Institute for Medical Biochemistry, University of Veterinary Medicine Vienna, Vienna, Austria.
Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria.
Cytokine. 2019 Dec;124:154577. doi: 10.1016/j.cyto.2018.10.018. Epub 2018 Nov 14.
An excessive inflammatory response is frequently associated with cellular dysfunction and cell death. The latter may cause single and multiple organ failure. The most susceptible organs are liver, lung, kidney, heart and intestine. This review will focus on the liver as a target organ for an excessive inflammatory response. It is commonly accepted that organ failure is caused by the action of inflammatory cytokines released in excess during the inflammatory response. It has been suggested that inflammation mediated liver failure is not due to an increased death rate of parenchymal cells, but due to an intracellular metabolic disorder. This metabolic disorder is associated with mitochondrial and endoplasmic reticulum (ER) dysfunction during the acute phase response elicited by systemic inflammation. An overproduction of acute phase proteins in the liver as well as elevated reactive oxygen species (ROS) generation induce ER stress, triggering the unfolded protein response (UPR), which may initiate or aggravate inflammation. It is known that certain inflammatory mediators, such as the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α induce ER stress. These findings suggest that ER stress and the subsequent UPR on the one hand, and the inflammatory response on the other create a kind of feed forward loop, which can be either beneficial (e.g., elimination of the pathogen and restoration of tissue homeostasis) or deleterious (e.g., excessive cell dysfunction and cell death). This review aims to unfurl the different pathways contributing to this loop and to highlight the relevance of UPR signaling (IRE1α, ATF6, and PERK) and mediators of the inflammatory response (NF-κB, STAT3, IL-1β, IL-6, TLR) which have a particular role as pathophysiological triggers in the liver.
过度的炎症反应通常与细胞功能障碍和细胞死亡有关。后者可能导致单个和多个器官衰竭。最易受影响的器官是肝脏、肺、肾、心脏和肠道。本篇综述将重点关注肝脏作为过度炎症反应的靶器官。人们普遍认为,器官衰竭是由炎症反应过程中过量释放的炎症细胞因子引起的。有人提出,炎症介导的肝衰竭不是由于实质细胞死亡率增加,而是由于细胞内代谢紊乱。这种代谢紊乱与系统性炎症引起的急性期反应中内质网(ER)和线粒体功能障碍有关。肝脏中急性期蛋白的过度产生以及活性氧(ROS)生成的增加会诱发内质网应激,触发未折叠蛋白反应(UPR),这可能引发或加重炎症。已知某些炎症介质,如促炎细胞因子 IL-1β、IL-6 和 TNF-α,可诱导 ER 应激。这些发现表明,内质网应激和随后的 UPR 一方面,以及炎症反应另一方面,形成了一种正反馈环,这种正反馈环可能既有益处(例如,消除病原体和恢复组织内稳态),也有有害作用(例如,过度的细胞功能障碍和细胞死亡)。本篇综述旨在阐述导致这种正反馈环的不同途径,并强调 UPR 信号通路(IRE1α、ATF6 和 PERK)和炎症反应介质(NF-κB、STAT3、IL-1β、IL-6、TLR)的相关性,这些信号通路和介质在肝脏作为病理生理触发因素方面具有特殊作用。
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