BACKGROUND: Over the past two decades, the global incidence of gout has markedly increased, affecting people worldwide. Considering the side effects of xanthine oxidase (XO) inhibitor drugs (e.g. allopurinol and febuxostat) used in the treatment of hyperuricemia and gout, the potential application of phytochemicals has been widely studied. In addition, XO also takes part in the elimination of certain drugs, including 6-mercaptopurine. In the current explorative study, we aimed to examine the potential effects of tea catechins, resveratrol, silymarin flavonolignans and some of their conjugated metabolites on XO-catalyzed xanthine and 6-mercaptopurine oxidation, applying in vitro assays and modeling studies. RESULTS: Catechins, resveratrol and resveratrol conjugates exerted no or only weak inhibitory effects on XO. Silybin A, silybin B and isosilybin A were weak, silychristin was a moderate, while 2,3-dehydrosilychristin was a potent inhibitor of the enzyme. Sulfate metabolites of silybin A, silybin B and isosilybin A were considerably stronger inhibitors compared to the parent flavonolignans, and the sulfation of 2,3-dehydrosilychristin slightly increased its inhibitory potency. Silychristin was the sole flavonolignan tested, where sulfate conjugation decreased its inhibitory effect. CONCLUSION: 2,3-Dehydrosilychristin seems to be a promising candidate for examining its in vivo antihyperuricemic effects, because both the parent compound and its sulfate conjugate are highly potent inhibitors of XO. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
- MeSH
- Enzyme Inhibitors * chemistry pharmacology MeSH
- Catalysis MeSH
- Catechin * chemistry analogs & derivatives pharmacology MeSH
- Humans MeSH
- Mercaptopurine * chemistry pharmacology metabolism MeSH
- Oxidation-Reduction * MeSH
- Resveratrol * chemistry pharmacology MeSH
- Silymarin * pharmacology chemistry MeSH
- Xanthine chemistry metabolism pharmacology MeSH
- Xanthine Oxidase * antagonists & inhibitors metabolism chemistry MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Metabolism of purine bases remains poorly understood in the pathogenic bacterium Mycobacterium tuberculosis and closely related, nonpathogenic Mycobacterium smegmatis (Msm). To gain insight into the purine metabolism in mycobacteria, we tested uptake of purine bases with a ΔpurF Msm mutant with an inactive purine de novo biosynthesis pathway and confirmed that hypoxanthine and guanine, but not xanthine, can serve as nucleotide precursors for recycling in the salvage pathway. Further, we focused on purine catabolism in wild-type (wt) Msm. We found that only xanthine and guanine could serve as a sole nitrogen source for wt Msm. These data confirm that Msm catabolism of purines is directed mainly via oxidative guanine to xanthine interconversion and not through metabolic conversion of hypoxanthine to xanthine. Our data represent the first experimental evidence confirming the use of 8-oxo-purines as a nitrogen source by Msm.
- MeSH
- Mycobacterium Infections, Nontuberculous metabolism microbiology MeSH
- Guanine metabolism MeSH
- Humans MeSH
- Mycobacterium smegmatis isolation & purification metabolism MeSH
- Purines metabolism MeSH
- Xanthine metabolism MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Quercetin is an abundant flavonoid in nature and is used in several dietary supplements. Although quercetin is extensively metabolized by human enzymes and the colonic microflora, we have only few data regarding the pharmacokinetic interactions of its metabolites. Therefore, we investigated the interaction of human and microbial metabolites of quercetin with the xanthine oxidase enzyme. Inhibitory effects of five conjugates and 23 microbial metabolites were examined with 6-mercaptopurine and xanthine substrates (both at 5 μM), employing allopurinol as a positive control. Quercetin-3'-sulfate, isorhamnetin, tamarixetin, and pyrogallol proved to be strong inhibitors of xanthine oxidase. Sulfate and methyl conjugates were similarly strong inhibitors of both 6-mercaptopurine and xanthine oxidations (IC50 = 0.2-0.7 μM); however, pyrogallol inhibited xanthine oxidation (IC50 = 1.8 μM) with higher potency vs. 6-MP oxidation (IC50 = 10.1 μM). Sulfate and methyl conjugates were approximately ten-fold stronger inhibitors (IC50 = 0.2-0.6 μM) of 6-mercaptopurine oxidation than allopurinol (IC50 = 7.0 μM), and induced more potent inhibition compared to quercetin (IC50 = 1.4 μM). These observations highlight that some quercetin metabolites can exert similar or even a stronger inhibitory effect on xanthine oxidase than the parent compound, which may lead to the development of quercetin-drug interactions (e.g., with 6-mercaptopurin or azathioprine).
