Cell culture
Human alveolar adenocarcinoma cells (A549) from passages four to six were used for the experiments. This cell line was used due to the constitutively expression of bradykinin receptors. Cells were cultured in DMEM medium supplemented with 10 % of fetal bovine serum at 37 °C. Cells were grown to confluence in 6-well plates and incubated in 2 ml of serum-free medium for 24 h. Cells were treated with vehicle, bradykinin (20 nM), bradykinin + the B2 receptor antagonist HOE-140 (1 μM), or bradykinin + the B1 receptor antagonist Lys (Des-Arg9-Leu8) bradykinin (1 μM). At the end of the treatment, culture medium was collected, centrifuged at 2500 g for 10 min, and stored at −80 °C. Cells were washed three times with PBS, scraped into PBS, and centrifuged for 5 min at 600xg. Cells were re-suspended in 250 μl of ice-cold sodium phosphate (100 mM, pH 6.5) and sonicated on ice. Cell lysate (220 μl) was mixed with 220 μl of perchloric acid (1.2 M), centrifuged at 2000 g for 10 min at 4 °C, and the supernatant collected and stored at −80 °C until further processing. Data was normalized by total protein content in the cells lysate and measured with the Pierce® BCA kit (Thermo Scientific, Rockford IL) according the manufacturer protocol.