title: Inhibition of human platelet aggregation by eosinophils.
abstract: OBJECTIVE
  The relationship between the activity of eosinophils and platelets has been observed in recent decades by many scientists. These observations include increased numbers of eosinophils associated with platelet disorders, including changes in the coagulation cascade and platelet aggregation. Based on these observations, the interaction between eosinophils and platelets in platelet aggregation was analyze.
  
  
  METHODS
  Human platelets were incubated with eosinophil cytosolic fraction, promyelocytic human HL-60 clone 15 cell lineage, and eosinophil cationic protein (ECP). Platelet rich plasma (PRP) aggregation was induced by adenosine diphosphate, platelet activating factor, arachidonic acid, and collagen, and washed platelets (WP) were activated by thrombin.
  
  
  RESULTS
  Aggregation induced by all agonists was dose dependently inhibited by eosinophil cytosolic fraction. This inhibition was only partially reversed by previous incubation of the eosinophils with l-Nitro-Arginine-Methyl-Ester (l-NAME). Previous incubation with indomethacin did not prevent the cytosolic fraction induced inhibition. The separation of eosinophil cytosolic fraction by gel filtration on Sephadex G-75 showed that the inhibitory activity was concentrated in the lower molecular weight fraction. HL-60 clone 15 cells differentiated into eosinophils for 5 and 7 day were able to inhibit platelet aggregation. The ECP protein inhibited the platelet aggregation on PRP and WP. This inhibition was more evident in WP, and the citotoxicity MTT assay proved the viability of tested platelets, showing that the observed inhibition by the ECP protein does not occur simply by cell death.
  
  
  CONCLUSIONS
  Our results indicate that eosinophils play a fundamental role in platelet aggregation inhibition.
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil. maziero@fcm.unicamp.br
authors.forename: Aline Mendes
authors.initials: AM
authors.lastname: Maziero
authors.forename: Raquel
authors.initials: R
authors.lastname: Lorenzetti
authors.forename: José Luiz
authors.initials: JL
authors.lastname: Donato
authors.forename: Sergio
authors.initials: S
authors.lastname: Lilla
authors.forename: Gilberto
authors.initials: G
authors.lastname: De Nucci
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002850:Chromatography, Gel / Q000379:methods; D003094:Collagen / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism*; D003911:Dextrans; D004804:Eosinophils / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008970:Molecular Weight; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013917:Thrombin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D003911:Dextrans; D010972:Platelet Activating Factor; D016718:Arachidonic Acid; D000244:Adenosine Diphosphate; D003094:Collagen; C025614:sephadex; D013917:Thrombin; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin
keywords: Eosinophil cationic protein; Eosinophil cytosolic fraction; Eosinophil proteins; Platelet aggregation inhibition