Systemic Lupus Erythematosus and dysbiosis in the microbiome: cause or effect or both?

Gut microbiota regulation of T lymphocyte subsets during systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by disturbance of pro-inflammatory and anti-inflammatory lymphocytes. Growing evidence shown that gut microbiota participated in the occurrence and development of SLE by affecting the differentiation and function of intestinal immune cells. The purpose of this study was to investigate the changes of gut microbiota in SLE and judge its associations with peripheral T lymphocytes.

METHODS

A total of 19 SLE patients and 16 HCs were enrolled in this study. Flow cytometry was used to detect the number of peripheral T lymphocyte subsets, and 16 s rRNA was used to detect the relative abundance of gut microbiota. Analyzed the correlation between gut microbiota with SLEDAI, ESR, ds-DNA and complement. SPSS26.0 software was used to analyze the experimental data. Mann-Whitney U test was applied to compare T lymphocyte subsets. Spearman analysis was used for calculating correlation.

RESULTS

Compared with HCs, the proportions of Tregs (P = 0.001), Tfh cells (P = 0.018) and Naïve CD4 + T cells (P = 0.004) significantly decreased in SLE patients, and proportions of Th17 cells (P = 0.020) and γδT cells (P = 0.018) increased in SLE. The diversity of SLE patients were significantly decreased. Addition, there were 11 species of flora were discovered to be distinctly different in SLE group (P < 0.05). In the correlation analysis of SLE, Tregs were positively correlated with Ruminococcus2 (P = 0.042), Th17 cells were positively correlated with Megamonas (P = 0.009), γδT cells were positively correlated with Megamonas (P = 0.003) and Streptococcus (P = 0.004), Tfh cells were positively correlated with Bacteroides (P = 0.040), and Th1 cells were negatively correlated with Bifidobacterium (P = 0.005). As for clinical indicators, the level of Tregs was negatively correlated with ESR (P = 0.031), but not with C3 and C4, and the remaining cells were not significantly correlated with ESR, C3 and C4.

CONCLUSION

Gut microbiota and T lymphocyte subsets of SLE changed and related to each other, which may break the immune balance and affect the occurrence and development of SLE. Therefore, it is necessary to pay attention to the changes of gut microbiota and provide new ideas for the treatment of SLE.

The role of the aryl hydrocarbon receptor (AhR) in modulating intestinal ILC3s to optimise gut pathogen resistance in lupus and benefits of nutritional AhR ligands

BACKGROUND AND AIMS

Dysbiosis is emerging as a potential trigger of systemic lupus erythematosus (SLE). Group 3 innate lymphoid cells (ILC3s) are recognised as key regulators of intestinal homeostasis. The aryl hydrocarbon receptor (AhR) is critical to intestinal ILC3 development and function. This mechanistic review aimed to investigate whether AhR activation of gut ILC3s facilitates IL-22-mediated antimicrobial peptide (AMP) production to enhance colonisation resistance and ameliorate SLE pathology associated with intestinal dysbiosis. Furthermore, nutritional AhR ligand potential to enhance pathogen resistance was explored.

METHODOLOGY

This mechanistic review involved a three-tranche systematic literature search (review, mechanism, intervention) using PubMed with critical appraisal. Data was synthesised into themes and summarised in a narrative analysis.

RESULTS

Preclinical mechanistic data indicate that AhR modulation of intestinal ILC3s optimises pathogen resistance via IL-22-derived AMPs. Pre-clinical research is required to validate this mechanism in SLE. Data on systemic immune consequences of AhR modulation in lupus suggest UVB-activated ligands induce aberrant AhR signalling while many dietary ligands exert beneficial effects. Data on xenobiotic-origin ligands is varied, although considerable evidence has demonstrated negative effects on Th17 to Treg balance. Limited human evidence supports the role of nutritional AhR ligands in modulating SLE pathology. Preclinical and clinical data support anti-inflammatory effects of dietary AhR ligands.

CONCLUSION

Current evidence is insufficient to fully validate the hypothesis that AhR modulation of intestinal ILC3s can enhance pathogen resistance to ameliorate lupus pathology driven by dysbiosis. However, anti-inflammatory effects of dietary AhR ligands suggest a promising role as a therapeutic intervention for SLE.

