Reactive oxidant species induced by antifungal drugs: identity, origins, functions, and connection to stress-induced cell death

Antifungal Effects of the Phloroglucinol Derivative DPPG Against Pathogenic Aspergillus fumigatus

Background: Fungal infections pose an increasingly predominant threat to human and animal health. Modified compounds derived from chemo-diverse natural products offer enhanced therapeutic efficacies and promising approaches to combat life-threatening fungal pathogens. Methods: We performed biosynthetic gene clusters analysis of 2,4-diacetylchloroglucoside (DAPG) in 4292 shotgun metagenomes samples from the healthy and diseased skin. Then, we assessed the antifungal activity of DAPG and the derivative 2,4-diproylphloroglucinol (DPPG) against pathogenic fungi by minimum inhibitory concentrations. The inhibitory effects of DPPG were measured using hyphal growth assay and spore germination assay. Concurrently, the mechanism of DPPG on Aspergillus fumigatus was investigated in membrane permeability and fluidity. The therapeutic efficacy was evaluated in a Galleria mellonella infection model. Results: We observed a significantly higher abundance of bacteria harboring DAPG biosynthetic clusters on healthy skin compared to diseased skin. Further, we designed and synthesized a series of phloroglucinol derivatives based on DAPG and obtained an antifungal candidate DPPG. DPPG not only exhibited robust antifungal activity against Aspergillus spp. and Candida spp. but also impaired hyphal growth and spore germination of A. fumigatus in vitro. A mechanism study showed that DPPG reduced membrane fluidity and increased the leakage of cellular contents, resulting in membrane perturbation and fungal death. Lastly, the therapeutic efficacy of DPPG was confirmed in a G. mellonella infection model. Conclusions: Our study demonstrates that DPPG is a potent scaffold to combat invasive fungal infections.

Gold nanorods non-functionalised and associated with gallic acid exhibit activity against non-albicans Candida species

Strategies focusing on natural compounds and nanotechnology have been explored to overcome the limitations of conventional therapies in managing Candida infections. In this context, metal nanoparticles, both non-functionalised and combined with gallic acid, may offer a promising alternative. This study investigated the effects of gold nanoparticles non-functionalised (AuNp) and associated with gallic acid (AuNpGA) against planktonic cells and biofilms of Nakaseomyces glabratus, Pichia kudriavzevii, Candida parapsilosis, and Candida tropicalis. Both AuNp and AuNpGA inhibited the growth of all strains at 1.56 µg/mL and exhibited fungicidal effects at concentrations ranging from 1.56 to 3.12 µg/mL. The time-kill curve revealed that AuNpGA and AuNp completely inhibited the viability of all strains in planktonic cultures at 8 and 24 h, respectively, exhibiting greater antifungal activity compared to fluconazole. Treatment with AuNp increased ROS production against N. glabratus and P. kudriavzevii. Oxidative stress was enhanced against all strains after treatment with AuNpGA, and exposure to this compound reduced ergosterol levels of P. kudriavzevii and C. parapsilosis. Furthermore, AuNpGA and AuNp significantly decreased the viability of all Candida biofilms at 7.8 and 15.6 µg/mL, respectively. In summary, both gold nanoparticles exhibited activity against planktonic cells and biofilms, suggesting their potential as agents for treating Candida infections.

Antifungal and Antioxidant Activity of Thiourea Derivatives Against Nosocomial Candida auris Strains Isolated in Romania

Nosocomial fungal infections caused by Candida auris pose a threat to public health due to their increased resistance to common antifungal drugs. Four thiourea derivatives of 2-thiophenecarboxylic acid were evaluated for their antifungal and antioxidant activity. The antifungal activity of the compounds was tested against strains of C. auris isolated from a hospital in Romania. With a notable inhibitory effect on C. auris biofilm growth and microbial adherence, the ortho-methylated derivative (SB2) showed the highest antifungal activity. Furthermore, emphasizing the impact of structural factors on the electron-donating capacity of these compounds, antioxidant activity assays (DPPH, FRAP, TEAC and CUPRAC) identified the SB2 compound as having the highest antihemolytic and antioxidant effects. The low cytotoxicity validated by hemocompatibility assays makes these compounds options for antifungal treatment. The results show that antifungal and antioxidant action is greatly influenced by structural modifications, especially the position of the methyl group on the aromatic ring. The possible clinical uses of these molecules as drugs for the treatment of multidrug-resistant C. auris infections needs further investigation.

