| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Cholesterol modulation of lipid-protein interactions in liver microsomal membrane: a spin label study Castuma, C. E., R. R. Brenner, et al. (1991), Biochemistry 30(39): 9492-7. Abstract: ESR spectra of spin probes were used to monitor lipid-protein interactions in native and cholesterol-enriched microsomal membranes. In both systems composite spectra were obtained, one characteristic of bulk bilayer organization and another due to a motionally restricted population, which was ascribed to lipids in a protein microenvironment. Computer spectral subtractions revealed that cholesterol modulates the order/mobility of both populations in opposite ways, i.e., while the lipid bilayer region gives rise to more anisotropic spectra upon cholesterol enrichment, the spectra of the motionally restricted population become indicative of increased mobility and/or decreased order. These events were evidenced by measurement of both effective order parameters and correlation times. The percentages of the motionally restricted component were invariant in native and cholesterol-enriched microsomes. Variable temperature studies also indicated a lack of variation of the percentages of both spectral components, suggesting that the motionally restricted one was not due to protein aggregation. The results correlate well with the effect of cholesterol enrichment on membrane-bound enzyme kinetics and on the behavior of fluorescent probes Castuma & Brenner (1986) Biochemistry 25, 4733-4738. Several hypothesis are put forward to explain the molecular mechanism of the cholesterol-induced spectral changes. |
| Cholesterol modulation of membrane fluidity and VIP receptor/effector system in rat prostatic epithelial cells Carmena, M. J., C. Hueso, et al. (1991), Regul Pept 33(3): 287-97. Abstract: Treatment of rat prostatic epithelial cells with cholesteryl hemisuccinate (ChH) resulted in a time- and dose-dependent inhibition of the stimulatory effect of the neuropeptide vasoactive intestinal peptide (VIP) on cyclic AMP accumulation, with a 40% decrease in the response to a maximally effective VIP concentration. Cell treatment with ChH led also to a similar blocking of isoproterenol (a beta-adrenergic agonist) action but did not modify forskolin (which is assumed to act directly on the catalytic unit of adenylate cyclase) activity upon cyclic AMP levels. The levels of the transduction protein Gs were similar in membranes from both control and ChH-treated cells as suggested by experiments on cholera toxin-catalyzed ADP-ribosylation. The inhibitory effect of ChH was accompanied by an increase of membrane microviscosity as estimated by measurements of fluorescence polarization. Experiments on VIP binding indicated that increasing cholesterol concentration in the plasma membrane led to a higher VIP binding capacity without changes in the affinity of VIP receptors. These data suggest that membrane cholesterol incorporation diminishes the coupling efficiency between adenylate cyclase and the VIP-receptor complex or other receptor systems (i.e., desensitization) due to an increase of plasma membrane rigidity. |
| Cholesterol modulation of molecular activity of reconstituted shark Na+,K(+)-ATPase Cornelius, F. (1995), Biochim Biophys Acta 1235(2): 205-12. Abstract: The cholesterol content of liposome bilayers has been varied between 0-40 mol% to study the effects on reconstituted Na+,K(+)-ATPase. The maximum hydrolytic activity of reconstituted Na+,K(+)-ATPase was increased by cholesterol at concentrations above 10 mol% for both the physiological Na+/K(+)-exchange reactions, as well as for the partial reactions Na+/Na(+)-exchange and uncoupled Na+ efflux. Omission of cholesterol from the liposome bilayer modified the activation by cytoplasmic Na+, indicating effects on both Vmax and on the Na(+)-affinity. Several other kinetic parameters were found to be strongly influenced as well, most notable the steady-state phosphorylation level, and the characteristics of the phosphorylation/dephosphorylation reactions. These results indicate that cholesterol interacts directly with the Na+,K(+)-ATPase as an essential effector perhaps by affecting its conformational mobility or monomer interaction. |
| Cholesterol modulation of photoreceptor function in bovine retinal rod outer segments Boesze-Battaglia, K. and A. D. Albert (1990), J Biol Chem 265(34): 20727-30. Abstract: Rhodopsin, a prototypical G protein receptor, is found both in the plasma membrane and in discs of bovine rod outer segments. The ability of each of these membranes to activate phosphodiesterase upon stimulation by light in the presence of GTP and cGMP was investigated. The plasma membrane showed little or no activity when compared with disc membranes. The plasma membrane contains approximately 28 mol% cholesterol compared to 8 mol % found in discs. Upon oxidation of at least 70 % of the cholesterol in the plasma membrane to cholestenone, the phosphodiesterase activity in the plasma membrane approached that initiated by the disc membranes. When a 50:50 mixture of disc and plasma membrane rhodopsin was tested for phosphodiesterase activity, the results were found to be additive. Therefore, cholesterol is implicated in regulation of the receptor activity. |
