Role of peptidoglycan subtypes in the pathogenesis of bacterial cell wall arthritis

Exploring the significance of microbiota metabolites in rheumatoid arthritis: uncovering their contribution from disease development to biomarker potential

Rheumatoid arthritis (RA) is a multifaceted autoimmune disorder characterized by chronic inflammation and joint destruction. Recent research has elucidated the intricate interplay between gut microbiota and RA pathogenesis, underscoring the role of microbiota-derived metabolites as pivotal contributors to disease development and progression. The human gut microbiota, comprising a vast array of microorganisms and their metabolic byproducts, plays a crucial role in maintaining immune homeostasis. Dysbiosis of this microbial community has been linked to numerous autoimmune disorders, including RA. Microbiota-derived metabolites, such as short-chain fatty acids (SCFAs), tryptophan derivatives, Trimethylamine-N-oxide (TMAO), bile acids, peptidoglycan, and lipopolysaccharide (LPS), exhibit immunomodulatory properties that can either exacerbate or ameliorate inflammation in RA. Mechanistically, these metabolites influence immune cell differentiation, cytokine production, and gut barrier integrity, collectively shaping the autoimmune milieu. This review highlights recent advances in understanding the intricate crosstalk between microbiota metabolites and RA pathogenesis and also discusses the potential of specific metabolites to trigger or suppress autoimmunity, shedding light on their molecular interactions with immune cells and signaling pathways. Additionally, this review explores the translational aspects of microbiota metabolites as diagnostic and prognostic tools in RA. Furthermore, the challenges and prospects of translating these findings into clinical practice are critically examined.

High fat diet increases the severity of collagen-induced arthritis in mice by altering the gut microbial community

OBJECTIVES

Research has demonstrated that obesity may be associated with rheumatoid arthritis (RA). In addition, gut microbiota and its metabolites contribute to the occurrence and development of RA and obesity. However, the mechanism by which obesity affects RA remains unclear. In this study, we aimed to investigate whether gut microbiota and their metabolites alter the effects of high fat diet (HFD) on the severity of collagen-induced arthritis (CIA) in mice.

METHODS

Briefly, mice were divided into normal group (N), CIA model group (C), HFD group (T), and HFD CIA group (CT). Hematoxylin and Eosin staining(HE) and Safranin O-fast green staining were conducted, and levels of blood lipid and inflammatory cytokines were measured. 16S rDNA sequencing technique and liquid chromatography-mass spectrometry (LC-MS)-based metabolomics were performed to explore changes in the microbiota structure to further reveal the pathomechanism of HFD on CIA.

RESULTS

HFD aggravated the severity of CIA in mice. The CT group had the highest proportion of microbial abundance of Blautia, Oscillibacter, Ruminiclostridium-9, and Lachnospiraceae UCG 006 at the genus level, but had a lower proportion of Alistipes. Additionally, the fecal metabolic phenotype of the combined CT group shows significant changes, with differential metabolites enriched in 9 metabolic pathways, including primary bile acid biosynthesis, arginine biosynthesis, sphingolipid metabolism, purine metabolism, linoleic acid metabolism, oxytocin signaling pathway, aminoacyl-tRNA biosynthesis, the pentose phosphate pathway, and sphingolipid signaling pathway. Correlation analysis revealed that some of the altered gut microbiota genera were strongly correlated with changes in fecal metabolites, total cholesterol (TC), triglyceride (TG), and inflammatory cytokine levels.

CONCLUSIONS

This study shows that HFD may aggravate inflammatory reaction in CIA mice by altering the gut microbiota and metabolic pathways.

Effects of granular feed on reproductive metabolism of breeding pigeons, intestinal development and microbiota of squab pigeons-A double-edged sword

Pigeons like to eat raw grains, but meat pigeon enterprises often use compound feeds instead of raw grains to feed breeding pigeons to increase economic efficiency, which may change the pigeon's dietary behavior, and consequently lead to health and welfare problems. The purpose of this study was to investigate the effect of granular feeds on the health of high-yielding breeding pigeons and squabs in lactation. The results showed that, compared with raw grain group, the provision of granular feed resulted in lower total feed intake without affecting the weight of lactating breeding pigeons. Meanwhile, reproductive metabolism was improved and no oxidative stress was observed, which indicated that granular feeds had a positive effect on breeding pigeon's health. However, granular feed adversely affected jejunum development in squabs, compare wtih raw grain group, the growth rate of squab was reduced. Sequencing of the 16 s rRNA gene revealed that granular feed induced intestinal microbiota dysbiosis in the squabs. The use of granular feed reduced the relative abundance of gut microorganisms in functional categories related to lipid and energy metabolism, resulting in a decrease in the relative abundance of beneficial bacteria such as Bifidobacterium, Ligilactobacillus, Atopobium, and an increase in that of inflammation-related Limosilactobacillus, which likely inhibited squab intestinal development and growth. Although the use of granular feed can improve breeder metabolism, it affect the composition of the microbial community and gut development of squabs. Therefore, the use of granular feed in production should be more careful to avoid causing growth obstruction of squab.

