Extracellular Vesicle Biomarkers Reveal Inhibition of Neuroinflammation by Infliximab in Association with Antidepressant Response in Adults with Bipolar Depression

Correlations between multimodal neuroimaging and peripheral inflammation in different subtypes and mood states of bipolar disorder: a systematic review

BACKGROUND

Systemic inflammation-immune dysregulation and brain abnormalities are believed to contribute to the pathogenesis of bipolar disorder (BD). However, the connections between peripheral inflammation and the brain, especially the interactions between different BD subtypes and episodes, remain to be elucidated. Therefore, we conducted the present study to provide a comprehensive understanding of the complex association between peripheral inflammation and neuroimaging findings in patients with bipolar spectrum disorders.

METHODS

This systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42023447044) and conducted according to the Population, Intervention, Comparison, Outcomes, and Study Design (PICOS) framework. Online literature databases (PubMed, Web of Science, Scopus, EMBASE, MEDLINE, PsycINFO, and the Cochrane Library) were searched for studies that simultaneously investigated both peripheral inflammation-related factors and magnetic resonance neurography of BD patients up to July 01, 2023. Then, we analysed the correlations between peripheral inflammation and neuroimaging, as well as the variation trends and the shared and specific patterns of these correlations according to different clinical dimensions.

RESULTS

In total, 34 publications ultimately met the inclusion criteria for this systematic review, with 2993 subjects included. Among all patterns of interaction between peripheral inflammation and neuroimaging, the most common pattern was a positive relationship between elevated inflammation levels and decreased neuroimaging measurements. The brain regions most susceptible to inflammatory activation were the anterior cingulate cortex, amygdala, prefrontal cortex, striatum, hippocampus, orbitofrontal cortex, parahippocampal gyrus, postcentral gyrus, and posterior cingulate cortex.

LIMITATIONS

The small sample size, insufficiently explicit categorization of BD subtypes and episodes, and heterogeneity of the research methods limited further implementation of quantitative data synthesis.

CONCLUSIONS

Disturbed interactions between peripheral inflammation and the brain play a critical role in BD, and these interactions exhibit certain commonalities and differences across various clinical dimensions of BD. Our study further confirmed that the fronto-limbic-striatal system may be the central neural substrate in BD patients.

Exosomes: potential targets for the diagnosis and treatment of neuropsychiatric disorders

The field of neuropsychiatry is considered a middle ground between neurological and psychiatric disorders, thereby bridging the conventional boundaries between matter and mind, consciousness, and function. Neuropsychiatry aims to evaluate and treat cognitive, behavioral, and emotional disorders in individuals with neurological conditions. However, the pathophysiology of these disorders is not yet fully understood, and objective biological indicators for these conditions are currently lacking. Treatment options are also limited due to the blood-brain barrier, which results in poor treatment effects. Additionally, many drugs, particularly antipsychotic drugs, have adverse reactions, which make them difficult to tolerate for patients. As a result, patients often abandon treatment owing to these adverse reactions. Since the discovery of exosomes in 1983, they have been extensively studied in various diseases owing to their potential as nanocellulators for information exchange between cells. Because exosomes can freely travel between the center and periphery, brain-derived exosomes can reflect the state of the brain, which has considerable advantages in diagnosis and treatment. In addition, administration of engineered exosomes can improve therapeutic efficacy, allow lesion targeting, ensure drug stability, and prevent systemic adverse effects. Therefore, this article reviews the source and biological function of exosomes, relationship between exosomes and the blood-brain barrier, relationship between exosomes and the pathological mechanism of neuropsychiatric disorders, exosomes in the diagnosis and treatment of neuropsychiatric disorders, and application of engineered exosomes in neuropsychiatric disorders.

Biological function of Extracellular Vesicles (EVs): a review of the field

Extracellular vesicles (EVs) theranostic potential is under intense investigation. There is a wealth of information highlighting the role that EVs and the secretome play in disease and how these are being utilized for clinical trials and novel therapeutic possibilities. However, understanding of the physiological and pathological roles of EVs remain incomplete. The challenge lies in reaching a consensus concerning standardized quality-controlled isolation, storage, and sample preparation parameters. Interest in circulating EV cargo as diagnostic and prognostic biomarkers is steadily growing. Though promising, various limitations need to be addressed before there can be successful, full-scale therapeutic use of approved EVs. These limitations include obtaining or manufacturing from the appropriate medium (e.g., from bodily fluid or cell culture), loading and isolating EVs, stability, and storage, standardization of processing, and determining potency. This review highlights specific topics, including circulation of abnormal EVs contribute to human disease and the theranostic potential of EVs. Theranostics is defined as a combination of the word's therapeutics and diagnostics and describes how a specific medicine or technique can function as both. Key findings include, (1) EVs and the secretome are future theranostics which will be utilized as both biomarkers for diagnosis and as therapeutics, (2) basic and translational research supports clinical trials utilizing EVs/secretome, and (3) additional investigation is required to fully unmask the theranostic potential of EVs/secretome in specific diseases and injuries.

