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.