Mitochondrial Thioredoxin System

Glutathione dynamics in subcellular compartments and implications for drug development

Glutathione (GSH) is a pivotal tripeptide antioxidant essential for maintaining cellular redox homeostasis and regulating diverse cellular processes. Subcellular compartmentalization of GSH underscores its multifaceted roles across various organelles including the cytosol, mitochondria, endoplasmic reticulum, and nucleus, each exhibiting distinct regulatory mechanisms. Perturbations in GSH dynamics contribute to pathophysiological conditions, emphasizing the clinical significance of understanding its intricate regulation. This review consolidates current knowledge on subcellular GSH dynamics, highlighting its implications in drug development, particularly in covalent drug design and antitumor strategies targeting intracellular GSH levels. Challenges and future directions in deciphering subcellular GSH dynamics are discussed, advocating for innovative methodologies to advance our comprehension and facilitate the development of precise therapeutic interventions based on GSH modulation.

Inducing ubiquitination and degradation of TrxR1 protein by LW-216 promotes apoptosis in non-small cell lung cancer via triggering ROS production

Thioredoxin reductases are frequently overexpressed in various solid tumors as a protective mechanism against heightened oxidative stress. Inhibitors of this system, such as Auranofin, are effective in eradicating cancer cells. However, the clinical significance of thioredoxin reductase 1 (TrxR1) in lung cancer, as well as the potential for its antagonist as a treatment option, necessitated further experimental validation. In this study, we observed significant upregulation of TrxR1 specifically in non-small cell lung cancer (NSCLC), rather than small cell lung cancer. Moreover, TrxR1 expression exhibited associations with survival rate, tumor volume, and histological classification. We developed a novel TrxR1 inhibitor named LW-216 and assessed its antitumor efficacy in NSCLC. Our results revealed that LW-216 is effectively bound with intracellular TrxR1 at sites R371 and G442, facilitating TrxR1 ubiquitination and suppressing TrxR1 expression, while not affecting TrxR2 expression. Treatment of LW-216-induced DNA damage and cell apoptosis in NSCLC cells through the generation of reactive oxygen species (ROS). Importantly, supplementation with N-acetylcysteine (NAC) or ectopic TrxR1 expression reversed LW-216-induced apoptosis. Furthermore, LW-216 displayed potent tumor growth inhibition in NSCLC cell-implanted mice, reducing TrxR1 expression in xenografts. Remarkably, LW-216 exhibited superior antitumor activity compared to Auranofin in vivo. Collectively, our research provides compelling evidence supporting the potential of targeting TrxR1 by LW-216 as a promising therapeutic strategy for NSCLC.

Protective impacts of mitochondria enhancers against thermal stress in poultry

Heat stress (HS) is still the essential environmental agent influencing the poultry industry. Research on HS in poultry has progressively acquired growing interest because of increased attention to climate alteration. Poultry can survive at certain zone of environmental temperatures, so it could be considered homoeothermic. In poultry, the normal body temperature is essential to enhance the internal environment for growth, which is achieved by normal environmental temperature. Recently, many studies have revealed that HS could cause mitochondrial dysfunction in broilers by inducing redox dysfunction, increasing uncoupling protein, boosting lipid and protein oxidation, and oxidative stress. Moreover, HS diminished the energy suppliers supported by mitochondria activity. A novel strategy for combating the negative influences of HS via boosting the mitochondria function through enrichment of the diets with mitochondria enhancers was also described in this review. Finally, the current review highlights the mitochondria dysfunction induced by HS in broilers and attempts to boost mitochondria functionality by enriching mitochondria enhancers to broiler diets.

Thioredoxin reductase selenoproteins from different organisms as potential drug targets for treatment of human diseases

Human thioredoxin reductase (TrxR) is a selenoprotein with a central role in cellular redox homeostasis, utilizing a highly reactive and solvent-exposed selenocysteine (Sec) residue in its active site. Pharmacological modulation of TrxR can be obtained with several classes of small compounds showing different mechanisms of action, but most often dependent upon interactions with its Sec residue. The clinical implications of TrxR modulation as mediated by small compounds have been studied in diverse diseases, from rheumatoid arthritis and ischemia to cancer and parasitic infections. The possible involvement of TrxR in these diseases was in some cases serendipitously discovered, by finding that existing clinically used drugs are also TrxR inhibitors. Inhibiting isoforms of human TrxR is, however, not the only strategy for human disease treatment, as some pathogenic parasites also depend upon Sec-containing TrxR variants, including S. mansoni, B. malayi or O. volvulus. Inhibiting parasite TrxR has been shown to selectively kill parasites and can thus become a promising treatment strategy, especially in the context of quickly emerging resistance towards other drugs. Here we have summarized the basis for the targeting of selenoprotein TrxR variants with small molecules for therapeutic purposes in different human disease contexts. We discuss how Sec engagement appears to be an indispensable part of treatment efficacy and how some therapeutically promising compounds have been evaluated in preclinical or clinical studies. Several research questions remain before a wider application of selenoprotein TrxR inhibition as a first-line treatment strategy might be developed. These include further mechanistic studies of downstream effects that may mediate treatment efficacy, identification of isoform-specific enzyme inhibition patterns for some given therapeutic compounds, and the further elucidation of cell-specific effects in disease contexts such as in the tumor microenvironment or in host-parasite interactions, and which of these effects may be dependent upon the specific targeting of Sec in distinct TrxR isoforms.

An Overview on How Exercise with Green Tea Consumption Can Prevent the Production of Reactive Oxygen Species and Improve Sports Performance

Free radicals are reactive products that have multiple effects on the human body. Endogenous and exogenous antioxidants manage the overproduction of free radicals. However, an imbalance between free radicals and antioxidant factors causes oxidative stress. Exercise and physical activity are factors that increase oxidative stress and disrupts the body’s homeostasis. Intensity and duration of training, training characteristics, and fitness level can have positive or negative effects on oxidative stress. Green tea consumption is recommended for the prevention of a variety of diseases, health maintenance, and weight loss. The effectiveness of green tea is primarily due to the presence of catechins and polyphenols, specifically (–)-epigallocatechin-3-gallate, which has antioxidant and anti-inflammatory properties based on clinical and animal studies. This review investigates the effect of green tea exercise and their interactive effects on free radicals and sports improvement.

Optical/electrochemical methods for detecting mitochondrial energy metabolism

This review highlights the biological importance of mitochondrial energy metabolism and the applications of multiple optical/electrochemical approaches to determine energy metabolites. Mitochondria, the main sites of oxidative phosphorylation and adenosine triphosphate (ATP) biosynthesis, provide the majority of energy required by aerobic cells for maintaining their physiological activity. They also participate in cell growth, differentiation, information transmission, and apoptosis. Multiple mitochondrial diseases, caused by internal or external factors, including oxidative stress, intense fluctuations of the ionic concentration, abnormal oxidative phosphorylation, changes in electron transport chain complex enzymes and mutations in mitochondrial DNA, can occur during mitochondrial energy metabolism. Therefore, developing accurate, sensitive, and specific methods for the in vivo and in vitro detection of mitochondrial energy metabolites is of great importance. In this review, we summarise the mitochondrial structure, functions, and crucial energy metabolic signalling pathways. The mechanism and applications of different optical/electrochemical methods are thoroughly reviewed. Finally, future research directions and challenges are proposed.

