N-Myc Down-regulated Gene 1 Modulates the Response of Term Human Trophoblasts to Hypoxic Injury

The dual role of autophagy during porcine reproductive and respiratory syndrome virus infection: A review

Autophagy is a highly conserved catabolic process that transports cellular components to lysosomes for degradation and reuse. It impacts various cellular functions, including innate and adaptive immunity. It can exhibit a dual role in viral infections, either promoting or inhibiting viral replication depending on the virus and the stage of the infection cycle. Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant pathogen impacting the sustainable development of the global pork industry. Recent research has shown that PRRSV has evolved specific mechanisms to facilitate or impede autophagosome maturation, thereby evading innate and adaptive immune responses. These primary mechanisms involve viral proteins that target multiple regulators of autophagosome formation, including autophagy receptors, tethering proteins, autophagy-related (ATG) genes, as well as the functional proteins of autophagosomes and late endosomes/lysosomes. Additionally, these mechanisms are related to the post-translational modification of key components, viral antigens for presentation to T lymphocytes, interferon production, and the biogenesis and function of lysosomes. This review discusses the specific mechanisms by which PRRSV targets autophagy in host defence and virus survival, summarizes the role of viral proteins in subverting the autophagic process, and examines how the host utilizes the antiviral functions of autophagy to prevent PRRSV infection.

The VEGF-Hypoxia Signature Is Upregulated in Basal-like Breast Tumors from Women of African Ancestry and Associated with Poor Outcomes in Breast Cancer

PURPOSE

Black women experience the highest breast cancer mortality rate compared with women of other racial/ethnic groups. To gain a deeper understanding of breast cancer heterogeneity across diverse populations, we examined a VEGF-hypoxia gene expression signature in breast tumors from women of diverse ancestry.

EXPERIMENTAL DESIGN

We developed a NanoString nCounter gene expression panel and applied it to breast tumors from Nigeria (n = 182) and the University of Chicago (Chicago, IL; n = 161). We also analyzed RNA sequencing data from Nigeria (n = 84) and The Cancer Genome Atlas (TCGA) datasets (n = 863). Patient prognosis was analyzed using multiple datasets.

RESULTS

The VEGF-hypoxia signature was highest in the basal-like subtype compared with other subtypes, with greater expression in Black women compared with White women. In TCGA dataset, necrotic breast tumors had higher scores for the VEGF-hypoxia signature compared with non-necrosis tumors (P < 0.001), with the highest proportion in the basal-like subtype. Furthermore, necrotic breast tumors have higher scores for the proliferation signature, suggesting an interaction between the VEGF-hypoxia signature, proliferation, and necrosis. T-cell gene expression signatures also correlated with the VEGF-hypoxia signature when testing all tumors in TCGA dataset. Finally, we found a significant association of the VEGF-hypoxia profile with poor outcomes when using all patients in the METABRIC (P < 0.0001) and SCAN-B datasets (P = 0.002).

CONCLUSIONS

These data provide further evidence for breast cancer heterogeneity across diverse populations and molecular subtypes. Interventions selectively targeting VEGF-hypoxia and the immune microenvironment have the potential to improve overall survival in aggressive breast cancers that disproportionately impact Black women in the African Diaspora.

The Role of Sirtuin-1 (SIRT1) in the Physiology and Pathophysiology of the Human Placenta

Sirtuins, especially SIRT1, play a significant role in regulating inflammatory response, autophagy, and cell response to oxidative stress. Since their discovery, sirtuins have been regarded as anti-ageing and longevity-promoting enzymes. Sirtuin-regulated processes seem to participate in the most prevalent placental pathologies, such as pre-eclampsia. Furthermore, more and more research studies indicate that SIRT1 may prevent pre-eclampsia development or at least alleviate its manifestations. Having considered this, we reviewed recent studies on the role of sirtuins, especially SIRT1, in processes determining normal or abnormal development and functioning of the placenta.

NDRG1 Signaling Is Essential for Endothelial Inflammation and Vascular Remodeling

BACKGROUND

NDRG-1 (N-myc downstream-regulated gene 1) is a member of NDRG family that plays essential roles in cell differentiation, proliferation, and stress responses. Although the expression of NDRG1 is regulated by fluid shear stress, its roles in vascular biology remain poorly understood. The purpose of the study is to determine the functional significance of NDRG1 in vascular inflammation and remodeling.

METHODS AND RESULTS

By using quantitative polymerase chain reaction, western blot, and immunohistochemistry, we demonstrate that the expression of NDRG1 is markedly increased in cytokine-stimulated endothelial cells and in human and mouse atherosclerotic lesions. To determine the role of NDRG1 in endothelial activation, we performed loss-of-function studies using NDRG1 short hairpin RNA. Our results demonstrate that NDRG1 knockdown by lentivirus bearing NDRG1 short hairpin RNA substantially attenuates both IL-1β (interleukin-1β) and TNF-α (tumor necrosis factor-α)-induced expression of cytokines/chemokines and adhesion molecules. Intriguingly, inhibition of NDRG1 also significantly attenuates the expression of procoagulant molecules, such as PAI-1 (plasminogen activator inhibitor type 1) and TF (tissue factor), and increases the expression of TM (thrombomodulin) and t-PA (tissue-type plasminogen activator), thus exerting potent antithrombotic effects in endothelial cells. Mechanistically, we showed that NDRG1 interacts with orphan Nur77 (nuclear receptor) and functionally inhibits the transcriptional activity of Nur77 and NF-κB (nuclear factor Kappa B) in endothelial cells. Moreover, in NDRG1 knockdown cells, both cytokine-induced mitogen-activated protein kinase activation, c-Jun phosphorylation, and AP-1 (activator protein 1) transcriptional activity are substantially inhibited. Neointima and atherosclerosis formation induced by carotid artery ligation and arterial thrombosis were markedly attenuated in endothelial cell-specific NDRG1 knockout mice compared with their wild-type littermates.

CONCLUSIONS

Our results for the first time identify NDRG1 as a critical mediator implicated in regulating endothelial inflammation, thrombotic responses, and vascular remodeling, and suggest that inhibition of NDRG1 may represent a novel therapeutic strategy for inflammatory vascular diseases, such as atherothrombosis and restenosis.

Environmental oxygen affects ex vivo growth and proliferation of mesenchymal progenitors by modulating mitogen-activated protein kinase and mammalian target of rapamycin signaling

BACKGROUND AIMS

Stem and progenitor cells of hematopoietic and mesenchymal lineages reside in the bone marrow under low oxygen (O₂) saturation. O₂ levels used in ex vivo expansion of multipotent mesenchymal stromal cells (MSCs) affect proliferation, metabolism and differentiation.

METHODS

Using cell-based assays and transcriptome and proteome data, the authors compared MSC cultures simultaneously grown under a conventional 19.95% O₂ atmosphere or at 5% O₂.

RESULTS

In 5% O₂, MSCs showed better proliferation and higher self-renewal ability, most probably sustained by enhanced signaling activity of mitogen-activated protein kinase and mammalian target of rapamycin pathways. Non-oxidative glycolysis-based energy metabolism supported growth and proliferation in 5% O₂ cultures, whereas MSCs grown under 19.95% O₂ also utilized oxidative phosphorylation. Cytoprotection mechanisms used by cells under 5% O₂ differed from 19.95% O₂  suggesting differences in the triggers of cell stress between these two O₂  conditions.

CONCLUSIONS

Based on the potential benefits for the growth and metabolism of MSCs, the authors propose the use of 5% O₂ for MSC culture.

N-myc downstream regulated gene 1 (ndrg1) functions as a molecular switch for cellular adaptation to hypoxia

Lack of oxygen (hypoxia and anoxia) is detrimental to cell function and survival and underlies many disease conditions. Hence, metazoans have evolved mechanisms to adapt to low oxygen. One such mechanism, metabolic suppression, decreases the cellular demand for oxygen by downregulating ATP-demanding processes. However, the molecular mechanisms underlying this adaptation are poorly understood. Here, we report on the role of ndrg1a in hypoxia adaptation of the anoxia-tolerant zebrafish embryo. ndrg1a is expressed in the kidney and ionocytes, cell types that use large amounts of ATP to maintain ion homeostasis. ndrg1a mutants are viable and develop normally when raised under normal oxygen. However, their survival and kidney function is reduced relative to WT embryos following exposure to prolonged anoxia. We further demonstrate that Ndrg1a binds to the energy-demanding sodium-potassium ATPase (NKA) pump under anoxia and is required for its degradation, which may preserve ATP in the kidney and ionocytes and contribute to energy homeostasis. Lastly, we show that sodium azide treatment, which increases lactate levels under normoxia, is sufficient to trigger NKA degradation in an Ndrg1a-dependent manner. These findings support a model whereby Ndrg1a is essential for hypoxia adaptation and functions downstream of lactate signaling to induce NKA degradation, a process known to conserve cellular energy.

