title: Cigarette smoke regulates VEGFR2-mediated survival signaling in rat lungs.
abstract: BACKGROUND
  Vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2)-mediated survival signaling is critical to endothelial cell survival, maintenance of the vasculature and alveolar structure and regeneration of lung tissue. Reduced VEGF and VEGFR2 expression in emphysematous lungs has been linked to increased endothelial cell death and vascular regression. Previously, we have shown that CS down-regulated the VEGFR2 and its downstream signaling in mouse lungs. However, the VEGFR2-mediated survival signaling in response to oxidants/cigarette smoke (CS) is not known. We hypothesized that CS exposure leads to disruption of VEGFR2-mediated endothelial survival signaling in rat lungs.
  
  
  METHODS
  Adult male Sprague-Dawley rats were exposed CS for 3 days, 8 weeks and 6 months to investigate the effect of CS on VEGFR2-mediated survival signaling by measuring the Akt/PI3-kinase/eNOS downstream signaling in rat lungs.
  
  
  CONCLUSIONS
  We show that CS disrupts VEGFR2/PI3-kinase association leading to decreased Akt and eNOS phosphorylation. This may further alter the phosphorylation of the pro-apoptotic protein Bad and increase the Bad/Bcl-xl association. However, this was not associated with a significant lung cell death as evidenced by active caspase-3 levels. These data suggest that although CS altered the VEGFR2-mediated survival signaling in the rat lungs, but it was not sufficient to cause lung cell death.
  
  
  CONCLUSIONS
  The rat lungs exposed to CS in acute, sub-chronic and chronic levels may be representative of smokers where survival signaling is altered but was not associated with lung cell death whereas emphysema is known to be associated with lung cell apoptosis.
authors.affiliation: National Heart and Lung Institute, Imperial College London, UK. p.kirkham@imperial.ac.uk.
authors.forename: John A
authors.initials: JA
authors.lastname: Marwick
authors.forename: Indika
authors.initials: I
authors.lastname: Edirisinghe
authors.forename: Gnanapragasam
authors.initials: G
authors.lastname: Arunachalam
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Stevenson
authors.forename: William
authors.initials: W
authors.lastname: Macnee
authors.forename: Paul A
authors.initials: PA
authors.lastname: Kirkham
authors.forename: Irfan
authors.initials: I
authors.lastname: Rahman