A role for Nrf2 in redox signalling of the invasive extravillous trophoblast in severe early onset IUGR associated with preeclampsia

Nrf2 deficiency exacerbated pulmonary pyroptosis in maternal hypoxia-induced intrauterine growth restriction offspring mice

Maternal prenatal hypoxia is an important contributor to intrauterine growth restriction (IUGR), which impedes fetal lung maturation and leads to the development of chronic lung diseases. Although evidence suggests the involvement of pyroptosis in IUGR, the molecular mechanism of pyroptosis is still unclear. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been found to potentially interact with gasdermin D (GSDMD), the key protein responsible for pyroptosis, indicating its crucial role in inhibiting pyroptosis. Therefore, we hypothesized that Nrf2 deficiency is a key molecular responsible for lung pyroptosis in maternal hypoxia-induced IUGR offspring mice. Pregnant WT and Nrf2-/- mice were exposed to hypoxia (10.5 % O2) to mimic IUGR model. We assessed body weight, lung histopathology, pulmonary angiogenesis, oxidative stress levels, as well as mRNA and protein expressions related to inflammation in the 2-week-old offspring. Additionally, we conducted a dual-luciferase reporter assay to confirm the targeting relationship between Nrf2 and GSDMD. Our findings revealed that offspring with maternal hypoxia-induced IUGR exhibited reduced birth weight, catch-up growth delay, and pulmonary dysplasia. Furthermore, we observed impaired nuclear translocation of Nrf2 and increased GSDMD-mediated pyroptosis in these offspring with IUGR. Moreover, the dual-luciferase reporter assay demonstrated that Nrf2 could directly inhibit GSDMD transcription; deficiency of Nrf2 exacerbated pyroptosis and pulmonary dysplasia in offspring with maternal hypoxia-induced IUGR. Collectively, our findings suggest that Nrf2 deficiency induces GSDMD-mediated pyroptosis and pulmonary dysplasia in offspring with maternal hypoxia-induced IUGR; thus highlighting the potential therapeutic approach of targeting Nrf2 for treating prenatal hypoxia-induced pulmonary dysplasia in offspring.

The Nitrate-Nitrite-Nitric Oxide Pathway: Potential Role in Mitigating Oxidative Stress in Hypertensive Disorders of Pregnancy

Hypertensive diseases of pregnancy (HDPs) represent a global clinical challenge, affecting 5-10% of women and leading to complications for both maternal well-being and fetal development. At the heart of these complications is endothelial dysfunction, with oxidative stress emerging as a pivotal causative factor. The reduction in nitric oxide (NO) bioavailability is a vital indicator of this dysfunction, culminating in blood pressure dysregulation. In the therapeutic context, although antihypertensive medications are commonly used, they come with inherent concerns related to maternal-fetal safety, and a percentage of women do not respond to these therapies. Therefore, alternative strategies that directly address the pathophysiology of HDPs are required. This article focuses on the potential of the nitrate-nitrite-NO pathway, abundantly present in dark leafy greens and beetroot, as an alternative approach to treating HDPs. The objective of this review is to discuss the prospective antioxidant role of nitrate. We hope our discussion paves the way for using nitrate to improve endothelial dysfunction and control oxidative stress, offering a potential therapy for managing HDPs.

The influence of Nrf2 gene promoter methylation on gene expression and oxidative stress parameters in preeclampsia

BACKGROUND AND AIMS

Preeclampsia (PE) is a serious medical condition that usually causes high blood pressure and affects multiple organs. Considering the adverse effect of oxidative stress on the process of PE in pregnant women and regarding the role of the Nrf2 gene in placental oxidative pathways, this study was conducted to investigate the DNA methylation status of Nrf2 in PE and healthy pregnant women.

MATERIALS AND METHODS

The present case-control study consisted of 70 PE and 70 healthy pregnant women. Blood and placenta samples were taken from all subjects, and the percentage of the Nrf2 gene methylation in the samples was assessed by the Methyl Light PCR method. Also, the Nrf2 gene expression was evaluated by real-time PCR. The total antioxidant capacity (TAC) and total oxidative status (TOS) were measured by the colorimetric method.

RESULTS

In PE women, there was a significant increase in blood pressure, term of pregnancy, and BMI. In addition, there were enhanced Nrf2 DNA methylation percentage in placenta tissue and increased TOS levels in placenta tissue and blood compared to healthy pregnant women (P < 0.05). Also, in the PE group, there was a significant decrease in Nrf2 gene expression and TAC level in placenta tissue compared to the control group (P < 0.05).

CONCLUSION

The Nrf2 gene undergoes epigenetic modifications of DNA hypermethylation in the PE placenta. Decreased expression of this gene and the changes in the level of oxidative parameters (TAC, TOS) confirm it.

Gene-network based analysis of human placental trophoblast subtypes identifies critical genes as potential targets of therapeutic drugs

During early pregnancy, extravillous trophoblasts (EVTs) play a crucial role in modifying the maternal uterine environment. Failures in EVT lineage formation and differentiation can lead to pregnancy complications such as preeclampsia, fetal growth restriction, and pregnancy loss. Despite recent advances, our knowledge on molecular and external factors that control and affect EVT development remains incomplete. Using trophoblast organoid in vitro models, we recently discovered that coordinated manipulation of the transforming growth factor beta (TGFβ) signaling is essential for EVT development. To further investigate gene networks involved in EVT function and development, we performed weighted gene co-expression network analysis (WGCNA) on our RNA-Seq data. We identified 10 modules with a median module membership of over 0.8 and sizes ranging from 1005 (M1) to 72 (M27) network genes associated with TGFβ activation status or in vitro culturing, the latter being indicative for yet undiscovered factors that shape the EVT phenotypes. Lastly, we hypothesized that certain therapeutic drugs might unintentionally interfere with placentation by affecting EVT-specific gene expression. We used the STRING database to map correlations and the Drug-Gene Interaction database to identify drug targets. Our comprehensive dataset of drug-gene interactions provides insights into potential risks associated with certain drugs in early gestation.

