title: Mechanisms of antiplatelet activity of nifedipine: role of peroxisome proliferator-activated receptor-β-γ-dependent processes.
abstract: OBJECTIVE
  Nifedipine, an L-type calcium channel blocker, is widely used in the treatment of hypertension and coronary heart diseases, and also exhibits an antiplatelet activity. Activation of peroxisome proliferator-activated receptors (PPARs; α, β/δ, and γ) inhibits the platelet aggregation. Therefore, the purpose of this study was to evaluate the contribution of PPAR-mediated processes to the antiplatelet activity of nifedipine.
  
  
  RESULTS
  We assessed human platelet aggregation by using an aggregometer and measured several platelet activating markers and related signaling pathways in platelets treated with nifedipine in the presence or absence of PPAR agonists. Nifedipine treatment (1, 5  μmol/l) dose-dependently increased the activity and intracellular expression of PPAR-β/-γ by inhibiting the release of PPAR-β/-γ from activated platelets. Nifedipine treatment also upregulated cyclic 3',5'-cyclic monophosphate (GMP)/protein kinase G (PKG) expression, and increased PI(3)K/Akt pathway, endothelial nitric oxide synthase, and soluble guanylyl cyclase activities. In the presence of a selective PPAR-β antagonist (GSK0660) or PPAR-γ antagonist (GW9662), the inhibitory effects of nifedipine on collagen-induced platelet aggregation, intracellular Ca mobilization, and protein kinase C (PKC-α) activation were abrogated. Similarly, PPAR-β-γ antagonists markedly attenuated nifedipine-mediated upregulation of nitric oxide/cyclic GMP/PKG cascade. In a mouse model of thrombosis, the administration of nifedipine substantially inhibited fluorescein sodium-induced vessel thrombus formation; however, the antithrombotic effect was considerably reduced in the presence of PPAR-β/-γ antagonists.
  
  
  CONCLUSIONS
  This study is the first to show that the PPAR-β/-γ-dependent upregulation of PI(3)K/Akt/nitric oxide/cyclic GMP/PKG pathway and the inhibition of PKC-α activity and intracellular Ca(+) mobilization in platelets may be the mechanisms underlying the antiplatelet and antithrombotic activities of nifedipine.
authors.affiliation: aGraduate Institute of Life Sciences, National Defense Medical Center bDivision of Nuclear Medicine, Taipei City Hospital Zhongxiao Branch cDepartment of Biomedical Imaging and Radiological Sciences, National Yang Ming University dDepartment of Paediatrics, Tri-Service General Hospital eDepartment of Biomedical Engineering, National Defense Medical Center, Taipei fInstitute of Medical Sciences, Tzu Chi University, Hualien gDepartment of Biotechnology, Asia University hChina Medical University Hospital, China Medical University, Taichung, Taiwan.
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Shih
authors.forename: Ming-Hsien
authors.initials: MH
authors.lastname: Lin
authors.forename: Hueng-Chuen
authors.initials: HC
authors.lastname: Fan
authors.forename: Fu-Chi
authors.initials: FC
authors.lastname: Chen
authors.forename: Tz-Chong
authors.initials: TC
authors.lastname: Chou
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000097:blood; D051379:Mice; D008813:Mice, Inbred ICR; D009543:Nifedipine / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D047495:PPAR gamma / Q000502:physiology*; D048068:PPAR-beta / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D047495:PPAR gamma; D048068:PPAR-beta; D010975:Platelet Aggregation Inhibitors; D009569:Nitric Oxide; D007770:L-Lactate Dehydrogenase; D019001:Nitric Oxide Synthase; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D017869:Cyclic GMP-Dependent Protein Kinases; D009543:Nifedipine; D002118:Calcium