Characterization of serum biomarkers and antibody responses against Prevotella spp. in preclinical and new-onset phase of rheumatic diseases

MTX-induced gastrointestinal reactions in RA: Prevotella enrichment, gut dysbiosis, and PI3K/Akt/Ras/AMPK pathways

OBJECTIVES

To investigate the role of gut microbiota in methotrexate (MTX)-induced gastrointestinal reactions (MRGR) in patients with rheumatoid arthritis (RA).

METHODS

As a prospective, single-center, convenience sampling study, stool samples were obtained from 28 RA patients (male: female = 10:18) at Lanzhou University Second Hospital who were undergoing MTX treatment for analysis of their gut microbiota using 16S rRNA gene sequencing. Clinical disease activity (CDAI) and MRGR were assessed after two months of MTX therapy. All data collection periods exceeded one year. Intestinal germ-free mice, generated through antibiotic treatment, received fecal microbiota transplantation (FMT) from the patients, followed by varying doses of MTX to observe MRGR. Intestinal transcriptomics and markers related to intestinal barrier function were subsequently examined.

RESULTS

Females (84.6%) and high disease activity (CDAI scores, 39.6 ± 11.2 vs 26.3 ± 9.2) were prone to have MRGR in RA patients. Patients with MRGR (PT-GR) showed lower gut microbial diversity versus non-MRGR (PT-noGR). Prevotella abundance, positively correlated with CDAI and MRGR (p < 0.05), was elevated in PT-GR. Administering 10 mg/kg MTX to mice caused intestinal damage. FMT-GR-MTX mice exhibited weight loss (95.2%), morphological deterioration (86.4%), and reduced tight junction proteins (Claudin-1:72.4%; ZO-1:81.2%). Transcriptomics linked upregulated Gβγ/CREB/Atp4b to PI3K/Akt/Ras pathways and downregulated PFK2/PP2 to AMPK signaling in MRGR.

CONCLUSION

Our study identified notable gut microbiota alterations in RA patients prone to MRGR, with changes in intestinal gene expression and reduced intestinal barrier function potentially contributing to MRGR. These findings suggest potential strategies to mitigate MRGR in RA patients undergoing MTX treatment. Key Points • The RA-related MRGR is correlated with the intestinal microbiota. • Females, low gut diversity, and Prevotella enrichment are MRGR risks in RA. • Upregulated DEGs in MRGR linked to PI3K/Akt, Ras pathways. • Downregulated DEGs in MRGR focus on the AMPK pathway.

From a better knowledge of periodontal disease to Porphyromonas gingivalis target for rheumatoid arthritis disease activity

Periodontal disease (PD) and rheumatoid arthritis (RA) are both inflammatory diseases affecting the tooth and joint, with local inflammation associated with bone loss. Bacterial infections by oral bacteria are involved in periodontal inflammation, and the best known to be associated with PD is Porphyromonas gingivalis (Pg). A large body of recent data suggests a strong involvement of this specific bacteria, Pg, in PD outcomes, but also in RA. The aim of this review is to discuss the association between PD and Pg, RA and its mechanisms, and to determine whether targeting Pg bacteria could improve RA. Numerous epidemiological studies have already confirmed the association between PD and Pg, as well as between PD and RA, which is mainly associated with a common genetic background, the shared epitope. The involvement of Pg in pathogenesis of RA is supported by the induction of gingival citrullinated proteins and therefore of anti-citrullinated proteins antibodies, which constitute the most specific biomarker of RA. The prevalence of Pg in RA is still controversial, but studies should include patients with preclinical and early RA. Finally, recent data confirmed that targeting Pg is highly effective in improving RA.

Plasma proteins mediate the effects of the gut microbiota on the development of head and neck cancer: a two-sample and mediated Mendelian randomized study

BACKGROUND

Although previous observational studies have highlighted a possible association between the gut microbiota (GM) and head and neck cancer (HNC), the causal relationships remain unclear, particularly regarding the role of plasma proteins as potential mediators. Clarifying these connections is essential for uncovering the underlying mechanisms of HNC progression and may lead to new therapeutic strategies.

MATERIALS AND METHODS

First, we examined the causal link between the GM and HNC via a two-sample Mendelian randomization (MR) approach. We then investigated the causative relationships between plasma proteins and HNC via the same two-sample MR technique. The coefficient product approach was then used to clarify the role of plasma proteins in the causative pathway between the GM and HNC. Finally, sensitivity investigations were performed to assess the robustness and coherence of the results.

RESULTS

MR analyses revealed the protective effects of one family and six genera on HNC (Lachnospiraceae, Parabacteroides, Phascolarctobacterium, Alistipes, Sutterella, Roseburia and Alloprevotella). In contrast, three genera (Ruminococcus, Prevotella and Bacteroides) were significantly positively associated with HNC risk. Through further examination, researchers discovered 18 plasma proteins that have a causal relationship with HNC. Notably, the mediation MR illustrated that the causal protective effect of OTU97_86 (Phascolarctobacterium) on HNC (total effect IVW: OR = 0.879, 95% = 0.810-0.954, p = 0.002) was mediated by Proteasome subunit alpha type-1 (PSMA1) (- 0.020, 95% CI = - 0.039 ~ - 0.001, p = 0.036), accounting for 15.25% of the total effect. Similarly, the causal effect of OTU99_35 (Ruminococcus) on HNC risk (total effect IVW: OR = 1.109, 95% CI = 1.027-1.198, p = 0.008) was mediated by the protein FAM107B (0.015, 95% CI = 0.001-0.029, p = 0.031), accounting for 14.69% of the total effect.

