Abstract 526: 4-hydroxy-2-nonenal (HNE), a Lipid Peroxidation Product, Exerts Both Pro- and Anti-thrombotic Effects on Vascular Cells

Abstract

Background: Oxidative stress and generation of lipid peroxidation (LPO) products are detrimental in the pathogenesis of atherosclerosis and associated acute thrombotic events. However, recent studies suggest that moderate oxidative stress and low levels of LPO products can induce adaptive immune responses and exert beneficial effects. Tissue factor (TF) is a critical initiator of coagulation and aberrant TF expression on vascular cells under inflammation triggers intravascular thrombosis. HNE, a highly reactive LPO product and TF have been shown to be associated with atherosclerosis. Recently, we demonstrated that HNE decrypts procoagulant activity of pre-existing TF on activated monocytes and endothelial cells and generates TF+ microparticles. Here, we investigated the effect of HNE on induction of TF and cell adhesion molecules in monocytes and endothelial cells that were not perturbed earlier. Methods and results: THP-1 monocytic cells and endothelial cells (HUVEC) were stimulated with LPS and TNF-α/IL1-β, respectively, in the presence of a control vehicle or varying concentrations of HNE that are pathophysiologically relevant. TF induction was measured at mRNA (by qRT-PCR), protein (by immunoblotting) and activity levels (in factor X activation assay). Pre-treating cells with HNE inhibited TNF-α/IL1-β- or LPS-stimulated TF procoagulant activity in a dose-dependent manner. THP-1 and HUVEC varied in their sensitivities to HNE (THP-1> HUVEC). HNE-mediated inhibition of TF activity correlated with lower TF mRNA and protein levels. Our results demonstrate that HNE prevents TNF-α/IL1-β- and LPS-induced IKKβ degradation and thereby inhibits NFκβ activation. In addition to inhibiting TF expression, HNE significantly reduced monocyte adhesion to endothelial cells through downregulating TNF-α/IL1-β-induced expression of endothelial adhesion molecules VCAM-1 and ICAM-1. Conclusion: HNE may play a dual role in regulating TF activity in atherosclerosis. HNE could act as a prothrombotic mediator by increasing coagulant activity of pre-existing TF through decryption process. HNE can also elicit anti-thrombotic and anti-inflammatory effect by inhibiting TF and adhesion molecules in response to stimulus by impairing the NF-ĸB pathway.