The thioredoxin system in cancer

Chirality-driven strong thioredoxin reductase inhibition

Overexpression of thioredoxin reductase (TXNRD) plays crucial role in tumorigenesis. Therefore, designing TXNRD inhibitors is a promising strategy for targeted anticancer drug development. However, poor selectivity has always been a challenge, resulting in unavoidable toxicity in clinic. Herein we demonstrate a strategy to develop highly selective chiral metal complexes-based TXNRD inhibitors. By manipulating the conformation of two distinct weakly interacting groups, we optimize the compatibility between the drug and the electrophilic group within the active site of TXNRD to enhance their non-covalent interaction, thus effectively avoids the poor selectivity deriving from covalent drug interaction, on the basis of ensuring the strong inhibition. Detailed experimental and computational results demonstrate that the chiral isomeric drugs bind to the active site of TXNRD, and the interaction strength is well modulated by chirality. Especially, the meso-configuration, in which the two large sterically hindered active groups are positioned on opposite sides of the drug, exhibits the highest number of non-covalent interactions and most effective inhibition on TXNRD. Taken together, this work not only provides a novel approach for developing highly selective proteinase inhibitors, but also sheds light on possible underlying mechanisms for future application.

The interplay between doxorubicin chemotherapy, antioxidant system, and cardiotoxicity: Unrevealing of the protective potential of tannic acid

Cardiotoxicity is the leading side effect of anthracycline-based chemotherapy. Therefore, it has gained importance to reveal chemotherapy-supporting strategies and reliable agents with their mechanisms of action. Tannic acid (TA), a naturally occurring plant polyphenol, has diverse physiological effects, including anti-inflammatory, anticarcinogenic, antioxidant, and radical scavenging properties. Therefore, this study was designed to investigate whether TA exerts a protective effect on mechanisms contributing to anthracycline-induced cardiotoxicity in rat heart tissues exposed to doxorubicin (DOX). Rats were randomly divided into control and experimental groups and treated with (18 mg/kg) DOX, TA (50 mg/kg), and DOX + TA during the 2 weeks. Cardiac gene markers and mitochondrial DNA (mtDNA) content were evaluated in the heart tissues of all animals. In addition to major metabolites, mRNA expression changes and biological activity responses of components of antioxidant metabolism were examined in the heart tissues of all animals. The expression of cardiac gene markers increased by DOX exposure was significantly reduced by TA treatment, whereas mtDNA content, which was decreased by DOX exposure, was significantly increased. TA also improved antioxidant metabolism members' gene expression and enzymatic activity, including glutathione peroxidase, glutathione s-transferase, superoxide dismutase, catalase, and thioredoxin reductase. This study provides a detailed overview of the current understanding of DOX-induced cardiotoxicity and preventive or curative measures involving TA.

The significant role of amino acid metabolic reprogramming in cancer

Amino acid metabolism plays a pivotal role in tumor microenvironment, influencing various aspects of cancer progression. The metabolic reprogramming of amino acids in tumor cells is intricately linked to protein synthesis, nucleotide synthesis, modulation of signaling pathways, regulation of tumor cell metabolism, maintenance of oxidative stress homeostasis, and epigenetic modifications. Furthermore, the dysregulation of amino acid metabolism also impacts tumor microenvironment and tumor immunity. Amino acids can act as signaling molecules that modulate immune cell function and immune tolerance within the tumor microenvironment, reshaping the anti-tumor immune response and promoting immune evasion by cancer cells. Moreover, amino acid metabolism can influence the behavior of stromal cells, such as cancer-associated fibroblasts, regulate ECM remodeling and promote angiogenesis, thereby facilitating tumor growth and metastasis. Understanding the intricate interplay between amino acid metabolism and the tumor microenvironment is of crucial significance. Expanding our knowledge of the multifaceted roles of amino acid metabolism in tumor microenvironment holds significant promise for the development of more effective cancer therapies aimed at disrupting the metabolic dependencies of cancer cells and modulating the tumor microenvironment to enhance anti-tumor immune responses and inhibit tumor progression.

TrxT and dhd are dispensable for Drosophila brain development but essential for l(3)mbt brain tumour growth

Expression of the Drosophila cancer-germline (CG), X-linked, head-to-head gene pair TrxT and dhd is normally germline-specific but becomes upregulated in brain tumours caused by mutation in l(3)mbt. Here, we show that TrxT and dhd play a major synergistic role in the emergence of l(3)mbt tumour-linked transcriptomic signatures and tumour development, which is remarkable, taking into account that these two genes are never expressed together under normal conditions. We also show that TrxT, but not dhd, is crucial for the growth of l(3)mbt allografts, hence suggesting that the initial stages of tumour development and long-term tumour growth may depend on different molecular pathways. In humans, head-to-head inverted gene pairs are abundant among CG genes that map to the X chromosome. Our results identify a first example of an X-linked, head-to-head CG gene pair in Drosophila, underpinning the potential of such CG genes, dispensable for normal development and homoeostasis of somatic tissue, as targets to curtail malignant growth with minimal impact on overall health.

Unraveling redox pathways of the disulfide bond in dimethyl disulfide: Ab initio modeling

CONTEXT

In cellular environments, the reduction of disulfide bonds is pivotal for protein folding and synthesis. However, the intricate enzymatic mechanisms governing this process remain poorly understood. This study addresses this gap by investigating a disulfide bridge reduction reaction, serving as a model for comprehending electron and proton transfer in biological systems. Six potential mechanisms for reducing the dimethyl disulfide (DMDS) bridge through electron and proton capture were explored. Thermodynamic and kinetic analyses elucidated the sequence of proton and electron addition. MD-PMM, a method that combines molecular dynamics simulations and quantum-chemical calculations, was employed to compute the redox potential of the mechanism. This research provides valuable insights into the mechanisms and redox potentials involved in disulfide bridge reduction within proteins, offering an understanding of phenomena that are challenging to explore experimentally.

METHODS

All calculations used the Gaussian 09 software package at the MP2/6-311 + g(d,p) theory level. Visualization of the molecular orbitals and electron densities was conducted using Gaussview6. Molecular dynamics simulations were performed using GROMACS with the CHARMM36 force field. The PyMM program (Python Program for QM/MM Simulations Based on the Perturbed Matrix Method) is used to apply the Perturbed Matrix Method to MD simulations.

Antioxidant Enzymes and Their Potential Use in Breast Cancer Treatment

According to the World Health Organization (WHO), breast cancer (BC) is the deadliest and the most common type of cancer worldwide in women. Several factors associated with BC exert their effects by modulating the state of stress. They can induce genetic mutations or alterations in cell growth, encouraging neoplastic development and the production of reactive oxygen species (ROS). ROS are able to activate many signal transduction pathways, producing an inflammatory environment that leads to the suppression of programmed cell death and the promotion of tumor proliferation, angiogenesis, and metastasis; these effects promote the development and progression of malignant neoplasms. However, cells have both non-enzymatic and enzymatic antioxidant systems that protect them by neutralizing the harmful effects of ROS. In this sense, antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), thioredoxin reductase (TrxR), and peroxiredoxin (Prx) protect the body from diseases caused by oxidative damage. In this review, we will discuss mechanisms through which some enzymatic antioxidants inhibit or promote carcinogenesis, as well as the new therapeutic proposals developed to complement traditional treatments.