A Scoping Review of the Positive and Negative Bacteria Associated With the Gut Microbiomes of Systemic Lupus Erythematosus Patients

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that affects multiple systems of the body. Recent research on the gut microbiota dysbiosis associated with SLE patients has gained traction and warranted further exploration. It has not been determined whether the change in the gut microbiota is a cause of SLE or a symptom of SLE. However, based on the physiological and pathophysiological role of the bacteria in the gut microbiome, as levels of the bacteria rise or fall, symptomatology in SLE patients could be affected. This review analyzes the recent studies that examined the changes in the gut microbiota of SLE patients and highlights the correlations between gut dysbiosis and the clinical manifestations of SLE. A systematic search strategy was developed by combining the terms "SLE," "systemic lupus erythematosus," and "gut microbiome." Biomedical Reference Collection, CINAHL, Medline ProQuest, and PubMed Central databases were searched by combining the appropriate keywords with "AND." Only full-text, English-language articles were searched. The articles were restricted from 2013 to 2023. Only peer-reviewed controlled studies with both human and animal trials were included in this scoping review. Review articles, non-English articles, editorials, case studies, and duplicate articles from the four databases were excluded. Various species of bacteria were found to be positively or negatively associated with SLE gut microbiomes. Among the bacterial species increased were Clostridium, Lactobacilli, Streptococcus, Enterobacter, and Klebsiella. The bacterial species that decreased were Bifidobacteria, Prevotella, and the Firmicutes/Bacteroidetes ratio. Literature shows that Clostridium is one of several bacteria found in abundance, from pre-disease to the diseased state of SLE. Lachnospiraceae and Ruminococcaceae are both part of the family of butyrate-producing anaerobes that are known for their role in strengthening the skin barrier function and, therefore, may explain the cutaneous manifestations of SLE patients. Studies have also shown that the Firmicutes/Bacteroidetes ratio is significantly depressed, which may lead to appetite changes and weight loss seen in SLE patients. Based on the established role of these bacteria within the gut microbiome, the disruption in the gut ecosystem could explain the symptomatology common in SLE patients. By addressing these changes, our scoping review encourages further research to establish a true causal relationship between the bacterial changes in SLE patients as well as furthering the scope of microbiota changes in other systems and autoimmune diseases.

Gut microbiota compositional profile in patients with posner-schlossman syndrome

The cause of Posner-Schlossman syndrome (PSS) remains unknown and its frequent recurrence may eventually lead to irreversible damage of the optic nerve. The influence of immune factors in the pathophysiology of PSS is gaining more and more interest. Increasing evidence suggests that gut dysbiosis plays vital roles in a variety of neurodegenerative and immune-related diseases. However, alterations of the gut microbiota in PSS patients have not been well defined yet. In this study, 16S rRNA sequencing was used to explore the difference of gut microbiota between PSS patients and healthy controls, and the correlation between the microbiota profile and clinical features was also analyzed. Our data demonstrated a significant increase of Prevotella and Prevotellaceae, and a significant reduction of Bacteroides and Bacteroidaceae in PSS patients, and KEGG analysis showed dysfunction of gut microbiota between PSS patients and healthy controls. Interestingly, further analysis showed that the alteration of gut microbiota was correlated with the PSS attack frequency of PSS. This study demonstrated the gut microbiota compositional profile of PSS patients and speculated the risk microbiota of PSS, which is expected to provide new insights for the diagnosis and treatment of PSS.

The gut microbiome in systemic lupus erythematosus: lessons from rheumatic fever

For more than a century, certain bacterial infections that can breach the skin and mucosal barriers have been implicated as common triggers of autoimmune syndromes, especially post-infection autoimmune diseases that include rheumatic fever and post-streptococcal glomerulonephritis. However, only in the past few years has the importance of imbalances within our own commensal microbiota communities, and within the gut, in the absence of infection, in promoting autoimmune pathogenesis become fully appreciated. A diversity of species and mechanisms have been implicated, including disruption of the gut barrier. Emerging data suggest that expansions (or blooms) of pathobiont species are involved in autoimmune pathogenesis and stimulate clonal expansion of T cells and B cells that recognize microbial antigens. This Review discusses the relationship between the gut microbiome and the immune system, and the potential consequence of disrupting the community balance in terms of autoimmune development, focusing on systemic lupus erythematosus. Notably, inter-relationships between expansions of certain members within gut microbiota communities and concurrent autoimmune responses bear features reminiscent of classical post-infection autoimmune disease. From such insights, new therapeutic opportunities are being considered to restore the balance within microbiota communities or re-establishing the gut-barrier integrity to reinforce immune homeostasis in the host.

SLE serum induces altered goblet cell differentiation and leakiness in human intestinal organoids

Human intestinal epithelial cells are the interface between luminal content and basally residing immune cells. They form a tight monolayer that constantly secretes mucus creating a multilayered protective barrier. Alterations in this barrier can lead to increased permeability which is common in systemic lupus erythematosus (SLE) patients. However, it remains unexplored how the barrier is affected. Here, we present an in vitro model specifically designed to examine the effects of SLE on epithelial cells. We utilize human colon organoids that are stimulated with serum from SLE patients. Combining transcriptomic with functional analyses revealed that SLE serum induced an expression profile marked by a reduction of goblet cell markers and changed mucus composition. In addition, organoids exhibited imbalanced cellular composition along with enhanced permeability, altered mitochondrial function, and an interferon gene signature. Similarly, transcriptomic analysis of SLE colon biopsies revealed a downregulation of secretory markers. Our work uncovers a crucial connection between SLE and intestinal homeostasis that might be promoted in vivo through the blood, offering insights into the causal connection of barrier dysfunction and autoimmune diseases.

