Thiol redox transitions by thioredoxin and thioredoxin-binding protein-2 in cell signaling

TXNIP inhibition in the treatment of type 2 diabetes mellitus: design, synthesis, and biological evaluation of quinazoline derivatives

Thioredoxin interacting protein (TXNIP) is a potential drug target for type 2 diabetes mellitus (T2DM) treatment. A series of quinazoline derivatives were designed, synthesised, and evaluated to inhibit TXNIP expression and protect from palmitate (PA)-induced β cell injury. In vitro cell viability assay showed that compounds D-2 and C-1 could effectively protect β cell from PA-induced apoptosis, and subsequent results showed that these two compounds decreased TXNIP expression by accelerating its protein degradation. Mechanistically, compounds D-2 and C-1 reduced intracellular reactive oxygen species (ROS) production and modulated TXNIP-NLRP3 inflammasome signalling, and thus alleviating oxidative stress injury and inflammatory response under PA insult. Besides, these two compounds were predicted to possess better drug-likeness properties using SwissADME. The present study showed that compounds D-2 and C-1, especially compound D-2, were potent pancreatic β cell protective agents to inhibit TXNIP expression and might serve as promising lead candidates for the treatment of T2DM.

Biological and Catalytic Properties of Selenoproteins

Selenocysteine is a catalytic residue at the active site of all selenoenzymes in bacteria and mammals, and it is incorporated into the polypeptide backbone by a co-translational process that relies on the recoding of a UGA termination codon into a serine/selenocysteine codon. The best-characterized selenoproteins from mammalian species and bacteria are discussed with emphasis on their biological function and catalytic mechanisms. A total of 25 genes coding for selenoproteins have been identified in the genome of mammals. Unlike the selenoenzymes of anaerobic bacteria, most mammalian selenoenzymes work as antioxidants and as redox regulators of cell metabolism and functions. Selenoprotein P contains several selenocysteine residues and serves as a selenocysteine reservoir for other selenoproteins in mammals. Although extensively studied, glutathione peroxidases are incompletely understood in terms of local and time-dependent distribution, and regulatory functions. Selenoenzymes take advantage of the nucleophilic reactivity of the selenolate form of selenocysteine. It is used with peroxides and their by-products such as disulfides and sulfoxides, but also with iodine in iodinated phenolic substrates. This results in the formation of Se-X bonds (X = O, S, N, or I) from which a selenenylsulfide intermediate is invariably produced. The initial selenolate group is then recycled by thiol addition. In bacterial glycine reductase and D-proline reductase, an unusual catalytic rupture of selenium-carbon bonds is observed. The exchange of selenium for sulfur in selenoproteins, and information obtained from model reactions, suggest that a generic advantage of selenium compared with sulfur relies on faster kinetics and better reversibility of its oxidation reactions.

The role of Andrographolide in the prevention and treatment of liver diseases

BACKGROUND

The presence or absence of damage to the liver organ is crucial to a person's health. Nutritional disorders, alcohol consumption, and drug abuse are the main causes of liver disease. Liver transplantation is the last irrevocable option for liver disease and has become a serious economic burden worldwide. Andrographolide (AP) is one of the main active ingredients of Herba Andrographitis. It has several biological activities and has been reported to have protective and therapeutic effects against liver diseases. Earlier literature has been written on AP's role in treating inflammation and other diseases, and there has not been a systematic review on liver diseases. This review is dedicated to sorting out the research results of AP against liver diseases. Pharmacokinetics, toxicity, and nanotechnology to improve bioavailability are discussed. Finally, an outlook and assessment of its future are provided.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. PubMed and web of Science databases were used to search all relevant literature on AP for liver disease up to 2022.

RESULTS

Studies have shown that AP plays an important role in different liver disease phenotypes, mainly through anti-inflammatory and antioxidant activities. AP regulates HO-1 and inhibits hepatitis virus replication. It affects the NF-κB pathway, downregulates inflammatory factors such as IL-1β, IL-6, and TNF-α, and reduces liver damage. In preventing liver fibrosis, AP inhibits angiogenesis and activation of hepatic stellate cells and reduces oxidative stress involved in the Nrf2 and TGF-β1/Smad pathways. In addition, AP impedes the development of liver cancer by promoting apoptosis and autonomous phagocytosis in a cell-dependent way. Interestingly, miRNAs are involved in the therapeutic process of liver cancer and hepatic fibrosis. The poor solubility of AP limits the development of dosage forms. Therefore, the advent of nanoformulations has improved bioavailability. Although the effect of AP is dose- and time-dependent, the magnitude of its toxicity is not negligible. Some clinical trials have shown that AP has mild side effects.

CONCLUSIONS

AP, as an effective natural product, has a good effect on the liver disease through multiple pathways and targets. However, the dose reaches a certain level, leading to its toxicity and side effects. For better clinical application of AP, high-quality clinical and toxic intervention mechanisms are needed to validate current studies. In addition, modulation of miRNA-mediated hepatocellular carcinoma and liver fibrosis and synergistic action with drugs may be the future focus of AP. In conclusion, AP can be regarded as an important candidate for treating different liver diseases in the future.

Physiological and modulatory role of thioredoxins in the cellular function

Thioredoxins (TRXs) are a class of ubiquitous and multifunctional protein. Mammal cells present three isoforms: a cytosolic and extracellular called thioredoxin 1 (TRX1), a mitochondrial (TRX2), and one specific in spermatozoids (TRX3). Besides, a truncated form called TRX80 exists, which results from the post-translational cleavage performed on TRX1. TRXs' main function is to maintain the reduction-oxidation homeostasis of the cell, reducing the proteins through a thiol-disulfide exchange that depends on two cysteines located in the active site of the protein (Cys32-X-X-Cys35 in humans). In addition, TRX1 performs S-nitrosylation, a post-translational modification of proteins that depends on cysteines of its C-terminal region (Cys62, Cys69, and Cys73 in human TRX1). These modifications allow the TRXs to modulate the protein function and participate in regulating diverse cellular processes, such as oxidative stress, transcription, signaling cascades, apoptosis, inflammation, and immunologic response. This points out the crucial relevance of TRXs for cell function, signaling it as a strategic target for the treatment of many diseases and its possible use as a therapeutic factor.

