Overexpression of thioredoxin in transgenic mice attenuates focal ischemic brain damage

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.

Zebrafish as a Model Organism for Congenital Hydrocephalus: Characteristics and Insights

Hydrocephalus is a cerebrospinal fluid-related disease that usually manifests as abnormal dilation of the ventricles, with a triad of clinical findings including walking difficulty, reduced attention span, and urinary frequency or incontinence. The onset of congenital hydrocephalus is closely related to mutations in genes that regulate brain development. Currently, our understanding of the mechanisms of congenital hydrocephalus remains limited, and the prognosis of existing treatments is unsatisfactory. Additionally, there are no suitable or dedicated model organisms for congenital hydrocephalus. Therefore, it is significant to determine the mechanism and develop special animal models of congenital hydrocephalus. Recently, zebrafish have emerged as a popular model organism in many fields, including developmental biology, genetics, and toxicology. Its genome shares high similarity with that of humans, and it has fast and low-cost reproduction. These advantages make it suitable for studying the pathogenesis and therapeutic approaches for various diseases, specifically congenital diseases. This study explored the possibility of using zebrafish as a model organism for congenital hydrocephalus. This review describes the characteristics of zebrafish and discusses specific congenital hydrocephalus models. The advantages and limitations of using zebrafish for hydrocephalus research are highlighted, and insights for further model development are provided.

Role of NLRP3 Inflammasome in Stroke Pathobiology: Current Therapeutic Avenues and Future Perspective

Neuroinflammation is a key pathophysiological feature of stroke-associated brain injury. A local innate immune response triggers neuroinflammation following a stroke via activating inflammasomes. The nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome has been heavily implicated in stroke pathobiology. Following a stroke, several stimuli have been suggested to trigger the assembly of the NLRP3 inflammasome. Recent studies have advanced the understanding and revealed several new players regulating NLRP3 inflammasome-mediated neuroinflammation. This article discussed recent advancements in NLRP3 assembly and highlighted stroke-induced mitochondrial dysfunction as a major checkpoint to regulating NLRP3 activation. The NLRP3 inflammasome activation leads to caspase-1-dependent maturation and release of IL-1β, IL-18, and gasdermin D. In addition, genetic or pharmacological inhibition of the NLRP3 inflammasome activation and downstream signaling has been shown to attenuate brain infarction and improve the neurological outcome in experimental models of stroke. Several drug-like small molecules targeting the NLRP3 inflammasome are in different phases of development as novel therapeutics for various inflammatory conditions, including stroke. Understanding how these molecules interfere with NLRP3 inflammasome assembly is paramount for their better optimization and/or development of newer NLRP3 inhibitors. In this review, we summarized the assembly of the NLRP3 inflammasome and discussed the recent advances in understanding the upstream regulators of NLRP3 inflammasome-mediated neuroinflammation following stroke. Additionally, we critically examined the role of the NLRP3 inflammasome-mediated signaling in stroke pathophysiology and the development of therapeutic modalities to target the NLRP3 inflammasome-related signaling for stroke treatment.

Expression of thioredoxin-1 in the ASJ neuron corresponds with and enhances intrinsic regenerative capacity under lesion conditioning in C. elegans

A conditioning lesion of the peripheral sensory axon triggers robust central axon regeneration in mammals. We trigger conditioned regeneration in the Caenorhabditis elegans ASJ neuron by laser surgery or genetic disruption of sensory pathways. Conditioning upregulates thioredoxin-1 (trx-1) expression, as indicated by trx-1 promoter-driven expression of green fluorescent protein and fluorescence in situ hybridization (FISH), suggesting trx-1 levels and associated fluorescence indicate regenerative capacity. The redox activity of trx-1 functionally enhances conditioned regeneration, but both redox-dependent and -independent activity inhibit non-conditioned regeneration. Six strains isolated in a forward genetic screen for reduced fluorescence, which suggests diminished regenerative potential, also show reduced axon outgrowth. We demonstrate an association between trx-1 expression and the conditioned state that we leverage to rapidly assess regenerative capacity.

Retinoic Acid Has Neuroprotective effects by Modulating Thioredoxin in Ischemic Brain Damage and Glutamate-exposed Neurons

Ischemic stroke is a neurological disorder that causes pathological changes by increasing oxidative stress. Retinoic acid is one of the metabolites of vitamin A. It regulates oxidative stress and exerts neuroprotective effects. Thioredoxin is a small redox protein with antioxidant activity. The aim of this study was to investigate whether retinoic acid modulates the expression of thioredoxin in ischemic brain injury. Cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) surgery and retinoic acid (5 mg/kg) or vehicle was administered to adult male rats for four days prior to surgery. MCAO induced neurological deficits and increased oxidative stress and retinoic acid attenuated these changes. Retinoic acid ameliorated the MCAO-induced decrease in thioredoxin expression. MCAO decreases the interaction between thioredoxin and apoptosis signal-regulating kinase 1 (ASK1), and retinoic acid treatment alleviates this decrease. Glutamate (5 mM) exposure induced cell death and decreased thioredoxin expression in cultured neurons. Retinoic acid treatment attenuated these changes in a dose-dependent manner. Retinoic acid prevented the decrease of bcl-2 expression and the increase of bax expression caused by glutamate exposure. Moreover, retinoic acid attenuated the increases in caspase-3, cleaved caspase-3, and cytochrome c in glutamate-exposed neurons. However, the mitigation effects of retinoic acid were lower in thioredoxin siRNA-transfected neurons than in non-transfected neurons. These results demonstrate that retinoic acid regulates oxidative stress and thioredoxin expression, maintains the interaction between thioredoxin and ASK1, and modulates apoptosis-associated proteins. Taken together, these results suggest that retinoic acid has neuroprotective effects by regulating thioredoxin expression and modulating apoptotic pathway.

The effect of thioredoxin-1 in a rat model of traumatic brain injury depending on diurnal variation

INTRODUCTION

Traumatic brain injury (TBI) is a public health concern with limited treatment options because it causes a cascade of side effects that are the leading cause of hospital death. Thioredoxin is an enzyme with neuroprotective properties such as antioxidant, antiapoptotic, immune response modulator, and neurogenic, among others; it has been considered a therapeutic target for treating many disorders.

METHODS

The controlled cortical impact (CCI) model was used to assess the effect of recombinant human thioredoxin 1 (rhTrx1) (1 μg/2 μL, intracortical) on rats subjected to TBI at two different times of the light-dark cycle (01:00 and 13:00 h). We analyzed the food intake, body weight loss, motor coordination, pain perception, and histology in specific hippocampus (CA1, CA2, CA3, and Dental Gyrus) and striatum (caudate-putamen) areas.

RESULTS

Body weight loss, reduced food intake, spontaneous pain, motor impairment, and neuronal damage in specific hippocampus and striatum regions are more evident in rats subjected to TBI in the light phase than in the dark phase of the cycle and in groups that did not receive rhTrx1 or minocycline (as positive control). Three days after TBI, there is a recovery in body weight, food intake, motor impairment, and pain, which is more pronounced in the rats subjected to TBI at the dark phase of the cycle and those that received rhTrx1 or minocycline.

CONCLUSIONS

Knowing the time of day a TBI occurs in connection to the neuroprotective mechanisms of the immune response in diurnal variation and the usage of the Trx1 protein might have a beneficial therapeutic impact in promoting quick recovery after a TBI.

