Overexpression of thioredoxin-1 reduces oxidative stress in the placenta of transgenic mice and promotes fetal growth via glucose metabolism

Oxidative Stress in Pregnancy

Recent years have seen an increased interest in the role of oxidative stress (OS) in pregnancy. Pregnancy inherently heightens susceptibility to OS, a condition fueled by a systemic inflammatory response that culminates in an elevated presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the circulatory system. The amplified OS in pregnancy can trigger a series of detrimental outcomes such as underdevelopment, abnormal placental function, and a host of pregnancy complications, including pre-eclampsia, embryonic resorption, recurrent pregnancy loss, fetal developmental anomalies, intrauterine growth restriction, and, in extreme instances, fetal death. The body's response to mitigate the uncontrolled increase in RNS/ROS levels requires trace elements that take part in non-enzymatic and enzymatic defense processes, namely, copper (Cu), zinc (Zn), manganese (Mn), and selenium (Se). Determination of ROS concentrations poses a challenge due to their short half-lives, prompting the use of marker proteins, including malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), and glutathione (GSH). These markers, indicative of oxidative stress intensity, can offer indirect assessments of pregnancy complications. Given the limitations of conducting experimental studies on pregnant women, animal models serve as valuable substitutes for in-depth research. This review of such models delves into the mechanism of OS in pregnancy and underscores the pivotal role of OS markers in their evaluation.

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

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

Role of oxidative stress in the dysfunction of the placental endothelial nitric oxide synthase in preeclampsia

Preeclampsia (PE) is a multifactorial pregnancy disease, characterized by new-onset gestational hypertension with (or without) proteinuria or end-organ failure, exclusively observed in humans. It is a leading cause of maternal morbidity affecting 3–7% of pregnant women worldwide. PE pathophysiology could result from abnormal placentation due to a defective trophoblastic invasion and an impaired remodeling of uterine spiral arteries, leading to a poor adaptation of utero-placental circulation. This would be associated with hypoxia/reoxygenation phenomena, oxygen gradient fluctuations, altered antioxidant capacity, oxidative stress, and reduced nitric oxide (NO) bioavailability. This results in part from the reaction of NO with the radical anion superoxide (O₂^•−), which produces peroxynitrite ONOO^-, a powerful pro-oxidant and inflammatory agent. Another mechanism is the progressive inhibition of the placental endothelial nitric oxide synthase (eNOS) by oxidative stress, which results in eNOS uncoupling via several events such as a depletion of the eNOS substrate L-arginine due to increased arginase activity, an oxidation of the eNOS cofactor tetrahydrobiopterin (BH4), or eNOS post-translational modifications (for instance by S-glutathionylation). The uncoupling of eNOS triggers a switch of its activity from a NO-producing enzyme to a NADPH oxidase-like system generating O₂^•−, thereby potentiating ROS production and oxidative stress. Moreover, in PE placentas, eNOS could be post-translationally modified by lipid peroxidation-derived aldehydes such as 4-oxononenal (ONE) a highly bioreactive agent, able to inhibit eNOS activity and NO production. This review summarizes the dysfunction of placental eNOS evoked by oxidative stress and lipid peroxidation products, and the potential consequences on PE pathogenesis.

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Physiological ROS production is enhanced during pregnancy.

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eNOS is one of the main target of oxidative stress in PE placenta.

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eNOS is S-glutathionylated in PE placentas.

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eNOS is modified by lipid oxidation products in PE placentas.

