Article

Fungal antioxidant pathways promote survival against neutrophils during infection.

Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
The Journal of clinical investigation (Impact Factor: 13.77). 06/2012; 122(7):2482-98. DOI: 10.1172/JCI63239
Source: PubMed

ABSTRACT Filamentous fungi are a common cause of blindness and visual impairment worldwide. Using both murine model systems and in vitro human neutrophils, we found that NADPH oxidase produced by neutrophils was essential to control the growth of Aspergillus and Fusarium fungi in the cornea. We demonstrated that neutrophil oxidant production and antifungal activity are dependent on CD18, but not on the β-glucan receptor dectin-1. We used mutant A. fumigatus strains to show that the reactive oxygen species-sensing transcription factor Yap1, superoxide dismutases, and the Yap1-regulated thioredoxin antioxidant pathway are each required for protection against neutrophil-mediated oxidation of hyphae as well as optimal survival of fungal hyphae in vivo. We also demonstrated that thioredoxin inhibition using the anticancer drug PX-12 increased the sensitivity of fungal hyphae to both H2O2- and neutrophil-mediated killing in vitro. Additionally, topical application of PX-12 significantly enhanced neutrophil-mediated fungal killing in infected mouse corneas. Cumulatively, our data reveal critical host oxidative and fungal anti-oxidative mediators that regulate hyphal survival during infection. Further, these findings also indicate that targeting fungal anti-oxidative defenses via PX-12 may represent an efficacious strategy for treating fungal infections.

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    • "For example, in fungi, following activation by H 2 O 2 -induced oxidation of specific cysteines, AP-1-like transcription factors promote expression of ROS defense and repair enzymes (reviewed in Veal et al., 2007). In pathogenic fungi, this is a vital response to ROS generated by host immune cells (Guo et al., 2011; Leal et al., 2012). As well as the activation of ROS defenses, H 2 O 2 signals also regulate fundamental processes, including cell division, differentiation, migration, and death. "
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    ABSTRACT: H2O2 can cause oxidative damage associated with age-related diseases such as diabetes and cancer but is also used to initiate diverse responses, including increased antioxidant gene expression. Despite significant interest, H2O2-signaling mechanisms remain poorly understood. Here, we present a mechanism for the propagation of an H2O2 signal that is vital for the adaptation of the model yeast, Schizosaccharomyces pombe, to oxidative stress. Peroxiredoxins are abundant peroxidases with conserved antiaging and anticancer activities. Remarkably, we find that the only essential function for the thioredoxin peroxidase activity of the Prx Tpx1(hPrx1/2) in resistance to H2O2 is to inhibit a conserved thioredoxin family protein Txl1(hTxnl1/TRP32). Thioredoxins regulate many enzymes and signaling proteins. Thus, our discovery that a Prx amplifies an H2O2 signal by driving the oxidation of a thioredoxin-like protein has important implications, both for Prx function in oxidative stress resistance and for responses to H2O2.
    Cell Reports 11/2013; 5(5). DOI:10.1016/j.celrep.2013.10.036 · 7.21 Impact Factor
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    • "macrophages and dendritic cells (DCs) (Gross et al., 2006; Hara et al., 2007; Hsu et al., 2007), resulting in defects in the formation of T helper 17 (Th17) cells (LeibundGut-Landmann et al., 2007) and in susceptibility to mucosal candidiasis in humans (Glocker et al., 2009). Other studies link Dectin-1 (Li et al., 2011; Werner et al., 2009), CARD9 (Wu et al., 2009), integrins, and Syk to the activation of antimicrobial effectors, the latter exemplified by b2-integrin (CD18) and Syk-dependent neutrophil NADPH oxidase activity against sterile fungal hyphae (Boyle et al., 2011; Leal et al., 2012). In vitro, Syk (À/À) neutrophils are defective in the uptake of opsonized bacteria and in degranulation, resulting in delayed staphylococcal clearance (Van Ziffle and Lowell, 2009). "
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    Cell Reports 11/2012; DOI:10.1016/j.celrep.2012.10.026 · 7.21 Impact Factor
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    ABSTRACT: NADPH-oxidase mediated production of Reactive Oxygen Species (ROS) by alveolar macrophages and neutrophils is a critical mechanism for immune defence against Aspergillus fumigatus. Fungal oxidative stress response includes enzymatic response by superoxide dismutases (SOD), catalases, and enzymes from the thioredoxin and glutathione systems, which are regulated by the transcription factor Yap1. Secondary metabolites are also involved in defense against ROS. Some of the secondary metabolites clusters are controlled by the transcriptional regulator LaeA. The redundancy of antioxidant systems, and the variable impact of SOD or catalase gene deletions on in vitro oxidative stress sensitivity and in vivo virulence suggest a complex regulation of oxidative stress response in A. fumigatus, making high-throughput approaches, such as microarray or next generation sequencing (NGS), highly relevant to study their respective role. These approaches have been widely applied to A fumigatus, in order to characterize its metabolic response to different stresses mimicking in vivo conditions (such as antifungals, or neutrophils), or to transcription factor deletion (including laeA). In some studies, oxidative stress response process and antioxidant enzymes have been identified as key metabolic pathways. However, oxidative stress response has not been analysed systematically and a further data analysis could be helpful to clarify the role of A. fumigatus antioxidant systems and, potentially, to identify new drug targets. In this review, we synthesized available A. fumigatus microarrays and NGS data, focusing of the role of antioxidant systems. We analysed the different methodologies that were used for transcriptomic analysis, and we compared biological processes and antioxidant system modulations in A. fumigatus exposed to stress.
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