SciCombinator

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Journal: Free radical research

27

Abstract Myeloperoxidase (MPO), a major constituent of neutrophils, catalyzes the production of hypochlorous acid (HOCl) from hydrogen peroxide (H(2)O(2)) and chloride anion. We have previously reported that MPO-deficient (MPO(-/-)) neutrophils produce greater amount of macrophage inflammatory protein-2 (MIP-2) in vitro than do wild-type when stimulated with zymosan. In this study, we investigated the molecular mechanisms governing the up-regulation of MIP-2 production in the mutant neutrophils. Interestingly, we found that zymosan-induced production of MIP-2 was blocked by pre-treatment with U0126, an inhibitor of mitogen-activated protein kinase/extracellular-signal regulated kinase (ERK), and with BAY11-7082, an inhibitor of nuclear factor (NF)-κB. Western blot analysis indicated that U0126 also inhibited the phosphorylation of p65 subunit of NF-κB (p65), indicating that MIP-2 was produced via the ERK/NF-κB pathway. Intriguingly, we found that ERK1/2, p65, and alpha subunit of inhibitor of κB (IκBα) in the MPO(-/-) neutrophils were phosphorylated more strongly than in the wild-type when stimulated with zymosan. Exogenous H(2)O(2) treatment in addition to zymosan stimulation enhanced the phosphorylation of ERK1/2 without affecting the zymosan-induced MIP-2 production. In contrast, exogenous HOCl inhibited the production of MIP-2 as well as IκBα phosphorylation without affecting ERK activity. The zymosan-induced production of MIP-2 in the wild-type neutrophils was enhanced by pre-treatment of the MPO inhibitor 4-Aminobenzoic acid hydrazide. Collectively, these results strongly suggest that both lack of HOCl and accumulation of H(2)O(2 )due to MPO deficiency contribute to the up-regulation of MIP-2 production in mouse neutrophils stimulated with zymosan.

Concepts: Oxygen, Acid, Hydrogen, Western blot, Chlorine, Hypochlorous acid, Myeloperoxidase, Myeloperoxidase deficiency

25

Production of reactive oxygen species, including hydrogen peroxide (H2O2), is increased in diseased blood vessels. Although H2O2 leads to impairment of the nitric oxide (NO)/soluble guanylate cyclase (sGC)/cGMP signaling pathway, it is not clear whether this reactive molecule affects the redox state of sGC, a key determinant of NO bioavailability. To clarify this issue, mechanical responses of endothelium-denuded rat external iliac arteries to BAY 41-2272 (sGC stimulator), BAY 60-2770 (sGC activator), nitroglycerin (NO donor), acidified NaNO2 (exogenous NO), and 8-Br-cGMP (cGMP analog) were studied under exposure to H2O2. The relaxant response to BAY 41-2272 (pD2: 6.79 ± 0.10 and 6.62 ± 0.17), BAY 60-2770 (pD2: 9.57 ± 0.06 and 9.34 ± 0.15), or 8-Br-cGMP (pD2: 5.19 ± 0.06 and 5.24 ± 0.08) was not apparently affected by exposure to H2O2. In addition, vascular cGMP production stimulated with BAY 41-2272 or BAY 60-2770 in the presence of H2O2 was identical to that in its absence. On the other hand, nitroglycerin-induced relaxation was markedly attenuated by exposing the arteries to H2O2 (pD2: 8.73 ± 0.05 and 8.30 ± 0.05), which was normalized in the presence of catalase (pD2: 8.59 ± 0.05). Likewise, H2O2 exposure impaired the relaxant response to acidified NaNO2 (pD2: 6.52 ± 0.17 and 6.09 ± 0.16). These findings suggest that H2O2 interferes with the NO-mediated action, but the sGC redox equilibrium and the downstream target(s) of cGMP are unlikely to be affected in the vasculature.