Iron metabolism and ferroptosis: A pathway for understanding preeclampsia

Preeclampsia (PE) is a serious medical condition that poses a significant health risk to women and children worldwide, particularly in the middle- and low-income countries. It is a complex syndrome that occurs as a result of abnormal pregnancy. Hypertension is the most common symptom of PE, with proteinuria and specific organ systems as detrimental targets. PE's pathogenesis is diverse, and its symptoms can overlap with other diseases. In early pregnancy, when the placenta takes over control, oxidative stress may be closely associated with ferroptosis, a type of cell death caused by intracellular iron accumulation. Ferroptosis in the placenta is defined by redox-active iron availability, loss of antioxidant capacity and phospholipids containing polyunsaturated fatty acids (PUFA) oxidation. Recent studies suggest a compelling potential link between ferroptosis and PE. In this article, we comprehensively review the current understanding of PE and discuss one of its emerging underlying mechanisms, the ferroptosis pathway. We also provide perspective and analysis on the implications of this process in the diagnosis, prevention, and treatment of preeclampsia. We aim to bridge the gap between clinicians and basic scientists in understanding this harmful disease and challenge the research community to put more effort into this exciting new area.

The role of placental aging in adverse pregnancy outcomes: A mitochondrial perspective

Premature placental aging is associated with placental insufficiency, which reduces the functional capacity of the placenta, leading to adverse pregnancy outcomes. Placental mitochondria are vital organelles that provide energy and play essential roles in placental development and functional maintenance. In response to oxidative stress, damage, and senescence, an adaptive response is induced to selectively remove mitochondria through the mitochondrial equivalent of autophagy. However, adaptation can be disrupted when mitochondrial abnormalities or dysfunctions persist. This review focuses on the adaptation and transformation of mitochondria during pregnancy. These changes modify placental function throughout pregnancy and can cause complications. We discuss the relationship between placental aging and adverse pregnancy outcomes from the perspective of mitochondria and potential approaches to improve abnormal pregnancy outcomes.

Modulation of NRF2/KEAP1 Signaling in Preeclampsia

Placentation is a key and tightly regulated process that ensures the normal development of the placenta and fetal growth. Preeclampsia (PE) is a hypertensive pregnancy-related disorder involving about 5-8% of all pregnancies and clinically characterized by de novo maternal hypertension and proteinuria. In addition, PE pregnancies are also characterized by increased oxidative stress and inflammation. The NRF2/KEAP1 signaling pathway plays an important role in protecting cells against oxidative damage due to increased reactive oxygen species (ROS) levels. ROS activate NRF2, allowing its binding to the antioxidant response element (ARE) region present in the promoter of several antioxidant genes such as heme oxygenase, catalase, glutathione peroxidase and superoxide dismutase that neutralize ROS, protecting cells against oxidative stress damages. In this review, we analyze the current literature regarding the role of the NRF2/KEAP1 pathway in preeclamptic pregnancies, discussing the main cellular modulators of this pathway. Moreover, we also discuss the main natural and synthetic compounds that can regulate this pathway in in vivo and in vitro models.

Monosomy X in isogenic human iPSC-derived trophoblast model impacts expression modules preserved in human placenta

Mammalian sex chromosomes encode homologous X/Y gene pairs that were retained on the Y chromosome in males and escape X chromosome inactivation (XCI) in females. Inferred to reflect X/Y pair dosage sensitivity, monosomy X is a leading cause of miscarriage in humans with near full penetrance. This phenotype is shared with many other mammals but not the mouse, which offers sophisticated genetic tools to generate sex chromosomal aneuploidy but also tolerates its developmental impact. To address this critical gap, we generated X-monosomic human induced pluripotent stem cells (hiPSCs) alongside otherwise isogenic euploid controls from male and female mosaic samples. Phased genomic variants in these hiPSC panels enable systematic investigation of X/Y dosage-sensitive features using in vitro models of human development. Here, we demonstrate the utility of these validated hiPSC lines to test how X/Y-linked gene dosage impacts a widely used model for human syncytiotrophoblast development. While these isogenic panels trigger a GATA2/3- and TFAP2A/C-driven trophoblast gene circuit irrespective of karyotype, differential expression implicates monosomy X in altered levels of placental genes and in secretion of placental growth factor (PlGF) and human chorionic gonadotropin (hCG). Remarkably, weighted gene coexpression network modules that significantly reflect these changes are also preserved in first-trimester chorionic villi and term placenta. Our results suggest monosomy X may skew trophoblast cell type composition and function, and that the combined haploinsufficiency of the pseudoautosomal region likely plays a key role in these changes.

Divergent Regulation of Decidual Oxidative-Stress Response by NRF2 and KEAP1 in Preeclampsia with and without Fetal Growth Restriction

Utero-placental development in pregnancy depends on direct maternal–fetal interaction in the uterine wall decidua. Abnormal uterine vascular remodeling preceding placental oxidative stress and placental dysfunction are associated with preeclampsia and fetal growth restriction (FGR). Oxidative stress is counteracted by antioxidants and oxidative repair mechanisms regulated by the transcription factor nuclear factor erythroid 2-related factor 2 (NRF2). We aimed to determine the decidual regulation of the oxidative-stress response by NRF2 and its negative regulator Kelch-like ECH-associated protein 1 (KEAP1) in normal pregnancies and preeclamptic pregnancies with and without FGR. Decidual tissue from 145 pregnancies at delivery was assessed for oxidative stress, non-enzymatic antioxidant capacity, cellular NRF2- and KEAP1-protein expression, and NRF2-regulated transcriptional activation. Preeclampsia combined with FGR was associated with an increased oxidative-stress level and NRF2-regulated gene expression in the decidua, while decidual NRF2- and KEAP1-protein expression was unaffected. Although preeclampsia with normal fetal growth also showed increased decidual oxidative stress, NRF2-regulated gene expression was reduced, and KEAP1-protein expression was increased in areas of high trophoblast density. The trophoblast-dependent KEAP1-protein expression in preeclampsia with normal fetal growth indicates control of decidual oxidative stress by maternal–fetal interaction and underscores the importance of discriminating between preeclampsia with and without FGR.

