Abstract: Objective To observe the mechanism of Astragali Radix (AR) regulating the expression of transient receptor potential melastatin 2(TRPM2) on acetaminophen(APAP)-induced acute liver injury(ALI). Methods In vivo experient: thirty-nine male mice were randomly divided into control group(n=7) and study groups(n=8 each). The study groups were divided into the following groups at random: the APAP model group, the low-dose AR group(50 mg/kg), the high-dose AR group(75 mg/kg) and the N-acetylcysteine (NAC) treatment group(100 mg/kg). Both of AR and NAC were administered daily through oral gavage once a day for 3 consecutive days. On the 4th day, the mice in the study groups were given 350 mg/kg APAP by gavage. After 12 h of APAP treatment, samples were collected. Blood was collected to detect the serum levels of ALT and AST; Liver tissue slices were subjected to hematoxylin and eosin(HE) staining for observing the pathological changes, while immunohistochemical staining was performed to observe the expression of myeloperoxidase (MPO) and TRPM2. In vitro experiment: The AML12 mouse hepatocyte line was cultured in vitro and was stimulated by APAP (0, 5, 10, 20 mM) for 12 or 24 h. After the optimal stimulation concentration and duration of action were screened out, RT-PCR and Western blot were used to dynamically measure TRPM2 in hepatocytes. The ALI cell model was established with 5 mM APAP and divided into control group, APAP model group, low-dose AR group(125 μg/mL), high-dose AR group(250 μg/mL) and NAC control group. Except the control group, the other groups were incubated with NAC for 24 h. The CCK-8 assay was used to measure the viability of hepatocytes. RT-PCR and Western blot were used to measure TRPM2 in hepatocytes. Results In vivo experiment, compared with the normal group, the levels of serum ALT and AST in the APAP model group significantly increased (P<0.01). The liver tissue showed severe destruction of liver tissue structure, massive/submassive necrosis of hepatocytes, and central venous congestion. Compared with the APAP model group, AR had obvious hepatoprotective effects, including lowering the levels of serum ALT and AST in model mice, alleviating the necrosis of hepatocytes and down-regulated the expression of MPO and TRPM2 in liver tissue. While the high-dose AR group had the same efficacy as NAC. In vitro experiment: 5 mM APAP incubation could significantly induce hepatocyte damage (F=25.408, P<0.01), and the expression of TRPM2 in hepatocytes increased with time; compared with the APAP model group, AR could increase the viability of hepatocytes and reduce the expression of TRPM2 in hepatocytes. Conclusion AR has a good protective effect on APAP drug-induced liver injury, which may be related to down-regulation of TRPM2 expression.

Key words: Acetaminophen, Drug-induced liver injury, Astragali Radix, Transient receptor potential melastatin 2