| Cholesterol modulation of sphingomyelinase activity at physiological temperatures Contreras, F. X., J. Sot, et al. (2004), Chem Phys Lipids 130(2): 127-34. Abstract: Bacillus cereus sphingomyelinase activity was assayed on large unilamellar vesicles composed of sphingomyelin (SM)/cholesterol (Ch) mixtures at varying proportions. Natural (egg) SM was used with a gel-fluid transition temperature at ca. 40 degrees C. When the enzyme was assayed at 37 degrees C, the activity on pure SM was exceedingly low, but a small increase was observed as soon as some Ch was added, and a large enhancement of activity occurred with Ch proportions above 25 mol%. The data were interpreted in terms of sphingomyelinase activity being higher in the cholesterol-induced liquid-ordered phase than in the gel phase. The abrupt increase in activity above 25 mol% Ch would occur as a result of a change in domain connectivity, when the Ch-rich liquid-ordered domains coalesced. In equimolar SM/Ch mixtures, that were in the liquid-ordered state in a wide range of temperatures, sphingomyelinase activity was virtually constant in the 30-70 degrees C range. The results demonstrate that at the mammalian and bird physiological temperatures Ch modulates sphingomyelinase activity, and that this can occur precisely because most SM have a gel-fluid transition temperature above the physiological temperature range. In addition, Ch activation of sphingomyelinase and the strong affinity of Ch for SM allow the rapid, localised and self-contained production of the metabolic signal ceramide in specific microdomains (rafts). |
| Cholesterol modulation of transmembrane cation transport systems in human erythrocytes Lijnen, P. and V. Petrov (1995), Biochem Mol Med 56(1): 52-62. Abstract: The aim of this study was to investigate whether in vitro cholesterol enrichment of human erythrocytes affects transmembrane cation transport systems by changes induced in the membrane microviscosity of these cells. Human erythrocytes in suspension were incubated with cholesterol-lecithin dispersions to obtain an enrichment of their membrane cholesterol. The ouabain-sensitive Na+ efflux, the Na+, Li+(-)countertransport activity, the Na+, K+(-)cotransport activity, the basal transmembrane leakage of Na+ and K+, and the enzymatic activity of ATPases were determined in these cholesterol-rich cells and compared with control cells. Membrane core and surface microviscosity was also measured in the control and cholesterol-enriched cells, using the fluorescent probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethylammonium (TMA)-DPH, respectively. The cholesterol content of the erythrocytes incubated in the presence of cholesterol-rich dispersions increased gradually over time. A 47% increase membrane cholesterol content was obtained after 16 h of incubation, while no change in the erythrocyte phospholipid content was found. High membrane cholesterol in the human erythrocyte phospholipid content was found. High membrane cholesterol in the human erythrocyte, obtained by in vitro enrichment of the cells with cholesterol-lecithin dispersion, inhibited in intact cell suspensions the ouabain-sensitive Na+ efflux, an estimate of the Na+(-)pump activity, and in isolated erythrocyte membranes the enzymatic activity of Na+, K+(-)ATPase, and Mg2+(-)ATPase. The dissociation constant for internal sodium and the maximal rate of ouabain-sensitive Na+ efflux is decreased in cholesterol-rich erythrocytes compared to control cells. The elevated erythrocyte membrane cholesterol content was also accompanied by a decrease in the Na+,K+(-)cotransport activity, the Na+, Li+(-)countertransport activity, and the transmembrane basal leakage of Na+ and K+. Microviscosity, measured in the erythrocyte membrane core with the fluorescence probe DPH, was increased in the cholesterol-rich cells compared to the control cells. However, the membrane surface microviscosity, measured with the probe TMA-DPH, was not different between the control cell and the cholesterol-rich cells. The present data show that enrichment of the human erythrocyte membrane with cholesterol results in an increase of membrane core microviscosity, resulting in an inhibition of transmembrane cation transport systems in erythrocytes in suspensions and of erythrocyte membrane Na+,K+(-)ATPase, Ca2+(-)ATPase, and Mg2+(-)ATPase. |
