Oxidative stress and programmed cell death in yeast

Insight into the surface discharge cold plasma efficient inactivation of Pseudomonas fluorescens in water based on exogenous reactive oxygen and nitrogen species: Synergistic mechanism and energy benefits

As well known, surface discharge cold plasma has efficient inactivation ability and a variety of RONS are main active particles for inactivation, but their synergistic mechanism is still not clear. Therefore, surface discharge cold plasma system was applied to treat Pseudomonas fluorescens to study bacterial inactivation mechanism and energy benefit. Results showed that energy efficiency was directly proportional to applied voltage and inversely proportional to initial concentration. Cold plasma treatment for 20 min was inactivated by approximately > 4-log10Pseudomonas fluorescens and application of •OH and 1O2 scavengers significantly improved survival rate. In addition, •OH and 1O2 destroyed cell membrane structure and membrane permeability, which promoted diffusion of RONS into cells and affecting energy metabolism and antioxidant capacity, leading to bacterial inactivation. Furthermore, accumulation of intracellular NO and ONOOH was related to infiltration of exogenous RNS, while accumulation of •OH, H2O2, 1O2, O2- was the result of joint action of endogenous and exogenous ROS. Transcriptome analysis revealed that different RONS of cold plasma were responsible for Pseudomonas fluorescens inactivation and related to activation of intracellular antioxidant defense system and regulation of genes expression related to amino acid metabolism and energy metabolism, which promoting cellular process, catalytic activity and other biochemical pathways.

Screening and In Silico Analyses of the Yeast Saccharomyces cerevisiae Σ1278b Bank Mutants Using Citral as a Natural Antimicrobial

The antimicrobial function of citral, one of the main compounds of the essential oils (EO) of the Citrus genus, and widely used by the food industry toward spoilage yeast, was previously proven. In this study, the possible mode of action of citral against yeast cells was evaluated by using a global deletome approach. Firstly, the suitability of Saccharomyces cerevisiae Σ1278b to serve as model yeast was assessed by determining its sensitivity to citral (MIC = 0.5 μL/mL). Subsequently, the complete library of Σ1278b haploid mutants deleted in 4019 non-essential genes was screened to identify potential molecular targets of citral. Finally, the deleted genes in the 590 mutants showing increased citral resistance was analyzed with an in-silico approach (Gene Ontology). The significantly enriched GO Terms were "cytoplasm", "vacuole", and "mitochondrion" (cellular components); "catalytic activity" (molecular function); "pseudohyphal growth" (biological process). For molecular function, resistant mutants were grouped into thiosulfate sulfur transferase activity, transferase activity, and oxidoreductase activity; for cellular components, resistant mutants were grouped as: cytoplasm, intracellular organelle, membrane-bounded organelle, mitochondrion, organelle membrane, and vacuole; and finally, with regard to biological process, deleted genes were grouped as: pseudohyphal growth, mitochondrion organization, lipid metabolic process, DNA recombination and repair, and proteolysis. Interestingly, many identified genes were associated with the cellular response to oxidative stress and ROS scavenging. These findings have important implications for the development of citral-based antimicrobials and the elucidation of its mechanism of action.

Antifungal activity of human antimicrobial peptides targeting apoptosis in Candida auris

Introduction. Innovative antifungal therapies are of crucial importance to combat the potentially life-threatening infections linked to the multidrug-resistant fungal pathogen Candida auris. Induction of regulated cell death, apoptosis, could provide an outline for future therapeutics. Human antimicrobial peptides (AMPs), well-known antifungal compounds, have shown the ability to induce apoptosis in pathogenic fungi.Hypothesis/Gap Statement . Although it is known that AMPs possess antifungal activity against C. auris, their ability to induce apoptosis requires further investigations.Aim. This study evaluated the effects of AMPs on the induction of apoptosis in C. auris.Methods. Human neutrophil peptide-1 (HNP-1), human β-Defensins-3 (hBD-3) and human salivary histatin 5 (His 5) were assessed against two clinical C. auris isolates. Apoptosis hallmarks were examined using FITC-Annexin V/PI double labelling assay and terminal deoxynucleotidyl transferase deoxynucleotidyl transferase nick-end labelling (TUNEL) to detect phosphatidylserine externalization and DNA fragmentation, respectively. Then, several intracellular triggers were studied using JC-10 staining, spectrophotometric assay and 2',7'-dichlorofluorescin diacetate staining to measure the mitochondrial membrane potential, cytochrome-c release and reactive oxygen species (ROS) production, respectively.Results and conclusion. FITC-Annexin V/PI staining and TUNEL analysis revealed that exposure of C. auris cells to HNP-1 and hBD-3 triggered both early and late apoptosis, while His 5 caused significant necrosis. Furthermore, HNP-1 and hBD-3 induced significant mitochondrial membrane depolarization, which resulted in substantial cytochrome c release. In contrast to His 5, which showed minimal mitochondrial depolarization and no cytochrome c release. At last, all peptides significantly increased ROS production, which is related to both types of cell death. Therefore, these peptides represent promising and effective antifungal agents for treating invasive infections caused by multidrug-resistant C. auris.

Impact of Nitric Oxide-Release Kinetics on Antifungal Activity

Pathogenic fungi are an increasing health threat due to the rise in drug resistance. The limited number of antifungals currently available and growing incidence of multi-drug-resistant fungi has caused rising healthcare costs and a decreased quality of life for patients with fungal infections. Nitric oxide (NO) has previously been shown to act as an antimicrobial agent, albeit with a limited understanding of the effects of the NO-release kinetics against pathogenic fungi. Herein, the antifungal effects of four nitric oxide-releasing small molecules were studied against the pathogenic fungi Candida albicans, Candida auris, Cryptococcus neoformans, and Aspergillus fumigatus, to demonstrate the broad-spectrum antifungal activity of NO. A bolus dose of NO was found to eradicate fungi after 24 h, where nitric oxide donors with shorter half-lives achieved antifungal activity at lower concentrations and thus had wider selectivity indexes. Each NO donor was found to cause a severe surface destruction of fungi, and all NO donors exhibited compatibility with currently prescribed antifungals against several different fungi species.

Glucosylglycerol and proline reverse the effects of glucose on Rhodosporidium toruloides lifespan

Rhodosporidium toruloides is a novel cell factory used to synthesis carotenoids, biosurfactants, and biofuel feedstocks. However, research on R. toruloides has generally centred on the manufacture of biochemicals, while analyses of its longevity have received scant attention. Understanding of R. toruloides longevity under different nutrient conditions could help to improve its biotechnological significance and metabolite production. Glucosylglycerol (GG) and proline are osmoprotectants that could revert the harmful effects of environmental stress. This study examined how GG and proline affect R. toruloides strain longevity under glucose nutrimental stress. Herein, we provide evidence that GG and proline enhance cell performance and viability. These compatible solutes neutralises the pro-ageing effects of high glucose (10% glucose) on the yeast cell and reverse its cellular stress. GG exhibits the greatest impact on lifespan extension at 100 mM, whereas proline exerts effect at 2 mM. Our data reveal that these compounds significantly affect the culture medium osmolarity. Moreso, GG and proline decreased ROS production and mitohormetic lifespan regulation, respectively. The data indicates that these solutes (proline and GG) support the longevity of R. toruloides at a pro-ageing high glucose culture condition.

Calcineurin promotes adaptation to chronic stress through two distinct mechanisms

Adaptation to environmental stress requires coordination between stress-defense programs and cell cycle progression. The immediate response to many stressors has been well characterized, but how cells survive in challenging environments long-term is unknown. Here, we investigate the role of the stress-activated phosphatase calcineurin (CN) in adaptation to chronic CaCl2 stress in Saccharomyces cerevisiae. We find that prolonged exposure to CaCl2 impairs mitochondrial function and demonstrate that cells respond to this stressor using two CN-dependent mechanisms - one that requires the downstream transcription factor Crz1 and another that is Crz1-independent. Our data indicate that CN maintains cellular fitness by promoting cell cycle progression and preventing CaCl2-induced cell death. When Crz1 is present, transient CN activation suppresses cell death and promotes adaptation despite high levels of mitochondrial loss. However, in the absence of Crz1, prolonged activation of CN prevents mitochondrial loss and further cell death by upregulating glutathione (GSH) biosynthesis genes thereby mitigating damage from reactive oxygen species. These findings illustrate how cells maintain long-term fitness during chronic stress and suggest that CN promotes adaptation in challenging environments by multiple mechanisms.

