Prolonged endoplasmic reticulum stress alters placental morphology and causes low birth weight

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.

Mtnr1b deletion disrupts placental angiogenesis through the VEGF signaling pathway leading to fetal growth restriction

The placenta, as a "transit station" between mother and fetus, has functions delivering nutrients, excreting metabolic wastes and secreting hormones. A healthy placenta is essential for fetal growth and development while the melatonergic system seems to play a critical physiological role in this organ since melatonin, its synthetic enzymes and receptors are present in the placenta. In current study, Mtnr1a and Mtnr1b knockout mice were constructed to explore the potential roles of melatonergic system played on the placental function and intrauterine growth retardation (IUGR). The result showed that Mtnr1a knockout had little effect on placental function while Mtnr1b knockout reduced placental efficiency and increased IUGR. Considering the extremely high incidence of IURG in sows, the pregnant sows were treated with melatonin. This treatment reduced the incidence of IUGR. All the evidence suggests that the intact melatonergic system in placenta is required for its function. Mechanistical studies uncovered that Mtnr1b knockout increased placental oxidative stress and apoptosis but reduced the angiogenesis. The RNA sequencing combined with histochemistry study identified the reduced angiogenesis and placental vascular density in Mtnr1b knockout mice. These alterations were mediated by the disrupted STAT3/VEGFR2/PI3K/AKT pathway, i.e., Mtnr1b knockout reduced the phosphorylation of STAT3 which is the promotor of VEGFR2. The downregulated VEGFR2 and its downstream elements of PI3K and AKT expressions, then, jeopardizes the angiogenesis and placental development.

CHOP upregulation and dysregulation of the mature form of the SNAT2 amino acid transporter in the placentas from small for gestational age newborns

BACKGROUND

The placentas from newborns that are small for gestational age (SGA; birth weight < -2 SD for gestational age) may display multiple pathological characteristics. A key determinant of fetal growth and, therefore, birth weight is placental amino acid transport, which is under the control of the serine/threonine kinase mechanistic target of rapamycin (mTOR). The effects of endoplasmic reticulum (ER) stress on the mTOR pathway and the levels of amino acid transporters are not well established.

METHODS

Placentas from SGA and appropriate for gestational age (AGA) newborns and the human placental BeWo cell line exposed to the ER stressor tunicamycin were used.

RESULTS

We detected a significant increase in the levels of C/EBP homologous protein (CHOP) in the placentas from SGA newborns compared with those from AGA newborns, while the levels of other ER stress markers were barely affected. In addition, placental mTOR Complex 1 (mTORC1) activity and the levels of the mature form of the amino acid transporter sodium-coupled neutral amino acid transporter 2 (SNAT2) were also reduced in the SGA group. Interestingly, CHOP has been reported to upregulate growth arrest and DNA damage-inducible protein 34 (GADD34), which in turn suppresses mTORC1 activity. The GADD34 inhibitor guanabenz attenuated the increase in CHOP protein levels and the reduction in mTORC1 activity caused by the ER stressor tunicamycin in the human placental cell line BeWo, but it did not recover mature SNAT2 protein levels, which might be reduced as a result of defective glycosylation.

CONCLUSIONS

Collectively, these data reveal that GADD34A activity and glycosylation are key factors controlling mTORC1 signaling and mature SNAT2 levels in trophoblasts, respectively, and might contribute to the SGA condition. Video Abstract.

Urinary congophilia in pregnancy: a marker of kidney injury rather than preeclampsia

BACKGROUND

The differentiation between preeclampsia and similarly presenting kidney disease in pregnancy is a diagnostic challenge. Although some laboratory tests have been utilized, globally validated tools are yet needed, particularly in resource-limited settings. Congophilic proteins are abundantly detected in the urine of pregnant women who develop preeclampsia that is thought to be a marker of disease process. The present study aimed to assess the diagnostic and predictive utility of urinary congophilia in pregnant women with hypertensive disorders of pregnancy as well as kidney diseases.

METHODS

This cohort study included 157 pregnant women, classified as healthy controls ( n  = 38), preeclampsia/eclampsia ( n  = 45), gestational hypertension ( n  = 9), chronic hypertension ( n  = 8), chronic kidney disease (CKD) ( n  = 27), and pregnancy-related acute kidney injury (PR-AKI) ( n  = 30). Urinary congophilia was assessed by Congo Red Dot Blot assay.

RESULTS

Congo red retention (CRR) values were significantly higher in women with preeclampsia/eclampsia ( P  ≤ 0.001), chronic hypertension ( P  = 0.029), gestational hypertension ( P  = 0.017), CKD ( P  ≤ 0.001), PR-AKI secondary to preeclampsia ( P  ≤ 0.001), and PR-AKI secondary to other causes ( P  = 0.001), compared with healthy controls. Women with preeclampsia, CKD, and PR-AKI (non-preeclampsia related) exhibited the highest levels of CRR. CRR positively correlated to proteinuria ( P  = 0.006) and serum creatinine ( P  = 0.027). CRR did not significantly vary between women who presented antepartum and those presented postpartum after removal of the placenta ( P  = 0.707). CRR at a cut-off point of at least 1.272 had 91% specificity and 61.1% sensitivity in predicting renal recovery in PR-AKI patients. CRR had a poor specificity in discriminating preeclampsia from the other clinical presentations.

CONCLUSION

Urinary congophilia could not discriminate preeclampsia from similarly presenting kidney diseases in pregnancy. Further studies are needed to improve differentiation of these conditions.

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.

Methyltransferase-like 3 aggravates endoplasmic reticulum stress in preeclampsia by targeting TMBIM6 in YTHDF2-dependent manner

BACKGROUND

With the increasing morbidity and mortality of preeclampsia (PE), it has posed a huge challenge to public health. Previous studies have reported endoplasmic reticulum (ER) stress could contribute to trophoblastic dysfunction which was associated with the N⁶-methyladenosine (m⁶A) modification by methyltransferase-like 3 (METTL3), resulting in PE. However, little was known about the relationship between METTL3 and ER stress in PE. Thus, in vitro and in vivo studies were performed to clarify the mechanism about how METTL3 affects the trophoblasts under ER stress in PE and to explore a therapeutic approach for PE.

METHODS

An ER stress model in HTR-8/SVneo cells and a preeclamptic rat model were used to study the mechanism and explore a therapeutic approach for PE. Western blot, immunohistochemistry, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and methylated RNA immunoprecipitation (MeRIP)-qPCR were performed to detect the protein, RNA, and methylated transmembrane BAX inhibitor motif containing 6 (TMBIM6) expression levels. The m⁶A colorimetric and mRNA stability assays were used to measure the m⁶A levels and TMBIM6 stability, respectively. Short hairpin RNAs (shRNAs) were used to knockdown METTL3 and YTH N6-methyladenosine RNA binding protein 2 (YTHDF2). Flow cytometry and Transwell assays were performed to evaluate the apoptosis and invasion abilities of trophoblasts.

