Increased serum IL-6 and IL-1 receptor antagonist concentrations in major depression and treatment resistant 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.

Antidepressant-like effects of dietary gardenia blue pigment derived from genipin and tyrosine

Gardenia blue pigments derived from genipin reacting with amino acids have been used as natural food colorants for nearly 30 years in East Asia. However, their pharmacological effects, especially antidepressant-like effects, have not been reported so far. In this study, one of the gardenia blue pigments, was obtained from the reaction of genipin with tyrosine (genipin-tyrosine derivant (GTD)), and its antidepressant-like effects were investigated in lipopolysaccharide (LPS) or chronic unpredictable mild stress (CUMS) models. The results showed that GTD could attenuate depressive-like behaviors in both animal models. GTD reversed the LPS-induced cytokine increase of TNF-α, IL-6, and corticosterone (CORT) in mice plasma and hippocampus. In CUMS rats, GTD treatment significantly reduced hypothalamic-pituitary-adrenal (HPA) axis-related stress hormone levels in plasma including those of CORT, adrenocorticotropic hormone (ACTH), and corticotropin-releasing hormone (CRH). Besides, GTD increased plasma testosterone and hippocampal brain-derived neurotrophic factor (BDNF) levels in CUMS rats. GTD increased serotonin (5-HT), dopamine (DA), and norepinephrine (NE) in rat hippocampus and corpus striatum. Consistently, hippocampal metabolomic analysis demonstrated that GTD restored monoamine neurotransmitter metabolism, mitochondrial oxidative function, and membrane structural integrity. Our data suggested that GTD produced antidepressant-like activity through the restoration of the HPA axis hormone balance and the regulation of neurotransmitter release.

SCI and depression: Does inflammation commandeer the brain?

The incidence of depression is almost twice as high in the spinally injured population compared to the general population. While this incidence has long been attributed to the psychological, economic, and social burdens that accompany spinal cord injury (SCI), data from animal studies indicate that the biology of SCI may play an important role in the development of depression. Inflammation has been shown to impact stress response in rodents and humans, and inflammatory cytokines have been associated with depression for decades. The inflammation inherent to SCI may disrupt necessary mechanisms of mental homeostasis, such as serotonin production, dopamine production, and the hypothalamic pituitary adrenal axis. Additionally, gut dysbiosis that occurs after SCI can exacerbate inflammation and may cause further mood and behavior changes. These mediators combined may significantly contribute to the rise in depression seen after SCI. Currently, there are no therapies specific to depression after SCI. Elucidation of the molecular pathways that contribute to SCI-specific depression is crucial for the understanding of this disease and its potential treatments.

Association of purinergic receptor P2RX7 gene polymorphisms with depression symptoms

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Neuroendocrine and neurophysiological effects of interleukin 6 in rheumatoid arthritis

RA is a chronic, systemic, autoimmune disease characterized by inflammation and degradation of the joints, causing significant negative impact on quality of life. In addition to joint disease, symptoms and co-morbidities associated with RA-namely pain, fatigue and mood disorders-are often as debilitating as the disease itself. The pro-inflammatory cytokine IL-6 plays a critical role in RA-associated pathology. However, a greater understanding of the translational effects of IL-6 outside of the immune system is needed. This review discusses our current understanding of emerging aspects of IL-6 in RA-associated pain, fatigue and mood disorders such as depression and anxiety. This review also describes the clinical effects of IL-6 inhibition on these symptoms and co-morbidities in patients with RA.

Repeated social defeat in female mice induces anxiety-like behavior associated with enhanced myelopoiesis and increased monocyte accumulation in the brain

Anxiety and mood disorders affect both men and women. The majority of experimental models of stress, however, are completed using only male animals. For repeated social defeat (RSD), a rodent model, this is due to the inherent difficulty in eliciting male aggression toward female mice. To address this limitation, a recent study showed that a DREADD-based activation of the ventrolateral subdivision of the ventromedial hypothalamus (VMHvl) was effective in inducing aggressive behavior in male mice towards females in a social defeat paradigm. Therefore, the goal of this study was to determine if this modified version of RSD in females elicited behavioral, physiological, and immune responses similar to those reported in males. Here, we show that female mice subjected to RSD with the male DREADD aggressor developed anxiety-like behavior and social avoidance. These behavioral alterations coincided with enhanced neuronal and microglial activation in threat-appraisal regions of the brain. Moreover, stressed female mice had an enhanced peripheral immune response characterized by increased myelopoiesis, release of myeloid cells into circulation, and monocyte accumulation in the spleen and brain. These results are consistent with previously reported findings that male mice exposed to RSD exhibited increased fear and threat appraisal responses, enhanced myelopoiesis, myeloid cell release and trafficking, and anxiety-like behavior. These findings validate that RSD is a relevant model to study stress responses in female mice.

Mir363-3p attenuates post-stroke depressive-like behaviors in middle-aged female rats

Women are more likely to develop Post Stroke Depression (PSD) than men and generally do not respond well to anti-depressants with age. This study investigated the effect of microRNA mir363-3p treatment on PSD using a physiologically-relevant animal model. Our previous work showed that mir363-3p treatment, delivered post-stroke, effectively reduces infarct volume in the acute phase of stroke in middle-aged females but not males. Middle-aged female Sprague Dawley rats were tested for baseline sensory motor function and depressive-like behaviors, and then subjected to ischemic stroke via middle cerebral artery occlusion (MCAo) or sham surgery. Animals received either control oligos (MCAo+scrambled, Sham+scrambled) or mir363-3p (MCAo+mir363-3p, Sham+mir363-3p) treatment 4 h later. Sensory motor function and depressive-like behaviors were reassessed up to 100 d after stroke, and circulating levels of IL-6, TNF-alpha and Brain-Derived Neurotrophic Factor (BDNF) were quantified at regular intervals. Prior to termination, Fluorogold was injected into the striatum to assess meso-striatal projections. MCAo+scrambled animals had impaired sensorimotor performance in the acute phase (5 days) of stroke and developed anhedonia, decreased sociability and increased helplessness in the chronic phase. MCAo+mir363-3p animals showed significantly less sensory motor impairment and fewer depressive-like behaviors. IL-6 and TNF-alpha were elevated transiently at 4 weeks after MCAo in both groups. BDNF levels decreased progressively after stroke in the MCAo+scrambled group, and this was attenuated in the mir363-3p group. The number of retrogradely-labeled SNc and VTA cells was reduced in the ischemic hemisphere of the MCAo+scrambled group. In contrast, there was no interhemispheric difference in the number of retrogradely-labeled SNc and VTA cells of MCAo+mir363-3p treated animals. Our results support a therapeutic role for mir363-3p for long-term stroke disability.

