Estrogen attenuates TGF-β1 induced elastogenesis in rat urethral smooth muscle cells by inhibiting Smad response elements.

PURPOSE: We investigated the effect and mechanism of estrogen on elastogenesis in urethral smooth muscle cells in vitro.

MATERIALS AND METHODS: Urethral smooth muscle cells were isolated from normal adult female rats. For elastogenesis assay cells were treated with TGF-β1, the potent TGF-β1 receptor inhibitor SB431542 and estrogen for 2 weeks. Real-time polymerase chain reaction was performed to assay gene expression during this process. Activity of the TGF-β1 responsive elements CAGA(12)-Luc and GCCG(12)-Luc were also assayed. Estrogen receptor and Smad2/3 interaction was evaluated by immunoprecipitation and Western blot.

RESULTS: TGF-β1 induced elastogenesis in rat urethral smooth muscle cells. This effect was partially blocked by estrogen and completely abrogated by SB431542. SB431542 completely inhibited activation of the Smad2/3 response element CAGA(12)-Luc and estrogen significantly inhibited activation. The Smad1/4 response element GCCG(12)-Luc was not affected by SB431542 treatment but estrogen partially inhibited the activation of GCCG(12)-Luc induced by TGF-β1. Estrogen receptor bound to Smad 2 and 3 in vitro.

CONCLUSIONS: Estrogen attenuated TGF-β1 induced elastogenesis via binding of its activated receptor to Smad2/3 to inhibit the TGF-β1 response element in rat urethral smooth muscle cells.