title: Sildenafil potentiates bone morphogenetic protein signaling in pulmonary arterial smooth muscle cells and in experimental pulmonary hypertension.
abstract: OBJECTIVE
  Mutations in the bone morphogenetic protein type II receptor (BMPR-II) are responsible for the majority of cases of heritable pulmonary arterial hypertension (PAH), and BMPR-II deficiency contributes to idiopathic and experimental forms of PAH. Sildenafil, a potent type-5 nucleotide-dependent phosphodiesterase inhibitor, is an established treatment for PAH, but whether sildenafil affects bone morphogenetic protein (BMP) signaling in the pulmonary circulation remains unknown.
  
  
  RESULTS
  Studies were undertaken in human pulmonary arterial smooth muscle cells (PASMCs) and in vivo in the monocrotaline rat model of PAH. In PASMCs, sildenafil enhanced BMP4-induced phosphorylation of Smad1/5, Smad nuclear localization, and Inhibitor of DNA binding protein 1 gene and protein expression. This effect was mimicked by 8-bromo-cyclic GMP. Pharmacological inhibition or small interfering RNA knockdown of cyclic GMP-dependent protein kinase I inhibited the effect of sildenafil on BMP signaling. In functional studies, we observed that sildenafil potentiated the antiproliferative effects of BMP4 on PASMC proliferation. Furthermore, sildenafil restored the antiproliferative response to BMP4 in PASMCs harboring mutations in BMPR-II. In the monocrotaline rat model of PAH, which is characterized by BMPR-II deficiency, sildenafil prevented the development of pulmonary hypertension and vascular remodeling, and partly restored Smad1/5 phosphorylation and Inhibitor of DNA binding protein 1 gene expression in vivo in monocrotaline exposed rat lungs.
  
  
  CONCLUSIONS
  Sildenafil enhances canonical BMP signaling via cyclic GMP and cyclic GMP-dependent protein kinase I in vitro and in vivo, and partly restores deficient BMP signaling in BMPR-II mutant PASMCs. Our findings demonstrate a novel mechanism of action of sildenafil in the treatment of PAH and suggest that targeting BMP signaling may be beneficial in this disease.
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, University of Cambridge School of Clinical Medicine, Box 157, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Li
authors.forename: Rafia S
authors.initials: RS
authors.lastname: Al-Lamki
authors.forename: Changxin
authors.initials: C
authors.lastname: Wu
authors.forename: Astrid
authors.initials: A
authors.lastname: Weiss
authors.forename: Joachim
authors.initials: J
authors.lastname: Berk
authors.forename: Ralph T
authors.initials: RT
authors.lastname: Schermuly
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Morrell
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001665:Binding Sites; D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D062965:Cyclic GMP-Dependent Protein Kinase Type I / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D065627:Familial Primary Pulmonary Hypertension; D006801:Humans; D006976:Hypertension, Pulmonary / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control*; D051798:Inhibitor of Differentiation Protein 1 / Q000235:genetics / Q000378:metabolism; D008297:Male; D016686:Monocrotaline; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011651:Pulmonary Artery / Q000187:drug effects* / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D000068677:Sildenafil Citrate; D051898:Smad1 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism; D013450:Sulfones / Q000494:pharmacology*; D014162:Transfection; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D000959:Antihypertensive Agents; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; C497453:ID1 protein, human; C497454:ID1 protein, rat; D051798:Inhibitor of Differentiation Protein 1; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; C497399:SMAD1 protein, human; C497797:SMAD5 protein, human; D051898:Smad1 Protein; C497400:Smad1 protein, rat; D051902:Smad5 Protein; C497799:Smad5 protein, rat; D013450:Sulfones; D014665:Vasodilator Agents; C016276:8-bromocyclic GMP; D016686:Monocrotaline; D000068677:Sildenafil Citrate; D062965:Cyclic GMP-Dependent Protein Kinase Type I; C569718:PRKG1 protein, human; C498218:BMPR2 protein, human; C498220:Bmpr2 protein, rat; D052006:Bone Morphogenetic Protein Receptors, Type II; D006152:Cyclic GMP