OP0267 The padi4 gene promoter methylation level is associated with anti-padi4 antibodies level and ra activity
Authors: B. Kolarz, M. Dryglewska, M. Ciesla, A. Selwa, M. Majdan
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease that predominantly affects the synovial membrane leading to joint destruction. Anti-citrullinated protein antibodies (ACPA) are important markers of RA. They recognise post-translationally modified auto-antigens generated by enzymes peptidylarginine deiminases (PADIs) mostly type 4 (PADI4), which transform arginine to new amino acid citrulline in various proteins. There were also identified anti-PADI4 antibodies (anti-PADI4) which are a specific marker of RA. DNA methylation plays a key role in the control of gene expression. The process concerns CpG islands in promoter regions of about 75% of gens and leads to gene silencing when over-expressed. It is possible that PAD4 production is also regulated via methylation. <h3>Objectives</h3> We aimed to identify if there is an association between PADI4 gene promoter methylation degree, anti-PADI4 antibodies level and RA activity. <h3>Methods</h3> A total of 155 unrelated patients, 125 with RA, 83,2% female, aged 52.2±12.3 years (mean ±SD) and 30 healthy controls (HC), 76.7% female, aged 53.2±8,1 years, were enrolled. RA patients were divided according DAS28 score into 4 groups as shown in table 1. Whole blood and serum samples were collected and stored at −80°C until analysis. DNA was extracted from whole blood and stored at −80°C until analysis. Two single-nucleotide polimorphisms (SNPs) of the PADI4 gene (PADI-94, rs2240340 and PADI-104, rs1748033) were determined by TaqMan genotyping. Quantitative real-time methylation-specific PCR (qMSP) was used to analyse the methylation status of promoter region in PADI4 gene. Anti-PAD4 antibodies were evaluated in serum by ELISA. <h3>Results</h3> We found the differences in anti-PADI4 level between RA severe and HC group (p&lt;10–5), RA moderate and HC (p&lt;10–5), RA low activity and HC (p&lt;0.05) and in PADI4 methylation group between RA severe and RA remission (p&lt;0.05), RA moderate and RA remission (p&lt;10–3) and RA moderate and HC (p&lt;10–2). What is interesting is that methylation level in the RA remission group is higher than in the HC. The intensity of PADI4 methylation correlates with anti-PADI4 antibodies level and DAS28 score with r<sub>s</sub>=-0.2 and −0.36 respectively (both p-values&lt;0,05) and anti-PADI4 level is associated with DAS28 score (r<sub>s</sub>=0.38). <h3>Conclusions</h3> We demonstrate the novel finding that elevated methylation of PADI4 gene promoter is associated with lower RA activity and lower level of anti-PADI4 antibodies and might play a role in patophisiology of RA or be used as future therapeutic target. The data suggest that PADI4 enzyme synthesis is epigenetically regulated by its gene promoter methylation. <h3>References</h3> [1] Ospelt C, Frank-Bertoncelj M. Epigenetics: New insights into site-specific variations in RA and OA. Nat Rev Rheumatol2016;12:506–7. [2] Firestein GS, McInnes IB. Immunopathogenesis of Rheumatoid Arthritis. Immunity2017;46:183–96. <h3>Disclosure of Interest</h3> None declared