Timosaponin BII improved osteoporosis caused by hyperglycemia through promoting autophagy of osteoblasts via suppressing the mTOR/NFκB signaling pathway
Timosaponin BII improved osteoporosis caused by hyperglycemia through promoting autophagy of osteoblasts via suppressing the mTOR/NFκB signaling pathway
复制标题
Timosaponin BII 通过抑制 mTOR/NFκB 信号通路促进成骨细胞自噬，改善高血糖引起的骨质疏松症。
DOI：
10.1016/j.freeradbiomed.2021.05.014
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发表时间：
2021-05-18
影响因子：
7.4
通讯作者：
Zhang, Yan
中科院分区：
文献类型：
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作者：
Wang, Nani;Xu, Pingcui;Zhang, Yan
在高糖应激条件下，成骨细胞发生自噬缺陷，在糖尿病骨质疏松症的发生发展中起重要作用。知母皂苷BII是从知母根茎中分离得到的一种甾体皂苷，具有抗骨质疏松的作用。本研究探讨了刺五加皂苷BII对糖尿病骨质疏松的治疗作用及其机制。提摩皂苷BII可减轻糖尿病大鼠胫骨微结构的恶化。此外，硫代皂苷BII可剂量依赖性地减少高血糖诱导的大鼠颅骨原代成骨细胞的细胞凋亡。高糖暴露的成骨细胞表现为线粒体超氧化物歧化水平升高，线粒体膜电位降低，自噬通量降低，这种作用可被硫代皂苷BII减弱，表现为自噬小体数量、LC3B斑点形成和Beclin1表达上调。自噬抑制剂3-甲基腺嘌呤抑制了硫代皂苷BII的抗凋亡和抗氧化作用，而自噬诱导剂雷帕霉素则增强了其抗氧化作用。进一步的研究表明，硫代皂苷BII可以抑制mTOR和S6K的磷酸化，以及下游的核因子kappaB和ikappaB，从而激活自噬，减少细胞凋亡。值得注意的是，硫代皂苷BII与mTOR的药理激活剂MHY1485共同孵育，降低了硫代皂苷BII诱导的BC12的蛋白表达，同时减少了自噬，增加了核因子kappaB和I kappaB的磷酸化，促进了细胞凋亡。体内实验结果表明，口服知母皂苷BII可下调糖尿病大鼠胫骨近端mTOR和核因子kappaB的磷酸化，上调Beclinl的表达。这些结果表明，硫代皂苷BII通过抑制成骨细胞中的mTOR/NF-kappaB信号激活自噬，从而减轻高糖诱导的氧化应激和细胞凋亡。
Defective autophagy occurred in osteoblasts under stress induced by high glucose and played an essential role in the development of diabetic osteoporosis. Timosaponin BII, a steroidal saponin isolated from the rhizomes of Anemarrhena asphodeloides Bunge, possessed anti-osteoporosis properties. In this study, we investigated the efficacy and mechanism of timosaponin BII on diabetic osteoporosis. Timosaponin BII attenuated the deterioration in the microarchitecture of the tibias in diabetic rats. Furthermore, treatment with timosaponin BII dose-dependently reduced hyperglycemia-induced cell apoptosis in primary osteoblasts from rat calvaria. High glucose-exposed osteoblasts exhibited increased mitochondrial superoxide level, decreased mitochondrial membrane potential and impaired autophagic flux, which was attenuated by timosaponin BII, as evidenced by the upregulation of autophagosome numbers, LC3B puncta formation and Beclin1 expression. The antiapoptotic and antioxidative effect of timosaponin BII were repressed by the autophagy inhibitor 3-methyladenine and enhanced by the autophagy inducer rapamycin. Further studies showed that timosaponin BII suppressed the phosphorylation of mTOR and S6K, as well as the downstream factors NF kappa B and I kappa B, consequently activating autophagy and decreasing apoptosis. Of note, coincubation of timosaponin BII with MHY1485, a pharmacological activator of mTOR, diminished the protein expression of Bc12 induced by timosaponin BII, which was in parallel with decreased autophagy and increased phosphorylation of NF kappa B and I kappa B. Overexpression of NF kappa B reduced timosaponin BII-evoked autophagy and promoted apoptosis. The in vivo results showed that oral administration of timosaponin BII downregulated the phosphorylation of mTOR and NF kappa B and upregulated Beclinl expression in the proximal tibias of diabetic rats. These results suggested that timosaponin BII attenuated high glucose-induced oxidative stress and apoptosis through activating autophagy by inhibiting mTOR/NF kappa B signalling in osteoblasts.