title: Angiopoietin-1 regulates microvascular reactivity and protects the microcirculation during acute endothelial dysfunction: role of eNOS and VE-cadherin.
abstract: The growth factor angiopoietin-1 (Ang-1) plays an essential role in angiogenesis and vascular homeostasis. Nevertheless, the role of Ang-1 in regulating vascular tone and blood flow is largely unexplored. Endothelial nitric oxide synthase (eNOS) and the junctional protein VE-cadherin are part of the complex signalling cascade initiated by Ang-1 in endothelial cells. In this study, we aimed to investigate the mechanisms underlying acute effects of Ang-1 on microvascular reactivity, permeability and blood flow, and hypothesise that eNOS and VE-cadherin underpin Ang-1 mediated vascular effects that are independent of angiogenesis and proliferation. Myography of isolated microarterioles from male C3H/HeN mice (7-10 weeks) was employed to measure vascular reactivity in vitro. Microcirculatory function in vivo was evaluated by intravital microscopy and Doppler fluximetry in dorsal window chambers. Ang-1 and its stable variant MAT.Ang-1 induced a concentration-dependent vasodilation of arterioles in vitro, which was blocked with nitric oxide (NO) synthesis inhibitor l-NAME. In vivo, MAT.Ang-1 restored to control levels l-NAME induced peripheral vasoconstriction, decreased blood flow and microvascular hyperpermeability. Tissue protein expression of VE-cadherin was reduced by NOS inhibition and restored to control levels by MAT.Ang-1, whilst VE-cadherin phosphorylation was increased by l-NAME and subsequently reduced by MAT.Ang-1 administration. Moreover, MAT.Ang-1 alone did not modulate systemic levels of angiogenetic factors. Our novel findings report that Ang-1 induces arteriolar vasodilation via release of NO, suggesting that Ang-1 is an important regulator of microvascular tone. As MAT.Ang-1 ameliorates detrimental effects on the microcirculation induced by inhibition of NO synthesis and stabilizes the endothelial barrier function through VE-cadherin, we propose that this Ang-1 variant may serve as a novel therapeutic agent to protect the microcirculation against endothelial dysfunction.
authors.affiliation: Microcirculation Research Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK. Electronic address: alessio.alfieri@kcl.ac.uk.
authors.forename: Alessio
authors.initials: A
authors.lastname: Alfieri
authors.affiliation: Kidney Genetics Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK.
authors.forename: Albert C M
authors.initials: AC
authors.lastname: Ong
authors.affiliation: Laboratory of Biomolecular Research, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Kammerer
authors.affiliation: Microcirculation Research Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK; Kidney Genetics Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK.
authors.forename: Tirupa
authors.initials: T
authors.lastname: Solanky
authors.affiliation: Microcirculation Research Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Bate
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Tasab
authors.affiliation: Microcirculation Research Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Brown
authors.affiliation: Microcirculation Research Group, Faculty of Medicine, Dentistry and Health, University of Sheffield, Sheffield S10 2RX, UK.
authors.forename: Zoe L
authors.initials: ZL
authors.lastname: Brookes
mesh_terms: D042683:Angiopoietin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D015820:Cadherins / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D051379:Mice; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology*; D054792:Muscle, Striated / Q000098:blood supply / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000037:antagonists & inhibitors / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D000099152:Cadherin 5
chemical_list: D042683:Angiopoietin-1; D015703:Antigens, CD; D015820:Cadherins; D004791:Enzyme Inhibitors; D019331:NG-Nitroarginine Methyl Ester; D052250:Nitric Oxide Synthase Type III; D000099152:Cadherin 5; C467628:Angpt1 protein, mouse
keywords: Angiopoetin-1; Endothelium; Intravital microscopy; Microcirculation; VE-cadherin; eNOS