Xue Yansong, Du Min, Zhu Mei-Jun
School of Food Science, Washington State University, Pullman, WA 99164, USA.
Department of Animal Science, Washington State University, Pullman, WA 99164, USA.
Free Radic Biol Med. 2017 Jul;108:760-769. doi: 10.1016/j.freeradbiomed.2017.05.003. Epub 2017 May 2.
Inflammatory responses elicited by LRR and PYD domains-containing protein 3 (NLRP3) inflammasome is induced by a wide variety of stress signals including infectious agents and cellular disorders. E. coli O157:H7 causes serious gastrointestinal diseases that results in severe inflammation and oxidative stress, causing host cell damage. In this study, we found that E. coli O157:H7 infection induced NLRP3 assembly, caspase-1 activation and interleukin (IL)-1β and IL-18 release in Caco-2 cells. Infection also resulted in mitochondrial dysfunction with disrupted mitochondrial potential and mitochondrial complex-I activity, as well as the cytosolic release of cytochrome c and altered mitochondrial respiratory chain. The damage of mitochondria led to increased production of reactive oxygen species (ROS) and cytosolic release of mitochondrial DNA. Moreover, ROS was required for E. coli O157:H7 induced NLRP3 assembly as inhibiting mitochondrial ROS release by ROS scavengers Mito-TEMPO and N-acetylcysteine abrogated NLRP3 inflammasome activation in Caco-2 cells in response to E. coli O157:H7. Quercetin, one of the most important flavonoids in plant origin foods, had a protective role in inhibiting NLRP3 activation upon E. coli O157:H7 infection by protecting mitochondrial integrity and inhibiting mitochondrial ROS release. In addition, E. coli O157:H7 infection inhibited the host autophagy while quercetin treatment augmented autophagy activation, which further blocked ROS generation and IL-1β and IL-18 release. In summary, E. coli O157:H7 infection induced mitochondrial ROS release and NLRP3 assembly in host cells, while quercetin exerted a preventive role in host cells upon E. coli O157:H7 infection partially due to prevention of ROS production and activation of autophagy.
含亮氨酸丰富重复序列和吡啉结构域蛋白3（NLRP3）炎性小体引发的炎症反应由多种应激信号诱导，包括感染因子和细胞紊乱。大肠杆菌O157:H7可引发严重的胃肠道疾病，导致严重炎症和氧化应激，造成宿主细胞损伤。在本研究中，我们发现大肠杆菌O157:H7感染可诱导Caco-2细胞中NLRP3组装、半胱天冬酶-1激活以及白细胞介素（IL）-1β和IL-18释放。感染还导致线粒体功能障碍，线粒体膜电位和线粒体复合物I活性受到破坏，同时细胞色素c释放到胞质中，线粒体呼吸链发生改变。线粒体损伤导致活性氧（ROS）生成增加以及线粒体DNA释放到胞质中。此外，ROS是大肠杆菌O157:H7诱导NLRP3组装所必需的，因为用ROS清除剂Mito-TEMPO和N-乙酰半胱氨酸抑制线粒体ROS释放可消除Caco-2细胞中对大肠杆菌O157:H7应答的NLRP3炎性小体激活。槲皮素是植物源性食物中最重要的黄酮类化合物之一，通过保护线粒体完整性和抑制线粒体ROS释放，在抑制大肠杆菌O157:H7感染时的NLRP3激活方面具有保护作用。此外，大肠杆菌O157:H7感染会抑制宿主自噬，而槲皮素处理可增强自噬激活，进而阻断ROS生成以及IL-1β和IL-18释放。总之，大肠杆菌O157:H7感染可诱导宿主细胞中线粒体ROS释放和NLRP3组装，而槲皮素在大肠杆菌O157:H7感染时对宿主细胞发挥预防作用，部分原因是其可预防ROS产生并激活自噬。
