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Nannapaneni DT, Chinthapally K, Hatial I, Ashfeld BL, Blagg BS. A succinct synthesis of (25R)-cholesta-5,7-diene-3β,26-diol from ergosterol. Tetrahedron Lett 2022. [DOI: 10.1016/j.tetlet.2022.153974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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2
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Parish EJ, Aksara N, Boos TL, Kaneshiro ES. Remote Functionalization of the Cholestane Side-chain by Chromyl Acetates. JOURNAL OF CHEMICAL RESEARCH 2019. [DOI: 10.1177/174751989902301212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chromyl acetate and chromyl trifluoroacetate are effective reagents for the oxidation of C-25 on cholestane side-chains to the corresponding C-25 hydroxy derivative.
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Affiliation(s)
- Edward J. Parish
- Department of Chemistry, Auburn University, Auburn, AL 36849-5312, USA
| | - Nida Aksara
- Department of Chemistry, Auburn University, Auburn, AL 36849-5312, USA
| | - Terrence L. Boos
- Department of Chemistry, Auburn University, Auburn, AL 36849-5312, USA
| | - Edna S. Kaneshiro
- Department of Biological Sciences, University of Cincinnati, OH 45221, USA
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Nunomura S, Okayama Y, Matsumoto K, Hashimoto N, Endo-Umeda K, Terui T, Makishima M, Ra C. Activation of LXRs using the synthetic agonist GW3965 represses the production of pro-inflammatory cytokines by murine mast cells. Allergol Int 2015; 64 Suppl:S11-7. [PMID: 26344074 DOI: 10.1016/j.alit.2015.03.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 02/26/2015] [Accepted: 03/03/2015] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND The activation of liver X receptor (LXR) α or LXRβ negatively regulates the expression of pro-inflammatory genes in mammalian cells. We recently reported that 25-hydroxycholesterol, a representative LXR-activating oxysterol, suppresses IL-6 production in mouse mast cells (MCs) following its engagement of the high-affinity IgE receptor (FcεRI). This finding suggests that murine MCs express functional LXRs; however, the mechanisms underlying the LXR-dependent repression of the MC-mediated production of pro-inflammatory cytokines, including IL-6, are poorly understood. Therefore, we employed the synthetic LXR ligand GW3965 to examine the functions of LXRα and LXRβ in the production of pro-inflammatory cytokines by murine bone marrow-derived MCs (BMMCs). METHODS We prepared BMMCs from wild-type (WT), LXRα(-/-), and LXRα/β(-/-) mice. Each group of BMMCs was pretreated with GW3965 and then stimulated with IgE+antigen (Ag) or lipopolysaccharide (LPS). Cytokine production was then analyzed using specific ELISA kits. RESULTS The activation of LXRs by GW3965 significantly attenuated the production of IL-1α and IL-1β, but not of IL-6, in the WT and LXRα(-/-) BMMCs stimulated with IgE+Ag. However, GW3965 treatment decreased the production of IL-1α, IL-1β, and IL-6 in WT and LXRα(-/-) BMMCs upon stimulation with LPS, while the GW3965-mediated suppression of cytokine production was nearly absent from the LXRα/β(-/-) BMMCs. CONCLUSIONS These findings demonstrate, for the first time, that the activation of LXRs by GW3965 attenuates the antigen- or LPS-induced production of pro-inflammatory cytokines, such as IL-1α and IL-1β, in murine MCs and that LXRβ plays an important role in the LXR-mediated repression of cytokine production.
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Salvador JAR, Carvalho JFS, Neves MAC, Silvestre SM, Leitão AJ, Silva MMC, Sá e Melo ML. Anticancer steroids: linking natural and semi-synthetic compounds. Nat Prod Rep 2013; 30:324-74. [PMID: 23151898 DOI: 10.1039/c2np20082a] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.
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Affiliation(s)
- Jorge A R Salvador
- Laboratory of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Coimbra, Polo das Ciências da Saúde, 3000-508, Coimbra, Portugal.
