Breaking boundaries in neural-immune interactions

Histopathological observations and comparative transcriptome analysis of Ophiocordyceps sinensis infection of Hepialus xiaojinensis in the early stage

Hepialus xiaojinensis is a Lepidopteran insect and one of the hosts for the artificial cultivation of Cordyceps. Ophiocordyceps sinensis can infect and coexist with H. xiaojinensis larvae for a long time. Little studies focused on the interaction process through its early infection stage. In this research, we particularly study the interaction of infected and uninfected larvae in the 3rd (OS-3, CK-3) and 4th (OS-4, CK-4) instars. O. sinensis was distributed within the larvae and accompanied by pathological changes in some tissue structures. In response to O. sinensis infection, OS-3 enhanced the antioxidant defense ability, while OS-4 decreased. The transcriptome analysis showed that OS-3 resisted the invasion of O. sinensis by the immune and nervous systems. Correspondingly, OS-4 reduced immune response and utilized more energy for growth and development. This study provides a comprehensive resource for analyzing the mechanism of H. xiaojinensis and O. sinensis interaction.

A neural cell adhesion molecule from oyster Crassostrea gigas: Molecular identification and immune functional characterization

Neural cell adhesion molecules (NCAMs) are large cell-surface glycoproteins playing important roles in cell-cell and cell-extracellular matrix interactions in nervous system. Recent study identified a homologue of NCAM (CgNCAM) from the Pacific oyster Crassostrea gigas. Its ORF was of 2634 bp which encodes a protein (877 amino acids) consisting of five immunoglobulin domains and two fibronectin type III domains. CgNCAM transcripts were broadly distributed in oyster tissues especially in mantle, labial palp and haemolymph. CgNCAM showed up-regulated expression in haemocytes of oysters after Vibrio splendidus and Staphylococcus aureus stimulation. The recombinant CgNCAM protein (rCgNCAM) was able to bind manose, lipopolysaccharide and glucan, as well as different microbes including Gram-negative bacteria and fungi. rCgNCAM displayed bacterial agglutination and hemagglutination activity. CgNCAM improved the phagocytosis of haemocytes towards V. splendidus by regulating the expression of CgIntegrin, CgRho J and CgMAPKK. Moreover, CgNCAM was involved in the extracellular trap establishment of haemocytes after V. splendidus stimulation. The results collectively indicated that CgNCAM acted as a recognition receptor executing multiple immune functions to recognize and eliminate invading microorganisms in innate immunity of oysters.

Association study between genetic variants and the risk of schizophrenia in the Chinese population based on GWAS-implicated 6p21.3-23.1 human genome region: a case-control study

BACKGROUND

Schizophrenia is a polygenic disease; however, the specific risk genetic variants of schizophrenia are still largely unknown. Single nucleotide polymorphism (SNP) is important genetic factor for the susceptibility of schizophrenia. Investigating individual candidate gene contributing to disease risk remains important.

METHODS

In a case-control study, five SNPs located in 6p21.3-p23.1 including rs2021722 in human leukocyte antigen (HLA) locus and rs107822, rs383711, rs439205 and rs421446 within the upstream of microRNA-219a-1 were genotyped in 454 schizophrenia patients and 445 healthy controls to investigate the possible association between the loci and schizophrenia in a Han Chinese population.

RESULTS

Our results showed significant associations between the rs2021722 and schizophrenia in allele (A vs. G: adjusted OR = 1.661, 95%CI = 1.196-2.308), co-dominant (AG vs. GG: OR = 1.760, 95%CI = 1.234-2.510) and dominant genetic model (AG + AA vs. GG: OR = 1.756, 95%CI = 1.237-2.492), respectively. Haplotype analysis showed that TGGT and CAAC were protective factor for schizophrenia compared with TAAC haplotype (OR = 0.324, 95% CI = 0.157-0.672; OR = 0.423, 95% CI = 0.199-0.900).

CONCLUSIONS

These findings indicate that rs2021722 in HLA locus might be involved in pathogenesis of schizophrenia and that genotypes AG and allele A of the locus are risk factors for schizophrenia in the Han Chinese population, confirming the association between immune system and schizophrenia.

Impact of vitamin deficiency on microbiota composition and immunomodulation: relevance to autistic spectrum disorders

OBJECTIVES

Inappropriate vitamin supply is a public health problem and is related to abnormalities in brain development, immune response and, more recently, in changes of gut microbial composition. It is known that low levels of vitamin in early life are linked to increased susceptibility to neurodevelopmental disorders, such as Autism Spectrum Disorders (ASD). Unfortunately, the possible peripheral influences of vitamin deficiency that leads to alterations in the gut microbiota-immune-brain axis, one important modulator of the ASD pathology, remain unclear. This narrative review discusses how the impact of vitamin deficiency results in changes in the immune regulation and in the gut microbiota composition, trying to understand how these changes may contribute for the development and severity of ASD.

METHODS

The papers were selected using Pubmed and other databases. This review discusses the following topics: (1) vitamin deficiency in alterations of central nervous system in autism, (2) the impact of low levels of vitamins in immunomodulation and how it can favor imbalance in gut microbiota composition and gastrointestinal (GI) disturbances, (3) gut microbiota imbalance/inflammation associated with the ASD pathophysiology, and (4) possible evidences of the role of vitamin deficiency in dysfunctional gut microbiota-immune-brain axis in ASD.

RESULTS

Studies indicate that hypovitaminosis A, B12, D, and K have been co-related with the ASD neuropathology. Furthermore, it was shown that low levels of these vitamins favor the Th1/Th17 environment in the gut, as well as the growth of enteropathogens linked to GI disorders.

DISCUSSION

GI disorders and alterations in the gut microbiota-immune-brain axis seems to be linked with ASD severity. Although unclear, hypovitaminosis appears to regulate peripherally the ASD pathophysiology by modulating the gut microbiota-immune-brain axis, however, more research is still necessary to confirm this hypothesis.

Age-Dependent Reduction in Severity and Discrete Topographical Patterns in Rasmussen Encephalitis: A Link to Cortical Maturation?

BACKGROUND

Autopsy studies in Rasmussen encephalitis reveal areas of sparing within the affected hemisphere. Clinical progression and inflammation are milder with an older onset. We sought to demonstrate radiological corroboration for these patterns.

