Autophagy Prevents Osteocyte Cell Death under Hypoxic Conditions
Autophagy Prevents Osteocyte Cell Death under Hypoxic Conditions
复制标题
DOI：
10.1159/000519086
复制
发表时间：
2021-12-01
影响因子：
2.7
通讯作者：
Shirota, Tatsuo
中科院分区：
文献类型：
--
作者：
Kurihara, Mai;Mukudai, Yoshiki;Shirota, Tatsuo
缺氧发生在重要的临床条件下，如癌症、心脏病和局部缺血。然而，缺氧与骨细胞自噬的关系尚不清楚。本研究的目的是揭示调节机制，防止调节细胞死亡，如凋亡，坏死和自噬，缺氧。将小鼠骨细胞系MLO-Y 4细胞暴露于不同的O-2分压（PO 2）。随后，细胞发生凋亡、自噬、自噬性细胞死亡和/或坏死，因此我们将PO 2 = 2%指定为代表性缺氧条件。免疫荧光染色显示低氧暴露的MLO-Y 4细胞中LC 3增加，p62减少，表明诱导自噬。因此，我们推测β-雌二醇（E2）和维生素D在缺氧条件下骨细胞的凋亡和自噬中起重要作用。1，25 α-二羟维生素D3（VitD）保护MLO-Y 4细胞免于细胞死亡并诱导自噬。但E2的作用不大。最后，进行磷酸化mTOR和Akt的蛋白质印迹，以研究添加VitD和E2影响的改变的自噬信号通路。然而，无论是E2还是VitD都不能恢复这些因子降低的磷酸化。我们的研究结果表明，维生素D对缺氧条件下的自噬的影响依赖于Akt和mTOR途径。因此，本研究的结果表明，维生素D抑制骨细胞死亡的mTOR途径依赖性的方式在缺氧条件下。这表明维生素D作为骨细胞死亡主要通过缺氧发生的疾病的治疗干预的潜力。(C)2021年南Karger AG，巴塞尔
Hypoxia occurs under important clinical conditions such as cancers, heart disease, and ischemia. However, the relationship between hypoxia and autophagy in osteocytes is still unclear. The objective of the present study was to uncover the regulatory mechanisms that prevent regulated cell death, such as apoptosis, necrosis, and autophagy, under hypoxia. MLO-Y4 cells, a mouse osteocyte cell line, were exposed to various O-2 partial pressures (PO2). Subsequently, the cells underwent apoptosis, autophagy, autophagic cell death, and/or necrosis, and thereby we designated PO2 = 2% as a representative hypoxic condition. Immunofluorescence staining showed an increase of LC3 and a decrease of p62 in MLO-Y4 cells exposed to hypoxia, indicating the induction of autophagy. We then hypothesized that beta-estradiol (E2) and vitamin D play an important role in apoptosis and autophagy of osteocytes under hypoxia. 1,25 alpha-dihydroxyvitamin D3 (VitD) protected MLO-Y4 cells from cell death and induced autophagy. However, E2 showed little effect. Finally, Western blotting for phosphorylated mTOR and Akt was carried out in order to investigate the altered autophagy signaling pathways affected by the addition of VitD and E2. However, neither E2 nor VitD were capable of recovering the decreased phosphorylation of those factors. Our results indicated that the effects of VitD on autophagy under hypoxia were dependent on the Akt and mTOR pathways. Thus, the results of the present study showed that VitD suppresses osteocyte cell death in an mTOR pathway-dependent manner in hypoxic conditions. This suggests the potential of VitD as a therapeutic intervention for diseases in which the cell death of osteocytes mainly occurs via hypoxia. (C) 2021 S. Karger AG, Basel