硫氧还蛋白与肺部疾病的研究进展

硫氧还蛋白系统是一个广泛存在于自然界的巯基氧化还原系统,它能够维持细胞的氧化还原动态平衡及阻止炎症反应的发生。它由硫氧还蛋白（thioredoxin,Trx）、硫氧还蛋白还原酶（thioredoxin reductase,Tr x R）和还原型辅酶II（reduced coenzy me II,NADPH）三部分组成。人类Tr x作为一种分泌性蛋白,在细胞内外发挥着多种氧化还原调控作用。Trx通过直接抑制氧化应激和间接与关键信号转导分子结合而发挥了抗氧化、抗凋亡和抗炎症作用。最近的研究显示Trx作为机体内主要的氧化应激相关因子,可能在肺部疾病中发挥了一定作用,且有可能成为临床干预治疗的靶点。本文对Trx在呼吸系统的表达与慢性阻塞性肺疾病、支气管哮喘、急性肺损伤（acute lung disease,ALI）和间质性肺疾病（interstitial lung disease,ILD）的关系进行简述。     

Production and secretion of thioredoxin from transformed human trophoblast cells

Thioredoxin is a redox active protein which has been implicated in reproductive processes. In this study we investigated the intracellular production and extracellular secretion of placental thioredoxin by human cytotrophoblast cell lines which were used as in-vitro model systems. Results clearly demonstrated that thioredoxin is not only synthesized by these cells but is also secreted and that while the intracellular thioredoxin is present only as a 12 kDa form, it would appear that the extracellular thioredoxin is present in two forms, a predominant 12 kDa form accompanied by a lower amount of a 10 kDa form. The observed localization and possible secretion of thioredoxin at the feto-maternal interface suggest important roles for this protein during pregnancy. Intracellular thioredoxin may be involved in the prevention of cellular damage due to oxidative stress whereas extracellular thioredoxin may act to integrate the actions of the cytokine network operating at the feto-maternal interface thereby assisting with implantation and the successful establishment of pregnancy.      

Thioredoxin 1 promotes intracellular replication and virulence of Salmonella enterica serovar Typhimurium

The effect of the cytoplasmic reductase and protein chaperone thioredoxin 1 on the virulence of Salmonella enterica serovar Typhimurium was evaluated by deleting the trxA, trxB, or trxC gene of the cellular thioredoxin system, the grxA or gshA gene of the glutathione/glutaredoxin system, or the dsbC gene coding for a thioredoxin-dependent periplasmic disulfide bond isomerase. Mutants were tested for tolerance to oxidative and nitric oxide donor substances in vitro, for invasion and intracellular replication in cultured epithelial and macrophage-like cells, and for virulence in BALB/c mice. In these experiments only the gshA mutant, which was defective in glutathione synthesis, exhibited sensitization to oxidative stress in vitro and a small decrease in virulence. In contrast, the trxA mutant did not exhibit any growth defects or decreased tolerance to oxidative or nitric oxide stress in vitro, yet there were pronounced decreases in intracellular replication and mouse virulence. Complementation analyses using defined catalytic variants of thioredoxin 1 showed that there is a direct correlation between the redox potential of thioredoxin 1 and restoration of intracellular replication of the trxA mutant. Attenuation of mouse virulence that was caused by a deficiency in thioredoxin 1 was restored by expression of wild-type thioredoxin 1 in trans but not by expression of a catalytically inactive variant. These results clearly imply that in S. enterica serovar Typhimurium, the redox-active protein thioredoxin 1 promotes virulence, whereas in vitro tolerance to oxidative stress depends on production of glutathione.     

Redox regulation of human thioredoxin network

Oxidative stresses are largely mediated by intracellular protein oxidations by reactive oxygen species (ROS). Host cells are equipped with antioxidants that scavenge ROS. The cellular reduction/oxidation (redox) balance is maintained by ROS and antioxidants. Accumulating evidence suggests that the redox balance plays an important role in cellular signaling through the redox modification of cysteine residues in various important components of the signal transduction pathway. Thioredoxin (TRX) is a small protein playing important roles in cellular responses, including cell growth, cell cycle, gene expression, and apoptosis, to maintain the redox circumstance. Moreover, many recent papers have shown that the redox regulation by TRX is deeply involved in the pathogenesis of various oxidative stress-associated disorders. This review focuses on TRX and its related molecules, and discusses the role of TRX-dependent redox regulation in oxidative stress-induced signal transduction.     

