Sphingosine-1-Phosphate and Its Receptors: A Mutual Link between Blood Coagulation and Inflammation

Figure 4

Thrombin-stimulated S1P secretion in human platelets. Thrombin triggers COX-1-mediated synthesis of thromboxane A₂ (TXA₂) via activation of platelet PAR-1. Consecutive TX release and activation of thromboxane A₂ receptor (TXR) enhances platelet degranulation and aggregation. In parallel, TXA₂-TXR signaling stimulates platelet S1P secretion. This pathway involves activation protein kinase C (PKC) and appears to be mediated by an ATP-dependent transport mechanism (ABC, ATP-binding cassette transporter). In a paracrine manner, platelet-derived S1P may modulate endothelial and immune cell responses at sites of injury.