Beneficial or Harmful Role of Macrophages in Guillain-Barré Syndrome and Experimental Autoimmune Neuritis

Unlocking the Therapeutic Potential of Adipose-Derived Stem Cell Secretome in Oral and Maxillofacial Medicine: A Composition-Based Perspective

The secretome of adipose-derived stem cells (ADSCs) holds significant promise for oral and maxillofacial medicine due to its rich composition of growth factors, cytokines, and other soluble or vesicle-embedded bioactive mediators that promote tissue regeneration and immunomodulation. Potential applications include enhancing wound healing, reducing inflammation, and stimulating the regeneration of hard and soft tissues. This could lead to improved outcomes in procedures such as bone grafting, soft tissue reconstruction, and the treatment of oral and facial defects. By harnessing the regenerative properties of ADSC secretome, clinicians may be able to achieve more effective tissue repair, ultimately benefiting patient recovery and quality of life.

The adipose-derived stem cell (ADSC) secretome is widely studied for its immunomodulatory and regenerative properties, yet its potential in maxillofacial medicine remains largely underexplored. This review takes a composition-driven approach, beginning with a list of chemokines, cytokines, receptors, and inflammatory and growth factors quantified in the ADSC secretome to infer its potential applications in this medical field. First, a review of the literature confirmed the presence of 107 bioactive factors in the secretome of ADSCs or other types of mesenchymal stem cells. This list was then analyzed using the Search Tool for Retrieval of Interacting Genes/Proteins (STRING) software, revealing 844 enriched biological processes. From these, key processes were categorized into three major clinical application areas: immunoregulation (73 factors), bone regeneration (13 factors), and wound healing and soft tissue regeneration (27 factors), with several factors relevant to more than one area. The most relevant molecules were discussed in the context of existing literature to explore their therapeutic potential based on available evidence. Among these, TGFB1, IL10, and CSF2 have been shown to modulate immune and inflammatory responses, while OPG, IL6, HGF, and TIMP1 contribute to bone regeneration and tissue repair. Although the ADSC secretome holds great promise in oral and maxillofacial medicine, further research is needed to optimize its application and validate its clinical efficacy.

Differential regulation of tissue-resident and blood-derived macrophages in models of autoimmune and traumatic peripheral nerve injury

Introduction

The current study focuses on understanding the functional role of different subsets of endoneurial macrophages in autoimmune polyneuropathies (AP) and traumatic peripheral nerve injury (TPNI), which holds potential for clinical application. Recent studies have advanced our understanding of the diverse origins of macrophages within peripheral nerves. However, there remains a gap in our knowledge regarding how endoneurial macrophages from different origins affect disease progression in AP versus TPNI.

Methods

Flow cytometry was utilized to analyze macrophage phenotypes, including polarization states, cytokine production, and myelin phagocytosis in animal models of AP and TPNI. This study focuses on two distinct origins of macrophages, namely CD11b+F4/80hi tissue-resident (TRM) and CD11b+F4/80int blood-derived macrophages (BDM). The study utilized two animal models: the first was the spontaneous autoimmune peripheral polyneuropathy (SAPP) model in B7.2-null non-obese diabetic (NOD-B7.2-/-) mice, which serves as a model for inflammatory demyelinating polyneuropathy; the second model involved wild type C57BL/6 mice subjected to sciatic nerve crush injury, modeling TPNI. Behavioral, electrophysiological, and histological analyses were performed to assess peripheral nerve injury.

Results

The study found that pro-inflammatory M1 macrophage polarization and tumor necrosis factor-alpha production by macrophages were more pronounced in the peripheral nerves of SAPP mice compared to those with TPNI, with the majority of these macrophages being TRM. In contrast, endoneurial macrophages in mice with TPNI were mainly BDM, exhibiting a less defined macrophage polarization and cytokine profile than TRM in AP mice. Interestingly, myelin phagocytosis was primarily driven by BDM in both SAPP and TPNI mice.

Discussion

This study offers novel insights into origin-dependent macrophage functions in AP and TPNI. Furthermore, these findings may help the future development of novel therapies targeting macrophage subsets of specific origin in AP and TPNI.

Lactobacillus rhamnosus ameliorates experimental autoimmune neuritis via modulation of gut microbiota and metabolites

Background

Guillain-Barre syndrome (GBS), an autoimmune disease of the peripheral nervous system, is hallmarked by demyelination and immune cellular infiltration. Experimental autoimmune neuritis (EAN), considered a GBS prototype model, has been studied for its potential therapeutic benefits from lactobacilli. This study evaluated the protective role of Lactobacillus rhamnosus GG (GG) for treatment in EAN. T cell ratio, inflammation factors, sciatic nerve pathology, intestinal permeability, and gut inflammation were assessed on day 19 post-immunization to evaluate GG's effect on EAN. Fecal metabolomics and 16s rRNA microbiome analysis were conducted to elucidate its mechanism.

