| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Recombinant human macrophage colony-stimulating factor reduces plasma cholesterol and carrageenan granuloma foam cell formation in Watanabe heritable hyperlipidemic rabbits Schaub, R. G., M. P. Bree, et al. (1994), Arterioscler Thromb 14(1): 70-6. Abstract: Previous studies have demonstrated that short-term administration of recombinant human macrophage colony-stimulating factor (rhM-CSF) reduces plasma cholesterol in rabbits, nonhuman primates, and human subjects. This study extended the dose schedule of rhM-CSF to 8 weeks of continuous intravenous infusion (CIV) in the Watanabe heritable hyperlipidemic (WHHL) rabbit and expanded the scope to include an assessment of macrophage-derived foam cell development. Ten male WHHL rabbits were injected subcutaneously with 1% carrageenan to promote formation of a macrophage-rich foam cell granuloma. Rabbits were infused with either vehicle or rhM-CSF at 100 micrograms/kg per day (weeks 1 through 5) followed by 300 micrograms/kg per day (weeks 6 through 8). rhM-CSF (100 micrograms/kg per day) decreased total plasma cholesterol by 45% at 2 weeks compared with controls. The gradual return of plasma cholesterol toward control concentrations over the subsequent 3 weeks correlated with the appearance of circulating antibodies specific to rhM-CSF. Granuloma weights at harvest (8 weeks after infusion) were significantly lower (2.8 +/- 0.7 g, mean +/- SEM) in rhM-CSF-treated rabbits relative to controls (7.1 +/- 1.5 g, P <.05). Granulomas from rabbits treated with rhM-CSF contained lower concentrations of cholesterol (2.0 +/- 0.7 versus 6.1 +/- 1.5 micrograms/mg, P <.03) and cholesteryl ester (0.7 +/- 0.4 versus 3.9 +/- 1.2 micrograms/mg, P <.03) than controls. Histological evaluation revealed that granulomas from the rhM-CSF-treated rabbits were more fibrous and contained fewer foam cells than those from controls.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Recombinant human serum amyloid A (apoSAAp) binds cholesterol and modulates cholesterol flux Liang, J. S. and J. D. Sipe (1995), J Lipid Res 36(1): 37-46. Abstract: During acute inflammation, the serum amyloid A (apoSAA) proteins apoSAA1 and apoSAA2 are transiently associated with high density lipoproteins (HDL) in concentrations of as much as 1000-fold more than their concentrations during homeostasis; however, their effect on HDL function is unclear. Recombinant apoSAAp, a hybrid of the closely related human apoSAA1 and apoSAA2 isoforms, was found to exhibit a high affinity for cholesterol. The adsorption of apoSAAp to polystyrene microtiter wells at physiological pH, temperature, and salt concentration was inhibited and reversed by cholesterol. ApoSAAp, to a greater extent than apoA-I, albumin, or fetal bovine serum, enhanced diffusion of cholesterol from HDL across a membrane that retained molecules > 3.5 kDa. Cholesterol from 25 nM to 125 microM inhibited binding of 3Hcholesterol to 167 nM apoSAAp. A cholesterol binding assay was developed to determine the dissociation constant for binding of 3Hcholesterol to apoSAAp; Kd = 1.7 +/- 0.3 x 10(-7) M and the maximum binding capacity (Bmax) is 1.1 +/- 0.1 mol/mol. After binding cholesterol, the apparent size of apoSAAp as determined by gel filtration on Sephacryl S-100 was increased from 12 to 23 kDa. ApoSAAp enhanced free 14Ccholesterol uptake from tissue culture medium by HepG2 cells, an effect that was dose dependent and blocked by polyclonal antibodies to human apoSAA1 and apoSAA2. ApoSAAp, unlike apoA-I, was taken up from serum-free medium by HepG2 cells and appeared to be degraded by cell-associated enzymes. Unlike peritoneal exudate cells, human HepG2 hepatoma cells do not secrete an enzyme that degrades apoSAAp. These results suggest that apoSAA can potentially serve as a transient cholesterol-binding protein. |
