Bradykinin stimulates lung fibroblasts to release neutrophil and monocyte chemotactic activity

Activation of the kallikrein-kinin system in lung injury has long been reco gnized. However, the effects of bradykinin (BK) on human lung fibroblasts ( HLF) remain to be elucidated. We determined whether BK stimulates HLF to re lease chemotactic activity for neutrophils and monocytes (NCA and MCA, resp ectively). We evaluated HLF supernatant fluids for chemotactic activity thr ough a blind-well chamber technique. HLF released NCA and MCA in a dose- an d time-dependent manner in response to BK. The release of chemotactic activ ity was inhibited by lipoxygenase inhibitors and cycloheximide. Molecular s ieve column chromatography revealed that both NCA and MCA had multiple chem otactic peaks. NCA was inhibited by a leukotriene (LT) B-4 receptor antagon ist and by antibodies to interleukin (IL)-8 and granulocyte colony-stimulat ing factor (G-CSF). MCA was attenuated by the LTB4 receptor antagonist and by antibodies to monocyte chemoattractant protein-1 (MCP-1), granulocyte-ma crophage colony-stimulating factor (GM-CSF), and transforming growth factor (TGF)-beta. Both the LTB4 receptor antagonist and these antibodies inhibit ed chemotactic activity of the molecular weights corresponding to MCP-1, GM -CSF, and TGF-beta, separated by column chromatography. The concentrations of IL-8, G-CSF, MCP-1, GM-CSF, and TGF-beta in supernatant fluids increased significantly in a time-dependent manner in response to BK. The receptors responsible for the release of NCA, MCA, and individual chemokines included both BKB1 and BKB2 receptors. These data suggest that BK may stimulate lun g fibroblasts to release inflammatory cytokines, which may modulate lung in flammation.