The liver X receptor (LXR) and its target gene ABCA1 are regulated upon low oxygen in human trophoblast cells: a reason for alterations in preeclampsia?

Role of oxysterol 4β-hydroxycholesterol and liver X receptor alleles in pre-eclampsia

BACKGROUND

Liver X receptors (LXRs) are expressed in placenta and may be associated with pre-eclampsia (PE). Oxysterols act as agonists for LXRs. We recently proposed a new blood pressure-regulating circuit with oxysterol 4β-hydroxycholesterol (4βHC) acting as a hypotensive factor via LXRs.

MATERIALS AND METHODS

This study investigated the association between maternal plasma 4βHC, blood pressure (BP) indices, placental expression of LXR target genes, and patient characteristics using data from the Finnish Genetics of Pre-Eclampsia Consortium (FINNPEC) cohort. Plasma samples of 144 women with PE and 38 healthy pregnant controls as well as 44 PE and 40 control placental samples were available. In addition, genetic data from the FinnGen project was utilized to explore the associations of LXR alleles with PE and pregnancy hypertension.

RESULTS

There were no significant associations between 4βHC and BP or maternal and perinatal characteristics in FINNPEC cohort. However, plasma 4βHC was inversely correlated with the maternal body mass index. There were no associations with the genetic variants of LXRs with PE in FinnGen. LXR target genes APOD, SCARB1, TGM2, and LPCAT3 were expressed differently between PE and normal pregnancies in placental samples of FINNPEC.

CONCLUSIONS

Our results demonstrate that plasma 4βHC and genetic LXR variants do not play a major role in PE and BP regulation during pregnancy. However, key LXR target genes involved in lipid metabolism were expressed differently in normal and PE pregnancies. Further research is needed to understand the complexities of oxysterols, LXRs, and their potential contributions to placental function and pregnancy outcomes.

Role of Protein Regulators of Cholesterol Homeostasis in Immune Modulation and Cancer Pathophysiology

Cholesterol metabolism and homeostasis have emerged as important factors governing various aspects of cancer biology. Clinical associations between circulating cholesterol and poor prognosis or use of cholesterol-lowering medication and improved prognosis have been noted for several different solid tumors. Mechanistically, cholesterol has many different direct and indirect effects on cancer cells themselves but is also critically involved in shaping the function of other cells of the tumor microenvironment, especially immune cells. There are 2 major feedback loops regulating cholesterol homeostasis. Here we highlight the major proteins involved in the so-called oxysterol-bile acid feedback loop and discuss how each has been implicated in cancer biology. We focus on roles within the immune system with implications for cancer. Given that many of these proteins are enzymes or nuclear receptors, both of which are amenable to small molecule intervention, we posit that this axis may represent a promising area for therapeutic intervention.

Integrated analysis of single-cell and bulk RNA-sequencing reveals the poor prognostic value of ABCA1 in gastric adenocarcinoma

PURPOSE

ATP-binding cassette A1 (ABCA1) is a potential prognostic marker for various tumor types. However, the biological effects and prognostic value of ABCA1 in gastric adenocarcinoma (GAC) remain unknown.

METHODS

GAC-associated single-cell RNA and bulk RNA-sequencing (bulk-seq) data were obtained from the Gene Expression Omnibus and The Cancer Genome Atlas databases, respectively. The differential expression of ABCA1 between GAC and normal gastric tissues was analyzed based on the bulk-seq data. Additionally, the relationship between ABCA1 expression and various clinicopathological features was explored. Furthermore, Kaplan-Meier survival and Cox regression analyses were performed to establish the prognostic value of ABCA1. The relationships between ABCA1 expression and anti-tumor drug sensitivity and immune checkpoints were also explored. Finally, the biological functions of ABCA1 were evaluated at the single-cell level, and in vitro studies were performed to assess the effects of ABCA1 on GAC cell proliferation and invasion.

RESULTS

ABCA1 expression is significantly elevated in GAC samples compared with that in normal gastric tissues. Clinical features and survival analysis revealed that high ABCA1 expression is associated with poor clinical phenotypes and prognosis, whereas Cox analysis identified ABCA1 as an independent risk factor for patients with GAC. Furthermore, high ABCA1 expression suppresses sensitivity to various chemotherapeutic drugs, including cisplatin and mitomycin, while upregulating immune checkpoints. ABCA1-overexpressing macrophages are associated with adverse clinical phenotypes in GAC and express unique ligand-receptor pairs that drive GAC progression. In vitro, ABCA1-knockdown GAC cells exhibit significantly inhibited proliferative and invasive properties.

CONCLUSION

High ABCA1 expression promotes an adverse immune microenvironment and low survival rates in patients with GAC. Furthermore, ABCA1 and ABCA1-producing macrophages may serve as novel molecular targets in GAC treatment.

Role of miR-199a-5p in the post-transcriptional regulation of ABCA1 in response to hypoxia in peritoneal macrophages

Hypoxia is a crucial factor contributing to maintenance of atherosclerotic lesions. The ability of ABCA1 to stimulate the efflux of cholesterol from cells in the periphery, particularly foam cells in atherosclerotic plaques, is an important anti-atherosclerotic mechanism. The posttranscriptional regulation by miRNAs represents a key regulatory mechanism of a number of signaling pathways involved in atherosclerosis. Previously, miR-199a-5p has been shown to be implicated in the endocytic and retrograde intracellular transport. Although the regulation of miR-199a-5p and ABCA1 by hypoxia has been already reported independently, the role of miR-199a-5p in macrophages and its possible role in atherogenic processes such us regulation of lipid homeostasis through ABCA1 has not been yet investigated. Here, we demonstrate that both ABCA1 and miR-199a-5p show an inverse regulation by hypoxia and Ac-LDL in primary macrophages. Moreover, we demonstrated that miR-199a-5p regulates ABCA1 mRNA and protein levels by directly binding to its 3'UTR. As a result, manipulation of cellular miR-199a-5p levels alters ABCA1 expression and cholesterol efflux in primary mouse macrophages. Taken together, these results indicate that the correlation between ABCA1-miR-199a-5p could be exploited to control macrophage cholesterol efflux during the onset of atherosclerosis, where cholesterol alterations and hypoxia play a pathogenic role.

Expression of ABCA1 Transporter and LXRA/LXRB Receptors in Placenta of Women with Late Onset Preeclampsia

BACKGROUND

Appropriate levels of cholesterol are necessary for the mother and developing fetus, but theirexcess may cause preeclampsia. The ABCA1 transporter mediates the secretion of cholesterol and is highly regulated at the transcriptional level via the nuclear liver X receptors (LXRs).