Hydrogen peroxide sensitivity connects the activity of COX5A and NPR3 to the regulation of YAP1 expression

Reactive oxygen species (ROS) are among the most severe types of cellular stressors with the ability to damage essential cellular biomolecules. Excess levels of ROS are correlated with multiple pathophysiological conditions including neurodegeneration, diabetes, atherosclerosis, and cancer. Failure to regulate the severely imbalanced levels of ROS can ultimately lead to cell death, highlighting the importance of investigating the molecular mechanisms involved in the detoxification procedures that counteract the effects of these compounds in living organisms. One of the most abundant forms of ROS is H2 O2 , mainly produced by the electron transport chain in the mitochondria. Numerous genes have been identified as essential to the process of cellular detoxification. Yeast YAP1, which is homologous to mammalian AP-1 type transcriptional factors, has a key role in oxidative detoxification by upregulating the expression of antioxidant genes in yeast. The current study reveals novel functions for COX5A and NPR3 in H2 O2 -induced stress by demonstrating that their deletions result in a sensitive phenotype. Our follow-up investigations indicate that COX5A and NPR3 regulate the expression of YAP1 through an alternative mode of translation initiation. These novel gene functions expand our understanding of the regulation of gene expression and defense mechanism of yeast against oxidative stress.

3-bromopyruvate induces morphological alteration and may initiate programmed cell death in Cryptococcus neoformans cells

3-Bromopyruvate (3BP), known for its potent anticancer properties, also exhibits remarkable efficacy against the pathogenic fungus Cryptococcus neoformans. So far it has been proven that the main fungicidal activity of 3BP is based on ATP depletion and a reduction of intracellular level of glutathione. The presented study includes a broad range of methods to further investigate the mechanistic effects of 3BP on C. neoformans cells. The use of flow cytometry allowed a thorough examination of their survival during 3BP treatment, while observations using electron microscopy made it possible to note the changes in cellular morphology. Utilizing ruthenium red, the study suggests a mitochondrial pathway may initiate programmed cell death in response to 3BP. Analysis of free radical generation and gene expression changes supports this hypothesis. These findings enhance comprehension of 3BP's mechanisms in fungal cells, paving the way for its potential application as a therapeutic agent against cryptococcosis.

Hydrogen sulfide regulates arsenic-induced cell death in yeast cells by modulating the antioxidative system

Arsenic (As) is a metal with potentially toxic effects on different organisms. Hydrogen sulfide (H2S) plays a vital role in mitigating heavy metal toxicity by reducing oxidative stress in plants and animals. However, the role of H2S in alleviating arsenic toxicity in yeast cells remains unclear. In this study, the role of NaHS (exogenous physiological H2S) in alleviating As-induced yeast cell death was investigated. Yeast cells in the logarithmic phase were pretreated with 0.05 mmol/L NaHS for 6 h, and then incubated in the YPD medium with or without 1 mmol/L As. After 12 h of treatment, relative survival rate, H2S content, oxidative stress biomarkers, and antioxidant machinery were measured. Our results showed that sodium arsenite-induced yeast cell death and pretreatment with 0.05 mmol/L NaHS significantly alleviated sodium arsenite-induced cell death. Under sodium arsenite conditions, the levels of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) increased, accompanied by the inhibition of the catalase (CAT) activity and the downregulation of CTT1 expression. However, the activities of the superoxide dismutase (SOD) and glutathion peroxidase (GPX) increased, and the expression of SOD1 and GPX2 was markedly upregulated in the group treated with sodium arsenite. When yeast cells were pretreated with NaHS, the intracellular ROS and MDA levels decreased significantly, and the activities of SOD, CAT, and GPX increased significantly. This was associated with a significant increase in relative survival rate and H2S content compared to the arsenic treatment alone. Our findings indicate that NaHS alleviates sodium arsenite-induced yeast cell death, mainly by enhancing the antioxidant defense system.

Morphological Changes and Strong Cytotoxicity in Yarrowia lipolytica by Overexpressing Delta-12-Desaturase

In this study, delta-12 desaturase was overexpressed in Yarrowia lipolytica using the single-copy integrative vector pINA1312 and multicopy integrative vector pINA1292, resulting in the engineered yeast strains 1312-12 and 1292-12, respectively. The content of intracellular linoleic acid (LA) in the 1292-12 strain was much higher than in the 1312-12 strain and the control group. One interesting finding was that the 1292-12 strain showed obvious changes in surface morphology. The 1292-12 colonies were much smaller and smoother, whereas their single cells became much larger compared to the control strain. In addition, the dry cell weight (DCW) of the 1292-12 strain was obviously increased from 8.5 to 12.7 g/L, but the viable cell number sharply decreased from 107 to 105/mL. These results indicated that increased LA content in Yarrowia lipolytica could induce morphological changes or even oxidative stress-dependent cell death. The reactive oxygen species (ROS) and malondialdehyde (MDA) were accumulated in the 1292-12 strain, while the antioxidant activities of intracellular catalase (CAT) and superoxide dismutase (SOD) were significantly decreased by 27.6 and 32.0%, respectively. Furthermore, it was also revealed that these issues could be ameliorated by the exogenous supplementation of vitamin C, fish and colza oil.

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

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.

Bactericidal effect of low-temperature atmospheric plasma against the Shigella flexneri

BACKGROUND

Shigella flexneri (S. flexneri) is a common intestinal pathogenic bacteria that mainly causes bacillary dysentery, especially in low socioeconomic countries. This study aimed to apply cold atmospheric plasma (CAP) on S. flexneri directly to achieve rapid, efficient and environmentally friendly sterilization.

METHODS

The operating parameters of the equipment were determined by plasma diagnostics. The plate count and transmission electron microscope were employed to calculate bacterial mortality rates and observe the morphological damage of bacterial cells. Measurement of intracellular reactive oxygen species (ROS) and superoxide anions were detected by 2,7-dichlorodihydrofluorescein (DCFH) and Dihydroethidium fluorescence probes, respectively. The fluorescence intensity (a. u.) reflects the relative contents. Additionally, the experiment about the single effect of temperature, ultraviolet (UV), and ROS on bacteria was conducted.

RESULTS

The peak discharge voltage and current during plasma operation were 3.92kV and 66mA. After discharge, the bacterial mortality rate of 10, 20, 30 and 40 s of plasma treatment was 60.71%, 74.02%, 88.11% and 98.76%, respectively. It was shown that the intracellular ROS content was proportional to the plasma treatment time and ROS was the major contributor to bacterial death.

CONCLUSION

In summary, our results illustrated that the plasma treatment could inactivate S. flexneri efficiently, and the ROS produced by plasma is the leading cause of bacterial mortality. This highly efficient sterilization method renders plasma a highly promising solution for hospitals, clinics, and daily life.

