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Total redox capacity (TRC) and oxidative stress (OxiStress) of biological objects (such as cells, tissues, and body fluids) are some of the most frequently analyzed parameters in life science. Development of highly sensitive molecular probes and analytical methods for detection of these parameters is a rapidly growing sector of BioTech's R&D industry. The aim of the present study was to develop quantum sensors for tracking the TRC and/or OxiStress in living biological objects using electron-paramagnetic resonance (EPR), magnetic resonance imaging (MRI), and optical imaging. We describe a two-set sensor system: (i) TRC sensor QD@CD-TEMPO and (ii) OxiStress sensor QD@CD-TEMPOH. Both redox sensors are composed of small-size quantum dots (QDs), coated with multinitroxide-functionalized cyclodextrin (paramagnetic CD-TEMPO or diamagnetic CD-TEMPOH) conjugated with triphenylphosphonium (TPP) groups. The TPP groups were added to achieve intracellular delivery and mitochondrial localization. Nitroxide residues interact simultaneously with various oxidizers and reducers, and the sensors are transformed from the paramagnetic radical form (QD@CD-TEMPO) into diamagnetic hydroxylamine form (QD@CD-TEMPOH) and vice-versa, because of nitroxide redox-cycling. These chemical transformations are accompanied by characteristic dynamics of their contrast features because of quenching of QD fluorescence by nitroxide radicals. The TRC sensor was applied for EPR analysis of cellular redox-status in vitro on isolated cells with different proliferative indexes, as well as for noninvasive MRI of redox imbalance and severe oxidative stress in vivo on mice with renal dysfunction.

Time courses of the redox status in the brains of mice after X-ray or carbon-ion beam irradiation were observed by magnetic resonance redox imaging (MRRI). The relationship between radiation-induced oxidative stress on the cerebral nervous system and the redox status in the brain was discussed. The mice were irradiated by 8-Gy X-ray or carbon-ion beam (C-beam) on their head under anesthesia. C-beam irradiation was performed at HIMAC (Heavy-Ion Medical Accelerator in Chiba, NIRS/QST, Chiba, Japan). MRRI measurements using a blood-brain-barrier-permeable nitroxyl contrast agent, MCP or TEMPOL, were performed using 7-T scanner at several different times, i.e., 5-10 h, 1, 2, 4, and 8 day(s) after irradiation. Decay rates of the nitroxyl-enhanced T 1 -weighted MR signals in the brains were estimated from MRRI data sets, and variation in the decay rates after irradiation was assessed. The variation in decay rates of MCP and TEMPOL after X-ray or C-beam irradiation was similar, but different variation patterns were observed between X-ray and C-beam. The apparent decay rate of both MCP and TEMPOL decreased due to the temporal reduction of blood flow in the brain several hours after X-ray and/or C-beam irradiation. After decreasing, the apparent decay rates of nitroxyl radicals in the brain gradually increased during the following days after X-ray irradiation or rapidly increased 1 day after C-beam irradiation. The sequential increase in nitroxyl decay rates may have been due to the oxidative atmosphere in the tissue due to ROS generation. X-ray and C-beam irradiation resulted in different redox responses, which may have been due to time-varying oxidative stress/injury, in the mouse brain. The C-beam irradiation effects were more acute and larger than those of X-ray irradiation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

This study reports a non-invasive magnetic resonance imaging (MRI) of kidney dysfunction in mice, based on the induction of redox-imbalance and oxidative stress in the renal tissues, using mito-TEMPO as redox-sensitive contrast probe. Kidney dysfunction was triggered by hypercholesterolemia. The mice were divided in three groups: (i) on normal diet (ND); (ii) on cholesterol diet (CD); (iii) on cholesterol plus cholestyramine diet (CC). After 15 weeks feeding, the mice were subjected to the following analyses: plasma cholesterol levels; serum test for renal functionality; nitroxide-enhanced MRI of tissue redox-status in vivo; histochemical staining of tissue section to visualize renal damage; evaluation of total antioxidant capacity and oxidative stress on isolated tissue specimens. MRI signal of mito-TEMPO in the kidney was characterized by: high intensity and long life-time in CD mice, indicating a high oxidative capacity of renal tissues; poor intensity and short life-time in ND mice, indicating a high reducing capacity; moderate intensity and relatively short life-time in CC mice, indicating a protective effect of lipid-lowering drug. The data were confirmed on isolated tissue specimens, using conventional tests. They suggest that hypercholesterolemia induces redox-imbalance in kidney and this process could be visualized using MRI and mito-TEMPO as a redox-sensitive contrast.

