ATL-derived factor (ADF), an IL-2 receptor/Tac inducer homologous to thioredoxin; possible involvement of dithiol-reduction in the IL-2 receptor induction

Thioredoxin, oxidative stress, cancer and aging

The Free Radical or Oxidative Stress Theory of Aging is one of the most popular theories in aging research and has been extensively studied over the past several decades. However, recent evidence using transgenic/knockout mice that overexpress or down-regulate antioxidant enzymes challenge the veracity of this theory since the animals show no increase or decrease in lifespan. These results seriously call into question the role of oxidative damage/stress in the aging process in mammals. Therefore, the theory requires significant modifications if we are to understand the relationship between aging and the regulation of oxidative stress. Our laboratory has been examining the impacts of thioredoxins (Trxs), in the cytosol and mitochondria, on aging and age-related diseases. Our data from mice that are either up-regulating or down-regulating Trx in different cellular compartments, that is, the cytosol or mitochondria, could shed some light on the role of oxidative stress and its pathophysiological effects. The results generated from our lab and others may indicate that: 1) changes in oxidative stress and the redox state in the cytosol, mitochondria or nucleus might play different roles in the aging process; 2) the role of oxidative stress and redox state could have different pathophysiological consequences in different tissues/cells, for example, mitotic vs. post-mitotic; 3) oxidative stress could have different pathophysiological impacts in young and old animals; and 4) the pathophysiological roles of oxidative stress and redox state could be controlled through changes in redox-sensitive signaling, which could have more diverse effects on pathophysiology than the accumulation of oxidative damage to various molecules. To critically test the role of oxidative stress on aging and age-related diseases, further study is required using animal models that regulate oxidative stress levels differently in each cellular compartment, each tissue/organ, and/or at different stages of life (young, middle and old) to change redox sensitive signaling pathways.

Cynoglossus semilaevis thioredoxin: a reductase and an antioxidant with immunostimulatory property

Thioredoxin (Trx) is a small redox protein existing ubiquitously in all living organisms and plays an important role in multiple cellular processes, including transcriptional regulation and immune response. To date very few studies have been carried out to examine the function of piscine Trx. In this study, we identified and analyzed the function of a Trx homologue, CsTrx1, from half-smooth tongue sole (Cynoglossus semilaevis). The deduced amino acid sequence of CsTrx1 is composed of 107 residues and shares 54.1-60.8% overall identities with the Trx of other teleosts. CsTrx1 contains the highly conserved CXXC motif, which in mammals is known to be the active site, in the form of CQPC. Expression of CsTrx1 as determined by quantitative real-time reverse transcriptase PCR was highest in liver and upregulated in time-dependent manners by bacterial infection and by exposure to iron, copper, and hydrogen peroxide. Purified recombinant CsTrx1 (rCsTrx1) exhibited insulin disulfide reductase activity and antioxidant activity, both which, however, were lost when the two cysteine residues in the CQPC motif were mutated to serine. Further analysis showed that rCsTrx1 was able to stimulate the proliferation of head kidney leukocytes, upregulate the expression of immune relevant genes, and enhance the resistance of leukocytes against bacterial infection. Taken together, these results indicate that CsTrx1 is a biologically active reductase and an antioxidant that requires the CXXC motif for activity and that CsTrx1 possesses cytokine-like immunoregulatory property. These results suggest a role for CsTrx1 in protecting cells against oxidative stress caused by oxidant exposure and pathogen infection.

Thioredoxin-1 Promotes Anti-Inflammatory Macrophages of the M2 Phenotype and Antagonizes Atherosclerosis

Objective—

Oxidative stress is believed to play a key role in cardiovascular disorders. Thioredoxin (Trx) is an oxidative stress-limiting protein with anti-inflammatory and antiapoptotic properties. Here, we analyzed whether Trx-1 might exert atheroprotective effects by promoting macrophage differentiation into the M2 anti-inflammatory phenotype.

Methods and Results—

Trx-1 at 1 μg/mL induced downregulation of p16 INK4a and significantly promoted the polarization of anti-inflammatory M2 macrophages in macrophages exposed to interleukin (IL)-4 at 15 ng/mL or IL-4/IL-13 (10 ng/mL each) in vitro, as evidenced by the expression of the CD206 and IL-10 markers. In addition, Trx-1 induced downregulation of nuclear translocation of activator protein-1 and Ref-1, and significantly reduced the lipopolysaccharide-induced differentiation of inflammatory M1 macrophages, as indicated by the decreased expression of the M1 cytokines, tumor necrosis factor-α and monocyte chemoattractant protein-1. Consistently, Trx-1 administered to hyperlipoproteinemic ApoE2.Ki mice at 30 μg/30 g body weight challenged either with lipopolysaccharide at 30 μg/30 g body weight or with IL-4 at 500 ng/30 g body weight significantly induced the M2 phenotype while inhibiting differentiation of macrophages into the M1 phenotype in liver and thymus. ApoE2.Ki mice challenged once weekly with lipopolysaccharide for 5 weeks developed severe atherosclerotic lesions enriched with macrophages expressing predominantly M1 over M2 markers. In contrast, however, daily injections of Trx-1 shifted the phenotype pattern of lesional macrophages in these animals to predominantly M2 over M1, and the aortic lesion area was significantly reduced (from 100%±18% to 62.8%±9.8%; n=8; P <0.01). Consistently, Trx-1 colocalized with M2 but not with M1 macrophage markers in human atherosclerotic vessel specimens.

Conclusion—

The ability of Trx-1 to promote differentiation of macrophages into an alternative, anti-inflammatory phenotype may explain its protective effects in cardiovascular diseases. These data provide novel insight into the link between oxidative stress and cardiovascular diseases.

Thioredoxin-1 and protein disulfide isomerase catalyze the reduction of similar disulfides in HIV gp120

HIV-1 enters cells via interaction of the viral glycoprotein gp120, the host cell surface receptor CD4 and the co-receptors CCR5 or CXCR4. For entry, gp120 undergoes conformational changes that depend on the reduction of one or more disulfides. Previous studies indicate that protein disulfide isomerase (PDI), thioredoxin-1 (Trx1), and glutaredoxin-1 (Grx1) catalyze gp120 reduction, but their specific disulfide targets are not known. Here, it was demonstrated that PDI and Trx1 have similar gp120 disulfide targets as determined by labeling after reduction, but with some pattern differences, including overall stronger labeling with Trx1 than with PDI. Furthermore, uneven labeling of the residues of a disulfide may reflect altered accessibility by conformational changes upon the reduction process. Since both PDI and Trx1 may be involved in viral entry, compounds that target the host redox system or the viral gp120 were tested in vitro to investigate whether redox regulation is a target for anti-HIV therapy. Carbohydrate binding agents (CBAs), previously shown to bind gp120 and inhibit HIV entry, were now demonstrated to inhibit gp120 disulfide reduction. Auranofin, an inhibitor of thioredoxin reductase 1 (TrxR1), also showed inhibitory activity towards HIV infection, although close to its cytotoxic concentration. Our results demonstrate that both the host redox system and the viral surface glycoproteins are of interest for the development of new generations of anti-HIV therapeutics.

