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1.
Fonseca CP Montezinho LP Baltazar G Layden B Freitas DM Geraldes CF Castro MM 《Metal-Based Drugs》2000,7(6):357-364
Li(+) influx by bovine chromaffin cells, obtained from bovine adrenal medulla, was studied in intact cell suspensions using (7)Li NMR spectroscopy with the shift reagent [Tm(HDOTP)](4-). The influx rate constants, k(i), were determined in the absence and in the presence of two Na(+) membrane transport inhibitors. The values obtained indicate that both voltage sensitive Na(+) channels and (Na(+)/K(+))-ATPase play an important role in Li(+) uptake by these cells. (7)Li NMR T(1) and T(2) relaxation times for intracellular Li(+) in bovine chromaffin cells provided a T(1)/T(2) ratio of 305, showing that Li(+) is highly, immobilized due to strong binding to intracellular structures. Using fluorescence spectroscopy and the Mg(2+) fluorescent probe, furaptra, the free intracellular Mg(2+) concentration in the bovine chromaffin cells incubated with 15 mM LiCl was found to increase by about mM after the intracellular Li(+) concentration reached a steady state. Therefore, once inside the cell, Li(+) is able to displace Mg(2+) from its binding sites. 相似文献
2.
Vladimir A. Kosykh Vadim Z. Lankin Eugeniy A. Podrez Dmitriy K. Novikov Sergey A. Volgushev Alexander V. Victorov Vaddim S. Repin Vladimir N. Smirnov 《Lipids》1989,24(2):109-115
The main objectives of this study were to compare the effects of dietary commercial cholesterol (containing 5% of oxidized
cholesterol derivatives) and purified cholesterol on the secretion rate of very low density lipoprotein apolipoproteins and
lipids by cultured rabbit hepatocytes and to verify the hypothesis that products of cholesterol autoxidation stimulate the
rapid development of hypercholesterolemia. Rabbits fed dietary (old) commercial cholesterol for six weeks showed a fivefold
increase in the serum concentration of cholesterol compared with that in purified cholesterol-fed rabbits. The secretion rates
of very low density lipoprotein total protein and very low density lipoprotein [3H]apolipoproteins were similar for the hepatocytes of these two cholesterol-fed groups of animals and were two- and threefold
greater, respectively, than for cells from control rabbits. Cholesteryl ester content of the hepatocytes from dietary (old)
commercial cholesterol-fed rabbits was dramatically increased in comparison with hepatocytes from control and purified cholesterol-fed
rabbits. The elevated intracellular cholesteryl ester content is assumed to account for such an increase of very low density
lipoprotein-cholesteryl ester secretion by cells prepared from dietary (old) commercial cholesterol-fed rabbits. These effects
appear to be caused by activation of cholesterol esterification by oxidized cholesterol derivatives. The rapid development
of hypercholesterolemia induced by dietary (old) commercial cholesterol is associated, at least in part, with the stimulated
production of hepatic very low density lipoprotein apolipoproteins and cholesteryl esters. 相似文献
3.
