Apical uptake of choline and cationic drugs in epithelial cell lines derived from human placenta

An exploratory study on the effect of choline and folate deficiency on levels of vascularization proteins and transcription factors in first trimester trophoblast HTR-8/SVneo cells

AIMS

We studied the effect of choline and folate deficiencies on levels of predetermined placental proteins during early development.

METHODS

We incubated HTR-8/SVneo cells under choline and folate deficiency conditions and measured levels of some placental proteins using ELISA methods.

RESULTS

Concentrations of LRP2 protein in cell lysates were higher in cells incubated in choline and folate deficient media compared to the control media (mean [SD] = 2.95 [1.30] vs. 1.65 [0.27] ng/mg protein, p = 0.004). The levels of LRP2 protein in lysates of cells incubated in choline and folate deficient media were significantly higher than the concentrations in lysates of cells incubated in choline deficient but folate sufficient media (1.96 [0.28] ng/mg protein) or those incubated in choline sufficient but folate deficient media (1.77 [0.24] ng/mg protein) (p < 0.05 for both). The cellular levels of CDX2 protein were significantly higher in cells incubated in choline and folate deficient media compared to the control media (1.78 [0.60] vs. 0.99 [0.42] pg/mg protein, p = 0.002); and compared to CDX2 levels in cells incubated in choline deficient but folate sufficient media (0.87 [0.13] pg/mg protein, p < 0.001) or in choline sufficient but folate deficient media (0.96 [0.16] pg/mg protein, p < 0.001). The levels of sFLT-1 and IGF1 in culture media and that of EOMES in HTR-8/SVneo cell lysates remained unchanged under all deficiency conditions.

DISCUSSION

LRP2 and CDX2 are likely to be molecular targets for early choline and folate deficiencies in human trophoblast cells. The results should be confirmed in animal models and in other models of placental cells.

Protective Effects of Choline against Inflammatory Cytokines and Characterization of Transport in Motor Neuron-like Cell Lines (NSC-34)

Choline, a component of the neurotransmitter acetylcholine, is essential for nervous system functions, brain development, and gene expression. In our study, we investigated the protective effect and transport characteristics of choline in amyotrophic lateral sclerosis (ALS) model cell lines. We used the wild-type (WT) motor neuron-like hybrid cell line (NSC-34/hSOD1WT) as a control and the mutant-type (MT; NSC-34/hSOD1G93A) as a disease model. The uptake of [3H]choline was time-, pH-, and concentration-dependent. [3H]Choline transport was sodium-dependent, and, upon pretreatment with valinomycin, induced membrane depolarization. Gene knockdown of Slc44a1 revealed that choline-like transporter 1 (CTL1) mediates the transport of choline. In NSC-34 cell lines, the specific choline transporter inhibitor, hemicholinium-3 demonstrated significant inhibition. Donepezil and nifedipine caused dose-dependent inhibition of [3H]choline uptake by the MT cell line with minimal half inhibitory concentration (IC50) values of 0.14 mM and 3.06 mM, respectively. Four-day pretreatment with nerve growth factor (NGF) resulted in an inhibitory effect on [3H]choline uptake. Choline exerted protective and compensatory effects against cytokines mediators. Hence, the choline transport system CLT1 may act as a potential target for the delivery of novel pharmacological drugs, and the combination of drugs with choline can help treat symptoms related to ALS.

Study protocol for the BUSCopan in LABor (BUSCLAB) study: A randomized placebo-controlled trial investigating the effect of butylscopolamine bromide to prevent prolonged labor

Background

First-time mothers are prone to prolonged labor, defined as the crossing of partograph alert or action lines. Prolonged labor may occur among as many as one out of five women, and is associated with a range of adverse birth outcomes. Oxytocin is the standard treatment for prolonged labor, but has a narrow therapeutic window, several adverse effects and limited efficacy. Despite poor evidence, labor wards often use antispasmodic agents to treat prolonged labor. The antispasmodic drug butylscopolamine bromide (Buscopan^®) may shorten duration of labor, but studies on prevention of prolonged labor are lacking. In this randomized double-blind placebo-controlled clinical trial, we aim to evaluate the effect of butylscopolamine bromide on duration of labor in first-time mothers showing first signs of slow labor progress by crossing the World Health Organization partograph alert line.

Methods and analysis

The study is a single center study at Oslo University Hospital, Oslo, Norway. We will recruit 250 primiparous women with spontaneous labor start at term. Women are included in the first stage of labor if they show signs of slow labor progress, defined as the crossing of the partograph alert line with a cervical dilation between 3–9 cm. Participants are randomized 1:1 to either 20 mg intravenous butylscopolamine bromide or intravenous placebo (1 mL sodium chlorine 9 mg/mL). We considered a mean difference of 60 minutes in labor duration clinically relevant. The primary outcome is duration of labor from the provision of the investigational medicinal product to vaginal delivery. The secondary outcomes include change in labor pain, use of oxytocin augmentation, delivery mode, and maternal birth experience. The primary data for the statistical analysis will be the full analysis set and will occur on completion of the study as per the prespecified statistical analysis plan. The primary outcome will be analyzed using Weibull regression, and we will treat cesarean delivery as a censoring event.