Transcriptomic and proteomic analyses provide insights into the adaptive responses to the combined impact of salinity and alkalinity in Gymnocypris przewalskii

Gymnocypris przewalskii is the only high-land endemic teleost living in Qinghai Lake, the largest saline-alkaline lake in China. Its osmoregulatory physiology remains elusive due to a lack of precise identification of the response proteins. In the present study, DIA/SWATH was used to identify differentially expressed proteins (DEPs) under alkaline (pH = 10.1, carbonate buffer), saline (12‰, sodium chloride), and saline-alkaline [carbonate buffer (pH = 10.1) plus 11‰ sodium chloride] stresses. A total of 66,056 unique peptides representing 7,150 proteins and 230 DEPs [the false discovery rate (FDR) ≤ 0.05, fold change (FC) ≥ 1.5] were identified under different stresses. Comparative analyses of the proteome and transcriptome indicated that over 86% of DEPs did not show consistent trends with mRNA. In addition to consistent enrichment results under different stresses, the specific DEPs involved in saline-alkaline adaptation were primarily enriched in functions of homeostasis, hormone synthesis and reactions of defense response, complement activation and reproductive development. Meanwhile, a protein-protein interaction (PPI) network analysis of these specific DEPs indicated that the hub genes were ITGAX, MMP9, C3, F2, CD74, BTK, ANXA1, NCKAP1L, and CASP8. This study accurately isolated the genes that respond to stress, and the results could be helpful for understanding the physiological regulation mechanisms regarding salinity, alkalinity, and salinity-alkalinity interactions.

Identification and characterization of Eimeria tenella EtTrx1 protein

Thioredoxin (Trx) is a widespread protein regulator of redox reactions in all organisms. It operates together with NADPH and thioredoxin reductase as a general protein disulfide catalytic system. Recently, Trx has been found to be related to the process by which apicomplexan protozoa invade host cells. In this study, Eimeria tenella thioredoxin (EtTrx1) was identified and its gene structural features, expression levels at different developmental stages, localization in sporozoites, roles in adhesion and invasion, and immunogenicity were investigated. Sequence analysis indicated that EtTrx1 contains a Trx domain with a WCGPC motif in 29-33 aa and a typical Trx fold, and belongs to thioredoxin family. EtTrx1 was detected on the surface of sporozoites using anti-EtTrx1 polyclonal antibodies under non-permeabilized conditions by indirect immunofluorescence assay (IFA) and also in a secretion form. EtTrx1 protein was highly transcribed and expressed in merozoites and sporozoites by quantitative PCR and western blot. The attachment assay showed that the adherence rates of yeast cells expressing EtTrx1 on the surface to host cells were 3.1-fold higher than those of the blank control. Specific anti-EtTrx1 antibodies inhibited the invasion of sporozoites into DF-1 cells. The highest inhibition rate was up to 36.75% compared to the control group. Immunization with recombinant EtTrx1 peptides also showed significant protection against lethal infections in chickens. It could offer moderate protective efficacy (Anticoccidial Index [ACI]: 163.70), induce humoral responses, and be an effective candidate for the development of new vaccines.

Adapting Physiology in Functional Human Islet Organogenesis

Generation of three-dimensional (3D)-structured functional human islets is expected to be an alternative cell source for cadaveric human islet transplantation for the treatment of insulin-dependent diabetes. Human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), offer infinite resources for newly synthesized human islets. Recent advancements in hPSCs technology have enabled direct differentiation to human islet-like clusters, which can sense glucose and secrete insulin, and those islet clusters can ameliorate diabetes when transplanted into rodents or non-human primates (NHPs). However, the generated hPSC-derived human islet-like clusters are functionally immature compared with primary human islets. There remains a challenge to establish a technology to create fully functional human islets in vitro, which are functionally and transcriptionally indistinguishable from cadaveric human islets. Understanding the complex differentiation and maturation pathway is necessary to generate fully functional human islets for a tremendous supply of high-quality human islets with less batch-to-batch difference for millions of patients. In this review, I summarized the current progress in the generation of 3D-structured human islets from pluripotent stem cells and discussed the importance of adapting physiology for in vitro functional human islet organogenesis and possible improvements with environmental cues.

Stem Cell-Derived Islets for Type 2 Diabetes

Since the discovery of insulin a century ago, insulin injection has been a primary treatment for both type 1 (T1D) and type 2 diabetes (T2D). T2D is a complicated disea se that is triggered by the dysfunction of insulin-producing β cells and insulin resistance in peripheral tissues. Insulin injection partially compensates for the role of endogenous insulin which promotes glucose uptake, lipid synthesis and organ growth. However, lacking the continuous, rapid, and accurate glucose regulation by endogenous functional β cells, the current insulin injection therapy is unable to treat the root causes of the disease. Thus, new technologies such as human pluripotent stem cell (hPSC)-derived islets are needed for both identifying the key molecular and genetic causes of T2D and for achieving a long-term treatment. This perspective review will provide insight into the efficacy of hPSC-derived human islets for treating and understanding T2D. We discuss the evidence that β cells should be the primary target for T2D treatment, the use of stem cells for the modeling of T2D and the potential use of hPSC-derived islet transplantation for treating T2D.

Thioguanine restoration through type I photosensitization-superoxide oxidation-glutathione reduction cycles

UVA-induced deleterious effect of thiopurine prodrugs including azathioprine, 6-mercaptopurine and 6-thioguanine (6-TG) increases the risk of cancer development due to the incorporation of 6-TG in patients' DNA. The catalytic mechanism by which thiobases act as a sustained oxidant producer has yet to be explored, especially through the Type I electron transfer pathway that produces superoxide radicals (O2˙-). Under Fenton-like conditions O2˙- radicals convert to extremely reactive hydroxyl radicals (˙OH), thus carrying even higher risk of biological damage than that induced by the well-studied type II reaction. By monitoring 6-TG/UVA-induced photochemistry in mass spectra and superoxide radicals (O2˙-) via nitro blue tetrazolium (NBT) reduction, this work provides two new findings: (1) in the presence of reduced glutathione (GSH), the production of O2˙-via the type I reaction is enhanced 10-fold. 6-TG thiyl radicals are identified as the primary intermediate formed in the reaction of 6-TG with O2˙-. The restoration of 6-TG and concurrent generation of O2˙- occur via a 3-step-cycle: 6-TG type I photosensitization, O2˙- oxidation and GSH reduction. (2) In the absence of GSH, 6-TG thiyl radicals undergo oxygen addition and sulfur dioxide removal to form carbon radicals (C6) which further convert to thioether by reacting with 6-TG molecules. These findings help explain not only thiol-regulation in a biological system but chemoprevention of cancer.

