Identification of proteins in Sporothrix schenckii sensu stricto in response to oxidative stress induced by hydrogen peroxide

Neutrophil Oxidative Burst Profile Is Related to a Satisfactory Response to Itraconazole and Clinical Cure in Feline Sporotrichosis

Despite the central role of cats in the transmission and amplification of Sporothrix, studies regarding immune response in feline sporotrichosis are scarce. In cats with sporotrichosis, neutrophil-rich lesions are usually associated to good general condition and lower fungal burden. However, the role of neutrophils in anti-Sporothrix immunity has been little explored in cats. Thus, the aim of this study was to evaluate the neutrophil oxidative burst in the blood of cats with sporotrichosis. Cats with sporotrichosis included in the study were treated with itraconazole (ITZ) alone or combined with potassium iodide (KI). The neutrophil oxidative burst was evaluated through a flow-cytometry-based assay using dihydrorhodamine 123 (background) and stimulation with Zymosan and heat-killed Sporothrix yeasts. The cure rate was 50.0% in cats under treatment with ITZ monotherapy and 90.9% in cats treated with ITZ + KI (p = 0.014), endorsing the combination therapy as an excellent alternative for the treatment of feline sporotrichosis. Higher percentages of Sporothrix-stimulated neutrophils were associated with good general condition (p = 0.003). Higher percentages of Sporothrix- (p = 0.05) and Zymosan-activated (p = 0.014) neutrophils before and early in the treatment were related to clinical cure in ITZ-treated cats. The correlation between oxidative burst and successful use of KI could not be properly assessed given the low number of failures (n = 2) in this treatment group. Nasal mucosa involvement, typically linked to treatment failure, was related to lower percentages of activated neutrophils in the background at the treatment outcome (p = 0.02). Our results suggest a beneficial role of neutrophils in feline sporotrichosis and a positive correlation between neutrophil activation and the cure process in ITZ-treated cats.

The State of the Art in Transcriptomics and Proteomics of Clinically Relevant Sporothrix Species

Proteomics provide a robust approach to profile and quantify proteins within cells, organs, or tissues, providing comprehensive insights about the dynamics of cellular processes, modifications, and interactions. Similarly, understanding the transcriptome is essential to decipher functional elements of the genome, unraveling the mechanisms of disease development and the molecular constituents of cells and tissues. Some thermodimorphic fungi of the genus Sporothrix cause sporotrichosis, a subcutaneous mycosis of worldwide relevance. The transcriptome and proteome of the main Sporothrix species of clinical interest can elucidate the mechanisms underlying pathogenesis and host interactions. Studies of these techniques can contribute to the advancement of novel diagnostic and therapeutic strategies. A literature review was carried out, addressing all articles based on proteomics using mass spectrometry and transcriptomics of Sporothrix spp. Twenty-one studies were eligible for this review. The main findings include proteins and genes involved in dimorphism, cell differentiation, thermotolerance, virulence, immune evasion, metabolism, cell adhesion, cell transport, and biosynthesis. With the spread and emergence of sporotrichosis in different countries, ongoing research efforts and new discoveries are welcome to advance knowledge about this mycosis and its agents.

Anti-Sporotrichotic Activity, Lambert-W Inhibition Kinetics and 3D Structural Characterization of Sporothrix schenckii Catalase as Target of Glucosinolates from Moringa oleifera