Colon tumor cells, unlike normal human fibroblasts, exhibited an uncoupling of low density lipoprotein (LDL)-derived cholesterol
from cellular growth, when endogenous cholesterol synthesis was inhibited by mevinolin, a hydroxymethylglutaryl-CoA reductase
(HMG-CoAR) competitive inhibitor [Fabricant, M., and Broitman, S.A. (1990)Cancer Res. 50, 632–636]. Further evaluation of cholesterol metabolism was conducted in two undifferentiated (SW480, SW1417) and two differentiated
(HT29, CACO2) colonic adenocarcinoma (adeno-CA) cell lines and an untransformed human fibroblast, AG1519A. Cells grown in
monolayer culture to near subconfluency were used to assess endogenous cholesterol synthesis by14C-acetate incorporation, in response to the following treatments in lipoprotein-deficient serum (LPDS)-supplemented minimum
essential medium (MEM): LPDS alone, LDL, mevinolin, mevinolin with LDL, and 25-hydroxy-cholesterol (25-OH-CH). Complete fetal
bovine serum (FBS)-supplemented MEM was used as control. All colon tumor lines exhibited similarly high endogenous cholesterol
synthesis in both FBS and LPDS relative to the fibroblasts which demonstrated low basal levels in FBS and maximal synthesis
in LPDS. LDL treatment did not inhibit cholesterol synthesis in colon tumor cells, but suppressed that in the fibroblast by
70%. Sterol repression of cholesterol synthesis mediated by 25-OH-CH occurred in all cells. Mevinolin caused a reduction in
cholesterol synthesis in the colonic cancer cell lines, which was not further decreased by concurrent addition of LDL. In
contrast, in mevinolin-treated fibroblasts, LDL further inhibited cholesterol synthesis. When the effect of cell density on
cholesterol synthesis regulation was evaluated under conditions of sparse density in SW480 and SW1417, results indicated that
(i) basal rates of cholesterol synthesis were higher, (ii) LDL inhibited cholesterol synthesis more effectively, and (iii)
mevinolin or 25-OH-CH had a more pronounced effect than in subconfluent cells. Evaluation of LDL receptor activity through125I-LDL binding and internalization studies demonstrated LDL receptor expression was reduced by 37% in normal density cells
relative to the low density cultures. In contrast to cholesterol synthesis, exogenous LDL could inhibit LDL receptor activity
at both densities. Thus subconfluent growing colonic adenoCA cell lines retain the capacity for sterol repression, but, in
contrast to normal fibroblasts, exhibit a high endogenous cholesterol synthesis which LDL cannot regulate. 相似文献
4.
Hui Gao Lingyan Li Lan Li Bo Gong Pengzhi Dong Patrick Asare Fordjour Yan Zhu Guanwei Fan 《Lipids》2016,51(9):1083-1092
Contemporary research suggests that macrophage foam cell and cholesterol efflux defect play pivotal role in atherogenesis. We reported on the heretofore unknown therapeutic effect of Danshensu (DSS) in reducing intracellular cholesterol level and unraveled the mechanism of DSS promotes cholesterol efflux. Oxidized low‐density lipoprotein stimulation of Raw264.7 cells into foam cells, which were treated with DSS and co‐treated with Simvastatin and Rosiglitazone. PPARγ, ABCA1, ABCG1, SR‐BI, CD36, and LXR‐α mRNA were quantified by Real‐Time PCR. Western blotting was used to determine protein expression of PPARγ, ABCA1 and CD36. Cellular cholesterol handling was studied by measurement of intracellular lipid droplets concentration and cholesterol efflux. DSS significantly reduced scavenger receptor CD36 and its orthologue SR‐BI. In addition, DSS stimulated the upregulation of cellular cholesterol exporters ABCA1 and ABCG1 to reduce intracellular lipid accumulation. DSS can reduce lipid deposition in Raw264.7 foam cells by balancing CD36 and ABCA1 protein expression. 相似文献
5.
Evgeniy A. Podrez Vladimir A. Kosykh Yuri V. Lakeev Evgeniy I. Kosenkov Elvira T. Mambetisaeva Vadim S. Repin Vladimir N. Sminov Tatu A. Miettinen 《Lipids》1993,28(8):709-713
Two groups of rabbits, either hyperresponsive or hyporesponsive to dietary cholesterol, wereselected after ten weeks of cholesterol
feeding (0.2 g cholesterol/kg body weight per day). Bile acids and very low density lipoprotein (VLDL) production were determined
in primary hepatocyte cultures from control, hyper- and hyporesponsive rabbits. Free cholesterol and cholesteryl ester contents
in hepatocytes of the hyperresponsive rabbits was significantly increased. In contrast, lipid composition in hepatocytes of
the hyporesponders was similar to that of control cells. Cholic acid was the predominant bile acid in the culture medium of
hepatocytes together with small amounts of chenodeoxycholic and deoxycholic acids. The rate of cholic acid production by hepatocytes
in the hyporesponsive group was two times higher than that in the hyperresponsive group. Bile acid production by control hepatocytes
was slightly higher than in the hyperresponsive group. In contrast, secretion of VLDL cholesteryl ester was significantly
increased by hepatocytes of the hyperresponsive rabbits. Similar differences, in bile acid production were found between hypo-
and hyperresponsive rabbits selected after five days of cholesterol feeding and subsequent maintenance on a low cholesterol
diet for a period of one month. The results suggest that the increased rate of bile acid production could contribute to the
apparent resistance of hyporesponders to the atherogenic diet. 相似文献
6.
