Ellagic acid attenuates myocardial fibrosis by suppressing Bmi1-mediated inhibition of the p53/p21 pathway in cardiac fibroblasts

Myocardial fibrosis is characterized by excessive cardiac fibroblasts (CF) proliferation and extracellular matrix deposition. The p53 tumor suppressor is known to inhibit CF proliferation, while the polycomb protein Bmi1 negatively regulates p53. Ellagic acid (EA), a natural polyphenol, has demonstrated anti-fibrotic potential, but its mechanism of action in the heart remains unclear. This study investigated whether EA reduces myocardial fibrosis by inhibiting Bmi1 expression. A rat model of myocardial fibrosis was established using isoproterenol (ISO), and rat cardiac fibroblasts were treated with TGF-β to induce a pro-fibrotic phenotype in vitro. Echocardiography and histology confirmed that EA treatment improved cardiac function and reduced fibrosis in ISO-induced rats. In vitro, EA significantly inhibited TGF-β-induced CF proliferation, migration, and differentiation into myofibroblasts. Mechanistically, EA upregulated p53 and its downstream target p21, leading to G1/S cell cycle arrest. Molecular docking and dynamics simulations predicted that EA binds to Bmi1, and subsequent experiments showed EA treatment reduced Bmi1 protein levels. Using a Bmi1 inhibitor (PTC-209) and overexpression plasmids, we demonstrated that the anti-fibrotic effects of EA are mediated in part through inhibition of Bmi1, which in turn activates the p53 pathway. Ellagic acid reduces myocardial fibrosis, at least in part, through suppression of Bmi1 expression. This suppression is associated with relief of the inhibitory effect of Bmi1 on p53, leading to p53/p21 pathway activation, cell cycle arrest, and subsequent inhibition of cardiac fibroblasts proliferation, migration, and differentiation. These findings suggest that Bmi1 may represent a novel therapeutic target for EA treatment of myocardial fibrosis.