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5
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Li S, Parish E, Bell A. Chemistry of Waxes and Sterols. FOOD SCIENCE AND TECHNOLOGY 2008. [DOI: 10.1201/9781420046649.ch4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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6
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Lange Y, Ory DS, Ye J, Lanier MH, Hsu FF, Steck TL. Effectors of rapid homeostatic responses of endoplasmic reticulum cholesterol and 3-hydroxy-3-methylglutaryl-CoA reductase. J Biol Chem 2007; 283:1445-1455. [PMID: 18024962 DOI: 10.1074/jbc.m706967200] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cholesterol content of the endoplasmic reticulum (ER) and the activity of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) imbedded therein respond homeostatically within minutes to changes in the level of plasma membrane cholesterol. We have now examined the roles of sterol regulatory element-binding protein (SREBP)-dependent gene expression, side chain oxysterol biosynthesis, and cholesterol precursors in the short term regulation of ER cholesterol levels and HMGR activity. We found that SREBP-dependent gene expression is not required for the response to changes in cell cholesterol of either the pool of ER cholesterol or the rate of cholesterol esterification. It was also found that the acute proteolytic inactivation of HMGR triggered by cholesterol loading required the conversion of cholesterol to 27-hydroxycholesterol. High levels of exogenous 24,25-dihydrolanosterol drove the inactivation of HMGR; lanosterol did not. However, purging endogenous 24,25-dihydrolanosterol, lanosterol, and other biosynthetic sterol intermediates by treating cells with NB-598 did not greatly affect either the setting of their ER cholesterol pool or the inactivation of their HMGR. In summary, neither SREBP-regulated genes nor 27-hydroxycholesterol is involved in setting the ER cholesterol pool. On the other hand, 27-hydroxycholesterol, rather than cholesterol itself or biosynthetic precursors of cholesterol, stimulates the rapid inactivation of HMGR in response to high levels of cholesterol.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois 60612.
| | - Daniel S Ory
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Jin Ye
- Department of Pathology, Rush University Medical Center, Chicago, Illinois 60612
| | - Michael H Lanier
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Fong-Fu Hsu
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637
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7
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Parish EJ, Luo C, Webb T, Gorden JD. Syntheses of Ring C Oxysterols: Inhibitors of Sterol Biosynthesis. Lipids 2007; 42:35-40. [PMID: 17393208 DOI: 10.1007/s11745-006-3000-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Accepted: 11/18/2006] [Indexed: 11/26/2022]
Abstract
Oxygenated derivates of cholesterol and lanosterol, known as oxysterols, have consistently displayed significant activity as inhibitors of 3-hydroxy-3-methylglutaryl (HMG) CoA reductase, a key regulatory enzyme in sterol biosynthesis. We have developed the chemical syntheses of ring C oxysterols for evaluation as inhibitors of sterol biosynthesis. A key intermediate in the chemical synthesis was 3beta-benzoyloxy-9alpha, 1alpha-epoxy-5alpha-cholest-7-ene (1), whose structure was confirmed by X-ray crystallographic analysis and is presented herein.
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Affiliation(s)
- Edward J Parish
- Department of Chemistry and Biochemistry, Auburn University, Auburn, AL 336849, USA,
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Heverin M, Meaney S, Lütjohann D, Diczfalusy U, Wahren J, Björkhem I. Crossing the barrier: net flux of 27-hydroxycholesterol into the human brain. J Lipid Res 2005; 46:1047-52. [PMID: 15741649 DOI: 10.1194/jlr.m500024-jlr200] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Side chain oxidized oxysterols have a unique ability to traverse lipophilic membranes. We tested the hypothesis that there is a net flux of 27-hydroxycholesterol from the circulation into the brain using plasma samples collected from the internal jugular vein and an artery of healthy male volunteers. Two independent studies were performed, one in which total levels of 27-hydroxycholesterol were measured and one in which the free fraction of 27-hydroxycholesterol was measured. In the majority of subjects studied, the level of 27-hydroxycholesterol was higher in the artery than in the vein, and uptake from the circulation was calculated to be about 5 mg/24 h. The distribution of 27-hydroxycholesterol in human brain was found to be consistent with an extracerebral origin, with a concentration gradient from the white to the gray matter--a situation opposite that of 24S-hydroxycholesterol, which os exclusively formed in brain. In view of the fact that the blood-brain barrier is impermeable to cholesterol and that 27-hydroxycholesterol is a potent regulator of several cholesterol-sensitive genes, the flux of 27-hydroxycholesterol into the brain may be and important link between intra- and extracerebral cholesterol homeostasis.
