Gut microbiota differently contributes to intestinal immune phenotype and systemic autoimmune progression in female and male lupus-prone mice

The role of gut microbiota in different murine models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by immune system dysfunction that can lead to serious health issues and mortality. Recent investigations highlight the role of gut microbiota alterations in modulating inflammation and disease severity in SLE. This review specifically summaries the variations in gut microbiota composition across various murine models of lupus. By focusing on these differences, we aim to elucidate the intricate relationship between gut microbiota dysbiosis and the development and progression of SLE in preclinical settings.

Fecal microbiota transplantation for the treatment of chronic inflammatory skin diseases

The regulation of immune functions and the maintenance of homeostasis in the internal environment are both integral to human gut microbiota (GM). If GM is disturbed, it can result in a range of autoimmune diseases, including chronic inflammatory skin conditions. Chronic inflammatory skin diseases driven by T or B-cell-mediated immune reactions are complex, including the most prevalent diseases and some rare diseases. Expanding knowledge of GM dysbiosis in chronic inflammatory skin diseases has emerged. The GM has some causal roles in the pathogenesis of these skin conditions. Targeting microbiota treatment, particularly fecal microbiota transplantation (FMT), is considered to be a promising strategy. FMT was commonly used in intestinal diseases by reshaping and balancing GM, serving as a reasonable administration in these skin inflammatory diseases. This paper summarizes the existing knowledge of GM dysbiosis in chronic inflammatory skin diseases and the research data on FMT treatment for such conditions.

Exploring the pathogenesis of RA through the gut-articular axis-dysbiosis a potential factor

Rheumatoid arthritis (RA) is a chronic autoimmune disease with a complex etiology. It has been suggested that the pathogenesis of RA begins in the mucosa and then transitions to the joints when many factors interact, including microbial dysbiosis, inflammatory responses, and immune abnormalities at the mucosal site. Data from RA animals and patients suggest there are changes in the mucosal microflora before the onset of RA, and that dysbiosis of the mucosal ecology continues to play a role in the development of arthritis. Microbial dysbiosis of the mucosa reduces the normal barrier function of the intestinal tract, promotes inflammatory reactions in the mucosal areas of the intestines, and then activates the intestinal immune cells abnormally to produce a large number of auto-reactive antibodies that exacerbate arthritis. Current findings do not clarify whether dysbiosis is only a potential trigger for the development of RA. If it is possible to intervene in such microbial changes before the onset of RA, could the clinical symptoms of arthritis be prevented or reduced? Finding new ways to regulate gut flora composition to maintain gut barrier function is an ongoing challenge for the prevention and treatment of RA.

Emerging role of gut microbiota in autoimmune diseases

Accumulating studies have indicated that the gut microbiota plays a pivotal role in the onset of autoimmune diseases by engaging in complex interactions with the host. This review aims to provide a comprehensive overview of the existing literatures concerning the relationship between the gut microbiota and autoimmune diseases, shedding light on the complex interplay between the gut microbiota, the host and the immune system. Furthermore, we aim to summarize the impacts and potential mechanisms that underlie the interactions between the gut microbiota and the host in autoimmune diseases, primarily focusing on systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, type 1 diabetes mellitus, ulcerative colitis and psoriasis. The present review will emphasize the clinical significance and potential applications of interventions based on the gut microbiota as innovative adjunctive therapies for autoimmune diseases.

Intestinal permeability and inflammatory features of juvenile age correlate with the eventual systemic autoimmunity in lupus-prone female SWR × NZB F1 (SNF1) mice

The incidence of systemic lupus erythematosus (SLE) is about nine times higher in women than in men, and the underlying mechanisms that contribute to this gender bias are not fully understood. Previously, using lupus-prone (SWR × NZB)F1 (SNF1) mice, we have shown that the intestinal immune system could play a role in the initiation and progression of disease in SLE, and depletion of gut microbiota produces more pronounced disease protection in females than in males. Here, we show that the gut permeability features of lupus-prone female SNF1 mice at juvenile ages directly correlate with the expression levels of pro-inflammatory factors, faecal IgA abundance and nAg reactivity and the eventual systemic autoantibody levels and proteinuria onset. Furthermore, we observed that the disease protection achieved in female SNF1 mice upon depletion of gut microbiota correlates with the diminished gut inflammatory protein levels, intestinal permeability and circulating microbial DNA levels. However, faecal microbiota transplant from juvenile male and females did not result in modulation of gut inflammatory features or permeability. Overall, these observations suggest that the early onset of intestinal inflammation, systemic autoantibody production and clinical stage disease in lupus-prone females is linked to higher gut permeability in them starting at as early as juvenile age. While the higher gut permeability in juvenile lupus-prone females is dependent on the presence of gut microbes, it appears to be independent of the composition of gut microbiota.

High-Throughput Sequencing Technology Assisted Investigation of the Correlation Between Intestinal Flora, Serum Biochemistry, Blood Lipids, and Tumour Markers in Patients with Gastric Cancer and Healthy Plateau Residents

AIM

The goal is to use high-throughput sequencing technology to compare and study the structure and variety of intestinal flora in people with gastric cancer and healthy people in the Qinghai-Tibet Plateau.

BACKGROUND

Recent research has connected gut flora structure to numerous disorders. Metabolites, endotoxins, and immunomodulatory modulation might cause gastrointestinal or other systemic diseases and affect gastric cancer treatment and prognosis. We used the correlation study to uncover biomarkers associated with good intestinal flora and gastric cancer groups on the plateau to investigate their involvement in gastric cancer development.

