AB0096 FCER1G GENE METHYLATION AND MIR-106/MIR-17 AS A NEW POTENTIAL EPIGENETIC MARKERS IN RHEUMATOID ARTHRITIS

Abstract

Background:Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to joints destruction. One of the most important cytokine responsible for this process is interleukin 6 (IL-6). Fc receptor gamma chain (FcRγ), encoded byFCER1Ggene, is responsible for neutrophils activation, phagocytosis, cell surface signaling pathway as well as IL-4, IL-6, IL-10 and tumor necrosis factor production. Epigenetic factors, including DNA methylation and micro-RNAs (miRs) expression regulate the genes expression on transcriptional and post-transcriptional mechanisms. There are miRs responsible for cytokines production, for example GU rich miRs, miR-106b and miR-155 were reported as associated with IL-6 overproduction.Objectives:The aim of our study was to evaluateFCER1Ggene methylation and miR-17 family members as epigenetic markers associated with RA, disease activity and IL-6 expression.Methods:Bioinformatics analysis were applied to select the miRs with a possible target sites in a promoter region ofFCER1Ggene. The MiR-17 family members, including miR-17, miR-93 and miR-106b were selected for investigation.A total of 74 individuals, 50 RA patients, 84% female, aged 53,7±12,3 years (mean±SD) and 24 healthy controls (HC), 87,5% female, aged 53±8,49 years were enrolled. RA patients were selected based on DAS-28 scoring. RA patients with high disease activity (DAS28 >5,1; 58%) and remission (≤2,6; 42%) were included in the analysis. DNA was extracted from a whole blood and miRs were extracted from plasma. Quantitative real-time PCR was use for analyze both methylation and expression levels. In a randomly selected samples (16 from high disease activity group; 9 from remission and 19 from HC) the level of IL-6 in serum was evaluated.Results:Patients with RA in comparison to HC have had a lowerFCER1Gmethylation (0.98 [0.73-1.46] vs 1.96 [1.44-3], p<0.00001; median [interquartile range]) and miR-106b (0.79 [0.49-1.68] vs 1.54 [0.88-2.51], p=0.008) and miR-17 (1.26 [0.41-2.04] vs 2.44 [2.09-3.47], p=0.0001) expressions. No difference in methylation between high and remission RA groups was found. MiR-106b and miR-17 expressions were different between RA patients with high disease activity and remission (p=0.009 and p=0.003, respectively), however a high disease activity group was not different to HC (p=0.82 and p=0.12, respectively). Detailed results are presented in Table 1. A strong correlation between IL-6 levels andFCER1Gmethylation (rs= -0.46) was found.Table 1.Methylation and expression between patients divided by disease activity in compare to controls.High disease activity, n=29Remission, n=21HC, n=24FCER1Gmethylation1.11 [0.83-1.52]0.96 [0.61-1.18]1.96 [1.44-3]miR-106b expression1.36 [0.63-1.76]0.54 [0.19-1.19]1.54 [0.88-2.51]miR-93 expression0.63 [0.49-1.21]0.59 [0.15-1.5]1.03 [0.65-1.38]miR-17 expression1.46 [1.05-2.54]0.34 [0.11-1.26]2.44 [2.09-3.47]Data are given by median [interquartile range]. FCER1G, Fc receptor gamma chain gene; HC, healthy controls; miR, micro-RNA; RA, rheumatoid arthritis patients.Conclusion:FCER1Gmethylation was found as a new epigenetic marker of RA, which is independent of disease activity and may be associated with IL-6 production. Plasma miR-17 and miR-106b can be considered as a novel molecular biomarkers of disease severity in RA.FcRγ may plays a significant role in RA pathogenesis andFCER1Ggene methylation was found as a new, epigenetic and promising marker of RA.