IL-6 knockout mice exhibit resistance to stress-induced development of depression-like behaviors

Innate immunity-mediated neuroinflammation promotes the onset and progression of post-stroke depression

Post-stroke depression (PSD) is a prevalent psychiatric disorder after stroke, with the incidence of approximately one-third among stroke survivors. It is classified as an organic mental disorder and has a well-documented association with stroke affecting various aspects of patients, such as the recovery of limb motor function, daily living self-care ability, and increasing the mortality of stroke survivors. However, the pathogenesis of PSD is not yet fully understood. Currently, immune inflammation is a research hotspot. This review focuses on the pathogenesis of PSD, particularly elucidating the role of inflammation in mediating neuroinflammation through innate immunity. Simultaneously, we highlight that peripheral inflammation following a stroke may trigger a detrimental cycle of neuroinflammation by activating innate immune pathways within the central nervous system, which could potentially contribute to the development of PSD. Lastly, we summarize potential treatments for PSD and propose targeting cytokines and innate immune pathways as novel therapeutic approaches.

Association between peripheral plasma cytokine levels and suicidal ideation in first-episode, drug-naïve major depressive disorder

BACKGROUND

Inflammatory processes could potentially impact both mood and suicide risk, however, the relationship between cytokines and suicidal ideation remains unclear. This study aimed to investigate the association between plasma levels of cytokines and suicidal ideation in population with major depressive disorders (MDD).

METHODS

A cross-sectional study was performed to assess the peripheral plasma levels of interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-10 and tumor necrosis factor-α (TNF-α) in 88 Chinese Han first-episode drug-naïve MDD patients. Suicidal ideation in the past week were identified using the Beck Scale for Suicide Ideation-Chinese Version (BSI-CV). The Hamilton Depression Rating Scale-17 (HAMD-17), the Hamilton Anxiety Rating Scale-14 (HAMA-14) and the Childhood Trauma Questionnaire (CTQ) was used to assess depression, anxiety and childhood trauma. Multivariable logistic regression models were used to estimate the association between cytokines and suicidal ideation. Interaction and stratified analyses were conducted according to age, sex, marital status, education, smoking status, BMI and physical activity.

RESULTS

Among the 88 participants, 42 individuals (47.7%) reported suicidal ideation within the past week. In the fully adjusted model, a statistically significant trend was observed in the association between IL-2 level and suicidal ideation (OR: 1.40, 95% CI: 1.00-1.97). The stratified analysis showed a statistically significant association between IL-6 level and suicidal ideation among younger people (OR: 1.17, 95% CI: 1.01-1.36) and a significant positive association between IL-8 (OR: 1.59, 95% CI: 1.03-2.44) and IL-10 (OR: 2.51, 95% CI: 1.27-4.96) levels and suicide ideation among higher educated populations.

LIMITATIONS

The cross-sectional design, residual confounding effects and small sample size CONCLUSION: Our findings indicate a significant positive association between plasma IL-2 level and suicidal ideation in MDD patients. IL-2 has the potential to be a biomarker of suicidal ideation in patients with depression.

Antidepressant Effect of Heracleum moellendorffii Extract on Behavioral Changes in Astrocyte Ablation Mouse Model of Depression by Modulating Neuroinflammation through the Inhibition of Lipocalin-2

Astrocyte dysfunction and inflammation play a pivotal role in depression. In this study, we evaluated the antidepressant properties of Heracleum moellendorffii root extract (HME), which is traditionally used for inflammation-related diseases, in a mouse model with astrocyte depletion that resembles the prefrontal cortex pathology of depressive patients. Mice were divided into four groups, with 10 mice per group. To induce astrocyte ablation in the mice's prefrontal cortex (PFC), we used astrocytic toxin L-alpha-aminoadipic acid (L-AAA) and administered HME orally at 200 and 500 mg/kg for 22 days. We utilized the tail suspension test (TST) to assess depression-like behaviors and the open field test (OFT) to evaluate anxiety-like activities. Additionally, astrocytic and inflammatory markers in the PFC were evaluated using immunohistochemistry and ELISA. The results showed that infusion of L-AAA significantly decreased the expression of astrocytic glial fibrillary acidic protein (GFAP), which was accompanied by increased depression and anxiety-like behaviors. However, HME significantly reversed these effects by dose-dependently enhancing GFAP expression and modulating inflammatory markers, such as TNF-α, IL-6, and particularly lipocalin-2, a master proinflammatory mediator. These results imply that HME contributes to the alleviation of depression and anxiety-like behaviors by promoting astrocyte recovery and reducing neuroinflammation, especially through lipocalin-2 inhibition.

Chronic Stress-Induced Neuroinflammation: Relevance of Rodent Models to Human Disease

The brain is the central organ of adaptation to stress because it perceives and determines threats that induce behavioral, physiological, and molecular responses. In humans, chronic stress manifests as an enduring consistent feeling of pressure and being overwhelmed for an extended duration. This can result in a persistent proinflammatory response in the peripheral and central nervous system (CNS), resulting in cellular, physiological, and behavioral effects. Compounding stressors may increase the risk of chronic-stress-induced inflammation, which can yield serious health consequences, including mental health disorders. This review summarizes the current knowledge surrounding the neuroinflammatory response in rodent models of chronic stress-a relationship that is continually being defined. Many studies investigating the effects of chronic stress on neuroinflammation in rodent models have identified significant changes in inflammatory modulators, including nuclear factor-κB (NF-κB) and toll-like receptors (TLRs), and cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and IL-6. This suggests that these are key inflammatory factors in the chronic stress response, which may contribute to the establishment of anxiety and depression-like symptoms. The behavioral and neurological effects of modulating inflammatory factors through gene knockdown (KD) and knockout (KO), and conventional and alternative medicine approaches, are discussed.

The Emerging Role of Toll-Like Receptor-Mediated Neuroinflammatory Signals in Psychiatric Disorders and Acquired Epilepsy

The new and evolving paradigms of psychiatric disorders pathogenesis are deeply inclined toward chronic inflammation that leads to disturbances in the neuronal networks of patients. A strong association has been established between the inflammation and neurobiology of depression which is mediated by different toll-like receptors (TLRs). TLRs and associated signalling pathways are identified as key immune regulators to stress and infections in neurobiology. They are a special class of transmembrane proteins, which are one of the broadly studied members of the Pattern Recognition Patterns family. This review focuses on summarizing the important findings on the role of TLRs associated with psychotic disorders and acquired epilepsy. This review also shows the promising potential of TLRs in immune response mediated through antidepressant therapies and TLRs polymorphism associated with various psychotic disorders. Moreover, this also sheds light on future directions to further target TLRs as a therapeutic approach for psychiatric disorders.

Blocking IL-17A prevents oxycodone-induced depression-like effects and elevation of IL-6 levels in the ventral tegmental area and reduces oxycodone-derived physical dependence in rats

Oxycodone is the most prescribed opioid for pain management and has been available in clinics for almost a century, but effects of chronic oxycodone have been studied less than morphine in preclinical and clinical studies. Newly developed depression has been coupled with chronic oxycodone use in a few clinical studies, but no preclinical studies have investigated the pathogenesis of oxycodone-induced depression. Gut microbiome changes following oxycodone use is an understudied area, and interleukin-17A (IL-17A) is linked to both the development of mood disorders and regulation of gut microbiome. The present study investigated effects of chronic oxycodone exposure on mood-related behaviors (depression and anxiety), pain hypersensitivity, physical dependence, immune markers, and the gut microbiome and tested the hypothesis that blocking IL-17A with a systemically administered monoclonal antibody reduces oxycodone-derived effects. Oxycodone (using an incremental dosing regimen) or saline was injected twice a day for 12 days. IL-17A Ab (200 µg/100 µl) or saline was administered every 3rd day during the 12-day interval. Chronic oxycodone induced a depression-like effect, but not anxiogenic- or anxiolytic-like effects; promoted hyperalgesia; increased IL-17A and IL-6 levels in the ventral tegmental area (VTA); and induced physical dependence. IL-17A Ab co-administration with oxycodone prevented the depression-like effect and hyperalgesia, reduced naloxone-precipitated withdrawal signs, and normalized the increase in cytokine levels. Chronic oxycodone exposure did not affect gut microbiome and integrity. Our results identify a role for IL-17A in oxycodone-related behavioral and neuroimmune effects and show that IL-17A Ab has potential therapeutic value in blocking these effects. Given that humanized IL-17A Ab is approved for treatment of psoriasis and psoriatic arthritis, our findings point toward studying it for use in the treatment of oxycodone use disorder.

