Substance P triggered pyroptotic cell death in human bronchial epithelial cell lines. (a, b): 16-HBE and BEAS-2B cells were treated with different doses (0, 0.1, 0.5 and 1 μM) of SP for 8 h. Cell viability was determined using the CCK8 assay. (c, d): The cell viability of 16-HBE and BEAS-2B cells were treated by SP was detected by colony formation. (e): ASC and Caspase-1 immunofluorescence of 16-HBE and BEAS-2B cells treated with 0.5 μM SP. (f): The release of LDH from SP-treated 16-HBE and BEAS-2B cells was measured by LDH assay kit. (g-i): Protein levels of NLRP3, ASC and Caspase-1 were detected by Western blot. (j): The levels of IL-1β were determined by ELISA. (k): The le ansvels of IL-18 were determined by ELISA. Each experiment was conducted in triplicate. *P < 0.05, ** P < 0.01, ***P < 0.001, ****P < 0.0001.