| Recombinant lecithin:cholesterol acyltransferase containing a Thr123-->Ile mutation esterifies cholesterol in low density lipoprotein but not in high density lipoprotein O, K., J. S. Hill, et al. (1993), J Lipid Res 34(1): 81-8. Abstract: Fish-eye disease is a rare genetic disorder of high density lipoprotein (HDL) metabolism that is characterized biochemically by a partial deficiency of the enzyme lecithin:cholesterol acyltransferase (LCAT). One of the mutations that is causative for fish-eye disease occurs at codon 123 of the LCAT gene. This mutation results in the exchange of a threonine residue for an isoleucine in the LCAT protein (Thr123-->Ile). In order to understand the functional significance of this exchange, we have used site-directed mutagenesis to reconstruct this mutation in an LCAT cDNA followed by expression of the mutant LCAT in COS-1 cells. The fish-eye disease mutation resulted in a 50% decrease in LCAT mass in the culture medium compared to wild type enzyme. The secreted mutant protein was incapable of esterifying cholesterol in HDL and HDL analogues. However, this protein retained the ability to esterify cholesterol in plasma and low density lipoprotein. These results support the hypothesis that this mutation is responsible for biochemical abnormalities of LCAT observed in fish-eye disease and the mutant LCAT protein has lost the potential to esterify cholesterol in the HDL pool but retains the ability to esterify cholesterol from other lipoproteins. |
| Recommendations for cholesterol levels in Finland Salminen, K. (1993), Duodecim 109(14): 1268-71. |
| Reconstitution and further characterization of the cholesterol transport activity of the small-intestinal brush border membrane Boffelli, D., F. E. Weber, et al. (1997), Biochemistry 36(35): 10784-92. Abstract: The sterol (free and esterified cholesterol) transport activity of the small-intestinal brush border membrane was solubilized with the short-chain detergent diheptanoylphosphatidylcholine and reconstituted to an artificial membrane system (proteoliposomes). The resulting proteoliposomes were identified as unilamellar membrane vesicles ranging in size between 50 and 200 nm with a broad maximum at 70-110 nm. That the sterol transport protein was indeed incorporated into the lipid bilayer was shown by density gradient centrifugation on a Ficoll gradient: the proteoliposomes yielded a single band with an apparent density of 1.035 g/mL. By subjecting solubilized brush border membrane vesicles (BBMV) to gel filtration on Sephadex G-200 prior to reconstitution, a 7-fold enrichment of the sterol transport activity was achieved relative to the original BBMV. The experimental evidence presented lends strong support to the notion that the sterol transport protein is an integral protein of the brush border membrane which is anchored in the lipid bilayer by at least one hydrophobic domain. The active center(s) is (are) exposed to the external side of the membrane. Anchoring of this protein to the lipid bilayer by a glycosylphosphatidylinositol moiety is unlikely. The reconstituted proteoliposomes behaved very similarly to the original BBMV in terms of facilitated sterol uptake. Using these proteoliposomes, a hitherto unknown activity of the brush border membrane was discovered. Long-chain triacylglycerols can be taken up by this membrane as such and need not be hydrolyzed prior to absorption. |
| Reconstitution of non-ionic monoalkyl amphiphile-cholesterol vesicles by dilution of lipids-octylglucoside mixed micelles Seras, M., M. Ollivon, et al. (1993), Chem Phys Lipids 66(1-2): 93-109. Abstract: Kinetic aspects of the formation of non-ionic surfactant vesicles (NSV) using the mixed micelle dilution procedure are examined. Mixed micelles composed of a mixture of lipids, i.e. diglycerol hexadecylether (C16G2), cholesterol (CHOL), dicetylphosphate (DCP) and detergent, octylglucoside (OG), were diluted with detergent-free buffer added either instantaneously or progressively at different rates ranging from 3.47 x 10(-2) to 6.94 x 10(-4) ml/min. The resulting particles were analysed by quasielastic light scattering (QELS), high performance liquid chromatography (HPLC) on gel exclusion column and cryogenic transmission electron microscopy (cryo-TEM). NSV exhibit mean diameters (MD) varying from 100 to 600 nm depending on the kinetics of OG removal. When the dilution of mixed micelles is instantaneous the vesicles are characterized by a