Protective effects of lycopene on mitochondrial oxidative injury and dysfunction in the liver of aflatoxin B1-exposed broilers

This study was conducted to investigate the effects of lycopene (LYC) on mitochondrial oxidative injury and dysfunction in the liver of aflatoxin B₁ (AFB₁)-exposed broilers. A total of 192 healthy 1-day-old male broilers were randomly divided into 3 groups with 8 replicates of 8 birds each. Birds in the 3 groups were fed basal diet (control), basal diet with 100 µg/kg AFB₁, and basal diet with 100 µg/kg AFB₁ and 200 mg/kg LYC, respectively. The experiment lasted 42 d. The results showed that AFB₁ decreased average daily body weight gain (ADG), average daily feed intake, and gain to feed ratio (G :F) compared to the control group, the LYC supplementation increased ADG and G/F compared to AFB₁ group (P < 0.05). Broilers in the AFB₁ group had lower mitochondrial glutathione (mGSH) concentration and glutathione peroxidase (GSH-Px), manganese superoxide dismutase (MnSOD), and thioredoxin reductase activities, and higher hydrogen peroxide (H₂O₂) and reactive oxygen species (ROS) concentrations than the control group (P < 0.05). The LYC increased mGSH concentration and GSH-Px and MnSOD activities, and decreased H₂O₂ and ROS concentrations compared to AFB₁ group (P < 0.05). Broilers fed the AFB₁ diet showed increased mitochondrial swelling and decreased adenosine triphosphate concentration than the control group, and LYC had opposite effects (P < 0.05). The AFB₁ decreased the activities of mitochondrial electron transfer chain (ETC) complexes I, II, III, and V, downregulated the mRNA expression levels of hepatic MnSOD, thioredoxin 2, thioredoxin reductase, peroxiredoxin-3, peroxisome proliferator-activated receptor γ coactivator 1α, nuclear respiratory factor 1, and mitochondrial transcription factor A compared with the control group (P < 0.05), and LYC increased activities of mitochondrial ETC complexes III and V, and upregulated mRNA expression levels of these genes in comparison to AFB₁ group (P < 0.05). In conclusion, the LYC protected broilers from AFB₁-induced liver mitochondrial oxidative injury and dysfunction by stimulating mitochondrial antioxidant capacity and maintaining mitochondrial biogenesis.

miR-195-5p exerts tumor-suppressive functions in human lung cancer cells through targeting TrxR2

miR-195-5p has been widely explored in various cancers and is considered as a tumor-suppressive microRNA. However, its roles in human lung cancer pathogenesis are not fully elucidated. In this study, we aimed to explore how miR-195-5p is involved in malignant behaviors of lung adenocarcinoma (LUAD) cells. miR-195-5p expression was examined in the tumor tissues of patients with LUAD and human LUAD cell lines including A549 and PC-9. Thioredoxin reductase 2 (TrxR2) was predicted to be an mRNA target of miR-195-5p using online tools and validated by the Dual-Luciferase Reporter Assay. Lentivirus infection was used for gene overexpression, while gene knockdown was achieved by RNA interference. Cell proliferation was determined by Cell Counting Kit-8 and 5-ethynyl-2'-deoxyuridine methods, and cell migration and invasion were assayed with transwell experiments. Cell apoptosis was determined by annexin V staining-based flow cytometry. The antitumor effects of miR-195-5p were also evaluated in nude mice xenografted with A549 cells. We found that miR-195-5p was lowly expressed in human LUAD cells, and its overexpression markedly suppressed cell proliferation, migration, and invasion and increased the apoptosis of LUAD cells in vitro. TrxR2 knockdown phenocopied the tumor-suppressive effects of miR-195-5p overexpression, while simultaneous TrxR2 overexpression remarkably reversed the effects of miR-195-5p overexpression on malignant behaviors of A549 and PC-9 cells. Additionally, miR-195-5p overexpression inhibited the growth of xenografted A549 tumor in nude mice. Our work verified that miR-195-5p exerts tumor-suppressive functions in LUAD cells through targeting TrxR2 and suggested that the miR-195-5p/TrxR2 axis is a potential biomarker for LUAD therapy.

Anti-colon cancer activity tracking isolation of peptide from ginseng leaves and potential mechanisms evaluation in vitro and in vivo

The ginseng has been used for over hundred years, in the belief of promoting longevity. However, the anticancer activity of ginseng leaf peptide (GP) has been never explored. In current study, we isolated the GPs and explored the anti-colon cancer activity in vitro and in vivo. MTT results showed that the GP-1 (GP-1~FKEHGY) performed most antiproliferative activity against colon cancer CT-26 cells with an IC₅₀ of 86.4 ± 9.46 μM (48 h). Further study indicated that GP-1 activated the caspases, regulated the p53/murine double minute 2 (MDM2) state, and induced the CT-26 cells apoptosis in a mitochondrial pathway. Meanwhile, the GP-1 arrested the CT-26 cells in G0/G1 phase accompanied with cyclin expression regulation. In addition, GP-1 significantly suppressed the tumor growth and induced the tumor cells apoptosis in vivo. Notably, the GP-1 would be a potential anti-colon cancer candidate.

Effect of antioxidants on preimplantation embryo development in vitro: a review

In vitro culture of the embryo is a useful method to treat infertility that shows embryo potential for selecting the best one to transfer and successfully implantation. However, embryo development in vitro is affected by oxidative stresses such as reactive oxygen species that may damage embryo development. Antioxidants are molecules found in fruits, vegetables, and fish that play an important role in reducing oxidative processes. In the natural environment, there is a physiological antioxidant system that protects embryos against oxidative damage. This antioxidant system does not exist in vitro. Antioxidants act as free radical scavengers and protect cells or repair damage done by free radicals. Various studies have shown that adding antioxidants into embryo culture medium improves embryo development in vitro. This review article emphasizes different aspects of various antioxidants, including types, functions and mechanisms, on the growth improvement of different species of embryos in vitro.

The Role of Signaling Pathways of Inflammation and Oxidative Stress in Development of Senescence and Aging Phenotypes in Cardiovascular Disease

The ASK1-signalosome→p38 MAPK and SAPK/JNK signaling networks promote senescence (in vitro) and aging (in vivo, animal models and human cohorts) in response to oxidative stress and inflammation. These networks contribute to the promotion of age-associated cardiovascular diseases of oxidative stress and inflammation. Furthermore, their inhibition delays the onset of these cardiovascular diseases as well as senescence and aging. In this review we focus on whether the (a) ASK1-signalosome, a major center of distribution of reactive oxygen species (ROS)-mediated stress signals, plays a role in the promotion of cardiovascular diseases of oxidative stress and inflammation; (b) The ASK1-signalosome links ROS signals generated by dysfunctional mitochondrial electron transport chain complexes to the p38 MAPK stress response pathway; (c) the pathway contributes to the sensitivity and vulnerability of aged tissues to diseases of oxidative stress; and (d) the importance of inhibitors of these pathways to the development of cardioprotection and pharmaceutical interventions. We propose that the ASK1-signalosome regulates the progression of cardiovascular diseases. The resultant attenuation of the physiological characteristics of cardiomyopathies and aging by inhibition of the ASK1-signalosome network lends support to this conclusion. Importantly the ROS-mediated activation of the ASK1-signalosome p38 MAPK pathway suggests it is a major center of dissemination of the ROS signals that promote senescence, aging and cardiovascular diseases. Pharmacological intervention is, therefore, feasible through the continued identification of potent, non-toxic small molecule inhibitors of either ASK1 or p38 MAPK activity. This is a fruitful future approach to the attenuation of physiological aspects of mammalian cardiomyopathies and aging.

