Survival by self-destruction: a role for autophagy in the placenta?

Physiological and pathological evidence of O-GlcNAcylation regulation during pregnancy related process

O-GlcNAcylation is a dynamic and reversible post-translational modification (PTM) controlled by the enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Changes in its expression lead to a breakdown in cellular homeostasis, which is linked to several pathological processes. Placentation and embryonic development are periods of high cell activity, and imbalances in cell signaling pathways can result in infertility, miscarriage, or pregnancy complications. O-GlcNAcylation is involved in cellular processes such as genome maintenance, epigenetic regulation, protein synthesis/degradation, metabolic pathways, signaling pathways, apoptosis, and stress response. Trophoblastic differentiation/invasion and placental vasculogenesis, as well as zygote viability and embryonic neuronal development, are all dependent on O-GlcNAcylation. This PTM is required for pluripotency, which is a required condition for embryonic development. Further, this pathway is a nutritional sensor and cell stress marker, which is primarily measured by the OGT enzyme and its product, protein O-GlcNAcylation. Yet, this post-translational modification is enrolled in metabolic and cardiovascular adaptations during pregnancy. Finally, evidence of how O-GlcNAc impacts pregnancy during pathological conditions such as hyperglycemia, gestational diabetes, hypertension, and stress disorders are reviewed. Considering this scenario, progress in understanding the role of O- GlcNAcylation in pregnancy is required.

Recent insight into autophagy and immunity at the maternal-fetal interface

Autophagy is a lysosomal degradation pathway that supports metabolic adaptation and energy cycling. It is essential for cell homeostasis, differentiation, development, and survival. Recent studies have shown that autophagy could influence immune responses by regulating immune cell functions. Reciprocally, immune cells strongly influence autophagy. Immune cells at the maternal-fetal interface are thought to play essential roles in pregnancy. Here, we review the induction of autophagy at the maternal-fetal interface and its role in decidualization and placental development. Additionally, we emphasize the role of autophagy in the immune microenvironment at the maternal-fetal interface, including innate immunity, adaptive immunity, and immune tolerance molecules. It also suggests new research directions and prospects.

Homeostasis Maintenance in Plasmodium-Infected Placentas: Is There a Role for Placental Autophagy During Malaria in Pregnancy?

Malaria represents a significant public health burden to populations living in developing countries. The disease takes a relevant toll on pregnant women, who are more prone to developing severe clinical manifestations. Inflammation triggered in response to P. falciparum sequestration inside the placenta leads to physiological and structural changes in the organ, reflecting locally disrupted homeostasis. Altogether, these events have been associated with poor gestational outcomes, such as intrauterine growth restriction and premature delivery, contributing to the parturition of thousands of African children with low birth weight. Despite significant advances in the field, the molecular mechanisms that govern these outcomes are still poorly understood. Herein, we discuss the idea of how some housekeeping molecular mechanisms, such as those related to autophagy, might be intertwined with the outcomes of malaria in pregnancy. We contextualize previous findings suggesting that placental autophagy is dysregulated in P. falciparum-infected pregnant women with complementary research describing the importance of autophagy in healthy pregnancies. Since the functional role of autophagy in pregnancy outcomes is still unclear, we hypothesize that autophagy might be essential for circumventing inflammation-induced stress in the placenta, acting as a cytoprotective mechanism that attempts to ensure local homeostasis and better gestational prognosis in women with malaria in pregnancy.

Tricin attenuates cerebral ischemia/reperfusion injury through inhibiting nerve cell autophagy, apoptosis and inflammation by regulating the PI3K/Akt pathway

To elucidate the effect of tricin in cerebral ischemia/reperfusion (I/R) injury and examine its possible underlying mechanisms. Rats were randomly divided into Sham (exposed the right internal carotid arteries), I/R, and tricin (administered at various doses) groups. After the cerebral I/R injury model was established, a Morris water maze test and a tetrazolium chloride assay were performed. Apoptosis and autophagy were assessed in the nerve cells of hippocampus tissue, and the levels of inflammatory markers within animal serum were detected. Proteins related to apoptosis and the PI3K/Akt pathway were evaluated. To further investigate the mechanisms by which tricin affects brain damage, mouse neuroblastoma cells N2a were divided into control, oxygen-glucose deprivation and reoxygenation (OGD/R), tricin, PI3K/Akt activator, and tricin + PI3K/Akt inhibitor groups. The cell viability, apoptosis, inflammatory factors, and PI3K/Akt pathway related proteins in N2a cells were also detected. The results revealed that I/R-induced learning and memory dysfunction was improved by tricin treatment. The area of cerebral infarction, the levels of apoptosis and autophagy in nerve cells, and the serum inflammatory marker content were all decreased following tricin treatment. Additionally, the expression of Beclin-1 protein was downregulated, while the expression of Bcl-2 protein, p-PI3K/PI3K and p-Akt/Akt was upregulated after tricin treatment. Mechanistically, tricin or PI3K/Akt activator ameliorated OGD/R-induced apoptosis, autophagy, and inflammation. However, these effects were reversed following PI3K/Akt inhibitor treatment in OGD/R-induced N2a cells. In summary, this study suggested that tricin can against I/R-induced brain injury by inhibiting autophagy, apoptosis and inflammation, and activating the PI3K/Akt signaling pathway.

Cell dynamics in human villous trophoblast

BACKGROUND

Villous cytotrophoblast (vCTB) is a precursor cell population that supports the development of syncytiotrophoblast (vSTB), the high surface area barrier epithelium of the placental villus, and the primary interface between maternal and fetal tissue. In light of increasing evidence that the placenta can adapt to changing maternal environments or, under stress, can trigger maternal disease, we consider what properties of these cells empower them to exert a controlling influence on pregnancy progression and outcome.

OBJECTIVE AND RATIONALE

How are cytotrophoblast proliferation and differentiation regulated in the human placental villus to allow for the increasing demands of the fetal and environmental challenges and stresses that may arise during pregnancy?

