Brain cytokines and neuropsychiatric disorders

Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation

Mast cells (MC) are ubiquitous in the body, and they are critical for not only in allergic diseases but also in immunity and inflammation, including having potential involvement in the pathophysiology of dysautonomias and neuroinflammatory disorders. MC are located perivascularly close to nerve endings and sites such as the carotid bodies, heart, hypothalamus, the pineal gland, and the adrenal gland that would allow them not only to regulate but also to be affected by the autonomic nervous system (ANS). MC are stimulated not only by allergens but also many other triggers including some from the ANS that can affect MC release of neurosensitizing, proinflammatory, and vasoactive mediators. Hence, MC may be able to regulate homeostatic functions that seem to be dysfunctional in many conditions, such as postural orthostatic tachycardia syndrome, autism spectrum disorder, myalgic encephalomyelitis/chronic fatigue syndrome, and Long-COVID syndrome. The evidence indicates that there is a possible association between these conditions and diseases associated with MC activation. There is no effective treatment for any form of these conditions other than minimizing symptoms. Given the many ways MC could be activated and the numerous mediators released, it would be important to develop ways to inhibit stimulation of MC and the release of ANS-relevant mediators.

Brain Fog: a Narrative Review of the Most Common Mysterious Cognitive Disorder in COVID-19

It has been more than three years since COVID-19 impacted the lives of millions of people, many of whom suffer from long-term effects known as long-haulers. Notwithstanding multiorgan complaints in long-haulers, signs and symptoms associated with cognitive characteristics commonly known as "brain fog" occur in COVID patients over 50, women, obesity, and asthma at excessive. Brain fog is a set of symptoms that include cognitive impairment, inability to concentrate and multitask, and short-term and long-term memory loss. Of course, brain fog contributes to high levels of anxiety and stress, necessitating an empathetic response to this group of COVID patients. Although the etiology of brain fog in COVID-19 is currently unknown, regarding the mechanisms of pathogenesis, the following hypotheses exist: activation of astrocytes and microglia to release pro-inflammatory cytokines, aggregation of tau protein, and COVID-19 entry in the brain can trigger an autoimmune reaction. There are currently no specific tests to detect brain fog or any specific cognitive rehabilitation methods. However, a healthy lifestyle can help reduce symptoms to some extent, and symptom-based clinical management is also well suited to minimize brain fog side effects in COVID-19 patients. Therefore, this review discusses mechanisms of SARS-CoV-2 pathogenesis that may contribute to brain fog, as well as some approaches to providing therapies that may help COVID-19 patients avoid annoying brain fog symptoms.

Investigation of structural and neurobiochemical differences in brains from high-performance and native hen breeds

Selection of livestock has not only led to changes in the level of their performance but also modified their behavior. As a result, within a single species, we have to deal with different behaviors of different breeds. In our study, we assumed that the different behaviors within a species are due to differences in the morphology and physiology of behavior-related systems. Two breeds of hens were used as a model: the highly reactive, fearful and high-performance Leghorn breed and proactive, unselected Green-legged Partridge breed. The higher reactivity and fearfulness of Leghorn hens in comparison to the Green-legged Partridge breed may be related to the greater number of neurons in the paraventricular nucleus and anterior hypothalamus and the higher content of zinc and iron in the brain, as these elements are involved in neuronal conduction and myelination processes. The reactive behaviours of Green-legged Partridge hens may be associated with the lower number of neurons in the paraventricular nucleus and the anterior hypothalamus and the higher concentration of dopamine and copper ions in the brain. The analyses confirmed the hypothesis of the existence of interbreed differences in the morphology and physiology of behaviour-related systems, which most probably emerged through unintentional and correlated selection towards high production performance. Consequently, attention should be drawn that the selection of a given genotype (breed) towards a specific environment could lead to creation of highly specialised lines that may not achieve homeostasis in every maintenance system.

Exosome-associated mitochondrial DNA from patients with myalgic encephalomyelitis/chronic fatigue syndrome stimulates human microglia to release IL-1β

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease that presents with fatigue, sleep disturbances, malaise, and cognitive problems. The pathogenesis of ME/CFS is presently unknown, and serum levels of potential biomarkers have been inconsistent. Here, we show that mitochondrial DNA (mtDNA) associated with serum exosomes, is increased in ME/CFS patients only after exercise. Moreover, exosomes isolated from patients with ME/CFS stimulate significant release of IL-1β from cultured human microglia. These results provide evidence that activation of microglia by serum-derived exosomes may serve as a potential novel pathogenetic factor and target for treatment of ME/CFS.