Results

GG dynamically balanced CD4+/CD8+T cell ratio, reduced serum IL-1β and TNF-α expression, improved sciatic nerve demyelination and inflammation, and enhanced neurological scores during peak disease period. Intestinal mucosal damage was evident in EAN rats, with downregulated Occludin and ZO-1 and upregulated IL-1β, TNF-α, and Reg3γ. GG treatment restored intestinal mucosal integrity, upregulated Occludin and ZO-1, and downregulated IL-1, TNF-α, and Reg3γ. GG partially rectified the gut microbiota and metabolite imbalance in EAN rats.

Conclusion

GG mitigates EAN through immune response modulation and inflammation reduction via the gut microbiota and metabolites.

Causal relationship between immune cells and Guillain-Barré syndrome: a Mendelian randomization study

Objective

The aim of this study was to investigate the causal effect of immune cell phenotype on GBS using two-sample Mendelian randomization (MR) approach.

Methods

This study used MR to investigate the causal relationship between 731 immune cell phenotypes and GBS. We used Inverse variance weighted, Weighted median, MR Egger, Simple mode, Weighted mode for MR analysis. We also used the Cochran Q test, MR-Egger intercept test, IVW regression and MR-PRESSO, leave-one-out analysis to assess the presence of horizontal pleiotropy, heterogeneity and stability, respectively.

Results

Our study revealed a causal relationship between 33 immune cell phenotypes and GBS. Twenty immunophenotypes were observed to be associated with GBS as risk factors. For example, CD20 on IgD+ CD38dim in the B cell group (OR = 1.313, 95%CI:1.042-1.654, p = 0.021), CD3 on CD4 Treg in Treg cell group (OR = 1.395, 95%CI:1.069-1.819, p = 0.014), CD3 on TD CD8br in Maturation stages of T cell group (OR = 1.486, 95%CI:1.025-2.154, p = 0.037), CD16 on CD14+ CD16+ monocyte in Monocyte group (OR = 1.285, 95%CI:1.018-1.621, p = 0.035), CD33dim HLA DR+ CD11b + %CD33dim HLA DR+ in Myeloid cell group (OR = 1.262, 95%CI:1.020-1.561, p = 0.032), HLA DR+ NK AC in TBNK cell group (OR = 1.568, 95%CI:1.100-2.237, p = 0.013). Thirteen immune phenotypes are associated with GBS as protective factors. For example, CD19 on PB/PC in the B cell group (OR = 0.577, 95%CI:0.370-0.902, p = 0.016), CD4 Treg AC in Treg cell group (OR = 0.727, 95%CI:0.538-0.983, p = 0.038), CD11c + monocyte %monocyte in cDC group (OR = 0.704, 95%CI:0.514-0.966, p = 0.030), CX3CR1 on CD14+ CD16- monocyte in Monocyte group (OR = 0.717, 95%CI:0.548-0.939, p = 0.016), Mo MDSC AC in Myeloid cell group (OR = 0.763, 95%CI:0.619-0.939, p = 0.011), CD45 on granulocyte in TBNK group (OR = 0.621, 95%CI:0.391-0.984, p = 0.042).

Conclusion

The findings suggest that certain specific immune cell phenotypes, particularly B cell and Treg cell subpopulations, are causally associated with GBS, providing potential targets for the clinical treatment of GBS.

Advances in Exosome-Based Therapies for the Repair of Peripheral Nerve Injuries

Peripheral nerve injuries (PNIs) are the term used to describe injuries that occur to the nerve fibers of the peripheral nervous system (PNS). Such injuries may be caused by trauma, infection, or aberrant immunological response. Although the peripheral nervous system has a limited capacity for self-repair, in cases of severe damage, this process is either interrupted entirely or is only partially completed. The evaluation of variables that promote the repair of peripheral nerves has consistently been a focal point. Exosomes are a subtype of extracellular vesicles that originate from cellular sources and possess abundant proteins, lipids, and nucleic acids, play a critical role in facilitating intercellular communication. Due to their modifiable composition, they possess exceptional capabilities as carriers for therapeutic compounds, including but not limited to mRNAs or microRNAs. Exosome-based therapies have gained significant attention in the treatment of several nervous system diseases due to their advantageous properties, such as low toxicity, high stability, and limited immune system activation. The objective of this review article is to provide an overview of exosome-based treatments that have been developed in recent years for a range of PNIs, including nerve trauma, diabetic neuropathy, amyotrophic lateral sclerosis (ALS), glaucoma, and Guillain-Barre syndrome (GBS). It was concluded that exosomes could provide favorable results in the improvement of peripheral PNIs by facilitating the transfer of regenerative factors. The development of bioengineered exosome therapy for PNIs should be given more attention to enhance the efficacy of exosome treatment for PNIs.

CYBA allelic variants are associated with severity and recovery in Guillain-Barré syndrome

BACKGROUND AND AIMS

Guillain-Barré syndrome (GBS) is a rare, acute neuropathy characterized by ascending muscle weakness. Age, axonal GBS variants, and antecedent Campylobacter jejuni infection are associated with severe GBS, but the detailed mechanisms of nerve damage are only partly explored. Pro-inflammatory myeloid cells express NADPH oxidases (NOX) that generate tissue-toxic reactive oxygen species (ROS) that are implicated in neurodegenerative diseases. This study analyzed the impact of variants of the gene encoding the functional NOX subunit CYBA (p22phox ) on acute severity, axonal damage, and recovery in adult GBS patients.

