Inhibition of leukocyte chemiluminescence by platelets: role of platelet-bound fibrinogen.
Tethering of PMNL by platelets via CD62P has been shown to cause PMNL activation. Co-incubation of purified PMNL with platelets that were activated with thrombin and then fixed and washed, resulted in the formation of platelet-PMNL conjugates as well as in a generation of reactive oxygen species that were measured as luminol-enhanced chemiluminescence. When platelets were thrombin activated in the presence of RGDS to prevent binding of fibrinogen to membrane receptors, they had a reduced capacity to adhere to PMNL, but ROS generation was enhanced. In samples of citrated whole blood RGDS as well as the more specific platelet fibrinogen receptor antagonist GR144053F or a dissociation of the platelet glycoprotein IIb/IIIa complex markedly enhanced ROS generation that was induced by stirring the samples for 10 min at 1000 rpm, by 175%, 95% and 138%, respectively. Removal of platelets from the whole blood samples also resulted in an enhancement of stirring-induced ROS generation, which was inversely correlated to the platelet count. These data provide some evidence that platelets are capable of inhibiting ROS generation in PMNL by a mechanism that involves platelet-bound fibrinogen and probably depends on fibrinogen-mediated platelet-PMNL contact.
Lösche
W
W
Friedrich-Schiller-University of Jena, Faculty of Medicine, Centre for Vascular Biology and Medicine/Erfurt, Germany. loesche@zmkh.ef.uni-jena.de
Temmler
U
U
Redlich
H
H
Vickers
J
J
Krause
S
S
Spangenberg
P
P
D001792:Blood Platelets / Q000378:metabolism* / Q000502:physiology; D018920:Coculture Techniques; D005340:Fibrinogen / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008163:Luminescent Measurements; D009504:Neutrophils / Q000378:metabolism*; D019007:P-Selectin / Q000378:metabolism; D010973:Platelet Adhesiveness; D011485:Protein Binding / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism
D019007:P-Selectin; D017382:Reactive Oxygen Species; D005340:Fibrinogen