Activation of human platelets by C5a-stimulated neutrophils: a role for cathepsin G.
Human platelets can be stimulated by recombinant human fifth component of complement (rhC5a) in the presence of human neutrophils. After challenge with N-formyl-Met-Leu-Phe or rhC5a, concentrated neutrophils release cathepsin G into the supernatant. The concentrations of cathepsin G recovered by titration of the enzymatic activity correlate with the capability of these supernatants to induce platelet stimulation as measured by serotonin release. Cathepsin G purified from neutrophil granules triggered platelet aggregation and serotonin release independent of arachidonic acid metabolites and platelet-activating factor formation. A concentration of 100 nM of cathepsin G, which was reached in the surrounding space of activated neutrophils, induced a 50% platelet stimulation. Three distinct antiproteinases were tested against cathepsin G-induced platelet activation. Z-Gly-Leu-Phe-CH2Cl, a specific inhibitor of cathepsin G enzymatic activity, proved to be nonspecific in our biological system. By contrast, alpha 1-antichymotrypsin and alpha 1-antitrypsin displayed specific activities. The physiological specific inhibitor of cathepsin G, alpha 1-antichymotrypsin, was the most potent and was used in the rhC5a-induced neutrophils-mediated platelet activation. A complete inhibition was achieved, showing that release of cathepsin G from neutrophils accounts for platelet activation. Such a chain of events involving C5a, neutrophils, cathepsin G, and platelets may be of relevance in certain inflammatory states, particularly the adult respiratory distress syndrome.
Ferrer-Lopez
P
P
Unité Associée IP-Institut National de la Santé et de la Recherche, Médicale 285, Institut Pasteur, France.
Renesto
P
P
Schattner
M
M
Bassot
S
S
Laurent
P
P
Chignard
M
M
D000595:Amino Acid Sequence; D001241:Aspirin / Q000494:pharmacology; D001381:Azepines / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D056649:Cathepsin G; D002403:Cathepsins / Q000097:blood* / Q000302:isolation & purification / Q000494:pharmacology; D015936:Complement C5a / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D010196:Pancreatic Elastase / Q000097:blood / Q000302:isolation & purification; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors; D015539:Platelet Activation; D011480:Protease Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D012697:Serine Endopeptidases; D012701:Serotonin / Q000097:blood; D014230:Triazoles / Q000494:pharmacology
D001381:Azepines; D009842:Oligopeptides; D010972:Platelet Activating Factor; D011480:Protease Inhibitors; D011994:Recombinant Proteins; D014230:Triazoles; C052518:WEB 2086; D012701:Serotonin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015936:Complement C5a; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D010196:Pancreatic Elastase; D001241:Aspirin