NIR-II imaging-guided precise photodynamic therapy for augmenting tumor-starvation therapy by glucose metabolism reprogramming interference

Metabolic reprogramming is a mechanism by which cancer cells alter their metabolic patterns to promote cell proliferation and growth, thereby enabling their resistance to external stress. 2-Deoxy-D-glucose (2DG) can eliminate their energy source by inhibiting glucose glycolysis, leading to cancer cell death through starvation. However, a compensatory increase in mitochondrial metabolism inhibits its efficacy. Herein, we propose a synergistic approach that combines photodynamic therapy (PDT) with starvation therapy to address this challenge. To monitor the nanodrugs and determine the optimal triggering time for precise tumor therapy, a multifunctional nano-platform comprising lanthanide-doped nanoparticle (LnNP) cores was constructed and combined with mesoporous silicon shells loaded with 2DG and photosensitizer chlorin e6 (Ce6) in the mesopore channels. Under 980 nm near-infrared light excitation, the downshifted 1550 nm fluorescence signal in the second near-infrared (NIR-II, 1000-1700 nm) window from the LnNPs was used to monitor the accumulation of nanomaterials in tumors. Furthermore, upconverted 650 nm light excited the Ce6 to generate singlet oxygen for PDT, which damaged mitochondrial function and enhanced the efficacy of 2DG by inhibiting hexokinase 2 and lactate dehydrogenase A expressions. As a result, glucose metabolism reprogramming was inhibited and the efficiency of starvation therapy was significantly enhanced. Overall, the proposed NIR-II bioimaging-guided PDT-augmented starvation therapy, which simultaneously inhibited glycolysis and mitochondria, facilitated the effects of a cancer theranostic system.

Oxidative Stress in Breast Cancer: A Biochemical Map of Reactive Oxygen Species Production

This review systematizes information about the metabolic features of breast cancer directly related to oxidative stress. It has been shown those redox changes occur at all levels and affect many regulatory systems in the human body. The features of the biochemical processes occurring in breast cancer are described, ranging from nonspecific, at first glance, and strictly biochemical to hormone-induced reactions, genetic and epigenetic regulation, which allows for a broader and deeper understanding of the principles of oncogenesis, as well as maintaining the viability of cancer cells in the mammary gland. Specific pathways of the activation of oxidative stress have been studied as a response to the overproduction of stress hormones and estrogens, and specific ways to reduce its negative impact have been described. The diversity of participants that trigger redox reactions from different sides is considered more fully: glycolytic activity in breast cancer, and the nature of consumption of amino acids and metals. The role of metals in oxidative stress is discussed in detail. They can act as both co-factors and direct participants in oxidative stress, since they are either a trigger mechanism for lipid peroxidation or capable of activating signaling pathways that affect tumorigenesis. Special attention has been paid to the genetic and epigenetic regulation of breast tumors. A complex cascade of mechanisms of epigenetic regulation is explained, which made it possible to reconsider the existing opinion about the triggers and pathways for launching the oncological process, the survival of cancer cells and their ability to localize.

Unresolved questions regarding cellular cysteine sources and their possible relationships to ferroptosis

Cysteine is required for synthesis of glutathione (GSH), coenzyme A, other sulfur-containing metabolites, and most proteins. In most cells, cysteine comes from extracellular disulfide sources including cystine, glutathione-disulfide, and peptides. The thioredoxin reductase-1 (TrxR1)- or glutathione-disulfide reductase (GSR)-driven enzymatic systems can fuel cystine reduction via thioredoxins, glutaredoxins, or other thioredoxin-fold proteins. Free cystine enters cells thorough the cystine-glutamate antiporter, xCT, but systemically, plasma glutathione-disulfide might predominate as a cystine source. Erastin, inhibiting both xCT and voltage-dependent anion channels, induces ferroptotic cell death, so named because this type of cell death is antagonized by iron-chelators. Many cancer cells seem to be predisposed to ferroptosis, which has been proposed as a targetable cancer liability. Ferroptosis is associated with lipid peroxidation and loss of either glutathione peroxidase-4 (GPX4) or ferroptosis suppressor protein-1 (FSP1), which each prevent accumulation of lipid peroxides. It has been suggested that an xCT inhibition-induced cellular cysteine-deficiency lowers GSH levels, starving GPX4 for reducing power and allowing membrane lipid peroxides to accumulate, thereby causing ferroptosis. Aspects of ferroptosis are however not fully understood and need to be further scrutinized, for example that neither disruption of GSH synthesis, loss of GSH, nor disruption of glutathione disulfide reductase (GSR), triggers ferroptosis in animal models. Here we reevaluate the relationships between Erastin, xCT, GPX4, cellular cysteine and GSH, RSL3 or ML162, and ferroptosis. We conclude that, whereas both Cys and ferroptosis are potential liabilities in cancer, their relationship to each other remains insufficiently understood.

Can Compounds of Natural Origin Be Important in Chemoprevention? Anticancer Properties of Quercetin, Resveratrol, and Curcumin-A Comprehensive Review

Malignant tumors are the second most common cause of death worldwide. More attention is being paid to the link between the body's impaired oxidoreductive balance and cancer incidence. Much attention is being paid to polyphenols derived from plants, as one of their properties is an antioxidant character: the ability to eliminate reactive oxygen and nitrogen species, chelate specific metal ions, modulate signaling pathways affecting inflammation, and raise the level and activity of antioxidant enzymes while lowering those with oxidative effects. The following three compounds, resveratrol, quercetin, and curcumin, are polyphenols modulating multiple molecular targets, or increasing pro-apoptotic protein expression levels and decreasing anti-apoptotic protein expression levels. Experiments conducted in vitro and in vivo on animals and humans suggest using them as chemopreventive agents based on antioxidant properties. The advantage of these natural polyphenols is low toxicity and weak adverse effects at higher doses. However, the compounds discussed are characterized by low bioavailability and solubility, which may make achieving the blood concentrations needed for the desired effect challenging. The solution may lie in derivatives of naturally occurring polyphenols subjected to structural modifications that enhance their beneficial effects or work on implementing new ways of delivering antioxidants that improve their solubility and bioavailability.

Thioredoxin (Trx): A redox target and modulator of cellular senescence and aging-related diseases

Thioredoxin (Trx) is a compact redox-regulatory protein that modulates cellular redox state by reducing oxidized proteins. Trx exhibits dual functionality as an antioxidant and a cofactor for diverse enzymes and transcription factors, thereby exerting influence over their activity and function. Trx has emerged as a pivotal biomarker for various diseases, particularly those associated with oxidative stress, inflammation, and aging. Recent clinical investigations have underscored the significance of Trx in disease diagnosis, treatment, and mechanistic elucidation. Despite its paramount importance, the intricate interplay between Trx and cellular senescence-a condition characterized by irreversible growth arrest induced by multiple aging stimuli-remains inadequately understood. In this review, our objective is to present a comprehensive and up-to-date overview of the structure and function of Trx, its involvement in redox signaling pathways and cellular senescence, its association with aging and age-related diseases, as well as its potential as a therapeutic target. Our review aims to elucidate the novel and extensive role of Trx in senescence while highlighting its implications for aging and age-related diseases.

Roles of reactive oxygen species in inflammation and cancer

Reactive oxygen species (ROS) constitute a spectrum of oxygenic metabolites crucial in modulating pathological organism functions. Disruptions in ROS equilibrium span various diseases, and current insights suggest a dual role for ROS in tumorigenesis and the immune response within cancer. This review rigorously examines ROS production and its role in normal cells, elucidating the subsequent regulatory network in inflammation and cancer. Comprehensive synthesis details the documented impacts of ROS on diverse immune cells. Exploring the intricate relationship between ROS and cancer immunity, we highlight its influence on existing immunotherapies, including immune checkpoint blockade, chimeric antigen receptors, and cancer vaccines. Additionally, we underscore the promising prospects of utilizing ROS and targeting ROS modulators as novel immunotherapeutic interventions for cancer. This review discusses the complex interplay between ROS, inflammation, and tumorigenesis, emphasizing the multifaceted functions of ROS in both physiological and pathological conditions. It also underscores the potential implications of ROS in cancer immunotherapy and suggests future research directions, including the development of targeted therapies and precision oncology approaches. In summary, this review emphasizes the significance of understanding ROS-mediated mechanisms for advancing cancer therapy and developing personalized treatments.

