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Zielinski ZAM, Pratt DA. H-Atom Abstraction vs Addition: Accounting for the Diverse Product Distribution in the Autoxidation of Cholesterol and Its Esters. J Am Chem Soc 2019; 141:3037-3051. [DOI: 10.1021/jacs.8b11524] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Zosia A. M. Zielinski
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Derek A. Pratt
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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2
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Hanashima S, Ibata Y, Watanabe H, Yasuda T, Tsuchikawa H, Murata M. Side-chain deuterated cholesterol as a molecular probe to determine membrane order and cholesterol partitioning. Org Biomol Chem 2019; 17:8601-8610. [DOI: 10.1039/c9ob01342c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
24dCho, which perfectly retains the cholesterol's membrane properties, was developed to examine cholesterol's interactions and membrane partitions using solid state 2H NMR.
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Affiliation(s)
- Shinya Hanashima
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Yuki Ibata
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Hirofumi Watanabe
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Tomokazu Yasuda
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Hiroshi Tsuchikawa
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
| | - Michio Murata
- Department of Chemistry
- Graduate School of Science
- Osaka University
- Toyonaka
- Japan
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3
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Human meibum chain branching variability with age, gender and meibomian gland dysfunction. Ocul Surf 2018; 17:327-335. [PMID: 30553000 DOI: 10.1016/j.jtos.2018.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 11/07/2018] [Accepted: 12/11/2018] [Indexed: 12/26/2022]
Abstract
NMR spectroscopy was used to measure hydrocarbon chain branching variability in meibum with age, gender and Meibomian gland dysfuction (MGD). A cohort of 65 meibum donors without dry eye and 31 donors with MGD was studied. Heteronuclear 2D NMR was used to confirm CH3 resonance assignments allowing us to positively identify 23 of the 27 proton resonances of cholesteryl ester and 1H resonances due to straight chain, iso-branched and anteiso-branched hydrocarbons. Meibum from donors without dry eye contained 57 ± 1% straight-chains, 23 ± 1% iso-branched chains and 20 ± 1% anteiso-branched hydrocarbon chains. Compared with meibum from donors without dry eye, meibum from donors with MGD contained less, 50 ± 2% straight-chains, more, 32 ± 2% iso-branched chains and the same amount, 18.0 ± 0.07%, of anteiso-branched hydrocarbon chains. Meibum hydrocarbon chain branching did not change with age between 22 and 68 years of age, nor was it influenced by gender. Based on previous studies, one would expect anteiso-branched chains would contribute to lowering the phase transition temperature of meibum, decrease the elasticity of the tear film lipid layer and increase the molecular area and spreading of meibum on the surface of the eye. Although we speculate that the observed differences in iso-chain branching do not influence tear film stability or rheology, the speculation has yet to be tested.
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4
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Borchman D, Stimmelmayr R, George JC. Whales, lifespan, phospholipids, and cataracts. J Lipid Res 2017; 58:2289-2298. [PMID: 29038122 DOI: 10.1194/jlr.m079368] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/04/2017] [Indexed: 12/18/2022] Open
Abstract
This study addresses the question: why do rats get cataracts at 2 years, dogs at 8 years, and whales do not develop cataracts for 200 years? Whale lens lipid phase transitions were compared with the phase transitions of other species that were recalculated. The major phospholipids of the whale lens were sphingolipids, mostly dihydrosphingomyelins with an average molar cholesterol/phospholipid ratio of 10. There was a linear correlation between the percentage of lens sphingolipid and lens lipid hydrocarbon chain order until about 60% sphingolipid. The percentage of lens sphingolipid correlated with the lens lipid phase transition temperature. The lifespan of the bowhead whale was the longest of the species measured and the percentage of whale lens sphingolipid fit well in the correlation between the percentage of lens sphingolipid and lifespan for many species. In conclusion, bowhead whale lens membranes have a high sphingolipid content that confers resistance to oxidation, allowing these lenses to stay clear relatively longer than many other species. The strong correlation between sphingolipid and lifespan may form a basis for future studies, which are needed because correlations do not infer cause. One could hope that if human lenses could be made to have a lipid composition similar to whales, like the bowhead, humans would not develop age-related cataracts for over 100 years.
