Properties and biological activities of thioredoxins

Thioredoxin System Protein Expression in Carcinomas of the Pancreas, Distal Bile Duct, and Ampulla in the United Kingdom

Background: Poor survival outcomes in periampullary cancer highlight the need for improvement in biomarkers and the development of novel therapies. Redox proteins, including the thioredoxin system, play vital roles in cellular antioxidant systems. Methods: In this retrospective study, thioredoxin (Trx), thioredoxin-interacting protein (TxNIP), and thioredoxin reductase (TrxR) protein expression was assessed in 85 patients with pancreatic ductal adenocarcinoma (PDAC) and 145 patients with distal bile duct or ampullary carcinoma using conventional immunohistochemistry. Results: In patients with PDAC, high cytoplasmic TrxR expression was significantly associated with lymph node metastasis (p = 0.033). High cytoplasmic and nuclear Trx expression was significantly associated with better overall survival (p = 0.018 and p = 0.006, respectively), and nuclear Trx expression remained significant in multivariate Cox regression analysis (p < 0.0001). In distal bile duct and ampullary carcinomas, high nuclear TrxR expression was associated with vascular (p = 0.001) and perineural (p = 0.021) invasion, and low cytoplasmic TxNIP expression was associated with perineural invasion (p = 0.025). High cytoplasmic TxNIP expression was significantly associated with better overall survival (p = 0.0002), which remained significant in multivariate Cox regression analysis (p = 0.013). Conclusions: These findings demonstrate the prognostic importance of Trx system protein expression in periampullary cancers.

Influence of Redox-Active Chitosan-Polyaminoxyl Micelles Loaded with Daunorubicin on Activity of Nrf2 Transcription Factor

A new system for delivery of anthracycline antibiotics based on chitosan-polyaminoxyls (CPA) was studied in a model of non-tumor (human embryonic mesenchymal stem cells) and tumor cells (human hepatocellular carcinoma) in vitro. The presence of CPA micelles considerably suppresses daunorubicin-induced ROS generation in normal cells without affecting this process in tumor cells. CPA micelles do not reduce the cytotoxic effect of daunorubicin and do not prevent its accumulation in cells. The use of CPA significantly increases accumulation of Nrf2 transcription factor in the nuclei of both normal and tumor cells in comparison with free daunorubicin. Increased nuclear translocation of Nrf2 leads to a significant increase in the expression of its target gene TXN1, but not the NQO1, GPX1, and HMOX1 genes, the increased expression of which can lead to the development of resistance to anthracycline antibiotics. Redox-active CPA micelles have great potential for the development of nanoparticles for the transport of anthracycline antibiotics in experimental tumor chemotherapy, and also as promising activators of Nrf2 transcription factor.

Molecular identification of two thioredoxin genes and their function in antioxidant defense in Arma chinensis diapause

Thioredoxin (Trx), an important part of thioredoxin systems, plays crucial role in maintaining the intracellular redox balance by scavenging reactive oxygen species (ROS). However, few Trxs have been functionally characterized in Arma chinensis, especially in diapause. In this study, diapause induction condition promoted hydrogen peroxide accumulation and increased CAT enzymatic activity and ascorbate content, suggesting that A. chinensis was exposed to high level of ROS. Therefore, we identified AcTrx2 and AcTrx-like, and investigated the relationship with antioxidant defense. It was found that AcTrx2 expression was significantly induced, whereas AcTrx-like expression was the highest on day 10 under diapause conditions. The expression of AcTrx2 and AcTrx-like in fat body, a central metabolic organ of resisting oxidative stress, was significantly increased under diapause conditions, and was significantly improved by 5/15°C (diapause temperature). We investigated the knockdown of AcTrx2 and AcTrx-like in A. chinensis and found that some selected antioxidant genes were upregulated, indicating that the upregulated genes may be functional compensation for AcTrx2 and AcTrx-like silencing. We also found that the enzymatic activities of SOD and CAT, and the metabolite contents of hydrogen peroxide, ascorbate increased after AcTrx2 and AcTrx-like knockdown. These results suggested the AcTrx2 and AcTrx-like may play critical roles in antioxidant defense of A. chinensis diapause.

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.

CdbC: a disulfide bond isomerase involved in the refolding of mycoloyltransferases in Corynebacterium glutamicum cells exposed to oxidative conditions

In Corynebacterium glutamicum cells, cdbC, which encodes a protein containing the CysXXCys motif, is regulated by the global redox-responsive regulator OsnR. In this study, we assessed the role of the periplasmic protein CdbC in disulfide bond formation and its involvement in mycomembrane biosynthesis. Purified CdbC efficiently refolded scrambled RNaseA, exhibiting prominent disulfide bond isomerase activity. The transcription of cdbC was decreased in cells grown in the presence of the reductant dithiothreitol (DTT). Moreover, unlike wild-type and cdbC-deleted cells, cdbC-overexpressing (P180-cdbC) cells grown in the presence of DTT exhibited retarded growth, abnormal cell morphology, increased cell surface hydrophobicity and altered mycolic acid composition. P180-cdbC cells cultured in a reducing environment accumulated trehalose monocorynomycolate, indicating mycomembrane deformation. Similarly, a two-hybrid analysis demonstrated the interaction of CdbC with the mycoloyltransferases MytA and MytB. Collectively, our findings suggest that CdbC, a periplasmic disulfide bond isomerase, refolds misfolded MytA and MytB and thereby assists in mycomembrane biosynthesis in cells exposed to oxidative conditions.

Three-dimensional solution structure, dynamics and binding of thioredoxin m from Pisum sativum

Thioredoxins (TRXs) are ubiquitous small, globular proteins involved in cell redox processes. In this work, we report the solution structure of TRX m from Pisum sativum (pea), which has been determined on the basis of 1444 nuclear Overhauser effect- (NOE-) derived distance constraints. The average pairwise root-mean-square deviation (RMSD) for the 20 best structures for the backbone residues (Val7-Glu102) was 1.42 ± 0.15 Å, and 1.97 ± 0.15 Å when all heavy atoms were considered. The structure corresponds to the typical fold of TRXs, with a central five-stranded β-sheet flanked by four α-helices. Some residues had an important exchange dynamic contribution: those around the active site; at the C terminus of β-strand 3; and in the loop preceding α-helix 4. Smaller NOE values were observed at the N and C-terminal residues forming the elements of the secondary structure or, alternatively, in the residues belonging to the loops between those elements. A peptide derived from pea fructose-1,6-biphosphatase (FBPase), comprising the preceding region to the regulatory sequence of FBPase (residues Glu152 to Gln179), was bound to TRX m with an affinity in the low micromolar range, as measured by fluorescence and NMR titration experiments. Upon peptide addition, the intensities of the cross-peaks of all the residues of TRX m were affected, as shown by NMR. The value of the dissociation constant of the peptide from TRX m was larger than that of the intact FBPase, indicating that there are additional factors in other regions of the polypeptide chain of the latter protein affecting the binding to thioredoxin.

The Importance of Thioredoxin-1 in Health and Disease

Thioredoxin-1 (Trx-1) is a multifunctional protein ubiquitously found in the human body. Trx-1 plays an important role in various cellular functions such as maintenance of redox homeostasis, proliferation, and DNA synthesis, but also modulation of transcription factors and control of cell death. Thus, Trx-1 is one of the most important proteins for proper cell and organ function. Therefore, modulation of Trx gene expression or modulation of Trx activity by various mechanisms, including post-translational modifications or protein-protein interactions, could cause a transition from the physiological state of cells and organs to various pathologies such as cancer, and neurodegenerative and cardiovascular diseases. In this review, we not only discuss the current knowledge of Trx in health and disease, but also highlight its potential function as a biomarker.