RESULTS

Upregulated METTL3 and m⁶A levels and downregulated TMBIM6 levels were observed in preeclamptic placentas under ER stress. The ER stress model was successfully constructed, and knockdown of METTL3 had a beneficial effect on HTR-8/SVneo cells under ER stress as it decreased the levels of methylated TMBIM6 mRNA. Moreover, overexpression of TMBIM6 was beneficial to HTR-8/SVneo cells under ER stress as it could neutralize the harmful effects of METTL3 overexpression. Similar to the knockdown of METTL3, downregulation of YTHDF2 expression resulted in the increased expression and mRNA stability of TMBIM6. Finally, improved systemic symptoms as well as protected placentas and fetuses were demonstrated in vivo.

CONCLUSIONS

METTL3/YTHDF2/TMBIM6 axis exerts a significant role in trophoblast dysfunction resulting in PE while inhibiting METTL3 may provide a novel therapeutic approach for PE.

Obesity impacts placental function through activation of p-IRE1a-XBP1s signaling

Maternal obesity is associated with a variety of obstetrical outcomes including stillbirth, preeclampsia, and gestational diabetes, and increases the risk of fetuses for congenital heart defects. Obesity during pregnancy represents a major contribution to metabolic dysregulation, which not only plays a key role in the pathogenesis of adverse outcome but also can potently induce endoplasmic reticulum (ER) stress. However, the mechanism associating such an obesogenic metabolic environment and adverse pregnancy outcomes has remained poorly understood. In this study, we aimed to determine whether the ER stress pathways (also named unfolded protein response (UPR)) were activated in the placenta by obesity. We collected placenta from the obese pregnancy (n = 12) and non-obese pregnancy (n = 12) following delivery by Caesarean-section at term. The specimens were assessed with immunocytochemistry staining and RT-QPCR. Our results revealed that in the obese placenta, p-IRE1α and XBP1s were significantly increased, CHOP and nine UPR chaperone genes were upregulated, including GRP95, PDIA6, Calnexin, p58IPK, SIL-1, EDEM, Herp, GRP58 and Calreticulin. However, Perk and BiP are not activated in the obese placenta. Our data suggest that upregulated p-IRE1α and XBP1s signaling, and UPR chaperone genes may play an important role in maternal obesity-induced placental pathology. In conclusion, this is the first report on ER stress and UPR activation in the placenta of maternal obesity. Our findings represent the first step in the understanding of one of the key ER signaling pathways, also referred to IRE1α-XBP1, in placental pathophysiology affected by obesity, which may be an important mechanism accounting for the observed higher maternal and perinatal risks.

Placenta: an organ with high energy requirements

Placenta is a unique organ, without which the very phenomenon of human pregnancy is impossible. Semiallogeneous nature, localization of the placenta, complex and heterogeneous cellular composition determines its complex and multifaceted role in the course of physiological pregnancy, indicates the importance of studying this organ in a number of reproductive pathologies. The purpose of this review was to analyze the literature sources illustrating the importance of energydependent processes in placental metabolism and to determine the molecular basis of placental energy conversion. Publications of foreign and Russian authors from PubMed database and scientific electronic library eLIBRARY.ru were used when writing the review. The review highlights the main functions of the placenta: transport and synthetic functions in terms of their place in the structure of energy expenditure of the organ. The systems by which the transport of ions and gases from maternal blood through the placental barrier is performed, are considered. The role of the placenta in the synthesis of steroid hormones and glucocorticoids is detailed. The main bioenergetic systems are also considered: placental glucose metabolism, the functional activity of mitochondria and the creatine kinase system of the placenta. These data allow us to put the placenta on a par with other organs with high energy requirements (brain, transverse striated skeletal muscles, heart, kidneys, liver), which are most susceptible to metabolic disorders. Maintaining a balance between expenditure and synthesis of macroergic compounds in the placenta is critical for an adequate course of physiological pregnancy, and imbalances can lead to such pathologies as fetal retardation syndrome or preeclampsia. Further study of placental energy supply systems seems important for understanding the mechanisms of intrauterine development disorders and developing their pathogenetic treatment.

Gestational Exposure to Cyfluthrin through Endoplasmic Reticulum (ER) Stress-Mediated PERK Signaling Pathway Impairs Placental Development

Cyfluthrin, a typical type II pyrethroid pesticide, is widely used in house hygiene and agricultural pest control. Several epidemiological investigations have found that maternal pyrethroid exposure is connected to adverse pregnancy outcomes. However, the underlying mechanisms remain to be elucidated. Thus, we evaluated the effect of cyfluthrin exposure during pregnancy on placenta development in vivo. In the current study, Pregnant SD rats were randomly divided into four groups and administered 6.25, 12.5, and 25 mg/kg body weight cyfluthrin or an equivalent volume of corn oil by gavage from GD0 to GD19. The results have shown that gestational exposure to cyfluthrin exerted no effect on the fetal birth defect, survival to PND4, or fetal resorption and death. However, live fetuses and implantation sites significantly decreased in the high-dose cyfluthrin-treated group. Moreover, a significant reduction in placenta weight and diameter was observed in rats. Correspondingly, the fetal weight and crown-rump length from dams exposed to cyfluthrin were reduced. Cyfluthrin-treat groups, the total area of the placenta, spongiotrophoblast area, and labyrinth area had abnormal changes. Meanwhile, the area of blood sinusoid and CD34-positive blood vessel numbers in the placenta were considerably reduced, as well as abnormal expression of placental pro-angiogenic and anti-angiogenic factors in dams exposed to cyfluthrin. Further observation by transmission electron microscopy revealed significant changes in the ultrastructure of the medium-dose and high-dose groups. Additional experiments showed gestational exposure to cyfluthrin inhibited proliferation and induced apoptosis of placentas, as decreased PCNA-positive cells and increased TUNEL-positive cells. Furthermore, western blot and qPCR analysis revealed that gestational exposure to medium-dose and high-dose cyfluthrin increased the expression of GRP78, and three downstream mRNA and proteins (p-eIF2α, ATF4, and CHOP) of the PERK signaling, indicating that endoplasmic reticulum (ER) stress-mediated PERK/eIF2α/ATF4/CHOP signaling pathway in rat placentas was activated. Our study demonstrated that gestational exposure to cyfluthrin leads to placental developmental disorder, which might be associated with ER stress-mediated PERK signaling pathway.

