Effects of quercitrin on platelet spreading
Upon ligand binding to αIIbβ3 integrin, it mediates outside-in signaling events involved in platelet spreading, thrombus contraction, and clot retraction.(Lee, Fong, King, Brass & Hammer, 2012) Therefore, we examined whether outside-in signaling events are affected by quercitrin using the platelet spreading assay (Figure 5). We found that vehicle- and quercitrin-pretreated platelets adhered to and spread on immobilized fibrinogen (FG) during the 2-hour incubation (Figure 5A). However, the number of adherent platelets was significantly inhibited by quercitrin treatment in a concentration-dependent manner (Figure 5B). The spreading of platelets was also reduced by approximately 1.5-fold in quercitrin–pretreated platelets compared with the findings for vehicle platelets (Figure 5C). No differences in lamellipodial actin assembly and surface coverage were observed between vehicle- and quercitrin-treated platelets spread on FG-coated surfaces (Figure 5A and 5D). These results suggest that the effects of quercitrin are likely limited to initial platelet adhesion to the FG-coated surface, and these effects occur through the regulation of the ligand-binding activity of αIIbβ3 integrin.