Discovery of ATL: an odyssey in restrospect

Forty years have passed since our initial description of peculiar cases of adult-onset leukemia with abnormal cells having multi-convoluted nuclei and T cell properties, frequent in the southern regions of Japan in the early 1970s. Retrospectively, the study of adult T cell leukemia (ATL) and the related virus HTLV-I was a forerunner for all of human retrovirology, in which AIDS and the related retrovirus HIV were identified a few years later in the 1980s. Using the anti-TAC monoclonal antibody generated by the late Takashi Uchiyama during his stay in T. A. Waldmann's laboratory in NIH Bethesda, a cDNA encoding IL-2Rα chain was cloned by our group in Kyoto and by Waldmann's group in Bethesda. Abnormal IL-2Rα chain expression and the IL-2 dependency of ATL cell lines greatly contributed to the study of leukemogenesis of ATL. A new soluble factor named ADF/ATL-derived factor was also detected in ATL cell lines. After years of study, ADF proved to be a first human counterpart of thiol-related oxido-reductase thioredoxin/TRX, which opened the field of redox regulation of cell signaling involved in a variety of diseases. Close interaction among Drs. Kimishige Ishizaka, Kiyoshi Takastuki and T. A. Waldmanns before ATL and HTLV-I study was an essential base for our initiation of ATL research with Takashi Uchiyama and many other colleagues.

Thiol regulation of pro-inflammatory cytokines and innate immunity: protein S-thiolation as a novel molecular mechanism

Inflammation or inflammatory cytokines and oxidative stress have often been associated, and thiol antioxidants, particularly glutathione, have often been seen as possible anti-inflammatory mediators. However, whereas several cytokine inhibitors have been approved for drug use in chronic inflammatory diseases, this has not happened with antioxidant molecules. We outline the complexity of the role of protein thiol–disulfide oxidoreduction in the regulation of immunity and inflammation, the underlying molecular mechanisms (such as protein glutathionylation) and the key enzyme players such as Trx (thioredoxin) or Grx (glutaredoxin).

Thioredoxin 1 overexpression extends mainly the earlier part of life span in mice

We examined the effects of increased levels of thioredoxin 1 (Trx1) on resistance to oxidative stress and aging in transgenic mice overexpressing Trx1 [Tg(TRX1)(+/0)]. The Tg(TRX1)(+/0) mice showed significantly higher Trx1 protein levels in all the tissues examined compared with the wild-type littermates. Oxidative damage to proteins and levels of lipid peroxidation were significantly lower in the livers of Tg(TRX1)(+/0) mice compared with wild-type littermates. The survival study demonstrated that male Tg(TRX1)(+/0) mice significantly extended the earlier part of life span compared with wild-type littermates, but no significant life extension was observed in females. Neither male nor female Tg(TRX1)(+/0) mice showed changes in maximum life span. Our findings suggested that the increased levels of Trx1 in the Tg(TRX1)(+/0) mice were correlated to increased resistance to oxidative stress, which could be beneficial in the earlier part of life span but not the maximum life span in the C57BL/6 mice.

Is serum thioredoxin-1 a useful clinical marker for malignant pleural mesothelioma?

Malignant pleural mesothelioma (MPM), an asbestos-related aggressive malignant tumor of mesothelial origin, shows limited response to therapy and overall survival remains very poor. Reactive oxygen species play an important role in asbestos toxicity. Here, we found that the patients with MPM had significantly higher serum levels of thioredoxin-1 (TRX) than control population. The patients with advanced-stage MPM showed higher levels of TRX than those with early-stage MPM. The difference in overall survival between the groups with lower and higher serum TRX levels was significant. Our data suggest that serum TRX concentration could be a useful clinical marker for MPM.

Molecular cloning and expression analysis of a thioredoxin from rock bream, Oplegnathus fasciatus, and biological activity of the recombinant protein

Thioredoxins (TRxs) are a family of small, highly conserved proteins that are essential for the maintenance of cellular homeostasis. TRx1, which contains a conserved redox-active site, Cys-Gly-Pro-Cys, is a proinflammatory cytokine, B cell growth factor, macrophage migration inhibiting factor (MIF), and an immune regulatory cytokine. The TRx1 homologue cDNA was isolated from the rock bream LPS-stimulated liver cDNA library, RbTRx1. RbTRx1 consists of 730 bp full-length cDNA with a 324 bp open reading frame encoding 108 amino acids. When compared with other known TRx1 peptide sequences, the most conserved region of the RbTRx1 peptide was the redox-active site Cys-Gly-Pro-Cys. Phylogenetic analysis grouped the RbTRx1 with other vertebrate TRx1 peptides. Quantitative real-time PCR analysis revealed the presence of RbTRx1 transcripts in liver, gill, kidney, and muscle. The expression of RbTRx1 mRNA in kidney leukocytes was upregulated after bacterial and viral challenge. The kidney leukocytes were treated with a high concentration of rRbTRx1, which significantly enhanced cell proliferation (1 μg/ml and 10 μg/ml) and viability under oxidative stress (10 μg/ml).

Production of biologically active human thioredoxin 1 protein in lettuce chloroplasts

The production of human therapeutic proteins in plants provides opportunities for low-cost production, and minimizes the risk of contamination from potential human pathogens. Chloroplast genetic engineering is a particularly promising strategy, because plant chloroplasts can produce large amounts of foreign target proteins. Oxidative stress is a key factor in various human diseases. Human thioredoxin 1 (hTrx1) is a stress-induced protein that functions as an antioxidant against oxidative stress, and overexpression of hTrx1 has been shown to suppress various diseases in mice. Therefore, hTrx1 is a prospective candidate as a new human therapeutic protein. We created transplastomic lettuce expressing hTrx1 under the control of the psbA promoter. Transplastomic plants grew normally and were fertile. The hTrx1 protein accumulated to approximately 1% of total soluble protein in mature leaves. The hTrx1 protein purified from lettuce leaves was functionally active, and reduced insulin disulfides. The purified protein protected mouse insulinoma line 6 cells from damage by hydrogen peroxide, as reported previously for a recombinant hTrx1 expressed in Escherichia coli. This is the first report of expression of the biologically active hTrx1 protein in plant chloroplasts. This research opens up possibilities for plant-based production of hTrx1. Considering that this expression host is an edible crop plant, this transplastomic lettuce may be suitable for oral delivery of hTrx1.

Macrophage migration inhibitory factor provides cardioprotection during ischemia/reperfusion by reducing oxidative stress

Macrophage migration inhibitory factor (MIF) is a multifunctional protein that exhibits an intrinsic thiol protein oxidoreductase activity and proinflammatory activities. In the present study to examine intracellular MIF redox function, exposure of MIF-deficient cardiac fibroblasts to oxidizing conditions resulted in a 2.3-fold increase (p < 0.001) in intracellular ROS that could be significantly reduced by adenoviral-mediated reexpression of recombinant MIF. In an animal model of myocardial injury by ischemia/reperfusion (I/R), MIF-deficient hearts exhibited higher levels of oxidative stress than did wild-type hearts, as measured by significantly higher oxidized glutathione levels (decreased GSH/GSSG ratio), increased protein oxidation, reduced aconitase activity, and increased mitochondrial injury (increased cytochrome c release). The increased myocardial oxidative stress after I/R was reflected by larger infarct size (INF) in MIF-deficient hearts versus wild-type (WT) hearts (21 ± 6% vs. 8 ± 3% INF/LV; p < 0.05). In vivo hemodynamic measurements showed that left ventricular (LV) contractile function of MIF-deficient hearts subjected to 15-min ischemia failed to recover during reperfusion compared with WT hearts (LV developed pressure and ± dP/dt; p = 0.02). These data represent the first in vivo evidence in support of a cardioprotective role of MIF in the postischemic heart by reducing oxidative stress.