METHODS

Extracted DNA from 121 patients was genotyped for allelic variation at rs1049254 and rs4673 within CYBA using real-time quantitative polymerase chain reaction. Serum neurofilament light chain was quantified by single molecule array. Patients were followed for severity and motor function recovery for up to 13 years.

RESULTS

CYBA genotypes linked to reduced formation of ROS, i.e. rs1049254/G and rs4673/A, were significantly associated with unassisted ventilation, shorter time to normalization of serum neurofilament light chain and shorter time to regained motor function. Residual disability at follow-up was confined to patients carrying CYBA alleles associated with high formation of ROS.

INTERPRETATION

These findings implicate NOX-derived ROS in GBS pathophysiology and CYBA alleles as biomarkers of severity.

Regulatory Mechanism of M1/M2 Macrophage Polarization in the Development of Autoimmune Diseases

Macrophages are innate immune cells in the organism and can be found in almost tissues and organs. They are highly plastic and heterogeneous cells and can participate in the immune response, thereby playing a crucial role in maintaining the immune homeostasis of the body. It is well known that undifferentiated macrophages can polarize into classically activated macrophages (M1 macrophages) and alternatively activated macrophages (M2 macrophages) under different microenvironmental conditions. The directions of macrophage polarization can be regulated by a series of factors, including interferon, lipopolysaccharide, interleukin, and noncoding RNAs. To elucidate the role of macrophages in various autoimmune diseases, we searched the literature on macrophages with the PubMed database. Search terms are as follows: macrophages, polarization, signaling pathways, noncoding RNA, inflammation, autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, lupus nephritis, Sjogren's syndrome, Guillain-Barré syndrome, and multiple sclerosis. In the present study, we summarize the role of macrophage polarization in common autoimmune diseases. In addition, we also summarize the features and recent advances with a particular focus on the immunotherapeutic potential of macrophage polarization in autoimmune diseases and the potentially effective therapeutic targets.

Lactobacillus paracasei L9 affects disease progression in experimental autoimmune neuritis by regulating intestinal flora structure and arginine metabolism

BACKGROUND

Autoimmune neuropathies are common peripheral nervous system (PNS) disorders. Environmental influences and dietary components are known to affect the course of autoimmune diseases. Intestinal microorganisms can be dynamically regulated through diet, and this study combines intestinal microorganisms with diseases to open up new therapeutic ideas.

METHODS

In Lewis rats, a model of EAN was established with P0 peptide, Lactobacillus were used as treatment, serum T-cell ratio, inflammatory factors, sciatic neuropathological changes, and pathological inflammatory effects on intestinal mucosa were detected, and fecal metabolomics and 16 s microbiome analysis were performed to further explore the mechanism.

RESULTS

In the EAN rat model, Lactobacillus paracasei L9 (LP) could dynamically regulate the CD4⁺/CD8⁺T balance in serum, reduce serum IL-1, IL-6 and TNF-α expression levels, improve sciatic nerve demyelination and inflammatory infiltration, and reduce nervous system score. In the rat model of EAN, intestinal mucosa was damaged. Occludin and ZO-1 were downregulated. IL-1, TNF-α and Reg3γ were upregulated. LP gavage induced intestinal mucosa recovery; occludin and ZO-1 upregulation; IL-1, TNF-α and Reg3γ downregulation. Finally, metabolomics and 16 s microbiome analysis were performed, and differential metabolites were enriched with an important metabolic pathway, arginine and proline metabolism.

CONCLUSION

LP improved EAN in rats by influencing intestinal community and the lysine and proline metabolism.

Single-cell analysis reveals novel clonally expanded monocytes associated with IL1β-IL1R2 pair in acute inflammatory demyelinating polyneuropathy

Guillain-Barré syndrome (GBS) is an autoimmune disorder wherein the composition and gene expression patterns of peripheral blood immune cells change significantly. It is triggered by antigens with similar epitopes to Schwann cells that stimulate a maladaptive immune response against peripheral nerves. However, an atlas for peripheral blood immune cells in patients with GBS has not yet been constructed. This is a monocentric, prospective study. We collected 5 acute inflammatory demyelinating polyneuropathy (AIDP) patients and 3 healthy controls hospitalized in the First Affiliated Hospital of Harbin Medical University from December 2020 to May 2021, 3 AIDP patients were in the peak stage and 2 were in the convalescent stage. We performed single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) from these patients. Furthermore, we performed cell clustering, cell annotation, cell-cell communication, differentially expressed genes (DEGs) identification and pseudotime trajectory analysis. Our study identified a novel clonally expanded CD14+ CD163+ monocyte subtype in the peripheral blood of patients with AIDP, and it was enriched in cellular response to IL1 and chemokine signaling pathways. Furthermore, we observed increased IL1β-IL1R2 cell-cell communication between CD14+ and CD16+ monocytes. In short, by analyzing the single-cell landscape of the PBMCs in patients with AIDP we hope to widen our understanding of the composition of peripheral immune cells in patients with GBS and provide a theoretical basis for future studies.

