Abstract
Endothelial-to-mesenchymal transition (EndMT) is an essential mechanism in myocardial fibrosis (MF). Tongxinluo (TXL) has been confirmed to protect the endothelium against reperfusion injury after acute myocardial infarction (AMI). However, whether TXL can inhibit MF after AMI via inhibiting EndMT remained unknown. This study aims to identify the role of EndMT in MF after AMI as well as the protective effects and underlying mechanisms of TXL on MF. The AMI model was established in rats by ligating left anterior descending coronary artery. Then, rats were administered with high- (0.8 g·kg−1·d−1), mid- (0.4 g·kg−1·d−1), and low- (0.2 g·kg−1·d−1) dose Tongxinluo and benazepril for 4 weeks, respectively. Cardiac function, infarct size, MF, and related indicators of EndMT were measured. In vitro, human cardiac microvascular endothelial cells (HCMECs) were pretreated with TXL for 4 h and then incubated in hypoxia conditions for 3 days to induce EndMT. Under this hypoxic condition, neuregulin-1 (NRG-1) siRNA were further applied to silence NRG-1 expression. Immunofluorescence microscopy was used to assess expression of endothelial marker of vWF and fibrotic marker of Vimentin. Related factors of EndMT were determined by Western blot analysis. TXL treatment significantly improved cardiac function, ameliorated MF, reduced collagen of fibrosis area (types I and III collagen) and limited excessive extracellular matrix deposition (mmp2 and mmp9). In addition, TXL inhibited EndMT in cardiac tissue and hypoxia-induced HCMECs. In hypoxia-induced HCMECs, TXL increased the expression of endothelial markers, whereas decreasing the expression of fibrotic markers, partially through enhanced expressions of NRG-1, phosphorylation of ErbB2, ErbB4, AKT, and downregulated expressions of hypoxia inducible factor-1a and transcription factor snail. After NRG-1 knockdown, the protective effect of TXL on HCMEC was partially abolished. In conclusion, TXL attenuates MF after AMI by inhibiting EndMT and through activating the NRG-1/ErbB- PI3K/AKT signalling cascade.
Highlights
The cardiac remodeling and heart failure induced by acute myocardial infarction (AMI), as the dominating pathogenesis of chronic heart failure, has emerged as an increasingly serious health problem [1, 2]
The low-dose TXL had no significant effect on cardiac function; middose and high-dose TXL significantly decreased LVEDD, LVESD and increased ejection fraction (EF), fractional shortening (FS) as compared with model group
We found that the levels of NRG-1, p-ErbB2, p-ErbB4, and pAKT were decreased in human cardiac microvascular endothelial cells (HCMECs) under hypoxia
Summary
The cardiac remodeling and heart failure induced by acute myocardial infarction (AMI), as the dominating pathogenesis of chronic heart failure, has emerged as an increasingly serious health problem [1, 2]. Myocardial fibrosis (MF), featured by myocardial fibroblast accumulation, and deposition of extracellular matrix, is associated with sparseness of cardiac microvessels [3]. It is the main pathological marker of cardiac remodeling, and the contributor to BioMed Research International cardiac dysfunction [4, 5]. Endothelial-tomesenchymal transition (EndMT) is one subgroup of EMT, which is characterized by the gradual loss of endothelial phenotype and simultaneous acquirement of mesenchymal or fibroblastic features by endothelial cells [8]. Little is known about the mechanisms for hypoxia-induced EndMT
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