Myocarditis, characterized by myocyte necrosis, fibrosis, and degeneration with mononuclear cell infiltration, always causes heart failure in patients. Phosphoinositide 3-kinase (PI3K) is a pivotal kinase known to regulate inflammatory responses in cardiac diseases. Although previous research has suggested that PI3K was involved in cardiac diseases such as myocardial infarction, it is still unclear whether the inhibition of PI3K is essential for the treatment of myosin-induced myocarditis. The aim of this study was to explore whether pharmacological blockade of PI3K is able to protect mice against experimental autoimmune myocarditis (EAM).

We used the cardiac myosin-induced murine EAM model to investigate the therapeutic effect of PI3K inhibitor LY294002 on autoimmune myocarditis in mice.

LY294002 significantly alleviated EAM injury in mice, as indicated by the reduction of cardiac necrosis, inflammatory infiltrates, and CD3⁺ T cells. LY294002 also decreased the expression of p-Akt upon cardiac myosin treatment in the cardiac tissue of the mice. In the present study, LY294002 resulted in a moderate reduction in absolute CD4⁺ cell numbers and a significant decrease in the absolute numbers of CD8⁺ cells. Consequently, LY294002 increased the CD4⁺/CD8⁺ ratio compared with peptide treatment alone.

This report provides evidence that PI3K inhibitor LY294002 has potent effects against cardiac injury caused by EAM, suggesting that it has therapeutic value for the treatment of myocarditis.