Inflammasome Activation in Ankylosing Spondylitis Is Associated With Gut Dysbiosis

Differential Composition and Structure of the Microbiota from Active and Inactive Stages of HLA-B27-associated Uveitis by Paired Fecal Metagenomes

PURPOSE

To compare the diversities and abundances of bacterial taxa in the microbiome of patients with HLA B27-positive acute anterior uveitis (AAU) in the active and inactive phases.

METHODS

An observational descriptive prospective and comparative study was conducted in ten HLA-B27-positive AAU patients (44.6 ± 13.4 years). The microbiome of the stool samples obtained in the active and inactive stages was analyzed by sequencing the V3 region of the 16S rRNA gene.

RESULTS

The differences in the bacteria profile between active and inactive stages in each individual were confirmed (p < 0.0001). Ten OTUs were found exclusively in the active phase of 90% of the individuals, suggesting a proinflammatory association. Blautia OUT_4 and Faecalibacterium OUT_2 abundances showed a direct relationship between abundance and severity of ocular inflammation. Two OTUs were exclusive of the inactive stage, suggesting an anti-inflammatory role.

CONCLUSION

The metagenomic profile of the fecal microbiota differs in the acute phase of the AAU compared to when the inflammation subsides, despite being the same individual and a short time-lapse. AAU is a fertile field for studying the connection between subtle rapid changes in microbiota and their systemic consequences.

Industrial-produced lemon nanovesicles ameliorate experimental colitis-associated damages in rats via the activation of anti-inflammatory and antioxidant responses and microbiota modification

Plant-derived nanovesicles (PDNVs) have recently emerged as natural delivery systems of biofunctional compounds toward mammalian cells. Considering their already described composition, anti-inflammatory properties, stability, and low toxicity, PDNVs offer a promising path for developing new preventive strategies for several inflammatory diseases, among which the inflammatory bowel disease (IBD). In this study, we explore the protective effects of industrially produced lemon vesicles (iLNVs) in a rat model of IBD. Characterization of iLNVs reveals the presence of small particles less than 200 nm in size and a profile of bioactive compounds enriched in flavonoids and organic acids with known beneficial properties. In vitro studies on human macrophages confirm the safety and anti-inflammatory effects of iLNVs, as evidenced by the reduced expression of pro-inflammatory cytokines and increased levels of anti-inflammatory markers. As evidenced by in vivo experiments, pre-treatment with iLNVs significantly alleviates symptoms and histological features in 2,4 dinitrobenzensulfuric acid (DNBS)-induced colitis in rats. Molecular pathway analysis reveals modulation of NF-κB and Nrf2, indicating anti-inflammatory and antioxidant effects. Finally, iLNVs affects gut microbiota composition, improving the consistent colitis-related alterations. Overall, we demonstrated the protective role of industrially produced lemon nanovesicles against colitis and emphasized their potential in managing IBD through multifaceted mechanisms.

Gut microbiome and metabolome to discover pathogenic bacteria and probiotics in ankylosing spondylitis

Objective

Previous research has partially revealed distinct gut microbiota in ankylosing spondylitis (AS). In this study, we performed non-targeted fecal metabolomics in AS in order to discover the microbiome-metabolome interface in AS. Based on prospective cohort studies, we further explored the impact of the tumor necrosis factor inhibitor (TNFi) on the gut microbiota and metabolites in AS.

Methods

To further understand the gut microbiota and metabolites in AS, along with the influence of TNFi, we initiated a prospective cohort study. Fecal samples were collected from 29 patients with AS before and after TNFi therapy and 31 healthy controls. Metagenomic and metabolomic experiments were performed on the fecal samples; moreover, validation experiments were conducted based on the association between the microbiota and metabolites.

Results

A total of 7,703 species were annotated using the metagenomic sequencing system and by profiling the microbial community taxonomic composition, while 50,046 metabolites were identified using metabolite profiling. Differential microbials and metabolites were discovered between patients with AS and healthy controls. Moreover, TNFi was confirmed to partially restore the gut microbiota and the metabolites. Multi-omics analysis of the microbiota and metabolites was performed to determine the associations between the differential microbes and metabolites, identifying compounds such as oxypurinol and biotin, which were correlated with the inhibition of the pathogenic bacteria Ruminococcus gnavus and the promotion of the probiotic bacteria Bacteroides uniformis. Through experimental studies, the relationship between microbes and metabolites was further confirmed, and the impact of these two types of microbes on the enterocytes and the inflammatory cytokine interleukin-18 (IL-18) was explored.

Conclusion

In summary, multi-omics exploration elucidated the impact of TNFi on the gut microbiota and metabolites and proposed a novel therapeutic perspective: supplementation of compounds to inhibit potential pathogenic bacteria and to promote potential probiotics, therefore controlling inflammation in AS.

