Skeletal Muscle Laboratory, University College, Kurukshetra University, Kurukshetra, Haryana 136119, India.
Department of Microbiology, Center for Free Radical Biology, University of Alabama, Birmingham 35205, USA; Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029, India.
Biochim Biophys Acta Gen Subj. 2018 Apr;1862(4):895-906. doi: 10.1016/j.bbagen.2017.12.015. Epub 2017 Dec 28.
Elevated levels of inflammatory molecules are key players in muscle wasting/atrophy leading to human morbidity. TNFα is a well-known pro-inflammatory cytokine implicated in the pathogenesis of muscle wasting under diverse clinical settings. S-allyl cysteine (SAC), an active component of garlic (Allium sativum), has established anti-oxidant and anti-inflammatory effects in various cell types. However, the impact of SAC on skeletal muscle pathology remains unexplored. Owing to the known anti-inflammatory properties of SAC, we investigated whether pre-treatment with SAC has a protective role in TNFα-induced atrophy in cultured myotubes.
C2C12 myotubes were treated with TNFα (100ng/ml) in the presence or absence of SAC (0.01mM). TNFα treatment induced atrophy in myotubes by up-regulating various proteolytic systems i.e. cathepsin L, calpain, ubiquitin-proteasome E3-ligases (MuRF1/atrogin1), caspase 3 and autophagy (Beclin1/LC3B). TNFα also induced the activation of NFκB by stimulating the degradation of IκBα (inhibitor of NFκB), in myotubes. The alterations in proteolytic systems likely contribute to the degradation of muscle-specific proteins and reduce the myotube length, diameter and fusion index. The SAC supplementation significantly impedes TNFα-induced protein loss and protects myotube morphology by suppressing protein catabolic systems and endogenous level of inflammatory molecules namely TNFα, IL-6, IL-1β, TNF-like weak inducer of apoptosis (TWEAK), fibroblast growth factor-inducible 14 (Fn14) and Nox.
Our findings reveal anti-atrophic role for SAC, as it prevents alterations in protein metabolism and protects myotubes by regulating the level of inflammatory molecules and multiple proteolytic systems responsible for muscle atrophy.
升高的炎症分子水平是导致人类发病率的肌肉消耗/萎缩的关键因素。TNFα 是一种众所周知的促炎细胞因子，在多种临床情况下与肌肉消耗的发病机制有关。S-烯丙基半胱氨酸（SAC），大蒜（Allium sativum）的一种活性成分，在各种细胞类型中具有抗氧化和抗炎作用。然而，SAC 对骨骼肌病理学的影响仍未得到探索。由于 SAC 已知的抗炎特性，我们研究了 SAC 预处理是否对 TNFα 诱导的培养肌管萎缩具有保护作用。
用 TNFα（100ng/ml）处理 C2C12 肌管，同时存在或不存在 SAC（0.01mM）。TNFα 处理通过上调各种蛋白水解系统（即组织蛋白酶 L、钙蛋白酶、泛素-蛋白酶体 E3 连接酶（MuRF1/atrogin1）、半胱天冬酶 3 和自噬（Beclin1/LC3B））诱导肌管萎缩。TNFα 通过刺激 IκBα（NFκB 抑制剂）降解，还诱导 NFκB 的激活，在肌管中。蛋白水解系统的改变可能导致肌肉特异性蛋白的降解，并降低肌管的长度、直径和融合指数。SAC 补充显著阻碍 TNFα 诱导的蛋白丢失，并通过抑制蛋白分解系统和内源性炎症分子水平（即 TNFα、IL-6、IL-1β、TNF 样弱凋亡诱导剂（TWEAK）、成纤维细胞生长因子诱导 14（Fn14）和 Nox）来保护肌管形态。
我们的发现揭示了 SAC 的抗萎缩作用，因为它通过调节炎症分子和多个负责肌肉萎缩的蛋白水解系统的水平，防止蛋白代谢的改变并保护肌管。
