Assessment of the relationship between serum uric acid levels and liver enzymes activity in Bangladeshi adults.

Serum uric acid (SUA) level has been suggested to be associated with cardiovascular disease, diabetes and metabolic syndrome. However, little is known about the relationship between SUA and liver enzymes activity in the general population. The present study aimed to assess the relationship between SUA and serum liver enzymes in an adult population in Bangladesh. In this cross-sectional study, a total of 410 blood samples were collected from apparently healthy adults aged > 18 years. SUA, liver enzymes, lipid profile and other biochemical markers were measured in the collected samples by using standard methods. Multinomial logistic regression model was used to assess the relationship between SUA and elevated levels of liver enzymes among the participants. Overall, the prevalence of hyperuricemia was 30.1% with 32.2% in male and 18.6% in female participants. About 33% of the participants had at least one or more elevated levels of liver enzymes. The mean level of SUA was significantly higher in males (389.3 ± 96.9 µmol/L) than in the female (290.4 ± 89.8 µmol/L) subjects (p < 0.001). There was a significant difference in the mean levels of serum ALT and GGT between the male (34.5 ± 16.0 U/L and 26.7 ± 19.5 U/L, respectively) and female (25.0 ± 13.0 U/L and 19.5 ± 13.2 U/L, respectively) participants (p < 0.001 and p < 0.01, respectively). An increasing trend was observed in the mean levels of serum ALT and GGT across the SUA quartile groups (p < 0.001 and p < 0.01, respectively). SUA showed a positive and significant correlation with serum ALT (p < 0.001) and GGT (p < 0.01). In further statistical analysis after adjustment for potential confounders, SUA showed an independent and significant association with serum ALT and GGT in all regression models. In conclusion, SUA was strongly associated with serum levels of ALT and GGT after adjustment for potential confounders. More prospective studies are needed to clarify the complex relationship between SUA and liver enzymes in the general population.

Xanthine oxidase inhibitory peptides derived from tuna protein: virtual screening, inhibitory activity, and molecular mechanisms.

BACKGROUND: There has been growing interest in the use of xanthine oxidase (XO) as a therapeutic agent to prevent gout and hyperuricemia. In the present study, XO inhibitory peptides were identified from tuna protein by virtual screening, and molecular docking was used to elicit the interaction mechanism between XO and peptides. RESULTS: A novel tetrapeptide, EEAK, exhibited high XO inhibitory activity with an IC50 of 173.00 ± 0.06 µM. Molecular docking analysis revealed that EEAK bound with the pivotal residues of XO's active sites (i.e., Glu802, Arg880, Glu1261) through two conventional hydrogen bond interactions, two attractive charge interactions, and one salt bridge. EEAK could also bind with the residues Phe649, Leu648, Lys771, Ser876, Phe914, and Thr1010 of XO. CONCLUSION: This study suggested that conventional hydrogen bond interactions and electrostatic interactions play an important role in XO inhibition. The novel XO inhibitory peptide EEAK from tuna protein could be used as potential candidate for controlling gout and hyperuricemia. © 2020 Society of Chemical Industry.

Anti-Hyperuricemic Effects of Astaxanthin by Regulating Xanthine Oxidase, Adenosine Deaminase and Urate Transporters in Rats.

This study was designed to investigate the effects and underlying mechanisms of Astaxanthin (AST) on high-fructose-induced hyperuricemia (HUA) from the perspectives of the uric acid (UA) synthesis and excretion in rat models. Following six weeks of a 10% fructose diet, the level of serum UA effectively decreased in the AST groups as compared to the model group. The enzymatic activities of xanthine oxidase (XOD) and adenosine deaminase (ADA) were significantly inhibited, and the mRNA expression levels of XOD and ADA significantly decreased after the AST administration. These results suggested that the AST reduced UA synthesis by inhibiting the mRNA expressions and enzyme activities of XOD and ADA, thereby contributing to HUA improvement. On the hand, the relative expressions of the mRNA and protein of kidney reabsorption transport proteins (GLUT9 and URAT1) were significantly down-regulated by AST, while that of the kidney secretion proteins (OAT1, OAT3 and ABCG2) were significantly up-regulated by AST. These results indicated that the AST promoted UA excretion by regulating the urate transport proteins, and thus alleviated HUA. This study suggested that the AST could serve as an effective alternative to traditional medicinal drugs for the prevention of fructose-induced HUA.

