Shuangxinfang prevents S100A9-induced macrophage/microglial inflammation to improve cardiac function and depression-like behaviour in rats after acute myocardial infarction

Background Depression is a common complication of cardiovascular disease, which deteriorated the cardiac function. Shuangxinfang (Psycho-cardiology Formula, PCF) was reported to alleviate myocardial ischemia injury and improve depression-like behavior. Interestingly, our previous proteomics study predicted that the protein S100A9 appeared as an important target, and macrophage/microglial inflammation might be involved in the process of PCF treating depressive disorder induced by acute myocardial infarction (AMI). The aim of this study is to validate the proteomics results. Methods AMI rat models were established in vivo , followed by the administration of PCF or ABR-215757 (also named paquinimod, inhibiting S100A9 binding to TLR4) for 5 days. Forced swimming test (FST) and open field test (OFT) were applied to record depression-like behavior, and echocardiography was employed to evaluate cardiac function. Morphological changes of cardiomyocytes were assessed by HE staining and TUNEL staining on day 7 after cardiac surgery, as well as masson trichrome staining on day 21. Hippocampal neurogenesis was determined by Nissl staining, while 5-hydroxytryptamine (5-HT) and brain-derived neurotrophic factor (BDNF) in the hippocampus were detected as biochemical indicators of depression. Myocardial and hippocampal expression of inflammatory factors were analyzed by western blotting, immunofluorescence, and ELISA. The activation state of macrophage and microglia was assessed via immunoreaction respectively using CD68 and Iba1. For in vitro confirmation, BV2 cells were primed with recombinant protein S100A9, and then pretreated with PCF serum, to determine alterations in microglial activation and inflammation. Results Rats in the AMI group showed heart function deterioration, as well as depression-like behavior. Coronary ligation not only brought about myocardial inflammation, cell apoptosis and fibrosis, but also reduced the neurogenesis and decreased the content of 5-HT. PCF could ameliorate the pathological and phenotypic changes of the heart and brain, and inhibited the expression of S100A9/TLR4/NF-κB pathway, the activation of microglial cell and the secretion of IL-1β and TNF-α raised by AMI. ABR-215757 showed therapeutic effect and molecular biological mechanisms similar to PCF. Pretreatment with PCF serum in vitro was proved to efficiently block the hyperactivation of BV2 cells and increasement of cytokine contents induced by recombinant protein S100A9. Conclusion We identify S100A9 as a novel and potent regulator of inflammation in both heart and brain. Macrophage/microglia inflammation mediated by S100A9 is considered as a pivotal pathogenic in depression post-AMI, as well as a major pathway for the treatment of PCF, suggesting that PCF is a promising therapeutic candidate for psycho-cardiology disease.