METHODS

Sixteen preeclamptic and 39 normotensives healthy women with uncomplicated pregnancies were involved in the case-control study. The placental levels of ABCA1, LXRA and LXRB mRNA were quantified by real-time quantitative PCR. The concentrations of ABCA1, LXRA and LXRB proteins from the placenta were determined using an enzyme-linked immunosorbent assay Results: We found in the logistic regression model significantly lower placental expression of LXRB mRNA (crude OR = 0.26, 95% CI: 0.07-0.94, p = 0.040) and LXRA protein level (crude OR = 0.19, 95% CI: 0.05-0.69, p = 0.012) in late-onset preeclamptic women compared to healthy pregnant women. The values remained statistically significant after adjustment for possible confounders.

CONCLUSIONS

Our results suggest that high placenta LXRA mRNA and LXRA protein expression levels decrease the risk of late-onset preeclampsia. These nuclear receptors could play a role in the development of preeclampsia through disturbances of lipid metabolism.

HIF-1-dependent heme synthesis promotes gemcitabine resistance in human non-small cell lung cancers via enhanced ABCB6 expression

Gemcitabine is commonly used to treat various cancer types, including human non-small cell lung cancer (NSCLC). However, even cases that initially respond rapidly commonly develop acquired resistance, limiting our ability to effectively treat advanced NSCLC. To gain insight for developing a strategy to overcome gemcitabine resistance, the present study investigated the mechanism of gemcitabine resistance in NSCLC according to the involvement of ATP-binding cassette subfamily B member 6 (ABCB6) and heme biosynthesis. First, an analysis of ABCB6 expression in human NSCLCs was found to be associated with poor prognosis and gemcitabine resistance in a hypoxia-inducible factor (HIF)-1-dependent manner. Further experiments showed that activation of HIF-1α/ABCB6 signaling led to intracellular heme metabolic reprogramming and a corresponding increase in heme biosynthesis to enhance the activation and accumulation of catalase. Increased catalase levels diminished the effective levels of reactive oxygen species, thereby promoting gemcitabine-based resistance. In a mouse NSCLC model, inhibition of HIF-1α or ABCB6, in combination with gemcitabine, strongly restrained tumor proliferation, increased tumor cell apoptosis, and prolonged animal survival. These results suggest that, in combination with gemcitabine-based chemotherapy, targeting HIF-1α/ABCB6 signaling could result in enhanced tumor chemosensitivity and, thus, may improve outcomes in NSCLC patients.

Expression of ABC transporters during syncytialization in preeclampsia

Preeclampsia complicates 2-8% of pregnancies and is associated with prematurity and intrauterine growth restriction. Cholesterol and sterol transport is a key function of the placenta and it is elicited through ATP binding cassette (ABC) transporters. ABCA1 expression changes during trophoblast cell fusion, a process required to form the placental syncytium that enables maternal-fetal nutrient transfer. ABCA1 expression is dysregulated in preeclamptic placentas. But whether ABC transporters expression during trophoblast fusion is disrupted in preeclampsia remains unknown. We investigated if cholesterol and sterol ABC transporters are altered in term and preterm preeclampsia placentas and during human cytotrophoblast syncytialization. Human placental biopsies were collected from healthy term (≥37 weeks; n = 11) and term preeclamptic (≥36 6/7 weeks; n = 8) and pre-term preeclamptic (28-35 weeks; n = 8) pregnancies. Both, protein and mRNA expression for ABCA1, ABCG1, ABCG5, and ABCG8 were evaluated. Primary cytotrophoblasts isolated from a subset of placentas were induced to syncytialize for 96 h and ABCA1, ABCG1 and ABCG8 mRNA expression evaluated at 0 h and 96 h. Protein and gene expression of ABC transporters were not altered in preeclamptic placentas. In the healthy Term group, ABCA1 expression was similar before and after syncytialization. After 96 h of syncytialization, mRNA expression of ABCA1 and ABCG1 increased significantly, while ABCG8 decreased significantly in term-preeclampsia, but not pre-term preeclampsia. While placental expression of ABCA1 and ABCG1 remained unaltered in term preeclampsia, the disruption in their dynamic expression pattern during cytotrophoblast syncytialization suggests that cholesterol transport may contribute to the pathophysiologic role of the placenta in preeclampsia.

Stimulation of soluble guanylate cyclase diminishes intrauterine growth restriction in a rat model of placental ischemia

Placental ischemia in preeclampsia (PE) results in hypertension and intrauterine growth restriction (IUGR). Stimulation of soluble guanylate cyclase (sGC) reduces blood pressure in the clinically relevant reduced uterine perfusion pressure (RUPP) rat model of PE, implicating involvement in RUPP-induced hypertension. However, the contribution of sGC in the development of IUGR in PE is not known. Thus, this study demonstrated the efficacy of Riociguat, an sGC stimulator, in IUGR reversion in the RUPP rat model of PE, and tested the hypothesis that improvement in fetal weight occurs in association with improvement in placental perfusion, placental morphology, and placental nutrient transport protein expression. Sham or RUPP surgery was performed at gestational day 14 (G14) with administration of vehicle (Sham or RUPP) or the sGC stimulator (Riociguat, 10 mg/kg/day sc; sGC-treated) until G20. Fetal weight was reduced (P = 0.004) at G20 in RUPP but not in sGC-treated RUPP compared with Sham, the control group. At G20, uterine artery resistance index (UARI) was increased (P = 0.010) in RUPP, indicating poor placental perfusion; proportional junctional zone surface area was elevated (P = 0.035), indicating impaired placental development. These effects were ameliorated in sGC-treated RUPP. Placental protein expression of nutrient transporter heart fatty acid-binding protein (hFABP) was increased (P = 0.008) in RUPP but not in sGC-treated RUPP, suggesting a compensatory mechanism to maintain normal neurodevelopment. Yet, UARI (P < 0.001), proportional junctional zone surface area (P = 0.013), and placental hFABP protein expression (P = 0.008) were increased in sGC-treated Sham, suggesting a potential adverse effect of Riociguat. Collectively, these results suggest sGC contributes to IUGR in PE.

