(E)-2-(4-bromophenyl)-1-(2, 4-dihydroxyphenyl)ethanone oxime is a potential therapeutic agent for treatment of hyperuricemia through its dual inhibitory effects on XOD and URAT1

Discovery of digallic acid as XOD/URAT1 dual target inhibitor for the treatment of hyperuricemia

The development of XOD/URAT1 dual target inhibitors has emerged as a promising therapeutic strategy for the management of hyperuricemia. Here, through virtual screening, we have identified digallic acid as a novel dual target inhibitor of XOD/URAT1 and subsequently evaluated its pharmacological properties, pharmacokinetics, and toxicities. Digallic acid inhibited URAT1 with an IC50 of 5.34 ± 0.65 μM, which is less potent than benzbromarone (2.01 ± 0.36 μM) but more potent than lesinurad (10.36 ± 1.23 μM). Docking and mutation analysis indicated that residues S35, F241 and R477 of URAT1 confer a high affinity for digallic acid. Digallic acid inhibited XOD with an IC50 of 1.04 ± 0.23 μM. Its metabolic product, gallic acid, inhibited XOD with an IC50 of 0.91 ± 0.14 μM. Enzyme kinetic studies indicated that both digallic acid and gallic acid act as mixed-type XOD inhibitors. It shares the same binding mode as digallic acid, and residues E802, R880, F914, T1010, N768 and F1009 contribute to their high affinity. The anion group (carboxyl) of digallic acid contribute significantly to its inhibition activity on both XOD and URAT1 as indicated by docking analysis. Remarkably, at a dosage of 10 mg/kg in vivo, digallic acid exhibited a stronger urate-lowering and uricosuric effect compared to the positive drug benzbromarone and lesinurad. Pharmacokinetic study indicated that digallic acid can be hydrolyzed into gallic acid in vivo and has a t1/2 of 0.77 ± 0.10 h. Further toxicity evaluation indicated that digallic acid exhibited no obvious renal toxicity, as reflected by CCK-8, biochemical analysis (CR and BUN) and HE examination. The findings of our study can provide valuable insights for the development of XOD/URAT1 dual target inhibitors, and digallic acid deserves further investigation as a potential anti-hyperuricemic drug.

Recent Advances in Xanthine Oxidase Inhibitors

Uric acid is a product of purine nucleotide metabolism, and high concentrations of uric acid can lead to hyperuricemia, gout and other related diseases. Xanthine oxidase, the only enzyme that catalyzes xanthine and hypoxanthine into uric acid, has become a target for drug development against hyperuricemia and gout. Inhibition of xanthine oxidase can reduce the production of uric acid, so xanthine oxidase inhibitors are used to treat hyperuricemia and related diseases, including gout. In recent years, researchers have obtained new xanthine oxidase inhibitors through drug design, synthesis, or separation of natural products. This paper summarizes the research on xanthine oxidase inhibitors since 2015, mainly including natural products, pyrimidine derivatives, triazole derivatives, isonicotinamide derivatives, chalcone derivatives, furan derivatives, coumarin derivatives, pyrazole derivatives, and imidazole derivatives, hoping to provide valuable information for the research and development of novel xanthine oxidase inhibitors.

Sanghuangporus vaninii ethanol extract alleviates hyperuricemic renal injury by regulating the uric acid transporters and inhibiting HK-2 apoptosis

AIM OF THE STUDY

To investigate the acute toxicity of Sanghuangporus ethanol extract (SHEE) on ICR mice and the underlying mechanism of anti-hyperuricemic renal injury.

MATERIALS AND METHODS

ICR mice were given a single gavage of 1250, 2500, and 5000 mg/kg SHEE, and the general behavior, mortality, body weight, dietary, and water intake were evaluated within 14 days to determine the acute toxicity level. The hyperuricemic kidney injury model in ICR mice was induced with potassium oxonate (PO) and adenine, and the mice were subsequently treated with SHEE (125, 250, 500 mg/kg). HE and hexamine silver staining (PASM) were used to observe the pathology of the kidney. Biochemical markers were tested by uric acid (UA), creatinine (Cr), blood urea nitrogen (BUN), xanthine oxidase (XOD), alanine transferase (ALT), and aspartate transaminase (AST) kits. An MTT assay was used to measure the effects of SHEE on the proliferation of HK-2 damaged by UA. Western blotting and RT-PCR were used to determine the expression of Bcl-2 family-related proteins and major UA transporters, including URAT1, GLUT9, OAT1, OAT3, and ABCG2, respectively.

