title: Antithrombotic potential of blockers of store-operated calcium channels in platelets.
abstract: OBJECTIVE
  Platelet Orai1 channels mediate store-operated Ca(2+) entry (SOCE), which is required for procoagulant activity and arterial thrombus formation. Pharmacological blockage of these channels may provide a novel way of antithrombotic therapy. Therefore, the thromboprotective effect of SOCE blockers directed against platelet Orai1 is determined.
  
  
  RESULTS
  Candidate inhibitors were screened for their effects on SOCE in washed human platelets. Tested antagonists included the known compounds, SKF96365, 2-aminoethyl diphenylborate, and MRS1845 and the novel compounds, Synta66 and GSK-7975A. The potency of SOCE inhibition was in the order of Synta66>2-aminoethyl diphenylborate>GSK-7975A>SKF96365>MRS1845. The specificity of the first 3 compounds was verified with platelets from Orai1-deficient mice. Inhibitory activity on procoagulant activity and high-shear thrombus formation was assessed in plasma and whole blood. In the presence of plasma, all 3 compounds suppressed platelet responses and restrained thrombus formation under flow. Using a murine stroke model, arterial thrombus formation was provoked in vivo by transient middle cerebral artery occlusion. Postoperative administration of 2-aminoethyl diphenylborate markedly diminished brain infarct size.
  
  
  CONCLUSIONS
  Plasma-soluble SOCE blockers such as 2-aminoethyl diphenylborate suppress platelet-dependent coagulation and thrombus formation. The platelet Orai1 channel is a novel target for preventing thrombotic events causing brain infarction.
authors.affiliation: Department of Biochemistry and Cardiovascular Centre, Cardiovascular Research Institute Maastricht, University of Maastricht, The Netherlands.
authors.forename: Roger
authors.initials: R
authors.lastname: van Kruchten
authors.forename: Attila
authors.initials: A
authors.lastname: Braun
authors.forename: Marion A H
authors.initials: MA
authors.lastname: Feijge
authors.forename: Marijke J E
authors.initials: MJ
authors.lastname: Kuijpers
authors.forename: Ronmy
authors.initials: R
authors.lastname: Rivera-Galdos
authors.forename: Peter
authors.initials: P
authors.lastname: Kraft
authors.forename: Guido
authors.initials: G
authors.lastname: Stoll
authors.forename: Christoph
authors.initials: C
authors.lastname: Kleinschnitz
authors.forename: Edouard M
authors.initials: EM
authors.lastname: Bevers
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nieswandt
authors.forename: Johan W M
authors.initials: JW
authors.lastname: Heemskerk
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000502:physiology; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D000071740:ORAI1 Protein; D015539:Platelet Activation / Q000187:drug effects
chemical_list: C538758:2-aminoethyl diphenylborinate; D001896:Boron Compounds; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D005343:Fibrinolytic Agents; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse; D002118:Calcium