Structural and solution speciation studies on selected [Cu(NN)(OO)] complexes and an investigation of their biomimetic activity, ROS generation and their cytotoxicity in normoxic, hypoxic and anoxic environments in MCF-7 breast cancer-derived cells

Reactive oxygen species(ROS) generation with subsequent DNA damage is one of the principle mechanisms of action assigned to copper-based anticancer complexes. The efficacy of this type of chemotherapeutic may be reduced in the low oxygen environment of tumours. In this study the cytotoxicity of three complexes, [Cu(dips)(phen)] (1), [Cu(ph)(phen)]·2H2O (2) and [Cu(ph)(bpy)]·H2O (3) (disp: 3,5-diisopropylsalicylate, phen: 1,10- phenanthroline, ph: phthalate, bpy: 2,2'-bipyridyl) were assessed for anticancer activity in the breast-cancer derived MCF-7 line under normoxic, hypoxic and anoxic conditions. In an immortalised keratinocyte HaCaT cell line, the cytotoxicity of complexes 2 and 3 was significantly reduced under both normoxic and hypoxic conditions, whilst the cytotoxicity of complex 1 was increased under hypoxic conditions. The ability of the complexes to generate ROS in the MCF-7 cell line was evaluated as was their ability to act as superoxide dismutase(SOD) and catalase mimics using a yeast cell assay. ROS generation was significant for complexes 2 and 3, less so for complex 1 though all three complexes had SOD mimetic ability. Given the ternary nature of the complexes, solution speciation studies were undertaken but were only successful for complex 3, due to solubility issues with the other two complexes. The concentration distribution of various species, formed in aqueous solution, was evaluated as a function of pH and confirmed that complex 3 is the dominant species at physiological pH in the mM concentration range. However, as its concentration diminishes, it experiences a progressive dissociation, leading to the formation of binary complexes of bpy alongside unbound phthalate.

The Reaction of the Yeast Saccharomyces cerevisiae to Contamination of the Medium with Aflatoxins B2 and G1, Ochratoxin A and Zearalenone in Aerobic Cultures

The mechanisms by which yeast cells respond to environmental stress include the production of heat shock proteins (HSPs) and the reduction of oxidative stress. The response of yeast exposed to aflatoxins B2+G1 (AFB2+G1), ochratoxin A (OTA), and zearalenone (ZEA) in aerobic conditions was studied. After 72 h of yeast cultivation in media contaminated with mycotoxins, the growth of yeast biomass, the level of malondialdehyde, and the activity of superoxide dismutase, glutathione S-transferase and glutathione peroxidase were examined; the expression profile of the following heat shock proteins was also determined: HSP31, HSP40, HSP60, HSP70, and HSP104. It was demonstrated that at the tested concentrations, both AFB2+G1 and ZEA inhibited yeast biomass growth. OTA at a concentration of 8.4 [µg/L] raised the MDA level. Intensified lipoperoxidation and increased activity of SOD and GPx were observed, regardless of the level of contamination with ZEA (300 µg/L or 900 µg/L). Increased contamination with AFB2+G1 and OTA caused an increase in the production of most HSPs tested (HSP31, HSP40, HSP70, HSP104). ZEA contamination in the used concentration ranges reduced the production of HSP31. The response of yeast cells to the presence of mycotoxin as a stressor resulted in the expression of certain HSPs, but the response was not systematic, which was manifested in different profiles of protein expression depending on the mycotoxin used. The tested mycotoxins influenced the induction of oxidative stress in yeast cells to varying degrees, which resulted in the activation of mainly SOD without GST mobilization or with a small involvement of GPx.

Exogenous glucosylglycerol and proline extend the chronological lifespan of Rhodosporidium toruloides

Glucosylglycerol (GG) is an osmolyte found in a few bacteria (e.g., cyanobacteria) and plants grown in harsh environments. GG protects microbes and plants from salinity and desiccation stress. In the industry, GG is synthesized from a combination of ADP-glucose and glycerol-3-phosphate in a condensation reaction catalyzed by glucosylglycerol phosphate synthase. Proline, on the other hand, is an amino acid-based osmolyte that plays a key role in cellular reprograming. It functions as a protectant and a scavenger of reactive oxygen species. Studies on lifespan extension have focused on the use of Saccharomyces cerevisiae. Rhodosporidium toruloides, also known as Rhodotorula toruloides, is a basidiomycetous oleaginous yeast known to accumulate lipids to more than 70% of its dry cell weight. The oleaginous red yeast (R. toruloides) has not been intensely studied in the lifespan domain. We designed this work to investigate how GG and proline promote the longevity of this red yeast strain. The results obtained in our study confirmed that these molecules increased R. toruloides' viability, survival percentage, and lifespan upon supplementation. GG exerts the most promising effects at a relatively high concentration (100 mM), while proline functions best at a low level (2 mM). Elucidation of the processes underlying these favorable responses revealed that GG promotes the yeast chronological lifespan (CLS) through increased catalase activity, modulation of the culture medium pH, a rise in ATP, and an increase in reactive oxygen species (ROS) accumulation (mitohormesis). It is critical to understand the mechanisms of these geroprotector molecules, particularly GG, and the proclivity of its lifespan application; this will aid in offering clarity on its potential application in aging research.

Dung beetle-associated yeasts display multiple stress tolerance: a desirable trait of potential industrial strains

BACKGROUND

Stress-tolerant yeasts are highly desirable for cost-effective bioprocessing. Several strategies have been documented to develop robust yeasts, such as genetic and metabolic engineering, artificial selection, and natural selection strategies, among others. However, the significant drawbacks of such techniques have motivated the exploration of naturally occurring stress-tolerant yeasts. We previously explored the biodiversity of non-conventional dung beetle-associated yeasts from extremophilic and pristine environments in Botswana (Nwaefuna AE et.al., Yeast, 2023). Here, we assessed their tolerance to industrially relevant stressors individually, such as elevated concentrations of osmolytes, organic acids, ethanol, and oxidizing agents, as well as elevated temperatures.

RESULTS

Our findings suggest that these dung beetle-associated yeasts tolerate various stresses comparable to those of the robust bioethanol yeast strain, Saccharomyces cerevisiae (Ethanol Red™). Fifty-six percent of the yeast isolates were tolerant of temperatures up to 42 °C, 12.4% of them could tolerate ethanol concentrations up to 9% (v/v), 43.2% of them were tolerant to formic acid concentrations up to 20 mM, 22.7% were tolerant to acetic acid concentrations up to 45 mM, 34.0% of them could tolerate hydrogen peroxide up to 7 mM, and 44.3% of the yeasts could tolerate osmotic stress up to 1.5 M.

CONCLUSION

The ability to tolerate multiple stresses is a desirable trait in the selection of novel production strains for diverse biotechnological applications, such as bioethanol production. Our study shows that the exploration of natural diversity in the search for stress-tolerant yeasts is an appealing approach for the development of robust yeasts.

Harnessing Efficient ROS Generation in Carbon Dots Derived from Methyl Red for Antimicrobial Photodynamic Therapy

The emergence of drug-resistant pathogenic microorganisms has become a public health concern, with demand for strategies to suppress their proliferation in healthcare facilities. The present study investigates the physicochemical and antimicrobial properties of carbon dots (CD-MR) derived from the methyl red azo dye. The morphological and structural analyses reveal that such carbon dots present a significant fraction of graphitic nitrogen in their structures, providing a wide emission range. Based on their low cytotoxicity against mammalian cells and tunable photoluminescence, these carbon dots are applied to bioimaging in vitro living cells. The possibility of using CD-MR to generate reactive oxygen species (ROS) is also analyzed, and a high singlet oxygen quantum efficiency is verified. Moreover, the antimicrobial activity of CD-MR is analyzed against pathogenic microorganisms Staphylococcus aureus, Candida albicans, and Cryptococcus neoformans. Kirby-Bauer susceptibility tests show that carbon dots synthesized from methyl red possess antimicrobial activity upon photoexcitation at 532 nm. The growth inhibition of C. neoformans from CD-MR photosensitization is investigated. Our results show that N-doped carbon dots synthesized from methyl red efficiently generate ROS and possess a strong antimicrobial activity against healthcare-relevant pathogens.