SRT1720 plays a role in oxidative stress and the senescence of human trophoblast HTR8/SVneo cells induced by D-galactose through the SIRT1/FOXO3a/ROS signalling pathway

D-galactose (D-gal) is a reducing sugar widely distributed in food. In a pregnant animal model exposed to D-gal, D-gal was found to have toxic effects on both the mother and foetus through oxidative stress. However, little is known about the effect of D-gal exposure on the placenta and its underlying mechanism. In this study, we evaluated the effects of D-gal on HTR8/SVneo cells and the mechanisms in vitro. In the present study, the activity of HTR8/SVneo human trophoblasts decreased in a time- and concentration-dependent manner after exposure to D-gal. D-gal resulted in premature senescence of HTR8/SVneo cells, as confirmed by assessing β-galactosidase (SA-β-gal) activity and the expression of senescence-related factor p21. We also verified the damage of oxidative stress induced by D-gal by measuring the expression of reactive oxygen species (ROS), sirtuin 1 (SIRT1) and forkhead box O (FOXO) 3a. SRT1720, as a SIRT1 activator, mitigated D-gal-induced oxidative stress and senescence by upregulating SIRT1 and FOXO3a expression and reducing ROS production. Our data suggest that D-gal may induce HTR8/SVneo premature ageing through the SIRT1/FOXO3a/ROS signalling pathway mediated by oxidative stress and that SIRT1 protects cells from this damage.

Prognostic and biological role of the N-Myc downstream-regulated gene family in hepatocellular carcinoma

BACKGROUND

The N-Myc downstream-regulated gene (NDRG) family is comprised of four members (NDRG1-4) involved in various important biological processes. However, there is no systematic evaluation of the prognostic of the NDRG family in hepatocellular carcinoma (HCC).

AIM

To analyze comprehensively the biological role of the NDRG family in HCC.

METHODS

The NDRG family expression was explored using The Cancer Genome Atlas. DNA methylation interactive visualization database was used for methylation analysis of the NDRG family. The NDRG family genomic alteration was assessed using the cBioPortal. Single-sample Gene Set Enrichment Analysis was used to determine the degree of immune cell infiltration in tumors.

RESULTS

NDRG1 and NDRG3 were up-regulated in HCC, while NDRG2 was down-regulated. Consistent with expression patterns, high expression of NDRG1 and NDRG3 was associated with poor survival outcomes (P < 0.05). High expression of NDRG2 was associated with favorable survival (P < 0.005). An NDRG-based signature that statistically stratified the prognosis of the patients was constructed. The percentage of genetic alterations in the NDRG family varied from 0.3% to 11.0%, and the NDRG1 mutation rate was the highest. NDRG 1-3 expression was associated with various types of infiltrated immune cells. Gene ontology analysis revealed that organic acid catabolism was the most important biological process related to the NDRG family. Gene Set Enrichment Analysis showed that metabolic, proliferation, and immune-related gene sets were enriched during NDRG1 and NDRG3 high expression and NDRG2 low expression.

CONCLUSION

Overexpression of NDRG1 and NDRG3 and down-expression of NDRG2 are correlated with poor overall HCC prognosis. Our results may provide new insights into the indispensable role of NDRG1, 2, and 3 in the development of HCC and guide a promising new strategy for treating HCC.

N-myc downstream regulated family member 1 (NDRG1) is enriched in myelinating oligodendrocytes and impacts myelin degradation in response to demyelination

The N-myc downstream regulated gene family member 1 (NDRG1) is a gene whose mutation results in peripheral neuropathy with central manifestations. While most of previous studies characterized NDRG1 role in Schwann cells, the detection of central nervous system symptoms and the identification of NDRG1 as a gene silenced in the white matter of multiple sclerosis brains raise the question regarding its role in oligodendrocytes. Here, we show that NDRG1 is enriched in oligodendrocytes and myelin preparations, and we characterize its expression using a novel reporter mouse (TgNdrg1-EGFP). We report NDRG1 expression during developmental myelination and during remyelination after cuprizone-induced demyelination of the adult corpus callosum. The transcriptome of Ndrg1-EGFP+ cells further supports the identification of late myelinating oligodendrocytes, characterized by expression of genes regulating lipid metabolism and bioenergetics. We also generate a lineage specific conditional knockout (Olig1^cre/+ ;Ndrg1^fl/fl ) line to study its function. Null mice develop normally, and despite similar numbers of progenitor cells as wild type, they have fewer mature oligodendrocytes and lower levels of myelin proteins than controls, thereby suggesting NDRG1 as important for the maintenance of late myelinating oligodendrocytes. In addition, when control and Ndrg1 null mice are subject to cuprizone-induced demyelination, we observe a higher degree of demyelination in the mutants. Together these data identify NDRG1 as an important molecule for adult myelinating oligodendrocytes, whose decreased levels in the normal appearing white matter of human MS brains may result in greater susceptibility of myelin to damage.

NDRG1 is expressed in human granulosa cells: An implicative role of NDRG1 in the ovary

Purpose

N-myc downstream-regulated gene 1 (NDRG1) is expressed in various human tissues and plays a role in regulating cellular proliferation, angiogenesis, and hypoxia sensing. However, the role of NDRG1 in the ovary remains poorly understood. Therefore, we investigated NDRG1 expression and the role of NDRG1 in the human ovary.

Methods

Follicular fluid (FF) and luteinized granulosa cells were collected from follicles during oocyte retrieval. KGN cells were cultured with cobalt chloride (CoCl2, a hypoxia-mimicking agent) and/or echinomycin. mRNA, protein levels and secretion, and localization were assessed by real-time PCR, Western blotting, ELISA, and immunohistochemical analysis, respectively. KGN cells were also transfected with NDRG1 siRNA for 72 h.

Results

NDRG1 protein was expressed in luteinized granulosa cells. NDRG1 concentration was positively correlated with vascular endothelial growth factor (VEGF) and progesterone concentrations in FF. CoCl2-induced hypoxic stress significantly increased NDRG1 and VEGF mRNA and protein and hypoxia-inducible factor-1α expression compared with those in the controls. The CoCl2-induced overexpression of NDRG1 and VEGF was suppressed by echinomycin. Transfection with NDRG1 siRNA significantly suppressed the release of progesterone in the culture medium.

Conclusions

These results indicate that ovarian NDRG1 may play important roles in follicular development, especially in the early luteinization of pre-ovulatory follicles.

Differential expression and hypoxia-mediated regulation of the N-myc downstream regulated gene family

Many organisms rely on oxygen to generate cellular energy (adenosine triphosphate or ATP). During severe hypoxia, the production of ATP decreases, leading to cell damage or death. Conversely, excessive oxygen causes oxidative stress that is equally damaging to cells. To mitigate pathological outcomes, organisms have evolved mechanisms to adapt to fluctuations in oxygen levels. Zebrafish embryos are remarkably hypoxia-tolerant, surviving anoxia (zero oxygen) for hours in a hypometabolic, energy-conserving state. To begin to unravel underlying mechanisms, we analyze here the distribution of the N-myc Downstream Regulated Gene (ndrg) family, ndrg1-4, and their transcriptional response to hypoxia. These genes have been primarily studied in cancer cells and hence little is understood about their normal function and regulation. We show here using in situ hybridization that ndrgs are expressed in metabolically demanding organs of the zebrafish embryo, such as the brain, kidney, and heart. To investigate whether ndrgs are hypoxia-responsive, we exposed embryos to different durations and severity of hypoxia and analyzed transcript levels. We observed that ndrgs are differentially regulated by hypoxia and that ndrg1a has the most robust response, with a ninefold increase following prolonged anoxia. We further show that this treatment resulted in de novo expression of ndrg1a in tissues where the transcript is not observed under normoxic conditions and changes in Ndrg1a protein expression post-reoxygenation. These findings provide an entry point into understanding the role of this conserved gene family in the adaptation of normal cells to hypoxia and reoxygenation.

