Characterization of the bone morphogenetic protein (BMP) system in human pulmonary arterial smooth muscle cells isolated from a sporadic case of primary pulmonary hypertension: roles of BMP type IB receptor (activin receptor-like kinase-6) in the mitotic action.
The functional involvement of bone morphogenetic protein (BMP) system in primary pulmonary hypertension (PPH) remains unclear. Here we demonstrate a crucial role of the BMP type IB receptor, activin receptor-like kinase (ALK)-6 for pulmonary arterial smooth muscle cell (pphPASMC) mitosis isolated from a sporadic PPH patient bearing no mutations in BMPR2 gene. A striking increase in the levels of ALK-6 mRNA was revealed in pphPASMC compared with control PASMCs, in which ALK-6 transcripts were hardly detectable. BMP-2 and -7 stimulated the mitosis of pphPASMCs, which was opposite to their suppressive effects on the mitosis of the control PASMCs. BMP-4 and -6 and activin inhibited pphPASMC mitosis, whereas these did not affect control PASMCs. The presence of BMP signaling machinery in pphPASMCs was elucidated based on the analysis on Id-1 transcription and Smad-reporter genes. Overexpression of a dominant-negative ALK-6 construct revealed that ALK-6 plays a key role in the mitosis as well as intracellular BMP signaling of pphPASMCs. Gene silencing of ALK-6 using small interfering RNA also reduced DNA synthesis as well as Id-1 transcription in pphPASMCs regardless of BMP-2 stimulation. Although Id-1 response was not stimulated by BMP-2 in control PASMCs, the gene delivery of wild-type ALK-6 caused significant increase in the Id-1 transcripts in response to BMP-2. Additionally, inhibitors of ERK and p38 MAPK pathways suppressed pphPASMC mitosis induced by BMP-2, implying that the mitotic action is in part MAPK dependent. Thus, the BMP system is strongly involved in pphPASMC mitosis through ALK-6, which possibly leads to activation of Smad and MAPK, resulting in the progression of vascular remodeling of pulmonary arteries in PPH.
Takeda
Masaya
M
Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, Okayama City 700-8558, Japan.
Otsuka
Fumio
F
Nakamura
Kazufumi
K
Inagaki
Kenichi
K
Suzuki
Jiro
J
Miura
Daiji
D
Fujio
Hideki
H
Matsubara
Hiromi
H
Date
Hiroshi
H
Ohe
Tohru
T
Makino
Hirofumi
H
D000293:Adolescent; D000328:Adult; D000368:Aged; D052005:Bone Morphogenetic Protein Receptors, Type I; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D007093:Imidazoles / Q000494:pharmacology; D008024:Ligands; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008938:Mitosis / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D017978:Receptors, Growth Factor / Q000235:genetics* / Q000378:metabolism
D019485:Bone Morphogenetic Proteins; D002070:Butadienes; D004791:Enzyme Inhibitors; D007093:Imidazoles; D008024:Ligands; D009570:Nitriles; D011725:Pyridines; D012333:RNA, Messenger; D017978:Receptors, Growth Factor; C113580:U 0126; D017346:Protein Serine-Threonine Kinases; C498214:BMPR1B protein, human; D052005:Bone Morphogenetic Protein Receptors, Type I; C093642:SB 203580