Overexpression of thioredoxin in transgenic mice attenuates focal ischemic brain damage

Thioredoxin and hematologic malignancies

Thioredoxin (Trx) is an inflammation-inducible small oxidoreductase protein ubiquitously expressed in all organisms. Trx acts both intracellularly and extracellularly and is involved in a wide range of physiological cellular responses. Inside the cell, Trx alleviates oxidative stress by scavenging reactive oxygen species (ROS), regulates a variety of redox-sensitive signaling pathways as well as ROS-independent genes, and exerts cytoprotective effects. Outside the cell, Trx acts as growth factors or cytokines and promotes cell growth and many other cellular responses. Trx is also implicated in tumorigenesis. Trx is a proto-oncogene and is overexpressed in many cancers and correlates with poor prognosis. Trx stimulates cancer cell survival, promotes tumor angiogenesis, and inhibits both spontaneous apoptosis and drug-induced apoptosis. Inhibitors targeting Trx pathway provide a promising therapeutic strategy for cancer prevention and intervention. More recently, data from our laboratory demonstrate an important role of Trx in expanding long-term repopulating hematopoietic stem cells. In this chapter, we first provide an overview of Trx including its isoforms, compartmentation, and functions. We then discuss the roles of Trx in hematologic malignancies. Finally, we summarize the most recent findings from our lab on the use of Trx to enhance hematopoietic reconstitution following hematopoietic stem cell transplantation.

Inhibition of thioredoxin-1 with siRNA exacerbates apoptosis by activating the ASK1-JNK/p38 pathway in brain of a stroke model rats

Apoptosis is critical for the development of cerebral ischemia/reperfusion injury. Thioredoxin-1(Trx-1) protein has been reported to have anti-apoptotic effects in a variety of cell types, and it has been implicated in brain injury after middle cerebral artery occlusion (MCAO). Thus, we studied the effects of Trx1 silencing after MCAO in rats and examined whether inhibition of endogenous Trx1 could increase tissue levels of apoptosis. Male Sprague-Dawley rats (N=170) were subjected to 1h of middle cerebral arterial occlusion followed by 24h of reperfusion. Trx1 siRNAs were injected into rat brains 24h prior to MCAO. Then, 24h after MCAO, brains were collected from euthanized rats for investigation. Treatment with Trx1 siRNA significantly increased mortality, behavioral deficits, and cerebral infarction volume and exacerbated neuronal cell apoptotic death after MCAO injury. Western blot revealed increased expression of apoptotic proteins such as P-ASK1, P-JNK, P-p38, cleaved caspase-3 and increased the level of cytochrome c in the cytosolic fraction in the Trx1 siRNA-treated group. Co-immunoprecipitation assay suggested an interaction between Trx1 and ASK1 in normal rat brains and Trx1 siRNA dissociated ASK1-Trx1 binding complex. Our data suggest that Trx1 siRNA increases apoptotic stress-induced ASK1 activation and this represents further evidence that Trx1 is an endogenous anti-apoptotic molecule that diminishes focal cerebral ischemia/reperfusion injury. Its mechanism of action is likely related to attenuation of the ASK1-JNK/p38 signaling pathway.

Delayed administration of alpha-difluoromethylornithine prevents hippocampus-dependent cognitive impairment after single and combined injury in mice

Radiation exposure due to radiological terrorism and military circumstances are a continuing threat for the civilian population. In an uncontrolled radiation event, it is likely that there will be other types of injury involved, including trauma. While radiation combined injury is recognized as an area of great significance, overall there is a paucity of information regarding the mechanisms underlying the interactions between irradiation and other forms of injury, or what countermeasures might be effective in ameliorating such changes. The objective of this study was to determine if difluoromethylornithine (DFMO) could reduce the adverse effects of single or combined injury if administered beginning 24 h after exposure. Eight-week-old C57BL/J6 young-adult male mice received whole-body cesium-137 ((137)Cs) irradiation with 4 Gy. Immediately after irradiation, unilateral traumatic brain injury was induced using a controlled cortical impact system. Forty-four days postirradiation, animals were tested for hippocampus-dependent cognitive performance in the Morris water maze. After cognitive testing, animals were euthanized and their brains snap frozen for immunohistochemical assessment of neuroinflammation (activated microglia) and neurogenesis in the hippocampal dentate gyrus. Our data show that single and combined injuries induced variable degrees of hippocampus-dependent cognitive dysfunction, and when given 24 h post trauma, DFMO treatment ameliorated those effects. Cellular changes including neurogenesis and numbers of activated microglia were generally not associated with the cognitive changes. Further analyses also revealed that DFMO increased hippocampal protein levels of the antioxidants thioredoxin 1 and peroxiredoxin 3 compared to vehicle treated animals. While the mechanisms responsible for the improvement in cognition after DFMO treatment are not yet clear, these results constitute a basis for further development of DFMO as a countermeasure for ameliorating the of risks for cognitive dysfunction in individuals subjected to trauma and radiation combined injury.

Identification of novel nuclear targets of human thioredoxin 1

The dysregulation of protein oxidative post-translational modifications has been implicated in stress-related diseases. Trx1 is a key reductase that reduces specific disulfide bonds and other cysteine post-translational modifications. Although commonly in the cytoplasm, Trx1 can also modulate transcription in the nucleus. However, few Trx1 nuclear targets have been identified because of the low Trx1 abundance in the nucleus. Here, we report the large-scale proteomics identification of nuclear Trx1 targets in human neuroblastoma cells using an affinity capture strategy wherein a Trx1C35S mutant is expressed. The wild-type Trx1 contains a conserved C32XXC35 motif, and the C32 thiol initiates the reduction of a target disulfide bond by forming an intermolecular disulfide with one of the oxidized target cysteines, resulting in a transient Trx1-target protein complex. The reduction is rapidly consummated by the donation of a C35 proton to the target molecule, forming a Trx1 C32-C35 disulfide, and results in the concurrent release of the target protein containing reduced thiols. By introducing a point mutation (C35 to S35) in Trx1, we ablated the rapid dissociation of Trx1 from its reduction targets, thereby allowing the identification of 45 putative nuclear Trx1 targets. Unexpectedly, we found that PSIP1, also known as LEDGF, was sensitive to both oxidation and Trx1 reduction at Cys 204. LEDGF is a transcription activator that is vital for regulating cell survival during HIV-1 infection. Overall, this study suggests that Trx1 may play a broader role than previously believed that might include regulating transcription, RNA processing, and nuclear pore function in human cells.

