Rapid transport of CCL11 across the blood-brain barrier: regional variation and importance of blood cells

Differences in Eotaxin Serum Levels between Polytraumatized Patients with and without Concomitant Traumatic Brain Injury-A Matched Pair Analysis

Background/Objectives: Early detection of traumatic brain injury (TBI) is crucial for minimizing secondary neurological damage. Our study aimed to assess the potential of IL-4, IL-6, IL-7, IL-8, IL-10, TNF, and eotaxin serum levels-as a single clinical tool or combined into a panel-for diagnosing TBI in multiple injured patients. Methods: Out of 110 prospectively enrolled polytrauma victims (median age, 39 years; median ISS, 33; 70.9% male) admitted to our level I trauma center over four years, we matched 41 individuals with concomitant TBI (TBI cohort) to 41 individuals without TBI (non-TBI cohort) based on age, gender, Injury Severity Score (ISS), and mortality. Patients' protein levels were measured upon admission (day 0) and on days 1, 3, 5, 7, and 10 during routine blood withdrawal using one separation gel tube each time. Results: The median serum levels of IL-4, IL-6, IL-7, IL-8, IL-10, and TNF exhibited non-similar time courses in the two cohorts and showed no significant differences on days 0, 1, 3, 5, and 7. However, the median eotaxin levels had similar trend lines in both cohorts, with consistently higher levels in the TBI cohort, reaching significance on days 0, 3, and 5. In both cohorts, the median eotaxin level significantly decreased from day 0 to day 1, then significantly increased until day 10. We also found a significant positive association between day 0 eotaxin serum levels and the presence of TBI, indicating that for every 20 pg/mL increase in eotaxin level, the odds of a prevalent TBI rose by 10.5%. ROC analysis provided a cutoff value of 154 pg/mL for the diagnostic test (sensitivity, 0.707; specificity, 0.683; AUC = 0.718). Conclusions: Our findings identified the brain as a significant source, solely of eotaxin release in humans who have suffered a TBI. Nevertheless, the eotaxin serum level assessed upon admission has limited diagnostic value. IL-4, IL-6, IL-7, IL-8, IL-10, and TNF do not indicate TBI in polytraumatized patients.

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.

Spotlight on pro-inflammatory chemokines: regulators of cellular communication in cognitive impairment

Cognitive impairment is a decline in people's ability to think, learn, and remember, and so forth. Cognitive impairment is a global health challenge that affects the quality of life of thousands of people. The condition covers a wide range from mild cognitive impairment to severe dementia, which includes Alzheimer's disease (AD) and Parkinson's disease (PD), among others. While the etiology of cognitive impairment is diverse, the role of chemokines is increasingly evident, especially in the presence of chronic inflammation and neuroinflammation. Although inflammatory chemokines have been linked to cognitive impairment, cognitive impairment is usually multifactorial. Researchers are exploring the role of chemokines and other inflammatory mediators in cognitive dysfunction and trying to develop therapeutic strategies to mitigate their effects. The pathogenesis of cognitive disorders is very complex, their underlying causative mechanisms have not been clarified, and their treatment is always one of the challenges in the field of medicine. Therefore, exploring its pathogenesis and treatment has important socioeconomic value. Chemokines are a growing family of structurally and functionally related small (8-10 kDa) proteins, and there is growing evidence that pro-inflammatory chemokines are associated with many neurobiological processes that may be relevant to neurological disorders beyond their classical chemotactic function and play a crucial role in the pathogenesis and progression of cognitive disorders. In this paper, we review the roles and regulatory mechanisms of pro-inflammatory chemokines (CCL2, CCL3, CCL4, CCL5, CCL11, CCL20, and CXCL8) in cognitive impairment. We also discuss the intrinsic relationship between the two, hoping to provide some valuable references for the treatment of cognitive impairment.

Blood-based therapies to combat neurodegenerative diseases

Neurodegeneration, known as the progressive loss of neurons in terms of their structure and function, is the principal pathophysiological change found in the majority of brain-related disorders. Ageing has been considered the most well-established risk factor in most common neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease (AD). There is currently no effective treatment or cure for these diseases; the approved therapeutic options to date are only for palliative care. Ageing and neurodegenerative diseases are closely intertwined; reversing the aspects of brain ageing could theoretically mitigate age-related neurodegeneration. Ever since the regenerative properties of young blood on aged tissues came to light, substantial efforts have been focused on identifying and characterizing the circulating factors in the young and old systemic milieu that may attenuate or accentuate brain ageing and neurodegeneration. Later studies discovered the superiority of old plasma dilution in tissue rejuvenation, which is achieved through a molecular reset of the systemic proteome. These findings supported the use of therapeutic blood exchange for the treatment of degenerative diseases in older individuals. The first objective of this article is to explore the rejuvenating properties of blood-based therapies in the ageing brains and their therapeutic effects on AD. Then, we also look into the clinical applications, various limitations, and challenges associated with blood-based therapies for AD patients.

Senescent-like microglia limit remyelination through the senescence associated secretory phenotype

The capacity to regenerate myelin in the central nervous system (CNS) diminishes with age. This decline is particularly evident in multiple sclerosis (MS), which has been suggested to exhibit features of accelerated biological aging. Whether cellular senescence, a hallmark of aging, contributes to remyelination impairment remains unknown. Here, we show that senescent cells (SCs) accumulate within demyelinated lesions after injury, and their elimination enhances remyelination in young mice but not in aged mice. In young mice, we observed the upregulation of senescence-associated transcripts primarily in microglia after demyelination, followed by their reduction during remyelination. However, in aged mice, senescence-associated factors persisted within lesions, correlating with inefficient remyelination. We found that SC elimination enhanced remyelination in young mice but was ineffective in aged mice. Proteomic analysis of senescence-associated secretory phenotype (SASP) revealed elevated levels of CCL11/Eotaxin-1 in lesions, which was found to inhibit efficient oligodendrocyte maturation. These results suggest therapeutic targeting of SASP components, such as CCL11, may improve remyelination in aging and MS.

Exploring causal association between circulating inflammatory cytokines and functional outcomes following ischemic stroke: A bidirectional Mendelian randomization study

OBJECTIVES

Previous observational studies have indicated correlations between various inflammatory cytokines and functional outcomes following ischemic stroke (IS); however, the causality remains unclear. We aimed to further evaluate the causal association between 41 circulating inflammatory cytokines and functional outcomes following IS.

METHODS

Two-sample bidirectional Mendelian randomization (MR) analysis was used in this study. The genetic variation of 41 circulating inflammatory cytokines were derived from genome-wide association study (GWAS) data of European ancestry (n = 8293). The corresponding genetic association of functional outcomes following IS were derived from European ancestry GWAS data (n = 6021).

RESULTS

Inverse variance weighted (IVW) analysis showed that genetically predicted increased levels of regulation and activation in normal T-cell expression and secretion factor (RANTES/CCL5) and eosinophilic chemotactic factor (EOTAXIN/CCL11) were positively correlated with the increased adverse functional outcomes (modified Rankin Scale [mRS≥3] following IS (OR: 1.40, 95% CI: 1.002-1.96, p = 0.049; OR: 1.33, 95% CI: 1.15-1.54, p = 0.0001). Interleukin 18 (IL-18) level might be the downstream consequence of adverse functional outcomes following IS (β: -0.09, p = 0.039). Other inflammatory cytokines and functional outcomes following IS did not appear to be causally related.

CONCLUSIONS

This study suggests a causality between inflammation and adverse functional outcomes following IS. RANTES (CCL5) and EOTAXIN (CCL11) may be the upstream factors of adverse functional outcomes following IS, while IL-18 may be the downstream effect of adverse functional outcomes following IS. Whether these cytokines can be used to predict or improve adverse functional outcomes after IS requires further researches.

Alzheimer's disease: The role of T lymphocytes in neuroinflammation and neurodegeneration

Alzheimer's disease, the leading cause of progressive cognitive decline globally, has been reported to be enhanced by neuroinflammation. Brain-resident innate immune cells and adaptive immune cells work together to produce neuroinflammation. Studies over the past decade have established the neuroimmune axis present in Alzheimer's disease; the crosstalk between adaptive and innate immune cells within and outside the brain is crucial to the onset and progression of Alzheimer's disease. Although the role of the adaptive immune system in Alzheimer's disease is not fully understood, it has been hypothesized that the brain's immune homeostasis is significantly disrupted, which greatly contributes to neuroinflammation. Brain-infiltrating T cells possess proinflammatory phenotypes and activities that directly contribute to neuroinflammation. The pro-inflammatory activities of the adaptive immune system in Alzheimer's disease are characterized by the upregulation of effector T cell activities and the downregulation of regulatory T cell activities in the brain, blood, and cerebrospinal fluid. In this review, we discuss the major impact of T lymphocytes on the pathogenesis and progression of Alzheimer's disease. Understanding the role and mechanism of action of T cells in Alzheimer's disease would significantly contribute to the identification of novel biomarkers for diagnosing and monitoring the progression of the disease. This knowledge could also be crucial to the development of immunotherapies for Alzheimer's disease.

