Regulation of Urinary Tract Infection (UTI) Susceptibility by Stat3-Driven DMBT1 Expression

Background: Innate immune effectors like antimicrobial peptides exist to reduce UTI susceptibility in humans. We focus on studying the regulation of innate immune mechanisms by transcription factor, Stat3, to limit UTI susceptibility. Deleted in Malignant Brain Tumors-1 (DMBT1) protein is an antimicrobial peptide with antibacterial properties likely due to its function as a pattern recognition receptor. A clinical study shows lower DNA copy number of DMBT1 leads to increase the odds of recurrent UTI. While DMBT1 has been demonstrated to be regulated by Stat3 in models of Crohn’s disease, it has not been associated with Stat3 expression in models of UTI. We hypothesized that Stat3 manipulation in UTI would impact DMBT1 expression. Methods: 6-8 weeks old female FVB/N wild type (WT) and constitutively active Stat3 (Stat3C) mice underwent experimental UTI. Urine and bladder tissue was collected up to 7 days post infection (dpi). Dilution plating was performed to quantify bladder and urine bacterial burden. Qiagen RT2 profiler PCR mouse antimicrobial array was performed on bladders followed by confirmatory qRT-PCR. Results were evaluated by unpaired t-test or Mann-Whitney U test when appropriate, with p<0.05 being significant. Results: Stat3C mice demonstrated reduced urine and then bladder burden by 7 dpi (p=0.0123). Evaluation of antibacterial responses on PCR array between the Stat3C and WT mice demonstrated significant differences in DMBT1 at baseline, peaking at 24hpi, and then persisting at 7dpi (p<0.01). Upon confirmatory qRT-PCR, DMBT1 was significantly elevated at baseline and 24hpi between Stat3C and WT mice (p<0.008). DMBT1 induction in infected Stat3C mice peaked at 24hpi with a 46-fold increase over baseline. This induction persisted even at 7dpi (8 fold over baseline). Conclusion: Urothelial Stat3 overexpression results in baseline up-regulation of DMBT1 gene expression with a further increase during infection, particularly peaking at 24hpi. This is the first evidence of DMBT1 expression being regulated by Stat3 during UTI. Funding: NIDDK Support