Changes in the Expression of TBP-2 in Response to Histone Deacetylase Inhibitor Treatment in Human Endometrial Cells

Histone deacetylase inhibitors (HDACi) induce apoptosis preferentially in cancer cells by caspase pathway activation and reactive oxygen species (ROS) accumulation. Suberoylanilide hydroxamic acid (SAHA), a HDACi, increases apoptosis via altering intracellular oxidative stress through thioredoxin (TRX) and TRX binding protein-2 (TBP-2). Because ROS accumulation, as well as the redox status determined by TBP-2 and TRX, are suggested as possible mechanisms for endometriosis, we queried whether SAHA induces apoptosis of human endometrial cells via the TRX–TBP-2 system in endometriosis. Eutopic endometrium from participants without endometriosis, and ectopic endometrium from patients with endometriosis, was obtained surgically. Human endometrial stromal cells (HESCs) and Ishikawa cells were treated with SAHA and cell proliferation was assessed using the CCK-8 assay. Real-time PCR and Western blotting were used to quantify TRX and TBP-2 mRNA and protein expression. After inducing oxidative stress, SAHA was applied. Short-interfering TRX (SiTRX) transfection was performed to see the changes after TRX inhibition. The mRNA and protein expression of TBP-2 was increased with SAHA concentrations in HESCs significantly. The mRNA TBP-2 expression was decreased after oxidative stress, upregulated by adding 2.5 μM of SAHA. The TRX/TBP-2 ratio decreased, apoptosis increased significantly, and SiTRX transfection decreased with SAHA. In conclusion, SAHA induces apoptosis by modulating the TRX/TBP-2 system, suggesting its potential as a therapeutic agent for endometriosis.

TRIAP1 knockdown sensitizes non-small cell lung cancer to ionizing radiation by disrupting redox homeostasis

Background

Radioresistance of some non‐small cell lung cancer (NSCLC) types increases the risk of recurrence or metastasis in afflicted patients, following radiotherapy. As such, further improvements to NSCLC radiotherapy are needed. The expression of oncogene TP53‐regulated inhibitor of apoptosis 1 (TRIAP1) in NSCLC is increased following irradiation. Furthermore, gene set enrichment analysis (GSEA) has suggested that TRIAP1 might be involved in maintaining redox homeostasis. This in turn might enhance cell radioresistance.

Methods

In this study we irradiated human NSCLC cell lines (A549 and H460), while knocking down TRIAP1, to determine whether a disrupted redox homeostasis could attenuate radioresistance.

Results

Irradiation notably increased both mRNA and protein levels of TRIAP1. In addition, TRIAP1 knockdown decreased the expression of several antioxidant proteins, including thioredoxin‐related transmembrane protein (TMX) 1, TMX2, thioredoxin (TXN), glutaredoxin (GLRX) 2, GLRX3, peroxiredoxin (PRDX) 3, PRDX4, and PRDX6 in A549 and H460 cells. In addition, silencing TRIAP1 impaired the radiation‐induced increase of the aforementioned proteins. Continuing along this line, we observed a radiation‐induced reduction of cell viability and invasion, as well as increased apoptosis and intracellular reactive oxygen species following TRIAP1 knockdown.

Conclusions

In summary, we identified TRIAP1 as a key contributor to the radioresistance of NSCLC by maintaining redox homeostasis.

Dunaliella salina Attenuates Diabetic Neuropathy Induced by STZ in Rats: Involvement of Thioredoxin

Diabetic neuropathy (DN) is a widespread disabling disorder including peripheral nerves' damage. The aim of the current study was to estimate the potential ameliorative effect of Dunaliella salina (D. salina) on DN and the involvement of the thioredoxin. Diabetes was induced by streptozotocin (STZ; 50 mg/kg; i.p). Glimepiride (0.5 mg/kg) or D. salina powder (100 or 200 mg/kg) were given orally, after 2 days of STZ injection for 4 weeks. Glucose, total antioxidant capacity (TAC), superoxide dismutase (SOD), and catalase (CAT) serum levels as well as brain contents of thioredoxin (Trx), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) were measured with the histopathological study. STZ-induced DN resulted in a significant (P < 0.05) rise in glucose blood level and brain contents of TNF-α and IL-6 and produced a reduction in serum TAC, SOD, CAT, and brain Trx levels with irregular islets of Langerhans cells and loss of brain Purkinje cells. Treatment with glimepiride or both doses of D. salina alleviated these biochemical and histological parameters as compared to the STZ group. D. salina has a neurotherapeutic effect against DN via its inhibitory effect on inflammatory mediators and oxidative stress molecules with its upregulation of Trx activity.

TMX2 Is a Crucial Regulator of Cellular Redox State, and Its Dysfunction Causes Severe Brain Developmental Abnormalities

The redox state of the neural progenitors regulates physiological processes such as neuronal differentiation and dendritic and axonal growth. The relevance of endoplasmic reticulum (ER)-associated oxidoreductases in these processes is largely unexplored. We describe a severe neurological disorder caused by bi-allelic loss-of-function variants in thioredoxin (TRX)-related transmembrane-2 (TMX2); these variants were detected by exome sequencing in 14 affected individuals from ten unrelated families presenting with congenital microcephaly, cortical polymicrogyria, and other migration disorders. TMX2 encodes one of the five TMX proteins of the protein disulfide isomerase family, hitherto not linked to human developmental brain disease. Our mechanistic studies on protein function show that TMX2 localizes to the ER mitochondria-associated membranes (MAMs), is involved in posttranslational modification and protein folding, and undergoes physical interaction with the MAM-associated and ER folding chaperone calnexin and ER calcium pump SERCA2. These interactions are functionally relevant because TMX2-deficient fibroblasts show decreased mitochondrial respiratory reserve capacity and compensatory increased glycolytic activity. Intriguingly, under basal conditions TMX2 occurs in both reduced and oxidized monomeric form, while it forms a stable dimer under treatment with hydrogen peroxide, recently recognized as a signaling molecule in neural morphogenesis and axonal pathfinding. Exogenous expression of the pathogenic TMX2 variants or of variants with an in vitro mutagenized TRX domain induces a constitutive TMX2 polymerization, mimicking an increased oxidative state. Altogether these data uncover TMX2 as a sensor in the MAM-regulated redox signaling pathway and identify it as a key adaptive regulator of neuronal proliferation, migration, and organization in the developing brain.

Andrographolide enhances redox status of liver cells by regulating microRNA expression

Andrographis paniculata Nees and its principal compound andrographolide are well known for exerting beneficial effects by modulating signaling pathways in different biological systems. Our earlier studies have demonstrated the ability of andrographolide as well as andrographolide enriched extracts to activate Nrf2/HO-1 pathway through adenosine A_2a receptor. Present study investigated ability of andrographolide to regulate Nrf2 induced antioxidant defense systems by miRNAs using HepG2 cells. Andrographolide strongly induced Nrf2 which in turn modulated enzymes of glutathione and thioredoxin antioxidant systems. It also regulated crucial transcription factors viz. hepatocyte nuclear factor alpha (HNF4A) and tumor suppressor protein 53 (p53). Downregulation of HNF4A by andrographolide led to decrease in miRNAs regulating Heme oxygenase-1 (miR-377) and glutathione cysteine ligase (miR-433). Upregulation of p53 on the other hand led to increase in miRNAs regulating thioredoxin interacting protein (miR-17, miR-224) and glutathione peroxidase (miR-181a). Involvement of p53 and HNF4A in modulation of these miRNAs was confirmed by chromatin immunoprecipitation assay. Overall, the work reveals that andrographolide through modulation of p53 and HNF4A, regulates miRNAs leading to upregulation of HO-1, glutathione and thioredoxin systems. Andrographolide thus, can play a beneficial role in modulating antioxidant defense in oxidative stress induced diseases such as diabetes, ageing etc.

