title: Downregulation of type II bone morphogenetic protein receptor in hypoxic pulmonary hypertension.
abstract: Heterozygous mutations in the type II receptor for bone morphogenetic protein (BMPR-II) and dysfunction of BMPR-II have been implicated in patients with primary pulmonary hypertension (PH). To clarify the possible involvement of BMP and BMPR-II in the development of hypoxic PH, the expression of BMP-2, BMPR-II, and their downstream signals were investigated in rat lung under normal and hypoxic conditions by RT-PCR, immunoblot, and immunohistochemical methods. In rats under normal conditions, BMP-2 is localized in the endothelium of the pulmonary artery, whereas BMPR-II is abundantly expressed in the endothelium, smooth muscle cells, and adventitial fibroblasts. After 0.5 and 3 days of exposure to hypoxia, upregulation of BMP-2 was observed in the intrapulmonary arteries. The change was accompanied by activation of its downstream signaling, p38 MAPK, and Erk1/2 MAPK, and the apoptotic process, measured by caspase-3 activity and TdT-mediated dUTP nick end labeling-positive cells. In contrast, a significant decrease in the expression of BMPR-II and inactivation of p38 MAPK and caspase-3 were observed in the pulmonary vasculature after 7-21 days of hypoxia exposure. Because BMP-2 is known to inhibit proliferation of vascular smooth muscle cells and promote cellular apoptosis, disruption of BMP signaling pathway through downregulation of BMPR-II in chronic hypoxia may result in pulmonary vascular remodeling due to the failure of critical antiproliferative/differentiation programs in the pulmonary vasculature. These results suggest abrogation of BMP signaling may be a common molecular pathogenesis in the development of PH with various pathophysiological events, including primary and hypoxic PH.
authors.affiliation: Department of Respiratory Medicine, Juntendo University School of Medicine, Tokyo Metropolitan Geriatric Hospital, 35-2 Sakae-Machi, Itabashi-Ku, Tokyo 173-0015, Japan. htakahashi@tmgh.metro.tokyo.jp
authors.forename: Hideki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Naoto
authors.initials: N
authors.lastname: Goto
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kojima
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Tsuda
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Morio
authors.forename: Masashi
authors.initials: M
authors.lastname: Muramatsu
authors.forename: Yoshinosuke
authors.initials: Y
authors.lastname: Fukuchi
mesh_terms: D000818:Animals; D017209:Apoptosis; D055396:Bone Morphogenetic Protein 2; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000235:genetics / Q000378:metabolism*; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D008168:Lung / Q000098:blood supply / Q000378:metabolism / Q000473:pathology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D011651:Pulmonary Artery / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D016212:Transforming Growth Factor beta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; C498220:Bmpr2 protein, rat; D052006:Bone Morphogenetic Protein Receptors, Type II; D020169:Caspases