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.

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The Role of Apolipoprotein A-I Helix 10 in Apolipoprotein-mediated Cholesterol Efflux via the ATP-binding Cassette Transporter ABCA1

Journal of Biological Chemistry ◽

10.1074/jbc.m207005200 ◽

2002 ◽

Vol 277 (42) ◽

pp. 39477-39484 ◽

Cited By ~ 90

Author(s):

Stacey E. Panagotopulos ◽

Scott R. Witting ◽

Erica M. Horace ◽

David Y. Hui ◽

J. Nicholas Maiorano ◽

...

Keyword(s):

Cholesterol Efflux ◽

Atp Binding ◽

Atp Binding Cassette Transporter ◽

Apolipoprotein A ◽

Atp Binding Cassette

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The role of nitric oxide on matrix metalloproteinase 2 (MMP2) and MMP9 in placenta and fetus from diabetic rats

Reproduction ◽

10.1530/rep-06-0267 ◽

2007 ◽

Vol 134 (4) ◽

pp. 605-613 ◽

Cited By ~ 18

Author(s):

M C Pustovrh ◽

A Jawerbaum ◽

V White ◽

E Capobianco ◽

R Higa ◽

...

Keyword(s):

Nitric Oxide ◽

Structural Changes ◽

Diabetic Rats ◽

Matrix Metalloproteinase 2 ◽

No Donor ◽

Diaphorase Activity ◽

Nos Inhibitor ◽

And Function ◽

Fetal Organs

Matrix metalloproteinases (MMPs) play an important role in tissue remodeling that accompanies the rapid growth, differentiation, and structural changes of the placenta and several fetal organs. In the present study, we investigated whether the diabetic maternal environment may alter the regulatory homeostasis exerted by nitric oxide (NO) on MMPs activity in the feto-placental unit from rats at midgestation. We found that NADPH-diaphorase activity, which reflects the distribution and activity of NO synthases (NOS), was increased in both placenta and fetuses from diabetic rats when compared with controls. In addition, while a NO donor enhanced MMP2 and MMP9 activities, a NOS inhibitor reduced these activities in the maternal side of the placenta from control rats. This regulatory effect of NO was only observed on MMP9 in the diabetic group. On the other hand, the NO donor did not modify MMP2 and MMP9 activities, while the NOS inhibitor reduced MMP9 activity in the fetal side of both control and diabetic placentas. In the fetuses, MMP2 was enhanced by the NO donor and reduced by the NO inhibitor in both fetuses from control and diabetic rats. Overall, this study demonstrates that NO is able to modulate the activation of MMPs in the feto-placental unit, and provides supportive evidence that increased NOS activity leads to NO overproduction in the feto-placental unit from diabetic rats, an alteration closely related to the observed MMPs dysregulation that may have profound implications in the formation and function of the placenta and the fetal organs.

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Abstract 257: Apolipoprotein M Is Not Present in Prebeta-1 HDL Particles

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.32.suppl_1.a257 ◽

2012 ◽

Vol 32 (suppl_1) ◽

Author(s):

Lita A Freeman ◽

Robert Shamburek ◽

Angel Aponte ◽

Gregory J Kato ◽

Alan T Remaley

Keyword(s):

