Secretion of thioredoxin enhances cellular resistance to cis-diamminedichloroplatinum (II)

Potential Role of APEX1 During Ferroptosis

Ferroptosis is a recently discovered category of programmed cell death. It is much different from other types of cell death such as apoptosis, necrosis and autophagy. The main pathological feature of ferroptosis is the accumulation of iron-dependent lipid peroxidation. The typical changes in the morphological features of ferroptosis include cell volume shrinkage and increased mitochondrial membrane area. The mechanisms of ferroptosis may be mainly related to lipid peroxidation accumulation, imbalance in amino acid antioxidant system, and disturbance of iron metabolism. Besides, hypoxia-inducible factor (HIF), nuclear factor-E2-related factor 2 (Nrf2), and p53 pathway have been demonstrated to be involved in ferroptosis. At present, the molecular mechanisms of ferroptosis pathway are still unmapped. In this review, an outlook has been put forward about the crucial role of apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1) in the regulation of ferroptosis. APEX1 plays an important role in the regulation of intracellular redox balance and can be used as a potential inhibitor of ferroptotic cell death. Bioinformatics analysis indicated that the mRNA level of APEX1 is decreased in cases of ferroptosis triggered by erastin. Besides, it was found that there was a significant correlation between APEX1 and genes in the ferroptosis pathway. We have discussed the possibility to employ APEX1 inducers or inhibitors in the regulation of ferroptosis as a new strategy for the treatment of various human diseases.

Cisplatin Resistance and Redox-Metabolic Vulnerability: A Second Alteration

The development of drug resistance in tumors is a major obstacle to effective cancer chemotherapy and represents one of the most significant complications to improving long-term patient outcomes. Despite early positive responsiveness to platinum-based chemotherapy, the majority of lung cancer patients develop resistance. The development of a new combination therapy targeting cisplatin-resistant (CR) tumors may mark a major improvement as salvage therapy in these patients. The recent resurgence in research into cellular metabolism has again confirmed that cancer cells utilize aerobic glycolysis ("the Warburg effect") to produce energy. Hence, this observation still remains a characteristic hallmark of altered metabolism in certain cancer cells. However, recent evidence promotes another concept wherein some tumors that acquire resistance to cisplatin undergo further metabolic alterations that increase tumor reliance on oxidative metabolism (OXMET) instead of glycolysis. Our review focuses on molecular changes that occur in tumors due to the relationship between metabolic demands and the importance of NAD⁺ in redox (ROS) metabolism and the crosstalk between PARP-1 (Poly (ADP ribose) polymerase-1) and SIRTs (sirtuins) in CR tumors. Finally, we discuss a role for the tumor metabolites of the kynurenine pathway (tryptophan catabolism) as effectors of immune cells in the tumor microenvironment during acquisition of resistance in CR cells. Understanding these concepts will form the basis for future targeting of CR cells by exploiting redox-metabolic changes and their consequences on immune cells in the tumor microenvironment as a new approach to improve overall therapeutic outcomes and survival in patients who fail cisplatin.

Thioredoxin as a novel sensitive marker of biological stress response in smoking

Thioredoxin is a low molecular weight (approximately 12 kDa) redox protein, and protects against harmful stimuli such as oxidative stress. Smoking evokes oxidative stress, among other biological responses. The clinical relevance of thioredoxin in smoking has not been fully investigated. Here, we examined the effects of smoking on serum and urinary thioredoxin levels, in comparison with various stress markers. Serum thioredoxin levels in the smoking group (10 subjects) were significantly higher than those of the non-smoking group (5 subjects). After smoking, serum thioredoxin levels significantly decreased, while urinary levels significantly increased. On the other hand, the levels of serum and salivary cortisol, plasma norepinephrine, salivary amylase, salivary thioredoxin, and urinary 8-hydroxy-2'-deoxyguanosine levels before and after smoking were not significantly different. These results suggest that a decrease in thioredoxin in the serum and the concomitant increase in the urine is a novel sensitive marker of biological stress responses induced by smoking. The change seems to be evoked by mechanisms different from hormonal or 8-hydroxy-2'-deoxyguanosine-forming stress responses.

Analytical and clinical validation of rapid chemiluminescence enzyme immunoassay for urinary thioredoxin, an oxidative stress-dependent early biomarker of acute kidney injury

BACKGROUND

Oxidative stress is now recognized to be an important therapeutic target in kidney diseases. However, there are currently no biomarkers that can be used clinically to diagnose renal oxidative stress.

