Host-derived Reactive Nitrogen Species mediate the<i>Cryptococcus neoformans</i>yeast-to-titan switch via fungal-derived superoxide

Zhou, Xin; Desanti, GE; May, Robin C.; Im, Dambuza; Ballou, Elizabeth R.

doi:10.1101/2021.03.01.433276

“…Our findings are also in agreement with a recent report that also highlights the importance of reactive nitrogen species (RNS) and ROS in TC formation (88). These authors also demonstrate that treatment of the cells with a SOD mimetic drug (MnTBAP) can also block titanization, a finding that supports the results presented in our work.…”

Section: Discussionsupporting

confidence: 93%

Pharmacological inhibition of titan-like cells formation suggests that accumulation of endogenous free radicals that correlate with mitochondrial changes are required to induce this transition inCryptococcus neoformans

García-Barbazán

¹

,

García-Rodas

²

,

Sachse

³

et al. 2022

Preprint

1

2

0

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Cryptococcus neoformans is an encapsulated yeast able to cause disease (mainly meningoencephalitis) among immunosuppressed patients, mostly HIV+. This yeast can form the so-called titan cells in vivo, which are cells of an abnormal larger size due to an increase in both the capsule and the cell body size (total size reaching between 50-70 microns). This phenomenon can be partially reproduced in vitro to obtain cells of an intermediate size (25-30 um), which have been denominated titan-like cells. In this work, we have screened 1,520 compounds from the Prestwick Chemical Library and identified off-patent drugs that inhibited titan-like cell formation in vitro. We developed an automated fluorescence-based microscopy assay and identified 64 compounds as possible inhibitors of titan-like cells in vitro. We chose 10 of these compounds to confirm their inhibitory effect and confirmed them as inhibitors of titan-like cells with dose-response curves. Several of the compounds identified had antioxidant properties (i.e., retinoic acid), indicating a possible role of free radicals during titan cell formation. Using fluorescent probes, we found that there was an endogenous accumulation of ROS during cell growth, which was inhibited in the presence of retinoic acid. Furthermore, we found that during titanization, there were significant changes in the mitochondria, which is the main organelle where ROS are produced. We hypothesize that an intracellular increase of free radicals at the mitochondria might be a triggering signal to induce titanization.

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“…Our findings are also in agreement with a recent report that also highlights the importance of reactive nitrogen species and ROS in TC formation ( 74 ). These authors demonstrated that treatment of the cells with a superoxide dismutase (SOD) mimetic drug (MnTBAP) can also block titanization, a finding that supports the results presented in our work.…”

Section: Discussionsupporting

confidence: 94%

Accumulation of endogenous free radicals is required to induce titan-like cell formation in Cryptococcus neoformans

García-Barbazán,

Torres-Cano,

García-Rodas

et al. 2024

mBio

1

0

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Cryptococcus neoformans is an encapsulated yeast able to cause disease (mainly meningoencephalitis) among immunosuppressed patients, mostly HIV+. This yeast can form the so-called titan cells in vivo , which are cells of an abnormally larger size due to an increase in both the capsule and the cell body size (total size reaching between 50–70 μm). This phenomenon can be partially reproduced in vitro to obtain cells of an intermediate size (25–30 μm), which have been denominated titan-like cells. In this work, we have screened 1,520 compounds from the Prestwick Chemical Library and identified off-patent drugs that inhibited titan-like cell formation in vitro . We developed an automated fluorescence-based microscopy assay and identified 64 compounds as possible inhibitors of titan-like cells. We chose 10 of these compounds to perform dose-response curves and confirmed them as inhibitors of titan-like cell formation. Several of the compounds identified had antioxidant properties (i.e., retinoic acid), indicating a possible role of free radicals during titan cell formation. Using fluorescent probes, we found that there was an endogenous accumulation of reactive oxygen species (ROS) during cell growth, which was inhibited in the presence of retinoic acid. Furthermore, we found that during titanization, there were significant changes in the mitochondria, which is the main organelle where ROS are produced. We hypothesize that an intracellular increase of free radicals at the mitochondria might be a triggering signal to induce titanization. IMPORTANCE Cryptococcus neoformans is an excellent model to investigate fungal pathogenesis. This yeast can produce “titan cells,” which are cells of an abnormally larger size that contribute to the persistence of the yeast in the host. In this work, we have used a new approach to characterize them by identifying drugs that inhibit this process. We have used a repurposing off-patent drug library, combined with an automatic method to image and analyze fungal cell size. In this way, we have identified many compounds that inhibit this transition. Interestingly, several compounds were antioxidants, allowing us to confirm that endogenous ROS and mitochondrial changes are important for titan cell formation. This work provides new evidence of the mechanisms required for titanization. Furthermore, the future characterization of the inhibitory mechanisms of the identified compounds by the scientific community will contribute to better understand the role of titan cells in virulence.

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“…Growth at 37 • C also reduced melanin production [21]. Similarly, in a recent study by Zhou et al [22], it has been found that the presence of ROS/RNS during fungal infection is a major determinant of the outcome of the disease.…”

Section: Melaninmentioning

confidence: 63%

The Environmental Effects on Virulence Factors and the Antifungal Susceptibility of Cryptococcus neoformans

Momin

¹

,

Webb

²

2021

IJMS

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Cryptococcus neoformans is a facultative intracellular pathogen responsible for fungal meningoencephalitis primarily in immunocompromised individuals. It has become evident the pathogenicity of C. neoformans is dependent on the fungal cell’s environment. The differential expression of virulence factors, based on the cell’s environmental conditions, is one mechanism allowing for the environmental control of the pathogenic ability of C. neoformans. Here, we discuss how these virulence factors (including melanin, the polysaccharide capsule, and Antiphagocytic protein 1) have been shown to be differentially expressed dependent on the cell’s environment. The genetics and signaling pathways leading to the environmental-dependent regulation of virulence factors will also be examined. Susceptibility to antifungal therapeutics is also regulated by the environment, and thus affects the pathogenic abilities of C. neoformans and disease outcomes. This review will also examine the role of the C. neoformans’s environment on antifungal susceptibilities, and the genetics and signaling pathways responsible for these susceptibility alterations. By examining the complex interplay between the environment and the pathogenicity of C. neoformans, we have a better understanding of the intricacies of the pathogen–environment interaction and how to exploit this interaction to develop the most effective treatment protocols.

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Host-derived Reactive Nitrogen Species mediate theCryptococcus neoformansyeast-to-titan switch via fungal-derived superoxide

Cited by 8 publications

References 81 publications

Pharmacological inhibition of titan-like cells formation suggests that accumulation of endogenous free radicals that correlate with mitochondrial changes are required to induce this transition inCryptococcus neoformans

Pharmacological inhibition of titan-like cells formation suggests that accumulation of endogenous free radicals that correlate with mitochondrial changes are required to induce this transition inCryptococcus neoformans

Accumulation of endogenous free radicals is required to induce titan-like cell formation in Cryptococcus neoformans

The Environmental Effects on Virulence Factors and the Antifungal Susceptibility of Cryptococcus neoformans

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