Revisiting an age-old question regarding oxidative stress

Significant advances in maintaining health throughout life can be made through a clear understanding of the fundamental mechanisms that regulate aging. The Oxidative Stress Theory of Aging (OSTA) is probably the most well studied mechanistic theory of aging and suggests that the rate of aging is controlled by accumulation of oxidative damage. To directly test the OSTA, aging has been measured in several lines of mice with genetic alterations in the expression of enzymatic antioxidants. Under its strictest interpretation, these studies do not support the OSTA, as modulation of antioxidant expression does not generally affect mouse life span. However, the incidence of many age-related diseases and pathologies is altered in these models, suggesting that oxidative stress does significantly influence some aspects of the aging process. Further, oxidative stress may affect aging in disparate patterns among tissues or under various environmental conditions. In this review, we summarize the current literature regarding aging in antioxidant mutant mice and offer several interpretations of their support of the OSTA.

Antioxidant gene therapy against neuronal cell death

Oxidative stress is a common hallmark of neuronal cell death associated with neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, as well as brain stroke/ischemia and traumatic brain injury. Increased accumulation of reactive species of both oxygen (ROS) and nitrogen (RNS) has been implicated in mitochondrial dysfunction, energy impairment, alterations in metal homeostasis and accumulation of aggregated proteins observed in neurodegenerative disorders, which lead to the activation/modulation of cell death mechanisms that include apoptotic, necrotic and autophagic pathways. Thus, the design of novel antioxidant strategies to selectively target oxidative stress and redox imbalance might represent important therapeutic approaches against neurological disorders. This work reviews the evidence demonstrating the ability of genetically encoded antioxidant systems to selectively counteract neuronal cell loss in neurodegenerative diseases and ischemic brain damage. Because gene therapy approaches to treat inherited and acquired disorders offer many unique advantages over conventional therapeutic approaches, we discussed basic research/clinical evidence and the potential of virus-mediated gene delivery techniques for antioxidant gene therapy.

Thioredoxin system regulation in the central nervous system: experimental models and clinical evidence

The reactive oxygen species produced continuously during oxidative metabolism are generated at very high rates in the brain. Therefore, defending against oxidative stress is an essential task within the brain. An important cellular system against oxidative stress is the thioredoxin system (TS). TS is composed of thioredoxin, thioredoxin reductase, and NADPH. This review focuses on the evidence gathered in recent investigations into the central nervous system, specifically the different brain regions in which the TS is expressed. Furthermore, we address the conditions that modulate the thioredoxin system in both, animal models and the postmortem brains of human patients associated with the most common neurodegenerative disorders, in which the thioredoxin system could play an important part.

Ferulic acid attenuates the cerebral ischemic injury-induced decrease in peroxiredoxin-2 and thioredoxin expression

Ferulic acid, a phenolic phytochemical compound found in various plants, has a neuroprotective effect through its anti-oxidant and anti-inflammation functions. Peroxiredoxin-2 and thioredoxin play a potent neuroprotective function against oxidative stress. We investigated whether ferulic acid regulates peroxiredoxin-2 and thioredoxin levels in cerebral ischemia. Sprague-Dawley rats (male, 210-230g) were treated with vehicle or ferulic acid (100mg/kg) after middle cerebral artery occlusion (MCAO), and cerebral cortex tissues were collected 24h after MCAO. Decreases in peroxiredoxin-2 and thioredoxin levels were elucidated in MCAO-operated animals using a proteomics approach. We found that ferulic acid treatment prevented the MCAO-induced decrease in the expression of peroxiredoxin-2 and thioredoxin. RT-PCR and Western blot analyses confirmed that ferulic acid treatment attenuated the MCAO-induced decrease in peroxiredoxin-2 and thioredoxin levels. Moreover, immunoprecipitation analysis showed that the interaction between thioredoxin and apoptosis signal-regulating kinase 1 (ASK1) decreased during MCAO, whereas ferulic acid prevented the MCAO-induced decrease in this interaction. Our findings suggest that ferulic acid plays a neuroprotective role by attenuating injury-induced decreases in peroxiredoxin-2 and thioredoxin levels in neuronal cell injury.

The role of thioredoxin-1 in suppression of endoplasmic reticulum stress in Parkinson disease

Endoplasmic reticulum (ER) stress has been implicated in Parkinson disease. We previously reported that thioredoxin 1 (Trx-1) suppressed the ER stress caused by 1-methy-4-phenyl-1,2,3,6-tetrahydropyridine; however, its molecular mechanism remains largely unknown. In the present study, we showed that 1-methyl-4-phenylpyridinium ion (MPP(+)) induced ER stress by activating glucose-regulated protein 78 (GRP78), inositol-requiring enzyme 1α (IRE1α), tumor necrosis factor receptor-associated factor 2 (TRAF2), c-Jun N-terminal kinase (JNK), caspase-12, and C/EBP homologous protein (CHOP) in PC12 cells. The downregulation of Trx-1 aggravated the ER stress and further increased the expression of the above molecules induced by MPP(+). In contrast, overexpression of Trx-1 attenuated the ER stress and repressed the expression of the above molecules induced by MPP(+). More importantly, the overexpression of Trx-1 in transgenic mice suppressed ER stress by inhibiting the activation of these molecules. We present, for the first time, the molecular mechanism of Trx-1 suppression of endoplasmic reticulum stress in Parkinson disease in vitro and in vivo. Based on our findings, we conclude that Trx-1 plays a neuroprotective role in Parkinson disease by suppressing ER stress by regulating the activation of GRP78, IRE1α, TRAF2, JNK, caspase-12, and CHOP.

Comparative analysis of the neuroprotective effects of ginsenosides Rg1 and Rb1 extracted from Panax notoginseng against cerebral ischemia

Panax notoginseng, a traditional Chinese medicine, has been used for thousands of years to treat ischemic patients. More than 20 saponin components have been isolated from P. notoginseng root and identified chemically. However, these different chemical components have different roles. In this study we compared the neuroprotective mechanisms of ginsenosides Rg1, Rb1, Rg1/Rb1, and panax notoginsenoside (PNS) against injuries caused by cerebral ischemia-reperfusion (I/R). Our results show that all of these treatments significantly reduced infarction volume and alleviated neurological deficits caused by cerebral I/R. The increase in malondialdehyde (MDA) concentration was inhibited by these treatments in the hippocampus. The decreased expressions of thioredoxin-1 (Trx-1), copper-zinc superoxide dismutase (SOD-1), protein kinase B (PKB/Akt), and nuclear factor-kappa B (NF-κB) caused by cerebral I/R were restored by these treatments. The expression of heat shock protein 70 (HSP70) was enhanced in the middle cerebral artery occlusion (MCAO) group, as well as in all of the treatment groups. These results suggest that Rg1 and Rb1 have similar roles in protecting the brain from ischemic damage; however, neither Rg1/Rb1 nor PNS have synergistic effects, thus either Rg1 or the Rb1 monomer should be considered as a pharmacological neuroprotective strategy for use in the case of ischemic stroke.