Xanthine oxidase inhibitors: patent landscape and clinical development (2015-2020).

INTRODUCTION: Xanthine oxidase (XO) is a molybdoflavoprotein that catalyzes the oxidative hydroxylation of purines to produce uric acid and reactive oxygen species. These reaction products can cause severe disease conditions like hyperuricemia which makes XO enzyme, an important therapeutic target in diseases like gout. AREAS COVERED: Herein, patents from 2015 to 2020 are discussed to disclose the synthetic, as well as natural compounds, claimed to inhibit XO enzyme. The article also presents the last five years of clinical progression of some prominent XO inhibitors. EXPERT OPINION: There has been considerable creativity in the discovery of novel XO inhibitors in the last five years that falls outside the purine scaffold. Along with the evaluation of synthetic compounds, natural compounds can also be an area of interest for the discovery of novel XO inhibitors. Based on the patent literature of last five years, we can expect a burst of novel alternate compounds in the near future which could have the ability to reduce the uric acid level, by inhibiting XO enzyme in patients, which at the moment are striving hard to fight against the dreadful disease condition like gout.

Hereditary hemochromatosis disrupts uric acid homeostasis and causes hyperuricemia via altered expression/activity of xanthine oxidase and ABCG2.

Hereditary hemochromatosis (HH) is mostly caused by mutations in the iron-regulatory gene HFE. The disease is associated with iron overload, resulting in liver cirrhosis/cancer, cardiomegaly, kidney dysfunction, diabetes, and arthritis. Fe2+-induced oxidative damage is suspected in the etiology of these symptoms. Here we examined, using Hfe-/- mice, whether disruption of uric acid (UA) homeostasis plays any role in HH-associated arthritis. We detected elevated levels of UA in serum and intestine in Hfe-/- mice compared with controls. Though the expression of xanthine oxidase, which generates UA, was not different in liver and intestine between wild type and Hfe-/- mice, the enzymatic activity was higher in Hfe-/- mice. We then examined various transporters involved in UA absorption/excretion. Glut9 expression did not change; however, there was an increase in Mrp4 and a decrease in Abcg2 in Hfe-/- mice. As ABCG2 mediates intestinal excretion of UA and mutations in ABCG2 cause hyperuricemia, we examined the potential connection between iron and ABCG2. We found p53-responsive elements in hABCG2 promoter and confirmed with chromatin immunoprecipitation that p53 binds to this promoter. p53 protein was reduced in Hfe-/- mouse intestine. p53 is a heme-binding protein and p53-heme complex is subjected to proteasomal degradation. We conclude that iron/heme overload in HH increases xanthine oxidase activity and also promotes p53 degradation resulting in decreased ABCG2 expression. As a result, systemic UA production is increased and intestinal excretion of UA via ABCG2 is decreased, causing serum and tissue accumulation of UA, a potential factor in the etiology of HH-associated arthritis.

Phloroglucinol Derivatives from Dryopteris crassirhizoma as Potent Xanthine Oxidase Inhibitors.

Dryopteris crassirhizoma rhizomes are used as a traditional medicine in Asia. The EtOAc extract of these roots has shown potent xanthine oxidase (XO) inhibitory activity. However, the main phloroglucinols in D. crassirhizoma rhizomes have not been analyzed. Thus, we investigated the major constituents responsible for this effect. Bioassay-guided purification isolated four compounds: flavaspidic acid AP (1), flavaspidic acid AB (2), flavaspidic acid PB (3), and flavaspidic acid BB (4). Among these, 1 showed the most potent inhibitory activity with a half-maximal inhibitory concentration (IC50) value of 6.3 µM, similar to that of allopurinol (IC50 = 5.7 µM) and better than that of oxypurinol (IC50 = 43.1 µM), which are XO inhibitors. A comparative activity screen indicated that the acetyl group at C3 and C3' is crucial for XO inhibition. For example, 1 showed nearly 4-fold higher efficacy than 4 (IC50 = 20.9 µM). Representative inhibitors (1-4) in the rhizomes of D. crassirhizoma showed reversible and noncompetitive inhibition toward XO. Furthermore, the potent inhibitors were shown to be present in high quantities in the rhizomes by a UPLC-QTOF-MS analysis. Therefore, the rhizomes of D. crassirhizoma could be used to develop nutraceuticals and medicines for the treatment of gout.

