scholarly journals The Na+-Translocating NADH:Quinone Oxidoreductase Enhances Oxidative Stress in the Cytoplasm of Vibrio cholerae

2016 ◽  
Vol 198 (17) ◽  
pp. 2307-2317 ◽  
Author(s):  
Valentin Muras ◽  
Paul Dogaru-Kinn ◽  
Yusuke Minato ◽  
Claudia C. Häse ◽  
Julia Steuber
Keyword(s):  
Reactive Oxygen Species ◽  
Vibrio Cholerae ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Content Type ◽  
Nadh:Quinone Oxidoreductase ◽  
Quinone Reduction ◽  
Superoxide Formation ◽  
The Impact

ABSTRACTWe searched for a source of reactive oxygen species (ROS) in the cytoplasm of the human pathogenVibrio choleraeand addressed the mechanism of ROS formation using the dye 2′,7′-dichlorofluorescein diacetate (DCFH-DA) in respiring cells. By comparingV. choleraestrains with or without active Na+-translocating NADH:quinone oxidoreductase (Na+-NQR), this respiratory sodium ion redox pump was identified as a producer of ROSin vivo. The amount of cytoplasmic ROS detected inV. choleraecells producing variants of Na+-NQR correlated well with rates of superoxide formation by the corresponding membrane fractions. Membranes from wild-typeV. choleraeshowed increased superoxide production activity (9.8 ± 0.6 μmol superoxide min−1mg−1membrane protein) compared to membranes from the mutant lacking Na+-NQR (0.18 ± 0.01 μmol min−1mg−1). Overexpression of plasmid-encoded Na+-NQR in thenqrdeletion strain resulted in a drastic increase in the formation of superoxide (42.6 ± 2.8 μmol min−1mg−1). By analyzing a variant of Na+-NQR devoid of quinone reduction activity, we identified the reduced flavin adenine dinucleotide (FAD) cofactor of cytoplasmic NqrF subunit as the site for intracellular superoxide formation inV. cholerae. The impact of superoxide formation by the Na+-NQR on the virulence ofV. choleraeis discussed.IMPORTANCEIn several studies, it was demonstrated that the Na+-NQR inV. choleraeaffects virulence in a yet unknown manner. We identified the reduced FAD cofactor in the NADH-oxidizing NqrF subunit of the Na+-NQR as the site of superoxide formation in the cytoplasm ofV. cholerae. Our study provides the framework to understand how reactive oxygen species formed during respiration could participate in the regulated expression of virulence factors during the transition from aerobic to microaerophilic (intestinal) habitats. This hypothesis may turn out to be right for many other pathogens which, likeV. cholerae, depend on the Na+-NQR as the sole electrogenic NADH dehydrogenase.

scholarly journals Antibiotic Korormicin A Kills Bacteria by Producing Reactive Oxygen Species

2019 ◽  
Vol 201 (11) ◽  
Author(s):  
Adam Maynard ◽  
Nicole L. Butler ◽  
Takeshi Ito ◽  
Adilson José da Silva ◽  
Masatoshi Murai ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Pseudomonas Aeruginosa ◽  
Vibrio Cholerae ◽  
Pathogenic Bacteria ◽  
Reactive Oxygen ◽  
Direct Result ◽  
Oxygen Species ◽  
Gram Negative ◽  
Content Type ◽  
Nadh:Quinone Oxidoreductase

