Transgenic mice overproducing human thioredoxin-1, an antioxidative and anti-apoptotic protein, prevents diabetic embryopathy

Diabetes and Early Development: Epigenetics, Biological Stress, and Aging

Pregestational diabetes, either type 1 or type 2 diabetes, induces structural birth defects including neural tube defects and congenital heart defects in human fetuses. Rodent models of type 1 and type 2 diabetic embryopathy have been established and faithfully mimic human conditions. Hyperglycemia of maternal diabetes triggers oxidative stress in the developing neuroepithelium and the embryonic heart leading to the activation of proapoptotic kinases and excessive cell death. Oxidative stress also activates the unfolded protein response and endoplasmic reticulum stress. Hyperglycemia alters epigenetic landscapes by suppressing histone deacetylation, perturbing microRNA (miRNA) expression, and increasing DNA methylation. At cellular levels, besides the induction of cell apoptosis, hyperglycemia suppresses cell proliferation and induces premature senescence. Stress signaling elicited by maternal diabetes disrupts cellular organelle homeostasis leading to mitochondrial dysfunction, mitochondrial dynamic alteration, and autophagy impairment. Blocking oxidative stress, kinase activation, and cellular senescence ameliorates diabetic embryopathy. Deleting the mir200c gene or restoring mir322 expression abolishes maternal diabetes hyperglycemia-induced senescence and cellular stress, respectively. Both the autophagy activator trehalose and the senomorphic rapamycin can alleviate diabetic embryopathy. Thus, targeting cellular stress, miRNAs, senescence, or restoring autophagy or mitochondrial fusion is a promising approach to prevent poorly controlled maternal diabetes-induced structural birth defects. In this review, we summarize the causal events in diabetic embryopathy and propose preventions for this pathological condition. KEY POINTS: · Maternal diabetes induces structural birth defects.. · Kinase signaling and cellular organelle stress are critically involved in neural tube defects.. · Maternal diabetes increases DNA methylation and suppresses developmental gene expression.. · Cellular apoptosis and senescence are induced by maternal diabetes in the neuroepithelium.. · microRNAs disrupt mitochondrial fusion leading to congenital heart diseases in diabetic pregnancy..

Embryonic diapause due to high glucose is related to changes in glycolysis and oxidative phosphorylation, as well as abnormalities in the TCA cycle and amino acid metabolism

Introduction

The adverse effects of high glucose on embryos can be traced to the preimplantation stage. This study aimed to observe the effect of high glucose on early-stage embryos.

Methods and results

Seven-week-old ICR female mice were superovulated and mated, and the zygotes were collected. The zygotes were randomly cultured in 5 different glucose concentrations (control, 20mM, 40mM, 60mM and 80mM glucose). The cleavage rate, blastocyst rate and total cell number of blastocyst were used to assess the embryo quality. 40 mM glucose was selected to model high glucose levels in this study. 40mM glucose arrested early embryonic development, and the blastocyst rate and total cell number of the blastocyst decreased significantly as glucose concentration was increased. The reduction in the total cell number of blastocysts in the high glucose group was attributed to decreased proliferation and increased cell apoptosis, which is associated with the diminished expression of GLUTs (GLUT1, GLUT2, GLUT3). Furthermore, the metabolic characterization of blastocyst culture was observed in the high-glucose environment.

Discussion

The balance of glycolysis and oxidative phosphorylation at the blastocyst stage was disrupted. And embryo development arrest due to high glucose is associated with changes in glycolysis and oxidative phosphorylation, as well as abnormalities in the TCA cycle and amino acid metabolism.

Comparison of the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress

This study was conducted to compare the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress. Increased Il-1 and Il-6 expressions, markers of inflammation, were represented by inflammation models in mouse liver and kidney tissues injected intraperitoneally with LPS. After establishing the model, the GSH level and the GSH/GSSG ratio, which are oxidative stress markers, were investigated in both tissues treated with LPS and the control group. The expression of Trx1, TrxR, and Txnip genes increased in the liver tissues of LPS-treated mice. In the kidney tissue, while Trx1 expression decreased, no change was observed in TrxR1 expression, and Txnip expression increased. In the kidneys, TRXR1 and GR activities decreased, whereas GPx activity increased. In both tissues, the TRXR1 protein expression decreased significantly, while TXNIP expression increased. In conclusion, different behaviors of antioxidant system members were observed during acute inflammation in both tissues. Additionally, it can be said that the kidney tissue is more sensitive and takes earlier measures than the liver tissue against cellular damage caused by inflammation and inflammation-induced oxidative stress.

