Increased endoplasmic reticulum stress in decidual tissue from pregnancies complicated by fetal growth restriction with and without pre-eclampsia

Comparison of Maternal and Fetal Plasma X Box Binding Protein 1 Levels Between Pregnancies With Fetal Growth Retardation and Healthy Controls

OBJECTIVE

This study aimed to compare maternal and cord serum X box binding protein 1 (XBP-1) levels in pregnant women with fetal growth restriction (FGR) with healthy pregnancies.

MATERIALS AND METHODS

This prospective case-control study was conducted between January 1, 2022, and May 31, 2022, at the Gynecology and Obstetrics Clinic of Selçuk University Faculty of Medicine Hospital. Forty-three pregnant women and fetuses with isolated FGR with abdominal circumference (AC) or estimated fetal weight (EFW) below the 10th percentile according to ultrasonographic measurements constituted the study group; 43 healthy pregnant women and fetuses constituted the control group. Serum XBP-1 levels in prenatal maternal and cord blood were measured by ELISA and compared between the two groups.

RESULTS

The mean maternal blood XBP-1 level was 1910.22 ± 607.07 ng/L in the FGR group and 1638.89 ± 385.80 ng/L in the control group (p = 0.044). Cord blood XBP-1 levels were 1837.72 ± 942.67 and 1346.14 ± 664.09 ng/L in the study and control groups, respectively (p = 0.006). Maternal XBP-1 levels were found to discriminate FGR with a sensitivity of 80% and specificity of 60% at a value of 1405 ng/L. For cord blood XBP-1, 869.2 ng/L was the best cut-off, with 98% sensitivity and 67% specificity. In ROC analysis, the area under the curve was found to be 0.626 and 0.671, and p values were found to be 0.044 and 0.006 for maternal serum XBP-1 and cord blood XBP-1, respectively.

CONCLUSIONS

In the study, serum XBP-1 levels in both maternal and fetal umbilical cord blood were found to be higher in patients with FGR. Considering the role of XBP-1 in metabolic pathways and cellular functions, XBP-1 may have an important role in the pathophysiology of FGR.

A stress paradox: the dual role of the unfolded protein response in the placenta

The placenta is a temporary organ that forms during pregnancy and is essential for fetal development and maternal health. As an endocrine organ, proper placental function requires continual production, folding, and transport of proteins and lipids. Central to these processes is the endoplasmic reticulum (ER), a dynamic organelle responsible for maintaining cellular protein and lipid synthesis and processing. ER stress occurs when there is an accumulation of unfolded or misfolded proteins, which triggers the activation of cellular pathways collectively called the unfolded protein response. Unfolded protein response pathways act to alleviate the misfolded protein burden and restore ER homeostasis, or if unresolved, initiate cell death. While prolonged ER stress has been linked to deficient placental function and adverse pregnancy outcomes, basal activation of unfolded protein response pathways is required for placental development and function. This review explores the importance of ER homeostasis in placental development and function, examining how disruptions in ER stress responses may contribute to adverse pregnancy outcomes.

Manganese porphyrin-based treatment improves fetal-placental development and protects against oxidative damage and NLRP3 inflammasome activation in a rat maternal hypothyroidism model

Oxidative stress (OS) and endoplasmic reticulum stress (ERS) are at the genesis of placental disorders observed in preeclampsia, intrauterine growth restriction, and maternal hypothyroidism. In this regard, cationic manganese porphyrins (MnPs) comprise potent redox-active therapeutics of high antioxidant and anti-inflammatory potential, which have not been evaluated in metabolic gestational diseases yet. This study evaluated the therapeutic potential of two MnPs, [MnTE-2-PyP]5+ (MnP I) and [MnT(5-Br-3-E-Py)P]5+ (MnP II), in the fetal-placental dysfunction of hypothyroid rats. Hypothyroidism was induced by administration of 6-Propyl-2-thiouracil (PTU) and treatment with MnPs I and II 0.1 mg/kg/day started on the 8th day of gestation (DG). The fetal and placental development, and protein and/or mRNA expression of antioxidant mediators (SOD1, CAT, GPx1), hypoxia (HIF1α), oxidative damage (8-OHdG, MDA), ERS (GRP78 and CHOP), immunological (TNFα, IL-6, IL-10, IL-1β, IL-18, NLRP3, Caspase1, Gasdermin D) and angiogenic (VEGF) were evaluated in the placenta and decidua on the 18th DG using immunohistochemistry and qPCR. ROS and peroxynitrite (PRX) were quantified by fluorometric assay, while enzyme activities of SOD, GST, and catalase were evaluated by colorimetric assay. MnPs I and II increased fetal body mass in hypothyroid rats, and MnP I increased fetal organ mass. MnPs restored the junctional zone morphology in hypothyroid rats and increased placental vascularization. MnPs blocked the increase of OS and ERS mediators caused by hypothyroidism, showing similar levels of expression of HIFα, 8-OHdG, MDA, Gpx1, GRP78, and Chop to the control. Moreover, MnPs I and/or II increased the protein expression of SOD1, Cat, and GPx1 and restored the expression of IL10, Nlrp3, and Caspase1 in the decidua and/or placenta. However, MnPs did not restore the low placental enzyme activity of SOD, CAT, and GST caused by hypothyroidism, while increased the decidual and placental protein expression of TNFα. The results show that treatment with MnPs improves the fetal-placental development and the placental inflammatory state of hypothyroid rats and protects against oxidative stress and reticular stress caused by hypothyroidism at the maternal-fetal interface.

Aβ1-42 stimulates an increase in autophagic activity through tunicamycin-induced endoplasmic reticulum stress in HTR-8/SVneo cells and late-onset pre-eclampsia

Environmental changes can trigger endoplasmic reticulum (ER) stress and misfolded protein accumulation, potentially leading to pre-eclampsia (PE). Amyloid-β (Aβ) is a crucial misfolded protein that can overactivate autophagy. Our study assessed the expression of Aβ1-42 and autophagic activity in PE placental tissues and trophoblasts under ER stress. Placental tissues were surgically collected from normal pregnant women (NP) and pregnant women with late-onset PE (LOPE) delivering through cesarean section. The expression levels of Aβ1-42 were detected in both PE and NP placental tissues, as well as in tunicamycin (TM)-induced HTR-8/SVneo cells. Autophagy-related proteins, such as Beclin-1, the ratio of LC3-II to LC3-I, ATG5, and SQSTM1/p62 in the placental tissues and HTR-8/SVneo cells were measured by Western blot. The number and morphology of autophagosomes were observed using transmission electron microscopy (TEM). Potential targets associated with the unfolded protein response (UPR) in the placental tissues of NP and PE cases were screened using PCR Arrays. The misfolded protein was significantly upregulated in the PE group. In both PE placental tissues and TM-induced HTR-8/SVneo cells, not only was Aβ1-42 upregulated, but also Beclin-1, ATG5, and LC3BII/I were significantly increased, accompanied by an increase in autophagosome count, while SQSTM1/P62 was downregulated. A total of 17 differentially expressed genes (DEGs) associated with the UPR were identified, among which elevated calnexin (CANX) was validated in the placenta from both PE and TM-induced HTR-8/SVneo cells. Autophagy is significantly upregulated in PE cases due to ER stress-induced Aβ1-42 accumulation, likely mediated by autophagy-related proteins involved in the UPR.

Relationship Between Recurrent Pregnancy Loss With Unknown Etiology and Endoplasmic Reticulum Stress

INTRODUCTION

Recurrent pregnancy loss (RPL) is characterized by consecutive pregnancy losses before 20 weeks of gestation, with evolving definitions necessitating adjustments to prevent delays in couples' evaluation. Limited etiological data on RPL prompts comprehensive evaluations, often yielding no pathological findings. Emerging research implicates endoplasmic reticulum (ER) stress in various reproductive processes, yet its association with RPL remains understudied.

AIM

To evaluate ER stress in patients with RPL with unknown etiology by determining the plasma concentration of X-box binding protein-1 (XBP-1).

MATERIALS AND METHODS

A total of 45 patients aged 18 to 35 years with at least two pregnancy losses with unknown etiology before the completion of 20 weeks of gestation between March 2020 and September 2020 were included in the study group. The control group consisted of 45 healthy women with at least two previous live births, no pregnancy-associated complications, and no history of pregnancy loss or infertility. The XBP-1 levels were determined from serum samples. Statistical analyses assessed differences between groups, and receiver operating characteristic (ROC) curve analysis determined XBP-1's predictive value for RPL.