The net clinical benefits of febuxostat versus allopurinol in patients with gout or asymptomatic hyperuricemia - A systematic review and meta-analysis.

BACKGROUND AND AIMS: Systemic reviews and meta-analyses suggest hyperuricemia is a cardiovascular risk factor. The effects of xanthine oxidase inhibitors on cardiac outcomes remain unclear. We assessed the effects of febuxostat and allopurinol on mortality and adverse reactions in adult patients with hyperuricemia. METHODS AND RESULTS: PubMed and EMBASE were searched to retrieve randomized controlled trials of febuxostat and allopurinol from January 2005 to July 2018. The meta-analysis consisted of 13 randomized controlled trials with a combined sample size of 13,539 patients. Febuxostat vs. allopurinol was not associated with an increased risk of cardiac-related mortality in the overall population (OR: 0.72, 95% CI: 0.24-2.13, P = 0.55). Regarding adverse skin reactions, the patients receiving febuxostat had significantly fewer adverse skin reactions than those receiving allopurinol treatment (OR: 0.50, 95% CI: 0.30-085, P = 0.01). Compared with allopurinol, febuxostat was associated with an improved safety outcome of cardiac-related mortality and adverse skin reactions (OR: 0.72, 95% CI: 0.55-0.96, P = 0.02). The net clinical outcome, composite of incident gout and the safety outcome, was not different significantly in the patients receiving febuxostat or allopurinol (OR: 1.04, 95% CI: 0.76-0.1.42, P = 0.79). In sensitivity analyses, a borderline significance was found in the patients randomized to febuxostat vs. allopurinol regarding cardiac-related mortality (OR: 1.29, 95% CI: 1.00-1.67, P = 0.05) after the CARES study was included. CONCLUSION: Febuxostat vs. allopurinol was associated with the improved safety outcome and have comparable mortality and net clinical outcome in patients with hyperuricemia. REGISTRATION NUMBER: PROSPERO(CRD42018091657).

Actions of Inonotus obliquus against Hyperuricemia through XOD and Bioactives Screened by Molecular Modeling.

Inonotus obliquus is an edible mushroom and also a remedy against various diseases, especially metabolic syndrome. In this paper we report the actions of an ethanol extract of I. obliquus (IOE) against hyperuricemia in hyperuricemic mice, and the screen of bioactives. The extract (IOE) was prepared by extracting I. obliquus at 65 °C with ethanol, and characterized by HPLC. IOE at low, middle, and high doses reduced serum uric acid (SUA) of hyperuricemic mice (353 µmol/L) to 215, 174, and 152 µmol/L (p < 0.01), respectively, showing similar hypouricemic effectiveness to the positive controls. IOE showed a non-toxic impact on kidney and liver functions. Of note, IOE suppressed xanthine oxidase (XOD) activity in serum and liver, and also down-regulated renal uric acid transporter 1 (URAT1). Four compounds hit highly against XOD in molecular docking. Overall, the four compounds all occupied the active tunnel, which may inhibit the substrate from entering. The IC50 of betulin was assayed at 121.10 ± 4.57 µM, which was near to that of allopurinol (148.10 ± 5.27 µM). Betulin may be one of the anti-hyperuricemia bioactives in I. obliquus.

Anti-hyperuricemic peptides derived from bonito hydrolysates based on in vivo hyperuricemic model and in vitro xanthine oxidase inhibitory activity.

Traditional drugs used to treat hyperuricemia have adverse effects. In this study, to identify safer anti-hyperuricemic bioactive peptides isolated from food-derived protein hydrolysates, a hyperuricemia rat model induced by potassium oxonate (PO) was used to evaluate the activity of bonito hydrolysates (BH), dephenolised walnut hydrolysates (DWH), and soybean hydrolysates (SH). The serum uric acid level of rats in the BH group (95.4 ± 27.4 µM, p < 0.01) was significantly reduced compared to that in the model group (212.00 ± 30.00 µM) to a level even lower than that in allopurinol group (114.3 ± 53.0 µM). Furthermore, BH alleviated renal impairment caused by PO in vivo and exhibited the greatest xanthine oxidase (XOD) inhibitory activity (65.5 ± 8.0%) in vitro compared to the other hydrolysates. Two peptides identified from BH bound the catalytic site of XOD, among which the hydrophobic peptide WML entered the active site of XOD more easily compared to the hydrophilic peptide PGACSN, possibly because of hydrophobic interactions. The chemically synthesized WML demonstrated high XOD inhibitory effect compared to PGACSN and a significant change in the secondary structure of XOD. Therefore, hexapeptide PGACSN and tripeptide WML are partially responsible for the anti-hyperuricemic activity of BH, and hydrophobic amino acids play important roles in the XOD inhibitory activity of peptides.