Apoptotic Factors Are Evolutionarily Conserved Since Mitochondrial Domestication

The mechanisms initiating apoptotic programmed cell death in diverse eukaryotes are very similar. Basically, the mitochondrial permeability transition activates apoptotic proteases, DNases, and flavoproteins such as apoptosis-inducing factors (AIFs). According to the hypothesis of the endosymbiotic origin of apoptosis, these mechanisms evolved during mitochondrial domestication. Various phylogenetic analyses, including ours, have suggested that apoptotic factors were eubacterial protomitochondrial toxins used for killing protoeukaryotic hosts. Here, we tested whether the function of yeast Saccharomyces cerevisiae apoptotic proteases (metacaspases Mca1 and Nma111), DNase Nuc1, and flavoprotein Ndi1 can be substituted with orthologs from remotely related eukaryotes such as plants, protists, and eubacteria. We found that orthologs of remotely related eukaryotic and even eubacterial proteins can initiate apoptosis in yeast when triggered by chemical stresses. This observation suggests that apoptotic mechanisms have been maintained since mitochondrial domestication, which occurred approximately 1,800 Mya. Additionally, it supports the hypothesis that some of these apoptotic factors could be modified eubacterial toxins.

Transcranial Photosensitizer-Free Laser Treatment of Glioblastoma in Rat Brain

Over sixty years, laser technologies have undergone a technological revolution and become one of the main tools in biomedicine, particularly in neuroscience, neurodegenerative diseases and brain tumors. Glioblastoma is the most lethal form of brain cancer, with very limited treatment options and a poor prognosis. In this study on rats, we demonstrate that glioblastoma (GBM) growth can be suppressed by photosensitizer-free laser treatment (PS-free-LT) using a quantum-dot-based 1267 nm laser diode. This wavelength, highly absorbed by oxygen, is capable of turning triplet oxygen to singlet form. Applying 1267 nm laser irradiation for a 4 week course with a total dose of 12.7 kJ/cm2 firmly suppresses GBM growth and increases survival rate from 34% to 64%, presumably via LT-activated apoptosis, inhibition of the proliferation of tumor cells, a reduction in intracranial pressure and stimulation of the lymphatic drainage and clearing functions. PS-free-LT is a promising breakthrough technology in non- or minimally invasive therapy for superficial GBMs in infants as well as in adult patients with high photosensitivity or an allergic reaction to PSs.

Crucial aspects of metabolism and cell biology relating to industrial production and processing of Saccharomyces biomass

The multitude of applications to which Saccharomyces spp. are put makes these yeasts the most prolific of industrial microorganisms. This review considers biological aspects pertaining to the manufacture of industrial yeast biomass. It is proposed that the production of yeast biomass can be considered in two distinct but interdependent phases. Firstly, there is a cell replication phase that involves reproduction of cells by their transitions through multiple budding and metabolic cycles. Secondly, there needs to be a cell conditioning phase that enables the accrued biomass to withstand the physicochemical challenges associated with downstream processing and storage. The production of yeast biomass is not simply a case of providing sugar, nutrients, and other growth conditions to enable multiple budding cycles to occur. In the latter stages of culturing, it is important that all cells are induced to complete their current budding cycle and subsequently enter into a quiescent state engendering robustness. Both the cell replication and conditioning phases need to be optimized and considered in concert to ensure good biomass production economics, and optimum performance of industrial yeasts in food and fermentation applications. Key features of metabolism and cell biology affecting replication and conditioning of industrial Saccharomyces are presented. Alternatives for growth substrates are discussed, along with the challenges and prospects associated with defining the genetic bases of industrially important phenotypes, and the generation of new yeast strains."I must be cruel only to be kind: Thus bad begins, and worse remains behind." William Shakespeare: Hamlet, Act 3, Scene 4.

Water extract from Ligusticum chuanxiong delays the aging of Saccharomyces cerevisiae via improving antioxidant activity

Ligusticum chuanxiong is a common traditional edible-medicinal herb that has various pharmacological activities. However, its effects on Saccharomyces cerevisiae (S. cerevisiae) remains unknown. In this study, we found that water extract of Ligusticum chuanxiong (abbreviated as WEL) exhibited excellent free radical scavenging ability in-vitro. Moreover, WEL treatment could delay the aging of S. cerevisiae, an important food microorganism sensitive to reactive oxygen species (ROS) stress. Biochemical analyses revealed that WEL significantly increased the activity of antioxidant enzymes in S. cerevisiae, including superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR), as well as their gene expression. As a result, ROS level was significantly decreased and accompanied with the decline of malondialdehyde (MDA), which represented a state of low oxidative stress. The reduction of oxidative stress could elevate S. cerevisiae's ethanol fermentation efficiency. Taken together, WEL plays a protective role against S. cerevisiae aging via improving antioxidant activity.

Autophagy mediates an amplification loop during ferroptosis

Ferroptosis, a programmed cell death, has been identified and associated with cancer and various other diseases. Ferroptosis is defined as a reactive oxygen species (ROS)-dependent cell death related to iron accumulation and lipid peroxidation, which is different from apoptosis, necrosis, autophagy, and other forms of cell death. However, accumulating evidence has revealed a link between autophagy and ferroptosis at the molecular level and has suggested that autophagy is involved in regulating the accumulation of iron-dependent lipid peroxidation and ROS during ferroptosis. Understanding the roles and pathophysiological processes of autophagy during ferroptosis may provide effective strategies for the treatment of ferroptosis-related diseases. In this review, we summarize the current knowledge regarding the regulatory mechanisms underlying ferroptosis, including iron and lipid metabolism, and its association with the autophagy pathway. In addition, we discuss the contribution of autophagy to ferroptosis and elucidate the role of autophagy as a ferroptosis enhancer during ROS-dependent ferroptosis.

Tacrolimus (FK506) Exhibits Fungicidal Effects against Candida parapsilosis Sensu Stricto via Inducing Apoptosis

Tacrolimus (FK506), an immunosuppressant and calcineurin inhibitor, has fungicidal effects. However, its fungicidal effect is thought to be limited to basidiomycetes, such as Cryptococcus and Malassezia, and not to ascomycetes. FK506 had no fungicidal effect on Candida albicans, C. auris, C. glabrata, C. guilliermondii, C. kefyr, C. krusei, and C. tropicalis (>8 µg/mL); however, C. parapsilosis was susceptible to it at low concentrations of 0.125-0.5 µg/mL. C. metapsilosis and C. orthopsils, previously classified as C. parapsilosis, are molecularly and phylogenetically closely related to C. parapsilosis, but neither species was sensitive to FK506. FK506 increased the mitochondrial reactive oxygen species production and cytoplasmic and mitochondrial calcium concentration and activated metacaspases, nuclear condensation, and DNA fragmentation, suggesting that it induced mitochondria-mediated apoptosis in C. parapsilosis. Elucidating why FK506 exhibits fungicidal activity only against C. parapsilosis will provide new information for developing novel antifungal drugs.

Metabolism: How a eukaryote adapted to life without respiration

A new study finds that Schizosaccharomyces japonicus, a eukaryote that lost the ability to respire, modified its central carbon metabolism to maintain efficient ATP production, cofactor regeneration, and amino-acid production. This remarkable metabolic flexibility opens new avenues towards applications.

MPA-capped CdTequantum dots induces endoplasmic reticulum stress-mediated autophagy and apoptosis through generation of reactive oxygen species in human liver normal cell and liver tumor cell

The rapid developments in nanotechnology have brought increased attention to the safety of Quantum Dots (QDs). Exploring their mechanisms of toxicity and characterizing their toxic effects in different cell lines will help us better understand and apply QDs appropriately. This study aims to elucidate the importance of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress-induced autophagy for CdTe QDs toxicity, that is, the importance of the nanoparticles in mediating cellular uptake and consequent intracellular stress effects inside the cell. The results of the study showed that cancer cells and normal cells have different cell outcomes as a result of intracellular stress effects. In normal human liver cells (L02), CdTe QDs leads to ROS generation and prolong ER stress. The subsequent autophagosome accumulation eventually triggers apoptosis by activating proapoptotic signaling pathways and the expression of proapoptotic Bax. In contrast, in human liver cancer cells (HepG2 cells), expression of UPR restrains proapoptotic signaling and downregulates Bax, and activated protective cellular autophagy, as a result of protecting these liver cancer cells from CdTe QDs-induced apoptosis. In summary, we assess the safety of CdTe QDs and recounted the molecular mechanism underlying its nanotoxicity in normal and cancerous cells. Notwithstanding, additional detailed studies on the deleterious effects of these nanoparticles in the organisms of interest are required to ensure low-risk application.