Extracellular vesicle approach to major psychiatric disorders

Over the last few years, extracellular vesicles (EVs) have received increasing attention as potential non-invasive diagnostic and therapeutic biomarkers for various diseases. The interest in EVs is related to their structure and content, as well as to their changing cargo in response to different stimuli. One of the potential areas of use of EVs as biomarkers is the central nervous system (CNS), in particular the brain, because EVs can cross the blood-brain barrier, exist also in peripheral tissues and have a diverse cargo. Thus, they may represent "liquid biopsies" of the CNS that can reflect brain pathophysiology without the need for invasive surgical procedures. Overall, few studies to date have examined EVs in neuropsychiatric disorders, and the present evidence appears to lack reproducibility. This situation might be due to a variety of technical obstacles related to working with EVs, such as the use of different isolation strategies, which results in non-uniform vesicular and molecular outputs. Multi-omics approaches and improvements in the standardization of isolation procedures will allow highly pure EV fractions to be obtained in which the molecular cargo, particularly microRNAs and proteins, can be identified and accurately quantified. Eventually, these advances will enable researchers to decipher disease-relevant molecular signatures of the brain-derived EVs involved in synaptic plasticity, neuronal development, neuro-immune communication, and other related pathways. This narrative review summarizes the findings of studies on EVs in major psychiatric disorders, particularly in the field of biomarkers, and discusses the respective therapeutic potential of EVs.

Depression among Patients with an Implanted Left Ventricular Assist Device: Uncovering Pathophysiological Mechanisms and Implications for Patient Care

Depression is a common and devastating mental illness associated with increased morbidity and mortality, partially due to elevated rates of suicidal attempts and death. Select patients with end-stage heart failure on a waiting-list for a donor heart undergo left ventricular assist device (LVAD) implantation. The LVAD provides a circulatory flow of oxygenated blood to the body, mimicking heart functionality by operating on a mechanical technique. LVAD improves functional capacity and survivability among patients with end-stage heart failure. However, accumulating data suggests that LVAD recipients suffer from an increased incidence of depression and suicide attempts. There is scarce knowledge regarding the pathological mechanism and appropriate treatment approach for depressed LVAD patients. This article summarizes the current evidence on the association between LVAD implantation and occurrence of depression, suggesting possible pathological mechanisms underlying the device-associated depression and reviewing the current treatment strategies. The summarized data underscores the need for a rigorous pre-(LVAD)-implantation psychiatric evaluation, continued post-implantation mental health assessment, and administration of antidepressant treatment as necessary.

Cannabidiol-Loaded Nanoparticles Based on Crosslinked Starch: Anti-Inflammatory Activity and Improved Nose-to-Brain Delivery

Cannabidiol (CBD) has previously been shown to inhibit inflammatory cytokine production in both in vitro and in vivo studies of neurodegenerative diseases. To date, the CBD treatment of these diseases by quantitative targeting directly to the brain is one of the greatest challenges. In this paper, we present a new particulate system capable of delivering CBD into the brain via the intranasal route. Intranasal administration of CBD-loaded starch nanoparticles resulted in higher levels of cannabidiol in the brain compared to an identically administered cannabidiol solution. The production and the characterization of starch-based nanoparticles was reported, as well as the evaluation of their penetration and anti-inflammatory activity in cells. Cannabidiol-loaded starch nanoparticles were prepared by crosslinking with divanillin, using the nanoprecipitation method. Evaluation of the anti-inflammatory activity in vitro was performed using the BV2 microglia cell line. The starch nanoparticles appeared under electron microscopy in clusters sized approximately 200 nm in diameter. In cultures of lipopolysaccharide-induced inflamed BV2 cells, the cannabidiol-loaded starch nanoparticles demonstrated low toxicity while effectively reducing nitric oxide production and IL-6 levels. The anti-inflammatory effect was comparable to that of a glucocorticoid. Starch-based nanoparticle formulations combined with intranasal administration may provide a suitable platform for efficacious cannabidiol delivery and activity in the central nervous system.

Saikosaponin B2 ameliorates depression-induced microglia activation by inhibiting ferroptosis-mediated neuroinflammation and ER stress

ETHNOPHARMACOLOGICAL RELEVANCE

Saikosaponins B2 (SSB2) is one of the main active components isolated from Radix Bupleuri (Bupleurum chinense DC.), a herb widely used of traditional Chinese medicine. It has been used for the treatment of depression for more than two thousand years. However, the molecular mechanisms remain to be determined.

AIM OF THE STUDY

In this study, we evaluated the anti-inflammatory effect and elucidated underlying molecular mechanisms of SSB2 in LPS-induced primary microglia and CUMS-induced mice model of depression.

METHOD

The effects of SSB2 treatment were investigated both in vitro and in vivo. The chronic unpredictable mild stimulation (CUMS) procedure was applied to establish the animal model of depression. Behavioural tests were used to evaluate the depressive-like behaviors in CUMS-exposed mice, including sucrose preference test, open field test, tail suspension test, and forced swimming test. The GPX4 gene of microglia was silenced using shRNA, and inflammatory cytokines were determined by Western Blot and immunofluorescence analysis. Endoplasmic reticulum stress and ferroptosis-related markers were detected by qPCR, flow cytometry and confocal microscopy.

