Plasma antiproteinase screen and neutrophil-mediated platelet activation. A major role played by alpha 1 antitrypsin.
Upon activation, human polymorphonuclear neutrophils (PMN) release two serine proteinases, cathepsin G (Cat.G) and elastase (HLE), which in turn synergize to activate nearby platelets. We looked for the inhibitory effect of plasma and the involvement of alpha 1 antichymotrypsin (alpha 1 ACT) and alpha 1 antitrypsin (alpha 1 AT), on this cell-to-cell cooperation. It was observed that inhibition by plasma of PMN-mediated platelet activation was rather correlated with an effect on HLE (r = 0.95) than on Cat.G (r = 0.65) enzymatic activity. Purified alpha 1 AT suppressed in a concentration-dependent manner HLE activity present in the supernatant of activated PMN. When HLE was fully blocked, alpha 1 AT started to inhibit Cat.G activity. By contrast and as expected, purified alpha 1 ACT inhibited only Cat.G activity. Using specific blocking polyclonal antibodies against alpha 1 AT and alpha 1 ACT, it was demonstrated that the inhibitory effect of plasma vs. HLE was entirely mediated by alpha 1 AT. By contrast, blockade of Cat.G activity was only partly due to plasma alpha 1 ACT and around 50% was attributable to alpha 1 AT. When plasma from patients with an acute inflammatory state was used in place of plasma from normal subjects, the inhibitory effect was more pronounced, while plasma depleted in alpha 1 AT and alpha 1 ACT was less effective. These data indicate a predominant role of alpha 1 AT in the inhibition by plasma of the PMN-mediated platelet activation.
Chignard
M
M
Unité de Pharmacologie Cellulaire, Unité Associée IP/INSERM no. 285, Institut Pasteur, Paris, France.
Hazouard
E
E
Renesto
P
P
Laine
A
A
Guidet
B
B
Offenstadt
G
G
D000595:Amino Acid Sequence; D001769:Blood; D056649:Cathepsin G; D002403:Cathepsins / Q000037:antagonists & inhibitors; D006801:Humans; D019272:Leukocyte Elastase; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000201:enzymology / Q000502:physiology*; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors; D015539:Platelet Activation / Q000502:physiology*; D011480:Protease Inhibitors / Q000097:blood* / Q000276:immunology; D012697:Serine Endopeptidases; D000515:alpha 1-Antitrypsin / Q000502:physiology*
D011480:Protease Inhibitors; D000515:alpha 1-Antitrypsin; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D010196:Pancreatic Elastase; D019272:Leukocyte Elastase