Dept. of Cellular and Molecular Physiology, The Penn State College of Medicine, Hershey, PA, USA.
J Cachexia Sarcopenia Muscle. 2021 Dec;12(6):1597-1612. doi: 10.1002/jcsm.12795. Epub 2021 Oct 19.
Chemotherapy is an essential treatment to combat solid tumours and mitigate metastasis. Chemotherapy causes side effects including muscle wasting and weakness. Regulated in Development and DNA Damage Response 1 (REDD1) is a stress-response protein that represses the mechanistic target of rapamycin (mTOR) in complex 1 (mTORC1), and its expression is increased in models of muscle wasting. The aim of this study was to determine if deletion of REDD1 is sufficient to attenuate chemotherapy-induced muscle wasting and weakness in mice.
C2C12 myotubes were treated with carboplatin, and changes in myotube diameter were measured. Protein synthesis was measured by puromycin incorporation, and REDD1 mRNA and protein expression were analysed in myotubes treated with carboplatin. Markers of mTORC1 signalling were measured by western blot. REDD1 global knockout mice and wild-type mice were treated with a single dose of carboplatin and euthanized 7 days later. Body weight, hindlimb muscle weights, forelimb grip strength, and extensor digitorum longus whole muscle contractility were measured in all groups. Thirty minutes prior to euthanasia, mice were injected with puromycin to measure puromycin incorporation in skeletal muscle.
C2C12 myotube diameter was decreased at 24 (P = 0.0002) and 48 h (P < 0.0001) after carboplatin treatment. Puromycin incorporation was decreased in myotubes treated with carboplatin for 24 (P = 0.0068) and 48 h (P = 0.0008). REDD1 mRNA and protein expression were increased with carboplatin treatment (P = 0.0267 and P = 0.0015, respectively), and this was accompanied by decreased phosphorylation of Akt T (P < 0.0001) and S (P = 0.0006), p70S6K T (P = 0.0002), and 4E-binding protein 1 S (P = 0.0341), all markers of mTORC1 activity. REDD1 mRNA expression was increased in muscles from mice treated with carboplatin (P = 0.0295). Loss of REDD1 reduced carboplatin-induced body weight loss (P = 0.0013) and prevented muscle atrophy in mice. REDD1 deletion prevented carboplatin-induced decrease of protein synthesis (P = 0.7626) and prevented muscle weakness.
Carboplatin caused loss of body weight, muscle atrophy, muscle weakness, and inhibition of protein synthesis. Loss of REDD1 attenuates muscle atrophy and weakness in mice treated with carboplatin. Our study illustrates the importance of REDD1 in the regulation of muscle mass with chemotherapy treatment and may be an attractive therapeutic target to combat cachexia.
化疗是对抗实体瘤和减轻转移的重要治疗方法。化疗会引起副作用，包括肌肉减少和虚弱。调节发育和 DNA 损伤反应 1（REDD1）是一种应激反应蛋白，可在复合物 1（mTORC1）中抑制雷帕霉素的机制靶标（mTOR），其在肌肉减少的模型中表达增加。本研究的目的是确定 REDD1 的缺失是否足以减轻小鼠化疗引起的肌肉减少和虚弱。
用卡铂处理 C2C12 肌管，测量肌管直径的变化。通过嘌呤霉素掺入测量蛋白质合成，并用卡铂处理的肌管分析 REDD1 mRNA 和蛋白质表达。通过 Western blot 测量 mTORC1 信号通路的标志物。用卡铂处理 REDD1 全局敲除小鼠和野生型小鼠，并在 7 天后安乐死。测量所有组的体重、后肢肌肉重量、前肢握力和伸趾长肌整体肌肉收缩性。在安乐死前 30 分钟，向小鼠注射嘌呤霉素以测量骨骼肌中的嘌呤霉素掺入。
卡铂处理后 24 小时（P = 0.0002）和 48 小时（P < 0.0001），C2C12 肌管直径减小。用卡铂处理 24 小时（P = 0.0068）和 48 小时（P = 0.0008），嘌呤霉素掺入减少。卡铂处理后 REDD1 mRNA 和蛋白质表达增加（P = 0.0267 和 P = 0.0015），这伴随着 Akt T（P < 0.0001）和 S（P = 0.0006）、p70S6K T（P = 0.0002）和 4E-结合蛋白 1 S（P = 0.0341）的磷酸化减少，所有这些都是 mTORC1 活性的标志物。卡铂处理的肌肉中 REDD1 mRNA 表达增加（P = 0.0295）。REDD1 的缺失减少了卡铂引起的体重减轻（P = 0.0013）并预防了小鼠的肌肉萎缩。REDD1 缺失可防止卡铂引起的蛋白质合成减少（P = 0.7626）并防止肌肉无力。
卡铂导致体重减轻、肌肉萎缩、肌肉无力和蛋白质合成抑制。REDD1 的缺失可减轻卡铂治疗小鼠的肌肉萎缩和虚弱。我们的研究说明了 REDD1 在化疗治疗肌肉质量调节中的重要性，并且可能是对抗恶病质的有吸引力的治疗靶点。