Significance of the mitochondrial thioredoxin reductase in cancer cells: An update on role, targets and inhibitors

Thioredoxin reductase 2 (TrxR2) is a key component of the mitochondrial thioredoxin system able to transfer electrons to peroxiredoxin 3 (Prx3) in a reaction mediated by thioredoxin 2 (Trx2). In this way, both the level of hydrogen peroxide and thiol redox state are modulated. TrxR2 is often overexpressed in cancer cells conferring apoptosis resistance. Due to their exposed flexible arm containing selenocysteine, both cytosolic and mitochondrial TrxRs are inhibited by a large number of molecules. The various classes of inhibitors are listed and the molecules acting specifically on TrxR2 are extensively described. Particular emphasis is given to gold(I/III) complexes with phosphine, carbene or other ligands and to tamoxifen-like metallocifens. Also chemically unrelated organic molecules, including natural compounds and their derivatives, are taken into account. An important feature of many TrxR2 inhibitors is provided by their nature of delocalized lipophilic cations that allows their accumulation in mitochondria exploiting the organelle membrane potential. The consequences of TrxR2 inhibition are presented focusing especially on the impact on mitochondrial pathophysiology. Inhibition of TrxR2, by hindering the activity of Trx2 and Prx3, increases the mitochondrial concentration of reactive oxygen species and shifts the thiol redox state toward a more oxidized condition. This is reflected by alterations of specific targets involved in the release of pro-apoptotic factors such as cyclophilin D which acts as a regulator of the mitochondrial permeability transition pore. Therefore, the selective inhibition of TrxR2 could be utilized to induce cancer cell apoptosis.

Curcumin attenuates hepatic mitochondrial dysfunction through the maintenance of thiol pool, inhibition of mtDNA damage, and stimulation of the mitochondrial thioredoxin system in heat-stressed broilers

The aim of this study was to investigate the effects of dietary curcumin supplementation on the performance, mitochondrial redox system, mitochondrial DNA (mtDNA) integrity, and antioxidant-related gene expression in the liver of broiler chickens after heat stress treatment. At day 21, a total of 400 Arbor Acres broiler chickens with similar body weight (BW) were divided into 5 groups with 8 replicates per group and then reared either at a normal temperature (22 ± 1 °C) or at a high ambient temperature (34 ± 1 °C for 8 h and 22 ± 1 °C for the remaining time) for 20 d. Broilers in the 5 groups were fed a basal diet at a normal temperature (NT group) and a basal diet with 0, 50, 100, and 200 mg/kg curcumin at a high ambient temperature (HT, CUR50, CUR100, and CUR200 groups), respectively. The serum and liver samples were analyzed for the parameters related to hepatic damage, mitochondrial function, and redox status. The results showed that the G:F was increased in the CUR50 and CUR100 groups, and the final BW was increased in CUR100 group in comparison with the HT group (P < 0.05). When compared with those in the HT group, both serum aspartate and alanine aminotransferase activities were decreased in the curcumin-supplemented groups (P < 0.05). Curcumin decreased the reactive oxygen species (ROS) production but increased the mitochondrial membrane potential in the hepatocytes of the broilers after heat stress (P < 0.05). The broilers in curcumin-supplemented groups had lower malondialdehyde and protein carbonyl concentrations as well as greater thiol concentrations (P < 0.05). The mitochondrial manganese superoxide dismutase (MnSOD) activity in the liver was increased (P < 0.05) in the CUR100 group compared with the HT group. Compared with the heat-stressed broilers, the broilers that were fed curcumin had greater (P < 0.05) mtDNA copy number and ATP concentrations than those in the HT group. Curcumin supplementation attenuated the depression of the thioredoxin 2 and peroxiredoxin-3 gene expressions (P < 0.05). The MnSOD gene expression was increased in the CUR100 and CUR200 groups, and the thioredoxin reductase 2 gene expression was increased in the CUR50 group in comparison with the HT group (P < 0.05). In conclusion, curcumin mitigated the mitochondrial dysfunction in heat-stressed broilers, as evidenced by the suppression of the ROS burst, the maintenance of the thiol pool and mtDNA content, and the enhanced mitochondrial antioxidant gene expression.

The A to Z of modulated cell patterning by mammalian thioredoxin reductases

Mammalian thioredoxin reductases (TrxRs) are selenocysteine-containing proteins (selenoproteins) that propel a large number of functions through reduction of several substrates including the active site disulfide of thioredoxins (Trxs). Well-known enzymatic systems that in turn are supported by Trxs and TrxRs include deoxyribonucleotide synthesis through ribonucleotide reductase, antioxidant defense through peroxiredoxins and methionine sulfoxide reductases, and redox modulation of a number of transcription factors. Although these functions may be essential for cells due to crucial roles in maintenance of cell viability and proliferation, findings during the last decade reveal that mammals have major redundancy in their cellular reductive systems. The synthesis of glutathione (GSH) and reductive functions of GSH-dependent pathways typically act in parallel with Trx-dependent pathways, with only one of these systems often being sufficient to support viability. Importantly, this does not imply that a modulation of the Trx system will remain without consequences, even when GSH-dependent pathways remain functional. As suggested by several recent findings, the Trx system in general and the TrxRs in particular, function as key regulators of signaling pathways. In this review article we will discuss findings that collectively suggest that modulation in mammalian systems of cytosolic TrxR1 (TXNRD1) or mitochondrial TrxR2 (TXNRD2) influence cell patterning and cellular stress responses. Effects of lower activities include increased adipogenesis, insulin responsiveness, glycogen accumulation, hyperproliferation, and distorted embryonic development, while increased activities correlate with decreased proliferation and extended lifespan, as well as worse cancer prognosis. The molecular mechanisms that underlie these diverse effects, involving regulation of protein phosphorylation cascades and of key transcription factors that guide cellular differentiation pathways, will be discussed. We conclude that the selenium-dependent oxidoreductases TrxR1 and TrxR2 should be considered as key components of signaling pathways that control cell differentiation and cellular stress responses.

Disulfide bond based polymeric drug carriers for cancer chemotherapy and relevant redox environments in mammals

Increasing numbers of disulfide linkage-employing polymeric drug carriers that utilize the reversible peculiarity of this unique covalent bond have been reported. The reduction-sensitive disulfide bond is usually employed as a linkage between hydrophilic and hydrophobic polymers, polymers and drugs, or as cross-linkers in polymeric drug carriers. These polymeric drug carriers are designed to exploit the significant redox potential difference between the reducing intracellular environments and relatively oxidizing extracellular spaces. In addition, these drug carriers can release a considerable amount of anticancer drug in response to the reducing environment when they reach tumor tissues, effectively improving antitumor efficacy. This review focuses on various disulfide linkage-employing polymeric drug carriers. Important redox thiol pools, including GSH/GSSG, Cys/CySS, and Trx1, as well as redox environments in mammals, will be introduced.

The Antioxidant System in the Anhydrobiotic Midge as an Essential, Adaptive Mechanism for Desiccation Survival

One of the major damaging factors for living organisms experiencing water insufficiency is oxidative stress. Loss of water causes a dramatic increase in the production of reactive oxygen species (ROS). Thus, the ability for some organisms to survive almost complete desiccation (called anhydrobiosis) is tightly related to the ability to overcome extraordinary oxidative stress. The most complex anhydrobiotic organism known is the larva of the chironomid Polypedilum vanderplanki. Its antioxidant system shows remarkable features, such as an expansion of antioxidant genes, their overexpression, as well as the absence or low expression of enzymes required for the synthesis of ascorbate and glutathione and their antioxidant function. In this chapter, we summarize existing data about the antioxidant system of this insect, which is able to cope with substantial oxidative damage, even in an intracellular environment that is severely disturbed due to water loss.

