Transactivation of an inducible anti-oxidative stress protein, human thioredoxin by HTLV-I Tax

Trans-Activation of the Coactivator-Associated Arginine Methyltransferase 1 (Carm1) Gene by the Oncogene Product Tax of Human T-Cell Leukemia Virus Type 1

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma. The oncogene product Tax of HTLV-I is thought to play crucial roles in leukemogenesis by promoting proliferation of the virus-infected cells through activation of growth-promoting genes. These genes code for growth factors and their receptors, cytokines, cell adhesion molecules, growth signal transducers, transcription factors and cell cycle regulators. We show here that Tax activates the gene coding for coactivator-associated arginine methyltransferase 1 (CARM1), which epigenetically enhances gene expression through methylation of histones. Tax activated the Carm1 gene and increased protein expression, not only in human T-cell lines but also in normal peripheral blood lymphocytes (PHA-PBLs). Tax increased R17-methylated histone H3 on the target gene IL-2Rα, concomitant with increased expression of CARM1. Short hairpin RNA (shRNA)-mediated knockdown of CARM1 decreased Tax-mediated induction of IL-2Rα and Cyclin D2 gene expression, reduced E2F activation and inhibited cell cycle progression. Tax acted via response elements in intron 1 of the Carm1 gene, through the NF-κB pathway. These results suggest that Tax-mediated activation of the Carm1 gene contributes to leukemogenic target-gene expression and cell cycle progression, identifying the first epigenetic target gene for Tax-mediated trans-activation in cell growth promotion.

The thioredoxin expression of Cristaria plicata is regulated by Nrf2/ARE pathway under microcystin stimulation

Thioredoxin plays an important role in inhibiting apoptosis and protecting cells from oxidative stress. This study was aimed to clarify how the expression of Trx from Cristaria plicata is regulated by Nrf2/ARE pathway. The expression of CpTrx mRNA was significantly up-regulated in gill and kidney tissues under microcystin stress. The Nrf2 gene of Cristaria plicata was identified to possess an auto active domain bit. While CpNrf2 was knocked down by specific small RNA, CpTrx mRNA expression was significantly down-regulated. The promoter of CpTrx gene had high transcriptional activity, and this basic transcriptional activity persisted after ARE element mutation. The region of promoter -206 to +217 bp was a core promoter region and had forward regulatory elements. Gel shift Assay exhibited that the CpTrx promoter could bind to the purified proteins CpNrf2 and CpMafK in vitro. The binding phenomenon disappeared after the ARE element mutation in promoter region. Subcellular localization experiments displayed that fluorescence overlap between CpNrf2 and Trx promoter increased under microcystin toxin stress. These results suggested that Trx expression was regulated by Nrf2/ARE pathway under oxidative stress.

HTLV-1 infection-induced motor dysfunction, memory impairment, depression, and brain tissues oxidative damage in female BALB/c mice

AIMS

The HTLV-1 infection is associated with a neuro-inflammatory disease. In the present study, the behavioral consequences and brain oxidative damages were evaluated in HTLV-1-infected BALB/c mice.

MATERIAL AND METHODS

20 female BALB/c mice were divided into two groups comprising control and HTLV-1-infected. The HTLV-1-infected group was inoculated with a 10⁶ MT-2 HTLV-1-infected cell line. Two months later, the behavioral tests were conducted. Finally, oxidative stress was assessed in the cortex and hippocampus tissues.

KEY FINDINGS

In the HTLV-1-infected group, running time and latency to fall, travel distance and time spent in the peripheral zone, total crossing number and total traveled distance in open field test, the latency of entrance into the dark compartment in the passive avoidance test, the new object exploration percentage, and discrimination ratio were significantly lower than in the control group. The immobility time, time spent in the dark compartment in passive avoidance test, and total exploration time significantly increased in the HTLV-1-infected group compared to the control group. In the cortical tissue of the HTLV-1 group, the malondialdehyde levels were elevated while the total thiol levels decreased in comparison to the control group. The activity of superoxide dismutase in the cortical and hippocampal tissues, and catalase activity in cortical tissue significantly decreased in the HTLV-1 group in comparison to the control group.

SIGNIFICANCE

The HTLV-1 infection seems to induce depression-like behavior, motor dysfunction, disruption in working and fear memory and also oxidative stress in the cortex and hippocampus.

Anti-Inflammatory Thioredoxin Family Proteins for Medicare, Healthcare and Aging Care

Human thioredoxin (TRX) is a 12-kDa protein with redox-active dithiol in the active site -Cys-Gly-Pro-Cys-, which is induced by biological stress due to oxidative damage, metabolic dysfunction, chemicals, infection/inflammation, irradiation, or hypoxia/ischemia-reperfusion. Our research has demonstrated that exogenous TRX is effective in a wide variety of inflammatory diseases, including viral pneumonia, acute lung injury, gastric injury, and dermatitis, as well as in the prevention and amelioration of food allergies. Preclinical and clinical studies using recombinant TRX (rhTRX) are now underway. We have also identified substances that induce the expression of TRX in the body, in vegetables and other plant ingredients. Skincare products are being developed that take advantage of the anti-inflammatory and anti-allergic action of TRX. Furthermore, we are currently engaged in the highly efficient production of pure rhTRX in several plants, such as lettuce, grain and rice.

