title: Sildenafil prevents change in RhoA expression induced by chronic hypoxia in rat pulmonary artery.
abstract: Exposure to chronic hypoxia (CH) induces a sustained pulmonary hypertension associated with structural and functional changes in the pulmonary arterial bed, including alterations of contractile properties. The small G-protein RhoA and its effector Rho kinase play a major role in the sustained rise in tension induced by vasoconstrictors. The aim of this study was to analyze the effect of CH on the RhoA/Rho kinase signaling pathway in the rat pulmonary artery. Maximal contraction of pulmonary artery rings to endothelin-1, noradrenaline, and the thromboxane A2 analog U46619 was markedly decreased in rats exposed to CH (10% O2, 2 weeks). This CH-induced decrease response to agonists was attributable to the abolition of RhoA-mediated Ca2+ sensitization of the contraction. Real-time reverse transcriptase-polymerase chain reaction and Western blot analysis revealed a decrease in RhoA mRNA (79.4+/-6.0%, n=4) and RhoA (81.1+/-8.0%, n=4) expression in the main pulmonary artery from CH rats, whereas RhoA expression was not modified in arterial smooth muscle cells and arteries exposed to hypoxia and high intraluminal pressure, respectively. Treatment of rats with sildenafil (25 mg/kg per day) throughout 2 weeks of exposure to CH prevented CH-induced downregulation of RhoA, reduction of contraction, and pulmonary artery remodeling. These findings indicate that CH-induced downregulation of RhoA expression, leading to the abolition of RhoA/Rho kinase-mediated Ca2+ sensitization of contraction, is responsible for the decreased responses to contracting agonists in the pulmonary artery of CH rats. These alterations are prevented by sildenafil, indicating a major role of the NO/cyclic GMP pathway in CH-induced altered RhoA signaling in the pulmonary artery.
authors.affiliation: Inserm U-533, Faculté des Sciences, Nantes, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Sauzeau
authors.forename: Malvyne
authors.initials: M
authors.lastname: Rolli-Derkinderen
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Lehoux
authors.forename: Gervaise
authors.initials: G
authors.lastname: Loirand
authors.forename: Pierre
authors.initials: P
authors.lastname: Pacaud
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D009638:Norepinephrine / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011651:Pulmonary Artery / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D011687:Purines; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D000068677:Sildenafil Citrate; D013450:Sulfones; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D047908:Intracellular Signaling Peptides and Proteins; D010879:Piperazines; D011687:Purines; D012333:RNA, Messenger; D013450:Sulfones; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D011189:Potassium Chloride; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D000068677:Sildenafil Citrate; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D002118:Calcium; D009638:Norepinephrine