title: Timosaponin AIII induces antiplatelet and antithrombotic activity via Gq-mediated signaling by the thromboxane A2 receptor.
abstract: The thromboxane (Tx) A2pathway is a major contributor to the amplification of initial platelet activation and is therefore a key drug target. To identify potent small-molecule inhibitors of the thromboxane prostaglandin (TP) receptor, we screened a small steroidal saponin library using U46619-induced rat platelet aggregation assays. Timosaponin AIII (TAIII) was identified as a potent inhibitor of U46619-induced rat platelet aggregation and exhibited superior selectivity for the TP receptor versus other G protein-coupled receptors and a PKC activator. TAIII inhibited U46619-induced rat platelet aggregation independent of increases in cAMP and cGMP and the inhibition of TxA2 production. Both PKC and PLC activators restored TAIII-inhibited platelet aggregation, whereas TAIII did not inhibit platelet aggregation induced by co-activation of the G12/13and Gzpathways. Furthermore, TAIII did not affect the platelet shape change or ROCK2 phosphorylation evoked by low-dose U46619. In vivo, TAIII prolonged tail bleeding time, reduced the mortality of animals with acute pulmonary thromboembolism and significantly reduced venous thrombus weight. Our study suggests that TAIII, by preferentially targeting Gq-mediated PLC/PKC signaling from the TP receptor, induces stronger in vitro antiplatelet activity and in vivo antithrombotic effects and may be an excellent candidate for the treatment of thrombotic disorders.
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.|National Resource Center for Chinese Materia Medica, Institute of Clinical Pharmacy of Beijing Municipal Health Bureau, No. 13 Shuiche Alley, Beijing 100035, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Cong
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Renjun
authors.initials: R
authors.lastname: Peng
authors.affiliation: Department of Biotechnology, Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Bai
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Liu
authors.affiliation: National Resource Center for Chinese Materia Medica, Institute of Clinical Pharmacy of Beijing Municipal Health Bureau, No. 13 Shuiche Alley, Beijing 100035, China.
authors.forename: Daqian
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Biotechnology, Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Baiping
authors.initials: B
authors.lastname: Ma
authors.affiliation: Department of Pathophysiology, Beijing Key Laboratory for Radiobiology (BKLRB), Beijing Institute of Radiation Medicine, No. 27 Taiping Road, Beijing 100850, China.
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Cong
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D000991:Antithrombins / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004357:Drug Synergism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000502:physiology*; D012503:Saponins / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology*; D013256:Steroids / Q000494:pharmacology*; D013928:Thromboxane A2 / Q000096:biosynthesis
chemical_list: D000991:Antithrombins; D010975:Platelet Aggregation Inhibitors; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D012503:Saponins; D013256:Steroids; C543146:timosaponin AIII; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000242:Cyclic AMP; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D006152:Cyclic GMP