title: Glaucocalyxin A inhibits platelet activation and thrombus formation preferentially via GPVI signaling pathway.
abstract: Platelets play a pivotal role in atherothrombosis and the antiplatelet agents have been proved to be useful in preventing onset of acute clinical events including myocardial infarction and stroke. Increasing number of natural compounds has been identified to be potential antiplatelet agents. Here we report the antiplatelet effect of glaucocalyxin A (GLA), an ent-diterpenoid that we isolated and purified from the aerial parts of Rabdosia japonica (Burm. f.) var. glaucocalyx (Maxim.) Hara, and investigate the molecular mechanisms by which GLA inhibits platelet activation and thrombus formation. The effect of GLA on platelet activation was measured using platelets freshly isolated from peripheral blood of healthy donors. Results showed that pretreatment of human platelets with lower concentrations of GLA (0.01 μg/ml, 0.1 μg/ml) significantly inhibited platelet aggregation induced by collagen (P<0.001) and CRP (P<0.01), a synthetic GPVI ligand, but not by ADP and U46619. Accordingly, GLA inhibited collagen-stimulated tyrosine phosphorylation of Syk, LAT, and phospholipase Cγ2, the signaling events in collagen receptor GPⅥ pathway. GLA also inhibited platelet p-selectin secretion and integrin activation by convulxin, a GPVI selective ligand. Additionally, GLA was found to inhibit low-dose thrombin-induced platelet activation. Using a flow chamber device, GLA was found to attenuate platelet adhesion on collagen surfaces in high shear condition. In vivo studies showed that GLA administration increased the time for complete occlusion upon vascular injury in mice, but did not extend tail-bleeding time when mice were administered with relatively lower doses of GLA. Therefore, the present results provide the molecular basis for the inhibition effect of GLA on platelet activation and its in vivo effect on thrombus formation, suggesting that GLA could potentially be developed as an antiplatelet and antithrombotic agent.
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Tang
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Wenxiu
authors.initials: W
authors.lastname: Yi
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Lijie
authors.initials: L
authors.lastname: Ren
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Liu
authors.affiliation: College of Pharmaceutical Science, Soochow University, Suzhou, China.
authors.forename: Chunjun
authors.initials: C
authors.lastname: Chu
authors.affiliation: Department of Laboratory Medicine, Faculty of Medicine, University of Yamanashi, Chuo, Yamanashi, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ozaki
authors.affiliation: College of Pharmaceutical Science, Soochow University, Suzhou, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Cyrus Tang Hematology Center, Soochow University, Suzhou, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhu
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D001777:Blood Coagulation / Q000187:drug effects*; D001792:Blood Platelets / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology; D045786:Diterpenes, Kaurane / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D006801:Humans; D037602:Isodon / Q000737:chemistry; D008297:Male; D051379:Mice; D010973:Platelet Adhesiveness / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D015398:Signal Transduction; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D045786:Diterpenes, Kaurane; D010980:Platelet Membrane Glycoproteins; D014662:Vasoconstrictor Agents; C098341:platelet membrane glycoprotein VI; D000244:Adenosine Diphosphate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C055124:glaucocalyxin A; D003094:Collagen