Sphingosine inhibits monocyte tissue factor-initiated coagulation by altering factor VII binding

Area of Science:

• Biochemistry
• Hematology
• Cell Biology

Background:

• Tissue factor (TF) is a cell surface lipoprotein crucial for initiating the extrinsic coagulation pathway.
• TF-initiated coagulation plays a significant role in inflammatory conditions and disseminated intravascular coagulation.
• Understanding regulators of TF activity is vital for developing hemostasis therapies.

Purpose of the Study:

• To investigate the effect of sphingosine on tissue factor-initiated coagulation in human monocytes.
• To elucidate the mechanism by which sphingosine modulates coagulation.
• To explore the potential of sphingosine as a novel hemostasis inhibitor.

Main Methods:

• Lipopolysaccharide (LPS)-stimulated human monocytes were used to initiate coagulation.
• Thromboplastin-initiated coagulation assays were performed in the presence of varying sphingosine concentrations.
• Binding assays were conducted to assess the interaction of Factor VII with monocytes using radiolabeled Factor VII.
• Analogues of sphingosine (sphingomyelin, ceramide, N-acetylsphingosine) were tested for their effects.

Main Results:

• Sphingosine significantly inhibited LPS-stimulated monocyte coagulation in a dose- and time-dependent manner.
• Sphingosine demonstrated over 90% inhibition of thromboplastin activity.
• Sphingosine did not affect the intrinsic coagulation pathway or thrombin generation.
• Sphingosine specifically inhibited the binding of Factor VII to monocytes, unlike its analogues.
• The polar head group of sphingosine appears essential for its anticoagulant activity.

Conclusions:

• Sphingosine effectively inhibits tissue factor-initiated coagulation by interfering with Factor VII binding to monocytes.
• Sphingosine represents a potential new class of hemostasis inhibitors.
• Further research into sphingosine's mechanism and therapeutic potential is warranted.