OBJECTIVES

To investigate the possible links between intestinal flora and gastric cancer in the Qinghai Plateau region using a variety of clinical phenotypic data and to investigate the flora that may be linked to gastric cancer.

METHODS

The 22 Qinghai Province tertiary hospital gastric cancer patients and 30 healthy people had their fresh faeces collected. To examine intestinal flora diversity and composition, 52 patients underwent 16S rDNA high-throughput gene sequencing of intestinal bacteria. The correlation between clinical phenotypes and the top 15 dominant intestinal flora at the phylum level was analyzed.

RESULTS

The difference in total protein TP between the healthy group and the gastric cancer group was statistically significant (P<0.001). Globulin was significantly different (P<0.05), TC of total cholesterol was significantly different (P<0.05). High-density lipoprotein showed statistical significance (P<0.05).The difference in low-density lipoprotein was statistically significant (P<0.001). Alphafetoprotein was significantly different (P<0.05). CA72-4 carbohydrate antigen (P<0.05).

CONCLUSION

There were significant differences in total protein, globulin, total cholesterol, high density lipoprotein, low-density lipoprotein, alpha-fetoprotein and carbohydrate antigen CA72-4 in patients with gastric cancer in the plateau area compared with the healthy group, and the different clinical variables were correlated with intestinal flora at some phylum and genus levels.

Possible Role of Dysbiosis of the Gut Microbiome in SLE

PURPOSE OF REVIEW

The resident gut microbiota serves as a double-edged sword that aids the host in multiple ways to preserve a healthy equilibrium and serve as early companions and boosters for the gradual evolution of our immune defensive layers; nevertheless, the perturbation of the symbiotic resident intestinal communities has a profound impact on autoimmunity induction, particularly in systemic lupus erythematosus (SLE). Herein, we seek to critically evaluate the microbiome research in SLE with a focus on intestinal dysbiosis.

RECENT FINDINGS

SLE is a complex and heterogeneous disorder with self-attack due to loss of tolerance, and there is aberrant excessive immune system activation. There is mounting evidence suggesting that intestinal flora disturbances may accelerate the formation and progression of SLE, presumably through a variety of mechanisms, including intestinal barrier dysfunction and leaky gut, molecular mimicry, bystander activation, epitope spreading, gender bias, and biofilms. Gut microbiome plays a critical role in SLE pathogenesis, and additional studies are warranted to properly define the impact of gut microbiome in SLE, which can eventually lead to new and potentially safer management approaches for this debilitating disease.

Gut microbiota mediated the effects of high relative humidity on lupus in female MRL/lpr mice

INTRODUCTION

The relationship between humidity and systemic lupus erythematosus (SLE) has yielded inconsistent results in prior research, while the effects of humidity on lupus in animal experiments and its underlying mechanism remain inadequately explored.

METHODS

The present study aimed to investigate the impact of high humidity (80 ± 5%) on lupus using female and male MRL/lpr mice, with a particular focus on elucidating the role of gut microbiota in this process. To this end, fecal microbiota transplantation (FMT) was employed to transfer the gut microbiota of MRL/lpr mice under high humidity to blank MRL/lpr mice under normal humidity (50 ± 5%), allowing for an assessment of the effect of FMT on lupus.

RESULTS

The study revealed that high humidity exacerbated lupus indices (serum anti-dsDNA, ANA, IL-6, and IFN- g, and renal pathology) in female MRL/lpr mice but had no significant effect on male MRL/lpr mice. The aggravation of lupus caused by high humidity may be attributed to the increased abundances of the Rikenella, Romboutsia, Turicibacter, and Escherichia-Shigella genera in female MRL/lpr mice. Furthermore, FMT also exacerbated lupus in female MRL/lpr mice but not in male MRL/lpr mice.

CONCLUSION

In summary, this study has demonstrated that high humidity exacerbated lupus by modulating gut microbiota in female MRL/lpr mice. The findings underscore the importance of considering environmental factors and gut microbiota in the development and progression of lupus, particularly among female patients.

Gut microbiota in SLE: from animal models to clinical evidence and pharmacological perspectives

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease driven by complex interactions between genetics and environmental factors. SLE is characterised by breaking self-immune tolerance and autoantibody production that triggers inflammation and damage of multiple organs. Given the highly heterogeneous nature of SLE, the treatments currently used are still not satisfactory with considerable side effects, and the development of new therapies is a major health issue for better patient management. In this context, mouse models significantly contribute to our knowledge of the pathogenesis of SLE and are an invaluable tool for testing novel therapeutic targets. Here, we discuss the role of the most used SLE mouse models and their contribution to therapeutic improvement. Considering the complexity of developing targeted therapies for SLE, adjuvant therapies are also increasingly proposed. Indeed, murine and human studies have recently revealed that gut microbiota is a potential target and holds great promises for successful new SLE therapies. However, the mechanisms of gut microbiota dysbiosis in SLE remain unclear to date. In this review, we propose an inventory of existing studies investigating the relationship between gut microbiota dysbiosis and SLE to establish microbiome signature that may serve as a potential biomarker of the disease and its severity as well as a new potential therapy target. This approach may open new possibilities for early diagnosis, prevention and therapeutic perspectives of SLE based on gut microbiome.