Evolutionarily Conserved Role of Thioredoxin Systems in Determining Longevity

Thioredoxin and thioredoxin reductase are evolutionarily conserved antioxidant enzymes that protect organisms from oxidative stress. These proteins also play roles in redox signaling and can act as a redox-independent cellular chaperone. In most organisms, there is a cytoplasmic and mitochondrial thioredoxin system. A number of studies have examined the role of thioredoxin and thioredoxin reductase in determining longevity. Disruption of either thioredoxin or thioredoxin reductase is sufficient to shorten lifespan in model organisms including yeast, worms, flies and mice, thereby indicating conservation across species. Similarly, increasing the expression of thioredoxin or thioredoxin reductase can extend longevity in multiple model organisms. In humans, there is an association between a specific genetic variant of thioredoxin reductase and lifespan. Overall, the cytoplasmic and mitochondrial thioredoxin systems are both important for longevity.

Advances in the Functions of Thioredoxin System in Central Nervous System Diseases

Significance: The thioredoxin system comprises thioredoxin (Trx), thioredoxin reductase (TrxR), and nicotinamide adenine dinucleotide phosphate, besides an endogenous Trx inhibitor, the thioredoxin-interacting protein (TXNIP). The Trx system plays critical roles in maintaining the redox homeostasis in the central nervous system (CNS), in which oxidative stress damage is prone to occurrence due to its high-energy demand. Recent Advances: Increasing studies have demonstrated that the expression or activity of Trx/TrxR is usually decreased and that TXNIP expression is increased in patients with CNS diseases, including neurodegenerative diseases, cerebral ischemia, traumatic brain injury, and depression, as well as in their cellular and animal models. The compromise of Trx/TrxR enhances the susceptibility of neurons to related pathological state. Increased TXNIP not only enhances the inhibition of Trx activity, but also activates the NOD-like receptor protein 3 inflammasome, resulting in neuroinflammation in the brain. Critical Issues: In this review, we highlight the sources of oxidative stress in the CNS. The expression and function of the Trx system are summarized in different CNS diseases. This review also mentions that some inducers of Trx show neuroprotection in CNS diseases. Future Directions: Accumulating evidence has demonstrated the important roles of the Trx system in CNS diseases, suggesting that the Trx system may be a promising therapeutic target for CNS diseases. Further study should aim to develop the most effective inducers of Trx and specific inhibitors of TXNIP and to apply them in the clinical trials for the treatment of CNS diseases. Antioxid. Redox Signal. 38, 425-441.

The Role of the Thioredoxin System in Brain Diseases

The thioredoxin system, consisting of thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH, plays a fundamental role in the control of antioxidant defenses, cell proliferation, redox states, and apoptosis. Aberrations in the Trx system may lead to increased oxidative stress toxicity and neurodegenerative processes. This study reviews the role of the Trx system in the pathophysiology and treatment of Alzheimer's, Parkinson's and Huntington's diseases, brain stroke, and multiple sclerosis. Trx system plays an important role in the pathophysiology of those disorders via multiple interactions through oxidative stress, apoptotic, neuro-immune, and pro-survival pathways. Multiple aberrations in Trx and TrxR systems related to other redox systems and their multiple reciprocal relationships with the neurodegenerative, neuro-inflammatory, and neuro-oxidative pathways are here analyzed. Genetic and environmental factors (nutrition, metals, and toxins) may impact the function of the Trx system, thereby contributing to neuropsychiatric disease. Aberrations in the Trx and TrxR systems could be a promising drug target to prevent and treat neurodegenerative, neuro-inflammatory, neuro-oxidative stress processes, and related brain disorders.

Relationship between Oxidative Stress and Endometritis: Exploiting Knowledge Gained in Mares and Cows

The etiopathogenesis of endometritis in mares and cows differs significantly; this could depend on a different sensitivity and reactivity of the uterus but also on endocrine and rearing factors and different stress sources. In both species, microorganisms and the immune system play a primary role in the generation of this pathology. Microbiological and cytological tests support clinical examination and significantly improve diagnostic accuracy. For both species, during the inflammation, immune cells invade the endometrium and release bioactive substances to contrast primary or secondary pathogen contamination. These molecules are traceable to cytokines, chemokines, and prostaglandins as well as reactive oxygen and nitrogen species (ROS and RNS), collectively known as RONS. The RONS-mediated oxidation causes morphological and functional alterations of macromolecules, such as proteins, lipids, and nucleic acids, with the consequent production of derivative compounds capable of playing harmful effects. These bioactive molecules and by-products, which have recently become increasingly popular as diagnostic biomarkers, enter the bloodstream, influencing the functionality of organs and tissues. This review has collected and compared information obtained in cows and mares related to the diagnostic potential of these biomarkers that are assessed by using different methods in samples from either blood plasma or uterine fluid.

Emerging Evidence of the Significance of Thioredoxin-1 in Hematopoietic Stem Cell Aging

The United States is undergoing a demographic shift towards an older population with profound economic, social, and healthcare implications. The number of Americans aged 65 and older will reach 80 million by 2040. The shift will be even more dramatic in the extremes of age, with a projected 400% increase in the population over 85 years old in the next two decades. Understanding the molecular and cellular mechanisms of ageing is crucial to reduce ageing-associated disease and to improve the quality of life for the elderly. In this review, we summarized the changes associated with the ageing of hematopoietic stem cells (HSCs) and what is known about some of the key underlying cellular and molecular pathways. We focus here on the effects of reactive oxygen species and the thioredoxin redox homeostasis system on ageing biology in HSCs and the HSC microenvironment. We present additional data from our lab demonstrating the key role of thioredoxin-1 in regulating HSC ageing.

The Functions of Thioredoxin 1 in Neurodegeneration

Significance: Thioredoxin 1 (Trx1) is a ubiquitous protein that is found in organisms ranging from prokaryotes to eukaryotes. Trx1 acts as reductases in redox regulation and protects proteins from oxidative aggregation and inactivation. Trx1 helps the cells to cope with various environmental stresses and inhibits programmed cell death. It is beneficial to neuroregeneration and resistance against oxidative stress-associated neuron damage. Trx1 also plays important roles in suppressing neurodegenerative disorders. Recent Advances: Trx1 is a redox regulating protein involved in neuronal protection. According to a previous study, Trx1 expression is increased by nerve growth factor (NGF) and necessary for neurite outgrowth of PC12 cells. Trx1 has been shown to promote the growth of neurons. Trx1 knockout or knockdown has the worse impact on cell viability and survival. Critical Issues: Trx1 has functions in central nervous system. Trx1 plays the defensive roles against oxidative stress in neurodegenerative diseases. Future Directions: In this review, we focus on the structure of Trx1 and basic functions of Trx1. Trx1 plays a neuroprotective role by suppressing endoplasmic reticulum stress in Parkinson's disease. Neurodegenerative diseases have no cure and carry a high cost to the health care system and patient's families. Trx1 may be taken as a new target for neurodegenerative disorder therapy. Further studies of the Trx1 roles and mechanisms on neurodegenerative diseases are needed. Antioxid. Redox Signal. 36, 1023-1036.

Thioredoxin-1 Ameliorates Oxygen-Induced Retinopathy in Newborn Mice Through Modulation of Proinflammatory and Angiogenic Factors

Oxygen-induced retinopathy (OIR) is an animal model for retinopathy of prematurity, which is a leading cause of blindness in children. Thioredoxin-1 (TRX) is a small redox protein that has cytoprotective and anti-inflammatory properties in response to oxidative stress. The purpose of this study was to determine the effect of TRX on OIR in newborn mice. From postnatal day 7, C57BL/6 wild type (WT) and TRX transgenic (TRX-Tg) mice were exposed to either 21% or 75% oxygen for 5 days. Avascular and neovascular regions of the retinas were investigated using fluorescence immunostaining. Fluorescein isothiocyanate-dextran and Hoechst staining were used to measure retinal vascular leakage. mRNA expression levels of proinflammatory and angiogenic factors were analyzed using quantitative polymerase chain reaction. Retinal histological changes were detected using immunohistochemistry. In room air, the WT mice developed well-organized retinas. In contrast, exposing WT newborn mice to hyperoxia hampered retinal development, increasing the retinal avascular and neovascular areas. After hyperoxia exposure, TRX-Tg mice had enhanced retinal avascularization compared with WT mice. TRX-Tg mice had lower retinal neovascularization and retinal permeability during recovery from hyperoxia compared with WT mice. In the early stages after hyperoxia exposure, VEGF-A and CXCL-2 expression levels decreased, while IL-6 expression levels increased in WT newborn mice. Conversely, no differences in gene expressions were observed in the TRX-Tg mouse retina. IGF-1 and Angpt1 levels did not decrease during recovery from hyperoxia in TRX-Tg newborn mice. As a result, overexpression of TRX improves OIR in newborn mice by modulating proinflammatory and angiogenic factors.

