The response of Paracoccidioides spp. to nitrosative stress

Mucorales fungi suppress nitric oxide production by macrophages

IMPORTANCE

In October 2022, Mucorales fungi were listed in the "High Priority Group" on the first-ever list of fungal priority pathogens by the World Health Organization. As the causative agent of mucormycosis, Mucorales have become of great clinical and public health importance with growing mucormycosis numbers, notably with the exponential rise of COVID-19-associated mucormycosis cases. Despite the dire need, there are limited therapeutic options to treat mucormycosis. Our research fills in critical gaps of knowledge about how Mucorales fungi evade the host immune system. Specifically, we offer evidence that Mucorales block nitric oxide production, which is a key mediator and signaling molecule of the mammalian innate immune response to microbial pathogens. Our work offers new insight into immune evasion mechanisms by Mucorales fungi.

Subversion strategies of lysosomal killing by intracellular pathogens

Many pathogenic organisms need to reach either an intracellular compartment or the cytoplasm of a target cell for their survival, replication or immune system evasion. Intracellular pathogens frequently penetrate into the cell through the endocytic and phagocytic pathways (clathrin-mediated endocytosis, phagocytosis and macropinocytosis) that culminates in fusion with lysosomes. However, several mechanisms are triggered by pathogenic microorganisms - protozoan, bacteria, virus and fungus - to avoid destruction by lysosome fusion, such as rupture of the phagosome and thereby release into the cytoplasm, avoidance of autophagy, delaying in both phagolysosome biogenesis and phagosomal maturation and survival/replication inside the phagolysosome. Here we reviewed the main data dealing with phagosome maturation and evasion from lysosomal killing by different bacteria, protozoa, fungi and virus.

iTRAQ-based proteomic analysis of Paracoccidioides brasiliensis in response to hypoxia

Aerobic organisms require oxygen for energy. In the course of the infection, adaptation to hypoxia is crucial for survival of human pathogenic fungi. Members of the Paracoccidioides complex face decreased oxygen tensions during the life cycle stages. In Paracoccidioides brasiliensis proteomic responses to hypoxia have not been investigated and the regulation of the adaptive process is still unknown, and this approach allowed the identification of 216 differentially expressed proteins in hypoxia using iTRAQ-labelling. Data suggest that P. brasiliensis reprograms its metabolism when submitted to hypoxia. The fungus reduces its basal metabolism and general transport proteins. Energy and general metabolism were more representative and up regulated. Glucose is apparently directed towards glycolysis or the production of cell wall polymers. Plasma membrane/cell wall are modulated by increasing ergosterol and glucan, respectively. In addition, molecules such as ethanol and acetate are produced by this fungus indicating that alternative carbon sources probably are activated to obtain energy. Also, detoxification mechanisms are activated. The results were compared with label free proteomics data from Paracoccidioides lutzii. Biochemical pathways involved with acetyl-CoA, pyruvate and ergosterol synthesis were up-regulated in both fungi. On the other hand, proteins from TCA, transcription, protein fate/degradation, cellular transport, signal transduction and cell defense/virulence processes presented different profiles between species. Particularly, proteins related to methylcitrate cycle and those involved with acetate and ethanol synthesis were increased in P. brasiliensis proteome, whereas GABA shunt were accumulated only in P. lutzii. The results emphasize metabolic adaptation processes for distinct Paracoccidioides species.

