title: Differential effects of formoterol on thrombin- and PDGF-induced proliferation of human pulmonary arterial vascular smooth muscle cells.
abstract: BACKGROUND
  Increased pulmonary arterial vascular smooth muscle (PAVSM) cell proliferation is a key pathophysiological component of pulmonary vascular remodeling in pulmonary arterial hypertension (PH). The long-acting β2-adrenergic receptor (β2AR) agonist formoterol, a racemate comprised of (R,R)- and (S,S)-enantiomers, is commonly used as a vasodilator in chronic obstructive pulmonary disease (COPD). PH, a common complication of COPD, increases patients' morbidity and reduces survival. Recent studies demonstrate that formoterol has anti-proliferative effects on airway smooth muscle cells and bronchial fibroblasts. The effects of formoterol and its enantiomers on PAVSM cell proliferation are not determined. The goals of this study were to examine effects of racemic formoterol and its enantiomers on PAVSM cell proliferation as it relates to COPD-associated PH.
  
  
  METHODS
  Basal, thrombin-, PDGF- and chronic hypoxia-induced proliferation of primary human PAVSM cells was examined by DNA synthesis analysis using BrdU incorporation assay. ERK1/2, mTORC1 and mTORC2 activation were determined by phosphorylation levels of ERK1/2, ribosomal protein S6 and S473-Akt using immunoblot analysis.
  
  
  RESULTS
  We found that (R,R) and racemic formoterol inhibited basal, thrombin- and chronic hypoxia-induced proliferation of human PAVSM cells while (S,S) formoterol had lesser inhibitory effect. The β2AR blocker propranolol abrogated the growth inhibitory effect of formoterol. (R,R), but not (S,S) formoterol attenuated basal, thrombin- and chronic hypoxia-induced ERK1/2 phosphorylation, but had little effect on Akt and S6 phosphorylation levels. Formoterol and its enantiomers did not significantly affect PDGF-induced DNA synthesis and PDGF-dependent ERK1/2, S473-Akt and S6 phosphorylation in human PAVSM cells.
  
  
  CONCLUSIONS
  Formoterol inhibits basal, thrombin-, and chronic hypoxia-, but not PDGF-induced human PAVSM cell proliferation and ERK1/2, but has little effect on mTORC1 and mTORC2 signaling. Anti-proliferative effects of formoterol depend predominantly on its (R,R) enantiomer and require the binding with β2AR. These data suggest that (R,R) formoterol may be considered as potential adjuvant therapy to inhibit PAVSM cell proliferation in COPD-associated PH.
authors.affiliation: Pulmonary, Allergy & Critical Care Division, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA. goncharo@mail.med.upenn.edu
authors.forename: Elena A
authors.initials: EA
authors.lastname: Goncharova
authors.forename: Irene S
authors.initials: IS
authors.lastname: Khavin
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Goncharov
authors.forename: Vera P
authors.initials: VP
authors.lastname: Krymskaya
mesh_terms: D001993:Bronchodilator Agents / Q000008:administration & dosage; D002478:Cells, Cultured; D004983:Ethanolamines / Q000008:administration & dosage*; D000068759:Formoterol Fumarate; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects; D010982:Platelet-Derived Growth Factor; D011651:Pulmonary Artery / Q000187:drug effects / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000139:chemically induced* / Q000188:drug therapy / Q000503:physiopathology*; D013917:Thrombin
chemical_list: D001993:Bronchodilator Agents; D004983:Ethanolamines; D010982:Platelet-Derived Growth Factor; D013917:Thrombin; D000068759:Formoterol Fumarate