Thioredoxin-mimetic peptide CB3 lowers MAPKinase activity in the Zucker rat brain

Diabetes is a high risk factor for dementia. High glucose may be a risk factor for dementia even among persons without diabetes, and in transgenic animals it has been shown to cause a potentiation of indices that are pre-symptomatic of Alzheimer's disease. To further elucidate the underlying mechanisms linking inflammatory events elicited in the brain during oxidative stress and diabetes, we monitored the activation of mitogen-activated kinsase (MAPKs), c-jun NH₂-terminal kinase (JNK), p38 MAP kinases (p38^MAPK), and extracellular activating kinsae1/2 (ERK1/2) and the anti-inflammatory effects of the thioredoxin mimetic (TxM) peptides, Ac-Cys-Pro-Cys-amide (CB3) and Ac-Cys-Gly-Pro-Cys-amide (CB4) in the brain of male leptin-receptor-deficient Zucker diabetic fatty (ZDF) rats and human neuroblastoma SH-SY5Y cells. Daily i.p. injection of CB3 to ZDF rats inhibited the phosphorylation of JNK and p38^MAPK, and prevented the expression of thioredoxin-interacting-protein (TXNIP/TBP-2) in ZDF rat brain. Although plasma glucose/insulin remained high, CB3 also increased the phosphorylation of AMP-ribose activating kinase (AMPK) and inhibited p70^S6K kinase in the brain. Both CB3 and CB4 reversed apoptosis induced by inhibiting thioredoxin reductase as monitored by decreasing caspase 3 cleavage and PARP dissociation in SH-SY5Y cells. The decrease in JNK and p38^MAPK activity in the absence of a change in plasma glucose implies a decrease in oxidative or neuroinflammatory stress in the ZDF rat brain. CB3 not only attenuated MAPK phosphorylation and activated AMPK in the brain, but it also diminished apoptotic markers, most likely acting via the MAPK–AMPK–mTOR pathway. These results were correlated with CB3 and CB4 inhibiting inflammation progression and protection from oxidative stress induced apoptosis in human neuronal cells. We suggest that by attenuating neuro-inflammatory processes in the brain Trx1 mimetic peptides could become beneficial for preventing neurological disorders associated with diabetes.

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Thioredoxin mimeitics peptides (TXM) lower apoptosis in the brain of ZDF rat.

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TxM peptides prevent TXNIP/TBP-2 expression in the brain of ZDF rat.

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TxM peptides could become beneficial for preventing diabetes associated neurological disorders.

Thioredoxin/Txnip: redoxisome, as a redox switch for the pathogenesis of diseases

During the past few decades, it has been widely recognized that Reduction-Oxidation (redox) responses occurring at the intra- and extra-cellular levels are one of most important biological phenomena and dysregulated redox responses are involved in the initiation and progression of multiple diseases. Thioredoxin1 (Trx1) and Thioredoxin2 (Trx2), mainly located in the cytoplasm and mitochondria, respectively, are ubiquitously expressed in variety of cells and control cellular reactive oxygen species by reducing the disulfides into thiol groups. Thioredoxin interacting protein (Txnip/thioredoxin binding protein-2/vitamin D3 upregulated protein) directly binds to Trx1 and Trx2 (Trx) and inhibit the reducing activity of Trx through their disulfide exchange. Recent studies have revealed that Trx1 and Txnip are involved in some critical redox-dependent signal pathways including NLRP-3 inflammasome activation in a redox-dependent manner. Therefore, Trx/Txnip, a redox-sensitive signaling complex is a regulator of cellular redox status and has emerged as a key component in the link between redox regulation and the pathogenesis of diseases. Here, we review the novel functional concept of the redox-related protein complex, named “Redoxisome,” consisting of Trx/Txnip, as a critical regulator for intra- and extra-cellular redox signaling, involved in the pathogenesis of various diseases such as cancer, autoimmune disease, and diabetes.

The induction of thioredoxin-1 by epinephrine withdraws stress via interaction with β-arrestin-1

Stress regulates a panel of important physiological functions and disease states. Epinephrine is produced under stresses threaten to homeostasis. Thioredoxin-1(Trx-1) is a redox regulating protein which is induced to resist stresses and related with various diseases. Thus, it is important to examine whether Trx-1 is induced by epinephrine and to understand the underlying molecular mechanisms that Trx-1 modulates epinephrine stress. Here, we show that the expression of Trx-1 was induced by epinephrine via β-adrenergic receptor/Cyclic AMP/protein kinase A (PKA) signaling pathway in PC12 cells. The down-regulation of Trx-1 by siRNA aggravated accumulation of γ-H2AX and further decreased expression of p53 by epinephrine. Accordingly, Trx-1 overexpression alleviated accumulation of γ-H2AX and restored the expressions of p53 and C/EBP homologous protein (CHOP) in the cortex, hippocampus and thymus of mice. Moreover, Trx-1 overexpression reduced the malondialdehyde concentration by epinephrine. We further explored the mechanism on p53 and γ-H2AX regulated by Trx-1. We found that overexpression of Trx-1 suppressed β-arrestin-1 expression through interaction with β-arrestin-1. Consequently, the downregulation of β-arrestin-1 suppressed the cell viability and the expressions of γ-H2AX and cyclin D1, and increased p53 expression. Taken together, our data suggest that Trx-1/β-arrestin-1 interaction may represent a novel endogenous mechanism on protecting against stress.

The induction of thioredoxin-1 by epinephrine withdraws stress via interaction with β-arrestin-1

Stress regulates a panel of important physiological functions and disease states. Epinephrine is produced under stresses threaten to homeostasis. Thioredoxin-1(Trx-1) is a redox regulating protein which is induced to resist stresses and related with various diseases. Thus, it is important to examine whether Trx-1 is induced by epinephrine and to understand the underlying molecular mechanisms that Trx-1 modulates epinephrine stress. Here, we show that the expression of Trx-1 was induced by epinephrine via β-adrenergic receptor/Cyclic AMP/protein kinase A (PKA) signaling pathway in PC12 cells. The down-regulation of Trx-1 by siRNA aggravated accumulation of γ-H2AX and further decreased expression of p53 by epinephrine. Accordingly, Trx-1 overexpression alleviated accumulation of γ-H2AX and restored the expressions of p53 and C/EBP homologous protein (CHOP) in the cortex, hippocampus and thymus of mice. Moreover, Trx-1 overexpression reduced the malondialdehyde concentration by epinephrine. We further explored the mechanism on p53 and γ-H2AX regulated by Trx-1. We found that overexpression of Trx-1 suppressed β-arrestin-1 expression through interaction with β-arrestin-1. Consequently, the downregulation of β-arrestin-1 suppressed the cell viability and the expressions of γ-H2AX and cyclin D1, and increased p53 expression. Taken together, our data suggest that Trx-1/β-arrestin-1 interaction may represent a novel endogenous mechanism on protecting against stress.

