Maeva Guillaume

The activation function-1 of estrogen receptor alpha prevents arterial neointima development through a direct effect on smooth muscle cells

Supplemental Digital Content is available in the text.

Role of ERα in the Effect of Estradiol on Cancellous and Cortical Femoral Bone in Growing Female Mice

Estrogen receptor-α (ERα) acts primarily in the nucleus as a transcription factor involving two activation functions, AF1 and AF2, but it can also induce membrane-initiated steroid signaling (MISS) through the modulation of various kinase activities and/or secondary messenger levels. Previous work has demonstrated that nuclear ERα is required for the protective effect of the estrogen 17β-estradiol (E2), whereas the selective activation of ERαMISS is sufficient to confer protection in cortical but not cancellous bone. The aim of this study was to define whether ERαMISS is necessary for the beneficial actions of chronic E2 exposure on bone. We used a mouse model in which ERα membrane localization had been abrogated due to a point mutation of the palmitoylation site of ERα (ERα-C451A). Alterations of the sex hormones in ERα-C451A precluded the interpretation of bone parameters that were thus analyzed on ovariectomized and supplemented or not with E2 (8 μg/kg/d) to circumvent this bias. We found the beneficial action of E2 on femoral bone mineral density as well as in both cortical and cancellous bone was decreased in ERα-C451A mice compared with their wild-type littermates. Histological and biochemical approaches concurred with the results from bone marrow chimeras to demonstrate that ERαMISS signaling affects the osteoblast but not the osteoclast lineage in response to E2. Thus, in contrast to the uterine and endothelial effects of E2 that are specifically mediated by nuclear ERα and ERαMISS effects, respectively, bone protection is dependent on both, underlining the exquisite tissue-specific actions and interactions of membrane and nuclear ERα.

Effect of chronic estradiol plus progesterone treatment on experimental arterial and venous thrombosis in mouse

Postmenopausal hormone replacement therapy (HRT) with estrogen plus progestogens is the first line therapy to treat menopausal symptoms. The progestogen is added to estrogen to reduce or eliminate the excess risk of endometrial cancer due to the unopposed effect of estrogen. Whereas progestin clearly opposes the proliferative and deleterious long-term actions of estrogen on the endometrium, the interference of progestin on the other estrogen action remains unclear. We previously reported that chronic subcutaneous 17α-estradiol (E2) in mice decreases platelet responsiveness, prolongs the tail-bleeding time and protects against acute thromboembolism. Here, we report the tissue-specific interference of progesterone (P4) on the action of E2 in ovariectomized mice. We first confirm that, in our experimental conditions, P4 attenuates the proliferative action of E2 on the uterus and the effects of E2 on vagina weight and lubrication. We then studied the effect of E2 combined with P4 on hemostasis and thrombosis in vivo in mice and found that P4 did not interfere with the main actions of E2 on platelets, bleeding time and arterial and venous thrombosis. Thus, whereas activation of progesterone receptor interferes with the action of E2 on its classic sex targets, P4 appears to have minimal effect on the hemostasis and thrombosis actions of E2, supporting the prominent role of estrogens and the accessory role of natural progestin on the extra-reproductive cells and tissues involved in thrombosis.

Protective Hematopoietic Effect of Estrogens in a Mouse Model of Thrombosis: Respective Roles of Nuclear Versus Membrane Estrogen Receptor α

We recently reported that chronic 17β-estradiol (E2) treatment in mice decreases platelet responsiveness, prolongs the tail-bleeding time and protects against acute thromboembolism via the hematopoietic estrogen receptor alpha (ERα), and independently of ERβ. Here, we have explored the respective roles of membrane vs nuclear actions of ERα in this process, using: 1) the selective activator of membrane ERα: estrogen dendrimer conjugate, and 2) mouse models with mutations in ERα. The selective targeting of activation function 2 of ERα provides a model of nuclear ERα loss-of-function, whereas mutation of the ERα palmitoylation site leads to a model of membrane ERα deficiency. The combination of pharmacological and genetic approaches including hematopoietic chimera mice demonstrated that absence of either membrane or nuclear ERα activation in bone marrow does not prevent the prolongation of the tail-bleeding time, suggesting a redundancy of these two functions for this E2 effect. In addition, although hematopoietic membrane ERα is neither sufficient nor necessary to protect E2-treated mice from collagen/epinephrine-induced thromboembolism, the protection against death-induced thromboembolism is significantly reduced in the absence of hematopoietic nuclear ERα activation. Overall, this study emphasizes that hematopoietic cells (likely megakaryocytes and possibly immune cells) constitute an important target in the antithrombotic effects of estrogens, and delineate for the first time in vivo the respective roles of membrane vs nuclear ERα effects, with a prominent role of the latter.