Identification of thioredoxin-interacting protein (TXNIP) as a downstream target for IGF1 action

Laron syndrome (LS), or primary growth hormone (GH) insensitivity, is the best-characterized entity among the congenital insulin-like growth factor 1 (IGF1) deficiencies. Life-long exposure to minute endogenous IGF1 levels is linked to low stature as well as a number of endocrine and metabolic abnormalities. While elevated IGF1 is correlated with increased cancer incidence, epidemiological studies revealed that patients with LS do not develop tumors. The mechanisms associated with cancer protection in LS are yet to be discovered. Recent genomic analyses identified a series of metabolic genes that are overrepresented in patients with LS. Given the augmented expression of these genes in a low IGF1 milieu, we hypothesized that they may constitute targets for IGF1 action. Thioredoxin-interacting protein (TXNIP) plays a critical role in cellular redox control by thioredoxin. TXNIP serves as a glucose and oxidative stress sensor, being commonly silenced by genetic or epigenetic events in cancer cells. Consistent with its enhanced expression in LS, we provide evidence that TXNIP gene expression is negatively regulated by IGF1. These results were corroborated in animal studies. In addition, we show that oxidative and glucose stresses led to marked increases in TXNIP expression. Supplementation of IGF1 attenuated TXNIP levels, suggesting that IGF1 exerts its antiapoptotic effect via inhibition of TXNIP Augmented TXNIP expression in LS may account for cancer protection in this condition. Finally, TXNIP levels could be potentially useful in the clinic as a predictive or diagnostic biomarker for IGF1R-targeted therapies.

PKCα and HMGB1 antagonistically control hydrogen peroxide-induced poly-ADP-ribose formation

Harmful oxidation of proteins, lipids and nucleic acids is observed when reactive oxygen species (ROS) are produced excessively and/or the antioxidant capacity is reduced, causing ‘oxidative stress’. Nuclear poly-ADP-ribose (PAR) formation is thought to be induced in response to oxidative DNA damage and to promote cell death under sustained oxidative stress conditions. However, what exactly triggers PAR induction in response to oxidative stress is incompletely understood. Using reverse phase protein array (RPPA) and in-depth analysis of key stress signaling components, we observed that PAR formation induced by H₂O₂ was mediated by the PLC/IP3R/Ca²⁺/PKCα signaling axis. Mechanistically, H₂O₂-induced PAR formation correlated with Ca²⁺-dependent DNA damage, which, however, was PKCα-independent. In contrast, PAR formation was completely lost upon knockdown of PKCα, suggesting that DNA damage alone was not sufficient for inducing PAR formation, but required a PKCα-dependent process. Intriguingly, the loss of PAR formation observed upon PKCα depletion was overcome when the chromatin structure-modifying protein HMGB1 was co-depleted with PKCα, suggesting that activation and nuclear translocation of PKCα releases the inhibitory effect of HMGB1 on PAR formation. Together, these results identify PKCα and HMGB1 as important co-regulators involved in H₂O₂-induced PAR formation, a finding that may have important relevance for oxidative stress-associated pathophysiological conditions.

TrxR1 as a potent regulator of the Nrf2-Keap1 response system

SIGNIFICANCE

All cells must maintain a balance between oxidants and reductants, while allowing for fluctuations in redox states triggered by signaling, altered metabolic flow, or extracellular stimuli. Furthermore, they must be able to rapidly sense and react to various challenges that would disrupt the redox homeostasis.

RECENT ADVANCES

Many studies have identified Keap1 as a key sensor for oxidative or electrophilic stress, with modification of Keap1 by oxidation or electrophiles triggering Nrf2-mediated transcriptional induction of enzymes supporting reductive and detoxification pathways. However, additional mechanisms for Nrf2 regulation are likely to exist upstream of, or in parallel with, Keap1.

CRITICAL ISSUES

Here, we propose that the mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a potent regulator of Nrf2. A high chemical reactivity of TrxR1 and its vital role for the thioredoxin (Trx) system distinguishes TrxR1 as a prime target for electrophilic challenges. Chemical modification of the selenocysteine (Sec) in TrxR1 by electrophiles leads to rapid inhibition of thioredoxin disulfide reductase activity, often combined with induction of NADPH oxidase activity of the derivatized enzyme, thereby affecting many downstream redox pathways. The notion of TrxR1 as a regulator of Nrf2 is supported by many publications on effects in human cells of selenium deficiency, oxidative stress or electrophile exposure, as well as the phenotypes of genetic mouse models.

FUTURE DIRECTIONS

Investigation of the role of TrxR1 as a regulator of Nrf2 activation will facilitate further studies of redox control in diverse cells and tissues of mammals, and possibly also in animals of other classes.

Inflammation-induced DNA damage and damage-induced inflammation: a vicious cycle

Inflammation is the ultimate response to the constant challenges of the immune system by microbes, irritants or injury. The inflammatory cascade initiates with the recognition of microorganism-derived pathogen associated molecular patterns (PAMPs) and host cell-derived damage associated molecular patterns (DAMPs) by the pattern recognition receptors (PRRs). DNA as a molecular PAMP or DAMP is sensed directly or via specific binding proteins to instigate pro-inflammatory response. Some of these DNA binding proteins also participate in canonical DNA repair pathways and recognise damaged DNA to initiate DNA damage response. In this review we aim to capture the essence of the complex interplay between DNA damage response and the pro-inflammatory signalling through representative examples.

Neuroprotective Activity of Coptisine from Coptis chinensis (Franch)

Coptis chinensis rhizomes (CR) are one important ingredient of traditional Chinese herbal formulas such as San-Huang-Xie-Xin-Tang which is used for treatment of cardiovascular and neurodegenerative diseases. Recent studies suggest that the extract of CR might be a potential therapeutic agent for amelioration of neurological disorders associated with oxidative stress. In the present study we aimed at revealing the main active compound(s) of the CR extract and at investigating the mechanism of action. Four main alkaloids of the CR extract (berberine, coptisine, jatrorrhizine, and palmatine) were selected for this study. Results showed that out of those alkaloids only pretreatment with coptisine significantly attenuated tert-butylhydroperoxide induced reduction of cell viability, increased rate of apoptosis, and declined mitochondrial membrane potential. Elisa assay and quantitative real-time PCR analyses revealed that thioredoxin-interacting protein (TXNIP) gene expression was downregulated by coptisine, which could explain the neuroprotective effect, hypothetically, by strengthening the thioredoxin defense system against oxidative stress and attenuation of apoptosis signal-regulating kinase (Ask1) mediated apoptotic signaling. A comparison between coptisine and CR extract identified coptisine as the main single component responsible for the neuroprotective effect. Based on the results the CR extract and coptisine are promising candidate agents for prevention or improvement of diabetic neuropathy and neurodegenerative disorders.