Retinoic Acid ◽

Small Particle ◽

Plasma Levels ◽

Reverse Cholesterol Transport ◽

Cholesterol Efflux ◽

Cholesterol Transport ◽

Apolipoprotein M ◽

Sphingosine 1 Phosphate ◽

2D Gel

BACKGROUND: Apolipoprotein M (apoM) is a 25 kD plasma protein present mainly in HDL. It has a hydrophobic pocket for carrying ligands variously reported as retinol, all- trans -retinoic acid, 9- cis -retinoic acid, sphingosine-1-phosphate (S1P) and oxidized phospholipids. In addition to mediating the effects of S1P and modulating oxidative stress, apoM has been reported to enhance cholesterol efflux and to increase plasma levels of small, preβ1 HDL, a particle that efficiently accepts cholesterol effluxed from cholesterol-loaded cells and plays a key role in reverse cholesterol transport. ApoM is present in α-migrating HDL particles but whether it is also present in small preβ1 HDL particles is disputed. Establishing the absence or presence of apoM in preβ1 HDL particles is essential for understanding its role in reverse cholesterol transport. METHODS: We performed native-native 2D gel electrophoresis on healthy volunteer plasma to separate native HDL particles by size and charge. Particles were blotted onto a membrane and probed with antibodies to apoM or apoA-I to identify specific HDL particles associated with apoM. Similar experiments were performed with plasma from patients with apoE-deficiency or from patients with low plasma levels of apoA-I and HDL. We also performed native 1D electrophoresis to visualize lipoprotein particles containing apoM. Finally, native-native 2D gels of purified HDL were used for proteomics of preβ1 particles. RESULTS: apoM was present in two large α-migrating HDL particles and in LDL-sized particles, as well as in one small particle that did not contain apoA-I. apoA-I but not apoE was required for formation of the large apoM-containing HDL particles. The small apoM particle was unaffected in apoA-I- and apoE-deficient patients. apoM was not present in preβ1 particles. CONCLUSION: apoM is not a stable component of small preβ1 apoA-I-containing HDL particles but instead resides mainly in two large HDL molecules and in LDL-sized particles, as well as a small particle that does not contain apoA-I. The role of apoM in cholesterol efflux requires further evaluation.

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Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood

The Journal of Lipid Research ◽

10.1194/jlr.ra120000635 ◽

2020 ◽

Vol 61 (12) ◽

pp. 1577-1588

Author(s):

Ryunosuke Ohkawa ◽

Hann Low ◽

Nigora Mukhamedova ◽

Ying Fu ◽

Shao-Jui Lai ◽

...

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Cholesterol Efflux ◽

Cholesterol Metabolism ◽

Plasma Cholesterol ◽

Translocator Protein ◽

Plasma Lipoproteins ◽

Cholesterol Transport ◽

Autologous Plasma

Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1+/+ and Abca1−/− mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.

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The Role of Different Regions of ATP-Binding Cassette Transporter A1 in Cholesterol Efflux†

Biochemistry ◽

10.1021/bi700473t ◽

2007 ◽

Vol 46 (33) ◽

pp. 9388-9398 ◽

Cited By ~ 20

Author(s):

Nigora Mukhamedova ◽

Ying Fu ◽

Michael Bukrinsky ◽

Alan T. Remaley ◽

Dmitri Sviridov

Keyword(s):

Cholesterol Efflux ◽

Atp Binding ◽

Atp Binding Cassette Transporter ◽

Atp Binding Cassette

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Characterization of the cholesterol efflux of apolipoprotein E-containing high-density lipoprotein in THP-1 cells

Biological Chemistry ◽

10.1515/hsz-2018-0284 ◽

2019 ◽

Vol 400 (2) ◽

pp. 209-218 ◽

Cited By ~ 5

Author(s):

Yuna Horiuchi ◽

Ryunosuke Ohkawa ◽

Shao-Jui Lai ◽

Azusa Yamazaki ◽

Hayato Ikoma ◽

...

Keyword(s):

High Density Lipoprotein ◽

Apolipoprotein E ◽

Cholesterol Efflux ◽

Density Lipoprotein ◽

High Density ◽

Response To Treatment ◽

Atp Binding Cassette Transporter ◽

A Minor

Abstract High-density lipoprotein (HDL), also known as antiatherogenic lipoprotein, consists of heterogeneous particles in terms of size, density and composition, suggesting differences among HDL subclasses in characteristics and functions. We investigated the role of apolipoprotein E (apoE)-containing HDL, a minor HDL subclass, in the cholesterol efflux capacity (CEC) of HDL, which is its predominant atheroprotective function. The CEC of apoE-containing HDL was similar to that of apoE-deficient HDL, but the former exhibited a greater rate increase (1.48-fold) compared to that of the latter (1.10-fold) by the stimulation of THP-1 macrophages with the Liver X Receptor (LXR) agonist. No difference in CEC was observed without the LXR agonist between apoA-I, the main apolipoprotein in HDL, and apoE, whereas the increase in CEC in response to treatment with the LXR agonist was greater for apoA-I (4.25-fold) than for apoE (2.22-fold). Furthermore, the increase in the CEC of apoE-containing HDL induced by the LXR agonist was significantly reduced by treatment with glyburide, an inhibitor of ATP-binding cassette transporter A1 (ABCA1). These results suggest that apoE-containing HDL, unlike apoE-deficient HDL, is involved in cholesterol efflux via ABCA1.