Prenatal smoke (Nicotine) exposure and offspring's metabolic disease susceptibility in adulthood

Exposure to smoking (nicotine) during pregnancy not only directly affects fetal development, but also increases susceptibility to metabolic diseases in adulthood, but the mechanism of action remains unclear. Here, we review epidemiological and laboratory studies linking these relationships. In addition to the direct effect of nicotine on the fetus, intrauterine neuroendocrine-metabolic programming mediated by maternal glucocorticoid overexposure also plays an important role, involving glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis, hypothalamic-pituitary-adrenal (HPA) axis, renin-angiotensin system (RAS) and other endocrine systems. Epigenetics is involved in intrauterine neuroendocrine-metabolic programming, metabolic disease susceptibility and multigenerational inheritance. There are "two programming" and "two strikes" mechanisms for the occurrence of fetal-originated metabolic diseases in adulthood. These innovative research summaries and academic viewpoints provide experimental and theoretical basis for systematically elucidating the occurrence and development of fetal-originated metabolic diseases.

Gestational cholestasis induced intrauterine growth restriction through triggering IRE1α-mediated apoptosis of placental trophoblast cells

Epidemiological and animal experimental studies suggest an association between gestational cholestasis and intrauterine growth restriction (IUGR). Here, we explored the mechanism through which gestational cholestasis induced IUGR. To establish gestational cholestasis model, pregnant mice were subcutaneously injected with 17α-Ethynylestradiol (E2) on gestational day 13 (GD13)-GD17. Some pregnant mice were intraperitoneally injected with 4μ8C on GD13-GD17. The results found that the apoptosis of trophoblast cells was elevated in placentas of mice with gestational cholestasis and in deoxycholic acid (DCA)-treated human trophoblast cell lines and primary mouse trophoblast cells. Correspondingly, the levels of placental cleaved caspase-3 and Bax were increased, while placental Bcl2 level was decreased in mice with gestational cholestasis and in DCA-treated trophoblast cells. Further analysis found that placental IRE1α pathway was activated in mice with gestational cholestasis and in DCA-treated trophoblast cells. Interestingly, 4μ8C, an IRE1α RNase inhibitor, significantly inhibited caspase-3 activity and apoptosis of trophoblast cells in vivo and in vitro. Importantly, 4μ8C rescued gestational cholestasis-induced placental insufficiency and IUGR. Furthermore, a case-control study demonstrated that placental IRE1α and caspase-3 pathways were activated in cholestasis cases. Our results provide evidence that gestational cholestasis induces placental insufficiency and IUGR may be via triggering IRE1α-mediated apoptosis of placental trophoblast cells.

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.

Decidual NK cells kill Zika virus-infected trophoblasts

Zika virus (ZIKV) during pregnancy infects fetal trophoblasts and causes placental damage and birth defects including microcephaly. Little is known about the anti-ZIKV cellular immune response at the maternal-fetal interface. Decidual natural killer cells (dNK), which directly contact fetal trophoblasts, are the dominant maternal immune cells in the first-trimester placenta, when ZIKV infection is most hazardous. Although dNK express all the cytolytic molecules needed to kill, they usually do not kill infected fetal cells but promote placentation. Here, we show that dNK degranulate and kill ZIKV-infected placental trophoblasts. ZIKV infection of trophoblasts causes endoplasmic reticulum (ER) stress, which makes them dNK targets by down-regulating HLA-C/G, natural killer (NK) inhibitory receptor ligands that help maintain tolerance of the semiallogeneic fetus. ER stress also activates the NK activating receptor NKp46. ZIKV infection of Ifnar1 ^-/- pregnant mice results in high viral titers and severe intrauterine growth restriction, which are exacerbated by depletion of NK or CD8 T cells, indicating that killer lymphocytes, on balance, protect the fetus from ZIKV by eliminating infected cells and reducing the spread of infection.

Primary HSV-2 Infection in Early Pregnancy Results in Transplacental Viral Transmission and Dose-Dependent Adverse Pregnancy Outcomes in a Novel Mouse Model

Herpes simplex virus type 2 (HSV-2) infection affects 24 million births annually and is associated with adverse pregnancy outcomes, including neonatal herpes; however, the mechanisms underlying in utero transmission of HSV-2 are largely unknown. We examined the effects of primary HSV-2 infection during early pregnancy on gestational outcomes in a novel, clinically relevant mouse model. Pregnant C57BL/6 mice were infected intravaginally with 10²–10⁵ pfu/mL HSV-2 on gestation day (gd) 4.5. Controls were infected, nonpregnant, diestrus-staged mice and pregnant, uninfected mice. Compared to nonpregnant mice, pregnant mice were 100-fold more susceptible to HSV-2 infection. Three days post-inoculation (gd7.5), viral DNA was present in implantation sites, but pregnancy outcomes were largely unaffected by infection. Eight days post-inoculation (gd12.5), HSV-2 DNA persisted in placental tissues, resulting in inflammation and hemorrhage. Fetal and placental weights were reduced and fetal loss was observed with high viral doses. HSV-2 DNA and increased expression of pro-inflammatory mediators were detected in fetal tissues at gd12.5, signifying viral transmission and fetal infection, even with low viral doses. This mouse model shows a dose-dependent effect of primary HSV-2 infection on pregnancy outcomes and suggests that fetal loss may occur due to placental inflammation, thus providing valuable insight into in utero transmission of HSV-2.

Metabolic Consequences of Gestational Cannabinoid Exposure

Up to 20% of pregnant women ages 18-24 consume cannabis during pregnancy. Moreover, clinical studies indicate that cannabis consumption during pregnancy leads to fetal growth restriction (FGR), which is associated with an increased risk of obesity, type II diabetes (T2D), and cardiovascular disease in the offspring. This is of great concern considering that the concentration of Δ9- tetrahydrocannabinol (Δ9-THC), a major psychoactive component of cannabis, has doubled over the last decade and can readily cross the placenta and enter fetal circulation, with the potential to negatively impact fetal development via the endocannabinoid (eCB) system. Cannabis exposure in utero could also lead to FGR via placental insufficiency. In this review, we aim to examine current pre-clinical and clinical findings on the direct effects of exposure to cannabis and its constituents on fetal development as well as indirect effects, namely placental insufficiency, on postnatal metabolic diseases.

Exercise in Pregnancy Increases Placental Angiogenin without Changes in Oxidative or Endoplasmic Reticulum Stress

PURPOSE

Despite immense research highlighting maternal-fetal benefits of exercise during pregnancy, there remain concerns that exercise may undermine placental function. Although maternal exercise has demonstrated favorable aerobic conditioning responses in the mother, it is not known whether maternal exercise promotes increased angiogenesis in the placenta, perhaps at the expense of impaired endoplasmic reticulum (ER) homeostasis and/or oxidative stress. We investigated if a mild (30% heart rate reserve) and/or moderate (70% heart rate reserve) exercise regime in healthy pregnant women affected placental markers of angiogenesis, ER stress, and oxidative stress. We hypothesized that the improved aerobic conditioning of mothers who exercise is beneficial to enhance placental angiogenesis and normal maternal-fetal outcomes.

METHODS

Placental tissues were collected within 1 h of delivery from a convenience sample of 29 healthy mothers of full-term infants. Twenty-one women participated in routine exercise from midgestation (16-20 wk) until term of either mild or moderate intensity, whereas eight sedentary women served as controls.