SEARCH METHODS

PubMed was interrogated using relevant keywords and word roots combining trophoblast, villus/villous, syncytio/syncytium, placenta, stem, transcription factor (and the individual genes), signalling, apoptosis, autophagy (and the respective genes) from 1960 to the present. Since removal of trophoblast from its tissue environment is known to fundamentally change cell growth and differentiation kinetics, research that relied exclusively on cell culture has not been the main focus of this review, though it is mentioned where appropriate. Work on non-human placenta is not systematically covered, though mention is made where relevant hypotheses have emerged.

OUTCOMES

The synthesis of data from the literature has led to a new hypothesis for vCTB dynamics. We propose that a reversible transition can occur from a reserve population in G0 to a mitotically active state. Cells from the in-cycle population can then differentiate irreversibly to intermediate cells that leave the cycle and turn on genes that confer the capacity to fuse with the overlying vSTB as well as other functions associated with syncytial barrier and transport function. We speculate that alterations in the rate of entry to the cell cycle, or return of cells in the mitotic fraction to G0, can occur in response to environmental challenge. We also review evidence on the life cycle of trophoblast from the time that fusion occurs, and point to gaps in knowledge of how large quantities of fetal DNA arrive in maternal circulation. We critique historical methodology and make a case for research to re-address questions about trophoblast lifecycle and dynamics in normal pregnancy and the common diseases of pre-eclampsia and fetal growth restriction, where altered trophoblast kinetics have long been postulated.

WIDER IMPLICATIONS

The hypothesis requires experimental testing, moving research away from currently accepted methodology towards a new standard that includes representative cell and tissue sampling, assessment of cell cycle and differentiation parameters, and robust classification of cell subpopulations in villous trophoblast, with due attention to gestational age, maternal and fetal phenotype, disease and outcome.

Autophagy in the HTR-8/SVneo Cell Oxidative Stress Model Is Associated with the NLRP1 Inflammasome

We investigated whether there was activation of NLRP1 inflammasomes and excessive autophagy in oxidative stress damage. And we further demonstrate whether there is a cascade relationship between the activation of NLRP1 inflammasomes and the phenomenon of excessive autophagy. To observe the expression level of the NLRP1 inflammasome group in the pathological process of trophoblast cell oxidative stress, western blot, immunofluorescence, and qRT-PCR were performed. Autophagy in trophoblast cells after the action of H₂O₂ was detected by using normal trophoblast cells' NLRP1-specific activator (MDP) as a positive control. The presence of excessive autophagy was determined by comparing it with the autophagy-related proteins in normal trophoblast cells. Through siRNA-NLRP1, we investigated the role of oxidative stress and the NLRP1 inflammasome in autophagy in cells. 100 μmol MDP for 24 hours can be used as the optimal concentration of the NLRP1 activator. In human placental trophoblast oxidative stress, the model group significantly increased the expression level of inflammasome IL-1β, CASP1, and NLRP1, compared with the control group NLRP3, and LC3-II, Beclin-1, ATG5, ATG7, and p62 overactivated the autophagy ability of cells. After the activation of NLRP1, the expression of these inflammasomes increased, accompanied by the decrease in autophagy. After the expression of NLRP1 was silenced by RNAi, the expression of inflammasome IL-1β, CASP1, and NLRP3 was also decreased. Still, the autophagy level was increased, which was manifested by the high expression of LC3-II, Beclin-1, ATG5, and ATG7 and the decrease in p62. Trophoblast cells showed the expression of NLRP1 protein and excessive autophagy under oxidative stress. Simultaneously, the NLRP1 inflammasome of trophoblast cells in the state of oxidative stress was correlated with autophagy. Inflammasome activation and autophagy were shown to be linked and to influence each other mutually. These may also provide new therapeutic targets in a pathological pregnancy.

The Effect and Mechanism of Asymmetric Dimethylarginine Regulating Trophoblastic Autophagy on Fetal Growth Restriction

Fetal growth restriction (FGR) is an important cause of perinatal death and adverse pregnancy outcomes. Asymmetric dimethylarginine (ADMA) is associated with FGR, but the mechanisms have not been thoroughly studied. Here, we determined the levels of ADMA and autophagy-related molecules in human blood samples and placental tissues. And we also used the human chorionic carcinoma cell line BeWo to investigate the mechanism of ADMA-induced FGR in vitro. Compared with the control group, ADMA levels in maternal blood and placenta were increased in patients with FGR, and the birth weight (BW) percentile was negatively correlated with maternal serum ADMA concentration in the FGR group. The expression of mammalian target of rapamycin (mTOR) in the placenta of the FGR group was lower than the control group, while the expression of Beclin-1 and microtubule-associated protein 1 light chain 3-II (LC3-II)/LC3-I was significantly increased in the FGR group. And the expression of matrix metalloproteinase 9 (MMP9) was decreased in the placenta of patients with FGR. In in vitro cell experiments, compared with the control group, the expression of mTOR and MMP9 in BeWo cells was decreased and the expression of Beclin-1 and LC3-II/LC3-I was increased in the ADMA-treated group. Moreover, ADMA had favorable effects on the formation of autophagic vacuoles, and the autophagy inhibitor 3-Methyladenine (3-MA) could reduce the autophagy-induction effect of ADMA on BeWo cells. This study found that ADMA could participate in the occurrence of FGR through inducing autophagy in trophoblasts.

UL16-Binding Protein 1 Induced HTR-8/SVneo Autophagy via NF-κB Suppression Mediated by TNF-α Secreted through uNK Cells

UL16-binding protein 1(ULBP1) has been reported to inhibit trophoblast invasion through the modification of secretion functions of uNK cells in the previous study, but its mechanisms remain unclear. In this study, we investigated the related mechanism by which upregulated ULBP1 expression impaired trophoblast invasion. We found that conditioned media with ULBP1 increased autophagy in HTR-8/SVneo, and anti-TNF-α-neutralizing antibody rescued the autophagy caused by the conditioned medium. We further found TNF-α induced autophagy in trophoblast cells in a dose-dependent way and accompanied by a decreased activity of nuclear factor-kappa B (NF-κB). Inhibition of NF-κB activation by chemical inhibitor augmented these autophagic responses to TNF-α in the cells. In addition, interruption NF-κB caused a significant decrease in HTR-8/SVneo invasion and enhanced the inhibition effect of TNF-α on HTR-8/SVneo invasion. Taken together, these findings suggest that TNF-α is able to regulate autophagic activity via suppressing NF-κB, which might be the mechanism related to ULBP1 in preeclampsia pathogenesis.