spherical shape and MD values close to 100 nm. They show narrow size distribution and stability for 2 months. NSV recovered with progressive micelle dilution, at fast buffer addition rates (3.47 x 10(-2) and 1.39 x 10(-2) ml/min) exhibit MD values of 170-240 nm, elongated shapes, low polydispersities and 2-month stabilities. When the rate of buffer addition is lowered to 6.94 x 10(-4) ml/min, unstable particles with larger MD values and broad size distributions are obtained. Turbidity monitoring at 350 nm and 25 degrees C was used to characterize the lipids-OG mixed aggregate rearrangements either as a function of time when detergent-free buffer was continously added to the mixed micelles or after equilibrium setting when the micelles were instantaneously diluted. In the latter case the intermediate aggregates were also analysed by QELS. For continuous dilutions, the molecular composition of aggregates, OG/lipagg, as well as the OG concentration in the aqueous medium, OGbulk, were determined at the break points observed on the plots of optical density (OD) versus total OG concentration (OGtot). OG/lipagg and OGbulk values are independent of the rate of buffer addition, suggesting that the micelle to NSV transition is not mainly limited by the kinetics of the molecular processes involved during detergent removal from the mixed aggregates. The examination of the apparent partition coefficient of OG between the aqueous phase and the lipidic aggregates shows, however, that OG depletion from the bilayered structures is more difficult than its elimination from the mixed micelles. QELS analysis of the intermediate lipids-detergent aggregates, performed with time, demonstrates very slow supramolecular rearrangements during the vesicle closure. These rearrangements explain the significant increase in both size and polydisperity of the final vesicles observed with slow rates of buffer addition. |
| Reconstitution of sphingolipid-cholesterol plasma membrane microdomains for studies of virus-glycolipid interactions Hammache, D., G. Pieroni, et al. (2000), Methods Enzymol 312: 495-506. |
| Reconstitution of the cholesterol-hydroxylating system from adrenal cortex mitochondria by cytochrome P-450scc, adrenodoxin and the redox-mediator neutral red Gur'ev, O. L., S. N. Gilevich, et al. (1990), Biokhimiia 55(9): 1553-62. Abstract: It has been found that 3-amino-7-dimethylamino-2-methylphenazine (neutral red, NR) is responsible for the electron transport from the cathode to adrenodoxin (Ad) and cytochrome P-450 (P-450scc) from adrenal cortex mitochondria inaccessible to direct electrochemical reduction under native conditions. The rate constant for Ad reduction by this mediator is equal to 1.1 x 10(5) M-1 s-1 at 25 degrees C; the values of enthalpy and entropy for the activation reaction are 26.6 kJ.mol-1 and -59.6 J.mol-1 deg-1, respectively. Using the shunted electron transport chain NR----Ad----P-450scc, the cholesterol conversion into pregnenolone in an electrochemical cell was performed. Pregnenolone was found to be the sole steroid product of this reaction. Superoxide dismutase and catalase had no effect on the activity of the shunted system. After removal or substitution of Ad the apo-Ad hemoprotein was reduced in a non-productive manner. Under identical reconstitution conditions methylviologen was ineffective as an electron carrier. |
| Reconstitution of the myometrial oxytocin receptor into proteoliposomes. Dependence of oxytocin binding on cholesterol Klein, U. and F. Fahrenholz (1994), Eur J Biochem 220(2): 559-67. Abstract: The requirements for regaining high-affinity binding of the myometrial oxytocin receptor after detergent solubilization were investigated by reconstitution experiments. Large unilamellar liposomes were prepared by reverse-phase evaporation from different mixtures of phospholipids, cholesterol and cholesteryl hemisuccinate. In the presence of the oxytocin receptor solubilized from myometrial membranes from pregnant guinea pig uterus, liposomes were treated with 3-(3-cholamidopropyl)-dimethylammonio-2-hydroxy-1-propanesulfonate (Chapso) throughout the range of detergent concentrations that cause the transformation of lamellar structures to mixed micelles. Detergent removal was achieved using bio-beads SM-2 as adsorbent. The presence of cholesterol was a prerequisite for regaining high-affinity binding of 3Hoxytocin and 125I-oxytocin antagonist to reconstituted proteoliposomes. Binding of 3Hoxytocin but not of the antagonist was dependent on the presence of Mn2+ ions. Reconstitution after lectin chromatography and photoaffinity labeling of reconstituted vesicles resulted in the exclusive labeling of the oxytocin receptor with a molecular mass of 68-80 kDa. |