Brain response in asthma: the role of "lung-brain" axis mediated by neuroimmune crosstalk

In addition to typical respiratory symptoms, patients with asthma are frequently accompanied by cognitive decline, mood disorders (anxiety and depression), sleep disorders, olfactory disorders, and other brain response manifestations, all of which worsen asthma symptoms, form a vicious cycle, and exacerbate the burden on families and society. Therefore, studying the mechanism of neurological symptoms in patients with asthma is necessary to identify the appropriate preventative and therapeutic measures. In order to provide a comprehensive reference for related research, we compiled the pertinent literature, systematically summarized the latest research progress of asthma and its brain response, and attempted to reveal the possible "lung-brain" crosstalk mechanism and treatment methods at the onset of asthma, which will promote more related research to provide asthmatic patients with neurological symptoms new hope.

Young Astrocytic Mitochondria Attenuate the Elevated Level of CCL11 in the Aged Mice, Contributing to Cognitive Function Improvement

Aging drives cognitive decline, and mitochondrial dysfunction is a hallmark of age-induced neurodegeneration. Recently, we demonstrated that astrocytes secrete functional mitochondria (Mt), which help adjacent cells to resist damage and promote repair after neurological injuries. However, the relationship between age-dependent changes in astrocytic Mt function and cognitive decline remains poorly understood. Here, we established that aged astrocytes secret less functional Mt compared to young astrocytes. We found the aging factor C-C motif chemokine 11 (CCL11) is elevated in the hippocampus of aged mice, and that its level is reduced upon systemic administration of young Mt, in vivo. Aged mice receiving young Mt, but not aged Mt improved cognitive function and hippocampal integrity. Using a CCL11-induced aging-like model in vitro, we found that astrocytic Mt protect hippocampal neurons and enhance a regenerative environment through upregulating synaptogenesis-related gene expression and anti-oxidants that were suppressed by CCL11. Moreover, the inhibition of CCL11-specific receptor C-C chemokine receptor 3 (CCR3) boosted the expression of synaptogenesis-related genes in the cultured hippocampal neurons and restored the neurite outgrowth. This study suggests that young astrocytic Mt can preserve cognitive function in the CCL11-mediated aging brain by promoting neuronal survival and neuroplasticity in the hippocampus.

Blood-to-brain communication in aging and rejuvenation

Aging induces molecular, cellular and functional changes in the adult brain that drive cognitive decline and increase vulnerability to dementia-related neurodegenerative diseases. Leveraging systemic and lifestyle interventions, such as heterochronic parabiosis, administration of 'young blood', exercise and caloric restriction, has challenged prevalent views of brain aging as a rigid process and has demonstrated that aging-associated cognitive and cellular impairments can be restored to more youthful levels. Technological advances in proteomic and transcriptomic analyses have further facilitated investigations into the functional impact of intertissue communication on brain aging and have led to the identification of a growing number of pro-aging and pro-youthful factors in blood. In this review, we discuss blood-to-brain communication from a systems physiology perspective with an emphasis on blood-derived signals as potent drivers of both age-related brain dysfunction and brain rejuvenation.

Quantitative Model Analysis and Simulation of Pharmacokinetics and Metastasis-Associated Lung Adenocarcinoma 1 RNA Knockdown Effect After Systemic Administration of Cholesterol-Conjugated DNA/RNA Heteroduplex Oligonucleotide Crossing Blood-Brain Barrier of Mice

The cholesterol-conjugated heteroduplex oligonucleotide (Chol-HDO) is a double-stranded complex; it comprises an antisense oligonucleotide (ASO) and its complementary strand with a cholesterol ligand. Chol-HDO is a powerful tool for achieving target RNA knockdown in the brains of mice after systemic injection. Here, a quantitative model analysis was conducted to characterize the relationship between the pharmacokinetics (PK) and pharmacodynamics (PD), non-coding RNA metastasis-associated lung adenocarcinoma 1 (Malat1) RNA, of Chol-HDO, in a time-dependent manner. The established PK model could describe regional differences in the observed brain concentration-time profiles. Incorporating the PD model enabled the unique knockdown profiles in the brain to be explained in terms of the time delay after single dosing and enhancement following repeated dosing. Moreover, sensitivity analysis of PK exposure/persistency, target RNA turnover, and knockdown potency identified key factors for the efficient and sustained target RNA knockdown in the brain. The simulation of an adequate dosing regimen quantitatively supported the benefit of Chol-HDO in terms of achieving a suitable dosing interval. This was achieved via sufficient and sustained brain exposure and subsequent strong and sustained target RNA knockdown in the brain, even after systemic injection. The present study provides new insights into drug discoveries and development strategies for HDO in patients with neurogenic disorders. SIGNIFICANCE STATEMENT: The quantitative model analysis presented here characterized the PK/PD relationship of Chol-HDO, enabled its simulation under various conditions or assumptions, and identified key factors for efficient and sustained RNA knockdown, such as PK exposure and persistency. Chol-HDO appears to be an efficient drug delivery system for the systemic administration of desired drugs to brain targets.

Transport of the Proinflammatory Chemokines C-C Motif Chemokine Ligand 2 (MCP-1) and C-C Motif Chemokine Ligand 5 (RANTES) across the Intact Mouse Blood-Brain Barrier Is Inhibited by Heparin and Eprodisate and Increased with Systemic Inflammation

One important function of the vascular blood-brain barrier (BBB) is to facilitate neuroimmune communication. The BBB fulfills this function, in part, through its ability to transport cytokines and chemokines. C-C motif chemokine receptor 2 (CCL2) (MCP-1) and C-C motif chemokine receptor 5 (CCL5) (RANTES) are proinflammatory chemokines that mediate neuroimmune responses to acute insults and aspects of brain injury and neurodegenerative diseases; however, a blood-to-brain transport system has not been evaluated for either chemokine in vivo. Therefore, we determined whether CCL2 and CCL5 in blood can cross the intact BBB and enter the brain. Using CD-1 mice, we found that ¹²⁵I-labeled CCL2 and CCL5 crossed the BBB and entered the brain parenchyma. We next aimed to identify the mechanisms of ¹²⁵I-CCL2 and ¹²⁵I-CCL5 transport in an in situ brain perfusion model. We found that both heparin and eprodisate inhibited brain uptake of ¹²⁵I-CCL2 and ¹²⁵I-CCL5 in situ, whereas antagonists of their receptors, CCR2 or CCR5, respectively, did not, suggesting that heparan sulfates at the endothelial surface mediate BBB transport. Finally, we showed that CCL2 and CCL5 transport across the BBB increased following a single injection of 0.3 mg/kg lipopolysaccharide. These data demonstrate that CCL2 and CCL5 in the brain can derive, in part, from the circulation, especially during systemic inflammation. Further, binding to the BBB-associated heparan sulfate is a mechanism by which both chemokines can cross the intact BBB, highlighting a novel therapeutic target for treating neuroinflammation. SIGNIFICANCE STATEMENT: Our work demonstrates that C-C motif chemokine ligand 2 (CCL2) and C-C motif chemokine ligand 5 (CCL5) can cross the intact blood-brain barrier and that transport is robustly increased during inflammation. These data suggest that circulating CCL2 and CCL5 can contribute to brain levels of each chemokine. We further show that the transport of both chemokines is inhibited by heparin and eprodisate, suggesting that CCL2/CCL5-heparan sulfate interactions could be therapeutically targeted to limit accumulation of these chemokines in the brain.

