nonpain stimuli. One of the main theories of the CS development consider this phenomenon as an inflammatory reaction of the neuronenvironmentthe activation of astrocytes and microglial cells, local hyperproduction of cytokines, inflammatory mediators and neurotrophic factors. Factors contributing to the development of CS in IIRD are obesity, depression and anxiety, damage of the somatosensory system, insufficient relief of pain in the onset of the disease. Clinical manifestations of CS in IIRD is hyperalgesia, allodinia, «expanded pain» and secondary fibromyalgia. An important role in the development of chronic pain and CS plays the intracellular inflammatory pathway JAK-STAT. Therefore, JAK inhibitors, such as tofacitinib, used in RA and PsA, can also be considered as an effective means of controlling chronic pain in these diseases.

A New Schizophrenia Model: Immune Activation is Associated with the Induction of Different Neurotoxic Products which Together Determine Memory Impairments and Schizophrenia Symptom Dimensions

Methods:

Serum levels of macrophage inflammatory protein-1 (MIP-1), soluble interleukin (IL)-1 receptor antagonist (sIL-1RA), IL-10, eotaxin, IgA/IgM responses to TRYCATs, and Consortium to Establish a Registry for Alzheimer’s disease (CERAD) tests were assessed in 40 controls and 80 schizophrenia patients.

Results:

Schizophrenia and MNP were predicted by significantly increased levels of IL-10, eotaxin and TRYCATs. A large part of variance in both PHEMN/DAPS symptom dimensions (42.8%) was explained by cytokine levels and TRYCATs combined. The MIP+sIL-1RA+IL-10 composite score and eotaxin explained each around on the basis of 19% of the variance in symptom dimensions, and approximately 18% of memory deficits. Moreover, MIP+sIL-1RA+IL-10 was significantly associated with elevations in picolinic acid, xanthurenic acid and 3-OH-kynurenine. Partial Least Squares path modeling shows that highly significant effects of MIP+sIL-1RA+IL-10 on symptomatology are mediated by the effects of noxious TRYCATs on memory deficits.

Conclusion:

Current findings indicate that in schizophrenia, immune activation may underpin activation of indoleamine-2,3-dioxygenase and kynurenine monooxygenase, while impairments in episodic and semantic memory may be caused by the neurotoxic effects of TRYCATs and eotaxin. The combined effects of immune activation, eotaxin and memory defects determine to a large extent, PHEMN/DAPS symptoms and the MNP phenotype. These findings indicate that schizophrenia phenomenology is largely mediated by multiple neuro-immune pathways and that immune activation, increased production of eotaxin and neurotoxic TRYCATs (picolinic acid, xanthurenic acid and 3-HOkynurenine) are new drug targets in schizophrenia and MNP.

Cytokine Research in Depression: Principles, Challenges, and Open Questions

Cytokines have been implicated in the pathology of depression. Currently, the evidence is based on cross-sectional studies and meta-analytic research comparing blood concentrations of T helper type 1 (TH1), T helper type 2 (TH2), pro-inflammatory or anti-inflammatory cytokines of patients with a depressive disorder to those of healthy controls. Additionally, multiple longitudinal studies have investigated cytokine levels during antidepressant treatment. According to the current literature, it seems that peripheral levels of interleukin (IL)-6, IL-10, IL-12, IL-13, and tumor necrosis factor (TNF)-α are elevated and that interferon (IFN)-γ levels are lower in patients with depression compared to healthy controls. However, the overlap of cytokine values between acutely depressed patients, remitted and recovered patients and healthy controls is considerable. Thus, the discriminative power of cytokine concentrations between depressed and non-depressed people is likely weak. Treatment with certain antidepressants appears to decrease peripheral levels of IL-6, IL-10, and TNF-α. However, weight gain-inducing psychopharmacological substances, such as the antidepressant mirtazapine, have been reported to potentially increase the production of pro-inflammatory cytokines. Even though cytokines are often discussed as biomarkers for depression, they have also been shown to be altered in other psychiatric disorders. Moreover, many environmental, social, psychological, biological, and medical factors are also associated with cytokine changes. Thus, cytokine alterations seem extremely unspecific. The interpretation of the results of these studies remains a challenge because it is unknown which type of cells are most responsible for cytokine changes measured in the blood nor have the main target cells or target tissues been identified. The same cytokine can be produced by multiple cell types, and the same cell can produce various cytokines. Additionally, redundancy, synergy, antagonism, and signaling cascades of cytokine signaling must be considered. Cytokines might not be associated with the diagnosis of depression according to the currently used diagnostic manuals, but rather with specific subtypes of depression, or with depressive symptoms across different psychiatric diagnoses. Therefore, the currently available diagnostic systems may not be the ideal starting point for psychiatric cytokine research.

High concentrations of serum interleukin-6 and interleukin-8 in patients with bipolar disorder

Immune system dysregulation plays a key role in the physiopathology of bipolar disorder (BD) and major depressive disorder (MDD). However, whether interleukins might be biomarkers to distinguish these 2 affective disorders is unclear. Here, we assessed the differences in serum levels of interleukin 6 (IL-6) and interleukin 8 (IL-8) as well as C-reactive protein (CRP) in patients with MDD and BD. In total, we enrolled 21 MDD patients, 26 BD patients, and 20 healthy controls. We collected a total of 35 samples from BD patients in 3 different phases, depression phase, manic phase, and remission stage, and 27 samples from MDD patients in acute and remission phases. Serum IL-6 and IL-8 levels were assessed with solid phase sandwich ELISA-based quantitative arrays, and CRP levels were determined with an automatic analyzer. Both serum IL-6 and IL-8 levels were elevated in BD patients but not MDD patients. Subgroup analysis indicated elevated serum IL-6 in both the depression and manic phases in BD patients. The serum CRP levels did not change in either BD or MDD patients. However, sex differences in CRP concentrations were observed in healthy controls. Furthermore, there were linear correlations between the CRP levels and Bech-Rafaelsen Mania Rating Scale (BRMS) scores in BD patients. IL-6 and IL-8 levels may serve as biomarkers to differentiate between MDD and BD patients, even when the clinical manifestations are atypical. IL-6 may be used for the differential diagnosis of MDD and depressive episodes in BD.

IL-10 is associated with increased mu-opioid receptor levels in major depressive disorder

Objective:

Activation of the immune-inflammatory response system (IRS) and the compensatory immune-regulatory system (CIRS) and aberrations in endogenous opioids play a role in the pathophysiology of major depressive disorder (MDD). There are no studies which examined the associations between both systems in MDD. The aim of the present study was to examine the relation between β-Endorphin (β-EP), Endomorphin-2, and their mu-opioid receptor (MOR) as well as interleukin (IL)-6 and IL-10, an anti-inflammatory cytokine, in MDD patients.

Method:

The study included 60 depressed drug-free male patients and 30 matched controls. Serum β-EP, Endomorphin-2, MOR, IL-6 and IL-10 levels were measured using ELISA techniques.

Results:

The results revealed a significant increase in serum β-EP, MOR, IL-6 and IL-10 in MDD patients versus healthy controls. MOR levels were strongly associated with IL-10 levels. There were no significant correlations between endogenous opioids and IL-6 and IL-10.

Conclusion:

The results show that MOR levels may function as a possible component of the CIRS whilst there is no evidence that β-EP and EM-2 may modify the IRS. The significant correlation between MOR levels and IL-10 may be explained through central activation of the HPA-axis and increased B-cell numbers expressing MOR as a response to cytokine over-secretion in MDD.

COX-2 Inhibitors, Aspirin, and Other Potential Anti-Inflammatory Treatments for Psychiatric Disorders

Inflammatory processes associated with persistent (chronic) infection have long been discussed as etiological factors in psychiatric disorders. Studies have found that people with major depression have higher levels of pro-inflammatory cytokines, for example, IL-1, IL-6, and tumor necrosis factor-alpha, and C-reactive protein. In schizophrenia, many reports have described raised levels of cytokines, for example, IL-6; and meta-analyses have confirmed these findings. Microglia cells are important in inflammatory processes, and positron emission tomography studies have shown microglia activation in both depression and schizophrenia.As a consequence of the above findings, immunomodulation is widely discussed as a potential treatment approach in both major depression and schizophrenia. The COX-2 inhibitor celecoxib was found to have a significant positive effect on major depression, not only in single studies but also in meta-analyses. Celecoxib has also been studied in schizophrenia and has shown efficacy, in particular, in early disease stages. The mixed COX inhibitor aspirin (acetylsalicylic acid) seems to have both protective and therapeutic effects on schizophrenia.This paper discusses the hypothesized role of inflammation in major depression and schizophrenia, including markers of inflammation; pertinent studies on celecoxib and aspirin; and additional immunomodulatory therapeutic strategies.