Reduced monomeric CD4 is the preferred receptor for HIV

CD4 is a co-receptor for binding of T cells to antigen-presenting cells and the primary receptor for the human immunodeficiency virus type 1 (HIV). CD4 exists in three different forms on the cell surface defined by the state of the domain 2 cysteine residues: an oxidized monomer, a reduced monomer, and a covalent dimer linked through the domain 2 cysteines. The disulfide-linked dimer is the preferred immune co-receptor. The form of CD4 that is preferred by HIV was examined in this study. HIV entry and envelope-mediated cell-cell fusion were tested using cells expressing comparable levels of wild-type or disulfide bond mutant CD4 in which the domain 2 cysteines were mutated to alanine. Eliminating the domain 2 disulfide bond increased entry of HIV reporter viruses and enhanced HIV envelope-mediated cell-cell fusion 2-4-fold. These observations suggest that HIV enters susceptible cells preferably through monomeric reduced CD4, whereas dimeric CD4 is the preferred receptor for binding to antigen-presenting cells. Cleavage of the domain 2 disulfide bond is possibly involved in the conformational change in CD4 associated with fusion of the HIV and cell membranes.

Disulfide bond that constrains the HIV-1 gp120 V3 domain is cleaved by thioredoxin

A functional disulfide bond in both the HIV envelope glycoprotein, gp120, and its immune cell receptor, CD4, is involved in viral entry, and compounds that block cleavage of the disulfide bond in these proteins inhibit HIV entry and infection. The disulfide bonds in both proteins are cleaved at the cell surface by the small redox protein, thioredoxin. The target gp120 disulfide and its mechanism of cleavage were determined using a thioredoxin kinetic trapping mutant and mass spectrometry. A single disulfide bond was cleaved in isolated and cell surface gp120, but not the gp160 precursor, and the extent of the reaction was enhanced when gp120 was bound to CD4. The Cys(32) sulfur ion of thioredoxin attacks the Cys(296) sulfur ion of the gp120 V3 domain Cys(296)-Cys(331) disulfide bond, cleaving the bond. Considering that V3 sequences largely determine the chemokine receptor preference of HIV, we propose that cleavage of the V3 domain disulfide, which is facilitated by CD4 binding, regulates chemokine receptor binding. There are 20 possible disulfide bond configurations, and, notably, the V3 domain disulfide has the same unusual -RHStaple configuration as the functional disulfide bond cleaved in CD4.

Redox responses in patients with sepsis: high correlation of thioredoxin-1 and macrophage migration inhibitory factor plasma levels

Background. Redox active substances (e.g., Thioredoxin-1, Macrophage Migration Inhibitory Factor) seem to be central hubs in the septic inflammatory process. Materials and Methods. Blood samples from patients with severe sepsis or septic shock (n = 15) were collected at the time of sepsis diagnosis (t0), and 24 (t24) and 48 (t48) hours later; samples from healthy volunteers (n = 18) were collected once; samples from postoperative patients (n = 28) were taken one time immediately after surgery. In all patients, we measured plasma levels of IL-6, TRX1 and MIF. Results. The plasma levels of MIF and TRX1 were significantly elevated in patients with severe sepsis or septic shock. Furthermore, TRX1 and MIF plasma levels showed a strong correlation (t0: r_sp = 0.720, ρ = 0.698/t24: r_sp = 0.771, ρ = 0.949). Conclusions. Proinflammatory/~oxidative and anti-inflammatory/~oxidative agents show a high correlation in order to maintain a redox homeostasis and to avoid the harmful effects of an excessive inflammatory/oxidative response.

Thiol redox transitions by thioredoxin and thioredoxin-binding protein-2 in cell signaling

The cellular thiol redox state is a crucial mediator of metabolic, signaling and transcriptional processes in cells, and an exquisite balance between the oxidizing and reducing states is essential for the normal function and survival of cells. Reactive oxygen species (ROS) are widely known to function as a kind of second messenger for intracellular signaling and to modulate the thiol redox state. Thiol reduction is mainly controlled by the thioredoxin (TRX) system and glutathione (GSH) systems as scavengers of ROS and regulators of the protein redox states. The thioredoxin system is composed of several related molecules interacting through the cysteine residues at the active site, including thioredoxin, thioredoxin-2, a mitochondrial thioredoxin family, and transmembrane thioredoxin-related protein (TMX), an endoplasmic reticulum (ER)-specific thioredoxin family. Thioredoxin couples with thioredoxin-dependent peroxidases (peroxiredoxin) to scavenge hydrogen peroxide. In addition, thioredoxin does not simply act only as a scavenger of ROS but also as an important regulator of oxidative stress response through protein-protein interaction. The interaction of thioredoxin and thioredoxin-binding proteins such as thioredoxin-binding protein-2 (TBP-2, also called as Txnip or VDUP1), apoptosis signal kinase (ASK-1), redox factor 1 (Ref-1), Forkhead box class O 4 (FoxO4), and nod-like receptor proteins (NLRPs) suggested unconventional functions of thioredoxin and a novel mechanism of redox regulation. Here, we introduce the central mechanism of thiol redox transition in cell signaling regulated by thioredoxin and related molecules.

Macrophage migration inhibitory factor (MIF) and manganese superoxide dismutase (MnSOD) as early predictors for survival in patients with severe sepsis or septic shock

BACKGROUND

Severe sepsis, septic shock, and resulting organ failure appear as the most common cause of death in intensive care medicine. Inflammatory mediators (interleukin-6/IL-6), cell adhesion molecules (intercellular adhesion molecule-1/ICAM-1, vascular cell adhesion molecule-1/VCAM-1), and redox active substances (manganese superoxide dismutase/MnSOD, macrophage migration inhibitory factor/MIF) must be considered to be central hubs in the inflammatory process. However, their exact pathophysiologic function and prognostic value are still poorly understood.

MATERIALS AND METHODS

In total, 133 individuals (87 patients with severe sepsis or septic shock, 28 postoperative patients after major abdominal surgery, 18 healthy volunteers) were enrolled in the study. Blood samples from septic patients were collected within 24 h after the time of sepsis diagnosis, and 48 and 120 h later; samples from healthy volunteers were collected once, and samples from postoperative patients once immediately after surgery. In all patients we measured plasma levels of IL-6, sICAM-1, sVCAM-1, MnSOD, and MIF using enzyme linked immunosorbent assay (ELISA) kits.

RESULTS

Healthy volunteers and postoperative patients showed comparable levels of cell adhesion molecules. Furthermore, their redox system was activated in a comparable manner, whereas in postoperative patients IL-6 was significantly elevated. Plasma levels of inflammatory mediators, cell adhesion molecules and redox active substances were significantly elevated in septic patients. In patients with sepsis who had died, plasma levels of MIF and MnSOD were significantly elevated in comparison with survivors.

CONCLUSIONS

Our results therefore demonstrate that redox active substances may play an important role in the septic inflammatory response. MIF and MnSOD appear to be early predictors for survival in septic patients.

