title: Sildenafil potentiates the proliferative effect of porcine pulmonary artery smooth muscle cells induced by serotonin in vitro.
abstract: BACKGROUND
  Sildenafil is one of the selective phosphodiesterase 5 inhibitors that has been proven by many investigators to suppress growth factor stimulated (e.g. platelet-derived growth factor (PDGF) or epidermal growth factor (EGF)) proliferation and hypertrophy of pulmonary artery smooth muscle cells (PASMCs) via cGMP/cGKIa pathway. Serotonin promotes cell cycle progression leading to cell mitogenesis and plays a key role in the pathogenesis of pulmonary artery hypertension. The role of sildenafil in proliferation of PASMCs induced by serotonin has not been investigated so far. In this study we explored the underlying mechanism of the effect of sildenafil on serotonin induced proliferation of porcine PASMCs.
  
  
  METHODS
  PASMCs were cells from primary cultures by the explant method from the pulmonary artery of swine and cells at passage 3 - 5 were used in this study. MTT colorimetric assay and flow cytometry analysis were used to evaluate the cell proliferation and alterations in cell cycle progression respectively. Western blotting analysis was applied to determine the expression of phosphorylated extracellular signal-regulated kinase (ERK), proliferating cell nuclear antigen (PCNA) and mitogen activated protein kinase (MAPK) phosphatase-1 (MKP-1).
  
  
  RESULTS
  Serotonin (10 µmol/L) induced the upregulation of phosphorylation of ERK1/ERK2 and PCNA, an increase in the percentage of cells in S phase and subsequent cell proliferation. Pretreatment with 1 µmol/L sildenafil potentiated the phosphorylation of ERK1/ERK2, an increase in the percentage of cells in S phase and cell proliferation, compared with serotonin stimulation alone (P < 0.05). Furthermore, 30-minute pretreatment with 10 µmol/L U0126, specific antagonist for ERK kinase (MEK) prevented the increase in phosphorylation of ERK1/ERK2 and abolished cell cycle progression and the proliferation of PASMCs induced by sildenafil.
  
  
  CONCLUSIONS
  This study shows that sildenafil potentiated the proliferative effect of serotonin on PASMCs via phosphorylation of ERK1/ERK2.
authors: Department of Anesthesiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Nanjing University Medical School, Nanjing, Jiangsu 210008, China. icecolor@163.com
authors: Bing-bing
authors: BB
authors: Li
authors: Zhen
authors: Z
authors: Jiang
authors: Jian-yin
authors: JY
authors: Sheng
authors: Kang
authors: K
authors: Yao
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D054638:Dual Specificity Phosphatase 1 / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology*; D011687:Purines / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology*; D013552:Swine
chemical_list: D010879:Piperazines; D018809:Proliferating Cell Nuclear Antigen; D011687:Purines; D013450:Sulfones; D012701:Serotonin; D000068677:Sildenafil Citrate; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054638:Dual Specificity Phosphatase 1