The intracellular redox balance (redox status) is a dynamic system that may change via many factors. Mitochondria are one of the most important among them. These organelles are the main intracellular source of energy. They are essential for maintaining cellular homeostasis due to regulation of many biochemical processes. The mitochondrial dynamics change during cellular activities and in some cases, can cause an overproduction of reactive oxygen species (ROS), which encourages the induction of oxidative DNA damage and up- or down-regulation of phosphatases, proliferative/anti-proliferative factors, apoptotic/anti-apoptotic factors, etc. Moreover, mitochondrial dysfunction and redox imbalance can continuously support and contribute to a wide range of pathologies, termed as "free radical diseases" (e.g., cancer, neurodegeneration, atherosclerosis, inflammation, etc.). This review article is focused on the mitochondrial dysfunction and cellular redox status as a hallmark of cell homeostasis and diagnostic marker of cancer. It is intended to broad readership - from students to specialists in the field., (Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: The study aimed to investigate the effect of multi-targeted combinations (SN38/EF24; SN38/EF24/melatonin) on the growth of colon cancer in experimental animals and their impact on the ratio "oncogenic"/"onco-suppressive" reactive oxygen species (ROS) - a crucial factor for triggering carcinogenesis, as well as for development of effective therapeutic strategies., Materials and Methods: The experiments were conducted on colon cancer-grafted mice - non-treated, SN38/EF24-treated and SN38/EF24/melatonin-treated within 22 days. The balance between different types of ROS was measured in vivo by nitroxide-enhanced magnetic resonance imaging (MRI), as well as on isolated tissue specimens by conventional analytical tests., Results: Both combinations significantly suppressed the tumor growth. Impressive anticancer effect was observed in SN38/EF24/melatonin-treated mice - almost complete destruction of the tumor. Both types of ROS (superoxide and hydroperoxides) were elevated in cancer, but the MRI data suggest that the ratio between them tends towards superoxide. SN38/EF24 decreased the level of superoxide, but did not affect the level of hydroperoxides in the cancerous tissue, while SN38/EF24/melatonin decreased the level of superoxide below the control and increased significantly the level of hydroperoxides., Conclusion: The most important observations are that: (i) colon cancer was characterized by a vicious cycle, that ensures a permanent domination of "oncogenic" ROS (as superoxide) over "onco-suppressive" ROS (as hydrogen peroxide); (ii) the anticancer effect of the triple combination EF24/SN38/melatonin was accompanied by decreasing "oncogenic" and increasing "onco-suppressive" ROS; (iii) the ratio between both types of ROS could be a new onco-target for combined therapy; and (iv) nitroxide-enhanced MRI is a valuable tool for analyzing of this ratio., (Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

The present study describes a new approach for direct imaging of redox status in live cells using paramagnetic spin-probes, which allows evaluation of the level of oxidative stress due to overproduction of superoxide. The method is based on redox cycling of cell/mitochondria-penetrating nitroxide radicals (e.g. mito-TEMPO) and their electron-paramagnetic resonance (EPR) contrast, which makes them useful molecular sensors for analysis of redox status and oxidative stress in cells and tissues. Oxidative stress was induced in normal human lymphocytes by treatment with 2-methoxyestradiol and rotenone (ME/Rot) at different concentrations. This combination provokes mitochondrial dysfunction, which is accompanied by overproduction of superoxide. The EPR measurements were performed in dynamics on X-Band spectrometer after addition of mito-TEMPO to cell suspensions. The intensity of the EPR signal in untreated cells decreased significantly, which indicates a conversion of paramagnetic mito-TEMPO to its non-contrast diamagnetic form (hydroxylamine - mito-TEMPOH) due to reduction. In ME/Rot-treated cells, the signal decreased more slowly and to a lower level with increasing the concentration of ME/Rot. These data indicate an induction of oxidative stress in the cells in a concentration-dependent manner. A very good positive correlation between the intensity of EPR signal of mito-TEMPO and the intracellular level of superoxide was found, analyzed by conventional dihydroethidium test (R=0.9143, p<0.001). In conclusion, our study demonstrated that cell-penetrating paramagnetic spin-probes, such as mito-TEMPO, are valuable tools for EPR imaging of the superoxide level in live cells, as well as for EPR imaging of mitochondrial dysfunction and metabolic activity, accompanied by superoxide imbalance., (Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)

