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

Crystal structure of the catalytic domain of a human thioredoxin-like protein

Thioredoxin is a ubiquitous dithiol oxidoreductase found in many organisms and involved in numerous biochemical processes. Human thioredoxin-like protein (hTRXL) is differentially expressed at different development stages of human fetal cerebrum and belongs to an expanding family of thioredoxins. We have solved the crystal structure of the recombinant N-terminal catalytic domain (hTRXL-N) of hTRXL in its oxidized form at 2.2-A resolution. Although this domain shares a similar three-dimensional structure with human thioredoxin (hTRX), a unique feature of hTRXL-N is the large number of positively charged residues distributed around the active site, which has been implicated in substrate specificity. Furthermore, the hTRXL-N crystal structure is monomeric while hTRX is dimeric in its four crystal structures (reduced, oxidized, C73S and C32S/C35S mutants) reported to date. As dimerization is the key regulatory factor in hTRX, the positive charge and lack of dimer formation of hTRXL-N suggest that it could interact with the acidic amino-acid rich C-terminal region, thereby suggesting a novel regulation mechanism.

Thioredoxin suppresses 1-methyl-4-phenylpyridinium-induced neurotoxicity in rat PC12 cells

Thioredoxin (TRX) is a redox-active protein which plays a cytoprotective role against oxidative stress. Geranylgeranylacetone (GGA), used widely as an anti-ulcer drug, has been reported to induce TRX as well as heat shock protein 70 (HSP70) in hepatocytes and other cells. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), causes dopaminergic denervation and Parkinsonism in humans. The 1-methyl-4-phenylpyridinium ion (MPP(+)), an active metabolite of MPTP, induces cell death in a rat pheochromocytoma cell line (PC12 cells). We found that MPP(+) suppresses TRX expression in PC12 cells. Overexpression or administration of TRX attenuates MPP(+)-induced neurotoxicity on PC12 cells. Moreover, GGA induces expression of TRX and HSP70 and attenuates MPP(+)-induced toxicity in PC12 cells. These results indicate that TRX and GGA have a possible potential as new therapeutic agents for Parkinson disease.

Redox regulation of stress signals: possible roles of dendritic stellate TRX producer cells (DST cell types)

Thioredoxin (TRX) is a 12 kDa protein with redox-active dithiol (Cys-Gly-Pro-Cys) in the active site. TRX is induced by a variety of stresses including viral infection and inflammation. The promoter sequences of the TRX gene contain a series of stress-responsive elements including ORE, ARE, XRE, CRE and SP-1. TRX promotes DNA binding of transcription factors such as NF-kappaB, AP-1 and p53. TRX interacts with target proteins modulating the activity of those proteins. We have identified TRX binding protein-2 (TBP-2), which was identical to vitamin D3 up-regulated protein 1 (VDUP1). Potential action of TBP-2/VDUP1 as a redox-sensitive tumor suppressor will be discussed. There is accumulating evidence for the involvement of TRX in the protection against infectious and inflammatory disorders. We will discuss the role of TRX-dependent redox regulation of the host defense mechanism, in particular its relation to the emerging concept of constitutive and/or inducible TRX on special cell types with dendritic and stellate morphology in the immune, endocrine and nervous systems, which we provisionally designate as dendritic stellate TRX producer cells (DST cell types).

Thioredoxin-mediated redox control of human T cell lymphotropic virus type I (HTLV-I) gene expression

Thioredoxin (TRX) is a small ubiquitous protein with multiple biological functions, including the thiol-mediated redox-regulation of gene expression. We have previously demonstrated that human TRX is overexpressed as a major protein oxidoreductase in human T cell lymphotropic virus type I (HTLV-I)-infected cells. In the present study, we investigated the relationship between TRX and viral gene expression in HTLV-I infection. To study the mechanism that causes overexpression of TRX in HTLV-I-infected cells, we first examined the effect of the HTLV-I transactivator, Tax, on TRX expression. Induction of HTLV-I Tax protein increased the expression of TRX protein in a Tax-transfected Jurkat cell line, JPX-9. Moreover, chloramphenicol acetyltransferase (CAT) analysis with a reporter gene containing the TRX promoter revealed that Tax activates the transcription of TRX gene. To study the role of overexpressed TRX in HTLV-I infection, we next examined the effect of TRX on HTLV-I long terminal repeat (LTR)-mediated transcription using CAT analysis. In an HTLV-I-infected human T cell line MT-2, the HTLV-I LTR transactivation was suppressed by the overexpression of wild-type TRX, but activated by the introduction of inactive mutant TRX. Moreover, in HTLV-I negative Jurkat T cells, the HTLV-I LTR transactivation induced by Tax was also repressed by overexpression of wild-type TRX. Because cellular redox changes were shown to affect the HTLV-I gene expression, it is likely that TRX modulates the HTLV-I gene expression by regulating cellular redox state. Taken together, these findings suggest that overexpressed TRX, which is induced by HTLV-I Tax, may play an important role in HTLV-I infection through the negative regulation of viral gene expression.

Thioredoxin as a biomarker for oxidative stress in patients with rheumatoid arthritis

There is no doubt that oxidative stress occurs in patients with rheumatoid arthritis (RA) and play an important role in both inflammation and destruction of RA joints. Thioredoxin (TRX) is a ubiquitous redox-active protein and is known to be induced in several cells against oxidative stress and to be secreted extracellularly. To clarify whether plasma thioredoxin levels could be a marker for oxidative stress in patients with RA, we measured plasma TRX levels in patients with RA using a sensitive sandwich enzyme-linked immunosorbent assay (ELISA) and investigated its relationship to TRX concentrations in the inflammatory joints. We have found that the plasma TRX levels of RA patients were significantly higher than those of normal subjects (86.8 +/-54.1 ng/ml versus 38.6 +/-18.5 ng/ml, P<0.0001). The plasma levels were correlated with the disease activity of RA and also with serum C-reactive protein (CRP) values (P<0.01). The concentration of TRX in synovial fluid (SF) from RA was 353.3 +/- 220.1 ng/ml (mean +/- S.D.) which was significantly higher than that in SF from osteoarthritis patients (70.6 +/- 31.0 ng/ml, P<0.0001). The SF TRX concentration was significantly correlated with the number of leukocytes infiltrating in SF and with the serum CRP levels. The serum TRX levels were significantly positively correlated with the SF TRX concentrations in RA patients (P<0.05). By the histological examination for synovial tissue of RA patients, TRX was shown to be present on the surface of synovial lining layer as well as in the leukocytes.Moreover, urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage by endogenously generated oxygen radicals, was significantly higher in RA patients than in healthy subjects (11.55 +/- 4.71 versus 7.76 +/- 2.26 ng/mg creatinine, P<0.0001). Plasma TRX levels were significantly correlated with urinary excretion of 8-OHdG (P<0.005). We concluded that plasma TRX level is a new biomarker for the disease activity of RA and may reflect higher levels of oxidative stress in RA patients.