Regulation of redox signaling by selenoproteins

The unique chemistry of oxygen has been both a resource and threat for life on Earth for at least the last 2.4 billion years. Reduction of oxygen to water allows extraction of more metabolic energy from organic fuels than is possible through anaerobic glycolysis. On the other hand, partially reduced oxygen can react indiscriminately with biomolecules to cause genetic damage, disease, and even death. Organisms in all three superkingdoms of life have developed elaborate mechanisms to protect against such oxidative damage and to exploit reactive oxygen species as sensors and signals in myriad processes. The sulfur amino acids, cysteine and methionine, are the main targets of reactive oxygen species in proteins. Oxidative modifications to cysteine and methionine can have profound effects on a protein's activity, structure, stability, and subcellular localization. Non-reversible oxidative modifications (oxidative damage) may contribute to molecular, cellular, and organismal aging and serve as signals for repair, removal, or programmed cell death. Reversible oxidation events can function as transient signals of physiological status, extracellular environment, nutrient availability, metabolic state, cell cycle phase, immune function, or sensory stimuli. Because of its chemical similarity to sulfur and stronger nucleophilicity and acidity, selenium is an extremely efficient catalyst of reactions between sulfur and oxygen. Most of the biological activity of selenium is due to selenoproteins containing selenocysteine, the 21st genetically encoded protein amino acid. The most abundant selenoproteins in mammals are the glutathione peroxidases (five to six genes) that reduce hydrogen peroxide and lipid hydroperoxides at the expense of glutathione and serve to limit the strength and duration of reactive oxygen signals. Thioredoxin reductases (three genes) use nicotinamide adenine dinucleotide phosphate to reduce oxidized thioredoxin and its homologs, which regulate a plethora of redox signaling events. Methionine sulfoxide reductase B1 reduces methionine sulfoxide back to methionine using thioredoxin as a reductant. Several selenoproteins in the endoplasmic reticulum are involved in the regulation of protein disulfide formation and unfolded protein response signaling, although their precise biological activities have not been determined. The most widely distributed selenoprotein family in Nature is represented by the highly conserved thioredoxin-like selenoprotein W and its homologs that have not yet been assigned specific biological functions. Recent evidence suggests selenoprotein W and the six other small thioredoxin-like mammalian selenoproteins may serve to transduce hydrogen peroxide signals into regulatory disulfide bonds in specific target proteins.

Molecular chaperones and protein-folding catalysts as intercellular signaling regulators in immunity and inflammation

This review critically examines the hypothesis that molecular chaperones and protein-folding catalysts from prokaryotes and eukaryotes can be secreted by cells and function as intercellular signals, principally but not exclusively, for leukocytes. A growing number of molecular chaperones have been reported to function as ligands for selected receptors and/or receptors for specific ligands. Molecular chaperones initially appeared to act primarily as stimulatory signals for leukocytes and thus, were seen as proinflammatory mediators. However, evidence is now emerging that molecular chaperones can have anti-inflammatory actions or, depending on the protein and concentration, anti- and proinflammatory functions. Recasting the original hypothesis, we propose that molecular chaperones and protein-folding catalysts are "moonlighting" proteins that function as homeostatic immune regulators but may also under certain circumstances, contribute to tissue pathology. One of the key issues in the field of molecular chaperone biology relates to the role of microbial contaminants in their signaling activity; this too will be evaluated critically. The most fascinating aspect of molecular chaperones probably relates to evidence for their therapeutic potential in human disease, and ongoing studies are evaluating this potential in a range of clinical settings.

Elevated levels of thioredoxin 1 in the lungs and sera of idiopathic pulmonary fibrosis, non-specific interstitial pneumonia and cryptogenic organizing pneumonia

OBJECTIVE

Oxidant stress is thought to be involved in the establishment of idiopathic interstitial pneumonia (IIP). Thioredoxin 1 (TRX1) plays a role as a strong antioxidant in vivo, suggesting that TRX1 may be involved in the pathogenesis of IIPs. However, there is no report on TRX1 levels in the sera of IIPs. In addition, TRX1 expression in the lungs of non-specific interstitial pneumonia (NSIP) and cryptogenic organizing pneumonia (COP) patients also has not been reported. Here, we investigated whether or not TRX1 levels are altered in the lungs and sera of patients with idiopathic pulmonary fibrosis (IPF), NSIP, and COP.

METHODS

Immunohistochemical analysis was performed to examine the expression of TRX1. TRX1 levels in sera were measured using an ELISA kit.

RESULTS

TRX1 was expressed in the bronchiole-alveolar epithelium, especially with regenerative or metaplastic feature, and in alveolar macrophages in usual interstitial pneumonia (UIP) and fibrotic NSIP. TRX1 was weakly expressed in the lungs of cellular NSIP and COP. TRX1 producing cells in UIP (n=16), fibrotic NSIP (n=15), cellular NSIP (n=4), and COP (n=5) were significantly increased when compared to nonsmokers (n=7). TRX1 producing cells in UIP and fibrotic NSIP were significantly increased when compared to cellular NSIP and COP. TRX1 levels in the sera of the patients with IPF (n=32; 74.2 ± 7.5 ng/mL), fibrotic NSIP (n=7; 82.5 ± 18.4 ng/mL), cellular NSIP (n=3; 62.2 ± 3.2 ng/mL) and COP (n=17; 88.8 ± 19.7 ng/mL) were significantly higher than those of control subjects (n=74; 35.3 ± 2.7 ng/mL). Furthermore, TRX1 levels in the sera of IPF patients who later showed acute exacerbation (n=7; 106.6 ± 16.3 ng/mL) were significantly higher than those of IPF patients without acute exacerbation (n=25; 65.1 ± 7.6 ng/mL).

CONCLUSION

Overproduction of TRX1 in the lungs and sera may play an important role in the pathogenesis of IIPs.

Changes in thioredoxin concentrations: an observation in an ultra-marathon race

OBJECTIVES

Changes in plasma thioredoxin (TRX) concentrations before, during, and after a 130-km endurance race were measured with the aim of elucidating the relationship between exercise and oxidative stress (OS).

METHODS

Blood samples were taken from 18 runners participating in a 2-day-long 130-km ultra-marathon during the 2 days of the race and for 1 week thereafter. There were six sampling time points: at baseline, after the goal had been reached on the first and second day of the endurance race, respectively, and on 1, 3, and 5/6 days post-endurance race. The samples were analyzed for plasma TRX concentrations, platelet count, and blood lipid profiles.

RESULTS

Concentrations of plasma TRX increased from 17.9 ± 1.2 ng/mL (mean ± standard error of the mean) at baseline to 57.3 ± 5.0 ng/mL after the first day's goal had been reached and to 70.1 ± 6.9 ng/mL after the second day's goal had been reached; it then returned to the baseline level 1 day after the race. Platelet counts of 21.3 ± 1.2 × 10(4) cell/μL at baseline increased to 23.9 ± 1.5 × 10(4) cells/μL on Day 1 and to 26.1 ± 1.0 × 10(4) cells/μL on Day 2. On Day 7, the platelet counts had fallen to 22.1 ± 1.2 × 10(4) cell/μL. There was a significant positive correlation between plasma TRX and platelet count.

CONCLUSIONS

These data suggest that plasma TRX is an OS marker during physical exercise. Further studies are needed to determine the appropriate level of exercise for the promotion of health.

Thioredoxin regulates cell cycle via the ERK1/2-cyclin D1 pathway

Thioredoxin (TRX) is a key component of redox regulation and has been indicated to play an essential role in cell survival and growth. Here, we investigated the molecular mechanism of TRX in the regulation of cell survival and growth by using RNA interference (RNAi) in A549 lung cancer and MCF7 breast cancer cells. TRX knockdown did not significantly increase the basal level of cell death without exposure to stress, but CDDP-induced cell death was enhanced. Meanwhile, TRX knockdown resulted in significant cell-cycle arrest at the G(1) phase. Cyclin D1 expression was reduced by TRX knockdown at the protein and mRNA levels. TRX knockdown caused suppression of activation of the cyclin D1 promoter through elements including AP-1. TRX knockdown also reduced the levels of phosphorylated ERK1/2 and the nuclear translocation of ERK 1/2 induced by EGF. These results suggest that TRX is an important regulator of the cell cycle in the G(1) phase via cyclin D1 transcription and the ERK/AP-1 signaling pathways.

