P-selectin-mediated platelet-neutrophil aggregate formation activates neutrophils in mouse and human sickle cell disease.
OBJECTIVE
To determine the role of platelets in stimulating mouse and human neutrophil activation and pulmonary injury in sickle cell disease (SCD).


RESULTS
Both platelet and neutrophil activation occur in SCD, but the interdependence of these events is unknown. Platelet activation and binding to leukocytes were measured in mice and patients with SCD and in controls. Relative to controls, blood obtained from mice or patients with SCD contained significantly elevated platelet-neutrophil aggregates (PNAs). Both platelets and neutrophils found in sickle PNAs were activated. Multispectral imaging (ImageStream) and conventional flow cytometry revealed a subpopulation of activated neutrophils with multiple adhered platelets that expressed significantly more CD11b and exhibited greater oxidative activity than single neutrophils. On average, wild-type and sickle PNAs contained 1.1 and 2.6 platelets per neutrophil, respectively. Hypoxia/reoxygenation induced a further increase in PNAs in mice with SCD and additional activation of both platelets and neutrophils. The pretreatment of mice with SCD with clopidogrel or P-selectin antibody reduced the formation of PNAs and neutrophil activation and decreased lung vascular permeability.


CONCLUSIONS
Our findings suggest that platelet binding activates neutrophils and contributes to a chronic inflammatory state and pulmonary dysfunction in SCD. The inhibition of platelet activation may be useful to decrease tissue injury in SCD, particularly during the early stages of vaso-occlusive crises.
Department of Medicine, University of Virginia, Charlottesville, USA.
Renata
R
Polanowska-Grabowska
Kori
K
Wallace
Joshua J
JJ
Field
Lanlin
L
Chen
Melissa A
MA
Marshall
Robert
R
Figler
Adrian R L
AR
Gear
Joel
J
Linden
D000755:Anemia, Sickle Cell / Q000097:blood* / Q000235:genetics / Q000276:immunology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D039481:CD11b Antigen / Q000378:metabolism; D023201:CD40 Ligand / Q000097:blood; D002199:Capillary Permeability; D016022:Case-Control Studies; D000077144:Clopidogrel; D005434:Flow Cytometry; D055554:Hemoglobin Subunits / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000276:immunology; D008168:Lung / Q000098:blood supply; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology*; D019007:P-Selectin / Q000037:antagonists & inhibitors / Q000097:blood*; D015539:Platelet Activation / Q000187:drug effects; D010973:Platelet Adhesiveness / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D016897:Respiratory Burst; D013988:Ticlopidine / Q000031:analogs & derivatives / Q000494:pharmacology
D000906:Antibodies; D039481:CD11b Antigen; D055554:Hemoglobin Subunits; D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D023201:CD40 Ligand; D000077144:Clopidogrel; D013988:Ticlopidine