SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Free radical research

0

The aim of this study was to examine the effects of scuba diving on oxidative damage markers in erythrocytes and plasma, antioxidant system in peripheral blood mononuclear cells (PBMCs), as well as sirtuin 1 (SIRT1) and sirtuin 3 (SIRT3) gene expressions in recreational divers after a winter nondive period (at least 5 months). For that purpose, 17 male recreational divers performed an immersion at a depth of 30 m for 30 min. Blood samples were collected immediately before and after diving, 3 and 6 h after diving. Erythrocyte lipid peroxidation measured by thiobarbituric-reactive substances (TBARS) method was significantly increased immediately after diving, but returned to the baseline 6 h after diving, while no significant change was found for plasma TBARS and protein carbonyl derivates in both plasma and erythrocytes. Diving-induced catalase (CAT), superoxide dismutase 2 (SOD2), and consequently total superoxide dismutase (SOD) activities in the PBMC samples (significantly increased immediately after diving, reached the maximum activities 3 h after diving, while 6 h after diving only CAT activity remained significantly increased). No significant change was observed for SOD1 activity and gene expression, as well as SOD2 expression, while CAT and SIRT1 expressions were slightly decreased immediately after diving and 3 h after diving. Interestingly, SIRT3 expression was significantly increased 6 h after diving. In conclusion, after the first dive to 30 m after a nondive season, activation of antioxidant defence was not sufficient to prevent oxidative damage, while SIRT3 upregulation could be a step towards an adaptive response to the diving.

Concepts: Gene, Cell nucleus, Gene expression, Blood, Antioxidant, Reactive oxygen species, Superoxide dismutase, PBMC

0

In vivo decay rates of a nitroxyl contrast agent were estimated by a MR redox imaging (MRRI) technique and compared with the decay rates obtained by the electron paramagnetic resonance spectroscopy (EPRS) and imaging (EPRI). MRRI is a dynamic imaging technique employing T1-weighted pulse sequence, which can visualize a nitroxyl-induced enhancement of signal intensity by T1-weighted contrast. EPR techniques can directly measure the paramagnetic nitroxyl radical. Both the squamous cell carcinoma (SCC) tumor-bearing and normal legs of a female C3H mouse were scanned by T1-weighted SPGR sequence at 4.7 T with the nitroxyl radical, carbamoyl-proxyl (CmP), as the contrast agent. Similarly, the time course of CmP in normal muscle and tumor tissues was obtained using an 700-MHz EPR spectrometer with a surface coil. The time course imaging of CmP was also performed by 300 MHz CW EPR imager. EPRS and EPRI gave slower decay rates of CmP compared to the MRRI. Relatively slow decay rate at peripheral region of the tumor tissues, which was found in the image obtained by MRRI, may contribute to the slower decay rates observed by EPRS and/or the EPRI measurements. To reliably determine the tissue redox status from the reduction rates of nitroxyls such as CmP, heterogenic structure in the tumor tissue must be considered. The high spatial and temporal resolution of T1-weighted MRI and the T1-enhancing capabilities of nitroxyls support the use of this method to map tissue redox status which can be a useful biomarker to guide appropriate treatments based on the tumor microenvironment.

Concepts: Cancer, Medical imaging, Magnetic resonance imaging, Radical, Radioactive decay, Squamous cell carcinoma, Squamous epithelium, Electron paramagnetic resonance

0

The ability of certain cancer cells to maintain a highly reduced intracellular environment is correlated with aggressiveness and drug resistance. Since the gluthathione (GSH) and thioredoxin (TRX) systems cooperate to a tight regulation of ROS in cell physiology, and to a stimulation of tumor initiation and progression, modulation of the GSH and TRX pathways are emerging as new potential targets in cancer. In vivo methods to assess changes in tumor redox status are critically needed to assess the relevance of redox-targeted agents. The current study assesses in vitro and in vivo biomarkers of tumor redox status in response to treatments targeting the GSH and TRX pathways, by comparing cytosolic and mitochondrial redox nitroxide Electron Paramagnetic Resonance (EPR) probes, and cross-validation with redox dynamic fluorescent measurement. For that purpose, the effect of the GSH modulator buthionine sulfoximine (BSO) and of the TRX reductase inhibitor auranofin were measured in vitro using both cytosolic and mitochondrial EPR and roGFP probes in breast and cervical cancer cells. In vivo, mice bearing breast or cervical cancer xenografts were treated with the GSH or TRX modulators and monitored using the mito-TEMPO spin probe. Our data highlight the importance of using mitochondria targeted spin probes to assess changes in tumor redox status induced by redox modulators. Further in vivo validation of the mito-tempo spin probe with alternative in vivo methods should be considered, yet the spin probe used in vivo in xenografts demonstrated sensitivity to the redox status modulators.