Tumor-Adhesive Chitosan-Derived Multi-Immune Agonist Unleashes Strong and Durable Anti-Cancer Immunity

The immunomodulation of the tumor microenvironment is critical for effective cancer immunotherapy, particularly for tumors that exhibit limited responses to conventional treatments. However, current immune agonists developed for tumor immunomodulation face several challenges, such as poor intratumoral retention, inadequate biocompatibility, and restricted cellular targets, which ultimately hamper their therapeutic efficacy and clinical application. In this study, a tumor-adhesive chitosan-tethered immune agonist construct (TACTIC) is introduced, which demonstrates good biocompatibility and robust immunostimulatory effects, enhancing the immunogenicity of tumor cells while simultaneously stimulating pro-inflammatory responses in various immune cell populations. Mechanistic investigations reveal that TACTIC targets multiple signaling pathways, conferring it to effectively remodel the irradiated tumor microenvironment, improve tumor control on murine cancer models post-radiotherapy, and elicit systemic immune responses with memory effects. The findings highlight the potential of TACTIC as a powerful macromolecular immune adjuvant, paving the way for its broader application in innovative cancer immunotherapies.

Kaempferol attenuates cyclosporine-induced renal tubular injury via inhibiting the ROS-ASK1-MAPK pathway

Cyclosporine (CSA) is a widely used immunosuppressive medication. CSA nephrotoxicity severely limits its application. Kaempferol (KPF), a naturally occurring phenolic compound, has a promising protective effect in reducing CSA-induced renal tubular injury, but the mechanism remains unknown. Our study aimed to determine the protective role of KPF against CSA-induced renal tubular injury. C57/B6 mice and the NRK-52E cell line were employed. CSA worsened renal function in mice, causing detachment and necrosis of tubular cells, leading to tubular vacuolation and renal interstitial fibrosis. CSA caused the detachment, rupture, and death of tubular cells in vitro, resulting in cell viability loss. KPF mitigated all these injurious alterations. KPF hindered CSA-induced ROS generation and protected renal tubular epithelial cells, similar to the antioxidant NAC. CSA lowered SOD activity and GSH levels while increasing MDA levels, and KPF ameliorated these changes. CSA caused phosphorylation of ASK1, JNK, and p38, similar to H2O2, whereas KPF significantly inhibited these changes. In conclusion, KPF reduces CSA-induced tubular epithelial cell injury via its antioxidant properties, inhibits the phosphorylation of ASK1, and inhibits the phosphorylation of p38 and JNK, implying that the synergistic use of KPF in CSA immunotherapy may be a promising option to reduce CSA-evoked renal injury.

Suppressed Protein Translation Caused by MSP-8 Deficiency Determines Fungal Multidrug Resistance with Fitness Cost

Antifungal resistance, particularly the rise of multidrug-resistance strains, poses a significant public health threat. In this study, the study identifies a novel multidrug-resistance gene, msp-8, encoding a helicase, through experimental evolution with Neurospora crassa as a model. Deletion of msp-8 conferred multidrug resistance in N. crassa, Aspergillus fumigatus, and Fusarium verticillioides. However, the transcript levels of genes encoding known drug targets or efflux pumps remain unaltered with msp-8 deletion. Interestingly, MSP-8 interacted with ribosomal proteins, and this mutant displays compromised ribosomal function, causing translational disturbance. Notably, inhibition of protein translation enhances resistance to azoles, amphotericin B, and polyoxin B. Furthermore, MSP-8 deficiency or inhibition of translation reduces intracellular ketoconazole accumulation and membrane-bound amphotericin B content, directly causing antifungal resistance. Additionaly, MSP-8 deficiency induces cell wall remodeling, and decreases intracellular ROS levels, further contributing to resistance. The findings reveal a novel multidrug resistance mechanism independent of changes in drug target or efflux pump, while MSP-8 deficiency suppresses protein translation, thereby facilitating the development of resistance with fitness cost. This study provides the first evidence that MSP-8 participates in protein translation and that translation suppression can cause multidrug resistance in fungi, offering new insights into resistance mechanisms in clinical and environmental fungal strains.