Nod-like receptors in inflammatory arthritis

Nod-like receptors (NLRs) are innate immune receptors that play a key role in sensing components from pathogens and from damaged cells or organelles. NLRs form signaling complexes that can lead to activation of transcription factors or effector caspases - by means of inflammasome activation -Inflammatory arthritis (IA) culminating in promoting inflammation. An increasing body of research supports the role of NLRs in driving pathogenesis of IA, a collection of diseases that include rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis, and pediatric arthritis. In this review, we briefly discuss the main drivers of IA diseases and dive into the evidence for - and against - various NLRs in driving these diseases. We also review the studies examining the use of NLR and inflammasome inhibitors as potential therapies for IA.

MICA and NLRP3 gene polymorphisms interact synergistically affecting the risk of ankylosing spondylitis

Ankylosing spondylitis (AS) is an autoinflammatory disease that affects the sacroiliac joints, causing stiffness and pain in the back. MICA is a ligand of the NKG2D receptor, and an increase in its expression affects the immune response in various diseases. NLRP3 is a multiprotein complex that promotes the release of IL-1β, but its role in AS has been minimally explored. The objective of this study was to analyze the association and interaction of polymorphic variants of the MICA and NLRP3 genes in patients with AS. In this case-control study, patients with AS were included and compared with healthy controls of Mexican origin. The polymorphisms rs4349859 and rs116488202 of MICA and rs3806268 and rs10754558 of NLRP3 were genotyped using TaqMan probes. Associations were determined using logistic regression models, while interactions were analyzed by the multifactorial dimensionality reduction (MDR) method. A P value < 0.05 was considered statistically significant. The minor allele of rs4349859 (A) and rs116488202 (T) of MICA polymorphisms showed risk associations with AS (OR = 9.22, 95% CI = 4.26-20.0, P < 0.001; OR = 9.36, 95% CI = 4.17-21.0, P < 0.001), while the minor allele of the rs3806268 (A) polymorphism of NLRP3 was associated with protection (OR = 0.55, 95% CI = 0.33-0.91, P = 0.019). MDR analysis revealed synergistic interactions between the MICA and NLRP3 polymorphisms (P = 0.012). In addition, high- and low-risk genotypes were identified among these variants. The study findings suggest that the MICA rs4349859 A allele and rs116488202 T allele are associated with AS risk. An interaction between MICA and NLRP3 was observed which could increase the genetic risk in AS.

PLCG2 and IFNAR1: The Potential Biomarkers Mediated by Immune Infiltration and Osteoclast Differentiation of Ankylosing Spondylitis in the Peripheral Blood

Objectives

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease characterized by chronic spinal inflammation, arthritis, gut inflammation, and enthesitis. We aimed to identify the key biomarkers related to immune infiltration and osteoclast differentiation in the pathological process of AS by bioinformatic methods.

Methods

GSE25101 from the Gene Expression Omnibus was used to obtain AS-associated microarray datasets. We performed bioinformatics analysis using R software to validate different expression levels. The purpose of the GO and KEGG enrichment analyses of DEGs was to exclude key genes. Using weighted correlation network analysis (WGCNA), we examined all expression profile data and identified differentially expressed genes. The objective was to investigate the interaction between genetic and clinical features and to identify the essential relationships underlying coexpression modules. The CIBERSORT method was used to make a comparison of the immune infiltration in whole blood between the AS group and the control group. The WGCNA R program from Bioconductor was used to identify hub genes. RNA extraction reverse transcription and quantitative polymerase chain reaction were conducted in the peripheral blood collected from six AS patients and six health volunteers matched by age and sex.

Results

125 DEGs were identified, consisting of 36 upregulated and 89 downregulated genes that are involved in the cell cycle and replication processes. In the WGCNA, modules of MCODE with different algorithms were used to find 33 key genes that were related to each other in a strong way. Immune infiltration analysis found that naive CD4+ T cells and monocytes may be involved in the process of AS. PLCG2 and IFNAR1 genes were obtained by screening genes meeting the conditions of immune cell infiltration and osteoclast differentiation in AS patients among IGF2R, GRN, SH2D1A, LILRB3, IFNAR1, PLCG2, and TNFRSF1B. The results demonstrated that the levels of PLCG2 mRNA expression in AS were considerably higher than those in healthy individuals (P=0.003). IFNAR1 mRNA expression levels were considerably lower in AS than in healthy individuals (P < 0.0001).