Clarification of the molecular mechanisms underlying glyphosate-induced major depressive disorder: a network toxicology approach

Major depressive disorder (MDD) is predicted to become the second most common cause of disability in the near future. Exposure to glyphosate (Gly)-based herbicides has been linked to the onset of MDD. However, the underlying mechanisms remain unclear. The aim of this study was to investigate the potential molecular mechanisms of MDD induced by Gly using network toxicology approach. The MDD dataset GSE76826 from the Gene Expression Omnibus database was referenced to identify differentially expressed genes (DEGs) in peripheral blood leukocytes of MDD patients and controls. The potential intersection targets of Gly-induced MDD were screened by network toxicology. The intersection targets were used for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and to construct protein-protein interaction networks. The binding potentials of hub targets with Gly were validated by molecular docking. In total, 1216 DEGs associated with Gly-induced MDD were identified. Subsequent network pharmacology further refined the search to 43 targets. GO and KEGG enrichment analyses revealed multiple signaling pathways involved in GLY-induced MDD. Six potential core targets (CD40, FOXO3, FOS, IL6, TP53, and VEGFA) were identified. Finally, molecular docking demonstrated that Gly exhibited strong binding affinity to the core targets. The results of this study identified potential molecular mechanisms underlying Gly induced MDD and provided new insights for prevention and treatment.

Lactobacillus from the Altered Schaedler Flora maintain IFNγ homeostasis to promote behavioral stress resilience

The gut microbiome consists of trillions of bacteria, fungi, and viruses that inhabit the digestive tract. These communities are sensitive to disruption from environmental exposures ranging from diet changes to illness. Disruption of the community of lactic acid producing bacteria, Lactobaccillacea, has been well documented in mood disorders and stress exposure. In fact, oral supplement with many Lactobacillus species can ameliorate these effects, preventing depression- and anxiety-like behavior. Here, we utilize a gnotobiotic mouse colonized with the Altered Schaedler Flora to remove the two native species of Lactobaccillacea: L. intestinalis and L. murinus. Using this microbial community, we found that the Lactobacillus species themselves, and not the disrupted microbial communities are protective from environmental stressors. Further, we determine that Lactobaccillacea are maintaining homeostatic IFNγ levels which are mediating these behavioral and circuit level responses. By utilizing the Altered Schaedler Flora, we have gained new insight into how probiotics influence behavior and provide novel methods to study potential therapies to treat mood disorders.

Investigating the Potential Mechanisms and Therapeutic Targets of Inflammatory Cytokines in Post-stroke Depression

Post-stroke depression (PSD) affects approximately one-third of stroke survivors, severely impacting general recovery and quality of life. Despite extensive studies, the exact mechanisms underlying PSD remain elusive. However, emerging evidence implicates proinflammatory cytokines, including interleukin-1β, interleukin-6, tumor necrosis factor-alpha, and interleukin-18, play critical roles in PSD development. These cytokines contribute to PSD through various mechanisms, including hypothalamic-pituitary-adrenal (HPA) axis dysfunction, neurotransmitter alterations, neurotrophic factor changes, gut microbiota imbalances, and genetic predispositions. This review is aimed at exploring the role of cytokines in stroke and PSD while identifying their potential as specific therapeutic targets for managing PSD. A more profound understanding of the mechanisms regulating inflammatory cytokine expression and anti-inflammatory cytokines like interleukin-10 in PSD may facilitate the development of innovative interventions to improve outcomes for stroke survivors experiencing depression.

Voluntary wheel running from early adolescence reduces disease progression, and anxiety- and depression-related symptoms in an adult male mouse model of rheumatoid arthritis

Rheumatoid arthritis (RA) is a multifactorial autoimmune disease that progressively destroys synovial joints and leads to chronic systemic inflammation. This autoimmune disorder is associated with increased anxiety- and depression-related symptoms, which reduces quality of life. Clinical and experimental evidence suggests that higher physical activity from early adolescence may prevent chronic diseases and reduce the risk of mental health problems in adulthood. This study aimed to assess whether voluntary wheel running from early adolescence can decrease clinical symptoms, anxiety- and depression-related behaviors in adult mice with rheumatoid arthritis. Adolescent male mice were exposed to voluntary wheel running until adulthood and got collagen-induced arthritis. We measured body weight, the thickness of the hind paw and knee joint (clinical signs), anxiety- and depression-related behaviors, serum testosterone, and cytokines (IFN-γ IL-1β, IL-6, TNF-α, IL-10). The findings showed that collagen-induced arthritis resulted in anxious-like behavior, increased anhedonia, elevated IL-6, IL-1β, TNF-α, and IFN-γ, and decreased testosterone levels in the serum of mice. However, no change was observed in behavioral despair. We found that higher physical activity from early adolescence significantly reduced the severity of clinical signs, anxiety- and anhedonia-like behaviors, and decreased behavioral despair in RA-induced mice. In addition, the running wheel exposure normalized RA-induced abnormalities in testosterone and inflammatory cytokines in mice. Altogether, this study suggests that higher physical activity from early adolescence may make mice less vulnerable or resistant to RA-induced clinical symptoms and anxiety- and depression-related behaviors by changing testosterone and inflammatory cytokines productions in adulthood.

Can selective serotonin reuptake inhibitors/serotonin and norepinephrine reuptake inhibitor antidepressants decrease the "cytokine storm" in the course of COVID-19 pneumonia?

BACKGROUND

Lots of research has been conducted to fight COVID-19 since the outbreak of the pandemic in 2020. The role of "cytokine storm" in the pathogenesis of COVID-19 pneumonia is well known. Relationship between interleukins and depression is still subject matter of the research, but a correlation between interleukin-6 and depressive disorders is proven by now. The aim of this study is to verify differences among interleukin-6 blood levels of inpatients treated with selective serotonin reuptake inhibitors and/or serotonin and norepinephrine reuptake inhibitor before and during hospitalization and of inpatients not treated with these drugs.

METHODS

This is an observational study performed during the first wave of SARS Cov-2 pandemic in Italy for three months. The hospitalized patients of Internal Medicine wards and Infectious and Tropical Diseases ward of Azienda Ospedaliero-Universitaria Careggi of Florence for COVID-19 pneumonia have been divided into two subgroups (treated / not treated with antidepressants). Patients admitted to Intensive Care Unit previously have been excluded. Each patient has been evaluated concerning demographic, clinical and therapeutic features. The first dosage of interleukin-6 detected during hospitalization has been noticed.

RESULTS

The entire sample included 402 patients and 8.5% (N.=34) had been treated with an antidepressant of the two considered categories before admission until discharge from hospital. Significant lower levels of interleukin-6 of recovered patients of the treated subgroup have been highlighted as compared to recovered patients of not-treated subgroup (12.1 vs. 25.4 P<0.001). These results have been pointed out in spite of higher mean age and more serious comorbidities of the treated subgroup. Nevertheless, the incidence of severe acute respiratory distress syndrome is significantly lower in the subgroup of patients with antidepressant treatment (20.6% vs. 43.2% P<0.02) as well as endotracheal intubation employment (0.0% vs. 11.7% P<0.04). The rate of deceased patients of treated-subgroup is not significantly lower than the rate of not-treated subgroup (23.5% vs. 26.4% P=0.13).

CONCLUSIONS

During COVID-19 pneumonia, the production of interleukin-6 seems to be modulated in presence of antidepressant therapy. Further proofs and broader surveys are necessary.

Elevated Plasma Levels of Mature Brain-Derived Neurotrophic Factor in Major Depressive Disorder Patients with Higher Suicidal Ideation

Several pieces of evidence show that signaling via brain-derived neurotrophic factor (BDNF) and its receptor, tropomycin receptor kinase B (TrkB), as well as inflammation, play a crucial part in the pathophysiology of depression. The purpose of our study was to evaluate plasma levels of BDNF-TrkB signaling, which are inflammatory factors in major depressive disorder (MDD) patients, and assess their associations with clinical performance. This study recruited a total sample of 83 MDD patients and 93 healthy controls (CON). All the participants were tested with the Hamilton Depression Scale (HAMD), the Beck Scale for Suicide Ideation, and the NEO Five-Factor Inventory. The plasma level of selected BDNF-TrkB signaling components (mature BDNF (mBDNF), precursor BDNF (proBDNF), tyrosine kinase B (TrkB), and tissue plasminogen activator (tPA)) and selected inflammatory factors (interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α)) were measured using an enzyme-linked immunosorbent assay (ELISA). Further, we performed correlation analysis to indicate the relationship between the plasma levels of the factors and clinical characteristics. Results: (i) A higher level of mBDNF and lower openness were observed in MDD patients with higher suicidal ideation than patients with lower suicidal ideation. (ii) In MDD patients, mBDNF was positively correlated with the sum score of the Beck Scale for Suicide Ideation (BSS). (iii) The levels of mBDNF, tPA, IL-1 β and IL-6 were significantly higher in all MDD subjects compared to the healthy controls, while the levels of TrkB and proBDNF were lower in MDD subjects. Conclusion: Our study provides novel insights regarding the potential role of mBDNF in the neurobiology of the association between depression and suicidal ideation and, in particular, the relationship between BDNF-TrkB signaling, inflammatory factors, and clinical characteristics in MDD.