Nrf2 rs6721961 and Oxidative Stress in Preeclampsia: Association with the Risk of Preeclampsia and Early-Onset Preeclampsia

Preeclampsia as a multifactor hypertensive disorder of pregnancy is associated with enhanced placental oxidative stress. The Keap1-Nrf2 pathway protects cells against oxidative stress. We examined the possible association between the Nrf2 variants in relation to oxidative stress parameters with the risk of preeclampsia. We studied 150 preeclampsia women and 150 women with a normal pregnancy to find the frequency of Nrf2 rs6721961 genotypes using the PCR-RFLP method. Also, an association between the Nrf2 genotypes with the levels of malondialdehyde (MDA) and total antioxidant capacity (TAC) was analyzed. Significantly lower TAC and higher MDA levels were found in preeclampsia patients compared to controls (P<0.0001). For the first time, we report an association between the Nrf2 rs6721961 polymorphism and preeclampsia risk. The present study indicated that the GT genotype and the T allele of the Nrf2 rs6721961 increased the risk of preeclampsia by 2.81 and 2.39 times, respectively. Also, the Nrf2 TT genotype was associated with a 3.9-fold increased risk of early-onset preeclampsia. We detected a positive association between the levels of body mass index, MDA, and the Nrf2 polymorphism with the risk of preeclampsia and a negative correlation between the level of TAC with the preeclampsia risk. Also, an association between the rs6721961 TT genotype with higher serum MDA levels was found. Our study suggests oxidative stress is involved in the pathogenesis of preeclampsia and the Nrf2 rs6721961 polymorphism through alteration in the levels of oxidative stress parameters might increase the risk of preeclampsia and early-onset preeclampsia.

Combined apocyanin and aspirin treatment activates the PI3K/Nrf2/HO-1 signaling pathway and ameliorates preeclampsia symptoms in rats

OBJECTIVE

Pre-eclampsia (PE) is a pregnancy-associated disease characterized by placental dysfunction and increased oxidative stress. Apocyanin is a potent antioxidant and anti-inflammatory which has shown beneficial effects on PE pathogenesis. Aspirin is recognized as the recommendable drug in PE prevention and therapy. Therefore, we aimed to investigate the effects of combining apocyanin and aspirin to treat PE on rat models induced by N-nitro-L-arginine methyl ester (L-NAME) from gestational day (GD) 6 to 16 and elucidate the potential mechanisms.

METHODS

First, female pregnant rats were divided into five different groups: pregnant control, PE, PE + apocyanin, PE + aspirin, and PE + apocyanin + aspirin. Animals received apocyanin (16 mg/kg/day) orally or aspirin by gavage (1.5 mg/kg BM/day) from GD 4 to 16. Blood pressure and urine protein content were monitored every 4 days.

RESULTS

In the PE rat model, elevated systolic blood pressure and proteinuria were ameliorated by the combination of apocyanin and aspirin. Meanwhile, compared with single-dose apocyanin or aspirin, the combined treatment significantly corrected abnormal pregnancy outcomes, decreased sFlt-1 and PlGF, and alleviated oxidative stress both in blood and placental tissues. Moreover, the combined treatment upregulated PI3K, Akt, Nrf2, and HO-1 protein levels in the placental tissues from PE rats.Conclusion: Overall, our results suggested that combined treatment of apocyanin and aspirin ameliorates the PE symptoms compared with single-dose apocyanin or aspirin in a PE rat model. Also, we demonstrated that activating the PI3K/Nrf2/HO-1 pathway can be a valuable therapeutic target to improve the pregnancy outcomes of PE.

The role of nuclear factor erythroid 2-related factor 2 (NRF2) in normal and pathological pregnancy: A systematic review

OBJECTIVE

A homeostatic balance between reactive oxygen species production and the antioxidant redox system is an important component of normal pregnancy. Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) preserves cellular homeostasis by enhancing the cell's innate antioxidant status to reduce oxidative stress and inflammatory damage to the cell during pregnancy. Active Nrf2, in the nucleus of the cell, transactivates various antioxidant genes. The objective of this systematic review was to synthesize evidence on the role of Nrf2 in various adverse pregnancy outcomes (APOs).

METHODS

We conducted a systematic review of the role of Nrf2 in pregnancy. Articles written in English, Portuguese, and Spanish were obtained from three different databases from inception until January 2021. The titles, abstracts and full text were reviewed independently by six reviewers. The quality of the included studies was assessed using a quality assessment tool developed to assess basic science and clinical studies. Nrf2 expression (gene and protein), functional contributions, and association with APOs were assessed.

RESULTS

A total of 747 citations were identified; 80 were retained for full review. Most studies on Nrf2 have been carried out using placental tissues and placenta-derived cells. Limited studies have been conducted using fetal membranes, uterus, and cervix. Nuclear translocation of Nrf2 results in transactivation of antioxidant enzymes, including glutathione peroxidase, hemeoxygenase-1, and superoxide dismutase in gestational cells during pregnancy. This antioxidant response maintains cellular homeostasis during pregnancy. This promotes trophoblast cell survival and prevents cell death and abnormal angiogenesis in the placenta. Excessive and insufficient Nrf2 response may promote oxidative and reductive stress, respectively. This Nrf2 dysregulation has been associated with APOs including gestational diabetes mellitus, intrauterine growth restriction, reproductive toxicity, preeclampsia, and preterm birth.

CONCLUSION

Several studies have localized and reported an association between Nrf2's differential expression in reproductive tissues and the pathogenesis of APOs. However, a comprehensive functional understanding of Nrf2 in reproductive tissues is still lacking. Nrf2's activation and functions are complex, and therefore, current in vitro and in vivo studies are limited in their experimental approaches. We have identified key areas for future Nrf2 research that is needed to fill knowledge gaps.

AOPPs induce HTR-8/SVneo cell apoptosis by downregulating the Nrf-2/ARE/HO-1 anti-oxidative pathway: Potential implications for preeclampsia

INTRODUCTION

Advanced oxidation protein products (AOPPs), which are novel markers of oxidant-mediated protein damage, are prevalent in numerous diseases. We previously demonstrated that AOPPs act as a new class of pathogenic mediators in preeclampsia by causing trophoblast damage and dysfunction. Herein, we explored whether AOPPs could regulate the Nrf-2/ARE/HO-1 anti-oxidative pathway to facilitate the progression of preeclampsia.

METHODS

To investigate the pathophysiology of preeclampsia, we evaluated the effects of AOPPs on trophoblast damage, apoptotic proteins, and Nrf-2/ARE/HO-1 anti-oxidative pathway expression, as well as their underlying mechanisms.