ABSTRACT Korormicin is an antibiotic produced by some pseudoalteromonads which selectively kills Gram-negative bacteria that express the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR.) We show that although korormicin is an inhibitor of Na+-NQR, the antibiotic action is not a direct result of inhibiting enzyme activity. Instead, perturbation of electron transfer inside the enzyme promotes a reaction between O2 and one or more redox cofactors in the enzyme (likely the flavin adenine dinucleotide [FAD] and 2Fe-2S center), leading to the production of reactive oxygen species (ROS). All Pseudoalteromonas contain the nqr operon in their genomes, including Pseudoalteromonas strain J010, which produces korormicin. We present activity data indicating that this strain expresses an active Na+-NQR and that this enzyme is not susceptible to korormicin inhibition. On the basis of our DNA sequence data, we show that the Na+-NQR of Pseudoalteromonas J010 carries an amino acid substitution (NqrB-G141A; Vibrio cholerae numbering) that in other Na+-NQRs confers resistance against korormicin. This is likely the reason that a functional Na+-NQR is able to exist in a bacterium that produces a compound that typically inhibits this enzyme and causes cell death. Korormicin is an effective antibiotic against such pathogens as Vibrio cholerae, Aliivibrio fischeri, and Pseudomonas aeruginosa but has no effect on Bacteroides fragilis and Bacteroides thetaiotaomicron, microorganisms that are important members of the human intestinal microflora. IMPORTANCE As multidrug antibiotic resistance in pathogenic bacteria continues to rise, there is a critical need for novel antimicrobial agents. An essential requirement for a useful antibiotic is that it selectively targets bacteria without significant effects on the eukaryotic hosts. Korormicin is an excellent candidate in this respect because it targets a unique respiratory enzyme found only in prokaryotes, the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR). Korormicin is synthesized by some species of the marine bacterium Pseudoalteromonas and is a potent and specific inhibitor of Na+-NQR, an enzyme that is essential for the survival and proliferation of many Gram-negative human pathogens, including Vibrio cholerae and Pseudomonas aeruginosa, among others. Here, we identified how korormicin selectively kills these bacteria. The binding of korormicin to Na+-NQR promotes the formation of reactive oxygen species generated by the reaction of the FAD and the 2Fe-2S center cofactors with O2.

scholarly journals Treatment of Human Lens Epithelium with High Levels of Nanoceria Leads to Reactive Oxygen Species Mediated Apoptosis

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 441 ◽  
Author(s):  
Belal I. Hanafy ◽  
Gareth W. V. Cave ◽  
Yvonne Barnett ◽  
Barbara Pierscionek
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Dose Effect ◽  
Human Lens ◽  
Mitochondrial Morphology ◽  
Oxygen Species ◽  
Significant Uptake ◽  
The Impact

Nanoceria (cerium oxide nanoparticles) have been shown to protect human lens epithelial cells (HLECs) from oxidative stress when used at low concentrations. However, there is a lack of understanding about the mechanism of the cytotoxic and genotoxic effects of nanoceria when used at higher concentrations. Here, we investigated the impact of 24-hour exposure to nanoceria in HLECs. Nanoceria’s effects on basal reactive oxygen species (ROS), mitochondrial morphology, membrane potential, ATP, genotoxicity, caspase activation and apoptotic hallmarks were investigated. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) studies on isolated mitochondria revealed significant uptake and localization of nanoceria in the mitochondria. At high nanoceria concentrations (400 µg mL−1), intracellular levels of ROS were increased and the HLECs exhibited classical hallmarks of apoptosis. These findings concur with the cells maintaining normal ATP levels necessary to execute the apoptotic process. These results highlight the need for nanoceria dose-effect studies on a range of cells and tissues to identify therapeutic concentrations in vitro or in vivo.

scholarly journals Probing the Molecular Mechanism of Hypericin-Induced Parasite Death Provides Insight into the Role of Spermidine beyond Redox Metabolism in Leishmania donovani

2014 ◽  
Vol 59 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Shalini Singh ◽  
Shyamali Sarma ◽  
Shashank P. Katiyar ◽  
Mousumi Das ◽  
Ruchika Bhardwaj ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Leishmania Donovani ◽  
Specific Inhibitor ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Inhibitor Molecule ◽  
Redox Metabolism ◽  
Content Type ◽  
Novel Scaffold