Gut-Joint Axis: Impact of Bifidobacterial Cell Wall Lipoproteins on Arthritis Development

Gut microbiota affect progression of rheumatoid arthritis (RA). The present study aims at investigating the protective potential of Bifidobacterium longum cell wall lipoproteins (Lpps) shown to modulate the intestinal microbiome and prevent osteoarthritis. Arthritis was induced by collagen (CIA) or anti-collagen antibodies (CAIA) injection. Intake of 0.5 mg of Lpps/L, but not 0.25 and 1 mg of Lpps/L, significantly alleviated RA symptoms in CIA DBA/1OOaHsd mice. The arthritis index (AI) was also reduced in CAIA mice. In the CIA-protected group, colon Ligilactobacillus murinus, caecal Lactobacillus johnsonii and spleen weight correlated with AI, whereas the reverse was observed with splenic CD11c+ dendritic cells (cDCs). The unprotected CIA Lpps group harbored higher cecal and colon E. coli and lower caecal L. murinus. Lpps administration to CAIA mice after arthritis induction led to lower colon E. plexicaudatum counts. Splenocytes from CIA-protected mice triggered by LPS secreted higher Il-10 than control ones. However, a higher IL-10 response was not elicited in gnotobiotic RA mice splenocytes with lower cDCs' recruitment. Labeled bacteria with the Lpps signal were detected in CIA mice bone marrow (BM) cDCs 5 and 16 h post-gavage but not in Peyer's patches and the spleen. In vitro uptake of Lpps by primary BM and thymus cells was observed within 24 h. An FACS analysis detected the Lpps signal in the plasmacytoid cell compartment but not in cDCs. In conclusion, Lpps dosing is critical for preventing arthritis progression and appropriately modulating the microbiome. Our results also highlight the possible triggering of the immune system by Lpps.

Clinically proven natural products, vitamins and mineral in boosting up immunity: A comprehensive review

BACKGROUND

and Purposes: The terminology "immune boost-up" was the talk of the topic in this Covid-19 pandemic. A significant number of the people took initiative to increase the body's defense capacity through boosting up immunity worldwide. Considering this, the study was designed to explain the natural products, vitamins and mineral that were proved by clinical trail as immunity enhancer.

METHODS

Information was retrieved from SciVerse Scopus ® (Elsevier Properties S. A, USA), Web of Science® (Thomson Reuters, USA), and PubMed based on immunity, nutrients, natural products in boosting up immunity, minerals and vitamins in boosting up immunity, and immune booster agents.

RESULT

A well-defined immune cells response provide a-well functioning defense system for the human physiological system. Cells of the immune system must require adequate stimulation so that these cells can prepare themselves competent enough to fight against any unintended onslaught. Several pharmacologically active medicinal plants and plants derived probiotics or micronutrients have played a pivotal role in enhancing the immune boost-up process. Their role has been well established from the previous study. Immune stimulating cells, especially cells of acquired immunity are closely associated with the immune-boosting up process because all the immunological reactions and mechanisms are mediated through these cells.

CONCLUSION

This article highlighted the mechanism of action of different natural products, vitamins and mineral in boosting up the immunity of the human body and strengthening the body's defense system. Therefore, it is recommended that until the specific immune-boosting drugs are available in pharma markets, anyone can consider the mentioned products as dietary supplements to boost up the immunity.

Interactions between NSAIDs, opioids and the gut microbiota - Future perspectives in the management of inflammation and pain

The composition of intestinal microbiota is influenced by a number of factors, including medications, which may have a substantial impact on host physiology. Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics are among those widely used medications that have been shown to alter microbiota composition in both animals and humans. Although much effort has been devoted to identify microbiota signatures associated with these medications, much less is known about the underlying mechanisms. Mucosal inflammation, changes in intestinal motility, luminal pH and bile acid metabolism, or direct drug-induced inhibitory effect on bacterial growth are all potential contributors to NSAID- and opioid-induced dysbiosis, however, only a few studies have addressed directly these issues. In addition, there is a notable overlap between the microbiota signatures of these drugs and certain diseases in which they are used, such as spondyloarthritis (SpA), rheumatoid arthritis (RA) and neuropathic pain associated with type 2 diabetes (T2D). The aims of the present review are threefold. First, we aim to provide a comprehensive up-to-date summary on the bacterial alterations caused by NSAIDs and opioids. Second, we critically review the available data on the possible underlying mechanisms of dysbiosis. Third, we review the current knowledge on gut dysbiosis associated with SpA, RA and neuropathic pain in T2D, and highlight the similarities between them and those caused by NSAIDs and opioids. We posit that drug-induced dysbiosis may contribute to the persistence of these diseases, and may potentially limit the therapeutic effect of these medications by long-term use. In this context, we will review the available literature data on the effect of probiotic supplementation and fecal microbiota transplantation on the therapeutic efficacy of NSAIDs and opioids in these diseases.

The change of plasma metabolic profile and gut microbiome dysbiosis in patients with rheumatoid arthritis

Objective

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease, which is associated with progressive disability, systemic complications, and early death. But its etiology and pathogenesis are not fully understood. We aimed to investigate the alterations in plasma metabolite profiles, gut bacteria, and fungi and their role of them in the pathogenesis of RA.

Methods

Metabolomics profiling of plasma from 363 participants including RA (n = 244), systemic lupus erythematosus (SLE, n = 50), and healthy control (HC, n = 69) were performed using the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The differentially expressed metabolites were selected among groups and used to explore important metabolic pathways. Gut microbial diversity analysis was performed by 16S rRNA sequencing and ITS sequencing (RA = 195, HC = 269), and the specific microbial floras were identified afterward. The diagnosis models were established based on significant differential metabolites and microbial floras, respectively.

Results

There were 63 differential metabolites discovered between RA and HC groups, mainly significantly enriched in the arginine and proline metabolism, glycine, serine, and threonine metabolism, and glycerophospholipid metabolism between RA and HC groups. The core differential metabolites included L-arginine, creatine, D-proline, ornithine, choline, betaine, L-threonine, LysoPC (18:0), phosphorylcholine, and glycerophosphocholine. The L-arginine and phosphorylcholine were increased in the RA group. The AUC of the predictive model was 0.992, based on the combination of the 10 differential metabolites. Compared with the SLE group, 23 metabolites increased and 61 metabolites decreased in the RA group. However, no significant metabolic pathways were enriched between RA and SLE groups. On the genus level, a total of 117 differential bacteria genera and 531 differential fungal genera were identified between RA and HC groups. The results indicated that three bacteria genera (Eubacterium_hallii_group, Escherichia-Shigella, Streptococcus) and two fungal genera (Candida and Debaryomyces) significantly increased in RA patients. The AUC was 0.80 based on a combination of six differential bacterial genera and the AUC was 0.812 based on a combination of seven differential fungal genera. Functional predictive analysis displayed that differential bacterial and differential fungus both were associated with KEGG pathways involving superpathway of L-serine and glycine biosynthesis I, arginine, ornithine, and proline interconversion.