RESULTS

AOPPs directly increased the expression of apoptotic proteins and significantly inhibited the expression of Nrf-2/ARE/HO-1 pathway in trophoblasts. Nrf-2 silencing aggravated the AOPPs-induced cell apoptosis in vitro by activating p53 and caspase cascade, whereas Nrf-2 overexpression had the opposite effect. Moreover, Nrf-2 exerted cytoprotective effects by increasing HO-1.

DISCUSSION

These findings suggest that AOPPs induce trophoblast apoptosis by triggering p53 and caspase activation via inhibition of the Nrf-2/ARE/HO-1 anti-oxidative pathway. Hence, Nrf-2/ARE/HO-1 pathway activation plays a protective role in AOPPs-induced cell apoptosis; thus, holding potential as a therapeutic target against preeclampsia.

Hypoxia and Mitochondrial Dysfunction in Pregnancy Complications

Hypoxia is a common and severe stress to an organism's homeostatic mechanisms, and hypoxia during gestation is associated with significantly increased incidence of maternal complications of preeclampsia, adversely impacting on the fetal development and subsequent risk for cardiovascular and metabolic disease. Human and animal studies have revealed a causative role of increased uterine vascular resistance and placental hypoxia in preeclampsia and fetal/intrauterine growth restriction (FGR/IUGR) associated with gestational hypoxia. Gestational hypoxia has a major effect on mitochondria of uteroplacental cells to overproduce reactive oxygen species (ROS), leading to oxidative stress. Excess mitochondrial ROS in turn cause uteroplacental dysfunction by damaging cellular macromolecules, which underlies the pathogenesis of preeclampsia and FGR. In this article, we review the current understanding of hypoxia-induced mitochondrial ROS and their role in placental dysfunction and the pathogenesis of pregnancy complications. In addition, therapeutic approaches selectively targeting mitochondrial ROS in the placental cells are discussed.

Downregulation of CD151 induces oxidative stress and apoptosis in trophoblast cells via inhibiting ERK/Nrf2 signaling pathway in preeclampsia

Preeclampsia (PE) is a pregnancy-related syndrome characterized by new-onset hypertension and proteinuria after gestational 20 weeks. Oxidative stress, resulting from the imbalance between the production of oxidants and antioxidants in placentas, is recognized as a key pathology of PE. To date, the molecules that regulate antioxidants production remain unclear. CD151, a member of tetraspanins, is an important regulator of many physiological functions. However, the function of CD151 in oxidative stress and its association with pregnancy-related complications are currently unknown. In the present study, we have demonstrated that CD151 was a key regulator of antioxidants in placentas. Compared with the placentas of the controls, the placentas of PE patients exhibited decreased CD151 expression accompanying with decreased antioxidant gene expression (HO-1, NQO-1, GCLC and SOD-1). In vitro, overexpression of CD151 in trophoblast cells could enhance HO-1, NQO-1, GCLC and SOD-1 expression but downregulation of CD151 decreased those antioxidant genes expression, which indicates CD151 is the upstream of antioxidants. Importantly, the phenotype of PE (hypertension and proteinuria) was mimicked in the downregulating CD151 induced mouse model. Moreover, the beneficial effect of CD151 in trophoblast cells was hindered when ERK and Nrf2 signaling were blocked. Overall, our results revealed CD151 might be a new target for PE treatment.

Embryo implantation in the laboratory: an update on current techniques

BACKGROUND

The embryo implantation process is crucial for the correct establishment and progress of pregnancy. During implantation, the blastocyst trophectoderm cells attach to the epithelium of the endometrium, triggering intense cell-to-cell crosstalk that leads to trophoblast outgrowth, invasion of the endometrial tissue, and formation of the placenta. However, this process, which is vital for embryo and foetal development in utero, is still elusive to experimentation because of its inaccessibility. Experimental implantation is cumbersome and impractical in adult animal models and is inconceivable in humans.

OBJECTIVE AND RATIONALE

A number of custom experimental solutions have been proposed to recreate different stages of the implantation process in vitro, by combining a human embryo (or a human embryo surrogate) and endometrial cells (or a surrogate for the endometrial tissue). In vitro models allow rapid high-throughput interrogation of embryos and cells, and efficient screening of molecules, such as cytokines, drugs, or transcription factors, that control embryo implantation and the receptivity of the endometrium. However, the broad selection of available in vitro systems makes it complicated to decide which system best fits the needs of a specific experiment or scientific question. To orient the reader, this review will explore the experimental options proposed in the literature, and classify them into amenable categories based on the embryo/cell pairs employed.The goal is to give an overview of the tools available to study the complex process of human embryo implantation, and explain the differences between them, including the advantages and disadvantages of each system.

SEARCH METHODS

We performed a comprehensive review of the literature to come up with different categories that mimic the different stages of embryo implantation in vitro, ranging from initial blastocyst apposition to later stages of trophoblast invasion or gastrulation. We will also review recent breakthrough advances on stem cells and organoids, assembling embryo-like structures and endometrial tissues.

OUTCOMES

We highlight the most relevant systems and describe the most significant experiments. We focus on in vitro systems that have contributed to the study of human reproduction by discovering molecules that control implantation, including hormones, signalling molecules, transcription factors and cytokines.

WIDER IMPLICATIONS

The momentum of this field is growing thanks to the use of stem cells to build embryo-like structures and endometrial tissues, and the use of bioengineering to extend the life of embryos in culture. We propose to merge bioengineering methods derived from the fields of stem cells and reproduction to develop new systems covering a wider window of the implantation process.