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Affiliation(s)
- Douglas Borchman
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY
| | - Raphaela Stimmelmayr
- Department of Wildlife Management, North Slope Borough, Utqiagvik, AK.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK
| | - J Craig George
- Department of Wildlife Management, North Slope Borough, Utqiagvik, AK
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5
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Nury T, Samadi M, Zarrouk A, Riedinger JM, Lizard G. Improved synthesis and in vitro evaluation of the cytotoxic profile of oxysterols oxidized at C4 (4α- and 4β-hydroxycholesterol) and C7 (7-ketocholesterol, 7α- and 7β-hydroxycholesterol) on cells of the central nervous system. Eur J Med Chem 2013; 70:558-67. [DOI: 10.1016/j.ejmech.2013.09.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 09/05/2013] [Accepted: 09/08/2013] [Indexed: 01/08/2023]
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6
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Kawamoto H, Ohmori Y, Maekawa M, Shimada M, Mano N, Iida T. An efficient synthesis of 4α- and 4β-hydroxy- 7-dehydrocholesterol, biomarkers for patients with and animal models of the Smith–Lemli–Opitz syndrome. Chem Phys Lipids 2013; 175-176:73-8. [DOI: 10.1016/j.chemphyslip.2013.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Revised: 07/15/2013] [Accepted: 07/16/2013] [Indexed: 11/26/2022]
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7
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Ogawa S, Zhou B, Kimoto Y, Omura K, Kobayashi A, Higashi T, Mitamura K, Ikegawa S, Hagey LR, Hofmann AF, Iida T. An efficient synthesis of 7α,12α-dihydroxy-4-cholesten-3-one and its biological precursor 7α-hydroxy-4-cholesten-3-one: Key intermediates in bile acid biosynthesis. Steroids 2013; 78:927-37. [PMID: 23707572 DOI: 10.1016/j.steroids.2013.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 04/10/2013] [Accepted: 05/16/2013] [Indexed: 11/27/2022]
Abstract
This paper describes a method for the chemical synthesis of 7α,12α-dihydroxy-4-cholesten-3-one (1a) and its biological precursor, 7α-hydroxy-4-cholesten-3-one (1b), both of which are key intermediates in the major pathway of bile acid biosynthesis from cholesterol. The principal reactions involved were (1) building of the cholesterol (iso-octane) side chain by 3-carbon elongation of the cholane (iso-pentane) one, (2) oxidation sequence to transform the 3α-hydroxy group of the steroidal A/B-ring to the desired 4-en-3-one system, and (3) appropriate protection strategy for hydroxy groups in the positions at C-7 and C-12 in the steroid nucleus. The absolute structure of 1a and 1b were confirmed by NMR and X-ray crystallography. The targeted compounds 1a and 1b, prepared in 11 steps from 2a and 2b respectively, should be useful for biochemical studies of bile acid biosynthesis or clinical studies of bile acid metabolism, as plasma levels of 1b (also termed C4) have been shown to correlate highly with the rate of bile acid biosynthesis in man.
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Affiliation(s)
- Shoujiro Ogawa
- Faculty of Pharmaceutical Sciences, Tokyo University of Science, Noda, Chiba 278-8510, Japan
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8
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Borchman D, Yappert MC, Milliner SE, Duran D, Cox GW, Smith RJ, Bhola R. 13C and 1H NMR ester region resonance assignments and the composition of human infant and child meibum. Exp Eye Res 2013; 112:151-9. [DOI: 10.1016/j.exer.2013.04.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 04/17/2013] [Accepted: 04/20/2013] [Indexed: 11/29/2022]
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9
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Poirot M, Silvente-Poirot S. Cholesterol-5,6-epoxides: Chemistry, biochemistry, metabolic fate and cancer. Biochimie 2013; 95:622-31. [DOI: 10.1016/j.biochi.2012.05.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/08/2012] [Indexed: 12/02/2022]
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10
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Ubhayasekera SJKA, Dutta PC. Assessment of Sterol Oxidation in Oils Recovered from Exhausted Bleaching Earth by Coupled Capillary Column GC and GC–MS Methods. J AM OIL CHEM SOC 2012. [DOI: 10.1007/s11746-012-2053-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
| | - Paresh C. Dutta
- Division of Food Chemistry, Department of Food ScienceSwedish University of Agricultural SciencesBox 7051 Uppsala BioCentrumUppsalaSE‐75007Sweden
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11
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Jiang X, Sidhu R, Porter FD, Yanjanin NM, Speak AO, te Vruchte DT, Platt FM, Fujiwara H, Scherrer DE, Zhang J, Dietzen DJ, Schaffer JE, Ory DS. A sensitive and specific LC-MS/MS method for rapid diagnosis of Niemann-Pick C1 disease from human plasma. J Lipid Res 2011; 52:1435-45. [PMID: 21518695 DOI: 10.1194/jlr.d015735] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Niemann-Pick type C1 (NPC1) disease is a rare, progressively fatal neurodegenerative disease for which there are no FDA-approved therapies. A major barrier to developing new therapies for this disorder has been the lack of a sensitive and noninvasive diagnostic test. Recently, we demonstrated that two cholesterol oxidation products, specifically cholestane-3β,5α,6β-triol (3β,5α,6β-triol) and 7-ketocholesterol (7-KC), were markedly increased in the plasma of human NPC1 subjects, suggesting a role for these oxysterols in diagnosis of NPC1 disease and evaluation of therapeutics in clinical trials. In the present study, we describe the development of a sensitive and specific LC-MS/MS method for quantifying 3β,5α,6β-triol and 7-KC human plasma after derivatization with N,N-dimethylglycine. We show that dimethylglycine derivatization successfully enhanced the ionization and fragmentation of 3β,5α,6β-triol and 7-KC for mass spectrometric detection of the oxysterol species in human plasma. The oxysterol dimethylglycinates were resolved with high sensitivity and selectivity, and enabled accurate quantification of 3β,5α,6β-triol and 7-KC concentrations in human plasma. The LC-MS/MS assay was able to discriminate with high sensitivity and specificity between control and NPC1 subjects, and offers for the first time a noninvasive, rapid, and highly sensitive method for diagnosis of NPC1 disease.
