Department of Biomedical Science, Chosun University, Gwangju, South Korea.
Department of Bioinformatics, Kongju National University, Kongju, South Korea.
J Cachexia Sarcopenia Muscle. 2022 Dec;13(6):3091-3105. doi: 10.1002/jcsm.13065. Epub 2022 Sep 4.
Cathelicidin, an antimicrobial peptide, plays a key role in regulating bacterial killing and innate immunity; however, its role in skeletal muscle function is unknown. We investigated the potential role of cathelicidin in skeletal muscle pathology resulting from acute injury and Duchenne muscular dystrophy (DMD) in mice.
Expression changes and muscular localization of mouse cathelicidin-related antimicrobial peptide (Cramp) were examined in the skeletal muscle of normal mice treated with chemicals (cardiotoxin and BaCl ) or in dystrophic muscle of DMD mouse models (mdx, mdx/Utrn and mdx/Utrn ). Cramp penetration into myofibres and effects on muscle damage were studied by treating synthetic peptides to mouse skeletal muscles or C2C12 myotubes. Cramp knockout (KO) mice and mdx/Utrn/Cramp KO lines were used to determine whether Cramp mediates muscle degeneration. Muscle pathophysiology was assessed by histological methods, serum analysis, grip strength and lifespan. Molecular factors targeted by Cramp were identified by the pull-down assay and proteomic analysis.
In response to acute muscle injury, Cramp was activated in muscle-infiltrating neutrophils and internalized into myofibres. Cramp treatments of mouse skeletal muscles or C2C12 myotubes resulted in muscle degeneration and myotube damage, respectively. Genetic ablation of Cramp reduced neutrophil infiltration and ameliorated muscle pathology, such as fibre size (P < 0.001; n = 6) and fibrofatty infiltration (P < 0.05). Genetic reduction of Cramp in mdx/Utrn mice not only attenuated muscle damage (35%, P < 0.05; n = 9-10), myonecrosis (53%, P < 0.05), inflammation (37-65%, P < 0.01) and fibrosis (14%, P < 0.05) but also restored muscle fibre size (14%, P < 0.05) and muscle force (18%, P < 0.05). Reducing Cramp levels led to a 63% (male, P < 0.05; n = 10-14) and a 124% (female, P < 0.001; n = 20) increase in the lifespan of mdx/Utrn mice. Proteomic and mechanistic studies revealed that Cramp cross-talks with Ca signalling in skeletal muscle through sarcoplasmic/endoplasmic reticulum Ca -ATPase1 (SERCA1). Cramp binds and inactivates SERCA1, leading to the activation of Ca -dependent calpain proteases that exacerbate DMD progression.
These findings identify Cramp as an immune cell-derived regulator of skeletal muscle degeneration and provide a potential therapeutic target for DMD.
抗菌肽 cathelicidin 在调节细菌杀伤和先天免疫方面发挥着关键作用；然而，其在骨骼肌功能中的作用尚不清楚。我们研究了 cathelicidin 在急性损伤和 Duchenne 肌营养不良症（DMD）小鼠骨骼肌病理中的潜在作用。
在接受化学物质（心脏毒素和 BaCl ）治疗的正常小鼠的骨骼肌中或 DMD 小鼠模型（mdx、mdx/Utrn 和 mdx/Utrn ）的肌肉中，检查了小鼠 cathelicidin 相关抗菌肽（Cramp）的表达变化和肌肉定位。通过将合成肽处理到小鼠骨骼肌或 C2C12 肌管中，研究了 Cramp 渗透到肌纤维和对肌肉损伤的影响。使用 Cramp 敲除（KO）小鼠和 mdx/Utrn/Cramp KO 系来确定 Cramp 是否介导肌肉退化。通过组织学方法、血清分析、握力和寿命来评估肌肉病理生理学。通过下拉测定和蛋白质组学分析鉴定 Cramp 靶向的分子因子。
在急性肌肉损伤时，Cramp 在肌肉浸润的中性粒细胞中被激活并内化到肌纤维中。Cramp 处理小鼠骨骼肌或 C2C12 肌管分别导致肌肉退化和肌管损伤。Cramp 的遗传缺失减少了中性粒细胞浸润，并改善了纤维大小（P < 0.001；n = 6）和纤维脂肪浸润（P < 0.05）等肌肉病理学。在 mdx/Utrn 小鼠中，Cramp 的遗传减少不仅减弱了肌肉损伤（35%，P < 0.05；n = 9-10）、肌坏死（53%，P < 0.05）、炎症（37-65%，P < 0.01）和纤维化（14%，P < 0.05），而且还恢复了肌肉纤维大小（14%，P < 0.05）和肌肉力量（18%，P < 0.05）。降低 Cramp 水平使 mdx/Utrn 小鼠的寿命分别增加了 63%（雄性，P < 0.05；n = 10-14）和 124%（雌性，P < 0.001；n = 20）。蛋白质组学和机制研究表明，Cramp 通过肌浆网/内质网 Ca -ATPase1（SERCA1）与骨骼肌中的 Ca 信号转导相互作用。Cramp 结合并使 SERCA1 失活，导致 Ca 依赖性钙蛋白酶的激活，从而加剧 DMD 的进展。
这些发现将 Cramp 鉴定为调节骨骼肌退化的免疫细胞衍生调节剂，并为 DMD 提供了一个潜在的治疗靶点。