Redox regulation of cell survival by the thioredoxin superfamily: an implication of redox gene therapy in the heart

Reactive oxygen species (ROS) are the key mediators of pathogenesis in cardiovascular diseases. Members of the thioredoxin superfamily take an active part in scavenging reactive oxygen species, thus playing an essential role in maintaining the intracellular redox status. The alteration in the expression levels of thioredoxin family members and related molecules constitute effective biomarkers in various diseases, including cardiovascular complications that involve oxidative stress. Thioredoxin, glutaredoxin, peroxiredoxin, and glutathione peroxidase, along with their isoforms, are involved in interaction with the members of metabolic and signaling pathways, thus making them attractive targets for clinical intervention. Studies with cells and transgenic animals have supported this notion and raised the hope for possible gene therapy as modern genetic medicine. Of all the molecules, thioredoxins, glutaredoxins, and peroxiredoxins are emphasized, because a growing body of evidence reveals their essential and regulatory role in several steps of redox regulation. In this review, we discuss some pertinent observations regarding their distribution, structure, functions, and interactions with the several survival- and death-signaling pathways, especially in the myocardium.

Stress as an intercellular signal: the emergence of stress-associated molecular patterns (SAMP)

Abstrct Cells are continuously exposed to stressful situations that generally entail generation of reactive oxygen species and other redox alterations. Low levels of stress are physiological and can transmit essential survival or adaptive signals. At higher levels, however, the responses become maladaptive and cause damage. Frequently, stressful events occurring in a few cells propagate, resulting in tissue or even systemic response. Here we review recent evidence suggesting that stressed cells signal their state by expressing on their surface and secreting suitable molecular clues, which we propose to term Stress-Associated Molecular Patterns (SAMP). A unifying mechanism seems to involve the release of oxidoreductases and redox modifiers into the intercellular space, with structural and functional alterations in key signaling molecules. These observations open the way to novel therapeutic strategies.

Direct association of thioredoxin-1 (TRX) with macrophage migration inhibitory factor (MIF): regulatory role of TRX on MIF internalization and signaling

Thioredoxin-1 (TRX) is a small (14 kDa) multifunctional protein with the redox-active site Cys-Gly-Pro-Cys. Macrophage migration inhibitory factor (MIF) is a 12 kDa cytokine belonging to the TRX family. Historically, when we purified TRX from the supernatant of ATL-2 cells, a 12 kDa protein was identified along with TRX, which was later proved to be MIF. Here, we show that TRX and MIF form a complex in the cell and the culture supernatant of ATL-2 cells. Using a BIAcore assay, we confirmed that TRX has a specific affinity with MIF. We also found that extracellular MIF was more effectively internalized into the ATL-2 cells expressing TRX on the cell surface, than the Jurkat T cells which do not express surface TRX. Moreover, anti-TRX antibody blocked the MIF internalization, suggesting that the cell surface TRX is involved in MIF internalization into the cells. Furthermore, anti-TRX antibody inhibited MIF-mediated enhancement of TNF-alpha production from macrophage RAW264.7 cells. These results suggest that the cell surface TRX serves as one of the MIF binding molecules or MIF receptor component and inhibits MIF-mediated inflammatory signals.

Stereochemical configuration of 4-hydroxy-2-nonenal-cysteine adducts and their stereoselective formation in a redox-regulated protein

4-Hydroxy-2-nonenal (HNE), a major racemic product of lipid peroxidation, preferentially reacts with cysteine residues to form a stable HNE-cysteine Michael addition adduct possessing three chiral centers. Here, to gain more insight into sulfhydryl modification by HNE, we characterized the stereochemical configuration of the HNE-cysteine adducts and investigated their stereoselective formation in redox-regulated proteins. To characterize the HNE-cysteine adducts by NMR, the authentic (R)-HNE- and (S)-HNE-cysteine adducts were prepared by incubating N-acetylcysteine with each HNE enantiomer, both of which provided two peaks in reversed-phase high performance liquid chromatography (HPLC). The NMR analysis revealed that each peak was a mixture of anomeric isomers. In addition, mutarotation at the anomeric center was also observed in the analysis of the nuclear Overhauser effect. To analyze these adducts in proteins, we adapted a pyridylamination-based approach, using 2-aminopyridine in the presence of sodium cyanoborohydride, which enabled analyzing the individual (R)-HNE- and (S)-HNE-cysteine adducts by reversed-phase HPLC following acid hydrolysis. Using the pyridylamination method along with mass spectrometry, we characterized the stereoselective formation of the HNE-cysteine adducts in human thioredoxin and found that HNE preferentially modifies Cys(73) and, to the lesser extent, the active site Cys(32). More interestingly, the (R)-HNE- and (S)-HNE-cysteine adducts were almost equally formed at Cys(73), whereas Cys(32) exhibited a remarkable preference for the adduct formation with (R)-HNE. Finally, the utility of the method for the determination of the HNE-cysteine adducts was confirmed by an in vitro study using HeLa cells. The present results not only offer structural insight into sulfhydryl modification by lipid peroxidation products but also provide a platform for the chemical analysis of protein S-associated aldehydes in vitro and in vivo.

Thioredoxin in human and experimental sepsis

INTRODUCTION

Thioredoxin (TRX) is assumed to be beneficial in acute inflammatory diseases because of its potent antioxidant properties and an inhibitory effect on neutrophil evasion into sites of inflammation.

OBJECTIVE

To compare plasma levels of thioredoxin in septic patients and to investigate the role of thioredoxin in a polymicrobial septic mouse model.

DESIGN AND INTERVENTIONS

A combined single-center noninterventional clinical observation study and randomized controlled experimental investigation.

SETTING

Intensive care unit of a university hospital and laboratories of four university hospitals.

MEASUREMENTS AND MAIN RESULTS

To evaluate the role of TRX in sepsis, we measured TRX in plasma of septic patients and compared its levels in survivors and patients who did not survive sepsis. In addition, we examined the effect of neutralization of endogenous TRX as well as of treatment with recombinant TRX in a mouse peritonitis model of cecal ligation and puncture (CLP). We found that the serum plasma levels of TRX were significantly higher in patients with sepsis compared with healthy individuals. Furthermore, nonsurvivors showed even higher TRX levels than survivors of sepsis. The CLP septic mouse model revealed that neutralization of endogenous TRX impaired survival of septic mice, whereas treatment with recombinant TRX after CLP strongly enhanced the survival of mice.

CONCLUSIONS

Our results therefore demonstrate a critical role for TRX in the septic inflammatory response and suggest TRX as a potential therapeutic target for septic shock.

Recombinant human thioredoxin-1 becomes oxidized in circulation and suppresses bleomycin-induced neutrophil recruitment in the rat airway

Thioredoxin-1 (TRX) is a redox-active protein with anti-inflammatory effects. This study investigated the optimal delivery method and the mechanisms of recombinant human TRX (rhTRX) to suppress neutrophil recruitment in a rat bleomycin (BLM)-induced sustained acute lung injury model. In male Wister rats intratracheally administered with 0.125 mg/kg BLM, 8 mg/kg/day rhTRX was intravenously administered on days 3-6 using one of three protocols: daily bolus injection, 3 h daily infusion or continuous infusion for 96 h. Only the continuous-infusion of rhTRX significantly reduced the neutrophil infiltration compared with the other two methods. The BLM-induced down-regulation of L-selectin expression on circulating neutrophils was inhibited by rhTRX. Oxidized rhTRX showed a comparable effect with reduced rhTRX and rhTRX incubated with plasma or circulating in plasma was more than 99% oxidized. These results suggest that rhTRX becomes oxidized in circulation and continuous infusion of rhTRX suppresses neutrophil recruitment in the airway.

