Chemokines in depression in health and in inflammatory illness: a systematic review and meta-analysis

Peripheral mitochondrial DNA as a neuroinflammatory biomarker for major depressive disorder

In the pathogenesis of major depressive disorder, chronic stress-related neuroinflammation hinders favorable prognosis and antidepressant response. Mitochondrial DNA may be an inflammatory trigger, after its release from stress-induced dysfunctional central nervous system mitochondria into peripheral circulation. This evidence supports the potential use of peripheral mitochondrial DNA as a neuroinflammatory biomarker for the diagnosis and treatment of major depressive disorder. Herein, we critically review the neuroinflammation theory in major depressive disorder, providing compelling evidence that mitochondrial DNA release acts as a critical biological substrate, and that it constitutes the neuroinflammatory disease pathway. After its release, mitochondrial DNA can be carried in the exosomes and transported to extracellular spaces in the central nervous system and peripheral circulation. Detectable exosomes render encaged mitochondrial DNA relatively stable. This mitochondrial DNA in peripheral circulation can thus be directly detected in clinical practice. These characteristics illustrate the potential for mitochondrial DNA to serve as an innovative clinical biomarker and molecular treatment target for major depressive disorder. This review also highlights the future potential value of clinical applications combining mitochondrial DNA with a panel of other biomarkers, to improve diagnostic precision in major depressive disorder.

Integrated network pharmacology and transcriptomics to reveal the mechanism of Passiflora against depressive disorder: An observational study

Relevant studies have pointed out that Passiflora could relieve depressive disorder (DD) related symptoms, such as anxiety and insomnia, but its mechanism in DD has not been reported. In this study, DD-related transcriptome data was extracted from the Gene Expression Omnibus (GEO) database. Subsequently, 50 differentially expressed genes (DEGs) were screened by "limma," and the enrichment analysis of these DEGs revealed that they were associated with neuro-inflammatory-related signaling pathways, including IL-17, TNF, NF-kappa B, etc signaling pathways. Then, CCDC58, CXCL5, EGR1, LOC101929855, SCML1, and THBS1 were screened as biomarkers of DD by the least absolute shrinkage and selection operator (LASSO) analysis. Moreover, Harmaline, Harmine, Quercetin, and Kaempferol were the key chemically active ingredients of Passiflora. Noticeable, THBS1 and Quercetin were connected closely. In addition, the quantitative real-time polymerase chain reaction (qRT-PCR) confirmed that the key biomarkers (EGR1 and THBS1) were significantly lowly expressed in DD samples. In summary, we identified 2 key biomarkers of DD and 4 key chemically active ingredients of Passiflora. The potential mechanism of antidepressant effect of DD associated with neuro-inflammatory responses and neurotransmitter function. These might related to the synergistic activity of its key active ingredients with TNF-α, IL-1β, IL-6, etc, which work with EGR1 and THBS1 to regulate IL-17, NF-kappa B, TNF, etc signaling pathways. These findings might help to deepen the understanding of the mechanism of Passiflora in clinical treatment of DD.

Major depressive disorder, neuroticism, suicidal behaviors, and depression severity are associated with cytokine networks and their intricate interactions with metabolic syndrome

OBJECTIVES

To identify alterations in the immune profiles in outpatients with major depression (MDD), and its associations with key features, such as suicidal ideation, neuroticism, cognitive symptoms, and the depression phenome while accounting for metabolic syndrome (MetS).

METHODS

In this case-control study, we assayed 48 serum cytokines, chemokines, and growth factors in 67 healthy controls and 66 MDD outpatients. Around 50 % of the outpatient MDD and control participants had a diagnosis of MetS.

RESULTS

Ten differentially expressed proteins (DEPs) were upregulated in outpatient MDD (i.e., CXCL12, tumor necrosis factor [TNF]β, platelet-derived growth factor [PDGF], CCL11, interleukins [IL]9, IL4, CCL5, CCL2, CCL4, IL1 receptor antagonist [IL1RN]), indicating an immune and defense response. Six DEPs were downregulated (vascular endothelial growth factor A [VEGFA], IL12, CCL3, colony stimulating factor [CSF]1, IL1B, nerve growth factor [NGF]), indicating lowered neurogenesis and neuron death regulation. Significant interactions between outpatient MDD and MetS caused a) substantial increases in IL4, IL17, TNF, TNFB, CCL2, CCL5, PDGF, IL1RN; and b) downregulation of VEGFA and FGF. A large part of the variance in neuroticism (26 %), suicidal behaviors (23 %), and the MDD phenome (31 %) was predicted by immunological data and interactions between MetS and CCL5, TNFB or VEGFA.

CONCLUSION

Outpatient MDD is characterized by a cytokine profile with neurotoxic potential which partly explains neuroticism, suicidal behaviors, and the phenome's severity. Lowered IL-10 and activated cytokine profiles with neurotoxic potential are characteristics of outpatient MDD and other depression phenotypes, including severe first-episode inpatient MDD. The presence of MetS in outpatient MDD considerably activates immune profiles with neurotoxic potential. Consequently, immune studies in MDD should always be performed in subjects with and without MetS.

Genetic association and drug target exploration of inflammation-related proteins with risk of major depressive disorder

BACKGROUND

In numerous observational studies, circulating inflammation-related proteins have been linked with major depressive disorder (MDD), yet the precise causal direction of this relationship remains unclear. This study aims to investigate the potential causal link between inflammation-related proteins and the risk of developing MDD.

METHODS

We utilized summary data from a genome-wide association study (GWAS) of 91 circulating inflammation-associated proteins in 14,824 individuals of European descent. Additionally, we incorporated findings from a substantial GWAS on MDD, which included 294,322 cases and 741,438 controls. Our analysis employed a two-sample bidirectional Mendelian randomization (MR) approach, with inverse variance weighting (IVW) as the primary method. We augmented this with two supplementary techniques (MR-Egger and weighted median approaches) to detect and address potential pleiotropy. Furthermore, to identify and evaluate possible drug targets, we conducted a thorough search within the Drug-Gene Interaction Database (DGIdb).

RESULTS

Analysis using MR unveiled significant and causative associations between genetically determined CASP-8 (odds ratio (OR): 0.97), CD40 (OR: 0.96), IL-18 (OR: 0.98), SLAMF1 (OR: 0.97), and uPA (OR: 0.98) with MDD. Conversely, reverse MR analysis indicated causal associations between MDD and CCL19 (OR: 1.15), HGF (OR: 1.15), IL-8 (OR: 1.10), IL-18 (OR: 1.11), IL20RA (OR: 1.12), TGFA (OR: 1.12) and TNFSF14 (OR: 1.16). Notably, a significant bidirectional causal link was observed between IL-18 and MDD. Gene-drug analysis identified CD40, HGF, IL-8, IL-18, SLAMF1, and TGFA as potential therapeutic targets.

CONCLUSIONS

We've pinpointed causal links between inflammation-related proteins and MDD, offering compelling and innovative evidence to enhance our understanding of the inflammatory mechanisms involved in MDD and to investigate potential targets for anti-MDD medications.

Balancing the mind: Toward a complete picture of the interplay between gut microbiota, inflammation and major depressive disorder

The intricate interplay existing between gut microbiota and homeostasis extends to the realm of the brain, where emerging research underscores the significant impact of the microbiota on mood regulation and overall neurological well-being and vice-versa, with inflammation playing a pivotal role in mediating these complex interactions. This comprehensive review explores the complex interplay between inflammation, alterations in gut microbiota, and their impact on major depressive disorder (MDD). It provides a cohesive framework for the puzzle pieces of this triad, emphasizing recent advancements in understanding the gut microbiota and inflammatory states' contribution to the depressive features. Two directions of communication between the gut and the brain in depression are discussed, with inflammation serving as a potential modulator. Therapeutic implications were discussed as well, drawing insights from interventional studies on the effects of probiotics on gut bacterial composition and depressive symptoms. Ultimately, this review will attempt to provide a complete and valuable framework for future research and therapeutic interventions in MDD.

Additive effects of depression and obesity on neural correlates of inhibitory control

BACKGROUND

Depression and obesity are associated with impaired inhibitory control. Behavioral evidence indicates an exacerbating additive effect when both conditions co-occur. However, the underlying neural mechanisms remain unclear. Moreover, systemic inflammation affects neurocognitive performance in both individuals with depression and obesity. Here, we investigate additive effects of depression and obesity on neural correlates of inhibitory control, and examine inflammation as a connecting pathway.

METHODS

We assessed inhibitory control processing in 64 individuals with obesity and varying degrees of depressed mood by probing neural activation and connectivity during an fMRI Stroop task. Additionally, we explored associations of altered neural responses with individual differences in systemic inflammation. Data were collected as part of the BARICO (Bariatric surgery Rijnstate and Radboudumc neuroimaging and Cognition in Obesity) study.

RESULTS

Concurrent depression and obesity were linked to increased functional connectivity between the supplementary motor area and precuneus and between the inferior occipital and inferior parietal gyrus. Exploratory analysis revealed that circulating inflammation markers, including plasma leptin, IL-6, IL-8, and CCL-3 correlated with the additive effect of depression and obesity on altered functional connectivity.

