ResearchPad - oxides https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Flavonoids and antioxidant activity of rare and endangered fern: <i>Isoetes sinensis</i>]]> https://www.researchpad.co/article/elastic_article_7844 Isoetes sinensis Palmer is a critically endangered, first-class protected plant in China. Until now, researchers have primarily focused on the ultrastructure, phylogeny, and transcriptomes of the plant. However, flavonoid profiles and bioactivity of I. sinensis have not been extensively investigated. To develop the endangered I. sinensis for edible and medicinal purposes, flavonoid content, chemical constitution, and antioxidant activities were investigated in this study. Results revealed the following. 1) The total flavonoid content was determined as 10.74 ± 0.25 mg/g., 2) Antioxidant activities were stronger than most ferns, especially ABTS free radical scavenging activities. 3) Four flavones, containing apigenin, apigenin-7-glucuronide, acacetin-7-O-glcopyranoside, and homoplantageninisoetin; four flavonols, namely, isoetin, kaempferol-3-O-glucoside, quercetin-3-O-[6”-O-(3-hydroxy-3-methylglutaryl)-β-D-glucopyranoside], and limocitrin-Neo; one prodelphinidin (procyanidins;) and one nothofagin (dihydrochalcone) were tentatively identified in the mass spectrometry-DAD (254nm) chromatograms. This study was the first to report on flavonoid content and antioxidant activities of I. sinensis. Stronger antioxidant activity and flavonoid content suggests that the endangered I. sinensis is an important and potentially edible and medicinal plant.

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<![CDATA[Constitutive hydrogen inhalation prevents vascular remodeling via reduction of oxidative stress]]> https://www.researchpad.co/article/Ne1330967-900e-43ee-b1f2-140543b0d511

Molecular hydrogen is thought to have an inhibitory effect on oxidative stress, thereby attenuating the onset and progression of various diseases including cardiovascular disease; however, few reports have assessed the preventive effect of constitutive inhalation of hydrogen gas on of vascular remodeling. Here, we investigated the effect of constitutive inhalation of hydrogen gas on vascular neointima formation using a cuff-induced vascular injury mouse model. After constitutive inhalation of compressed hydrogen gas (O2 21%, N2 77.7%, hydrogen 1.3%) or compressed air only (O2 21%, N2 79%) by C57BL/6 mice for 2 weeks from 8 weeks of age in a closed chamber, inflammatory cuff injury was induced by polyethylene cuff placement around the femoral artery under anesthesia, and hydrogen gas administration was continued until sampling of the femoral artery. Neointima formation, accompanied by an increase in cell proliferation, was significantly attenuated in the hydrogen group compared with the control group. NADPH oxidase NOX1 downregulation in response to cuff injury was shown in the hydrogen group, but the expression levels of NADPH oxidase subunits, p40phox and p47phox, did not differ significantly between the hydrogen and control groups. Although the increase in superoxide anion production did not significantly differ between the hydrogen and control groups, DNA damage was decreased as a result of reduction of reactive oxygen species such as hydroxyl radical (⋅OH) and peroxynitrite (ONOO-) in the hydrogen group. These results demonstrate that constitutive inhalation of hydrogen gas attenuates vascular remodeling partly via reduction of oxidative stress, suggesting that constitutive inhalation of hydrogen gas at a safe concentration in the living environment could be an effective strategy for prevention of vascular diseases such as atherosclerosis.

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<![CDATA[Retraction: DJ-1 Modulates α-Synuclein Aggregation State in a Cellular Model of Oxidative Stress: Relevance for Parkinson's Disease and Involvement of HSP70]]> https://www.researchpad.co/article/N05d3b52b-2e52-4bb2-9470-b0dedbc652af ]]> <![CDATA[Validation of a simple sample preparation method for multielement analysis of bovine serum]]> https://www.researchpad.co/article/5c633931d5eed0c484ae61f2