Conclusions

Dysregulation of PLCG2 and IFNAR1 are key factors in disease occurrence and development of AS through regulating immune infiltration and osteoclast differentiation. Explaining the differences in immune infiltration and osteoclast differentiation between AS and normal samples will contribute to understanding the development of spondyloarthritis.

Causal effects of gut microbiota on scoliosis: A bidirectional two-sample mendelian randomization study

Background

Recent studies have shown altered gut microbiome composition in patients with scoliosis. However, the causal effect of gut microbiota on scoliosis remains unknown.

Methods

A Mendelian randomization (MR) study was conducted to quantify the impact of 191 gut microbiome taxa's instrumental variables from the MibioGen Genome-wide association study (GWAS) on scoliosis risk using data from the FinnGen GWAS (1168 cases and 16,4682 controls). Inverse variance weighted (IVW) was the main method, and MR results were verified by sensitive analysis.

Results

Bilophila, Eubacterium (eligens group), Prevotella9, and Ruminococcus2 were discovered to have a protective effect on the risk of scoliosis. Ruminococcaceae UCG009, Catenibacterium, Coprococcus2, Eubacterium (ventriosum group), Lachnospiraceae (FCS020 group), Ruminiclostridium6, and Mollicutes RF9 may increase the occurrence of scoliosis. Heterogeneity (P > 0.05) and pleiotropy (P > 0.05) analysis confirmed the robustness of the MR results.

Conclusion

Our study identified four protective bacteria taxa on scoliosis and seven microbiota that may increase scoliosis occurrence. Further MR analysis is required to corroborate our findings, using a more sophisticated technique to obtain estimates with less bias and greater precision or GWAS summary data with more gut microbiome and scoliosis patients.

Gut-spine axis: a possible correlation between gut microbiota and spinal degenerative diseases

As society ages, the number of patients with spinal degenerative diseases (SDD) is increasing, posing a major socioeconomic problem for patients and their families. SDD refers to a generic term for degenerative diseases of spinal structures, including osteoporosis (bone), facet osteoarthritis (joint), intervertebral disk degeneration (disk), lumbar spinal canal stenosis (yellow ligament), and spinal sarcopenia (muscle). We propose the term "gut-spine axis" for the first time, given the influence of gut microbiota (GM) on the metabolic, immune, and endocrine environment in hosts through various potential mechanisms. A close cross-talk is noted between the aforementioned spinal components and degenerative diseases. This review outlines the nature and role of GM, highlighting GM abnormalities associated with the degeneration of spinal components. It also summarizes the evidence linking GM to various SDD. The gut-spine axis perspective can provide novel insights into the pathogenesis and treatment of SDD.

Sterile triggers drive joint inflammation in TNF- and IL-1β-dependent mouse arthritis models

Arthritis is the most common extra-intestinal complication in inflammatory bowel disease (IBD). Conversely, arthritis patients are at risk for developing IBD and often display subclinical gut inflammation. These observations suggest a shared disease etiology, commonly termed "the gut-joint-axis." The clinical association between gut and joint inflammation is further supported by the success of common therapeutic strategies and microbiota dysbiosis in both conditions. Most data, however, support a correlative relationship between gut and joint inflammation, while causative evidence is lacking. Using two independent transgenic mouse arthritis models, either TNF- or IL-1β dependent, we demonstrate that arthritis develops independently of the microbiota and intestinal inflammation, since both lines develop full-blown articular inflammation under germ-free conditions. In contrast, TNF-driven gut inflammation is fully rescued in germ-free conditions, indicating that the microbiota is driving TNF-induced gut inflammation. Together, our study demonstrates that although common inflammatory pathways may drive both gut and joint inflammation, the molecular triggers initiating such pathways are distinct in these tissues.

The role of inflammation in autoimmune disease: a therapeutic target

Autoimmune diseases (AIDs) are immune disorders whose incidence and prevalence are increasing year by year. AIDs are produced by the immune system's misidentification of self-antigens, seemingly caused by excessive immune function, but in fact they are the result of reduced accuracy due to the decline in immune system function, which cannot clearly identify foreign invaders and self-antigens, thus issuing false attacks, and eventually leading to disease. The occurrence of AIDs is often accompanied by the emergence of inflammation, and inflammatory mediators (inflammatory factors, inflammasomes) play an important role in the pathogenesis of AIDs, which mediate the immune process by affecting innate cells (such as macrophages) and adaptive cells (such as T and B cells), and ultimately promote the occurrence of autoimmune responses, so targeting inflammatory mediators/pathways is one of emerging the treatment strategies of AIDs. This review will briefly describe the role of inflammation in the pathogenesis of different AIDs, and give a rough introduction to inhibitors targeting inflammatory factors, hoping to have reference significance for subsequent treatment options for AIDs.