Microscopic Characterization of the Infectious Process, ROS Production, and Fungi Cellular Death of Alternaria alternata on Tangerine Resistant to QoIs

Quinone outside inhibitor (QoI) fungicide resistance in Alternaria alternata populations was reported in Brazil for the first time in 2019, in São Paulo orchards, and the mutation G143A in cytochrome b (cytb) was found in resistant isolates. Our study investigated the infectious process, production of reactive oxygen species (ROS), and fungal cell death in resistant (QoI-R) and sensitive (QoI-S) A. alternata pathotype tangerine (Aapt) isolates. Morphological characterization of Aapt isolates was performed using confocal laser scanning microscopy (CLSM). Alternaria brown spot (ABS) symptoms were produced by Aapt isolates on tangelo cv. BRS Piemonte. Germination of QoI-R conidia and production of germ tubes on tangelo leaflets treated with 100 μg mL-1 of pyraclostrobin 18 h after inoculation (hai) was observed using scanning electron microscopy (SEM). At the same time, QoI-S conidial germination was inhibited on tangelo leaflets treated with pyraclostrobin. ROS production and cell death in Aapt isolates at high fungicide concentrations were observed using CLSM. QoI-S conidia exhibited high ROS production, indicating high oxidative stress. When dyed with propidium iodate (PI), QoI-S conidia emitted red fluorescence, showing cell death and confirming their sensitive phenotype. In contrast, QoI-R conidia neither produced ROS nor exhibited red fluorescence, indicating no cell death and confirming their resistant phenotype. Therefore, our findings evidence that microscopic techniques may help characterize events during fungi-plant interactions, ROS production, cell death, and Aapt phenotypes resistant and sensitive to QoIs using fluorometric protocols.

The Role of Oxidative Stress in the Antifungal Activity of Two Mollusk Fractions on Resistant Fungal Strains

Fungal infections are a significant global public health challenge because of their widespread occurrence, morbidity, and profound social and economic consequences. Antifungal resistance is also an increasing concern, posing a substantial risk to public health. There is a growing interest in searching for new antifungal drugs isolated from natural sources. This study aimed to evaluate the antifungal activity of novel mollusk fractions against fungal strains resistant to nystatin and amphotericin B. In addition, the role of oxidative stress in the mechanism of damage was determined. The mucus from the garden snail Cornu aspersum (MCa/1-20) and the hemolymph fraction from the marine snail Rapana venosa (HLRv/3-100) were obtained and characterized via 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometric -analyses. The results demonstrate that the spores and biomass of both mollusk fractions have a significant fungicidal effect against Penicillium griseofulvum, and Aspergillus niger. Compared to the control group, the release of intracellular proteins and reducing sugars was significantly increased in the treated groups. The data showed increased levels of oxidative stress biomarkers (lipid peroxidation and oxidatively damaged proteins) and a downregulated antioxidant enzyme defense, corresponding to increased antifungal activity. To our knowledge, this is the first study evaluating oxidative stress as a factor in mollusk fractions' antifungal activity.

Miconazole-splitomicin combined β-glucan hydrogel for effective prevention of Candida albicans periprosthetic joint infection

As one of the most common and serious infections caused by Candida albicans (C. albicans), periprosthetic joint infection (PJI) increasingly concerns surgeons and scientists. Generally, biofilms shield C. albicans from antifungal agents and immune clearance and induce drug-resistant strains. Developing novel strategies for PJI to get rid of current drug-resistant problems is highly needed. In our study, splitomicin (SP) can inhibit the mycelium formation of C. albicans and enhance the drug sensitivity of C. albicans to miconazole nitrate (MCZ). The combination of SP and MCZ significantly inhibited the viability, proliferation and adhesion of C. albicans, reduced the yeast to hyphae transition and biofilm formation. When SP and MCZ were coloaded in the β-glucan hydrogel, a viscoelastic solid with porous 3D network, sustained release and erosion properties was obtained. In the in vivo PJI mice model, SP-MCZ-β-glucan hydrogel effectively reduced the colonization and aggregation of C. albicans around the implant, reduced the pathological changes caused by C. albicans in the femur tissue. Therefore, SP-MCZ-β-glucan hydrogel holds a great promise for the management of C. albicans infection around joint prosthesis.

