Lymphocyte transformation and thiol compounds; the role of ADF/thioredoxin as an endogenous reducing agent

Can the protective actions of JAK-STAT in the heart be exploited therapeutically? Parsing the regulation of interleukin-6-type cytokine signaling

Activation of the transcription factor signal transducers and activators of transcription (STAT) 3 is a defining feature of the interleukin (IL)-6 family of cytokines, which include IL-6, leukemia inhibitory factor, and cardiotrophin-1. These cytokines, as well as STAT3 activation, have been shown to be protective for cardiac myocytes and necessary for ischemia preconditioning. However, the mechanisms that regulate IL-6-type cytokine signaling in cardiac myocytes are largely unexplored. We propose that the protective character of IL-6-type cytokine signaling in cardiac myocytes is determined principally by three mechanisms: redox status of the nonreceptor tyrosine kinase Janus kinase 1 (JAK) 1 that activates STAT3, phosphorylation of STAT3 within the transcriptional activation domain on serine 727, and STAT3-mediated induction of suppressor of cytokine signaling (SOCS) 3 that terminates IL-6-type cytokine signaling. Moreover, we hypothesize that hyperactivation of the JAK kinases, particularly JAK2, mismatched STAT3 serine-tyrosine phosphorylation or heightened STAT3 transcriptional activity, and SOCS3 induction may ultimately prove detrimental. Here we summarize recent evidence that supports this hypothesis, as well as additional possible mechanisms of JAK-STAT regulation. Understanding how IL-6-type cytokine signaling is regulated in cardiac myocytes has great significance for exploiting the therapeutic potential of these cytokines and the phenomenon of preconditioning.

The roles of selenium and mercury in the pathogenesis of viral cardiomyopathy

Research on the pathogenesis of nonischemic dilated cardiomyopathy (DCM) has largely been focused on the role of viral pathogens and altered immunity. Trace elements have only rarely been considered; however, clinical observations that trace elements influence cardiovascular disease have been made in populations with extreme dietary deficiency or occupational exposure. Recently, animal models of DCM have been used to explore interactions among trace elements, viral pathogens, and the immune system. Discovery of interactions of trace elements with causes for DCM has heightened awareness of potential contributions of environmental variables to DCM pathogenesis. This article reviews the present knowledge regarding trace elements, in particular selenium and mercury, in the pathogenesis of viral and immune-mediated DCM. Based on recent studies, the authors propose a novel paradigm for the pathogenesis of viral DCM that incorporates trace element imbalance and its interactions with the cellular physiology of viral-induced cardiomyocyte dysfunction.

Truncated thioredoxin: physiological functions and mechanism

Human cytosolic thioredoxin (Trx), which is the 12-kDa protein disulfide reductase with the Cys-Gly-Pro-Cys active site and a key component of cellular redox biochemistry and regulation, acts as cocytokine upon leaderless secretion. A 10-kDa C-terminally truncated thioredoxin (Trx80) comprising the 80 or 84 N-terminal amino acids is also secreted and present in plasma, where it originally was purified and identified as eosinophilic cytotoxicity enhancing factor. Recombinant Trx80 was discovered to be a potent mitogenic cytokine that stimulates growth of resting human peripheral blood mononuclear cells (PBMC) in a synthetic medium, an effect that Trx lacks. Trx80 is very different from Trx because it is a dimer lacking reductase activity and the cytokine activity is not dependent on the Cys residues of the Trx active-site motif. The primary targets of Trx80 in PBMC are monocytes that are activated to proliferate and increase expression of CD14, CD40, CD54, and CD86. Trx80 induces secretion of interleukin (IL)-12 in CD40+ monocytes from PBMC. Trx80 and IL-2 together were strongly synergistic to induce secretion of interferon-gamma in PBMC. Trx80 is a potent cytokine for monocytes directing the immune system to a Th1 response via IL-12 production.

Glutathione S-transferases and related proteins from pathogenic human parasites behave as immunomodulatory factors

There is a rapidly expanding interest into the glutathione S-transferases (GSTs) and the structurally related molecules. Many of the latter have been identified as members of conserved protein families sharing structural and some times functional properties being particularly involved in heat-shock response, drug resistance and carcinogenesis. Also, evidence is emerging that members of the GST super family from some pathogens could exert immunomodulatory functions toward the cell of the immune system, involving separate profiles of cytokine gene transcription and different patterns of cell growth, illustrating therefore the 'one gene-dual function' phenomenon. The implication of these biological properties for pathogenesis is discussed.