The time course of the inhibition of cholesterol synthesis by low and high doses of mevinolin and monacolin X were studied
in normal human skin fibroblasts, fibroblasts without low density lipoprotein receptor and HepG2 hepatome cells. Low doses
of the inhibitors (0.2 ng/mL) caused a sharp decrease in the rate of cholesterol synthesis during the firt 2–3 h, which gradually
increased to about 40% during the next 6 h. Further incubation led to a decrease or stabilization of the cholesterol synthesis
rate. High doses of the drugs (100 mg/mL) strongly inhibited cholesterol synthesis during the first 2–3 h, followed by a moderate
increase during the next 20 h. No drug or tissue selectivity was observed. 相似文献
7.
Cholesteryl-3β-phosphoserine (CPHS) is a synthetic steroid affecting intracellular cholesterol transport. To compare CPHS
with the well-known inhibitors progesterone and U18666A, we examined cholesterol transport in three human cell lines: the
monocytic U-937, the endothelial ECV-304, and the lymphoid Jurkat. Under low density lipoprotein (LDL) loading, CPHS inhibited
cholesterol esterification in U-937 and ECV-304 cells but not in Jurkat cells. In contrast, CPHS inhibited the mobilization
of plasma membrane cholesterol induced by 25-hydroxycholesterol, brefeldin A, or sphingomyelinase in all cell lines. In cells
pulse-labeled with [3H] cholesterol, CPHS decreased incorporation of cholesterol and inhibited its esterification. In prelabeled cells, CPHS promoted
cholesterol efflux and enhanced the cyclodextrin-mediated removal of plasma membrane cholesterol. CPHS did not affect endogenous
cholesterol synthesis nor acylcoenzyme A: cholesterol acyltransferase activity. These data suggest that, unlike progesterone
and U18666A, CPHS inhibits intracellular cholesterol transport by specifically affecting the movements of cholesterol in the
plasma membrane. Owing to this restricted site of action, CPHS may help to clarify the role of the plasma membrane in cholesterol
trafficking. For example, the lack of an effect of CPHS on the esterification of LDL-derived cholesterol in Jurkat cells suggests
that most of the LDL-derived cholesterol in these cells is directly delivered to the endoplasmic reticulum without cycling
through the plasma membrane. 相似文献
8.
Tchoua U Rosales C Tang D Gillard BK Vaughan A Lin HY Courtney HS Pownall HJ 《Lipids》2010,45(12):1117-1126
Serum opacity factor (SOF) is a streptococcal protein that disrupts the structure of human high density lipoproteins (HDL)
releasing lipid-free apo A-I while forming a large cholesteryl ester-rich particle and a small neo HDL. Given its low cholesterol
and high phospholipid contents, we tested the hypotheses that neo HDL is a better substrate for cholesterol esterification
via lecithin:cholesterol acyltransferase (LCAT), better than HDL as an acceptor of THP-1 macrophage cholesterol efflux, and
improves reduction of oxidized LDL-induced production of inflammatory markers. We observed that both cholesterol efflux and
esterification were improved by recombinant (r)SOF treatment of whole plasma and that the underlying cause of the improved
cholesterol esterification in plasma and macrophage cholesterol efflux to rSOF-treated plasma was due to the rSOF-mediated
conversion of HDL to neo HDL. Moreover, the reduction of secretion of TNF-α and IL-6 by THP-1 cells by neo HDL was twice that
of HDL. Studies in BHK cells overexpressing cholesterol transporters showed that efflux to neo HDL occurred primarily via
ABCA1 not ABCG1. Thus, rSOF improves two steps in reverse cholesterol transport with a concomitant reduction in the release
of macrophage markers of inflammation. We conclude that rSOF catalyzes a novel reaction that might be developed as a new therapy
that prevents or reverses atherosclerosis via improved reverse cholesterol transport. 相似文献
9.