LIMITATIONS

The observational design limits causal inferences. Future research employing longitudinal or intervention designs is required to validate these findings and elucidate causal pathways.

CONCLUSION

These findings suggest increased neural crosstalk underlying impaired inhibitory control in individuals with concurrent obesity and depressed mood. Our results support a model of an additive detrimental effect of concurrent depression and obesity on neurocognitive functioning, with a possible role of inflammation.

Mental disorders after myocardial infarction: potential mediator role for chemokines in heart-brain interaction?

Acute myocardial infarction (MI) remains one of the leading causes of mortality and morbidity in the global communities. A prevailing topic that has attracted increasing attentions over the past few decades is the so-called heart-brain interaction, in particular following a major traumatic event such as MI. Increased prevalence of depression and other mental disorders has been recognized in cardiac patients after MI, coronary catheterization, or cardiothoracic surgeries. In this review, we focus on the potential pathogenic mechanisms and pre-clinical transcriptomic evidence for identifying potential mediators of post-MI depression. We first summarize the conventional mechanistic understanding that leads to the current clinical management of post-MI depression with the use of selective serotonin reuptake inhibitors (SSRIs) and cognitive behavior and exercise therapies. We further envisage a possible role played by certain chemokines, e.g., Chemokine (C-X-C motif) ligand 12 (CXCL12) and Chemokine (C-C motif) ligand 2 (CCL22), in serving as signaling molecules to connect the MI-induced heart damage to the pro-depressive changes in brain during the post-MI period. Future in-depth investigations into this chemokine hypothesis will be instrumental in developing new chemokine-targeted therapies for better management of the cardiac patients suffering from post-MI depression.

Dissecting depression symptoms: Multi-omics clustering uncovers immune-related subgroups and cell-type specific dysregulation

In a subset of patients with mental disorders, such as depression, low-grade inflammation and altered immune marker concentrations are observed. However, these immune alterations are often assessed by only one data type and small marker panels. Here, we used a transdiagnostic approach and combined data from two cohorts to define subgroups of depression symptoms across the diagnostic spectrum through a large-scale multi-omics clustering approach in 237 individuals. The method incorporated age, body mass index (BMI), 43 plasma immune markers and RNA-seq data from peripheral mononuclear blood cells (PBMCs). Our initial clustering revealed four clusters, including two immune-related depression symptom clusters characterized by elevated BMI, higher depression severity and elevated levels of immune markers such as interleukin-1 receptor antagonist (IL-1RA), C-reactive protein (CRP) and C-C motif chemokine 2 (CCL2 or MCP-1). In contrast, the RNA-seq data mostly differentiated a cluster with low depression severity, enriched in brain related gene sets. This cluster was also distinguished by electrocardiography data, while structural imaging data revealed differences in ventricle volumes across the clusters. Incorporating predicted cell type proportions into the clustering resulted in three clusters, with one showing elevated immune marker concentrations. The cell type proportion and genes related to cell types were most pronounced in an intermediate depression symptoms cluster, suggesting that RNA-seq and immune markers measure different aspects of immune dysregulation. Lastly, we found a dysregulation of the SERPINF1/VEGF-A pathway that was specific to dendritic cells by integrating immune marker and RNA-seq data. This shows the advantages of combining different data modalities and highlights possible markers for further stratification research of depression symptoms.

Involvement of CXCL10 rs4256246, CXCR4 rs2228014, CCR2 rs1799864 and CXCL16 rs2277680 in the Predisposition to Schizophrenia

Chemokine ligands and their receptors have acquired less attention than pro- and anti-inflammatory cytokines in schizophrenia (SCZ). Thus, we aimed to examine the impact of functional polymorphisms of the chemokine genes CXCL10, CXCL16, CXCR4, and CCR2 in the development of SCZ. Using PCR-RFLP, we analyzed the selected polymorphisms in a Tunisian cohort composed of 200 patients with SCZ and 200 healthy controls. Our preliminary data suggest that the minor allele A of CXCL10 rs4256246 is significantly associated with likelihood of SCZ (PAdjusted = 0.00002) and more precisely to paranoid patients with late-onset SCZ (PAdjusted = 0.0007). However, the mutated allele T of CXCR4 rs2228014 showed a significant protective impact against SCZ (PAdjusted = 0.000007) and especially to male sex (PAdjusted = 0.000003). This effect persists among the undifferentiated patients with early-onset SCZ (PAdjusted = 0.002). Following the stratified analyses, CCR2 rs1799864 and CXCL16 rs2277680 were significantly correlated with the clinical symptoms among disorganized patients. As regards haplotype analysis, we noted that GATG haplotype was associated with protection against SCZ (PAdjusted = 0.0087) but the AGCG haplotype was correlated with susceptibility to this disease (PAdjusted = 0.014). Our preliminary results suggested that CXCL10 rs4256246 enhanced susceptibility to SCZ, while CXCR4 rs2228014 seemed to be protective factor. Furthermore, we identified a substantial correlation between CCR2 rs1799864 and CXCL16 rs2277680 with the clinical signs of the disorder. To validate these results and clarify the functional significance of the targeted polymorphisms in SCZ, more independent research is needed.

Contribution of copy number variations to education, socioeconomic status and cognition from a genome-wide study of 305,401 subjects

Educational attainment (EA), socioeconomic status (SES) and cognition are phenotypically and genetically linked to health outcomes. However, the role of copy number variations (CNVs) in influencing EA/SES/cognition remains unclear. Using a large-scale (n = 305,401) genome-wide CNV-level association analysis, we discovered 33 CNV loci significantly associated with EA/SES/cognition, 20 of which were novel (deletions at 2p22.2, 2p16.2, 2p12, 3p25.3, 4p15.2, 5p15.33, 5q21.1, 8p21.3, 9p21.1, 11p14.3, 13q12.13, 17q21.31, and 20q13.33, as well as duplications at 3q12.2, 3q23, 7p22.3, 8p23.1, 8p23.2, 17q12 (105 kb), and 19q13.32). The genes identified in gene-level tests were enriched in biological pathways such as neurodegeneration, telomere maintenance and axon guidance. Phenome-wide association studies further identified novel associations of EA/SES/cognition-associated CNVs with mental and physical diseases, such as 6q27 duplication with upper respiratory disease and 17q12 (105 kb) duplication with mood disorders. Our findings provide a genome-wide CNV profile for EA/SES/cognition and bridge their connections to health. The expanded candidate CNVs database and the residing genes would be a valuable resource for future studies aimed at uncovering the biological mechanisms underlying cognitive function and related clinical phenotypes.

Identification of Pyroptosis-Related Molecular Subtypes and Diagnostic Model development in Major Depressive Disorder

Major depressive disorder (MDD) is a prevalent psychological disorder associated with inflammation, with complex pathological mechanisms. Pyroptosis has been suggested to contribute to inflammation in central nervous system diseases. Little research, however, has examined what role pyroptosis played in MDD. In the present study, the differential expression pyroptosis-related genes (DE-PRGs) in MDD were identified from the GEO database (GSE98793 and GSE19738). Then, consensus clustering analysis was used to evaluate differences in MDD molecular subtypes characteristics based on PRGs. The characteristic diagnostic biomarkers for MDD were identified by Weighted Correlation Network Analysis (WGCNA) and multiple machine learning algorithms. Three intersection genes (GZMA, AKR1C3, and CD52) were obtained, which are expected to become potential biomarkers for MDD with excellent reliability and accuracy. Subsequently, the immune infiltration characteristics result indicated that the development of MDD is mediated by immune-related function, where three DE-PRGs were strongly related to the immune infiltration landscape of MDD. The biological experiments in vitro further proved that three unique PRGs are emerging as important players in MDD diagnosis. Our research aimed to provide novel ideas and biomarkers targeting MDD.

PI3K/AKT signaling pathway: Molecular mechanisms and therapeutic potential in depression

Depression is a serious global mental disorder. Numerous studies have found that depression may be closely related to decreased neurogenesis, neuroinflammation, neurotransmitter imbalance, and synaptic plasticity dysfunction. The pathogenesis of depression is complex and involves multiple signal transduction pathways and molecular changes. The PI3K/AKT pathway is an essential signaling pathways in neurons, which is widely expressed in emotion-related regions of the brain. Therefore, the PI3K/AKT pathway may play a moderating role in mood disorders. However, the role and mechanism of the PI3K/AKT signaling pathway in depression have not been fully described. This review systematically summarized the role of the PI3K/AKT signaling pathway in the pathogenesis of depression and discussed its potential in the treatment of depression. This will help in the treatment of depression and the development of antidepressants.

The Role of Estrogen across Multiple Disease Mechanisms

Estrogen is a significant hormone that is involved in a multitude of physiological and pathological processes. In addition to its pivotal role in the reproductive system, estrogen is also implicated in the pathogenesis of a multitude of diseases. Nevertheless, previous research on the role of estrogen in a multitude of diseases, including Alzheimer's disease, depression, cardiovascular disease, diabetes, osteoporosis, gastrointestinal diseases, and estrogen-dependent cancers, has concentrated on a single disease area, resulting in a lack of comprehensive understanding of cross-disease mechanisms. This has brought some challenges to the current treatment methods for these diseases, because estrogen as a potential therapeutic tool has not yet fully developed its potential. Therefore, this review aims to comprehensively explore the mechanism of estrogen in these seven types of diseases. The objective of this study is to describe the relationship between each disease and estrogen, including the ways in which estrogen participates in regulating disease mechanisms, and to outline the efficacy of estrogen in treating these diseases in clinical practice. By studying the role of estrogen in a variety of disease mechanisms, it is hoped that a more accurate theoretical basis and clinical guidance for future treatment strategies will be provided, thus promoting the effective management and treatment of these diseases.

