Expression of Nitric Oxide-Transporting Aquaporin-1 Is Controlled by KLF2 and Marks Non-Activated Endothelium In Vivo

• Published in: PloS one Vol. 10; no. 12; p. e0145777
• Main Authors: Fontijn, Ruud D, Volger, Oscar L, van der Pouw-Kraan, Tineke C, Doddaballapur, Anuradha, Leyen, Thomas, Baggen, Josefien M, Boon, Reinier A, Horrevoets, Anton J G
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 30.12.2015; Public Library of Science (PLoS)
• Subjects: Aquaporin 1; Aquaporin 1 - genetics; Aquaporin 1 - metabolism; Aquaporins; Arteriosclerosis; Atherosclerosis; Bioavailability; Biological Transport - drug effects; Biomechanics; Cell adhesion & migration; Coagulants; Endothelial cells; Endothelium; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Gene expression; Gene silencing; Human Umbilical Vein Endothelial Cells - drug effects; Human Umbilical Vein Endothelial Cells - metabolism; Humans; Immunohistochemistry; Immunoprecipitation; Inflammation; Inflammation Mediators - pharmacology; Kinases; Krueppel-like factor; Kruppel-Like Transcription Factors - genetics; Kruppel-Like Transcription Factors - metabolism; Lung Kruppel-like factor; Macrophages; Mechanical stimuli; Nitric oxide; Nitric Oxide - metabolism; Pathogenesis; Physiological aspects; Plaque, Atherosclerotic - pathology; Promoter Regions, Genetic - genetics; Protein Binding - drug effects; Protein Binding - genetics; RNA, Messenger - genetics; RNA, Messenger - metabolism; Shear stress; Shear stresses; Stress, Mechanical; Transcription, Genetic - drug effects; Transportation; Tumor Necrosis Factor-alpha - pharmacology; Vascular tissue
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0145777

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.