Synthetic Derivatives of Natural ent-Kaurane Atractyligenin Disclose Anticancer Properties in Colon Cancer Cells, Triggering Apoptotic Cell Demise

The antitumor activity of different ent-kaurane diterpenes has been extensively studied. Several investigations have demonstrated the excellent antitumor activity of synthetic derivatives of the diterpene atractyligenin. In this research, a series of new synthetic amides and their 15,19-di-oxo analogues obtained from atractyligenin by modifying the C-2, C-15, and C-19 positions were designed in order to dispose of a set of derivatives with different substitutions at the amidic nitrogen. Using different concentrations of the obtained compounds (10-300 μM) a reduction in cell viability of HCT116 colon cancer cells was observed at 48 h of treatment. All the di-oxidized compounds were more effective than their alcoholic precursors. The di-oxidized compounds had already reduced the viability of two colon cancer cells (HCT116 and Caco-2) at 24 h when used at low doses (2.5-15 μM), while they turned out to be poorly effective in differentiated Caco-2 cells, a model of polarized enterocytes. The data reported here provide evidence that di-oxidized compounds induced apoptotic cell death, as demonstrated by the appearance of condensed and fragmented DNA in treated cells, as well as the activation of caspase-3 and fragmentation of its target PARP-1.

Inhibition of the thioredoxin system for radiosensitization therapy of cancer

Radiotherapy (RT) stands as a cornerstone in the clinical armamentarium against various cancers due to its proven efficacy. However, the intrinsic radiation resistance exhibited by cancer cells, coupled with the adverse effects of RT on normal tissues, often compromises its therapeutic potential and leads to unwanted side effects. This comprehensive review aims to consolidate our understanding of how radiosensitizers inhibit the thioredoxin (Trx) system in cellular contexts. Notable radiosensitizers, including gold nanoparticles (GNPs), gold triethylphosphine cyanide ([Au(SCN) (PEt3)]), auranofin, ceria nanoparticles (CONPs), curcumin and its derivatives, piperlongamide, indolequinone derivatives, micheliolide, motexafin gadolinium, and ethane selenide selenidazole derivatives (SeDs), are meticulously elucidated in terms of their applications in radiotherapy. In this review, the sensitization mechanisms and the current research progress of these radiosensitizers are discussed in detail, with the overall aim of providing valuable insights for the judicious application of Trx system inhibitors in the field of cancer radiosensitization therapy.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

Exploring the immune interactions between Oncomelania hupensis and Schistosoma japonicum, with a cross-comparison of immunological research progress in other intermediate host snails

Schistosomiasis, the second largest parasitic disease in the world after malaria, poses a significant threat to human health and causes public health issues. The disease primarily affects populations in economically underdeveloped tropical regions, earning it the title of "neglected tropical disease". Schistosomiasis is difficult to eradicate globally if medication alone is used. One of the essential elements of thorough schistosomiasis prevention and control is the management and disruption of the life cycle of intermediate host snails. The key approach to controlling the transmission of schistosomiasis is to control the intermediate hosts of the schistosome to disrupt its life cycle. We believe that approaching it from the perspective of the intermediate host's immunity could be an environmentally friendly and potentially effective method. Currently, globally significant intermediate host snails for schistosomes include Oncomelania hupensis, Biomphalaria glabrata, and Bulinus truncatus. The immune interaction research between B. glabrata and Schistosoma mansoni has a history of several decades, and the complete genome sequencing of both B. glabrata and B. truncatus has been accomplished. We have summarized the immune-related factors and research progress primarily studied in B. glabrata and B. truncatus and compared them with several humoral immune factors that O. hupensis research focuses on: macrophage migration inhibitory factor (MIF), Toll-like receptors (TLRs), and thioredoxin (Trx). We believe that continued exploration of the immune interactions between O. hupensis and Schistosoma japonicum is valuable. This comparative analysis can provide some direction and clues for further in-depth research. Comparative immunological studies between them not only expand our understanding of the immune defense responses of snails that act as intermediaries for schistosomes but also facilitate the development of more comprehensive and integrated strategies for schistosomiasis prevention and control. Furthermore, it offers an excellent opportunity to study the immune system of gastropods and their co-evolution with pathogenic organisms.

Discovery of novel organoarsenicals as robust thioredoxin reductase inhibitors for oxidative stress mediated cancer therapy

Targeting overexpressed thioredoxin reductase (TrxR) in cancer cells to induce oxidative stress has been proved to be an effective strategy for cancer therapy. However, the treatment was hindered by the low efficiency and frequent administration of TrxR inhibitors, and hence more potent TrxR inhibitors were urgently needed. Herein, we designed and synthesized a series of TrxR inhibitors based on arsenicals. Among these, compound 1d inhibited the proliferation of a variety of cancer cells at low micromolar concentrations and exhibited low toxicity to normal cells. Importantly, compound 1d induced the accumulation of reactive oxygen species (ROS) by inhibiting the TrxR activity, further causing the collapse of the redox system, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and DNA damage, followed by oxidative stress-induced cell apoptosis. In vivo data showed that, compared with the clinical TrxR inhibitor auranofin (AUR), compound 1d could more effectively eliminate tumors by 90 % at a dose of 1.5 mg/kg without any obvious side effects. These results indicated that compound 1d was a potent TrxR inhibitor against cancer.

Vagus nerve stimulation and acetylcholinesterase inhibitor donepezil provide cardioprotection against trastuzumab-induced cardiotoxicity in rats by attenuating mitochondrial dysfunction

Trastuzumab (Trz) is a targeted anticancer drug for human epidermal growth factor receptor 2 (HER2)-positive tumors, as Trz-induced cardiotoxicity (TIC) is commonly observed in Trz-treated patients. Since cardiac autonomic modulation with electrical vagus nerve stimulation (VNS) and acetylcholinesterase (AChE) inhibitors exerts cardioprotection against various heart diseases, the comparative effects of electrical VNS and an AChE inhibitor (donepezil) on cardiac and mitochondrial functions and programmed cell death pathways in TIC are not known. VNS devices were implanted in thirty-two male Wistar rats and were divided into 4 groups: (i) Control-Sham (CSham), (ii) Trz-Sham (TSham), (iii) Trz-VNS (TVNS), and (iv) Trz-donepezil (TDPZ). Rats in the Trz-treated groups were intraperitoneally injected with Trz (4 mg/kg/day) for 7 days, while CSham rats were injected with NSS. VNS devices were activated in the TVNS rats during the 7-day Trz treatment, but not in the sham rats. Rats in the TDPZ group received donepezil orally (5 mg/kg/day) for 7 days. At the end, left ventricular (LV) function and heart rate variability were evaluated, and heart tissue was collected for biochemical and histological analysis. Trz rats showed LV dysfunction and cardiac sympathovagal imbalance. In addition, mitochondrial function and dynamics were impaired in TIC rats. Trz also increased cardiomyocyte death by inducing apoptosis, pyroptosis, and ferroptosis. Electrical VNS and donepezil had similar efficacy in alleviating cardiac mitochondrial dysfunction, dynamic imbalances, and cardiomyocyte death, leading to improved LV function. These findings suggested that parasympathetic activation via either VNS or an AChE inhibitor could be a promising therapeutic intervention against TIC.

Evaluation of Oxidative Stress Levels and Dynamic Thiol-disulfide Balance in Patients with Retinopathy of Prematurity

PURPOSE

The aim of this study is to evaluate both dynamic thiol-disulfide homeostasis and oxidative stress (OS) levels in patients with retinopathy of prematurity (ROP).

METHODS

A total of 129 infants of <34 weeks gestational age were enrolled in the present study. The thiol-disulfide homeostasis was determined by using the new, cost-effective and fully automated colorimetric method. Total antioxidant status (TAS), Total oxidant status (TOS) and Oxidative stress index (OSI) levels were evaluated.

RESULTS

We found serum TAS levels were lower while serum TOS and OSI levels were significantly higher in patients with ROP compare to the without ROP group (p < .05). However, native, total and disulfide values were not statistically significant between the groups (p > .05). In addition, we also evaluated the native, total and disulfide levels in patients with ROP according to grades and no statistically significant results were found (p > .05). Low birth weight (p = .001), gestational age (p = .001) and 5-min Apgar score were significantly lower in the ROP group.