Innate immune activation and depressive and anxious symptoms across the peripartum: An exploratory study

BACKGROUND

There are complex associations between immune function and mental illness, yet studies in the perinatal period focus primarily on individual inflammatory markers and depressive symptoms only, cross-sectionally. We sought to examine associations between both depressive and anxious symptoms and immune activation longitudinally across the peripartum.

METHODS

We measured mood (Beck Depression Inventory, BDI-1 A) and anxiety (State-Trait Anxiety Inventory, STATE) and levels of 23 cytokines at 5 points in pregnancy and postpartum in 51 women. Within subject cytokine trajectories over time by depressive and anxious symptom grouping were assessed using linear mixed effects models with random intercept and slope. We also undertook an exploratory cluster analysis based on third trimester cytokine values.

RESULTS

Based on categorical BDI scores, IL-6 (p <  0.001), IL-15 (p =  0.047), GCSF (p = 0.003), and CCL3 (p < .001) were significantly different across time, with IL-6 (p <  0.001), IL-15 (p =  0.003), and CCL3 (p <  0.001) higher at the third trimester visit in more depressed subjects. Based on categorical STATE scores, GM-CSF significantly decreased across pregnancy for the less anxious group (p = 0.016), but not for the more anxious, and CCL3 (p = 0.017), CXCL8 (p = 0.011), and IL-6 (p < 0.001) were higher at the third trimester visit for more anxious subjects. In exploratory cluster analysis based on cytokine level, there were no differences in mood or anxiety scores, but significant differences by race/ethnicity and overweight/obesity status. Women with higher pro-inflammatory cytokine values are more likely to be Hispanics (69.2% vs. 21.4%, p =  0.015), but less likely to be African American (23.1% vs. 60.7%, p = 0.015) or overweight/obese (25% vs. 69.2%, p =  0.016) compared to women with lower pro-inflammatory cytokine values.

CONCLUSION

We identified a pro-inflammatory burst at the third trimester, indicative of innate immune activation, in women with higher levels of both depressive and anxious symptoms, as well as differences in pro-inflammatory changes across time. We also found significant differences in cytokine levels by race, ethnicity, and overweight/obesity status. These results point the way toward future longitudinal work that considers race/ethnicity, timing, and weight status, and evaluates perinatal mood and anxiety disorders in the context of changing immune functioning across the peripartum.

The Two-Faced Cytokine IL-6 in Host Defense and Diseases

Interleukein-6 (IL-6), is produced locally from infectious or injured lesions and is delivered to the whole body via the blood stream, promptly activating the host defense system to perform diverse functions. However, excessive or sustained production of IL-6 is involved in various diseases. In diseases, the IL-6 inhibitory strategy begins with the development of the anti-IL-6 receptor antibody, tocilizumab (TCZ). This antibody has shown remarkable effects on Castleman disease, rheumatoid arthritis and juvenile idiopathic arthritis. In 2017, TCZ was proven to work effectively against giant cell arteritis, Takayasu arteritis and cytokine releasing syndrome, initiating a new era for the treatment of these diseases. In this study, the defensive functions of IL-6 and various pathological conditions are compared. Further, the diseases of which TCZ has been approved for treatment are summarized, the updated results of increasing off-label use of TCZ for various diseases are reviewed and the conditions for which IL-6 inhibition might have a beneficial role are discussed. Given the involvement of IL-6 in many pathologies, the diseases that can be improved by IL-6 inhibition will expand. However, the important role of IL-6 in host defense should always be kept in mind in clinical practice.

Inhibition of interleukin-6 trans-signaling prevents inflammation and endothelial barrier disruption in retinal endothelial cells

Vascular inflammation plays a critical role in the pathogenesis of diabetic retinopathy. Recently, Interleukin-6 (IL-6) trans-signaling via soluble IL-6 receptor (sIL-6R) has emerged as a prominent regulator of inflammation in endothelial cells. This study was designed to test the hypothesis that selective inhibition of the IL-6 trans-signaling pathway will attenuate inflammation and subsequent barrier disruption in retinal endothelial cells. Human retinal endothelial cells (HRECs) were exposed to IL-6 and sIL-6R to induce IL-6 trans-signaling and the commercially available compound sgp130Fc (soluble gp-130 fused chimera) was used to selectively inhibit IL-6 trans-signaling. IL-6 trans-signaling activation caused a significant increase in STAT3 phosphorylation, expression of adhesion molecules, ROS production and apoptosis in HRECs whereas a significant decrease in mitochondrial membrane potential and NO production was observed in IL-6 trans-signaling activated cells. These changes were not observed in cells pre-treated with sgp130Fc. IL-6 trans-signaling activation was sufficient to cause barrier disruption in endothelial monolayers and pre-treatment of HRECs with sgp130Fc, maintained endothelial barrier function similar to that of untreated cells. Thus, in conclusion, these results indicate that IL-6 trans-signaling is an important mediator of inflammation, apoptosis and barrier disruptive effects in the retinal endothelial cells and inhibition of the IL-6 trans-signaling pathway using sgp130-Fc attenuates vascular inflammation and endothelial barrier disruption.

IL-1β, IL-6, TNF- α and CRP in Elderly Patients with Depression or Alzheimer's disease: Systematic Review and Meta-Analysis

We carried out systematic review and meta-analysis to evaluate whether peripheral levels of pro-inflammatory markers including Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF- α) and C-Reactive Protein (CRP) are significantly higher in elderly with depression and Alzheimer's disease. We searched Pubmed, PsycINFO and Embase, and thirty-four relevant studies (2609 with Depression, 1645 with Alzheimer's disease and 14363 Controls) were included. Compared with controls, IL-1β (pooled standardized mean difference [SMD]: 0.642; 95% confidence interval [CI]: 0.078-1.206; significant heterogeneity: I2 = 86.28%) and IL-6 (pooled SMD: 0.377; 95% CI: 0.156-0.598; significant heterogeneity: I2 = 88.75%) were significantly elevated in depression. There was no difference in TNF-α (p = 0.351) and CRP (p = 0.05) between those with depression and controls. Compared with controls, IL-1β (pooled SMD: 1.37, 95% CI: 0.06-2.68, significant heterogeneity: I2 = 96.01%) was significantly elevated in Alzheimer's disease. There were no differences in IL-6 (p = 0.138), TNF-α (p = 0.451) and CRP (p = 0.07) between elderly with Alzheimer's disease and controls. After Bonferroni adjustment, only IL-6 remained significantly higher in depression. Elderly with depression have higher IL-6 than controls, while those with Alzheimer's disease did not have higher peripheral inflammatory markers.

Higher concentration of interleukin 6 - A possible link between major depressive disorder and childhood abuse

Little is known about the correlation between IL-6 and childhood abuse and neglect which may be risk factors for the development of affective disorders in adulthood. The aim of this study was to analyze differences in serum concentrations of IL-6 between patients with major depressive disorder and healthy controls, and to investigate possible correlations with adverse childhood experiences. Peripheral venous blood samples were obtained from 64 patients who fulfilled DSM-IV-R criteria for a current major depressive episode without psychotic symptoms (MDD) and 53 healthy controls, matched for age and gender. Participants were assessed by the Beck Depression Inventory (BDI), Childhood Trauma Questionnaire (CTQ), Hamilton Depression Rating Scale (HDRS) and Hamilton Anxiety Rating Scale (HARS). The concentration of IL-6 was significantly higher in patients with major depressive disorder compared to healthy controls. The total score of childhood trauma questionnaire highly statistically significantly correlated with IL-6 levels in patient group. Persons who were physically abused, physically neglected and emotionally abused had higher levels of IL-6. Interleukin 6 as a pro-inflammatory immune marker could be an important developmental mediator linking physical and emotional abuse in early life with the development of depressive disorder in adulthood.

