CD14+-Monocytes Exposed to Apolipoprotein CIII Express Tissue Factor

Apolipoprotein CIII (ApoCIII) represents a key regulator of plasma lipid metabolism and a recognized risk factor for atherosclerosis and cardiovascular diseases. Beyond the regulation of lipoprotein trafficking, ApoCIII is also involved in endothelial dysfunction and monocyte recruitment related to atherothrombosis. With tissue factor (TF) being the primary initiator of the blood coagulation cascade, we hypothesized that ApoCIII-treated monocytes could express it. Hence, human CD14(+)-monocytes and autologous neutrophils were incubated with ApoCIII and sera from human subjects containing previously measured ApoCIII amounts. By RT-qPCR and ELISA, CD14(+)-monocytes, but not neutrophils, were found to show increased mRNA expression and production of TNF alpha, IL-1 beta and IL-6 as well as TF mRNA once exposed to ultra-purified ApoCIII. By flow cytometry, CD14(+)-monocytes were found to rapidly express TF on their cell surface membrane when incubated with either ApoCIII or sera with known concentrations of ApoCIII. Finally, preincubation with specific ApoCIII-neutralizing antibodies significantly reduced the ability of most sera with known concentrations of ApoCIII to upregulate TF protein, other than partially inhibiting cytokine release, in CD14(+)-monocytes. In sum, herein we demonstrate that ApoCIII activates CD14(+)-monocytes to express TF. The data identify a potential mechanism which links circulating apolipoproteins with inflammation and atherothrombosis-related processes underlying cardiovascular risk.