IL-1RA is part of the inflammasome-regulated immune response in bladder epithelial cells and influences colonization of uropathogenic E. coli.

The NLRP3 inflammasome, IL-1β release and pyroptosis (cell lysis) have recently been proposed to be essential for the progression of urinary tract infection (UTI) and elimination of intracellular bacterial niches. However, the effects of IL-1R antagonist (IL-1RA) on immune responses during UTI, except for its ability to disrupt IL-1β signalling, are not well understood. The aim of this study was to investigate the role of IL-1RA in UPEC colonization of bladder epithelial cells and the subsequent host inflammatory response. Human bladder epithelial cells (5637) and CRISPR/Cas9 generated NLRP3 and caspase-1 knockdown cells and IL-1RA knockout cells were stimulated with the UPEC isolate CFT073. The results showed that the UPEC virulence factor α-hemolysin is essential for IL-1RA release, and that the inflammasome-associated proteins caspase-1 and NLRP3 affect the release of IL-1RA. IL-1RA deficient cells showed a reduced adherence and invasion by CFT073 compared to wild-type cells, suggesting that IL-1RA may oppose mechanisms that protects against bacterial colonization. A targeted protein analysis of inflammation-related proteins showed that the basal expression of 23 proteins and the UPEC-induced expression of 10 proteins were significantly altered in IL-1RA deficient bladder epithelial cells compared to Cas9 control cells. This suggests that IL-1RA has a broad effect on the inflammatory response in bladder epithelial cells.