Most human fungal infections exhibit significant defensive oxidative stress responses, which contribute to their pathogenicity. An important component of these reactions is the activation of catalase for detoxification. To discover new antifungal chemicals, the antifungal activity of methanol extracts of Moringa oleifera from two commercial products (Akuanandi and Mas Lait) was investigated. The methanolic extracts’ activity against Sporothrix schenckii was determined using an assay for minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC). The MIC concentrations varied between 0.5 μg/mL and 8 μg/mL. Akuanandi extract had the lowest MIC (0.5 μg/mL) and MLC (1 μg/mL) values. M. oleifera methanolic extracts were tested for catalase inhibition. The Ki values of the M. oleifera extract against S. schenckii catalase (SsCAT) was found to be 0.7 μg/mL for MOE-AK and 0.08 μg/mL for MOE-ML. Catalase’s 3D structure in SsCAT is unknown. The homology of SsCAT was modeled with an in silico study using a 3D structure from SWISS MODEL and validation the predicted 3D structure was carried out using PROCHECK and MolProbity. Docking simulations were used to analyze protein interactions using Pymol, PoseView, and PLIP. The results revealed that M. oleifera glucosinolates interacts with SsCAT. A molecular interaction analysis revealed two inhibitor compounds (glucosinalbin and glucomoringin) with high binding affinity to key allosteric-site residues. The binding energies revealed that glucosinalbin and glucomoringin bind with high affinity to SsCAT (docking energy values: −9.8 and −9.0 kcal/mol, respectively). The findings of this study suggest that glucosinolates derived from M. oleifera could be used instead of synthetic fungicides to control S. schenckii infections. We hope that the findings of this work will be valuable for developing and testing novel natural anti-sporothrix therapeutic agents in the future.

Moonlighting proteins in medically relevant fungi

Moonlighting proteins represent an intriguing area of cell biology, due to their ability to perform two or more unrelated functions in one or many cellular compartments. These proteins have been described in all kingdoms of life and are usually constitutively expressed and conserved proteins with housekeeping functions. Although widely studied in pathogenic bacteria, the information about these proteins in pathogenic fungi is scarce, but there are some reports of their functions in the etiological agents of the main human mycoses, such as Candida spp., Paracoccidioides brasiliensis, Histoplasma capsulatum, Aspergillus fumigatus, Cryptococcus neoformans, and Sporothrix schenckii. In these fungi, most of the described moonlighting proteins are metabolic enzymes, such as enolase and glyceraldehyde-3-phosphate dehydrogenase; chaperones, transcription factors, and redox response proteins, such as peroxiredoxin and catalase, which moonlight at the cell surface and perform virulence-related processes, contributing to immune evasion, adhesions, invasion, and dissemination to host cells and tissues. All moonlighting proteins and their functions described in this review highlight the limited information about this biological aspect in pathogenic fungi, representing this a relevant opportunity area that will contribute to expanding our current knowledge of these organisms' pathogenesis.

Proteomic Analysis of Sporothrix schenckii Exposed to Oxidative Stress Induced by Hydrogen Peroxide

Sporothrix schenckii modulates the expression of its cell wall proteins (CWPs) in response to reactive oxygen species (ROS) generated by the phagocytic cells of the human host, which allows it to evade and escape the immune system. In this study, we performed a comparative proteomic analysis of the CW of S. schenckii after exposure and nonexposure to H₂O₂. Several CWPs involved in CW remodeling and fungal pathogenesis that modulated their expression in response to this oxidizing agent were identified, as were a number of antioxidant enzymes and atypical CWPs, called moonlighting proteins, such as the Hsp70-5, lipase 1 (Lip1), enolase (Eno), and pyruvate kinase (Pk). Moreover, RT-qPCR assays demonstrated that the transcription of genes HSP70-5, LIP1, ENO, and PK is regulated in response to the oxidant. The results indicated that S. schenckii differentially expressed CWPs to confer protection against ROS upon this fungus. Furthermore, among these proteins, antioxidant enzymes and interestingly, moonlighting-like CWPs play a role in protecting the fungus from oxidative stress (OS), allowing it to infect human host cells.

Enzyme activity and expression of catalases in response to oxidative stress in Sporothrix schenckii

Sporothrix schenckii is a dimorphic fungus, pathogenic to humans and animals, which is usually infective in the yeast form. Reactive oxygen species (ROS) play an important role in the host's defense, damaging the pathogen's DNA, proteins, and lipids. To prevent oxidative damage, the ROS are detoxified by pathogen-derived antioxidant enzymes such as catalases (CATs). In this work, we analyzed the activity and expression level of three S. schenckii genes, designated as CAT1, CAT2, and CAT3, that putatively encoded for three isoforms of monofunctional CAT with a predicted molecular weight of 57.6, 56.2, and 81.4 kDa, respectively. Our results demonstrate that oxidative stress induced by exogenous H₂O₂ leads to an altered lipid peroxidation, modifying CAT activity and the expression levels of the CAT genes, being CAT1 and CAT3 the genes with the highest expression in response to the oxidizing agent. These results show that CAT isoforms in S. schenckii can be regulated in response to oxidative stress and might help to control ROS homeostasis in the fungus-host interaction.

