Smad-dependent and smad-independent induction of id1 by prostacyclin analogues inhibits proliferation of pulmonary artery smooth muscle cells in vitro and in vivo.
BACKGROUND
Mutations in the bone morphogenetic protein type II receptor (BMPR-II) are responsible for the majority of cases of heritable pulmonary arterial hypertension (PAH). Mutations lead to reduced Smad1/5-driven expression of inhibitor of DNA binding protein 1 (Id1) and loss of the growth suppressive effects of BMPs. The impact of existing PAH therapies on BMP signaling is lacking.


OBJECTIVE
Because prostacyclin analogues are effective treatments for clinical PAH, we hypothesized that these agents enhance Smad1/Id1 signaling.


RESULTS
Iloprost alone induced Id1 expression in human pulmonary artery smooth muscle cells (PASMCs), an effect that was independent of Smad1/5 activation but dependent on a cAMP-responsive element in the Id1 promoter. In addition, iloprost and treprostinil enhanced BMP-induced phosphorylation of Smad1/5 and Id1 expression in a cAMP-dependent manner. The mechanism involved suppression of inhibitory Smad, Smad6. Furthermore, iloprost rescued the deficit in Smad1/5 phosphorylation and Id gene expression in PASMCs harboring mutations in BMPR-II and restored growth suppression to BMP4 in mutant PASMCs. We confirmed a critical role for Id1 in PASMC proliferation. Reduced expression of Id1 was observed in concentric intimal lesions of heritable PAH cases. In the monocrotaline rat model of PAH, associated with reduced BMPR-II expression, we confirmed that treprostinil inhibited smooth muscle cell proliferation and prevented progression of PAH while enhancing Smad1/5 phosphorylation and Id1 gene expression.


CONCLUSIONS
Prostacyclin analogues enhance Id1 expression in vitro and in vivo and restore deficient BMP signaling in BMPR-II mutant PASMCs.
Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's and Papworth Hospital, Cambridge CB20QQ, UK.
Jun
J
Yang
Xiaohui
X
Li
Rafia S
RS
Al-Lamki
Mark
M
Southwood
Jing
J
Zhao
Andrew M
AM
Lever
Friedrich
F
Grimminger
Ralph T
RT
Schermuly
Nicholas W
NW
Morrell
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004195:Disease Models, Animal; D011464:Epoprostenol / Q000031:analogs & derivatives / Q000494:pharmacology*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000139:chemically induced / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016285:Iloprost / Q000494:pharmacology; D051798:Inhibitor of Differentiation Protein 1 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D016686:Monocrotaline; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism*; D051898:Smad1 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism; D051905:Smad6 Protein / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
D000959:Antihypertensive Agents; D055415:Bone Morphogenetic Protein 4; C497453:ID1 protein, human; C497454:ID1 protein, rat; D051798:Inhibitor of Differentiation Protein 1; C497399:SMAD1 protein, human; C497797:SMAD5 protein, human; C497802:SMAD6 protein, human; D051785:Smad Proteins; D051898:Smad1 Protein; C497400:Smad1 protein, rat; D051902:Smad5 Protein; C497799:Smad5 protein, rat; D051905:Smad6 Protein; D016686:Monocrotaline; D011464:Epoprostenol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C498218:BMPR2 protein, human; D052006:Bone Morphogenetic Protein Receptors, Type II; D016285:Iloprost; C427248:treprostinil