Effects of a new anti-rheumatic drug KE-298 and its active metabolite: KE-758 on secretion of thioredoxin and on the level of intracellular glutathione in human monocytes and T cells

Thioredoxin (TRX) and glutathione (GSH) are key regulators of the cellular balance of reduction/oxidation (redox). The impaired redox balance in joint cellular circumstances participates in immune dysfunctions seen in patients with rheumatoid arthritis (RA). We analyzed effects of a newly developed anti-rheumatic drug, KE-298 (2-acetylthiomethyl-4-(4-methylphenyl)-4-oxobutanoic acid) and it is active metabolite; KE-758 (2-mercaptomethyl-4-(4-methylphenyl)-4-oxobutanoic acid) on the secretion of TRX and the level of intracellular GSH in THP-1 cells, a human monocytic cell line and in Jurkat cells, a human T cell leukemia cell line, then we compared their effects with N-acetyl-L-cysteine (NAC). KE-298 (10-100 microg/ml) and KE-758 (10-100 microg/ml) as well as a high concentration of NAC (10mM) dose-dependently inhibited the secretion of TRX by THP-1 and Jurkat cells. RT-PCR analysis indicated that the suppressive effects of KE-298 and KE-758 on TRX secretion could be partly explained by the inhibition of TRX mRNA expression. On the other hand, KE-758 as well as a high concentration of NAC significantly increased the level of intracellular GSH. Thus, KE-298 is a novel sulphydryl drug which regulates the redox state of cellular circumstances. The potential of KE-298 to suppress the secretion of TRX and to increase the level of intracellular GSH may partly explain the efficacy in cases of RA.

Circulating thioredoxin suppresses lipopolysaccharide-induced neutrophil chemotaxis

Thioredoxin (Trx), a redox enzyme with a conserved active site (Cys-32-Gly-Pro-Cys-35), is induced and secreted into circulation in response to inflammation. Studies here demonstrate that elevating Trx levels in circulation either by i.v. injection of recombinant Trx or stimulating Trx release in Trx-transgenic mice dramatically blocks lipopolysaccharide (LPS)-stimulated neutrophil migration in the murine air pouch chemotaxis model. Furthermore, we show that leukocyte recruitment induced by the murine chemokines KC/GROalpha, RANTES (regulated upon activation, normal T cell expressed and secreted), and monocyte chemoattractant protein-1 (MCP-1) is suppressed also in Trx-transgenic mice. Addressing the mechanism responsible for this suppression, we show that circulating Trx blocks (i) the LPS-stimulated in vitro activation of neutrophil p38 mitogen-activated protein kinase, (ii) the normal down-regulation of CD62L on neutrophils migrating into the LPS-stimulated air pouch, and (iii) the in vitro adhesion of LPS-activated neutrophils on endothelial cells. However, as we also show, Trx does not alter the expression of endothelial cell adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, CD62P, and CD62E) within 3 h. Collectively, these findings indicate that elevated levels of circulating Trx interfere with chemotaxis by acting directly on neutrophils. We discuss these findings in the context of recent studies reporting beneficial effects of acutely elevated Trx in ischemic injury and negative effects associated with chronically elevated Trx in HIV disease.

Sptrx-2, a fusion protein composed of one thioredoxin and three tandemly repeated NDP-kinase domains is expressed in human testis germ cells

BACKGROUND

Thioredoxins (Trx) are small redox proteins that function as general protein disulphide reductases and regulate several cellular processes such as transcription factor DNA binding activity, apoptosis and DNA synthesis. In mammalian organisms, thioredoxins are generally ubiquitously expressed in all tissues, with the exception of Sptrx-1 which is specifically expressed in sperm cells.

RESULTS

We report here the identification and characterization of a novel member of the thioredoxin family, the second with a tissue-specific distribution in human sperm, termed Sptrx-2. The Sptrx-2 ORF (open reading frame) encodes for a protein of 588 amino acids with two different domains: an N-terminal thioredoxin domain encompassing the first 105 residues and a C-terminal domain composed of three repeats of a NDP kinase domain. The Sptrx-2 gene spans about 51 kb organized in 17 exons and maps at locus 7p13-14. Sptrx-2 mRNA is exclusively expressed in human testis, mainly in primary spermatocytes, while Sptrx-2 protein expression is detected from the pachytene spermatocytes stage onwards, peaking at round spermatids stage. Recombinant full-length Sptrx-2 expressed in bacteria displayed neither thioredoxin nor NDP kinase enzymatic activity.

CONCLUSIONS

The sperm specific expression of Sptrx-2, together with its chromosomal assignment to a position reported as a potential locus for flagellar anomalies and male infertility phenotypes such as primary ciliary dyskinesia, suggests that it might be a novel component of the human sperm axonemal organization.

The effect of thioredoxin on the expression of proopiomelanocortin-derived peptides, the melanocortin 1 receptor and cell survival of normal human keratinocytes

An important constituent of the cellular antioxidant buffering system that controls the redox state of proteins is thioredoxin (TRX), a 13 kDa protein that catalyzes thiol-disulfide exchange reactions, regulates activation of transcription factors, and possesses several other biologic functions similar to cytokines. We have previously reported that TRX released from UVB-irradiated keratinocytes stimulates melanogenesis by upregulating MSH receptor expression and its binding activity in melanocytes. The purpose of this study was to examine the effects of TRX on keratinocytes as an autocrine factor. TRX suppressed the UVB-induced production and secretion of alpha-melanocyte stimulating hormone (alpha-MSH) and of adrenocorticotropic hormone (ACTH), and also suppressed proopiomelanocortin (POMC) mRNA expression by normal human keratinocytes; however, TRX upregulated melanocortin 1 receptor (MC1-R) expression synergistically with UVB in normal human keratinocytes. These results suggest that exogenous TRX regulates expression of those genes in different manners. Furthermore, addition of an antibody against TRX induced cell death in keratinocytes, probably due to enhanced signaling of MSH, as it has been shown that MSH suppresses heat shock protein (hsp) 70 expression in differentiated keratinocytes, which express high levels of MC1-R and decreases their survival rate during oxidative stress. Taken together, the results suggest that keratinocyte-derived TRX regulates the expression of stress inducible neuropeptides and their receptor, and is critically involved in the survival of keratinocytes.

Treatment of adult T-cell leukaemia/lymphoma: current strategy and future perspectives

Human T-cell leukaemia virus type I (HTLV-I) associated adult T-cell leukaemia/lymphoma (ATL) carries a very poor prognosis due to an intrinsic resistance of leukaemic cells to conventional or even high doses of chemotherapy and to an associated severe immunosuppression. Therefore, the potential role of conventional chemotherapy, high dose chemotherapy with autologous or allogeneic bone marrow transplantation remains to be defined. Important progress was achieved in the treatment of ATL with the combination of zidovudine (AZT) and interferon-alpha (IFN) which produces a high response rate in ATL patients with minimal side effects. This treatment seems to prolong the survival of patients much more than intensive chemotherapy. The success of this potentially anti-retroviral approach in the treatment of ATL suggests the existence of continuous HTLV-I replication in vivo. These encouraging results may be improved by the use of higher doses of AZT and IFN combined with other anti-retroviral agents. However, since cure seems still elusive, new therapeutic approaches or new combinations are required. For example, biological mediators such as retinoid acid, which induces apoptosis of ATL cells in vitro, may reduce drug resistance and stimulates immunity to restore anti-tumour activity against ATL cells. Alternatively, immunotherapy with anti-interleukin-2 receptor monoclonal antibodies or injection of cytotoxic T-cells directed against virus antigens could be interesting approaches which may merit further investigations in the near future. Finally, the recent demonstration that the combination of arsenic trioxide (As) and IFN induces a specific degradation of the viral transactivator Tax followed by cell cycle arrest and apoptosis of HTLV-I positive cells may constitute a valuable addition to ATL treatment.