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Affiliation(s)
- Maura Heverin
- Department of Surgical Sciences, Karolinska University Hospital, Solna, Sweden
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Abstract
A sensitive method was developed for measuring farnesyl diphosphate (FPP) accumulation in a mutant strain of Saccharomyces cerevisiae. The strain was blocked at squalene synthase (ERG9 gene) in the isoprenoid pathway and had the catalytic domain of the 3-hydroxy-3-methylglutaryl coenzyme A reductase gene integrated into the chromosome. It required ergosterol for growth and produced E,E-farnesol. The method was based on the isolation of FPP using the anion exchanger Macro Prep High Q and conversion of FPP to E,E-farnesol with alkaline phosphatase. Farnesol was measured using gas chromatography-mass spectrometry. Background farnesol in the cell-free extract was also retained by the anion exchanger, but was removed with repeated washing with methanol. Both 1M NaCl and 40% (v/v) methanol were required in the elution buffer to effectively elute FPP. The preparation of cell-free extract in Bis-Tris propane/HCl, pH 7, buffer containing 0.025% (w/v) Triton X-100 and 15 mM MgCl(2) provided optimum conditions for the stabilization of FPP.
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Affiliation(s)
- Linsheng Song
- Bio-Technical Resources, 1035 South 7th Street, Manitowoc, WI 54220, USA.
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10
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O'Sullivan AJ, O'Callaghan YC, Woods JA, O'Brien NM. Toxicity of cholesterol oxidation products to Caco-2 and HepG2 cells: modulatory effects of alpha- and gamma-tocopherol. J Appl Toxicol 2003; 23:191-7. [PMID: 12794941 DOI: 10.1002/jat.906] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Cholesterol can be oxidized to form a variety of cholesterol oxidation products also known as oxysterols. The aims of the present study were to compare the cytotoxic effects of four oxysterols, namely 25-hydroxycholesterol (25-OHC), 7beta-hydroxycholesterol (7beta-OHC), cholesterol-5beta,6beta-epoxide (beta-epox) and cholesterol-5alpha,6alpha-epoxide (alpha-epox), in two human cell culture models. Further, the ability of 10 and 100 micro m alpha- and gamma-tocopherol (alpha-TOC and gamma-TOC, respectively) to protect against oxysterol-induced cytotoxicity was also assessed. Human colonic adenocarcinoma Caco-2 and human hepatoma HepG2 cells were supplemented with increasing concentrations of 25-OHC, 7beta-OHC, beta-epox and alpha-epox (0-25 micro g ml(-1)) for 24, 48 or 96 h. Following 24-h and 48-h exposure, test media were replaced with normal growth media and the cells were maintained for 72 and 48 h, respectively. The 96-h exposure represented a constant challenge to the cells. Cytotoxicity was assessed using the neutral red uptake assay. The concentration of compound that inhibited cell viability by 50% (ic(50) value) was calculated. All four oxysterols investigated induced the greatest cytotoxic effects following 96 h of exposure. 25-Hydroxycholesterol exhibited the greatest cytotoxicity in both cell lines. Both beta-epox and alpha-epox were more toxic to HepG2 cells than to Caco-2 cells after the 48-h exposure. Pretreatment of cells with either alpha- or gamma-TOC did not protect against oxysterol-induced cytotoxicity. The caco-2 cells treated with the high concentration (100 micro m) of gamma-TOC were found to be more susceptible to oxysterol-induced toxicity under the conditions employed in this study.
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Affiliation(s)
- A J O'Sullivan
- Department of Food and Nutritional Sciences, University College Cork, Ireland
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Abstract
The identification of caveolin-1 more than a decade ago initiated active research into its role in the formation of caveolae, membrane trafficking, signal transduction pathways, and lipid homeostasis. Although caveolins are ubiquitously expressed, the majority of the available information comes from differentiated cells rich in caveolins, such as fibroblasts, adipocytes, and endothelial cells. During the development of atherosclerosis, macrophages play a pivotal role in the formation of the fatty streak lesions. They take up large amounts of lipids and accumulate in the subendothelial space, forming foam cells that fill up the lesion area. Since caveolins have been implicated in the regulation of cellular cholesterol metabolism in several cell types, it is of interest to examine their potential function in macrophages. In this review, we attempt to summarize current knowledge and views on the role of caveolins in cholesterol metabolism with emphasis on macrophages.