Evaluation of citrus pectin capped copper sulfide nanoparticles against Candidiasis causing Candida biofilms

The incidence of candidiasis has significantly increased globally in recent decades, and it is a significant source of morbidity and mortality, particularly in critically ill patients. Candida sp. ability to generate biofilms is one of its primary pathogenic traits. Drug-resistant strains have led to clinical failures of traditional antifungals, necessitating the development of a more modern therapy that can inhibit biofilm formation and enhance Candida sp. sensitivity to the immune system. The present study reports the anticandidal potential of pectin-capped copper sulfide nanoparticles (pCuS NPs) against Candida albicans. The pCuS NPs inhibit C. albicans growth at a minimum inhibitory concentration (MIC) of 31.25 μM and exhibit antifungal action by compromising membrane integrity and overproducing reactive oxygen species. The pCuS NPs, at their biofilm inhibitory concentration (BIC) of 15.63 μM, effectively inhibited C. albicans cells adhering to the glass slides, confirmed by light microscopy and scanning electron microscopy. Phase contrast microscopy pictures revealed that NPs controlled the morphological transitions between the yeast and hyphal forms by limiting conditions that led to filamentation and reducing hyphal extension. In addition, C. albicans showed reduced exopolysaccharide (EPS) production and exhibited less cell surface hydrophobicity (CSH) after pCuS NPs treatment. The findings suggest that pCuS NPs may be able to inhibit the emergence of virulence traits that lead to the formation of biofilms, such as EPS, CSH, and hyphal morphogenesis. The results raise the possibility of developing NPs-based therapies for C. albicans infections associated with biofilms.

Evaluating proteome allocation of Saccharomyces cerevisiae phenotypes with resource balance analysis

Saccharomyces cerevisiae is an important model organism and a workhorse in bioproduction. Here, we reconstructed a compact and tractable genome-scale resource balance analysis (RBA) model (i.e., named scRBA) to analyze metabolic fluxes and proteome allocation in a computationally efficient manner. Resource capacity models such as scRBA provide the quantitative means to identify bottlenecks in biosynthetic pathways due to enzyme, compartment size, and/or ribosome availability limitations. ATP maintenance rate and in vivo apparent turnover numbers (k_app) were regressed from metabolic flux and protein concentration data to capture observed physiological growth yield and proteome efficiency and allocation, respectively. Estimated parameter values were found to vary with oxygen and nutrient availability. Overall, this work (i) provides condition-specific model parameters to recapitulate phenotypes corresponding to different extracellular environments, (ii) alludes to the enhancing effect of substrate channeling and post-translational activation on in vivo enzyme efficiency in glycolysis and electron transport chain, and (iii) reveals that the Crabtree effect is underpinned by specific limitations in mitochondrial proteome capacity and secondarily ribosome availability rather than overall proteome capacity.

Selenium Alleviates Ammonia-Induced Splenic Cell Apoptosis and Inflammation by Regulating the Interleukin Family/Death Receptor Axis and Nrf2 Signaling Pathway

Ammonia (NH₃) is a harmful gas in livestock houses. So far, many researchers have demonstrated that NH₃ is detrimental to animal and human organs. Selenium (Se) is one of the essential trace elements in the body and has a good antioxidant effect. However, there was little conclusive evidence that Se alleviated NH₃ poisoning. To investigate the toxic mechanism of NH₃ on pig spleen and the antagonistic effect of L-selenomethionine, a porcine NH₃-poisoning model and an L-selenomethionine intervention model were established in this study. Our results showed that NH₃ exposure increased the apoptosis rate, while L-selenomethionine supplementation alleviated the process of excessive apoptosis. Immunofluorescence staining, real-time quantitative polymerase chain reaction (qRT-PCR), and western blot results confirmed that exposure to NH₃ changed the expression levels of interleukin family factors, apoptosis, death receptor, and oxidative stress factors. Our study further confirmed that excessive NH₃ induced inflammatory response and mediated necroptosis leading to cell apoptosis by activating the Nrf2 signaling pathway. Excessive NH₃ could mediate spleen injury through oxidative stress-induced mitochondrial dynamics disorder. L-Selenomethionine could alleviate inflammation and abnormal apoptosis by inhibiting the IL-17/TNF-α/FADD axis. Our study would pave the way for comparative medicine and environmental toxicology.

Glucosylglycerol Extends Chronological Lifespan of the Budding Yeast via an Increased Osmolarity Response

Glucosylglycerol (GG) is an osmolyte that protects cells from extreme conditions. It is produced by sucrose phosphorylase, an enzyme that uses sucrose and glycerol as substrate. GG protects tissue integrity in desert plants during harsh conditions and guards cyanobacteria against high salinity (halotolerant). However, no extensive research has been conducted on the lifespan application of this compound on the yeast Saccharomyces cerevisiae. We designed this study to (1) characterize GG's effect on yeast chronological lifespan (CLS) and (2) to determine the mechanisms underlying its lifespan promotion on strain DBY746. The results obtained in our study confirm that GG causes increased longevity when administered at moderate doses (48 mM and 120 mM). In addition, we discovered that GG promotes yeast cell longevity by increasing the osmolarity of the culture medium. The maximum lifespan increased by approximately 15.38% and 34.6%, (i.e., 115.38 and 134.61) respectively, upon administration of GG at 48 mM and 120 mM concentrations. Elucidation of the mechanisms underlying this positive response suggests that GG promotes CLS by activities that modulate reactive oxygen species (ROS) generation, as evident in its increased ROS generation (mitohormesis). An increase in medium osmolarity caused by GG supplementation triggers ROS production and promotes longevity in the yeast (S. cerevisiae). An in-depth study on the potential application of this molecule in aging research is crucial; this will aid in expounding the mechanisms of this geroprotector and its longevity supportive tendencies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01055-y.

Myosin II regulatory light chain phosphorylation and formin availability modulate cytokinesis upon changes in carbohydrate metabolism

Cytokinesis, the separation of daughter cells at the end of mitosis, relies in animal cells on a contractile actomyosin ring (CAR) composed of actin and class II myosins, whose activity is strongly influenced by regulatory light chain (RLC) phosphorylation. However, in simple eukaryotes such as the fission yeast Schizosaccharomyces pombe, RLC phosphorylation appears dispensable for regulating CAR dynamics. We found that redundant phosphorylation at Ser35 of the S. pombe RLC homolog Rlc1 by the p21-activated kinases Pak1 and Pak2, modulates myosin II Myo2 activity and becomes essential for cytokinesis and cell growth during respiration. Previously, we showed that the stress-activated protein kinase pathway (SAPK) MAPK Sty1 controls fission yeast CAR integrity by downregulating formin For3 levels (Gómez-Gil et al., 2020). Here, we report that the reduced availability of formin For3-nucleated actin filaments for the CAR is the main reason for the required control of myosin II contractile activity by RLC phosphorylation during respiration-induced oxidative stress. Thus, the restoration of For3 levels by antioxidants overrides the control of myosin II function regulated by RLC phosphorylation, allowing cytokinesis and cell proliferation during respiration. Therefore, fine-tuned interplay between myosin II function through Rlc1 phosphorylation and environmentally controlled actin filament availability is critical for a successful cytokinesis in response to a switch to a respiratory carbohydrate metabolism.