Selective killing of gastric cancer cells by a small molecule via targeting TrxR1 and ROS-mediated ER stress activation

The thioredoxin reductase (TrxR) 1 is often overexpressed in numerous cancer cells. Targeting TrxR1 leads to a reduction in tumor progression and metastasis, making the enzyme an attractive target for cancer treatment. Our previous research revealed that the curcumin derivative B19 could induce cancer cell apoptosis via activation of endoplasmic reticulum (ER) stress. However, the upstream mechanism and molecular target of B19 is still unclear. In this study, we demonstrate that B19 directly inhibits TrxR1 enzyme activity to elevate oxidative stress and then induce ROS-mediated ER Stress and mitochondrial dysfunction, subsequently resulting in cell cycle arrest and apoptosis in human gastric cancer cells. A computer-assistant docking showed that B19 may bind TrxR1 protein via formation of a covalent bond with the residue Cys-498. Blockage of ROS production totally reversed B19-induced anti-cancer actions. In addition, the results of xenograft experiments in mice were highly consistent with in vitro studies. Taken together, targeting TrxR1 with B19 provides deep insight into the understanding of how B19 exerts its anticancer effects. More importantly, this work indicates that targeting TrxR1 and manipulating ROS levels are effective therapeutic strategy for the treatment of gastric cancer.

Altered Mitochondrial Signalling and Metabolism in Cancer

Mitochondria being the central organelle for metabolism and other cell signalling pathways have remained the topic of interest to tumour biologists. In spite of the wide acceptance of Warburg’s hypothesis, role of mitochondrial metabolism in cancer is still unclear. Uncontrolled growth and proliferation, hallmarks of tumour cells, are maintained when the cells adapt to metabolic reprogramming with the help of altered metabolism of mitochondria. This review has focussed on different aspects of mitochondrial metabolism and inter-related signalling pathways which have been found to be modified in cancer.

System-based proteomic and metabonomic analysis of the Df(16)A+/- mouse identifies potential miR-185 targets and molecular pathway alterations

Deletions on chromosome 22q11.2 are a strong genetic risk factor for development of schizophrenia and cognitive dysfunction. We employed shotgun liquid chromatography-mass spectrometry (LC-MS) proteomic and metabonomic profiling approaches on prefrontal cortex (PFC) and hippocampal (HPC) tissue from Df(16)A^+/- mice, a model of the 22q11.2 deletion syndrome. Proteomic results were compared with previous transcriptomic profiling studies of the same brain regions. The aim was to investigate how the combined effect of the 22q11.2 deletion and the corresponding miRNA dysregulation affects the cell biology at the systems level. The proteomic brain profiling analysis revealed PFC and HPC changes in various molecular pathways associated with chromatin remodelling and RNA transcription, indicative of an epigenetic component of the 22q11.2DS. Further, alterations in glycolysis/gluconeogenesis, mitochondrial function and lipid biosynthesis were identified. Metabonomic profiling substantiated the proteomic findings by identifying changes in 22q11.2 deletion syndrome (22q11.2DS)-related pathways, such as changes in ceramide phosphoethanolamines, sphingomyelin, carnitines, tyrosine derivates and panthothenic acid. The proteomic findings were confirmed using selected reaction monitoring mass spectrometry, validating decreased levels of several proteins encoded on 22q11.2, increased levels of the computationally predicted putative miR-185 targets UDP-N-acetylglucosamine-peptide N-acetylglucosaminyltransferase 110 kDa subunit (OGT1) and kinesin heavy chain isoform 5A and alterations in the non-miR-185 targets serine/threonine-protein phosphatase 2B catalytic subunit gamma isoform, neurofilament light chain and vesicular glutamate transporter 1. Furthermore, alterations in the proteins associated with mammalian target of rapamycin signalling were detected in the PFC and with glutamatergic signalling in the hippocampus. Based on the proteomic and metabonomic findings, we were able to develop a schematic model summarizing the most prominent molecular network findings in the Df(16)A^+/- mouse. Interestingly, the implicated pathways can be linked to one of the most consistent and strongest proteomic candidates, (OGT1), which is a predicted miR-185 target. Our results provide novel insights into system-biological mechanisms associated with the 22q11DS, which may be linked to cognitive dysfunction and an increased risk to develop schizophrenia. Further investigation of these pathways could help to identify novel drug targets for the treatment of schizophrenia.

Mitochondria as a Signaling Hub and Target for Phenoptosis Shutdown

Mitochondria have long been studied as the main energy source and one of the most important generators of reactive oxygen species in the eukaryotic cell. Yet, new data suggest mitochondria serve as a powerful cellular regulator, pathway trigger, and signal hub. Some of these crucial mitochondrial functions appear to be associated with RNP-granules. Deep and versatile involvement of mitochondria in general cellular regulation may be the legacy of parasitic behavior of the ancestors of mitochondria in the host cells. In this regard, we also discuss here the perspectives of using mitochondria-targeted compounds for systemic correction of phenoptotic shifts.

Energy metabolism and inflammation in brain aging and Alzheimer's disease

The high energy demand of the brain renders it sensitive to changes in energy fuel supply and mitochondrial function. Deficits in glucose availability and mitochondrial function are well-known hallmarks of brain aging and are particularly accentuated in neurodegenerative disorders such as Alzheimer's disease. As important cellular sources of H₂O₂, mitochondrial dysfunction is usually associated with altered redox status. Bioenergetic deficits and chronic oxidative stress are both major contributors to cognitive decline associated with brain aging and Alzheimer's disease. Neuroinflammatory changes, including microglial activation and production of inflammatory cytokines, are observed in neurodegenerative diseases and normal aging. The bioenergetic hypothesis advocates for sequential events from metabolic deficits to propagation of neuronal dysfunction, to aging, and to neurodegeneration, while the inflammatory hypothesis supports microglia activation as the driving force for neuroinflammation. Nevertheless, growing evidence suggests that these diverse mechanisms have redox dysregulation as a common denominator and connector. An independent view of the mechanisms underlying brain aging and neurodegeneration is being replaced by one that entails multiple mechanisms coordinating and interacting with each other. This review focuses on the alterations in energy metabolism and inflammatory responses and their connection via redox regulation in normal brain aging and Alzheimer's disease. Interaction of these systems is reviewed based on basic research and clinical studies.

Single nucleotide polymorphisms in the Trx2/TXNIP and TrxR2 genes of the mitochondrial thioredoxin antioxidant system and the risk of diabetic retinopathy in patients with Type 2 diabetes mellitus

BACKGROUND

Oxidative stress plays an important role in the pathogenesis of diabetes and its complications. The aim of this study was to examine the possible association between seven single nucleotide polymorphisms (SNPs) of the Trx2/TXNIP and TrxR2 genes encoding proteins involved in the thioredoxin antioxidant defence system and the risk of diabetic retinopthy (DR).

DESIGN

Cross-sectional case-control study.

PARTICIPANTS

A total of 802 Slovenian patients with Type 2 diabetes mellitus; 277 patients with DR and 525 with no DR were enrolled.

METHODS

Patients genotypes of the SNPs; including rs8140110, rs7211, rs7212, rs4755, rs1548357, rs4485648 and rs5748469 were determined by the competitive allele specific PCR method.

MAIN OUTCOME MEASURES

Each genotype of examined SNPs was regressed in a logistic model, assuming the co-dominant, dominant and the recessive models of inheritance with covariates of duration of diabetes, HbA1c, insulin therapy, total cholesterol and LDL cholesterol levels.