Oleoylethanolamide restores stress-induced prepulse inhibition deficits and modulates inflammatory signaling in a sex-dependent manner

RATIONALE

Social stress contributes to the development of depressive and anxiety symptomatology and promotes pro-inflammatory signaling in the central nervous system. In this study, we explored the effects of a lipid messenger with anti-inflammatory properties - oleoylethanolamide (OEA) - on the behavioral deficits caused by social stress in both male and female mice.

METHODS

Adult mice were assigned to an experimental group according to the stress condition (control or stress) and treatment (vehicle or OEA, 10 mg/kg, i.p.). Male mice in the stress condition underwent a protocol consisting of four social defeat (SD) encounters. In the case of female mice, we employed a procedure of vicarious SD. After the stress protocol resumed, anxiety, depressive-like behavior, social interaction, and prepulse inhibition (PPI) were assessed. In addition, we characterized the stress-induced inflammatory profile by measuring IL-6 and CX3CL1 levels in the striatum and hippocampus.

RESULTS

Our results showed that both SD and VSD induced behavioral alterations. We found that OEA treatment restored PPI deficits in socially defeated mice. Also, OEA affected differently stress-induced anxiety and depressive-like behavior in male and female mice. Biochemical analyses showed that both male and female stressed mice showed increased levels of IL-6 in the striatum compared to control mice. Similarly, VSD female mice exhibited increased striatal CX3CL1 levels. These neuroinflammation-associated signals were not affected by OEA treatment.

CONCLUSIONS

In summary, our results confirm that SD and VSD induced behavioral deficits together with inflammatory signaling in the striatum and hippocampus. We observed that OEA treatment reverses stress-induced PPI alterations in male and female mice. These data suggest that OEA can exert a buffering effect on stress-related sensorimotor gating behavioral processing.

Lactobacillus maintains IFNγ homeostasis to promote behavioral stress resilience

The gut microbiome consists of the trillions of bacteria, fungi, and viruses that inhabit the digestive tract. These communities are sensitive to disruption from environmental exposures ranging from diet changes to illness. Disruption of the community of lactic acid producing bacteria, Lactobaccillacea , has been well documented in mood disorders and stress exposure. In fact, oral supplement with many Lactobacillus species can ameliorate these effects, preventing depression- and anxiety-like behavior. Here, for the first time, we utilize a gnotobiotic mouse colonized with the Altered Schaedler Flora to remove the two native species of Lactobaccillacea . Using this novel microbial community, we found that the Lactobacillus species themselves, and not the disrupted microbial communities are protective from environmental stressors. Further, we determine that Lactobaccillacea are maintaining homeostatic IFNγ levels which are mediating these behavioral and circuit level responses. By utilizing the Altered Schaedler Flora, we have gained new insight into how probiotics influence behavior and give novel methods to study potential therapies developed to treat mood disorders.

Meal-Based Intervention on Health Promotion in Middle-Aged Women: A Pilot Study

Middle-aged women belong to a risk group for metabolic dysregulation and menopausal symptoms, mainly due to a dramatic hormonal shift. Supplementation with functional compounds or a single nutrient has been dominantly explored as a nutritional approach for improving aging-related health parameters. However, a meal-based approach might be another strategy for promoting the overall health of the target population. This pilot study aimed to develop a meal-based intervention for middle-aged women and to evaluate its potential health benefits. Considering the nutrient intake status of Korean middle-aged women, diets enriched with four major nutrients (isoflavone, omega-3, fiber, and calcium) were designed and provided to forty-nine women aged 50 to 65 with mild levels of menopausal symptoms for 8 weeks. In the post-intervention phase, they showed reduced body weight and body fat, and improved biochemical metabolic parameters with decreased levels of cholesterol, low-density lipoprotein-cholesterol, ApoB, and fasting insulin. Moreover, bone resorption markers and menopause symptoms were lower in the post-intervention phase. In conclusion, the meal-based intervention might be a prominent strategy for overall health promotion in relatively healthy middle-aged women and further investigation is needed to test its efficacy with a randomized controlled study.

Memory impairments in rodent depression models: A link with depression theories

More than 80% of depressed patients struggle with learning new tasks, remembering positive events, or concentrating on a single topic. These neurocognitive deficits accompanying depression may be linked to functional and structural changes in the prefrontal cortex and hippocampus. However, their mechanisms are not yet completely understood. We conducted a narrative review of articles regarding animal studies to assess the state of knowledge. First, we argue the contribution of changes in neurotransmitters and hormone levels in the pathomechanism of cognitive dysfunction in animal depression models. Then, we used numerous neuroinflammation studies to explore its possible implication in cognitive decline. Encouragingly, we also observed a positive correlation between increased oxidative stress and a depressive-like state with concomitant memory deficits. Finally, we discuss the undeniable role of neurotrophin deficits in developing cognitive decline in animal models of depression. This review reveals the complexity of depression-related memory impairments and highlights the potential clinical importance of gathered findings for developing more reliable animal models and designing novel antidepressants with procognitive properties.

Pristane induced lupus mice as a model for neuropsychiatric lupus (NPSLE)

BACKGROUND

The pristane-induced lupus (PIL) model is a useful tool for studying environmental-related systemic lupus erythematosus (SLE). However, neuropsychiatric manifestations in this model have not been investigated in detail. Because neuropsychiatric lupus (NPSLE) is an important complication of SLE, we investigated the neuropsychiatric symptoms in the PIL mouse model to evaluate its suitability for NPSLE studies.

RESULTS

PIL mice showed olfactory dysfunction accompanied by an anxiety- and depression-like phenotype at month 2 or 4 after pristane injection. The levels of cytokines (IL-1β, IFN-α, IFN-β, IL-10, IFN-γ, IL-6, TNF-α and IL-17A) and chemokines (CCL2 and CXCL10) in the brain and blood-brain barrier (BBB) permeability increased significantly from week 2 or month 1, and persisted throughout the observed course of the disease. Notably, IgG deposition in the choroid plexus and lateral ventricle wall were observed at month 1 and both astrocytes and microglia were activated. Persistent activation of astrocytes was detected throughout the observed course of the disease, while microglial activation diminished dramatically at month 4. Lipofuscin deposition, a sign of neuronal damage, was detected in cortical and hippocampal neurons from month 4 to 8.

CONCLUSION

PIL mice exhibit a series of characteristic behavioral deficits and pathological changes in the brain, and therefore might be suitable for investigating disease pathogenesis and for evaluating potential therapeutic targets for environmental-related NPSLE.

Neuro-immune crosstalk in depressive symptoms of multiple sclerosis

Depressive disorders can occur in up to 50% of people with multiple sclerosis in their lifetime. If left untreated, comorbid major depressive disorders may not spontaneously remit and is associated with an increased morbidity and mortality. Conversely, epidemiological evidence supports increased psychiatric visit as a significant prodromal event prior to diagnosis of MS. Are there common molecular pathways that contribute to the co-development of MS and psychiatric illnesses? We discuss immune cells that are dysregulated in MS and how such dysregulation can induce or protect against depressive symptoms. This is not meant to be a comprehensive review of all molecular pathways but rather a framework to guide future investigations of immune responses in depressed versus euthymic people with MS. Currently, there is weak evidence supporting the use of antidepressant medication in comorbid MS patients. It is our hope that by better understanding the neuroimmune crosstalk in the context of depression in MS, we can enhance the potential for future therapeutic options.

Therapeutic modulation of JAK-STAT, mTOR, and PPAR-γ signaling in neurological dysfunctions

The cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.

Major depressive disorder (mdd): emerging immune targets at preclinical level

BACKGROUND

Major depressive disorder is a mental health disorder that is characterized by a persistently low mood and loss of interest. MDD is affecting over 3.8% of the global population as a major health problem. Its etiology is complex, and involves the interaction between a number of factors, including genetic predisposition and the presence of environmental stresses.

AREAS COVERED

The role of the immune and inflammatory systems in depression has been gaining interest, with evidence suggesting the potential involvement of pro-inflammatory molecules like TNF, interleukins, prostaglandins, and other cytokines, among others, has been put forth. Along with this, the potential of agents, from NSAIDs to antibiotics, are being evaluated in therapy for depression. The current review will discuss emerging immune targets at the preclinical level.

