Dose-dependent modulation of tissue factor protein and procoagulant activity in human monocyte-derived macrophages by oxidized low density lipoprotein.
ABSTRACT Oxidized low-density lipoprotein (oxLDL) interacts with macrophages and is implicated in atherogenesis. Macrophages are also the major source within the atherosclerotic plaque of tissue factor (TF), the membrane-bound glycoprotein receptor that triggers the coagulation cascade in vivo and contributes to plaque thrombogenicity. In this study we tested the hypothesis that oxLDL modulates TF expression in human monocyte-derived macrophages (MDMs).
Mononuclear cells were isolated from human blood, allowed to differentiate into MDMs during 8 days in cell culture, and then exposed to varying concentrations of oxLDL in the presence or absence of lipopolysaccharide (LPS). TF procoagulant activity (TF-PCA) of MDMs was measured by one-stage recalcification clotting assay using human recombinant TF as standard. TF protein was evaluated by Western blotting, and TF mRNA was determined by Northern blot analysis.
OxLDL at 5-10 µg/mL increased TF-PCA, TF protein, and mRNA in MDMs, whereas 20-100 µg/mL oxLDL inhibited TF-PCA, protein expression, and mRNA expression in these cells even in the face of LPS stimulation.
Low concentrations of oxLDL enhance TF expression in MDMs, whereas higher concentrations attenuate TF expression both at baseline as well as following LPS stimulation. Both TF-PCA and TF protein follow this dose-response pattern that is preceded by concordant mRNA changes. Thus, we have demonstrated modulation by oxLDL of TF protein and bioactivity in MDMs.
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ABSTRACT: Background Although cholesterol levels are known to be decreased in sickle cell disease (SCD), the level of pro-inflammatory high-density lipoprotein cholesterol (proHDL) and its association with clinical complications and laboratory variables has not been evaluated. Design and methods Plasma levels of total cholesterol, high-density lipoprotein cholesterol (HDL), proHDL, and selected clinical and laboratory variables were ascertained in a cohort of SCD patients and healthy African American control subjects in this single-center, cross-sectional study. Results Although total cholesterol was significantly lower in SCD patients compared with control subjects, HDL and proHDL levels were similar in both the SCD and control groups. In univariate analyses, proHDL was correlated with echocardiography-derived tricuspid regurgitant jet velocity. ProHDL was higher in SCD patients with suspected pulmonary hypertension (PHT) compared to patients without suspected PHT. ProHDL was positively correlated with lactate dehydrogenase, total bilirubin, direct bilirubin, indirect bilirubin, prothrombin fragment 1+2, D-dimer, and thrombin-antithrombin complexes. In multivariable analyses, only higher lactate dehydrogenase and direct bilirubin levels were associated with higher levels of proHDL. Conclusions SCD is characterized by hypocholesterolemia. Although proHDL is not increased in SCD patients compared with healthy controls, it is significantly associated with markers of liver disease. In addition, proHDL is associated with tricuspid regurgitant jet velocity and markers of coagulation, although these associations are not significant in multivariable analyses.Hematology (Amsterdam, Netherlands) 05/2014; 20(5). DOI:10.1179/1607845414Y.0000000171 · 1.19 Impact Factor
Article: Tissue Factor Structure and Function[Show abstract] [Hide abstract]
ABSTRACT: Tissue factor (TF) is an integral membrane protein that is essential to life. It is a component of the factor VIIa-TF complex enzyme and plays a primary role in both normal hemostasis and thrombosis. With a vascular injury, TF becomes exposed to blood and binds plasma factor VIIa, and the resulting complex initiates a series of enzymatic reactions leading to clot formation and vascular sealing. Many cells, both healthy, and tumor cells, produce detectable amounts of TF, especially when they are stimulated by various agents. Despite the relative simplicity and small size of TF, there are numerous contradictory reports about the synthesis and presentation of TF on blood cells and circulation in normal blood either on microparticles or as a soluble protein. Another subject of controversy is related to the structure/function of TF. It has been almost commonly accepted that cell-surface-associated TF has low (if any) activity, that is, is "encrypted" and requires specific conditions/reagents to become active, that is, "decrypted." However there is a lack of agreement related to the mechanism and processes leading to alterations in TF function. In this paper TF structure, presentation, and function, and controversies concerning these features are discussed.12/2012; 2012:964862. DOI:10.6064/2012/964862
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ABSTRACT: Hyperlipidemia leads to the formation of oxidized LDL (oxLDL), vessel dysfunction, atherosclerotic disease, and ultimately to plaque rupture and thrombosis. OxLDL induces tissue factor (TF) expression in various cell types, including monocytes and macrophages. High levels of TF are present in atherosclerotic plaques and this represents that major source of TF that triggers thrombosis after plaque rupture. In addition, increased levels of "circulating TF" are observed in hyperlipidemic animals and patients. This is due to induced TF expression in monocytes and release of monocyte-derived, TF(+) microparticles, which represents a minor source of TF that likely contributes to thrombosis after plaques rupture. This review will summarize the connections between hyperlipidemia and TF expression within atherosclerotic plaques and circulating monocytes, as well as its inhibition by statins.Thrombosis Research 03/2012; 129 Suppl 2:S30-3. DOI:10.1016/j.thromres.2012.02.026 · 2.43 Impact Factor