Discordant placental oxygenation and autophagy in twin anemia-polycythemia sequence (TAPS)

BACKGROUND

(Macro)autophagy is an important process of self-degradation of macromolecules and organelles that ensures cellular homeostasis and energy preservation during stressful conditions. Dysregulated placental autophagy has been implicated in a wide range of pregnancy complications. Recent studies identified hypoxia as a key regulator of trophoblast autophagy in vitro; however, its effects on placental autophagy in vivo remain incompletely understood. In this study, we evaluated the monochorionic twin anemia-polycythemia sequence (TAPS) placenta as model of discordant placental oxygenation to determine the effects of hypoxia on placental autophagy in utero.

METHODS

We performed a retrospective comparative analysis of tissue oxygenation and autophagy in anemic and polycythemic territories of TAPS placentas (N = 12). Archival tissues were subjected to immunohistochemical, immunofluorescence and Western blot analyses of carbonic anhydrase (CA) IX (hypoxia marker) and key autophagy/lysosomal markers.

RESULTS

CAIX protein levels were significantly higher in anemic twin territories than in corresponding polycythemic territories, consistent with relative tissue hypoxia. Anemic placental shares further displayed significantly higher levels of LC3I/II (autophagosome markers) and LAMP1/2 (lysosome markers), associated with upregulated expression of lysosome/autophagosome activity-associated markers, transcription factor EB and cathepsin D. The accumulation of autophagosomes and lysosomes in anemic shares was accompanied by elevated p62 protein expression, suggestive of inhibition of the downstream autophagy pathway.

CONCLUSIONS

TAPS placentas display striking intertwin discordance in tissue oxygenation and autophagic activity and may provide a suitable model for study of the interrelationship between hypoxia, autophagy, and pregnancy outcome in a monochorionic twin setting.

Decreased placental apoptosis and autophagy in pregnancies complicated by gestational diabetes with large-for-gestational age fetuses

INTRODUCTION

Dysregulation of placental apoptosis and autophagy are observed in pregnancy complications including preeclampsia and fetal growth restriction. However, studies of their changes in the placentas of women with gestational diabetes mellitus (GDM) show inconsistent results. We aimed to compare the changes in apoptosis, autophagy, and Bcl-2 family proteins in the placentas from women with normal pregnancies and those with GDM, with or without large-for-gestational age (LGA) infants and to investigate the effect of hyperglycemia on the changes in apoptosis, autophagy, and Bcl-2 family proteins in primary cytotrophoblastic cells.

METHODS

Villous tissues were obtained from normal pregnant women and those with GDM, with or without LGA infants. Primary cytotrophoblast cells were isolated from normal term placentas and cultured under standard, hyperglycemic, or hyperosmotic conditions.

RESULTS

Compared to placentas from normal pregnant women, those from GDM women with LGA infants were heavier, had lower beclin-1 and DRAM levels, less M30 and cleaved PARP immunoreactivity, and increased Ki-67 immunoreactivity. These changes were associated with increased Bcl-xL and decreased Bak levels. Increased glucose concentration led to lower ATG5, beclin-1, LC3B-II, p62, and DRAM levels, lower annexin V and M30-positive cell percentages, and less cleaved PARP changes compared with standard culture conditions. Hyperglycemia caused higher Bcl-xL levels and lower Bak and Bad levels than did standard culture conditions.

DISCUSSION

There were differential changes in apoptosis and autophagy between placentas from normal pregnant women and those from GDM women with LGA infants. Bcl-2 family proteins are likely involved in the regulation of these changes.

Sevoflurane attenuates brain damage through inhibiting autophagy and apoptosis in cerebral ischemia‑reperfusion rats

The present study aimed to investigate the effects of sevoflurane post-conditioning in a rat brain cerebral ischemia-reperfusion (I/R) model and examine its possible mechanism. Rats were randomly divided into six groups: Sham control group (Sham), I/R group, sevoflurane group (Se), Toll-like receptor-4 (TLR4) inhibitor group (Tak-242), nuclear factor (NF)-κB inhibitor group (QNZ) and Sevoflurane post-conditioning combined with TLR4-NF-κB signaling pathway inhibitor group (Se + Tak-242). Morris water maze test and tetrazolium chloride staining were used to investigate the I/R injury. The nerve cell apoptosis and autophagy in cortical tissue were detected by TUNEL and transmission electron microscopy, respectively. The expression of TLR4 protein in cortical tissue was observed by immunohistochemical staining. The expression of autophagy and apoptotic associated proteins in cortical tissues and the activity of TLR4-NF-κB signaling pathway were assayed by western blot analysis. Sevoflurane post-conditioning improved the learning and memory dysfunction caused by cerebral I/R injury. The cerebral infarction area, nerve cell apoptosis and formation of autophagic vacuoles were reduced after sevoflurane administration. The expression of light chain 3II/I, Beclin-1, Bad and Cleaved-Caspase-3 proteins were inhibited and the expression of Bcl-2 protein was upregulated after sevoflurane administration. Sevoflurane post-conditioning also inhibited the TLR4 protein and NF-κB phosphorylation, and increased inhibitor of kBα phosphorylation. The treatment effect of Tak-242 and QNZ groups were not significantly different compared with the Se group (P>0.05), and the Se + Tak-242 group had the best results. The present study demonstrated that sevoflurane post-conditioning could protect middle cerebral artery occlusion-induced brain injury rats by inhibiting autophagy and apoptosis, and that its mechanism is related to the TLR4-NF-κB signaling pathway.

