Nitric oxide donors augment interleukin-1β-induced vascular endothelial growth factor in airway smooth muscle cells

Angiogenesis and microvascular leakage are features of chronic inflammatory diseases of which molecular mechanisms are poorly understood. We investigated the effects of interleukin-1β (IL-1β) on the expression and secretion of vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in porcine airway smooth muscle cells (PASMC) in relation to a nitric oxide (NO) pathway. Serum-deprived (48 h) PASMC were stimulated with IL-1β alone or with NO donor, L-arginine and/or NO synthase inhibitor L-NAME for 4 and 24 h. IL-1β did not affect PlGF release, but augmented VEGF release (2.4-fold) after 24 h. VEGF release was inhibited by L-NAME (531.8 ± 52 pg/ml), but restored and further elevated by L-arginine (1,529 ± 287 pg/ml). IL-1β up-regulated VEGF mRNA (1.8-fold) and this response was attenuated by L-NAME (1.1-fold) and augmented by L-arginine (3.8-fold) at 4 h. Restoration of a NO pathway by L-arginine in L-NAME-treated cells resulted in elevated VEGF mRNA levels (2.2-fold). [(3)H]Thymidine incorporation assay revealed enhanced porcine pulmonary artery endothelial cell proliferation in response to IL-1β, VEGF and PlGF, and this mitogenic effect was not influenced via the NO pathway. Our results suggest that a NO pathway modulates VEGF synthesis during inflammation contributing to bronchial angiogenesis and vascular leakage.