Functional cargos of exosomes derived from Flk-1+ vascular progenitors enable neurulation and ameliorate embryonic anomalies in diabetic pregnancy

Various types of progenitors initiate individual organ formation and their crosstalk orchestrates morphogenesis for the entire embryo. Here we show that progenitor exosomal communication across embryonic organs occurs in normal development and is altered in embryos of diabetic pregnancy. Endoderm fibroblast growth factor 2 (FGF2) stimulates mesoderm Flk-1+ vascular progenitors to produce exosomes containing the anti-stress protein Survivin. These exosomes act on neural stem cells of the neuroepithelium to facilitate neurulation by inhibiting cellular stress and apoptosis. Maternal diabetes causes Flk-1+ progenitor dysfunction by suppressing FGF2 through DNA hypermethylation. Restoring endoderm FGF2 prevents diabetes-induced survivin reduction in Flk-1+ progenitor exosomes. Transgenic Survivin expression in Flk-1+ progenitors or in utero delivery of survivin-enriched exosomes restores cellular homeostasis and prevents diabetes-induced neural tube defects (NTDs), whereas inhibiting exosome production induces NTDs. Thus, functional inter-organ communication via Flk-1 exosomes is vital for neurulation and its disruption leads to embryonic anomalies.

Diabetic Embryopathy Susceptibility in Mice Is Associated with Differential Dependence on Glucosamine and Modulation of High Glucose-Induced Oxidative Stress

The high K_M glucose transporter, GLUT2 (SLC2A2), is expressed by embryos and causes high rates of glucose transport during maternal hyperglycemic episodes in diabetic pregnancies and causes congenital malformations (diabetic embryopathy). GLUT2 is also a low K_M transporter of the amino sugar, glucosamine (GlcN), which enters the hexosamine biosynthetic pathway (HBP) and provides substrate for glycosylation reactions. Exogenous GlcN also increases activity of the pentose phosphate pathway (PPP), which increases production of NADPH reducing equivalents. GLUT2-transported GlcN is inhibited by high glucose concentrations. Not all mouse strains are susceptible to diabetic embryopathy. The aim of this study was to test the hypothesis that susceptibility to diabetic embryopathy is related to differential dependence on exogenous GlcN for glycosylation or stimulation of the PPP. We tested this using murine embryonic stem cell (ESC) lines that were derived from embryopathy-susceptible FVB/NJ (FVB), and embryopathy-resistant C57Bl/6J (B6), embryos in the presence of low or high glucose, and in the presence or absence of GlcN. There were no significant differences in Glut2 expression, or of glucose or GlcN transport, between FVB and B6 ESC. GlcN effects on growth and incorporation into glycoproteins indicated that FVB ESC are more dependent on exogenous GlcN than are B6 ESC. GlcN stimulated PPP activity in FVB but not in B6 ESC. High glucose induced oxidative stress in FVB ESC but not in B6 ESC. These results indicate that FVB embryos are more dependent on exogenous GlcN for glycosylation, but also for stimulation of the PPP and NADPH production, than are B6 embryos, thereby rendering FVB embryos more susceptible to high glucose to induce oxidative stress.

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

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

Berberine accelerated wound healing by restoring TrxR1/JNK in diabetes

The high disability, mortality and morbidity of diabetic ulcers make it urgent to explore effective strategies for diabetic wound repair. TrxR1 plays a vital role in regulating redox homeostasis in various pathologies. In the present study, the effect of berberine (BBR) on diabetic wounds was investigated in streptozotocin (STZ)-induced diabetic rats and a high glucose (HG)-induced cell model, and the mechanism of BBR on TrxR1 was elucidated. BBR treatment remarkably accelerated wound healing and enhanced extracellular matrix (ECM) synthesis and significantly inhibited HG-induced HaCaT cell damage. Further analysis indicated that BBR activated TrxR1, suppressed its downstream JNK signaling, thereby inhibiting oxidative stress and apoptosis, promoted cell proliferation, down-regulated matrix metalloproteinase (MMP) 9 (MMP9) and up-regulated transforming growth factor-β1 (TGF-β1) and tissue inhibitors of MMP 1 (TIMP1), resulting in accelerated wound healing. Importantly, the enhancement of BBR on wound repair was further abolished by TrxR1 inhibitor. Moreover, in diabetic wounds induced by a combination of STZ injection and high-fat diet, BBR significantly increased wound closure rate and TrxR1 expression, and this was reversed by TrxR1 inhibitor. These data indicated that topical BBR treatment accelerated diabetic wound healing by activating TrxR1. Targeting TrxR1 may be a novel, effective strategy for restoring redox homeostasis and promoting diabetic wound healing.