17β-estradiol increases expression of the oxidative stress response and DNA repair protein apurinic endonuclease (Ape1) in the cerebral cortex of female mice following hypoxia

While it is well established that 17β-estradiol (E2) protects the rodent brain from ischemia-induced damage, it has been unclear how this neuroprotective effect is mediated. Interestingly, convincing evidence has also demonstrated that maintaining or increasing the expression of the oxidative stress response and DNA repair protein apurinic endonuclease 1 (Ape1) is instrumental in reducing ischemia-induced damage in the brain. Since E2 increases expression of the oxidative stress response proteins Cu/Zn superoxide dismutase and thioredoxin in the brain, we hypothesized that E2 may also increase Ape1 expression and that this E2-induced expression of Ape1 may help to mediate the neuroprotective effects of E2 in the brain. To test this hypothesis, we utilized three model systems including primary cortical neurons, brain slice cultures, and whole animals. Although estrogen receptor α and Ape1 were expressed in primary cortical neurons, E2 did not alter Ape1 expression in these cells. However, immunofluorescent staining and quantitative Western blot analysis demonstrated that estrogen receptor α and Ape1 were expressed in the nuclei of cortical neurons in brain slice cultures and that E2 increased Ape1 expression in the cerebral cortex of these cultures. Furthermore, Ape1 expression was increased and oxidative DNA damage was decreased in the cerebral cortices of ovariectomized female C57Bl/6J mice that had been treated with E2 and exposed to hypoxia. Taken together, our studies demonstrate that the neuronal microenvironment may be required for increased Ape1 expression and that E2 enhances expression of Ape1 and reduces oxidative DNA damage, which may in turn help to reduce ischemia-induced damage in the cerebral cortex and mediate the neuroprotective effects of E2.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

The thioredoxin system as a therapeutic target in human health and disease

The thioredoxin (Trx) system comprises Trx, truncated Trx (Trx-80), Trx reductase, and NADPH, besides a natural Trx inhibitor, the thioredoxin-interacting protein (TXNIP). This system is essential for maintaining the balance of the cellular redox status, and it is involved in the regulation of redox signaling. It is also pivotal for growth promotion, neuroprotection, inflammatory modulation, antiapoptosis, immune function, and atherosclerosis. As an ubiquitous and multifunctional protein, Trx is expressed in all forms of life, executing its function through its antioxidative, protein-reducing, and signal-transducing activities. In this review, the biological properties of the Trx system are highlighted, and its implications in several human diseases are discussed, including cardiovascular diseases, heart failure, stroke, inflammation, metabolic syndrome, neurodegenerative diseases, arthritis, and cancer. The last chapter addresses the emerging therapeutic approaches targeting the Trx system in human diseases.

Thioredoxin inhibits MPK38-induced ASK1, TGF-β, and p53 function in a phosphorylation-dependent manner

Murine protein serine-threonine kinase 38 (MPK38) is a member of the AMP-activated protein kinase-related serine/threonine kinase family. The factors that regulate MPK38 activity and function are not yet elucidated. Here, thioredoxin (Trx) was shown to be a negative regulator of MPK38. The redox-dependent association of MPK38 and Trx was mediated through the C-terminal domain of MPK38. Single and double amino acid substitution mutagenesis of MPK38 (C286S, C339S, C377S, and C339S/C377S) and Trx (C32S, C35S, and C32S/C35S) demonstrated that Cys(339) and Cys(377) of MPK38 and Cys(32) and Cys(35) of Trx are required for MPK38-Trx complex formation. MPK38 directly interacted with and phosphorylated Trx at Thr(76). Expression of wild-type Trx, but not the Trx mutants C32S/C35S and T76A, inhibited MPK38-induced ASK1, TGF-β, and p53 function by destabilizing MPK38. The E3 ubiquitin-protein ligase Mdm2 played a critical role in the regulation of MPK38 stability by Trx. Treatment of cells with 1-chloro-2,4-dinitrobenzene, a specific inhibitor of Trx reductase, decreased MPK38-Trx complex formation and subsequently increased MPK38 stability and activity, indicating that Trx negatively regulates MPK38 activity in vivo. Finally, we used ASK1-, Smad3-, and p53-null mouse embryonic fibroblasts to demonstrate that ASK1, Smad3, and p53 play important roles in the activity and function of MPK38, suggesting a functional link between MPK38 and ASK1, TGF-β, and p53 signaling pathways. These results indicate that Trx functions as a physiological inhibitor of MPK38, which plays an important role in inducing ASK1-, TGF-β-, and p53-mediated activity.

Sulforaphane enhances the ability of human retinal pigment epithelial cell against oxidative stress, and its effect on gene expression profile evaluated by microarray analysis

To gain further insights into the molecular basis of Sulforaphane (SF) mediated retinal pigment epithelial (RPE) 19 cell against oxidative stress, we investigated the effects of SF on the regulation of gene expression on a global scale and tested whether SF can endow RPE cells with the ability to resist apoptosis. The data revealed that after exposure to H₂O₂, RPE 19 cell viability was increased in the cells pretreated with SF compared to the cell not treated with SF. Microarray analysis revealed significant changes in the expression of 69 genes in RPE 19 cells after 6 hours of SF treatment. Based on the functional relevance, eight of the SF-responsive genes, that belong to antioxidant redox system, and inflammatory responsive factors were validated. The up-regulating translation of thioredoxin-1 (Trx1) and the nuclear translocation of Nuclear factor-like2 (Nrf2) were demonstrated by immunoblot analysis in SF treated RPE cells. Our data indicate that SF increases the ability of RPE 19 cell against oxidative stress through up-regulating antioxidative enzymes and down-regulating inflammatory mediators and chemokines. The results suggest that the antioxidant, SF, may be a valuable supplement for preventing and retarding the development of Age Related Macular Degeneration.

Thioredoxin-1 attenuates early graft loss after intraportal islet transplantation in mice

AIMS

Recent studies suggest that decreasing oxidative stress is crucial to achieve successful islet transplantation. Thioredoxin-1 (TRX), which is a multifunctional redox-active protein, has been reported to suppress oxidative stress. Furthermore, it also has anti-inflammatory and anti-apoptotic effects. In this study, we investigated the effects of TRX on early graft loss after islet transplantation.

