Effect of xiaotan huayu liqiao traditional Chinese medicine compound on myocardial fibrosis in rats with chronic intermittent hypoxia and its mechanism

Abstract

Objective: To explore the role of transforming growth factor-β (TGF-β) signaling pathway in xiaotan huayu liqiao traditional Chinese medicine compound (XC)'s anti-myocardial fibrosis in chronic intermittent hypoxia (CIH) rats. Methods: Forty SD rats were randomly divided into normoxia group, oxygen + traditional Chinese medicine compound group ( TCMC), Chronic intermittent hypoxia model group (CIH), TCMC + CIH, 10 in each group. CIH cabin was built by filling with nitrogen and oxygen. Firstly, the volume fraction of oxygen in the cabin reduced from 21% to 9% in 90 s by filling the cabin with nitrogen. And then it gradually rose to 21% by reoxygenating in 90s, as a cycle. CIH and TCMC+CIH group rats were placed in the CIH device, while normoxia and TCMC group rats were placed in the normal oxygen chamber. In addition, rats in TCMC +CIH group and TCMC group were treated with XC crude drug (24 g/kg) daily by gavage, while rats in CIH group and normoxia group were given equal volume normal saline. Using sirius red staining, the collagen in myocardial interstitium was visualized. The protein expressions of collagen I, collagen III and fibronectin were detected by Western blot, p-Smad3, p-Smad2 and TGF-β protein in the TGF-β/Smads signaling pathway were also analyzed by Western blot. The mRNA expressions of matrix metalloproteinase-2 (MMP-2) and tissue inhibitors of metalloproteinase -2(TIMP-2) were measured by real-time quantitative polymerase chain reaction (PCR). Results: Compared with the rats exposed to normoxia, the CIH rats showed obvious collagen deposition, protein expressions of collagen I, collagen III and fibronectin were significantly increased in the myocardial tissue (P＜0.01). The protein expression levels of TGF-β, p-smad2 and p-smad3 in the myocardial tissue of the CIH rats were also significantly increased (P＜0.01). The up-regulation of TIMP-2 mRNA in the myocardial tissues resulted in the decrease of MMP-2 mRNA(P＜0.01). XC reduced myocardial fibrosis of CIH rats and inhibited the expressions of collagen I and collagen III and fibronectin protein (P＜0.05,P＜0.01,P＜0.05, respectively). The further mechanism study showed that XC inhibited the expression of TGF-β (P＜0.01), which down-regulated the expressions of p-smad2, p-smad3 and TIMP-2 (P＜0.05). Conclusion: XC could reduce the expression of TGF-β and smad2/3 phosphorylation, down-regulate the expression of TIMP-2, which would inhibit the formation of myocardial fibrosis in CIH rats, and improve the myocardial function of CIH rats.