- MeSH
- Allopurinol chemistry pharmacology MeSH
- Enzyme Inhibitors chemistry metabolism pharmacology MeSH
- Catalysis MeSH
- Humans MeSH
- Molecular Conformation MeSH
- Models, Molecular MeSH
- Molecular Structure MeSH
- Oxidation-Reduction MeSH
- Quercetin analogs & derivatives chemistry metabolism pharmacology MeSH
- Protein Binding MeSH
- Dose-Response Relationship, Drug MeSH
- Structure-Activity Relationship MeSH
- Xanthine chemistry pharmacology MeSH
- Xanthine Oxidase antagonists & inhibitors MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Uric acid (UA) levels are associated with many diseases including those related to lifestyle. The aim of this study was to evaluate the influence of clinical and anthropometric parameters on UA and xanthine (X) levels during pregnancy and postpartum in women with physiological pregnancy and pregnancy complicated by gestational diabetes mellitus (GDM), and to evaluate their impact on adverse perinatal outcomes. A total of 143 participants were included. Analyte levels were determined by HPLC with ultraviolet detection (HPLC-UV). Several single-nucleotide polymorphisms (SNPs) in UA transporters were genotyped using commercial assays. UA levels were higher within GDM women with pre-gestational obesity, those in high-risk groups, and those who required insulin during pregnancy. X levels were higher in the GDM group during pregnancy and also postpartum. Positive correlations between UA and X levels with body mass index (BMI) and glycemia levels were found. Gestational age at delivery was negatively correlated with UA and X levels postpartum. Postpartum X levels were significantly higher in women who underwent caesarean sections. Our data support a possible link between increased UA levels and a high-risk GDM subtype. UA levels were higher among women whose glucose tolerance was severely disturbed. Mid-gestational UA and X levels were not linked to adverse perinatal outcomes.
- MeSH
- Biomarkers blood MeSH
- Adult MeSH
- Diabetes, Gestational blood epidemiology MeSH
- Uric Acid blood MeSH
- Humans MeSH
- Case-Control Studies MeSH
- Pregnancy MeSH
- Pregnancy Outcome epidemiology MeSH
- Xanthine blood MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Pregnancy MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
BACKGROUND: The aim of our study was to identify the genetic background of thiopurine-induced toxicity in a patient with a wild-type thiopurine methyltransferase genotype and activity. A 38-year-old Caucasian woman presented with cutaneous necrotizing vasculitis pancytopenia one month after starting azathioprine therapy. METHODS: During a routine biochemical follow-up of the patient, undetectable serum uric acid (<10 μl) was observed. A high performance liquid chromatography analysis of urinary purines revealed increased levels of xanthine (137 mmol/mol creatinine). The suspected diagnosis of hereditary xanthinuria, a rare autosomal recessive disorder of the last two steps of purine metabolism, was confirmed by sequence analysis. RESULTS: An analysis of XDH/XO and AOX1 revealed common polymorphisms, while analysis of the MOCOS gene identified a rare homozygous variant c.362C > T. Dysfunction of this variant was confirmed by significantly decreased xanthine dehydrogenase/oxidase activity in the patient's plasma (<2% of control mean activity). CONCLUSIONS: We present a biochemical, enzymatic, and molecular genetic case study suggesting an important association between a hitherto undescribed dysfunction variant in the MOCOS gene and thiopurine-induced toxicity. The identified variant c.362C > T results in slower thiopurine metabolism caused by inhibition of 6-mercaptopurine oxidation (catabolism) to 6-thioxanthine and 6-thiouric acid, which increases the formation of the nucleotide 6-thioguanine, which is toxic. This is the first clinical case to identify the crucial role of the MOCOS gene in thiopurine intolerance and confirm the impact of genetic variability of purine enzymes on different therapeutic outcomes in patients undergoing thiopurine treatment.