Transcriptional profiling reveals the role of Candida albicans Rap1 in oxidative stress response

Candida albicans is a member of the human commensal microbiota but can also cause opportunistic infections, including life-threatening invasive candidiasis, particularly in immunocompromised patients. One of the important features of C. albicans commensalism and virulence is its ability to adapt to diverse environmental stress conditions within the host. Rap1 is a DNA-binding protein identified in yeasts, protozoa, and mammalian cells, and it plays multiple functions, including telomere regulation. Intriguingly, our previous study showed that Rap1 is also involved in cell wall integrity, biofilm formation, and virulence in C. albicans. In this work, using RNA-seq analysis and other approaches, the role of C. albicans Rap1 in oxidative stress response was further revealed. The RAP1-deletion mutant exhibited greater resistance to the superoxide generator menadione, a lower level of intracellular reactive oxygen species (ROS) upon menadione treatment, and higher expression levels of superoxide dismutase genes, all in response to oxidative stress. Moreover, the association between Rap1-mediated oxidative stress response and the mitogen-activated protein kinase (MAPK) Hog1, the transcription factor Cap1 and the TOR signalling was also determined. Together, these findings expand our understanding of the complex signalling and transcriptional mechanisms regulating stress responses in C. albicans.

Effect of Combination of Blue and Red Light with Terbinafine on Cell Viability and Reactive Oxygen Species in Human Keratinocytes: Potential Implications for Cutaneous Mycosis

Cutaneous mycoses are common infections whose treatment has become more complex due to increasing antifungal resistance and the need for prolonged therapies, hindering patient adherence and increasing the incidence of adverse effects. Consequently, the use of physical therapies, especially photodynamic therapy (PDT), has increased for the treatment of onychomycosis due to its antimicrobial capacity being mediated by the production of reactive oxygen species. This study investigates the in vitro effect of applying blue light (448 nm) or red light (645 nm), alone or together with terbinafine, on the viability of human keratinocytes and the production of reactive oxygen species. The combination of terbinafine and blue light significantly increases ROS production and caspase-3 expression, while red light together with terbinafine increases catalase, superoxide dismutase (SOD) and PPARγ expression, which reduces the amount of ROS in the cultures. The effect of both treatments could be useful in clinical practice to improve the response of cutaneous mycoses to pharmacological treatment, reduce their toxicity and shorten their duration.

Overcoming amphotericin B resistance in Candida auris using the antiemetic drug rolapitant

The emergence of Candida auris poses a significant health challenge that has led to a new era of multidrug-resistant fungal infections. Invasive infections caused by C. auris are usually associated with remarkable morbidity and mortality. For many years, amphotericin B (AmB) remained the most efficient and the last line of treatment against most hard-to-treat fungal infections. However, strains of C. auris possess extraordinary resistance to most antifungal agents, including AmB. In this study, we screened ~2,600 FDA-approved drugs and clinical compounds to identify the antiemetic drug rolapitant as a promising enhancer to AmB against C. auris. Rolapitant exhibited potent synergistic interactions with AmB against all tested (29/29) C. auris isolates. In a time-kill assay, rolapitant restored the fungicidal activity of AmB within 4 h. Additionally, the synergistic relationship between rolapitant and AmB was observed against other medically crucial Candida, Cryptococcus, and Aspergillus species. A transcriptomic study revealed that exposure to rolapitant affects oxidation reduction processes, ion transporters, and ATP production. Rolapitant triggers an elevation in cytosolic and mitochondrial calcium levels and induces oxidative stress within fungal cells. An ATP luminescence assay confirmed that rolapitant, at sub-inhibitory concentrations, significantly interfered with ATP production in C. auris. Moreover, rolapitant enhanced the in vivo activity of AmB in a mouse model of disseminated C. auris infection, as the combination reduced the fungal burden in murine kidneys by ~1 log (~90%) colony forming units. Our findings warrant further investigation of using rolapitant to overcome AmB resistance in C. auris and other fungal species.

