Pharmacological modification of the redox properties of tumor cells is a promising approach to enhance the efficiency of antitumor therapy. Currently, the transcription factor Nrf2 is considered as a new target for the development of selective chemosensitizers. Nrf2 plays a key role in regulation of cellular redox homeostasis against stress and during adaptation processes. Many natural and synthetic phenolic antioxidants are inducers of Nrf2 transcriptional activity. Due to differences in Nrf2 transcriptional activity between normal and tumor cells, phenolic antioxidants at certain concentrations act as biological regulators the antioxidant activity of which has two different effects: in tumor cells they promote the development of oxidative stress and enhance the effect of antitumor drugs, in normal cells these antioxidants exhibit protective properties. The review discusses the possible molecular mechanisms of action and the prospects for the clinical use of natural and synthetic phenolic antioxidants in antitumor therapy.

Understanding the role of reactive oxygen and nitrogen species in eustress (redox balance) and distress (oxidative stress) development poses new challenges for biomedical scientists and pharmacologists in the search for compounds that can not only have a direct antioxidant (antiradical) effect, but also affect redox-sensitive signaling pathways, primarily Keap1/Nrf2/ARE system. Aim of the study was to investigate the influence of novel water-soluble structurally related monophenols on key elements of Keap1/Nrf2/ARE system induction (activity of Nrf2-driven enzymes, the state of the glutathione system, and intracellular redistribution of transcription factor Nrf2). Material and methods . Five original hydrophilic structurally related monophenols, differing in the number of tert-butyl ortho-substituents, the length of the para-alkyl substituent, and the presence of a divalent sulfur or selenium atom in it were investigated (phenoxane, the potassium salt of phenosan acid, was used as a reference compound). Cell lines U937 and J774 were cultured for 24 h in the presence of tested compounds, and comparative analysis was performed of its ability to induce the synthesis of Nrf2-driven enzymes of phase II xenobiotic detoxification pathway and antioxidant enzymes (NAD(P)H: quinone oxidoreductase 1 (NQO1), glutathione S-transferases (GST), glutathione peroxidases, glutathione reductase (biochemical spectrophotometric methods were used to study their activity), as well as to influence the state of glutathione system (spectrophotometry) and translocation of transcription factor Nrf2 into the nucleus (immunofluorescent staining, confocal microscopy) (key events of Keap1/Nrf2/ARE signaling system activation). Results and discussion . Monophenol TS-13 have found to be the most effective inducer of tested enzymes in U937 cells among the structural analogs, while the structure of the para-alkyl substituent and the degree of OH group hindrance are important for the implementation of this effect; TS-13 also effectively enhanced Nrf2 import into J774 cell nucleus. The NQO1- and GST-inducing abilities of structurally related monophenols are closely interrelated, which indicates the possibility of coordinated induction of these enzymes and the presence of a common regulatory system that ensures their activation in response to cell treatment with phenolic antioxidants.

The free-radical theory of aging, advanced more than 50 years ago by D. Harman, remains popular today. The review analyzes age-related changes in the main endogenous mechanisms of reactive oxygen species (ROS) production and antioxidant defense mechanisms. With age, ROS generation by mitochondria, peroxisomes, and NAD(P)H oxidases is enhanced, while the transcriptional activity of the important system Keap1/Nrf2/ARE maintaining redox balance decreases. In old animals, autophagy activity is also low, which removes damaged organelles and aggregated structures from cells. The age-related shift of the redox balance towards oxidative stress can cause the development of age-associated neurodegenerative, autoimmune and inflammatory pathologies.

Endogenous mechanisms of reactive oxygen (ROS) and nitrogen species production and of antioxidant defense systems in tumor cells are analyzed. Increased ROS production is an important regulator of metabolic changes in these cells: enhanced proliferation, apoptosis inhibition, resistance to hypoxia and to cytostatics (doxorubicin, carboplatin, cisplatin, etc.). The most active ROS sources in tumor cells are mitochondria, NAD(P)H oxidases and peroxisomes, which synthesize O2 • – and H2O2. In mitochondria, the superoxide anion radical is generated mainly by complexes I and III; membrane NAD(P)H oxidases Nox1, Nox2, Nox3, and Nox5 produce O2 • –, Nox4, and dual oxidases DUOX-1, DUOX-2 – mainly H2O2. Increasing ROS stationary concentration activates endogenous antioxidant defense mechanisms, such as redox-dependent antioxidant respons(iv)e element system Keap1/Nrf2/ARE and autophagy, which allows tumor cells to survive under oxidative stress and may underlie resistance to radio- and chemotherapy. The possibilities of tumor cell redox balance regulation by antioxidants with targeted action and by specific inhibitors of ROS enzymatic production are discussed.

ROS are important intracellular messengers; their ambiguous role in malignant processes was demonstrated in many studies. The effects of a synthetic phenolic antioxidant sodium 3-(3’-tert-butyl-4’-hydroxyphenyl)propyl thiosulfonate sodium (TS-13) on the tumor growth and oncolytic properties of doxorubicin were studied in the experimental model of Lewis lung carcinoma in mice. In mice receiving TS-13 with drinking water (100 mg/kg), suppression of tumor growth by 32.3% was observed on day 21 after inoculation of Lewis lung carcinoma cells. Two-fold intraperitoneal injections of doxorubicin in a cumulative dose of 8 mg/kg were followed by inhibition of tumor growth by 49.5%. Combined treatment with TS-13 and doxorubicin suppressed the tumor growth by 55.4%. In contrast to doxorubicin, TS-13 inhibited NO generation by peritoneal macrophages. The results show the prospect of studying TS-13 in the context of overcoming drug-resistance of tumors.

