Effect of electroacupuncture of “Neiguan” (PC6) and “Shenmen” (HT7) on cardiac function and neovascularization in rats with chronic heart failure based on Notch signaling pathway

To observe the effect of electroacupuncture (EA) on the activities of N-terminal B-type natriuretic peptide (NT-proBNP)/vascular endothelial growth factor (VEGF)/neurogenic site-gap homologous protein (Notch) signaling pathway and related factors in rats with chronic heart failure (CHF), so as to explore its regulatory mechanism underlying improvement of CHF.

Male SD rats were randomly divided into sham-operation, CHF model, EA and EA+inhibitor [DAPT (GSI-IX), a γ-secretase inhibitor] groups (n=6 in each group). The CHF model was established by ligating the anterior descending branch of the left coronary artery. EA (2 Hz, an electric current intensity to induce slight shaking of the inserted acupuncture needles) was applied to bilateral "Neiguan"(PC6) and "Shenmen"(HT7) for 30 min, once daily, for 7 d. Rats of the EA+inhibitor group received intraperitoneal injection of DAPT (3 mg/kg) 30 min before each EA intervention. A small animal color Doppler ultrasound machine was used to collect the left ventricular ejection fraction (LVEF), left ventricular fractional shortening rate (LVFS), left ventricular end-systolic diameter (LVIDs) for evaluating the left ventricle function. Histopathological changes of the cardiac tissue were observed by H.E. staining and Masson staining. The contents of serum NT-proBNP and VEGF were detected by using ELISA. The microvascular density (MVD) of the left ventricular myocardium was observed by CD34 immunohistochemistry. The expression levels of myocardial Notch signaling pathway-related proteins Notch1 and Delta-like 4 ligand (DLL4) were detected by using Western blot.

Compared with the sham operation group, the model group had a significant increase in the LVIDs, serum NF-proBNP content, MVD and expression levels of Notch1 and DLL4 protein in the left ventricular myocardial tissue (P < 0.0001, P < 0.001, P < 0.01), and a significant decrease in the LVEF, LVFS and serum VEGF content (P < 0.0001). In comparison with the model group, the EA group had a significant decrease in the LVIDs and serum NF-proBNP content (P < 0.001), and a significant increase in the LVEF, LVFS and serum VEGF content (P < 0.001, P < 0.0001), while the MVD and expression levels of Notch1 and DLL4 protein in the left ventricular myocardial tissue were more increased (P < 0.001, P < 0.05, P < 0.01). In comparison with the EA group, both the striking increase and decrease of the indexes mentioned above were all reversed in the EA+inhibitor group (P < 0.05, P < 0.01, P < 0.0001, P < 0.001) except LVIDs. Histopathological observation showed obvious myocardial fiber rupture, irregular arrangement, cell necrosis, unclear nucleoli, fibrous hyperplasia, deposition of collagenous fibers, and a large number of inflammatory infiltration in the myocardial tissue of the model group, which was relatively milder in the EA group but not in the EA+inhibitor group.

EA of PC6 and HT7 can improve the cardiac function of rats with CHF, which may be associated with its functions in promoting the neovascularization of ischemic myocardium, reducing ischemic injury, and protecting myocardial tissue structure via up-regulation of the serum VEGF content and the expressions of Notch1 and DLL4 protein.