Browsing by Subject "Reactive oxygen species"

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    Open Access
    The arabidopsis cyclic nucleotide interactome
    (BioMed Central, 2016-05-11) Donaldson, Lara; Meier, Stuart; Gehring, Christoph
    Background: Cyclic nucleotides have been shown to play important signaling roles in many physiological processes in plants including photosynthesis and defence. Despite this, little is known about cyclic nucleotidedependent signaling mechanisms in plants since the downstream target proteins remain unknown. This is largely due to the fact that bioinformatics searches fail to identify plant homologs of protein kinases and phosphodiesterases that are the main targets of cyclic nucleotides in animals. Methods: An affinity purification technique was used to identify cyclic nucleotide binding proteins in Arabidopsis thaliana. The identified proteins were subjected to a computational analysis that included a sequence, transcriptional co-expression and functional annotation analysis in order to assess their potential role in plant cyclic nucleotide signaling. Results: A total of twelve cyclic nucleotide binding proteins were identified experimentally including key enzymes in the Calvin cycle and photorespiration pathway. Importantly, eight of the twelve proteins were shown to contain putative cyclic nucleotide binding domains. Moreover, the identified proteins are post-translationally modified by nitric oxide, transcriptionally co-expressed and annotated to function in hydrogen peroxide signaling and the defence response. The activity of one of these proteins, GLYGOLATE OXIDASE 1, a photorespiratory enzyme that produces hydrogen peroxide in response to Pseudomonas, was shown to be repressed by a combination of cGMP and nitric oxide treatment. Conclusions: We propose that the identified proteins function together as points of cross-talk between cyclic nucleotide, nitric oxide and reactive oxygen species signaling during the defence response.
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    The generation of toxic reactive oxygen species (ROS) from mechanically activated sulphide concentrates and its effect on thermophilic bioleaching.
    (Elsevier, 2011) Jones, Gavin C; Corin, Kirsten C; van Hille, Robert P; Harrison, Susan T L
    Two types of laboratory mills, planetary and vibratory, were used to activate sulphide mineral concentrates mechanically before thermophilic (bio)leaching. These samples were analysed in terms of particle size, surface area, density, SEM, XRD line profile analysis and reactivity. The product particle size distributions indicated different particle breakage mechanisms of the two mills. The surface area for pyrite milled with the planetary mill was three fold that milled in the vibratory mill for the same length of time. Planetary milled samples showed lower densities, up to 4% less for pyrite samples, compared to vibratory milled samples. Particle surface oxidation, observed by SEM, occurred post milling. Surface oxidation products were more prevalent with planetary milled sulphide samples. XRD line profile analysis showed more line broadening effects with the planetary mill. This indicated that more bulk particle-related structural defects were present in the planetary milled samples. The reactivity in acidic solution was measured in terms of the generation of toxic reactive oxygen species (ROS): hydrogen peroxide and hydroxyl radicals. The ROS generation from milled sulphides, normalised to constant surface area loading, increased with increased mechanical activation. The planetary milled samples generated greater ROS per sample surface area than vibratory milled samples, more than 4-fold for pyrite after 60 min of milling. Increased ROS generation was postulated to result from increased surface area defects, solubilisation of iron oxidation products and bulk particle-related defects. The effect of mechanical activation on performance on thermophilic leaching and bioleaching tests was investigated using milled samples at 2% (w/v) pulp density. Short mill times improved leach rates from both mills, up to 7-fold cf. unactivated feed leach rates. Poor bioleaching performance resulted following long periods of mechanical activation (20–60 min). Pyrite and chalcopyrite bioleaching performance decreased dramatically above surface area loadings of 25 and 125 m2 /L respectively. Planetary milled samples were less amenable to bioleaching. For pyrite milled for 20 and 60 min and chalcopyrite milled for 40 min, no viable cells were observed following inoculation via fluorescence microscopy, suggesting culture death supported by compromised ferrous iron oxidation. The generation of ROS was postulated to cause poor bioleaching performance under these conditions.
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    Open Access
    Impact of exercise intensity on oxidative stress and selected metabolic markers in young adults in Ghana
    (BioMed Central, 2018-09-03) Diaba-Nuhoho, Patrick; Ofori, Emmanuel K; Asare-Anane, Henry; Oppong, Sylvester Y; Boamah, Isaac; Blackhurst, Dee
    Objective This study aimed to evaluate the effect of different levels of exercise on markers of oxidative stress and selected metabolic parameters in Ghanaian young adults. Results Significant increases in a marker of oxidative stress malondialdehyde and antioxidants such as superoxide dismutase and uric acid were observed in the exercisers compared with the inactive group (p < 0.05). Total cholesterol and high density lipoprotein levels were significantly different (p < 0.05) between the two groups. Positive associations between exercise intensity, antioxidant concentration and malondialdehyde were observed within the exercise group for vigorous exercise with regards to uric acid, superoxide dismutase and malondialdehyde (r = 0.512, p = 0.004; r = 0.810, p = 0.001; r = 0.715, p = 0.001) respectively and moderate exercise vs malondialdehyde (r = 0.841, p = 0.001) compared to the inactive group. Exercise participants performed more vigorous exercise (p < 0.001), moderate exercise (p < 0.001) and more walking (p < 0.001) compared with the inactive group while the inactive group exhibited more sitting (p < 0.001). The study provides a first report on the risk associated with increase in oxidative stress and the importance of walking as a health promotion intervention among young Ghanaian adults.