Stroke Proteomics: From Discovery to Diagnostic and Therapeutic Applications

Stroke remains a leading cause of death and disability, with limited therapeutic options and suboptimal tools for diagnosis and prognosis. High throughput technologies such as proteomics generate large volumes of experimental data at once, thus providing an advanced opportunity to improve the status quo by facilitating identification of novel therapeutic targets and molecular biomarkers. Proteomics studies in animals are largely designed to decipher molecular pathways and targets altered in brain tissue after stroke, whereas studies in human patients primarily focus on biomarker discovery in biofluids and, more recently, in thrombi and extracellular vesicles. Here, we offer a comprehensive review of stroke proteomics studies conducted in both animal and human specimen and present our view on limitations, challenges, and future perspectives in the field. In addition, as a unique resource for the scientific community, we provide extensive lists of all proteins identified in proteomic studies as altered by stroke and perform postanalysis of animal data to reveal stroke-related cellular processes and pathways.

Thioredoxin interacting protein, a key molecular switch between oxidative stress and sterile inflammation in cellular response

Tissue and systemic inflammation have been the main culprit behind the cellular response to multiple insults and maintaining homeostasis. Obesity is an independent disease state that has been reported as a common risk factor for multiple metabolic and microvascular diseases including nonalcoholic fatty liver disease (NAFLD), retinopathy, critical limb ischemia, and impaired angiogenesis. Sterile inflammation driven by high-fat diet, increased formation of reactive oxygen species, alteration of intracellular calcium level and associated release of inflammatory mediators, are the main common underlying forces in the pathophysiology of NAFLD, ischemic retinopathy, stroke, and aging brain. This work aims to examine the contribution of the pro-oxidative and pro-inflammatory thioredoxin interacting protein (TXNIP) to the expression and activation of NLRP3-inflammasome resulting in initiation or exacerbation of sterile inflammation in these disease states. Finally, the potential for TXNIP as a therapeutic target and whether TXNIP expression can be modulated using natural antioxidants or repurposing other drugs will be discussed.

Thioredoxin - a magic bullet or a double-edged sword for mammalian aging?

After the discovery of thioredoxin as a reductant for many important enzymes in the early 1960s, biological roles of thioredoxin in pathophysiology have been examined using various species and experimental models, e.g., yeast, invertebrates, rodents, and humans. A large number of studies demonstrated that thioredoxin plays an essential role to maintain a reduced cellular environment and possesses many beneficial effects by maintaining cellular/organ functions and against diseases. However, an important question that remains to be answered is whether thioredoxin could attenuate aging by reducing oxidative damage and changing cellular redox state, which alters redox-sensitive signaling pathways. To address this important question, we have been conducting aging studies with transgenic and knockout mice, and transgenic rats to examine whether the upregulation or downregulation of thioredoxin alters lifespan and age-related pathology. Aging studies conducted by our laboratory and others revealed that the roles of thioredoxin on pathophysiology seem to be more complex than our initial expectations as a potential magic bullet to solve the issues with age. Recent studies indicate that thioredoxin could have both beneficial and potentially deleterious effects on aging and age-related diseases. To critically evaluate the biological effects of thioredoxin on aging and age-related diseases, studies require further consideration to assess additional factors, e.g. levels of thioredoxin in different cellular compartments, different effects in each cell/tissue/organ, physiological aging vs. pathology, and/or at different life stages.

Redox-dependent and independent effects of thioredoxin interacting protein

Thioredoxin interacting protein (TXNIP) is an important physiological inhibitor of the thioredoxin (TXN) redox system in cells. Regulation of TXNIP expression and/or activity not only plays an important role in redox regulation but also exerts redox-independent physiological effects that exhibit direct pathophysiological consequences including elevated inflammatory response, aberrant glucose metabolism, cellular senescence and apoptosis, cellular immunity, and tumorigenesis. This review provides a brief overview of the current knowledge concerning the redox-dependent and independent roles of TXNIP and its relevance to various disease states. The implications for the therapeutic targeting of TXNIP will also be discussed.

Natural Molecules Targeting Thioredoxin System and Their Therapeutic Potential

Significance: Thioredoxin (Trx) and thioredoxin reductase are two core members of the Trx system. The system bridges the gap between the universal reducing equivalent NADPH and various biological molecules and plays an essential role in maintaining cellular redox homeostasis and regulating multiple cellular redox signaling pathways. Recent Advance: In recent years, the Trx system has been well documented as an important regulator of many diseases, especially tumorigenesis. Thus, the development of potential therapeutic molecules targeting the system is of great significance for disease treatment. Critical Issues: We herein first discuss the physiological functions of the Trx system and the role that the Trx system plays in various diseases. Then, we focus on the introduction of natural small molecules with potential therapeutic applications, especially the anticancer activity, and review their mechanisms of pharmacological actions via interfering with the Trx system. Finally, we further discuss several natural molecules that harbor therapeutic potential and have entered different clinical trials. Future Directions: Further studies on the functions of the Trx system in multiple diseases will not only improve our understanding of the pathogenesis of many human disorders but also help develop novel therapeutic strategies against these diseases. Antioxid. Redox Signal. 34, 1083-1107.

Thioredoxin-Interacting Protein (TXNIP) with Focus on Brain and Neurodegenerative Diseases

The development of new therapeutic approaches to diseases relies on the identification of key molecular targets involved in amplifying disease processes. One such molecule is thioredoxin-interacting protein (TXNIP), also designated thioredoxin-binding protein-2 (TBP-2), a member of the α-arrestin family of proteins and a central regulator of glucose and lipid metabolism, involved in diabetes-associated vascular endothelial dysfunction and inflammation. TXNIP sequesters reduced thioredoxin (TRX), inhibiting its function, resulting in increased oxidative stress. Many different cellular stress factors regulate TXNIP expression, including high glucose, endoplasmic reticulum stress, free radicals, hypoxia, nitric oxide, insulin, and adenosine-containing molecules. TXNIP is also directly involved in inflammatory activation through its interaction with the nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) inflammasome complex. Neurodegenerative diseases such as Alzheimer’s disease have significant pathologies associated with increased oxidative stress, inflammation, and vascular dysfunctions. In addition, as dysfunctions in glucose and cellular metabolism have been associated with such brain diseases, a role for TXNIP in neurodegeneration has actively been investigated. In this review, we will focus on the current state of the understanding of possible normal and pathological functions of TXNIP in the central nervous system from studies of in vitro neural cells and the brains of humans and experimental animals with reference to other studies. As TXNIP can be expressed by neurons, microglia, astrocytes, and endothelial cells, a complex pattern of regulation and function in the brain is suggested. We will examine data suggesting TXNIP as a therapeutic target for neurodegenerative diseases where further research is needed.

