Background/Purpose: It is known that rheumatoid arthritis (RA) should be treated early and a delay in treatment increases the rate of treatment non-response, joint damage, and disability. This is often explained by a diversity of molecular processes in the early and established phases of RA. The purpose of this study was to assess cytokine-dependent change in DNA methylation in CD4+ T cells of patients with early and established RA.

Methods: A cross-sectional RA cohort was analysed by comparing patients with the disease duration < 3y (mean 1.7y, n=23), 3-10y (mean 5.6y, n=94) and >10y (mean 19y, n=68). Serum levels of cytokines were measured by ELISA. Genome-wide DNA methylation was performed in sorted and activated CD4+ T cells of early (mean 1.3y, n=10) and established (mean 12.6y, n=14) RA patients using Infinium MethylationEPIC BeadChip (Illumina). Chromatin was immunoprecipitated with survivin (BIRC5) of CD4+T cells and coupled with high throughput sequencing (Hiseq2000, Illumina). False discovery rate was calculated using the Benjamini method.

Results: The groups differed with respect to the serum levels of IFNg, IL9, and IL6. The patients with RA< 3y had low cytokine levels and high serum survivin, while the patients with RA >10y had high IFN, IL9, and BIRC5 mRNA, suggesting IFNg and IL9 to be important for maintaining disease activity in patients with the established RA. The differential DNA methylation in CD4+ T cells of early and established RA (p< 10-5) identified IFNg- and IL9-dependent change in CpG rich areas. In dominating majority of CpG areas, an increase of cytokines was associated with a reduction of DNA methylation, which is known to precede the initiation of gene transcription. Since patients with established RA frequently combined high cytokines with high BIRC, we analyzed if this affects DNA methylation. Comparing CD4 with high and low BIRC5, we found that 85% of IFNg-dependent and 67% of IL9-dependent DNA methylation changes occurred in presence of high BIRC5. To study if BIRC5 is found attached to chromatin, we performed chromatin immunoprecipitation in CD4+T cells. Analysis of the BIRC5-bound chromatin revealed enrichment for IRF-specific sequences where IRF1- and IRF8-binding sequences, but not IRF3 and IRF2 were predominantly found. We also found enrichment with complex sequences specific for binding bZIP-IRF (and not IRF-bZIP) and IRF-BATF sequences.

Conclusion: IFNg and IL9 are important for maintaining disease activity in patients with the established RA. In collaboration with intracellular survivin (BIRC5), these cytokines change the DNA methylation and gene transcription in CD4+ cells.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interferon-gamma-supports-transcriptional-activity-of-birc5-in-cd4-t-cells-in-established-rheumatoid-arthritis/