Multiple sclerosis, the microbiome, TLR2, and the hygiene hypothesis

Mendelian randomization identifies proteins involved in neurodegenerative diseases

Proteins are involved in multiple biological functions. High-throughput technologies have allowed the measurement of thousands of proteins in population biobanks. In this study, we aimed to identify proteins related to Alzheimer's disease, Parkinson's disease, multiple sclerosis and amyotrophic lateral sclerosis by leveraging large-scale genetic and proteomic data. We performed a two-sample cis Mendelian randomization study by selecting instrumental variables for the abundance of >2700 proteins measured by either Olink or SomaScan platforms in plasma from the UK Biobank and the deCODE Health Study. We also used the latest publicly available genome-wide association studies for the neurodegenerative diseases of interest. The potentially causal effect of proteins on neurodegenerative diseases was estimated based on the Wald ratio. We tested 13 377 protein-disease associations, identifying 169 associations that were statistically significant (5% false discovery rate). Evidence of co-localization between plasma protein abundance and disease risk (posterior probability > 0.80) was identified for 61 protein-disease pairs, leading to 50 unique protein-disease associations. Notably, 23 of 50 protein-disease associations corresponded to genetic loci not previously reported by genome-wide association studies. The two-sample Mendelian randomization and co-localization analysis also showed that APOE abundance in plasma was associated with three subcortical volumes (hippocampus, amygdala and nucleus accumbens) and white matter hyper-intensities, whereas PILRA and PILRB abundance in plasma was associated with caudate nucleus volume. Our study provided a comprehensive assessment of the effect of the human proteome that is currently measurable through two different platforms on neurodegenerative diseases. The newly associated proteins indicated the involvement of complement (C1S and C1R), microglia (SIRPA, SIGLEC9 and PRSS8) and lysosomes (CLN5) in Alzheimer's disease; the interleukin-6 pathway (CTF1) in Parkinson's disease; lysosomes (TPP1), blood-brain barrier integrity (MFAP2) and astrocytes (TNFSF13) in amyotrophic lateral sclerosis; and blood-brain barrier integrity (VEGFB), oligodendrocytes (PARP1), node of Ranvier and dorsal root ganglion (NCS1, FLRT3 and CDH15) and the innate immune system (CR1, AHSG and WARS) in multiple sclerosis. Our study demonstrates how harnessing large-scale genomic and proteomic data can yield new insights into the role of the plasma proteome in the pathogenesis of neurodegenerative diseases.

Activation of NR2A-Wnt-TLR2 Signaling Axis in Satellite Glial Cells of the Dorsal Root Ganglion Contributes to Neuropathic Pain Induced by Nerve Injury in Diabetic Mice

Diabetic peripheral neuropathic pain (DPNP), a common diabetic mellitus (DM) complication, may result from the activation of satellite glial cells (SGCs) in the dorsal root ganglion (DRG), potentially enhancing peripheral sensitization. The N-methyl-D-aspartate receptor (NMDAR) subtype NR2A and Toll-like receptor (TLR)2 play key roles in neuroimmune interactions. However, their roles in SGCs of DRG and the precise mechanisms mediating peripheral sensitization in DPNP remain unclear. Here, we found that the expression of glial fibrillary acidic protein (GFAP), NR2A, and TLR2 in SGCs from DRG significantly increased under increased glucose and NMDA stimulation in vitro. Additionally, upregulation of interleukin (IL)-6 and nerve growth factor (NGF) was observed. Notably, lentivirus-induced NR2A knockdown (KD) and C29 (TLR2 inhibitor) significantly blocked the above SGCs changes induced by NMDA and increased glucose. Behavior tests showed mechanical and thermal sensitivities induced by sciatic nerve ligation (SNL) were more obvious in DM background related to streptozotocin (STZ) injection than non-DM background mice, which were significantly alleviated by NR2A conditional knockout (CKO) in SGCs and TLR2 KO. Moreover, immunofluorescence (IF) results revealed the co-expression of NR2A and TLR2 in neurons and SGCs in the DRG. Following SNL in DM mice, the upregulation of NR2A, TLR2, GFAP, β-catenin, p-GSK-3β, p-nuclear factor kappa (NF-κ)-B, IL-6, NGF, Bcl-2-associated X protein (Bax), and Caspase 3, and the significant downregulation of Bcl-2 were consistent with the changes observed after increased glucose and NMDA treatment. The upregulation of TLR2 was blocked by NR2A CKO and Wnt signal pathway inhibition. Additionally, the activation of SGCs, upregulated IL-6 as well as NGF secretion and increased apoptosis, associated with nerve injury in DM background were altered by TLR2 KO and NF-κB pathway inhibition. In conclusion, the activation of the NR2A-Wnt-TLR2 signaling axis mediated peripheral sensitization in the DRG by influencing SGCs' activation, and the synthesis and secretion of pro-inflammatory cytokines and NGF, promoting SGCs' apoptosis, thus exacerbating a peripheral nerve injury related-NP in DM background. Our study provided insights into the role of NR2A-Wnt-TLR2 signaling axis of SGCs in mediating the generation and maintenance of DPNP and suggested targeting this signaling axis may be a promising therapeutic approach for DPNP.

Exploring the hub Genes and Potential Mechanisms of Complement system-related Genes in Parkinson Disease: Based on Transcriptome Sequencing and Mendelian Randomization

An accurate diagnosis of Parkinson's disease (PD) remains challenging and the exact cause of the disease is unclean. The aims are to identify hub genes associated with the complement system in PD and to explore their underlying molecular mechanisms. Initially, differentially expressed genes (DEGs) and key module genes related to PD were mined through differential expression analysis and WGCNA. Then, differentially expressed CSRGs (DE-CSRGs) were obtained by intersecting the DEGs, key module genes and CSRGs. Subsequently, MR analysis was executed to identify genes causally associated with PD. Based on genes with significant MR results, the expression level and diagnostic performance verification were achieved to yield hub genes. Functional enrichment and immune infiltration analyses were accomplished to insight into the pathogenesis of PD. qRT-PCR was employed to evaluate the expression levels of hub genes. After MR analysis and related verification, CD93, CTSS, PRKCD and TLR2 were finally identified as hub genes. Enrichment analysis indicated that the main enriched pathways for hub genes. Immune infiltration analysis found that the hub genes showed significant correlation with a variety of immune cells (such as myeloid-derived suppressor cell and macrophage). In the qRT-PCR results, the expression levels of CTSS, PRKCD and TLR2 were consistent with those we obtained from public databases. Hence, we mined four hub genes associated with complement system in PD which provided novel perspectives for the diagnosis and treatment of PD.

