One in two women experience urinary tract infection (UTI) at least once in their lifetime, and after menopause one in four women with UTI develops recurrence. Though antibiotic treatment for UTI primarily centers on antibiotics, topical estrogen administered transvaginally has been shown to reduce UTI prevalence in randomized controlled trials. How estrogen status governs susceptibility to UTIs remains unknown but we previously reported that ERβ likely has a protective effect.  We created a transgenic C57BL/6 mice with restricted urothelial overexpression of ERβ (uERβ-OE+) leveraging the uroplakins II promoter to drive downstream ERβ expression.  This uERβ-OE+ mice has been shown to clear uropathogenic E. coli (UPEC) quicker than wildtype (WT) mice suggesting a protective role of ERβ. We measured changes in bladder mucosal ERβ mRNA expression 24 hours after experimentally induced UTI in both uERβ-OE+ and controls.

All experiments were IACUC approved.  A total of 20 female mice (n=10 uERβ-OE+; n=10 controls), aged 4-6 months, were used.  One mouse died during the experiment.  The control mice were the non-ERβ gene carrying littermates of the uERβ-OE+ animals.  uERβ-OE+ and control mice underwent intravesical instillation with phosphate buffered saline (n=5) or UPEC (n=5, UTI89 at 108 colony forming units (CFU). Twenty-four hours later, the bladder was harvested and mucosa isolated for mRNA isolation. Quantitative PCR (qPCR) was performed to compare expression changes of ERβ mRNA after UTI induction.   Normalization gene was GAPDH.  The relative expression levels of ERβ were measured, averaged per animal group and standard deviation was calculated. Students t-test was used to compare the means.

See Figure 1.  As expected, mucosal expression of ERβ is about 4-fold higher in the uERβ-OE+ mice compared to controls (relative expression of 1.95 in uERβ-OE+ compared to 0.49 in controls).  24-hours after UPEC inoculation (UTI), mucosal expression of ERβ was significantly decreased in both uERβ-OE+ (relative expression 0.99) and control mice (relative expression 0.036). However, the downregulation was much less in uERβ-OE+ (48.84% downregulation) than the control mice (92.75% downregulation).

The ERβ gene expression in mouse mucosa is downregulated during the first 24 hours of UTI infection. This effect is blunted in ERβ-OE+ by nature of the genetic construct from the design of the transgenic animal. Downregulation of ERβ after UTI seems contradictory when ERβ signaling is a protective mechanism in UTI pathogenesis.  This was an unexpected result.

The effect of ERβ signaling is complex and is affected during interaction with UPEC.  Future studies of consequences of the ERβ downregulation remains to be investigated.