Sphingosine 1-phosphate regulates IL-8 expression and secretion via S1PR1 and S1PR2 receptors-mediated signaling in extravillous trophoblast derived HTR-8/SVneo cells

Sphingosine 1-Phosphate Activates S1PR3 to Induce a Proinflammatory Phenotype in Human Myometrial Cells

One of the common mechanisms responsible for obstetric complications, affecting millions of women every year, is abnormal uterine contractility. Despite the critical importance of this process for women's health, the mechanisms of uterine contraction regulation remain poorly understood. The initiation of uterine smooth muscle (myometrial) contraction is an inflammatory process, accompanied by upregulation of proinflammatory genes and cytokine release. In this study, we show that sphingolipid metabolism is activated during human labor and that sphingosine 1-phosphate (S1P), the main bioactive sphingolipid, may modify the myometrial proinflammatory phenotype. Our data in both primary and immortalized human myometrial cells show that exogenous S1P induces a proinflammatory gene signature and upregulates the expression of known inflammatory markers of parturition, such as IL8 and COX2. Using expression of IL8 as a readout for S1P activity in myometrial cells, we established that these S1P effects are mediated through the activation of S1P receptor 3 (S1PR3) and downstream activation of ERK1/2 pathways. Inhibition of S1PR3 in human myometrial cells attenuates upregulation of IL8, COX2, and JUNB both at the mRNA and protein levels. Furthermore, activation of S1PR3 with a receptor-specific agonist recapitulated the effects seen after treatment with exogenous S1P. Collectively, these results suggest a signaling pathway activated by S1P in human myometrium during parturition and propose new targets for development of novel therapeutics to alter uterine contractility during management of preterm labor or labor dystocia.

Sphingolipid Metabolism and Signaling in Lung Cancer: A Potential Therapeutic Target

Sphingolipids are important bioactive lipids that not only play an important role in maintaining the barrier function and fluidity of cell membranes but also regulate multiple processes in cancer development by controlling multiple signaling pathways in the signal transduction network. Dysregulation of sphingolipid metabolism is thought to be one of the most important dysregulated pathways in lung cancer, the most prevalent type of cancer in terms of incidence and mortality worldwide. This article focuses on lung cancer, reviewing the important lipids in sphingolipid metabolism and the related enzymes in relation to lung cancer progression and their effects on the tumor microenvironment and discussing their roles in the diagnosis and treatment of lung cancer.

Sphingosine kinases negatively regulate the expression of matrix metalloproteases (MMP1 and MMP3) and their inhibitor TIMP3 genes via sphingosine 1-phosphate in extravillous trophoblasts

PURPOSE

Extracellular matrix remodeling is essential for extravillous trophoblast (EVT) cell migration and invasion during placental development and regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs). Sphingosine kinases (SPHK1 and SPHK2) synthesize sphingosine-1-phosphate (S1P), which works either intracellularly or extracellularly via its receptors S1PR1-5 in an autocrine or paracrine manner. The role of SPHKs/S1P in regulating the expression of MMPs and TIMPs in EVT is mostly unknown and forms the primary objective of the study.

METHODS

HTR-8/SVneo cells were used as a model of EVT. To inhibit the expression of SPHKs, cells were treated with specific inhibitors, SK1-I and SKI-II, or gene-specific siRNAs. The expressions of MMPs and TIMPs were estimated by qPCR.

RESULTS

We demonstrated that SPHK1, MMP1-3, and TIMP1-3 were highly expressed in HTR-8/SVneo cells. We found that treatment of cells with SK1-I, SKI-II, and knockdown of SPHK1 or SPHK2 increased the expression of MMP1, MMP3, and TIMP3. The addition of extracellular S1P inhibits the upregulation of MMPs and TIMPs in treated cells.

CONCLUSIONS

SPHKs negatively regulate the expression of MMP1, MMP3, and TIMP3. The level of intracellular S1P acts as a negative feedback switch for MMP1, MMP3, and TIMP3 expression in EVT cells.