METHODS

In our retrospective study, 38 cases were dichotomized into severe pan-hemispheric (all lobes involved) and sub-hemispheric groups (others) to identify age demographics and other severity predictors. The extent and patterns of radiological pathology in the cortex and subcortical structures were assessed by structured visual grading. Relevant clinical data were also reported.

RESULTS

Children with pan-hemispheric involvement were younger at onset (P < 0.001) and were more likely to present with status epilepticus (odds ratio 8.5, 95% confidence interval 1.5 to 50.0, P = 0.022). A history of perinatal asphyxia/hospitalization (P < 0.001) and delayed milestones (P = 0.013) were encountered exclusively in this group, and progression to a low-amplitude record background on electroencephalography, suggesting that cortical damage was identified frequently (P = 0.038, odds ratio = 5.7, 95% confidence interval 1.3 to 25.0). Visual grading revealed significant differences among both cortical (P < 0.001) and subcortical (P < 0.001) regions. On multivariate analysis, the odds for pan-hemispheric disease decreased per year of age at onset (P = 0.022, odds ratio 0.51, 95% confidence interval 0.085 to 0.725). Epilepsy surgery (n = 14) was associated with Engel Class 1 seizure control (P < 0.001). Immunosuppressive therapy (n = 20) did not demonstrate a significant seizure remission (P = 0.157, odds ratio 0.39, 95% confidence interval 0.10 to 1.55).

CONCLUSIONS

Our case series confirms the presence of specific topographical patterns of macroscopic radiological pathology over the affected hemisphere with a marked age-associated reduction in the odds for severe pan-hemispheric disease.

Spatial and temporal transcriptomic analyses reveal locust initiation of immune responses to Metarhizium acridum at the pre-penetration stage

Insect hemocyte and fat body tissues play critical functional roles in insect immunity. Little, however, is known concerning the dynamic responses of these tissues to fungal infection. Here, we report on a time course of locust hemocyte and fat body transcriptomic responses to infection by the acridid specific fungal pathogen, Metarhizium acridum. Fat body responses were more pronounced at all infection stages as compared to hemocytes. Immune and other related genes were induced far earlier than previously considered including at pre-penetration stages. Differential expression in hemocyte and fat body tissues persisted throughout the course of infection up until host death. Our data indicate selective pressure on the host to recognize the infection as early as possible in order to limit its spread. Overall, fat body and hemocyte tissues launch a robust multi-tiered response to combat the fungal pathogen, with our data providing potential host targets for exploitation in pest control.

Cerebrospinal fluid and the early brain development of autism

BACKGROUND

There is currently a renaissance of interest in the many functions of cerebrospinal fluid (CSF). Altered flow of CSF, for example, has been shown to impair the clearance of pathogenic inflammatory proteins involved in neurodegenerative diseases, such as amyloid-β. In addition, the role of CSF in the newly discovered lymphatic system of the brain has become a prominently researched area in clinical neuroscience, as CSF serves as a conduit between the central nervous system and immune system.

MAIN BODY

This article will review the importance of CSF in regulating normal brain development and function, from the prenatal period throughout the lifespan, and highlight recent research that CSF abnormalities in autism spectrum disorder (ASD) are present in infancy, are detectable by conventional structural MRI, and could serve as an early indicator of altered neurodevelopment.

CONCLUSION

The identification of early CSF abnormalities in children with ASD, along with emerging knowledge of the underlying pathogenic mechanisms, has the potential to serve as early stratification biomarkers that separate children with ASD into biological subtypes that share a common pathophysiology. Such subtypes could help parse the phenotypic heterogeneity of ASD and map on to targeted, biologically based treatments.

The role of neutrophil granulocytes in immune-to-brain communication

Immune-to-brain communication has been studied in a variety of experimental models. Crucial insights into signalling and mechanisms were previously revealed in studies investigating fever induction pathways. The scientific community has primarily focused on neuronal and humoral pathways in the manifestation of this response. Emerging evidence has now shown that immune-to-brain signalling via immune cells is pivotal for normal brain function and brain pathology. The present manuscript aims to provide a brief overview on the current understanding of how immune cells signal to the brain. Insights are summarized on the potential physiological significance of some immune cells signalling from the periphery to the brain. A particular focus is laid on the role of neutrophil granulocytes. As such, IL-1β expressing neutrophil granulocytes have been shown to transfer inflammatory information to the brain and contribute to prolonged behavioural changes due to septic encephalopathy in rats during severe systemic inflammation induced by the bacterial component and TLR4 agonist lipopolysaccharide. Modulation of immune cell recruitment to the brain is discussed by various confounding factors including sleep, exercise, the nutritional status e.g. obesity, leptin and omega 3 fatty acids, and psychological or inflammatory stressors. The physiological significance of immune cell mediated communication between the immune system and the brain is highlighted by the fact that systemic inflammatory insults can exacerbate ongoing brain pathologies via immune cell trafficking. New insights into mechanisms and mediators of immune cell mediated immune-to-brain communication are important for the development of new therapeutic strategies and the better understanding of existing ones. Abbreviations: ACTH: adrenocorticotropic hormone; BBB: blood-brain barrier; BBI: blood-brain interface; CD: cluster of differentiation; CINC: cytokine-induced neutrophil chemoattractant; CRH: corticotropin releasing hormone; CVOs: circumventricular organs; CXCR: chemokine receptor; DAPI: 40:6-diamidino-2-phenylindole dilactate; DHA: docosahexaenoid acid; ICAM: intracellular adhesion molecule; IL: interleukin; i.p.: intraperitoneal; i.v.: intravenous; KC: keratinocytes-derived chemokine; LPS: lipopolysaccharide; MIP: macrophage inflammatory protein; MS: multiple sclerosis; NFκB: nuclear factor kappa B; NF-IL6: nuclear factor IL-6; PCTR: protectin conjugates in tissue regeneration; PG: prostaglandin; p.i.: post injection; PVN: paraventricular nucleus; ra: receptor antagonist; STAT3: signal transducer and activator of transcription 3; TIMP: tissue inhibitors of metalloproteinases; TLR: toll-like receptor; TNFα: tumor necrosis factor alpha.