Clioquinol influences cell membrane, attenuates virulence factors, induces apoptosis to inhibit Candida albicans growth

Aim: To investigate the antifungal mechanism of clioquinol and indicate that clioquinol has potential as a novel therapeutic antifungal agent.Materials & methods: Analyze differentially expressed genes of Candida albicans treated with clioquinol using RNA-sequencing. The effects on cell wall and membrane features, virulence factors, apoptosis-induced cell death were also investigated.Results: The differentially expressed genes of C. albicans after treated with clioquinol focused on cell wall and membrane synthesis, antioxidant system and energy metabolism. Clioquinol did not change cell wall components levels while it decreased squalene epoxidase activity to influence the ergosterol biosynthesis in cell membrane. It also decreased cellular surface hydrophobicity and induced β-glucan unmasking to attenuate virulence factors. Meanwhile, clioquinol influenced enzyme activities involved in antioxidant system, citrate cycle, oxidative phosphorylation and decreased the ATP levels. Clioquinol induced apoptosis in C. albicans to exert its fungicidal activity. It induced reactive oxygen species and calcium ion elevation, leading to loss of mitochondrial membrane potential, cytochrome C release, metacaspase activation, thereby triggering apoptosis.Conclusion: Clioquinol exerted anti-C. albicans activity through influencing cell membrane, attenuating virulence factors and inducing apoptosis.

Role of NF-κB signaling pathway in H2O2-induced oxidative stress of hiPSCs

The balance between oxidation and antioxidation is crucial for the development of embryo. It is harmful to the early embryonic development if embryonic stem cells (ESCs) encounter the serious oxidative stress in vivo. Induced pluripotent stem cells (iPSCs) are very similar to ESCs and are the important cell source to replace ESCs for research and therapy. Studies show that iPSCs have better resistant ability to oxidative stress, but the involved mechanism remains unclear. In this study, we predicted that the NF-κB pathway might be involved in H2O2-induced developmental damage by network toxicology analysis. Then, the oxidative stress model was established with different concentrations of H2O2 to investigate the mechanism of NF-κB pathway in oxidative stress of human induced pluripotent stem cells (hiPSCs). The results showed as follows: With the increase of H2O2 concentration, the ROS level gradually went up leading to an increasing damage degree of hiPSCs; however, the MDA content was obviously high only in the 400 μM H2O2 group; the activities of some antioxidant indexes such as SOD2 and T-AOC were significantly upregulated in the 100 μM group, while most of antioxidant indexes showed downregulated tendency to different degrees with the increase of H2O2 concentration. The expression levels of P65, P50, IκB, SOD2, and FHC mRNA were upregulated in most H2O2-treated groups, showing a dose-dependent relationship. In subsequent experiments, the inhibitor of IκB-α phosphorylation, Bay11-7082, reversed the upregulation of P65, IκB, and FHC mRNA expression induced by 400 μM H2O2. The protein levels of P65, p-P65, P50, p-P50, IκB, p-IκB, SOD2, and FHC were upregulated in most H2O2-treated groups. However, the upregulation induced by 400 μM H2O2 could be reversed by BAY 11-7082, except for IκB and SOD2. In conclusion, H2O2 could promote the expressions and phosphorylations of NF-κB that could upregulate the expressions of its downstream antioxidant genes to minimize the damage of hiPSCs caused by oxidative stress. These results contribute to a fundamental understanding of the antioxidant mechanism of iPSCs and will further facilitate the application of iPSCs, as well as provide a reference for controlling the oxidative stress encountered in the early development stage of embryo.

Unraveling the effective inhibition of α-terpinol and terpene-4-ol against Aspergillus carbonarius: Antifungal mechanism, ochratoxin A biosynthesis inhibition and degradation perspectives