Deciphering the Role of Schwann Cells in Inflammatory Peripheral Neuropathies Post Alphavirus Infection

Old world alphaviruses (e.g., chikungunya) are known to cause severe acute and chronic debilitating arthralgia/arthritis. However, atypical neurological manifestations and, in particular, unexpected cases of acute inflammatory Guillain-Barre syndrome (GBS) have been associated with the arthritogenic alphaviruses. The pathogenesis of alphavirus-associated GBS remains unclear. We herein addressed for the first time the role of Schwann cells (SC) in peripheral neuropathy post-alphaviral infection using the prototypical ONNV alphavirus model. We demonstrated that human SC expressed the recently identified alphavirus receptor MxRA8 and granting viral entry and robust replication. A canonical innate immune response was engaged by ONNV-infected SC with elevated gene expression for RIG-I, MDA5, IFN-β, and ISG15 and inflammatory chemokine CCL5. Transcription levels of prostaglandin E2-metabolizing enzymes including cPLA2α, COX-2, and mPGES-1 were also upregulated in ONNV-infected SC. Counterintuitively, we found that ONNV failed to affect SC regenerative properties as indicated by elevated expression of the pro-myelinating genes MPZ and MBP1 as well as the major pro-myelin transcription factor Egr2. While ONNV infection led to decreased expression of CD55 and CD59, essential to control complement bystander cytotoxicity, it increased TRAIL expression, a major pro-apoptotic T cell signal. Anti-apoptotic Bcl2 transcription levels were also increased in infected SC. Hence, our study provides new insights regarding the remarkable immunomodulatory role of SC of potential importance in the pathogenesis of GBS following alphavirus infection.

Immune Modifying Effect of Drug Free Biodegradable Nanoparticles on Disease Course of Experimental Autoimmune Neuritis

Guillain-Barre syndrome (GBS) is an autoimmune disease of demyelination and inflammation of peripheral nerves. Current treatments are limited to plasma exchange and intravenous immunoglobulins. Cargo-free nanoparticles (NPs) have been evaluated here for their therapeutic benefit on the disease course of experimental autoimmune neuritis (EAN), mimicking the human GBS. NPs prepared from poly-lactic co-glycolic acid (PLGA) with variable size and surface charge (i.e., 500 nm vs. 130 nm, polyvinyl alcohol (PVA) vs. sodium cholate), were intravenously administered in before- or early-onset treatment schedules in a rat EAN model. NP treatment mitigated distinctly the clinical severity of EAN as compared to the P2-peptide control group (P2) in all treatments and reduced the trafficking of inflammatory monocytes at inflammatory loci and diverted them towards the spleen. Therapeutic treatment with NPs reduced the expression of proinflammatory markers (CD68 (P2: 34.8 ± 6.6 vs. NP: 11.9 ± 2.3), IL-1β (P2: 18.3 ± 0.8 vs. NP: 5.8 ± 2.2), TNF-α (P2: 23.5 ± 3.7 vs. NP: 8.3 ± 1.7) and elevated the expression levels of anti-inflammatory markers CD163 (P2: 19.7 ± 3.0 vs. NP: 41.1 ± 6.5; all for NP-PVA of 130 nm; relative to healthy control). These results highlight the therapeutic potential of such cargo-free NPs in treating EAN, which would be easily translatable into clinical use due to their well-known low-toxicity profile.

Macrophages play a key role in tissue repair and regeneration

Tissue regeneration after body injury has always been a complex problem to resolve for mammals. In adult mammals, the repair process after tissue injury is often accompanied by continuous and extensive fibrosis, which leads to scars. This process has been shown to severely hinder regeneration. Macrophages, as widely distributed innate immune cells, not only play an important role in various pathological processes, but also participate in the repair process before tissue regeneration and coordinate the regeneration process after repair. This review will discuss the various forms and indispensability of macrophages involved in repair and regeneration, and how macrophages play a role in the repair and regeneration of different tissues.

Comparison of the effects of different doses of Glucocorticoids on distinct subtypes of Guillain-Barré syndrome in Southern China

Background

The effect of Glucocorticoids (GCs) on the treatment of Guillain-Barré syndrome (GBS) has been controversial. There is no information on whether specific subtypes of GBS respond differently to GCs. In this setting, we aimed to discuss whether GCs treating yield different effects in the distinct subtypes (acute inflammatory demyelinating polyneuropathy, AIDP; acute motor axonal neuropathy, AMAN). And further, we analyzed the impact of different doses on the outcome.

Methods

Medical records of 448 patients with a diagnosis of classic GBS admitted to 31 tertiary hospitals, located in 14 provinces of Southern China, from 1 January 2013 to 30 September 2016, were retrospectively collected. And 251 patients treated with GCs alone (AIDP=189, AMAN=62) were reviewed and analyzed.

