Activation of kinin B1 receptors induces chemotaxis of human neutrophils

Kinins are biologically active peptides that are powerful mediators of cellular inflammation. They mimic the cardinal signs of inflammation by inducing vasodilatation and by increasing vascular permeability and pain. Neutrophils are chemoattracted to sites of inflammation by several stimuli. However, the evidence concerning the chemotactic effect of kinin peptides has been contradictory. We analyzed the chemotactic effect of kinin B1 receptor agonists on neutrophils isolated from peripheral blood of human healthy subjects. Chemotaxis was performed using the migration under agarose technique. To test the effect of B1 receptor agonists, each assay was carried out overnight at 37°C in 5% CO2-95% air on neutrophils primed with 1 ng/ml interleukin-1ß. Simultaneous experiments were performed using unprimed cells or cells challenged with formyl-Met-Leu-Phe (fMLP). A clear chemotactic activity was observed when primed neutrophils were challenged with Lys-des[Arg9]-bradykinin (LDBK) or des[Arg9]-bradykinin at 10–10 M but not when unprimed cells were used. A reduction in the chemotactic response was observed after priming of cells in the presence of 0.5 mM cycloheximide and 10 µg/ml brefeldin A, suggesting that some protein biosynthesis is required. Techniques such as reverse transcriptase-polymerase chain reaction and in situ hybridization confirmed the expression of the B1 receptor mRNA, and immunocytochemistry and autoradiography demonstrated the expression of the B1 receptor protein. In contrast to other chemoattractants such as fMLP, cytosolic intracellular calcium did not increase in response to the B1 receptor agonist LDBK. A generation of kinin B1 receptor agonists during the early phase of acute inflammation may favor the recruitment of neutrophils to the inflammatory site.