| Cholesterol monohydrate nucleation in ultrathin films on water Rapaport, H., I. Kuzmenko, et al. (2001), Biophys J 81(5): 2729-36. Abstract: The growth of a cholesterol crystalline phase, three molecular layers thick at the air-water interface, was monitored by grazing incidence x-ray diffraction and x-ray reflectivity. Upon compression, a cholesterol film transforms from a monolayer of trigonal symmetry and low crystallinity to a trilayer, composed of a highly crystalline bilayer in a rectangular lattice and a disordered top cholesterol layer. This system undergoes a phase transition into a crystalline trilayer incorporating ordered water between the hydroxyl groups of the top and middle sterol layers in an arrangement akin to the triclinic 3-D crystal structure of cholesterol x H(2)O. By comparison, the cholesterol derivative stigmasterol transforms, upon compression, directly into a crystalline trilayer in the rectangular lattice. These results may contribute to an understanding of the onset of cholesterol crystallization in pathological lipid deposits. |
| Cholesterol monomer activity and its role in understanding cholesterol saturation and crystallization Higuchi, W. I., P. H. Lee, et al. (1990), Hepatology 12(3 Pt 2): 88S-91S; discussion 91S-93S. Abstract: Cholesterol in bile has been linked to the incidence of gallstone disease through the concept of supersaturation as measured by the cholesterol saturation index. The latter is a linear function of cholesterol concentration and is based on the assumption that all cholesterol in bile is solubilized and transported in bile salt-lecithin mixed micelles and in bile salt simple micelles. In light of the discovery of the cholesterol-lecithin vesicles as significant cholesterol carriers, there is a need to reevaluate this old concept. This study examined the feasibility of the silicone polymer uptake method for the direct determination of the cholesterol thermodynamic activity in model bile systems. In cases of unsaturation and near saturation, a linear relationship was observed between the cholesterol concentration in the silicone polymer at equilibrium and the cholesterol saturation index (the cholesterol concentration in the aqueous micellar solution at equilibrium/cholesterol monohydrate solubility in the same medium) for taurocholate and taurochenodeoxycholate systems either containing or not containing lecithin. In taurocholate-lecithin solutions supersaturated with cholesterol, the linear relationship continued to hold up to the point where vesicles started to form. Vesicle formation initiated a negative deviation from linearity. At constant lecithin concentration, the cholesterol thermodynamic activity at which vesicle formation began was a function of the taurocholate/lecithin ratio; the larger the taurocholate/lecithin ratio, the higher the cholesterol thermodynamic activity for the onset of vesicle formation.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Cholesterol movement between the plasma membrane and the cholesteryl ester droplets of cultured Leydig tumour cells Nagy, L. and D. A. Freeman (1990), Biochem J 271(3): 809-14. Abstract: The present studies characterize the turnover of plasma membrane cholesterol in MA-10 Leydig tumour cells. Plasma membrane cholesterol of MA-10 cells was slowly internalized and converted into cholesteryl ester. Low-density lipoprotein (LDL) stimulated, in a dose- and time-dependent fashion, plasma membrane cholesterol conversion into intracellular esters. Stimulation of membrane internalization was not simply the consequence of accelerated uptake of membrane with LDL, since binding and internalization of epidermal growth factor and transferrin had no effect on turnover of plasma membrane cholesterol. The protein of LDL is unimportant as well, since delipidated LDL had no effect on membrane turnover. The action of LDL on cholesterol turnover was explained entirely by its contribution to cholesteryl ester stores. The degree of plasma membrane cholesterol internalization and esterification was directly proportional to the size of cellular ester stores. |
| Cholesterol movement from plasma membrane to rough endoplasmic reticulum. Inhibition by progesterone Lange, Y. (1994), J Biol Chem 269(5): 3411-4. Abstract: The effect of progesterone on the movement of sterols from the cell surface to the rough endoplasmic reticulum (ER) was examined in rat hepatoma cells. Plasma membranes were labeled exogenously with 3Hcholesterol or 3Hzymosterol. Translocation of the labeled sterols to the rough ER was inferred from their conversion to 3Hcholesteryl esters and 3Hcholesterol, respectively. Progesterone inhibited both of these reactions by more than 90%. The concentration for half-maximal inhibition was 0.7 microgram/ml. Progesterone did not inhibit acyl-CoA:cholesterol acyltransferase activity itself, since the steroid had no effect on the esterification of 3Hcholesterol synthesized in vitro in the rough ER from 3Hzymosterol. Moreover, the small amount of 3Hcholesterol synthesized from plasma membrane 3Hzymosterol in progesterone-treated intact cells was esterified at the same fractional rate as cholesterol in control cells. Subcellular fractionation of cells pulse-labeled with 3Hcholesterol and treated with progesterone suggested that the block in plasma membrane cholesterol transfer to the rough ER occurred at the level of the plasma membrane. |