Suppression of bromodomain-containing protein 4 protects trophoblast cells from oxidative stress injury by enhancing Nrf2 activation

Oxidative stress is considered a key hallmark of preeclampsia, which causes the dysregulation of trophoblast cells, and it contributes to the pathogenesis of preeclampsia. Emerging evidence has suggested bromodomain-containing protein 4 (BRD4) as a key regulator of oxidative stress in multiple cell types. However, whether BRD4 participates in regulating oxidative stress in trophoblast cells remains undetermined. The current study was designed to explore the potential function of BRD4 in the regulation of oxidative stress in trophoblast cells. Our data revealed that BRD4 expression was elevated in trophoblast cells stimulated with hydrogen peroxide. Exposure to hydrogen peroxide caused marked decreases in the levels of proliferation and invasion but promoted apoptosis and the production of ROS in trophoblast cells. Knockdown of BRD4, or treatment with a BRD4 inhibitor, markedly increased the levels of cell proliferation and invasion and decreased apoptosis and ROS production following the hydrogen peroxide challenge. Further data indicated that suppression of BRD4 markedly decreased the expression levels of Keap1, but increased the nuclear expression of Nrf2 and enhanced Nrf2-mediated transcriptional activity. BRD4 inhibition-mediated protective effects were markedly reversed by Keap1 overexpression or Nrf2 inhibition. Overall, these results demonstrated that BRD4 inhibition attenuated hydrogen peroxide-induced oxidative stress injury in trophoblast cells by enhancing Nrf2 activation via the downregulation of Keap1. Our study highlights the potential importance of the BRD4/Keap1/Nrf2 axis in the modulation of the oxidative stress response in trophoblast cells. Targeted inhibition of BRD4 may offer new opportunities for the development of innovative therapeutic approaches to treat preeclampsia.

PLA2G6 guards placental trophoblasts against ferroptotic injury

The recently identified ferroptotic cell death is characterized by excessive accumulation of hydroperoxy-arachidonoyl (C20:4)- or adrenoyl (C22:4)- phosphatidylethanolamine (Hp-PE). The selenium-dependent glutathione peroxidase 4 (GPX4) inhibits ferroptosis, converting unstable ferroptotic lipid hydroperoxides to nontoxic lipid alcohols in a tissue-specific manner. While placental oxidative stress and lipotoxicity are hallmarks of placental dysfunction, the possible role of ferroptosis in placental dysfunction is largely unknown. We found that spontaneous preterm birth is associated with ferroptosis and that inhibition of GPX4 causes ferroptotic injury in primary human trophoblasts and during mouse pregnancy. Importantly, we uncovered a role for the phospholipase PLA2G6 (PNPLA9, iPLA2beta), known to metabolize Hp-PE to lyso-PE and oxidized fatty acid, in mitigating ferroptosis induced by GPX4 inhibition in vitro or by hypoxia/reoxygenation injury in vivo. Together, we identified ferroptosis signaling in the human and mouse placenta, established a role for PLA2G6 in attenuating trophoblastic ferroptosis, and provided mechanistic insights into the ill-defined placental lipotoxicity that may inspire PLA2G6-targeted therapeutic strategies.

Class I HDAC inhibitors enhance YB-1 acetylation and oxidative stress to block sarcoma metastasis

Outcomes for metastatic Ewing sarcoma and osteosarcoma are dismal and have not changed for decades. Oxidative stress attenuates melanoma metastasis, and melanoma cells must reduce oxidative stress to metastasize. We explored this in sarcomas by screening for oxidative stress sensitizers, which identified the class I HDAC inhibitor MS-275 as enhancing vulnerability to reactive oxygen species (ROS) in sarcoma cells. Mechanistically, MS-275 inhibits YB-1 deacetylation, decreasing its binding to 5'-UTRs of NFE2L2 encoding the antioxidant factor NRF2, thereby reducing NFE2L2 translation and synthesis of NRF2 to increase cellular ROS. By global acetylomics, MS-275 promotes rapid acetylation of the YB-1 RNA-binding protein at lysine-81, blocking binding and translational activation of NFE2L2, as well as known YB-1 mRNA targets, HIF1A, and the stress granule nucleator, G3BP1. MS-275 dramatically reduces sarcoma metastasis in vivo, but an MS-275-resistant YB-1K81-to-alanine mutant restores metastatic capacity and NRF2, HIF1α, and G3BP1 synthesis in MS-275-treated mice. These studies describe a novel function for MS-275 through enhanced YB-1 acetylation, thus inhibiting YB-1 translational control of key cytoprotective factors and its pro-metastatic activity.

Resveratrol mitigates trophoblast and endothelial dysfunction partly via activation of nuclear factor erythroid 2-related factor-2

INTRODUCTION

Maternal endothelial dysfunction underlying preeclampsia arises from excessive placental release of anti-angiogenic factors, such as soluble fms-like tyrosine kinase-1 (sFlt1), soluble endoglin (sEng) and activin A. Resveratrol, an activator of the nuclear factor erythroid 2-related factor-2 (Nrf2) transcription factor, mediates the gene expression of antioxidant and vasoprotective factors that may counter the endothelial damage imposed by these anti-angiogenic factors. The objective of this study was to assess whether resveratrol could reduce placental oxidative stress and production of anti-angiogenic factors in vitro and/or improve in vitro markers of endothelial dysfunction via Nrf2 activation.

METHOD

We used in vitro term placental explants to assess the effects of resveratrol on placental oxidative stress and production of sFlt1, sEng and activin A. Using human umbilical vein endothelial cells we investigated the effects of resveratrol on markers of in vitro endothelial dysfunction, including the expression of intercellular adhesion molecule 1 (ICAM1), vascular cell adhesion molecule 1 (VCAM1), E-selectin and endothelin-1, and endothelial permeability. To confirm that resveratrol mediated its effects via Nrf2, we examined the impact of resveratrol on the same in vitro markers of endothelial and placental dysfunction following Nrf2 knockdown.

RESULTS

Resveratrol significantly decreased placental oxidative stress and the production of sFlt1 and activin A. Resveratrol significantly mitigated tumor necrosis factor-α stimulated endothelial expression of ICAM1, VCAM1, E-selectin and endothelin-1 and prevented an increase in endothelial monolayer permeability. Nrf2 knockdown abolished some of the protective effects of resveratrol on endothelial cells, but not in primary trophoblast cells.

CONCLUSION

Features of placental and endothelial dysfunction characteristic of preeclampsia are improved by resveratrol in vitro, partially via the modulation of Nrf2.