The cysteine proteome

The cysteine (Cys) proteome is a major component of the adaptive interface between the genome and the exposome. The thiol moiety of Cys undergoes a range of biologic modifications enabling biological switching of structure and reactivity. These biological modifications include sulfenylation and disulfide formation, formation of higher oxidation states, S-nitrosylation, persulfidation, metalation, and other modifications. Extensive knowledge about these systems and their compartmentalization now provides a foundation to develop advanced integrative models of Cys proteome regulation. In particular, detailed understanding of redox signaling pathways and sensing networks is becoming available to allow the discrimination of network structures. This research focuses attention on the need for atlases of Cys modifications to develop systems biology models. Such atlases will be especially useful for integrative studies linking the Cys proteome to imaging and other omics platforms, providing a basis for improved redox-based therapeutics. Thus, a framework is emerging to place the Cys proteome as a complement to the quantitative proteome in the omics continuum connecting the genome to the exposome.

Coptis chinensis Franch. exhibits neuroprotective properties against oxidative stress in human neuroblastoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

The dried rhizome of Coptis chinensis Franch. (family Ranunculaceae) is traditionally used in Chinese medicine for the treatment of inflammatory diseases and diabetes. Recent studies showed a variety of activities of Coptis chinensis Franch. alkaloids, including neuroprotective, neuroregenerative, anti-diabetic, anti-oxidative and anti-inflammatory effects. However, there is no report on the neuroprotective effect of Coptis chinensis Franch. watery extract against tert-butylhydroperoxide (t-BOOH) induced oxidative damage. The aim of the study is to investigate neuroprotective properties of Coptis chinensis Franch. rhizome watery extract (CRE) and to evaluate its potential mechanism of action.

MATERIALS AND METHODS

Neuroprotective properties on t-BOOH induced oxidative stress were investigated in SH-SY5Y human neuroblastoma cells. Cells were pretreated with CRE for 2 h or 24 h followed by 2 h of treatment with t-BOOH. To evaluate the neuroprotective effect of CRE, cell viability, cellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP) and the apoptotic rate were determined and microarray analyses, as well as qRT-PCR analyses were conducted.

RESULTS

Two hours of exposure to 100 µM t-BOOH resulted in a significant reduction of cell viability, increased apoptotic rate, declined mitochondrial membrane potential (MMP) and increased ROS production. Reduction of cell viability, increased apoptotic rate and declined mitochondrial membrane potential (MMP) could be significantly reduced in cells pretreated with CRE (100 µg/ml) for 2h or 24h ahead of t-BOOH exposure with the greatest effect after 24h of pretreatment; however ROS production was not changed significantly. Furthermore, microarray analyses revealed that the expressions of 2 genes; thioredoxin-interacting protein (TXNIP) and mitochondrially encoded NADH dehydrogenase 1, were significantly regulated. Down regulation of TXNIP was confirmed by qRT-PCR.

CONCLUSION

Due to its neuroprotective properties CRE might be a potential therapeutic agent for the prevention or amelioration of diseases like diabetic neuropathy and neurodegenerative disorders like Alzheimer and Parkinsons disease.

3-Acetyl-bis(2-chloro-4-nitrophenyl)triazene is a potent antitumor agent that induces oxidative stress and independently activates the stress-activated protein kinase/c-Jun NH2-terminal kinase pathway

Previously, we described the synthesis and biological activity of a new class of anticancer molecules that preferentially target malignant cells and may serve as potential antitumor agents. Among several synthesized agents, we selected 3-acetyl-1,3-bis(2-chloro-4-nitrophenyl)-1-triazene (8b) as a representative of the group of 4-nitro-substituted 1,3-diaryltriazenes. The aim of this study was to further investigate the mechanism of cell response to the 8b compound. The HeLa human cervical carcinoma cell line was used as an experimental model to further investigate the mechanism of cell response to the 8b compound. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay was used to address cell survival, and western blot (immunoblotting) was used for the expression of relevant proteins after 8b drug exposure. The pretreatment of HeLa cells with salubrinal, a specific inhibitor of endoplasmic reticulum (ER) stress, confirmed the importance of ER stress in apoptosis induced by 8b. We also demonstrate that 8b triggers the activation of stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) in a time-dependent and dose-dependent manner. Moreover, the inhibition of SAPK/JNK activity by JNK II before 8b treatment increased the survival rate of HeLa cells relative to survival in the presence of 8b alone, indicating the importance of this kinase in cell death. The simultaneous inhibition of ER stress induction and SAPK/JNK activation increased the survival of HeLa cells upon 8b treatment more than inhibition of both pathways independently, suggesting the separate triggering of both signaling pathways. Our data indicate that cytotoxic activity of the novel compound 8b is based on its ability to induce ER stress and SAPK/JNK signaling pathways independently, driving cells to cell death.

Identification of UACA, EXOSC9, and ΤΜX2 in bovine periosteal cells by mass spectrometry and immunohistochemistry

Inspection of patient-derived cells used in transplantation is non-invasive. Therefore, proteomics analysis using supernatants of cells cultured before transplantation is informative. In order to investigate the cell niche of bovine periosteal cells, supernatants of these cultured cells were subjected to 2-D electrophoresis followed by mass spectrometry, which identified type 1 collagen and the C-terminus of type 3 collagen. Only the C-terminal peptide from type 3 collagen was found in supernatants. It is known that type 3 collagen may be expressed intra- or extra-cellularly. Paraffin sections of the cultured cells were next examined by immunohistochemistry, which revealed that type 3 collagen regions besides the C-terminal peptide were present around the bovine periosteal cells but were not found in supernatants. Full-length type 3 collagen was closely associated with the cells, and only the C-terminal peptide was detectable in culture supernatants. Mass spectrometry analysis of partial peptide data combined with immunohistochemistry also indicated that uveal autoantigen with coiled coil domains and ankyrin repeats (UACA), exosome complex component RRP45 (EXOSC9), and thioredoxin-related transmembrane protein 2 (TMX2) were expressed in bovine periosteal cells. Results of this study indicate that analysis of culture supernatants before cell transplantation can provide useful biomarkers indicating the niche of cells used for transplantation.

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.

