title: Angiopoietin-1 Regulates Brain Endothelial Permeability through PTPN-2 Mediated Tyrosine Dephosphorylation of Occludin.
abstract: OBJECTIVE
  Blood brain barrier (BBB) breakdown and increased endothelial permeability is a hallmark of neuro-vascular inflammation. Angiopoietin-1 (Ang-1), a Tie-2 receptor agonist ligand, is known to modulate barrier function of endothelial cells; however the molecular mechanisms related to Ang-1 mediated repair of Tight Junctions (TJs) in brain endothelium still remain elusive. In this study, we investigated a novel role of non-receptor protein tyrosine phosphatase N-2 (PTPN-2) in Ang-1 mediated stabilization of tight junction proteins.
  
  
  RESULTS
  To study the barrier protective mechanism of Ang-1, we challenged human brain microvascular endothelial cells in-vitro, with a potent inflammatory mediator thrombin. By using confocal microscopy and transwell permeability assay, we show that pretreatment of brain endothelial cells with Ang-1 diminish thrombin mediated disruption of TJs and increase in endothelial permeability. We also found that Ang-1 inhibits thrombin induced tyrosine phosphorylation of Occludin and promote Occludin interaction with Zona Occludens-1 (ZO-1) to stabilize TJs. Interestingly, our study revealed that depletion of PTPN-2 by siRNAs abolishes Ang-1 ability to promote tyrosine dephosphorylation of Occludin, resulting Occludin disassociation from ZO-1 and endothelial hyperpermeability.
  
  
  CONCLUSIONS
  Collectively, our findings suggest that in brain endothelial cells blocking PTPN-2 mediated tyrosine phosphorylation of Occludin is a novel mechanism to maintain BBB function, and may offer a key therapeutic strategy for neuro-inflammatory disorders associated with BBB disruption.
authors.affiliation: Division of Pediatric Neurosurgery, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America.
authors.forename: M Rizwan
authors.initials: MR
authors.lastname: Siddiqui
authors.affiliation: Division of Pediatric Neurosurgery, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America; Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America.
authors.forename: Chandra S
authors.initials: CS
authors.lastname: Mayanil
authors.affiliation: Division of Pediatric Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Kwang Sik
authors.initials: KS
authors.lastname: Kim
authors.affiliation: Division of Pediatric Neurosurgery, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America; Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, United States of America.
authors.forename: Tadanori
authors.initials: T
authors.lastname: Tomita
mesh_terms: D042683:Angiopoietin-1 / Q000378:metabolism* / Q000494:pharmacology; D001812:Blood-Brain Barrier / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002199:Capillary Permeability / Q000187:drug effects / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D017353:Gene Deletion; D015870:Gene Expression; D006801:Humans; D007365:Intercellular Junctions / Q000187:drug effects / Q000378:metabolism; D062793:Occludin / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2 / Q000235:genetics / Q000378:metabolism*; D042787:Receptor, TIE-2 / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology; D062725:Tight Junction Proteins / Q000235:genetics / Q000378:metabolism; D062826:Zonula Occludens-1 Protein / Q000378:metabolism
chemical_list: D042683:Angiopoietin-1; D062793:Occludin; D062725:Tight Junction Proteins; D062826:Zonula Occludens-1 Protein; D042787:Receptor, TIE-2; D048049:Extracellular Signal-Regulated MAP Kinases; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D013917:Thrombin