Expression of thioredoxin, 8Hydroxy-deguanosine and peroxiredoxins in placental tissues

In this study we analyzed the expression of 8-hydroxy-deguanosine (8OHdG), thioredoxin (Trx) and peroxiredoxins (Prx) 2, 3, 4, 5 and 6 in 80 cases of placental samples representing both normal and diseased placentas. The staining was evaluated separately in the stromal, trophoblastic and vascular components of the tissues. The results indicate that during the first trimester the level of reactive oxygen species (ROS) as indicated by 8OHdG was highest in the stromal component, which was also the case for Trx, Prx3, Prx4 and Prx6. In diseased placentas stromal 8OHdG was lower in cases with chromosomal aberrations but higher in molar disease in both trophoblastic and stromal cells. In chorioamnionitis stromal prx 5 and prx6 were high. Stromal prx4 and trophoblastic prx6 and stromal and endothelial Trx were also higher in molar disease. The results show that the oxidative stress is high in placentas during the first trimester. This probably reflects the oxidation burst of the placental tissues due to development of vascularity. In diseased placentas elevated levels of Prxs were seen in chorioamnionitis reflecting the ROS stress induced by inflammatory cells. The higher values of antioxidative enzymes in molar disease are possibly due to defective placentation. All in all, the results underline the importance on ROS associated mechanisms in placental development and the function of placenta to protect the developing fetus from harmful effects of reactive oxygen species as evidenced by their abundant expression in different cellular compartments of the placenta.

Biomarkers of oxidative stress in pregnancy complications

Pregnancy complications including pre-eclampsia, gestational-diabetes mellitus, preterm birth and intrauterine growth restriction can cause acute and chronic health problems for the mother and lead to fetal loss or dysregulation of infant physiology. The human placenta is susceptible to oxidative stress and oxidative damage in early gestation contributes to the onset of these conditions later in pregnancy. Current methods of predicting pregnancy complications are limited and although a large number of factors are associated with disease progression, few biomarkers have been used to aid in disease diagnosis early in gestation. This review discusses the detection of oxidative stress markers in biological fluids and highlights the need for further studies to validate their use in the prediction or diagnosis of pregnancy disorders.

Increased Heme Oxygenase-1 and Nuclear Factor Erythroid 2-Related Factor-2 in the Placenta Have a Cooperative Action on Preeclampsia

BACKGROUND

Previous studies have shown that oxidative stress is an important factor in preeclampsia (PE). Heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor-2 (Nrf2) are protective proteins that are involved in combating oxidative stress in the body. Nrf2 is also an essential upstream transcription factor regulating HO-1. This study was aimed at exploring the physiological roles of HO-1 and Nrf2 in PE.

METHODS

Serum and placenta were collected from 30 patients who presented with severe PE and 30 healthy pregnant females. HO-1 and Nrf2 levels in placenta were measured. Following stimulation of the HTR-8/SVneo cell line with tert-butylhydroquinone (tBHQ), an Nrf2 activator, nuclear Nrf2 protein and HO-1 mRNA levels were determined.

RESULTS

Compared with the healthy pregnancy group, HO-1 protein and mRNA levels were increased in placental samples obtained from the severe PE group (p < 0.01, p < 0.05). Similar increases were also observed for Nrf2 protein levels (p < 0.01). Nuclear Nrf2 protein and HO-1 mRNA levels were both increased in the HTR-8/SVneo cell line following stimulation with tBHQ (p < 0.05).

CONCLUSION

Patients with severe PE may be protected against oxidative injury following an elevation in HO-1 and Nrf2 levels. Nrf2 is likely to have a synergistic effect on HO-1 in PE.

The effects of Nrf2 deletion on placental morphology and exchange capacity in the mouse

OBJECTIVES

Intrauterine growth restriction (IUGR) is defined as a pathological decreased fetal growth. Oxidative stress has been connected to the restriction in the fetal growth. The transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) is a potent activator of the cellular antioxidant response. The effect Nrf2 on fetal-placental development has not yet been sufficiently investigated. Here, we evaluated the placental and fetal growth in Nrf2 knockout (Nrf2-KO) and Nrf2-wild type mice (Nrf2-WT) throughout pregnancy.

METHODS

Heterozygote Nrf2 (Nrf2^+/-) mice were paired to get Nrf2-KO and Nrf2-WT in the litters. Placentae and embryos from both genotypes were collected and weighed on days 13.5, 15.5 and 18.5 post coitum. The absolute volumes of the labyrinth zone and the total volume of the placenta were determined using the Cavalieri principle.

RESULTS

On E 18.5 the fetal weight in Nrf2-KO was significantly reduced versus Nrf2-WT indicating a decrease in placental efficiency. A significant reduction in both total and labyrinth-volume in the placenta of Nrf2-KO mice was observed.

CONCLUSION

This data points out the necessity of functional Nrf2 for fetal and placental growth. A deficiency in Nrf2 signaling may negatively affect nutrient transfer capacity which is then no longer able to meet fetal growth demands.

Perspectives on the design and methodology of periconceptional nutrient supplementation trials

Periconceptional supplementation could extend the period over which maternal and fetal nutrition is improved, but there are many challenges facing early-life intervention studies. Periconceptional trials differ from pregnancy supplementation trials, not only because of the very early or pre-gestational timing of nutrient exposure but also because they generate subsidiary information on participants who remain non-pregnant. The methodological challenges are more complex although, if well designed, they provide opportunities to evaluate concurrent hypotheses related to the health of non-pregnant women, especially nulliparous adolescents. This review examines the framework of published and ongoing randomised trial designs. Four cohorts typically arise from the periconceptional trial design--two of which are non-pregnant and two are pregnant--and this structure provides assessment options related to pre-pregnant, maternal, pregnancy and fetal outcomes. Conceptually the initial decision for single or micronutrient intervention is central--as is the choice of dosage and content--in order to establish a comparative framework across trials, improve standardisation, and facilitate interpretation of mechanistic hypotheses. Other trial features considered in the review include: measurement options for baseline and outcome assessments; adherence to long-term supplementation; sample size considerations in relation to duration of nutrient supplementation; cohort size for non-pregnant and pregnant cohorts as the latter is influenced by parity selection; integrating qualitative studies and data management issues. Emphasis is given to low resource settings where high infection rates and the possibility of nutrient-infection interactions may require appropriate safety monitoring. The focus is on pragmatic issues that may help investigators planning a periconceptional trial.

