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Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are aggressive sarcomas that can arise both sporadically and in patients with the genetic syndrome Neurofibromatosis type 1 (NF1). Prognosis is dismal, as large dimensions, risk of relapse, and anatomical localization make surgery poorly effective, and no therapy is known. Hence, the identification of MPNST molecular features that could be hit in an efficient and selective way is mandatory to envision treatment options. Here, we find that MPNSTs express high levels of the glycolytic enzyme Hexokinase 2 (HK2), which is known to shield cancer cells from noxious stimuli when it localizes at MAMs (mitochondria-associated membranes), contact sites between mitochondria and endoplasmic reticulum. A HK2-targeting peptide that dislodges HK2 from MAMs rapidly induces a massive death of MPNST cells. After identifying different matrix metalloproteases (MMPs) expressed in the MPNST microenvironment, we have designed HK2-targeting peptide variants that harbor cleavage sites for these MMPs, making such peptides activatable in the proximity of cancer cells. We find that the peptide carrying the MMP2/9 cleavage site is the most effective, both in inhibiting the in vitro tumorigenicity of MPNST cells and in hampering their growth in mice. Our data indicate that detaching HK2 from MAMs could pave the way for a novel anti-MPNST therapeutic strategy, which could be flexibly adapted to the protease expression features of the tumor microenvironment. [ABSTRACT FROM AUTHOR]

Nitroxide probes have been commonly used for biomedical EPR imaging applications; however, image quality has been limited by the number of image projections, as well as the probe linewidth and hyperfine structure. In the current study, we evaluate the use of fast millisecond scan EPR projection acquisition along with a novel reconstruction algorithm optimized for 3D spatial EPR image reconstruction from a high number of noisy projections. This reconstruction method utilizes the raw image projection data and zero gradient spectrum to account for EPR line shape and hyperfine structure of any given paramagnetic probe without the need for deconvolution that is poorly suited for high noise data. Using fast scan EPR imaging with this reconstruction method, we image non-deuterated, deuterated and 15N substituted nitroxide probes in experimental phantoms of complex geometries. We evaluate the image resolution that can be obtained and the imaging time required. With 16,384 projections acquired over 1 min, and a field gradient of 8 G/cm, with a 2503 voxel 3D matrix, spatial resolutions of up to 100 µm are theoretically possible for a cubical volume of 25 × 25 × 25 mm3. In experiments with a variety of phantoms with mM nitroxide radical probes, resolutions of 600–250 µm were obtained with 1–10 min acquisitions, respectively. The presently obtainable signal sensitivity and noise levels of these acquisitions limited the obtainable resolution. With longer time acquisitions or further improvements in sensitivity and noise reduction, image resolutions approaching 100 µm should be possible. [ABSTRACT FROM AUTHOR]

Purpose: To develop a novel resonator for high‐quality fast scan electron paramagnetic resonance (EPR) and EPR/NMR co‐imaging of the head and brain of mice at 1.25 GHz. Methods: Resonator dimensions were scaled to fit the mouse head with maximum filling factor. A single‐loop 6‐gap resonator of 20 mm diameter and 20 mm length was constructed. High resonator stability was achieved utilizing a fixed position double coupling loop. Symmetrical mutually inverted connections rendered it insensitive to field modulation and fast scan. Coupling adjustment was provided by a parallel‐connected variable capacitor located at the feeding line at λ/4 distance. To minimize radiation loss, the shield around the resonator was supplemented with a planar conductive disc that focuses return magnetic flux. Results: Coupling of the resonator loaded with the mouse head was efficient and easy. This resonator enabled high‐quality in vivo 3D EPR imaging of the mouse head following intravenous infusion of nitroxide probes. With this resonator and rapid scan EPR system, 4 ms scans were acquired in forward and reverse directions so that images with 2‐scan 3,136 projections were acquired in 25 s. Head images were achieved with resolutions of 0.4 mm, enabling visualization of probe localization and uptake across the blood–brain barrier. Conclusions: This resonator design provides good sensitivity, high stability, and B1 field homogeneity for in vivo fast scan EPR of the mouse head and brain, enabling faster measurements and higher resolution imaging of probe uptake, localization, and metabolism than previously possible. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and investigation of a novel phenazine derivative M1 with oligomeric ethylene glycol ether substituents as a promising anolyte material for non-aqueous organic redox flow batteries (RFBs). The designed material undergoes a reversible and stable reduction at −1.72 V VS. Ag/AgNO3 and demonstrates excellent (>2.5 M) solubility in MeCN. A non-aqueous organic redox flow battery assembled using the novel phenazine derivative as an anolyte and a substituted triarylamine derivative as a catholyte exhibited high specific capacity (∼93% from the theoretical value), >95% Coulombic efficiency, 65% utilization of active materials and good charge–discharge cycling stability. [ABSTRACT FROM AUTHOR]