Tip60- and sirtuin 2-regulated MARCKS acetylation and phosphorylation are required for diabetic embryopathy

Failure of neural tube closure results in severe birth defects and can be induced by high glucose levels resulting from maternal diabetes. MARCKS is required for neural tube closure, but the regulation and of its biological activity and function have remained elusive. Here, we show that high maternal glucose induced MARCKS acetylation at lysine 165 by the acetyltransferase Tip60, which is a prerequisite for its phosphorylation, whereas Sirtuin 2 (SIRT2) deacetylated MARCKS. Phosphorylated MARCKS dissociates from organelles, leading to mitochondrial abnormalities and endoplasmic reticulum stress. Phosphorylation dead MARCKS (PD-MARCKS) reversed maternal diabetes-induced cellular organelle stress, apoptosis and delayed neurogenesis in the neuroepithelium and ameliorated neural tube defects. Restoring SIRT2 expression in the developing neuroepithelium exerted identical effects as those of PD-MARCKS. Our studies reveal a new regulatory mechanism for MARCKS acetylation and phosphorylation that disrupts neurulation under diabetic conditions by diminishing the cellular organelle protective effect of MARCKS.

Endoplasmic Reticulum Stress-Induced CHOP Inhibits PGC-1α and Causes Mitochondrial Dysfunction in Diabetic Embryopathy

Endoplasmic reticulum (ER) stress has been implicated in the development of maternal diabetes-induced neural tube defects (NTDs). ER stress-induced C/EBP homologous protein (CHOP) plays an important role in the pro-apoptotic execution pathways. However, the molecular mechanism underlying ER stress- and CHOP-induced neuroepithelium cell apoptosis in diabetic embryopathy is still unclear. Deletion of the Chop gene significantly reduced maternal diabetes-induced NTDs. CHOP deficiency abrogated maternal diabetes-induced mitochondrial dysfunction and neuroepithelium cell apoptosis. Further analysis demonstrated that CHOP repressed the expression of peroxisome-proliferator-activated receptor-γ coactivator-1α (PGC-1α), an essential regulator for mitochondrial biogenesis and function. Both CHOP deficiency in vivo and knockdown in vitro restore high glucose-suppressed PGC-1α expression. In contrast, CHOP overexpression mimicked inhibition of PGC-1α by high glucose. In response to the ER stress inducer tunicamycin, PGC-1α expression was decreased, whereas the ER stress inhibitor 4-phenylbutyric acid blocked high glucose-suppressed PGC-1α expression. Moreover, maternal diabetes in vivo and high glucose in vitro promoted the interaction between CHOP and the PGC-1α transcriptional regulator CCAAT/enhancer binding protein-β (C/EBPβ), and reduced C/EBPβ binding to the PGC-1α promoter leading to markedly decrease in PGC-1α expression. Together, our findings support the hypothesis that maternal diabetes-induced ER stress increases CHOP expression which represses PGC-1α through suppressing the C/EBPβ transcriptional activity, subsequently induces mitochondrial dysfunction and ultimately results in NTDs.

Recombinant Human Thioredoxin-1 Protects Macrophages from Oxidized Low-Density Lipoprotein-Induced Foam Cell Formation and Cell Apoptosis

Oxidized low-density lipoprotein (ox-LDL)-induced macrophage foam cell formation and apoptosis play critical roles in the pathogenesis of atherosclerosis. Thioredoxin-1 (Trx) is an antioxidant that potently protects various cells from oxidative stress-induced cell death. However, the protective effect of Trx on ox-LDL-induced macrophage foam cell formation and apoptosis has not been studied. This study aims to investigate the effect of recombinant human Trx (rhTrx) on ox-LDL-stimulated RAW264.7 macrophages and elucidate the possible mechanisms. RhTrx significantly inhibited ox-LDL-induced cholesterol accumulation and apoptosis in RAW264.7 macrophages. RhTrx also suppressed the ox-LDL-induced overproduction of lectin-like oxidized LDL receptor (LOX-1), Bax and activated caspase-3, but it increased the expression of Bcl-2. In addition, rhTrx markedly inhibited the ox-LDL-induced production of intracellular reactive oxygen species (ROS) and phosphorylation of p38 mitogen-activated protein kinases (MAPK). Furthermore, anisomycin (a p38 MAPK activator) abolished the protective effect of rhTrx on ox-LDL-stimulated RAW264.7 cells, and SB203580 (a p38 MAPK inhibitor) exerted a similar effect as rhTrx. Collectively, these findings indicate that rhTrx suppresses ox-LDL-stimulated foam cell formation and macrophage apoptosis by inhibiting ROS generation, p38 MAPK activation and LOX-1 expression. Therefore, we propose that rhTrx has therapeutic potential in the prevention and treatment of atherosclerosis.

