scholarly journals Suppression of Reactive Oxygen Species Accumulation Accounts for Paradoxical Bacterial Survival at High Quinolone Concentration

2017 ◽  
Vol 62 (3) ◽  
Author(s):  
Gan Luan ◽  
Yuzhi Hong ◽  
Karl Drlica ◽  
Xilin Zhao
Keyword(s):  
Reactive Oxygen Species ◽  
Protein Synthesis ◽  
Nalidixic Acid ◽  
Dominant Role ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Bacterial Survival ◽  
High Concentration ◽  
Ros Accumulation ◽  
High Concentrations

ABSTRACTWhen bacterial cells are exposed to increasing concentrations of quinolone-class antibacterials, survival drops, reaches a minimum, and then recovers, sometimes to 100%. Despite decades of study, events underlying this paradoxical high-concentration survival remain obscure. Since reactive oxygen species (ROS) have been implicated in antimicrobial lethality, conditions generating paradoxical survival were examined for diminished ROS accumulation.Escherichia colicultures were treated with various concentrations of nalidixic acid, followed by measurements of survival, rate of protein synthesis, and ROS accumulation. The last measurement used a dye (carboxy-H2DCFDA) that fluoresces in the presence of ROS; fluorescence was assessed by microscopy (individual cells) and flow cytometry (batch cultures). High, nonlethal concentrations of nalidixic acid induced lower levels of ROS than moderate, lethal concentrations. Sublethal doses of exogenous hydrogen peroxide became lethal and eliminated the nalidixic acid-associated paradoxical survival. Thus, quinolone-mediated lesions needed for ROS-executed killing persist at high, nonlethal quinolone concentrations, thereby implicating ROS as a key factor in cell death. Chloramphenicol suppressed nalidixic acid-induced ROS accumulation and blocked lethality, further supporting a role for ROS in killing. Nalidixic acid also inhibited protein synthesis, with extensive inhibition at high concentrations correlating with lower ROS accumulation and paradoxical survival. A catalase deficiency, which elevated ROS levels, overcame the inhibitory effect of chloramphenicol on nalidixic acid-mediated killing, emphasizing the importance of ROS. The data collectively indicate that ROS play a dominant role in the lethal action of narrow-spectrum quinolone-class compounds; a drop in ROS levels accounted for the quinolone tolerance observed at very high concentrations.

scholarly journals Reactive oxygen species play a dominant role in all pathways of rapid quinolone-mediated killing

2019 ◽  
Vol 75 (3) ◽  
pp. 576-585 ◽  
Author(s):  
Yuzhi Hong ◽  
Qiming Li ◽  
Qiong Gao ◽  
Jianping Xie ◽  
Haihui Huang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Dominant Role ◽  
Reactive Oxygen ◽  
Dna Lesions ◽  
Dominant Factor ◽  
Oxygen Species ◽  
Protective Effects ◽  
Dna Breaks ◽  
E Coli ◽  
Ros Accumulation

Abstract Background Quinolones have been thought to rapidly kill bacteria in two ways: (i) quinolone-topoisomerase-DNA lesions stimulate the accumulation of toxic reactive oxygen species (ROS); and (ii) the lesions directly cause lethal DNA breaks. Traditional killing assays may have underestimated the ROS contribution by overlooking the possibility that ROS continue to accumulate and kill cells on drug-free agar after quinolone removal. Methods Quinolone-induced, ROS-mediated killing of Escherichia coli was measured by plating post-treatment samples on agar with/without anti-ROS agents. Results When E. coli cultures were treated with ciprofloxacin or moxifloxacin in the presence of chloramphenicol (to accentuate DNA-break-mediated killing), lethal activity, revealed by plating on quinolone-free agar, was inhibited by supplementing agar with ROS-mitigating agents. Moreover, norfloxacin-mediated lethality, observed with cells suspended in saline, was blocked by inhibitors of ROS accumulation and exacerbated by a katG catalase deficiency that impairs peroxide detoxification. Unlike WT cells, the katG mutant was killed by nalidixic acid or norfloxacin with chloramphenicol present and by nalidixic or oxolinic acid with cells suspended in saline. ROS accumulated after quinolone removal with cultures either co-treated with chloramphenicol or suspended in saline. Deficiencies in recA or recB reduced the protective effects of ROS-mitigating agents, supporting the idea that repair of quinolone-mediated DNA lesions suppresses the direct lethal effects of such lesions. Conclusions ROS are the dominant factor in all modes of quinolone-mediated lethality, as quinolone-mediated primary DNA lesions are insufficient to kill without triggering ROS accumulation. ROS-stimulating adjuvants may enhance the lethality of quinolones and perhaps other antimicrobials.