Thioredoxin domain-containing protein 12 from Oplegnathus fasciatus: Molecular characterization, expression against immune stimuli, and biological activities related to oxidative stress

Thioredoxin domain-containing protein 12 (TXNDC12) is a small, disulfide-containing protein that belongs to the thioredoxin (TXN) superfamily. In the present study, we identified and characterized a TXNDC12-like gene, designated OfTXNDC12, from rock bream, Oplegnathus fasciatus. OfTXNDC12 consists of seven exons interrupted by six introns. Comparative genomic structural analysis revealed that the TXNDC12 of vertebrates is a structurally conserved gene. The coding sequence of OfTXNDC12 comprises 522 bp, which encodes 173 amino acid residues with the conserved thioredoxin active site motif, CGAC, and a probable C-terminal ER retrieval motif, GDEL. Transcriptional analysis of OfTXNDC12 showed the highest concentrations of the mRNA transcript in the liver, implying that it has a significant role in the liver under normal physiological conditions. In comparison, injection of lipopolysaccharide, Edwardsiella tarda, Streptococcus iniae, polyinosinic:polycytidylic acid (poly[I:C]) and rock bream iridovirus mostly triggered greater upregulation of OfTXNDC12 transcript levels in liver than in gill tissue, supporting its potential functional importance in the liver. Insulin disulfide reduction assay showed that the recombinant fusion protein (rOfTXNDC12) possesses significant thioredoxin activity. Treatment of LNCaP cells with the recombinant protein along with H2O2 revealed that rOfTXNDC12 increased the viability of cells and further supported its putative antioxidant capacity. Taken together, the results from our study suggest that OfTXNDC12 encodes for a potent antioxidant involved in redox regulation that shows significant responses to immune stimuli.

Insights into the fish thioredoxin system: expression profile of thioredoxin and thioredoxin reductase in rainbow trout (Oncorhynchus mykiss) during infection and in vitro stimulation

Production of reactive oxygen species (ROS) is the first biological response during a disease outbreak and after injury. ROS are highly reactive molecules that can either endanger cell homeostasis or mediate cell signaling in several physiological pathways, including the immune response. Thioredoxin (Trx) and thioredoxin reductase (TrxR) are the essential components of the thioredoxin system, one of the main intracellular redox systems and are therefore important regulators of ROS accumulation. Through the regulation of the intracellular redox milieu, the thioredoxin system plays a key role within the immune system, linking immunology and free radical science. In this study we have firstly identified TrxRs in fish and used this new sequence information to reevaluate the evolution of the thioredoxin system within the vertebrate lineage. We next measured the expression of rainbow trout (Oncorhynchus mykiss) Trx and TrxR transcripts during infection in vivo and in vitro after stimulation of a macrophage cell line and primary macrophage cultures with pathogen associated molecular patterns (PAMPs). Our results showed that both Trx and TrxR were induced during infection at the transcriptional level, confirming their likely involvement in the innate immune response of fish. Since TrxRs are selenium-containing proteins (selenoproteins), we also measured the modulation of their expression upon organic and inorganic selenium exposure in vitro. TrxR was found to be responsive to selenium exposure in vitro, suggesting that it may represent a key mediator in the selenium modulation of innate immunity. In conclusion, our study highlights the need to investigate the involvement of the cell antioxidant pathways, especially the thioredoxin system, within the immune system of vertebrate species.

Reciprocal regulation of NO signaling and TXNIP expression in humans: impact of aging and ramipril therapy

BACKGROUND

Impaired tissue responsiveness to nitric oxide (NO) occurs in many cardiovascular diseases as well as with advanced age and is a correlate of poor outcomes. This phenomenon results from oxidative stress, with NO "scavenging" and dysfunction of soluble guanylate cyclase (sGC). Thioredoxin-interacting protein (TXNIP) is a major intracellular regulator of inflammatory activation and redox stress, but its interactions with NO/sGC are poorly understood. We have now evaluated the relationship between platelet TXNIP expression and function of the NO/sGC axis in subjects of varying age and during therapy with ramipril.

METHODS & RESULTS

Young (n=42) and aging (n=49) subjects underwent evaluation of platelet TXNIP content. Aging subjects additionally had measurements of platelet NO responsiveness and routine biochemistry. Platelet TXNIP content was greater (376±33 units) in the aging compared to younger subjects (289±13 units; p<0.05). In the aging subjects there was a significant negative correlation (r=-0.50, p<0.001) between platelet TXNIP content and NO responsiveness. In a separate cohort of 15 subjects two week treatment with ramipril, which reversed platelet NO resistance and potentiated sGC activity, also decreased platelet TXNIP content by 40% (p=0.011).

CONCLUSIONS

Platelet TXNIP content increases with aging, varies inversely with responsiveness to NO, and diminishes rapidly following treatment with ramipril. These data suggest that TXNIP-induced oxidative stress may be a critical modulator of tissue resistance to NO, a fundamental basis for cardiovascular disease. Analogously suppression of TXNIP expression can potentially be utilized as an index of restoration of cardiovascular homeostasis.

Emerging roles of Nrf2 and phase II antioxidant enzymes in neuroprotection

Phase II metabolic enzymes are a battery of critical proteins that detoxify xenobiotics by increasing their hydrophilicity and enhancing their disposal. These enzymes have long been studied for their preventative and protective effects against mutagens and carcinogens and for their regulation via the Keap1 (Kelch-like ECH associated protein 1)/Nrf2 (Nuclear factor erythroid 2 related factor 2)/ARE (antioxidant response elements) pathway. Recently, a series of studies have reported the altered expression of phase II genes in postmortem tissue of patients with various neurological diseases. These observations hint at a role for phase II enzymes in the evolution of such conditions. Furthermore, promising findings reveal that overexpression of phase II genes, either by genetic or chemical approaches, confers neuroprotection in vitro and in vivo. Therefore, there is a need to summarize the current literature on phase II genes in the central nervous system (CNS). This should help guide future studies on phase II genes as therapeutic targets in neurological diseases. In this review, we first briefly introduce the concept of phase I, II and III enzymes, with a special focus on phase II enzymes. We then discuss their expression regulation, their inducers and executors. Following this background, we expand our discussion to the neuroprotective effects of phase II enzymes and the potential application of Nrf2 inducers to the treatment of neurological diseases.

Penaeus monodon thioredoxin restores the DNA binding activity of oxidized white spot syndrome virus IE1

AIMS

In this study we identified viral gene targets of the important redox regulator thioredoxin (Trx), and explored in depth how Trx interacts with the immediate early gene #1 (IE1) of the white spot syndrome virus (WSSV).