| Reconstitution of the steroidogenic pathway from cholesterol to aldosterone in liposome membranes Kominami, S., N. Nishida, et al. (1996), Biochim Biophys Acta 1301(3): 199-206. Abstract: A steroidogenic pathway from cholesterol to aldosterone was reconstituted in liposome membranes using cytochromes P-450scc, P-450C21 and P-450(11) beta, and 3 beta-hydroxysteroid dehydrogenase/ delta 5-delta 4 isomerase (3 beta HSD/I) with their electron transfer systems. All of the enzymes were purified from bovine adrenocortical mitochondria and microsomes. The cholesterol metabolism in the liposomal reconstituted system was compared with that in the combined organella system composed of bovine adrenocortical mitochondria and microsomes, where the activity of P-450(17) alpha,lyase was inhibited by bifonazole. The metabolic activities in these two systems were similar except for aldosterone production. Aldosterone was produced in the liposomal system but not in the combined organella system. 4-fold increase in the amount of P-450scc in the liposomal system enhanced the activity of 3 beta HSD/I, P-450C21 and 11 beta-hydroxylase of P-450(11) beta but decreased 18-hydroxycorticosterone and aldosterone production by P-450(11) beta, supporting our previous findings describing the regulation mechanism of aldosterone synthesis (Kominami, S., Harada, D. and Takemori, S. (1994) Biochim. Biophys. Acta 1192, 234). It was demonstrated using the liposomal reconstituted system that the increase in the amount of one enzyme did not only increase the metabolizing activity of that enzyme but also affect other enzyme in various ways. |
| Recovery of cholesterol and triacylglycerol in very-fast ultracentrifugation of human lipoproteins in a large range of concentrations Leonhardt, W., J. Pietzsch, et al. (1994), Eur J Clin Chem Clin Biochem 32(12): 929-33. Abstract: Very-fast ultracentrifugation using a benchtop ultracentrifuge was applied to the analysis of lipoproteins in 0.5 ml of human plasma. VLDL, IDL and LDL were flotated at densities of 1.006, 1.019 and 1.063 kg/l in runs lasting 30, 100 and 100 minutes. Chylomicrons, if present, were flotated in a separate run. HDL were isolated by precipitation of the apolipoprotein B-containing lipoproteins from total plasma using polyethylene glycol. Three series of separations were routinely performed: 1. VLDL run alone (632 samples), 2. VLDL run + LDL run (122 samples), and 3. Chylomicron separation + VLDL run + IDL run (92 samples). The concentrations of cholesterol and triacylglycerol were obtained for plasma, chylomicrons, VLDL, IDL, LDL and HDL. Plasma values ranged from 1.8 to 37.1 mmol/l cholesterol and 0.26 to 50.2 mmol/l triacylglycerol. The plasma triacylglycerol concentrations were corrected for free glycerol by 3% (for triacylglycerols < 2.5 mmol/l) and by 2% (for triacylglycerols > or = 2.5 mmol/l). The recovery rate of lipids after ultracentrifugation was determined by comparing the concentrations in lipoproteins and in plasma. It was near to 100% and decreased for samples with extremely high lipid concentrations. |