Oxidative stress-induced miR-27a targets the redox gene nuclear factor erythroid 2-related factor 2 in diabetic embryopathy

BACKGROUND

Maternal diabetes induces neural tube defects, and oxidative stress is a causal factor for maternal diabetes-induced neural tube defects. The redox gene nuclear factor erythroid 2-related factor 2 is the master regulator of the cellular antioxidant system.

OBJECTIVE

In this study, we aimed to determine whether maternal diabetes inhibits nuclear factor erythroid 2-related factor 2 expression and nuclear factor erythroid 2-related factor 2-controlled antioxidant genes through the redox-sensitive miR-27a.

STUDY DESIGN

We used a well-established type 1 diabetic embryopathy mouse model induced by streptozotocin for our in vivo studies. Embryos at embryonic day 8.5 were harvested for analysis of nuclear factor erythroid 2-related factor 2, nuclear factor erythroid 2-related factor 2-controlled antioxidant genes, and miR-27a expression. To determine if mitigating oxidative stress inhibits the increase of miR-27a and the decrease of nuclear factor erythroid 2-related factor 2 expression, we induced diabetic embryopathy in superoxide dismutase 2 (mitochondrial-associated antioxidant gene)-overexpressing mice. This model exhibits reduced mitochondria reactive oxygen species even in the presence of hyperglycemia. To investigate the causal relationship between miR-27a and nuclear factor erythroid 2-related factor 2 in vitro, we examined C17.2 neural stem cells under normal and high-glucose conditions.

RESULTS

We observed that the messenger RNA and protein levels of nuclear factor erythroid 2-related factor 2 were significantly decreased in embryos on embryonic day 8.5 from diabetic dams compared to those from nondiabetic dams. High-glucose also significantly decreased nuclear factor erythroid 2-related factor 2 expression in a dose- and time-dependent manner in cultured neural stem cells. Our data revealed that miR-27a was up-regulated in embryos on embryonic day 8.5 exposed to diabetes, and that high glucose increased miR-27a levels in a dose- and time-dependent manner in cultured neural stem cells. In addition, we found that a miR-27a inhibitor abrogated the inhibitory effect of high glucose on nuclear factor erythroid 2-related factor 2 expression, and a miR-27a mimic suppressed nuclear factor erythroid 2-related factor 2 expression in cultured neural stem cells. Furthermore, our data indicated that the nuclear factor erythroid 2-related factor 2-controlled antioxidant enzymes glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, and glutathione S-transferase A1 were down-regulated by maternal diabetes in embryos on embryonic day 8.5 and high glucose in cultured neural stem cells. Inhibiting miR-27a restored expression of glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, and glutathione S-transferase A1. Overexpressing superoxide dismutase 2 reversed the maternal diabetes-induced increase of miR-27a and suppression of nuclear factor erythroid 2-related factor 2 and nuclear factor erythroid 2-related factor 2-controlled antioxidant enzymes.

CONCLUSION

Our study demonstrates that maternal diabetes-induced oxidative stress increases miR-27a, which, in turn, suppresses nuclear factor erythroid 2-related factor 2 and its responsive antioxidant enzymes, resulting in diabetic embryopathy.

Tadalafil Improves L-NG-Nitroarginine Methyl Ester-Induced Preeclampsia With Fetal Growth Restriction-Like Symptoms in Pregnant Mice

BACKGROUND

We investigated the efficacy and mechanisms of tadalafil, a selective phosphodiesterase 5 inhibitor, in treating preeclampsia (PE) with fetal growth restriction (FGR) using L-NG-nitroarginine methyl ester (L-NAME)-induced PE with FGR in pregnant mice as our experimental model.

METHODS

C57BL/6 mice were divided into 2 groups 11 days postcoitum (d.p.c.). A control group of dams (C dam) received 0.5% carboxymethylcellulose (CMC). A L-NAME-treated group received 1 mg/ml L-NAME dissolved in CMC. The L-NAME-treated dams were divided into 2 subgroups 13 d.p.c. One subgroup continued to receive L-NAME (L dams). The other subgroup received L-NAME with 0.08 mg/ml tadalafil suspended in CMC (TL dams). Maternal systolic blood pressure (SBP) and proteinuria were assessed 16 d.p.c. Fetal weight was recorded, and placentas and maternal kidneys were collected 17 d.p.c.

RESULTS

Maternal SBP, proteinuria, and fetal weight were improved for TL dams compared to L dams. The placental concentration of placental growth factor (PlGF) was higher for TL dams than for the C and L dams. The placental maternal blood sinuses of L dams were narrower than those of C dams, but those of TL dams improved to a similar width as C dams. Glomerular oxidative stress was ameliorated in TL dams compared to L dams.

