BackgroundIntensive care unit‐acquired weakness (ICU‐AW) is a syndrome characterized by a long‐term muscle weakness often observed in sepsis‐surviving patients during the chronic phase. Although ICU‐AW is independently associated with increased mortality, effective therapies have yet to be established. Programmed death‐1 (PD‐1) inhibitors have attracted attention as potential treatments for reversing immune exhaustion in sepsis; however, its impact on ICU‐AW remains to be elucidated. Here, we study how PD‐1 deficiency affects sepsis‐induced skeletal muscle dysfunction in a preclinical sepsis model.MethodsChronic sepsis model was developed by treating wild‐type (WT) and PD‐1 knockout (KO) mice with caecal slurry, followed by resuscitation with antibiotics and saline. Mice were euthanized on days 15–17. Body weights, muscle weights, and limb muscle strengths were measured. Interleukin 13 (IL‐13) and PD‐1 expressions were examined by flow cytometry. Messenger RNA (mRNA) expressions of slow‐twitch muscles were measured by reverse transcription and quantitative polymerase chain reaction (RT‐qPCR). In an in vitro study, C2C12 myotubes were treated with lipopolysaccharide (LPS) and recombinant IL‐13 followed by gene expression measurements.ResultsWT septic mice exhibited decreased muscle weight (quadriceps, P < 0.01; gastrocnemius, P < 0.05; and tibialis anterior, P < 0.01) and long‐term muscle weakness (P < 0.0001), whereas PD‐1 KO septic mice did not exhibit any reduction in muscle weights and strengths. Slow‐twitch specific mRNAs, including myoglobin (Mb), troponin I type 1 (Tnni1), and myosin heavy chain 7 (Myh7) were decreased in WT skeletal muscle (Mb, P < 0.0001; Tnni1, P < 0.05; and Myh7, P < 0.05) after sepsis induction, but mRNA expressions of Tnni1 and Myh7 were increased in PD‐1 KO septic mice (Mb, not significant; Tnni1, P < 0.0001; and Myh7, P < 0.05). Treatment of C2C12 myotube cells with LPS decreased the expression of slow‐twitch mRNAs, which was restored by IL‐13 (Mb, P < 0.0001; Tnni1, P < 0.001; and Myh7, P < 0.05). IL‐13 production was significantly higher in ILC2s compared to T cells in skeletal muscle (P < 0.05). IL‐13‐producing ILC2s in skeletal muscle were examined and found to increase in PD‐1 KO septic mice, compared with WT septic mice (P < 0.05). ILC2‐derived IL‐13 was increased by PD‐1 KO septic mice and thought to protect the muscles from experimental ICU‐AW.ConclusionsLong‐term muscle weakness in experimental ICU‐AW was ameliorated in PD‐1 KO mice. ILC2‐derived IL‐13 production in skeletal muscles was increased in PD‐1 KO mice, thereby suggesting that IL‐13 alleviates muscle weakness during sepsis. This study demonstrates the effects of PD‐1 blockade in preserving muscle strength during sepsis through an increase in ILC2‐derived IL‐13 and may be an attractive therapeutic target for sepsis‐induced ICU‐AW.

中文翻译：

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程序性死亡 1 和肌肉先天淋巴细胞来源的白细胞介素 13 在脓毒症引起的重症监护病房获得性无力中的作用


背景重症监护病房获得性无力（ICU-AW）是一种以长期肌肉无力为特征的综合征，通常在慢性期脓毒症幸存患者中观察到。尽管 ICU-AW 与死亡率增加独立相关，但有效的治疗方法尚未建立。程序性死亡-1（PD-1）抑制剂作为逆转脓毒症免疫衰竭的潜在治疗方法而引起了人们的关注；然而，其对 ICU-AW 的影响仍有待阐明。在这里，我们在临床前脓毒症模型中研究 PD-1 缺乏如何影响脓毒症引起的骨骼肌功能障碍。方法通过用盲肠浆处理野生型 (WT) 和 PD-1 敲除 (KO) 小鼠，然后用用抗生素和生理盐水进行复苏。第 15-17 天对小鼠实施安乐死。测量体重、肌肉重量和四肢肌肉力量。通过流式细胞术检查白细胞介素 13 (IL-13) 和 PD-1 的表达。通过逆转录和定量聚合酶链反应（RT-qPCR）测量慢肌的信使RNA（mRNA）表达。在一个体外研究中，C2C12 肌管用脂多糖 (LPS) 和重组 IL-13 处理，然后进行基因表达测量。结果WT 脓毒症小鼠表现出肌肉重量下降（股四头肌、磷< 0.01；腓肠肌,磷< 0.05；和胫骨前肌，磷< 0.01）和长期肌无力（磷< 0.0001），而 PD-1 KO 脓毒症小鼠没有表现出肌肉重量和力量的任何减少。 慢肌特异性 mRNA，包括肌红蛋白（ MB ），肌钙蛋白 I 型 1（肌钙蛋白1 ）和肌球蛋白重链 7（米哈7 ) WT 骨骼肌 ( MB ,磷< 0.0001； TNNI1 ,磷< 0.05；和米哈7 ,磷< 0.05）脓毒症诱导后，但 PD-1 KO 脓毒症小鼠中 Tnni1 和 Myh7 的 mRNA 表达增加（ MB ，不显着； TNNI1 ,磷< 0.0001；和米哈7 ,磷< 0.05）。用 LPS 处理 C2C12 肌管细胞会降低慢肌 mRNA 的表达，而 IL-13 可以恢复这种表达（ MB ,磷< 0.0001；肌钙蛋白1 ,磷< 0.001；和米哈7 ,磷< 0.05）。与骨骼肌中的 T 细胞相比，ILC2 中的 IL-13 产量显着更高（磷< 0.05）。对骨骼肌中产生 IL-13 的 ILC2 进行了检查，发现与 WT 脓毒症小鼠相比，PD-1 KO 脓毒症小鼠中产生 IL-13 的 ILC2 有所增加（磷< 0.05）。 PD-1 KO 脓毒症小鼠中 ILC2 衍生的 IL-13 增加，并被认为可以保护肌肉免受实验性 ICU-AW 的影响。结论：实验性 ICU-AW 中的长期肌肉无力在 PD-1 KO 小鼠中得到改善。在 PD-1 KO 小鼠中，骨骼肌中 ILC2 衍生的 IL-13 产量增加，从而表明 IL-13 可以缓解脓毒症期间的肌肉无力。这项研究证明了 PD-1 阻断通过增加 ILC2 衍生的 IL-13 在脓毒症期间保持肌肉力量的作用，并且可能是脓毒症引起的 ICU-AW 的一个有吸引力的治疗靶点。