Placental function in maternal obesity

Maternal obesity is associated with pregnancy complications and increases the risk for the infant to develop obesity, diabetes and cardiovascular disease later in life. However, the mechanisms linking the maternal obesogenic environment to adverse short- and long-term outcomes remain poorly understood. As compared with pregnant women with normal BMI, women entering pregnancy obese have more pronounced insulin resistance, higher circulating plasma insulin, leptin, IGF-1, lipids and possibly proinflammatory cytokines and lower plasma adiponectin. Importantly, the changes in maternal levels of nutrients, growth factors and hormones in maternal obesity modulate placental function. For example, high insulin, leptin, IGF-1 and low adiponectin in obese pregnant women activate mTOR signaling in the placenta, promoting protein synthesis, mitochondrial function and nutrient transport. These changes are believed to increase fetal nutrient supply and contribute to fetal overgrowth and/or adiposity in offspring, which increases the risk to develop disease later in life. However, the majority of obese women give birth to normal weight infants and these pregnancies are also associated with activation of inflammatory signaling pathways, oxidative stress, decreased oxidative phosphorylation and lipid accumulation in the placenta. Recent bioinformatics approaches have expanded our understanding of how maternal obesity affects the placenta; however, the link between changes in placental function and adverse outcomes in obese women giving birth to normal sized infants is unclear. Interventions that specifically target placental function, such as activation of placental adiponectin receptors, may prevent the transmission of metabolic disease from obese women to the next generation.

Metabolism of cholesterol and progesterone is differentially regulated in primary trophoblastic subtypes and might be disturbed in recurrent miscarriages

During pregnancy, extravillous trophoblasts (EVTs) invade the maternal decidua and remodel the local vasculature to establish blood supply for the growing fetus. Compromised EVT function has been linked to aberrant pregnancy associated with maternal and fetal morbidity and mortality. However, metabolic features of this invasive trophoblast subtype are largely unknown. Using primary human trophoblasts isolated from first trimester placental tissues, we show that cellular cholesterol homeostasis is differentially regulated in EVTs compared with villous cytotrophoblasts. Utilizing RNA-sequencing, gene set-enrichment analysis, and functional validation, we provide evidence that EVTs display increased levels of free and esterified cholesterol. Accordingly, EVTs are characterized by increased expression of the HDL-receptor, scavenger receptor class B type I, and reduced expression of the LXR and its target genes. We further reveal that EVTs express elevated levels of hydroxy-delta-5-steroid dehydrogenase 3 beta- and steroid delta-isomerase 1 (HSD3B1) (a rate-limiting enzyme in progesterone synthesis) and are capable of secreting progesterone. Increasing cholesterol export by LXR activation reduced progesterone secretion in an ABCA1-dependent manner. Importantly, HSD3B1 expression was decreased in EVTs of idiopathic recurrent spontaneous abortions, pointing toward compromised progesterone metabolism in EVTs of early miscarriages. Here, we provide insights into the regulation of cholesterol and progesterone metabolism in trophoblastic subtypes and its putative relevance in human miscarriage.

Genistein and daidzein decrease food intake and body weight gain in mice, and alter LXR signaling in vivo and in vitro

The study is designed to determine whether consumption of the soy isoflavones, genistein and daidzein, differentially influence metabolic syndrome, and to further investigate the involvement of Liver X Receptor (LXR) regulation. C57BL/6J mice were fed diets as follows: low fat diet (LF), western-style diet (WD), and WD containing 0.16% (w/w) of genistein (WD + G) or daidzein (WD + D) for 10 weeks. Intake of WD + G and WD + D produced a robust decrease in body weight gain by 40% and 19%, respectively (p < 0.05). Genistein reduced energy intake by 26%, and daidzein decreased energy intake by 8% (p < 0.05). A glucose tolerance test indicated that genistein consumption significantly decreased the incremental areas under the curve (AUC) from 60-120 min, compared to WD-fed mice. Gene array profiling of hepatic mRNA, and cell studies utilizing transiently-transfected HepG2 cells and mouse embryonic fibroblast cells devoid of or expressing LXRα, indicate that genistein and daidzein induce LXR-mediated pathways. In summary, addition of genistein, compared to daidzein, to a western-style diet, more profoundly decreased food intake, body weight gain, while both appear to regulate LXR-mediated pathways.

Cancer Stem Cells: Emergent Nature of Tumor Emergency

A functional analysis of 167 genes overexpressed in Krebs-2 tumor initiating cells was performed. In the first part of the study, the genes were analyzed for their belonging to one or more of the three groups, which represent the three major phenotypic manifestation of malignancy of cancer cells, namely (1) proliferative self-sufficiency, (2) invasive growth and metastasis, and (3) multiple drug resistance. 96 genes out of 167 were identified as possible contributors to at least one of these fundamental properties. It was also found that substantial part of these genes are also known as genes responsible for formation and/or maintenance of the stemness of normal pluri-/multipotent stem cells. These results suggest that the malignancy is simply the ability to maintain the stem cell specific genes expression profile, and, as a consequence, the stemness itself regardless of the controlling effect of stem niches. In the second part of the study, three stress factors combined into the single concept of "generalized cellular stress," which are assumed to activate the expression of these genes, were defined. In addition, possible mechanisms for such activation were identified. The data obtained suggest the existence of a mechanism for the de novo formation of a pluripotent/stem phenotype in the subpopulation of "committed" tumor cells.

Physiology and Pathophysiology of Steroid Biosynthesis, Transport and Metabolism in the Human Placenta

The steroid hormones progestagens, estrogens, androgens, and glucocorticoids as well as their precursor cholesterol are required for successful establishment and maintenance of pregnancy and proper development of the fetus. The human placenta forms at the interface of maternal and fetal circulation. It participates in biosynthesis and metabolism of steroids as well as their regulated exchange between maternal and fetal compartment. This review outlines the mechanisms of human placental handling of steroid compounds. Cholesterol is transported from mother to offspring involving lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SRB1) as well as ATP-binding cassette (ABC)-transporters, ABCA1 and ABCG1. Additionally, cholesterol is also a precursor for placental progesterone and estrogen synthesis. Hormone synthesis is predominantly performed by members of the cytochrome P-450 (CYP) enzyme family including CYP11A1 or CYP19A1 and hydroxysteroid dehydrogenases (HSDs) such as 3β-HSD and 17β-HSD. Placental estrogen synthesis requires delivery of sulfate-conjugated precursor molecules from fetal and maternal serum. Placental uptake of these precursors is mediated by members of the solute carrier (SLC) family including sodium-dependent organic anion transporter (SOAT), organic anion transporter 4 (OAT4), and organic anion transporting polypeptide 2B1 (OATP2B1). Maternal-fetal glucocorticoid transport has to be tightly regulated in order to ensure healthy fetal growth and development. For that purpose, the placenta expresses the enzymes 11β-HSD 1 and 2 as well as the transporter ABCB1. This article also summarizes the impact of diverse compounds and diseases on the expression level and activity of the involved transporters, receptors, and metabolizing enzymes and concludes that the regulatory mechanisms changing the physiological to a pathophysiological state are barely explored. The structure and the cellular composition of the human placental barrier are introduced. While steroid production, metabolism and transport in the placental syncytiotrophoblast have been explored for decades, few information is available for the role of placental-fetal endothelial cells in these processes. With regard to placental structure and function, significant differences exist between species. To further decipher physiologic pathways and their pathologic alterations in placental steroid handling, proper model systems are mandatory.

