Abstract
Acute myocardial infarction (AMI) is among the most serious cardiovascular diseases and is a leading cause of mortality in developed countries. Previous studies have indicated the central role played by the bromodomain (BRD) proteins, which belong to the BRD and extra-terminal (BET) family, in gene control during heart failure pathogenesis. In addition, BET inhibition has been shown to suppress cardiomyocyte hypertrophy. However, the role of BET proteins in myocardial infarction remains unclear. The present study aimed to investigate whether BETs inhibition mitigates AMI, and explore the molecular mechanism underlying this effect. A rat model of acute myocardial infarction was established, and rats were divided into the sham, AMI and AMI + JQ1 groups. JQ1, a well-known selective BRD inhibitor, was used to suppress BET domain family activity. The mRNA and protein expression levels of BRD2, BRD3 and BRD4 were evaluated using quantitative polymerase chain reaction and western blot analysis, respectively. In addition, the expression levels of markers of cardiac damage were determined using commercial kits. The results indicated that BRD2 and BRD4 mRNA and protein expression levels were significantly increased in the AMI group compared with those in the sham group. In addition, BET inhibition decreased AMI damage in vivo by reversing cardiac function injury, decreasing serum lactate dehydrogenase and creatine kinase-MB isozyme activity, in addition to decreasing the expression levels of high-sensitivity C-reactive protein and interleukin-6. Furthermore, the results suggested that Toll-like receptor 4 (TLR4) signaling was activated by the increased expression of TLR4, TNF receptor-associated factor 6 (TRAF6) and nuclear factor (NF)-κB during AMI. However, JQ1 treatment suppressed TLR4 signaling activation. In conclusion, the present results demonstrated that the inhibition of BET family proteins suppresses AMI, and that this effect was partially mediated by the inhibition of TLR4/TRAF6/NF-κB signaling.