Adaptation of Proteome and Metabolism in Different Haplotypes of Rhodosporidium toruloides during Cu(I) and Cu(II) Stress

Rhodosporidium toruloides is a carotenogenic, oleogenic yeast that is able to grow in diverse environments. In this study, the proteomic and metabolic responses to copper stress in the two haplotypes IFO0559 and IFO0880 were assessed. 0.5 mM Cu(I) extended the lag phase of both strains significantly, while only a small effect was observed for Cu(II) treatment. Other carotenogenic yeasts such as Rhodotorula mucilaginosa are known to accumulate high amounts of carotenoids as a response to oxidative stress, posed by excess copper ion activity. However, no significant increase in carotenoid accumulation for both haplotypes of R. toruloides after 144 h of 0.5 mM Cu(I) or Cu(II) stress was observed. Yet, an increase in lipid production was detected, when exposed to Cu(II), additionally, proteins related to fatty acid biosynthesis were detected in increased amounts under stress conditions. Proteomic analysis revealed that besides the activation of the enzymatic oxidative stress response, excess copper affected iron–sulfur and zinc-containing proteins and caused proteomic adaptation indicative of copper ion accumulation in the vacuole, mitochondria, and Golgi apparatus.

Stress-Induced Phenoptosis: Mechanistic Insights and Evolutionary Implications

Evolution by natural selection results in biological traits that enable organismic adaptation and survival under various stressful environments. External stresses can be sometimes too severe to overcome, leading to organismic death either because of failure in adapting to such stress, or alternatively, through a regulated form of organismic death (phenoptosis). While regulated cell deaths, including apoptosis, have been extensively studied, little is known about the molecular and cellular mechanisms underlying phenoptosis and its evolutionary significance for multicellular organisms. In this article, we review documented phenomena and mechanistic evidence emerging from studies of stress-induced phenoptosis in the multicellular organism C. elegans and stress-induced deaths at cellular levels in organisms ranging from bacteria to mammals, focusing on abiotic and pathogen stresses. Genes and signaling pathways involved in phenoptosis appear to promote organismic death during severe stress and aging, while conferring fitness and immune defense during mild stress and early life, consistent with their antagonistic pleiotropy actions. As cell apoptosis during development can shape tissues and organs, stress-induced phenoptosis may also contribute to possible benefits at the population level, through mechanisms including kin selection, abortive infection, and soma-to-germline resource allocation. Current models can generate experimentally testable predictions and conceptual frameworks with implications for understanding both stress-induced phenoptosis and natural aging.

Rosemary essential oil and its components 1,8-cineole and α-pinene induce ROS-dependent lethality and ROS-independent virulence inhibition in Candida albicans

The essential oil from Rosmarinus officinalis L., a composite mixture of plant-derived secondary metabolites, exhibits antifungal activity against virulent candidal species. Here we report the impact of rosemary oil and two of its components, the monoterpene α-pinene and the monoterpenoid 1,8-cineole, against Candida albicans, which induce ROS-dependent cell death at high concentrations and inhibit hyphal morphogenesis and biofilm formation at lower concentrations. The minimum inhibitory concentrations (100% inhibition) for both rosemary oil and 1,8-cineole were 4500 μg/ml and 3125 μg/ml for α-pinene, with the two components exhibiting partial synergy (FICI = 0.55 ± 0.07). At MIC and 1/2 MIC, rosemary oil and its components induced a generalized cell wall stress response, causing damage to cellular and organelle membranes, along with elevated chitin production and increased cell surface adhesion and elasticity, leading to complete vacuolar segregation, mitochondrial depolarization, elevated reactive oxygen species, microtubule dysfunction, and cell cycle arrest mainly at the G1/S phase, consequently triggering cell death. Interestingly, the same oils at lower fractional MIC (1/8-1/4) inhibited virulence traits, including reduction of mycelium (up to 2-fold) and biofilm (up to 4-fold) formation, through a ROS-independent mechanism.

Study of the synergistic effect of singlet oxygen with other plasma-generated ROS in fungi inactivation during water disinfection

Cold atmospheric plasma (CAP) possesses the ability of high-efficiency disinfection. It is reported that mixtures of reactive oxygen species (ROS) including ^·OH, ¹O₂, O₂^- and H₂O₂ generated from CAP have better antimicrobial ability than mimicked solution of mixture of single ROS type, but the reason is not clear. In this study, CAP was applied to treat yeasts in water in order to investigate the fungal inactivation efficiency and mechanism. The results showed that plasma treatment for 5 min could result in >2-log reduction of yeast cells, and application of varied ROS scavengers could significantly increase the yeast survival rate, indicating that ^·OH and ¹O₂ played the pivotal role in yeast inactivation. Moreover, the synergistic effect of ¹O₂ with other plasma-generated ROS was revealed. ¹O₂ could diffuse into cells and induce the depolarization of mitochondrial membrane potential (MMP), and different levels of MMP depolarization determined different cell death modes. Mild damage of mitochondria during short-term plasma treatment could lead to apoptosis. For long-term plasma treatment, the cell membrane could be severely damaged by the plasma-generated ^·OH, so a large amount of ¹O₂ could induce more depolarization of MMP, leading to increase of intracellular O₂^- and Fe²⁺ which subsequently caused cell inactivation. ¹O₂ could also induce protein aggregation and increase of RIP1/RIP3 necrosome, leading to necroptosis. With participation of ¹O₂, endogenous ^·OH could also be generated via Fenton and Haber-Weiss reactions during plasma treatment, which potentiated necroptosis. Adding l-His could mitigate membrane damage, inhibit the drop of MMP and the formation of necrosome, and thus prevent the happening of necroptosis. These findings may deepen the understanding of plasma sterilization mechanisms and provide guidance for microbial killing in the environment.

SLX5 deletion confers tolerance to oxidative stress in Saccharomyces cerevisiae

Slx5, a subunit of a SUMO-targeted ubiquitin ligase (STUbL) in yeast, has been implicated in maintenance of genomic stability. SUMOylation is an important post-translational modification involved in the regulation of several important cellular processes and cellular response to various environmental stressors. Oxidative stress occurs when production of reactive oxygen species (ROS) exceeds the antioxidant defense capacity of the cell. Elevated ROS levels cause oxidative damage to important cellular macromolecules such as DNA, lipids and proteins, which is associated with several diseases. Herein, we investigated the role of Slx5 in oxidative stress tolerance in Saccharomyces cerevisiae. We show that deletion of SLX5 increases survival of yeast cells in response to H2O2-induced oxidative stress in a cell cycle independent manner. Accumulation of intracellular ROS as well as DNA and lipid damages were reduced; expressions of antioxidant defense mechanism related genes were increased in slx5Δ cells compared to wild type (WT) under oxidative stress. We also show that slx5Δ cells have increased intracellular ROS levels and oxidative damage to DNA and lipids compared to WT in the absence of oxidative stress. Thus, our data together suggest that an adaptive stress induced by SLX5 deletion increases tolerance to oxidative stress in slx5∆ cells.

Unique thiol metabolism in trypanosomatids: Redox homeostasis and drug resistance

Trypanosomatids are mainly responsible for heterogeneous parasitic diseases: Leishmaniasis, Sleeping sickness, and Chagas disease and control of these diseases implicates serious challenges due to the emergence of drug resistance. Redox-active biomolecules are the endogenous substances in organisms, which play important role in the regulation of redox homeostasis. The redox-active substances like glutathione, trypanothione, cysteine, cysteine persulfides, etc., and other inorganic intermediates (hydrogen peroxide, nitric oxide) are very useful as defence mechanism. In the present review, the suitability of trypanothione and other essential thiol molecules of trypanosomatids as drug targets are described in Leishmania and Trypanosoma. We have explored the role of tryparedoxin, tryparedoxin peroxidase, ascorbate peroxidase, superoxide dismutase, and glutaredoxins in the anti-oxidant mechanism and drug resistance. Up-regulation of some proteins in trypanothione metabolism helps the parasites in survival against drug pressure (sodium stibogluconate, Amphotericin B, etc.) and oxidative stress. These molecules accept electrons from the reduced trypanothione and donate their electrons to other proteins, and these proteins reduce toxic molecules, neutralize reactive oxygen, or nitrogen species; and help parasites to cope with oxidative stress. Thus, a better understanding of the role of these molecules in drug resistance and redox homeostasis will help to target metabolic pathway proteins to combat Leishmaniasis and trypanosomiases.

