Radix Astragali decoction improves liver regeneration by upregulating hepatic expression of aquaporin-9

Abstract

Background: The therapeutic efficacy of liver injuries heavily relies on the liver's remarkable regenerative capacity, necessitating the maintenance of glycose/lipids homeostasis and oxidative eustasis during the recovery process. Astragali Radix, an herbal tonic widely used in China and many other countries, is believed to have many positive effects, including immune stimulation, nourishing, antioxidant, liver protection, diuresis, anti-diabetes, anti-cancer and expectorant. Astragali Radix is widely integrated into hepatoprotective formulas as it is believed to facilitate liver regeneration. Nevertheless, the precise molecular pharmacological mechanisms underlying this hepatoprotective effect remain elusive.

Purpose: To investigate the improving effects of Astragali Radix on liver regeneration and the underlying mechanisms.

Methods: A mouse model of 70% partial hepatectomy (PHx) was employed to investigate the impact of Radix Astragali decoction (HQD) on liver regeneration. HQD was orally administered for 7 days before the PHx procedure and throughout the experiment. N-acetylcysteine (NAC) was used as a positive control for liver regeneration. Liver regeneration was assessed by evaluating the liver-to-body weight ratio (LW/BW) and the expression of representative cell proliferation marker proteins. Oxidative stress and glucose metabolism were analyzed using biochemical assays, Western blotting, dihydroethidium (DHE) fluorescence, and periodic acid-Schiff (PAS) staining methods. To understand the role of AQP9 as a potential molecular target of HQD in promoting liver regeneration, td-Tomato-tagged AQP9 transgenic mice (AQP9-RFP) were employed to determine the expression pattern of AQP9 protein. AQP9 knockout mice (AQP9^-/-) were used to assess the specific targeting of AQP9 in the promotion of liver regeneration by HQD.

Results: HQD significantly upregulated hepatic AQP9 expression, alleviated liver injury and promoted liver regeneration in wild-type (AQP9^+/+) mice after 70% PHx. However, the beneficial impact of HQD on liver regeneration was absent in AQP9 gene knockout (AQP9^-/-) mice. Moreover, HQD facilitated the uptake of glycerol by hepatocytes, enhanced gluconeogenesis, and concurrently reduced H₂O₂ content and oxidative stress levels in AQP9^+/+ but not AQP9^-/- mouse livers. Additionally, main active substance of Radix Astragali, astragaloside IV (AS-IV) and cycloastragenol (CAG), demonstrated substantial upregulation of AQP9 expression and promoted liver regeneration in AQP9^+/+ but not AQP9^-/- mice.

Conclusion: This study is the first to demonstrate that Radix Astragali and its main active constituents (AS-IV and CAG) improve liver regeneration by upregulating the expression of AQP9 in hepatocytes to increase gluconeogenesis and reduce oxidative stress. The study revealed novel molecular pharmacological mechanisms of Radix Astragali and provided a promising therapeutic target of liver diseases.

Keywords: Aquaporin-9; Gluconeogenesis; Liver Regeneration; Oxidative stress; Radix Astragali.