METHODS

Intraportal islet transplantation was performed for two groups of streptozotocin-induced diabetic mice: a control and a TRX group. In addition, TRX-transgenic (Tg) mice were alternately used as islet donors or recipients.

RESULTS

The changes in blood glucose levels were significantly lower in the TRX group compared with the TRX-Tg donor and control groups (p<0.01). Glucose tolerance and the residual graft mass were considerably better in the TRX group. TRX significantly suppressed the serum levels of interleukin-1β (p<0.05), although neither anti-apoptotic nor anti-chemotactic effects were observed. Notably, no increase in the 8-hydroxy-2'-deoxyguanosine level was observed after islet infusion, irrespective of TRX administration.

CONCLUSIONS

The present study demonstrates that overexpression of TRX on the islet grafts is not sufficient to improve engraftment. In contrast, TRX administration to the recipients exerts protective effects on transplanted islet grafts by suppressing the serum levels of interleukin-1β. However, TRX alone appears to be insufficient to completely prevent early graft loss after islet transplantation. We therefore propose that a combination of TRX and other anti-inflammatory treatments represents a promising regimen for improving the efficacy of islet transplantation.

Repeated short-term daily exercise ameliorates oxidative cerebral damage and the resultant motor dysfunction after transient ischemia in rats

Long-term exercise prior to brain ischemia enhances the activities of antioxidant enzymes and leads to a significant reduction in brain damage and neurological deficits in rats subjected to transient middle cerebral artery occlusion. However, it has not been established whether relatively short-term exercise generates similar results following middle cerebral artery occlusion. We aimed to determine whether short-term exercise could reduce oxidative damage and prevent sensori-motor dysfunction. Male Wistar rats were subjected to perform daily exercise on a treadmill for 30 min at a speed of 15 m/min for 3 weeks, followed by a 90-min middle cerebral artery occlusion. Animals were assessed after middle cerebral artery occlusion for neurological deficits and sensori-motor function. Brain tissues were processed to evaluate infarct volume and oxidative damage. Oxidative stress was assessed using immunohistochemistry for 4-hydroxy-2-nonenal-modified proteins and 8-hydroxy-2'-deoxyguanosine. Antioxidant enzymes were evaluated using immunohistochemistry for thioredoxin and activity assay for superoxide dismutase. Exercise for 3 weeks decreased the severity of paralysis and impairment in forelimb motor coordination. Furthermore, exercise had effect on superoxide dismutase and reduced the infarct volume and the number of cells immunopositive for 4-hydroxy-2-nonenal-modified proteins and 8-hydroxy-2'-deoxyguanosine. Our results suggest that pre-conditioning treadmill exercise for 3 weeks is useful for ameliorating ischemia-induced brain injury.

Redox-active protein thioredoxin-1 administration ameliorates influenza A virus (H1N1)-induced acute lung injury in mice

OBJECTIVES

Influenza virus infections can cause severe acute lung injury leading to significant morbidity and mortality. Thioredoxin-1 is a redox-active defensive protein induced in response to stress conditions. Animal experiments have revealed that thioredoxin-1 has protective effects against various severe disorders. This study was undertaken to evaluate the protective effects of recombinant human thioredoxin-1 administration on influenza A virus (H1N1)-induced acute lung injury in mice.

DESIGN

Prospective animal trial.

SETTING

Research laboratory.

SUBJECTS

Nine-week-old male C57BL/6 mice inoculated with H1N1.

INTERVENTION

The mice were divided into a vehicle-treated group and recombinant human thioredoxin-1-treated group. For survival rate analysis, the vehicle or recombinant human thioredoxin-1 was administered intraperitoneally every second day from day -1 to day 13. For lung lavage and pathological analyses, vehicle or recombinant human thioredoxin-1 was administered intraperitoneally on days -1, 1, and 3.

MEASUREMENTS AND MAIN RESULTS

Lung lavage and pathological analyses were performed at 24, 72, and 120 hrs after inoculation. The recombinant human thioredoxin-1 treatment significantly improved the survival rate of H1N1-inoculated mice, although the treatment did not affect virus propagation in the lung. The treatment significantly attenuated the histological changes and neutrophil infiltration in the lung of H1N1-inoculated mice. The treatment significantly attenuated the production of tumor necrosis factor-α and chemokine (C-X-C motif) ligand 1 in the lung and oxidative stress enhancement, which were observed in H1N1-inoculated mice. H1N1 induced expressions of tumor necrosis factor-α and chemokine (C-X-C motif) ligand 1 in murine lung epithelial cells MLE-12, which were inhibited by the addition of recombinant human thioredoxin-1. The recombinant human thioredoxin-1 treatment started 30 mins after H1N1 inoculation also significantly improved the survival of the mice.

CONCLUSIONS

Exogenous administration of recombinant human thioredoxin-1 significantly improved the survival rate and attenuated lung histological changes in the murine model of influenza pneumonia. The protective mechanism of thioredoxin-1 might be explained by its potent antioxidative and anti-inflammatory actions. Consequently, recombinant human thioredoxin-1 might be a possible pharmacological strategy for severe influenza virus infection in humans.

Serum thioredoxin-1 as a diagnostic marker for malignant peritoneal mesothelioma

BACKGROUND

Diffuse malignant peritoneal mesothelioma (DMPM) is an aggressive malignant tumor of mesothelial origin that shows a limited response to cytoreductive surgery along with intraperitoneal chemotherapy. Therefore, diagnosing DMPM early is very important. Reactive oxygen species play an important role in asbestos toxicity, which is associated with the pathogenesis of DMPM growth. Thioredoxin-1 (TRX) is a small redox-active protein that demonstrates antioxidative activity associated with tumor growth. Here, we investigated the serum levels of TRX in patients with DMPM and compared them with those of a population that had been exposed to asbestos but did not have DMPM.

STUDY

The serum concentrations of TRX were measured in 15 DMPM patients and 34 individuals with benign asbestos-related diseases.

RESULTS

We demonstrated that the patients with DMPM had significantly higher serum levels of TRX than the population that had been exposed to asbestos but did not have DMPM.

CONCLUSIONS

Our data suggest that serum TRX concentration is a useful serum marker for DMPM.

Hypoxic preconditioning modifies the activity of prond antioxidant systems in rat hippocampus

The effects of repetitive mild hypobaric hypoxic preconditioning upon pro- and antioxidant systems in rat hippocampus were studied. It was found that three-trial preconditioning by mild hypobaric hypoxia (360 mm Hg, 2 h) induced moderate oxidative stress immediately after the last preconditioning trial. In addition, it down-regualted the levels of peptide antioxidants (Trx-1, Trx-2, Cu,Zn-SOD) and several lipid peroxidation products 24 h later.