EXPERT OPINION

With increasing evidence to show that immune and inflammatory mediators are implicated in MDD, increasing research toward their potential as drug targets is encouraged. At the same time, agents acting on these mediators and possessing anti-inflammatory potential are also being evaluated as future therapeutic options for MDD, and increasing focus toward non-conventional drugs which can act through these mechanisms is important as regards the future prospects of the use of anti-inflammatory agents in depression.

The translational genetics of ADHD and related phenotypes in model organisms

Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent neurodevelopmental disorder resulting from the interaction between genetic and environmental risk factors. It is well known that ADHD co-occurs frequently with other psychiatric disorders due, in part, to shared genetics factors. Although many studies have contributed to delineate the genetic landscape of psychiatric disorders, their specific molecular underpinnings are still not fully understood. The use of animal models can help us to understand the role of specific genes and environmental stimuli-induced epigenetic modifications in the pathogenesis of ADHD and its comorbidities. The aim of this review is to provide an overview on the functional work performed in rodents, zebrafish and fruit fly and highlight the generated insights into the biology of ADHD, with a special focus on genetics and epigenetics. We also describe the behavioral tests that are available to study ADHD-relevant phenotypes and comorbid traits in these models. Furthermore, we have searched for new models to study ADHD and its comorbidities, which can be useful to test potential pharmacological treatments.

Mechanisms of Xiong-Pi-Fang in treating coronary heart disease associated with depression: A systematic pharmacology strategy and in vivo pharmacological validation

BACKGROUND

Coronary heart disease (CHD) and depression are very common and often co-existing disorders. Xiong-Pi-Fang (XPF), a therapeutic classical traditional Chinese medicine (TCM) formula, has shown satisfactory efficacy in treating CHD associated with depression. However, its mechanism of action is still unknown.

PURPOSE

To employ a systematic pharmacology approach for identifying the action mechanisms of XPF in treating CHD associated with depression.

METHODS

We used a systematic pharmacology approach to identify the potential active mechanisms of XPF in treating CHD with depression. Potential active compounds in XPF and the diseases targets were screened using relevant databases to build corresponding pathways, following the experiments that were conducted to confirm whether the presumptive results of systemic pharmacology were correct.

RESULTS

Network pharmacology predicted 42 key targets and 20 signaling pathways involved in XPF-mediated treatment, with IL-6/JAK2/STAT3/HIF-1α/VEGF-A pathway significantly affected. The common influences were hypothalamic-pituitary-adrenal axis (HPA axis) and glucocorticoid signaling, validated through chronic unexpected mild stress (CUMS) with isoprenaline (ISO) for inducing CHD within the depression model in rats. In addition, XPF intake reduced depressive-like behaviors and improved ECG ischemic changes. Furthermore, XPF exerted some anti-inflammatory effects by inhibiting the interleukin-6 (IL-6) induced phosphorylation of janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), ultimately downregulating hypoxia-inducible factor 1-α (HIF-1α) and vascular endothelial growth factor-A (VEGF-A) activation. The dysfunctional HPA axis feedback loop was also regulated, which enhanced the glucocorticoid receptor (GR) expression. In contrast, it improved glucocorticoid resistance by reducing the mineralocorticoid receptor expression.

CONCLUSIONS

Suppressing IL-6 release and maintaining the HPA feedback loop balance could be the primary mechanism of XPF against CHD with depression. The significance of the IL-6 and HPA axis identified indicates their potential as essential targets for CHD therapy with depression.

Effects of vitamin D supplementation on depression and some selected pro-inflammatory biomarkers: a double-blind randomized clinical trial

BACKGROUND

Both augmented inflammatory reaction and low vitamin D status are associated with depression but the magnitude of their relationships is unclear. This study was, therefore, conducted to evaluate the effects of vitamin D supplementation on serum 25(OH)D concentration, depression severity and some pro-inflammatory biomarkers in patients with mild to moderate depression.

METHODS

An 8-week double-blind randomized clinical trial (RCT) was performed on 56 (18-60 yrs) patients with mild to moderate depression, randomly assigned to intervention (50,000 IU cholecalciferol 2wks^-1) and control (placebo) groups. Serum 25(OH)D, intact parathyroid hormone (iPTH), interlukin (IL)-1β, IL-6, high-sensitivity C-reactive protein (hs-CRP) and depression severity (Beck Depression Inventory-II) (BDI-II)) were initially and finally assessed.

RESULTS

At the end point, statistically significant changes were observed only in intervention group as compared with controls including increased 25(OH)D concentration (+ 40.83 ± 28.57 vs. + 5.14 ± 23.44 nmol L^-1, P < 0.001) and decreased depression severity (-11.75 ± 6.40 vs. -3.61 ± 10.40, P = 0.003). No significant within- or between group differences were observed in serum IL-1β, IL-6 and hs-CRP concentrations.

CONCLUSION

Increased circulating 25(OH)D concentrations following 8-week vitamin D supplementation (50,000 IU 2wks^-1) resulted in a significant decrease in BDI-II scores in patients with mild to moderate depression. However, this effect was independent of the serum concentrations of the studied inflammatory biomarkers.

TRIAL REGISTRATION

The clinical trial registration code was obtained from the Iranian Registry of Clinical Trials (date of registration: 17/09/2018, registration number: IRCT20170926036425N1) and ClinicalTrials.gov (date of registration: 04/12/2018, registration number: NCT03766074).

Exploring the association of interleukin polymorphisms with aggression and internalizing behaviors in children and adolescents

BACKGROUND

There is growing evidence that inflammation influences mental health. Blood interleukin levels, which regulate inflammation, have been linked to aggression and internalizing behaviors. We performed a hypothesis-driven genetic study to (1) evaluate the association of IL1B, IL2, and IL6 gene variants with aggression and internalizing behaviors and (2) explore gene-environment interactions with childhood adversity in a deeply phenotyped childhood-onset aggression sample including 255 cases and 226 controls of European ancestry.

METHODS

We evaluated the association of putative functional and tag SNPs within IL1B, IL2, and IL6 with aggression case status, parent-reported internalizing problems, self-reported anxiety symptoms, and self-reported depressive symptoms in our sample. We also performed exploratory GxE analyses within cases, testing for statistical interaction between interleukin SNP genotype and childhood adversity for depressive symptoms.

RESULTS

No significant association was observed between any of the interleukin SNPs and childhood-onset aggression. We observed association of IL6 variant rs2069827 with depressive symptoms (p = 7.15×10^-4 ), and trends for an interaction between severe childhood adversity and SNPs in IL1B and IL2 for depressive symptoms.

CONCLUSIONS

Our findings provide preliminary evidence that common variation in IL6 may be associated with depressive symptoms in children and adolescents, and that common variation in interleukin genes may sensitize individuals to the depressogenic effects of traumatic life experiences. Replication in independent samples is needed.

Betaine Inhibits NLRP3 Inflammasome Hyperactivation and Regulates Microglial M1/M2 Phenotypic Differentiation, Thereby Attenuating Lipopolysaccharide-Induced Depression-Like Behavior

Depression is one of the most important mental illnesses and is closely related to inflammation. Betaine is a natural product with an anti-inflammatory and antioxidant activities. However, the mechanism by which betaine ameliorates depression-like behaviors induced by lipopolysaccharide (LPS) is poorly understood. The purpose of this study was to investigate the neuroprotective effect of betaine on LPS-induced depression-like behavior in mice and its mechanism of action. ICR mice were randomly divided into four groups: the control group, the LPS model group (0.83 mg/kg), the positive drug group (MIDO, 50 mg/kg), and the betaine group (5% and 1% in drinking water). The betaine group was administered for 21 days, and on the 22nd day, except for the blank group, LPS (0.83 mg/kg) was intraperitoneally injected to establish a lipopolysaccharide-induced mice depression-like model. Twenty-four hours after LPS injection, the tail suspension test (TST), open field test (OFT), and sucrose preference test (SPT) were performed to evaluate the effect of betaine on LPS-induced depressive behavior in mice. After the behavioral study, the mouse brain, hippocampus, and serum were taken for detection. The expressions of cytokines and inflammatory mediators were detected by ELISA, HE staining, immunofluorescence, immunohistochemistry, and western blotting. Western blotting was used to detect the protein expression levels of the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, and ASC, the protein expression levels of the microglial polarization markers COX-2, inducible nitric oxide synthase (iNOS), and CD206. The results showed that betaine significantly ameliorated the depression-like behavior in LPS-induced mice, significantly attenuated the production of proinflammatory cytokines and increased the release of an anti-inflammatory cytokines. Betaine decreased the expression of the NLRP3 inflammasome, decreased the expression of M1 polarization markers, tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), COX-2, and iNOS and promoted the expression of M2 polarization marker CD206. Our study suggests that betaine may promote the transition of microglia from the M1 to the M2 phenotype by inhibiting NLRP3 inflammasome activation, thereby attenuating lipopolysaccharide-induced depression-like behavior.