Inhibition of microglial receptor-interacting protein kinase 1 ameliorates neuroinflammation following cerebral ischaemic stroke

Microglia are rapidly activated following ischaemic stroke and participate in the induction of neuroinflammation, which exacerbates the injury of ischaemic stroke. However, the mechanisms regulating ischaemic microglia remain unclear. In the present study, middle cerebral artery occlusion and oxygen and glucose deprivation models were established for in vivo and vitro monitoring of experimental stroke. We applied recombinant human thioredoxin‐1 (rhTrx‐1) and Necrostatin‐1 (Nec‐1, inhibitor of RIPK1) to examine the role of receptor‐interacting protein kinase 1 (RIPK1) in the development of inflammation in ischaemic microglia via explored the inflammatory responses and the associated mechanisms. Molecular docking results indicated that rhTrx‐1 could directly bind to RIPK1. In vivo and vitro data revealed that rhTrx‐1 reduced necroptosis, mitochondrial membrane potential damage, reactive oxygen species accumulation and NLR Family, pyrin domain‐containing 3 protein (NLRP3) inflammasome activation and regulated the microglial M1/M2 phenotypic changes by inhibiting RIPK1 expression in ischaemic microglia. Consistent with these findings, further in vivo experiments revealed that rhTrx‐1 treatment attenuated cerebral ischaemic injury by inhibiting the inflammatory response. Our data demonstrated the role of RIPK1 in microglia‐induced neuroinflammation following cerebral ischaemia. Administration of rhTrx‐1 provides neuroprotection in ischaemic stroke‐induced microglial neuroinflammation by inhibiting RIPK1 expression.

Neuroprotective Effect of Antioxidants in the Brain

The brain is vulnerable to excessive oxidative insults because of its abundant lipid content, high energy requirements, and weak antioxidant capacity. Reactive oxygen species (ROS) increase susceptibility to neuronal damage and functional deficits, via oxidative changes in the brain in neurodegenerative diseases. Overabundance and abnormal levels of ROS and/or overload of metals are regulated by cellular defense mechanisms, intracellular signaling, and physiological functions of antioxidants in the brain. Single and/or complex antioxidant compounds targeting oxidative stress, redox metals, and neuronal cell death have been evaluated in multiple preclinical and clinical trials as a complementary therapeutic strategy for combating oxidative stress associated with neurodegenerative diseases. Herein, we present a general analysis and overview of various antioxidants and suggest potential courses of antioxidant treatments for the neuroprotection of the brain from oxidative injury. This review focuses on enzymatic and non-enzymatic antioxidant mechanisms in the brain and examines the relative advantages and methodological concerns when assessing antioxidant compounds for the treatment of neurodegenerative disorders.

Analytical and clinical validation of rapid chemiluminescence enzyme immunoassay for urinary thioredoxin, an oxidative stress-dependent early biomarker of acute kidney injury

BACKGROUND

Oxidative stress is now recognized to be an important therapeutic target in kidney diseases. However, there are currently no biomarkers that can be used clinically to diagnose renal oxidative stress.

METHODS

A rapid assay system for urinary thioredoxin 1, an oxidative stress-dependent biomarker of acute kidney injury (AKI), was developed as a chemiluminescence enzyme immunoassay and validated analytically and clinically.

RESULTS

Analytic evaluation revealed that hemolytic hemoglobin caused measurements to be abnormally high, above the detectable range. However, urine sediment containing red blood cells did not affect the measurements. Assays using our proposed chemiluminescence enzyme immunoassay were completed within as little as 6 min, whereas a conventional ELISA > 4 h. Aciduria <pH 6.0 led to a significant underestimation of thioredoxin 1 concentrations. However, the effects of aciduria were completely reversible with use of a buffer developed for pH adjustment. Urinary thioredoxin 1 was increased in patients with AKI, but was unaffected by extrarenal oxidative stress diseases, including hypoxemia and myocardial infarction, or by chronic kidney disease in which serum creatinine concentrations were comparable.

CONCLUSIONS

These results suggest that the chemiluminescent enzyme immunoassay system for urinary thioredoxin 1 enables rapid and specific diagnosis of AKI associated with oxidative stress.

Thioredoxin overexpression in mitochondria showed minimum effects on aging and age-related diseases in male C57BL/6 mice

Objective:

In this study, the effects of overexpression of thioredoxin 2 (Trx2) on aging and age-related diseases were examined using Trx2 transgenic mice [Tg(TXN2]^+/0]. Because our previous studies demonstrated that thioredoxin (Trx) overexpression in the cytosol (Trx1) did not extend maximum lifespan, this study was conducted to test if increased Trx2 expression in mitochondria shows beneficial effects on aging and age-related pathology.

Methods:

Trx2 transgenic mice were generated using a fragment of the human genome containing the TXN2 gene. Effects of Trx2 overexpression on survival, age-related pathology, oxidative stress, and redox-sensitive signaling pathways were examined in male Tg(TXN2)^+/0 mice.

Results:

Trx2 levels were significantly higher (approximately 1.6- to 5-fold) in all of the tissues we examined in Tg(TXN2)^+/0 mice compared to wild-type (WT) littermates, and the expression levels were maintained during aging (up to 22-24 months old). Trx2 overexpression did not alter the levels of Trx1, glutaredoxin, glutathione, or other major antioxidant enzymes. Overexpression of Trx2 was associated with reduced reactive oxygen species (ROS) production from mitochondria and lower isoprostane levels compared to WT mice. When we conducted the survival study, male Tg(TXN2)^+/0 mice showed a slight extension (approximately 8-9%] of mean, median, and 10th percentile lifespans; however, the survival curve was not significantly different from WT mice. Cross-sectional pathological analysis (22-24 months old) showed that Tg(TXN2)^+/0 mice had a slightly higher severity of lymphoma; however, tumor burden, disease burden, and severity of glomerulonephritis and inflammation were similar to WT mice. Trx2 overexpression was also associated with higher c-Jun and c-Fos levels; however, mTOR activity and levels of NFκB p65 and p50 were similar to WT littermates.

Conclusions:

Our findings suggest that the increased levels of Trx2 in mitochondria over the lifespan in Tg(TXN2)^+/0 mice showed a slight life-extending effect, reduced ROS production from mitochondria and oxidative damage to lipids, but showed no significant effects on aging and age-related diseases.

Attenuation of Hyperoxic Lung Injury in Newborn Thioredoxin-1-Overexpressing Mice through the Suppression of Proinflammatory Cytokine mRNA Expression

The role of thioredoxin-1 (TRX), a small redox-active protein with antioxidant effects, during hyperoxic lung injury in newborns remains undetermined. We investigated TRX impact on hyperoxic lung injury in newborn TRX transgenic (TRX-Tg) and wildtype (WT) mice exposed to 21% or 95% O₂ for four days, after which some mice were allowed to recover in room air for up to 14 days. Lung morphology was assessed by hematoxylin/eosin and elastin staining, as well as immunostaining for macrophages. The gene expression levels of proinflammatory cytokines were evaluated using quantitative real-time polymerase chain reaction. During recovery from hyperoxia, TRX-Tg mice exhibited an improved mean linear intercept length and increased number of secondary septa in lungs compared with the WT mice. Neonatal hyperoxia enhanced the mRNA expression levels of proinflammatory cytokines in the lungs of both TRX-Tg and WT mice. However, interleukin-6, monocyte chemoattractant protein-1, and chemokine (C-X-C motif) ligand 2 mRNA expression levels were reduced in the lungs of TRX-Tg mice compared with the WT mice during recovery from hyperoxia. Furthermore, TRX-Tg mice exhibited reduced macrophage infiltration in lungs during recovery. These results suggest that in newborn mice TRX ameliorates hyperoxic lung injury during recovery likely through the suppression of proinflammatory cytokines.

Thioredoxin and aging: What have we learned from the survival studies?