Male microbiota-associated metabolite restores macrophage efferocytosis in female lupus-prone mice via activation of PPARγ/LXR signaling pathways

Systemic lupus erythematosus development is influenced by both sex and the gut microbiota. Metabolite production is a major mechanism by which the gut microbiota influences the immune system, and we have previously found differences in the fecal metabolomic profiles of lupus-prone female and lupus-resistant male BWF1 mice. Here we determine how sex and microbiota metabolite production may interact to affect lupus. Transcriptomic analysis of female and male splenocytes showed genes that promote phagocytosis were upregulated in BWF1 male mice. Because patients with systemic lupus erythematosus exhibit defects in macrophage-mediated phagocytosis of apoptotic cells (efferocytosis), we compared splenic macrophage efferocytosis in vitro between female and male BWF1 mice. Macrophage efferocytosis was deficient in female compared to male BWF1 mice but could be restored by feeding male microbiota. Further transcriptomic analysis of the genes upregulated in male BWF1 mice revealed enrichment of genes stimulated by PPARγ and LXR signaling. Our previous fecal metabolomics analyses identified metabolites in male BWF1 mice that can activate PPARγ and LXR signaling and identified one in particular, phytanic acid, that is a very potent agonist. We show here that treatment of female BWF1 splenic macrophages with phytanic acid restores efferocytic activity via activation of the PPARγ and LXR signaling pathways. Furthermore, we found phytanic acid may restore female BWF1 macrophage efferocytosis through upregulation of the proefferocytic gene CD36. Taken together, our data indicate that metabolites produced by BWF1 male microbiota can enhance macrophage efferocytosis and, through this mechanism, could potentially influence lupus progression.

The effects and significance of gut microbiota and its metabolites on the regulation of osteoarthritis: Close coordination of gut-bone axis

Osteoarthritis (OA) is a common chronic degenerative disease of articular cartilage in middle-aged and older individuals, which can result in the joint pain and dysfunction, and even cause the joint deformity or disability. With the enhancing process of global aging, OA has gradually become a major public health problem worldwide. Explaining pathogenesis of OA is critical for the development of new preventive and therapeutic interventions. In recent years, gut microbiota (GM) has been generally regarded as a “multifunctional organ,” which is closely relevant with a variety of immune, metabolic and inflammatory functions. Meanwhile, more and more human and animal researches have indicated the existence of gut-bone axis and suggested that GM and its metabolites are closely involved in the pathogenic process of OA, which might become a potential and promising intervention target. Based on the close coordination of gut-bone axis, this review aims to summarize and discuss the mechanisms of GM and its metabolites influencing OA from the aspects of the intestinal mucosal barrier modulation, intestinal metabolites modulation, immune modulation and strategies for the prevention or treatment of OA based on perspectives of GM and its metabolites, thus providing a profound knowledge and recognition of it.

Fecal immunoglobulin A (IgA) and its subclasses in systemic lupus erythematosus patients are nuclear antigen reactive and this feature correlates with gut permeability marker levels

Systemic lupus erythematosus (SLE) is characterized by the production of anti-nuclear autoantibodies. Here, for the first time, we show that the abundances of gut permeability marker Zonulin and IgA1- and IgA2- subclasses are significantly higher in the fecal samples of SLE patients compared to HCs. Importantly, IgA-total, and IgA1- and IgA2-subclasses from SLE patients showed higher nAg reactivity titers. Notably, we found that not only the nuclear antigen (nAg) reactive fecal IgA1:IgA2 ratio is higher in SLE patients, but also the abundance and nAg reactivity of fecal IgA and subclasses, IgA1 particularly, correlate with the fecal levels of Zonulin, which is produced primarily in the small intestine. These observations that higher amounts of nAg-reactive IgA and gut permeability marker are produced, particularly, in the proximal gut suggest a compromised epithelial barrier function and pro-inflammatory characteristics of small intestine in SLE patients.

Immune-relevant genes of systemic lupus erythematosus by transcriptome profiling analysis

OBJECTIVE

Our study aimed to reveal the roles of long noncoding RNA (lncRNA) and immune-relevant genes in systemic lupus erythematosus (SLE).

METHODS

Expression profiling dataset GSE65391 consisted of 72 healthy blood samples and 924 SLE blood samples was downloaded from the Gene Expression Omnibus. Differentially expressed RNAs (DERs) in SLE samples were identified using the Limma package. Immune-relevant DERs were uncovered after assessing the immune cell infiltration types of different samples. Modules significantly related to the disease were extracted via weighted gene co-expression network analysis (WGCNA), followed by module-trait analysis. LncRNA-mRNA co-expression network was constructed for DERs in immune-relevant modules. Genes related to SLE were further revealed via the Comparative Toxicogenomics Database (CTD). Validation assay was conducted by another independent expression profiling dataset, GSE46907 (consisted of 5 healthy blood samples and 5 SLE blood samples) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis of 15 healthy blood samples and 15 SLE blood samples.

