Bacterial Apoptosis-Like Death through Accumulation of Reactive Oxygen Species by Quercetin in Escherichia coli.

The antimicrobial activity of the natural compounds from plant and food have well discovered since the interest on the beneficial effect of the natural compounds was risen. Quercetin, a flavonoid derived from vegetables, including onions, red leaf lettuces and cherries has been studied for diverse biological characteristics as anti-cancer and anti-microbial activities. The aim of current study is to investigate the specific antibacterial modes of action of quercetin against Escherichia coli. Quercetin decreased the E. coli cell viability and induced the severe damages (oxidative stress, DNA fragmentation) leading to cell death. Reactive oxygen species (ROS) generation was observed during the process, which we confirmed that oxidative stress was the key action of antibacterial activity of quercetin exerting its influence potently. Based on the results of Annexin V and Caspace FITC-VAD-FMK assay, the oxidative damage in E. coli has led to the bacterial apoptosis-like death in E. coli. To sum up, the contribution of ROS generation exerts crucial impact in antibacterial activity of quercetin.

Ferroptosis-Like Death in Microorganisms: A Novel Programmed Cell Death Following Lipid Peroxidation.

Ferroptosis is a new kind of programmed cell death of which occurrence in microorganisms is not clearly verified. The elevated level of reactive oxygen species (ROS) influences cellular metabolisms through highly reactive hydroxyl radical formation under the iron-dependent Fenton reaction. Iron contributes to ROS production and acts as a cofactor for lipoxygenase to catalyze poly unsaturated fatty acid (PUFA) oxidation, exerting oxidative damage in cells. While ferroptosis is known to take place only in mammalian cells, recent studies discovered the possible ferroptosis-like death in few specific microorganisms. Capacity of integrating PUFA into intracellular membrane phospholipid has been considered as a key factor in bacterial or fungal ferroptosis-like death. Vibrio species in bacteria and Saccharomyces cerevisiae in fungi exhibited certain characteristics. Therefore, this review focus on introducing the occurrence of ferroptosis-like death in microorganisms and investigating the mode of action underlying the cells based on contribution of lipid peroxidation and iron-dependent reaction.

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.

Microbial Enzymatic Synthesis of Amikacin Analogs With Antibacterial Activity Against Multidrug-Resistant Pathogens.

With the constant emergence of multidrug-resistant gram-negative bacteria, interest in the development of new aminoglycoside (AG) antibiotics for clinical use has increased. The regioselective modification of AG scaffolds could be an efficient approach for the development of new antibiotics with improved therapeutic potency. We enzymatically synthesized three amikacin analogs containing structural modifications in the amino groups and evaluated their antibacterial activity and cytotoxicity. Among them, 6'-N-acyl-3″-N-methylated analogs showed improved antibacterial activity against the multidrug-resistant gram-negative bacteria tested, while exhibiting reduced in vitro nephrotoxicity compared to amikacin. This study demonstrated that the modifications of the 6'-amino group as well as the 3″-amino group have noteworthy advantages for circumventing the AG-resistance mechanism. The regiospecific enzymatic modification could be exploited to develop novel antibacterial agents with improved pharmacological potential.

Apoptosis-like death-inducing property of tachyplesin I in Escherichia coli.

 Antimicrobial peptide (AMP) derived from the horseshoe crab, tachyplesin I (KWCFRVCYRGICYRRCR-NH2 ), displayed the apparent antimicrobial activity with low cytotoxicity, suggesting its efficacy as an attractive agent but still lacks the understandings regarding its mechanism(s). Hence, the study focused on investigating the antibacterial mode of action of tachyplesin I against Escherichia coli. Based on the reactive oxygen species generation displayed in several antimicrobial effects, the detection of superoxide anion and nitric oxide were verified after tachyplesin I treatment. Substantial increment of two molecules was followed by the imbalance in intracellular ion concentration, noticeably magnesium and calcium. The series of stages led to hydroxyl radical generation with reduced glutathione, followed by damage in DNA due to oxidative stress. Eventually, the apoptosis-like death in E. coli was monitored in DNA fragmentation-dependent manner due to the tachyplesin I treatment, verified by membrane depolarization, caspase-like protein activation, and phosphatidylserine exposure. Accordingly, tachyplesin I induces apoptosis-like death in E. coli, suggesting the potential of being a candidate for regulating bacterial infection.

ß-amyrin-induced apoptosis in Candida albicans triggered by calcium.

The emergence of drug-resistant pathogens has urged researchers to discover alternatives for traditional antibiotics. ß-amyrin, which is included in the category of triterpenoids extracted from plants, is known for its antimicrobial activity, although the underlying mechanism has not yet been revealed. This study was conducted to elucidate the antifungal mode of action of ß-amyrin against Candida albicans. Based on the relevance between triterpenoids and oxidative molecules, reactive oxygen species (ROS) concentrations were detected, which showed a noticeable increment. Disruption of Ca2+ homeostasis in the cytosol was additionally analyzed, which was supported by interactions between two. Subsequently, decrease in mitochondrial membrane potential, increment of mitochondrial Ca2+, and ROS concentration were monitored, which suggested mitochondrial dysfunction modulated by Ca2+. Further investigation confirmed oxidative damage through glutathione reduction and DNA fragmentation. Accumulation of lethal damages resulted in the activation of caspases and externalization of phosphatidylserine, indicating the induction of yeast apoptosis by ß-amyrin in C. albicans.

