Dispensary of 3rd Wing, Air Force, Taichung, Taiwan; Department of Biology and Anatomy, National Defense Medical Center, Taipei, Taiwan.
Department of Biology and Anatomy, National Defense Medical Center, Taipei, Taiwan.
Chem Biol Interact. 2019 May 1;304:43-51. doi: 10.1016/j.cbi.2019.02.023. Epub 2019 Mar 5.
Accumulations of uremic toxins has been widely recognized as the major trigger of skeletal muscle loss in chronic kidney disease (CKD), which is defined as uremic sarcopenia. Current study was aimed to examine the effects of representative uremic toxin, indoxyl sulfate (IS), on C2C12 myotubes. The incubation of IS (from 0.1 mM to 1.2 mM) exerted the reduction in myotube diameter without cell survival impairment. Elevated oxidative stress and mitogen-activated protein kinase (MAPKs) phosphorylation were observed after IS stimulation for 1 and 24 h. After N-acetylcysteine (NAC) treatment as antioxidants, the recovery in IS-induced decrease myotube diameter and ERK phosphorylation was observed. This findings were implicit the transduction of p-ERK in IS-induced ROS toxicity. Moreover, the increase of LC3β was found closely with IS treatment in C2C12 myotubes. The reverse effect of NAC on LC3β expression revealed the ROS-responsibility in autophagy regulation of CKD myopathy. The evaluation of IS-treated proteasome system showed increased phospho-myosin light chain, along with the upregulation of muscle atrophy F-box (MAFbx) mRNA and protein. This alteration in MAFbx was also identified in nephrectomy-induced CKD model. Besides, the inhibition of p-JNK was capable to attenuate IS-induced upward change in MAFbx protein expression. These findings indicated that IS-mediated myotube atrophy may manipulate through ROS-ERK axis and JNK-MAFbx regulation in C2C12 cells.
尿毒症毒素的积累已被广泛认为是慢性肾脏病（CKD）中骨骼肌丧失的主要触发因素，这种骨骼肌丧失被定义为尿毒症性肌肉减少症。本研究旨在研究代表性尿毒症毒素吲哚硫酸（IS）对 C2C12 肌管的影响。IS（从 0.1mM 到 1.2mM）孵育对肌管直径没有细胞存活损害的影响。在 IS 刺激 1 和 24 小时后，观察到氧化应激和丝裂原激活的蛋白激酶（MAPKs）磷酸化升高。用抗氧化剂 N-乙酰半胱氨酸（NAC）处理后，观察到 IS 诱导的肌管直径减小和 ERK 磷酸化的恢复。这些发现暗示了 p-ERK 在 IS 诱导的 ROS 毒性中的转导。此外，在 C2C12 肌管中发现 LC3β 的增加与 IS 处理密切相关。NAC 对 LC3β 表达的反向作用揭示了 CKD 肌病中自噬调节的 ROS 反应性。对 IS 处理的蛋白酶体系统的评估显示磷酸化肌球蛋白轻链增加，同时肌肉萎缩 F 盒（MAFbx）mRNA 和蛋白质上调。这种 MAFbx 的改变也在肾切除诱导的 CKD 模型中被鉴定出来。此外，抑制 p-JNK 能够减弱 IS 诱导的 MAFbx 蛋白表达的上调。这些发现表明，IS 介导的肌管萎缩可能通过 C2C12 细胞中的 ROS-ERK 轴和 JNK-MAFbx 调节来操纵。
