Xinbao pill attenuated water retention by regulating the CaSR/AQP2 pathway in LAD-induced chronic heart failure rats.

BACKGROUND

Water retention is one of the important factors in the development and exacerbation of chronic heart failure (CHF). Xinbao Pill (XBP) is widely used as an adjuvant therapy for CHF. However, the therapeutic effect of XBP on water retention in CHF remains unclear.

PURPOSE

Our research was aimed to investigate the effect and mechanism of XBP on water retention in CHF.

METHODS

Male Sprague-Dawley (SD) rats underwent left anterior descending (LAD) artery ligation to establish the CHF model and were subsequently administrated with different doses of XBP or Qili Qiangxin (QLQX). Cardiac functions were assessed using M-mode echocardiography. Cardiac remodeling and myocardial fibrosis were observed using HE and Masson staining. Additionally, the expression of the CaSR/AQP2 signaling pathway in the renal was detected using western blotting analysis, quantitative PCR analysis, immunofluorescence staining, immunohistochemistry, and co-immunoprecipitation assays. Furthermore, CaSR inhibitor NPS2143 was used to confirm the role of CaSR on the effect of XBP for water retention.

RESULTS

In the LAD-induced CHF rat model, XBP improved EF (ejection fraction) and LVFS (fractional shortening), and alleviated cardiac fibrosis. Importantly, XBP significantly increased the 24-h urine volume and decreased urinary protein level after CHF. Further mechanism studies showed that XBP treatment could decrease the expression of renal AQP2 at the protein and mRNA levels. Moreover, XBP promoted renal AQP2 ubiquitination by upregulating CaSR and p-p38-MAPK expression. Meanwhile, XBP suppressed the expression of p-CREB to inhibit the mRNA expression of AQP2 in the renal tissue. However, NPS2143 blocked the beneficial effects of XBP on cardiac function and water retention, even stopped the inhibitory effect on AQP2 expression by XBP.

CONCLUSION

Our study revealed that XBP improved water retention against CHF via promoting CaSR/p38-MAPK-mediated AQP2 ubiquitination and regulating CaSR/CREB-mediated AQP2 transcription.