Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

Spontaneous Tumor Lysis Syndrome in Blastoid-Variant Mantle Cell Lymphoma: Considerations for the General Internist

Spontaneous tumor lysis syndrome (SPTLS) is a rare phenomenon that can manifest in rapidly proliferating hematological malignancies and solid tumors prior to initiating cytotoxic therapy. We encountered a patient who originally presented with diffuse lymphadenopathy, abdominal distention, and dyspnea, who had laboratory abnormalities suggestive of SPTLS. His peripheral flow cytometry and lymph node biopsy revealed blastoid-variant mantle cell lymphoma. Prior to initiating chemotherapy, acute kidney injury (AKI) and uric acid had improved with intravenous fluids and the initiation of allopurinol. However, after beginning chemotherapy, the patient developed a second AKI concerning for tumor lysis syndrome (TLS). He went on to have renal recovery and did not require renal replacement therapy. With the exception of case reports, there is limited evidence to guide general medicine clinicians who encounter cases of SPTLS. Expert-based guidelines are available to guide use of rasburicase, an uricase enzyme, before initiation of chemotherapy for certain malignancies when risk for TLS is considered high. Despite these guidelines, the role of rasburicase in preventing AKI remains controversial after inconclusive results in a meta-analysis. The causative relationship between uric acid and AKI in TLS is based on a mechanism of tubular obstruction. There are also mechanisms by which uric acid may cause AKI without tubular obstruction related to acute hyperuricemic nephropathy. Further characterization of the role of uric acid in causing AKI in patients without tubular obstruction may identify new mechanisms of injury and offer insight into new treatment strategies.

Serum uric acid, predicts heart failure in a large Italian cohort: search for a cut-off value the URic acid Right for heArt Health study

OBJECTIVE

To assess the prognostic cut-off values of serum uric acid (SUA) in predicting fatal and morbid heart failure in a large Italian cohort in the frame of the Working Group on Uric Acid and Cardiovascular Risk of the Italian Society of Hypertension.

METHODS

The URic acid Right for heArt Health (URRAH) study is a nationwide, multicentre, cohort study involving data on individuals aged 18-95 years, recruited on a community basis from all regions of Italy under the patronage of the Italian Society of Hypertension with a mean follow-up period of 128 ± 65 months. Incident heart failure was defined on the basis of International Classification of Diseases Tenth Revision codes and double-checked with general practitioners and hospital files. Multivariate Cox regression models having fatal and morbid heart failure as dependent variables, adjusted for sex, age, SBP, diabetes, estimated glomerular filtration rate, smoking habit, ethanol intake, BMI, haematocrit, LDL cholesterol, previous diagnosis of heart failure and use of diuretics as possible confounders, were used to search for an association between SUA as a continuous variable and heart failure. By means of receiver operating characteristic curves, two prognostic cut-off values (one for all heart failure and one for fatal heart failure) were identified as able to discriminate between individuals doomed to develop the event. These cut-off values were used as independent predictors to divide individuals according to prognostic cut-off values in a multivariate Cox models, adjusted for confounders.

RESULTS

A total of 21 386 individuals were included in the analysis. In Cox analyses, SUA as a continuous variable was a significant predictor of all [hazard ratio 1.29 (1.23-1.359), P < 0.0001] and fatal [hazard ratio 1.268 (1.121-1.35), P < 0.0001] incident heart failure. Cut-off values of SUA able to discriminate all and fatal heart failure status were identified by mean of receiver operating characteristic curves in the whole database: SUA more than 5.34 mg/dl (confidence interval 4.37-5.6, sensitivity 52.32, specificity 63.96, P < 0.0001) was the univariate prognostic cut-off value for all heart failure, whereas SUA more than 4.89 mg/dl (confidence interval 4.78-5.78, sensitivity 68.29, specificity 49.11, P < 0.0001) for fatal heart failure. The cut-off for all heart failure and the cut-off value for fatal heart failure were accepted as independent predictors in the Cox analysis models, the hazard ratios being 1.645 (1.284-2.109, P < 0.0001) for all heart failure and 1.645 (1.284-2.109, P < 0.0001) for fatal heart failure, respectively.