RESULTS

In the present study, for the first time we identified an association between the rs4485648 polymorphism of the TrxR2 gene and DR in Caucasians with Type 2 DM. The estimated ORs of adjusted logistic regression models were found to be as follows: 4.4 for CT heterozygotes, 4.3 for TT homozygotes (co-dominant genetic model) and 4.4 for CT+TT genotypes (dominant genetic model).

CONCLUSIONS

In our case-control study we were not able to demonstrate any association between rs8140110, rs7211, rs7212, rs4755, rs1548357, and rs5748469 and DR, however, our findings provide evidence that the rs4485648 polymorphism of the TrxR2 gene might exert an independent effect on the development of DR.

Mitochondria-Targeted Approach: Remarkably Enhanced Cellular Bioactivities of TPP2a as Selective Inhibitor and Probe toward TrxR

A mitochondria-targeted approach was developed to increase the cellular bioactivities of thioredoxin reductase (TrxR) inhibitors. By being conjugated with a triphenylphosphine (TPP) motif to a previously found TrxR inhibitor 2a, the resulted compound TPP2a can target subcellular mitochondria and efficiently inhibit cellular TrxR, leading to remarkably increased cellular ROS level and mitochondrial apoptosis of HeLa cancer cells. The cellular bioactivities of TPP2a, including its cytotoxicity against a panel of cancer cell lines, dramatically elevated compared with its parental compound 2a. The selectively and covalently interaction of TPP2a with subcellular mitochondrial TrxR was validated by fluorescent microscopy. Moreover, a nonspecific signal quenching coupled strategy was proposed based on the environmentally sensitive fluorescence of TPP2a, which makes it possible to label TrxR by removing the nonspecific backgrounds caused by TPP2a under complex biosettings such as cellular lysates and living cells, implicating a potential of TPP2a for TrxR-specific labeling.

The rs6060566 of the reactive oxygen species modulator 1 (Romo-1) gene affects Romo-1 expression and the development of diabetic retinopathy in Caucasians with type 2 diabetes

PURPOSE

The aim of this study was to examine the role of the rs6060566 polymorphism of the reactive oxygen species modulator 1 (Romo-1) gene in the development of diabetic retinopathy (DR) in Caucasians with type 2 diabetes (T2DM). Moreover, another aim was to investigate the effect of Romo-1 genotypes on Romo-1 expression in fibrovascular membranes from patients with proliferative DR.

METHODS

A total of 806 subjects with T2DM were enrolled in cross-sectional case-control study: 278 patients with DR and 528 subjects without clinical signs of DR. Genetical analysis was performed in 806 subjects with T2DM. Moreover, immunohistochemical analysis of 40 fibrovascular membranes of patients with proliferative DR was performed. The number of positive (labelled) cells per area - numerical areal density of the Romo-1-positive cells (the number of positive cells/mm(2) ) - was calculated.

RESULTS

A significantly higher frequency of the CC genotype of the rs6060566 polymorphism of the Romo-1 gene was found in subjects with T2DM with DR compared to those without DR (odds ratio=3.3, 95% confidence interval=1.1-8.8; p = 0.024). Moreover, the Romo-1 C allele was found to effect Romo-1 expression in fibrovascular membranes of patients with proliferative DR.

CONCLUSIONS

The rs6060566 polymorphism of the Romo-1 gene was found to be an independent risk factor for DR in Caucasians with T2DM. Moreover, the rs6060566 is most probably functional and its effect might be mediated through the increased expression of Romo-1 in the retina.

Chronic Ethanol Exposure: Pathogenesis of Pulmonary Disease and Dysfunction

Ethanol (EtOH) is the world’s most commonly used drug, and has been widely recognized as a risk factor for developing lung disorders. Chronic EtOH exposure affects all of the organ systems in the body and increases the risk of developing pulmonary diseases such as acute lung injury and pneumonia, while exacerbating the symptoms and resulting in increased mortality in many other lung disorders. EtOH and its metabolites inhibit the immune response of alveolar macrophages (AMs), increase airway leakage, produce damaging reactive oxygen species (ROS), and disrupt the balance of antioxidants/oxidants within the lungs. In this article, we review the role of EtOH exposure in the pathogenesis and progression of pulmonary disease.

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

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

Promoting thiol expression increases the durability of antitumor T-cell functions

Ex vivo-expanded CD8(+) T cells used for adoptive immunotherapy generally acquire an effector memory-like phenotype (TEM cells). With regard to therapeutic applications, two undesired features of this phenotype in vivo are limited persistence and reduced antitumor efficacy, relative to CD8(+) T cells with a central memory-like phenotype (TCM cells). Furthermore, there is incomplete knowledge about all the differences between TEM and TCM cells that may influence tumor treatment outcomes. Given that TCM cells survive relatively longer in oxidative tumor microenvironments, we investigated the hypothesis that TCM cells possess relatively greater antioxidative capacity than TEM cells. Here, we report that TCM cells exhibit a relative increase compared with TEM cells in the expression of cell surface thiols, a key target of cellular redox controls, along with other antioxidant molecules. Increased expression of redox regulators in TCM cells inversely correlated with the generation of reactive oxygen and nitrogen species, proliferative capacity, and glycolytic enzyme levels. Notably, T-cell receptor-transduced T cells pretreated with thiol donors, such as N-acetyl cysteine or rapamycin, upregulated thiol levels and antioxidant genes. A comparison of antitumor CD8(+) T-cell populations on the basis of surface thiol expression showed that thiol-high cells persisted longer in vivo and exerted superior tumor control. Our results suggest that higher levels of reduced cell surface thiols are a key characteristic of T cells that can control tumor growth and that profiling this biomarker may have benefits to adoptive T-cell immunotherapy protocols.

Resolution of oxidative stress by thioredoxin reductase: Cysteine versus selenocysteine

Thioredoxin reductase (TR) catalyzes the reduction of thioredoxin (TRX), which in turn reduces mammalian typical 2-Cys peroxiredoxins (PRXs 1-4), thiol peroxidases implicated in redox homeostasis and cell signaling. Typical 2-Cys PRXs are inactivated by hyperoxidation of the peroxidatic cysteine to cysteine-sulfinic acid, and regenerated in a two-step process involving retro-reduction by sulfiredoxin (SRX) and reduction by TRX. Here transient exposure to menadione and glucose oxidase was used to examine the dynamics of oxidative inactivation and reactivation of PRXs in mouse C10 cells expressing various isoforms of TR, including wild type cytoplasmic TR1 (Sec-TR1) and mitochondrial TR2 (Sec-TR2) that encode selenocysteine, as well as mutants of TR1 and TR2 in which the selenocysteine codon was changed to encode cysteine (Cys-TR1 or Cys-TR2). In C10 cells endogenous TR activity was insensitive to levels of hydrogen peroxide that hyperoxidize PRXs. Expression of Sec-TR1 increased TR activity, reduced the basal cytoplasmic redox state, and increased the rate of reduction of a redox-responsive cytoplasmic GFP probe (roGFP), but did not influence either the rate of inactivation or the rate of retro-reduction of PRXs. In comparison to roGFP, which was reduced within minutes once oxidants were removed reduction of 2-Cys PRXs occurred over many hours. Expression of wild type Sec-TR1 or Sec-TR2, but not Cys-TR1 or TR2, increased the rate of reduction of PRXs and improved cell survival after menadione exposure. These results indicate that expression levels of TR do not reduce the severity of initial oxidative insults, but rather govern the rate of reduction of cellular factors required for cell viability. Because Sec-TR is completely insensitive to cytotoxic levels of hydrogen peroxide, we suggest TR functions at the top of a redox pyramid that governs the oxidation state of peroxiredoxins and other protein factors, thereby dictating a hierarchy of phenotypic responses to oxidative insults.