Properties and biological activities of thioredoxins

The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin- 1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.

Regulation of interferon and retinoic acid-induced cell death activation through thioredoxin reductase

Interferons (IFNs) and retinoids are potent biological response modifiers. The IFN-beta and all-trans-retinoic acid combination, but not these single agents individually, induces death in several tumor cell lines. To elucidate the molecular basis for these actions, we have employed an antisense knockout approach to identify the gene products that mediate cell death and isolated several genes associated with retinoid-IFN-induced mortality (GRIMs). One of the GRIM cDNAs, GRIM-12, was identical to human thioredoxin reductase (TR). To define the functional relevance of TR to cell death and to define its mechanism of death-modulating functions, we generated mutants of TR and studied their influence on the IFN/RA-induced death regulatory functions of caspases. Wild-type TR activates cell death that was inhibited in the presence of caspase inhibitors or catalytically inactive caspases. A mutant TR, lacking the active site cysteines, inhibits the cell death induced by caspase 8. IFN/all-trans-retinoic acid-induced cytochrome c release from the mitochondrion was promoted in the presence of wild type and was inhibited in the presence of mutant TR. We find that TR modulates the activity of caspase 8 to promote death. This effect is in part caused by the stimulation of death receptor gene expression. These studies identify a new mechanism of cell death regulation by the IFN/all-trans-retinoic acid combination involving redox enzymes.

Geranylgeranylacetone promotes induction and secretion of thioredoxin in gastric mucosal cells and peripheral blood lymphocytes

Thioredoxin (TRX) is a redox-active protein which is induced by oxidative stresses and shows a variety of biological activities including cytoprotection against oxidative stress. We recently reported that geranylgeranylacetone (GGA), an anti-ulcer drug, induces TRX in rat hepatocytes. In this study, we demonstrate that GGA promotes induction and secretion of TRX in rat gastric mucosal cells and human peripheral blood lymphocytes (PBLs). Western blotting and a sensitive sandwich ELISA showed that TRX was induced by GGA in the cell lysates and culture supernatants of rat gastric mucosal RGM-1 cells and human PBLs. LDH releasing assay showed that GGA protected rat gastric mucosal RGM-1 cells from ethanol-induced cytotoxicity. Moreover, exogenous recombinant wild type TRX decreased 51Cr release from primary cultured rat gastric mucosal cells incubated with ethanol or hydrogen peroxide in a dose-dependent manner, whereas recombinant mutant TRX (C32S/C35S), in which the two cysteines were replaced with serines in its active site, did not. These results indicate that GGA promotes the induction and secretion of TRX in a variety of types of cells and suggest that induced or secreted TRX may play an important role in the cytoprotective action of GGA on gastric mucosal cells.

Properties and biological activities of thioredoxins

The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin-1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.

Thioredoxin participates in a cell death pathway induced by interferon and retinoid combination

Interferons (IFNs) and retinoids are potent tumor growth suppressors. We have shown earlier that the IFN-beta and all-trans retinoic acid combination, but not the single agents, induces death in several tumor cell lines. Employing a genetic approach we have recently identified several Genes associated with Retinoid-IFN induced Mortality (GRIM) that mediate the cell death effect of IFN/RA combination. One of the GRIMs, GRIM-12, was identical to human thioredoxin reductase (TR), an enzyme that controls intracellular redox state. To define the participants of TR mediated death pathway we have examined the role of thioredoxin (Trx), its downstream substrate, and its influence on IFN/RA-induced death regulation. Inhibition of the thioredoxin expression by antisense RNA suppressed cell death. Similarly, a mutant Trx1 lacking the critical cysteine residues blocked cell death. In contrast, overexpression of wildtype thioredoxin augmented cell death. This effect of Trx1 was in part due to its ability to augment cell death via caspase-8. The redox inactive Trx1 mutant inhibits the cell death induced by caspase-8 but not caspase-3. These studies identify a novel mechanism of cell death regulation by IFN/RA combination involving redox enzymes.

Serum thioredoxin (TRX) levels in patients with heart failure

An increase in oxidative stress is thought to be involved in the progression of heart disease, but the serum level of thioredoxin (TRX), which regulates the cellular redox state, has not been investigated in patients with heart diseases. The present study determined serum TRX levels with a sandwich enzyme-linked immunosorbent assay in a total of 39 patients with dilated cardiomyopathy (DCM) (n=5), acute coronary syndrome (ACS) (n=7) or stable angina (n=18), including effort angina (n=7) and vasospastic angina (n=11), and in control subjects (n=7). The serum TRX level in patients with New York Heart Association (NYHA) functional classes III and IV (n=8, 33.3+/-8.6 ng/ml) was significantly higher than in the control subjects (n=7, 14.0+/-4.6 ng/ml). In addition, the serum TRX levels correlated positively with the severity of NYHA class, and negatively with the left ventricular ejection fraction. The serum TRX levels were elevated in patients with ACS and DCM compared with the controls. These results indicate a possible association between TRX concentration and the severity of heart failure.

Difference in thioredoxin expression in viral myocarditis in inbred strains of mice

Redox regulating mechanisms may be involved in the pathogenesis of viral myocarditis and thioredoxin (TRX) is a small multifunctional protein that contains a redox active sequence. The present study investigated the histopathology and characteristics of TRX expression in acute coxsackievirus B3 myocarditis in inbred strains of mice (severe myocarditis in DBA/2 mice, moderate myocarditis in BALB/c mice and mild myocarditis in C57BL/6 mice). Thioredoxin was upregulated and its expression correlated with the severity of the disease. In addition, 8-hydroxy-2'-deoxyguanosine, which is an established marker for oxidative stress, was concominantly positive in damaged myocytes. Thus, TRX may be specifically induced by the acute inflammatory stimuli in murine viral myocarditis, and the severity and development of acute viral myocarditis may be regulated by the cellular redox state.

Molecular biology and pathogenesis of the human T-cell leukaemia/lymphotropic virus Type-1 (HTLV-1)

Retroviruses are associated with a variety of diseases, including immunological and neurological disorders, and various forms of cancer. In humans, the Human T-cell Leukaemia/Lymphotropic virus type 1 (HTLV-1), which belongs to the Oncovirus family, is the aetiological agent of two diverse diseases: Adult T-cell leukaemia/lymphoma (ATLL) (Poiesz et al. 1980; Hinuma et al. 1981; Yoshida et al. 1982), as well as the neurological disorder tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM) (Gessain et al. 1985; Rodgers-Johnson et al. 1985; Osame et al. 1986). HTLV-1 is the only human retrovirus known to be the aetiological agent of cancer. A genetically related virus, HTLV-2, has been identified and isolated (Kalyanaraman et al. 1982). However, there has been no demonstration of a definitive aetiological role for HTLV-2 in human disease to date. Simian T-cell lymphotropic viruses types 1 and 2 (STLV-1 and -2) and bovine leukaemia virus (BLV) have also been classified in same group, Oncoviridae, based upon their similarities in genetic sequence and structure to HTLV-1 and -2 (Burny et al. 1988; Dekaban et al. 1995; Slattery et al. 1999). This article will focus on HTLV-1, reviewing its discovery, molecular biology, and its role in disease pathogenesis.