Results

After GCs treatment, the Hughes score of AIDP patients was significantly lower than that of AMAN patients at discharge (P=0.005) and 3 months after onset (P<0.001). Further analysis revealed that among AIDP patients, the high-dose group had significantly shorter hospital stay (P=0.023), lower Hughes score at nadir (P<0.001), at discharge (P=0.005), and 3 months after onset (P<0.001), compared with the low-dose group. However, for AMAN patients, the outcome difference between groups was nonsignificant.

Conclusion

Our data suggest that the high doses of GCs may result, at least in part, from the side of the duration of hospital stay and short-term outcome, favorable outcomes in AIDP patients. Therefore, we cannot completely deny the priority of GCs in the treatment of GBS, because the effect of different doses of GCs varies in treating different subtypes. More studies are needed in the future to further validate this issue.

Trial registration

ChiCTR-RRC-17014152. Registered 26 December 2017- Retrospectively registered.

Attenuation of Experimental Autoimmune Uveitis in Lewis Rats by Betaine

Experimental autoimmune uveitis (EAU) is an animal model of human autoimmune uveitis that is characterized by the infiltration of autoimmune T cells with concurrent increases in pro-inflammatory cytokines and reactive oxygen species. This study aimed to assess whether betaine regulates the progression of EAU in Lewis rats. EAU was induced via immunization with the interphotoreceptor retinoid-binding protein (IRBP) and oral administration of either a vehicle or betaine (100 mg/kg) for 9 consecutive days. Spleens, blood, and retinas were sampled from the experimental rats at the time of sacrifice and used for the T cell proliferation assay, serological analysis, real-time polymerase chain reaction, and immunohistochemistry. The T cell proliferation assay revealed that betaine had little effect on the proliferation of splenic T cells against the IRBP antigen in an in vitro assay on day 9 post-immunization. The serological analysis showed that the level of serum superoxide dismutase increased in the betaine-treated group compared with that in the vehicle-treated group. The anti-inflammatory effect of betaine was confirmed by the downregulation of pro-inflammation-related molecules, including vascular cell adhesion molecule 1 and interleukin-1β in the retinas of rats with EAU. The histopathological findings agreed with those of ionized calcium-binding adaptor molecule 1 immunohistochemistry, further verifying that inflammation in the retina and ciliary bodies was significantly suppressed in the betaine-treated group compared with the vehicle-treated group. Results of the present study suggest that betaine is involved in mitigating EAU through anti-oxidation and anti-inflammatory activities.

PD-1/PD-L1 Axis as a Potential Therapeutic Target for Multiple Sclerosis: A T Cell Perspective

The programmed cell death protein-1/programmed death ligand-1 (PD-1/PD-L1) axis is a widely studied immune checkpoint that modulates signaling pathways related to T cell activation. The use of PD-1/PD-L1 inhibitors is a promising immune therapy strategy for cancer patients. However, individuals treated with PD-1/PD-L1 inhibitors may develop immune-related adverse events due to excessive immune reactions. Multiple sclerosis (MS) is a chronic demyelinating and neurodegenerative disease of the central nervous system. T cells and the PD-1/PD-L1 axis play vital roles in the pathogenesis of MS. A better understanding of the complex relationship between the PD-1/PD-L1 axis and T cells may extend our knowledge of the molecular mechanisms and therapeutic approaches for MS. In this review, we summarize the most recent findings regarding the role of the PD-1/PD-L1 axis in MS and discuss the potential therapeutic strategies to modulate the expression of PD-1/PD-L1 in MS.

Nuclear factor kappa B inhibitor suppresses experimental autoimmune neuritis in mice via declining macrophages polarization to M1 type

Guillain-Barré syndrome (GBS) is an acute inflammatory and immune-mediated demyelinating disease of the peripheral nervous system (PNS). Macrophages play a central role in its animal model, experimental autoimmune neuritis (EAN), which has been well accepted. Additionally, nuclear factor (NF)-κB inhibitors have been used to treat cancers and have shown beneficial effects. Here, we investigated the therapeutic effect of M2 macrophage and the NF-κB pathway's correlation with macrophage activation in EAN in C57BL/6 mice. We demonstrate that M2 macrophage transfusion could alleviate the clinical symptoms of EAN by reducing the proportion of M1 macrophage in the peak period, inhibiting the phosphorylation of NF-κB p65. The NF-κB inhibitor (BAY-11-7082) could alleviate the clinical symptoms of EAN and shorten the duration of symptoms by reducing the proportion of M1 macrophages and the expression of proinflammatory cytokines. Consequently, BAY-11-7082 exhibits strong potential as a therapeutic strategy for ameliorating EAN by influencing the balance of M1/M2 macrophages and inflammatory cytokines.

