FGL2 knockdown improves heart function through regulation of TLR9 signaling in the experimental autoimmune myocarditis rats

Fibrinogen-like protein 2 (FGL2) is an important immune regulator of both innate and adaptive response. It is present on the surface of macrophages and endothelial cells, and can be constitutively secreted by CD4⁺CD8⁺ T cells. Previous studies showed that FGL2 is a potential target for the treatment of experimental autoimmune myocarditis. However, the molecular mechanism of the roles of FGL2 in experimental autoimmune myocarditis is poorly understood. Here, we silenced FGL2 gene by using FGL2-RNAi lentivirus to reveal the heart function in experimental autoimmune myocarditis rats. We found that the cardiac myosin of pigs’ hearts induced Lewis rats to come into being as autoimmune myocarditis. TLR9 was upregulated in the heart of experimental autoimmune myocarditis rats. After primary immunization (21 day), the cardiac function of the myocarditis model group improved (P < 0.05). Significantly, the levels of INF-α and NF-κB in the FGL2-RNAi-treated group were lower compared to those in the myocarditis model (EAM) group (P < 0.05). Notably, the inflammation score correspondence with the protein and mRNA levels of TLR9 in myocardial tissues was markedly reduced compared to that in the EAM group (P < 0.05). These results support a role of FGL2 to alleviate inflammatory situation in the myocardium through regulation of the TLR9 signaling pathway in the experimental autoimmune myocarditis rats.