Effect of evernic acid on human breast cancer MCF-7 and MDA-MB-453 cell lines via thioredoxin reductase 1: A molecular approach

Thioredoxin reductase 1 (TrxR1) has emerged as an important target for anticancer drug development due to its overexpression in many human tumors including breast cancer. Due to the serious side effects of currently used commercial anticancer drugs, new natural compounds with very few side effects and high efficacy are of great importance in cancer treatment. Lichen secondary metabolites, known as natural compounds, have diverse biological properties, including antioxidant and anticancer activities. Herein, we aimed to determine the potential antiproliferative, antimigratory, and apoptotic effects of evernic acid, a lichen secondary metabolite, on breast cancer MCF-7 and MDA-MB-453 cell lines and afterward to investigate whether its anticancer effect is exerted by TrxR1-targeting. The cytotoxicity results indicated that evernic acid suppressed the proliferation of MCF-7 and MDA-MB-453 cells in a dose-dependent manner and the IC₅₀ values were calculated as 33.79 and 121.40 μg/mL, respectively. Migration assay results revealed the notable antimigratory ability of evernic acid against both cell types. The expression of apoptotic markers Bcl2 associated X, apoptosis regulator, Bcl2 apoptosis regulator, and tumor protein p53 by quantitative real-time polymerase chain reaction and western blot analysis showed that evernic acid did not induce apoptosis in both cell lines, consistent with flow cytometry results. Evernic acid showed its anticancer effect via inhibiting TrxR1 enzyme activity rather than mRNA and protein expression levels in both cell lines. In conclusion, these findings suggest that evernic acid has the potential to be evaluated as a therapeutic agent in breast cancer treatment.

Low-dose arsenite causes overexpression of EGF, TGFα, and HSP90 through Trx1-TXNIP-NLRP3 axis mediated signaling pathways in the human bladder epithelial cells

Epidemiological studies have demonstrated an increased incidence of bladder cancer in arseniasis- endemic areas; however, the precise molecular mechanisms remain unknown. Our previous results have shown that the protein levels of EGF, TGFα, and HSP90 in arsenite-treated bladder uroepithelial cells increased markedly and contributed to hyperactivation of EGF receptors. The aim of this study was to further explore the regulatory ways underlying overexpression of EGF, TGFα, and HSP90 in these cells. The present results showed that both Trx and GSH systems were stimulated in arsenite-treated cells, and ROS levels in 2 μM arsenite-treated cells did not changed obviously; however, ROS levels in 4 μM arsenite-treated cells increased significantly. By using the antioxidant and specific inhibitors, we found that in 2 μM arsenite-treated cells, JNK/NF-κB signaling pathway was involved in overexpression of EGF and TGFα, and ERK/NF-κB signaling pathway contributed to HSP90 overexpression, however in 4 μM arsenite-treated cells, both ERK/ and JNK/NF-κB signaling pathways were involved in overexpression of EGF, TGFα, and HSP90, and PI3K/AKT/NF-κB signaling pathway contributed to overexpression of EGF and TGFα. Furthermore, our results also showed that the Trx1-TXNIP-NLRP3 axis was activated in arsenite-treated cells, and played a pivotal role in activation of the signaling pathways involved in overexpression of EGF, TGFα, and HSP90. In conclusion, the Trx1-TXNIP-NLRP3 axis might be activated by arsenite-induced redox imbalance in bladder uroepithelial cells, and mediate the activation of signaling pathways involved in overexpression of EGF, TGFα, and HSP90.

The adipocyte-enriched secretory protein tetranectin exacerbates type 2 diabetes by inhibiting insulin secretion from β cells

Pancreatic β cell failure is a hallmark of diabetes. However, the causes of β cell failure remain incomplete. Here, we report the identification of tetranectin (TN), an adipose tissue-enriched secretory molecule, as a negative regulator of insulin secretion in β cells in diabetes. TN expression is stimulated by high glucose in adipocytes via the p38 MAPK/TXNIP/thioredoxin/OCT4 signaling pathway, and elevated serum TN levels are associated with diabetes. TN treatment greatly exacerbates hyperglycemia in mice and suppresses glucose-stimulated insulin secretion in islets. Conversely, knockout of TN or neutralization of TN function notably improves insulin secretion and glucose tolerance in high-fat diet-fed mice. Mechanistically, TN binds with high selectivity to β cells and inhibits insulin secretion by blocking L-type Ca²⁺ channels. Our study uncovers an adipocyte-β cell cross-talk that contributes to β cell dysfunction in diabetes and suggests that neutralization of TN levels may provide a new treatment strategy for type 2 diabetes.

Identification and characterization of Eimeria tenella EtTrx1 protein

Thioredoxin (Trx) is a widespread protein regulator of redox reactions in all organisms. It operates together with NADPH and thioredoxin reductase as a general protein disulfide catalytic system. Recently, Trx has been found to be related to the process by which apicomplexan protozoa invade host cells. In this study, Eimeria tenella thioredoxin (EtTrx1) was identified and its gene structural features, expression levels at different developmental stages, localization in sporozoites, roles in adhesion and invasion, and immunogenicity were investigated. Sequence analysis indicated that EtTrx1 contains a Trx domain with a WCGPC motif in 29-33 aa and a typical Trx fold, and belongs to thioredoxin family. EtTrx1 was detected on the surface of sporozoites using anti-EtTrx1 polyclonal antibodies under non-permeabilized conditions by indirect immunofluorescence assay (IFA) and also in a secretion form. EtTrx1 protein was highly transcribed and expressed in merozoites and sporozoites by quantitative PCR and western blot. The attachment assay showed that the adherence rates of yeast cells expressing EtTrx1 on the surface to host cells were 3.1-fold higher than those of the blank control. Specific anti-EtTrx1 antibodies inhibited the invasion of sporozoites into DF-1 cells. The highest inhibition rate was up to 36.75% compared to the control group. Immunization with recombinant EtTrx1 peptides also showed significant protection against lethal infections in chickens. It could offer moderate protective efficacy (Anticoccidial Index [ACI]: 163.70), induce humoral responses, and be an effective candidate for the development of new vaccines.

Helicobacter pylori Thioredoxin1 May Play a Highly Pathogenic Role via the IL6/STAT3 Pathway

Background

Recent studies have shown that CagA is considered highly pathogenic to helicobacter pylori (HP) in Western populations. However, in East Asia, CagA positive HP can be up to 90%, but not all patients will lead to gastric cancer. Our research group has found that HP thioredoxin1 (Trx1) may be a marker of high pathogenicity. Here, we investigate whether HP Trx1 exerts high pathogenicity and its internal molecular mechanism.

Materials and Methods

We constructed the coculture system of high-Trx1 HP and low-Trx1 HP strains with gastric epithelial cell lines separately and detected the influence of HP strains. The cells were stained by AM/PI, and the cell's mortality was assessed by fluorescence microscope. The cell's supernatants or precipitates were collected to detect the expression of IL6. In addition, the cell's precipitates were collected, and the expression of p-STAT3 was detected by western blot. Furthermore, the cell's supernatants were collected for detecting the expression of 8-OHDG to investigate the extent of DNA damage.

