title: Expression of Nitric Oxide-Transporting Aquaporin-1 Is Controlled by KLF2 and Marks Non-Activated Endothelium In Vivo.
abstract: The flow-responsive transcription factor Krüppel-like factor 2 (KLF2) maintains an anti-coagulant, anti-inflammatory endothelium with sufficient nitric oxide (NO)-bioavailability. In this study, we aimed to explore, both in vitro and in human vascular tissue, expression of the NO-transporting transmembrane pore aquaporin-1 (AQP1) and its regulation by atheroprotective KLF2 and atherogenic inflammatory stimuli. In silico analysis of gene expression profiles from studies that assessed the effects of KLF2 overexpression in vitro and atherosclerosis in vivo on endothelial cells, identifies AQP1 as KLF2 downstream gene with elevated expression in the plaque-free vessel wall. Biomechanical and pharmaceutical induction of KLF2 in vitro is accompanied by induction of AQP1. Chromosome immunoprecipitation (CHIP) confirms binding of KLF2 to the AQP1 promoter. Inflammatory stimulation of endothelial cells leads to repression of AQP1 transcription, which is restrained by KLF2 overexpression. Immunohistochemistry reveals expression of aquaporin-1 in non-activated endothelium overlying macrophage-poor intimae, irrespective whether these intimae are characterized as being plaque-free or as containing advanced plaque. We conclude that AQP1 expression is subject to KLF2-mediated positive regulation by atheroprotective shear stress and is downregulated under inflammatory conditions both in vitro and in vivo. Thus, endothelial expression of AQP1 characterizes the atheroprotected, non-inflamed vessel wall. Our data provide support for a continuous role of KLF2 in stabilizing the vessel wall via co-temporal expression of eNOS and AQP1 both preceding and during the pathogenesis of atherosclerosis.
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU Medical Center, Amsterdam, the Netherlands.
authors.forename: Ruud D
authors.initials: RD
authors.lastname: Fontijn
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU Medical Center, Amsterdam, the Netherlands.
authors.forename: Oscar L
authors.initials: OL
authors.lastname: Volger
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU Medical Center, Amsterdam, the Netherlands.
authors.forename: Tineke C
authors.initials: TC
authors.lastname: van der Pouw-Kraan
authors.affiliation: Institute for Cardiovascular Regeneration, Centre of Molecular Medicine, Goethe University, Frankfurt am Main, Germany.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Doddaballapur
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU Medical Center, Amsterdam, the Netherlands.
authors.forename: Thomas
authors.initials: T
authors.lastname: Leyen
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU Medical Center, Amsterdam, the Netherlands.
authors.forename: Josefien M
authors.initials: JM
authors.lastname: Baggen
authors.affiliation: Institute for Cardiovascular Regeneration, Centre of Molecular Medicine, Goethe University, Frankfurt am Main, Germany.
authors.forename: Reinier A
authors.initials: RA
authors.lastname: Boon
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU Medical Center, Amsterdam, the Netherlands.
authors.forename: Anton J G
authors.initials: AJ
authors.lastname: Horrevoets
mesh_terms: D051398:Aquaporin 1 / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D018836:Inflammation Mediators / Q000494:pharmacology; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D058226:Plaque, Atherosclerotic / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013314:Stress, Mechanical; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D018836:Inflammation Mediators; C096161:KLF2 protein, human; D051741:Kruppel-Like Transcription Factors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D051398:Aquaporin 1; D009569:Nitric Oxide