Conclusion

The plasma metabolism profile and gut microbe profile changed markedly in RA. The glycine, serine, and threonine metabolism and arginine and proline metabolism played an important role in RA.

Glucose metabolism and glycosylation link the gut microbiota to autoimmune diseases

Carbohydrates serve as important energy sources and structural substances for human body as well as for gut microbes. As evidenced by the advances in immunometabolism, glucose metabolism and adenosine triphosphate (ATP) generation are deeply involved in immune cell activation, proliferation, and signaling transduction as well as trafficking and effector functions, thus contributing to immune response programming and assisting in host adaption to microenvironment changes. Increased glucose uptake, aberrant expression of glucose transporter 1 (e.g., GLU1), and abnormal glycosylation patterns have been identified in autoimmunity and are suggested as partially responsible for the dysregulated immune response and the modification of gut microbiome composition in the autoimmune pathogenesis. The interaction between gut microbiota and host carbohydrate metabolism is complex and bidirectional. Their impact on host immune homeostasis and the development of autoimmune diseases remains to be elucidated. This review summarized the current knowledge on the crosstalk of glucose metabolism and glycosylation in the host with intestinal microbiota and discussed their possible role in the development and progression of autoimmune diseases. Potential therapeutic strategies targeting glucose metabolism and glycosylation in modulating gut ecosystem and treating autoimmune diseases were discussed as well.

Streptococcus species enriched in the oral cavity of patients with RA are a source of peptidoglycan-polysaccharide polymers that can induce arthritis in mice

OBJECTIVES

Analysis of oral dysbiosis in individuals sharing genetic and environmental risk factors with rheumatoid arthritis (RA) patients may illuminate how microbiota contribute to disease susceptibility. We studied the oral microbiota in a prospective cohort of patients with RA, first-degree relatives (FDR) and healthy controls (HC), then genomically and functionally characterised streptococcal species from each group to understand their potential contribution to RA development.

METHODS

After DNA extraction from tongue swabs, targeted 16S rRNA gene sequencing and statistical analysis, we defined a microbial dysbiosis score based on an operational taxonomic unit signature of disease. After selective culture from swabs, we identified streptococci by sequencing. We examined the ability of streptococcal cell walls (SCW) from isolates to induce cytokines from splenocytes and arthritis in ZAP-70-mutant SKG mice.

RESULTS

RA and FDR were more likely to have periodontitis symptoms. An oral microbial dysbiosis score discriminated RA and HC subjects and predicted similarity of FDR to RA. Streptococcaceae were major contributors to the score. We identified 10 out of 15 streptococcal isolates as S. parasalivarius sp. nov., a distinct sister species to S. salivarius. Tumour necrosis factor and interleukin 6 production in vitro differed in response to individual S. parasalivarius isolates, suggesting strain specific effects on innate immunity. Cytokine secretion was associated with the presence of proteins potentially involved in S. parasalivarius SCW synthesis. Systemic administration of SCW from RA and HC-associated S. parasalivarius strains induced similar chronic arthritis.

CONCLUSIONS

Dysbiosis-associated periodontal inflammation and barrier dysfunction may permit arthritogenic insoluble pro-inflammatory pathogen-associated molecules, like SCW, to reach synovial tissue.

Gram-positive bacteria control the rapid anabolism of protein-sized soil organic nitrogen compounds questioning the present paradigm

The cycling of especially large size organic nitrogen (N) from plants into stable microbial derived soil organic carbon (C) and N pools is understudied, in spite of organic N composing 90% of soil N and the intimate link between organic N and soil C stabilization. We investigated the fate of peptide-size and protein-size organic N fractions in soils from two long-term field experiments markedly differing in conditions for microorganisms. We combined amino acid stable isotope probing (AA-SIP) fingerprinting with PLFA-SIP to trace organic N into the soil microbial biomass. Contrary to the present paradigm, we found for both soils that greater molecular size did not protect against decomposition of these compounds neither did protection via strong sorption to the soil mineral phase. Instead, we found strong evidence that gram-positive bacteria are the key actors in the decomposition of protein-sized nitrogen compounds and that amino acids bound in large organic nitrogen compounds directly contribute to the build-up of bacterial tissue. We conclude that when large organic nitrogen compounds are dissolved, turnover occurs rapidly, irrespective of molecular size, and the bacterial incorporation of these rapid cycling compounds makes an important contribution to soil organic matter formation.

Recombinant bacteriophage LysKB317 endolysin mitigates Lactobacillus infection of corn mash fermentations

BACKGROUND

Commercial ethanol fermentation facilities traditionally rely on antibiotics for bacterial contamination control. Here we demonstrate an alternative approach to treat contamination using a novel peptidoglycan hydrolase (LysKB317) isolated from a bacteriophage, EcoSau. This endolysin was specially selected against Lactobacillus strains that were isolated as contaminants from a fuel ethanol plant. The LysKB317 gene was recombinantly expressed in Escherichia coli as a 33 kDa purified enzyme.