Alcohol induced mitochondrial oxidative stress and alveolar macrophage dysfunction

An alcohol use disorder increases the risk of invasive and antimicrobial resistant community-acquired pneumonia and tuberculosis. Since the alveolar macrophage (AM) orchestrates the immune response in the alveolar space, understanding the underlying mechanisms by which alcohol suppresses AM phagocytosis is critical to improving clinical outcomes. In the alveolar space, chronic alcohol ingestion causes severe oxidative stress and depletes antioxidants which are critical for AM function. The mitochondrion is important in maintaining cellular redox balance and providing the ATP critical for phagocytosis. The focus of this study was to understand how alcohol triggers mitochondrial reactive oxygen species (ROS), stimulates cellular oxidative stress, and induces AM dysfunction. The current study also investigated the capacity of the mitochondrial targeted antioxidant, mitoTEMPOL (mitoT), in modulating mitochondrial oxidative stress, and AM dysfunction. Using in vitro ethanol exposure and AMs from ethanol-fed mice, ethanol promoted mitochondrial dysfunction including increased mitochondrial ROS, decreased mitochondrial membrane potential, and decreased ATP. Treatment with mitoT reversed these effects. Ethanol-induced decreases in phagocytosis and cell viability were also attenuated with mitoT. Therefore, antioxidants targeted to the mitochondria have the potential to ameliorate ethanol-induced mitochondrial oxidative stress and subsequent decreases in AM phagocytosis and cell viability.

Insights into the fish thioredoxin system: expression profile of thioredoxin and thioredoxin reductase in rainbow trout (Oncorhynchus mykiss) during infection and in vitro stimulation

Production of reactive oxygen species (ROS) is the first biological response during a disease outbreak and after injury. ROS are highly reactive molecules that can either endanger cell homeostasis or mediate cell signaling in several physiological pathways, including the immune response. Thioredoxin (Trx) and thioredoxin reductase (TrxR) are the essential components of the thioredoxin system, one of the main intracellular redox systems and are therefore important regulators of ROS accumulation. Through the regulation of the intracellular redox milieu, the thioredoxin system plays a key role within the immune system, linking immunology and free radical science. In this study we have firstly identified TrxRs in fish and used this new sequence information to reevaluate the evolution of the thioredoxin system within the vertebrate lineage. We next measured the expression of rainbow trout (Oncorhynchus mykiss) Trx and TrxR transcripts during infection in vivo and in vitro after stimulation of a macrophage cell line and primary macrophage cultures with pathogen associated molecular patterns (PAMPs). Our results showed that both Trx and TrxR were induced during infection at the transcriptional level, confirming their likely involvement in the innate immune response of fish. Since TrxRs are selenium-containing proteins (selenoproteins), we also measured the modulation of their expression upon organic and inorganic selenium exposure in vitro. TrxR was found to be responsive to selenium exposure in vitro, suggesting that it may represent a key mediator in the selenium modulation of innate immunity. In conclusion, our study highlights the need to investigate the involvement of the cell antioxidant pathways, especially the thioredoxin system, within the immune system of vertebrate species.

Mitochondrial energy metabolism and redox signaling in brain aging and neurodegeneration

SIGNIFICANCE

The mitochondrial energy-transducing capacity is essential for the maintenance of neuronal function, and the impairment of energy metabolism and redox homeostasis is a hallmark of brain aging, which is particularly accentuated in the early stages of neurodegenerative diseases.

RECENT ADVANCES

The communications between mitochondria and the rest of the cell by energy- and redox-sensitive signaling establish a master regulatory device that controls cellular energy levels and the redox environment. Impairment of this regulatory devise is critical for aging and the early stages of neurodegenerative diseases.

CRITICAL ISSUES

This review focuses on a coordinated metabolic network-cytosolic signaling, transcriptional regulation, and mitochondrial function-that controls the cellular energy levels and redox status as well as factors which impair this metabolic network during brain aging and neurodegeneration.

FUTURE DIRECTIONS

Characterization of mitochondrial function and mitochondria-cytosol communications will provide pivotal opportunities for identifying targets and developing new strategies aimed at restoring the mitochondrial energy-redox axis that is compromised in brain aging and neurodegeneration.

Alcohol induces mitochondrial redox imbalance in alveolar macrophages

Alcohol abuse suppresses the immune responses of alveolar macrophages (AMs) and increases the risk of a respiratory infection via chronic oxidative stress and depletion of critical antioxidants within alveolar cells and the alveolar lining fluid. Although alcohol-induced mitochondrial oxidative stress has been demonstrated, the oxidation of the mitochondrial thioredoxin redox circuit in response to alcohol has not been examined. In vitro ethanol exposure of a mouse AM cell line and AMs from ethanol-fed mice demonstrated NADPH depletion concomitant with oxidation of mitochondrial glutathione and oxidation of the thioredoxin redox circuit system including thioredoxin 2 (Trx2) and thioredoxin 2 reductase (Trx2R). Mitochondrial peroxiredoxins (Prdx's), which are critical for the reduction of the thioredoxin circuit, were irreversibly hyperoxidized to an inactive form. Ethanol also decreased the mRNAs for Trx2, Trx2R, Prdx3, and Prdx5 plus the mitochondrial thiol-disulfide proteins glutaredoxin 2, glutathione reductase, and glutathione peroxidase 2. Thus, the mitochondrial thioredoxin circuit was highly oxidized by ethanol, thereby compromising the mitochondrial antioxidant capacity and ability to detoxify mitochondrial reactive oxygen species. Oxidation of the mitochondrial thioredoxin redox circuit would further compromise the transient oxidation of thiol groups within specific proteins, the basis of redox signaling, and the processes by which cells respond to oxidants. Impaired mitochondria can then jeopardize cellular function of AMs, such as phagocytosis, which may explain the increased risk of respiratory infection in subjects with an alcohol use disorder.

Distinct redox profiles of selected human prostate carcinoma cell lines: implications for rational design of redox therapy

The effects of several cancer chemotherapeutic drugs and radiation are mediated, at least in part, by oxidative stress. To better understand this process, we analyzed certain biochemical properties affecting reduction-oxidation (redox) balance in normal prostate epithelial cells and several prostate cancer cell lines. Highly aggressive androgen-independent prostate cancer PC3 cells demonstrated significantly higher levels of total antioxidant capacity (AC) and intra- and extracellular glutathione (GSH)/glutathione disulfide (GSSG) ratios when compared with normal prostate epithelial PrEC cells. WPE1-NB26 cells, a prostate cancer cell line derived from immortalized RWPE1 human prostate epithelial cells, demonstrated significantly higher levels of total AC and intra- and extracellular GSH/GSSG ratios, but lower levels of intracellular reactive oxygen/nitrogen species and lipid peroxidation compared with RWPE1 cells. LNCaP-C4-2 cells, a more aggressive prostate cancer derived from less aggressive androgen-responsive LNCaP cells, exhibited higher levels of AC and extracellular GSH/GSSG ratio when compared to LNCaP cells. Specific cell types showed distinct cytotoxic responses to redox-modulating compounds. WPE1-NB26 cells were more sensitive to phenethyl isothiocyanate and tumor necrosis factor (TNF) than RWPE1 cells, while PC3 cells were more sensitive to TNF than PrEC cells. These results are consistent with the hypothesis that cancer cell redox state may modulate responses to redox-modulating therapeutic regimens.