METHODS

A rapid assay system for urinary thioredoxin 1, an oxidative stress-dependent biomarker of acute kidney injury (AKI), was developed as a chemiluminescence enzyme immunoassay and validated analytically and clinically.

RESULTS

Analytic evaluation revealed that hemolytic hemoglobin caused measurements to be abnormally high, above the detectable range. However, urine sediment containing red blood cells did not affect the measurements. Assays using our proposed chemiluminescence enzyme immunoassay were completed within as little as 6 min, whereas a conventional ELISA > 4 h. Aciduria <pH 6.0 led to a significant underestimation of thioredoxin 1 concentrations. However, the effects of aciduria were completely reversible with use of a buffer developed for pH adjustment. Urinary thioredoxin 1 was increased in patients with AKI, but was unaffected by extrarenal oxidative stress diseases, including hypoxemia and myocardial infarction, or by chronic kidney disease in which serum creatinine concentrations were comparable.

CONCLUSIONS

These results suggest that the chemiluminescent enzyme immunoassay system for urinary thioredoxin 1 enables rapid and specific diagnosis of AKI associated with oxidative stress.

Relationship of Metabolic Alterations and PD-L1 Expression in Cisplatin Resistant Lung Cancer

Despite numerous reports on immune checkpoint inhibitor for the treatment of non-small cell lung cancer (NSCLC), the response rate remains low but durable. Thus cisplatin still plays a major role in the treatment of NSCLC. While there are many mechanisms involved in cisplatin resistance, alteration in metabolic phenotypes with elevated levels of reactive oxygen species (ROS) are found in several cisplatin resistant tumors. These resistant cells become more reliant on mitochondria oxidative metabolism instead of glucose. Consequently, high ROS and metabolic alteration contributed to epithelial-mesenchymal transition (EMT). Importantly, recent findings indicated that EMT has a crucial role in upregulating PD-L1 expression in cancer cells. Thus, it is very likely that cisplatin resistance will lead to high expression of PD-L1/PD-1 which makes them vulnerable to anti PD-1 or anti PD-L1 antibody treatment. An understanding of the interactions between cancer cells metabolic reprogramming and immune checkpoints is critical for combining metabolism targeted therapies with immunotherapies.

Renal redox dysregulation in AKI: application for oxidative stress marker of AKI

Oxidative stress is a major determinant of acute kidney injury (AKI); however, the effects of an AKI on renal redox system are unclear, and few existing AKI markers are suitable for evaluating oxidative stress. We measured urinary levels of the redox-regulatory protein thioredoxin 1 (TRX1) in patients with various kinds of kidney disease and in mice with renal ischemia-reperfusion injury. Urinary TRX1 levels were markedly higher in patients with AKI than in those with chronic kidney disease or in healthy subjects. In a receiver operating characteristic curve analysis to differentiate between AKI and other renal diseases, the area under the curve for urinary TRX1 was 0.94 (95% confidence interval, 0.90-0.98), and the sensitivity and specificity were 0.88 and 0.88, respectively, at the optimal cutoff value of 43.0 μg/g creatinine. Immunostaining revealed TRX1 to be diffusely distributed in the tubules of normal kidneys, but to be shifted to the brush borders or urinary lumen in injured tubules in both mice and humans with AKI. Urinary TRX1 in AKI was predominantly in the oxidized form. In cultured human proximal tubular epithelial cells, hydrogen peroxide specifically and dose dependently increased TRX1 levels in the culture supernatant, while reducing intracellular levels. These findings suggest that urinary TRX1 is an oxidative stress-specific biomarker useful for distinguishing AKI from chronic kidney disease and healthy kidneys.