CONCLUSIONS

Tadalafil dilates the placental maternal blood sinuses, which leads to increase PlGF production, and contributes to facilitate fetal growth and improve maternal SBP. Moreover, tadalafil ameliorates glomerular damage by reducing oxidative stress. These results suggest that tadalafil is a candidate for treatment of PE with FGR.

Protein kinase C-alpha suppresses autophagy and induces neural tube defects via miR-129-2 in diabetic pregnancy

Gene deletion-induced autophagy deficiency leads to neural tube defects (NTDs), similar to those in diabetic pregnancy. Here we report the key autophagy regulators modulated by diabetes in the murine developing neuroepithelium. Diabetes predominantly leads to exencephaly, induces neuroepithelial cell apoptosis and suppresses autophagy in the forebrain and midbrain of NTD embryos. Deleting the Prkca gene, which encodes PKCα, reverses diabetes-induced autophagy impairment, cellular organelle stress and apoptosis, leading to an NTD reduction. PKCα increases the expression of miR-129-2, which is a negative regulator of autophagy. miR-129-2 represses autophagy by directly targeting PGC-1α, a positive regulator for mitochondrial function, which is disturbed by maternal diabetes. PGC-1α supports neurulation by stimulating autophagy in neuroepithelial cells. These findings identify two negative autophagy regulators, PKCα and miR-129-2, which mediate the teratogenicity of hyperglycaemia leading to NTDs. We also reveal a function for PGC-1α in embryonic development through promoting autophagy and ameliorating hyperglycaemia-induced NTDs.

The status of diabetic embryopathy

Diabetic embryopathy is a theoretical enigma and a clinical challenge. Both type 1 and type 2 diabetic pregnancy carry a significant risk for fetal maldevelopment, and the precise reasons for the diabetes-induced teratogenicity are not clearly identified. The experimental work in this field has revealed a partial, however complex, answer to the teratological question, and we will review some of the latest suggestions.

Relationship between thioredoxin and thioredoxin-binding protein in patients with gestational diabetes mellitus

OBJECTIVE

This study examined the clinical and biological significance of thioredoxin (Trx) and thioredoxin-binding protein (TrxBP), which are redox-active proteins that control multiple biological functions, in gestational diabetes.

METHODS

We measured serum concentrations of Trx, TrxBP, insulin and other blood parameters, as well as insulin resistance and glucose tolerance in pregnant women with or without gestational dieabetes mellitus (GDM) (34/34) at the early second trimester.

RESULTS

Contrary to diabetes patients, serum TrxBP levels were lower in women with GDM than healthy pregnant controls. The serum insulin concentrations were higher in GDM, but the difference was not statistically significant. Furthermore, the intracellular redox potential ratio (Trx/TrxBP) of GDM patients was higher than that of the control group.

CONCLUSION

During pregnancy, the mother is potentially subjected to glucotoxicity as well as oxidative stress (OS) to help the foetus absorb more nutrients. Our results suggest that the Trx/TrxBP system may mediate a compensating mechanism. Reduced TrxBP levels and consequent enhanced Trx activity may alleviate OS and protect the foetus from hypoglycaemia. We hypothesise that the decrease in TrxBP levels is not a consequence of GDM, but rather is an instance of the active functional role of TrxBP in maternal development, unifying redox regulation and glucose metabolism.

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.

Cellular Stress, Excessive Apoptosis, and the Effect of Metformin in a Mouse Model of Type 2 Diabetic Embryopathy

Increasing prevalence of type 2 diabetes in women of childbearing age has led to a higher incidence of diabetes-associated birth defects. We established a model of type 2 diabetic embryopathy by feeding 4-week-old female mice a high-fat diet (HFD) (60% fat). After 15 weeks on HFD, the mice showed characteristics of type 2 diabetes mellitus (DM) and were mated with lean male mice. During pregnancy, control dams fed a normal diet (10% fat) were maintained on either normal diet or HFD, serving as a control group with elevated circulating free fatty acids. DM dams produced offspring at a rate of 11.3% for neural tube defect (NTD) formation, whereas no embryos in the control groups developed NTDs. Elevated markers of oxidative stress, endoplasmic reticulum stress, caspase activation, and neuroepithelial cell apoptosis (causal events in type 1 diabetic embryopathy) were observed in embryos of DM dams. DM dams treated with 200 mg/kg metformin in drinking water ameliorated fasting hyperglycemia, glucose intolerance, and insulin resistance with consequent reduction of cellular stress, apoptosis, and NTDs in their embryos. We conclude that cellular stress and apoptosis occur and that metformin effectively reduces type 2 diabetic embryopathy in a useful rodent model.

