title: TGFβ1 exacerbates blood-brain barrier permeability in a mouse model of hepatic encephalopathy via upregulation of MMP9 and downregulation of claudin-5.
abstract: Recent studies have found that vasogenic brain edema is present during hepatic encephalopathy following acute liver failure and is dependent on increased matrix metalloproteinase 9 (MMP9) activity and downregulation of tight junction proteins. Furthermore, circulating transforming growth factor β1 (TGFβ1) is increased following liver damage and may promote endothelial cell permeability. This study aimed to assess whether increased circulating TGFβ1 drives changes in tight junction protein expression and MMP9 activity following acute liver failure. Blood-brain barrier permeability was assessed in azoxymethane (AOM)-treated mice at 6, 12, and 18 h post-injection via Evan's blue extravasation. Monolayers of immortalized mouse brain endothelial cells (bEnd.3) were treated with recombinant TGFβ1 (rTGFβ1) and permeability to fluorescein isothiocyanate-dextran (FITC-dextran), MMP9 and claudin-5 expression was assessed. Antagonism of TGFβ1 signaling was performed in vivo to determine its role in blood-brain barrier permeability. Blood-brain barrier permeability was increased in mice at 18 h following AOM injection. Treatment of bEnd.3 cells with rTGFβ1 led to a dose-dependent increase of MMP9 expression as well as a suppression of claudin-5 expression. These effects of rTGFβ1 on MMP9 and claudin-5 expression could be reversed following treatment with a SMAD3 inhibitor. AOM-treated mice injected with neutralizing antibodies against TGFβ demonstrated significantly reduced blood-brain barrier permeability. Blood-brain barrier permeability is induced in AOM mice via a mechanism involving the TGFβ1-driven SMAD3-dependent upregulation of MMP9 expression and decrease of claudin-5 expression. Therefore, treatment modalities aimed at reducing TGFβ1 levels or SMAD3 activity may be beneficial in promoting blood-brain barrier integrity following liver failure.
authors.affiliation: Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, TX, USA.
authors.forename: Matthew A
authors.identifier: 0000000259800921
authors.initials: MA
authors.lastname: McMillin
authors.affiliation: Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, TX, USA.
authors.forename: Gabriel A
authors.initials: GA
authors.lastname: Frampton
authors.affiliation: Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, TX, USA.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Seiwell
authors.affiliation: Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, TX, USA.
authors.forename: Nisha S
authors.initials: NS
authors.lastname: Patel
authors.affiliation: University of Texas Health Science Center, Houston, TX, USA.
authors.forename: Amber N
authors.initials: AN
authors.lastname: Jacobs
authors.affiliation: 1] Department of Internal Medicine, Texas A&M Health Science Center College of Medicine, Temple, TX, USA [2] Baylor Scott & White Health Digestive Disease Research Center, Temple, TX, USA [3] Central Texas Veterans Health Care System, Temple, TX, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: DeMorrow
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002199:Capillary Permeability / Q000502:physiology*; D002460:Cell Line; D062507:Claudin-5 / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D006501:Hepatic Encephalopathy / Q000378:metabolism*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D051900:Smad3 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D062507:Claudin-5; C491511:Cldn5 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D053773:Transforming Growth Factor beta1; D020780:Matrix Metalloproteinase 9