RESULT

SSB2 reversed depressive-like behaviours in CUMS-exposed mice and relieved central neuroinflammation and ameliorated hippocampal neural damage. SSB2 alleviated LPS-induced activation of microglia through the TLR4/NF-κB pathway. LPS-induced ferroptosis, with increased levels of ROS, intracellular Fe²⁺, mitochondrial membrane potential, lipid peroxidation, GSH, SLC7A11, FTH, GPX4 and Nrf2, and decreased transcription levels of ACSL4 and TFR1, was attenuated with SSB2 treatment in primary microglia cells. GPX4 knockdown activated ferroptosis, induced endoplasmic reticulum (ER) stress, and abrogated the protective effects of SSB2. Further, SSB2 attenuated ER stress, balanced calcium homeostasis, reduced lipid peroxidation and intracellular Fe²⁺ content by regulating the level of intracellular Ca²⁺.

CONCLUSIONS

Our study suggested that SSB2 treatment can inhibit ferroptosis, maintain calcium homeostasis, relieve endoplasmic reticulum stress and attenuate central neuroinflammation. SSB2 exhibited anti-ferroptosis and anti-neuroinflammatory effects through the TLR4/NF-κB pathway in a GPX4-dependent manner.

The human neurosecretome: extracellular vesicles and particles (EVPs) of the brain for intercellular communication, therapy, and liquid-biopsy applications

Emerging evidence suggests that brain derived extracellular vesicles (EVs) and particles (EPs) can cross blood-brain barrier and mediate communication among neurons, astrocytes, microglial, and other cells of the central nervous system (CNS). Yet, a complete understanding of the molecular landscape and function of circulating EVs & EPs (EVPs) remain a major gap in knowledge. This is mainly due to the lack of technologies to isolate and separate all EVPs of heterogeneous dimensions and low buoyant density. In this review, we aim to provide a comprehensive understanding of the neurosecretome, including the extracellular vesicles that carry the molecular signature of the brain in both its microenvironment and the systemic circulation. We discuss the biogenesis of EVPs, their function, cell-to-cell communication, past and emerging isolation technologies, therapeutics, and liquid-biopsy applications. It is important to highlight that the landscape of EVPs is in a constant state of evolution; hence, we not only discuss the past literature and current landscape of the EVPs, but we also speculate as to how novel EVPs may contribute to the etiology of addiction, depression, psychiatric, neurodegenerative diseases, and aid in the real time monitoring of the "living brain". Overall, the neurosecretome is a concept we introduce here to embody the compendium of circulating particles of the brain for their function and disease pathogenesis. Finally, for the purpose of inclusion of all extracellular particles, we have used the term EVPs as defined by the International Society of Extracellular Vesicles (ISEV).

Biomarkers for parkinsonian disorders in CNS-originating EVs: promise and challenges

Extracellular vesicles (EVs), including exosomes, microvesicles, and oncosomes, are nano-sized particles enclosed by a lipid bilayer. EVs are released by virtually all eukaryotic cells and have been shown to contribute to intercellular communication by transporting proteins, lipids, and nucleic acids. In the context of neurodegenerative diseases, EVs may carry toxic, misfolded forms of amyloidogenic proteins and facilitate their spread to recipient cells in the central nervous system (CNS). CNS-originating EVs can cross the blood-brain barrier into the bloodstream and may be found in other body fluids, including saliva, tears, and urine. EVs originating in the CNS represent an attractive source of biomarkers for neurodegenerative diseases, because they contain cell- and cell state-specific biological materials. In recent years, multiple papers have reported the use of this strategy for identification and quantitation of biomarkers for neurodegenerative diseases, including Parkinson's disease and atypical parkinsonian disorders. However, certain technical issues have yet to be standardized, such as the best surface markers for isolation of cell type-specific EVs and validating the cellular origin of the EVs. Here, we review recent research using CNS-originating EVs for biomarker studies, primarily in parkinsonian disorders, highlight technical challenges, and propose strategies for overcoming them.

Structural and functional MRI correlates of inflammation in bipolar disorder: A systematic review

BACKGROUND

Bipolar disorder (BD) is a common affective disorder characterized by recurrent oscillations between mood states and associated with inflammatory diseases and chronic inflammation. However, data on MRI abnormalities in BD and their relationship with inflammation are heterogeneous and no review has recapitulated them.

METHODS

In this pre-registered (PROSPERO: CRD42022308461) systematic review we searched Web of Science Core Collection and PubMed for articles correlating functional or structural MRI measures with immune-related markers in BD.

RESULTS

We included 23 studies (6 on functional, 16 on structural MRI findings, 1 on both, including 1'233 BD patients). Overall, the quality of the studies included was fair, with a low risk of bias.

LIMITATIONS

Heterogeneity in the methods and results of the studies and small sample sizes limit the generalizability of the conclusions.

CONCLUSIONS

A qualitative synthesis suggests that the links between immune traits and functional or structural MRI alterations point toward brain areas involved in affective and somatomotor processing, with a trend toward a negative correlation between peripheral inflammatory markers and brain regions volume. We discuss how disentangling the complex relationship between the immune system and MRI alterations in BD may unveil mechanisms underlying symptoms pathophysiology, potentially with quickly translatable diagnostic, prognostic, and therapeutic implications.