Serum neurofilament light chain levels are associated with depression among US adults: a cross-sectional analysis among US adults, 2013-2014

BACKGROUND

Serum neurofilament light chain (sNfL) has been identified as a biomarker for neurologic diseases. However, sNfL remains unknown to be responsible for depression.

AIMS

The aim of this research was to explore the relationship between sNfL levels and depression in US adults.

METHODS

In this cross-sectional survey of the general population, we investigated representative data involving 10,175 participants from the 2013-2014 cycle of the National Health and Nutrition Examination Survey (NHANES). Depression was diagnosed using the Patient Health Questionnaire-9 (PHQ-9). The effect of related factors on depression was analyzed by conducting a univariate analysis. Stratified analysis was utilized to detect the stability and sensitivity of the relationship. After adjusting for race, education, marital status, smoking status, body mass index (BMI), sleep duration, income, and a history of hypertension, sedentary behavior and stroke, multivariable linear regression was performed to demonstrate the correlation between sNfL and depression.

RESULTS

A total of 1301 individuals between the ages of 20 and 75 were involved in this investigation, of which 108 (8.3%) were diagnosed with depression. A significant positive correlation between sNfL and depression among adults in the US was observed by conducting univariable analyses. After adjusting for confounding factors, the multivariate analyses indicated that elevated sNfL levels might play a pivotal role in the development of depression (odds ratio (OR) = 3.0; 95% confidence interval (CI): (1.5, 6.1), P = 0.002).

CONCLUSION

These results indicated that sNfL is closely linked to depression in a nationally representative individual. However, further studies are needed to confirm the biological mechanism as well as the clinical implications of sNfL and depression.

Immunometabolic Blood Biomarkers of Developmental Trajectories of Depressive Symptoms: Findings From the ALSPAC Birth Cohort

Studies of longitudinal trends of depressive symptoms in young people could provide insight into aetiologic mechanism, heterogeneity and origin of common cardiometabolic comorbidities for depression. Depression is associated with immunological and metabolic alterations, but immunometabolic characteristics of developmental trajectories of depressive symptoms remain unclear. Using depressive symptoms scores measured on 10 occasions between ages 10 and 25 years in the Avon Longitudinal Study of Parents and Children (n=7302), we identified four distinct trajectories: low-stable (70% of the sample), adolescent-limited (13%), adulthood-onset (10%) and adolescent-persistent (7%). We examined associations of these trajectories with: i) anthropometric, cardiometabolic and psychiatric phenotypes using multivariable regression (n=1709-3410); ii) 67 blood immunological proteins and 57 metabolomic features using empirical Bayes moderated linear models (n=2059 and n=2240 respectively); and iii) 28 blood cell counts and biochemical measures using multivariable regression (n=2256). Relative to the low-stable group, risk of depression and anxiety in adulthood was higher for all other groups, especially in the adolescent-persistent (ORdepression=22.80, 95% CI 15.25-34.37; ORGAD=19.32, 95% CI 12.86-29.22) and adulthood-onset (ORdepression=7.68, 95% CI 5.31-11.17; ORGAD=5.39, 95% CI 3.65-7.94) groups. The three depression-related trajectories vary in their immunometabolic profile, with evidence of little or no alterations in the adolescent-limited group. The adulthood-onset group shows widespread classical immunometabolic changes (e.g., increased immune cell counts and insulin resistance), while the adolescent-persistent group is characterised by higher BMI both in childhood and adulthood with few other immunometabolic changes. These findings point to distinct mechanisms and intervention opportunities for adverse cardiometabolic profile in different groups of young people with depression.

Evaluation of serum MIP-1β and MCP-2 levels in major depressive disorder: A case-control study

BACKGROUND

Major depressive disorder (MDD) is a common and debilitating mental illness characterized by persistent feelings of sadness, hopelessness, and a lack of interest in daily activities. The objective of this study was to investigate whether levels of macrophage inflammatory protein-1β (MIP-1β) and macrophage chemoattractant protein-2 (MCP-2) in the blood were associated with the pathophysiology and development of MDD compared to healthy controls (HCs).

METHODS

This case-control study was conducted involving 50 MDD patients and 38 HCs. We performed a comprehensive assessment to match age, sex, BMI, and socio-demographic profile between the groups. The study excluded participants with chronic infection, inflammatory diseases, coexisting psychiatric disorder, history of liver and kidney diseases, and individuals who are under antipsychotic medications. A professional psychiatrist diagnosed MDD patients and evaluated HCs based on the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) criteria. The severity of depression was assessed using the Hamilton Depression (Ham-D) rating scale. Commercially available enzyme-linked immunosorbent assay (ELISA) kits were used to quantify the serum MIP-1β and MCP-2 levels.

RESULTS

The results indicated elevated serum MIP-1β levels (207.73±24.24 pg/ml) in MDD patients compared to HCs (58.77±9.14 pg/ml). This difference in concentration is positively correlated with severity of disease symptoms (r = 0.451; p<0.001). Similarly, the levels of MCP-2 were found to be elevated in patients compared to controls (143.61±19.92 vs. 56.84±4.02 pg/ml; p = 0.003), with a positive correlation with the Ham-D scores (r = 0.373; p = 0.004).

CONCLUSION

According to this study, elevated levels of MIP-1β and MCP-2 may be associated with the pathophysiology and development of MDD. These increased serum MIP-1β and MCP-2 levels could be used as risk assessment tools for MDD. The present findings urge further research and the development of therapeutic and diagnostic approaches for depression.

Inflammatory mediators in major depression and bipolar disorder

Major depressive disorder (MDD) and bipolar disorder (BD) are highly disabling illnesses defined by different psychopathological, neuroimaging, and cognitive profiles. In the last decades, immune dysregulation has received increasing attention as a central factor in the pathophysiology of these disorders. Several aspects of immune dysregulations have been investigated, including, low-grade inflammation cytokines, chemokines, cell populations, gene expression, and markers of both peripheral and central immune activation. Understanding the distinct immune profiles characterizing the two disorders is indeed of crucial importance for differential diagnosis and the implementation of personalized treatment strategies. In this paper, we reviewed the current literature on the dysregulation of the immune response system focusing our attention on studies using inflammatory markers to discriminate between MDD and BD. High heterogeneity characterized the available literature, reflecting the heterogeneity of the disorders. Common alterations in the immune response system include high pro-inflammatory cytokines such as IL-6 and TNF-α. On the contrary, a greater involvement of chemokines and markers associated with innate immunity has been reported in BD together with dynamic changes in T cells with differentiation defects during childhood which normalize in adulthood, whereas classic mediators of immune responses such as IL-4 and IL-10 are present in MDD together with signs of immune-senescence.

Inflammation and immune system pathways as biological signatures of adolescent depression-the IDEA-RiSCo study

The biological mechanisms underlying the onset of major depressive disorder (MDD) have predominantly been studied in adult populations from high-income countries, despite the onset of depression typically occurring in adolescence and the majority of the world's adolescents living in low- and middle-income countries (LMIC). Taking advantage of a unique adolescent sample in an LMIC (Brazil), this study aimed to identify biological pathways characterizing the presence and increased risk of depression in adolescence, and sex-specific differences in such biological signatures. We collected blood samples from a risk-stratified cohort of 150 Brazilian adolescents (aged 14-16 years old) comprising 50 adolescents with MDD, 50 adolescents at high risk of developing MDD but without current MDD, and 50 adolescents at low risk of developing MDD and without MDD (25 females and 25 males in each group). We conducted RNA-Seq and pathway analysis on whole blood. Inflammatory-related biological pathways, such as role of hypercytokinemia/hyperchemokinemia in the pathogenesis of influenza (z-score = 3.464, p < 0.001), interferon signaling (z-score = 2.464, p < 0.001), interferon alpha/beta signaling (z-score = 3.873, p < 0.001), and complement signaling (z-score = 2, p = 0.002) were upregulated in adolescents with MDD compared with adolescents without MDD independently from their level of risk. The up-regulation of such inflammation-related pathways was observed in females but not in males. Inflammatory-related pathways involved in the production of cytokines and in interferon and complement signaling were identified as key indicators of adolescent depression, and this effect was present only in females.