Here we propose a single acid digestion (SAD) sample preparation method for ICP-MS analysis of animal serum samples to determine trace element contents. The method was evaluated in comparison with a commonly used procedure involving dilution of samples in an alkaline solution (AKD). In the SAD procedure, aliquots (1 mL) of bovine serum samples were treated at low temperature with a mixture of concentrated nitric acid and hydrogen peroxide. Trace elements (As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sb, Se, Sr, U, and Zn) were directly determined by ICP-MS analysis of diluted solutions of samples. Both methods were sufficiently sensitive to enable quantification of most trace elements, with the exception of the AKD method for Cd, Hg and Pb. The quality of the data was verified by using certified reference material. Good results were obtained for the SAD procedure and all elements, but recoveries were unacceptable with the AKD procedure for Se (recovery: 57%), Cd (154%) and Fe (139%). Strong associations (R2>0.90, P = 0.000) between the data obtained by both methods were demonstrated for the elements considered. The proposed SAD sample preparation method produced satisfactory results for determining most toxic and essential trace elements targeted in monitoring studies.

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<![CDATA[Determinants of corrosion resistance of Ti-6Al-4V alloy dental implants in an In Vitro model of peri-implant inflammation]]> https://www.researchpad.co/article/5c5ca287d5eed0c48441e57d

Background

Titanium (Ti) and its alloys possess high biocompatibility and corrosion resistance due to Ti ability to form a passive oxide film, i.e. TiO2, immediately after contact with oxygen. This passive layer is considered stable during function in the oral cavity, however, emerging information associate inflammatory peri-implantitis to vast increases in Ti corrosion products around diseased implants as compared to healthy ones. Thus, it is imperative to identify which factors in the peri-implant micro-environment may reduce Ti corrosion resistance.

Methods

The aim of this work is to simulate peri-implant inflammatory conditions in vitro to determine which factors affect corrosion susceptibility of Ti-6Al-4V dental implants. The effects of hydrogen peroxide (surrogate for reactive oxygen species, ROS, found during inflammation), albumin (a protein typical of physiological fluids), deaeration (to simulate reduced pO2 conditions during inflammation), in an acidic environment (pH 3), which is typical of inflammation condition, were investigated. Corrosion resistance of Ti-6Al-4V clinically-relevant acid etched surfaces was investigated by electrochemical techniques: Open Circuit Potential; Electrochemical Impedance Spectroscopy; and Anodic Polarization.

Results

Electrochemical tests confirmed that most aggressive conditions to the Ti-6Al-4V alloy were those typical of occluded cells, i.e. oxidizing conditions (H2O2), in the presence of protein and deaeration of the physiological medium.

Conclusions

Our results provide evidence that titanium’s corrosion resistance can be reduced by intense inflammatory conditions. This observation indicates that the micro-environment to which the implant is exposed during peri-implant inflammation is highly aggressive and may lead to TiO2 passive layer attack. Further investigation of the effect of these aggressive conditions on titanium dissolution is warranted.

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<![CDATA[Cell type-specific differences in redox regulation and proliferation after low UVA doses]]> https://www.researchpad.co/article/5c57e6d0d5eed0c484ef3ec4

Ultraviolet A (UVA) radiation is harmful for living organisms but in low doses may stimulate cell proliferation. Our aim was to examine the relationships between exposure to different low UVA doses, cellular proliferation, and changes in cellular reactive oxygen species levels. In human colon cancer (HCT116) and melanoma (Me45) cells exposed to UVA doses comparable to environmental, the highest doses (30–50 kJ/m2) reduced clonogenic potential but some lower doses (1 and 10 kJ/m2) induced proliferation. This effect was cell type and dose specific. In both cell lines the levels of reactive oxygen species and nitric oxide fluctuated with dynamics which were influenced differently by UVA; in Me45 cells decreased proliferation accompanied the changes in the dynamics of H2O2 while in HCT116 cells those of superoxide. Genes coding for proteins engaged in redox systems were expressed differently in each cell line; transcripts for thioredoxin, peroxiredoxin and glutathione peroxidase showed higher expression in HCT116 cells whereas those for glutathione transferases and copper chaperone were more abundant in Me45 cells. We conclude that these two cell types utilize different pathways for regulating their redox status. Many mechanisms engaged in maintaining cellular redox balance have been described. Here we show that the different cellular responses to a stimulus such as a specific dose of UVA may be consequences of the use of different redox control pathways. Assays of superoxide and hydrogen peroxide level changes after exposure to UVA may clarify mechanisms of cellular redox regulation and help in understanding responses to stressing factors.