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Affiliation(s)
- Peter Gargalovic
- Department of Molecular Biology & Immunology, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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Lyons NM, Woods JA, O'Brien NM. alpha-Tocopherol, but not gamma-tocopherol inhibits 7 beta-hydroxycholesterol-induced apoptosis in human U937 cells. Free Radic Res 2001; 35:329-39. [PMID: 11697131 DOI: 10.1080/10715760100300861] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Oxysterols, particularly those oxidised at position 7, are toxic to cells in culture and have been shown to induce apoptosis in cell types such as vascular endothelial cells, smooth muscle cells and monocytes. The precise mechanism by which oxysterols induce apoptosis is unknown but may involve the generation of oxidative stress. In the present study we examined the ability of alpha-TOC, alpha-TOC acetate (alpha-TOCA) and gamma-TOC to protect against 7 beta-hydroxycholesterol (7 beta-OHC)-induced apoptosis of human monocytic U937 cells. 7 beta-OHC is one of the most commonly detected oxysterols in foods and its level in plasma has been positively associated with an increased risk of atherosclerosis. The present study demonstrates a significant decrease in cell membrane integrity and cellular glutathione levels when U937 cells were treated with 30 microM 7 beta-OHC. DNA fragmentation also occurred, as measured by agarose gel electrophoresis, and the number of apoptotic cells increased as assessed by nuclear morphology. Analysis by HPLC showed that there was a greater incorporation of gamma-TOC into U937 cells after a 48 h incubation, than either alpha-TOC or alpha-TOCA. However, despite the increased uptake of gamma-TOC, only alpha-TOC, and not gamma-TOC or alpha-TOCA was effective at inhibiting 7 beta-OHC-induced apoptosis in U937 cells.
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Affiliation(s)
- N M Lyons
- Department of Food Science, Food Technology and Nutrition, University College Cork, Republic of Ireland
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13
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Abstract
Excessive cholesterol is eliminated from extrahepatic cells by reverse cholesterol transport, a process by which neutral sterols are transferred to extracellular acceptor lipoproteins for further transport to the liver. Another process independent of lipoproteins involves excretion of 3beta-hydroxy-5-cholesten-25(R)-26-carboxylic (cholestenoic) acid, a metabolite of 27-hydroxycholesterol. Physiological concentrations of cholestenoic acid activated the nuclear receptor liver X receptor alpha (LXR alpha; NR1H3), but not other oxysterol receptors. As a ligand, cholestenoic acid modulated interaction of LXR alpha with the nuclear receptor coactivator Grip-1. Cholestenoic acid, therefore, may function as a signaling molecule for regulation of lipid metabolism via LXR alpha.
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Affiliation(s)
- C Song
- Ben May Institute for Cancer Research, University of Chicago, Illinois 60637, USA
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Osada K, Minehira K, Inoue S, Nakamura S, Yamada K, Sugano M. Effect of oxidized cholesterol on age-associated changes to immune parameters in spleen lymphocytes and peritoneal exudate cells derived from rats. Biosci Biotechnol Biochem 2000; 64:1047-51. [PMID: 10879478 DOI: 10.1271/bbb.64.1047] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of oxidized cholesterol on immune parameters were examined by using spleen lymphocytes and peritoneal exudate cells (PEC) derived from 5-week- (Young) and 9-month-old (Adult) rats. The immunoglobulin (Ig) G and IgM production was inhibited by oxidized cholesterol in the rats of both ages when lymphocytes were exposed to 30 micrograms/ml of oxidized cholesterol for 24 hr. The intracellular IgA level was also lowered by 30 micrograms/ml of oxidized cholesterol, irrespective of age. In contrast, IgE production was significantly increased by the addition of 30 micrograms/ml of oxidized cholesterol in only young lymphocytes. Moreover, oxidized cholesterol enhanced the intracellular histamine accumulation in only adult PEC, although the total histamine level produced by PEC was similar in the rats of both ages. These results thus suggest the possibility that oxidized cholesterol can have different effects on the age-related modulation of immune functions such as Igs production and histamine release.
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Affiliation(s)
- K Osada
- Laboratory of Applied Life Science, Faculty of Agriculture and Life Science, Hirosaki University, Japan.