Mycobacterium paratuberculosis: A HERV Turn-On for Autoimmunity, Neurodegeneration, and Cancer?

Human endogenous retroviruses (HERVs) are remnants of ancient retroviral infections that, over millions of years, became integrated into the human genome. While normally inactive, environmental stimuli such as infections have contributed to the transcriptional reactivation of HERV-promoting pathological conditions, including the development of autoimmunity, neurodegenerative disease and cancer. What infections trigger HERV activation? Mycobacterium avium subspecies paratuberculosis (MAP) is a pluripotent driver of human disease. Aside from granulomatous diseases, Crohn's disease, sarcoidosis and Blau syndrome, MAP is associated with autoimmune disease: type one diabetes (T1D), multiple sclerosis (MS), rheumatoid arthritis (RA) and autoimmune thyroiditis. MAP is also associated with Alzheimer's disease (AD) and Parkinson's disease (PD). Autoimmune diabetes, MS and RA are the diseases with the strongest MAP/HERV association. There are several other diseases associated with HERV activation, including diseases whose epidemiology and/or pathology would prompt speculation for a causal role of MAP. These include non-solar uveal melanoma, colon cancer, glioblastoma and amyotrophic lateral sclerosis (ALS). This article further points to MAP infection as a contributor to autoimmunity, neurodegenerative disease and cancer via the un-silencing of HERV. We examine the link between the ever-increasing number of MAP-associated diseases and the MAP/HERV intersection with these diverse medical conditions, and propose treatment opportunities based upon this association.

The known and unknown of post-pump chorea: a case report on robust steroid responsiveness implicating occult neuroinflammation

Post-pump chorea (PPC) is characterized by the development of choreiform movements following cardiopulmonary bypass (CPB) surgery. PPC occurs almost exclusively in children, and its pathophysiology remains unclear. Here we present an adult case of PPC after bovine aortic valve replacement (AVR) which exhibited dramatic and reproducible response to steroid, suggesting the presence of occult neuroinflammation. This observation suggests a novel underlying mechanism in certain subgroups of PPC, which is likely a heterogeneous condition to start with. Further research into the pathomechanisms of PPC could offer insights into managing this otherwise symptomatic control-only condition.

Key Genes in Olfactory Disorder in Experimental Autoimmune Encephalomyelitis Identified by Transcriptomic Analysis of the Olfactory Bulbs

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis that shows demyelination in the central nervous system and functional deficits, including olfactory impairment. However, the genes related to olfactory impairment in EAE are unknown. We evaluated hub genes of the olfactory bulb in EAE mice. Differentially expressed genes (cut-offs, fold change > 2 and adjusted p < 0.05) and their related pathways in olfactory bulbs were subjected to gene ontology (GO) pathway analysis, gene set enrichment analysis (GSEA). Protein-protein interactions with selected genes were evaluated using the Search Tool for the Retrieval of Interacting Genes/Proteins. Gene regulatory networks (GRNs) which were constructed at the post-transcriptional level, including the genes-transcription factors (TFs) and gene-microRNAs (miRNAs) interaction networks. Twelve hub genes were found, three of which (Ctss, Itgb2, and Tlr2) were validated by RT-qPCR to be related to GO pathways such as immune response and regulation of immune response. GSEA showed that neuron-related genes-including Atp6v1g2, Egr1, and Gap43-and their pathways were significantly downregulated. GRNs analysis of six genes (Ctss, Itgb2, Tlr2, Atp6v1g2, Egr1, and Gap43) revealed 37 TFs and 84 miRNAs were identified as potential regulators of six genes, indicating significant interaction among six genes, TFs, and miRNAs. Collectively, these results suggest that transcriptomic analysis of the olfactory bulb of EAE mice can provide insight into olfactory dysfunction and reveal therapeutic targets for olfactory impairment.

How to and should we target EBV in MS?

INTRODUCTION

The etiology of multiple sclerosis (MS) remains unknown. Pathogenesis likely relies on a complex interaction between multiple environmental, genetic, and behavioral risk factors. However, a growing body of literature supports the role of a preceding Epstein-Barr virus (EBV) infection in the majority of cases.

AREAS COVERED

In this narrative review, we summarize the latest findings regarding the potential role of EBV as a predisposing event inducing new onset of MS. EBV interactions with the genetic background and other infectious agents such as human endogenous retrovirus are explored. Additional data regarding the role of EBV regarding the rate of mid- and long-term disease progression is also discussed. Lastly, the effect of currently approved disease-modifying therapies (DMT) for MS treatment on the EBV-based molecular mechanisms and the development of new EBV-specific therapies are further reviewed.

EXPERT OPINION

Recent strong epidemiological findings support that EBV may be the primary inducing event in certain individuals that shortly thereafter develop MS. More studies are needed in order to better understand the significant variability in susceptibility based on environmental factors such as EBV exposure. Future investigations should focus on determining the specific EBV-related risk antigen(s) and phenotyping people with likely EBV-induced MS. Targeting EBV via several different avenues, including development of an EBV vaccine, may become the mainstay of MS treatment in the future.