Geranylgeranylacetone protects against morphine-induced hepatic and renal damage in mice

The acute or chronic administration of opioid drugs may induce oxidative damage and cellular apoptosis in the liver and kidney, and hence result in hepatic and renal damage. Thioredoxin-1 (Trx-1) and heat shock protein 70 (Hsp70) are emerging as important modulators of cellular functions. They have been shown to be involved in cellular protective mechanisms against a variety of toxic stressors. The present study was designed to investigate the effects of geranylgeranylacetone (GGA), a pharmacological inducer of Trx-1 and Hsp70, on morphine-induced hepatic and renal damage. Morphine induced apoptosis in the liver and kidney through the mitochondria-mediated apoptosis pathway, but not the endoplasmic reticulum-mediated pathway. The activation of caspases-9 and -3 was attenuated by pre‑treatment with GGA. In addition, the morphine-induced increase of malondialdehyde (MDA) levels was suppressed by GGA. Furthermore, GGA enhanced morphine-induced expression of Trx-1 and Hsp70 in the liver and kidney. The findings of this study suggest that GGA may be a safe and novel therapeutic agent for morphine‑induced hepatic and renal damage.

Thioredoxin-1 and oxidative stress status in pregnant women at early third trimester of pregnancy: relation to maternal and neonatal characteristics

This study examined the clinical and biological importance of thioredoxin-1, a redox-active defensive protein that controls multiple biological functions, in pregnant women. We measured serum concentrations of thioredoxin-1, total hydroperoxides, and redox potential in 60 pregnant women at the early third trimester: gestational age of 27-29 weeks. The thioredoxin-1 concentration (mean ± SD) was 90 ± 42 ng/ml. Total hydroperoxides was 471 ± 105 U.CARR (1 U.CARR = 0.08 mg/dl H(2)O(2)). Redox potential was 2142 ± 273 µmol/l. The total hydroperoxides: redox potential ratio (oxidative stress index) was 0.23 ± 0.08. Thioredoxin-1, total hydroperoxides, and oxidative stress index were higher and redox potential was lower than in blood of healthy adults. Total hydroperoxides and redox potential were mutually correlated significantly and negatively. Thioredoxin-1 correlated significantly and negatively and redox potential correlated significantly and positively with body weight and body mass index. Thioredoxin-1 and redox potential correlated significantly and positively with uric acid and albumin, respectively. Thioredoxin-1 and oxidative stress index correlated significantly and negatively and redox potential significantly and positively with neonatal birth weight. These results suggest that high concentrations of thioredoxin-1 are linked to high oxidative stress status in pregnant women and that neonatal birth weight is affected by the maternal oxidative condition during later pregnancy.

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.

Thioredoxin, oxidative stress, cancer and aging

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

Walking the oxidative stress tightrope: a perspective from the naked mole-rat, the longest-living rodent

Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells and tissue and not surprisingly many theories have arisen to link ROS-induced oxidative stress to aging and health. While studies clearly link ROS to a plethora of divergent diseases, their role in aging is still debatable. Genetic knock-down manipulations of antioxidants alter the levels of accrued oxidative damage, however, the resultant effect of increased oxidative stress on lifespan are equivocal. Similarly the impact of elevating antioxidant levels through transgenic manipulations yield inconsistent effects on longevity. Furthermore, comparative data from a wide range of endotherms with disparate longevity remain inconclusive. Many long-living species such as birds, bats and mole-rats exhibit high-levels of oxidative damage, evident already at young ages. Clearly, neither the amount of ROS per se nor the sensitivity in neutralizing ROS are as important as whether or not the accrued oxidative stress leads to oxidative-damage-linked age-associated diseases. In this review we examine the literature on ROS, its relation to disease and the lessons gleaned from a comparative approach based upon species with widely divergent responses. We specifically focus on the longest lived rodent, the naked mole-rat, which maintains good health and provides novel insights into the paradox of maintaining both an extended healthspan and lifespan despite high oxidative stress from a young age.

Suppressive effect of recombinant human thioredoxin on ultraviolet light-induced inflammation and apoptosis in murine skin

Thioredoxin (TRX) is a small ubiquitous protein, which regulates cellular redox status and scavenges reactive oxygen species. The present study was conducted to investigate the effect of TRX on ultraviolet (UV)-B-mediated inflammatory and apoptotic responses. Ear swelling after UV-B irradiation was significantly reduced in TRX-transgenic mice compared to wild-type mice. Administration i.p. of recombinant human TRX also reduced acute skin inflammatory reaction, such as skin erythema and swelling. Histologically, numbers of inflammatory cells including neutrophils and lymphocytes were significantly reduced and the average size of the caliber of blood vessels were also reduced in recombinant human TRX-injected mice. The number of apoptotic keratinocytes, in terms of sunburn cells, activated-caspase-3-positive cells and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were all significantly reduced in recombinant human TRX-injected mice. Immunohistochemical intensity of 8-hydroxy-2'-deoxyguanosine was strikingly reduced in recombinant human TRX-injected mouse. Western blotting showed that administration of recombinant human TRX attenuated duration of phosphorylation of p38 mitogen-activated protein kinases and intensity of phosphorylation of c-Jun N-terminal kinase in the early phase, which play important roles in inflammatory and apoptotic signaling. Collectively, these findings indicated that recombinant human TRX attenuated inflammatory and apoptotic responses caused by UV-B. Possible mechanisms for this might be via redox regulation of stress signaling and reduction of reactive oxygen species.

Induction of thioredoxin-interacting protein is mediated by oxidative stress, calcium, and glucose after brain injury in mice

Oxidative stress and glucose affect the expression of various genes that contribute to both reactive oxygen species generation and antioxidant systems. However, systemic alteration of oxidative stress-related gene expression in normal brains and in brains with a high-glucose status after ischemic-reperfusion has not been explored. Using a polymerase chain reaction array system, we demonstrate that thioredoxin-interacting protein (Txnip) is induced by both oxidative stress and glucose. We found that Txnip mRNA is induced by ischemic-reperfusion injury and that Txnip is located in the cytoplasm of neurons. Moreover, in vitro oxygen-glucose deprivation (OGD) and subsequent reoxygenation without glucose and in vivo administration of 3-nitropropionic acid also promoted an increase in Txnip in a time-dependent manner, indicating that oxidative stress without glucose can induce Txnip expression in the brain. However, calcium channel blockers inhibit induction of Txnip after OGD and reoxygenation. Using the polymerase chain reaction array with ischemic and hyperglycemic-ischemic samples, we confirmed that enhanced expression of Txnip was observed in hyperglycemic-ischemic brains after middle cerebral artery occlusion. Finally, transfection of Txnip small interfering RNA into primary neurons reduced lactate dehydrogenase release after OGD and reoxygenation. This is the first report showing that Txnip expression is induced in neurons after oxidative or glucose stress under either ischemic or hyperglycemic-ischemic conditions, and that Txnip is proapoptotic under these conditions.