Alterations of Plasma Pro-Inflammatory Cytokine Levels in Children with Refractory Epilepsies

Paediatric epilepsy is a multifaceted neurological disorder with various aetiologies. Up to 30% of patients are considered drug-resistant. The background impact of interfering inflammatory and neuronal pathways has been closely linked to paediatric epilepsy. The characteristics of the inflamed state have been described not only in epilepsies, which are considered prototypes of an inflammatory pathophysiology, but also in patients with drug-resistant epilepsy, especially in epileptic encephalopathies. The imbalance of different cytokine levels was confirmed in several epileptic models. Chemokines are new targets for exploring neuroimmune communication in epileptogenesis, which control leukocyte migration and have a possible role in neuromodulation. Additionally, prostaglandin E2 (PGE2) is an important effector molecule for central neural inflammatory responses and may influence drug responsiveness. We measured the serum interictal quantitative levels of chemokines (CCL2, CCL4, CCL11) and PGE2 in correlation with the seizure frequency and severity in controlled and intractable childhood epilepsies. Our refractory seizure group demonstrated significantly increased concentrations of eotaxin (CCL11) compared to the controlled epilepsy group. The higher level of CCL11 was correlated with an increased seizure frequency, while the PGE2 levels were associated with the severity of seizure and epilepsy, supporting the findings that proinflammatory cytokines may contribute to epileptogenesis and possibly have a role in developing seizure resistance.

Advances in the study of the relationship between Alzheimer's disease and the gastrointestinal microbiome

There are many trillions of bacteria in the gastrointestinal microbiome (GM). Their ecological dysregulation can contribute to the development of certain neurodegenerative diseases, including Alzheimer's disease (AD). AD is common dementia and its incidence is increasing year by year. However, the relationship between GM and AD is unclear. Therefore, this review discusses the relationship between GM and AD, elaborates on the possible factors that can affect this relationship through the inflammation of the brain induced by blood-brain damage and accumulation of amyloid deposit, and proposes feasible ways to treat AD through GM-related substances, such as probiotics, Mega-3, and gut hormones, including their shortcomings as well.

Systemic inflammatory markers of persistent cerebral edema after aneurysmal subarachnoid hemorrhage

Background

Cerebral edema (CE) at admission is a surrogate marker of ‘early brain injury’ (EBI) after subarachnoid hemorrhage (SAH). Only recently has the focus on the changes in CE after SAH such as delayed resolution or newly developed CE been examined. Among several factors, an early systemic inflammatory response has been shown to be associated with CE. We investigate inflammatory markers in subjects with early CE which does not resolve, i.e., persistent CE after SAH.

Methods

Computed tomography scans of SAH patients were graded at admission and at 7 days after SAH for CE using the 0–4 ‘subarachnoid hemorrhage early brain edema score’ (SEBES). SEBES ≤ 2 and SEBES ≥ 3 were considered good and poor grade, respectively. Serum samples from the same subject cohort were collected at 4 time periods (at < 24 h [T1], at 24 to 48 h [T2]. 3–5 days [T3] and 6–8 days [T4] post-admission) and concentration levels of 17 cytokines (implicated in peripheral inflammatory processes) were measured by multiplex immunoassay. Multivariable logistic regression analyses were step-wisely performed to identify cytokines independently associated with persistent CE adjusting for covariables including age, sex and past medical history (model 1), and additional inclusion of clinical and radiographic severity of SAH and treatment modality (model 2).

Results

Of the 135 patients enrolled in the study, 21 of 135 subjects (15.6%) showed a persistently poor SEBES grade. In multivariate model 1, higher Eotaxin (at T1 and T4), sCD40L (at T4), IL-6 (at T1 and T3) and TNF-α (at T4) were independently associated with persistent CE. In multivariate model 2, Eotaxin (at T4: odds ratio [OR] = 1.019, 95% confidence interval [CI] = 1.002–1.035) and possibly PDGF-AA (at T4), sCD40L (at T4), and TNF-α (at T4) was associated with persistent CE.

Conclusions

We identified serum cytokines at different time points that were independently associated with persistent CE. Specifically, persistent elevations of Eotaxin is associated with persistent CE after SAH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02564-1.

Eotaxin-1 (CCL11) in neuroinflammatory disorders and possible role in COVID-19 neurologic complications

The related neurologic complications of SARS-CoV-2 infection in COVID-19 patients and survivors comprise symptoms including depression, anxiety, muscle pain, dizziness, headaches, fatigue, and anosmia/hyposmia that may continue for months. Recent studies have been demonstrated that chemokines have brain-specific attraction and effects such as chemotaxis, cell adhesion, modulation of neuroendocrine functions, and neuroinflammation. CCL11 is a member of the eotaxin family that is chemotactic agents for eosinophils and participate in innate immunity. Eotaxins may exert physiological and pathological functions in the central nerve system, and CCL11 may induce neuronal cytotoxicity effects by inducing the production of reactive oxygen species (ROS) in microglia cells. Plasma levels of CCL11 elevated in neuroinflammation and neurodegenerative disorders. COVID-19 patients display elevations in CCL11 levels. As CCL11 plays roles in physiosomatic and neuroinflammation, analyzing the level of this chemokine in COVID-19 patients during hospitalization and to predicting post-COVID-19-related neurologic complications may be worthwhile. Moreover, using chemokine modulators may be helpful in lessening the neurologic complications in such patients.

Cytokines in the Brain and Neuroinflammation: We Didn’t Starve the Fire!

In spite of the brain-protecting tissues of the skull, meninges, and blood-brain barrier, some forms of injury to or infection of the CNS can give rise to cerebral cytokine production and action and result in drastic changes in brain function and behavior. Interestingly, peripheral infection-induced systemic inflammation can also be accompanied by increased cerebral cytokine production. Furthermore, it has been recently proposed that some forms of psychological stress may have similar CNS effects. Different conditions of cerebral cytokine production and action will be reviewed here against the background of neuroinflammation. Within this context, it is important to both deepen our understanding along already taken paths as well as to explore new ways in which neural functioning can be modified by cytokines. This, in turn, should enable us to put forward different modes of cerebral cytokine production and action in relation to distinct forms of neuroinflammation.

Increase in plasma CCL11 (Eotaxin-1) in patients with alcohol dependence and changes during detoxification

BACKGROUND

Alcohol is known to modulate the immune system. Neuroinflammatory cytokine dysregulation plays an essential role in the pathophysiology of alcohol dependence (AD). Preclinical studies have indicated that alcohol consumption upregulates the pro-inflammatory cytokine CC motif ligand 11 (CCL11, also known as eotaxin-1). We examined CCL11 levels in patients with AD and in mice administered alcohol.

METHODS

The plasma CCL11 levels of 151 patients with AD and 116 healthy controls were measured. In addition, we followed the CCL11 levels, alcohol cravings and psychological symptoms in patients with AD after 1 and 2 weeks of detoxification. Furthermore, we examined CCL11 changes in mice administered alcohol for 5 days.

RESULTS

CCL11 levels were higher in patients with AD than in controls and declined during detoxification. CCL11 levels were positively correlated with AD severity (p < 0.001). Furthermore, mice exposed to alcohol exhibited a higher CCL11 level. The receiver operating characteristic curve revealed that a CCL11 level of 72.5 pg/mL could significantly differentiate patients with AD from controls (area under the curve: 0.77; p < 0.001). Reductions in CCL11 levels during detoxification were correlated with reductions in alcohol craving, depression, and anxiety.

CONCLUSIONS

Our data from humans and mice suggest that chronic alcohol consumption is associated with an increase in CCL11 levels. CCL11 levels are correlated with AD severity and may be a potential indicator of AD. The CCL11 reduction after alcohol discontinuation is associated with alleviation of clinical symptoms. Collectively, our findings suggest that CCL11 is involved in the neurobiological mechanisms underlying AD.

Elevated sCD40L in Secondary Progressive Multiple Sclerosis in Comparison to Non-progressive Benign and Relapsing Remitting Multiple Sclerosis

Background

The long-term prognosis of relapsing-remitting multiple sclerosis (RRMS) is usually unfavorable as most patients transition to secondary progressive multiple sclerosis (SPMS) with accumulative disability. A rare form of non-progressive multiple sclerosis (MS) also exists, known as benign MS (BMS or NPMS), which lacks disease progression defined as Expanded Disability Status Scale (EDSS) ≤3 after 15 years of disease onset without treatment.

Purpose

Our study aims to identify soluble plasma factors predicting disease progression in multiple sclerosis (MS).

Research Design and Study Sample

We utilized Luminex multiplex to analyze plasma levels of 33 soluble factors, comparing 32 SPMS patients to age-, sex-, and disease duration-matched non-progressive BMS patients, as well as to RRMS patients and healthy controls.

Results

Plasma levels of EGF, sCD40L, MCP1/CCL2, fractalkine/CX3CL1, IL-13, Eotaxin, TNFβ/LTα, and IL-12p40 were significantly different between the various types of MS. Plasma sCD40L was significantly elevated in SPMS compared to BMS and RRMS. The combination of MCP1/CCL2 and sCD40L discriminated between RRMS and SPMS. MCP1/CCL2 was found to be the most effective classifier between BMS and RRMS, while BMS was most effectively distinguished from SPMS by the combination of sCD40L and IFNγ levels.

