Various machine learning approaches coupled with molecule simulation in the screening of natural compounds with xanthine oxidase inhibitory activity.

Gout is a common inflammatory arthritis associated with various comorbidities, such as cardiovascular disease and metabolic syndrome. Xanthine oxidase inhibitors (XOIs) have emerged as effective substances to control gout. Much attention has been given to the search for natural XOIs. In this study, a molecular database of natural XOIs was created for modeling purposes. Quantitative structure-activity relationship models were developed by combining various machine learning approaches and three descriptor pools. The models revealed several features of XOIs, including hydrophobicity and steric molecular structures. Experimental results showed the xanthine oxidase (XO) inhibitory activity of predicted compounds. Vanillic acid was identified as a promising new XOI candidate, with an IC50 of 0.593 µg mL-1. The functions of hydrogen bonds and hydrophobic interactions in XO activity inhibition were confirmed by molecular docking. This study fills knowledge gaps pertaining to the discovery of natural XOIs and to the interaction mechanisms between XOIs and XO.

Antihyperuricemic efficacy of Scopoletin-loaded Soluplus micelles in yeast extract/potassium oxonate-induced hyperuricemic mice.

Scopoletin (Sco) has great potential for hyperuricemia therapy. However, the relatively low oral bioavailability of Sco limits its further applications. Soluplus-based Sco micelles (Sco-Ms) were successfully prepared in our previous work. The oral bioavailability of Sco-Ms was increased by 438% compared with free Sco. In this study, we aimed to compare the biodistribution and antihyperuricemic efficacy of Sco and Sco-Ms, and explore their therapeutic mechanisms as well. We studied the tissue biodistribution of Sco and Sco-Ms after they were orally administered to mice. The antihyperuricemic effect and the therapeutic mechanisms of Sco and Sco-Ms were evaluated using yeast extract/potassium oxonate-induced hyperuricemia model in mice. The Sco concentration in each tissue was significantly higher than that of Sco suspension after orally administrating Sco-Ms to mice. Oral delivery of Sco-Ms exhibited significantly stronger hypouricemic efficacy in hyperuricemic mice than Sco. Meanwhile, Sco-Ms showed a better protective effect on mice kidney injury. The hypouricemic efficacy of Sco was due to promoting the excretion of uric acid via modulating the alteration of gene expression levels of renal uric acid transporter (URAT1), glucose transporter (GLUT9), and organic anion transporter 1 (OAT1). Sco-Ms could not only restore the dysregulation of URAT1, GLUT9, and OAT1 more effectively, but also down-regulate the activity of hepatic xanthine oxidase (XOD) to inhibit the production of uric acid. In conclusion, taken together, Sco-Ms represents a potential oral strategy for the treatment of hyperuricemia.

"Kidney Tea" and Its Bioactive Secondary Metabolites for Treatment of Gout.

Clerodendranthus spicatus, popularly known as "kidney tea" in China, is consumed traditionally as a functional food for treatment of renal inflammation, dysuria, and gout. We evaluated the effects of C. spicatus on gout by assessing activities of antihyperuricemia, anti-gouty arthritis, and analgesia in vivo, and the results indicated that the ethyl acetate fraction shows potential activities. Subsequent phytochemical investigation of this fraction led to the isolation of 32 compounds, consisting of 20 diterpenoids (including the new orthosiphonones E and F), 2 triterpenoids, 6 flavonoids, 2 lignanoids, and 2 phenolic acid derivatives. Pharmacological investigation of the pure compounds in the cellular model of hyperuricemia indicated that 12 compounds could promote the excretion of uric acid at 10 µg/mL, and compounds 3, 4, 5, and 21 had better effects than that of benzbromarone, a famous uricosuric drug. Furthermore, compounds 4, 6, 7, 9, 14, 15, 23, 26, and 31 showed significant anti-gouty arthritis activity in monosodium urate (MSU)-induced joint swelling at the dose of 50 mg/kg, while compounds 4, 5, 7, 9, and 26 exhibited significant inhibition of pain induced by acetic acid. Our findings provided scientific justification to support the traditional application of "kidney tea" for treating gout and suggested its good application prospects in the future.

