L-Arginine Alleviates LPS-induced Oxidative Stress and Apoptosis via Activating SIRT1-AKT-Nrf2 and SIRT1-FOXO3a Signaling Pathways in C2C12 Myotube Cells

Abstract BackgroundAs a highly plasticized tissue, muscle could exert a spontaneous immune behavior in response to external pathogen stimulation. L-arginine (L-Arg) has been reported to possess a wide range of functions, including anti-inflammatory, anti-oxidative, and anti-apoptosis. However, the role of L-Arg in LPS-induced muscle injury and its potential protective mechanism has not been well elucidated. This study aimed to investigate the effects of L-Arg on the LPS-induced oxidative stress and apoptosis in vitro models of well-differentiated C2C12 myotube cells. ResultsIn the present study, we first demonstrated that myotube cells treated with 0.2 mg/mL lipopolysaccharide (LPS) significantly decreased cell viability. Then, different concentrations of L-Arg (0, 0.5, 2.5, 5 mM)-pretreated myotube cells were exposed to LPS. The results showed that L-Arg treatment significantly suppressed reactive oxygen species (ROS) accumulation and cell apoptosis. Furthermore, L-Arg improved antioxidant-related enzymes’ activities; increased antioxidant ability via Akt-Nrf2 signaling pathway; maintained the mitochondrial membrane potential (MMP) and enhanced forkhead box protein 3a (FOXO3a) expression, lead to a decrease in the mitochondrial-associated apoptotic proteins. In addition, L-Arg exposure dramatically increased the mRNA and protein expressions of Sirtuin1 (SIRT1). The cytoprotective effect of L-Arg was restricted by the SIRT1 inhibitor EX527, which led to an increase in ROS level, apoptosis rate, and decreased cell MMP. The results also demonstrated that EX527 treatment significantly eliminated the effect of L-Arg on LPS-induced oxidative damage and mitochondria-mediated cell apoptosis. ConclusionsOur findings revealed that L-Arg could be used as a potential nutraceutical in reducing muscle injury via regulating SIRT1-Akt-Nrf2 and SIRT1-FOXO3a-mitochondria apoptosis signaling pathways.