Hypoxia enhances glucocorticoid-induced apoptosis and cell cycle arrest via the PI3K/Akt signaling pathway in osteoblastic cells
Hypoxia enhances glucocorticoid-induced apoptosis and cell cycle arrest via the PI3K/Akt signaling pathway in osteoblastic cells
复制标题
缺氧通过 PI3K/Akt 信号通路增强成骨细胞中糖皮质激素诱导的细胞凋亡和细胞周期停滞
DOI：
10.1007/s00774-014-0627-1
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发表时间：
2015-11-01
影响因子：
3.3
通讯作者：
Zhou, Deshan
中科院分区：
文献类型：
--
作者：
Zou, Wanjing;Yang, Shu;Zhou, Deshan
虽然股骨头坏死是已知的长期或大剂量临床应用糖皮质激素的主要限制因素，但这种副作用的机制仍不清楚。缺氧是多种病理条件下的一种重要的生物学状态。在这项研究中，我们利用细胞毒试验、流式细胞术和Western blotting研究了低氧条件下糖皮质激素诱导的成骨细胞系MC3T3-E1的骨坏死。6α-甲基强的松龙琥珀酸钠在低氧条件下比常氧条件下更有效地诱导MC3T3-E1成骨细胞的凋亡和G0/G1期停滞。相应地，MPSL能更有效地上调caspase-3、p53及其靶基因p21的裂解水平，下调细胞周期蛋白D1的表达。此外，Akt的过表达可抑制MPSL对P53、p21的激活、caspase3的裂解和细胞周期蛋白D1表达的减弱，使成骨细胞免于MPSL诱导的细胞周期停滞和凋亡，提示PI3K/Akt信号通路可能在MPSL诱导的成骨细胞抑制中起重要作用。此外，MPSL对PI3K/AKT信号通路的抑制和细胞内P85α单体水平的上调在低氧条件下比常氧条件下更为明显。最后，我们发现MPSL在低氧条件下作用的增强归因于低氧上调糖皮质激素受体的活性。综上所述，我们的结果表明，合成的糖皮质激素受体激动剂MPSL可以促进P85α的表达，抑制PI3K/AKT信号通路，从而诱导成骨细胞凋亡和细胞周期停滞，并且这种作用在低氧条件下增强。
Although osteonecrosis of the femoral head is a known primary limitation of long-term or high-dose clinical administration of glucocorticoids, the mechanisms underlying this side effect remain unclear. Hypoxia is an important biological state under numerous pathological conditions. In this study, we investigated glucocorticoid-induced osteonecrosis under hypoxic conditions in the MC3T3-E1 osteoblast cell line using a cell cytotoxicity assay, flow cytometry, and western blotting. 6α-Methylprednisolone sodium succinate (MPSL) more effectively induced apoptosis and G0/G1 arrest of MC3T3-E1 osteoblasts under hypoxic conditions than under normoxic conditions. Correspondingly, MPSL more effectively upregulated cellular levels of cleaved caspase 3, p53, and its target p21, and downregulated cyclin D1 levels in hypoxia. Moreover, overexpression of Akt abrogated the MPSL activation of p53, p21, and cleaved caspase 3 and the attenuation of cyclin D1 expression and rescued osteoblasts from MPSL-induced cell cycle arrest and apoptosis, indicating that phosphatidylinositol 3-kinase (PI3K)/Akt signaling might play an essential role in MPSL-induced inhibition of osteoblasts. Furthermore, the suppression of PI3K/Akt signaling and upregualtion of cellular p85α monomer levels by MPSL were more pronounced under hypoxic conditions than under normoxic conditions. Finally, we found that the enhancement of the effects of MPSL under hypoxic conditions was attributed to hypoxia-upregulated glucocorticoid receptor activity. In conclusion, our results demonstrate that MPSL, a synthetic glucocorticoid receptor agonist, promotes the level of p85α and inhibits PI3K/Akt signaling to induce apoptosis and cell cycle arrest in osteoblasts, and that this effect is enhanced under hypoxic conditions.