Bisphenol A increases BeWo trophoblast survival in stress-induced paradigms through regulation of oxidative stress and apoptosis

Bisphenol A (BPA) is ubiquitous in the environment and is reported to be present at high concentrations in placental tissue, where its presence raises concerns over its potential to disrupt placental function. This report investigates how BPA interferes with the survival of human choriocarcinoma BeWo cells (a model of placental trophoblasts) under stress-induced paradigms reminiscent of pathways activated in placental development. These include conditions that promote oxidative stress (glutathione depletion) and apoptosis (serum withdrawal) or mimic hypoxia (HIF-1α accumulation via dimethyloxalylglycine treatment). Treatment of BeWo cells with BPA during stress-induced paradigms led to a consistent and significant increase in cell viability, with a concomitant increase in glutathione levels and a reduction in apoptosis. Assessment of the antioxidant capacity of BPA revealed its ability to quench reactive oxygen species and reduce the levels generated during glutathione and serum depletion. BPA was also able to reduce the activation of the antioxidant response element (ARE) through mediation of its activators, nuclear factor erythroid related factor family members (Nrf's). Indeed, the expression and nuclear translocation of Nrf2 (an important ARE activator) were impaired by BPA, while Nrf1 and Nrf3 expression levels were increased. Furthermore, BPA increased the levels of the anti-apoptotic proteins (Bcl-2 and Hsp70) and decreased HIF-1α levels during stress-induced conditions. Together, these results indicate that BPA inhibits trophoblast cell death under conditions of cellular stress. This could have implications on placental trophoblasts during development.

Angiogenesis in the placenta: the role of reactive oxygen species signaling

Proper placental development and function are central to the health of both the mother and the fetus during pregnancy. A critical component of healthy placental function is the proper development of its vascular network. Poor vascularization of the placenta can lead to fetal growth restriction, preeclampsia, and in some cases fetal death. Therefore, understanding the mechanisms by which uterine stressors influence the development of the placental vasculature and contribute to placental dysfunction is of central importance to ensuring a healthy pregnancy. In this review we discuss how oxidative stress observed in maternal smoking, maternal obesity, and preeclampsia has been associated with aberrant angiogenesis and placental dysfunction resulting in adverse pregnancy outcomes. We also highlight that oxidative stress can influence the expression of a number of transcription factors important in mediating angiogenesis. Therefore, understanding how oxidative stress affects redox-sensitive transcription factors within the placenta may elucidate potential therapeutic targets for correcting abnormal placental angiogenesis and function.

Detecting reactive oxygen species by immunohistochemistry

In cultured cells, an increase in cellular levels of reactive oxygen species (ROS) can be detected using multiple techniques including colorimetric assays, immunoblotting, and immunofluorescence. These methods can also be applied for ROS measurement in tissue samples, but often require tissue homogenization, and therefore do not distinguish between the different cell types within a tissue. Here, we describe a detailed protocol for determination of altered oxidative stress levels in different cell types in tissues, by detecting ROS-caused alteration of macromolecules using immunohistochemistry (IHC). This method is demonstrated by using 4HNE as a marker for lipid peroxidation in mouse pancreas tissue that contains precancerous lesions high in cellular oxidative stress.

Discordant HIF1A mRNA levels and oxidative stress in placental shares of monochorionic twins with selective intra-uterine growth restriction

INTRODUCTION

Oxidative stress is a key factor in the pathogenesis of intra-uterine growth restriction in singleton. However, its role in selective intra-uterine growth restriction (sIUGR) in monochorionic twins (MCT) is still unknown. This study explored the characteristics of oxidative stresses in the placenta shares of MCT and analyzed their possible connections with sIUGR.

METHODS

The placental levels of hypoxia inducible factor-1α gene (HIF1A)mRNA, malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) were evaluated in normal MCT (Group A) and sIUGR MCT (Group B). The results were compared between the placental shares of the larger twins (A1/B1) and smaller twins (A2/B2).

RESULTS

Placental HIF1A mRNA level significantly increased in Group B. Particularly, HIF1A mRNA level was elevated in the placenta share of the growth-restricted fetus (B2) than the co-twin (B1) (P = 0.036). More discordant HIF1A mRNA level was detected in Group B than Group A with larger inter-twin difference (P = 0.021). The levels of MDA and 8-OHdG were significantly higher in B2 than B1 in sIUGR MCT (P < 0.05). Both the inter-twin differences of MDA and 8-OHdG were also significantly larger in Group B (P < 0.05), indicating that discordant oxidative stress existed in the placental shares of sIUGR pregnancies. Finally, MDA concentration was found inversely correlated with neonatal birth weight, in both sIUGR (r = -0.650, P = 0.022) and normal MCT (r = -0.632, P = 0.027) pregnancies.

DISCUSSION

The elevation of HIF1A mRNA, and MDA/8-OHdG levels in placenta shares of sIUGR MCT suggests that oxidative stress may be involved in the pathogenesis of sIUGR.

Protective effect of nuclear factor E2-related factor 2 on inflammatory cytokine response to brominated diphenyl ether-47 in the HTR-8/SVneo human first trimester extravillous trophoblast cell line

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants, and BDE-47 is a prevalent PBDE congener detected in human tissues. Exposure to PBDEs has been linked to adverse pregnancy outcomes in humans. Although the underlying mechanisms of adverse birth outcomes are poorly understood, critical roles for oxidative stress and inflammation are implicated. The present study investigated antioxidant responses in a human extravillous trophoblast cell line, HTR-8/SVneo, and examined the role of nuclear factor E2-related factor 2 (Nrf2), an antioxidative transcription factor, in BDE-47-induced inflammatory responses in the cells. Treatment of HTR-8/SVneo cells with 5, 10, 15, and 20μM BDE-47 for 24h increased intracellular glutathione (GSH) levels compared to solvent control. Treatment of HTR-8/SVneo cells with 20μM BDE-47 for 24h induced the antioxidant response element (ARE) activity, indicating Nrf2 transactivation by BDE-47 treatment, and resulted in differential expression of redox-sensitive genes compared to solvent control. Pretreatment with tert-butyl hydroquinone (tBHQ) or sulforaphane, known Nrf2 inducers, reduced BDE-47-stimulated IL-6 release with increased ARE reporter activity, reduced nuclear factor kappa B (NF-κB) reporter activity, increased GSH production, and stimulated expression of antioxidant genes compared to non-Nrf2 inducer pretreated groups, suggesting that Nrf2 may play a protective role against BDE-47-mediated inflammatory responses in HTR-8/SVneo cells. These results suggest that Nrf2 activation significantly attenuated BDE-47-induced IL-6 release by augmentation of cellular antioxidative system via upregulation of Nrf2 signaling pathways, and that Nrf2 induction may be a potential therapeutic target to reduce adverse pregnancy outcomes associated with toxicant-induced oxidative stress and inflammation.

Expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and peroxiredoxin 6 (Prdx6) proteins in healthy and pathologic placentas of human and rat

A relationship has been shown between preeclampsia (PE) and intrauterine growth restriction (IUGR) and oxidative stress (OS). Since such pregnancies experience OS, we aimed to detect the distribution pattern and expression levels of a transcription factor, Nuclear factor erythroid 2-related factor-2 (Nrf2) that has a role in the regulation of antioxidant enzymes, and peroxiredoxin 6 (Prdx6) an antioxidant enzyme, in human healthy, IUGR, PE and in groups of rat healthy and IUGR placentas using immunohistochemistry and Western blotting. Both Nrf2 and Prdx6 immunoreactivities were weaker in human and rat IUGR group placentas compared to human and rat control group placentas, respectively. Nrf2 and Prdx6 were immunostained in labyrinth trophoblasts, decidua, giant, glycogen and fetal vessel endothelial cells in rat control and IUGR group placentas. Nrf2 and Prdx6 immunoreactivities were seen in the decidua, syncytiotrophoblasts, villous stromal cells, and vascular endothelium in human control, IUGR and PE group placentas. Results of Nrf2 and Prdx6 Western blotting applied for rat and human placentas were compatible with the results of Nrf2 and Prdx6 immunohistochemical observations with regard to rat and human placentas. Down-regulation of Nrf2 and Prdx6 proteins in human and rat IUGR group placentas may have led to the formation of OS which may have impaired proliferation and invasion of cytotrophoblasts.

A possible protective role of Nrf2 in preeclampsia

Excess release of reactive oxygen species (ROS) is a major cause of oxidative stress. This disturbance has been implicated as a cause of preeclampsia, a pregnancy-related disorder characterized by hypertension and proteinuria. Increased oxidative stress leads to trophoblast apoptosis/necrosis and alters the balance between pro- and anti-angiogenic factors, resulting in generalized maternal endothelial dysfunction. Trials using antioxidants have significantly failed to improve the condition of, or in any way protect, the mother from the life-threatening complications of this syndrome. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a potent transcription activator that regulates the expression of a multitude of genes that encode detoxification enzymes and anti-oxidative proteins. Recent discussion on evidence of a link between Nrf2 and vascular angiogenic balance has focussed on the downstream target protein, heme oxygenase-1 (HO-1). HO-1 metabolizes heme to biliverdin, iron and carbon monoxide (CO). HO-1/CO protects against hypertensive cardiovascular disease and contributes to the sustained health of the vascular system. In one animal model, sFlt-1 (soluble fms-like tyrosine kinase-1) has induced blood pressure elevation, but the induction of HO-1 attenuated the hypertensive response in the pregnant animals. The special conditions under which Nrf2 participates in the pathogenesis of preeclampsia are still unclear, as is whether Nrf2 attenuates or stimulates the processes involved in this syndrome. In this review, we summarize recent theories about how Nrf2 is involved in the pathogenesis of preeclampsia and present the reasons for considering Nrf2 as a therapeutic target for the treatment of preeclampsia.

Beyond pregnancy: modulation of trophoblast invasion and its consequences for fetal growth and long-term children's health

Invasion of extravillous trophoblast cells (EVTs) into the maternal tissues is a key step in the development of a successful pregnancy, excessive and insufficient EVT invasion being associated with pregnancy complications. These pregnancy complications include preeclampsia and fetal growth restriction, both of which are associated with maternal and fetal morbidity and mortality at the time of birth and with increased risk of cardiovascular disease, diabetes and obesity in adult life for infants born from these conditions. In addition, women who develop preeclampsia are also at a greater risk of cardiovascular disease in later life. Many factors, protein and environmental, have been shown to both up- and down-regulate this process in vitro via different mechanisms. The redundancy observed in the regulation of this system suggests that dysregulation of one factor may not contribute to the pathological conditions of EVT invasion and that the relative local concentrations of many different factors may be more important. This review article explores the possibility that the modulation of EVT invasion as a therapeutic target for pregnancies affected by preeclampsia and fetal growth restriction may not be possible or needs to concentrate on the modulation of cell activity as a whole and not of one particular factor.

New Insights into the Pathogenesis of Preeclampsia - The Role of Nrf2 Activators and their Potential Therapeutic Impact

Preeclampsia (PE), characterized by proteinuric hypertension and occurring in 2-3 % of all pregnancies, is one of the leading causes of maternal, fetal and neonatal morbidity and mortality. The etiology of PE still remains unclear and current treatments for this devastating disorder are still limited to symptomatic therapies. Placental oxidative stress may be a key intermediate step in the pathogenesis of PE; it has been related to excessive secretion of multiple antiangiogenic factors, mainly soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng). The nuclear factor-erythroid 2-like 2 (Nrf2) pathway is one of the most important systems that enhance cellular protection against oxidative stress. Nrf2 serves as a master transcriptional regulator of the basal and inducible expression of a multitude of genes encoding detoxification enzymes and antioxidative proteins. Evidence for a link between Nrf2 and restoring the balance between pro- and antiangiogenic factors mainly through its downstream target protein heme oxygenase-1 (HO-1) has lately been discussed. HO-1 metabolizes heme to biliverdin, iron and carbon monoxide (CO). CO enhances vascular endothelial growth factor (VEGF) synthesis in vascular smooth muscle and promotes its relaxation and hence vasodilatation. In addition, HO-1 has been shown in vitro to inhibit the production of sFlt-1. A recent animal study demonstrated that the induction of HO-1 in a mouse model of PE attenuates the induced hypertension in pregnant mice. This provides compelling evidence for the protective role of Nrf2/HO-1 in pregnancy and identifies this pathway as a target to treat women with PE. We summarize the recent findings on the involvement of Nrf2 in the pathogenesis of PE, and provide an overview of the possible beneficial effects of Nrf2 inducers in PE.