Results

The high-Trx1 HP can cause higher mortality of GES-1 cells compared with the low-Trx1 HP group (high-Trx1 HP (4.53 ± 0.56) %, low-Trx1 HP (0.39 ± 0.10) %, P < 0.001). The mRNA and protein level of IL-6 in AGS and GES-1 cells were increased during HP infection, and the expression of IL-6 in the High-Trx1 HP group was much higher than the low-Trx1 HP group. Besides, the expression of p-STAT3 was higher in the HP-positive gastric mucosa. And the expression of p-STAT3 in the high-Trx1 HP group was significantly upregulated compared with the low-Trx1 HP group. Furthermore, the expression of 8-OHDG in the high-Trx1 group was much higher than the low-Trx1 group (high-Trx1 HP (5.47 ± 1.73) ng/ml, low-Trx1 HP (2.89 ± 1.72) ng/ml, P < 0.05).

Conclusion

HP Trx1 may play as a marker of high pathogenicity, and the high-Trx1 HP could mediate the pathogenic process of HP infection via the IL6/STAT3 pathway.

TXN inhibitor impedes radioresistance of colorectal cancer cells with decreased ALDH1L2 expression via TXN/NF-κB signaling pathway

Background

Colorectal cancer (CRC) is prevalent worldwide and is often challenged by treatment failure and recurrence due to resistance to radiotherapy. Here, we aimed to identify the elusive underlying molecular mechanisms of radioresistance in CRC.

Methods

Weighted gene co-expression network analysis was used to identify potential radiation-related genes. Colony formation and comet assays and multi-target single-hit survival and xenograft animal models were used to validate the results obtained from the bioinformatic analysis. Immunohistochemistry was performed to examine the clinical characteristics of ALDH1L2. Co-immunoprecipitation, immunofluorescence and flow cytometry were used to understand the molecular mechanisms underlying radioresistance.

Results

Bioinformatic analysis, in vitro, and in vivo experiments revealed that ALDH1L2 is a radiation-related gene, and a decrease in its expression induces radioresistance in CRC cells by inhibiting ROS-mediated apoptosis. Patients with low ALDH1L2 expression exhibit resistance to radiotherapy. Mechanistically, ALDH1L2 interacts with thioredoxin (TXN) and regulates the downstream NF-κB signaling pathway. PX-12, the TXN inhibitor, overcomes radioresistance due to decreased ALDH1L2.

Conclusions

Our results provide valuable insights into the potential role of ALDH1L2 in CRC radiotherapy. We propose that the simultaneous application of TXN inhibitors and radiotherapy would significantly ameliorate the clinical outcomes of patients with CRC having low ALDH1L2.

Intrinsic disorder in proteins associated with oxidative stress-induced JNK signaling

The c-Jun N-terminal kinase (JNK) signaling cascade is a mitogen-activated protein kinase (MAPK) signaling pathway that can be activated in response to a wide range of environmental stimuli. Based on the type, degree, and duration of the stimulus, the JNK signaling cascade dictates the fate of the cell by influencing gene expression through its substrate transcription factors. Oxidative stress is a result of a disturbance in the pro-oxidant/antioxidant homeostasis of the cell and is associated with a large number of diseases, such as neurodegenerative disorders, cancer, diabetes, cardiovascular diseases, and disorders of the immune system, where it activates the JNK signaling pathway. Among different biological roles ascribed to the intrinsically disordered proteins (IDPs) and hybrid proteins containing ordered domains and intrinsically disordered protein regions (IDPRs) are signaling hub functions, as intrinsic disorder allows proteins to undertake multiple interactions, each with a different consequence. In order to ensure precise signaling, the cellular abundance of IDPs is highly regulated, and mutations or changes in abundance of IDPs/IDPRs are often associated with disease. In this study, we have used a combination of six disorder predictors to evaluate the presence of intrinsic disorder in proteins of the oxidative stress-induced JNK signaling cascade, and as per our findings, none of the 18 proteins involved in this pathway are ordered. The highest level of intrinsic disorder was observed in the scaffold proteins, JIP1, JIP2, JIP3; dual specificity phosphatases, MKP5, MKP7; 14-3-3ζ and transcription factor c-Jun. The MAP3Ks, MAP2Ks, MAPKs, TRAFs, and thioredoxin were the proteins that were predicted to be moderately disordered. Furthermore, to characterize the predicted IDPs/IDPRs in the proteins of the JNK signaling cascade, we identified the molecular recognition features (MoRFs), posttranslational modification (PTM) sites, and short linear motifs (SLiMs) associated with the disordered regions. These findings will serve as a foundation for experimental characterization of disordered regions in these proteins, which represents a crucial step for a better understanding of the roles of IDPRs in diseases associated with this important pathway.

Improved Red Fluorescent Redox Indicators for Monitoring Cytosolic and Mitochondrial Thioredoxin Redox Dynamics

Thioredoxin (Trx) is one of the major thiol-dependent antioxidants in living systems. The study of Trx functions in redox biology was impeded by the lack of practical tools to track Trx redox dynamics in live cells. Our previous work developed TrxRFP1, the first genetically encoded fluorescent indicator for Trx redox. In this work, we report an improved fluorescent indicator, TrxRFP2, for tracking the redox of Trx1, which is primarily cytosolic and nuclear. Furthermore, because mitochondria specifically express Trx2, we have created a new genetically encoded fluorescent indicator, MtrxRFP2, for the redox of mitochondrial Trx. We characterized MtrxRFP2 as a purified protein and used subcellularly localized MtrxRFP2 to image mitochondrial redox changes in live cells.

Au-24 as a Potential Thioredoxin Reductase Inhibitor in Hepatocellular Carcinoma Cells

A novel TrxR inhibitor Au-24 and its inhibitory ability to hepatocellular carcinoma in vitro and in vivo is reported herein. Au-24 can suppress HepG2 cells from proliferating by lowering mitochondrial membrane potential (MMP) and increasing reactive oxygen species (ROS) levels, resulting in oxidative stress, which causes DNA damage, autophagy, cell cycle arrest, and apoptosis. This compound can also affect the normal function of apoptosis, MAPK, PI3K/AKT/mTOR, NF-κB, STAT3 signaling pathways. In vivo experiments revealed that Au-24 inhibited HepG2 tumor growth more effectively than AA1 (chloro(triethylphosphine)gold(I)) by decreasing Ki67 and CD31 protein expression and promoting tumor cell apoptosis and necrosis lesions. As a result, Au-24 was found to be a promising candidate as a TrxR inhibitor for the treatment of hepatocellular carcinoma (HCC) in both in vivo and in vitro experiments.

OsnR is an autoregulatory negative transcription factor controlling redox-dependent stress responses in Corynebacterium glutamicum

Background

Corynebacterium glutamicum is used in the industrial production of amino acids and nucleotides. During the course of fermentation, C. glutamicum cells face various stresses and employ multiple regulatory genes to cope with the oxidative stress. The osnR gene plays a negative regulatory role in redox-dependent oxidative-stress responses, but the underlying mechanism is not known yet.

Results

Overexpression of the osnR gene in C. glutamicum affected the expression of genes involved in the mycothiol metabolism. ChIP-seq analysis revealed that OsnR binds to the promoter region of multiple genes, including osnR and cg0026, which seems to function in the membrane-associated redox metabolism. Studies on the role of the osnR gene involving in vitro assays employing purified OsnR proteins and in vivo physiological analyses have identified that OsnR inhibits the transcription of its own gene. Further, oxidant diamide stimulates OsnR-binding to the promoter region of the osnR gene. The genes affected by the overexpression of osnR have been found to be under the control of σ^H. In the osnR-overexpressing strain, the transcription of sigH is significantly decreased and the stimulation of sigH transcription by external stress is lost, suggesting that osnR and sigH form an intimate regulatory network.