Thrombin impairs the angiogenic activity of extravillous trophoblast cells via monocyte chemotactic protein-1 (MCP-1): A possible link with preeclampsia

Cytokines' secretion from the decidua and trophoblast cells has been known to regulate trophoblast cell functions, such as Extravillous trophoblasts (EVTs) cell migration and invasion and remodeling of spiral arteries. Defective angiogenesis and spiral arteries transformation are mainly caused by proinflammatory cytokines and excessive thrombin generation during preeclampsia. Monocyte chemotactic protein-1 (MCP-1), a crucial cytokine, has a role in maintaining normal pregnancy. In this study, we explored whether thrombin regulates the secretion of MCP-1 in HTR-8/SVneo cells; if yes, what is its function? We used HTR-8/SVneo cells, developed from first trimester villous explants of early pregnancy, as the model of EVTs. MCP-1 gene silencing was performed using gene-specific siRNA. qPCR and ELISA were performed to estimate the expression and secretion of MCP-1. Here, we found that thrombin enhanced the secretion of MCP-1 in HTR-8/SVneo cells. Proteinase-activated receptor-1 (PAR-1) was found as the primary receptor, regulating MCP-1 secretion in these cells. Furthermore, MCP-1 secretion is modulated via protein kinase C (PKC) α, β, and Rho/Rho-kinase-dependent pathways. Thrombin negatively regulates HTR-8/SVneo cells' ability to mimic tube formation in an MCP-1 dependent manner. In conclusion, we propose that thrombin-controlled MCP-1 secretion may play an essential role in normal placental development and successful pregnancy maintenance. Improper thrombin production and MCP-1 secretion during pregnancy might cause inadequate vascular formation and transformation of spiral arteries, which may contribute to pregnancy disorders, such as preeclampsia.

Physiological and pathological functions of sphingolipids in pregnancy

Signaling by the bioactive sphingolipid, sphingosine 1-phosphate (S1P), and its precursors are emerging areas in pregnancy research. S1P and ceramide levels increase towards end of gestation, suggesting a physiological role in parturition. However, high levels of circulating S1P and ceramide are correlated with pregnancy disorders such as preeclampsia, gestational diabetes mellitus and intrauterine growth restriction. Expression of placental and decidual enzymes that metabolize S1P and S1P receptors are also dysregulated during pregnancy complications. In this review, we provide an in-depth examination of the signaling mechanism of S1P and ceramide in various reproductive tissues during gestation. These factors determine implantation and early pregnancy success by modulating corpus luteum function from progesterone production to luteolysis through to apoptosis. We also highlight the role of S1P through receptor signaling in inducing decidualization and angiogenesis in the decidua, as well as regulating extravillous trophoblast migration to anchor the placenta into the uterine wall. Recent advances on the role of the S1P:ceramide rheostat in controlling the fate of villous trophoblasts and the role of S1P as a negative regulator of trophoblast syncytialization to a multinucleated placental barrier are discussed. This review also explores the role of S1P in anti-inflammatory and pro-inflammatory signaling, its role as a vasoconstrictor, and the effects of S1P metabolizing enzymes and receptors in pregnancy.

Long intergenic ncRNA 00473 improves the invasion of trophoblastic cells via miR-16-5p

Preeclampsia (PE) is a common disease among pregnant women and is characterized by high blood pressure, edemas, proteinuria, etc. However, the underlying mechanism of PE is still not clear. Our results may provide a new understanding of the pathogenesis of PE and a therapeutical target for the treatment of the disease. Levels of long intergenic ncRNA 00473 (LINC00473), miR-16-5p, MMP2, MMP9, Bcl-2, Bax, and C caspase-3 in placental tissues or human trophoblastic cells were assessed. HTR8/SVneo and JEG-3 cells were transfected with LINC00473, miR-16-5p mimic, LINC00473 siRNA, or miR-16-5p inhibitor alone, or co-transfected with LINC00473 and miR-16-5p mimic or LINC00473 siRNA and miR-16-5p inhibitor. Viability, apoptosis, migration and invasion of cells were assessed by Cell Counting Kit-8, flow cytometry, wound healing assay and Transwell assay, respectively. The target gene of LINC00473 was analyzed using Starbase and dual-luciferase reporter assay. LINC00473 level was down-regulated in placental tissues of PE patients. LINC00473 overexpression increased cell viability, migration, invasion, and MMP2, MMP9 and Bcl-2 levels, yet decreased the apoptosis rates and Bax and C caspase-3 levels in cells; however, LINC00473 silencing had the opposite effect. LINC00473 targeted miR-16-5p and miR-16-5p level was negatively related to LINC00473 level. MiR-16-5p mimic reversed the promoting effect of LINC00473 overexpression on the invasion of HTR8/SVneo and JEG-3 cells, while miR-16-5p inhibitor reversed the inhibitory effect of LINC00473 silencing on the invasion of these cells. In conclusion, LINC00473 improved the invasion of human trophoblastic cells via miR-16-5p.