Macrophages and Autoantibodies in Demyelinating Diseases

Myelin phagocytosis by macrophages has been an essential feature of demyelinating diseases in the central and peripheral nervous systems, including Guillain–Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), and multiple sclerosis (MS). The discovery of autoantibodies, including anti-ganglioside GM1 antibodies in the axonal form of GBS, anti-neurofascin 155 and anti-contactin 1 antibodies in typical and distal forms of CIDP, and anti-aquaporin 4 antibodies in neuromyelitis optica, contributed to the understanding of the disease process in a subpopulation of patients conventionally diagnosed with demyelinating diseases. However, patients with these antibodies are now considered to have independent disease entities, including acute motor axonal neuropathy, nodopathy or paranodopathy, and neuromyelitis optica spectrum disorder, because primary lesions in these diseases are distinct from those in conventional demyelinating diseases. Therefore, the mechanisms underlying demyelination caused by macrophages remain unclear. Electron microscopy studies revealed that macrophages destroy myelin as if they are the principal players in the demyelination process. Recent studies suggest that macrophages seem to select specific sites of myelinated fibers, including the nodes of Ranvier, paranodes, and internodes, for the initiation of demyelination in individual cases, indicating that specific components localized to these sites play an important role in the behavior of macrophages that initiate myelin phagocytosis. Along with the search for autoantibodies, the ultrastructural characterization of myelin phagocytosis by macrophages is a crucial step in understanding the pathophysiology of demyelinating diseases and for the future development of targeted therapies.

Inhibition of TLR4 signaling protects mice from sensory and motor dysfunction in an animal model of autoimmune peripheral neuropathy

BACKGROUND

While the etiology remains elusive, macrophages and T cells in peripheral nerves are considered as effector cells mediating autoimmune peripheral neuropathy (APN), such as Guillain-Barre syndrome. By recognizing both pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) signals, TLRs play a central role in the initiation of both innate and adaptive immune responses. In this study, we aimed to understand the involvement of TLR4 in the pathogenesis of APN and explore the potential of TLR4 as a drug target for therapeutic use.

METHODS

APN was induced by a partial ligation on one of the sciatic nerves in B7.2 (L31) transgenic mice which possess a predisposed inflammatory background. APN pathology and neurological function were evaluated on the other non-injured sciatic nerve.

RESULTS

TLR4 and its endogenous ligand HMGB1 were highly expressed in L31 mice, in circulating immune cells and in peripheral nerves. Enhanced TLR4 signaling was blocked with TAK 242, a selective TLR4 inhibitor, before and after disease onset. Intraperitoneal administration of TAK 242 not only inhibited monocyte, macrophage and CD8⁺ T cell activation, but also reduced the release of pro-inflammatory cytokines. TAK 242 protected mice from severe myelin and axonal loss, resulting in a remarkable improvement in mouse motor and sensory functions. TAK 242 was effective in alleviating the disease in both preventive and reversal paradigms.

CONCLUSION

The study identified the critical contribution of TLR4-mediated macrophage activation in disease course and provided strong evidence to support TLR4 as a useful drug target for treating inflammatory autoimmune neuropathy.

Low-Dose Exposure to Ganglioside-Mimicking Bacteria Tolerizes Human Macrophages to Guillain-Barré Syndrome-Associated Antigens

Early in life, commensal bacteria play a major role in immune development, helping to guide the host response toward harmful stimuli while tolerating harmless antigens to prevent autoimmunity. Guillain-Barré syndrome (GBS) is an autoimmune disease caused by errant immune attack of antibody-bound ganglioside receptors on host nerve cells, resulting in paralysis. Lipooligosaccharides enveloping the prevalent enteric pathogen, Campylobacter jejuni, frequently mimic human gangliosides and can trigger GBS by stimulating the autoimmune response. In low- to middle-income countries, young children are consistently exposed to C. jejuni, and it is not known if this impacts GBS susceptibility later in life. Using a macrophage model, we examined the effect of training these cells with low doses of ganglioside-mimicking bacteria prior to challenge with GBS-associated antigens. This training caused decreased production of proinflammatory cytokines, suggesting tolerance induction. We then screened Campylobacter isolates from 154 infant fecal samples for GM1 ganglioside mimicry, finding that 23.4% of strains from both symptomatic and asymptomatic infants displayed GM1-like structures. Training macrophages with one of these asymptomatic carrier isolates also induced tolerance against GBS-associated antigens, supporting that children can be exposed to the tolerizing antigen early in life. RNA interference of Toll-like receptor 2 (TLR2) and TLR4 suggests that these receptors are not involved in tolerance associated with decreases in tumor necrosis factor (TNF), interleukin-6 (IL-6), or IL-1β levels. The results of this study suggest that exposure to ganglioside-mimicking bacteria early in life occurs naturally and impacts host susceptibility to GBS development. IMPORTANCE In this study, we demonstrated that it is possible to tolerize immune cells to potentially dampen the autoreactive proinflammatory immune response against Guillain-Barré syndrome (GBS)-associated antigens. The innate immune response functions to arm the host against bacterial attack, but it can be tricked into recognizing the host's own cells when infectious bacteria display sugar structures that mimic human glycans. It is this errant response that leads to the autoimmunity and paralysis associated with GBS. By presenting immune cells with small amounts of the bacterial glycan mimic, we were able to suppress the proinflammatory immune response upon subsequent high exposure to glycan-mimicking bacteria. This suggests that individuals who have already been exposed to the glycan mimics in small amounts are less sensitive to autoimmune reactions against these glycans, and this could be a factor in determining susceptibility to GBS.