Conclusions

Our study suggests that OsnR not only functions as a transcriptional repressor of its own gene and of those involved in redox-dependent stress responses but also participates in the global transcriptional regulation by controlling the transcription of other master regulators, such as sigH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01693-1.

NADPH debt drives redox bankruptcy: SLC7A11/xCT-mediated cystine uptake as a double-edged sword in cellular redox regulation

Cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11; also known as xCT) plays a key role in antioxidant defense by mediating cystine uptake, promoting glutathione synthesis, and maintaining cell survival under oxidative stress conditions. Recent studies showed that, to prevent toxic buildup of highly insoluble cystine inside cells, cancer cells with high expression of SLC7A11 (SLC7A11^high) are forced to quickly reduce cystine to more soluble cysteine, which requires substantial NADPH supply from the glucose-pentose phosphate pathway (PPP) route, thereby inducing glucose- and PPP-dependency in SLC7A11^high cancer cells. Limiting glucose supply to SLC7A11^high cancer cells results in significant NADPH “debt”, redox “bankruptcy”, and subsequent cell death. This review summarizes our current understanding of NADPH-generating and -consuming pathways, discusses the opposing role of SLC7A11 in protecting cells from oxidative stress–induced cell death such as ferroptosis but promoting glucose starvation–induced cell death, and proposes the concept that SLC7A11-mediated cystine uptake acts as a double-edged sword in cellular redox regulation. A detailed understanding of SLC7A11 in redox biology may identify metabolic vulnerabilities in SLC7A11^high cancer for therapeutic targeting.

Micro RNAs in Regulation of Cellular Redox Homeostasis

In living cells Reactive Oxygen Species (ROS) participate in intra- and inter-cellular signaling and all cells contain specific systems that guard redox homeostasis. These systems contain both enzymes which may produce ROS such as NADPH-dependent and other oxidases or nitric oxide synthases, and ROS-neutralizing enzymes such as catalase, peroxiredoxins, thioredoxins, thioredoxin reductases, glutathione reductases, and many others. Most of the genes coding for these enzymes contain sequences targeted by micro RNAs (miRNAs), which are components of RNA-induced silencing complexes and play important roles in inhibiting translation of their targeted messenger RNAs (mRNAs). In this review we describe miRNAs that directly target and can influence enzymes responsible for scavenging of ROS and their possible role in cellular redox homeostasis. Regulation of antioxidant enzymes aims to adjust cells to survive in unstable oxidative environments; however, sometimes seemingly paradoxical phenomena appear where oxidative stress induces an increase in the levels of miRNAs which target genes which are supposed to neutralize ROS and therefore would be expected to decrease antioxidant levels. Here we show examples of such cellular behaviors and discuss the possible roles of miRNAs in redox regulatory circuits and further cell responses to stress.

Thioredoxin Delays Photoreceptor Degeneration, Oxidative and Inflammation Alterations in Retinitis Pigmentosa

Retinitis pigmentosa (RP) is an inherited ocular disorder with no effective treatment. RP onset and progression trigger a cascade of retinal disorders that lead to the death of photoreceptors. After photoreceptors death, neuronal, glial and vascular remodeling can be observed in the retina. The purpose of this study was to study if thioredoxin (TRX) administration is able to decrease photoreceptor death in an animal model of RP (rd1 mouse), but also if it is able to modulate the retinal oxidative stress, glial and vascular changes that can be observed as the disease progresses. Wild type and rd1 mice received several doses of TRX. After treatment, animals were euthanized at postnatals days 11, 17, or 28. Glutathione (GSH) and other thiol compounds were determined by high performance liquid chromatography (HPLC). Glial fibrilary acidic protein (GFAP) and anti-ionized calcium binding adaptor molecule 1 (Iba1) were studied by immunohistochemistry. Vascular endothelial growth factor (VEGF) and hepatic growth factor (HGF) expression were determined by western blot. TRX administration significantly diminished cell death in rd1 mouse retinas and increased GSH retinal concentrations at postnatal day 11 (PN11). TRX was also able to reverse glial alterations at PN11 and PN17. No alterations were observed in retinal VEGF and HGF expression in rd1 mice. In conclusion, TRX treatment decreases photoreceptor death in the first stages of RP and this protective effect may be due in part to the GSH system activation and to a partially decrease in inflammation.

SOD2 deficiency-induced oxidative stress attenuates steroidogenesis in mouse ovarian granulosa cells

This study investigated the effects of SOD2 (MnSOD)-deficiency-induced excessive oxidative stress on ovarian steroidogenesis in vivo and isolated and cultured granulosa cells using WT and Sod2+/- mice. Basal and 48 h eCG-stimulated plasma progesterone levels were decreased ~50% in female Sod2+/- mice, whereas plasma progesterone levels were decreased ~70% in Sod2+/- mice after sequential stimulation with eCG followed by hCG. Sod2+/- deficiency caused about 50% reduction in SOD2 activity in granulosa cells. SOD2-deficiency also caused a marked reduction in progestins and estradiol in isolated granulosa cells. qRT-PCR measurements indicated that the mRNA expression levels of StAR protein and steroidogenic enzymes are decreased in the ovaries of Sod2+/- mice. Further studies showed a defect in the movement of mobilized cytosolic cholesterol to mitochondria. The ovarian membrane from Sod2+/- mice showed higher susceptibility to lipid peroxidation. These data indicates that SOD2-deficiency induced oxidative stress inhibits ovarian granulosa cell steroidogenesis primarily by interfering with cholesterol transport to mitochondria and attenuating the expression of Star protein gene and key steroidogenic enzyme genes.

Thioredoxin-1 attenuates atherosclerosis development through inhibiting NLRP3 inflammasome

BACKGROUNDS

The thioredoxin-1 has atheroprotective effects via regulating oxidative stress and inflammation. In addition, the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome also contributes to atherosclerosis development. However, whether the thioredoxin-1 suppresses atherosclerosis development by modulating the NLRP3 inflammasome remains unclear.

METHODS

The regulation of NLRP3 inflammasome by thioredoxin-1 was determined in vitro on macrophage cells after ox-LDL (oxidized low-density lipoprotein) stimulation. The IL-1β and caspase-1 p10 secretion were assessed by ELISA and western blot. Finally, the thioredoxin-1/NLRP3 inflammasome pathway was confirmed in apolipoprotein E-deficient mice.

RESULTS

Thioredoxin-1 suppressed the expression of NLRP3, the secretion of IL-1β and caspase-1 p10 in vitro. And ROS stimulation activated the NLRP3 inflammasome which was inhibited by thioredoxin-1. In the mouse model of atherosclerosis, thioredoxin-1 delivered by lentivirus vector inhibited atherosclerosis development. And the atheroprotective effects of thioredoxin-1 were attenuated by ROS stimulation. Furthermore, the regulation of NLRP3 inflammasome by thioredoxin-1 was also confirmed in vivo.

CONCLUSIONS

We demonstrated here that the thioredoxin-1 had atheroprotective functions through thioredoxin-1/NLRP3 inflammasome pathway.