Genetics of COVID-19 and myalgic encephalomyelitis/chronic fatigue syndrome: a systematic review

COVID‐19 and ME/CFS present with some similar symptoms, especially physical and mental fatigue. In order to understand the basis of these similarities and the possibility of underlying common genetic components, we performed a systematic review of all published genetic association and cohort studies regarding COVID‐19 and ME/CFS and extracted the genes along with the genetic variants investigated. We then performed gene ontology and pathway analysis of those genes that gave significant results in the individual studies to yield functional annotations of the studied genes using protein analysis through evolutionary relationships (PANTHER) VERSION 17.0 software. Finally, we identified the common genetic components of these two conditions. Seventy‐one studies for COVID‐19 and 26 studies for ME/CFS were included in the systematic review in which the expression of 97 genes for COVID‐19 and 429 genes for ME/CFS were significantly affected. We found that ACE, HLA‐A, HLA‐C, HLA‐DQA1, HLA‐DRB1, and TYK2 are the common genes that gave significant results. The findings of the pathway analysis highlight the contribution of inflammation mediated by chemokine and cytokine signaling pathways, and the T cell activation and Toll receptor signaling pathways. Protein class analysis revealed the contribution of defense/immunity proteins, as well as protein‐modifying enzymes. Our results suggest that the pathogenesis of both syndromes could involve some immune dysfunction.

mTOR Signaling Pathway Regulates the Release of Proinflammatory Molecule CCL5 Implicated in the Pathogenesis of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex pervasive neurodevelopmental disorder and neuroinflammation may contribute to the pathogenesis of ASD. However, the exact mechanisms of abnormal release of proinflammatory mediators in ASD remain poorly understood. This study reports elevated plasma levels of the proinflammatory chemokine (C-C motif) ligand 5 (CCL5) in children with ASD, suggesting an aberrant inflammatory response appearing in the development of ASD. Mining of the expression data of brain or blood tissue from individuals with ASD reveals that mTOR signaling is aberrantly activated in ASD patients. Our in vitro study shows that suppression of mTOR reduces the gene expression and release of CCL5 from human microglia, supporting that CCL5 expression is regulated by mTOR activity. Furthermore, bacterial lipopolysaccharide (LPS)-induced CCL5 expression can be counteracted by siRNA against NF-κB, suggests a determining role of NF-κB in upregulating CCL5 expression. However, a direct regulatory relationship between the NF-κB element and the mTOR signaling pathway was not observed in rapamycin-treated cells. Our results show that the phosphorylated CREB can be induced to suppress CCL5 expression by outcompeting NF-κB in binding to CREB-binding protein (CREBBP) once the mTOR signaling pathway is inhibited. We propose that the activation of mTOR signaling in ASD may induce the suppression of phosphorylation of CREB, which in turn results in the increased binding of CREBBP to NF-κB, a competitor of phosphorylated CREB to drive expression of CCL5. Our study sheds new light on the inflammatory mechanisms of ASD and paves the way for the development of therapeutic strategy for ASD.

Bidirectional communication between mast cells and the gut-brain axis in neurodegenerative diseases: Avenues for therapeutic intervention

Although the global incidence of neurodegenerative diseases has been steadily increasing, especially in adults, there are no effective therapeutic interventions. Neurodegeneration is a heterogeneous group of disorders that is characterized by the activation of immune cells in the central nervous system (CNS) (e.g., mast cells and microglia) and subsequent neuroinflammation. Mast cells are found in the brain and the gastrointestinal tract and play a role in "tuning" neuroimmune responses. The complex bidirectional communication between mast cells and gut microbiota coordinates various dynamic neuro-cellular responses, which propagates neuronal impulses from the gastrointestinal tract into the CNS. Numerous inflammatory mediators from degranulated mast cells alter intestinal gut permeability and disrupt blood-brain barrier, which results in the promotion of neuroinflammatory processes leading to neurological disorders, thereby offsetting the balance in immune-surveillance. Emerging evidence supports the hypothesis that gut-microbiota exert a pivotal role in inflammatory signaling through the activation of immune and inflammatory cells. Communication between inflammatory cytokines and neurocircuits via the gut-brain axis (GBA) affects behavioral responses, activates mast cells and microglia that causes neuroinflammation, which is associated with neurological diseases. In this comprehensive review, we focus on what is currently known about mast cells and the gut-brain axis relationship, and how this relationship is connected to neurodegenerative diseases. We hope that further elucidating the bidirectional communication between mast cells and the GBA will not only stimulate future research on neurodegenerative diseases but will also identify new opportunities for therapeutic interventions.

Unravelling the potential of gut microbiota in sustaining brain health and their current prospective towards development of neurotherapeutics

Increasing incidences of neurological disorders, such as Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS) are being reported, but an insight into their pathology remains elusive. Findings have suggested that gut microbiota play a major role in regulating brain functions through the gut-brain axis. A unique bidirectional communication between gut microbiota and maintenance of brain health could play a pivotal role in regulating incidences of neurodegenerative diseases. Contrarily, the present life style with changing food habits and disturbed circadian rhythm may contribute to gut homeostatic imbalance and dysbiosis leading to progression of several neurological disorders. Therefore, dysbiosis, as a primary factor behind intestinal disorders, may also augment inflammation, intestinal and blood-brain barrier permeability through microbiota-gut-brain axis. This review primarily focuses on the gut-brain axis functions, specific gut microbial population, metabolites produced by gut microbiota, their role in regulating various metabolic processes and role of gut microbiota towards development of neurodegenerative diseases. However, several studies have reported a decrease in abundance of a specific gut microbial population and a corresponding increase in other microbial family, with few findings revealing some contradictions. Reports also showed that colonization of gut microbiota isolated from patients suffering from neurodegenerative disease leads to the development of enhance pathological outcomes in animal models. Hence, a systematic understanding of the dominant role of specific gut microbiome towards development of different neurodegenerative diseases could possibly provide novel insight into the use of probiotics and microbial transplantation as a substitute approach for treating/preventing such health maladies.