RESULTS

The mean XBP-1 concentration in the RPL group was significantly higher than in the control group (p < 0.001). The mean values were 2243.65 ± 9425.27 pg/mL and 1196.32 ± 4378.81 pg/mL, respectively. The use of XBP-1 levels for the prediction of RPL was evaluated. In an ROC curve analysis, the area under the curve was found to be 87% (95% CI: 80% to 94.8%). The specificity was 78%, the sensitivity was 88%, the positive likelihood ratio (LR) was 4, the negative LR was 0.15, the positive predictive value was 80%, and the negative predictive value was 87% for the cut-off XBP-1 level at 1364.68 pg/mL.

CONCLUSION

This study highlights the potential role of ER stress in RPL and proposes XBP-1 as a predictive biomarker for pregnancy loss. Understanding ER stress mechanisms in RPL could inform diagnostic and therapeutic strategies. Further research is essential to validate these findings and explore their clinical implications.

Protein Misfolding in Pregnancy: Current Insights, Potential Mechanisms, and Implications for the Pathogenesis of Preeclampsia

Protein misfolding disorders are a group of diseases characterized by supra-physiologic accumulation and aggregation of pathogenic proteoforms resulting from improper protein folding and/or insufficiency in clearance mechanisms. Although these processes have been historically linked to neurodegenerative disorders, such as Alzheimer's disease, evidence linking protein misfolding to other pathologies continues to emerge. Indeed, the deposition of toxic protein aggregates in the form of oligomers or large amyloid fibrils has been linked to type 2 diabetes, various types of cancer, and, in more recent years, to preeclampsia, a life-threatening pregnancy-specific disorder. While extensive physiological mechanisms are in place to maintain proteostasis, processes, such as aging, genetic factors, or environmental stress in the form of hypoxia, nutrient deprivation or xenobiotic exposures can induce failure in these systems. As such, pregnancy, a natural physical state that already places the maternal body under significant physiological stress, creates an environment with a lower threshold for aberrant aggregation. In this review, we set out to discuss current evidence of protein misfolding in pregnancy and potential mechanisms supporting a key role for this process in preeclampsia pathogenesis. Improving our understanding of this emerging pathophysiological process in preeclampsia can lead to vital discoveries that can be harnessed to create better diagnoses and treatment modalities for the disorder.

Stress regulation of WFS1 and PERK-p-eIF2α-ATF4 signaling pathway in placental tissue cells of intrahepatic cholestasis of pregnancy

INTRODUCTION

The placental tissue stress of intrahepatic cholestasis of pregnancy (ICP) is activated by ERS under hypoxia condition. PERK signaling pathway is the key pathway for UPR regulation, and is first to activated during ERS. WFS1, as an important regulatory gene of UPR pathway, participates in ERS regulation. The purpose of our study is to explore the expression level and mutual regulation mechanisms of WFS1 and PERK-mediated UPR pathway in ICP placental tissue cell under stress.

METHODS

Blood and placenta samples were obtained from the ICP patients and ethinylestradiol (EE)-induced intrahepatic cholestasis pregnant rats. IHC and WB were used to detect the expression of WFS1, key factors of PERK pathway (GRP78, PERK, eIF2a, P-eIF2α, ATF4) and placental stress peptides (CRH, UCN). Furthermore, qPCR was carried out to detect mRNA expression of above indicators.

RESULTS

The expression levels of WFS1 and key factors of PERK pathway were significantly increased in severe ICP placental tissues. Moreover, qPCR and WB showed that relative mRNA and protein expression levels of WFS1 and key factors of PERK pathways in placenta tissues of severe ICP and EE-induced intrahepatic cholestasis pregnant rats were higher than those in control group to varying degrees, while CRH and UCN were descended. Meanwhile, after WFS1-siRNA targeted silencing of the WFS1 gene, the protein expression levels of PERK, P-eIF2α, ATF4 were significantly increased, while CRH and UCN protein were significantly decreased.

DISCUSSION

Our study revealed that the activation of WFS1 and PERK-p-eIF2α-ATF4 signaling pathway may contribute to stress regulation in placental tissue cells of intrahepatic cholestasis of pregnancy, thereby avoiding adverse pregnancy outcomes.

Maternal exposure to a glyphosate-based herbicide impairs placental development through endoplasmic reticulum stress in mice

Glyphosate-based herbicides (GBHs) are the most widely used agrochemicals worldwide, increasing the risk of their occurrence in the environment. This study aimed to explore effects and mechanisms of GBH exposure on placental development in vivo during pregnancy in mice. Pregnant mice received GBH by gavage at 0, 5, and 50 mg⋅kg^-1⋅day^-1 doses from gestational day (GD) 1 to GD 13 and were sacrificed on GD 13 or GD19. Our data indicated that GBH administration significantly increased the number of resorbed fetuses, reduced the weight of fetuses and placentas, and inhibited placental growth, as evident from decreased placental total area and spongiotrophoblast area on GD 19. GBH treatment also inhibited proliferation and induced apoptosis of placenta via upregulation of Bax, cleaved caspase-3 and -12 expression, and downregulation of B cell lymphoma (Bcl)-2 expression. Further study showed that GBH exposure significantly increased expression levels of glucose-regulated protein 78 (GRP78), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and C/EBP homologous protein (CHOP) mRNAs and proteins and triggered oxidative stress in placenta on GD 13 and GD 19. In conclusion, our findings suggest that maternal exposure to GBH can impair placental development through the endoplasmic reticulum stress-mediated activation of GRP78/PERK/CHOP signaling pathway in mice.

Pre-Existing Diabetes Mellitus, Hypertension and KidneyDisease as Risk Factors of Pre-Eclampsia: A Disease of Theories and Its Association with Genetic Polymorphism

Pre-existing diabetes, hypertension and kidney disorders are prominent risk factors of pre-eclampsia (PE). It is a multifactorial pregnancy disorder associated with high blood pressure, proteinuria, and multiorgan failure, which develops after the 20th week of pregnancy. It is one of the most feared pregnancy disorders, as it consumes thousands of fetomaternal lives per annum. According to clinical and pathological studies, the placenta appears to be a key player in the pathogenesis of PE; however, the exact origin of this disorder is still under debate. Defective placentation and angiogenesis are the hallmarks of PE progression. This angiogenic imbalance, together with maternal susceptibility, might determine the severity and clinical presentation of PE. This article comprehensively examines the mechanisms of pathogenesis of PE and current evidence of the factors involved in its progression. Finally, this article will explore the genetic association of PE, various candidate genes, their proposed mechanisms and variants involved in its pathogenesis.

Maternal hypothyroidism causes oxidative stress and endoplasmic reticulum stress in the maternal-fetal interface of rats

Maternal hypothyroidism is associated with pre-eclampsia and intrauterine growth restriction, gestational diseases involving oxidative stress (OS) and endoplasmic reticulum stress (ERS) in the placenta. However, it is not known whether hypothyroidism also causes OS and ERS at the maternal-fetal interface. The aim was to evaluate the fetal-placental development and the expression of mediators of OS and of the unfolded protein response (UPR) in the maternal-fetal interface of hypothyroid rats. Hypothyroidism was induced in Wistar rats with propylthiouracil and the fetal-placental development and placental and decidual expression of antioxidant, hypoxia, and UPR mediators were analyzed at 14 and 18 days of gestation (DG), as well the expression of 8-OHdG and MDA, and reactive oxygen species (ROS) and peroxynitrite levels. Hypothyroidism reduced fetal weight at 14 and 18 DG, in addition to increasing the percentage of fetal death and reducing the weight of the uteroplacental unit at 18 DG. At 14 DG, there was greater decidual and/or placental immunostaining of Hif1α, 8-OHdG, MDA, SOD1, GPx1/2, Grp78 and CHOP in hypothyroid rats, while there was a reduction in placental and/or decidual gene expression of Sod1, Gpx1, Atf6, Perk, Ho1, Xbp1, Grp78 and Chop in the same gestational period. At 18 DG, hypothyroidism increased the placental ROS levels and the decidual and/or placental immunostaining of HIF1α, 8-OHdG, MDA, ATF4, GRP78 and CHOP, while it reduced the immunostaining and enzymatic activity of SOD1, CAT, GST. Hypothyroidism increased the placental mRNA expression of Hifα, Nrf2, Sod2, Gpx1, Cat, Perk, Atf6 and Chop at 18 DG, while decreasing the decidual expression of Sod2, Cat and Atf6. These findings demonstrated that fetal-placental restriction in female rats with hypothyroidism is associated with hypoxia and dysregulation in placental and decidual expression of UPR mediators and antioxidant enzymes, and activation of oxidative stress and endoplasmic reticulum stress at the maternal-fetal interface.