RESULTS

No differences were identified between groups including gestational length, fetal-placental weight ratio, or APGAR scoring. All exercisers exhibited a significant 20-fold increase in the mRNA (as assessed by quantitative real-time polymerase chain reaction) and a 10-fold increase in the protein expression of angiogenin (e.g., ANG1) in the placenta. However, in both exercising groups, no increases in placental markers (i.e., HIF1α, VEGF), ER stress (i.e., spliced XBP1, ATF4, ATF6, CHOP, and BAX), or oxidative stress (i.e., SOD1, SOD2) were observed.

CONCLUSIONS

Overall, our study suggests that mild- and moderate-intensity exercise increases angiogenesis but does not increase placental oxidative or ER stress in healthy pregnancies, bolstering support for routine exercise as a part of standard care in pregnant women. Future studies are warranted to investigate the potential benefits of exercise on ANG1 in pathological pregnancies.

Hypoxia and the integrated stress response promote pulmonary hypertension and preeclampsia: Implications in drug development

Chronic hypoxia is a common cause of pulmonary hypertension, preeclampsia, and intrauterine growth restriction (IUGR). The molecular mechanisms underlying these diseases are not completely understood. Chronic hypoxia may induce the generation of reactive oxygen species (ROS) in mitochondria, promote endoplasmic reticulum (ER) stress, and result in the integrated stress response (ISR) in the pulmonary artery and uteroplacental tissues. Numerous studies have implicated hypoxia-inducible factors (HIFs), oxidative stress, and ER stress/unfolded protein response (UPR) in the development of pulmonary hypertension, preeclampsia and IUGR. This review highlights the roles of HIFs, mitochondria-derived ROS and UPR, as well as their interplay, in the pathogenesis of pulmonary hypertension and preeclampsia, and their implications in drug development.

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.

Aggrephagy Deficiency in the Placenta: A New Pathogenesis of Preeclampsia

Aggrephagy is defined as the selective degradation of aggregated proteins by autophagosomes. Protein aggregation in organs and cells has been highlighted as a cause of multiple diseases, including neurodegenerative diseases, cardiac failure, and renal failure. Aggregates could pose a hazard for cell survival. Cells exhibit three main mechanisms against the accumulation of aggregates: protein refolding by upregulation of chaperones, reduction of protein overload by translational inhibition, and protein degradation by the ubiquitin-proteasome and autophagy-lysosome systems. Deletion of autophagy-related genes reportedly contributes to intracellular protein aggregation in vivo. Some proteins recognized in aggregates in preeclamptic placentas include those involved in neurodegenerative diseases. As aggregates are derived both intracellularly and extracellularly, special endocytosis for extracellular aggregates also employs the autophagy machinery. In this review, we discuss how the deficiency of aggrephagy and/or macroautophagy leads to poor placentation, resulting in preeclampsia or fetal growth restriction.

Placental autophagy failure: A risk factor for preeclampsia

Hypertensive disorders of pregnancy, including preeclampsia, directly affect maternal and perinatal morbidity and mortality. As the pathophysiology of preeclampsia is multi-factorial and has been studied using different approaches, we have demonstrated that impaired autophagy is an intertwined risk factor for preeclampsia. This concept has been verified in both in vitro and in vivo experiments. Autophagy is primarily involved in maintaining cellular homeostasis, and in immune regulation, longevity, cytokines secretion and a variety of other biological functions. Here, we review the role of autophagy in normal embryogenesis and placentation. Once placental autophagy is impaired by metabolic stress such as hypoxia, endoplasmic reticulum stress or starvation, placental development could be disrupted, resulting in functional maladaptations at the maternal-fetal interface. These malfunctions may result in fetal growth restriction or preeclampsia.

Disruption of Placental Homeostasis Leads to Preeclampsia

Placental homeostasis is directly linked to fetal well-being and normal fetal growth. Placentas are sensitive to various environmental stressors, including hypoxia, endoplasmic reticulum stress, and oxidative stress. Once placental homeostasis is disrupted, the placenta may rebel against the mother and fetus. Autophagy is an evolutionally conservative mechanism for the maintenance of cellular and organic homeostasis. Evidence suggests that autophagy plays a crucial role throughout pregnancy, including fertilization, placentation, and delivery in human and mouse models. This study reviews the available literature discussing the role of autophagy in preeclampsia.

Δ9-tetrahydrocannabinol exposure during rat pregnancy leads to symmetrical fetal growth restriction and labyrinth-specific vascular defects in the placenta

1 in 5 women report cannabis use during pregnancy, with nausea cited as their primary motivation. Studies show that (-)-△9-tetrahydrocannabinol (Δ9-THC), the major psychoactive ingredient in cannabis, causes fetal growth restriction, though the mechanisms are not well understood. Given the critical role of the placenta to transfer oxygen and nutrients from mother, to the fetus, any compromise in the development of fetal-placental circulation significantly affects maternal-fetal exchange and thereby, fetal growth. The goal of this study was to examine, in rats, the impact of maternal Δ9-THC exposure on fetal development, neonatal outcomes, and placental development. Dams received a daily intraperitoneal injection (i.p.) of vehicle control or Δ9-THC (3 mg/kg) from embryonic (E)6.5 through 22. Dams were allowed to deliver normally to measure pregnancy and neonatal outcomes, with a subset sacrificed at E19.5 for placenta assessment via immunohistochemistry and qPCR. Gestational Δ9-THC exposure resulted in pups born with symmetrical fetal growth restriction, with catch up growth by post-natal day (PND)21. During pregnancy there were no changes to maternal food intake, maternal weight gain, litter size, or gestational length. E19.5 placentas from Δ9-THC-exposed pregnancies exhibited a phenotype characterized by increased labyrinth area, reduced Epcam expression (marker of labyrinth trophoblast progenitors), altered maternal blood space, decreased fetal capillary area and an increased recruitment of pericytes with greater collagen deposition, when compared to vehicle controls. Further, at E19.5 labyrinth trophoblast had reduced glucose transporter 1 (GLUT1) and glucocorticoid receptor (GR) expression in response to Δ9-THC exposure. In conclusion, maternal exposure to Δ9-THC effectively compromised fetal growth, which may be a result of the adversely affected labyrinth zone development. These findings implicate GLUT1 as a Δ9-THC target and provide a potential mechanism for the fetal growth restriction observed in women who use cannabis during pregnancy.

