Electroacupuncture at “Xinshu” (BL15) improves myocardial ischemia by inhibiting the ferroptosis pathway in rats

To explore the role of the ferroptosis pathway of myocardial cells in electroacupuncture (EA) at “Xinshu” (BL15)-induced improvement of myocardial ischemia (MI) in rats.

A total of 18 male SD rats were randomly divided into control, model and EA groups, with 6 rats in each group. The MI model was established by subcutaneous injection of isoproterenol (ISO, 60 mg/kg) for consecutive 2 d. The rats of the control group received the same volume of 0.9% sodium chloride solution for 2 d. EA was applied to bilateral BL15 for 30 min, once a day for 3 d. The electrocardiogram (ECG) of the standard limb lead Ⅱ was recorded before and after modeling, and after the intervention using a multi-channel physiological recorder. Histopathological changes of the myocardial tissue were observed by hematoxylin-eosin staining (HE staining), and the ultrastructural changes of the myocardial cell mitochondria were observed under a transmission electron microscope (TEM). The contents of divalent iron ions (Fe²⁺), malondialdehyde (MDA), and glutathione (GSH), as well as the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) in the myocardial tissue were detected using biochemical methods. The expression levels of ferritin heavy chain 1 (FTH1), nuclear factor E2-related factor 2 (Nrf2), solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4) and acyl-CoA synthetase long-chain family member 4 (ACSL4) mRNAs and proteins in the myocardial tissue were detected using real-time fluorescence quantitative PCR and Western blot, separately.

Compared with the control group, the model group had a significant increase in the ECG ST segment after modeling and a decrease after interventions, content of Fe²⁺, and the expression levels of ACSL4 mRNA and protein (P<0.01, P<0.05), and a considerable decrease in the content of GSH, activity of SOD and GSH-PX, and the expression levels of FTH1, Nrf2, SLC7A11, and GPX4 mRNAs and proteins (P<0.01). In contrast to the model group, modeling induced abnormalities of ECG-ST segment, content of Fe²⁺, and the expression levels of ACSL4 mRNA and protein and the decrease of the content of GSH, activity of SOD and GSH-PX, and the expression levels of FTH1, Nrf2, SLC7A11, and GPX4 mRNAs and proteins were all reversed by EA (P<0.01, P<0.05). Histopathological and ultrastructural observations showed a reduction in the number of cardiomyocytes, with loose arrangement, extracellular inflammatory cell infiltration, vacuolated myocardial fibers and increased extracellular space, and a decrease in the mitochondrial volume, with an increase of density and breakage of crista in the model group, which was relatively milder in the injury degree of cardiomyocytes and their mitochondria, etc. in the EA group.

EA at BL15 can alleviate ischemic myocardium injury in rats with MI, which may be achieved by inhibiting the ferroptosis signaling pathway in the myocardial cells.