Factor VIIa binding to endothelial cell protein C receptor

Multiple receptor-mediated functions of activated protein C

The central effector protease of the protein C pathway, activated protein C (APC), interacts with the endothelial cell protein C receptor, with protease activated receptors (PAR), the apolipoprotein E2 receptor, and integrins to exert multiple effects on haemostasis and immune cell function. Such receptor interactions modify the activation of PC and determine the biological response to endogenous and therapeutically administered APC. This review summarizes the current knowledge about interactions of APC with cell surface-associated receptors, novel substrates such as histones and tissue factor pathway inhibitor, and their implications for the biologic function of APC in the control of coagulation and inflammation.

Recombinant human factor VIIa (rFVIIa) cleared principally by antithrombin following intravenous administration in hemophilia patients

OBJECTIVE

The objective of the present study was to evaluate the pharmacokinetics and the clearance pathways of rFVIIa after intravenous administration to hemophilia patients.

METHODS

Ten severe hemophilia patients were included in the study; all patients were intravenously administered a clinically relevant dose of 90 μg kg(-1) (1.8 nmol kg(-1)) rFVIIa. Blood samples were collected consecutively to describe the pharmacokinetics of rFVIIa. All samples were analyzed using three different assays: a clot assay to measure the activity (FVIIa:C), an enzyme immunoassay (EIA) to measure the antigen levels (FVII:Ag), and an EIA (FVIIa-AT) to measure the FVIIa antithrombin III (AT) complex. Pharmacokinetic parameters were evaluated both by use of standard non-compartmental methods and by use of mixed effects methods. A population pharmacokinetic model was used to simultaneously model all three datasets. The total body clearance of rFVIIa:C was estimated to be 38 mL h(-1) kg(-1). The rFVII-AT complex formation was responsible for 65% of the total rFVIIa:C clearance. The initial and the terminal half-life of rFVIIa:C was estimated to be 0.6 and 2.6 h, respectively. The formation of rFVII-AT complex was able to explain the difference observed between the rFVIIa:C and the rFVII:Ag concentration. The non-compartmental analysis resulted in almost identical parameters.

Silencing CX3CR1 production modulates the interaction between dendritic and endothelial cells

CX3CR1, an important chemokine receptor in dendritic cells (DCs), is linked to the progression of atherosclerotic plaques. However, the mechanism(s) determining the role of CX3CR1 in atherosclerosis have not been clearly elucidated. In this study, we developed DCs from monocytes of Sprague-Dawley (SD) rats in the presence of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) and recombinant human interleukin-4 (IL-4). The presence of recombinant human TNF-α and LPS forced the cells to mature. When compared to immature DCs, flow cytometry (FACS) analysis revealed that mature DCs display a sustained increase in the levels of CD11c, CD86, and CD80 expression. The expression of Fractalkine (FKN) in endothelial cells (ECs) contributes to the maturation of DCs and expression of CX3CR1. We revealed that mRNA expression levels of CX3CR1 in mature DCs are significantly higher than those of immature DCs (P<0.001). Transfection of DCs with siRNA specific for the CX3CR1 gene resulted in potent suppression of gene expression and inhibition of interactions between DCs and ECs. Based on these data, we hypothesized that CX3CR1 contributes to the DC-EC interaction. CX3CR1 may serve as a new target molecule for increasing therapeutic interactions in atherosclerosis.