Calnexin Is Involved in Forskolin-induced Syncytialization in Cytotrophoblast Model BeWo Cells

Calnexin (CNX), a membrane-bound molecular chaperone, is involved in protein folding and quality control of nascent glycoproteins in the endoplasmic reticulum. We previously suggested critical roles of calreticulin, a functional paralogue of CNX, in placentation, including invasion of extravillous trophoblasts and syncytialization of cytotrophoblasts. However, the roles of CNX in placentation are unclear. In human choriocarcinoma BeWo cells, which serve as an experimental model of syncytialization, CNX knockdown suppressed forskolin-induced cell fusion and β-human chorionic gonadotropin (β-hCG) induction. Cell-surface luteinizing hormone/chorionic gonadotropin receptor, a β-hCG receptor, was significantly down-regulated in CNX-knockdown cells, which suggested the presence of a dysfunctional autocrine loop of β-hCG up-regulation. In this study, we also found abundant CNX expression in normal human placentas. Collectively, our results revealed the critical role of CNX in the syncytialization-related signaling in a villous trophoblast model and suggest a link between CNX expression and placenta development.

Enhancement of Rubella Virus Infection in Immortalized Human First-Trimester Trophoblasts Under Low-Glucose Stress Conditions

Rubella virus (RuV) infections in pregnant women, especially first-trimester infections, can lead to congenital rubella syndrome (CRS). However, the mechanisms of fetal RuV infection are not completely understood, and it is not observed in every pregnant woman infected with RuV. As gestational diabetes mellitus is a risk factor for congenital viral infections, we investigated the possible roles of hypoglycemia-related endoplasmic reticulum (ER) stress as a key factor for vertical RuV infection using immortalized human first-trimester trophoblasts. Low-glucose stress was induced prior to RuV infection by culturing HTR-8/SVneo and Swan.71 cells in low-glucose (LG) medium for 24 h or high-glucose medium for 6 h and then LG medium for an additional 18 h. Clinically isolated RuV was inoculated at a multiplicity of infection of 5 to 10. The intracellular localization of the RuV capsid protein was investigated 24 to 48 h post-infection (pi) with flow cytometry (FCM) analysis and fluorescence microscopy. Viral progeny production was monitored by FCM analysis. Increases in RuV infection in LG-induced ER-stressed trophoblasts were observed. No significant increase in apoptosis of RuV-infected cells was noted at days 2 and 5 pi, and substantial viral progeny production was observed until day 5 pi. An approximate fivefold increase in viral binding was noted for the LG-stressed cells. Although the detailed mechanisms underlying viral entry into LG-stressed cells are not known and require further investigation, these findings suggest that a certain degree of LG stress in early pregnancy may facilitate infection and cause CRS.

Gestational exposure to BDE-209 induces placental injury via the endoplasmic reticulum stress-mediated PERK/ATF4/CHOP signaling pathway

Several epidemiological studies have reported significant associations between prenatal polybrominated diphenyl ethers (PBDEs) exposure and adverse birth outcomes. Placental injury is thought to mediate these associations. However, few study has investigated the adverse effects of PBDEs exposure on placental growth and development. We examined the impacts of gestational exposure to BDE-209, the most abundant PBDE conger detected in human samples, on placental structure and function, and its model of action in vivo and in vitro. Pregnant mice were exposed to 0, 2, 20, 200 mg/kg/day of BDE-209 by gavages from gestational day (GD) 0 to GD18. Results showed that gestational BDE-209 exposure significantly reduced placental weight, impaired placental vascular development and induced placental cell apoptosis. In addition, gestational BDE-209 exposure impaired placental transport and endocrine function as demonstrated by markedly downregulated expression of Glut1, Znt1, Pgf and Igf2 in BDE-209-treated placentas. Mechanistically, gestational exposure to BDE-209 upregulated the expression of GRP78, and 3 downstream proteins (p-eIF2α, ATF4 and CHOP) of the PERK signaling, suggesting the activation of endoplasmic reticulum (ER) stress and PERK signaling pathway in mouse placentas. Further in vitro study showed that PERK siRNA pretreatment markedly reversed BDE-209-induced cell apoptosis in human JEG-3 cells. Collectively, our results suggest that the activation of the ER stress-mediated PERK/ATF4/CHOP signaling pathway played a role in BDE-209-induced placental injury. Our findings provide new insight into the mechanisms of BDE-209 induced reproductive and developmental toxicity.

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.

Pathological Role of Reactive Oxygen Species on Female Reproduction

Oxidative stress (OS), a clinical predicament characterized by a shift in homeostatic imbalance among prooxidant molecules embracing reactive oxygen species (ROS) and reactive nitrogen species (RNS), along with antioxidant defenses, has been established to play an indispensable part in the pathophysiology of subfertility in both human males and females. ROS are highly reactive oxidizing by-products generated during critical oxygen-consuming processes or aerobic metabolism. A healthy body system has its own course of action to maintain the equilibrium between prooxidants and antioxidants with an efficient defense system to fight against ROS. But when ROS production crosses its threshold, the disturbance in homeostatic balance results in OS. Besides their noxious effects, literature studies have depicted that controlled and adequate ROS concentrations exert physiologic functions, especially that gynecologic OS is an important mediator of conception in females. Yet the impact of ROS on oocytes and reproductive functions still needs a strong attestation for further analysis because the disruption in prooxidant and antioxidant balance leads to abrupt ROS generation initiating multiple reproductive diseases such as polycystic ovary syndrome (PCOS), endometriosis, and unexplained infertility in addition to other impediments in pregnancy such as recurrent pregnancy loss, spontaneous abortion, and preeclampsia. The current article elucidates the skeptical state of affairs created by ROS that influences female fertility.

The association of NPHS1 and ACNT4 gene polymorphisms with pre-eclampsia

OBJECTIVE

The main objective of this study is to investigate the association of the NPHS1 gene polymorphisms (rs437168) and ACTN4 (rs3745895) in the pathogenesis of PE in women of African Ancestry.

MATERIALS AND METHODS

637 blood samples, normotensive pregnant (n = 280) and pre-eclampsia (n = 357) were included. The PE group was sub-divided into early onset pre-eclampsia (n = 187) and late onset pre-eclampsia (n = 170). rs74315346, rs869025495, rs121908415, rs3745895, and rs437168 were genotyped from isolated DNA using real time PCR.

RESULTS

The C allele of rs437168 (NPHS1) was significantly higher in PE compared to controls. [C vs T; p = 0.0323*] and [CC vs CT/TT; p = 0.0464*]. A comparison between the subtypes of PE and controls showed that the C allele was significantly higher in EOPE compared to controls [p = 0.0027^**], [CC vs CT/TT; p = 0.0111*], [CC/CT vs TT p = 0.0198*] and LOPE. [p = 0.0259*]. The other SNPs genotyped showed no signification associations with PE.

CONCLUSION

This study found that the C allele of rs437168 is significantly associated with the pathogenesis of early onset PE and may be accountable for renal injury, which is a risk factor for the development of EOPE in women of African Ancestry.

The unfolded protein response and apoptotic regulation in the human placenta due to maternal cigarette smoking and pre-eclampsia

Maternal cigarette smoking (CS) and pre-eclampsia (PE) alter placental function and expression of important proteins which maintain homeostasis. Two interlinked pathways of interest are the unfolded protein response (UPR) and apoptosis. The UPR is upregulated in the PE placenta, but no data is available on the effects of CS and how it correlates with apoptotic expression. Samples of human placental tissue from normotensive non-smokers (n = 8), women with PE (n = 8), and CS (n = 8) were analysed using immunohistochemistry for 3 UPR markers (phosphorylated PKR-like endoplasmic reticulum (ER) kinase (pPERK), inositol-requiring enzyme 1 (IRE1), activating transcription factor 6 (ATF6)), and an antibody microarray for 19 apoptotic and stress regulating markers. For the PE group compared to the normotensive group, staining for pPERK was increased in decidual tissue and villi, and for IRE1, the overall percentage of stained villi per field of view was increased. There were no differences in UPR expression comparing CS to controls. Of the apoptotic markers, only IκBα (Ser32/36), which is part of an inhibitory pathway, showed a significant decrease in the PE and CS groups compared to controls. These findings suggest UPR regulation is more evident in PE with a general increase in ER stress due to decreased inhibition of apoptosis as compared to CS for which UPR was not altered.