RESULTS

In turbidity reduction assays, the recombinant enzyme was subjected to a panel of 32 bacterial strains and was active against 28 bacterial strains representing 1 species of Acetobacter, 8 species of Lactobacillus, 1 species of Pediococcus, 3 species of Streptococcus, and 1 species of Weissella. The activity of LysKB317 was optimal around pH 6, but it has broad activity and stability from pH 4.5-7.5 up to at least 48 h. Maximum activity was observed at 50 °C up to at least 72 h. In addition, LysKB317 was stable in 30% ethanol up to at least 72 h. In experimentally infected corn mash fermentations, 1 µM endolysin reduced bacterial load by 3-log fold change, while 0.01 µM reduced bacteria by 2-log fold change. Concentration of fermentation products (ethanol, residual glucose, lactic acid, and acetic acids) for infected cultures treated with ≥ 0.01 µM LysKB317 was similar to uncontaminated controls.

CONCLUSION

Exogenously added LysKB317 endolysin is functional in conditions typically found in fuel ethanol fermentations tanks and may be developed as an alternative to antibiotics for contamination control during fuel ethanol fermentations.

The Gut Microbiota and Respiratory Diseases: New Evidence

Human body surfaces, such as the skin, intestines, and respiratory and urogenital tracts, are colonized by a large number of microorganisms, including bacteria, fungi, and viruses, with the gut being the most densely and extensively colonized organ. The microbiome plays an essential role in immune system development and tissue homeostasis. Gut microbiota dysbiosis not only modulates the immune responses of the gastrointestinal (GI) tract but also impacts the immunity of distal organs, such as the lung, further affecting lung health and respiratory diseases. Here, we review the recent evidence of the correlations and underlying mechanisms of the relationship between the gut microbiota and common respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), lung cancer, and respiratory infection, and probiotic development as a therapeutic intervention for these diseases.

The mechanisms and safety of probiotics against toxigenic clostridium difficile

INTRODUCTION

Toxigenic Clostridium difficile (C. difficile) is the main cause of antibiotic-associated diarrhea and can induce pseudomembranous colitis and infrequent toxic megacolon, which are potentially fatal. The standard antibiotic therapy for C. difficile infection (CDI) is limited by antibiotics' broad spectrum and further disruptive effects on indigenous microbiota. Probiotics may offer a prospective and alternative strategy for the prevention and treatment of CDI.

AREAS COVERED

In this article, the mechanisms implying the probiotic effect against C. difficile and the safety profile highlighting the patient groups with inappropriate application of probiotics were reviewed from 2015 to 2020.

EXPERT OPINION

Although many strains with ability against C. difficile have been reported, the usage of probiotics for CDI prevention and/or treatment is scarce since the number of clinical trials is not sufficient to prove probiotics' efficacy and safety in CDI treatment, especially for premature infant and immunocompromised patient. Especially, there are few well-defined clinical studies supporting safety of probiotics for CDI. A few strains from Lactobacillus and Saccharomyces genus have been studied more extensively than other probiotic strains through clinical trials for CDI. Thus, more clinical intervention studies regarding the benefit and the comprehensive safety assessments of probiotics for CDI are needed.

Emerging Insights on the Interaction Between Anticancer and Immunosuppressant Drugs and Intestinal Microbiota in Pediatric Patients

Diseases affecting the immune system, such as inflammatory bowel disease (IBD), juvenile idiopathic arthritis (JIA), and acute lymphoblastic leukemia (ALL), are pathological conditions affecting the pediatric population and are often associated with alterations in the intestinal microbiota, such as a decrease in bacterial diversity. Growing evidence suggests that gut microbiota can interfere with chemotherapeutic and immunosuppressant drugs, used in the treatment of these diseases, reducing or facilitating drug efficacy. In particular, the effect of intestinal microflora through translocation, immunomodulation, metabolism, enzymatic degradation, and reduction of bacterial diversity seems to be one of the reasons of interindividual variability in the therapeutic response. Although the extent of the role of intestinal microflora in chemotherapy and immunosuppression remains still unresolved, current evidence on bacterial compositional shifts will be taken in consideration together with clinical response to drugs for a better and personalized therapy. This review is focused on the effect of the intestinal microbiota on the efficacy of pharmacological therapy of agents used to treat IBD, JIA, and ALL.

Newly depolymerized large organic N contributes directly to amino acid uptake in young maize plants

The contribution of large molecular size organic nitrogen (N) to plant N uptake is unclear. Soils with and without maize, at three pH levels, were treated with (carbon-14 and -13 (¹⁴ C, ¹³ C), ¹⁵ N) triple-labelled > 100 kDa organic N. After 48 h, soil and maize were sampled for bulk and compound specific isotope analysis to study the turnover in soil and plant ¹³ C and ¹⁵ N uptake. Mineralization of > 100 kDa organic N increased with higher pH only in soil without maize. The > 100 kDa organic N disappeared rapidly in soils with and without maize, but surprisingly more > 100 kDa organic N derived amino acids remained in soil with than without maize - most likely in the microbial biomass. Total ¹⁵ N uptake in maize increased with higher soil pH. The organic N uptake was estimated to account for 20-30% of the total ¹⁵ N uptake. Organic N uptake was confirmed by the presence of ¹³ C-labelled amino acids in maize roots. The study suggests that the importance of plant organic N uptake increases when N is derived from complex molecules such as proteins compared to studies using single amino acids as N source, and that rhizosphere microorganisms increase anabolic utilization of organic N compared to microorganisms in the bulk soil.