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Affiliation(s)
- Xuntian Jiang
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St. Louis, MO, USA
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12
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Busch TP, King AJ. Stability of Cholesterol, 7-Ketocholesterol and β-Sitosterol during Saponification: Ramifications for Artifact Monitoring of Sterol Oxide Products. J AM OIL CHEM SOC 2010; 87:955-962. [PMID: 20835297 PMCID: PMC2923713 DOI: 10.1007/s11746-010-1572-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 01/29/2010] [Accepted: 03/09/2010] [Indexed: 12/01/2022]
Abstract
Cholesterol has been used to monitor artifact generation. Stability differences among cholesterol oxide products (COPs) and cholesterol in thermal and alkaline conditions are theorized. Thus, use of cholesterol may be unsuitable for detection of artifacts generated from COPs. Stability of cholesterol was compared to that of 7-ketocholesterol (7-keto) and β-sitosterol (βS) under various thermal and alkaline saponification conditions: 1 M methanolic KOH for 18 h at 24 °C (1 M18hr24°C, Control), 18 h at 37 °C (1M18hr37°C), 3 h at 45 °C (1M3hr45°C), and 3.6 M methanolic KOH for 3 h at 24 °C (3.6M3hr24°C). Trends indicated that cholesterol in solution was more stable than 7-keto under all conditions. Compared to βS, cholesterol was more stable under all conditions except for 1M18hr37°C for which stabilities were similar. Compounds were more labile in heat than alkalinity. Poor recoveries of 7-keto during cold saponification with high alkalinity were attributed to alkaline instability. 7-Keto, less stable than cholesterol, should be used to monitor artifact generation during screening of various methods that include thermal and alkaline conditions. In a preliminary analysis of turkey meat, more 3,5-7-one was generated from spiking with cholesterol than with 7-keto.
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Affiliation(s)
- T. P. Busch
- Kraft Oscar Mayer, 910 Mayer Blvd, Madison, WI 53704 USA
| | - A. J. King
- Department of Animal Science, University of California, Davis, One Shields Avenue, Davis, CA 95616 USA
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13
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Carvalho JFS, Cruz Silva MM, Moreira JN, Simões S, Sá e Melo ML. Efficient Chemoenzymatic Synthesis, Cytotoxic Evaluation, and SAR of Epoxysterols. J Med Chem 2009; 52:4007-19. [DOI: 10.1021/jm9003973] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- João F. S. Carvalho
- Centro de Estudos Farmacêuticos, Laboratório Quíımica Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Laboratório de Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Center for Neurosciense and Cell Biology, University of Coimbra, Portugal
| | - M. Manuel Cruz Silva
- Centro de Estudos Farmacêuticos, Laboratório Quíımica Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Laboratório de Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Center for Neurosciense and Cell Biology, University of Coimbra, Portugal
| | - João N. Moreira
- Centro de Estudos Farmacêuticos, Laboratório Quíımica Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Laboratório de Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Center for Neurosciense and Cell Biology, University of Coimbra, Portugal
| | - Sérgio Simões
- Centro de Estudos Farmacêuticos, Laboratório Quíımica Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Laboratório de Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Center for Neurosciense and Cell Biology, University of Coimbra, Portugal
| | - M. Luisa Sá e Melo
- Centro de Estudos Farmacêuticos, Laboratório Quíımica Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Laboratório de Tecnologia Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-548 Coimbra, Portugal, Center for Neurosciense and Cell Biology, University of Coimbra, Portugal
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14
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Sterols and Oxidized Sterols in Feed Ingredients Obtained from Chemical and Physical Refining Processes of Fats and Oils. J AM OIL CHEM SOC 2009. [DOI: 10.1007/s11746-009-1388-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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15
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Artifact generation and monitoring in analysis of cholesterol oxide products. Anal Biochem 2009; 388:1-14. [DOI: 10.1016/j.ab.2008.12.034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Revised: 12/24/2008] [Accepted: 12/26/2008] [Indexed: 11/17/2022]
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16
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Abdel-Sattar E, Harraz FM, Al-ansari SMA, El-Mekkawy S, Ichino C, Kiyohara H, Ishiyama A, Otoguro K, Omura S, Yamada H. Acylated pregnane glycosides from Caralluma tuberculata and their antiparasitic activity. PHYTOCHEMISTRY 2008; 69:2180-6. [PMID: 18614190 DOI: 10.1016/j.phytochem.2008.05.017] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 04/12/2008] [Accepted: 05/27/2008] [Indexed: 05/19/2023]
Abstract
Five pregnane glycosides were isolated from Caralluma tuberculata (1-5), in addition to a known one (russelioside E, 6). The structures of the isolated compounds were elucidated by the analysis of NMR data and FAB-MS experiments. All the isolated compounds were tested for their antimalarial and antitrypanosomal activities as well as their cytotoxicity against human diploid embryonic cell line (MRC5).