Updates in Paracoccidioides Biology and Genetic Advances in Fungus Manipulation

The dimorphic fungi of the Paracoccidioides genus are the causative agents of paracoccidioidomycosis (PCM). This disease is endemic in Latin America and primarily affects workers in rural areas. PCM is considered a neglected disease, despite being a disabling disease that has a notable impact on the public health system. Paracoccidioides spp. are thermally dimorphic fungi that present infective mycelia at 25 °C and differentiate into pathogenic yeast forms at 37 °C. This transition involves a series of morphological, structural, and metabolic changes which are essential for their survival inside hosts. As a pathogen, the fungus is subjected to several varieties of stress conditions, including the host immune response, which involves the production of reactive nitrogen and oxygen species, thermal stress due to temperature changes during the transition, pH alterations within phagolysosomes, and hypoxia inside granulomas. Over the years, studies focusing on understanding the establishment and development of PCM have been conducted with several limitations due to the low effectiveness of strategies for the genetic manipulation of Paracoccidioides spp. This review describes the most relevant biological features of Paracoccidioides spp., including aspects of the phylogeny, ecology, stress response, infection, and evasion mechanisms of the fungus. We also discuss the genetic aspects and difficulties of fungal manipulation, and, finally, describe the advances in molecular biology that may be employed in molecular research on this fungus in the future.

An Overview of Genomics, Phylogenomics and Proteomics Approaches in Ascomycota

Fungi are among the most successful eukaryotes on Earth: they have evolved strategies to survive in the most diverse environments and stressful conditions and have been selected and exploited for multiple aims by humans. The characteristic features intrinsic of Fungi have required evolutionary changes and adaptations at deep molecular levels. Omics approaches, nowadays including genomics, metagenomics, phylogenomics, transcriptomics, metabolomics, and proteomics have enormously advanced the way to understand fungal diversity at diverse taxonomic levels, under changeable conditions and in still under-investigated environments. These approaches can be applied both on environmental communities and on individual organisms, either in nature or in axenic culture and have led the traditional morphology-based fungal systematic to increasingly implement molecular-based approaches. The advent of next-generation sequencing technologies was key to boost advances in fungal genomics and proteomics research. Much effort has also been directed towards the development of methodologies for optimal genomic DNA and protein extraction and separation. To date, the amount of proteomics investigations in Ascomycetes exceeds those carried out in any other fungal group. This is primarily due to the preponderance of their involvement in plant and animal diseases and multiple industrial applications, and therefore the need to understand the biological basis of the infectious process to develop mechanisms for biologic control, as well as to detect key proteins with roles in stress survival. Here we chose to present an overview as much comprehensive as possible of the major advances, mainly of the past decade, in the fields of genomics (including phylogenomics) and proteomics of Ascomycota, focusing particularly on those reporting on opportunistic pathogenic, extremophilic, polyextremotolerant and lichenized fungi. We also present a review of the mostly used genome sequencing technologies and methods for DNA sequence and protein analyses applied so far for fungi.

Characterization of a heme-protein responsive to hypoxia in Paracoccidioides brasiliensis

Oxygen is fundamental to the life of aerobic organisms and is not always available to Paracoccidioides cells. During the life cycle stages, reduced oxygen levels directly affect general metabolic processes and oxygen adaptation mechanisms may play a fundamental role on fungal ability to survive under such condition. Heme proteins can bind to oxygen and participate in important biological processes. Several fungi, including Paracoccidioides, express a heme-binding globin (fungoglobin - FglA) presumable to regulate fungal adaptation to hypoxia. However, the characterization of fungoglobin in Paracoccidioides spp. has not yet been performed. In this study, we predicted the structure of fungoglobin and determined its level of expression during hypoxic-mimetic conditions. Genomic screening revealed that the fungoglobin gene is conserved in all species of the Paracoccidioides genus. Molecular modeling showed biochemical and biophysical characteristics that support the hypothesis that FglA binds to the heme group and oxygen as well. The fungoglobin transcript and proteins are expressed at higher levels at the early treatment time, remaining elevated while oxygen is limited. A P. brasiliensis fglA knockdown strain depicted reduced growth in hypoxia indicating that this protein can be essential for growth at low oxygen. Biochemical analysis confirmed the binding of fungoglobin to heme. Initial analyzes were carried out to establish the relationship between FlglA and iron metabolism. The FglA transcript was up regulated in pulmonary infection, suggesting its potential role in the disease establishment. We believe that this study can contribute to the understanding of fungal biology and open new perspectives for scientific investigations.

