LAUSR

Apigenin, a flavonoid isolated from Apium graveolens, is an effective natural active ingredient that inhibits transforming growth factor‐β1 (TGF‐β1)‐induced cardiac fibroblasts (CFs) differentiation and collagen synthesis. However, its effects on isoproterenol‐induced myocardial fibrosis in mice remain unknown. This study aimed to examine the effect of apigenin in the prevention of myocardial fibrosis. A mouse model of myocardial fibrosis induced by isoproterenol was established, and the mice were given apigenin 75–300 mg/kg orally for 40 days. The results showed that the heart weight coefficient, myocardial hydroxyproline, collagen accumulation, and malondialdehyde levels in the apigenin‐treated groups were significantly reduced. In contrast, the activity of myocardial superoxide dismutase and glutathione peroxidase were significantly enhanced. The results of real‐time quantitative polymerase chain reaction and western blot assays showed that apigenin could significantly upregulate the expressions of myocardial microRNA‐122‐5p (miR‐122‐5p), c‐Ski, and Smad7 and downregulate the expressions of myocardial miR‐155‐5p, α‐smooth muscle actin, collagen I/III, NF‐κB, TGF‐β1, hypoxia‐inducible factor‐1α (HIF‐1α), Smad2/3, and p‐Smad2/3. In vitro, the differentiation and extracellular matrix production, as well as TGF‐β1/Smads axis, were further reduced after treatment of miR‐122‐5p mimic or miR‐155‐5p inhibitor‐transfected and TGF‐β1‐stimulated CFs with apigenin. These results suggested that apigenin increased the expression of miR‐122‐5p and decreased the expression of miR‐155‐5p, which subsequently downregulated and upregulated the target genes HIF‐1α and c‐Ski, respectively. Furthermore, apigenin administration downregulated TGF‐β1‐induced Smad2/3 and upregulated Smad7. In addition, it reduced the NF‐κB/TGF‐β1 signaling pathway axis by increasing antioxidant ability to exert the antifibrotic effects.