CONCLUSION

The results of the current study confirm that SUA is an independent risk factor for all heart failure and fatal heart failure, after adjusting for potential confounding variables and demonstrate that a prognostic cut-off value can be identified for all heart failure (>5.34 mg/dl) and for fatal heart failure (>4.89 mg/dl).

Hydrogen sulfide stimulates xanthine oxidoreductase conversion to nitrite reductase and formation of NO

Cardiovascular disease is the leading cause of death and disability worldwide with increased oxidative stress and reduced NO bioavailability serving as key risk factors. For decades, elevation in protein abundance and enzymatic activity of xanthine oxidoreductase (XOR) under hypoxic/inflammatory conditions has been associated with organ damage and vascular dysfunction. Recent reports have challenged this dogma by identifying a beneficial function for XOR, under similar hypoxic/acidic conditions, whereby XOR catalyzes the reduction of nitrite (NO2-) to nitric oxide (NO) through poorly defined mechanisms. We previously reported that hydrogen sulfide (H2S/sulfide) confers significant vascular benefit under these same conditions via NO2- mediated mechanisms independent of nitric oxide synthase (NOS). Here we report for the first time the convergence of H2S, XOR, and nitrite to form a concerted triad for NO generation. Specifically, hypoxic endothelial cells show a dose-dependent, sulfide and polysulfide (diallyl trisulfide (DATS)-induced, NOS-independent NO2- reduction to NO that is dependent upon the enzymatic activity of XOR. Interestingly, nitrite reduction to NO was found to be slower and more sustained with DATS compared to H2S. Capacity for sulfide/polysulfide to produce an XOR-dependent impact on NO generation translates to salutary actions in vivo as DATS administration in cystathionine-γ-lyase (CSE) knockout mice significantly improved hindlimb ischemia blood flow post ligation, while the XOR-specific inhibitor, febuxostat (Febx), abrogated this benefit. Moreover, flow-mediated vasodilation (FMD) in CSE knockout mice following administration of DATS resulted in greater than 4-fold enhancement in femoral artery dilation while co-treatment with Febx completely completely abrogated this effect. Together, these results identify XOR as a focal point of convergence between sulfide- and nitrite-mediated signaling, as well as affirm the critical need to reexamine current dogma regarding inhibition of XOR in the context of vascular dysfunction.

Prevention of Hyperuricemia by Clerodendrum trichotomum Leaf Extract in Potassium Oxonate-Induced Mice

Clerodendrum trichotomum is a folk medicine exhibiting anti-hypertension, anti-arthritis, and anti-rheumatism properties. However, little is known about whether the material might prevent hyperuricemia and associated inflammation. In this study, we explored whether C. trichotomum leaf extract (CTE) prevented hyperuricemia induced by potassium oxonate (PO) in mice. CTE (400 mg/kg body weight) significantly reduced the serum uric acid (UA), blood urea nitrogen (BUN), and serum creatinine levels and increased urine UA and creatinine levels. CTE ameliorated PO-induced inflammation and apoptosis by reducing the levels of relevant proteins in kidney tissues. Also, CTE ameliorated both UA-induced inflammatory response in RAW 263.7 cells and UA-induced cytotoxicity in HK-2 cells. In addition, liver transcriptome analysis showed that CTE enriched mainly the genes for mediating positive regulation of MAPK cascade and apoptotic signaling pathways. Together, the results show that CTE effectively prevents hyperuricemia and associated inflammation in PO-induced mice.

In Silico Design and Synthesis of Targeted Curcumin Derivatives as Xanthine Oxidase Inhibitors

BACKGROUND

Curcumin is a well-known pharmacophore and some of its derivatives are shown to target xanthine oxidase (XO) to alleviate disorders caused by the excess production of uric acid.

OBJECTIVE

Curcumin based derivatives were designed, synthesized and evaluated for their antioxidant and xanthine oxidase inhibitory potential.