Natural Compound 2-Chloro-1,3-dimethoxy-5-methylbenzene, Isolated from Hericium Erinaceus, Inhibits Fungal Growth by Disrupting Membranes and Triggering Apoptosis

In this study, 2-chloro-1,3-dimethoxy-5-methylbenzene (CDM), a natural product with anti-Candida albicans activity, was discovered from the Hericium erinaceus mycelium. The minimum inhibitory concentration of CDM was 62.5 μg/mL. Moreover, structural analogues of CDM obtained from chemical synthesis were applied to explore the structure-activity relationship (SAR) of CDM against C. albicans. It was found that methoxy groups, halogen atoms (except fluorine atoms), and methoxy-meta-position methyl groups in the structure of CDM were the key active groups. Furthermore, we investigated the anti-C. albicans mechanism of CDM. Experiments suggested that CDM destroyed the cell membrane of C. albicans, including the cytoplasmic membrane and mitochondrial membrane, and caused the accumulation of reactive oxygen species and mitochondrial dysfunction, which ultimately led to apoptosis of C. albicans. In addition, CDM had no toxicity on human normal gastric mucosal epithelial cells exposed to a concentration of 125 μg/mL. Experiments showed that CDM reduced the damage of C. albicans to the visceral tissue of infected mice and improved the survival rate of mice. Our research provides a scientific basis for the discovery of effective and safe anti-C. albicans drugs from H. erinaceus.

In vitro and in vivo Activity of Phibilin Against Candida albicans

The increase in the occurrence of antifungal-resistant Candida albicans infections necessitates more research to explore alternative effective and safe agents against this fungus. In this work, Phibilin, a new antimicrobial peptide obtained from Philomycus bilineatus and used in traditional Chinese medicine, effectively inhibits the growth and activities of C. albicans, including the clinical resistant strains. Phibilin is a fungicidal antimicrobial peptide that exhibited its antimicrobial effect against C. albicans mainly by disrupting the membrane and interacting with the DNA of the fungi. In particular, Phibilin induces the necrosis of C. albicans via the ROS-related pathway. Moreover, this antifungal compound inhibited the biofilm formation of C. albicans by preventing the development of hyphae in a dose-dependent manner. Furthermore, Phibilin and clotrimazole displayed a synergistic effect in inhibiting the growth of the fungi. In the mouse cutaneous infection model, Phibilin significantly inhibited the formation of skin abscesses and decreased the counts of C. albicans cells in the infected area. Overall, Phibilin is potentially an effective agent against skin infections caused by C. albicans.

Oxidative stress response pathways in fungi

Fungal response to any stress is intricate, specific, and multilayered, though it employs only a few evolutionarily conserved regulators. This comes with the assumption that one regulator operates more than one stress-specific response. Although the assumption holds true, the current understanding of molecular mechanisms that drive response specificity and adequacy remains rudimentary. Deciphering the response of fungi to oxidative stress may help fill those knowledge gaps since it is one of the most encountered stress types in any kind of fungal niche. Data have been accumulating on the roles of the HOG pathway and Yap1- and Skn7-related pathways in mounting distinct and robust responses in fungi upon exposure to oxidative stress. Herein, we review recent and most relevant studies reporting the contribution of each of these pathways in response to oxidative stress in pathogenic and opportunistic fungi after giving a paralleled overview in two divergent models, the budding and fission yeasts. With the concept of stress-specific response and the importance of reactive oxygen species in fungal development, we first present a preface on the expanding domain of redox biology and oxidative stress.

Heavy metal exposure induces Yap1 and Hac1 mediated derepression of GSH1 and KAR2 by Tup1-Cyc8 complex

Heavy metal pollution is one of the most severe environmental problem. The toxicity of heavy metals is correlated with the production of increased reactive oxygen species and misfolded protein accumulation. Exposures of these metals even at low concentrations adversely affect human health. The Tup1-Cyc8 complex has been identified as a general repressor complex, is also involved in the derepression of few target genes in association with gene-specific activator proteins. Exposure to heavy metals activates the antioxidant defense mechanism, essential for cellular homeostasis. Here we present evidence that TUP1/CYC8 deleted cells are compromised to tolerate heavy metals exposure. Upon metal-induced oxidative stress, Yeast AP-1p (Yap1) recruits the Tup1-Cyc8 complex to the promoter of oxidative stress response gene GSH1 and derepresses its expression. We also found that the TUP1/CYC8 deficient cells have altered endoplasmic reticulum (ER) homeostasis and fail to activate the unfolded protein response pathway. In response to ER stress, the Tup1-Cyc8 complex, with the help of activated Hac1, binds to the promoter of ER chaperone KAR2 and activates its transcription. Altogether, our findings suggest that the Tup1-Cyc8 complex is crucial for the activation of genes that are involved in the mitigation of oxidative and ER stress during heavy metal exposure.

Antiaging Effect of 4-N-Furfurylcytosine in Yeast Model Manifests through Enhancement of Mitochondrial Activity and ROS Reduction

Small compounds are a large group of chemicals characterized by various biological properties. Some of them also have antiaging potential, which is mainly attributed to their antioxidant activity. In this study, we examined the antiaging effect of 4-N-Furfurylcytosine (FC), a cytosine derivative belonging to a group of small compounds, on budding yeast Saccharomyces cerevisiae. We chose this yeast model as it is known to contain multiple conserved genes and mechanisms identical to that of humans and has been proven to be successful in aging research. The chronological lifespan assay performed in the study revealed that FC improved the viability of yeast cells in a concentration-dependent manner. Furthermore, enhanced mitochondrial activity, together with reduced intracellular ROS level, was observed in FC-treated yeast cells. The gene expression analysis confirmed that FC treatment resulted in the restriction of the TORC1 signaling pathway. These results indicate that FC has antiaging properties.

Antioxidant Properties of Salvia officinalis Decoction Extract and Mechanism of Its Protective Effects on Ethanol-Induced Liver and Kidney Injuries

This study assessed the hepato- and nephroprotective effects of Salvia officinalis flowers decoction extract (SODE) against ethanol (EtOH)-induced oxidative stress in rats as well as the possible mechanism implicated in such protection. Animals were divided into four groups: control, EtOH, and EtOH+SODE. Wistar rats were pretreated with SODE (50, 100, and 200 mg/kg, body weight [b.w.], p.o.) for 15 days and intoxicated during 2 h by acute oral administration of EtOH (4 g/kg, b.w.) 60 min after the last dose of SODE. We found that SODE pretreatment, in vivo, protected against EtOH-induced liver and kidney injuries evident by plasma transaminases activity and preservation of the hepatic tissue structure. Compared with the control group, the animals treated with the SODE showed a significant decrease (68.81 ± 6.89-50.65 ± 3.97 UI/L) of alanine aminotransferase (ALT) and aspartate aminotransferase (AST; 144.38 ± 6.58-113.64 ± 8.03 UI/L) in a dose-dependent manner. By contrast, the plant extract significantly and dose dependently increased (0.175 ± 0.077-0.302 ± 0.011 mmol/L) the uric acid. The SODE counteracted EtOH-induced liver and kidney lipoperoxidation, preserved sulfhydryl groups (-SH) and glutathione reduced (GSH) contents. Our extract prevented the depletion of antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). We also showed that acute alcohol administration increased tissue and plasma hydrogen peroxide (H₂O₂), calcium and free iron levels. Of interest, SODE pretreatment reversed all EtOH-induced disturbances in intracellular mediators. More importantly, SODE treatment significantly protected against alcohol-induced inflammation by reducing C-reactive protein (CRP) and alkaline phosphatase (ALP) activities in plasma. It was concluded that the SODE exerted a potential protective effect against EtOH-induced inflammation and oxidative stress in the rat organs. This study recommends that the consumption of sage flowers is useful for patients who suffer from hepato- and nephrotoxicity.