Microbiome-derived bacterial lipids regulate gene expression of proinflammatory pathway inhibitors in systemic monocytes

How the microbiome regulates responses of systemic innate immune cells is unclear. In the present study, our purpose was to document a novel mechanism by which the microbiome mediates crosstalk with the systemic innate immune system. We have identified a family of microbiome Bacteroidota-derived lipopeptides-the serine-glycine (S/G) lipids, which are TLR2 ligands, access the systemic circulation, and regulate proinflammatory responses of splenic monocytes. To document the role of these lipids in regulating systemic immunity, we used oral gavage with an antibiotic to decrease the production of these lipids and administered exogenously purified lipids to increase the systemic level of these lipids. We found that decreasing systemic S/G lipids by decreasing microbiome Bacteroidota significantly enhanced splenic monocyte proinflammatory responses. Replenishing systemic levels of S/G lipids via exogenous administration returned splenic monocyte responses to control levels. Transcriptomic analysis demonstrated that S/G lipids regulate monocyte proinflammatory responses at the level of gene expression of a small set of upstream inhibitors of TLR and NF-κB pathways that include Trem2 and Irf4. Consistent with enhancement in proinflammatory cytokine responses, decreasing S/G lipids lowered gene expression of specific pathway inhibitors. Replenishing S/G lipids normalized gene expression of these inhibitors. In conclusion, our results suggest that microbiome-derived S/G lipids normally establish a level of buffered signaling activation necessary for well-regulated innate immune responses in systemic monocytes. By regulating gene expression of inflammatory pathway inhibitors such as Trem2, S/G lipids merit broader investigation into the potential dysfunction of other innate immune cells, such as microglia, in diseases such as Alzheimer's disease.

Game of microbes: the battle within - gut microbiota and multiple sclerosis

Multiple sclerosis (MS) is a chronic and progressive autoimmune disease of the central nervous system (CNS), with both genetic and environmental factors contributing to the pathobiology of the disease. While human leukocyte antigen (HLA) genes have emerged as the strongest genetic factor, consensus on environmental risk factors are lacking. Recently, trillions of microbes residing in our gut (microbiome) have emerged as a potential environmental factor linked with the pathobiology of MS as PwMS show gut microbial dysbiosis (altered gut microbiome). Thus, there has been a strong emphasis on understanding the factors (host and environmental) regulating the composition of the gut microbiota and the mechanism(s) through which gut microbes contribute to MS disease, especially through immune system modulation. A better understanding of these interactions will help harness the enormous potential of the gut microbiota as a therapeutic approach to treating MS.

Metagenome-wide association study of gut microbiome features for myositis

PURPOSE

The clinical relevance and pathogenic role of gut microbiome in both myositis and its associated interstitial lung disease (ILD) are still unclear. The purpose of this study was to investigate the role of gut microbiome in myositis through comprehensive metagenomic-wide association studies (MWAS).

METHODS

We conducted MWAS of the myositis gut microbiome in a Chinese cohort by using whole-genome shotgun sequencing of high depth, including 30 myositis patients and 31 healthy controls (HC). Among the myositis patients, 11 developed rapidly progressive interstitial lung disease (RP-ILD) and 10 had chronic ILD (C-ILD).

RESULTS

Analysis for overall distribution level of the bacteria showed Alistipes onderdonkii, Parabacteroides distasonis and Escherichia coli were upregulated, Lachnospiraceae bacterium GAM79, Roseburia intestinalis, and Akkermansia muciniphila were downregulated in patients with myositis compared to HC. Bacteroides thetaiotaomicron, Parabacteroides distasonis and Escherichia coli were upregulated, Bacteroides A1C1 and Bacteroides xylanisolvens were downregulated in RP-ILD cases compared with C-ILD cases. A variety of biological pathways related to metabolism were enriched in the myositis and HC, RP-ILD and C-ILD comparison. And in the analyses for microbial contribution in metagenomic biological pathways, we have found that E. coli played an important role in the pathway expression in both myositis group and myositis-associated RP-ILD group. Anti-PL-12 antibody, anti-Ro-52 antibody, and anti-EJ antibody were found to have positive correlation with bacterial diversity (Shannon-wiener diversity index and Chao1, richness estimator) between myositis group and control groups. The combination of E. coli and R. intestinalis could distinguish myositis group from HC effectively. R. intestinalis can also be applied in the distinguishment of RP-ILD group vs. C-ILD group in myositis patients.

CONCLUSION

Our MWAS study first revealed the link between gut microbiome and pathgenesis of myositis, which may help us understand the role of gut microbiome in the etiology of myositis and myositis-associated RP-ILD.

An Update on Toll-like Receptor 2, Its Function and Dimerization in Pro- and Anti-Inflammatory Processes

While a certain level of inflammation is critical for humans to survive infection and injury, a prolonged inflammatory response can have fatal consequences. Pattern recognition Toll-like receptors (TLRs) are key players in the initiation of an inflammatory process. TLR2 is one of the most studied pattern recognition receptors (PRRs) and is known to form heterodimers with either TLR1, TLR4, TLR6, and TLR10, allowing it to recognize a wide range of pathogens. Although a large number of studies have been conducted over the past decades, there are still many unanswered questions regarding TLR2 mechanisms in health and disease. In this review, we provide an up-to-date overview of TLR2, including its homo- and heterodimers. Furthermore, we will discuss the pro- and anti-inflammatory properties of TLR2 and recent findings in prominent TLR2-associated infectious and neurodegenerative diseases.

Conditioning of the immune system by the microbiome

The human intestinal microbiome has coevolved with its host to establish a stable homeostatic relationship with hallmark features of mutualistic symbioses, yet the mechanistic underpinnings of host-microbiome interactions are incompletely understood. Thus, it is an opportune time to conceive a common framework for microbiome-mediated regulation of immune function. We propose the term conditioned immunity to describe the multifaceted mechanisms by which the microbiome modulates immunity. In this regard, microbial colonization is a conditioning exposure that has durable effects on immune function through the action of secondary metabolites, foreign molecular patterns, and antigens. Here, we discuss how spatial niches impact host exposure to microbial products at the level of dose and timing, which elicit diverse conditioned responses.

