title: Intermedin (adrenomedullin2) stabilizes the endothelial barrier and antagonizes thrombin-induced barrier failure in endothelial cell monolayers.
abstract: OBJECTIVE
  Intermedin is a member of the calcitonin gene-related-peptide (CGRP) family expressed in endothelial cells and acts via calcitonin receptor-like receptors (CLRs). Here we have analysed the receptors for intermedin and its effect on the endothelial barrier in monolayers of human umbilical vein endothelial cells (HUVECs).
  
  
  METHODS
  We analysed the effect of intermedin on albumin permeability, contractile machinery, actin cytoskeleton and VE-cadherin in cultured HUVECs.
  
  
  RESULTS
  Intermedin concentration-dependently reduced basal endothelial permeability to albumin and antagonized thrombin-induced hyperpermeability. Intermedin was less potent (EC(50) 1.29 ± 0.12 nM) than adrenomedullin (EC(50) 0.24 ± 0.07 nM) in reducing endothelial permeability. These intermedin effects were inhibited by AM(22-52) and higher concentrations of αCGRP(8-37), with pA(2) values of αCGRP(8-37) of 6.4 for both intermedin and adrenomedullin. PCR data showed that HUVEC expressed only the CLR/RAMP2 receptor complex. Intermedin activated cAMP/PKA and cAMP/Epac signalling pathways. Intermedin's effect on permeability was blocked by inhibition of PKA but not of eNOS. Intermedin antagonized thrombin-induced contractile activation, RhoA activation and stress fibre formation. It also induced Rac1 activation, enhanced cell-cell adhesion and antagonized thrombin-induced loss of cell-cell adhesion. Treatment with a specific inhibitor of Rac1 prevented intermedin-mediated barrier stabilization.
  
  
  CONCLUSIONS
  Intermedin stabilized endothelial barriers in HUVEC monolayers via CLR/RAMP2 receptors. These effects were mediated via cAMP-mediated inactivation of contractility and strengthening of cell-cell adhesion. These findings identify intermedin as a barrier stabilizing agent and suggest intermedin as a potential treatment for vascular leakage in inflammatory conditions.
authors.affiliation: Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany. muhammad.aslam@physiologie.med.uni-giessen.de
authors.forename: M
authors.initials: M
authors.lastname: Aslam
authors.forename: U
authors.initials: U
authors.lastname: Pfeil
authors.forename: D
authors.initials: D
authors.lastname: Gündüz
authors.forename: A
authors.initials: A
authors.lastname: Rafiq
authors.forename: W
authors.initials: W
authors.lastname: Kummer
authors.forename: H M
authors.initials: HM
authors.lastname: Piper
authors.forename: T
authors.initials: T
authors.lastname: Noll
mesh_terms: D022005:Adherens Junctions / Q000187:drug effects / Q000502:physiology; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects* / Q000502:physiology*; D004730:Endothelium, Vascular / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D018994:Myosin Light Chains / Q000235:genetics / Q000378:metabolism; D036361:Peptide Hormones / Q000494:pharmacology*; D012313:RNA / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D058265:Receptors, Adrenomedullin / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013917:Thrombin / Q000494:pharmacology*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C484330:ADM2 protein, human; D018994:Myosin Light Chains; D036361:Peptide Hormones; D058265:Receptors, Adrenomedullin; D012313:RNA; D000242:Cyclic AMP; D013917:Thrombin; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; D015740:Calcitonin Gene-Related Peptide