RESULTS

A total of 606 DERs, including 19 lncRNAs and 587 mRNAs, were identified. Obvious differences were observed in the proportions of 20 immune cell types, and 378 immune-relevant DERs were revealed. Genes in the lncRNA-mRNA co-expression network were significantly enriched in primary immunodeficiency, hematopoietic cell lineage, B cell receptor signaling pathway, SLE (up-regulated FCGR3A, down-regulated CD40LG, up-regulated HIST1H2BE, down-regulated human leukocyte antigen [HLA]-DOA, down-regulated HLA-DOB, up-regulated HIST1H3D, and up-regulated HIST1H2BC), and intestinal immune network for IgA production. SLE-related gene, CD40LG, retrieved from CTD has co-expression interactions with seven differentially expressed lncRNAs (HCG27, LINC02555, LINC02210, DHRS4-AS1, MIR600HG, DANCR, and LINC01278). CD40LG and HLA-DOA, were observed down-regulated, and FCGR3A, and HIST1H2BE were up-regulated in validation dataset GES46907. Moreover, CD40LG was validated to be down-regulated using qRT-PCR.

CONCLUSIONS

Our results provide new insight in understanding the pathogenesis of SLE and might be helpful for developing new therapeutic approaches of SLE by modulating immune response.

Estrogen-gut microbiota interactions and irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder with a complex pathogenesis that has a serious impact on the quality of life of patients. Abnormal visceral sensation, disordered gut motility, dysregulated immunity, and damaged intestinal barrier are thought to be involved in the pathogenesis of IBS. Female predisposition to IBS strongly suggests that sex hormones such as estrogen are involved in the development of IBS. In addition, dysbiosis of the intestinal flora is closely related to IBS. The interaction between estrogen and gut microbiota in IBS has not been fully elucidated. This review summarizes and evaluates the progress of related studies. Based on the new findings and shortcomings of current studies, we discuss the directions and issues that need to be resolved in future research.

Gut Microbiota, Leaky Gut, and Autoimmune Diseases

With the rising prevalence of autoimmune diseases, the role of the environment, specifically the gut microbiota, in disease development has grown to be a major area of study. Recent advances show a relationship and possible cause and effect between the gut microbiota and the initiation or exacerbation of autoimmune diseases. Furthermore, microbial dysbiosis and leaky gut are frequent phenomena in both human autoimmune diseases and the murine autoimmunity models. This review will focus on literature in recent years concerning the gut microbiota and leaky gut in relation to the autoimmune diseases, including systemic lupus erythematosus, type 1 diabetes, and multiple sclerosis.

Negative correlation between IL-1β, IL-12 and TNF-γ, and cortisol levels in patients with panic disorder

INTRODUCTION

Chronic exposure to stress is a major risk factor in anxiety disorders (ADs) and can be accompanied by an altered microbiome-gut-brain axis and a compromised immune system. In recent years, the study of inflammatory processes in AD has gained special attention. Continued stress causes the reactivity of the hypothalamic-pituitary-adrenal (HPA) axis, the alteration of the intestinal microbiota and the consequent release of pro-inflammatory cytokines, affecting the sensitivity to stress and the similar behavior of anxiety.

METHOD

The aim of the present study was to evaluate the interrelationships between measures of proinflammatory cytokines and cortisol in patients with panic disorder (PD).

RESULTS

The main results of the correlation analysis revealed that the levels of pro-inflammatory cytokines interleukin (IL)-1β, IL-12, and tumor necrosis factor gamma were negatively correlated with cortisol scores (area under the curve with respect to the ground).

CONCLUSIONS

These results suggest that the inflammatory response is associated with the reactivity of the HPA axis in patients with PD and may influence the maintenance of anxiety behavior.

Dysbiosis of the Female Murine Gut Microbiome Exacerbates Neutrophil-Mediated Vascular Allograft Injury by Affecting Immunoregulation by Acetate

BACKGROUND

The gut microbiota affects immune responses that cause organ transplant rejection, but the mechanisms by which this occurs remain poorly understood.

METHODS

We have examined, in a murine model, how disruption of the gut microbiota with antibiotics early in life alters this microbial community later in life to affect immune responses that injure vascular allografts.

RESULTS

Analysis of 16S rRNA and whole genome sequencing of the gut microbiota demonstrated that early life disruption of this microbial community with antibiotics caused a reduction in taxa and enzymatic genes involved in the synthesis of acetate, an immunoregulatory metabolite in mice and humans. When allograft vascular injury was examined, early life disruption of the gut microbiota increased neutrophil accumulation and related medial injury of transplanted arteries. Normalizing the gut microbiota by co-housing and oral administration of acetate prevented neutrophil-mediated vascular allograft injury.

CONCLUSIONS

Dysbiosis of the gut microbiome that reduces its production of the immunoregulatory metabolite acetate exacerbates neutrophil-mediated allograft vascular injury.

Preclinical stage abundance and nuclear antigen reactivity of fecal Immunoglobulin A (IgA) varies among males and females of lupus-prone mouse models

Systemic lupus erythematosus (SLE) is characterized by the production of pathogenic autoantibodies with nuclear antigen (nAg) specificity. Using (SWRxNZB)F1 (SNF1) mice, we showed higher levels of IgA production in the intestine and the nAg reactivity of fecal IgA under lupus susceptibility. Here, we determined if the fecal IgA abundance and nAg reactivity are higher in, different among, various lupus-prone preclinical models (MRL/lpr, NZBxNZW-F1, SNF1, NZM2410 and NZM2328). We also determined if the fecal IgA nAg reactivity at pre-seropositive ages correlates with the eventual serum autoantibody levels in males and females of these mouse models. We show that age dependent increase in the abundance and nAg reactivity of fecal IgA can vary among different lupus-prone mouse models. Importantly, fecal IgA in these mice show significant levels of nAg reactivity, starting as early as at juvenile age. Furthermore, the pre-seropositive stage nAg reactivity of fecal IgA in most lupus-prone strains correlates well with that of eventual, seropositive stage systemic autoantibody levels. Gender differences in serum autoantibody levels were preceded by similar differences in the fecal IgA abundance and nAg reactivity. These observations suggest that fecal IgA features, nAg reactivity particularly, could serve as a biomarker for early prediction of the eventual systemic autoimmunity in lupus-prone subjects.