Understanding the roles of the microbiome in autoimmune rheumatic diseases

The gut microbiome represents a potential promising therapeutic target for autoimmune diseases. This review summarizes the current knowledge on the links between the gut microbiome and several autoimmune rheumatic diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) spondyloarthropathies (SpA), Sjogren's syndrome (SS), and systemic sclerosis (SSc). Evidence from studies of RA and SLE patients suggests that alterations in the gut microbiome composition and function contribute to disease development and progression through increased gut permeability, with microbes and microbial metabolites driving an excessive systemic activation of the immune system. Also, there is growing evidence that gut dysbiosis and subsequent immune cell activation may contribute to disease pathogenesis in SpA and SS. For SSc, there are fewer, but these are still informative, reports on alterations in the gut microbiome. In general, the complex interplay between the microbiome and the immune system is still not fully understood. Here we discuss the current knowledge of the link between the gut microbiome and autoimmune rheumatic diseases, highlighting potentially fertile areas for future research and make considerations on the potential benefits of strategies that restore gut microbiome homeostasis.

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.

Pathogenesis of systemic lupus erythematosus: risks, mechanisms and therapeutic targets

Research elucidating the pathogenesis of systemic lupus erythematosus (SLE) has defined two critical families of mediators, type I interferon (IFN-I) and autoantibodies targeting nucleic acids and nucleic acid-binding proteins, as fundamental contributors to the disease. On the fertile background of significant genetic risk, a triggering stimulus, perhaps microbial, induces IFN-I, autoantibody production or most likely both. When innate and adaptive immune system cells are engaged and collaborate in the autoimmune response, clinical SLE can develop. This review describes recent data from genetic analyses of patients with SLE, along with current studies of innate and adaptive immune function that contribute to sustained IFN-I pathway activation, immune activation and autoantibody production, generation of inflammatory mediators and tissue damage. The goal of these studies is to understand disease mechanisms, identify therapeutic targets and stimulate development of therapeutics that can achieve improved outcomes for patients.

The Disease with a Thousand Faces and the Human Microbiome-A Physiopathogenic Intercorrelation in Pediatric Practice

Numerous interrelationships are known in the literature that have the final effect of unmasking or influencing various pathologies. Among these, the present article aims to discuss the connection between systemic lupus erythematosus (SLE) and the human microbiome. The main purpose of this work is to popularize information about the impact of dysbiosis on the pathogenesis and evolutionary course of pediatric patients with SLE. Added to this is the interest in knowledge and awareness of adjunctive therapeutic means that has the ultimate goal of increasing the quality of life. The means by which this can be achieved can be briefly divided into prophylactic or curative, depending on the phase of the condition in which the patient is. We thus reiterate the importance of the clinician acquiring an overview of SLE and the human microbiome, doubled by in-depth knowledge of the physio-pathogenic interactions between the two (in part achieved through the much-studied gut-target organ axes-brain, heart, lung, skin), with the target objective being that of obtaining individualized, multimodal and efficient management for each individual patient.

Megamonas funiformis, Plasma Zonulin, and Sodium Intake Affect C3 Complement Levels in Inactive Systemic Lupus Erythematosus

The etiology of systemic lupus erythematosus (SLE) remains unclear, with both genetic and environmental factors potentially contributing. This study aimed to explore the relationship among gut microbiota (GM), intestinal permeability, and food intake with inflammatory markers in inactive SLE patients. A total of 22 women with inactive SLE and 20 healthy volunteers were enrolled, and dietary intake was assessed through 24-h dietary recalls. Plasma zonulin was used to evaluate intestinal permeability, while GM was determined by 16S rRNA sequencing. Regression models were used to analyze laboratory markers of lupus disease (C3 and C4 complement and C-reactive protein). Our results showed that the genus Megamonas was significantly enriched in the iSLE group (p < 0.001), with Megamonas funiformis associated with all evaluated laboratory tests (p < 0.05). Plasma zonulin was associated with C3 levels (p = 0.016), and sodium intake was negatively associated with C3 and C4 levels (p < 0.05). A combined model incorporating variables from each group (GM, intestinal permeability, and food intake) demonstrated a significant association with C3 complement levels (p < 0.01). These findings suggest that increased Megamonas funiformis abundance, elevated plasma zonulin, and higher sodium intake may contribute to reduced C3 complement levels in women with inactive SLE.

The oral microbiome in autoimmune diseases: friend or foe?

