Antibody response against gastrointestinal antigens in demyelinating diseases of the central nervous system

Mechanisms of enteric neuropathy in diverse contexts of gastrointestinal dysfunction

The enteric nervous system (ENS) commands moment-to-moment gut functions through integrative neurocircuitry housed in the gut wall. The functional continuity of ENS networks is disrupted in enteric neuropathies and contributes to major disturbances in normal gut activities including abnormal gut motility, secretions, pain, immune dysregulation, and disrupted signaling along the gut-brain axis. The conditions under which enteric neuropathy occurs are diverse and the mechanistic underpinnings are incompletely understood. The purpose of this brief review is to summarize the current understanding of the cell types involved, the conditions in which neuropathy occurs, and the mechanisms implicated in enteric neuropathy such as oxidative stress, toll like receptor signaling, purines, and pre-programmed cell death.

Therapeutic effects and mechanisms of fecal microbiota transplantation on EAE partly through HPA axis-mediated neuroendocrine regulation

Background

The pathogenesis of multiple sclerosis (MS) may be closely related to immune regulation and inflammatory cytokines induced by specific flora. Repairing the intestinal flora may alter the immune response in MS patients, thus opening up novel approaches for the treatment of MS.

Objective

We aimed to test the therapeutic effect of fecal microbiota transplantation (FMT) on experimental autoimmune encephalomyelitis (EAE) and the characteristics of intestinal microbiota composition changes, explore the potential mechanisms of FMT treatment.

Methods

EAE animals were treated with FMT, with the therapeutic effects were evaluated by observing neurological scores and measuring serum levels of cortisol, IL-17, and TLR-2. Fecal microbiome 16S rRNA sequencing was used to profile changes in microbiota composition, and adrenalectomy pretreatment was used to test whether FMT effects were dependent on HPA axis function.

Results

FMT improved neurological function and reduced serum IL-17 to levels that were close to the control group. FMT reestablished intestinal homeostasis by altering the structure of the intestinal flora, increasing the abundance of beneficial flora, and regulating intestinal metabolites. We found that the therapeutic effects of FMT depended partly on the efferent function of the HPA axis; surgical disruption of the HPA axis altered the abundance and diversity of the intestinal flora.

Conclusion

FMT showed a neuroprotective effect on EAE by increasing the abundance of the beneficial flora, rebuilding intestinal homeostasis, reducing IL-17 and cortisol serum levels, and promoting serum TLR-2; the therapeutic effect of FMT on EAE is partly dependent on the HPA axis.

From ASCA breakthrough in Crohn's disease and Candida albicans research to thirty years of investigations about their meaning in human health

Anti-Saccharomyces cerevisiae antibodies (ASCA) are human antibodies that can be detected using an enzyme-linked immunosorbent assay involving a mannose polymer (mannan) extracted from the cell wall of the yeast S. cerevisiae. The ASCA test was developed in 1993 with the aim of differentiating the serological response in two forms of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. The test, which is based on the detection of anti-oligomannosidic antibodies, has been extensively performed worldwide and there have been hundreds of publications on ASCA. The earlier studies concerned the initial diagnostic indications of ASCA and investigations then extended to many human diseases, generally in association with studies on intestinal microorganisms and the interaction of the micro-mycobiome with the immune system. The more information accumulates, the more the mystery of the meaning of ASCA deepens. Many fundamental questions remain unanswered. These questions concern the heterogeneity of ASCA, the mechanisms of their generation and persistence, the existence of self-antigens, and the relationship between ASCA and inflammation and autoimmunity. This review aims to discuss the gray areas concerning the origin of ASCA from an analysis of the literature. Structured around glycobiology and the mannosylated antigens of S. cerevisiae and Candida albicans, this review will address these questions and will try to clarify some lines of thought. The importance of the questions relating to the pathophysiological significance of ASCA goes far beyond IBD, even though these diseases remain the preferred models for their understanding.

Probiotic supplementation and systemic inflammation in relapsing-remitting multiple sclerosis: A randomized, double-blind, placebo-controlled trial

Background

Multiple sclerosis (MS) is a complex inflammatory disease in which demyelination occurs in the central nervous system affecting approximately 2.5 million people worldwide. Intestinal microbiome changes play an important role in the etiology of chronic diseases.

