Modulatory effect of aquaporin 5 on estrogen-induced epithelial-mesenchymal transition in prostate epithelial cells

Background Estrogen is involved in the pathophysiological process of benign prostatic hyperplasia (BPH), in which epithelial-mesenchymal transition (EMT) plays an important role. Upregulation of aquaporin (AQP) 5, which is directly activated by estrogen, has been reported to promote EMT in multiple cells. This study aimed to examine the effects of AQP5 on estrogen-induced EMT in the prostate. Methods Normal prostate (NP) tissue samples without any histopathological changes and BPH tissue samples with pathologically confirmed hyperplasia were obtained. An EMT cell model was subsequently established by adding estradiol (E2) to RWPE-1 cells, after which AQP5 knockdown was performed. Tissue morphological and immunohistochemical features were examined using hematoxylin-eosin and immunohistochemical staining. Western blot analysis was performed to determine the expression of AQPs, estrogen receptors, and EMT-related proteins. Cell proliferation was assessed and supernatants were collected for enzyme-linked immunosorbent assay to determine transforming growth factor-beta 1 (TGF-beta 1) concentrations. Immunofluorescence staining was performed to assess protein expressions in RWPE-1 cells. Results BPH tissues exhibited greater EMT (TGF-beta 1: 1.362 +/- 0.196 vs. 0.107 +/- 0.067, P = 0.003; vimentin: 1.581 +/- 0.508 vs. 0.221 +/- 0.047, P vs. 1.344 +/- 0.088, P < 0.001), higher AQP5 (1.268 +/- 0.136 vs. 0.227 +/- 0.055, P < 0.001) and estrogen receptor (ER) alpha (1.250 +/- 0.117 vs. 0.329 +/- 0.134, P < 0.001) expression but lower ER beta (0.271 +/- 0.184 vs. 1.564 +/- 0.130, P < 0.001) expression than NP tissues. E2-stimulated cells had higher AQP5 expression (1.298 +/- 0.058 vs. 1.085 +/- 0.104, P = 0.049), increased cell proliferation (1.510 +/- 0.089 vs.1.000 +/- 0.038, P < 0.001), and EMT (TGF-beta 1 concentration: 0.352 +/- 0.021 ng/mL vs. 0.125 +/- 0.014 ng/mL, P vs. 0.188 +/- 0.020, P = 0.002; E-cadherin: 0.075 +/- 0.030 vs. 0.843 +/- 0.046, P < 0.001) than controls. E2-stimulated cells with AQP5 knockdown exhibited decreased EMT (TGF-beta 1 concentration: 0.223 +/- 0.041 ng/mL vs. 0.352 +/- 0.021 ng/mL, P = 0.016; vimentin: 0.675 +/- 0.056 vs. 1.641 +/- 0.120, P = 0.001; E-cadherin: 0.159 +/- 0.037 vs. 0.075 +/- 0.030, P = 0.040) than E2-stimulated cells with non-related small interfering RNA (siRNA). Conclusion Our findings suggest that estrogen induces BPH possibly by promoting AQP5 expression. Hence, AQP5 might be a novel target for modulating EMT in prostate epithelial cells.

Automated summary

Estrogen plays a role in the development of benign prostatic hyperplasia (BPH) through promoting AQP5 expression and subsequent epithelial-mesenchymal transition (EMT) in prostate cells. This study found that BPH tissues had higher AQP5 expression and EMT levels compared to normal prostate tissues. Estrogen-stimulated cells had increased AQP5 expression, cell proliferation, and EMT, which could be partially reversed by AQP5 knockdown.