Long non‑coding RNA HR1 participates in the expression of SREBP‑1c through phosphorylation of the PDK1/AKT/FoxO1 pathway

Sterol regulatory element binding protein‑1c (SREBP‑1c), which serves an essential role in the process of fat synthesis, is a key adjustment factor that regulates the dynamic balance of lipid metabolism. SREBP‑1c activates the transcription of multiple genes encoding for enzymes involved in the synthesis of triglycerides (TG) and fatty acids (FA) and accelerates lipid synthesis. Previous analysis indicated that long non‑coding RNA HCV regulated 1 (lncHR1) participates in lipid metabolism in vivo and regulates the level of SREBP‑1c protein. However, the mechanism of lncHR1 in regulating SREBP‑1c levels has not been revealed. In the present study, a fatty degeneration cell model was used to study how lncHR1 regulates the SREBP‑1c protein at the cellular level. Furthermore TG accumulation was assessed according to morphological analysis. Reverse transcription‑quantitative polymerase chain reaction and western blotting were used to detected the expression of SREBP‑1c. An activator and an inhibitor of phosphoinositide 3‑kinase/AKT phosphorylation (IGF‑1 and LY294002, respectively) were used to study the effect of lncHR1 on this pathway. It was verified that lncHR1 regulated SREBP‑1c levels and the phosphorylation of AKT in the steatosis cell model. Detailed molecular mechanisms mediated by lncHR1 were associated with the phosphorylation AKT/FoxO1 in Huh7 cell lines. Simultaneously, lncHR1 affected the location of FoxO1 inside and outside of the nucleus. Furthermore, the phosphorylation of PDK1 upstream of AKT was regulated through overexpression or knockdown lncHR1, as determined by western blotting. Taken together, these data show that lncHR1 inhibits SREBP‑1c levels through the phosphorylation of the PDK1/AKT/FoxO1 axis.

Novel Insights into Concepts and Directionality of Maternal⁻Fetal Cholesterol Transfer across the Human Placenta

Cholesterol is indispensable for cellular membrane composition and function. It is also a precursor for the synthesis of steroid hormones, which promote, among others, the maturation of fetal organs. A role of the ATP-binding-cassette-transporter-A1 (ABCA1) in the transport of maternal cholesterol to the fetus was suggested by transferring cholesterol to apolipoprotein-A-1 (apo-A1), but the directionality of the apoA-1/ABCA1-dependent cholesterol transport remains unclear. We isolated primary trophoblasts from term placentae to test the hypotheses that (1) apoA-1/ABCA1 dispatches cholesterol mainly towards the fetus to support fetal developmental maturation at term, and (2) differentiated syncytiotrophoblasts (STB) exert higher cholesterol transport activity than undifferentiated cytotrophoblasts (CTB). As experimental models, we used (1) trophoblast monolayers grown on Transwell^® system consisting of apical (maternal-like) and basal (fetal-like) compartments, and (2) trophoblasts grown on conventional culture plates at CTB and STB stages. Surprisingly, apoA-1-mediated cholesterol efflux operated almost exclusively at the apical-maternal side, where ABCA1 was also localized by immunofluorescence. We found greater cholesterol efflux capacity in STB, which was increased by liver-X-receptor agonist treatment and decreased by ABCA1 inhibition. We conclude that at term the apoA-1/ABCA1 pathway is rather involved in cholesterol transport to the mother than in transfer to the fully developed fetus.

Liver X Receptors: A Possible Link between Lipid Disorders and Female Infertility

A close relationship exists between cholesterol and female reproductive physiology. Indeed, cholesterol is crucial for steroid synthesis by ovary and placenta, and primordial for cell structure during folliculogenesis. Furthermore, oxysterols, cholesterol-derived ligands, play a potential role in oocyte maturation. Anomalies of cholesterol metabolism are frequently linked to infertility. However, little is known about the molecular mechanisms. In parallel, increasing evidence describing the biological roles of liver X receptors (LXRs) in the regulation of steroid synthesis and inflammation, two processes necessary for follicle maturation and ovulation. Both of the isoforms of LXRs and their bona fide ligands are present in the ovary. LXR-deficient mice develop late sterility due to abnormal oocyte maturation and increased oocyte atresia. These mice also have an ovarian hyper stimulation syndrome in response to gonadotropin stimulation. Hence, further studies are necessary to explore their specific roles in oocyte, granulosa, and theca cells. LXRs also modulate estrogen signaling and this could explain the putative protective role of the LXRs in breast cancer growth. Altogether, clinical studies would be important for determining the physiological relevance of LXRs in reproductive disorders in women.

Placental mechanism of prenatal nicotine exposure-reduced blood cholesterol levels in female fetal rats

Clinical studies showed that intrauterine growth retardation (IUGR) neonatus had lower cholesterol concentrations in cord blood, which might be associated with increased risk of metabolic syndrome and cardiovascular diseases in adulthood. We previously observed lower blood cholesterol levels in prenatal nicotine exposure (PNE)-induced IUGR fetal rats, and this study aimed to elucidate the placental mechanism. Pregnant Wistar rats were subcutaneously injected with nicotine (2.0 mg/kg⋅d) on gestational day 9-20. In vivo, PNE increased levels of total cholesterol (TCH), high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) in maternal serum, while decreased levels of TCH and LDL-C in female fetal serum. Meanwhile, the expression of scavenger receptor class B type 1 (SR-B1), ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1) were decreased, and the expression of liver X receptor (LXR) α and β were also decreased in female placentas. In vitro, nicotine (0.1-10 μM) reduced the expression of LXRα, LXRβ, SR-B1, ABCA1 and ABCG1 in a concentration dependent manner, which could be annulled by nAChR antagonist and LXR agonist. Taken together, nicotine could inhibit the expression of SR-B1, ABCA1 and ABCG1 via nAChR and LXR α/β in female placentas, finally leading to reduced blood cholesterol levels in fetal rats.