Paradoxical Effect of LTB4 on the Regulation of Stress-Induced Corticosterone Production

Depression is a mental illness with a complex and multifactorial etiology, which has been associated with stress and inflammation. Infections, autoimmune diseases, envenomation, and trauma induce an inflammatory response that is characterized by increasing levels of circulating cytokines (e.g., IL-1β) and lipid mediators [e.g., PGE₂ and leukotrienes B₄ (LTB₄)]. Recently, we showed that LTB₄ production by the 5-lipoxygenase (5-LO) pathway regulates IL-1β and PGE₂ release, reducing tissue damage in a model of sterile inflammation. Since IL-1β and PGE₂ increase in serum of stressed patients and potentially trigger depression, we used an animal model of chronic unpredictable stress (CUS) to investigate the potential impact of LTB₄ over depression-like symptoms. At basal conditions, 5-LO deficiency (Alox5^−/−) reduces the preference for sucrose, while inducing a higher immobilization time on the tail suspension test when compared 129sv. Moreover, Alox5^−/− mice present increased caspase-1 expression and elevated levels of IL-1β, IL-17 and PGE₂ in the spleen, with increasing corticosterone levels in the frontal cortex but reducing systemic levels. Compared to 129sv mice, CUS induced higher levels of systemic, frontal cortex and hippocampal corticosterone, and also reduced sucrose preference, increased levels of splenic IL-1β, IL-17 and PGE₂ and reduced levels of LTB₄. Interestingly, CUS exposure did not alter the reduced sucrose preference shown by Alox5^−/− mice but greatly enhanced splenic PGE₂ production. Compared to Alox5^−/− mice at basal conditions, CUS exposure also increased levels of systemic corticosterone, which remained lower than those of CUS-129sv animals. We also observed that treatment with LTB₄ decreased caspase-1 expression and systemic levels of corticosterone in CUS-Alox5^−/− mice but there was no significant impact on the reduced sucrose preference. Our results demonstrate that LTB₄ controls the hypothalamic-pituitary-adrenal (HPA) axis by regulating levels of systemic corticosterone associated with the repression of caspase-1 expression and production of inflammatory mediators. One limitation of our study is that 129sv and Alox5^−/− mice were not littermates, not sharing, therefore, the same intra-uterine and preweaning environment. Even so, taken together our results indicate that 5-LO activity is critical for the regulation of stress-induced symptoms, suggesting that the Alox5^−/− mouse could be a natural model of corticosterone-independent reduced reward sensitivity.

Reversal of a Treatment-Resistant, Depression-Related Brain State with the Kv7 Channel Opener Retigabine

Neuroinflammation is associated with increased vulnerability to diverse psychiatric conditions, including treatment-resistant major depressive disorder (MDD). Here we assessed whether high fat diet (HFD) induced neuroinflammation may be suitable to model a treatment-resistant depressive-like brain state in mice. Male and female mice were fed a HFD for 18 weeks, followed by quantitation of glucose tolerance, inflammatory markers of brain tissue (TNFα, IL-6, IL-1β, Iba-1), neural excitability in the prelimbic cortex (PLC), as well as assessment of emotional reactivity and hedonic behavior in a battery of behavioral tests. In addition, we assessed the behavioral responsiveness of mice to fluoxetine, desipramine, ketamine, and the Kv7 channel opener and anticonvulsant retigabine. HFD exposure led to glucose intolerance and neuroinflammation in male mice, with similar but non-significant trends in females. Neuroinflammation of males was associated with anxious-depressive-like behavior and defects in working memory, along with neural hyperexcitability and increased I_h currents of pyramidal cells in the PLC. The behavioral changes were largely resistant to chronic treatment with fluoxetine and desipramine, as well as ketamine. By contrast, retigabine (also known as ezogabine) normalized neural excitability and I_h currents recorded from slices of HFD-treated animals and significantly ameliorated most of the behavioral impairments, without effects in control diet exposed animals. Thus, treatment resistant depressive-like brain states that are associated with chronic neuroinflammation may involve hyperexcitability of pyramidal neurons and may be effectively treated by retigabine.

Central and Peripheral Inflammation Link Metabolic Syndrome and Major Depressive Disorder

Metabolic syndrome and major depression are two of the most common and debilitating disorders worldwide, occurring with significant rates of comorbidity. Recent studies have uncovered that each of these conditions is associated with chronic, low-grade inflammation. This is characterized by increased circulating pro-inflammatory cytokines, altered leukocyte population frequencies in blood, accumulation of immune cells in tissues including the brain, and activation of these immune cells. Cytokines that become elevated during obesity can contribute to the progression of metabolic syndrome by directly causing insulin resistance. During chronic stress, there is evidence that these cytokines promote depression-like behavior by disrupting neurotransmitter synthesis and signal transduction. Animal models of obesity and depression have revealed a bi-directional relationship whereby high-fat feeding and chronic stress synergize and exacerbate metabolic dysregulation and behavioral abnormalities. Although far from conclusive, emerging evidence suggests that inflammation in the central and peripheral immune system may link metabolic syndrome to major depressive disorder. In this review, we will synthesize available data supporting this view and identify critical areas for future investigation.

Inflammatory profiles of severe treatment-resistant depression

BACKGROUND

Treatment-resistant depression (TRD) contributes substantially to the burden of mood disorders and is undoubtedly an important subpopulation in whom there are clear unmet treatment needs. Despite a paucity of research focusing specifically on TRD, recent studies indicate that inflammatory activity may be particularly elevated in these patients.

METHODS

36 patients with TRD were investigated longitudinally before and after undertaking a specialist inpatient treatment program. 27 inflammatory proteins were compared between patients and a matched sample of non-depressed controls, as well as between treatment responders and non-responders. Treatment outcomes were calculated from depression severity scores before and after admission, and at a long-term follow-up 3-12 months after discharge.

RESULTS

TRD patients had higher levels of numerous inflammatory proteins than controls, and elevated interleukins 6 and 8, tumour necrosis factor, c-reactive protein and macrophage inflammatory protein-1 were associated with poorer treatment outcomes. A separate set of proteins (either anti-inflammatory in nature or attenuated at baseline) showed increases during treatment, regardless of clinical response. Participants with the greatest elevations in inflammation tended to be older, more cognitively impaired and more treatment-resistant at baseline.

LIMITATIONS

The small sample and large number of comparisons examined in this study must be taken into account when interpreting these results.

CONCLUSIONS

However, this study provides empirical support for theories that more severe, chronic or treatment-resistant depressive disorders are associated with dysregulated inflammatory activity. If a predictor or predictors of response in TRD are established, improved and targeted care might be more reliably provided to this vulnerable population.

Current and emerging biomarkers of frailty in the elderly

The term “frailty” is used to describe a subset of older adults who appear weaker and more vulnerable than their age-matched counterparts, despite having similar comorbidities, demography, sex, and age. The diagnosis of frailty is usually clinical and based on specific criteria, which are sometimes inconsistent. Therefore, there is an increasing need to identify and validate robust biomarkers for this condition. In this review, we summarize current evidence on the validity and practicality of the most commonly used biomarkers for frailty, while also comparing them with new upcoming strategies to identify this condition.

Old Friends, immunoregulation, and stress resilience

There is a considerable body of evidence indicating that chronic adverse experience, especially chronic psychosocial stress/trauma, represents a major risk factor for the development of many somatic and affective disorders, including inflammatory bowel disease (IBD) and posttraumatic stress disorder (PTSD). However, the mechanisms underlying the development of chronic stress-associated disorders are still in large part unknown, and current treatment and prevention strategies lack efficacy and reliability. A greater understanding of mechanisms involved in the development and persistence of chronic stress-induced disorders may lead to novel approaches to prevention and treatment of these disorders. In this review, we provide evidence indicating that increases in immune (re-)activity and inflammation, potentially promoted by a reduced exposure to immunoregulatory microorganisms ("Old Friends") in today's modern society, may be causal factors in mediating the vulnerability to development and persistence of stress-related pathologies. Moreover, we discuss strategies to increase immunoregulatory processes and attenuate inflammation, as for instance contact with immunoregulatory Old Friends, which appears to be a promising strategy to promote stress resilience and to prevent/treat chronic stress-related disorders.

