scholarly journals Factors Contributing to Hydrogen Peroxide Resistance in Streptococcus pneumoniae Include Pyruvate Oxidase (SpxB) and Avoidance of the Toxic Effects of the Fenton Reaction

2003 ◽  
Vol 185 (23) ◽  
pp. 6815-6825 ◽  
Author(s):  
Christopher D. Pericone ◽  
Sunny Park ◽  
James A. Imlay ◽  
Jeffrey N. Weiser
Keyword(s):  
Hydrogen Peroxide ◽  
Streptococcus Pneumoniae ◽  
Fenton Reaction ◽  
Bacterial Species ◽  
Atp Depletion ◽  
Host Cells ◽  
Toxic Effects ◽  
Aerobic Growth ◽  
Pyruvate Oxidase ◽  
Cytotoxic Effects

ABSTRACT Aerobic growth of Streptococcus pneumoniae results in production of amounts of hydrogen peroxide (H2O2) that may exceed 1 mM in the surrounding media. H2O2 production by S. pneumoniae has been shown to kill or inhibit the growth of other respiratory tract flora, as well as to have cytotoxic effects on host cells and tissue. The mechanisms allowing S. pneumoniae, a catalase-deficient species, to survive endogenously generated concentrations of H2O2 that are sufficient to kill other bacterial species is unknown. In the present study, pyruvate oxidase (SpxB), the enzyme responsible for endogenous H2O2 production, was required for survival during exposure to high levels (20 mM) of exogenously added H2O2. Pretreatment with H2O2 did not increase H2O2 resistance in the mutant, suggesting that SpxB activity itself is required, rather than an H2O2-inducible pathway. SpxB mutants synthesized 85% less acetyl-phosphate, a potential source of ATP. During H2O2 exposure, ATP levels decreased more rapidly in spxB mutants than in wild-type cells, suggesting that the increased killing of spxB mutants was due to more rapid ATP depletion. Together, these data support the hypothesis that S. pneumoniae SpxB contributes to an H2O2-resistant energy source that maintains viability during oxidative stress. Thus, SpxB is required for resistance to the toxic by-product of its own activity. Although H2O2-dependent hydroxyl radical production and the intracellular concentration of free iron were similar to that of Escherichia coli, killing by H2O2 was unaffected by iron chelators, suggesting that S. pneumoniae has a novel mechanism to avoid the toxic effects of the Fenton reaction.

scholarly journals Interference between Streptococcus pneumoniae and Staphylococcus aureus: In Vitro Hydrogen Peroxide-Mediated Killing by Streptococcus pneumoniae

2006 ◽  
Vol 188 (13) ◽  
pp. 4996-5001 ◽  
Author(s):  
Gili Regev-Yochay ◽  
Krzysztof Trzciński ◽  
Claudette M. Thompson ◽  
Richard Malley ◽  
Marc Lipsitch
Keyword(s):  
Hydrogen Peroxide ◽  
Staphylococcus Aureus ◽  
Streptococcus Pneumoniae ◽  
Bactericidal Activity ◽  
Mechanistic Explanation ◽  
Epidemiologic Studies ◽  
Pyruvate Oxidase ◽  
And Staphylococcus Aureus

ABSTRACT The bactericidal activity of Streptococcus pneumoniae toward Staphylococcus aureus is mediated by hydrogen peroxide. Catalase eliminated this activity. Pneumococci grown anaerobically or genetically lacking pyruvate oxidase (SpxB) were not bactericidal, nor were nonpneumococcal streptococci. These results provide a possible mechanistic explanation for the interspecies interference observed in epidemiologic studies.

Cytotoxic Effects of Hydrogen Peroxide on Human Gingival Fibroblasts In Vitro

2015 ◽  
Vol 40 (4) ◽  
pp. 430-439 ◽  
Author(s):  
M Furukawa ◽  
Jr K-Kaneyama ◽  
M Yamada ◽  
A Senda ◽  
A Manabe ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Vitamin E ◽  
Survival Rates ◽  
Human Gingival Fibroblasts ◽  
Toxic Effects ◽  
Bleaching Agent ◽  
Gingival Fibroblasts ◽  
Cytotoxic Effects ◽  
Peripheral Tissues ◽  
Tnf Α