Maternal High-Fat Diet Consumption and Chronic Hyperandrogenemia Are Associated With Placental Dysfunction in Female Rhesus Macaques

The risk of adverse perinatal outcomes with maternal polycystic ovary syndrome may differ among hyperandrogenic and nonhyperandrogenic phenotypes and is likely modulated by maternal obesity and diet. The relative contribution of maternal hyperandrogenism and nutritional status to placental dysfunction is unknown. Female rhesus macaques (N = 39) were assigned at puberty to one of four treatment groups: subcutaneous cholesterol implants and a standard chow diet (controls); testosterone (T) implants and a normal diet; cholesterol implants and a high-fat, Western-style diet (WSD); and testosterone implants in combination with a high-fat diet. After 3.5 years of treatment, contrast-enhanced and Doppler ultrasound analyses of placental blood flow were performed for a representative subset of animals from each treatment group during pregnancy, and placental architecture assessed with stereological analysis. Placental growth factors, cellular nutrient sensors, and angiogenic markers were measured with ELISA and Western blotting. WSD consumption was associated with a 30% increase in placental flux rate relative to that in animals receiving a normal diet. T and WSD treatments were each independently associated with increased villous volume, and T also was associated with an ∼ 40% decrease fetal capillary volume on stereological analysis. T treatment was associated with significantly increased mTOR and SOCS3 expression. WSD consumption was associated with decreased GLUT1 expression and microvillous membrane localization. Hyperandrogenemic and nonhyperandrogenemic phenotypes are associated with altered placental angiogenesis, nutrient sensing, and glucose transport. WSD and T appear to have distinct effects on vascular impedance and capillary angiogenesis.

Impact of vitamin D and vitamin D receptor on the trophoblast survival capacity in preeclampsia

BACKGROUND

Preeclampsia and intra-uterine growth restriction (IUGR) are major health problems during pregnancy affecting both mother and child. Defective placental development and failure of trophoblast differentiation during pregnancy are important aspects in the pathogenesis of both syndromes. Recent studies have shown that autophagy is involved in the trophoblast survival capacity. As vitamin D has a central role in many cellular processes, we studied the relation of vitamin D and autophagy in those processes of preeclampsia and IUGR.

METHODS

Serum and placental samples from four groups of cases; normal term, IUGR, early-onset and late-onset preeclampsia, were analyzed for 25(OH)D vitamin D, sFLT1, PGF, LGALS13 in serum and vitamin D receptor (VDR), MAP1LC3B and BECN1 in placental tissues.

RESULTS

There was a significant difference in the sFLT1/PGF ratio in preeclamptic cases compared to controls and IUGR. There was a significant difference between these groups in the MAP1LC3B/BECN1 ratio as marker of the trophoblast survival capacity with a significantly reduced ratio in villous trophoblast of early-onset preeclampsia. Maternal vitamin D deficiency was found in all pathological pregnancies combined with significantly reduced staining levels of placental VDR in IUGR. Finally, there was a strong and significant negative correlation between the survival capacity (MAP1LC3B/BECN1) and both maternal vitamin D and placental VDR in the preeclampsia groups.

CONCLUSION

Vitamin D and intracellular VDR are strongly related to the trophoblast survival capacity in preeclampsia.

ULK1 prevents cardiac dysfunction in obesity through autophagy-meditated regulation of lipid metabolism

Aims

Autophagy is essential to maintain tissue homeostasis, particularly in long-lived cells such as cardiomyocytes. Whereas many studies support the importance of autophagy in the mechanisms underlying obesity-related cardiac dysfunction, the role of autophagy in cardiac lipid metabolism remains unclear. In the heart, lipotoxicity is exacerbated by cardiac lipoprotein lipase (LPL), which mediates accumulation of fatty acids to the heart through intravascular triglyceride (TG) hydrolysis.

Methods and results

In both genetic and dietary models of obesity, we observed a substantial increase in cardiac LPL protein levels without any change in messenger ribonucleic acid (mRNA). This was accompanied by a dramatic down-regulation of autophagy in the heart, as revealed by reduced levels of unc-51 like kinase-1 (ULK1) protein. To further explore the relationship between cardiac LPL and autophagy, we generated cardiomyocyte-specific knockout mice for ulk1 (Myh6-cre/ulk1fl/fl), Lpl (Myh6-cre/Lplfl/fl), and mice with a combined deficiency (Myh6-cre/ulk1fl/flLplfl/fl). Similar to genetic and dietary models of obesity, Myh6-cre/ulk1fl/fl mice had a substantial increase in cardiac LPL levels. When these mice were fed a high-fat diet (HFD), they showed elevated cardiac TG levels and deterioration in heart function. However, with combined deletion of LPL and ULK1 in Myh6-cre/ulk1fl/flLplfl/fl mice, HFD feeding did not lead to alterations in levels of TG or diacylglycerol, or in cardiac function. To further elucidate the role of autophagy in cardiac lipid metabolism, we infused a peptide that enhanced autophagy (D-Tat-beclin1). This effectively lowered LPL levels at the coronary lumen by restoring autophagy in the genetic model of obesity. This decrease in cardiac luminal LPL was associated with a reduction in TG levels and recovery of cardiac function.

Conclusion

These results provide clear evidence of the critical role of modulating cardiac LPL activity through autophagy-mediated proteolytic clearance as a potential novel strategy to overcome obesity-related cardiomyopathy.

Journey to the Center of the Fetal Brain: Environmental Exposures and Autophagy

Fetal brain development is known to be affected by adverse environmental exposures during pregnancy, including infection, inflammation, hypoxia, alcohol, starvation, and toxins. These exposures are thought to alter autophagy activity in the fetal brain, leading to adverse perinatal outcomes, such as cognitive and sensorimotor deficits. This review introduces the physiologic autophagy pathways in the fetal brain. Next, methods to detect and monitor fetal brain autophagy activity are outlined. An additional discussion explores possible mechanisms by which environmental exposures during pregnancy alter fetal brain autophagy activity. In the final section, a correlation of fetal autophagy activity with the observed postnatal phenotype is attempted. Our main purpose is to provide the current understanding or a lack thereof mechanisms on autophagy, underlying the fetal brain injury exposed to environmental insults.

