Endocrine disruptors, polychlorinated biphenyls-induced gC1qR-dependent apoptosis in human trophoblast cell line HTR-8/SVneo

Preeclampsia: From Cellular Wellness to Inappropriate Cell Death, and the Roles of Nutrition

Preeclampsia is one of the most common obstetrical complications worldwide. The pathomechanism of this disease begins with abnormal placentation in early pregnancy, which is associated with inappropriate decidualization, vasculogenesis, angiogenesis, and spiral artery remodeling, leading to endothelial dysfunction. In these processes, appropriate cellular deaths have been proposed to play a pivotal role, including apoptosis and autophagy. The proper functioning of these physiological cell deaths for placentation depends on the wellbeing of the trophoblasts, affected by the structural and functional integrity of each cellular component including the cell membrane, mitochondria, endoplasmic reticulum, genetics, and epigenetics. This cellular wellness, which includes optimal cellular integrity and function, is heavily influenced by nutritional adequacy. In contrast, nutritional deficiencies may result in the alteration of plasma membrane, mitochondrial dysfunction, endoplasmic reticulum stress, and changes in gene expression, DNA methylation, and miRNA expression, as well as weakened defense against environmental contaminants, hence inducing a series of inappropriate cellular deaths such as abnormal apoptosis and necrosis, and autophagy dysfunction and resulting in abnormal trophoblast invasion. Despite their inherent connection, the currently available studies examined the functions of each organelle, the cellular death mechanisms and the nutrition involved, both physiologically in the placenta and in preeclampsia, separately. Therefore, this review aims to comprehensively discuss the relationship between each organelle in maintaining the physiological cell death mechanisms and the nutrition involved, and the interconnection between the disruptions in the cellular organelles and inappropriate cell death mechanisms, resulting in poor trophoblast invasion and differentiation, as seen in preeclampsia.

Placenta Disrupted: Endocrine Disrupting Chemicals and Pregnancy

Endocrine disrupting chemicals (EDCs) are chemicals that can interfere with normal endocrine signals. Human exposure to EDCs is particularly concerning during vulnerable periods of life, such as pregnancy. However, often overlooked is the effect that EDCs may pose to the placenta. The abundance of hormone receptors makes the placenta highly sensitive to EDCs. We have reviewed the most recent advances in our understanding of EDC exposures on the development and function of the placenta such as steroidogenesis, spiral artery remodeling, drug-transporter expression, implantation and cellular invasion, fusion, and proliferation. EDCs reviewed include those ubiquitous in the environment with available human biomonitoring data. This review also identifies critical gaps in knowledge to drive future research in the field.

The Possible Involvement of miR-371a-5p Regulating XIAP in the Pathogenesis of Recurrent Pregnancy Loss

Apoptosis is an interactive and dynamic biological process involved in all phases of embryogenesis. If apoptosis dominates the trophoblast cell growth process, it will result in adverse pregnancy outcomes. X-linked inhibitor of apoptosis protein (XIAP) is a potent caspase inhibitor and an important barrier to apoptotic cell death. MicroRNAs involve in posttranscriptional gene expression regulation and apoptosis. Online sequence alignment analysis showed that there was a putative binding site of miR-371a-5p on the 3'-untranslated region (UTR) of XIAP. Thirty chorionic villi samples were collected to examine the expression of miR-371a-5p and XIAP. The dual-luciferase reporter assay was applied to determine the relationship between miR-371a-5p and XIAP by human placental choriocarcinoma cells (JEG-3) cells in vitro. After 48-hour transfection of mimics and inhibitor by JEG-3 cells in vitro, Western blotting was used to, respectively, detect the protein expression levels of XIAP and caspase-3. Flow cytometry was used to validate the apoptosis ratio of transfection. The expression of miR-371a-5p and XIAP in recurrent pregnancy loss was greatly decreased. The results from the luciferase reporter assay strongly suggested binding of the XIAP 3'-UTR by miR-371a-5p. Apoptosis percentage of miR-371a-5p mimic was significantly greater than that of normal control. However, apoptosis percentage of miR-371a-5p inhibitor was significantly lower than that of normal control. A significant decrease in luciferase activity was observed in miR-371a-5p mimics-transfected JEG-3 cells compared with controls. These findings provide the evidence that miR-371a-5p is one of the regulating factors according to apoptosis pathway of XIAP-caspase-3 and may be involved in the pathogenesis of recurrent pregnancy loss.