Anti-Neuroinflammatory Effects of a Macrocyclic Peptide-Peptoid Hybrid in Lipopolysaccharide-Stimulated BV2 Microglial Cells

Inflammation processes of the central nervous system (CNS) play a vital role in the pathogenesis of several neurological and psychiatric disorders like depression. These processes are characterized by the activation of glia cells, such as microglia. Clinical studies showed a decrease in symptoms associated with the mentioned diseases after the treatment with anti-inflammatory drugs. Therefore, the investigation of novel anti-inflammatory drugs could hold substantial potential in the treatment of disorders with a neuroinflammatory background. In this in vitro study, we report the anti-inflammatory effects of a novel hexacyclic peptide-peptoid hybrid in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. The macrocyclic compound X15856 significantly suppressed Interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), c-c motif chemokine ligand 2 (CCL2), CCL3, C-X-C motif chemokine ligand 2 (CXCL2), and CXCL10 expression and release in LPS-treated BV2 microglial cells. The anti-inflammatory effects of the compound are partially explained by the modulation of the phosphorylation of p38 mitogen-activated protein kinases (MAPK), p42/44 MAPK (ERK 1/2), protein kinase C (PKC), and the nuclear factor (NF)-κB, respectively. Due to its remarkable anti-inflammatory properties, this compound emerges as an encouraging option for additional research and potential utilization in disorders influenced by inflammation, such as depression.

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Efficacy and safety of celecoxib for treatment of mild to moderate postpartum depression: a randomized, double-blind, placebo-controlled trial

PURPOSE

Evidence has demonstrated the roles of inflammatory processes in pathogenesis of depression. We aim to assess the effects of adjunctive celecoxib with cognitive behavioral therapy (CBT), an anti-inflammatory agent, in treatment of postpartum depression and on levels of Brain-derived neurotrophic factor (BDNF) and inflammatory cytokines.

METHODS

This was a randomized, double-blind, placebo-controlled trial to investigate the effects of adjunctive celecoxib with CBT on postpartum depression. Fifty outpatient women with postpartum depression, participated in this study. Patients randomly received either a celecoxib capsule twice a day or a placebo capsule twice a day for 6 weeks. Patients were assessed using the Hamilton Depression Rating Scale (HDRS) and the adverse event checklist at baseline and weeks 2, 4, and 6.

RESULTS

Patients in the celecoxib group showed a greater decline in HDRS scores from baseline to all three study time points compared to the placebo group (p = 0.12 for week 2, p = 0.001 for week 4, p < 0.001 for week 6). Rate of response to treatment was significantly higher in the celecoxib group compared to the placebo group at week 4 (60 vs 24%, p = 0.010) and week 6 (96 vs 44%, p < 0.001). Rate of remission was significantly higher in the celecoxib group compared to the placebo group at week 4 (52 vs 20%, p = 0.018) and week 6 (96 vs 36%, p < 0.001). Levels of most inflammatory markers were significantly lower in the celecoxib group compared to the placebo group at week 6. Levels of BDNF were significantly higher in the celecoxib group compared to the placebo group at week 6 (p < 0.001).

CONCLUSIONS

Findings suggest adjunctive celecoxib is an effective treatment for the improvement of postpartum depressive symptoms.

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

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

Vagus Nerve Stimulation Modulates Inflammation in Treatment-Resistant Depression Patients: A Pilot Study

Vagal neurostimulation (VNS) is used for the treatment of epilepsy and major medical-refractory depression. VNS has neuropsychiatric functions and systemic anti-inflammatory activity. The objective of this study is to measure the clinical efficacy and impact of VNS modulation in depressive patients. Six patients with refractory depression were enrolled. Depression symptoms were assessed with the Montgomery-Asberg Depression Rating, and anxiety symptoms with the Hamilton Anxiety Rating Scale. Plasmas were harvested prospectively before the implantation of VNS (baseline) and up to 4 years or more after continuous therapy. Forty soluble molecules were measured in the plasma by multiplex assays. Following VNS, the reduction in the mean depression severity score was 59.9% and the response rate was 87%. Anxiety levels were also greatly reduced. IL-7, CXCL8, CCL2, CCL13, CCL17, CCL22, Flt-1 and VEGFc levels were significantly lowered, whereas bFGF levels were increased (p values ranging from 0.004 to 0.02). This exploratory study is the first to focus on the long-term efficacy of VNS and its consequences on inflammatory biomarkers. VNS may modulate inflammation via an increase in blood-brain barrier integrity and a reduction in inflammatory cell recruitment. This opens the door to new pathways involved in the treatment of refractory depression.

Decreased IL-4 is the risk factor of depression in patients with Takayasu arteritis

Objective

Depression is a common complication in Takayasu arteritis (TA). Disorders of the immune system play an important role in both diseases. This study aimed to clarify the feature of cytokines in TA patients with depression.

Methods

In this cross-sectional study, serum cytokines were tested in 40 TA patients and 11 healthy controls using the Bio-Plex Magpix System (Bio-Rad®). The state of depression was measured by the Zung Self-Rating Depression Scale (SDS) in TA patients. Logistic regression analysis was performed to find the risk factors of depression in patients with TA.

Results

TA patients with depression had higher ESR, hsCRP, NIH, and ITAS.A than patients without depression (16.00 [10.00, 58.50]mm/H vs. 7.50 [4.50, 17.75]mm/H, p = 0.013; 7.60 [2.32, 46.52]mg/L vs. 0.71 [0.32, 4.37]mg/L, p = 0.001; 2.00 [2.00, 3.00] vs. 1.00 [0.00, 2.00], p = 0.007; 7.00 [4.00, 9.50] vs. 1.50 [0.00, 5.75], p = 0.012, respectively). Additionally, the lower age of onset and levels of IL-4, IL-13, eotaxin, and IP-10 were observed in the depressed group compared with the non-depressed (23.50 [19.25, 32.50]pg./ml vs. 37.00 [23.25, 42.50]pg./ml, p = 0.017; 2.80 [2.17, 3.18]pg./ml vs. 3.51 [3.22, 4.66]pg./ml, p < 0.001; 0.66 [0.60, 1.12]pg./ml vs. 1.04 [0.82, 1.25]pg./ml, p = 0.008; 46.48 [37.06, 61.75]pg./ml vs. 69.14 [59.30, 92.80]pg./ml, p = 0.001; 184.50 [138.23, 257.25]pg./ml vs. 322.32 [241.98, 412.60]pg./ml, p = 0.005, respectively). The lower level of IL-4 and age of onset were the independent risk factors for depression in TA patients (OR [95% CI] 0.124 [0.018, 0.827], p = 0.031; 0.870 [0.765, 0.990], p = 0.035, respectively).

Conclusion

Our data suggested that lower cytokine levels, especially IL-4, might be involved in the development of TA patients with depression. Clinicians can probably use serum IL-4 level testing as a potential indicator of depression in TA.

The molecular mechanism of polysaccharides in combating major depressive disorder: A comprehensive review

Major depressive disorder (MDD) is a complex psychiatric condition with diverse etiological factors. Typical pathological features include decreased cerebral cortex, subcortical structures, and grey matter volumes, as well as monoamine transmitter dysregulation. Although medications exist to treat MDD, unmet needs persist due to limited efficacy, induced side effects, and relapse upon drug withdrawal. Polysaccharides offer promising new therapies for MDD, demonstrating antidepressant effects with minimal side effects and multiple targets. These include neurotransmitter, neurotrophin, neuroinflammation, hypothalamic-pituitary-adrenal axis, mitochondrial function, oxidative stress, and intestinal flora regulation. This review explores the latest advancements in understanding the pharmacological actions and mechanisms of polysaccharides in treating major depression. We discuss the impact of polysaccharides' diverse structures and properties on their pharmacological actions, aiming to inspire new research directions and facilitate the discovery of novel anti-depressive drugs.

Longitudinal associations between dimensions of maltreatment and internalizing symptoms in late adolescence: The role of inflammation during the COVID-19 pandemic

Childhood adversity and depression have been linked with heightened inflammation. However, few longitudinal studies examine how dimensions of maltreatment (i.e., abuse and neglect) differentially impact pathways to heightened inflammation and internalizing symptoms. The present study examined effects of abuse and neglect on (1) internalizing symptoms through inflammation, and (2) on inflammation through internalizing symptoms across 3 years of adolescence in the context of the COVID-19 pandemic. In a sample of 78 adolescents, significant indirect effects revealed that childhood abuse, not neglect, significantly predicted future internalizing symptoms, which predicted future heighted C-reactive protein (CRP). Using prospective longitudinal data, these findings emphasize the importance of examining distinct forms of maltreatment in understanding the developmental pathways connecting early adversity, internalizing symptoms, and inflammation.

Genetic evidence for causal effects of immune dysfunction in psychiatric disorders: where are we?

The question of whether immune dysfunction contributes to risk of psychiatric disorders has long been a subject of interest. To assert this hypothesis a plethora of correlative evidence has been accumulated from the past decades; however, a variety of technical and practical obstacles impeded on a cause-effect interpretation of these data. With the advent of large-scale omics technology and advanced statistical models, particularly Mendelian randomization, new studies testing this old hypothesis are accruing. Here we synthesize these new findings from genomics and genetic causal inference studies on the role of immune dysfunction in major psychiatric disorders and reconcile these new data with pre-omics findings. By reconciling these evidences, we aim to identify key gaps and propose directions for future studies in the field.