Thioredoxins, glutaredoxins, and peroxiredoxins--molecular mechanisms and health significance: from cofactors to antioxidants to redox signaling

Thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs) have been characterized as electron donors, guards of the intracellular redox state, and "antioxidants". Today, these redox catalysts are increasingly recognized for their specific role in redox signaling. The number of publications published on the functions of these proteins continues to increase exponentially. The field is experiencing an exciting transformation, from looking at a general redox homeostasis and the pathological oxidative stress model to realizing redox changes as a part of localized, rapid, specific, and reversible redox-regulated signaling events. This review summarizes the almost 50 years of research on these proteins, focusing primarily on data from vertebrates and mammals. The role of Trx fold proteins in redox signaling is discussed by looking at reaction mechanisms, reversible oxidative post-translational modifications of proteins, and characterized interaction partners. On the basis of this analysis, the specific regulatory functions are exemplified for the cellular processes of apoptosis, proliferation, and iron metabolism. The importance of Trxs, Grxs, and Prxs for human health is addressed in the second part of this review, that is, their potential impact and functions in different cell types, tissues, and various pathological conditions.

The thioredoxin system as a therapeutic target in human health and disease

The thioredoxin (Trx) system comprises Trx, truncated Trx (Trx-80), Trx reductase, and NADPH, besides a natural Trx inhibitor, the thioredoxin-interacting protein (TXNIP). This system is essential for maintaining the balance of the cellular redox status, and it is involved in the regulation of redox signaling. It is also pivotal for growth promotion, neuroprotection, inflammatory modulation, antiapoptosis, immune function, and atherosclerosis. As an ubiquitous and multifunctional protein, Trx is expressed in all forms of life, executing its function through its antioxidative, protein-reducing, and signal-transducing activities. In this review, the biological properties of the Trx system are highlighted, and its implications in several human diseases are discussed, including cardiovascular diseases, heart failure, stroke, inflammation, metabolic syndrome, neurodegenerative diseases, arthritis, and cancer. The last chapter addresses the emerging therapeutic approaches targeting the Trx system in human diseases.

Trehalose prevents neural tube defects by correcting maternal diabetes-suppressed autophagy and neurogenesis

Preexisting maternal diabetes increases the risk of neural tube defects (NTDs). The mechanism underlying maternal diabetes-induced NTDs is not totally defined, and its prevention remains a challenge. Autophagy, an intracellular process to degrade dysfunction protein and damaged cellular organelles, regulates cell proliferation, differentiation, and apoptosis. Because autophagy impairment causes NTDs reminiscent of those observed in diabetic pregnancies, we hypothesize that maternal diabetes-induced autophagy impairment causes NTD formation by disrupting cellular homeostasis, leading to endoplasmic reticulum (ER) stress and apoptosis, and that restoration of autophagy by trehalose, a natural disaccharide, prevents diabetes-induced NTDs. Embryos from nondiabetic and type 1 diabetic mice fed with or without 2 or 5% trehalose water were used to assess markers of autophagy, ER stress, and neurogenesis, numbers of autophagosomes, gene expression that regulates autophagy, NTD rates, indices of mitochondrial dysfunction, and neuroepithelial cell apoptosis. Maternal diabetes suppressed autophagy by significantly reducing LC3-II expression, autophagosome numbers, and GFP-LC3 punctate foci in neuroepithelial cells and by altering autophagy-related gene expression. Maternal diabetes delayed neurogenesis by blocking Sox1 neural progenitor differentiation. Trehalose treatment reversed autophagy impairment and prevented NTDs in diabetic pregnancies. Trehalose resolved homeostatic imbalance by correcting mitochondrial defects, dysfunctional proteins, ER stress, apoptosis, and delayed neurogenesis in the neural tubes exposed to hyperglycemia. Our study demonstrates for the first time that maternal diabetes suppresses autophagy in neuroepithelial cells of the developing neural tube, leading to NTD formation, and provides evidence for the potential efficacy of trehalose as an intervention against hyperglycemia-induced NTDs.

Maternal hyperglycemia activates an ASK1-FoxO3a-caspase 8 pathway that leads to embryonic neural tube defects

Neural tube defects result from failure to completely close neural tubes during development. Maternal diabetes is a substantial risk factor for neural tube defects, and available evidence suggests that the mechanism that links hyperglycemia to neural tube defects involves oxidative stress and apoptosis. We demonstrated that maternal hyperglycemia correlated with activation of the apoptosis signal-regulating kinase 1 (ASK1) in the developing neural tube, and Ask1 gene deletion was associated with reduced neuroepithelial cell apoptosis and development of neural tube defects. ASK1 activation stimulated the activity of the transcription factor FoxO3a, which increased the abundance of the apoptosis-promoting adaptor protein TRADD, leading to activation of caspase 8. Hyperglycemia-induced apoptosis and the development of neural tube defects were reduced with genetic ablation of either FoxO3a or Casp8 or inhibition of ASK1 by thioredoxin. Examination of human neural tissues affected by neural tube defects revealed increased activation or abundance of ASK1, FoxO3a, TRADD, and caspase 8. Thus, activation of an ASK1-FoxO3a-TRADD-caspase 8 pathway participates in the development of neural tube defects, which could be prevented by inhibiting intermediates in this cascade.