Integrative single-cell omics analyses reveal epigenetic heterogeneity in mouse embryonic stem cells

Embryonic stem cells (ESCs) consist of a population of self-renewing cells displaying extensive phenotypic and functional heterogeneity. Research towards the understanding of the epigenetic mechanisms underlying the heterogeneity among ESCs is still in its initial stage. Key issues, such as how to identify cell-subset specifically methylated loci and how to interpret the biological meanings of methylation variations remain largely unexplored. To fill in the research gap, we implemented a computational pipeline to analyze single-cell methylome and to perform an integrative analysis with single-cell transcriptome data. According to the origins of variation in DNA methylation, we determined the genomic loci associated with allelic-specific methylation or asymmetric DNA methylation, and explored a beta mixture model to infer the genomic loci exhibiting cell-subset specific methylation (CSM). We observed that the putative CSM loci in ESCs are significantly enriched in CpG island (CGI) shelves and regions with histone marks for promoter and enhancer, and the genes hosting putative CSM loci show wide-ranging expression among ESCs. More interestingly, the putative CSM loci may be clustered into co-methylated modules enriching the binding motifs of distinct sets of transcription factors. Taken together, our study provided a novel tool to explore single-cell methylome and transcriptome to reveal the underlying transcriptional regulatory networks associated with epigenetic heterogeneity of ESCs.

DNA methylation is an epigenetic mark with covalent modification that occurs directly on genetic material. In vertebrates, the most common form of DNA methylation is 5-methylcytosine (5-mC) at which a methyl group (CH3) is attached to the cytosine nucleotide, especially in the context of CpG dinucleotide. DNA methylation has important regulatory roles in a broad range of biological processes and diseases, such as embryonic stem cells (ESCs) differentiation and development. ESC populations can be strikingly heterogeneous in DNA methylation. Emerging single-cell methods for capturing DNA methylation are being developed with the exciting potential to investigate the DNA methylation feature within complex and heterogeneous tissues. In this study, we implemented a computational pipeline to infer cell-subset specific methylation of ESCs from single-cell methylome. Through integrative analyses with transcription factor binding and single-cell transcriptome, we explored the underlying regulatory mechanisms associated with methylation heterogeneity in ESCs to interpret the biological functional relevance of methylation variations.

Impaired placental autophagy in placental malaria

Background

Placental malaria is a major cause of low birthweight, principally due to impaired fetal growth. Intervillositis, a local inflammatory response to placental malaria, is central to the pathogenesis of poor fetal growth as it impairs transplacental amino acid transport. Given the link between inflammation and autophagy, we investigated whether placental malaria-associated intervillositis increased placental autophagy as a potential mechanism in impaired fetal growth.

Methods

We examined placental biopsies collected after delivery from uninfected women (n = 17) and from women with Plasmodium falciparum infection with (n = 14) and without (n = 7) intervillositis. Western blotting and immunofluorescence staining coupled with advanced image analysis were used to quantify the expression of autophagic markers (LC3-II, LC3-I, Rab7, ATG4B and p62) and the density of autophagosomes (LC3-positive puncta) and lysosomes (LAMP1-positive puncta).

Results

Placental malaria with intervillositis was associated with higher LC3-II:LC3-I ratio, suggesting increased autophagosome formation. We found higher density of autophagosomes and lysosomes in the syncytiotrophoblast of malaria-infected placentas with intervillositis. However, there appear to be no biologically relevant increase in LC3B/LAMP1 colocalization and expression of Rab7, a molecule involved in autophagosome/lysosome fusion, was lower in placental malaria with intervillositis, indicating a block in the later stage of autophagy. ATG4B and p62 expression showed no significant difference across histological groups suggesting normal autophagosome maturation and loading of cargo proteins into autophagosomes. The density of autophagosomes and lysosomes in the syncytiotrophoblast was negatively correlated with placental amino acid uptake.

Conclusions

Placental malaria-associated intervillositis is associated with dysregulated autophagy that may impair transplacental amino acid transport, possibly contributing to poor fetal growth.

The trophoblast survival capacity in preeclampsia

BACKGROUND

Preeclampsia has become the world's major maternal health problem putting a huge burden on mothers, newborns and also on the health systems. The pathogenesis of preeclampsia seems to include events in very early pregnancy affecting differentiation of placental villous trophoblast. The arising changes of the cell death spectrum from apoptosis via increased autophagy and aponecrosis to necrosis in turn induce systemic inflammation of the mother.

METHODS

Placental tissue samples and maternal serum samples from 40 pregnant women were collected from normal pregnancy, IUGR, early-onset and late-onset preeclampsia. Immunohistochemistry for LC3B and Beclin-1 was quantified using systematic random sampling techniques. Serum levels of LDH and other markers were assessed in serum.

RESULTS

Expression of the autophagy markers LC3B and Beclin-1 was significantly different between groups as was the LC3B/Beclin-1 ratio. Early-onset preeclampsia and IUGR had the highest autophagy protein expression levels, while normal pregnancy and late-onset preeclampsia had the highest LC3B/Beclin-1 ratio. Early-onset preeclampsia had the highest negative correlation with free LDH as cell defect marker.

CONCLUSIONS

Autophagy plays a critical role in the cell death spectrum and cellular survival capacity of villous trophoblast. Alterations in autophagic protein expression are involved in pathological pregnancies such as preeclampsia.

Abnormal CYP11A1 gene expression induces excessive autophagy, contributing to the pathogenesis of preeclampsia

Objective

In this study, we investigated the exact mechanism by which excessive CYP11A1 expression impairs the placentation process and whether this causes preeclampsia (PE) in an in vivo model.

Setting and Design

In order to study CYP11A1 overexpression, BeWo cells were transfected with CYP11A1. Pregnenolone, progesterone, and testosterone levels were measured by enzyme linked immunosorbent assays, and levels of autophagy markers were quantified by western blotting and immunofluorescence. Trophoblastic cell invasion was assessed using transwell assays; BeWo cells were treated with testosterone and an androgen receptor (AR) inhibitor (flutamide) to elucidate the invasion mechanism. An adenovirus overexpression rat model was established to investigate CYP11A1 overexpression in vivo and the phenotype was examined. Furthermore, human placenta samples (n = 24) were used to determine whether PE patient placentas showed altered CYP11A1 and autophagy marker expression.