Rheumatoid arthritis and depression: an inflammatory perspective

The coexistence of immune-mediated inflammatory diseases with depression has long been recognised. Data that illustrate the intimate associations between peripheral and brain immune responses raise the possibility of shared pathophysiological mechanisms. These associations include the negative effects of proinflammatory cytokines on monoaminergic neurotransmission, neurotrophic factors, and measures of synaptic plasticity. The evidence supporting this association is accumulating and includes findings from clinical trials of immunomodulatory therapy, indicating that these interventions can provide benefits to mental health independent of improvements in physical disease scores. In this Review, we assess this evidence in relation to rheumatoid arthritis and depression, with a focus on innate immune and molecular responses to inflammation, and discuss the challenges of assessing causation in this population, acknowledging the difficulty of assessing the confounding and contributory effects of pain and fatigue. We also discuss how future clinical and preclinical research might improve diagnosis of depression in people with rheumatoid arthritis and shed light on mechanisms that could be substrates for therapeutic interventions.

Longitudinal association between inflammatory markers and specific symptoms of depression in a prospective birth cohort

BACKGROUND

Low-grade inflammation is associated with depression, but studies of specific symptoms are relatively scarce. Association between inflammatory markers and specific symptoms may provide insights into potential mechanism of inflammation-related depression. Using longitudinal data, we have tested whether childhood serum interleukin 6 (IL-6) and C-reactive protein (CRP) levels are associated with specific depressive symptoms in early adulthood.

METHODS

In the ALSPAC birth cohort, serum IL-6 and CRP levels were assessed at age 9 years and 19 depressive symptoms were assessed at age 18 years. We used modified Poisson generalised linear regression with robust error variance to estimate the risk ratio (RR) and 95% confidence interval (95% CI) for each depressive symptom. In addition, we used confirmatory factor analysis to create two continuous latent variables representing somatic/neurovegetative and psychological dimension scores. Structural equation modelling was used to test the associations between IL-6 and these dimension scores.

RESULTS

Based on data from 2731 participants, IL-6 was associated with diurnal mood variation, concentration difficulties, fatigue and sleep disturbances. The adjusted RRs for these symptoms at age 18 years for participants in top, compared with bottom, third of IL-6 at age 9 years were 1.75 (95% CI, 1.13-2.69) for diurnal mood variation, 1.50 (95% CI, 1.11-2.02) for concentration difficulties, 1.31 (95% CI, 1.12-1.54) for fatigue, and 1.24 (95% CI, 1.01-1.52) for sleep disturbances. At dimension level, IL-6 was associated with both somatic/neurovegetative (β = 0.059, SE = 0.024, P = 0.013) and psychological (β = 0.056, SE = 0.023, P = 0.016) scores.

CONCLUSIONS

Inflammation is associated with specific symptoms of depression. Associations with so-called somatic/neurovegetative symptoms of depression such as fatigue, sleep disturbances and diurnal mood variation indicate that these symptoms could be useful treatment targets and markers of treatment response in clinical trials of anti-inflammatory treatment for depression.

miR‑155 mediates inflammatory injury of hippocampal neuronal cells via the activation of microglia

MicroRNA (miR)-155 has a crucial role in various cellular functions, including differentiation of hematopoietic cells, immunization, inflammation and cardiovascular diseases. The present study aimed to investigate the roles and mechanisms of miR-155 in treatment-resistant depression (TRD). A Cell Counting Kit-8 assay and flow cytometry were performed to assess the cell viability and apoptosis of microglial cells, respectively. Western blotting and reverse transcription-quantitative polymerase chain reaction assays were used to evaluate the associated protein and mRNA expression, respectively. The results revealed that miR-155 reduced the cell viability of BV-2 microglial cells, and miR-155 enhanced the expression levels of pro-inflammatory cytokines in BV-2 microglial cells. Furthermore, conditioned medium from miR-155-treated microglia decreased the cell viability of HT22 hippocampal cells. miR-155-treated microglia increased the apoptosis of neuronal hippocampal cells by modulating the expression levels of apoptosis regulator Bax, apoptosis regulator Bcl-2, pro-caspase-3 and cleaved-caspase-3. The cell cycle distribution was disrupted by miR-155-treated microglia through induction of S phase arrest. Furthermore, the overexpression of suppressor of cytokine signaling 1 reversed the pro-apoptotic effect of activated microglia on hippocampal neuronal cells. In conclusion, the present results suggested that miR-155 mediated the inflammatory injury in hippocampal neuronal cells by activating the microglial cells. The potential effects of miR-155 on the activation of microglial cells suggest that miR-155 may be an effective target for TRD therapies.

Evaluation of Serum Interleukin-6 and C-reactive Protein Levels in Drug-naïve Major Depressive Disorder Patients

Background Major depressive disorder (MDD) is a disabling health problem with a very high global prevalence and burden. Alteration of inflammatory markers in depression is of growing interest to many psychiatry researchers. This study aimed to examine the serum levels of interleukin-6 (IL-6) and C-reactive protein (CRP) in MDD patients to find out their association with depression. Materials and methods The present study recruited 88 MDD patients and 86 control subjects matched by age, gender, and body mass index (BMI). The Hamilton depression rating scale (Ham-D) was used on all patients to measure their severity of depression. Serum levels of IL-6 and CRP were analyzed by commercially available enzyme-linked immunosorbent assay (ELISA) kits (Abcam, Cambridge, MA, USA). Results The mean values of serum levels of IL-6 and CRP were 2.94 ± 0.12 pg/mL and 0.99 ± 0.02 mg/L for the patient group and 2.42 ± 0.21 pg/mL and 1.09 ± 0.06 mg/L for the control group, respectively. We found significantly elevated concentrations of serum IL-6 in MDD patients compared with control subjects (p < 0.001). However, the alteration of serum CRP levels was not significant between the groups (p = 0.126). Ham-D scores of patients were positively correlated with serum IL-6 (r = 0.552; p = 0.004) and CRP (r = 0.621; p < 0.001) levels. Moreover, serum IL-6 and CRP levels were observed to be positively correlated (r = 0.452; p = 0.043) with each other in depression. Conclusions The present study suggests that increased serum IL-6 level might be a contributing factor to the pathogenesis of depression.

Repetitive transcranial magnetic stimulation increases serum brain-derived neurotrophic factor and decreases interleukin-1β and tumor necrosis factor-α in elderly patients with refractory depression

Objective

To investigate the effects of repetitive transcranial magnetic stimulation (rTMS) on serum levels of brain-derived neurotrophic factor (BDNF), interleukin (IL)-1β, and tumor necrosis factor (TNF)-α in elderly patients with refractory depression.

Methods

A total of 58 elderly patients diagnosed with refractory depression between January 2015 and December 2016 were divided randomly into two groups: 29 patients who received rTMS and 29 controls without rTMS. Thirty healthy individuals were also enrolled and all received rTMS. Serum levels of BDNF, IL-1β, and TNF-α were measured before the study (0 days), and at 48 hours and 1, 2, 3, and 4 weeks after the first TMS treatment.

Results

BDNF levels gradually increased with treatment duration in the rTMS group and were significantly higher compared with the control group. In contrast, IL-1β and TNF-α levels gradually decreased and were significantly lower than in the control group. None of the serum factors were affected by rTMS in the healthy individuals. BDNF levels were negatively correlated and IL-1β and TNF-α levels were positively correlated with Hamilton Depression Rating Scale-24 scores.