A diterpenoid derivate compound targets selenocysteine of thioredoxin reductases and induces Bax/Bak-independent apoptosis

We have previously shown that the natural diterpenoid derivative S3 induced Bim upregulation and apoptosis in a Bax/Bak-independent manner. However, the exact molecular target(s) of S3 and the mechanism controlling Bim upregulation are still not clear. Here, we identify that S3 targets the selenoproteins TrxR1 and TrxR2 at the selenocysteine residue of the reactive center of the enzymes and inhibits their antioxidant activities. Consequently, cellular ROS is elevated, leading to the activation of FOXO3a, which contributes to Bim upregulation in Bax/Bak-deficient cells. Moreover, S3 retards tumor growth in subcutaneous xenograft tumors by inhibiting TrxR activity in vivo. Our studies delineate the signaling pathway controlling Bim upregulation, which results in Bax/Bak-independent apoptosis and provide evidence that the compounds can act as anticancer agents based on mammalian TrxRs inhibition.

A direct and continuous assay for the determination of thioredoxin reductase activity in cell lysates

Thioredoxin reductase (TR) is an oxidoreductase responsible for maintaining thioredoxin in the reduced state, thereby contributing to proper cellular redox homeostasis. The C-terminal active site of mammalian TR contains the rare amino acid selenocysteine, which is essential to its activity. Alterations in TR activity due to changes in cellular redox homeostasis are found in clinical conditions such as cancer, viral infection, and various inflammatory processes; therefore, quantification of thioredoxin activity can be a valuable indicator of clinical conditions. Here we describe a new direct assay, termed the SC-TR assay, to determine the activity of TR based on the reduction of selenocystine, a diselenide-bridged amino acid. Rather than being an end-point assay as in older methods, the SC-TR assay directly monitors the continuous consumption of NADPH at 340 nm by TR as it reduces selenocystine. The SC-TR assay can be used in a cuvette using traditional spectrophotometry or as a 96-well plate-based format using a plate reader. In addition, the SC-TR assay is compatible with the use of nonionic detergents, making it more versatile than other methods using cell lysates.

Cardiac dysfunction and oxidative stress in the metabolic syndrome: an update on antioxidant therapies

The metabolic syndrome (MetS) is a cluster of risk factors including obesity, insulin resistance, dyslipidemia, elevated blood pressure and glucose intolerance. The MetS increases the risk for cardiovascular disease (CVD) and type 2 diabetes. Each component of the MetS causes cardiac dysfunction and their combination carries additional risk. The mechanisms underlying cardiac dysfunction in the MetS are complex and might include lipid accumulation, increased fibrosis and stiffness, altered calcium homeostasis, abnormal autophagy, altered substrate utilization, mitochondrial dysfunction and increased oxidative stress. Mitochondrial and extra-mitochondrial sources of reactive oxygen species (ROS) and reduced antioxidant defense mechanisms characterize the myocardium of humans and animals with the MetS. The mechanisms for increased cardiac oxidative stress in the MetS are not fully understood but include increased fatty acid oxidation, mitochondrial dysfunction and enhanced NADPH oxidase activity. Therapies aimed to reduce oxidative stress and enhance antioxidant defense have been employed to reduce cardiac dysfunction in the MetS in animals. In contrast, large scale clinical trials using antioxidants therapies for the treatment of CVD have been disappointing because of the lack of efficacy and undesired side effects. The focus of this review is to summarize the current knowledge about the mechanisms underlying cardiac dysfunction in the MetS with a special interest in the role of oxidative stress. Finally, we will update the reader on the results obtained with natural antioxidant and mitochondria-targeted antioxidant therapies for the treatment of CVD in the MetS.

Chronic-alcohol-abuse-induced oxidative stress in the development of acute respiratory distress syndrome

Chronic alcohol ingestion increases the risk of developing acute respiratory distress syndrome (ARDS), a severe form of acute lung injury, characterized by alveolar epithelial and endothelial barrier disruption and intense inflammation. Alcohol abuse is also associated with a higher incidence of sepsis or pneumonia resulting in a higher rate of admittance to intensive care, longer inpatient stays, higher healthcare costs, and a 2-4 times greater mortality rate. Chronic alcohol ingestion induced severe oxidative stress associated with increased ROS generation, depletion of the critical antioxidant glutathione (GSH), and oxidation of the thiol/disulfide redox potential in the alveolar epithelial lining fluid and exhaled breath condensate. Across intracellular and extracellular GSH pools in alveolar type II cells and alveolar macrophages, chronic alcohol ingestion consistently induced a 40-60 mV oxidation of GSH/GSSG suggesting that the redox potentials of different alveolar GSH pools are in equilibrium. Alcohol-induced GSH depletion or oxidation was associated with impaired functions of alveolar type II cells and alveolar macrophages but could be reversed by restoring GSH pools in the alveolar lining fluid. The aims of this paper are to address the mechanisms for alcohol-induced GSH depletion and oxidation and the subsequent effects in alveolar barrier integrity, modulation of the immune response, and apoptosis.

The characterization of the Caenorhabditis elegans mitochondrial thioredoxin system uncovers an unexpected protective role of thioredoxin reductase 2 in β-amyloid peptide toxicity

AIM

Functional in vivo studies on the mitochondrial thioredoxin system are hampered by the embryonic or larval lethal phenotypes displayed by murine or Drosophila knock-out models. Thus, the access to alternative metazoan knock-out models for the mitochondrial thioredoxin system is of critical importance.

RESULTS

We report here the characterization of the mitochondrial thioredoxin system of Caenorhabditis elegans that is composed of the genes trx-2 and trxr-2. We demonstrate that the proteins thioredoxin 2 (TRX-2) and thioredoxin reductase 2 (TRXR-2) localize to the mitochondria of several cells and tissues of the nematode and that trx-2 and trxr-2 are upregulated upon induction of the mitochondrial unfolded protein response. Surprisingly, C. elegans trx-2 (lof ) and trxr-2 (null) single and double mutants are viable and display similar growth rates as wild-type controls. Moreover, the lack of the mitochondrial thioredoxin system does not affect longevity, reactive oxygen species production or the apoptotic program. Interestingly, we found a protective role of TRXR-2 in a transgenic nematode model of Alzheimer's disease (AD) that expresses human β-amyloid peptide and causes an age-dependent progressive paralysis. Hence, trxr-2 downregulation enhanced the paralysis phenotype, while a strong decrease of β-amyloid peptide and amyloid deposits occurred when TRXR-2 was overexpressed.

INNOVATION

C. elegans provides the first viable metazoan knock-out model for the mitochondrial thioredoxin system and identifies a novel role of this system in β-amyloid peptide toxicity and AD.

CONCLUSION

The nematode strains characterized in this work make C. elegans an ideal model organism to study the pathophysiology of the mitochondrial thioredoxin system at the level of a complete organism.

Mitochondria: redox metabolism and dysfunction

Mitochondria are the main intracellular location for fuel generation; however, they are not just power plants but involved in a range of other intracellular functions including regulation of redox homeostasis and cell fate. Dysfunction of mitochondria will result in oxidative stress which is one of the underlying causal factors for a variety of diseases including neurodegenerative diseases, diabetes, cardiovascular diseases, and cancer. In this paper, generation of reactive oxygen/nitrogen species (ROS/RNS) in the mitochondria, redox regulatory roles of certain mitochondrial proteins, and the impact on cell fate will be discussed. The current state of our understanding in mitochondrial dysfunction in pathological states and how we could target them for therapeutic purpose will also be briefly reviewed.

Overexpression of thioredoxin reductase 1 inhibits migration of HEK-293 cells

BACKGROUND INFORMATION

TrxR (thioredoxin reductase), in addition to protecting against oxidative stress, plays a role in the redox regulation of intracellular signalling pathways controlling, among others, cell proliferation and apoptosis. The aim of the present study was to determine whether TrxR1 is involved in the regulation of cell migration.