Conclusions

These differences may facilitate personalized precision medicine and aid in the discovery of new therapeutic targets for disease progression through the improvement of patient stratification.

Reduced ccl11/eotaxin mediates the beneficial effects of environmental stimulation on the aged hippocampus

A deterioration in cognitive performance accompanies brain aging, even in the absence of neurodegenerative pathologies. However, the rate of cognitive decline can be slowed down by enhanced cognitive and sensorimotor stimulation protocols, such as environmental enrichment (EE). Understanding how EE exerts its beneficial effects on the aged brain pathophysiology can help in identifying new therapeutic targets. In this regard, the inflammatory chemokine ccl11/eotaxin-1 is a marker of aging with a strong relevance for neurodegenerative processes. Here, we demonstrate that EE in both elderly humans and aged mice decreases circulating levels of ccl11. Interfering, in mice, with the ccl11 decrease induced by EE ablated the beneficial effects on long-term memory retention, hippocampal neurogenesis, activation of local microglia and of ribosomal protein S6. On the other hand, treatment of standard-reared aged mice with an anti-ccl11 antibody resulted in EE-like improvements in spatial memory, hippocampal neurogenesis, and microglial activation. Taken together, our findings point to a decrease in circulating ccl11 concentration as a key mediator of the enhanced hippocampal function resulting from exposure to EE.

Association of accelerated long-term forgetting and senescence-related blood-borne factors in asymptomatic individuals from families with autosomal dominant Alzheimer's disease

Background

Accelerated long-term forgetting has been identified in preclinical Alzheimer’s disease (AD) and is attributed to a selective impairment of memory consolidation in which the hippocampus plays a key role. As blood may contain multiple senescence-related factors that involved in neurogenesis and synaptic plasticity in the hippocampus, we tested whether there is an association between blood-borne factors and accelerated long-term forgetting in asymptomatic individuals from families with autosomal dominant AD (ADAD).

Methods

We analyzed data of 39 asymptomatic participants (n = 18 ADAD mutation carriers, n = 21 non-carriers) from the Chinese Familial Alzheimer’s Disease Network (CFAN) study. Long-term forgetting rates were calculated based on recall or recognition of two materials (word list and complex figure) at three delays comprising immediate, 30 min, and 7 days. Peripheral blood concentrations of candidate pro-aging factors (CC chemokine ligand 11 [CCL11] and monocyte chemotactic protein 1 [MCP1]) and rejuvenation factors (growth differentiation factor 11 [GDF11], thrombospondin-4 [THBS4], and secreted protein acidic and rich in cysteine like 1 [SPARCL1]) were evaluated in all participants.

Results

Despite normal performance on standard 30-min delayed testing, mutation carriers exhibited accelerated forgetting of verbal and visual material over 7 days in comparison with matched non-carriers. In the whole sample, lower plasma THBS4 was associated with accelerated long-term forgetting in list recall (β = −0.46, p = 0.002), figure recall (β = −0.44, p = 0.004), and list recognition (β = −0.37, p = 0.010). Additionally, higher plasma GDF11 and CCL11 were both associated with accelerated long-term forgetting (GDF11 versus figure recall: β = 0.39, p = 0.007; CCL11 versus list recognition: β = 0.44, p = 0.002).

Conclusions

Accelerated long-term forgetting is a cognitive feature of presymptomatic AD. Senescence-related blood-borne factors, especially THBS4, GDF11, and CCL11, may be promising biomarkers for the prediction of accelerated long-term forgetting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00845-0.

Inflammation-driven brain and gut barrier dysfunction in stress and mood disorders

Regulation of emotions is generally associated exclusively with the brain. However, there is evidence that peripheral systems are also involved in mood, stress vulnerability vs. resilience, and emotion‐related memory encoding. Prevalence of stress and mood disorders such as major depression, bipolar disorder, and post‐traumatic stress disorder is increasing in our modern societies. Unfortunately, 30%–50% of individuals respond poorly to currently available treatments highlighting the need to further investigate emotion‐related biology to gain mechanistic insights that could lead to innovative therapies. Here, we provide an overview of inflammation‐related mechanisms involved in mood regulation and stress responses discovered using animal models. If clinical studies are available, we discuss translational value of these findings including limitations. Neuroimmune mechanisms of depression and maladaptive stress responses have been receiving increasing attention, and thus, the first part is centered on inflammation and dysregulation of brain and circulating cytokines in stress and mood disorders. Next, recent studies supporting a role for inflammation‐driven leakiness of the blood–brain and gut barriers in emotion regulation and mood are highlighted. Stress‐induced exacerbated inflammation fragilizes these barriers which become hyperpermeable through loss of integrity and altered biology. At the gut level, this could be associated with dysbiosis, an imbalance in microbial communities, and alteration of the gut–brain axis which is central to production of mood‐related neurotransmitter serotonin. Novel therapeutic approaches such as anti‐inflammatory drugs, the fast‐acting antidepressant ketamine, and probiotics could directly act on the mechanisms described here improving mood disorder‐associated symptomatology. Discovery of biomarkers has been a challenging quest in psychiatry, and we end by listing promising targets worth further investigation.

Vascular Senescence: A Potential Bridge Between Physiological Aging and Neurogenic Decline

The adult mammalian brain contains distinct neurogenic niches harboring populations of neural stem cells (NSCs) with the capacity to sustain the generation of specific subtypes of neurons during the lifetime. However, their ability to produce new progeny declines with age. The microenvironment of these specialized niches provides multiple cellular and molecular signals that condition NSC behavior and potential. Among the different niche components, vasculature has gained increasing interest over the years due to its undeniable role in NSC regulation and its therapeutic potential for neurogenesis enhancement. NSCs are uniquely positioned to receive both locally secreted factors and adhesion-mediated signals derived from vascular elements. Furthermore, studies of parabiosis indicate that NSCs are also exposed to blood-borne factors, sensing and responding to the systemic circulation. Both structural and functional alterations occur in vasculature with age at the cellular level that can affect the proper extrinsic regulation of NSCs. Additionally, blood exchange experiments in heterochronic parabionts have revealed that age-associated changes in blood composition also contribute to adult neurogenesis impairment in the elderly. Although the mechanisms of vascular- or blood-derived signaling in aging are still not fully understood, a general feature of organismal aging is the accumulation of senescent cells, which act as sources of inflammatory and other detrimental signals that can negatively impact on neighboring cells. This review focuses on the interactions between vascular senescence, circulating pro-senescence factors and the decrease in NSC potential during aging. Understanding the mechanisms of NSC dynamics in the aging brain could lead to new therapeutic approaches, potentially include senolysis, to target age-dependent brain decline.

Constitutive PGC-1α Overexpression in Skeletal Muscle Does Not Contribute to Exercise-Induced Neurogenesis

Physical exercise can improve age-dependent decline in cognition, which in rodent is partly mediated by restoration of an age-dependent decline in neurogenesis. Exercise-inducible myokines in the circulation present a link in muscle-brain crosstalk. The transcription factor PGC-1α regulates the release of such myokines with neurotrophic properties into the circulation. We study how chronic muscular overexpression of PGC-1α could contribute to exercise-induced effects on hippocampal neurogenesis and if this effect could be enhanced in a running wheel paradigm. We used 3- and 11-month-old transgenic mice with overexpression of PGC-1α under the control of muscle creatinine kinase promoter (MCK-PGC-1α), which have a constitutively developed endurance muscle phenotype. Wild-type and MCK-PGC-1α mice were single housed with free access to running wheels. Four weeks of running in female animals increased the levels of newborn cells, immature neurons, and, for young animals, new mature neurons, compared to sedentary controls. However, no difference in these parameters was observed between wild-type and transgenic mice under sedentary or running conditions. Multiplex analysis of serum cytokines, chemokines, and myokines suggested several differences in serum protein concentrations between genotypes with musclin found to be significantly upregulated 4-fold in male MCK-PGC-1α animals. We conclude that constitutive muscular overexpression of PGC-1α, despite systemic changes and difference in serum composition, does not translate into exercise-induced effects on hippocampal neurogenesis, independent of the age of the animal. This suggests that chronic activation of PGC-1α in skeletal muscle is by itself not sufficient to mimic exercise-induced effects or to prevent decline of neurogenesis in aging.

