title: Leucocyte activation by collagen-stimulated platelets in whole blood.
abstract: Interaction between vascular cells plays an important role in the initial phases of the inflammatory process, but the mechanisms responsible for cell-cell communication are not fully understood. In this study, activation of leucocytes and platelets in heparinized whole blood was assessed using lumi-aggregometry. This technique enables simultaneous measurement of aggregation and oxygen radical production by monitoring impedance and luminol-amplified chemiluminescence (CL), respectively. Collagen induced aggregation and CL, depending on dose, and markedly enhanced subsequent aggregation and CL-response triggered by the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe). Collagen stimulation of whole blood down- and upregulated the expression of L-selectin and CD11b, respectively. Monoclonal antibodies against sialyl LewisX and P-selectin caused a pronounced inhibition of the oxidative burst, triggered by collagen itself or by a combination of collagen and fMet-Leu-Phe. Furthermore, the Arg-Gly-Asp-Ser(RGDS)-peptide effectively inhibited collagen-triggered aggregation and CL, and the subsequent enhancement of the fMet-Leu-Phe-induced responses. This suggests that fibrinogen plays a part in linking platelet GpIIb/IIIa with CD11b on the leucocyte surface. However, neither anti-CD11b nor the PI-peptide (containing the gamma-chain motif in fibrinogen that interacts with CD11b) counteracted the stimulatory effects of activated platelets on leucocyte functions. The selectin- and integrin-antagonizing substances were ineffective on the CL-responses induced by fMet-Leu-Phe itself. This study suggests that, through selectin- and integrin-dependent interaction, activated platelets potentiate leucocyte aggregation and oxygen radical production, which might be important for the outcome of inflammatory reactions.
authors.affiliation: Division of Medical Microbiology, Department of Molecular and Clinical Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden. torbe@mme.liu.se
authors.forename: T
authors.initials: T
authors.lastname: Bengtsson
authors.forename: M
authors.initials: M
authors.lastname: Grenegård
mesh_terms: D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology*; D006801:Humans; D007249:Inflammation; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; D017382:Reactive Oxygen Species; D009240:N-Formylmethionine Leucyl-Phenylalanine; C042205:methionyl-leucyl-phenylalanine; D003094:Collagen