Thioredoxin system in premature and newborn biology

Thioredoxin is an important redox protein that is ubiquitously distributed. Thioredoxin exists in dynamic equilibrium between the oxidized and reduced forms, making it an ideal redox-regulatory protein. Thioredoxin, together with thioredoxin reductase and peroxiredoxins, forms a complete redox system that is similar to the glutathione system, but with distinct and divergent functions. This review provides a brief general summary of the thioredoxin system with particular emphasis on its role in premature birth and newborn physiology and disease states. Although extensive studies have examined the role of the thioredoxin system in antioxidant defense, cell proliferation, and signal transduction, further studies are needed to understand its role in embryogenesis and development. Such studies will facilitate our understanding of how thioredoxin may modulate newborn diseases via redox regulation.     

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.     

Expression and localization of thioredoxin during early implantation in the marmoset monkey.

Thioredoxin is a powerful redox protein expressed in invasive cytotrophoblasts and essential for blastocyst implantation in mice. Isolated marmoset thioredoxin cDNA showed that the deduced amino acid sequence differed from the human sequence by four amino acids. The close homology of thioredoxin in the two species enabled us to use monoclonal antibodies against human thioredoxin to detect marmoset thioredoxin in implantation sites, blastocysts and culture medium. Immunocytochemistry on marmoset implantation sites, on pregnancy days 12 and 15, showed that thioredoxin is highly expressed in uterine luminal epithelium, glands and in some endometrial stromal cells. In attached blastocysts, thioredoxin staining was detected in mural and polar trophoblast cells and both visceral and parietal endoderm, whereas no staining was present in the inner cell mass. A similar pattern of thioredoxin expression was detected in hatched blastocysts attached to Matrigel in tissue culture. Trophoblastic vesicles derived from blastocysts expressed thioredoxin in inner endoderm-like cells and outer trophoblast-like cells and secreted thioredoxin into the culture medium. These experiments have demonstrated thioredoxin expression during early stages of embryo-maternal interaction. We propose that thioredoxin protects the early placenta from oxidative damage and that the marmoset is a valuable model for studying thioredoxin regulation and function during implantation and blastocyst differentiation.     

Up-regulation of the redox mediators thioredoxin and apurinic/apyrimidinic excision (APE)/Ref-1 in hypoxic microregions of invasive cervical carcinomas, mapped using multispectral, wide-field fluorescence image analysis

Thioredoxin and apurinic/apyrimidinic excision (APE)/ref-1 are important redox mediators in biochemical pathways that promote cell survival under adverse conditions including hypoxia and oxidative stress. For example, elevated levels occur surrounding vascular infarcts and protect from reperfusion injury. Because elevated thioredoxin or APE/ref-1 is also associated with resistance to certain forms of cancer treatment, we examined their tissue distribution in a series of 110 cervical carcinoma biopsies. Analysis was done using a quadruple fluorescence imaging technique, incorporating carbonic anhydrase IX (CAIX) immunofluorescence to outline hypoxic microregions and 4',6-diamidino-2-phenylindole to localize nuclear staining of thioredoxin and APE/ref-1. A scanning autostage was used to image the entire tissue section. Thioredoxin and APE/ref-1 levels were expressed as the average pixel brightness in tumor tissue, subdivided based on CAIX and 4',6-diamidino-2-phenylindole staining. Results showed that the nuclear and cytoplasmic levels of thioredoxin were similar, whereas APE/ref-1 expression was greater in nuclei. Neither of these markers was predictive of outcome in this series of patients treated with radical radiotherapy. Both proteins showed highly significant elevations in CAIX-positive regions compared to CAIX-negative regions, and there was a nonsignificant trend for this effect to be greater in adenocarcinomas compared to squamous cell carcinomas. Levels of APE/ref-1 decreased with increasing tumor grade, but the expression was similar in CAIX-positive regions of poorly differentiated tumors compared to moderately or well-differentiated tumors. Elevated expression of thioredoxin and APE/ref-1 might promote cancer cell survival in hypoxic microenvironments of cervical carcinomas.     

RS Virus-Induced Inflammation and the Intracellular Glutathione Redox State in Cultured Human Airway Epithelial Cells

