Induction of LOX by TGF‐β1/Smad/AP‐1 signaling aggravates rat myocardial fibrosis and heart failure

Abstract This study aims to evaluate the efficacy of lysyl oxidase (LOX) inhibition in regulating rat myocardial fibrosis and chronic heart failure (CHF) and to validate the regulation of LOX by TGF‐β1/Smad2/3 signaling in this process. A rat model of CHF was established by abdominal aortic coarctation. The renin‐angiotensin‐aldosterone system (RAAS) indexes (PRA, ACE2, Ang II, and ALD), cardiac function indicators (LVEF, LVFS, SAP, DAP, and LVEDP), ventricular remodeling‐ and fibrosis‐related indicators (hydroxyproline, collagen deposition,and MMP‐2/9), and morphological changes of myocardial tissues were examined. Rat cardiac fibroblasts (RCFs) were used in vitro assays. CHF patients showed increased LOX activity, accompanied by activated RAAS and TGF‐β1. Furthermore, inhibition of LOX by β‐aminopropionitrile (BAPN) mitigated the RAAS activation and attenuated cardiac dysfunction, ventricular remodeling, myocardial fibrosis, and collagen deposition in CHF rats. Moreover, TGF‐β1 signaling diminished the LOX inhibition‐mediated antiheart failure effect. Further assays showed that TGF‐β1/Smad2/3 signaling increased expression of c‐jun (AP‐1 transcription factor subunit), which transcriptionally induced LOX expression. Additionally, BAPN abrogated the TGF‐β1‐mediated increase in cell proliferation and levels of MMP‐2/9 and collagen I/III in RCFs. In conclusion, LOX can be induced by TGF‐β1/Smad/AP‐1 signaling and LOX inhibition attenuates rat myocardial fibrosis and CHF.