Lactobacillus fermentum PC1 has the Capacity to Attenuate Joint Inflammation in Collagen-Induced Arthritis in DBA/1 Mice

Lactobacillus strains have shown efficacy in attenuating inflammation. This study evaluated the potential of Lactobacillus fermentum PC1 for the treatment of rheumatoid arthritis (RA) using a murine model of collagen-induced arthritis. On Day 1, healthy DBA/1 mice (six to eight weeks of age) were immunized, with 100 μg of Chicken Type 11 collagen emulsified in complete Freund’s adjuvant (CFA) by intradermal injection, at the base of the tail. On Day 21, the mice were immunized intraperitoneally with 100 μg of Bovine Type11 collagen in phosphate buffered saline (PBS). On Day 28, the mice were immunized intraperitoneally with 50 μg of lipopolysaccharide (LPS). Viable L. fermentum PC1 (1 × 10⁹ colony forming units) was given daily from Day two until the end of the experiment. From Day 21 onwards, the mice were monitored daily for clinical signs of arthritis. On Day 44, the experiment was terminated. Paws were obtained for histology and serum for cytokine assays. L. fermentum PC1-fed mice had significantly reduced paw inflammation as well as decreased synovial infiltration and less cartilage damage. Circulating serum cytokine profiles revealed decreased IL-12 and increased anti-inflammatory cytokines, namely IL-4 and IL-10. Thus, early administration of L.fermentum PC1 could prove to be a valuable therapeutic agent in the management of RA.

Gut microbiota and probiotics: novel immune system modulators in myasthenia gravis?

Gut microorganisms (microbiota) live in symbiosis with the host and influence human nutrition, metabolism, physiology, and immune development and function. The microbiota prevents pathogen infection to the host, and in turn the host provides a niche for survival. The alteration of gut bacteria composition (dysbiosis) could contribute to the development of immune-mediated diseases by influencing the immune system activation and driving the pro- and anti-inflammatory responses in order to promote or counteract immune reactions. Probiotics are nonpathogenic microorganisms able to interact with the gut microbiota and provide health benefits; their use has recently been exploited to dampen immunological response in several experimental models of autoimmune diseases. Here, we focus on the relationships among commensal bacteria, probiotics, and the gut, describing the main interactions occurring with the immune system and recent data supporting the clinical efficacy of probiotic administration in rheumatoid arthritis, multiple sclerosis, and myasthenia gravis (MG) animal models. The encouraging results suggest that selected strains of probiotics should be evaluated in clinical trials as adjuvant therapy to restore the disrupted tolerance in myasthenia gravis.

Altered gut microbiota in RA: implications for treatment

Rheumatoid arthritis (RA) is an autoimmune disease with progressive joint disorder. The complex interplay of genetic and environmental influences is important for the development of the disease. A growing body of evidence has shed light on the association of dysbiosis of gut microbiota with RA. Certain gut microbial strains have been shown to inhibit or attenuate immune responses in RA experimental models, suggesting that specific species among intestinal commensal bacteria may play either a pathogenic or a protective role in the development of RA. Oral intake of probiotics/prebiotics can therefore represent a therapeutic approach for RA treatment. However, the relevant scientific work has only just begun, and the available data in this field remain limited. Fortunately, utilization of new sequencing technologies allows expanded research on the association of intestinal bacterial flora and human diseases to be attempted. In this review, we summarize the role of gut microbiota in RA progression and address how specific bacterial strains regulate the immune response in disease process. Probiotics/prebiotics in the treatment of RA is also discussed.

Lactobacillus salivarius Isolated from Patients with Rheumatoid Arthritis Suppresses Collagen-Induced Arthritis and Increases Treg Frequency in Mice

Previously, we demonstrated that Lactobacillus salivarius was more abundant in patients with rheumatoid arthritis (RA), an inflammatory autoimmune disease wherein the gut microbiota is altered, than in healthy individuals. However, the effect of L. salivarius in RA is unclear. Hence, we investigated the effect of L. salivarius isolated from patients with RA on collagen-induced arthritis (CIA) in mice. L. salivarius UCC118 or L. plantarum WCFS1 isolated from patients with RA was administered orally for 5 weeks, starting from 2 weeks before the induction of arthritis in DBA/1 mice. Clinical score progression, histological changes, serum cytokine concentrations, and the proportion of interleukin (IL)-17-producing T cells [T helper 17 (Th17)] and regulatory T cells (Tregs) in the spleen were evaluated. Bone erosion was evaluated by micro-computed tomography. CIA mice treated with either L. salivarius or L. plantarum showed lower arthritis scores, milder synovial infiltration, and less bone erosion when compared with phosphate-buffered, saline-treated CIA mice. Administration of L. salivarius and L. plantarum reduced the Th17 cell fraction and increased the Treg fraction. L. salivarius-treated CIA mice displayed a significant increase in serum anti-inflammatory IL-10 levels. Thus, pretreatment with L. salivarius could significantly improve CIA in mice and may help alleviate RA in a clinical setting.

Alteration of Fecal Microbiota Profiles in Juvenile Idiopathic Arthritis. Associations with HLA-B27 Allele and Disease Status

Alteration of gut microbiota is involved in several chronic inflammatory and autoimmune diseases, including rheumatoid arthritis, and gut microbial “pro-arthritogenic” profiles have been hypothesized. Intestinal inflammation may be involved in spondyloarthropathies and in a subset of patients affected by Juvenile Idiopathic Arthritis (JIA), the most common chronic rheumatic disease of childhood. We compared the fecal microbiota composition of JIA patients with healthy subjects (HS), evaluating differences in microbial profiles between sub-categories of JIA, such as enthesitis-related arthritis (JIA-ERA), in which inflammation of entheses occurs, and polyarticular JIA, non-enthesitis related arthritis (JIA-nERA). Through taxon-level analysis, we discovered alteration of fecal microbiota components that could be involved in subclinical gut inflammation, and promotion of joint inflammation. We observed abundance in Ruminococcaceae in both JIA categories, reduction in Clostridiaceae and Peptostreptococcaceae in JIA-ERA, and increase in Veillonellaceae in JIA-nERA, respectively, compared with HS. Among the more relevant genera, we found an increase in Clostridium cluster XIVb, involved in colitis and arthritis, in JIA-ERA patients compared with HS, and a trend of decrease in Faecalibacterium, known for anti-inflammatory properties, in JIA-nERA compared with JIA-ERA and HS. Differential abundant taxa identified JIA patients for the HLA-B27 allele, including Bilophila, Clostridium cluster XIVb, Oscillibacter, and Parvimonas. Prediction analysis of metabolic functions showed that JIA-ERA metagenome was differentially enriched in bacterial functions related to cell motility and chemotaxis, suggesting selection of potential virulence traits. We also discovered differential microbial profiles and intra-group variability among active disease and remission, suggesting instability of microbial ecosystem in autoimmune diseases with respect to healthy status. Similarly to other chronic autoimmune and inflammatory diseases, different microbial profiles, as observed among different JIA subgroups compared to HS, and potential functional acquisition related to migration, could promote inflammation and contribute to the disease pathogenesis.