Conclusion

These results suggest that rTMS may increase BDNF and decrease IL-1β and TNF-α serum levels in elderly patients with refractory depression.

Proteomic Studies of Psychiatric Disorders

Many diseases result from programming effects in utero. This chapter describes recent advances in proteomic studies which have improved our understanding of the underlying pathophysiological pathways in the major psychiatric disorders, resulting in the development of potential novel biomarker tests. Such tests should be based on measurement of blood-based proteins given the ease of accessibility of this medium and the known connections between the periphery and the central nervous system. Most importantly, emerging biomarker tests should be developed on lab-on-a-chip and other handheld devices to enable point-of-care use. This should help to identify individuals with psychiatric disorders much sooner than ever before, which will allow more rapid treatment options for the best possible patient outcomes.

New lung cancer treatments (immunotherapy and targeted therapies) and their associations with depression and other psychological side effects as compared to chemotherapy

OBJECTIVE

Lung cancer carries a high prevalence of distress, anxiety and depression. New treatments, targeted therapy and immunotherapy have changed the disease course for subsets of patients and confer longer survival, but their psychological associations and possible mechanisms (e.g., inflammation and physical symptoms) are not well described.

METHOD

Patients with metastatic lung cancer undergoing systemic treatment (n = 109) were evaluated for distress, self-endorsed problems using the Distress Thermometer and Problem List, and depression and anxiety using the Hospital Anxiety and Depression Scale. Demography, cancer-related information, and inflammation were evaluated for their associations with chemotherapy, targeted therapy, and immunotherapy. Inflammation was measured by C-reactive protein, albumin, and neutrophil to lymphocyte ratio.

RESULTS

Chemotherapies were given most often followed by immunotherapy and targeted therapies. Depression and anxiety were endorsed by 23.9%, respectively, and 41.1% had significant distress. Chemotherapy was associated with depression (p = .006) and inflammation (p < .001). Physical symptoms were the same among treatment types. Targeted therapy and immunotherapy predicted for less depression (p = .04, p = .04 respectively) than chemotherapy when controlling for age, sex, and performance status however these predictors where not significant when controlled for inflammation.

CONCLUSION

New immunotherapy and targeted therapies are associated with less depression and inflammation among patients who are living longer while their physical symptoms are the same.

Role of Inflammation in Depression and Treatment Implications

Approximately one third of depressed patients fail to respond to currently available antidepressant therapies. Therefore, new conceptual frameworks are needed to identify pathophysiologic pathways and neurobiological targets for the development of novel treatment strategies. In this regard, recent evidence suggests that inflammation may contribute to symptoms relevant to a number of psychiatric disorders and particularly depression. Numerous studies (including meta-analyses) have found elevated peripheral and central inflammatory cytokines and acute phase proteins in depression. Chronic exposure to increased inflammation is thought to drive changes in neurotransmitters and neurocircuits that lead to depressive symptoms and that may also interfere with or circumvent the efficacy of antidepressants. Indeed, patients with high inflammation have been shown to exhibit poor response to conventional antidepressant therapies. Recent developments in our ability to understand and measure the effects of inflammation on the brain in patients have opened new doors for the testing of novel treatment strategies that target the immune system or its consequences on neurotransmitter systems. Such recent developments in the field of behavioral immunology and their translational implications for the treatment of depression are discussed herein.

Factors influencing subjective symptoms in dry eye disease

AIM

To retrospectively investigate the association between dry eye symptoms and clinical or in vivo confocal microscopy parameters in patients with dry eye disease (DED), and to compare these parameters between eyes with DED and normal subjects.

METHODS

This retrospective, cross-sectional, controlled study comprised 25 consecutive patients with non-Sjögren dry eye disease and age- and sex-matched 25 healthy subjects. Each patient underwent a complete examination of the ocular surface in the following order: tear osmolarity measurements, InflammaDry test, tear break-up time, corneal fluorescein staining, Schirmer I test, subjective symptoms questionnaire using the dry eye-related quality-of-life score (DEQS), and in vivo confocal microscopy analysis of the central cornea. Beck depression inventory (BDI) as depressive scale and history of medications and smoking were also evaluated. Stepwise multiple regression analysis was used to assess the factors affecting the DEQS.

RESULTS

In univariate analysis, DEQS was associated with tear break-up time (ρ=-0.48, P=0.01), oral medications, such as hypotensive drug (ρ=0.56, P=0.004) and anti-depressant (ρ=0.57, P=0.003), and BDI (ρ=0.61, P=0.001) in patients with DED. In multiple regression analysis, explanatory variables relevant to the DEQS were the anti-depressant medications (P=0.04, partial regression coefficient B=21.04) and BDI (P=0.02, B=0.76, adjusted R ²=0.54) in these patients.

CONCLUSION

Our study shows a significant association between depression and dry eye symptoms. It suggests that dry eye symptoms associate with higher depressive symptoms and its medications, although our patients were not followed longitudinally.

C-reactive protein and its association with depression in patients receiving treatment for metastatic lung cancer

BACKGROUND

Depression is highly prevalent in lung cancer. Although there is a known association between inflammation and depression, this relationship has not been examined in patients with lung cancer who undergo treatment with immune and other targeted drug therapies. Peripheral blood C-reactive protein (CRP), a marker of systemic inflammation, may help identify metastatic lung cancer patients with inflammation-associated depression.

METHOD

Patients with metastatic lung cancer undergoing treatment were evaluated for depression using the Hospital Anxiety and Depression Scale (HADS). Inflammation (CRP and CRP cutoffs ≥1 and ≥3 mg/mL) and demographic and treatment variables were analyzed for association with depression.

RESULTS

One hundred nine consecutive participants exhibited an average plasma CRP concentration of 1.79 mg/mL (median, 0.75 mg/mL [standard deviation, 2.5 mg/mL), and 20.7% had a CRP concentration of ≥3.0 mg/mL; 23.9% met depression screening criteria (HADS ≥8). A log transformation of CRP was significantly correlated with depression severity (r = 0.47, P < .001). CRP was the only covariate to predict depression severity (P = .008) in a multivariate model including lung cancer disease subtype and type of systemic treatment. Receiver operating characteristic analysis indicated that CRP had moderate predictive accuracy in identifying elevated depression (area under the curve = 0.74). A cutoff of CRP ≥3.0 generated high specificity (88%) but identified only 50% of those with elevated depression.

CONCLUSION

Elevated CRP is associated with depression in patients with metastatic lung cancer. Thus, CRP may identify a subset of lung cancer patients with inflammation-induced depression and may be useful in predicting response to treatments that target inflammation or its downstream mediators on the brain.

Psoriasis and suicidality: A review of the literature

Psoriasis is a chronic systemic inflammatory skin disease, which has been associated with an increased risk of numerous medical and psychiatric comorbidities, including suicidality. Suicidality, which can be divided into the categories of suicidal ideation, suicide attempt, and completed suicide, is highly prevalent in the psoriasis population, and multiple studies have been published on the subject of psoriasis and suicidal ideation and behavior (SIB), including two recent meta-analyses. However, the available literature is limited and inconsistent, and the association between the two remains incompletely understood. The present review aims to cohesively synthesize and summarize the available evidence, while making a clinically relevant distinction between the sub-categories of suicidality, by examining not only the epidemiology of the association but also the plausible molecular mechanisms and the potential influence of biologic therapies. Additionally, this review aims to critically examine and understand the potential contribution of depression in the psoriasis and suicidality relationship. This will allow us to better understand the complex and multi-faceted relationship between psoriasis and suicidality, to identify those who may be most at risk for SIB, to make evidence-based clinical decisions regarding treatment and management, and to more completely address the needs of psoriasis patients.