Our laboratory has conducted the first systematic survival studies to examine the biological effects of the antioxidant protein thioredoxin (Trx) on aging and age-related pathology. Our studies with C57BL/6 mice overexpressing Trx1 [Tg(act-TRX1)^+/0 and Tg(TXN)^+/0) demonstrated a slight extension in early lifespan compared to wild-type (WT) mice; however, no significant effects were observed in the later part of life. Overexpression of Trx2 in male C57BL/6 mice [Tg(TXN2)^+/0] demonstrated a slightly extended lifespan compared to WT mice. The pathology results from two lines of Trx1 transgenic mice showed a slightly higher incidence of age-related neoplastic diseases compared to WT mice, and a slight increase in the severity of lymphoma, a major neoplastic disease, was observed in Trx2 transgenic mice. Together these studies indicate that Trx overexpression in one compartment of the cell (cytosol or mitochondria alone) has marginal beneficial effects on lifespan. On the other hand, down-regulation of Trx in either the cytosol (Trx1KO) or mitochondria (Trx2KO) showed no significant changes in lifespan compared to WT mice, despite several changes in pathophysiology of these knockout mice. When we examined the synergetic effects of overexpressing Trx1 and Trx2, TXNTg x TXN2Tg mice showed a significantly shorter lifespan with accelerated cancer development compared to WT mice. These results suggest that synergetic effects of Trx overexpression in both the cytosol and mitochondria on aging are deleterious and the development of age-related cancer is accelerated. On the other hand, we have recently found that down-regulation of Trx in both the cytosol and mitochondria in Trx1KO x Trx2KO mice has beneficial effects on aging. The results generated from our lab along with our ongoing study using Trx1KO x Trx2KO mice could elucidate the key pathways (i.e., apoptosis and autophagy) that prevent accumulation of damaged cells and genomic instability leading to reduced cancer formation.

Blood biomarkers for stroke: the role of thioredoxin in diagnosis and prognosis of acute ischemic stroke

Background

Oxidative stress plays a crucial role in the pathophysiology of acute ischemic stroke. Thioredoxin exists and released from cells during inflammation and oxidative stress and was recognized as an oxidative-stress marker.

Objective

The objective of this study was to assess the role of thioredoxin as an oxidative stress biomarker in diagnosis and prognosis of acute ischemic stroke in a sample of patients recruited from Beni-Suef Governorate, north Upper Egypt.

Methods

A case control study included 100 subjects; 50 patients with first-ever acute ischemic stroke presented within 24 h from the onset and 50 healthy volunteers as a control. Clinical, functional, and radiological evaluation was done for the patients, and all patients and control were subjected to routine laboratory tests and assessment of serum level of thioredoxin by solid-phase sandwich enzyme-linked immunosorbent assay.

Results

Thioredoxin was significantly higher in acute stroke patients compared to control group (p value = 0.001). Thioredoxin level was significantly higher in hypertensive patients (p value = 0.007), patients who had carotid stenosis ≥50% (p value = 0.001), patients with poor outcome (p value = 0.009), and in patients with cardio-embolic stroke (p value = 0.001).

Significant positive correlation was found between thioredoxin level and volume of infarction (r = 0.501 and p = 0.001), stroke severity at presentation (r = 0.503 and p = 0.021) and clinical outcome after 3 months (r = 0.551 and p value = 0.001).

Conclusion

Thioredoxin as a marker of oxidative stress can be used as a new diagnostic and prognostic blood biomarker for stroke.

Silencing of TXNIP Alleviated Oxidative Stress Injury by Regulating MAPK-Nrf2 Axis in Ischemic Stroke

Ischemic stroke is a life-threatening cerebrovascular thrombotic disease, oxidative stress is considered to be a critical factor to stroke pathophysiology. This study aimed to investigate the underlying molecular mechanism and propose the potential therapeutic strategy for ischemic stroke. Bioinformatics analysis based on a public microarray profile (GSE 61616) of ischemic stroke rats was performed as a pilot research. Oxidative stress was enriched as a significantly gene ontology item, and thioredoxin-interacting protein (TXNIP) and MAPK signaling were identified as the hub gene and pathway, respectively. The experiments in middle cerebral artery occlusion rats demonstrated that ischemia induced the activation of oxidative stress. The expressions of TXNIP, p-p38, p-JNK, p-ERK were significantly increased while Nrf2 and HO-1 expressions were decreased after stroke. Rescue assays were conducted in primary cultured neurons to explore the accurate interrelations among these factors. The results indicated that MAPK specific inhibitor and siRNA-TXNIP significantly alleviated the oxidative stress injury induced by oxygen-glucose deprivation. In addition, knocking down of TXNIP inhibited the activation of MAPK pathway and promoted Nrf2 pathway. Taken together, these findings indicated that TXNIP aggravated the oxidative stress injury by regulating MAPK-Nrf2 axis in ischemic stroke. Silencing of TXNIP seems a promising therapeutic strategy to alleviate ischemic stroke.

Identification of proteins differentially expressed by glutamate treatment in cerebral cortex of neonatal rats

Glutamate leads to neuronal cell damage by generating neurotoxicity during brain development. The objective of this study is to identify proteins that differently expressed by glutamate treatment in neonatal cerebral cortex. Sprague-Dawley rat pups (post-natal day 7) were intraperitoneally injected with vehicle or glutamate (10 mg/kg). Brain tissues were isolated 4 h after drug treatment and fixed for morphological study. Moreover, cerebral cortices were collected for protein study. Two-dimensional gel electrophoresis and mass spectrometry were carried out to identify specific proteins. We observed severe histopathological changes in glutamate-exposed cerebral cortex. We identified various proteins that differentially expressed by glutamate exposure. Identified proteins were thioredoxin, peroxiredoxin 5, ubiquitin carboxy-terminal hydrolase L1, proteasome subunit alpha proteins, isocitrate dehydrogenase, and heat shock protein 60. Heat shock protein 60 was increased in glutamate exposed condition. However, other proteins were decreased in glutamate-treated animals. These proteins are related to anti-oxidant, protein degradation, metabolism, signal transduction, and anti-apoptotic function. Thus, our findings can suggest that glutamate leads to neonatal cerebral cortex damage by regulation of specific proteins that mediated with various functions.

Genomic insights into the non-histamine production and proteolytic and lipolytic activities of Tetragenococcus halophilus KUD23

Tetragenococcus halophilus KUD23, a non-histamine producer, was isolated from a traditional Korean high-salt fermented soybean paste, doenjang. The strain was safe in terms of antibiotic susceptibility, hemolytic activity and biofilm formation. It could grow on De Man-Rogosa-Sharpe agar containing 21% (w/v) NaCl, exhibited acid production at 15% NaCl, and had strain-specific proteolytic and lipolytic activities under salt stress. Complete genome analysis of T. halophilus KUD23 and comparative genomic analysis shed light on the genetic background behind these phenotypic characteristics, including non-production of histamine and proteolytic and lipolytic activities.

Increased Thioredoxin-1 Expression Promotes Cancer Progression and Predicts Poor Prognosis in Patients with Gastric Cancer

BACKGROUND

Thioredoxin-1 (Trx-1) is a small redox protein, which plays an important role in many biological processes. Although increased expression of Trx-1 in various solid tumors has been reported, the prognostic significance and function of Trx-1 in human gastric cancer (GC) are still unclear. Here, we investigated the clinical and prognostic significance of Trx-1 expression and the function and mechanism of Trx-1 in human GC.

METHODS

We analyzed Trx-1 mRNA expression from the GEO database and Trx-1 protein expression in 144 GC tissues using immunohistochemistry. Effects of Trx-1 on GC cell were assessed in vitro and in vivo through Trx-1 knockdown or overexpression. The antitumor effects of the Trx-1 inhibitor, PX-12, on GC cells were investigated. PTEN and p-AKT expressions were evaluated by Western blotting.