Impact of hypoxia on the pathogenesis and therapy resistance in multiple myeloma

Multiple myeloma (MM) is a refractory plasma cell tumor. In myeloma cells, the transcription factor IRF4, the master regulator of plasma cells, is aberrantly upregulated and plays an essential role in oncogenesis. IRF4 forms a positive feedback loop with MYC, leading to additional tumorigenic properties. In recent years, molecular targeted therapies have contributed to a significant improvement in the prognosis of MM. Nevertheless, almost all patients experience disease progression, which is thought to be a result of treatment resistance induced by various elements of the bone marrow microenvironment. Among these, the hypoxic response, one of the key processes for cellular homeostasis, induces hypoxia‐adapted traits such as undifferentiation, altered metabolism, and dissemination, leading to drug resistance. These inductions are caused by ectopic gene expression changes mediated by the activation of hypoxia‐inducible factors (HIFs). By contrast, the expression levels of IRF4 and MYC are markedly reduced by hypoxic stress. Notably, an anti‐apoptotic capability is usually acquired under both normoxic and hypoxic conditions, but the mechanism is distinct. This fact strongly suggests that myeloma cells may survive by switching their dependent regulatory factors from IRF4 and MYC (normoxic bone marrow region) to HIF (hypoxic bone marrow microenvironment). Therefore, to achieve deep remission, combination therapeutic agents, which are complementarily effective against both IRF4‐MYC‐dominant and HIF‐dominated fractions, may become an important therapeutic strategy for MM.

RNA Network Interactions During Differentiation of Human Trophoblasts

In the human placenta, two trophoblast cell layers separate the maternal blood from the villous basement membrane and fetal capillary endothelial cells. The inner layer, which is complete early in pregnancy and later becomes discontinuous, comprises the proliferative mononuclear cytotrophoblasts, which fuse together and differentiate to form the outer layer of multinucleated syncytiotrophoblasts. Because the syncytiotrophoblasts are responsible for key maternal-fetal exchange functions, tight regulation of this differentiation process is critical for the proper development and the functional role of the placenta. The molecular mechanisms regulating the fusion and differentiation of trophoblasts during human pregnancy remain poorly understood. To decipher the interactions of non-coding RNAs (ncRNAs) in this process, we exposed cultured primary human trophoblasts to standard in vitro differentiation conditions or to conditions known to hinder this differentiation process, namely exposure to hypoxia (O₂ < 1%) or to the addition of dimethyl sulfoxide (DMSO, 1.5%) to the culture medium. Using next generation sequencing technology, we analyzed the differential expression of trophoblastic lncRNAs, miRNAs, and mRNAs that are concordantly modulated by both hypoxia and DMSO. Additionally, we developed a model to construct a lncRNA-miRNA-mRNA co-expression network and inferred the functions of lncRNAs and miRNAs via indirect gene ontology analysis. This study improves our knowledge of the interactions between ncRNAs and mRNAs during trophoblast differentiation and identifies key biological processes that may be impaired in common gestational diseases, such as fetal growth restriction or preeclampsia.

RNA-Seq identifies genes whose proteins are upregulated during syncytia development in murine C2C12 myoblasts and human BeWo trophoblasts

The fusion of villous cytotrophoblasts into the multinucleated syncytiotrophoblast is critical for the essential functions of the mammalian placenta. Using RNA-Seq gene expression, quantitative protein expression, and siRNA knockdown we identified genes and their cognate proteins which are similarly upregulated in two cellular models of mammalian syncytia development (human BeWo cytotrophoblast to syncytiotrophoblast and murine C2C12 myoblast to myotube). These include DYSF, PDE4DIP, SPIRE2, NDRG1, PLEC, GPR146, HSPB8, DHCR7, and HDAC5. These findings provide avenues for further understanding of the mechanisms underlying mammalian placental syncytiotrophoblast development.

Pharmacological targeting and the diverse functions of the metastasis suppressor, NDRG1, in cancer

N-myc downstream regulated gene-1 (NDRG1) is a potent metastasis suppressor that is regulated by hypoxia, metal ions including iron, the free radical nitric oxide (NO^.), and various stress stimuli. This intriguing molecule exhibits diverse functions in cancer, inhibiting epithelial-mesenchymal transition (EMT), cell migration and angiogenesis by modulation of a plethora of oncogenes via cellular signaling. Thus, pharmacological targeting of NDRG1 signaling in cancer is a promising therapeutic strategy. Of note, novel anti-tumor agents of the di-2-pyridylketone thiosemicarbazone series, which exert the "double punch" mechanism by binding metal ions to form redox-active complexes, have been demonstrated to markedly up-regulate NDRG1 expression in cancer cells. This review describes the mechanisms underlying NDRG1 modulation by the thiosemicarbazones and the diverse effects NDRG1 exerts in cancer. As a major induction mechanism, iron depletion appears critical, with NO^. also inducing NDRG1 through its ability to bind iron and generate dinitrosyl-dithiol iron complexes, which are then effluxed from cells. Apart from its potent anti-metastatic role, several studies have reported a pro-oncogenic role of NDRG1 in a number of cancer-types. Hence, it has been suggested that NDRG1 plays pleiotropic roles depending on the cancer-type. The molecular mechanism(s) underlying NDRG1 pleiotropy remain elusive, but are linked to differential regulation of WNT signaling and potentially differential interaction with the tumor suppressor, PTEN. This review discusses NDRG1 induction mechanisms by metal ions and NO^. and both the anti- and possible pro-oncogenic functions of NDRG1 in multiple cancer-types and compares the opposite effects this protein exerts on cancer progression.

Modeling human trophoblast, the placental epithelium at the maternal fetal interface

Appropriate human trophoblast lineage specification and differentiation is crucial for the establishment of normal placentation and maintenance of pregnancy. However, due to the lack of proper modeling systems, the molecular mechanisms of these processes are still largely unknown. Much of the early studies in this area have been based on animal models and tumor-derived trophoblast cell lines, both of which are suboptimal for modeling this unique human organ. Recent advances in regenerative and stem cell biology methods have led to development of novel in vitro model systems for studying human trophoblast. These include derivation of human embryonic and induced pluripotent stem cells and establishment of methods for the differentiation of these cells into trophoblast, as well as the more recent derivation of human trophoblast stem cells. In addition, advances in culture conditions, from traditional two-dimensional monolayer culture to 3D culturing systems, have led to development of trophoblast organoid and placenta-on-a-chip model, enabling us to study human trophoblast function in context of more physiologically accurate environment. In this review, we will discuss these various model systems, with a focus on human trophoblast, and their ability to help elucidate the key mechanisms underlying placental development and function. This review focuses on model systems of human trophoblast differentiation, including advantages and limitations of stem cell-based culture, trophoblast organoid, and organ-on-a-chip methods and their applications in understanding placental development and disease.

NDRG1 activates VEGF-A-induced angiogenesis through PLCγ1/ERK signaling in mouse vascular endothelial cells

Many diseases, including cancer, have been associated with impaired regulation of angiogenesis, of which vascular endothelial growth factor (VEGF)-A is a key regulator. Here, we test the contribution of N-myc downstream regulated gene 1 (NDRG1) to VEGF-A-induced angiogenesis in vascular endothelial cells (ECs). Ndrg1^−/− mice exhibit impaired VEGF-A-induced angiogenesis in corneas. Tumor angiogenesis induced by cancer cells that express high levels of VEGF-A was also reduced in a mouse dorsal air sac assay. Furthermore, NDRG1 deficiency in ECs prevented angiogenic sprouting from the aorta and the activation of phospholipase Cγ1 (PLCγ1) and ERK1/2 by VEGF-A without affecting the expression and function of VEGFR2. Finally, we show that NDRG1 formed a complex with PLCγ1 through its phosphorylation sites, and the inhibition of PLCγ1 dramatically suppressed VEGF-A-induced angiogenesis in the mouse cornea, suggesting an essential role of NDRG1 in VEGF-A-induced angiogenesis through PLCγ1 signaling.