There is ample evidence that asthma is mediated by oxidative stress and that viral infection, which is associated with asthma onset and exacerbation in infants, acts as one type of oxidative stress. The goal of this study was to determine whether respiratory syncytial virus (RSV) induces oxidative stress in cultured A549 human airway epithelial cells and normal human bronchial epithelial cells (NHBE), and whether such RSV-induced oxidative stress can induce airway inflammation. To evaluate the direct effect of RSV infection as an oxidative stressor, the intracellular levels of reduced glutathione (GSH) or oxidized glutathione (GSSG) were measured. Their ratio (GSH/GSSG) was calculated to indicate intracellular oxidation–reduction (redox) status in A549 and NHBE. To evaluate the extent to which glutathione redox regulation affected cytokine/chemokine production, the effect of pretreatment with a reductive agent, glutathione monoethyl ester (GSH-OEt) and RSV-specific monoclonal antibody was thus studied. RSV acted as a potent oxidative stressor on the intracellular glutathione redox state in human airway epithelial cells, activating signals to increase the production of cytokine/chemokine. Pretreatment with GSH-OEt significantly suppressed RSV-induced time-dependent changes in the intracellular redox state, and also suppressed RSV-induced up-regulation of epithelial cell-derived IL-8, IL-6 and eotaxin production, as well as RSV-specific monoclonal antibody. RSV-induced oxidative stress is likely to contribute to the perpetuation and amplification of the inflammatory response. Therapeutic intervention against oxidative stress might therefore be beneficial as adjunctive therapies for respiratory disorders that are caused by an RSV infection.     

Targeting thioredoxin reductase: anticancer agents and chemopreventive compounds

Thioredoxin reductase plays a critical role in the regulation of cancer cell apoptosis, making it an attractive target for the design of new anticancer drugs. Several classes of compounds have been considered as potential antitumor or chemopreventive agents; most of them apparently interact with thioredoxin reductase's C-terminal redox center.     

硫氧还蛋白(Trx)及Trx80在免疫系统中的作用

硫氧还蛋白(thioredoxin,Trx)是一种广泛存在于真核生物和原核生物体内,具有多种生理学功能(如抗ROS侵害、保护大脑、调节免疫)的小分子(Mr12 000)蛋白质.它有一个活性位点Cys-Gly-Pro-Cys,通过该活性位点的二巯基/二硫键转化反应(即氧化还原反应),对生物体内的多种蛋白质进行氧化还原调节.而Trx的天然剪切产物(Trx80)没有氧化还原调节活性.本文综述了近年来有关Trx/Trx80与免疫系统的关系的研究新进展.     

Thioredoxin is related to life span regulation and oxidative stress response in Caenorhabditis elegans

Thioredoxin, an oxidoreductase, is a multifunction protein. The thioredoxin system is composed of NADPH, thioredoxin reductase and thioredoxin. This enzyme is highly conserved from bacteria to humans. We have characterized TRX-1, a thioredoxin homolog in C. elegans, which has about 36% identity in amino acid sequence with human thioredoxin. By gfp reporter system, trx-1 has been shown to be restrictedly expressed in ASI and ASJ neurons and in intestine. Immunostaining confirmed the intestinal expression. Full-length cDNA of trx-1 has been isolated by cDNA library PCR and subsequently cloned and sequenced. We have shown that the encoded protein functions as a reductase in the insulin reducing assay. Moreover, we have isolated a deletion mutant by PCR-based TMP-UV mutagenesis method. Mutant animals have reduced life span and are sensitive to oxidative stress. Reintroduction of trx-1 into mutant worms fully restored the wild-type phenotype. Our results suggest that trx-1 has important functions in life span regulation and oxidative stress response in C. elegans.     

Thioredoxin and glutathione systems in Plasmodium falciparum

Despite a 50% decrease in malaria infections between 2000 and 2010, malaria is still one of the three leading infectious diseases with an estimated 216 million cases worldwide in 2010. More than 90% of all malaria infections were caused by Plasmodium falciparum, a unicellular eukaryotic parasite that faces oxidative stress challenges while developing in Anopheles mosquitoes and humans. Reactive oxygen and nitrogen species threatening the parasite are either endogenously produced by heme derived from hemoglobin degradation or they are from exogenous sources such as the host immune defense. In order to maintain the intracellular redox balance, P. falciparum employs a complex thioredoxin and glutathione system based on the thioredoxin reductase/thioredoxin and glutathione reductase/glutathione couples. P. falciparum thioredoxin reductase reduces thioredoxin and a range of low molecular weight compounds, while glutathione reductase is highly specific for its substrate glutathione disulfide. Since Plasmodium spp. lack catalase and a classical glutathione peroxidase, their redox balance depends on a complex set of five peroxiredoxins differentially located in the cytosol, apicoplast, mitochondria, and nucleus with partially overlapping substrate preferences. Moreover, P. falciparum employs a set of members belonging to the thioredoxin superfamily such as three thioredoxins, two thioredoxin-like proteins, a dithiol and three monocysteine glutaredoxins, and a redox-active plasmoredoxin with largely redundant functions. This review aims at summarizing our current knowledge on the functional redox networks of the malaria parasite P. falciparum.