Identification and pharmacological characterization of cholesterol-5,6-epoxide hydrolase as a target for tamoxifen and AEBS ligands

Médina, Philippe de; Paillasse, Michaël R.; Ségala, Grégory; Poirot, Marc; Silvente-Poirot, Sandrine

doi:10.1073/pnas.1002922107

Cited by 109 publications

(100 citation statements)

References 39 publications

(38 reference statements)

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“…Cholesterol biosynthesis involves enzymes organized at the site of the Anti Estrogen Binding Site (AEBS). AEBS is a molecular complex constituted by two cholesterogenic enzymes, the DHCR7 reductase and the D8D7I isomerase, whose association makes a third catalytic activity, namely the cholesterol epoxyde hydrolase [32]. Ligands of AEBS trigger macroautophagy in tumor cells through modulation of cholesterol metabolism [33],and a link between microautophagy of the late endosome compartment and exosome 6 production has been proposed [22], suggesting a role of cholesterol in exosome biogenesis.…”

Section: Sorting Lipids In Exosomes (Figure 2)mentioning

confidence: 99%

Exosomes as intercellular signalosomes and pharmacological effectors

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Silvente-Poirot

et al. 2011

Biochemical Pharmacology

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International audienceCell secretion is a general process involved in various biological responses. Exosomes are part of this process and have gained considerable scientific interest in the past five years. Several steps through investigations across the last 20years can explain this interest. First characterized during reticulocyte maturation, they were next characterized as a key player in the immune response and cancer immunotherapy. More recently they were characterized as vectors of mRNAs, miRNAs and also lipid mediators able to act on target cells. They are the only type of vesicles released from an intracellular compartment from cells in viable conditions. They appear as a vectorized signaling system operating from inside a donor cell towards either the periphery, the cytosol, or possibly to the nucleus of target cells. Exosomes from normal cells trigger positive effects, whereas those from pathological ones, such as tumor cells or infected ones may trigger non-positive health effects. Therefore regulating the biogenesis and secretion of exosomes appear as a pharmacological challenge to intervene in various pathophysiologies. Exosome biogenesis and molecular content, interaction with target cells, utilisation as biomarkers, and functional effects in various pathophysiologies are considered in this review

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Section: Sorting Lipids In Exosomes (Figure 2)mentioning

confidence: 99%

Exosomes as intercellular signalosomes and pharmacological effectors

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Subra

Silvente-Poirot

et al. 2011

Biochemical Pharmacology

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“…Retention factors (R f ) were determined for each spot on the TLC plates as the ratio of the distance of migration of the eluate from the origin and the distance of the solvent from the origin. 5,6-EC have a R f = 0.67 ( 2 ).…”

Section: Procedures For Comparing Epoxide Reactivity In Cell Culture Mmentioning

confidence: 99%

Surprising unreactivity of cholesterol-5,6-epoxides towards nucleophiles

Paillasse

Saffon

Gornitzka

et al. 2012

Journal of Lipid Research

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This article is available online at http://www.jlr.org thesis ( 2 ). We showed that ChEH was fully inhibited by therapeutic doses of AEBS ligands, including drugs belonging to different pharmacological classes and widely used nutritional compounds. These compounds include tamoxifen (tam), one of the main drugs used for the fi rstline and long-term hormone therapy of breast cancers; raloxifene, which has been approved for the prevention of osteoporosis ( 3 ); amiodarone, which is widely used for the prevention and the treatment of anti-arrhythmia ( 4 ); trifluoroperazine, an antipsychotic drug used for the treatment of schizophrenia ( 5 ); and the omega-3 fatty acid docosahexaenoic acid, which is widely proposed as dietary supplement with health benefi ts ( 2 ). Extensive knowledge of the mechanism of action of all these molecules is required to prevent toxicity to patients submitted to longterm treatment with such inhibitors of ChEH.AEBS/ChEH ligands, such as tam and raloxifene, were recently shown to induce cell differentiation and death of breast cancer cells through a mechanism involving sterol accumulation and autoxidation ( 6-8 ) leading to the production of 5,6-EC, suggesting that 5,6-EC accumulation is involved in their anticancer and chemopreventitive activity. This is contrary to the initial hypothesis that the biological function of ChEH was to detoxify 5,6-EC. This hypothesis emerged because it was initially postulated that 5,6-EC could, like other chemicals bearing epoxide groups, be potent alkylating substances and, hence, carcinogenic ( 9 ).Abstract We recently established that drugs used for the treatment and the prophylaxis of breast cancers, such as tamoxifen, were potent inhibitors of cholesterol-5,6-epoxide hydrolase (ChEH), which led to the accumulation of 5,6 ␣ -epoxy-cholesterol (5,6 ␣ -EC) and 5,6 ␤ -epoxy-cholesterol (5,6 ␤ -EC). This could be considered a paradox because epoxides are known as alkylating agents with putative carcinogenic properties. We report here that, as opposed to the carcinogen styrene-oxide, neither of the ECs reacted spontaneously with nucleophiles. Under catalytic conditions, 5,6 ␤ -EC remains unreactive whereas 5,6 ␣ -EC gives cholestan-3 ␤ ,5 ␣ -diol-6 ␤ -substituted compounds. These data showed that 5,6-ECs are stable epoxides and unreactive toward nucleophiles in the absence of a catalyst, which contrasts with the well-known reactivity of aromatic and aliphatic epoxides. These data rule out 5,6-EC acting as spontaneous alkylating agents. In addition, these data support the existence of a stereoselective metabolism of 5,6 ␣ -EC. Cholesterol-5,6-epoxide hydrolase (ChEH; EC 3.3.2.11) catalyzes the stereoselective hydration of cholesterol-5,6-epoxide diastereoisomers (5,6-EC: 5,6 ␣ -EC and 5,6 ␤ -EC) into cholestane-3 ␤ ,5 ␣ ,6 ␤ -triol (CT) ( 1 ). We recently reported the molecular identifi cation of this enzyme and established that ChEH activity was carried out by the microsomal antiestrogen binding site (AEBS), which consists of two subunits: the 3 ␤ -hydroxyste...

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“…Neither styrene 7,8-oxide, a generic substrate that is hydrolyzed by most EHs ( 32 ), nor cholesterol 5,6-epoxide, a substrate for a membrane-bound human EH of which the identifi cation has been reported during the preparation of this article ( 33 ), was converted to the corresponding diol by EH3. In contrast, we did detect a high turnover of 9,10-epoxystearic acid with the recombinant cell lysate, an enzymatic activity that was essentially absent from mock-infected insect cell lysates.…”

Section: Cloning and Expression Of Eh3mentioning

confidence: 99%