Effects of <i>Ginkgo biloba</i> Leaf Ethanol Extract on the Nrf2/HO-1 Signaling Pathway in C2C12 Myoblasts: Focus on Masticatory Muscle Health

Background: Masticatory muscles exhibit high metabolic activity due to their continuous contraction.Excessive production of reactive oxygen species in the masticatory muscles has been associated with muscle atrophy, temporomandibular disorders and bruxism.Ginkgo biloba leaf ethanol extract (GLE) has been reported to suppress oxidative stress by activating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway, however, no studies have examined whether it can regulate antioxidant activity by itself without external stimuli.The aim of this study was to investigate whether GLE can induce antioxidant activity by activating the Nrf2/HO-1 signaling pathway without external oxidative stress stimulation in C2C12 myoblasts and to propose the potential of GLE as a functional material for the prevention of oxidative damage and pathological symptoms in masticatory muscles.Methods: C2C12 myoblasts were treated with GLE at concentrations of 0∼50 μg/ml for 24 hours.GLE-induced changes in cell viability were evaluated using an MTT assay.The effects of GLE on antioxidant-related responses without external stimulation were assessed based on the protein expression levels of Nrf2, phosphorylated Nrf2 (p-Nrf2), Kelch-like ECH-associated protein 1 (Keap1), and HO-1 by western blot analysis.Results: GLE did not significantly affect the proliferation of C2C12 myoblasts in the tested concentration ranges.As the concentration of GLE increased, GLE significantly decreased the protein expression levels of Nrf2 and Keap1, while significantly increasing the expression levels of p-Nrf2 and HO-1 in C2C12 myoblasts without external stimulation, suggesting possible modulation of the Nrf2/HO-1 signaling pathway.Conclusion: GLE may modulate the Nrf2/HO-1 signaling pathway, which plays a key role in antioxidant defense, in C2C12 myoblasts.Therefore, GLE has potential as a functional material for the prevention and improvement of oxidative damage and pathological symptoms that may occur in masticatory muscles.