Abstract: Objective  To study and explore the role and molecular mechanism of all-trans retinoic acid(atRA) in inflammatory response of epididymal epithelium cells induced by lipopolysaccharide(LPS).
Methods  Epididymal epithelial cells treated with LPS and different concentrations of atRA, atRA receptor inhibitors and Si-TGF-β1. Real-time quantitative PCR was used to detect the  mRNA expression levels of interleukin-1β(IL-1β)，interleukin-6(IL-6), Tumor Necrosis Factor-α(TNF-α) and Transforming growth factor β1(TGF-β1), enzyme-linked immunosorbent assay was used to detect the content of IL-1β， IL-6 and TNF-α in  the supernatants of cultured epididymal epithelial cells and the protein expression level of TGF-β1 in epididymal epithelial cells was determined by Western blot.
Results  The mRNA expression levels of IL-1β, IL-6 and TNF-ɑ in the epididymal epithelial cells in the LPS group were significantly higher than those of the control group. The mRNA expression levels of inflammatory cytokines IL-1β, IL-6 and TNF-ɑ in the epididymal epithelial cells treated with atRA at different concentrations were significantly decreased in a concentration dependence(P＜0.01). The contents of IL-1β， IL-6 and TNF-α in  the supernatants of cultured LPS induced epididymal epithelial cells were significantly higher than those in the control group. The contents of IL-1β， IL-6 and TNF-α in  the supernatants of  cultured LPS induced epididymal epithelial cells after treating with atRA at different concentrations were significantly decreased(P＜0.01).The mRNA expression level of TGF- 1β  in the epididymal epithelial cells in the LPS group was significantly lower than that in the control group and was significantly increased after treatment with different concentrations of atRA(P＜0.01). The mRNA expression level of TGF-β1  in Si-TGF-β1 group was significantly lower than that in Si-Ctl group(P＜0.01).The relative mRNA levels of IL-1β, IL-6 and TNF-ɑ in the atRA+ Si-Ctl +LPS group were lower than those of the Control+LPS group, and the relative mRNA levels of IL-1β, IL-6 and TNF-ɑ in the atRA+Si-TGF-β1 +LPS group were significantly higher than those of the atRA group(P＜0.01). The levels of IL-1β, IL-6 and TNF-ɑ in the supernatants of cultured epididymal epithelial cells in atRA+Si-Ctl+LPS group were lower than those of Control+LPS group, and the levels of IL-1β, IL-6 and TNF-ɑ in the supernatants of cultured epididymal epithelial cells in atRA+Si-TGF-β1+LPS group were significantly higher than those of atRA group(P＜0.01). The mRNA expressions of Retinoic acid alpha(RARɑ) and Retinoic acid beta(RARβ) in the epididymal epithelial cells in atRA group were significantly higher than those in the Normal group(P＜0.01). The relative expression level of TGF-β1 mRNA in the atRA+BMS195614 group were significantly lower than those in the Control group(P＜0.01).
Conclusion  atRA can inhibit the inflammatory response of epididymal epithelial cells induced by LPS in mice, and its possible molecular mechanism may be up-regulating the expression of TGF-β1 by binding to RARɑ receptor.

Key words: epididymitis, all-trans-retinoic acid, lipopolysaccharide