Hemin-induced activation of the thioredoxin gene by Nrf2. A differential regulation of the antioxidant responsive element by a switch of its binding factors

Thioredoxin plays an important role in various cellular processes through redox regulation. Here, we have demonstrated that thioredoxin expression is transcriptionally induced in K562 cells by hemin (ferriprotoporphyrin IX) through activation of a regulatory region positioned from -452 to -420 bp of the thioredoxin gene. Insertion of a mutation in the antioxidant responsive element (ARE)/AP-1 consensus binding sequence in this region abolished the response to hemin. With electrophoretic mobility shift and DNA affinity assays, we have shown that the NF-E2p45/small Maf complex constitutively binds to the ARE. The binding of the Nrf2/small Maf complex to ARE was induced by hemin, whereas the binding of Jun/Fos proteins to ARE was induced by phorbol 12-myristate 13-acetate, but not hemin. Hemin induced nuclear translocation of Nrf2 but did not affect nuclear expression of Jun/Fos proteins. Overexpression of Nrf2 augmented the response to hemin in a dose-dependent manner. In contrast, overexpression of the dominant negative mutant of Nrf2 suppressed hemin-induced activation through the ARE. We show here hemin-induced activation of the thioredoxin gene by Nrf2 through the ARE and propose a novel mechanism of the regulation of the ARE through a switch of its binding factors.

Truncated thioredoxin (Trx80) induces production of interleukin-12 and enhances CD14 expression in human monocytes

Human thioredoxin (Trx) is the major 12-kd cellular disulfide-reductase that on secretion acts as a cocytokine with several interleukins. Truncated Trx with the 80 N-terminal residues (Trx80), also present in plasma, was by itself a mitogenic cytokine for human peripheral blood mononuclear cells (PBMC). This study investigated which cells in PBMC are targets of recombinant Trx80. Purified human CD14(+) monocytes, but not B or T cells, in a synthetic medium were activated to differentiation by Trx80 as measured by flow cytometry of surface antigens because exposure to 100 nM Trx80 increased expression of CD14, CD40, CD54, and CD86. Proliferation of the monocytes was increased in a dose-dependent manner by Trx80 in concentrations ranging from 10 nM to 1 microM. Trx or interleukin (IL) 2 did not induce proliferation or expression of surface antigens on monocytes. Trx80 alone induced secretion of IL-12 from CD40(+) monocytes in the PBMC cultures and this effect was enhanced by IL-2. Trx80 and IL-2 together were strongly synergistic to induce secretion of interferon-gamma in PBMC cultures. The results showed that Trx80 is a potent cytokine for normal human monocytes and directs the immune system in favor of a Th1 response via IL-12 production.

Identification of a novel thioredoxin-related transmembrane protein

We recently identified a series of transforming growth factor-beta-responsive genes in A549 human adenocarcinoma cell line by a gene trap screening method. Here we report the molecular cloning and characterization of one of these genes, designated TMX, that encodes a novel protein of 280 amino acid residues. The TMX protein possesses an N-terminal signal peptide followed by one thioredoxin (Trx)-like domain with a unique active site sequence, Cys-Pro-Ala-Cys, and a potential transmembrane domain. There are putative TMX homologs with identical active site sequences in the Caenorhabditis elegans and Drosophila genomes. Using recombinant proteins expressed in Escherichia coli, we demonstrated the activity of the Trx domain of TMX to cleave the interchain disulfide bridges in insulin in vitro. The TMX transcript is widely expressed in normal human tissues, and subcellular fractionation and immunostaining for an epitope-tagged TMX protein suggest that TMX is predominantly localized in the endoplasmic reticulum (ER). When TMX was expressed in HEK293 cells, it significantly suppressed the apoptosis induced by brefeldin A, an inhibitor of ER-Golgi transport. This activity was abolished when two Cys residues in the active site sequence were mutated to Ser, suggesting that the Trx-like activity of TMX may help relieve ER stress caused by brefeldin A.

Modulation of exogenous and endogenous levels of thioredoxin in human skin fibroblasts prevents DNA damaging effect of ultraviolet A radiation

Thioredoxin (Trx) plays important biological roles both intra- and extracellularly via thiol redox control. We have previously demonstrated that Trx exhibited protective effects against UVA cytotoxicity in human skin fibroblasts. As an extension of the latter investigation, the present work is aimed at assessing ability of Trx to maintain genomic integrity in human skin fibroblasts upon exposure to UVA radiation. Indeed, UVA (320--380 nm) is mutagenic and induces genomic damage to skin cells. The alkaline comet assay was used in association with DNA repair enzyme including formamido pyrimidine glycosylase (Fpg) and endonuclease III (endo III) to estimate the amount of modified bases together with the level of strand breaks and alkali-labile sites. The HPLC-EC assay was applied to assess 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) levels and to permit the calibration of comet assay as previously described. We reported that overexpression of human Trx (transient transfection) as well as exogenous human recombinant Trx added to the culture medium, decreased the level of DNA damage in UVA irradiated cells. Interestingly, transfection appeared to prevent UVA-induced 8-oxodGuo (3.06 au per Joules.cm(-2) compared to 4.94 au per Joules.cm(-2) for nontransfected cells). Moreover, Trx accumulates into nuclei in transfected cells. This finding supports the notion that Trx is important for the maintenance of the integrity of genetic information. This work demonstrated that under conditions of UVA oxidative stress, Trx prevented the UVA-induced DNA damage.

Thioredoxin acts as a B cell growth factor in channel catfish

To identify differentially expressed genes from channel catfish macrophages, a cDNA library from LPS-stimulated catfish macrophages was screened by subtractive hybridization. This screening yielded a 552-bp cDNA coding for catfish thioredoxin (CF-TRX). The deduced amino acid sequence revealed that CF-TRX contains 107 amino acids and is 59% homologous to human adult T cell leukemia-derived factor/TRX, originally described as an IL-2R alpha-inducing factor. Northern blot analyses showed that CF-TRX is expressed in catfish T and macrophage cell lines, but weakly in B cell lines. Similar results were also observed in Western blot analyses using a mAb specific for recombinant CF-TRX (rTRX). The use of rTRX in functional studies demonstrated that rTRX induces in vitro proliferative responses of catfish PBL that were synergistically enhanced by the addition of culture supernatants from catfish T cell lines. In addition, cell separation studies and flow cytometric analyses revealed that the cells proliferating in rTRX-stimulated cultures were mostly B cells. These results suggest that CF-TRX may have an important role in the activation and proliferation of channel catfish B cells.