Transplacental Nutrient Transport Mechanisms of Intrauterine Growth Restriction in Rodent Models and Humans

Although the causes of intrauterine growth restriction (IUGR) have been intensively investigated, important information is still lacking about the role of the placenta as a link from adverse maternal environment to adverse pregnancy outcomes of IUGR and preterm birth. IUGR is associated with an increased risk of cardiovascular, metabolic, and neurological diseases later in life. Determination of the most important pathways that regulate transplacental transport systems is necessary for identifying marker genes as diagnostic tools and for developing drugs that target the molecular pathways. Besides oxygen, the main nutrients required for appropriate fetal development and growth are glucose, amino acids, and fatty acids. Dysfunction in transplacental transport is caused by impairments in both placental morphology and blood flow, as well as by factors such as alterations in the expression of insulin-like growth factors and changes in the mTOR signaling pathway leading to a change in nutrient transport. Animal models are important tools for systematically studying such complex events. Debate centers on whether the rodent placenta is an appropriate tool for investigating the alterations in the human placenta that result in IUGR. This review provides an overview of the alterations in expression and activity of nutrient transporters and alterations in signaling associated with IUGR and compares these findings in rodents and humans. In general, the data obtained by studies of the various types of rodent and human nutrient transporters are similar. However, direct comparison is complicated by the fact that the results of such studies are controversial even within the same species, making the interpretation of the results challenging. This difficulty could be due to the absence of guidelines of the experimental design and, especially in humans, the use of trophoblast cell culture studies instead of clinical trials. Nonetheless, developing new therapy concepts for IUGR will require the use of animal models for gathering robust data about mechanisms leading to IUGR and for testing the effectiveness and safety of the intervention among pregnant women.

Serum estradiol levels in controlled ovarian stimulation directly affect the endometrium

Previous studies have shown that increasing estradiol concentrations had a toxic effect on the embryo and were deleterious to embryo adhesion. In this study, we evaluated the physiological impact of estradiol concentrations on endometrial cells to reveal that serum estradiol levels probably targeted the endometrium in controlled ovarian hyperstimulation (COH) protocols. An attachment model of human choriocarcinoma (JAr) cell spheroids to receptive-phase endometrial epithelial cells and Ishikawa cells treated with different estradiol (10^-9 M or 10^-7 M) concentrations was developed. Differentially expressed protein profiling of the Ishikawa cells was performed by proteomic analysis. Estradiol at 10^-7 M demonstrated a high attachment rate of JAr spheroids to the endometrial cell monolayers. Using iTRAQ coupled with LC-MS/MS, we identified 45 differentially expressed proteins containing 43 significantly upregulated and 2 downregulated proteins in Ishikawa cells treated with 10^-7 M estradiol. Differential expression of C₃, plasminogen and kininogen-1 by Western blot confirmed the proteomic results. C₃, plasminogen and kininogen-1 localization in human receptive endometrial luminal epithelium highlighted the key proteins as possible targets for endometrial receptivity and interception. Ingenuity pathway analysis of differentially expressed proteins exhibited a variety of signaling pathways, including LXR/RXR activation pathway and acute-phase response signaling and upstream regulators (TNF, IL6, Hmgn3 and miR-140-3p) associated with endometrial receptivity. The observed estrogenic effect on differential proteome dynamics in Ishikawa cells indicates that the human endometrium is the probable target for serum estradiol levels in COH cycles. The findings are also important for future functional studies with the identified proteins that may influence embryo implantation.

Placental ABC Transporters: Biological Impact and Pharmaceutical Significance

The human placenta fulfills a variety of essential functions during prenatal life. Several ABC transporters are expressed in the human placenta, where they play a role in the transport of endogenous compounds and may protect the fetus from exogenous compounds such as therapeutic agents, drugs of abuse, and other xenobiotics. To date, considerable progress has been made toward understanding ABC transporters in the placenta. Recent studies on the expression and functional activities are discussed. This review discusses the placental expression and functional roles of several members of ABC transporter subfamilies B, C, and G including MDR1/P-glycoprotein, the MRPs, and BCRP, respectively. Since placental ABC transporters modulate fetal exposure to various compounds, an understanding of their functional and regulatory mechanisms will lead to more optimal medication use when necessary in pregnancy.

Expression and clinical significance of LXRα and SREBP-1c in placentas of preeclampsia

Objective

To evaluate the expression and correlations of liver X receptor alpha (LXRa) and its target gene sterol regulatory element-binding protein-1c (SREBP-1c) in placentas of preeclampsia (PE) and their significance in PE.

Methods

Pregnancies were divided into two groups, 60 cases (29 cases of mild and 31 cases of severe) of PE group and 56 cases of normal group. The level of mRNA and protein of LXRa and SREBP-1c were analyzed by reverse transcription-polymerase chain reaction (RTPCR) and immunohistochemistry (IHC) in the placentas.

Results

RT-PCR and IHC results showed that the mRNA and protein expression of both LXRa and SREBP-1c increased gradually with the extent of PE among normal pregnancy, mild PE and severe PE groups, and the differences were of statistically significance (P<0.01 or P<0.05). There were positive correlations between the expression of LXRa mRNA and SREBP-1c mRNA, also between LXRa mRNA and LXRa protein (r=0.521, P<0.01; r=0.422, P<0.01). The expression of SREBP-1c mRNA positively correlated with its protein level (r=0.598, P<0.01). There were positive correlations between the expression of LXRa protein and SREBP-1c protein (r=0.612, P<0.01).

Conclusion

The expression of LXRa is elevated significantly in placentas of PE patients, and might contribute for promoting the transcription and translation of its target gene SREBP1-c, which is related to the occurrence and development of PE.

Oxygen Sensitivity of Placental Trophoblast Connexins 43 and 46: A Role in Preeclampsia?

