Proteomic analysis of urethral protein expression in an estrogen receptor α-deficient murine model of stress urinary incontinence.

PURPOSE: The roles of estrogen receptor α (ERα) in stress urinary incontinence (SUI) remain elusive. This study was conducted to understand the molecular mechanism of ERα against SUI.

METHODS: Wild-type (ERα(+/+)) and ACTB-cre ERα knockout (ERα(-/-)) female mice were generated. Urethral function and protein expression were measured. Leak point pressures (LPP) and maximum urethral closure pressure (MUCP) were assessed in mice under urethane anesthesia. After the measurements, the urethras were removed for proteomic analysis using the two-dimensional differential gel electrophoresis and liquid chromatography-mass spectrometry technology. Interaction between these ERα pathway proteins was further analyzed by using MetaCore. Lastly, Western blot and immunochemistry (IHC) were used to confirm the candidate protein expression levels and locations, respectively.

RESULTS: Compared with the ERα(+/+) group, the LPP and MUCP values of the ERα(-/-) group were significantly decreased. Additionally, we identified 11 differentially expressed proteins in the urethra of ERα(-/-) female mice; five proteins were down-regulated and six were up-regulated. The majority of the ERα knockout-modified proteins were involved in muscle development, contraction, and regulation, as well as immune response (amphoterin signaling and phagocytosis), proteolysis, and cell adhesion (platelet aggregation and integrin-mediated cell-matrix adhesion). IHC and Western blot confirmed the down-regulation of tropomyosin and up-regulation of myosin in urethra.

CONCLUSIONS: This is the first study to estimate protein expression changes in urethras from ERα(-/-) female mice. These changes could be related to the molecular mechanism of ERα in SUI.