- MeSH
- Aldehyde Oxidase deficiency genetics MeSH
- Adult MeSH
- Uric Acid blood MeSH
- Humans MeSH
- Mercaptopurine adverse effects analogs & derivatives metabolism MeSH
- Methyltransferases genetics MeSH
- Polymorphism, Genetic genetics MeSH
- Purine-Pyrimidine Metabolism, Inborn Errors genetics MeSH
- Sulfurtransferases genetics MeSH
- Xanthine urine MeSH
- Xanthine Dehydrogenase deficiency genetics MeSH
- Xanthine Oxidase genetics MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Case Reports MeSH
- Research Support, Non-U.S. Gov't MeSH
Hereditary xanthinuria (type I) is caused by an inherited deficiency of the xanthine oxidorectase (XDH/XO), and is characterized by very low concentration of uric acid in blood and urine and high concentration of urinary xanthine, leading to urolithiasis. Type II results from a combined deficiency of XDH/XO and aldehyde oxidase. Patients present with hematuria, renal colic, urolithiasis or even acute renal failure. Clinical symptoms are the same for both types. In a third type, clinically distinct, sulfite oxidase activity is missing as well as XDH/XO and aldehyde oxidase. The prevalence is not known, but about 150 cases have been described so far. Hypouricemia is sometimes overlooked, that´s why we have set up the diagnostic flowchart. This consists of a) evaluation of uric acid concentrations in serum and urine with exclusion of primary renal hypouricemia, b) estimation of urinary xanthine, c) allopurinol loading test, which enables to distinguish type I and II; and finally assay of xanthine oxidoreductase activity in plasma with molecular genetic analysis. Following this diagnostic procedure we were able to find first patients with hereditary xanthinuria in our Czech population. We have detected nine cases, which is one of the largest group worldwide. Four patients were asymptomatic. All had profound hypouricemia, which was the first sign and led to referral to our department. Urinary concentrations of xanthine were in the range of 170-598 mmol/mol creatinine (normal < 30 mmol/mol creatinine). Hereditary xanthinuria is still unrecognized disorder and subjects with unexplained hypouricemia need detailed purine metabolic investigation.
- MeSH
- Aldehyde Oxidase blood deficiency urine MeSH
- Allopurinol metabolism MeSH
- Diagnosis, Differential MeSH
- Child MeSH
- Adult MeSH
- Uric Acid blood urine MeSH
- Humans MeSH
- Urinary Calculi blood epidemiology urine MeSH
- Purine-Pyrimidine Metabolism, Inborn Errors blood diagnosis epidemiology urine MeSH
- Child, Preschool MeSH
- Purines metabolism MeSH
- Metabolism, Inborn Errors blood diagnosis epidemiology urine MeSH
- Renal Tubular Transport, Inborn Errors blood epidemiology urine MeSH
- Xanthine blood urine MeSH
- Xanthine Dehydrogenase blood deficiency metabolism urine MeSH
- Check Tag
- Child MeSH
- Adult MeSH
- Humans MeSH
- Child, Preschool MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Czech Republic MeSH
BACKGROUND: X-linked hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency in an inherited disorder of purine metabolism is usually associated with the clinical manifestations of hyperuricemia. A variable spectrum of neurological involvement occurs predominantly in males. Females are usually asymptomatic. Carrier status cannot be confirmed by biochemical and enzymatic methods reliably. METHODS: We studied clinical, biochemical and molecular genetic characteristics of Czech families with hyperuricemia and HPRT deficiency. We analyzed age at diagnosis, clinical symptoms, uricemia, urinary hypoxanthine and xanthine, HPRT activity in erythrocytes, mutation in the HPRT1 gene, X-inactivation, and major urate transporters. RESULTS: A mutation in the HPRT1 gene in family A was confirmed in one boy and four females. Three females with hyperuricemia had normal excretion of purine. One female was normouricemic. An 8-month-old boy with neurological symptoms showed hyperuricemia, increased excretion of urinary hypoxanthine and xanthine and a very low HPRT activity in erythrocytes. We have found three other unrelated female carriers with hyperuricemia and normal excretion of hypoxanthine and xanthine among other families with HPRT deficiency. CONCLUSIONS: HPRT deficiency needs to be considered in females with hyperuricemia with normal excretion of purine metabolites. Familiar hyperuricemia and/or nonfamiliar gout should always be further investigated, especially in children.
