The combinations of rat anti-mouse CD11b-APC, CD45-PerCP-Cy5

The combinations of rat anti-mouse CD11b-APC, CD45-PerCP-Cy5.5 and GR-1-FITC antibodies and isotype controls (all from BD Biosciences PharMigen) were used for labeling leukocytes. activates neutrophils and contributes to a chronic inflammatory state and pulmonary dysfunction in PTC299 SCD. Inhibition of platelet activation may be useful to decrease tissue injury in SCD, particularly during the early stages Rabbit Polyclonal to EDG4 of vaso-occlusive crises. Keywords:platelet activation, sickle cell disease (SCD), inflammation, neutrophil activation, oxidative burst, clopidogrel, P-selectin == INTRODUCTION == Sickle cell disease (SCD) is the most common genetic hematological disorder in the United States. Vaso-occlusion characteristic of SCD has been viewed historically as resulting PTC299 from deformed red blood cells (RBCs) that mechanically obstruct capillaries to produce tissue hypoxia.1Present therapies for SCD are geared toward decreasing the concentration or polymerization rate of sickle hemoglobin.2Recently, a modified paradigm has emerged suggesting that this wide spectrum of clinical manifestations of SCD results in part from recurrent episodes of disseminated microvascular ischemia/reperfusion PTC299 (I/R) injury.3,4I/R triggers vascular inflammation characterized by increased adhesion of leukocytes58and sickle RBCs9to vascular endothelium as well as activation of coagulation,1012blood platelets,1320neutrophils,7monocytes8,2123and NKT cells.24Since it has seen demonstrated that blockade of P-selectin-mediated platelet-leukocyte aggregation is beneficial in the animal models of vascular injury,25we reasoned that platelet-leukocyte aggregation might contribute to the vascular inflammation and tissue injury that occurs in SCD. While increased formation of platelet-monocyte21and platelet-RBC15aggregates in SCD is usually well established, there are conflicting data regarding the occurrence of platelet-neutrophil aggregates (PNAs) in patients with SCD.18,21The question of neutrophil activation in SCD is an important one, since activated neutrophils play a major role in evoking vascular injury during I/R by adhering to blood vessels and releasing reactive oxygen species26. In vitro, binding of activated washed platelets to purified neutrophils results in their activation2729and in vivo studies demonstrate increased formation of neutrophil-platelet aggregates as a result of inflammation.30,31 In this study, we investigated platelet-neutrophil aggregation in SCD using blood obtained from NY1DD sickle mice32,33and SCD patients. We found that both mice and people with SCD have markedly increased platelet-neutrophil aggregates (PNAs) compared to appropriate controls. Anti-platelet brokers such as clopidogrel or anti-P-selectin PTC299 antibodies as well as platelet depletion strongly suppressed formation of platelet-leukocyte aggregates and platelet-dependent neutrophil activation and pulmonary injury in sickle mice, indicating that anti-platelet therapy may be helpful for limiting vascular inflammation and injury in SCD. == MATERIALS AND METHODS == == Human subjects == Peripheral venous blood samples were obtained from consenting adult SCD patients (hemoglobin S homozygotes) and age and race matched healthy control subjects (normal hemoglobin A) during a routine health examination at the Adult Hemoglobinopathy Clinic at the Washington University. All patients were at steady state, i.e. reported no more than common pain at the time of phlebotomy. The human protocol was approved by the Institutional Review Boards of the Washington University and the University of Virginia. == Mice == Transgenic NY1DD mice on a C57BL6 genetic background were obtained from Robert P. Hebbel (University of Minnesota) and used as a model for SCD.33NY1DD mice are deficient in mouse -globin and express a fused human -S-globin transgene. These mice have a normal hematocrit at baseline, but exhibit multiple organ damage and leukocytosis.32H/R evokes hemolysis associated with the development of increased inflammation. Congenic C57BL/6 female mice 812 weeks old were used as wild-type (WT) sex and age matched controls (Jackson Laboratory, Bar Harbor, ME). Experimental procedures were approved by the University of Virginia Animal Care and Use Committee. == Assessment of platelet activation in whole blood == Attempts to prepare platelets from sickle mice were complicated by the presence of platelet-platelet and platelet-leukocyte aggregates. Hence, platelet function was assessed in whole blood. Details about mouse blood collection and assessment of platelet activation in whole blood are described in theSupplemental Methods. == Platelet-leukocyte aggregates in whole blood == For mouse studies, heparin-anticoagulated blood was incubated with rat antimouse CD16/CD32 antibody to block the Fc III/II receptor. A 4-color flow cytometry assay was developed to analyze simultaneous platelet binding to neutrophils and monocytes in whole blood. Rat anti-mouse CD41-PE or rat anti-mouse.