CONCLUSION

This study revealed that dynamic thiol-disulfide homeostasis was changed in patients with ROP. Increased TOS and decreased TAS levels may be associated with functional reduction of the antioxidant system due to increased OS. This indicate that ROP patients are highly sensitive to OS. The dynamic thiol-disulfide homeostasis may conduce to the pathophysiological mechanism and disease follow-up in patients with ROP. The results of this study show that ROP patients are highly sensitive to oxidative stress.

Effects of Arbutin on Potassium Bromate-Induced Erythrocyte Toxicity in Rats: Biochemical Evaluation of Some Metabolic Enzyme Activities In Vivo and In Vitro

In the present study, the inhibitory effect of potassium bromate on the pentose phosphate pathway and intracellular antioxidant systems enzymes (glucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), glutathione reductase (GR), glutathione S-transferase (GST), and thioredoxin reductase (TrxR)) and the role of arbutin in ameliorating this inhibition were investigated. In the in vivo phase of the study, Wistar Albino rats (28 male adults) were randomly divided into four groups. Control (n = 7): isotonic serum (0.5 mL, i.p), potassium bromate group (n = 7): potassium bromate (100 mg/kg), arbutin group (n = 7): arbutin (i.p.) (50 mg/kg/day), potassium bromate + arbutin, and Group (n = 7): potassium bromate (100 mg/kg) + arbutin (50 mg/kg/day) (i.p). The results of in vivo study showed that the activities of G6PD, 6PGD, GR, and TrxR enzymes were strongly inhibited in potassium bromate groups (p < 0.05). It was determined that GST enzyme activity decreased in the potassium bromate group, but this decrease was not statistically significant compared to the control group (p ⩾ 0.05). A statistically significant increase was found in G6PD, 6PGD, GST, and TrxR enzyme activities in the arbutin group compared to the control group (p < 0.05). The increase in GR enzyme activity was not statistically significant (p ⩾ 0.05). The potassium bromate + arbutin group's enzyme activity increased in comparison to the potassium bromate group and was discovered to be closer to the control group. It was found that potassium bromate inhibited the 6PGD enzyme obtained from rat erythrocyte tissues with IC50 = 346 μM value and Ki = 434.4 μM ± 6.1 value, and the inhibition was noncompetitive.

Synthesis and evaluation of Piperine analogs as thioredoxin reductase inhibitors to cause oxidative stress-induced cancer cell apoptosis

Inhibiting thioredoxin reductase (TrxR) to disrupt the redox equilibrium and induce tumor cell apoptosis is a significant tumor therapeutic strategy. Piperine, a natural product from black pepper, has been demonstrated to suppress tumor cell proliferation by enhancing reactive oxygen species (ROS), subsequently leading to cell death. However, the development of Piperine as an active molecule is hampered by its weak cytotoxicity. To develop a compound with higher activity, we synthesized 22 Piperine analogs and evaluated their pharmacological properties. Ultimately, B5 was screened by the results of cytotoxicity and inhibition of TrxR activity. In contrast to Piperine, B5 had significant cytotoxicity with a 4-fold increase. The structure-activity relationship demonstrated that the introduction of an electron-withdrawing group into the benzene ring adjacent to the amino group, particularly in the meta-position, was positive and that shortening the olefin double bond had no appreciable impact on cytotoxicity. Further investigating the physiological activity of B5 in HeLa cells, we found that B5 selectively inhibits the activity of TrxR by binding to Sec residues on TrxR. B5 then induces cellular oxidative stress and finally leads to apoptosis. As a result, the study of B5 paved the way for further investigation into the modification and function of Piperine analogs as TrxR inhibitors.

Thiol-Mediated Uptake of a Cysteine-Containing Nanobody for Anticancer Drug Delivery

The identification of tumor-specific biomarkers is one of the bottlenecks in the development of cancer therapies. Previous work revealed altered surface levels of reduced/oxidized cysteines in many cancers due to overexpression of redox-controlling proteins such as protein disulfide isomerases on the cell surface. Alterations in surface thiols can promote cell adhesion and metastasis, making thiols attractive targets for treatment. Few tools are available to study surface thiols on cancer cells and exploit them for theranostics. Here, we describe a nanobody (CB2) that specifically recognizes B cell lymphoma and breast cancer in a thiol-dependent manner. CB2 binding strictly requires the presence of a nonconserved cysteine in the antigen-binding region and correlates with elevated surface levels of free thiols on B cell lymphoma compared to healthy lymphocytes. Nanobody CB2 can induce complement-dependent cytotoxicity against lymphoma cells when functionalized with synthetic rhamnose trimers. Lymphoma cells internalize CB2 via thiol-mediated endocytosis which can be exploited to deliver cytotoxic agents. CB2 internalization combined with functionalization forms the basis for a wide range of diagnostic and therapeutic applications, rendering thiol-reactive nanobodies promising tools for targeting cancer.

Anticancer properties of sulforaphane: current insights at the molecular level

Sulforaphane (SFN) is an isothiocyanate with multiple biomedical applications. Sulforaphane can be extracted from the plants of the genus Brassica. However, broccoli sprouts are the chief source of sulforaphane and are 20 to 50 times richer than mature broccoli as they contain 1,153 mg/100 g. SFN is a secondary metabolite that is produced as a result of the hydrolysis of glucoraphanin (a glucosinolate) by the enzyme myrosinase. This review paper aims to summarize and understand the mechanisms behind the anticancer potential of sulforaphane. The data was collected by searching PubMed/MedLine, Scopus, Web of Science, and Google Scholar. This paper concludes that sulforaphane provides cancer protection through the alteration of various epigenetic and non-epigenetic pathways. It is a potent anticancer phytochemical that is safe to consume with minimal side effects. However, there is still a need for further research regarding SFN and the development of a standard dose.

Selenium and Selenoproteins in Health

Selenium is a trace mineral that is essential for health. After being obtained from food and taken up by the liver, selenium performs various physiological functions in the body in the form of selenoproteins, which are best known for their redox activity and anti-inflammatory properties. Selenium stimulates the activation of immune cells and is important for the activation of the immune system. Selenium is also essential for the maintenance of brain function. Selenium supplements can regulate lipid metabolism, cell apoptosis, and autophagy, and have displayed significant alleviating effects in most cardiovascular diseases. However, the effect of increased selenium intake on the risk of cancer remains unclear. Elevated serum selenium levels are associated with an increased risk of type 2 diabetes, and this relationship is complex and nonlinear. Selenium supplementation seems beneficial to some extent; however, existing studies have not fully explained the influence of selenium on various diseases. Further, more intervention trials are needed to verify the beneficial or harmful effects of selenium supplementation in various diseases.

Protoporphyrin IX-loaded albumin nanoparticles reverse cancer chemoresistance by enhancing intracellular reactive oxygen species

Chemoresistance is the main cause of chemotherapy failure in ovarian cancer (OC). The enhanced scavenging of reactive oxygen species (ROS) by the thioredoxin system resulted in insufficient intracellular concentrations of effective ROS, leading to chemoresistance. To induce OC cell apoptosis by enhancing intracellular ROS levels, protoporphyrin IX (PpIX) and albumin-bound PTX nanoparticles (APNP) were utilized to fabricate APNP-PpIX nanoparticles. APNP-PpIX effectively generated ROS and increased the effective ROS concentration in chemoresistant cancer cells. The in vitro and in vivo experiments confirmed the effective inhibition of APNP-PpIX on chemoresistant OC cell proliferation and tumor formation. APNP-PpIX significantly improved the effectiveness of chemotherapy and photodynamic therapy, thus providing a new approach for the clinical treatment of chemoresistant OC.

Transcriptomic analysis: the protection of over-expression thioredoxin reductase 1 in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease. The pathologic characteristic feature is the loss of dopaminergic neurons in the substantia nigra (SN). However, the biochemical mechanisms are unclear. A large number of studies have shown that oxidative damage is the primary cause of PD. Hence, antioxidants could become a suitable option to treat PD. The thioredoxin (Trx) system represents a useful, potentially disease-relevant oxidation-reduction system. Thioredoxin reductase 1 (TR1) is a significant component of the Trx system.