Aspergillus carbonarius, a common food-contaminating fungus, produces ochratoxin A (OTA) and poses a risk to human health. This study aimed to assess the inhibitory activity of tea tree essential oil and its main components, Terpene-4-ol (T4), α-terpineol (αS), and 3-carene (3C) against A. carbonarius. The study showed αS and T4 were the main antifungal components of tea tree essential oil, which primarily inhibit A. carbonarius growth through cell membrane disruption, reducing antioxidant enzyme activities (catalase, peroxidase, superoxide dismutase) and interrupting the tricarboxylic acid cycle. Furthermore, αS and T4 interacted with enzymes related to OTA biosynthesis. Molecular docking and molecular dynamics show that they bound mainly to P450 with a minimum binding energy of -7.232 kcal/mol, we infered that blocking the synthesis of OTA precursor OTβ. Our hypothesis was preliminarily verified by the detection of key substances in the OTA synthesis pathway. The results of UHPLC-QTOF-MS2 analysis demonstrated that T4 achieved a degradation rate of 43 % for OTA, while αS reached 29.6 %, resulting in final breakdown products such as OTα and phenylalanine. These results indicated that α-terpinol and Terpene-4-ol have the potential to be used as naturally safe and efficient preservatives or active packaging to prevent OTA contamination.

Inhibitory effects and mode of antifungal action of isobavachalcone on Candida albicans growth and virulence factors

The fungus Candida albicans causes various kinds of human infections, including oral thrush, vulvovaginitis and life-endangering bloodstream infections, the incidence of which are rising. Worsening this, the clinical antifungals are limited to a few, highlighting the necessity to develop novel antifungal therapies. In this study, the antifungal activities of isobavachalcone against C. albicans SC5314 and nine C. albicans clinical isolates were tested. The effects of isobavachalcone (IBC) on C. albicans virulence factors, such as hyphal formation, adhesion, biofilm formation and extracellular phospholipase production, as well as the underlying mechanism, were also evaluated. Antifungal susceptibility test revealed that IBC has significant anti-Candida activities, with both MIC and MFC being 4-5 μg/mL against all strains tested. Hyphal formation in RPMI-1640, Spider and GlcNAc medium, adhesion to abiotic polystyrene surfaces and surfaces of A549 cells, could be inhibited by IBC. Most important, IBC could inhibit the C. albicans biofilm formation and development. PI staining tests showed that IBC could increase the cell membrane permeability, suggesting the damages to the fungal cell membrane. IBC was further demonstrated to induce excessive ROS production in C. albicans planktonic cells and its mature biofilms, as revealed by DCFH fluorescence detection through flowcytometry and relative fluorescence intensity analysis (with a microplate reader). The roles of ROS in the antifungal activity of IBC were further confirmed through antioxidant rescue assays in MIC and biofilm formation tests. Compared to its antifungal activity, the cytotoxicity against mammalian cells was low, indicating its potential in developing antifungal therapies.

Pan-omics-based characterization and prediction of highly multidrug-adapted strains from an outbreak fungal species complex

Strains from the Cryptococcus gattii species complex (CGSC) have caused the Pacific Northwest cryptococcosis outbreak, the largest cluster of life-threatening fungal infections in otherwise healthy human hosts known to date. In this study, we utilized a pan-phenome-based method to assess the fitness outcomes of CGSC strains under 31 stress conditions, providing a comprehensive overview of 2,821 phenotype-strain associations within this pathogenic clade. Phenotypic clustering analysis revealed a strong correlation between distinct types of stress phenotypes in a subset of CGSC strains, suggesting that shared determinants coordinate their adaptations to various stresses. Notably, a specific group of strains, including the outbreak isolates, exhibited a remarkable ability to adapt to all three of the most commonly used antifungal drugs for treating cryptococcosis (amphotericin B, 5-fluorocytosine, and fluconazole). By integrating pan-genomic and pan-transcriptomic analyses, we identified previously unrecognized genes that play crucial roles in conferring multidrug resistance in an outbreak strain with high multidrug adaptation. From these genes, we identified biomarkers that enable the accurate prediction of highly multidrug-adapted CGSC strains, achieving maximum accuracy and area under the curve (AUC) of 0.79 and 0.86, respectively, using machine learning algorithms. Overall, we developed a pan-omic approach to identify cryptococcal multidrug resistance determinants and predict highly multidrug-adapted CGSC strains that may pose significant clinical concern.