Chronic elevation of plasma thioredoxin: inhibition of chemotaxis and curtailment of life expectancy in AIDS

Thioredoxin (Trx) is an intracellular redox protein with extracellular cytokine-like and chemokine-like activities. We show here that, although plasma Trx levels are unrelated to survival of HIV-infected individuals with CD4 cell counts above 200/microl blood, survival is significantly impaired (P = 0.003) when plasma Trx is chronically elevated in HIV-infected subjects with CD4 T cell counts below this level (i.e., with Centers for Disease Control (CDC)-defined AIDS). Relevant to the mechanism potentially underlying this finding, we also present data from experimental studies in mice showing that elevated plasma Trx efficiently blocks lipopolysaccharide (LPS)-induced chemotaxis, an innate immune mechanism that is particularly crucial when adaptive immunity is compromised. Thus, we propose that elevated plasma Trx in HIV-infected individuals with low CD4 T cell counts directly impairs survival by blocking pathogen-induced chemotaxis, effectively eliminating the last (innate) barrier against establishment of opportunistic and other infections in these immunodeficient individuals.

Localization of the thioredoxin system in normal rat kidney

Components of the thioredoxin system were localized in normal rat kidney using immunoperoxidase techniques at the light microscopic level and immunogold techniques at the ultrastructural level. Results from both methods were similar. Thioredoxin, thioredoxin reductases, and peroxiredoxins showed cell-type-specific localization, with the same cell types (proximal and distal tubular epithelial, papillary collecting duct, and transitional epithelial cells) previously identified as having high amounts of antioxidant enzyme immunoreactive proteins and oxidative damage products also having high levels of proteins of the thioredoxin system. In addition, peroxiredoxins II and IV were found in high levels in the cytoplasm of red blood cells, identified in kidney blood vessels. While thioredoxin and thioredoxin reductase 1 were found in all subcellular locations in kidney cells, thioredoxin reductase 2 was found predominantly in mitochondria. Thioredoxin reductase 1 was identified in rat plasma, suggesting it is a secreted protein. Peroxiredoxins often had specific subcellular locations, with peroxiredoxins III and V found in mitochondria and peroxiredoxin IV found in lysosomes. Our results emphasize the complex nature of the thioredoxin system, demonstrating unique cell-type and organelle specificity.

Cloning and expression of the Actinobacillus actinomycetemcomitans thioredoxin (trx) gene and assessment of cytokine inhibitory activity

Thioredoxin is a ubiquitous redox control and cell stress protein. Unexpectedly, in recent years, thioredoxins have been found to exhibit both cytokine and chemokine activities, and there is increasing evidence that this class of protein plays a role in the pathogenesis of inflammatory diseases. In spite of this evidence, it has been reported that the oral bacterium and periodontopathogen Actinobacillus actinomycetemcomitans secretes an immunosuppressive factor (termed suppressive factor 1 [SF1] [T. Kurita-Ochiai and K. Ochiai, Infect. Immun. 64:50-54, 1996]) whose N-terminal sequence, we have determined, identifies it as thioredoxin. We have cloned and expressed the gene encoding the thioredoxin of A. actinomycetemcomitans and have purified the protein to homogeneity. The A. actinomycetemcomitans trx gene has 52 and 76% identities, respectively, to the trx genes of Escherichia coli and Haemophilus influenzae. Enzymatic analysis revealed that the recombinant protein had the expected redox activity. When the recombinant thioredoxin was tested for its capacity to inhibit the production of cytokines by human peripheral blood mononuclear cells, it showed no significant inhibitory capacity. We therefore conclude that the thioredoxin of A. actinomycetemcomitans does not act as an immunosuppressive factor, at least with human leukocytes in cultures, and that the identity of SF1 remains to be elucidated.

Dissection of the enzymatic and immunologic functions of macrophage migration inhibitory factor. Full immunologic activity of N-terminally truncated mutants

Macrophage migration inhibitory factor (MIF) is a cytokine with broad regulatory functions in innate immunity. MIF belongs to the few cytokines displaying catalytic activities, i.e. MIF has a Pro2-dependent tautomerase and a Cys-Ala-Leu-Cys (CALC) cysteine-based thiol-protein oxidoreductase activity. Previous studies have addressed the roles of the catalytic site residues and the C-terminus. The two activities have not been directly compared. Here we report on the N-terminal mutational analysis and minimization of MIF and on a dissection of the two catalytic activities by comparing mutants P2AMIF, Delta4MIF, Delta5MIF, Delta6MIF, Delta7MIF, Delta8MIF, and Delta10MIF with the cysteine mutants of MIF. As N-terminal deletion was predicted to interfere with protein structure due to disruption of the central beta sheet, it was surprising that deletion of up to six N-terminal residues resulted in normally expressed proteins with wild-type conformation. Strikingly, such mutants exhibited full MIF-specific immunologic activity. While mutation of Pro2 eliminated tautomerase activity, the CALC cysteine residues had no influence on this activity. However, mutant C81SMIF, which otherwise has full biologic activity, only had 32% tautomerase activity. Deletion of four N-terminal residues did not interfere with insulin reduction by MIF. By contrast, reduction of 2-hydroxyethyldisulfide (HED) was markedly affected by N-terminal manipulation, with P2AMIF and Delta2MIF exhibiting 40% activity, and Delta4MIF completely failing to reduce HED. This study constitutes the first comparison of the two catalytic activities of MIF and should assist in understanding the molecular links between the catalytic and immunologic activities of this cytokine and in providing guidelines for N-terminal protein minimization.

Possible association of thioredoxin and p53 in breast cancer

Expression of thioredoxin (TRX), a dithiol-reducing enzyme, and mutations of p53 have been detected in various cancer tissues. We recently reported that TRX-dependent redox regulation plays a crucial role in DNA binding activity of p53. In this study, we investigated the possibility of functional association between TRX and p53 in breast cancer. First, we examined the expression of TRX and mutated p53 in 100 primary breast cancer tissues by immunohistochemistry. Expression of TRX was detected in cases of 84/100 (84%) and expression of p53, which means existence of mutated p53, in cases of 63/100 (63%). TRX positive cases was 89% (56/63) in mutant p53 positive cases. Next, we examined the expression of TRX and p53 in breast cancer cell line MCF-7 cells after CDDP treatment or irradiation. CDDP treatment or irradiation augmented expression of TRX and p53 in MCF-7 cells by western blotting. Immunofluorescence cell analysis by confocal microscopy showed that CDDP treatment induced translocation of TRX into nuclei. These results suggest the possible association of TRX with p53-dependent function including DNA repair in breast cancer.

The role of the redox protein thioredoxin in cell growth and cancer

The thioredoxins are ubiquitous proteins containing a conserved -Trp-Cys-Gly-Pro-Cys-Lys- redox catalytic site. Mammalian thioredoxin family members include thioredoxin-1 (Trx1), mitochondrial thioredoxin-2 (Trx2), and a larger thioredoxin-like protein, p32TrxL. Thioredoxin is reduced by NADPH and thioredoxin reductase and, in turn reduces oxidized cysteine groups on proteins. When thioredoxin levels are elevated there is increased cell growth and resistance to the normal mechanism of programmed cell death. An increase in thioredoxin levels seen in many human primary cancers compared to normal tissue appears to contribute to increased cancer cell growth and resistance to chemotherapy. Mechanisms by which thioredoxin increases cell growth include an increased supply of reducing equivalents for DNA synthesis, activation of transcription factors that regulate cell growth, and an increase in the sensitivity of cells to other cytokines and growth factors. The mechanisms for the inhibition of apoptosis by thioredoxin are just now being elucidated. Because of its role in stimulating cancer cell growth and as an inhibitor of apoptosis, thioredoxin offers a target for the development of drugs to treat and prevent cancer.