The human body is colonized by abundant and diverse microorganisms, collectively known as the microbiome. The oral cavity has more than 700 species of bacteria and consists of unique microbiome niches on mucosal surfaces, on tooth hard tissue, and in saliva. The homeostatic balance between the oral microbiota and the immune system plays an indispensable role in maintaining the well-being and health status of the human host. Growing evidence has demonstrated that oral microbiota dysbiosis is actively involved in regulating the initiation and progression of an array of autoimmune diseases.Oral microbiota dysbiosis is driven by multiple factors, such as host genetic factors, dietary habits, stress, smoking, administration of antibiotics, tissue injury and infection. The dysregulation in the oral microbiome plays a crucial role in triggering and promoting autoimmune diseases via several mechanisms, including microbial translocation, molecular mimicry, autoantigen overproduction, and amplification of autoimmune responses by cytokines. Good oral hygiene behaviors, low carbohydrate diets, healthy lifestyles, usage of prebiotics, probiotics or synbiotics, oral microbiota transplantation and nanomedicine-based therapeutics are promising avenues for maintaining a balanced oral microbiome and treating oral microbiota-mediated autoimmune diseases. Thus, a comprehensive understanding of the relationship between oral microbiota dysbiosis and autoimmune diseases is critical for providing novel insights into the development of oral microbiota-based therapeutic approaches for combating these refractory diseases.

The Role of Diet in Influencing the Diversity of Gut Microbiome Related to Lupus Disease Activities: A Systematic Review

Gut microbiome dysbiosis can affect the host immune system. The balance and activity of the gut microbiome, which are influenced by daily diet, might be associated with disease activity in systemic lupus erythematosus (SLE). Therefore, we conducted a systematic review based on the PRISMA guideline to explore the role and types of diet that affects the gut microbiome related to changes in SLE disease activity. All original and full-text English articles in the last ten years were included using predefined keywords according to PEO (population, exposure, and outcome) design in PubMed. The study subjects were carefully analyzed, including lupus-susceptible mice and humans with SLE on various diets. Children and pregnant women populations were excluded. Of 134 studies found, only seven full-text articles had met the inclusion criteria of which only one study conducted in human. This human study showed that dietary polyphenol as dihydrochalcones and flavanones affected the gut microbiome and ameliorated lupus disease activity. On the contrary, dietary flavones increased Blautia (family: Lachnospiraceae), and that often found in active lupus diseases. Furthermore, six studies in lupus-prone mice models showed that resistant starch (RS), retinoic acid (RA) or all-trans retinoic acid (tRA), and acidic water (AW) had influenced the gut microbiome, leading to an improved lupus development. Conversely, the 2018 commercial rodent diet, vitamin A-retinoic acid (VARA), neutral water (NW), and high tryptophan diet had impacted various microbiomes, resulting in increased lupus activity. Interestingly, several diets have the effect of either increasing or decreasing lupus disease activity depending on the microbiome they affect, such as AW associated with Turicibacter spp., which is frequently found in active lupus disease, and tRA in Bacteroidetes associated with renal pathology. To conclude, diet can influence the gut microbiome, which is related to the disease activity process of SLE.

Bidirectional crosstalk between dysbiotic gut microbiota and systemic lupus erythematosus: What is new in therapeutic approaches?

Systemic lupus erythematosus is an autoimmune disease characterized by chronic inflammation and multiple organs damage. Its pathogenesis is complex and involves multiple factors including gut microbiota. Accumulating evidence indicates the interaction of microbial communities with the host immune system to maintain a state of homeostasis. Imbalances within the gut microbial composition and function may contribute to the development of many autoimmune diseases including SLE. In this review, we aim to highlight the dysregulation of commensal bacteria and their metabolites in the gastrointestinal tract and the resulting autoimmune responses in lupus and to decrypt the cross-link between the altered gut microbiota and the immune system in the SLE condition. We also provide new insights into targeting gut microbiota as a promising therapeutic approach to treat and manage SLE.

Sex-dependent Lupus Blautia (Ruminococcus) gnavus strain induction of zonulin-mediated intestinal permeability and autoimmunity

Imbalances in the gut microbiome are suspected contributors to the pathogenesis of Systemic Lupus Erythematosus, and our studies and others have documented that patients with active Lupus nephritis have expansions of the obligate anaerobe, Blautia (Ruminococcus) gnavus (RG). To investigate whether the RG strains in Lupus patients have in vivo pathogenic properties in a gnotobiotic system, we colonized C57BL/6 mice with individual RG strains from healthy adults or those from Lupus patients. These strains were similar in their capacity for murine intestinal colonization of antibiotic-preconditioned specific-pathogen-free, as well as of germ-free adults and of their neonatally colonized litters. Lupus-derived RG strains induced high levels of intestinal permeability that was significantly greater in female than male mice, whereas the RG species-type strain (ATCC29149/VPI C7-1) from a healthy donor had little or no effects. These Lupus RG strain-induced functional alterations were associated with RG translocation to mesenteric lymph nodes, and raised serum levels of zonulin, a regulator of tight junction formation between cells that form the gut barrier. Notably, the level of Lupus RG-induced intestinal permeability was significantly correlated with serum IgG anti RG cell-wall lipoglycan antibodies, and with anti-native DNA autoantibodies that are a biomarker for SLE. Strikingly, gut permeability was completely reversed by oral treatment with larazotide acetate, an octapeptide that is a specific molecular antagonist of zonulin. Taken together, these studies document a pathway by which RG strains from Lupus patients contribute to a leaky gut and features of autoimmunity implicated in the pathogenesis of flares of clinical Lupus disease.