Antifungal Synergy: Mechanistic Insights into the R-1-R Peptide and Bidens pilosa Extract as Potent Therapeutics against Candida spp. through Proteomics

Previous reports have demonstrated that the peptide derived from LfcinB, R-1-R, exhibits anti-Candida activity, which is enhanced when combined with an extract from the Bidens pilosa plant. However, the mechanism of action remains unexplored. In this research, a proteomic study was carried out, followed by a bioinformatic analysis and biological assays in both the SC5314 strain and a fluconazole-resistant isolate of Candida albicans after incubation with R-1-R. The proteomic data revealed that treatment with R-1-R led to the up-regulation of most differentially expressed proteins compared to the controls in both strains. These proteins are primarily involved in membrane and cell wall biosynthesis, membrane transport, oxidative stress response, the mitochondrial respiratory chain, and DNA damage response. Additionally, proteomic analysis of the C. albicans parental strain SC5314 treated with R-1-R combined with an ethanolic extract of B. pilosa was performed. The differentially expressed proteins following this combined treatment were involved in similar functional processes as those treated with the R-1-R peptide alone but were mostly down-regulated (data are available through ProteomeXchange with identifier PXD053558). Biological assays validated the proteomic results, evidencing cell surface damage, reactive oxygen species generation, and decreased mitochondrial membrane potential. These findings provide insights into the complex antifungal mechanisms of the R-1-R peptide and its combination with the B. pilosa extract, potentially informing future studies on natural product derivatives.

Machine learning-assisted SERS approach enables the biochemical discrimination in Bcl-2 and Mcl-1 expressing yeast cells treated with ketoconazole and fluconazole antifungals

Antifungal medications are important due to their potential application in cancer treatment either on their own or with traditional treatments. The mechanisms that prevent the effects of these medications and restrict their usage in cancer treatment are not completely understood. The evaluation and discrimination of the possible protective effects of the anti-apoptotic members of the Bcl-2 family of proteins, critical regulators of mitochondrial apoptosis, against antifungal drug-induced cell death has still scientific uncertainties that must be considered. Novel, simple, and reliable strategies are highly demanded to identify the biochemical signature of this phenomenon. However, the complex nature of cells poses challenges for the analysis of cellular biochemical changes or classification. In this study, for the first time, we investigated the probable protective activities of Bcl-2 and Mcl-1 proteins against cell damage induced by ketoconazole (KET) and fluconazole (FLU) antifungal drugs in a yeast model through surface-enhanced Raman spectroscopy (SERS) approach. The proposed SERS platform created robust Raman spectra with a high signal-to-noise ratio. The analysis of SERS spectral data via advanced unsupervised and supervised machine learning methods enabled unquestionable differentiation (100 %) in samples and biomolecular identification. Various SERS bands related to lipids and proteins observed in the analyses suggest that the expression of these anti-apoptotic proteins reduces oxidative biomolecule damage induced by the antifungals. Also, cell viability assay, Annexin V-FITC/PI double staining, and total oxidant and antioxidant status analyses were performed to support Raman measurements. We strongly believe that the proposed approach paves the way for the evaluation of various biochemical structures/changes in various cells.

Adaptative survival of Aspergillus fumigatus to echinocandins arises from cell wall remodeling beyond β-1,3-glucan synthesis inhibition

Antifungal echinocandins inhibit the biosynthesis of β-1,3-glucan, a major and essential polysaccharide component of the fungal cell wall. However, the efficacy of echinocandins against the pathogen Aspergillus fumigatus is limited. Here, we use solid-state nuclear magnetic resonance (ssNMR) and other techniques to show that echinocandins induce dynamic changes in the assembly of mobile and rigid polymers within the A. fumigatus cell wall. The reduction of β-1,3-glucan induced by echinocandins is accompanied by a concurrent increase in levels of chitin, chitosan, and highly polymorphic α-1,3-glucans, whose physical association with chitin maintains cell wall integrity and modulates water permeability. The rearrangement of the macromolecular network is dynamic and controls the permeability and circulation of the drug throughout the cell wall. Thus, our results indicate that echinocandin treatment triggers compensatory rearrangements in the cell wall that may help A. fumigatus to tolerate the drugs' antifungal effects.

