Enzyme replacement with liposomes containing beta-galactosidase from Charonia lumpas in murine globoid cell leukodystrophy (twitcher)

Enzyme replacement with liposomes containing beta-galactosidase obtained from charonia lumpas was carried out in murine globoid cell leukodystrophy (GLD). Charonia lumpas beta-galactosidase was able to hydrolyze galactocerebroside trapped into liposomes prepared from lecithin, cholesterol and sulfatide (molar ratio; 7:2:1). Liposomes containing charonia lumpas beta-galactosidase were successfully incorporated into the mouse tissues. 3H-galactocerebroside labeled liposomes were also incorporated into mouse liver, spleen and other tissues. The accumulation rate of 3H-galactocerebroside into twithcer mice liver and spleen was almost 40 to 100 times higher than those of controls and degraded to 70 to 80% of accumulated radioactivity of 3H-galactocerebroside by single injection of liposomes containing charonia lumpas beta-galactosidase. Results suggest that exogeneous enzyme trapped in liposomes can be useful for the correction of accumulated compound.     

Dog GM1 gangliosidosis: characterization of the residual liver acid beta-galactosidase.

The residual liver acid beta-galactosidase activity from the first documented case of GM1 gangliosidosis in dogs was partially purified and characterized with respect to kinetic properties, thermostability, isoelectric point, molecular weight, and antigenicity. The GM1 dog liver beta-galactosidase appears to be identical with the normal dog liver enzyme in all properties examined. The canine disease is strikingly different from the human disease in the amount of enzyme that is present in the tissue. Unlike the human disease, in which normal amounts of catalytically defective beta-galactosidase are present, in dog GM1 gangliosidosis, only 1% of normal beta-galactosidase protein is detectable.     

Large liposomes containing ganglioside GM1 accumulate effectively in spleen

Large liposomes, with a composition of egg phosphatidylcholine, cholesterol and ganglioside GM1, prepared by an extrusion method, were injected intravenously into mice. After 24 h, up to 50% of injected dose was accumulated in spleen compared with about 15% in spleen for liposomes containing no GM1. The effect of GM1 on spleen accumulation of liposomes was liposome size dependent. Only relatively large liposomes (d greater than 300 nm) showed high accumulation; smaller liposomes were progressively less accumulated. The spleen accumulation increased with increasing injection dose of the liposomes. It was noted that the enhanced uptake by spleen was accompanied by a decrease in the liver uptake, but the total uptake of liposomes by liver and spleen was not dependent on the diameter of liposome or the presence of the ganglioside GM1. Autoradiographs of fixed and sectioned spleen using 125I-labeled tyraminylinulin as a content marker for the liposomes, showed that liposomes localized at the reticular meshwork of the red pulp. These results suggest that larger liposomes containing GM1 are filtered by the spleen during the circulation in blood. The smaller ones with a mean diameter of less than 100 nm are not retained by the filter. The function of GM1 is to prevent liposomes from a rapid uptake by the liver so that liposomes may circulate through the spleen and be filtered. These results, together with the observation that the liposome-entrapped proteins were degraded by the spleen, suggest the potential use of these liposomes for specific drug delivery to the spleen.     

Multiplicity of bovine liver GM1 ganglioside beta-galactosidase

The multiplicity of bovine liver acid beta-galactosidase was investigated. Acid beta-galactosidase activity was measured in the presence of glucono-delta-lactone, which inhibited the neutral beta-galactosidase activity but not the acid beta-galactosidase activity in bovine liver. Three forms of acid beta-galactosidase were separated by Sephadex G-200 gel filtration and the elution pattern of the 4-methylumbelliferyl-beta-galactosidase activity coincided with that of the GM1-beta-galactosidase activity. These forms were relatively stable under acidic conditions (pH 4.5), but the two high molecular weight forms were inclined to dissociate into the low molecular weight form under neutral conditions (pH 7.0). The three forms of the enzyme showed similar pH-optima and apparent Michaelis constants for GM1 ganglioside.     

