Decrease of vascular endothelial growth factor in macrophages from long-term smokers

Abstract

Vascular endothelial growth factor (VEGF), a survival factor for endothelial cells and a promoter of angiogenesis, is reportedly expressed in alveolar macrophages (AMs). To investigate whether long-term smoking with age affects VEGF expression in AMs, bronchoalveolar lavage (BAL) was performed on 18 young and 23 older volunteers with various smoking histories. The expressions of VEGF and its functional receptor, fms-like tyrosine kinase (Flt)-1, were quantified in AMs by real-time RT-PCR and, further, the level of VEGF in BAL fluid was determined by ELISA. VEGF mRNA in AMs demonstrated a 1.8-fold reduction in current smokers compared with nonsmokers in older subjects and, furthermore, a 1.5-fold downregulation in those with emphysema, although there was no difference between current smokers and nonsmokers among the young subjects. The downregulation in total VEGF mRNA was supported by the substantial reduction of VEGF121 and VEGF165 isoforms. However, in contrast, Flt-1 mRNA did not differ within the older groups, whereas it was upregulated in young current smokers compared with age-matched nonsmokers. VEGF in BAL fluid is significantly decreased in current smokers compared with nonsmokers, regardless of their age. In conclusion, these data imply that the biological availability of vascular endothelial growth factor in alveolar macrophages is impaired in older current smokers with long-term smoking histories.