RESULTS

Firstly, the acute toxicity study data showed that the median lethal dose (LD₅₀) of SHEE was above 5000 mg/kg, and its oral administration was nontoxic at 2500 mg/kg and below. In addition, SHEE alleviated HUA and its renal injury in ICR mice. SHEE reduced the contents of UA, Cr, BUN and XOD in blood and the contents of ALT and AST in the liver. Furthermore, SHEE inhibited the expression of URAT1 and GLUT9 and promoted the expression of OAT1, OAT3, and ABCG2. More importantly, SHEE could downregulate the apoptosis level and caspase-3 activity.

CONCLUSIONS

Overall, an oral dose of SHEE below 2500 mg/kg is safe. SHEE inhibits HUA-induced kidney injury by regulating the UA transporters URAT1, GLUT9, OAT1, OAT3 and ABCG2 and inhibiting HK-2 apoptosis.

Novel urate transporter 1 (URAT1) inhibitors: a review of recent patent literature (2020-present)

INTRODUCTION

The urate transporter 1 (URAT1) is a membrane transporter located in the apical membrane of human renal proximal tubule epithelial cells, which mediates most of the reabsorption of urate. Hyperuricemia (HUA) is a common disease caused by metabolic disorders, which has been considered as the key factor of gout. Approximately 90% of patients suffer from hyperuricemia due to insufficient or poor uric acid excretion. Therefore, the drug design of URAT1 inhibitors targeting improve the renal urate excretion by reducing the reabsorption of urate anions represent a hot topic in searching for anti-gout drugs currently.

AREAS COVERED

In this review, we summarize URAT1 inhibitors patents reported since 2020 to present through the public database at https://worldwide.espacenet.com and some medicinal chemistry strategies employed to develop novel drug candidates.

EXPERT OPINION

Ligand-based drug design (LBDD) strategies have been frequently used developing new URAT1 inhibitors. Meanwhile, the discovery of dual drugs targeting both inhibition of xanthine oxidase (XOD) and URAT1 may be an emerging horizon for designing novel uric acid-lowering candidates in future. Furthermore, advanced techniques in the field of molecular biology and computer science can increase the chances to discover and/or optimize URAT1 inhibitors, contributing to the development of novel drug candidates.

Enhancement of oral bioavailability and anti-hyperuricemic activity of aloe emodin via novel Soluplus®-glycyrrhizic acid mixed micelle system

The objective of this study was to fabricate a novel drug delivery system using Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) and glycyrrhizic acid to improve solubility, bioavailability, and anti-hyperuricemic activity of aloe emodin (AE). The AE-loaded mixed micelles (AE-M) were prepared by thin-film hydration method. The optimal AE-M contained small-sized (30.13 ± 1.34 nm) particles with high encapsulation efficiency (m/m, %) of 90.3 ± 1.08%. The release rate of AE increased in the micellar formulation than that of free AE in the four media (DDW, pH 7.0; phosphate buffer solution, pH 7.4; phosphate buffer solution, pH 6.8; and hydrochloric acid aqueous solution, pH 1.2). In comparison to free AE, the pharmacokinetic study of AE-M showed that its relative oral bioavailability increased by 3.09 times, indicating that mixed micelles may promote gastrointestinal absorption. More importantly, AE-M effectively reduced uric acid level by inhibiting xanthine oxidase (XOD) activity in model rats. The degree of ankle swelling, serum levels of interleukin (IL)-1, and IL-6-related inflammatory factors levels all decreased in the gouty arthritis model established via monosodium urate (MSU) crystals. Taken together, the AE-M demonstrated the potential to improve the bioavailability, anti-hyperuricemic activity, and anti-inflammation of AE.