A lysosomal storage disorder in mice characterized by a dual deficiency of sphingomyelinase and glucocerebrosidase

Lipid and lysosomal enzyme levels in the tissues of a strain of mice afflicted with an autosomal rescessive neuroviscereal storage disorder were examined. Sphingomyelinase and glucocerebrosidase activities were consistently diminished in a wide variety of tissues obtained from the affected mice. The activities of these enzymes were clearly attenuated in new-born mice, which at this age, were otherwise indistinguishable from littermates and age-matched controls. The deficiency of sphingomyelinase was more pronounced than glucocerebrosidase. There was progressive accumulation of sphingomyelin, glucocerebroside, lactosylceramide and unesterified cholesterol in the tissues of these mice in the postnatal period. Gangliosides GM2 and GM3 accumulated in the brain of the animals, and GM3 and asialo-GM2 were stored in the liver. Furthermore, there was a large increase in the quantity of hepatic bis(monoacylglycero)phosphate. The accumulation of lipids was parallelled by a progressive elevation in the activity of several lysosomal hydrolases in various tissues. Heterozygous mice were biochemically indistinguishable from normal controls. The phenotypic manifestations in these metabolically mutated animals are compared with those in Niemann-Pick disease and Gaucher's disease in humans.     

Effects of ethanol on lipid metabolism.

Alcohol promotes accumulation of fat in the liver mainly by substitution of ethanol for fatty acids as the major hepatic fuel. The degree of lipid accumulation depends on the supply of dietary fat. Progressive alteration of the mitochondria, which occurs during chronic alcohol consumption, decreases fatty acid oxidation by interfering with citric acid cycle activity. This block is partially compensated for by increased ketone body production, which results in ketonemia. Thus, mitochondrial damage perpetuates fatty acid accumulation even in the absence of ethanol oxidation. Alcohol facilitates esterification of the accumulated fatty acids to triglycerides, phospholipids, and cholesterol esters, all of which accumulate in the liver. The accumulated lipids are disposed of in part as serum lipoprotein, resulting in moderate hyperlipemia. In some individuals with pre-existing alterations of lipid metabolism, small ethanol dose may provoke marked hyperlipemia which responds to alcohol withdrawal. Inhibition of the catabolism of cholesterol to bile salt may contribute to the hepatic accumulation and hypercholesterolemia. The capacity of lipoprotein production and hyperlipemia development increases during chronic alcohol consumption, probably as a result of the concomitant hypertrophy of the endoplasmic reticulum and Golgi apparatus. However, this compensation is relatively inefficient in ridding the liver of fat. This inefficiency may be linked to alterations of hepatic microtubules induced by ethanol or its metabolites, which interfere with the export of protein from liver to serum, promoting hepatic accumulation of proteins as well as fat. As liver injury aggravates, hyperlipemia wanes and liver steatosis is exaggerated. Derangements of serum lipids similar to those found in other types of liver disease also become apparent. The changes in serum lipids may be a sensitive indicator of the progression of liver damage in the alcoholic.     

Cholesterol-rich Very Low Density Lipoproteins and Fatty Liver in Rats Fee Polychlorinated Biphenyls

Feeding xenobiotics such as polychlorinated biphenyls (PCB) causes hypercholesterolemia and fatty liver in rats. The hypercholesterolemia was characterized by high levels of high density lipoproteins (HDL) and apolipoprotein A-I (apo A-I), and by very low density lipoproteins (VLDL) rich in cholesterol and apo E (designated “PCB-VLDL”). The mechanisms for the generation of “PCB-VLDL” and fatty liver, and for hyper-α-lipoproteinemia in rats fed PCB were investigated. The secretion rate of VLDL-lipids was increased by PCB on day 3, while the secretion rate of only VLDL-cholesterol and phospholipid were increased by PCB on days 8 and 57. Although all liver lipids were accumulated by PCB, the accumulation of esterified cholesterol was the most drastic. These results suggested that PCB stimulated the secretion of VLDL at the early period of PCB feeding (on day 3), and that cholesterol-rich VLDL, “PCB-VLDL”, was not generated in the circulation, but was originally secreted from the liver. In spite of the stimulation of VLDL secretion, liver lipids accumulated within 8 days on the PCB diet. On days 3 and 8, serum levels of free fatty acids were not changed by PCB feeding. These data and our previous findings that PCB induced hepatic lipogenic enzymes lead us to speculate that fatty liver induced by PCB may be attributed to a stimulation of de novo synthesis of liver lipids. Even when hepatic secretion of VLDL was blocked by orotic acid, HDL-cholesterol was increased by PCB feeding, suggesting that the increase in serum level of HDL by PCB was not due to stimulation of cholesterol transport into HDL from VLDL.     

