Immunomodulatory interplay of the microbiome and therapy of rheumatic diseases

Harnessing the Microbiome: A Comprehensive Review on Advancing Therapeutic Strategies for Rheumatic Diseases

Rheumatic diseases are a group of disorders that affect the joints, muscles, and bones. These diseases, such as rheumatoid arthritis, lupus, and psoriatic arthritis, can cause pain, stiffness, and swelling, leading to reduced mobility and disability. Recent studies have identified the microbiome, the diverse community of microorganisms that live in and on the human body, as a potential factor in the development and progression of rheumatic diseases. Harnessing the microbiome offers a promising new avenue for developing therapeutic strategies for these debilitating conditions. There is growing interest in the role of oral and gut microbiomes in the management of rheumatoid arthritis and other autoimmune disease. Microbial metabolites have immunomodulatory properties that could be exploited for rheumatic disorders. A wide range of microorganisms are present in the oral cavity and are found to be vulnerable to the effects of the environment. The physiology and ecology of the microbiota become intimately connected with those of the host, and they critically influence the promotion of health or progression toward disease. This article aims to provide a comprehensive overview of the current state of knowledge on oral and gut microbiome and its potential future role in the management of rheumatic diseases. This article will also discuss newer treatment strategies such as bioinformatic analyses and fecal transplantation.

Rheumatic diseases and gut microbiota publications in 2002-2022: a Scopus‑based bibliometric analysis

Rheumatic diseases (RDs) include a variety of autoimmune disorders defined by severe inflammation, primarily affecting the joints, tendons, ligaments, bones, and muscles. Recent research has revealed the association between rheumatic diseases and gut microbiota, thereby providing insights into the underlying mechanisms of disease pathogenesis. The objective of this study was to evaluate the quantity and quality of scientific research regarding the association between RDs and gut microbiota, as well as to elucidate the characteristics of worldwide research output in this field. The present bibliometric analysis was carried out using the Scopus database, using the keywords "rheumatology," "arthritis," and "gut microbiota." The study involved determining the number of articles, the number of active countries with journals, the identification of prolific authors, and the collection of citation data. Additionally, analyses of trends were conducted. 503 articles in all were reviewed. Collaboration networks were visualized using mapping techniques. The number of articles on RDs and gut microbiota exhibited a consistent pattern from 2002 to 2022 (p < 0.05). The five most productive countries were China (n = 128; 25.45%), the United States (n = 101; 20.07%), Italy (n = 40; 7.95%), the United Kingdom (n = 20; 3.98%), and Japan (n = 17; 3.38%). Israel, Italy, Belgium, and Portugal had the highest values regarding the number of articles per million population. Australia, Canada, and the United Kingdom were the top three countries regarding average citation count. This bibliometric analysis evaluates and synthesizes global scientific output on RDs and gut microbiota. The literature on the association between rheumatic diseases and gut microbiota is growing. Supporting researchers in countries with limited involvement in this field will contribute to its growth.

Using the Microbiome as a Regenerative Medicine Strategy for Autoimmune Diseases

Autoimmune (AI) diseases, which present in a multitude of systemic manifestations, have been connected to many underlying factors. These factors include the environment, genetics, individual microbiomes, and diet. An individual's gut microbiota is an integral aspect of human functioning, as it is intimately integrated into the metabolic, mechanical, immunological, and neurologic pathways of the body. The microbiota dynamically changes throughout our lifetimes and is individually unique. While the gut microbiome is ever-adaptive, gut dysbiosis can exert a significant influence on physical and mental health. Gut dysbiosis is a common factor in various AI, and diets with elevated fat and sugar content have been linked to gut microbiome alterations, contributing to increased systemic inflammation. Additionally, multiple AI's have increased levels of certain inflammatory markers such as TNF-a, IL-6, and IL-17 that have been shown to contribute to arthropathy and are also linked to increased levels of gut dysbiosis. While chronic inflammation has been shown to affect many physiologic systems, this review explores the connection between gut microbiota, bone metabolism, and the skeletal and joint destruction associated with various AI, including psoriatic arthritis, systemic lupus erythematosus, irritable bowel disease, and rheumatoid arthritis. This review aims to define the mechanisms of microbiome crosstalk between the cells of bone and cartilage, as well as to investigate the potential bidirectional connections between AI, bony and cartilaginous tissue, and the gut microbiome. By doing this, the review also introduces the concept of altering an individual's specific gut microbiota as a form of regenerative medicine and potential tailored therapy for joint destruction seen in AI. We hope to show multiple, specific ways to target the microbiome through diet changes, rebalancing microbial diversity, or decreasing specific microbes associated with increased gut permeability, leading to reduced systemic inflammation contributing to joint pathology. Additionally, we plan to show that diet alterations can promote beneficial changes in the gut microbiota, supporting the body's own endogenous processes to decrease inflammation and increase healing. This concept of microbial alteration falls under the definition of regenerative medicine and should be included accordingly. By implementing microbial alterations in regenerative medicine, this current study could lend increasing support to the current research on the associations of the gut microbiota, bone metabolism, and AI-related musculoskeletal pathology.