Mycobacterium avium subsp. paratuberculosis Antigens Elicit a Strong IgG4 Response in Patients with Multiple Sclerosis and Exacerbate Experimental Autoimmune Encephalomyelitis

Neuroinflammation can be triggered by microbial products disrupting immune regulation. In this study, we investigated the levels of IgG1, IgG2, IgG3, and IgG4 subclasses against the heat shock protein (HSP)70_533-545 peptide and lipopentapeptide (MAP_Lp5) derived from Mycobacterium avium subsp. paratuberculosis (MAP) in the blood samples of Japanese and Italian individuals with relapsing remitting multiple sclerosis (MS). Additionally, we examined the impact of this peptide on MOG-induced experimental autoimmune encephalomyelitis (EAE). A total of 130 Japanese and 130 Italian subjects were retrospectively analyzed using the indirect ELISA method. Furthermore, a group of C57BL/6J mice received immunization with the MAP_HSP70_533-545 peptide two weeks prior to the active induction of MOG_35-55 EAE. The results revealed a significantly robust antibody response against MAP_HSP70_533-545 in serum of both Japanese and Italian MS patients compared to their respective control groups. Moreover, heightened levels of serum IgG4 antibodies specific to MAP antigens were correlated with the severity of the disease. Additionally, EAE mice that were immunized with MAP_HSP70_533-545 peptide exhibited more severe disease symptoms and increased reactivity of MOG_35-55-specific T-cell compared to untreated mice. These findings provide evidence suggesting a potential link between MAP and the development or exacerbation of MS, particularly in a subgroup of MS patients with elevated serum IgG4 levels.

Role of Microglial Cells in the Pathophysiology of MS: Synergistic or Antagonistic?

Many studies indicate an important role of microglia and their cytokines in the pathophysiology of multiple sclerosis (MS). Microglia are the macrophages of the central nervous system (CNS). They have many functions, such as being "controllers" of the CNS homeostasis in pathological and healthy conditions, playing a key role in the active immune defense of the CNS. Macroglia exhibit a dual role, depending on the phenotype they adopt. First, they can exhibit neurotoxic effects, which are harmful in the case of MS. However, they also show neuroprotective and regenerative effects in this disease. Many of the effects of microglia are mediated through the cytokines they secrete, which have either positive or negative properties. Neurotoxic and pro-inflammatory effects can be mediated by microglia via lipopolysaccharide and gamma interferon. On the other hand, the mediators of anti-inflammatory and protective effects secreted by microglia can be, for example, interleukin-4 and -13. Further investigation into the role of microglia in MS pathophysiology may perhaps lead to the discovery of new therapies for MS, as recent research in this area has been very promising.

Mechanisms of Toll-like receptor tolerance induced by microbial ligands

Some microorganisms can develop tolerance. On the one hand, it allows pathogenic microbes to escape immune surveillance, on the other hand, it provides the possibility to microbiota representatives to colonize different biotopes and build a symbiotic relationship with the host. Complex regulatory interactions between innate and adaptive immune systems as well as stimulation by antigens help microbes control and maintain immunological tolerance. An important role in this process belongs to innate immune cells, which recognize microbial components through pattern-recognition receptors. Toll-like receptors (TLRs) represent the main class of these receptors. Despite the universality of the activated signaling pathways, different cellular responses are induced by interaction of TLRs with microbiota representatives and pathogenic microbes, and they vary during acute and chronic infection. The research on mechanisms underlying the development of TLR tolerance is significant, as the above receptors are involved in a wide range of infectious and noninfectious diseases; they also play an important role in development of allergic diseases, autoimmune diseases, and cancers. The knowledge of TLR tolerance mechanisms can be critically important for development of TLR ligand-based therapeutic agents for treatment and prevention of multiple diseases.

Microbiome-Induced Autoimmunity and Novel Therapeutic Intervention

Microorganisms' flora, which colonize in many parts of our body, stand out as one of the most important components for a healthy life. This microbial organization called microbiome lives in integration with the body as a single and whole organ/system. Perhaps, the human first encounters the microbial activity it carries through the immune system. This encounter and interaction are vital for the development of immune system cells that protect the body against pathogenic organisms and infections throughout life. In recent years, it has been determined that some disruptions in the host-microbiome interaction play an important role in the physiopathology of autoimmune diseases. Although the details of this interaction have not been clarified yet, the focus is on leaky gut syndrome, dysbiosis, toll-like receptor ligands, and B cell dysfunction. Nutritional regulations, prebiotics, probiotics, fecal microbiota transplantation, bacterial engineering, and vaccination are being investigated as new therapeutic approaches in the treatment of problems in these areas. This article reviews recent research in this area.

Biological Properties and Health-Promoting Functions of Laminarin: A Comprehensive Review of Preclinical and Clinical Studies

Marine algal species comprise of a large portion of polysaccharides which have shown multifunctional properties and health benefits for treating and preventing human diseases. Laminarin, or β-glucan, a storage polysaccharide from brown algae, has been reported to have potential pharmacological properties such as antioxidant, anti-tumor, anti-coagulant, anticancer, immunomodulatory, anti-obesity, anti-diabetic, anti-inflammatory, wound healing, and neuroprotective potential. It has been widely investigated as a functional material in biomedical applications as it is biodegradable, biocompatible, and is low toxic substances. The reported preclinical and clinical studies demonstrate the potential of laminarin as natural alternative agents in biomedical and industrial applications such as nutraceuticals, pharmaceuticals, functional food, drug development/delivery, and cosmeceuticals. This review summarizes the biological activities of laminarin, including mechanisms of action, impacts on human health, and reported health benefits. Additionally, this review also provides an overview of recent advances and identifies gaps and opportunities for further research in this field. It further emphasizes the molecular characteristics and biological activities of laminarin in both preclinical and clinical settings for the prevention of the diseases and as potential therapeutic interventions.

Risk Factors from Pregnancy to Adulthood in Multiple Sclerosis Outcome

Multiple sclerosis (MS) is an autoimmune disease characterized by a robust inflammatory response against myelin sheath antigens, which causes astrocyte and microglial activation and demyelination of the central nervous system (CNS). Multiple genetic predispositions and environmental factors are known to influence the immune response in autoimmune diseases, such as MS, and in the experimental autoimmune encephalomyelitis (EAE) model. Although the predisposition to suffer from MS seems to be a multifactorial process, a highly sensitive period is pregnancy due to factors that alter the development and differentiation of the CNS and the immune system, which increases the offspring’s susceptibility to develop MS. In this regard, there is evidence that thyroid hormone deficiency during gestation, such as hypothyroidism or hypothyroxinemia, may increase susceptibility to autoimmune diseases such as MS. In this review, we discuss the relevance of the gestational period for the development of MS in adulthood.