Maternal selenium deficiency during pregnancy in mice increases thyroid hormone concentrations, alters placental function and reduces fetal growth

KEY POINTS

Inappropriate intake of key micronutrients in pregnancy is known to alter maternal endocrine status, impair placental development and induce fetal growth restriction. Selenium is an essential micronutrient required for the function of approximately 25 important proteins. However, the specific effects of selenium deficiency during pregnancy on maternal, placental and fetal outcomes are poorly understood. The present study demonstrates that maternal selenium deficiency increases maternal triiodothyronine and tetraiodothyronine concentrations, reduces fetal blood glucose concentrations, and induces fetal growth restriction. Placental expression of key selenium-dependent thyroid hormone converting enzymes were reduced, whereas the expression of key placental nutrient transporters was dysregulated. Selenium deficiency had minimal impact on selenium-dependent anti-oxidants but increased placental copper concentrations and expression of superoxide dismutase 1. These results highlight the idea that selenium deficiency during pregnancy may contribute to thyroid dysfunction, causing reduced fetal growth, that may precede programmed disease outcomes in offspring.

ABSTRACT

Selenium is a trace element fundamental to diverse homeostatic processes, including anti-oxidant regulation and thyroid hormone metabolism. Selenium deficiency in pregnancy is common and increases the risk of pregnancy complications including fetal growth restriction. Although altered placental formation may contribute to these poor outcomes, the mechanism by which selenium deficiency contributes to complications in pregnancy is poorly understood. Female C57BL/6 mice were randomly allocated to control (>190 µg kg-1 , n = 8) or low selenium (<50 µg kg-1 , n = 8) diets 4 weeks prior to mating and throughout gestation. Pregnant mice were killed at embryonic day 18.5 followed by collection of maternal and fetal tissue. Maternal and fetal plasma thyroid hormone concentrations were analysed, as was placental expression of key selenoproteins involved in thyroid metabolism and anti-oxidant defences. Selenium deficiency increased plasma tetraiodothyronine and triiodothyronine concentrations. This was associated with a reduction in placental expression of key selenodependent deiodinases, DIO2 and DIO3. Placental expression of selenium-dependent anti-oxidants was unaffected by selenium deficiency. Selenium deficiency reduced fetal glucose concentrations, leading to reduced fetal weight. Placental glycogen content was increased within the placenta, as was Slc2a3 mRNA expression. This is the first study to demonstrate that selenium deficiency may reduce fetal weight through increased maternal thyroid hormone concentrations, impaired placental thyroid hormone metabolism and dysregulated placental nutrient transporter expression. The study suggests that the magnitude of selenium deficiency commonly reported in pregnant women may be sufficient to impair thyroid metabolism but not placental anti-oxidant concentrations.

Stress-induced antioxidant defense and protein chaperone response in the freeze-tolerant wood frog Rana sylvatica

Freeze tolerance is an adaptive response utilized by the wood frog Rana sylvatica to endure the sub-zero temperatures of winter. Survival of whole body freezing requires wood frogs to trigger cryoprotective mechanisms to deal with potential injuries associated with conversion of 65-70% of total body water into ice, including multiple consequences of ice formation such as cessation of blood flow and cell dehydration caused by water loss into ice masses. To understand how wood frogs defend against these stressors, we measured the expression of proteins known to be involved in the antioxidant defense and protein chaperone stress responses in brain and heart of wood frogs comparing freezing, anoxia, and dehydration stress. Our results showed that most stress proteins were regulated in a tissue- and stress-specific manner. Notably, protein levels of the cytosolic superoxide dismutase (SOD1) were upregulated by 1.37 ± 0.11-fold in frozen brain, whereas the mitochondrial SOD2 isoform rose by 1.38 ± 0.37-fold in the heart during freezing. Catalase protein levels were upregulated by 3.01 ± 0.47-fold in the brain under anoxia stress, but remained unchanged in the heart. Similar context-specific regulatory patterns were also observed for the heat shock protein (Hsp) molecular chaperones. Hsp27 protein was down-regulated in the brain across the three stress conditions, whereas the mitochondrial Hsp60 was upregulated in anoxic brain by 1.73 ± 0.38-fold and by 2.13 ± 0.57-fold in the frozen heart. Overall, our study provides a snapshot of the regulatory expression of stress proteins in wood frogs under harsh environment conditions and shows that they are controlled in a tissue- and stress-specific manner.