Thioredoxin interacting protein and its association with clinical outcome in gastro-oesophageal adenocarcinoma

The overall prognosis for operable gastro-oesophageal adenocarcinoma remains poor and therefore neoadjuvant chemotherapy has become the standard of care, in addition to radical surgery. Certain anticancer agents (e.g. anthracyclines and cisplatin) generate damaging reactive oxygen species as by-products of their mechanism of action. Drug effectiveness can therefore depend upon the presence of cellular redox buffering systems that are often deregulated in cancer. The expression of the redox protein, thioredoxin interacting protein, was assessed in gastro-oesophageal adenocarcinomas. Thioredoxin interacting protein expression was assessed using conventional immunohistochemistry on a tissue microarray of 140 adenocarcinoma patients treated by primary surgery alone and 88 operable cases treated with neoadjuvant chemotherapy. In the primary surgery cases, high thioredoxin interacting protein expression associated with a lack of lymph node involvement (p=0.005), no perineural invasion (p=0.030) and well/moderate tumour differentiation (p=0.033). In the neoadjuvant tumours, high thioredoxin interacting protein expression was an independent marker for improved disease specific survival (p=0.002) especially in cases with anthracycline-based regimes (p=0.008). This study highlights the potential of thioredoxin interacting protein as a biomarker for response in neoadjuvant treated gastro-oesophageal adenocarcinoma and may represent a useful therapeutic target due to its association with tumour progression.

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In primary surgery cases, high TxNIP associates with disease progression markers.

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TxNIP expression is higher in tumours from chemotherapy treated patients.

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High TxNIP associates with improved survival in neoadjuvant treated cases.

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High TxNIP expression may be a biomarker for anthracycline based treatment.

The relationship of thioredoxin-1 and cisplatin resistance: its impact on ROS and oxidative metabolism in lung cancer cells

Elimination of cisplatin-resistant lung cancer cells remains a major obstacle. We have shown that cisplatin-resistant tumors have higher reactive oxygen species (ROS) levels and can be exploited for targeted therapy. Here, we show that increased secretion of the antioxidant thioredoxin-1 (TRX1) resulted in lowered intracellular TRX1 and contributed to higher ROS in cisplatin-resistant tumors in vivo and in vitro. By reconstituting TRX1 protein in cisplatin-resistant cells, we increased sensitivity to cisplatin but decreased sensitivity to elesclomol (ROS inducer). Conversely, decreased TRX1 protein in parental cells reduced the sensitivity to cisplatin but increased sensitivity to elesclomol. Cisplatin-resistant cells had increased endogenous oxygen consumption and mitochondrial activity but decreased lactic acid production. They also exhibited higher levels of argininosuccinate synthetase (ASS) and fumarase mRNA, which contributed to oxidative metabolism (OXMET) when compared with parental cells. Restoring intracellular TRX1 protein in cisplatin-resistant cells resulted in lowering ASS and fumarase mRNAs, which in turn sensitized them to arginine deprivation. Interestingly, cisplatin-resistant cells also had significantly higher basal levels of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). Overexpressing TRX1 lowered ACC and FAS proteins expressions in cisplatin-resistant cells. Chemical inhibition and short interfering RNA of ACC resulted in significant cell death in cisplatin-resistant compared with parental cells. Conversely, TRX1 overexpressed cisplatin-resistant cells resisted 5-(tetradecyloxy)-2-furoic acid (TOFA)-induced death. Collectively, lowering TRX1 expression through increased secretion leads cisplatin-resistant cells to higher ROS production and increased dependency on OXMET. These changes raise an intriguing therapeutic potential for future therapy in cisplatin-resistant lung cancer.

Activation of the phosphatidylinositol 3'-kinase/AKT pathway in neuroblastoma and its regulation by thioredoxin 1

