Activation of the UPR Protects against Cigarette Smoke-induced RPE Apoptosis through Up-Regulation of Nrf2
Activation of the UPR Protects against Cigarette Smoke-induced RPE Apoptosis through Up-Regulation of Nrf2
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DOI：
10.1074/jbc.m114.603738
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发表时间：
2015-02-27
影响因子：
4.8
通讯作者：
Zhang, Sarah X.
中科院分区：
文献类型：
--
作者：
Huang, Chuangxin;Wang, Joshua J.;Zhang, Sarah X.
最近的研究揭示了内质网（ER）应激诱导的未折叠蛋白反应（UPR）在调节RPE细胞活性和存活中的作用。在此，我们研究了UPR调节香烟烟雾提取物（CSE）刺激的人RPE细胞凋亡信号传导的机制。我们的研究结果表明，CSE暴露诱导ER应激标志物的剂量和时间依赖性增加，增强活性氧（ROS），线粒体片段化和RPE细胞凋亡。这些变化被抗氧化剂NAC或化学伴侣TMAO阻止，表明CSE诱导的细胞凋亡中氧化和ER应激之间存在密切的相互作用。为了解释UPR的作用，通过腺病毒或siRNA操纵XBP 1和CHOP基因的过表达或下调。过度表达XBP 1通过减少CHOP、p-p38和caspase-3的激活来保护CSE诱导的细胞凋亡。相反，XBP 1敲低使细胞对CSE诱导的凋亡敏感，这可能是通过CHOP非依赖性途径。令人惊讶的是，CHOP的敲低减少了p-eIF 2 α和Nrf 2，导致胱天蛋白酶-3活化和细胞凋亡的显著增加。此外，Nrf 2抑制增加ER应激并加剧细胞凋亡，而Nrf 2过表达减少CHOP并保护RPE细胞。我们的数据表明，虽然CHOP可能作为一个促凋亡基因在ER压力，它也需要Nrf 2上调和RPE细胞存活。此外，增强Nrf 2和XBP 1活性可能有助于减少氧化和ER应激，并保护RPE细胞免受香烟烟雾诱导的损伤。
Recent studies have revealed a role of endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) in the regulation of RPE cell activity and survival. Herein, we examined the mechanisms by which the UPR modulates apoptotic signaling in human RPE cells challenged with cigarette smoking extract (CSE). Our results show that CSE exposure induced a dose-and time-dependent increase in ER stress markers, enhanced reactive oxygen species (ROS), mitochondrial fragmentation, and apoptosis of RPE cells. These changes were prevented by the anti-oxidant NAC or chemical chaperone TMAO, suggesting a close interaction between oxidative and ER stress in CSE-induced apoptosis. To decipher the role of the UPR, overexpression or down-regulation of XBP1 and CHOP genes was manipulated by adenovirus or siRNA. Overexpressing XBP1 protected against CSE-induced apoptosis by reducing CHOP, p-p38, and caspase-3 activation. In contrast, XBP1 knockdown sensitized the cells to CSE-induced apoptosis, which is likely through a CHOP-independent pathway. Surprisingly, knockdown of CHOP reduced p-eIF2 alpha and Nrf2 resulting in a marked increase in caspase-3 activation and apoptosis. Furthermore, Nrf2 inhibition increased ER stress and exacerbated cell apoptosis, while Nrf2 overexpression reduced CHOP and protected RPE cells. Our data suggest that although CHOP may function as a pro-apoptotic gene during ER stress, it is also required for Nrf2 up-regulation and RPE cell survival. In addition, enhancing Nrf2 and XBP1 activity may help reduce oxidative and ER stress and protect RPE cells from cigarette smoke-induced damage.