Novel mechanism of miRNA-365-regulated trophoblast apoptosis in recurrent miscarriage

Clinical pregnancies increasingly end in recurrent miscarriage (RM) during the first trimester, with genetic factors shouldering the main responsibility. MicroRNAs (miRNAs) regulate gene expression in a wide array of important biological processes. We examined the potential role of dysregulated miRNAs in RM pathogenesis and trophoblast development as an approach to elucidate the molecular mechanism behind RM. miRNA profiles from clinical specimens of RM and induced abortion (IA) were compared, and several miRNAs were found to be aberrantly expressed in RM samples. Among the miRNAs, miR-365 was significantly differentially expressed in RM decidual tissues. Furthermore, our results demonstrate that miR-365 functions as an upstream regulator of MDM2/p53 expression, cell cycle progression and apoptosis in trophoblasts. Bioinformatic prediction and experimental validation assays identified SGK1 as a direct target of miR-365; consistently, its protein levels were low in decidual tissues. Additionally, functional studies revealed that SGK1 silencing elicits cell cycle arrest and apoptosis in trophoblasts and that SGK1 overexpression attenuates the effects of miR-365 on apoptosis and MDM2/p53 expression. Collectively, our data provide evidence that the up-regulation of miR-365 may contribute to RM by decreasing SGK1 expression, which suggests its potential utility as a prognostic biomarker and therapeutic target for RM.

Abnormal Expression of TRAIL Receptors in Decidual Tissue of Chlamydia trachomatis-Infected Rats During Early Pregnancy Loss

Chlamydia trachomatis is the scientific name of pathogenic bacteria causing infection that has been linked to spontaneous abortion. In this study, the expression pattern of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; a cytokine related to cell apoptosis) and its receptors was monitored in the decidua of C trachomatis-infected pregnant rats during early gestation to investigate the potential role of this molecular system in C trachomatis-induced spontaneous abortion. The data showed that C trachomatis infection significantly altered the messenger RNA (mRNA) expression of the receptors; death receptor (DR) 4 and DR5 increased, but decoy receptor (DcR) 1 and DcR2 decreased. Consistent with mRNA data, immunohistochemical staining of TRAIL and its receptors indicated that both DR4 and DR5 protein levels were elevated in infected tissues, primarily, decidual cells, decidual vessel wall, and uterine glands, whereas DcR1 and DcR2 showed lower levels compared to the noninfected group. Although receptor expression was altered, there was no difference detected in TRAIL expression. The observed altered expression of TRAIL receptors in C trachomatis-infected rats compared to noninfected rats during the embryo implantation phase suggests a possible mechanism for spontaneous abortion due to apoptosis and therefore failed embryo implantation. In addition, the observed increase in caspase-3 levels in infected cells further supports this finding. Taken together, the data presented in this study suggests C trachomatis infection altered the expression of TRAIL receptors, thus representing a general mechanism for C trachomatis-induced spontaneous abortion in C trachomatis-infected rats during early pregnancy loss.

Increased apoptosis rate of human decidual cells and cytotrophoblasts in patients with recurrent spontaneous abortion as a result of abnormal expression of CDKN1A and Bax

In the present study, we analyzed the proliferation and apoptosis of trophoblasts and human decidual cells in patients with recurrent spontaneous abortion and the related cellular pathway mechanism. Thirty-four patients with recurrent abortion and 30 healthy pregnant women undergoing planned artificial abortion were selected. The trophoblast and decidual cells were collected by negative pressure aspiration technique. TUNEL method was used to detect the apoptosis rate. Immunohistochemical method was used for detection of TP53 protein. Quantitative real-time PCR was used for detection of the relative expression level of CDKN1A and Bax mRNA. It was found that the cell apoptosis rate in the recurrent miscarriage group was significantly increased and the expression levels of TP53 protein, CDKN1A and Bax mRNA were also significantly increased (p<0.05). In conclusion, the trophoblast and decidual cells of patients with recurrent abortion were obviously apoptotic, which was probably related to abnormal expression of the CDKN1A and Bax genes mediated by TP53 protein through cellular pathways.

