Differential CpG methylation of the promoter of interleukin 8 and the first intron of tissue factor in Antiphospholipid syndrome

Background: Antiphospholipid syndrome (APS) is an autoimmune thrombophilia characterized by recurrent thromboembolism and/or pregnancy morbidity in the presence of Antiphospholipid antibodies, mainly anti-β2 glycoprotein I (anti-β2GPI). The autoantibodies lead to monocyte and endothelial cell activation and subsequent secretion of tissue factor (F3) and proinflammatory cytokines, like interleukins 6 (IL6) and 8 (IL8). The etiology of the syndrome remains largely unknown, with the contribution of environmental, genetic and epigenetic factors considered significant.

Purpose: We aimed to identify epigenetic changes and factors potentially implicated in the pathophysiology of APS. To this end, we compared DNA methylation levels of the IL8 and F3 genes between healthy donors (HDs) and APS patients, using whole blood as a source.

Results: Methylation was significantly reduced in the IL8 promoter and significantly increased in the F3 gene body in APS patients compared to HDs and correlated with specific clinical parameters. In an ex vivo model partially mimicking APS, stimulation of monocytes with a mixture of β2GPI, anti-β2GPI and CXCL4 also induces DNA methylation changes in the above genes, along with increase of their expression. Stimulation of human umbilical vein endothelial cells (HUVECs) with the same mixture also results in transcriptional upregulation of epigenetic factors, including MΕCP2, DNMT3, TET1, HDAC9 and ARID5B.

Conclusions: The above data support that epigenetic alterations could be implicated in the pathophysiology of APS and prompt further investigation of their potential diagnostic or therapeutic utility.