Study on mechanism of Fangji Huangqi Decoction on hypouricemic effect and renal protection in hyperuricemia mice

The aim of this paper was to study the specific mechanism of Fangji Huangqi Decoction(FHT) in decreasing uric acid and improving renal function in mice with hyperuricemia(HUA) induced by potassium oxonate, so as to provide theoretical basis for the research and development of drugs for clinical prevention and treatment of HUA and the modernization of traditional Chinese medicine. Sixty Kunming male mice were randomly divided into 6 groups, with 10 mice in each group, namely normal group, model group(250 mg·kg~(-1) potassium oxonate), FHT high, medium and low-dose groups(10 920, 5 460, and 2 730 mg·kg~(-1)) and positive drug allopurinol group(5 mg·kg~(-1)). Drug administration was given once a day for 7 days. On the 6 th day, mice of each group were kept in metabolic cages, and their urine was collected for 24 hours for determination of uric acid, creatinine, and β2-microglobulin(β2-MG) levels. After 7 days, the animals were sacrificed to determine serum uric acid, creatinine β2-MG and interleukin-1β(IL-1β) levels, and their liver and kidney tissues were collected. The liver tissues were used for subsequent determination of xanthine oxidase(XOD) activity, and the kidney tissues were used for subsequent determination of IL-1β levels, pathological tests and related Western blot experiments. In the cell transfection experiment, the cells were divided into blank group, model group(4.8 mmol·L~(-1) uric acid treatment), FHT administration group(4.8 mmol·L~(-1) uric acid+200 μg·mL~(-1) FHT), leucine-rich repeat kinase 1(LRRK1)-small interfering RNA(siRNA) group(4.8 mmol·L~(-1) uric acid+LRRK1-siRNA transfection) and LRRK1-siRNA+FHT group(4.8 mmol·L~(-1) uric acid+LRRK1-siRNA transfection+200 μg·mL~(-1) FHT). After 24 h incubation, the level of IL-1β in the cell supernatant was detected, and the cellular proteins were extracted and used to determine LRRK1, epidermal growth factor receptor(EGFR), PDZ kinase 1(PDZK1) and nuclear factor-kappa B(NF-κB) protein expression levels. The results showed that, FHT could significantly reduce the uric acid, creatinine and β2-MG levels in serum and β2-MG levels in urine, increase the uric acid and creatinine levels in urine, and improve the renal pathological results of the HUA mice, but showed no effect on liver XOD activity; at the same time, we found that the expression level of IL-1β in serum and kidney, NF-κB, LRRK1 and EGFR protein levels in kidney of HUA mice were significantly increased, and the expression level of PDZK1 protein was significantly decreased, while FHT could significantly improve the abnormal expression of these proteins, and FHT increased protein expression of renal organic anion transporter 1(OAT1), OAT3 and ATP bin-ding transporter G2(ABCG2) in HUA mice, but FHT had no effect on the expression of urate transporter 1(URAT1). In the cell transfection experiment, after transfection of LRRK1-siRNA, the levels of IL-1β, EGFR and NF-κB in supernatant were significantly reduced, and the expression of PDZK1 protein was significantly increased. As compared with the LRRK1-siRNA group, the levels of IL-1β, EGFR, PDZK1 and NF-κB did not change significantly with the additional FHT. This study showed that FHT may regulate the renal uric acid transport system through LRRK1 gene, improve the capacity of uric acid excretion, so as to reduce the level of serum uric acid. At the same time, FHT can not only protect the kidney directly, but also in an indirect manner by reducing the level of uric acid.