| Cholesterol movement in Niemann-Pick type C cells and in cells treated with amphiphiles Lange, Y., J. Ye, et al. (2000), J Biol Chem 275(23): 17468-75. Abstract: Cholesterol accumulates to massive levels in cells from Niemann-Pick type C (NP-C) patients and in cells treated with class 2 amphiphiles that mimic NP-C disease. This behavior has been attributed to the failure of cholesterol released from ingested low density lipoproteins to exit the lysosomes. However, we now show that the rate of movement of cholesterol from lysosomes to plasma membranes in NP-C cells is at least as great as normal, as was also found previously for amphiphile-treated cells. Furthermore, the lysosomes in these cells filled with plasma membrane cholesterol in the absence of lipoproteins. In addition, we showed that the size of the endoplasmic reticulum cholesterol pool and the set point of the homeostatic sensor of cell cholesterol were approximately normal in NP-C cells. The plasma membrane cholesterol pools in both NP-C and amphiphile-treated cells were also normal. Furthermore, the build up of cholesterol in NP-C lysosomes was not a physiological response to cholesterol overload. Rather, it appeared that the accumulation in NP-C lysosomes results from an imbalance in the brisk flow of cholesterol among membrane compartments. In related experiments, we found that NP-C cells did not respond to class 2 amphiphiles (e.g. trifluoperazine, imipramine, and U18666A); these agents may therefore act directly on the NPC1 protein or on its pathway. Finally, we showed that the lysosomal cholesterol pool in NP-C cells was substantially and preferentially reduced by incubating cells with the oxysterols, 25-hydroxycholesterol and 7-ketocholesterol; these findings suggest a new pharmacological approach to the treatment of NP-C disease. |
| Cholesterol myth club on par with flat earth society Griffin, G. C. (1990), Postgrad Med 87(1): 13, 16. |
| Cholesterol non-consensus in primary prevention of coronary heart disease. Methodologic problems in the interpretation of epidemiologic studies Berger, M. (1993), Z Kardiol 82(7): 399-405. Abstract: Evidence for a population intervention to lower mean serum cholesterol levels with the aim of a primary prevention of coronary artery disease and a reduction of cardiovascular mortality is critically reviewed. The arguments brought forward in favor of such interventions are frequently flawed by methodological shortcomings. Quite often, descriptive associations are taken as proofs of causal relationship--or results of prospective studies on selected cohorts are extrapolated to the general population without justification. For adolescents, women, and persons above 60 years of age (i.e., for the majority of the population) there is actually no evidence in favor of initiatives to screen for and generally lower serum cholesterol levels. Even for middle-aged men, lowering of hypercholesterolemia in an attempt of primary prevention of coronary heart disease was not followed by the expected decrease in overall mortality. A public discussion of the apparent cholesterol non-consensus is urgently needed in Germany in order to protect both the population, as well as the reputation of the medical profession against unjustified health campaigns. |
| Cholesterol nucleates rapidly from mixed micelles in the prairie dog Ahrendt, S. A., K. Fox-Talbot, et al. (1994), Biochim Biophys Acta 1211(1): 7-13. Abstract: Current theory suggests that the nucleation of cholesterol in human bile requires the aggregation and fusion of cholesterol-enriched phospholipid vesicles. This theory is based on observations which do not exclude the precipitation of cholesterol from mixed micelles. The present study examines the role of mixed micelles and vesicles in the formation of cholesterol monohydrate crystals in the prairie dog. The intermicellar bile salt concentration of prairie dog gallbladder bile was determined using equilibrium dialysis. Model bile equivalent to gallbladder bile from cholesterol-fed prairie dogs was used as dialysant yielding the intermicellar (dialysate) concentration of 9 mM. Cholesterol carriers in gallbladder bile from 11 cholesterol-fed animals were then separated by Sephacryl S200 gel filtration chromatography using eluant buffer containing the intermicellar bile salt concentration. Gel filtration chromatography of fresh bile demonstrated that 100% of cholesterol was carried in the mixed micellar fraction with no vesicles observed in any of the 11 animals. The gallbladder bile nucleation time was 2.0 +/- 0.3 days for the cholesterol-fed animals. Gel filtration chromatography immediately after nucleation again revealed a single mixed micellar peak. These data indicate that cholesterol is carried exclusively in and nucleates rapidly from mixed micelles in the cholesterol-fed prairie dog and that cholesterol-phospholipid vesicles are not required in this process. |