Gut microbiome-derived glycine lipids are diet-dependent modulators of hepatic injury and atherosclerosis

Oral and gut Bacteroidetes produce unique classes of serine-glycine lipodipeptides and glycine aminolipids that signal through host Toll-like receptor 2. These glycine lipids have also been detected in human arteries, but their effects on atherosclerosis are unknown. Here, we sought to investigate the bioactivity of bacterial glycine lipids in mouse models of atherosclerosis. Lipid 654 (L654), a serine-glycine lipodipeptide species, was first tested in a high-fat diet (HFD)-fed Ldlr-/- model of atherosclerosis. Intraperitoneal administration of L654 over 7 weeks to HFD-fed Ldlr-/- mice resulted in hypocholesterolemic effects and significantly attenuated the progression of atherosclerosis. We found that L654 also reduced liver inflammatory and extracellular matrix gene expression, which may be related to inhibition of macrophage activation as demonstrated in vivo by lower major histocompatibility complex class II gene expression and confirmed in cell experiments. In addition, L654 and other bacterial glycine lipids in feces, liver, and serum were markedly reduced alongside changes in Bacteroidetes relative abundance in HFD-fed mice. Finally, we tested the bioactivities of L654 and related lipid 567 in chow-fed Apoe-/- mice, which displayed much higher fecal glycine lipids relative to HFD-fed Ldlr-/- mice. Administration of L654 or lipid 567 for 7 weeks to these mice reduced the liver injury marker alanine aminotransferase, but other effects seen in Ldlr-/- were not observed. Therefore, we conclude that conditions in which gut microbiome-derived glycine lipids are lost, such as HFD, may exacerbate the development of atherosclerosis and liver injury, whereas correction of such depletion may protect from these disorders.

Multiple Sclerosis and Microbiome

The composition of microbiota and the gut-brain axis is increasingly considered a factor in the development of various pathological conditions. The etiology of multiple sclerosis (MS), a chronic autoimmune disease affecting the CNS, is complex and interactions within the gut-brain axis may be relevant in the development and the course of MS. In this article, we focus on the relationship between gut microbiota and the pathophysiology of MS. We review the contribution of germ-free mouse studies to our understanding of MS pathology and its implications for treatment strategies to modulate the microbiome in MS. This summary highlights the need for a better understanding of the role of the microbiota in patients’ responses to disease-modifying drugs in MS and disease activity overall.

Leveraging diet to engineer the gut microbiome

Autoimmune diseases, including inflammatory bowel disease, multiple sclerosis and rheumatoid arthritis, have distinct clinical presentations but share underlying patterns of gut microbiome perturbation and intestinal barrier dysfunction. Their potentially common microbial drivers advocate for treatment strategies aimed at restoring appropriate microbiome function, but individual variation in host factors makes a uniform approach unlikely. In this Perspective, we consolidate knowledge on diet-microbiome interactions in local inflammation, gut microbiota imbalance and host immune dysregulation. By understanding and incorporating the effects of individual dietary components on microbial metabolic output and host physiology, we examine the potential for diet-based therapies for autoimmune disease prevention and treatment. We also discuss tools targeting the gut microbiome, such as faecal microbiota transplantation, probiotics and orthogonal niche engineering, which could be optimized using custom dietary interventions. These approaches highlight paths towards leveraging diet for precise engineering of the gut microbiome at a time of increasing autoimmune disease.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

A global view of comorbidity in multiple sclerosis: a systematic review with a focus on regional differences, methodology, and clinical implications

Multiple sclerosis (MS) is a chronic autoimmune disorder of the central nervous system which is associated with numerous comorbidities. These include cardiovascular disease, psychiatric and neurologic disturbances, restless leg syndrome, migraine, cancer, autoimmune diseases, and metabolic disorders. Comorbid disease is an important consideration for clinicians treating patients with MS; early presentation of comorbidities can obscure or delay MS diagnosis, as well as significantly impacting the disease course. Improved understanding of comorbidities and their emergence in MS populations is important for improving the quality of life and optimizing treatment for patients. Therefore, we evaluated published studies reporting epidemiologic data on comorbidities and their associated impact on disease progression in patients with MS (PwMS). The prevalence of neurologic, cardiovascular, metabolic, and autoimmune comorbidities was elevated in PwMS in general, and furthermore, this adversely affected a broad range of outcomes. Compared with PwMS, cancer rates in people without MS or the general population were lower, which should prompt further studies into the mechanisms of both diseases. Studies were under-represented in many regions owing to the latitudinal gradient of MS and possible underfunding of studies.

The potential of outdoor environments to supply beneficial butyrate-producing bacteria to humans

Butyrate is an important mediator of human health and disease. The mechanisms of action of butyrate are becoming increasingly well-known. Many commensal bacteria that inhabit the human gut can synthesise butyrate, which is then absorbed into the human host. Simultaneously, several immune- and inflammatory-mediated diseases are being linked to insufficient exposure to beneficial microbes from our environment, including butyrate-producing bacteria. However, the role of outdoor environmental exposure to butyrate-producing bacteria remains poorly understood. Here we review the literature on the human exposure pathways to butyrate-producing bacteria, with a particular focus on outdoor environmental sources (e.g. associated with plants, plant-based residues, and soil), and the health implications of exposure to them. Emerging evidence suggests that environmental butyrate-producers may help supplement the human gut microbiota and represent an important component of the Biodiversity and Old Friends hypotheses. Improving our understanding of potential sources, precursors, and exposure pathways of environmental butyrate-producers that influence the gut microbiota and butyrate production offers promise to advance multiple disciplines of health and environmental science. We outline research priorities to address knowledge gaps in the outdoor environment-butyrate-health nexus and build knowledge of the potential pathways to help optimise exposure to human-beneficial butyrate-producing bacteria from the outdoor environment during childhood and adulthood.