Comparative analysis of gut microbial composition and potential functions in captive forest and alpine musk deer

Gut microbiota forms a unique microecosystem and performs various irreplaceable metabolic functions for ruminants. The gut microbiota is important for host health and provides new insight into endangered species conservation. Forest musk deer (FMD) and alpine musk deer (AMD) are typical small ruminants, globally endangered due to excessive hunting and habitat loss. Although nearly 60 years of captive musk deer breeding has reduced the hunting pressure in the wild, fatal gastrointestinal diseases restrict the growth of captive populations. In this study, 16S rRNA high-throughput sequencing revealed the differences in gut microbiota between FMD and AMD based on 166 fecal samples. The alpha diversity was higher in FMD than in AMD, probably helping FMD adapt to different and wider habitats. The ß-diversity was higher between adult FMD and AMD than juveniles and in winter than late spring. The phylum Firmicutes and the genera Christensenellaceae R7 group, Ruminococcus, Prevotellaceae UCG-004, and Monoglobus were significantly higher in abundance in FMD than in AMD. However, the phylum Bacteroidetes and genera Bacteroides, UCG-005, Rikenellaceae RC9 gut group, and Alistipes were significantly higher in AMD than FMD. The expression of metabolic functions was higher in AMD than in FMD, a beneficial pattern for AMD to maintain higher energy and substance metabolism. Captive AMD may be at higher risk of intestinal diseases than FMD, with higher relative abundances of most opportunistic pathogens and the expression of disease-related functions. These results provide valuable data for breeding healthy captive musk deer and assessing their adaptability in the wild. KEY POINTS: • Alpha diversity of gut microbiota was higher in FMD than that in AMD • Expression of metabolic and disease-related functions was higher in AMD than in FMD.

Gut Microbiota Dysbiosis in Systemic Lupus Erythematosus: Novel Insights into Mechanisms and Promising Therapeutic Strategies

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that was traditionally thought to be closely related to genetic and environmental risk factors. Although treatment options for SLE with hormones, immunosuppressants, and biologic drugs are now available, the rates of clinical response and functional remission of these drugs are still not satisfactory. Currently, emerging evidence suggests that gut microbiota dysbiosis may play crucial roles in the occurrence and development of SLE, and manipulation of targeting the gut microbiota holds great promises for the successful treatment of SLE. The possible mechanisms of gut microbiota dysbiosis in SLE have not yet been well identified to date, although they may include molecular mimicry, impaired intestinal barrier function and leaky gut, bacterial biofilms, intestinal specific pathogen infection, gender bias, intestinal epithelial cells autophagy, and extracellular vesicles and microRNAs. Potential therapies for modulating gut microbiota in SLE include oral antibiotic therapy, fecal microbiota transplantation, glucocorticoid therapy, regulation of intestinal epithelial cells autophagy, extracellular vesicle-derived miRNA therapy, mesenchymal stem cell therapy, and vaccination. This review summarizes novel insights into the mechanisms of microbiota dysbiosis in SLE and promising therapeutic strategies, which may help improve our understanding of the pathogenesis of SLE and provide novel therapies for SLE.

Gut Microbiota-Medication Interaction in Rheumatic Diseases

Besides its contribution to the development of rheumatic diseases, the gut microbiota interact with anti-rheumatic drugs. The intestinal microbiota can directly metabolize many drugs and indirectly change drug metabolism through a complex multi-dimensional interaction with the host, thus affecting individual response to drug therapy and adverse effects. The focus of the current review is to address recent advances and important progress in our understanding of how the gut microbiota interact with anti-rheumatic drugs and provide perspectives on promoting precision treatment, drug discovery, and better therapy for rheumatic diseases.

Of mice and men and women: Sexual dimorphism of the gut microbiome

The gut microbiome plays a critical role in developing and educating our immune system. Therefore, its now well-established role in autoimmunity and immune disorders is in some ways not surprising. However, it is well-documented in the literature that there is a female predisposition to autoimmune disorders, while sexual dimorphisms in the human microbiome have been confined largely to areas outside of the gut. Herein, we will review the evidence of sexual dimorphism in the gut microbiome in both mice and humans, how this differs in animal models versus humans, and how such dimorphisms may be established and influenced by both host and environmental factors. We will conclude with a discussion on how these aspects of the gut microbiome may contribute to both the study and pathogenesis of gender-specific autoimmunity and immune disorders.

Roles of Sex Hormones and Gender in the Gut Microbiota

The distribution of gut microbiota varies according to age (childhood, puberty, pregnancy, menopause, and old age) and sex. Gut microbiota are known to contribute to gastrointestinal (GI) diseases such as irritable bowel syndrome, inflammatory bowel disease, and colon cancer; however, the exact etiology remains elusive. Recently, sex and gender differences in GI diseases and their relation to gut microbiota has been suggested. Furthermore, the metabolism of estrogen and androgen was reported to be related to the gut microbiome. As gut microbiome is involved in the excretion and circulation process of sex hormones, the concept of “microgenderome” indicating the role of sex hormone on the gut microbiota has been suggested. However, further research is needed for this concept to be universally accepted. In this review, we summarize sex- and gender-differences in gut microbiota and the interplay of microbiota and GI diseases, focusing on sex hormones. We also describe the metabolic role of the microbiota in this regard. Finally, current subjects, such as medication including probiotics, are briefly discussed.