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<![CDATA[Comparison of the response of alternative oxidase and uncoupling proteins to bacterial elicitor induced oxidative burst]]> https://www.researchpad.co/article/5c40f80fd5eed0c484386f5b

Plant UCPs are proved to take part in the fine-tuning of mitochondrial ROS generation. It has emerged that mitochondrion can be an important early source of intracellular ROS during plant-pathogen interaction thus plant UCPs must also play key role in this redox fine-tuning during the early phase of plant–pathogen interaction. On the contrary of this well-established assumption, the expression of plant UCPs and their activity has not been investigated in elicitor induced oxidative burst. Thus, the level of plant UCPs both at RNA and protein level and their activity was investigated and compared to AOX as a reference in Arabidopsis thaliana cells due to bacterial harpin treatments. Similar to the expression and activity of AOX, the transcript level of UCP4, UCP5 and the UCP activity increased due to harpin treatment and the consequential oxidative burst. The expression of UCP4 and UCP5 elevated 15-18-fold after 1 h of treatment, then the activity of UCP reached its maximal value at 4h of treatment. The quite rapid activation of UCP due to harpin treatment gives another possibility to fine tune the redox balance of plant cell, furthermore explains the earlier observed rapid decrease of mitochondrial membrane potential and consequent decrease of ATP synthesis after harpin treatment.

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<![CDATA[Structural characterization of a pathogenicity-related superoxide dismutase codified by a probably essential gene in Xanthomonas citri subsp. citri]]> https://www.researchpad.co/article/5c3d015bd5eed0c48403a8e5

Citrus canker is a plant disease caused by the bacteria Xanthomonas citri subsp. citri that affects all domestic varieties of citrus. Some annotated genes from the X. citri subsp. citri genome are assigned to an interesting class named "pathogenicity, virulence and adaptation". Amongst these is sodM, which encodes for the gene product XcSOD, one of four superoxide dismutase homologs predicted from the genome. SODs are widespread enzymes that play roles in the oxidative stress response, catalyzing the degradation of the deleterious superoxide radical. In Xanthomonas, SOD has been associated with pathogenesis as a counter measure against the plant defense response. In this work we initially present the 1.8 Å crystal structure of XcSOD, a manganese containing superoxide dismutase from Xanthomonas citri subsp. citri. The structure bears all the hallmarks of a dimeric member of the MnSOD family, including the conserved hydrogen-bonding network residues. Despite the apparent gene redundancy, several attempts to obtain a sodM deletion mutant were unsuccessful, suggesting the encoded protein to be essential for bacterial survival. This intriguing observation led us to extend our structural studies to the remaining three SOD homologs, for which comparative models were built. The models imply that X. citri subsp. citri produces an iron-containing SOD which is unlikely to be catalytically active along with two conventional Cu,ZnSODs. Although the latter are expected to possess catalytic activity, we propose they may not be able to replace XcSOD for reasons such as distinct subcellular compartmentalization or differential gene expression in pathogenicity-inducing conditions.

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<![CDATA[Effects of different pretreatments on flavonoids and antioxidant activity of Dryopteris erythrosora leave]]> https://www.researchpad.co/article/5c3667dad5eed0c4841a66be

Flavonoids are secondary metabolites of plants that often have medical applications. The influences of different sample drying pretreatments on flavonoids and antioxidant activity of ferns have not studies. Dryopteris erythrosora leaves used to analyze flavonoid alterations resulting from drying pretreatments. The total flavonoid content of D. erythrosora leaves exposed to different pretreatments was significantly different. The total flavonoid content of samples initially air-dried in shade and then oven-dried at 75°C were the highest (7.6%), while samples initially dried at 75°C had the lowest content (2.17%). Antioxidant activities of D. erythrosora leaves with different pretreatments varied. Group B first air-dried in the shade and then oven-dried at 75°C and group C first air-dried in the sun and then oven-dried at 75°C, both showed relatively stronger antioxidant activity. The best pretreatment for preserving the flavonoids was to first dry the plant material in the shade and then complete the drying process in an oven at 75°C. It was tentatively identified 22 flavonoids among the four different pretreatments by HPLC-ESI-TOF-MS.