Proteome characterization of Paracoccidioides lutzii conidia by using nanoUPLC-MSE

Fungi of the genus Paracoccidioides are the etiological agents of Paracoccidioidomycosis (PCM), the most prevalent mycosis in Latin America. Paracoccidioidomycosis infection is acquired by inhalation of Paracoccidioides conidia, which have first contact with the lungs and can subsequently spread to other organs/tissues. Until now, there have been no proteomic studies focusing on this infectious particle of Paracoccidioides. In order to identify the Paracoccidioides lutzii conidia proteome, conidia were produced and purified. Proteins were characterized by use of the nanoUPLC-MS^E approach. The strategy allowed us to identify a total of 242 proteins in P. lutzii conidia. In the conidia proteome, proteins were classified in functional categories such as protein synthesis, energy production, metabolism, cellular defense/virulence processes, as well as other processes that can be important for conidia survival. Through this analysis, a pool of ribosomal proteins was identified, which may be important for the initial processes of dimorphic transition. In addition, molecules related to energetic and metabolic processes were identified, suggesting a possible basal metabolism during this form of resistance of the fungus. In addition, adhesins and virulence factors were identified in the P. lutzii conidia proteome. Our results demonstrate the potential role that these molecules can play during early cell-host interaction processes, as well as the way in which these molecules are involved in environmental survival during this form of propagation.

Effect of Nitrosative Stress on the S-Nitroso-Proteome of Paracoccidioides brasiliensis

The fungi Paracoccidioides brasiliensis and Paracoccidioides lutzii are the causative agents of paracoccidioidomycosis (PCM), a systemic mycosis endemic to Latin America. This fungus is considered a facultative intracellular pathogen that is able to survive and replicate inside macrophages. The survival of the fungus during infection depends on its adaptability to various conditions, such as nitrosative/oxidative stress produced by the host immune cells, particularly alveolar macrophages. Currently, there is little knowledge about the Paracoccidioides spp. signaling pathways involved in the fungus evasion mechanism of the host defense response. However, it is known that some of these pathways are triggered by reactive oxygen species and reactive nitrogen species (ROS/RNS) produced by host cells. Considering that the effects of NO (nitric oxide) on pathogens are concentration dependent, such effects could alter the redox state of cysteine residues by influencing (activating or inhibiting) a variety of protein functions, notably S-nitrosylation, a highly important NO-dependent posttranslational modification that regulates cellular functions and signaling pathways. It has been demonstrated by our group that P. brasiliensis yeast cells proliferate when exposed to low NO concentrations. Thus, this work investigated the modulation profile of S-nitrosylated proteins of P. brasiliensis, as well as identifying S-nitrosylation sites after treatment with RNS. Through mass spectrometry analysis (LC-MS/MS) and label-free quantification, it was possible to identify 474 proteins in the S-nitrosylated proteome study. With this approach, we observed that proteins treated with NO at low concentrations presented a proliferative response pattern, with several proteins involved in cellular cycle regulation and growth being activated. These proteins appear to play important roles in fungal virulence. On the other hand, fungus stimulated by high NO concentrations exhibited a survival response pattern. Among these S-nitrosylated proteins we identified several potential molecular targets for fungal disease therapy, including cell wall integrity (CWI) pathway, amino acid and folic acid metabolisms. In addition, we detected that the transnitrosylation/denitrosylation redox signaling are preserved in this fungus. Finally, this work may help to uncover the beneficial and antifungal properties of NO in the P. brasiliensis and point to useful targets for the development of antifungal drugs.

Proteomic analysis of Paracoccidioides brasiliensis complex isolates: Correlation of the levels of differentially expressed proteins with in vivo virulence

BACKGROUND

Paracoccidioidomycosis (PCM) is a systemic mycosis commonly found in Latin America that is caused by distinct species of Paracoccidioides genus: Paracoccidioides brasiliensis complex (S1, PS2, PS3 and PS4) and Paracoccidioides lutzii. Its pathobiology has been recently explored by different approaches to clarify the mechanisms of host-pathogen interactions underpinning PCM. The diversity of clinical forms of this disease has been attributed to both host- and fungus-related factors.