The role of lipoproteins and serum in the formation and accumulation of cholesteryl esters in human monocyte-derived macrophages
(HMD macrophages) was investigated; studies were also carried out with IC21 cells (a cell line derived from mouse peritoneal
macrophages). Following preincubation of HMD macrophages with lipoprotein-depleted serum (LPDS), both native and acetylated
low density lipoprotein (LDL and AcLDL, respectively) stimulated the formation of cholesteryl esters with a resultant increase
in cellular cholesteryl ester content. Cholesteryl ester formation and accumulation was also stimulated in macrophages exposed
continuously to 25-hydroxycholesterol. However, the stimulation of cholesterol esterification by either lipoproteins or 25-hydroxycholesterol
was not inhibited by progesterone in HMD macrophages, but was in the IC21 cells. Cholesterol efflux and the hydrolysis of
cellular cholesterol ester, promoted by serum components, were studied in HMD macrophages preloaded with cholesteryl ester
by incubation with 25-hydroxy cholesterol. Replacement of the medium with one devoid of 25-hydroxycholesterol resulted within
24 hr in at least a 30% decrease in the cholesteryl ester content of the HMD macrophages; replacement with a medium high in
cholesterol acceptor content (LPDS or high density lipoprotein) and incubation for three days led to the most marked decreases
in cellular cholesterol content. Thus, hydrolysis of the cholesteryl esters by HMD macrophages was not dependent on the presence
of cholesterol acceptors in the medium, but cellular cholesterol content was. 相似文献
10.
John C. Stanley 《Lipid Technology》2008,20(9):208-210
The high circulating LDL‐cholesterol levels seen in the inherited disease familial hypercholesterolaemia cause high rates of cardiovascular disease whereas the low circulating LDL‐cholesterol levels following statin treatment cause low rates of cardiovascular disease. This is why LDL‐cholesterol is referred to as bad cholesterol by the media. Atherosclerosis is caused not by native circulating LDL particles but rather by oxidized LDL particles in the arterial wall. Oxidized LDL particles unlike native particles are taken up by macrophages via scavenger receptors to form foam cells and are treated as autoantigens by the immune system provoking inflammation. Hence many of the characteristics of the atherosclerotic plaque including its tendency to rupture and cause thrombosis and heart attacks can be explained in molecular detail by the effects of oxidized LDL particles. 相似文献
11.