Fluorescence polarization immunoassay of colchicine.

In this study, a fluorescence polarization immunoassay (FPIA) technique was developed to determine colchicine (COL), an alkaloid of noxious plants of the order Liliales that is used in a number of medications to treat gout. An optimal combination of the polyclonal antibody and the antigen labelled with fluorescein isothiocyanate (FITC) was selected. Conditions for the competitive interaction of the antigen in the tested samples and its fluorophore conjugate (COL-FITC) with anti-COL antibodies were optimised, and the analytical characteristics of the assay were determined. The developed FPIA was characterised by a detection limit of 1.8 ng/mL and a detectable analyte concentration range of 4.1-74.3 ng/mL. The duration of the analysis was 10 min. The applicability of the developed FPIA for quality control of ready-made drug formulations and for the estimation of COL content in various matrices (urine, milk), with recovery values ranging from 79 to 108%, was demonstrated.

Colchicine Pharmacokinetics and Mechanism of Action.

Colchicine is a tricyclic, lipid-soluble alkaloid derived from the plant of the Lily family Colchicum autumnale, sometimes called the "autumn crocus". It is predominantly metabolized in the gastrointestinal tract. Two proteins, P-glycoprotein (P-gp) and CYP3A4 seem to play a pivotal role, governing its pharmacokinetic. The commonest side effects are gastrointestinal (nausea, vomiting and particularly dose-related-diarrhea) occurring in 5-10% of patients. Colchicine exerts its unique action mainly through inhibition of microtubule polymerization. Microtubule polymerization affects a variety of cellular processes including maintenance of shape, signaling, division, migration, and cellular transport. Colchicine interferes with several inflammatory pathways including adhesion and recruitment of neutrophils, superoxide production, inflammasome activation, the RhoA/Rho effector kinase (ROCK) pathway and the tumor necrosis factor alpha (TNF-α) -induced nuclear factor κΒ (NF-κΒ) pathway attenuating the inflammatory response. This concise paper attempts to give a brief review of its pharmacokinetic properties and its main mechanisms of action.

Improving Solubility and Oral Bioavailability of Febuxostat by Polymer-Coated Nanomatrix.

Here, the mesoporous silica (Sylysia 350) was selected as mesoporous material, hydroxypropyl methylcellulose (HPMC) was selected as crystallization inhibitor, and febuxostat (FBT) was selected as model drug, respectively. The FBT-Sylysia-HPMC nanomatrix (FBT@SHN) was prepared. The characteristics of FBT@SHN were investigated in vitro and in vivo. Our results indicated that the FBT in FBT@SHN was in amorphous form. The solubility and dissolution of FBT in FBT@SHN were significantly increased. The oral bioavailability of FBT in FBT@SHN was greatly improved 5.8-fold compared with that in FBT suspension. This nanomatrix could be used as a drug delivery platform for improving the oral bioavailability.

Genomic sequencing of uric acid metabolizing and clearing genes in relationship to xanthine oxidase inhibitor dose.

