Inhibition of Mogroside IIIE on isoproterenol-induced myocardial fibrosis through the TLR4/MyD88/NF-κB signaling pathway

OBJECTIVE(S): To investigate the effect of mogroside IIIE (MGIIIE) on isoproterenol (ISO)-induced myocardial fibrosis and explore its possible mechanisms. MATERIALS AND METHODS: Forty C57BL/6 male mice (6-8 weeks) were randomly divided into a control group (n=10), model group (n=10), low MGIIIE dose group (n=10), and high MGIIIE dose group (n=10). Myocardial fibrosis was established by subcutaneous ISO injection. After 2 weeks of continuous gastric administration of MGIIIE, the cardiac structure was evaluated by echocardiography. Myocardial inflammation and fibrosis were evaluated by histology examination. Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), p-IκBα, p-NF-κB, transforming growth factor β1 (TGF-β1), and α-smooth muscle actin (α-SMA) expression were detected by western blot. Inflammatory cytokines (IL-1β, IL-6, and TNF-α) in the serum were examined by ELISA. In the in vitro study, Ang II (1 μmol/l) was used to stimulate the fibroblasts, then inflammation and fibrosis index were detected. RESULTS: MGIIIE inhibited inflammation and fibrosis and down-regulated TLR4, MyD88, TGF-β1, and α-SMA expression in the myocardium. In the in vitro study, MGIIIE ameliorates the deposition of Col Ш and Col I and decreases the release of inflammatory cytokines. MGIIIE increased p-IκBα and reduced p-NF-κB expression both in vivo and in vitro. CONCLUSION: MGIIIE plays a role in anti-myocardial fibrosis, by inhibiting TLR4/MyD88/NF-κB signaling expression, and decreasing inflammatory cytokine release. MGIIIE may represent a novel therapeutic strategy for treating cardiac fibrosis.