Vascular endothelial growth factor synthesis in the acute phase of experimental and clinical lung injury

Vascular endothelial growth factor (VEGF) is a potent angiogenic and endoth elial survival factor, which is abundantly expressed in the normal lung. Co nceivably, VEGF may be released by numerous cell types found around the air spaces, including alveolar type 2 cells, alveolar macrophages, and polymorp honuclear neutrophils. Using a bacteria-induced lung injury model in rats, VEGF expression in lung was investigated. Both VEGF protein and VEGF messenger ribonucleic acid (m RNA), 4 and 24 h after bacterial challenge (Pseudomonas aeruginosa), were d ecreased compared with sham rats. VEGF protein was also investigated in bronchoalveolar lavage (BAL) from pat ients studied within 7 days of acute respiratory distress syndrome (ARDS) o nset and in patients without ARDS. VEGF protein levels in BAL were decrease d in patients with ARDS versus those without (14.3 +/- 11.1 pg.mL(-1) versu s 76.8 +/- 51.1 pg.mL(-1), p=0.03). In aggregate, these findings show that the initial phase of acute lung inju ry is associated with a decrease in vascular endothelial growth factor in t he lung. This downregulation may represent a protective mechanism aimed at limiting endothelial permeability, and may participate in the decrease in c apillary number that is observed during early acute respiratory distress sy ndrome.