Abstract:

Objective To investigate the expression and nuclear translocation of Yin Yang 1 （YY1） in an inflammatory model of human fallopian tube epithelial cells， as well as its regulatory role in fibrosis and epithelial-mesenchymal transition. Methods Human fallopian tube epithelial cells were cultured in vitro， and an inflammatory cell model was established via lipopolysaccharide （LPS） stimulation. Enzyme-linked immunosorbent assay （ELISA） was applied to detect the levels of inflammatory cytokines in cell culture supernatant to identify the optimal stimulation conditions. Real-time quantitative PCR （RT-qPCR） was performed to quantify YY1 mRNA expression， and Western blot analysis was conducted to evaluate YY1 protein nuclear translocation. YY1 expression was knocked down via transfection with human YY1-targeted siRNA interference plasmids， and cells were divided into four groups： the Control group， the LPS group， the LPS + si-NC group， and the LPS + si-YY1 group. Immunofluorescence staining was performed to detect the expression levels of α-SMA and YY1. RT-qPCR and Western blot were used to assess the expression changes of fibrosis markers including α-smooth muscle actin （α-SMA） and collagen type I alpha chain （Collagen Ⅰα）， as well as epithelial-mesenchymal transition markers N-cadherin and E-cadherin. Results Based on the levels of the inflammatory cytokine IL-1β in the cell supernatant， the optimal LPS concentration and treatment duration were determined as 200 ng/mL and 24 h， respectively， which were applied in all subsequent experiments. Compared with the control group， the levels of IL-6， IL-8， IFN-γ， and IL-1β were significantly increased in the LPS group （P < 0.05）， confirming the successful establishment of the inflammatory cell model. After LPS stimulation， YY1 mRNA levels were significantly upregulated （P < 0.05）， and YY1 protein expression was increased in the nucleus， indicating nuclear translocation of YY1. Immunofluorescence staining showed that the nuclear fluorescence intensity of YY1 was enhanced and α-SMA expression was upregulated in the LPS group， while YY1 knockdown significantly inhibited these changes. Results from RT-qPCR and Western blot consistently showed that， compared with the control group， the LPS group had increased expression of α-SMA， Collagen Ⅰα， and N-cadherin， accompanied by decreased expression of E-cadherin （P < 0.05）. Compared with the LPS group， the LPS+si-YY1 group exhibited a significant reversal of the expression trends of these fibrosis and epithelial-mesenchymal transition markers （P < 0.05）. Conclusion LPS induces the upregulation of YY1 and promotes its nuclear translocation in human fallopian tube epithelial cells. Knockdown of YY1 suppresses fibrosis and EMT in fallopian tube epithelial cells， ultimately ameliorating tubal inflammatory infertility.

Key words: Yin Yang1, tubal inflammatory infertility, fibrosis, mesenchymal transition