Fungal antioxidant pathways promote survival against neutrophils during infection
Sixto M. Leal Jr., Chairut Vareechon, Susan Cowden, Brian A. Cobb, Jean-Paul Latgé, Michelle Momany, Eric Pearlman
Sixto M. Leal Jr., Chairut Vareechon, Susan Cowden, Brian A. Cobb, Jean-Paul Latgé, Michelle Momany, Eric Pearlman
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Research Article Immunology

Fungal antioxidant pathways promote survival against neutrophils during infection

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.

Authors

Sixto M. Leal Jr., Chairut Vareechon, Susan Cowden, Brian A. Cobb, Jean-Paul Latgé, Michelle Momany, Eric Pearlman

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Figure 9

Thioredoxin is required for hyphal survival during neutrophil exposure, oxidative stress, and corneal infection.

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Thioredoxin is required for hyphal survival during neutrophil exposure, ...
(A) To ascertain the role of the 5 putative thioredoxin proteins encoded in the A. fumigatus genome, hyphae were coincubated with a sublethal MOI of human neutrophils in RPMI or neutrophils plus varying doses of the thioredoxin inhibitor PX-12. (B) To examine the effect of thioredoxin inhibition on fungal growth during oxidative stress, Af-dsRed was coincubated with PX-12 and lethal and sublethal doses of H2O2. (C) To test the role of thioredoxin in mediating fungal survival during corneal infection, C57BL/6 mice were infected with Af-dsRed. At 0 and 6 hours after infection, 3 mM PX-12 or vehicle was applied topically to the infected mouse corneas. At 24 hours after infection, corneas were imaged, and (D) fungal dsRed expression and (E) CFU were quantified after infection. Three independent experiments (n = 5) were performed. *P < 0.05.