Consistency of mouse models with human intracerebral hemorrhage: core targets and non-coding RNA regulatory axis

Intracerebral hemorrhage (ICH) has a high mortality and disability rate. Numerous basic studies on pathogenesis and therapeutics have been performed in mice. However, the consistency of the experimental mouse model and the human ICH patient remains unclear. This has slowed progress in translational medicine. Furthermore, effective therapeutic targets and reliable regulatory networks for ICH are needed. Therefore, we determined the differentially expressed (DE) messenger RNAs (mRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) before and after murine ICH and analyzed their regulatory relationships. Subsequently, data on mRNAs from human peripheral blood after ICH were obtained from the Gene Expression Omnibus database. The DE mRNAs after human ICH were compared with those of the mouse. Finally, we obtained seven genes with translational medicine research value and verified them in mice. Then the regulatory network of these genes was analyzed in humans. Similarly, species homologies of these regulatory pathways were identified. In conclusion, we found that the mouse ICH model mimics the human disease mainly in terms of chemokines and inflammatory factors. This has important implications for future research into the mechanisms of ICH injury and repair.

Anti-inflammatory Drugs in the Treatment of Depression

The last two decades have seen a flourishing of research into the immunobiology of psychiatric phenotypes, in particular major depressive disorder. Both preclinical and clinical data have highlighted pathways and possible mechanisms that might link changes in immunobiology, most especially inflammation, to clinically relevant behaviour. From a therapeutics perspective, a major impetus has been the action of Biologics, often monoclonal antibodies, that target specific cytokines acting as "molecular scalpels" helping to uncover the actions of those proteins. These interventions have been associated with improvements in mood and related symptoms. There are now enough studies and participants to permit meta-analytic analyses of the actions of these and other anti-inflammatory agents.In this chapter, the focus is on the evidence for the role of inflammation biology in depression and the meta-analytic data from trials. The putative mechanisms that might underpin the antidepressant effect of anti-inflammatory drugs are also explored. Lastly, I describe the more stubborn difficulties around heterogeneity, deep phenotyping and stratification as well as improved animal models and greater understanding of the biology that might be addressed by future studies.

Chronic pain accelerates cognitive impairment by reducing hippocampal neurogenesis may via CCL2/CCR2 signaling in APP/PS1 mice

Patients with chronic pain often have cognitive impairment; this is especially true in elderly patients with neurodegenerative diseases such as Alzheimer's disease (AD), but the mechanism underlying this association remains unclear. This was addressed in the present study by investigating the effect of chronic neuropathic pain on hippocampal neurogenesis and cognitive impairment using amyloid precursor protein/presenilin 1 (APP/PS1) double transgenic mice subjected to spared-nerve injury (SNI). The Von Frey test was performed to determine the mechanical threshold of mouse hind limbs after SNI. The Morris water maze test was used to evaluate spatial learning and memory. Doublecortin-positive (DCX+), 5-bromo-2'-deoxyuridine (BrdU)+, BrdU+/neuronal nuclei (NeuN)+, and C-C motif chemokine ligand 2 (CCL2)+ neurons in the dentate gyrus of the hippocampus were detected by immunohistochemistry and immunofluorescence analysis. CCL2 and C-C chemokine receptor type 2 (CCR2) protein levels in the mouse hippocampus were analyzed by western blotting. The results showed that APP/PS1 mice with chronic neuropathic pain induced by SNI had significant learning and memory impairment. This was accompanied by increased CCL2 and CCR2 expression and decreases in the number of DCX+, BrdU+, and BrdU+/NeuN+ neurons. These results suggest that chronic neuropathic pain is associated with cognitive impairment, which may be caused by CCL2/CCR2 signaling-mediated inhibition of hippocampal neurogenesis. Thus, therapeutic strategies that alleviate neuropathic pain can potentially slow cognitive decline in patients with AD and other neurodegenerative diseases.

Inflammatory markers in persons with clinically-significant depression, anxiety or PTSD: A systematic review and meta-analysis

BACKGROUND

Depression, anxiety and PTSD appear to be risk factors for dementia, but it is unclear whether they are causal or prodromal. The inflammatory-mediated neurodegeneration hypothesis suggests a causal link, proposing that mental illness is associated with an inflammatory response which, in turn, triggers neurodegenerative changes that lead to dementia. Existing meta-analyses have yet to examine inflammatory markers in depression, anxiety or PTSD with the view to exploring the inflammatory-mediated neurodegeneration hypothesis. The current meta-analysis therefore examined whether: a) depression, anxiety and PTSD are individually associated with inflammation, independently of comorbid mental illnesses and physical health problems with known inflammatory responses, and b) there are any similarities in the inflammatory profiles of these disorders in order to provide a basis for exploring inflammation in people with dementia who have a history of clinically-significant anxiety, depression or PTSD.

METHODS

PubMed, EMBASE, PsycINFO and CINAHL searches identified 64 eligible studies.

RESULTS

Depression is associated with an inflammatory response, with tentative evidence to suggest anxiety and PTSD are also associated with inflammation. However, the specific response may differ across these disorders.

LIMITATIONS

The data for anxiety, PTSD and multiple inflammatory markers were limited.

CONCLUSIONS

Depression, anxiety, and PTSD each appear to be associated with an inflammatory response in persons who do not have comorbid mental or physical health problems that are known to be associated with inflammation. Whether this inflammatory response underlies the increased risk of dementia in persons with a history of depression and anxiety, and possibly PTSD, remains to be determined.

Immune mechanisms of depression in rheumatoid arthritis

Depression is a common and disabling comorbidity in rheumatoid arthritis that not only decreases the likelihood of remission and treatment adherence but also increases the risk of disability and mortality in patients with rheumatoid arthritis. Compelling data that link immune mechanisms to major depressive disorder indicate possible common mechanisms that drive the pathology of the two conditions. Preclinical evidence suggests that pro-inflammatory cytokines, which are prevalent in rheumatoid arthritis, have various effects on monoaminergic neurotransmission, neurotrophic factors and measures of synaptic plasticity. Neuroimaging studies provide insight into the consequences of inflammation on the brain (for example, on neural connectivity), and clinical trial data highlight the beneficial effects of immune modulation on comorbid depression. Major depressive disorder occurs more frequently in patients with rheumatoid arthritis than in the general population, and major depressive disorder also increases the risk of a future diagnosis of rheumatoid arthritis, further highlighting the link between rheumatoid arthritis and major depressive disorder. This Review focuses on interactions between peripheral and central immunobiological mechanisms in the context of both rheumatoid arthritis and major depressive disorder. Understanding these mechanisms will provide a basis for future therapeutic development, not least in depression.

Altered serum TNF-α and MCP-4 levels are associated with the pathophysiology of major depressive disorder: A case-control study results

BACKGROUND

Major Depressive Disorder (MDD) is a debilitating mental health condition with complex etiology, and recent research has focused on pro-inflammatory cytokines and chemokines as potential contributors to its pathogenesis. However, studies investigating the roles of TNF-α and MCP-4 in MDD within the Bangladeshi population are scarce. This study aimed to assess the association between serum TNF-α and MCP-4 levels and the severity of MDD, exploring their potential as risk indicators for MDD development.

METHODS

This case-control study enrolled 58 MDD patients from Bangabandhu Sheikh Mujib Medical University (BSMMU) Hospital, Dhaka, Bangladesh, alongside 30 age, sex, and BMI-matched healthy controls. MDD diagnosis followed DSM-5 criteria and disease severity using the 17-item Hamilton Depression Rating Scale (Ham-D). We measured serum TNF-α and MCP-4 levels using ELISA assays according to the supplied protocols.

RESULTS

The study revealed significantly elevated serum TNF-α levels in MDD patients (47±6.6 pg/ml, mean±SEM) compared to controls (28.06±1.07 pg/ml). These increased TNF-α levels positively correlated with Ham-D scores (Pearson's r = 0.300, p = 0.038), suggesting a potential association between peripheral TNF-α levels and MDD pathology. Additionally, MDD patients exhibited significantly higher serum MCP-4 levels (70.49±6.45 pg/ml) than controls (40.21±4.08 pg/ml). However, serum MCP-4 levels showed a significant negative correlation (r = -0.270, P = 0.048) with Ham-D scores in MDD patients, indicating a more complex role for MCP-4 in MDD pathogenesis.

CONCLUSION

This study highlights that Bangladeshi MDD patients exhibit heightened inflammatory and immune responses compared to controls, supporting the cytokine hypothesis in MDD pathogenesis. Serum TNF-α, but not MCP-4, shows promise as a potential biomarker for assessing the risk of MDD development, which could aid in early detection. Future investigations involving larger populations and longitudinal studies are essential to confirm the utility of these cytokines as biomarkers for MDD.

Itaconate: A promising precursor for treatment of neuroinflammation associated depression

Neuroinflammation triggers the production of inflammatory factors, influences neuron generation and synaptic plasticity, thus playing an important role in the pathogenesis of depression and becoming an important direction of depression prevention and treatment. Itaconate is a metabolite secreted by macrophages in immunomodulatory responses, that has potent immunomodulatory effects and has been proven to exert anti-inflammatory effects in a variety of diseases. Microglia are mononuclear macrophages that reside in the central nervous system (CNS), and may be the source of endogenous itaconate in the brain. Itaconate can directly inhibit succinate dehydrogenase (SDH), reduce the production of NOD-like receptor thermal protein domain associated protein 3 (NLRP3), activate nuclear factor erythroid-2 related factor 2 (Nrf2), and block glycolysis, and thereby improving the depressive symptoms associated with the above mechanisms. Notably, itaconate also indirectly ameliorates the depressive symptoms associated with some inflammatory diseases. With the optimization of the structure and the development of new delivery systems, the application value and therapeutic potential of itaconate have been significantly improved. Dimethyl itaconate (DI) and 4-octyl itaconate (4-OI), cell-permeable derivatives of itaconate, are more suitable for crossing the blood-brain barrier (BBB), exhibiting therapeutic effects in the research of multiple diseases. This article provides an overview of the immunomodulatory effects of itaconate and its potential therapeutic efficacy in inflammatory depression, focusing on the promising application of itaconate as a precursor of antidepressants.