Several gap junction connexins have been shown to be essential for appropriate placental development and function. It is known that the expression and distribution of connexins change in response to environmental oxygen levels. The placenta develops under various oxygen levels, beginning at a low oxygen tension of approximately 2% and increasing to a tension of 8% after the onset of the uteroplacental circulation. Moreover, it has been shown that during preeclampsia (PE) placentas are subjected to chronic hypoxia. Therefore, we investigated oxygen sensitivity of placental connexins 43 and 46. Using the trophoblast cell line Jar, we demonstrated that the expression of connexin43 increased during acute hypoxia but decreased during chronic hypoxia. Chronic hypoxia resulted in the translocation of connexin43 from the membrane to the cytoplasm and in a reduction in its communication properties. In contrast, the expression of connexin46 was down-regulated during chronic hypoxia and was translocated from perinuclear areas to the cell membrane. Hypoxia-inducible factor (HIF) knockdown showed that the translocation of connexin43 but not that of connexin46 was HIF-2α dependent and was mediated by phosphoinositide 3-kinase. The up-regulation of connexin43 in combination with the down-regulation of connexin46 was confirmed in placental explants cultivated under low oxygen and in placentas with early-onset PE. Taken together, in Jar cells, placental connexins 43 and 46 are regulated during periods of low oxygen in opposite manners. The oxygen sensing of connexins in the trophoblast may play a role in physiological and pathophysiological oxygen conditions and thus may contribute to PE.

ATP-binding cassette transporters in reproduction: a new frontier

BACKGROUND

The transmembrane ATP-binding cassette (ABC) transporters actively efflux an array of clinically relevant compounds across biological barriers, and modulate biodistribution of many physiological and pharmacological factors. To date, over 48 ABC transporters have been identified and shown to be directly and indirectly involved in peri-implantation events and fetal/placental development. They efflux cholesterol, steroid hormones, vitamins, cytokines, chemokines, prostaglandins, diverse xenobiotics and environmental toxins, playing a critical role in regulating drug disposition, immunological responses and lipid trafficking, as well as preventing fetal accumulation of drugs and environmental toxins.

METHODS

This review examines ABC transporters as important mediators of placental barrier functions and key reproductive processes. Expression, localization and function of all identified ABC transporters were systematically reviewed using PubMed and Google Scholar websites to identify relevant studies examining ABC transporters in reproductive tissues in physiological and pathophysiological states. Only reports written in English were incorporated with no restriction on year of publication. While a major focus has been placed on the human, extensive evidence from animal studies is utilized to describe current understanding of the regulation and function of ABC transporters relevant to human reproduction.

RESULTS

ABC transporters are modulators of steroidogenesis, fertilization, implantation, nutrient transport and immunological responses, and function as 'gatekeepers' at various barrier sites (i.e. blood-testes barrier and placenta) against potentially harmful xenobiotic factors, including drugs and environmental toxins. These roles appear to be species dependent and change as a function of gestation and development. The best-described ABC transporters in reproductive tissues (primarily in the placenta) are the multidrug transporters p-glycoprotein and breast cancer-related protein, the multidrug resistance proteins 1 through 5 and the cholesterol transporters ABCA1 and ABCG1.

CONCLUSIONS

The ABC transporters have various roles across multiple reproductive tissues. Knowledge of efflux direction, tissue distribution, substrate specificity and regulation of the ABC transporters in the placenta and other reproductive tissues is rapidly expanding. This will allow better understanding of the disposition of specific substrates within reproductive tissues, and facilitate development of novel treatments for reproductive disorders as well as improved approaches to protecting the developing fetus.

Gender differences in response to acute and chronic angiotensin II infusion: a translational approach

Women with renal disease progress at a slower rate to end stage renal disease than men. As angiotensin II has both hemodynamic and direct renal effects, we hypothesized that the female protection may result from gender differences in responses to angiotensin II. Therefore, we studied gender differences in response to angiotensin II, during acute (human) and chronic (rats) angiotensin II administration. In young healthy men (n = 18) and women (n = 18) we studied the responses of renal hemodynamics (¹²⁵I-iothalamate and ¹³¹I-Hippuran) and blood pressure to graded angiotensin II infusion (0.3, 1.0, and 3.0 ng/kg/min for 1 h). Men had increased responses of diastolic blood pressure (P = 0.01), mean arterial pressure (P = 0.05), and a more pronounced decrease in effective renal plasma flow (P = 0.009) than women. We measured the changes in proteinuria and blood pressure in response to chronic administration (200 ng/kg/min for 3 weeks) of angiotensin II in rats. Male rats had an increased response of proteinuria compared with females (GEE analysis, P = 0.001). Male, but not female, angiotensin II-treated rats had increased numbers of renal interstitial macrophages compared to sham-treated rats (P < 0.001). In conclusion, gender differences are present in the response to acute and chronic infusion of angiotensin II. Difference in angiotensin II sensitivity could play a role in gender differences in progression of renal disease.

Endothelium-dependent relaxation and angiotensin II sensitivity in experimental preeclampsia

Objective

We investigated endothelial dysfunction and the role of angiotensin (Ang)-II type I (AT1-R) and type II (AT2-R) receptor in the changes in the Ang-II sensitivity in experimental preeclampsia in the rat.

Methods

Aortic rings were isolated from low dose lipopolysaccharide (LPS) infused pregnant rats (experimental preeclampsia; n=9), saline-infused pregnant rats (n=8), and saline (n=8) and LPS (n=8) infused non-pregnant rats. Endothelium-dependent acetylcholine--mediated relaxation was studied in phenylephrine-preconstricted aortic rings in the presence of vehicle, N^G-nitro-L-arginine methyl ester and/or indomethacin. To evaluate the role for AT1-R and AT2-R in Ang-II sensitivity, full concentration response curves were obtained for Ang-II in the presence of losartan or PD123319. mRNA expression of the AT1-R and AT2-R, eNOS and iNOS, COX1 and COX2 in aorta were evaluated using real-time RT-PCR.

Results

The role of vasodilator prostaglandins in the aorta was increased and the role of endothelium-derived hyperpolarizing factor and response of the AT1-R and AT2-R to Ang-II was decreased in pregnant saline infused rats as compared with non-pregnant rats. These changes were not observed during preeclampsia.

Conclusion

Pregnancy induced adaptations in endothelial function, which were not observed in the rat model for preeclampsia. This role of lack of pregnancy induced endothelial adaptation in the pathophysiology of experimental preeclampsia needs further investigation.

Placental ABCA1 and ABCG1 expression in gestational disease: Pre-eclampsia affects ABCA1 levels in syncytiotrophoblasts

INTRODUCTION

Transplacental feto-maternal lipid exchange through the ATP-binding cassette transporters ABCA1 and ABCG1 is important for normal fetal development. However, only scarce and conflicting data exist on the involvement of these transporters in gestational disease.