Role of the Gut Microbiome in Modulating Arthritis Progression in Mice

Genetics alone cannot explain most cases of rheumatoid arthritis (RA). Thus, investigating environmental factors such as the gut microbiota may provide new insights into the initiation and progression of RA. In this study, we performed 16S rRNA sequencing to characterise the gut microbiota of DBA1 mice that did or did not develop arthritis after induction with collagen. We found that divergence in the distribution of microbiota after induction was pronounced and significant. Mice susceptible to collagen-induced arthritis (CIA) showed enriched operational taxonomic units (OTUs) affiliated with the genus Lactobacillus as the dominant genus prior to arthritis onset. With disease development, the abundance of OTUs affiliated with the families Bacteroidaceae, Lachnospiraceae, and S24-7 increased significantly in CIA-susceptible mice. Notably, germ-free mice conventionalized with the microbiota from CIA-susceptible mice showed a higher frequency of arthritis induction than those conventionalized with the microbiota from CIA-resistant mice. Consistently, the concentration of the cytokine interleukin-17 in serum and the proportions of CD8+T cells and Th17 lymphocytes in the spleen were significantly higher in the former group, whereas the abundances of dendritic cells, B cells, and Treg cells in the spleen were significantly lower. Our results suggest that the gut microbiome influences arthritis susceptibility.

Construction and verification of the transcriptional regulatory response network of Streptococcus mutans upon treatment with the biofilm inhibitor carolacton

Background

Carolacton is a newly identified secondary metabolite causing altered cell morphology and death of Streptococcus mutans biofilm cells. To unravel key regulators mediating these effects, the transcriptional regulatory response network of S. mutans biofilms upon carolacton treatment was constructed and analyzed. A systems biological approach integrating time-resolved transcriptomic data, reverse engineering, transcription factor binding sites, and experimental validation was carried out.

Results

The co-expression response network constructed from transcriptomic data using the reverse engineering algorithm called the Trend Correlation method consisted of 8284 gene pairs. The regulatory response network inferred by superimposing transcription factor binding site information into the co-expression network comprised 329 putative transcriptional regulatory interactions and could be classified into 27 sub-networks each co-regulated by a transcription factor. These sub-networks were significantly enriched with genes sharing common functions. The regulatory response network displayed global hierarchy and network motifs as observed in model organisms. The sub-networks modulated by the pyrimidine biosynthesis regulator PyrR, the glutamine synthetase repressor GlnR, the cysteine metabolism regulator CysR, global regulators CcpA and CodY and the two component system response regulators VicR and MbrC among others could putatively be related to the physiological effect of carolacton. The predicted interactions from the regulatory network between MbrC, known to be involved in cell envelope stress response, and the murMN-SMU_718c genes encoding peptidoglycan biosynthetic enzymes were experimentally confirmed using Electro Mobility Shift Assays. Furthermore, gene deletion mutants of five predicted key regulators from the response networks were constructed and their sensitivities towards carolacton were investigated. Deletion of cysR, the node having the highest connectivity among the regulators chosen from the regulatory network, resulted in a mutant which was insensitive to carolacton thus demonstrating not only the essentiality of cysR for the response of S. mutans biofilms to carolacton but also the relevance of the predicted network.

Conclusion

The network approach used in this study revealed important regulators and interactions as part of the response mechanisms of S. mutans biofilm cells to carolacton. It also opens a door for further studies into novel drug targets against streptococci.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-362) contains supplementary material, which is available to authorized users.

Analysis of fecal Lactobacillus community structure in patients with early rheumatoid arthritis

The objective of this study was to analyze human fecal Lactobacillus community and its relationship with rheumatoid arthritis. Samples taken from rheumatoid arthritis (RA) patients and healthy individuals were analyzed by quantitative real-time PCR. Bacterial DNA was extracted from feces, and amplicons of the Lactobacillus-specific regions of 16S rRNA were analyzed by denaturing gradient gel electrophoresis. The richness, Shannon-Wiener index, and evenness of gut microbiota of both groups were analyzed to compare fecal Lactobacillus community structures. Results of this study demonstrated that fecal microbiota of RA patients contained significantly more Lactobacillus (10.62 ± 1.72 copies/g) than the control group (8.93 ± 1.60 copies/g). Significant increases were observed in RA patients in terms of the richness, Shannon-Wiener, and evenness measures, indicating more bacterial species, and increased bacterial diversity and abundance. These results suggest a potential relationship between Lactobacillus communities and the development and progression of rheumatoid arthritis.

Microbial Infection and Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complex autoimmune disease affecting 1–2% of general worldwide population. The etiopathogenesis of RA involves the interplay of multiple genetic risk factors and environmental triggers. Microbial infections are believed to play an important role in the initiation and perpetuation of RA. Recent clinical studies have shown the association of microbial infections with RA. Accumulated studies using animal models have also found that microbial infections can induce and/or exaggerate the symptoms of experimental arthritis. In this review, we have identified the most common microbial infections associated with RA in the literature and summarized the current evidence supporting their pathogenic role in RA. We also discussed the potential mechanisms whereby infection may promote the development of RA, such as generation of neo-autoantigens, induction of loss of tolerance by molecular mimicry, and bystander activation of the immune system.