SUMMARY In-office bleaching is a popular treatment in modern esthetic dentistry. However, bleaching agents sometimes accidentally adhere to the gingiva and peripheral tissues, even when applied by well-trained dentists. This can lead to transient pain and whitish changes in the gingiva. Although these symptoms disappear within several hours, the effects of bleaching agents on gingiva have not been well described in the literature. The present study aimed to elucidate the cytotoxic effects of a bleaching agent on cultured human gingival fibroblasts (HGFs). We performed a comprehensive analysis of the toxic effects of in-office bleaching agents on gingiva using cultured HGFs and DNA microarray. Survival rates of HGFs decreased with increases in the concentration of hydrogen peroxide, which became significant at concentrations of 1.5 × 10−3% or higher at every time point. Concentrations lower than 1.5 × 10−3% did not affect survival rates of HGFs. Cytotoxicity of hydrogen peroxide was significantly weakened by the addition of vitamin E. Stimulation by in-office bleaching agents triggered the proinflammatory cytokine tumor necrosis factor (TNF)–α cascade in gingival fibroblasts. As the TNF-α cascade can be inhibited by vitamin E additives, treatment with vitamin E may protect gingival fibroblasts against the toxic effects of an in-office bleaching agent. The present results suggest that local administration of vitamin E to gingiva before in-office bleaching may be useful for preventing gingival irritation due to accidental adhesion of a bleaching agent.

scholarly journals The MerR/NmlR Family Transcription Factor of Streptococcus pneumoniae Responds to Carbonyl Stress and Modulates Hydrogen Peroxide Production

2010 ◽  
Vol 192 (15) ◽  
pp. 4063-4066 ◽  
Author(s):  
Adam J. Potter ◽  
Stephen P. Kidd ◽  
Alastair G. McEwan ◽  
James C. Paton
Keyword(s):  
Hydrogen Peroxide ◽  
Transcription Factor ◽  
Streptococcus Pneumoniae ◽  
Alcohol Dehydrogenase ◽  
Carbon Metabolism ◽  
Carbonyl Stress ◽  
Aerobic Growth ◽  
Carbamoyl Phosphate ◽  
Hydrogen Peroxide Production ◽  
Mutant Strains

ABSTRACT The NmlRsp transcription factor of Streptococcus pneumoniae is shown to induce adhC (alcohol dehydrogenase) expression in the presence of both formaldehyde and methylglyoxal. nmlRsp and adhC mutant strains display altered and opposite aerobic growth phenotypes. The nmlRsp strain exhibits increased resistance to high oxygen tension, attributable to decreased H2O2 production, which correlated with downregulation of carbamoyl phosphate synthase (carB). This indicates a possible role for AdhC in aldehyde metabolism and a broader role for NmlRsp in the regulation of carbon metabolism.

scholarly journals Prevalence of ExoY Activity in Pseudomonas aeruginosa Reference Panel Strains and Impact on Cytotoxicity in Epithelial Cells

2021 ◽  
Vol 12 ◽  
Author(s):  
Hazel Silistre ◽  
Dorothée Raoux-Barbot ◽  
Federica Mancinelli ◽  
Flora Sangouard ◽  
Alice Dupin ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Epithelial Cells ◽  
Bacterial Species ◽  
Lung Epithelial Cells ◽  
Reference Panel ◽  
Host Cells ◽  
Cytotoxic Effects ◽  
Infection Models ◽  
Significant Difference

ExoY is among the effectors that are injected by the type III secretion system (T3SS) of Pseudomonas aeruginosa into host cells. Inside eukaryotic cells, ExoY interacts with F-actin, which stimulates its potent nucleotidyl cyclase activity to produce cyclic nucleotide monophosphates (cNMPs). ExoY has broad substrate specificity with GTP as a preferential substrate in vitro. How ExoY contributes to the virulence of P. aeruginosa remains largely unknown. Here, we examined the prevalence of active ExoY among strains from the international P. aeruginosa reference panel, a collection of strains that includes environmental and clinical isolates, commonly used laboratory strains, and sequential clonal isolates from cystic fibrosis (CF) patients and thus represents the large diversity of this bacterial species. The ability to secrete active ExoY was determined by measuring the F-actin stimulated guanylate cyclase (GC) activity in bacterial culture supernatants. We found an overall ExoY activity prevalence of about 60% among the 40 examined strains with no significant difference between CF and non-CF isolates. In parallel, we used cellular infection models of human lung epithelial cells to compare the cytotoxic effects of isogenic reference strains expressing active ExoY or lacking the exoY gene. We found that P. aeruginosa strains lacking ExoY were in fact more cytotoxic to the epithelial cells than those secreting active ExoY. This suggests that under certain conditions, ExoY might partly alleviate the cytotoxic effects of other virulence factors of P. aeruginosa.