METHODOLOGY/PRINCIPAL FINDINGS

For better understanding of the molecular underpinnings of host-fungus interactions, we evaluated in vivo virulence of nine Paracoccidioides brasiliensis complex isolates and correlated it to protein expression profiles obtained by two-dimensional gel electrophoresis. Based on the recovery of viable fungi from mouse organs, the isolates were classified as those having low, moderate, or high virulence. Highly virulent isolates overexpressed proteins related to adhesion process and stress response, probably indicating important roles of those fungal proteins in regulating the colonization capacity, survival, and ability to escape host immune system reaction. Moreover, highly virulent isolates exhibited enhanced expression of glycolytic pathway enzymes concomitantly with repressed expression of succinyl-CoA ligase beta chain, a protein related to the tricarboxylic acid cycle.

CONCLUSIONS/SIGNIFICANCE

Our findings may point to the mechanisms used by highly virulent P. brasiliensis isolates to withstand host immune reactions and to adapt to transient iron availability as strategies to survive and overcome stress conditions inside the host.

TLR3 Is a Negative Regulator of Immune Responses Against Paracoccidioides brasiliensis

Toll-like receptors (TLRs) comprise the best-characterized pattern-recognition receptor (PRR) family able to activate distinct immune responses depending on the receptor/adaptor set assembled. TLRs, such as TLR2, TLR4 and TLR9, and their signaling were shown to be important in Paracoccidioides brasiliensis infections. However, the role of the endosomal TLR3 in experimental paracoccidioidomycosys remains obscure. In vitro assays, macrophages of the bone marrow of WT or TLR3^−/− mice were differentiated for evaluation of their microbicidal activity. In vivo assays, WT or TLR3^−/− mice were infected intratracheally with Paracoccidioides brasiliensis yeasts for investigation of the lung response type induced. The cytotoxic activity of CD8⁺ T cells was assessed by cytotoxicity assay. To confirm the importance of CD8⁺ T cells in the control of infection in the absence of tlr3, a depletion assay of these cells was performed. Here, we show for the first time that TLR3 modulate the infection against Paracoccidioides brasiliensis by dampening pro-inflammatory response, NO production, IFN⁺CD8⁺T, and IL-17⁺CD8⁺T cell activation and cytotoxic function, associated with granzyme B and perforin down regulation. As conclusion, we suggest that TLR3 could be used as an escape mechanism of the fungus in an experimental paracoccidioidomycosis.

Response of Paracoccidioides lutzii to the antifungal camphene thiosemicarbazide determined by proteomic analysis

Aim: To perform the proteomic profile of Paracoccidioides lutzii after treatment with the compound camphene thiosemicarbazide (TSC-C) in order to study its mode of action. Methods: Proteomic analysis was carried out after cells were incubated with TSC-C in a subinhibitory concentration. Validation of the proteomic results comprised the azocasein assay, western blot and determination of the susceptibility of a mutant to the compound. Results: Proteins related to metabolism, energy and protein fate were regulated after treatment. In addition, TSC-C reduces the proteolytic activity of the protein extract similarly to different types of protease inhibitors. Conclusion: TSC-C showed encouraging antifungal activity, working as a protease inhibitor and downregulating important pathways impairing the ability of the fungi cells to produce important precursors.

Reactive nitrogen species (RNS)-resistant microbes: adaptation and medical implications

Nitrosative stress results from an increase in reactive nitrogen species (RNS) within the cell. Though the RNS - nitric oxide (·NO) and peroxynitrite (ONOO-) - play pivotal physiological roles, at elevated concentrations, these moieties can be poisonous to both prokaryotic and eukaryotic cells alike due to their capacity to disrupt a variety of essential biological processes. Numerous microbes are known to adapt to nitrosative stress by elaborating intricate strategies aimed at neutralizing RNS. In this review, we will discuss both the enzymatic systems dedicated to the elimination of RNS as well as the metabolic networks that are tailored to generate RNS-detoxifying metabolites - α-keto-acids. The latter has been demonstrated to nullify RNS via non-enzymatic decarboxylation resulting in the production of a carboxylic acid, many of which are potent signaling molecules. Furthermore, as aerobic energy production is severely impeded during nitrosative stress, alternative ATP-generating modules will be explored. To that end, a holistic understanding of the molecular adaptation to nitrosative stress, reinforces the notion that neutralization of toxicants necessitates significant metabolic reconfiguration to facilitate cell survival. As the alarming rise in antimicrobial resistant pathogens continues unabated, this review will also discuss the potential for developing therapies that target the alternative ATP-generating machinery of bacteria.