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Nascent HDL (High-Density Lipoprotein) Discs Carry Cholesterol to HDL Spheres

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvbaha.120.313906 ◽

2020 ◽

Vol 40 (5) ◽

pp. 1182-1194 ◽

Cited By ~ 1

Author(s):

Alexei V. Navdaev ◽

Lorenzo Sborgi ◽

Samuel D. Wright ◽

Svetlana A. Didichenko

Keyword(s):

High Density Lipoprotein ◽

Cholesterol Efflux ◽

Density Lipoprotein ◽

Fluorescent Labeling ◽

High Density ◽

Atp Binding Cassette Transporter ◽

Spherical Plasma ◽

Apo Ai

Objective: To characterize the fate of protein and lipid in nascent HDL (high-density lipoprotein) in plasma and explore the role of interaction between nascent HDL and mature HDL in promoting ABCA1 (ATP-binding cassette transporter 1)-dependent cholesterol efflux. Approach and Results: Two discoidal species, nascent HDL produced by RAW264.7 cells expressing ABCA1 (LpA-I [apo AI containing particles formed by incubating ABCA1-expressing cells with apo AI]), and CSL112, human apo AI (apolipoprotein AI) reconstituted with phospholipids, were used for in vitro incubations with human plasma or purified spherical plasma HDL. Fluorescent labeling and biotinylation of HDL were employed to follow the redistribution of cholesterol and apo AI, cholesterol efflux was measured using cholesterol-loaded cells. We show that both nascent LpA-I and CSL112 can rapidly fuse with spherical HDL. Redistribution of the apo AI molecules and cholesterol after particle fusion leads to the formation of (1) enlarged, remodeled, lipid-rich HDL particles carrying lipid and apo AI from LpA-I and (2) lipid-poor apo AI particles carrying apo AI from both discs and spheres. The interaction of discs and spheres led to a greater than additive elevation of ABCA1-dependent cholesterol efflux. Conclusions: These data demonstrate that although newly formed discs are relatively poor substrates for ABCA1, they can interact with spheres to produce lipid-poor apo AI, a much better substrate for ABCA1. Because the lipid-poor apo AI generated in this interaction can itself become discoid by the action of ABCA1, cycles of cholesterol efflux and disc-sphere fusion may result in net ABCA1-dependent transfer of cholesterol from cells to HDL spheres. This process may be of particular importance in atherosclerotic plaque where cholesterol acceptors may be limiting.

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SREBP-2 positively regulates transcription of the cholesterol efflux gene, ABCA1, by generating oxysterol ligands for LXR

Biochemical Journal ◽

10.1042/bj20060914 ◽

2006 ◽

Vol 400 (3) ◽

pp. 485-491 ◽

Cited By ~ 84

Author(s):

Jenny Wong ◽

Carmel M. Quinn ◽

Andrew J. Brown

Keyword(s):

Gene Expression ◽

Cell Lines ◽

Cholesterol Efflux ◽

Statin Treatment ◽

Atp Binding ◽

Abca1 Gene ◽

Atp Binding Cassette Transporter ◽

Abca1 Expression ◽

E Box

Cholesterol accumulation and removal are regulated by two different transcription factors. SREBP-2 (sterol-regulatory-element-binding protein-2) is best known to up-regulate genes involved in cholesterol biosynthesis and uptake, whereas LXR (liver X receptor) is best known for up-regulating cholesterol efflux genes. An important cholesterol efflux gene that is regulated by LXR is the ATP-binding cassette transporter, ABCA1 (ATP-binding cassette transporter-A1). We have previously shown that statin treatment down-regulated ABCA1 expression in human macrophages, probably by inhibiting synthesis of the LXR ligand 24(S),25-epoxycholesterol. However, it was subsequently reported that ABCA1 expression is down-regulated by SREBP-2 through binding of SREBP-2 to an E-box element in ABCA1's proximal promoter. As statin treatment induces SREBP-2 activation, this may provide an alternative explanation for the statin-mediated down-regulation of ABCA1. In the present study, we employed a set of CHO (Chinese-hamster ovary) mutant cell lines to investigate the role of SREBP-2 in the regulation of ABCA1. We observed increased ABCA1 mRNA levels in SREBP-2-overexpressing cells and decreased levels in cells lacking a functional SREBP-2 pathway, which were restored when the SREBP-2 pathway was reinstated. Moreover, ABCA1 gene expression was positively associated with synthesis of 24(S),25-epoxycholesterol in these cell lines. In studies using a human ABCA1 promoter reporter assay, mutation of the E-box motif had a similar response as the wild-type construct to either statin treatment or addition of 24(S),25-epoxycholesterol. By contrast, these responses were completely ablated when the DR4 element to which LXR binds was mutated. These results support the idea that 24(S),25-epoxycholesterol and statin treatment influence ABCA1 transcription via supply of an LXR ligand and not through an SREBP-2/E-box-related mechanism. In addition, our results indicate a critical role of SREBP-2 as a positive regulator of ABCA1 gene expression by enabling the generation of oxysterol ligands for LXR.