Impaired Na+-K+-ATPase signaling in renal proximal tubule contributes to hyperuricemia-induced renal tubular injury.

Hyperuricemia contributes to renal inflammation. We aimed to investigate the role of Na+-K+-ATPase (NKA) in hyperuricemia-induced renal tubular injury. Human primary proximal tubular epithelial cells (PTECs) were incubated with uric acid (UA) at increasing doses or for increasing lengths of time. PTECs were then stimulated by pre-incubation with an NKA α1 expression vector or small interfering RNA before UA (100 µg ml-1, 48 h) stimulation. Hyperuricemic rats were induced by gastric oxonic acid and treated with febuxostat (Feb). ATP levels, the activity of NKA and expression of its α1 subunit, Src, NOD-like receptor pyrin domain-containing protein 3 (NLRP3) and interleukin 1ß (IL-1ß) were measured both in vitro and in vivo. Beginning at concentrations of 100 µg ml-1, UA started to dose-dependently reduce NKA activity. UA at a concentration of 100 µg ml-1 time-dependently affected the NKA activity, with the maximal increased NKA activity at 24 h, but the activity started to decrease after 48 h. This inhibitory effect of UA on NKA activity at 48 h was in addition to a decrease in NKA α1 expression in the cell membrane, but an increase in lysosomes. This process also involved the subsequent activation of Src kinase and NLRP3, promoting IL-1ß processing. In hyperuricemic rats, renal cortex NKA activity and its α1 expression were upregulated at the 7th week and both decreased at the 10th week, accompanied with increased renal cortex expression of Src, NLRP3 and IL-1ß. The UA levels were reduced and renal tubular injuries in hyperuricemic rats were alleviated in the Feb group. Our data suggested that the impairment of NKA and its consequent regulation of Src, NLRP3 and IL-1ß in the renal proximal tubule contributed to hyperuricemia-induced renal tubular injury.

Bisphenol A promotes hyperuricemia via activating xanthine oxidase.

The prevalence of hyperuricemia has increased rapidly over the past decades. Bisphenol A (BPA) is an environmental endocrine disruptor. We investigated the effects of BPA on uric acid metabolism and its potential mechanisms. Experiments were performed in different animal models, cell cultures, and humans. In 3 different animal models, BPA exposure increased serum and hepatic uric acid with enhanced activity of xanthine oxidase (XO) in liver, whereas the excretion of uric acid was unchanged. Both in vivo and in vitro, BPA-induced uric acid production was decreased after treatment with allopurinol, which is a XO inhibitor. XO led to the accumulation of uric acid after xanthine was added, with the enzyme-catalyzed reaction, which was enhanced by BPA. Altered secondary structures of XO were found by circular dichroism analysis in the conditions of different BPA concentrations. Molecular docking portrayed Asp360 and Lys422 of XO to be the preferred binding sites for BPA. Mutation of both sites significantly blocked the effect of BPA on XO activity. In humans, patients with hyperuricemia exhibited higher levels of serum BPA than subjects without hyperuricemia. These findings demonstrate BPA promotes hyperuricemia by increasing hepatic uric acid synthesis via the activation of XO, probably through direct binding.-Ma, L., Hu, J., Li, J., Yang, Y., Zhang, L., Zou, L., Gao, R., Peng, C., Wang, Y., Luo, T., Xiang, X., Qing, H., Xiao, X., Wu, C., Wang, Z., He, J. C., Li, Q., Yang, S. Bisphenol A promotes hyperuricemia via activating xanthine oxidase.

Moderation of hyperuricemia in rats via consuming walnut protein hydrolysate diet and identification of new antihyperuricemic peptides.

