A novel mouse model for the identification of thioredoxin-1 protein interactions

Thioredoxin-1 protein interactions in neuronal survival and neurodegeneration

Neuronal cell death remains the principal pathophysiologic hallmark of neurodegenerative diseases and the main challenge for treatment strategies. Thioredoxin1 (Trx1) is a major cytoplasmic thiol oxidoreductase protein involved in redox signaling, hence a crucial player in maintaining neuronal health. Trx1 levels are notably reduced in neurodegenerative diseases including Alzheimer's and Parkinson's diseases, however, the impact of this decrease on neuronal physiology remains largely unexplored. This is mainly due to the nature of Trx1 redox regulatory role which is afforded by a rapid electron transfer to its oxidized protein substrates. During this reaction, Trx1 forms a transient bond with the oxidized disulfide bond in the substrate. This is a highly fast reaction which makes the identification of Trx1 substrates a technically challenging task. In this project, we utilized a transgenic mouse model expressing a Flag-tagged mutant form of Trx1 that can form stable disulfide bonds with its substrates, hence allowing identification of the Trx1 target proteins. Autophagy is a vital housekeeping process in neurons that is critical for degradation of damaged proteins under oxidative stress conditions and is interrupted in neurodegenerative diseases. Given Trx1's suggested involvement in autophagy, we aimed to identify potential Trx1 substrates following pharmacologic induction of autophagy in primary cortical neurons. Treatment with rapamycin, an autophagy inducer, significantly reduced neurite outgrowth and caused cytoskeletal alterations. Using immunoprecipitation and mass spectrometry, we have identified 77 Trx1 target proteins associated with a wide range of cellular functions including cytoskeletal organization and neurodegenerative diseases. Focusing on neuronal cytoskeleton organization, we identified a novel interaction between Trx1 and RhoB which was confirmed in genetic models of Trx1 downregulation in primary neuronal cultures and HT22 mouse immortalized hippocampal neurons. The applicability of these findings was also tested against the publicly available proteomic data from Alzheimer's patients. Our study uncovers a novel role for Trx1 in regulating neuronal cytoskeleton organization and provides a mechanistic explanation for its multifaceted role in the physiology and pathology of the nervous system, offering new insights into the molecular mechanisms underlying neurodegeneration.

Transcriptomic analysis: the protection of over-expression thioredoxin reductase 1 in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease. The pathologic characteristic feature is the loss of dopaminergic neurons in the substantia nigra (SN). However, the biochemical mechanisms are unclear. A large number of studies have shown that oxidative damage is the primary cause of PD. Hence, antioxidants could become a suitable option to treat PD. The thioredoxin (Trx) system represents a useful, potentially disease-relevant oxidation-reduction system. Thioredoxin reductase 1 (TR1) is a significant component of the Trx system.

METHODS

The overexpression lentivirus (LV) or LV-TR1 in the TR1-A53T model of PD by the stereotactic brain, and successful overexpression of LV or LV-TR1 in the MPP⁺-induced cellular model by LV or LV-TR1 transfection.

RESULTS

We confirmed that interleukin-7 mRNA levels increased in MPP⁺ compared to that in the control and MPP⁺-TR1 groups using quantitative polymerase chain reaction. The γ-H₂AX level was increased in the Tg-A53T group compared to that in the TR1-A53T group by western blotting. The expression of Na⁺-K⁺-ATP was decreased in the MPP⁺ group compared to that in the control and MPP⁺-TR1 groups by high content screening. Tg-A53T(the C57BL/6 mice transferred with mutant human a-syn); TR1-A53T(A53T mice which were injected TR1-LV 2 µl in SNc on two sides with minipump).The mice were fed for 10 months. control (the N2a cells cultivated with DMEM); MPP⁺(the N2a cells dealt with MPP⁺(1 mM) 48 h), MPP⁺-LV (the N2a cells over-expressed LV for 24 h then dealt with MPP⁺(1 mM) 48 h). MPP⁺-TR1(the N2a cell over-expressed TR1-LV for 24 h then dealt with MPP⁺(1 mM) 48 h). From the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, we confirmed that the overexpression of TR1 in SN pars compacta cells decreased oxidative stress, apoptosis, DNA damage, and inflammatory response and increased NADPH, Na⁺-K⁺-ATP, and immune response in this PD model.

CONCLUSIONS

Our study shows that overexpressed TR1 can be developed as a neuroprotective agent for PD. Therefore, our findings demonstrate a new targeted protein for the treatment of PD.

