DataSheet1_Taurine Protects C2C12 Myoblasts From Impaired Cell Proliferation and Myotube Differentiation Under Cisplatin-Induced ROS Exposure.docx

In cancer patients, chemotherapeutic medication induces aberrant ROS (reactive oxygen species) accumulation in skeletal muscles, resulting in myofiber degradation, muscle weakness, and even cachexia, which further leads to poor therapeutic outcomes. Acting as an antioxidant, taurine is extensively used to accelerate postexercise muscle recovery in athletes. The antioxidant effects of taurine have been shown in mature myotubes and myofibers but not yet in myoblasts, the myotube precursor. The proliferation and differentiation ability of myoblasts play a very important role in myofiber repair and regeneration, which is usually impaired during chemotherapeutics in cancer patients as well. Here, we explored the effects of taurine supplementation on C2C12 myoblasts exposed to cisplatin-induced ROS. We found that cisplatin treatment led to dramatically decreased cell viability; accumulated ROS level; down-regulated expressions of MyoD1 (myoblast determination protein 1), myogenin, and MHC (myosin heavy chain); and impaired myotube differentiation in myoblasts. Significantly, taurine supplementation protected myoblasts against cisplatin-induced cell viability decrease, promoted cellular ROS clearance, and, most importantly, preserved the expressions of MyoD1, myogenin, and MHC as well as myotube differentiation ability. We further conducted NMR-based metabolomic analysis to clarify the underlying molecular mechanisms. We identified 14 characteristic metabolites primarily responsible for the discrimination of metabolic profiles between cisplatin-treated cells and normal counterparts, including increased levels of BCAAs (branched-chain amino acids: leucine and isoleucine), alanine, glycine, threonine, glucose, ADP (adenosine diphosphate), phenylalanine, and PC (O-phosphocholine), and decreased levels of lysine, β-alanine, choline, GPC (sn-glycero-3-phosphocholine), and myo-inositol. Evidently, taurine supplementation partially reversed the changing trends of several metabolites (isoleucine, threonine, glycine, PC, β-alanine, lysine, and myo-inositol). Furthermore, taurine supplementation promoted the proliferation and myotube differentiation of myoblasts by alleviating cellular catabolism, facilitating GSH (reduced glutathione) biosynthesis, improving glucose utilization and TCA (tricarboxylic acid) cycle anaplerosis, and stabilizing cellular membranes. Our results demonstrated the protective effects of taurine on cisplatin-impaired myoblasts and elucidated the mechanistic rationale for the use of taurine to ameliorate muscle toxicity in clinical chemotherapy cancer patients.

针对癌症患者，化疗药物会诱导骨骼肌内活性氧（ROS, reactive oxygen species）异常蓄积，进而引发肌纤维降解、肌肉无力甚至恶病质，最终导致治疗效果不佳。牛磺酸作为抗氧化剂，已被广泛应用于加速运动员运动后肌肉恢复。其抗氧化作用已在成熟肌管与肌纤维中得到证实，但尚未在肌母细胞——肌管的前体细胞——中得到验证。肌母细胞的增殖与分化能力对肌纤维修复与再生至关重要，而该过程在癌症患者化疗期间同样会受到损伤。本研究探讨了补充牛磺酸对经顺铂诱导氧化应激的C2C12肌母细胞的影响。研究发现，顺铂处理会显著降低细胞活力、升高活性氧水平，并下调肌分化因子1（MyoD1, myoblast determination protein 1）、肌细胞生成素与肌球蛋白重链（MHC, myosin heavy chain）的表达，同时损伤肌母细胞的肌管分化能力。值得注意的是，补充牛磺酸可保护肌母细胞免受顺铂诱导的细胞活力下降，促进细胞内活性氧清除，更为关键的是，可维持MyoD1、肌细胞生成素与MHC的表达水平，并恢复肌管分化能力。本研究进一步开展了基于核磁共振（NMR, nuclear magnetic resonance）的代谢组学分析，以阐明潜在的分子机制。我们鉴定出14种特征代谢物，主要用于区分顺铂处理组与正常对照组的代谢谱，其中包括支链氨基酸（BCAAs, branched-chain amino acids：亮氨酸与异亮氨酸）、丙氨酸、甘氨酸、苏氨酸、葡萄糖、二磷酸腺苷（ADP, adenosine diphosphate）、苯丙氨酸与磷酸胆碱（PC, O-phosphocholine）水平升高，以及赖氨酸、β-丙氨酸、胆碱、sn-甘油-3-磷酸胆碱（GPC, sn-glycero-3-phosphocholine）与肌醇水平降低。显然，补充牛磺酸可部分逆转部分代谢物的变化趋势（异亮氨酸、苏氨酸、甘氨酸、PC、β-丙氨酸、赖氨酸与肌醇）。此外，补充牛磺酸可通过减轻细胞分解代谢、促进谷胱甘肽（GSH, reduced glutathione）生物合成、改善葡萄糖利用与三羧酸（TCA, tricarboxylic acid）循环回补反应以及稳定细胞膜，来促进肌母细胞的增殖与肌管分化。本研究结果证实了牛磺酸对顺铂损伤肌母细胞的保护作用，并阐明了利用牛磺酸改善临床癌症化疗患者肌肉毒性的机制依据。