RESULTS

Stably transfected HEK-293 (human embryonic kidney) cells which overexpress cytosolic TrxR1 (HEK-TrxR15 and HEK-TrxR11 cells) were used in the present study. We found that the stimulation of cell motility induced by PKC (protein kinase C) activators, PMA and DPhT (diphenyltin), was inhibited significantly in the HEK-TrxR15 and HEK-TrxR11 cells compared with control cells. The overexpression of TrxR1 also inhibited characteristic morphological changes and reorganization of the F-actin cytoskeleton induced by PMA and DPhT. In addition, the selective activation of PKCdelta by DPhT was inhibited in cells that overexpressed cytosolic TrxR1. Furthermore, rottlerin, a selective inhibitor of PKCdelta, and PKCdelta siRNA (small interfering RNA), suppressed the morphological changes induced by DPhT in the control cells.

CONCLUSIONS

The overexpression of TrxR1 inhibits migration of HEK-293 cells stimulated with PMA and DPhT. Moreover, our observations suggest that this effect is mediated by the inhibition of PKCdelta activation.

Mitochondrial thioredoxin reductase is essential for early postischemic myocardial protection

BACKGROUND

Excessive formation of reactive oxygen species contributes to tissue injury and functional deterioration after myocardial ischemia/reperfusion. Especially, mitochondrial reactive oxygen species are capable of opening the mitochondrial permeability transition pore, a harmful event in cardiac ischemia/reperfusion. Thioredoxins are key players in the cardiac defense against oxidative stress. Mutations in the mitochondrial thioredoxin reductase (thioredoxin reductase-2, Txnrd2) gene have been recently identified to cause dilated cardiomyopathy in patients. Here, we investigated whether mitochondrial thioredoxin reductase is protective against myocardial ischemia/reperfusion injury.

METHODS AND RESULTS

In mice, α-MHC-restricted Cre-mediated Txnrd2 deficiency, induced by tamoxifen (Txnrd2-/-ic), aggravated systolic dysfunction and cardiomyocyte cell death after ischemia (90 minutes) and reperfusion (24 hours). Txnrd2-/-ic was accompanied by a loss of mitochondrial integrity and function, which was resolved on pretreatment with the reactive oxygen species scavenger N-acetylcysteine and the mitochondrial permeability transition pore blocker cyclosporin A. Likewise, Txnrd2 deletion in embryonic endothelial precursor cells and embryonic stem cell-derived cardiomyocytes, as well as introduction of Txnrd2-shRNA into adult HL-1 cardiomyocytes, increased cell death on hypoxia and reoxygenation, unless N-acetylcysteine was coadministered.

CONCLUSIONS

We report that Txnrd2 exerts a crucial function during postischemic reperfusion via thiol regeneration. The efficacy of cyclosporin A in cardiac Txnrd2 deficiency may indicate a role for Txnrd2 in reducing mitochondrial reactive oxygen species, thereby preventing opening of the mitochondrial permeability transition pore.

Identification of a redox-modulatory interaction between uncoupling protein 3 and thioredoxin 2 in the mitochondrial intermembrane space

Uncoupling protein 3 (UCP3) is a member of the mitochondrial solute carrier superfamily that is enriched in skeletal muscle and controls mitochondrial reactive oxygen species (ROS) production, but the mechanisms underlying this function are unclear.

AIMS

The goal of this work focused on the identification of mechanisms underlying UCP3 functions.

RESULTS

Here we report that the N-terminal, intermembrane space (IMS)-localized hydrophilic domain of mouse UCP3 interacts with the N-terminal mitochondrial targeting signal of thioredoxin 2 (Trx2), a mitochondrial thiol reductase. Cellular immunoprecipitation and in vitro pull-down assays show that the UCP3-Trx2 complex forms directly, and that the Trx2 N-terminus is both necessary and sufficient to confer UCP3 binding. Mutation studies show that neither a catalytically inactivated Trx2 mutant, nor a mutant Trx2 bearing the N-terminal targeting sequence of cytochrome c oxidase (COXMTS-Trx2) bind UCP3. Biochemical analyses using permeabilized mitochondria, and live cell experiments using bimolecular fluorescence complementation show that the UCP3-Trx2 complex forms specifically in the IMS. Finally, studies in C2C12 myocytes stably overexpressing UCP3 (2.5-fold) and subjected to Trx2 knockdown show that Trx2 is required for the UCP3-dependent mitigation of complex III-driven mitochondrial ROS generation. UCP3 expression was increased in mice fed a high fat diet, leading to increased localization of Trx2 to the IMS. UCP3 overexpression also increased expression of the glucose transporter GLUT4 in a Trx2-dependent fashion.

INNOVATION

This is the first report of a mitochondrial protein-protein interaction with UCP3 and the first demonstration that UCP3 binds directly, and in cells and tissues with mitochondrial thioredoxin 2.

CONCLUSION

These studies identify a novel UCP3-Trx2 complex, a novel submitochondrial localization of Trx2, and a mechanism underlying UCP3-regulated mitochondrial ROS production.

FK506 neuroprotection after cavernous nerve injury is mediated by thioredoxin and glutathione redox systems

INTRODUCTION

Immunophilin ligands such as FK506 (FK) preserve erectile function (EF) following cavernous nerve injury (CNI), although the precise mechanisms are unclear. We examined whether the thioredoxin (Trx) and glutathione (GSH) redox systems mediate this effect after CNI.

AIM

To investigate the roles of Trx reductase 2 (TrxR2) and S-Nitrosoglutathione reductase (GSNOR) as antioxidative/nitrosative and antiapoptotic mediators of the neuroprotective effect of FK in the penis after CNI.

METHODS

Adult male rats, wild-type (WT) mice, and GSNOR deficient (GSNOR -/-) mice were divided into four groups: sham surgery (CN [cavernous nerves] exposure only) + vehicle; sham surgery + FK (5 mg/kg/day/rat or 2 mg/kg/day/mouse, for 2 days, subcutaneous); CNI + vehicle; and CNI + FK. At day 4 after injury, electrically stimulated changes in intracavernosal pressure (ICP) were measured. Penises were collected for Western blot analysis of TrxR2, GSNOR, and Bcl-2, and for immunolocalization of TrxR2 and GSNOR.

MAIN OUTCOME MEASURES

EF assessment represented by maximal ICP and total ICP in response to electrical stimulation. Evaluation of protein expression levels and distribution patterns of antioxidative/nitrosative and antiapoptotic factors in penile tissue.

RESULTS

EF decreased after CNI compared with sham surgery values in both rats (P < 0.01) and WT and GSNOR -/- mice (P < 0.05). FK treatment preserved EF after CNI compared with vehicle treatment in rats (P < 0.01) and WT mice (P < 0.05) but not in GSNOR -/- mice. In rats, GSNOR (P < 0.01) and Bcl-2 (P < 0.05) expressions were significantly decreased after CNI. FK treatment in CN-injured rats restored expression of GSNOR and upregulated TrxR2 (P < 0.001) and Bcl-2 (P < 0.001) expressions compared with vehicle treatment. Localizations of proteins in the penis were observed for TrxR2 (endothelium, smooth muscle) and for GSNOR (nerves, endothelium, smooth muscle).

CONCLUSIONS

The neuroprotective effect of FK in preserving EF after CNI involves antioxidative/nitrosative and antiapoptotic mechanisms mediated, to some extent, by Trx and GSH systems.