Selenium deficiency-induced thioredoxin suppression and thioredoxin knock down disbalanced insulin responsiveness in chicken cardiomyocytes through PI3K/Akt pathway inhibition

Thioredoxin (Txn) system is the most crucial antioxidant defense mechanism in cell consisting of Txn, thioredoxin reductase (TR) and Nicotinamide Adenine Dinucleotide Phosphate (NADPH). Perturbations in Txn system may compromise cell survival through oxidative stress induction. Metabolic activity of insulin plays important roles in fulfilling the stable and persistent demands of heart through glucose metabolism. However, the roles of Txn and Txn system in insulin modulated cardiac energy metabolism have been less reported. Therefore, to investigate the role of Txn in myocardial metabolism, we developed a Se-deficient chicken model (0.033mg/kg) for in-vivo and Txn knock down cardiomyocytes culture model (siRNA) for in-vitro studies. Quantitative real time PCR and western blotting was performed. Se deficiency suppressed Txn and TR in cardiac tissues. Significant increases in ROS (P<0.05) levels signify the onset of oxidative stress and in both models. Se deficiency-induced Txn suppression model and Txn knock down cardiomyocytes models significantly decreased (P<0.05), the mRNA and protein levels of insulin-like growth factors (IGF1, IGF2), IGF-binding proteins (IGFBP2, IGFBP4), insulin receptor (IR), insulin receptor substrates (IRS1, IRS2), and glucose transporters (GLUT1, GLUT3, GLUT8), however, IGFBP3 expression increased in Txn knock down cardiomyocytes. In addition, in contrast to their respective controls, Se deficiency-induced Txn depleted tissues and Txn deleted cardiomyocytes showed suppression in mRNA and protein levels of PI3K, AKT, P-PI3K, and repression in FOX, P-FOX JNK genes. Combing the in vitro and in vivo experiments, we demonstrate that Txn gene suppression can cause dysfunction of insulin-modulated cardiac energy metabolism and increase insulin resistance through PI3K-Akt pathway inhibition. Herein, we conclude that inactivation of Txn system can alter cellular insulin response through IRS/PI3K/Akt pathway repression and JNK and FOX expression. These findings point out that Txn system can redox regulate the insulin dependent glucose metabolism in heart and is essential for cell vitality. Moreover, the increased expression of IGFBP3 indicates that it can be a potential negative modulator of metabolic activity of insulin in Txn deficient cells.

Hypoxia inhibits expression and function of mitochondrial thioredoxin 2 to promote pulmonary hypertension

Pulmonary hypertension (PH) is characterized by increased pulmonary vascular resistance, pulmonary vascular remodeling, and increased pulmonary vascular pressures that often result in right ventricular dysfunction, leading to right heart failure. Evidence suggests that reactive oxygen species (ROS) contribute to PH pathogenesis by altering pulmonary vascular cell proliferation and intracellular signaling pathways. However, the role of mitochondrial antioxidants and oxidant-derived stress signaling in the development of hypoxia-induced PH is largely unknown. Therefore, we examined the role of the major mitochondrial redox regulator thioredoxin 2 (Trx2). Levels of Trx2 mRNA and protein were examined in human pulmonary arterial endothelial cells (HPAECs) and smooth muscle cells (HPASMCs) exposed to hypoxia, a common stimulus for PH, for 72 h. Hypoxia decreased Trx2 mRNA and protein levels. In vitro overexpression of Trx2 reduced hypoxia-induced H₂O₂ production. The effects of increased Trx2 protein level were examined in transgenic mice expressing human Trx2 (Tg^hTrx2) that were exposed to hypoxia (10% O₂) for 3 wk. Tg^hTrx2 mice exposed to hypoxia had exacerbated increases in right ventricular systolic pressures, right ventricular hypertrophy, and increased ROS in the lung tissue. Trx2 overexpression did not attenuate hypoxia-induced increases in Trx2 oxidation or Nox4 expression. Expression of a dominant negative C93S Trx2 mutant that mimics Trx2 oxidation exacerbated hypoxia-induced increases in HPASMC H₂O₂ levels and cell proliferation. In conclusion, Trx2 overexpression failed to attenuate hypoxia-induced HPASMC proliferation in vitro or hypoxia-induced PH in vivo. These findings indicate that strategies to enhance Trx2 expression are unlikely to exert therapeutic effects in PH pathogenesis.