Redox metabolism in Trypanosoma cruzi: functional characterization of tryparedoxins revisited

Tryparedoxins (TXNs) are multipurpose oxidoreductases from trypanosomatids that transfer reducing equivalents from trypanothione to various thiol proteins. In Trypanosoma cruzi, two genes coding for TXN-like proteins have been identified: TXNI, previously characterized as a cytoplasmic protein, and TXNII, a putative tail-anchored membrane protein. In this work, we performed a comparative functional characterization of T. cruzi TXNs. Particularly, we cloned the gene region coding for the soluble version of TXNII for its heterologous expression. The truncated recombinant protein (without its 22 C-terminal transmembrane amino acids) showed TXN activity. It was also able to transfer reducing equivalents from trypanothione, glutathione, or dihydrolipoamide to various acceptors, including methionine sulfoxide reductases and peroxiredoxins. The results support the occurrence and functionality of a second tryparedoxin, which appears as a new component in the redox scenario for T. cruzi.

Thioredoxin 1 is inactivated due to oxidation induced by peroxiredoxin under oxidative stress and reactivated by the glutaredoxin system

The mammalian cytosolic thioredoxin system, comprising thioredoxin (Trx), Trx reductase, and NADPH, is the major protein-disulfide reductase of the cell and has numerous functions. Besides the active site thiols, human Trx1 contains three non-active site cysteine residues at positions 62, 69, and 73. A two-disulfide form of Trx1, containing an active site disulfide between Cys-32 and Cys-35 and a non-active site disulfide between Cys-62 and Cys-69, is inactive either as a disulfide reductase or as a substrate for Trx reductase. This could possibly provide a structural switch affecting Trx1 function during oxidative stress and redox signaling. We found that two-disulfide Trx1 was generated in A549 cells under oxidative stress. In vitro data showed that two-disulfide Trx1 was generated from oxidation of Trx1 catalyzed by peroxiredoxin 1 in the presence of H2O2. The redox Western blot data indicated that the glutaredoxin system protected Trx1 in HeLa cells from oxidation caused by ebselen, a superfast oxidant for Trx1. Our results also showed that physiological concentrations of glutathione, NADPH, and glutathione reductase reduced the non-active site disulfide in vitro. This reaction was stimulated by glutaredoxin 1 via the so-called monothiol mechanism. In conclusion, reversible oxidation of the non-active site disulfide of Trx1 is suggested to play an important role in redox regulation and cell signaling via temporal inhibition of its protein-disulfide reductase activity for the transmission of oxidative signals under oxidative stress.

Rat retinal transcriptome: effects of aging and AMD-like retinopathy

Pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly, remains poorly understood due to the paucity of animal models that fully replicate the human disease. Recently, we showed that senescence-accelerated OXYS rats develop a retinopathy similar to human AMD. To identify alterations in response to normal aging and progression of AMD-like retinopathy, we compared gene expression profiles of retina from 3- and 18-mo-old OXYS and control Wistar rats by means of high-throughput RNA sequencing (RNA-Seq). We identified 160 and 146 age-regulated genes in Wistar and OXYS retinas, respectively. The majority of them are related to the immune system and extracellular matrix turnover. Only 24 age-regulated genes were common for the two strains, suggestive of different rates and mechanisms of aging. Over 600 genes showed significant differences in expression between the two strains. These genes are involved in disease-associated pathways such as immune response, inflammation, apoptosis, Ca ( 2+) homeostasis and oxidative stress. The altered expression for selected genes was confirmed by qRT-PCR analysis. To our knowledge, this study represents the first analysis of retinal transcriptome from young and old rats with biologic replicates generated by RNA-Seq technology. We can conclude that the development of AMD-like retinopathy in OXYS rats is associated with an imbalance in immune and inflammatory responses. Aging alters the expression profile of numerous genes in the retina, and the genetic background of OXYS rats has a profound impact on the development of AMD-like retinopathy.

Oxygen consumption and usage during physical exercise: the balance between oxidative stress and ROS-dependent adaptive signaling

The complexity of human DNA has been affected by aerobic metabolism, including endurance exercise and oxygen toxicity. Aerobic endurance exercise could play an important role in the evolution of Homo sapiens, and oxygen was not important just for survival, but it was crucial to redox-mediated adaptation. The metabolic challenge during physical exercise results in an elevated generation of reactive oxygen species (ROS) that are important modulators of muscle contraction, antioxidant protection, and oxidative damage repair, which at moderate levels generate physiological responses. Several factors of mitochondrial biogenesis, such as peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitogen-activated protein kinase, and SIRT1, are modulated by exercise-associated changes in the redox milieu. PGC-1α activation could result in decreased oxidative challenge, either by upregulation of antioxidant enzymes and/or by an increased number of mitochondria that allows lower levels of respiratory activity for the same degree of ATP generation. Endogenous thiol antioxidants glutathione and thioredoxin are modulated with high oxygen consumption and ROS generation during physical exercise, controlling cellular function through redox-sensitive signaling and protein-protein interactions. Endurance exercise-related angiogenesis, up to a significant degree, is regulated by ROS-mediated activation of hypoxia-inducible factor 1α. Moreover, the exercise-associated ROS production could be important to DNA methylation and post-translation modifications of histone residues, which create heritable adaptive conditions based on epigenetic features of chromosomes. Accumulating data indicate that exercise with moderate intensity has systemic and complex health-promoting effects, which undoubtedly involve regulation of redox homeostasis and signaling.

Thioredoxin and thioredoxin reductase in relation to reversible S-nitrosylation

SIGNIFICANCE

Nitric oxide (NO) regulates a diverse range of cellular processes, including vasodilation, neurotransmission, and antimicrobial and anti-tumor activities. S-nitrosylation with the formation of S-nitrosothiols (RSNOs) is an important feature of NO signaling regulating protein function. In mammalian cells, glutathione (GSH), S-nitrosoglutathione reductase (GSNOR), and thioredoxin (Trx) have been identified as the major protein denitrosylases.

RECENT ADVANCES

Human cytosolic/nuclear Trx1 in the disulfide form can be nitrosylated at Cys73 and transnitrosylate target proteins, including caspase 3. Thus, similar to GSH, which by forming S-nitrosoglutathione (GSNO) can transnitrosylate proteins, Trx can either denitrosylate or nitrosylate proteins depending on its oxidation state.

CRITICAL ISSUES

In this review, we discuss the regulation of cellular processes by reversible S-nitrosylation and Trx-mediated cellular homeostasis of RSNOs and S-nitrosoproteins.

FUTURE DIRECTIONS

Functions of RSNOs in vivo and their pharmacological uses have not yet been fully studied. Further investigations on the role of Trx systems in relation to biologically relevant RSNOs, their functions, and the mechanisms of denitrosylation will facilitate the development of drugs and therapies. Antioxid. Redox Signal. 18, 259-269.

Thioredoxin system in cell death progression

SIGNIFICANCE

The thioredoxin (Trx) system, comprising nicotinamide adenine dinucleotide phosphate, Trx reductase (TrxR), and Trx, is critical for maintaining cellular redox balance and antioxidant function, including control of oxidative stress and cell death.