Potential for Antigen-Specific Tolerizing Immunotherapy in Systematic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic complex systemic autoimmune disease characterized by multiple autoantibodies and clinical manifestations, with the potential to affect nearly every organ. SLE treatments, including corticosteroids and immunosuppressive drugs, have greatly increased survival rates, but there is no curative therapy and SLE management is limited by drug complications and toxicities. There is an obvious clinical need for safe, effective SLE treatments. A promising treatment avenue is to restore immunological tolerance to reduce inflammatory clinical manifestations of SLE. Indeed, recent clinical trials of low-dose IL-2 supplementation in SLE patients showed that in vivo expansion of regulatory T cells (Treg cells) is associated with dramatic but transient improvement in SLE disease markers and clinical manifestations. However, the Treg cells that expanded were short-lived and unstable. Alternatively, antigen-specific tolerance (ASIT) approaches that establish long-lived immunological tolerance could be deployed in the context of SLE. In this review, we discuss the potential benefits and challenges of nanoparticle ASIT approaches to induce prolonged immunological tolerance in SLE.

Gut Microbiome and Metabolites in Systemic Lupus Erythematosus: Link, Mechanisms and Intervention

Systemic lupus erythematosus (SLE), often considered the prototype of autoimmune diseases, is characterized by over-activation of the autoimmune system with abnormal functions of innate and adaptive immune cells and the production of a large number of autoantibodies against nuclear components. Given the highly complex and heterogeneous nature of SLE, the pathogenesis of this disease remains incompletely understood and is presumed to involve both genetic and environmental factors. Currently, disturbance of the gut microbiota has emerged as a novel player involved in the pathogenesis of SLE. With in-depth research, the understanding of the intestinal bacteria-host interaction in SLE is much more comprehensive. Recent years have also seen an increase in metabolomics studies in SLE with the attempt to identify potential biomarkers for diagnosis or disease activity monitoring. An intricate relationship between gut microbiome changes and metabolic alterations could help explain the mechanisms by which gut bacteria play roles in the pathogenesis of SLE. Here, we review the role of microbiota dysbiosis in the aetiology of SLE and how intestinal microbiota interact with the host metabolism axis. A proposed treatment strategy for SLE based on gut microbiome (GM) regulation is also discussed in this review. Increasing our understanding of gut microbiota and their function in lupus will provide us with novel opportunities to develop effective and precise diagnostic strategies and to explore potential microbiota-based treatments for patients with lupus.

Gut Microbiota in Lupus: a Butterfly Effect?

PURPOSE OF REVIEW

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease that typically displays chronic inflammatory tissue damage and miscellaneous circulatory autoantibodies, as well as distinctive type 1 interferon signatures. The etiology of SLE is unclear and currently is attributed to genetic predisposition and environmental triggers. Gut microbiota has recently been considered a critical environmental pathogenic factor in immune-related disorders, and studies are ongoing to uncover the key pathogens and the imputative mechanisms. Fundamental advancements on the role of the microbiota in SLE pathology have been achieved in recent years and are summarized in this review.

RECENT FINDINGS

Recent findings suggested that gut commensals could propagate autoimmunity via molecular mimicry in which ortholog-carrying microbes cross-activate autoreactive T/B cells and trigger the response against host autoantigens, or via bystander activation by stimulating antigen-presenting cells that present autoantigens and enhancing the expression of co-stimulatory molecules and cytokines, thus leading to the loss of self-tolerance and the production of autoantibodies. Additionally, the break of gut barrier and the translocation of gut commensals to inner organs can trigger immune dysregulation and inappropriate systemic inflammation. All these microbiota-mediated mechanisms could contribute to lupus immunopathogenesis and promote disease development in susceptible individuals. Evidence of the causative role of disturbed gut microbiome in SLE is still limited, and the related molecular mechanisms and pathways are largely elusive. However, the modification of gut microbiota, such as pathobiont vaccine, special diet, restricted consortium transplantation, as well as regulatory metabolites supplementation, might be promising strategies for lupus prophylaxis and treatment.

How biological sex of the host shapes its gut microbiota

The gut microbiota is a complex system, consisting of a dynamic population of microorganisms, involved in the regulation of the host's homeostasis. A vast number of factors are driving the gut microbiota composition including diet, antibiotics, environment, and lifestyle. However, in the past decade, a growing number of studies also focused on the role of sex in relationship to changes in the gut microbiota composition in animal experiments as well as in human beings. Despite the progress in investigation techniques, still little is known about the mechanism behind the observed sex-related differences. In this review, we summarized current knowledge on the sex-dependent differences of the intestinal commensals and discuss the probable direct impact of sex hormones and more indirect effects such as dietary habits or antibiotics. While we have to conclude limited data on specific developmental stages, a clear role for sexual hormones and most probably for testosterone emerges.