Wojciech Szlasa Aleksander Kiebik Anna Szewczyk Vitalij Novickij Mounir Tarek Zofia apiska Jolanta Saczko Julita Kulbacka Nina Rembiakowska 《International journal of molecular sciences》2021,22(20)
Electroporation is influenced by the features of the targeted cell membranes, e.g., the cholesterol content and the surface tension of the membrane. The latter is eventually affected by the organization of actin fibers. Atorvastatin is a statin known to influence both the cholesterol content and the organization of actin. This work analyzes the effects of the latter on the efficacy of electroporation of cancer cells. In addition, herein, electroporation was combined with calcium chloride (CaEP) to assess as well the effects of the statin on the efficacy of electrochemotherapy. Cholesterol-rich cell lines MDA-MB231, DU 145, and A375 underwent (1) 48 h preincubation or (2) direct treatment with 50 nM atorvastatin. We studied the impact of the statin on cholesterol and actin fiber organization and analyzed the cells’ membrane permeability. The viability of cells subjected to PEF (pulsed electric field) treatments and CaEP with 5 mM CaCl2 was examined. Finally, to assess the safety of the therapy, we analyzed the N-and E-cadherin localization using confocal laser microscopy. The results of our investigation revealed that depending on the cell line, atorvastatin preincubation decreases the total cholesterol in the steroidogenic cells and induces reorganization of actin nearby the cell membrane. Under low voltage PEFs, actin reorganization is responsible for the increase in the electroporation threshold. However, when subject to high voltage PEF, the lipid composition of the cell membrane becomes the regulatory factor. Namely, preincubation with atorvastatin reduces the cytotoxic effect of low voltage pulses and enhances the cytotoxicity and cellular changes induced by high voltage pulses. The study confirms that the surface tension regulates of membrane permeability under low voltage PEF treatment. Accordingly, to reduce the unfavorable effects of preincubation with atorvastatin, electroporation of steroidogenic cells should be performed at high voltage and combined with a calcium supply. 相似文献
12.
Vladimir A. Kosykh Dmitri K. Novikov Iliya N. Trakht Eugeni A. Podrez Alexander V. Victorov Vadim S. Repin Viadimir N. Smirnov 《Lipids》1991,26(10):799-805
The interrelationship between very low density lipoprotein (VLDL) secretion and bile acid production was studied in primary
culture of rabbit hepatocytes. Chylomicron remnants (CR) were added to the cultures to study their effect on VLDL secretion
and bile acid production. After 24 hr preincubation of cells with CR (10–50 μg protein/mL), intercellular neutral lipid content
was increased 1.5–4-fold in a dose-dependent manner. Neutral lipid accumulation was accompanied by a 70–90% reduction of [14C]acetate incorporation into cholesterol, while no stimulation of [14C]oleate incorporation into cholesteryl esters was observed. Incubation of cells with CR increased secretion of free cholesterol,
triacylglycerol and apoproteins B and E in VLDL. Stimulation of VLDL cholesterol secretion was accompanied by a reduction
of taurocholic acid synthesis. These data demonstrate the existence of an inverse relationship between secretion of VLDL cholesterol
and bile acid production under conditions of effective uptake of triacylglycerol-rich CR by hepatocytes. 相似文献
13.
14.
Adonis Z. Wu Tzu-Lun Ohn Ren-Jay Shei Huei-Fang Wu Yong-Cyuan Chen Hsiang-Chun Lee Dao-Fu Dai Sheng-Nan Wu 《International journal of molecular sciences》2021,22(4)
Sphingosine-1-phosphate (S1P), is a signaling sphingolipid which acts as a bioactive lipid mediator. We assessed whether S1P had multiplex effects in regulating the large-conductance Ca2+-activated K+ channel (BKCa) in catecholamine-secreting chromaffin cells. Using multiple patch-clamp modes, Ca2+ imaging, and computational modeling, we evaluated the effects of S1P on the Ca2+-activated K+ currents (IK(Ca)) in bovine adrenal chromaffin cells and in a pheochromocytoma cell line (PC12). In outside-out patches, the open probability of BKCa channel was reduced with a mean-closed time increment, but without a conductance change in response to a low-concentration S1P (1 µM). The intracellular Ca2+ concentration (Cai) was elevated in response to a high-dose (10 µM) but not low-dose of S1P. The single-channel activity of BKCa was also enhanced by S1P (10 µM) in the cell-attached recording of chromaffin cells. In the whole-cell voltage-clamp, a low-dose S1P (1 µM) suppressed IK(Ca), whereas a high-dose S1P (10 µM) produced a biphasic response in the amplitude of IK(Ca), i.e., an initial decrease followed by a sustained increase. The S1P-induced IK(Ca) enhancement was abolished by BAPTA. Current-clamp studies showed that S1P (1 µM) increased the action potential (AP) firing. Simulation data revealed that the decreased BKCa conductance leads to increased AP firings in a modeling chromaffin cell. Over a similar dosage range, S1P (1 µM) inhibited IK(Ca) and the permissive role of S1P on the BKCa activity was also effectively observed in the PC12 cell system. The S1P-mediated IK(Ca) stimulation may result from the elevated Cai, whereas the inhibition of BKCa activity by S1P appears to be direct. By the differentiated tailoring BKCa channel function, S1P can modulate stimulus-secretion coupling in chromaffin cells. 相似文献
15.