Dendritic Cells as an Alternate Approach for Treatment of Neurodegenerative Disorders

Despite years of research, Alzheimer's disease (AD) remains incurable and thus poses a major health challenge in coming years. This neurodegenerative disease belongs to a heterogeneous group of human tauopathies, characterized by the extracellular deposition of beta amyloid-Aβ and intracellular accumulation of tau protein in neuronal and glial cells, whereby tau pathology best correlates with disease progression. For decades, several disease-modifying agents were brought to clinical studies with promising efficacy in preclinical trials; however, all of the subsequent clinical trials failed. Therefore, the pursuit for therapeutic agents for the treatment of AD and other tauopathies still continue. Recent evidences show previously unidentified role of peripheral immune system in regulating the inflammatory status of the brain, mainly the dendritic cells. A decrease in functionality and count of dendritic cells has been observed in Alzheimer's disease. Here, we discuss a potential role of dendritic cell-based vaccines as therapeutic approach in ameliorating disease pathogenesis in AD and other tauopathies.

Friend or foe: the dichotomous impact of T cells on neuro-de/re-generation during aging

The interaction between T cells and the central nervous system (CNS) in homeostasis and injury has been recognized being both pathogenic (CD4⁺ T-helper 1 - Th1, Th17 and γδT) and ameliorative (Th2 and regulatory T cells - Tregs). However, in-depth studies aimed to elucidate the precise in the aged microenvironment and the dichotomous role of Tregs have just begun and many aspects remain unclear. This is due, not only to a mutual dependency and reciprocal causation of alterations and diseases between the nervous and T cell immune systems, but also to an inconsistent aging of the two systems, which dynamically changes with CNS injury/recovery and/or aging process. Cellular immune system aging, particularly immunosenescence and T cell aging initiated by thymic involution - sources of chronic inflammation in the elderly (termed inflammaging), potentially induces an acceleration of brain aging and memory loss. In turn, aging of the brain via neuro-endocrine-immune network drives total body systemic aging, including that of the immune system. Therefore, immunotherapeutics including vaccination and “protective autoimmunity” provide promising means to rejuvenate neuro-inflammatory disorders and repair CNS acute injury and chronic neuro-degeneration. We review the current understanding and recent discoveries linking the aging immune system with CNS injury and neuro-degeneration. Additionally, we discuss potential recovery and rejuvenation strategies, focusing on targeting the aging T cell immune system in an effort to alleviate acute brain injury and chronic neuro-degeneration during aging, via the “thymus-inflammaging-neurodegeneration axis”.

NLRP3 inflammasome activation in the thymus of MPTP-induced Parkinsonian mouse model

Ample evidence shows that Parkinson's disease (PD) is more than simply a central nervous system (CNS) disorder: the immune system appears to participate in PD pathogenesis. Extracellular misfolded α-synuclein (α-syn) may trigger an inflammatory response in the brain. Abnormal immune responses are involved in the development of PD, but little is known about the relationship between the thymus malfunction and the pathogenesis of PD. The present study investigated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced impairment in thymus and explored possible mechanisms involved in PD pathogenesis. After subcutaneous injection of MPTP (25 mg/kg) every 4 days for 40-days, immune responses became unbalanced, with increased IL-1β concentrations. On histopathology, mice treated with MPTP displayed pathological involution and damaged ultrastructure of the thymus. Both the PD-related oligomeric α-synuclein and oxidative stress related nitrated-α-synuclein (Tyr125, Tyr133) in mice treated with MPTP were elevated. Correspondingly, oxidative stress damage was detected in the form of increased 8-hydroxyguanosine staining. Moreover, MPTP significantly increased expression of caspase-8, NF-κB, NLPR3, and caspase-1 in the thymus. These results suggested that MPTP was toxic to mouse thymus via a mechanism involving the NF-κB and NLRP3 inflammasome pathway. These results suggested that environmental factors may lead to pathological changes in the thymus that are similar to those in the central nervous system. A disordered thymus might take part in the development of PD, and its enhanced immune response might promote the degenerative changes in the brain.

Impact of aging immune system on neurodegeneration and potential immunotherapies

The interaction between the nervous and immune systems during aging is an area of avid interest, but many aspects remain unclear. This is due, not only to the complexity of the aging process, but also to a mutual dependency and reciprocal causation of alterations and diseases between both the nervous and immune systems. Aging of the brain drives whole body systemic aging, including aging-related changes of the immune system. In turn, the immune system aging, particularly immunosenescence and T cell aging initiated by thymic involution that are sources of chronic inflammation in the elderly (termed inflammaging), potentially induces brain aging and memory loss in a reciprocal manner. Therefore, immunotherapeutics including modulation of inflammation, vaccination, cellular immune therapies and "protective autoimmunity" provide promising approaches to rejuvenate neuroinflammatory disorders and repair brain injury. In this review, we summarize recent discoveries linking the aging immune system with the development of neurodegeneration. Additionally, we discuss potential rejuvenation strategies, focusing aimed at targeting the aging immune system in an effort to prevent acute brain injury and chronic neurodegeneration during aging.

Neuroimmunology and neuroepigenetics in the establishment of sex differences in the brain

The study of sex differences in the brain is a topic of neuroscientific study that has broad reaching implications for culture, society and biomedical science. Recent research in rodent models has led to dramatic shifts in our views of the mechanisms underlying the sexual differentiation of the brain. These include the surprising discoveries of a role for immune cells and inflammatory mediators in brain masculinization and a role for epigenetic suppression in brain feminization. How and to what degree these findings will translate to human brain development will be questions of central importance in future research in this field.

The Major Histocompatibility Complex (MHC) in Schizophrenia: A Review

Epidemiological studies and mouse models suggest that maternal immune activation, induced clinically through prenatal exposure to one of several infectious diseases, is a risk factor in the development of schizophrenia. This is supported by the strong genetic association established by genome wide association studies (GWAS) between the human leukocyte antigen (HLA) locus and schizophrenia. HLA proteins (also known in mice as the major histocompatibility complex; MHC) are mediators of the T-lymphocyte responses, and genetic variability is well-established as a risk factor for autoimmune diseases and susceptibility to infectious diseases. Taken together, the findings strongly suggest that schizophrenia risk in a subgroup of patients is caused by an infectious disease, and/or an autoimmune phenomenon. However, this view may be overly simplistic. First, MHC proteins have a non-immune effect on synaptogenesis by modulating synaptic pruning by microglia and other mechanisms, suggesting that genetic variability could be compromising this physiological process. Second, some GWAS signals in the HLA locus map near non-HLA genes, such as the histone gene cluster. On the other hand, recent GWAS data show association signals near B-lymphocyte enhancers, which lend support for an infectious disease etiology. Thus, although the genetic findings implicating the HLA locus are very robust, how genetic variability in this region leads to schizophrenia remains to be elucidated.