| Recruitment of cell phospholipids and cholesterol by apolipoproteins A-II and A-I: formation of nascent apolipoprotein-specific HDL that differ in size, phospholipid composition, and reactivity with LCAT Forte, T. M., J. K. Bielicki, et al. (1995), J Lipid Res 36(1): 148-57. Abstract: Studies were carried out to determine whether apolipoprotein (apo) A-II, like apoA-I, can recruit phospholipid and cholesterol from cell membranes, thereby forming nascent apoA-II-specific HDL. ApoA-II and apoA-I were purified from plasma and each was incubated with CHO cells at a concentration of 10 micrograms/ml. Lipid-containing complexes were isolated from the medium in both cases; the composition of the apoA-II- and apoA-I-specific complexes were similar where percent protein, phospholipid, and cholesterol were 35 +/- 3, 38 +/- 2, and 25 +/- 1 for apoA-II, respectively, and 40 +/- 2, 35 +/- 1, and 24 +/- 2 for apoA-I, respectively. On a per mole of apolipoprotein basis, apoA-I recruited significantly more phospholipid and cholesterol than dimeric apoA-II suggesting that apoA-I with its greater number of alpha helices binds more lipid. By electron microscopy, nascent apoA-II- and apoA-I-specific particles were predominantly discoidal in morphology. ApoA-II complexes were unique in their nondenaturing polyacrylamide gradient gel size distribution as six distinct populations of particles with diameters of 8.1, 9.3, 10.4, 11.8, 13.1, and 14.6 nm were routinely noted, compared with apoA-I which formed only three major populations with diameters of 7.3, 9.2, and 11.0 nm. Nascent apoA-I complexes incubated with purified lecithin:cholesterol acyltransferase (LCAT) were transformed into predominantly 8.4 nm particles. The latter is similar in size to plasma HDL3a, LpA-I particles, suggesting that extracellularly assembled apoA-I-lipid complexes can directly give rise to a major plasma LpA-I subpopulation upon interaction with LCAT. Unlike apoA-I, apoA-II-lipid complexes could not serve as substrates for LCAT and did not undergo transformation. This study also demonstrates, for the first time, that apoA-II and apoA-I show a preference in phospholipid recruitment from membranes. Although phosphatidylcholine is the major phospholipid removed by both apolipoproteins, apoA-II preferentially recruits phosphatidylethanolamine (PE) as its second most abundant phospholipid while apoA-I recruits sphingomyelin. As PE is usually associated with the inner leaflet of the membrane, it is likely that dimeric apoA-II, compared with apoA-I, can penetrate farther into the membrane and extract PE. This ability of apoA-II to insert more deeply into the lipid milieu may explain the known ability of apoA-II to resist dissociation from the mature HDL particle. |
| Rectangular solid domains in ceramide-cholesterol monolayers - 2D crystals Ekelund, K., L. Eriksson, et al. (2000), Biochim Biophys Acta 1464(1): 1-6. Abstract: Very small rectangular domains were observed by atomic force microscopy in binary monolayers of synthetic ceramides and cholesterol. When the cholesterol content is increased the domains are bigger although the rectangular shape is retained. The almost perfect shape of the domains indicates two-dimensional single ceramide crystals. Lipid domains in monolayers of this particular shape and size have to our knowledge not been reported in the literature previously. |
| Recurrent anaemia due to ischaemic colonic ulceration caused by cholesterol embolism Grant, D. J., D. S. Sanders, et al. (1993), Postgrad Med J 69(810): 320-2. Abstract: We describe an elderly patient with generalized atherosclerosis who presented with recurrent iron-deficiency anaemia. He underwent right hemicolectomy which revealed ischaemic colonic ulceration caused by cholesterol embolism. Surgery appeared to be curative. Cholesterol embolism should be considered as a possible cause of unexplained gastrointestinal blood loss in the elderly. |
| Recycling compartments and the internal vesicles of multivesicular bodies harbor most of the cholesterol found in the endocytic pathway Mobius, W., E. van Donselaar, et al. (2003), Traffic 4(4): 222-31. Abstract: We employed our recently developed immuno-electron microscopic method (W. Mobius, Y. Ohno-Iwashita, E. G. van Donselaar, V. M. Oorschot, Y. Shimada, T. Fujimoto, H. F. Heijnen, H. J. Geuze and J. W. Slot, J Histochem Cytochem 2002; 50: 43-55) to analyze the distribution of cholesterol in the endocytic pathway of human B lymphocytes. We could distinguish 6 categories of endocytic compartments on the basis of morphology, BSA gold uptake kinetics and organelle marker analysis. Of all cholesterol detected in the endocytic pathway, we found 20% in the recycling tubulo-vesicles and 63% present in two types of multivesicular bodies. In the multivesicular bodies, most of the cholesterol was contained in the internal membrane vesicles, the precursors of exosomes secreted by B cells. Cholesterol was almost absent from lysosomes, that contained the bulk of the lipid bis(monoacylglycero)phosphate, also termed lysobisphosphatidic acid. Thus, cholesterol displays a highly differential distribution in the various membrane domains of the endocytic pathway. |
