Proinflammatory cytokines upregulate mRNA expression and secretion of vascular endothelial growth factor in cultured human airway smooth muscle cells.

Airflow obstruction in chronic airway disease is associated with airway and pulmonary vascular remodeling, of which the molecular mechanisms are poorly understood. Paracrine actions of angiogenic factors released by resident or infiltrating inflammatory cells following activation by proinflammatory cytokines in diseased airways could play a major role in the airway vascular remodeling process. Here, the proinflammatory cytokines interleukin (IL)-1beta, and tumor necrosis factor (TNF)-alpha were investigated on cell cultures of human airway smooth muscle (ASM) for their effects on mRNA induction and protein release of the angiogenic peptide, vascular endothelial growth factor (VEGF). IL-1beta (0.5 ng/mL) and TNF-alpha (10 ng/mL) each increased VEGF mRNA (3.9 and 1.7 kb) expression in human ASM cells, reaching maximal levels between 16 and 24 and 4 and 8 h, respectively. Both cytokines also induced a time-dependent release of VEGF, which was not associated with increased ASM growth. Preincubation of cells with 1 microM dexamethasone abolished enhanced release of VEGF by TNF-alpha. The data suggest that human ASM cells express and secrete VEGF in response to proinflammatory cytokines and may participate in paracrine inflammatory mechanisms of vascular remodeling in chronic airway disease.

Enhanced bronchial expression of vascular endothelial growth factor and receptors (Flk-1 and Flt-1) in patients with chronic obstructive pulmonary disease.

BACKGROUND: Ongoing inflammatory processes resulting in airway and vascular remodelling characterise chronic obstructive pulmonary disease (COPD). Vascular endothelial growth factor (VEGF) and its receptors VEGFR-1 (Flt-1) and VEGFR-2 (KDR/Flk-1) could play a role in tissue remodelling and angiogenesis in COPD. METHODS: The cellular expression pattern of VEGF, Flt-1, and KDR/Flk-1 was examined by immunohistochemistry in central and peripheral lung tissues obtained from ex-smokers with COPD (forced expiratory volume in 1 second (FEV(1)) <75% predicted; n = 14) or without COPD (FEV(1) >85% predicted; n = 14). The immunohistochemical staining of each molecule was quantified using a visual scoring method with grades ranging from 0 (no) to 3 (intense). RESULTS: VEGF, Flt-1, and KDR/Flk-1 immunostaining was localised in vascular and airway smooth muscle (VSM and ASM) cells, bronchial, bronchiolar and alveolar epithelium, and macrophages. Pulmonary endothelial cells expressed Flt-1 and KDR/Flk-1 abundantly but not VEGF. Bronchial VEGF expression was higher in microvascular VSM cells and ASM cells of patients with COPD than in patients without COPD (1.7 and 1.6-fold, p<0.01, respectively). VEGF expression in intimal and medial VSM (1.7 and 1.3-fold, p<0.05) of peripheral pulmonary arteries associated with the bronchiolar airways was more intense in COPD, as was VEGF expression in the small pulmonary vessels in the alveolar region (1.5 and 1.7-fold, p<0.02). In patients with COPD, KDR/Flk-1 expression was enhanced in endothelial cells and in intimal and medial VSM (1.3, 1.9 and 1.5-fold, p<0.02) while endothelial Flt-1 expression was 1.7 times higher (p<0.03). VEGF expression was significantly increased in bronchiolar and alveolar epithelium as well as in bronchiolar macrophages (1.5-fold, p<0.001). The expression of VEGF in bronchial VSM and mucosal microvessels as well as bronchiolar epithelium was inversely correlated with FEV(1) (r<-0.45; p<0.01). CONCLUSIONS: VEGF and its receptors Flt-1 and KDR/Flk-1 may be involved in peripheral vascular and airway remodelling processes in an autocrine and/or paracrine manner. This system may also be associated with epithelial cell viability during airway wall remodelling in COPD.