Neuronal Rho GTPase Rac1 elimination confers neuroprotection in a mouse model of permanent ischemic stroke
Neuronal Rho GTPase Rac1 elimination confers neuroprotection in a mouse model of permanent ischemic stroke
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DOI：
10.1111/bpa.12562
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发表时间：
2018-07-01
期刊：
影响因子：
6.4
通讯作者：
Santos, Sofia Duque
中科院分区：
文献类型：
--
作者：
Karabiyik, Cansu;Fernandes, Rui;Santos, Sofia Duque
Rho GTCRac 1是一种多功能蛋白，参与从发育到病理的不同途径。本研究的目的是阐明神经元Rac 1在调节永久性局灶性脑缺血（pMCAO）引起的脑损伤反应中的作用。我们的研究结果表明，pMCAO显着增加野生型小鼠的总Rac 1水平，主要是通过增加核Rac 1，而减少Rac 1的激活。这些变化发生在兴奋性毒性应激诱导的细胞死亡之前。Rac 1在原代神经元皮层细胞中的药理学抑制防止谷氨酸受体过度激活后诱导的氧化应激增加。然而，这不足以防止相关的神经元细胞死亡。相反，RNAi介导的Rac 1在原代皮层神经元中的敲低阻止了由谷氨酸兴奋性毒性引起的细胞死亡，并降低了NADPH氧化酶的活性。为了测试体内下调神经元Rac 1是否对pMCAO后的神经有保护作用，我们使用了他莫昔芬诱导的神经元特异性条件性Rac 1敲除小鼠。与同窝对照小鼠相比，我们观察到基因敲除小鼠脑梗死体积显著减少50%，同时HIF-1表达增加，表明Rac 1在神经元中的消融具有神经保护作用。在缺血性脑中进行的透射电子显微镜检查显示，Rac 1敲除小鼠梗死区的溶酶体与非梗死组织的溶酶体保持相似的水平，而同窝小鼠的溶酶体数量减少，进一步证实了Rac 1消融神经元具有神经保护作用的观点。我们的研究结果表明，Rac 1在缺血性病理级联反应中起着重要作用，调节其水平具有治疗意义。
The Rho GTPase Rac1 is a multifunctional protein involved in distinct pathways ranging from development to pathology. The aim of the present study was to unravel the contribution of neuronal Rac1 in regulating the response to brain injury induced by permanent focal cerebral ischemia (pMCAO). Our results show that pMCAO significantly increased total Rac1 levels in wild type mice, mainly through rising nuclear Rac1, while a reduction in Rac1 activation was observed. Such changes preceded cell death induced by excitotoxic stress. Pharmacological inhibition of Rac1 in primary neuronal cortical cells prevented the increase in oxidative stress induced after overactivation of glutamate receptors. However, this was not sufficient to prevent the associated neuronal cell death. In contrast, RNAi-mediated knock down of Rac1 in primary cortical neurons prevented cell death elicited by glutamate excitotoxicity and decreased the activity of NADPH oxidase. To test whether in vivo down regulation of neuronal Rac1 was neuroprotective after pMCAO, we used tamoxifen-inducible neuron-specific conditional Rac1-knockout mice. We observed a significant 50% decrease in brain infarct volume of knockout mice and a concomitant increase in HIF-1 expression compared to littermate control mice, demonstrating that ablation of Rac1 in neurons is neuroprotective. Transmission electron microscopy performed in the ischemic brain showed that lysosomes in the infarct of Rac1- knockout mice were preserved at similar levels to those of non-infarcted tissue, while littermate mice displayed a decrease in the number of lysosomes, further corroborating the notion that Rac1 ablation in neurons is neuroprotective. Our results demonstrate that Rac1 plays important roles in the ischemic pathological cascade and that modulation of its levels is of therapeutic interest.