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<![CDATA[Study of the ichthyotoxic microalga Heterosigma akashiwo by transcriptional activation of sublethal marker Hsp70b in Transwell co-culture assays]]> https://www.researchpad.co/article/5b6da1a5463d7e4dccc5fae5

Despite the advance of knowledge about the factors and potential mechanisms triggering the ichthyotoxicity in microalgae, these remain unclear or are controversial for several species (e.g. Heterosigma). Neither typical toxicity tests carried out with cell extracts nor direct exposure to harmful species were proved suitable to unravel the mechanism of harm. Ichthyotoxic species show a complex harmful effect on fish, which is mediated through various mechanisms depending on the species. In this work, we present a method to study sub-lethal effects triggered by reactive oxygen species of a population of harmful algae in vivo over a fish cell line. To that end, Transwell co-cultures in which causative and target species are separated by a 0.4 μm pore membrane were carried out. This allowed the evaluation of the effect of the released molecules by cells in a rapid and compact test. In our method, the harmful effect was sensed through the transcriptional activation of sub-lethal marker Hsp70b in the CHSE214 salmon cell line. The method was tested with the raphidophyte Heterosigma akashiwo and Dunaliella tertiolecta (as negative control). It was shown that superoxide intracellular content and its release are not linked in these species. The methodology allowed proving that reactive oxygen species produced by H. akashiwo are able to induce the transcriptional activation of sub-lethal marker Hsp70b. However, neither loss of viability nor apoptosis was observed in CHSE214 salmon cell line except when exposed to direct contact with the raphidophyte cells (or their extract). Consequently, ROS was not concluded to be the main cause of ichthyotoxicity in H. akashiwo.

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<![CDATA[RitR is an archetype for a novel family of redox sensors in the streptococci that has evolved from two-component response regulators and is required for pneumococcal colonization]]> https://www.researchpad.co/article/5b04166d463d7e0b28e418a9

To survive diverse host environments, the human pathogen Streptococcus pneumoniae must prevent its self-produced, extremely high levels of peroxide from reacting with intracellular iron. However, the regulatory mechanism(s) by which the pneumococcus accomplishes this balance remains largely enigmatic, as this pathogen and other related streptococci lack all known redox-sensing transcription factors. Here we describe a two-component-derived response regulator, RitR, as the archetype for a novel family of redox sensors in a subset of streptococcal species. We show that RitR works to both repress iron transport and enable nasopharyngeal colonization through a mechanism that exploits a single cysteine (Cys128) redox switch located within its linker domain. Biochemical experiments and phylogenetics reveal that RitR has diverged from the canonical two-component virulence regulator CovR to instead dimerize and bind DNA only upon Cys128 oxidation in air-rich environments. Atomic structures show that Cys128 oxidation initiates a “helical unravelling” of the RitR linker region, suggesting a mechanism by which the DNA-binding domain is then released to interact with its cognate regulatory DNA. Expanded computational studies indicate this mechanism could be shared by many microbial species outside the streptococcus genus.

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<![CDATA[Pimaradienoic Acid Inhibits Carrageenan-Induced Inflammatory Leukocyte Recruitment and Edema in Mice: Inhibition of Oxidative Stress, Nitric Oxide and Cytokine Production]]> https://www.researchpad.co/article/5989da1fab0ee8fa60b7e548

