17β-estradiol transiently disrupts adherens junctions in endothelial cells

Interendothelial junctions are important regulators of endothelial cell functions such as migration and proliferation, major features in angiogenesis, and endothelial cell monolayer wound healing. 17 beta-estradiol regulates these functions in vivo and in vitro and also increases endothelial monolayer permeability as it results from impaired monolayer integrity and intercellular adhesion. We hypothesized that 17 beta-estradiol affects these cell adhesion-dependent functions in endothelial cells by targeting the adherens junction complex. Here, we show that 17 beta-estradiol increases uterine microvascular endothelial cell monolayer permeability and transiently redistributes interendothelial junction-forming proteins in endothelial cells. Concomitantly, adherens junction proteins are disconnected from the cytoskeleton and alpha-catenin, which links VE-cadherin to the cytoskeleton, is redistributed from the membrane and the adherens junction complex. Furthermore, 17 beta-estradiol increased tyrosine phosphorylation of the adherens junction complex. These effects were inhibited by the estrogen receptor antagonist ICI 182,780 but could be provoked using non-cell membrane-permeable 17 beta-estradiol-BSA in all cells tested, including EA.hy 926 cells, which have been shown unable to stimulate 17 beta-estradiol- dependent gene transcription. Additionally, 17 beta-estradiol treatment enhanced the angiogenic effect of vascular endothelial growth factor in an in vitro angiogenesis model, as a potential implication of the adherens junction disruption. Cotreatment with the Src-family kinase inhibitor PP2 prevented the redistribution and phosphorylation of the adherens junction proteins. Taken together, our data show that adherens junctions in endothelial cells are a downstream target of membrane-associated 17 beta-estradiol signaling, possibly through Src-family kinases.