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.

Potential role of recombinant adeno-associated virus human thioredoxin-PR39 in cell and vascular protection against hypoxia

The aim of the present study was to successfully construct a recombinant adeno-associated virus (rAAV) vector containing the human thioredoxin (hTRX)-PR39 chimeric gene (rAAV/hTRX-PR39), and verify that the vector was able to maintain a sustained, stable and efficient expression to achieve protein production in the cell. In the present study, a chicken embryo model was utilized to analyze the therapeutical effect of rAAV/hTRX-PR39 in cerebral ischemia diseases. ECV304 cells were transfected with rAAV/hTRX-PR39 and incubated under conditions of 20, 5 and 1% O₂. Subsequently, the expression levels of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, fibroblast growth factor receptor (FGFR)-1 and syndecan-4 were detected by reverse transcription-quantitative polymerase chain reaction. Under hypoxic conditions, the mRNA expression levels of VEGF, VEGFR-1, VEGFR-2, FGFR-1 and syndecan-4 were found to increase in the PR39-transfected group when compared with the control group, while no statistically significant difference was observed between the PR39-transfected group and the control group under conditions of 20% O₂. In addition, hTRX-PR39 was shown to increase the density of the vasculature and the survival rate of the chick embryos. Under hypoxic conditions, it was hypothesized that rAAV/hTRX-PR39 was capable of promoting angiogenesis, which may subsequently protect the cells from impairment by hypoxia. In conclusion, rAAV/hTRX-PR39 was demonstrated to promote vascularization and cell survival in hypoxia; thus, rAAV/hTRX-PR39 may have potential for use in therapy targeting cerebral ischemia.

A maternal mouse diet with moderately high-fat levels does not lead to maternal obesity but causes mesenteric adipose tissue dysfunction in male offspring

The impact of an increase in maternal fat consumption on fetal metabolic programming separately from maternal obesity remains unclear. The purpose of this study was to document the effect of in utero high-fat diet exposure on the development of metabolic syndrome characteristics in offspring. C57BL/6 female mice were fed either a control diet (10% fat) or a moderately high-fat (MHF) diet (45% fat) until delivery. All pups were fostered to mothers fed with the control diet. Pups were raised on the control diet and assessed until 35 weeks of age. The caloric intake from fat was significantly increased in the MHF dams compared with the control dams. There were no significant differences in the maternal weight at mating or at gestational Day 18 between the two groups. The MHF offspring did not become obese, but they developed hypertension and glucose intolerance. Moreover, the MHF offspring had significantly higher serum non-esterified fatty acid and triglyceride levels during the refeeding state following fasting as compared with the control offspring. Serum adiponectin levels were significantly lower, and the cell size of the mesenteric adipose tissue was significantly larger in the MHF offspring than in the control offspring. The mRNA levels of the proinflammatory macrophage markers in the mesenteric adipose tissue were significantly higher in the MHF offspring than those of the control offspring. These results suggest that in utero high-fat diet exposure causes hypertension and glucose intolerance resulting from mesenteric adipose tissue dysfunction in offspring, independently of maternal obesity.

