Quercitrin regulates GPVI-mediated platelet activation via PTPs activation
Previous research demonstrated that intracellular ROS participate in the regulation of protein tyrosine phosphorylation by oxidizing the catalytic cysteine residues of PTPs (SHP1, SHP2, and PTEN), which play a negative regulatory role in GPVI-mediated platelet activation.(Jang et al., 2014; Senis, 2013) Since quercitrin serves as an antioxidant, we next examined whether quercitrin affects the activation of PTPs during platelet activation. We found that the phosphorylation levels of SHP1, SHP2, and PTEN were increased in CRP-activated vehicle–pretreated platelets, whereas their phosphorylation was abrogated by quercitrin treatment in a concentration-dependent manner (Figure 6E and 6F). These results suggest that ROS generation upon GPVI stimulation leads to PTP inactivation and promotes tyrosine phosphorylation-based signal transduction, whereas quercitrin, as an anti-oxidant, scavenges ROS and promotes PTP dephosphorylation, thereby reducing GPVI-mediated platelet activation.