Oxidative stress and diabetes: what can we learn about insulin resistance from antioxidant mutant mouse models?

The development of metabolic dysfunctions like diabetes and insulin resistance in mammals is regulated by a myriad of factors. Oxidative stress seems to play a central role in this process as recent evidence shows a general increase in oxidative damage and a decrease in oxidative defense associated with several metabolic diseases. These changes in oxidative stress can be directly correlated with increased fat accumulation, obesity, and consumption of high-calorie/high-fat diets. Modulation of oxidant protection through either genetic mutation or treatment with antioxidants can significantly alter oxidative stress resistance and accumulation of oxidative damage in laboratory rodents. Antioxidant mutant mice have previously been utilized to examine the role of oxidative stress in other disease models, but have been relatively unexplored as models to study the regulation of glucose metabolism. In this review, we will discuss the evidence for oxidative stress as a primary mechanism linking obesity and metabolic disorders and whether alteration of antioxidant status in laboratory rodents can significantly alter the development of insulin resistance or diabetes.

Attenuation of indomethacin-induced gastric mucosal injury by prophylactic administration of sake yeast-derived thioredoxin

BACKGROUND

Indomethacin is one of the group of nonsteroidal anti-inflammatory drugs, which often cause gastric mucosal injury as a side effect. Infiltration and activation of inflammatory cells, production of proinflammatory cytokines and chemokines, generation of reactive oxygen species, and activation of apoptotic signaling are involved in the pathogenesis of indomethacin-induced gastric injury. We examined whether sake yeast-derived thioredoxin (a small redox-active protein with anti-oxidative activity and various redox-regulating functions) reduced indomethacin-induced gastric injury.

METHODS

Gastric injury was produced by the intraperitoneal administration of indomethacin (40 mg/kg body weight) to C57BL/6 mice. Prior to the administration of indomethacin, the mice were offered food pellets containing non-genetically modified sake yeast-derived thioredoxin (thioredoxin 200 μg/g) for 3 days. Histological examinations, assessment of myeloperoxidase activity, and analysis of the gene expressions of proinflammatory cytokines and a chemokine (interleukin [IL]-1β, IL-6, and CXCL1) were statistically evaluated. Indomethacin cytotoxicity was determined by lactate dehydrogenase release from murine gastric epithelial GSM06 cells induced by 24-h treatment with 200 and 400 μM indomethacin after 1-h preincubation with 100 μg/ml sake yeast-derived thioredoxin.

RESULTS

Macroscopic (edema, hemorrhage, and ulcers) and histological (necrosis, submucosal edema, neutrophil infiltration) findings induced by indomethacin were significantly reduced by pretreatment with food pellets containing thioredoxin. Gastric myeloperoxidase activity and the gene expressions of proinflammatory cytokines (IL-1β and IL-6) were also significantly reduced by this pretreatment compared with findings in the mice not pretreated with thioredoxin-containing food pellets. The administration of sake yeast-derived thioredoxin significantly reduced indomethacin-induced cytotoxicity in GSM06 cells.

CONCLUSIONS

We conclude that oral administration of sake yeast-derived thioredoxin reduces indomethacin-induced gastric injury. Sake yeast-derived thioredoxin may have therapeutic potential against indomethacin-induced gastric injury.

Kinetic analyses of Keap1-Nrf2 interaction and determination of the minimal Nrf2 peptide sequence required for Keap1 binding using surface plasmon resonance

The Keap1-Nrf2 interaction plays important roles in regulation of Nrf2 activity and induction of chemopreventive enzymes. To better understand the interaction and to determine the minimal Nrf2 sequence required for Keap1 binding, we synthesized a series of Nrf2 peptides containing ETGE motif and determined their binding affinities to the Kelch domain of Keap1 in solution using a surface plasmon resonance-based competition assay. The equilibrium dissociation constant for the interaction between 16mer Nrf2 peptide and Keap1 Kelch domain in solution (K(solution)(D)) was found to be 23.9 nM, which is 10× lower than the surface binding constant (K(surface)(D)) of 252 nM obtained for the direct binding of Keap1 Kelch domain to the immobilized 16mer Nrf2 peptide on a surface plasmon resonance sensor chip surface. The binding affinity of Nrf2 peptides to Keap1 Kelch domain was not lost until after deletion of eight residues from the N-terminus of the 16mer Nrf2 peptide. The 9mer Nrf2 peptide has a moderate binding affinity with a (K(solution)(D)) of 352 nM and the affinity was increased 15× upon removal of the positive charge at the peptide N-terminus by acetylation. These results suggest that the minimal Nrf2 peptide sequence required for Keap1 binding is the 9mer sequence of LDEETGEFL.

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

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

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

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

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.

Depletion of cytosolic or mitochondrial thioredoxin increases CYP2E1-induced oxidative stress via an ASK-1-JNK1 pathway in HepG2 cells

Thioredoxin is an important reducing molecule in biological systems. Increasing CYP2E1 activity induces oxidative stress and cell toxicity. However, whether thioredoxin protects cells against CYP2E1-induced oxidative stress and toxicity is unknown. SiRNA were used to knockdown either cytosolic (TRX-1) or mitochondrial thioredoxin (TRX-2) in HepG2 cells expressing CYP2E1 (E47 cells) or without expressing CYP2E1 (C34 cells). Cell viability decreased 40-60% in E47 but not C34 cells with 80-90% knockdown of either TRX-1 or TRX-2. Depletion of either thioredoxin also potentiated the toxicity produced either by a glutathione synthesis inhibitor or by TNFα in E47 cells. Generation of reactive oxygen species and 4-HNE protein adducts increased in E47 but not C34 cells with either thioredoxin knockdown. GSH was decreased and adding GSH completely blocked E47 cell death induced by either thioredoxin knockdown. Lowering TRX-1 or TRX-2 in E47 cells caused an early activation of ASK-1, followed by phosphorylation of JNK1 after 48 h of siRNA treatment. A JNK inhibitor caused a partial recovery of E47 cell viability after thioredoxin knockdown. In conclusion, knockdown of TRX-1 or TRX-2 sensitizes cells to CYP2E1-induced oxidant stress partially via ASK-1 and JNK1 signaling pathways. Both TRX-1 and TRX-2 are important for defense against CYP2E1-induced oxidative stress.