ABSTRACTHypericin, a natural compound fromHypericum perforatum(St. John's wort), has been identified as a specific inhibitor ofLeishmania donovanispermidine synthase (LdSS) using integrated computational and biochemical approaches. Hypericin showedin vitroinhibition of recombinant LdSS enzyme activity. Thein vivoestimation of spermidine levels inLeishmaniapromastigotes after hypericin treatment showed significant decreases in the spermidine pools of the parasites, indicating target specificity of the inhibitor molecule. The inhibitor, hypericin, showed significant antileishmanial activity, and the mode of death showed necrosis-like features. Further, decreased trypanothione levels and increased glutathione levels with elevated reactive oxygen species (ROS) levels were observed after hypericin treatment. Supplementation with trypanothione in the medium with hypericin treatment restoredin vivotrypanothione levels and ROS levels but could not prevent necrosis-like death of the parasites. However, supplementation with spermidine in the medium with hypericin treatment restoredin vivospermidine levels and parasite death was prevented to a large extent. The data overall suggest that the parasite death due to spermidine starvation as a result of LdSS inhibition is not related to elevated levels of reactive oxygen species. This suggests the involvement of spermidine in processes other than redox metabolism inLeishmaniaparasites. Moreover, the work provides a novel scaffold, i.e., hypericin, as a potent antileishmanial molecule.

scholarly journals Vibrio cholerae Virulence Activator ToxR Regulates Manganese Transport and Resistance to Reactive Oxygen Species

2019 ◽  
Vol 88 (3) ◽  
Author(s):  
Hang-hang Jiang ◽  
Yitian Zhou ◽  
Ming Liu ◽  
Jessie Larios-Valencia ◽  
Zachariah Lee ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Vibrio Cholerae ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Content Type ◽  
Genome Wide ◽  
A Genome ◽  
Its Gene ◽  
Virulence Regulator ◽  
Manganese Transport

ABSTRACT Like many other pathogens, Vibrio cholerae, the causative agent of cholera, can modulate its gene expression to combat stresses encountered in both aquatic and host environments, including stress posed by reactive oxygen species (ROS). We previously reported that the virulence activator AphB in V. cholerae is involved in ROS resistance. In this study, we found that another key virulence regulator, ToxR, was important for V. cholerae resistance to hydrogen peroxide. Through a genome-wide transposon screen, we discovered that a deletion in mneA, which encodes a manganese exporter, restored ROS resistance of the toxR mutant. We then showed that ToxR did not affect mneA transcription but that the ToxR-regulated major porin OmpU was critical for ROS resistance. The addition of manganese in culture medium restored ROS resistance in both the toxR and ompU mutants. Furthermore, elemental analysis indicated that the intracellular concentration of manganese in both the toxR and ompU mutants was reduced. This may result in intracellular ROS accumulation in these mutants. Our data suggest that ToxR plays an important role in the resistance to reactive oxygen species through the regulation of manganese transport.

scholarly journals Arterial Smooth Muscle Mitochondria Amplify Hydrogen Peroxide Microdomains Functionally Coupled to L-Type Calcium Channels

2015 ◽  
Vol 117 (12) ◽  
pp. 1013-1023 ◽  
Author(s):  
Nathan L. Chaplin ◽  
Madeline Nieves-Cintrón ◽  
Adriana M. Fresquez ◽  
Manuel F. Navedo ◽  
Gregory C. Amberg
Keyword(s):  
Reactive Oxygen Species ◽  
Hydrogen Peroxide ◽  
Smooth Muscle ◽  
Calcium Channels ◽  
Intracellular Signaling ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Arterial Smooth Muscle ◽  
The Impact

Rationale: Mitochondria are key integrators of convergent intracellular signaling pathways. Two important second messengers modulated by mitochondria are calcium and reactive oxygen species. To date, coherent mechanisms describing mitochondrial integration of calcium and oxidative signaling in arterial smooth muscle are incomplete. Objective: To address and add clarity to this issue, we tested the hypothesis that mitochondria regulate subplasmalemmal calcium and hydrogen peroxide microdomain signaling in cerebral arterial smooth muscle. Methods and Results: Using an image-based approach, we investigated the impact of mitochondrial regulation of L-type calcium channels on subcellular calcium and reactive oxygen species signaling microdomains in isolated arterial smooth muscle cells. Our single-cell observations were then related experimentally to intact arterial segments and to living animals. We found that subplasmalemmal mitochondrial amplification of hydrogen peroxide microdomain signaling stimulates L-type calcium channels, and that this mechanism strongly impacts the functional capacity of the vasoconstrictor angiotensin II. Importantly, we also found that disrupting this mitochondrial amplification mechanism in vivo normalized arterial function and attenuated the hypertensive response to systemic endothelial dysfunction. Conclusions: From these observations, we conclude that mitochondrial amplification of subplasmalemmal calcium and hydrogen peroxide microdomain signaling is a fundamental mechanism regulating arterial smooth muscle function. As the principle components involved are fairly ubiquitous and positioning of mitochondria near the plasma membrane is not restricted to arterial smooth muscle, this mechanism could occur in many cell types and contribute to pathological elevations of intracellular calcium and increased oxidative stress associated with many diseases.

