Endothelial Estrogen Receptor-&agr; Plays a Crucial Role in the Atheroprotective Action of 17&bgr;-Estradiol in Low-Density Lipoprotein Receptor–Deficient Mice

Background— The prevention of early atheroma by estrogens has been clearly demonstrated in all animal models and appears to be mediated through a direct action on the arterial wall rather than through an effect on the lipoprotein profile. The goal of the present study was to evaluate which cellular target is crucial in this beneficial action of estradiol. Methods and Results— We first confirmed the key role of estrogen receptor-&agr; (ER&agr;) in the atheroprotective effect of estradiol, because this action was completely abolished in mice deficient in both the low-density lipoprotein receptor (LDLr) and ER&agr;. Second, using chimeric mice with an ER&agr; deficiency in the hematopoietic lineage, we showed the persistence of the protective action of estradiol, which suggests the involvement of extrahematopoietic ER&agr;. Third, we showed that loxP-flanked ER&agr; mice (ER&agr;flox/flox) bred with Tie2-Cre+ mice on an LDLr−/− background had complete inactivation of ER&agr; in most hematopoietic and all endothelial cells. Remarkably, in this mouse model, the atheroprotective effect of estradiol was completely abolished. Fourth, the atheroprotective effect of estradiol remained abolished in Tie2-Cre+ ER&agr;flox/flox LDLr−/− mice transplanted with either Tie2-Cre+ ER&agr;flox/flox or ER&agr;−/− bone marrow, whereas it was present in analogous chimeric Tie2-Cre− ER&agr;flox/flox LDLr−/− receivers expressing endothelial ER&agr;. Conclusions— We demonstrate directly and for the first time that endothelial ER&agr; represents a key target of the atheroprotective effect of estradiol, whereas hematopoietic ER&agr; is dispensable. Selective estrogen receptor modulators that mimic the endothelial action of estradiol should now be considered in atheroprotection.

[1]  F. Lenfant,et al.  Estrogen Receptor &agr; Expression in Both Endothelium and Hematopoietic Cells Is Required for the Accelerative Effect of Estradiol on Reendothelialization , 2009, Arteriosclerosis, thrombosis, and vascular biology.

[2]  F. Ginhoux,et al.  Conventional Dendritic Cells at the Crossroads Between Immunity and Cholesterol Homeostasis in Atherosclerosis , 2009, Circulation.

[3]  P. Chambon,et al.  The transactivating function-1 of estrogen receptor alpha is dispensable for the vasculoprotective actions of 17 beta-estradiol. , 2009 .

[4]  P. Chambon,et al.  The transactivating function 1 of estrogen receptor α is dispensable for the vasculoprotective actions of 17β-estradiol , 2009, Proceedings of the National Academy of Sciences.

[5]  P. Libby,et al.  The multifaceted contributions of leukocyte subsets to atherosclerosis: lessons from mouse models , 2008, Nature Reviews Immunology.

[6]  J. Arnal,et al.  Chronic Estradiol Administration In Vivo Promotes the Proinflammatory Response of Macrophages to TLR4 Activation: Involvement of the Phosphatidylinositol 3-Kinase Pathway1 , 2008, The Journal of Immunology.

[7]  W. Bremner,et al.  Advances in male contraception. , 2008, Endocrine reviews.

[8]  J. Arnal,et al.  Estrogens in vascular biology and disease: where do we stand today? , 2007, Current opinion in lipidology.

[9]  R. Straub,et al.  The complex role of estrogens in inflammation. , 2007, Endocrine reviews.

[10]  J. Manson,et al.  Postmenopausal hormone therapy and risk of cardiovascular disease by age and years since menopause. , 2007, JAMA.

[11]  Peter Libby,et al.  The immune response in atherosclerosis: a double-edged sword , 2006, Nature Reviews Immunology.

[12]  A. Tedgui,et al.  Cytokines in atherosclerosis: pathogenic and regulatory pathways. , 2006, Physiological reviews.

[13]  P. Kincade,et al.  Bone marrow dysfunction in mice lacking the cytokine receptor gp130 in endothelial cells. , 2005, Blood.

[14]  G. Hansson,et al.  The atheroprotective effect of 17beta-estradiol depends on complex interactions in adaptive immunity. , 2005, The American journal of pathology.

[15]  T. Clarkson,et al.  Controversies about HRT--lessons from monkey models. , 2005, Maturitas.

[16]  D. Rader,et al.  COX-2-Derived Prostacyclin Confers Atheroprotection on Female Mice , 2004, Science.

[17]  J. Isner,et al.  Estrogen-Mediated, Endothelial Nitric Oxide Synthase–Dependent Mobilization of Bone Marrow–Derived Endothelial Progenitor Cells Contributes to Reendothelialization After Arterial Injury , 2003, Circulation.

[18]  S. Schwartz,et al.  Estrogen inhibits the initiation of fatty streaks throughout the vasculature but does not inhibit intra-plaque hemorrhage and the progression of established lesions in apolipoprotein E deficient mice. , 2002, Atherosclerosis.

[19]  Charles Kooperberg,et al.  Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results From the Women's Health Initiative randomized controlled trial. , 2002, JAMA.

[20]  P. Chambon,et al.  Estrogen Receptor-&agr; Mediates the Protective Effects of Estrogen Against Vascular Injury , 2002, Circulation research.