Thioredoxin Signaling Pathways in Cancer

Significance: Thioredoxin (Trx) is a powerful antioxidant that reduces protein disulfides to maintain redox stability in cells and is involved in regulating multiple redox-dependent signaling pathways. Recent Advance: The current accumulation of findings suggests that Trx participates in signaling pathways that interact with various proteins to manipulate their dynamic regulation of structure and function. These network pathways are critical for cancer pathogenesis and therapy. Promising clinical advances have been presented by most anticancer agents targeting such signaling pathways. Critical Issues: We herein link the signaling pathways regulated by the Trx system to potential cancer therapeutic opportunities, focusing on the coordination and strengths of the Trx signaling pathways in apoptosis, ferroptosis, immunomodulation, and drug resistance. We also provide a mechanistic network for the exploitation of therapeutic small molecules targeting the Trx signaling pathways. Future Directions: As research data accumulate, future complex networks of Trx-related signaling pathways will gain in detail. In-depth exploration and establishment of these signaling pathways, including Trx upstream and downstream regulatory proteins, will be critical to advancing novel cancer therapeutics. Antioxid. Redox Signal. 38, 403-424.

Tat-thioredoxin 1 reduces inflammation by inhibiting pro-inflammatory cytokines and modulating MAPK signaling

Thioredoxin 1 (Trx1) serves a central role in redox homeostasis. It is involved in numerous other processes, including oxidative stress and apoptosis. However, to the best of our knowledge, the role of Trx1 in inflammation remains to be explored. The present study investigated the function and mechanism of cell permeable fused Tat-Trx1 protein in macrophages and a mouse model. Transduction levels of Tat-Trx1 were determined via western blotting. Cellular distribution of transduced Tat-Trx1 was determined by fluorescence microscopy. 2',7'-Dichlorofluorescein diacetate and TUNEL staining were performed to determine the production of reactive oxygen species and DNA fragmentation. Protein and gene expression were measured by western blotting and reverse transcription-quantitative PCR (RT-qPCR), respectively. Effects of skin inflammation were determined using hematoxylin and eosin staining, changes in ear weight and ear thickness, and RT-qPCR in ear edema animal models. Transduced Tat-Trx1 inhibited lipopolysaccharide-induced cytotoxicity and activation of NF-κB, MAPK and Akt. Additionally, Tat-Trx1 markedly reduced the production of inducible nitric oxide synthase, cyclooxygenase-2, IL-1β, IL-6 and TNF-α in macrophages. In a 12-O-tetradecanoylphorbol-13-acetate-induced mouse model, Tat-Trx1 reduced inflammatory damage by inhibiting inflammatory mediator and cytokine production. Collectively, these results demonstrated that Tat-Trx1 could exert anti-inflammatory effects by inhibiting the production of pro-inflammatory mediators and cytokines and by modulating MAPK signaling. Therefore, Tat-Trx1 may be a useful therapeutic agent for diseases induced by inflammatory damage.

Protective Role of Transduced Tat-Thioredoxin1 (Trx1) against Oxidative Stress-Induced Neuronal Cell Death via ASK1-MAPK Signal Pathway

Oxidative stress plays a crucial role in the development of neuronal disorders including brain ischemic injury. Thioredoxin 1 (Trx1), a 12 kDa oxidoreductase, has anti-oxidant and anti-apoptotic functions in various cells. It has been highly implicated in brain ischemic injury. However, the protective mechanism of Trx1 against hippocampal neuronal cell death is not identified yet. Using a cell permeable Tat-Trx1 protein, protective mechanism of Trx1 against hydrogen peroxide-induced cell death was examined using HT-22 cells and an ischemic animal model. Transduced Tat-Trx1 markedly inhibited intracellular ROS levels, DNA fragmentation, and cell death in H₂O₂-treatment HT-22 cells. Tat-Trx1 also significantly inhibited phosphorylation of ASK1 and MAPKs in signaling pathways of HT-22 cells. In addition, Tat-Trx1 regulated expression levels of Akt, NF-κB, and apoptosis related proteins. In an ischemia animal model, Tat-Trx1 markedly protected hippocampal neuronal cell death and reduced astrocytes and microglia activation. These findings indicate that transduced Tat-Trx1 might be a potential therapeutic agent for treating ischemic injury.

