title: Nicergoline inhibits human platelet Ca(2+) signalling through triggering a microtubule-dependent reorganization of the platelet ultrastructure.
abstract: OBJECTIVE
  Recently, we demonstrated that a pericellular Ca(2+) recycling system potentiates agonist-evoked Ca(2+) signalling and granule secretion in human platelets and hypothesized a role for the membrane complex (MC) in orchestrating the accumulation of Ca(2+) in the pericellular region. Previous work has demonstrated that treatment with high concentrations of nicergoline may disrupt the MC through an ability to trigger a re-organization of the dense tubular system. Experiments were therefore performed to assess whether nicergoline-induced changes in platelet ultrastructure affects thrombin-evoked Ca(2+) fluxes and dense granule secretion.
  
  
  METHODS
  Thrombin-evoked Ca(2+) fluxes were monitored in Fura-2- or Fluo-5N-loaded human platelets, or using platelet suspensions containing Fluo-4 or Rhod-5N K(+) salts. Fluorescence microscopy was utilized to monitor microtubule structure and intracellular Ca(2+) store distribution in TubulinTracker- and Fluo-5N-loaded platelets respectively. Dense granule secretion was monitored using luciferin-luciferase.
  
  
  RESULTS
  Nicergoline treatment inhibited thrombin-evoked Ca(2+) signalling and induced alterations in the microtubule structure and the distribution of intracellular Ca(2+) stores in platelets. Nicergoline altered the generation and spreading of thrombin-induced pericellular Ca(2+) signals and almost completely prevented dense granule secretion. Stabilization of microtubules using taxol reversed most effects of nicergoline on platelet Ca(2+) signalling and partially reversed its effects on dense granule secretion.
  
  
  CONCLUSIONS
  Nicergoline-induced alterations to platelet ultrastructure disrupt platelet Ca(2+) signalling in a manner that would be predicted if the MC had been disrupted. These data suggest that nicergoline may be a useful prototype for the discovery of novel MC-disrupting anti-thrombotics.
authors.affiliation: Institute for Science and Technology in Medicine, Keele University, Guy Hilton Research Centre, Stoke-on-Trent, Staffordshire, UK.
authors.forename: T
authors.initials: T
authors.lastname: Walford
authors.affiliation: Institute for Science and Technology in Medicine, Keele University, Guy Hilton Research Centre, Stoke-on-Trent, Staffordshire, UK.
authors.forename: F I
authors.initials: FI
authors.lastname: Musa
authors.affiliation: Institute for Science and Technology in Medicine, Keele University, Guy Hilton Research Centre, Stoke-on-Trent, Staffordshire, UK.
authors.forename: A G S
authors.identifier: http://orcid.org/0000-0003-2413-4823
authors.initials: AG
authors.lastname: Harper
mesh_terms: D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D006801:Humans; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects* / Q000648:ultrastructure; D009530:Nicergoline / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D017239:Paclitaxel / Q000494:pharmacology; D022142:Secretory Vesicles / Q000187:drug effects; D013917:Thrombin / Q000037:antagonists & inhibitors / Q000494:pharmacology
chemical_list: D013917:Thrombin; D009530:Nicergoline; D017239:Paclitaxel; D002118:Calcium