Thioredoxin Decreases Anthracycline Cardiotoxicity, But Sensitizes Cancer Cell Apoptosis

Cardiotoxicity is a major limitation for anthracycline chemotherapy although anthracyclines are potent antitumor agents. The precise mechanism underlying clinical heart failure due to anthracycline treatment is not fully understood, but is believed to be due, in part, to lipid peroxidation and the generation of free radicals by anthracycline-iron complexes. Thioredoxin (Trx) is a small redox-active antioxidant protein with potent disulfide reductase properties. Here, we present evidence that cancer cells overexpressing Trx undergo enhanced apoptosis in response to daunomycin. In contrast, cells overexpressing redox-inactive mutant Trx were not effectively killed. However, rat embryonic cardiomyocytes (H9c2 cells) overexpressing Trx were protected against daunomycin-mediated apoptosis, but H9c2 cells with decreased levels of active Trx showed enhanced apoptosis in response to daunomycin. We further demonstrate that increased level of Trx is specifically effective in anthracycline toxicity, but not with other topoisomerase II inhibitors such as etoposide. Collectively these data demonstrate that whereas high levels of Trx protect cardiomyocytes against anthracycline toxicity, it potentiates toxicity of anthracyclines in cancer cells.

Circuits Regulating Superoxide and Nitric Oxide Production and Neutralization in Different Cell Types: Expression of Participating Genes and Changes Induced by Ionizing Radiation

Superoxide radicals, together with nitric oxide (NO), determine the oxidative status of cells, which use different pathways to control their levels in response to stressing conditions. Using gene expression data available in the Cancer Cell Line Encyclopedia and microarray results, we compared the expression of genes engaged in pathways controlling reactive oxygen species and NO production, neutralization, and changes in response to the exposure of cells to ionizing radiation (IR) in human cancer cell lines originating from different tissues. The expression of NADPH oxidases and NO synthases that participate in superoxide radical and NO production was low in all cell types. Superoxide dismutase, glutathione peroxidase, thioredoxin, and peroxiredoxins participating in radical neutralization showed high expression in nearly all cell types. Some enzymes that may indirectly influence superoxide radical and NO levels showed tissue-specific expression and differences in response to IR. Using fluorescence microscopy and specific dyes, we followed the levels and the distribution of superoxide and NO radicals in living melanoma cells at different times after exposure to IR. Directly after irradiation, we observed an increase of superoxide radicals and NO coexistent in the same subcellular locations, suggesting a switch of NO synthase to the production of superoxide radicals.

The Thioredoxin System: A Promising Target for Cancer Drug Development

The thioredoxin system is highly conserved system found in all living cells and comprises NADPH, thioredoxin, and thioredoxin reductase. This system plays a critical role in preserving a reduced intracellular environment, and its involvement in regulating a wide range of cellular functions makes it especially vital to cellular homeostasis. Its critical role is not limited to healthy cells, it is also involved in cancer development, and is overexpressed in many cancers. This makes the thioredoxin system a promising target for cancer drug development. As such, over the last decade, many inhibitors have been developed that target the thioredoxin system, most of which are small molecules targeting the thioredoxin reductase C-terminal redox center. A few inhibitors of thioredoxin have also been developed. We believe that more efforts should be invested in developing protein/peptide-based inhibitors against both thioredoxin reductase and/or thioredoxin.

Enhanced expression of nicotinamide nucleotide transhydrogenase (NNT) and its role in a human T cell line continuously exposed to asbestos

The effects of asbestos fibers on human immune cells have not been well documented. We have developed a continuously exposed cell line model using the human T-lymphotropic virus 1 (HTLV-1)-immortalized human T cell line MT-2. Sublines continuously exposed to chrysotile (CH) or crocidolite (CR) showed acquired resistance to asbestos-induced apoptosis following transient and high-dose re-exposure with fibers. These sublines in addition to other immune cells such as natural killer cells or cytotoxic T lymphocytes exposed to asbestos showed a reduction in anti-tumor immunity. In this study, the expression of genes and molecules related to antioxidative stress was examined. Furthermore, complexes related to oxidative phosphorylation were investigated since the production of reactive oxygen species (ROS) is important when considering the effects of asbestos in carcinogenesis and the mechanisms involved in resistance to asbestos-induced apoptosis. In sublines continuously exposed to CH or CR, the expression of thioredoxin decreased. Interestingly, nicotinamide nucleotide transhydrogenase (NNT) expression was markedly enhanced. Thus, knockdown of NNT was then performed. Although the knockdown clones did not show any changes in proliferation or occurrence of apoptosis, these clones showed recovery of ROS production with returning NADPH/NADP+ ratio that increased with decreased production of ROS in continuously exposed sublines. These results indicated that NNT is a key factor in preventing ROS-induced cytotoxicity in T cells continuously exposed to asbestos. Considering that these sublines showed a reduction in anti-tumor immunity, modification of NNT may contribute to recovery of the anti-tumor effects in asbestos-exposed T cells.

Anti-Allergic and Anti-Inflammatory Effects and Molecular Mechanisms of Thioredoxin on Respiratory System Diseases

Significance: The pathogenesis and progression of allergic inflammation in the respiratory system are closely linked to oxidative stress. Thioredoxin (TRX) is an essential redox balance regulator in organisms and is induced by various oxidative stress factors, including ultraviolet rays, radiation, oxidation, viral infections, ischemia reperfusion, and anticancer agents. Recent Advances: We demonstrated that systemic administration and transgenic overexpression of TRX is useful in a wide variety of in vivo inflammatory respiratory diseases models, such as viral pneumonia, interstitial lung disease, chronic obstructive pulmonary disease, asthma, acute respiratory distress syndrome, and obstructive sleep apnea syndrome, by removing reactive oxygen species, blocking production of inflammatory cytokines, inhibiting migration and activation of neutrophils and eosinophils, and regulating the cellular redox status. In addition, TRX's anti-inflammatory mechanism is different from the mechanisms associated with anti-inflammatory agents, such as glucocorticoids, which regulate the inflammatory reaction in association with suppressing immune responses. Critical Issues: Understanding the molecular mechanism of TRX is very helpful for understanding the role of TRX in respiratory diseases. In this review, we show the protective effect of TRX in various respiratory diseases. In addition, we discuss its anti-allergic and anti-inflammatory molecular mechanism in detail. Future Directions: The application of TRX may be useful for treating respiratory allergic inflammatory disorders. Antioxid. Redox Signal. 32, 785-801.

Trxlp, a thioredoxin-like effector from Edwardsiella piscicida inhibits cellular redox signaling and nuclear translocation of NF-κB

Redox signaling and homeostasis are essential for cell survival and the immune response. Peroxiredoxin (Prx) modulates the level of H₂O₂ as a redox signal through H₂O₂ decomposition. The redox activity of thioredoxin (Trx) is required as a reducing equivalent to regenerate Prx. Edwardsiella piscicida is an opportunistic Gram-negative enteric pathogen that secretes a novel Trx-like effector protein, ETAE_2186 (Trxlp). Trxlp has unique structural properties compared with other Trx proteins. In enzymatic and binding assays, we confirmed Trxlp to be redox-inactive due to the low reactivity and flexibility of the resolving cysteine residue, C35, at the active site motif "³¹WCXXC³⁵". We identified key residues near the active site that are critical for reactivity and flexibility of C35 by site-directed mutagenesis analysis. NMR titration experiment demonstrated prolong inhibitory interaction of Trxlp with Prx1 resulting in the repression of Prx1-mediated H₂O₂ decomposition leading to increased ROS accumulation in infected host cells. Increased ROS in turn prevented nuclear translocation of NF-κB and inhibition of NF-κB target genes, leading to bacterial survival and enhanced replication inside host cells. Targeting Trxlp-mediated virulence promises to attenuate E. piscicida infection.

