title: P-selectin- and CD63-exposing platelet microparticles reflect platelet activation in peripheral arterial disease and myocardial infarction.
abstract: BACKGROUND
  Platelet-derived microparticles (PMPs) are generally considered a marker of platelet activation in cardiovascular disease. We studied the extent to which PMP subpopulations parallel platelet activation in vitro and in vivo.
  
  
  METHODS
  Using flow cytometry, we analyzed PMP subpopulations from resting and activated platelets in vitro (n = 6) as well as from plasma samples of patients with stable angina, peripheral arterial disease, or myocardial infarction [non-ST-elevation (NSTEMI) and ST-elevation (STEMI)] and from older, age- and sex-matched and young healthy individuals [n = 10 for all groups except NSTEMI (n = 11)]. Coagulation markers prothrombin fragment F(1 + 2) and thrombin-antithrombin complexes were determined by ELISA. The PMP-associated fraction of soluble (s)P-selectin was estimated by ELISA.
  
  
  RESULTS
  In vitro, stimulation of platelets with thrombin receptor-activating peptide (15 micromol/L) or the calcium ionophore A23187 (2.5 micromol/L) increased fractions of both platelets and PMPs exposing P-selectin or CD63 (P <0.001 for all). Whereas the number of PMPs released by A23187-stimulated platelets increased significantly (P <0.001), the number of PMPs released from thrombin receptor-activating peptide-stimulated platelets remained constant (P >0.05). Ex vivo, numbers of circulating PMPs were comparable in all groups. Compared with young persons, P-selectin-exposing PMPs were increased in older persons (P = 0.02) and were further increased in patients with NSTEMI (P = 0.007) and STEMI (P = 0.045). CD63-exposing PMPs were increased in patients with peripheral arterial disease (P = 0.041), NSTEMI (P = 0.001), and STEMI (P = 0.049). Subpopulations exposing P-selectin or CD63 correlated with each other (r = 0.581; P <0.001), but neither correlated with the plasma concentrations of F(1 + 2) or thrombin-antithrombin complexes. The PMP-associated fraction of sP-selectin constituted only 2.2 (4.7)% [mean (SD)] of total sP-selectin.
  
  
  CONCLUSIONS
  PMP subpopulations reflect platelet activation status better than the total number of PMPs. Increased concentrations of circulating PMP subpopulations are found in aging, and further increases are encountered in peripheral arterial disease and myocardial infarction.
authors.affiliation: Department of Cardiology and Laboratory of Experimental Clinical Chemistry, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands. p.m.vanderzee@amc.uva.nl
authors.forename: P Marc
authors.initials: PM
authors.lastname: van der Zee
authors.forename: Eva
authors.initials: E
authors.lastname: Biró
authors.forename: Yung
authors.initials: Y
authors.lastname: Ko
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: de Winter
authors.forename: C Erik
authors.initials: CE
authors.lastname: Hack
authors.forename: Augueste
authors.initials: A
authors.lastname: Sturk
authors.forename: Rienk
authors.initials: R
authors.lastname: Nieuwland
mesh_terms: D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000097:blood; D015703:Antigens, CD / Q000378:metabolism*; D000990:Antithrombin III; D001161:Arteriosclerosis / Q000097:blood*; D001792:Blood Platelets / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood*; D019007:P-Selectin / Q000378:metabolism*; D010446:Peptide Fragments / Q000097:blood; D010447:Peptide Hydrolases / Q000097:blood; D016491:Peripheral Vascular Diseases / Q000097:blood*; D015539:Platelet Activation; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D011516:Prothrombin; D060149:Tetraspanin 30
chemical_list: D015703:Antigens, CD; C554586:CD63 protein, human; D019007:P-Selectin; D010446:Peptide Fragments; D010980:Platelet Membrane Glycoproteins; D060149:Tetraspanin 30; C046193:antithrombin III-protease complex; C045879:prothrombin fragment 1.2; D000990:Antithrombin III; D011516:Prothrombin; D010447:Peptide Hydrolases