The promise and challenges of extracellular vesicles in the diagnosis of neurodegenerative diseases

Extracellular vesicles (EVs) have emerged as essential means of intercommunication for all cell types, and their role in CNS physiology is increasingly appreciated. Accumulating evidence has demonstrated that EVs play important roles in neural cell maintenance, plasticity, and growth. However, EVs have also been demonstrated to spread amyloids and inflammation characteristic of neurodegenerative disease. Such dual roles suggest that EVs may be prime candidates for neurodegenerative disease biomarker analysis. This is supported by several intrinsic properties of EVs: Populations can be enriched by capturing surface proteins from their cell of origin, their diverse cargo represent the complex intracellular states of the cells they derive from, and they can pass the blood-brain barrier. Despite this promise, there are important questions outstanding in this young field that will need to be answered before it can fulfill its potential. Namely, overcoming the technical challenges of isolating rare EV populations, the difficulties inherent in detecting neurodegeneration, and the ethical considerations of diagnosing asymptomatic individuals. Although daunting, succeeding to answer these questions has the potential to provide unprecedented insight and improved treatment of neurodegenerative disease in the future.

The NLRP3 Inflammasome in Stress Response: Another Target for the Promiscuous Cannabidiol

Many psychiatric patients do not respond to conventional therapy. There is a vast effort to investigate possible mechanisms involved in treatment resistance, trying to provide better treatment options, and several data points toward a possible involvement of inflammatory mechanisms. Microglia, glial, and resident immune cells are involved in complex responses in the brain, orchestrating homeostatic functions, such as synaptic pruning and maintaining neuronal activity. In contrast, microglia play a major role in neuroinflammation, neurodegeneration, and cell death. Increasing evidence implicate microglia dysfunction in neuropsychiatric disorders. The mechanisms are still unclear, but one pathway in microglia has received increased attention in the last 8 years, i.e., the NLRP3 inflammasome pathway. Stress response and inflammation, including microglia activation, can be attenuated by Cannabidiol (CBD). CBD has antidepressant, anti-stress, antipsychotic, anti-inflammatory, and other properties. CBD effects are mediated by direct or indirect modulation of many receptors, enzymes, and other targets. This review will highlight some findings for neuroinflammation and microglia involvement in stress-related psychiatric disorders, particularly addressing the NLRP3 inflammasome pathway. Moreover, we will discuss evidence and mechanisms for CBD effects in psychiatric disorders and animal models and address its potential effects on stress response via neuroinflammation and NLRP3 inflammasome modulation.

Suicide and Inflammation

Suicide is a leading cause of death worldwide. Although the neurobiological dysfunction underlying suicidal behavior remains unclear, recent work suggests that the immune system may play a role in the pathophysiology of suicide. In this chapter, we discuss a nascent body of literature suggesting that peripheral and central nervous systems (CNS) inflammation are associated with suicidal behavior. Because early-life stress is a major risk factor for suicidal behavior and is also associated with immune dysregulation, we hypothesize that such immune dysregulation may be the mechanism by which childhood maltreatment leads to an increased risk of suicidal behavior and suicide. Targeting inflammatory processes may be a novel treatment strategy, especially in populations that have experienced childhood trauma and exhibit elevated inflammation. Future work should directly test the hypothesis that reducing inflammation would result in a reduction in suicidal behavior.

Evidence for Anti-inflammatory Effects of Adalimumab in Treatment of Patients With Major Depressive Disorder: A Pilot, Randomized, Controlled Trial

BACKGROUND

Literature has suggested that major depressive disorder (MDD) is accompanied by higher concentrations of inflammatory biomarkers, which could sabotage response to conventional treatments.

AIMS

This study aimed to evaluate the efficacy and safety of adalimumab adjunct to sertraline in adults with MDD and increased levels of systemic inflammation.

METHODS

In a 6-week, randomized, double-blind, placebo-controlled trial, 36 patients with MDD and high-sensitivity C-reactive protein ≥3 mg/L were equally assigned to receive sertraline plus either adalimumab or placebo. Participants were assessed using the Hamilton Depression Rating Scale (HAM-D) at baseline, week 3, and week 6. Moreover, serum concentrations of inflammatory biomarkers were measured at baseline and trial end point. Finally, patients were assessed for any adverse event during the trial.

RESULTS

Fifteen patients in each group completed the trial course. All baseline characteristics of participants were similar between the groups. Adalimumab adjunct to sertraline resulted in a greater improvement in HAM-D score compared with placebo over the trial period ( P < 0.001). Participants receiving adalimumab significantly experienced greater response to treatment (≥50% reduction in the HAM-D score) than those receiving placebo ( P = 0.042). Furthermore, after 6 weeks of adalimumab combination therapy with sertraline, inflammatory biomarkers significantly decreased ( P ≤ 0.001), whereas no significant alteration was found in the placebo group. No serious adverse event was documented in the treatment arms.

CONCLUSIONS

Adalimumab adjunctive therapy remarkably improves depressive symptoms of patients with MDD. Further investigations with larger sample sizes and longer follow-up periods are required to confirm the findings.