scholarly journals Environmentally persistent free radicals are ubiquitous in wildfire charcoals and remain stable for years

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Gabriel Sigmund ◽  
Cristina Santín ◽  
Marc Pignitter ◽  
Nathalie Tepe ◽  
Stefan H. Doerr ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Reactive Oxygen ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Pyrogenic Carbon ◽  
Spin Resonance ◽  
Long Time ◽  
High Concentrations

AbstractGlobally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as well as surface fires in forest, shrubland and grassland spanning different boreal, temperate, subtropical and tropical climate. Using electron spin resonance spectroscopy, we measure high concentrations of environmentally persistent free radicals in charcoal samples, much higher than those found in soils. Concentrations increased with degree of carbonization and woody fuels favoured higher concentrations. Moreover, environmentally persistent free radicals remained stable for an unexpectedly long time of at least 5 years. We suggest that wildfire charcoal is an important global source of environmentally persistent free radicals, and therefore potentially of harmful reactive oxygen species.

scholarly journals Development, characterization and first deployment of an improved online reactive oxygen species analyzer

2018 ◽  
Vol 11 (1) ◽  
pp. 65-80 ◽  
Author(s):  
Jun Zhou ◽  
Emily A. Bruns ◽  
Peter Zotter ◽  
Giulia Stefenelli ◽  
André S. H. Prévôt ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Detection Limit ◽  
Atmospheric Aerosols ◽  
Half Life ◽  
Matrix Effects ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Wood Combustion ◽  
Storage Duration ◽  
High Concentrations

Abstract. Inhalation of atmospheric particles is linked to human diseases. Reactive oxygen species (ROS) present in these atmospheric aerosols may play an important role. However, the ROS content in aerosols and their formation pathways are still largely unknown. Here, we have developed an online and offline ROS analyzer using a 2′,7′-dichlorofluorescin (DCFH) based assay. The ROS analyzer was calibrated with H2O2 and its sensitivity was characterized using a suite of model organic compounds. The instrument detection limit determined as 3 times the noise is 1.3 nmol L−1 for offline analysis and 2 nmol m−3 of sampled air when the instrument is operated online at a fluorescence response time of approximately 8 min, while the offline method detection limit is 18 nmol L−1. Potential interferences from gas-phase O3 and NO2 as well as matrix effects of particulate SO42− and NO3− were tested, but not observed. Fe3+ had no influence on the ROS signal, while soluble Fe2+ reduced it if present at high concentrations in the extracts. Both online and offline methods were applied to identify the ROS content of different aerosol types, i.e., ambient aerosols as well as fresh and aged aerosols from wood combustion emissions. The stability of the ROS was assessed by comparing the ROS concentration measured by the same instrumentation online in situ with offline measurements. We also analyzed the evolution of ROS in specific samples by conducting the analysis after storage times of up to 4 months. The ROS were observed to decay with increasing storage duration. From their decay behavior, ROS in secondary organic aerosol (SOA) can be separated into short- and long-lived fractions. The half-life of the short-lived fraction was 1.7 ± 0.4 h, while the half-life of the long-lived fraction could not be determined with our uncertainties. All these measurements showed consistently that on average 60 ± 20 % of the ROS were very reactive and disappeared during the filter storage time. This demonstrates the importance of a fast online measurement of ROS.

scholarly journals Decitabine Induces Delayed Reactive Oxygen Species (ROS) Accumulation in Leukemia Cells and Induces the Expression of ROS Generating Enzymes