Health, pre-disease and critical transition to disease in the psycho-immune-neuroendocrine network: Are there distinct states in the progression from health to major depressive disorder?

The psycho-immune-neuroendocrine (PINE) network is a regulatory network of interrelated physiological pathways that have been implicated in major depressive disorder (MDD). A model of disease progression for MDD is presented where the stable, healthy state of the PINE network (PINE physiome) undergoes progressive pathophysiological changes to an unstable but reversible pre-disease state (PINE pre-diseasome) with chronic stress. The PINE network may then undergo critical transition to a stable, possibly irreversible disease state of MDD (PINE pathome). Critical transition to disease is heralded by early warning signs which are detectible by biomarkers specific to the PINE network and may be used as a screening test for MDD. Critical transition to MDD may be different for each individual, as it is reliant on diathesis, which comprises genetic predisposition, intrauterine and developmental factors. Finally, we propose the PINE pre-disease state may form a "universal pre-disease state" for several non-communicable diseases (NCDs), and critical transition of the PINE network may lead to one of several frequently associated disease states (influenced by diathesis), supporting the existence of a common Chronic Illness Risk Network (CIRN). This may provide insight into both the puzzle of multifinality and the growing clinical challenge of multimorbidity.

Medial Forebrain Bundle Deep Brain Stimulation Reverses Anhedonic-Like Behavior in a Chronic Model of Depression: Importance of BDNF and Inflammatory Cytokines

Deep brain stimulation (DBS) of the medial forebrain bundle (MFB) displays a promising antidepressant effects in patients with treatment-refractory depression; however, a clear consensus on underlying mechanisms is still enigmatic. Herein, we investigated the effects of MFB-DBS on anhedonic-like behavior using the Froot Loops® consumption in a chronic unpredictable mild stress (CUS) model of depression, biochemical estimation of peripheral and central inflammatory cytokines, stress hormone, and brain-derived neurotrophic factor (BDNF). Seven days of MFB-DBS significantly reversed the 42-day CUS-generated anhedonic-like phenotype (p < 0.02) indicated by an increase in Froot Loops® consumption. Gross locomotor activity and body weight remained unaffected across the different groups. A dramatic augmentation of adrenocorticotropic hormone levels was seen in the plasma and cerebrospinal fluid (CSF) samples of CUS rats, which significantly reduced following MFB-DBS treatment. However, C-reactive protein levels were found to be unaffected. Interestingly, decreased levels of BDNF in the CUS animals were augmented in the plasma, CSF, and hippocampus following MFB-DBS, but remained unaltered in the nucleus accumbens (NAc). While multiplex assay revealed no change in the neuronal levels of inflammatory cytokines including IL-1α, IL-4, IL-10, IL-12, IL-13, and IL-17 in the neuroanatomical framework of the hippocampus and NAc, increased levels of IL-1β, IL-2, IL-5, IL-6, IL-7, IL-18, TNF-α, and INF-γ were seen in these brain structures after CUS and were differentially modulated in the presence of MFB stimulation. Here, we show that there is dysregulation of BDNF and neuroimmune mediators in a stress-driven chronic depression model, and that chronic MFB-DBS has the potential to undo these aberrations.

Nicotinamide's Ups and Downs: Consequences for Fertility, Development, Longevity and Diseases of Poverty and Affluence

To further explore the role of dietary nicotinamide in both brain development and diseases, particularly those of ageing. Articles cover neurodegenerative disease and cancer. Also discussed are the effects of nicotinamide, contained in meat and supplements and derived from symbionts, on the major transitions of disease and fertility from ancient times up to the present day. A key role for the tryptophan - NAD 'de novo' and immune tolerance pathway are discussed at length in the context of fertility and longevity and the transitions from immune paresis to Treg-mediated immune tolerance and then finally to intolerance and their associated diseases. Abstract: Nicotinamide in human evolution increased cognitive power in a positive feedback loop originally involving hunting. As the precursor to metabolic master molecule NAD it is, as vitamin B3, vital for health. Paradoxically, a lower dose on a diverse plant then cereal-based diet fuelled population booms from the Mesolithic onwards, by upping immune tolerance of the foetus. Increased tolerance of risky symbionts, whether in the gut or TB, that excrete nicotinamide co-evolved as buffers for when diet was inadequate. High biological fertility, despite disease trade-offs, avoided the extinction of Homo sapiens and heralded the dawn of a conscious, creative, and pro-fertility culture. Nicotinamide equity now would stabilise populations and prevent NAD-based diseases of poverty and affluence.

Protocol for the insight study: a randomised controlled trial of single-dose tocilizumab in patients with depression and low-grade inflammation

INTRODUCTION

Observational studies indicate a potentially causal role for interleukin 6 (IL-6), a proinflammatory cytokine, in pathogenesis of depression, but interventional studies based on patients with depression have not been conducted. Tocilizumab, anti-inflammatory drug, is a humanised monoclonal antibody that inhibits IL-6 signalling and is licensed in the UK for treatment of rheumatoid arthritis. The main objectives of this study are to test whether IL-6 contributes to the pathogenesis of depression and to examine potential mechanisms by which IL-6 affects mood and cognition. A secondary objective is to compare depressed participants with and without evidence of low-grade systemic inflammation.

METHODS AND ANALYSIS

This is a proof-of-concept, randomised, parallel-group, double-blind, placebo-controlled clinical trial. Approximately 50 participants with International Classification of Diseases 10th revision (ICD-10) diagnosis of depression who have evidence of low-grade inflammation, defined as serum high-sensitivity C reactive protein (hs-CRP) level ≥3 mg/L, will receive either a single intravenous infusion of tocilizumab or normal saline. Blood samples, behavioural and cognitive measures will be collected at baseline and after infusion around day 7, 14 and 28. The primary outcome is somatic symptoms score around day 14 postinfusion. In addition, approximately, 50 depressed participants without low-grade inflammation (serum hs-CRP level <3 mg/L) will complete the same baseline assessments as the randomised cohort.

ETHICS AND DISSEMINATION

The study has been approved by the South Central-Oxford B Research Ethics Committee (REC) (Reference: 18/SC/0118). Study findings will be published in peer-review journals. Findings will be also disseminated by conference/departmental presentations and by social and traditional media.

TRIAL REGISTRATION NUMBER

ISRCTN16942542; Pre-results.

Essential Role of Ovarian Hormones in Susceptibility to the Consequences of Witnessing Social Defeat in Female Rats

BACKGROUND

Women are at greater risk than men of developing depression and comorbid disorders such as cardiovascular disease. This enhanced risk begins at puberty and ends following menopause, suggesting a role for ovarian hormones in this sensitivity. Here we used a model of psychosocial witness stress in female rats to determine the stress-induced neurobiological adaptations that underlie stress susceptibility in an ovarian hormone-dependent manner.

METHODS

Intact or ovariectomized (OVX) female rats were exposed to five daily 15-minute witness-stress exposures. Witness-stress-evoked burying, behavioral despair, and anhedonia were measured. Cardiovascular telemetry was combined with plasma measurements of inflammation, epinephrine, and corticosterone as indices of cardiovascular dysfunction. Finally, levels of interleukin-1β and corticotropin-releasing factor were assessed in the central amygdala.