Exploring the role of biologics in depression

Depression is a chronic and prevalent neuropsychiatric disorder; clinical symptoms include excessive sad mood, anhedonia, increased anxiety, disturbed sleep, and cognitive deficits. The exact etiopathogenesis of depression is not well understood. Studies have suggested that tumor necrosis factor-alpha (TNF-α) and interleukins (ILs) perform vital roles in the pathogenesis and treatment of depression. Increasing evidence suggests the upregulation of TNF-α and ILs expression in patients with depression. Therefore, biologics like TNF inhibitors (etanercept, infliximab, adalimumab) and IL inhibitors (ustekinumab) have become key compounds in the treatment of depression. Interestingly, treatment with an antidepressant has been found to decrease the TNF-α level and improve depression-like behaviors in several preclinical and clinical studies. In the current article, we have reviewed the recent findings linking TNF-α and the pathogenesis of depression proving TNF-α inhibitors as potential new therapeutic agents. Animal models and clinical studies further support that TNF-α inhibitors are effective in ameliorating depression-like behaviors. Moreover, studies showed that peripheral injection of TNF-α exhibits depressive symptoms. These symptoms have been improved by treatment with TNF-α inhibitors. Hence suggesting TNF-α inhibitors as potential new antidepressants for the management of depressive disorder.

No Sex Differences in Self-Reported Childhood Maltreatment in Major Depressive and Bipolar Disorders: A Retrospective Study

Background: We investigated, for the first time, whether there are any sex differences in retrospective self-reported childhood maltreatment (CM) in Italian adult patients with major depressive disorder (MDD) or bipolar disorder (BD). Furthermore, the potential impacts of patients’ age on the CM self-report were investigated. Methods: This retrospective study used the data documented in the electronic medical records of patients who were hospitalized for a 4-week psychiatric rehabilitation program. CM was assessed using the 28-item Childhood Trauma Questionnaire (CTQ), which evaluates emotional, physical, and sexual abuse, as well as emotional and physical neglect. The linear and logistic regression models were used (α = 0.01). Results: Three hundred thirty-five patients with MDD (255 women and 80 men) and 168 with BD (97 women and 71 men) were included. In both samples, considerable CM rates were identified, but no statistically significant sex differences were detected in the variety of CTQ-based CM aspects. There was a significant association, with no sex differences, between increasing patients’ age and a decreasing burden of CM. Conclusion: Both women and men with MDD or BD experienced a similar and considerable CM burden. Our findings support routine CM assessment in psychiatric clinical practice.

Going beyond risk factor: Childhood maltreatment and associated modifiable targets to improve life-long outcomes in mood disorders

Childhood maltreatment increases risk for mood disorders and is associated with earlier onset-and more pernicious disease course following onset-of mood disorders. While the majority of studies to date have been cross-sectional, longitudinal studies are emerging and support the devastating role(s) childhood maltreatment has on development of, and illness course in, mood disorders. This manuscript extends prior reviews to emphasize more recent work, highlighting longitudinal data, and discusses treatment studies that provide clues to mechanisms that mediate disease risk, course, relapse, and treatment response. Evidence suggesting systemic inflammation, alterations in hypothalamic-pituitary-adrenal (HPA) axis function and corticotropin-releasing factor (CRF) neural systems, genetic and other familial factors as mechanisms that mediate risk and onset of, and illness course in, mood disorders following childhood maltreatment is discussed. Risky behaviors following maltreatment, e.g., substance use and unhealthy lifestyles, may further exacerbate alterations in the HPA axis, CRF neural systems, and systematic inflammation to contribute to a more pernicious disease course. More research on sex differences and the impact of maltreatment in vulnerable populations is needed. Future research needs to be aimed at leveraging knowledge on modifiable targets, going beyond childhood maltreatment as a risk factor, to inform prevention and treatment strategies and foster trauma-informed care.

Role of Inflammation in Traumatic Brain Injury-Associated Risk for Neuropsychiatric Disorders: State of the Evidence and Where Do We Go From Here

In the past decade, there has been an increasing awareness that traumatic brain injury (TBI) and concussion substantially increase the risk for developing psychiatric disorders. Even mild TBI increases the risk for depression and anxiety disorders such as posttraumatic stress disorder by two- to threefold, predisposing patients to further functional impairment. This strong epidemiological link supports examination of potential mechanisms driving neuropsychiatric symptom development after TBI. One potential mechanism for increased neuropsychiatric symptoms after TBI is via inflammatory processes, as central nervous system inflammation can last years after initial injury. There is emerging preliminary evidence that TBI patients with posttraumatic stress disorder or depression exhibit increased central and peripheral inflammatory markers compared with TBI patients without these comorbidities. Growing evidence has demonstrated that immune signaling in animals plays an integral role in depressive- and anxiety-like behaviors after severe stress or brain injury. In this review, we will 1) discuss current evidence for chronic inflammation after TBI in the development of neuropsychiatric symptoms, 2) highlight potential microglial activation and cytokine signaling contributions, and 3) discuss potential promise and pitfalls for immune-targeted interventions and biomarker strategies to identify and treat TBI patients with immune-related neuropsychiatric symptoms.

