淫羊藿总黄酮改善自然衰老大鼠睾丸支持细胞分泌功能衰退的作用

目的研究淫羊藿总黄酮(TFE)对衰老睾丸支持细胞(Sertoli细胞)分泌功能衰退的影响,并从肌醇需酶1α(IRE1α)/ X盒结合蛋白1(XBP1)信号通路探讨其分子机制。方法将36只SPF级18月龄SD雄性大鼠随机分为自然衰老组和TFE 10及40 mg·kg^-1组,每组12只;另取10只2月龄大鼠作为壮龄对照组。每天定时ig 给TFE 1次,每5 d间隔2 d再继续ig给药,给药共计4个月。计算睾丸指数;HE染色观察睾丸组织形态;实时定量PCR和Western 印迹法检测睾丸组织中胶质细胞源性神经营养因子(GDNF)、骨形态形成蛋白 4(BMP4)及干细胞因子(SCF)mRNA 和蛋白表达水平;检测睾丸组织中磷酸化 IRE1α(p-IRE1α)和XBP1蛋白表达水平;免疫荧光法检测睾丸组织内Sertoli细胞数量和p-IRE1α定位。结果与壮龄对照组比较,自然衰老组大鼠睾丸指数显著降低(P<0.01);与自然衰老组相比,TFE 40 mg·kg^-1组睾丸指数显著升高(P<0.05)。HE结果显示,自然衰老组睾丸曲细精管的形态结构紊乱,部分生精细胞发生脱落;TFE给药组能改善睾丸曲细精管的形态结构。实时定量PCR结果显示,与壮龄对照组比较,自然衰老组Sertoli细胞分泌因子GDNF和SCF mRNA表达水平均显著下调(P<0.01);Western印迹结果显示,GDNF,BMP4和SCF蛋白显著下调(P<0.01)。与自然衰老组相比,TFE给药组分泌因子mRNA和蛋白表达水平均显著上调(P<0.05,P<0.01)。Western印迹结果显示,与壮龄对照组比较,自然衰老组睾丸组织中p-IRE1α和XBP1蛋白表达均显著下调(P<0.01);与自然衰老组相比,TFE给药组p-IRE1α和XBP1蛋白表达显著上调(P<0.01)。免疫荧光结果显示,壮龄对照组、自然衰老组和TFE给药组Sertoli细胞数量无显著差异。不仅在生精细胞胞质广泛表达,在Sertoli细胞胞质亦有表达。结论 TFE可显著改善自然衰老所致大鼠睾丸Sertoli细胞分泌功能衰退,其机制可能与调节IRE1α/XBP1信号通路有关。

Effect of Epimedium flavonoids on decreasing secretion function of Sertoli cells in testis of natural aging rats

OBJECTIVE To investigate the effect of total flavonoids of Epimedium (TFE) on the decline of secretion function of senile testis-supporting cells (Sertoli cells), and to explore their molecular mechanism from inositol-requiring enzyme 1α(IRE1α)/X-box-binding protein 1(XBP1) signaling pathway. METHODS Thirty-six SPF 18-month-old SD male rats were randomly divided into natural aging group, low and high dose TFE groups, with 12 rats in each group. Another ten 2-month-old rats were used as a youth control group. TFE was ig given once a day, and the ig administration was continued every five days after a two-day interval, and the administration lasted for 4 months. Then, the testicular index was calculated. The testicular histomorphology was observed by HE staining;while quantitative-PCR (qPCR) and Western blotting were used to detect the mRNA and protein expression levels of glial cell derived neurotrophic factor (GDNF), bone morphogenetic protein 4 (BMP4) and stem cell factor (SCF), and Western blotting protein expression levels of p-IRE1α and XBP1 in testes. The number of sertoli cells in the testis and the localization of p- IRE1α in the testis were detected by immunofluorescence. RESULTS Compared with the young control group, the testicular index decreased significantly in the natural aging group (P<0.01), but was significantly up-regulated after TFE 40 mg·kg^-1 (P<0.05). The results of HE showed that the morphological structure of the testicular seminiferous tubules in the natural aging group were disorderly, and some spermatogenic cells were shed. The TFE group could improve the morphological structure of the seminiferous tubules of the testis. qPCR and Western blotting results showed that compared with the young control group, the mRNA and protein expression levels of GDNF, BMP4 and SCF in sertoli cells in the natural aging group were significantly down-regulated (P<0.01). However, the expression of secretory factors in TFE group was significantly up-regulated (P<0.05, P<0.01). Western blotting results showed that compared with the young control group, the expression of p-IRE1α and XBP1 protein in the testis of the natural aging group was significantly down-regulated (P<0.01), but the expression of p-IRE1α and XBP1 protein in the TFE group was significantly up-regulated (P<0.01). The results of immunofluorescence also showed that there was no significant difference in the number of sertoli cells between the natural aging group and the TFE group compared with the young control group, while the expression of p-IRE1α was localized both in cytoplasm of sertoli cells and spermatogenic cells. CONCLUSION TFE can significantly improve the decline of secretion function of testicular sertoli cells induced by aging, and the mechanism may be related to the regulation of IRE1α/XBP1 signaling pathway.