Overexpression of thioredoxin reductase 1 can reduce DNA damage, mitochondrial autophagy and endoplasmic reticulum stress in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra (SN). Several factors, including neuroinflammation, neuronal excitotoxicity, genetic mutations and incorrect protein folding are involved in PD pathophysiology. However, the precise mechanism that contributes to the decreased number of dopaminergic neurons is unknown. A growing body of research suggests that oxidative stress is a major factor in PD. Therefore, antioxidant therapy is an important approach for treating PD. The thioredoxin system is an important antioxidant system, and thioredoxin reductase 1 (TR1) is a major member of the thioredoxin system. The present study demonstrates that oxidative stress is increased and that the expression of TR1 is decreased in the SNc of A53T mice; TR1 has emerged as an important antioxidant agent in dopaminergic neurons. Therefore, we over-expressed TR1 in the MPP⁺-induced cellular model and in the A53T transgenic mouse model of PD. We confirmed that the overexpression of TR1 in neuronal cells decreased DNA damage and malondialdehyde (MDA) and ROS generation, increased T-SOD and GSH production, and decreased the ER stress, and autophagy in the PD model. In summary, our findings demonstrate that the overexpression of TR1 could be effective as a novel neuroprotective strategy for PD. This research suggests a novel direction in the treatment of PD.

Integrase-Mediated Targeted Transgenics Through Pronuclear Microinjection

Transgenic technology allows a gene of interest to be introduced into the genome of a laboratory animal and provides an extremely powerful tool to dissect the molecular mechanisms of disease. Transgenic mouse models made by microinjection of DNA into zygotic pronuclei, in particular, have been widely used by the genetics community for over 35 years. However, up till 5 years ago, it remained a rather crude approach: injected sequences randomly insert in multiple copies as concatemers, and they can be mutagenic and have variable, ectopic, or silenced expression depending on the site of integration, a phenomenon called position effects. As a result, multiple lines are required in order to confirm appropriate transgene expression. This can be partially overcome by flanking transgenes with insulator sequences to protect the transgene from influence of surrounding regulatory elements. Large (<300 kb) BAC-based transgenic vectors have also been shown to be more resistant to position effects. However, animals carrying extra copies of fairly large regions of the genome could have unpredictable phenotypes.These problems can be overcome by targeting the transgene to a specific chromosomal locus via homologous recombination in embryonic stem (ES) cells. However, this method is significantly more laborious and time consuming, as it involves creation of modified ES cells and mouse chimeras, as well as eventual germline transmission of the transgene.Here, I describe an integrase-based approach, trademarked as "TARGATT™" (target attP), to produce site-specific transgenic mice via pronuclear microinjection, whereby an intact single-copy transgene can be inserted into predetermined chromosomal loci with high efficiency (up to 40%), and faithfully transmitted through generations. This system allows high-level global transgene expression or tissue-specific expression depending on the promoter used, or inducible expression such as induced by tetracycline or doxycycline. Using this approach, site-specific transgenic mice can be generated as fast as in 3 months. The technique presented here greatly facilitates murine transgenesis and precise structure/function dissection of mammalian gene function and regulation in vivo.

Dysregulation of CRMP2 Post-Translational Modifications Drive Its Pathological Functions

Collapsin response mediator proteins (CRMPs) are a family of ubiquitously expressed, homologous phosphoproteins best known for coordinating cytoskeletal formation and regulating cellular division, migration, polarity, and synaptic connection. CRMP2, the most studied of the five family members, is best known for its affinity for tubulin heterodimers and function in regulating the microtubule network. These functions are tightly regulated by post-translational modifications including phosphorylation, SUMOylation, oxidation, and O-GlcNAcylation. While CRMP2's physiological functions rely mostly on its non-phosphorylated state, dysregulation of CRMP2 phosphorylation and SUMOylation has been reported to be involved in the pathophysiology of multiple diseases including cancer, chronic pain, spinal cord injury, neurofibromatosis type 1, and others. Here, we provide a consolidated update on what is known about CRMP2 signaling and function, first focusing on axonal growth and neuronal polarity, then illustrating the link between dysregulated CRMP2 post-translational modifications and diseases. We additionally discuss the roles of CRMP2 in non-neuronal cells, both in the CNS and regions of the periphery. Finally, we offer thoughts on the therapeutic implications of modulating CRMP2 function in a variety of diseases.