Chronic fatigue syndrome and fibromyalgia-like symptoms are an integral component of the phenome of schizophrenia: neuro-immune and opioid system correlates

Physiosomatic symptoms are an important part of schizophrenia phenomenology. The aim of this study is to examine the biomarker, neurocognitive and symptomatic correlates of physiosomatic symptoms in schizophrenia. We recruited 115 schizophrenia patients and 43 healthy controls and measured the Fibromyalgia and Chronic Fatigue Syndrome Rating (FF) scale, schizophrenia symptom dimensions, and the Brief Assessment of Cognition in Schizophrenia. We measured neuro-immune markers including plasma CCL11 (eotaxin), interleukin-(IL)-6, IL-10, Dickkopf protein 1 (DKK1), high mobility group box 1 protein (HMGB1) and endogenous opioid system (EOS) markers including κ-opioid receptor (KOR), μ-opioid receptor (MOR), endomorphin-2 (EM2) and β-endorphin. Patients with an increased FF score display increased ratings of psychosis, hostility, excitement, formal though disorders, psycho-motor retardation and negative symptoms as compared with patients with lower FF scores. A large part of the variance in the FF score (55.1%) is explained by the regression on digit sequencing task, token motor task, list learning, IL-10, age (all inversely) and IL-6 (positively). Neural network analysis shows that the top-6 predictors of the FF score are (in descending order): IL-6, HMGB1, education, MOR, KOR and IL-10. We found that 45.1% of the variance in a latent vector extracted from cognitive test scores, schizophrenia symptoms and the FF score was explained by HMGB1, MOR, EM2, DKK1, and CCL11. Physiosomatic symptoms are an integral part of the phenome of schizophrenia. Neurotoxic immune pathways and lowered immune regulation coupled with alterations in the EOS appear to drive the physiosomatic symptoms of schizophrenia.

Elevated inflammatory proteins in cerebrospinal fluid from patients with painful knee osteoarthritis are associated with reduced symptom severity

Neuroinflammation and periphery-to-CNS neuroimmune cross-talk in patients with painful knee osteoarthritis (OA) are poorly understood. We utilized proximity extension assay to measure the level of 91 inflammatory proteins in CSF and serum from OA patients and controls. The patients had elevated levels of 48 proteins in CSF indicating neuroinflammation. Ten proteins were correlated between CSF and serum and potentially involved in periphery-to-CNS neuroimmune cross-talk. Seven CSF proteins, all with previously reported neuroprotective effects, were associated with lower pain intensity and milder knee-related symptoms. Our findings indicate that neuroinflammation in OA could be protective and associated with less severe symptoms.

CCL-11 or Eotaxin-1: An Immune Marker for Ageing and Accelerated Ageing in Neuro-Psychiatric Disorders

Background: CCL-11 (eotaxin) is a chemokine with an important role in allergic conditions. Recent evidence indicates that CCL-11 plays a role in brain disorders as well. This paper reviews the associations between CCL-11 and aging, neurodegenerative, neuroinflammatory and neuropsychiatric disorders. Methods: Electronic databases were searched for original articles examining CCL-11 in neuropsychiatric disorders. Results: CCL-11 is rapidly transported from the blood to the brain through the blood-brain barrier. Age-related increases in CCL-11 are associated with cognitive impairments in executive functions and episodic and semantic memory, and therefore, this chemokine has been described as an “Endogenous Cognition Deteriorating Chemokine” (ECDC) or “Accelerated Brain-Aging Chemokine” (ABAC). In schizophrenia, increased CCL-11 is not only associated with impairments in cognitive functions, but also with key symptoms including formal thought disorders. Some patients with mood disorders and premenstrual syndrome show increased plasma CCL-11 levels. In diseases of old age, CCL-11 is associated with lowered neurogenesis and neurodegenerative processes, and as a consequence, increased CCL-11 increases risk towards Alzheimer’s disease. Polymorphisms in the CCL-11 gene are associated with stroke. Increased CCL-11 also plays a role in neuroinflammatory disease including multiple sclerosis. In animal models, neutralization of CCL-11 may protect against nigrostriatal neurodegeneration. Increased production of CCL-11 may be attenuated by glucocorticoids, minocycline, resveratrol and anti-CCL11 antibodies. Conclusions: Increased CCL-11 production during inflammatory conditions may play a role in human disease including age-related cognitive decline, schizophrenia, mood disorders and neurodegenerative disorders. Increased CCL-11 production is a new drug target in the treatment and prevention of those disorders.

Potential chemokine biomarkers associated with PTSD onset, risk and resilience as well as stress responses in US military service members

Cytokines, including chemokines, are small secreted proteins, which specifically effect on the interactions and communications between cells. Pro-inflammatory cytokines are produced predominantly by activated macrophages and are involved in the upregulation of inflammatory reactions. Dysregulation of cytokines is associated with post-traumatic stress disorder (PTSD). Here, we use both before-and-after and case-control studies to search for potential chemokine biomarkers associated with PTSD onset, risk, and resilience as well as stress responses in US military service members deployed to Iraq and Afghanistan. Blood samples and scores of the PTSD Checklist (PCL) were obtained from soldiers pre- and post deployment (pre, post). Forty chemokines were measured using the Bio-Plex Pro Human Chemokine Panel Assays. The before-and-after analysis showed potential markers (CCL2, CCL15, CCL22, CCL25, CXCL2, and CXCL12) are associated with PTSD onset, and CCL3, CXCL11, and CXCL16 are related to stress response. The case-control study demonstrated that CCL13, CCL20, and CXCL6 were possible PTSD risk markers, and CX3CL1 might be a resilience marker. In addition, CCL11, CCL13, CCL20, and CCL25 were correlated with the PCL scores, indicating their association with PTSD symptom severity. Our data, for the first time, suggest that these dysregulated chemokines may serve as biomarkers for PTSD onset, risk, and resilience as well as stress responses, and may benefit developing approaches not only for PTSD diagnosis but also for PTSD treatment.

The Neuroimmune and Neurotoxic Fingerprint of Major Neurocognitive Psychosis or Deficit Schizophrenia: a Supervised Machine Learning Study

No studies have examined the immune fingerprint of major neurocognitive psychosis (MNP) or deficit schizophrenia using M1 macrophage cytokines in combination with chemokines such as CCL2 and CCL11. The present study delineated the neuroimmune fingerprint of MNP by analyzing plasma levels of IL-1β, sIL-1RA, TNFα, sTNFR1, sTNFR2, CCL2, and CCL11 in 120 MNP versus 54 healthy controls in association with neurocognitive scores (as assessed with the Brief Assessment of Cognition in Schizophrenia) and PHEMN (psychotic, hostility, excitation, mannerism and negative) symptoms. MNP was best predicted by a combination of CCL11, TNFα, IL-1β, and sIL-1RA which yielded a bootstrapped (n = 2000) area under the receiver operating curve of 0.985. Composite scores reflecting M1 macrophage activity and neurotoxic potential including effects of CCL11 and CCL2 were significantly increased in MNP. A large part of the variance in PHEM (38.4-52.6%) and negative (65.8-74.4%) symptoms were explained by combinations of immune markers whereby CCL11 was the most important. The same markers explained a large part of the variance in the Mini-Mental State examination, list learning, digit sequencing task, category instances, controlled word association, symbol coding, and Tower of London. Partial least squares analysis showed that 72.7% of the variance in overall severity of schizophrenia was explained by the regression on IL-1β, sIL-1RA, CCL11, TNFα, and education. It is concluded that the combination of the abovementioned markers defines MNP as a distinct neuroimmune disorder and that increased immune neurotoxicity determines memory and executive impairments and PHEMN symptoms as well.

CCL11 Differentially Affects Post-Stroke Brain Injury and Neuroregeneration in Mice Depending on Age

CCL11 has recently been shown to differentially affect cell survival under various pathological conditions including stroke. Indeed, CCL11 promotes neuroregeneration in neonatal stroke mice. The impact of CCL11 on the adult ischemic brain, however, remains elusive. We therefore studied the effect of ectopic CCL11 on both adolescent (six-week) and adult (six-month) C57BL6 mice exposed to stroke. Intraperitoneal application of CCL11 significantly aggravated acute brain injury in adult mice but not in adolescent mice. Likewise, post-stroke neurological recovery after four weeks was significantly impaired in adult mice whilst CCL11 was present. On the contrary, CCL11 stimulated gliogenesis and neurogenesis in adolescent mice. Flow cytometry analysis of blood and brain samples revealed a modification of inflammation by CCL11 at subacute stages of the disease. In adolescent mice, CCL11 enhances microglial cell, B and T lymphocyte migration towards the brain, whereas only the number of B lymphocytes is increased in the adult brain. Finally, the CCL11 inhibitor SB297006 significantly reversed the aforementioned effects. Our study, for the first time, demonstrates CCL11 to be a key player in mediating secondary cell injury under stroke conditions. Interfering with this pathway, as shown for SB297006, might thus be an interesting approach for future stroke treatment paradigms.