The endocannabinoid 2-arachidonoylglycerol promotes endoplasmic reticulum stress in placental cells

Proliferation, differentiation and apoptosis of trophoblast cells are required for normal placental development. Impairment of those processes may lead to pregnancy-related diseases. Disruption of endoplasmic reticulum (ER) homeostasis has been associated with several reproductive pathologies including recurrent pregnancy loss and preeclampsia. In the unfolded protein response (UPR), specific ER-stress signalling pathways are activated to restore ER homeostasis, but if the adaptive response fails, apoptosis is triggered. Protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and Activating transcription factor 6 (ATF6) are central players in UPR and in ER-stress-induced apoptosis, as well as downstream transcription factors, as C/EBP homologous protein (CHOP). Our previous studies have shown that the endocannabinoid 2-arachidonoylglycerol (2-AG) modulates trophoblast cell turnover. Nevertheless, the role of ER-stress on 2-AG induced apoptosis and cannabinoid signalling in trophoblast has never been addressed. In this work, we used BeWo cells and human primary cytotrophoblasts isolated from term-placenta. The expression of ER-stress markers was analysed by qRT-PCR and Western blotting. ROS generation was assessed by fluorometric methods, while apoptosis was detected by the evaluation of caspase -3/-7 activities and Poly (ADP-ribose) polymerase (PARP) cleavage. Our findings indicate that 2-AG is able to induce ER-stress and apoptosis. Moreover, the eukaryotic initiation factor 2 (eIF2α)/CHOP pathway involved in ER-stress-induced apoptosis is triggered through a mechanism dependent on cannabinoid receptor CB2 activation. The results bring novel insights on the importance of ER-stress and cannabinoid signalling on 2-AG mechanisms of action in placenta.

Extracellularly Released Calreticulin Induced by Endoplasmic Reticulum Stress Impairs Syncytialization of Cytotrophoblast Model BeWo Cells

The pregnancy-specific syndrome preeclampsia is a major cause of maternal mortality throughout the world. The initial insult resulting in the development of preeclampsia is inadequate trophoblast invasion, which may lead to reduced maternal perfusion of the placenta and placental dysfunction, such as insufficient trophoblast syncytialization. Endoplasmic reticulum (ER) stress has been implicated in the pathology of preeclampsia and serves as the major risk factor. Our previous studies suggested critical roles of calreticulin (CRT), which is an ER-resident stress response protein, in extravillous trophoblast invasion and cytotrophoblast syncytialization. Here, we studied the mechanism by which ER stress exposes the placenta to the risk of preeclampsia. We found that CRT was upregulated in the serum samples, but not in the placental specimens, from preeclamptic women. By using BeWo cells, an established model of cytotrophoblasts that syncytialize in the presence of forskolin, we demonstrated that thapsigargin-induced ER stress caused extracellular release of CRT from BeWo cells and that the extracellular CRT suppressed forskolin-induced release of β-human chorionic gonadotropin and altered subcellular localization of E-cadherin, which is a key adhesion molecule associated with syncytialization. Our results together provide evidence that induction of ER stress leads to extracellular CRT release, which may contribute to placental dysfunction by suppressing cytotrophoblast syncytialization.

No evidence of the unfolded protein response in the placenta of two rodent models of preeclampsia and intrauterine growth restriction

In humans, intrauterine growth restriction (IUGR) and preeclampsia (PE) are associated with induction of the unfolded protein response (UPR) and increased placental endoplasmic reticulum (ER) stress. Especially in PE, oxidative stress occurs relative to the severity of maternal vascular underperfusion (MVU) of the placental bed. On the premise that understanding the mechanisms of placental dysfunction could lead to targeted therapeutic options for human IUGR and PE, we investigated the roles of the placental UPR and oxidative stress in two rodent models of these human gestational pathologies. We employed a rat IUGR model of gestational maternal protein restriction, as well as an endothelial nitric oxide synthase knockout mouse model (eNOS-/-) of PE/IUGR. Placental expression of UPR members was analyzed via qRT-PCR (Grp78, Calnexin, Perk, Chop, Atf6, and Ern1), immunohistochemistry, and Western blotting (Calnexin, ATF6, GRP78, CHOP, phospho-eIF2α, and phospho-IRE1). Oxidative stress was determined via Western blotting (3-nitrotyrosine and 4-hydroxy-2-nonenal). Both animal models showed a significant reduction of fetal and placental weight. These effects did not induce placental UPR. In contrast to human data, results from our rodent models suggest retention of placental plasticity in the setting of ER stress under an adverse gestational environment. Oxidative stress was significantly increased only in female IUGR rat placentas, suggesting a sexually dimorphic response to maternal malnutrition. Our study advances understanding of the involvement of the placental UPR in IUGR and PE. Moreover, it emphasizes the appropriate choice of animal models researching various aspects of these pregnancy complications.

Preeclampsia: Linking Placental Ischemia with Maternal Endothelial and Vascular Dysfunction

Preeclampsia (PE), a hypertensive disorder, occurs in 3% to 8% of pregnancies in the United States and affects over 200,000 women and newborns per year. The United States has seen a 25% increase in the incidence of PE, largely owing to increases in risk factors, including obesity and cardiovascular disease. Although the etiology of PE is not clear, it is believed that impaired spiral artery remodeling of the placenta reduces perfusion, leading to placental ischemia. Subsequently, the ischemic placenta releases antiangiogenic and pro-inflammatory factors, such as cytokines, reactive oxygen species, and the angiotensin II type 1 receptor autoantibody (AT1-AA), among others, into the maternal circulation. These factors cause widespread endothelial activation, upregulation of the endothelin system, and vasoconstriction. In turn, these changes affect the function of multiple organ systems including the kidneys, brain, liver, and heart. Despite extensive research into the pathophysiology of PE, the only treatment option remains early delivery of the baby and importantly, the placenta. While premature delivery is effective in ameliorating immediate risk to the mother, mounting evidence suggests that PE increases risk of cardiovascular disease later in life for both mother and baby. Notably, these women are at increased risk of hypertension, heart disease, and stroke, while offspring are at risk of obesity, hypertension, and neurological disease, among other complications, later in life. This article aims to discuss the current understanding of the diagnosis and pathophysiology of PE, as well as associated organ damage, maternal and fetal outcomes, and potential therapeutic avenues. © 2021 American Physiological Society. Compr Physiol 11:1315-1349, 2021.

Gestational Hypoxia Inhibits Pregnancy-Induced Upregulation of Ca2+ Sparks and Spontaneous Transient Outward Currents in Uterine Arteries Via Heightened Endoplasmic Reticulum/Oxidative Stress

Hypoxia during pregnancy profoundly affects uterine vascular adaptation and increases the risk of pregnancy complications, including preeclampsia and fetal intrauterine growth restriction. We recently demonstrated that increases in Ca2+ sparks and spontaneous transient outward currents (STOCs) played an essential role in pregnancy-induced uterine vascular adaptation. In the present study, we hypothesize that gestational hypoxia suppresses Ca2+ sparks/STOCs coupling leading to increased uterine vascular tone via enhanced endoplasmic reticulum (ER)/oxidative stress. Uterine arteries were obtained from nonpregnant and near-term pregnant sheep residing in low altitude or acclimatizing to high-altitude (3801 m) hypoxia for ≈110 days. High-altitude hypoxia suppressed pregnancy-induced upregulation of RyR1 and RyR2 (ryanodine receptor 1 and 2) protein abundance, Ca2+ sparks, and STOCs in uterine arteries. Inhibition of Ca2+ sparks/STOCs with the RyR inhibitor ryanodine significantly increased pressure-dependent myogenic tone in uterine arteries from low-altitude normoxic pregnant animals but not those from high-altitude hypoxic pregnant animals. Gestational hypoxia significantly increased ER/oxidative stress in uterine arteries. Of importance, the hypoxia-mediated suppression of Ca2+ sparks/STOCs and increase in myogenic tone in uterine arteries of pregnant animals were reversed by inhibiting ER/oxidative stress. Of great interest, the impaired sex hormonal regulation of STOCs in high-altitude animals was annulled by scavenging reactive oxygen species but not by inhibiting ER stress. Together, the findings reveal the differential mechanisms of ER and oxidative stresses in suppressing Ca2+ sparks/STOCs and increasing myogenic tone of uterine arteries in hypoxia during gestation, providing new insights into the understanding of pregnancy complications associated with hypoxia.