Microcystin-LR exposure decreased the fetal weight of mice by disturbance of placental development and ROS-mediated endoplasmic reticulum stress in the placenta

The placenta is essential for sustaining the growth of the fetus. The aim of this study was to investigate the role of the placenta in MCLR-induced significant reduction in fetal weight, especially the changes in placental structure and function. Pregnant mice were intraperitoneally injected with MCLR (5 or 20 μg/kg) from gestational day (GD) 13 to GD17. The results showed MCLR reduced fetal weight and placenta weight. The histological specimens of the placentas were taken for light and electron microscopy studies. The internal space of blood vessels decreased obviously in the placental labyrinth layer of mice treated with MCLR. After the ultrastructural examination, the edema and intracytoplasmic vacuolization, dilation of the endoplasmic reticulum and corrugation of the nucleus were observed. In addition, maternal MCLR exposure caused a reduction of 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2) expression in placentae, a critical regulator of fetal development. Several genes of placental growth factors, such as Vegfα and Pgf and several genes of nutrient transport pumps, such as Glut1 and Pcft were depressed in placentas of MCLR-treated mice, however nutrient transporters Fatp1 and Snat4 were promoted. Moreover, significant increases in malondialdehyde (MDA) revealed the occurrence of oxidative stress caused by MCLR, which was also verified by remarkable decrease in the glutathione levels, total antioxidant capacity (T-AOC) as well as the activity of antioxidant enzymes. Real-time PCR and western blot analysis revealed that GRP78, CHOP, XBP-1, peIF2α and pIRE1 were remarkable increased in placentas of MCLR-treated mice, indicating that endoplasmic reticulum (ER) stress pathway was activated by MCLR. Furthermore, oxidative stress and ER stress consequently triggered apoptosis which contributed to the impairment of placental development. Collectively, these results suggest maternal MCLR exposure results in reduced fetal body weight, which might be associated with ROS-mediated endoplasmic reticulum stress and impairment in placental structure and function.

Tobacco and Pituri Use in Pregnancy: A Protocol for Measuring Maternal and Perinatal Exposure and Outcomes in Central Australian Aboriginal Women

Maternal tobacco smoking is a recognized risk behavior that has adverse impacts onmaternal and fetal health. However, in some populations, the use of smokeless tobacco exceeds theuse of smoked tobacco. In central Australia, Aboriginal populations utilize wild tobacco plants(Nicotiana spp.) as a smokeless product. These plants are known by a variety of names, one of whichis pituri. The plants are masticated and retained in the oral cavity for extended periods of time andtheir use continues throughout pregnancy, birth, and lactation. In contrast to the evidence related tocombusted tobacco use, there is no evidence as to the effects of pituri use in pregnancy. CentralAustralian Aboriginal women who were at least 28 weeks pregnant were stratified into three tobaccoexposure groups: (a) Pituri chewers, (b) smokers, and (c) non-tobacco users. Routine antenatal andbirth information, pre-existing and pregnancy-related maternal characteristics, fetal characteristics,and biological samples were collected and compared. The biological samples were analysed fortobacco and nicotine metabolite concentrations. Samples from the mother included venous blood,urine, hair and colostrum and/or breast milk. From the neonate, this included Day 1 and Day 3 urineand meconium, and from the placenta, arterial and venous cord blood following delivery. This is thefirst study to correlate the pregnancy outcomes of central Australian Aboriginal women with differenttobacco exposures. The findings will provide the foundation for epidemiological data collection inrelated studies. Note to readers: In this article, the term "Aboriginal" was chosen by central Australianwomen to refer to both themselves and the Aboriginal people in their communities. "Indigenous" waschosen to refer to the wider Australian Aboriginal and Torres Strait Islander people.

Time-restricted feeding reduces high-fat diet associated placental inflammation and limits adverse effects on fetal organ development

Maternal nutrition has become a major public health concern over recent years and is a known predictor of adverse long-term metabolic derangement in offspring. Time-restricted feeding (TRF), wherein food consumption is restricted to the metabolically active phase of the day, is a dietary approach that improves metabolic parameters when consuming a high-fat diet (HFD). Here, we tested whether TRF could reduce maternal HFD associated inflammation and thereby mitigate defects in fetal organ developmental. Female rats were kept on following three dietary regimens; Ad libitum normal chow diet (NCD-AL), Ad libitum HFD (HFD-AL) and Time-restricted fed HFD (HFD-TRF) from 5 months prior to mating and continued throughout pregnancy. Rat dams were sacrificed at embryonic day 18.5 (ED18.5) and placental tissues from these rats were processed for the analysis of cellular apoptosis, inflammatory cytokines (TNFα and IL-6), oxidative stress, endoplasmic reticulum (ER) stress and autophagy. Furthermore, fetal hepatic triglyceride (TG) content and fetal lung maturation were assessed at ED18.5. Biochemical analysis revealed that HFD-TRF rat had significantly lower serum TG levels and body weight compared to HFD-AL rats. Additionally, TRF significantly blocked HFD-induced placental apoptosis and inflammation via minimizing cellular stress, and restoring autophagic flux. In addition, fetal hepatosteatosis and delayed fetal lung maturation induced by HFD was significantly ameliorated in HFD-TRF compared to HFD-AL. Collectively, our results suggest that reducing placental inflammation via TRF could prevent adverse fetal metabolic outcomes in pregnancies complicated by maternal obesity.

Δ9-Tetrahydrocannabinol leads to endoplasmic reticulum stress and mitochondrial dysfunction in human BeWo trophoblasts

While studies have demonstrated that the main psychoactive component of cannabis, Δ9-tetrahydrocannabinol (Δ9-THC) alone induces placental insufficiency and fetal growth restriction, the underlying mechanisms remain elusive. Given that both (i) endoplasmic reticulum (ER) stress in pregnancy and (ii) gestational exposure to Δ9-THC leads to placental deficiency, we hypothesized that Δ9-THC may directly induce placental ER stress, influencing trophoblast gene expression and mitochondrial function. BeWo human trophoblast cells treated with Δ9-THC (3-30 μM) led to a dose-dependent increase in all ER stress markers and CHOP; these effects could be blocked with CB1R/CB2R antagonists. Moreover, expression of ER stress-sensitive genes ERRγ, VEGFA, and FLT-1 were increased by Δ9-THC, and abrogated with the ER stress inhibitor TUDCA. Δ9-THC also diminished mitochondrial respiration and ATP-coupling due to decreased abundance of mitochondrial chain complex proteins. Collectively, these findings indicate that Δ9-THC can directly augment ER stress resulting in aberrant placental gene expression and impaired mitochondrial function.

Activation of CCL20 and its receptor CCR6 promotes endometrium preparation for implantation and placenta development during the early pregnancy period in pigs

The success of implantation and placentation during early pregnancy depends on the intrauterine environment of diverse histotrophs, including nutrients, growth factors, cytokines, and chemokines. Here, we determined the functional role and signal transduction of CC-motif chemokine 20 (CCL20) in the porcine endometrium during pregnancy. The expression of CCL20 and its receptor CCR6 was abundant in the glandular epithelium (GE) and luminal epithelium (LE) of the porcine endometrium during early pregnancy. Administration of CCL20 to porcine endometrial LE cells increased cellular proliferation with strong PCNA expression by activation of PI3K and MAPK signaling. Blocking PI3K and MAPK decreased the CCL20-mediated elevated proliferation of pLE cells. Moreover, the proliferation of pLE cells was enhanced by inhibiting the LPS-induced cytokines and tunicamycin-induced endoplasmic reticulum (ER) stress response proteins. Overall, these results suggest that CCL20 may improve the endometrial receptivity through inducing proliferative signal transduction in the porcine endometrium during the early gestational period.