Human Keratinocytes Use Sphingosine 1-Phosphate and its Receptors to Communicate Staphylococcus aureus Invasion and Activate Host Defense

Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator generated when a cell membrane or its components are damaged by various factors. S1P regulates diverse cell activities via S1P receptors (S1PRs). Keratinocytes express S1PR1-5. Although it is known that S1PRs control keratinocyte differentiation, apoptosis, and wound healing, S1PR functions in keratinocyte infections have not been fully elucidated. We propose that the S1P-S1PR axis in keratinocytes works as a biosensor for bacterial invasion. Indeed, in human impetigo infection, we found high epidermal expression of S1PR1 and S1PR2 in the skin. Furthermore, in normal human epidermal keratinocytes in vitro, treatment with Staphylococcus aureus bacterial supernatant not only induced S1P production but also increased the transcription of S1PR2, confirming our in vivo observation, as well as increased the levels of TNFA, IL36G, IL6, and IL8 mRNAs. However, direct treatment of normal human epidermal keratinocytes with S1P increased the expressions of IL36G, TNFA, and IL8, but not IL6. In both S1P- and S. aureus bacterial supernatant-treated normal human epidermal keratinocytes, S1PR1 knockdown reduced IL36G, TNFA, and IL8 transcription, and the S1PR2 antagonist JTE013 blocked the secretion of these cytokines. Overall, we have proven that during infections, keratinocytes communicate damage by using S1P release and tight control of S1PR1 and 2.

Measles Virus Infection Fosters Dendritic Cell Motility in a 3D Environment to Enhance Transmission to Target Cells in the Respiratory Epithelium

Transmission of measles virus (MV) from dendritic to airway epithelial cells is considered as crucial to viral spread late in infection. Therefore, pathways and effectors governing this process are promising targets for intervention. To identify these, we established a 3D respiratory tract model where MV transmission by infected dendritic cells (DCs) relied on the presence of nectin-4 on H358 lung epithelial cells. Access to recipient cells is an important prerequisite for transmission, and we therefore analyzed migration of MV-exposed DC cultures within the model. Surprisingly, enhanced motility toward the epithelial layer was observed for MV-infected DCs as compared to their uninfected siblings. This occurred independently of factors released from H358 cells indicating that MV infection triggered cytoskeletal remodeling associated with DC polarization enforced velocity. Accordingly, the latter was also observed for MV-infected DCs in collagen matrices and was particularly sensitive to ROCK inhibition indicating infected DCs preferentially employed the amoeboid migration mode. This was also implicated by loss of podosomes and reduced filopodial activity both of which were retained in MV-exposed uninfected DCs. Evidently, sphingosine kinase (SphK) and sphingosine-1-phosphate (S1P) as produced in response to virus-infection in DCs contributed to enhanced velocity because this was abrogated upon inhibition of sphingosine kinase activity. These findings indicate that MV infection promotes a push-and-squeeze fast amoeboid migration mode via the SphK/S1P system characterized by loss of filopodia and podosome dissolution. Consequently, this enables rapid trafficking of virus toward epithelial cells during viral exit.

Role of STAT signaling and autocrine action of chemokines during H2 O 2 induced HTR-8/SVneo trophoblastic cells invasion

During pregnancy, regulated generation of reactive oxygen species (ROS) is important for activation of signaling pathways and placentation. In the current study, the effect of H₂ O₂ on invasion of HTR-8/SVneo cells, a human extravillous trophoblast cell line, is investigated. Treatment of HTR-8/SVneo cells for 24 hr with H ₂ O₂ (25 µM) leads to a significant increase in invasion without affecting cell proliferation, viability, and apoptosis. Concomitantly, a significant increase in the matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinases-1 (TIMP-1) ratio is observed. Further, significant increase in phosphorylation of signal transducer and activator of transcription 1 (STAT-1) and STAT-3 (both at ser727 residue) is observed on treating HTR-8/SVneo cells with 25 µM of H₂ O₂ accompanied by an increase in the secretion of interleukin-8 (IL-8) and macrophage inflammatory protein-1β (MIP-1β). A significant decrease in H₂ O₂ -mediated invasion of HTR-8/SVneo cells and reduced expression of IL-8 and MIP-1β accompanied by decrease in MMP-9/TIMP-1 ratio are observed on inhibiting STAT-1 and STAT-3 by small interfering RNA (siRNA). Inhibition of STAT-1 activity by fludarabine and STAT-3 activity by Stattic also leads to a decrease in H₂ O₂ -mediated increase in HTR-8/SVneo cell invasion. Inhibition of IL-8 and MIP-1β by siRNA also leads to a significant decrease in both basal and H₂ O₂ -mediated invasion. Interestingly, inhibition of MIP-1β by siRNA leads to a significant reduction in H₂ O₂ -mediated increase in IL-8. However, no significant effect of IL-8 silencing on H₂ O₂ -mediated MIP-1β expression was observed. From the above results, it can be concluded that H₂ O₂ activates STAT signaling, MIP-1β & IL-8 secretion and increases MMP-9/TIMP-1 ratio leading to an increased invasion of HTR-8/SVneo cells without affecting their viability.