The Active Components of Sunflower (Helianthus annuus L.) Calathide and the Effects on Urate Nephropathy Based on COX-2/PGE2 Signaling Pathway and the Urate Transporter URAT1, ABCG2, and GLUT9

The sunflower (Helianthus annuus L.) calathide is gradually used as an alternative treatment for hyperuricemia; nevertheless, evidence regarding its main components and therapeutic capacity for urate nephropathy is lacking. Identification of sunflower calathide aqueous extract (SCE) was rapidly done by UPLC-ESI-Q-Orbitrap, and 32 water-soluble compounds with a comprehensive score >80 were discovered. Besides, yeast extract was administrated to induce high UA levels and hyperuricemic renal injury. We found that SCE treatment not only decreased UA levels to a comparable degree as allopurinol and benzbromarone, but also reduced the BUN levels and participated in kidney injury repair induced by uric acid. Moreover, it regulated the expression of URAT1 and ABCG2, especially inhibiting the GLUT9 in the normal kidney. Results were multifacetedly evaluated with a view to suggesting a possible mechanism of action as compared with those of allopurinol and benzbromarone by western blotting, H&E staining, and immunohistochemistry. However, the H&E staining showed histological changes in model, benzbromarone, and allopurinol groups rather than SCE treatments, and at the same time, the uric acid was identified as a cause of renal damage. The antiinflammatory effects and the regulations of COX-2/PGE2 signaling pathway were revealed on the LPS-induced RAW264.7 cells, indicating that the SCE not only increased cellular proliferation but also downregulated the COX-2, PGE2, NO, and IFN-γ cytokines in the RAW264.7 cells. To conclude, the SCE acts on urate transporters and contributes to prevent urate nephropathy via alleviating inflammatory process involving COX-2/PGE2 signaling pathway. It is available to develop SCE as food supplemental applications for hyperuricemia and nephritic inflammation.

Discovery of Novel Bicyclic Imidazolopyridine-Containing Human Urate Transporter 1 Inhibitors as Hypouricemic Drug Candidates with Improved Efficacy and Favorable Druggability

Lesinurad is a uricosuric agent for the treatment of hyperuricemia associated with gout, which was found lacking in efficacy and safety. Here, scaffold hopping and molecular hybridization were exploited to modify all the structural components of lesinurad, and 36 novel compounds bearing bicyclic imidazolopyridine core were obtained. In a mouse model of acute hyperuricemia, 29 compounds demonstrated increased serum uric acid (SUA)-reducing activity; SUA was treated with 12, 23, and 29 about fourfold lower compared with that of lesinurad. Moreover, 23 exhibited stronger URAT1 inhibition activity (IC₅₀ = 1.36 μM) than lesinurad (IC₅₀ = 5.54 μM). Additionally, 23 showed favorable safety profiles, and no obvious acute toxicity was observed in Kunming mice under a single dose of 1000 mg·kg^-1. 23 also achieved excellent pharmacokinetic properties with the oral bioavailability of 59.3%. Overall, all the results indicated that 23 is a promising drug candidate in the treatment of hyperuricemia and gout.

Recent Updates of Natural and Synthetic URAT1 Inhibitors and Novel Screening Methods

Human urate anion transporter 1 (hURAT1) is responsible for the reabsorption of uric acid in the proximal renal tubules and is a promising therapeutic target for treating hyperuricemia. To mitigate the side effects of URAT1-targeted clinical agents such as benzbromarone, there is significant interest in discovering new URAT1 inhibitors and developing technology that can evaluate URAT1 inhibition. This review summarizes the methods for assay of URAT1 inhibition and the progress on the discovery of natural and synthetic URAT1 inhibitors in the past five years.

A brief review of urate transporter 1 (URAT1) inhibitors for the treatment of hyperuricemia and gout: Current therapeutic options and potential applications

Hyperuricemia is a common metabolic condition, cause by increased levels of serum urate (SUA). Reduced excretion of uric acid is reported as the key factor of primary hyperuricemia, accounting for approximately 90% of the cases. Urate transporter 1 (URAT1) is a major protein involved in uric acid reabsorption (about 90%). Therefore, URAT1 inhibitors are considered to be a highly effective and promising class of uricosuric agents for treating hyperuricemia. This review summarizes the development of URAT1 inhibitors for the treatment of hyperuricemia, including approved URAT1 inhibitors, URAT1 inhibitors under development in clinical trials, substances with URAT1 inhibitory effects from derivatives and natural products, and conventional drugs with new uses. This review provides new ideas regarding research on URAT1 inhibitors by introducing the structure, properties, and side effects of chemical drugs, as well as the sources and categories of natural drugs. We also discuss new mechanisms of classic drugs, which may provide guidance to many practicing clinicians. The research and discovery of new inhibitors remain in full swing, and tremendous developments are expected in the field.