Involvement of the IL-6 Signaling Pathway in the Anti-Anhedonic Effect of the Antidepressant Agomelatine in the Chronic Mild Stress Model of Depression

Neuroinflammation has emerged as an important factor in the molecular underpinnings of major depressive disorder (MDD) pathophysiology and in the mechanism of action of antidepressants. Among the inflammatory mediators dysregulated in depressed patients, interleukin (IL)-6 has recently been proposed to play a crucial role. IL-6 activates a signaling pathway comprising the JAK/STAT proteins and characterized by a specific negative feedback loop exerted by the cytoplasmic protein suppressor of cytokine signalling-3 (SOCS3). On these bases, here, we explored the potential involvement of IL-6 signaling in the ability of the antidepressant drug agomelatine to normalize the anhedonic-like phenotype induced in the rat by chronic stress exposure. To this aim, adult male Wistar rats were subjected to the chronic mild stress (CMS) paradigm and chronically treated with vehicle or agomelatine. The behavioral evaluation was assessed by the sucrose consumption test, whereas molecular analyses were performed in the prefrontal cortex. We found that CMS was able to stimulate IL-6 production and signaling, including SOCS3 gene and protein expression, but the SOCS3-mediated feedback-loop inhibition failed to suppress the IL-6 cascade in stressed animals. Conversely, agomelatine treatment normalized the stress-induced decrease in sucrose consumption and restored the negative modulation of the IL-6 signaling via SOCS3 expression and activity. Our results provide additional information about the pleiotropic mechanisms that contribute to agomelatine’s therapeutic effects.

Autoantibodies in Neuropsychiatric Systemic Lupus Erythematosus (NPSLE): Can They Be Used as Biomarkers for the Differential Diagnosis of This Disease?

Systemic lupus erythematosus is a complex immunological disease where both environmental factors and genetic predisposition lead to the dysregulation of important immune mechanisms. Eventually, the combination of these factors leads to the production of self-reactive antibodies that can target any organ or tissue of the human body. Autoantibodies can form immune complexes responsible for both the organ damage and the most severe complications. Involvement of the central nervous system defines a subcategory of the disease, generally known with the denomination of neuropsychiatric systemic lupus erythematosus. Neuropsychiatric symptoms can range from relatively mild manifestations, such as headache, to more severe complications, such as psychosis. The evaluation of the presence of the autoantibodies in the serum of these patients is the most helpful diagnostic tool for the assessment of the disease. The scientific progresses achieved in the last decades helped researchers and physicians to discover some of autoepitopes targeted by the autoantibodies, although the majority of them have not been identified yet. Additionally, the central nervous system is full of epitopes that cannot be found elsewhere in the human body, for this reason, autoantibodies that selectively target these epitopes might be used for the differential diagnosis between patients with and without the neuropsychiatric symptoms. In this review, the most relevant data is reported with regard to mechanisms implicated in the production of autoantibodies and the most important autoantibodies found among patients with systemic lupus erythematosus with and without the neuropsychiatric manifestations.

Effects of early life stress on brain cytokines: A systematic review and meta-analysis of rodent studies

Exposure to early life stress (ELS) may lead to long-lasting neurobiological and behavioral impairments. Alterations in the immune system and neuroinflammatory state induced by ELS exposure are considered risk factors for developing psychiatric disorders. Here, we performed a systematic review and meta-analysis of rodent studies investigating the short and long-term effects of ELS exposure on anti and pro-inflammatory cytokines in brain tissues. Our analysis shows that animals exposed to ELS present an increase in pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. On the other hand, no alteration was observed in the anti-inflammatory cytokine IL-10. Meta-regression revealed that alterations were more prominent in the hippocampus of adult animals that were exposed to more extended periods of ELS. These inflammatory effects were not permanent since few alterations were identified in aged animals. Our findings suggest that ELS exposure alters pro-inflammatory cytokines expression and may act as a primer for a secondary challenge that may induce lifelong immune alterations. Moreover, the actual evidence is insufficient to comprehend the relationship between anti-inflammatory cytokines and ELS fully.

ST2825, a Small Molecule Inhibitor of MyD88, Suppresses NF-κB Activation and the ROS/NLRP3/Cleaved Caspase-1 Signaling Pathway to Attenuate Lipopolysaccharide-Stimulated Neuroinflammation

Neuroinflammation characterized by microglia activation is the mechanism of the occurrence and development of various central nervous system diseases. ST2825, as a peptide-mimetic MyD88 homodimerization inhibitor, has been identified as crucial molecule with an anti-inflammatory role in several immune cells, especially microglia. The purpose of the study was to investigate the anti-neuroinflammatory effects and the possible mechanism of ST2825. Methods: Lipopolysaccharide (LPS) was used to stimulate neuroinflammation in male BALB/c mice and BV2 microglia cells. The NO level was determined by Griess Reagents. The levels of pro-inflammatory cytokines and chemokines were determined by ELISA. The expressions of inflammatory proteins were determined by real-time PCR and Western blotting analysis. The level of ROS was detected by DCFH-DA staining. Results: In vivo, the improved levels of LPS-induced pro-inflammatory factors, including TNF-α, IL-6, IL-1β, MCP-1 and ICAM-1 in the cortex and hippocampus, were reduced after ST2825 treatment. In vitro, the levels of LPS-induced pro-inflammatory factors, including NO, TNF-α, IL-6, IL-1β, MCP-1, iNOS, COX2 and ROS, were remarkably decreased after ST2825 treatment. Further research found that the mechanism of its anti-neuroinflammatory effects appeared to be associated with inhibition of NF-κB activation and down-regulation of the NLRP3/cleaved caspase-1 signaling pathway. Conclusions: The current findings provide new insights into the activity and molecular mechanism of ST2825 for the treatment of neuroinflammation.

Dietary inflammatory index and depression risk in patients with chronic diseases and comorbidity

BACKGROUND

The coexistence of depression and chronic diseases can lead to greater disability and increased mortality. The objective of this study was to examine the association between Dietary Inflammatory Index (DII) and depression in patients with chronic diseases and comorbidity.

METHODS

Multivariable logistic regression analysis was used to investigate the relationship between DII and depression. Dose response relationship was analyzed using a generalized additive model with the smoothing plot.

RESULTS

A total of 7870 chronic diseases patients were enrolled. In multivariate model, the highest quintile of DII was associated with increased risk of depression in patients with diabetes (OR:1.73, 95CI%: 1.17, 2.57), hypertension (OR:1.93, 95CI%: 1.47, 2.52), coronary heart disease (OR:2.65, 95CI%: 1.18, 5.94). The dose response relationship curve suggested the DII tended to be linearly associated with depression in patients with chronic diseases and comorbidity, and the ORs for risk of depression increased with the increase of DII. Furthermore, in patients had at least one chronic comorbidity, the subgroup analysis results showed that those who age<60 years or male participants had higher risk of depression, with ORs (95% CIs) of 2.60 (1.81, 3.74) and 2.51 (1.65, 3.81), respectively.

CONCLUSION

The current study demonstrates that a higher DII is associated with an increased risk of depression in participants with chronic diseases and comorbidity, especially among those less than 60 years and men. Considering diet as a modifiable factor, limiting pro-inflammatory diet or encouraging anti-inflammatory diet may be an effective way to prevent depression and reduce depressive symptoms.

Inflammatory cytokines and callosal white matter microstructure in adolescents

Adolescent depression is characterized by heightened inflammation and altered connectivity of fronto-cingulate-limbic tracts, including the genu of the corpus callosum (CCG) and the uncinate fasciculus (UF). No studies, however, have yet examined the association between inflammation, measured by peripheral levels of cytokines, and white matter connectivity of fronto-cingulate-limbic tracts in adolescents. Here, 56 depressed adolescents (32 females, 3 non-binary; 16.23 ± 1.28 years) and 19 controls (10 females; 15.72 ± 1.17 years) completed a diffusion-weighted MRI scan at 3 Tesla. We conducted deterministic tractography to segment bilateral corpus callosum (genu and splenium) and UF and computed mean fractional anisotropy (FA) in each tract. A subset of participants (43 depressed and 17 healthy controls) also provided dried blood spot samples from which we assayed interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-ɑ) using a Luminex multiplex array. Depressed participants did not differ from controls in FA of the corpus callosum or UF (all FDR-corrected ps > 0.056) but exhibited higher levels of inflammation than did controls (IL-6: β = 0.91, FDR-corrected p = 0.006; TNF-α: β = 0.76, FDR-corrected p = 0.006). Although diagnostic group did not moderate the associations between inflammatory cytokines and FA in the CCG and UF, across both groups, greater peripheral inflammation was associated with lower FA in the CCG (IL-6: β = -0.38; FDR-corrected p = 0.044; TNF-ɑ: β = -0.41, FDR-corrected p = 0.044). This study is the first to examine associations between peripheral inflammation and white matter microstructure of fronto-cingulate-limbic tracts in depressed and nondepressed adolescents. Future mechanistic studies are needed to confirm our findings; nevertheless, our results suggest that heightened inflammation is an important component of neurophenotypes that are relevant to adolescent depression.