[21]  B. Katzenellenbogen,et al.  Defining the "S" in SERMs , 2002, Science.

[22]  Toulouse,et al.  Estradiol Alters Nitric Oxide Production in the Mouse Aorta Through the α-, but not β-, Estrogen Receptor , 2002 .

[23]  P. Chambon,et al.  The AF-1 activation-function of ERα may be dispensable to mediate the effect of estradiol on endothelial NO production in mice , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[24]  J. Keaney,et al.  Hormone replacement therapy and endothelial function: the exception that proves the rule? , 2001, Arteriosclerosis, thrombosis, and vascular biology.

[25]  V. Jordan.  The Past, Present, and Future of Selective Estrogen Receptor Modulation , 2001, Annals of the New York Academy of Sciences.

[26]  Rainer Constien,et al.  Characterization of a novel EGFP reporter mouse to monitor Cre recombination as demonstrated by a Tie2 Cre mouse line , 2001, Genesis.

[27]  R. Flavell,et al.  Conditional Vascular Cell Adhesion Molecule 1 Deletion in Mice , 2001, The Journal of experimental medicine.

[28]  K. Korach,et al.  Estrogen receptor α is a major mediator of 17β-estradiol’s atheroprotective effects on lesion size in Apoe–/– mice , 2001 .

[29]  P. Chambon,et al.  Estradiol Accelerates Reendothelialization in Mouse Carotid Artery Through Estrogen Receptor-&agr; but Not Estrogen Receptor-&bgr; , 2001, Circulation.

[30]  P. Chambon,et al.  Estradiol Accelerates Reendothelialization in Mouse Carotid Artery Through Estrogen Receptor-α but Not Estrogen Receptor-β , 2001 .

[31]  J. Isner,et al.  Estrogen and Angiogenesis: A Review , 2001, Arteriosclerosis, thrombosis, and vascular biology.

[32]  P. Chambon,et al.  Effect of single and compound knockouts of estrogen receptors alpha (ERalpha) and beta (ERbeta) on mouse reproductive phenotypes. , 2000, Development.

[33]  M. R. Andersen,et al.  The direct antiatherogenic effect of estrogen is present, absent, or reversed, depending on the state of the arterial endothelium. A time course study in cholesterol-clamped rabbits. , 1999, Circulation.

[34]  M. Rosenfeld,et al.  Estradiol inhibits leukocyte adhesion and transendothelial migration in rabbits in vivo : possible mechanisms for gender differences in atherosclerosis. , 1999, Circulation research.

[35]  L. Curtiss,et al.  Protection against atherosclerosis by estrogen is independent of plasma cholesterol levels in LDL receptor-deficient mice. , 1999, Journal of lipid research.

[36]  J. Rutledge,et al.  Modified LDL-mediated increases in endothelial layer permeability are attenuated with 17 beta-estradiol. , 1999, Arteriosclerosis, thrombosis, and vascular biology.

[37]  G. Yancopoulos,et al.  Critical role of the TIE2 endothelial cell receptor in the development of definitive hematopoiesis. , 1998, Immunity.

[38]  V. Richard,et al.  Prevention of fatty streak formation of 17beta-estradiol is not mediated by the production of nitric oxide in apolipoprotein E-deficient mice. , 1997, Circulation.

[39]  J. Arnal,et al.  17β-Estradiol Prevents Fatty Streak Formation in Apolipoprotein E–Deficient Mice , 1997 .

[40]  P. Hougaard,et al.  Significant reduction of the antiatherogenic effect of estrogen by long-term inhibition of nitric oxide synthesis in cholesterol-clamped rabbits. , 1997, The Journal of clinical investigation.

[41]  P. Libby,et al.  Role of macrophage colony-stimulating factor in atherosclerosis: studies of osteopetrotic mice. , 1997, The American journal of pathology.

[42]  J. Isner,et al.  Estradiol accelerates functional endothelial recovery after arterial injury. , 1997, Circulation.

[43]  J. Isner,et al.  Estrogen-receptor-mediated inhibition of human endothelial cell apoptosis. Estradiol as a survival factor. , 1997, Circulation.

[44]  P. Milos,et al.  Estrogen reduces atherosclerotic lesion development in apolipoprotein E-deficient mice. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[45]  Michael Ginsberg,et al.  Decreased atherosclerosis in mice deficient in both macrophage colony-stimulating factor (op) and apolipoprotein E. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[46]  K. Korach,et al.  Alteration of reproductive function but not prenatal sexual development after insertional disruption of the mouse estrogen receptor gene. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[47]  B. Garmy-Susini,et al.  The atheroprotective effect of 17 beta-estradiol is not altered in P-selectin- or ICAM-1-deficient hypercholesterolemic mice. , 2003, Atherosclerosis.

[48]  P. Chambon,et al.  Estradiol alters nitric oxide production in the mouse aorta through the alpha-, but not beta-, estrogen receptor. , 2002, Circulation research.

[49]  K. Korach,et al.  Estrogen receptor alpha is a major mediator of 17beta-estradiol's atheroprotective effects on lesion size in Apoe-/- mice. , 2001, The Journal of clinical investigation.

[50]  G. Getz,et al.  Loss of atheroprotective effect of estradiol in immunodeficient mice. , 2000, Endocrinology.