In vitro, ex vivo and in vivo models: A comparative analysis of Paracoccidioides spp. proteomic studies

Members of the Paracoccidioides complex are human pathogens that infect different anatomic sites in the host. The ability of Paracoccidioides spp. to infect host niches is putatively supported by a wide range of virulence factors, as well as fitness attributes that may comprise the transition from mycelia/conidia to yeast cells, response to deprivation of micronutrients in the host, expression of adhesins on the cell surface, response to oxidative and nitrosative stresses, as well as the secretion of hydrolytic enzymes in the host tissue. Our understanding of how those molecules can contribute to the infection establishment has been increasing significantly, through the utilization of several models, including in vitro, ex vivo and in vivo infection in animal models. In this review we present an update of our understanding on the strategies used by the pathogen to establish infection. Our results were obtained through a comparative proteomic analysis of Paracoccidioides spp. in models of infection.

Fungal Strategies to Evade the Host Immune Recognition

The recognition of fungal cells by the host immune system is key during the establishment of a protective anti-fungal response. Even though the immune system has evolved a vast number of processes to control these organisms, they have developed strategies to fight back, avoiding the proper recognition by immune components and thus interfering with the host protective mechanisms. Therefore, the strategies to evade the immune system are as important as the virulence factors and attributes that damage the host tissues and cells. Here, we performed a thorough revision of the main fungal tactics to escape from the host immunosurveillance processes. These include the composition and organization of the cell wall, the fungal capsule, the formation of titan cells, biofilms, and asteroid bodies; the ability to undergo dimorphism; and the escape from nutritional immunity, extracellular traps, phagocytosis, and the action of humoral immune effectors.

Employing proteomic analysis to compare Paracoccidioides lutzii yeast and mycelium cell wall proteins

Paracoccidioidomycosis is an important systemic mycosis caused by thermodimorphic fungi of the Paracoccidioides genus. During the infective process, the cell wall acts at the interface between the fungus and the host. In this way, the cell wall has a key role in growth, environment sensing and interaction, as well as morphogenesis of the fungus. Since the cell wall is absent in mammals, it may present molecules that are described as target sites for new antifungal drugs. Despite its importance, up to now few studies have been conducted employing proteomics in for the identification of cell wall proteins in Paracoccidioides spp. Here, a detailed proteomic approach, including cell wall-fractionation coupled to NanoUPLC-MS^E, was used to study and compare the cell wall fractions from Paracoccidioides lutzii mycelia and yeast cells. The analyzed samples consisted of cell wall proteins extracted by hot SDS followed by extraction by mild alkali. In summary, 512 proteins constituting different cell wall fractions were identified, including 7 predicted GPI-dependent cell wall proteins that are potentially involved in cell wall metabolism. Adhesins previously described in Paracoccidioides spp. such as enolase, glyceraldehyde-3-phosphate dehydrogenase were identified. Comparing the proteins in mycelium and yeast cells, we detected some that are common to both fungal phases, such as Ecm33, and some specific proteins, as glucanase Crf1. All of those proteins were described in the metabolism of cell wall. Our study provides an important elucidation of cell wall composition of fractions in Paracoccidioides, opening a way to understand the fungus cell wall architecture.