Objective

This study aimed to investigate the effect of probiotic supplementation on systemic inflammation in patients with MS.

Methods

A 12-week double-blind clinical trial study was designed and seventy patients with MS were randomly divided into two groups receiving probiotics and placebo. Patients in the intervention group received two capsules containing multi-strain probiotics daily and patients in the control group received the same amount of placebo. Factors associated with systemic inflammation were assessed at the beginning and end of the study.

Results

Sixty-five patients were included in the final analysis. There was no significant difference between the two groups in terms of baseline variables except for the duration of the disease (P > 0.05). At the end of the study, probiotic supplementation compared to the placebo caused a significant reduction in the serum levels of CRP (-0.93 ± 1.62 vs. 0.05 ± 1.74, P = 0.03), TNF-α (-2.09 ± 1.88 vs. 0.48 ± 2.53, P = 0.015) and IFN-γ (-13.18 ± 7.33 vs. -1.93 ± 5.99, P < 0.001). Also, we found a significant increase in the FOXP3 and TGF-β levels in the intervention group (P < 0.05).

Conclusion

The results of our study showed that supplementation with probiotics can have beneficial effects on serum levels of some factors associated with systemic inflammation.

Clinical trial registration

[http://www.irct.ir], identifier [IRCT20181210041 918N1].

Differentiating central nervous system demyelinating disorders: The role of clinical, laboratory, imaging characteristics and peripheral blood type I interferon activity

Objective: While multiple sclerosis (MS) is considered the cornerstone of autoimmune demyelinating CNS disorders, systemic autoimmune diseases (SADs) are important MS mimickers. We sought to explore whether distinct clinical, laboratory, and imaging characteristics along with quantitation of peripheral blood type I interferon (IFN) activity could aid in differentiating between them.

Methods: A total of 193 consecutive patients with imaging features suggesting the presence of CNS demyelinating disease with or without relevant clinical manifestations underwent full clinical, laboratory, and imaging evaluation, including testing for specific antibodies against 15 cellular antigens. Expression analysis of type I IFN-inducible genes (MX-1, IFIT-1, and IFI44) was performed by real-time PCR, and a type I IFN score, reflecting type I IFN peripheral activity, was calculated. After joint neurological/rheumatological evaluation and 1 year of follow-up, patients were classified into MS spectrum and CNS autoimmune disorders.

Results: While 66.3% (n = 128) of the patients were diagnosed with MS spectrum disorders (predominantly relapsing–remitting MS), 24.9% (n = 48) were included in the CNS autoimmune group, and out of those, one-fourth met the criteria for SAD (6.7% of the cohort, n = 13); the rest (18.1% of the cohort, n = 35), despite showing evidence of systemic autoimmunity, did not fulfill SAD criteria and comprised the “demyelinating disease with autoimmune features” (DAF) subgroup. Compared to the MS spectrum, CNS autoimmune patients were older, more frequently females, with increased rates of hypertension/hyperlipidemia, family history of autoimmunity, cortical dysfunction, anti-nuclear antibody titers ≥1/320, anticardiolipin IgM positivity, and atypical for MS magnetic resonance imaging lesions. Conversely, lower rates of infratentorial and callosal MRI lesions, CSF T2 oligoclonal bands, and IgG-index positivity were observed in CNS autoimmune patients. Patients fulfilling SAD criteria, but not the DAF group, had significantly higher peripheral blood type I IFN scores at baseline compared to MS spectrum [median (IQR)]: 50.18 (152.50) vs. −0.64 (6.75), p-value: 0.0001.

Conclusion: Our study suggests that underlying systemic autoimmunity is not uncommon in patients evaluated for possible CNS demyelination. Distinct clinical, imaging and laboratory characteristics can aid in early differentiation between MS and CNS-involving systemic autoimmunity allowing for optimal therapeutic strategies. Activated type I IFN pathway could represent a key mediator among MS-like-presenting SADs and therefore a potential therapeutic target.

