Loureirin B Alleviates Myocardial Ischemia/Reperfusion Injury via Inhibiting PAI-1/TGF-β1/Smad Signaling Pathway

Myocardial ischemia/reperfusion (MI/R) injury is a common clinical problem after myocardial infarction without effective therapy. Loureirin B (LrB) is a kind of flavonoid with anti-inflammatory and antifibrotic activities. However, the effect of LrB on MI/R and its underlying mechanism remains elusive. In the present study, a mouse model of MI/R was established by coronary artery occlusion. Administration of LrB (0.5 mg/kg or 1 mg/kg) for 4 weeks effectively improved left ventricular (LV) function and reduced myocardial infarction in MI/R mice. MI/R-induced expression of IL-6, TNF-α, and IL-1β in the hearts was reduced by LrB treatment. Histological analysis showed that LrB attenuated myocardial collagen deposition. LrB downregulated fibronectin, collagen I, collagen III, and α-SMA expression. Notably, LrB inhibited the expression of profibrotic plasminogen activator inhibitor-1 (PAI-1), transforming growth factor (TGF)-β1, TGF-β1R, and p-Smad2/3. Consistently, LrB inhibited the activation of TGF-β1/Smad signaling pathway and the expression of fibrosis-related proteins in angiotensin (Ang) II-treated cardiac fibroblasts (CFs). Overexpression of PAI-1 abolished the effects of LrB on Ang II-treated CFs, suggesting that LrB may function through regulating PAI-1. These results indicated that LrB may alleviate MI/R-induced myocardial fibrosis by inhibiting PAI-1/TGF-β1/Smad signaling pathway. Thus, LrB may be a potential drug in the treatment of MI/R injury.