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  • Title: Plasma antiproteinase screen and neutrophil-mediated platelet activation. A major role played by alpha 1 antitrypsin.
    Author: Chignard M, Hazouard E, Renesto P, Laine A, Guidet B, Offenstadt G.
    Journal: Biochim Biophys Acta; 1994 Dec 30; 1224(3):433-40. PubMed ID: 7803500.
    Abstract:
    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.
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