We studied differences in the production of pro- and anti-inflammatory cytokines and IRF3 transcription factor by peritoneal macrophages from mice of opposite strains CBA/J and C57Bl/6 and the effect of 60-kDa oxidized dextran on these parameters. Macrophages from C57Bl/6 mice were mainly characterized by the production of proinflammatory cytokines TNFα, IL-12, and MCP-1 (markers of M1 polarization). By contrast, CBA/J mice exhibited a relatively high level of anti-inflammatory cytokine IL-10 and lower expression of proinflammatory cytokines (M2 phenotype). IRF3 content in peritoneal macrophages of CBA/J mice was higher than in C57Bl/6 mice. Oxidized dextran decreased the expression of IRF3 upon stimulation of cells from CBA/J mice with LPS, but increased this process in C57Bl/6 mice. Despite a diversity of oxidized dextran-induced changes in cytokine production, the data confirm our hypothesis that this agent can stimulate the alternative activation of macrophages.

Differences in peritoneal macrophage polarization in mice of opposite lines CBA and C57Bl/6 and the effects of 60 kDa oxidized dextran were studied. Macrophages of C57Bl/6 mice demonstrated a phenotype close to M1, with increasing expression of CD86 costimulatory molecule and unchanged CD206 expression in response to activation. Macrophages of CBA mice demonstrated higher plasticity in response to activating agents; expression of the markers increased irrespectively on stimulated receptor (TLR-4 or mannose receptor) and both CD86 (classical activation) and CD206 (alternative activation) increased. Macrophage response to addition of oxidized dextran (60 kDa) to the culture medium could be characterized as potentiation of their alternative activation: expression of CD86 in CBA mice in response to LPS and LPS+IL-4 and in C57Bl/6 mice in response to IFN-γ and LPS+IFN-γ decreased, while expression of CD206 by intact macrophages of CBA mice and by macrophages stimulated by IFN-γ and IL-4 increased under the effect of 60 kDa oxidized dextran.

We studied the effects of liposomal pharmaceutical compositions with oxidized dextrans on functional activity of U937 monocyte/macrophage-like cells. Liposomes in the emulsion contained oxidized dextran with a molecular weights of 40 kDa or 70 kDa or isonicotinic acid hydrazide (INAH) conjugated with oxidized dextran (40 kDa). Cell viability was evaluated by MTT test; mitochondrial transmembrane potential and production of superoxide anion and H2O2 were studied by fluorescent methods. The studied compositions exhibited no cytotoxic effect and even improved cell viability and mitochondrial respiration. Liposomes with oxidized 40 kDa dextran, including those with INAH-conjugated dextran, inhibited production of superoxide anion, but increased H2O2 generation.

The effect of hydrophilic synthetic antioxidant TC-13 (3-(3'-tert-butyl-4'-hydroxyphenyl)propylthiosulfonate sodium) inducing the antioxidant-responsive element on the lifespan of Drosophila melanogaster was studied. Addition of 1% TC-13 to diets prolonged the lifespan of long-lived D. melanogaster Canton S strain females and males, but not of short-lived Oregon R insects and reduced the mean lifespan of D. melanogaster males of the lgl558OR/Cy strain containing a recessive lethal mutation of tumor suppressor in the heterozygotic state. The geroprotective effects of TC-13 synthetic phenol antioxidant depended on D. melanogaster genotype and gender.

The effect of water-soluble synthetic antioxidant TS-13 (sodium 3-(3'-tert-butyl-4'-hydroxyphenyl) propyl thiosulfonate) on life span of different lines of Drosophila melanogaster under normal conditions and survival under oxidative stress induced by hydrogen peroxide and paraquat has been investigated. Introduction to the diet of 1% TS-13 prolonged the life span of males and females of D. melanogaster long-living line Canton S, had no effect on short-living Oregon R life span and reduced the life span of male D. melanogaster line IgI(558)OR/Cy, heterozygous on tumor suppressor recessive lethal mutation. When flies were exposed to hydrogen perexide, TS-13 significantly enhanced Canton Smale and Oregon R female survival. Under the influence of paraquat antioxidant protected Canton S female and Oregon R flies of both sexes. Despite the fact that the anti-aging and protective properties of synthetic phenol antioxidant TS-13 depend essentially on the genotype and gender, in the extreme conditions of oxidative stress its positive effect pronounced.

Chemiluminescence assay showed that oxygen reduction and production of superoxide anion and hydrogen peroxide by liver mitochondria in OXYS rats highly sensitive to oxidative stress were less intensive than in Wistar rats. Experiments with cytochrome c oxidase inhibitors showed that decreased O2-. generation in mitochondria of OXYS rats is probably associated with changes in complex III of the electron transport chain.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The paper deals with the physicochemical properties of nitric oxide (NO) and with the mechanisms of its action and synthesis in man and animals. The cytotoxic, vasodilatory, neuromediator, and other properties of NO are analyzed. NO is shown to perform many functions in health and in diseases of various genesis. Analyzing the structure and functions of NO in health and in diseases suggests that they all have both structural and functional properties and their own features. The currently available data lead to the conclusion that the NO-synthase mechanism that is responsible for the production of NO is its synthesis in the presence of oxygen. During functional exercises and hypoxia of various origin, another mechanism of NO may become active, which is associated with the reduction of NO2- in NO.

Oxidative metabolism of murine peritoneal macrophages was studied after cultivation in a mixture containing acetylated low density lipoproteins within 24 and 48 hr using luminol- and lucigenin-dependent chemiluminescence. Chemiluminescence of foamy cells, induced by opsonized zymosan, was not distinctly altered as compared with native macrophages; at the same time, the rate of both lucigenin- and luminol-dependent spontaneous chemiluminescence was distinctly decreased. The imbalance of the oxidative reactions observed enables the authors to propose the antioxidative mechanism of atherosclerotic lesion.