Results

BeWo cells overexpressing CYP11A1 had significantly increased levels of pregnenolone, progesterone, and testosterone. Additionally, the expression levels of autophagy markers in CYP11A1-overexpressing BeWo cells were significantly increased. Trophoblast invasion was significantly reduced in CYP11A1-overexpressing cells as well as in cells treated with high testosterone. This reduction could be significantly rescued when cells were pretreated with flutamide. Overexpression of CYP11A1 in rat pregnancies led to PE-like symptoms and an over-activation of the AR-mediated pathway in the placenta. Elevated expression of CYP11A1 and autophagy markers could also be detected in PE placenta samples.

Conclusions

These results suggest that abnormally high expression of CYP11A1 induces trophoblast autophagy and inhibits trophoblastic invasion, which is associated with the etiology of PE.

Consistency and Variability of DNA Methylation in Women During Puberty, Young Adulthood, and Pregnancy

Prior DNA methylation (DNA-m) analyses have identified cytosine-phosphate-guanine (CpG) sites, which show either a significant change or consistency during lifetime. However, the proportion of CpGs that are neither significantly different nor consistent over time (indifferent CpGs) is unknown. We investigated the methylation dynamics, both longitudinal changes and consistency, in women from preadolescence to late pregnancy using DNA-m of peripheral blood cells. Consistency of cell type–adjusted DNA-m between paired individuals was assessed by regressing CpGs of subsequent age on the prior, stability by intraclass correlation coefficients (>0.5), and changes by linear mixed models. In the first 2 transitions (10-18 years and 18 years to early pregnancy), 19.5% and 20.9% CpGs were consistent, but only 0.35% in the third transition (from early to late pregnancy). Significant changes in methylation were found in 0.7%, 5.6%, and 0% CpGs, respectively. Functional enrichment analyses of genes with significant changes in DNA-m in early pregnancy (5.6%) showed that the maternal DNA-m seems to reflect signaling pathways between the uterus and the trophoblast. The transition from early to late pregnancy showed low consistency/stability and no changes, suggesting the presence of a large proportion of indifferent CpGs in late pregnancy.

Moderate mammalian target of rapamycin inhibition induces autophagy in HTR8/SVneo cells via O-linked β-N-acetylglucosamine signaling

AIM

Autophagy, a highly regulated process with a dual role (pro-survival or pro-death), has been implicated in adverse pregnancy outcomes. The aim of this study was to explore the mechanism whereby mammalian target of rapamycin (mTOR) signaling regulates autophagy by modulating protein O-GlcNAcylation in human trophoblasts.

METHODS

HTR8/SVneo cells were incubated in serum-free medium for different time intervals or treated with varying doses of Torin1. Protein expression and cell apoptosis were detected by immunoblotting and flow cytometry, respectively.

RESULTS

Short-term serum starvation or slight suppression of mTOR signaling promoted autophagy and decreased apoptosis in HTR8/SVneo cells. Conversely, prolonged serum starvation or excessive inhibition of mTOR reduced autophagy and enhanced cell apoptosis. Both serum starvation and mTOR signaling suppression reduced protein O-GlcNAcylation. Upregulation and downregulation of O-linked β-N-acetylglucosamine (O-GlcNAc) levels attenuated and augmented autophagy, respectively. Moderate mTOR inhibition-induced autophagy was blocked by upregulation of protein O-GlcNAcylation. Furthermore, immunoprecipitation studies revealed that Beclin1 and synaptosome associated protein 29 (SNAP29) could be O-GlcNAcylated, and that slight mTOR inhibition resulted in decreased O-GlcNAc modification of Beclin1 and SNAP29. Notably, we observed an inverse correlation between phosphorylation (Ser15) and O-GlcNAcylation of Beclin1.

CONCLUSION

mTOR signaling inhibition played dual roles in regulating autophagy and apoptosis in HTR8/SVneo cells. Moderate mTOR suppression might induce autophagy via modulating O-GlcNAcylation of Beclin1 and SNAP29. Moreover, the negative interplay between Beclin1 O-GlcNAcylation and phosphorylation (Ser15) may be involved in autophagy regulation by mTOR signaling.

ATG16L1 governs placental infection risk and preterm birth in mice and women

The placenta is a barrier against maternal-fetal transmission of pathogens. Placental infections can cause several adverse pregnancy outcomes, including preterm birth (PTB). Yet, we have limited knowledge regarding the mechanisms the placenta uses to control infections. Here, we show that autophagy, a cellular recycling pathway important for host defense against pathogens, and the autophagy gene Atg16L1 play a key role in placental defense and are negatively associated with PTB in pregnant women. First, we demonstrate that placentas from women who delivered preterm exhibit reduced autophagy activity and are associated with higher infection indicators. Second, we identify the cellular location of the autophagy activity as being in syncytial trophoblasts. Third, we demonstrate that higher levels of autophagy and ATG16L1 in human trophoblasts were associated with increased resistance to infection. Accordingly, loss of autophagy or ATG16L1 impaired trophoblast antibacterial defenses. Fourth, we show that Atg16l1-deficient mice gave birth prematurely upon an inflammatory stimulus and their placentas were significantly less able to withstand infection. Finally, global induction of autophagy in both mouse placentas and human trophoblasts increased infection resistance. Our study has significant implications for understanding the etiology of placental infections and prematurity and developing strategies to mitigate placental infection-induced PTB.

The Placenta as a Barrier to Viral Infections

Throughout pregnancy, the placenta acts as a physical and immunological barrier against the hematogenous transmission of viruses from mother to fetus. Despite this, very little is known regarding the specific mechanisms by which the placenta shields the developing fetus from viral infections or about the strategies utilized by select viruses to bypass and/or weaken the placental barrier. In this review, we summarize studies regarding virus-host interactions at the placental interface and explore key areas for future investigation. We focus our review on placental trophoblasts, which form the barrier between maternal and fetal circulations and thus govern the cross talk between the maternal and fetal microenvironments.