Fasudil Enhances Therapeutic Efficacy of Neural Stem Cells in the Mouse Model of MPTP-Induced Parkinson's Disease

Bone marrow-derived neural stem cells (NSCs) are ideal cells for cellular therapy because of their therapeutic potential for repairing and regenerating damaged neurons. However, the optimization of implanted cells and the improvement of microenvironment in the central nervous system (CNS) are still two critical elements for enhancing therapeutic effect. In the current study, we observed the combined therapeutic effect of NSCs with fasudil in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse model and explored the possible cellular and molecular mechanisms. The results clearly show that combined treatment of NSCs with fasudil further improves motor capacity of PD mice, thus exerting double effect in treating MPTP-PD. The combined intervention more effectively protected dopaminergic (DA) neurons from loss in the substantia nigra pars compacta (SNpc), which may be associated with the increased number and survival of transplanted NSCs in the brain. Compared with the treatment of fasudil or NSCs alone, the combined intervention more effectively inhibited the activation and aggregation of microglia and astrocytes, displayed stronger anti-inflammatory and antioxidant effects, induced more neurotrophic factor NT-3, and affected the dynamic homeostasis of NMDA and AMPA receptors in MPTP-PD mice. Our study demonstrates that intranasal administration of NSCs, followed by fasudil administration, is a promising cell-based therapy for neuronal lesions.

Successful treatment of urodynamic detrusor over-activity in a young patient with Myasthenia gravis using pretibial nerve stimulation with follow-up to two years

We report a rare case of Myasthenia gravis and overactive bladder successfully treated with pretibial nerve stimulation.

Overview of Innovative Mouse Models for Imaging Neuroinflammation

Neuroinflammation demands a comprehensive appraisal in situ to gain in-depth knowledge on the roles of particular cells and molecules and their potential roles in therapy. Because of the lack of appropriate tools, direct visualization of cells has been poorly investigated up to the present. In this context, reporter mice expressing cell-specific fluorescent proteins, combined with multiphoton microscopy, provide a window into cellular processes in living animals. In addition, the ability to collect multiple fluorescent colors from the same sample makes in vivo microscopy uniquely useful for characterizing many parameters from the same area, supporting powerful correlative analyses. Here, we present an overview of the advantages and limitations of this approach, with the purpose of providing insight into the neuroinflammation field. We also provide a review of existing fluorescent mouse models and describe how these models have been used in studies of neuroinflammation. Finally, the potential for developing advanced genetic tools and imaging resources is discussed. © 2016 by John Wiley & Sons, Inc.

Myeloid Dendritic Cells are Potential Players in Human Neurodegenerative Diseases

Alzheimer’s diseases (AD) and Parkinson’s diseases (PD) are devastating neurodegenerative disturbances, wherein neuroinflammation is a chronic pathogenic process with high therapeutic potential. Major mediators of AD/PD neuroimmune processes are resident immune cells, but immune cells derived from periphery may also participate and to some extent modify neuroinflammation. Specifically, blood borne myeloid cells emerge as crucial components of AD/PD progression and susceptibility. Among these, dendritic cells (DCs) are key immune orchestrators and players of brain immune surveillance; we candidate them as potential mediators of both AD and PD and as relevant cell model for unraveling myeloid cell role in neurodegeneration. Hence, we recapitulate and discuss emerging data suggesting that blood-derived DCs play a role in experimental and human neurodegenerative diseases. In humans, in particular, DCs are modified by in vitro culture with neurodegeneration-associated pathogenic factors and dysregulated in AD patients, while the levels of DC precursors are decreased in AD and PD patients’ blood, possibly as an index of their recruitment to the brain. Overall, we emphasize the need to explore the impact of DCs on neurodegeneration to uncover peripheral immune mechanisms of pathogenic importance, recognize potential biomarkers, and improve therapeutic approaches for neurodegenerative diseases.

From cartoon to real time MRI: in vivo monitoring of phagocyte migration in mouse brain

Recent studies have demonstrated that immune cells play an important role in the pathogenesis of many neurological conditions. Immune cells constantly survey the brain microvasculature for irregularities in levels of factors that signal homeostasis. Immune responses are initiated when necessary, resulting in mobilisation of the microglial cells resident in the central nervous system (CNS) and/or of infiltrating peripheral cells. However, little is known about the kinetics of immune cells in healthy and diseased CNS, because it is difficult to perform long-term visualisation of cell motility in live tissue with minimal invasion. Here, we describe highly sensitive in vivo MRI techniques for sequential monitoring of cell migration in the CNS at the single-cell level. We show that MRI combined with intravenous administration of super-paramagnetic particles of iron oxide (SPIO) can be used to monitor the transmigration of peripheral phagocytes into healthy or LPS-treated mouse brains. We also demonstrate dynamic cell migration in live animal brains with time-lapse MRI videos. Time-lapse MRI was used to visualise and track cells with low motility in a control mouse brain. High-sensitivity MRI cell tracking using SPIO offers new insights into immune cell kinetics in the brain and the mechanisms of CNS homeostasis.

Microglial VPAC1R mediates a novel mechanism of neuroimmune-modulation of hippocampal precursor cells via IL-4 release

Neurogenesis, the production of new neurons from neural stem/progenitor cells (NSPCs), occurs throughout adulthood in the dentate gyrus of the hippocampus, where it supports learning and memory. The innate and adaptive immune systems are increasingly recognized as important modulators of hippocampal neurogenesis under both physiological and pathological conditions. However, the mechanisms by which the immune system regulates hippocampal neurogenesis are incompletely understood. In particular, the role of microglia, the brains resident immune cell is complex, as they have been reported to both positively and negatively regulate neurogenesis. Interestingly, neuronal activity can also regulate the function of the immune system. Here, we show that depleting microglia from hippocampal cultures reduces NSPC survival and proliferation. Furthermore, addition of purified hippocampal microglia, or their conditioned media, is trophic and proliferative to NSPCs. VIP, a neuropeptide released by dentate gyrus interneurons, enhances the proliferative and pro-neurogenic effect of microglia via the VPAC1 receptor. This VIP-induced enhancement is mediated by IL-4 release, which directly targets NSPCs. This demonstrates a potential neuro-immuno-neurogenic pathway, disruption of which may have significant implications in conditions where combined cognitive impairments, interneuron loss, and immune system activation occurs, such as temporal lobe epilepsy and Alzheimer's disease.