RESULTS

In a pull-down assay, we found that recombinant Trx bound to IE1 under oxidizing conditions, and a coimmunoprecipitation assay showed that Trx bound to WSSV IE1 when the transfected cells were subjected to oxidative stress. A pull-down assay with Trx mutants showed that no IE1 binding occurred when cysteine 62 was replaced by serine. Electrophoretic mobility shift assay (EMSA) showed that the DNA binding activity of WSSV IE1 was downregulated under oxidative conditions, and that Penaeus monodon Trx (PmTrx) restored the DNA binding activity of the inactivated, oxidized WSSV IE1. Another EMSA experiment showed that IE1's Cys-X-X-Cys motif and cysteine residue 55 were necessary for DNA binding. Measurement of the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) in WSSV-infected shrimp showed that oxidative stress was significantly increased at 48 h postinfection. The biological significance of Trx was also demonstrated in a double-strand RNA Trx knockdown experiment where suppression of shrimp Trx led to significant decreases in mortality and viral copy numbers.

INNOVATION AND CONCLUSION

WSSV's pathogenicity is enhanced by the virus' use of host Trx to rescue the DNA binding activity of WSSV IE1 under oxidizing conditions.

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.

Direct inhibition of RNAse T2 expression by the HTLV-1 viral protein Tax

Adult T-cell leukemia (ATL) is one of the primary diseases caused by Human T-cell Leukemia Virus type 1 (HTLV-1) infection. The virally-encoded Tax protein is believed to initiate early events in the development of this disease, as it is able to promote immortalization of T-cells and transformation of other cell types. These processes may be aided by the ability of the viral protein to directly deregulate expression of specific cellular genes through interactions with numerous transcriptional regulators. To identify gene promoters where Tax is localized, we isolated Tax-DNA complexes from an HTLV-1-infected T-cell line through a chromatin immunoprecipitation (ChIP) assay and used the DNA to probe a CpG island microarray. A site within the RNASET2 gene was found to be occupied by Tax. Real-time PCR analysis confirmed this result, and transient expression of Tax in uninfected cells led to the recruitment of the viral protein to the promoter. This event correlated with a decrease in the level of RNase T2 mRNA and protein, suggesting that Tax represses expression of this gene. Loss of RNase T2 expression occurs in certain hematological malignancies and other forms of cancer, and RNase T2 was recently reported to function as a tumor suppressor. Consequently, a reduction in the level of RNase T2 by Tax may play a role in ATL development.

Segment-specific overexpression of redoxins after renal ischemia and reperfusion: protective roles of glutaredoxin 2, peroxiredoxin 3, and peroxiredoxin 6

The disruption of redox control, i.e., oxidative stress, is one of the most destructive causes of ischemia-reperfusion (IR) injury. Thioredoxin (Trx) family proteins play a major role in the cellular response to oxidative stress. Here, we systematically investigated the levels and tissue distribution of 15 members of this family (Trx and TrxR 1 and 2, Nrx, Prx 1-6, and Grx 1-3 and 5) in mouse kidneys after induction of IR by comparing control, clamped, and contralateral organs. After IR, levels of various redoxins were quantified. Immunohistochemical analysis revealed segment-specific alterations induced by the ischemic insult. Grx2, Prx3, and Prx6 were highly expressed in proximal tubule cells. Overexpression of these proteins in HEK293 and HeLa cells subjected to hypoxia and reoxygenation revealed higher survival and proliferation rates and lower oxidative damage compared to controls. Furthermore, we report for the first time the accumulation of Grx1 at the apical side of distal convoluted cells and the specific secretion of Grx1 into the urine after IR. The differences in both the basal equipment and the segment-specific responses of the antioxidant proteins may contribute to the distinct susceptibilities and regeneration processes of the various segments of the nephron to the IR insult.

Induction of reactive oxygen species by human T-cell leukemia virus type 1 tax correlates with DNA damage and expression of cellular senescence marker

Human T-cell leukemia virus type 1 (HTLV-1) Tax affects cellular genomic stability and senescence. As yet, the mechanism(s) for these events caused by Tax is incompletely understood. Here, we show that Tax expression in primary human cells induces reactive oxygen species (ROS), which elicits DNA damage and the expression of senescence marker. Treatment with a ROS scavenger or knockdown of Tax expression by small interfering RNA (siRNA) abrogated Tax-induced DNA damage and the expression of senescence marker. Our data suggest that ROS induction explains Tax-induced cellular DNA damage and cellular senescence.

HTLV-1 p13, a small protein with a busy agenda

Human T-cell leukemia virus type 1 (HTLV-1) infection is characterized by life-long persistence of the virus in the host. While most infected individuals remain asymptomatic, 3-5% will eventually develop adult T-cell leukemia/lymphoma (ATLL) or tropical spastic paraparesis/HTLV-associated myelopathy (TSP/HAM) after a clinical latency that can span years (TSP/HAM) to decades (ATLL). The major oncogenic determinant among HTLV-1 proteins is the Tax transactivator, which influences the expression and function of a great number of cellular proteins, drives cell proliferation, reduces cell death, and induces genetic instability. The present review is focused on the current knowledge of p13, an HTLV-1 accessory protein targeted to the inner mitochondrial membrane and, under certain conditions, to the nucleus. In mitochondria, p13 produces an inward K+current that results in an increased production of ROS by mitochondria. These effects are linked to the protein's effects on cell turnover which include activation of primary T-cells and reduced proliferation/sensitization to death of tumor cells. Recent findings suggest that in the presence of Tax, p13 is subjected to ubiquitylation and partly targeted to the nucleus. Nuclear p13 binds Tax and inhibits its transcriptional activity. These findings suggest that the protein might exert distinct functions depending on its intracellular localization and influence both the turnover of infected cells and the balance between viral latency and productive infection.

Reduced levels of reactive oxygen species correlate with inhibition of apoptosis, rise in thioredoxin expression and increased bovine leukemia virus proviral loads

Background

Bovine Leukemia virus (BLV) is a deltaretrovirus that induces lymphoproliferation and leukemia in ruminants. In ex vivo cultures of B lymphocytes isolated from BLV-infected sheep show that spontaneous apoptosis is reduced. Here, we investigated the involvement of reactive oxygen species (ROS) in this process.