Folate and choline absorption and uptake: Their role in fetal development

SCOPE

In this review, we attempt to assess how choline and folate transporters affect fetal development. We focus on how the expression of these transporters in response to choline and folate intake affects transport effectiveness. We additionally describe allelic variants of the genes encoding these transporters and their phenotypic effects.

METHODS AND RESULTS

We made an extensive review of recent articles describing role of choline and folate - with particularly emphasize on their transporters - in fetal development. Folate and choline are necessary for the proper functioning of the cell and body. During pregnancy, the requirements of these nutrients increase because of elevated maternal demand and the rapid division of fetal cells. The concentrations of folate and choline in cells depend on food intake, the absorption of nutrients, and the cellular transport system, which is tissue-specific and developmentally regulated. Relatively few studies have investigated the role of choline transporters in fetal development.

CONCLUSIONS

In this review we show relations between functioning of folate and choline transporters and fetal development.

Characterization of choline transporters in the human placenta over gestation

INTRODUCTION

The developing fetus relies on the maternal blood supply to provide the choline it requires for making membrane lipids, synthesizing acetylcholine, and performing important methylation reactions. It is vital, therefore, that the placenta is efficient at transporting choline from the maternal to the fetal circulation. Although choline transporters have been found in term placenta samples, little is known about what cell types express specific choline transporters and how expression of the transporters may change over gestation. The objective of this study was to characterize choline transporter expression levels and localization in the human placenta throughout placental development.

METHODS

We analyzed CTL1 and -2 expression over gestation in human placental biopsies from 6 to 40 weeks gestation (n = 6-10 per gestational window) by immunoblot analysis. To determine the cellular expression pattern of the choline transporters throughout gestation, immunofluorescence analysis was then performed.

RESULTS

Both CTL1 and CTL2 were expressed in the chorionic villi from 6 weeks gestation to term. Labor did not alter expression levels of either transporter. CTL1 localized to the syncytial trophoblasts and the endothelium of the fetal vasculature within the chorionic villous structure. CTL2 localized mainly to the stroma early in gestation and by the second trimester co-localized with CTL1 at the fetal vasculature.

DISCUSSION

The differential expression pattern of CTL1 and CTL2 suggests that CTL1 is the key transporter involved in choline transport from maternal circulation and both transporters are likely involved in stromal and endothelial cell choline transport.

Molecular and functional characterization of choline transporter in the human trophoblastic cell line JEG-3 cells

INTRODUCTION

Choline is essential for the synthesis of the major membrane phospholipid phosphatidylcholine (PC), the methyl donor betaine and the neurotransmitter acetylcholine (ACh), which is involved in several vital biological functions that play key roles in fetal development. In this study, we examined the molecular and functional characteristics of choline uptake in the human trophoblastic cell line JEG-3.

METHODS

We examined [(3)H]choline uptake in the human trophoblastic cell line JEG-3. The expression of CTL1 and CTL2 was evaluated by quantitative real-time PCR, western blotting and immunocytochemistry.

RESULTS

We demonstrated that JEG-3 cells take up [(3)H] choline by a saturable process that is mediated by a Na(+)-independent and pH-dependent transport system. The cells have two different [(3)H] choline transport systems, high- and low-affinity, with Km values of 28.4 ± 5.0 μM and 210.6 ± 55.1 μM, respectively. Cationic compounds and hemicholinium-3 (HC-3) inhibited choline uptake. Choline transporter-like protein 1 (CTL1) and CTL2 mRNA and protein were highly expressed in JEG-3 cells and were localized to the plasma membrane.

DISCUSSION

The present results suggest that choline is mainly transported via a high-affinity choline transport system (CTL1) and a low-affinity choline transport system (CTL2) in human trophoblastic JEG-3 cells. These transporters play an important role in the growth of the fetus.