Autism

Autism is a set of heterogeneous neurodevelopmental conditions, characterised by early-onset difficulties in social communication and unusually restricted, repetitive behaviour and interests. The worldwide population prevalence is about 1%. Autism affects more male than female individuals, and comorbidity is common (>70% have concurrent conditions). Individuals with autism have atypical cognitive profiles, such as impaired social cognition and social perception, executive dysfunction, and atypical perceptual and information processing. These profiles are underpinned by atypical neural development at the systems level. Genetics has a key role in the aetiology of autism, in conjunction with developmentally early environmental factors. Large-effect rare mutations and small-effect common variants contribute to risk. Assessment needs to be multidisciplinary and developmental, and early detection is essential for early intervention. Early comprehensive and targeted behavioural interventions can improve social communication and reduce anxiety and aggression. Drugs can reduce comorbid symptoms, but do not directly improve social communication. Creation of a supportive environment that accepts and respects that the individual is different is crucial.

Learning and memory ... and the immune system

The nervous system and the immune system are two main regulators of homeostasis in the body. Communication between them ensures normal functioning of the organism. Immune cells and molecules are required for sculpting the circuitry and determining the activity of the nervous system. Within the parenchyma of the central nervous system (CNS), microglia constantly monitor synapses and participate in their pruning during development and possibly also throughout life. Classical inflammatory cytokines, such as interleukin (IL)-1β and tumor necrosis factor (TNF), are released during neuronal activity and play a crucial role in regulating the strength of synaptic transmission. Systemically, proper functioning of the immune system is critical for maintaining normal nervous system function. Disruption of the immune system functioning leads to impairments in cognition and in neurogenesis. In this review we provide examples of the communication between the nervous and the immune systems in the interest of normal CNS development and function.

MHC class I immune proteins are critical for hippocampus-dependent memory and gate NMDAR-dependent hippocampal long-term depression

Memory impairment is a common feature of conditions that involve changes in inflammatory signaling in the brain, including traumatic brain injury, infection, neurodegenerative disorders, and normal aging. However, the causal importance of inflammatory mediators in cognitive impairments in these conditions remains unclear. Here we show that specific immune proteins, members of the major histocompatibility complex class I (MHC class I), are essential for normal hippocampus-dependent memory, and are specifically required for NMDAR-dependent forms of long-term depression (LTD) in the healthy adult hippocampus. In β2m^−/−TAP^−/−mice, which lack stable cell-surface expression of most MHC class I proteins, NMDAR-dependent LTD in area CA1 of adult hippocampus is abolished, while NMDAR-independent forms of potentiation, facilitation, and depression are unaffected. Altered NMDAR-dependent synaptic plasticity in the hippocampus of β2m^−/−TAP^−/−mice is accompanied by pervasive deficits in hippocampus-dependent memory, including contextual fear memory, object recognition memory, and social recognition memory. Thus normal MHC class I expression is essential for NMDAR-dependent hippocampal synaptic depression and hippocampus-dependent memory. These results suggest that changes in MHC class I expression could be an unexpected cause of disrupted synaptic plasticity and cognitive deficits in the aging, damaged, and diseased brain.

Role of NAD(+), Oxidative Stress, and Tryptophan Metabolism in Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a pervasive neuro-developmental disorder characterized by impaired social interaction, reduced/absent verbal and non-verbal communication, and repetitive behavior during early childhood. The etiology of this developmental disorder is poorly understood, and no biomarkers have been identified. Identification of novel biochemical markers related to autism would be advantageous for earlier clinical diagnosis and intervention. Studies suggest that oxidative stress-induced mechanisms and reduced antioxidant defense, mitochondrial dysfunction, and impaired energy metabolism (NAD(+), NADH, ATP, pyruvate, and lactate), are major causes of ASD. This review provides renewed insight regarding current autism research related to oxidative stress, mitochondrial dysfunction, and altered tryptophan metabolism in ASD.

The spatio-temporal expression of MHC class I molecules during human hippocampal formation development

In the immune system, the major histocompatibility complex (MHC) class I molecules mediate both the innate and adaptive immune responses in vertebrates. There has been a dogma that the central nervous system (CNS) is immune privileged and healthy neurons do not express MHC class I molecules. However, recent studies have indicated that the expression and non-immunobiologic roles of MHC class I in mammalian CNS. But data referring to humans are scarce. In this study we report the expression and cellular localization of MHC class I in the human fetal, early postnatal and adult hippocampal formation. The expression of MHC class I was very low in the hippocampus at 20 (gestational weeks) GW and slowly increased at 27-33 GW. The gradually increased expression in the somata of some granular cells in dentate gyrus (DG) was observed at 30-33 GW. Whereas, a rapid increase in MHC class I molecules expression was found in the subiculum and it reached high levels at 31-33 GW and maintained at postnatal 55 days. No expression of MHC class I was found in hippocampal formation in adult. MHC class I heavy chain and β2 microglobulin (β2M) showed similar expression in some cells of the hippocampal formation at 30-33 GW. Moreover, MHC class I molecules were mainly expressed in neurons and most MHC class I-expressing neurons were glutamatergic. The temporal and spatial patterns of MHC class I expression appeared to follow gradients of pyramidal neurons maturation in the subiculum at prenatal stages and suggested that MHC class I molecules are likely to regulate neuron maturation. This article is part of a Special Issue entitled Priority to Publish.

Altered cytokine and BDNF levels in autism spectrum disorder

The contribution of neuroimmune functioning and brain-derived neurotrophic factor (BDNF) to functional dysregulation in autism spectrum disorder was assessed in 29 patients under treatment in two specialized centers of Basilicata (Chiaromonte and Matera), Southern Italy, through analysis of serum levels of cytokines and BDNF. Elevated levels of the pro-inflammatory cytokine, including interleukin-1, interleukin-6, interleukin-12, interleukin-23, tumor necrosis factor-α and BDNF were observed, regardless of age and gender. Comparisons were made with age- and gender-related healthy controls. The present findings reinforce current notions regarding immunoexcitotoxic mechanisms contributing to the pathophysiology of autistic disorder.