Results

We demonstrate that (i) the levels of ROS and a major product of oxidative stress (8-OHdG) are reduced, while the thioredoxin antioxidant protein is highly expressed in BLV-infected B lymphocytes, (ii) induction of ROS by valproate (VPA) is pro-apoptotic, (iii) inversely, the scavenging of ROS with N-acetylcysteine inhibits apoptosis, and finally (iv) the levels of ROS inversely correlate with the proviral loads.

Conclusion

Together, these observations underline the importance of ROS in the mechanisms of inhibition of apoptosis linked to BLV infection.

Redox-based regulation of signal transduction: principles, pitfalls, and promises

Oxidants are produced as a by-product of aerobic metabolism, and organisms ranging from prokaryotes to mammals have evolved with an elaborate and redundant complement of antioxidant defenses to confer protection against oxidative insults. Compelling data now exist demonstrating that oxidants are used in physiological settings as signaling molecules with important regulatory functions controlling cell division, migration, contraction, and mediator production. These physiological functions are carried out in an exquisitely regulated and compartmentalized manner by mild oxidants, through subtle oxidative events that involve targeted amino acids in proteins. The precise understanding of the physiological relevance of redox signal transduction has been hampered by the lack of specificity of reagents and the need for chemical derivatization to visualize reversible oxidations. In addition, it is difficult to measure these subtle oxidation events in vivo. This article reviews some of the recent findings that illuminate the significance of redox signaling and exciting future perspectives. We also attempt to highlight some of the current pitfalls and the approaches needed to advance this important area of biochemical and biomedical research.

Basal and angiotensin II-inhibited neuronal delayed-rectifier K+ current are regulated by thioredoxin

In previous studies, we determined that macrophage migration inhibitory factor (MIF), acting intracellularly via its intrinsic thiol-protein oxidoreductase (TPOR) activity, stimulates basal neuronal delayed-rectifier K+ current ( IKv) and inhibits basal and angiotensin (ANG) II-induced increases in neuronal activity. These findings are the basis for our hypothesis that MIF is a negative regulator of ANG II actions in neurons. MIF has recently been recategorized as a member of the thioredoxin (Trx) superfamily of small proteins. In the present study we have examined whether Trx influences basal and ANG II-modulated IKv in an effort to determine whether the Trx superfamily can exert a general regulatory influence over neuronal activity and the actions of ANG II. Intracellular application of Trx (0.8–80 nM) into rat hypothalamic/brain stem neurons in culture increased neuronal IKv, as measured by voltage-clamp recordings. This effect of Trx was abolished in the presence of the TPOR inhibitor PMX 464 (800 nM). Furthermore, the mutant protein recombinant human C32S/C35S-Trx, which lacks TPOR activity, failed to alter neuronal IKv. Trx applied at a concentration (0.08 nM) that does not alter basal IKv abolished the inhibition of neuronal IKv produced by ANG II (100 nM). Given our observation that ANG II increases Trx levels in neuronal cultures, it is possible that Trx (like MIF) has a negative regulatory role over basal and ANG II-stimulated neuronal activity via modulation of IKv. Moreover, these data suggest that TPOR may be a general mechanism for negatively regulating neuronal activity.

Thioredoxin and related molecules--from biology to health and disease

Thioredoxin and glutaredoxin systems in mammalian cells utilize thiol and selenol groups to maintain a reducing intracellular redox state acting as antioxidants and reducing agents in redox signaling with oxidizing reactive oxygen species. During the last decade, the functional roles of thioredoxin in particular have continued to expand, also including novel functions such as a secreted growth factor or a chemokine for immune cells. The role of thioredoxin and glutaredoxin in antioxidant defense and the role of thioredoxin in controlling recruitment of inflammatory cells offer potential use in clinical therapy. The fundamental differences between bacterial and mammalian thioredoxin reductases offer new principles for treatment of infections. Clinical drugs already in use target the active site selenol in thioredoxin reductases, inducing cell death in tumor cells. Thioredoxin and binding proteins (ASK1 and TBP2) appear to control apoptosis or metabolic states such as carbohydrate and lipid metabolism related to diseases such as diabetes and atherosclerosis.

Thiol-based mechanisms of the thioredoxin and glutaredoxin systems: implications for diseases in the cardiovascular system

Reactive oxygen species (ROS) and the cellular thiol redox state are crucial mediators of multiple cell processes like growth, differentiation, and apoptosis. Excessive ROS production or oxidative stress is associated with several diseases, including cardiovascular disorders like ischemia-reperfusion. To prevent ROS-induced disorders, the heart is equipped with effective antioxidant systems. Key players in defense against oxidative stress are members of the thioredoxin-fold family of proteins. Of these, thioredoxins and glutaredoxins maintain a reduced intracellular redox state in mammalian cells by the reduction of protein thiols. The reversible oxidation of Cys-Gly-Pro-Cys or Cys-Pro(Ser)-Tyr-Cys active site cysteine residues is used in reversible electron transport. Thioredoxins and glutaredoxins belong to corresponding systems consisting of NADPH, thioredoxin reductase, and thioredoxin or NADPH, glutathione reductase, glutathione, and glutaredoxin, respectively. Thioredoxin as well as glutaredoxin activities appear to be very important for the progression and severity of several cardiovascular disorders. These proteins function not only as antioxidants, they inhibit or activate apoptotic signaling molecules like apoptosis signal-regulating kinase 1 and Ras or transcription factors like NF-kappaB. Thioredoxin activity is regulated by the endogenous inhibitor thioredoxin-binding protein 2 (TBP-2), indicating an important role of the balance between thioredoxin and TBP-2 levels in cardiovascular diseases. In this review, we will summarize cardioprotective effects of endogenous thioredoxin and glutaredoxin systems as well as the high potential in clinical applications of exogenously applied thioredoxin or glutaredoxin or the induction of endogenous thioredoxin and glutaredoxin systems.