The separation and characterization of the methylumbelliferyl beta-galactosidases of human liver.

1. A previously uncharacterized form of human liver acid beta-galactosidase (EC 3.2.1.23), possibly a dimer of molecular weight 160 000, was resolved by gel filtration. It has the same ability to hydrolyse GM1 ganglioside as the two other acid beta-galactosidase forms. 2. The low-molecular-weight forms of acid beta-galactosidase undergo salt-dependent aggregation. 3. The high-molecular-weight component may consist of the low-molecular-weight forms bound to membrane fragments. It can be converted completely into a mixture of these forms. 4. The neutral beta-galactosidase activity can be resolved into two forms by DEAE-cellulose chromatography. They differ in their response to Cl-ions. 5. A new nomenclature is suggested for the six beta-galactosidases so far found in human liver. 6. The enzymic constituents of the beta-galactosidase bands resolved by electrophoresis were re-examined. The A band contains three components. A two-dimensional electrophoretic procedure for resolving the A band is described. 7. The effect of neuraminidase treatment on the behaviour of beta-galactosidases in various separation systems is examined.     

Accumulation of Lysosphingolipids in Tissues from Patients with GM1 and GM2 Gangliosidoses

By using a sensitive method, we assayed lysocompounds of gangliosides and asialogangliosides in tissues from four patients with GM2 gangliosidosis (one with Sandhoff disease and three with Tay-Sachs disease) and from three patients with GM1 gangliosidosis [one with infantile type (fetus), one with late-infantile, and one with adult type]. In the brain and spinal cord of all the patients except for an adult GM1 gangliosidosis patient, abnormal accumulation of the lipids was observed, though the concentration in the fetal tissue was low. In GM2 gangliosidosis, the amounts of lyso GM2 ganglioside accumulated in the brain were similar among the patient with Sandhoff disease and the patients with Tay-Sachs disease, whereas the concentration of asialo lyso GM2 ganglioside in the brain was higher in the former patient than in the latter patients. By comparing the sphingoid bases of neutral sphingolipids, gangliosides, and lysosphingolipids, it was suggested that lysosphingolipids in the diseased tissue are synthesized by sequential glycosylation from free sphingoid bases, but not by deacylation of the sphingolipids. Because lysosphingolipids are known to be cytotoxic, the abnormally accumulated lysophingolipids may well be the pathogenetic agent for the neuronal degeneration in gangliosidoses.     

Characterization of Neutral and Acidic Glycosphingolipids in Brains of Two Patients with GM1 Gangliosidosis Type 1 and Type 2

Brains of two patients with GM1 gangliosidosis type 1 and type 2, together with the age-matched control brains, were analyzed for glycosphingolipids. Six species of neutral glycolipids, eight species of gangliosides, and sulfatide were isolated from the diseased brains and identified. In addition to GM1 ganglioside and its asialo derivative, the diseased brains accumulated considerable amounts of gangliotriaosylceramide and glycolipids belonging to the globo series, the accumulation of which cannot be explained by deficient beta-galactosidase activity in this disease. GM4 ganglioside was detected in the type 2 brain, but not in type 1. As to fatty acid composition of monohexosylceramides and sulfatide in the two diseased brains, stearic acid was more predominant in the type 1 brain than in the type 2 brain. In light of our previous observations on a Tay-Sachs brain and present results, it appears that metabolism of the globo series glycolipids, which is active in normal brain at early infancy but inactive thereafter, remains in brains with GM1 gangliosidosis (types 1 and 2) and Tay-Sachs disease, reflecting a disturbance in development of the brain.     

Incorporation and degradation of GM1 ganglioside and asialoGM1 ganglioside in cultured fibroblasts from normal individuals and patients with beta-galactosidase deficiency