The chemokine CXCL1 and its receptor CXCR2 contribute to chronic stress-induced depression in mice

Depression is increasingly recognized as an inflammatory disease, with inflammatory crosstalk in the brain contributing its pathogenesis. Life stresses may up-regulate inflammatory processes and promote depression. Although cytokines are central to stress-related immune responses, their contribution to stress-induced depression remains unclear. Here, we used unpredictable chronic mild stress (UCMS) to induce depression-like behaviors in mice, as assessed through a suite of behavioral tests. C-X-C motif chemokine ligand 1 (CXCL1)-related molecular networks responsible for depression-like behaviors were assessed through intrahippocampal microinjection of lenti-CXCL1, the antidepressant fluoxetine, the C-X-C motif chemokine receptor 2 (CXCR2) inhibitor SB265610, and the glycogen synthase kinase-3β (GSK3β) inhibitor AR-A014418. Modulation of apoptosis-related pathways and neuronal plasticity were assessed via quantification of cleaved caspase-3, B-cell lymphoma 2-associated X protein, cAMP response element-binding protein (CREB), and brain-derived neurotrophic factor (BDNF) protein expression. CXCL1/CXCL2 expression was correlated with depression-like behaviors in response to chronic stress or antidepressant treatment in the UCMS depression model. Intrahippocampal microinjection of lenti-CXCL1 increased depression-like behaviors, activated GSK3β, increased apoptosis pathways, suppressed CREB activation, and decreased BDNF. Administration of the selective GSK3β inhibitor AR-A014418 abolished the effects of lenti-CXCL1, and the CXCR2 inhibitor SB265610 prevented chronic stress-induced depression-like behaviors, inhibited GSK3β activity, blocked apoptosis pathways, and restored BDNF expression. The CXCL1/CXCR2 axis appears to play a critical role in stress-induced depression, and CXCR2 is a potential novel therapeutic target for patients with depression.-Chai, H.-H., Fu, X.-C., Ma, L., Sun, H.-T., Chen, G.-Z., Song, M.-Y., Chen, W.-X., Chen, Y.-S., Tan, M.-X., Guo, Y.-W., Li, S.-P. The chemokine CXCL1 and its receptor CXCR2 contribute to chronic stress-induced depression in mice.

Cathepsin B inhibition ameliorates leukocyte-endothelial adhesion in the BTBR mouse model of autism

AIMS

Autism spectrum disorder (ASD) is a wide range of neurodevelopmental disorders involving deficits in social interaction and communication. Unfortunately, autism remains a scientific and clinical challenge owing to the lack of understanding the cellular and molecular mechanisms underlying it. This study aimed to investigate the pathophysiological mechanism underlying leukocyte-endothelial adhesion in autism-related neurovascular inflammation.

METHODS

Male BTBR T+tf/J mice were used as an autism model. The dynamic pattern of leukocyte-endothelial adhesion in mouse cerebral vessels was detected by two-photon laser scanning microscopy (TPLSM). Using FACS, RT-PCR, and Western blotting, we explored the expression of cell adhesion molecules, the mRNA expression of endothelial chemokine, the protein levels of cathepsin B, and inflammatory mediators.

RESULTS

We found a significant increase in leukocyte-endothelial adhesion in BTBR mice, accompanied by elevated expression of the adhesion molecule neutrophils CD11b and endothelial ICAM-1. Our data further indicate that elevated neutrophil cathepsin B levels contribute to elevated endothelial chemokine CXCL7 levels in BTBR mice. The pharmacological inhibition of cathepsin B reverses the enhanced leukocyte-endothelial adhesion in the cerebral vessels of autistic mice.

CONCLUSION

Our results revealed the prominent role of cathepsin B in modulating leukocyte-endothelial adhesion during autism-related neurovascular inflammation and identified a promising novel approach for autism treatment.

Leveraging Prior Knowledge of Endocrine Immune Regulation in the Therapeutically Relevant Phenotyping of Women With Chronic Fatigue Syndrome

PURPOSE

The complex and varied presentation of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has made it difficult to diagnose, study, and treat. Its symptoms and likely etiology involve multiple components of endocrine and immune regulation, including the hypothalamic-pituitary-adrenal axis, the hypothalamic-pituitary-gonadal axis, and their interactive oversight of immune function. We propose that the persistence of ME/CFS may involve changes in the regulatory interactions across these physiological axes. We also propose that the robustness of this new pathogenic equilibrium may at least in part explain the limited success of conventional single-target therapies.

METHODS

A comprehensive model was constructed of female endocrine-immune signaling consisting of 28 markers linked by 214 documented regulatory interactions. This detailed model was then constrained to adhere to experimental measurements in a subset of 17 candidate immune markers measured in peripheral blood of patients with ME/CFS and healthy control subjects before, during, and after a maximal exercise challenge. A set of 26 competing numerical models satisfied these data to within 5% error.