Updates on ankylosing spondylitis: pathogenesis and therapeutic agents

Ankylosing spondylitis (AS) is an autoinflammatory disease that manifests with the unique feature of enthesitis. Gut microbiota, HLA-B*27, and biomechanical stress mutually influence and interact resulting in setting off a flame of inflammation. In the HLA-B*27 positive group, dysbiosis in the gut environment disrupts the barrier to exogenous bacteria or viruses. Additionally, biomechanical stress induces inflammation through enthesial resident or gut-origin immune cells. On this basis, innate and adaptive immunity can propagate inflammation and lead to chronic disease. Finally, bone homeostasis is regulated by cytokines, by which the inflamed region is substituted into new bone. Agents that block cytokines are constantly being developed to provide diverse therapeutic options for preventing the progression of inflammation. In addition, some antibodies have been shown to distinguish disease selectively, which support the involvement of autoimmune immunity in AS. In this review, we critically analyze the complexity and uniqueness of the pathogenesis with updates on the findings of immunity and provide new information about biologics and biomarkers.

The Immunomodulatory Role of Microbiota in Rheumatic Heart Disease: What Do We Know and What Can We Learn from Other Rheumatic Diseases?

Rheumatic heart disease (RHD) represents a serious cardiac sequela of acute rheumatic fever, occurring in 30-45% of patients. RHD is multifactorial, with a strong familial predisposition and known environmental risk factors that drive loss of immunological tolerance. The gut and oral microbiome have recently been implicated in the pathogenesis of RHD. Disruption of the delicate balance of the microbiome, or dysbiosis, is thought to lead to autoimmune responses through several different mechanisms including molecular mimicry, epitope spreading, and bystander activation. However, data on the microbiomes of RHD patients are scarce. Therefore, in this comprehensive review, we explore the various dimensions of the intricate relationship between the microbiome and the immune system in RHD and other rheumatic diseases to explore the potential effect of microbiota on RHD and opportunities for diagnosis and treatment.

Causal effects of specific gut microbiota on musculoskeletal diseases: a bidirectional two-sample Mendelian randomization study

Background

Recent observational studies and clinical trials demonstrated an association between gut microbiota and musculoskeletal (MSK) diseases. Nonetheless, whether the gut microbiota composition has a causal effect on the risk of MSK diseases remains unclear.

Methods

Based on large-scale genome-wide association studies (GWAS), we performed a two-sample Mendelian randomization (MR) analysis to investigate the causal relationship between gut microbiota and six MSK diseases, namely osteoporosis (OP), fracture, sarcopenia, low back pain (LBP), rheumatoid arthritis (RA), and ankylosing spondylitis (AS). Instrumental variables for 211 gut microbiota taxa were obtained from the largest available GWAS meta-analysis (n = 18,340) conducted by the MiBioGen consortium. And the summary-level data for six MSK diseases were derived from published GWAS. The inverse-variance weighted (IVW) method was conducted as a primary analysis to estimate the causal effect, and the robustness of the results was tested via sensitivity analyses using multiple methods. The Bonferroni-corrected test was used to determine the strength of the causal relationship between gut microbiota and various MSK diseases. Finally, a reverse MR analysis was applied to evaluate reverse causality.

Results

According to the IVW method, we found 57 suggestive causal relationships and 3 significant causal relationships between gut microbiota and MSK diseases. Among them, Genus Bifidobacterium (β: 0.035, 95% CI: 0.013-0.058, p = 0.0002) was associated with increased left handgrip strength, Genus Oxalobacter (OR: 1.151, 95% CI: 1.065-1.245, p = 0.0003) was correlated with an increased risk of LBP, and Family Oxalobacteraceae (OR: 0.792, 95% CI: 0.698-0.899, p = 0.0003) was linked with a decreased risk of RA. Subsequently, sensitivity analyses revealed no heterogeneity, directional pleiotropy, or outliers for the causal effect of specific gut microbiota on MSK diseases (p > 0.05). Reverse MR analysis showed fracture may result in a higher abundance of Family Bacteroidales (p = 0.030) and sarcopenia may lead to a higher abundance of Genus Sellimonas (p = 0.032).

Conclusion

Genetic evidence suggested a causal relationship between specific bacteria taxa and six MSK diseases, which highlights the association of the "gut-bone/muscle" axis. Further exploration of the potential microbiota-related mechanisms of bone and muscle metabolism might provide novel insights into the prevention and treatment of MSK diseases.