Bioactive lysolipids in cancer and angiogenesis

While normal angiogenesis is critical for development and tissue growth, pathological angiogenesis is important for the growth and spread of cancers by supplying nutrients and oxygen as well as providing a conduit for distant metastasis. The interaction among extracellular matrix molecules, tumor cells, endothelial cells, fibroblasts, and immune cells is critical in pathological angiogenesis, in which various angiogenic growth factors, chemokines, and lipid mediators produced from these cells as well as hypoxic microenvironment promote angiogenesis by regulating expression and/or activity of various related genes. Sphingosine 1-phosphate and lysophosphatidic acid, bioactive lipid mediators which act via specific G protein-coupled receptors, play critical roles in angiogenesis. In addition, other lipid mediators including prostaglandin E₂, lipoxin, and resolvins are produced in a stimulus-dependent manner and have pro- or anti-angiogenic effects, presumably through their specific GPCRs. Dysregulated lipid mediator signaling pathways are observed in the contxt of some tumors. This review will focus on LPA and S1P, two bioactive lipid mediators in their regulation of angiogenesis and cell migration that are critical for tumor growth and spread.

Long Noncoding RNA 00473 Is Involved in Preeclampsia by LSD1 Binding-Regulated TFPI2 Transcription in Trophoblast Cells

Preeclampsia (PE) is a syndrome manifested by high blood pressure that could develop in the latter half of pregnancy; however, the underlying mechanisms are not understood. Recent evidence points to the function of noncoding RNAs (ncRNAs) as novel regulators of the invasion, migration, proliferation, and apoptosis of trophoblasts involved in the development of placental vasculature. Here, we investigated the role of long intergenic ncRNA 00473 (linc00473) in PE and the associated molecular mechanisms. The expression of linc00473 was downregulated in the placenta of patients with severe PE as revealed by qRT-PCR analysis. In vitro, linc00473 knockdown in trophoblast cell lines HTR-8/SVneo, JAR, and JEG3 significantly inhibited cell proliferation and promoted apoptosis, whereas linc00473 overexpression stimulated trophoblast proliferation. The mechanistic insights were provided by RNA-seq and qRT-PCR, which revealed that linc00473 could regulate the transcription of genes relevant to cell growth, migration, and apoptosis. In particular, linc00473 inhibited the expression of tissue factor pathway inhibitor 2 (TFPI2) through binding to lysine-specific demethylase 1 (LSD1). These results indicate that linc00473 could be involved in the pathogenesis and development of PE and may be a candidate biomarker as well as therapeutic target for this disease.

Interferon-Gamma and Fas Are Involved in Porphyromonas gingivalis-Induced Apoptosis of Human Extravillous Trophoblast-Derived HTR8/SVneo Cells via Extracellular Signal-Regulated Kinase 1/2 Pathway

BACKGROUND

A number of studies recently revealed a link between periodontal disease and preterm birth (PTB). PTB can be induced by dental infection with Porphyromonas gingivalis (Pg), a periodontopathic bacterium. This study aims to investigate responses of human extravillous trophoblast-derived HTR8/SVneo cells to Pg infection.

METHODS

Cell apoptosis, cell viability, protein expression, and cytokine production in HTR8 cells were measured via: 1) flow cytometry, 2) CCK-8 assay, 3) western blot, and 4) enzyme-linked immunosorbent assay methods, respectively.

RESULTS

Pg decreased cell viability and increased cell apoptosis, active caspase-3 and Fas expression, and interferon-gamma (IFN-γ) secretion in HTR8 cells. Extracellular signal-regulated kinase (ERK) 1/2 inhibitor U0126 and FasL neutralizing antibody NOK1 that blocks FasL/Fas interaction both significantly suppressed Pg-induced apoptosis. U0126 also inhibited IFN-γ secretion and Fas expression close to control levels. Moreover, treatment with recombinant IFN-γ also significantly decreased number of viable HTR8 cells and increased Fas expression, suggesting IFN-γ may play an important role in Pg-induced apoptosis of HTR8 cells, at least partially through regulation of Fas expression.

CONCLUSIONS

To the best of the authors' knowledge, this is the first study to demonstrate Pg induces IFN-γ secretion, Fas expression, and apoptosis in human extravillous trophoblast-derived HTR8/SVneo cells in an ERK1/2-dependent manner, and IFN-γ (explored by recombinant IFN-γ) and Fas are involved in Pg-induced apoptosis. The finding that Pg infection abnormally regulates inflammation and apoptosis of human trophoblasts may give new insights into the possible link of PTB with maternal periodontal disease and periodontal pathogens.