IL-6 and IL-8 are likely associated with psychological status in treatment naïve general population

BACKGROUND

Levels of inflammatory markers are elevated in patients with psychological disorders. However, anti-psychological drugs have an effect on proinflammatory cytokine production and disturb their relationship. Limited evidence focuses on the inflammatory marker profile of psychological status before treatment. This study aimed to investigate the inflammatory biomarker profiles of psychological treatment-naive individuals.

METHODS

We included 790 psychological treatment-naive individuals from a longitudinal cohort study of Midlife in the United States (MIDUS). Symptoms of depression, anxiety, and stress were assessed by the Center for Epidemiologic Studies Depression Scale (CES-D) subscales, the Social Anxiety Scale (STAI), and Liebowitz Social Anxiety Scale (LSAS), the Perceived Stress Scale (PSS), respectively.

RESULTS

Spearman correlation analysis showed that a higher CESD total score was correlated with higher CRP (p=0.009), IL-6 (p=0.007), fibrinogen (p=0.036), E-selectin (p=0.018), ICAM-1 (p=0.013), and IL-8 (p=0.05) levels. Multivariate linear regression analysis showed that the CESD total score was positively associated with the levels of IL-6 (p=0.024) after adjustments. Moreover, the perceived stress score (PSS) was negatively associated with the levels of IL-8 (p=0.025). However, these associations were not significant after multiple testing (p=0.088, 0.091, respectively).

LIMITATIONS

The casual relationship cannot be drawn due to the cross-sectional design CONCLUSION: Overall, our results suggested IL-6 and IL-8 might play a important role in the pathogenesis of psychological disorder. Larger and longitude studies are needed to confirm our results.

Possible Involvement of the IL-6/JAK2/STAT3 Pathway in the Hypothalamus in Depressive-Like Behavior of Rats Exposed to Chronic Mild Stress

INTRODUCTION

The interleukin-6/janus kinase 2/signal transducer and activator of transcription 3 (IL-6/JAK2/STAT3) pathway plays an important role in immune function, but little research has focused on this pathway in depression. We sought to examine the relationship between the IL-6/JAK2/STAT3 pathway and depressive-like behavior.

METHODS

Using a chronic mild stress (CMS) paradigm, a total of 36 adult male Sprague-Dawley rats were divided into four matched groups: (1) control + vehicle, (2) CMS + vehicle, (3) control + paroxetine, and (4) CMS + paroxetine. We investigated the effects of CMS on depressive-like behavior by using the forced swimming test (FST). Subsequently, the mRNA levels of members of the IL-6/JAK2/STAT3 pathway were assessed by qRT-PCR.

RESULTS

We found that rats exposed to CMS displayed a significant increase in immobility time and a decrease in climbing time in the FST. Moreover, mRNA levels of IL-6, JAK2, and STAT3 in the hypothalamus were increased following CMS. We also found that mRNA levels of IL-6, JAK2, and STAT3 were normalized by paroxetine administration, which coincided with normalization of the depressive-like behavior.

CONCLUSIONS

The IL-6/JAK2/STAT3 pathway may be activated in depression, and targeting this pathway may provide a novel effective therapeutic approach for the treatment of depression.

Mouse models of immune dysfunction: their neuroanatomical differences reflect their anxiety-behavioural phenotype

Extensive evidence supports the role of the immune system in modulating brain function and behaviour. However, past studies have revealed striking heterogeneity in behavioural phenotypes produced from immune system dysfunction. Using magnetic resonance imaging, we studied the neuroanatomical differences among 11 distinct genetically modified mouse lines (n = 371), each deficient in a different element of the immune system. We found a significant and heterogeneous effect of immune dysfunction on the brains of both male and female mice. However, by imaging the whole brain and using Bayesian hierarchical modelling, we were able to identify patterns within the heterogeneous phenotype. Certain structures-such as the corpus callosum, midbrain, and thalamus-were more likely to be affected by immune dysfunction. A notable brain-behaviour relationship was identified with neuroanatomy endophenotypes across mouse models clustering according to anxiety-like behaviour phenotypes reported in literature, such as altered volume in brains regions associated with promoting fear response (e.g., the lateral septum and cerebellum). Interestingly, genes with preferential spatial expression in the most commonly affected regions are also associated with multiple sclerosis and other immune-mediated diseases. In total, our data suggest that the immune system modulates anxiety behaviour through well-established brain networks.

Protease-activated receptor 2 activation induces behavioural changes associated with depression-like behaviour through microglial-independent modulation of inflammatory cytokines

RATIONALE

Major depressive disorder (MDD) is a leading cause of disability worldwide but currently prescribed treatments do not adequately ameliorate the disorder in a significant portion of patients. Hence, a better appreciation of its aetiology may lead to the development of novel therapies.

OBJECTIVES

In the present study, we have built on our previous findings indicating a role for protease-activated receptor-2 (PAR2) in sickness behaviour to determine whether the PAR2 activator, AC264613, induces behavioural changes similar to those observed in depression-like behaviour.

METHODS

AC264613-induced behavioural changes were examined using the open field test (OFT), sucrose preference test (SPT), elevated plus maze (EPM), and novel object recognition test (NOR). Whole-cell patch clamping was used to investigate the effects of PAR2 activation in the lateral habenula with peripheral and central cytokine levels determined using ELISA and quantitative PCR.

RESULTS

Using a blood-brain barrier (BBB) permeable PAR2 activator, we reveal that AC-264613 (AC) injection leads to reduced locomotor activity and sucrose preference in mice but is without effect in anxiety and memory-related tasks. In addition, we show that AC injection leads to elevated blood sera IL-6 levels and altered cytokine mRNA expression within the brain. However, neither microglia nor peripheral lymphocytes are the source of these altered cytokine profiles.

CONCLUSIONS

These data reveal that PAR2 activation results in behavioural changes often associated with depression-like behaviour and an inflammatory profile that resembles that seen in patients with MDD and therefore PAR2 may be a target for novel antidepressant therapies.

Neurocircuitry basis of the opioid use disorder-post-traumatic stress disorder comorbid state: conceptual analyses using a dimensional framework

Understanding the interface between opioid use disorder (OUD) and post-traumatic stress disorder (PTSD) is challenging. By use of a dimensional framework, such as research domain criteria, convergent and targetable neurobiological processes in OUD-PTSD comorbidity can be identified. We hypothesise that, in OUD-PTSD, circuitry that is implicated in two research domain criteria systems (ie, negative valence and cognitive control) underpins dysregulation of incentive salience, negative emotionality, and executive function. We also propose that the OUD-PTSD state might be systematically investigated with approaches outlined within a neuroclinical assessment framework for addictions and PTSD. Our dimensional analysis of the OUD-PTSD state shows how first-line therapeutic approaches (ie, partial μ-type opioid receptor [MOR1] agonism) modulate overlapping neurobiological and clinical features and also provides mechanistic rationale for evaluating polytherapeutic strategies (ie, partial MOR1 agonism, κ-type opioid receptor [KOR1] antagonism, and α-2A adrenergic receptor [ADRA2A] agonism). A combination of these therapeutic mechanisms is projected to facilitate recovery in patients with OUD-PTSD by mitigating negative valence states and enhancing executive control.

Associations of Serum Cytokines, Growth Factors, and High-Sensitivity C-Reactive Protein Levels in Patients with Major Depression with and without Type 2 Diabetes Mellitus: An Explanatory Investigation

PURPOSE

We investigated the serum levels of cytokines, including interleukin 1β (IL-β), IL-6, IL-8, IL-10, tumor necrosis factor-alpha (TNF-α), and growth factors, including brain-derived neurotrophic factor, vascular endothelial growth factor, and insulin-like growth factor 1, and their association with major depression in patients with and without type 2 diabetes mellitus. We also investigated the response to antidepressant treatment in both groups.

PATIENTS AND METHODS

Forty-one patients with major depression were recruited at the University Hospital of Occupational and Environmental Health. All patients were diagnosed with major depression using the Diagnostic and Statistical Manual for Mental Disorders, Fifth Edition. Type 2 diabetes mellitus was diagnosed according to the criteria of the Japan Diabetes Society. Six healthy controls with no history of psychiatric or physical diseases were also enrolled. Serum levels of several cytokines, growth factors, and high-sensitivity C-reactive protein (hs-CRP) were measured. The clinical symptoms of patients with major depression were assessed using the Montgomery-Asberg Depression Rating Scale.