Kosuke Watari et al. show that N-myc downstream-regulated gene 1 (NDRG1) stimulates new blood vessel formation that is induced by VEGF-A, using Ndrg1 knockout mice. They find that PLCγ1/ERK signaling mediates this regulation, providing mechanistic insights into how vascular endothelial cells form new vessels.

N-myc downstream-regulated gene 1 inhibits the proliferation of colorectal cancer through emulative antagonizing NEDD4-mediated ubiquitylation of p21

BACKGROUND

N-myc downstream-regulated gene 1 (NDRG1) has been shown to play a key role in tumor metastasis. Recent studies demonstrate that NDRG1 can suppress tumor growth and is related to tumor proliferation; however, the mechanisms underlying these effects remain obscure.

METHODS

Immunohistochemistry (IHC) was used to detect NDRG1 and p21 protein expression in colorectal cancer tissue, and clinical significance of NDRG1 was also analyzed. CCK-8 assay, colony formation assay, flow cytometry, and xenograft model were used to assess the effect of NDRG1 on tumor proliferation in vivo and in vitro. The mechanisms underlying the effect of NDRG1 were investigated using western blotting, immunofluorescence, immunoprecipitation, and ubiquitylation assay.

RESULTS

NDRG1 was down-regulated in CRC tissues and correlated with tumor size and patient survival. NDRG1 inhibited tumor proliferation through increasing p21 expression via suppressing p21 ubiquitylation. NDRG1 and p21 had a positive correlation both in vivo and in vitro. Mechanistically, E3 ligase NEDD4 could directly interact with and target p21 for degradation. Moreover, NDRG1 could emulatively antagonize NEDD4-mediated ubiquitylation of p21, increasing p21 expression and inhibit tumor proliferation.

CONCLUSION

Our study could fulfill potential mechanisms of the NDRG1 during tumorigenesis and metastasis, which may serve as a tumor suppressor and potential target for new therapies in human colorectal cancer.

Bidirectional Regulation between NDRG1 and GSK3β Controls Tumor Growth and Is Targeted by Differentiation Inducing Factor-1 in Glioblastoma

The development of potent and selective therapeutic approaches to glioblastoma (GBM), one of the most aggressive primary brain tumors, requires identification of molecular pathways that critically regulate the survival and proliferation of GBM. Previous studies have reported that deregulated expression of N-myc downstream regulated gene 1 (NDRG1) affects tumor growth and clinical outcomes of patients with various types of cancer including glioma. Here, we show that high level expression of NDRG1 in tumors significantly correlated with better prognosis of patients with GBM. Loss of NDRG1 in GBM cells upregulated GSK3β levels and promoted cell proliferation, which was reversed by selective inhibitors of GSK3β. In contrast, NDRG1 overexpression suppressed growth of GBM cells by decreasing GSK3β levels via proteasomal degradation and by suppressing AKT and S6 cell growth signaling, as well as cell-cycle signaling pathways. Conversely, GSK3β phosphorylated serine and threonine sites in the C-terminal domain of NDRG1 and limited the protein stability of NDRG1. Furthermore, treatment with differentiation inducing factor-1, a small molecule derived from Dictyostelium discoideum, enhanced NDRG1 expression, decreased GSK3β expression, and exerted marked NDRG1-dependent antitumor effects in vitro and in vivo. Taken together, this study revealed a novel molecular mechanism by which NDRG1 inhibits GBM proliferation and progression. Our study thus identifies the NDRG1/GSK3β signaling pathway as a key growth regulatory program in GBM, and suggests enhancing NDRG1 expression in GBM as a potent strategy toward the development of anti-GBM therapeutics. SIGNIFICANCE: This study identifies NDRG1 as a potent and endogenous suppressor of glioblastoma cell growth, suggesting the clinical benefits of NDRG1-targeted therapeutics against glioblastoma.

Porcine Reproductive and Respiratory Syndrome Virus Activates Lipophagy To Facilitate Viral Replication through Downregulation of NDRG1 Expression

Autophagy maintains cellular homeostasis by degrading organelles, proteins, and lipids in lysosomes. Autophagy is involved in the innate and adaptive immune responses to a variety of pathogens. Some viruses can hijack host autophagy to enhance their replication. However, the role of autophagy in porcine reproductive and respiratory syndrome virus (PRRSV) infection is unclear. Here, we show that N-Myc downstream-regulated gene 1 (NDRG1) deficiency induced autophagy, which facilitated PRRSV replication by regulating lipid metabolism. NDRG1 mRNA is expressed ubiquitously in most porcine tissues and most strongly in white adipose tissue. PRRSV infection downregulated the expression of NDRG1 mRNA and protein, while NDRG1 deficiency contributed to PRRSV RNA replication and progeny virus assembly. NDRG1 deficiency reduced the number of intracellular lipid droplets (LDs), but the expression levels of key genes in lipogenesis and lipolysis were not altered. Our results also show that NDRG1 deficiency promoted autophagy and increased the subsequent yields of hydrolyzed free fatty acids (FFAs). The reduced LD numbers, increased FFA levels, and enhanced PRRSV replication were abrogated in the presence of an autophagy inhibitor. Overall, our findings suggest that NDRG1 plays a negative role in PRRSV replication by suppressing autophagy and LD degradation.IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV), an enveloped single-positive-stranded RNA virus, causes acute respiratory distress in piglets and reproductive failure in sows. It has led to tremendous economic losses in the swine industry worldwide since it was first documented in the late 1980s. Vaccination is currently the major strategy used to control the disease. However, conventional vaccines and other strategies do not provide satisfactory or sustainable prevention. Therefore, safe and effective strategies to control PRRSV are urgently required. The significance of our research is that we demonstrate a previously unreported relationship between PRRSV, NDRG1, and lipophagy in the context of viral infection. Furthermore, our data point to a new role for NDRG1 in autophagy and lipid metabolism. Thus, NDRG1 and lipophagy will have significant implications for understanding PRRSV pathogenesis for developing new therapeutics.

A combined ANXA2-NDRG1-STAT1 gene signature predicts response to chemoradiotherapy in cervical cancer

BACKGROUND

A better understanding of locally advanced cervical cancer (LACC) is mandatory for further improving the rates of disease control, since a significant proportion of patients still fail to respond or undergo relapse after concurrent chemoradiation treatment (CRT), and survival for these patients has generally remained poor.

METHODS

To identify specific markers of CRT response, we compared pretreatment biopsies from LACC patients with pathological complete response (sensitive) with those from patients showing macroscopic residual tumor (resistant) after neoadjuvant CRT, using a proteomic approach integrated with gene expression profiling. The study of the underpinning mechanisms of chemoradiation response was carried out through in vitro models of cervical cancer.

RESULTS

We identified annexin A2 (ANXA2), N-myc downstream regulated gene 1 (NDRG1) and signal transducer and activator of transcription 1 (STAT1) as biomarkers of LACC patients' responsiveness to CRT. The dataset collected through qPCR on these genes was used as training dataset to implement a Random Forest algorithm able to predict the response of new patients to this treatment. Mechanistic investigations demonstrated the key role of the identified genes in the balance between death and survival of tumor cells.

CONCLUSIONS

Our results define a predictive gene signature that can help in cervical cancer patient stratification, thus providing a useful tool towards more personalized treatment modalities.

