An Insight on the Role of Nitric Oxide in Yeast Apoptosis of Curcumin-Treated Candida albicans

Study of the effect of calcium signal participating in the antioxidant mechanism of yeast under high-sugar environment

BACKGROUND

Saccharomyces cerevisiae is susceptible to high-sugar stress in the production of bioethanol, wine and bread. Calcium signal is widely involved in various physiological and metabolic activities of cells. The present study aimed to explore the effects of Ca2+ signal on the antioxidant mechanism of yeast during high-sugar fermentation.

RESULTS

Compared to yeast without available Ca2+, yeast in the high glucose with Ca2+ group had higher dry weight, higher ethanol output at 12 and 24 h and higher glycerol output at 24 and 36 h. During the whole growth process, the trehalose synthesis capacity of yeast in the high glucose with Ca2+ group was lower and intracellular reactive oxygen species content was higher compared to yeast without available Ca2+. Intracellular malondialdehyde content of yeast under high glucose with Ca2+ was significantly lower than yeast under high glucose without available Ca2+ except for 6 h. The superoxide dismutase and catalase activities of yeast and glutathione content were higher in the high glucose with Ca2+ group compared to yeast in high glucose without available Ca2+. The expression levels of SOD1, GSH1, GPX2 genes were higher for high glucose without available Ca2+ at 6 h, while yeast in the high glucose with Ca2+ group had a higher expression of antioxidant-related genes except SOD1 and CTT1 at 12 h. The expression levels of antioxidant-related genes of yeast for high glucose with Ca2+ were higher at 24 h, and those of genes except SOD1 of yeast in the high glucose with Ca2+ group were higher at 36 h.

CONCLUSION

High-glucose stress limited the growth of yeast, while a moderate extracellular Ca2+ signal could improve the antioxidant capacity of yeast in a high-glucose environment by regulating protectant metabolism and enhancing the antioxidant enzyme activity and expression of antioxidant genes in a high-sugar environment. © 2024 Society of Chemical Industry.

Antimicrobial Mechanisms of Enterocin CHQS Against Candida albicans

Candida albicans is the most common fungal pathogen in hospital-acquired infections, which is extremely harmful to health. The increasing fungal infections is requiring the rapid development of novel antifungal agents. In this study, the antimicrobial activity of CHQS, an enterocin isolated from Enterococcus faecalis TG2 against C. albicans was confirmed by the minimum inhibitory concentration, minimum fungicidal concentration, and time-kill curve. Aniline blue and calcofluor white staining methods showed that CHQS remarkably affected β-1,3-glucan and chitin cell wall components and made cell wall more vulnerable. The C. albicans cell wall rupture and intracellular vacuolation were observed by TEM and SEM. Moreover, CHQS induced the accumulation of intracellular reactive oxygen species and decreased mitochondrial membrane potential. These results suggested that CHQS might have a complex multi-target antimicrobial mechanism against C. albicans. In addition, the use of CHQS combined with amphotericin B showed synergistic antimicrobial effects against C. albicans. In conclusion, enterocin CHQS, a natural product with antimicrobial effect, might has a bright future for the development of new antifungal drugs.

Investigation of distinct contribution of nitric oxide and each reactive oxygen species in indole-3-propionic-acid-induced apoptosis-like death in Escherichia coli

AIMS

Indole-3-propionic acid (IPA) is a natural product from human microbiota, exhibiting diverse biological activities. The study focused on investigating the antibacterial mode of action(s) triggered by IPA in Escherichia coli. Separate influence of nitric oxide (NO) and each reactive oxygen species, including superoxide anion (O₂^-), hydrogen peroxide (H₂O₂), hydroxyl radical (OH^-), was specifically analyzed throughout the process.

MAIN METHODS

The generation of respective reactive oxygen species (ROS), NO, and ONOO^- was conducted using flow cytometer using different dyes. Further analysis of separate influences was held based on usage of each scavenger: sodium pyruvate, thiourea, tiron, and L-NAME. Oxidative cell damage was observed through the detection of glutathione depletion and lipid peroxidation. DNA fragmentation and membrane depolarization were observed by TUNEL and DiBAC₄(3) staining agent. Finally, Annexin V/PI and FITC-VAD-FMK were applied to detect apoptosis-like death.

KEY FINDINGS

IPA exhibited antibacterial activity in E. coli through the accumulation of ROS, NO, ONOO^-, and DNA damage, eventually leading to apoptosis-like death. NO and O₂^- exerted the most potent influence on oxidative damage of E. coli, whereas H₂O₂ accounts for the least impact. Moreover, the results reveal the major contribution of ONOO^- in IPA-induced apoptosis-like death in E. coli.

SIGNIFICANCE

This is the first study that introduces the antibacterial activity and apoptosis-like death induced by IPA and suggests the possibility of being an alternative for current antibiotics. Furthermore, the distinct influence of each ROS and NO was analyzed to investigate their contribution to oxidative damage leading to bacterial apoptosis-like death.

Indole propionic acid induced Ca2+ -dependent apoptosis in Candida albicans

Indole propionic acid (IPA) which majorly influences the modulation of cellular respiration is a metabolite generated by gut microbiota. The antimicrobial effects of IPA have not been previously demonstrated. Therefore, this study focused on investigating the antimicrobial activity of IPA. Initially, antifungal activity of IPA against Candida albicans was observed, accompanied by variations in mitochondrial respiration indicating modulation of NAD⁺ /NADH ratios. Consumption of O₂ contributes to the respiratory regulation and triggered by Ca²⁺ overloading. After treatment with IPA, the cells were monitored, and Ca²⁺ increases leading to membrane depolarization and reactive oxygen species (ROS) accumulation in mitochondria were noted. Depolarization of mitochondria membrane induced release of proapoptotic proteins in mitochondria. Oxidative stress exerted by ROS contributed to glutathione depletion and oxidation of glutathione (GSH). Fragmentation of DNA is a characteristic event leading to apoptosis and accompanies major hallmarks of apoptosis including phosphatidylserine exposure and metacaspase activation. In addition, phosphatidylserine exposure and metacaspase activation were detected in the cell treated with IPA. In conclusion, IPA triggered apoptosis in C. albicans under the influence of Ca²⁺ .