The bone marrow side of axial spondyloarthritis

Spondyloarthritis (SpA) is characterized by the infiltration of innate and adaptive immune cells into entheses and bone marrow. Molecular, cellular and imaging evidence demonstrates the presence of bone marrow inflammation, a hallmark of SpA. In the spine and the peripheral joints, bone marrow is critically involved in the pathogenesis of SpA. Evidence suggests that bone marrow inflammation is associated with enthesitis and that there are roles for mechano-inflammation and intestinal inflammation in bone marrow involvement in SpA. Specific cell types (including mesenchymal stem cells, innate lymphoid cells and γδ T cells) and mediators (Toll-like receptors and cytokines such as TNF, IL-17A, IL-22, IL-23, GM-CSF and TGFβ) are involved in these processes. Using this evidence to demonstrate a bone marrow rather than an entheseal origin for SpA could change our understanding of the disease pathogenesis and the relevant therapeutic approach.

Increased gut permeability and intestinal inflammation precede arthritis onset in the adjuvant-induced model of arthritis

BACKGROUND

Intestinal inflammation, dysbiosis, intestinal permeability (IP), and bacterial translocation (BT) have been identified in patients with spondyloarthritis but the time at which they appear and their contribution to the pathogenesis of the disease is still a matter of debate.

OBJECTIVES

To study the time-course of intestinal inflammation (I-Inf), IP, microbiota modification BT in a rat model of reactive arthritis, the adjuvant-induced arthritis model (AIA).

METHODS

Analysis was performed at 3 phases of arthritis in control and AIA rats: preclinical phase (day 4), onset phase (day 11), and acute phase (day 28). IP was assessed by measuring levels of zonulin and ileal mRNA expression of zonulin. I-inf was assessed by lymphocyte count from rat ileum and by measuring ileal mRNA expression of proinflammatory cytokines. The integrity of the intestinal barrier was evaluated by levels of iFABP. BT and gut microbiota were assessed by LPS, soluble CD14 levels, and 16S RNA sequencing in mesenteric lymph node and by 16S rRNA sequencing in stool, respectively.

RESULTS

Plasma zonulin levels increased at the preclinical and onset phase in the AIA group. Plasma levels of iFABP were increased in AIA rats at all stages of the arthritis course. The preclinical phase was characterized by a transient dysbiosis and increased mRNA ileal expression of IL-8, IL-33, and IL-17. At the onset phase, TNF-α, IL-23p19, and IL-8 mRNA expression were increased. No changes in cytokines mRNA expression were observed at the acute phase. Increased CD4⁺ and CD8⁺ T cell number was measured in the AIA ileum at day 4 and day 11. No increase in BT was observed.

CONCLUSION

These data show that intestinal changes precede the development of arthritis but argue against a strict "correlative" model in which arthritis and gut changes are inseparable.

Genetically encoded Runx3 and CD4+ intestinal epithelial lymphocyte deficiencies link SKG mouse and human predisposition to spondyloarthropathy

Disturbances in immune regulation, intestinal dysbiosis and inflammation characterize ankylosing spondylitis (AS), which is associated with RUNX3 loss-of-function variants. ZAP70^W163C mutant (SKG) mice have reduced ZAP70 signaling, spondyloarthritis and ileitis. In small intestine, Foxp3⁺ regulatory T cells (Treg) and CD4⁺CD8αα⁺TCRαβ⁺ intraepithelial lymphocytes (CD4-IEL) control inflammation. TGF-β and retinoic acid (RA)-producing dendritic cells and MHC-class II⁺ intestinal epithelial cells (IEC) are required for Treg and CD4-IEL differentiation from CD4⁺ conventional or Treg precursors, with upregulation of Runx3 and suppression of ThPOK. We show in SKG mouse ileum, that ZAP70^W163C or ZAP70 inhibition prevented CD4-IEL but not Treg differentiation, dysregulating Runx3 and ThPOK. TGF-β/RA-mediated CD4-IEL development, T-cell IFN-γ production, MHC class-II⁺ IEC, tissue-resident memory T-cell and Runx3-regulated genes were reduced. In AS intestine, CD4-IEL were decreased, while in AS blood CD4⁺CD8⁺ T cells were reduced and Treg increased. Thus, genetically-encoded TCR signaling dysfunction links intestinal T-cell immunodeficiency in mouse and human spondyloarthropathy.

The microbiome in HLA-B27-associated disease: implications for acute anterior uveitis and recommendations for future studies

The pathogenesis of human leukocyte antigen (HLA)-B27-associated diseases such as acute anterior uveitis (AAU) and ankylosing spondylitis (AS) remains poorly understood, though Gram-negative bacteria and subclinical bowel inflammation are strongly implicated. Accumulating evidence from animal models and clinical studies supports several hypotheses, including HLA-B27-dependent dysbiosis, altered intestinal permeability, and molecular mimicry. However, the existing literature is hampered by inadequate studies designed to establish causation or uncover the role of viruses and fungi. Moreover, the unique disease model afforded by AAU to study the gut microbiota has been neglected. This review critically evaluates the current literature and prevailing hypotheses on the link between the gut microbiota and HLA-B27-associated disease. We propose a new potential role for HLA-B27-driven altered antibody responses to gut microbiota in disease pathogenesis and outline recommendations for future well-controlled human studies, focusing on AAU.