Paracoccidioides brasiliensis presents metabolic reprogramming and secretes a serine proteinase during murine infection

Paracoccidoides brasiliensis and Paracoccidioides lutzii, the etiologic agents of paracoccidioidomycosis, cause disease in healthy and immunocompromised persons in Latin America. We developed a method for harvesting P. brasiliensis yeast cells from infected murine lung to facilitate in vivo transcriptional and proteomic profiling. P. brasiliensis harvested at 6 h post-infection were analyzed using RNAseq and LC-MS^E. In vivo yeast cells had 594 differentially expressed transcripts and 350 differentially expressed proteins. Integration of transcriptional and proteomic data indicated that early in infection (6 h), P. brasiliensis yeast cells underwent a shift in metabolism from glycolysis to β-oxidation, upregulated detoxifying enzymes to defend against oxidative stress, and repressed cell wall biosynthesis. Bioinformatics and functional analyses also demonstrated that a serine proteinase was upregulated and secreted in vivo. To our knowledge this is the first study depicting transcriptional and proteomic data of P. brasiliensis yeast cells upon 6 h post-infection of mouse lung.

Antifungal Resistance, Metabolic Routes as Drug Targets, and New Antifungal Agents: An Overview about Endemic Dimorphic Fungi

Diseases caused by fungi can occur in healthy people, but immunocompromised patients are the major risk group for invasive fungal infections. Cases of fungal resistance and the difficulty of treatment make fungal infections a public health problem. This review explores mechanisms used by fungi to promote fungal resistance, such as the mutation or overexpression of drug targets, efflux and degradation systems, and pleiotropic drug responses. Alternative novel drug targets have been investigated; these include metabolic routes used by fungi during infection, such as trehalose and amino acid metabolism and mitochondrial proteins. An overview of new antifungal agents, including nanostructured antifungals, as well as of repositioning approaches is discussed. Studies focusing on the development of vaccines against antifungal diseases have increased in recent years, as these strategies can be applied in combination with antifungal therapy to prevent posttreatment sequelae. Studies focused on the development of a pan-fungal vaccine and antifungal drugs can improve the treatment of immunocompromised patients and reduce treatment costs.

Paracoccidioides Spp.: Virulence Factors and Immune-Evasion Strategies

Paracoccidioides spp. are dimorphic fungal pathogens responsible for one of the most relevant systemic mycoses in Latin America, paracoccidioidomycosis (PCM). Their exact ecological niche remains unknown; however, they have been isolated from soil samples and armadillos (Dasypus novemcinctus), which have been proposed as animal reservoir for these fungi. Human infection occurs by inhalation of conidia or mycelia fragments and is mostly associated with immunocompetent hosts inhabiting and/or working in endemic rural areas. In this review focusing on the pathogen perspective, we will discuss some of the microbial attributes and molecular mechanisms that enable Paracoccidioides spp. to tolerate, adapt, and ultimately avoid the host immune response, establishing infection.

Anti-Immune Strategies of Pathogenic Fungi

Pathogenic fungi have developed many strategies to evade the host immune system. Multiple escape mechanisms appear to function together to inhibit attack by the various stages of both the adaptive and the innate immune response. Thus, after entering the host, such pathogens fight to overcome the immune system to allow their survival, colonization and spread to different sites of infection. Consequently, the establishment of a successful infectious process is closely related to the ability of the pathogen to modulate attack by the immune system. Most strategies employed to subvert or exploit the immune system are shared among different species of fungi. In this review, we summarize the main strategies employed for immune evasion by some of the major pathogenic fungi.

Characterizing the nuclear proteome of Paracoccidioides spp

Paracoccidioidomycosis is an endemic disease in Latin America, caused by thermo dimorphic fungi of the genus Paracoccidioides. Although previous proteome analyses of Paracoccidioides spp. have been carried out, the nuclear subproteome of this pathogen has not been described. In this way, we aimed to characterize the nuclear proteome of Paracoccidioides species, in the yeast form. For that, yeast cells were disrupted and submitted to cell fractionation. The purity of the nuclear fraction was confirmed by fluorescence and electron microscopy. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) allowed the identification of 867 proteins. In order to support our enrichment method for nuclear proteins, bioinformatics analysis were applied that allowed the identification of 281 proteins with nuclear localization. The analysis revealed proteins related to DNA maintenance, gene expression, synthesis and processing of messenger and ribosomal RNAs, likewise proteins of nuclear-cytoplasmic traffic. It was also possible to detect some proteins that are poorly expressed, like transcription factors involved in important roles such as resistance to abiotic stress, sporulation, cellular growth and DNA and chromatin maintenance. This is the first descriptive nuclear proteome of Paracoccidioides spp. that can be useful as an important platform base for fungi-specific nuclear processes.