RESULTS

Significant differences in cytokines, growth factors, and hs-CRP were observed between the major depression and healthy control groups. Serum TNF-α levels were significantly higher in patients with major depression and type 2 diabetes mellitus than in those without type 2 diabetes mellitus. In the major depression group, serum IL-6 and hs-CRP levels tended to be higher in patients with type 2 diabetes mellitus than in those without. Several correlations among cytokines, growth factors, and hs-CRP were observed in patients with major depression with and without type 2 diabetes mellitus. Responses to pharmacological interventions for major depression did not differ between patients with and without type 2 diabetes mellitus.

CONCLUSION

Serum levels of TNF-α, hs-CRP, and IL-6 were different between patients with major depression with and without type 2 diabetes mellitus. Also, correlations were found between serum levels of cytokines, growth factors, and hs-CRP in patients with major depression. Inflammatory factors, which may be associated with growth factors, may be involved in the pathophysiology of major depression, particularly among patients with comorbid type 2 diabetes mellitus.

The effect and mechanism of Jiao-tai-wan in the treatment of diabetes mellitus with depression based on network pharmacology and experimental analysis

BACKGROUND

The incidence of diabetes mellitus (DM) and depression is increasing year by year around the world, bringing a serious burden to patients and their families. Jiao-tai-wan (JTW), a well-known traditional Chinese medicine (TCM), has been approved to have hypoglycemic and antidepressant effects, respectively, but whether JTW has such dual effects and its potential mechanisms is still unknown. This study is to evaluate the dual therapeutic effects of JTW on chronic restraint stress (CRS)-induced DM combined with depression mice, and to explore the underlying mechanisms through network pharmacology.

METHODS

CRS was used on db/db mice for 21 days to induce depression-like behaviors, so as to obtain the DM combined with depression mouse model. Mice were treated with 0.9% saline (0.1 ml/10 g), JTW (3.2 mg/kg) and Fluoxetine (2.0 mg/kg), respectively. The effect of JTW was accessed by measuring fasting blood glucose (FBG) levels, conducting behavioral tests and observing histopathological change. The ELISA assay was used to evaluate the levels of inflammatory cytokines and the UHPLC-MS/MS method was used to determine the depression-related neurotransmitters levels in serum. The mechanism exploration of JTW against DM and depression were performed via a network pharmacological method.

RESULTS

The results of blood glucose measurement showed that JTW has a therapeutic effect on db/db mice. Behavioral tests and the levels of depression-related neurotransmitters proved that JTW can effectively ameliorate depression-like symptoms in mice induced by CRS. In addition, JTW can also improve the inflammatory state and reduce the number of apoptotic cells in the hippocampus. According to network pharmacology, 28 active compounds and 484 corresponding targets of JTW, 1407 DM targets and 1842 depression targets were collected by screening the databases, and a total of 117 targets were obtained after taking the intersection. JTW plays a role in reducing blood glucose level and antidepressant mainly through active compounds such as quercetin, styrene, cinnamic acid, ethyl cinnamate, (R)-Canadine, palmatine and berberine, etc., the key targets of its therapeutic effect include INS, AKT1, IL-6, VEGF-A, TNF and so on, mainly involved in HIF-1 signal pathway, pathways in cancer, Hepatitis B, TNF signal pathway, PI3K-Akt signal pathway and MAPK signaling pathway, etc. CONCLUSION: Our experimental study showed that JTW has hypoglycemic and antidepressant effects. The possible mechanism was explored by network pharmacology, reflecting the characteristics of multi-component, multi-target and multi-pathway, which provides a theoretical basis for the experimental research and clinical application of JTW in the future.

Systemic effects of IL-6 blockade in rheumatoid arthritis beyond the joints

Interleukin (IL)-6 is produced locally in response to an inflammatory stimulus, and is able to induce systemic manifestations at distance from the site of inflammation. Its unique signaling mechanism, including classical and trans-signaling pathways, leads to a major expansion in the number of cell types responding to IL-6. This pleiotropic cytokine is a key factor in the pathogenesis of rheumatoid arthritis (RA) and is involved in many extra-articular manifestations that accompany the disease. Thus, IL-6 blockade is associated with various biological effects beyond the joints. In this review, the systemic effects of IL-6 in RA comorbidities and the consequences of its blockade will be discussed, including anemia of chronic disease, cardiovascular risks, bone and muscle functions, and neuro-psychological manifestations.

How Inflammation Affects the Brain in Depression: A Review of Functional and Structural MRI Studies

This narrative review discusses how peripheral and central inflammation processes affect brain function and structure in depression, and reports on recent peripheral inflammatory marker-based functional and structural magnetic resonance imaging (MRI) studies from the perspective of neural-circuit dysfunction in depression. Chronic stress stimulates the activity of microglial cells, which increases the production of pro-inflammatory cytokines in the brain. In addition, microglial activation promotes a shift from the synthesis of serotonin to the synthesis of neurotoxic metabolites of the kynurenine pathway, which induces glutamate-mediated excitotoxicity in neurons. Furthermore, the region specificity of microglial activation is hypothesized to contribute to the vulnerability of specific brain regions in the depression-related neural circuits to inflammation-mediated brain injury. MRI studies are increasingly investigating how the blood levels of inflammatory markers such as C-reactive protein, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α are associated with functional and structural neuroimaging markers in depression. Functional MRI studies have found that peripheral inflammatory markers are associated with aberrant activation patterns and altered functional connectivity in neural circuits involved in emotion regulation, reward processing, and cognitive control in depression. Structural MRI studies have suggested that peripheral inflammatory markers are related to reduced cortical gray matter and subcortical volumes, cortical thinning, and decreased integrity of white matter tracts within depression-related neural circuits. These neuroimaging findings may improve our understanding of the relationships between neuroinflammatory processes at the molecular level and macroscale in vivo neuralcircuit dysfunction in depression.

P2X7R antagonists in chronic stress-based depression models: a review

Depression affects around 320 million people worldwide. Growing evidence proposes the immune system to be the core interface between psychosocial stress and the neurobiological and behavioural features of depression. Many studies have identified purinergic signalling via the P2X7 receptor (P2X7R) to be of great importance in depression genesis yet only a few have evaluated P2X7R antagonists in chronic stress-based depression models. This review summarizes their findings and analyses their methodology. The four available studies used three to nine weeks of unpredictable, chronic mild stress or unpredictable, chronic stress in male mice or rats. Stress paradigm composition varied moderately, with stimuli being primarily psychophysical rather than psychosocial. Behavioural testing was performed during or after the last week of stress application and resulted in depressive-like behaviours, immune changes (NLRP3 assembly, interleukin-1β level increase, microglia activation) and neuroplasticity impairment. During the second half of each stress paradigm, a P2X7R antagonist (Brilliant Blue G, A-438079, A-804598) was applied. Studies differed with regard to antagonist dosage and application timing. Nonetheless, all treatments attenuated the stress-induced neurobiological changes and depressive-like behaviours. The evidence at hand underpins the importance of P2X7R signalling in chronic stress and depression. However, improvements in study planning and reporting are necessary to minimize experimental bias and increase data purview. To achieve this, we propose adherence to the Research Domain Criteria and the STRANGE framework.

Exposure to polybrominated diphenyl ether-47 increases the risk of post-partum depression

INTRODUCTION

Post-partum depression (PPD) affects up to 19.1% of pregnancies and is associated with increased levels of proinflammatory cytokines, inflammation, and reductions in brain-derived neurotrophic factor (BDNF). Previous work by our team suggests that environmental toxins such as polybrominated diphenyl ethers (PBDEs) enhance placental inflammation and reduce BDNF production. Nearly, 100% of studied women in California have some level of exposure to these compounds due to extensive use of the flame retardants. High levels of exposure to PBDEs has been linked to increased risk of adverse pregnancy complications associated with placental inflammation such as preterm birth and gestational diabetes but their effects on risk of PPD is unclear.

OBJECTIVE

To determine if PPD is associated with higher levels of PBDE-47, the most common PBDE congener in maternal plasma.

METHODS

PBDE-47 was quantified in first trimester plasma samples collected from a cohort of 367 asymptomatic pregnant women that were routinely screened for depressive symptoms for 1 year post-partum. Data were analyzed using general linear models and multivariable logistic regression to determine if higher levels of PBDE-47 in the first trimester are associated with development of PPD.

