Effect of fetal calf serum and serum protein fractions on the uptake of liposomal phosphatidylcholine by rat hepatocytes in primary monolayer culture (original) (raw)
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Hepatology, 1997
thelial cells. Liver endothelial cells have numerous pores (fe-Liposomes with diameters of 200 to 400 nm containing nestrae), with an average diameter of 150 nm. 1 Larger bloodphosphatidylserine (PS) or phosphatidylglycerol (PG) were borne particles are therefore supposed to be prevented from injected intravenously into rats. Two hours after injection, contact with the hepatocytes situated across the endothelial 75% of the injected dose of PS liposomes was found in the lining. liver and only 10% found in the spleen, while 35% of the PG In a previous study 2 we found that the hepatic uptake of liposomes was found in the liver and as much as 40% was 200-nm liposomes (ie, phosphatidylcholine (PC), cholesterol found in the spleen. Cell-isolation experiments revealed the (chol), and phosphatidylserine (PS) in a 4:5:1 molar ratio) following remarkable difference in the intrahepatic distribuwas virtually unaffected in rats that were depleted of their tion between the two liposome formulations: the PS liposomes
Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2005
Phospholipids carried by very low density lipoprotein (VLDL) are hydrolysed in circulation by lipoprotein and hepatic lipases and lecithin-cholesterol acyltransferase. We have previously demonstrated [6] [J.J. 2gren, A. Ravandi, A. Kuksis, G. Steiner, Structural and compositional changes in very low density lipoprotein triacylglycerols during basal lipolysis, Eur. J. Biochem. 269 (2002) 6223-6232] that the infusion of Triton WR 1339 (TWR), which inhibits these lipases, leads in 2 h to five-fold increase in VLDL triacylglycerol concentration along with major differences in the composition of their molecular species. The present study demonstrates that the accumulation of triacylglycerols is accompanied by major changes in the content of the VLDL phospholipids, of which the most significant is the enrichment of phosphatidylethanolamine (PtdEtn). This finding coincides with the enrichment in PtdEtn demonstrated in the VLDL of a hepatocytic Golgi fraction but it had not been demonstrated that the Golgi VLDL, along with its unusual phospholipid composition, can be directly transferred to plasma. Aside from providing an easy access to nascent plasma VLDL, the TWR infusion demonstrates that lipoprotein and hepatic lipases are also responsible for the degradation of plasma VLDL PtdEtn, as independently demonstrated for plasma phosphatidylcholine. Our results indicate also, with the exception of lysophosphatidylcholine, that preferential basal hydrolysis no dot lead to major differences in molecular species composition between circulating and newly secreted VLDL phospholipids. The comparison of the molecular species composition of VLDL and liver phospholipids suggests a selective secretion of PtdEtn and sphingomyelin molecular species during VLDL secretion.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1981
Previous observations on serum-induced leakage of liposome contents from egg phosphatidylcholine liposomes (Allen, T.M. and Cleland, L.G. (1980) Biochim. Biophys. Acta 597, 418--426) have been extended in order to examine the role of the phase transition and phospholipid backbone in leakage. The high-density lipoprotein (HDL) fraction has been purified from human serum and the rate of transfer of radioactively labelled phospholipids from sonicated liposomes to high~lensity lipoproteins has been examined. Results obtained from the caicein dequenching method for serum-induced leakage of liposome contents showed that as the proportion of solid phospholipid (distearoyl phosphatidylcholine, Tc = 56°C) increased, relative to the proportion of egg phosphatidylcholine, the half-time for retention of liposome contents at 37°C in the presence of serum also increased. Including increasing amounts of bovine brain sphingomyelin (Tc = 30 ° C) in egg phosphatidylcholine liposomes also substantially decreased leakage from liposomes in the presence of serum at 37°C. 14C-labeiled egg phosphatidylcholine was found to transfer readily from liposomes to purified HDL, as did 14C-labelled dioleoyl phosphatidylcholine. Including cholesterol in egg phosphatidylcholine liposomes decreased the rate of transfer of phospholipid to HDL. ~4C-labelled distearoyl phosphatidylcholine did not exchange readily with HDL. These .results are consistent with the interpretation that tightening bilayer packing prevents the apolipoprotein-mediated transfer of phospholipid to HDL and slows the leakage of liposome contents associated with this transfer.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1984