Cx43 phosphorylation-mediated effects on ERK and Akt protect against ischemia reperfusion injury and alter the stability of the stress-inducible protein NDRG1

Gap junctions contain intercellular channels that enable intercellular communication of small molecules while also serving as a signaling scaffold. Connexins, the proteins that form gap junctions in vertebrates, are highly regulated and typically have short (<2 h) half-lives. Connexin43 (Cx43), the predominate connexin in the myocardium and epithelial tissues, is phosphorylated on more than a dozen serine residues and interacts with a variety of protein kinases. These interactions regulate Cx43 and gap junction formation and stability. Casein kinase 1 (CK1)-mediated phosphorylation of Cx43 promotes gap junction assembly. Using murine knock-in technology and quantitative PCR, immunoblotting, and immunoprecipitation assays, we show here that mutation of the CK1 phosphorylation sites in Cx43 reduces the levels of total Cx43 in the myocardium and increases Cx43 phosphorylation on sites phosphorylated by extracellular signal-regulated kinase (ERK). In aged myocardium, we found that, compared with WT Cx43, mutant Cx43 expression increases ERK activation, phosphorylation of Akt substrates, and protection from ischemia-induced injury. Our findings also uncovered that Cx43 interacts with the hypoxia-inducible protein N-Myc downstream-regulated gene 1 protein (NDRG1) and that Cx43 phosphorylation status controls this interaction and dramatically affects NDRG1 stability. We propose that, in addition to altering gap junction stability, Cx43 phosphorylation directly and dynamically regulates cellular signaling through ERK and Akt in response to ischemic injury. We conclude that gap junction-dependent NDRG1 regulation might explain some cellular responses to hypoxia.

MORC2 promotes development of an aggressive colorectal cancer phenotype through inhibition of NDRG1

MORC2 (microrchidia family CW‐type zinc finger 2) is a newly identified chromatin remodeling protein that functions in diverse biological processes including gene transcription. NDRG1 is a metastasis suppressor and a prognostic biomarker for colorectal cancer (CRC). However, the relationship between MORC2 and NDRG1 transcriptional regulation and the roles of MORC2 in CRC remain elusive. Here, we showed that MORC2 downregulated NDRG1 mRNA, protein levels, and promoter activity in CRC cells. We also found that MORC2 bound to the −446 to −213 bp region of the NDRG1 promoter. Mechanistically, histone deacetylase sirtuin 1 (SIRT1) was involved in NDRG1 transcriptional regulation. MORC2 was able to interact with SIRT1 and inhibit NDRG1 promoter activity cumulatively with SIRT1. MORC2 overexpression led to a decrease of H3Ac and H4Ac of the NDRG1 promoter. Importantly, we showed that NDRG1 was essential in MORC2‐mediated promotion of CRC cell migration and invasion in vitro, as well as lung metastasis of CRC cells in vivo. Moreover, MORC2 expression correlated negatively with NDRG1 expression in CRC patients. High expression of MORC2 was significantly associated with lymph node metastasis (P = 0.019) and poor pTNM stage (P = 0.02) and the expression of MORC2 correlated with poor prognosis in colon cancer patients. Our findings thus contribute to the knowledge of the regulatory mechanism of MORC2 in downregulating NDRG1, and suggest MORC2 as a potential therapeutic target for CRC.

PLIN2 Is Essential for Trophoblastic Lipid Droplet Accumulation and Cell Survival During Hypoxia

Trophoblast hypoxia and injury, key components of placental dysfunction, are associated with fetal growth restriction and other complications of pregnancy. Accumulation of lipid droplets has been found in hypoxic nonplacental cells. Unique to pregnancy, lipid accumulation in the placenta might perturb lipid transport to the fetus. We tested the hypothesis that hypoxia leads to accumulation of lipid droplets in human trophoblasts and that trophoblastic PLIN proteins play a key role in this process. We found that hypoxia promotes the accumulation of lipid droplets in primary human trophoblasts. A similar accretion of lipid droplets was found in placental villi in vivo from pregnancies complicated by fetal growth restriction. In both situations, these changes were associated with an increased level of cellular triglycerides. Exposure of trophoblasts to hypoxia led to reduced fatty acid efflux and oxidation with no change in fatty acid uptake or synthesis. We further found that hypoxia markedly stimulated PLIN2 mRNA synthesis and protein expression, which colocalized to lipid droplets. Knockdown of PLIN2, but not PLIN3, enhanced trophoblast apoptotic death, and overexpression of PLIN2 promoted cell viability. Collectively, our data indicate that hypoxia enhances trophoblastic lipid retention in the form of lipid droplets and that PLIN2 plays a key role in this process and in trophoblast defense against apoptotic death. These findings also imply that this protective mechanism may lead to diminished trafficking of lipids to the developing fetus.

The role of Sirtuin1-PPARγ axis in placental development and function

Placental development is important for proper in utero growth and development of the fetus, as well as maternal well-being during pregnancy. Abnormal differentiation of placental epithelial cells, called trophoblast, is at the root of multiple pregnancy complications, including miscarriage, the maternal hypertensive disorder preeclampsia and intrauterine growth restriction. The ligand-activated nuclear receptor, PPARγ, and nutrient sensor, Sirtuin-1, both play a role in numerous pathways important to cell survival and differentiation, metabolism and inflammation. However, each has also been identified as a key player in trophoblast differentiation and placental development. This review details these studies, and also describes how various stressors, including hypoxia and inflammation, alter the expression or activity of PPARγ and Sirtuin-1, thereby contributing to placenta-based pregnancy complications.

N-Myc Downstream-Regulated Gene 1 Restricts Hepatitis C Virus Propagation by Regulating Lipid Droplet Biogenesis and Viral Assembly

Host cells harbor various intrinsic mechanisms to restrict viral infections as a first line of antiviral defense. Viruses have evolved various countermeasures against these antiviral mechanisms. Here we show that N-Myc downstream-regulated gene 1 (NDRG1) limits productive hepatitis C virus (HCV) infection by inhibiting viral assembly. Interestingly, HCV infection downregulates NDRG1 protein and mRNA expression. The loss of NDRG1 increases the size and number of lipid droplets, which are the sites of HCV assembly. HCV suppresses NDRG1 expression by upregulating MYC, which directly inhibits the transcription of NDRG1 The upregulation of MYC also leads to the reduced expression of the NDRG1-specific kinase serum/glucocorticoid-regulated kinase 1 (SGK1), resulting in a markedly diminished phosphorylation of NDRG1. The knockdown of MYC during HCV infection rescues NDRG1 expression and phosphorylation, suggesting that MYC regulates NDRG1 at both the transcriptional and posttranslational levels. Overall, our results suggest that NDRG1 restricts HCV assembly by limiting lipid droplet formation. HCV counteracts this intrinsic antiviral mechanism by downregulating NDRG1 via a MYC-dependent mechanism.IMPORTANCE Hepatitis C virus (HCV) is an enveloped single-stranded RNA virus that targets hepatocytes in the liver. HCV is a leading cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma, and estimates suggest a global prevalence of 2.35%. Up to 80% of acutely infected individuals will develop chronic infection, and as many as 5% eventually progress to liver cancer. An understanding of the mechanisms behind virus-host interactions and viral carcinogenesis is still lacking. The significance of our research is that it identifies a previously unknown relationship between HCV and a known tumor-associated gene. Furthermore, our data point to a new role for this gene in the liver and in lipid metabolism. Thus, HCV infection serves as a great biological model to advance our knowledge of liver functions and the development of liver cancer.

Sirtuin1 is required for proper trophoblast differentiation and placental development in mice

INTRODUCTION

Placental insufficiency, arising from abnormal trophoblast differentiation and function, is a major cause of fetal growth restriction. Sirtuin-1 (Sirt1) is a ubiquitously-expressed NAD-dependent protein deacetylase which plays a key role in numerous cellular processes, including cellular differentiation and metabolism. Though Sirt1 has been widely studied, its role in placentation and trophoblast differentiation is unclear.

METHOD

Sirt1-heterozygous mice were mated and evaluated at various points during embryogenesis. In situ hybridization and immunohistochemistry were used to further characterize the placental phenotype of Sirt1-null mice. Wild-type (WT) and Sirt1-null mouse trophoblast stem cell (TSC) lines were derived from e3.5 littermate blastocysts. These cells were then evaluated at various points following differentiation. Differentiation was evaluated by expression of lineage specific markers using qPCR and flow cytometry, as well as Matrigel invasion assays. Global gene expression changes were evaluated using microarray-based RNA profiling; changes in specific pathways were validated using qPCR and western blot.

RESULTS

In the absence of Sirt1, both embryos and placentas were small, with placentas showing abnormalities in both the labyrinthine layer and junctional zone. Sirt1-null TSCs exhibited an altered phenotype in both undifferentiated and differentiated states, phenotypes which corresponded to changes in pathways relevant to both TSC maintenance and differentiation. Specifically, Sirt1-null TSC showed blunted differentiation, and appeared to be suspended in an Epcam^high trophoblast progenitor state.