Hygiene hypothesis and autoimmune diseases: A narrative review of clinical evidences and mechanisms

Since the start of the "modern era", characterized by the increase in urbanization, a progressive attention to hygiene and autoimmune conditions has considerably grown. Although these diseases are often multifactorial, it was demonstrated that environment factors such as pollution, diet and lifestyles may play a crucial role together with genetic signature. Our research, based on the newest and most significant literature of this topic, highlights that the progressive depletion of microbes and parasites due to increased socioeconomic improvement, may lead to a derangement of immunoregulatory mechanisms. Moreover, special attention was given to the complex interplay between microbial agents, as gut microbiome, diet and vitamin D supplementation with the aim of identifying promising future therapeutic options. In conclusion, autoimmunity cannot be limited to hygiene-hypothesis, but from the point of view of precision medicine, this theory represents a fundamental element together with the study of genomics, the microbiome and proteomics, in order to understand the complex functioning of the immune system.

Early life exposures and the risk of inflammatory bowel disease: Systematic review and meta-analyses

BACKGROUND

Early life exposures impact immune system development and therefore the risk of immune-mediated diseases, including inflammatory bowel disease (IBD). We systematically reviewed the impact of pre-, peri‑, and postnatal exposures up to the age of five years on subsequent IBD diagnosis.

METHODS

We identified case-control and cohort studies reporting on the association between early life environmental factors and Crohn's disease (CD), ulcerative colitis (UC), or IBD overall. Databases were search from their inception until May 24th, 2019 until July 14th, 2020. We conducted meta-analyses for quantitative review of relevant risk factors that were comparable across studies and qualitative synthesis of the literature for a wide range of early life exposures, including maternal health and exposures during pregnancy, perinatal factors, birth month and related-factors, breastfeeding, hygiene-related factors and social factors, immigration, antibiotics, offspring health, including infections, and passive smoking. PROSPERO registration: CRD42019134980.

FINDINGS

Prenatal exposure to antibiotics (OR 1.8; 95% CI 1.2-2.5) and tobacco smoke (OR 1.5; 95% CI 1.2-1.9), and early life otitis media (OR 2.1; 95% CI 1.2-3.6) were associated with IBD. There was a trend towards an association between exposure to antibiotics in infancy and IBD (OR: 1.7, 95% CI 0.97, 2.9), supported by positive data on population-based data. Breastfeeding was protective against IBD. Other early life risk factors had no association with IBD, but data were limited and heterogenous.

INTERPRETATION

Early life is an important period of susceptibility for IBD development later in life. Tobacco smoke, infections and antibiotics were associated positively, and breastfeeding was associated negatively with IBD. Our findings offer an opportunity to develop primary prevention strategies.

FUNDING

This study did not receive any funding.

Plasma Interleukin-33 level in relapsing-remitting multiple sclerosis. Is it negatively correlated with central nervous system lesions in patients with mild disability?

BACKGROUND

Cytokines and chemokines are undoubtedly involved in the pathogenesis of multiple sclerosis (MS). There are many reports that suggest a significant role for Interleukin-33 (IL-33) in the course of MS development, but it is not clear whether negative or positive. We therefore investigated plasma IL-33 levels in patients with relapsing-remitting MS (RRMS).

METHODS

The study consisted of RRMS patients (n = 73) and healthy subjects (n = 54). Blood samples were taken from all and plasma IL-33 levels were then determined using an enzyme-linked immunosorbent assay method. Patients also underwent laboratory and imaging tests and their disability status was assessed.

RESULTS

Plasma IL-33 levels were marginally significantly higher in patients with RRMS (p = 0.07). Higher IL-33 levels are significantly associated with higher age (p = 0.01). There was also a statistically significant negative correlation between plasma IL-33 levels and the number of high signal intensity lesions in T2-weighted MRI (p = 0.03). After dividing the number of lesions into groups < 9 and ≥ 9 T2-weighted lesions, the Student's t-test for unrelated variables showed a negative correlation, but not statistically significant (p = 0.22), while the Spearman's correlation showed a marginally significant correlation (p = 0.06) between IL-33 level and number of T2-weighted lesions. IL-33 was also shown to have a significant ability to differentiate RRMS patients from healthy subjects with a sensitivity of 99% and specificity of 70% (p = 0.00).

CONCLUSIONS

Patients with RRMS have elevated plasma IL-33 levels. In RRMS patients with mild disability, high plasma levels of IL-33 may have neuroprotective effects potentially by stimulating remyelination and/or suppressing autoimmune inflammation and damage. Further studies on this matter on a larger number of patients are needed.

Gut dysbiosis during early life: causes, health outcomes, and amelioration via dietary intervention

The colonization and maturation of gut microbiota (GM) is a delicate and precise process, which continues to influence not only infancy and childhood but also adulthood health by affecting immunity. However, many perinatal factors, including gestational age, delivery mode, antibiotic administration, feeding mode, and environmental and maternal factors, can disturb this well-designed process, increasing the morbidity of various gut dysbiosis-related diseases, such as type-1-diabetes, allergies, necrotizing enterocolitis, and obesity. In this review, we discussed the early-life colonization and maturation of the GM, factors influencing this process, and diseases related to the disruption of this process. Moreover, we focused on discussing dietary interventions, including probiotics, oligosaccharides, nutritional supplementation, and exclusive enteral nutrition, in ameliorating early-life dysbiosis and diseases related to it. Furthermore, possible mechanisms, and shortcomings, as well as potential solutions to the drawbacks of dietary interventions, were also discussed.

Gut microbiota-microRNA interactions in ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic autoimmune inflammatory disability that is part of the rheumatic disease group of spondyloarthropathies. AS commonly influences the joints of the axial skeleton. The contributions to AS pathogenesis of genetic susceptibility (particularly HLA-B27 and ERAP-1) and epigenetic modifications, like non-coding RNAs, as well as environmental factors, have been investigated over the last few years. But the fundamental etiology of AS remains elusive to date. The evidence summarized here indicates that in the immunopathogenesis of AS, microRNAs and the gut microbiome perform critical functions. We discuss significant advances in the immunological mechanisms underlying AS and address potential cross-talk between the gut microbiome and host microRNAs. This critical interaction implicates a co-evolutionary symbiotic link between host immunity and the gut microbiome.