Osthole interacts with an ER-mitochondria axis and facilitates tumor suppression in ovarian cancer

Osthole is a natural coumarin found in a variety of plants and has been reported to have diverse biological functions, including antimicrobial, antiviral, immunomodulatory, and anticancer effects. Here, we investigated the natural derivative osthole as a promising anticancer compound against ovarian cancer and evaluated its ability to suppress and abrogate tumor progression. In addition, we found the endoplasmic reticulum-mitochondrial axis-mediated anticancer mechanisms of osthole against ES2 and OV90 ovarian cancer cells and demonstrated its calcium-dependent pharmacological potential. Mechanistically, osthole was found to target the phosphatidylinositol 3-kinase/mitogen-activated protein kinase signaling pathway to facilitate tumor suppression in ovarian cancer. Furthermore, we identified the effects of osthole in a three-dimensional tumor-formation model using the zebrafish xenograft assay, providing convincing evidence of the pharmacological effects of osthole within the anchorage-independent tumor microenvironment. These findings suggest that osthole has strong potential as a pharmacological agent for targeting ovarian cancer.

Protective effect of the NAC and Sal on zinc oxide nanoparticles-induced reproductive and development toxicity in pregnant mice

The growing use of zinc oxide nanoparticles (ZnO NPs) in various applications has raised many concerns about the potential risks to human health. In this research, the protective effects of cellular oxidative stress inhibitor N-Acetyl-cysteine (NAC) and endoplasmic reticulum (ER) stress inhibitor Salubrinal (Sal) on reproductive toxicity induced by ZnO NPs were investigated. The results showed that application of these two kinds of cell stress inhibitors after oral ingestion of ZnO NPs could prevent the weight loss of pregnant mice; reduce zinc content in the uterus, placenta and fetus; reduce abnormal development of the offspring; and decrease fetal abortion. Furthermore, RT-qPCR, Western blot and immunofluorescence assay results indicated that NAC restored the expression of Gclc, reduced the expression of ATF4, JNK and Caspase-12, and decreased the expression of eNOS and IGF-1, in the placenta. Sal decreased the expression of ATF4, JNK and Caspase-12, and increased the expression of eNOS and IGF-1caused by the oral ingestion of ZnO NPs. These results indicated that treatment with NAC and Sal after oral exposure could reduce reproductive and development toxicity caused by ZnO NPs which induced reproductive and development toxicity that was probably caused by the activation of oxide stress and ER stress.

Stigmasterol Causes Ovarian Cancer Cell Apoptosis by Inducing Endoplasmic Reticulum and Mitochondrial Dysfunction

Background: Phytosterols have physiological effects and are used as medicines or food supplements. Stigmasterol has shown anticancer effects against various cancers such as hepatoma, cholangiocarcinoma, gall bladder carcinoma, endometrial adenocarcinoma and skin, gastric, breast, prostate, and cervical cancer. However, there are no reports on stigmasterol’s effects on ovarian cancer. Methods: We investigated the effects of stigmasterol on proapoptotic signals, mitochondrial function, reactive oxygen species production, and the cytosolic and mitochondrial calcium levels in human ovarian cancer cells, to understand the mechanisms underlying the effects of stigmasterol on ovarian cancer cells. We also conducted migration assay to confirm whether that stigmasterol inhibits ovarian cancer cell migration. Results: Stigmasterol inhibited development of human ovarian cancer cells. However, it induced cell apoptosis, ROS production, and calcium overload in ES2 and OV90 cells. In addition, stigmasterol stimulated cell death by activating the ER-mitochondrial axis. We confirmed that stigmasterol suppressed cell migration and angiogenesis genes in human ovarian cancer cells. Conclusions: Our findings suggest that stigmasterol can be used as a new treatment for ovarian cancer.

Fucosterol Suppresses the Progression of Human Ovarian Cancer by Inducing Mitochondrial Dysfunction and Endoplasmic Reticulum Stress

Ovarian cancer is difficult to diagnose early and has high rates of relapse and mortality. Therefore, the treatment of ovarian cancer needs to be improved. Recently, several studies have been conducted in an attempt to develop anticancer drugs from naturally derived ingredients. Compared to traditional chemotherapy, natural compounds can overcome drug resistance with lower side effects. Fucosterol, a phytosterol present in brown algae, reportedly possesses many bioactive effects, including anticancer properties. However, the anticancer effects of fucosterol in ovarian cancer remain unexplored. Therefore, we investigated the effects of fucosterol on progression in human ovarian cancer cells. Fucosterol inhibited cell proliferation and cell-cycle progression in ovarian cancer cells. Additionally, fucosterol regulated the proliferation-related signaling pathways, the production of reactive oxygen species, mitochondrial function, endoplasmic reticulum stress, angiogenesis, and calcium homeostasis. Moreover, it decreased tumor formation in a zebrafish xenograft model. These results indicate that fucosterol could be used as a potential therapeutic agent in ovarian cancer.

Function of CCL5 in maternal-fetal interface of pig during early pregnancy

Chemokines refer to chemoattractant cytokines, which have crucial functions in inflammation and immune responses in multiple cellular processes. In the present study, we described the potential role of porcine CCL5 in embryo implantation and fetal-maternal environment during early pregnancy. We first carried out phylogenetic analysis of porcine CCL5, and analyzed the cell specific localization of CCL5 and its receptor CCR3 in a kinetic approach within porcine estrous cycles and early gestation stage. In addition, CCL5 stimulated porcine uterine luminal epithelial (pLE) and porcine trophectoderm (pTr) cell proliferations, and cell cycle progressions via AKT and MAPK intracellular signaling tractions. Furthermore, CCL5 attenuated tunicamycin-induced endoplasmic reticulum (ER) stress signaling, and lipopolysaccharides-triggered inflammatory responses in pLE and pTr cells. Taken together, our study showed that CCL5 is involved in the placental development or promotes the placental development.

Epitranscriptomic profiling in human placenta: N6-methyladenosine modification at the 5'-untranslated region is related to fetal growth and preeclampsia

Intracellular mRNA levels are not always proportional to their respective protein levels, especially in the placenta. This discrepancy may be attributed to various factors including post‐transcriptional regulation, such as mRNA methylation (N6‐methyladenosine: m⁶A). Here, we conducted a comprehensive m⁶A analysis of human placental tissue from neonates with various birth weights to clarify the involvement of m⁶A in placental biology. The augmented m⁶A levels at the 5′‐untranslated region (UTR) in mRNAs of small‐for‐date placenta samples were dominant compared to reduction of m⁶A levels, whereas a decrease in m⁶A in the vicinity of stop codons was common in heavy‐for‐date placenta samples. Notably, most of these genes showed similar expression levels between the different birth weight categories. In particular, preeclampsia placenta samples showed consistently upregulated SMPD1 protein levels and increased m⁶A at 5′‐UTR but did not show increased mRNA levels. Mutagenesis of adenosines at 5′‐UTR of SMPD1 mRNAs actually decreased protein levels in luciferase assay. Collectively, our findings suggest that m⁶A both at the 5′‐UTR and in the vicinity of stop codon in placental mRNA may play important roles in fetal growth and disease.

Role of endoplasmic reticulum stress on developmental competency and cryo-tolerance in bovine embryos

Endoplasmic reticulum (ER) stress, a dysfunction in protein folding capacity of the ER, is involved in many physiological responses including mammalian reproductive systems. Studies have shown that ER stress interferes with the developmental process of in vitro oocyte maturation and embryo development; however, little is known about its effects on bovine preimplantation embryonic development. In this study, we examined the effects of ER stress during IVC on developmental competency and cryo-tolerance in bovine embryos. IVF-derived zygotes were cultured in CR1aa medium supplemented with tauroursodeoxycholic acid (TUDCA) and/or tunicamycin (TM), which are ER stress-inhibitory and stress-inducing agents, respectively, for 8 days. TM treatment decreased the blastocyst developmental rate and increased the percentage of apoptotic cells compared to that in the control group (10.2 ± 2.3% vs. 39.75 ± 1.3% and 17.8 ± 1.2% vs. 3.6 ± 1.1%, respectively; P < 0.01). However, the blastocyst developmental rate was increased and the percentage of apoptotic cells was decreased by addition of TUDCA in IVC medium compared to that in the control group (50.9 ± 0.9% vs. 39.75 ± 1.3% and 1.13 ± 1.0% vs. 3.6 ± 1.1%, respectively; P < 0.01). Importantly, in the group treated with TM plus TUDCA, the developmental rate and the percentage of apoptotic cells in blastocysts were similar to that in the control group, indicating that TUDCA ameliorates the adverse effects of TM alone on embryo development. In addition, TUDCA treatment significantly reduced the reactive oxygen species, expression of ER stress (GRP78, ATF4, ATF6, IER1, and sXBP1) and pro-apoptotic (CHOP and BAX) genes, while it increased anti-apoptotic BCL2 gene expression and glutathione levels. Moreover, TUDCA improved blastocyst cryo-tolerance as marked by a significantly increased hatching rate and decreased the number of apoptotic cells recorded at 48 h after a post-warming. Therefore, in concordance with a previous report in mice or pig, we showed that TUDCA supplementation during IVC increases the developmental competency of bovine in vitro-derived embryos. Additionally, we found that the presence of TUDCA in IVC medium improves the cryo-tolerance of bovine embryos. These results suggest that modulation of ER stress during IVC contributes to the production of high-quality bovine embryos in terms of cryo-tolerance.