Bacterial exopolysaccharides: functionality and prospects

Diverse structural, functional and valuable polysaccharides are synthesized by bacteria of all taxa and secreted into the external environment. These polysaccharides are referred to as exopolysaccharides and they may either be homopolymeric or heteropolymeric in composition and of diverse high molecular weights (10 to 1000 kDa). The material properties of exopolysaccharides have revolutionized the industrial and medical sectors due to their retinue of functional applications and prospects. These applications have been extensive in areas such as pharmacological, nutraceutical, functional food, cosmeceutical, herbicides and insecticides among others, while prospects includes uses as anticoagulant, antithrombotic, immunomodulation, anticancer and as bioflocculants. Due to the extensive applications of bacterial exopolysaccharides, this overview provides basic information on their physiologic and morphologic functions as well as their applications and prospects in the medical and industrial sectors.

Exploring symbioses by single-cell genomics

Single-cell genomics has advanced the field of microbiology from the analysis of microbial metagenomes where information is "drowning in a sea of sequences," to recognizing each microbial cell as a separate and unique entity. Single-cell genomics employs Phi29 polymerase-mediated whole-genome amplification to yield microgram-range genomic DNA from single microbial cells. This method has now been applied to a handful of symbiotic systems, including bacterial symbionts of marine sponges, insects (grasshoppers, termites), and vertebrates (mouse, human). In each case, novel insights were obtained into the functional genomic repertoire of the bacterial partner, which, in turn, led to an improved understanding of the corresponding host. Single-cell genomics is particularly valuable when dealing with uncultivated microorganisms, as is still the case for many bacterial symbionts. In this review, we explore the power of single-cell genomics for symbiosis research and highlight recent insights into the symbiotic systems that were obtained by this approach.

In vitro macrophage response to polyethylene and polycarbonate-urethane particles

This study was undertaken to compare macrophage response to polycarbonate-urethane (PCU), a proposed alternative material to polyethylene in acetabular components of total hip arthroplasty to cross-linked ultra-high molecular weight polyethylene (xUHMWPE) in the presence or absence of endotoxin. Polyethylene wear debris that is generated by total hip and knee replacements has been linked to osteolysis and limiting the lifespan of the implant. We added both lipopolysaccharide (LPS)-free and endotoxin-associated xUHMWPE and PCU particles to a human monocyte cell line (TH1) in culture and measured cell viability and tumor necrosis factor (TNF)alpha, interleukin (IL)-1beta, and prostaglandin E(2) (PGE(2)) in the medium after 24 h. Results indicate that particles (both xUHMWPE and PCU) free of endotoxin did not significantly induce secretion of TNFalpha, IL-1beta, or PGE(2) above basal levels. However, endotoxin-exposed PCU particles induced significantly less TNFalpha and IL-1beta than endotoxin-exposed xUHMWPE particles. This indicates that if endotoxin is available for binding to particles in vivo, then xUHMWPE may be more inflammatory to periprosthetic tissue and bone in part because of its affinity/reactivity with endotoxin when compared with PCU.

Induction of intestinal Th17 cells by segmented filamentous bacteria

The gastrointestinal tract of mammals is inhabited by hundreds of distinct species of commensal microorganisms that exist in a mutualistic relationship with the host. How commensal microbiota influence the host immune system is poorly understood. We show here that colonization of the small intestine of mice with a single commensal microbe, segmented filamentous bacterium (SFB), is sufficient to induce the appearance of CD4(+) T helper cells that produce IL-17 and IL-22 (Th17 cells) in the lamina propria. SFB adhere tightly to the surface of epithelial cells in the terminal ileum of mice with Th17 cells but are absent from mice that have few Th17 cells. Colonization with SFB was correlated with increased expression of genes associated with inflammation and antimicrobial defenses and resulted in enhanced resistance to the intestinal pathogen Citrobacter rodentium. Thus, manipulation of this commensal-regulated pathway may provide new opportunities for enhancing mucosal immunity and treating autoimmune disease.

PGLYRP-2 and Nod2 are both required for peptidoglycan-induced arthritis and local inflammation

Peptidoglycan recognition proteins (PGRPs) are structurally conserved from insects to mammals. Insect PGRPs have diverse host-defense functions. Mammalian PGRPs PGLYRP-1, PGLYRP-3, and PGLYRP-4 have bactericidal activity, while PGLYRP-2 has amidase activity. To extend the known functions of mammalian PGRPs, we examined whether they have immunomodulating activities in peptidoglycan-induced arthritis in mice. We demonstrate that PGLYRP-2 and Nod2 are both required for arthritis in this model. The sequence of events in peptidoglycan-induced arthritis is activation of Nod2, local expression of PGLYRP-2, chemokine production, and recruitment of neutrophils into the limbs, which induces acute arthritis. Only PGLYRP-2 among the four mammalian PGRPs displays this proinflammatory function, and PGLYRP-1 is anti-inflammatory. Toll-like receptor 4 (TLR4) and MyD88 are required for maturation of neutrophils before peptidoglycan challenge. Our results demonstrate that PGRPs, Nod2, and TLR4, representing three different types of pattern-recognition molecules, play interdependent in vivo roles in local inflammation.

Dissecting biological "dark matter" with single-cell genetic analysis of rare and uncultivated TM7 microbes from the human mouth

We have developed a microfluidic device that allows the isolation and genome amplification of individual microbial cells, thereby enabling organism-level genomic analysis of complex microbial ecosystems without the need for culture. This device was used to perform a directed survey of the human subgingival crevice and to isolate bacteria having rod-like morphology. Several isolated microbes had a 16S rRNA sequence that placed them in candidate phylum TM7, which has no cultivated or sequenced members. Genome amplification from individual TM7 cells allowed us to sequence and assemble >1,000 genes, providing insight into the physiology of members of this phylum. This approach enables single-cell genetic analysis of any uncultivated minority member of a microbial community.