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Affiliation(s)
- Essam Abdel-Sattar
- Department of Natural Products and Alternative Medicine, Faculty of Pharmacy, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
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17
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Drozdov FV, Mekhtiev AR, Morozevich GE, Timofeev VP, Misharin AI. Cytotoxic derivatives of (22R,23R)-dihydroxystigmastane. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2007; 33:349-56. [PMID: 17682392 DOI: 10.1134/s1068162007030090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
(22R,23R)-22,23-dihydroxystigmast-4-en-3-one, (22R,23R)-22,23-dihydroxystigmast-4-en-3,6-dione, (22R,23R)-3beta,5alpha,6beta,22,23-pentahydroxystigmastane, (22R,23R)-5alpha,6alpha-oxido-3beta,22,23-trihydroxystigmastane, (22R,23R)-5beta,6beta-oxido-3beta,22,23-trihydroxystigmastane, and (22R,23R)-3beta,6beta,22,23-tetrahydroxystigmast-4-ene were synthesized. Their cytotoxicities were comparatively studied using the MCF-7 line of carcinoma cells of human mammary gland and cells of human hepatoma of the Hep G2 line.
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18
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Ryan E, Chopra J, McCarthy F, Maguire AR, O'Brien NM. Qualitative and quantitative comparison of the cytotoxic and apoptotic potential of phytosterol oxidation products with their corresponding cholesterol oxidation products. Br J Nutr 2007; 94:443-51. [PMID: 16176617 DOI: 10.1079/bjn20051500] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phytosterols contain an unsaturated ring structure and therefore are susceptible to oxidation under certain conditions. Whilst the cytotoxicity of the analogous cholesterol oxidation products (COP) has been well documented, the biological effects of phytosterol oxidation products (POP)have not yet been fully ascertained. The objective of the present study was to examine the cytotoxicity of β-sitosterol oxides and their corresponding COP in a human monocytic cell line (U937), a colonic adenocarcinoma cell line (CaCo-2) and a hepatoma liver cell line (HepG2). 7β-Hydroxysitosterol, 7-ketositosterol, sitosterol-3β,5α,6β-triol and a sitosterol-5α,6α-epoxide–sitosterol-5β,6β-epoxide (6:1) mixture were found to be cytotoxic to all three cell lines employed; the mode of cell death was by apoptosis in the U937 cell line and necrosis in the CaCo-2 and HepG2 cells. 7β-Hydroxysitosterol was the only β-sitosterol oxide to cause depletion in glutathione, indicating that POP-induced apoptosis may not be dependent on the generation of an oxidative stress. A further objective of this study was to assess the ability of the antioxidants α-tocopherol, γ-tocopherol and β-carotene to modulate POP-induced cytotoxicity in U937 cells. Whilst α/γ-tocopherol protected against 7β-hydroxycholesterol-induced apoptosis, they did not confer protection against 7β-hydroxysitosterol-or 7-ketositosterol-induced toxicity, indicating that perhaps COP provoke different apoptotic pathways than POP. β-Carotene did not protect against COP- or POP-induced toxicity. In general, results indicate that POP have qualitatively similar toxic effects to COP. However, higher concentrations of POP are required to elicit comparable levels of toxicity.
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Affiliation(s)
- Eileen Ryan
- Department of Food and Nutritional Sciences, University College, Cork, Ireland
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19
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Zhao K, Wang Y, Han L. 4,5-Epoxycholestane-3,6-diols: templates for generating the full set of eight cholestane-3,5,6-triol stereoisomers in multigram scales, but not for a cholestane-3,4,6-triol. Steroids 2007; 72:95-104. [PMID: 17174367 DOI: 10.1016/j.steroids.2006.11.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2005] [Revised: 10/27/2006] [Accepted: 11/13/2006] [Indexed: 11/16/2022]
Abstract
Cholestane-3beta,5alpha,6beta-triol is an extensively studied biologically important oxysterol. The full set of eight cholestane-3,5,6-triol stereoisomers was synthesised in diastereomerically pure forms by the stereoselective cleavage of eight diastereomerically pure 4,5-epoxycholestane-3,6-diols with LiAlH4, in high yields on multigram scales and without chromatography for most of them. However, applying various reportedly successful combinations of a hydride donor and a Lewis acid to the same substrates under a variety of conditions failed to generate a single unsubstituted cholestane-3,4,6-triol. The products of the eight cholestane-3,5,6-triol stereoisomers will serve as a good probe in the study of biological functions of oxysterols in a biological process.