Ischemic preconditioning triggers nuclear translocation of thioredoxin and its interaction with Ref-1 potentiating a survival signal through the PI-3-kinase-Akt pathway

Thioredoxin (Trx-1), a key mediator of cellular redox homeostasis and cell survival, is implicated in redox signaling in the ischemic myocardium. To investigate further its mechanism of action, Trx expression in rat heart was suppressed by direct injection of small hairpin RNA against Trx-1 (shRNA-Trx-1). Forty-eight hours after treatment, hearts were excised for isolated working-heart preparation. A group of hearts was preconditioned (PC) by subjecting them to four cyclic episodes of 5-min ischemia, each followed by 10 min of reperfusion. All the hearts, PC or non-PC, were subjected to 30-min ischemia followed by 2 h of reperfusion. As expected, the PC hearts exhibited improved ventricular function, reduced infarct size, and cardiomyocyte apoptosis. Also in PC hearts, an increase was noted in Trx-1 and other cardioprotective and redox-regulated proteins like Ref-1, phospho-Akt, and NF-kappaB DNA-binding activity. PC also caused nuclear translocation of Trx-1 and Ref-1 followed by their association. However, in hearts treated with shRNA-Trx 1, the cardioprotective effects of PC were abolished along with a concomitant decrease in nuclear localized Trx-1 and Ref-1, along with a decrease in phospho-Akt and NF-kappaB. These results demonstrate that PC triggers translocation of Trx-1 into the nucleus, where it becomes associated with Ref-1 and performs redox signaling through the activation of NF-kappaB and an increase in prosurvival signal inducer phospho-Akt.

The thioredoxin system in retroviral infection and apoptosis

Human thioredoxin (TRX) was first identified in human T-cell leukemia virus type I (HTLV-I)-positive T-cell lines and is associated with the pathophysiology of retroviral infections. TRX is a vital component of the thiol-reducing system and regulates various cellular function (redox regulation). Members of the TRX system regulate apoptosis through a wide variety of mechanisms. A family of thioredoxin-dependent peroxidases (peroxiredoxins) protects against apoptosis by scavenging hydrogen peroxide. Thioredoxin 2 is a critical regulator of cytochrome c release and mitochondrial apoptosis; transmembrane thioredoxin-related molecule (TMX) has a protective role in endoplasmic reticulum (ER) stress-induced apoptosis. TRX interacts with apoptosis signal-regulating kinase 1 (ASK1) and is a sensor of oxidative stress. Thioredoxin binding protein-2/vitamin D(3) upregulated protein 1 is a growth suppressor and its expression is suppressed in HTLV-I-transformed cells. Studies of these molecules of the TRX system provide novel insights into the apoptosis associated with retroviral diseases.

The augmentation of brain thioredoxin-1 expression after severe hypobaric hypoxia by the preconditioning in rats

Induction of endogenous antioxidants is one of the key molecular mechanisms of cell resistance to hypoxia/ischemia. The effect of severe hypoxia on the expression of cytosolic antioxidant thioredoxin-1 (Trx) in hippocampus and neocortex was studied in preconditioned and non-preconditioned rats. The preconditioning consisted of three trials of mild hypobaric hypoxia (360 Torr, 2 h) spaced at 24 h. Twenty-four hours after the last trial rats were subjected to severe hypobaric hypoxia (180 Torr, 3 h). Trx expression was studied by immunocytochemistry. In hippocampus severe hypobaric hypoxia rapidly induced Trx expression, which remained elevated still at 24 h. In neocortex the enhanced expression appeared only at 24 h. The preconditioning significantly augmented severe hypoxia-induced Trx-immunoreactivity at 3 h but not at 24 h. These findings point out that Trx contributes to mechanisms of brain tolerance to hypobaric hypoxia, especially in early periods after the exposure.

Redox regulation of cell growth and cell death

Oxidative stress evokes various cellular events, including activation of transcription factors, apoptosis, and cell cycle arrest. Accumulating evidence shows that reduction/oxidation (redox) plays an important role in the regulation of apoptosis and cell cycle arrest elicited by oxidative stress. Cellular redox is controlled by the thioredoxin (TRX) and glutathione (GSH) systems. TRX and GSH systems regulate cell growth and cell death by the activation of transcription factors, the sensitivity of cells to cytokines and growth factors, and the components of the apoptosis pathways. This brief review describes the current knowledge on the redox regulation of cell growth and apoptosis.

Role of endogenous retroviruses in autoimmune diseases

Endogenous retroviruses (ERVs) correspond to the integrated proviral form of infectious retroviruses that are trapped within the genome by mutations. Endogenous retroviruses represent a key molecular link between the host genome and infectious viral particles. Proteins encoded by ERVs are recognized by antiviral immune responses and become targets of autoreactivity. Activation of ERVs, such as human ERV-K or a human T-cell lymphotropic virus-related endogenous sequence, may also mediate pathogenicity of Epstein-Barr virus. Endogenous retrovirus peptides can directly regulate immune responses. Thus, molecular mimicry and immunomodulation by ERVs may account for self-reactivity and abnormal T- and B-cell functions in autoimmune disorders.

Modulation of the thioredoxin system during inflammatory responses and its effect on heme oxygenase-1 expression

Heme oxygenase (HO) enzymes catalyze the initial reaction in heme catabolism. HO-1 is an inducible isoform that is up-regulated by diverse stimuli, including inflammatory cytokines and factors that promote oxidative stress. HO-1 is a cytoprotective enzyme that degrades heme, a potent oxidant, to generate carbon monoxide, biliverdin (subsequently reduced to bilirubin), and iron. Recently, we found that thioredoxin (TRX), a disulfide reductase enzyme known to be important for the binding of transcription factors to DNA, contributes to the induction of HO-1 by inflammatory mediators. In the present study, we extended this observation and determined that, similar to HO-1, TRX and TRX reductase (TR) are induced by bacterial lipopolysaccharide in macrophages at the level of mRNA and protein. However, maximal induction of TRX and TR precedes that of HO-1. Increased expression of HO-1 in the cytoplasm of inflammatory cells corresponds to a translocation of TRX into the nucleus of these cells. Finally, transfection of TRX into macrophages promoted an increase in HO-1 protein. Taken together, these data support the concept that the TRX system contributes to the up-regulation of HO-1 under conditions associated with increased oxidative stress.