Is 'bench-to-bedside' realistic for autism? An integrative neuroscience approach

Given the prevalence and societal impact of autism spectrum disorder (ASD), there is an urgent need to develop innovative treatments that will improve core social deficits, for which there is currently no reliable pharmacological treatment, prevention or cure. Development of novel biological interventions will depend upon the successful translation of basic neuroscience research into safe and effective medicines. This article outlines steps to bring neuroscience research from 'the bench' to treatment at 'bedside', from phenotyping the disorder to animal models to patient treatment. Although these steps appear simplistic, this is a daunting challenge because of the inherent complexity of the human brain, our lack of understanding of disease neurobiology underlying ASD, and the incredible heterogeneity of the disorder. For ASD, perhaps more than any other neurological or psychiatric disorder, progress will depend on integrative multidisciplinary approaches between basic scientists from varying neuroscience disciplines and clinicians to make 'bench to bedside' treatment a reality.

RFX transcription factor DAF-19 regulates 5-HT and innate immune responses to pathogenic bacteria in Caenorhabditis elegans

In Caenorhabditis elegans the Toll-interleukin receptor domain adaptor protein TIR-1 via a conserved mitogen-activated protein kinase (MAPK) signaling cascade induces innate immunity and upregulates serotonin (5-HT) biosynthesis gene tph-1 in a pair of ADF chemosensory neurons in response to infection. Here, we identify transcription factors downstream of the TIR-1 signaling pathway. We show that common transcription factors control the innate immunity and 5-HT biosynthesis. We demonstrate that a cysteine to tyrosine substitution in an ARM motif of the HEAT/Arm repeat region of the TIR-1 protein confers TIR-1 hyperactivation, leading to constitutive tph-1 upregulation in the ADF neurons, increased expression of intestinal antimicrobial genes, and enhanced resistance to killing by the human opportunistic pathogen Pseudomonas aeruginosa PA14. A forward genetic screen for suppressors of the hyperactive TIR-1 led to the identification of DAF-19, an ortholog of regulatory factor X (RFX) transcription factors that are required for human adaptive immunity. We show that DAF-19 concerts with ATF-7, a member of the activating transcription factor (ATF)/cAMP response element-binding B (CREB) family of transcription factors, to regulate tph-1 and antimicrobial genes, reminiscent of RFX-CREB interaction in human immune cells. daf-19 mutants display heightened susceptibility to killing by PA14. Remarkably, whereas the TIR-1-MAPK-DAF-19/ATF-7 pathway in the intestinal immunity is regulated by DKF-2/protein kinase D, we found that the regulation of tph-1 expression is independent of DKF-2 but requires UNC-43/Ca²⁺/calmodulin-dependent protein kinase (CaMK) II. Our results suggest that pathogenic cues trigger a common core-signaling pathway via tissue-specific mechanisms and demonstrate a novel role for RFX factors in neuronal and innate immune responses to infection.

Toll-interleukin receptor (TIR)–domain adaptor proteins are keys to activate signaling cascades inducing transcriptional responses to internal and external pathogenic signals in evolutionary disparate organisms. Despite lacking a homolog of the mammalian innate immunity transcriptional regulator nuclear factor-kappaB (NF-κB), the nematode Caenorhabditis elegans responds to infections by activating TIR-1 signaling targets in the innate immune system and in neurons. Through a genetic screen for factors required for TIR-1 signaling to upregulate the serotonin biosynthesis gene tph-1, we identified DAF-19, an ortholog of regulatory factor X (RFX) transcription factors that were initially discovered in human immune cells. We show that DAF-19 concerts with ATF-7, a member of the activating transcription factor (ATF)/cAMP response element-binding B (CREB) family of transcription factors, to upregulate tph-1 in the ADF chemosensory neurons and antimicrobial genes in the intestine in response to bacterial infection, reminiscent of RFX-CREB interaction in human immune cells. daf-19 mutants display heightened susceptibility to killing by the human pathogen Pseudomonas aeruginosa PA14. Our studies suggest that RFX transcriptional regulation, which is essential for human adaptive immunity, has an ancient role in controlling serotonin biosynthesis and innate immunity.

ROCK/Cdc42-mediated microglial motility and gliapse formation lead to phagocytosis of degenerating dopaminergic neurons in vivo

The role of microglial motility in the context of adult neurodegeneration is poorly understood. In the present work, we investigated the microanatomical details of microglia-neuron interactions in an experimental mouse model of Parkinson's disease following the intraperitoneal injection of MPTP. The specific intoxication of dopaminergic neurons induces the cellular polarization of microglia, leading to the formation of body-to-body neuron-glia contacts, called gliapses, which precede neuron elimination. Inhibiting ROCK/Cdc42-mediated microglial motility in vivo blocks the activating features of microglia, such as increased cell size and number of filopodia and diminishes their phagocyting/secreting domains, as the reduction of the Golgi apparatus and the number of microglia-neuron contacts has shown. High-resolution confocal images and three-dimensional rendering demonstrate that microglia engulf entire neurons at one-to-one ratio, and the microglial cell body participates in the formation of the phagocytic cup, engulfing and eliminating neurons in areas of dopaminergic degeneration in adult mammals.

The major histocompatibility complex and autism spectrum disorder

Autism spectrum disorder (ASD) is a complex disorder that appears to be caused by interactions between genetic changes and environmental insults during early development. A wide range of factors have been linked to the onset of ASD, but recently both genetic associations and environmental factors point to a central role for immune-related genes and immune responses to environmental stimuli. Specifically, many of the proteins encoded by the major histocompatibility complex (MHC) play a vital role in the formation, refinement, maintenance, and plasticity of the brain. Manipulations of levels of MHC molecules have illustrated how disrupted MHC signaling can significantly alter brain connectivity and function. Thus, an emerging hypothesis in our field is that disruptions in MHC expression in the developing brain caused by mutations and/or immune dysregulation may contribute to the altered brain connectivity and function characteristic of ASD. This review provides an overview of the structure and function of the three classes of MHC molecules in the immune system, healthy brain, and their possible involvement in ASD.