| Recycling of apoprotein E is associated with cholesterol efflux and high density lipoprotein internalization Heeren, J., T. Grewal, et al. (2003), J Biol Chem 278(16): 14370-8. Abstract: After receptor-mediated endocytosis of triglyceride-rich lipoproteins (TRL) into the liver, TRL particles are immediately disintegrated in peripheral endosomal compartments. Whereas core lipids and apoprotein B are delivered for degradation into lysosomes, TRL-derived apoE is efficiently recycled back to the plasma membrane. This is followed by apoE re-secretion and association of apoE with high density lipoproteins (HDL). Because HDL and apoE can independently promote cholesterol efflux, we investigated whether recycling of TRL-derived apoE in human hepatoma cells and fibroblasts could be linked to intracellular cholesterol transport. In this study we demonstrate that HDL(3) does not only act as an extracellular acceptor for recycled apoE but also stimulates the recycling of internalized TRL-derived apoE. Furthermore, radioactive pulse-chase experiments indicate that apoE recycling is accompanied by cholesterol efflux. Confocal imaging reveals co-localization of apoE and cholesterol in early endosome antigen 1-positive endosomes. During apoE re-secretion, HDL(3)-derived apoA-I is found in these early endosome antigen 1, cholesterol-containing endosomes. As shown by time-lapse fluorescence microscopy, apoE recycling involves the intracellular trafficking of apoA-I to pre-existing and TRL-derived apoE/cholesterol-containing endosomes in the periphery. Thus, these studies provide evidence for a new intracellular link between TRL-derived apoE, cellular cholesterol transport, and HDL metabolism. |
| Red pepper attenuates cholesteryl ester transfer protein activity and atherosclerosis in cholesterol-fed rabbits Kwon, M. J., Y. S. Song, et al. (2003), Clin Chim Acta 332(1-2): 37-44. Abstract: BACKGROUND: The current study was conducted to examine the effect of red pepper supplementation on cholesteryl ester transfer protein (CETP) activity, along with its anti-atherosclerotic effect in cholesterol-fed rabbits. METHODS: Rabbits were fed a 1% cholesterol diet for 12 weeks, including a 1% red pepper powder supplement. RESULTS: The red pepper supplemented group exhibited significantly lower CETP activity than the control group during the experimental period (P<0.05). The total cholesterol, triglyceride (TG), LDL-C, VLDL-C, and VLDL-TG levels and atherogenic index (AI) were all significantly lower in the red pepper group than in the control group (P<0.05), whereas the HDL-C level was significantly higher in the red pepper group than in the control group during the experimental period (P<0.05). Furthermore, the red pepper supplementation increased the fecal TG excretion (P<0.05). Based on a morphological examination, the red pepper supplemented group exhibited fewer fat droplet deposits than the control group. CONCLUSIONS: The current results suggest that red pepper attenuates atherosclerosis, plus plasma CETP would appear to be a risk marker of atherosclerosis in cholesterol-fed rabbits. |
