Estrogen inhibits starvation-induced apoptosis in osteocytes by a redox-independent process involving association of JNK and glutathione S-transferase P1-1.
Estrogen inhibits starvation-induced apoptosis in osteocytes by a redox-independent process involving association of JNK and glutathione S-transferase P1-1.
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DOI：
10.1002/2211-5463.12216
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发表时间：
2017-05
期刊：
影响因子：
2.6
通讯作者：
Vincenzini MT
中科院分区：
文献类型：
--
作者：
Domazetovic V;Fontani F;Marcucci G;Iantomasi T;Brandi ML;Vincenzini MT
雌激素缺乏会因微损伤、氧化应激和骨细胞凋亡而导致骨质流失。骨细胞中已证实氧化应激诱导的细胞凋亡、c-Jun N 末端激酶 (JNK) 激活以及参与骨重塑的因子表达之间的关系。然而，用 17β-雌二醇 (17β-E2) 处理的骨细胞中这些事件的分子调控仍未得到探索。使用 MLO-Y4 小鼠骨细胞样细胞系作为模型来研究 17β-E2 治疗期间饥饿诱导的细胞凋亡和 ROS 产生。通过蛋白质印迹法测量谷胱甘肽 S-转移酶 P1-1 (GSTP1-1)、受体激活剂 kB 配体 (RANKL)、骨保护素 (OPG)、硬化素和激酶激活的表达。此外，通过免疫沉淀评估了 GSTP1-1/JNK 关联，并通过特异性 siRNA 转染检测了 GSTP1-1 参与骨细胞对 17β-E2 的反应。 17β-E2 可防止饥饿诱导的细胞凋亡（DNA 断裂和 caspase 激活）、硬化蛋白表达和 RANKL/OPG 比值的增加，这些都与骨细胞氧化应激导致的 JNK 激活有关。这是通过 GSTP1-1 过表达发生的，GSTP1-1 过表达可以通过形成 GSTP1-1/JNK 复合物来抑制 JNK 激活。尚未发现 17β-E2 的早期抗氧化作用，但雌激素作用类似于 N-乙酰半胱氨酸，通过增加细胞内氧化还原状态，维持 JNK 与 GSTP1-1 的结合。因此，MLO-Y4 中 17β-E2 的抗凋亡和成骨作用是通过涉及 GSTP1-1/JNK 关联的氧化还原独立过程发生的。这项研究在分子水平上阐明了 17β-E2 对骨细胞活性的影响，并确定了 GSTP1-1 和 JNK 活性在骨重塑和修复机制中的可能作用。
Estrogen deficiency causes bone loss as a result of microdamage, oxidative stress, and osteocyte apoptosis. A relationship between oxidative stress‐induced apoptosis, c‐Jun N‐terminal kinase (JNK) activation, and expression of factors involved in bone remodeling has been demonstrated in osteocytes. However, the molecular regulation of these events in osteocytes treated with 17β‐estradiol (17β‐E2) remains unexplored. The MLO‐Y4 murine osteocyte‐like cell line was used as a model to study starvation‐induced apoptosis and ROS production during 17β‐E2 treatment. Expression of glutathione S‐transferase P1‐1 (GSTP1‐1), receptor activator kB ligand (RANKL), osteoprotegerin (OPG), sclerostin, and kinases activation were measured by western blot. In addition, the GSTP1‐1/JNK association was assessed by immunoprecipitation, and GSTP1‐1 involvement in the osteocyte response to 17β‐E2 was detected by specific siRNA transfection. 17β‐E2 prevents starvation‐induced apoptosis (DNA fragmentation and caspase activation), the increase in sclerostin expression and the RANKL/OPG ratio, which are all related to JNK activation due to oxidative stress in osteocytes. This occurs through GSTP1‐1 overexpression, which can inhibit JNK activation by formation of a GSTP1‐1/JNK complex. No early antioxidant action of 17β‐E2 has been found but the estrogen effect is similar to N‐acetylcysteine which, by increasing the intracellular redox state, maintains JNK bound to GSTP1‐1. Thus, the antiapoptotic and osteogenic effect of 17β‐E2 in MLO‐Y4 occurs by a redox‐independent process involving GSTP1‐1/JNK association. This study clarifies at molecular level the effect of 17β‐E2 on osteocyte activity and identifies a possible role of GSTP1‐1 and JNK activity in bone remodeling and repair mechanisms.