Article

Tryptophan/kynurenine metabolism in human leukocytes is independent of superoxide and is fully maintained in chronic granulomatous disease

Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Blood (Impact Factor: 10.45). 09/2010; 116(10):1755-60. DOI: 10.1182/blood-2009-07-233734
Source: PubMed

ABSTRACT

In chronic granulomatous disease (CGD), defective phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity causes reduced superoxide anion (O(2)(·)) radical production leading to frequent infections as well as granulomas and impaired wound healing indicative of excessive inflammation. Based on recent mouse studies, the lack of O(2)(·)-dependent interferon γ (IFNγ)-induced synthesis of kynurenine (kyn), an anti-inflammatory tryptophan metabolite produced by indolamine 2,3 deoxygenase (IDO), was proposed as a cause of hyperinflammation in CGD and this pathway has been considered for clinical intervention. Here, we show that IFNγ induces normal levels of kynurenine in cultures of O(2)(·)-deficient monocytes, dendritic cells, and polymorphonuclear leukocytes from gp91(PHOX)- or p47(PHOX)-deficient human CGD donors. Kynurenine accumulation was dose- and time-dependent as was that of a downstream metabolite, anthranilic acid. Furthermore, urinary and serum levels of kynurenine and a variety of other tryptophan metabolites were elevated rather than suppressed in CGD donors. Although we did not specifically evaluate kyn metabolism in local tissue or inflamed sites in humans, our data demonstrates that O(2)(·) anion is dispensable for the rate-limiting step in tryptophan degradation, and CGD patients do not appear to have either hematopoietic cell or systemic deficits in the production of the anti-inflammatory kynurenine molecule.