Punicalagin promotes autophagy to protect primary human syncytiotrophoblasts from apoptosis

Punicalagin is a prominent polyphenol in pomegranate juice that protects cultured syncytiotrophoblasts from stress-induced apoptosis. Here, we test the hypothesis that punicalagin has this effect by inhibiting the mTOR kinase pathway to enhance autophagic turnover and limit apoptosis in cultured primary human syncytiotrophoblasts. In syncytiotrophoblasts, starvation, rapamycin, or punicalagin all decreased the expression of phosphorylated ribosomal protein S6, a downstream target of the mTOR kinase, and of the autophagy markers, LC3-II and p62. In contrast, in the presence of bafilomycin, an inhibitor of late stages of autophagy and degradation in the autophagolysosome, syncytiotrophoblasts exposed to starvation, rapamycin, or punicalagin all showed increased levels of LC3-II and p62. The number of LC3-II punctae also increased in punicalagin-treated syncytiotrophoblasts exposed to chloroquine, another inhibitor of autophagic degradation, and punicalagin increased the number of lysosomes. The apoptosis-reducing effect of punicalagin was attenuated by inhibition of autophagy using bafilomycin or knockdown of the autophagy related gene, ATG16L1. Collectively, these data support the hypothesis that punicalagin modulates the crosstalk between autophagy and apoptosis to promote survival in cultured syncytiotrophoblasts.

Dexamethasone Downregulates SLC7A5 Expression and Promotes Cell Cycle Arrest, Autophagy and Apoptosis in BeWo Cells

Synthetic glucocorticoids (GCs) such as dexamethasone (Dex) are widely given to pregnant women to induce maturation and improve viability of preterm infants. Despite the beneficial effects, synthetic GCs have adverse effects on placental growth and nutrient transport system. However, the molecular mechanisms involved in these events remain unknown. Here we use a human placental choriocarcinoma cell line (BeWo) as model to explore the pathway linking amino acids transport with cell viability under Dex challenge. BeWo cells treated with Dex (100 nM) for 24 h demonstrated G1/S cell cycle arrest together with enhanced autophagy and apoptosis. Concurrently, the amino acid carrier SLC7A5 was down-regulated in association with impaired cellular amino acids uptake and inhibition of mammalian target of rapamycin (mTOR) signaling. Similar cellular responses were observed in BeWo cells treated with BCH, a classical System L inhibitor which inactivates SLC7A5. The glucocorticoid receptor (GR) antagonist RU486 was able to diminish Dex-induced translocation of GR into nucleus and to abolish these effects. Furthermore, Dex treatment significantly promoted the binding of GR to the proximal promoter sequence of SLC7A5 gene. Taken together, our results show that Dex downregulates SLC7A5 expression via GR-mediated transrepression. The impaired amino acids uptake leads to inhibition of mTOR signaling which in turn causes inhibited proliferation and enhanced autophagy and apoptosis in BeWo cells. These findings indicate that SLC7A5 mediates the effect of Dex on cell viability, thus providing a novel molecular target for the prevention and treatment of Dex-induced cell cycle arrest and apoptosis in placental cells.

Autophagy induced by tumor necrosis factor α mediates intrinsic apoptosis in trophoblastic cells

To investigate the interconnection of apoptosis and autophagy in trophoblastic cells, we treated JEG-3 cells with tumor necrosis factor α (TNF-α) after transfecting LC3 or Beclin 1 or calpain small interfering RNA (siRNA), which blocks cleavage of autophagy-related gene 5 (Atg5) into N-terminal truncated Atg5 (tAtg5), a mediator between apoptosis and autophagy, and assessed the changes in LC3-II, caspase 9, caspase 3, and tAtg5. We also assessed the TNF-α-induced changes in LC3-II, caspase 9, and caspase 3 in primary trophoblasts from term placentae after transfecting siRNA for LC3 or Beclin 1. In both types of cells, transfection of LC3 or Beclin 1 siRNA significantly attenuated TNF-α-induced increases in LC3-II and activations of caspase 9 and caspase 3. There was significant abrogation of TNF-α-induced expression of tAtg5 after transfection with LC3 or Beclin 1 siRNA. Moreover, transfection with calpain siRNA significantly decreased TNF-α-induced changes in caspase 3 and caspase 9 in addition to tAtg5 in JEG-3 cells. Our data suggest that TNF-α-induced autophagy mediates intrinsic apoptosis, probably through tAtg5, in trophoblastic cells.

The role of autophagy in reproduction from gametogenesis to parturition

Autophagy is an intracellular process responsible for maintaining cellular homeostasis by the removal of cytoplasmic organelles, intracellular bacteria and viruses, and is a critical component of both the innate and acquired immune systems. A failure in physiological activation, assembly and function of the autophagic pathway has been implicated in a broad range of diseases including neurogenerative diseases, cardiopathy, infectious diseases, autoimmunity and cancer. Its involvement in reproduction, however, has not been extensively studied. Its activity is fundamental to many processes across the reproduction spectrum from development of the primordial follicle and spermatozoa to embryogenesis, placental development and maintaining uterine quiescence during pregnancy. Malfunctions in autophagy are associated with deleterious repercussions throughout reproduction. In this review we examine what is known about the involvement of autophagy in gamete formation, early post-fertilization embryogenesis, placental development and parturition, and propose promising areas for future research.

A review of the mechanism for poor placentation in early-onset preeclampsia: the role of autophagy in trophoblast invasion and vascular remodeling

Shallow trophoblast invasion and impaired vascular remodeling of spiral arteries have been recognized in early-onset preeclampsia. Placentation and vascular remodeling are multistep processes, and hypoxia, placental oxidative stress, excessive or atypical maternal immune response to trophoblasts, exaggerated inflammation, and increased production of anti-angiogenic factors such as the soluble form of the vascular endothelial growth factor (VEGF) receptor (sFlt-1) and soluble endoglin (sENG) may play a role in poor placentation in preeclampsia. Recent findings suggest that autophagy plays an important role in extravillous trophoblast (EVT) invasion and vascular remodeling under hypoxia, and sENG inhibits EVT invasion and vascular remodeling by the inhibition of autophagy under hypoxic conditions. In this review, we discuss the relationship between inadequate autophagy and poor placentation in preeclampsia.