DISCUSSION

Our results suggest that Sirt1 is required for proper TSC differentiation and placental development.

The expression level of C19MC miRNAs in early pregnancy and in response to viral infection

INTRODUCTION

We have previously shown that miRNAs produced from the Chromosome 19 MiRNA Cluster (C19MC), which are expressed almost exclusively in primate trophoblasts and are released into the maternal circulation, reduce viral replication in non-placental cells and can modulate migratory behavior of extravillous trophoblast. We sought to define the expression pattern of C19MC miRNA in early pregnancy and in response to viral infection in vitro and in vivo.

METHODS

We prospectively followed women undergoing in vitro fertilization (IVF) and determined their blood level of C19MC miRNA using RT-qPCR. To examine the effect of viral exposure on C19MC miRNAs expression, we used three systems: (1) a transgenic mouse overexpressing the C19MC cluster and exposed to Togaviridae during pregnancy, (2) cultured primary human trophoblasts exposed to Vesicular Stomatitis Virus in vitro, and (3) amniotic fluid from women exposed to cytomegalovirus during pregnancy.

RESULTS

In 27 IVF pregnancies, C19MC miRNAs were detected as early as 2 weeks after implantation, and their levels increased thereafter. There was no change in C19MC miRNA expression levels in the mouse placenta in response to viral exposure. Similarly, Vesicular Stomatitis Virus infection of primary human trophoblast did not selectively increase C19MC miRNA expression. C19MC miRNA expression in the amniotic fluid was not affected by vertical transmission of cytomegalovirus.

DISCUSSION

The expression of C19MC miRNAs in maternal circulation very early in pregnancy suggests a role in the establishment of the maternal-fetal interface. The levels of C19MC miRNA are not influenced by diverse types of viral infection.

Increased NDRG1 expression attenuate trophoblast invasion through ERK/MMP-9 pathway in preeclampsia

OBJECTIVE

The aim of this study was to investigate the expression of N-myc downstream-regulated gene1(NDRG1)in the placentas of pregnancies complicated with early-onset and late-onset preeclampsia (PE) and its underlying mechanism on the pathophysiology of PE.

METHODS

The expressions of NDRG-1 in placentas of pregnancies complicated with early-onset PE and late-onset PE were detected using immunohistochemistry, western blot assays and fluorescence quantitative PCR. The expressions of MMP-2, MMP-9 and ERK1/2 protein were detected by western blot analysis and cell invasion assay was performed using transwell chambers in NDRG1 silenced JEG-3 cells.

RESULTS

Compared with the normal term pregnancies, the expression of both NDRG1 mRNA and protein were significantly high in placentas from PE, and the expression of NDRG1 in early-onset PE was higher than that in late-onset PE. In NDRG1-silenced JEG-3 cells, MMP-2, MMP-9 and phosphorylation of ERK1/2 protein increased obviously and the number of cells that penetrated the membrane increased.

CONCLUSION

Upregulation of NDRG1 is associated with impaired trophoblast invasion in PE by inhibition ERK/MMP-2 and MMP-9 Pathway.

RNA Sequencing Reveals that Kaposi Sarcoma-Associated Herpesvirus Infection Mimics Hypoxia Gene Expression Signature

Kaposi sarcoma-associated herpesvirus (KSHV) causes several tumors and hyperproliferative disorders. Hypoxia and hypoxia-inducible factors (HIFs) activate latent and lytic KSHV genes, and several KSHV proteins increase the cellular levels of HIF. Here, we used RNA sequencing, qRT-PCR, Taqman assays, and pathway analysis to explore the miRNA and mRNA response of uninfected and KSHV-infected cells to hypoxia, to compare this with the genetic changes seen in chronic latent KSHV infection, and to explore the degree to which hypoxia and KSHV infection interact in modulating mRNA and miRNA expression. We found that the gene expression signatures for KSHV infection and hypoxia have a 34% overlap. Moreover, there were considerable similarities between the genes up-regulated by hypoxia in uninfected (SLK) and in KSHV-infected (SLKK) cells. hsa-miR-210, a HIF-target known to have pro-angiogenic and anti-apoptotic properties, was significantly up-regulated by both KSHV infection and hypoxia using Taqman assays. Interestingly, expression of KSHV-encoded miRNAs was not affected by hypoxia. These results demonstrate that KSHV harnesses a part of the hypoxic cellular response and that a substantial portion of hypoxia-induced changes in cellular gene expression are induced by KSHV infection. Therefore, targeting hypoxic pathways may be a useful way to develop therapeutic strategies for KSHV-related diseases.

How much successful are the medicinal chemists in modulation of SIRT1: A critical review

Silent information regulator two homologue one (SIRT1) is the most widely studied member of the sirtuin family related to histone deacetylases class III super-family using nicotinamide adenine dinucleotide (NAD(+)) as its cofactor. It is located in the nucleus but also modulates the targets in cytoplasm and mainly acts as transacetylase rather than deacetylase. SIRT1 specifically cleaves the nicotinamide ribosyl bond of NAD(+) and transfers the acetyl group from proteins to their co-substrate through an ADP- ribose-peptidyl imidate intermediate. It has been indicated that SIRT1 and its histone as well as non histone targets are involved in a wide range of biological courses including metabolic diseases, age related diseases, viral infection, inflammation, tumor-cell growth and metastasis. Modulation of SIRT1 expression may present a new insight in the discovery of a number of therapeutics. This review summarizes studies about SIRT1 and mainly focuses on the various modulators of SIRT1 evolved by natural as well as synthetic means.

Studies of the dynamics of nuclear clustering in human syncytiotrophoblast

Syncytial nuclear aggregates (SNAs), clusters of nuclei in the syncytiotrophoblast of the human placenta, are increased as gestation advances and in pregnancy pathologies. The origins of increased SNAs are unclear; however, a better appreciation of the mechanism may give insight into placental ageing and factors underpinning dysfunction. We developed three models to investigate whether SNA formation results from a dynamic process of nuclear movement and to generate alternative hypotheses. SNA count and size were measured in placental explants cultured over 16 days and particles released into culture medium were quantified. Primary trophoblasts were cultured for 6 days. Explants and trophoblasts were cultured with and without cytoskeletal inhibitors. An in silico model was developed to examine the effects of modulating nuclear behaviour on clustering. In explants, neither median SNA number (108 SNA/mm² villous area) nor size (283 μm²) changed over time. Subcellular particles from conditioned culture medium showed a wide range of sizes that overlapped with those of SNAs. Nuclei in primary trophoblasts did not change position relative to other nuclei; apparent movement was associated with positional changes of the syncytial cell membrane. In both models, SNAs and nuclear clusters were stable despite pharmacological disruption of cytoskeletal activity. In silico, increased nuclear movement, adhesiveness and sites of cytotrophoblast fusion were related to nuclear clustering. The prominence of SNAs in pregnancy disorders may not result from an active process involving cytoskeleton-mediated rearrangement of syncytial nuclei. Further insights into the mechanism(s) of SNA formation will aid understanding of their increased presence in pregnancy pathologies.

A three-dimensional culture system recapitulates placental syncytiotrophoblast development and microbial resistance

In eutherians, the placenta acts as a barrier and conduit at the maternal-fetal interface. Syncytiotrophoblasts, the multinucleated cells that cover the placental villous tree surfaces of the human placenta, are directly bathed in maternal blood and are formed by the fusion of progenitor cytotrophoblasts that underlie them. Despite their crucial role in fetal protection, many of the events that govern trophoblast fusion and protection from microbial infection are unknown. We describe a three-dimensional (3D)-based culture model using human JEG-3 trophoblast cells that develop syncytiotrophoblast phenotypes when cocultured with human microvascular endothelial cells. JEG-3 cells cultured in this system exhibit enhanced fusogenic activity and morphological and secretory activities strikingly similar to those of primary human syncytiotrophoblasts. RNASeq analyses extend the observed functional similarities to the transcriptome, where we observed significant overlap between syncytiotrophoblast-specific genes and 3D JEG-3 cultures. Furthermore, JEG-3 cells cultured in 3D are resistant to infection by viruses and Toxoplasma gondii, which mimics the high resistance of syncytiotrophoblasts to microbial infections in vivo. Given that this system is genetically manipulatable, it provides a new platform to dissect the mechanisms involved in syncytiotrophoblast development and microbial resistance.