RESULTS

Witness stress produced anxiety-like burying, depressive-like anhedonia, and behavioral despair selectively in intact female rats, which was associated with enhanced sympathetic responses during stress, including increased blood pressure, heart rate, and arrhythmias. Moreover, intact female rats exhibited increases in 12-hour resting systolic pressure and heart rate and reductions in heart rate variability. Notably, OVX female rats remained resilient. Moreover, intact, but not OVX, female rats exposed to witness stress exhibited a sensitized cytokine and epinephrine response to stress and distinct increases in levels of corticotropin-releasing factor and interleukin-1β in the central amygdala.

CONCLUSIONS

Together these data suggest that ovarian hormones play a critical role in the behavioral, inflammatory, and cardiovascular susceptibility to social stress in female rats and reveal putative systems that are sensitized to stress in an ovarian hormone-dependent manner.

Involvement of Innate and Adaptive Immune Systems Alterations in the Pathophysiology and Treatment of Depression

Major depressive disorder (MDD) is a prevalent and debilitating disorder, often fatal. Treatment options are few and often do not provide immediate relief to the patients. The increasing involvement of inflammation in the pathology of MDD has provided new potential therapeutic avenues. Cytokine levels are elevated in the blood and cerebrospinal fluid of MDD patients whereas immune cells often exhibit an immunosuppressed phenotype in MDD patients. Blocking cytokine actions in patients exhibiting MDD show some antidepressant efficacy. However, the role of cytokines, and the immune response in MDD patients remain to be determined. We reviewed here the roles of the innate and adaptive immune systems in MDD, as well as potential mechanisms whereby the immune response might be regulated in MDD.

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.

Depression and Obesity: Integrating the Role of Stress, Neuroendocrine Dysfunction and Inflammatory Pathways

Literature on depression and obesity describes the relevance of the hypothalamic pituitary adrenal axis dysfunction, sympathetic nervous system (SNS) activation, and inflammatory processes as well as the interaction of genetic and environmental factors. Recent investigation in obesity highlights the involvement of several regulation systems, particularly in white adipose tissue. The hypothalamic pituitary adrenal axis, gonadal, growth hormone, leptin, sympathetic nervous system and adrenergic, dopaminergic, and serotoninergic central pathways, all seem interconnected and involved in obesity. From another perspective, the role of psychosocial chronic stressors, determining poor mental and physical health, is well documented. Empirical data can support biologically conceivable theories describing how perceptions of the external social environment are transduced into cellular inflammation and depression. Although in neurobiological models of depression, stress responses are associated with neuroendocrine and neuro-inflammatory processes, concerning similar pathways to those described in obesity, an integrating model is still lacking. The aim of this mini-review is to offer a reflexion on the interplay between the neuroendocrine dysfunctions related to chronic stress and the nature of the shared biologic mechanisms in the pathophysiology of both clinical entities, depression and obesity. We highlight dysfunctional answers of mind body systems that are usually activated to promote regulation and adaptation. Stress response, as a mediator between different level phenomena, may undertake the role of a plausible link between psychological and biological determinants of disease. Depression and obesity are major public health issues, urging for new insights and novel interventions and this discussion points to the need of a more in-depth approach.

Biological Mechanisms of Cancer-Induced Depression

Patients with cancer are more likely to develop depression than the general population, which negatively impacts their quality of life and prognosis. In order to identify effective antidepressants catered toward cancer patients, the biology of depression in the context of cancer must be well-understood. Many theories have emerged postulating the mechanisms underlying the development of depressive disorder. Here, we review the role inflammation, a hyperactive hypothalamic-pituitary-adrenal (HPA) axis, and glutamate excitotoxicity may play in cancer-induced depression. Hopefully, novel therapeutics targeting these dysregulated pathways may be potent in ameliorating depressive symptoms in the cancer population.

Difference in proinflammatory cytokines produced by monocytes between patients with major depressive disorder and healthy controls

BACKGROUND

Immune activation and suppression in patients with major depressive disorders (MDD) have been both reported in different studies. We assume that these findings may indicate innate immunological tolerance in MDD, with subclinical elevated level of proinflammatory cytokines and the decrease in innate immune response while encountering pathogens.

METHODS

Peripheral monocytes of 50 untreated patients with MDD and 40 healthy controls were isolated and cultured, with or without 10 ng/ml lipopolysacchride (LPS) for 6 h (6 h, LPS+/-), and with LPS for 18 h (18, LPS+). The cell culture supernatants were collected to measure concentrations of tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1 beta (IL-1β).

RESULTS

The baseline concentrations of IL-6 and IL-1β (6 h, LPS-) were significantly higher in the MDD group than those in the control group. There was no significant difference of TNF-α between the two groups. The fold changes of LPS-induced secretion of IL-6 and TNF-α from monocytes cultured for 6 and 18 h were all lower in the patient groups, and that was true for IL-1β as monocytes cultured for 18 h.

LIMITATIONS

Given the gap between the results of in vitro experiments and the actual response that happens in vivo when the immune system encounters pathogens from the external world, future research should include in vivo methods to test the results of the current study.

CONCLUSIONS

Patients with MDD may have subclinical inflammation during a depressive episode, and the reduced response to LPS in monocytes indicates innate immunological tolerance.

Antidepressant-like Effects of p-Coumaric Acid on LPS-induced Depressive and Inflammatory Changes in Rats

Depression causes mental and physical changes which affect quality of life. It is estimated to become the second most prevalent disease, but despite its commonness, the pathophysiology of depression remains unclear and medicine is not sufficiently protective. p-Coumaric acid (p-CA) is a dietary phenolic acid which has been proven to have antifungal, anti-HIV, anti-melanogenic, antioxidant and anti-inflammatory effects. Considering these effects, we investigated whether p-CA can prevent depressive symptoms by reducing inflammatory cytokines in animals injected with lipopolysaccharide (LPS). Changes in despair-related behaviors, inflammatory cytokines, neurotrophic factors and synaptic activity were measured. In these animals, p-CA improved despair-related behavioral symptoms induced by LPS in the forced swim test (FST), tail suspension test (TST) and sucrose splash test (SST). p-CA also prevented the increase of inflammatory cytokines in the hippocampus such as cycloxigenase-2 and tumor necrosis factor-α due to LPS. Similarly, it prevented the reduction of brain-derived neurotrophic factor (BDNF) by LPS. Electrophysiologically, p-CA blocked the reduction of long-term depression in LPS-treated organotypic tissue slices. In conclusion, p-CA prevented LPS-induced depressive symptoms in animals, as determined by behavioral, biochemical and electrophysiological measures. These findings suggest the potential use of p-CA as a preventive and therapeutic medicine for depression.

Effects of Uric Acid on the Alterations of White Matter Connectivity in Patients with Major Depression

OBJECTIVE

Uric acid is a non-enzymatic antioxidant associated with depression. Despite its known protective role in other brain disorders, little is known about its influence on the structural characteristics of brains of patients with major depressive disorder (MDD). This study explored the association between uric acid and characteristics of white matter (WM) in patients with MDD.

METHODS

A total of 32 patients with MDD and 23 healthy controls (HCs) were examined. All participants were scored based on the Beck Depression Inventory and Beck Anxiety Inventory at baseline. All patients were also rated with the Hamilton Depression Rating Scale. We collected blood samples from all participants immediately after their enrollment and before the initiation of antidepressants in case of patients. Tract-based spatial statistics were used for all imaging analyses.