METHODS

Placenta samples (n = 72) derived from common gestational diseases, including pre-eclampsia (PE), HELLP, intrauterine growth restriction (IUGR), intrahepatic cholestasis of pregnancy and gestational diabetes, were assessed for their ABCA1 and ABCG1 expression levels and compared to age-matched control placentas with qRT-PCR and immunohistochemistry. ABCA1 expression was additionally investigated with immunoblot in placental membrane vesicles. Furthermore, placental cholesterol and phospholipid contents were assessed.

RESULTS

ABCA1 mRNA levels differed significantly between preterm and term control placentas (p = 0.0013). They were down-regulated in isolated PE and PE with IUGR (p = 0.0006 and p = 0.0012, respectively), but unchanged in isolated IUGR, isolated HELLP and other gestational diseases compared to gestational age-matched controls. Correspondingly, in PE, ABCA1 protein expression was significantly reduced in the apical membrane of the villous syncytiotrophoblast (p = 0.011) and in villous fetal endothelial cells (p = 0.036). Furthermore, in PE there was a significant increase in the placental content of total and individual classes of phospholipids which were partially correlated with diminished ABCA1 expression. Conversely, ABCG1 mRNA and protein levels were stable in the investigated conditions.

CONCLUSIONS

In gestational disease, there is a specific down-regulation of placental ABCA1 expression at sites of feto-maternal lipid exchange in PE. At a functional level, the increase in placental lipid concentrations provides indirect evidence of an impaired transport capacity of ABCA1 in this disease.

Placental regulation of fetal nutrient supply

PURPOSE OF REVIEW

Placental nutrient uptake and transfer may have a unique role, as changes in trophoblast nutrient-sensing signaling pathways regulate cell metabolism and may affect the fetal growth and health programming in the offspring.

RECENT FINDINGS

The functionality of the placenta could affect the neonatal adiposity and the fetal levels of key nutrients such as long-chain polyunsaturated fatty acids. Insulin, oxygen and amino acid concentrations may regulate the mammalian target of rapamycin (mTOR) nutrient sensor in the human placenta affecting trophoblast metabolism and nutrient delivery.

SUMMARY

The mechanisms involved in both placental uptake and transfer of macronutrients are reviewed. Fatty acid, cholesterol and amino acid transport across the placenta involves a complex system to ensure nutrient delivery to the growing fetus. The placental glucose transfer is important for fetal macrosomia, but lipid disturbances in both maternal and placental compartments may contribute to neonatal fat accretion. Maternal insulin has little effect on the avidity of glucose transport by the placenta, but may interfere in placental metabolism via mTOR nutrient sensor. mTOR is a positive regulator of the amino acid carriers and constitutes a critical link between maternal nutrient availability and fetal growth, thereby influencing the long-term health of the fetus.

Choline's role in maintaining liver function: new evidence for epigenetic mechanisms

PURPOSE OF REVIEW

Humans eating diets low in choline develop fatty liver and liver damage. Rodents fed choline-methionine-deficient diets not only develop fatty liver, but also progress to develop fibrosis and hepatocarcinoma. This review focuses on the role of choline in liver function, with special emphasis on the epigenetic mechanisms of action.

RECENT FINDINGS

Dietary intake of methyl donors like choline influences the methylation of DNA and histones, thereby altering the epigenetic regulation of gene expression. The liver is the major organ within which methylation reactions occur, and many of the hepatic genes involved in pathways for the development of fatty liver, hepatic fibrosis, and hepatocarcinomas are epigenetically regulated.

SUMMARY

Dietary intake of choline varies over a three-fold range and many humans have genetic polymorphisms that increase their demand for choline. Choline is an important methyl donor needed for the generation of S-adenosylmethionine. Dietary choline intake is an important modifier of epigenetic marks on DNA and histones, and thereby modulates the gene expression in many of the pathways involved in liver function and dysfunction.

Emerging roles for LXRs and LRH-1 in female reproduction

Nutritional status is known to control female reproductive physiology. Many reproductive pathologies such as anorexia nervosa, dystocia and preeclampsia, have been linked to body mass index and to metabolic syndrome. Lipid metabolism has also been associated with ovarian, uterine and placental functions. Among the regulators of lipid homeostasis, the Liver X Receptors (LXRs) and the Liver Receptor Homolog-1 (LRH-1), two members of the nuclear receptor superfamily, play a central role. LXRs are sensitive to intracellular cholesterol concentration and decrease plasma cholesterol, allowing to considering them as "cholesterol sensors". LRH-1 shares many target-genes with LXRs and has been considered for a long time as a real orphan nuclear receptor, but recent findings showed that phospholipids are ligands for this nuclear receptor. Acting in concert, LXRs and LRH-1 could thus be sensitive to slight modifications in cellular lipid balance, tightly maintaining their cellular concentrations. These last years, the use of transgenic mice clarified the roles of these nuclear receptors in many physiological functions. This review will be focused on the roles of LXRs and LRH-1 on female reproduction. Their contribution to ovarian endocrine and exocrine functions, as well as uterine and placental physiology will be discussed. The future challenge will thus be to target these nuclear receptors to prevent lipid-associated reproductive diseases in women.

Placental ABC transporters, cellular toxicity and stress in pregnancy

The human placenta, in addition to its roles as a nutrient transfer and endocrine organ, functions as a selective barrier to protect the fetus against the harmful effects of exogenous and endogenous toxins. Members of the ATP-binding cassette (ABC) family of transport proteins limit the entry of xenobiotics into the fetal circulation via vectorial efflux from the placenta to the maternal circulation. Several members of the ABC family, including proteins from the ABCA, ABCB, ABCC and ABCG subfamilies, have been shown to be functional in the placenta with clinically significant roles in xenobiotic efflux. However, recent findings suggest that these transporters also protect placental tissue by preventing the cellular accumulation of cytotoxic compounds such as lipids, sterols and their derivatives. Such protective functions are likely to be particularly important in pregnancies complicated by inflammatory or oxidative stress, where the generation of toxic metabolites is enhanced. For example, ABC transporters have been shown to protect against the harmful effects of hypoxia and oxidative stress through increased expression and efflux of oxysterols and glutathione conjugated xenobiotics. However, this protective capacity may be diminished in response to the same stressors. Several studies in primary human trophoblast cells and animal models have demonstrated decreased expression and activity of placental ABC transporters with inflammatory, oxidative or metabolic stress. Several clinical studies in pregnancies complicated by inflammatory conditions such as preeclampsia and gestational diabetes support these findings, although further studies are required to determine the clinical relevance of the relationships between placental ABC transporter expression and activity, and placental function in stressed pregnancies. Such studies are necessary to fully understand the consequences of pregnancy disorders on placental function and viability in order to optimise pregnancy care and maximise fetal growth and health.