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Affiliation(s)
- Kejun Zhao
- School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
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20
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Roussi S, Winter A, Gosse F, Werner D, Zhang X, Marchioni E, Geoffroy P, Miesch M, Raul F. Different apoptotic mechanisms are involved in the antiproliferative effects of 7beta-hydroxysitosterol and 7beta-hydroxycholesterol in human colon cancer cells. Cell Death Differ 2005; 12:128-35. [PMID: 15550935 DOI: 10.1038/sj.cdd.4401530] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Plant sterols are found in fruits and vegetables. Their cholesterol-lowering effect is well documented. Our study aimed at comparing antiproliferative effects of 7beta-hydroxysitosterol (7beta-OHsito) versus 7beta-hydroxycholesterol (7beta-OHchol) on the human colon cancer cell line Caco-2. When cells were exposed for 32 h to 60 microM 7beta-OHsito or to 30 microM 7beta-OHchol, both compounds caused 50% growth inhibition. Cells treated with 7beta-OHsito showed enhanced caspase-9 and -3 activities followed by DNA fragmentation. In contrast, 7beta-OHchol did not activate caspase-3 and activation of caspase-9 and DNA fragmentation were delayed. The treatment of cells with the caspase inhibitor Z-VAD.fmk retarded the 7beta-OHsito-induced apoptotic process but not that triggered by 7beta-OHchol. Our data suggest that the two compounds in spite of their structural similarities target different cellular pathways, which lead to cell death.
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Affiliation(s)
- S Roussi
- Laboratoire d'Oncologie Nutritionnelle, Inserm UMR S392/IRCAD, 1, place de l'Hôpital, BP 406, Strasbourg Cedex 67091, France
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21
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Flegentov GI, Piĭr EA, Medvedeva NV, Tkachev IV, Timofeev VP, Misharin AI. [New delta8(14)-ketosterols with an oxygenated side chain]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2005; 31:312-9. [PMID: 16004390 DOI: 10.1007/s11171-005-0038-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
New analogues of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one (15-ketosterol) with modified 17-chains [(22S,23S,24S)- and (22R,23R,24S)-3beta-hydroxy-24-methyl-22,23-oxido-5alpha-cholest-8(14)-en-15-ones and (22RS,23xi,24S)-24-methyl-5alpha-cholesta-3beta,22,23-triol-15-one] were synthesized from (22E,24S)-3beta-acetoxy-24-methyl-5alpha-cholesta-8(14),22-dien-15-one. The chiralities of their 22 and 23 centers were determined by NMR spectroscopy. The isomeric 22,23-epoxides effectively inhibited cholesterol biosynthesis in hepatoma Hep G2 cells (IC50 0.9 +/- 0.2 and 0.7 +/- 0.2 microM, respectively), and their activities significantly exceeded those of 15-ketosterol (IC50 4.0 +/- 0.5 microM), (22E,24S)-3beta-hydroxy-24-methyl-5alpha-cholesta-8(14),22-dien-15-one (IC50 3.1 +/- 0.4 microM), and the 3beta,22,23-triol synthesized (IC50 6.0 +/- 1.0 microM). The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 3; see also http://www.maik.ru.
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22
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McCarthy FO, Chopra J, Ford A, Hogan SA, Kerry JP, O'Brien NM, Ryan E, Maguire AR. Synthesis, isolation and characterisation of β-sitosterol and β-sitosterol oxide derivatives. Org Biomol Chem 2005; 3:3059-65. [PMID: 16186940 DOI: 10.1039/b505069c] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Beta-sitosterol is the most prevalent plant cholesterol derivative (phytosterol) and can undergo similar oxidation to cholesterol, leading to beta-sitosterol oxides. The biological impact of phytosterol oxides has only been evaluated in a phytosterol blend (usually of beta-sitosterol, campesterol, stigmasterol and dihydrobrassicasterol). The lack of pure phytosterols, including beta-sitosterol, hinders the collection of significant toxicity data on the individual beta-sitosterol oxides. An efficient synthetic route to multi-gram quantities of pure beta-sitosterol is described here, together with the first syntheses and characterisation of pure beta-sitosterol oxides.
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Affiliation(s)
- Florence O McCarthy
- Department of Chemistry, School of Pharmacy, Analytical and Biological Chemistry Research Facility, University College Cork, Cork, Ireland.
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23
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Lu W, Zhang C, Zeng L, Su J. Synthesis of polyhydroxysterols (V): efficient and stereospecific synthesis of 24-methylene-cholest-5-ene-3beta,7alpha-diol and its C-7 epimer. Steroids 2004; 69:803-8. [PMID: 15582535 DOI: 10.1016/j.steroids.2004.09.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Revised: 09/08/2004] [Accepted: 09/10/2004] [Indexed: 11/28/2022]
Abstract
This paper describes the efficient and stereospecific synthesis of cytotoxic dihydroxylated sterols, 24-methylene-cholest-5-ene-3beta,7alpha-diol 1, and its C-7 epimer, 24-methylene-cholest-5-ene-3beta,7beta-diol 2. The crux of the synthesis is that the selective allylic oxidation of 24-methylene-cholesteryl acetate proceeds to 24-methylene-7-keto-cholesteryl acetate without extensive byproduct formation from reaction at the Delta24(28) double bond. This methodology may be useful for the preparation of other oxysterols with non-standard side chains.