Novel Pharmacological Approaches to the Treatment of Depression

Major depressive disorder is one of the most prevalent mental health disorders. Monoamine-based antidepressants were the first drugs developed to treat major depressive disorder. More recently, ketamine and other analogues were introduced as fast-acting antidepressants. Unfortunately, currently available therapeutics are inadequate; lack of efficacy, adverse effects, and risks leave patients with limited treatment options. Efforts are now focused on understanding the etiology of depression and identifying novel targets for pharmacological treatment. In this review, we discuss promising novel pharmacological targets for the treatment of major depressive disorder. Targeting receptors including N-methyl-D-aspartate receptors, peroxisome proliferator-activated receptors, G-protein-coupled receptor 39, metabotropic glutamate receptors, galanin and opioid receptors has potential antidepressant effects. Compounds targeting biological processes: inflammation, the hypothalamic-pituitary-adrenal axis, the cholesterol biosynthesis pathway, and gut microbiota have also shown therapeutic potential. Additionally, natural products including plants, herbs, and fatty acids improved depressive symptoms and behaviors. In this review, a brief history of clinically available antidepressants will be provided, with a primary focus on novel pharmaceutical approaches with promising antidepressant effects in preclinical and clinical studies.

Neuronal-enriched extracellular vesicles in individuals with IBS: A pilot study of COMT and BDNF

BACKGROUND

Irritable bowel syndrome (IBS) is characterized by abdominal pain, bowel habit alterations, and psychiatric comorbidities. Although pathophysiology remains incompletely understood, prior work demonstrates associations with brain-derived neurotrophic factor (BDNF) and catechol-O-methyltransferase (COMT). The purpose of this study was to quantify BDNF and COMT in plasma and in neuronal-enriched extracellular vesicles (nEVs), assess relationships with psychological symptoms, and gain insight on the brain-gut connection in IBS.

METHODS

Clinical data and biorepository samples from a parent investigation were used, including scores on the Perceived Stress Scale (PSS) and Center for Epidemiological Studies Depression Scale (CES-D). Distinct subpopulations of nEVs were isolated using neural cell adhesion molecule L1CAM; levels of COMT, mature BDNF, and pro-BDNF were quantified in plasma and in nEVs using ELISA.

KEY RESULTS

Data from 47 females (28.11 ± 6.85 years) included 18 IBS and 29 healthy control (HC) participants. IBS participants displayed reduced plasma levels of mature BDNF compared with HC (p = 0.024). Levels of COMT plasma and IBS grouping significantly predicted CES-D scores (p = 0.034). Exploratory analyses by IBS subtype and race revealed African American HC display lower levels of COMT EV than Caucasian HC (p = 0.022).

CONCLUSIONS & INFERENCES

Lower levels of mature BDNF in IBS participants, preliminary patterns detected in cargo content of nEVs, and relevance of COMT and IBS status to CES-D scores, offer insight on depressive symptomatology and brain-gut dysregulation in IBS. Lower COMT levels in nEVs of African Americans highlight the relevance of race when conducting such analyses across diverse populations.

Neuronal exosome proteins: novel biomarkers for predicting neonatal response to therapeutic hypothermia

OBJECTIVE

Central nervous system (CNS) derived exosomes can be purified from peripheral blood and have been used widely in adult neurological disease. Application to neonatal neurological disease deserves investigation in the setting of hypoxic-ischaemic encephalopathy (HIE).

DESIGN

Observational cohort.

SETTING

Level III neonatal intensive care unit.

PARTICIPANTS

Term/near-term neonates undergoing therapeutic hypothermia (TH) for HIE.

INTERVENTIONS

Blood samples were collected at 0-6, 12, 24, 48 and 96 hours of life.

MAIN OUTCOMES AND MEASURES

CNS exosomes were purified from serum using previously described methods. Biomarker protein levels were quantified using standard ELISA methods and normalised to exosome marker CD-81. The slope of change for biomarker levels was calculated for each time interval. Our primary outcome was MRI basal ganglia/watershed score of ≥3.

RESULTS

26 subjects were included (umbilical artery pH range 6.6-7.29; 35% seizures). An increasing MRI injury score was significantly associated with decreasing levels of synaptopodin between 0-6 and 12 hours (p=0.03) and increasing levels of lipocalin-2 (NGAL) between 12 and 48 hours (p<0.0001). Neuronal pentraxin was not significant. The negative predictive values for increasing synaptopodin and decreasing NGAL was 70.0% and 90.9%, respectively.

CONCLUSIONS AND RELEVANCE

Our results indicate that CNS exosome cargo has the potential to act as biomarkers of the severity of brain injury and response to TH as well as quantify pharmacological response to neuroactive therapeutic/adjuvant agents. Rigorous prospective trials are critical to evaluate potential clinical use of exosome biomarkers.