2014 ◽  
Vol 20 (5) ◽  
pp. 1249-1258 ◽  
Author(s):  
Tamer E. Fandy ◽  
Anchalee Jiemjit ◽  
Manjusha Thakar ◽  
Paulette Rhoden ◽  
Lauren Suarez ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Leukemia Cells ◽  
Oxygen Species ◽  
Ros Accumulation

UV-Vis Spectrophotometrical and Analytical Methodology for the Determination of Singlet Oxygen in New Antibacterials Drugs

2007 ◽  
Vol 2 ◽  
pp. 117739010700200 ◽  
Author(s):  
Tamara Zoltan ◽  
Franklin Vargas ◽  
Carla Izzo
Keyword(s):  
Reactive Oxygen Species ◽  
Singlet Oxygen ◽  
Nalidixic Acid ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Inexpensive Method ◽  
Analytical Methodology ◽  
First Time

We have determined and quantified spectrophotometrically the capacity of producing reactive oxygen species (ROS) as 1O2 during the photolysis with UV-A light of 5 new synthesized naphthyl ester derivates of well-known quinolone antibacterials (nalidixic acid (1), cinoxacin (2), norfloxacin (3), ciprofloxacin (4) and enoxacin (5)). The ability of the naphthyl ester derivatives (6-10) to generate singlet oxygen were detecting and for the first time quantified by the histidine assay, a sensitive, fast and inexpensive method. The following tendency of generation of singlet oxygen was observed: compounds 7 >10 > 6 > 8 > 9 >> parent drugs 1-5.

scholarly journals Role of Reactive Oxygen Species in Cancer Progression: Molecular Mechanisms and Recent Advancements

Biomolecules ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 735 ◽  
Author(s):  
Vaishali Aggarwal ◽  
Hardeep Tuli ◽  
Ayşegül Varol ◽  
Falak Thakral ◽  
Mukerrem Yerer ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Protein Kinase ◽  
Cancer Cell ◽  
Cancer Progression ◽  
Molecular Mechanisms ◽  
Reactive Oxygen ◽  
Mitogen Activated Protein Kinase ◽  
Oxygen Species ◽  
Mitogen Activated Protein ◽  
High Concentrations

Reactive oxygen species (ROS) play a pivotal role in biological processes and continuous ROS production in normal cells is controlled by the appropriate regulation between the silver lining of low and high ROS concentration mediated effects. Interestingly, ROS also dynamically influences the tumor microenvironment and is known to initiate cancer angiogenesis, metastasis, and survival at different concentrations. At moderate concentration, ROS activates the cancer cell survival signaling cascade involving mitogen-activated protein kinase/extracellular signal-regulated protein kinases 1/2 (MAPK/ERK1/2), p38, c-Jun N-terminal kinase (JNK), and phosphoinositide-3-kinase/ protein kinase B (PI3K/Akt), which in turn activate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), matrix metalloproteinases (MMPs), and vascular endothelial growth factor (VEGF). At high concentrations, ROS can cause cancer cell apoptosis. Hence, it critically depends upon the ROS levels, to either augment tumorigenesis or lead to apoptosis. The major issue is targeting the dual actions of ROS effectively with respect to the concentration bias, which needs to be monitored carefully to impede tumor angiogenesis and metastasis for ROS to serve as potential therapeutic targets exogenously/endogenously. Overall, additional research is required to comprehend the potential of ROS as an effective anti-tumor modality and therapeutic target for treating malignancies.

scholarly journals AToxoplasmaProlyl Hydroxylase Mediates Oxygen Stress Responses by Regulating Translation Elongation

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Celia Florimond ◽  
Charlotte Cordonnier ◽  
Rahil Taujale ◽  
Hanke van der Wel ◽  
Natarajan Kannan ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Protein Synthesis ◽  
Toxoplasma Gondii ◽  
Oxygen Sensing ◽  
Reactive Oxygen ◽  
Protozoan Parasite ◽  
Cellular Responses ◽  
Parasite Growth ◽  
Oxygen Species ◽  
Prolyl Hydroxylases