Maternal dietary omega-3 fatty acids and placental function

The developing fetus requires substantial amounts of fatty acids to support rapid cellular growth and activity. Although the fatty acid composition delivered to the fetus is largely determined by maternal circulating levels, the placenta preferentially transfers physiologically important long-chain polyunsaturated fatty acids (LC-PUFAs), particularly omega-3 (n-3) PUFAs. Maternal dietary supplementation with n-3 PUFAs during pregnancy has been shown to increase gestation length, enhance fetal growth, and reduce the risk of pregnancy complications, although the precise mechanisms governing these effects remain uncertain. Omega-3 PUFAs are involved in several physiological pathways which could account for these effects, including anti-inflammatory, pro-resolving, and anti-oxidative pathways. Recent studies have shown that maternal dietary n-3 PUFA supplementation during rat pregnancy can reduce placental oxidative damage and increase placental levels of pro-resolving mediators, effects associated with enhanced fetal and placental growth. Because several placental disorders, such as intrauterine growth restriction, preeclampsia, and gestational diabetes mellitus, are associated with heightened placental inflammation and oxidative stress, there is considerable interest in the potential for dietary n-3 PUFAs as a therapeutic intervention for these disorders. In this study, we review the impact of dietary n-3 PUFAs on placental function, with particular focus on placental inflammation, inflammatory resolution, and oxidative stress.

Maternal omega-3 fatty acid intake increases placental labyrinthine antioxidant capacity but does not protect against fetal growth restriction induced by placental ischaemia-reperfusion injury

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders. Oxidative stress occurs when excess reactive oxygen species (ROS) damages cellular components, an outcome limited by antioxidant enzymes; mitochondrial uncoupling protein 2 (UCP2) also limits ROS production. We recently reported that maternal dietary omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation reduced placental oxidative damage and enhanced fetal and placental growth in the rats. Here, we examined the effect of n-3 PUFAs on placental antioxidant defences and whether n-3 PUFA supplementation could prevent growth restriction induced by placental ischaemia-reperfusion (IR), a known inducer of oxidative stress. Rats were fed either standard or high-n-3 PUFA diets from day 1 of pregnancy. Placentas were collected on days 17 and 22 in untreated pregnancies (term=day 23) and at day 22 following IR treatment on day 17. Expression of several antioxidant enzyme genes (Sod1, Sod2, Sod3, Cat, Txn1 and Gpx3) and Ucp2 was measured by quantitative RT-PCR in the placental labyrinth zone (LZ) and junctional zone (JZ). Cytosolic superoxide dismutase (SOD), mitochondrial SOD and catalase (CAT) activities were also analyzed. Maternal n-3 PUFA supplementation increased LZ mRNA expression of Cat at both gestational days (2- and 1.5-fold respectively; P<0.01) and female Sod2 at day 22 (1.4-fold, P<0.01). Cytosolic SOD activity increased with n-3 PUFA supplementation at day 22 (1.3-fold, P<0.05). Sod1 and Txn1 expression decreased marginally (30 and 22%, P<0.05). JZ antioxidant defences were largely unaffected by diet. Despite increased LZ antioxidant defences, maternal n-3 PUFA supplementation did not protect against placental IR-induced growth restriction of the fetus and placental LZ.

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.

Maternal high-fat diets cause insulin resistance through inflammatory changes in fetal adipose tissue

OBJECTIVES

Epidemiological and animal studies have shown that maternal obesity predisposes the offspring to obesity and the metabolic syndrome, possibly via late-onset metabolic programming of the fetus. Little is known, however, about the metabolic effect of maternal obesity on the fetus. This study investigated the effect of a maternal high-fat diet (HFD) on fetal growth and glucose metabolism using a diet-induced obesity mouse model.

STUDY DESIGN

Female mice (6 weeks old; C57BL/6N) were fed either a normal chow diet (NCD, 10 kcal% fat) or an HFD (60 kcal% fat) for 4 weeks before mating and throughout pregnancy. At 17 days of gestation, gene expression of inflammatory markers and adipokines in fetal subcutaneous adipose tissue was analyzed by quantitative real-time polymerase chain reaction.

