Role of pyroptosis in bilirubin-induced microglial injury

Abstract:

Objective To study whether pyroptosis is involved in the bilirubin-induced injury of primary cultured rat cortical microglial cells. Methods Primary cultured rat cortical microglial cells were randomly administered with 30 μmol/L bilirubin (bilirubin group), 30 μmol/L bilirubin following 30 μmol/L VX-765 pretreatment (VX-765+bilirubin group), or an equal volume of dimethyl sulfoxide (control group). Modified MTT assay was used to measure the viability of microglial cells. Western blot was used to measure the expression of the pyroptosis-related proteins Caspase-1 and gasdermin D (GSDMD). Lactate dehydrogenase (LDH)-release assay was used to evaluate the cytotoxicity of microglial cells. EtBr/EthD2 with different molecular weights (394 Da/1 293 Da) was used to measure the size of plasma membrane pores. ELISA was used to measure the level of the inflammatory factor interleukin-1β (IL-1β) in culture supernatant. Results After bilirubin stimulation, the viability of microglial cells decreased and LDH release increased, both in a time-dependent manner. Compared with the control group, the bilirubin group had a significantly higher positive rate of small-molecule EtBr passing through the cell membrane (P < 0.001), while there was no significant difference in the pass rate of large-molecule EthD2 between groups (P > 0.05). The expression of activated Caspase-1 significantly increased at 0.5 hour after bilirubin stimulation (P < 0.05), and that of activated GSDMD significantly increased at 6 hours after bilirubin stimulation (P < 0.05). The release of IL-1β significantly increased at 6 hours after bilirubin stimulation and reached the peak at 24 hours (P < 0.001). Compared with the bilirubin group, the VX-765+bilirubin group had a significant increase in cell viability (P < 0.05) and significant reductions in the expression of activated GSDMD, the pass rate of EtBr, and the release of LDH and IL-1β (P < 0.05). Conclusions Pyroptosis is involved in bilirubin-induced injury of primary cultured microglial cells.