Thioredoxin and protein-disulfide isomerase selectivity for redox regulation of proteins in Corynebacterium glutamicum

Thioredoxins (Trxs) and protein-disulfide isomerases (PDIs) are believed to play a pivotal role in ensuring the proper folding of proteins, facilitating appropriate functioning of proteins, and maintaining intracellular redox homeostasis in bacteria. Two thioredoxins (Trxs) and three thiol-disulfide isomerases (PDIs) have been annotated in Corynebacterium glutamicum. However, nothing is known about their functional diversity in the redox regulation of proteins. Thus, we here analyzed the Trx- and PDI-dependent redox shifts of ribonucleotide reductase (RNR), insulin, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), and several thiol-dependent peroxidases by measuring enzyme activity and thiol status in vitro. We found that the two Trxs and the three PDIs had activities in the cleavage of the disulfidebond, whereas the PDIs had a lower efficiency than the two Trxs. Trx2 could activate thiol-dependent peroxidases with an efficiency comparable with that of Trx1, but the PDIs were inefficient. The redox-active Cys-X-X-Cys motif harbored in both Trxs and PDIs was essential to supply efficiently the donor of reducing equivalents for protein disulfides. In addition, stress-responsive extracytoplasmic function (ECF)-sigma factor H (SigH)-dependent Trxs and PDIs expressions were observed. These results contributed importantly to our overall understanding of reducing functionality of the Trx and PDI systems, and also highlighted the complexity and plasticity of the intracellular redox network.

Expression of thioredoxin 1 and peroxiredoxins in squamous cervical carcinoma and its predictive role in NACT

BACKGROUND

This study aims to investigate the expression of thioredoxin 1, peroxiredoxin 1 and peroxiredoxin 2 in bulky cervical squamous carcinoma and its predictive role in cisplatin-based neoadjuvant chemotherapy.

METHODS

Initially, the expression of thioredoxin 1, peroxiredoxin 1 and peroxiredoxin 2 protein was analyzed in 13 human cervical squamous cancer tissues and their paired adjacent non-cancerous tissues by western-blotting and immunohistochemistry. Then, correlation between the expression of thioredoxin 1, peroxiredoxin 1, peroxiredoxin 2 and responses to cisplatin-based neoadjuvant chemotherapy was analyzed in 35 paired tumor samples (pre- and post-chemotherapy) from bulky cervical squamous cancer patients by immunohistochemistry.

RESULTS

A clinical response occurred in 48.6% (17/35) of patients, including 14.3% (5/35) with a complete response and 34.3% (12/35) with a partial response. The expression of thioredoxin 1, peroxiredoxin 1 and peroxiredoxin 2 was much higher in cervical squamous cancer tissues compared with paired adjacent non-cancerous tissues by western-blotting and immunohistochemistry. Additionally, the expression of thioredoxin 1, peroxiredoxin 1 and peroxiredoxin 2 was significantly up-regulated in post-chemotherapy tissues compared to pre-chemotherapy cervical cancer tissues. High levels of thioredoxin 1, peroxiredoxin 1 and peroxiredoxin 2 were associated with a poor chemotherapy response in cervical squamous cancer patients.

CONCLUSIONS

Thioredoxin 1, peroxiredoxin 1 and peroxiredoxin 2 are frequently over-expressed in cervical squamous cancer. High expression levels of these proteins were related to a poor response to cisplatin-based neoadjuvant chemotherapy. The present study is the first report that thioredoxin peroxidase system may serve as a prediction of the responses to neoadjuvant chemotherapy in cervical squamous cancer.

The thioredoxin system and cancer therapy: a review

Thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH are key members of the Trx system that is involved in redox regulation and antioxidant defense. In recent years, several researchers have provided information about the roles of the Trx system in cancer development and progression. These reports indicated that many tumor cells express high levels of Trx and TrxR, which can be responsible for drug resistance in tumorigenesis. Inhibition of the Trx system may thus contribute to cancer therapy and improving chemotherapeutic agents. There are now a number of effective natural and synthetic inhibitors with chemotherapy applications possessing antitumor activity ranging from oxidative stress induction to apoptosis. In this article, we first described the features and functions of the Trx system and then reviewed briefly its correlations with cancer. Finally, we summarized the present knowledge about the Trx/TrxR inhibitors as anticancer drugs.

Role of calreticulin in biotic and abiotic stress signalling and tolerance mechanisms in plants

Calreticulin (CRT) is calcium binding protein of endoplasmic reticulum (ER) which performs plethora of functions besides it's role as molecular chaperone. Among the three different isoforms of this protein, CRT3 is most closely related to primitive CRT gene of higher plants. Based on their distinct structural and functional organisation, the plant CRTs have been known to contain three different domains: N, P and the C domain. The domain organisation and various biochemical characterstics of plant and animal CRTs are common with the exception of some differences. In plant calreticulin, the important N-glycosylation site(s) are replaced by the glycan chain(s) and several consensus sequences for in vitro phosphorylation by protein kinase CK2 (casein kinase-2), are also present unlike the animal calreticulin. Biotic and abiotic stresses play a significant role in bringing down the crop production. The role of various phytohormones in defense against fungal pathogens is well documented. CRT3 has been reported to play important role in protecting the plants against fungal and bacterial pathogens and in maintaining plant innate immunity. There is remarkable crosstalk between CRT mediated signalling and biotic, abiotic stress, and phytohormone mediated signalling pathways The role of CRT mediated pathway in mitigating biotic and abiotic stress can be further explored in plants so as to strategically modify it for development of stress tolerant plants.

Genetic Deletion or Pharmacological Inhibition of Soluble Epoxide Hydrolase Ameliorates Cardiac Ischemia/Reperfusion Injury by Attenuating NLRP3 Inflammasome Activation

Activation of the nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome cascade has a role in the pathogenesis of ischemia/reperfusion (IR) injury. There is growing evidence indicating cytochrome p450 (CYP450)-derived metabolites of n-3 and n-6 polyunsaturated fatty acids (PUFAs) possess both adverse and protective effects in the heart. CYP-derived epoxy metabolites are rapidly hydrolyzed by the soluble epoxide hydrolase (sEH). The current study hypothesized that the cardioprotective effects of inhibiting sEH involves limiting activation of the NLRP3 inflammasome. Isolated hearts from young wild-type (WT) and sEH null mice were perfused in the Langendorff mode with either vehicle or the specific sEH inhibitor t-AUCB. Improved post-ischemic functional recovery and better mitochondrial respiration were observed in both sEH null hearts or WT hearts perfused with t-AUCB. Inhibition of sEH markedly attenuated the activation of the NLRP3 inflammasome complex and limited the mitochondrial localization of the fission protein dynamin-related protein-1 (Drp-1) triggered by IR injury. Cardioprotective effects stemming from the inhibition of sEH included preserved activities of both cytosolic thioredoxin (Trx)-1 and mitochondrial Trx-2 antioxidant enzymes. Together, these data demonstrate that inhibiting sEH imparts cardioprotection against IR injury via maintaining post-ischemic mitochondrial function and attenuating a detrimental innate inflammatory response.