Impact of Camellia japonica Bee Pollen Polyphenols on Hyperuricemia and Gut Microbiota in Potassium Oxonate-Induced Mice

Camellia japonica bee pollen is one of the major types of bee pollen in China and exhibits antioxidant and anti-inflammatory activities. The aims of our study were to evaluate the effects and the possible mechanism of Camellia japonica bee pollen polyphenols on the treatment of hyperuricemia induced by potassium oxonate (PO). The results showed that Camellia japonica bee pollen ethyl acetate extract (CPE-E) owned abundant phenolic compounds and strong antioxidant capabilities. Administration with CPE-E for two weeks greatly reduced serum uric acid and improved renal function. It inhibited liver xanthine oxidase (XOD) activity and regulated the expression of urate transporter 1 (URAT1), glucose transporter 9 (GLUT9), organic anion transporter 1 (OAT1), organic cation transporter 1 (OCT1) and ATP-binding cassette superfamily gmember 2 (ABCG2) in kidneys. Moreover, CPE-E suppressed the activation of the toll-like receptor 4/myeloid differentiation factor 88/nuclear factor-κB (TLR4/MyD88/NF-κB) signaling pathway and nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome in PO-treated mice, and related inflammatory cytokines were reduced. CPE-E also modulated gut microbiota structure, showing that the abundance of Lactobacillus and Clostridiaceae increased in hyperuicemic mice. This study was conducted to explore the protective effect of CPE-E on hyperuricemia and provide new thoughts for the exploitation of Camellia japonica bee pollen.

From Xanthine Oxidase Inhibition to In Vivo Hypouricemic Effect: An Integrated Overview of In Vitro and In Vivo Studies with Focus on Natural Molecules and Analogues

Hyperuricemia is characterized by elevated uric acid (UA) levels on blood, which can lead to gout, a common pathology. These high UA levels are associated with increased purine ingestion and metabolization and/or its decreased excretion. In this field, xanthine oxidase (XO), by converting hypoxanthine and xanthine to UA, plays an important role in hyperuricemia control. Based on limitations and adverse effects associated with the use of allopurinol and febuxostat, the most known approved drugs with XO inhibitory effect, the search for new molecules with XO activity is growing. However, despite the high number of studies, it was found that the majority of tested products with relevant XO inhibition were left out, and no further pharmacological evaluation was performed. Thus, in the present review, available information published in the past six years concerning isolated molecules with in vitro XO inhibition complemented with cytotoxicity evaluation as well as other relevant studies, including in vivo hypouricemic effect, and pharmacokinetic/pharmacodynamic profile was compiled. Interestingly, the analysis of data collected demonstrated that molecules from natural sources or their mimetics and semisynthetic derivatives constitute the majority of compounds being explored at the moment by means of in vitro and in vivo animal studies. Therefore, several of these molecules can be useful as lead compounds and some of them can even have the potential to be considered in the future clinical candidates for the treatment of hyperuricemia.

DKB114, A Mixture of Chrysanthemum Indicum Linne Flower and Cinnamomum Cassia (L.) J. Presl Bark Extracts, Improves Hyperuricemia through Inhibition of Xanthine Oxidase Activity and Increasing Urine Excretion

Chrysanthemum indicum Linne flower (CF) and Cinnamomum cassia (L.) J. Presl bark (CB) extracts have been used as the main ingredients in several prescriptions to treat the hyperuricemia and gout in traditional medicine. In the present study, we investigated the antihyperuricemic effects of DKB114, a CF, and CB mixture, and the underlying mechanisms in vitro and in vivo. DKB114 markedly reduced serum uric acid levels in normal rats and rats with PO-induced hyperuricemia, while increasing renal uric acid excretion. Furthermore, it inhibited the activity of xanthine oxidase (XOD) in vitro and in the liver in addition to reducing hepatic uric acid production. DKB114 decreased cellular uric acid uptake in oocytes and HEK293 cells expressing human urate transporter (hURAT)1 and decreased the protein expression levels of urate transporters, URAT1, and glucose transporter, GLUT9, associated with the reabsorption of uric acid in the kidney. DKB114 exerts antihyperuricemic effects and uricosuric effects, which are accompanied, partially, by a reduction in the production of uric acid and promotion of uric acid excretion via the inhibition of XOD activity and reabsorption of uric acid. Therefore, it may have potential as a treatment for hyperuricemia and gout.