Redox control of cell death

Cellular redox is controlled by the thioredoxin (Trx) and glutathione (GSH) systems that scavenge harmful intracellular reactive oxygen species (ROS). Oxidative stress also evokes many intracellular events including apoptosis. There are two major pathways through which apoptosis is induced; one involves death receptors and is exemplified by Fas-mediated caspase-8 activation, and another is the stress- or mitochondria-mediated caspase-9 activation pathway. Both pathways converge on caspase-3 activation, resulting in nuclear degradation and cellular morphological change. Oxidative stress induces cytochrome c release from mitochondria and activation of caspases, p53, and kinases, including apoptosis signal-regulating kinase 1 (ASK1), c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase. Trx inhibits apoptosis signaling not only by scavenging intracellular ROS in cooperation with the GSH system, but also by inhibiting the activity of ASK1 and p38. Mitochondria-specific thioredoxin (Trx-2) and Trx peroxidases (peroxiredoxins) are suggested to regulate cytochrome c release from mitochondria, which is a critical early step in the apoptotis-signaling pathway. dATP/ATP and reducing factors including Trx determine the manifestation of cell death, apoptosis or necrosis, by regulating the activation process and the activity of redox-sensitive caspases. As mitochondria are the most redox-active organelle and indispensable for cells to initiate or inhibit the apoptosis process, the regulation of mitochondrial function is the central focus in the research field of apoptosis and redox.

Redox events in HTLV-1 Tax-induced apoptotic T-cell death

A number of studies implicate reactive oxygen intermediates in the induction of DNA damage and apoptosis. Recent studies suggest that the human T-cell leukemia virus type 1 (HTLV-1) Tax protein induces oxidative stress and apoptotic T-cell death. Activation of the T-cell receptor/CD3 pathway enhances the Tax-mediated oxidative and apoptotic effects. Tax-mediated apoptosis and oxidative stress as well as activation of nuclear factor-kappaB can be potently suppressed by antioxidants. This review focuses on Tax-dependent changes in the intracellular redox status and their role in Tax-mediated DNA damage and apoptosis. The relevance of these observations to HTLV-1 virus-mediated T-cell transformation and leukemogenesis are discussed.

Thioredoxin superfamily and thioredoxin-inducing agents

Mammalian thioredoxin (TRX) with redox-active dithiol in the active site plays multiple roles in intracellular signaling and resistance against oxidative stress. TRX is induced by a variety of stresses including infectious agents as well as hormones and chemicals. TRX is secreted from activated cells such as HTLV-I-transformed T-cells as a redox-sensitive molecule with cytokine-like and chemokine-like activities. The promoter of the TRX gene contains a series of stress-responsive elements. In turn, TRX promotes activation of transcription factors such as NF-kappa B, AP-1, and p53. We have reported that natural substances including estrogen, prostaglandins, and cAMP induce mRNA, protein, and secretion of TRX. These agents seemed to exert their physiological functions including cytoprotective actions partly through the induction of TRX without massive oxidative stress, which induces TRX strongly as well as other stress proteins. We report here a new TRX inducer substance, geranylgeranylacetone (GGA), which is originally derived from a natural plant constituent and has been used in the clinical field as an anti-ulcer drug. We have demonstrated that GGA induces the messenger RNA and protein of TRX and affects the activation of transcription factors, AP-1 and NF-kappa B, and that GGA blunted ethanol-induced cytotoxicity of cultured hepatocytes and gastrointestine mucosal cells. We will discuss a possible novel molecular mechanism of GGA, which is to protect cells via the induction of TRX and activation of transcription factors such as NF-kappa B and AP-1. Identification of the particular TRX-inducing components may contribute to the elucidation of the molecular basis of the "French Paradox," in which good red wines are beneficial for the cardiovascular system.

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.

The UV-inducible RNA-binding protein A18 (A18 hnRNP) plays a protective role in the genotoxic stress response

We have previously shown that specific RNA-binding proteins (RBP) are activated by genotoxic stress. The role and function of these stress-activated RBP are, however, poorly understood. The data presented here indicate that the RBP A18 heterogeneous ribonucleoprotein (hnRNP) is induced and translocated from the nuclei to the cytoplasm after exposure to UV radiation. Using a new in vitro system we identified potential cellular targets for A18 hnRNP. Forty-six mRNA transcripts were identified, most of which are stress- or UV-responsive genes. Two important stress-responsive transcripts, the replication protein A (RPA2) and thioredoxin, were studied in more detail. Northwestern analyses indicate that A18 hnRNP binds specifically to the 3'-untranslated region of RPA2 transcript independently of its poly(A) tail, whereas the poly(A) tail of thioredoxin mRNA reinforces binding. Overexpression of A18 hnRNP increases the mRNAs stability and consequently enhances translation in a dose-dependent manner. Moreover, cell lines expressing reduced levels of A18 hnRNP are more sensitive to UV radiation. These data suggest that A18 hnRNP plays a protective role against genotoxic stresses by translocating to the cytosol and stabilizing specific transcripts involved in cell survival.

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.

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.

The role of phagocytes in HIV-related oxidative stress

BACKGROUND

in response to a variety of stimuli, phagocytes release large quantities of reactive oxygen species (ROS), which are essential for bacterial killing. However, excessive ROS production not appropriately compensated by antioxidant molecules can lead to oxidative stress, which may also play an important role in pathogenesis of HIV infection. In fact, ROS participate in chronic inflammation, HIV replication and the apoptosis of cells of the immune system.

OBJECTIVE AND STUDY DESIGN

we used flow cytometry to study, in whole blood, the activation and redox status of polymorphonuclear neutrophils (PMN) and monocytes at different stages of the disease.