Purinergic signaling in peripheral nervous system glial cells

To facilitate analyses of purinergic signaling in peripheral nerve glia, we review recent literature and catalog purinergic receptor mRNA expression in cultured mouse Schwann cells (SCs). Purinergic signaling can decrease developmental SC proliferation, and promote SC differentiation. The purinergic receptors P2RY2 and P2RX7 are implicated in nerve development and in the ratio of Remak SCs to myelinating SCs in differentiated peripheral nerve. P2RY2, P2RX7, and other receptors are also implicated in peripheral neuropathies and SC tumors. In SC tumors lacking the tumor suppressor NF1, the SC pathway that suppresses SC growth through P2RY2‐driven β‐arrestin‐mediated AKT signaling is aberrant. SC‐released purinergic agonists acting through SC and/or neuronal purinergic receptors activate pain responses. In all these settings, purinergic receptor activation can result in calcium‐independent and calcium‐dependent release of SC ATP and UDP, growth factors, and cytokines that may contribute to disease and nerve repair. Thus, current research suggests that purinergic agonists and/or antagonists might have the potential to modulate peripheral glia function in development and in disease.

Macrophage roles in peripheral nervous system injury and pathology: Allies in neuromuscular junction recovery

Peripheral nerve injuries remain challenging to treat despite extensive research on reparative processes at the injury site. Recent studies have emphasized the importance of immune cells, particularly macrophages, in recovery from nerve injury. Macrophage plasticity enables numerous functions at the injury site. At early time points, macrophages perform inflammatory functions, but at later time points, they adopt pro-regenerative phenotypes to support nerve regeneration. Research has largely been limited, however, to the injury site. The neuromuscular junction (NMJ), the synapse between the nerve terminal and end target muscle, has received comparatively less attention, despite the importance of NMJ reinnervation for motor recovery. Macrophages are present at the NMJ following nerve injury. Moreover, in denervating diseases, such as amyotrophic lateral sclerosis (ALS), macrophages may also play beneficial roles at the NMJ. Evidence of positive macrophages roles at the injury site after peripheral nerve injury and at the NMJ in denervating pathologies suggest that macrophages may promote NMJ reinnervation. In this review, we discuss the intersection of nerve injury and immunity, with a focus on macrophages.

Associations of body mass index and waist circumference with risk of Guillain-Barré syndrome in women and men: A prospective analysis of three cohort studies

BACKGROUND

The association of body mass index (BMI) and waist circumference (WC) with risk of Guillain-Barré syndrome (GBS) has been inconsistent in previous studies.

METHODS

We examined the associations of BMI and WC in relation to risk of GBS among 252,980 participants from the Nurses' Health Study (NHS), NHS-II, and the Health Professional Follow-up Study (HPFS). BMI and WC were assessed by self-reported questionnaire, and GBS cases were self-reported.

RESULTS

We documented 328 incident GBS cases during a total of 5,422,788 person years of follow-up. Compared to participants with BMI<25kg/m2, the multivariate pooled hazard ratio (HR) of GBS was 1.34 (95% CI: 1.04, 1.73) for overweight participants (25kg/m2≤BMI<30 kg/m2), and 1.68 (95% CI: 1.21, 2.35) for obese participants (BMI≥30 kg/m2) (P for trend = 0.001). Compared to participants with normal WC (<35 inches for women and <40 inches for men), the HR of GBS was 1.55 (95% CI: 1.10, 2.18) for participants with high WC (≥35 inches for women, and ≥40 inches for men). The positive associations of BMI and WC with risk of GBS were attenuated to null after mutually adjusting for BMI and WC. Joint analysis showed that the HR was 1.84 (95% CI: 1.27, 2.66) for participants with high WC and BMI≥25 kg/m2 in comparison to participants with normal WC and BMI<25kg/m2.

CONCLUSION

These data from large cohorts showed that higher BMI and WC jointly were associated with higher risk of GBS. Our study highlighted the importance of maintaining a normal body weight and waist circumference in prevention of GBS.

Role of Ginkgolides in the Inflammatory Immune Response of Neurological Diseases: A Review of Current Literatures

The inflammatory immune response (IIR) is a physiological or excessive systemic response, induced by inflammatory immune cells according to changes in the internal and external environments. An excessive IIR is the pathological basis for the generation and development of neurological diseases. Ginkgolides are one of the important medicinal ingredients in Ginkgo biloba. Many studies have verified that ginkgolides have anti-platelet-activating, anti-apoptotic, anti-oxidative, neurotrophic, and neuroimmunomodulatory effects. Inflammatory immunomodulation is mediated by inhibition of the mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways. They also inhibit the platelet-activating factor (PAF)-mediated signal transduction to attenuate the inflammatory response. Herein, we reviewed the studies on the roles of ginkgolides in inflammatory immunomodulation and suggested its potential role in novel treatments for neurological diseases.

