OBJECTIVETo explore whether coal tar pitch smoke extract (CTP) induced pyroptosis in human bronchial epithelial cells (BEAS-2B).

METHODSBEAS-2B cells were treated with different concentrations of CTP (1, 3 µg/ml) for 8h and 24 h, respectively. Lactic dehydrogenase (LDH) activity and interleukin-1 beta (IL-1β) levels in the supernatants of cell culture media were measured with LDH activity or human IL-1β ELISA kit, respectively. The activity of Caspase-1 was measured with Caspase-1 colorimetric assay kit.

RESULTSThe activity of caspase-1 in 1 and 3 µg/ml CTP groups were (9.29 ± 0.30) and (8.67 ± 0.59) µmol/ml respectively which were both significantly increased compared to that (7.42 ± 0.59) µmol/ml in the control group (P < 0.05) after 8 h exposure, but there was no significant difference in the activity of LDH and levels of IL-1β in the cell culture media among the CTP and control groups. 24 h after exposure, the activity of LDH in the CTP (1, 3 µg/ml) groups were (1323.03 ± 28.53) and (1148.45 ± 16.42) U/dl respectively which were significantly higher than that (1091.93 ± 26.64) U/dl in the control group (P < 0.05), and the levels of IL-1β in the CTP (1 and 3 µg/ml) groups were (125.37 ± 25.00) pg/ml and (92.04 ± 19.09) pg/ml respectively which were significantly higher than that (46.20 ± 14.43) pg/ml in the control group (P < 0.05), but there was no significant difference in the activity of Caspase-1 among CTP and control groups (P < 0.05).

CONCLUSIONCTP treatment induced early increase in caspase-1 activity followed by the increase in LDH activity and IL-1 levels, indicative of pyroptosis in human bronchial epithelial cells.