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Abstract: TH-PO966

IL-6 Signaling Triggers Expulsion of Uropathogenic Bacteria from Host Epithelial Cells to Limit UTI Chronicity

Session Information

Category: Pathology and Lab Medicine

  • 1501 Pathology and Lab Medicine: Basic

Authors

  • Gupta, Sudipti, Nationwide Children's Hospital, Columbus, Ohio, United States
  • Ching, Christina B., Nationwide Children's Hospital, Columbus, Ohio, United States
  • Becknell, Brian, Nationwide Children's Hospital, Columbus, Ohio, United States
Background

Treatment of urinary tract infections (UTIs) has historically relied on the use of antibiotics which are limited by patient intolerance and rising bacterial resistance. Innate immunity represents an attractive alternative in UTI treatment and prevention; however, its influence on bacterial virulence is not well known. Specifically, IL-6 is induced during UTI, but our understanding of its role in UTI pathogenesis is limited. We sought to determine how IL-6 expression alters urothelial susceptibility to infection and impacts bacterial clearance.

Methods

6-8 week old female wild type (WT) C57BL/6J and IL-6 knock out (KO) mice were transurethrally infected with uropathogenic Escherichia coli (UPEC). Bacterial burden was assessed by dilution plating; and intracellular bacterial communities (IBC) were enumerated by beta-galactosidase staining. Gentamicin protection assay quantified intracellular bladder bacterial burden. The impact of IL-6 neutralization and IL-6 rescue on IBC formation was studied in WT and IL-6 KO mice, respectively. Neutralization of serum IL-6 was confirmed by ELISA. In vitro gentamicin protection assay was used to study the impact of recombinant IL-6 on bacterial attachment, invasion, and expulsion in bladder epithelial cells (BECs). Results were evaluated by Mann-Whitney U test with p <0.05 being significant.

Results

A significant increase in IBCs was observed in IL-6 KO mice vs. WT controls early during infection but resolved 24 hours post infection (hpi). These findings were recapitulated by antibody neutralization of IL-6 in WT mice. The increase in IBCs in IL-6 KO animals was reversed with recombinant IL-6. We confirmed an increase in bladder bacterial burden in IL-6 KO mice by ex vivo gentamicin protection assay, which accounts for increased bacteriuria in IL-6 KO compared to WT mice beginning after 24 hpi. In vitro experiments in BEC demonstrated that IL-6 treatment significantly increased UPEC expulsion but did not impact invasion or attachment.

Conclusion

IL-6 reduces UTI susceptibility by promoting UPEC expulsion from host epithelial cells, thereby limiting the ability of UPEC to persist intracellularly and form IBCs. Given that IBC formation represents a significant bottleneck event in UPEC survival, these findings suggest a mechanism whereby IL-6 reduces UTI chronicity.

Funding

  • NIDDK Support