Concepts: Oxygen, Blood, Blood vessel, Redox, Reactive oxygen species, Hydrogen peroxide, Nitric oxide, Peroxide

25

In Type 2 diabetes, it has been proposed that pancreatic beta-cell dysfunction is promoted by oxidative stress caused by NADPH oxidase (NOX) over-activity. Five different NOX enzymes (NOX1-5) have been characterized, among which NOX1 and NOX2 have been proposed to negatively affect beta-cells, but the putative role of NOX4 in type 2 diabetes-associated beta-cell dysfunction and glucose intolerance is largely unknown. Therefore, we presently investigated the importance of NOX4 for high-fat diet (HFD)-induced glucose intolerance using male C57BL/6 mice using the new NOX4 inhibitor GLX351322, which has relative NOX4 selectivity over NOX2. In HFD-treated male C57BL/6 mice a two-week treatment with GLX351322 counteracted non-fasting hyperglycemia and impaired glucose tolerance. This effect occurred without any change in peripheral insulin sensitivity. To ascertain that NOX4 also plays a role for the function of human beta-cells, we observed that glucose- and sodium palmitate-induced insulin release from human islets in vitro was increased in response to NOX4 inhibitors. In long-term experiments (1-3 days), high glucose-induced human islet cell ROS production and death were prevented by GLX351322. We propose that whilst short-term NOX4-generated ROS production is a physiological requirement for beta-cell function, persistent NOX4-activity, e.g. during conditions of high-fat feeding, promotes ROS-mediated beta-cell dysfunction. Thus, selective NOX-inhibition may be a therapeutic strategy in Type 2 diabetes.

Concepts: Insulin, Diabetes mellitus type 2, Diabetes mellitus, Obesity, Islets of Langerhans, Pancreas, Beta cell, Glucose tolerance test

24

Metformin (N,N-dimethylbiguanide), buformin (1-butylbiguanide) and phenformin (1-phenethylbiguanide) are anti-diabetic biguanide drugs, expected to having anti-cancer effect. The mechanism of anti-cancer effect by these drugs is not completely understood. In this study, we demonstrated that these drugs dramatically enhanced oxidative DNA damage under oxidative condition. Metformin, buformin and phenformin enhanced generation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in isolated DNA reacted with hydrogen peroxide (H2O2) and Cu(II), although these drugs did not form 8-oxodG in the absence of H2O2 or Cu(II). An electron paramagnetic resonance (EPR) study, utilizing alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide as spin trapping agents, showed that nitrogen-centered radicals were generated from biguanides in the presence of Cu(II) and H2O2, and that these radicals were decreased by the addition of DNA. These results suggest that biguanides enhance Cu(II)/H2O2 -mediated 8-oxodG generation via nitrogen-centered radical formation. The enhancing effect on oxidative DNA damage may play a role on anti-cancer activity.

Concepts: Oxygen, Oxidative stress, Hydrogen peroxide, Anti-diabetic drug, Metformin, Biguanide, Phenformin, Buformin

22

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

22

The aim of this study was to investigate the role of miR-138 in osteoporosis and its underlying mechanism.

Concepts: Endoplasmic reticulum

5

Abstract Vascular dysfunction is one of the major causes of cardiovascular (CV) mortality and increases with age. Epidemiological studies suggest that Mediterranean diets and high nut consumption reduce CV disease risk and mortality while increasing plasma α-tocopherol. Therefore, we have investigated whether almond supplementation can improve oxidative stress markers and CV risk factors over 4 weeks in young and middle-aged men. Healthy middle-aged men (56+5.8years), healthy young men (22.1+2.9years) and young men with two or more CV risk factors (27.3+5years) consumed 50g almond /day for 4 weeks. A control group maintained habitual diets over the same period. Plasma α-tocopherol/cholesterol ratios were not different between groups at baseline and were significantly elevated by almond intervention with 50g almond/day for four weeks (p<0.05). Plasma protein oxidation and nitrite levels were not different between groups whereas total, HDL and LDL cholesterols and triglycerides were significantly higher in healthy middle-aged and young men with CV risk factors but were not affected by almond intake. In the almond consuming groups, flow mediated dilatation (FMD) was improved and diastolic blood pressure was reduced significantly after 4 weeks, but systolic blood pressure was only reduced in healthy men. In conclusion, a short-term almond-enriched diet can increase plasma α-tocopherol and improve vascular function in asymptomatic healthy mean men aged between 20 and 70 without effect on plasma lipids or markers of oxidative stress.