Stress, anxiety, and depression of both partners in infertile couples are associated with cytokine levels and adverse IVF outcome

PROBLEM

Psychiatric disorders and stress in women have been associated with poor IVF outcome. We hypothesized that both partners in the infertile couples are emotionally affected, and cytokines in both may link psychological to reproductive outcome.

METHOD OF STUDY

Forty-five IVF couples completed questionnaires and visual analog scales for stress and psychiatric disorders and had cytokines measured in serum, semen, cervicovaginal, and follicular fluids. Multivariable analyses, t tests, maximum likelihood estimates, Spearman correlation, and data mining were applied.

RESULTS

Psychopathology was found in 72% of the couples. Female and male stress were associated with stress, anxiety, and depression in the respective partner, and with a lower likelihood of clinical pregnancy and live birth. Lower serum TGF-β and higher cervicovaginal IL-6 and IL-1β were associated with stress. In data decision trees, cytokines in relation to stress and depression in both partners were found indicative of IVF failure.

CONCLUSION

Infertile couples may benefit from psychiatric evaluation and treatment of both partners.

Increased plasma nesfatin-1 levels may be associated with corticosterone, IL-6, and CRP levels in patients with major depressive disorder

OBJECTIVES

The aim of the present study was to evaluate the plasma nesfatin-1, corticosterone, and inflammatory cytokine (IL-6, CRP, and TNF-α) concentrations cross-sectionally in patients with major depressive disorder.

METHODS

Subjects in the patient group were randomly selected from the Anhui Mental Health Center, and subjects in the control group were selected from healthy volunteers. Healthy control subjects were matched in terms of weight and body mass index. The Hamilton Depression Rating Scale (HAM-D) was used to evaluate both groups. ELISAs were used for the measurement of plasma nesfatin-1, corticosterone, IL-6, CRP, and TNF-α levels.

RESULTS

The HAM-D scores and average nesfatin-1, corticosterone, IL-6, and CRP levels were significantly higher in patients with major depressive disorder than those in the control group. Positive correlation was found between nesfatin-1 and corticosterone (r = 0.305, P = 0.007), IL-6 (r = 0.333, P = 0.003), and CRP (r = 0.244, P = 0.034) concentrations.

CONCLUSIONS

Increased plasma nesfatin-1 levels may be associated with corticosterone, IL-6, and CRP levels in patients with major depressive disorder.

A neuro-immune, neuro-oxidative and neuro-nitrosative model of prenatal and postpartum depression

A large body of evidence indicates that major affective disorders are accompanied by activated neuro-immune, neuro-oxidative and neuro-nitrosative stress (IO&NS) pathways. Postpartum depression is predicted by end of term prenatal depressive symptoms whilst a lifetime history of mood disorders appears to increase the risk for both prenatal and postpartum depression. This review provides a critical appraisal of available evidence linking IO&NS pathways to prenatal and postpartum depression. The electronic databases Google Scholar, PubMed and Scopus were sources for this narrative review focusing on keywords, including perinatal depression, (auto)immune, inflammation, oxidative, nitric oxide, nitrosative, tryptophan catabolites (TRYCATs), kynurenine, leaky gut and microbiome. Prenatal depressive symptoms are associated with exaggerated pregnancy-specific changes in IO&NS pathways, including increased C-reactive protein, advanced oxidation protein products and nitric oxide metabolites, lowered antioxidant levels, such as zinc, as well as lowered regulatory IgM-mediated autoimmune responses. The latter pathways coupled with lowered levels of endogenous anti-inflammatory compounds, including ω3 polyunsaturated fatty acids, may also underpin the pathophysiology of postpartum depression. Although increased bacterial translocation, lipid peroxidation and TRYCAT pathway activation play a role in mood disorders, similar changes do not appear to be relevant in perinatal depression. Some IO&NS biomarker characteristics of mood disorders are found in prenatal depression indicating that these pathways partly contribute to the association of a lifetime history of mood disorders and perinatal depression. However, available evidence suggests that some IO&NS pathways differ significantly between perinatal depression and mood disorders in general. This review provides a new IO&NS model of prenatal and postpartum depression.

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

BACKGROUND

There is evidence that major depression (MDD) and bipolar disorder (BD) are accompanied by activated immune & oxidative (I&O) pathways.

METHODS

To compare I&O biomarkers between MDD and BD we assessed serum levels of thiobarbituric acid reactive substances (TBARS; a lipid peroxidation marker), soluble interleukin-2 receptor (sIL-2R), sIL-6R, IL-α, sIL-1R antagonist (sIL-1RA), tumor necrosis factor receptor 60kDa/80kDa (sTNFR60/R80) in 114 MDD and 133 BD patients, and 50 healthy controls. We computed z-unit weighted indices reflecting the 5 cytokine receptor levels (zCytR), cell-mediated immunity (zCMI) and I&O pathways (zCMI+TBARS).

RESULTS

There are no significant differences in biomarkers between MDD and BD. BD/MDD with atypical features is characterized by increased sIL-6R and TBARS, whereas melancholia is associated with higher TBARS and lower sTNFR60 levels. Severity of illness, as measured with the Hamilton Depression Rating Scale, is correlated with increased sIL-6R, sTNFR80, TBARS, zCytR and zCMI+TBARS. The number of episodes the year prior to blood sampling is positively associated with sTNFR80, TBARS, zCMI, zCMI+TBARS, while number of hospitalizations is positively associated with sIL-1RA. Prior suicidal attempts are associated with increased sIL-1RA, IL-1α, zCMI, TBARS and zCMI+TBARS, while TBARS is associated with current suicidal ideation.

CONCLUSIONS

There are no I&O biomarker differences between MDD and BD. Atypical depression is associated with increased IL-6 trans-signaling and lipid peroxidation. Severity of depression, number of episodes and suicidal attempts are associated with activated I&O pathways. Increased TBARS is the single best predictor of BD/MDD, atypical depression, melancholia and current suicidal ideation.

Molecular changes associated with escitalopram response in a stress-based model of depression

Converging evidence points at hypothalamus-pituitary-adrenal (HPA) axis hyperactivity and neuroinflammation as important factors involved in the etiopathogenesis of major depressive disorder (MDD) and in therapeutic efficacy of antidepressants. In this study, we examined the molecular effects associated with a response to a week-long treatment with escitalopram in the chronic escape deficit (CED) model, a validated model of depression based on the induction of an escape deficit after exposure of rats to an unavoidable stress. We confirmed our previous result that a treatment with escitalopram (10mg/kg) was effective after 7days in reverting the stress-induced escape deficit in approximately 50% of the animals, separating responders from non-responders. Expression of markers of HPA axis functionality as well as several inflammatory mediators were evaluated in the hypothalamus, a key structure integrating signals from the neuro, immune, endocrine systems. In the hypothalamus of responder animals we observed a decrease in the expression of CRH and its receptors and an increase in GR protein in total and nuclear extracts; this effect was accompanied by a significant decrease in circulating corticosterone in the same cohort. Hypothalamic IL-1β and TNFα expression were increased in stressed animals, while CXCL2, IL-6, and ADAM17 mRNA levels were decreased in escitalopram treated rats regardless of the treatment response. These data suggest that efficacy of a one week treatment with escitalopram may be partially mediated by a decrease HPA axis activity, while in the hypothalamus the drug-induced effects on the expression of immune modulators did not correlate with the behavioural outcome.

FoxO1, A2M, and TGF-β1: three novel genes predicting depression in gene X environment interactions are identified using cross-species and cross-tissues transcriptomic and miRNomic analyses

To date, gene-environment (GxE) interaction studies in depression have been limited to hypothesis-based candidate genes, since genome-wide (GWAS)-based GxE interaction studies would require enormous datasets with genetics, environmental, and clinical variables. We used a novel, cross-species and cross-tissues "omics" approach to identify genes predicting depression in response to stress in GxE interactions. We integrated the transcriptome and miRNome profiles from the hippocampus of adult rats exposed to prenatal stress (PNS) with transcriptome data obtained from blood mRNA of adult humans exposed to early life trauma, using a stringent statistical analyses pathway. Network analysis of the integrated gene lists identified the Forkhead box protein O1 (FoxO1), Alpha-2-Macroglobulin (A2M), and Transforming Growth Factor Beta 1 (TGF-β1) as candidates to be tested for GxE interactions, in two GWAS samples of adults either with a range of childhood traumatic experiences (Grady Study Project, Atlanta, USA) or with separation from parents in childhood only (Helsinki Birth Cohort Study, Finland). After correction for multiple testing, a meta-analysis across both samples confirmed six FoxO1 SNPs showing significant GxE interactions with early life emotional stress in predicting depressive symptoms. Moreover, in vitro experiments in a human hippocampal progenitor cell line confirmed a functional role of FoxO1 in stress responsivity. In secondary analyses, A2M and TGF-β1 showed significant GxE interactions with emotional, physical, and sexual abuse in the Grady Study. We therefore provide a successful 'hypothesis-free' approach for the identification and prioritization of candidate genes for GxE interaction studies that can be investigated in GWAS datasets.