Loss of Gut Barrier Integrity In Lupus

Systemic Lupus Erythematosus is a complex autoimmune disease and its etiology remains unknown. Increased gut permeability has been reported in lupus patients, yet whether it promotes or results from lupus progression is unclear. Recent studies indicate that an impaired intestinal barrier allows the translocation of bacteria and bacterial components into systemic organs, increasing immune cell activation and autoantibody generation. Indeed, induced gut leakage in a mouse model of lupus enhanced disease characteristics, including the production of anti-dsDNA antibody, serum IL-6 as well as cell apoptosis. Gut microbiota dysbiosis has been suggested to be one of the factors that decreases gut barrier integrity by outgrowing harmful bacteria and their products, or by perturbation of gut immune homeostasis, which in turn affects gut barrier integrity. The restoration of microbial balance eliminates gut leakage in mice, further confirming the role of microbiota in maintaining gut barrier integrity. In this review, we discuss recent advances on the association between microbiota dysbiosis and leaky gut, as well as their influences on the progression of lupus. The modifications on host microbiota and gut integrity may offer insights into the development of new lupus treatment.

Spectroscopic investigation of faeces with surface-enhanced Raman scattering: a case study with coeliac patients on gluten-free diet

Surface-enhanced Raman scattering (SERS) spectra of faecal samples can be obtained by adding AuNP to their methanol extracts according to the reported protocol, and display bands that are due to bilirubin-like species but also to xanthine and hypoxanthine, two metabolic products secreted by gut bacteria. A total of 27 faecal samples from three different groups, i.e. coeliac patients (n = 9), coeliac patients on gluten-free diet (n = 10) and a control group (n = 8), were characterized with both SERS spectroscopy and 16S rRNA sequencing analysis. Significant differences are present between SERS spectra of coeliac patients and those on gluten-free diet, with a marked increase in the relative intensity of both xanthine and hypoxanthine for the latter. Interestingly, these differences do not correlate with bacterial composition as derived from 16S rRNA sequencing.

Regulation of B Cell Responses in SLE by Three Classes of Interferons

There are three classes of interferons (type 1, 2, and 3) that can contribute to the development and maintenance of various autoimmune diseases, including systemic lupus erythematosus (SLE). Each class of interferons promotes the generation of autoreactive B cells and SLE-associated autoantibodies by distinct signaling mechanisms. SLE patients treated with various type 1 interferon-blocking biologics have diverse outcomes, suggesting that additional environmental and genetic factors may dictate how these cytokines contribute to the development of autoreactive B cells and SLE. Understanding how each class of interferons controls B cell responses in SLE is necessary for developing optimized B cell- and interferon-targeted therapeutics. In this review, we will discuss how each class of interferons differentially promotes the loss of peripheral B cell tolerance and leads to the development of autoreactive B cells, autoantibodies, and SLE.

Gut microbiota mediated the therapeutic efficacies and the side effects of prednisone in the treatment of MRL/lpr mice

Background

Growing evidences indicate that the alterations in gut microbiota are associated with the efficacy of glucocorticoids (GCs) in the treatment of systemic lupus erythematosus (SLE). However, there is no evidence to prove whether gut microbiota directly mediates the effects of GCs.

Methods

Using the MRL/lpr mice, this study firstly addressed the effects of three doses of prednisone on gut microbiota. Then, this study used fecal microbiota transplantation (FMT) to transfer the gut microbiota of prednisone-treated MRL/lpr mice into the blank MRL/lpr mice to reveal whether the gut microbiota regulated by prednisone had similar therapeutic efficiency and side effects as prednisone.

Results

The effects of prednisone on gut microbiota were dose-dependent in the treatment of MRL/lpr mice. After transplantation into MRL/lpr mice, prednisone-regulated gut microbiota could alleviate lupus, which might be due to decreasing Ruminococcus and Alistipes and retaining the abundance of Lactobacillus. However, prednisone-regulated gut microbiota did not exhibit side effects as prednisone. The reason might be that the pathogens upregulated by prednisone could not survive in the MRL/lpr mice as exogenous microbiota, such as Parasutterella, Parabacteroides, and Escherichia-Shigella.

Conclusions

These data demonstrated that the transplantation of gut microbiota may be an effective method to obtain the therapeutic effects of GCs and avoid the side effects of GCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02620-w.

