Expression and clinical significance of ATP-binding cassette transporter 1 in serum and placental tissue in Chinese patients with preeclampsia

A theoretical model of dietary lipid variance as the origin of primary ciliary dysfunction in preeclampsia

Serving as the cell's key interface in communicating with the outside world, primary cilia have emerged as an area of multidisciplinary research interest over the last 2 decades. Although the term "ciliopathy" was first used to describe abnormal cilia caused by gene mutations, recent studies focus on abnormalities of cilia that are found in diseases without clear genetic antecedents, such as obesity, diabetes, cancer, and cardiovascular disease. Preeclampsia, a hypertensive disease of pregnancy, is intensely studied as a model for cardiovascular disease partially due to many shared pathophysiologic elements, but also because changes that develop over decades in cardiovascular disease arise in days with preeclampsia yet resolve rapidly after delivery, thus providing a time-lapse view of the development of cardiovascular pathology. As with genetic primary ciliopathies, preeclampsia affects multiple organ systems. While aspirin delays the onset of preeclampsia, there is no cure other than delivery. The primary etiology of preeclampsia is unknown; however, recent reviews emphasize the fundamental role of abnormal placentation. During normal embryonic development, trophoblastic cells, which arise from the outer layer of the 4-day-old blastocyst, invade the maternal endometrium and establish extensive placental vascular connections between mother and fetus. In primary cilia of trophoblasts, Hedgehog and Wnt/catenin signaling operate upstream of vascular endothelial growth factor to advance placental angiogenesis in a process that is promoted by accessible membrane cholesterol. In preeclampsia, impaired proangiogenic signaling combined with an increase in apoptotic signaling results in shallow invasion and inadequate placental function. Recent studies show primary cilia in preeclampsia to be fewer in number and shortened with functional signaling abnormalities. Presented here is a model that integrates preeclampsia lipidomics and physiology with the molecular mechanisms of liquid-liquid phase separation in model membrane studies and the known changes in human dietary lipids over the last century to explain how changes in dietary lipids might reduce accessible membrane cholesterol and give rise to shortened cilia and defects in angiogenic signaling, which underlie placental dysfunction of preeclampsia. This model offers a possible mechanism for non-genetic dysfunction in cilia and proposes a proof-of-concept study to treat preeclampsia with dietary lipids.

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.

Vitamin D Counteracts Lipid Accumulation, Augments Free Fatty Acid-Induced ABCA1 and CPT-1A Expression While Reducing CD36 and C/EBPβ Protein Levels in Monocyte-Derived Macrophages

The biologically active form of vitamin D, calcitriol (VD3), has received great attention for its extraskeletal effects, such as a protective role on the cardiovascular system. The aim of the present work is to test the capacity of VD3 to affect lipid metabolism and fatty acid accumulation in an in vitro model of monocyte (THP-1)-derived macrophages. Cells were treated for 24 h with oleic/palmitic acid (500 μM, 2:1 ratio) and different VD3 concentrations (0.1, 1, 10, 50 and 100 nM). Lipid accumulation was quantified spectrophotometrically (excitation: 544 nm, emission: 590 nm). C/EBPβ, PPAR-γ1, CD36, CPT-1A, and ABCA1 protein levels were assessed by ELISA kits at different time-points (1, 2, 4, 8, and 24 h). VD3 at 50 and 100 nM significantly reduced fatty acids accumulation in macrophages by 27% and 32%, respectively. In addition, tested at 50 nM, VD3 decreased CD36, PPAR-γ1, and C/EBPβ, while it increased ABCA1 and CPT-1A protein levels in free fatty acid-exposed cells. In conclusion, VD3 reduced fatty acid accumulation in THP-1-derived macrophages exposed to lipid excess. The anti-atherogenic effect of VD3 could be ascribable to the regulation of proteins involved in lipid transport and clearance.

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.

A Common R219K Variant of ATP-Binding Cassette Transporter A1 Gene Alters Atherometabolic Traits in Pregnant Women With Gestational Diabetes Mellitus

BACKGROUND

ATP-binding cassette transporter A1 (ABCA1) has important roles in high-density lipoprotein (HDL) metabolism and reverse cholesterol transport, and is implicated in lipid-related disorders. Genetic variants are involved in the pathogenesis of gestational diabetes mellitus (GDM). The objective of this study was to investigate the association of rs2230806 (R219K), a single nucleotide polymorphism (SNP) in the lipid-related gene, with the risk of GDM and related traits.

METHODS

The SNP, rs2230806, was genotyped, and clinical and metabolic parameters were determined in 660 GDM patients and 1,097 control subjects. Genetic associations with related traits were also analyzed.

RESULTS

The genotype distributions were similar in GDM patients and normal controls. However, significant differences in the variables examined in the study subjects were noted across the three genotypes. The genotype at the rs2230806 polymorphism was significantly associated with HDL-cholesterol (HDL-C) levels and atherogenic index (AI) values in GDM patients and total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) levels in control subjects. Subgroup analysis showed that the polymorphism was associated with diastolic blood pressure, in addition to HDL-C levels and AI, in overweight/obese GDM patients, while it was associated with TC levels, AI, pre-pregnancy body mass index (BMI), and BMI at delivery in non-obese GDM patients. In addition, this polymorphism was associated with TC, LDL-C, and apoB levels in overweight/obese control subjects.

CONCLUSIONS

The rs2230806 polymorphism in the ABCA1 gene was associated with variations in atherometabolic traits in GDM patients, with characteristics of BMI dependency, but not with GDM. Our findings highlight a link between related phenotypes in women with GDM and genetic factors.

Apolipoprotein A1 mimetic peptide ATI-5261 reverses arterial stiffness at late pregnancy and early postpartum in a COMT-/- mouse model of preeclampsia

Background

Preeclampsia (PE) is a serious maternal complication during pregnancy. Associated arterial stiffness in PE patients leads to increased risks of cardiovascular diseases later in life. Cholesterol efflux capacity, especially ATP binding cassette transporter A1 (ABCA1) dependent capacity, has been proposed to be a likely mediator of arterial stiffness. In the present study, we aimed to evaluate the effect of an apolipoprotein A1 mimetic peptide ATI-5261 on arterial stiffness in a mouse model of PE.

Methods

Pregnant COMT^-/- mice were randomized to receive vehicle or ATI-5261 (30 mg/kg per day) via subcutaneous injection from gestational days (GD) 10.5 to GD 18.5 or to 10 days postpartum. Pregnant C57BL/6 J mice received vehicle during paralleled periods were served as normal controls.

Results

COMT^-/- mice displayed maternal hypertension and proteinuria during pregnancy. Carotid-femoral pulse wave velocity (PWV) was increased at GD 18.5 and 10 days postpartum. ATI-5261 treatment in COMT^-/- mice significantly reduced PWV and partially normalized impaired ex vivo vascular function at late pregnancy and early postpartum. ATI-5261 treatment also increased serum ABCA1 concentrations and cholesterol efflux capacity, as well as ABCA1 expressions in the placenta. Pup weights, crown to rump lengths and abdominal circumferences were reduced in COMT^-/- mice. Treatment with ATI-5261 did not alter these fetal measurements but significantly reduced placental weights and increased fetal to placental ratios in COMT^-/- mice.

Conclusion

ATI-5261 reversed arterial stiffness at late pregnancy and early postpartum in a COMT^-/- mouse model of PE and may be a potential therapy for arterial stiffness associated with PE.

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.