METHODS

The overexpression lentivirus (LV) or LV-TR1 in the TR1-A53T model of PD by the stereotactic brain, and successful overexpression of LV or LV-TR1 in the MPP⁺-induced cellular model by LV or LV-TR1 transfection.

RESULTS

We confirmed that interleukin-7 mRNA levels increased in MPP⁺ compared to that in the control and MPP⁺-TR1 groups using quantitative polymerase chain reaction. The γ-H₂AX level was increased in the Tg-A53T group compared to that in the TR1-A53T group by western blotting. The expression of Na⁺-K⁺-ATP was decreased in the MPP⁺ group compared to that in the control and MPP⁺-TR1 groups by high content screening. Tg-A53T(the C57BL/6 mice transferred with mutant human a-syn); TR1-A53T(A53T mice which were injected TR1-LV 2 µl in SNc on two sides with minipump).The mice were fed for 10 months. control (the N2a cells cultivated with DMEM); MPP⁺(the N2a cells dealt with MPP⁺(1 mM) 48 h), MPP⁺-LV (the N2a cells over-expressed LV for 24 h then dealt with MPP⁺(1 mM) 48 h). MPP⁺-TR1(the N2a cell over-expressed TR1-LV for 24 h then dealt with MPP⁺(1 mM) 48 h). From the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, we confirmed that the overexpression of TR1 in SN pars compacta cells decreased oxidative stress, apoptosis, DNA damage, and inflammatory response and increased NADPH, Na⁺-K⁺-ATP, and immune response in this PD model.

CONCLUSIONS

Our study shows that overexpressed TR1 can be developed as a neuroprotective agent for PD. Therefore, our findings demonstrate a new targeted protein for the treatment of PD.

Thimerosal, a competitive thioredoxin reductase 1 (TrxR1) inhibitor discovered via high-throughput screening

Thioredoxin reductase 1 (TrxR1) is considered as an important anti-cancer drug target, inhibition of which can induce reactive oxygen species (ROS)-mediated apoptosis of human cancer cells. Here, we developed and optimized a high-throughput screening (HTS) assay based on enzyme kinetics for the discovery of TrxR1 inhibitors. By utilizing this assay, we performed a HTS for 2500 compounds from an in-house library against TrxR1. We found that a vaccine preservative, thimerosal, strongly inhibited TrxR1 in a competitive and reversible manner with an IC₅₀ of 24.08 ± 0.86 nM. In addition, we determined that thiomersal has an inhibitory effect on the proliferation of A549 lung cancer cell line, with a GI₅₀ of 6.81 ± 0.09 μM, slightly more potent than auranofin (GI₅₀ = 11.85 ± 0.56 μM). Furthermore, we showed by flow cytometer that thimerosal effectively increased the content of ROS in A549 cells. Therefore, our work provided a high-throughput screening assay to quickly and effectively discover TrxR1 inhibitors, identifying thiomersal as a novel TrxR1 inhibitor and chemical probe.

Higher serum selenium concentration is associated with lower risk of all-cause and cardiovascular mortality among individuals with chronic kidney disease: A population-based cohort study of NHANES

Background

Selenium is an essential nutrient and trace element required for human health and plays an important role in antioxidative and anti-inflammatory processes. However, the long-term impact of selenium levels on the health of patients with chronic kidney disease remains unclear.

Method

Participants in this study were 3,063 CKD adults from the Third National Health and Nutrition Examination Survey (NHANES 1999–2000, 2003–2004, and 2011–2018). The mortality status and the cause of death of the study participants were obtained from the National Death Index records. For all-cause and cardiovascular disease (CVD) mortality, the models employed to estimate hazard ratios (HRs) and 95% CI were Cox proportional hazard models and competing risk models, respectively.

Result

During the follow-up period, 884 deaths occurred, including 336 heart-disease-associated deaths. The median (IQR) concentration of serum selenium was 181.7 (156.1, 201.5) μg/L. After full adjustment, serum selenium levels were associated with a decreased risk of mortality in patients with CKD, including all-cause and CVD mortality (P &lt; 0.001). The multivariate-adjusted HRs (95%CI) were 0.684 (0.549–0.852) for all-cause mortality (Ptrend &lt; 0.001) and 0.513 (0.356–0.739) for CVD mortality (Ptrend &lt; 0.001) when selenium concentrations were compared according to the extreme quartiles. Selenium levels are inversely associated with an increased risk of all-cause mortality and CVD mortality. Similar results were observed in subgroup and sensitivity analyses.

Conclusion

Higher serum selenium concentration was independently associated with a decreased risk of all-cause and CVD mortality in patients with CKD.

Selenium, selenoproteins and cancer of the thyroid

Selenium is an essential mineral element with important biological functions for the whole body through incorporation into selenoproteins. This element is highly concentrated in the thyroid gland. Selenoproteins provide antioxidant protection for this tissue against the oxidative stress caused by free radicals and contribute, via iodothyronine deiodinases, to the metabolism of thyroid hormones. It is known that oxidative stress plays a major role in carcinogenesis and that in recent decades there has been an increase in the incidence of thyroid cancer. The anti-carcinogenic action of selenium, although not fully understood, is mainly attributable to selenoproteins antioxidant properties, and to the ability to modulate cell proliferation (cell cycle and apoptosis), energy metabolism, and cellular immune response, significantly altered during tumorigenesis. Researchers have suggested that different forms of selenium supplementation may be beneficial in the prevention and treatment of thyroid cancer; however, the studies have several methodological limitations. This review is a summary of the current knowledge on how selenium and selenoproteins related to thyroid cancer.

Comparison of the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress

This study was conducted to compare the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress. Increased Il-1 and Il-6 expressions, markers of inflammation, were represented by inflammation models in mouse liver and kidney tissues injected intraperitoneally with LPS. After establishing the model, the GSH level and the GSH/GSSG ratio, which are oxidative stress markers, were investigated in both tissues treated with LPS and the control group. The expression of Trx1, TrxR, and Txnip genes increased in the liver tissues of LPS-treated mice. In the kidney tissue, while Trx1 expression decreased, no change was observed in TrxR1 expression, and Txnip expression increased. In the kidneys, TRXR1 and GR activities decreased, whereas GPx activity increased. In both tissues, the TRXR1 protein expression decreased significantly, while TXNIP expression increased. In conclusion, different behaviors of antioxidant system members were observed during acute inflammation in both tissues. Additionally, it can be said that the kidney tissue is more sensitive and takes earlier measures than the liver tissue against cellular damage caused by inflammation and inflammation-induced oxidative stress.

Thioredoxin Signaling Pathways in Cancer

Significance: Thioredoxin (Trx) is a powerful antioxidant that reduces protein disulfides to maintain redox stability in cells and is involved in regulating multiple redox-dependent signaling pathways. Recent Advance: The current accumulation of findings suggests that Trx participates in signaling pathways that interact with various proteins to manipulate their dynamic regulation of structure and function. These network pathways are critical for cancer pathogenesis and therapy. Promising clinical advances have been presented by most anticancer agents targeting such signaling pathways. Critical Issues: We herein link the signaling pathways regulated by the Trx system to potential cancer therapeutic opportunities, focusing on the coordination and strengths of the Trx signaling pathways in apoptosis, ferroptosis, immunomodulation, and drug resistance. We also provide a mechanistic network for the exploitation of therapeutic small molecules targeting the Trx signaling pathways. Future Directions: As research data accumulate, future complex networks of Trx-related signaling pathways will gain in detail. In-depth exploration and establishment of these signaling pathways, including Trx upstream and downstream regulatory proteins, will be critical to advancing novel cancer therapeutics. Antioxid. Redox Signal. 38, 403-424.