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    • "On the host side, the activation of immune cell IDO (functional homolog of KynA in the host) was proposed to explain autoinflammatory disease in CGD patients. However, this role continues to be debated [10] [11] [12]. In addition, the impact of the kynurenine pathway on fungicidal activity of neutrophils was briefly discussed in one paper [47]. "
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    ABSTRACT: Pseudomonas aeruginosa is responsible for persistent infections in cystic fibrosis patients, suggesting an ability to circumvent innate immune defenses. This bacterium uses the kynurenine pathway to catabolize tryptophan. Interestingly, many host cells also produce kynurenine, which is known to control immune system homeostasis. We showed that most strains of P. aeruginosa isolated from cystic fibrosis patients produce a high level of kynurenine. Moreover, a strong transcriptional activation of kynA (the first gene involved in the kynurenine pathway) was observed upon contact with immune cells and particularly with neutrophils. In addition, using coculture of human neutrophils with various strains of P. aeruginosa producing no (ΔkynA) or a high level of kynurenine (ΔkynU or ΔkynA pkynA), we demonstrated that kynurenine promotes bacterial survival. In addition, increasing the amount kynurenine inhibits reactive oxygen species production by activated neutrophils, as evaluated by chemiluminescence with luminol or isoluminol or SOD-sensitive cytochrome c reduction assay. This inhibition is due neither to a phagocytosis defect nor to direct NADPH oxidase inhibition. Indeed, kynurenine has no effect on oxygen consumption by neutrophils activated by PMA or opsonized zymosan. Using in vitro reactive oxygen species-producing systems, we showed that kynurenine scavenges hydrogen peroxide and, to a lesser extent, superoxide. Kynurenine's scavenging effect occurs mainly intracellularly after bacterial stimulation, probably in the phagosome. In conclusion, the kynurenine pathway allows P. aeruginosa to circumvent the innate immune response by scavenging neutrophil reactive oxygen species production.
    Full-text · Article · Jun 2014 · Free Radical Biology and Medicine
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    • "O2- is produced by the NADPH oxidase, a multi-protein enzyme complex, which is inactive in resting phagocytes, but becomes activated after interaction of the phagocyte with pathogens and their subsequent engulfment in the phagosome [5]. Defects in the function of the NADPH oxidase result in a severe immunodeficiency, and individuals suffering from CGD (chronic granulomatous disease), a rare genetic disorder that is caused by mutations in NADPH oxidase genes, are highly susceptible to frequent and often life-threatening infections by bacteria and fungi [6,7]. "
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    ABSTRACT: Objective Molecular regulation of inflammation, especially, the role of effector cells in NADPH oxidase-mediated redox reactions for producing O2- (superoxide anion) is a critical step. This study explores the roles of macrophages and neutrophils and their cross-talk with extra-cellular matrix components in the light of the role essayed by T cells. Materials and Methods and Treatment: To clarify the role of NADPH oxidase in the pathophysiology of T cell-initiatedmacrophage-associated allergic asthma, we induced allergen dependent inflammation in a gp91phox−/− SKO (single knockout) and a gp91phox−/− MMP-12−/− DKO (double knockout) mouse and analysed trafficking and functionality of various cell types, the T cell function and T cell-macrophage interaction being given special emphasis. Results Composite asthma symptoms expressed in a more aggravated manner in both the KO (SKO and DKO) mice compared to WT indicating that some redundancy may exist in the response pathways of gp91phox and MMP-12. On the one hand, upregulation in macrophage functions such as proliferation, mixed lymphocyte reaction, and MCP-1 directed chemotaxis, may indicate that a regulatory cross-talk is switched on between T cell and macrophage and on the other, downregulation of respiratory burst response hints at a dichotomy in their signaling pathways. Increased B7.1 but reduced B7.2 and MHC class II expression on KO alveolar macrophages may suggest that a switching on-off mechanism is operative where alteration of co-stimulatory molecule expression selectively activating T cell is a critical step. Inference T cell mediated functions such as Th2 cytokine secretion, and T cell proliferation in response to OVA were upregulated synchronous with the overall robustness of the asthma phenotype. Conclusions As far as cell-cell interaction is concerned, the data is indicative of the existence of a plethora of networks where molecular switches may exist that selectively induce activation and deactivation of regulatory pathways that ultimately manifest in the overall response. gp91phox and MMP-12 either redundantly or synergistically but not additively, provide a regulatory checkpoint for restricting T cell cross-talk with macrophages and keep excessive tissue damage and ECM degradation during acute allergic inflammation under control.
    Full-text · Article · Feb 2013 · Allergy Asthma and Clinical Immunology
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    • "O2- is produced by the NADPH oxidase, a multi-protein enzyme complex, which is inactive in resting phagocytes, but becomes activated after interaction of the phagocyte with pathogens and their subsequent engulfment in the phagosome [4]. Defects in the function of the NADPH oxidase result in a severe immunodeficiency, and individuals suffering from CGD (chronic granulomatous disease), a rare genetic disorder that is caused by mutations in NADPH oxidase genes, are highly susceptible to frequent and often life-threatening infections by bacteria and fungi [5]. The microbicidal activity of ROS has generally been seen as the only beneficial function of these chemicals, and uncontrolled production of ROS has been implicated in tissue destruction and a number of disease states. "
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    ABSTRACT: The phenomena manifested during inflammation require interplay between circulating effector cells, local resident cells, soluble mediators and genetic host factors to establish, develop and maintain itself. Of the molecues involed in the initiation and perpetuation of acute allergic inflammation in asthma, the involvement of effector cells in redox reactions for producing O2- (superoxide anion) through the mediation of NADPH oxidase is a critical step. Prior data suggest that reactive oxygen species (ROS) produced by NADPH oxidase homologues in non-phagocytic cells play an important role in the regulation of signal transduction, while macrophages use a membrane-associated NADPH oxidase to generate an array of oxidizing intermediates which inactivate MMPs on or near them. Materials and Methods and Treatment To clarify the role of gp91phox subunit of NADPH oxidase in the development and progression of an acute allergic asthma phenotype, we induced allergen dependent inflammation in a gp91phox-/- single knockout and a gp91phox-/-MMP-12-/- double knockout mouse models. In the knockout mice, both inflammation and airway hyperreactivity were more extensive than in wildtype mice post-OVA. Although OVA-specific IgE in plasma were comparable in wildtype and knockout mice, enhanced inflammatory cell recruitment from circulation and cytokine release in lung and BALf, accompanied by higher airway resistance as well as Penh in response to methacholine, indicate a regulatory role for NADPH oxidase in development of allergic asthma. While T cell mediated functions like Th2 cytokine secretion, and proliferation to OVA were upregulated synchronous with the overall robustness of the asthma phenotype, macrophage upregulation in functions such as proliferation, and mixed lymphocyte reaction indicate a regulatory role for gp91phox and an overall non-involvement or synergistic involvement of MMP12 in the response pathway (comparing data from gp91phox-/- and gp91phox-/-MMP-12-/- mice).
    Full-text · Article · Jan 2012 · Clinical and Molecular Allergy
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