New insights into a complex fungal pathogen: the case of Paracoccidioides spp

Paracoccidioidomycosis is a systemic mycosis endemic to Latin America, with Paracoccidioides brasiliensis and P. lutzii being the causal agents of this disorder. Several issues have been raised in the 100 years since its discovery and in this article we discuss features of this fascinating fungal pathogen, including its biology, eco-epidemiology and aspects of its pathogenicity. We also consider some of its virulence determinants, the most recent advances in the study of its metabolic pathways and the molecular and genetic research tools developed for this research. We also review the animal models used to study host-fungal interactions and how the host defence mechanisms against this pathogen work.

Effects of Argentilactone on the Transcriptional Profile, Cell Wall and Oxidative Stress of Paracoccidioides spp

Paracoccidioides spp., a dimorphic pathogenic fungus, is the etiologic agent of paracoccidioidomycosis (PCM). PCM is an endemic disease that affects at least 10 million people in Latin America, causing severe public health problems. The drugs used against pathogenic fungi have various side effects and limited efficacy; therefore, there is an inevitable and urgent medical need for the development of new antifungal drugs. In the present study, we evaluated the transcriptional profile of Paracoccidioides lutzii exposed to argentilactone, a constituent of the essential oil of Hyptis ovalifolia. A total of 1,058 genes were identified, of which 208 were up-regulated and 850 were down-regulated. Cell rescue, defense and virulence, with a total of 26 genes, was a functional category with a large number of genes induced, including heat shock protein 90 (hsp90), cytochrome c peroxidase (ccp), the hemoglobin ligand RBT5 (rbt5) and superoxide dismutase (sod). Quantitative real-time PCR revealed an increase in the expression level of all of those genes. An enzymatic assay showed a significant increase in SOD activity. The reduced growth of Pbhsp90-aRNA, Pbccp-aRNA, Pbsod-aRNA and Pbrbt5-aRNA isolates in the presence of argentilactone indicates the importance of these genes in the response of Paracoccidioides spp. to argentilactone. The response of the P. lutzii cell wall to argentilactone treatment was also evaluated. The results showed that argentilactone caused a decrease in the levels of polymers in the cell wall. These results suggest that argentilactone is a potential candidate for antifungal therapy.

Paracoccidioidomycosis (PCM) is a neglected human systemic mycosis caused by Paracoccidioides spp. fungus that invades the host’s lungs and can disseminate to many other organs. Treatment usually involves amphotericin B, sulfadiazine, trimethoprim-sulfamethoxazole, itraconazole, ketoconazole or fluconazole for six months to two years. In this way, many adverse effects are associated with treatment, and patients can have many co-morbidities and difficulties in complying with treatment. For those reasons, more effective and less toxic drugs are needed. The discovery of a potentially bioactive molecule and its correlation with a biological target is an important step in the research and development of drugs. One of the ways in which cells adjust to environmental change is by changing the pattern of gene expression. Thus, the transcriptome is potential experimental strategy to elucidate the mode of action of bioactive molecules. Here, Paracoccidoides spp. altered the expression of genes, leading to a further understanding of the action of the compound argentilactone in the fungal cells. Argentilactone seems to be able to modulate cellular targets, to induce oxidative stress and to interfere with the biosynthesis of the P. lutzii cell wall.