Mitochondria-targeted iridium-based photosensitizers enhancing photodynamic therapy effect by disturbing cellular redox balance

Photodynamic therapy (PDT) is a non-invasive, light-activated treatment approach that has been broadly employed in cancer. Cyclometallic iridium (Ш) complexes are candidates for ideal photosensitizers due to their unique photophysical and photochemical features, such as high quantum yield, large Stokes shift, strong resistance to photobleaching, and high cellular permeability. We evaluated a panel of iridium complexes and identified PC9 as a powerful photosensitizer to kill cancer cells. PC9 shows an 8-fold increase of cytotoxicity to HeLa cells under light irradiation. Further investigation discloses that PC9 has a strong mitochondrial-targeting ability and can inhibit the antioxidant enzyme thioredoxin reductase, which contributes to improving PDT efficacy. Our data indicate that iridium complexes are efficient photosensitizers with distinct physicochemical properties and cellular actions, and deserve further development as promising agents for PDT.

The thioredoxin system: Balancing redox responses in immune cells and tumors

The thioredoxin (TRX) system is an important contributor to cellular redox balance and regulates cell growth, apoptosis, gene expression, and antioxidant defense in nearly all living cells. Oxidative stress, the imbalance between reactive oxygen species (ROS) and antioxidants, can lead to cell death and tissue damage, thereby contributing to aging and to the development of several diseases, including cardiovascular and allergic diseases, diabetes, and neurological disorders. Targeting its activity is also considered as a promising strategy in the treatment of cancer. Over the past years, immunologists have established an essential function of TRX for activation, proliferation, and responses in T cells, B cells, and macrophages. Upon activation, immune cells rearrange their redox system and activate the TRX pathway to promote proliferation through sustainment of nucleotide biosynthesis, and to support inflammatory responses in myeloid cells by allowing NF-κB and NLRP3 inflammasome responses. Consequently, targeting the TRX system may therapeutically be exploited to inhibit immune responses in inflammatory conditions. In this review, we summarize recent insights revealing key roles of the TRX pathway in immune cells in health and disease, and lessons learnt for cancer therapy.

Evaluation of dynamic thiol-disulfide homeostasis and ischemia-modified albumin levels in patients with chronic lymphocytic leukemia

This is the first study to evaluate both the dynamic thiol-disulfide homeostasis and ischemia-modified albumin (IMA) levels in patients with chronic lymphocytic leukemia (CLL). Twenty-nine patients with CLL and 20 controls were included in the study. The dynamic thiol-disulfide balance was determined by the newly developed colorimetric method by Erel. IMA levels were determined by the cobalt binding test. We found that total antioxidant status levels were lower while total oxidant status (TOS) and oxidative stress index (OSI) levels were significantly higher in patients with CLL than controls. Moreover, native and total thiol levels were found to be statistically significant between the study and control groups (p<0.001), whereas no statistically significant difference was noted for IMA levels (p=0.365). A negative correlation was observed between native and total thiol levels, leukocyte, lymphocyte, and TOS. Total bilirubin showed positive correlation with direct bilirubin and alkaline phosphatase. In addition, IMA levels showed a positive correlation with OSI. This study highlights measurement of native and total thiol and IMA levels in patients with CLL for the first time. Dynamic thiol-disulfide homeostasis may contribute in the pathophysiological mechanism, and follow-up to disease in patients with CLL.

Thioredoxin Reductase-1 as a Potential Biomarker in Fibroblast-Associated HCT116 Cancer Cell Progression and Dissemination in a Zebrafish Model

The tumor microenvironment, especially that of fibroblasts, strongly promotes colorectal cancer (CRC) progression. Progressive cancers usually accumulate high reactive oxygen species (ROS), leading to oxidative stress. The stress relates to the expression of thioredoxin reductase-1 (TrxR-1), which is an oxidative stress sensitivity molecule. This study aimed to investigate TrxR-1 expression as an indication of colon-fibroblast-inducing colorectal cancer progression and metastasis. We found that the high proliferative fibroblast-cultured media (FCM) contained pro-inflammatory cytokines that have a high ability to influence HCT116 and CRC cell progression, when compared with complete media (CM) as a control in terms of growth (CM = 100.00%, FCM = 165.96%), migration (CM = 32.22%, FCM = 83.07%), invasion (CM = 130 cells/field, FCM = 449 cells/field), and EMT transformation while decreasing E-cadherin expression (CM = 1.00, FCM = 0.69) and shape factor (CM = 0.94, FCM = 0.61). In addition, the overexpression of TrxR-1 is associated with cellular oxidant enchantment in FCM-treated cells. A dot plot analysis showed a strong relation between the EMT process and the overexpression of TrxR-1 in FCM-treated cells (CM = 13/100 cells, FCM = 45/100 cells). The cancer transplantation of the adult zebrafish model illustrated a significantly higher number of microtumors in FCM-treated cells (CM = 4.33 ± 1.51/HPF, FCM = 25.00 ± 13.18/HPF) disseminated in the intraperitoneal cavity with TrxR-1 positive cells. The overexpression of TrxR-1 indicated fibroblast-associated CRC progression in HCT116 cells and the zebrafish model. Therefore, TrxR-1 could be applied as a novel biomarker for colorectal cancer progression and prognostic evaluation.

Ferrocifen stealth LNCs and conventional chemotherapy: A promising combination against multidrug-resistant ovarian adenocarcinoma

Ovarian cancer is one of the deadliest epithelial malignancies in women, owing to the multidrug resistance that restricts the success of conventional chemotherapy, carboplatin and paclitaxel. High grade serous ovarian carcinoma can be classified into two subtypes, the chemosensitive High OXPHOS and the Low OXPHOS tumour, less sensitive to chemotherapy. This difference of treatment efficacy could be explained by the redox status of these tumours, High OXPHOS exhibiting a chronic oxidative stress and an accumulation of reactive oxygen species. Ferrocifens, bio-organometallic compounds, are believed to be ROS producers with a good cytotoxicity on ovarian cancer cell lines. The aim of this study was to evaluate the in vivo efficacy of ferrocifen stealth lipid nanocapsules on High and Low OXPHOS ovarian Patient-Derived Xenograft models, alone or in combination to standard chemotherapy. Accordingly, two ferrocifens, P53 and P722, were encapsulated in stealth LNCs. The treatment by stealth P722-LNCs in combination with standard chemotherapy induced, with a concentration eight time lower than in stealth P53-LNCs, similar tumour reduction on a Low OXPHOS model, allowing us to conclude that P722 could be a leading ferrocifen to treat ovarian cancer. This combination of treatments may represent a promising synergistic approach to treat resistant ovarian adenocarcinoma.

Synthesis and SAR Analysis of Novel 4-Hydroxytamoxifen Analogues Based on Their Cytotoxic Activity and Electron-Donor Character

Utilizing McMurry reactions of 4,4′-dihydroxybenzophenone with appropriate carbonyl compounds, a series of 4-Hydroxytamoxifen analogues were synthesized. Their cytotoxic activity was evaluated in vitro on four human malignant cell lines (MCF-7, MDA-MB 231, A2058, HT-29). It was found that some of these novel Tamoxifen analogues show marked cytotoxicity in a dose-dependent manner. The relative ROS-generating capability of the synthetized analogues was evaluated by cyclic voltammetry (CV) and DFT modeling studies. The results of cell-viability assays, CV measurements and DFT calculations suggest that the cytotoxicity of the majority of the novel compounds is mainly elicited by their interactions with cellular targets including estrogen receptors rather than triggered by redox processes. However, three novel compounds could be involved in ROS-production and subsequent formation of quinone-methide preventing proliferation and disrupting the redox balance of the treated cells. Among the cell lines studied, HT-29 proved to be the most susceptible to the treatment with compounds having ROS-generating potency.