Anxiety and Depression in Heart Failure: An Updated Review

Anxiety and depression are commonly experienced by individuals with heart conditions, significantly impacting their overall well-being and prognosis. This review aims to provide an updated examination of the relationship between anxiety, depression, and heart disease. The review begins by exploring the prevalence of anxiety and depression in heart patients, highlighting the substantial rates at which these mental health disorders co-occur in this population. It further elucidates the risk factors that contribute to the development and exacerbation of anxiety and depression in individuals with heart conditions, including biological, psychological, and social factors. The impact of anxiety and depression on cardiac outcomes is a central focus of this review. It explores the intricate bi-directional relationship between mental health and cardiovascular health, discussing the mechanisms through which anxiety and depression can lead to adverse cardiac events and worsen existing heart conditions. Additionally, it examines the potential impact of anxiety and depression on treatment adherence, lifestyle modifications, and overall quality of life in heart patients. The review also investigates the diagnostic and assessment methods for anxiety and depression in heart patients, emphasizing the importance of implementing comprehensive screening protocols in clinical settings. In conclusion, this updated review provides valuable insights into the prevalence, impact, assessment, and management of anxiety and depression in heart patients. It underscores the importance of recognizing and addressing these mental health disorders within the context of cardiac care, ultimately aiming to enhance the overall well-being and prognosis of individuals living with heart conditions.

Persistent endothelial dysfunction in post-COVID-19 syndrome and its associations with symptom severity and chronic inflammation

BACKGROUND

Post-COVID-19 syndrome (PCS) is a lingering disease with ongoing symptoms such as fatigue and cognitive impairment resulting in a high impact on the daily life of patients. Understanding the pathophysiology of PCS is a public health priority, as it still poses a diagnostic and treatment challenge for physicians.

METHODS

In this prospective observational cohort study, we analyzed the retinal microcirculation using Retinal Vessel Analysis (RVA) in a cohort of patients with PCS and compared it to an age- and gender-matched healthy cohort (n = 41, matched out of n = 204).

MEASUREMENTS AND MAIN RESULTS

PCS patients exhibit persistent endothelial dysfunction (ED), as indicated by significantly lower venular flicker-induced dilation (vFID; 3.42% ± 1.77% vs. 4.64% ± 2.59%; p = 0.02), narrower central retinal artery equivalent (CRAE; 178.1 [167.5-190.2] vs. 189.1 [179.4-197.2], p = 0.01) and lower arteriolar-venular ratio (AVR; (0.84 [0.8-0.9] vs. 0.88 [0.8-0.9], p = 0.007). When combining AVR and vFID, predicted scores reached good ability to discriminate groups (area under the curve: 0.75). Higher PCS severity scores correlated with lower AVR (R = - 0.37 p = 0.017). The association of microvascular changes with PCS severity were amplified in PCS patients exhibiting higher levels of inflammatory parameters.

CONCLUSION

Our results demonstrate that prolonged endothelial dysfunction is a hallmark of PCS, and impairments of the microcirculation seem to explain ongoing symptoms in patients. As potential therapies for PCS emerge, RVA parameters may become relevant as clinical biomarkers for diagnosis and therapy management.

TRIAL REGISTRATION

This study was previously registered at ClinicalTrials ("All Eyes on PCS-Analysis of the Retinal Microvasculature in Patients with Post-COVID-19 Syndrome". NCT05635552. https://clinicaltrials.gov/ct2/show/NCT05635552 ). Persistent endothelial dysfunction in post-COVID-19 syndrome. Acute SARS-CoV-2 infection indirectly or directly causes endotheliitis in patients. N = 41 PCS patients were recruited and retinal vessel analysis was performed to assess microvascular endothelial function. Images of SVA and DVA are illustrative for RVA data analysis. For each PCS patient and healthy cohort, venular vessel diameter of the three measurement cycles was calculated and plotted on a diameter-time curve. Patients exhibited reduced flicker-induced dilation in veins (vFID) measured by dynamic vessel analysis (DVA) and lower central retinal arteriolar equivalent (CRAE) and arteriolar-venular ratio (AVR) and a tendency towards higher central retinal venular equivalent (CRVE) when compared to SARS-CoV-2 infection naïve participants. Created with BioRender.com.

Stress-induced red nucleus attenuation induces anxiety-like behavior and lymph node CCL5 secretion

Previous studies have speculated that brain activity directly controls immune responses in lymphoid organs. However, the upstream brain regions that control lymphoid organs and how they interface with lymphoid organs to produce stress-induced anxiety-like behavior remain elusive. Using stressed human participants and rat models, we show that CCL5 levels are increased in stressed individuals compared to controls. Stress-inducible CCL5 is mainly produced from cervical lymph nodes (CLN). Retrograde tracing from CLN identifies glutamatergic neurons in the red nucleus (RN), the activities of which are tightly correlated with CCL5 levels and anxiety-like behavior in male rats. Ablation or chemogenetic inhibition of RN glutamatergic neurons increases anxiety levels and CCL5 expression in the serum and CLNs, whereas pharmacogenetic activation of these neurons reduces anxiety levels and CCL5 synthesis after restraint stress exposure. Chemogenetic inhibition of the projection from primary motor cortex to RN elicits anxiety-like behavior and CCL5 synthesis. This brain-lymph node axis provides insights into lymph node tissue as a stress-responsive endocrine organ.

Identification of Plasma Inflammatory Markers of Adolescent Depression Using the Olink Proteomics Platform

Purpose

The quality of life of worldwide adolescents has been seriously affected by depression. Notably, the inflammatory response is closely associated with the pathophysiology of depression. The present study applied a novel targeted proteomics technology, Olink proximity extension assay (PEA), to profile circulating immune-related proteins in adolescents with depression.

Methods

In the present study, the expression levels of 92 inflammation-related proteins were compared between adolescents with depression (ADs) (n=15) and healthy controls (HCs) (n=15), using the OLINK PEA inflammation panel. We further validated 5 top proteins that were identified through KEGG and GO analyses between 40 HCs and 50 ADs, including CCL4, CXCL5, CXCL6, CXCL11, and IL-18 using enzyme linked immunosorbent assay (ELISA).

Results

We identified 13 differentially expressed proteins between the two cohorts, including 5 up-regulated and 8 down-regulated proteins. Among them, the TRAIL protein levels were significantly negatively correlated with the HAMA-14 score (r=-0.538, p= 0.038), and the levels of transforming growth factor α (TGF-α) were significantly associated with a change in appetite (r = -0.658, p = 0.008). After validation by ELISA, CCL4, CXCL5, CXCL11, and IL-18 showed significant changes between ADs and HCs (p < 0.05), while CXCL6 showed an up-regulated tendency in ADs (p=0.0673). The pooled diagnostic efficacy (area under the curve [AUC]) of these five inflammation markers in clinical diagnosis for adolescent depression was 0.819 (95% CI: 0.735-0.904).

Conclusion

We report a number of inflammation-related plasma biomarkers, which uncover a potential involvement of chemokines, cytokines, and cytokine receptors in adolescent depression. Their roles in the pathophysiology of depression need to be further elucidated.

Central regulation of stress-evoked peripheral immune responses

Stress-linked psychiatric disorders, including anxiety and major depressive disorder, are associated with systemic inflammation. Recent studies have reported stress-induced alterations in haematopoiesis that result in monocytosis, neutrophilia, lymphocytopenia and, consequently, in the upregulation of pro-inflammatory processes in immunologically relevant peripheral tissues. There is now evidence that this peripheral inflammation contributes to the development of psychiatric symptoms as well as to common co-morbidities of psychiatric disorders such as metabolic syndrome and immunosuppression. Here, we review the specific brain and spinal regions, and the neuronal populations within them, that respond to stress and transmit signals to peripheral tissues via the autonomic nervous system or neuroendocrine pathways to influence immunological function. We comprehensively summarize studies that have employed retrograde tracing to define neurocircuits linking the brain to the bone marrow, spleen, gut, adipose tissue and liver. Moreover, we highlight studies that have used chemogenetic or optogenetic manipulation or intracerebroventricular administration of peptide hormones to control somatic immune responses. Collectively, this growing body of literature illustrates potential mechanisms through which stress signals are conveyed from the CNS to immune cells to regulate stress-relevant behaviours and comorbid pathophysiology.