FINDINGS

Mechanistically informed predictions of endocrine and immune markers that were either unmeasured or exhibited high subject-to-subject variability pointed to possible context-specific overexpression in ME/CFS at rest of corticotropin-releasing hormone, chemokine (C-X-C motif) ligand 8, estrogen, follicle-stimulating hormone (FSH), gonadotropin-releasing hormone 1, interleukin (IL)-23, and luteinizing hormone, and underexpression of adrenocorticotropic hormone, cortisol, interferon-γ, IL-10, IL-17, and IL-1α. Simulations of rintatolimod and rituximab treatment predicted a shift in the repertoire of available endocrine-immune regulatory regimens. Rintatolimod was predicted to make available substantial remission in a significant subset of subjects, in particular those with low levels of IL-1α, IL-17, and cortisol; intermediate levels of progesterone and FSH; and high estrogen levels. Rituximab treatment was predicted to support partial remission in a smaller subset of patients with ME/CFS, specifically those with low norepinephrine, IL-1α, chemokine (C-X-C motif) ligand 8, and cortisol levels; intermediate FSH and gonadotropin-releasing hormone 1 levels; and elevated expression of tumor necrosis factor-α, luteinizing hormone, IL-12, and B-cell activation.

IMPLICATIONS

Applying a rigorous filter of known signaling mechanisms to experimentally measured immune marker expression in ME/CFS has highlighted potential new context-specific markers of illness. These novel endocrine and immune markers may offer useful candidates in delineating new subtypes of ME/CFS and may inform on refinements to the inclusion criteria and instrumentation of new and ongoing trials involving rintatolimod and rituximab treatment protocols.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-Metabolic Disease or Disturbed Homeostasis due to Focal Inflammation in the Hypothalamus?

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex disease characterized by debilitating fatigue, lasting for at least 6 months, with associated malaise, headaches, sleep disturbance, and cognitive impairment, which severely impacts quality of life. A significant percentage of ME/CFS patients remain undiagnosed, mainly due to the complexity of the disease and the lack of reliable objective biomarkers. ME/CFS patients display decreased metabolism and the severity of symptoms appears to be directly correlated to the degree of metabolic reduction that may be unique to each individual patient. However, the precise pathogenesis is still unknown, preventing the development of effective treatments. The ME/CFS phenotype has been associated with abnormalities in energy metabolism, which are apparently due to mitochondrial dysfunction in the absence of mitochondrial diseases, resulting in reduced oxidative metabolism. Such mitochondria may be further contributing to the ME/CFS symptomatology by extracellular secretion of mitochondrial DNA, which could act as an innate pathogen and create an autoinflammatory state in the hypothalamus. We propose that stimulation of hypothalamic mast cells by environmental, neuroimmune, pathogenic and stress triggers activates microglia, leading to focal inflammation in the brain and disturbed homeostasis. This process could be targeted for the development of novel effective treatments.

Prenatal inflammation and risk for schizophrenia: A role for immune proteins in neurodevelopment

Prenatal inflammation is an established risk factor for schizophrenia. However, the specific inflammatory pathways that mediate this association remain unclear. Potential candidate systems include inflammatory markers produced by microglia, such as cytokines and complement. Accumulating evidence suggests that these markers play a role in typical neurodevelopmental processes, such as synapse formation and interneuron migration. Rodent models demonstrate that altered marker levels during the prenatal period can cause lasting deficits in these systems, leading to cognitive deficits that resemble schizophrenia. This review assesses the potential role of prenatal cytokine and complement elevations on the etiology of schizophrenia. The current neurobiological understanding of the development of schizophrenia is reviewed to identify candidate cellular mechanisms that may be influenced by prenatal inflammation. We discuss the functions that cytokines and complement may play in prenatal neurodevelopment, review evidence that links exposure to these factors with risk for schizophrenia, and consider how these markers may interact with genetic vulnerabilities to influence the neurodevelopment of schizophrenia. We consider how prenatal inflammatory exposure may influence childhood and adolescent developmental risk trajectories for schizophrenia. Finally, we identify areas of further research needed to support the development of anti-inflammatory treatments to prevent the development of schizophrenia in at-risk neonates.

The role of neuroinflammation and neurovascular dysfunction in major depressive disorder

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

Altered Vessel Signalling Molecules in Subjects with Down's Syndrome

Down's syndrome (DS) is the most frequent human chromosomal abnormality and is associated with mental retardation. Some evidence indicates that certain inflammatory molecules may be increased in DS. Proinflammatory and vasoactive molecules in the blood of non demented subjects with DS were measured in the present investigation. Plasma levels of interleukin-6 (IL-6), vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1) and C reactive protein (CRP) were measured in child (2–14 years), adult (20–50 yrs) and elderly (> 60 yrs) DS subjects. Increased plasma levels of IL-6 and MCP-1 were present in DS. Plasma levels of VEGF were increased only in DS adults. Positive linear correlation between IL-6 and MCP-1 levels was present. However, no subclinical inflammation was apparent in DS, since neopterin and CRP levels were within the normal range. An altered regulation of these molecules might interfere with some processes involved in cognitive performances of DS subjects.