Tonic interferon restricts pathogenic IL-17-driven inflammatory disease via balancing the microbiome

Maintenance of immune homeostasis involves a synergistic relationship between the host and the microbiome. Canonical interferon (IFN) signaling controls responses to acute microbial infection, through engagement of the STAT1 transcription factor. However, the contribution of tonic levels of IFN to immune homeostasis in the absence of acute infection remains largely unexplored. We report that STAT1 KO mice spontaneously developed an inflammatory disease marked by myeloid hyperplasia and splenic accumulation of hematopoietic stem cells. Moreover, these animals developed inflammatory bowel disease. Profiling gut bacteria revealed a profound dysbiosis in the absence of tonic IFN signaling, which triggered expansion of T_H17 cells and loss of splenic T_reg cells. Reduction of bacterial load by antibiotic treatment averted the T_H17 bias and blocking IL17 signaling prevented myeloid expansion and splenic stem cell accumulation. Thus, tonic IFNs regulate gut microbial ecology, which is crucial for maintaining physiologic immune homeostasis and preventing inflammation.

Immune Response to Enterococcus gallinarum in Lupus Patients Is Associated With a Subset of Lupus-Associated Autoantibodies

Interactions between gut microbes and the immune system influence autoimmune disorders like systemic lupus erythematosus (SLE). Recently, Enterococcus gallinarum, a gram-positive commensal gut bacterium, was implicated as a candidate pathobiont in SLE. The present study was undertaken to evaluate the influence of E. gallinarum exposure on clinical parameters of SLE. Since circulating IgG antibodies to whole bacteria have been established as a surrogate marker for bacterial exposure, anti-E. gallinarum IgG antibodies were measured in banked serum samples from SLE patients and healthy controls in the Oklahoma Cohort for Rheumatic Diseases. The associations between anti-E. gallinarum antibody titers and clinical indicators of lupus were studied. Antibodies to human RNA were studied in a subset of patients. Our results show that sera from both patients and healthy controls had IgG and IgA antibodies reactive with E. gallinarum. The antibody titers between the two groups were not different. However, SLE patients with Ribosomal P autoantibodies had higher anti-E. gallinarum IgG titers compared to healthy controls. In addition to anti-Ribosomal P, higher anti-E. gallinarum titers were also significantly associated with the presence of anti-dsDNA and anti-Sm autoantibodies. In the subset of patients with anti-Ribosomal P and anti-dsDNA, the anti-E. gallinarum titers correlated significantly with antibodies to human RNA. Our data show that both healthy individuals and SLE patients were sero-reactive to E. gallinarum. In SLE patients, the immune response to E. gallinarum was associated with antibody response to a specific subset of lupus autoantigens. These findings provide additional evidence that E. gallinarum may be a pathobiont for SLE in susceptible individuals.

Best Practices for Microbiome Study Design in Companion Animal Research

The gut microbiome is a community of microorganisms that inhabits an animal host's gastrointestinal tract, with important effects on animal health that are shaped by multiple environmental, dietary, and host-associated factors. Clinical and dietary trials in companion animals are increasingly including assessment of the microbiome, but interpretation of these results is often hampered by suboptimal choices in study design. Here, we review best practices for conducting feeding trials or clinical trials that intend to study the effects of an intervention on the microbiota. Choices for experimental design, including a review of basic designs, controls, and comparison groups, are discussed in the context of special considerations necessary for microbiome studies. Diet is one of the strongest influences on the composition of gut microbiota, so applications specific to nutritional interventions are discussed in detail. Lastly, we provide specific advice for successful recruitment of colony animals and household pets into an intervention study. This review is intended to serve as a resource to academic and industry researchers, clinicians, and veterinarians alike, for studies that test many different types of interventions.

Changes induced by chronic exposure to high arsenic concentrations in the intestine and its microenvironment

The perturbation of intestinal microbes may serve as a mechanism by which arsenic exposure causes or exacerbates diseases in humans. However, the changes in the intestinal microbiome and metabolome induced by long-term exposure to high concentrations of arsenic have not been extensively studied. In this study, C57BL/6 mice were exposed to sodium arsenite (As) (50 ppm) for 6 months. Our results show that long-term exposure to high As concentrations changed the structure of intestinal tissues and the expression of As resistance related genes in intestinal microbes. In addition, 16S rRNA gene sequencing revealed that As exposure significantly affected the Beta diversity of intestinal flora but had no significant effect on the Alpha diversity (except ACE index). Moreover, As exposure altered the composition of the intestinal microbiota from phylum to species. Non-targeted metabolomics profiling revealed that As exposure significantly changed the composition of metabolites, specifically those related to phenylalanine metabolism. Correlation analysis demonstrated that the changes in microbial communities and metabolites were highly correlated under As exposure. Overall, this study demonstrates that long-term exposure to high As concentrations disrupted the intestinal microbiome and metabolome, which may indicate the role of As exposure at inducing human diseases under similar conditions.