Comorbidity between major depressive disorder and physical diseases: a comprehensive review of epidemiology, mechanisms and management

Populations with common physical diseases - such as cardiovascular diseases, cancer and neurodegenerative disorders - experience substantially higher rates of major depressive disorder (MDD) than the general population. On the other hand, people living with MDD have a greater risk for many physical diseases. This high level of comorbidity is associated with worse outcomes, reduced adherence to treatment, increased mortality, and greater health care utilization and costs. Comorbidity can also result in a range of clinical challenges, such as a more complicated therapeutic alliance, issues pertaining to adaptive health behaviors, drug-drug interactions and adverse events induced by medications used for physical and mental disorders. Potential explanations for the high prevalence of the above comorbidity involve shared genetic and biological pathways. These latter include inflammation, the gut microbiome, mitochondrial function and energy metabolism, hypothalamic-pituitary-adrenal axis dysregulation, and brain structure and function. Furthermore, MDD and physical diseases have in common several antecedents related to social factors (e.g., socioeconomic status), lifestyle variables (e.g., physical activity, diet, sleep), and stressful live events (e.g., childhood trauma). Pharmacotherapies and psychotherapies are effective treatments for comorbid MDD, and the introduction of lifestyle interventions as well as collaborative care models and digital technologies provide promising strategies for improving management. This paper aims to provide a detailed overview of the epidemiology of the comorbidity of MDD and specific physical diseases, including prevalence and bidirectional risk; of shared biological pathways potentially implicated in the pathogenesis of MDD and common physical diseases; of socio-environmental factors that serve as both shared risk and protective factors; and of management of MDD and physical diseases, including prevention and treatment. We conclude with future directions and emerging research related to optimal care of people with comorbid MDD and physical diseases.

Are cytokine profiles associated with the cognitive performance of adults with severe major depression?

Cognitive impairment often occurs in major depressive disorder (MDD). Studies suggest that these cognitive deficits may be associated with inflammatory biomarkers, but data are limited. Therefore, this study aims to investigate the relationship between 48 peripheral blood cytokines and cognitive performance in patients with severe depressive disorder. One hundred consecutive hospitalized adult patients with severe depression who participated in the Depression long-term Augsburg (DELTA) study were included in the present analysis. To test working memory (WM) the Wechsler Adult Intelligence Scale (WAIS) IV and to assess interference control (IC) the Stroop Color and Word Test (SCWT) were performed. The serum concentrations of the biomarkers were measured using the Bio-Plex Pro™ Human Cytokine Screening Panel 1. Multiple linear regression models adjusted for possible confounders were fitted to examine associations. WM was impaired in 11% of the patients. IC was impaired in 1%-3% of the cases depending on the subtest. Eotaxin, IL-1β, IL-4, MCP-1, G-CSF, and PGF-BB were negatively associated with the WM. Eotaxin, IL-1β, IL-4, IL-16, IL-18, MCP-1, G-CSF, SCF, and MIP-1α were negatively associated with IC. None of these associations remained significant after adjustment for multiple testing. The present study identified eotaxin, IL-1β, IL-4, IL-16, IL-18, MCP-1, G-CSF, SCF, PGF-BB and MIP-1α as being associated with cognitive performance. After confirmation of these results in further studies, these cytokines may be potential targets for new treatments.

Berberine attenuates depression-like behavior by modulating the hippocampal NLRP3 ubiquitination signaling pathway through Trim65

OBJECTIVE

Increasing evidence suggests that inflammation appears to play a role in the genesis of depression. Berberine has potent anti-inflammatory effects and potential antidepressant activity, although the mechanism by which it works is yet unclear. Our study aimed to investigate the molecular mechanisms through which berberine treats depression and reduces inflammation.

METHODS

The CUMS model and behavioral evaluation were utilized in this study to evaluate the efficacy of berberine in the treatment of depression. Berberine's effect on the inflammatory response in CUMS mice was evaluated via ELISA assays and western blotting. Nissl staining was used to observe hippocampal neuronal functional damage. Western blotting, ELISA, ubiquitination tests, and immunoprecipitation were utilized in conjunction with in vitro experiments to study the involvement of Trim65 in the antidepressant effects of berberine.

RESULTS

The results suggest that berberine effectively alleviates depressive symptoms, suppresses the expression of genes associated with the NLRP3 inflammasome (NLRP3, cleaved caspase-1, ASC, GSDMD-N, Pro-IL-1β, IL-1β, Pro-IL-18, and IL-18), and reduces hippocampal neuronal functional damage in CUMS mice. Further studies showed that knockdown of Trim65 reversed the effects of berberine and increased NLRP3 inflammasome activity. Finally, K285, an important site for Trim65 binding to NLRP3, was identified.

CONCLUSION

Our study describes the mechanism of berberine limiting NLRP3 inflammasome activity by promoting the conjugation of Trim65 to NLRP3 and NLRP3 ubiquitination, and suggests NLRP3 inflammasome activation as a prospective target for treating inflammation-associated disorders such as depression.

Serum CXCL8 and CXCR2 as diagnostic biomarkers for noninvasive screening of cervical cancer

BACKGROUND

Cervical cancer (CC) is the fourth most frequently diagnosed cancer and the fourth leading cause of cancer-related death in women. Identifying new biomarkers for the early detection of CC is an essential requirement in this field. CXCL8 was originally discovered because of its role in inflammation by binding to CXCR1 and CXCR2; however, it is now known to play an important role in cancer. In this study, we aimed to evaluate the expression levels of potential biomarkers (CXCL8, CXCR1, and CXCR2) and to explore their diagnostic potential in CC.

METHODS

The expression levels of serum CXCL8, CXCR1, and CXCR2 were investigated by kit method on Immulite-1000 in 30 healthy volunteers, 30 precancerous patients and 70 CC patients.

RESULTS

The results indicated that the expression of CXCL8 and CXCR2 was significantly higher in the serum of CC patients than in healthy volunteers, similar to the well-established tumor marker (squamous-cell cancerantigen [SCC]). Receiver operating characteristic analyses showed that the combination of CXCL8, CXCR2, and SCC had the highest diagnostic sensitivity and area under the curve value. Meanwhile, the positive predictive value and negative predictive value were not very low. Moreover, high concentrations of CXCL8 and CXCR2 are associated with an increased risk of CC.

CONCLUSIONS

In conclusion, our data demonstrated that combined serum CXCL8, CXCR2, and SCC measurements are helpful for CC diagnosis and can be used as potential biomarkers for the early detection of CC. Cytokines, such as CXCL8 and CXCR2, can be easily measured in most university hospital laboratories and in some private laboratories with a routine test.

Combining inflammatory miRNA molecules as diagnostic biomarkers for depression: a clinical study

Background

Inflammation has been implicated in core features of depression pathophysiology and treatment resistance. Therefore, new challenges in the discovery of inflammatory mediators implicated in depression have emerged. MicroRNAs (miRNAs) have been found aberrantly expressed in several pathologies, increasing their potential as biomarkers and therapeutical targets. In this study, the aim was to assess the changes and biomarker potential of inflammation-related miRNAs in depression patients.

Methods

Depression diagnosis was performed according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). 40 healthy controls and 32 depression patients were included in the study. The levels of inflammatory cytokines were measured in plasma, and expression levels of cytokines and inflammation-related miRNAs were evaluated in peripheral blood mononuclear cells (PBMCs).

Results

Depression patients were found to have a pro-inflammatory profile in plasma, with significantly higher levels of TNF-α and CCL2 compared with controls. In PBMCs of depression patients, TNF-α and IL-6 expression levels were significantly up and downregulated, respectively. Moreover, miR-342 levels were found upregulated, while miR-146a and miR-155 were significantly downregulated. miR-342 expression levels were positively correlated with TNF-α. Importantly, when analyzed as a diagnostic panel, receiver operating characteristics (ROC) analysis of miR-342, miR-146a, miR-155 in combination, showed to be highly specific and sensitive in distinguishing between depression patients and healthy controls.

Conclusion

In summary, these findings suggest that inflammation-related miRNAs are aberrantly expressed in depression patients. Moreover, we show evidences on the potential of the combination of dysregulated miRNAs as a powerful diagnostic tool for depression.

Impact of the COVID-19 pandemic on adults with Fetal Alcohol Spectrum Disorder: linking immune function to mental health status

Prenatal alcohol exposure (PAE) is known to cause a variety of cognitive, behavioral, and neurological changes. Importantly, mental health problems are also overrepresented in individuals with Fetal Alcohol Spectrum Disorder (FASD), the group of neurodevelopmental conditions that can occur following PAE. Approximately 90% of individuals with FASD report experiencing mental health problems over their lifespan, compared to approximately 30% in the overall population. Individuals with FASD also display impairments in coping skills and increased vulnerability to stress. Here, we investigated whether the COVID-19 pandemic would have a differential impact on mental health and inflammation-to-mood associations in adults with FASD, compared to unexposed controls (no PAE). We capitalized on our pre-pandemic study examining health and immune function and invited past-participants to enroll in the current study. Participants completed mental health assessments and COVID-related questionnaires by phone. In addition, blood samples collected at baseline (pre-pandemic) were used to probe for inflammation-to-mood associations. Overall, our results indicate that lower SES was predictive of higher coronavirus anxiety scores, with no differences between adults with FASD and controls. In addition, while there were no differences in depression or anxiety measures at baseline (pre-pandemic) or during the pandemic, examination of inflammation-to-mood associations identified differential relationships in adults with FASD compared to unexposed controls. Specifically, there was a positive association between baseline neutrophil counts and both baseline and pandemic mental health scores in unexposed controls only. In addition, for unexposed controls there was also a negative association between baseline interferon-ɣ (IFN-ɣ) and pandemic mental health scores. By contrast, only adults with FASD showed positive associations between baseline interleukin-12p70 (IL-12p70), IL-8, soluble intercellular adhesion molecule-1 (sICAM-1), and soluble vascular cell adhesion molecule-1 (sVCAM-1) and pandemic mental health scores. Taken together, to our knowledge, this study is the first to examine the impact of the pandemic in adults with FASD. And while it may be too soon to predict the long-term effects of the pandemic on mental health, our data suggest that it will be important that future work also takes into account how immune function may be modulating mental health outcomes in this population.