Neuroblastoma is a malignant pediatric tumor with poor survival. The phosphatidylinositol 3'-kinase/AKT pathway is a crucial regulator of cellular processes including apoptosis. Thioredoxin 1, an inhibitor of tumor-suppressor phosphatase and tensin homolog, is overexpressed in many tumors. The objective of this study was to explore phosphatidylinositol 3'-kinase/AKT pathway activation and regulation by thioredoxin 1 to identify potential therapeutic targets. Immunohistochemical analysis was done on tissue microarrays from tumor samples of 101 patients, using antibodies against phosphatidylinositol 3'-kinase, AKT, activated AKT, phosphatase and tensin homolog, phosphorylated phosphatase and tensin homolog, thioredoxin 1, epidermal growth factor receptor, vascular endothelial growth factor and receptors (vascular endothelial growth factor 1 and vascular endothelial growth receptor 2), platelet-derived growth factor receptors, insulin-like growth factor 1 receptor, neurotrophic tyrosine kinase receptor type 2, phosphorylated 70-kd S6 protein kinase, 4E-binding protein 1, and phosphorylated mammalian target of rapamycin. Using 3 neuroblastoma cell lines, we investigated cell viability with AKT-specific inhibitors (LY294002, RAD001) and thioredoxin 1 alone or in combination. We found activated AKT and AKT expressed in 97% and 98%, respectively, of neuroblastomas, despite a high expression of phosphatase and tensin homolog correlated with thioredoxin 1. AKT expression was greater in metastatic than primary tumors. Insulin-like growth factor 1 receptor, tyrosine kinase receptor type 2, vascular endothelial growth receptor 1, and downstream phosphorylated 70-kd S6 protein kinase were correlated with activated AKT. LY294002 and RAD001 significantly reduced AKT activity and cell viability and induced a G(1) cell cycle arrest. Thioredoxin 1 decreased cytotoxicity of AKT inhibitors and doxorubicin, up-regulated AKT activation, and induced cell growth. Thus, vascular endothelial growth receptor 1, tyrosine kinase receptor type 2, insulin-like growth factor 1 receptor, and thioredoxin 1 emerged as preferentially committed to phosphatidylinositol 3'-kinase/AKT pathway activation as observed in neuroblastoma. Thioredoxin 1 is a potential target for therapeutic intervention.

Chloroethyl urea derivatives block tumour growth and thioredoxin-1 nuclear translocation

Aryl chloroethyl ureas (CEUs) are new protein alkylating agents exhibiting anticancer activity both in vitro and in vivo. We report herein that 14C-labeled CEU derivatives, designated CEU-025 and CEU-027, covalently bind to thioredoxin-1 (TRX1). Covalent binding of these molecules slightly decreases the disulfide-reducing activity of recombinant TRX1, when compared with the effect of strong thioalkylating agents such as N-ethylmaleimide. Moreover, site-directed mutagenesis and diamide competition assays demonstrated that TRX1 cysteinyl residues are not the prime targets of CEUs. CEU-025 abrogates the nuclear translocation of TRX1 in human cancer cells. In addition, we show that CEU-025 can block TRX1 nuclear translocation induced by cisplatin. Unexpectedly, pretreatment with sublethal CEU-025 concentrations that block TRX1 nuclear translocation protected the cells against cisplatin cytotoxicity. Overexpression of TRX1 in HT1080 fibrosarcoma cells attenuated CEU-025 cytotoxicity, while its suppression using TRX1-specific siRNA increased the effects of CEU-025, suggesting that loss of function of TRX1 is involved, at least in part, in the cytotoxic activity of CEU-025. These results suggest that CEU-025 and CEU-027 exhibit anticancer activity through a novel, unique mechanism of action. The importance of TRX1 and the dependence of the cytotoxicity of CEU-025 and CEU-027 on TRX1 intracellular localization are also discussed.

Role of glutathione in the regulation of Cisplatin resistance in cancer chemotherapy

Three mechanisms have been proposed for the role of glutathione (GSH) in regulating cisplatin (CDDP) sensitivities that affects its ultimate cell-killing ability: (i) GSH may serve as a cofactor in facilitating multidrug resistance protein 2- (MRP2-) mediated CDDP efflux in mammalian cells, since MRP2-transfected cells were shown to confer CDDP resistance; (ii) GSH may serve as a redox-regulating cytoprotector based on the observations that many CDDP-resistant cells overexpress GSH and γ-glutamylcysteine synthesis (γ-GCS), the rate-limiting enzyme for GSH biosynthesis; (iii) GSH may function as a copper (Cu) chelator. Elevated GSH expression depletes the cellular bioavailable Cu pool, resulting in upregulation of the high-affinity Cu transporter (hCtr1) which is also a CDDP transporter. This has been demonstrated that overexpression of GSH by transfection with γ-GCS conferred sensitization to CDDP toxicity. This review describes how these three models were developed and critically reviews their importance to overall CDDP cytotoxicity in cancer cell treatments.