Characterization of the Paracoccidioides Hypoxia Response Reveals New Insights into Pathogenesis Mechanisms of This Important Human Pathogenic Fungus

BACKGROUND

Hypoxic microenvironments are generated during fungal infection. It has been described that to survive in the human host, fungi must also tolerate and overcome in vivo microenvironmental stress conditions including low oxygen tension; however nothing is known how Paracoccidioides species respond to hypoxia. The genus Paracoccidioides comprises human thermal dimorphic fungi and are causative agents of paracoccidioidomycosis (PCM), an important mycosis in Latin America.

METHODOLOGY/PRINCIPAL FINDINGS

In this work, a detailed hypoxia characterization was performed in Paracoccidioides. Using NanoUPLC-MSE proteomic approach, we obtained a total of 288 proteins differentially regulated in 12 and 24 h of hypoxia, providing a global view of metabolic changes during this stress. In addition, a functional characterization of the homologue to the most important molecule involved in hypoxia responses in other fungi, the SREBP (sterol regulatory element binding protein) was performed. We observed that Paracoccidioides species have a functional homologue of SREBP, named here as SrbA, detected by using a heterologous genetic approach in the srbA null mutant in Aspergillus fumigatus. Paracoccidioides srbA (PbsrbA), in addition to involvement in hypoxia, is probable involved in iron adaptation and azole drug resistance responses.

CONCLUSIONS/SIGNIFICANCE

In this study, the hypoxia was characterized in Paracoccidioides. The first results can be important for a better understanding of the fungal adaptation to the host and improve the arsenal of molecules for the development of alternative treatment options in future, since molecules related to fungal adaptation to low oxygen levels are important to virulence and pathogenesis in human pathogenic fungi.

Distinct patterns of yeast cell morphology and host responses induced by representative strains of Paracoccidioides brasiliensis (Pb18) and Paracoccidioides lutzii (Pb01)

Paracoccidioidomycosis (PCM) is a systemic mycosis, widespread in Latin America. PCM is a granulomatous disease characterized by a polymorphism of lesions depending on the pathogen's virulence, the immune status of the host and its genetic susceptibility. The thermodimorphic fungus Paracoccidioides brasiliensis was considered the only etiologic agent of PCM, yet recent works have shown significant genetic diversity among different strains of P. brasiliensis. Therefore, it has been proposed for a new species within the Paracoccidioides genus, named Paracoccidioides lutzii. To better understand the fungus-host interactions elicited by strains Pb01 and Pb18 as key representatives of P. lutzii and P. brasiliensis, respectively, we carried out studies to investigate differences in morphology, induced immune response, virulence and pathology between these two Paracoccidioides species. Our results demonstrate distinct patterns of host-parasite interaction and pathology caused by Pb18 and Pb01. These results open up new fronts for NEW: clinical studies, which may result in significant consequences for the diagnosis and treatment of PCM. Considering that our results cannot be extended to all strains of both species, more studies about the virulence among Paracoccioides must be explored in the future.

Macrophage Interaction with Paracoccidioides brasiliensis Yeast Cells Modulates Fungal Metabolism and Generates a Response to Oxidative Stress

Macrophages are key players during Paracoccidioides brasiliensis infection. However, the relative contribution of the fungal response to counteracting macrophage activity remains poorly understood. In this work, we evaluated the P. brasiliensis proteomic response to macrophage internalization. A total of 308 differentially expressed proteins were detected in P. brasiliensis during infection. The positively regulated proteins included those involved in alternative carbon metabolism, such as enzymes involved in gluconeogenesis, beta-oxidation of fatty acids and amino acids catabolism. The down-regulated proteins during P. brasiliensis internalization in macrophages included those related to glycolysis and protein synthesis. Proteins involved in the oxidative stress response in P. brasiliensis yeast cells were also up-regulated during macrophage infection, including superoxide dismutases (SOD), thioredoxins (THX) and cytochrome c peroxidase (CCP). Antisense knockdown mutants evaluated the importance of CCP during macrophage infection. The results suggested that CCP is involved in a complex system of protection against oxidative stress and that gene silencing of this component of the antioxidant system diminished the survival of P. brasiliensis in macrophages and in a murine model of infection.