Proinflammatory mucosal-associated invariant CD8+ T cells react to gut flora yeasts and infiltrate multiple sclerosis brain

The composition of the intestinal microbiota plays a critical role in shaping the immune system. Modern lifestyle, the inappropriate use of antibiotics, and exposure to pollution have significantly affected the composition of commensal microorganisms. The intestinal microbiota has been shown to sustain inappropriate autoimmune responses at distant sites in animal models of disease, and may also have a role in immune-mediated central nervous system (CNS) diseases such as multiple sclerosis (MS). We studied the composition of the gut mycobiota in fecal samples from 27 persons with MS (pwMS) and in 18 healthy donors (HD), including 5 pairs of homozygous twins discordant for MS. We found a tendency towards higher fungal abundance and richness in the MS group, and we observed that MS twins showed a higher rate of food-associated strains, such as Saccharomyces cerevisiae. We then found that in pwMS, a distinct population of cells with antibacterial and antifungal activity is expanded during the remitting phase and markedly decreases during clinically and/or radiologically active disease. These cells, named MAIT (mucosal-associated invariant T cells) lymphocytes, were significantly more activated in pwMS compared to HD in response to S. cerevisiae and Candida albicans strains isolated from fecal samples. This activation was also mediated by fungal-induced IL-23 secretion by innate immune cells. Finally, immunofluorescent stainings of MS post-mortem brain tissues from persons with the secondary progressive form of the disease showed that MAIT cells cross the blood–brain barrier (BBB) and produce pro-inflammatory cytokines in the brain. These results were in agreement with the hypothesis that dysbiosis of the gut microbiota might determine the inappropriate response of a subset of pathogenic mucosal T cells and favor the development of systemic inflammatory and autoimmune diseases.

Implications of Gut Microbiota in Complex Human Diseases

Humans, throughout the life cycle, from birth to death, are accompanied by the presence of gut microbes. Environmental factors, lifestyle, age and other factors can affect the balance of intestinal microbiota and their impact on human health. A large amount of data show that dietary, prebiotics, antibiotics can regulate various diseases through gut microbes. In this review, we focus on the role of gut microbes in the development of metabolic, gastrointestinal, neurological, immune diseases and, cancer. We also discuss the interaction between gut microbes and the host with respect to their beneficial and harmful effects, including their metabolites, microbial enzymes, small molecules and inflammatory molecules. More specifically, we evaluate the potential ability of gut microbes to cure diseases through Fecal Microbial Transplantation (FMT), which is expected to become a new type of clinical strategy for the treatment of various diseases.

Autoantibodies Against the Complement Regulator Factor H in the Serum of Patients With Neuromyelitis Optica Spectrum Disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune inflammatory disease of the central nervous system (CNS), characterized by pathogenic, complement-activating autoantibodies against the main water channel in the CNS, aquaporin 4 (AQP4). NMOSD is frequently associated with additional autoantibodies and antibody-mediated diseases. Because the alternative pathway amplifies complement activation, our aim was to evaluate the presence of autoantibodies against the alternative pathway C3 convertase, its components C3b and factor B, and the complement regulator factor H (FH) in NMOSD. Four out of 45 AQP4-seropositive NMOSD patients (~9%) had FH autoantibodies in serum and none had antibodies to C3b, factor B and C3bBb. The FH autoantibody titers were low in three and high in one of the patients, and the avidity indexes were low. FH-IgG complexes were detected in the purified IgG fractions by Western blot. The autoantibodies bound to FH domains 19-20, and also recognized the homologous FH-related protein 1 (FHR-1), similar to FH autoantibodies associated with atypical hemolytic uremic syndrome (aHUS). However, in contrast to the majority of autoantibody-positive aHUS patients, these four NMOSD patients did not lack FHR-1. Analysis of autoantibody binding to FH19-20 mutants and linear synthetic peptides of the C-terminal FH and FHR-1 domains, as well as reduced FH, revealed differences in the exact binding sites of the autoantibodies. Importantly, all four autoantibodies inhibited C3b binding to FH. In conclusion, our results demonstrate that FH autoantibodies are not uncommon in NMOSD and suggest that generation of antibodies against complement regulating factors among other autoantibodies may contribute to the complement-mediated damage in NMOSD.