Circulating factors in young blood as potential therapeutic agents for age-related neurodegenerative and neurovascular diseases

Recent animal studies on heterochronic parabiosis (a technique combining the blood circulation of two animals) have revealed that young blood has a powerful rejuvenating effect on brain aging. Circulating factors, especially growth differentiation factor 11 (GDF11) and C-C motif chemokine 11 (CCL11), may play a key role in this effect, which inspires hope for novel approaches to treating age-related cerebral diseases in humans, such as neurodegenerative and neurovascular diseases. Recently, attempts have begun to translate these astonishing and exciting findings from mice to humans and from bench to bedside. However, increasing reports have shown contradictory data, questioning the capacity of these circulating factors to reverse age-related brain dysfunction. In this review, we summarize the current research on the role of young blood, as well as the circulating factors GDF11 and CCL11, in the aging brain and age-related cerebral diseases. We highlight recent controversies, discuss related challenges and provide a future outlook.

Impairment of amyloid precursor protein alpha-processing in cerebral microvessels of type 1 diabetic mice

The mechanisms underlying dysfunction of cerebral microvasculature induced by type 1 diabetes (T1D) are not fully understood. We hypothesized that in cerebral microvascular endothelium, α-processing of amyloid precursor protein (APP) is impaired by T1D. In cerebral microvessels derived from streptozotocin (STZ)-induced T1D mice protein levels of APP and its α-processing enzyme, a disintegrin and metalloprotease 10 (ADAM10) were significantly decreased, along with down-regulation of adenylate cyclase 3 (AC3) and enhanced production of thromboxane A₂ (TXA₂). In vitro studies in human brain microvascular endothelial cells (BMECs) revealed that knockdown of AC3 significantly suppressed ADAM10 protein levels, and that activation of TXA₂ receptor decreased APP expression. Furthermore, levels of soluble APPα (sAPPα, a product of α-processing of APP) were significantly reduced in hippocampus of T1D mice. In contrast, amyloidogenic processing of APP was not affected by T1D in both cerebral microvessels and hippocampus. Most notably, studies in endothelial specific APP knockout mice established that genetic inactivation of APP in endothelium was sufficient to significantly reduce sAPPα levels in the hippocampus. In aggregate, our findings suggest that T1D impairs non-amyloidogenic processing of APP in cerebral microvessels. This may exert detrimental effect on local concentration of neuroprotective molecule, sAPPα, in the hippocampus.

Breakdown of the Paracellular Tight and Adherens Junctions in the Gut and Blood Brain Barrier and Damage to the Vascular Barrier in Patients with Deficit Schizophrenia

Deficit schizophrenia is characterized by leaky intestinal tight and adherens junctions and bacterial translocation. Here we examine whether (deficit) schizophrenia is accompanied by leaky paracellular, transcellular, and vascular barriers in the gut and blood-brain barriers. We measured IgA responses to occludin, claudin-5, E-cadherin, and β-catenin (paracellular pathway, PARA); talin, actin, vinculin, and epithelial intermediate filament (transcellular pathway, TRANS); and plasmalemma vesicle-associated protein (PLVAP, vascular pathway) in 78 schizophrenia patients and 40 controls. IgA responses to claudin-5, E-cadherin, and β-catenin, the sum of the four PARA proteins, and the ratio PARA/TRANS were significantly higher in deficit schizophrenia patients than in nondeficit schizophrenia patients and controls. A large part of the variance in PHEMN (psychosis, hostility, excitation, mannerism, and negative) symptoms, psychomotor retardation, formal thought disorders, verbal fluency, word list memory, word list recall, and executive functions was explained by the PARA/TRANS ratio coupled with plasma IgA responses to Gram-negative bacteria, IgM to malondialdehyde, CCL-11 (eotaxin), IgA levels of the ratio of noxious to more protective tryptophan catabolites (NOX/PRO TRYCATs), and a plasma immune activation index. Moreover, IgA levels to Gram-negative bacteria were significantly associated with IgA to E-cadherin, β-catenin, and PLVAP, while IgA levels to claudin-5 were significantly predicted by IgA to E-cadherin, NOX/PRO TRYCAT ratio, Gram-negative bacteria, and CCL11. The phenomenology of the deficit syndrome is to a large extent explained by the cumulative effects of lowered natural IgM, breakdown of the paracellular and vascular pathways, increased bacterial translocation, peripheral immune-inflammatory responses, and indices of BBB breakdown.

Age-Associated Changes in the Immune System and Blood⁻Brain Barrier Functions

Age is associated with altered immune functions that may affect the brain. Brain barriers, including the blood-brain barrier (BBB) and blood-CSF barrier (BCSFB), are important interfaces for neuroimmune communication, and are affected by aging. In this review, we explore novel mechanisms by which the aging immune system alters central nervous system functions and neuroimmune responses, with a focus on brain barriers. Specific emphasis will be on recent works that have identified novel mechanisms by which BBB/BCSFB functions change with age, interactions of the BBB with age-associated immune factors, and contributions of the BBB to age-associated neurological disorders. Understanding how age alters BBB functions and responses to pathological insults could provide important insight on the role of the BBB in the progression of cognitive decline and neurodegenerative disease.

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

Methods:

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

Results:

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

Conclusion:

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

Young bone marrow transplantation preserves learning and memory in old mice

Restoration of cognitive function in old mice by transfer of blood or plasma from young mice has been attributed to reduced C–C motif chemokine ligand 11 (CCL11) and β2-microglobulin, which are thought to suppress neurogenesis in the aging brain. However, the specific role of the hematopoietic system in this rejuvenation has not been defined and the importance of neurogenesis in old mice is unclear. Here we report that transplantation of young bone marrow to rejuvenate the hematopoietic system preserved cognitive function in old recipient mice, despite irradiation-induced suppression of neurogenesis, and without reducing β2-microglobulin. Instead, young bone marrow transplantation preserved synaptic connections and reduced microglial activation in the hippocampus. Circulating CCL11 levels were lower in young bone marrow recipients, and CCL11 administration in young mice had the opposite effect, reducing synapses and increasing microglial activation. In conclusion, young blood or bone marrow may represent a future therapeutic strategy for neurodegenerative disease.

Melanie Das et al. demonstrate that transplantation of young bone marrow preserves the cognitive function of old recipient mice. This study suggests that microglial rejuvenation via peripheral manipulation of the hematopoietic system may be sufficient to delay a cognitive decline during aging.

Distribution of bioactive factors in human milk samples

Background

Breast milk provides nutrition for infants and also contains a variety of bioactive factors that influence the development of the newborn. Human milk is a complex biological fluid that can be separated into different layers (water phase and lipid phase with its component water and lipid fractions). It can affect the developing human body along the whole length of the gastrointestinal tract, and through the circulation, its factors may reach every organ.

Methods

In the present study, we analyzed milk samples collected monthly for 6 months from 16 mothers from the 4^th week postpartum between 2014 and 2016 in Baranya County, Hungary. The 96 samples provided us information about the fluctuation of certain bioactive factors during the first 6 months of lactation. We investigated with Luminex technology the concentrations of several cytokines (CD40, Flt-3L), chemokines (MCP-1, RANTES, GRO, MIP-1ß, MDC, eotaxin, fractalkine), and epidermal growth factor (EGF). Paired t-tests and one-way ANOVA followed by Bonferroni post-hoc tests were used to compare the data.

Results

We detected the presence of each bioactive factor in every layer of the milk samples during the first 6 months of breastfeeding in widespread concentration ranges. In the case of GRO, MIP-1ß, MDC, Flt-3L, fractalkine, and eotaxin, the concentrations were constant during the first 6 months of lactation. The water phase of human milk contained higher factor concentrations compared to both fractions of the lipid phase for most factors (except eotaxin and MIP-1ß). The concentrations of CD40, EGF, MCP-1, and RANTES in the first 3 months were significantly different compared to the values detected between 4^th and 6^th months. In the water phase, the level of MCP-1 was significantly decreased, while all of the other factors increased during the 4^th through 6^th months. We found significantly higher EGF, GRO, and RANTES levels in the water fraction compared to the lipid fraction of the lipid phase.

Conclusions

The novel findings of this investigation were the presence of Flt-3L and MDC in all layers of breast milk, and nearly all bioactive factors in the lipid phase. Due to their widespread physiological effects these factors may have an essential role in organogenesis.

