Phillyrin and its metabolites treat pulmonary embolism by targeting PLCβ3 to inhibit platelet activation

Ethnopharmacological relevance Lian Qiao (LQ), the dried fruit of Forsythia suspensa (Thunb.) Vahl, is a well-documented traditional Chinese medicine known for its detoxifying and heat-clearing properties. Clinically, compounds containing LQ are widely used to treat thrombotic diseases, indicating that it may have antithrombotic effects. However, its exact mechanism of action remains unknown. Aim of the study This study aimed to verify the antithrombotic effect of LQ and further explore the material basis and target mechanism of its antithrombotic effect using various biological methods. Materials and methods An epinephrine-collagen-thrombin-induced mouse model of acute pulmonary embolism (APE) was established to study the effects of LQ on thrombus development. A UPLC/Q/TOF-MS screening and identification system based on the inhibition of platelet aggregation and Ca2+ antagonism was established to determine the pharmacodynamic components of LQ that inhibit platelet activation. The inhibitory effect of active ingredients on platelet activation, and the determination of the target of their inhibitory effect on platelet activation have been studied using chemical proteomics. Furthermore, based on the structure and function of the target protein, a multidisciplinary approach was adopted to analyze the molecular mechanism of active ingredient binding to target proteins and to evaluate the effects of active ingredients on the downstream signaling pathways of target proteins. Results LQ showed significant anticoagulant effects in APE model mice. Phillyrin and phillygenin were the antiplatelet-activating components of LQ. PLCβ3 was identified as a target for inhibiting platelet activation by phillyrin and its metabolites. The mechanism underlying the effect involves phillyrin and its metabolites inhibiting PLCβ3 activity by blocking the binding of PLCβ3 to Gαq through non-covalently targeting the ASN260 of PLCβ3, thus inhibiting the downstream Gαq-PLCβ3-Ca2+ signaling pathway, effectively hindering platelet activation and therefore playing an anticoagulant role. Conclusion This study not only proposes and validates the antithrombotic effect of LQ for the first time but also finds that phillyrin and phillygenin are the main pharmacological substances through which LQ exerts antithrombotic activity and reveals a novel mechanism by which they exert antiplatelet activity by directly targeting and inhibiting PLCβ3 activity. These findings significantly contribute to our understanding of the therapeutic potential of phillyrin and provide important clues for the discovery and development of new antiplatelet drugs.