You Talking to Me? Says the Enteric Nervous System (ENS) to the Microbe. How Intestinal Microbes Interact with the ENS

Mammalian organisms form intimate interfaces with commensal and pathogenic gut microorganisms. Increasing evidence suggests a close interaction between gut microorganisms and the enteric nervous system (ENS), as the first interface to the central nervous system. Each microorganism can exert a different effect on the ENS, including phenotypical neuronal changes or the induction of chemical transmitters that interact with ENS neurons. Some pathogenic bacteria take advantage of the ENS to create a more suitable environment for their growth or to promote the effects of their toxins. In addition, some commensal bacteria can affect the central nervous system (CNS) by locally interacting with the ENS. From the current knowledge emerges an interesting field that may shape future concepts on the pathogen-host synergic interaction. The aim of this narrative review is to report the current findings regarding the inter-relationships between bacteria, viruses, and parasites and the ENS.

Current Evidence on the Efficacy of Gluten-Free Diets in Multiple Sclerosis, Psoriasis, Type 1 Diabetes and Autoimmune Thyroid Diseases

In this review, we summarize the clinical data addressing a potential role for gluten in multiple sclerosis (MS), psoriasis, type 1 diabetes (T1D) and autoimmune thyroid diseases (ATDs). Furthermore, data on the prevalence of celiac disease (CD) and gluten-related antibodies in the above patient groups are presented. Adequately powered and properly controlled intervention trials investigating the effects of a gluten-free diet (GFD) in non-celiac patients with MS, psoriasis, T1D or ATDs are lacking. Only one clinical trial has studied the effects of a GFD among patients with MS. The trial found significant results, but it is subject to major methodological limitations. A few publications have found beneficial effects of a GFD in a subgroup of patients with psoriasis that were seropositive for anti-gliadin or deamidated gliadin antibodies, but no effects were seen among seronegative patients. Studies on the role of gluten in T1D are contradictive, however, it seems likely that a GFD may contribute to normalizing metabolic control without affecting levels of islet autoantibodies. Lastly, the effects of a GFD in non-celiac patients with ATDs have not been studied yet, but some publications report that thyroid-related antibodies respond to a GFD in patients with concomitant CD and ATDs. Overall, there is currently not enough evidence to recommend a GFD to non-celiac patients with MS, psoriasis, ATDs or T1D.

Cytomegalovirus Infection in an Adult Patient With Neuromyelitis Optica and Acute Hemorrhagic Rectal Ulcer: Case Report and Literature Review

Background: Previous infectious or inflammatory events may be involved in the pathogenesis of neuromyelitis optica (NMO), potentially by triggering an autoimmune response. Cytomegalovirus (CMV)-related NMO (CMV-NMO) is rarely reported. Acute hemorrhagic rectal ulcer (AHRU) is a rare disease with a largely unknown pathogenesis. Herein, we reported a co-NMO and AHRU case associated with CMV infection. In addition, we review previously reported cases of CMV-NMO and CMV-AHRU. Case presentation: A 40-year-old female diagnosed with aquaporin4 (AQP4)-IgG⁺ NMO and a poor response to high-dose intravenous methylprednisolone and immunoglobulin, followed by three rounds of plasma exchange was transferred to Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China. She developed repeated acute lower gastrointestinal hemorrhage from the third day of admission. Abdominal computed tomography angiography (CTA) and interventional angiography did not detect any bleeding vessel. Bedside colonoscopy revealed a large ulcer-like lesion at 10 cm above the anus. Rectal biopsy pathology confirmed a CMV infection on day 23 post-admission, and cerebrospinal fluid (CSF) pathogen gene sequencing detected CMV gene copies on day 25 post-admission. After 2 weeks of treatment with ganciclovir and sodium phosphinate, the patient's lower gastrointestinal bleeding stopped, and her limb muscle strength and visual acuity gradually improved. After 4 weeks of antiviral therapy, colonoscopy showed that the intestinal wall of the original lesion was smooth. Hematoxylin and eosin (HE) staining and immunohistochemistry (IHC) of a biopsy specimen was negative for CMV, her right eye vision was normal, and limb muscle strength had recovered. Serum AQP4-IgG was negative, and lesions on brain magnetic resonance imaging (MRI) manifested shrinkage. Conclusions: The benefits of antiviral therapy remain unclear; however, clinicians should be aware of the possibility of CMV-related NMO, if NMO was refractory to high-dose intravenous methylprednisolone, immunoglobulin, and plasma exchange. Moreover, clinicians should consider the possibility of CMV-related AHRU when recurrent acute lower gastrointestinal bleeding occurs in a patient.