It remains unclear why the dose of xanthine oxidase inhibitors (XOI) allopurinol or febuxostat varies among patients though they reach similar serum uric acid (SUA) goal. We pursued genomic sequencing of XOI metabolism and clearance genes to identify single-nucleotide polymorphisms (SNPs) relate to differences in XOI dose. Subjects with a diagnosis of Gout based on the 1977 American College of Rheumatology Classification Criteria for the disorder, who were on stable doses of a XOI, and who were at their goal SUA level, were enrolled. The primary outcome was relationship between SNPs in any of these genes to XOI dose. The secondary outcome was relationship between SNPs and change in pre- and post-treatment SUA. We enrolled 100 subjects. The average patient age was 68.6 ± 10.6 years old. Over 80% were men and 77% were Caucasian. One SNP was associated with a higher XOI dose: rs75995567 (p = 0.031). Two SNPs were associated with 300 mg daily of allopurinol: rs11678615 (p = 0.022) and rs3731722 on Aldehyde Oxidase (AO) (His1297Arg) (p = 0.001). Two SNPs were associated with a lower dose of allopurinol: rs1884725 (p = 0.033) and rs34650714 (p = 0.006). For the secondary outcome, rs13415401 was the only SNP related to a smaller mean SUA change. Ten SNPs were identified with a larger change in SUA. Though multiple SNPs were identified in the primary and secondary outcomes of this study, rs3731722 is known to alter catalytic function for some aldehyde oxidase substrates.

Hypouricaemic action of mangiferin results from metabolite norathyriol via inhibiting xanthine oxidase activity.

Context Mangiferin has been reported to possess a potential hypouricaemic effect. However, the pharmacokinetic studies in rats showed that its oral bioavailability was only 1.2%, suggesting that mangiferin metabolites might exert the action. Objective The hypouricaemic effect and the xanthine oxidase inhibition of mangiferin and norathyriol, a mangiferin metabolite, were investigated. Inhibition of norathyriol analogues (compounds 3-9) toward xanthine oxidase was also evaluated. Materials and methods For a dose-dependent study, mangiferin (1.5-6.0 mg/kg) and norathyriol (0.92-3.7 mg/kg) were administered intragastrically to mice twice daily for five times. For a time-course study, mice received mangiferin and norathyriol both at a single dose of 7.1 µmol/kg. In vitro, inhibition of test compounds (2.4-2.4 mM) against xanthine oxidase activity was evaluated by the spectrophotometrical method. The inhibition type was identified from Lineweaver-Burk plots. Results Norathyriol (0.92, 1.85 and 3.7 mg/kg) dose dependently decreased the serum urate levels by 27.0, 33.6 and 37.4%, respectively. The action was more potent than that of mangiferin at the low dose, but was equivalent at the higher doses. Additionally, the hypouricaemic action of them exhibited a time dependence. In vitro, norathyriol markedly inhibited the xanthine oxidase activities, with the IC50 value of 44.6 µM, but mangiferin did not. The kinetic studies showed that norathyriol was an uncompetitive inhibitor by Lineweaver-Burk plots. The structure-activity relationships exhibited that three hydroxyl groups in norathyriol at the C-1, C-3 and C-6 positions were essential for maintaining xanthine oxidase inhibition. Discussion and conclusion Norathyriol was responsible for the hypouricaemic effect of mangiferin via inhibiting xanthine oxidase activity.

Febuxostat: a review of its use in the treatment of hyperuricaemia in patients with gout.

Febuxostat (Adenuric(®), Uloric(®), Feburic(®)) is an orally-active, potent, non-purine, selective xanthine oxidase inhibitor. In the EU, it is indicated in adults for the treatment of chronic hyperuricaemia in conditions where urate deposition has already occurred. Unlike allopurinol, the prototypical xanthine oxidase inhibitor that is the cornerstone therapy for chronic gout, febuxostat does not require dosage adjustment in patients with mild or moderate renal impairment. In randomized, double-blind studies, 6-12 months' treatment with febuxostat at dosages approved for use in the EU (80 and 120 mg/day) was significantly more effective in lowering serum uric acid (sUA) levels in patients with hyperuricaemia and gout than allopurinol at dosages commonly prescribed in practice (100-300 mg/day); febuxostat demonstrated greater urate-lowering efficacy than allopurinol in patients with renal impairment. In open-label extension studies, 3-5 years' treatment with febuxostat maintained a target sUA level of <6.0 mg/dL in most patients; sustained reduction in sUA level was associated with near elimination of gout flares and improved tophus status. Febuxostat therapy was generally well tolerated during clinical development; frequently reported adverse events included liver function abnormalities, diarrhoea and rash. Cardiovascular (CV) events were the most common serious adverse events; the comparative safety of febuxostat and allopurinol is being examined further in large, ongoing trials in patients with gout who already have, or are at risk of developing, CV disease. In conclusion, febuxostat is a well established antihyperuricaemic agent that provides an effective alternative to allopurinol for the management of chronic gout.

