title: Role of RhoB in the regulation of pulmonary endothelial and smooth muscle cell responses to hypoxia.
abstract: BACKGROUND
  RhoA and Rho kinase contribute to pulmonary vasoconstriction and vascular remodeling in pulmonary hypertension. RhoB, a protein homologous to RhoA and activated by hypoxia, regulates neoplastic growth and vasoconstriction but its role in the regulation of pulmonary vascular function is not known.
  
  
  OBJECTIVE
  To determine the role of RhoB in pulmonary endothelial and smooth muscle cell responses to hypoxia and in pulmonary vascular remodeling in chronic hypoxia-induced pulmonary hypertension.
  
  
  RESULTS
  Hypoxia increased expression and activity of RhoB in human pulmonary artery endothelial and smooth muscle cells, coincidental with activation of RhoA. Hypoxia or adenoviral overexpression of constitutively activated RhoB increased actomyosin contractility, induced endothelial permeability, and promoted cell growth; dominant negative RhoB or manumycin, a farnesyltransferase inhibitor that targets the vascular function of RhoB, inhibited the effects of hypoxia. Coordinated activation of RhoA and RhoB maximized the hypoxia-induced stress fiber formation caused by RhoB/mammalian homolog of Drosophila diaphanous-induced actin polymerization and RhoA/Rho kinase-induced phosphorylation of myosin light chain on Ser19. Notably, RhoB was specifically required for hypoxia-induced factor-1α stabilization and for hypoxia- and platelet-derived growth factor-induced cell proliferation and migration. RhoB deficiency in mice markedly attenuated development of chronic hypoxia-induced pulmonary hypertension, despite compensatory expression of RhoA in the lung.
  
  
  CONCLUSIONS
  RhoB mediates adaptational changes to acute hypoxia in the vasculature, but its continual activation by chronic hypoxia can accentuate vascular remodeling to promote development of pulmonary hypertension. RhoB is a potential target for novel approaches (eg, farnesyltransferase inhibitors) aimed at regulating pulmonary vascular tone and structure.
authors.affiliation: Centre for Pharmacology and Therapeutics, Experimental Medicine, Imperial College London, London, UK. b.wojciak-stothard@imperial.ac.uk
authors.forename: Beata
authors.initials: B
authors.lastname: Wojciak-Stothard
authors.forename: Lan
authors.initials: L
authors.lastname: Zhao
authors.forename: Eduardo
authors.initials: E
authors.lastname: Oliver
authors.forename: Olivier
authors.initials: O
authors.lastname: Dubois
authors.forename: Yixing
authors.initials: Y
authors.lastname: Wu
authors.forename: Dimitris
authors.initials: D
authors.lastname: Kardassis
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Vasilaki
authors.forename: Minzhou
authors.initials: M
authors.lastname: Huang
authors.forename: Jane A
authors.initials: JA
authors.lastname: Mitchell
authors.forename: Louise S
authors.initials: LS
authors.lastname: Harrington
authors.forename: Harrington
authors.initials: H
authors.lastname: Louise
authors.forename: George C
authors.initials: GC
authors.lastname: Prendergast
authors.forename: Martin R
authors.initials: MR
authors.lastname: Wilkins
mesh_terms: D000205:Actomyosin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002199:Capillary Permeability; D015687:Cell Hypoxia; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D002908:Chronic Disease; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D065627:Familial Primary Pulmonary Hypertension; D051231:Farnesyltranstransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy / Q000201:enzymology / Q000209:etiology* / Q000235:genetics; D000860:Hypoxia / Q000150:complications* / Q000201:enzymology / Q000235:genetics; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology*; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D011090:Polyenes / Q000494:pharmacology; D053284:Polyunsaturated Alkamides / Q000494:pharmacology; D011651:Pulmonary Artery / Q000201:enzymology; D034622:RNA Interference; D012694:Serine; D022502:Stress Fibers / Q000201:enzymology; D013997:Time Factors; D014162:Transfection; D014661:Vasoconstriction; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D020743:rhoB GTP-Binding Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018994:Myosin Light Chains; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D012694:Serine; D000205:Actomyosin; D051231:Farnesyltranstransferase; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein; C054474:manumycin