Neurological manifestations related to Crohn's disease: a boon for the workforce

The neurological manifestations of Crohn's disease and its prevalence are not well known. Here, we report five patients of confirmed Crohn's disease with different neurological presentations. The neurological presentations include anterior ischemic optic neuropathy, myelopathy, posterior reversible encephalopathy syndrome, chronic inflammatory demyelinating polyneuropathy, and chronic axonal sensory and motor polyneuropathy. These manifestations should be kept in mind in the assessment of Crohn's disease.

Manipulation of Gut Microbiota Influences Immune Responses, Axon Preservation, and Motor Disability in a Model of Progressive Multiple Sclerosis

Gut microbiota dysbiosis has been implicated in MS and other immune diseases, although it remains unclear how manipulating the gut microbiota may affect the disease course. Using a well-established model of progressive MS triggered by intracranial infection with Theiler's murine encephalomyelitis virus (TMEV), we sought to determine whether dysbiosis induced by oral antibiotics (ABX) administered on pre-symptomatic and symptomatic phases of the disease influences its course. We also addressed the effects of microbiota recolonization after ABX withdrawn in the presence or absence of probiotics. Central and peripheral immunity, plasma acetate and butyrate levels, axon damage and motor disability were evaluated. The cocktail of ABX prevented motor dysfunction and limited axon damage in mice, which had fewer CD4⁺ and CD8⁺ T cells in the CNS, while gut microbiota recolonization worsened motor function and axonal integrity. The underlying mechanisms of ABX protective effects seem to involve CD4⁺CD39⁺ T cells and CD5⁺CD1d⁺ B cells into the CNS. In addition, microglia adopted a round amoeboid morphology associated to an anti-inflammatory gene profile in the spinal cord of TMEV mice administered ABX. The immune changes in the spleen and mesenteric lymph nodes were modest, yet ABX treatment of mice limited IL-17 production ex vivo. Collectively, our results provide evidence of the functional relevance of gut microbiota manipulation on the neurodegenerative state and disease severity in a model of progressive MS and reinforce the role of gut microbiota as target for MS treatment.

The Gut-Microglia Connection: Implications for Central Nervous System Diseases

The importance of the gut microbiome in central nervous system (CNS) diseases has long been recognized; however, research into this connection is limited, in part, owing to a lack of convincing mechanisms because the brain is a distant target of the gut. Previous studies on the brain revealed that most of the CNS diseases affected by the gut microbiome are closely associated with microglial dysfunction. Microglia, the major CNS-resident macrophages, are crucial for the immune response of the CNS against infection and injury, as well as for brain development and function. However, the current understanding of the mechanisms controlling the maturation and function of microglia is obscure, especially regarding the extrinsic factors affecting microglial function during the developmental process. The gut microflora has been shown to significantly influence microglia from before birth until adulthood, and the metabolites generated by the microbiota regulate the inflammation response mediated by microglia in the CNS; this inspired our hypothesis that microglia act as a critical mediator between the gut microbiome and CNS diseases. Herein, we highlight and discuss current findings that show the influence of host microbiome, as a crucial extrinsic factor, on microglia within the CNS. In addition, we summarize the CNS diseases associated with both the host microbiome and microglia and explore the potential pathways by which the gut bacteria influence the pathogenesis of CNS diseases. Our work is thus a comprehensive theoretical foundation for studies on the gut-microglia connection in the development of CNS diseases; and provides great potential for researchers to target pathways associated with the gut-microglia connection and overcome CNS diseases.

