title: Mechanical activation of angiotensin II type 1 receptors causes actin remodelling and myogenic responsiveness in skeletal muscle arterioles.
abstract: Candesartan, an inverse agonist of the type 1 angiotensin II receptor (AT1R), causes a concentration-dependent inhibition of pressure-dependent myogenic tone consistent with previous reports of mechanosensitivity of this G protein-coupled receptor. Mechanoactivation of the AT1R occurs independently of local angiotensin II production and the type 2 angiotensin receptor. Mechanoactivation of the AT1R stimulates actin polymerization by a protein kinase C-dependent mechanism, but independently of a change in intracellular Ca2+. Using atomic force microscopy, changes in single vascular smooth muscle cell cortical actin are observed to remodel following mechanoactivation of the AT1R.
  
  
  
  The Gq/11protein-coupled angiotensin II type 1 receptor (AT1R) has been shown to be activated by mechanical stimuli. In the vascular system, evidence supports the AT1R being a mechanosensor that contributes to arteriolar myogenic constriction. The aim of this study was to determine if AT1R mechanoactivation affects myogenic constriction in skeletal muscle arterioles and to determine underlying cellular mechanisms. Using pressure myography to study rat isolated first-order cremaster muscle arterioles the AT1R inhibitor candesartan (10-7-10-5m) showed partial but concentration-dependent inhibition of myogenic reactivity. Inhibition was demonstrated by a rightward shift in the pressure-diameter relationship over the intraluminal pressure range, 30-110 mmHg. Pressure-induced changes in global vascular smooth muscle intracellular Ca2+(using Fura-2) were similar in the absence or presence of candesartan, indicating that AT1R-mediated myogenic constriction relies on Ca2+-independent downstream signalling. The diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) reversed the inhibitory effect of candesartan, while this rescue effect was prevented by the protein kinase C (PKC) inhibitor GF 109203X. Both candesartan and PKC inhibition caused increased G-actin levels, as determined by Western blotting of vessel lysates, supporting involvement of cytoskeletal remodelling. At the single vascular smooth muscle cell level, atomic force microscopy showed that cell swelling (stretch) with hypotonic buffer also caused thickening of cortical actin fibres and this was blocked by candesartan. Collectively, the present studies support growing evidence for novel modes of activation of the AT1R in arterioles and suggest that mechanically activated AT1R generates diacylglycerol, which in turn activates PKC which induces the actin cytoskeleton reorganization that is required for pressure-induced vasoconstriction.
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.|Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, 65211, USA.|Robert M. Berne Cardiovascular Research Centre and Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, 22908, USA.
authors.forename: Kwangseok
authors.initials: K
authors.lastname: Hong
authors.affiliation: College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, 60612, USA.
authors.forename: Guiling
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.|Department of Biomedical Engineering, University of South Dakota, Sioux Falls, SD, 57107, USA.
authors.forename: Zhongkui
authors.initials: Z
authors.lastname: Hong
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.|Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, 65211, USA.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, 60612, USA.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Clifford
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.|Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, 65211, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Davis
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.|Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, 65211, USA.
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Meininger
authors.affiliation: Dalton Cardiovascular Research Centre, University of Missouri, Columbia, MO, 65211, USA.|Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, 65211, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hill
mesh_terms: D000009:Abdominal Muscles / Q000502:physiology*; D000199:Actins / Q000502:physiology*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001160:Arterioles / Q000187:drug effects / Q000502:physiology*; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D002216:Captopril / Q000494:pharmacology; D002478:Cells, Cultured; D004075:Diglycerides / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D019808:Losartan / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D011312:Pressure; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000502:physiology*; D013777:Tetrazoles / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D000199:Actins; D047228:Angiotensin II Type 1 Receptor Blockers; D000959:Antihypertensive Agents; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D004075:Diglycerides; D007093:Imidazoles; D007211:Indoles; D008301:Maleimides; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D014662:Vasoconstrictor Agents; C073402:PD 123319; C038237:1-oleoyl-2-acetylglycerol; C437965:olmesartan; D002216:Captopril; D011493:Protein Kinase C; C066026:losartan carboxylic acid; D019808:Losartan; C070515:bisindolylmaleimide I; C081643:candesartan
keywords: actin stress fibres; cytoskeleton; mechanotransduction; myogenic response; protein kinase C; type 1 angiotensin II receptor; vascular smooth muscle cell signalling