RESULTS

HFD mice were overweight, glucose intolerant and insulin resistant compared with NCD mice of the same gestational age. Although fetal body weight was not significantly different, fetal plasma glucose and insulin levels were higher in the HFD group than the NCD group. Furthermore, examination of fetal subcutaneous adipose tissue in the HFD group revealed hypertrophy with an increase in the levels of cluster of differentiation-68, chemokine receptor-2 and tumor necrosis factor-α mRNA, but a decrease in the level of glucose transporter-4 mRNA.

CONCLUSION

Maternal HFD causes inflammatory changes in the adipose tissue of offspring.

Maternal dietary omega-3 fatty acid supplementation reduces placental oxidative stress and increases fetal and placental growth in the rat

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders including intrauterine growth restriction. Oxidative stress occurs when accumulation of reactive oxygen species damages DNA, proteins, and lipids, an outcome normally limited by antioxidant defenses. Dietary supplementation with omega-3 polyunsaturated fatty acids (n-3 PUFAs) may limit oxidative stress by increasing antioxidant capacity, but n-3 PUFAs are also highly susceptible to lipid peroxidation; so n-3 PUFA supplementation is potentially harmful. Here we examined the effect of n-3 PUFAs on placental oxidative stress and on placental and fetal growth in the rat. We also investigated whether diet-induced changes in maternal plasma fatty acid profiles are associated with comparable changes in placental and fetal tissues. Rats were fed either standard or high n-3 PUFA diets from Day 1 of pregnancy, and tissues were collected on Day 17 or 22 (term = Day 23). Dietary supplementation with n-3 PUFAs increased fetal (6%) and placental (12%) weights at Day 22, the latter attributable primarily to growth of the labyrinth zone (LZ). Increased LZ weight was accompanied by reduced LZ F(2)-isoprostanes (by 31% and 11% at Days 17 and 22, respectively), a marker of oxidative damage. Maternal plasma PUFA profiles were altered by dietary fatty acid intake and were strongly predictive of corresponding profiles in placental and fetal tissues. Our data indicate that n-3 PUFA supplementation reduces placental oxidative stress and enhances placental and fetal growth. Moreover, fatty acid profiles in the mother, placenta, and fetus are highly dependent on dietary fatty acid intake.

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.

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).

Hypoxanthine-xanthine oxidase down-regulates GLUT1 transcription via SIRT1 resulting in decreased glucose uptake in human placenta

Appropriate foetal growth and development is dependent on adequate placental glucose uptake. Oxidative stress regulates glucose uptake in various tissues. The effect of oxidative stress on placental glucose transport is not known. Thus, the aim of this study was to determine the effect of oxidative stress on glucose uptake and glucose transporters (GLUTs) in human placenta. Human placenta was incubated in the absence or presence of 0.5 mM hypoxanthine+15 mU/ml xanthine oxidase (HX/XO) for 24 h. Gene and protein expressions of the GLUTs were analysed by quantitative RT-PCR and western blotting respectively. Glucose uptake was measured using radiolabelled ((14)C) glucose. HX/XO significantly decreased GLUT1 gene and protein expression and resultant glucose uptake. There was no effect of the antioxidants N-acetylcysteine, catalase and superoxide dismutase or the NF-κB inhibitor BAY 11-0782 on HX/XO-induced decrease in glucose uptake. However, HX/XO treatment significantly decreased both gene and protein expression of SIRT1. In the presence of the SIRT1 activator resveratrol, the decrease in GLUT1 expression and glucose uptake mediated by HX/XO was abolished. Collectively, the data presented here demonstrate that oxidative stress reduces placental glucose uptake and GLUT1 expression by a SIRT1-dependent mechanism.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Depletion of cytosolic or mitochondrial thioredoxin increases CYP2E1-induced oxidative stress via an ASK-1-JNK1 pathway in HepG2 cells