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    Reactive oxygen species generated in the presence of fine pyrite particles and its implication in thermophilic mineral bioleaching
    (Springer Verlag, 2012) Jones, G C; van Hille, R P; Harrison, S T L
    In the tank bioleaching process, maximising solid loading and mineral availability, the latter through decreasing particle size, are key to maximising metal extraction. In this study, the effect of particle size distribution on bioleaching performance and microbial growth was studied through applying knowledge based on medical geology research to understand the adverse effects of suspended fine pyrite particles. Small-scale leaching studies, using pyrite concentrate fractions (106–75, 75–25, −25 μm fines), were used to confirm decreasing performance with decreasing particle size (D50 <40 μm). Under equivalent experimental conditions, the generation of the reactive oxygen species (ROS), hydrogen peroxide and hydroxyl radicals from pyrite was illustrated. ROS generation measured from the different pyrite fractions was found to increase with increasing pyrite surface area loading (1.79–74.01 m2 L−1) and Fe2+ concentration (0.1–2.8 g L−1) in solution. The highest concentration of ROS was measured from the finest fraction of pyrite (0.85 mM) and from the largest concentration of Fe2+ (0.78 mM). No ROS was detected from solutions containing only Fe3+ under the same conditions tested. The potential of ROS to inhibit microbial performance under bioleaching conditions was demonstrated. Pyrite-free Sulfolobus metallicus cultures challenged with hydrogen peroxide (0.5–2.5 mM) showed significant decrease in both cell growth and Fe2+ oxidation rates within the concentration range 1.5–2.5 mM. In combination, the results from this study suggest that conditions of large pyrite surface area loading, coupled with high concentrations of dissolved Fe2+, can lead to the generation of ROS, resulting in oxidative stress of the microorganisms.
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    Reactive oxygen species generated in the presence of fine pyrite particles and its implication in thermophilic mineral bioleaching.
    (Springer Verlag, 2013) Jones, G C; van Hille, R P; Harrison, S T L
    In the tank bioleaching process, maximising solid loading and mineral availability, the latter through decreasing particle size, are key to maximising metal extraction. In this study, the effect of particle size distribution on bioleaching performance and microbial growth was studied through applying knowledge based on medical geology research to understand the adverse effects of suspended fine pyrite particles. Small-scale leaching studies, using pyrite concentrate fractions (106–75, 75–25, −25 μm fines), were used to confirm decreasing performance with decreasing particle size (D 50 <40 μm). Under equivalent experimental conditions, the generation of the reactive oxygen species (ROS), hydrogen peroxide and hydroxyl radicals from pyrite was illustrated. ROS generation measured from the different pyrite fractions was found to increase with increasing pyrite surface area loading (1.79–74.01 m2 L−1) and Fe2+ concentration (0.1–2.8 g L−1) in solution. The highest concentration of ROS was measured from the finest fraction of pyrite (0.85 mM) and from the largest concentration of Fe2+ (0.78 mM). No ROS was detected from solutions containing only Fe3+ under the same conditions tested. The potential of ROS to inhibit microbial performance under bioleaching conditions was demonstrated. Pyrite-free Sulfolobus metallicus cultures challenged with hydrogen peroxide (0.5–2.5 mM) showed significant decrease in both cell growth and Fe2+ oxidation rates within the concentration range 1.5–2.5 mM. In combination, the results from this study suggest that conditions of large pyrite surface area loading, coupled with high concentrations of dissolved Fe2+, can lead to the generation of ROS, resulting in oxidative stress of the microorganisms.
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    Open Access
    SB225002 induces cell death and cell cycle arrest in acute lymphoblastic leukemia cells through the activation of GLIPR1
    (Public Library of Science, 2015) De Vasconcellos, Jaíra Ferreira; Laranjeira, Angelo Brunelli Albertoni; Leal, Paulo C; Bhasin, Manoj K; Zenatti, Priscila Pini; Nunes, Ricardo J; Yunes, Rosendo A; Nowill, Alexandre E; Libermann, Towia A; Zerbini, Luiz Fernando; Yunes, José Andrés
    Acute Lymphoblastic Leukemia (ALL) is the most frequent childhood malignancy. In the effort to find new anti-leukemic agents, we evaluated the small drug SB225002 (N-(2-hydroxy-4-nitrophenyl)-N'-(2-bromophenyl)urea). Although initially described as a selective antagonist of CXCR2, later studies have identified other cellular targets for SB225002, with potential medicinal use in cancer. We found that SB225002 has a significant pro-apoptotic effect against both B- and T-ALL cell lines. Cell cycle analysis demonstrated that treatment with SB225002 induces G2-M cell cycle arrest. Transcriptional profiling revealed that SB225002-mediated apoptosis triggered a transcriptional program typical of tubulin binding agents. Network analysis revealed the activation of genes linked to the JUN and p53 pathways and inhibition of genes linked to the TNF pathway. Early cellular effects activated by SB225002 included the up-regulation of GLIPR1 , a p53-target gene shown to have pro-apoptotic activities in prostate and bladder cancer. Silencing of GLIPR1 in B- and T-ALL cell lines resulted in increased resistance to SB225002. Although SB225002 promoted ROS increase in ALL cells, antioxidant N-Acetyl Cysteine pre-treatment only modestly attenuated cell death, implying that the pro-apoptotic effects of SB225002 are not exclusively mediated by ROS. Moreover, GLIPR1 silencing resulted in increased ROS levels both in untreated and SB225002-treated cells. In conclusion, SB225002 induces cell cycle arrest and apoptosis in different B- and T-ALL cell lines. Inhibition of tubulin function with concurrent activation of the p53 pathway, in particular, its downstream target GLIPR1 , seems to underlie the anti-leukemic effect of SB225002.