Unfolding the relationship between secreted molecular chaperones and macrophage activation states

Over the last 20 years, it has emerged that many molecular chaperones and protein-folding catalysts are secreted from cells and function, somewhat in the manner of cytokines, as pleiotropic signals for a variety of cells, with much attention being focused on the macrophage. During the last decade, it has become clear that macrophages respond to bacterial, protozoal, parasitic and host signals to generate phenotypically distinct states of activation. These activation states have been termed 'classical' and 'alternative' and represent not a simple bifurcation in response to external signals but a range of cellular phenotypes. From an examination of the literature, the hypothesis is propounded that mammalian molecular chaperones are able to induce a wide variety of alternative macrophage activation states, and this may be a system for relating cellular or tissue stress to appropriate macrophage responses to restore homeostatic equilibrium.

DAMPs and inflammatory processes: the role of redox in the different outcomes

Inflammation is deeply entangled with redox modulation. Triggering of PRRs on inflammatory cells induces ROS generation. As a consequence, activated cells mount antioxidant responses to counteract the possible harmful effects of oxidation. Therefore, when repair is completed, homeostasis is restored. Here, we describe some recent results showing that an exuberant antioxidant response to pro-oxidant inflammatory stimuli modifies not only the intra- but also the extracellular redox and contributes to the outcome of the inflammatory process. In particular, the role of redox modulation in IL-1beta secretion, in B lymphocyte differentiation to plasma cells, and in tumor progression will be discussed, and the potential consequences of extracellular redox alterations on DAMP activity will be considered.

Thioredoxin suppresses the contact hypersensitivity response by inhibiting leukocyte recruitment during the elicitation phase

Thioredoxin, a redox-regulating protein that scavenges reactive oxygen species, appears to show an excellent antiinflammatory effect in treating animal models of various human inflammatory diseases. The aim of this study was to clarify whether thioredoxin is useful for treating inflammatory skin diseases, such as contact dermatitis, caused by epicutaneous exposure to environmental and occupational antigens. The allergic contact hypersensitivity response was suppressed in thioredoxin-transgenic mice. This suppressive effect of thioredoxin appeared to be via the inhibition of the efferent limb of contact hypersensitivity because administration of recombinant thioredoxin suppressed the inflammatory response in the elicitation phase but not in the induction phase. Adoptive-transfer studies revealed that the host environment, but not donor leukocytes, is critical in this suppressive effect. In thioredoxin-transgenic mice, the infiltration of neutrophils in the elicitation site was diminished, whereas the migratory function of cutaneous dendritic cells and hapten-specific cell proliferation were not disturbed. Thioredoxin-transgenic mice had also an attenuated inflammatory response to croton oil. These findings suggest that thioredoxin prevents skin inflammatory responses and could be a suitable candidate for the treatment of contact dermatitis.

Fragrant unsaturated aldehydes elicit activation of the Keap1/Nrf2 system leading to the upregulation of thioredoxin expression and protection against oxidative stress

Thioredoxin, a key molecule in redox regulation, and many redox enzymes are regulated through the antioxidant responsive element (ARE). To search for antioxidative constituents, we screened extracts from vegetables and found that the extracts of Perilla frutescens and Artemisia princeps have potent thioredoxin-inducing activities. By activity-guided purification of Perilla frutescens extracts, we identified perillaldehyde as a novel thioredoxin inducer. Fragrant unsaturated aldehydes, such as trans-cinnamaldehyde, safranal, 2,4-octadienal, citral, trans-2, cis-6-nonadienal, and trans-2-hexenal showed the ability to activate ARE. Perillaldehyde-induced activation through the ARE was suppressed by the overexpression of wild-type Keap1, whereas sulforaphane-induced activation seemed to be partially suppressed. Mutant Keap1 (R272A/K287A or C273A/C288A) did not suppress this activation. Pretreatment with perillaldehyde reduced the H(2)O(2)-induced cytotoxicity. Thus, we show that fragrant unsaturated aldehydes from edible plants are novel thioredoxin inducers and ARE activators and may be beneficial for protection against oxidative stress-induced cellular damage. These results also suggest that perillaldehyde activates the Nrf2-Keap1 system and that the lysine and arginine residues juxtaposed to the critical cysteine residues of Keap1 are required for signal sensing.

Thioredoxin 1 delivery as new therapeutics

Thioredoxin 1 (Trx 1) is a redox-active small protein ubiquitously present in human body. It is one of the defensive proteins induced in response to various stress conditions. In addition to its anti-oxidative effect by dithiol-disulfide exchange in its active site, Trx 1 has anti-apoptotic and anti-inflammatory effects. Trx 1 overexpression has been shown to be effective in a wide variety of animal models for oxidative and inflammatory disorders. An administration of recombinant Trx 1 protein is also effective in animal models especially for severe acute lung diseases where Trx 1 is likely to act with its anti-inflammatory properties. Trx 1 in circulation shows anti-chemotactic effects for neutrophils and inhibitory effects against macrophage migration inhibitory factor (MIF). Neovascularization is also suppressed by Trx 1 via inhibition of the complement activation. Here we discuss precise mechanisms of Trx 1 and potential therapeutic approach of this molecule.

Attenuation of neuronal degeneration in thioredoxin-1 overexpressing mice after mild focal ischemia

Thioredoxin (Trx) is a 12-kDa protein ubiquitously expressed in all living cells that fulfills a variety of biological functions related to cell proliferation and apoptosis. It is characterized by the highly conserved reduction/oxidation (redox)-active site sequence Trp-Cys-Gly-Pro-Cys-Lys. Trx acts as a powerful antioxidant and plays an important role in maintaining critical protein thiols in the reduced state. Moreover, it has been shown to scavenge reactive oxygen species (ROS) and to protect against oxidative stress. We have reported that Trx-1 protects against neuronal damage during focal ischemia. However, the mechanisms underlying this protective effect and the effect of Trx-1 on neuronal apoptosis during ischemia have not been fully clarified. In this study, we analyzed the effect of Trx-1 overexpression against neuronal degeneration after a short duration of transient brain ischemia. Mild focal ischemia was reported to induce neuronal death through apoptosis. We employed Fluorojade-B staining to detect neuronal degeneration. In Trx transgenic mice, a smaller number of Fluorojade-B-positive neurons were detected after ischemia-reperfusion than in wild-type mice. In addition, we detected cleaved caspase-3- and TUNEL-positive cells, which indicated caspase-dependent apoptosis. Fewer caspase-3- and TUNEL-positive neurons were detected after ischemia-reperfusion in Trx transgenic mice than in wild-type mice. Furthermore, Akt signaling was reported to play a role in neuronal survival in Trx-1 overexpressing mice. After ischemia-reperfusion, Western blot and immunohistochemical analysis indicated that phosphorylation of Akt was enhanced in Trx transgenic mice after ischemia-reperfusion. Intraventricular injection of LY294002,which is a phosphoinositide 3-kinase (PI3K), vanished the neuroprotective effect in Trx-1 transgenic mice. These results indicate that Trx-1 overexpression protects neurons from apoptosis after ischemia-reperfusion.

Correlation of decreased survival and IL-18 in bone metastasis

OBJECTIVE

Previous studies have reported that serum IL-18 levels are increased in some cancers. We investigated whether IL-18 production is increased in sera and cancer cells of patients with non-small cell lung cancer (NSCLC).