Implications of the mitochondrial interactome of mammalian thioredoxin 2 for normal cellular function and disease

Multiple thioredoxin isoforms exist in all living cells. To explore the possible functions of mammalian mitochondrial thioredoxin 2 (Trx2), an interactome of mouse Trx2 was initially created using (i) a monothiol mouse Trx2 species for capturing protein partners from different organs and (ii) yeast two hybrid screens on human liver and rat brain cDNA libraries. The resulting interactome consisted of 195 proteins (Trx2 included) plus the mitochondrial 16S RNA. 48 of these proteins were classified as mitochondrial (MitoCarta2.0 human inventory). In a second step, the mouse interactome was combined with the current four-membered mitochondrial sub-network of human Trx2 (BioGRID) to give a 53-membered human Trx2 mitochondrial interactome (52 interactor proteins plus the mitochondrial 16S RNA). Although thioredoxins are thiol-employing disulfide oxidoreductases, approximately half of the detected interactions were not due to covalent disulfide bonds. This finding reinstates the extended role of thioredoxins as moderators of protein function by specific non-covalent, protein-protein interactions. Analysis of the mitochondrial interactome suggested that human Trx2 was involved potentially in mitochondrial integrity, formation of iron sulfur clusters, detoxification of aldehydes, mitoribosome assembly and protein synthesis, protein folding, ADP ribosylation, amino acid and lipid metabolism, glycolysis, the TCA cycle and the electron transport chain. The oxidoreductase functions of Trx2 were verified by its detected interactions with mitochondrial peroxiredoxins and methionine sulfoxide reductase. Parkinson's disease, triosephosphate isomerase deficiency, combined oxidative phosphorylation deficiency, and lactate dehydrogenase b deficiency are some of the diseases where the proposed mitochondrial network of Trx2 may be implicated.

Thioredoxin system as a gatekeeper in caspase-6 activation and nuclear lamina integrity: Implications for Alzheimer's disease

Recent reports in pathophysiology of neurodegenerative diseases (ND) have linked nuclear lamina degradation/deficits to neuronal cell death. Lamin-B1 damage is specifically involved in this process leading to nuclear envelope invagination and heterochromatin rearrangement. The underlying mechanisms involved in these events are not yet defined. In this study, while examining the effect of Thioredoxin-1(Trx1) inhibition on cell death in a model of oxidative stress, we noted robust nuclear invagination in SH-SY5Y cells. Evaluation of nuclear lamina proteins revealed lamin-B1 cleavage that was prevented by caspase-6 (CASP6) inhibitor and exacerbated after pharmacologic/genetic inhibition of Trx1 system, but not after glutathione depletion. Activation of CASP6 was upstream of CASP3/7 activation and its inhibition was sufficient to prevent cell death in our system. The effect of Trx1 redox status on CASP6 activation was assessed by administration of reduced/oxidized forms in cell-free nuclei preparation and purified enzymatic assays. Although reduced Trx1 decreased CASP6 enzymatic activity and lamin-B1 cleavage, the fully oxidized Trx1 showed opposite effects. The enhanced CASP6 activation was also associated with lower levels of DJ-1, a neuroprotective and master regulator of cellular antioxidants. The implication of our findings in ND pathophysiology was strengthened with detection of lower Trx1 levels in the hippocampi tissue of a mouse model of Alzheimer's disease. This coincided with higher CASP6 activation resulting in increased lamin-B1 and DJ-1 depletion. This study provides a first mechanistic explanation for the key regulatory role of Trx1 as a gatekeeper in activation of CASP6 and induction of nuclear invagination, an important player in ND pathophysiology.

Up-regulation of antioxidative proteins TRX1, TXNL1 and TXNRD1 in the cortex of PTZ kindling seizure model mice

Oxidative stress has been considered as one of pathogenesis of brain damage led by epilepsy. Reducing oxidative stress can ameliorate brain damage during seizures. However, expression levels of important antioxidative enzymes such as thioredoxin-1 (TRX1), thioredoxin-like 1 protein (TXNL1) and thioredoxin reductase 1 (TXNRD1) during seizures have not been investigated. In this study, we examined protein and mRNA expression levels of TRX1, TXNL1 and TXNRD1 in different brain regions in PTZ induced seizure model mice. We found that protein expression levels of TRX1, TXNL1 and TXNRD1 are simultaneously up-regulated by 2- or 3-fold in the cortex of both acute and chronic seizure model mice. But there is no unified expression pattern change of these enzymes in the hippocampus, cerebellum and diencephalon in the seizure model mice. Less extent up-regulation of mRNA expression of these enzymes were also observed in the cortex of seizure mice. These data suggest that antioxidative enzymes may provide a protective effect against oxidative stress in the cortex during seizures.