Role of collectins and complement protein C1q in pregnancy and parturition

Collectins such as surfactant proteins SP-A, SP-D, and mannan-binding lectin (MBL), as well as complement protein C1q are evolutionarily conserved innate immune molecules. They are known to opsonize a range of microbial pathogens (bacteria, fungi, virus, and parasites) and trigger effector clearance mechanisms involving phagocytosis and/or complement activation. Collectins and C1q have also attracted attention in studies involving pregnancy as they are expressed in the female reproductive tissues during pregnancy; a unique state of immune suppression with increased susceptibility to infectious diseases. Recent studies are beginning to unravel their functional significance in implantation, placentation, pregnancy maintenance and parturition in normal and adverse pregnancies. Collectins and C1q, expressed in gestational tissues during pregnancy, might alter the status of mother's immune response to the allogenic fetus and the microenvironment, thereby serving as important regulators of fetus-mother interaction. Here, we discuss the functional roles that have been assigned to SP-A, SP-D, MBL and C1q in pregnancy and parturition.

Emerging and Novel Functions of Complement Protein C1q

Complement protein C1q, the recognition molecule of the classical pathway, performs a diverse range of complement and non-complement functions. It can bind various ligands derived from self, non-self, and altered self and modulate the functions of immune and non-immune cells including dendritic cells and microglia. C1q involvement in the clearance of apoptotic cells and subsequent B cell tolerance is more established now. Recent evidence appears to suggest that C1q plays an important role in pregnancy where its deficiency and dysregulation can have adverse effects, leading to preeclampsia, missed abortion, miscarriage or spontaneous loss, and various infections. C1q is also produced locally in the central nervous system, and has a protective role against pathogens and possible inflammatory functions while interacting with aggregated proteins leading to neurodegenerative diseases. C1q role in synaptic pruning, and thus CNS development, its anti-cancer effects as an immune surveillance molecule, and possibly in aging are currently areas of extensive research.

The globular heads of the C1q receptor regulate apoptosis in human extravillous cytotrophoblast-derived transformed cells via a mitochondria-dependent pathway

PROBLEM

The receptor for the globular head of human C1q (gC1qR) predominantly localizes to the mitochondrial matrix. gC1qR mediates many biological responses, including growth perturbations, morphological abnormalities and the initiation of apoptosis. The purpose of this study was to investigate the relationship between gC1qR expression, mitochondrial dysfunction and the regulation of apoptosis in human extravillous cytotrophoblast (EVCT)-derived transformed cell lines (HTR-8/SVneo and HPT-8).

METHOD OF STUDY

gC1qR expression was examined in human placental villi using real-time qPCR and Western blot analysis. The apoptotic death of HTR-8/SVneo and HPT-8 cells was assessed using flow cytometric analysis. Mitochondrial function was assessed via ROS generation, the amount of cytosolic Ca(2+) and changes in the mitochondrial membrane potential (Δψm).

RESULTS

The expression of the gC1qR gene was significantly increased in spontaneous abortion samples relative to induced abortion samples. HTR-8/SVneo and HPT-8 cells transfected with a gC1qR vector showed upregulation of cellular apoptosis and mitochondrial dysfunction, interestingly, which were abrogated by the addition of metformin. Metformin may protect mitochondrial function.

CONCLUSION

These data support a mechanism whereby gC1qR induces apoptosis through mitochondria-dependent pathways in human EVCT-derived transformed cells.

A calreticulin/gC1qR complex prevents cells from dying: a conserved mechanism from arthropods to humans

The crossroad between cell death and proliferation is a general target for viral infections because viruses need to obstruct apoptosis to use cells for their own replication. Inducing immunogenic cell death in proliferating cells is also an important aim of anticancer chemotherapy. The C1q-binding proteins calreticulin (CRT) and gC1qR are highly conserved ubiquitous proteins, which are putative targets for viral manipulation and are associated with cancer. Here we show that these proteins form a complex in the cytoplasm as a response to viral infection resulting in apoptosis prevention. The formation of a cytosolic CRT/gC1qR complex prevents cell death by reducing gC1qR translocation into the mitochondria, and we provide evidence that this mechanism is conserved from arthropods to human cancer cells. Furthermore, we show that it is possible to prevent this complex from being formed in cancer cells. When the peptides of the complex proteins are overexpressed in these cells, the cells undergo apoptosis. This finding shows a causal link between virus and cancer and may be used to develop new tools in anticancer or antiviral therapy.