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 Emerging World of Microbiome in Autoimmune Disorders: Opportunities and Challenges

Trillions of commensal bacteria colonizing humans (microbiome) have emerged as essential player(s) in human health. The alteration of the same has been linked with diseases including autoimmune disorders such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, and ankylosing spondylitis. Gut bacteria are separated from the host through a physical barrier such as skin or gut epithelial lining. However, the perturbation in the healthy bacterial community (gut dysbiosis) can compromise gut barrier integrity, resulting in translocation of bacterial contents across the epithelial barrier (leaky gut). Bacterial contents such as lipopolysaccharide and bacterial antigens can induce a systemic inflammatory environment through activation and induction of immune cells. The biggest question in the field is whether inflammation causes gut dysbiosis or dysbiosis leads to disease induction or propagation, i.e., it is inside out or outside in or both. In this review, we first discuss the microbiome profiling studies in various autoimmune disorders, followed by a discussion of potential mechanisms through which microbiome is involved in the pathobiology of diseases. A better understanding of the role of the microbiome in health and disease will help us harness the power of commensal bacteria for the development of novel therapeutic agents to treat autoimmune disorders.

New insights in gut-liver axis in wild-type murine imiquimod-induced lupus

BACKGROUND

Intestinal and hepatic manifestations of lupus seem to be underestimated in comparison to other major organ lesions. Although recent data point to gut-liver axis involvement in lupus, gut permeability dysfunction and liver inflammation need to be more investigated.

OBJECTIVE

This study aims to assess fecal calprotectin, intestinal tight junction proteins and liver inflammation pathway in wild-type murine imiquimod- induced lupus.

METHODS

C57BL/6 mice were topically treated on their right ears with 1.25 mg of 5% imiquimod cream, three times per week for six weeks. Fecal calprotectin was collected at day 0, 22 and 45. Renal, liver and intestinal pathology, as well as inflammatory markers, intestinal tight junction proteins, and E. coli protein in liver were assessed at sacrifice.

RESULTS

At six weeks, lupus nephritis was confirmed on histopathology and NGAL and KIM-1 expression. Calprotectin rise started at day 22 and persists at day 45. Protein expression of Claudine, ZO-1 and occludin was significantly decreased. E. coli protein was significantly increased in liver with necro-inflammation and increased TLR4, TLR7, and pNFκB/NFκB liver expression.

CONCLUSION

This study is the first to demonstrate early fecal calprotectin increase and liver activation of TLR4- NFκB pathway in wild-type murine imiquimod-induced lupus.

Putative Pathobionts in HLA-B27-Associated Spondyloarthropathy

Spondyloarthritis (SpA) is a group of immune mediated inflammatory diseases with a strong association to the major histocompatibility (MHC) class I molecule, HLA-B27. Although the association between HLA-B27 and AS has been known for almost 50 years, the mechanisms underlying disease pathogenesis are elusive. Over the years, three hypotheses have been proposed to explain HLA-B27 and disease association: 1) HLA B27 presents arthritogenic peptides and thus creates a pathological immune response; 2) HLA-B27 misfolding causes endoplasmic reticulum (ER) stress which activates the unfolded protein response (UPR); 3) HLA-B27 dimerizes on the cell surface and acts as a target for natural killer (NK) cells. None of these hypotheses explains SpA pathogenesis completely. Evidence supports the hypothesis that HLA-B27-related diseases have a microbial pathogenesis. In animal models of various SpAs, a germ-free environment abrogates disease development and colonizing these animals with gut commensal microbes can restore disease manifestations. The depth of microbial influence on SpA development has been realized due to our ability to characterize microbial communities in the gut using next-generation sequencing approaches. In this review, we will discuss various putative pathobionts in the pathogenesis of HLA-B27-associated diseases. We pursue whether a single pathobiont or a disruption of microbial community and function is associated with HLA-B27-related diseases. Furthermore, rather than a specific pathobiont, metabolic functions of various disease-associated microbes might be key. While the use of germ-free models of SpA have facilitated understanding the role of microbes in disease development, future studies with animal models that mimic diverse microbial communities instead of mono-colonization are indispensable. We discuss the causal mechanisms underlying disease pathogenesis including the role of these pathobionts on mucin degradation, mucosal adherence, and gut epithelial barrier disruption and inflammation. Finally, we review the various uses of microbes as therapeutic modalities including pre/probiotics, diet, microbial metabolites and fecal microbiota transplant. Unravelling these complex host-microbe interactions will lead to the development of new targets/therapies for alleviation of SpA and other HLA-B27 associated diseases.

The microbiome links between aging and lupus

BACKGROUND AND AIMS

Many forms of immune dysregulation, which lead to inflammaging and senescence, have been demonstrated in patients with systemic lupus erythematosus (SLE; lupus) and in the aging population. The discovery of the microbiome and its association with human health and pathology has led it to be the center of investigation as a major contributor to the pathogenesis of immunosenescence in both populations. Similar alterations to the microbiome in the form of dysbiosis, that are demonstrated in both aging and in lupus patients, may help explain the significant overlap in clinical manifestations seen in these groups.

