title: Cyclic strain activates the pro-survival Akt protein kinase in bovine aortic smooth muscle cells.
abstract: BACKGROUND
  Pulsatile pressure induced by the beating heart causes cyclic strain on arterial endothelial cells and smooth muscle cells (SMCs). This study examined whether Akt, a serine/threonine protein kinase known to promote cell survival by inhibiting apoptosis, is activated by cyclic strain in bovine aortic SMCs.
  
  
  METHODS
  Bovine aortic SMCs were cultured on flexible-bottomed membranes and then serum-starved for 24 to 36 hours. The cells were then exposed to 150-mm Hg repetitive deformations, which created an average of 10% strain on the monolayer SMCs at a frequency of 60 cycles/minute for 0 (negative control) and 30 minutes. Platelet-derived growth factor (PDGF)--stimulated SMCs were used as positive controls. Phosphorylation of Akt was determined by means of Western blot analysis. An apoptosis assay (TUNEL) was also performed on SMCs exposed to cyclic strain.
  
  
  RESULTS
  Akt phosphorylation was significantly increased over that of the negative control after 30 minutes of cyclic strain and in the PDGF group. Cyclic strain did not increase the prevalence of apoptosis in SMCs over the control.
  
  
  CONCLUSIONS
  Cyclic strain activated the pro-survival Akt kinase. The pro-survival function was supported by the fact that cyclic strain did not increase apoptosis in bovine aortic SMCs. This experiment suggests that cyclic strain may induce arterial wall thickening by tipping the balance toward arterial SMC proliferation through the inhibition of apoptosis.
authors.affiliation: Section of Vascular Surgery, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Chen
authors.forename: D S
authors.initials: DS
authors.lastname: Gortler
authors.forename: S
authors.initials: S
authors.lastname: Kilaru
authors.forename: O
authors.initials: O
authors.lastname: Araim
authors.forename: S G
authors.initials: SG
authors.lastname: Frangos
authors.forename: B E
authors.initials: BE
authors.lastname: Sumpio
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D017209:Apoptosis / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D020287:In Situ Nick-End Labeling; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000201:enzymology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt
chemical_list: D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt