Sujin Kim1,2,3,4, Min-Jae Lee1,2,3, Ji-Young Choi2,3, Dong-Ho Park1,4, Hyo-Bum Kwak1,4, Sohee Moon2,3, Je-Woo Koh2,3, Hun-Kyu Shin5, Ji-Kan Ryu3,6, Chang-Shin Park2,3, Jai Hyung Park5, Ju-Hee Kang2,3,4. 1. Department of Kinesiology, Inha University, Incheon, Republic of Korea. 2. Department of Pharmacology and Medicinal Toxicology Research Center, Inha University, Incheon, Republic of Korea. 3. Hypoxia-related Disease Research Center, Inha University School of Medicine, Incheon, Republic of Korea. 4. WCSL, Inha University, Incheon, Republic of Korea. 5. Department of Orthopaedic Surgery, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. 6. Department of Urology, Inha University School of Medicine, Incheon, Republic of Korea.
Abstract
BACKGROUND/AIMS: The complicated differentiation processes of cells in skeletal muscle against inflammation that induce muscle atrophy are not fully elucidated. Given that skeletal muscle is a secretory organ, we evaluated the effects of inflammation on myogenic signals and myokine expression, and the roles of inflammatory exosomes released by myotubes in myogenic differentiation. METHODS: Inflammation was induced by treatment of fully differentiated C2C12 myotubes with a cytokine mixture of TNF-α and INF-γ. Exosome-like vesicles (ELVs) were isolated from conditioned media of control or inflamed myotubes and incubated with myoblasts. The expression of molecular switches that contribute to myogenic differentiation, including several kinases, their downstream targets, and myokines, were evaluated using immunoblot analysis in inflamed myotubes and in myoblasts treated with ELVs. RESULTS: Inflammation activated molecular mechanisms contributing to muscle atrophy, including AMPK, p-38 MAPK and JNK, while inhibiting Akt-mediated myogenic signals. In addition, inflammation induced myostatin expression with suppression of a myostatin-counteracting myokine, decorin. Well-characterized ELVs released from inflamed myotubes induced myoblast inflammation and inhibited myogenic mechanisms while stimulating atrophic signals. CONCLUSION: Inflammation of skeletal muscle induces muscle atrophy via multiple mechanisms, including the regulation of myokines and kinases. Inflammatory ELVs are likely to contribute to inflammation-induced muscle atrophy.
BACKGROUND/AIMS: The complicated differentiation processes of cells in skeletal muscle against inflammation that induce muscle atrophy are not fully elucidated. Given that skeletal muscle is a secretory organ, we evaluated the effects of inflammation on myogenic signals and myokine expression, and the roles of inflammatory exosomes released by myotubes in myogenic differentiation. METHODS:Inflammation was induced by treatment of fully differentiated C2C12 myotubes with a cytokine mixture of TNF-α and INF-γ. Exosome-like vesicles (ELVs) were isolated from conditioned media of control or inflamed myotubes and incubated with myoblasts. The expression of molecular switches that contribute to myogenic differentiation, including several kinases, their downstream targets, and myokines, were evaluated using immunoblot analysis in inflamed myotubes and in myoblasts treated with ELVs. RESULTS:Inflammation activated molecular mechanisms contributing to muscle atrophy, including AMPK, p-38 MAPK and JNK, while inhibiting Akt-mediated myogenic signals. In addition, inflammation induced myostatin expression with suppression of a myostatin-counteracting myokine, decorin. Well-characterized ELVs released from inflamed myotubes induced myoblast inflammation and inhibited myogenic mechanisms while stimulating atrophic signals. CONCLUSION:Inflammation of skeletal muscle induces muscle atrophy via multiple mechanisms, including the regulation of myokines and kinases. Inflammatory ELVs are likely to contribute to inflammation-induced muscle atrophy.
Authors: Maxime R F Gosselin; Virginie Mournetas; Malgorzata Borczyk; Suraj Verma; Annalisa Occhipinti; Justyna Róg; Lukasz Bozycki; Michal Korostynski; Samuel C Robson; Claudio Angione; Christian Pinset; Dariusz C Gorecki Journal: Elife Date: 2022-09-27 Impact factor: 8.713