Selective modulation of estrogen receptor alpha in metabolic and vascular protection : medical implication for a new hormonal treatment of menopause

La diminution de la production de 17&dièse946;-estradiol (E2) à la ménopause s’accompagne de nombreux troubles affectant la qualité de vie des femmes et augmente la survenue de pathologies telles que l’ostéoporose, l’obésité et les maladies cardiovasculaires. Cependant, en raison de préoccupations vis-à-vis du risque de maladies veineuses thromboemboliques et de cancer du sein, moins de 10% des femmes ont recours au traitement de la ménopause actuellement. Il est donc nécessaire de développer de nouvelles options thérapeutiques pour améliorer la santé des femmes. L’estétrol (E4), un œstrogène naturel de la grossesse, est actuellement en essai clinique de phase 3 comme nouveau traitement de la ménopause. Contrairement aux œstrogènes utilisés classiquement, l’E4 n’augmente pas les facteurs de la coagulation et pourrait limiter le risque de thrombose. Les travaux de mon équipe d’accueil ont mis en évidence que l’E4 confère plusieurs effets protecteurs sur le plan artériel dans des modèles précliniques de souris. Cette action bénéfique implique l’activation du récepteur aux œstrogènes (ER)&dièse945;. Toutefois, l’impact de cet œstrogène dans un contexte de perturbations métaboliques en réponse à un régime gras restait inconnu. L’objectif de mon travail de thèse a été double : déterminer l’impact de l’E4 dans un contexte de désordres métaboliques et progresser dans les mécanismes d’action de cet œstrogène dans la protection artérielle. Ainsi, j’ai pu montrer que : L’E4 offre une protection face aux effets délétères d’un régime gras sur différents paramètres métaboliques (prévention de l’obésité et de la stéatose hépatique, normalisation de la glycémie et de l’hyperlipidémie) et sur la paroi artérielle (prévention de l’athérosclérose). L’E4, comme l’E2, accélère la cicatrisation endothéliale après agression de la carotide. Cependant alors que l’E2 active directement ER&dièse945; dans la cellule endothéliale, l’action de l’E4 est relayée par ER&dièse945; dans les cellules musculaires lisses. Cette spécificité d’action de l’E4 est associée à une signature transcriptionnelle qui lui est propre, différente de l’E2 dans la carotide. Ce travail contribue à améliorer notre compréhension du mode d’action de l’E4 sur le plan métabolique et artériel et repositionne cet œstrogène naturel non pas comme un « œstrogène faible » mais comme un véritable modulateur sélectif de ER&dièse945;The decrease in 17&dièse946;-estradiol (E2) production occurring at the time of menopause is associated to a variety of disorders, which can affect greatly the quality of life of women. They also cause an increase in the occurrence of different pathologies such as osteoporosis and metabolic and cardiovascular diseases. However, due to concerns regarding the risk of thromboembolism and of breast cancer, less than 10% of women are currently taking a menopausal hormone treatment. Thus, developing new therapeutic strategies is of great necessity in order to improve women’s health. Estetrol (E4) is a natural estrogen produced by the fetal liver during pregnancy and is currently developed in phase III clinical trial as new hormone treatment. E4 does not increase the production of coagulation factors and thus could lessen the risk of thrombosis. My team’s research work demonstrated that E4 mediates several arterial protective effects in pre-clinical mouse models. These beneficial actions rely on the activation of estrogen receptor (ER)&dièse945;. However, the effect of E4 under metabolic stress, i.e. in response to a high fat diet, was unknown. My PhD project aimed at defining the impact of E4 on metabolic disorders and at exploring the mechanisms of action of this estrogen on the arterial wall. In this context, I shown that: E4 prevents the development of atheroma induced by a high fat diet and the associated metabolic disorders including obesity, liver steatosis, glucose intolerance and hyperlipidemia. As E2, E4 accelerates endothelial healing after injury of the carotid artery. In response to E2, this action depends on the activation of ER&dièse945; directly in endothelial cells, whereas the effect of E4 relies on ER&dièse945; in smooth muscle cells. This differential cellular targeting in response to E4 is associated to a unique transcriptional profile in the carotid, different from E2. Globally, this work refines our understanding of E4 action in metabolic and vascular tissues. Rather than a “weak estrogen”, E4 could be redefined as a selective estrogen receptor modulato

Estetrol prevents western diet-induced obesity and atheroma independently of hepatic estrogen receptor (ER)α

International audienceEstetrol (E4), a natural estrogen synthesized by the human fetal liver, is currently evaluated in phase III clinical studies as a new menopause hormone therapy. Indeed, E4 significantly improves vasomotor and genito-urinary menopausal symptoms and prevents bone demineralization. Compared to other estrogens, E4 was found to have limited effects on coagulation factors in the liver of women allowing to expect less thrombotic events. To fully delineate its clinical potential, the aim of this study was to assess the effect of E4 on metabolic disorders. Here, we studied the pathophysiological consequences of a western diet (42% kcal fat, 0.2% cholesterol) in ovariectomized female mice under chronic E4 treatment. We showed that E4 reduces body weight gain and improves glucose tolerance in both C57Bl/6 and LDLR(-/-) mice. To evaluate the role of hepatic ERα in the preventive effect of E4 against obesity and associated disorders such as atherosclerosis and steatosis, mice harbouring a hepatocyte-specific ERα deletion (LERKO) were crossed with LDLR(-/-) mice. Our results demonstrated that, whereas liver ERα is dispensable for the E4 beneficial actions on obesity and atheroma, it is necessary to prevent steatosis in mice. Overall, these findings suggest that E4 could prevent metabolic, hepatic and vascular disorders occurring at menopause, extending the potential medical interest of this natural estrogen as a new hormonal treatment