METHOD

In this report, we designed and synthesized two series of curcumin derivatives modified by inserting pyrazole and pyrimidine ring to central keto group. The synthesized compounds were evaluated for their antioxidant and xanthine oxidase inhibitory potential.

RESULTS

Results showed that pyrazole analogues of curcumin produced excellent XO inhibitory potency with the IC50 values varying from 06.255 µM to 10.503 µM. Among pyrimidine derivatives compound CU3a1 having ortho nitro substitution exhibited more potent xanthine oxidase inhibitory activity than any other curcumin derivative of this series.

CONCLUSION

Curcumin derivatives CU5b1, CU5b2, CU5b3, and CU3a1 showed a potent inhibitory activity against xanthine oxidase along with good antioxidant potential.

Melatonin inhibits apoptosis and oxidative tissue damage in cisplatin-induced pulmonary toxicity in rats

Introduction

Cisplatin is one of the most frequently used chemotherapeutics, which is known to cause both tumor and normal lung tissue damage through the generation of free radicals and cells apoptosis/necrosis. Melatonin is a neurohormone that regulates numerous physiological processes in the body both through receptor pathways and by maintaining tissue redox homeostasis.

Material and methods

The extent of rat lung damage induced by cisplatin and the effects of melatonin on this process was determined based on the pathohistological changes and biochemical disturbances in tissue lipid peroxidation, protein carbonyl modification and in the activity of xanthine oxidase (XO), caspase-3 and DNases.

Results

Histopathological analysis of rat lung tissue obtained from animals that received cisplatin found them to be edematous, with significant deterioration of alveolar epithelium. These morphological changes are accompanied by a significant increase in all studied oxidative stress-related parameters, as well as with the activity of apoptosis-related enzymes. A five-day treatment with melatonin completely prevented a cisplatin-induced increase in oxidative stress-related parameters and in the activity of XO, caspase-3 and alkaline DNase. Also, the histopathological changes observed during microscopic analysis were much less pronounced than in the group that received cisplatin only.

Conclusions

These results can potentially be connected with the ability of melatonin to inhibit the activity of XO, caspase-3 and alkaline DNase and/or its ability to scavenge free radicals, thus preventing lung damage induced by cisplatin.

Xanthine oxidoreductase inhibition – A review of computational aspect

Xanthine Oxidoreductase (XOR) exists in a variety of organisms from bacteria to humans and catalyzes the oxidation of hypoxanthine to xanthine and from xanthine to uric acid. Excessive uric acid could lead to gout and hyperuricemia. In this paper, we have reviewed the recent computational studies on xanthine oxidase inhibition. Computational methods, such as molecular dynamics (molecular mechanics), quantum mechanics, and quantum mechanics/molecular mechanics (QM/MM), have been employed to investigate the binding affinity of xanthine oxidase with synthesized and isolated nature inhibitors. The limitations of different computational methods for xanthine oxidase inhibition studies were also discussed. Implications of the computational approach could be used to help to understand the existing arguments on substrate/product orientation in xanthine oxidase inhibition, which allows designing new inhibitors with higher efficacy.

Evaluation of xanthine oxidase inhibitory activity of flavonoids by an online capillary electrophoresis-based immobilized enzyme microreactor

Xanthine oxidase (XOD) is a key enzyme in the human body to produce uric acid, and its inhibitor can be used for the treatment of hyperuricemia and gout. In this study, an online CE-based XOD immobilized enzyme microreactor (IMER) was developed for the enzyme kinetics assays and inhibitor screening. After 30 consecutive runs, the XOD activity remained about 95.6% of the initial immobilized activity. The Michaelis-Menten constant (K_m ) of the immobilized XOD was determined as 0.39 mM using xanthine as substrate. The half-maximal inhibitory concentration and inhibition constant of the known inhibitor 4-aminopyrazolo[3,4-d]pyrimidine on XOD were determined as 11.9 and 5.2 μM, respectively. Then, the developed method was applied to evaluate the XOD inhibitory activity of 10 flavonoids, which indicated that dihydroquercetin, quercetin, biochanin A, and epicatechin had significant inhibitory effect on XOD. In addition, molecular docking results verified that the binding energy of the flavonoids with enzyme were in line with their inhibitory activity determined by XOD-IMER. Therefore, the developed XOD-IMER is a potential tool for the primary screening of XOD inhibitors from natural products.