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Terpenes, hormones and life: isoprene rule revisited

Journal of Endocrinology ◽

10.1530/joe-19-0084 ◽

2019 ◽

Vol 242 (2) ◽

pp. R9-R22 ◽

Cited By ~ 8

Author(s):

Stephen G Hillier ◽

Richard Lathe

Keyword(s):

Characteristic Number ◽

Cellular Membrane ◽

Molecular Structures ◽

Evolutionary Perspective ◽

80Th Anniversary ◽

Cellular Life ◽

Male Sex ◽

The Origin Of Life ◽

And Function

The year 2019 marks the 80th anniversary of the 1939 Nobel Prize in Chemistry awarded to Leopold Ruzicka (1887–1976) for work on higher terpene molecular structures, including the first chemical synthesis of male sex hormones. Arguably his crowning achievement was the ‘biogenetic isoprene rule’, which helped to unravel the complexities of terpenoid biosynthesis. The rule declares terpenoids to be enzymatically cyclized products of substrate alkene chains containing a characteristic number of linear, head-to-tail condensed, C5 isoprene units. The number of repeat isoprene units dictates the type of terpene produced (i.e., 2, monoterpene; 3, sesquiterpene; 4, diterpene, etc.). In the case of triterpenes, six C5 isoprene units combine into C30 squalene, which is cyclized into one of the signature carbon skeletons from which myriad downstream triterpenoid structures are derived, including sterols and steroids. Ruzicka also had a keen interest in the origin of life, but the pivotal role of terpenoids has generally been overshadowed by nucleobases, amino acids, and sugars. To redress the balance, we provide a historical and evolutionary perspective. We address the potential abiotic generation of isoprene, the crucial role that polyprene terpenoids played in early membranes and cellular life, and emphasize that endocrinology from microbes to plants and vertebrates is firmly grounded on Ruzicka’s pivotal insights into the structure and function of terpenes. A harmonizing feature is that all known lifeforms (including bacteria) biosynthesize triterpenoid substances that are essential for cellular membrane formation and function, from which signaling molecules such as steroid hormones and cognate receptors are likely to have evolved.

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Spinal cord microglia in health and disease

Acta Naturae ◽

10.32607/actanaturae.10934 ◽

2020 ◽

Vol 12 (1) ◽

pp. 4-17

Author(s):

Elena Kolos ◽

Dmitry Korzhevsky

Keyword(s):

Spinal Cord ◽

Experimental Studies ◽

Experimental Models ◽

Specific Marker ◽

Marker Proteins ◽

Health And Disease ◽

And Function ◽

Lateral Sclerosis

The review summarizes data of recent experimental studies on spinal microglia, the least explored cells of the spinal cord. It focuses on the origin and function of microglia in mammalian spinal cord embryogenesis. The main approaches to the classification of microgliocytes based on their structure, function, and immunophenotypic characteristics are analyzed. We discuss the results of studies conducted on experimental models of spinal cord diseases such as multiple sclerosis, amyotrophic lateral sclerosis, systemic inflammation, and some others, with special emphasis on the key role of microglia in the pathogenesis of these diseases. The review highlights the need to detect the new microglia-specific marker proteins expressed at all stages of ontogeny. New sensitive and selective microglial markers are necessary in order to improve identification of spinal cord microgliocytes in normal and pathological conditions. Possible morphometric methods to assess the functional activity of microglial cells are presented.

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