Cigarette smoke and α,β-unsaturated aldehydes elicit VEGF release through the p38 MAPK pathway in human airway smooth muscle cells and lung fibroblasts

BACKGROUND AND PURPOSE Vascular endothelial growth factor (VEGF) is an angiogenic factor known to be elevated in the sputum of asymptomatic smokers as well as smokers with bronchitis type of chronic obstructive pulmonary disease. The aim of this study was to investigate whether acute exposure to cigarette smoke extract altered VEGF production in lung parenchymal cells. EXPERIMENTAL APPROACH We exposed human airway smooth muscle cells (ASMC), normal human lung fibroblasts (NHLF) and small airways epithelial cells (SAEC) to aqueous cigarette smoke extract (CSE) in order to investigate the effect of cigarette smoke on VEGF expression and release. KEY RESULTS Vascular endothelial growth factor release was elevated by sub-toxic concentrations of CSE in both ASMC and NHLF, but not in SAEC. CSE-evoked VEGF release was mimicked by its component acrolein at concentrations (10-100 mu M) found in CSE, and prevented by the antioxidant and alpha,beta-unsaturated aldehyde scavenger, N-acetylcysteine (NAC). Both CSE and acrolein (30 mu M) induced VEGF mRNA expression in ASMC cultures, suggesting an effect at transcriptional level. Crotonaldehyde and 4-hydroxy-2-nonenal, an endogenous alpha,beta-unsaturated aldehyde, stimulated VEGF release, as did H2O2. CSE-evoked VEGF release was accompanied by rapid and lasting phosphorylation of p38 MAPK (mitogen-activated protein kinase), which was abolished by NAC and mimicked by acrolein. Both CSE- and acrolein-evoked VEGF release were blocked by selective inhibition of p38 MAPK signalling. CONCLUSIONS AND IMPLICATIONS alpha,beta-Unsaturated aldehydes and possibly reactive oxygen species contained in cigarette smoke stimulate VEGF expression and release from pulmonary cells through p38 MAPK signalling.