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Affiliation(s)
- Weigang Lu
- School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China
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24
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Grandgirard A, Martine L, Joffre C, Juaneda P, Berdeaux O. Gas chromatographic separation and mass spectrometric identification of mixtures of oxyphytosterol and oxycholesterol derivatives. J Chromatogr A 2004; 1040:239-50. [PMID: 15230531 DOI: 10.1016/j.chroma.2004.04.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pure individual phytosterols were prepared using reversed-phase HPLC in order to obtain the oxidized compounds of sitosterol, campesterol, stigmasterol and brassicasterol. 7-Hydroxy-, 7-keto-, 5,6-epoxy-, 4beta-hydroxy-, 4-ene-6-hydroxy-, 6-keto- and 5alpha,6beta-dihydroxyphytosterols were obtained as well as analogous compounds of cholesterol. The gas chromatographic properties as well as the electronic impact mass spectra of these compounds (as trimethylsilyl ether derivatives) were studied. These data were used to identify oxyphytosterols in a spread enriched in phytosterols: the oxyphytosterols represented no more than 68 microg/g of spread (about 0.08% of phytosterols were oxidised).
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Affiliation(s)
- A Grandgirard
- Unité de Nutrition Lipidique, INRA, 17 Rue Sully, B.P. 86510, 21065 Dijon Cedex, France.
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25
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Johannes C, Lorenz RL. Preparation and mass spectrometry of 14 pure and 18O2-labeled oxidation products from the phytosterols β-sitosterol and stigmasterol. Anal Biochem 2004; 325:107-16. [PMID: 14715290 DOI: 10.1016/j.ab.2003.10.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
To lower cholesterol, phytosterols are currently introduced as food additives, where they may become oxidized. In addition, specific biological effects of oxyphytosterols are suggested by the recent molecular clarification of the phytosterol storage disease as a dysfunctional mutation of an active sterol reexporter potentially regulated by oxidized phytosterols. We therefore studied the hydroxybenzotriazole-mediated PbO(2)-driven oxidation of phytosterols and compared it to the oxidation of cholesterol. We prepared, identified, and purified standards of 14 oxidation products of two major phytosterols. The gas chromatographic mass spectrometric characteristics of the 7alpha- and 7beta-hydroxy-, 5alpha,6alpha-epoxy, 5beta,6beta-epoxy, 7keto-, 3beta,5alpha,6beta-trihydroxy-, 3keto-, and 7-dehydro-derivatives of beta-sitosterol and stigmasterol are presented. The method also provided a convenient access to prepare 18O-labeled oxyphytosterols of high chemical and isotopic purity and can easily be extended to further phytosterols and -stanols. This enables the gas chromatography-mass spectrometry analysis of oxyphytosterols and the study of their biological effects.
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Affiliation(s)
- Christian Johannes
- Institute for Prophylaxis of Cardiovascular Diseases, University of Munich, Pettenkofer Str. 9, 80336 Munich, Germany
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26
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Motta GE, Jackson EM, Klein ML, Shan H, Pang J, Wilson WK, McMahan CA. Programming of initial steps in bile acid synthesis by breat-feeding vs. Formula-feeding in the baboon. Lipids 2003; 38:1213-20. [PMID: 14870923 DOI: 10.1007/s11745-003-1181-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We tested the hypothesis that breast- vs. formula-feeding differentially affects the enzymatic activity of three sterol hydroxylases critical in the initial steps of bile acid formation. Thirty baboons were either breast-fed or formula-fed for the first 14 wk of life before weaning to baboon chow. At 14 and 34 wk of age, liver biopsies were assayed for cholesterol 7alpha-hydroxylase (CYP7A1), 27-hydroxycholesterol-7alpha-hydroxylase (CYP7B1), and cholesterol 27-hydroxylase (CYP27A1). We also determined the kinetics of 3H-27-hydroxycholesterol (27-OHC) turnover in vivo at both ages. At 14 wk of age, hepatic CYP7A1 activity was low but sevenfold higher among formula-fed vs. breast-fed baboons. By 34 wk, CYP7A1 activity had increased nearly 10-fold in both infant diet groups, and the sevenfold difference in CYP7A1 between previously breast- and formula-fed animals persisted. There were no differences in CYP7B1 activities between infant diet groups at either 14 or 34 wk of age although the activity increased in both groups by about 50% from 14 to 34 wk. CYP27A1 activity also increased between 14 and 34 wk of age, and, compared with CYP7A1, relatively small differences in CYP27A1 activity due to infant diet were observed at each age. Plasma 27-OHC turnover had a half-time of 2-4 min. We had previously reported that after weaning, the total bile acid synthesis rate was higher among baboons that were formula-fed than among breast-fed animals. The present results suggest that this difference is most likely due to significantly higher CYP7A1 activity among formula-fed vs. breast-fed animals.
