Baicalein alleviates cardiomyocyte death in EAM mice by inhibiting the JAK-STAT1/4 signalling pathway

Background: The experimental autoimmune myocarditis (EAM) model is valuable for investigating myocarditis pathogenesis. M1-type macrophages and CD4+T cells exert key pathogenic effects on EAM initiation and progression. Baicalein (5,6,7-trihydroxyflavone, C15H10O5, BAI), which is derived from the Scutellaria baicalensis root, is a primary bioactive compound with potent anti-inflammatory and antioxidant properties. BAI exerts good therapeutic effects against various autoimmune diseases; however, its effect in EAM has not been thoroughly researched. Purpose: This study aimed to explore the possible inhibitory effect of BAI on M1 macrophage polarisation and CD4+T cell differentiation into Th1 cells via modulation of the JAK-STAT1/4 signalling pathway, which reduces the secretion of pro-inflammatory factors, namely, TNF-alpha and IFN-gamma, and consequently inhibits TNF-alpha- and IFN gamma-triggered apoptosis in cardiomyocytes of the EAM model mice. Study design and methods: Flow cytometry, immunofluorescence, real-time quantitative polymerase chain reaction (q-PCR), and western blotting were performed to determine whether BAI alleviated M1/Th1-secreted TNF-alpha and IFN-gamma-induced myocyte death in the EAM model mice through the inhibition of the JAK-STAT1/4 signalling pathway. Results: These results indicate that BAI intervention in mice resulted in mild inflammatory infiltrates. BAI inhibited JAK-STAT1 signalling in macrophages both in vivo and in vitro, which attenuated macrophage polarisation to the M1 type and reduced TNF-alpha secretion. Additionally, BAI significantly inhibited the differentiation of CD4+ T cells to Th1 cells and IFN-gamma secretion both in vivo and in vitro by modulating the JAKSTAT1/4 signalling pathway. This ultimately led to decreased TNF-alpha and IFN-gamma levels in cardiac tissues and reduced myocardial cell apoptosis. Conclusion: This study demonstrates that BAI alleviates M1/Th1-secreted TNF-alpha- and IFN-gamma-induced cardiomyocyte death in EAM mice by inhibiting the JAK-STAT1/4 signalling pathway.