Urechistachykinin I triggers mitochondrial dysfunction leading to a ferroptosis-like response in Saccharomyces cerevisiae.

AIMS: The purpose of this paper was to demonstrate the antimicrobial activity of urechistachykinin I (LRQSQFVGSR-NH2) extracted from Urechis unicinctus,and its mode of action dependent on mitochondrial dysfunction. METHODS AND RESULTS: The antifungal activity of urechistachykinin I generated reactive oxygen species (ROS), as demonstrated with MitoSOX Red and hydroxyphenyl fluorescein (HPF). Overaccumulation of ROS caused oxidative damage to cells by inducing mitochondrial dysfunction. Mitochondrial disruption resulted in cell death, creating several hallmarks that included lipid peroxidation, glutathione oxidation, and depolarization. Moreover, the loss of mitochondria changed the calcium ion imbalance by depolarization of the mitochondrial membrane. In particular, iron accumulation and DNA fragmentation measurement determined the type of cell death. Our results indicate that urechistachykinin I treatment induced ferroptosis-like death in Saccharomyces cerevisiae via mitochondrial dysfunction. CONCLUSIONS: Urechistachykinin I treatment induced mitochondrial dysfunction in S. cerevisiae by generating ROS, and the subsequent oxidative damage caused the ferroptosis-like cell death.

Urechistachykinin I induced ferroptosis by accumulating reactive oxygen species in Vibrio vulnificus.

Antimicrobial peptides (AMPs), such as urechistachykinin I (LRQSQFVGSR-NH2), derived from urechis unicinctus, have demonstrated antimicrobial activities. It exhibits low cytotoxicity and selectivity between microbial and mammalian cells suggesting its potent antimicrobial ability. However, the underlying antimicrobial mechanisms remain unknown. Herein, we elucidated the antibacterial action against Vibrio vulnificus, focusing on the reactive oxygen species (ROS). ROS is crucial for antibiotic-mediated killing and oxidative stress. After treatment with urechistachykinin I, superoxide anions and hydroxyl radicals increase, and the overproduction of ROS leads to oxidative damage and destruction of the redox system. Oxidation of the defense system like glutathione or glutathione peroxidase 4 illustrates the dysfunction of cellular metabolism and induces lipid peroxidation attributed to depolarization and integrity brokerage. Cell death demonstrated these properties, and additional experiments, including iron accumulation, liperfluo, and DNA fragmentation, were promoted. The results demonstrated that urechistachykinin I-induced ferroptosis-like death in Vibrio vulnificus is dependent on ROS production. KEY POINTS: • Urechistachykinin I induce reactive oxygen species production • Urechistachykinin I cause oxidative damaged on the V. vulnificus • Urechistachykinin I ferroptosis-like death in V. vulnificus.

Antibacterial Mode of Action of ß-Amyrin Promotes Apoptosis-Like Death in Escherichia coli by Producing Reactive Oxygen Species.

ß-Amyrin is a pentacyclic triterpene widely distributed in leaves and stems worldwide. The ability of ß-amyrin to induce the production of reactive oxygen species (ROS) in microorganisms suggests its potential as an antimicrobial agent. Thus, this study aimed to elucidate the antibacterial mode of action of ß-amyrin. We treated Escherichia coli cells with ß-amyrin and found that it triggered ROS accumulation. Excessive stress caused by ROS, particularly hydroxyl radicals, induces glutathione (GSH) dysfunction. GSH protects cells from oxidative and osmotic stresses; thus, its dysfunction leads to membrane depolarization. The resultant change in membrane potential leads to the release of apoptotic proteins, such as caspases. The activated caspases-like protein promotes the cleavage of DNA into single strands, which is a hallmark of apoptosis-like death in bacteria. Apoptotic cells usually undergo events such as DNA fragmentation and phosphatidylserine exposure, differentiating them from necrotic cells, and the cells treated with ß-amyrin in this study were positive for annexin V and negative for propidium iodide, indicating apoptosis-like death. In conclusion, our findings suggest that the antibacterial mode of action of ß-amyrin involves the induction of ROS, which resulted in apoptosis-like death in E. coli.

Naringin generates three types of reactive oxygen species contributing differently to apoptosis-like death in Escherichia coli.

AIMS: Naringin is a flavonoid with a polyphenolic structure which induces formation of reactive oxygen species (ROS). Although the antibacterial effect of naringin has been demonstrated, the mechanism underlying this effect has not yet been elucidated. We focused on investigating the antibacterial mode of action of naringin in Escherichia coli following ROS generation. The contributions of ROS, hydroxy radicals (OH-), super oxide (O2-), and hydrogen peroxide (H2O2) were investigated. MAIN METHODS: ROS accumulation was detected using fluorescence dyes, and all experiments were conducted using the scavenger including tiron, sodium pyruvate, and thiourea to assess the contribution of each ROS. Western blotting assays were used to observe the activation of the SOS response for DNA repair. DNA fragmentation, membrane depolarization, and phosphatidylserine exposure were estimated using TUNEL, DiBAC4(3), and Annexin V/PI. KEY FINDINGS: Accumulation of ROS was observed in Escherichia coli after treatment with naringin. Oxidative stress induced cellular dysfunction including DNA damage, which results in SOS response activation. Eventually, apoptosis-like death occurred in cells treated with naringin. The cells had different contributions of each ROS and accompanying apoptotic factors. The ROS most destructive to E. coli was OH-, followed by H2O2 and O2-. SIGNIFICANCE: Due to its efficacy, naringin is a useful antimicrobial agent. An initial investigation into the antibacterial mode of action of naringin is presented in this paper. The contribution of each ROS to apoptosis-like cell death (ALD) was investigated, and the results enhanced our understanding of the correlation between the SOS response and oxidative stress in bacteria.

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+ .