scholarly journals Assessment of Physico-Chemical and Toxicological Properties of Commercial 2D Boron Nitride Nanopowder and Nanoplatelets

2021 ◽  
Vol 22 (2) ◽  
pp. 567
Author(s):  
Brixhilda Domi ◽  
Kapil Bhorkar ◽  
Carlos Rumbo ◽  
Labrini Sygellou ◽  
Spyros N. Yannopoulos ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Boron Nitride ◽  
A549 Cells ◽  
Reactive Oxygen ◽  
Slight Reduction ◽  
Oxygen Species ◽  
Potential Toxicity ◽  
Cellular Models ◽  
Physico Chemical ◽  
The Impact

Boron nitride (BN) nanomaterials have been increasingly explored for potential applications in chemistry and biology fields (e.g., biomedical, pharmaceutical, and energy industries) due to their unique physico-chemical properties. However, their safe utilization requires a profound knowledge on their potential toxicological and environmental impact. To date, BN nanoparticles have been considered to have a high biocompatibility degree, but in some cases, contradictory results on their potential toxicity have been reported. Therefore, in the present study, we assessed two commercial 2D BN samples, namely BN-nanopowder (BN-PW) and BN-nanoplatelet (BN-PL), with the objective to identify whether distinct physico-chemical features may have an influence on the biological responses of exposed cellular models. Morphological, structural, and composition analyses showed that the most remarkable difference between both commercial samples was the diameter of their disk-like shape, which was of 200–300 nm for BN-PL and 100–150 nm for BN-PW. Their potential toxicity was investigated using adenocarcinomic human alveolar basal epithelial cells (A549 cells) and the unicellular fungus Saccharomycescerevisiae, as human and environmental eukaryotic models respectively, employing in vitro assays. In both cases, cellular viability assays and reactive oxygen species (ROS) determinations where performed. The impact of the selected nanomaterials in the viability of both unicellular models was very low, with only a slight reduction of S. cerevisiae colony forming units being observed after a long exposure period (24 h) to high concentrations (800 mg/L) of both nanomaterials. Similarly, BN-PW and BN-PL showed a low capacity to induce the formation of reactive oxygen species in the studied conditions. Even at the highest concentration and exposure times, no major cytotoxicity indicators were observed in human cells and yeast. The results obtained in the present study provide novel insights into the safety of 2D BN nanomaterials, indicating no significant differences in the toxicological potential of similar commercial products with a distinct lateral size, which showed to be safe products in the concentrations and exposure conditions tested.

scholarly journals Targeting autophagy enhances atezolizumab-induced mitochondria-related apoptosis in osteosarcoma

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Zhuochao Liu ◽  
Hongyi Wang ◽  
Chuanzhen Hu ◽  
Chuanlong Wu ◽  
Jun Wang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Antitumor Immunity ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Specific Monoclonal Antibody ◽  
Osteosarcoma Cells ◽  
Jnk Pathway ◽  
In Vivo Experiments

AbstractIn this study, we identified the multifaceted effects of atezolizumab, a specific monoclonal antibody against PD-L1, in tumor suppression except for restoring antitumor immunity, and investigated the promising ways to improve its efficacy. Atezolizumab could inhibit the proliferation and induce immune-independent apoptosis of osteosarcoma cells. With further exploration, we found that atezolizumab could impair mitochondria of osteosarcoma cells, resulting in increased release of reactive oxygen species and cytochrome-c, eventually leading to mitochondrial-related apoptosis via activating JNK pathway. Nevertheless, the excessive release of reactive oxygen species also activated the protective autophagy of osteosarcoma cells. Therefore, when we combined atezolizumab with autophagy inhibitors, the cytotoxic effect of atezolizumab on osteosarcoma cells was significantly enhanced in vitro. Further in vivo experiments also confirmed that atezolizumab combined with chloroquine achieved the most significant antitumor effect. Taken together, our study indicates that atezolizumab can induce mitochondrial-related apoptosis and protective autophagy independently of the immune system, and targeting autophagy is a promising combinatorial approach to amplify its cytotoxicity.