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.

Gestational 1-nitropyrene exposure causes fetal growth restriction through disturbing placental vascularity and proliferation

1-Nitropyrene (1-NP) is a widely distributed pollutant in the environment and is best known for its mutagenicity and carcinogenicity. In this study, we evaluated the effects of 1-NP exposure in different gestational stages on the pregnant outcomes. Pregnant mice were administered with 1-NP by gavage daily in early (GD1-GD6), middle (GD7-GD12) or late pregnancy (GD13-GD17), respectively. We found that gestational 1-NP exposure had no effect on implantation sites per litter, preterm delivery and fetal death. Interestingly, mice exposed to 1-NP in late pregnancy showed a significant reduction in fetal weight and crown-rump length. Correspondingly, placental weight and diameter were markedly reduced in dams exposed to 1-NP in late pregnancy. Additional experiment showed maternal 1-NP exposure in late pregnancy reduced blood sinusoid area of placental labyrinthine region in a dose-dependent manner. Although gestational 1-NP exposure had little effect on placental cell apoptosis, as determined by the TUNEL assay, the rate of Ki67-positive cell, a marker of cell proliferation, was reduced in placental labyrinthine region of mice exposed to 1-NP in late pregnancy. These findings provide evidence that gestational 1-NP exposure induces fetal growth restriction in a stage-dependent manner. Placenta is a toxic target in the process of 1-NP-induced fetal growth restriction.

Differential effects of high-fat diets before pregnancy and/or during pregnancy on fetal growth development

AIMS

The aim of the study was to investigate the effects of high-fat diets before pregnancy and/or during pregnancy on fetal development.

MAIN METHODS

Female mice were fed with standard diets (SD) or high-fat diets (HFD). After 12 weeks, females were mated. In the SD + SD and HFD + SD groups, pregnant mice were fed with standard diets. In the SD + HFD and HFD + HFD groups, pregnant mice were fed with high-fat diets. All pregnant mice were sacrificed on gestational day (GD) 16.

KEY FINDINGS

Fetal weight and crown-rump length were increased in SD + HFD-fed mice, whereas were decreased in HFD + SD-fed mice. The levels of CRP and TNF-α in maternal serum and amniotic fluid were elevated in all HFD-fed mice. Placenta weight was elevated in SD + HFD-fed but not in HFD + SD-fed mice. Blood sinusoid areas, and the number of Ki67-positive cells, a marker of cell proliferation, were elevated in placental labyrinth layer of SD + HFD-fed mice, but decreased in HFD + SD-fed mice. Finally, placental Fatp1, a fatty acid transporter gene, was up-regulated in SD + HFD-fed mice. By contrary, placental Fatp1, and Snat2, an amino acid transporter, were down-regulated in HFD + SD-fed mice. Moreover, the levels of placental FATP4 and SNAT2 were up-regulated in SD + HFD-fed mice.

SIGNIFICANCE

HFD before pregnancy and HFD during pregnancy differentially disturb fetal growth development. HFD before pregnancy-induced fetal SGA might be partially attributed to inflammatory cytokines and mediators derived from maternal adipose tissue. By contrary, HFD during pregnancy-induced fetal overweight may be partially attributed to the increase of placental nutrient transport capacity.

Impact of the Reticular Stress and Unfolded Protein Response on the inflammatory response in endometrial stromal cells

During decidualization, endometrial stromal cells undergo reticular stress (RS) and unfolded protein response (UPR), allowing the endoplasmic reticulum-expansion and immunomodulators production. Physiological RS generates the activation of sensing proteins, inflammasome activation and mature-IL-1β secretion, associated with pro-implantatory effects. We focus on the impact of RS and UPR on decidualized cells and whether they induce a physiological sterile inflammatory response through IL-1β production. Human endometrial stromal cell line (HESC) after decidualization treatment with MPA + dibutyryl-cAMP (Dec) increased the expression of RS-sensors (ATF6, PERK and IRE1α) and UPR markers (sXBP1 and CHOP) in comparison with Non-dec cells. Then we found increased NLRP3 expression in Dec cells compared with Non-dec cells. In fact STF-083010 (an IRE1α inhibitor) prevented this increase. Downstream, increased levels of active caspase-1 on Dec cells were detected by FAM-Flica Caspase-1 associated with an increase in IL-1β production. Moreover, the treatment with STF-083010 decreased the invasion index observed in Dec cells, evaluated by an in vitro model of implantation. In endometrial biopsies from recurrent spontaneous abortion patients an increased expression of IRE1α was found in comparison with fertile women; while recurrent implantation failure samples showed a lower expression of sXBP1, TXNIP and NLRP3 than fertile women, suggesting that RS/UPR tenors might condition endometrial receptivity.

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.

Decanoic acid suppresses proliferation and invasiveness of human trophoblast cells by disrupting mitochondrial function

Decanoic acid (DA) is a medium-chain fatty acid used in the manufacture of various products including plastics, cosmetics, and lubricants. In addition to antiviral and antibacterial effects, DA's, reported biological activities include regulation of signaling pathways and redox homeostasis in various human cell types. The influence of DA on functional properties of human trophoblasts, including proliferation, invasion and apoptosis is currently unknown. In the present study, we evaluated the anti-proliferative and anti-invasive effects of DA on the human trophoblast cell line HTR8/SVneo. In addition, DA induced oxidative stress, as evidenced by generation of reactive oxygen species (ROS) and induction of lipid peroxidation (LPO). This oxidative stress was accompanied by activation of the mitochondria-dependent apoptotic pathway in HTR8/SVneo cells. We also observed elevated mitochondrial Ca²⁺, and loss of mitochondrial membrane potential in response to DA treatment. Chelation of mitochondrial Ca²⁺ using BAPTA-AM rescued cellular proliferation suppressed by DA. We also verified that signaling proteins including AKT, P70S6K, S6, and ERK1/2 and their targets were significantly reduced in HTR8/SVneo cells by DA treatment. Pre-treatment of cells with selective inhibitors of AKT (LY294002) and ERK1/2 (U0126) revealed that the AKT and ERK1/2 signaling pathways regulated by DA displayed cross-talk in HTR8/SVneo cells. Collectively, these results suggest that personal products containing DA will have harmful effects on human trophoblasts, and could cause implantation and placentation failure during early pregnancy.