Hypoxia in murine atherosclerotic plaques and its adverse effects on macrophages

Hypoxia has been found in the atherosclerotic plaques of larger mammals, including humans. Whether hypoxia occurs in the plaques of standard mouse models with atherosclerosis has been controversial, given their small size. In this review, we summarize the findings of a recent report demonstrating that direct evidence of hypoxia can indeed be found in the plaques of mice deficient in apolipoprotein E (apoE-/-mice). Furthermore, studies in vitro showed that hypoxia promoted lipid synthesis and reduced cholesterol efflux through the ABCA1 pathway, and that the transcription factor HIF-1α mediated many, but not all, of the effects. These results are discussed in the context of the literature and clinical practice.

ATP-binding cassette transporter A1 expression is decreased in preeclamptic placentas

Preeclampsia is a pregnancy-specific multisystem disorder characterized by hypertension and proteinuria. Accentuated maternal hyperlipidemia, especially high serum levels of oxidized low-density lipoprotein (oxLDL), is one of the features of preeclampsia. We previously reported that lectin-like oxidized LDL receptor 1 (LOX-1) expression was decreased in preeclamptic placentas. Here, we show that decreased LOX-1 expression is associated with low expression of adenosine triphosphate-binding cassette transporter A1 (ABCA1) in the placenta. The ABCA1 mediates cellular efflux of cholesterol, and liver X receptors (LXRs) are its predominant transcriptional regulators. Both ABCA1 and LXR expressions were significantly lower in preeclamptic placentas than those in normal controls. Oxidized LDL upregulated ABCA1 expression, while LOX-1 blockade resulted in the alleviation of increasing ABCA1 messenger RNA in JAR cells. These results suggest that low LOX-1 expression may lead to insufficient oxLDL uptake, thereby contributing to reduced LXR activation and decreased ABCA1 expression in preeclamptic placentas.

The origin of fetal sterols in second-trimester amniotic fluid: endogenous synthesis or maternal-fetal transport?

OBJECTIVE

Cholesterol is crucial for fetal development. To gain more insight into the origin of the fetal cholesterol pool in early human pregnancy, we determined cholesterol and its precursors in the amniotic fluid of uncomplicated, singleton human pregnancies.

STUDY DESIGN

Total sterols were characterized by gas chromatography-mass spectrometry in the second-trimester amniotic fluid of 126 healthy fetuses from week 15 until week 22.

RESULTS

The markers of cholesterol biosynthesis, lanosterol, dihydrolanosterol, and lathosterol, were present in low levels until the 19th week of gestation, after which their levels increased strongly. β-sitosterol, a marker for maternal-fetal cholesterol transport, was detectable in the amniotic fluid. The total cholesterol levels increased slightly between weeks 15 and 22.

CONCLUSION

Our results support the hypothesis that during early life the fetus depends on maternal cholesterol supply because endogenous synthesis is relatively low. Therefore, maternal cholesterol can play a crucial role in fetal development.

Early detection of maternal risk for preeclampsia

Preeclampsia is one of the leading causes of maternal and fetal morbidity and mortality. New molecular insights offer new possibilities of early diagnosis of elevated maternal risk. Maternal risk factors, biophysical parameters like Doppler examination of the uterine arteries and biochemical parameters allow early risk calculation. Preventive and effective therapeutic agents like acetylsalicylacid can be started in the early second trimester. This article reviews the diagnostic possibilities of early risk calculation to detect women having high risk for preeclampsia and the potential benefits for them, the offspring and health care systems. We provide risk calculation for preeclampsia as an important and sensible part of first trimester screening.

DNA methylation and hepatic insulin resistance and steatosis

PURPOSE OF REVIEW

In this review, we show novel evidence about the role of the liver in the development of insulin resistance and suggest that abnormal hepatic triglyceride accumulation is not an innocent bystander comorbidity but adversely affects the peripheral insulin sensitivity.

RECENT FINDINGS

The core of this review is built up around the concept that liver DNA methylation of the peroxisome proliferative activated receptor gamma coactivator one alpha gene promoter modulates the status of peripheral insulin resistance and is strongly associated with plasma fasting insulin levels. We discuss about other mechanisms associated with peroxisome proliferative activated receptor gamma coactivator one alpha regulation, such as an acetylation and deacetylation switch and how these events impact on the liver metabolic function. We suggest a mitochondrial-centric approach to understand the connection between nonalcoholic fatty liver disease and insulin resistance. We finally show new data about how the liver epigenome is modulated by nutritional cues and introduce the role of epigenetics in liver metabolic programming.

SUMMARY

The implications of these findings for clinical practice are promising, as the inherent plasticity of epigenetic modifications, produced either physiologically or pathologically, suggests that early therapeutic intervention in patients with fatty liver can potentially revert the systemic phenotype associated with insulin resistance.

A common polymorphism in NR1H2 (LXRbeta) is associated with preeclampsia

Background

Preeclampsia is a frequent complication of pregnancy and a leading cause of perinatal mortality. Both genetic and environmental risk factors have been identified. Lipid metabolism, particularly cholesterol metabolism, is associated with this disease. Liver X receptors alpha (NR1H3, also known as LXRalpha) and beta (NR1H2, also known as LXRbeta) play a key role in lipid metabolism. They belong to the nuclear receptor superfamily and are activated by cholesterol derivatives. They have been implicated in preeclampsia because they modulate trophoblast invasion and regulate the expression of the endoglin (CD105) gene, a marker of preeclampsia. The aim of this study was to investigate associations between the NR1H3 and NR1H2 genes and preeclampsia.

Methods

We assessed associations between single nucleotide polymorphisms of NR1H3 (rs2279238 and rs7120118) and NR1H2 (rs35463555 and rs2695121) and the disease in 155 individuals with preeclampsia and 305 controls. Genotypes were determined by high-resolution melting analysis. We then used a logistic regression model to analyze the different alleles and genotypes for those polymorphisms as a function of case/control status.

Results

We found no association between NR1H3 SNPs and the disease, but the NR1H2 polymorphism rs2695121 was found to be strongly associated with preeclampsia (genotype C/C: adjusted odds ratio, 2.05; 95% CI, 1.04-4.05; p = 0.039 and genotype T/C: adjusted odds ratio, 1.85; 95% CI, 1.01-3.42; p = 0.049).

Conclusions

This study provides the first evidence of an association between the NR1H2 gene and preeclampsia, adding to our understanding of the links between cholesterol metabolism and this disease.