Nephropathogenic infectious bronchitis virus-induced pyroptosis of chicken renal tubular epithelial cells via the MDA5/NF-κB/NLRP3 signalling pathway

MDA5 is an innate pattern recognition receptor that is involved in the recognition of various viruses. It can recognize RNA viruses, activate downstream signalling pathways, facilitate the transcription of inflammatory factors, and induce cell pyroptosis. Pyroptosis is a form of programmed cell death accompanied by the release of inflammatory factors and an inflammatory response. In this study, we hypothesize that pyroptosis is elicited by the signalling cascade subsequent to the recognition of nephropathogenic infectious bronchitis virus (NIBV) by MDA5. Thus, we infected chicken renal tubular epithelial cells with NIBV and discovered that NIBV infection induced pyroptosis and increased the mRNA levels of MDA5. Consequently, we infected primary chicken renal tubular epithelial cells with NIBV and inhibited TRAF6 expression using the exogenous inhibitor C25-140. We found that NIBV could increase lactate dehydrogenase (LDH) levels, increase the proportion of pyroptotic cells, and increase the mRNA and protein levels of the MDA5/NF-κB signalling pathway and the classical pyroptosis pathway. Here, we selected the ubiquitin ligase TRAF6, a key node in the MDA5/NF-κB signalling pathway, from molecular biological and genetic perspectives to explore the molecular mechanism of NIBV-induced pyroptosis. After the inhibitor C25-140 was used, NIBV-induced apoptosis and the activity of the MDA5/NF-κB/NLRP3 pathway were reversed. In addition, the amount of NIBV replication in the cells was reduced. In conclusion, the MDA5/NF-κB/NLRP3 signalling pathway is involved in the regulation of pyroptosis in a NIBV-infected chicken renal tubular epithelial cell model. The inhibition of this signalling pathway can alleviate NIBV-induced pyroptosis and reduce the replication of NIBV in cells, which could become one strategy for treating NIBV.