Neuropathology markers and pathways associated with molecular targets for antipsychotic drugs in postmortem brain tissues: exploration of drug targets through the Stanley Neuropathology Integrative Database

The atypical antipsychotics bind multiple receptor targets, including dopamine D₂ receptors (DRD2), 5-HT₂ receptors (HTR2A), α-2 adrenergic receptors (ADRA2A), and muscarinic receptors (CHRM1/4). Deficits in antipsychotic targets, their associated pathways, and the causal relationships between the various targets were explored using the Stanley Neuropathology Consortium Integrative Database (SNCID; http://sncid.stanleyresearch.org) and the Network Edge Orienting (NEO) software. There were brain region-specific deficits in the level of the antipsychotic targets, and the level of each target correlated with the mRNA level of the neurotrophic factor BDNF. While myelination was a common process correlated with both DRD2 mRNA levels and ADRA2A activity in the frontal cortex, metabolic processes were specifically correlated with DRD2 mRNA. Immune and inflammatory responses and apoptosis pathways were correlated with group II metabotropic glutamate receptors (GRM2), which are a target for the development of the next-generation antipsychotics. The NEO analysis revealed that HTR2A and GRM2 are likely to regulate BDNF levels in the hippocampus and frontal cortex, respectively, whereas DRD2 and ADRA2A activity are likely to be regulated by BDNF in the frontal cortex. BDNF may play an important role in mechanisms of action of the current antipsychotics and the next-generation antipsychotics that target GRM2. However, this data-mining approach indicates that the next-generation antipsychotics are likely to work through pathways that are distinct from those through which the current antipsychotics work. Exploratory analyses such as these may initiate future hypothesis-driven studies to reveal the mechanisms of action underlying the efficacy and side-effects of the antipsychotics.

Major histocompatibility complex class I proteins in brain development and plasticity

Proper development of the central nervous system (CNS) requires the establishment of appropriate connections between neurons. Recent work suggests that this process is controlled by a balance between synaptogenic molecules and proteins that negatively regulate synapse formation and plasticity. Surprisingly, many of these newly identified synapse-limiting molecules are classic 'immune' proteins. In particular, major histocompatibility complex class I (MHCI) molecules regulate neurite outgrowth, the establishment and function of cortical connections, activity-dependent refinement in the visual system, and long-term and homeostatic plasticity. This review summarizes our current understanding of MHCI expression and function in the CNS, as well as the potential mechanisms used by MHCI to regulate brain development and plasticity.

Schizophrenia and the immune system: pathophysiology, prevention, and treatment

PURPOSE

Published evidence on established and theoretical connections between immune system dysfunction and schizophrenia is reviewed, with a discussion of developments in the search for immunologically-targeted treatments.

SUMMARY

A growing body of evidence indicates that immunologic influences may play an important role in the etiology and course of schizophrenia. A literature search identified more than 100 articles pertaining to suspected immunologic influences on schizophrenia published over the past 15 years. Schizophrenia researchers have explored a wide range of potential immune system-related causal or contributory factors, including neurobiological and neuroanatomical disorders, genetic abnormalities, and environmental influences such as maternal perinatal infection. Efforts to establish an immunologic basis for schizophrenia and identify reliable immune markers continue to be hindered by sampling challenges and methodological problems. In aggregate, the available evidence indicates that at least some cases of schizophrenia have an immunologic component, suggesting that immune-focused prevention strategies (e.g., counseling of pregnant women to avoid immune stressors) and close monitoring of at-risk children are appropriate. While antipsychotics remain the standard treatments for schizophrenia, a variety of drugs with immunologic effects have been investigated as adjunctive therapies, with variable and sometimes conflicting results; these include the cyclooxygenase-2 inhibitor celecoxib, immune-modulating agents (e.g., azathioprine and various anticytokine agents such as atlizumab, anakinra, and tumor necrosis factor-α blockers), and an investigational anti-interferon-γ agent.

CONCLUSION

The published evidence indicates that immune system dysfunction related to genetic, environmental, and neurobiological influences may play a role in the etiology of schizophrenia in a subset of patients.

Dynamic gene expression in the human cerebral cortex distinguishes children from adults

In comparison with other primate species, humans have an extended juvenile period during which the brain is more plastic. In the current study we sought to examine gene expression in the cerebral cortex during development in the context of this adaptive plasticity. We introduce an approach designed to discriminate genes with variable as opposed to uniform patterns of gene expression and found that greater inter-individual variance is observed among children than among adults. For the 337 transcripts that show this pattern, we found a significant overrepresentation of genes annotated to the immune system process (pFDR≅0). Moreover, genes known to be important in neuronal function, such as brain-derived neurotrophic factor (BDNF), are included among the genes more variably expressed in childhood. We propose that the developmental period of heightened childhood neuronal plasticity is characterized by more dynamic patterns of gene expression in the cerebral cortex compared to adulthood when the brain is less plastic. That an overabundance of these genes are annotated to the immune system suggests that the functions of these genes can be thought of not only in the context of antigen processing and presentation, but also in the context of nervous system development.

The role of immune dysfunction in the pathophysiology of autism

Autism spectrum disorders (ASD) are a complex group of neurodevelopmental disorders encompassing impairments in communication, social interactions and restricted stereotypical behaviors. Although a link between altered immune responses and ASD was first recognized nearly 40 years ago, only recently has new evidence started to shed light on the complex multifaceted relationship between immune dysfunction and behavior in ASD. Neurobiological research in ASD has highlighted pathways involved in neural development, synapse plasticity, structural brain abnormalities, cognition and behavior. At the same time, several lines of evidence point to altered immune dysfunction in ASD that directly impacts some or all these neurological processes. Extensive alterations in immune function have now been described in both children and adults with ASD, including ongoing inflammation in brain specimens, elevated pro-inflammatory cytokine profiles in the CSF and blood, increased presence of brain-specific auto-antibodies and altered immune cell function. Furthermore, these dysfunctional immune responses are associated with increased impairments in behaviors characteristic of core features of ASD, in particular, deficits in social interactions and communication. This accumulating evidence suggests that immune processes play a key role in the pathophysiology of ASD. This review will discuss the current state of our knowledge of immune dysfunction in ASD, how these findings may impact on underlying neuro-immune mechanisms and implicate potential areas where the manipulation of the immune response could have an impact on behavior and immunity in ASD.