Objectives: The present study describes a pharmacological strategy for the treatment of glioblastoma by redoxcycling 'mitocans' such as quinone/ascorbate combination drugs, based on their tumor-selective redox-modulating effects and tolerance to normal cells and tissues. Methods: Experiments were performed on glioblastoma mice (orthotopic model) treated with coenzyme Q0/ascorbate (Q0/A). The drug was injected intracranially in a single dose. The following parameters were analyzed in vivo using MRI orex vivo using conventional assays: tumor growth, survival, cerebral and tumor perfusion, tumor cell density, tissue redox-state, and expression of tumor-associated NADH oxidase (tNOX). Results: Q0/A markedly suppressed tumor growth and significantly increased survival of glioblastoma mice. This was accompanied by increased oxidative stress in the tumor but not in non-cancerous tissues, increased tumor blood flow, and downregulation of tNOX. The redox-modulating and anticancer effects of Q0/A were more pronounced than those of menadione/ascorbate (M/A) obtained in our previous study. No adverse drug-related side-effects were observed in glioblastoma mice treated with Q0/A. Discussion: Q0/A differentiated cancer cells and tissues, particularly glioblastoma, from normal ones by redox targeting, causing a severe oxidative stress in the tumor but not in non-cancerous tissues. Q0/A had a pronounced anticancer activity and could be considered safe for the organism within certain concentration limits. The results suggest that the rate of tumor resorption and metabolism of toxic residues must be controlled and maintained within tolerable limits to achieve longer survival, especially at intracranial drug administration. [ABSTRACT FROM AUTHOR]

Our study proposes a pharmacological strategy to target cancerous mitochondria via redox-cycling "mitocans" such as quinone/ascorbate (Q/A) redox-pairs, which makes cancer cells fragile and sensitive without adverse effects on normal cells and tissues. Eleven Q/A redox-pairs were tested on cultured cells and cancer-bearing mice. The following parameters were analyzed: cell proliferation/viability, mitochondrial superoxide, steady-state ATP, tissue redox-state, tumor-associated NADH oxidase (tNOX) expression, tumor growth, and survival. Q/A redox-pairs containing unprenylated quinones exhibited strong dose-dependent antiproliferative and cytotoxic effects on cancer cells, accompanied by overproduction of mitochondrial superoxide and accelerated ATP depletion. In normal cells, the same redox-pairs did not significantly affect the viability and energy homeostasis, but induced mild mitochondrial oxidative stress, which is well tolerated. Benzoquinone/ascorbate redox-pairs were more effective than naphthoquinone/ascorbate, with coenzyme Q0/ascorbate exhibiting the most pronounced anticancer effects in vitro and in vivo. Targeted anticancer effects of Q/A redox-pairs and their tolerance to normal cells and tissues are attributed to: (i) downregulation of quinone prenylation in cancer, leading to increased mitochondrial production of semiquinone and, consequently, superoxide; (ii) specific and accelerated redox-cycling of unprenylated quinones and ascorbate mainly in the impaired cancerous mitochondria due to their redox imbalance; and (iii) downregulation of tNOX. [ABSTRACT FROM AUTHOR]

We used a mitochondria-penetrating nitroxide, mito-TEMPO, as a contrast probe for imaging of kidney dysfunction in mice, based on the redox-imbalance and oxidative stress in the renal tissues. Kidney dysfunction was triggered by hypercholesterolemia. The mice were divided in three groups: (i) on normal diet (ND; control); (ii) on cholesterol diet (CD); (iii) on cholesterol plus cholestyramine diet (CC). CD mice showed increased plasma levels of total cholesterol and non-HDL-cholesterol, as well as increased serum levels of blood urea nitrogen, uric acid and creatinine, compared to ND mice. CC mice showed slightly increased plasma levels of total cholesterol and HDL-cholesterol, but not non-HDL-cholesterol, compared to ND mice. The serum levels of blood urea nitrogen, uric acid and creatinine in CC mice were equal to those in ND mice. The MRI signal of mito-TEMPO in the kidneys was characterized by: high intensity and long life-time in CD mice, indicating a high oxidative capacity of renal tissues; poor intensity and short life-time in ND mice, indicating a high reducing capacity of renal tissues; moderate intensity and relatively short life-time in CC mice, which shows the protective effect of lipid-lowering agents against oxidative damage. The data suggest that hypercholesterolemia induces redox-imbalance and oxidative stress in kidneys and this process could be visualized using MRI and mito-TEMPO as a redox-sensitive contrast substance. [ABSTRACT FROM AUTHOR]