Cardioprotective effects of CYP-derived epoxy metabolites of docosahexaenoic acid involve limiting NLRP3 inflammasome activation

Impaired mitochondrial function and activation of NLRP3 inflammasome cascade has a significant role in the pathogenesis of myocardial ischemia–reperfusion (IR) injury. The current study investigated whether eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), or their corresponding CYP epoxygenase metabolites 17,18-epoxyeicosatetraenoic acid (17,18-EEQ) and 19,20-epoxydocosapentaenoic acid (19,20-EDP) protect against IR injury. Isolated mouse hearts were perfused in the Langendorff mode with vehicle, DHA, 19,20-EDP, EPA, or 17,18-EEQ and subjected to 30 min of ischemia and followed by 40 min of reperfusion. In contrast with EPA and 17,18-EEQ, DHA and 19,20-EDP exerted cardioprotection, as shown by a significant improvement in postischemic functional recovery associated with significant attenuation of NLRP3 inflammasome complex activation and preserved mitochondrial function. Hearts perfused with DHA or 19,20-EDP displayed a marked reduction in localization of mitochondrial Drp-1 and Mfn-2 as well as maintained Opa-1 levels. DHA and 19,20-EDP preserved the activities of both the cytosolic Trx-1 and mitochondrial Trx-2. DHA cardioprotective effect was attenuated by the CYP epoxygenase inhibitor N-(methysulfonyl)-2-(2-propynyloxy)-benzenehexanamide. In conclusion, our data indicate a differential cardioprotective response between DHA, EPA, and their active metabolites toward IR injury. Interestingly, 19,20-EDP provided the best protection against IR injury via maintaining mitochondrial function and thereby reducing the detrimental NLRP3 inflammasome responses.

Cloning and functional characterization of thioredoxin gene from kuruma shrimp Marsupenaeus japonicus

As an important disulfide reductase of the intracellular antioxidant system, Thioredoxin (Trx) plays an important role in maintaining oxidative stress balance and protecting cells from oxidative damage. In recent years, there is increasing evidence that Trx is a key molecule in the pathogenesis of various diseases and a potential therapeutic target for major diseases including lung, colon, cervical, gastric and pancreatic cancer. However, few knowledge is known about the function of Trx in virus infection. In this study, we reported the cloning and functional investigation of a Trx homologue gene, named MjTrx, in shrimp Marsupenaeus japonicus suffered white spot syndrome virus (WSSV) infection. MjTrx is a 105-amino acid polypeptide with a conservative Cys-Gly-Pro-Cys motif in the catalytic center. Phylogenetic trees analysis showed that MjTrx has a higher relationship with Trx from other invertebrate and clustered with Trx1 from arthropod. MjTrx transcripts is abundant in the gill and intestine tissues and can be detected in the hemocytes, heart, stomach, and hepatopancreas tissues. The transcription levels of MjTrx in hemocytes, gills and intestine tissues of shrimp were significantly up-regulated after white spot syndrome virus infection. MjTrx was recombinant expressed in vitro and exhibited obvious disulfide reductase activity. In addition, overexpression MjTrx in shrimp resulted in the increase of hydrogen peroxide (H₂O₂) concentration in vivo. All these results strongly suggested that MjTrx functioned in redox homeostasis regulating and played an important role in shrimp antiviral immunity.

Redox and "Antioxidant" Properties of Fe2(μ-SH)2(CO)4(PPh3)2

The chemistry of Fe₂(μ-SH)₂(CO)₄(PPh₃)₂ (2^HH) is described with attention to S-S coupling reactions. Produced by the reduction of Fe₂(μ-S₂)(CO)₄(PPh₃)₂ (2), 2^HH is an analogue of Fe₂(μ-SH)₂(CO)₆ (1^HH), which exhibits well-behaved S-centered redox. Both 2^HH and the related 2^MeH exist as isomers that differ with respect to the stereochemistry of the μ-SR ligands (R = H, Me). Compounds 2^HH, 2^MeH, and 2 protonate to give rare examples of Fe-SH and Fe-S₂ hydrides. Salts of [H2]⁺, [H2^HH]⁺, and [H2^MeH]⁺ were characterized crystallographically. Complex 2^HH reduces O₂, H₂O₂, (PhCO₂)₂, and Ph₂N₂, giving 2. Related reactions involving 1^HH gave uncharacterizable polymers. The differing behaviors of 2^HH and 1^HH reflect stabilization of the ferrous intermediates by the PPh₃ ligands. When independently generated by the reaction of 2^HH with 2,2,6,6-tetramethyl-1-piperidinyloxy, 2* quantitatively converts to 2 or, in the presence of C₂H₄, is trapped as the ethanedithiolate Fe₂(μ-S₂C₂H₄)(CO)₄(PPh₃)₂. Evidence is presented that the Hieber-Gruber synthesis of 1 involves polysulfido intermediates [Fe₂(μ-S _n)₂(CO)₆]^2- ( n > 1). Two relevant experiments are as follows: (i) protonation of [Fe₄(μ-S)₂(μ-S₂)CO)₁₂]^2- gives 1 and 1^HH, and (ii) oxidation of 1^HH by sulfur gives 1.

Preventive and Protective Roles of Dietary Nrf2 Activators Against Central Nervous System Diseases

Central nervous system diseases are major health issues and are often associated with disability or death. Most central nervous system disorders are characterized by high levels of oxidative stress. Nuclear factor erythroid 2 related factor (Nrf2) is known for its ability to regulate the expression of a series of enzymes with antioxidative, prosurvival, and detoxification effects. Under basal conditions, Nrf2 forms a complex with Kelch-like ECH associated protein 1, leading to Nrf2 inactivation via ubiquitination and degradation. However, following exposure of Keap1 to oxidative stress, Nrf2 is released from Keap1, activated, and translocated into the nucleus. Upon nuclear entry, Nrf2 binds to antioxidant response elements (ARE), thereby inducing the expression of genes such as glutathione s-transferase, heme oxygenase 1, and NADPH quinine oxidoreductase 1. Many dietary phytochemicals have been reported to activate the protective Nrf2/ARE pathway. Here, we review the preventive and protective effects of dietary Nrf2 activators against CNS diseases, including stroke, traumatic brain injury, Alzheimer's disease, and Parkinson's disease.

Mechanisms of Persistence of the Ammonia-Oxidizing Bacteria Nitrosomonas to the Biocide Free Nitrous Acid

Free nitrous acid (FNA) exerts a broad range of antimicrobial effects on bacteria, although susceptibility varies considerably among microorganisms. Among nitrifiers found in activated sludge of wastewater treatment processes (WWTPs), nitrite-oxidizing bacteria (NOB) are more susceptible to FNA compared to ammonia-oxidizing bacteria (AOB). This selective inhibition of NOB over AOB in WWTPs bypasses nitrate production and improves the efficiency and costs of the nitrogen removal process in both the activated sludge and anaerobic ammonium oxidation (Anammox) system. However, the molecular mechanisms governing this atypical tolerance of AOB to FNA have yet to be understood. Herein we investigate the varying effects of the antimicrobial FNA on activated sludge containing AOB and NOB using an integrated metagenomics and label-free quantitative sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) metaproteomic approach. The Nitrosomonas genus of AOB, on exposure to FNA, maintains internal homeostasis by upregulating a number of known oxidative stress enzymes, such as pteridine reductase and dihydrolipoyl dehydrogenase. Denitrifying enzymes were upregulated on exposure to FNA, suggesting the detoxification of nitrite to nitric oxide. Interestingly, proteins involved in stress response mechanisms, such as DNA and protein repair enzymes, phage prevention proteins, and iron transport proteins, were upregulated on exposure to FNA. In addition enzymes involved in energy generation were also upregulated on exposure to FNA. The total proteins specifically derived from the NOB genus Nitrobacter was low and, as such, did not allow for the elucidation of the response mechanism to FNA exposure. These findings give us an understanding of the adaptive mechanisms of tolerance within the AOB Nitrosomonas to the biocidal agent FNA.