Implication of Human Bacterial Gut Microbiota on Immune-Mediated and Autoimmune Dermatological Diseases and Their Comorbidities: A Narrative Review

During the last decade, the advent of modern sequencing methods (next generation techniques, NGS) has helped describe the composition of the human gut microbiome, enabling us to understand the main characteristics of a healthy gut microbiome and, conversely, the magnitude of its disease-related changes. This new knowledge has revealed that healthy gut microbiota allow the maintenance of several crucial physiological functions, such as the ability to regulate the innate and adaptive immune systems. Increasing evidence has pointed out a condition of dysbiosis in several autoimmune/immune mediated dermatological conditions and specific gut microbial signatures have also been reported to correlate with clinical and prognostic parameters of such diseases. Based on a literature search of relevant published articles, this review debates the current knowledge and the possible pathogenic implications of bacterial gut microbiota composition assessed through NGS techniques in systemic lupus erythematosus, atopic dermatitis, psoriasis, and alopecia areata. Evidence of a potential role of specific gut microbiota signatures in modulating the clinical course of such diseases and their main comorbidities has been also reviewed.

The gut-joint axis in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder that primarily affects the joints. One hypothesis for the pathogenesis of RA is that disease begins at mucosal sites as a consequence of interactions between the mucosal immune system and an aberrant local microbiota, and then transitions to involve the synovial joints. Alterations in the composition of the microbial flora in the lungs, mouth and gut in individuals with preclinical and established RA suggest a role for mucosal dysbiosis in the development and perpetuation of RA, although establishing whether these alterations are the specific consequence of intestinal involvement in the setting of a systemic inflammatory process, or whether they represent a specific localization of disease, is an ongoing challenge. Data from mouse models of RA and investigations into the preclinical stages of disease also support the hypothesis that these alterations to the microbiota predate the onset of disease. In addition, several therapeutic options widely used for the treatment of RA are associated with alterations in intestinal microbiota, suggesting that modulation of intestinal microbiota and/or intestinal barrier function might be useful in preventing or treating RA.

Why women have more autoimmune diseases than men: An evolutionary perspective

Women have up to a fourfold increase in risk for autoimmune disease compared to men. Many explanations have been proposed, including sex hormones, the X chromosome, microchimerism, environmental factors, and the microbiome. However, the mechanism for this autoimmune sex bias remains obscure. In this manuscript, we evaluate the hypothesis that qualitative or quantitative differences in circulating antibodies may explain, at least in part, the pathogenesis of autoimmune disease and its sex bias-especially when considering an evolutionary perspective. Indeed, women have higher absolute levels of antibodies than men, and (auto)antibodies are also associated with most autoimmune diseases. Several facts suggest differences in antibodies may cause increased prevalence of autoimmune disease in women. First, the association between increased quantities of serum antibodies and increased prevalence of autoimmunity is found not only in women, but also in men with Klinefelter syndrome. Second, both serum antibody levels and autoimmunity spike in the postpartum period. Third, a dose-response effect exists between parity and both serum antibodies and prevalence of autoimmune disease. Fourth, many biologically plausible mechanisms explain the association, such as T cell-dependent activation of B cells and/or VGLL3. The evolutionary underpinning of increased antibodies in women is likely to be protection of offspring from infections. Overall, this evolutionary paradigm can help explain why the phenomenon of autoimmunity occurs preferentially in women and raises the possibility of new treatment options.

Epstein-Barr Functional Mimicry: Pathogenicity of Oncogenic Latent Membrane Protein-1 in Systemic Lupus Erythematosus and Autoimmunity

Systemic lupus erythematosus (SLE) and other autoimmune diseases are propelled by immune dysregulation and pathogenic, disease-specific autoantibodies. Autoimmunity against the lupus autoantigen Sm is associated with cross-reactivity to Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1). Additionally, EBV latent membrane protein-1 (LMP1), initially noted for its oncogenic activity, is an aberrantly active functional mimic of the B cell co-stimulatory molecule CD40. Mice expressing a transgene (Tg) for the mCD40-LMP1 hybrid molecule (containing the cytoplasmic tail of LMP1) have mild autoantibody production and other features of immune dysregulation by 2-3 months of age, but no overt autoimmune disease. This study evaluates whether exposure to the EBV molecular mimic, EBNA-1, stimulates antigen-specific and concurrently-reactive humoral and cellular immunity, as well as lupus-like features. After immunization with EBNA-1, mCD40-LMP1 Tg mice exhibited enhanced, antigen-specific, cellular and humoral responses compared to immunized WT congenic mice. EBNA-1 specific proliferative and inflammatory cytokine responses, including IL-17 and IFN-γ, were significantly increased (p<0.0001) in mCD40-LMP1 Tg mice, as well as antibody responses to amino- and carboxy-domains of EBNA-1. Of particular interest was the ability of mCD40-LMP1 to drive EBNA-1 associated molecular mimicry with the lupus-associated autoantigen, Sm. EBNA-1 immunized mCD40-LMP1 Tg mice exhibited enhanced proliferative and cytokine cellular responses (p<0.0001) to the EBNA-1 homologous epitope PPPGRRP and the Sm B/B' cross-reactive sequence PPPGMRPP. When immunized with the SLE autoantigen Sm, mCD40-LMP1 Tg mice again exhibited enhanced cellular and humoral immune responses to both Sm and EBNA-1. Cellular immune dysregulation with EBNA-1 immunization in mCD40-LMP1 Tg mice was accompanied by enhanced splenomegaly, increased serum blood urea nitrogen (BUN) and creatinine levels, and elevated anti-dsDNA and antinuclear antibody (ANA) levels (p<0.0001 compared to mCD40 WT mice). However, no evidence of immune-complex glomerulonephritis pathology was noted, suggesting that a combination of EBV and genetic factors may be required to drive lupus-associated renal disease. These data support that the expression of LMP1 in the context of EBNA-1 may interact to increase immune dysregulation that leads to pathogenic, autoantigen-specific lupus inflammation.