Loss of class I MHC function alters behavior and stress reactivity

The importance of the classical immune molecule, class I major histocompatibility complex to central nervous system function is one of the most surprising discoveries related to neuroimmunology in the past decade. Mice lacking both β-2microglobulin and transporter associated with antigen processing (β2M-/-TAP-/-) showed differences in basal behavior. In response to saline injection, β2M-/-TAP-/- mice showed a significant hypothalamic pituitary adrenal activation that was not observed in wild type mice, while lipopolysaccharide-induced cytokine expression in the hypothalamus was similar in β2M-/-TAP-/- and wild type mice. Overall, these data show that class I MHC plays an important role in behavior and stress reactivity.

The immune molecule CD3zeta and its downstream effectors ZAP-70/Syk mediate ephrin signaling in neurons to regulate early neuritogenesis

Recent studies have highlighted the key role of the immune protein CD3ζ in the maturation of neuronal circuits in the CNS. Yet, the upstream signals that might recruit and activate CD3ζ in neurons are still unknown. In this study, we show that CD3ζ functions early in neuronal development and we identify ephrinA1-dependent EphA4 receptor activation as an upstream regulator of CD3ζ. When newly born neurons are still spherical, before neurite extension, we found a transient CD3ζ aggregation at the cell periphery matching the initiation site of the future neurite. This accumulation of CD3ζ correlated with a stimulatory effect on filopodia extension via a Rho-GEF Vav2 pathway and a repression of neurite outgrowth. Conversely, cultured neurons lacking CD3ζ isolated from CD3ζ(-/-) mice showed a decreased number of filopodia and an enhanced neurite number. Stimulation with ephrinA1 induces the translocation of both CD3ζ and its activated effector molecules, ZAP-70/Syk tyrosine kinases, to EphA4 receptor clusters. EphrinA1-induced growth cone collapse was abrogated in CD3ζ(-/-) neurons and was markedly reduced by ZAP-70/Syk inhibition. Moreover, ephrinA1-induced ZAP-70/Syk activation was inhibited in CD3ζ(-/-) neurons. Altogether, our data suggest that CD3ζ mediates the ZAP-70/Syk kinase activation triggered by ephrinA-activated pathway to regulate early neuronal morphogenesis.

Tumor necrosis factor-α increases brain-derived neurotrophic factor expression in trigeminal ganglion neurons in an activity-dependent manner

Many chronic trigeminal pain conditions, such as migraine or temporo-mandibular disorders, are associated with inflammation within peripheral endings of trigeminal ganglion (TG) sensory neurons. A critical role in mechanisms of neuroinflammation is attributed to proinflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α (TNFα) that also contribute to mechanisms of persistent neuropathic pain resulting from nerve injury. However, the mechanisms of cytokine-mediated synaptic plasticity and nociceptor sensitization are not completely understood. In the present study, we examined the effects of TNFα on neuronal expression of brain-derived neurotrophic factor (BDNF), whose role in synaptic plasticity and sensitization of nociceptive pathways is well documented. We show that 4- and 24-h treatment with TNFα increases BDNF mRNA and protein, respectively, in neuron-enriched dissociated cultures of rat TG. TNFα increases the phosphorylated form of the cyclic AMP-responsive element binding protein (CREB), a transcription factor involved in regulation of BDNF expression in neurons, and activates transcription of BDNF exon IV (former exon III) and, to a lesser extent, exon VI (former exon IV), but not exon I. TNFα-mediated increase in BDNF expression is accompanied by increase in calcitonin gene-related peptide (CGRP), which is consistent with previously published studies, and indicates that both peptides are similarly regulated in TG neurons by inflammatory mediators. The effect of TNFα on BDNF expression is dependent on sodium influx through TTX-sensitive channels and on p38-mitogen-activated protein kinase. Moreover, electrical stimulation and forskolin, known to increase intracellular cAMP, potentiate the TNFα-mediated upregulation of BDNF expression. This study provides new evidence for a direct action of proinflammatory cytokines on TG primary sensory neurons, and reveals a mechanism through which TNFα stimulates de novo synthesis of BDNF in these neurons. Thus, TNFα should be considered in mechanisms of BDNF-dependent neuronal plasticity.

A proteomic investigation of B lymphocytes in an autistic family: a pilot study of exposure to natural rubber latex (NRL) may lead to autism

Autism is a multi-factorial neurodevelopmental disorder. We have investigated the molecular mechanism involved in a Chinese family with autism by a proteomic approach. Antibody chips containing 500 spots of human protein antibodies were used to screen for differentially expressed proteins in the peripheral B lymphocytes between autistic and non-autistic siblings in this family. Four proteins relevant to immuno-pathway, including IKKα that was up-regulated and Tyk2, EIF4G1 and PRKCI that were down-regulated, were identified differentially expressed in autistic versus non-autistic siblings. Western blot analysis and reverse transcription quantitative polymerase chain reaction validated the differential expression of these four proteins. Based on the function of these differentially expressed proteins, relevant studies on immunoglobulin E (IgE) level, nuclear factor kappa B signaling activation and cell cycle were conducted in both autistic and non-autistic children of this family. Considering the fact that the family members were in close contact with natural rubber latex (NRL) and that IgE-mediated cross-reactions could be triggered by Hevea brasiliensis (Hev-b) proteins in NRL, we hypothesize that immune reactions triggered by close contact with NRL might influence the functions of B lymphocytes by altering expression of certain proteins identified in our experiments thus contributing to the occurrence of autism.

Linking cardiometabolic disorders to sporadic Alzheimer's disease: a perspective on potential mechanisms and mediators

There is increasing evidence that the incidence of Alzheimer's disease (AD) is significantly influenced by cardiovascular risk factors in association with a cluster of metabolic diseases including diabetes and atherosclerosis. The shared risk is also reflected in the dietary and lifestyle links to both metabolic disorders and AD-type cognitive dysfunction. Recent studies with genetic and diet-induced animal models have begun to illuminate convergent mechanisms and mediators between these two categories of disease conditions with distinct tissue-specific pathologies. Although it is clear that peripheral inflammation and insulin resistance are central to the pathogenesis of the disorders of metabolic syndrome, it seems that the same mechanisms are also in play across the blood-brain barrier that lead to AD-like molecular and cognitive changes. This review highlights these convergent mechanisms and discusses the role of cerebrovascular dysfunction as a conduit to brain emergence of these pathogenic processes that might also represent future therapeutic targets in AD in common with metabolic disorders.