Protective effect of Xin-Ji-Er-Kang on cardiovascular remodeling in high-salt induced hypertensive mice: Role ofoxidative stress and endothelial dysfunction

Abstract Background Xin-Ji-Er-Kang (XJEK) is a Chinese herbal formula that has beenreported to exert effective protection against cardiovascular diseases, such as hypertension and myocarditis. Objective The aim of the present study was to investigate the effect of XJEK on high-salt-induced hypertensive mice and its possible mechanism. Methods The model of hypertension was established through a high-salt diet. Sixty male Kunming mice were randomized into six groups, namely the Control, Model, Low-dose XJEK, Middle-dose XJEK, High-dose XJEK and Fosinopril groups ( n= 10 per group). Different steady interventions were given to each group: 0.9% Sodium chloride was added to the diet of the Control group and 8% sodium chloride to the diet of the other five groups from the very beginning. An additional 4, 8 and 12 g/kg/day XJEK were intragastrically administered to the Low-dose, Middle-dose and High-dose XJEK groups, respectively, and 2 mg/kg/day fosinopril to the fosinopril group, from the start of week 5. Systolic blood pressure (SBP) was measured weekly from weeks 1 to 8 using the tail-cuff method. At the end of week 8, left ventricular (LV) systolic pressure, LV end-diastolic pressure and rate of rise of LV pressure were examined using a TransonicScisense catheter (Transonic Systems Inc,Ithaca, NY,USA). Endothelium-dependent relaxations induced by acetylcholine were observed in an isolated thoracic aorta ring. Serum and heartsweresampled for the measurement of the following indexes:Serum nitric oxide (NO), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content (determined by colorimetricanalysis); serum angiotensin II(Ang II), endothelin-1, endothelial NO synthase (eNOS), asymmetric dimethylarginine (ADMA), tetrahydrobiopterin (BH 4 ) concentration and l -arginine (determined by enzyme-linked immunosorbent assay); heart to body weight (HW/BW) ratio; myocardial morphological change (determined by HE and VG staining); myocardial eNOS expression (determined by immunofluorescence), and myocardial endothelin receptor A (ET A ) expression (determined by western blotting). Results:Statistical data showed that the HW/BW ratio was significantly decreased in the drug treatment group. XJEK treatment could improve the heart systolic and diastolic function and ameliorate hemodynamic parameters and vascular remodeling indexes. Colorimetric results showed that, compared with the model group, XJEK increased serum SOD, NOlevels, and decreased those of serum MDA and Ang II. XJEK reverted changes in cardiac pathology, decreased the myocardial cross-sectional area, collagen volume fraction and perivascular collagen area and improved endothelial dysfunction (ED) by promoting eNOS activity, enhancing NO bioavailability, increasing the expression of BH 4 and decreasing ET A content. In addition, treatment with XJEK decreased ADMA content in the myocardium. Conclusion:In conclusion, XJEK mitigates cardiac remodeling in high-salt-induced hypertensive mice. The potential mechanism involves improved oxidative stress and endothelial dysfunction, independently of ameliorating BP.