Prenatal and perinatal factors associated with developing multiple sclerosis later in life: A systematic review and meta-analysis

OBJECTIVE

Both genetic and environmental factors play roles in Multiple Sclerosis (MS) etiopathogenesis. The relationship between prenatal/perinatal factors/exposures and future MS occurrence in the offspring remains controversial. Here, we aimed to review the available evidence on prenatal/perinatal factors associated with later MS occurrence.

METHOD

We performed systematic search of PubMed, Web of Science, and Scopus from inception to October 2020. We included original observational studies conducted on human participants addressing the association between prenatal/perinatal factors and MS occurrence. Data were extracted according to the PRISMA guideline. The adjusted odds ratio (OR) with 95% confidence interval (CI) was considered as the desired effect size. The heterogeneity was evaluated by Cochran's Q and I² and the publication bias was assessed. We excluded gestational/neonatal vitamin D level, season of birth, and latitude because of recently published systematic reviews/meta-analyses on these subjects.

RESULTS

Overall, 2306 records were identified in the primary search. After excluding irrelevant studies, we evaluated 34 studies with contributing data on 100 prenatal/perinatal factors associated with an increased or decreased risk of MS occurrence. In the meta-analyses, we found no statistically significant associations between later MS occurrence in offspring and prenatal smoking exposure (OR = 1.01, 95% CI = 0.77-1.34), mode of delivery (OR = 0.90, 95% CI = 0.52-1.56), birth order (OR = 0.85, 95% CI = 0.72-1.00), and maternal age (OR = 1.34, 95% CI = 0.88-2.04). Paternal age and parents' marital status at the time of childbirth, maternal preeclampsia/ toxemia, forceps use, birth weight, plurality, and preterm birth were the other most studied factors, and none reported to affect MS risk.

CONCLUSION

We found that prenatal smoking exposure, mode of delivery, birth order, and maternal age do not affect risk of future MS development. Moreover, most of the other investigated factors were reported not to affect MS risk in the offspring.

The role of innate immunity in myasthenia gravis

Myasthenia gravis (MG) is a T cell-driven, B cell-mediated and autoantibody-dependent autoimmune disorder against neuromuscular junctions (NMJ). Accumulated evidence has emerged regarding the role of innate immunity in the pathogenesis of MG. In this review, we proposed two hypothesis underlying the pathological mechanism. In the context of gene predisposition, on the one hand, Toll-like receptors (TLRs) pathways were initiated by viral infection in the thymus with MG to generate chemokines and pro-inflammatory cytokines such as Type I interferon (IFN), which facilitate the thymus to function as a tertiary lymphoid organ (TLO). On the another hand, the antibodies against acetylcholine receptors (AChR) generated by thymus then activated the classical pathways on thymus and neuromuscular junction (NMJ). Futher, we also highlight the role of innate immune cells in the pathogenic response. Finally, we provide some future perspectives in developing new therapeutic approaches particularly targeting the innate immunity for MG.

Revisiting the Hygiene Hypothesis in the Context of Autoimmunity

Initially described for allergic diseases, the hygiene hypothesis was extended to autoimmune diseases in the early 2000s. A historical overview allows appreciation of the development of this concept over the last two decades and its discussion in the context of evolution. While the epidemiological data are convergent, with a few exceptions, the underlying mechanisms are multiple and complex. A major question is to determine what is the respective role of pathogens, bacteria, viruses, and parasites, versus commensals. The role of the intestinal microbiota has elicited much interest, but is it a cause or a consequence of autoimmune-mediated inflammation? Our hypothesis is that both pathogens and commensals intervene. Another question is to dissect what are the underlying cellular and molecular mechanisms. The role of immunoregulatory cytokines, in particular interleukin-10 and TGF beta is probably essential. An important place should also be given to ligands of innate immunity receptors present in bacteria, viruses or parasites acting independently of their immunogenicity. The role of Toll-Like Receptor (TLR) ligands is well documented including via TLR ligand desensitization.

Role of pattern recognition receptors and the microbiota in neurological disorders

In recent years, the gut microbiota has been increasingly implicated in the development of many extraintestinal disorders, including neurodevelopmental and neurodegenerative disorders. Despite this growing connection, our understanding of the precise mechanisms behind these effects is currently lacking. Pattern recognition receptors (PRRs) are important innate immune proteins expressed on the surface and within the cytoplasm of a multitude of cells, both immune and otherwise, including epithelial, endothelial and neuronal. PRRs comprise four major subfamilies: the Toll-like receptors (TLRs), the nucleotide-binding oligomerization domain leucine rich repeats-containing receptors (NLRs), the retinoic acid inducible gene 1-like receptors and the C-type lectin receptors. Recognition of commensal bacteria by PRRs is critical for maintaining host-microbe interactions and homeostasis, including behaviour. The expression of PRRs on multiple cell types makes them a highly interesting and novel target for regulation of host-microbe signalling, which may lead to gut-brain signalling. Emerging evidence indicates that two of the four known families of PRRs (the NLRs and the TLRs) are involved in the pathogenesis of neurodevelopmental and neurodegenerative disorders via the gut-brain axis. Taken together, increasing evidence supports a role for these PRRs in the development of neurological disorders, including Alzheimer's disease, Parkinson's disease and multiple sclerosis, via the microbiota-gut-brain axis.

Toll-like receptor-2 gene knockout results in neurobehavioral dysfunctions and multiple brain structural and functional abnormalities in mice

OBJECTIVE

Toll-like receptor-2 (TLR2), a member of TLR family, plays an important role in the induction and regulation of immune/inflammation. TLR2 gene knockout (TLR2KO) mice have been widely used for animal models of neurological diseases. Since there is close relationship between immune system and neurobehavioral functions, it is important to clarify the exact role of TLR2 defect itself in neurobehavioral functions. The present study aimed to investigate the effect of TLR2KO on neurobehavioral functions in mice and the mechanisms underlying the observed changes.

METHODS

Male TLR2KO and wild type (WT) mice aged 3, 7, and 12 months were used for neurobehavioral testing and detection of protein expression by Western blot. Brain magnetic resonance imaging (MRI), electrophysiological recording, and Evans blue (EB) assay were applied to evaluate regional cerebral blood flow (rCBF), synaptic function, and blood-brain barrier (BBB) integrity in 12-month-old TLR2KO and age-matched WT mice.