Revealing PACMA 31 as a new chemical type TrxR inhibitor to promote cancer cell apoptosis

Thioredoxin reductase (TrxR) is a pivotal regulator of redox homeostasis, while dysregulation of redox homeostasis is a hallmark for cancer cells. Thus, there is considerable potential to inhibit the aberrantly upregulated TrxR in cancer cells to discover selective cancer therapeutic agents. Nevertheless, the structural types of TrxR inhibitors presented currently are still relatively limited. We herein report that PACMA 31, previously reported to inhibit protein disulfide isomerase (PDI), is a potent TrxR inhibitor. PACMA 31 possesses a pharmacophore scaffold that is structurally different from the announced TrxR inhibitors and exhibits effective cytotoxicity against cervical cancer cells. Our results reveal that PACMA 31 selectively inhibits TrxR over the related glutathione reductase (GR) and in the presence of reduced glutathione (GSH). Further studies with mutant enzyme and molecular docking suggest that the propynamide fragment of PACMA 31 interacts covalently with the selenocysteine residue of TrxR. Moreover, PACMA 31 effectively and selectively curbs TrxR activity in cells and further stimulates the production of reactive oxygen species (ROS) at low micromolar concentrations, which in turn triggers the accumulation of oxidized thioredoxin (Trx) and GSSG in cells. Follow-up studies demonstrate that PACMA 31 targets TrxR in cells to induce oxidative stress-mediated cancer cell apoptosis. Our results provide a new structural type of TrxR inhibitor that may serve as a useful probe for investigating the biology of TrxR-implicated pathways, and uncover a new target of PACMA 31 that contributes to it becoming a candidate for cancer treatment.

S-Denitrosylation: A Crosstalk between Glutathione and Redoxin Systems

S-nitrosylation of proteins occurs as a consequence of the derivatization of cysteine thiols with nitric oxide (NO) and is often associated with diseases and protein malfunction. Aberrant S-nitrosylation, in addition to other genetic and epigenetic factors, has gained rapid importance as a prime cause of various metabolic, respiratory, and cardiac disorders, with a major emphasis on cancer and neurodegeneration. The S-nitrosoproteome, a term used to collectively refer to the diverse and dynamic repertoire of S-nitrosylated proteins, is relatively less explored in the field of redox biochemistry, in contrast to other covalently modified versions of the same set of proteins. Advancing research is gradually unveiling the enormous clinical importance of S-nitrosylation in the etiology of diseases and is opening up new avenues of prompt diagnosis that harness this phenomenon. Ever since the discovery of the two robust and highly conserved S-nitrosoglutathione reductase and thioredoxin systems as candidate denitrosylases, years of rampant speculation centered around the identification of specific substrates and other candidate denitrosylases, subcellular localization of both substrates and denitrosylases, the position of susceptible thiols, mechanisms of S-denitrosylation under basal and stimulus-dependent conditions, impact on protein conformation and function, and extrapolating these findings towards the understanding of diseases, aging and the development of novel therapeutic strategies. However, newer insights in the ever-expanding field of redox biology reveal distinct gaps in exploring the crucial crosstalk between the redoxins/major denitrosylase systems. Clarifying the importance of the functional overlap of the glutaredoxin, glutathione, and thioredoxin systems and examining their complementary functions as denitrosylases and antioxidant enzymatic defense systems are essential prerequisites for devising a rationale that could aid in predicting the extent of cell survival under high oxidative/nitrosative stress while taking into account the existence of the alternative and compensatory regulatory mechanisms. This review thus attempts to highlight major gaps in our understanding of the robust cellular redox regulation system, which is upheld by the concerted efforts of various denitrosylases and antioxidants.

Thioredoxin reductase selenoproteins from different organisms as potential drug targets for treatment of human diseases

Human thioredoxin reductase (TrxR) is a selenoprotein with a central role in cellular redox homeostasis, utilizing a highly reactive and solvent-exposed selenocysteine (Sec) residue in its active site. Pharmacological modulation of TrxR can be obtained with several classes of small compounds showing different mechanisms of action, but most often dependent upon interactions with its Sec residue. The clinical implications of TrxR modulation as mediated by small compounds have been studied in diverse diseases, from rheumatoid arthritis and ischemia to cancer and parasitic infections. The possible involvement of TrxR in these diseases was in some cases serendipitously discovered, by finding that existing clinically used drugs are also TrxR inhibitors. Inhibiting isoforms of human TrxR is, however, not the only strategy for human disease treatment, as some pathogenic parasites also depend upon Sec-containing TrxR variants, including S. mansoni, B. malayi or O. volvulus. Inhibiting parasite TrxR has been shown to selectively kill parasites and can thus become a promising treatment strategy, especially in the context of quickly emerging resistance towards other drugs. Here we have summarized the basis for the targeting of selenoprotein TrxR variants with small molecules for therapeutic purposes in different human disease contexts. We discuss how Sec engagement appears to be an indispensable part of treatment efficacy and how some therapeutically promising compounds have been evaluated in preclinical or clinical studies. Several research questions remain before a wider application of selenoprotein TrxR inhibition as a first-line treatment strategy might be developed. These include further mechanistic studies of downstream effects that may mediate treatment efficacy, identification of isoform-specific enzyme inhibition patterns for some given therapeutic compounds, and the further elucidation of cell-specific effects in disease contexts such as in the tumor microenvironment or in host-parasite interactions, and which of these effects may be dependent upon the specific targeting of Sec in distinct TrxR isoforms.

Analysis of Pleurotin binding to human thioredoxin reductase using docking and molecular dynamics simulation

Thioredoxin reductase (TrxR) has been considered a potential target for cancer chemotherapy. It acts by controlling the redox homeostasis of human cells and, therefore, interfering in its function may trigger apoptosis, which is a crucial tumor suppression mechanism. Despite the great effort in the search for TrxR inhibitors, none was approved for human therapy. In the present study a virtual screening for natural organic compounds is discussed for a set of 72 compounds with known IC-50 for TrxR inhibition. The results suggest the Pleurotin, a naphthoquinone obtained from Hohenbuehelia grisea fungus, as a potential TrxR inhibitor, which acts by binding to the active site of the enzyme, between the N- and C-terminal domains. The presence of the ligand blocks the approximation of the C-terminal arm to the N-terminal, which is an essential step of the enzyme function. Besides, the two equivalent binding sites of TrxR were explored, by docking two ligands simultaneously. The results indicate that both sites have an allosteric correlation and, the presence of the ligand in one site may interfere, or even prevent, the binding of the second ligand at the other site. All these findings are quantitatively discussed based on the analysis of long molecular dynamics trajectories, which provides a full description of the ligand-receptor binding modes, average binding energies and conformational changes.Communicated by Ramaswamy H. Sarma.

Thioredoxin Reductase Inhibitors as Potential Antitumors: Mercury Compounds Efficacy in Glioma Cells

Glioblastoma multiforme (GBM) is the most aggressive and common form of glioma. GBM, like many other tumors, expresses high levels of redox proteins, such as thioredoxin (Trx) and thioredoxin reductase (TrxR), allowing tumor cells to cope with high levels of reactive oxygen species (ROS) and resist chemotherapy and radiotherapy. Thus, tackling the activity of these enzymes is a strategy to reduce cell viability and proliferation and most importantly achieve tumor cell death. Mercury (Hg) compounds are among the most effective inhibitors of TrxR and Trx due to their high affinity for binding thiols and selenols. Moreover, organomercurials such as thimerosal, have a history of clinical use in humans. Thimerosal effectively crosses the blood–brain barrier (BBB), thus reaching effective concentrations for the treatment of GBM. Therefore, this study evaluated the effects of thimerosal (TmHg) and its metabolite ethylmercury (EtHg) over the mouse glioma cell line (GL261), namely, the inhibition of the thioredoxin system and the occurrence of oxidative cellular stress. The results showed that both TmHg and EtHg increased oxidative events and triggered cell death primarily by apoptosis, leading to a significant reduction in GL261 cell viability. Moreover, the cytotoxicity of TmHg and ETHg in GL261 was significantly higher when compared to temozolomide (TMZ). These results indicate that EtHg and TmHg have the potential to be used in GBM therapy since they strongly reduce the redox capability of tumor cells at exceedingly low exposure levels.

