Impaired Immunity and Enhanced Resistance to Endotoxin in the Absence of Neutrophil Elastase and Cathepsin G

Abstract

While the critical role of reactive oxygen intermediates (ROI) in the microbicidal activity of polymorphonuclear granulocytes is well established, the function of the nonoxidative effector mechanisms in vivo remains unclear. Here we show that mice deficient in the neutrophil granule serine proteases elastase and/or cathepsin G are susceptible to fungal infections, despite normal neutrophil development and recruitment. The protease deficiencies but not the absence of ROI leads to enhanced resistance to the lethal effects of endotoxin LPS, although normal levels of TNFalpha are produced. The data demonstrate a critical role of the nonoxidative effector mechanisms of neutrophils in host immunity and immunopathology and identify elastase and cathepsin G as effectors in the endotoxic shock cascade downstream of TNFalpha.

The contribution of PARs to inflammation and immunity to fungi

“…41 PMN proteases triggered by fungi could be responsible for PAR 1 activation as well as PAR 2 deactivation, a finding consistent with the ability of proteases to contribute to fungal septic shock through vascular damage and plasma leakage associated with tissue destruction in the lungs. 42 TLR4 and TLR2 induced distinct patterns of degranulation against either fungus, 22 and degranulated PMNs from TLR2-or TLR4-deficient PMNs have disparate activity on PAR functioning. It is therefore conceivable that an action on the protease / antiprotease balance may contribute to the ability of TLRs to condition heterologous or homologous PAR activation / desensitization at the infectious site.…”

ATP-Mediated Killing of Intracellular Mycobacteria by Macrophages Is a P2X7-Dependent Process Inducing Bacterial Death by Phagosome-Lysosome Fusion

“…These were cultured in RPMI (Life Technologies) supplemented with 10% FCS and 2 mM glutamine. P2X 7 Ϫ/Ϫ , p47 phoxϪ/Ϫ , and inducible NO synthase (iNOS) Ϫ/Ϫ mice were kind gifts from I. P. Chessell (Glaxo Wellcome, Cambridge, U.K.), A. W. Segal (University College of London, London, U.K.), and F. Y. Liew (University of Glasgow, Glasgow, U.K.), respectively, and have been previously described (23)(24)(25). The genetic backgrounds of these knockout mice were, respectively, C57/129, C57, and 129.…”

“…Macrophages from iNOS Ϫ/Ϫ mice are therefore unable to up-regulate nitrogen radical production (25). p47 phox is a key enzyme in the NADPH reductase pathway, and mice with a targeted disruption of this gene are unable to produce reactive oxygen radicals (24).…”

The tetraspanin CD63 is involved in granule targeting of neutrophil elastase

“…3,4 The precise functions of the hematopoietic serine proteases-neutrophil elastase (NE), cathepsin G, proteinase 3, and azurocidin-are not fully known, but all 4 are thought to be important in the innate immunity function provided by neutrophils. 5,6 These proteases are synthesized as transient proforms that become catalytically active (except for azurocidin) by removal of an N-terminal propeptide after granule targeting. 7,8 Lysosome hydrolases and granzymes use a mannose-6-phosphate (MP) signal and binding to an MP receptor for targeting, 9,10 but the signals for the targeting of hematopoietic serine proteases are not yet known.…”