Small unilamellar vesicles consisting of sphingomyelin, cholesterol and phosphatidylserine in a molar ratio of 4:5:1 containing 13H]inulin as a marker of the aqueous space or [Me-t4C]choline.labeled sphingomyelin as a marker of the lipid phase were injected intravenously into rats. After separation of the non-parenchymal cells into a Kupffer cell fraction and an endothelial cell fraction by elutriation centrifugation analysis of the radioactivity contents demonstrated that Kupffer cells were actively involved in the uptake of the vesicles whereas endothelial cells did not contribute at all. Uptake by total parenchymal cells was also substantial but, on a per cell base, significantly lower than that by the Kupffer cells. By comparising the fate of the [3H]inulin label and the [14C]sphingomyelin label it was concluded that release of liposomal lipid degradation products especially occurred from Kupffer cells rather than from parenchymal cells. In both cell types, however, substantial proportions of the t4C-iabel accumulated in the phosphatidylcholine fraction, indicating intracellular degradation of sphingomyelin and subsequent phosphatidylcholine synthesis. Treatment of the animals with the lysosomotropic agent chioroquine prior to liposome injection effectively blocked the conversion of the choline-labeled sphingomyelin into phosphatidylcholine in both cell types. This observation indicates that uptake of the vesicles occurred by way of an endocytic mechanism.
Biochimica et biophysica acta, 1988
Lipid emulsions were prepared with a similar size and lipid composition to natural lymph chylomicrons, but in which the surface phospholipid was either egg phosphatidylcholine, dioleoyl-, dimyristoyl-, dipalmitoyl- or 1-palmitoyl-2-oleoylphosphatidylcholine (EYPC, DOPC, DMPC, DPPC or POPC). When injected into the bloodstream of conscious rats, the emulsions containing EYPC or POPC were metabolized similarly to natural chylomicrons, consistent with rapid lipoprotein lipase-mediated hydrolysis of triacylglycerols, followed by hepatic uptake of the remnants derived from the emulsions. Phospholipids from the injected emulsions were removed more slowly and became associated with the high-density lipoprotein fractions of the plasma. Emulsions containing DPPC were metabolized differently. Triacylglycerols disappeared very slowly from plasma, indicating lack of hydrolysis by lipoprotein lipase, and phospholipid radioactivity did not transfer to high-density lipoprotein. With emulsions conta...
The deposition of lipids from serum into cells cultured in vitro
Atherosclerosis, 1971
The deposition of lipid into a line of fibroblasts cultured in vitro was studied_ When cells were transferred from a low lipid serum to high lipid serum prepared from a cholesterol fed rabbit, an increased amount of lipid was deposited within the cells. An increase in all major classes of lipid was observed. Particularly striking, however, was the increase in the amount of cholesterol esters relative to cholesterol during growth in lipemic serum. The source of the major part of this lipid was the serum of the medium, less than 6% arising from de no~o synthesis. In normal serum 80% of the radioactivity incorporated into neutral cell lipids from [I-14C]acetate was recovered in cholesterol, only 7% in cholesterol esters and 8 o/o in triglycerides. In lipemic serum only 3 "/0 was recovered in cholesterol whereas. 65 o/o was recovered in cholesterol esters and 25 o/o in triglycerides.
Biochemical and Biophysical Research Communications, 1999
The interaction with liver cells of liposomes containing different mol fractions of phosphatidylserine was investigated in vivo and in vitro. Increasing the amount of liposomal phosphatidylserine from 10 to 30 mol% leads to a faster blood disappearance of the liposomes. Within the liver, which is mainly responsible for this elimination, these liposomes are only taken up by the hepatocytes and Kupffer cells. By contrast, sinusoidal endothelial cells, in vitro, do bind and internalize liposomes containing >30% phosphatidylserine at least as actively as Kupffer cells. The uptake by endothelial and Kupffer cells is inhibited by poly-(inosinic acid) and other anionic macromolecules, suggesting the involvement of scavenger receptors. The lack of liposome uptake by endothelial cells under in vivo conditions can be attributed to plasma effects since addition of various sera caused severe reduction of in vitro uptake of liposomes. In vivo the phosphatidylserine head groups may be masked by plasma proteins adsorbed to the liposomal surface, thus preventing recognition by receptors, which are intrinsically able to recognize phosphatidylserine.