Concepts: Epidemiology, Blood, Atherosclerosis, Blood pressure, Artery, Ventricle, Cardiac cycle, Systole

1

The oxidized nucleoside 8-hydroxy-2'-deoxyguanosine has been widely studied as a marker of DNA oxidation; however, data on the occurrence in plasma of other metabolites related to DNA damage are scarce. We have applied an improved, sensitive, robust, and reliable method, involving solid phase extraction and UHPLC-MS/MS, to the precise quantitation of seven metabolites in the plasma of 15 elite triathletes after a 2-week training program. All compounds eluted in the first 1.6 min with limits of detection and quantification ranging between 0.001 and 0.3 ng.mL(-1) and 0.009 and 0.6 ng.mL(-1), respectively. Four compounds were detected in plasma: guanosine- 3'-5'-cyclic monophosphate , 8-hydroxyguanine , 8-hydroxy-2'-deoxyguanosine, and 8-nitroguanosine. After two weeks of training, 8-hydroxyguanine exhibited the highest increase (from 0.031 ± 0.008 nM to 0.036 ± 0.012 nM) (p < 0.05), which could be related to enhanced activity of DNA repairing enzymes that excise this oxidized base. Increases in guanosine- 3'-5'-cyclic monophosphate and 8-hydroxy-2'-deoxyguanosine were also observed. In contrast, levels of 8-nitroguanosine (p < 0.05) were significantly reduced, which might be a protective measure as this compound strongly stimulates the generation of superoxide radicals and its excess is related to pathologies such as microbial (viral) infections and other inflammatory and degenerative disorders. . The results obtained indicate an induced adaptive response to the increased oxidative stress related to the elite training and point to the benefits associated with regular exercise.

Concepts: Photosynthesis, Adenosine triphosphate, Redox, Electrochemistry, DNA repair, Nicotinamide adenine dinucleotide, Nitrogen, Radical

0

Redox homeostasis is necessary for maintenance of living systems. Chikungunya viral infection manifests into joint inflammation and debilitating polyarthralgia affecting the life style of the patient badly. The disease pathophysiology is poorly understood and there is a lack of targeted therapeutics. The pathogenic role of free radicals in arthritis is well established. This study aims for the first time to evaluate the status of several standard oxidative stress markers and their correlation in Chikungunya patients suffering with polyarthralgia. Expression of Siglec-9 on monocytes; which can modulate oxidative stress is studied along with intracellular reactive oxygen species (ROS), cellular lipid and protein damage markers in Chikungunya patients with/without persisting polyarthralgia along with healthy controls. Furthermore, plasma NO level, antioxidant status was investigated along with some inflammatory cytokines namely IL-6, IFN-γ, CXCL-9, IL-10 and TGFβ1. Interestingly, all oxidative damage markers are altered significantly in groups but their alteration levels vary in patients with/without persisting polyarthralgia. Siglec-9 expression level is increased in patients revealing cellular response to manage oxidative stress with respect to controls. Correlation studies reveal that intracellular ROS correlates well with most of the studied parameters but the correlation coefficient (Pearson r) differs with disease manifestation demonstrating strong role of these factors in a pro-oxidant milieu. Presence of free radicals increases the availability of neoantigens continuously, which possibly further cascades oxidative damage and development of persisting polyarthralgia.

0

Upregulation of mitochondrial function and oxidative metabolism is a hallmark in the differentiation of stem cells. However, the mechanism underlying the metabolic reprogramming and upregulation of mitochondrial function during the differentiation of human mesenchymal stem cells (hMSCs) is largely unclear. Sirt3 has emerged as a sensor in regulating mitochondrial function and antioxidant defense system in cellular response to energy demand or environmental stimuli, but its roles in stem cell differentiation has not been fully understood. In this study, we used adipose-derived hMSCs (ad-hMSCs) to investigate the role of Sirt3 in adipogenic differentiation and in the function of mature adipocytes. We showed that at the early stage of adipogenic differentiation, Sirt3 upregulation is essential for the activation of biogenesis and bioenergetic function of mitochondria. In addition, we found that induction of Forkhead Box O 3a (FoxO3a), an upstream factor that regulates MnSOD gene transcription, is involved in the upregulation of antioxidant enzymes at the early stage of adipogenic differentiation. Silencing of Sirt3 by shRNA decreased the protein level of FoxO3a and subsequently downregulated a number of FoxO3a-mediated antioxidant enzymes and increased oxidative stress in ad-hMSCs after adipogenic induction. Importantly, depletion of Sirt3 compromised the ability of ad-hMSCs to undergo adipogenic differentiation and led to adipocyte dysfunction and insulin resistance. These findings suggest that Sirt3-mediated protein deacetylation plays an important role in regulating oxidative metabolism and antioxidant defense in stem cell differentiation, and that Sirt3 deficiency may be related to insulin resistance.