The uptake and degradation of GM1 ganglioside (GM1) and asialoGM1 ganglioside (GA1) were studied in cultured fibroblasts from normal individuals and patients with beta-galactosidase deficiency, using the lipid-loading test. The glycolipids were incorporated from the media into the fibroblasts and the terminal galactose was hydrolyzed in normal cells. The hydrolysis rates of GA1 were 80-86% of normal on the 3rd day after loading, while GM1 was hydrolyzed slowly; 35-54% on the 14th day. In infantile GM1 gangliosidosis and I-cell disease, little GM1 and GA1 was hydrolyzed on any day of culture, while fibroblasts from patients with adult GM1 gangliosidosis, Morquio disease type B and galactosialidosis hydrolyzed the lipids at nearly normal rates. The intracellular accumulation of the glycolipids, on the basis of protein content, was abnormally high in the case of infantile GM1 gangliosidosis and I-cell disease, but normal in the other disorders examined. These observations indicate that the in situ metabolism of GM1 and GA1 is probably normal in fibroblasts from patients with adult GM1 gangliosidosis, Morquio disease type B and galactosialidosis, although in vitro beta-galactosidase activities in these disorders are very low. The results are compatible with findings that GM1 and GA1 do not accumulate in the somatic organs of patients with adult GM1 gangliosidosis and galactosialidosis. In I-cell disease, however, the results of the loading test did not agree with the finding that there is little accumulation of glycolipids in postmortem tissues.     

Dog and human acid beta-D-galactosidases are structurally similar.

The purification of dog liver acid beta-galactosidase is described. The dog enzyme migrated as a single major band on polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate, with a molecular weight of 60000. Antiserum raised against purified human liver acid beta-galactosidase cross-reacted with beta-galactosidase from dog liver, but not with those from cat liver or Escherichia coli. Tryptic peptide maps of the dog and human acid beta-galactosidases indicate that 21 of the 24 peptides observed were homologous; a similar result was obtained after chymotryptic peptide mapping. We conclude that dog and human acid beta-galactosidases are structurally similar, and that canine GM1 gangliosidosis (acid beta-galactosidase deficiency) is an excellent model for the same disease in man.     

Accumulation of cholesterol 3-sulfate during in vitro squamous differentiation of rabbit tracheal epithelial cells and its regulation by retinoids

Rabbit tracheal epithelial (RbTE) cells in culture undergo terminal squamous differentiation characterized by enhanced transglutaminase activity, synthesis of specific keratins, and the formation of cross-linked envelopes. The expression of each of these markers of differentiation occurs spontaneously after the cells reach confluency, but this expression can be inhibited by the inclusion of retinoids in the extracellular medium. In the current work, we demonstrate that radioactive sulfate incorporation into the organic phase of a CHCl3/CH3OH (2:1) extract of RbTE cells increases 50- to 100-fold upon differentiation and that this accumulation can be completely blocked by the inclusion of retinoic acid in the culture medium. By the techniques of specific metabolic radiolabeling, thin layer chromatography, gas chromatography-mass spectrometry, and fast atom bombardment-mass spectrometry, the sulfated amphiphile was shown to be cholesterol 3-sulfate. Cholesterol sulfate accumulation begins 1 to 2 days after the RbTE cells reach the stationary phase of growth which is the same time that other differentiated functions begin to be expressed. The inhibition of accumulation by retinoic acid is concentration-dependent and half-maximal at 5 X 10(-11) M. The relative efficacy of a series of synthetic retinoids in inhibiting cholesterol sulfate accumulation correlated with their binding to the cellular retinoic acid-binding protein. These data taken together indicate that cholesterol sulfate is a marker of squamous differentiation in RbTE cells in culture. Possible biochemical mechanisms of the regulation of cholesterol sulfate levels during differentiation are discussed.     

Human placental sialidase: partial purification and characterization

A sialidase [EC 3.2.1.18] has been partially purified from human placenta by means of procedures comprising Con A-Sepharose adsorption, ammonium sulfate precipitation, sucrose density gradient centrifugation, and high-pressure liquid chromatography on a Shim pack Diol 300 column. On high-pressure liquid chromatography, most of the beta-galactosidase that comigrated with the sialidase on sucrose density gradient centrifugation was removed. The sialidase was purified 3,600-fold from the preparation obtained by Con A-Sepharose adsorption. The enzyme liberated the sialic acid residues from (alpha 2-3) and (alpha 2-6) sialyllactose, colomic acid, fetuin, and transferrin, but not from bovine submaxillary mucin. The enzyme also hydrolyzed gangliosides GM3, GD1a, and GD1b in the presence of sodium cholate as a detergent, but GM1 and GM2 were less susceptible to the enzyme. The optimum pHs for 4-methylumbelliferyl-N-acetylneuraminate, sialyllactose, fetuin, and GM3 lay between 4.0 and 5.0.     

