NADPH Oxidase Promotes Neutrophil Extracellular Trap Formation in Pulmonary Aspergillosis

Abstract

f NADPH oxidase is a crucial enzyme in antimicrobial host defense and in regulating inflammation. Chronic granulomatous disease (CGD) is an inherited disorder of NADPH oxidase in which phagocytes are defective in generation of reactive oxidant intermediates. Aspergillus species are ubiquitous, filamentous fungi, which can cause invasive aspergillosis, a major cause of morbidity and mortality in CGD, reflecting the critical role for NADPH oxidase in antifungal host defense. Activation of NADPH oxidase in neutrophils can be coupled to the release of proteins and chromatin that comingle in neutrophil extracellular traps (NETs), which can augment extracellular antimicrobial host defense. NETosis can be driven by NADPH oxidase-dependent and -independent pathways. We therefore undertook an analysis of whether NADPH oxidase was required for NETosis in Aspergillus fumigatus pneumonia. Oropharyngeal instillation of live Aspergillus hyphae induced neutrophilic pneumonitis in both wildtype and NADPH oxidase-deficient (p47 phox؊/؊ ) mice which had resolved in wild-type mice by day 5 but progressed in p47 phox؊/؊ mice. NETs, identified by immunostaining, were observed in lungs of wild-type mice but were absent in p47 phox؊/؊ mice. Using bona fide NETs and nuclear chromatin decondensation as an early NETosis marker, we found that NETosis required a functional NADPH oxidase in vivo and ex vivo. In addition, NADPH oxidase increased the proportion of apoptotic neutrophils. Together, our results show that NADPH oxidase is required for pulmonary clearance of Aspergillus hyphae and generation of NETs in vivo. We speculate that dual modulation of NETosis and apoptosis by NADPH oxidase enhances antifungal host defense and promotes resolution of inflammation upon infection clearance.

Zinc and Manganese Chelation by Neutrophil S100A8/A9 (Calprotectin) Limits Extracellular Aspergillus fumigatus Hyphal Growth and Corneal Infection

“…The anti-fungal activity of NETs has been attributed to CP in Candida albicans dermal abscess and intranasal infection models and in vitro in response to Aspergillus nidulans (37, 38). NETs have been identified in lungs of A. fumigatus infected mice (39, 40); however, rather than using resting conidia as used in the current study and which are the form that is normally inhaled and phagocytosed, those reports instilled the lungs with conidia that had been previously incubated for 7h, or with hyphal fragments. Although we are investigating NET formation during fungal corneal infection, those studies and ours indicate that CP, and therefore CP-laden NETs, are important to regulate growth of extracellular hyphae rather than conidia.…”

Effects ofAggregatibacter actinomycetemcomitansleukotoxin on neutrophil migration and extracellular trap formation

“…Our finding that some neutrophils were capable of performing NETosis although exhibiting osmotic swelling requires further attention in future research, but has in part been investigated by Ting-Beall et al (49), who reported that neutrophils can tolerate a certain range of osmolalities and regulate their volume in response to osmotic stress. Importantly, it is known that NETosis occurs only under conditions where oxygen is present and that the enzyme NADPH-oxidase, which requires oxygen to form ROS, is required for NET formation (34, 50). Therefore, it can be concluded that in an oxygenated setting, some neutrophils mount ROS-mediated defences to A. actinomycetemcomitans , while others are lysed by Ltx.…”

Elevated homocysteine levels in type 2 diabetes induce constitutive neutrophil extracellular traps

“…Chemical inducers such as PMA, LPS and microbes ( S. aureus and Aspergillus sp .) that induce NETs are NADPH oxidase dependent and are abrogated upon pharmacological inhibition of the enzyme284142. Mutations in gene(s) coding for NADPH oxidase subunit proteins leads to chronic granulomatous disease and these patients fail to make NETs43.…”