c-Jun NH2-terminal kinase 1/2 and endoplasmic reticulum stress as interdependent and reciprocal causation in diabetic embryopathy

Embryos exposed to high glucose exhibit aberrant maturational and cytoarchitectural cellular changes, implicating cellular organelle stress in diabetic embryopathy. c-Jun-N-terminal kinase 1/2 (JNK1/2) activation is a causal event in maternal diabetes-induced neural tube defects (NTD). However, the relationship between JNK1/2 activation and endoplasmic reticulum (ER) stress in diabetic embryopathy has never been explored. We found that maternal diabetes significantly increased ER stress markers and induced swollen/enlarged ER lumens in embryonic neuroepithelial cells during neurulation. Deletion of either jnk1 or jnk2 gene diminished hyperglycemia-increased ER stress markers and ER chaperone gene expression. In embryos cultured under high-glucose conditions (20 mmol/L), the use of 4-phenylbutyric acid (4-PBA), an ER chemical chaperone, diminished ER stress markers and abolished the activation of JNK1/2 and its downstream transcription factors, caspase 3 and caspase 8, and Sox1 neural progenitor apoptosis. Consequently, both 1 and 2 mmol/L 4-PBA significantly ameliorated high glucose-induced NTD. We conclude that hyperglycemia induces ER stress, which is responsible for the proapoptotic JNK1/2 pathway activation, apoptosis, and NTD induction. Suppressing JNK1/2 activation by either jnk1 or jnk2 gene deletion prevents ER stress. Thus, our study reveals a reciprocal causation of ER stress and JNK1/2 in mediating the teratogenicity of maternal diabetes.

Thioredoxin-1 and oxidative stress status in pregnant women at early third trimester of pregnancy: relation to maternal and neonatal characteristics

This study examined the clinical and biological importance of thioredoxin-1, a redox-active defensive protein that controls multiple biological functions, in pregnant women. We measured serum concentrations of thioredoxin-1, total hydroperoxides, and redox potential in 60 pregnant women at the early third trimester: gestational age of 27-29 weeks. The thioredoxin-1 concentration (mean ± SD) was 90 ± 42 ng/ml. Total hydroperoxides was 471 ± 105 U.CARR (1 U.CARR = 0.08 mg/dl H(2)O(2)). Redox potential was 2142 ± 273 µmol/l. The total hydroperoxides: redox potential ratio (oxidative stress index) was 0.23 ± 0.08. Thioredoxin-1, total hydroperoxides, and oxidative stress index were higher and redox potential was lower than in blood of healthy adults. Total hydroperoxides and redox potential were mutually correlated significantly and negatively. Thioredoxin-1 correlated significantly and negatively and redox potential correlated significantly and positively with body weight and body mass index. Thioredoxin-1 and redox potential correlated significantly and positively with uric acid and albumin, respectively. Thioredoxin-1 and oxidative stress index correlated significantly and negatively and redox potential significantly and positively with neonatal birth weight. These results suggest that high concentrations of thioredoxin-1 are linked to high oxidative stress status in pregnant women and that neonatal birth weight is affected by the maternal oxidative condition during later pregnancy.

Oxidative stress-induced JNK1/2 activation triggers proapoptotic signaling and apoptosis that leads to diabetic embryopathy

Oxidative stress and apoptosis are implicated in the pathogenesis of diabetic embryopathy. The proapoptotic c-Jun NH(2)-terminal kinases (JNK)1/2 activation is associated with diabetic embryopathy. We sought to determine whether 1) hyperglycemia-induced oxidative stress is responsible for the activation of JNK1/2 signaling, 2) JNK1 contributes to the teratogenicity of hyperglycemia, and 3) both JNK1 and JNK2 activation cause activation of downstream transcription factors, caspase activation, and apoptosis, resulting in neural tube defects (NTDs). Wild-type (WT) embryos from nondiabetic WT dams and WT, superoxide dismutase (SOD)1-overexpressing, jnk1(+/-), jnk1(-/-), and jnk2(-/-) embryos exposed to maternal hyperglycemia were used to assess JNK1/2 activation, NTDs, activation of transcription factors downstream of JNK1/2, caspase cascade, and apoptosis. SOD1 overexpression abolished diabetes-induced activation of JNK1/2 and their downstream effectors: phosphorylation of c-Jun, activating transcription factor 2, and E twenty-six-like transcription factor 1 and dephosphorylation of forkhead box class O3a. jnk1(-/-) embryos had significantly lower incidences of NTDs than those of WT or jnk1(+/-) embryos. Either jnk1 or jnk2 gene deletion blocked diabetes-induced activation of JNK1/2 signaling, caspases 3 and 8, and apoptosis in Sox1(+) neural progenitors of the developing neural tube. Our results show that JNK1 and JNK2 are equally involved in diabetic embryopathy and that the oxidative stress-JNK1/2-caspase pathway mediates the proapoptotic signals and the teratogenicity of maternal diabetes.