Emerging Role of Diet and Microbiota Interactions in Neuroinflammation

Commensal gut microbiota exerts multifarious effects on intestinal and extra-intestinal immune homeostasis. A disruption in the microbial composition of the gut has been associated with many neurological disorders with inflammatory components. Here we review known associations between gut microbiota and neurological disorders. Further we highlight the emerging role of diet and microbiota interrelationship in regulating neuroinflammation.

Altered gastrointestinal motility involving autoantibodies in the experimental autoimmune encephalomyelitis model of multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system that, in addition to motor, sensory, and cognitive symptoms, also causes constipation, which is poorly understood. Here, we characterize gastrointestinal (GI) dysmotility in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS and evaluate whether autoantibodies target the enteric nervous system (ENS) and cause dysmotility.

METHODS

EAE was induced in male SJL and B6 mice. GI motility was assessed in vivo and ex vivo in wild type (WT) and B cell-deficient mice. MS and EAE serum was used to survey potential targets in the ENS and changes in the ENS structure were characterized using immunohistochemistry.

KEY RESULTS

EAE mice developed accelerated gastric emptying and delayed whole GI transit with reduced colonic motility. Fecal water content was reduced, and colonic migrating myoelectrical complexes (CMMC) and slow waves were less frequent. Colons from EAE mice exhibited decreased GFAP levels in glia. Sera from MS patients and from EAE mice targeted ENS neurons and glia. B-cell deficiency in EAE protected against colonic dysmotility.

CONCLUSIONS & INFERENCES

Consistent with symptoms experienced in MS, we demonstrate that EAE mice widely exhibit features of GI dysmotility that persisted in the absence of extrinsic innervation, suggesting direct involvement of ENS neurocircuitry. The absence of GI dysmotility in B cell-deficient mice with EAE together with EAE and MS serum immunoreactivity against ENS targets suggests that MS could be classified among other diseases known to induce autoimmune GI dysmotility.

Metformin Alters Gut Microbiota of Healthy Mice: Implication for Its Potential Role in Gut Microbiota Homeostasis

In recent years, the first-line anti-diabetic drug metformin has been shown to be also useful for the treatment of other diseases like cancer. To date, few reports were about the impact of metformin on gut microbiota. To fully understand the mechanism of action of metformin in treating diseases other than diabetes, it is especially important to investigate the impact of long-term metformin treatment on the gut microbiome in non-diabetic status. In this study, we treated healthy mice with metformin for 30 days, and observed 46 significantly changed gut microbes by using the 16S rRNA-based microbiome profiling technique. We found that microbes from the Verrucomicrobiaceae and Prevotellaceae classes were enriched, while those from Lachnospiraceae and Rhodobacteraceae were depleted. We further compared the altered microbiome profile with the profiles under various disease conditions using our recently developed comparative microbiome tool known as MicroPattern. Interestingly, the treatment of diabetes patients with metformin positively correlates with colon cancer and type 1 diabetes, indicating a confounding effect on the gut microbiome in patients with diabetes. However, the treatment of healthy mice with metformin exhibits a negative correlation with multiple inflammatory diseases, indicating a protective anti-inflammatory role of metformin in non-diabetes status. This result underscores the potential effect of metformin on gut microbiome homeostasis, which may contribute to the treatment of non-diabetic diseases.

Gut dysbiosis and neuroimmune responses to brain infection with Theiler's murine encephalomyelitis virus

