title: Antagonists to endothelin receptor type B promote apoptosis in human pulmonary arterial smooth muscle cells.
abstract: OBJECTIVE
  Vascular remodeling results from aberrations in the balance between cell proliferation and death, which is seen in the obstructive vasculature of pulmonary arterial hypertension (PAH). Endothelin (ET)-1 has a potent proliferative activity on vascular smooth muscle cells, and ET receptor inhibitors are used to treat PAH; however, it remains unclear whether ET receptor inhibition contributes to the apoptosis of pulmonary arterial smooth muscle cells (PASMCs), another cause of pulmonary vascular remodeling.
  
  
  METHODS
  Cultured human PASMCs were treated with the ETA receptor antagonist BQ-123 (100μM), or the ETB antagonist A-192621 (1-100μM) or BQ-788 (1-100μM) for 48h. The cells were then incubated for another 24h with or without doxorubicin (DOX, 1μM), an anthracyclin antitumor antibiotic that promotes p53-mediated apoptosis. Cell viability and apoptosis were evaluated by MTT assays, caspase-3/7 activity assays, and Western blots for cleaved caspase-3 expression.
  
  
  RESULTS
  The viability of PASMCs was significantly decreased by A-192621 and BQ-788, in a dose-dependent manner. A-192621 and BQ-788 significantly increased the caspase-3/7 activity and cleaved caspase-3 expression in PASMCs. The PASMCs' susceptibility to DOX-induced apoptosis was significantly higher in the presence of A-192621 and BQ-788 than with vehicle. However, BQ-123 did not affect these parameters.
  
  
  CONCLUSIONS
  Blockade of the ETB receptor increases the extent of apoptosis and susceptibility to DOX-induced apoptosis in PASMCs. Apoptosis caused by ETB receptor blockade in PASMCs may be one of the mechanisms by which vascular remodeling is reduced in ET receptor inhibitor-based PAH treatments.
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan. Electronic address: ssakai@md.tsukuba.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sakai
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Maruyama
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Taizo
authors.initials: T
authors.lastname: Kimura
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Tajiri
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Junya
authors.initials: J
authors.lastname: Honda
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Homma
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Aonuma
authors.affiliation: Division of Cardiovascular Medicine, Department of Clinical Medicine, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyauchi
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D002478:Cells, Cultured; D065128:Endothelin Receptor Antagonists / Q000494:pharmacology*; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000187:drug effects*
chemical_list: D065128:Endothelin Receptor Antagonists; D044023:Receptor, Endothelin B; D053148:Caspase 3; D053179:Caspase 7
keywords: Apoptosis; Endothelin receptor antagonist; Pulmonary arterial smooth muscle cell; Pulmonary vascular remodeling