A redox-inactive thioredoxin reduces growth and enhances apoptosis in WEHI7.2 cells

Cancer cell lines transfected with thioredoxin show increased anchorage-independent growth and decreased sensitivity to induction of apoptosis by a number of anticancer drugs. The present studies were undertaken to evaluate further the role of thioredoxin in cell growth and drug-induced apoptosis. A redox-inactive mutant thioredoxin was stably transfected into WEHI7.2 mouse lymphocytic leukemia cells and two clones were examined for growth characteristics and the induction of apoptosis by dexamethasone, etoposide, doxorubicin, and staurosporine. These clones each exhibited a 71% increase in doubling time in solution and a 20 and 75% reduction in colony formation in soft agarose. The transfected cells also showed increased susceptibility to apoptosis induced by dexamethasone, etoposide, doxorubicin, and staurosporine compared with controls. The results of this study suggest that thioredoxin can regulate the growth rate of cells and that thioredoxin is a critical component in the pathway leading to drug-induced apoptosis in WEHI7.2 cells.

Vitamin D3 up-regulated protein 1 mediates oxidative stress via suppressing the thioredoxin function

As a result of identifying the regulatory proteins of thioredoxin (TRX), a murine homologue for human vitamin D3 up-regulated protein 1 (VDUP1) was identified from a yeast two-hybrid screen. Cotransfection into 293 cells and precipitation assays confirmed that mouse VDUP1 (mVDUP1) bound to TRX, but it failed to bind to a Cys32 and Cys35 mutant TRX, suggesting the redox-active site is critical for binding. mVDUP1 was ubiquitously expressed in various tissues and located in the cytoplasm. Biochemical analysis showed that mVDUP1 inhibited the insulin-reducing activity of TRX. When cells were treated with various stress stimuli such as H2O2 and heat shock, mVDUP1 was significantly induced. TRX is known to interact with other proteins such as proliferation-associated gene and apoptosis signal-regulating kinase 1. Coexpression of mVDUP1 interfered with the interaction between TRX and proliferation-associated gene or TRX and ASK-1, suggesting its roles in cell proliferation and oxidative stress. To investigate the roles of mVDUP1 in oxidative stress, mVDUP1 was overexpressed in NIH 3T3 cells. When cells were exposed to stress, cell proliferation was declined with elevated apoptotic cell death compared with control cells. In addition, c-Jun N-terminal kinase activation and IL-6 expression were elevated. Taken together, these results demonstrate that mVDUP1 functions as an oxidative stress mediator by inhibiting TRX activity.

A possible interaction of thioredoxin with VDUP1 in HeLa cells detected in a yeast two-hybrid system

Human thioredoxin (hTrx), a small ubiquitous protein with strong reducing potential, has multiple biological functions, including signal transduction and regulation of the activity of transcription factors. hTrx expression is enhanced in HPV-transformed cancer cells; however, the role of hTrx in the malignant cells is not fully understood. We employed a yeast two-hybrid system to search for proteins that bind to hTrx in HeLa cells, a type of HPV-transformed human cervical cancer cell. In a screen of 1.62 x 10(6) yeast cotransformed with a HeLa cDNA library and an hTrx vector, 13 clones were identified as candidates for hTrx-binding proteins. Among them, 3 clones were found to code in frame for the carboxyl-terminal portion of VDUP1 protein, lacking at most the first 155 residues from the start codon. A reconstructed clone carrying the full-length VDUP1 coding sequence also showed the ability to bind to an hTrx fusion protein. Loss of interaction between VDUP1 and hTrx was observed either when two cysteines (Cys 32 and 35) in hTrx were substituted by serines or when the deletion in VDUP1 was extended from amino acid position 155 to 225 or beyond. The 71-mer peptide fragment (position 155-225) of VDUP-1 alone did not bind to hTrx.

Prominent expression of the selenoprotein thioredoxin reductase in the medullary rays of the rat kidney and thioredoxin reductase mRNA variants differing at the 5' untranslated region

The mammalian selenoprotein thioredoxin reductase is a central enzyme in protection against oxidative damage or the redox control of cell function. Previously a neuroblastoma-cell-derived 2193 bp cDNA for rat thioredoxin reductase 1 (TrxR1) was characterized [Zhong, Arnér, Ljung, Aslund and Holmgren (1998) J. Biol. Chem. 273, 8581-8591]. Here, the major rat TrxR1 mRNA was determined as 3.5 kb by Northern blotting. A corresponding full-length 3360 bp liver-derived cDNA was cloned and sequenced, being extended in the 3' untranslated region (3' UTR) compared with the previous clone. Among tissues examined, lowest TrxR1 mRNA levels were found in spleen and testis and highest in liver and kidney. High expression in kidney was unexpected and in situ hybridization of adult rat kidney was performed. This revealed a highly structured expression pattern with the mRNA being prominently synthesized in the proximal tubules of the medullary rays. Analysing rat kidney cDNA, a 5' UTR domain of TrxR1 was found that was different from that in liver- or neuroblastoma-derived cDNA clones. The kidney-derived 5' UTR mRNA domain was instead highly similar to kidney-derived cDNA variants of murine apolipoprotein E. By sequence determination of the rat genomic sequence upstream of the open reading frame for TrxR1, an exon was encountered that encoded a third alternative 5' UTR domain that could also be expressed, as confirmed by its presence in a mouse skin TrxR1 cDNA clone. It can therefore be concluded that TrxR1 mRNA is expressed in at least three different variants that differ at their 5' UTRs.

Excitotoxic hippocampal injury is attenuated in thioredoxin transgenic mice

Thioredoxin is a small, multifunctional protein with a redox-active disulfide/dithiol in the active site. Thioredoxin plays several important biologic roles both in intracellular and extracellular compartments with its redox-regulating and reactive oxygen intermediates scavenging activities. We assayed the seizure response and the excitotoxic hippocampal injury in thioredoxin transgenic and wild-type C57BL/6 mice. Seizure score after kainic acid treatment was significantly lower in thioredoxin transgenic mice. Seven days after kainic acid administration, the damage in the hippocampal CA1 and CA3 regions was significantly attenuated in thioredoxin transgenic mice. Thioredoxin and redox regulation play an important role in excitotoxic brain damage.

Upregulation of thioredoxin (TRX) expression in giant cell myocarditis in rats

To examine the possible involvement of a redox regulating mechanism in the pathogenesis of immune-mediated myocarditis, myocarditis was induced by immunization of porcine cardiac myosin in rats and immunohistochemistry and Western blot for thioredoxin (TRX) were performed. Immunohistochemistry for 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nuclear factor kappa-B (NF-kappaB) was also performed. TRX was upregulated in the acute stage, but not in the chronic stage, and the expression was correlated with the severity of the disease. Damaged myocytes were strongly immunostained for 8-OHdG and NF-kappaB. Thus, TRX may be specifically induced by acute inflammatory stimuli, and the development of acute immune-mediated myocarditis may be regulated by the cellular redox state via TRX.