Thioredoxin is an important reducing molecule in biological systems. Increasing CYP2E1 activity induces oxidative stress and cell toxicity. However, whether thioredoxin protects cells against CYP2E1-induced oxidative stress and toxicity is unknown. SiRNA were used to knockdown either cytosolic (TRX-1) or mitochondrial thioredoxin (TRX-2) in HepG2 cells expressing CYP2E1 (E47 cells) or without expressing CYP2E1 (C34 cells). Cell viability decreased 40-60% in E47 but not C34 cells with 80-90% knockdown of either TRX-1 or TRX-2. Depletion of either thioredoxin also potentiated the toxicity produced either by a glutathione synthesis inhibitor or by TNFα in E47 cells. Generation of reactive oxygen species and 4-HNE protein adducts increased in E47 but not C34 cells with either thioredoxin knockdown. GSH was decreased and adding GSH completely blocked E47 cell death induced by either thioredoxin knockdown. Lowering TRX-1 or TRX-2 in E47 cells caused an early activation of ASK-1, followed by phosphorylation of JNK1 after 48 h of siRNA treatment. A JNK inhibitor caused a partial recovery of E47 cell viability after thioredoxin knockdown. In conclusion, knockdown of TRX-1 or TRX-2 sensitizes cells to CYP2E1-induced oxidant stress partially via ASK-1 and JNK1 signaling pathways. Both TRX-1 and TRX-2 are important for defense against CYP2E1-induced oxidative stress.

Reactive oxygen species: A radical role in development?

Reactive oxygen species (ROS), mostly derived from mitochondrial activity, can damage various macromolecules and consequently cause cell death. This ROS activity has been characterized in vitro, and correlative evidence suggests a role in various pathological conditions. In addition to this passive ROS activity, ROS also participate in cell signaling processes, though the relevance of this function in vivo is poorly understood. Throughout development, elevated cell activity is probably accompanied by highly active metabolism and, consequently, the production of large amounts of ROS. To allow proper development, cells must protect themselves from these potentially damaging ROS. However, to what degree ROS could participate as signaling molecules controlling fundamental and developmentally relevant cellular processes such as proliferation, differentiation, and death is an open question. Here we discuss why available data do not yet provide conclusive evidence on the role of ROS in development, and we review recent methods to detect ROS in vivo and genetic strategies that can be exploited specifically to resolve these uncertainties.

Antioxidant defenses in the rat placenta in late gestation: increased labyrinthine expression of superoxide dismutases, glutathione peroxidase 3, and uncoupling protein 2

Placental oxidative stress plays a key role in the pathophysiology of placenta-related disorders, most notably preeclampsia (PE) and intrauterine growth restriction (IUGR). Oxidative stress occurs when accumulation of reactive oxygen species (ROS) damages DNA, proteins and lipids, an outcome that is limited by antioxidant enzymes; mitochondrial uncoupling protein 2 (UCP2) may also limit oxidative stress by reducing ROS production. Here we characterized placental antioxidant defenses during normal gestation and following glucocorticoid-induced IUGR. Placentas were collected on Days 16 and 22 of normal rat pregnancy (term = Day 23) and at Day 22 after dexamethasone treatment from Day 13. Expression of several genes encoding antioxidant enzymes (Sod1, Sod2, Sod3, Cat, Gpx3, Txn1, Txnrd1, Txnrd2, and Txnrd3) and Ucp2 was measured by quantitative RT-PCR in the labyrinth (LZ) and junctional zones (JZ) of the placenta. Expression of Sod1 and Ucp2 mRNAs and the activity of xanthine oxidase, a source of ROS, all increased from Days 16 to 22 in both placental zones, whereas Sod2 and Gpx3 increased only in the rapidly growing LZ. In contrast, Sod3 and Txnrd1 expression fell in the LZ over this period, whereas total superoxide dismutase activity remained stable. Dexamethasone treatment reduced fetal-placental growth and LZ expression of Ucp2 but increased JZ expression of Txn1. Indices of placental oxidative damage (TBARS, F(2)-isoprostanes, and 8-OHdG) did not change with gestational age or dexamethasone, indicative of adequate antioxidant protection. Overall, our data suggest that the rat placenta is protected from oxidative stress by the dynamic zone- and stage-dependent expression of antioxidant defense genes.