Encephalitis, Mild Encephalitis, Neuroprogression, or Encephalopathy-Not Merely a Question of Terminology

Background: Psychoneuroimmunology research has presented emerging evidence of the involvement of inflammatory and immune mechanisms in the pathogenesis of severe mental disorders. In this context, new terms with increasing clinical relevance have been proposed, challenging the existing terms, and requiring consensus definitions of the new ones. Method: From a perspective of longstanding personal involvement in clinical settings and research in psychoneuroimmunology, the new and the existing terms are critically reconsidered. Results: Meningoencephalitis and encephalitis are comparably well defined clinical terms in neuropsychiatry, although in the individual case approach diagnosis can be difficult, for example in some cases of encephalitis that are described with normal cerebrospinal fluid findings, or often in chronic encephalitis. Encephalopathy is also a widely accepted term, however, with a surprisingly broad meaning with regard to the assigned underlying pathophysiology, ranging from one-hit traumatic encephalopathy to inflammatory encephalopathy, the latter term addressing a type of brain dysfunction secondary to acute systemic inflammation without proven brain autochthonus inflammation (neuroinflammation). However, this latter assumption and term may be wrong as neuroinflammation is difficult to prove in vivo. With emerging insights into prevailing inflammatory and neuroinflammatory mechanisms that are involved in the pathogenesis of severe mental disorders, the interdependent aspects of sensitive assessment and potential clinical relevance of mild neuroinflammation are becoming more apparent and of increasing clinical interest. The new terms "mild encephalitis," "parainflammation," and "neuroprogression" show considerable overlap in addition to gaps and hardly defined borders. However, details are hard to discuss as available studies use many biomarkers, but most of these are done without an established categorical attribution to exclusive terms. Most important, the three new concepts (neruoprogression, parainflammation, and mild encephalitis) are not mutually exclusive, even at the individual case level, and therefore will require state-related individual assessment approaches beyond large confirmatory studies. Conclusion: The newly proposed terms of mild encephalitis, parainflammation, and neuroprogression have an emerging clinical relevance, but respective borders, gaps and overlap in between them remain unclear, and these concepts may even be seen as complementary. Categorical delineation of the new and reconsideration of the existing terms with respect to individualized psychiatric treatment is required for better clinical use, eventually requiring a consensus approach. Here, a critique based on available data and a focus on clinical perspective was outlined, which may help to enhance fruitful discussion. The idea followed here is in line with pillar number six as proposed for the Research Diagnostic Domains, i.e., to provide and follow new concepts in psychiatric research.

Antidepressant-Like Effect of Lipid Extract of Channa striatus in Postpartum Model of Depression in Rats

Postpartum depression affects 15% of women. Channa striatus, a freshwater fish, is consumed in local Malay population as a rejuvenating diet during postpartum period. This study evaluated the antidepressant-like effect of lipid extract of C. striatus fillet and its mechanism of action in female Sprague-Dawley rats in postpartum model of depression. The rats were ovariectomized and treated with high dose of progesterone and estradiol benzoate for 23 days to have hormone-simulated pregnancy. The day 24 and afterwards were considered as the postpartum period. During the postpartum period, lipid extract was administered at 125, 250, and 500 mg/kg through intraperitoneal route for 15 days. Fluoxetine (10 mg/kg) was used as the positive control. On postpartum day 15, the animals were tested in forced swimming test (FST) and open field test (OFT) followed by biochemical analysis. Withdrawal of hormone administration during the postpartum period induced depressive-like behavior in FST. Administration of lipid extract reversed that depressive-like behavior at 125, 250, and 500 mg/kg in FST. In OFT, it decreased the exploratory activity. The mechanism of the antidepressant-like effect may be mediated through the decrease in plasma corticosterone, increase in plasma oxytocin, and decrease in nuclear factor-kappa B in prefrontal cortex of rats.

Lipid Peroxidation and Immune Biomarkers Are Associated with Major Depression and Its Phenotypes, Including Treatment-Resistant Depression and Melancholia

To examine immune-inflammatory and oxidative (I&O) biomarkers in major depression (MDD) and its related phenotypes, we recruited 114 well-phenotyped depressed patients and 50 healthy controls and measured serum levels of interleukin (IL)-1α, soluble IL-1 receptor antagonist (sIL-1RA), soluble IL-2 receptor (sIL-2R), soluble IL-6 receptor (sIL-6R), soluble tumor necrosis factor receptor 60 and 80 kDa (sTNF-R1/R2), and thiobarbituric acid reactive substances (TBARS). Obtained results indicate that MDD is characterized by increased sIL-1RA, sTNF-R1, and TBARS concentrations. Melancholic depression is associated with increased sIL-6R but lowered IL-1α levels. A current episode of depression is accompanied by significantly increased sIL-6R compared to the remitted state. Treatment-resistant depression (TRD) is accompanied by increased sIL-6R and TBARS but lowered sTNF-R2 levels compared to non-TRD patients. These immune markers are not significantly correlated with Hamilton Depression Rating Scale (HDRS), Montgomery-Asberg Depression Scale (MADRS), number episodes, or age at onset. Our findings show that increased sIL-1RA, sTNF-R1, and TBARS levels may be trait markers of depression, while increased sIL-6R levels may be a state marker of melancholia and an acute phase of depression. MDD is accompanied by increased lipid peroxidation and simultaneous activation of immune pathways, and the compensatory anti-inflammatory reflex system (CIRS). TRD is characterized by highly increased oxidative stress and probably increased TNFα and IL-6 trans-signalling. Novel treatments for major depression should target oxidative stress pathways, while new treatments for TRD should primary target lipid peroxidation and also activated immune-inflammatory pathways.

The effects of interleukin-6 neutralizing antibodies on symptoms of depressed mood and anhedonia in patients with rheumatoid arthritis and multicentric Castleman's disease

Cytokines, including interleukin-6 (IL-6), modulate neuronal plasticity and stress coping. Depressive symptoms and major depressive disorder (MDD) have been associated with changes in cytokines and their signaling. The current study examined the effect of IL-6 monoclonal antibody administration on depressive symptoms in patients with rheumatoid arthritis (RA) or multicentric Castleman's disease (MCD). The data were obtained from two phase 2, double-blind, placebo-controlled trials designed to test the efficacy of sirukumab in RA (N=176) or of siltuximab in MCD (N=65), and were analyzed post hoc to investigate the effects of these IL-6 antibodies on depressive symptoms. The SF-36 questionnaire items on depressed-mood and anhedonia were combined as the measure for depressive symptoms. The study participants were grouped by the presence/absence of prevalent depressed mood and anhedonia (PDMA, meaning either depressed mood or anhedonia was present at least 'most of the time' and the other at least 'some of the time' for four weeks) at baseline; 26.1% of the RA sample and 15.4% of the MCD sample met criteria for PDMA at baseline. Compared with placebo, sirukumab and siltuximab produced significantly greater improvements on depressive symptoms. To account for an effect on mood due to changes in RA or MCD, the analysis was (1) adjusted for symptom severities using DAS28-CRP for RA and MCDOS for MCD alone or together with bodily pain and physical functioning, and (2) performed within RA and MCD non-responders. Improvement in depressive symptoms remained significant in the treated group for both drugs. The significance over placebo was also observed in the siltuximab study. The improvement in depressive symptoms by sirukumab correlated positively with the baseline soluble IL-6 receptor levels. The data together suggest that the IL-6 antibodies improve depressive symptoms in patients with RA and MCD. Further studies are needed to elucidate to what extents the IL-6 antibodies improve depressive symptoms through improving primary disease dependent and independent mechanisms, especially in RA patients, and the brain mechanisms underlying depressive symptom improvements.