- MeSH
- Diagnosis, Differential MeSH
- Child MeSH
- Gout etiology genetics MeSH
- Adult MeSH
- Heterozygote MeSH
- Hyperuricemia diagnosis etiology MeSH
- Hypoxanthine urine MeSH
- Hypoxanthine Phosphoribosyltransferase deficiency genetics MeSH
- Humans MeSH
- Mutation * MeSH
- Infant, Newborn MeSH
- Pedigree MeSH
- Xanthine urine MeSH
- Check Tag
- Child MeSH
- Adult MeSH
- Humans MeSH
- Male MeSH
- Infant, Newborn MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Case Reports MeSH
- Research Support, Non-U.S. Gov't MeSH
UNLABELLED: FerB is a flavin mononucleotide (FMN)-containing NAD(P)H: acceptor oxidoreductase of unknown function that is found in the cytoplasm of the bacterium Paracoccus denitrificans. Based on measurements of fluorescence anisotropy, we report here that recombinant FerB readily binds to artificial membrane vesicles. If ubiquinone is incorporated into the membrane, FerB catalyzes its conversion to ubihydroquinone, which may be followed fluorimetrically (with ferricyanide and pyranine entrapped inside the liposomes) or by HPLC. FerB also reduces exogenously added superoxide or superoxide that has been enzymatically generated by the xanthine/xanthine oxidase system or P. denitrificans membrane vesicles. In whole cells, deficiency of FerB increases sensitivity to methyl viologen, as indicated by a lower growth rate and increased production of reactive aldehydes (by-products of lipid oxidation). Taken together, these data support a role for FerB in protection of cells against lipid peroxidation-mediated oxidative stress, and suggest that FerB is a prokaryotic counterpart of mammalian NAD(P)H: quinone oxidoreductase 1.
- MeSH
- Antioxidants chemistry metabolism MeSH
- Flavoproteins chemistry metabolism MeSH
- Kinetics MeSH
- Membrane Proteins chemistry metabolism MeSH
- Oxidation-Reduction MeSH
- Oxidative Stress * MeSH
- Paracoccus denitrificans enzymology MeSH
- Superoxides metabolism MeSH
- Ubiquinone metabolism MeSH
- Xanthine metabolism MeSH
- Xanthine Oxidase metabolism MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The protective influence of seminal plasma and the antioxidants catalase (CAT), superoxide dismutase (SOD), and glutathione (GTH) on quality parameters, oxidative stress indices, and antioxidant activity was studied in common carp (Cyprinus carpio) spermatozoa exposed to the xanthine-xanthine oxidase (X-XO) system. Fish spermatozoa were incubated for 5 and 20 min at 4 °C with X-XO concentrations of 1 mM X-0.1 U/mL, 0.6 mM X-0.05 U/mL, 0.3 mM X-0.025 U/mL, and 0.1 mM X-0.0125 U/mL. A dose-dependent reduction in spermatozoa motility and velocity was observed at concentrations of 0.1 mM X-0.0125 U/mL to 1 mM X-0.1 U/mL XO. Increase in spermatozoa motility parameters was recorded following treatment with antioxidants and seminal plasma. The level of the oxidative stress indices lipid peroxidation (LPO) and carbonyl derivatives of proteins (CP) was significantly reduced after addition of CAT, SOD, or GTH along with seminal plasma. Significant differences in SOD, glutathione reductase, and glutathione peroxidase activity were seen in spermatozoa incubated with, compared to that without, seminal plasma at all studied X-XO concentrations. The data demonstrated that CAT, SOD, or GTH in combination with SP can reduce reactive oxygen species stress in fish spermatozoa and improve spermatozoa quality.
- MeSH
- Antioxidants metabolism MeSH
- Glutathione Reductase MeSH
- Carps physiology MeSH
- Sperm Motility physiology MeSH
- Oxidative Stress physiology MeSH
- Semen physiology MeSH
- Spermatozoa physiology MeSH
- Xanthine metabolism MeSH
- Xanthine Oxidase metabolism MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The behavior of monomers and dimers of methylated xanthine derivatives in their excited states is investigated by means of the ADC(2), CASSCF, and CASPT2 methods. The results of the calculations of stationary points in the ground and excited states, minima on the S0/S1 crossing seams and the relaxation pathways are used to provide the interpretation of experimental observations of the monomer xanthine derivatives. The effect of dimerization on the excited state properties is studied for various relative orientations of the monomers in the dimer complexes in comparison with the relevant monomer species. A significant stabilization in the excited state minima of dimers is observed. These can act as trapping sites. Various types of conical intersections, with both localized and delocalized characters of wavefunctions, have been found, mainly energetically above the lowest bright excited state in the FC region. In addition, structures with the bonds formed between the two monomers were also found on the crossing seams. The possibility of ultrafast relaxation via these conical intersections is discussed.