Pimaradienoic acid (PA; ent-pimara-8(14),15-dien-19-oic acid) is a pimarane diterpene found in plants such as Vigueira arenaria Baker (Asteraceae) in the Brazilian savannas. Although there is evidence on the analgesic and in vitro inhibition of inflammatory signaling pathways, and paw edema by PA, its anti-inflammatory effect deserves further investigation. Thus, the objective of present study was to investigate the anti-inflammatory effect of PA in carrageenan-induced peritoneal and paw inflammation in mice. Firstly, we assessed the effect of PA in carrageenan-induced leukocyte recruitment in the peritoneal cavity and paw edema and myeloperoxidase activity. Next, we investigated the mechanisms involved in the anti-inflammatory effect of PA. The effect of PA on carrageenan-induced oxidative stress in the paw skin and peritoneal cavity was assessed. We also tested the effect of PA on nitric oxide, superoxide anion, and inflammatory cytokine production in the peritoneal cavity. PA inhibited carrageenan-induced recruitment of total leukocytes and neutrophils to the peritoneal cavity in a dose-dependent manner. PA also inhibited carrageenan-induced paw edema and myeloperoxidase activity in the paw skin. The anti-inflammatory mechanism of PA depended on maintaining paw skin antioxidant activity as observed by the levels of reduced glutathione, ability to scavenge the ABTS cation and reduce iron as well as by the inhibition of superoxide anion and nitric oxide production in the peritoneal cavity. Furthermore, PA inhibited carrageenan-induced peritoneal production of inflammatory cytokines TNF-α and IL-1β. PA presents prominent anti-inflammatory effect in carrageenan-induced inflammation by reducing oxidative stress, nitric oxide, and cytokine production. Therefore, it seems to be a promising anti-inflammatory molecule that merits further investigation.

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<![CDATA[A Unique Collection of Palaeolithic Painted Portable Art: Characterization of Red and Yellow Pigments from the Parpalló Cave (Spain)]]> https://www.researchpad.co/article/5989da08ab0ee8fa60b7684a

In this work we analyze the pigments used in the decoration of red and yellow motifs present in the portable art of the Parpalló Cave (Gandía, Spain), one of the most important Palaeolithic sites in the Spanish Mediterranean region. Energy dispersive X-ray fluorescence spectrometry (EDXRF) and spectrophotometry in the visible region (CIEL*a*b*color coordinates and spectral reflectance curves) were used to perform in situ fast analyses of the red and yellow motifs with portable equipment and to characterize their elemental composition and their colorimetric perception, respectively. According to the elemental composition, the intensity of the fluorescence iron signals in red and yellow motifs are higher than average values in the rock substrates. As expected, red motifs possess high values of the chromatic coordinate a* and yellow motifs possess high values of b*. This characterization was complemented with FT-IR analyses of microsamples detached from the red and yellow colored zones of a small set of plaquettes. Our results show that the artists used red and yellow pigments in the decoration likely derived from natural iron oxides as hematite and goethite.

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<![CDATA[cGMP-Phosphodiesterase Inhibition Prevents Hypoxia-Induced Cell Death Activation in Porcine Retinal Explants]]> https://www.researchpad.co/article/5989da07ab0ee8fa60b76416

Retinal hypoxia and oxidative stress are involved in several retinal degenerations including diabetic retinopathy, glaucoma, central retinal artery occlusion, or retinopathy of prematurity. The second messenger cyclic guanosine monophosphate (cGMP) has been reported to be protective for neuronal cells under several pathological conditions including ischemia/hypoxia. The purpose of this study was to evaluate whether the accumulation of cGMP through the pharmacological inhibition of phosphodiesterase (PDE) with Zaprinast prevented retinal degeneration induced by mild hypoxia in cultures of porcine retina. Exposure to mild hypoxia (5% O2) for 24h reduced cGMP content and induced retinal degeneration by caspase dependent and independent (PARP activation) mechanisms. Hypoxia also produced a redox imbalance reducing antioxidant response (superoxide dismutase and catalase activities) and increasing superoxide free radical release. Zaprinast reduced mild hypoxia-induced cell death through inhibition of caspase-3 or PARP activation depending on the cell layer. PDE inhibition also ameliorated the effects of mild hypoxia on antioxidant response and the release of superoxide radical in the photoreceptor layer. The use of a PKG inhibitor, KT5823, suggested that cGMP-PKG pathway is involved in cell survival and antioxidant response. The inhibition of PDE, therefore, could be useful for reducing retinal degeneration under hypoxic/ischemic conditions.