In this study, walnut meal hydrolysates (WMH) and dephenolized walnut meal hydrolysates (DWMH) were found to effectively decrease the serum uric acid level and protect the renal function in potassium oxonate-induced hyperuricemic rats in vivo as well as inhibit xanthine oxidase in vitro. Two novel antihyperuricemic peptides including WPPKN (640.8 Da) and ADIYTE (710.7 Da) were purified from DWMH via Sephadex G-15 gel filtration and reverse-phase high-performance liquid chromatography and identified by LC-ESI-MS/MS. These peptides displayed high in vitro xanthine oxidase inhibition (XOI) activity with IC50 values of 17.75 ± 0.12 mg mL-1 (WPPKN) and 19.01 ± 0.23 mg mL-1 (ADIYTE). Based on the results of molecular simulation, WPPKN entered into the hydrophobic channel and even obstructed the interaction between xanthine and xanthine oxidase (XO), while ADIYTE was positioned on the surface of the B-chain and blocked the entrance of the substrate to the hydrophobic channel. Therefore, the two peptides are partially responsible for the antihyperuricemic properties of DWMH.

Efficacy and Safety of Febuxostat in Kidney Transplant Patients.

OBJECTIVES: Febuxostat, a nonpurine xanthine oxidase, is known to be effective and safe, even in patients with chronic kidney disease. However, there are insufficient data about the efficacy and safety of febuxostat in kidney transplant patients. MATERIALS AND METHODS: We reviewed medical records of all kidney transplant patients who were prescribed febuxostat between August 2012 and May 2015 at Asan Medical Center in Seoul, Korea. The efficacy and safety results of febuxostat in transplant patients were evaluated. To compare the efficacy of febuxostat, results of kidney transplant patients who were prescribed benzbromarone or allopurinol for more than 1 year during the same period were also reviewed. RESULTS: Thirty-one patients were included in this study. The initial serum uric acid level of 481.83 ± 143.36 µmol/L decreased to 302.18 ± 150.50 µmol/L after 1 month of febuxostat use. Only 1 patient had altered sense of taste after taking febuxostat, but this symptom quickly improved and he continued treatment. No other adverse events were reported. In addition, at 12 months, mean serum uric acid levels were 280.77 ± 78.52 µmol/L in the febuxostat, 332.52 ± 72.57 µmol/L in the benzbromarone, and 363.45 ± 60.08 µmol/L in the allopurinol group. However, we found no apparent effect on estimated glomerular filtration rate (P = .344). The mean doses of febuxostat, benzbromarone, and allopurinol were 52.31 ± 5.33 mg/day, 42.19 ± 1.69 mg/day, and 146.67 ± 16.52 mg/day. CONCLUSIONS: Febuxostat reduced serum uric acid levels effectively in kidney transplant patients without severe adverse events.

Knockout of the urate oxidase gene provides a stable mouse model of hyperuricemia associated with metabolic disorders.

The urate oxidase (Uox) gene encodes uricase that in the rodent liver degrades uric acid into allantoin, forming an obstacle for establishing stable mouse models of hyperuricemia. The loss of uricase in humans during primate evolution causes their vulnerability to hyperuricemia. Thus, we generated a Uox-knockout mouse model on a pure C57BL/6J background using the transcription activator-like effector nuclease (TALEN) technique. These Uox-knockout mice spontaneously developed hyperuricemia (over 420 µmol/l) with about 40% survival up to 62 weeks. Renal dysfunction (elevated serum creatinine and blood urea nitrogen) and glomerular/tubular lesions were observed in these Uox-knockout mice. Male Uox-knockout mice developed glycol-metabolic disorders associated with compromised insulin secretion and elevated vulnerability to streptozotocin-induced diabetes, whereas female mice developed hypertension accompanied by aberrant lipo-metabolism. Urate-lowering drugs reduced serum uric acid and improved hyperuricemia-induced disorders. Thus, uricase knockout provides a suitable mouse model to investigate hyperuricemia and associated disorders mimicking the human condition, suggesting that hyperuricemia has a causal role in the development of metabolic disorders and hypertension.

Xanthine Oxidase and its Role as Target in Cardiovascular Disease: Cardiovascular Protection by Enzyme Inhibition?