RESULTS

Lower fractional anisotropy (FA) and higher radial diffusivity (RD) values were found in the MDD group than in the HC group. Voxelwise correlation analysis revealed that the serum uric acid levels positively correlated with the FA and negatively with the RD in WM regions that previously showed significant group differences in the MDD group. The correlated areas were located in the left anterior corona radiata, left frontal lobe WM, and left anterior cingulate cortex WM.

CONCLUSION

The present study suggests a significant association between altered WM connectivity and serum uric acid levels in patients with MDD, possibly through demyelination.

Review of biologic and behavioral risk factors linking depression and peripheral artery disease

The incidence of depression has been rising rapidly, and depression has been recognized as one of the world’s leading causes of disability. More recently, depression has been associated with an increased risk of symptomatic atherosclerotic disease as well as worse perioperative outcomes in patients with cardiovascular disease. Additionally, recent studies have demonstrated an association between depression and peripheral artery disease (PAD), which has been estimated to affect more than 200 million people worldwide. These studies have identified that depression is associated with poor functional and surgical outcomes in patients with PAD. Although the directionality and specific mechanisms underlying this association have yet to be clearly defined, several biologic and behavioral risk factors have been identified to play a role in this relationship. These factors include tobacco use, physical inactivity, medical non-adherence, endothelial and coagulation dysfunction, and dysregulation of the hypothalamic-pituitary-adrenal axis, autonomic system, and immune system. In this article, we review these potential mechanisms and the current evidence linking depression and PAD, as well as future directions for research and interventional strategies. Understanding and elucidating this relationship may assist in preventing the development of PAD and may improve the care that patients with PAD and comorbid depression receive.

The role of neuroinflammation and neurovascular dysfunction in major depressive disorder

Although depression has generally been explained with monoamine theory, it is far more multifactorial, and therapies that address the disease’s pathway have not been developed. In this context, an understanding of neuroinflammation and neurovascular dysfunction would enable a more comprehensive approach to depression. Inflammation is in a sense a type of allostatic load involving the immune, endocrine, and nervous systems. Neuroinflammation is involved in the pathophysiology of depression by increasing proinflammatory cytokines, activating the hypothalamus–pituitary–adrenal axis, increasing glucocorticoid resistance, and affecting serotonin synthesis and metabolism, neuronal apoptosis and neurogenesis, and neuroplasticity. In future, identifying the subtypes of depression with increased vulnerability to inflammation and testing the effects of inflammatory modulating agents in these patient groups through clinical trials will lead to more concrete conclusions on the matter. The vascular depression hypothesis is supported by evidence for the association between vascular disease and late-onset depression and between ischemic brain lesions and distinctive depressive symptoms. Vascular depression may be the entity most suitable for studies of the mechanisms of depression. Pharmacotherapies used in the prevention and treatment of cerebrovascular disease may help prevent vascular depression. In future, developments in structural and functional imaging, electrophysiology, chronobiology, and genetics will reveal the association between depression and brain lesions. This article aims to give a general review of the existing issues examined in the literature pertaining to depression-related neuroinflammatory and vascular functions, related pathophysiology, applicability to depression treatment, and directions for future research.

Kynurenine pathway metabolism and the neurobiology of treatment-resistant depression: Comparison of multiple ketamine infusions and electroconvulsive therapy

Current first-line antidepressants can take weeks or months to decrease depressive symptoms. Low dose ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, shows potential for a more rapid antidepressant effect, with efficacy also evident in previously treatment-resistant populations. However, a greater understanding of the physiological mechanisms underlying such effects is required. We assessed the potential impact of ketamine infusion on neurobiological drivers of kynurenine pathway metabolism in major depression (HPA axis hyperactivity, inflammation) in patients with treatment-resistant depression compared to gender-matched healthy controls. Furthermore, we assessed these biomarkers before and after electroconvulsive therapy (ECT), which is currently the gold standard for management of treatment-resistant depression. As previously demonstrated, treatment with ketamine and ECT was associated with improved depressive symptoms in patients. At baseline, waking cortisol output was greater in the ECT cohort, kynurenine was greater in the ketamine cohort, and kynurenic acid was lower in patients compared to healthy controls, although inflammatory markers (IL-6, IL-8, IL-10 or IFN-γ) were similar in patients and controls. Furthermore, in patients who responded to ECT, the cortisol awakening response was decreased following treatment. Despite a trend towards reduced kynurenine concentrations in those who responded to ketamine, ketamine was not associated with significant alterations in any of the biomarkers assessed.

Prevalence and correlates of low-grade systemic inflammation in adult psychiatric inpatients: An electronic health record-based study

Low-grade inflammation is a risk factor for depression, psychosis and other major psychiatric disorders. It is associated with poor response to antidepressant and antipsychotics, and could potentially be a treatment target. However, there is limited data on the prevalence of low-grade inflammation in major psychiatric disorders, and on the characteristics of patients who show evidence of inflammation. We examined the prevalence of low-grade inflammation and associated socio-demographic and clinical factors in acute psychiatric inpatients. An anonymised search of the electronic patient records of Cambridgeshire and Peterborough NHS Foundation Trust was used to identify patients aged 18-65 years who were hospitalised between 2013 and 2016 (inclusive). We excluded patients on antibiotics or oral steroids, or with missing data. Inflammation was defined using serum C-reactive protein (>3 mg/L) or total white cell count (>9.4 × 10⁹/L) as measured within 14 days of admission. Out of all 599 admissions, the prevalence of inflammation (serum CRP >3 mg/L) in the ICD-10 diagnostic groups of psychotic disorders (F20-29), mood disorders (F30-39), neurotic disorders (F40-48) and personality disorders (F60-69) was 32%, 21%, 22% and 42%, respectively. In multivariable analyses, low-grade inflammation was associated with older age, black ethnicity, being single, self-harm, diagnoses of schizophrenia, bipolar disorder, current treatments with antidepressants, benzodiazepines, and with current treatment for medical comorbidities. A notable proportion of acutely unwell psychiatric patients from all ICD-10 major diagnostic groups show evidence of low-grade inflammation, suggesting inflammation may be relevant for all psychiatric disorders.

Population scale retrospective analysis reveals distinctive antidepressant and anxiolytic effects of diclofenac, ketoprofen and naproxen in patients with pain

Currently approved monoamine modulating antidepressant and anxiolytic pharmaceutics fail in over one third of patients due to delayed and variable therapeutic effect, adverse reactions preceding the therapeutic action, and adherence issues. Even with adequate adherence to the regimen and tolerability, one third of the patients do not respond to any class of antidepressants. There is a strong correlation between treatment resistant depression and increase in inflammatory cytokines in plasma and cerebrospinal fluid. Furthermore, epidemiological studies suggest that depression and anxiety are commonly comorbid with pain and inflammation. While a link between pain, inflammation and depression has been suggested it remains unclear which anti-inflammatory treatment may be beneficial to patients with depression and anxiety due to pain. Here, we analyzed 430,783 FDA adverse effect reports of patients treated for pain to identify potential antidepressant and anxiolytic effects of various anti-inflammatory medications. Patients treated for depression or patients taking any known antidepressants were excluded. The odds ratio analysis of 139,072 NSAID reports revealed that ketoprofen was associated with decreased reports of depression by a factor of 2.32 (OR 0.43 and 95% Confidence Interval [0.31, 0.59]) and decreased reports of anxiety by a factor of 2.86 (OR 0.35 [0.22, 0.56]), diclofenac with decreased depression reports by a factor of 2.22 (OR 0.45 [0.40, 0.49]) and anxiety by a factor of 2.13 (OR 0.47 [0.41, 0.54]), while naproxen decreased depression reports by a factor of 1.92 (OR 0.52 [0.49, 0.57]) and anxiety by a factor of 1.23 (OR 0.81 [0.75, 0.88]). Other NSAIDs did not exhibit any noticeable antidepressant and/or anxiolytic effect.