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<![CDATA[Sevoflurane Inhalation Accelerates the Long-Term Memory Consolidation via Small GTPase Overexpression in the Hippocampus of Mice in Adolescence]]> https://www.researchpad.co/article/5989dad0ab0ee8fa60bb618a

Sevoflurane exposure impairs the long-term memory in neonates. Whether the exposure to animals in adolescence affects the memory, however, has been unclear. A small hydrolase enzyme of guanosine triphosphate (GTPase) rac1 plays a role in the F-actin dynamics related to the synaptic plasticity, as well as superoxide production via reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation. The current study was designed to examine whether sevoflurane exposure to mice in early adolescence modifies the long-term learning ability concomitantly with the changes in F-actin constitution as well as superoxide production in the hippocampus according to the levels of rac1 protein expression. Four-week-old mice were subjected to the evaluation of long-term learning ability for three days. On day one, each mouse was allowed to enter a dark chamber for five min to acclimatization. On day two, the procedure was repeated with the addition of an electric shock as soon as a mouse entered the dark chamber. All mice subsequently inhaled 2 L/min air with (Sevoflurane group) and without (Control group) 2.5% sevoflurane for three hours. On day three, each mouse was placed on the platform and retention time, which is the latency to enter the dark chamber, was examined. The brain removed after the behavior test, was used for analyses of immunofluorescence, Western immunoblotting and intracellular levels of superoxide. Sevoflurane exposure significantly prolonged retention time, indicating the enhanced long-term memory. Sevoflurane inhalation augmented F-actin constitution coexisting with the rac1 protein overexpression in the hippocampus whereas it did not alter the levels of superoxide. Sevoflurane exposure to 4-week-old mice accelerates the long-term memory concomitantly with the enhanced F-actin constitution coexisting with the small GTPase rac1 overexpression in the hippocampus. These results suggest that sevoflurane inhalation may amplify long-term memory consolidation via the increased cytoskeleton constitution in the hippocampus of animals in early adolescence.

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<![CDATA[Robust DNA Damage Response and Elevated Reactive Oxygen Species in TINF2-Mutated Dyskeratosis Congenita Cells]]> https://www.researchpad.co/article/5989da04ab0ee8fa60b75163

Dyskeratosis Congenita (DC) is an inherited multisystem premature aging disorder with characteristic skin and mucosal findings as well as a predisposition to cancer and bone marrow failure. DC arises due to gene mutations associated with the telomerase complex or telomere maintenance, resulting in critically shortened telomeres. The pathogenesis of DC, as well as several congenital bone marrow failure (BMF) syndromes, converges on the DNA damage response (DDR) pathway and subsequent elevation of reactive oxygen species (ROS). Historically, DC patients have had poor outcomes following bone marrow transplantation (BMT), perhaps as a consequence of an underlying DNA hypersensitivity to cytotoxic agents. Previously, we demonstrated an activated DDR and increased ROS, augmented by chemotherapy and radiation, in somatic cells isolated from DC patients with a mutation in the RNA component of telomerase, TERC. The current study was undertaken to determine whether previous findings related to ROS and DDR in TERC patients’ cells could be extended to other DC mutations. Of particular interest was whether an antioxidant approach could counter increased ROS and decrease DC pathologies. To test this, we examined lymphocytes from DC patients from different DC mutations (TERT, TINF2, and TERC) for the presence of an active DDR and increased ROS. All DC mutations led to increased steady-state p53 (2-fold to 10-fold) and ROS (1.5-fold to 2-fold). Upon exposure to ionizing radiation (XRT), DC cells increased in both DDR and ROS to a significant degree. Exposing DC cells to hydrogen peroxide also revealed that DC cells maintain a significant oxidant burden compared to controls (1.5-fold to 3-fold). DC cell culture supplemented with N-acetylcysteine, or alternatively grown in low oxygen, afforded significant proliferative benefits (proliferation: maximum 2-fold increase; NAC: 5-fold p53 decrease; low oxygen: maximum 3.5-fold p53 decrease). Together, our data supports a mechanism whereby telomerase deficiency and subsequent shortened telomeres initiate a DDR and create a pro-oxidant environment, especially in cells carrying the TINF2 mutations. Finally, the ameliorative effects of antioxidants in vitro suggest this could translate to therapeutic benefits in DC patients.

