title: Inhibitory effect of ginkgolide B on platelet aggregation in a cAMP- and cGMP-dependent manner by activated MMP-9.
abstract: Extracts from the leaves of the Ginkgo biloba are becoming increasingly popular as a treatment that is claimed to reduce atherosclerosis, coronary artery disease, and thrombosis. In this study, the effect of ginkgolide B (GB) from Ginkgo biloba leaves in collagen (10 microg/ml)- stimulated platelet aggregation was investigated. It has been known that human platelets release matrix metalloproteinase- 9 (MMP-9), and that it significantly inhibited platelet aggregation stimulated by collagen. Zymographic analysis confirmed that pro-MMP-9 (92-kDa) was activated by GB to form an MMP-9 (86-kDa) on gelatinolytic activities. And then, activated MMP-9 by GB dose-dependently inhibited platelet aggregation, intracellular Ca2+ mobilization, and thromboxane A2 (TXA2) formation in collagen-stimulated platelets. Activated MMP-9 by GB directly affects down-regulations of cyclooxygenase-1 (COX-1) or TXA2 synthase in a cell free system. In addition, activated MMP-9 significantly increased the formation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which have the anti-platelet function in resting and collagen-stimulated platelets. Therefore, we suggest that activated MMP-9 by GB may increase the intracellular cAMP and cGMP production, inhibit the intracellular Ca2+ mobilization and TXA2 production, thereby leading to inhibition of platelet aggregation. These results strongly indicate that activated MMP-9 is a potent inhibitor of collagen-stimulated platelet aggregation. It may act a crucial role as a negative regulator during platelet activation.
authors.affiliation: College of Medicine and Cardiovascular Medical Research Center, Dongguk University, Gyeongju 780-714, Republic of Korea.
authors.forename: Hyun-Jeong
authors.initials: HJ
authors.lastname: Cho
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Nam
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D046934:Ginkgolides / Q000737:chemistry / Q000494:pharmacology*; D007783:Lactones / Q000737:chemistry / Q000494:pharmacology*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D015394:Molecular Structure; D010974:Platelet Aggregation / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013928:Thromboxane A2 / Q000378:metabolism
chemical_list: D046934:Ginkgolides; D007783:Lactones; D013928:Thromboxane A2; D003094:Collagen; C045856:ginkgolide B; D000242:Cyclic AMP; D020780:Matrix Metalloproteinase 9; D006152:Cyclic GMP; D002118:Calcium