title: Up-regulation of gap junctional intercellular communication and connexin43 expression by retinoic acid in human endometrial stromal cells.
abstract: BACKGROUND
  Gap junctions, made up of connexins (Cxs), play fundamental roles in coordinating a number of cellular processes through their ability to directly regulate cell-cell communication. Cx43 is the most widely expressed Cx in the endometrium and is known to be important in a variety of physiological and pathological processes in this tissue.
  
  
  OBJECTIVE
  In this study, we investigated the ability of the retinoid, all-trans-retinoic acid (RA), to regulate Cx43 expression in human endometrial stromal cells.
  
  
  METHODS
  Primary endometrial stromal cells obtained from patients undegoing surgery for infertility workup were treated in vitro with RA and control compounds for different time periods, up to 48 h. Cx43 mRNA and protein levels, protein phosphorylation, and gap junctional intercellular communication (GJIC) were analyzed.
  
  
  RESULTS
  Treatment of the cells with RA showed a dose-dependent increase in Cx43 expression at both the mRNA and protein levels. In addition, RA induced a relative decrease in the phosphorylated species of Cx43 while causing a corresponding increase in the nonphosphorylated form. Concomitant with these changes, RA-treated cells demonstrated up to a 250% enhancement of GJIC as assessed by dye transfer experiments. Augmentation of GJIC and alterations of Cx43 expression were observed over the same range of RA concentrations. Treatment of cells with the protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate increased the phosphorylated species of Cx43 and correspondingly inhibited GJIC.
  
  
  CONCLUSIONS
  Phosphorylation of Cx43 is inversely related to GJIC in endometrial stromal cells. Retinoids increase GJIC in endomentrial stromal cells through upregulation of Cx43 expression while inducing a decrease in the phosphorylated species of the protein. The data suggest a novel mechanism by which retinoids can influence endometrial cell biology.
authors.affiliation: Division of Research, Department of Gynecology and Obstetrics, Emory University School of Medicine, 1639 Pierce Drive, Atlanta, Georgia 30322, USA.
authors.forename: Prasong
authors.initials: P
authors.lastname: Tanmahasamut
authors.forename: Neil
authors.initials: N
authors.lastname: Sidell
mesh_terms: D002450:Cell Communication / Q000187:drug effects*; D002478:Cells, Cultured; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D004717:Endometrium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D017629:Gap Junctions / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: D018031:Connexin 43; D012333:RNA, Messenger; D014212:Tretinoin; D013755:Tetradecanoylphorbol Acetate