Choline transport via choline transporter-like protein 1 in conditionally immortalized rat syncytiotrophoblast cell lines TR-TBT

Choline is an essential nutrient for phospholipids and acetylcholine biosynthesis in normal development of fetus. In the present study, we investigated the functional characteristics of choline transport system and inhibitory effect of cationic drugs on choline transport in rat conditionally immortalized syncytiotrophoblast cell line (TR-TBT). Choline transport was weakly Na(+) dependent and significantly influenced by extracellular pH and by membrane depolarization. The transport process of choline is saturable with Michaelis-Menten constants (K(m)) of 68microM and 130microM in TR-TBT 18d-1 and TR-TBT 18d-2 respectively. Choline uptake in the cells was inhibited by unlabeled choline and hemicholinium-3 as well as various organic cations including guanidine, amiloride and acetylcholine. However, the prototypical organic cation tetraethylammonium and cimetidine showed very little inhibitory effect of choline uptake in TR-TBT cells. RT-PCR revealed that choline transporter-like protein 1 (CTL1) and organic cation transporter 2 (OCT2) are expressed in TR-TBT cells. The transport properties of choline in TR-TBT cells were similar or identical to that of CTL1 but not OCT2. CTL1 was also detected in human placenta. In addition, several cationic drugs such as diphenhydramine and verapamil competitively inhibited choline uptake in TR-TBT 18d-1 with K(i) of 115microM and 55microM, respectively. Our results suggest that choline transport system, which has intermediate affinity and weakly Na(+) dependent, in TR-TBT seems to occur through a CTL1 and this system may have relevance with the uptake of pharmacologically important organic cation drugs.

Homogeneous chemiluminescent assays for free choline in human plasma and whole blood

Choline was oxidized in the presence of choline oxidase and the hydrogen peroxide generated was detected using a chemiluminescent acridinium-9-carboxamide. The dose response for choline (0-150 microM) was established in buffer and was validated for the quantification of choline in human plasma and whole blood. This homogeneous assay was performed in a 96-well microplate format and required minimal sample volume (4 microL) and short analysis time (<5s per well). The new assay(s) correlated well (R>0.98, plasma; R>0.97, whole blood) with LC-MS/MS.

Choline transport for phospholipid synthesis

Choline is an essential nutrient for all cells because it plays a role in the synthesis of the membrane phospholipid components of the cell membranes, as a methyl-group donor in methionine metabolism as well as in the synthesis of the neurotransmitter acetylcholine. Choline deficiency affects the expression of genes involved in cell proliferation, differentiation, and apoptosis, and it has been associated with liver dysfunction and cancer. Abnormal choline transport and metabolism have been implicated in a number of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Therefore, the study of choline transport and the characteristics of choline transporters are of central importance to understanding the mechanisms that underlie membrane integrity and cell signaling in such disorders. Kinetic studies with radiolabeled choline and inhibitors distinguish three systems for choline transport: (i) low-affinity facilitated diffusion, (ii) high-affinity, Na+-dependent transport, and (iii) intermediate-affinity, Na+-independent transport. It is only recently, however, that the proteins having transport characteristics of at least one of these systems have been identified. They include (i) polyspecific organic cation transporters (OCTs) with low affinity for choline, (ii) high-affinity choline transporters (CHT1s), and (iii) intermediate-affinity choline transporter-like (CTL1) proteins. CHT1 and CTL1 but not OCT transporters are selectively inhibited with hemicholinium-3 and essentially display characteristics of specialized transporters for targeted choline metabolism. CHT1 is abundant in neurons and almost exclusively supplies choline for acetyl-choline synthesis. The focus here is more on newly-discovered CTL1 choline transporters. They are expressed in different organisms and cell types, apparently not for the biosynthesis of acetylcholine but for the production of the most abundant metabolite of choline, the membrane lipid phosphatidylcholine.

Drug specificity and intestinal membrane localization of human organic cation transporters (OCT)

This study was performed to investigate which human organic cation transporter, hOCT1, hOCT2 or hOCT3, participates with regard to cation specificity and membrane localization in the intestinal absorption of orally available cationic drugs. Inhibition of N-[methyl-3H]4-phenylpyridinium ([3H]MPP+) uptake by various compounds into Caco-2 cells and into cells (HEK-293 or CHO) that were stably transfected with hOCT1, hOCT2 or hOCT3 was compared. The uptake of [3H]MPP+ into Caco-2 cells was inhibited by atropine, butylscopolamine, clonidine, diphenhydramine, etilefrine, quinine and ranitidine with IC50 values between 6 microM and 4 mM. Transepithelial, apical to basal flux of [3H]MPP+ across Caco-2 cell monolayers was also strongly inhibited by these compounds. The inhibitory potency of the cationic drugs and prototypical organic cations at Caco-2 cells correlated well with the inhibitory potency measured at CHO-hOCT3 cells but much less with that at HEK-hOCT1 and -hOCT2 cells. This is functional evidence for the predominant role of hOCT3. Etilefrine and atropine were specifically transported into CHO cells by hOCT3. In Caco-2 cells, the mRNA of all three hOCT and the proteins hOCT2 and hOCT3 were detected. More importantly, immunocytochemical analyses of human jejunum revealed for the first time that hOCT3 is localized to the brush border membrane whereas hOCT1 immunolabeling was mainly observed at the lateral membranes of the enterocytes.