Previous investigations had demonstrated that Fu5AH rat hepatoma cells accumulated large quantities of esterified cholesterol
when grown in hyperlipemic rabbit serum. The present investigation has determined the sources of the cellular esterified cholesterol
when the cells were grown in hyperlipemic serum. Cellular esterification of endogenous and exogenous free cholesterol contributed
10% and 30%, respectively. The remaining 60% of the accumulated cellular esterified cholesterol was derived from exogenous
(serum) cholesteryl esters. Evidence for the hydrolysis of a portion of the incorporated esterified cholesterol is presented.
A stimulation of free cholesterol incorporation and cellular esterification is elicited by hyperlipemic serum and serum lipoproteins
when compared to normolipemic serum present at equivalent exogenous cholesterol concentrations. The effect of hyperlipemic
serum is reduced by Tween-80 and Triton WR-1339. Comparative data on esterified cholesterol accumulation, free cholesterol
incorporation, and cellular cholesterol esterification in Fu5-5 rat hepatoma cells, L-cells, and rabbit aortic medial cells
are presented.
This work was done during the tenure as Established Investigator of the American Heart Association. 相似文献
16.
The isolated perfused rat lung was used as an experimental model in the study of the lipoprotein regulation of surfactant
cholesterol metabolism. Addition of low density lipoproteins (LDL) to the perfusion medium at a cholesterol concentration
of 0.5 mM had no inhibitory effect on [1-14C]-acetate incorporation into cholesterol of either the surfactant or residual fractions. Increasing the concentration of
cholesterol in the medium to 2.5 mM resulted in significant inhibition of incorporation into cholesterol of both fractions.
A similar inhibition resulted when lungs were perfused with 2.5 mM cholesterol in the form of high density lipoproteins (HDL).
No inhibition of fatty acid synthesis, measured as incorporation into cholesteryl esters, was observed. The rate of uptake
by perfused lung of cholesterol from both high and low density lipoproteins was similar. Competitive binding studies with125I-labeled lipoproteins indicated the existence of lung receptors for both classes of lipoprotein. The rate of uptake of the
apoprotein moiety of low density lipoproteins was significantly greater than that of high density lipoproteins. These data
suggest that lung cholesterol metabolism may be subject to regulation by both low and high density serum lipoproteins. 相似文献
17.
In experiments with 4 different types of cells, we evaluated the cholesterogenic activity by incorporation of 14C-acetic acid into cholesterol and digitonin-precipitable sterols. In every case, the cholesterogenesis appeared considerably faster when expressed as digitonid than when expressed as real cholesterol production, and sometimes the data obtained by the 2 methods were contradictory. Detailed analysis of both digitonid components and nonprecipitable radioactive metabolites showed that a very variable fraction of methyl sterols (including bifunctional methyl sterols) co-precipitates with the C-27 sterols. In cholesterol regulation studies and particularly when the cells exhibit a low cholesterogenesis, the digitonin method is unsuitable and can lead to erroneous interpretations. 相似文献
18.
