Antihyperuricemic effect of mangiferin aglycon derivative J99745 by inhibiting xanthine oxidase activity and urate transporter 1 expression in mice

A mangiferin aglycon derivative J99745 has been identified as a potent xanthine oxidase(XOD) inhibitor by previous in vitro study. This study aimed to evaluate the hypouricemic effects of J99745 in experimental hyperuricemia mice, and explore the underlying mechanisms. Mice were orally administered 600 mg/kg xanthine once daily for 7 days and intraperitoneally injected 250 mg/kg oxonic acid on the 7 th day to induce hyperuricemia. Meanwhile, J99745(3, 10, and 30 mg/kg), allopurinol(20 mg/kg) or benzbromarone(20 mg/kg) were orally administered to mice for 7 days. On the 7 th day,uric acid and creatinine in serum and urine, blood urea nitrogen(BUN), malondialdehyde(MDA) content and XOD activities in serum and liver were determined. Morphological changes in kidney were observed using hematoxylin and eosin(H&E) staining. Hepatic XOD, renal urate transporter 1(URAT1), glucose transporter type 9(GLUT9), organic anion transporter 1(OAT1) and ATP-binding cassette transporter G2(ABCG2) were detected by Western blot and real time polymerase chain reaction(PCR). The results showed that J99745 at doses of 10 and 30 mg/kg significantly reduced serum urate, and enhanced fractional excretion of uric acid(FEUA). H&E staining confirmed that J99745 provided greater nephroprotective effects than allopurinol and benzbromarone. Moreover, serum and hepatic XOD activities and renal URAT1 expression declined in J99745-treated hyperuricemia mice. In consistence with the ability to inhibit XOD, J99745 lowered serum MDA content in hyperuricemia mice. Our resultssuggest that J99745 exerts urate-lowering effect by inhibiting XOD activity and URAT1 expression, thus representing a promising candidate as an anti-hyperuricemia agent.

The inhibitory effect of lotus leaf extract on hyperuricemia and its potential mechanism

Objective:Lotus leaf is a traditional Chinese herb that has been used successfully for centuries for relieving edema by inducing diuresis.Based on its good clinical evidence and anti-hypertensive effectiveness,this study aimed to investigate the potential mechanism of the hyperuricemic inhibitory effects of lotus leaf crude extract(LL)and lotus leaf total alkaloids fraction(LA).Methods:The xanthine oxidase(XOD)inhibitory effect of LL and LA was analyzed in vitro by determining mRNA expression and protein expression levels of hepatic XOD.The hyperuricemic inhibitory effect of the lotus leaf was analyzed in vivo in a potassium oxonate(PO)-induced rat model by determining mRNA expression for renal urate transporters.Results:At a concentration of 40mg/mL,LL and LA suppressed XOD enzymatic activity by 37.35%±9.50%and 47.73%±8.32%,respectively.Both LL and LA administration significantly reduced the concentration of uric acid in the serum and liver of PO-induced hyperuricemic rats.Both LL and LA administration could inhibit XOD mRNA and protein expression,activate renal organic anion transporter 1/3 mRNA expression,and inhibit renal urate reabsorption by decreasing renal GLUT9 and renal urate transporter 1.Conclusions:Insight was gained into the mechanism behind the hyperuricemic inhibitory effects of LL and LA.Our results suggest that they act on two targets:decreasing the production of uric acid by inhibiting mRNA and protein expression of XOD in the liver,and regulating the mRNA expression of renal urate transporters in the kidneys.

Effect of Eurycoma longifolia stem extract on uric acid excretion in hyperuricemia mice

OBJECTIVE Eurycoma longifolia is a tropical medicinal plant belonging to Simaroubaceae distributed in South East Asia.The aim of this study is to explore the effect and mechanism of E.longifolia stem 70%ethanol extract(EL)and its active com⁃poundson uric acid excretion.METHODS Potassium oxonate(PO)induced hyperuricemia rats and adenine-PO induced hyperuricemia mouse model were used to evaluate the effects of EL.Ultra Performance Liquid Chromatography was used to determine the levels of plasma or serum uric acid and creatinine.Hematoxylin-eosin staining was applied to observe kidney pathological changes,Western blot⁃ting was applied to detect protein expression levels of uric acid transporters.Effects of constituents on urate uptake were tested in hU⁃RAT1-expressing HEK293T cells.RESULTS EL significantly reduced serum and plasma uric acid levels at dosages of 100,200 and 400 mg·kg^-1 in hyperuricemia rats and mice,and increased the clearance rate of uric acid and creatinine,improved therenal pathological injury.The protein expression levels of urate reabsorption transporter 1(URAT1)and glucose transporter 9 were down-regulated while sodium-dependent phosphate transporter 1 and ATP-binding cassette transporter G2 were up-regulated in the kidney after EL treat⁃ment.The diterpenes(50μmol·L^-1)isolated from EL showed inhibitory effects on urate uptake in hURAT1-expressing HEK293T cells,and the effect of eurycomanol was further confirmed in vivo.CONCLUSION EL significantly reduced blood uric acid levels and prevented pathological changes of kidney in PO induced hyperuricemia animal model,improved renal urate transports.We partly clarified the mechanism was related to suppressing effect of URAT1 by diterpene in EL.This study is the first to demonstrate that EL plays a role in hyperuricemia by promoting renal uric acid excretion.

Antihyperuricemic and Nephroprotective Effects of the Total Flavonoids from Carya cathayensis Leaves(CCTF)in Potassium Oxonate/hypoxanthine-induced Hyperuricemic Mice

Background:Abnormally high level of uric acid in the blood,defined as hyperuricemia(HUA),increases the chance of developing various disorders,such as gout,hypertension,and diabetes.There is a critical need to create safer and more potent therapeutic medications since the current clinical treatment for HUA has a number of negative effects.Objective:To explore the antihyperuricemic benefits of the total flavonoids from Carya cathayensis leaves(CCTF)in HUA model mice and to elucidate the underlying mechanisms.Methods:The mouse HUA model was induced with potassium oxonate and hypoxanthine and then the mice were given normal saline,allopurinol,or various dosages of CCTF for one week.The weight of the mice was recorded,followed by measurements of their blood uric acid(UA),creatinine(Cr),urea nitrogen(BUN),aspar-tate aminotransferase(AST),alanine aminotransferase(ALT),and xanthine oxidase(XOD)activity.Hematoxylin and eosin(H&E)staining and Manson staining were used to simultaneously detect pathological abnormalities in the liver and kidney tissues.Afterward,the mRNA expression of urate transporters in kidney was determined by qRT‒PCR experiments,including ATP-binding cassette transporter subfamily G member 2(Abcg2),urate trans-porter 1(Urat1),and glucose transporter 9(Glut9).Finally,immunohistochemistry(IHC)staining was performed to confirm ABCG2 protein expression in the kidney.Results:In contrast to the model group,the CCTF group lowered blood levels of UA,Cr,BUN,ALT,and AST in serum,downregulated XOD levels in serum and liver,and significantly improved liver and renal damage,exhibiting outstanding antihyperuricemic effects.The levels of Urat1 and Glut9 were further shown to be much lower in the kidney,whereas both Abcg2 expression and ABCG2 level were increased,according to the findings.Conclusion:CCTF ameliorated hyperuricemia-related kidney damage and had antihyperuricemic effects,suggest-ing that CCTF might have the potential to protect against HUA by regulating the expression of relative urate transporters and XOD.