RESULTS

Increased Trx-1 expression was found in GC tissues and associated with poor prognosis and aggressive clinicopathological characteristics in patients with GC. High Trx-1 expression predicted poor prognosis, and its expression was an independent prognostic factor for overall survival of GC patients. Knockdown of Trx-1 expression inhibited GC cell growth, migration, and invasion in vitro and tumor growth and lung metastasis in vivo. Conversely, overexpression of Trx-1 promoted GC cell growth, migration, and invasion. We also found that PX-12 inhibited GC cell growth, migration, and invasion. Overexpression of Trx-1 caused a decrease in PTEN and increase in p-AKT levels whereas silencing Trx-1 caused an increase in PTEN and decrease in p-AKT levels in GC cells. Inhibition of AKT signaling pathway by MK2206 also inhibited GC cell growth, migration, and invasion.

CONCLUSION

Our results indicate that Trx-1 may be a promising prognostic indicator and therapeutic target for GC patients.

Continuous overexpression of thioredoxin 1 enhances cancer development and does not extend maximum lifespan in male C57BL/6 mice

We examined the effects of continuous overexpression of thioredoxin (Trx) 1 on aging in Trx1 transgenic mice [Tg(TXN)^+/0]. This study was conducted to test whether increased thioredoxin expression over the lifespan in mice would alter aging and age-related pathology because our previous study demonstrated that Tg(act-TXN)^+/0 mice had no significant maximum life extension, possibly due to the use of actin as a promoter, which may have resulted in loss of Trx1 overexpression during aging. To test this hypothesis, we generated new Trx1 transgenic mice using a fragment of the human genome containing the TXN gene with an endogenous promoter to ensure continuous overexpression of Trx1 throughout the lifespan. Universal overexpression of Trx1 was observed, and Trx1 overexpression was maintained during aging (up to 22–24 months old) in the Tg(TXN)^+/0 mice. The levels of Trx1 are significantly higher (approximately 4 to 31 fold) in all of the tissues examined in the Tg(TXN)^+/0 mice compared to the wild-type (WT) littermates. The overexpression of Trx1 did not cause any changes in the levels of Trx2, glutaredoxin, glutathione, or other major antioxidant enzymes. The survival study demonstrated that male Tg(TXN)^+/0 mice slightly extended the earlier part of the lifespan compared to WT littermates, but no significant life extension was observed over the lifespan. The cross-sectional pathological analysis (22–25 months old) showed that Tg(TXN)^+/0 mice had a significantly higher severity of lymphoma and more tumor burden than WT mice, which was associated with the suppression of the apoptosis signal-regulating kinase 1 (ASK1) pathway. Our findings suggest that the increased levels of Trx1 over the lifespan in Tg(TXN)^+/0 mice showed some beneficial effects (slight extension of lifespan) in the earlier part of life but had no significant effects on median or maximum lifespans, and increased Trx1 levels enhanced tumor development in old mice.

Thioredoxin overexpression in both the cytosol and mitochondria accelerates age-related disease and shortens lifespan in male C57BL/6 mice

To investigate the role of increased levels of thioredoxin (Trx) in both the cytosol (Trx1) and mitochondria (Trx2) on aging, we have conducted a study to examine survival and age-related diseases using male mice overexpressing Trx1 and Trx2 (TXNTg × TXN2Tg). Our study demonstrated that the upregulation of Trx in both the cytosol and mitochondria in male TXNTg × TXN2Tg C57BL/6 mice resulted in a significantly shorter lifespan compared to wild-type (WT) mice. Cross-sectional pathology data showed a slightly higher incidence of neoplastic diseases in TXNTg × TXN2Tg mice than WT mice. The incidence of lymphoma, a major neoplastic disease in C57BL/6 mice, was slightly higher in TXNTg × TXN2Tg mice than in WT mice, and more importantly, the severity of lymphoma was significantly higher in TXNTg × TXN2Tg mice compared to WT mice. Furthermore, the total number of histopathological changes in the whole body (disease burden) was significantly higher in TXNTg × TXN2Tg mice compared to WT mice. Therefore, our study suggests that overexpression of Trx in both the cytosol and mitochondria resulted in deleterious effects on aging and accelerated the development of age-related diseases, especially cancer, in male C57BL/6 mice.

Thioredoxin-1 downregulation in the nucleus accumbens promotes methamphetamine-primed reinstatement in mice

Relapse of drug abuse after abstinence is a major challenge to the treatment of addicts. Thioredoxin-1 (Trx-1) is an important regulator of neuroprotection, and inhibits morphine-induced hyperlocomotion, reward and withdrawal signs, as well as blocks methamphetamine (METH)-induced conditioned place preference (CPP). The nucleus accumbens (NAc) is essential for relapse like behavior in reinstatement animal models. In the present study, we aimed to investigate the role of Trx-1 in the NAc in METH-primed reinstatement by using a reinstatement procedure in mice. Adeno-associated virus vectors expressing shRNA-mTrx-1 (AAV-shRNA-mTrx-1) were bilaterally microinjected into the NAc after METH-CPP extinction. The results showed that Trx-1 downregulation in the NAc promoted the reinstatement of METH-CPP. We also examined the expression of N-methyl-D-asparate (NMDA) receptor 2B subunit (GluN2b), the levels of phosphorylated extracellular signal-regulated kinase (p-ERK) and phosphorylated cAMP-response element binding protein (p-CREB) in the NAc by western blot analysis, and found that the GluN2b expression, p-ERK and p-CREB levels were increased in the NAc in response to low-dose METH in AAV-shRNA-mTrx-1 mice, but were not changed in control and AAV-vehicle mice. These data indicate that the increased GluN2b expression, and p-ERK and p-CREB levels in the NAc of AAV-shRNA-mTrx-1 mice may be responsible for the METH-primed reinstatement. Thus, we suggest that downregulation of Trx-1 in the NAc may make mice more sensitive to METH reinstatement.

Thioredoxin-Interacting Protein (TXNIP) in Cerebrovascular and Neurodegenerative Diseases: Regulation and Implication

Neurological diseases, including acute attacks (e.g., ischemic stroke) and chronic neurodegenerative diseases (e.g., Alzheimer's disease), have always been one of the leading cause of morbidity and mortality worldwide. These debilitating diseases represent an enormous disease burden, not only in terms of health suffering but also in economic costs. Although the clinical presentations differ for these diseases, a growing body of evidence suggests that oxidative stress and inflammatory responses in brain tissue significantly contribute to their pathology. However, therapies attempting to prevent oxidative damage or inhibiting inflammation have shown little success. Identification and targeting endogenous "upstream" mediators that normalize such processes will lead to improve therapeutic strategy of these diseases. Thioredoxin-interacting protein (TXNIP) is an endogenous inhibitor of the thioredoxin (TRX) system, a major cellular thiol-reducing and antioxidant system. TXNIP regulating redox/glucose-induced stress and inflammation, now is known to get upregulated in stroke and other brain diseases, and represents a promising therapeutic target. In particular, there is growing evidence that glucose strongly induces TXNIP in multiple cell types, suggesting possible physiological roles of TXNIP in glucose metabolism. Recently, a significant body of literature has supported an essential role of TXNIP in the activation of the NOD-like receptor protein (NLRP3)-inflammasome, a well-established multi-molecular protein complex and a pivotal mediator of sterile inflammation. Accordingly, TXNIP has been postulated to reside centrally in detecting cellular damage and mediating inflammatory responses to tissue injury. The majority of recent studies have shown that pharmacological inhibition or genetic deletion of TXNIP is neuroprotective and able to reduce detrimental aspects of pathology following cerebrovascular and neurodegenerative diseases. Conspicuously, the mainstream of the emerging evidences is highlighting TXNIP link to damaging signals in endothelial cells. Thereby, here, we keep the trend to present the accumulative data on CNS diseases dealing with vascular integrity. This review aims to summarize evidence supporting the significant contribution of regulatory mechanisms of TXNIP with the development of brain diseases, explore pharmacological strategies of targeting TXNIP, and outline obstacles to be considered for efficient clinical translation.