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<![CDATA[Candida albicans FRE8 encodes a member of the NADPH oxidase family that produces a burst of ROS during fungal morphogenesis]]> https://www.researchpad.co/article/5ab4bc27463d7e0533a1be6e

Until recently, NADPH oxidase (NOX) enzymes were thought to be a property of multicellularity, where the reactive oxygen species (ROS) produced by NOX acts in signaling processes or in attacking invading microbes through oxidative damage. We demonstrate here that the unicellular yeast and opportunistic fungal pathogen Candida albicans is capable of a ROS burst using a member of the NOX enzyme family, which we identify as Fre8. C. albicans can exist in either a unicellular yeast-like budding form or as filamentous multicellular hyphae or pseudohyphae, and the ROS burst of Fre8 begins as cells transition to the hyphal state. Fre8 is induced during hyphal morphogenesis and specifically produces ROS at the growing tip of the polarized cell. The superoxide dismutase Sod5 is co-induced with Fre8 and our findings are consistent with a model in which extracellular Sod5 acts as partner for Fre8, converting Fre8-derived superoxide to the diffusible H2O2 molecule. Mutants of fre8Δ/Δ exhibit a morphogenesis defect in vitro and are specifically impaired in development or maintenance of elongated hyphae, a defect that is rescued by exogenous sources of H2O2. A fre8Δ/Δ deficiency in hyphal development was similarly observed in vivo during C. albicans invasion of the kidney in a mouse model for disseminated candidiasis. Moreover C. albicans fre8Δ/Δ mutants showed defects in a rat catheter model for biofilms. Together these studies demonstrate that like multicellular organisms, C. albicans expresses NOX to produce ROS and this ROS helps drive fungal morphogenesis in the animal host.

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<![CDATA[Genetic Determinants for Pyomelanin Production and Its Protective Effect against Oxidative Stress in Ralstonia solanacearum]]> https://www.researchpad.co/article/5989dad4ab0ee8fa60bb7502

Ralstonia solanacearum is a soil-borne plant pathogen that infects more than 200 plant species. Its broad host range and long-term survival under different environmental stress conditions suggest that it uses a variety of mechanisms to protect itself against various types of biotic and abiotic stress. R. solanacearum produces a melanin-like brown pigment in the stationary phase when grown in minimal medium containing tyrosine. To gain deeper insight into the genetic determinants involved in melanin production, transposon-inserted mutants of R. solanacearum strain SL341 were screened for strains with defective melanin-producing capability. In addition to one mutant already known to be involved in pyomelanin production (viz., strain SL341D, with disruption of the hydroxphenylpyruvate dioxygenase gene), we identified three other mutants with disruption in the regulatory genes rpoS, hrpG, and oxyR, respectively. Wild-type SL341 produced pyomelanin in minimal medium containing tyrosine whereas the mutant strains did not. Likewise, homogentisate, a major precursor of pyomelanin, was detected in the culture filtrate of the wild-type strain but not in those of the mutant strains. A gene encoding hydroxyphenylpyruvate dioxygenase exhibited a significant high expression in wild type SL341 compared to other mutant strains, suggesting that pyomelanin production is regulated by three different regulatory proteins. However, analysis of the gene encoding homogentisate dioxygenase revealed no significant difference in its relative expression over time in the wild-type SL341 and mutant strains, except for SL341D, at 72 h incubation. The pigmented SL341 strain also exhibited a high tolerance to hydrogen peroxide stress compared with the non-pigmented SL341D strain. Our study suggests that pyomelanin production is controlled by several regulatory factors in R. solanacearum to confer protection under oxidative stress.