Obesity in mares promotes uterine inflammation and alters embryo lipid fingerprints and homeostasis

Maternal body composition can be an important determinant for development of obesity and metabolic syndrome in adult offspring. Obesity-related outcomes in offspring may include epigenetic alterations; however, mechanisms of fetal programming remain to be fully elucidated. This study was conducted to determine the impact of maternal obesity in the absence of a high fat diet on equine endometrium and preimplantation embryos. Embryos were collected from normal and obese mares at 8 and 16 days and a uterine biopsy at 16 days (0 day = ovulation). With the exception of 8 day embryos, each sample was divided into two pieces. One piece was analyzed for gene expression markers related to carbohydrate metabolism, lipid homeostasis, inflammation, endoplasmic reticulum stress, oxidative stress, mitochondrial stress, and components of the insulin-like growth factor (IGF) system. The second piece was analyzed for lipid content using matrix-assisted laser desorption/ionization mass spectrometry. Obese mares had elevated concentrations of insulin, leptin, and total cholesterol, and they tended to have increased triglycerides and decreased insulin sensitivity. Embryos from obese mares had altered transcript abundance in genes for inflammation and lipid homeostasis, as well as endoplasmic reticulum, oxidative and mitochondrial stress and altered lipid fingerprints. Endometrium from obese mares had increased expression of inflammatory cytokines, lipid homeostasis regulation, mitochondrial stress, and the IGF2 system. This study demonstrates that increased adiposity in mares alters the uterine environment, transcript abundance of genes for cellular functions, and lipid profiles of embryos. These alterations could affect prenatal programming, with potential long-term effects in offspring.

Pre-eclampsia: pathogenesis, novel diagnostics and therapies

Pre-eclampsia is a complication of pregnancy that is associated with substantial maternal and fetal morbidity and mortality. The disease presents with new-onset hypertension and often proteinuria in the mother, which can progress to multi-organ dysfunction, including hepatic, renal and cerebral disease, if the fetus and placenta are not delivered. Maternal endothelial dysfunction due to circulating factors of fetal origin from the placenta is a hallmark of pre-eclampsia. Risk factors for the disease include maternal comorbidities, such as chronic kidney disease, hypertension and obesity; a family history of pre-eclampsia, nulliparity or multiple pregnancies; and previous pre-eclampsia or intrauterine fetal growth restriction. In the past decade, the discovery and characterization of novel antiangiogenic pathways have been particularly impactful both in increasing understanding of the disease pathophysiology and in directing predictive and therapeutic efforts. In this Review, we discuss the pathogenic role of antiangiogenic proteins released by the placenta in the development of pre-eclampsia and review novel therapeutic strategies directed at restoring the angiogenic imbalance observed during pre-eclampsia. We also highlight other notable advances in the field, including the identification of long-term maternal and fetal risks conferred by pre-eclampsia.

Tetramethylpyrazine reduces the consequences of nitric oxide inhibition in pregnant rats

Pre-eclampsia (PE) is closely associated with perinatal morbidity and mortality and we want to investigate tetramethylpyrazine (TMP)'s effects on PE. Pregnant Sprague-Dawley rats were randomly divided into five groups: normal pregnant (PC), PE, PE+TMP 20 mg/kg, PE+TMP 40 mg/kg, and PE+TMP 60 mg/kg group. The PE rat model was established via L-NAME treatment. Systolic blood pressures (SBP) and urinary protein concentration were detected via the tail-cuff method and CBB kit, respectively. mRNA levels of key genes were analyzed via quantitative PCR and protein levels of key genes were measured by ELISA or western blot. TMP decreased SBP and urinary protein concentration of PE rats. TMP inhibited L-NAME-induced decrease in pups alive ratio, pups weight, and the ratio of pups/placenta weight and reversed L-NAME induced changes in placental histology, whereas it had little effect on placental weight. Urinary nephrin and podocin expressions were enhanced and serum placental growth factor level was decreased in PE rats, whereas TMP inhibited the above phenomena. TMP suppressed L-NAME-induced sFlt-1 upregulation in serums and kidneys of PE rats, whereas it downregulated IL-6 and MCP-1 expression in PE rats' serums, placentas and kidneys. TMP also suppressed the increase in placental sFlt-1 and vascular endothelial growth factor level caused by L-NAME. In addition, TMP inhibited CHOP and GRP78 expressions and decreased the ratio of p-elF2α/elF2α in PE rats. TMP attenuated the consequences of NO inhibition in pregnant rats.

The potential contribution of stromal cell-derived factor 2 (SDF2) in endoplasmic reticulum stress response in severe preeclampsia and labor-onset

Endoplasmic reticulum (ER) stress occurs when the protein folding machinery in the cell is unable to cope with newly synthesized proteins, which results in an accumulation of misfolded proteins in the ER lumen. In response, the cell activates a cellular signaling pathway known as the Unfolded Protein Response (UPR), aiming to restore cellular homeostasis. Activation and exacerbation of the UPR have been described in several human pathologies, including cancer and neurological disorders, and in some gestational diseases such as preeclampsia and gestational diabetes. This review explores the participation of stromal cell-derived factor 2 (SDF2) in UPR pathways, shows new information and discusses its exacerbation regarding protein expression in severe preeclampsia and labor, both of which are associated with ER stress.

Endoplasmic Reticulum (ER) Stress and Unfolded Protein Response (UPR) in Mammalian Oocyte Maturation and Preimplantation Embryo Development

Mammalian oocytes and early embryos derived from in vitro production are highly susceptible to a variety of cellular stresses. During oocyte maturation and preimplantation embryo development, functional proteins must be folded properly in the endoplasmic reticulum (ER) to maintain oocyte and embryo development. However, some adverse factors negatively impact ER functions and protein synthesis, resulting in the activation of ER stress and unfolded protein response (UPR) signaling pathways. ER stress and UPR signaling have been identified in mammalian oocytes and embryos produced in vitro, suggesting that modulation of ER stress and UPR signaling play very important roles in oocyte maturation and the development of preimplantation embryos. In this review, we briefly describe the current state of knowledge regarding ER stress, UPR signaling pathways, and their roles and mechanisms in mammalian (excluding human) oocyte maturation and preimplantation embryo development.

Preeclampsia: A close look at renal dysfunction

Preeclampsia (PE) is a unique pathophysiologic situation that physiologic interests of mother, fetus, and placenta diverge. PE is related to the increased circulating antiangiogenic factors originated from hypoxic placenta. It is simply defined by the new onset of hypertension (≥140/90 mmHg) and proteinuria (≥0.3 g/day) after 20 weeks of gestation. PE is associated with kidney dysfunction due to deficiency in podocyte specific vascular endothelial growth factor (VEGF). Hypoxic placenta in PE patients produces increased levels of fms-like tyrosine kinase 1(sFlt-1), a soluble receptor of VEGF. sFlt-1 abrogates binding of VEGF to its receptor on endothelial cells and podocytes, and ultimately damages the filtration barrier. Glomerular endotheliosis and thrombotic microangiopathy (TMA) are the main features of kidney involvement in PE and can induce clotting and vessel occlusion. This complex pathophysiology is ameliorated after delivery; however, permanent kidney damages may remain and is intensified thereafter. This review aims to highlight the biochemical, genetic, and immunological-involved factors in the initiation of PE and explores the relationship between the kidney and PE. This work mainly discusses the pathologic mechanisms of kidney involvement in PE through the lens of the imbalanced VEGF-VEGF receptor signaling pathway.