Plasma xanthine oxidoreductase (XOR) activity in patients who require cardiovascular intensive care

Hyperuricemia is known to be associated with adverse outcomes in cardiovascular intensive care patients, but its mechanisms are unknown. A total of 569 emergency department patients were prospectively analyzed and assigned to intensive care (ICU group, n = 431) or other departments (n = 138). Uric acid (UA) levels were significantly higher in the intensive care patients (6.3 [5.1-7.6] mg/dl vs. 5.8 [4.6-6.8] mg/dL). The plasma xanthine oxidoreductase (XOR) activity in the ICU group (68.3 [21.2-359.5] pmol/h/mL) was also significantly higher than that in other departments (37.2 [15.1-93.6] pmol/h/mL). Intensive care patients were divided into three groups according to plasma XOR quartiles (Q1, low-XOR, Q2/Q3, normal-XOR, and Q4, high-XOR group). A multivariate logistic regression model showed that lactate (per 1.0 mmol/L increase, OR 1.326; 95%, CI 1.166-1.508, p < 0.001) and the Acute Physiology and Chronic Health Evaluation II score (per 1.0 point increase, OR 1.095, 95% CI 1.034-1.160, p = 0.002) were independently associated with the high-XOR group. In-hospital mortality was significantly higher in the high-XOR group (n = 28, 26.2%) than in the normal- (n = 11, 5.1%) and low- (n = 9, 8.3%) XOR groups. The high-XOR group (vs. normal-XOR group) was independently associated with the in-hospital mortality (OR 2.934; 95% CI 1.170-7.358; p = 0.022). Serum UA levels and plasma XOR activity were high in patients admitted to intensive care. The enhanced XOR activity may be one of the mechanisms under which hyperuricemia was associated with adverse outcomes in patients requiring cardiovascular intensive care.

Determining the role for uric acid in non-alcoholic steatohepatitis development and the utility of urate metabolites in diagnosis: An opinion review

There has long been a recognised association between non-alcoholic fatty liver disease (NAFLD) and the composite aspects of the metabolic syndrome. Part of this association highlighted the supposed co-existence of elevated uric acid levels in those with NAFLD. There is interest in exploitation of this as a putative diagnostic and prognostic biomarker in NAFLD. Given the increased economic and health burden associated with the NAFLD epidemic, improved methods of population-based, minimally-invasive methods and biomarkers are clearly highly sought and necessary. In this opinion review we review the proposed role of uric acid in the pathogenesis of NAFLD and its potential utilisation in the diagnosis and monitoring of the disease process.

Studies on the structure-activity relationship and interaction mechanism of flavonoids and xanthine oxidase through enzyme kinetics, spectroscopy methods and molecular simulations

In this study, some flavonoids were screened as potent xanthine oxidase (XO) inhibitors in vitro. Flavonoid 9 was demonstrated to exhibit the inhibitory activity through a ping-pong mechanism. Further structure-activity relationship revealed that different structural elements had greatly influenced the inhibition effect on XO and underlined the requirement of hydroxyl groups at C5 and C4' of flavonoid type I. Moreover, some bioactive flavonoids could efficiently quench the intrinsic fluorescence of XO by either static or static-dynamic mixed mechanism. The synchronous fluorescence, ANS-binding fluorescence, Fourier transform infrared spectra and circular dichroism suggested that active flavonoids could bind to the active center of XO, prevent the entrance of substrate, and induce the rearrangement and conformation change of its secondary structures, ultimately resulting in the significant inhibition effect. Additionally, molecular docking further confirmed these conclusions and highlighted the great importance of hydrophobic interactions and hydrogen bonds for the formation of stable complex conformation.