RECENT ADVANCES

Here, we focus on the research progress that is involved in the regulation of apoptosis by Trx systems. In mammalian cells, cytosolic Trx1 and mitochondrial Trx2 systems are the major disulfide reductases supplying electrons to enzymes for cell proliferation and viability. The reduced/dithiol form of Trxs binds to apoptosis signal-regulating kinase 1 (ASK1) and inhibits its activity to prevent stress- and cytokine-induced apoptosis. When Trx is oxidized, it dissociates from ASK1 and apoptosis is stimulated. The binding of Trx by its inhibitor Trx interacting protein (TXNIP) also contributes to the apoptosis process by removing Trx from ASK1. TrxRs are large homodimeric selenoproteins with an overall structure which is similar to that of glutathione reductase, and contain an active site GCUG in the C-terminus.

CRITICAL ISSUES AND FUTURE DIRECTIONS

In the regulation of cell death processes, Trx redox state and TrxR activities are key factors that determine the cell fate. The high reactivity of Sec in TrxRs and its accessible location make TrxR enzymes emerge as targets for pharmaceutic drugs. TrxR inactivation by covalent modification does not only change the redox state and activity of Trx, but may also convert TrxR into a reactive oxygen species generator. Numerous electrophilic compounds including some environmental toxins and pharmaceutical drugs inhibit TrxR. We have classified these compounds into four types and propose some useful principles to understand the reaction mechanism of the TrxR inhibition by these compounds.

Mitochondrial function in cardiac hypertrophy

Cardiac hypertrophic program is a chronic, complex process, and occurs in response to long-term increases of hemodynamic load related to a variety of pathophysiological conditions. Mitochondria, known as "the cellular power plants", occupy about one-third of cardiomyocyte volume and supply roughly 90% of the adenosine triphosphate (ATP). Impairment of energy metabolism has been regarded as one of the main pathogenesis of cardiac hypertrophy. Thus, we summarize here the molecular events of mitochondrial adaptations, including the mitochondrial genesis, ATP generation, ROS signaling and Ca(2+) homeostasis in cardiac hypertrophy, expecting that this effort will shed new light on understanding the maladaptive cardiac remodeling.

Roles of thioredoxin binding protein (TXNIP) in oxidative stress, apoptosis and cancer

Thioredoxin binding protein (TXNIP) has multiple functions and plays an important role in redox homeostasis. TXNIP increases the production of reactive oxygen species (ROS), and oxidative stress, resulting in cellular apoptosis. It has been identified as a tumor suppressor gene (TSG) in various solid tumors and hematological malignancies. In the present review, we will first provide an overview of TXNIP protein and function, followed by a summary of the major studies that have demonstrated the frequent repression of TXNIP in cancers. Functional characterization of TXNIP knockout mouse model is summarized. We will then discuss the use of small molecular inhibitors to reactivate TXNIP expression as a novel anticancer strategy.

Evidence for premature aging due to oxidative stress in iPSCs from Cockayne syndrome

Cockayne syndrome (CS) is a human premature aging disorder associated with neurological and developmental abnormalities, caused by mutations mainly in the CS group B gene (ERCC6). At the molecular level, CS is characterized by a deficiency in the transcription-couple DNA repair pathway. To understand the role of this molecular pathway in a pluripotent cell and the impact of CSB mutation during human cellular development, we generated induced pluripotent stem cells (iPSCs) from CSB skin fibroblasts (CSB-iPSC). Here, we showed that the lack of functional CSB does not represent a barrier to genetic reprogramming. However, iPSCs derived from CSB patient's fibroblasts exhibited elevated cell death rate and higher reactive oxygen species (ROS) production. Moreover, these cellular phenotypes were accompanied by an up-regulation of TXNIP and TP53 transcriptional expression. Our findings suggest that CSB modulates cell viability in pluripotent stem cells, regulating the expression of TP53 and TXNIP and ROS production.

Thioredoxin-interacting protein mediates nuclear-to-plasma membrane communication: role in vascular endothelial growth factor 2 signaling

OBJECTIVE

Thioredoxin-interacting protein (TXNIP) and poly-ADP-ribose polymerase 1 (PARP1) are both regulated by changes in cellular reduction-oxidation (redox) state and localize to the nucleus basally in human umbilical vein endothelial cells (HUVEC). Previously we showed a novel mechanism for PARP1 inhibition-mediated HUVEC survival through activation of vascular endothelial growth factor receptor 2 (VEGFR2) signaling in response to stress-induced apoptosis. In addition, we showed TXNIP translocation to the plasma membrane (PM) and activation of VEGFR2 in response to physiological stimuli. Because TXNIP is an α-arrestin that regulates VEGFR2 signaling, we hypothesized that PARP1 regulates TXNIP localization and function that might affect HUVEC stress-induced apoptosis.

METHODS AND RESULTS

HUVEC treated with 10 μmol/L PARP1 inhibitor (PJ34) were protected from TNF (10 ng/mL) or H(2)O(2) (300 μmol/L) mediated cell death. HUVEC transfected with TXNIP siRNA lost the protective effect of PARP1 inhibition, suggesting a protective role for TXNIP. Using immunofluorescence, cell fractionation analysis, and plasma membrane sheet assay, TXNIP was shown to translocate to the plasma membrane after PARP1 inhibition. TXNIP translocation was associated with activation of VEGFR2 signaling. Functionally, TXNIP-PARP1 interaction was decreased on PJ34 treatment, suggesting PARP1 as a novel regulator of TXNIP localization and function.

CONCLUSIONS

These findings demonstrate a novel regulatory mechanism of TXNIP by PARP1 to mediate activation of plasma membrane signaling and cell survival.

Mouse Models of Oxidative Stress Indicate a Role for Modulating Healthy Aging

Aging is a complex process that affects every major system at the molecular, cellular and organ levels. Although the exact cause of aging is unknown, there is significant evidence that oxidative stress plays a major role in the aging process. The basis of the oxidative stress hypothesis is that aging occurs as a result of an imbalance between oxidants and antioxidants, which leads to the accrual of damaged proteins, lipids and DNA macromolecules with age. Age-dependent increases in protein oxidation and aggregates, lipofuscin, and DNA mutations contribute to age-related pathologies. Many transgenic/knockout mouse models over expressing or deficient in key antioxidant enzymes have been generated to examine the effect of oxidative stress on aging and age-related diseases. Based on currently reported lifespan studies using mice with altered antioxidant defense, there is little evidence that oxidative stress plays a role in determining lifespan. However, mice deficient in antioxidant enzymes are often more susceptible to age-related disease while mice overexpressing antioxidant enzymes often have an increase in the amount of time spent without disease, i.e., healthspan. Thus, by understanding the mechanisms that affect healthy aging, we may discover potential therapeutic targets to extend human healthspan.

Expression of TRX and TXNIP in patients with ulcerative colitis

AIM: To detect the expression of thioredoxin (TRX) and thioredoxin-interacting protein (TXNIP) in peripheral blood and colonic mucosa of patients with ulcerative colitis (UC) and to analyze their relationship with UC disease severity.