Role of Endoplasmic Reticulum Stress in Proinflammatory Cytokine-Mediated Inhibition of Trophoblast Invasion in Placenta-Related Complications of Pregnancy

Shallow extravillous trophoblast (EVT) invasion is central to the pathophysiology of many pregnancy complications. Invasion is mediated partially by matrix metalloproteinases (MMPs). MMP-2 is highly expressed in early pregnancy. MMP activity can be regulated by proinflammatory cytokines, which also induce endoplasmic reticulum (ER) stress in other cells. We investigated whether proinflammatory cytokines regulate MMP-2 activity through ER stress response pathways in trophoblast before exploring potential regulatory mechanisms. There was increased immunoreactivity of heat shock 70-kDa protein 5, also known as 78-kDa glucose regulated protein, in cells of the placental bed, including EVTs, in cases of early-onset preeclampsia compared with normotensive controls. Treating EVT-like JEG-3 and HTR8/SVneo cells with ER stress inducers (tunicamycin and thapsigargin) suppressed MMP2 mRNA and protein expression, secretion, and activity and reduced their invasiveness. A cocktail of proinflammatory cytokines (IL-1β, tumor necrosis factor-α, and interferon-γ) suppressed MMP-2 activity in JEG-3 cells and was accompanied by activation of the PKR-like ER kinase (PERK)-eukaryotic translation initiation factor 2A (EIF2A) arm of the ER stress pathway. Knockdown of ATF4, a downstream transcriptional factor of the PERK-EIF2A pathway, by small interference RNA, restored MMP2 expression but not cellular proteins. However, suppression of EIF2A phosphorylation with a PERK inhibitor, GSK2606414, under ER stress, restored MMP-2 protein. ER stress regulates MMP-2 expression at both the transcriptional and translational levels. This study provides the first mechanistic linkage by which proinflammatory cytokines may modulate trophoblast invasion through ER stress pathways.

Ephrin A1 promotes proliferation of bovine endometrial cells with abundant expression of proliferating cell nuclear antigen and cyclin D1 changing the cell population at each stage of the cell cycle

Ephrin A1 has a role in a variety of biological events, including cell proliferation, differentiation, migration, and angiogenesis. Ephrin A1 expression is abundant in trophoblasts and endometrial cells during the implantation period; however, its intracellular activities have not yet been reported in bovine endometrial (BEND) epithelial cells. The aim of this study was to identify the functional role of ephrin A1 in BEND cells, which have served as a good model system for investigating the regulation of signal transduction following treatment with interferon-τ (IFNT) in vitro. Supplementation of ephrin A1 to BEND cells increased cell proliferation and increased levels of proliferating cell nuclear antigen and cyclin D1 protein in BEND cell nuclei. To investigate intracellular mechanisms regulated by ephrin A1, we performed Western blot analysis focused on mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) signaling, which are significantly involved in the successful maintenance of pregnancy. Ephrin A1 dose-dependently increased phosphorylation of extracellular signal-regulated kinases (ERK)1/2, c-Jun N-terminal kinases (JNK), P38, protein kinase B (AKT), P70S6K, S6, and cyclin D1, and the activated proteins were suppressed by pharmacological inhibitors including wortmannin (a PI3K inhibitor), U0126 (an ERK1/2 inhibitor), and SP600125 (a JNK inhibitor). Among ephrin A1 receptors, abundant expression of EPHA2 and EPHA4 messenger RNA was detected in BEND cells by reverse transcription polymerase chain reaction analysis. Furthermore, tunicamycin-induced endoplasmic reticulum (ER) stress was inactivated by ephrin A1 treatment of BEND cells. Our findings suggest that ephrin A1 promotes the development of BEND cells and likely enhances uterine capacity and maintenance of pregnancy by activating MAPK and PI3K signaling cascades and by restoring ER stress.

N-acetylcysteine alleviates cadmium-induced placental endoplasmic reticulum stress and fetal growth restriction in mice

Cadmium (Cd) is a developmental toxicant that induces fetal growth restriction (FGR). Placental endoplasmic reticulum (ER) stress is associated with FGR. This study investigated the effects of N-acetylcysteine (NAC) on Cd-induced placental ER stress and FGR. Pregnant mice were intraperitoneally injected with CdCl₂ daily from gestational day (GD)13 to GD17. As expected, Cd reduced fetal weight and crown-rump length. Cd decreased the internal space of blood vessels in the placental labyrinth layer and inhibited placental cell proliferation. Several genes of growth factors, such as Vegf-a, placental growth factor, Igf1 and Igf1r, and several genes of nutrient transport pumps, such as Glut1, Fatp1 and Snat2, were down-regulated in placenta of Cd-treated mice. Moreover, Cd evoked placental ER stress. Of interest, NAC alleviated Cd-induced FGR. Additional experiment showed that NAC inhibited Cd-induced impairment of placental development and placental ER stress. Therefore, NAC may be exploited for prevention of Cd-induced placental insufficiency and FGR.

The high concentration of progesterone is harmful for endometrial receptivity and decidualization

Progesterone is required for the establishment and maintenance of mammalian pregnancy and widely used for conservative treatment of luteal phase deficiency in clinics. However, there are limited solid evidences available for the optimal timing and dose of progesterone therapy, especially for the possible adverse effects on implantation and decidualization when progesterone is administrated empirically. In our study, mouse models were used to examine effects of excess progesterone on embryo implantation and decidualization. Our data indicate that excess progesterone is not only harmful for mouse implantation, but also impairs mouse decidualization. In excess progesterone-treated mice, the impaired LIF/STAT3 pathway and dysregulated endoplasmic reticulum stress may lead to the inhibition of embryo implantation and decidualization. It is possible that the decrease in birth weight of excess progesterone-treated mice is due to a compromised embryo implantation and decidualization. Furthermore, excess progesterone compromises in vitro decidualization of human endometrial stromal cells.

Progesterone Receptor Signaling in Uterine Myometrial Physiology and Preterm Birth

Myometrium holds the structural integrity for the uterus and generates force for parturition with its primary component, the smooth muscle cells. The progesterone receptor mediates progesterone-dependent signaling and connects to a network of pathways for regulation of contractility and inflammatory responses in myometrium. Dysfunctional progesterone signaling has been linked to pregnancy complications including preterm birth. In the present review, we summarize recent findings on modifiers and effectors of the progesterone receptor signaling. Discussions include novel conceptual discoveries and new development in legacy pathways such as the signal transducers NF-κB, ZEB, microRNA, and the unfolded protein response pathways. We also discuss the impact of progesterone receptor isoform composition and ligand accessibility in modification of the progesterone receptor genomic actions.

Endoplasmic Reticulum Stress and Homeostasis in Reproductive Physiology and Pathology

The endoplasmic reticulum (ER), comprises 60% of the total cell membrane and interacts directly or indirectly with several cell organelles i.e., Golgi bodies, mitochondria and proteasomes. The ER is usually associated with large numbers of attached ribosomes. During evolution, ER developed as the specific cellular site of synthesis, folding, modification and trafficking of secretory and cell-surface proteins. The ER is also the major intracellular calcium storage compartment that maintains cellular calcium homeostasis. During the production of functionally effective proteins, several ER-specific molecular steps sense quantity and quality of synthesized proteins as well as proper folding into their native structures. During this process, excess accumulation of unfolded/misfolded proteins in the ER lumen results in ER stress, the homeostatic coping mechanism that activates an ER-specific adaptation program, (the unfolded protein response; UPR) to increase ER-associated degradation of structurally and/or functionally defective proteins, thus sustaining ER homeostasis. Impaired ER homeostasis results in aberrant cellular responses, contributing to the pathogenesis of various diseases. Both female and male reproductive tissues undergo highly dynamic cellular, molecular and genetic changes such as oogenesis and spermatogenesis starting in prenatal life, mainly controlled by sex-steroids but also cytokines and growth factors throughout reproductive life. These reproductive changes require ER to provide extensive protein synthesis, folding, maturation and then their trafficking to appropriate cellular location as well as destroying unfolded/misfolded proteins via activating ER-associated degradation mediated proteasomes. Many studies have now shown roles for ER stress/UPR signaling cascades in the endometrial menstrual cycle, ovarian folliculogenesis and oocyte maturation, spermatogenesis, fertilization, pre-implantation embryo development and pregnancy and parturition. Conversely, the contribution of impaired ER homeostasis by severe/prolong ER stress-mediated UPR signaling pathways to several reproductive tissue pathologies including endometriosis, cancers, recurrent pregnancy loss and pregnancy complications associated with pre-term birth have been reported. This review focuses on ER stress and UPR signaling mechanisms, and their potential roles in female and male reproductive physiopathology involving in menstrual cycle changes, gametogenesis, preimplantation embryo development, implantation and placentation, labor, endometriosis, pregnancy complications and preterm birth as well as reproductive system tumorigenesis.