Evaluation of Dynamic Thiol-Disulfide Balance and Ischemia Modified Albumin Levels in Patients with Chronic Kidney Disease

Objective: We aimed to measure the dynamic thiol-disulfide balance and ischemia modified albumin (IMA) levels in patients with chronic kidney disease (CKD). Materials and methods: Thirty hemodialysis (HD), 30 CKD patients (stage3-5) and 30 controls were included in the study. The dynamic thiol-disulfide balance was determined by the colorimetric method developed by Erel et al. IMA levels were determined by using cobalt binding test developed by Bar- Or et al. Results: Native and total thiol levels of CKD and HD patients were significantly lower than that of the control group (p=0.001for both). However, disulfide levels were significantly higher in the HD group (p=0.001), but there was no significant difference between control and CKD groups(p=0.547). A notable negative correlation was found between the native and total thiol levels and IMA(r=-0.628;-0.631),BUN (r=-0.747;-0.747),and creatinine(r=-0.732;-0.721). There was a significant positive correlation between GFR and the thiol levels (r=0.835;0.824). TrxR levels were significantly higher in the patient groups compared to the controls (p=0.001). CRP levels of the patient groups were significantly higher compared to the controls (p=0.001). Conclusions: We have demonstrated that measurement of dynamic thiol-disulfide levels by using colorimetric method can contribute to the diagnosis and follow-up of the disease as a marker, because, it is easily applicable in routine clinical biochemistry laboratories and related with disease severity in CKD patients. Also, we showed that albumin correction due to dialysis process should be consider in studies dealing with plasma thiol values and the final results should be given after the correction process.

The Role of the Thioredoxin Detoxification System in Cancer Progression and Resistance

The intracellular redox homeostasis is a dynamic balancing system between the levels of free radical species and antioxidant enzymes and small molecules at the core of cellular defense mechanisms. The thioredoxin (Trx) system is an important detoxification system regulating the redox milieu. This system is one of the key regulators of cells’ proliferative potential as well, through the reduction of key proteins. Increased oxidative stress characterizes highly proliferative, metabolically hyperactive cancer cells, which are forced to mobilize antioxidant enzymes to balance the increase in free radical concentration and prevent irreversible damage and cell death. Components of the Trx system are involved in high-rate proliferation and activation of pro-survival mechanisms in cancer cells, particularly those facing increased oxidative stress. This review addresses the importance of the targetable redox-regulating Trx system in tumor progression, as well as in detoxification and protection of cancer cells from oxidative stress and drug-induced cytotoxicity. It also discusses the cancer cells’ counteracting mechanisms to the Trx system inhibition and presents several inhibitors of the Trx system as prospective candidates for cytostatics’ adjuvants. This manuscript further emphasizes the importance of developing novel multitarget therapies encompassing the Trx system inhibition to overcome cancer treatment limitations.

Mecheliolide elicits ROS-mediated ERS driven immunogenic cell death in hepatocellular carcinoma

The nonnegligible reason for the poor prognosis of hepatocellular carcinoma (HCC) is resistance to conventional chemotherapy. Immunogenic cell death (ICD) is a rare immunostimulatory form of cell death that can reengage the tumor-specific immune system. ICD can improve the clinical outcomes of chemotherapeutics by promoting a long-term cancer immunity. The discovery of potential ICD inducers is emerging as a promising direction. In the present study, micheliolide (MCL), a natural guaianolide sesquiterpene lactone, was screened out by the virtual screening strategies, identified as an inhibitor of thioredoxin reductase (TrxR) and was evaluated to have high potential to induce ICD. Here, we showed that MCL induced ICD-associated DAMPs (damage-associated molecular patterns, such as CRT exposure, ATP secretion and HMGB1 release). MCL significantly triggered the regression of established tumors in an immunocompetent mouse vaccine model, and induced ICD (DCs maturation, the stimulation of CD4⁺, and CD8⁺ T-cells responses) in vivo. Mechanistically, we found that the magnitude of ICD-associated effects induced upon exposure of HCC cells to MCL was dependent on the generation of reactive oxygen species (ROS)-mediated endoplasmic reticulum stress (ERS). In addition, the suppression of ROS normalized MCL-induced ERS, in contrast, the downregulation of TrxR synergized with the ERS driven by MCL. We also systematically detected the H₂O₂ generation using Hyper7 sensors in HCC cells exposed to MCL. Notably, MCL inhibited the development of HCC organoids. Collectively, our results reveal a potential association between the TrxR inhibitors and ICD, presenting valuable insights into the MCL-activated ICD in HCC cells.

Thiol-Based Antioxidants and the Epithelial/Mesenchymal Transition in Cancer

Significance: The epithelial/mesenchymal transition (EMT) is commonly associated with tumor metastasis. Oxidative and nitrosative stress is maintained in cancer cells and is involved in the EMT. Cancer cells are endowed with high levels of enzymatic and nonenzymatic antioxidants, which counteract the effects of oxidative and nitrosative stress. Thiol-based antioxidant systems such as the thioredoxin/thioredoxin reductase (Trx/TrxR) and glutathione/glutaredoxin (GSH/Grx) are continually active in cancer cells, while the thioredoxin-interacting protein (Txnip), the negative regulator of the Trx/TrxR system, is downregulated. Recent Advances: Trx/TrxR and GSH/Grx systems play a major role in maintaining EMT signaling and cancer cell progression. Critical Issues: Enhanced stress conditions stimulated in cancer cells inhibit EMT signaling. The elevated expression levels of the Trx/TrxR and GSH/Grx systems in these cells provide the antioxidant protection necessary to guarantee the occurrence of the EMT. Future Directions: Elevation of the intracellular reactive oxygen species and nitric oxide concentrations in cancer cells has been viewed as a promising strategy for elimination of these cells. The development of inhibitors of GSH synthesis and of the Trx/TrxR system together with genetic-based strategies to enhance Txnip levels may provide the necessary means to achieve this goal. Antioxid. Redox Signal. 36, 1037-1050.

Cyclic 5-membered disulfides are not selective substrates of thioredoxin reductase, but are opened nonspecifically

The cyclic five-membered disulfide 1,2-dithiolane has been widely used in chemical biology and in redox probes. Contradictory reports have described it either as nonspecifically reduced in cells, or else as a highly specific substrate for thioredoxin reductase (TrxR). Here we show that 1,2-dithiolane probes, such as "TRFS" probes, are nonspecifically reduced by thiol reductants and redox-active proteins, and their cellular performance is barely affected by TrxR inhibition or knockout. Therefore, results of cellular imaging or inhibitor screening using 1,2-dithiolanes should not be interpreted as reflecting TrxR activity, and previous studies may need re-evaluation. To understand 1,2-dithiolanes' complex behaviour, probe localisation, environment-dependent fluorescence, reduction-independent ring-opening polymerisation, and thiol-dependent cellular uptake must all be considered; particular caution is needed when co-applying thiophilic inhibitors. We present a general approach controlling against assay misinterpretation with reducible probes, to ensure future TrxR-targeted designs are robustly evaluated for selectivity, and to better orient future research.

Novel strategies for targeting the thioredoxin system for cancer therapy

INTRODUCTION

: The thioredoxin system is increasingly recognized as an important executor for maintaining cell redox homeostasis and regulating multiple cell signaling pathways. Targeting this system for cancer treatment has therefore attracted much attention.

AREAS COVERED

: The authors focus on providing coverage and emphasizing the strategy of targeting the thioredoxin system to develop anticancer therapeutics in the past five years, especially from the perspective of discovering novel protein functions or new downstream regulatory pathways, and designing new therapeutic reagents. The authors also provide the readers with their expert perspectives for future development.

EXPERT OPINION

: The limited pharmacophore of inhibitors and the slow progress of clinical research partially restrict the development of anticancer drugs targeting the thioredoxin system, necessitating thus novel strategies to accelerate the system for treating cancer. Nevertheless, the synergistic targeting of thioredoxin system for cancer therapy is a promising strategy, particularly with regards to chemotherapy resistance and/or sensitization immunotherapy.