Hyperglycemia perturbs biochemical networks in human trophoblast BeWo cells

Determining the effects of hyperglycemia on gene expression in placental trophoblast is important to gain a better understanding of how diabetes adversely affects pregnancy. In this study, we examined whether exposure to high glucose during forskolin-induced differentiation affects gene expression in differentiated trophoblasts. Human trophoblast BeWo cells were differentiated under low glucose (LG: 11 mM) or high glucose (HG: 25 mM) conditions. Gene expression was analyzed using a GeneChip system and the obtained data were analyzed using Ingenuity Pathways Analysis. In HG conditions, there were marked alterations in gene expression in differentiated BeWo cells compared with LG conditions. In particular, BeWo cells responded to HG with major changes in the expression levels of cell cycle- and metabolism-related genes. We selected the aromatase gene for further investigation of the molecular mechanisms. Mannitol or 3-O-methylglucose did not mimic the expression changes caused by HG, indicating that the effect of glucose was not due to a difference in osmotic pressure, and that glucose metabolism plays an essential role in inducing the HG effects. Cotreatment with N-acetylcysteine reduced the effect of HG on aromatase gene expression, suggesting that hyperglycemia may perturb biochemical networks because of the elevation of oxidative stress. Overall, our results will aid further understanding of the effect of diabetes on the regulation of trophoblast differentiation and function.

Placental efficiency and adaptation: endocrine regulation

Size at birth is critical in determining life expectancy and is dependent primarily on the placental supply of nutrients. However, the fetus is not just a passive recipient of nutrients from the placenta. It exerts a significant acquisitive drive for nutrients, which acts through morphological and functional adaptations in the placenta, particularly when the genetically determined drive for fetal growth is compromised by adverse intrauterine conditions. These adaptations alter the efficiency with which the placenta supports fetal growth, which results in optimal growth for prevailing conditions in utero. This review examines placental efficiency as a means of altering fetal growth, the morphological and functional adaptations that influence placental efficiency and the endocrine regulation of these processes.

High-fat diet before and during pregnancy causes marked up-regulation of placental nutrient transport and fetal overgrowth in C57/BL6 mice

Maternal overweight and obesity in pregnancy often result in fetal overgrowth, which increases the risk for the baby to develop metabolic syndrome later in life. However, the mechanisms underlying fetal overgrowth are not established. We developed a mouse model and hypothesized that a maternal high-fat (HF) diet causes up-regulation of placental nutrient transport, resulting in fetal overgrowth. C57BL/6J female mice were fed a control (11% energy from fat) or HF (32% energy from fat) diet for 8 wk before mating and throughout gestation and were studied at embryonic day 18.5. The HF diet increased maternal adiposity, as assessed by fat pad weight, and circulating maternal leptin, decreased serum adiponectin concentrations, and caused a marked increase in fetal growth (+43%). The HF diet also increased transplacental transport of glucose (5-fold) and neutral amino acids (10-fold) in vivo. In microvillous plasma membranes (MVMs) isolated from placentas of HF-fed animals, protein expression of glucose transporter 1 (GLUT1) was increased 5-fold, and protein expression of sodium-coupled neutral amino acid transporter (SNAT) 2 was elevated 9-fold. In contrast, MVM protein expression of GLUT 3 or SNAT4 was unaltered. These data suggest that up-regulation of specific placental nutrient transporter isoforms constitute a mechanism linking maternal high-fat diet and obesity to fetal overgrowth.