Dynamics of circulating follicular helper T cell subsets and follicular regulatory T cells in rheumatoid arthritis patients according to HLA-DRB1 locus

Impaired immune tolerance mediated by reduced Tfr cells in rheumatoid arthritis linked to gut microbiota dysbiosis and altered metabolites

BACKGROUND

Patients with rheumatoid arthritis (RA) showed impaired immune tolerance characterized by reduced follicular regulatory T (Tfr) cells, and they also exhibited altered gut microbiotas and their metabolites in RA. However, the association of gut microbiotas and their metabolites with the immune tolerance mediated by Tfr cells in RA remains unclear.

METHODS

Peripheral blood and stool samples were collected from 32 new-onset RA patients and 17 healthy controls (HCs) in the Second Hospital of Shanxi Medical University between January 2022 and June 2022. The peripheral blood was used to detect the circulating regulatory T (Treg), helper T(Th)17, Tfr, and follicular helper T (Tfh) cells by modified flow cytometry. The stool samples were used to analyze the gut microbiotas and their metabolites via 16S rDNA sequencing and metabolomic profiling. We aimed to characterize the gut microbiotas and their metabolites in RA and identified their association with Tfr cell-mediated immune tolerance.

RESULTS

The new-onset RA demonstrated reduced Treg and Tfr cells, associated with the disease activity and autoantibodies. There were significant differences in gut microbiotas between the two groups as the results of β diversity analysis (P = 0.039) including 21 differential gut microbiotas from the phylum to genus levels. In which, Ruminococcus 2 was associated with the disease activity and autoantibodies of RA, and it was identified as the potential biomarker of RA [area under curve (AUC) = 0.782, 95% confidence interval (CI) = 0.636-0.929, P = 0.001]. Eleven differential metabolites were identified and participated in four main pathways related to RA. Arachidonic acid might be the potential biomarker of RA (AUC = 0.724, 95% CI = 0.595-0.909, P = 0.038), and it was the core metabolite as the positive association with six gut microbiotas enriched in RA. The reduced Tfr cells were associated with the altered gut microbiotas and their metabolites including the Ruminococcus 2, the arachidonic acid involved in the biosynthesis of unsaturated fatty acid pathway and the 3-methyldioxyindole involved in the tryptophan metabolism pathway.

CONCLUSION

The breakdown of immune tolerance mediated by reduced Tfr cells was associated with the altered gut microbiotas and their metabolites implying the possible mechanism of RA pathogenesis from the perspective of microecology-metabolism-immune.

E3 ubiquitin ligase STUB1 affects the mTORC1 pathway through p62 and participates in regulating the differentiation of follicular helper T cells in rheumatoid arthritis

OBJECTIVE

The abnormal expansion of Tfh cells plays a key role in chronic inflammation of RA joint. We speculated that STUB1 is an important regulatory factor in promoting the differentiation of Tfh cells in RA.

CONTENT AND METHODS

The proportion of Tfh cells and the level of STUB1 in Tfh cells was measured. CD4+T cells were isolated from PBMCs of RA patients, and the percentage of Tfh cells was detected after up- or down-regulating the expression of STUB1. The levels of mTORC1 pathway activator p-mTOR and p-S6K were measured by Western blot. The ubiquitination of p62 by STUB1 and its ubiquitination type as well as the activation of mTORC1 was detected in vitro, and the activation of the mTORC1 and the differentiation of Tfh cells was detected in STUB1-upregulated CD4+ T cells with overexpressed p62.

RESULTS

The level of STUB1 is elevated in Tfh cells of patients. Up-regulation of STUB1 can promote the differentiation of Tfh cells. STUB1 promotes the degradation of p62 via K48-linked ubiquitination and promotes the activation of mTORC1. Overexpression of p62 can reverse the promoting effect of STUB1 on the differentiation of Tfh cells and the activation of mTORC1.

CONCLUSION

STUB1 can promote the differentiation of Tfh cells in RA by mediating the activation of mTORC1 pathway through ubiquitination of p62.