Genome-wide association study identifies ABCG2 (BCRP) as an allopurinol transporter and a determinant of drug response.

The first-line treatment of hyperuricemia, which causes gout, is allopurinol. The allopurinol response is highly variable, with many users failing to achieve target serum uric acid (SUA) levels. No genome-wide association study (GWAS) has examined the genetic factors affecting allopurinol effectiveness. Using 2,027 subjects in Kaiser Permanente's Genetic Epidemiology Research on Adult Health and Aging (GERA) Cohort, we conducted a GWAS of allopurinol-related SUA reduction, first in the largest ethnic group, non-Hispanic white (NHW) subjects, and then in a stratified transethnic meta-analysis. ABCG2, encoding the efflux pump BCRP, was associated with SUA reduction in NHW subjects (P = 2 × 10(-8) ), and a missense allele (rs2231142) was associated with a reduced response (P = 3 × 10(-7) ) in the meta-analysis. Isotopic uptake studies in cells demonstrated that BCRP transports allopurinol and genetic variants in ABCG2 affect this transport. Collectively, this first GWAS of allopurinol response demonstrates that ABCG2 is a key determinant of response to the drug.

Colchicine: old and new.

Although colchicine has been a focus of research, debate, and controversy for thousands of years, the US Food and Drug Administration just approved it in 2009. Over the past decade, advances in the knowledge of colchicine pharmacology, drug safety, and mechanisms of action have led to changes in colchicine dosing and to potential new uses for this very old drug. In this review, we discuss the pharmacologic properties of colchicine and summarize what is currently known about its mechanisms of action. We then discuss and update the use of colchicine in a variety of illnesses, including rheumatic and, most recently, cardiovascular diseases.

PEGylation enhancement of pH stability of uricase via inhibitive tetramer dissociation.

OBJECTIVES: Previously, PEGylated uricase was demonstrated to maintain catalytic activity at pH 5.8, the isoelectric point of uricase, where native uricase ceases to function. To find out whether PEGylation could enhance pH stability of uricase, the enzyme activity to pH curve was completely characterized. METHODS: Complete characterization of the enzyme activity to pH curve, indicating an inverted bell-shaped relationship not previously documented, is presented. PEGylation enhancement of uricase stability at a pH lower than that commonly found in the liver, can be explored by dynamic dissociation of uricase using ultrafiltration and size-exclusion chromatography. KEY FINDINGS: The results suggest the role of PEGylation in enhanced pH stability is via inhibition of subunit disintegration. The mechanism of this effect is characterized by the wrapping of PEG chains around uricase, providing a flexible shell preventing subunit disintegration. The presence of notable PEGylation-induced changes in uricase supports this mechanism and include improved enzyme-substrate affinity and elevated thermal stability. CONCLUSIONS: Characterization of PEGylated uricase provides a basis for the rational design of therapeutic PEGylated proteins.

Severe colchicine intoxication in a renal transplant recipient on cyclosporine.

Using colchicine to treat an acute gout crisis in an organ transplant recipient (TR) on cyclosporine (CsA) may result in life-threatening intoxication. We report the case of a 59-year-old kidney transplant recipient on CsA who was treated with colchicine for acute gout crisis. Seven days later, he developed rhabdomyolysis with progressive quadriparesis, hematologic toxicity and acute renal failure. CsA inhibits P-glycoprotein resulting in decreased hepatic metabolism and renal excretion of colchicine. Colchicine and CsA withdrawal as well as appropriate supportive treatments were effective to manage all of these complications.