METHODS

We performed an extensive literature review, utilizing the Pubmed search engine and Google Scholar for studies evaluating the microbiome in two groups, elderly populations and lupus patients (both murine and human models), between the years 2000-2019. We searched for the terms: microbiome, dysbiosis, lupus, elderly, aging and inflammaging, which yielded hundreds of articles, of which 114 were used for preparation of this paper. We compared the similarities between the populations.

RESULTS

We found that the similar processes of immune dysregulation, in both aging populations and lupus patients, extend to the microbiome, in the form of dysbiosis. Some of these similarities include loss of microbiota biodiversity, increased representation of microbes that are associated with inflammation and disease (i.e Proteobacteria, Bacteroidetes), a relative decrease in protective microbes with "anti-inflammatory" properties (i.e Firmicutes) and a subsequent compromise to the intestinal barrier, leading to leakage of proinflammatory microbial components in both groups.

CONCLUSIONS

We conclude that there are several similar alterations in the composition and function of the microbiome of lupus patients and aging individuals, leading to immunosenescence, which may also be a contributing mechanism in lupus. It seems in fact that the microbiome of SLE may actually be analogous to immunosenescence. This knowledge may help the continuous efforts in finding a solution for both conditions.

New insights into the role of antinuclear antibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by antinuclear antibodies (ANAs) that form immune complexes that mediate pathogenesis by tissue deposition or cytokine induction. Some ANAs bind DNA or associated nucleosome proteins, whereas other ANAs bind protein components of complexes of RNA and RNA-binding proteins (RBPs). Levels of anti-DNA antibodies can fluctuate widely, unlike those of anti-RBP antibodies, which tend to be stable. Because anti-DNA antibody levels can reflect disease activity, repeat testing is common; by contrast, a single anti-RBP antibody determination is thought to suffice for clinical purposes. Experience from clinical trials of novel therapies has provided a new perspective on ANA expression during disease, as many patients with SLE are ANA negative at screening despite previously testing positive. Because trial results suggest that patients who are ANA negative might not respond to certain agents, screening strategies now involve ANA and anti-DNA antibody testing to identify patients with so-called 'active, autoantibody-positive SLE'. Evidence suggests that ANA responses can decrease over time because of the natural history of disease or the effects of therapy. Together, these findings suggest that, during established disease, more regular serological testing could illuminate changes relevant to pathogenesis and disease status.

Immunomodulatory Effects of Diet and Nutrients in Systemic Lupus Erythematosus (SLE): A Systematic Review

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple organ involvement, including the skin, joints, kidneys, lungs, central nervous system and the haematopoietic system, with a large number of complications. Despite years of study, the etiology of SLE remains unclear; thus, safe and specifically targeted therapies are lacking. In the last 20 years, researchers have explored the potential of nutritional factors on SLE and have suggested complementary treatment options through diet. This study systematically reviews and evaluates the clinical and preclinical scientific evidence of diet and dietary supplementation that either alleviate or exacerbate the symptoms of SLE. For this review, a systematic literature search was conducted using PubMed, Scopus and Google Scholar databases only for articles written in the English language. Based on the currently published literature, it was observed that a low-calorie and low-protein diet with high contents of fiber, polyunsaturated fatty acids, vitamins, minerals and polyphenols contain sufficient potential macronutrients and micronutrients to regulate the activity of the overall disease by modulating the inflammation and immune functions of SLE.

Phages and Their Role in Gastrointestinal Disease: Focus on Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) are a group of chronic autoinflammatory diseases including Crohn's disease and ulcerative colitis. Although the molecular mechanisms governing the pathogenesis of gastrointestinal inflammation are not completely clear, the main factors are presumed to be genetic predisposition, environmental exposure, and the intestinal microbiome. Hitherto, most of the studies focusing on the role of the microbiome studied the action and effect of bacteria. However, the intestinal microbiome comprises other members of the microbial community as well, namely, fungi, protozoa, and viruses. We believe that bacteriophages are among the main orchestrators of the effect of microbiota on the gut mucosa. Therefore, this review aims to summarize the knowledge of the role of intestinal phageome in IBD and to discuss the concept of phage therapy and its future applications.

Uveitis and the gut microbiota

Uveitis is a heterogeneous collection of inflammatory diseases of the intraocular uveal tissues and adjacent structures, and they collectively are a significant cause of visual morbidity. In recent years, investigating the contribution of the gut microbiota to autoimmunity, including the development of uveitis, has gained interest. Decreased disease severity has been observed in both the induced experimental autoimmune model of uveitis and the spontaneous RI61H model of uveitis in mice treated with oral broad-spectrum antibiotics and raised in germ-free conditions, implicating a role for the gut microbiota in the development of disease in these models. Also, in support of these findings are the differences in the composition of the microbiota that have been reported in uveitis patients. Proposed mechanisms accounting for the microbiota triggering uveitis include antigenic mimicry and dysbiosis leading to dysregulation of the immune system. An improved understanding of these mechanisms will facilitate potential therapeutic approaches including alteration of the microbiota with probiotic treatment and fecal microbiota transplants.