Astragaloside IV Exerts a Protective Effect on Down-regulation of IL6 Expression by inhibiting the Tlr2/Tlr4 Signaling Pathway in Mice with Experimental Autoimmune Myocarditis

Objective To investigate the effect and possible mechanism of Astragaloside IV (AST) in the treatment of Experimental Autoimmune Myocarditis (EAM) mouse model.Methods Forty-eight Balb/c male mice were equally divided into control group, EAM group, 0.5%DMSO group, 40mg/kg, 80mg/kg and 160mg/kg AST treatment groups. The EAM mouse model was constructed using the peptide MyHC-α614-629. Starting from day 8, mice were treated with AST at doses of 40 mg/kg, 80 mg/kg, and 160 mg/kg via intragastric administration daily. All groups were euthanized by day 21. Body weight, heart weight and spleen weight were measured after dissection. The proportion of immune cells in peripheral blood was detected. HE staining was used to detect the inflammatory infiltration of myocardial tissue. Myocardial fibrosis was detected by Masson staining. The expressions of cTnⅠ, CD4, CD8 and F4/80 were detected by immunohistochemistry. qRT-PCR and Western blotting were used to detect the expression of CD4, CD8, cTnⅠ, IL1α, IL1β, IL6, Notch1, Hes1, Jag1, Jag2, Tlr2 and Tlr4 in myocardial tissue.Results AST treatment could improve heart whitening, increase HW, SW and HW/e-BW, reduce BW, and increase cTnⅠ expression in EAM mice. In EAM mice, the inflammatory infiltration of myocardial tissue and the increase of the proportion of lymphocytes were improved. The treatment with 80mg/kg and 160mg/kg AST showed the most significant improvement in EAM mice. Mechanism studies have found that the expression of IL1α, IL1β, and IL6 increases, but the expression difference of IL6 is most significant in EAM mice. The Notch pathway and TLRs signaling pathway were significantly activated, and the gene up-regulation of Notch pathway was consistent with the previous results. Studies have confirmed that the activation of TLRs signaling pathway is closely related to the occurrence of myocarditis. AST treatment significantly down-regulated the expression of Tlr2 and Tlr4 in EAM mice, especially in 80mg/kg and 160mg/kg AST treatment.Conclusion AST exerts a protective effect on down-regulation of IL6 expression by inhibiting the Tlr2/Tlr4 signaling pathway in mice with EAM.