METHODS: Colonic mucosa and venous blood samples were collected from 29 patients with UC. According to the Sutherland activity index, the patients were divided into two groups: patients with mild to moderate disease (n = 17, group A) and those with severe disease (n = 12, group B). Meanwhile, samples from 25 normal persons were used as controls (group C). The expression of TRX and TXNIP in the colonic mucosa was detected by immunohistochemistry, and serum levels of TRX and TXNIP were determined by ELISA. Statistical analysis was carried out to analyze the correlation between expression of TRX/TXNIP and UC severity.

RESULTS: Serum levels of TRX and TXNIP were lowest in group C, followed by groups A and B. Serum levels of TRX and TXNIP showed no significant differences between groups A and C (both P > 0.05), but differed significantly among the three groups (P < 0.05). The expression of TRX in the colonic mucosa was lowest in group C, followed by groups A and B, while a reverse trend was observed for the expression of TXNIP. Significant differences were found in the expression of TRX and TXNIP between any of the two groups (all P < 0.05). Serum levels of TRX and TXNIP were correlated with the severity of UC activity (r = 0.421, 0.439; both P < 0.01). Expression of TRX and TXNIP in the colonic mucosa was also correlated with the severity of UC activity (r = 0.940, -0.940; both P < 0.01).

CONCLUSION: There is a significant correlation between TRX/TXNIP expression and the severity of UC. TRX and TXNIP may be involved in the pathogenesis of UC via mechanisms associated with oxidative stress.

Discovery of ATL: an odyssey in restrospect

Forty years have passed since our initial description of peculiar cases of adult-onset leukemia with abnormal cells having multi-convoluted nuclei and T cell properties, frequent in the southern regions of Japan in the early 1970s. Retrospectively, the study of adult T cell leukemia (ATL) and the related virus HTLV-I was a forerunner for all of human retrovirology, in which AIDS and the related retrovirus HIV were identified a few years later in the 1980s. Using the anti-TAC monoclonal antibody generated by the late Takashi Uchiyama during his stay in T. A. Waldmann's laboratory in NIH Bethesda, a cDNA encoding IL-2Rα chain was cloned by our group in Kyoto and by Waldmann's group in Bethesda. Abnormal IL-2Rα chain expression and the IL-2 dependency of ATL cell lines greatly contributed to the study of leukemogenesis of ATL. A new soluble factor named ADF/ATL-derived factor was also detected in ATL cell lines. After years of study, ADF proved to be a first human counterpart of thiol-related oxido-reductase thioredoxin/TRX, which opened the field of redox regulation of cell signaling involved in a variety of diseases. Close interaction among Drs. Kimishige Ishizaka, Kiyoshi Takastuki and T. A. Waldmanns before ATL and HTLV-I study was an essential base for our initiation of ATL research with Takashi Uchiyama and many other colleagues.

The role of thioredoxin in the regulation of cellular processes by S-nitrosylation

BACKGROUND

S-nitrosylation (or S-nitrosation) by Nitric Oxide (NO), i.e., the covalent attachment of a NO group to a cysteine thiol and formation of S-nitrosothiols (R-S-N=O or RSNO), has emerged as an important feature of NO biology and pathobiology. Many NO-related biological functions have been directly associated with the S-nitrosothiols and a considerable number of S-nitrosylated proteins have been identified which can positively or negatively regulate various cellular processes including signaling and metabolic pathways.

SCOPE OF THE REVIEW

Taking account of the recent progress in the field of research, this review focuses on the regulation of cellular processes by S-nitrosylation and Trx-mediated cellular homeostasis of S-nitrosothiols.

MAJOR CONCLUSIONS

Thioredoxin (Trx) system in mammalian cells utilizes thiol and selenol groups to maintain a reducing intracellular environment to combat oxidative/nitrosative stress. Reduced glutathione (GSH) and Trx system perform the major role in denitrosylation of S-nitrosylated proteins. However, under certain conditions, oxidized form of mammalian Trx can be S-nitrosylated and then it can trans-S-nitrosylate target proteins, such as caspase 3.

GENERAL SIGNIFICANCE

Investigations on the role of thioredoxin system in relation to biologically relevant RSNOs, their functions, and the mechanisms of S-denitrosylation facilitate the development of drugs and therapies. This article is part of a Special Issue entitled Regulation of Cellular Processes.

The use of thiols by ribonucleotide reductase

Ribonucleotide reductase (RNR) catalyzes the rate-limiting de novo synthesis of 2'-deoxyribonucleotides from the corresponding ribonucleotides and thereby provides balanced deoxyribonucleotide pools required for error-free DNA replication and repair. The essential role of RNR in DNA synthesis and the use of DNA as genetic material has made it an important target for the development of anticancer and antiviral agents. The most well known feature of the universal RNR reaction in all kingdoms of life is the involvement of protein free radicals. Redox-active cysteines, thiyl radicals, and thiol redox proteins of the thioredoxin superfamily play major roles in the catalytic mechanism. The involvement of cysteine residues in catalysis is common to all three classes of RNR. Taking account of the recent progress in this field of research, this review focuses on the use of thiols in the redox mechanism of RNR enzymes.

Disruption of TBP-2 ameliorates insulin sensitivity and secretion without affecting obesity

Type 2 diabetes mellitus (T2DM) is characterized by defects in both insulin sensitivity and glucose-stimulated insulin secretion (GSIS) and is often accompanied by obesity. In this study, we show that disruption of thioredoxin binding protein-2 (TBP-2, also called Txnip) in obese mice (ob/ob) dramatically improves hyperglycaemia and glucose intolerance, without affecting obesity or adipocytokine concentrations. TBP-2-deficient ob/ob mice exhibited enhanced insulin sensitivity with activated insulin receptor substrate-1/Akt signalling in skeletal muscle and GSIS in islets compared with ob/ob mice. The elevation of uncoupling protein-2 (UCP-2) expression in ob/ob islets was downregulated by TBP-2 deficiency. TBP-2 overexpression suppressed glucose-induced adenosine triphosphate production, Ca²⁺ influx and GSIS. In β-cells, TBP-2 enhanced the expression level and transcriptional activity of UCP-2 by recruitment of peroxisome proliferator-activated receptor-γ co-activator-1α to the UCP-2 promoter. Thus, TBP-2 is a key regulatory molecule of both insulin sensitivity and GSIS in diabetes, raising the possibility that inhibition of TBP-2 may be a novel therapeutic approach for T2DM.

Thioredoxin binding protein-2 (TBP-2) mutant mice have abnormal insulin sensitivity and secretion. In this study, TBP-2-null obese mice are shown to have improved insulin sensitivity and glucose intolerance, suggesting a potential role for TBP-2 inhibition in diabetes treatment.