Expression of thioredoxin-1 and hypoxia inducible factor-1α in cerebral arteriovenous malformations: Possible role of redox regulatory factor in neoangiogenic property

Background:

Recently it is reported that proliferative activity remains in vascular walls of cerebral arteriovenous malformations (AVMs). These reports indicate that endothelial cells in AVMs have the neoangiogenic property. In this study, we assess the role of thioredoxin-1 (Trx-1) and hypoxia-inducible factor 1a (HIF-1α) in AVMs. These factors are reported to play a role in neoangiogenesis.

Methods:

We analyzed the expressions of Trx1 in the specimens of human cerebral AVMs. In addition, we also analyzed the expression of HIF-1α in these specimens by immunohistochemical method and RT-PCR. Furthermore, we assessed the effect of redox state and expression of Trx-1 during neoangiogenesis using in vitro angiogenesis assay.

Findings:

Trx-1 and HIF-1α immunoreactivity was detected in almost all 17 specimens of AVMs. Trx-1 and HIF-1α immunoreactive cells were distributed mainly endothelium of intranidal arteries and enlarged veins with thickened vascular walls. Double staining shows that Trx-1 and VEGF (vascular endothelial growth factor) immunoreactivity were colocalized in the same cells. These cells were considered to be endothelial cells. HIF-1α immunoreactivity was also colocalized with VEGF immunoreactivity in endothelium. As for influencing factors, the presence of deep drainers and convulsion significantly associated with HIF-1α expression. Trx-1 assessed by western blotting decreased at 6 hours and 12 hours after plating on Matrigel, which is a model of angiogenesis.

Conclusions:

We have shown that the endothelial induction of Trx-1 and HIF-1α in cerebral AVMs. Based on all findings obtained in this study, Trx-1 may affect the neoangiogenic property of cerebral AVMs.

Increased inflammatory signaling and lethality of influenza H1N1 by nuclear thioredoxin-1

Background

Cell culture studies show that the antioxidant thiol protein, thioredoxin-1 (Trx1), translocates to cell nuclei during stress, facilitates DNA binding of transcription factors NF-κB and glucocorticoid receptor (GR) and potentiates signaling in immune cells. Excessive proinflammatory signaling in vivo contributes to immune hyper-responsiveness and disease severity, but no studies have addressed whether nuclear Trx1 mediates such responses.

Methodology/Principal Findings

Transgenic mice (Tg) expressing human Trx1 (hTrx1) with added nuclear localization signal (NLS) showed broad tissue expression and nuclear localization. The role of nuclear Trx1 in inflammatory signaling was examined in Tg and wild-type (WT) mice following infection with influenza (H1N1) virus. Results showed that Tg mice had earlier and more extensive NF-κB activation, increased TNF-α and IL-6 expression, greater weight loss, slower recovery and increased mortality compared to WT. Decreased plasma glutathione (GSH) and oxidized plasma GSH/GSSG redox potential (E_hGSSG) following infection in Tg mice showed that the increased nuclear thiol antioxidant caused a paradoxical downstream oxidative stress. An independent test of this nuclear reductive stress showed that glucocorticoid-induced thymocyte apoptosis was increased by NLS-Trx1.

Conclusion/Significance

Increased Trx1 in cell nuclei can increase severity of disease responses by potentiation of redox-sensitive transcription factor activation.

CNS peroxiredoxins and their regulation in health and disease

Oxidative stress is thought to be a contributing factor in many chronic neurodegenerative pathologies, as well as acute cerebrovascular disorders such as stroke. Peroxiredoxins are a family of antioxidant enzymes that reduce peroxides directly through the use of a redox active cysteine within their active site, which in the process becomes oxidized. In order to cycle back to the reduced state, many peroxiredoxins rely on thiol-dependent reduction by the ubiquitous antioxidant enzyme thioredoxin. Peroxiredoxins, together with thioredoxin and thioredoxin's own 'recycling enzyme', thioredoxin reductase, represent an antioxidant enzymic system of growing significance in the context of neuronal physiology and pathology. Overexpression, knockdown, and knockout approaches have demonstrated an important role for peroxiredoxins in protecting neurons from oxidative insults. It is also becoming clear that neuronal peroxiredoxins are subjected to post-translational modifications that impair function as part of disease pathology. Conversely, components of this pathway are also subject to dynamic upregulation such as via endogenous synaptic activity-dependent signaling and induction of the Nrf2-dependent Phase II response. As such, the thioredoxin-peroxiredoxin system represents a potential therapeutic target for central nervous system disorders associated with oxidative stress.

Thioredoxin increases exocytosis by denitrosylating N-ethylmaleimide-sensitive factor

Exocytosis involves membrane fusion between granules and the plasma membrane. Nitric oxide (NO) inhibits exocytosis by chemically modifying N-ethylmaleimide-sensitive factor (NSF), a key component of the exocytic machinery. However, cells recover the ability to release messenger molecules within hours of exposure to NO through unknown mechanisms. We now identify thioredoxin (TRX1) as a denitrosylase that reverses NO inhibition of exocytosis. Endogenously synthesized NO increases S-nitrosylated NSF levels, but S-nitrosylated NSF levels decrease within 3 h after exposure to NO. We found that NO increases the interaction between TRX1 and NSF, and endogenous TRX1 removes NO from S-nitrosylated NSF. Knockdown of TRX1 increases the level of S-nitrosylated NSF, prolongs the inhibition of exocytosis, and suppresses leukocyte adhesion. Taken together, these data show that TRX1 promotes exocytosis by denitrosylating NSF. Our findings suggest that TRX1 might regulate exocytosis in a variety of physiological settings, such as vascular inflammation, thrombosis, and insulin release.

Proteomic investigation of a neural substrate intimately related to brain death

Our current understanding on brain death remains limited despite its clinical importance. This study evaluated whether the proteome expressed in the rat rostral ventrolateral medulla (RVLM), a neural substrate that our laboratory identified previously to be intimately related to brain death, is uniquely different from other brain areas, using the cerebral cortex, which is defunct under persistent vegetative state for comparison. We found that a group of antioxidant proteins, including members of the peroxiredoxin (Prx) family (Prx-1, Prx-2, Prx-5, Prx-6), thioredoxin and mitochondrial manganese superoxide dismutase, exhibited significantly higher protein and mRNA expression levels in RVLM when compared to cerebral cortex. Tissue oxygen, ATP contents and ATP synthase subunits α and β in RVLM were also significantly elevated. On the other hand, protein and mRNA levels of members of the ubiquitin-proteasome system, including proteasome subunit α type-1, ubiquitin, uniquitin-conjugating enzyme E2 N, ubiquitin carboxyl-terminal hydrolase isozyme L1 and L3, were comparable in both brain regions. We conclude that a significantly elevated level of antioxidant proteins and mRNA in RVLM is consistent with the exhibition of higher tissue oxygen tension and metabolic energy production in this neural substrate, which together constitute a safeguard mechanism against brain death.