| Red Star Ruby (Sunrise) and blond qualities of Jaffa grapefruits and their influence on plasma lipid levels and plasma antioxidant activity in rats fed with cholesterol-containing and cholesterol-free diets Gorinstein, S., H. Leontowicz, et al. (2005), Life Sci 77(19): 2384-97. Abstract: Bioactive compounds of peels and peeled red Star Ruby (Sunrise) and blond qualities of Jaffa grapefruits were analyzed and their antioxidant potential was assessed. The dietary fibers were determined according to Prosky et al., the total polyphenol content by Folin-Ciocalteu method and measured at 765 nm, minerals and trace elements by atomic absorption spectrometer, phenolic and ascorbic acids by HPLC and the antioxidant potential by two different antioxidant assays (DPPH and beta-carotene linoleate model system). It was found that the contents of most studied bioactive compounds in both qualities are comparable. Only the contents of total polyphenols and flavonoids were higher in red grapefruits, but not significant. The antioxidant potentials of red peeled grapefruits and their peels were significantly higher than of blond peeled grapefruits and their peels (P<0.05 in both cases). Diets supplemented with peeled red and blond qualities of Jaffa grapefruits and their peels have increased the plasma antioxidant capacity and improved plasma lipid levels, especially in rats fed with cholesterol added diet. In conclusion, both qualities of Jaffa grapefruits contain high quantities of bioactive compounds, but the antioxidant potential of red grapefruits is significantly higher. Diets supplemented with both qualities of Jaffa grapefruits improve the plasma lipid levels and increase the plasma antioxidant activity, especially in rats fed with cholesterol added diets. Jaffa grapefruits, especially their red Star Ruby quality, could be a valuable supplementation for diseases-preventing diets. |
| Redefining cholesterol's role in the mechanism of the cholesterol-dependent cytolysins Giddings, K. S., A. E. Johnson, et al. (2003), Proc Natl Acad Sci U S A 100(20): 11315-20. Abstract: The cholesterol-dependent cytolysins (CDCs) constitute a large family of pore-forming toxins that function exclusively on cholesterol-containing membranes. A detailed analysis of the various stages in the cytolytic mechanism of three members of the CDC family revealed that significant depletion of cholesterol from the erythrocyte membrane stalls these toxins in the prepore complex. Therefore, the depletion of membrane cholesterol prevents the insertion of the transmembrane beta-barrel and pore formation. These unprecedented findings provide a paradigm for the involvement of cholesterol in the CDC cytolytic mechanism and that of other pore-forming toxins whose activity is enhanced by the presence of membrane cholesterol. |
| Redistribution of cholesterol in oligodendrocyte membrane sheets after activation of distinct signal transduction pathways Lintner, R. N. and C. A. Dyer (2000), J Neurosci Res 60(4): 437-49. Abstract: Cultured oligodendrocytes produce extensive membrane sheets that contain an internal lacy network of vein-like structures composed of microtubules, actin filaments, and 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase). These cytoplasmic vein-like structures surround domains of myelin basic protein (MBP). Using the antibiotic filipin, that binds to cholesterol, the relationship between plasma membrane cholesterol and cytoskeleton in membrane sheets was examined. Our results show that cholesterol was relatively uniformly distributed within the plasma membranes of prefixed control oligodendrocyte membrane sheets. When live cultures were extracted with Triton X-100, however, a subpopulation of cholesterol molecules remained colocalized with cytoskeleton in the membrane sheets. Activation of two well-characterized signaling pathways that differentially affect microtubule and actin filament stability in membrane sheets resulted in an apparent massive lateral movement of cholesterol molecules away from membrane regions overlying internal MBP domains to membrane tracts directly overlying cytoplasmic cytoskeletal veins. Depolymerization of microtubules by colchicine resulted in redistribution of cholesterol directly over actin filaments, whereas depolymerization of actin filaments by cytochalasin B resulted in redistribution of cholesterol directly over CNPase/microtubular veins. These data suggest that cholesterol forms an association with cytoskeletal components or proteins associated with cytoskeleton. These data also suggest that cholesterol, via interactions with cytoskeleton, plays a role in signaling pathways in oligodendrocyte membrane sheets. |