BACKGROUND: Formerly, hyperuricemia was mainly restricted to the rich population, but now-a-days it is a condition affecting wide parts of western civilization. Although only a minority of our population develops clinically relevant symptomatic hyperuricemia, there is growing evidence that elevated serum uric acid levels might be associated with elevated cardiovascular risk and cardiovascular disease progression. But it is not clear whether uric acid is just a biomarker or exerts detrimental effects itself. The xanthine oxidoreductase (XOR) is an essential enzyme for the generation of uric acid. A typical pharmacological therapy to reduce the uric acid amounts is inhibition of XOR. There is good evidence that inhibition of uric acid reduces cardiovascular events in patients. The question arises if XOR inhibition might be an attractive target to reduce cardiovascular events in patients with high or even normal uric acid levels. METHOD: This review summarizes the available publications on the relationship between XOR and cardiovascular co-morbidities. RESULTS: The association of elevated serum uric acid level with oxidative damage in the vessel wall, inflammatory and proliferative vascular changes, hypertension and impaired kidney function are depicted. In addition, the therapeutics currently approved for the treatments of hyperuricemia are outlined and an overview regarding novel, currently researched XOR inhibitors is provided. CONCLUSION: Observational and small prospective studies already have given hints for positive cardiovascular effects of XOR inhibition. However, larger prospective studies investigating cardiovascular outcomes are awaited to validate the potential beneficial effect of XOR inhibition for reduction of the cardiovascular burden.

Modeling and optimizing inhibitory activities of Nelumbinis folium extract on xanthine oxidase using response surface methodology.

Xanthine oxidase (XOD), which could oxidize hypoxanthine to xanthine and then to uric acid, is a key enzyme in the pathogenesis of hyperuricemia and also a well-known target for the drug development to treat gout. In our study, the total alkaloids of Nelumbinis folium markedly inhibited XOD activity, with IC50 value being 3.313µg/mL. UHPLC-Q-TOF-MS and 3D docking analysis indicated that roemerine was a potential active ingredient. A response surface methodology combined with central composite design experiment was further developed and validated for the optimization of the reaction conditions between the total alkaloids of Nelumbinis folium and XOD, which could be considered as a meaningful research for the development of XOD inhibitor rapidly and sensitively.

Gypenosides Inhibits Xanthine Oxidoreductase and Ameliorates Urate Excretion in Hyperuricemic Rats Induced by High Cholesterol and High Fat Food (Lipid Emulsion).

BACKGROUND The aim of this study was to study the effects of gypenosides (GPS) on lowering uric acid (UA) levels in hyperuricemic rats induced by lipid emulsion (LE) and the related mechanisms. GPS are natural saponins extracted from Gynostemma pentaphyllum. MATERIAL AND METHODS Forty-eight male SD rats were randomly divided into six groups: normal, model, two positive controls, and two GPS treated groups (two different doses of GPS). The normal group rats were fed a basic diet, and the other rats were orally pretreated with LE. Urine and blood were collected at regular intervals. Full automatic biochemical analyzer was used to detect the concentration levels of serum UA (SUA), serum creatinine (SCr), BUN, and urine UA (UUA), and urine creatinine (UCr) and fractional excretion of UA (FEUA). ELISA kits were used to detect enzymes activities: xanthine oxidase (XOD), adenosime deaminase (ADA), guanine deaminase (GDA), and xanthine dehydrogenase (XDH). Immunohistochemistry was used to observe kidney changes and protein (URAT1, GLUT9, and OAT1) expression levels. RT-PCR was used to detect the relevant mRNA expression levels. RESULTS Treatment with GPS significantly reduced the SUA, prevented abnormal weight loss caused by LE, and improved kidney pathomorphology. Treatment with GPS also decreased the levels of XOD, ADA, and XDH expression, increased the kidney index and FEUA, downregulated URAT1 and GLUT9 expression and upregulated OAT1 expression in the kidney. CONCLUSIONS GPS may be an effective treatment for hyperuricemia via a decrease in xanthine oxidoreductase through the XOD/XDH system; and via an increase in urate excretion through regulating URAT1, GLUT9, and OAT1 transporters.

Dinuclear Cyclam Complex as a Non-Cytotoxic, Anti-Hyperurecemic Lead: In vitro to In vivo Studies.

