Hubei Key Laboratory of Animal Nutrition and Feed Science, Wuhan Polytechnic University, Wuhan 430023, China.
Department of Animal Science, Division of Agriculture, University of Arkansas, Fayetteville, AR 72701, USA.
Int J Mol Sci. 2023 Jun 30;24(13):10923. doi: 10.3390/ijms241310923.
Necroptosis, an actively researched form of programmed cell death closely related to the inflammatory response, is important in a variety of disorders and diseases. However, the relationship between necroptosis and muscle protein degradation in cachexia is rarely reported. This study aimed to elucidate whether necroptosis played a crucial role in muscle protein degradation in a cachexia model of weaned piglets induced by lipopolysaccharide (LPS). In Experiment 1, the piglets were intraperitoneally injected with LPS to construct the cachexia model, and sacrificed at different time points after LPS injection (1, 2, 4, 8, 12, and 24 h). In Experiment 2, necrostatin-1 (Nec-1), a necroptosis blocker, was pretreated in piglets before the injection of LPS to inhibit the occurrence of necroptosis. Blood and longissimus dorsi muscle samples were collected for further analysis. In the piglet model with LPS-induced cachexia, the morphological and ultrastructural damage, and the release of pro-inflammatory cytokines including tumor necrosis factor (), interleukin (), and were dynamically elicited in longissimus dorsi muscle. Further, protein concentration and protein/DNA ratio were dynamically decreased, and protein degradation signaling pathway, containing serine/threonine kinase (), Forkhead box O (), muscular atrophy F-box (), and muscle ring finger protein 1 (MuRF1), was dynamically activated in piglets after LPS challenge. Moreover, mRNA and protein expression of necroptosis signals including receptor-interacting protein kinase (), , and mixed lineage kinase domain-like pseudokinase (), were time-independently upregulated. Subsequently, when Nec-1 was used to inhibit necroptosis, the morphological damage, the increase in expression of pro-inflammatory cytokines, the reduction in protein content and protein/DNA ratio, and the activation of the protein degradation signaling pathway were alleviated. These results provide the first evidence that necroptosis mediates muscle protein degradation in cachexia by LPS challenge.
细胞程序性死亡的一种形式，即细胞坏死，与炎症反应密切相关，它在多种疾病和障碍中发挥着重要作用。然而，坏死与恶病质中肌肉蛋白降解的关系鲜有报道。本研究旨在阐明坏死是否在脂多糖（LPS）诱导的断奶仔猪恶病质模型的肌肉蛋白降解中发挥关键作用。在实验 1 中，猪只经腹腔注射 LPS 构建恶病质模型，并于 LPS 注射后不同时间点（1、2、4、8、12 和 24 h）处死。在实验 2 中，预先用坏死抑制剂 necrostatin-1（Nec-1）预处理猪只，以抑制坏死的发生。采集血液和背最长肌样本进行进一步分析。在 LPS 诱导的断奶仔猪恶病质模型中，背最长肌的形态和超微结构损伤以及促炎细胞因子（肿瘤坏死因子（TNF）-、白细胞介素（IL）-1β 和 IL-6）的释放呈动态变化。此外，蛋白质浓度和蛋白质/DNA 比值呈动态下降，并且在 LPS 刺激后，包含丝氨酸/苏氨酸激酶（p38MAPK）、叉头框 O（FoxO）、肌肉萎缩 F 盒（Atrogin-1）和肌肉环指蛋白 1（MuRF1）的蛋白降解信号通路被动态激活。此外，坏死信号受体相互作用蛋白激酶（RIPK）、RIPK3 和混合谱系激酶结构域样伪激酶（MLKL）的 mRNA 和蛋白表达也呈时间依赖性上调。随后，当使用 Nec-1 抑制坏死时，形态损伤、促炎细胞因子表达增加、蛋白质含量和蛋白质/DNA 比值降低以及蛋白降解信号通路的激活均得到缓解。这些结果首次提供了证据，表明坏死通过 LPS 刺激介导恶病质中的肌肉蛋白降解。
