Xinbao Pill attenuated chronic heart failure by suppressing the ubiquitination of β-adrenergic receptors

Xinbao Pill (XBP) is extensively used in the adjuvant treatment of chronic heart failure in China. However, the pharmacological effect and underlying mechanism on CHF remains unclear.Our research was performed to investigate the cardioprotective effect of XBP against CHF and uncover the potential mechanism.Male Sprague-Dawley (SD) rats were subjected to the left anterior descending (LAD) artery ligation for 8 weeks and were treated with different doses of XBP (from the 4th week to the end). Cardiac function and morphology assessment were performed by using M-mode echocardiography, H&E and Masson staining. Western blotting analysis, co-immunoprecipitation (IP) assays, siRNA transfection were used to evaluate the mechanism of XBP.XBP improved cardiac function and alleviated cardiac fibrosis in LAD-induced chronic heart failure rats. Meanwhile, XBP protected cardiomyocytes against oxygen-glucose deprivation (OGD) injury in AC16 cells and H9c2 cells. Additionally, XBP could increase the expression of β1-AR and β2-AR and inhibit their ubiquitanation. Further mechanism study showed that XBP upregulated USP18 expression, while silence of USP18 attenuated the cardioprotective effect of XBP and the increase of β1-AR by XBP. Moreover, XBP increased MDM2 and β-arrestin2, and disrupted the interaction between Nedd4 and β2-AR. After using the inhibitor of MDM2, SP141, the cardioprotective effect of XBP and the inhibitory effect on the ubiquitanation of β2-AR were also blocked.Our study firstly revealed that XBP improved cardiac function against CHF through suppressing USP18 and MDM2/β-arrestin2/Nedd4-mediated the ubiquitination of β1-AR and β2-AR.