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Johnson BH, Russell MJ, Krylov AS, Medh RD, Ayala-Torres S, Regner JL, Thompson EB. Structure-apoptotic potency evaluations of novel sterols using human leukemic cells. Lipids 2000; 35:305-15. [PMID: 10783008 DOI: 10.1007/s11745-000-0527-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Three oxidized analogs of cholesterol have been characterized for their ability to cause apoptotic cell death in CEM-C7-14 human leukemic cells. In addition to testing 15-ketocholestenol (K15), 15-ketocholestenol hydroxyethyl ether (CK15), and 7-ketocholesterol hydroxyethyl ether (CK7), an oxysterol of known apoptotic response, 25-hydroxycholesterol (25OHC), served as a standard for comparison. Growth studies based on dye exclusion by viable cells while using a sublethal concentration of oxysterols ranked their potency for cell kill as 25OHC > K15 > CK15 > CK7. Both the TUNEL assay (terminal deoxynucleotidyl transferase-mediated dUTP-X nick end labeling), which quantifies the amount of DNA nicks caused by a toxic agent, and the MTT assay, which measures cell metabolism and thus reflects cell viability, substantiated the same rank order. An ELISA assay for evaluating release of DNA fragments into the cytosol after treatment gave a similar potency order. The oncogene c-myc mRNA was suppressed by all three oxysterols, with 25OHC and K15 being the most potent suppressors. Hoechst and Annexin V staining documented that these oxysterols kill cells by an apoptotic pathway as evidenced by condensation of nuclear chromatin and plasma membrane inversion, respectively. From these in vitro studies, we believe that 25OHC, K15, and possibly CK15 have the potential to be chemotherapeutic agents.
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Affiliation(s)
- B H Johnson
- Department of Human Biological Chemistry and Genetics, The University of Texas Medical Branch, Galveston 77555-0645, USA
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Minehira K, Inoue S, Nonaka M, Osada K, Yamada K, Sugano M. Effects of dietary protein type on oxidized cholesterol-induced alteration in age-related modulation of lipid metabolism and indices of immune function in rats. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1483:141-53. [PMID: 10601703 DOI: 10.1016/s1388-1981(99)00169-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Exogenous oxidized cholesterol disturbs both lipid metabolism and immune functions. Therefore, it may perturb these modulations with ageing. Effects of the dietary protein type on oxidized cholesterol-induced modulations of age-related changes in lipid metabolism and immune function was examined using differently aged (4 weeks versus 8 months) male Sprague-Dawley rats when casein, soybean protein or milk whey protein isolate (WPI) was the dietary protein source, respectively. The rats were given one of the three proteins in diet containing 0.2% oxidized cholesterols mixture. Soybean protein, as compared with the other two proteins, significantly lowered both the serum thiobarbituric acid reactive substances value and cholesterol, whereas it elevated the ratio of high density lipoprotein-cholesterol/cholesterol in young rats, but not in adult. Moreover, soybean protein, but not casein and WPI, suppressed the elevation of Delta6 desaturation indices of phospholipids in both liver and spleen, particularly in young. On the other hand, WPI, compared to the other two proteins, inhibited the leukotriene B4 production of spleen, irrespective of age. Soybean protein reduced the ratio of CD4(+)/CD8(+) T-cells in splenic lymphocytes. Therefore, the levels of immunoglobulin (Ig)A, IgE and IgG in serum were lowered in rats given soybean protein in both age groups except for IgA in adult, although these observations were not shown in rats given other proteins. Thus, various perturbations of lipid metabolism and immune function caused by oxidized cholesterol were modified depending on the type of dietary protein. The moderation by soybean protein on the change of lipid metabolism seems to be susceptible in young rats whose homeostatic ability is immature. These observations may be exerted through both the promotion of oxidized cholesterol excretion to feces and the change of hormonal release, while WPI may suppress the disturbance of immune function by oxidized cholesterol in both ages. This alleviation may be associated with a large amount of lactoglobulin in WPI. These results thus showed a possibility that oxidized cholesterol-induced perturbations of age-related changes of lipid metabolism and immune function can be moderated by both the selection and combination of dietary protein.
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Affiliation(s)
- K Minehira
- Laboratory of Food Science, Kyushu University, School of Agriculture, Fukuoka, Japan
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Abstract
Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.
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Affiliation(s)
- G J Schroepfer
- Departments of Biochemistry, Rice University, Houston, Texas, USA.
