High-dose parecoxib induces stress-associated pathological remodeling in C2C12 myotubes

Parecoxib is a selective COX-2 inhibitor widely used for postoperative analgesia. Although NSAIDs can influence cellular metabolism and stress responses, whether parecoxib alters skeletal muscle cell homeostasis has not been systematically examined. Here, differentiated C2C12 myotubes were used as an in vitro model to investigate parecoxib-induced stress remodeling. Parecoxib caused limited changes in myotube morphology at 1 and 4 μM, whereas significant structural changes were observed at 10, 50, and 100 μM compared with control. Protein-normalized ATP content was reduced, whereas LDH release was not increased across the tested concentration range. Parecoxib also reduced Akt and FoxO3a phosphorylation, increased atrogin-1 and Bax expression, and increased AMPK phosphorylation. RNA sequencing identified changes in Gadd45a, Hmox1, Tnfaip3, Depp1, Tfrc, and Abra. Functional enrichment analyses highlighted pathways related to PI3K-Akt, FoxO, MAPK, cytoskeletal organization, muscle differentiation, and myofibril assembly. Parecoxib exposure during differentiation produced limited changes at 1 and 4 μM, whereas significant impairment was observed at 10, 50, and 100 μM compared with control. Together the results show structural and stress-related changes in C2C12 myotubes at higher parecoxib concentrations. They do not establish skeletal muscle toxicity under clinical exposure conditions.