Effects of intestinal microbes on rheumatic diseases: A bibliometric analysis

Background

Rheumatic diseases (RD) are a group of multi-system inflammatory autoimmune diseases whose causes are still under study. In the past few decades, researchers have found traces of the association between rheumatic diseases and intestinal microbiota, which can partially explain the pathogenesis of rheumatic diseases. We aimed to describe the research trend and main divisions on how gut flora interreacts with rheumatic diseases, and discussed about the possible clinical applications.

Methods

We analyzed bibliometric data from the Web of Science core collection (dated 15th May 2022). Biblioshiny R language software packages (bibliometrix) were used to obtain the annual publication and citations, core sources according to Bradford's law, and country collaboration map. We designed and verified the keyword co-occurrence network and strategic diagram with the help of VOSviewer and CiteSpace, subdivided the research topic into several themes and identified research dimensions. The tables of most local cited documents and core sources were processed manually. Furthermore, the Altmetric Attention Score and the annual Altmetric Top 100 were applied to analyze the annual publication and citation.

Results

From a total of 541 documents, we found that the overall trend of annual publication and citation is increasing. The major research method is to compare the intestinal microbial composition of patients with certain rheumatic disease and that of the control group to determine microbial alterations related to the disease's occurrence and development. According to Bradford's law, the core sources are Arthritis and Rheumatology, Annals of the Rheumatic Diseases, Current Opinion in Rheumatology, Nutrients, Rheumatology, and Journal of Rheumatology. Since 1976, 101 countries or regions have participated in studies of rheumatology and intestinal microbes. The United States ranks at the top and has the broadest academic association with other countries. Five themes were identified, including the pivotal role of inflammation caused by intestinal bacteria in the rheumatic pathogenesis, the close relationship between rheumatic diseases and inflammatory bowel disease, immunoregulation mechanism as a mediator of the interaction between rheumatic diseases and gut flora, dysbiosis and decreased diversity in intestine of patients with rheumatic diseases, and the influence of oral flora on rheumatic diseases. Additionally, four research dimensions were identified, including pathology, treatment, disease, and experiments.

Conclusion

Studies on rheumatic diseases and the intestinal microbiota are growing. Attention should be paid to the mechanism of their interaction, such as the microbe-immune-RD crosstalk. Hopefully, the research achievements can be applied to diseases' prevention, diagnosis, and treatment, and our work can contribute to the readers' future research.

Targeting inflammasome-dependent mechanisms as an emerging pharmacological approach for osteoarthritis therapy

Arthritic diseases have attracted enormous scientific interest because of increased worldwide prevalence and represent a significant socioeconomic burden. Osteoarthritis (OA) is the most prevalent form of arthritis. It is a disorder of the diarthrodial joints, characterized by degeneration and loss of articular cartilage associated with adjacent subchondral bone changes. Chronic and unresolving inflammation has been identified as a critical factor driving joint degeneration and pain in OA. Despite numerous attempts at therapeutic intervention, no effective disease-modifying agents targeting OA inflammation are available to the patients. Inflammasomes are protein complexes known to play a critical role in the inflammatory pathology of several diseases, and their roles in OA pathogenesis have become evident over the last decade. In this sense, it is relevant to evaluate the vital role of inflammasomes as potential modulators of pathogenic features in OA. This review will provide an overview and perspectives on why understanding inflammasome activation is critical for identifying effective OA therapies. We elaborate on the contribution of extracellular mediators from the circulatory system and synovial fluid as well as intracellular activators within the synovial fibroblasts and articular chondrocytes toward invoking the inflammasome in OA. We further discuss the merits of emerging inflammasome targeting therapies and speculate on the potential strategies for inflammasome blockade for OA therapy.