Using TARGATT™ Technology to Generate Site-Specific Transgenic Mice

The discovery of new gene editing tools in the past several years has moved the transgenic field to a new level. The traditional random transgenesis method by pronuclear microinjection has been largely replaced by targeted or site-specific transgenic technologies without the need of homologous recombination in embryonic stem (ES) cells. In this chapter, I describe detailed protocols of an integrase-based approach, trademarked as "TARGATT™" (target attP), to produce site-specific transgenic mice via pronuclear microinjection, whereby an intact single-copy transgene can be inserted into a predetermined chromosomal locus with high efficiency (up to 40%), and faithfully transmitted through generations. This system allows high-level global transgene expression or tissue-specific expression depending on the promoter used, or inducible expression such as induced by tetracycline or doxycycline. Using this approach, site-specific transgenic mice can be generated as fast as in 3 months. The technique presented here greatly facilitates murine transgenesis and precise structure/function dissection of mammalian gene function and regulation in vivo.

Modulation of signaling mechanisms in the heart by thioredoxin 1

Myocardial ischemia/reperfusion and heart failure are the major cardiac conditions in which an imbalance between oxidative stress and anti-oxidant mechanisms is observed. The myocardium has endogenous reducing mechanisms, including the thioredoxin (Trx) and glutathione systems, that act to scavenge reactive oxygen species (ROS) and reduce oxidized proteins. The Trx system consists of Trx, Trx reductase (TrxR), and an electron donor, NADPH, where Trx is maintained in a reduced state in the presence of TrxR and NADPH. Trx1, a major isoform of Trx, is abundantly expressed in the heart and exerts its oxidoreductase activity through conserved Cys32 and Cys35, reducing oxidized proteins through thiol disulfide exchange reactions. In this review, we will focus on molecular targets of Trx1 in the heart, including transcription factors, microRNAs, histone deactylases, and protein kinases. We will then discuss how Trx1 regulates the functions of its targets, thereby affecting the extent of myocardial injury caused by myocardial ischemia/reperfusion and the progression of heart failure.

Overexpression of Thioredoxin1 enhances functional recovery in a mouse model of hind limb ischemia

BACKGROUND

There is keen interest in finding nonsurgical treatments for peripheral vascular disease (PVD). Previously, we demonstrated that selective activation of Thioredoxin1 (Trx1), a 12-kDa cytosolic protein, initiates redox-dependent signaling and promotes neovascularization after ischemic heart disease. Therefore, Trx1 might possess immense potential to not only treat murine hind limb ischemia (HLI) through effective angiogenesis but also provide PVD patients with nonsurgical therapy to enhance neovascularization and improve blood perfusion.

METHODS

To determine whether activation of Trx1 increases blood perfusion in HLI, two different strategies were used-gene therapy and transgenic model system. In adenoviral-mediated gene therapy, 8- to 12-wk-old mice were divided into two groups: (1) control Adeno-LacZ (Ad-LacZ) and (2) Adeno-Thiroedoxin1 (Ad-Trx1). The mice underwent surgical intervention to induce right HLI followed by injection with Ad-LacZ or Ad-Trx1, respectively. In the second strategy, we used wild-type and transgenic mice overexpressing Trx1 (Trx1^Tg/+). All the animals underwent Doppler imaging for the assessment of limb perfusion followed by immunohistochemistry and Western blot analysis.

RESULTS

Significant increases in perfusion ratio were observed in all the Trx1 overexpressed groups compared with their corresponding controls. Expressions of heme oxygenase-1, vascular endothelial growth factor, and the vascular endothelial growth factor receptors Flk-1 and Flt-1 were increased in Trx1 overexpressed mice compared with their respective controls. Blood perfusion in the ischemic limb gradually improved and significantly recovered in Trx1^Tg/+ and Ad-Trx1 groups compared with their corresponding controls. The capillary and arteriolar density in the ischemic zone were found to be higher in Trx1^Tg/+ group compared with wild type.

CONCLUSIONS

The overall outcomes of our study demonstrate that Trx1 enhances blood perfusion and increases angiogenic protein expression in a rodent HLI model. These results suggest that Trx1 is a potential target for clinical trials and drug therapy for the treatment of PVD.