The Heat Shock Protein 60 and Pap1 Participate in the Sporothrixschenckii-Host Interaction

Sporothrixschenckii is one of the etiological agents of sporotrichosis, a worldwide-distributed subcutaneous mycosis. Its cell wall contains a glycoconjugate composed of rhamnose, mannose, glucuronic acid, and proteins, named peptidorhamnomannan, which harbors important Sporothrix-specific immunogenic epitopes. Although the peptidorhamnomannan carbohydrate moiety has been extensively studied, thus far, little is known about the protein core. Here, using LC-MS/MS, we analyzed the S.schenckii peptidorhamnomannan peptide fraction and generated mass signals of 325 proteins, most of them likely to be moonlighting proteins. Among the identified proteins, chaperonin GroEL/Hsp60 and the uncharacterized protein Pap1 were selected for further analysis. Both proteins were heterologously expressed in bacteria, and they showed adhesive properties to the extracellular matrix proteins laminin, elastin, fibrinogen, and fibronectin, although Pap1 also was bound to type-I and type-II collagen. The inoculation of concentrations higher than 40 μg of these proteins, separately, increased immune effectors in the hemolymph of Galleriamellonella larvae and protected animals from an S.schenckii lethal challenge. These observations were confirmed when yeast-like cells, pre-incubated with anti-rHsp60 or anti-rPap1 antibodies were used to inoculate larvae. The animals inoculated with pretreated cells showed increased survival rates when compared to the control groups. In conclusion, we report that Hsp60 and Pap1 are part of the cell wall peptidorhamnomannan, can bind extracellular matrix components, and contribute to the S.schenckii virulence. To our knowledge, this is the first report about moonlighting protein in the S.schenckii cell wall with an important role during the pathogen-host interaction.

Proteomic analysis of Sporothrix schenckii cell wall reveals proteins involved in oxidative stress response induced by menadione

Sporotrichosis is an emergent subcutaneous mycosis that is a threat to both humans and other animals. Sporotrichosis is acquired by the traumatic implantation of species of the Sporothrix genus. Added to the detoxification systems, pathogenic fungi possess different mechanisms that allow them to survive within the phagocytic cells of their human host during the oxidative burst. These mechanisms greatly depend from the cell wall (CW) since phagocytic cells recognize pathogens through specific receptors associated to the structure. To date, there are no studies addressing the modulation of the expression of S. schenckii CW proteins (CWP) in response to reactive oxygen species (ROS). Therefore, in this work, a proteomic analysis of the CW of S. schenckii in response to the oxidative agent menadione (O₂•^-) was performed. Proteins that modulate their expression were identified which can be related to the fungal survival mechanisms within the phagocyte. Among the up-regulated CWP in response to the oxidative agent, 13 proteins that could be involved in the mechanisms of oxidative stress response in S. schenckii were identified. The proteins identified were thioredoxin1 (Trx1), superoxide dismutase (Sod), GPI-anchored cell wall protein, β-1,3-endoglucanase EglC, glycoside hydrolase (Gh), chitinase, CFEM domain protein, glycosidase crf1, covalently-linked cell wall protein (Ccw), 30 kDa heat shock protein (Hsp30), lipase, trehalase (Treh), fructose-bisphosphate aldolase (Fba1) and citrate synthase (Cs). The identification of CWP that modulates their expression in response to superoxide ion (O₂•^-) in S. schenckii is a useful approach to understand how the fungus defends itself against ROS, in order to evade the phagocytic cells from the host and cause the infection.