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Affiliation(s)
- Glen E Motta
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
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27
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Shan H, Pang J, Li S, Chiang TB, Wilson WK, Schroepfer GJ. Chromatographic behavior of oxygenated derivatives of cholesterol. Steroids 2003; 68:221-33. [PMID: 12628685 DOI: 10.1016/s0039-128x(02)00185-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Oxygenated derivatives of cholesterol have important functions in many biochemical processes. These oxysterols are difficult to study because of their low physiological concentrations, the facile formation of cholesterol autoxidation artifacts, and lack of information on their chromatographic behavior. Focusing on metabolites and autoxidation products of cholesterol, we have documented the chromatographic mobilities of 35 oxysterols under a variety of conditions: eight solvent systems for thin-layer chromatography on silica gel, several mobile phases for reversed-phase high-performance liquid chromatography (HPLC), and two types of stationary phase for capillary gas chromatography (GC) using trimethylsilyl derivatives. Notable differences in selectivity could be obtained by modifying the stationary or mobile phases. Separations of oxysterol pairs isomeric at side-chain carbons or C-7 were achieved on normal-phase, reversed-phase, chiral, or silver-ion HPLC columns. Chromatographic behavior is also described for side-chain hexadeuterated and heptafluorinated oxysterols, which are useful as standards in isotope dilution analyses and autoxidation studies, respectively. The overall results are relevant to many problems of oxysterol analysis, including the initial separation of oxysterols from cholesterol, determination of highly polar and nonpolar oxysterols, separation of isomeric pairs, selection of derivatization conditions for GC analysis, and quantitation of the extent of cholesterol autoxidation.
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Affiliation(s)
- Hui Shan
- Department of Biochemistry and Cell Biology, Rice University, MS 140, 6100 Main Street, Houston, TX 77005-1892, USA
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28
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Ciuffreda P, Casati S, Bollini D, Santaniello E. Synthesis of (20S)-[7,7,21,21-2H4]-3beta-(tert-butyldimethylsilanyloxy)-20-methyl-pregn-5-en-21-ol, a useful intermediate for the preparation of deuterated isotopomers of sterols. Steroids 2003; 68:193-8. [PMID: 12606010 DOI: 10.1016/s0039-128x(02)00172-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
(20S)-[7,7,21,21-2H(4)]-3beta-(tert-Butyldimethylsilanyloxy)-20-methyl-pregn-5-en-21-ol, an intermediate for the preparation of deuterated isotopomers of sterols to be used as standards for biomedical studies, was prepared by reduction with dichloroaluminum deuteride of ethyl (20S)-3beta-(tert-butyldimethylsilanyloxy)-7-oxo-pregn-5-en-20-carboxylate. Using controlled experimental conditions, it has also been shown that the dichloroaluminum hydride reduction of a 7-keto steroid affords the corresponding 7beta-hydroxy derivative in a highly stereoselective manner.
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Affiliation(s)
- Pierangela Ciuffreda
- Dipartimento di Scienze Precliniche LITA Vialba, Via G.B. Grassi, 74-20157 Milano, Italy
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29
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Guo LW, Wilson WK, Pang J, Shackleton CHL. Chemical synthesis of 7- and 8-dehydro derivatives of pregnane-3,17alpha,20-triols, potential steroid metabolites in Smith-Lemli-Opitz syndrome. Steroids 2003; 68:31-42. [PMID: 12475721 DOI: 10.1016/s0039-128x(02)00113-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Pregnane-3,17 alpha,20-triols bearing unsaturation at delta(7), delta(8), delta(5,7), or delta(5,8) have been tentatively identified as steroid metabolites in Smith-Lemli-Opitz syndrome (SLOS). Starting with 17 alpha-hydroxypregnenolone diacetate, we have synthesized 13 unsaturated C(21) triols by four different routes in one to four steps. These multifunctional steroids were prepared by a series of regio- and stereoselective transformations chosen to minimize facile olefin isomerization and 17-deoxygenation. The results include a study of stereoselectivity in the reduction of 17 alpha-hydroxy-20-ketosteroids, an alternative method for reducing diethyl azodicarboxylate adducts of delta(5,7) steroids, and an efficient oxidation-isomerization of a delta(5,7) steroid using cholesterol oxidase. The 13 triols and their synthetic precursors were fully characterized by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The NMR data, together with molecular modeling, indicated unanticipated conformational heterogeneity for two synthetic intermediates, 17 alpha-hydroxypregna-4,7-diene-3,20-dione and 17 alpha-hydroxy-5 beta-pregn-7-ene-3,20-dione. The unsaturated C(21) triols are useful as reference standards to study adrenal steroid production in SLOS and to develop methods for pre- and postnatal diagnosis of this congenital disorder.
