Original article Estradiol enhances endothelial cell interactions with extracellular matrix proteins via an increase in integrin expression and function* Maria C. Cid 1 , Jordi Esparza 1 , H. William Schnaper 3 , Manel Juan 2 , Jordi Yague 3 , Derrick S. Grant 4 , Alvaro Urbano-MaÂrquez 1 , Gary S. Homan 5 & Hynda K. Kleinman 6 1 Department of Internal Medicine and 2 Immunology, Hospital ClõÂnic, University of Barcelona, Institut d'Investigacions BiomeÁdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain; 3 Department of Pediatrics, Northwestern University Medical School, Chicago, Illinois, USA; 4 Cardeza Foundation for Hematologic Research, Jeerson Medical College, Philadelphia, Pennsylvania, USA; 5 Department of Rheumatic and Immunologic Disease, The Cleveland Clinic Foundation, Cleveland, Ohio, USA; 6 Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, USA Received 3 June 1999; accepted in revised form 10 March 2000 Key words: estrogen, endothelial cell, integrins Abstract Premenopausal women have a lower cardiovascular risk and a higher incidence of several autoimmune diseases involving blood vessels than men. Although the precise eects of estrogens on the cardiovascular system are largely unknown, recent data suggest that estrogens can exert direct regulatory eects on endothelial cells. In the present study, we show that 17b-estradiol increases human umbilical vein endothelial cell attachment to the extracellular matrix proteins laminin-1, type IV collagen, type I collagen, and ®bronectin. Estradiol enhanced adhesion most signi®cantly to laminin-1 and to ®bronectin-derived synthetic peptides containing an RGD sequence. Upon exposure to estradiol, an increase in b1, a5 and a6 integrin mRNA was observed in subcon¯uent cells which was abrogated by treatment with cycloheximide. This increase was followed by a later enhancement in surface expression of the above integrins. In addition, integrin-mediated signaling was also enhanced by estrogens since an increase in tyrosine-phosphorylation of focal adhesion kinase induced by cell attachment was observed in estrogen- treated endothelial cells. Since integrins have an important role in mediating endothelial cell attachment, migration and dierentiation, the increase in integrin expression and function induced by estradiol may be an important mechanism through which estrogens can promote neovascularization and vessel repair. Abbreviations: HUVEC ± human umbilical vein endothelial cells; SLE ± systemic lupus erythematosus; mAb ± monoclonal antibodies; FGF-2 ± ®broblast growth factor-2; TNF ± tumor necrosis factor; TGFb ± transforming growth factor Introduction Estrogens exert important regulatory functions on the cardiovascular system. Epidemiological studies have shown that premenopausal women have a much lower cardiovascular risk than men and that estrogen replace- ment therapy signi®cantly decreases the incidence of coronary heart disease in postmenopausal women [1±4]. In contrast, several autoimmune disorders with vascular involvement such as Takayasu's arteritis or systemic lupus erythematosus (SLE) are much more frequent in young women [5]. The incidence of SLE decreases with menopause but has been recently demonstrated to increase among postmenopausal women on estrogen replacement therapy [6]. Although in these later diseases it is likely that the enhancing eect of estrogens relies primarily on immunoregulatory pathways [7, 8], we have demonstrated that estrogens also elicit proin¯amatory activities on endothelial cells. At physiological doses, estradiol increases endothelial cell expression of TNF- induced adhesion molecules for leukocytes thus facilitat- ing the development of vascular in¯ammatory lesions [9]. Early studies suggested that estrogens decrease the incidence of cardiovascular disease essentially through their bene®cial eects on lipid metabolism [10±13]. More * The US Government's right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged. Correspondence to: Hynda K. Kleinman, Craniofacial Development and Regeneration Branch, NIDCR, Bldg. 30, Room 421, 30, Convent Drive MSC 4370, Bethesda, MD 20892, USA. Tel: +1-301-496-4069; Fax: +1-301-402-0897; E-mail: HKleinman@dir.nidcr.nih.gov Angiogenesis 3: 271±280, 1999. 271 Ó 2000 Kluwer Academic Publishers. Printed in the Netherlands.