Role of inflammasomes in the pathogenesis of periodontal disease and therapeutics

Inflammasomes are a group of multimolecular intracellular complexes assembled around several innate immune proteins. Recognition of a diverse range of microbial, stress and damage signals by inflammasomes results in direct activation of caspase‐1, which subsequently induces the only known form of secretion of active interleukin‐1β and interleukin‐18. Although the importance of interleukin‐1β in the periodontium is not questioned, the impact of inflammasomes in periodontal disease and its potential for therapeutics in periodontology is still in its very early stages. Increasing evidence in preclinical models and human data strongly implicate the involvement of inflammasomes in a number of inflammatory, autoinflammatory and autoimmune disorders. Here we review: (a) the currently known inflammasome functions, (b) clinical/preclinical data supporting inflammasome involvement in the context of periodontal and comorbid diseases and (c) potential therapies targeting inflammasomes. To clarify further the inflammasome involvement in periodontitis, we present analyses of data from a large clinical study (n = 5809) that measured the gingival crevicular fluid‐interleukin‐1β and grouped the participants based on current periodontal disease classifications. We review data on 4910 European‐Americans that correlate 16 polymorphisms in the interleukin‐1B region with high gingival crevicular fluid‐interleukin‐1β levels. We show that inflammasome components are increased in diseased periodontal tissues and that the caspase‐1 inhibitor, VX‐765, inhibits ~50% of alveolar bone loss in experimental periodontitis. The literature review further supports that although patients clinically present with the same phenotype, the disease that develops probably has different underlying biological pathways. The current data indicate that inflammasomes have a role in periodontal disease pathogenesis. Understanding the contribution of different inflammasomes to disease development and distinct patient susceptibility will probably translate into improved, personalized therapies.

Sugar-Induced Obesity and Insulin Resistance Are Uncoupled from Shortened Survival in Drosophila

High-sugar diets cause thirst, obesity, and metabolic dysregulation, leading to diseases including type 2 diabetes and shortened lifespan. However, the impact of obesity and water imbalance on health and survival is complex and difficult to disentangle. Here, we show that high sugar induces dehydration in adult Drosophila, and water supplementation fully rescues their lifespan. Conversely, the metabolic defects are water-independent, showing uncoupling between sugar-induced obesity and insulin resistance with reduced survival in vivo. High-sugar diets promote accumulation of uric acid, an end-product of purine catabolism, and the formation of renal stones, a process aggravated by dehydration and physiological acidification. Importantly, regulating uric acid production impacts on lifespan in a water-dependent manner. Furthermore, metabolomics analysis in a human cohort reveals that dietary sugar intake strongly predicts circulating purine levels. Our model explains the pathophysiology of high-sugar diets independently of obesity and insulin resistance and highlights purine metabolism as a pro-longevity target.

Mitochondrial ROS Formation in the Pathogenesis of Diabetic Cardiomyopathy

Diabetic cardiomyopathy is a result of diabetes-induced changes in the structure and function of the heart. Hyperglycemia affects multiple pathways in the diabetic heart, but excessive reactive oxygen species (ROS) generation and oxidative stress represent common denominators associated with adverse tissue remodeling. Indeed, key processes underlying cardiac remodeling in diabetes are redox sensitive, including inflammation, organelle dysfunction, alteration in ion homeostasis, cardiomyocyte hypertrophy, apoptosis, fibrosis, and contractile dysfunction. Extensive experimental evidence supports the involvement of mitochondrial ROS formation in the alterations characterizing the diabetic heart. In this review we will outline the central role of mitochondrial ROS and alterations in the redox status contributing to the development of diabetic cardiomyopathy. We will discuss the role of different sources of ROS involved in this process, with a specific emphasis on mitochondrial ROS producing enzymes within cardiomyocytes. Finally, the therapeutic potential of pharmacological inhibitors of ROS sources within the mitochondria will be discussed.