Nuclear and Membrane Actions of Estrogen Receptor Alpha: Contribution to the Regulation of Energy and Glucose Homeostasis

Estrogen receptor alpha (ERα) has been demonstrated to play a key role in reproduction but also to exert numerous functions in nonreproductive tissues. Accordingly, ERα is now recognized as a key regulator of energy homeostasis and glucose metabolism and mediates the protective effects of estrogens against obesity and type 2 diabetes. This chapter attempts to summarize our current understanding of the mechanisms of ERα activation and their involvement in the modulation of energy balance and glucose metabolism. We first focus on the experimental studies that constitute the basis of the understanding of ERα as a nuclear receptor and more specifically on the key roles played by its two activation functions (AFs). We depict the consequences of the selective inactivation of these AFs in mouse models, which further underline the prominent role of nuclear ERα in the prevention of obesity and diabetes, as on the reproductive tract and the vascular system. Besides these nuclear actions, a fraction of ERα is associated with the plasma membrane and activates nonnuclear signaling from this site. Such rapid effects, called membrane-initiated steroid signals (MISS), have been characterized in a variety of cell lines and in particular in endothelial cells. The development of selective pharmacological tools that specifically activate MISS as well as the generation of mice expressing an ERα protein impeded for membrane localization has just begun to unravel the physiological role of MISS in vivo and their contribution to ERα-mediated metabolic protection. Finally, we discuss novel perspectives for the design of tissue-selective ER modulators.

Towards optimization of estrogen receptor modulation in medicine

ABSTRACT Women now spend more than one‐third of their lives in the postmenopausal years, and the decline of endogenous estrogen production during menopause is accompanied by a series of functional disorders that affect the quality of life. These symptoms could be alleviated or even totally suppressed by menopausal hormone therapy (MHT), initially based on natural estrogens extracted from the urine of pregnant mares (mainly in the USA, using the oral route) and later from the synthesis of the natural estrogen, 17&bgr;‐estradiol (mainly in Europe, in particular using the transdermal route). Estrogen receptor (ER) &agr; is the main receptor mediating the physiological effects of estrogens. ER&agr; belongs to the nuclear receptor superfamily and activates gene transcription in a time and tissue‐specific manner through two distinct activation functions (AF), AF1 and AF2. In addition to these classical genomic actions, ER&agr; also mediates membrane initiated signaling enabling rapid actions of estrogen, potentially along or in interaction with other receptors. Here, we provide a brief historical overview of MHT, and we then highlight recent advances in the characterization of new treatments based on the association of estrogens with selective estrogen receptor modulators (SERMs) or on the modulation of nuclear or membrane ER&agr;.

Estrogen receptor subcellular localization and cardiometabolism

Background In addition to their crucial role in reproduction, estrogens are key regulators of energy and glucose homeostasis and they also exert several cardiovascular protective effects. These beneficial actions are mainly mediated by estrogen receptor alpha (ERα), which is widely expressed in metabolic and vascular tissues. As a member of the nuclear receptor superfamily, ERα was primarily considered as a transcription factor that controls gene expression through the activation of its two activation functions (ERαAF-1 and ERαAF-2). However, besides these nuclear actions, a pool of ERα is localized in the vicinity of the plasma membrane, where it mediates rapid signaling effects called membrane-initiated steroid signals (MISS) that have been well described in vitro, especially in endothelial cells. Scope of the review This review aims to summarize our current knowledge of the mechanisms of nuclear vs membrane ERα activation that contribute to the cardiometabolic protection conferred by estrogens. Indeed, new transgenic mouse models (affecting either DNA binding, activation functions or membrane localization), together with the use of novel pharmacological tools that electively activate membrane ERα effects recently allowed to begin to unravel the different modes of ERα signaling in vivo. Conclusion Altogether, available data demonstrate the prominent role of ERα nuclear effects, and, more specifically, of ERαAF-2, in the preventive effects of estrogens against obesity, diabetes, and atheroma. However, membrane ERα signaling selectively mediates some of the estrogen endothelial/vascular effects (NO release, reendothelialization) and could also contribute to the regulation of energy balance, insulin sensitivity, and glucose metabolism. Such a dissection of ERα biological functions related to its subcellular localization will help to understand the mechanism of action of “old” ER modulators and to design new ones with an optimized benefit/risk profile.