Neurotensin stimulates sortilin and mTOR in human microglia inhibitable by methoxyluteolin, a potential therapeutic target for autism

We had reported elevated serum levels of the peptide neurotensin (NT) in children with autism spectrum disorders (ASD). Here, we show that NT stimulates primary human microglia, the resident immune cells of the brain, and the immortalized cell line of human microglia-SV40. NT (10 nM) increases the gene expression and release (P < 0.001) of the proinflammatory cytokine IL-1β and chemokine (C-X-C motif) ligand 8 (CXCL8), chemokine (C-C motif) ligand 2 (CCL2), and CCL5 from human microglia. NT also stimulates proliferation (P < 0.05) of microglia-SV40. Microglia express only the receptor 3 (NTR3)/sortilin and not the NTR1 or NTR2. The use of siRNA to target sortilin reduces (P < 0.001) the NT-stimulated cytokine and chemokine gene expression and release from human microglia. Stimulation with NT (10 nM) increases the gene expression of sortilin (P < 0.0001) and causes the receptor to be translocated from the cytoplasm to the cell surface, and to be secreted extracellularly. Our findings also show increased levels of sortilin (P < 0.0001) in the serum from children with ASD (n = 36), compared with healthy controls (n = 20). NT stimulation of microglia-SV40 causes activation of the mammalian target of rapamycin (mTOR) signaling kinase, as shown by phosphorylation of its substrates and inhibition of these responses by drugs that prevent mTOR activation. NT-stimulated responses are inhibited by the flavonoid methoxyluteolin (0.1-1 μM). The data provide a link between sortilin and the pathological findings of microglia and inflammation of the brain in ASD. Thus, inhibition of this pathway using methoxyluteolin could provide an effective treatment of ASD.

The Role of C-Reactive Protein in Mood Disorders

Recently, a possible relationship between C-Reactive Protein (CRP), a marker of underlying low-grade inflammation, and mood disorders has been proposed by some researchers. The aim of this review is to elucidate the current facts and views about CRP in mood disorders such as Depressive and Bipolar Disorders. Several studies have examined the relationship between affective disorders and CRP, but the majority of the studies in literature have been limited by retrospective, case-controlled study design, and very few studies have examined the relationship between depression and CRP in large study samples. In conclusion, the role of CRP in mood disorders is, to date, intriguing but somewhat unclear. Further prospective studies are needed to introduce the CRP in clinical settings as a marker of affective states and suicidability.

Gut-Microbiota-Brain Axis and Its Effect on Neuropsychiatric Disorders With Suspected Immune Dysregulation

PURPOSE

Gut microbiota regulate intestinal function and health. However, mounting evidence indicates that they can also influence the immune and nervous systems and vice versa. This article reviews the bidirectional relationship between the gut microbiota and the brain, termed the microbiota-gut-brain (MGB) axis, and discusses how it contributes to the pathogenesis of certain disorders that may involve brain inflammation.

METHODS

Articles were identified with a search of Medline (starting in 1980) by using the key words anxiety, attention-deficit hypersensitivity disorder (ADHD), autism, cytokines, depression, gut, hypothalamic-pituitary-adrenal (HPA) axis, inflammation, immune system, microbiota, nervous system, neurologic, neurotransmitters, neuroimmune conditions, psychiatric, and stress.

FINDINGS

Various afferent or efferent pathways are involved in the MGB axis. Antibiotics, environmental and infectious agents, intestinal neurotransmitters/neuromodulators, sensory vagal fibers, cytokines, and essential metabolites all convey information to the central nervous system about the intestinal state. Conversely, the hypothalamic-pituitary-adrenal axis, the central nervous system regulatory areas of satiety, and neuropeptides released from sensory nerve fibers affect the gut microbiota composition directly or through nutrient availability. Such interactions seem to influence the pathogenesis of a number of disorders in which inflammation is implicated, such as mood disorder, autism-spectrum disorders, attention-deficit hypersensitivity disorder, multiple sclerosis, and obesity.

IMPLICATIONS

Recognition of the relationship between the MGB axis and the neuroimmune systems provides a novel approach for better understanding and management of these disorders. Appropriate preventive measures early in life or corrective measures such as use of psychobiotics, fecal microbiota transplantation, and flavonoids are discussed.

Neuropeptides CRH, SP, HK-1, and Inflammatory Cytokines IL-6 and TNF Are Increased in Serum of Patients with Fibromyalgia Syndrome, Implicating Mast Cells