"Allergic mood" - Depressive and anxiety symptoms in patients with seasonal allergic rhinitis (SAR) and their association to inflammatory, endocrine, and allergic markers

A growing number of studies show an association between seasonal allergic rhinitis (SAR) with depression and anxiety. The underlying mechanisms of a link between SAR and affect, however, are still unclear. The objective of the present study was to investigate depressive symptoms and anxiety in SAR patients and their association to inflammatory and endocrine parameters. SAR patients (n=41) and non-allergic, healthy controls (n=42) were assessed during (pollen season) and out of symptomatic periods (non-pollen season). Inflammatory cytokine profile (Interleukin [IL]-2, IL-4, IL-6, IL-8, IL-10, IL-17, IFN-γ, TNF-α), Immunoglobulin-E (IgE), hair cortisol concentrations (HCC), as well as sleep quality were measured. The present data show that during acute allergic inflammation SAR patients experienced a significant increase in Beck Depression Inventory (BDI-) II scores when (a) compared to the asymptomatic period and (b) when compared to the non-allergic controls, while no differences in anxiety were observed. Increased BDI-II scores in SAR patients were significantly associated with levels of IL-6 as well as IL-6/IL-10 and IFN-γ/IL-10 ratios and further, to an early age at manifestation of SAR and poor sleep quality. These findings support a close relationship between acute allergic processes and affective states, with inflammatory cytokines, sleep, and age of manifestation as potentially relevant mediators.

The association of electroconvulsive therapy to pharmacological treatment and its influence on cytokines

INTRODUCTION

A growing body of evidence shows that disturbances in the immune system are involved in the pathogenesis of depression. Although the immune-modulating effects of antidepressants have been described, few studies have addressed the functioning of the immune system in relation to electroconvulsive therapy (ECT). This study aims to investigate if the addition of ECT to pharmacotherapy is associated with changes in cytokine levels.

METHODS

Adult inpatients were invited to participate in this study on admission to a psychiatric unit. Those with a diagnosis of depression by Mini-International Neuropsychiatric Interview were included. At treatment discharge, patients were retrospectively divided into those who used combined ECT and pharmacotherapy (31 subjects) and those who used only pharmacotherapy (68 subjects). Pro-inflammatory cytokines IL-2, IL-6, TNF-α, IFN-γ, and IL-17, and anti-inflammatory IL-4 and Il-10, were measured in blood samples collected at admission and discharge. A generalized estimating equation model and the post hoc Bonferroni test were performed for statistical analysis.

RESULTS

The combination of ECT with pharmacotherapy was associated with a decrease of IL-6 and an increase of TNF-α. Depressive inpatients, as a whole group, had a decrease of IL-6 and an increase of IFN-γ. No significant results were found for IL-2, IL-4, Il-10 and IL-17.

CONCLUSION

This study is clinically relevant because we highlight that, in agreement with the previous literature, IL-6 appears to be a useful marker in depression, and we show for the first time that its reduction is closely related to the use of ECT.

Blockade of interleukin-6 receptor in the periphery promotes rapid and sustained antidepressant actions: a possible role of gut-microbiota-brain axis

Depression is a common, severe and chronic psychiatric disease. Although the currently available antidepressants have been used in the treatment of depression, their beneficial effects are limited. Accumulating evidence suggests that pro-inflammatory cytokines such as interleukin-6 (IL-6) have an important role in the pathogenesis of depression. This study was undertaken to examine whether anti-mouse IL-6 receptor antibody (MR16-1) induces antidepressant effects in a social defeat stress model. Intravenous injection of MR16-1 induced rapid-onset and long-lasting antidepressant effects in susceptible mice after social defeat stress through its anti-inflammatory actions. In contrast, intracerebroventricular injection of MR16-1 induced no antidepressant effects in susceptible mice. Furthermore, treatment with MR16-1 could significantly normalize alterations in the expression of synaptic proteins (postsynaptic density protein 95 and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor 1) and dendritic spine density in the brain regions of susceptible mice. Gut microbiota analysis using 16S ribosomal RNA gene sequencing showed that MR16-1 significantly improved decreased Firmicutes/Bacteroidetes ratio in susceptible mice. It also significantly improved decreased levels of Oscillospira in susceptible mice. These findings suggest that peripheral IL-6 has a key role in the pathogenesis of depression and that the blockade of IL-6 receptor in the periphery might have rapid-onset and long-lasting antidepressant effects by normalizing the altered composition of gut microbiota in susceptible mice after social defeat stress. Therefore, the blockade of IL-6 receptor in the periphery shows promise as a novel therapeutic approach for depressed patients with higher IL-6 blood levels.

Peripheral cytokine and chemokine alterations in depression: a meta-analysis of 82 studies

OBJECTIVE

To conduct a systematic review and meta-analysis of studies that measured cytokine and chemokine levels in individuals with major depressive disorder (MDD) compared to healthy controls (HCs).

METHOD

The PubMed/MEDLINE, EMBASE, and PsycINFO databases were searched up until May 30, 2016. Effect sizes were estimated with random-effects models.

RESULT

Eighty-two studies comprising 3212 participants with MDD and 2798 HCs met inclusion criteria. Peripheral levels of interleukin-6 (IL-6), tumor necrosis factor (TNF)-alpha, IL-10, the soluble IL-2 receptor, C-C chemokine ligand 2, IL-13, IL-18, IL-12, the IL-1 receptor antagonist, and the soluble TNF receptor 2 were elevated in patients with MDD compared to HCs, whereas interferon-gamma levels were lower in MDD (Hedge's g = -0.477, P = 0.043). Levels of IL-1β, IL-2, IL-4, IL-8, the soluble IL-6 receptor (sIL-6R), IL-5, CCL-3, IL-17, and transforming growth factor-beta 1 were not significantly altered in individuals with MDD compared to HCs. Heterogeneity was large (I² : 51.6-97.7%), and sources of heterogeneity were explored (e.g., age, smoking status, and body mass index).

CONCLUSION

Our results further characterize a cytokine/chemokine profile associated with MDD. Future studies are warranted to further elucidate sources of heterogeneity, as well as biosignature cytokines secreted by other immune cells.

Consensus paper of the WFSBP Task Force on Genetics: Genetics, epigenetics and gene expression markers of major depressive disorder and antidepressant response

Major depressive disorder (MDD) is a heritable disease with a heavy personal and socio-economic burden. Antidepressants of different classes are prescribed to treat MDD, but reliable and reproducible markers of efficacy are not available for clinical use. Further complicating treatment, the diagnosis of MDD is not guided by objective criteria, resulting in the risk of under- or overtreatment. A number of markers of MDD and antidepressant response have been investigated at the genetic, epigenetic, gene expression and protein levels. Polymorphisms in genes involved in antidepressant metabolism (cytochrome P450 isoenzymes), antidepressant transport (ABCB1), glucocorticoid signalling (FKBP5) and serotonin neurotransmission (SLC6A4 and HTR2A) were among those included in the first pharmacogenetic assays that have been tested for clinical applicability. The results of these investigations were encouraging when examining patient-outcome improvement. Furthermore, a nine-serum biomarker panel (including BDNF, cortisol and soluble TNF-α receptor type II) showed good sensitivity and specificity in differentiating between MDD and healthy controls. These first diagnostic and response-predictive tests for MDD provided a source of optimism for future clinical applications. However, such findings should be considered very carefully because their benefit/cost ratio and clinical indications were not clearly demonstrated. Future tests may include combinations of different types of biomarkers and be specific for MDD subtypes or pathological dimensions.

