Oxidized low-density lipoproteins induce tissue factor expression in T-lymphocytes via activation of lectin-like oxidized low-density lipoprotein receptor-1

Abstract

Aims T-lymphocytes plays an important role in the pathophysiology of acute coronary syndromes. T-cell activation in vitro by pro-inflammatory cytokines may lead to functional tissue factor (TF) expression, indicating a possible contribution of immunity to thrombosis. Oxidized low-density lipoproteins (oxLDLs) are found abundantly in atherosclerotic plaques. We aimed at evaluating the effects of oxLDLs on TF expression in T cells and the role of the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1). Methods and results CD3+ cells were isolated from healthy volunteers. Gene, protein, and surface expression of TF, as well as of LOX-1, were assessed at different time-points after oxLDL stimulation. To determine whether oxLDL-induced TF was LOX-1 dependent, T cells were pre-incubated with an LOX-1 inhibiting peptide (L-RBP) or with an anti-LOX-1 blocking antibody. To exclude that TF expression was mediated by reactive oxygen species (ROS) generation, oxLDL-stimulated T cells were pre-incubated with superoxide dismutase + catalase or with 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol), an intracellular free radical scavenger. Finally, to determine if the observed findings in vitro may have a biological relevance, the presence of CD3+/TF+/LOX-1+ cells was evaluated by immunofluorescence in human carotid atherosclerotic lesions. oxLDLs induced functionally active TF expression in T cells in a dose- and time-dependent manner, independently on ROS generation. No effect was observed in native LDL-treated T cells. LOX-1 expression was also induced by oxLDLs in a time- and dose-dependent manner. Pre-incubation with L-RBP or anti-LOX-1 antibody almost completely inhibited oxLDL-mediated TF expression. Interestingly, human carotid plaques showed significant infiltration of CD3+ cells (mainly CD8+ cells), some of which were positive for both TF and LOX-1. Conclusion oxLDLs induce functional TF expression in T-lymphocytes in vitro via interaction of oxLDLs with LOX-1. Human carotid atherosclerotic plaques contain CD3+/CD8+cells that express both TF and LOX-1, indicating that also in patients these mechanisms may play an important role.

Relationship between lipoproteins, thrombosis, and atrial fibrillation

“…In this regard, patients with acute coronary syndrome demonstrate a positive correlation between oxLDL and tissue factor levels in plasma 106 . Activation of T lymphocytes by oxLDL, prepared by chemical oxidation of native LDL with copper sulfate, via the lectin-type oxLDL receptor 1 (LOX-1) has also been shown to increase the expression of tissue factor on the surface of leukocytes 107 . Furthermore, oxLDL generated with copper oxidation was noted to inhibit fibrinolysis, modify fibrin clot structure and increase thrombin generation 98,108 .…”

“… 110 Activation of T lymphocytes by oxLDL, prepared by chemical oxidation of native LDL with copper sulfate, via the lectin-type oxLDL receptor 1 (LOX-1) has also been shown to increase the expression of tissue factor on the surface of leukocytes. 111 Furthermore, oxLDL generated with copper oxidation was noted to inhibit fibrinolysis, modify fibrin clot structure and increase thrombin generation. 102 , 112 Finally, oxLDL (detected by 4E6) correlated to reduced clot permeability and prolonged clot lysis time.…”

The Impact of the Renin-Angiotensin-Aldosterone System on Inflammation, Coagulation, and Atherothrombotic Complications, and to Aggravated COVID-19

“…Also, CRP seems to have a role in coagulation as CRP can induce TF activation via a NF-κB pathway in both endothelial cells and VSMCs ( Cirillo et al, 2005 ). In addition, Other mediators like oxidized LDL ( Cimmino et al, 2019 ) and oxygen free radicals ( Cimmino et al, 2015 ) can enhance TF activation. This enables active TF to be exposed to blood and bind to FVII.…”

Tissue factor in atherosclerosis and atherothrombosis

“…OxLDL is likely to induce TF gene expression via activation of nuclear factor-κB because expression is regulated by this transcription factor and oxLDL has been shown to activate nuclear factor-κB [9,25]. Exposure of other cell types present in atherosclerotic plaques, including T lymphocytes and ECs, to minimally oxLDL has also been found to enhance TF expression [26,27]. Interestingly, TF expression in monocytes has been found to be increased in patients with hypercholesterolemia and in white blood cells in hypercholesterolemic mice and monkeys [28][29][30][31].…”