High Exploratory Phenotype Rats Exposed to Environmental Stressors Present Memory Deficits Accompanied by Immune-Inflammatory/Oxidative Alterations: Relevance to the Relationship Between Temperament and Mood Disorders

Low-exploratory (LE) and high-exploratory (HE) rodents mimic human depressive and hyperthymic temperaments, respectively. Mood disorders (MD) may be developed by the exposure of these temperaments to environmental stress (ES). Psychiatric symptoms severity in MD patients is related to the magnitude of memory impairment. Thus, we aimed at studying the consequences of the exposure of LE and HE male Wistar rats, during periadolescence, to a combination of ES, namely, paradoxical sleep deprivation (PSD) and unpredictable stress (US), on anxiety-related behavior in the plus maze test, working (WM) and declarative memory (DM) performance. We also evaluated hippocampal immune-inflammatory/oxidative, as consequences of ES, and prevention of ES-induced alterations by the mood-stabilizing drugs, lithium and valproate. Medium exploratory (ME) control rats were used for comparisons with HE- and LE-control rats. We observed that HE-controls presented increased anxiolytic behavior that was significantly increased by ES exposure, whereas LE-controls presented increased anxiety-like behavior relative to ME-controls. Lithium and valproate prevented anxiolytic alterations in HE+ES rats. HE+ES- and LE+ES-rats presented WM and DM deficits. Valproate and lithium prevented WM deficits in LE-PSD+US rats. Lithium prevented DM impairment in HE+ES-rats. Hippocampal levels of reduced glutathione (GSH) increased four-fold in HE+ES-rats, being prevented by valproate and lithium. All groups of LE+ES-rats presented increased levels of GSH in relation to controls. Increments in lipid peroxidation in LE+ES- and HE+ES-rats were prevented by valproate in HE+ES-rats and by both drugs in LE+ES-rats. Nitrite levels were increased in HE+ES- and LE+ES-rats (five-fold increase), which was prevented by both drugs in LE+ES-rats. HE+ES-rats presented a two-fold increase in the inducible nitric oxide synthase (iNOS) expression that was prevented by lithium. HE+ES-rats showed increased hippocampal and plasma levels of interleukin (IL)-1β and IL-4. Indoleamine 2, 3-dioxygenase 1 (IDO1) was increased in HE+ES- and LE+ES-rats, while tryptophan 2,3-dioxygenase (TDO2) was increased only in HE+ES-rats. Altogether, our results showed that LE- and HE-rats exposed to ES present distinct anxiety-related behavior and similar memory deficits. Furthermore, HE+ES-rats presented more brain and plasma inflammatory alterations that were partially prevented by the mood-stabilizing drugs. These alterations in HE+ES-rats may possibly be related to the development of mood symptoms.

Genetics and sex influence peripheral and central innate immune responses and blood-brain barrier integrity

Lipopolysaccharide (LPS) is a stimulator of the innate immune system and is routinely used in animal models to study blood-brain barrier (BBB) dysfunction under inflammatory conditions. It is appreciated that both humans and mice have sexually dimorphic immune responses, which could influence the brain’s response to a systemic inflammatory insult. Mouse strain is also an important factor that can contribute to pathophysiological responses to inflammatory stimuli. Therefore, we aimed to test whether BBB disruption and the associated cytokine profiles in response to LPS differed in male and female mice from two mouse strains most commonly used in blood-brain barrier studies: CD-1 and C57BL6/J (C57). Mice were treated with saline, a single injection of 0.3, or 3mg/kg LPS, or three injections of 3mg/kg LPS, and studied 28 hours after the first LPS injection. To assay BBB disruption, we utilized the tracer 99mTc-DTPA. A 23-plex panel of cytokines was assayed in brain and blood of the same cohort of mice, which allowed us to compare differences in the levels of individual cytokines as well as correlations among cytokines and 99mTc-DTPA uptake. We found that only the three-injection dose of LPS induced significant BBB disruption in all sexes and strains. The treatment, strain, and sex, as well as treatment-by- strain and treatment-by-sex interactions significantly contributed to the variance. The mean brain/serum ratios of 99mTc-DTPA in the three-injection LPS group were ranked CD-1 male < CD-1 female < C57 male < C57 female. There were significant sex and strain differences in cytokine profiles in brain and blood, and pro-inflammatory cytokines and chemokines in brain were most strongly correlated with 99mTc-DTPA brain/serum ratios.

Association between plasma CCL11 (eotaxin-1) and cognitive status in older adults: Differences between rural and urban dwellers

The chemokine CCL11 has been implicated in age-related cognitive deterioration in mice, yet evidence on the relationship between CCL11 and cognitive function in humans is limited. This study explored associations between CCL11 and cognition in rural and urban community-dwelling older adults. Participants were 515 urban dwellers from the 3C-Bordeaux cohort and 318 rural dwellers from the AMI cohort. Plasma CCL11 was measured using an enzyme-linked immunoassay. Mini Mental State Examination (MMSE) test scores were used as the main measure of cognitive performance. Multivariate regression analysis was used to evaluate the cross-sectional association between CCL11 and cognitive performance. CCL11 was significantly higher in rural dwellers compared to city dwellers (median [IQR]: 145 [115-201] pg/mL vs. 103 [85-129] pg/mL; p < 0.001). After adjustment for confounders, CCL11 was found to be negatively associated with cognitive performance in rural dwellers but not in city dwellers. These results suggest that CCL11 may be an independent determinant of cognitive function in older rural dwellers and that the residential environment modifies this association.

Eotaxin, an Endogenous Cognitive Deteriorating Chemokine (ECDC), Is a Major Contributor to Cognitive Decline in Normal People and to Executive, Memory, and Sustained Attention Deficits, Formal Thought Disorders, and Psychopathology in Schizophrenia Patients

Eotaxin is increased in neurodegenerative disorders and schizophrenia, and preclinical studies indicate that eotaxin may induce cognitive deficits. This study aims to examine whether peripheral levels of eotaxin impact cognitive functioning in healthy volunteers and formal thought disorder (FTD) and psychopathology in schizophrenia patients. Serum levels of eotaxin were assayed and cognitive tests were performed on a sample of 40 healthy participants and 80 schizophrenia patients. Among healthy participants, eotaxin levels were significantly associated with episodic/semantic memory, executive functions, Mini Mental State Examination, emotion recognition, and sustained attention. In addition, age-related effects on these cognitive measures were partly mediated by eotaxin. The super-variable "age-eotaxin" predicted a large part of the variance in cognitive functions among healthy participants, and hence, eotaxin may act as an "accelerated brain aging chemokine" (ABAC). In schizophrenia, eotaxin levels had a strong impact on formal thought disorders and psychopathology. In schizophrenia, increased eotaxin strongly impacts memory and sustained attention, which together to a large extent determine FTD. FTD together with memory deficits predicts around 92.5% of the variance in psychopathology. Moreover, the effects of eotaxin are partially mediated by executive functioning, while the effects of male sex on FTD and psychopathology are mediated by eotaxin. In healthy subjects, eotaxin strongly impacts executive functioning and multiple cognitive domains. In schizophrenia, peripheral levels of eotaxin strongly impact both negative symptoms and psychosis (hallucinations and delusions), and these eotaxin effects are mediated by impairments in frontal functioning, memory, sustained attention, and FTD. Eotaxin is an endogenous cognitive deteriorating chemokine (ECDC) and a novel therapeutic target for age-related cognitive decline and schizophrenia as well.

Neurovascular unit crosstalk: Pericytes and astrocytes modify cytokine secretion patterns of brain endothelial cells

Crosstalk among brain endothelial cells (BECs), pericytes, and astrocytes occurs by way of soluble factors, including cytokines. Here, we studied cytokine secretion from both mouse BEC monocultures and tri-cultured with pericytes and astrocytes. Four cytokines were constitutively secreted by BEC monolayers, 12 by LPS-stimulated BECs, 10 by tri-cultures, and 14 by LPS-stimulated tri-cultures. Cytokine levels were generally higher with either LPS stimulation or tri-culture when compared to monocultures and highest in tri-cultures stimulated by LPS. LPS-stimulated secretions fell into eight patterns as categorized by the polarization of cytokine secretions. To determine the cellular origin of cytokine increases in tri-cultures, we cultured mouse BECs with human pericytes and astrocytes and measured cytokines in species-specific assays. Thus, cytokines detected in the human immunoassay were from pericytes/astrocytes and those detected in the mouse immunoassay were from BECs. Several unique patterns were thus found. For example, TNF-alpha was only of pericyte/astrocyte origin; granulocyte colony-stimulating factor was only of BEC origin; IL-6, MCP-1, and GM-CSF of astrocyte/pericyte origin were found in both the luminal and abluminal chambers, suggesting the presence of brain-to-blood transporters. We conclude that crosstalk influences cytokine secretion under constitutive and stimulated conditions from both BECs and pericytes/astrocytes.

