title: A novel role of andrographolide, an NF-kappa B inhibitor, on inhibition of platelet activation: the pivotal mechanisms of endothelial nitric oxide synthase/cyclic GMP.
abstract: Andrographolide is a novel NF-κB inhibitor from the leaves of Andrographis paniculata. Platelet activation is relevant to a variety of thrombotic diseases. However, no data are available concerning the effects of andrographolide in platelet activation. The aim of this study was to examine the mechanisms of andrographolide in preventing platelet activation. Andrographolide (25-75 μΜ) exhibited a more potent activity of inhibiting platelet aggregation stimulated by collagen. Andrographolide inhibited collagen-stimulated platelet activation accompanied by relative Ca(2+) mobilization; thromboxane A(2) formation; and phospholipase C (PLC)γ2, protein kinase C (PKC), mitogen-activated protein kinase (MAPK), and Akt phosphorylation. Andrographolide markedly increased cyclic GMP, but not cyclic AMP levels. Andrographolide also stimulated endothelial nitric oxide synthase (eNOS) expression, NO release, and vasodilator-stimulated phosphoprotein (VASP) phosphorylation. ODQ, an inhibitor of guanylate cyclase, markedly reversed the andrographolide-mediated inhibitory effects on platelet aggregation, p38 MAPK and Akt phosphorylation, and the andrographolide-mediated stimulatory effect on VASP phosphorylation. Furthermore, a PI3 kinase inhibitor (LY294002) but not a PKC inhibitor (Ro318220) significantly diminished p38 MAPK phosphorylation; nevertheless, a p38 MAPK inhibitor (SB203580) and LY294002 diminished PKC activity stimulated by collagen. Andrographolide also reduced collagen-triggered hydroxyl radical (OH([Symbol: see text])) formation. In vivo studies revealed that andrographolide (22 and 55 μg/kg) is effective in reducing the mortality of ADP-induced acute pulmonary thromboembolism and significantly prolonged platelet plug formation in mice. This study demonstrates for the first time that andrographolide possesses a novel role of antiplatelet activity, which may involve the activation of the eNOS-NO/cyclic GMP pathway, resulting in the inhibition of the PI3 kinase/Akt-p38 MAPK and PLCγ2-PKC cascades, thereby leading to inhibition of platelet aggregation.
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Wan-Jung
authors.initials: WJ
authors.lastname: Lu
authors.forename: Jie-Jen
authors.initials: JJ
authors.lastname: Lee
authors.forename: Duen-Suey
authors.initials: DS
authors.lastname: Chou
authors.forename: Thanasekaran
authors.initials: T
authors.lastname: Jayakumar
authors.forename: Tsorng-Han
authors.initials: TH
authors.lastname: Fong
authors.forename: George
authors.initials: G
authors.lastname: Hsiao
authors.forename: Joen-Rong
authors.initials: JR
authors.lastname: Sheu
mesh_terms: D000244:Adenosine Diphosphate; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism*; D004224:Diterpenes / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D015539:Platelet Activation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D011655:Pulmonary Embolism / Q000139:chemically induced / Q000188:drug therapy; D013928:Thromboxane A2 / Q000378:metabolism
chemical_list: D004224:Diterpenes; D016328:NF-kappa B; D010975:Platelet Aggregation Inhibitors; D047428:Protein Kinase Inhibitors; D009569:Nitric Oxide; C030419:andrographolide; D013928:Thromboxane A2; D000244:Adenosine Diphosphate; D003094:Collagen; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D011494:Protein Kinases; D006152:Cyclic GMP; D002118:Calcium