The Lawrence D. Longo Center for Perinatal Biology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA, 92350, USA.
Mol Neurobiol. 2019 Aug;56(8):5608-5625. doi: 10.1007/s12035-019-1491-8. Epub 2019 Jan 17.
Neonatal hypoxic-ischemic (HI) brain injury causes significant mortality and long-term neurologic sequelae. We previously demonstrated that HI significantly increased microRNA-210 (miR-210) in the neonatal rat brain and inhibition of brain endogenous miR-210 was neuroprotective in HI brain injury. However, the molecular mechanisms underpinning this neuroprotection remain unclear. Using both in vivo and in vitro models, herein we uncover a novel mechanism mediating oxidative brain injury after neonatal HI, in which miR-210 induces mitochondrial dysfunction via downregulation of iron-sulfur cluster assembly protein (ISCU). Inhibition of miR-210 significantly ameliorates mitochondrial dysfunction, oxidative stress, and neuronal loss in the neonatal brain subjected to HI, as well as in primary cortical neurons exposed to oxygen-glucose deprivation (OGD). These effects are mediated through ISCU, in that miR-210 mimic decreases ISCU abundance in the brains of rat pups and primary cortical neurons, and inhibition of miR-210 protects ISCU against HI in vivo or OGD in vitro. Deletion of miR-210 binding sequences at the 3'UTR of ISCU transcript ablates miR-210-induced downregulation of ISCU protein abundance in PC12 cells. In primary cortical neurons, miR-210 mimic or silencing ISCU results in mitochondrial dysfunction, reactive oxygen species production, and activation of caspase-dependent death pathways. Of importance, knockdown of ISCU increases HI-induced injury in the neonatal rat brain and counteracts the neuroprotection of miR-210 inhibition. Therefore, miR-210 by downregulating ISCU and inducing mitochondrial dysfunction in neurons is a potent contributor of oxidative brain injury after neonatal HI.
新生儿缺氧缺血性（HI）脑损伤导致高死亡率和长期神经后遗症。我们之前的研究表明，HI 可显著增加新生大鼠脑内 microRNA-210（miR-210）的表达，而抑制脑内源性 miR-210 对 HI 脑损伤具有神经保护作用。然而，其神经保护作用的潜在分子机制尚不清楚。本文通过体内和体外模型，揭示了一种介导新生鼠 HI 后氧化脑损伤的新机制，即 miR-210 通过下调铁硫簇装配蛋白（ISCU）导致线粒体功能障碍。抑制 miR-210 可显著改善 HI 后新生鼠大脑和氧葡萄糖剥夺（OGD）暴露的原代皮质神经元中的线粒体功能障碍、氧化应激和神经元丢失。这些作用是通过 ISCU 介导的，因为 miR-210 模拟物降低了幼鼠和原代皮质神经元大脑中的 ISCU 丰度，抑制 miR-210 可保护 ISCU 免受体内 HI 或体外 OGD 的影响。ISCU 转录物 3'UTR 上 miR-210 结合序列的缺失消除了 PC12 细胞中 miR-210 诱导的 ISCU 蛋白丰度下调。在原代皮质神经元中，miR-210 模拟物或沉默 ISCU 导致线粒体功能障碍、活性氧物质产生和 caspase 依赖性死亡途径的激活。重要的是，ISCU 的敲低增加了新生鼠脑内 HI 诱导的损伤，并抵消了 miR-210 抑制的神经保护作用。因此，miR-210 通过下调 ISCU 并诱导神经元中线粒体功能障碍，是新生鼠 HI 后氧化脑损伤的重要因素。