Neuronal Damage Induced by Perinatal Asphyxia Is Attenuated by Postinjury Glutaredoxin-2 Administration

The general disruption of redox signaling following an ischemia-reperfusion episode has been proposed as a crucial component in neuronal death and consequently brain damage. Thioredoxin (Trx) family proteins control redox reactions and ensure protein regulation via specific, oxidative posttranslational modifications as part of cellular signaling processes. Trx proteins function in the manifestation, progression, and recovery following hypoxic/ischemic damage. Here, we analyzed the neuroprotective effects of postinjury, exogenous administration of Grx2 and Trx1 in a neonatal hypoxia/ischemia model. P7 Sprague-Dawley rats were subjected to right common carotid ligation or sham surgery, followed by an exposure to nitrogen. 1 h later, animals were injected i.p. with saline solution, 10 mg/kg recombinant Grx2 or Trx1, and euthanized 72 h postinjury. Results showed that Grx2 administration, and to some extent Trx1, attenuated part of the neuronal damage associated with a perinatal hypoxic/ischemic damage, such as glutamate excitotoxicity, axonal integrity, and astrogliosis. Moreover, these treatments also prevented some of the consequences of the induced neural injury, such as the delay of neurobehavioral development. To our knowledge, this is the first study demonstrating neuroprotective effects of recombinant Trx proteins on the outcome of neonatal hypoxia/ischemia, implying clinical potential as neuroprotective agents that might counteract neonatal hypoxia/ischemia injury.

Molecular imaging of nestin in neuroinflammatory conditions reveals marked signal induction in activated microglia

Background

Nestin is a known marker of neuronal progenitor cells in the adult brain. Following neuro- and gliogenesis, nestin is replaced by cell type-specific intermediate filaments, e.g., neurofilaments for panneuronal expression and glial fibrillary acidic protein as a specific marker of mature astrocytes. While previous work have been mostly focused on the neuronal fate of nestin-positive progenitors, in the present study, we sought to investigate in real time how nestin signals and cellular expression patterns are controlled in the context of neuroinflammatory challenge and ischemic brain injury.

Methods

To visualize effects of neuroinflammation on neurogenesis/gliogenesis, we created a transgenic model bearing the dual reporter system luciferase and GFP under transcriptional control of the murine nestin promoter. In this model, transcriptional activation of nestin was visualized from the brains of living animals using biophotonic/bioluminescence molecular imaging and a high resolution charged coupled device camera. Nestin induction profiles in vivo and in tissue sections were analyzed in two different experimental paradigms: middle cerebral artery occlusion and lipopolysaccharide-induced innate immune stimuli.

Results

We report here a context- and injury-dependent induction and cellular expression profile of nestin. While in the baseline conditions the nestin signal and/or GFP expression was restricted to neuronal progenitors, the cellular expression patterns of nestin following innate immune challenge and after stroke markedly differed shifting the cellular expression patterns towards activated microglia/macrophages and astrocytes.

Conclusions

Our results suggest that nestin may serve as a context-dependent biomarker of inflammatory response in glial cells including activated microglia/macrophages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0816-7) contains supplementary material, which is available to authorized users.

Chemical Speciation of Selenium and Mercury as Determinant of Their Neurotoxicity

The antagonism of mercury toxicity by selenium has been well documented. Mercury is a toxic metal, widespread in the environment. The main target organs (kidneys, lungs, or brain) of mercury vary depending on its chemical forms (inorganic or organic). Selenium is a semimetal essential to mammalian life as part of the amino acid selenocysteine, which is required to the synthesis of the selenoproteins. This chapter has the aim of disclosing the role of selenide or hydrogen selenide (Se^-2 or HSe^-) as central metabolite of selenium and as an important antidote of the electrophilic mercury forms (particularly, Hg²⁺ and MeHg). Emphasis will be centered on the neurotoxicity of electrophile forms of mercury and selenium. The controversial participation of electrophile mercury and selenium forms in the development of some neurodegenerative disease will be briefly presented. The potential pharmacological use of organoseleno compounds (Ebselen and diphenyl diselenide) in the treatment of mercury poisoning will be considered. The central role of thiol (-SH) and selenol (-SeH) groups as the generic targets of electrophile mercury forms and the need of new in silico tools to guide the future biological researches will be commented.

GL-V9, a new synthetic flavonoid derivative, ameliorates DSS-induced colitis against oxidative stress by up-regulating Trx-1 expression via activation of AMPK/FOXO3a pathway

GL-V9, a new synthesized flavonoid derivative, has been reported to possess anti-cancer properties in our previous studies. Uncontrolled overproduction of reactive oxygen species (ROS) has been implicated in oxidative damage of inflammatory bowel disease (IBD). In this study, we aimed to investigate the protective effect of GL-V9 against dextran sulfate sodium (DSS)-induced colitis. GL-V9 attenuated DSS-induced body weight loss, colon length shortening and colonic pathological damage. GL-V9 also inhibited inflammatory cells infiltration and decreased myeloperoxidase (MPO) and inducible nitric oxide synthase (iNOS) activities. Moreover, GL-V9 inhibited ROS and malondialdehyde (MDA) generation, but enhanced superoxide dismutase (SOD), glutathione (GSH) and total antioxidant capacity. GL-V9 reduced pro-inflammatory cytokines production in serum and colon as well. Mechanically, GL-V9 could increase Trx-1 via activation of AMPK/FOXO3a to suppress DSS-induced colonic oxidative stress. Furthermore, GL-V9 decreased pro-inflammatory cytokines and ROS production and increased the antioxidant defenses in the mouse macrophage cells RAW264.7 by promoting Trx-1 expression. In conclusion, our study demonstrated that GL-V9 attenuated DSS-induced colitis against oxidative stress by up-regulating Trx-1 via activation of AMPK/FOXO3a pathway, suggesting that GL-V9 might be a potential effective drug for colitis.

Neuroprotection of ischemic preconditioning is mediated by thioredoxin 2 in the hippocampal CA1 region following a subsequent transient cerebral ischemia

Preconditioning by brief ischemic episode induces tolerance to a subsequent lethal ischemic insult, and it has been suggested that reactive oxygen species are involved in this phenomenon. Thioredoxin 2 (Trx2), a small protein with redox-regulating function, shows cytoprotective roles against oxidative stress. Here, we had focused on the role of Trx2 in ischemic preconditioning (IPC)-mediated neuroprotection against oxidative stress followed by a subsequent lethal transient cerebral ischemia. Animals used in this study were randomly assigned to six groups; sham-operated group, ischemia-operated group, IPC plus (+) sham-operated group, IPC + ischemia-operated group, IPC + auranofin (a TrxR2 inhibitor) + sham-operated group and IPC + auranofin + ischemia-operated group. IPC was subjected to a 2 minutes of sublethal transient ischemia 1 day prior to a 5 minutes of lethal transient ischemia. A significant loss of neurons was found in the stratum pyramidale (SP) of the hippocampal CA1 region (CA1) in the ischemia-operated-group 5 days after ischemia-reperfusion; in the IPC + ischemia-operated-group, pyramidal neurons in the SP were well protected. In the IPC + ischemia-operated-group, Trx2 and TrxR2 immunoreactivities in the SP and its protein level in the CA1 were not significantly changed compared with those in the sham-operated-group after ischemia-reperfusion. In addition, superoxide dismutase 2 (SOD2) expression, superoxide anion radical ( O2-) production, denatured cytochrome c expression and TUNEL-positive cells in the IPC + ischemia-operated-group were similar to those in the sham-operated-group. Conversely, the treatment of auranofin to the IPC + ischemia-operated-group significantly increased cell damage/death and abolished the IPC-induced effect on Trx2 and TrxR2 expressions. Furthermore, the inhibition of Trx2R nearly cancelled the beneficial effects of IPC on SOD2 expression, O2- production, denatured cytochrome c expression and TUNEL-positive cells. In brief, this study shows that IPC conferred neuroprotection against ischemic injury by maintaining Trx2 and suggests that the maintenance or enhancement of Trx2 expression by IPC may be a legitimate strategy for therapeutic intervention of cerebral ischemia.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