Reversal of schizophrenia-like symptoms and immune alterations in mice by immunomodulatory drugs

Immune dysregulation observed in schizophrenia alters tryptophan metabolism. Tryptophan metabolism is triggered by indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO). Tryptophan is converted to quinolinic acid, a potent neurotoxin, and to kynurenic acid, an NMDA antagonist. 1-Methyl-D-tryptophan (MDT) inhibits IDO. Melatonin is metabolized by IDO while inhibiting TDO. We evaluated the reversal of ketamine-induced schizophrenia-like behavioral and neurochemical alterations in mice by the administration of MDT (20 or 40 mg/kg, i.p.) or melatonin (15 mg/kg, per os). Oxidative stress and inflammatory alterations, i.e. myeloperoxidase activity (MPO), reduced glutathione (GSH), lipid peroxidation (LPO) and interleukin (IL)-4 and IL-6 were measured in the prefrontal cortex (PFC), hippocampus and striatum. Risperidone was used as standard antipsychotic. Ketamine triggered positive- (PPI deficits and hyperlocomotion), cognitive- (working memory deficits) and negative (social interaction deficits) schizophrenia-like symptoms. These symptoms were accompanied by increased MPO activity, decreased GSH and increased LPO in all brain areas and increments in hippocampal IL-4 and IL-6. MDT and melatonin reversed all ketamine-induced behavioral alterations. Risperidone did not reverse working memory deficits. MDT and melatonin reversed alterations in MPO activity and GSH levels. LP was reversed only by melatonin and risperidone. Risperidone could not reverse MPO alterations in the PFC and striatum. All drugs reversed the alterations in IL-4 and IL-6. The hippocampus and striatum of ketamine+melatonin-treated animals had lower levels of IL-6. Our findings provide further preclinical evidence that immune-inflammatory and oxidative pathways are involved in schizophrenia and that targeting these pathways is a valid treatment option in schizophrenia.

Resveratrol ameliorates chronic unpredictable mild stress-induced depression-like behavior: involvement of the HPA axis, inflammatory markers, BDNF, and Wnt/β-catenin pathway in rats

Classic antidepressant drugs are modestly effective across the population and most are associated with intolerable side effects. Recently, numerous lines of evidence suggest that resveratrol (RES), a natural polyphenol, possesses beneficial therapeutic activity for depression. The aim of the present study was to explore whether RES exhibits an antidepressant-like effect in a depression model and to explore the possible mechanism. A depression model was established via chronic unpredictable mild stress (CUMS), after which the model rats in the RES and fluoxetine groups received a daily injection of RES or fluoxetine, respectively. The sucrose preference test, open field test, and forced swimming test were used to explore the antidepressant-like effects of RES. The activity of the hypothalamic-pituitary-adrenal (HPA) axis was evaluated by detecting the plasma corticosterone concentration and hypothalamic mRNA expression of corticotrophin-releasing hormone. The plasma interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-α (TNF-α) concentrations were measured by enzyme-linked immunosorbent assay. Hippocampal protein expression of brain-derived neurotrophic factor (BDNF) and the Wnt/β-catenin pathway were analyzed by western blot. The results showed that RES relieved depression-like behavior of CUMS rats, as indicated by the increased sucrose preference and the decreased immobile time. Rats that received RES treatment exhibited reduced plasma corticosterone levels and corticotrophin-releasing hormone mRNA expression in the hypothalamus, suggesting that the hyperactivity of the HPA axis in CUMS rats was reversed by RES. Moreover, after RES treatment, the rats exhibited increased plasma IL-6, CRP, and TNF-α concentrations. Furthermore, RES treatment upregulated the hippocampal protein levels of BDNF and the relative ratio of p-β-catenin/β-catenin while downregulating the relative ratio of p-GSK-3β/GSK-3β. Our findings suggest that RES improved depressive behavior in CUMS rats by downregulating HPA axis hyperactivity, increasing BDNF expression and plasma IL-6, CRP, and TNF-α concentrations, and regulating the hippocampal Wnt/β-catenin pathway.

Sirukumab: A Potential Treatment for Mood Disorders?

Convergent evidence indicates that abnormalities in the innate immune system may be pertinent to the pathogenesis, phenomenology, and possible treatment of several mental disorders. In keeping with this view, the targeting of interleukin-6 with the human monoclonal antibody sirukumab may represent a possible treatment and disease modification approach, for adults with brain-based disorders (e.g., major depressive disorder). A PubMed/Medline database search was performed using the following search terms: sirukumab; anti-IL-6; IL-6; major depressive disorder; inflammation. A systematic review was conducted of both preclinical and clinical trials reporting on the pharmacology of sirukumab or investigating the efficacy of targeting IL-6 signaling. Overall, sirukumab has been reported to be a safe and well-tolerated agent, capable of modulating the immune response in healthy populations as well as in subjects with inflammatory disorders (e.g., rheumatoid arthritis). Sirukumab's effects on cytokine networks as part of the innate immune system provide a coherent rationale for possible application in neuropsychiatric disorders with possible benefits across several domains of the biobehavioral Research Domain Criteria matrix (e.g., general cognitive processes, positive valence systems). Amongst individuals with complex brain-based disorders (e.g., mood disorders), the dimensions/domains most likely to benefit with sirukumab are negative valence disturbances (e.g., anxiety, depression, rumination), positive valence disturbances (e.g., anhedonia) as well as general cognitive processes. We suggest that sirukumab represents a prototype and possibly a proof-of-concept that agents that engage IL-6 targets have salutary effects in psychiatry.

Mast cells' involvement in inflammation pathways linked to depression: evidence in mastocytosis

Converging sources of evidence point to a role for inflammation in the development of depression, fatigue and cognitive dysfunction. More precisely, the tryptophan (TRP) catabolism is thought to play a major role in inflammation-induced depression. Mastocytosis is a rare disease in which chronic symptoms, including depression, are related to mast cell accumulation and activation. Our objectives were to study the correlations between neuropsychiatric features and the TRP catabolism pathway in mastocytosis in order to demonstrate mast cells' potential involvement in inflammation-induced depression. Fifty-four patients with mastocytosis and a mean age of 50.1 years were enrolled in the study and compared healthy age-matched controls. Depression and stress were evaluated with the Beck Depression Inventory revised and the Perceived Stress Scale. All patients had measurements of TRP, serotonin (5-HT), kynurenine (KYN), indoleamine 2,3-dioxygenase 1 (IDO1) activity (ratio KYN/TRP), kynurenic acid (KA) and quinolinic acid (QA). Patients displayed significantly lower levels of TRP and 5-HT without hypoalbuminemia or malabsorption, higher IDO1 activity, and higher levels of KA and QA, with an imbalance towards the latter. High perceived stress and high depression scores were associated with low TRP and high IDO1 activity. In conclusion, TRP metabolism is altered in mastocytosis and correlates with perceived stress and depression, demonstrating mast cells' involvement in inflammation pathways linked to depression.

Hypothalamic-Pituitary-Adrenal Hypofunction in Myalgic Encephalomyelitis (ME)/Chronic Fatigue Syndrome (CFS) as a Consequence of Activated Immune-Inflammatory and Oxidative and Nitrosative Pathways

There is evidence that immune-inflammatory and oxidative and nitrosative stress (O&NS) pathways play a role in the pathophysiology of myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS). There is also evidence that these neuroimmune diseases are accompanied by hypothalamic-pituitary-adrenal (HPA) axis hypoactivity as indicated by lowered baseline glucocorticoid levels. This paper aims to review the bidirectional communications between immune-inflammatory and O&NS pathways and HPA axis hypoactivity in ME/CFS, considering two possibilities: (a) Activation of immune-inflammatory pathways is secondary to HPA axis hypofunction via attenuated negative feedback mechanisms, or (b) chronic activated immune-inflammatory and O&NS pathways play a causative role in HPA axis hypoactivity. Electronic databases, i.e., PUBMED, Scopus, and Google Scholar, were used as sources for this narrative review by using keywords CFS, ME, cortisol, ACTH, CRH, HPA axis, glucocorticoid receptor, cytokines, immune, immunity, inflammation, and O&NS. Findings show that activation of immune-inflammatory and O&NS pathways in ME/CFS are probably not secondary to HPA axis hypoactivity and that activation of these pathways may underpin HPA axis hypofunction in ME/CFS. Mechanistic explanations comprise increased levels of tumor necrosis factor-α, T regulatory responses with elevated levels of interleukin-10 and transforming growth factor-β, elevated levels of nitric oxide, and viral/bacterial-mediated mechanisms. HPA axis hypoactivity in ME/CFS is most likely a consequence and not a cause of a wide variety of activated immune-inflammatory and O&NS pathways in that illness.

