THU0004 GENOME-WIDE DNA METHYLATION PROFILING IN MONOCYTES FROM PRIMARY ANTIPHOSPHOLIPID SYNDROME PATIENTS IDENTIFIES AN ABERRANT METHYLATION SIGNATURE ASSOCIATED WITH THEIR ATHEROTHROMBOTIC PHENOTYPE

Background: Recent studies underlined the crucial role of DNA methylation in several autoimmune diseases by altering gene expression profiles, thus influencing disease severity. Yet, aberrant methylation patterns in monocytes, key players in the pathogenesis of APS patients, has not been evaluated. Objectives: To analyze the genome-wide DNA methylation profile of monocytes from APS patients and its relationship with the cardiovascular (CV) pathology. 2. To evaluate the role of antiphospholipid antibodies (aPL) in the regulation of this process. Methods: Thirty-three APS patients and 15 healthy donors (HD) were included in the study. Monocytes were isolated from peripheral blood by positive immunomagnetic selection. The Illumina Infinium Methylation EPIC Beadchip was used to obtain DNA methylation profiles across approximately 850,000 CpGs (TSS1500, TSS200, 5UTR, 3UTR, first exon, intergenic, gene body). Beta values (β) estimating methylation levels were obtained at each CpG site, and differentially methylated genes (DMG) between APS and HD were identified. Functional classification of that genes was carried out by gene ontology analysis (PANTHER database). Gene expression of selected DMG genes was evaluated by RT-PCR. CV-risk parameters, including carotid intima-media thickness (CIMT) and microvascular endothelial function were further assessed, and correlation/association studies were developed with clinical and analytical variables. The effects of aPLs were also evaluated by in vitro studies. Results: Genome-wide DNA methylation analysis identified 813 DMG, including 279 hypomethylated and 534 hypermethylated. Functional classification of these genes revealed signatures associated with biological processes and pathways related to their clinical profile, including immune response, adhesion, oxidative stress and vascular signaling. Correlation and association studies showed that the methylation levels of genes related to immune response were associated with the CV-risk score, aGAPSS (CCR2, TXLNB, GLIPR), type of thrombosis (SIGLEC11, COLEC11, LRRC16A, AHSA1, TRIL) and aPL titers (CLEC4G, RGS4, HLA-DPA1, GBP6, RAET1E, HLA-G, HLA-DPA1, HLA-H, TXLNB). Besides, methylation levels of DMG related to vascular signaling and adhesion processes were associated with the presence of thrombotic recurrences (VEGFA, MAPK14, ITGA8, EPCAM, PCDHA6, DLG1) as well as with traditional CV-risk factor such as hypertension and dyslipidemia (ITGA11, DSCAM, CLEC4F, CDH4, LTBP2, PCDHB14). In addition, methylation levels of DMG genes related to oxidative stress (GP2, PGD, ADH1) were associated with microvascular endothelial dysfunction. An altered mRNA expression of some of those genes with aberrant methylation and related to increased CV-risk and thrombotic recurrences in APS was also identified. Both, abnormal methylation and transcription levels of several genes were further associated with a pathological increase of the CIMT. Finally, in vitro studies supported the role of aPLs as key players in the altered methylation and transcriptomic profiles of APS patients. Conclusion: APS patients showed an impaired methylation profile in monocytes of genes associated with clinical features of the disease, including aPL titers, CV risk, thrombotic recurrences, endothelial dysfunction and early atherosclerosis. These results offered a map to the monocytes methylome and shed light on the pathophysiology of APS, paving the way for the development of new, more effective biomarkers and therapeutics. Acknowledgments: Funded by ISCIII (PI18/0837 and RIER RD16/0012/0015) co-funded with FEDER. Disclosure of Interests: Carlos Perez-Sanchez: None declared, Alejandra M. Patino-Trives: None declared, Maria A Aguirre: None declared, Perez Sanchez Laura: None declared, Maria Luque-Tevar: None declared, Ivan Arias de la Rosa: None declared, Carmen Torres-Granados: None declared, Maria del Carmen Abalos-Aguilera: None declared, Pedro Segui Azpilcueta: None declared, Javier Rodriguez: None declared, Esteban Ballester: None declared, Nuria Barbarroja Puerto Grant/research support from: ROCHE and Pfizer., Speakers bureau: ROCHE and Celgene., Eduardo Collantes Estevez Grant/research support from: ROCHE and Pfizer, Speakers bureau: ROCHE, Lilly, Bristol and Celgene, Chary Lopez-Pedrera Grant/research support from: ROCHE and Pfizer.