Neuroinflammation, Early-Life Adversity, and Brain Development

The overarching objective is to review how early exposure to adversity interacts with inflammation to alter brain maturation. Both adversity and inflammation are significant risk factors for psychopathology. Literature relevant to the effects of adversity in children and adolescents on brain development is reviewed. These studies are supported by research in animals exposed to species-relevant stressors during development. While it is known that exposure to adversity at any age increases inflammation, the effects of inflammation are exacerbated at developmental stages when the immature brain is uniquely sensitive to experiences. Microglia play a vital role in this process, as they scavenge cellular debris and prune synapses to optimize performance. In essence, microglia modify the synapse to match environmental demands, which is necessary for someone with a history of adversity. Overall, by piecing together clinical and preclinical research areas, what emerges is a picture of how adversity uniquely sculpts the brain. Microglia interactions with the inhibitory neurotransmitter GABA (specifically, the subtype expressing parvalbumin) are discussed within contexts of development and adversity. A review of inflammation markers in individuals with a history of abuse is combined with preclinical studies to describe their effects on maturation. Inconsistencies within the literature are discussed, with a call for standardizing methodologies relating to the age of assessing adversity effects, measures to quantify stress and inflammation, and more brain-based measures of biochemistry. Preclinical studies pave the way for interventions using anti-inflammation-based agents (COX-2 inhibitors, CB2 agonists, meditation/yoga) by identifying where, when, and how the developmental trajectory goes awry.

Neuron-derived extracellular vesicles enriched from plasma show altered size and miRNA cargo as a function of antidepressant drug response

Previous work has demonstrated that microRNAs (miRNAs) change as a function of antidepressant treatment (ADT) response. However, it is unclear how representative these peripherally detected miRNA changes are to those occurring in the brain. This study aimed to use peripherally extracted neuron-derived extracellular vesicles (NDEV) to circumvent these limitations and investigate neuronal miRNA changes associated with antidepressant response. Samples were collected at two time points (baseline and after 8 weeks of follow-up) from depressed patients who responded (N = 20) and did not respond (N = 20) to escitalopram treatment, as well as controls (N = 20). Total extracellular vesicles (EVs) were extracted from plasma, and then further enriched for NDEV by immunoprecipitation with L1CAM. EVs and NDEVs were characterized, and NDEV miRNA cargo was extracted and sequenced. Subsequently, studies in cell lines and postmortem tissue were conducted. Characterization of NDEVs revealed that they were smaller than other EVs isolated from plasma (p < 0.0001), had brain-specific neuronal markers, and contained miRNAs enriched for brain functions (p < 0.0001) Furthermore, NDEVs from depressed patients were smaller than controls (p < 0.05), and NDEV size increased with ADT response (p < 0.01). Finally, changes in NDEV cargo, specifically changes in miR-21-5p, miR-30d-5p, and miR-486-5p together (p < 0.01), were associated with ADT response. Targets of these three miRNAs were altered in brain tissue from depressed individuals (p < 0.05). Together, this study indicates that changes in peripherally isolated NDEV can act as both a clinically accessible and informative biomarker of ADT response specifically through size and cargo.

Peripheral inflammatory biomarkers define biotypes of bipolar depression

We identified biologically relevant moderators of response to tumor necrosis factor (TNF)-α inhibitor, infliximab, among 60 individuals with bipolar depression. Data were derived from a 12-week, randomized, placebo-controlled clinical trial secondarily evaluating the efficacy of infliximab on a measure of anhedonia (i.e., Snaith-Hamilton Pleasure Scale). Three inflammatory biotypes were derived from peripheral cytokine measurements using an iterative, machine learning-based approach. Infliximab-randomized participants classified as biotype 3 exhibited lower baseline concentrations of pro- and anti-inflammatory cytokines and soluble TNF receptor-1 and reported greater pro-hedonic improvements, relative to those classified as biotype 1 or 2. Pretreatment biotypes also moderated changes in neuroinflammatory substrates relevant to infliximab's hypothesized mechanism of action. Neuronal origin-enriched extracellular vesicle (NEV) protein concentrations were reduced to two factors using principal axis factoring: phosphorylated nuclear factorκB (p-NFκB), Fas-associated death domain (p-FADD), and IκB kinase (p-IKKα/β) and TNF receptor-1 (TNFR1) comprised factor "NEV1," whereas phosphorylated insulin receptor substrate-1 (p-IRS1), p38 mitogen-activated protein kinase (p-p38), and c-Jun N-terminal kinase (p-JNK) constituted "NEV2". Among infliximab-randomized subjects classified as biotype 3, NEV1 scores were decreased at weeks 2 and 6 and increased at week 12, relative to baseline, and NEV2 scores increased over time. Decreases in NEV1 scores and increases in NEV2 scores were associated with greater reductions in anhedonic symptoms in our classification and regression tree model (r² = 0.22, RMSE = 0.08). Our findings provide preliminary evidence supporting the hypothesis that the pro-hedonic effects of infliximab require modulation of multiple TNF-α signaling pathways, including NF-κB, IRS1, and MAPK.

Anti-TNF-α Compounds as a Treatment for Depression

Millions of people around the world suffer from psychiatric illnesses, causing unbearable burden and immense distress to patients and their families. Accumulating evidence suggests that inflammation may contribute to the pathophysiology of psychiatric disorders such as major depression and bipolar disorder. Copious studies have consistently shown that patients with mood disorders have increased levels of plasma tumor necrosis factor (TNF)-α. Given these findings, selective anti-TNF-α compounds were tested as a potential therapeutic strategy for mood disorders. This mini-review summarizes the results of studies that examined the mood-modulating effects of anti-TNF-α drugs.