The interferon-beta and tamoxifen combination induces apoptosis using thioredoxin reductase

Interferons (IFNs) suppress cell growth by inducing cellular genes. The anti-estrogen tamoxifen (Tam), binds to estrogen receptor and inhibits transcription of estrogen stimulated genes. In cells resistant to IFN-induced growth suppression, IFN/Tam combination causes cell death. We previously reported that the combination of IFN-beta and Tam was a more potent growth suppressor of human tumor xenografts than either agent alone. The IFN/Tam combination acts in a manner similar to the IFN/retinoic acid combination. Using a genetic technique, we have recently identified several genes associated with retinoid-IFN-induced mortality (GRIM). One such gene, GRIM-12, was identical to human thioredoxin reductase (TR). In the present study we have examined whether the IFN/Tam combination also requires GRIM-12 for inducing cell death. We report here that GRIM-12 is necessary for mediating the cell death effects of IFN/Tam, and its expression is induced by IFN/Tam at a post-transcriptional stage. Repression of GRIM-12 levels either by antisense expression or by dominant negative inhibitors caused resistance to IFN/Tam induced death and promoted cell growth. Overexpression of GRIM-12 increased IFN/Tam induced apoptosis. Thus, these studies have identified a critical role for GRIM-12 (TR) in apoptosis.

cDNA sequence of bovine thioredoxin

In this paper, we report the cDNA sequence of bovine thioredoxin. We determined the full-length cDNA sequence of bovine thioredoxin by RT-PCR, 5'-RACE and 3'-RACE methods. Currently, the thioredoxin cDNA sequences of only five mammalian species (human, macaca, mouse, ovine and rat) are registered in the GenBank database. We performed sequence comparisons on the total cDNA sequence and the coding region, and produced a multialignment between the amino acid sequences of bovine and other mammalian thioredoxins. The amino acid sequences of thioredoxins are highly conserved among mammalian species, for example, only one difference exists between the amino acid sequences of bovine and ovine thioredoxin.

cDNA sequence of bovine thioredoxin

In this paper, we report the cDNA sequence of bovine thioredoxin. We determined the full-length cDNA sequence of bovine thioredoxin by RT-PCR, 5'-RACE and 3'-RACE methods. Currently, the thioredoxin cDNA sequences of only five mammalian species (human, macaca, mouse, ovine and rat) are registered in the GenBank database. We performed sequence comparisons on the total cDNA sequence and the coding region, and produced a multialignment between the amino acid sequences of bovine and other mammalian thioredoxins. The amino acid sequences of thioredoxins are highly conserved among mammalian species, for example, only one difference exists between the amino acid sequences of bovine and ovine thioredoxin.

Adaptive responses of the endothelium to stress

It is now established that endothelial cells acquire several functional properties in response to a diverse array of extracellular stimuli. This expression of an altered phenotype is referred to as endothelial cell activation, and it includes several activities that promote inflammation and coagulation. While it is recognized that endothelial cell activation has a principal role in host defense, recent studies also demonstrate that endothelial cells are capable of complex molecular responses that protect the endothelium against various forms of stress including heat shock, hypoxia, oxidative stress, shock, ischemia-reperfusion injury, toxins, wounds, and mechanical stress. In this review, we examine endothelial cell genotypic and phenotypic responses to stress. Also, we highlight important cellular stress responses that, although not yet demonstrated directly in endothelial cells, likely exist as part of the repertoire of stress responses in endothelium. A detailed understanding of the molecular mechanisms mediating the adaptive responses of endothelial cells to stress should facilitate the development of novel therapeutics to aid in the management of diverse surgical diseases and their complications.

The thioredoxin system of Helicobacter pylori

This paper describes the purification of thioredoxin reductase (TR) and the characterization, purification, and cloning of thioredoxin (Trx) from Helicobacter pylori. Purification, amino acid sequence analysis, and molecular cloning of the gene encoding thioredoxin revealed that it is a 12-kDa protein which possesses the conserved redox active motif CGPC. The gene encoding Trx was amplified by polymerase chain reaction and inserted into a pET expression vector and used to transform Escherichia coli. Trx was overexpressed by induction with isopropyl-1-thio-beta-D-galactopyranoside as a decahistidine fusion protein and was recovered from the cytoplasm as a soluble and active protein. The redox activity of this protein was characterized using several mammalian proteins of different architecture but all containing disulfide bonds. H. pylori thioredoxin efficiently reduced insulin, human immunoglobulins (IgG/IgA/sIgA), and soluble mucin. Subcellular fractionation analysis of H. pylori revealed that thioredoxin was associated largely with the cytoplasm and inner membrane fractions of the cell in addition to being recovered in the phosphate-buffered saline-soluble fraction of freshly harvested cells. H. pylori TR was purified to homogeneity by chromatography on DEAE-52, Cibacron blue 3GA, and 2',5'-ADP-agarose. Gel filtration revealed that the native TR had a molecular mass of 70 kDa which represented a homodimer composed of two 35-kDa subunits, as determined by SDS-polyacrylamide gel electrophoresis. H. pylori TR (NADPH-dependent) efficiently catalyzed the reduction of 5,5'-dithiobis(nitrobenzoic acid) in the presence of either native or recombinant H. pylori Trx. H. pylori Trx behaved also as a stress response element as broth grown bacteria secreted Trx in response to chemical, biological, and environmental stresses. These observations suggest that Trx may conceivably assist H. pylori in the process of colonization by inducing focal disruption of the oligomeric structure of mucin while rendering host antibody inactive through catalytic reduction.

Thioredoxin prolongs survival of B-type chronic lymphocytic leukemia cells

Thioredoxin (Trx) is a ubiquitous protein disulfide oxidoreductase with antioxidant, cytokine, and chemotactic properties. Previously, we showed that Trx, in synergy with interleukin 1 (IL-1), IL-2, IL-4, tumor necrosis factor  (TNF-), and CD40-ligation induced S-phase entry and mitosis in normal B cells and B-type chronic lymphocytic leukemia (B-CLL) cells. The viability of B-CLL cells stimulated by these protocols is high, and it has been hypothesized that the overexpression of Bcl-2 found in B-CLL protects the cells from apoptosis in vitro and in vivo. In this study, we have analyzed the response of cells derived from 12 samples of patients with B-CLL to recombinant human Trx in spontaneous apoptosis, with special reference to the Bcl-2 expression. Long-term cultures of B-CLL clones showed significantly higher viability when supplemented with human Trx (P = .031), also exemplified with clones surviving more than 2 months. Short-term cultures of B-CLL cells exposed to 1 μg/mL of Trx for 1, 5, or 12 days maintained expression or delayed down-regulation of Bcl-2 compared with control cultures containing RPMI 1640 medium and 10% fetal calf serum only (P = .032, .002, .026, respectively). All B-CLL cells expressed constitutive Trx at varying but low levels, in contrast to adult T-cell leukemias, which overexpress Trx, as previously reported. We found that Trx added to B-CLL cells increased in a dose-dependent fashion the release of TNF-, which has been suggested to be an autocrine growth factor for these cells. In conclusion, we have found that human recombinant Trx induced TNF- secretion, maintained Bcl-2, and reduced apoptosis in B-CLL cells.