Inhibition of IL-6 trans-signaling in the brain increases sociability in the BTBR mouse model of autism

Autism is a severe neurodevelopmental disorder with a large population prevalence, characterized by abnormal reciprocal social interactions, communication deficits, and repetitive behaviors with restricted interests. The BTBR T(+)Itpr3(tf) (BTBR) mice have emerged as strong candidates to serve as models of a range of autism-relevant behaviors. Increasing evidences suggest that interleukin (IL)-6, one of the most important neuroimmune factors, was involved in the pathophysiology of autism. It is of great importance to further investigate whether therapeutic interventions in autism can be achieved through the manipulation of IL-6. Our previous studies showed that IL-6 elevation in the brain could mediate autistic-like behaviors, possibly through the imbalances of neural circuitry and impairments of synaptic plasticity. In this study, we evaluate whether inhibiting IL-6 signaling in the brain is sufficient to modulate the autism-like behaviors on the BTBR mice. The results showed that chronic infusion of an analog of the endogenous IL-6 trans-signaling blocker sgp130Fc protein increased the sociability in BTBR mice. Furthermore, no change was observed in the number of excitatory synapse, level of synaptic proteins, density of dentitic spine and postsynaptic density in BTBR cortices after inhibiting IL-6 trans-signaling. However, inhibition of IL-6 trans-signaling increased the evoked glutamate release in synaptoneurosomes from the cerebral cortex of BTBR mice. Our findings suggest that inhibition of excessive production of IL-6 may have selective therapeutic efficacy in treating abnormal social behaviors in autism.

The role of the hypothalamic-pituitary-adrenal axis in modulating seasonal changes in immunity

Seasonal changes in environmental conditions are accompanied by significant adjustment of multiple biological processes. In temperate regions, the day fraction, or photoperiod, is a robust environmental cue that synchronizes seasonal variations in neuroendocrine and metabolic function. In this work, we propose a semimechanistic mathematical model that considers the influence of seasonal photoperiod changes as well as cellular and molecular adaptations to investigate the seasonality of immune function. Our model predicts that the circadian rhythms of cortisol, our proinflammatory mediator, and its receptor exhibit seasonal differences in amplitude and phase, oscillating at higher amplitudes in the winter season with peak times occurring later in the day. Furthermore, the reduced photoperiod of winter coupled with seasonal alterations in physiological activity induces a more exacerbated immune response to acute stress, simulated in our studies as the administration of an acute dose of endotoxin. Our findings are therefore in accordance with experimental data that reflect the predominance of a proinflammatory state during the winter months. These changes in circadian rhythm dynamics may play a significant role in the seasonality of disease incidence and regulate the diurnal and seasonal variation of disease symptom severity.

The health effects of ambient PM2.5 and potential mechanisms

The impacts of ambient PM2.5 on public health have become great concerns worldwide, especially in the developing countries. Epidemiological and toxicological studies have shown that PM2.5 does not only induce cardiopulmonary disorders and/or impairments, but also contributes to a variety of other adverse health effects, such as driving the initiation and progression of diabetes mellitus and eliciting adverse birth outcomes. Of note, recent findings have demonstrated that PM2.5 may still pose a hazard to public health even at very low levels (far below national standards) of exposure. The proposed underlying mechanisms whereby PM2.5 causes adverse effects to public health include inducing intracellular oxidative stress, mutagenicity/genotoxicity and inflammatory responses. The present review aims to provide an brief overview of new insights into the molecular mechanisms linking ambient PM2.5 exposure and health effects, which were explored with new technologies in recent years.

Role of neuro-immunological factors in the pathophysiology of mood disorders

Mood disorders, despite the widespread availability of monoamine-based antidepressant treatments, are associated with persistently high rates of disability, together with elevated rates of mortality due to suicide, cardiovascular disease, and other causes. The development of more effective treatments has been hindered by the lack of knowledge about the etiology and pathogenesis of mood disorders. An emerging area of science that promises novel pathways to antidepressant and mood stabilizing therapies surrounds evidence that immune cells and their signaling play a major role in the pathophysiology of major depressive disorder (MDD) and bipolar disorder (BD). Here, we review evidence that the release of neuroactive cytokines, particularly interleukins such as IL-1β, IL-6, and TNF-α, is altered in these disorders and discuss mechanisms such as the ATP-gated ion channel P2X7, through which cytokine signaling can influence neuro-glial interactions. Brain P2X7, an emerging target and antagonism of P2X7 holds promise as a novel mechanism for targeting treatment-resistant depression. We further discuss the role of microglia and astroglia in central neuroinflammation and their interaction with the peripheral immune system We present extant clinical evidence that bolsters the role of neuroinflammation and neuroactive cytokines in mood disorders. To that end, the role of clinical imaging by probing neuroinflammatory markers is also discussed briefly. Finally, we present data using preclinical neuroinflammation models that produce depression-like behaviors in experimental animals to identify neuroinflammatory mechanisms which may aid in novel neuroimmune target identification for the development of exciting pharmacological interventions in mood disorders.

Comorbidity between depression and inflammatory bowel disease explained by immune-inflammatory, oxidative, and nitrosative stress; tryptophan catabolite; and gut-brain pathways

The nature of depression has recently been reconceptualized, being conceived as the clinical expression of activated immune-inflammatory, oxidative, and nitrosative stress (IO&NS) pathways, including tryptophan catabolite (TRYCAT), autoimmune, and gut-brain pathways. IO&NS pathways are similarly integral to the pathogenesis of inflammatory bowel disease (IBD). The increased depression prevalence in IBD associates with a lower quality of life and increased morbidity in IBD, highlighting the role of depression in modulating the pathophysiology of IBD.This review covers data within such a wider conceptualization that better explains the heightened co-occurrence of IBD and depression. Common IO&NS underpinning between both disorders is evidenced by increased pro-inflammatory cytokine levels, eg, interleukin-1 (IL-1) and tumor necrosis factor-α, IL-6 trans-signalling; Th-1- and Th-17-like responses; neopterin and soluble IL-2 receptor levels; positive acute phase reactants (haptoglobin and C-reactive protein); lowered levels of negative acute phase reactants (albumin, transferrin, zinc) and anti-inflammatory cytokines (IL-10 and transforming growth factor-β); increased O&NS with damage to lipids, proteinsm and DNA; increased production of nitric oxide (NO) and inducible NO synthase; lowered plasma tryptophan but increased TRYCAT levels; autoimmune responses; and increased bacterial translocation. As such, heightened IO&NS processes in depression overlap with the biological underpinnings of IBD, potentially explaining their increased co-occurrence. This supports the perspective that there is a spectrum of IO&NS disorders that includes depression, both as an emergent comorbidity and as a contributor to IO&NS processes. Such a frame of reference has treatment implications for IBD when "comorbid" with depression.

IgA/IgM responses to tryptophan and tryptophan catabolites (TRYCATs) are differently associated with prenatal depression, physio-somatic symptoms at the end of term and premenstrual syndrome

There is some evidence that lowered tryptophan and an activated tryptophan catabolite (TRYCAT) pathway play a role in depression, somatoform disorder, and postpartum blues. The aim of this study is to delineate the associations between the TRYCAT pathway and premenstrual syndrome (PMS) and perinatal depressive and physio-somatic symptoms. We examine the associations between end of term serum IgM and IgA responses to tryptophan and 9 TRYCATs in relation to zinc, C-reactive protein (CRP), and haptoglobin and prenatal physio-somatic (previously known as psychosomatic) symptoms (fatigue, back pain, muscle pain, dyspepsia, obstipation) and prenatal and postnatal depression and anxiety symptoms as measured using the Edinburgh Postnatal Depression Scale (EPDS), Hamilton Depression Rating Scale (HAMD), and Spielberger's State Anxiety Inventory (STAI). We included pregnant females with (n = 24) and without depression (n = 25) and 24 non-pregnant females. There were no significant associations between the IgA/IgM responses to tryptophan and TRYCATs and prenatal and postnatal depression/anxiety symptoms, except for lowered IgA responses to anthranilic acid in prenatal depression. A large part of the variance in IgA responses to most TRYCATs was explained by PMS and haptoglobin (positively) and CRP (inversely) levels. The IgA responses to TRYCATs were significantly increased in PMS, in particular picolinic, anthranilic, xanthurenic and kynurenic acid, and 3OH-kynurenine. Variance (62.5%) in physio-somatic symptoms at the end of term was explained by PMS, previous depressions, zinc (inversely), CRP and haptoglobin (both positively), and the IgM responses to quinolinic acid (positively), anthranilic acid, and tryptophan (both negatively). The results suggest that mucosa-derived TRYCAT pathway activation is significantly associated with PMS, but not with perinatal depression/anxiety symptoms. Physio-somatic symptoms in pregnancy have an immune-inflammatory pathophysiology. Induction of the TRYCAT pathway appears to be more related to physio-somatic than to depression symptoms.