Lipid composition determines interaction of liposome membranes with Pluronic L61

Triblock copolymers of ethylene oxide (EO) and propylene oxide (PO) of EO(n/2)PO(m)EO(n/2) type (Pluronics) demonstrate a variety of biological effects that are mainly due to their interaction with cell membranes. Previously, we have shown that Pluronics can bind to artificial lipid membranes and enhance accumulation of the anti-tumor drug doxorubicin (DOX) inside the pH-gradient liposomes and transmembrane migration (flip-flop) of NBD-labeled phosphatidylethanolamine in the liposomes composed from one component-lecithin. Here, we describe the effects caused by insertion of other natural lipids in lecithin liposomes and the significance of the lipid composition for interaction of Pluronic L61 with the membrane. We used binary liposomes consisting of lecithin and one of the following lipids: cholesterol, phosphatidylethanolamine, ganglioside GM1, sphingomyelin, cardiolipin or phosphatidic acid. The influence of the additives on (1) membrane microviscosity; (2) binding of Pluronic L61; (3) the copolymer effect on lipid flip-flop and membrane permeability towards DOX was studied. The results showed that insertion of sphingomyelin and cardiolipin did not influence membrane microviscosity and effects of Pluronic on the membrane permeability. Addition of phosphatidic acid led to a decrease in microviscosity of the bilayer and provoked its destabilization by the copolymer. On the contrary, cholesterol increased microviscosity of the membrane and decreased binding of Pluronic and its capacity to enhance flip-flop and DOX accumulation. Analogous tendencies were revealed upon incorporation of egg phosphatidylethanolamine or bovine brain ganglioside GM1. Thus, a reverse dependence between the microviscosity of membranes and their sensitivity to Pluronic effects was demonstrated. The described data may be relevant to mechanisms of Pluronic L61 interaction with normal and tumor cells.     

Tissue distribution of EDTA encapsulated within liposomes containing glycolipids or brain phospholipids.

Multilameller liposomes were prepared with various asialoglycolipids, gangliosides, sialic acid, or brain phospholipids in the liposome membrane and with ethylenediaminetetraacetic acid (EDTA) encapsulated in the aqueous compartments. The liposomes containing glycolipids or sialic acid were prepared from a mixture of phosphatidylcholine, cholesterol, and one of the following test substances: galactocerebroside, glucocerebroside, galactocerebroside sulfate, mixed gangliosides, monosialoganglioside GM1, monosialoganglioside GM2, monosialoganglioside GM3, disialoganglioside GD1a, or sialic acid. The liposomes containing brain phospholipids were mixtures of either sphingomyelin and cholesterol or a brain total phospholipid extract and cholesterol. Distributions of 14C-labeled EDTA were determined in mouse tissues from 15 min to 6 h or 12 h after a single injection of liposome preparation. Liver uptake up encapsulated EDTA was lowest from all liposome preparations containing sialic acid or sialogangliosides, regardless of the amount of sialic acid moiety present or the identity of the particular ganglioside; highest uptake of encapsulated EDTA by liver was from liposomes containing galactocerebroside or brain phospholipids. Lungs and brain took up the largest amounts of EDTA from liposomes containing sphingomyelin and lesser amounts from liposomes containing GD1a. Use of mouse brain phospholipid extract to prepare liposomes did not increase uptake of encapsulated EDTA by the brain. EDTA in liposomes containing monosialogangliosides, brain phospholipids, galactocerebroside, or sialic acid was taken up well by spleen and marrow. Highest thymus uptake of encapsulated EDTA was from liposomes containing GD1a. These results demonstrate that inclusion of sialogangliosides in liposome membranes decreases uptake of liposomes by liver, thus making direction of encapsulated drugs to other organs more feasible. Liposomes containing glycolipids also have potential uses as probes of cell surface receptors.     