CONCLUSION

MR and mediation analysis revealed that specific GMs influence HNC risk through plasma proteins: Phascolarctobacterium protects against HNC via PSMA1, whereas Ruminococcus increases HNC risk through FAM107B. These pathways suggest that Phascolarctobacterium is a potential preventative factor and that Ruminococcus is a risk factor. This highlights the possibility of using specific GM and plasma proteins as biomarkers or therapeutic targets for HNC prevention, diagnosis, and treatment.

Differences in Salivary Cytokinome and Pathogen Load Between Rheumatoid Arthritis and Other Rheumatic Disease Patients

Rheumatoid arthritis (RA), an autoimmune disease with complex pathogenesis, is characterized by an immune imbalance reflected, e.g., in the disturbed cytokines' profile. Various viruses and bacteria can cause the upregulation of pro-inflammatory cytokines influencing RA development. In particular, oral cavity dysbiosis, observed in multiple chronic diseases including periodontitis, may be linked to RA. The cytokine profile (IL-1β, IP-10, IL-29, GM-CSF, IFN-α2, IFN-β, TGF-β1, MPC-1, TNF-α, IFN-γ, IL-6, IL-10, IL-17A, IL-12p70, IL-2, and IL-4) of RA patients' saliva was evaluated using flow cytometry and benchmarked with their levels in saliva of healthy controls and patients with other rheumatic diseases. The levels of IL-1β, IP-10, IL-2, and IL-4 were significantly elevated in RA patients' saliva compared to other studied groups. To define the potential role of the most suspicious microbial agents (Epstein-Barr Virus (EBV), Cytomegalovirus, Parvovirus B19, Porphyromonas gingivalis, and Segatella copri) for RA pathogenesis, the amounts of their DNA in the saliva of patients with RA were assessed in all the groups mentioned above. The EBV and P. gingivalis DNA levels measured by qRT-PCR were significantly higher in RA patients' saliva than in other groups, indicating either the important role of these agents in RA pathogenesis or the higher susceptibility of RA patients for those infectious factors. The comprehension of the association of specific cytokine profiles in RA and the occurrence of specific viral and/or bacterial infections can be a key to a better understanding of RA pathogenesis. These results illustrate the complexity of the immunological profile of RA, show the high diagnostic potential of saliva, and provide insight into how various infections can contribute to RA development.

Molecular Mimicry Between Gut Microbiome and Rheumatoid Arthritis: Current Concepts

Rheumatoid arthritis (RA) represents an autoimmune condition impacted by a combination of genetic and environmental factors, with the gut microbiome (GMB) being one of the influential environmental factors. Patients with RA display notable modifications in the composition of their GMB, characterised by decreased diversity and distinct bacterial alterations. The GMB, comprising an extensive array of approximately 35,000 bacterial species residing within the gastrointestinal tract, has garnered considerable attention as a pivotal contributor to both human health and the pathogenesis of diseases. This article provides an in-depth exploration of the intricate involvement of the GMB in the context of RA. The oral-GMB axis highlights the complex role of bacteria in RA pathogenesis by producing antibodies to citrullinated proteins (ACPAs) through molecular mimicry. Dysbiosis affects Tregs, cytokine levels, and RA disease activity, suggesting that regulating cytokines could be a strategy for managing inflammation in RA. The GMB also has significant implications for drug responses and toxicity, giving rise to the field of pharmacomicrobiomics. The composition of the microbiota can impact the efficacy and toxicity of drugs, while the microbiota's metabolites can influence drug response. Recent research has identified specific bacteria, metabolites, and immune responses associated with RA, offering potential targets for personalised management. However, several challenges, including the variation in microbial composition, establishing causality, accounting for confounding factors, and translating findings into clinical practice, need to be addressed. Microbiome-targeted therapy is still in its early stages and requires further research and standardisation for effective implementation.

Gut microbiome and intestinal inflammation in preclinical stages of rheumatoid arthritis

BACKGROUND

Faecal Prevotellaceae, and other microbes, have been associated with rheumatoid arthritis (RA) and preclinical RA. We have performed a quantitative microbiome profiling study in preclinical stages of RA.

METHODS

First-degree relatives of patients with RA (RA-FDRs) from the SCREEN-RA cohort were categorised into four groups: controls, healthy asymptomatic RA-FDRs; high genetic risk, asymptomatic RA-FDRs with two copies of the shared epitope; autoimmunity, asymptomatic RA-FDRs with RA-associated autoimmunity; and symptomatic, clinically suspect arthralgias or untreated new-onset RA.Faecal samples were collected and frozen. 16S sequencing was performed, processed with DADA2 pipeline and Silva database. Cell counts (cytometry) and faecal calprotectin (enzyme-linked immunosorbent assay, ELISA) were also obtained. Microbial community analyses were conducted using non-parametric tests, such as permutational multivariate analysis of variance (PERMANOVA), Wilcoxon and Kruskal-Wallis, or Aldex2.