Autophagy and human parturition: evaluation of LC3 expression in placenta from spontaneous or medically induced onset of labor

Induction of labor is one of the most used procedures in obstetrics, performed to achieve vaginal delivery through cervical ripening and stimulation of uterine contractions. We investigated the impact of induction of labor upon placental autophagy, a catabolic pathway activated in response to alteration of the physiological intracellular conditions. We collected 28 singleton placentas at the time of uncomplicated term vaginal delivery (7 spontaneous onset of labor, 21 induced labor). Autophagy was evaluated by immunohistochemistry, immunofluorescence, and immunoblotting. No significant difference in the autophagy expression was found between spontaneous or induced onset of labor. We found an inverse relationship between autophagy expression and the maternal prepregnancy body mass index, irrespective of the mode of labor onset. This result could be related to the nutritional maternal habits before and throughout pregnancy rather than rapid metabolic changes during labor.

Effect of Immortalization-Upregulated Protein-2 (IMUP-2) on Cell Death of Trophoblast

Trophoblasts, in the placenta, play a role for placental development as well as implantation in the early pregnancy. The characteristics and functions of trophoblast are identified by their localization and potency for proliferation, differentiation, and invasion. Thus, inadequate trophoblast cell death induces trophoblast dysfunction resulting in abnormal placental development and several gynecological diseases. Recently, it was reported that increased immortalization-upregulated protein-2 (IMUP-2) by hypoxia influences trophoblast apoptosis. However, IMUP-2 function on autophagy, which is type II programmed cell death remains unclear. In this study, we analyzed IMUP-2 expression in trophoblast cells (HTR8-SVneo) and compared IMUP-2 effects on cell death including apoptosis and autophagy in trophoblast regardless of IMUP-2 expression. Increased IMUP-2 in trophoblast by IMUP-2 gene transfection induces cell death, especially, apoptosis increases more than autophagy (p<0.05). However, the decreased IMUP-2 in trophoblasts after siRNA treatment decreased apoptosis with the decreased activities of caspase 3 and 7. The expressions of LC3 and MDC as an autophagosome makers and phosphorylated mTOR, which is a negative regulator for autophagy, increased. In addition, the S phase of cell cycle increased in trophoblasts when IMUP-2 expression decreased. Taken together, the alteration of IMUP-2 can control the balance between apoptosis and autophagy of trophoblasts resulting in functional involvement in placental development and in gynecological diseases by regulating the function of trophoblasts.

Autophagy-related protein LC3 and Beclin-1 in the first trimester of pregnancy

Autophagy is a degradation process that acts in response to environmental stressors. Recently, autophagy has been detected in normal term, preeclamptic and intrauterine growth-restricted placentas. The object of this work was to investigate the presence of autophagy in first trimester voluntary interruption of pregnancy placental villi by the expression of autophagy-related proteins, light chain 3 (LC3), and Beclin-1. In first trimester placental villi laser scanning confocal microscopy (LSCM) analysis revealed LC3 and Beclin-1 immunoreactivity prevalently located in villous cytotrophoblasts. Using LSCM, LC3, and Beclin-1 were localized to the cytoplasm of the trophoblast layer in human full-term placentas. Beclin-1 expression and LC3 activation were confirmed by western blotting. These data emphasize that autophagy activation is different among cytotrophoblasts and syncytiotrophoblasts depending on the gestational age and thus we speculate that autophagy might play a prosurvival role throughout human pregnancy.

Review: The role of autophagy in extravillous trophoblast function under hypoxia

Autophagy, a process for cellular cleaning through the removal of intracellular components in lysosomes, is a well conserved mechanism from yeast to mammalian cells, and also contributes to the maintenance of cellular homeostasis and of the energetic balance, in cellular and tissue remodeling, and cellular defense against extracellular insults and pathogens. The role of autophagy in placentation has been clarified. Autophagy is induced in trophoblasts under physiological hypoxia during early pregnancy and seems to have a role in placentation. Recent findings suggest that impaired autophagy might induce poor placentation in preeclamptic cases. In this review, we discuss the role of autophagy and summarize the role of autophagy-related genes in placentas.

Hypoxia induces autophagy in primary human trophoblasts

Autophagy is a highly regulated and dynamic process that maintains cellular homeostasis and plays a prosurvival role in most cells. Although hypoxia has been shown to induce apoptosis in placental trophoblasts, the hypoxic effect on autophagy has not been studied. We hypothesized that autophagy plays a prosurvival role in the placental trophoblasts by antagonizing hypoxia-induced apoptosis. Our data show that the expression of Light chain 3-II (LC3-II), an autophagic marker and cleaved poly(ADP-ribose) polymerase, an apoptosis marker, are inversely related in cultured trophoblasts. Exposure to rapamycin or hypoxia inactivated mammalian target of rapamycin, as reflected by reduced phosphorylation of ribosomal protein S6, indicating that mammalian target of rapamycin regulates autophagy in cultured cytotrophoblasts. Bafilomycin prevented the degradation of cargo and increased LC3-II and p62 in cytotrophoblasts exposed to hypoxia, revealing enhanced autophagic flux. Importantly, bafilomycin enhanced expression of autophagy-related protein 7 (Atg7), parallel to the increased apoptosis measured by cleaved poly(ADP-ribose) polymerase. LY294002, a phosphatidylinositol 3-kinase inhibitor, increased apoptosis in the trophoblasts under hypoxia or standard conditions. Silencing of Atg7 decreased both apoptosis and LC3-II in the trophoblasts, suggesting a dual role of Atg7 in both autophagy and apoptosis. We conclude that there is a cross talk between autophagy and apoptosis in the placental trophoblasts; autophagy plays a prosurvival role and Atg7 has roles in both autophagy and apoptosis under hypoxia.