PATIENTS OR MATERIALS

Serum levels of IFN-gamma and IL-18 and thioredoxin 1 (TRX1) were measured in 79 patients (51 males, 28 females, median age 67 years) with advanced NSCLC (57 adenocarcinoma, 22 squamous cell carcinoma; TNM stages IIIA [n=11], IIIB [n=24], and IV [n=44]) and 75 healthy age-matched controls (44 males, 31 females, median age 65 years) by enzyme-linked immunosorbent assay. We examined IL-18 production in the lungs and sites of bone metastasis of adenocarcinoma by immunohistochemistry.

RESULTS

Serum IL-18, IFN-gamma, and TRX1 levels in NSCLC patients were significantly (p<0.0001, p=0.0031, and p<0.0001, respectively) higher than in control subjects, while serum IFN-gamma levels in NSCLC were slightly increased. Serum IL-18, but not IFN-gamma or TRX1, levels were significantly (p=0.0102) and negatively associated with overall survival in NSCLC. The serum IL-18 level was identified as an independent prognostic factor for overall survival in multivariate survival analysis. Moreover, serum IL-18 levels were significantly (p=0.049) higher in NSCLC with bone metastasis than in NSCLC without bone metastasis. Based on immunohistochemistry, we observed that cancer cells in the lungs and bone metastases markedly produced IL-18.

CONCLUSION

Our results suggest that elevated serum IL-18 levels may be associated with IL-18 producing cancer cells in advanced NSCLC.

Thioredoxin and thioredoxin binding protein 2 in the liver

Thioredoxin (TRX) is a 12-kDa protein with redox-active dithiol in the active site -Cys-Gly-Pro-Cys- and constitutes a major thiol reducing system. TRX protects cells from stress-induced damage through antioxidative, antiapoptotic, and anti-inflammatory effect. In animal models, thioacetamide (TAA)-induced acute hepatitis and TAA-induced liver fibrosis was attenuated in TRX transgenic (TRXTG) mice. Plasma level of TRX is a good marker for hepatitis and nonalcoholic steatohepatitis (NASH) in human patients. Recently, we identified TRX binding protein 2 (TBP2) in a yeast two-hybrid screening. TBP2 regulates both the expression and reducing activity of TRX as well as cell growth. TBP2 knockout (TBP2KO) mice showed disorder in lipid metabolism. TBP2 plays a multiple role on cell growth and lipid and glucose metabolism. Thus, TRX and TBP2 play important roles in the pathophysiology of liver diseases, including NASH, indicating that ratio of TRX and TBP2 expression could be a novel marker of liver diseases like NASH.

Human glutaredoxin-1 catalyzes the reduction of HIV-1 gp120 and CD4 disulfides and its inhibition reduces HIV-1 replication

Reduction of intramolecular disulfides in the HIV-1 envelope protein gp120 occurs after its binding to the CD4 receptor. Protein disulfide isomerase (PDI) catalyzes the disulfide reduction in vitro and inhibition of this enzyme blocks viral entry. PDI belongs to the thioredoxin protein superfamily that also includes human glutaredoxin-1 (Grx1). Grx1 is secreted from cells and the protein has also been found within the HIV-1 virion. We show that Grx1 efficiently catalyzes gp120, and CD4 disulfide reduction in vitro, even at low plasma levels of glutathione. Grx1 catalyzes the reduction of two disulfide bridges in gp120 in a similar manner as PDI. Purified anti-Grx1 antibodies were shown to inhibit the Grx1 activity in vitro and block HIV-1 replication in cultured peripheral blood mononuclear cells. Also, the polyanion PRO2000, that was previously shown to prevent HIV entry, inhibits the Grx1- and PDI-dependent reduction of gp120 disulfides. Our findings suggest that Grx1 activity is important for HIV-1 entry and that Grx1 and the gp120 intramolecular disulfides are novel pharmacological targets for rational drug development.

Redox-regulated mechanisms in asthma

Homeostasis of the reduction-oxidation (redox) state is critical to protection from oxidative stress in the lungs. Therefore, the lungs have high levels of antioxidants, including glutathione, heme oxygenase, and superoxide dismutase. The numbers of inflammatory cells -- particularly eosinophils -- are increased in the airways of asthma patients, and these pulmonary inflammatory cells release large amounts of harmful reactive oxygen species and reactive nitrogen species. Human thioredoxin 1 (TRX1) is a redox-active protein of approximately 12 kDa that contains a (32)Cys-Gly-Pro-(35)Cys sequence necessary for its activity. The strong reducing activity of the sequence results from the cysteine residues acting as proton donors and cleaving disulfide (S-S) bonds in the target protein. Endogenous or exogenous TRX1 or both protect the lungs against ischemia-reperfusion injury, influenza infection, bleomycin-induced injury, or lethal pulmonary inflammation caused by interleukin-2 and interleukin-18. We showed that exogenous TRX1 inhibits airway hyperresponsiveness and pulmonary inflammation accompanied by eosinophilia in mouse models of asthma. Recently, we reported that exogenous TRX1 improves established airway remodeling in a prolonged antigen-exposure mouse asthma model. Exogenous and endogenous TRX1 also prevents the development of airway remodeling. Here, we discuss the role and clinical benefits of TRX1 in asthma.

Transgenic expression of antioxidant protein thioredoxin in pancreatic beta cells prevents progression of type 2 diabetes mellitus

The authors previously established a transgenic mouse line in the type 1 diabetes model, NOD mouse, in which thioredoxin (TRX), a redox protein, is overexpressed in pancreatic beta cells, and found that TRX overexpression slows the progression of type 1 diabetes. Recent reports on type 2 diabetes suggest that oxidative stress also degrades the function of beta cells. To elucidate whether TRX overexpression can prevent progressive beta cell failure from oxidative stress in type 2 diabetes, the authors transferred the TRX transgene from the NOD mouse onto a mouse model of type 2 diabetes, the db/db mouse. The progression of hyperglycemia and the reduction of body weight gain and insulin content of the db/db mouse were significantly suppressed by the TRX expression. Furthermore, TRX suppressed the reduction of Pdx-1 and MafA expression in the beta cells, which may be one of the cellular mechanisms for protecting beta cells from losing their insulin-secreting capacity. These results showed that TRX can protect beta cells from destruction not only in type 1 but also in type 2 diabetes, and that they provide evidence that oxidative stress plays a crucial role in the deterioration of beta cell function during the progression of type 2 diabetes.

Oxidoreductase Macrophage Migration Inhibitory Factor is simultaneously increased in leukocyte subsets of patients with severe sepsis

The oxidoreductase Macrophage Migration Inhibitory Factor (MIF) is discussed as a promising target for immunomodulatory therapy in patients with severe sepsis. Moreover, MIF expresses tautomerase as well as thiol-protein oxidoreductase activities and has a potential role in cellular redox homeostasis, apoptosis inhibition, endotoxin responsiveness as well as regulation of nuclear transcription factors. To further elucidate a potential role of intracellular MIF in severe sepsis, we assessed alterations of intracellular MIF content in peripheral blood leukocytes of patients with severe sepsis in comparison to healthy controls and non-septic patients after major surgery. Intracellular MIF was significantly elevated simultaneously in lymphocytes, B-cells, macrophages and granulocytes of patients with severe sepsis when compared to healthy control individuals (p < 0.05) and increased when compared to non-septic patients after major surgery. In parallel, plasma MIF levels were elevated in severe sepsis (p < 0.05). There was no difference of intracellular MIF in lymphocytes, B-cells, macrophages or granulocytes between surviving and non-surviving patients with severe sepsis (p > 0.05). However, in survivors LPS ex vivo stimulation increased MIF secretion but not in non-survivors of sepsis (p < 0.05). This finding underlines the role of intracellular MIF in inflammatory diseases. It suggests monitoring of intracellular MIF in further clinical and non-clinical research valuable.