Biomarkers of central and peripheral inflammation mediate the association between HIV and depressive symptoms

People living with HIV are at increased risk for depression, though the underlying mechanisms for this are unclear. In the general population, depression is associated with peripheral and central inflammation. Given this, and since HIV infection elicits inflammation, we hypothesised that peripheral and central inflammatory biomarkers would at least partly mediate the association between HIV and depressive symptoms. People living with HIV (n = 125) and without HIV (n = 79) from the COmorBidity in Relation to AIDS (COBRA) cohort were included in this study. Participants living with and without HIV had similar baseline characteristics. All participants living with HIV were on antiretroviral therapy and were virally suppressed. Plasma, CSF, and brain MR spectroscopy (MRS) biomarkers were measured. Using logistic regression models adjusted for sociodemographic factors, we found that participants with HIV were more likely to have Any Depressive Symptoms (Patient Health Questionnaire [PHQ-9] score >4) (odds ratio [95% confidence interval] 3.27 [1.46, 8.09]). We then sequentially adjusted the models for each biomarker separately to determine the mediating role of each biomarker, with a >10% reduction in OR considered as evidence of potential mediation. Of the biomarkers analysed, MIG (-15.0%) and TNF-α (-11.4%) in plasma and MIP1-α (-21.0%) and IL-6 (-18.0%) in CSF mediated the association between HIV and depressive symptoms in this sample. None of the other soluble or neuroimaging biomarkers substantially mediated this association. Our findings suggest that certain biomarkers of central and peripheral inflammation may at least partly mediate the relationship between HIV and depressive symptoms.

Serum cytokines-based biomarkers in the diagnosis and monitoring of therapeutic response in patients with major depressive disorder

BACKGROUND

Several lines of evidence have suggested that cytokines are implicated in the pathophysiology of depression and antidepressant treatment outcome. However, the results are not always congruent and partly contradictory. We therefore examined the serum levels of multiple cytokines in patients with major depressive disorder (MDD), with the aim to identify serum cytokines-based biomarkers for MDD diagnosis and antidepressant response.

METHODS

Fifty-nine patients with MDD and 61 healthy controls were included. The baseline levels of serum cytokines between MDD group and control group were compared, and the discriminative ability of different cytokines in predicting MDD patients from healthy controls was investigated using the receiver operating characteristic (ROC) curve method. The baseline levels of serum cytokines between antidepressant nonresponders and responders were compared, and the discriminative ability of different cytokines in predicting nonresponders from responders was evaluated using the ROC curve method.

RESULTS

Compared to controls, 15 of the 37 serum cytokines were increased, while 8 cytokines were decreased in MDD patients (all P < 0.05). The results of ROC curve showed that the Area Under Curve (AUC) values of 15 cytokines including IL-2, IL-5, IL-6, IL-8, IL-12, IL-13, IL-16, CCL3, CCL4, CCL17, CXCL10, TNF-α, TNF-β, VEGF-C, and FGF basic were greater than 0.7 in discriminating MDD patients from healthy control. Moreover, after 4-week treatment, levels of the 2 cytokines (IL-12 and TSLP) elevated at baseline significantly down-regulated, and levels of the 6 cytokines (IL-5, IL-16, CCL17, CXCL10, TNF-β, and PIGF) decreased at baseline significantly up-regulated (all P < 0.05). Furthermore, a positive relationship was found between TNF-α levels and Hamilton Depression Rating Scale-24 (HAMD-24) scores in patients with MDD at baseline (r = 0.302, P = 0.019). Additionally, compared to responders, nonresponders exhibited decreased levels of IL-1α, IL-5, IL-13, IL-15, VEGF, and ICAM-1 (all P < 0.05). The ROC curve analysis demonstrated that a combined panel of IL-1α, IL-5, and ICAM-1 achieved a high accuracy in discriminating antidepressant nonresponders from responders (AUC = 0.850, sensitivity = 83.3%, specificity = 81.8%).

CONCLUSIONS

These results suggested that alterations in peripheral cytokines levels hold significant promise as biomarkers for MDD diagnosis and antidepressant response.

Graves' disease as a driver of depression: a mechanistic insight

Graves' disease (GD) is characterized by diffuse enlargement and overactivity of the thyroid gland, which may be accompanied by other physical symptoms. Among them, depression can dramatically damage patients' quality of life, yet its prevalence in GD has not received adequate attention. Some studies have established a strong correlation between GD and increased risk of depression, though the data from current study remains limited. The summary of mechanistic insights regarding GD and depression has underpinned possible pathways by which GD contributes to depression. In this review, we first summarized the clinical evidence that supported the increased prevalence of depression by GD. We then concentrated on the mechanistic findings related to the acceleration of depression in the context of GD, as mounting evidence has indicated that GD promotes the development of depression through various mechanisms, including triggering autoimmune responses, inducing hormonal disorders, and influencing the thyroid-gut-microbiome-brain axis. Finally, we briefly presented potential therapeutic approaches to decreasing the risk of depression among patients with GD.

Comparisons of 25 cerebrospinal fluid cytokines in a case-control study of 106 patients with recent-onset depression and 106 individually matched healthy subjects

BACKGROUND

Neuroinflammation has been suggested as a contributor to the pathophysiology of depression; however, large case-control studies investigating cytokine levels in the cerebrospinal fluid (CSF) from patients with recent-onset depression by multiplex analyses are missing.

METHODS

An individually matched (sex and age) prospective case-control study comparing patients with recent-onset depression to healthy controls. CSF was analyzed with the Mesoscale V-PLEX Neuroinflammation Panel 1.

OUTCOMES

comparisons of analyte levels in the CSF between groups with interleukin (IL)-6 and IL-8 as primary outcomes and 23 other cytokines as secondary outcomes.

RESULTS

We included 106 patients (84.0% outpatients) with recent-onset depression and 106 healthy controls. There were no significant differences in the primary outcomes IL-6 (relative mean difference (MD): 1.10; 95% confidence interval (CI) 0.93-1.30; p = 0.276) or IL-8 levels (MD: 1.05; 95% CI 0.96-1.16; p = 0.249) relative to healthy controls. IL-4 was 40% higher (MD: 1.40; 95% CI 1.14-1.72; p = 0.001), monocyte chemoattractant protein (MCP)-1 was 25% higher (MD: 1.25; 95% CI 1.06-1.47; p = 0.009) and macrophage inflammatory protein (MIP)-1β was 16% higher (MD: 1.16; 95% CI 1.02-1.33; p = 0.025) in patients with depression relative to healthy controls. However, only IL-4 was significantly elevated after correction for multiple testing of secondary outcomes (p = 0.025).

CONCLUSION

We found no significant differences in CSF levels of the co-primary outcomes IL-6 and IL-8, however, the higher CSF levels of IL-4, MCP-1 and MIP-1β among patients with recent-onset depression compared to healthy controls indicate a potential role of these cytokines in the neuroinflammatory response to depression.

The Missing Piece? A Case for Microglia's Prominent Role in the Therapeutic Action of Anesthetics, Ketamine, and Psychedelics

There is much excitement surrounding recent research of promising, mechanistically novel psychotherapeutics - psychedelic, anesthetic, and dissociative agents - as they have demonstrated surprising efficacy in treating central nervous system (CNS) disorders, such as mood disorders and addiction. However, the mechanisms by which these drugs provide such profound psychological benefits are still to be fully elucidated. Microglia, the CNS's resident innate immune cells, are emerging as a cellular target for psychiatric disorders because of their critical role in regulating neuroplasticity and the inflammatory environment of the brain. The following paper is a review of recent literature surrounding these neuropharmacological therapies and their demonstrated or hypothesized interactions with microglia. Through investigating the mechanism of action of psychedelics, such as psilocybin and lysergic acid diethylamide, ketamine, and propofol, we demonstrate a largely under-investigated role for microglia in much of the emerging research surrounding these pharmacological agents. Among others, we detail sigma-1 receptors, serotonergic and γ-aminobutyric acid signalling, and tryptophan metabolism as pathways through which these agents modulate microglial phagocytic activity and inflammatory mediator release, inducing their therapeutic effects. The current review includes a discussion on future directions in the field of microglial pharmacology and covers bidirectional implications of microglia and these novel pharmacological agents in aging and age-related disease, glial cell heterogeneity, and state-of-the-art methodologies in microglial research.