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Affiliation(s)
- Li-Wei Guo
- Department of Biochemistry and Cell Biology, Rice University, 6100 Main Street, Houston, TX 77005-1892, USA
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30
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Plat J, Brzezinka H, Lütjohann D, Mensink RP, von Bergmann K. Oxidized plant sterols in human serum and lipid infusions as measured by combined gas-liquid chromatography-mass spectrometry. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31532-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Abstract
This article describes the most commonly used procedures and recent laboratory methodologies using gas and liquid chromatography developed for separation and quantitation of non-saponifiable steroidal lipids from clinical (human) studies, edible fats and oils or fatty foods.
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Affiliation(s)
- P Volin
- Caloniuksenk. 10 C 47, Helsinki, Finland
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32
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Javitt NB, Lee YC, Shimizu C, Fuda H, Strott CA. Cholesterol and hydroxycholesterol sulfotransferases: identification, distinction from dehydroepiandrosterone sulfotransferase, and differential tissue expression. Endocrinology 2001; 142:2978-84. [PMID: 11416019 DOI: 10.1210/endo.142.7.8244] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In humans, the biotransformation of cholesterol and its hydroxylated metabolites (oxysterols) by sulfonation is a fundamental process of great importance. Nevertheless, the sulfotransferase enzyme(s) that carries out this function has never been clearly identified. Cholesterol is a relatively poor substrate for the previously cloned hydroxysteroid sulfotransferase (HST), i.e. dehydroepiandrosterone (DHEA) sulfotransferase (HST1). Recently, cloning of a single human gene that encodes for two proteins related to HST1 was reported. These newly cloned sulfotransferases (HST2a and HST2b), while exhibiting sequence similarity to other members of the soluble sulfotransferase superfamily, also contain unique structural features. This latter aspect prompted an examination of their substrate specificity for comparison with HST1. Thus, HST1, HST2a, and HST2b were overexpressed as fusion proteins and purified. Furthermore, a novel procedure for the isolation of cholesterol and oxysterol sulfonates was developed that was used in association with HPLC to resolve specific sterol sulfonates. HST1 preferentially sulfonated DHEA and, to a lesser extent, oxysterols; whereas cholesterol was a negligible substrate. The reverse, however, was the case for the HST2 isoforms, particularly HST2b, which preferentially sulfonated cholesterol and oxysterols, in contrast to DHEA, which served as a poor substrate for this enzyme. RT-PCR analysis revealed distinct patterns of HST1, HST2a, and HST2b expression. It was particularly notable that both HST2 isoforms, but not HST1, were expressed in skin, a tissue where cholesterol sulfonation plays an important role in normal development of the skin barrier. In conclusion, substrate specificity and tissue distribution studies strongly suggest that HST2a and HST2b, in contrast to HST1, represent normal human cholesterol and oxysterol sulfotransferases. Furthermore, this study represents the first example of the sulfonation of oxysterols by a specific human HST.
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Affiliation(s)
- N B Javitt
- Section on Steroid Regulation, Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.
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33
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Biellmann JF. Resolution of alcohols by cholesterol oxidase fromRrhodococcus erythropolis: lack of enantiospecificity for the steroids. Chirality 2001; 13:34-9. [PMID: 11135412 DOI: 10.1002/1520-636x(2001)13:1<34::aid-chir7>3.0.co;2-o] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- J F Biellmann
- Laboratoire de Chimie Organique Biologique, Faculte de Chimie, Université Louis Pasteur, Strasbourg, France
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34
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Li S, Pang J, Jackson EM, Wilson WK, Mott GE, Schroepfer GJ. Kinetics and plasma concentrations of 26-hydroxycholesterol in baboons. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1485:173-84. [PMID: 10832098 DOI: 10.1016/s1388-1981(00)00058-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
26-Hydroxycholesterol (26OHC), a major oxysterol in human blood, is believed to play an important role in reverse cholesterol transport, bile acid formation, and regulation of various cellular processes. Using isotope dilution mass spectrometry, we measured plasma 26OHC concentrations in baboons fed either a high cholesterol/saturated fat (HC-SF) or normal chow diet. Plasma 26OHC levels in baboons were comparable to those reported for humans and were positively correlated with plasma cholesterol concentrations. Animals on the HC-SF diet had significantly higher 26OHC levels (0.274+/-0.058 microM, mean+/-S.D.) than those on the chow diet (0.156+/-0.046 microM). In separate experiments, [(3)H]26OHC was injected into four tethered baboons, and multiple blood samples drawn over a 1-h period were analyzed for [(3)H]26OHC and 26OHC. Fitting the specific radioactivity data to a two-pool compartmental model indicated a rapidly turning over plasma compartment (t(1/2) 2.9-6.0 min) and a second compartment with slow turnover (t(1/2) 76-333 min). The calculated 26OHC production rate was 2.5 micromol/kg body weight/day. Assuming all 26OHC is converted to bile acids, the 26OHC production rate corresponds to about 10% of total bile acid production in adult baboons. These results indicate that rapid turnover of plasma 26OHC at submicromolar concentrations could significantly contribute to bile acid synthesis.
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Affiliation(s)
- S Li
- Department of Biochemisrty and Cell Biology, Rice University, Houston, TX 77005-1892, USA
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35
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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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