Inflammasomes and their roles in arthritic disease pathogenesis

The inflammasome is a molecular platform that is created in the cytosolic compartment to mediate the host immunological response to cellular injury and infection. Caspase-1 may be activated by the inflammasome, which leads to the generation of the inflammatory cytokines interleukin-1β (IL-1β) and IL-18 and the beginning of pyroptosis, which is a type of proinflammatory cell death. Scientists have identified a number of different inflammasomes in the last 2 decades. The NLRP3 inflammasome has been studied the most, and its activity may be triggered by a broad range of different inducers. However, activation of the NLRP3 inflammasome in a manner that is not properly controlled is also a factor in the etiology of many human illnesses. Accumulating evidence indicates that the NLRP3 inflammasome plays a significant role in the innate and adaptive immune systems and the development of various arthritic illnesses, such as rheumatoid arthritis, ankylosing spondylitis, and gout. The present review provides a concise summary of the biological properties of the NLRP3 inflammasome and presents the fundamental processes behind its activation and control. We discuss the role of the inflammasome in the pathogenesis of arthritic diseases, such as rheumatoid arthritis, ankylosing spondylitis, and gout, and the potential of newly developed therapies that specifically target the inflammasome or its products for the treatment of inflammatory diseases, with a particular emphasis on treatment and clinical application.

Role of the microbiome and its metabolites in ankylosing spondylitis

Ankylosing spondylitis (AS), a chronic condition that commonly influences the spine and sacroiliac joints, usually progresses to stiffness and progressive functional limitation. Its fundamental etiology and pathogenesis are likely multifactorial and remain elusive. As environmental factors, gut microbiota performs critical functions in the pathogenesis of AS through various mechanisms, including interacting with genes, enhancing intestinal permeability, activating the gut mucosa immune system, and affecting the intestinal microbiota metabolites. This review provides an overview of recent advances in investigating gut microbiota in AS pathogenesis and discusses potential methods for future therapeutic intervention.

The interplay between HLA-B and NLRP3 polymorphisms may be associated with the genetic susceptibility of gout

BACKGROUND

HLA and NLRP3 play an important role in the development of various autoimmune and autoinflammatory diseases. Gout is an autoinflammatory disease associated with multiple genetic and environmental factors. The objective of the present study was to evaluate the interaction and association between genetic polymorphisms of HLA-B and the NLRP3 gene in Mexican patients with gout.

METHODS AND RESULTS

Eighty-one patients with gout were included and compared with 95 healthy subjects. The polymorphisms rs4349859, rs116488202, rs2734583 and rs3099844 (within the HLA-B region) and rs3806268 and rs10754558 of the NLRP3 gene were genotyped using TaqMan probes in a Rotor-Gene device. The interactions were determined using the multifactorial dimensionality reduction (MDR) method, while the associations were determined through logistic regression models. The MDR analysis revealed significant interactions between the rs116488202 and rs10754558 polymorphisms with an entropy value of 4.31% (p < 0.0001). Significant risk associations were observed with rs4349859 and rs116488202 polymorphisms (p < 0.01); however, no significant associations were observed with the polymorphisms of the NLRP3 gene.

CONCLUSIONS

The results suggest that HLA-B polymorphisms and their interaction with NLRP3 may contribute to the genetic susceptibility of gout.

DNA methylation and transcriptional profiles of IRF5 gene in ankylosing spondylitis: A case-control study

BACKGROUND

Interferon regulatory factor 5 (IRF5) plays an important role in the inflammation and immune responses, but its association with ankylosing spondylitis (AS) is under investigated. We aimed to examine the association of IRF5 promoter methylation patterns and transcript levels with the susceptibility to AS.

METHODS

A total of 60 AS patients and 60 healthy controls were included in this study. We used the bisulfite conversion to detect the DNA methylation pattern of IRF5 promoter in whole blood, and the quantitative real-time PCR (qRT-PCR) to detect the relative mRNA expression level in peripheral blood mononuclear cells (PBMCs).

RESULTS

The overall methylation level of IRF5 promoter was lower in AS patients compared to healthy controls (P < 0.001). The methylation level of IRF5 promoter was negatively correlated with mRNA level (P = 0.005). The results of receiver operating characteristic curve (ROC) showed that the area under the curve (AUC) was 0.810 (P < 0.001), and the sensitivity and specificity were 71.67% and 85.00%, respectively. There were significant differences between the severe dysfunction group and healthy control group, and between the mild dysfunction group and healthy control group (P = 0.006 and P < 0.001, respectively). Only CRP was significantly correlated with mRNA relative level, while the others were not significant.

CONCLUSION

These findings indicate that IRF5 methylation profile may be involved in the pathological process of AS, and that it may help identify AS patients.