Study of impurity carryover and impurity profile in Febuxostat drug substance by LC-MS/MS technique.

Febuxostat is used in the treatment of hyperuricemia and gout. Several impurities were detected in Febuxostat drug substance. Impurities were identified with the help of LC-MS/MS and were characterized after synthesis by IR and NMR. Reverse phase gradient system was used with Kromasil C18, 150mm×4.6mm, 5µm particle size column for the separation of impurities. Q-TOF mass spectrometer with electrospray ionization (ESI) source was used and operated in ESI positive mode, which gives exact mass up to four decimal places and fragmentation with mass accuracy, it is useful for the identification of impurities. Four impurities were identified as amide, sec-butyl, des-cyano and des-acid in Febuxostat drug analog. These impurities were further confirmed by NMR and FT-IR spectral data.

Effects of borneol on the intestinal transport and absorption of two P-glycoprotein substrates in rats.

As the most prevalent route of delivery, oral administration has the challenge of potentially low bioavailability in part because P-glycoprotein (P-gp) in the intestinal tract affects absorption. Therefore, absorption enhancers or P-gp inhibitors are strategies to solve this problem. The aim of the present study was to investigate the effects of borneol on transportation of colchicine and rhodamine123, two P-gp substrates, in rats. In vitro transportation was assessed with a diffusion chamber system with isolated rat intestines. Different concentrations of borneol (10, 40 and 80 µg/mL) were prepared in solutions with two P-gp substrates compared with blank solutions. The in vivo effects on colchicine were assessed by a pharmacokinetic study. Borneol enhanced the absorptive transport of two P-gp substrates, which was relevant to the concentration. A pharmacokinetic study showed that in the presence of borneol, a significant increase in C(max) and AUC(0→8) of colchicine occurred when compared to colchicine alone. The study showed that borneol affected two P-gp substrates in the intestine, possibly by inhibiting the effects of P-gp and enhancing intestinal absorption of drugs. Therefore, borneol could be developed as a P-gp inhibitor and absorptive enhancer.

Relationship between serum urate and plasma oxypurinol in the management of gout: determination of minimum plasma oxypurinol concentration to achieve a target serum urate level.

The treatment of gout requires a lowering of serum urate (SU) levels, and allopurinol is the drug that is most commonly used for this purpose. The objectives of this study were to define the relationships between allopurinol dose on the one hand and plasma oxypurinol, renal function, and SU levels on the other and to determine the minimum plasma oxypurinol concentration that would result in a target level of <6 mg/dl (0.36 mmol/l) of SU. For this purpose, 82 patients who had been receiving allopurinol for at least 1 month were recruited. Patients with SU <6 mg/dl were followed up quarterly for 12 months. In patients with SU ≥6 mg/dl, the dose of allopurinol was increased to bring the level of SU to <6 mg/dl. These patients were followed up once a month until the SU level remained at <6 mg/dl for 3 consecutive months; thereafter they were seen quarterly. SU, creatinine, and plasma oxypurinol were measured 6-9 hours after administration of the allopurinol dose. There were significant inverse correlations between creatinine clearance (CrCl) and plasma oxypurinol (P = 0.002), between allopurinol dose and SU (P < 0.0001) and between plasma oxypurinol and SU (P < 0.0001). Using receiver operating characteristic analysis, the target SU of <6 mg/dl was achieved in 75% of serum samples with plasma oxypurinol levels of >100 µmol/l (15.2 mg/l). Increasing the allopurinol dose resulted in increased plasma oxypurinol and reduced SU concentrations. Plasma oxypurinol concentrations >100 µmol/l were required to achieve SU <6 mg/dl.

Allopurinol-induced DRESS syndrome.