Thioredoxin is transcriptionally induced upon activation of heat shock factor 2

Heat shock gene expression is differentially regulated in cells exposed to stress stimuli and in cells undergoing processes of differentiation and development. Regulation of the classical heat shock response is mediated by heat shock factor 1 (HSF1), whereas heat shock factor 2 (HSF2) is activated in certain differentiating cells, for example during hemin-mediated differentiation of human K562 erythroleukemia cells. Hence, the signaling pathways leading to induction of heat shock gene expression upon different stimuli are likely to be distinct. We have used RNA arbitrarily primed polymerase chain reaction to identify genes that are differentially regulated upon activation of HSF1 and HSF2. In this study, we report that thioredoxin (TRX) expression is induced in K562 cells in response to hemin in an HSF2-dependent manner. Increased TRX expression was primarily detected on the transcriptional level, subsequently leading to elevated TRX mRNA and protein levels. Hemin treatment caused no reduction in cellular glutathione concentrations, indicating that the increased TRX expression was not due to oxidative stress. Studies using cell lines where overexpression of the HSF2-beta isoform represses HSF2 activation implied that active HSF2 is required for transcriptional induction of TRX. Unlike HSF2, activation of HSF1 did not induce TRX expression. Taken together, our results suggest that HSF1 and HSF2 may regulate distinct target genes, and activation of HSF2 could be involved in the regulation of TRX expression during hemin-mediated differentiation of K562 cells.

Amelioration of ischemia-reperfusion injury by human thioredoxin in rabbit lung

Human thioredoxin is a polypeptide with thiol groups, possessing reducing activity, which is proved to have the ability to reduce active oxygens. This study evaluated the effect of human thioredoxin on the ischemia-reperfusion lung injury and the roles of human thioredoxin on active oxygens by chemiluminescence examination. The left hilum of the lung of Japanese white rabbits was occluded for 110 minutes and then reperfused for 90 minutes. Ten, 30, 60, and 90 minutes after reperfusion the right hilum was occluded for 5 minutes and the pulmonary functions of the left lung were examined. The animals were divided into four groups, three ischemia groups and a sham group (without occlusion; n = 6). The ischemia groups received human thioredoxin, 60 mg/kg (n = 10), N-acetylcysteine, 150 mg/kg (n = 7), or saline solution (control, n = 10) during reperfusion. Three rabbits in the human thioredoxin group and the control group were used to measure active oxygens with a cypridina luciferin analog. An additional group of reperfused lungs (n = 3) that were given superoxide dismutase after 110 minutes of ischemia was established to identify chemiluminescence examination. Compared with the sham group, reperfusion after 110 minutes of ischemia produced a significant lung injury in the control group. Among the ischemia groups, the human thioredoxin group showed significantly higher arterial oxygen tension at 30, 60, and 90 minutes after reperfusion than the control group, although there was no significant difference between the N-acetylcysteine and control groups. Histologically, intraalveolar exudation, interstitial thickening, and cellular infiltration were seen in the control group, whereas in the thioredoxin group alveolar structure was well preserved. In the measurement of active oxygens the chemiluminescence in the human thioredoxin group was less than that in the control group and as little as that in the group administered superoxide dismutase. We concluded human thioredoxin attenuated ischemia-reperfusion injury by involving active oxygens in rabbit lungs.

