Role of Unique cartilage matrix-associated protein in Doxorubicin-induced skeletal muscle atrophy = 독소루비신으로 유도된 골격근 위축에서 연골 기질 특이 단백질 (UCMA)의 역할

다국어 초록 (Multilingual Abstract)

Skeletal muscle is the largest organ in the human body, playing a crucial role in body movement and metabolic homeostasis. Muscle atrophy, characterized by a progressive loss of muscle mass and function, can result from disuse, aging, cancer, and chemotherapy. Doxorubicin (Dox) is a widely used chemotherapeutic agent effective against various cancers. However, its clinical application is limited by off-target toxicity, particularly mitochondrial reactive oxygen species (ROS) generation, which induces oxidative stress and skeletal muscle atrophy. Unique cartilage matrix-associated protein (UCMA), a vitamin K-dependent secreted protein initially identified in cartilage, has been reported to suppress ROS production in osteoblasts and osteoclasts. This study investigated the role of UCMA in modulating Dox- induced oxidative stress and muscle atrophy in skeletal muscle. In vivo, wild-type (WT) and Ucma knockout (KO) mice received a single intraperitoneal injection of Dox (20 mg/kg). Five days post-injection, body composition, muscle weights, and the expression of muscle damage and antioxidant markers were analyzed. Dox administration significantly reduced body weight, muscle weight, and body composition in both WT and Ucma KO mice, without genotype-dependent differences in overall body weight or composition. Skeletal muscle from Dox-treated mice exhibited increased expression of muscle damage markers, with Ucma expression showing a tendency to rise following Dox treatment. To further evaluate the protective effects of UCMA, C2C12 myoblasts were supplemented with recombinant UCMA. Ucma expression was low in undifferentiated myoblasts but increased during myogenic differentiation and in response to Dox treatment. Dox exposure dose-dependently impaired C2C12 myotube formation and upregulated the expression of muscle-specific E3 ubiquitin ligases MuRF1 and Atrogin-1, as assessed by immunostaining and qRT-PCR, respectively. In contrast, UCMA supplementation reduced Dox-induced intracellular ROS levels, protected superoxide dismutase (SOD) activity, and improved myotube formation. Collectively, these findings demonstrate that UCMA supplementation ameliorates Dox-induced muscle atrophy, highlighting its protective role against oxidative stress in skeletal muscle. UCMA may thus represent a promising therapeutic target for mitigating chemotherapy-induced muscle damage.

목차 (Table of Contents)

• INTRODUCTION 1
• MATERIALS AND METHODS 5
• 1. Animals and genotyping 5
• 2. Doxorubicin-induced muscle atrophy model 5
• 3. Body composition analysis 6
• 4. Cell culture 6
• 5. RNA extraction and quantitative real-time PCR (qRT-PCR) 6
• 6. Determination of intracellular reactive oxygen species (ROS) production 7
• 7. Immunocytochemistry 8
• 8. Protein extraction and Western blotting 8
• 9. Measurement of total Superoxide Dismutase (SOD) activity 9
• 10. Statistical analysis 10
• RESULTS 11
• 1. Ucma deficiency does not affect skeletal muscle phenotype under physiological conditions 11
• 2. Dox administration reduces body weight, body composition, and skeletal muscle mass in vivo 11
• 3. UCMA deficiency alters the expression of antioxidant and Trim63 genes following Dox administration 12
• 4. UCMA expression increases in C2C12 myoblasts during differentiation 13
• 5. Dox induces myotube atrophy in a dose-dependent manner 13
• 6. UCMA protects C2C12 myotubes from Dox-induced ROS production and atrophy 14
• TABLES AND FIGURES 16
• DISCUSSION 38
• REFERENCES 46
• ABSTRACT IN KOREAN 51