Hyperuricemia is present in approximately 5% of the population, the vast majority of whom are asymptomatic and at no clinical risk. Complications, including renal calculi, uric acid nephropathy and gout, occur in a small proportion of patients. Allopurinol, an analog of hypoxanthine, has been widely used in clinical practice for over 30 years for the treatment of hyperuricemia and gout. Two percent of patients taking this medication develop a mild exanthema. A syndrome characterized by exfoliative dermatitis, hepatitis, interstitial nephritis and eosinophilia has been described previously. Termed allopurinol hypersensitivity syndrome, its etiology is related to the accumulation of one of the allopurinol metabolites, oxypurinol; clearance of oxypurinol is decreased in the setting of renal insufficiency and the use of thiazide diuretics. The term DRESS syndrome (Drug Rash with Eosinophilia and Systemic Symptoms) was recently introduced to describe a disorder associated with various drugs or viral infections and characterized by similar features. The pathophysiology of allopurinol-induced hypersensitivity, clinical presentation and treatment are reviewed.

Resveratrol analog (Z)-3,5,4'-trimethoxystilbene is a potent anti-mitotic drug inhibiting tubulin polymerization.

Resveratrol (3,5,4'-trihydroxystilbene) a natural polyphenol present in medicinal plants, grapes and wines, has potent chemopreventive properties on intestinal carcinogenesis. A methylated derivative (Z-3,5,4'-trimethoxystilbene: R3) was synthesized. R3 at 0.3 microM exerted a 80% growth inhibition of human colon cancer Caco-2 cells and arrested growth completely at 0.4 microM (R3 was 100-fold more active than resveratrol). The cis conformation of R3 was also 100-fold more potent than the trans isomer. R3 (0.3 microM) caused cell cycle arrest at the G2/M phase transition. The drug inhibited tubulin polymerization in a dose-dependent manner (IC50=4 microM), and it reduced also by 2-fold ornithine decarboxylase and s-adenosylmethionine decarboxylase activities. This caused the depletion of the polyamines, putrescine and spermidine, which are growth factors for cancer cells. R3 inhibited partially colchicine binding to its binding site on tubulin, indicating that R3 either partially overlaps with colchicine binding or that R3 binds to a specific site of tubulin that is not identical with the colchicine binding site modifying colchicine binding by allosteric influences. The resveratrol derivative (Z)-3,5,4'-trimethoxystilbene (R3) is an interesting anti-mitotic drug that exerts cytotoxic effects by depleting the intracellular pool of polyamines and by altering microtubule polymerization. Such a drug may be useful for the treatment of neoplastic diseases.

[Suicidal attempt with colchicine]. / Intento autolítico con colchicina.

Colchicine is an alkaloid that has been successfully used for a long time in the treatment of acute gout episodes. It's efficacy lies in its inhibition of inflammation cell migration and in the action of specific cytokines, as well as of the production of lactic acid and deposition of uric acid in affected tissues. Colchicine toxicity is rare but may entail highly negative consequences for health unless a rapid gastric decontamination with stomach lavage and active carbon is carried out, and adequate support measures are taken as wellas appropriate hydration and electrolyte replacement. We present the case of a patient who was admitted to hospital after ingesting colchicine with suicidal intention. Colchicine inhibits cell division, which explains its distinct toxicity stages. The lack of proportion existing between ingested dose and clinical impact may result from concomitant treatment with other drugs or from peculiarities in its metabolism.

Synthesis and structure-activity relationships of 1-phenylpyrazoles as xanthine oxidase inhibitors.

A series of 1-phenylpyrazoles was evaluated for inhibitory activity against xanthine oxidase in vitro. Of the compounds prepared, 1-(3-cyano-4-neopentyloxyphenyl)pyrazole-4-carboxylic acid (Y-700) had the most potent enzyme inhibition and displayed longer-lasting hypouricemic action than did allopurinol in a rat model of hyperuricemia induced by the uricase inhibitor potassium oxonate.