| Cholesterol nucleation in bile Holzbach, R. T. (1995), Ital J Gastroenterol 27(2): 101-5. Abstract: Protein factors, primarily glycoproteins, present in native human bile, have been found to modify, e.g., retard/accelerate, the process of de novo monohydrate crystal formation and, by inference, the rate of formation of cholesterol "nuclei" in such metastable cholesterol supersaturated systems. Neither the process of nucleation itself or how these modifiers work is yet well understood. From the health standpoint, an inhibitor type of protein has been found that may help explain why about 50% of the population have biliary cholesterol supersaturation; whereas, only about 10% actually form gallstones. To date, only one inhibitor glycoprotein has been isolated and characterized. Its role thus seems clear. This is in contrast to the situation with so-called promoter glycoproteins which accelerate nucleation and crystal formation. A number of these proteins have now been identified. An understanding of the comparative roles of each of these proteins has not yet been established. This is partly because of conflicting results, insufficient potencies or lack of information about physiologic concentrations. |
| Cholesterol nucleation time in gallbladder bile of patients with solitary or multiple cholesterol gallstones Jungst, D., T. Lang, et al. (1992), Hepatology 15(5): 804-8. Abstract: Patients with multiple cholesterol gallbladder stones have been found to be at a higher risk for the recurrence of gallstones after successful nonsurgical treatment than those with a solitary stone. Cholesterol gallstone recurrence, like primary gallstone formation, probably involves a triple defect with supersaturation, abnormally rapid nucleation of cholesterol in bile and altered gallbladder motor function. We investigated whether the increased recurrence rate of patients with multiple stones might be caused by more rapid nucleation. Therefore the time required for cholesterol monohydrate crystals to appear in ultracentrifuged bile of patients with solitary (n = 71) or multiple (n = 42) cholesterol gallstones was determined. The cholesterol nucleation time was significantly (p less than 0.01) longer in the bile from patients with solitary stones (less than 1 to 16 days, median = 2.0 days) than in the bile from patients with multiple stones (less than 1 to 8 days, median = 1.0 days). Moreover, 15 of 71 (21.1%) patients with solitary cholesterol stones but only 1 of 42 (2.4%) patients with multiple cholesterol stones showed a normal (greater than 4 days) nucleation time. However, no difference in the cholesterol saturation index was found between the bile samples from patients with solitary stones and the bile samples from patients with multiple stones (1.55 +/- 0.65 vs. 1.54 +/- 0.59, mean +/- S.D., respectively). The more rapid cholesterol nucleation in gallbladder bile may, therefore, be the major risk factor causing the higher percentage of stone recurrence in patients with multiple cholesterol stones as compared with patients with solitary cholesterol stones. |
| Cholesterol nucleation time measurement in nasobiliary or nasoduodenal bile. Comparison with surgical bile Petroni, M. L., R. P. Jazrawi, et al. (1993), Scand J Gastroenterol 28(9): 803-8. Abstract: The usual technique of collecting gallbladder bile at laparotomy is not suitable for sequential studies of cholesterol nucleation time (NT) in patients receiving therapy to prevent or dissolve cholesterol gallstones. Our aim was to study the feasibility of measuring NT in bile obtained by nasobiliary or nasoduodenal intubation. We studied a total of 10 cholesterol gallstone patients; in 8 bile was collected by nasobiliary drainage, in 7 it was collected by nasoduodenal intubation, and in 3 it was collected at laparotomy the next day. Three patients developed abdominal pain and increased serum amylase after endoscopic retrograde cannulation. All three biles obtained at operation nucleated quickly (NT, 1-4 days), whereas duodenal biles were all beyond the expected range (NT, > 21 days). Chymotrypsin activity, as a marker of pancreatic juice contamination, was detected in five of eight nasobiliary biles and in all seven duodenal biles but in none of the surgical biles. Free fatty acids (reflecting lipolysis) were significantly higher in duodenal than in surgical biles, with nasobiliary bile showing intermediate values. Nasobiliary bile showed either a rapid (median NT, 3 days) or a slow (median NT, 22 days) NT, depending on whether chymotrypsin activity was absent or present (p < 0.05). We conclude that duodenal bile is never suitable for NT determination because of contamination by pancreatic enzymes, and that nasobiliary bile, if not contaminated by pancreatic enzymes, may be suitable for NT determination but that its collection via a nasobiliary tube after cholecystokinin injection carries a risk of pancreatitis. |