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Kisseleva AF, Goryunova LE, Medvedeva NV, Alquier C, Morozkin AD. Distribution of exogenous 25-hydroxycholesterol in Hep G2 cells between two different pools. FEBS Lett 1999; 446:163-8. [PMID: 10100635 DOI: 10.1016/s0014-5793(99)00207-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Binding of [26,27-(3)H]25-hydroxycholesterol (25HC) to human hepatoma Hep G2 cells was saturated within 120 min. Two intracellular pools of 25HC were identified in a pulse-chase experiment: (i) an exchangeable pool which was in dynamic equilibrium with 25HC in the medium (t(1/2) of reversible exchange 15 min) and (ii) an unexchangeable pool which remained in cells during incubation in medium containing LPDS. 25HC from the exchangeable pool inhibits cholesterol biosynthesis, decreases the HMG CoA reductase mRNA level and stimulates cholesterol acylation. 25HC from the unexchangeable pool was partially bound to cytosolic proteins and apparently utilized for metabolic transformation. Incubation of Hep G2 cells with [26,27-(3)H]25HC in the presence of a 30-fold molar excess of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one was found to cause (i) 2-fold decrease in the binding of [26,27-(3)H]25HC to cytosolic proteins (sedimentation constant of radioactive complex was 4-5 S) and (ii) the 35% inhibition of 25HC transformation to polar metabolites.
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Affiliation(s)
- A F Kisseleva
- Institute of Experimental Cardiology, Cardiology Research Center, Moscow, Russia
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Woods JA, O'Brien NM. Investigation of the potential genotoxicity of cholesterol oxidation products in two mammalian fibroblast cell lines. Nutr Cancer 1998; 31:192-8. [PMID: 9795971 DOI: 10.1080/01635589809514702] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Cholesterol oxidation products (oxysterols) are generated during the cooking and processing of foods and may be produced endogenously in tissues and in the plasma membrane. A diverse range of biological functions have been ascribed to oxysterols, including atherogenicity, carcinogenicity, and mutagenicity, and in recent years concern has been expressed over the presence of oxysterols in food products. However, it is unclear whether oxysterols are capable of inducing genotoxic damage in cell culture systems. The aim of this study was to examine seven commonly occurring oxysterols (purity > 95%) for their cytotoxicity and ability to increase the frequency of DNA strand breaks and sister chromatid exchanges (SCE) in cells in culture. Two cell lines were employed in the study: Chinese hamster ovary (CHO) and Indian Muntjac (IM) fibroblasts. The 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide assay, which is a measure of intracellular reductive metabolism based on the activity of mitochondrial dehydrogenases, was used as an index of cytotoxicity. The most cytotoxic oxysterols in constantly challenged CHO or IM cells (24-h exposure) proved to be 5 alpha-cholestane-3 beta,5,6 beta-triol and 25-hydroxy-cholesterol. The genotoxic potential of the oxysterols was assessed in CHO cells using the comet assay and IM cells using the SCE assay. The comet assay measures breaks in the DNA strand, whereas the exact mechanism of SCE formation is unclear but is believed to require DNA repair where genetic material becomes exchanged between the two sister chromatids. None of the oxysterols examined in this study affected baseline levels of DNA strand breaks or SCE relative to the negative control samples. This study indicates that, under the conditions used, the oxysterols investigated were not genotoxic.
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Affiliation(s)
- J A Woods
- Department of Nutrition, University College, Cork, Republic of Ireland
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21
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Abstract
By using classical methods of organic synthesis, the introduction of chemical modifications into the saturated side-chains of steroids usually requires a multistep synthesis to construct new side-chains to be added to the steroid nucleus. In order to circumvent these earlier methods, new procedures have been developed to directly introduce functionality onto the steroid side-chain to produce useful products. These initial products may also provide an entry toward the further modification of the side-chain to produce steroids which could previously be obtained only with great difficulty.
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Affiliation(s)
- E J Parish
- Department of Chemistry, Auburn University, Alabama 36849, USA.
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22
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Abstract
Material dealing with the chemistry, biochemistry, and biological activities of oxysterols is reviewed for the period 1987-1995. Particular attention is paid to the presence of oxysterols in tissues and foods and to their physiological relevance.
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Affiliation(s)
- L L Smith
- University of Texas Medical Branch, Galveston 77555-0653, USA
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