The different natural estrogens promote endothelial healing through distinct cell targets

International audienceThe main estrogen, 17β-estradiol (E2), exerts several beneficial vascular actions through estrogen receptor α (ERα) in endothelial cells. However, the impact of other natural estrogens such as estriol (E3) and estetrol (E4) on arteries remains poorly described. In the present study, we report the effects of E3 and E4 on endothelial healing after carotid artery injuries in vivo. After endovascular injury, which preserves smooth muscle cells (SMCs), E2, E3, and E4 equally stimulated reendothelialization. By contrast, only E2 and E3 accelerated endothelial healing after perivascular injury that destroys both endothelial cells and SMCs, suggesting an important role of this latter cell type in E4’s action, which was confirmed using Cre/lox mice inactivating ERα in SMCs. In addition, E4 mediated its effects independently of ERα membrane-initiated signaling, in contrast with E2. Consistently, RNA sequencing analysis revealed that transcriptomic and cellular signatures in response to E4 profoundly differed from those of E2. Thus, whereas acceleration of endothelial healing by estrogens had been viewed as entirely dependent on endothelial ERα, these results highlight the very specific pharmacological profile of the natural estrogen E4, revealing the importance of dialogue between SMCs and endothelial cells in its arterial protection

Tamoxifen Accelerates Endothelial Healing by Targeting ERα in Smooth Muscle Cell.

Rationale: Tamoxifen prevents the recurrence of breast cancer and is also beneficial against bone demineralization and arterial diseases. It acts as an Estrogen Receptor (ER) α antagonist in ER-positive breast cancers, whereas it mimics the protective action of 17β-estradiol (E2) in other tissues such as arteries. However, the mechanisms of these tissue-specific actions remain unclear.Objective: Here, we tested whether tamoxifen is able to accelerate endothelial healing and analyzed the underlying mechanisms. Methods and Results: Using three complementary mouse models of carotid artery injury, we demonstrated that both tamoxifen and estradiol accelerated endothelial healing, but only tamoxifen required the presence of the underlying medial smooth muscle cells. Chronic treatment with E2 and tamoxifen elicited differential gene expression profiles in the carotid artery. The use of transgenic mouse models targeting either whole ERα in a cell-specific manner or ERα sub-functions (membrane/extra-nuclear versus genomic/transcriptional) demonstrated that E2-induced acceleration of endothelial healing is mediated by membrane ERα in endothelial cells, while the effect of tamoxifen is mediated by the nuclear actions of ERα in smooth muscle cells. Conclusions: Whereas tamoxifen acts as an anti-estrogen and ERα antagonist in breast cancer, but also on the membrane ERα of endothelial cells, it accelerates endothelial healing through activation of nuclear ERα in smooth muscle cells, inviting to revisit the mechanisms of action of selective modulation of ERα

Selective Liver Estrogen Receptor Modulation Prevents Steatosis, Diabetes, and Obesity Through the Anorectic Growth Differentiation Factor 15 Hepatokine in Mice

International audienceHepatocyte estrogen receptor α (ERα) was recently recognized as a relevant molecular target for nonalcoholic fatty liver disease (NAFLD) prevention. The present study defined to what extent hepatocyte ERα could be involved in preserving metabolic homeostasis in response to a full (17β-estradiol [E2]) or selective (selective estrogen receptor modulator [SERM]) activation. Ovariectomized mice harboring a hepatocyte-specific deletion ( mice) and their wild-type (WT) littermates were fed a high-fat diet (HFD) and concomitantly treated with E2, tamoxifen (TAM; the most used SERM), or vehicle. As expected, both E2 and TAM prevented all HFD-induced metabolic disorders in WT mice, and their protective effects against steatosis were abolished in mice. However, while E2 still prevented obesity and glucose intolerance in mice, hepatocyte deletion also abrogated TAM-mediated control of food intake as well as its beneficial actions on adiposity, insulin sensitivity, and glucose homeostasis, suggesting a whole-body protective role for liver-derived circulating factors. Moreover, unlike E2, TAM induced a rise in plasma concentration of the anorectic hepatokine growth differentiation factor 15 (Gdf15) through a transcriptional mechanism dependent on hepatocyte ERα activation. Accordingly, ERα was associated with specific binding sites in the regulatory region in hepatocytes from TAM-treated mice but not under E2 treatment due to specific epigenetic modifications. Finally, all the protective effects of TAM were abolished in HFD-fed knockout mice. We identified the selective modulation of hepatocyte ERα as a pharmacologic strategy to induce sufficient anorectic hepatokine Gdf15 to prevent experimental obesity, type 2 diabetes, and NAFLD

Membrane estrogen receptor alpha (ERα) participates in flow-mediated dilation in a ligand-independent manner

International audienceEstrogen receptor alpha (ERα) activation by estrogens prevents atheroma through its nuclear action whereas plasma membrane-located ERα accelerates endothelial healing. The genetic deficiency of ERα was associated with a reduction in flow-mediated dilation (FMD) in one man. Here, we evaluated ex vivo the role of ERα on FMD of resistance arteries. FMD, but not agonist (acetylcholine, insulin)-mediated dilation, was reduced in male and female mice lacking ERα ( Esr1 -/- mice) compared to wild-type mice and was not dependent on the presence of estrogens. In C451A-ERα mice lacking membrane ERα, not in mice lacking AF2-dependent nuclear ERα actions, FMD was reduced, and restored by antioxidant treatments. Compared to wild-type mice, isolated perfused kidneys of C451A-ERα mice revealed a decreased flow-mediated nitrate production and an increased H 2 O 2 production. Thus, endothelial membrane ERα promotes NO bioavailability through inhibition of oxidative stress and thereby participates in FMD in a ligand-independent manner