title: Red blood cell microparticles show altered inflammatory chemokine binding and release ligand upon interaction with platelets.
abstract: BACKGROUND
  Storage of red blood cells (RBCs) under standard blood bank conditions results in reduced structural integrity leading to membrane budding and release of microparticles. Microparticles express the blood group Duffy antigen known to bind multiple inflammatory chemokines, but the functional chemokine binding properties of microparticles are not known.
  
  
  METHODS
  We determined whether storage-induced microparticles show inflammatory chemokine binding through the expression of the Duffy antigen, comparing the binding properties to intact RBCs, and assessed microparticle interactions with platelets (PLTs) that release chemokines upon activation.
  
  
  RESULTS
  Intact RBCs retained similar equilibrium dissociation constants for CCL2 (Kd = 7.4 ± 0.9 nmol/L), CXCL8 (Kd = 7.9 ± 1.0 nmol/L), and CXCL1 (Kd = 4.4 ± 1.0 nmol/L) throughout storage. In contrast, microparticles increased in relative counts with storage, showed higher percentages of surface phosphatidylserine, and demonstrated impaired Duffy-dependent chemokine binding affinity with wider variability in dissociation constant for CXCL1(Kd = 362 ± 328 nmol/L; range, 0.6-2000 nmol/L). The altered chemokine binding affinity of RBC microparticles was associated with a propensity to release ligand upon incubation with PLTs. Relative quantification of microparticles, based on criteria of glycophorin A expression and size, underestimated particle numbers with functional chemokine binding, suggesting that glycophorin A-negative particles and nanoparticles contribute to overall chemokine binding capacity.
  
  
  CONCLUSIONS
  Microparticle burden in transfusates, as determined by functional chemokine binding, is considerable. Altered membrane properties of RBC microparticles enhance PLT interactions to increase inflammatory chemokine bioavailability in vitro.
authors.affiliation: Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Zeyu
authors.initials: Z
authors.lastname: Xiong
authors.forename: John
authors.initials: J
authors.lastname: Cavaretta
authors.forename: Lirong
authors.initials: L
authors.lastname: Qu
authors.forename: Donna Beer
authors.initials: DB
authors.lastname: Stolz
authors.forename: Darrell
authors.initials: D
authors.lastname: Triulzi
authors.forename: Janet S
authors.initials: JS
authors.lastname: Lee
mesh_terms: D001665:Binding Sites; D001792:Blood Platelets / Q000502:physiology*; D001793:Blood Preservation; D002450:Cell Communication; D018932:Chemokine CCL2 / Q000378:metabolism; D054360:Chemokine CXCL1 / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism*; D004375:Duffy Blood-Group System / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism
chemical_list: C111835:CCL2 protein, human; C475829:CXCL1 protein, human; C508606:CXCL8 protein, human; D018932:Chemokine CCL2; D054360:Chemokine CXCL1; D018925:Chemokines; D004375:Duffy Blood-Group System; D016209:Interleukin-8