Clinical characteristics and outcome of cirrhotic patients with high protein concentrations in ascites: a prospective study.

Background The protein concentration in ascites is usually low in cirrhosis because capillarization and defenestration of the sinusoids limit diffusion of large proteins from plasma to the space of Disse. However, some cirrhotic patients have high-protein ascites (HPA). Aim The aim of this study was to describe and compare the characteristics and prognosis between cirrhotic patients with HPA (>20 g/l) and patients with low-protein ascites (LPA). Patients and methods In this longitudinal observational prospective cohort study, all consecutive cirrhotic patients with ascites hospitalized in our tertiary liver center were included and followed for up to 2 years, provided that they had no other cause of HPA. HPA was defined as protein concentrations of more than 20 g/l. Results Among 107 patients included, 19 (17.8%) had HPA. HPA patients had more refractory ascites (63 vs. 34%), better liver functions, and a higher 1-year transplant-free survival rate compared with LPA patients (P<0.05). Portal hypertension parameters were not different. During follow-up, 47% of HPA patients were treated by transjugular intrahepatic portosystemic shunts versus 18% of LPA patients, whereas 15 LPA patients required liver transplantation for end-stage liver disease versus only one HPA patient. We observed higher protein filtration and less pericellular, centrilobular, and sinusoidal fibrosis in cirrhotic HPA livers compared with LPA livers. Conclusion Almost 20% of cirrhotic patients with ascites have HPA (>20 g/l). These patients have better liver functions and a higher 1-year survival than those with LPA, even though ascites are more often refractory.

Hypertension portale : physiopathologie, causes, diagnostic et traitement

La cirrhose est la premiere cause d’hypertension portale (HTP) dans les pays occidentaux. L’HTP est responsable de la majorite des deces chez les patients atteints d’une cirrhose et la consequence d’une augmentation des resistances vasculaires intrahepatiques et du debit sanguin splanchnique. L’endoscopie œsogastroduodenale est l’examen de choix pour le depistage des varices œsophagiennes (VO). En l’absence de VO ou en cas de petites varices, une surveillance endoscopique est recommandee. La prevention primaire de la rupture de VO repose sur la prescription de betabloquants non cardioselectifs ou la ligature endoscopique. Le traitement de la rupture de VO associe agent vasoactif, antibioprophylaxie et traitement endoscopique. La prophylaxie secondaire apres une rupture de VO associe les betabloquants non cardioselectifs a la ligature endoscopique. La pose d’un shunt intrahepatique par voie jugulaire (TIPS) est proposee en cas de non-controle du saignement, de recidive hemorragique precoce, ou en cas d’hemorragie a haut risque d’echec, et en cas d’hemorragie sous prophylaxie secondaire bien conduite. Le traitement de premiere intention de l’ascite est le regime peu sale associe aux diuretiques. En cas d’ascite refractaire, les ponctions iteratives avec compensation par albumine, le TIPS ou la transplantation hepatique sont a discuter. Un nombre de polynucleaires neutrophiles > 250/mm3 definit une infection du liquide d’ascite meme en l’absence de detection de germe a l’examen direct ou apres mise en culture. Le traitement de l’infection repose sur l’antibiotherapie associee aux perfusions d’albumine. La norfloxacine est prescrite en prophylaxie primaire de l’infection du liquide d’ascite chez les patients atteints d’une cirrhose avec insuffisance hepatique severe et une ascite pauvre en protides ou en prophylaxie secondaire.