Wang Xiaohong, Xin Hairui, Xing Mingjie, Gu Xianhong, Hao Yue
State Key Laboratory of Animal Nutrition, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China.
Front Physiol. 2022 Apr 13;13:857853. doi: 10.3389/fphys.2022.857853. eCollection 2022.
Endoplasmic reticulum stress (ERS) is closely associated with the occurrence and development of many liver diseases. ERS models mostly include experimental animals such as rats and mice. However, pigs are more similar to humans with regards to digestion and metabolism, especially liver construction, yet few reports on ERS in pigs exist. In order to explore changes in the liver under ERS, we used tunicamycin (TM), which can cause liver jaundice and damage liver function, to establish acute ERS models in piglets using a low TM dosage (LD, 0.1 mg/kg body weight (bw)), high TM dosage (HD, 0.3 mg/kg bw), or vehicle for 48 h. We found that both LD- and HD-induced ERS, as verified by the ERS-linked proteins. Furthermore, the concentrations of the proinflammatory cytokines, namely, TNF-α and IL-6 were elevated in TM-treated piglet livers, and the plasma levels of IL-6 and CRP were also higher, indicating the occurrence of inflammation in TM-treated piglets. The complement system was activated in TM-treated piglets, as indicated by increased levels of complement factors and activation products C3, C5a, and AP50. In order to gain insights into the global changes in liver proteins under ERS, we performed an isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis on the livers of HD- and vehicle-treated piglets. Proteomic analysis identified 311 differentially expressed proteins (DEPs) between the two groups, and a Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that the DEPs were mainly enriched in signaling pathways such as metabolic pathways, protein processing in the endoplasmic reticulum, and complement and coagulation cascades. Many proteins involved in protein folding, lipid transport, and oxidation were upregulated. Proteins involved in lipid synthesis were downregulated to alleviate liver steatosis, and most complement factors were upregulated to protect the body, and Pearson correlation analysis found that most of the DEPs in the complement and coagulation pathway were significantly correlated with plasma CRP, IL6 and AP50. Our results revealed that TM can activate ERS, marked by liver injury and steatosis, inflammatory reactions, and complement activation in piglets.
内质网应激（ERS）与多种肝脏疾病的发生和发展密切相关。ERS模型大多包括大鼠和小鼠等实验动物。然而，猪在消化和代谢方面，尤其是肝脏结构，与人类更为相似，但关于猪ERS的报道却很少。为了探究ERS状态下肝脏的变化，我们使用可导致肝脏黄疸并损害肝功能的衣霉素（TM），以低剂量TM（LD，0.1毫克/千克体重（bw））、高剂量TM（HD，0.3毫克/千克bw）或赋形剂处理仔猪48小时，建立急性ERS模型。我们发现，通过与ERS相关的蛋白证实，LD和HD均能诱导ERS。此外，TM处理的仔猪肝脏中促炎细胞因子TNF-α和IL-6的浓度升高，血浆中IL-6和CRP水平也更高，表明TM处理的仔猪发生了炎症。补体因子和激活产物C3、C5a及AP50水平升高，表明TM处理的仔猪补体系统被激活。为了深入了解ERS状态下肝脏蛋白质的整体变化，我们对HD处理和赋形剂处理的仔猪肝脏进行了基于相对和绝对定量等压标签（iTRAQ）的蛋白质组学分析。蛋白质组学分析确定两组之间有311种差异表达蛋白（DEP），京都基因与基因组百科全书（KEGG）通路分析表明，这些DEP主要富集于代谢途径、内质网中的蛋白质加工以及补体和凝血级联等信号通路。许多参与蛋白质折叠、脂质转运和氧化的蛋白质上调。参与脂质合成的蛋白质下调以减轻肝脏脂肪变性，大多数补体因子上调以保护机体，Pearson相关性分析发现补体和凝血途径中的大多数DEP与血浆CRP、IL6和AP50显著相关。我们的结果显示，TM可激活ERS，其标志为仔猪肝脏损伤和脂肪变性、炎症反应及补体激活。
