title: Low-Concentration Arsenic Trioxide Inhibits Skeletal Myoblast Cell Proliferation via a Reactive Oxygen Species-Independent Pathway.
abstract: Myoblast proliferation and differentiation are essential for skeletal muscle regeneration. Myoblast proliferation is a critical step in the growth and maintenance of skeletal muscle. The precise action of inorganic arsenic on myoblast growth has not been investigated. Here, we investigated the in vitro effect of inorganic arsenic trioxide (As2O3) on the growth of C2C12 myoblasts. As2O3 decreased myoblast growth at submicromolar concentrations (0.25-1 μM) after 72 h of treatment. Submicromolar concentrations of As2O3 did not induce the myoblast apoptosis. Low-concentration As2O3 (0.5 and 1 μM) significantly suppressed the myoblast cell proliferative activity, which was accompanied by a small proportion of bromodeoxyuridine (BrdU) incorporation and decreased proliferating cell nuclear antigen (PCNA) protein expression. As2O3 (0.5 and 1 μM) increased the intracellular arsenic content but did not affect the reactive oxygen species (ROS) levels in the myoblasts. Cell cycle analysis indicated that low-concentrations of As2O3 inhibited cell proliferation via cell cycle arrest in the G1 and G2/M phases. As2O3 also decreased the protein expressions of cyclin D1, cyclin E, cyclin B1, cyclin-dependent kinase (CDK) 2, and CDK4, but did not affect the protein expressions of p21 and p27. Furthermore, As2O3 inhibited the phosphorylation of Akt. Insulin-like growth factor-1 significantly reversed the inhibitory effect of As2O3 on Akt phosphorylation and cell proliferation in the myoblasts. These results suggest that submicromolar concentrations of As2O3 alter cell cycle progression and reduce myoblast proliferation, at least in part, through a ROS-independent Akt inhibition pathway.
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan.
authors.forename: Shing Hwa
authors.initials: SH
authors.lastname: Liu
authors.affiliation: Departments of Orthopaedic, College of Medicine and Hospital, National Taiwan University, Taipei, Taiwan.
authors.forename: Rong-Sen
authors.initials: RS
authors.lastname: Yang
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yuan-Peng
authors.initials: YP
authors.lastname: Yen
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Chen-Yuan
authors.initials: CY
authors.lastname: Chiu
authors.affiliation: Departments of Laboratory Medicine, College of Medicine and Hospital, National Taiwan University, Taipei, Taiwan.
authors.forename: Keh-Sung
authors.initials: KS
authors.lastname: Tsai
authors.affiliation: Department of Emergency Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Kuo-Cheng
authors.initials: KC
authors.lastname: Lan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D032448:Myoblasts, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D010087:Oxides / Q000494:pharmacology*; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D001152:Arsenicals; D018797:Cell Cycle Proteins; D010087:Oxides; D018809:Proliferating Cell Nuclear Antigen; D017382:Reactive Oxygen Species; D051057:Proto-Oncogene Proteins c-akt; D000077237:Arsenic Trioxide