GM2/GD2 and GM3 gangliosides have no effect on cellular cholesterol pools or turnover in normal or NPC1 mice

These studies investigated the role of gangliosides in governing the steady-state concentration and turnover of unesterified cholesterol in normal tissues and in those of mice carrying the NPC1 mutation. In animals lacking either GM2/GD2 or GM3 synthase, tissue cholesterol concentrations and synthesis rates were normal in nearly all organs, and whole-animal sterol pools and turnover also were not different from control animals. Mice lacking both synthases, however, had small elevations in cholesterol concentrations in several organs, and the whole-animal cholesterol pool was marginally elevated. None of these three groups, however, had changes in any parameter of cholesterol homeostasis in the major regions of the central nervous system. When either the GM2/GD2 or GM3 synthase activity was deleted in mice lacking NPC1 function, the clinical phenotype was not changed, but lifespan was shortened. However, the abnormal cholesterol accumulation seen in the tissues of the NPC1 mouse was unaffected by loss of either synthase, and clinical and molecular markers of hepatic and cerebellar disease also were unchanged. These studies demonstrate that hydrophobic interactions between cholesterol and various gangliosides do not play an important role in determining cellular cholesterol concentrations in the normal animal or in the mouse with the NPC1 mutation.     

Dicer1 敲除对肝脏胆酸代谢和转运功能的影响

目的:微小RNA(microRNAs,miRNAs)在胆固醇的合成,代谢和转运中起着重要作用,而mi RNAs在胆固醇代谢物胆酸的代谢和转运中的作用尚不清楚。Dicer基因是miRNAs生成过程的关键酶。本课题使用肝脏特异的Dicer1基因敲除小鼠,考察肝脏Dicer1基因敲除对C57BL/6小鼠肝脏胆酸代谢和转运的影响。方法:使用白蛋白启动子驱动的Cre重组酶和Loxp系统(Alb-Cre/Loxp)在小鼠肝脏中特异的敲除Dicer1基因;分别收集3~12周龄的小鼠血液和肝脏组织,使用Cobas生化仪检测小鼠血液和肝脏中总胆酸含量;利用实时定量PCR的方法分析肝脏中胆汁酸代谢转运相关基因的表达。结果:实验发现,肝脏Dicer基因敲除后,胆酸在血液和肝脏中明显蓄积,弥漫性肝细胞轻微空泡化,偶见单个肝细胞坏死。检测胆酸代谢和转运相关基因的表达发现,胆酸合成相关基因的表达有轻度升高,但缺乏统计学差异;在肝脏细胞血管侧的胆酸摄取转运体中,Oatp1a1在Dicer1敲除小鼠肝脏中明显下调,Ntcp和Oatp1b2则无明显改变;而肝细胞血管侧胆酸外排转运体的表达均有显著升高,胆管侧的外排转运体中Abcb11表达有明显增加。结论:Dicer基因敲除后,胆酸在血液和肝脏中明显蓄积,肝脏和血液中胆酸总量显著增加。血液中胆酸的蓄积可能与肝脏细胞血管侧摄取转运体的低表达和血管侧外排转运体的高表达有关;而肝脏中胆酸的蓄积可能部分来自于轻度升高的胆酸合成酶,胆酸在肝细胞内运输途径的紊乱可能与肝脏和血液中胆酸总量的显著增加相关。     

Effects of cholesterol sulfate on lipid metabolism in cultured human keratinocytes and fibroblasts

Effects of cholesterol sulfate on acetate incorporation into lipid fractions were examined in normal human fibroblast and keratinocyte cultures. Inhibition of sterologenesis in normal fibroblast cultures by cholesterol sulfate was less profound than that produced by either lipoprotein-containing serum or 25-hydroxycholesterol. Cholesterol sulfate also inhibited sterologenesis in low density lipoprotein receptor-deficient fibroblasts and inhibited both sterologenesis and 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in keratinocytes. Cholesterol sulfate increased incorporation of acetate into fatty acid-containing lipids in preconfluent cultures of both cell types in lipoprotein-depleted media. Similar effects were not observed either in response to lipoprotein-containing serum or 25-hydroxycholesterol. Cholesterol sulfate had no effect on oleic acid incorporation into diglycerides, triglycerides, or phospholipid fractions; neither did it inhibit acid lipase activity; nor did it inhibit fatty acid oxidation, indicating that cholesterol sulfate does not inhibit catabolism of acyl lipids. Because cholesterol sulfate had similar effects on fatty acid metabolism in steroid sulfatase-deficient fibroblasts lines, desulfation to cholesterol is not a prerequisite. Cholesterol sulfate did not significantly affect incorporation of oleic acid into sterol esters in fibroblast cultures, but in contrast, inhibited sterol esterification in keratinocyte cultures. These data suggest a novel role for cholesterol sulfate as a modulator of cellular lipid biosynthesis.