Discovery of Novel α,β-Unsaturated Amide Derivatives as Candidate Antifungals to Overcome Fungal Resistance

In our previous study, coumarin-containing CYP51 inhibitor A32 demonstrated potent antiresistance activity. However, compound A32 demonstrated unsatisfied metabolic stability, necessitating modifications to overcome these limitations. In this study, α,β-unsaturated amides were used to replace the unstable coumarin ring, which increased metabolic stability by four times while maintaining antifungal activity, including activity against resistant strains. Subsequently, the sterol composition analysis and morphological observation experiments indicated that the target of these novel compounds is lanosterol 14α-demethylase (CYP51). Meanwhile, biofilm growth was inhibited and resistance genes (ERG11, CDR1, CDR2, and MDR1) expression was downregulated to find out how the antiresistance works. Importantly, compound C07 demonstrated the capacity to stimulate reactive oxygen species, thus displaying potent fungicidal activity. Moreover, C07 exhibited encouraging effectiveness in vivo following intraperitoneal administration. Additionally, the most potent compound C07 showed satisfactory pharmacokinetic properties and low toxicity. These α,β-unsaturated amide derivatives, particularly C07, are potential candidates for treating azole-resistant candidiasis.

Oxidative effects of the human antifungal drug clotrimazole on the eucaryotic model organism Saccharomyces cerevisiae

Clotrimazole is a type of antifungal medication developed from azole compounds. It exhibits several biological actions linked to oxidative stress. This study focuses on the oxidative effects of clotrimazole on the eukaryotic model yeast, Saccharomyces cerevisiae. Our results showed that although initial nitric oxide levels were above control in clotrimazole exposed cells, they showed decreasing tendencies from the beginning of incubation and dropped below control at 125 µM from the 60th min. The highest superoxide anion and hydrogen peroxide levels were 1.95- and 2.85-folds of controls at 125 µM after 15 and 60 min, respectively. Hydroxyl radical levels slightly increased throughout the incubation period in all concentrations and reached 1.3-fold of control, similarly at 110 and 125 µM in the 90th min. The highest level of reactive oxygen species was observed at 110 µM, 2.31-fold of control. Although NADH/NADPH oxidase activities showed similar tendencies for all conditions, the highest activities were found as 3.07- and 2.27-folds of control at 125 and 110 µM in the 15th and 30th min, respectively. The highest superoxide dismutase and catalase activities were 1.59- and 1.21-folds of controls at 110 µM clotrimazole in 30 and 90 min, respectively. While the drug generally induced glutathione-related enzyme activities, the ratios of glutathione to oxidized glutathione were above the control only at low concentrations of the drug. The levels of lipid peroxidation in all treated cells were significantly higher than the controls. The findings crucially demonstrate that this medicine can generate serious oxidative stress in organisms.

Cyanide Trapping of Iminium Ion Reactive Metabolites: Implications for Clinical Hepatotoxicity

Reactive metabolite formation is a major mechanism of hepatotoxicity. Although reactive electrophiles can be soft or hard in nature, screening strategies have generally focused on the use of glutathione trapping assays to screen for soft electrophiles, with many data sets available to support their use. The use of a similar assay for hard electrophiles using cyanide as the trapping agent is far less common, and there is a lack of studies with sufficient supporting data. Using a set of 260 compounds with a defined hepatotoxicity status by the FDA, a comprehensive literature search yielded cyanide trapping data on an unbalanced set of 20 compounds that were all clinically hepatotoxic. Thus, a further set of 19 compounds was selected to generate cyanide trapping data, resulting in a more balanced data set of 39 compounds. Analysis of the data demonstrated that the cyanide trapping assay had high specificity (92%) and a positive predictive value (83%) such that hepatotoxic compounds would be confidently flagged. Structural analysis of the adducts formed revealed artifactual methylated cyanide adducts to also occur, highlighting the importance of full structural identification to confirm the nature of the adduct formed. The assay was demonstrated to add the most value for compounds containing typical structural alerts for hard electrophile formation: half of the severe hepatotoxins with these structural alerts formed cyanide adducts, while none of the severe hepatotoxins with no relevant structural alerts formed adducts. The assay conditions used included cytosolic enzymes (e.g., aldehyde oxidase) and an optimized cyanide concentration to minimize the inhibition of cytochrome P450 enzymes by cyanide. Based on the demonstrated added value of this assay, it is to be initiated for use at GSK as part of the integrated hepatotoxicity strategy, with its performance being reviewed periodically as more data is generated.