RESULTS

A total of 371 individuals were included and categorised according to their preclinical stage of the disease. Groups had similar age, gender and body mass index. We found no significant differences in the quantitative microbiome profiles by preclinical stages (PERMANOVA, R2=0.00798, p=0.56) and, in particular, no group differences in Prevotellaceae abundance. Results were similar when using relative microbiome profiling data (PERMANOVA, R2=0.0073, p=0.83) or Aldex2 on 16S sequence counts. Regarding faecal calprotectin, we found no differences between groups (p=0.3).

CONCLUSIONS

We could not identify microbiome profiles associated with preclinical stages of RA. Only in a subgroup of individuals with the most pronounced phenotypes did we modestly retrieve the previously reported associations.

Influence of oral microbiome on longitudinal patterns of oral mucositis severity in patients with squamous cell carcinoma of the head and neck

BACKGROUND

This study investigated the influence of oral microbial features on the trajectory of oral mucositis (OM) in patients with squamous cell carcinoma of the head and neck.

METHODS

OM severity was assessed and buccal swabs were collected at baseline, at the initiation of cancer treatment, weekly during cancer treatment, at the termination of cancer treatment, and after cancer treatment termination. The oral microbiome was characterized via the 16S ribosomal RNA V4 region with the Illumina platform. Latent class mixed-model analysis was used to group individuals with similar trajectories of OM severity. Locally estimated scatterplot smoothing was used to fit an average trend within each group and to assess the association between the longitudinal OM scores and longitudinal microbial abundances.

RESULTS

Four latent groups (LGs) with differing patterns of OM severity were identified for 142 subjects. LG1 has an early onset of high OM scores. LGs 2 and 3 begin with relatively low OM scores until the eighth and 11th week, respectively. LG4 has generally flat OM scores. These LGs did not vary by treatment or clinical or demographic variables. Correlation analysis showed that the abundances of Bacteroidota, Proteobacteria, Bacteroidia, Gammaproteobacteria, Enterobacterales, Bacteroidales, Aerococcaceae, Prevotellaceae, Abiotrophia, and Prevotella_7 were positively correlated with OM severity across the four LGs. Negative correlation was observed with OM severity for a few microbial features: Abiotrophia and Aerococcaceae for LGs 2 and 3; Gammaproteobacteria and Proteobacteria for LGs 2, 3, and 4; and Enterobacterales for LGs 2 and 4.

CONCLUSIONS

These findings suggest the potential to personalize treatment for OM.

PLAIN LANGUAGE SUMMARY

Oral mucositis (OM) is a common and debilitating after effect for patients treated for squamous cell carcinoma of the head and neck. Trends in the abundance of specific microbial features may be associated with patterns of OM severity over time. Our findings suggest the potential to personalize treatment plans for OM via tailored microbiome interventions.

Shared and Distinct Gut Microbiota in Spondyloarthritis, Acute Anterior Uveitis, and Crohn's Disease

OBJECTIVE

Spondyloarthritis (SpA) is a group of immune-mediated diseases highly concomitant with nonmusculoskeletal inflammatory disorders, such as acute anterior uveitis (AAU) and Crohn's disease (CD). The gut microbiome represents a promising avenue to elucidate shared and distinct underlying pathophysiology.

METHODS

We performed 16S ribosomal RNA sequencing on stool samples of 277 patients (72 CD, 103 AAU, and 102 SpA) included in the German Spondyloarthritis Inception Cohort and 62 back pain controls without any inflammatory disorder. Discriminatory statistical methods were used to disentangle microbial disease signals from one another and a wide range of potential confounders. Patients were naive to or had not received treatment with biological disease-modifying antirheumatic drugs (DMARDs) for >3 months before enrollment, providing a better approximation of a true baseline disease signal.

RESULTS

We identified a shared, immune-mediated disease signal represented by low abundances of Lachnospiraceae taxa relative to controls, most notably Fusicatenibacter, which was most abundant in controls receiving nonsteroidal antiinflammatory drug monotherapy and implied to partially mediate higher serum C-reactive protein. Patients with SpA showed an enrichment of Collinsella, whereas human leukocyte antigen (HLA)-B27+ individuals displayed enriched Faecalibacterium. CD patients had higher abundances of a Ruminococcus taxon, and previous conventional/synthetic DMARD therapy was associated with increased Akkermansia.

CONCLUSION

Our work supports the existence of a common gut dysbiosis in SpA and related inflammatory pathologies. We reveal shared and disease-specific microbial associations and suggest potential mediators of disease activity. Validation studies are needed to clarify the role of Fusicatenibacter in gut-joint inflammation, and metagenomic resolution is needed to understand the relationship between Faecalibacterium commensals and HLA-B27.