Maternal serum lead level during pregnancy is positively correlated with risk of preterm birth in a Chinese population

Lead (Pb) is a well-known developmental toxicant. The aim of the present study was to analyze the association between maternal serum Pb level and risk of preterm birth in a population-based birth cohort study. The present study analyzed a sub-study of the China-Anhui Birth Cohort that recruited 3125 eligible mother-and-singleton-offspring pairs. Maternal serum Pb level was measured by graphite furnace atomic absorption spectrometry. All subjects were classified into three groups by tertile division according to serum Pb level: Low-Pb (L-Pb, <1.18 μg/dl), Medium-Pb (M-Pb, 1.18-1.70 μg/dl), and High-Pb (H-Pb, ≥1.71 μg/dl). The rate of preterm birth was 2.8% among subjects with L-Pb, 6.1% among subjects with M-Pb, and 8.1% among subjects with H-Pb, respectively. After controlling confounding factors, the adjusted OR for preterm birth was 2.33 (95%CI: 1.49, 3.65) among subjects with M-Pb and 3.09 (95%CI: 2.01, 4.76) among subjects with H-Pb. Of interest, maternal Pb exposure in early gestational stage than in middle gestational stage was more susceptible to preterm birth. Moreover, maternal serum Pb level was only associated with increased risk of late preterm birth. The present study provides evidence that maternal serum Pb level during pregnancy is positively associated with risk of preterm birth in a Chinese population.

Endoplasmic reticulum stress responses in placentation - A true balancing act

The unfolded protein response (UPR) is recognized as a key mechanism to promote protein folding and processing in eukaryotes when endoplasmic reticulum stress (ERS) occurs. Some conditions such as hypoxia or glucose deprivation are factors that may elicit ERS response. Recent literature collectively proposes that ERS response is crucial for mammalian reproduction by allowing decidualization and placentation to occur. However, prolonged ERS and activation of UPR pathways can lead to apoptosis and autophagy, which in turn could pose adverse effects on pregnancy outcomes and placentation. ERS associated pregnancy pathologies include intrauterine growth restriction and early-onset preeclampsia. Given these findings, evidence suggests that overactivation of UPR may lead to harmful reproductive circumstances, whereas physiological regulation of ERS response is essential for mammalian reproduction and placental function. In this review, we discuss the dual role of UPR activation with respect to its contribution to placental development as well as pathologies caused by pathway overactivation. In addition, we suggest potential protein markers associated with the UPR, as circulating C-terminal GRP78 or anti-GRP78 autoantibodies which may prove to be of clinical interest.

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.

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.

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.

Stromal Cell-Derived Factor 2: A Novel Protein that Interferes in Endoplasmic Reticulum Stress Pathway in Human Placental Cells

Endoplasmic reticulum (ER) stress results from changes in ER homeostasis and folding of proteins. ER stress initiates cellular adaptive mechanisms to rescue cell homeostasis or, if that does not work, to elicit apoptosis. We have previously shown that mouse SDF2 is sublocalized in the ER, is ubiquitously expressed, and shows strong similarities with stromal cell-derived factor (SDF) 2L1 and SDF2-like from Arabidopsis, ER proteins involved in chaperone network and protein folding. Thus, we hypothesized that SDF2 plays a role in the ER stress and unfolded protein response. In this study, we investigated the possible role of SDF2 in the human placenta. Expression of SDF2 was present throughout gestation and was expressed by several cell types. Second-trimester cytotrophoblast cells (CTBs) in the differentiation process, monitored through chorionic gonadotropin production, showed upregulation of SDF2 protein. SDF2 expression, however, was significantly diminished in placentas from neonates small for gestational age and in hypoxic in vitro conditions (P ≤ 0.001, 2% O2), suggesting a link with cellular stress. ER stress-induced cells-CTB and BeWo-also showed SDF2 downregulation in different time points, emphasizing this relationship. SDF2 downregulation was also followed by an increase in binding immunoglobulin protein (BiP) expression, an ER protein-associated chaperone acting as a sensor for misfolded proteins and an ER stress cell survival marker. In line with this, SDF2 siRNA resulted in significant anticipation of BiP expression. Downregulation of SDF2 also interfered with C/EBP homologous protein expression, one of the highest inducible genes during ER stress. These findings suggest that SDF2 may be an important regulatory factor by which trophoblast cells can control cell survival under ER stress. In conclusion, this study identifies a novel factor with the ability to interfere with ER stress proteins, which may contribute to the understanding of ER stress associated with placental-related diseases of pregnancy.

Mitochondrial - Endoplasmic reticulum interactions in the trophoblast: Stress and senescence

Placental stress has been implicated in the pathophysiology of complications of pregnancy, including growth restriction and pre-eclampsia. Initially, attention focused on oxidative stress, but recently mitochondrial and endoplasmic reticulum stress have been identified. Complex molecular interactions exist among these different forms of stress, making it unlikely that any occurs in isolation. In part, this is due to close physiological connections between the two organelles principally involved, mitochondria and the endoplasmic reticulum (ER), mediated through Ca²⁺ signalling. Here, we review the involvement of the mitochondria-ER unit in the generation of stress within the trophoblast, and consider consequences for obstetric outcome. Mild stress may induce adaptive responses, including upregulation of antioxidant defences and autophagy, while moderate levels may affect stem cell behaviour and reduce cell proliferation, contributing to the growth-restricted phenotype. High levels of stress can stimulate release of pro-inflammatory cytokines and anti-angiogenic factors, increasing the risk of pre-eclampsia. In addition, chronic stress may promote senescence of the trophoblast, which in other cell types leads to a pro-inflammatory senescence-associated secretory phenotype. Evidence from rodents suggests that a degree of trophoblastic stress develops with increasing gestational age in normal pregnancies. The increase in maternal concentrations of soluble fms-like tyrosine kinase-1 (sFlt-1) and reduction in placental growth factor (PlGF) suggest the same may occur in the human, starting around 30 weeks of pregnancy. Placental malperfusion, or co-existing maternal conditions, such as diabetes, will exacerbate that stress. Amelioration of trophoblastic stress should remain a research priority, but will be difficult due to the complexity of the molecular pathways involved.

Maternal serum cadmium level during pregnancy and its association with small for gestational age infants: a population-based birth cohort study

The association between maternal cadmium (Cd) exposure during pregnancy and the increased risk of fetal growth restriction (FGR) remains controversial. The present study evaluated the association between maternal serum Cd level and risk of small for gestational age (SGA) infants in a Chinese population. The present study analyzed a subsample of the C-ABCS cohort that recruited 3254 eligible mother-and-singleton-offspring pairs. Maternal serum Cd level during pregnancy was measured by graphite furnace atomic absorption spectrometry. The rate and odds ratio (OR) for SGA infant were calculated. The rate for SGA infant was 10.6% among subjects with H-Cd (≥1.06 μg/L), significantly higher than 7.5% among subjects with L-Cd (<1.06 μg/L). OR was 1.45 (95% CI: 1.11, 1.90; P = 0.007) among subjects with H-Cd. Adjusted OR for SGA infants was 1.43 (95% CI: 1.09, 1.88; P = 0.007) among subjects with H-Cd. Taken together, we observe the fact that maternal Cd exposure at middle gestational stage, elevates the risk of SGA in contrast to early gestational stage. The present results might be interesting and worth more discussing, and guarantee to further studies.