Increased expression of thioredoxin-1, vascular endothelial growth factor, and redox factor-1 is associated with poor prognosis in patients with liver metastasis from colorectal cancer

We examined whether the expression of thioredoxin-1 (Trx-1) was associated with patient prognosis after liver resection for metastatic colorectal cancer. Eighty-four patients underwent resection of liver metastases from colorectal cancer, leaving no macroscopic evidence of residual tumor. Immunohistochemical study was performed to evaluate the relation among Trx-1, vascular endothelial growth factor (VEGF), and redox factor-1 (Ref-1) expression and the clinicopathologic characteristics and patient survival. Thirty-seven patients (44.0%) with Trx-1-positive metastases had shorter survival after primary liver resection (P = .0003) than the 47 patients (56.0%) with Trx-1-negative metastases. The percentage VEGF-positive and Ref-1-positive metastases was significantly higher in patients with Trx-1 expression (P = .0009 and .0002, respectively). Multivariate analysis revealed that Trx-1 expression was an independent prognostic factor. Expression of VEGF and Ref-1 is associated with Trx-1 overexpression, which is related to a poor prognosis in patients with liver metastases from colorectal cancer.

Thioredoxin-1 attenuates indomethacin-induced gastric mucosal injury in mice

Indomethacin is one of non-steroidal anti-inflammatory drugs that are commonly used clinically and often cause gastric mucosal injury as a side effect. Generation of reactive oxygen species (ROS) and activation of apoptotic signaling are involved in the pathogenesis of indomethacin-induced gastric mucosal injury. Thioredoxin-1 (Trx-1) is a small redox-active protein with anti-oxidative activity and redox-regulating functions. The aim of this study was to investigate the protective effect of Trx-1 against indomethacin-induced gastric mucosal injury. Trx-1 transgenic mice displayed less gastric mucosal damage than wild type (WT) C57BL/6 mice after intraperitoneal administration of indomethacin. Administration of recombinant human Trx-1 (rhTrx-1) or transfection of the Trx-1 gene reduced indomethacin-induced cytotoxicity in rat gastric epithelial RGM-1 cells. Pretreatment with rhTrx-1 suppressed indomethacininduced ROS production and downregulation of phosphorylated Akt in RGM-1 cells. Survivin, a member of inhibitors of apoptosis proteins family, was downregulated by indomethacin, which was suppressed in Trx-1 transgenic mice or by administration of rhTrx-1 in RGM-1 cells. Trx-1 inhibits indomethacin-induced apoptotic signaling and gastric ulcer formation, suggesting that it may have a preventive and therapeutic potential against indomethacin-induced gastric injury.

B- and T-cell-specific inactivation of thioredoxin reductase 2 does not impair lymphocyte development and maintenance

Thioredoxin reductases (Txnrds) are a group of selenoenzymes participating in cellular redox regulation. Three Txnrd isoforms are known, each of which exhibits distinct cellular localisation and tissue-specific expression pattern. Txnrd1 is found in the cytoplasm, expression of Txnrd2 is restricted to mitochondria and Txnrd3 shows testis-specific expression. Recently, it was shown that Txnrd2 strongly affects the development of blood cells, since mouse embryos deficient for Txnrd2 are severely anaemic, show increased apoptosis in foetal liver and possess haematopoietic liver stem cells of reduced capacity to proliferate in vitro. However, because Txnrd2-deficient mice die at embryonic day 13.5, it was not known how this enzyme affects blood cell function in the adult animal. In the present study we show that conditional Txnrd2 knockouts generated using CD4- and CD19Cre transgenic mice lack Txnrd2 expression in CD4-- and CD19-positive T- and B-lymphocytes, respectively. However, the development and differentiation of both cell types in thymus and bone marrow was not significantly impaired. In addition, B-cell proliferation and activation in response to CD40 and IL-4 was unaltered in Txnrd2-deficient B-cells.

Thioredoxin and thioredoxin-binding protein-2 in cancer and metabolic syndrome

Thioredoxin (TRX), a small redox-active multifunctional protein, acts as a potent antioxidant and a redox regulator in signal transduction. TRX expression is elevated in various types of human cancer. Overexpression of TRX introduces resistance to anti-cancer drugs or radiation-induced apoptosis; however, there is no evidence that the incidence of cancer is frequent in TRX-transgenic mice or that the administration of recombinant human TRX enhances tumor growth. Plasma/serum level of TRX is a good marker for oxidative stress-induced various disorders, including metabolic syndrome. Thioredoxin-binding protein-2 (TBP-2), which was originally identified as a negative regulator of TRX, acts as a growth suppressor and a regulator in lipid metabolism. TBP-2 expression is downregulated in various types of human cancer. TBP-2 deficiency induces lipid dysfunction and a phenotype resembling Reye syndrome. Thus, TRX and TBP-2 play important roles in the pathophysiology of cancer and metabolic syndrome by direct interaction or by independent mechanisms.

Lipid raft-mediated uptake of cysteine-modified thioredoxin-1: apoptosis enhancement by inhibiting the endogenous thioredoxin-1

Thioredoxin-1 (TRX) plays important roles in cellular signaling by controlling the redox state of cysteine residues in target proteins. TRX is released in response to oxidative stress and shows various biologic functions from the extracellular environment. However, the mechanism by which extracellular TRX transduces the signal into the cells remains unclear. Here we report that the cysteine modification at the active site of TRX promotes the internalization of TRX into the cells. TRX-C35S, in which the cysteine at residue 35 of the active site was replaced with serine, was internalized more effectively than wild-type TRX in human T-cell leukemia virus-transformed T cells. TRX-C35S bound rapidly to the cell surface and was internalized into the cells dependent on lipid rafts in the plasma membrane. This process was inhibited by wild-type TRX, reducing reagents such as dithiothreitol, and methyl-beta-cyclodextrin, which disrupts lipid rafts. Moreover, the internalized TRX-C35S binds to endogenous TRX, resulting in the generation of intracellular reactive oxygen species (ROS) and enhanced cis-diamine-dichloroplatinum (II) (CDDP)-induced apoptosis via a ROS-mediated pathway involving apoptosis signal-regulating kinase-1 (ASK-1) activation. These findings suggest that the cysteine at the active site of TRX plays a key role in the internalization and signal transduction of extracellular TRX into the cells.

Nucleoredoxin, a novel thioredoxin family member involved in cell growth and differentiation

Thioredoxin (TRX) family proteins are involved in various biologic processes by regulating the response to oxidative stress. Nucleoredoxin (NRX), a relatively uncharacterized member of the TRX family protein, has recently been reported to regulate the Wnt/beta-catenin pathway, which itself regulates cell fate and early development, in a redox-dependent manner. In this review, we describe the TRX family proteins and discuss in detail the similarities and differences between NRX and other TRX family proteins. Although NRX possesses a conserved TRX domain and a catalytic motif for oxidoreductase activity, its sequence homology to TRX is not as high as that of the close relatives of TRX. The sequence of NRX is more similar to that of tryparedoxin (TryX), a TRX family member originally identified in parasite trypanosomes. We also discuss the reported properties and potential physiologic roles of NRX.