ABSTRACTAs the protozoan parasiteToxoplasma gondiidisseminates through its host, it responds to environmental changes by altering its gene expression, metabolism, and other processes. Oxygen is one variable environmental factor, and properly adapting to changes in oxygen levels is critical to prevent the accumulation of reactive oxygen species and other cytotoxic factors. Thus, oxygen-sensing proteins are important, and among these, 2-oxoglutarate-dependent prolyl hydroxylases are highly conserved throughout evolution.Toxoplasmaexpresses two such enzymes, TgPHYa, which regulates the SCF-ubiquitin ligase complex, and TgPHYb. To characterize TgPHYb, we created aToxoplasmastrain that conditionally expresses TgPHYb and report that TgPHYb is required for optimal parasite growth under normal growth conditions. However, exposing TgPHYb-depleted parasites to extracellular stress leads to severe decreases in parasite invasion, which is likely due to decreased abundance of parasite adhesins. Adhesin protein abundance is reduced in TgPHYb-depleted parasites as a result of inactivation of the protein synthesis elongation factor eEF2 that is accompanied by decreased rates of translational elongation. In contrast to most other oxygen-sensing proteins that mediate cellular responses to low O2, TgPHYb is specifically required for parasite growth and protein synthesis at high, but not low, O2tensions as well as resistance to reactive oxygen species.In vivo, reduced TgPHYb expression leads to lower parasite burdens in oxygen-rich tissues. Taken together, these data identify TgPHYb as a sensor of high O2levels, in contrast to TgPHYa, which supports the parasite at low O2.IMPORTANCEBecause oxygen plays a key role in the growth of many organisms, cells must know how much oxygen is available. O2-sensing proteins are therefore critical cellular factors, and prolyl hydroxylases are the best-studied type of O2-sensing proteins. In general, prolyl hydroxylases trigger cellular responses to decreased oxygen availability. But, how does a cell react to high levels of oxygen? Using the protozoan parasiteToxoplasma gondii, we discovered a prolyl hydroxylase that allows the parasite to grow at elevated oxygen levels and does so by regulating protein synthesis. Loss of this enzyme also reduces parasite burden in oxygen-rich tissues, indicating that sensing both high and low levels of oxygen impacts the growth and physiology ofToxoplasma.

scholarly journals Post-stress bacterial cell death mediated by reactive oxygen species

2019 ◽  
Vol 116 (20) ◽  
pp. 10064-10071 ◽  
Author(s):  
Yuzhi Hong ◽  
Jie Zeng ◽  
Xiuhong Wang ◽  
Karl Drlica ◽  
Xilin Zhao
Keyword(s):  
Reactive Oxygen Species ◽  
Cell Death ◽  
Bacterial Resistance ◽  
Reactive Oxygen ◽  
Temperature Sensitive ◽  
Oxygen Species ◽  
Stress Genes ◽  
Primary Stress ◽  
Bacterial Cell Death ◽  
Ros Accumulation

Antimicrobial efficacy, which is central to many aspects of medicine, is being rapidly eroded by bacterial resistance. Since new resistance can be induced by antimicrobial action, highly lethal agents that rapidly reduce bacterial burden during infection should help restrict the emergence of resistance. To improve lethal activity, recent work has focused on toxic reactive oxygen species (ROS) as part of the bactericidal activity of diverse antimicrobials. We report that whenEscherichia coliwas subjected to antimicrobial stress and the stressor was subsequently removed, both ROS accumulation and cell death continued to occur. Blocking ROS accumulation by exogenous mitigating agents slowed or inhibited poststressor death. Similar results were obtained with a temperature-sensitive mutational inhibition of DNA replication. Thus, bacteria exposed to lethal stressors may not die during treatment, as has long been thought; instead, death can occur after plating on drug-free agar due to poststress ROS-mediated toxicity. Examples are described in which (i) primary stress-mediated damage was insufficient to kill bacteria due to repair; (ii) ROS overcame repair (i.e., protection from anti-ROS agents was reduced by repair deficiencies); and (iii) killing was reduced by anti-oxidative stress genes acting before stress exposure. Enzymatic suppression of poststress ROS-mediated lethality by exogenous catalase supports a causal rather than a coincidental role for ROS in stress-mediated lethality, thereby countering challenges to ROS involvement in antimicrobial killing. We conclude that for a variety of stressors, lethal action derives, at least in part, from stimulation of a self-amplifying accumulation of ROS that overwhelms the repair of primary damage.

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