ATF6 knockdown decreases apoptosis, arrests the S phase of the cell cycle, and increases steroid hormone production in mouse granulosa cells

Activating transcription factor 6 (ATF6), a sensor protein located in the endoplasmic reticulum (ER) membrane, is an important factor in the ER stress signaling pathway. ER stress is known to be involved in folliculogenesis, follicular growth, and ovulation; however, the physiological function of ATF6 in mouse granulosa cells remains largely unknown. The aim of this study was to assess the role of ATF6 in mouse granulosa cells with respect to apoptosis, the cell cycle, and steroid hormone production, as well as several key genes related to follicular development, via RNA interference, immunohistochemical staining, real-time quantitative PCR, Western blotting, flow cytometry, terminal deoxynucleotidyltransferase-mediated deoxy-UTP nick end labeling (TUNEL) assay, and ELISA. Immunohistochemical staining revealed that ATF6 was extensively distributed in the granulosa cells of various ovarian follicles and oocytes in adult female mice. FSH or LH treatment significantly increased ATF6 protein levels in mouse granulosa cells. In the meantime, a recombinant plasmid was used to deplete ATF6 successfully using short hairpin RNA-mediated interference technology, which was verified at both the mRNA and protein levels. Flow cytometry and TUNEL assay analysis indicated that ATF6 depletion decreased apoptosis and arrested the S phase of the cell cycle in mouse granulosa cells. Consistent with these results, p53, caspase-3, B cell lymphoma 2 (Bcl-2)-associated X protein, CCAAT-enhancer-binding protein homologous protein, cyclin A1, cyclin B1, and cyclin D2 mRNA expression decreased, whereas Bcl-2 and glucose-regulated protein 78 kDa mRNA expression increased. Interestingly, ATF6 knockdown obviously increased progesterone and estradiol production in mouse granulosa cells. Cytochrome P450 1b1 (Cyp1b1) mRNA levels were downregulated, whereas Cyp11a1, steroidogenic acute regulatory, and Cyp19a1 mRNA levels were upregulated, in keeping with the changes in steroid hormones. Furthermore, ATF6 disruption remarkably increased insulin-like growth factor binding protein4 (Igfbp4) expression and decreased hyaluronan synthase 2 (Has2), prostaglandin-endoperoxide synthase 2 (Ptgs2), and prostaglandin F receptor (Ptgfr) expression in mouse granulosa cells, which are proteins crucial for follicular development. But, after treating with tunicamycin, the levels of Has2, Ptgs2, and Ptgfr increased relatively, whereas Igfbp4 expression decreased. Collectively, these results imply that ATF6, as a key player in ER stress signaling, may regulate apoptosis, the cell cycle, steroid hormone synthesis, and other modulators related to folliculogenesis in mouse granulosa cells, which may indirectly be involved in the development, ovulation, and atresia of ovarian follicles by affecting the physiological function of granulosa cells. The present study extends our understanding and provides new insights into the physiological significance of ATF6, a key signal transducer of ER stress, in ovarian granulosa cells.

Roles of Grp78 in Female Mammalian Reproduction

The glucose-regulated protein (GRP78) also referred to as immunoglobulin heavy chain binding protein (Bip) is one of the best characterized endoplasmic reticulum (ER) chaperone proteins, which belongs to the heat-shock protein (HSP) family. GRP78 as a central regulator of ER stress (ERS) plays many important roles in cell survival and apoptosis through controlling the activation of transmembrane ERS sensors: PKR-like ER-associated kinase (PERK), inositol requiring kinase 1 (IRE1), and activating transcription factor 6 (ATF6). Many studies have reported that GRP78 is involved in the physiological and pathological process in female reproduction, including follicular development, corpus luteum (CL), oviduct, uterus, embryo, preimplantation development, implantation/decidualization, and the placenta. The present review summarizes the biological or pathological roles and signaling mechanisms of GRP78 during the reproductive processes. Further study on the functions and mechanisms of GRP78 may provide new insight into mammalian reproduction, which not only enhance the understanding of the physiological roles but also support therapy target against infertility.

eNOS/iNOS and endoplasmic reticulum stress-induced apoptosis in the placentas of patients with preeclampsia

Disruption of nitric oxide pathway and endoplasmic reticulum (ER) stress had been observed in preeclampsia (PE). However, the correlation and overall detailed expression profiles of ER stress-related markers and endothelial nitric oxide synthase/inducible nitric oxide synthase (eNOS/iNOS) in patients with PE were poorly understood. In this study, placental protein expression of ER stress-related markers as well as eNOS/iNOS in normotensive control (n=32) and PE pregnancies (n=32) was examined by western blot. In addition, apoptosis was detected by terminal deoxynucleotidyl transferase-mediated nick-end labelling (TUNEL) staining in placentas. Compared with control, we found elevated ER stress response was agreeable with iNOS upregulation in placenta tissue of PE patients. Placental protein expression of ER stress-related markers, including GRP78, GRP94, p-PERK, eIF2a, p-eIF2a, XBP1, CHOP, Ire1, p-Ire1 and iNOS, was higher, and eNOS expression was lower in PE (P<0.05 for all); however, the expression of ATF6 and PERK was similar in the PE and control groups. Upregulation of CHOP and iNOS was consistent of apoptosis increasing indicated by TUNEL staining and caspase 4 expression upregulation in PE placenta. Our datas suggest that the exaggerated ER stress response and upregulated iNOS are probably associated with increased apoptosis in placenta of PE patients and may contribute to the pathophysiology of PE.

Endoplasmic reticulum stress in mouse decidua during early pregnancy

Unfolded or misfolded protein accumulation in the endoplasmic reticulum lumen leads to endoplasmic reticulum stress (ER stress). Although it is known that ER stress is crucial for mammalian reproduction, little is known about its physiological significance and underlying mechanism during decidualization. Here we show that Ire-Xbp1 signal transduction pathway of unfolded protein response (UPR) is activated in decidual cells. The process of decidualization is compromised by ER stress inhibitor tauroursodeoxycholic acid sodium (TUDCA) and Ire specific inhibitor STF-083010 both in vivo and in vitro. A high concentration of ER stress inducer tunicamycin (TM) suppresses stromal cells proliferation and decidualization, while a lower concentration is beneficial. We further show that ER stress induces DNA damage and polyploidization in stromal cells. In conclusion, our data suggest that the GRP78/Ire1/Xbp1 signaling pathway of ER stress-UPR is activated and involved in mouse decidualization.

Expression and regulation of ATF6α in the mouse uterus during embryo implantation

BACKGROUND

ATF6α, one of the sensor proteins in the stress signaling pathway of the endoplasmic reticulum, is located in the membrane of the endoplasmic reticulum. To date, the physiological function of ATF6α in the process of embryo implantation has not been reported.

METHODS

In this study, the expression pattern of ATF6α in the mouse uterus during peri-implantation and the estrous cycle was detected by real-time PCR, western blot and immunohistochemistry.

RESULTS

ATF6α mRNA and protein levels were higher in the uterus near the implantation site on day 5 and were intensely expressed in the secondary decidual zone (SDZ) on days 7-8. In the uteri of pseudopregnant mice, ATF6α mRNA and protein levels were lower on day 5 than on other days. The activating blastocyst and artificial decidualization had an obvious effect of increasing the expression of ATF6α. In addition, the expression of ATF6α was affected by progesterone (P₄) and estrogen (E₂) in ovariectomized mice. This finding is further supported by evidence from mice during the estrous cycle.

CONCLUSIONS

Thus, we have concluded that ATF6α may play an important role during embryo implantation and decidualization.

Gestational food restriction decreases placental interleukin-10 expression and markers of autophagy and endoplasmic reticulum stress in murine intrauterine growth restriction

Intrauterine growth restriction (IUGR) affects up to 10% of pregnancies and often results in short- and long-term sequelae for offspring. The mechanisms underlying IUGR are poorly understood, but it is known that healthy placentation is essential for nutrient provision to fuel fetal growth, and is regulated by immunologic inputs. We hypothesized that in pregnancy, maternal food restriction (FR) resulting in IUGR would decrease the overall immunotolerant milieu in the placenta, leading to increased cellular stress and death. Our specific objectives were to evaluate (1) key cytokines (eg, IL-10) that regulate maternal-fetal tolerance, (2) cellular processes (autophagy and endoplasmic reticulum [ER] stress) that are immunologically mediated and important for cellular survival and functioning, and (3) the resulting IUGR phenotype and placental histopathology in this animal model. After subjecting pregnant mice to mild and moderate FR from gestational day 10 to 19, we collected placentas and embryos at gestational day 19. We examined RNA sequencing data to identify immunologic pathways affected in IUGR-associated placentas and validated messenger RNA expression changes of genes important in cellular integrity. We also evaluated histopathologic changes in vascular and trophoblastic structures as well as protein expression changes in autophagy, ER stress, and apoptosis in the mouse placentas. Several differentially expressed genes were identified in FR compared with control mice, including a considerable subset that regulates immune tolerance, inflammation, and cellular integrity. In summary, maternal FR decreases the anti-inflammatory effect of IL-10 and suppresses placental autophagic and ER stress responses, despite evidence of dysregulated vascular and trophoblast structures leading to IUGR.