Liquiritigenin attenuates thrombosis by inhibiting P2Y12R-mediated Src/PLCγ2 signaling and cytoplasmic Ca2+ mobilization in platelets

Background: Cardiovascular and cerebrovascular diseases are the leading causes of death worldwide. Pathological thrombosis is a major underlying mechanism, where excessive platelet activation triggered by vascular injury constitutes a key event. Liquiritigenin, a key flavonoid constituent of Glycyrrhiza glabra l., has been reported to possess diverse pharmacological properties, including anti-inflammatory, anti-tumor, neuroprotective, and cardiovascular protective effects. However, its specific role in platelet activation remains unclear.

Purpose: This study aims to explore the mechanism through which liquiritigenin inhibits platelet activation to attenuate thrombosis.

Methods: The inhibitory effect of Liquiritigenin on platelet activation was evaluated using Thrombin, ADP, and Collagen as agonists. A co-culture system of platelets with human umbilical vein endothelial cells (HUVECs) on a collagen-coated surface was established to simulate platelet adhesion to vascular endothelia and subendothelial matrix under flow conditions. Flow cytometry, transmission electron microscopy, fluorescence labeling, and Western blotting were employed to assess P-selectin (CD62P) expression, dense granule secretion, and platelet adhesion following activation. The effects of Liquiritigenin on the Src/PLCγ2 signaling pathway, cytoplasmic Ca²⁺ mobilization, and the interaction between P2Y12R and the guanine nucleotide-binding protein Gi subunit alpha-1 (Gαi1) were further investigated. Additionally, integrated analysis of multiple single-cell transcriptome datasets was performed to identify cell types interacting with activated platelets in heart and lung tissues. The anti-thrombotic efficacy of liquiritigenin was evaluated in two in vivo models: acute pulmonary thromboembolism (APE) and coronary microvascular dysfunction (CMD).

Results: Liquiritigenin demonstrated a more potent inhibitory effect on ADP-activated platelets than on those activated by Thrombin or Collagen. It significantly suppressed ADP-induced P-selectin expression, dense granule secretion, and platelet adhesion to HUVECs. Furthermore, Liquiritigenin inhibited the ADP-triggered Src/PLCγ2 signaling pathway, reduced cytoplasmic Ca²⁺ mobilization, and attenuated the interaction between P2Y12R and Gαi1. Molecular modeling indicated that Liquiritigenin binds to key P2Y12R residues-LYS179, CYS97, and ASN191-which are also involved in ADP binding. In animal models, Liquiritigenin administration significantly reduced thrombus formation in the lung tissue of APE and within the coronary micro vessels of CMD model Animals.

Conclusion: The findings indicate that Liquiritigenin inhibits platelet activation by targeting P2Y12R. This action disrupts the Src/PLCγ2 signaling pathway and subsequently reduces cytoplasmic calcium mobilization. These results suggest that Liquiritigenin may have therapeutic potential for the treatment of thrombotic diseases associated with platelet activation.

Ca(2+); Liquiritigenin; Platelet activation;P2Y12R; Src/PLCγ2 signaling pathway; Thrombosis.