Concepts: Cancer, Metastasis, Adenosine triphosphate, Mitochondrion, Reactive oxygen species, Cytoplasm, Glutathione, Modulation

0

Fever is a regulated increase in body temperature and a component of the acute-phase response, triggered mainly after the invasion of pathogens in the body. Reactive oxygen species (ROS) are generated during the physiological and pathological processes, and can act as both signaling molecules as well as promoters of oxidative stress. Male Wistar rats, pretreated with oral doses of acetaminophen, celecoxib, dipyrone, or ibuprofen 30 min before an intravenous lipopolysaccharide (LPS) or sterile saline injection, showed a reduced febrile response in all animals tested. The formation of ROS in the fresh blood, liver, brown adipose tissue (BAT), and hypothalamus of febrile and antipyretic-treated animals was assessed by electron paramagnetic resonance using the spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH). While the CM• concentrations remained unaltered in the blood samples examined 5 h after the induction of fever, we found increased CM• levels in the liver (in µM, saline: 290 ± 42; LPS: 512 ± 34), BAT (in µM, saline: 509 ± 79, LPS: 855 ± 79), and hypothalamus (in µM, saline: 292 ± 35; LPS: 467 ± 8) at the same time point. Importantly, none of the antipyretics were seen to alter the CM• accumulation profile. Data from this study suggest that there is an increased formation of ROS in the different tissues during fever, which may cause oxidative stress, and that the antipyretics tested do not interfere with ROS production.

Concepts: Oxygen, Oxidative phosphorylation, Reactive oxygen species, Hydrogen peroxide, Ibuprofen, Aspirin, Fever, Antipyretic

0

Oxidation by reactive species can cause changes in protein function and affect cell signaling pathways. Phosphatase and tensin homolog (PTEN) is a negative regulator of the PI3K/AKT pathway and is known to be inhibited by oxidation, but its oxidation by the myeloperoxidase-derived oxidant hypochlorous acid (HOCl) has not previously been investigated. PTEN-GST was treated with HOCl:protein ratios from 15:1 to 300:1. Decreases in PTEN phosphatase activity were observed at treatment ratios of 60:1 and higher, which correlated with the loss of the intact protein band and appearance of high molecular weight aggregates in SDS-PAGE. LC-MSMS was used to map oxidative modifications (oxPTMs) in PTEN-GST tryptic peptides and label-free quantitative proteomics used to determine their relative abundance. Twenty different oxPTMs of PTEN were identified, of which 14 were significantly elevated upon HOCl treatment in a dose-dependent manner. Methionine and cysteine residues were the most heavily oxidized; the percentage modification depended on their location in the sequence, reflecting differences in susceptibility. Other modifications included tyrosine chlorination and dichlorination, and hydroxylations of tyrosine, tryptophan, and proline. Much higher levels of oxidation occurred in the protein aggregates compared to the monomeric protein for certain methionine and tyrosine residues located in the C2 and C-terminal domains, suggesting that their oxidation promoted protein destabilization and aggregation; many of the residues modified were classified as buried according to their solvent accessibility. This study provides novel information on the susceptibility of PTEN to the inflammatory oxidant HOCl and its effects on the structure and activity of the protein.

Concepts: Protein, Amino acid, Acid, Enzyme, Redox, Oxidizing agent, Essential amino acid, Chlorine

0

Monocytes are recruited to injured tissue sites and differentiate into tissue macrophages or dendritic cells to protect against pathogens and repair the damaged tissues. Phorbol-12-myristate-13-acetate (PMA) is a well-known stimulus commonly used for differentiation of monocytes into macrophage-like cells (MɸLC). Here, we report the effect of Cold Atmospheric Plasma (CAP) on PMA induced U937 differentiation into MɸLC. Treatment of U937 cells with PMA for 3 days and resting for 4 days increased the size of cytoplasm as compared nucleus and exposure to CAP before addition of PMA led to further increase in cytoplasm indicating the ability of CAP to modulate the differentiation of monocytes. Exposure of U937 cells to CAP or PMA increased cellular reactive oxygen species (ROS) level and the combination led to further augmentation of ROS. Treatment of U937 cells with PMA displayed a biphasic activation of proinflammatory transcription factor NF-κB which plays an important role in differentiation and pretreatment with CAP further increased PMA induced NF-κB-DNA binding activity. CAP also increased LPS induced secretion of TNF-α and IL-6 in MɸLC. Further investigation revealed that MɸLC or CAP treated MɸLC were more resistant to anticancer drugs like doxorubicin and 5-fluorouracil (5-FU) than U937 cells. Our present studies suggest an alternate protocol to modulate the differentiation of U937 cells into MɸLC by combining CAP and PMA.

Concepts: Immune system, Monocyte, DNA, Cell nucleus, Gene expression, Mitochondrion, Reactive oxygen species, Tissue

0

Proteins represent extremely susceptible targets for oxidants. Oxidative modifications of proteins may bring about violation of their structure and functionality. It implies that the structures of proteins are not infallible in terms of their antioxidant defence. The protection mechanisms in preventing oxidative damages for proteins within cells are mainly related to a large variety of antioxidant enzymatic systems. In contrast, plasma proteins are scarcely protected by these systems, so the mechanism that provides their functioning in the conditions of generating reactive oxygen species (ROS) seems to be much more complicated. Oxidation of many proteins was long considered as a random process. However, the highly site-specific oxidation processes was convincingly demonstrated for some proteins, indicating that protein structure could be adapted to oxidation. According to our hypothesis, some of the structural elements present in proteins are capable of scavenging ROS to protect other protein structures against ROS toxicity. Various antioxidant elements (distinct subdomains, domains, regions, and polypeptide chains) may act as ROS interceptors, thus mitigating the ROS action on functionally crucial amino acid residues of proteins. In the review, the oxidative modifications of certain plasma proteins, such as α2-macroglobulin, serum human albumin, fibrinogen, and fibrin-stabilising factor, which differ drastically in their spatial structures and functions, are analysed. The arguments that demonstrate the possibility of existing hypothetical antioxidant structures are presented. For the first time, the emphasis is being placed on the programmed mechanism of protein oxidation.