Secreted Extracellular Vesicle Molecular Cargo as a Novel Liquid Biopsy Diagnostics of Central Nervous System Diseases

Secreted extracellular vesicles (EVs) are heterogeneous cell-derived membranous granules which carry a large diversity of molecules and participate in intercellular communication by transferring these molecules to target cells by endocytosis. In the last decade, EVs’ role in several pathological conditions, from etiology to disease progression or therapy evasion, has been consolidated, including in central nervous system (CNS)-related disorders. For this review, we performed a systematic search of original works published, reporting the presence of molecular components expressed in the CNS via EVs, which have been purified from plasma, serum or cerebrospinal fluid. Our aim is to provide a list of molecular EV components that have been identified from both nonpathological conditions and the most common CNS-related disorders. We discuss the methods used to isolate and enrich EVs from specific CNS-cells and the relevance of its components in each disease context.

Mitochondrial RNA in Alzheimer's Disease Circulating Extracellular Vesicles

Alzheimer’s disease (AD) is the most common type of dementia. Amyloid β (Aβ) plaques, tau-containing neurofibrillary tangles, and neuronal loss leading to brain atrophy are pathologic hallmarks of AD. Given the importance of early diagnosis, extensive efforts have been undertaken to identify diagnostic and prognostic biomarkers for AD. Circulating extracellular vesicles (EVs) provide a platform for “liquid biopsy” biomarkers for AD. Here, we characterized the RNA contents of plasma EVs of age-matched individuals who were cognitively normal (healthy controls (HC)) or had mild cognitive impairment (MCI) due to AD or had mild AD dementia (AD). Using RNA sequencing analysis, we found that mitochondrial (mt)-RNAs, including MT-ND1-6 mRNAs and other protein-coding and non-coding mt-RNAs, were strikingly elevated in plasma EVs of MCI and AD individuals compared with HC. EVs secreted from cultured astrocytes, microglia, and neurons after exposure to toxic conditions relevant to AD pathogenesis (Aβ aggregates and H₂O₂), contained mitochondrial structures (detected by electron microscopy) and mitochondrial RNA and protein. We propose that in the AD brain, toxicity-causing mitochondrial damage results in the packaging of mitochondrial components for export in EVs and further propose that mt-RNAs in plasma EVs can be diagnostic and prognostic biomarkers for MCI and AD.

TNF Production and Release from Microglia via Extracellular Vesicles: Impact on Brain Functions

Tumor necrosis factor (TNF) is a pleiotropic cytokine powerfully influencing diverse processes of the central nervous system (CNS) under both physiological and pathological conditions. Here, we analyze current literature describing the molecular processes involved in TNF synthesis and release from microglia, the resident immune cells of the CNS and the main source of this cytokine both in brain development and neurodegenerative diseases. A special attention has been given to the unconventional vesicular pathway of TNF, based on the emerging role of microglia-derived extracellular vesicles (EVs) in the propagation of inflammatory signals and in mediating cell-to-cell communication. Moreover, we describe the contribution of microglial TNF in regulating important CNS functions, including the neuroinflammatory response following brain injury, the neuronal circuit formation and synaptic plasticity, and the processes of myelin damage and repair. Specifically, the available data on the functions mediated by microglial EVs carrying TNF have been scrutinized to gain insights on possible novel therapeutic strategies targeting TNF to foster CNS repair.

Efficacy of adjunctive infliximab vs. placebo in the treatment of anhedonia in bipolar I/II depression

We investigated the efficacy of tumour necrosis factor (TNF)-α antagonist infliximab on a measure of anhedonia amongst individuals with bipolar I/II depression (ClinicalTrials.gov identifier NCT02363738). Adults (ages 18-65) with bipolar I/II disorder currently experiencing a major depressive episode with a higher probability of inflammatory activity (i.e., meeting one or more of the following inflammatory/metabolic criteria: obesity and dyslipidemia/hypertension, daily cigarette smoking, diabetes mellitus, migraine, inflammatory bowel disease, and/or C-reactive protein level of ⩾5 mg/L) were enrolled in a double-blind, 12-week clinical trial of adjunctive infliximab (5 mg/kg) and saline control, which were administered at weeks 0, 2, and 6. The primary outcome measure for the present secondary analysis was change in the Snaith-Hamilton Pleasure Scale (SHAPS) total score between placebo- and infliximab-treated subjects from baseline to weeks 6 and 12. Plasma concentrations of TNF-α and soluble TNF receptors (sTNFR) 1 and 2 were assessed at weeks 0, 2, 6, and 12. Sixty eligible adults received treatment with infliximab (n=29) or placebo (n=31); 47 subjects completed the study (infliximab: n=21, placebo: n=26). Overall, infliximab-randomized subjects exhibited significantly larger increases in SHAPS total score, denoting greater reductions in anhedonic symptoms, when compared to placebo-randomized subjects (treatment × time interaction effect: χ²=7.15,df=2,p=0.03). Anti-anhedonic efficacy was moderated by baseline plasma levels of TNF-α and sTNFR1, but not by changes in TNF-α or sTNFR1 concentrations. Baseline and changes in sTNFR2 concentrations did not moderate anti-anhedonic efficacy. Infliximab significantly improved a measure of anhedonia relative to placebo in adults with bipolar I/II depression at week 6; intervention efficacy was not sustained 6 weeks after the final infusion.