Endoplasmic reticulum stress-induced apoptosis in the development of reproduction

Proteins synthesized in the endoplasmic reticulum (ER) are properly folded with the assistance of ER chaperones. Accumulation of misfolded protein in the ER triggers an adaptive ER stress (ERS) response termed the unfolded protein response. Recent interest has focused on the possibility that the accumulation of misfolded proteins can also contribute to reproductive response, including preimplantation embryos, testicular germ cell, placenta, and unexplained intrauterine growth restriction (IUGR). The major ERS pathway constituents are present at all stages of preimplantation development and that the activation of ERS pathways can be induced at the 8-cell, morula and blastocyst stage. This review mainly introduced the research progress of ERS induced apoptosis of reproductive cells, providing a new direction for the research of reproductive disease therapy.

Placental endoplasmic reticulum stress negatively regulates transcription of placental growth factor via ATF4 and ATF6β: implications for the pathophysiology of human pregnancy complications

Low maternal circulating concentrations of placental growth factor (PlGF) are one of the hallmarks of human pregnancy complications, including fetal growth restriction (FGR) and early-onset pre-eclampsia (PE). Currently, PlGF is used clinically with other biomarkers to screen for high-risk cases, although the mechanisms underlying its regulation are largely unknown. Placental endoplasmic reticulum (ER) stress has recently been found to be elevated in cases of FGR, and to an even greater extent in early-onset PE complicated with FGR. ER stress activates the unfolded protein response (UPR); attenuation of protein translation and a reduction in cell growth and proliferation play crucial roles in the pathophysiology of these complications of pregnancy. In this study, we further identified that ER stress regulates release of PlGF. We first observed that down-regulation of PlGF protein was associated with nuclear localization of ATF4, ATF6α and ATF6β in the syncytiotrophoblast of placentae from PE patients. Transcript analysis showed a decrease of PlGF mRNA, and an increase from genes encoding those UPR transcription factors in placentae from cases of early-onset PE, but not of late-onset (>34 weeks) PE, compared to term controls. Further investigations indicated a strong correlation between ATF4 and PlGF mRNA levels only (r = - 0.73, p < 0.05). These results could be recapitulated in trophoblast-like cells exposed to chemical inducers of ER stress or hypoxia-reoxygenation. The stability of PlGF transcripts was unchanged. The use of small interfering RNA specific for transcription factors in the UPR pathways revealed that ATF4 and ATF6β, but not ATF6α, modulate PlGF transcription. To conclude, ATF4 and ATF6β act synergistically in the negative regulation of PlGF mRNA expression, resulting in reduced PlGF secretion by the trophoblast in response to stress. Therefore, these results further support the targeting of placental ER stress as a potential new therapeutic intervention for these pregnancy complications.

The role of the endoplasmic reticulum stress in stemness, pluripotency and development

The molecular machinery of endoplasmic reticulum (ER) integrates various intracellular and extracellular cues to maintain homeostasis in diverse physiological or pathological scenarios. ER stress and the unfolded protein response (UPR) have been found to mediate molecular and biochemical mechanisms that affect cell proliferation, differentiation, and apoptosis. Although a number of reviews on the ER stress response have been published, comprehensive reviews that broadly summarize ER physiology in the context of pluripotency, embryonic development, and tissue homeostasis are lacking. This review complements the current ER literature and provides a summary of the important findings on the role of the ER stress and UPR in embryonic development and pluripotent stem cells.

Nicotine Directly Induces Endoplasmic Reticulum Stress Response in Rat Placental Trophoblast Giant Cells

Nicotine exposure during pregnancy leads to placental insufficiency impairing both fetal and neonatal development. Previous studies from our laboratory have demonstrated that in rats, nicotine augmented endoplasmic reticulum (ER) stress in association with placental insufficiency; however, the underlying mechanisms remain elusive. Therefore, we sought to investigate the possible direct effect of nicotine on ER stress in Rcho-1 rat placental trophoblast giant (TG) cells during differentiation. Protein and/or mRNA expression of markers involved in ER stress (eg, phosphorylated PERK, eIF2α, CHOP, and BiP/GRP78) and TG cell differentiation and function (eg, Pl-1, placental growth factor [Pgf], Hsd11b1, and Hsd11b2) were quantified via Western blot or real-time polymerase chain reaction. Nicotine treatment led to dose-dependent increases in the phosphorylation of PERK[Thr981] and eIF2α[Ser51], whereas pretreatment with a nicotinic acetylcholine receptor (nAChR) antagonist (mecamylamine hydrochloride) blocked the induction of PERK phosphorylation, verifying the direct involvement of nicotine and nAChR binding. We next investigated select target genes known to play essential roles in placental TG cell differentiation and function (Pl-1, Pgf, Hsd11b1, and Hsd11b2), and found that nicotine significantly augmented the mRNA levels of Hsd11b1 in a dose-dependent manner. Furthermore, using tauroursodeoxycholic acid, a safe bile acid known to improve protein chaperoning and folding, we were able to prevent nicotine-induced increases in both PERK phosphorylation and Hsd11b1 mRNA levels, revealing a potential novel therapeutic approach to reverse the deleterious effects of nicotine exposure in pregnancy. Collectively, these results implicate that nicotine, acting through its receptor, can directly augment ER stress and impair placental function.

Understanding Pre-Eclampsia Using Alzheimer's Etiology: An Intriguing Viewpoint

Characterized by hypertension and proteinuria after the 20th week of gestation, pre-eclampsia (PE) is a major cause of maternal, fetal, and neonatal morbidity and mortality. Despite being recognized for centuries, PE still lacks a reliable, early means of diagnosis or prediction, and a safe and effective therapy. We have recently reported that the event of toxic protein misfolding and aggregation is a critical etiological manifestation in PE. Using comparative proteomic analysis of gestational age-matched sera from PE and normal pregnancy, we identified several proteins that appeared to be dysregulated in PE. Our efforts so far have focused on transthyretin (TTR), a transporter of thyroxine and retinol, and amyloid precursor protein whose aggregates were detected in the PE placenta. Based on these results and detection of TTR aggregates in sera from PE patients, we proposed that PE could be a disease of protein misfolding and aggregation. Protein misfolding and aggregation have long been linked with many neurodegenerative diseases such as Alzheimer's disease. However, linkage of protein misfolding and aggregation with the PE pathogenesis is a new and novel concept. This review aims to understand the roles of aggregated proteins in PE using the cues from the Alzheimer's etiology.