Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR.
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR; Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, PR China.
Phytomedicine. 2021 Feb;82:153413. doi: 10.1016/j.phymed.2020.153413. Epub 2020 Nov 19.
Rapid, non-genomic estrogen receptor (ER) signaling plays an integral role in mediating the tissue selective properties of ER modulators. Icariin, a bone bioactive flavonoid, has been reported to selectively activate non-genomic ERα signaling in in vitro and in vivo studies.
The mechanisms underlying the estrogen-like bone protective effects of icariin are not fully understood, especially those that are related to insulin-like growth factor I (IGF-1) signaling. The bone protective effects of icariin were investigated in female mature ovariectomized (OVX) rats and the signaling of IGF-IR- ERα cross-talk was determined in osteoblastic cells.
Icariin at 3 different dosages (50, 500 and 3000 ppm) were orally administrated to rats for 3 months through daily intake of phytoestrogen-free animal diets containing icariin. Bone marrow stromal cells (BMSCs) and osteoclast precursors from femurs were harvested for experiments and RNA-sequencing. The interactions between IGF-IR and non-genomic ERα signaling were examined in pre-osteoblastic MC3T3-E1 cells and mature osteoblasts differentiated from BMSCs.
Our results show that chronic administration of icariin to OVX rats significantly protected them against bone loss at the long bone and lumbar spine without inducing any uterotrophic effects. Ex vivo studies using BMSCs and osteoclast precursors confirmed the stimulatory effects of icariin on osteoblastogenesis and its inhibitory effects on osteoclastogenesis, respectively. RNA-sequencing analysis of mRNA from BMSCs revealed that icariin at 500 ppm significantly altered IGF-1 signaling as well as PI3K-Akt pathways. Our results demonstrated for the first time the rapid induction of interactions between IGF-IR and ERα as well as IGF-IR signaling and the downstream Akt phosphorylation by icariin in MC3T3-E1 cells. The activation of ERα and Akt phosphorylation by icariin in MC3T3-E1 cells and the osteogenic effects of icariin on ALP activity in mature osteoblasts were shown to be IGF-IR-dependent.
Our findings reveal that icariin activates both ERα and Akt via enhancing rapid induction of IGF-1 signaling in osteoblastic cells for osteogenesis and might be regarded as a novel pathway-selective phytoestrogen for management of postmenopausal osteoporosis.
快速非基因组雌激素受体（ER）信号转导在介导 ER 调节剂的组织选择性方面起着重要作用。淫羊藿苷是一种具有骨生物活性的黄酮类化合物，已被报道在体外和体内研究中选择性激活非基因组 ERα 信号转导。
淫羊藿苷具有雌激素样的骨保护作用的机制尚不完全清楚，特别是与胰岛素样生长因子 I（IGF-1）信号转导相关的机制。本研究旨在探讨淫羊藿苷对去卵巢雌性大鼠（OVX）的骨保护作用，并确定其在成骨细胞中 IGF-IR-ERα 交叉对话的信号转导。
通过每日摄入含有淫羊藿苷的植物雌激素自由动物饮食，3 种不同剂量（50、500 和 3000 ppm）的淫羊藿苷被口服给予大鼠 3 个月。从股骨中采集骨髓基质细胞（BMSCs）和破骨细胞前体进行实验，并进行 RNA 测序。在预成骨细胞 MC3T3-E1 细胞和成骨细胞分化自 BMSCs 中，检测 IGF-IR 和非基因组 ERα 信号之间的相互作用。
我们的结果表明，淫羊藿苷对 OVX 大鼠的慢性给药可显著防止长骨和腰椎的骨丢失，而不会引起任何子宫增重作用。BMSCs 和破骨细胞前体的离体研究证实了淫羊藿苷分别对成骨细胞的刺激作用和对破骨细胞的抑制作用。BMSCs 的 mRNA RNA 测序分析表明，500ppm 的淫羊藿苷显著改变了 IGF-1 信号以及 PI3K-Akt 途径。我们的研究首次证明了淫羊藿苷在 MC3T3-E1 细胞中快速诱导 IGF-IR 和 ERα 之间的相互作用以及 IGF-IR 信号及其下游 Akt 磷酸化。淫羊藿苷在 MC3T3-E1 细胞中激活 ERα 和 Akt 磷酸化以及淫羊藿苷对成熟成骨细胞中碱性磷酸酶活性的成骨作用均依赖于 IGF-IR。
我们的研究结果揭示了淫羊藿苷通过增强成骨细胞中 IGF-1 信号的快速诱导，激活 ERα 和 Akt，从而促进成骨作用，这可能被视为一种新的途径选择性植物雌激素，可用于治疗绝经后骨质疏松症。