Platinum transporters and drug resistance

Cisplatin, a platinum coordinated complex, is a widely used antineoplastic agent for the treatment of metastatic tumors of the testis, metastatic ovarian tumors, lung cancer, advanced bladder cancer and many other solid tumors. The cytotoxic action of the drug is often thought to be associated with its ability to bind DNA to form cisplatin-DNA adducts. The development of resistance to cisplatin during treatment is common and constitutes a major obstacle to the cure of sensitive tumors. Although to understand the clinically relevant mechanisms of resistance, many studies have been aimed at clarifying the biochemical/molecular alterations of cisplatin-resistance cells, these studies did not conclusively identify the basis of cellular resistance to cisplatin. In this review, cisplatin resistance was discussed in terms of the relevant transporters, such as copper transporters (CTRs), organic cation transporters (OCTs) and multi-drug resistance related transporters (MDRs). These transporters seem to be contributed to cisplatin resistance through the reduction of drug accumulation in the cell. Better understanding the mechanism of cisplatin resistance associated with transporters will provide the useful informations for overcoming the cisplatin resistance.

Cysteine-dependent immune regulation by TRX and MIF/GIF family proteins

Thioredoxin (TRX) superfamily proteins that contain a conserved redox-active site -Cys-Xa.a.-Xa.a.-Cys- includes proinflammatory cytokine, macrophage migration inhibiting factor (MIF) and the immune regulatory cytokine, glycosylation inhibiting factor (GIF) in which Cys-60 is cysteinylated. In this report, we have analyzed the functional interaction between TRX and MIF/GIF. The stable Jurkat T cell line transfected with human TRX gene (TRX-transfectant) was highly resistant to hydrogen peroxide-induced apoptosis, but not the cell line transfected with vector (mock-transfectant). The expression level of MIF/GIF protein of TRX-transfectant was lower than that of mock-transfectant. Conversely, the expression level of intracellular TRX protein in CD4(+)-T cells derived from MIF -/- mice were significantly higher than that from background BALB/c mice. These findings collectively suggest that oxidative stress-induced apoptosis on T lymphocytes might be protected by the reciprocal regulation of TRX and MIF/GIF expression.

The mammalian testis-specific thioredoxin system

Redox control of cell physiology is one of the most important regulatory mechanisms in all living organisms. The thioredoxin system, composed of thioredoxin and thioredoxin reductase, has emerged as a key player in cellular redox-mediated reactions. For many years, only one thioredoxin system had been described in higher organisms, ubiquitously expressed in the cytoplasm of eukaryotic cells. However, during the last decade, we and others have identified and characterized novel thioredoxin systems with unique properties, such as organelle-specific localization in mitochondria or endoplasmic reticulum, tissue-specific distribution mostly in the testis, and features novel for thioredoxins, such as microtubule-binding properties. In this review, we will focus on the mammalian testis-specific thioredoxin system that comprises three thioredoxins exclusively expressed in spermatids (named Sptrx-1, Sptrx-2, and Sptrx-3) and an additional thioredoxin highly expressed in testis, but also present in lung and other ciliated tissues (Txl-2). The implications of these findings in the context of male fertility and testicular cancer, as well as evolutionary aspects, will be discussed.

Redox-Sensing Release of Human Thioredoxin from T Lymphocytes with Negative Feedback Loops

Thioredoxin (TRX) is released from various types of mammalian cells despite no typical secretory signal sequence. We show here that a redox-active site in TRX is essential for its release from T lymphocytes in response to H2O2 and extracellular TRX regulates its own H2O2-induced release. Human T cell leukemia virus type I-transformed T lymphocytes constitutively release a large amount of TRX. The level of TRX release is augmented upon the addition of H2O2, but suppressed upon the addition of N-acetylcysteine. In the culture supernatant of a Jurkat transfectant expressing the tagged TRX-wild type (WT), the tagged TRX protein is rapidly released at 1 h and kept at a constant level until 6 h after the addition of H2O2. In contrast, another type of transfectant expressing the tagged TRX mutant (C32S/C35S; CS) fails to release the protein. H2O2-induced release of TRX from the transfectant is inhibited by the presence of rTRX-WT in a dose-dependent manner. Preincubation of the transfectant with rTRX-WT for 1 h at 37 degrees C, but not 0 degrees C, results in a significant suppression of the TRX release, reactive oxygen species, and caspase-3 activity induced by H2O2, respectively. Confocal microscopy and Western blot analysis show that extracellular rTRX-WT added to the culture does not obviously enter T lymphocytes until 24 h. These results collectively suggest that the oxidative stress-induced TRX release from T lymphocytes depends on a redox-sensitive event and may be regulated by negative feedback loops using reactive oxygen species-mediated signal transductions.