Myricetin ameliorates experimental autoimmune myocarditis in mice by modulating immune response and inhibiting MCP-1 expression.

Myocarditis is defined as an inflammatory disease of the myocardium, and the autoimmune response specific to myocardium plays an important role in chronic myocarditis. Inhibiting myocardial-specific autoimmune response and inflammation is crucial to treat myocarditis. Myricetin is a plant-derived flavonoid in nature which has potent anti-inflammatory and cardiovascular protective properties. However, the pharmacological effect of myricetin in autoimmune myocarditis is undefined. It is necessary to investigate the role and potential mechanisms of myricetin in autoimmune myocarditis. Therefore, purified cardiac myosin was subcutaneously injected to mice to establish the experimental autoimmune myocarditis (EAM) model. Myricetin was solubilized in normal saline and administered everyday by gavage from the day of immunization. After 21 days of treatment, it was found that myricetin significantly alleviated myocardial injury in EAM mice. The serum anti-cardiac myosin antibody, immunoglobulin (Ig) G, IgM levels and the proportion of T helper 17 (Th17) cells were decreased and the proportion of regulatory T (Treg) cells was increased with the treatment of myricetin in EAM mice. The myosin-specific T cell proliferation was inhibited by myricetin. Meanwhile, myricetin suppressed the expressions of monocyte chemoattractant protein-1 (MCP-1), phospho (p)-p65, p-c-Jun and Act1/TRAF6/TAK1 in H9C2 cells and myocardial tissues of EAM mice. These results revealed that myricetin inhibited the autoimmune response specific to myocardium and the expression of MCP-1 in cardiomyocytes, which suggested that myricetin ameliorated autoimmune myocarditis by modulating immune response and the expression of MCP-1. Therefore, myricetin may be a promising therapeutic strategy for autoimmune myocarditis.