Synthesis, Molecular Docking, DFT Study of Novel N-Benzyl-2-(3-cyano-4-isobutoxyphenyl)- 4-methylthiazole-5-carboxamide Derivatives and their Antibacterial Activity

A series of febuxostat based new chemical entities was synthesized using microwave method and characterized by NMR, mass and FT-IR spectral studies. Molecular docking of febuxostat amide nucleus substitution compounds 8c (-7.91kcal/mol), 8g (-7.94 kcal/mol) exhibiting high binding energy against ALK receptors. Theoretical investigation of MEPs, HOMO, LUMO and energy gap of HOMO-LUMO were calculated by B3LYP/6-31G method. Among the tested compounds, methoxy substituted compound 8g showed highest antibacterial activity against S. aereus and B. subtilis.

Allopurinol Effects on Residual Renal Function in End-Stage Renal Disease Patients Undergoing Peritoneal Dialysis: Randomized Controlled Trial

Objective

There is increasing evidence to show that hyperuricemia may have a pathogenic role in the progression of renal diseases. We performed a prospective, randomized, controlled trial to investigate the renal effects of allopurinol treatment in hyperuricemic patients with end-stage renal disease (ESRD) who undergo peritoneal dialysis.

Methods

This was a unicenter, randomized, controlled clinical trial conducted in "Alzahra Hospital, Isfahan, Iran." Patients were randomly assigned into treatment or control group. Treatment-group patients were administered a starting allopurinol dose of 100 mg/day. The dose was adjusted according to serum uric acid level, aiming to maintain uric acid levels within the normal range. Participants were followed up for 6 months after receiving the medicine. Residual renal function (RRF) was assessed by measuring the renal component of Kt/V urea and estimating the patient's glomerular filtration rate (GFR) by calculating the mean of urea and creatinine clearance. In addition, systolic and diastolic blood pressure and serum level of creatinine were measured every 3 months during the follow-up period.

Findings

Eighty patients were enrolled in the study and divided into two groups, including 40 ESRD patients receiving allopurinol and 40 ESRD did not receive allopurinol and considered as the control group. GFR measurements showed that there was not a significant difference between patients' RRF of two groups. However, allopurinol group had higher RRF than the control group during the follow-up period. Evaluating RRF by Kt/V showed the same results.

Conclusion

Our study demonstrated significant effects of allopurinol on decreasing serum levels of uric acid in ESRD patients undergoing peritoneal dialysis. On the other hand, renal residual function of patients under treatment with allopurinol was better than the control group. We recommend that further studies should be conducted on the effects of allopurinol with greater sample size and longer time of follow-up.

Inhibition of Xanthine Oxidoreductase Enhances the Potential of Tyrosine Kinase Inhibitors against Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is characterized by the expression of the oncogenic kinase BCR-ABL. Although tyrosine kinase inhibitors (TKIs) against BCR-ABL represent the standard therapeutic option for CML, resistances to TKIs can be a serious problem. Thus, the search for novel therapeutic approaches is still needed. CML cells show an increased ROS production, which is required for maintaining the BCR-ABL signaling cascade active. In line with that, reducing ROS levels could be an interesting therapeutic strategy for the clinical management of resistant CML. To analyze the therapeutic potential of xanthine oxidoreductase (XOR) in CML, we tested the effect of XOR inhibitor allopurinol. Here, we show for the first time the therapeutic potential of allopurinol against BCR-ABL-positive CML cells. Allopurinol reduces the proliferation and clonogenic ability of the CML model cell lines K562 and KCL22. More importantly, the combination of allopurinol with imatinib or nilotinib reduced cell proliferation in a synergistic manner. Moreover, the co-treatment arms hampered cell clonogenic capacity and induced cell death more strongly than each single-agent arm. The reduction of intracellular ROS levels and the attenuation of the BCR-ABL signaling cascade may explain these effects. Finally, the self-renewal potential of primary bone marrow cells from CML patients was also severely reduced especially by the combination of allopurinol with TKIs. In summary, here we show that XOR inhibition is an interesting therapeutic option for CML, which can enhance the effectiveness of the TKIs currently used in clinics.