FOXO3a Alleviates the Inflammation and Oxidative Stress via Regulating TGF-β and HO-1 in Ankylosing Spondylitis

This study aimed to investigate whether Forkhead box O3a (FOXO3a) modulates inflammation and oxidative stress in ankylosing spondylitis (AS). We applied bioinformatics analysis, quantitative real-time polymerase chain reaction, immunoblotting, enzyme linked immunosorbent assay, chromatin immunoprecipitation, and dual-luciferase reporter assay. Gene overexpression and knockdown of FOXO3a were conducted via lentivirus and small interfering RNA, respectively. Downregulated FOXO3a expression was first confirmed in AS patients. Interleukin-8 (IL-8) and IL-17A were highly expressed and negatively related with FOXO3a in AS. Total antioxidant capacity (T-AOC) were markedly decreased and positively associated with FOXO3a in AS. Overexpression of FOXO3a inhibited the secretion of inflammatory cytokines and promoted the production of antioxidant enzymes in Jurkat cells. Transforming growth factor-β (TGF-β) and heme oxygenase 1 (HO-1), which had binding sites to FOXO3a based on bioinformatics analysis, were abnormally expressed and positively related with FOXO3a. Accordingly, FOXO3a obviously elevated the protein and transcription levels of TGF-β and HO-1 in Jurkat cells. The above results were verified by silencing FOXO3a. Moreover, FOXO3a directly interacted with and promoted the transcription of TGF-β and HO-1. In summary, the modulation of cellular inflammation and oxidative stress via FOXO3a-mediated TGF-β and HO-1 activation is partly involved in the pathogenesis of AS.

Inflammasomes and the IL-1 Family in Bone Homeostasis and Disease

PURPOSE OF REVIEW

Inflammasomes are multimeric protein structures with crucial roles in host responses against infections and injuries. The importance of inflammasome activation goes beyond host defense as a dysregulated inflammasome and subsequent secretion of IL-1 family members is believed to be involved in the pathogenesis of various diseases, some of which also produce skeletal manifestations. The purpose of this review is to summarize recent developments in the understanding of inflammasome regulation and IL-1 family members in bone physiology and pathology and current therapeutics will be discussed.

RECENT FINDINGS

Small animal models have been vital to help understand how the inflammasome regulates bone dynamics. Animal models with gain or loss of function in various inflammasome components or IL-1 family signaling have illustrated how these systems can impact numerous bone pathologies and have been utilized to test new inflammasome therapeutics. It is increasingly clear that a tightly regulated inflammasome is required not only for host defense but for skeletal homeostasis, as a dysregulated inflammasome is linked to diseases of pathological bone accrual and loss. Given the complexities of inflammasome activation and redundancies in IL-1 activation and secretion, targeting these pathways is at times challenging. Ongoing research into inflammasome-mediated mechanisms will allow the development of new therapeutics for inflammasome/IL-1 diseases.

Intestinal Microbial Metabolites in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by inflammation of axial joints and the pelvis. It is known that intestinal dysbiosis may exert direct pathogenic effects on gut homeostasis and may act as a triggering factor for the host innate immune system to activate and cause inflammation in extraintestinal sites in the so-called "gut-joint axis", contributing to AS pathogenesis. However, although the intestinal microbiota's influence on the clinical manifestation of AS is widely accepted, the mechanisms mediating the cross-talk between the intestinal lumen and the immune system are still not completely defined. Recent evidence suggests that the metabolism of microbial species may be a source of metabolites and small molecules participating in the complex network existing between bacteria and host cells. These findings may give inputs for further research of novel pharmacological targets and pave the way to applying dietary interventions to prevent the onset and ameliorate the clinical presentation of the disease. In this review, we discuss the role of some of the biological mediators of microbial origin, with a particular focus on short-chain fatty acids, tryptophan and vitamin B derivatives, and their role in barrier integrity and type 3 immunity in the context of AS.

Ankylosing spondylitis: an autoimmune or autoinflammatory disease?

Ankylosing spondylitis (AS) is a chronic inflammatory disorder of unknown aetiology. Unlike other systemic autoimmune diseases, in AS, the innate immune system has a dominant role characterized by aberrant activity of innate and innate-like immune cells, including γδ T cells, group 3 innate lymphoid cells, neutrophils, mucosal-associated invariant T cells and mast cells, at sites predisposed to the disease. The intestine is involved in disease manifestations, as it is at the forefront of the interaction between the mucosal-associated immune cells and the intestinal microbiota. Similarly, biomechanical factors, such as entheseal micro-trauma, might also be involved in the pathogenesis of the articular manifestation of AS, and sentinel immune cells located in the entheses could provide links between local damage, genetic predisposition and the development of chronic inflammation. Although these elements might support the autoinflammatory nature of AS, studies demonstrating the presence of autoantibodies (such as anti-CD74, anti-sclerostin and anti-noggin antibodies) and evidence of activation and clonal expansion of T cell populations support an autoimmune component to the disease. This Review presents the evidence for autoinflammation and the evidence for autoimmunity in AS and, by discussing the pathophysiological factors associated with each, aims to reconcile the two hypotheses.