Redox regulation of cellular activation

Growing evidence has indicated that cellular reduction/oxidation (redox) status regulates various aspects of cellular function. Oxidative stress can elicit positive responses such as cellular proliferation or activation, as well as negative responses such as growth inhibition or cell death. Cellular redox status is maintained by intracellular redox-regulating molecules, including thioredoxin (TRX). TRX is a small multifunctional protein that has a redox-active disulfide/dithiol within the conserved active site sequence: Cys-Gly-Pro-Cys. Adult T cell leukemia-derived factor (ADF), which we originally defined as an IL-2 receptor alpha-chain/Tac inducer produced by human T cell lymphotrophic virus-I (HTLV-I)-transformed T cells, has been identified as human TRX. TRX/ADF is a stress-inducible protein secreted from cells. TRX/ADF has both intracellular and extracellular functions as one of the key regulators of signaling in the cellular responses against various stresses. Extracellularly, TRX/ADF shows a cytoprotective activity against oxidative stress-induced apoptosis and a growth-promoting effect as an autocrine growth factor. Intracellularly, TRX/ADF is involved in the regulation of protein-protein or protein-nucleic acid interactions through the reduction/oxidation of protein cysteine residues. For example, TRX/ADF translocates from the cytosol into the nucleus by a variety of cellular stresses, to regulate the expression of various genes through the redox factor-1 (Ref-1)/APEX. Further studies to clarify the regulatory roles of TRX/ADF and its target molecules may elucidate the intracellular signaling pathways in the responses against various stresses. The concept of "redox regulation" is emerging as an understanding of the novel mechanisms in the pathogenesis of several disorders, including viral infections, immunodeficiency, malignant transformation, and degenerative disease.

A novel promoter sequence is involved in the oxidative stress-induced expression of the adult T-cell leukemia-derived factor (ADF)/human thioredoxin (Trx) gene

Adult T cell leukemia-derived factor (ADF) is a human thioredoxin (Trx) and is a disulfide reducing protein with various biological functions. We found that expression of the ADF/Trx gene was increased by oxidative agents such as hydrogen peroxide, diamide and menadione in Jurkat cells. Analysis using a CAT expression vector plasmid under the control of the ADF/Trx gene promoter revealed that CAT gene expression in Jurkat cells was increased after exposure to oxidative agents. A series of deletion analyses showed that a region from -976 to -890 of the 5' flanking sequence was required for enhancement of ADF/Trx promoter activity against the oxidative agents. Gel mobility shift assay revealed the specific DNA binding activities to the sequences from -953 to -930 in the nuclear extracts from the Jurkat cells. The sequences in this region showed no homology with any known consensus sequences for DNA binding factors. It is suggested that ADF/Trx gene expression is enhanced through a novel cis-acting regulatory element responsive for the oxidative stress and a new factor(s) is involved in this oxidative stress responsive element.

NK-lysin, a disulfide-containing effector peptide of T-lymphocytes, is reduced and inactivated by human thioredoxin reductase. Implication for a protective mechanism against NK-lysin cytotoxicity

The cytotoxic and antibacterial polypeptide NK-lysin has a molecular mass of approximately 9 kDa and contains three disulfide bonds. The activity was highly dependent on intact disulfides, because the bactericidal effect on Escherichia coli and the cytolytic effect on human 3B6 lymphocytes was inhibited when NK-lysin was treated with dithiothreitol prior to incubation with the cells. NK-lysin was a direct substrate for human or calf thymus thioredoxin reductase and preincubation of the peptide with mammalian thioredoxin reductase, and NADPH abolished its antibacterial and cytolytic activities. The addition of human thioredoxin further enhanced the inhibitory effect of thioredoxin reductase and NADPH. In contrast, e. coli thioredoxin reductase showed no direct disulfide reductase activity with NK-lysin in agreement with previous data showing large differences in structure and substrate specificity between the mammalian and E. coli enzymes. NK-lysin is the first identified macromolecular disulfide substrate for human thioredoxin reductase apart from human thioredoxin. When 3B6 cells were incubated with NADPH, thioredoxin, and thioredoxin reductase prior to addition of NK-lysin, cytotoxicity was markedly reduced. These data suggest that thioredoxin reductase inactivates NK-lysin and provides a mechanism by which the cytotoxic activity of NK-lysin is regulated.

