Division of Pulmonary, Allergy & Critical Care Medicine, Emory University School of Medicine, 615 Michael St., Ste. 205, Atlanta, GA 30322, USA.
Am J Physiol Lung Cell Mol Physiol. 2013 Aug 1;305(3):L267-77. doi: 10.1152/ajplung.00288.2012. Epub 2013 Jun 7.
The master transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) regulates the expression of antioxidant and phase II-metabolizing enzymes by activating the antioxidant response element (ARE) and thereby protects cells and tissues from oxidative stress. Pulmonary complications remain the leading cause of death in human immunodeficiency virus (HIV)-1-infected individuals, who display systemic oxidative stress and glutathione deficiency that can be modeled in transgenic rats where HIV-1-related viral proteins decrease glutathione levels and cause epithelial barrier dysfunction within the alveolar space by as yet unknown mechanisms. We hypothesized that HIV-1-related proteins inhibit Nrf2-mediated antioxidant defenses and thereby disrupt the normally tight alveolar epithelial barrier. Nrf2 RNA silencing dampened Nrf2/ARE activity, decreased the expression of the tight junction proteins zonula occludens-1, occludin, and claudin-18, increased paracellular permeability of alveolar epithelial monolayers derived from wild-type rats, and therefore reproduced the effects of HIV-1 transgene expression on the epithelial barrier that we had previously described. In contrast, upregulating Nrf2 activity, either by plasmid-mediated overexpression or treatment with the Nrf2 activator sulforaphane, increased the expression of ARE-dependent antioxidants, including NAD(P)H dehydrogenase, quinone 1 and glutathione, improved the expression of tight junction proteins, and restored the ability to form tight barriers in alveolar epithelial cells from HIV-1 transgenic rats. Taken together, these new findings argue that HIV-1-related proteins downregulate Nrf2 expression and/or activity within the alveolar epithelium, which in turn impairs antioxidant defenses and barrier function, thereby rendering the lung susceptible to oxidative stress and injury. Furthermore, this study suggests that activating the Nrf2/ARE pathway with the dietary supplement sulforaphane could augment antioxidant defenses and lung health in HIV-1-infected individuals.
主要转录因子核因子（红系衍生 2）样 2（Nrf2）通过激活抗氧化反应元件（ARE）来调节抗氧化剂和 II 相代谢酶的表达，从而保护细胞和组织免受氧化应激。肺部并发症仍然是人类免疫缺陷病毒（HIV-1）感染个体死亡的主要原因，这些个体表现出全身氧化应激和谷胱甘肽缺乏，这种情况可以在转基因大鼠中建模，其中 HIV-1 相关病毒蛋白降低谷胱甘肽水平，并通过目前尚不清楚的机制导致肺泡空间内的上皮屏障功能障碍。我们假设 HIV-1 相关蛋白抑制 Nrf2 介导的抗氧化防御，从而破坏正常紧密的肺泡上皮屏障。Nrf2 RNA 沉默减弱了 Nrf2/ARE 活性，降低了紧密连接蛋白 zonula occludens-1、occludin 和 claudin-18 的表达，增加了来自野生型大鼠的肺泡上皮单层细胞的旁通透性，从而再现了我们之前描述的 HIV-1 转基因表达对上皮屏障的影响。相比之下，通过质粒介导的过表达或用 Nrf2 激活剂萝卜硫素处理来上调 Nrf2 活性，增加了 ARE 依赖性抗氧化剂的表达，包括 NAD（P）H 脱氢酶、醌 1 和谷胱甘肽，改善了紧密连接蛋白的表达，并恢复了 HIV-1 转基因大鼠肺泡上皮细胞形成紧密屏障的能力。总之，这些新发现表明，HIV-1 相关蛋白下调肺泡上皮细胞中的 Nrf2 表达和/或活性，从而损害抗氧化防御和屏障功能，使肺部易受氧化应激和损伤。此外，这项研究表明，用膳食补充剂萝卜硫素激活 Nrf2/ARE 途径可以增强 HIV-1 感染个体的抗氧化防御和肺部健康。
