Intestinal barrier dysfunction plays an integral role in arthritis pathology and can be targeted to ameliorate disease

Summary Background Evidence suggests an important role for gut-microbiota dysbiosis in the development of rheumatoid arthritis (RA). The link between changes in gut bacteria and the development of joint inflammation is missing. Here, we address whether there are changes to the gut environment and how they contribute to arthritis pathogenesis. Methods We analyzed changes in markers of gut permeability, damage, and inflammation in peripheral blood and serum of RA patients. Serum, intestines, and lymphoid organs isolated from K/BxN mice with spontaneous arthritis or from wild-type, genetically modified interleukin (IL)-10R−/−or claudin-8−/−mice with induced arthritis were analyzed by immunofluorescence/histology, ELISA, and flow cytometry. Findings RA patients display increased levels of serum markers of gut permeability and damage and cellular gut-homing markers, both parameters positively correlating with disease severity. Arthritic mice display increased gut permeability from early stages of disease, as well as bacterial translocation, inflammatory gut damage, increases in interferon γ (IFNγ)+and decreases in IL-10+intestinal-infiltrating leukocyte frequency, and reduced intestinal epithelial IL-10R expression. Mechanistically, both arthritogenic bacteria and leukocytes are required to disrupt gut-barrier integrity. We show that exposing intestinal organoids to IFNγ reduces IL-10R expression by epithelial cells and that mice lacking epithelial IL-10R display increased intestinal permeability and exacerbated arthritis. Claudin-8−/−mice with constitutively increased gut permeability also develop worse joint disease. Treatment of mice with AT-1001, a molecule that prevents development of gut permeability, ameliorates arthritis. Conclusions We suggest that breakdown of gut-barrier integrity contributes to arthritis development and propose restoration of gut-barrier homeostasis as a new therapeutic approach for RA. Funding Funded by Versus Arthritis (21140 and 21257) and UKRI/MRC (MR/T000910/1).
Graphical abstract
Highlights Serum gut-permeability markers LPB, LPS, and I-FABP are increased in RA Mice with arthritis have increased gut permeability and intestinal inflammation Both bacteria and leukocytes are needed to disrupt gut-barrier integrity Prevention of gut-barrier dysfunction in arthritis ameliorates joint inflammation
Context and significance Rheumatoid arthritis is an autoimmune disorder characterized by chronic joint inflammation. Accumulating evidence suggests that changes in the composition of the bacteria residing in the gut could be responsible for joint inflammation. Currently, it is unclear how bacteria or their products instruct cells of the immune system to become harmful and induce arthritis. Researchers at University College London have shown that, in arthritis, there is profound damage to the gut lining, which fails to work properly as a barrier, as well as an accumulation in the gut of white blood cells that cause inflammation. The authors show that, in arthritis, bacteria cross the prohibited border of the intestinal lining and that repairing gut permeability defects with specific drugs inhibits joint inflammation.
Changes to the gut bacteria have been associated with the development of arthritis; however, the mechanistic connection with disease remains unknown. Matei et al. identify pathological changes to the gut tissue in arthritis, including loss of gut-barrier integrity and inflammatory-cell infiltration, and show that restoration of gut homeostasis ameliorates disease.