Adult T cell leukemia-derived factor/human thioredoxin protects endothelial F-2 cell injury caused by activated neutrophils or hydrogen peroxide

Adult T cell leukemia-derived factor (ADF), originally defined as an interleukin 2 receptor/alpha (alpha) chain inducer produced by human T-lymphotropic virus type-I transformed cells, is identical to human thioredoxin (TRX). In this study, the protective effect of ADF/TRX on the cytotoxicity of endothelial cells caused by phorbol myristate acetate (PMA)-activated neutrophils or hydrogen peroxide (H2O2) was examined. When murine endothelial F-2 cells established from an ultraviolet light-induced tumor on a nude mouse were incubated with PMA-activated neutrophils or with 1 mM H2O2 for 6 hours, the cytotoxicity of F-2 cells was respectively 51 +/- 4% or 40 +/- 8% by the 51Cr releasing assay. Recombinant ADF/TRX (rADF/TRX) inhibited this cytotoxicity in a dose-dependent manner, although mutant ADF/TRX (cysteine 31 to serine), 2-mercaptoethanol and dithiothreitol did not. On a molar basis, rADF/TRX was more effective than glutathione but less effective than catalase. Immunoblotting analysis showed that treatment with 0.1 mM H2O2 induced murine TRX on F-2 cells. These findings indicate that ADF/TRX is an oxidative stress-inducible endogenous protein and rADF/TRX plays a protective role against activated neutrophils- or H2O2-induced endothelial cytotoxicity.

The predicted amino acid sequence of human thioredoxin is identical to that of the autocrine growth factor human adult T-cell derived factor (ADF): thioredoxin mRNA is elevated in some human tumors

The cDNA sequences of thioredoxin obtained by PCR cloning from human colon cancer cells, human lymphoblastoid cells, and human liver have been found to be identical with the cDNA sequence reported for the autocrine growth factor, human adult T-cell leukemia derived factor (ADF). Recombinant human thioredoxin was 95% reduced by dithiothreitol and was a substrate for reduction by human thioredoxin reductase. Human non-small cell primary lung tumors from subjects who were not cigarette smokers at the time of surgery showed significantly increased levels of thioredoxin mRNA compared to thioredoxin mRNA in paired normal human lung tissue. Subjects who were smokers did not show a significant increase in lung tumor thioredoxin mRNA. The results of the study show that human thioredoxin and ADF are identical species and suggest that there may be increased production of thioredoxin (ADF) by some human cancers.

Detection of adult T-cell leukemia-derived factor/human thioredoxin in human serum

Adult T-cell leukemia (ATL)-derived factor (ADF), originally defined as an inducer of interleukin-2 receptor/alpha-chain (IL-2R/p55) of human T-lymphotropic virus type I (HTLV-I) positive T cells, is a human homologue of redox-active coenzyme thioredoxin (Trx) of Escherichia coli. In this study, an enzymatic assay system based on the dithiol-dependent insulin-reducing activity of ADF/Trx was established (insulin-reducing assay) to determine the amount of ADF/Trx in human serum using NADPH and Trx reductase purified from human placenta. Insulin-reducing activity was detected in all of the serum samples from healthy volunteers (n = 30) screened by this assay, with a mean +/- SD of 10.9 +/- 2.4 U/l. This mean value corresponds with the concentration of 223 ng recombinant ADF/Trx (rADF/Trx)/ml. Human serum is known to contain several redox-active proteins with ADF/Trx motifs. To differentiate the contribution of these proteins and ADF/Trx to the insulin-reducing activity, the anti-rADF/Trx monoclonal antibody (mAb)-conjugated affinity column-depleted sera obtained from an identical source was used for analysis. The affinity column-depleted sera demonstrated a loss of over 99% of the original activity, while control column depleted sera lost less than 4%. Furthermore, the amount of affinity-purified ADF/Trx molecules eluted from the same column almost corresponded with the amount estimated by the insulin-reducing activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Distinct effects of glutathione disulphide on the nuclear transcription factor kappa B and the activator protein-1

Oxidative conditions potentiate the activation of the nuclear transcription factor kappa B (NF kappa B) and the activator protein-1 (AP-1) in intact cells, but inhibit their DNA binding activity in vitro. We now show that both the activation of NF kappa B and the inhibition of its DNA binding activity is modulated in intact cells by the physiological oxidant glutathione disulphide (GSSG). NF kappa B activation in human T lineage cells (Molt-4) by 12-O-tetradecanoyl-phorbol 13-acetate was inhibited by dithiothreitol, and this was partly reversed by the glutathione reductase inhibitor 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) or by hydrogen peroxide, indicating that GSSG may be required for NF kappa B activation. These effects of BCNU and hydrogen peroxide were not seen in glutathione-depleted cells. However, NF kappa B and AP-1 activation were potentiated by dithiothreitol if added to cell cultures 1 h after the phorbol ester, indicating that a shift of redox conditions may support optimal oxidative activation with minimal inhibition of DNA binding. The elevation of intracellular GSSG levels by BCNU before stimulation suppressed the chloramphenicol acetyltransferase expression dependent on NF kappa B but increased that dependent on AP-1. This selective suppression of NF kappa B was also demonstrable by electrophoretic mobility shift assays. In vitro, GSSG inhibited the DNA binding activity of NF kappa B more effectively than that of AP-1, while AP-1 was inhibited more effectively by oxidized thioredoxin.

