HIF-1 regulation of chondrocyte apoptosis - Induction of the autophagic pathway
HIF-1 regulation of chondrocyte apoptosis - Induction of the autophagic pathway
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DOI：
10.4161/auto.3708
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发表时间：
2007-05-01
期刊：
影响因子：
13.3
通讯作者：
Srinivas, Vickram
中科院分区：
文献类型：
--
作者：
Bohensky, Jolene;Shapiro, Irving M.;Srinivas, Vickram
我们研究的目的是探索低氧调节生长板软骨细胞存活的机制。在低0 2张力下，软骨细胞对星形孢菌素(即诱导细胞凋亡)的挑战是不耐受的。为了确定缺氧存活是否是由于HIF-1的表达，我们评估了HIF沉默的细胞对星形孢子素的反应。沉默的细胞和对照的软骨细胞对凋亡素的挑战同样敏感。为了了解抗性是否是由自噬途径的蛋白介导的，我们检测了Beclin I和LC3的表达。这两种蛋白都存在于生长板和N1511软骨细胞中。此外，沉默Beclin 1导致软骨细胞死亡增加。因此，该基因起到了维持软骨细胞存活的作用。除了起到细胞保护作用外，众所周知，自噬也可以在细胞死亡中发挥作用。因此，为了确定自噬是否也可能使细胞对凋亡敏感，我们激活了自噬，并在暴露于凋亡原后检查了细胞的活力。自噬抑制剂3-甲基腺嘌呤的处理使软骨细胞难以杀伤，这表明持续的自噬促进了细胞死亡。接下来，我们研究了Bid和caspase-8的表达。当自噬被抑制时，软骨细胞促进了caspase-8的激活和Bid的激活。最后，我们探讨了HIF-1和Beclin-1之间的关系。我们发现，在HIF沉默的细胞中，Beclin-1的表达减少，caspase-8的激活丧失，而Beclin-1-Bcl2在血清饥饿的情况下保持关联。本研究表明，HIF-1对自噬和细胞凋亡均有调节作用。
The goal of our investigation was to explore the mechanism by which hypoxia regulates growth plate chondrocyte survival. At low 0 2 tension, chondrocytes were refractory to a staurosporine (i.e., apoptosis-inducing) challenge. To determine whether hypoxic survival was due to the expression of HIF-1, we evaluated the response of HIF silenced cells to staurosporine. Both, silenced cells and control chondrocytes were equally sensitive to the apoptogen challenge. To learn if resistance was mediated by the proteins of the autophagic pathway, we examined the expression of Beclin I and LC3. Both proteins were present in the growth plate as well as in N 1511 chondrocytes. Moreover, silencing of Beclin 1 resulted in enhanced chondrocyte death. Thus, this gene served to maintain chondrocyte survival activity. Besides serving a cytoprotective role, it is known that autophagy can function in cell death. Accordingly, to ascertain if autophagy might also sensitize cells to apoptosis, we activated autophagy and examined viability following exposure to an apoptogen. Treatment with the autophagy inhibitor 3-methyladenine rendered the chondrocytes refractory to killing, suggesting that sustained autophagy promoted cell death. We next examined expression of BID and caspase-8. When autophagy was suppressed, chondrocytes promoted caspase-8 activation and activated BID. Finally, we explored the relationship between HIF-1 and Beclin 1. We noted a decrease in Beclin 1 expression and loss of caspase-8 activation in HIF silenced cells and Beclin 1-Bcl-2 association was maintained upon serum starvation. This study indicates that HIF-1 serves to regulate both autophagy and apoptosis.