Fibromyalgia syndrome (FMS) is a chronic, idiopathic condition of widespread musculoskeletal pain affecting more women than men. Even though clinical studies have provided evidence of altered central pain pathways, the lack of definitive pathogenesis or reliable objective markers has hampered development of effective treatments. Here we report that the neuropeptides corticotropin-releasing hormone (CRH), substance P (SP), and SP-structurally-related hemokinin-1 (HK-1) were significantly (P = 0.026, P < 0.0001, and P = 0.002, respectively) elevated (0.82 ± 0.57 ng/ml, 0.39 ± 0.18 ng/ml, and 7.98 ± 3.12 ng/ml, respectively) in the serum of patients with FMS compared with healthy controls (0.49 ± 0.26 ng/ml, 0.12 ± 0.1 ng/ml, and 5.71 ± 1.08 ng/ml, respectively). Moreover, SP and HK-1 levels were positively correlated (Pearson r = 0.45, P = 0.002) in FMS. The serum concentrations of the inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF) were also significantly (P = 0.029 and P = 0.006, respectively) higher (2.97 ± 2.35 pg/ml and 0.92 ± 0.31 pg/ml, respectively) in the FMS group compared with healthy subjects (1.79 ± 0.62 pg/ml and 0.69 ± 0.16 pg/ml, respectively). In contrast, serum IL-31 and IL-33 levels were significantly lower (P = 0.0001 and P = 0.044, respectively) in the FMS patients (849.5 ± 1005 pg/ml and 923.2 ± 1284 pg/ml, respectively) in comparison with healthy controls (1281 ± 806.4 pg/ml and 3149 ± 4073 pg/ml, respectively). FMS serum levels of neurotensin were not different from controls. We had previously shown that CRH and SP stimulate IL-6 and TNF release from mast cells (MCs). Our current results indicate that neuropeptides could stimulate MCs to secrete inflammatory cytokines that contribute importantly to the symptoms of FMS. Treatment directed at preventing the secretion or antagonizing these elevated neuroimmune markers, both centrally and peripherally, may prove to be useful in the management of FMS.

Children with autism spectrum disorders, who improved with a luteolin-containing dietary formulation, show reduced serum levels of TNF and IL-6

Autism spectrum disorders (ASDs) have been associated with brain inflammation as indicated by microglia activation, as well as brain expression and increased plasma levels of interleukin-6 (IL-6) and tumor necrosis factor (TNF). Here we report that serum levels of IL-6 and TNF were elevated (61.95 ± 94.76 pg ml(-1) and 313.8 ± 444.3 pg ml(-1), respectively) in the same cohort of patients with elevated serum levels of corticotropin-releasing hormone (CRH) and neurotensin (NT), while IL-9, IL-31 and IL-33 were not different from controls. The elevated CRH and NT levels did not change after treatment with a luteolin-containing dietary formulation. However, the mean serum IL-6 and TNF levels decreased significantly (P=0.036 and P=0.015, respectively) at the end of the treatment period (26 weeks) as compared with levels at the beginning; these decreases were strongly associated with children whose behavior improved the most after luteolin formulation treatment. Our results indicate that there are distinct subgroups of children within the ASDs that may be identifiable through serum levels of IL-6 and TNF and that these cytokines may constitute distinct prognostic markers for at least the beneficial effect of luteolin formulation.

Brain "fog," inflammation and obesity: key aspects of neuropsychiatric disorders improved by luteolin

Brain "fog" is a constellation of symptoms that include reduced cognition, inability to concentrate and multitask, as well as loss of short and long term memory. Brain "fog" characterizes patients with autism spectrum disorders (ASDs), celiac disease, chronic fatigue syndrome, fibromyalgia, mastocytosis, and postural tachycardia syndrome (POTS), as well as "minimal cognitive impairment," an early clinical presentation of Alzheimer's disease (AD), and other neuropsychiatric disorders. Brain "fog" may be due to inflammatory molecules, including adipocytokines and histamine released from mast cells (MCs) further stimulating microglia activation, and causing focal brain inflammation. Recent reviews have described the potential use of natural flavonoids for the treatment of neuropsychiatric and neurodegenerative diseases. The flavone luteolin has numerous useful actions that include: anti-oxidant, anti-inflammatory, microglia inhibition, neuroprotection, and memory increase. A liposomal luteolin formulation in olive fruit extract improved attention in children with ASDs and brain "fog" in mastocytosis patients. Methylated luteolin analogs with increased activity and better bioavailability could be developed into effective treatments for neuropsychiatric disorders and brain "fog."

Mast cells, brain inflammation and autism

Increasing evidence indicates that brain inflammation is involved in the pathogenesis of neuropsychiatric diseases. Mast cells (MCs) are located perivascularly close to neurons and microglia, primarily in the leptomeninges, thalamus, hypothalamus and especially the median eminence. Corticotropin-releasing factor (CRF) is secreted from the hypothalamus under stress and, together with neurotensin (NT), can stimulate brain MCs to release inflammatory and neurotoxic mediators that disrupt the blood-brain barrier (BBB), stimulate microglia and cause focal inflammation. CRF and NT synergistically stimulate MCs and increase vascular permeability; these peptides can also induce each other׳s surface receptors on MCs leading to autocrine and paracrine effects. As a result, brain MCs may be involved in the pathogenesis of "brain fog," headaches, and autism spectrum disorders (ASDs), which worsen with stress. CRF and NT are significantly increased in serum of ASD children compared to normotypic controls further strengthening their role in the pathogenesis of autism. There are no clinically affective treatments for the core symptoms of ASDs, but pilot clinical trials using natural-antioxidant and anti-inflammatory molecules reported statistically significant benefit.