RESULTS

Women who developed PPD (n = 22) had significantly higher PBDE-47 levels in their plasma (p=.031) relative to those in which PPD was not diagnosed. Logistic regression analysis suggested that each two-fold increase in PBDE-47 concentrations increased the risk of PPD by 22% (OR = 1.22, 95% CI: 1.03, 1.47). Groups were similar regarding PTB rate, race-ethnicity, parity, child's sex, maternal pre-pregnancy obesity status, maternal age, family income, and study center. Results remained significant after adjustment for these possible confounding factors.

CONCLUSIONS

These results suggest that PBDE-47 exposure in the first trimester is associated with increased risk of PPD.

Advances of Endothelial Progenitor Cells in the Development of Depression

Depression is a major psychological disease of human beings. With the severity of depression, it elevates the risk of cardiovascular disease (CVD), especially acute coronary syndrome (ACS), resulting in serious harm to human health. The number of endothelial progenitor cells (EPCs) is closely related to the development of depression. It has been reported that the number of peripheral blood EPCs in patients with depression was reduced. However, effects on the function of EPCs in depression are still unclear. This paper aims to analyze and summarize the research of EPCs in depression, and we envision that EPCs might act as a new target for evaluating the severity of depression and its complications.

Unravelling the broader complexity of IL-6 involvement in health and disease

The classification of interleukin-6 (IL-6) as a pro-inflammatory cytokine undervalues the biological impact of this cytokine in health and disease. With broad activities affecting the immune system, tissue homeostasis and metabolic processes, IL-6 displays complex biology. The significance of these involvements has become increasingly important in clinical settings where IL-6 is identified as a prominent target for therapy. Here, clinical experience with IL-6 antagonists emphasises the need to understand the context-dependent properties of IL-6 within an inflammatory environment and the anticipated or unexpected consequences of IL-6 blockade. In this review, we will describe the immunobiology of IL-6 and explore the gamut of IL-6 bioactivity affecting the clinical response to biological drugs targeting this cytokine pathway.

Characterisation of the Mouse Cerebellar Proteome in the GFAP-IL6 Model of Chronic Neuroinflammation

GFAP-IL6 transgenic mice are characterised by astroglial and microglial activation predominantly in the cerebellum, hallmarks of many neuroinflammatory conditions. However, information available regarding the proteome profile associated with IL-6 overexpression in the mouse brain is limited. This study investigated the cerebellum proteome using a top-down proteomics approach using 2-dimensional gel electrophoresis followed by liquid chromatography-coupled tandem mass spectrometry and correlated these data with motor deficits using the elevated beam walking and accelerod tests. In a detailed proteomic analysis, a total of 67 differentially expressed proteoforms including 47 cytosolic and 20 membrane-bound proteoforms were identified. Bioinformatics and literature mining analyses revealed that these proteins were associated with three distinct classes: metabolic and neurodegenerative processes as well as protein aggregation. The GFAP-IL6 mice exhibited impaired motor skills in the elevated beam walking test measured by their average scores of 'number of footslips' and 'time to traverse' values. Correlation of the proteoforms' expression levels with the motor test scores showed a significant positive correlation to peroxiredoxin-6 and negative correlation to alpha-internexin and mitochondrial cristae subunit Mic19. These findings suggest that the observed changes in the proteoform levels caused by IL-6 overexpression might contribute to the motor function deficits.

Depression and interleukin-6 signaling: A Mendelian Randomization study

BACKGROUND

A large body of research has reported associations between depression and elevated interleukin-6 (IL-6), a cytokine with several roles including pro-inflammatory signaling. The nature and directionality of this relationship are not yet clear. In this study we use Mendelian Randomization to examine the possibility of a causal relationship between IL-6 and depressive symptoms, and to explore multiple signaling pathways that could serve as mechanisms for this relationship.

METHODS

This study uses a two-sample Mendelian Randomization design. Data come from the UK Biobank (n = 89,119) and published summary statistics from six existing GWAS analyses. The primary analysis focuses on the soluble interleukin-6 receptor (sIL-6R), which is involved in multiple signaling pathways. Exploratory analyses use C-reactive protein (CRP) and soluble glycoprotein 130 (sgp130) to further examine potential underlying mechanisms.

RESULTS

Results are consistent with a causal effect of sIL-6R on depression (PCA-IVW Odds Ratio: 1.023 (95% Confidence Interval: 1.006-1.039), p = 0.006). Exploratory analyses demonstrate that the relationship could be consistent with either decreased classical signaling or increased trans signaling as the underlying mechanism.

DISCUSSION

These results strengthen the body evidence implicating IL-6 signaling in depression. When compared with existing observational and animal findings, the direction of these results suggests involvement of IL-6 trans signaling. Further study is needed to examine whether IL6R genetic variants might influence IL-6 trans signaling in the brain, as well as to explore other potential pathways linking depression and inflammation.

Pairing Binge Drinking and a High-Fat Diet in Adolescence Modulates the Inflammatory Effects of Subsequent Alcohol Consumption in Mice

Alcohol binge drinking (BD) and poor nutritional habits are two frequent behaviors among many adolescents that alter gut microbiota in a pro-inflammatory direction. Dysbiotic changes in the gut microbiome are observed after alcohol and high-fat diet (HFD) consumption, even before obesity onset. In this study, we investigate the neuroinflammatory response of adolescent BD when combined with a continuous or intermittent HFD and its effects on adult ethanol consumption by using a self-administration (SA) paradigm in mice. The inflammatory biomarkers IL-6 and CX3CL1 were measured in the striatum 24 h after BD, 3 weeks later and after the ethanol (EtOH) SA. Adolescent BD increased alcohol consumption in the oral SA and caused a greater motivation to seek the substance. Likewise, mice with intermittent access to HFD exhibited higher EtOH consumption, while the opposite effect was found in mice with continuous HFD access. Biochemical analyses showed that after BD and three weeks later, striatal levels of IL-6 and CX3CL1 were increased. In addition, in saline-treated mice, CX3CL1 was increased after continuous access to HFD. After oral SA procedure, striatal IL-6 was increased only in animals exposed to BD and HFD. In addition, striatal CX3CL1 levels were increased in all BD- and HFD-exposed groups. Overall, our findings show that adolescent BD and intermittent HFD increase adult alcohol intake and point to neuroinflammation as an important mechanism modulating this interaction.

Neuroimmunology of depression

Depression is one of the leading causes of disability worldwide and a major contributor to the global burden of disease, yet the cellular and molecular etiology of depression remain largely unknown. Major Depressive Disorder (MDD) is associated with a variety of chronic physical inflammatory and autoimmune disorders, and mood disorders may act synergistically with other medical disorders to worsen patient outcomes. Here, we outline the neuroimmune complement, explore the evidence for altered immune system function in MDD, and present some of the potential mechanisms by which immune cells and molecules may drive the onset and course of MDD. These include pro-inflammatory signaling, alterations in the hypothalamic-pituitary-adrenal axis, dysregulation of the serotonergic and noradrenergic neurotransmitter systems, neuroinflammation, and meningeal immune dysfunction. Finally, we discuss the interactions between current antidepressants and the immune system and propose the possibility of immunomodulatory drugs as potential novel antidepressant treatments.

Toll-like receptor 4-mediated cytokine synthesis and post-stroke depressive symptoms

Altered cytokine synthesis thought to contribute to the pathophysiology of post-stroke depression (PSD). Toll-like receptor 4 (TLR4) is a master regulator of innate immunity. The aim of this study was to explore the putative association between TLR4-mediated cytokine synthesis and subsequent symptoms of PSD. In total, 262 patients with ischemic stroke and without a history of PSD were included. Depressive symptoms were assessed using the Patient Health Questionnaire-9 in 170 patients on Day 8 and in 146 at 3 months after stroke. Blood samples taken on Day 3 after stroke were stimulated ex vivo with lipopolysaccharide (LPS). Ex vivo synthesized cytokines (TNFα, IP-10, IL-1β, IL-6, IL-8, IL-10, and IL-12p70) and circulating cytokines (TNFα, IL-6, sIL-6R, and IL-1ra) were measured using the enzyme-linked immunoassay or cytometric method. RNA sequencing was used to determine the gene expression profile of LPS-induced cytokines and chemokines. LPS-induced cytokine synthesis and the gene expression of TLR4-dependent cytokines and chemokines did not differ between patients with and without greater depressive symptoms. The plasma level of IL-6, but not TNFα, sIL-6R, and IL-1ra, was higher in patients who developed depressive symptoms at 3 months after stroke (median: 4.7 vs 3.4 pg/mL, P = 0.06). Plasma IL-6 predicted the severity of depressive symptoms at 3 months after stroke (β = 0.42, P = 0.03). In conclusion, TLR4-dependent cytokine synthesis was not associated with greater post-stroke depressive symptoms in this study. Circulating IL-6 might be associated with depressive symptoms occurring at 3 months after stroke.