Origin and Differentiation of Nerve-Associated Macrophages

The mature peripheral nervous system is a steady network structure yet shows remarkable regenerative properties. The interaction of peripheral nerves with myeloid cells has largely been investigated in the context of damage, following trauma or infection. Recently, specific macrophages dedicated to homeostatic peripheral nerves have come into focus. These macrophages are defined by tissue and nerve type, are seeded in part prenatally, and self-maintain via proliferation. Thus, they are markedly distinct from monocyte-derived macrophages invading after local disturbance of nerve integrity. The phenotypic and transcriptional adaptation of macrophages to the discrete nervous niche may exert axon guidance and nerve regeneration and thus contribute to the stability of the peripheral nervous network. Deciphering these conserved macrophage-nerve interactions offers new translational perspectives for chronic diseases of the peripheral nervous system, such as diabetic neuropathy and pain.

Effect of fasudil on experimental autoimmune neuritis and its mechanisms of action

This study aimed to investigate the therapeutic effect of fasudil on treating experimental autoimmune neuritis (EAN). Twenty-four EAN mice were randomly assigned to fasudil treatment (Fasudil group) or saline treatment (EAN model group) for 28 days. Clinical symptom score was evaluated every other day; inflammatory cell infiltration, demyelination, anti-myelin basic protein (MBP), inflammatory cytokines, inducible nitric oxide synthase (iNOS), and arginase-1 were detected in sciatic nerves at day 28. Th1, Th2, Th17, and Tregs proportions in splenocytes were detected at day 28. Clinical symptom score was found to be attenuated in the Fasudil group compared to the EAN model group from day 12 to day 28. Sciatic nerve inflammatory cell counts by HE staining and demyelination by luxol fast blue staining were both reduced, while MBP was increased in the Fasudil group compared to the EAN model group at day 28. Interferon γ (IFN-γ) and interleukin (IL)-17 were reduced, while IL-4 and IL-10 were elevated in the Fasudil group at day 28. Sciatic nerve M1 macrophages marker iNOS was decreased while M2 macrophages marker arginase-1 was increased in the Fasudil group at day 28. CD4⁺IFN-γ⁺ (Th1) and CD4⁺IL-17⁺ (Th17) cell proportions were both decreased, CD4⁺IL-4⁺ (Th2) cell proportion was similar, while CD25+FOXP3+ (Treg) cell proportion in splenocytes was increased in the Fasudil group. In summary, fasudil presented a good therapeutic effect for treating EAN by attenuating Th1/Th17 cells and promoting Tregs activation as well as M2 macrophages polarization.

Roles of Neuropeptide Y in Neurodegenerative and Neuroimmune Diseases

Neuropeptide Y (NPY) is a neurotransmitter or neuromodulator that mainly exists in the nervous system. It plays a neuroprotective role in organisms and widely participates in the regulation of various physiological processes in vivo. Studies in both humans and animal models have been revealed that NPY levels are altered in some neurodegenerative and neuroimmune disorders. NPY plays various roles in these diseases, such as exerting a neuroprotective effect, increasing trophic support, decreasing excitotoxicity, regulating calcium homeostasis, and attenuating neuroinflammation. In this review, we will focus on the roles of NPY in the pathological mechanisms of neurodegenerative and neuroimmune diseases, highlighting NPY as a potential therapeutic target in these diseases.

Macrophage biology in the peripheral nervous system after injury

Neuroinflammation has positive and negative effects. This review focuses on the roles of macrophage in the PNS. Transection of PNS axons leads to degeneration and clearance of the distal nerve and to changes in the region of the axotomized cell bodies. In both locations, resident and infiltrating macrophages are found. Macrophages enter these areas in response to expression of the chemokine CCL2 acting on the macrophage receptor CCR2. In the distal nerve, macrophages and other phagocytes are involved in clearance of axonal debris, which removes molecules that inhibit nerve regeneration. In the cell body region, macrophage trigger the conditioning lesion response, a process in which neurons increase their regeneration after a prior lesion. In mice in which the genes for CCL2 or CCR2 are deleted, neither macrophage infiltration nor the conditioning lesion response occurs in dorsal root ganglia (DRG). Macrophages exist in different phenotypes depending on their environment. These phenotypes have different effects on axonal clearance and neurite outgrowth. The mechanism by which macrophages affect neuronal cell bodies is still under study. Overexpression of CCL2 in DRG in uninjured animals leads to macrophage accumulation in the ganglia and to an increase in the growth potential of DRG neurons. This increased growth requires activation of neuronal STAT3. In contrast, in acute demyelinating neuropathies, macrophages are involved in stripping myelin from peripheral axons. The molecular mechanisms that trigger macrophage action after trauma and in autoimmune disease are receiving increased attention and should lead to avenues to promote regeneration and protect axonal integrity.