RESULTS

Compared to WT mice, TLR2KO mice showed decreased cognitive function and locomotor activity, as well as increased anxiety, which developed from middle age (before 7-month-old) to old age. In addition, significantly reduced regional cerebral blood flow (rCBF), inhibited long-term potentiation (LTP), and increased blood-brain barrier (BBB) permeability were observed in 12-month-old TLR2KO mice. Furthermore, compared with age-matched WT mice, significant reduction in protein levels of tight junction proteins (ZO-1, Occludin, and Claudin-5) and increased neurofilament protein (SMI32) were observed in 7 and 12-month-old TLR2KO mice, and that myelin basic protein (MBP) decreased in 12-month-old TLR2KO mice.

CONCLUSION

Our data demonstrated that TLR2 defect resulted in significantly observable neurobehavioral dysfunctions in mice starting from middle age, as well as multiple abnormalities in brain structure, function, and molecular metabolism.

Neuroimmune connections between corticotropin-releasing hormone and mast cells: novel strategies for the treatment of neurodegenerative diseases

Corticotropin-releasing hormone is a critical component of the hypothalamic–pituitary–adrenal axis, which plays a major role in the body’s immune response to stress. Mast cells are both sensors and effectors in the interaction between the nervous and immune systems. As first responders to stress, mast cells can initiate, amplify and prolong neuroimmune responses upon activation. Corticotropin-releasing hormone plays a pivotal role in triggering stress responses and related diseases by acting on its receptors in mast cells. Corticotropin-releasing hormone can stimulate mast cell activation, influence the activation of immune cells by peripheral nerves and modulate neuroimmune interactions. The latest evidence shows that the release of corticotropin-releasing hormone induces the degranulation of mast cells under stress conditions, leading to disruption of the blood-brain barrier, which plays an important role in neurological diseases, such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, autism spectrum disorder and amyotrophic lateral sclerosis. Recent studies suggest that stress increases intestinal permeability and disrupts the blood-brain barrier through corticotropin-releasing hormone-mediated activation of mast cells, providing new insight into the complex interplay between the brain and gastrointestinal tract. The neuroimmune target of mast cells is the site at which the corticotropin-releasing hormone directly participates in the inflammatory responses of nerve terminals. In this review, we focus on the neuroimmune connections between corticotropin-releasing hormone and mast cells, with the aim of providing novel potential therapeutic targets for inflammatory, autoimmune and nervous system diseases.

Quantitative proteomic analysis of cerebrospinal fluid of women newly diagnosed with multiple sclerosis

PURPOSE

The lack of reliable diagnostic and/or prognostic biomarkers for multiple sclerosis (MS) is the major obstacle to timely and accurate patient diagnosis in MS patients. To identify new proteins associated with MS we performed a detailed proteomic analysis of cerebrospinal fluid (CSF) of patients newly diagnosed with relapsing-remitting MS (RRMS) and healthy controls.

MATERIAL

Reflecting significantly higher prevalence of MS in women we included only women patients and controls in the study. To eliminate a potential effect of therapy on the CSF composition, only the therapy-naïve patients were included.

METHODS

Pooled CSF samples were processed in a technical duplicate, and labeled with stable-isotope coded TMT tags. To maximize the proteome coverage, peptide fractionation using 2D-LC preceded mass analysis using Orbitrap Fusion Tribrid Mass Spectrometer. Differential concentration of selected identified proteins between patients and controls was verified using specific antibodies.

RESULTS

Of the identified 900 CSF proteins, we found 69 proteins to be differentially abundant between patients and controls. In addition to several proteins identified as differentially abundant in MS patients previously, we observed several linked to MS for the first time, namely eosinophil-derived neurotoxin and Nogo receptor.

CONCLUSIONS

Our data confirm differential abundance of several previously proposed protein markers, and provide indirect support for involvement of copper-iron disbalance in MS. Most importantly, we identified two new differentially abundant CSF proteins that seem to be directly connected with myelin loss and axonal damage via TLR2 signaling and Nogo-receptor pathway in women newly diagnosed with RRMS.

The role of TH17 cells in multiple sclerosis: Therapeutic implications

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) where immunopathology is thought to be mediated by myelin-reactive CD4⁺ T helper (TH) cells. The TH cells most commonly implicated in the pathogenesis of the disease are of TH1 and TH17 lineage, which are defined by the production of interferon-γ and interleukin-17, respectively. Moreover, there is emerging evidence for the involvement of TH17.1 cells, which share the hallmarks of TH1 and TH17 subsets. In this review, we summarise current knowledge about the potential role of TH17 subsets in the initiation and progression of the disease and put a focus on their response to approved immunomodulatory MS drugs. In this regard, TH17 cells are abundant in peripheral blood, cerebrospinal fluid and brain lesions of MS patients, and their counts and inflammatory mediators are further increased during relapses. Fingolimod and alemtuzumab induce a paramount decrease in central memory T cells, which harbour the majority of peripheral TH17 cells, while the efficacy of natalizumab, dimethyl fumarate and importantly hematopoietic stem cell therapy correlates with TH17.1 cell inhibition. Interestingly, also CD20 antibodies target highly inflammatory TH cells and hamper TH17 differentiation by IL-6 reductions. Moreover, recovery rates of TH cells best correlate with long-term efficacy after therapeutical immunodepletion. We conclude that central memory TH17.1 cells play a pivotal role in MS pathogenesis and they represent a major target of MS therapeutics.

Precision health: A pragmatic approach to understanding and addressing key factors in autoimmune diseases

The past decade has witnessed a significant paradigm shift in the clinical approach to autoimmune diseases, lead primarily by initiatives in precision medicine, precision health and precision public health initiatives. An understanding and pragmatic implementation of these approaches require an understanding of the drivers, gaps and limitations of precision medicine. Gaining the trust of the public and patients is paramount but understanding that technologies such as artificial intelligences and machine learning still require context that can only be provided by human input or what is called augmented machine learning. The role of genomics, the microbiome and proteomics, such as autoantibody testing, requires continuing refinement through research and pragmatic approaches to their use in applied precision medicine.