| Cholesterol of myelin is the determinant of gray-white contrast in MRI of brain Koenig, S. H. (1991), Magn Reson Med 20(2): 285-91. Abstract: The relative brightness of adult white matter in T1-weighted MRI arises from myelin, but the mechanisms responsible remain to be clarified. Koenig et al. Magn. Reson. Med. 14, 482 (1990) conjectured that the cholesterol of myelin (approximately 30% of its lipid) was responsible. We present 1/T1 and magnetization transfer contrast imaging data Wolff and Balaban, Magn. Reson. Med. 10, 135 (1989) on a model system--50% lipid--50% water by weight, with the lipid one-half phosphatidyl choline (PC) and one-half cholesterol--and a control in which the lipid is all PC. The differences between the model and control samples mimic the myelin contribution to white matter in both experiments. |
| Cholesterol operational process specifications for assuring the quality required by CLIA proficiency testing Westgard, J. O. and D. A. Wiebe (1991), Clin Chem 37(11): 1938-44. Abstract: Current U.S. governmental regulations and requirements for the quality of laboratory tests do not provide a consistent form, comparable numbers, or practical specifications for the routine operation of laboratory testing processes. For cholesterol, as an example, the Health Care Financing Administration provides an analytical performance criterion for proficiency testing to enforce the Clinical Laboratory Improvement Act (CLIA), whereas the U.S. National Cholesterol Education Program (NCEP) provides clinical guidelines for test interpretation, as well as analytical goals for imprecision and inaccuracy. Routine operating process specifications for imprecision, inaccuracy, and quality control can be derived from the analytical and clinical requirements for quality. Use of an analytical "total error" model and a clinical "decision interval" model provides logically consistent and numerically comparable specifications. Studies with these coherent models indicate that a cholesterol testing process properly planned to satisfy the CLIA analytical requirement will also satisfy the NCEP clinical requirement. To provide 90% assurance of detecting systematic shifts of a magnitude that would cause the CLIA analytical requirement to be exceeded, the operational specifications for a cholesterol testing process are an allowable CV of less than or equal to 2%, an allowable bias of less than or equal to 1%, and a control procedure with two measurements per run interpreted by 1(3)s, 1(2.5)s, or 1(3)s/2(2)s/R4s control rules. |
| Cholesterol or triglyceride loading of human monocyte-derived macrophages by incubation with modified lipoproteins does not induce tissue factor expression van den Eijnden, M. M., J. T. van Noort, et al. (1999), Arterioscler Thromb Vasc Biol 19(2): 384-92. Abstract: Macrophages/foam cells localized in cholesterol- and triglyceride-rich regions of atherosclerotic plaques express high levels of tissue factor (TF), the essential cofactor and receptor of factor VIIa. It is not clear whether modified lipoproteins, for which several agonistic effects on macrophages have been described, are independent stimuli of TF expression in these cells. Therefore, we studied the effect of short-term (1 day) and long-term (4 to 7 days) incubation of human monocyte-derived macrophages cultured in suspension with modified and native LDLs or VLDLs on the expression of TF mRNA, antigen, and activity. We used native LDL or VLDL, moderately oxidized LDL or VLDL, severely oxidized LDL or VLDL, acetylated LDL, and beta-VLDL at a protein concentration of 100 microg/mL. Cholesterol loading occurred within 9 hours after the addition of acetylated LDL and continued during long-term incubation. Incubation of severely oxidized LDL for 7 days resulted in a slight increase in cholesterol content. Triglyceride loading was observed during short-term and long-term incubation with native and modified VLDLs. Neither cholesterol nor triglyceride loading resulted in expression of TF. Bacterial LPS still could induce TF expression in lipid-laden macrophages. Our results show that incubation with modified lipoproteins or lipid loading does not lead to TF expression in monocyte-derived macrophages cultured in suspension. This suggests that induction of TF expression in foam cells in the atherosclerotic lesion is triggered by additional or other components. |