Potential antiinflammatory effects of acupuncture in a chronic stress model of depression in rats

Accumulating evidence indicates that inflammation may contribute to the pathophysiology of depression. Acupuncture in traditional Chinese medicine has been considered an effective treatment for depression. However, whether the mechanisms that underlie the antidepressant effect of acupuncture are related to its antiinflammatory properties remains unclear. In the present study, rats were exposed to chronic unpredictable mild stress (CUMS) for 28 days to induce depressive-like behavior. Body weight, sucrose preference, and locomotor activity in the open field were measured. After the behavioral tests, reverse transcription polymerase chain reaction was used to determine the mRNA expression of proinflammatory cytokines (interleukin-1β [IL-1β], interleukin-6 [IL-6], and tumor necrosis factor-α [TNF-α]), and enzyme-linked immunosorbent assay was used to detect cytokine concentrations. CUMS rats exhibited decrease in body weight, sucrose preference, and locomotor activity in the open field test. Chronic acupuncture and fluoxetine treatment reversed CUMS-induced depressive-like behavior. Compared with control rats, the mRNA and protein expression of IL-1β, IL-6, and TNF-α in the hippocampus and prefrontal cortex and cytokine concentrations in serum significantly increased in CUMS rats. Acupuncture and fluoxetine treatment significantly decreased the levels of proinflammatory cytokines in the hippocampus, prefrontal cortex, and serum. These results suggest that acupuncture has antidepressant-like effects, and its mechanism of action appears to involve the inhibition of proinflammatory cytokines.

The role of oxidative and nitrosative stress in accelerated aging and major depressive disorder

Major depressive disorder (MDD) affects millions of individuals and is highly comorbid with many age associated diseases such as diabetes mellitus, immune-inflammatory dysregulation and cardiovascular diseases. Oxidative/nitrosative stress plays a fundamental role in aging, as well as in the pathogenesis of neurodegenerative/neuropsychiatric disorders including MDD. In this review, we critically review the evidence for an involvement of oxidative/nitrosative stress in acceleration of aging process in MDD. There are evidence of the association between MDD and changes in molecular mechanisms involved in aging. There is a significant association between telomere length, enzymatic antioxidant activities (SOD, CAT, GPx), glutathione (GSH), lipid peroxidation (MDA), nuclear factor κB, inflammatory cytokines with MDD. Major depression also is characterized by significantly lower concentration of antioxidants (zinc, coenzyme Q10, PON1). Since, aging and MDD share a common biological base in their pathophysiology, the potential therapeutic use of antioxidants and anti-aging molecules in MDD could be promising.

Acute experimental changes in mood state regulate immune function in relation to central opioid neurotransmission: a model of human CNS-peripheral inflammatory interaction

Although evidence shows depressed moods enhance risk for somatic diseases, molecular mechanisms underlying enhanced somatic susceptibility are ill-defined. Knowledge of these molecular mechanisms will inform development of treatment and prevention strategies across comorbid depressive and somatic illnesses. Existing evidence suggests that interleukin-18 (IL-18; an IL-1 family cytokine) is elevated in depression and implicated in pathophysiology underlying comorbid medical illnesses. We previously identified strong associations between baseline IL-18 and μ-opioid receptor availability in major depressive disorder (MDD) volunteers. Combined with the evidence in animal models, we hypothesized that experimental mood induction would change IL-18, the extent proportional to opioid neurotransmitter release. Using the Velten technique in a [(11)C]carfentanil positron emission tomography neuroimaging study, we examined the impact of experimentally induced mood (sad, neutral) on plasma IL-18 and relationships with concurrent changes in the central opioid neurotransmission in 28 volunteers (healthy, MDD). Results showed mood induction impacted IL-18 (F2,25=12.2, P<0.001), sadness increasing IL-18 (T27=2.6, P=0.01) and neutral mood reducing IL-18 (T27=-4.1, P<0.001). In depressed volunteers, changes in IL-18 were more pronounced (F2,25=3.6, P=0.03) and linearly proportional to sadness-induced μ-opioid activation (left ventral pallidum, bilateral anterior cingulate cortices, right hypothalamus and bilateral amygdala). These data demonstrate that dynamic changes of a pro-inflammatory IL-1 superfamily cytokine, IL-18, and its relationship to μ-opioid neurotransmission in response to experimentally induced sadness. Further testing is warranted to delineate the role of neuroimmune interactions involving IL-18 in enhancing susceptibility to medical illness (that is, diabetes, heart disease and persistent pain states) in depressed individuals.

Role of Neuro-Immunological Factors in the Pathophysiology of Mood Disorders: Implications for Novel Therapeutics for Treatment Resistant Depression

Mood disorders are associated with persistently high rates of morbidity and mortality, despite the widespread availability of antidepressant treatments. One limitation to extant therapeutic options has been that nearly all approved antidepressant pharmacotherapies exert a similar primary action of blocking monoamine transporters, and few options exist for transitioning treatment resistant patients to alternatives with distinct mechanisms. An emerging area of science that promises novel pathways to antidepressant and mood-stabilizing therapies has followed from evidence that immunological factors play major roles in the pathophysiology of at least some mood disorder subtypes. Here we review evidence that the compounds that reduce the release or signaling of neuroactive cytokines, particularly IL-1β, IL-6, and TNF-α, can exert antidepressant effects in subgroups of depressed patients who are identified by blood-based biomarkers associated with inflammation. Within this context we discuss the role of microglia in central neuroinflammation, and the interaction between the peripheral immune system and the central synaptic microenvironment during and after neuroinflammation. Finally we review data using preclinical neuroinflammation models that produce depression-like behaviors in experimental animals to guide the discovery of novel neuro-immune drug targets.

The Neurobiology of Bipolar Disorder: An Integrated Approach

Bipolar disorder is a heterogeneous condition with myriad clinical manifestations and many comorbidities leading to severe disabilities in the biopsychosocial realm. The objective of this review article was to underline recent advances in knowledge regarding the neurobiology of bipolar disorder. A further aim was to draw attention to new therapeutic targets in the treatment of bipolar disorder. To accomplish these goals, an electronic search was undertaken of the PubMed database in August 2015 of literature published during the last 10 years on the pathophysiology of bipolar disorder. A wide-ranging evaluation of the existing work was done with search terms such as "mood disorders and biology," "bipolar disorder and HPA axis," "bipolar disorder and cytokines," "mood disorders and circadian rhythm," "bipolar disorder and oxidative stress," etc. This endeavor showed that bipolar disorder is a diverse condition sharing neurobiological mechanisms with major depressive disorder and psychotic spectrum disorders. There is convincing evidence of crosstalk between different biological systems that act in a deleterious manner causing expression of the disease in genetically predisposed individuals. Inflammatory mediators act in concert with oxidative stress to dysregulate hormonal, metabolic, and circadian homeostasis in precipitating and perpetuating the illness. Stress, whether biologically or psychologically mediated, is responsible for the initiation and progression of the diathesis. Bipolar spectrum disorders have a strong genetic component; severe life stresses acting through various paths cause the illness phenotype.

Immune malfunction in the GPR39 zinc receptor of knockout mice: Its relationship to depressive disorder

Depression is a serious psychiatric disorder affecting not only the monaminergic, glutamatergic, and GABAergic neurosystems, but also the immune system. Patients suffering from depression show disturbance in the immune parameters as well as increased susceptibility to infections. Zinc is well known as an anti-inflammatory agent, and its link with depression has been proved, zinc deficiency causing depression- and anxiety-like behavior with immune malfunction. It has been discovered that trace-element zinc acts as a neurotransmitter in the central nervous system via zinc receptor GPR39. In this study we investigated whether GPR39 knockout would cause depressive-like behavior as measured by the forced swim test, and whether these changes would coexist with immune malfunction. In GPR39 knockout mice versus a wild-type control we found: i) depressive-like behavior; ii) significantly reduced thymus weight; (iii) reduced cell viability of splenocytes; iv) reduced proliferative response of splenocytes; and v) increased IL-6 production of splenocytes after ConA stimulation and decreased IL-1b and IL-6 release after LPS stimulation. The results indicate depressive-like behavior in GPR39 KO animals with an immune response similar to that observed in depressive disorder. Here for the first time we show immunological changes under GPR39-deficient conditions.