Findings on the Relationship Between Intestinal Microbiome and Vasculitis

Exploring the causal role of gut microbiota in giant cell arteritis: a Mendelian randomization analysis with mediator insights

Background

Giant Cell Arteritis (GCA) is a complex autoimmune condition. With growing interest in the role of gut microbiota in autoimmune diseases, this research aimed to explore the potential causal relationship between gut microbiota and GCA, and the mediating effects of specific intermediaries.

Methods

Using a bidirectional two-sample Mendelian randomization (MR) design, we investigated associations between 191 microbial taxa and GCA. A two-step MR technique discerned the significant mediators on this relationship, followed by Multivariable MR analyses to quantify the direct influence of gut microbiota on GCA and mediation effect proportion, adjusting for these mediators.

Results

Nine taxa displayed significant associations with GCA. Among them, families like Bacteroidales and Clostridiaceae1 had Odds Ratios (OR) of 1.48 (p=0.043) and 0.52 (p=5.51e-3), respectively. Genera like Clostridium sensu stricto1 and Desulfovibrio showed ORs of 0.48 (p=5.39e-4) and 1.48 (p=0.037), respectively. Mediation analyses identified 25 hydroxyvitamin D level (mediation effect of 19.95%), CD14+ CD16- monocyte counts (mediation effect of 27.40%), and CD4+ T cell counts (mediation effect of 28.51%) as significant intermediaries.

Conclusion

Our findings provide invaluable insights into the complex interplay between specific gut microbiota taxa and GCA. By highlighting the central role of gut microbiota in influencing GCA risk and long-term recurrence, and their interactions with vital immune mediators, this research paves the way for potential therapeutic interventions in GCA management.

[18F]FDG PET-MR characterization of aortitis in the IL1rn-/- mouse model of giant-cell arteritis

BACKGROUND

Metabolic imaging is routinely used to demonstrate aortitis in patients with giant-cell arteritis. We aimed to investigate the preclinical model of aortitis in BALB/c IL1rn-/- mice using [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography-magnetic resonance (PET-MR), gamma counting and immunostaining. We used 15 first-generation specific and opportunistic pathogen-free (SOPF) 9-week-old IL1rn-/- mice, 15 wild-type BALB/cAnN mice and 5 s-generation specific pathogen-free (SPF) 9-week-old IL1rn-/-. Aortic [18F]FDG uptake was assessed as the target-to-background ratio (TBR) using time-of-flight MR angiography as vascular landmarks.

RESULTS

[18F]FDG uptake measured by PET or gamma counting was similar in the first-generation SOPF IL1rn-/- mice and the wild-type group (p > 0.05). However, the first-generation IL1rn-/- mice exhibited more interleukin-1β (p = 0.021)- and interleukin-6 (p = 0.019)-positive cells within the abdominal aorta than the wild-type mice. In addition, the second-generation SPF group exhibited significantly higher TBR (p = 0.0068) than the wild-type mice on the descending thoracic aorta, unlike the first-generation SOPF IL1rn-/- mice.

CONCLUSIONS

In addition to the involvement of interleukin-1β and -6 in IL1rn-/- mouse aortitis, this study seems to validate [18F]FDG PET-MR as a useful tool for noninvasive monitoring of aortitis in this preclinical model.

Rheumatic complications of checkpoint inhibitors: Lessons from autoimmunity

Immune checkpoint inhibitors are now an established treatment in the management of a range of cancers. Their success means that their use is likely to increase in future in terms of the numbers of patients treated, the indications and the range of immune checkpoints targeted. They function by counteracting immune evasion by the tumor but, as a consequence, can breach self-tolerance at other sites leading to a range of immune-related adverse events. Included among these complications are a range of rheumatologic complications, including inflammatory arthritis and keratoconjunctivitis sicca. These superficially resemble immune-mediated rheumatic diseases (IMRDs) such as rheumatoid arthritis and Sjogren's disease but preliminary studies suggest they are clinically and immunologically distinct entities. However, there appear to be common processes that predispose to the development of both that may inform preventative interventions and predictive tools. Both groups of conditions highlight the centrality of immune checkpoints in controlling tolerance and how it can be restored. Here we will discuss some of these commonalities and differences between rheumatic irAEs and IMRDs.

Microbiome in Behcet's syndrome

This review will discuss the current understanding of the role of microbiomes in Behcet's Syndrome, their influence on immune response and disease and potential future studies.