The role of thrombospondin-1 in the pathogenesis of antiphospholipid syndrome.

OBJECTIVE: Antiphospholipid syndrome (APS) is an acquired thrombophilia characterized by recurrent thrombosis and/or pregnancy morbidity, in the presence of antibodies to ß2 glycoprotein-I (ß2GPI), prothrombin or Lupus anticoagulant (LA). Anti-ß2GPI antibodies recognize complexes of ß2GPI dimers with CXCL4 chemokine and activate platelets. Thrombospondin 1 (TSP-1) is secreted by platelets and exhibits prothrombotic and proinflammatory properties. Therefore, we investigated its implication in APS. METHODS: Plasma from APS patients (n = 100), Systemic Lupus Erythematosus (SLE) (n = 27) and healthy donors (HD) (n = 50) was analyzed for TSP-1, IL-1ß, IL-17A and free active TGF-ß1 by ELISA. Human Umbilical Vein Endothelial Cells (HUVECs) and HD monocytes were treated with total HD-IgG or anti-ß2GPI, ß2GPI and CXCL4 and CD4+ T-cells were stimulated by monocyte supernatants. TSP-1, IL-1ß, IL-17A TGF-ß1 levels were quantified by ELISA and Real-Time PCR. RESULTS: Higher plasma levels of TSP-1 and TGF-ß1, which positively correlated each other, were observed in APS but not HDs or SLE patients. Patients with arterial thrombotic events or those undergoing a clinical event had the highest TSP-1 levels. These patients also had detectable IL-1ß, IL-17A in their plasma. HD-derived monocytes and HUVECs stimulated with anti-ß2GPI-IgG-ß2GPI-CXCL4 secreted the highest TSP-1 and IL-1ß levels. Supernatants from anti-ß2GPI-ß2GPI-CXCL4 treated monocytes induced IL-17A expression from CD4+ T-cells. Transcript levels followed a similar pattern. CONCLUSIONS: TSP-1 is probably implicated in the pathogenesis of APS. In vitro cell treatments along with high TSP-1 levels in plasma of APS patients suggest that high TSP-1 levels could mark a prothrombotic state and an underlying inflammatory process.

Evidence of epigenetic alterations in thrombosis and coagulation: A systematic review.

Thrombosis in the context of Cardiovascular disease (CVD) affects mainly the blood vessels supplying the heart, brain and peripheries and it is the leading cause of death worldwide. The pathophysiological thrombotic mechanisms are largely unknown. Heritability contributes to a 30% of the incidence of CVD. The remaining variation can be explained by life style factors such as smoking, dietary and exercise habits, environmental exposure to toxins, and drug usage and other comorbidities. Epigenetic variation can be acquired or inherited and constitutes an interaction between genes and the environment. Epigenetics have been implicated in atherosclerosis, ischemia/reperfusion damage and the cardiovascular response to hypoxia. Epigenetic regulators of gene expression are mainly the methylation of CpG islands, histone post translational modifications (PTMs) and microRNAs (miRNAs). These epigenetic regulators control gene expression either through activation or silencing. Epigenetic control is mostly dynamic and can potentially be manipulated to prevent or reverse the uncontrolled expression of genes, a trait that renders them putative therapeutic targets. In the current review, we systematically studied and present available data on epigenetic alterations implicated in thrombosis derived from human studies. Evidence of epigenetic alterations is observed in several thrombotic diseases such as Coronary Artery Disease and Cerebrovascular Disease, Preeclampsia and Antiphospholipid Syndrome. Differential CpG methylation and specific histone PTMs that control transcription of prothrombotic and proinflammatory genes have also been associated with predisposing factors of thrombosis and CVD, such us smoking, air pollution, hypertriglyceridemia, occupational exposure to particulate matter and comorbidities including cancer, Chronic Obstructive Pulmonary Disease and Chronic Kidney Disease. These clinical observations are further supported by in vitro experiments and indicate that epigenetic regulation affects the pathophysiology of thrombotic disorders with potential diagnostic or therapeutic utility.

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-ß2 glycoprotein I (anti-ß2GPI). 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 ß2GPI, anti-ß2GPI 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.