Indole-3-carbinol induces apoptosis-like death in Escherichia coli on different contribution of respective reactive oxygen species.

AIMS: Indole-3-carbinol (I3C) is a natural compound derived from brassica vegetables, displaying antibacterial activity. The study aims to elucidate the antibacterial mode of action(s) induced by indole-3-carbionol in Escherichia coli and enhance the understandings on the respective contribution of each reactive oxygen species (ROS), superoxide anion (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH-) during the process. MAIN METHODS: The antibacterial activity of I3C was assessed through kinetic assay. The generation of ROS was measured by flow cytometer using H2DCFDA dye, while further analysis of respective contribution was done through application of each scavenger: tiron, thiourea and sodium pyruvate. DNA fragmentation and chromatin condensation were observed by TUNEL and DAPI staining agent. Finally, Annexin V/PI, FITC-VAD-FMK and DiBAC4(3) was applied for detection of apoptosis-like death. KEY FINDINGS: I3C exhibited antibacterial activity in E. coli through accumulation of ROS and DNA damage, eventually leading to apoptosis-like death. Contribution of each ROS displayed respective manner, OH- exerting the most potent influence whereas O2- showed least impact. SIGNIFICANCE: Our study is the first to link I3C to the bacterial apoptosis-like death and displays the potential of this agent as a candidate for potential drugs that could help regulating the E. coli, an opportunistic human pathogen. Moreover, the study focused on investigating the individual contribution of each ROS during the process, trying to enhance the understanding regarding ROS and cellular processes followed by oxidative stress in bacteria.

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

Nitric Oxide (NO) is a widely studied molecule due to its diverse biological functions. One of its activities, induction of apoptosis, is currently an area of active investigation in mammalian cells. However, there exists little information regarding the role of NO in yeast apoptosis. In an effort to investigate the mode of action by which NO induces programmed cell death in Candida albicans, we conducted a study on curcumin, a major bioactive compound, which is known as a potential apoptosis-inducing material due to several of its biological activities. First, NO generation was evaluated upon curcumin treatment. It is widely known that NO production is closely tied to cellular respiration, which is regulated by mitochondria. An increase in NO concentration leads to the inhibition of respiration and mitochondrial dysfunction. The hallmarks of mitochondrial dysfunction include a decrease in mitochondrial membrane potential along with increased mitochondrial mass, calcium concentration and ROS generation. A specific oxidative ROS compound, superoxide ([Formula: see text]), is strongly reactive with NO to form peroxynitrite (ONOO-). ONOO- disturbs intracellular redox levels, decreasing the overall ratio of glutathione (GSH). This leads to oxidative damage in C. albicans, triggering lethal DNA damage that eventually results in apoptosis. In the present study, a nitric oxide synthase (NOS) inhibitor, L-NG-Nitroarginine Methyl Ester (L-NAME), was used in each experiment. In all experiments, L-NAME pre-treatment of cells blocked the effects induced by curcumin, which indicates that nitric oxide is a component of the overall mechanism. In conclusion, NO account for an indispensable position in apoptosis of curcumin-treated C. albicans.

Quercetin-induced yeast apoptosis through mitochondrial dysfunction under the accumulation of magnesium in Candida albicans.

Latterly, the upsurge in use of antifungal drugs has brought about the emergence of several drug-resistance strains, making it skeptical to continue relying on current therapeutic regime. In the necessity of resistance-free antifungal agent, flavonoids presented possibilities of replacing existing drugs, displaying antifungal activity against pathogenic fungi. Among them, quercetin, one of the most representative flavonoids, exhibited antifungal activity against Candida albicans. To inspect the further understanding regarding quercetin, the antifungal mode of action of quercetin was investigated. In the initial step, the apoptosis was monitored after quercetin treatment. Moreover, intracellular levels of Mg2+ was assessed and was determined that Mg2+ increase occurred under the influence of quercetin. In addition, several features of mitochondrial dysfunction were monitored. Mitochondrial dysfunction triggers decrease in mitochondrial redox levels and leads to disruption in mitochondrial antioxidant system. Increased intracellular ROS and decreased intracellular redox levels were also displayed, indicating the occurrence of overall disruption in antioxidant systems. Sequentially, DNA fragmentation was observed and this DNA damage in turn induces apoptosis. In analyses, hexaamminecobalt(III) chloride (Cohex) was applied to inhibit Mg2+ transport between cytosol and mitochondria. Cohex attenuated the effects induced by quercetin, which demonstrates that the presence of Mg2+ is essential in quercetin-induced apoptosis.