A 750-MHz electronically tunable resonator was investigated in terms of the sensitivity of electron paramagnetic resonance (EPR) signal detection. The conversion efficiency of the radio-frequency magnetic field was calculated for resonators with 50- and 100-Ω coaxial coupling lines using three-dimensional (3D) microwave field and microwave circuit simulators. Based on the simulation results, two tunable resonators were physically constructed and compared in terms of EPR signal sensitivity using a nitroxyl radical solution. While the resonator with 100-Ω coaxial lines provided 14% greater signal intensity, its signal-to-noise ratio was lower than that of the resonator with 50-Ω lines. To demonstrate the capability of the constructed tunable resonator for EPR imaging experiments, a solution of nitroxyl radical and the leg of a tumor-bearing mouse were visualized. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this work was to develop an electronically tunable resonator operating at 750 MHz for continuous-wave electron paramagnetic resonance (CW-EPR) imaging of a mouse tumor-bearing leg. Methods: The resonator had a multi-coil parallel-gap structure with a sample space of 16 mm in diameter and 20 mm in length. Microstrip line couplers were used in conjunction with varactor diodes to enable resonance frequency adjustment and to reduce the nonlinear effects of the varactor diodes. The resonator was modeled by the finite-element method and a microwave circuit simulation was performed to clarify its radiofrequency characteristics. Results : A tunable resonator was evaluated in terms of its resonance frequency, tunable frequency band, and conversion efficiency of the RF magnetic field. The developed resonator provided a tunable frequency band of 4 MHz at a central frequency of 747 MHz and a conversion efficiency of 34 μT/W1/2. To demonstrate the application of this tunable resonator to EPR imaging, three-dimensional EPR images of a sample solution and a mouse tumor-bearing leg were obtained. Conclusion: The developed tunable resonator satisfied our initial requirements for in vivo EPR imaging and may be able to be further improved using the present finite-element and circuit models if any problems arise during future practical applications. Significance: This work may help to promote EPR imaging of tumor-bearing mice in cancer-related studies. [ABSTRACT FROM PUBLISHER]

Objectives: The aim of this study was to demonstrate the feasibility of in vivo three-dimensional (3D) relaxation time T mapping of a dicarboxy-PROXYL radical using continuous-wave electron paramagnetic resonance (CW-EPR) imaging. Materials and methods: Isotopically substituted dicarboxy-PROXYL radicals, 3,4-dicarboxy-2,2,5,5-tetra(H)methylpyrrolidin-(3,4-H)-(1-N)-1-oxyl (H,N-DCP) and 3,4-dicarboxy-2,2,5,5-tetra(H)methylpyrrolidin-(3,4-H)-1-oxyl (H-DCP), were used in the study. A clonogenic cell survival assay was performed with the H-DCP radical using squamous cell carcinoma (SCC VII) cells. The time course of EPR signal intensities of intravenously injected H,N-DCP and H-DCP radicals were determined in tumor-bearing hind legs of mice (C3H/HeJ, male, n = 5). CW-EPR-based single-point imaging (SPI) was performed for 3D T mapping. Results: H-DCP radical did not exhibit cytotoxicity at concentrations below 10 mM. The in vivo half-life of H,N-DCP in tumor tissues was 24.7 ± 2.9 min (mean ± standard deviation [SD], n = 5). The in vivo time course of the EPR signal intensity of the H,N-DCP radical showed a plateau of 10.2 ± 1.2 min (mean ± SD) where the EPR signal intensity remained at more than 90% of the maximum intensity. During the plateau, in vivo 3D T maps with H,N-DCP were obtained from tumor-bearing hind legs, with a total acquisition time of 7.5 min. Conclusion: EPR signals of H,N-DCP persisted long enough after bolus intravenous injection to conduct in vivo 3D T mapping with CW-EPR-based SPI. [ABSTRACT FROM AUTHOR]

