Zheng Qi, Wang Zhaoling, Tan Yejun, Zhu Kun, Lu Meiping
Department of Rheumatology, Immunology and Allergy, Children's Hospital, National Clinical Research Center for Child Health, Zhejiang University School of Medicine, Hangzhou, China.
School of Mathematics, University of Minnesota Twin Cities, Minneapolis, MN, USA.
Rheumatol Ther. 2024 Oct;11(5):1255-1269. doi: 10.1007/s40744-024-00699-6. Epub 2024 Jul 29.
Juvenile dermatomyositis (JDM) is characterized by persistent non-purulent inflammation in the muscle and skin. The underlying mechanisms still remain uncertain. This study aims to elucidate the mechanism of interleukin-6 (IL-6) activation of Janus kinase/signal transducer and activator of transcription 3 pathway (JAK/STAT3), contributing to the pathogenesis of JDM.
Serum IL-6 levels were compared between 72 newly diagnosed patients with JDM and the same patient cohort in treatment remission. Single-cell RNA sequencing (scRNA-seq) was employed to identify differential signaling pathway expression in muscle biopsy samples from two patients with JDM and healthy controls. Immunohistochemistry was used to examine differences in STAT3 phosphorylation between JDM and control muscle tissues. In vitro, skeletal muscle cell lines were stimulated with IL-6, and the transcription levels of genes related to mitochondrial calcium channels were quantified via reverse transcription-polymerase chain reaction (RT-PCR). Reactive oxygen species (ROS) production was measured in both IL-6 treated and untreated groups. ROS levels were then compared between IL-6 receptor antagonist pre-treated skeletal muscle cells and untreated cells.
IL-6 levels in newly onset patients with JDM were significantly higher compared to the same patient cohort in remission states (p < 0.0001). Serum IL-6 was significantly increased in patients with negative myositis specific antibody (MSA), positive melanoma differentiation associated protein 5 (MDA5) and positive nuclear matrix protein 2 (NXP2), yet not for JDM with positive transcriptional intermediary factor γ (TIF1γ), based on subgroup analysis. ScRNA-seq analysis of muscle biopsies from patients with MDA5-positive JDM and patients with MSA negative JDM revealed abnormal activation of the JAK/STAT3 pathway in skeletal myocytes, macrophages, and vascular endothelial cells. The phosphorylation levels of STAT3 were elevated in active JDM cases. Transcription of the calcium channel modulation gene sarcolipin (SLN) was significantly higher in JDM primary skeletal muscle cells compared to normal cells. In vitro, IL-6 enhanced SLN transcription and induced ROS production, and blocking the IL-6 receptor resulted in decreased ROS generation in skeletal muscle cells.
IL-6/JAK/STAT3 signaling pathway was abnormally activated in patients with JDM. IL-6 may be involved in the pathogenesis of muscle damage by triggering the development of calcium overload and production of ROS. Blockade of the IL-6/JAK/STAT3 pathway can be a potential treatment option for JDM, especially MDA5-positive patients and those who are negative for MSA.
青少年皮肌炎（JDM）的特征是肌肉和皮肤持续存在非化脓性炎症。其潜在机制仍不明确。本研究旨在阐明白细胞介素-6（IL-6）激活Janus激酶/信号转导子和转录激活子3通路（JAK/STAT3）的机制，这一机制与JDM的发病机制有关。
比较72例新诊断的JDM患者与处于治疗缓解期的同一患者队列的血清IL-6水平。采用单细胞RNA测序（scRNA-seq）来鉴定两名JDM患者和健康对照的肌肉活检样本中差异信号通路的表达。免疫组织化学用于检测JDM和对照肌肉组织中STAT3磷酸化的差异。在体外，用IL-6刺激骨骼肌细胞系，并通过逆转录-聚合酶链反应（RT-PCR）定量与线粒体钙通道相关基因的转录水平。在IL-6处理组和未处理组中均测量活性氧（ROS）的产生。然后比较IL-6受体拮抗剂预处理的骨骼肌细胞和未处理细胞之间的ROS水平。
新发病的JDM患者的IL-6水平显著高于处于缓解状态的同一患者队列（p < 0.0001）。根据亚组分析，肌炎特异性抗体（MSA）阴性、黑色素瘤分化相关蛋白5（MDA5）阳性和核基质蛋白2（NXP2）阳性的患者血清IL-6显著升高，但转录中介因子γ（TIF1γ）阳性的JDM患者血清IL-6未升高。对MDA5阳性JDM患者和MSA阴性JDM患者的肌肉活检进行scRNA-seq分析，发现骨骼肌细胞、巨噬细胞和血管内皮细胞中的JAK/STAT3通路异常激活。在活动期JDM病例中，STAT3的磷酸化水平升高。与正常细胞相比，JDM原代骨骼肌细胞中钙通道调节基因肌浆素（SLN）的转录显著更高。在体外，IL-6增强了SLN转录并诱导ROS产生，阻断IL-6受体导致骨骼肌细胞中ROS生成减少。
JDM患者中IL-6/JAK/STAT3信号通路异常激活。IL-6可能通过引发钙超载的发展和ROS的产生参与肌肉损伤的发病机制。阻断IL-6/JAK/STAT3通路可能是JDM的一种潜在治疗选择，尤其是MDA5阳性患者和MSA阴性患者。