Aggression, Social Stress, and the Immune System in Humans and Animal Models

Social stress can lead to the development of psychological problems ranging from exaggerated anxiety and depression to antisocial and violence-related behaviors. Increasing evidence suggests that the immune system is involved in responses to social stress in adulthood. For example, human studies show that individuals with high aggression traits display heightened inflammatory cytokine levels and dysregulated immune responses such as slower wound healing. Similar findings have been observed in patients with depression, and comorbidity of depression and aggression was correlated with stronger immune dysregulation. Therefore, dysregulation of the immune system may be one of the mediators of social stress that produces aggression and/or depression. Similar to humans, aggressive animals also show increased levels of several proinflammatory cytokines, however, unlike humans these animals are more protected from infectious organisms and have faster wound healing than animals with low aggression. On the other hand, subordinate animals that receive repeated social defeat stress have been shown to develop escalated and dysregulated immune responses such as glucocorticoid insensitivity in monocytes. In this review we synthesize the current evidence in humans, non-human primates, and rodents to show a role for the immune system in responses to social stress leading to psychiatric problems such as aggression or depression. We argue that while depression and aggression represent two fundamentally different behavioral and physiological responses to social stress, it is possible that some overlapped, as well as distinct, pattern of immune signaling may underlie both of them. We also argue the necessity of studying animal models of maladaptive aggression induced by social stress (i.e., social isolation) for understanding neuro-immune mechanism of aggression, which may be relevant to human aggression.

Association between a functional interleukin 6 receptor genetic variant and risk of depression and psychosis in a population-based birth cohort

OBJECTIVE

Interleukin 6 (IL-6) levels are commonly elevated in patients with depression and psychosis and in people who are at risk of developing these disorders. A common, functional variant in the IL6R gene (IL6R Asp358Ala; rs2228145 A > C) is known to dampen down inflammation by impairing IL6R signaling. We have examined the association of Asp358Ala with diagnosis of depression and psychosis, serum IL-6, CRP levels, and a number of risk factors commonly linked with inflammation, depression or psychosis. We predicted that if IL-6 were related to depression/psychosis risk causally, rather than due to confounding, Asp358Ala would be associated with risk of these disorders, serum IL-6, CRP levels, but not with any of the confounders.

METHOD

We used data from the population-based ALSPAC birth cohort. Serum IL-6 and CRP levels were measured at age 9 years. Psychotic disorder, ICD-10 diagnosis of severe depressive episode, and total depression score were assessed at age 18 years. IL6R Asp358Ala was genotyped using the Illumina HumanHap550 quad genome-wide SNP genotyping platform. Risk factors assessed include sex, body mass index, social class, ethnicity, maternal education, birth weight, gestational age, maternal post-natal depression, childhood psychological and behavioral problems, and total IQ score.

RESULTS

Asp358Ala was associated with decreased risk of severe depression and/or psychosis; adjusted odds ratio for those with CC, compared with AA, genotype was 0.38 (95% CI, 0.15-0.94). The variant was associated with increased serum IL-6 levels (P = 5.5 × 10-22) but decreased serum CRP levels (P = 3.5 × 10-5), consistent with an anti-inflammatory effect downstream of IL-6. Asp358Ala was not associated with total depression score. Asp358Ala was not associated with any of the other risk factors commonly linked with inflammation, depression or psychosis (all P > 0.20).

CONCLUSIONS

The findings provide further evidence that the IL-6/IL6R pathways are involved in pathogenesis of severe depression and psychosis, and may be novel therapeutic targets. Previously reported associations between IL-6, depression and psychosis are unlikely to be fully explained by confounding. Based on a small number of cases, findings from the current study need replication in other samples.

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.

Inflammation and depression: a causal or coincidental link to the pathophysiology?

This review summarises the evidence that chronic low grade inflammation triggers changes that contribute to the mental and physical ill health of patients with major depression. Inflammation, and the activation of the hypothalamic pituitary axis by stress, are normal components of the stress response but when stress is prolonged and the endocrine and immune system become chronic resulting in the activation of the peripheral macrophages, the central microglia and hypercortisolemia, the neuronal networks are damaged and become dysfunctional. The proinflammatory cytokines, in addition to activating the hypothalamic-pituitary-adrenal axis and thereby increasing cortisol synthesis, also activate the tryptophan-kynurenine pathway. This results in the synthesis of the neurotoxic N-methyl-d-aspartate (NMDA) glutamate agonist quinolinic acid and 3-hydroxykynurenine thereby enhancing oxidative stress and contributes to neurodegeneration which characterise major depression particularly in late life.While antidepressants attenuate some of the endocrine and immune changes caused by inflammation, not all therapeutically effective antidepressants do so. This suggests that drugs which specifically target the immune, endocrine and neurotransmitter systems may be more effective antidepressants.The preliminary clinical evidence that some non-steroidal anti-inflammatory drugs, such as the cyclooxygenase 2 inhibitor celecoxib, can enhance the response to standard antidepressant treatment is therefore considered and a critical assessment made of the possible limitations of such an approach to novel antidepressant development.

Antidepressant activity of anti-cytokine treatment: a systematic review and meta-analysis of clinical trials of chronic inflammatory conditions

Inflammatory cytokines are commonly elevated in acute depression and are associated with resistance to monoaminergic treatment. To examine the potential role of cytokines in the pathogenesis and treatment of depression, we carried out a systematic review and meta-analysis of antidepressant activity of anti-cytokine treatment using clinical trials of chronic inflammatory conditions where depressive symptoms were measured as a secondary outcome. Systematic search of the PubMed, EMBASE, PsycINFO and Cochrane databases, search of reference lists and conference abstracts, followed by study selection process yielded 20 clinical trials. Random effect meta-analysis of seven randomised controlled trials (RCTs) involving 2370 participants showed a significant antidepressant effect of anti-cytokine treatment compared with placebo (standardised mean difference (SMD)=0.40, 95% confidence interval (CI), 0.22-0.59). Anti-tumour necrosis factor drugs were most commonly studied (five RCTs); SMD=0.33 (95% CI; 0.06-0.60). Separate meta-analyses of two RCTs of adjunctive treatment with anti-cytokine therapy and eight non-randomised and/or non-placebo studies yielded similar small-to-medium effect estimates favouring anti-cytokine therapy; SMD=0.19 (95% CI, 0.00-0.37) and 0.51 (95% CI, 0.34-0.67), respectively. Adalimumab, etanercept, infliximab and tocilizumab all showed statistically significant improvements in depressive symptoms. Meta-regression exploring predictors of response found that the antidepressant effect was associated with baseline symptom severity (P=0.018) but not with improvement in primary physical illness, sex, age or study duration. The findings indicate a potentially causal role for cytokines in depression and that cytokine modulators may be novel drugs for depression in chronically inflamed subjects. The field now requires RCTs of cytokine modulators using depression as the primary outcome in subjects with high inflammation who are free of other physical illnesses.