Recent studies have begun to point out the contribution of microbiota to multiple sclerosis (MS) pathogenesis. Theiler's murine encephalomyelitis virus induced demyelinating disease (TMEV-IDD) is a model of progressive MS. Here, we first analyze the effect of intracerebral infection with TMEV on commensal microbiota and secondly, whether the early microbiota depletion influences the immune responses to TMEV on the acute phase (14 dpi) and its impact on the chronic phase (85 dpi). The intracranial inoculation of TMEV was associated with a moderate dysbiosis. The oral administration of antibiotics (ABX) of broad spectrum modified neuroimmune responses to TMEV dampening brain CD4⁺ and CD8⁺ T infiltration during the acute phase. The expression of cytokines, chemokines and VP2 capsid protein was enhanced and accompanied by clusters of activated microglia disseminated throughout the brain. Furthermore, ABX treated mice displayed lower levels of CD4⁺ and CD8⁺T cells in cervical and mesenteric lymph nodes. Increased mortality to TMEV was observed after ABX cessation at day 28pi. On the chronic phase, mice that survived after ABX withdrawal and recovered microbiota diversity showed subtle changes in brain cell infiltrates, microglia and gene expression of cytokines. Accordingly, the surviving mice of the group ABX-TMEV displayed similar disease severity than TMEV mice.

Does the Gut Microbiota Influence Immunity and Inflammation in Multiple Sclerosis Pathophysiology?

Aim. Evaluation of the impact of gut microflora on the pathophysiology of MS. Results. The etiopathogenesis of MS is not fully known. Gut microbiota may be of a great importance in the pathogenesis of MS, since recent findings suggest that substitutions of certain microbial population in the gut can lead to proinflammatory state, which can lead to MS in humans. In contrast, other commensal bacteria and their antigenic products may protect against inflammation within the central nervous system. The type of intestinal flora is affected by antibiotics, stress, or diet. The effects on MS through the intestinal microflora can also be achieved by antibiotic therapy and Lactobacillus. EAE, as an animal model of MS, indicates a strong influence of the gut microbiota on the immune system and shows that disturbances in gut physiology may contribute to the development of MS. Conclusions. The relationship between the central nervous system, the immune system, and the gut microbiota relates to the influence of microorganisms in the development of MS. A possible interaction between gut microbiota and the immune system can be perceived through regulation by the endocannabinoid system. It may offer an opportunity to understand the interaction comprised in the gut-immune-brain axis.

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.

Autism spectrum disorders and intestinal microbiota

Through extensive microbial-mammalian co-metabolism, the intestinal microbiota have evolved to exert a marked influence on health and disease via gut-brain-microbiota interactions. In this addendum, we summarize the findings of our recent study on the fecal microbiota and metabolomes of children with pervasive developmental disorder-not otherwise specified (PDD-NOS) or autism (AD) compared with healthy children (HC). Children with PDD-NOS or AD have altered fecal microbiota and metabolomes (including neurotransmitter molecules). We hypothesize that the degree of microbial alteration correlates with the severity of the disease since fecal microbiota and metabolomes alterations were higher in children with PDD-NOS and, especially, AD compared to HC. Our study indicates that the levels of free amino acids (FAA) and volatile organic compounds (VOC) differ in AD subjects compared to children with PDD-NOS, who are more similar to HC. Finally, we propose a new perspective on the implications for the interaction between intestinal microbiota and AD.

The role of microbiome in central nervous system disorders

Mammals live in a co-evolutionary association with the plethora of microorganisms that reside at a variety of tissue microenvironments. The microbiome represents the collective genomes of these co-existing microorganisms, which is shaped by host factors such as genetics and nutrients but in turn is able to influence host biology in health and disease. Niche-specific microbiome, prominently the gut microbiome, has the capacity to effect both local and distal sites within the host. The gut microbiome has played a crucial role in the bidirectional gut-brain axis that integrates the gut and central nervous system (CNS) activities, and thus the concept of microbiome-gut-brain axis is emerging. Studies are revealing how diverse forms of neuro-immune and neuro-psychiatric disorders are correlated with or modulated by variations of microbiome, microbiota-derived products and exogenous antibiotics and probiotics. The microbiome poises the peripheral immune homeostasis and predisposes host susceptibility to CNS autoimmune diseases such as multiple sclerosis. Neural, endocrine and metabolic mechanisms are also critical mediators of the microbiome-CNS signaling, which are more involved in neuro-psychiatric disorders such as autism, depression, anxiety, stress. Research on the role of microbiome in CNS disorders deepens our academic knowledge about host-microbiome commensalism in central regulation and in practicality, holds conceivable promise for developing novel prognostic and therapeutic avenues for CNS disorders.