Graduate School of Science, Nagoya City University, Nagoya, Japan.
Department of Orthopaedic Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.
J Physiol. 2024 Nov;602(22):6189-6207. doi: 10.1113/JP286534. Epub 2024 Oct 21.
Idiopathic inflammatory myopathies (IIMs) are systemic autoimmune diseases characterised by muscle weakness. Although multiple physiological and pathological processes are associated with IIMs, T-lymphocyte infiltration into muscle plays a key role in the development and exacerbation of IIMs. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor that regulates inflammatory responses; therefore, muscle Nrf2 may serve an important role in the development of IIMs. In this study, we demonstrated that experimental autoimmune myositis (EAM) causes loss of muscle mass and function in oxidative and glycolytic muscles in C57BL/6 mice. EAM increased CD4 and CD8 T-lymphocyte infiltration, as well as interferon-gamma (IFN-γ) and tumour necrosis factor-alpha (TNF-α) mRNA expression in oxidative soleus and glycolytic extensor digitorum longus muscles, along with elevated chemokine mRNA levels (i.e. CCL3, CCL5, CXCL9, CXCL10 and CXCL16). IFN-γ and TNF-α treatments increased the mRNA expression levels of these chemokines in C2C12 myotubes. EAM also increased phosphorylated Nrf2 at Ser40 in soleus and glycolytic white vastus lateralis muscle. Although the expression of several chemokines was affected by Nrf2 activation following tert-butylhydroquinone treatment or Keap1 knockdown, CCL5 mRNA expression significantly increased in C2C12 myotubes and mouse skeletal muscle. Moreover, muscle-specific Nrf2 knockout in mice attenuates EAM-induced loss of muscle mass and function, which was associated with the inhibition of CCL5 mRNA expression, CD8 T-lymphocyte infiltration and IFN-γ mRNA expression. Collectively, these findings reveal that regulating Nrf2 activity is a promising therapeutic approach for treating IIM-mediated muscle weakness. KEY POINTS: Experimental autoimmune myositis (EAM) causes loss of muscle mass and function. Loss of muscle mass and function in EAM were associated with increased chemokine mRNA expression (i.e. CCL3, CCL5, CXCL9, CXCL10 and CXCL16), T-lymphocyte infiltration and inflammatory cytokine mRNA expression (i.e. IFN-γ and TNF-α) in the skeletal muscle. EAM activated Nrf2 in muscle and increased Nrf2 activity in vivo and in vitro increased CCL5 mRNA expression. Muscle-specific Nrf2 knockout in mice attenuated EAM-induced muscle weakness by inhibiting CCL5 mRNA expression, CD8 T-lymphocyte migration and IFN-γ mRNA expression in muscles. These results provide further evidence for the potential therapeutic targeting of Nrf2 to mitigate EAM-induced muscle weakness.
特发性炎性肌病（IIM）是一种以肌肉无力为特征的系统性自身免疫性疾病。尽管多种生理和病理过程与 IIM 相关，但 T 淋巴细胞浸润肌肉在 IIM 的发展和恶化中起着关键作用。核因子红细胞 2 相关因子 2（Nrf2）是调节炎症反应的关键转录因子；因此，肌肉 Nrf2 在 IIM 的发展中可能发挥重要作用。在这项研究中，我们证明实验性自身免疫性肌炎（EAM）会导致 C57BL/6 小鼠的氧化和糖酵解肌肉的肌肉质量和功能丧失。EAM 增加了 CD4 和 CD8 T 淋巴细胞浸润，以及氧化比目鱼肌和糖酵解伸趾长肌中的干扰素-γ（IFN-γ）和肿瘤坏死因子-α（TNF-α）mRNA 表达，同时趋化因子 mRNA 水平升高（即 CCL3、CCL5、CXCL9、CXCL10 和 CXCL16）。IFN-γ 和 TNF-α 处理增加了 C2C12 肌管中这些趋化因子的 mRNA 表达水平。EAM 还增加了比目鱼肌和糖酵解白外侧股中的 Nrf2 在丝氨酸 40 位的磷酸化。尽管tert-丁基对苯二酚处理或 Keap1 敲低后，几种趋化因子的表达受 Nrf2 激活的影响，但 CCL5 mRNA 在 C2C12 肌管和小鼠骨骼肌中的表达显著增加。此外，肌肉特异性 Nrf2 敲除可减轻 EAM 引起的肌肉质量和功能丧失，这与 CCL5 mRNA 表达、CD8 T 淋巴细胞浸润和 IFN-γ mRNA 表达的抑制有关。总之，这些发现表明调节 Nrf2 活性是治疗 IIM 介导的肌肉无力的一种有前途的治疗方法。
实验性自身免疫性肌炎（EAM）导致肌肉质量和功能丧失。EAM 导致的肌肉质量和功能丧失与骨骼肌中趋化因子 mRNA 表达增加（即 CCL3、CCL5、CXCL9、CXCL10 和 CXCL16）、T 淋巴细胞浸润和炎症细胞因子 mRNA 表达（即 IFN-γ 和 TNF-α）有关。EAM 在肌肉中激活 Nrf2，并增加体内和体外的 Nrf2 活性，增加 CCL5 mRNA 表达。肌肉特异性 Nrf2 敲除可通过抑制肌肉中 CCL5 mRNA 表达、CD8 T 淋巴细胞迁移和 IFN-γ mRNA 表达来减轻 EAM 引起的肌肉无力。这些结果为通过靶向 Nrf2 减轻 EAM 引起的肌肉无力提供了进一步的证据。