Peptidoglycan: a major aetiological factor for psoriasis?

Peptidoglycan (PG), a major cell-wall component of Gram-positive bacteria, has been detected within antigen-presenting cells in various inflammatory conditions, including psoriasis. The additional presence of T-helper 1 cells specific for streptococcal or staphylococcal PG in psoriasis skin lesions implicates PG as an important T-cell stimulator for the disease. PG is a major target for the innate immune system, and associations between genetic polymorphisms of recognition receptors for PG and various auto-inflammatory diseases have been identified. The location of these genes within four linkage sites for psoriasis raises the possibility that an altered innate recognition of PG might contribute to the enhanced T-cell response to the bacterial antigen. These observations suggest that PG is a major aetiological factor for psoriasis and emphasize the importance of PG in bacterial-infection-induced inflammatory disease.

PGRP-SB1: an N-acetylmuramoyl L-alanine amidase with antibacterial activity

The peptidoglycan recognition protein (PGRP) family is conserved from insects to mammals and is involved in immune regulation and bacterial clearance. They form at least three functional classes; receptors required for immune gene expression; amidases that degrade peptidoglycan and scavenge the tissues from immune-stimulating peptidoglycan; and as proteins with antibacterial activity. We here report that PGRP-SB1 is an N-acetylmuramoyl l-alanine amidase, which (in contrast to the previously described PGRP-amidases) shows antibacterial activity. PGRP-SB1 is highly active against peptidoglycans that have a diaminopimelic acid (DAP) residue in the cross-linking peptide, but lack activity to most lysine-containing peptidoglycans. The antibacterial activity is pronounced against Bacillus megaterium with an LD(50) of 1.5microg ml(-1). The bactericidal effect of PGRP-SB1 is dependent on its enzymatic activity, as the zinc co-factor is essential. The bactericidal mode of action is thus different from non-enzymatic vertebrate PGRPs that have been reported to be antibacterial.

Peptidoglycan and peptidoglycan-specific Th1 cells in psoriatic skin lesions

We have previously demonstrated, in psoriatic skin lesions, the presence of a subset of dermal CD4+ T cells that produce interferon-gamma (IFN-gamma) in response to a mixture of cell wall proteins extracted from group A streptococci. However, the identity of the antigen(s) involved is unknown. To investigate the hypothesis that peptidoglycan (PG), the major constituent of the streptococcal cell wall, acts as a T cell activator in psoriasis, we performed in situ analysis to detect antigen-presenting cells containing PG in lesional versus non-lesional skin, and determined proliferation and IFN-gamma responses of lesional skin T cells. Increased numbers of PG-containing cells were detected in the dermal papillae and cellular infiltrates of guttate and chronic plaque skin lesions compared with normal and non-lesional psoriatic skin. A varying proportion of these were CD68+ macrophages, but the remaining cells did not double stain for either Langerhans' or dendritic cell markers. Psoriatic dermal streptococcal-specific CD4+ T cell lines proliferated and produced IFN-gamma in a self HLA-DR allele-restricted manner in response to streptococcal PG, excluding mitogenic or superantigenic stimulation, but were unresponsive to staphylococcal PG. Similarly, psoriatic staphylococcus-specific T cell lines recognized staphylococcal, but not streptococcal, PG by IFN-gamma production. The presence of PG-containing macrophages in close association with PG-specific CD4+ T cells in lesional skin suggests that PG may be responsible, at least in part, for T cell activation in psoriasis.

Ligand-induced dimerization of Drosophila peptidoglycan recognition proteins in vitro

Drosophila knockout mutants have placed peptidoglycan recognition proteins (PGRPs) in the two major pathways controlling immune gene expression. We now examine PGRP affinities for peptidoglycan. PGRP-SA and PGRP-LCx are bona fide pattern recognition receptors, and PGRP-SA, the peptidoglycan receptor of the Toll/Dif pathway, has selective affinity for different peptidoglycans. PGRP-LCx, the default peptidoglycan receptor of the Imd/Relish pathway, has strong affinity for all polymeric peptidoglycans tested and for monomeric peptidoglycan. PGRP-LCa does not have affinity for polymeric or monomeric peptidoglycan. Instead, PGRP-LCa can form heterodimers with LCx when the latter is bound to monomeric peptidoglycan. Hence, PGRP-LCa can be said to function as an adaptor, thus adding a new function to a member of the PGRP family.

Proinflammatory bacterial peptidoglycan as a cofactor for the development of central nervous system autoimmune disease

Upon stimulation by microbial products through TLR, dendritic cells (DC) acquire the capacity to prime naive T cells and to initiate a proinflammatory immune response. Recently, we have shown that APC within the CNS of multiple sclerosis (MS) patients contain peptidoglycan (PGN), a major cell wall component of Gram-positive bacteria, which signals through TLR and NOD. In this study, we report that Staphylococcus aureus PGN as a single component can support the induction of experimental autoimmune encephalomyelitis (EAE) in mice, an animal model for MS. Mice immunized with an encephalitogenic myelin oligodendrocyte glycoprotein peptide in IFA did not develop EAE. In contrast, addition of PGN to the emulsion was sufficient for priming of autoreactive Th1 cells and development of EAE. In vitro studies demonstrate that PGN stimulates DC-mediated processes, reflected by increased Ag uptake, DC maturation, Th1 cell expansion, activation, and proinflammatory cytokine production. These data indicate that PGN-mediated interactions result in proinflammatory stimulation of Ag-specific effector functions, which are important in the development of EAE. These PGN-mediated processes may occur both within the peripheral lymph nodes as well as in the CNS and likely involve recognition by TLR on DC. Thus, PGN may provide a physiological trigger of DC maturation, and in this way disrupt the normal tolerance to self Ag. As such, PGN signaling pathways may serve as novel targets for the treatment of MS.