Salvianolic acid B inhibits platelet adhesion under conditions of flow by a mechanism involving the collagen receptor alpha2beta1.

Salvianolic acid B (SAB) is a component of Danshen, a herb widely used in Chinese medicine, and was previously shown to exert a number of biological activities including inhibition of platelet function, but the exact mechanisms involved are unclear. SAB dose-dependently inhibited platelet deposition from flowing, anticoagulated whole blood to immobilized collagen at both venous and arterial shear rate, whereas platelet deposition to immobilized fibrinogen was not affected. The inhibitory effect of SAB on platelet adhesion to collagen was independent of alphaIIbbeta3, since SAB still inhibited platelet deposition in the presence of a alphaIIbbeta3-blocking peptide. SAB inhibited static platelet adhesion to a synthetic peptide specific for the collagen receptor alpha2beta1, whereas platelet adhesion to a glycoprotein VI-specific peptide was not affected. SAB inhibited binding of an antibody against alpha2beta1 to platelets as studied by flow cytometry, and inhibited the interaction of soluble alpha2beta1 to immobilized collagen in a solid phase binding assay. These combined results indicate that SAB inhibits platelet adhesion to immobilized collagen by interfering with the collagen receptor alpha2beta1.