Impaired differentiation of macrophage lineage cells attenuates bone remodeling and inflammatory angiogenesis in Ndrg1 deficient mice

N-myc downstream regulated gene 1 (NDRG1) is a responsible gene for a hereditary motor and sensory neuropathy-Lom (Charcot–Marie–Tooth disease type 4D). This is the first study aiming to assess the contribution of NDRG1 to differentiation of macrophage lineage cells, which has important implications for bone remodeling and inflammatory angiogenesis. Ndrg1 knockout (KO) mice exhibited abnormal curvature of the spine, high trabecular bone mass, and reduced number of osteoclasts. We observed that serum levels of macrophage colony-stimulating factor (M-CSF) and macrophage-related cytokines were markedly decreased in KO mice. Differentiation of bone marrow (BM) cells into osteoclasts, M1/M2-type macrophages and dendritic cells was all impaired. Furthermore, KO mice also showed reduced tumor growth and angiogenesis by cancer cells, accompanied by decreased infiltration of tumor-associated macrophages. The transfer of BM-derived macrophages from KO mice into BM-eradicated wild type (WT) mice induced much less tumor angiogenesis than observed in WT mice. Angiogenesis in corneas in response to inflammatory stimuli was also suppressed with decreased infiltration of macrophages. Taken together, these results indicate that NDRG1 deficiency attenuates the differentiation of macrophage lineage cells, suppressing bone remodeling and inflammatory angiogenesis. This study strongly suggests the crucial role of NDRG1 in differentiation process for macrophages.

Oxygen-regulated gene expression in murine cumulus cells

Oxygen is an important component of the environment of the cumulus-oocyte complex (COC), both in vivo within the ovarian follicle and during in vitro oocyte maturation (IVM). Cumulus cells have a key role in supporting oocyte development, and cumulus cell function and gene expression are known to be altered when the environment of the COC is perturbed. Oxygen-regulated gene expression is mediated through the actions of the transcription factors, the hypoxia-inducible factors (HIFs). In the present study, the effect of oxygen on cumulus cell gene expression was examined following in vitro maturation of the murine COC at 2%, 5% or 20% oxygen. Increased expression of HIF-responsive genes, including glucose transporter-1, lactate dehydrogenase A and BCL2/adenovirus E1B interacting protein 3, was observed in cumulus cells matured at 2% or 5%, compared with 20% oxygen. Stabilisation of HIF1α protein in cumulus cells exposed to low oxygen was confirmed by western blot and HIF-mediated transcriptional activity was demonstrated using a transgenic mouse expressing green fluorescent protein under the control of a promoter containing hypoxia response elements. These results indicate that oxygen concentration influences cumulus cell gene expression and support a role for HIF1α in mediating the cumulus cell response to varying oxygen.

The expression and post-transcriptional regulation of FSTL1 transcripts in placental trophoblasts

INTRODUCTION

Follistatin-like-1 (FSTL1) is a widely expressed secreted protein with diverse but poorly understood functions. Originally described as a pro-inflammatory molecule, it has recently been reported to play a role in signaling pathways that regulate development and homeostasis. Distinctively, FSTL1 harbors within its 3'-UTR the sequence encoding microRNA-198 (miR-198), shown to be inversely regulated relative to FSTL1 expression and to exhibit opposite actions on cellular processes such as cell migration. We sought to investigate the expression of FSTL1 and to assess its interplay with miR-198 in human trophoblasts.

METHODS

We used a combination of northern blot analyses, quantitative PCR, small RNA sequencing, western blot and immunohistochemistry to characterize FSTL1 and miR-198 expression in placental trophoblasts. We also used reporter assays to examine the post-transcriptional regulation of FSTL1 and assess its putative regulation by miR-198.

RESULTS

We detected the expression of FSTL1 transcript in both the human extravillous trophoblast line HTR-8/SVneo and in primary term human villous trophoblasts. We also found that the expression of FSTL1 was largely restricted to extravillous trophoblasts. Hypoxia enhanced the expression of FSTL1 protein in cultured primary villous trophoblasts. Interestingly, we did not detect any evidence for expression or function of mature miR-198 in human trophoblasts.

DISCUSSION

Our data indicate that placental FSTL1 is expressed particularly in extravillous trophoblasts. We also found no evidence for placental expression of miR-198, or for its regulation of FSTL1, implying that the post-transcriptional regulation of FSTL1 by miR-198 is tissue specific.

N-myc downstream-regulated gene 1 (NDRG1) mediates pomegranate juice protection from apoptosis in hypoxic BeWo cells but not in primary human trophoblasts

INTRODUCTION

N-Myc downstream-regulated gene 1 (NDRG1) expression is increased in placentas of human pregnancies with intrauterine growth restriction and in hypoxic cultured primary trophoblasts. We previously showed that elevated NDRG1 decreases trophoblast apoptosis induced by hypoxia. Separately, we found that pomegranate juice (PJ) decreases cell death induced by hypoxia in trophoblasts. Here, we test the hypothesis that PJ protects trophoblasts from hypoxia-induced apoptosis by modulating NDRG1 expression.

METHODS

Quantitative rtPCR was used to investigate the effects of PJ treatment on mRNA levels of 22 candidate genes involved in apoptosis, oxidative stress, and differentiation in trophoblasts. Western blotting and immunofluorescence were used to analyze NDRG1 protein levels. siRNA-mediated NDRG1 knockdown was used to investigate the role of NDRG1 in response to PJ in hypoxic BeWo choriocarcinoma cells and hypoxic cultured primary human trophoblasts.

RESULTS

The mRNA levels of eight genes were altered, with NDRG1 showing the largest response to PJ and thus, we pursued the role of NDRG1 here. PJ significantly increased NDRG1 protein expression in primary trophoblasts and in BeWo cells. Knockdown of NDRG1 in hypoxic BeWo cells in the presence of PJ yielded increased apoptosis. In contrast, knockdown of NDRG1 in hypoxic primary trophoblasts in the presence of PJ did not increase apoptosis.

DISCUSSION

We conclude that the PJ-mediated decrease in cell death in hypoxia is partially mediated by NDRG1 in BeWo cells but not in primary trophoblasts. The disparate effects of NDRG1 between BeWo cells and primary trophoblasts indicate caution is required when extrapolating from results obtained with cell lines to primary trophoblasts.

Human trophoblasts confer resistance to viruses implicated in perinatal infection

OBJECTIVE

Primary human trophoblasts were previously shown to be resistant to viral infection, and able to confer this resistance to nontrophoblast cells. Can trophoblasts protect nontrophoblastic cells from infection by viruses or other intracellular pathogens that are implicated in perinatal infection?

STUDY DESIGN

Isolated primary term human trophoblasts were cultured for 48-72 hours. Diverse nonplacental human cell lines (U2OS, human foreskin fibroblast, TZM-bl, MeWo, and Caco-2) were preexposed to either trophoblast conditioned medium, nonconditioned medium, or miR-517-3p for 24 hours. Cells were infected with several viral and nonviral pathogens known to be associated with perinatal infections. Cellular infection was defined and quantified by plaque assays, luciferase assays, microscopy, and/or colonization assays. Differences in infection were assessed by Student t test or analysis of variance with Bonferroni correction.

RESULTS

Infection by rubella and other togaviruses, human immunodeficiency virus-1, and varicella zoster was attenuated in cells preexposed to trophoblast-conditioned medium (P < .05), and a partial effect by the chromosome 19 microRNA miR-517-3p on specific pathogens. The conditioned medium had no effect on infection by Toxoplasma gondii or Listeria monocytogenes.

CONCLUSION

Our findings indicate that medium conditioned by primary human trophoblasts attenuates viral infection in nontrophoblastic cells. Our data point to a trophoblast-specific antiviral effect that may be exploited therapeutically.

Increased serum heme oxygenase-1 levels as a diagnostic marker of oxidative stress in preeclampsia

OBJECTIVE

To evaluate the utility of serum biomarkers in the diagnosis of preeclampsia (PE) and also investigate possible correlation with pathogenesis of PE.