Arecanut (Areca catechu L.) Seed Polyphenol-Ameliorated Osteoporosis by Altering Gut Microbiome via LYZ and the Immune System in Estrogen-Deficient Rats

Polyphenol can improve osteoporosis and is closely associated with gut microbiota, while the mechanism and the relationship among polyphenol, osteoporosis, and gut microbiota colonization remain unclear. Here, an osteoporosis rat model established by ovariectomy was employed to investigate the improving mechanism of arecanut (Areca catechu L.) seed polyphenol (ACP) on osteoporosis by regulating gut microbiota. We analyzed the bone microstructure, Paneth cells, regulating microbial protein (lysozyme (LYZ)), proinflammatory cytokines, macrophage infiltration levels, and gut microbial communities in a rat. ACP improved the trabecular microstructure compared to OVX, including the increased trabecular number (Tb.N) (P < 0.01) and trabecular thickness (Tb.Th) (P < 0.001) and decreased trabecular separation (Tb.Sp) (P < 0.01). At the phylum level, Bacteroidetes was increased after ovariectomy (P < 0.001) and Firmicutes and Proteobacteria were increased in ACP (P < 0.001). Antiosteoporosis groups with lower LYZ and Paneth cells (P < 0.001) showed that the microbiota Alistipes, which have a negative effect on bone metabolism were decreased in ACP (P < 0.001). Altogether, these studies showed that the estrogen deficiency could induce the shedding of Paneth cells, which leads to the decrease of LYZ, while ACP could increase the LYZ expression by maintaining the population of Paneth cells in an estrogen-deficient host, which were implicated in gut microbiota regulation and improved osteoporosis by controlling the inflammatory reaction.

The Interplay of Sex Steroids, the Immune Response, and the Intestinal Microbiota

The role of sex steroids in mammalian maturation is well established. Recently, it has been increasingly appreciated that sex steroids also play an important role in the propensity of adults to develop a myriad of diseases. The exposure and responsiveness of tissues to sex steroids varies among individuals and between the sexes, and this has been correlated with gender-specific differences in the composition of the intestinal microbiota and in susceptibility to metabolic, autoimmune, and neoplastic diseases. Here we focus on recent studies that demonstrate an interplay between sex steroids, the intestinal immune response, and the intestinal microbiota. While correlations between biological sex, the intestinal innate immune response, intestinal inflammation, and intestinal microbiota have been established, many gaps in our knowledge prevent the emergence of an overarching model for this complex interaction. Such a model could aid in the development of prebiotic, probiotic, or synthetic therapeutics that decrease the risk of autoimmune, metabolic, neoplastic, and infectious diseases of the intestine and mitigate the particular health risks faced by individuals receiving sex steroid treatment.

Abundance and nuclear antigen reactivity of intestinal and fecal Immunoglobulin A in lupus-prone mice at younger ages correlate with the onset of eventual systemic autoimmunity

Our recent studies, using (SWRxNZB)F1 (SNF1) mice, showed a potential contribution of the gut microbiota and pro-inflammatory immune responses of the gut mucosa to systemic autoimmunity in lupus. Here, using this mouse model, we determined the abundance and the nAg reactivity of IgA antibody produced in the intestine under lupus susceptibility. Intestinal lymphoid tissues from SNF1 mice, females particularly, showed significantly higher frequencies of nAg (dsDNA and nucleohistone) reactive IgA producing B cells compared to B6 females. Most importantly, younger age fecal IgA -abundance and -nAg reactivity of lupus-prone mice showed a positive correlation with eventual systemic autoimmunity and proteinuria onset. Depletion of gut microbiota in SNF1 mice resulted in the diminished production of IgA in the intestine and the nAg reactivity of these antibodies. Overall, these observations show that fecal IgA features, nuclear antigen reactivity particularly, at preclinical stages/in at-risk subjects could be predictive of autoimmune progression.

Chemically or surgically induced thyroid dysfunction altered gut microbiota in rat models

Thyroid hormones are essential for the regulation of energy homeostasis and metabolic processes. However, the relationship between thyroid function and host gut microbial communities is not properly understood. To determine whether and how gut microbiota is associated with thyroid function, metagenomics analysis of the bacterial population in fecal samples of rat models of hyperthyroidism (induced by levothyroxine) and hypothyroidism (induced by propylthiouracil or thyroidectomy) was conducted through 16S rRNA gene sequencing. Our results revealed that all thyroid dysfunction models were definitely established and gut microbial composition varied according to different thyroid functional status. The relative abundance of Ruminococcus was significantly higher in the hyperthyroidism group (HE) vs both the normal and hypothyroidism groups (HO) while S24-7 was significantly higher in the HO group. The population of Prevotellaceae and Prevotella were significantly lower in the HO group vs the normal. Firmicutes and Oscillospira were significantly higher in the SHO (surgery-induced hypothyroidism) group, while Prevotellaceae and Prevotella showed lower abundance in the SHO group than the SHAM group. Present results suggest that thyroid functions may have the potential to influence the profile of gut microbiota and could be used as foundation to investigate interaction mechanism between thyroid and gut microbiome.