Hideki Shige Toshitsugu Ishikawa Michio Suzukawa Masato Nishiwaki Takeshi Yamashita Kei Nakajima Toshimitsu Ito Kenji Higashi Makoto Ayaori Atsushi Yonemura Paul Nestel Haruo Nakamura 《Lipids》1998,33(12):1169-1175
The effects of vitamin E on cholesteryl ester (CE) metabolism in 1774 cells were examined. Pretreatment of 1774 cells with
vitamin E at concentrations above 50 μM significantly decreased acetylated low density lipoprotein (LDL)-induced incorporation
of [14C]oleate into CF in cells in a dose-dependent manner. This was partly due to vitamin E Also significantly inhibiting the uptake
of [3H]CE-labeled acetylated LDL by 1774 cells. A trend existed toward suppression of acyl-CoA:cholesterol acyltransferase (ACAT)
activity in the cell lysate at high vitamin E concentration, but there was no effect on hydrolysis of CE. These data indicate
that vitamin E reduces the uptake of modified LDL and suppresses ACAT activity, resulting in less cholesterol esterification
in macrophages; a novel mechanism underlying the antiatherogenic properties of vitamin E. 相似文献
19.
Roberte Aubert Dominique Perdereau Micheline Roubiscoul Jeannine Herzog Daniel Lemonnier 《Lipids》1988,23(1):48-54
The serum lipid contents of a number of inbred and congenic strains of mice were measured. There were interstrain variations
in each of the lipid fractions in mice fed a normal diet. Male and female C3H mice had the highest total cholesterol level;
AKR mice showed the lowest values. Serum phospholipids were correlated well with cholesterolemia. The greatest variations
between strains were in the triglyceride levels. There also was significant variation in the high density lipoprotein cholesterol
serum levels (from 73–88% of the total cholesterol). The response to a hypercholesterolemic diet (1% cholesterol) was tested
in seven inbred strains. All strains showed changes in serum cholesterol and in the proportions of the lipoproteins fractions.
There was a large increase in the low density lipoprotein+very low density lipoprotein fractions. Feeding the diet revealed
marked interstrain differences in the responses of the serum cholesterol and electrophoretic lipoprotein profiles. The C57BL/6
and B10.D2 strains were hyperresponders to the hypercholesterolemic diet with 71% and 63% of their serum cholesterol in the
low density lipoprotein plus very low density lipoprotein fractions, respectively. 相似文献
20.
Karel J. van Erpecum Michele Petruzzelli Albert K. Groen Antonio Moschetta 《European Journal of Lipid Science and Technology》2007,109(10):982-986
Phosphatidylcholine and sphingomyelin are the major phospholipids of the hepatocytic canalicular membrane outer leaflet. Sphingomyelin may preferentially reside with cholesterol in liquid‐ordered domains. In contrast, phosphatidylcholine is the exclusive phospholipid secreted in rat bile (enriched in hydrophilic species compared to the canalicular membrane), subsequently incorporated into bile salt‐cholesterol micelles. We determined the bile lipid composition in 95 vertebrate species (Moschetta et al., J Lipid Res. 2005, 46 , 2221–2232). Phospholipid was often virtually absent in bile of cartilaginous fish and reptiles, occurred in low relative amounts (compared to bile salts) in bony fish or birds and in high relative amounts in most mammals. Biles with low relative amounts of phospholipid often contained high proportions of sphingomyelin. Phosphatidylcholine was the predominant phospholipid in biles with high phospholipid contents. We then compared, in CaCo2 cells (without appreciable phospholipase A2 activity), the effects of incorporating sphingomyelin, egg yolk phosphatidylcholine or lyso‐phosphatidylcholine in apical bile salt‐cholesterol micelles. Egg yolk phosphatidylcholine and (more pronounced) sphingomyelin inhibited cholesterol absorption with decreased ABC‐A1 and ‐G1 expression. Lyso‐phosphatidylcholine enhanced cholesterol absorption with increased basolateral HDL‐dependent cholesterol efflux and high expression of ABC‐A1 and ‐G1. In conclusion, sphingomyelin plays a pivotal role in protecting hepatocytes against detergent bile salts. Dietary sphingomyelin may inhibit intestinal cholesterol absorption. 相似文献