Abstract 14623: ICAM-1 Mediates Hyperhomocysteinemia Accelerated Arteriolar Thrombosis and Endothelial -Platelets Interaction
Background: Hyperhomocysteinemia (HHcy) is an established risk factor for atherothrombogenic diseases. In this study we investigated the effect of HHcy on EC-platelets interaction and its role in thrombosis.
Methods and Results: We used a novel mouse model of HHcy (plasma homocysteine, Hcy 80 μ M) in which a Zn2+ inducible human cystathionine β-synthase (CBS) transgene was introduced to circumvent the neonatal lethality of Cbs deficiency (Tg-hCBS Cbs−/−mice). Hcy-lowering therapy was performed by giving ZnSO4 water to induce human CBS transgene expression in adult mice. Thrombus formation was examined by photo-dye induced cremaster microvasculature thrombosis using intra-vital microscope, which preserved the endothelium, and by FeCl3-induced carotid artery thrombosis, which denudated the endothelium. HHcy accelerated cremaster arteriolar thrombosis and decreased blood flow cessation time from 41.8 min in control mice to 30.5 min in Tg-hCBS Cbs−/− mice. Venular blood flow cessation time was slightly decreased from 5.6 to 5.0 min. Hcy-lowering therapy reduced Hcy level from 80 μ M to 2 μ M after 2 weeks of ZnSO4 water and prolonged arteriolar blood cessation time from 30.5 to 37.8 min. Interestingly, FeCl3-induced carotid artery thrombosis did not change. Hcy did not potentiate aggregation and secretion of washed human platelets from healthy donor treated with Hcy (50, 100 μ M) and from Tg-hCBS Cbs−/−mice. However, ICAM-1 levels, but not VCAM-1, were increased in cremaster tissues from Tg-hCBS Cbs−/− mice by western blot. In cultured human umbilical vein ECs (HUVEC), Hcy (100 μ M, 24h) promoted human platelet adhesion by 200% in static adhesion assay. Using western blot, FACS and RT-PCR, we found that Hcy increased protein and mRNA levels of ICAM-1, but not that of VCAM-1, in HUVEC. ICAM-1 blocking antibody partially reversed Hcy-increased platelets adhesion to HUVEC. Finally, Hcy induced ICAM-1 expression and reduced DNA methylation on ICAM-1 promoter, which were mimicked by DNA methyltransferase inhibitor azacytidine, and histone deacetylase inhibitors sodium butyrate and trichostatin A.
Conclusion: HHcy accelerates arteriolar thrombosis and increases EC-platelets interaction via ICAM-1 induction partially through promoter hypomethylation.
- © 2012 by American Heart Association, Inc.