BACKGROUND: Uric acid is the end product of purine metabolism in humans and its increased level in serum leads to hyperuricemia. Among the different regulatory factors to control the level of uric acid in humans, xanthine oxidase (XO) is a well-established pharmacological target, as it is directly involved in uric acid production. METHODS: The aim of the study was to present a systematic approach to analyze the xanthine oxidase inhibition studies from in vitro leading to in vivo. RESULTS: Initially, dinuclear cyclam complex 1 was evaluated for in-vitro XO inhibitory activity using a spectrophotometric assay. Significant results were obtained in XO inhibition assay (IC50 = 3.70 ± 0.07 µM), in comparison to the standard drug, allopurinol (IC50 = 2.00 ± 0.01 µM). Complex 1 showed a non-competitive type of inhibition in kinetic studies. Complex 1 was also found to be non-cytotoxic in MTT assay, as it did not affect the viability of 3T3-cell line. Based on these results, compound 1 was further evaluated for the in-vivo xanthine oxidase inhibitory activity. An in-vivo model was used to evaluate the XO inhibitory activity in plasma samples of male Wistar rats. Complex 1 showed a significant inhibition of xanthine oxidase activity (50%), in comparison to the standard inhibitor allopurinol (100%). Therefore, non-cytotoxic compound 1 could be considered as an anti-hyperurecemic lead for further studies. CONCLUSION: Our studies concluded that complex 1 is a non-cytotoxic inhibitor that decreases the activity of XO in a non-competitive manner. It can serve as a potential anti-hyperurecemic lead after further pre-clinical and clinical studies.

An evidence-based review on urate-lowering treatments: implications for optimal treatment of chronic hyperuricemia.

Several studies suggest that chronic hyperuricemia, the main precursor of gout, is involved in the pathogenesis of different systemic disorders that affect cardiovascular and renal systems, such as hypertension, obesity, hypercholesterolemia, atherosclerosis, metabolic syndrome, chronic heart failure, and chronic kidney disease. Recent epidemiological evidence has shown an increasing trend in the prevalence of hyperuricemia and gout in the Western world: a number of population-based studies estimate a prevalence of up to 21% for hyperuricemia and 1%-4% for gout. As such, early detection and careful management of this pathological condition is required, starting from lifestyle changes (mainly based on a diet low in red meat, sugars, and alcoholic beverages, with increased intake of vegetables, water, and vitamin C sources), adding specific drugs to lead serum uric acid (SUA) levels under the target value of 7 mg/dL. In particular, nonselective and selective XO inhibitors (allopurinol, oxypurinol, febuxostat) reduce SUA levels and the overproduction of reactive oxygen species, mainly related to XO overactivity that often causes inflammatory damage to the vascular endothelium. The effect of lowering SUA levels via XO inhibition includes an attenuation of oxidative stress and related endothelial dysfunction that largely contribute to the pathophysiology of metabolic syndrome and cardiovascular diseases. Therefore, the inhibition of XO overactivation seems to be an excellent therapeutic option to limit the harmful effects of excess UA and reactive oxygen species. In conclusion, rapid diagnosis and correct therapy for hyperuricemia may also improve the prevention and/or treatment of serious and multifactorial diseases. The available evidence supports the importance of promoting new experimental clinical trials to confirm the emerging antioxidant role of XO inhibitors, which could effectively contribute to cardiovascular and chronic kidney disease prevention.

COX-2/mPGES-1/PGE2 cascade activation mediates uric acid-induced mesangial cell proliferation.

Hyperuricemia is not only the main feature of gout but also a cause of gout-related organ injuries including glomerular hypertrophy and sclerosis. Uric acid (UA) has been proven to directly cause mesangial cell (MC) proliferation with elusive mechanisms. The present study was undertaken to examined the role of inflammatory cascade of COX-2/mPGES-1/PGE2 in UA-induced MC proliferation. In the dose- and time-dependent experiments, UA increased cell proliferation shown by the increased total cell number, DNA synthesis rate, and the number of cells in S and G2 phases in parallel with the upregulation of cyclin A2 and cyclin D1. Interestingly, UA-induced cell proliferation was accompanied with the upregulation of COX-2 and mPGES-1 at both mRNA and protein levels. Strikingly, inhibition of COX-2 via a specific COX-2 inhibitor NS-398 markedly blocked UA-induced MC proliferation. Meanwhile, UA-induced PGE2 production was almost entirely abolished. Furthermore, inhibiting mPGES-1 by a siRNA approach in MCs also ameliorated UA-induced MC proliferation in line with a significant blockade of PGE2 secretion. More importantly, in gout patients, we observed a significant elevation of urinary PGE2 excretion compared with healthy controls, indicating a translational potential of this study to the clinic. In conclusion, our findings indicated that COX-2/mPGES-1/PGE2 cascade activation mediated UA-induced MC proliferation. This study offered new insights into the understanding and the intervention of UA-related glomerular injury.