Icariin ameliorates viral myocarditis by inhibiting TLR4-mediated ferroptosis

Objective: To explore the mechanism by which icariin alleviates viral myocarditis. Methods: CVB3-induced cardiomyocytes were used as an in vitro model of viral myocarditis to assess the effects of icariin treatment on cell viability, inflammation, and apoptosis. Moreover, the effects of icariin on ferroptosis and TLR4 signaling were assessed. After AC16 cells were transfected with TLR4 overexpression plasmids, the role of TLR4 in mediating the regulatory effect of icariin in viral myocarditis was investigated. Results: Icariin significantly elevated cell viability and reduced inflammatory factors TNF-α, IL-1β, IL-6, and IL-18. Flow cytometry revealed that icariin decreased apoptosis rate, and the protein expression of Bax and cleaved caspase 3 and 9 in CVB3-induced cardiomyocytes. Additionally, it suppressed ferroptosis including lipid peroxidation and ferrous ion, as well as the TLR4 signaling. However, TLR4 overexpression abrogated the modulatory effects of icariin. Conclusions: Icariin mitigates CVB3-induced myocardial injury by inhibiting TLR4-mediated ferroptosis. Further animal study is needed to verify its efficacy.