scholarly journals Hydrogen Peroxide Levels in Freshly Brewed Coffee and the Effects of Storage

2020 ◽  
Author(s):  
Sannihith N. Uppu ◽  
Bianca K. London
Keyword(s):  
Hydrogen Peroxide ◽  
Xylenol Orange ◽  
Cell Types ◽  
Toxic Effects ◽  
Temperature Dependent ◽  
General Belief ◽  
Cytotoxic Effects ◽  
Future Studies ◽  
Aging Phenomenon ◽  
Fox Assay

SummaryOne of the world’s most consumed beverages, coffee has its origins as early as the 15th century Ethiopia. Although there are studies on caffeine and other components of coffee such as cafestol and kahweol, up until recently knowledge of the presence of hydrogen peroxide (H2O2) in coffee was confined to the scientific community and some informed public. It is a general belief that H2O2 is formed only after long periods of storage or with certain roasting practices. The present study is focused on dispelling the myths of H2O2 in coffee. We first measured H2O2 in freshly brewed coffee from different companies using the ferrous oxidation-xylenol orange binding (FOX) assay. Following this, we examined the time-dependent accumulation of H2O2 and its changes with temperature. Further, H2O2 was estimated in coffee obtained from several local vendors. Contrary to the general belief that the accumulation of H2O2 is an aging phenomenon of coffee, we found this toxicant even in freshly brewed coffee. This was true for all brands tested, and the H2O2 content increased upon storage. The highest increase was seen in coffee stored on the hot plate compared to the ones kept at room temperature (22-25 °C) or in the cold (0-4 °C). The H2O2 content of coffee from different vendors ranged between 0.29 and 0.82 mM, which is 5- to 20-fold higher than the typical H2O2 concentrations at which significant cytotoxic effects have been reported for assay systems using the human Fanconi deficient (PD20 FANCD2−/−) fibroblasts and other cell types. Our findings are deemed to shine new light on the probable toxic effects of a commonly consumed beverage like coffee, and the time and temperature dependent variations of keeping. While there are documented benefits of consumption of coffee, the possible H2O2-medicated toxic effects are critical and should be considered. Future studies are warranted to delineate the contribution of H2O2 in the healthy wellbeing of individuals who consume coffee extensively.

Pyruvate oxidase as a key determinant of pneumococcal viability during transcytosis across brain endothelium.

2021 ◽  
Author(s):  
Anjali Anil ◽  
Shruti Apte ◽  
Jincy Joseph ◽  
Akhila Parthasarathy ◽  
Shilpa Madhavan ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Streptococcus Pneumoniae ◽  
Acid Tolerance ◽  
Acetyl Phosphate ◽  
Brain Endothelium ◽  
Pyruvate Oxidase ◽  
Acid Tolerance Response ◽  
Virulence Determinant ◽  
Tolerance Response ◽  
Metabolizing Enzyme

Streptococcus pneumoniae (SPN/pneumococcus), invades myriad of host tissues following efficient breaching of cellular barriers. However, strategies adopted by pneumococcus for evasion of host intracellular defences governing successful transcytosis across host cellular barriers remain elusive. In this study, using brain endothelium as a model host barrier, we observed that pneumococcus containing endocytic vacuoles (PCVs) formed following SPN internalization into brain microvascular endothelial cells (BMECs), undergo early maturation and acidification, with a major subset acquiring lysosome-like characteristics. Exploration of measures that would preserve pneumococcal viability in the lethal acidic pH of these lysosome-like vacuoles revealed a critical role of the two-component system response regulator, CiaR, which has been previously implicated in induction of acid tolerance response. Pyruvate oxidase (SpxB), a key sugar metabolizing enzyme that catalyses oxidative decarboxylation of pyruvate to acetyl phosphate, was found to contribute to acid stress tolerance, presumably via acetyl phosphate-mediated phosphorylation and activation of CiaR, independent of its cognate kinase CiaH. Hydrogen peroxide, the by-product of SpxB catalysed reaction, was also found to improve pneumococcal intracellular survival by oxidative inactivation of lysosomal cysteine cathepsins, thus compromising the degradative capacity of the host lysosomes. Expectedly, a Δ spxB mutant was found to be significantly attenuated in its ability to survive inside the BMEC endocytic vacuoles, reflecting in its reduced transcytosis ability. Collectively, our studies establish SpxB as an important virulence determinant facilitating pneumococcal survival inside host cells, ensuring successful trafficking across host cellular barriers. IMPORTANCE Host cellular barriers have innate immune defences to restrict microbial passage into sterile compartments. Here, by focussing on the blood-brain barrier endothelium, we investigated mechanisms which enable Streptococcus pneumoniae to traverse through host barriers. Pyruvate oxidase, a pneumococcal sugar metabolizing enzyme was found to play a crucial role in this, via generation of acetyl phosphate and hydrogen peroxide. A two-pronged approach consisting of acetyl phosphate-mediated activation of acid tolerance response and hydrogen peroxide-mediated inactivation of lysosomal enzymes enabled pneumococci to maintain viability inside the degradative vacuoles of the brain endothelium, for successful transcytosis across the barrier. Thus, pyruvate oxidase is a key virulence determinant and can potentially serve as a viable candidate for therapeutic interventions for better management of invasive pneumococcal diseases.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