Purpose Electron paramagnetic resonance (EPR) imaging in the spectral-spatial domain with application of soluble paramagnetic probes provides an opportunity for spatially resolved functional measurements of living objects. The purpose of this study was to develop EPR methods for visualization of oxygenation and acidosis of ischemic myocardium. Methods EPR oxygen measurements were performed using isotopically substituted 2H,15N-dicarboxyproxyl. The radical has an EPR line width of 320 mG and oxygen-induced line broadening of 0.53 mG/mm Hg, providing oxygen sensitivity down to 5 μM. pH measurements were performed using previously developed pH-sensitive imidazoline nitroxide. The radical has an EPR spectrum with pH-dependable hyperfine splitting, pK = 6.6, providing pH sensitivity of approximately 0.05 U in the physiological range. Results EPR imaging of isolated and perfused rat hearts was performed in the two-dimensional + spectral domain. The spatial resolution of the measurements was about 1.4 mm. Marked tissue hypoxia was observed in the ischemic area of the heart after occlusion of the left anterior descending coronary artery. Tissue oxygenation was partly restored upon reperfusion. EPR mapping of myocardial pH indicated acidosis of the ischemic area down to pH 6.7-6.8. Conclusion This study demonstrates the capability of low-field EPR and the nitroxide spin probes for mapping of myocardial oxygenation and pH. The developed approaches might be used for noninvasive investigation of microenvironment on living objects. Magn Reson Med 76:350-358, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A new low-field electron paramagnetic resonance approach for noninvasive measurements of myocardial oxygen tension and tissue acidity was developed. The approach was applied to monitor myocardial pO2 and pH in a model of global no-flow ischemia (30 min) and reperfusion in isolated perfused rat hearts. The myocardial oxygen measurements were performed using deuterated Finland trityl radical probe. A rapid decrease in myocardial pO2 from 160 mmHg to about 2 ± 1 mmHg was observed within the first minute of ischemia followed by incomplete restoration of pO2 to 50 mmHg during 30 min of reperfusion. The lower oxygen concentration after ischemia was attributed to the 50% reduction in coronary flow after ischemia as a consequence of myocardial ischemia and reperfusion damage. Myocardial pH measurements using a specially designed imidazoline pH-sensitive nitroxide showed severe myocardial acidification to pH 6.25 during 30 min of ischemia. Preconditioning of the hearts with two 5-min periods of ischemia significantly reduced the acidification of myocardial tissue during sustained ischemia. Noninvasive electron paramagnetic resonance monitoring of myocardial oxygenation and pH may provide important insights into the mechanisms of ischemia and reperfusion injury and a background for development of new therapeutic approaches. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The main component of the insect immune system is melanotic encapsulation of pathogenic organisms. Molecular mechanisms of destruction of an encapsulated pathogen are poorly understood. Reactive oxygen species (ROS) are considered as probable cytotoxic agents responsible for destruction of pathogenic organisms in insect hemolymph. In the present work the formation of H2O2 during melanization in Galleria mellonella hemolymph in the presence of catalase inhibitor NaN3 was detected. Enhanced rates of H2O2 generation were observed in the hemolymph of insects activated by injection of bacterial cells. Using spin trapping technique in combination with electron paramagnetic resonance spectroscopy we demonstrated that production of H2O2 in the hemolymph causes the formation of highly toxic reactive oxygen species, hydroxyl radical. However, neither H2O2 nor hydroxyl radical were detected in the absence of NaN3 in agreement with the high catalase activity in the hemolymph. These observations allow us to propose a unique mechanism of pathogen-targeted cytotoxicity based on localized hydroxyl radical generation within a melanotic capsule. [ABSTRACT FROM AUTHOR]

Generation of superoxide anion and hydrogen peroxide during enzymatic oxidation of 3-(3,4-dihydroxyphenyl)-DL-alanine (DOPA) has been studied. The ability of DOPA to react with 2.- has been revealed. EPR spectrum of DOPA-semiquinone formed upon oxidation of DOPA by O2.-was observed using spin stabilization technique of ortho-semiquinones by Zn2+ ions. Simultaneously, the oxidation of DOPA by 2.- was found to produce hydrogen peroxide (H2O2). The analysis of H2O2 formation upon oxidation of DOPA by 2.- using 1-hydroxy-3-carboxy-pyrrolidine (CP-H), and SOD as competitive reagents for superoxide provides consistent values of the rate constant for the reaction between DOPA and 2.- being equal to (3.4 ± 0.6) × 105 M-1s-1. The formation of H2O2 during enzymatic oxidation of DOPA by phenoloxidase (PO) has been shown. The H2O2 production was found to be SOD-sensitive. The inhibition of H2O2 production by SOD was about 25% indicating that H2O2 is produced both from superoxide anion and via two-electron reduction of oxygen at the enzyme. The attempts to detect superoxide production during enzymatic oxidation of DOPA using a number of spin traps failed apparently due to high value of the rate constant for DOPA interaction with 2.-. [ABSTRACT FROM AUTHOR]