The influence of the gut microbiota on the bioavailability of oral drugs

Due to its safety, convenience, low cost and good compliance, oral administration attracts lots of attention. However, the efficacy of many oral drugs is limited to their unsatisfactory bioavailability in the gastrointestinal tract. One of the critical and most overlooked factors is the symbiotic gut microbiota that can modulate the bioavailability of oral drugs by participating in the biotransformation of oral drugs, influencing the drug transport process and altering some gastrointestinal properties. In this review, we summarized the existing research investigating the possible relationship between the gut microbiota and the bioavailability of oral drugs, which may provide great ideas and useful instructions for the design of novel drug delivery systems or the achievement of personalized medicine.

Immunomodulation by the Commensal Microbiome During Immune-Targeted Interventions: Focus on Cancer Immune Checkpoint Inhibitor Therapy and Vaccination

Emerging evidence in clinical and preclinical studies indicates that success of immunotherapies can be impacted by the state of the microbiome. Understanding the role of the microbiome during immune-targeted interventions could help us understand heterogeneity of treatment success, predict outcomes, and develop additional strategies to improve efficacy. In this review, we discuss key studies that reveal reciprocal interactions between the microbiome, the immune system, and the outcome of immune interventions. We focus on cancer immune checkpoint inhibitor treatment and vaccination as two crucial therapeutic areas with strong potential for immunomodulation by the microbiota. By juxtaposing studies across both therapeutic areas, we highlight three factors prominently involved in microbial immunomodulation: short-chain fatty acids, microbe-associate molecular patterns (MAMPs), and inflammatory cytokines. Continued interrogation of these models and pathways may reveal critical mechanistic synergies between the microbiome and the immune system, resulting in novel approaches designed to influence the efficacy of immune-targeted interventions.

Intestinal Dysbiosis and Tryptophan Metabolism in Autoimmunity

The development of autoimmunity involves complex interactions between genetics and environmental triggers. The gut microbiota is an important environmental constituent that can heavily influence both local and systemic immune reactivity through distinct mechanisms. It is therefore a relevant environmental trigger or amplifier to consider in autoimmunity. This review will examine recent evidence for an association between intestinal dysbiosis and autoimmune diseases, and the mechanisms by which the gut microbiota may contribute to autoimmune activation. We will specifically focus on recent studies connecting tryptophan metabolism to autoimmune disease pathogenesis and discuss evidence for a microbial origin. This will be discussed in the context of our current understanding of how tryptophan metabolites regulate immune responses, and how it may, or may not, be applicable to autoimmunity.

Dysregulation of gut microbiome is linked to disease activity of rheumatic diseases

Objective rheumatism refers to a large group of diseases with different etiology, mainly characterized by autoimmune disorder. Intestinal flora combines with the digestive organs of the human body to synthesize and secrete the key substances of growth. Several studies have reported abnormal intestinal flora in rheumatic diseases. The purposes of this research were to review the primary studies and figure out the relationship between intestinal flora and rheumatic disease activity. The article search was based on the database of PubMed (MEDLINE), EMBASE, Cochrane to collect English language studies that were published from 1985 to 2019. The articles concerning the intestinal flora and disease activities of rheumatic diseases were classified by disease types, and the relationship between disease activities and intestinal flora was summarized. Eight rheumatic diseases were included in the study. It was found that the changes of intestinal flora were significantly correlated with the activities of rheumatic diseases. There were significant differences in the classification of disease activity and the composition of intestinal flora. Interfering with the composition of intestinal flora can apparently modulate the development of disease. But how to apply such findings is rarely reported. The study finds out that intestinal flora disorder is linked to the activity of rheumatic diseases. But which specific gut flora is connected to the disease activity needs further researches. More discussion is needed on how to apply the results to clinical treatment.

OHMI: the ontology of host-microbiome interactions

BACKGROUND

Host-microbiome interactions (HMIs) are critical for the modulation of biological processes and are associated with several diseases. Extensive HMI studies have generated large amounts of data. We propose that the logical representation of the knowledge derived from these data and the standardized representation of experimental variables and processes can foster integration of data and reproducibility of experiments and thereby further HMI knowledge discovery.

METHODS

Through a multi-institutional collaboration, a community-based Ontology of Host-Microbiome Interactions (OHMI) was developed following the Open Biological/Biomedical Ontologies (OBO) Foundry principles. As an OBO library ontology, OHMI leverages established ontologies to create logically structured representations of (1) microbiomes, microbial taxonomy, host species, host anatomical entities, and HMIs under different conditions and (2) associated study protocols and types of data analysis and experimental results.

RESULTS

Aligned with the Basic Formal Ontology, OHMI comprises over 1000 terms, including terms imported from more than 10 existing ontologies together with some 500 OHMI-specific terms. A specific OHMI design pattern was generated to represent typical host-microbiome interaction studies. As one major OHMI use case, drawing on data from over 50 peer-reviewed publications, we identified over 100 bacteria and fungi from the gut, oral cavity, skin, and airway that are associated with six rheumatic diseases including rheumatoid arthritis. Our ontological study identified new high-level microbiota taxonomical structures. Two microbiome-related competency questions were also designed and addressed. We were also able to use OHMI to represent statistically significant results identified from a large existing microbiome database data analysis.

CONCLUSION

OHMI represents entities and relations in the domain of HMIs. It supports shared knowledge representation, data and metadata standardization and integration, and can be used in formulation of advanced queries for purposes of data analysis.