Mast cell and autoimmune diseases

Mast cells are important in innate immune system. They have been appreciated as potent contributors to allergic reaction. However, increasing evidence implicates the important role of mast cells in autoimmune disease like rheumatoid arthritis and multiple sclerosis. Here we review the current stage of knowledge about mast cells in autoimmune diseases.

Isoflavones inhibit poly(I:C)-induced serum, brain, and skin inflammatory mediators - relevance to chronic fatigue syndrome

Background

Chronic Fatigue Syndrome (CFS) is a neuroimmunoendocrine disease affecting about 1% of the US population, mostly women. It is characterized by debilitating fatigue for six or more months in the absence of cancer or other systemic diseases. Many CFS patients also have fibromyalgia and skin hypersensitivity that worsen with stress. Corticotropin-releasing hormone (CRH) and neurotensin (NT), secreted under stress, activate mast cells (MC) necessary for allergic reactions to release inflammatory mediators that could contribute to CFS symptoms.

Objective

To investigate the effect of isoflavones on the action of polyinosinic:polycytidylic acid (poly(I:C)), with or without swim stress, on mouse locomotor activity and inflammatory mediator expression, as well as on human MC activation.

Methods

Female C57BL/6 mice were randomly divided into four groups: (a) control/no-swim, (b) control/swim, (c) polyinosinic:polycytidylic acid (poly(I:C))/no swim, and (d) polyinosinic:polycytidylic acid (poly(I:C))/swim. Mice were provided with chow low or high in isoflavones for 2 weeks prior to ip injection with 20 mg/kg poly(I:C) followed or not by swim stress for 15 minutes. Locomotor activity was monitored overnight and animals were sacrificed the following day. Brain and skin gene expression, as well as serum levels, of inflammatory mediators were measured. Data were analyzed using the non-parametric Mann-Whitney U-test.

Results

Poly(I:C)-treated mice had decreased locomotor activity over 24 hours, and increased serum levels of TNF-α, IL-6, KC (IL-8/CXCL8 murine homolog), CCL2,3,4,5, CXCL10, as well as brain and skin gene expression of TNF, IL-6, KC (Cxcl1, IL8 murine homolog), CCL2, CCL4, CCL5 and CXCL10. Histidine decarboxylase (HDC) and NT expression were also increased, but only in the skin, over the same period. High isoflavone diet reversed these effects.

Conclusion

Poly(I:C) treatment decreased mouse locomotor activity and increased serum levels and brain and skin gene expression of inflammatory mediators. These effects were inhibited by isoflavones that may prove useful in CFS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0168-5) contains supplementary material, which is available to authorized users.

The MCP-1, CCL-5 and SDF-1 chemokines as pro-inflammatory markers in generalized anxiety disorder and personality disorders

INTRODUCTION

The co-occurrence of generalized anxiety disorder and personality disorders suggests the existence of association between the neurobiological predispositions leading to the development of these disorders and activation of cytokine system. Pro-inflammatory chemokines such as CCL-5/RANTES (regulated upon activation normal T cell expressed and secreted) and CXCL12/SDF-1 (stromal derived factor) play an important role in immune response.

METHODS

A total of 160 participants were enrolled in the study, 120 of whom comprised the study group (people with the dual diagnosis of personality disorder and generalized anxiety disorder). The mean age was 41.4 ± 3.5 years (range: 20-44 years). The control group consisted of 40 healthy individuals in the mean age of 40.8 ± 3.1 years (range: 20-43 years). A blood sample was collected from each participant and the plasma levels of the CCL-2/MCP-1 (monocyte chemoattractant protein-1), RANTES and SDF-1 chemokines were determined by ELISA.

RESULTS

Increased levels of MCP-1 and SDF-1 were found both in women and in men versus the control group for all types of personality disorders. The levels of CCL-5 in men were significantly increased versus the control group and significantly higher in women than in men. Neither women nor men with avoidant or obsessive-compulsive personality disorder showed any significant differences in MCP-1 or SFD-1 levels. In subjects with borderline personality disorder, the levels of the study chemokines were higher in women than in men.

CONCLUSIONS

Our study has shown the need for determination of proinflammatory interleukins which are considered as biomarkers of personality disorders and generalized anxiety disorders.

Mast cells and inflammation

Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.

Autism: an emerging 'neuroimmune disorder' in search of therapy

BACKGROUND

Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by difficulties in communication and by repetitive and stereotypic behaviors, as well as by social impairment, attention, cognitive, and learning defects. ASDs present in early childhood and their prevalence has increased significantly to 1/150 children. Despite a number of theories, the actual reasons for this increase are still not clear. There is no reliable screening test, and no definite pathogenesis or curative therapy. Consequently, there is a major gap hampering development of effective treatments.

OBJECTIVE

To review recent publications on ASDs pathogenesis and treatment with emphasis on neuroimmune processes and new therapeutic approaches.

METHODS

Mostly original papers (450) on epidemiology, possible pathogenesis or treatment of ASDs in Medline from 1990 to May 2009 were reviewed. All authors contributed to this review.