Human thioredoxin attenuates hypoxia-reoxygenation injury of murine endothelial cells in a thiol-free condition

The adult T cell leukemia-derived factor (ADF), or human thioredoxin (hTRX), has a radical scavenging effect similar to that of N-acetyl cysteine (NAC). We have recently shown that ADF/hTRX protects the lung and the heart from ischemia-reperfusion induced injury. To elucidate mechanisms of the protective effect, a hypoxia-reoxygenation (H-R) injury model was developed using a murine endothelial cell line, cultured in a thiol-free medium. In this condition, cells became much more vulnerable to H-R injury. The viability of cells decreased significantly after 1 h of hypoxic incubation followed by 1 h of reoxygenation. The injury was reduced by ADF/hTRX (100 microM) or NAC (10 mM). These two agents also demonstrated an additive protective effect. When cells were cultured in thiol-free medium for 2 h in a normoxic condition, intracellular hydrogen peroxide production was increased, which was associated with a decrease in glutathione level. NAC (10 mM) attenuated these changes whereas ADF/hTRX (100 microM) did not. These results suggest that although both ADF/hTRX and NAC protected cells from H-R injury, the underlying mechanisms are different. Because the cytoprotective effect of ADF/hTRX occurs in the thiol-free condition, it must be mediated via a novel mechanism other than enhancing thiol uptake. The additive cytoprotective effect between ADF/hTRX and NAC suggests that we should combine these two agents clinically.

Genetic and metabolic control of the mitochondrial transmembrane potential and reactive oxygen intermediate production in HIV disease

Redox mechanims play important roles in replication of human immunodeficiency virus type 1 (HIV-1) and cellular susceptibility to apoptosis signals. Viral replication and accelerated turnover of CD4+ T cells occur throughout a prolonged asymptomatic phase in patients infected by HIV-1. Disease development is associated with steady loss of CD4+ T cells by apoptosis, increased rate of opportunistic infections and lymphoproliferative diseases, disruption of energy metabolism, and generalized wasting. Such pathological states are preceded by: (i) depletion of intracellular antioxidants, glutathione (GSH) and thioredoxin (TRX), (ii) increased reactive oxygen species (ROS) production, and (iii) changes in mitochondrial transmembrane potential (deltapsi(m)). Disruption of deltapsi(m) appears to be the point of no return in the effector phase of apoptosis. Viral proteins Tat, Nef, Vpr, protease, and gp120, have been implicated in initiation and/or intensification of oxidative stress and disruption of deltapsi(m). Redox-sensitive transcription factors, NF-kappaB, AP-1, and p53, support expression of viral genes and proinflammatory lymphokines. ROS regulate apoptosis signaling through Fas, tumor necrosis factor (TNF), and related cell death receptors, as well as the T-cell receptor. Oxidative stress in HIV-infected donors is accompanied by increased glucose utilization both on the cellular and organismal levels. Generation of GSH and TRX from their corresponding oxidized forms is dependent on NADPH provided through the pentose phosphate pathway of glucose metabolism. This article seeks to delineate the genetic and metabolic bases of HIV-induced oxidative stress. Such understanding should lead to development of effective antioxidant therapies in HIV disease.

Cell death by 1-chloro-2,4-dinitrobenzene, an inhibitor of thioredoxin reductase and its dual regulation by nitric oxide in rats

Thioredoxin (Trx), the oxidized form of which is converted to a reduced form by Trx reductase, regulates cell proliferation and survival. We investigated the effect of 1-chloro-2,4-dinitrobenzene (DNCB), an inhibitor of Trx reductase, on cell death in neuronal PC12 cells and rat glial cells. In both types of cells, culture with DNCB for 4 h stimulated lactate dehydrogenase (LDH) leakage. LDH leakage by DNCB was inhibited by an inhibitor of caspases. Addition of 2,2-(hydroxynitrosohydrazino)bis-ethanamine, of which 50% decays and releases nitric oxide (NO) in 21 h, inhibited DNCB-induced LDH leakage. Addition of 10 microM N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethanamine (NOC-12), of which 50% decays and releases NO in 100 min, inhibited DNCB-induced LDH leakage, although 0.2 mM NOC-12 enhanced the leakage in PC12 cells. These findings suggest that DNCB induces cell death of neuronal and glial cells accompanied by caspase(s) activation. NO inhibits DNCB-induced cell death in both types of cells, although excess NO showed a toxic effect.

Thioredoxin-dependent redox regulation of p53-mediated p21 activation

Thioredoxin (TRX) is a dithiol-reducing enzyme that is induced by various oxidative stresses. TRX regulates the activity of DNA-binding proteins, including Jun/Fos and nuclear factor-kappaB. TRX also interacts with an intranuclear reducing molecule redox factor 1 (Ref-1), which enhances the activity of Jun/Fos. Here, we have investigated the role of TRX in the regulation of p53 activity. Electrophoretic mobility shift assay showed that TRX augmented the DNA binding activity of p53 and also further potentiated Ref-1-enhanced p53 activity. Luciferase assay revealed that transfection of TRX enhanced p53-dependent expression of p21 and further intensified Ref-1-mediated p53 activation. Furthermore, Western blot analysis revealed that p53-dependent induction of p21 protein was also facilitated by transfection with TRX. Overexpression of transdominant negative mutant TRX (mTRX) suppressed the effects of TRX or Ref-1, showing a functional interaction between TRX and Ref-1. cis-Diamminedichloroplatinum (II) (CDDP) induced p53 activation and p21 transactivation. The p53-dependent p21 transactivation induced by CDDP was inhibited by mTRX overexpression, suggesting that TRX-dependent redox regulation is physiologically involved in p53 regulation. CDDP also stimulated translocation of TRX from the cytosol into the nucleus. Hence, TRX-dependent redox regulation of p53 activity indicates coupling of the oxidative stress response and p53-dependent repair mechanism.

Lens-specific regulation of the thioredoxin-1 gene, but not thioredoxin-2, upon in vivo photochemical oxidative stress in the Emory mouse

Thioredoxin (TRX)-1 and TRX-2 redox-regulatory genes were analyzed in the lens and some other tissues of the Emory mouse, a model for age-related human cataract. The cDNA transcripts of mRNAs encoding TRX-1 and TRX-2 genes were isolated and cloned by RT-PCR from the lens, liver, kidney, and tail, and the cDNA sequences were similar to the reported sequences of murine TRX-1 and TRX-2 genes. In vivo photochemical oxidative stress to the Emory mice resulted in fivefold upregulation of the lens TRX-1 gene at 3 weeks and declined thereafter. Western blot analysis revealed a fourfold increase of TRX-1 protein in the lens at 3 weeks after oxidative stress. The TRX-2 gene in the lens was not changed up to 5 weeks and decreased by 50% thereafter. However, the expressions of these genes in the liver, kidney, and tail were not changed. Fluorescent light or riboflavin alone did not affect the expressions of TRX-1 and TRX-2 genes in the lens. Thus, we show the expressions of TRX-1 and TRX-2 genes in the lens, liver, kidney, and tail and lens-specific upregulation of the TRX-1 gene and protein expressions, possibly as a protective response to the altered redox state of the lens after in vivo oxidative stress to the Emory mouse.