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<![CDATA[Procainamide Inhibits DNA Methylation and Alleviates Multiple Organ Dysfunction in Rats with Endotoxic Shock]]> https://www.researchpad.co/article/5989da71ab0ee8fa60b95151

Excessive inflammatory and oxidative stress lead to circulatory failure, multiple organ dysfunction, and high mortality in patients with sepsis. Microbial infection-induced DNA hypermethylation is associated with the augmentation of inflammation and oxidative stress. In our previous study, the antiarrhythmic drug procainamide inhibits the expression of DNA methyltransferase 1 (DNMT1) and diminishes IL-6 levels in rats with rhabdomyolysis. Thus, we further evaluated the effects of procainamide on the development of circulatory failure and multiple organ dysfunction in rats with endotoxic shock. Male Wistar rats were intravenously infused with saline or lipopolysaccharide (LPS) followed by procainamide administration. The changes of hemodynamics, blood glucose, biochemical variables, and plasma nitric oxide (NO) levels were analyzed during the experimental period. At the end of experiments, animal organs were also obtained for examining superoxide production, neutrophil infiltration, and DNA methylation status. Our results showed that LPS induced circulatory failure, multiple organ dysfunction, and high mortality rate in endotoxemic rats. Overt neutrophil infiltration and superoxide production, accompanied by the elevations of DNMT1 and 5-methylcytosine levels in the lung of endotoxemic rats were also observed. Treatment of endotoxemic animals with procainamide not only inhibited the increased levels of DNMT1 and 5-methylcytosine but also ameliorated neutrophil infiltration and superoxide production in the lung. In addition, the anti-inflammatory gene, IL27RA, was down-regulated in the LPS group and up-regulated in the LPS + Procainamide group. Procainamide also diminished IL27RA methylation in the lung of endotoxemic rat. Moreover, both DNMT inhibitors procainamide and hydralazine improved hypotension, hypoglycemia, and multiple organ dysfunction of LPS-treated rats. Thus, we suggest that the beneficial effects of procainamide could be attributed to the suppression of DNA methylation, neutrophil infiltration, superoxide production, and NO formation. It seems that this old drug may have new potential uses in infectious diseases, in particular, associated with endotoxemia.

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<![CDATA[Magnetic Particle / Magnetic Resonance Imaging: In-Vitro MPI-Guided Real Time Catheter Tracking and 4D Angioplasty Using a Road Map and Blood Pool Tracer Approach]]> https://www.researchpad.co/article/5989da40ab0ee8fa60b8989b

Purpose

In-vitro evaluation of the feasibility of 4D real time tracking of endovascular devices and stenosis treatment with a magnetic particle imaging (MPI) / magnetic resonance imaging (MRI) road map approach and an MPI-guided approach using a blood pool tracer.

Materials and Methods

A guide wire and angioplasty-catheter were labeled with a thin layer of magnetic lacquer. For real time MPI a custom made software framework was developed. A stenotic vessel phantom filled with saline or superparamagnetic iron oxide nanoparticles (MM4) was equipped with bimodal fiducial markers for co-registration in preclinical 7T MRI and MPI. In-vitro angioplasty was performed inflating the balloon with saline or MM4. MPI data were acquired using a field of view of 37.3×37.3×18.6 mm3 and a frame rate of 46 volumes/sec. Analysis of the magnetic lacquer-marks on the devices were performed with electron microscopy, atomic absorption spectrometry and micro-computed tomography.

Results

Magnetic marks allowed for MPI/MRI guidance of interventional devices. Bimodal fiducial markers enable MPI/MRI image fusion for MRI based roadmapping. MRI roadmapping and the blood pool tracer approach facilitate MPI real time monitoring of in-vitro angioplasty. Successful angioplasty was verified with MPI and MRI. Magnetic marks consist of micrometer sized ferromagnetic plates mainly composed of iron and iron oxide.

Conclusions

4D real time MP imaging, tracking and guiding of endovascular instruments and in-vitro angioplasty is feasible. In addition to an approach that requires a blood pool tracer, MRI based roadmapping might emerge as a promising tool for radiation free 4D MPI-guided interventions.

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