RESULTS/CONCLUSION

Increased oxidative stress and immune dysregulation are present in ASDs. Mast-cell activation may contribute to gut-blood-brain barrier disruption and brain inflammation. No effective treatments have emerged. Well-designed clinical trials with nonpsychotropic drugs were few and ASD characteristics varied considerably, making conclusions difficult. Psychotropic drugs are often used for stereotypic and aggressive behaviors. Unique combinations with antioxidant and anti-inflammatory flavonoids hold promise. New potential translational research areas and possible treatments are suggested.

Novel therapeutic targets for autism

Autism spectrum disorders (ASDs) are pervasive neurodevelopmental disorders, diagnosed in early childhood when acquired skills are lost or the acquisition of new skills becomes delayed. ASDs are associated with varying degrees of dysfunctional communication and social skills, in addition to repetitive and stereotypic behaviors. The diagnosis has increased considerably to approximately one in 180 people, but it is not clear whether this is because of a higher prevalence of the disorder, improved awareness by clinicians or a combination of both. There are no defined mechanisms of pathogenesis or curative therapy presently available. Oxidative stress, overactivation of the hypothalamic-pituitary-adrenal axis and increased gut-blood-brain-barrier permeability might be involved. The scope of this article is to integrate these findings and present the opinion that non-allergic activation of gastrointestinal and brain mast cells could contribute to many of the pathologic findings and provide unique targets for ASD therapy. We make suggestions for new research directives and possible novel therapies from readily available molecules.

Evaluation of C-Reactive Protein and Total Serum Cholesterol in Adult Patients with Bipolar Disorder

The aim of the present study is to evaluate the role of CRP and Total Cholesterol (TC) in patients suffering from type I Bipolar Disorder (BD-I). Moreover, the goal is to elucidate possible CRP and TC differences in different phases of BD-I: acute mania, euthymia and bipolar depression. Medical records of 90 BD-I patients (30 patients with acute mania, 30 in euthymic state, full remission, and 30 in depressive phase) were reviewed to evaluate serum CRP and TC levels. Laboratory data of 30 healthy controls were also obtained. The scores of Young Mania Rating Scale (YMRS), Bech-Rafaelsen Manic Rating Scale (BRMRS) and Hamilton Rating Scale for Depression (HAM-D) were evaluated. CRP levels were higher in acute mania and depressive phase subgroups when compared to healthy controls. CRP was positively associated with BRMRS and YMRS scores in acute mania and with HAM-D in depressive phase subgroups. TC levels were lower in all clinical groups compared to controls. TC levels were negatively correlated to BRMRS, YMRS and HAM-D. In conclusion, the results of the present study support the notion that CRP and TC may be altered in patients with BP-I.

Depressive behavior in mice due to immune stimulation is accompanied by reduced neural activity in brain regions involved in positively motivated behavior

BACKGROUND

Immune stimulation inhibits positively motivated behavior and induces depressive illness. To help clarify the mechanism of these effects, neural activity in response to a positive stimulus was examined in brain regions associated with positively motivated activity defined on the basis of prior behavioral studies of central alpha1-adrenoceptor action.

METHODS

Mice pretreated with either lipopolysaccharide or, for comparison, reserpine were exposed to a motivating stimulus (fresh cage) and subsequently assayed for fos expression and mitogen-activated protein kinase (MAPK) phosphorylation, two measures associated with alpha1-adrenoceptor-dependent neural activity, in several positive-activity-related (motor, piriform, cingulate cortex, nucleus accumbens, locus coeruleus) and stress-related brain regions (paraventricular hypothalamus, bed nucleus stria terminalis).

RESULTS

Both lipopolysaccharide and reserpine pretreatment abolished fresh cage-induced fos expression and MAPK activation in the positive activity-related brain regions but enhanced these measures in the stress-related areas.

CONCLUSIONS

The results support the hypothesis that immune activation reduces alpha1-adrenoceptor-related signaling and neural activity in brain regions associated with positive activity while it increases these functions in stress-associated areas. It is suggested that neural activities of these two types of brain regions are mutually antagonistic and that a reciprocal shift toward the stress regions is a factor in the loss of positively motivated behaviors in sickness behavior and depressive illness.

The role of mast cells in migraine pathophysiology

Mast cells are critical players in allergic reactions, but they have also been shown to be important in immunity and recently also in inflammatory diseases, especially asthma. Migraines are episodic, typically unilateral, throbbing headaches that occur more frequently in patients with allergy and asthma implying involvement of meningeal and/or brain mast cells. These mast cells are located perivascularly, in close association with neurons especially in the dura, where they can be activated following trigeminal nerve, as well as cervical or sphenopalatine ganglion stimulation. Neuropeptides such as calcitonin gene-related peptide (CGRP), hemokinin A, neurotensin (NT), pituitary adenylate cyclase activating peptide (PACAP), and substance P (SP) activate mast cells leading to secretion of vasoactive, pro-inflammatory, and neurosensitizing mediators, thereby contributing to migraine pathogenesis. Brain mast cells can also secrete pro-inflammatory and vasodilatory molecules such as interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF), selectively in response to corticotropin-releasing hormone (CRH), a mediator of stress which is known to precipitate or exacerbate migraines. A better understanding of brain mast cell activation in migraines would be useful and could lead to several points of prophylactic intervention.