Vascular endothelial growth factor is increased by human pulmonary cells stimulated with Dermatophagoides sp. extract

Airway remodeling may lead to increased secretion of TGF-beta. TGF-beta is known to activate fibroblasts and to stimulate the secretion of vascular endothelial growth factor (VEGF). Soluble and cell-associated VEGF have been identified in subjects with chronic severe asthma. Dermatophagoides sp. has been shown to contribute to the pathogenesis of asthma. The aim of this study was to determine if the Dermatophagoides sp. extract can stimulate confluent A549 (cA549) to express soluble or cell-associated VEGF and to secrete other factors that stimulate normal human lung fibroblasts (NHLFs) to secrete VEGF. Immunocytochemistry for cell-associated VEGF (pg/mL) was performed on cA549 stimulated with 300, 600, and 1000 AU/mL of dialyzed Dermatophagoides sp. extract for 24 hours with serum-free media (SFM). The subsequent conditioned media (CM) was transferred to NHLF for 24 hours (CM-NHLF). VEGF in CM, CM-NHLF, and control media (CTLM; extract without cA549) were measured by ELISA and normalized to cell density as measured by absorbance of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide at A550 nm (VEGF pg/mL:A550). Parametric data were analyzed by t-test or ANOVA at alpha = 0.05. Dermatophagoides sp. extract increased normalized VEGF secretion by cA549. Immunochemical VEGF expression by cA549 was increased qualitatively by Dermatophagoides sp. extract. The 1000 CM-NHLF showed increased normalized VEGF relative to CTLM. Dermatophagoides sp. stimulates cA549 to increase soluble and immunochemical VEGF and to secrete mediators that stimulate NHLF to increase secretion of VEGF. This suggests that inhalation of dust-mite allergen may stimulate airway cells to increase VEGF secretion, potentially contributing to edema in airway remodeling.