scholarly journals Monoassociation with bacterial isolates reveals the role of colonization, community complexity and abundance on locomotor behavior in larval zebrafish

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Chelsea A. Weitekamp ◽  
Allison Kvasnicka ◽  
Scott P. Keely ◽  
Nichole E. Brinkman ◽  
Xia Meng Howey ◽  
...  
Keyword(s):  
Total Concentration ◽  
Bacterial Species ◽  
Locomotor Behavior ◽  
Host Cells ◽  
Individual Species ◽  
Zebrafish Model ◽  
Associated Bacteria ◽  
Larval Zebrafish ◽  
Toxicological Studies ◽  
Community Complexity

Abstract Background Across taxa, animals with depleted intestinal microbiomes show disrupted behavioral phenotypes. Axenic (i.e., microbe-free) mice, zebrafish, and fruit flies exhibit increased locomotor behavior, or hyperactivity. The mechanism through which bacteria interact with host cells to trigger normal neurobehavioral development in larval zebrafish is not well understood. Here, we monoassociated zebrafish with either one of six different zebrafish-associated bacteria, mixtures of these host-associates, or with an environmental bacterial isolate. Results As predicted, the axenic cohort was hyperactive. Monoassociation with three different host-associated bacterial species, as well as with the mixtures, resulted in control-like locomotor behavior. Monoassociation with one host-associate and the environmental isolate resulted in the hyperactive phenotype characteristic of axenic larvae, while monoassociation with two other host-associated bacteria partially blocked this phenotype. Furthermore, we found an inverse relationship between the total concentration of bacteria per larvae and locomotor behavior. Lastly, in the axenic and associated cohorts, but not in the larvae with complex communities, we detected unexpected bacteria, some of which may be present as facultative predators. Conclusions These data support a growing body of evidence that individual species of bacteria can have different effects on host behavior, potentially related to their success at intestinal colonization. Specific to the zebrafish model, our results suggest that differences in the composition of microbes in fish facilities could affect the results of behavioral assays within pharmacological and toxicological studies.

scholarly journals T6SS Mediated Stress Responses for Bacterial Environmental Survival and Host Adaptation

2021 ◽  
Vol 22 (2) ◽  
pp. 478
Author(s):  
Kai-Wei Yu ◽  
Peng Xue ◽  
Yang Fu ◽  
Liang Yang
Keyword(s):  
Protein Secretion ◽  
Stress Responses ◽  
Current Knowledge ◽  
Bacterial Species ◽  
Host Cells ◽  
Interspecies Interactions ◽  
Type Vi Secretion System ◽  
Membrane Complex ◽  
Type Vi Secretion ◽  
Bacterial Type

The bacterial type VI secretion system (T6SS) is a protein secretion apparatus widely distributed in Gram-negative bacterial species. Many bacterial pathogens employ T6SS to compete with the host and to coordinate the invasion process. The T6SS apparatus consists of a membrane complex and an inner tail tube-like structure that is surrounded by a contractile sheath and capped with a spike complex. A series of antibacterial or antieukaryotic effectors is delivered by the puncturing device consisting of a Hcp tube decorated by the VgrG/PAAR complex into the target following the contraction of the TssB/C sheath, which often leads to damage and death of the competitor and/or host cells. As a tool for protein secretion and interspecies interactions, T6SS can be triggered by many different mechanisms to respond to various physiological conditions. This review summarizes our current knowledge of T6SS in coordinating bacterial stress responses against the unfavorable environmental and host conditions.

Sign in / Sign up

Export Citation Format

Share Document