Augmentation of phorbol ester-induced T cell proliferation by agents which raise intracellular cyclic adenosine monophosphate

Although raising intracellular cyclic adenosine monophosphate (cAMP) levels is generally considered to be inhibitory on the mitogen-induced T cell proliferation, in this study we have shown that the addition of either dbcAMP (50 microM) or cholera toxin (1 ng/ml) resulted in an increase in [3H]thymidine uptake in PBMC cultures stimulated with phorbol ester, 12-tetradecanoylphorbol 13-acetate (TPA), or with a combination of TPA plus anti-CD3 mAb (mAb 235). In contrast, under similar culture conditions, the phytohemagglutinin-P (PHA-P) response was inhibited by these agents as has been reported. The augmentative effect of dbcAMP in PBMC cultures was due to an increase in IL-2 production and not to increased in IL-2R-alpha chain expression. The enhancing effect of dbcAMP and CT observed with PBMC was monocyte dependent and not seen with purified T cell preparations. The addition of monocytes reconstituted the ability of intracellular cAMP elevating agents to augment the T cell response to TPA with and without mAb to CD3. The monocytes mediate their action via soluble factor(s) with molecular weight (m.w.) of more than 10 kDa. Neither rIL-1, rIL-6, nor rTNF-alpha have any augmentative effect as contrast with the supernatant from treated monocytes. Taken together, our results indicate that cAMP can play a positive regulatory role in T cell proliferation due to factor(s) secreted by dbcAMP-treated monocytes resulting in increased IL-2 synthesis in T cells.

Diseases associated with HTLV-I: virus, IL-2 receptor dysregulation and redox regulation

HTLV-I, the etiological agent in adult T-cell leukemia, has also been strongly implicated in a number of non-neoplastic T-cell-associated diseases. Here, Junji Yodoi and Takashi Uchiyama review these associations and focus on the emerging concepts of IL-2R dysregulation and redox regulation by adult T-cell leukemia-derived factor in the pathogenesis of HTLV-I-related diseases.

Dysregulation of adult T-cell leukemia-derived factor (ADF)/thioredoxin in HIV infection: loss of ADF high-producer cells in lymphoid tissues of AIDS patients

Adult T-cell leukemia (ATL)-derived factor (ADF) is a multifunctional protein homologous to thioredoxin (TRX) with co-cytokine and thiol-dependent reducing activities. ADF/thioredoxin production is enhanced in T cells transformed by HTLV-I. We have examined the effect of HIV-1 infection on ADF/TRX expression using specific antibody against ADF/TRX. Lymph nodes from 5 AIDS and 1 AIDS-related complex (ARC) patients were examined. As a control, 8 HIV noninfected lymph nodes, including 3 cases with hyperplasia, were also examined. Immunohistopathological studies using normal HIV noninfected lymph nodes showed that ADF/TRX high-producer (ADFh) cells were macrophages and cells with dendritic morphology in the paracortical area. Abundant ADFh cells were observed in HIV noninfected hyperplastic lymph nodes. The number of ADFh cells was low in hyperplastic lymph nodes from an ARC patient. All of the lymph nodes of 5 AIDS cases were atrophic and the number of ADFh cells were extremely low. To verify these histochemical studies, we examined the effect of in vitro HIV infection on ADF/TRX expression in HTLV-I (+) T-cell lines. Western blot analysis showed that a reduction of ADF/TRX in HIV-1-infected SKT-1B and MT-2 cells, and the reduction inversely correlated with p24 antigen level. On the basis of the above in vivo and in vitro findings, we imply that the levels of ADF/TRX were down-regulated by HIV-1 infection and that the down-regulation may play a role for pathophysiology of HIV-infected individuals.