Insulin exerts epigenetic control of joint-specific memory T cells in rheumatoid arthritis
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Background
Insulin has epigenetic effect influencing gene expression. High peripheral insulin concentrations promote insulin resistance in autoimmunity. Oncoprotein survivin/ BIRC5 modulates glucose metabolism through chromatin binding and propagates IFNg effects in CD4 + cells. In this study, we explored how insulin influences chromatin binding and metabolic activity in autoimmune CD4 + cells of patients with rheumatoid arthritis (RA).
Methods
We profiled the metabolic activity of CD4 + cell clusters using single-cell transcriptome analysis in blood, synovial fluid and synovial tissue of RA patients. Through chromatin immunoprecipitation and sequencing, we identified the genes controlled by deposition of survivin and acetylated lysine 27 on histone H3 (H3K27ac) in CD4 + cells. Treating CD4 + cells with insulin and histone deacetylase inhibitors (HDACi), we identified changes in H3K27ac, linked those to transcription of the H3K27-survivin-controlled genes and the pathogenic phenotype of CD4 + cells using flow cytometry. Finally, we explored if anti-diabetic and anti-rheumatic drugs affect the metabolic profile and memory phenotype of the metabolic active CD4 + cells.
Results
Transcription of survivin/ BIRC5 and histone acetylation enzymes strongly correlate with active metabolism in blood CD4 + cells of RA patients. In RA synovial tissue, these BIRC5 hi active T cell clusters are inflammatory, exhausted, and memory-like. Genome co-deposition of H3K27ac-survivin pinpointed the insulin-dependent genes in metabolic active CD4 + cells. These genes favored histone acetylation by suppressing methylating enzymes EZH2 and KMT2A , and T cell development by activating CD27, CD3G, and SCIMP . Inhibition of histone deacetylation reverted these transcriptional effects and supported cellular sensitivity to insulin. Insulin stimulation increased H3K27ac and together with HDACi, suppressed PDCD1 and IFNg transcription and production in CD4 + CD27 + CD45RO + memory T cells. Immune modulation impacted metabolic activity and synergized with the effect of histone acetylation on insulin responsiveness in RA patients.
Conclusions
RA synovia is enriched with the metabolic active BIRC5 hi CD4 + T cell clusters. The metabolic activity of these cells is histone acetylation-dependent and mediates insulin effects through the H3K27ac-survivin epigenetic mechanism. Increasing plasma insulin levels when combined with insulin sensitivity, can be protective in RA dearmoring effector T cell function. Hence, increasing the insulin sensitivity by enabling histone acetylation presents a reasonable interventional goal to restore immune cell homeostasis in RA.