Neuroimmune Axes of the Blood-Brain Barriers and Blood-Brain Interfaces: Bases for Physiological Regulation, Disease States, and Pharmacological Interventions

Central nervous system (CNS) barriers predominantly mediate the immune-privileged status of the brain, and are also important regulators of neuroimmune communication. It is increasingly appreciated that communication between the brain and immune system contributes to physiologic processes, adaptive responses, and disease states. In this review, we discuss the highly specialized features of brain barriers that regulate neuroimmune communication in health and disease. In section I, we discuss the concept of immune privilege, provide working definitions of brain barriers, and outline the historical work that contributed to the understanding of CNS barrier functions. In section II, we discuss the unique anatomic, cellular, and molecular characteristics of the vascular blood-brain barrier (BBB), blood-cerebrospinal fluid barrier, and tanycytic barriers that confer their functions as neuroimmune interfaces. In section III, we consider BBB-mediated neuroimmune functions and interactions categorized as five neuroimmune axes: disruption, responses to immune stimuli, uptake and transport of immunoactive substances, immune cell trafficking, and secretions of immunoactive substances. In section IV, we discuss neuroimmune functions of CNS barriers in physiologic and disease states, as well as pharmacological interventions for CNS diseases. Throughout this review, we highlight many recent advances that have contributed to the modern understanding of CNS barriers and their interface functions.

Inflammatory chemokine eotaxin-1 is correlated with age in heroin dependent patients under methadone maintenance therapy

BACKGROUND

Degeneration of central neurons and fibers has been observed in postmortem brains of heroin dependent patients. However, there are no biomarkers to predict the severity of neurodegeneration related to heroin dependence. A correlation has been reported between inflammatory C-C motif chemokine ligand 11 (CCL11, or eotaxin-1) and neurodegeneration in Alzheimer's disease.

METHODS

Three-hundred-forty-four heroin dependent, Taiwanese patients under methadone maintenance treatment (MMT) were included with clinical assessment and genomics information. Eighty-seven normal control subjects were also recruited for comparison.

RESULTS

Using receiver operating characteristics curve analyses, CCL11 showed the strongest sensitivity and specificity in correlation with age by a cut-off at 45 years (AUC = 0.69, P < 0.0001) in MMT patients, but not normal controls. Patients 45 years of age or older had significantly higher plasma levels of CCL11, fibroblast growth factor 2 (FGF-2), nicotine metabolite cotinine, and a longer duration of addiction. Plasma level of CCL11 was correlated with that of FGF-2 (partial r² = 0.24, P < 0.0001). Carriers with the mutant allele of rs1129844, a functional single nucleotide polymorphism (Ala23Thr) in the CCL11 gene, showed a higher plasma level of Aß42, ratio of Aß42/Aß40, and insomnia side effect symptom score than the GG genotype carriers among MMT responders with morphine-negative urine results.

CONCLUSIONS

The results suggest possible novel mechanisms mediated through CCL11 involving neurotoxicity in heroin dependent patients.

Cytokine alterations and cognitive impairment in major depressive disorder: From putative mechanisms to novel treatment targets

Overwhelming evidence indicates the involvement of immune-inflammatory processes in the pathophysiology of major depressive disorder (MDD). Peripheral cytokine alterations serve as one of most consistently reported indices of subthreshold inflammatory state observed in MDD. Although cytokines cannot pass directly through the blood-brain barrier, a number of transport mechanisms have been reported. In addition, peripheral cytokines may impact central nervous system via downstream effectors of their biological activity. Animal model studies have provided evidence that cytokines might impact cognitive performance through direct and indirect effects on long-term potentiation, neurogenesis and synaptic plasticity. Therefore, it has been hypothesized that cytokine alterations might contribute to cognitive impairment that is widely observed in MDD and persists beyond episodes of acute relapse in the majority of patients. Although several studies have provided that peripheral cytokine alterations might be related to cognitive deficits in patients with MDD, the quality of evidence still leaves much to be desired due to methodological heterogeneity and limitations. In this article, we provide an overview of studies investigating the association between peripheral cytokine alterations and cognitive performance in MDD, discuss underlying mechanisms and neural substrates. Finally, we propose possible treatment targets related to cytokine alterations taking into account existing evidence for antidepressant efficacy of anti-inflammatory pharmacological treatment modalities.

Revisiting the Role of Eotaxin-1/CCL11 in Psychiatric Disorders

Eotaxin-1/CCL11 is a chemokine originally implicated in the selective recruitment of eosinophils into inflammatory sites during allergic reactions, being thoroughly investigated in asthma, allergic rhinitis, and other eosinophil-related conditions. Eotaxin-1/CCL11 is also involved with a skewed immune response toward a type-2 (Th2) profile. In addition to its role in immune response, recent studies have shown that eotaxin-1/CCL11 is associated with aging, neurogenesis and neurodegeneration, being able to influence neural progenitor cells, and microglia. Increased circulating levels of eotaxin-1/CCL11 have been described in major psychiatric disorders (schizophrenia, bipolar disorder, major depression), sometimes correlating with the severity of psychopathological and cognitive parameters. As similar findings have been reported in neurodegenerative conditions such as Alzheimer's disease, it has been hypothesized that mechanisms involving eotaxin-1/CCL11 signaling may underlie the "accelerated aging" profile commonly linked to psychiatric disorders. Future studies must determine whether eotaxin-1/CCL11 can be regarded as a prognostic biomarker and/or as therapeutic target for resistant/progressive cases.

The "Aging Factor" Eotaxin-1 (CCL11) Is Detectable in Transfusion Blood Products and Increases with the Donor's Age

Background: High blood levels of the chemokine eotaxin-1 (CCL11) have recently been associated with aging and dementia, as well as impaired memory and learning in humans. Importantly, eotaxin-1 was shown to pass the blood-brain-barrier (BBB) and has been identified as crucial mediator of decreased neurogenesis and cognitive impairment in young mice after being surgically connected to the vessel system of old animals in a parabiosis model. It thus has to be assumed that differences in eotaxin-1 levels between blood donors and recipients might influence cognitive functions also in humans. However, it is unknown if eotaxin-1 is stable during processing and storage of transfusion blood components. This study assesses eotaxin-1 concentrations in fresh-frozen plasma (FFP), erythrocyte concentrate (EC), and platelet concentrate (PC) in dependence of storage time as well as the donor’s age and gender.

Methods: Eotaxin-1 was measured in FFP (n = 168), EC (n = 160) and PC (n = 8) ready-to-use for transfusion employing a Q-Plex immunoassay for eotaxin-1. Absolute quantification of eotaxin-1 was performed with Q-view software.

Results: Eotaxin-1 was consistently detected at a physiological level in FFP and EC but not PC. Eotaxin-1 levels were comparable in male and female donors but increased significantly with rising age of donors in both, FFP and EC. Furthermore, eotaxin-1 was not influenced by storage time of either blood component. Finally, eotaxin-1 is subject to only minor fluctuations within one donor over a longer period of time.

Conclusion: Eotaxin-1 is detectable and stable in FFP and EC and increases with donor’s age. Considering the presumed involvement in aging and cognitive malfunction, differences in donor- and recipient eotaxin-1 levels might affect mental factors after blood transfusion.

The systemic environment: at the interface of aging and adult neurogenesis

Aging results in impaired neurogenesis in the two neurogenic niches of the adult mammalian brain, the dentate gyrus of the hippocampus and the subventricular zone of the lateral ventricle. While significant work has characterized intrinsic cellular changes that contribute to this decline, it is increasingly apparent that the systemic environment also represents a critical driver of brain aging. Indeed, emerging studies utilizing the model of heterochronic parabiosis have revealed that immune-related molecular and cellular changes in the aging systemic environment negatively regulate adult neurogenesis. Interestingly, these studies have also demonstrated that age-related decline in neurogenesis can be ameliorated by exposure to the young systemic environment. While this burgeoning field of research is increasingly garnering interest, as yet, the precise mechanisms driving either the pro-aging effects of aged blood or the rejuvenating effects of young blood remain to be thoroughly defined. Here, we review how age-related changes in blood, blood-borne factors, and peripheral immune cells contribute to the age-related decline in adult neurogenesis in the mammalian brain, and posit both direct neural stem cell and indirect neurogenic niche-mediated mechanisms.