METHODS

Maternal serum concentrations of heme oxygenase-1 (HO1) and N-myc downstream-regulated gene 1 (NDRG1) were measured at 27-34 weeks of gestation in a case-control study of 33 pregnant women diagnosed with PE and in 43 normotensive pregnant women without proteinuria. The Mann-Whitney U test and Spearman's correlation were used for statistical analysis.

RESULTS

The median serum HO1 level was found to be significantly higher in the PE group [76.7 ng/ml (23.4-445.7)] than control group [55.9 ng/ml (3.7-354.3)] (p = 0.006). Positive correlation was found between HO1 levels with presence of PE (r = 0.316, p = 0.005). There was no significant difference in NDRG1 values between the two groups (p = 0.226).

CONCLUSIONS

Serum HO1 levels were found to be increased in patients with PE compared with normotensive pregnant women.

NDRG1 deficiency attenuates fetal growth and the intrauterine response to hypoxic injury

Intrauterine mammalian development depends on the preservation of placental function. The expression of the protein N-myc downstream-regulated gene 1 (NDRG1) is increased in placentas of human pregnancies affected by fetal growth restriction and in hypoxic primary human trophoblasts, where NDRG1 attenuates cell injury. We sought to assess the function of placental NDRG1 in vivo and tested the hypothesis that NDRG1 deficiency in the mouse embryo impairs placental function and consequently intrauterine growth. We found that Ndrg1 knock-out embryos were growth restricted in comparison to wild-type or heterozygous counterparts. Furthermore, hypoxia reduced the survival of female, but not male, knock-out embryos. Ndrg1 deletion caused significant alterations in placental gene expression, with a marked reduction in transcription of several lipoproteins in the placental labyrinth. These transcriptional changes were associated with reduced fetal:maternal serum cholesterol ratio exclusively in hypoxic female embryos. Collectively, our findings indicate that NDRG1 promotes fetal growth and regulates the metabolic response to intrauterine hypoxic injury in a sexually dichotomous manner.

The metastasis suppressor, N-myc downstream-regulated gene 1 (NDRG1), inhibits stress-induced autophagy in cancer cells

N-myc downstream regulated gene 1 (NDRG1) is a potent metastasis suppressor with an undefined role in the stress response. Autophagy is a pro-survival pathway and can be regulated via the protein kinase-like endoplasmic reticulum kinase (PERK)/eIF2α-mediated endoplasmic reticulum (ER) stress pathway. Hence, we investigated the role of NDRG1 in stress-induced autophagy as a mechanism of inhibiting metastasis via the induction of apoptosis. As thiosemicarbazone chelators induce stress and up-regulate NDRG1 to inhibit metastasis, we studied their effects on the ER stress response and autophagy. This was important to assess, as little is understood regarding the role of the stress induced by iron depletion and its role in autophagy. We observed that the chelator, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), which forms redox-active iron and copper complexes, effectively induced ER stress as shown by activation of the PERK/eIF2α pathway. Dp44mT also increased the expression of the autophagic marker, LC3-II, and this was dependent on activation of the PERK/eIF2α axis, as silencing PERK prevented LC3-II accumulation. The effect of Dp44mT on LC3-II expression was at least partially due to iron-depletion, as this effect was also demonstrated with the classical iron chelator, desferrioxamine (DFO), and was not observed for the DFO-iron complex. NDRG1 overexpression also inhibited basal autophagic initiation and the ER stress-mediated autophagic pathway via suppression of the PERK/eIF2α axis. Moreover, NDRG1-mediated suppression of the pro-survival autophagic pathway probably plays a role in its anti-metastatic effects by inducing apoptosis. In fact, multiple pro-apoptotic markers were increased, whereas anti-apoptotic Bcl-2 was decreased upon NDRG1 overexpression. This study demonstrates the role of NDRG1 as an autophagic inhibitor that is important for understanding its mechanism of action.

The impact of ionizing radiation on placental trophoblasts

INTRODUCTION

Exposure to low-dose radiation is widespread and attributable to natural sources. However, occupational, medical, accidental, and terrorist-related exposures remain a significant threat. Information on radiation injury to the feto-placental unit is scant and largely observational. We hypothesized that radiation causes trophoblast injury, and alters the expression of injury-related transcripts in vitro or in vivo, thus affecting fetal growth.

METHODS

Primary human trophoblasts (PHTs), BeWo or NCCIT cells were irradiated in vitro, and cell number and viability were determined. Pregnant C57Bl/6HNsd mice were externally irradiated on E13.5, and placentas examined on E17.5. RNA expression was analyzed using microarrays and RT-qPCR. The experiments were repeated in the presence of the gramicidin S (GS)-derived nitroxide JP4-039, used to mitigate radiation-induced cell injury.

RESULTS

We found that survival of in vitro-irradiated PHT cell was better than that of irradiated BeWo trophoblast cell line or the radiosensitive NCCIT mixed germ cell tumor line. Radiation altered the expression of several trophoblast genes, with a most dramatic effect on CDKN1A (p21, CIP1). Mice exposed to radiation at E13.5 exhibited a 25% reduction in mean weight by E17.5, and a 9% reduction in placental weight, which was associated with relatively small changes in placental gene expression. JP4-039 had a minimal effect on feto-placental growth or on gene expression in irradiated PHT cells or mouse placenta.

DISCUSSION AND CONCLUSION

While radiation affects placental trophoblasts, the established placenta is fairly resistant to radiation, and changes in this tissue may not fully account for fetal growth restriction induced by ionizing radiation.

Molecular functions of the iron-regulated metastasis suppressor, NDRG1, and its potential as a molecular target for cancer therapy

N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.

Punicalagin, a polyphenol in pomegranate juice, downregulates p53 and attenuates hypoxia-induced apoptosis in cultured human placental syncytiotrophoblasts

Oxidative stress is associated with placental dysfunction and suboptimal pregnancy outcomes. Therapeutic interventions to limit placental injury from oxidative stress are lacking. Punicalagin is an ellagitannin and a potent antioxidant in pomegranate juice. We showed that both pomegranate juice and punicalagin decrease oxidative stress and apoptosis in cultured syncytiotrophoblasts. p53 is involved in the oxidative stress-induced apoptosis in trophoblasts. We now test the hypothesis that punicalagin limits trophoblast injury in vitro by regulating the levels of p53. We examined the expression of p53, mouse double minute 2 homolog, p21, hypoxia-inducible factor (HIF) α, and selected members of the B cell lymphoma 2 (BCL2) family of proteins in cultured syncytiotrophoblasts exposed to ≤1% oxygen in the absence or presence of punicalagin. We found that punicalagin attenuated hypoxia-induced apoptosis in syncytiotrophoblasts, as quantified by levels of cleaved poly-ADP ribose polymerase. This protective effect was in part mediated by reduced p53 activity shown by decreased expression of p21, lower HIF1α expression, and limited activity of caspases 9 and 3. There was no change in expression of proteins in the BCL2 family, which are also important in apoptosis. The data support a role for downregulation of p53 in the protection of human trophoblasts by punicalagin.

The expression and localization of N-myc downstream-regulated gene 1 in human trophoblasts

The protein N-Myc downstream-regulated gene 1 (NDRG1) is implicated in the regulation of cell proliferation, differentiation, and cellular stress response. NDRG1 is expressed in primary human trophoblasts, where it promotes cell viability and resistance to hypoxic injury. The mechanism of action of NDRG1 remains unknown. To gain further insight into the intracellular action of NDRG1, we analyzed the expression pattern and cellular localization of endogenous NDRG1 and transfected Myc-tagged NDRG1 in human trophoblasts exposed to diverse injuries. In standard conditions, NDRG1 was diffusely expressed in the cytoplasm at a low level. Hypoxia or the hypoxia mimetic cobalt chloride, but not serum deprivation, ultraviolet (UV) light, or ionizing radiation, induced the expression of NDRG1 in human trophoblasts and the redistribution of NDRG1 into the nucleus and cytoplasmic membranes associated with the endoplasmic reticulum (ER) and microtubules. Mutation of the phosphopantetheine attachment site (PPAS) within NDRG1 abrogated this pattern of redistribution. Our results shed new light on the impact of cell injury on NDRG1 expression patterns, and suggest that the PPAS domain plays a key role in NDRG1’s subcellular distribution.