Study on the role and mechanism of Biochanin A in inflammatory response and cardiac remodeling after myocardial infarction in mice

Objective: To explore the effect and mechanism of biochanin A (BCA) on the inflammatory response and cardiac remodeling following myocardial infarction (MI) in mice.

Methods: Using the simple random sampling method, 8-week-old male C57BL/6J mice were categorized into the sham operation control group (5 mice), sham operation experimental group (5 mice), BCA-MI control group (15 mice), BCA-MI experimental group (15 mice), azithromycin-MI control group (4 mice), and azithromycin-MI experimental group (4 mice). The mouse MI model was constructed by ligating the left anterior descending coronary artery. The BCA-MI experimental group was administered 200 mg/kg BCA by gavage, while the BCA-MI control group was given an equal volume of solvent once a day for 3 consecutive days. Mice in the azithromycin-MI experimental group were administered 160 mg/kg azithromycin by gavage, and those in the azithromycin-MI control group were given an equal volume of solvent once a day for 3 consecutive days. The azithromycin-MI experimental group served as a positive control for the influence of BCA on neutrophil infiltration. At 21 days after MI, cardiac MRI and ultrasound examinations were conducted on the sham operation control group, sham operation experimental group, BCA-MI control group, and BCA-MI experimental group, and the left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were recorded; The hearts of MI mice were extracted, and Masson staining was utilized to assess the MI area and collagen deposition. At 3 days after MI, the hearts of the BCA-MI control group, BCA-MI experimental group, azithromycin-MI control group, and azithromycin-MI experimental group were extracted for flow cytometry to evaluate the infiltration of neutrophils in the heart. At 3 days after MI, the peripheral blood of the BCA-MI control group and BCA-MI experimental group was collected, centrifuged to obtain serum, and the levels of inflammatory factors were evaluated using the enzyme-linked immunosorbent assay (ELISA); The hearts of the mice were extracted, and the infiltration of neutrophils and the level of apoptotic myocardial cells in the MI area were evaluated by immunofluorescence staining. Circulating neutrophils from one healthy mouse were stimulated with phorbol myristate acetate (PMA) (in vitro control group) or PMA+BCA (in vitro experimental group) for 4 hours to induce the inflammatory state of neutrophils, and the culture medium was obtained through centrifugation. The culture medium from the in vitro control group and in vitro experimental group was used to cultivate H9C2 cardiomyocytes to induce their injury. The inhibitory effect of BCA on the injury of cardiomyocytes by neutrophils was evaluated by Western blotting for apoptosis-related proteins BCL2-associated X protein (Bax) and Cleaved caspase 3.

Results: Compared with the BCA-MI control group, the BCA-MI experimental group exhibited a smaller infarct area (19.56%±3.48% vs 31.45%±2.27%, P=0.003), an increased LVEF (52.79%±0.36% vs 48.42%±1.04%, P=0.005), a decreased LVFS (24.31%±0.32% vs 26.41%±0.16%, P=0.001), and a lower proportion of neutrophils (79.52%±1.92% vs 87.20%±2.01%, P<0.001). There was no statistically significant difference in the proportion of neutrophils between the BCA-MI experimental group and the azithromycin-MI experimental group (P=0.517). The number of apoptotic myocardial cells in the heart and the levels of inflammatory factors, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, in the peripheral blood of mice in the BCA-MI experimental group were all lower than those in the BCA-MI control group at 3 days after MI (all P<0.05). In the in vitro experiment, the gray levels of Bax protein (65.63%±28.81% vs 100.80%±43.01%, P=0.023) and Cleaved caspase3 protein (77.59%±34.67% vs 108.40%±46.45%, P=0.047) in the experimental group were both lower than those in the control group.

Conclusion: BCA improves cardiac function after MI in mice by inhibiting neutrophil-mediated inflammatory responses and reducing myocardial cell apoptosis.