The epinephrine increases tyrosine hydroxylase expression through upregulating thioredoxin-1 in PC12 cells

Epinephrine is a stress hormone which is sharply increased in response to acute stress and is continuously elevated during persistent stress. Thioredoxin-1 (Trx-1) is a redox regulating protein and is induced under various stresses. Our previous study has shown that epinephrine induces the expression of Trx-1. Tyrosine hydroxylase (TH) is the major rate-limiting enzyme in catecholamine biosynthesis in response to stress. However, how TH is regulated by epinephrine is still unknown. In the present study, we found that epinephrine increased the expression of TH in a dose- and time-dependent manner in PC12 cells, which was inhibited by propranolol (β-adrenergic receptor inhibitor), but not by phenoxybenzamine (α-adrenergic receptor inhibitor). The increase of TH was also inhibited by SQ22536 (adenylyl cyclase inhibitor), H-89(PKA inhibitor) and LY294002 (phosphatidylinositol 3 kinase inhibitor). More importantly, overexpression of Trx-1 significantly enhanced the expression of TH, while Trx-1 siRNA suppressed TH expression induced by epinephrine. These results suggest that Trx-1 is involved in TH expression induced by epinephrine in PC12 cells.

Thioredoxin/thioredoxin reductase system involvement in cerebellar granule cell apoptosis

The involvement of thioredoxin/thioredoxin reductase system has been investigated in cerebellar granule cells (CGCs), a cellular system in which neurons are induced in apoptosis by the physiological stimulus of lowering extracellular potassium. Clarifying the sequence of events that occur during apoptosis is a critical issue as it can lead to the identification of those key events that, if blocked, can slow down or reverse the death process. The results reported in this work show that TrxR is involved in the early phase of CGC apoptosis with an increase in activity that coincides with the increased expression of the TrxR1 isoform and guarantees the maintenance of adequate level of Trx in its reduced, active form. However, in late apoptosis, when about 50 % of cells are dead, partial proteolysis of TrxR1 by calpain occurs and the reduction of TrxR1 mRNA, together with the overall decrease in TrxR activity, contribute to increase the levels of the oxidized form of Trx. When the reduced form of Trx is externally added to apoptotic cultures, a significant reduction in cell death is achieved confirming that a well-functioning thioredoxin/thioredoxin reductase system is required for survival of CGCs.

Thioredoxin-interacting protein: a novel target for neuroprotection in experimental thromboembolic stroke in mice

Redox imbalance in the brain significantly contributes to ischemic stroke pathogenesis, but antioxidant therapies have failed in clinical trials. Activation of endogenous defense mechanisms may provide better protection against stroke-induced oxidative injury. TXNIP (thioredoxin-interacting protein) is an endogenous inhibitor of thioredoxin (TRX), a key antioxidant system. We hypothesize that TXNIP inhibition attenuates redox imbalance and inflammation and provides protection against a clinically relevant model of embolic stroke. Male TXNIP-knockout (TKO), wild-type (WT), and WT mice treated with a pharmacological inhibitor of TXNIP, resveratrol (RES; 5 mg/kg body weight), were subjected to embolic middle cerebral artery occlusion (eMCAO). Behavior outcomes were monitored using neurological deficits score and grip strength meter at 24 h after eMCAO. Expression of oxidative, inflammatory, and apoptotic markers was analyzed by Western blot, immunohistochemistry, and slot blot at 24 h post-eMCAO. Our result showed that ischemic injury increases TXNIP in WT mice and that RES inhibits TXNIP expression and protects the brain against ischemic damage. TKO and RES-treated mice exhibited a 39.26 and 41.11 % decrease in infarct size and improved neurological score and grip strength compared to WT mice after eMCAO. Furthermore, the levels of TRX, nitrotyrosine, NOD-like receptor protein (NLRP3), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and activations of caspase-1, caspase-3, and poly-ADP-ribose polymerase (PARP) were significantly (P < 0.05) attenuated in TKO and RES-treated mice. The present study suggests that TXNIP is contributing to acute ischemic stroke through redox imbalance and inflammasome activation and inhibition of TXNIP may provide a new target for therapeutic interventions. This study also affirms the importance of the antioxidant effect of RES on the TRX/TXNIP system.

Thioredoxin 1 and glutaredoxin 2 contribute to maintain the phenotype and integrity of neurons following perinatal asphyxia

BACKGROUND

Thioredoxin (Trx) family proteins are crucial mediators of cell functions via regulation of the thiol redox state of various key proteins and the levels of the intracellular second messenger hydrogen peroxide. Their expression, localization and functions are altered in various pathologies. Here, we have analyzed the impact of Trx family proteins in neuronal development and recovery, following hypoxia/ischemia and reperfusion.

METHODS

We have analyzed the regulation and potential functions of Trx family proteins during hypoxia/ischemia and reoxygenation of the developing brain in both an animal and a cellular model of perinatal asphyxia. We have analyzed the distribution of 14 Trx family and related proteins in the cerebellum, striatum, and hippocampus, three areas of the rat brain that are especially susceptible to hypoxia. Using SH-SY5Y cells subjected to hypoxia and reoxygenation, we have analyzed the functions of some redoxins suggested by the animal experiment.

RESULTS AND CONCLUSIONS

We have described/discovered a complex, cell-type and tissue-specific expression pattern following the hypoxia/ischemia and reoxygenation. Particularly, Grx2 and Trx1 showed distinct changes during tissue recovery following hypoxia/ischemia and reoxygenation. Silencing of these proteins in SH-SY5Y cells subjected to hypoxia-reoxygenation confirmed that these proteins are required to maintain the normal neuronal phenotype.

GENERAL SIGNIFICANCE

These findings demonstrate the significance of redox signaling in cellular pathways. Grx2 and Trx1 contribute significantly to neuronal integrity and could be clinically relevant in neuronal damage following perinatal asphyxia and other neuronal disorders.

The paradoxical role of thioredoxin on oxidative stress and aging

In spite of intensive study, there is still controversy about the free radical or oxidative stress theory of aging, particularly in mammals. Our laboratory has conducted the first detailed studies on the role of thioredoxin (Trx) in the cytosol (Trx1) and in mitochondria (Trx2) on oxidative stress and aging using unique mouse models either overexpressing or down-regulating Trx1 or Trx2. The results generated from our lab and others indicate that: (1) oxidative stress and subsequent changes in signaling pathways could have different pathophysiological impacts at different stages of life; (2) changes in redox-sensitive signaling controlled by levels of oxidative stress and redox state could play more important roles in pathophysiology than accumulation of oxidative damage; (3) changes in oxidative stress and redox state in different cellular compartments (cytosol, mitochondria, or nucleus) could play different roles in pathophysiology during aging, and their combined effects show more impact on aging than changes in either oxidative stress or redox state alone; and (4) the roles of oxidative stress and redox state could have different pathophysiological consequences in different organs/tissues/cells or pathophysiological conditions. To critically test the role of oxidative stress on aging and investigate changes in redox-sensitive signaling pathways, further study is required.