scholarly journals MitoQ Is Able to Modulate Apoptosis and Inflammation

2021 ◽  
Vol 22 (9) ◽  
pp. 4753
Author(s):  
Elisa Piscianz ◽  
Alessandra Tesser ◽  
Erika Rimondi ◽  
Elisabetta Melloni ◽  
Claudio Celeghini ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Mevalonate Pathway ◽  
Neuronal Cell ◽  
Reactive Oxygen ◽  
Mitochondrial Activity ◽  
Oxygen Species ◽  
Short Period ◽  
Inflammatory Stimuli ◽  
Apoptosis And Inflammation ◽  
The Impact

Mitoquinone (MitoQ) is a mitochondrial reactive oxygen species scavenger that is characterized by high bioavailability. Prior studies have demonstrated its neuroprotective potential. Indeed, the release of reactive oxygen species due to damage to mitochondrial components plays a pivotal role in the pathogenesis of several neurodegenerative diseases. The present study aimed to examine the impact of the inflammation platform activation on the neuronal cell line (DAOY) treated with specific inflammatory stimuli and whether MitoQ addition can modulate these deregulations. DAOY cells were pre-treated with MitoQ and then stimulated by a blockade of the cholesterol pathway, also called mevalonate pathway, using a statin, mimicking cholesterol deregulation, a common parameter present in some neurodegenerative and autoinflammatory diseases. To verify the role played by MitoQ, we examined the expression of genes involved in the inflammation mechanism and the mitochondrial activity at different time points. In this experimental design, MitoQ showed a protective effect against the blockade of the mevalonate pathway in a short period (12 h) but did not persist for a long time (24 and 48 h). The results obtained highlight the anti-inflammatory properties of MitoQ and open the question about its application as an effective adjuvant for the treatment of the autoinflammatory disease characterized by a cholesterol deregulation pathway that involves mitochondrial homeostasis.

scholarly journals Plant Extracts and Reactive Oxygen Species as Two Counteracting Agents with Anti- and Pro-Obesity Properties

2019 ◽  
Vol 20 (18) ◽  
pp. 4556 ◽  
Author(s):  
Hanna Zielinska-Blizniewska ◽  
Przemyslaw Sitarek ◽  
Anna Merecz-Sadowska ◽  
Katarzyna Malinowska ◽  
Karolina Zajdel ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Plant Extracts ◽  
Complex Disease ◽  
Reactive Oxygen ◽  
Complementary Therapy ◽  
Biologically Active ◽  
Mitochondrial Activity ◽  
Oxygen Species

Obesity is a complex disease of great public health significance worldwide: It entails several complications including diabetes mellitus type 2, cardiovascular dysfunction and hypertension, and its prevalence is increasing around the world. The pathogenesis of obesity is closely related to reactive oxygen species. The role of reactive oxygen species as regulatory factors in mitochondrial activity in obese subjects, molecules taking part in inflammation processes linked to excessive size and number of adipocytes, and as agents governing the energy balance in hypothalamus neurons has been examined. Phytotherapy is the traditional form of treating health problems using plant-derived medications. Some plant extracts are known to act as anti-obesity agents and have been screened in in vitro models based on the inhibition of lipid accumulation in 3T3-L1 cells and activity of pancreatic lipase methods and in in vivo high-fat diet-induced obesity rat/mouse models and human models. Plant products may be a good natural alternative for weight management and a source of numerous biologically-active chemicals, including antioxidant polyphenols that can counteract the oxidative stress associated with obesity. This review presents polyphenols as natural complementary therapy, and a good nutritional strategy, for treating obesity without serious side effects.

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