Quantum proteolysis by neutrophils: implications for pulmonary emphysema in α1-antitrypsin deficiency
Edward J. Campbell, … , Steve S. Boukedes, Caroline A. Owen
Edward J. Campbell, … , Steve S. Boukedes, Caroline A. Owen
Published August 1, 1999
Citation Information: J Clin Invest. 1999;104(3):337-344. https://doi.org/10.1172/JCI6092.
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Article

Quantum proteolysis by neutrophils: implications for pulmonary emphysema in α1-antitrypsin deficiency

Abstract

Traditional enzyme kinetics provide a poor explanation for the increased risk of lung injury in α1-antitrypsin (AAT) deficiency. Millimolar concentrations of leukocyte elastase, when released from single azurophil granules of activated neutrophils, lead to evanescent quantum bursts of proteolytic activity before catalysis is quenched by pericellular inhibitors. Herein, we tested the possibility that quantum proteolytic events are abnormal in AAT deficiency. We incubated neutrophils on opsonized fluoresceinated fibronectin in serum from individuals with various AAT phenotypes, and then measured and modeled quantum proteolytic events. The mean areas of the events in serum from heterozygous individuals (Pi MZ and Pi SZ) were slightly, but significantly, larger than those in serum from normal patients (Pi M). In marked contrast, mean areas of events in serum from AAT-deficient individuals were 10-fold larger than those in serum from normal patients. Diffusion modeling predicted that local elastase concentrations exceed AAT concentrations for less than 20 milliseconds and for more than 80 milliseconds in Pi M and Pi Z individuals, respectively. Thus, quantum proteolytic events are abnormally large and prolonged in AAT deficiency, leading directly to an increased risk of tissue injury in the immediate vicinity of activated neutrophils. These results have potentially important implications for the pathogenesis and prevention of lung disease in AAT deficiency.

Authors

Edward J. Campbell, Melody A. Campbell, Steve S. Boukedes, Caroline A. Owen

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Figure 4

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Size of quantum proteolytic events in serial dilutions of Pi M serum. PM...
Size of quantum proteolytic events in serial dilutions of Pi M serum. PMNs were incubated on opsonized, fluoresceinated fibronectin while bathed in serum that was either undiluted or diluted in HBSS: Pi M serum, open bars; Pi Z serum, hatched bars. Quantum proteolytic events were imaged and measured as described in Methods. Note the increase in event area when inhibitor concentration is reduced by diluting Pi M serum. The event areas in Pi M serum diluted 1:16 did not differ from those in undiluted Pi Z serum (P = 0.50). Data are mean ± SEM. *P < 0.001 vs. cells bathed in undiluted Pi M serum. The numbers of events measured in Pi M serum (undiluted and diluted 1:2, 1:4, 1:8, and 1:16) and undiluted Pi Z serum were 82, 64, 32, 56, 38, and 18, respectively.