The effect of chlorothalonil on Saccharomyces cerevisiae under alcoholic fermentation

Chlorothalonil is a broad-spectrum fungicide largely used for the control of several diseases of grapevines. With a moderate persistence in plants, soil and, water, it can be carried to grape musts, particularly when applied to control grape rot diseases. This work aimed to determine the effect of chlorothalonil on Saccharomyces cerevisiae under fermentative conditions using a flow cytometry approach. Yeasts were cultivated in synthetic must with different concentrations of chlorothalonil (0 to 60 μM) and evaluated for culture-ability, membrane integrity, reactive oxygen species (ROS) accumulation, mitochondrial membrane potential, metacaspase activity, ATP, nonprotein SH and, SH-proteins. The results confirmed the oxidation of nonprotein SH, including glutathione, and the binding of the fungicide with sulfhydryl proteins, which led to changes in the cell and mitochondrial membranes that result in the necrotic death of part of the yeast population, and a reduction in metabolic activity. Moreover, the reduction in glutathione-SH concentration was responsible for the increase in ROS which in turn triggers metacaspase-dependent apoptotic cell death. Cells that escape death adapt and began to grow and ferment after a dose-dependent lag-phase period, exhibiting an almost normal fermentative behavior thereafter. Moreover, was observed unexpected protection of chlorothalonil sub-dosages on yeast cell membrane integrity during alcoholic fermentation. This study contributed insights into how chlorothalonil leads the non-target organism S. cerevisiae to cell death and explores the effect of the fungicide during alcoholic fermentation.

Oxidative reactivity across kingdoms in the gut: Host immunity, stressed microbiota and oxidized foods

Reactive oxygen species play a major role in the induction of programmed cell death and numerous diseases. Production of reactive oxygen species is ubiquitous in biological systems such as humans, bacteria, fungi/yeasts, and plants. Although reactive oxygen species are known to cause diseases, little is known about the importance of the combined oxidative stress burden in the gut. Understanding the dynamics and the level of oxidative stress 'reactivity' across kingdoms could help ascertain the combined consequences of free radical accumulation in the gut lumen. Here, we present fundamental similarities of oxidative stress derived from the host immune cells, bacteria, yeasts, plants, and the therein-derived diets, which often accentuate the burden of free radicals by accumulation during storage and cooking conditions. Given the described similarities, oxidative stress could be better understood and minimized by monitoring the levels of oxidative stress in the feces to identify pro-inflammatory factors. However, we illustrate that dietary studies rarely monitor oxidative stress markers in the feces, and therefore our knowledge on fecal oxidative stress monitoring is limited. A more holistic approach to understanding oxidative stress 'reactivity' in the gut could help improve strategies to use diet and microbiota to prevent intestinal diseases.

Effect of Light and p-Coumaric Acid on the Growth and Expression of Genes Related to Oxidative Stress in Brettanomyces bruxellensis LAMAP2480

Brettanomyces bruxellensis is considered the most significant contaminant yeast in the wine industry since it causes a deterioration in the organoleptic properties of the wine and significant economic losses. This deterioration is due to the production of volatile phenols from hydroxycinnamic acids. These compounds possess antimicrobial properties; however, B. bruxellensis can resist this effect because it metabolizes them into less toxic ones. Recent studies have reported that B. bruxellensis grows under different stress conditions, including p-coumaric acid (pCA) but effective methods for its control have not been found yet. Since that in other yeasts, such as Saccharomyces cerevisiae, it has been described that light affects its growth, and we evaluated whether the light would have a similar effect on B. bruxellensis. The results show that at light intensities of 2,500 and 4,000 lux in the absence of pCA, B. bruxellensis LAMAP2480 does not grow in the culture medium; however, when the medium contains this acid, the yeast adapts to both factors of stress managing to grow. The expression of genes related to oxidative stress in B. bruxellensis LAMAP2480, such as SOD1, GCN4, and ESBP6, showed a higher relative expression when the yeast was exposed to 2,500 lux compared to 4,000 lux, agreeing with the growth curves. This suggests that a higher expression of the genes studied would be related to stress-protective effects by pCA.

D319 induced antifungal effects through ROS-mediated apoptosis and inhibited isocitrate lyase in Candida albicans

BACKGROUND

Candida albicans (C. albicans) is an opportunistic pathogen that can cause superficial and life-threatening systemic infections in immunocompromised patients. However, the available clinically antifungals are limited. Therefore, the development of effective antifungal agents and therapies is urgently needed. Quinoline type of compounds were reported to possess potent anti-fungal effect. A series of quinoline derivatives were synthesized. Moreover their inhibitory activities and mechanisms on C. albicans were evaluated in this study.

METHODS

The structure of D319 was identified by extensive spectroscopic analysis. The antifungal activity of D319 on C. albicans was evaluated using conventional methods, including the inhibition zone diameters with filter paper, Clinical Laboratory Standard Institute (CLSI) broth microdilution method in vitro, and in a murine model in vivo. Flow cytometry, fluorescence microscopy, western blot, knockout mutant and revertant strain techniques, and molecular modeling were applied to explore the mechanism of action of D319 in anti-Candida.

RESULTS

D319 exhibited potent anti-Candida activity with Minimum Inhibitory Concentration value of 2.5 μg/mL in vitro. D319 significantly improved survival rate and reduced fungal burden compared to vehicle control in a murine model in vivo. The treatment of C. albicans with D319 resulted in fungal apoptosis through reactive oxygen species (ROS) accumulation in C. albicans. Furthermore, D319 inhibited the glyoxylate enzyme isocitrate lyase (ICL) of C. albicans, which was also confirmed by docking analysis.

CONCLUSIONS

Quinoline compound D319 exhibited strong anti-Candida activities in vitro and in vivo models through inhibiting ICL activity and ROS accumulation in C. albicans.

GENERAL SIGNIFICANCE

This study showed that compound D319 as a novel isocitrate lyase inhibitor, would be a promising anti-Candida lead compound, which provided a potential application of this type of compounds in fighting clinical fungal infections. Furthermore, this study also supported ICL as a potential target for anti-Candida drug discovery.

Adenylyl Cyclase and Protein Kinase A Play Redundant and Distinct Roles in Growth, Differentiation, Antifungal Drug Resistance, and Pathogenicity of Candida auris

Candida auris is a globally emerging multidrug-resistant fungal pathogen. Its pathogenicity-related signaling networks are largely unknown. Here, we characterized the pathobiological functions of the cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway in C. auris. We focused on adenylyl cyclase (CYR1), the PKA regulatory subunit (BCY1), and the PKA catalytic subunits (TPK1 and TPK2). We concluded that PKA acts both dependently and independently of Cyr1 in C. auris. Tpk1 and Tpk2 have major and minor roles, respectively, in PKA activity and functions. Both Cyr1 and PKA promote growth, thermotolerance, filamentous growth, and resistance to stress and antifungal drugs by regulating expression of multiple effector genes. In addition, Cyr1 and PKA subunits were involved in disinfectant resistance of C. auris. However, deletion of both TPK1 and TPK2 generally resulted in more severe defects than CYR1 deletion, indicating that Cyr1 and PKA play redundant and distinct roles. Notably, Tpk1 and Tpk2 have redundant but Cyr1-independent roles in haploid-to-diploid cell transition, which increases virulence of C. auris. However, Tpk1 and Tpk2 often play opposing roles in formation of biofilms and the cell wall components chitin and chitosan. Surprisingly, deletion of CYR1 or TPK1/TPK2, which resulted in severe in vitro growth defects at 37°C, did not attenuate virulence, and BCY1 deletion reduced virulence of C. auris in a systemic murine infection model. In conclusion, this study provides comprehensive insights into the role of the cAMP/PKA pathway in drug resistance and pathogenicity of C. auris and suggests a potential therapeutic option for treatment of C. auris-mediated candidemia.