Cell stress proteins in atherothrombosis

Cell stress proteins (CSPs) are a large and heterogenous family of proteins, sharing two main characteristics: their levels and/or location are modified under stress and most of them can exert a chaperon function inside the cells. Nonetheless, they are also involved in the modulation of several mechanisms, both at the intracellular and the extracellular compartments. There are more than 100 proteins belonging to the CSPs family, among them the thioredoxin (TRX) system, which is the focus of the present paper. TRX system is composed of several proteins such as TRX and peroxiredoxin (PRDX), two thiol-containing enzymes that are key players in redox homeostasis due to their ability to scavenge potential harmful reactive oxygen species. In addition to their main role as antioxidants, recent data highlights their function in several processes such as cell signalling, immune inflammatory responses, or apoptosis, all of them key mechanisms involved in atherothrombosis. Moreover, since TRX and PRDX are present in the pathological vascular wall and can be secreted under prooxidative conditions to the circulation, several studies have addressed their role as diagnostic, prognostic, and therapeutic biomarkers of cardiovascular diseases (CVDs).

SOD1 suppresses maternal hyperglycemia-increased iNOS expression and consequent nitrosative stress in diabetic embryopathy

OBJECTIVE

Hyperglycemia induces oxidative stress and increases inducible nitric oxide synthase (iNOS) expression. We hypothesized that oxidative stress is responsible for hyperglycemia-induced iNOS expression.

STUDY DESIGN

iNOS-luciferase activities, nitrosylated protein, and lipid peroxidation markers 4-hydroxynonenal and malondialdehyde were determined in parietal yolk sac-2 cells exposed to 5 mmol/L glucose or high glucose (25 mmol/L) with or without copper zinc superoxide dismutase 1 (SOD1) treatment. Levels of iNOS protein and messenger RNA, nitrosylated protein, and cleaved caspase-3 and -8 were assessed in wild-type embryos and SOD1-overexpressing embryos from nondiabetic and diabetic dams.

RESULTS

SOD1 treatment diminished high glucose-induced oxidative stress, as evidenced by 4-hydroxynonenal and malondialdehyde reductions, and it blocked high glucose-increased iNOS expression, iNOS-luciferase activities, and nitrosylated protein. In vivo SOD1 overexpression suppressed hyperglycemia-increased iNOS expression and nitrosylated protein, and it blocked caspase-3 and -8 cleavage.

CONCLUSION

We conclude that oxidative stress induces iNOS expression, nitrosative stress, and apoptosis in diabetic embryopathy.

Linkage study of embryopathy-polygenic inheritance of diabetes-induced skeletal malformations in the rat

We developed an inbred rat model of diabetic embryopathy, in which the offspring displays skeletal malformations (agnathia or micrognathia) when the mother is diabetic, and no malformations when she is not diabetic. Our aim was to find genes controlling the embryonic maldevelopment in a diabetic environment. We contrasted the fetal outcome in inbred Sprague-Dawley L rats (20% skeletal malformations in diabetic pregnancy) with that of inbred Wistar Furth rats (denotedW, no skeletal malformations in diabetic pregnancy). We used offspring from the backcross F(1)×L to probe for the genetic basis for malformation of the mandible in diabetic pregnancy. A set of 186 fetuses (93 affected, 93 unaffected) was subjected to a whole genome scan with 160 micro satellites. Analysis of genotype distribution indicated 7 loci on chromosome 4, 10 (3 loci), 14, 18, and 19 in the teratogenic process (and 14 other loci on 12 chromosomes with less strong association to the malformations), several of which contained genes implicated in other experimental studies of diabetic embryopathy. These candidate genes will be scrutinized in further experimentation. We conclude that the genetic involvement in rodent diabetic embryopathy is polygenic and predisposing for congenital malformations.

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

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

Expression of TRX and TXNIP in patients with ulcerative colitis

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

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

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

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