Concepts: Protein, Protein structure, Oxygen, Amino acid, Antioxidant, Nitrogen, Peptide, Glutathione

0

The reactions of proteins with biologically-relevant oxidants have been widely studied, although most of the work has been performed in diluted homogenous solutions conditions that differ from those in intracellular environments. Cellular compartments represent highly crowded milieu in which high concentrations of biomolecules are present, unspecific intermolecular interactions promoted and physicochemical properties of constituents modified. In this work, we propose that the high concentration at which proteins are present inside cells, favors radical oxidative reactions between polypeptides which propagate in an oxygen-dependent process similar to membrane lipid peroxidation. The results presented herein show that highly concentrated solutions of bovine serum albumin (BSA) exposed to peroxynitrite, or metmyoglobin/H2O2, initiate the formation and propagation of protein peroxyl radicals, as evidenced by oxygen consumption, fluorescence spectroscopy, chemiluminescence, and electron paramagnetic resonance studies. Moreover, peroxyl radicals are capable of converting nitrite to nitrogen dioxide, which can oxidize amino acid residues to further assist radical-mediated protein oxidation. In addition, we also show that nitrone spin traps stop these propagation reactions in proteins, in line with the previously reported antioxidant role of these compounds in vivo. In summary, our results suggest that in crowded environments such as cellular compartments radical chain reactions propagate protein oxidative damage, highlighting a previously under recognized mechanism of cellular nitroxidative stress.

Concepts: Protein, Oxygen, Amino acid, Redox, Nitrogen, Radical, Oxide, Nitric oxide

0

Patients with minimal hepatic encephalopathy (MHE) show increased oxidative stress in blood. We aimed to assess whether MHE patients show alterations in different types of blood cells in: a) basal reactive oxygen and nitrogen species levels; b) capacity to metabolize these species. To assess the mechanisms involved in the altered capacity to metabolize these species we also analyzed: c) peroxynitrite formation and d) peroxynitrite reaction with biological molecules. Levels of reactive oxygen and nitrogen species were measured by flow cytometry in blood cell populations from cirrhotic patients with and without MHE and controls, under basal conditions and after adding generators of superoxide (Plumbagin) or nitric oxide (NOR-1) to assess the capacity to eliminate them. Under basal conditions, MHE patients show reduced superoxide and peroxynitrite levels and increased nitric oxide and nitrotyrosine levels. In patients without MHE plumbagin strongly increases cellular superoxide, moderately peroxynitrite and reduces nitric oxide levels. In MHE patients, plumbagin increases slightly superoxide and strongly peroxynitrite levels and affects slightly nitric oxide levels. NOR-1 increases nitric oxide levels much less in patients with than without MHE. These data show that the mechanisms and the capacity to eliminate cellular superoxide, nitric oxide and peroxynitrite are enhanced in MHE patients. Superoxide elimination is enhanced through reaction with nitric oxide to form peroxynitrite which, in turn, is eliminated by enhanced reaction with biological molecules, which could contribute to cognitive impairment in MHE. The data show that basal free radicals levels do not reflect the oxidative stress status in MHE.

Concepts: Oxygen, Red blood cell, Redox, Oxidative phosphorylation, Nitrogen, Radical, Nitric oxide, Hepatic encephalopathy

0

The coordination of metabolic shift with genetic circuits is critical to cell specification, but the metabolic mechanisms that drive cardiac development are largely unknown. Reactive oxygen species (ROS) is not only the byproduct of mitochondrial metabolism, but play a critical role in signaling cascade of cardiac development as a second messenger. Various levels of ROS appear differential and even oppose effect on selfrenewal and cardiac differentiation of pluripotent stem cells (PSCs) at each stage of differentiation. The intracellular ROS and redox balance are meticulous regulated by several systems of ROS generation and scavenging, among which mitochondria and the NADPH oxidase (NOX) are major sources of intracellular ROS involved in cardiomyocyte differentiation. Some critical signaling modulators are activated or inactivated by oxidation, suggesting ROS can be involved in regulation of cell fate through these downstream targets. In this review, the literatures about major sources of ROS, the effect of ROS level on cardiac differentiation of PSCs, as well as the underlying mechanism of ROS in the control of cardiac fate of PSC are summarized and discussed.

Concepts: DNA, Photosynthesis, Adenosine triphosphate, Mitochondrion, Stem cell, Cell biology, Oxidative phosphorylation, Cellular respiration