RESULTS

we showed that neutrophils and monocytes from HIV-infected patients spontaneously produced increased amounts of H2O2. This increased H2O2 production was associated with alterations of adhesion molecules expression at the cell surface, which also reflected basal activation of phagocytes from the HIV-infected patients. In monocytes, basal H2O2 production correlated with viral load. This increased ROS production was associated with changes in the expression of the antiapoptotic/antioxidant compounds Bcl-2 and thioredoxin along the course of the disease. This modulation could result from a dual regulation by oxidative stress and could explain at least in part why monocyte numbers remain relatively stable throughout the disease. Monocytes expressed a normal maximal capacity to produce ROS in optimal conditions of stimulation. In contrast, after ex vivo priming with TNFalpha or IL-8, neutrophils showed a decreased H2O2 production in response to bacterial N-formyl peptides. This latter impairment correlated with the decrease in CD4+ lymphocyte numbers and with IL-8 and IL-6 plasma levels.

CONCLUSIONS

the increased basal ROS production by phagocytes could participate to the oxidative injury which has been implicated in the pathophysiology of HIV infection. In addition, the decreased priming of H2O2 production by neutrophils could contribute to the increased susceptibility of HIV-infected patients to bacterial infections.

Going APE over ref-1

The DNA base excision repair (BER) pathway is responsible for the repair of cellular alkylation and oxidative DNA damage. A crucial and the second step in the BER pathway involves the cleavage of baseless sites in DNA by an AP endonuclease. The major AP endonuclease in mammalian cells is Ape1/ref-1. Ape1/ref-1 is a multifunctional protein that is not only responsible for repair of AP sites, but also functions as a reduction-oxidation (redox) factor maintaining transcription factors in an active reduced state. Ape1/ref-1 has been shown to stimulate the DNA binding activity of numerous transcription factors that are involved in cancer promotion and progression such as Fos, Jun, NF(B, PAX, HIF-1(, HLF and p53. Ape1/ref-1 has also been implicated in the activation of bioreductive drugs which require reduction in order to be active and has been shown to interact with a subunit of the Ku antigen to act as a negative regulator of the parathyroid hormone promoter, as well as part of the HREBP transcription factor complex. Ape1/ref-1 levels have been found to be elevated in a number of cancers such as ovarian, cervical, prostate, rhabdomyosarcomas and germ cell tumors and correlated with the radiosensitivity of cervical cancers. In this review, we have attempted to try and assimilated as much data concerning Ape1/ref-1 and incorporate the rapidly growing information on Ape1/ref-1 in a wide variety of functions and systems.

Thioredoxin facilitates the induction of heme oxygenase-1 in response to inflammatory mediators

Heme oxygenase (HO)-1 is a stress response protein that is regulated by oxidative stress. HO-1 catalyzes the generation of biliverdin, carbon monoxide, and iron from heme. Lipopolysaccharide (LPS) and interleukin (IL)-1beta induce HO-1 through the binding of nuclear proteins to AP-1 motifs in enhancer regions upstream from the transcription start site. The DNA binding activity of AP-1 proteins depends on the reduction of cysteines in their DNA-binding domains. We found that agents that disrupt free sulfhydryl groups abolish AP-1 binding activity in nuclear proteins obtained from rat aortic smooth muscle cells and macrophages stimulated with IL-1beta or LPS. Thioredoxin (TRX) may regulate the redox status of nuclear transcription factors in response to oxidative stimuli, thus we determined the role of TRX in the physiologic regulation of HO-1. TRX underwent nuclear translocation in cells stimulated with IL-1beta and LPS. We transfected macrophages with a heterologous promoter construct containing two AP-1 sites from an upstream enhancer region in the HO-1 promoter. Recombinant TRX induced promoter activity to a level analogous to that induced by LPS, and this TRX response was abolished by mutation of the AP-1 sites. An inhibitor of TRX reductase, used to prevent TRX translocation in the reduced state, decreased HO-1 induction by IL-1beta and LPS. These data provide the first evidence that TRX contributes to the induction of HO-1 by inflammatory mediators.

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.

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.

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.

Molecular cloning and characterization of a thioredoxin gene from Echinococcus granulosus

The insert of a clone from a lambdagt11 Echinococcus granulosus (Platyhelminth, Cestoda) protoscolex cDNA library, showed an open reading frame whose deduced protein sequence presents a high homology with all described thioredoxins (TRX). The TRX active site (Trp-Cys-Gly-Pro-Cys) is completely conserved. With a monospecific antibody, selected from a total anti-protoscolex sera by the isolated clone, a 12 kDa polypeptide was immunoprecipitated from a protoscolex total protein extract. Furthermore, an antiserum raised against a recombinant EgTRX also recognizes a 12 kDa band in these extracts. The recombinant protein presents TRX activity, using the insulin reduction assay. Finally, a TRX activity was characterized in protoscolex extracts. In all organisms where TRXs were studied, they participate in a cascade of redox exchanges, contributing to the maintaining of cell homeostasis. Considering that the parasitic flatworm E. granulosus is probably submitted to an important oxidative stress due to host defences, EgTRX protein could be involved in the survival strategies of this parasite.

Redox and activation status of monocytes from human immunodeficiency virus-infected patients: relationship with viral load

Monocytes are precursors of tissue macrophages, which are major targets of human immunodeficiency virus type 1 (HIV-1) infection. Although few blood monocytes are infected, their resulting activation could play a key role in the pathogenesis of HIV disease by modulating their transendothelial migration and inducing the production of reactive oxygen species (ROS). ROS participate in chronic inflammation, HIV replication, and the apoptosis of immune system cells seen in HIV-infected subjects. Published data on monocyte activation are controversial, possibly because most studies have involved monocytes isolated from their blood environment by various procedures that may alter cell responses. We therefore used flow cytometry to study, in whole blood, the activation and redox status of monocytes from HIV-infected patients at different stages of the disease. We studied the expression of adhesion molecules, actin polymerization, and cellular levels of H2O2, Bcl-2, and thioredoxin. Basal H2O2 production correlated with viral load and was further enhanced by bacterial N-formyl peptides and endotoxin. The enhanced H2O2 production by monocytes from asymptomatic untreated patients with CD4(+) cell counts above 500/microliter was associated with a decrease in the levels of Bcl-2 and thioredoxin. In contrast, in patients with AIDS, Bcl-2 levels returned to normal and thioredoxin levels were higher than in healthy controls. Restoration of these antioxidant and antiapoptotic molecules might explain, at least in part, why monocyte numbers remain relatively stable throughout the disease. Alterations of adhesion molecule expression and increased actin polymerization could play a role in transendothelial migration of these activated monocytes.