Recombinant Human Thioredoxin-1 Protects Macrophages from Oxidized Low-Density Lipoprotein-Induced Foam Cell Formation and Cell Apoptosis

Oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cell formation and apoptosis play critical roles in the pathogenesis of atherosclerosis. Thioredoxin-1 (Trx) is an antioxidant that potently protects various cells from oxidative stress-induced cell death. However, the protective effect of Trx on ox-LDL-induced macrophage foam cell formation and apoptosis has not been studied. This study aims to investigate the effect of recombinant human Trx (rhTrx) on ox-LDL-stimulated RAW264.7 macrophages and elucidate the possible mechanisms. RhTrx significantly inhibited ox-LDL-induced cholesterol accumulation and apoptosis in RAW264.7 macrophages. RhTrx also suppressed the ox-LDL-induced overproduction of lectin-like oxidized LDL receptor (LOX-1), Bax and activated caspase-3, but it increased the expression of Bcl-2. In addition, rhTrx markedly inhibited the ox-LDL-induced production of intracellular reactive oxygen species (ROS) and phosphorylation of p38 mitogen-activated protein kinases (MAPK). Furthermore, anisomycin (a p38 MAPK activator) abolished the protective effect of rhTrx on ox-LDL-stimulated RAW264.7 cells, and SB203580 (a p38 MAPK inhibitor) exerted a similar effect as rhTrx. Collectively, these findings indicate that rhTrx suppresses ox-LDL-stimulated foam cell formation and macrophage apoptosis by inhibiting ROS generation, p38 MAPK activation and LOX-1 expression. Therefore, we propose that rhTrx has therapeutic potential in the prevention and treatment of atherosclerosis.

WSSV-responsive gene expression under the influence of PmVRP15 suppression

The viral responsive protein 15 from black tiger shrimp Penaeus monodon (PmVRP15), is highly up-regulated and produced in the hemocytes of shrimp with white spot syndrome virus (WSSV) infection. To investigate the differential expression of genes from P. monodon hemocytes that are involved in WSSV infection under the influence of PmVRP15 expression, suppression subtractive hybridization (SSH) of PmVRP15-silenced shrimp infected with WSSV was performed. The 189 cDNA clones of the forward library were generated by subtracting the cDNAs from WSSV-infected and PmVRP15 knockdown shrimp with cDNAs from WSSV-infected and GFP knockdown shrimp. For the opposite subtraction, the 176 cDNA clones in the reverse library was an alternative set of genes in WSSV-infected shrimp hemocytes in the presence of PmVRP15 expression. The abundant genes in forward SSH library had a defense/homeostasis of 26%, energy/metabolism of 23% and in the reverse SSH library a hypothetical protein with unknown function was found (30%). The differential expressed immune-related genes from each library were selected for expression analysis using qRT-PCR. All selected genes from the forward library showed high up-regulation in the WSSV-challenged PmVRP15 knockdown group as expected. Interestingly, PmHHAP, a hemocyte homeostasis associated protein, and granulin-like protein, a conserved growth factor, are extremely up-regulated in the absence of PmVRP15 expression in WSSV-infected shrimp. Only transcript level of transglutaminase II, that functions in regulating hematopoietic tissue differentiation and inhibits mature hemocyte production in shrimp, was obviously down-regulated as observed from SSH results. Taken together, our results suggest that PmVRP15 might have a function relevant to hemocyte homeostasis during WSSV infection.

Physical interaction between human ribonucleotide reductase large subunit and thioredoxin increases colorectal cancer malignancy

Ribonucleotide reductase (RR) is the rate-limiting enzyme in DNA synthesis, catalyzing the reduction of ribonucleotides to deoxyribonucleotides. During each enzymatic turnover, reduction of the active site disulfide in the catalytic large subunit is performed by a pair of shuttle cysteine residues in its C-terminal tail. Thioredoxin (Trx) and glutaredoxin (Grx) are ubiquitous redox proteins, catalyzing thiol-disulfide exchange reactions. Here, immunohistochemical examination of clinical colorectal cancer (CRC) specimens revealed that human thioredoxin1 (hTrx1), but not human glutaredoxin1 (hGrx1), was up-regulated along with human RR large subunit (RRM1) in cancer tissues, and the expression levels of both proteins were correlated with cancer malignancy stage. Ectopically expressed hTrx1 significantly increased RR activity, DNA synthesis, and cell proliferation and migration. Importantly, inhibition of both hTrx1 and RRM1 produced a synergistic anticancer effect in CRC cells and xenograft mice. Furthermore, hTrx1 rather than hGrx1 was the efficient reductase for RRM1 regeneration. We also observed a direct protein-protein interaction between RRM1 and hTrx1 in CRC cells. Interestingly, besides the known two conserved cysteines, a third cysteine (Cys⁷⁷⁹) in the RRM1 C terminus was essential for RRM1 regeneration and binding to hTrx1, whereas both Cys³² and Cys³⁵ in hTrx1 played a counterpart role. Our findings suggest that the up-regulated RRM1 and hTrx1 in CRC directly interact with each other and promote RR activity, resulting in enhanced DNA synthesis and cancer malignancy. We propose that the RRM1-hTrx1 interaction might be a novel potential therapeutic target for cancer treatment.

Targeting the NF-E2-Related Factor 2 Pathway: a Novel Strategy for Traumatic Brain Injury

As an essential component of cellular defense against a variety of endogenous and exogenous stresses, nuclear factor erythroid 2-related factor 2 (Nrf2) has received increased attention in the past decades. Multiple studies indicate that Nrf2 acts not only as an important protective factor in injury models but also as a downstream target of therapeutic agents. Activation of Nrf2 has increasingly been linked to many human diseases, especially in central nervous system (CNS) injury such as traumatic brain injury (TBI). Several researches have deciphered that activation of Nrf2 exerts antioxidative stress, antiapoptosis, and antiinflammation influence in TBI via different molecules and pathways including heme oxygenase-1 (HO-1), NADPH:quinine oxidoreductase-1 (NQO-1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2). Hence, Nrf2 shows great promise as a molecular target in TBI. In the present article, we provide an updated review of the current state of our knowledge about relationship between Nrf2 and TBI, highlighting the specific roles of Nrf2 in TBI.

Cotesia vestalis parasitization suppresses expression of a Plutella xylostella thioredoxin

Thioredoxins (Trxs) are a family of small, highly conserved and ubiquitous proteins involved in protecting organisms against toxic reactive oxygen species. In this study, a typical thioredoxin gene, PxTrx, was isolated from Plutella xylostella. The full-length cDNA sequence is composed of 959 bp containing a 321 bp open reading frame that encodes a predicted protein of 106 amino acids, a predicted molecular weight of 11.7 kDa and an isoelectric point of 5.03. PxTrx was mainly expressed in larval Malpighian tubules and the fat body. An enriched recombinant PxTrx had insulin disulphide reductase activity and stimulated Human Embryonic Kidney 293 (HEK293) cell proliferation. It also protected supercoiled DNA and living HEK293 cells from H₂ O₂ -induced damage. Parasitization by Cotesia vestalis and injections of 0.05 and 0.01 equivalents of C. vestalis Bracovirus (CvBv), the symbiotic virus carried by the parasitoid, led to down-regulation of PxTrx expression in host fat body. Taken together, our results indicate that PxTrx contributes to the maintenance of P. xylostella cellular haemostasis. Host fat body expression of PxTrx is strongly attenuated by parasitization and by injections of CvBv.