4-(2-(4-chlorophenyl)-1-((4-chlorophenyl)amino)ethyl)benzene-1, 3-diol is a potential agent for gout therapy as a dual inhibitor of XOD and NLRP3

BACKGOUND

Gout is an inflammatory arthritis characterized by abrupt self-limiting attacks of inflammation caused by precipitation of monosodium urate crystals (MSU) in the joint. Both anti-hyperuricemia and anti-inflammation could be gout therapeutic strategies, whereas ideal drugs for gout treatment are deficient.

PURPOSE

4-(2-(4-chlorophenyl)-1-((4-chlorophenyl)amino)ethyl)benzene-1, 3-diol (CBED) was obtained from a cluster of deoxybenzoins derivatives synthesized by our research group with potent anti-hyperuricemic and anti-inflammatory activities, which was expected to be a dual inhibitor of xanthine oxidase (XOD) and NOD-like receptor protein 3 (NLRP3). This study aimed to investigate effects of CBED on XOD and NLRP3 in vitro, as well as the possible mechanisms by which CBED improved gout in vivo.

METHODS

After molecular docking detection, inhibitory effects of CBED on XOD and NLRP3 were evaluated in vitro. Subsequently, hyperuricemia and acute gouty arthritis animal models were established by potassium oxonate or MSU, respectively. After CBED treatment, serum uric acid levels, synovial interleukin (IL)-1β concentrations, hepatic XOD activities, as well as synovial morphological changes were examined. More importantly, synovial expressions of NLRP3 inflammasome components including NLRP3, apoptosis-associated speck-like protein (ASC) and caspase-1 in rats were analyzed by immunofluorescence and western blot.

RESULTS

In vitro, CBED obviously inhibited XOD activity with an IC₅₀ value of 3.87 µM, moreover, it effectively inhibited MSU-induced NLRP3 inflammasome activation and IL-1β over-production in THP-1 cells. In addition, CBED dose-dependently decreased serum uric acid levels suppressed hepatic XOD activities in oxonate-induced hyperuricemic mice. On the other hand, CBED significantly improved MSU-induced ankle swelling and histopathological damage with elevated IL-1β. In addition, NLRP3 inflammasome activation could be blocked by CBED treatment in rats with acute gouty arthritis. Notbly, CBED exhibited no effects on all these indicators in normal animals, predicting its safety.

CONCLUSIONS

CBED might serve as a dual XOD and NLRP3 inhibitor for treatment of gout.

Development of benzoxazole deoxybenzoin oxime and acyloxylamine derivatives targeting innate immune sensors and xanthine oxidase for treatment of gout

Both the inhibition of inflammatory flares and the treatment of hyperuricemia itself are included in the management of gout. Extending our efforts to development of gout therapy, two series of benzoxazole deoxybenzoin oxime derivatives as inhibitors of innate immune sensors and xanthine oxidase (XOD) were discovered in improving hyperuricemia and acute gouty arthritis. In vitro studies revealed that most compounds not only suppressed XOD activity, but blocked activations of NOD-like receptor (NLRP3) inflammasome and Toll-like receptor 4 (TLR4) signaling pathway. More importantly, (E)-1-(6-methoxybenzo[d]oxazol-2-yl)-2-(4-methoxyphenyl)ethanone oxime (5d) exhibited anti-hyperuricemic and anti-acute gouty arthritis activities through regulating XOD, NLRP3 and TLR4. Compound 5d may serve as a tool compound for further design of anti-gout drugs targeting both innate immune sensors and XOD.

Antacids' side effect hyperuricaemia could be alleviated by long-term aerobic exercise via accelerating ATP turnover rate

Hyperuricemia is the term for an abnormally high serum uric acid level. Many factors contribute to hyperuricemia, however no definite correlation between proton pump inhibitors (PPIs) and hyperuricemia has been reported before. Physical exercise also decreases serum uric acid levels. However, the detailed biochemical-regulatory mechanisms remain unknown. Here we found that adenylate deaminase activities are much higher in hyperuricemia patients than in the healthy people. Therefore, the patients have higher levels of adenosine metabolites hypoxanthine and uric acid. Acid-inhibitory drugs (antacids) significantly increased serum uric acid level and may lead to gout in the hyperuricemia patient. Long-term aerobic exercise significantly increased serum phosphorus and decreased serum ATP and its metabolites, and therefore decreased serum uric acid. Antacids slow down the ATP turnover rate and result in serum uric acid elevation subsequently. While the long-term aerobic exercise decreases serum uric acid levels by accelerating ATP turnover rate. The results imply that long-term aerobic exercise may be a useful strategy to prevent and treat hyperuricaemia.