Author's Personal Copy Reproductive Hormones Regulate the Selective Permeability of the Blood-brain Barrier ☆

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a r t i c l e i n f o a b s t r a c t Reproductive hormones have been demonstrated to modulate both gap and tight junction protein expression in the ovary and other reproductive tissues, however the effects of changes in reproductive hormones on the selective permeability of the blood-brain barrier (BBB) remain unclear. Age-related declines in BBB integrity correlate with the loss of serum sex steroids and increase in gonadotropins with menopause/andropause. To examine the effect of reproductive senescence on BBB permeability and gap and tight junction protein expression/ localization, female mice at 3 months of age were either sham operated (normal serum E 2 and gonadotropins), ovariectomized (low serum E 2 and high serum gonadotropins) or ovariectomized and treated with the GnRH agonist leuprolide acetate (low serum E 2 and gonadotropins). Ovariectomy induced a 2.2-fold increase in Evan's blue dye extravasation into the brain. The expression and localization of the cytoplasmic membrane-associated tight junction protein zona occludens 1 (ZO-1) in microvessels was not altered among groups indicating that the increased paracellular permeability was not due to changes in this tight junction protein. However, ovariectomy induced a redistribution of the gap junction protein connexin-43 (Cx43) such that immunoreactivity relocalized from along the extracellular microvascular endothelium to become associated with endothelial cells. An increase in Cx43 expression in the mouse brain following ovariectomy was suppressed in ovariectomized animals treated with leuprolide acetate, indicating that serum gonadotropins rather than sex steroids were modulating Cx43 expression. These results suggest that elevated serum gonadotropins following reproductive senescence may be one possible cause of the loss of selective permeability of the BBB at this time. Furthermore, these findings implicate Cx43 in mediating changes in BBB permeability, and serum gonadotropins in the cerebropathophysiology of age-related neurodegenerative diseases such as stroke and Alzheimer's disease. Keywords: Blood-brain barrier Selective permeability Ovariectomy Tight junction Gap junction Connexin-43 Zona occludens 1 Luteinizing hormone Follicle-stimulating hormone Sex steroid Leuprolide acetate Receptor Stroke Alzheimer's disease 1. Introduction The blood-brain barrier (BBB) maintains brain homeostasis by limiting entry of substances to the central nervous system [1] through interaction of transmembrane and intracellular proteins that make up endothelial …