Thioredoxin in the endocrine response to stress

Adaptation to stress evokes a variety of biological responses, including activation of the hypothalamic--pituitary--adrenal (HPA) axis and synthesis of a panel of stress-response proteins at cellular levels: for example, expression of thioredoxin (TRX) is significantly induced under oxidative conditions. Glucocorticoids, as a peripheral effector of the HPA axis, exert their action via interaction with a ligand-inducible transcription factor glucocorticoid receptor (GR). However, how these stress responses coordinately regulate cellular metabolism is still unknown. We demonstrate that either antisense TRX expression or cellular treatment with H2O2 negatively modulates GR function and decreases glucocorticoid-inducible gene expression. Impaired cellular response to glucocorticoids is rescued by overexpression of TRX, most probably through the functional replenishment of the GR. Moreover, not only the ligand binding domain but the DNA binding domain of the GR is also suggested to be a direct target of TRX. Together, we propose that cellular glucocorticoid responsiveness is coordinately modulated by redox state and TRX level, suggesting that cross-talk between neuro-endocrine control of stress responses and cellular antioxidant systems may be essential for mammalian adaptation processes.

Direct association with thioredoxin allows redox regulation of glucocorticoid receptor function

The glucocorticoid receptor (GR) is considered to belong to a class of transcription factors, the functions of which are exposed to redox regulation. We have recently demonstrated that thioredoxin (TRX), a cellular reducing catalyst, plays an important role in restoration of GR function in vivo under oxidative conditions. Although both the ligand binding domain and other domains of the GR have been suggested to be modulated by TRX, the molecular mechanism of the interaction is largely unknown. In the present study, we hypothesized that the DNA binding domain (DBD) of the GR, which is highly conserved among the nuclear receptors, is also responsible for communication with TRX in vivo. Mammalian two-hybrid assay and glutathione S-transferase pull-down assay revealed the direct association between TRX and the GR DBD. Moreover, analysis of subcellular localization of TRX and the chimeric protein harboring herpes simplex viral protein 16 transactivation domain and the GR DBD indicated that the interaction might take place in the nucleus under oxidative conditions. Together these observations indicate that TRX, via a direct association with the conserved DBD motif, may represent a key mediator operating in interplay between cellular redox signaling and nuclear receptor-mediated signal transduction.

Redox regulation of the glucocorticoid receptor

Redox regulation is currently considered as a mode of signal transduction for coordinated regulation of a variety of cellular processes. The transcriptional regulation of gene expression is also influenced by cellular redox state, most possibly through the oxido-reductive modification of transcription factors. The glucocorticoid receptor belongs to a nuclear receptor superfamily and acts as a ligand-dependent transcription factor. We demonstrate that the glucocorticoid receptor function is regulated via redox-dependent mechanisms at multiple levels. Moreover, it is suggested that redox regulation of the receptor function is one of dynamic cellular responses to environmental stimuli and plays an important role in orchestrated crosstalk between central and peripheral stress responses.

Redox control of Epstein-Barr virus replication by human thioredoxin/ATL-derived factor: differential regulation of lytic and latent infection

Human thioredoxin (hTRX)/adult T-cell leukemia (ATL)-derived factor (ADF) was originally reported as an interleukin-2 (IL-2) receptor-alpha-inducing factor produced by human T-cell lymphotropic virus-1-positive (HTLV-1+) cell lines. Growing evidence indicates that hTRX/ADF plays important roles in cellular responses against oxidative stress and is involved in a variety of cellular functions. A high level of hTRX/ADF expression is also observed in other human virus-infected cell lines including those of Epstein-Barr virus (EBV) and human papillomavirus. In this report, we analyzed the effect of hTRX/ADF on lytic amplification and persistent replication of EBV as a model for lytic versus latent phase of viral replication in host cells. Addition of hTRX/ADF clearly suppressed lytic replication of EBV in Raji cells and B95-8 cells induced to the lytic phase of 12-O-tetradecanoylphorbol-13-acetate (TPA), and it prevented the death of these cells evoked by the lytic induction. In contrast, hTRX/ADF did not have any effect on persistent replication in the latent phase. These data indicated that hTRX/ADF prevents EBV-transformed cells from proceeding into the lytic phase and regulates cohabitation of EBV and its host cells.

Induction of thioredoxin, a redox-active protein, by ovarian steroid hormones during growth and differentiation of endometrial stromal cells in vitro

Human thioredoxin (hTrx) is a cellular redox-active protein that catalyzes dithiol/disulfide exchange reactions, thus controlling multiple biological functions, including cell growth-promoting activity. Here we show that the expression of hTrx protein and messenger RNA was up-regulated by incubation with 17beta-estradiol (E2) in primary culture of stromal cells isolated from human endometrium. Maximal enhancement of hTrx protein and messenger RNA was observed after 6-12 h of incubation with 10-100 nM E2, and the enhancing effect was suppressed by tamoxifen, an estrogen antagonist. Release of hTrx into the culture medium was markedly augmented after 5-day exposure of E2 plus progesterone (P) accompanied by in vitro differentiation of endometrial stromal cells (decidualization). Immunocytochemical studies showed that hTrx was localized in the nucleus, nucleolus, and cytosol in the stromal cells. Strongly enhanced immunoreactivity for hTrx was observed in the E2-treated cells, whereas there was no apparent difference in the pattern of subcellular localization among the untreated and E2- and/or P-treated cells. Although 1-50 microg/ml recombinant hTrx alone did not promote endometrial stromal cell growth, epidermal growth factor-dependent mitogenesis was additively enhanced by hTrx. Our results indicate that hTrx modulates endometrial cell growth, acting as a comitogenic factor for epidermal growth factor, which is known to be a mediator of estrogen action. It is also suggested that hTrx is deeply involved in the hormonal control of the endometrium by E2 and P, playing a regulatory role in endometrial cell growth and differentiation.