On-Flow LC-MS/MS method for screening of xanthine oxidase inhibitors

The screening of compounds is the initial step in research for the development of new drugs. For this reason, the availability of fast and reliable tools for the screening of a large number of compounds becomes essential. Among the therapeutic targets, the enzyme xanthine oxidase (XO) is of great interest for its importance as a biological source of superoxide radicals, which contribute to the oxidative stress on organisms and are involved in many pathological processes. In the present study, we validated a new method using an immobilized capillary enzyme reactor in an LC system directly coupled to triple quadrupole mass spectrometry to screen for XO ligands. The use of mass spectrometry provided selectivity and speed to the system, eliminating the analytical separation step. The Michaelis-Menten constant (K_M) value determined for the immobilized enzyme was 14.5 ± 0.4 μmol L^-1, which is consistent with the value previously reported for the XO-ICER with UV detection in a 2D LC method. The on-line approach was successfully applied to assay the XO inhibitory activities of thirty isolated compounds from different classes of natural products and provided greater productivity (288 analysis/day) than 2D LC method (84 analysis/day) of screened samples.

Computationally exploring novel xanthine oxidase inhibitors using docking-based 3D-QSAR, molecular dynamics, and virtual screening

Computationally exploring novel potential xanthine oxidase inhibitors using a systematic modeling study.

A novel mechanism of vitamin D anti-inflammatory/antioxidative potential in type 2 diabetic patients on metformin therapy

INTRODUCTION

The performed study focused on determining the effect of vitamin D supplementation on enzymes involved in both inflammation and reactive oxygen species (ROS) production and ROS degradation in patients with type 2 diabetes mellitus (T2DM).

MATERIAL AND METHODS

The 6-month follow-up, randomized, controlled study included 140 patients with T2DM, ≥ 30 years old, with good metabolic control, treated with metformin and lifestyle advice only. All patients were randomly assigned to two groups (70 each). Patients from the first group (Intervention group) were assigned to receive vitamin D3 50 000 IU or 14 000 IU regarding their vitamin D baseline levels. Patients from the second (Metformin) group continued to receive only metformin during the 6-month study period.

RESULTS

After 6 months, the myeloperoxidase activity was significantly lower and gradually decreased in the Intervention group by about 40%, compared to the baseline measurement (p = 0.015) and compared to the Metformin group (p = 0.001). After 6 months, the xanthine oxidase (XO) activity decreased significantly in the Intervention group compared to the baseline and 3^rd month levels (p < 0.001). In the Metformin group there was also a significant decrease in XO after 6 months compared to baseline (p < 0.001) and the 3^rd month (p = 0.003). The catalase activity significantly increased within the Intervention group only when comparing the 3^rd and 6^th month (p = 0.027).

CONCLUSIONS

Our study showed that vitamin D may improve endothelial dysfunction in patients with T2DM on metformin therapy by influencing two important factors implicated in the pathogenesis of diabetic complications - ROS production and inflammation, which can additionally contribute to a stable metabolic control during metformin therapy.

Enzymatic Bioautographic Methods

Enzymatic bioautography enables the detection of enzyme inhibitors absorbed on a thin-layer chromatography plate. Therefore, it is an assay format that is particularly useful for the detection of inhibitors present in complex mixtures. The inhibition properties of compounds separated by thin-layer chromatography can be directly analyzed to produce an inhibition profile. Here, we describe the conditions to detect inhibitor of the enzymes xanthine oxidase and β-glucosidase immobilized on agar gel.

Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives

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In recent years, the synthesis and evaluation of the biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole derivatives have been the subject of a large number of studies by academia and industry. In these studies it has been shown that this large and highly differentiated class of heteroarene derivatives includes high valuable compounds having important biological and pharmacological properties such as antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer, antiviral, antihypertensive, cholesterol-lowering, antifibrotic, antiuricemic, antidiabetic, antileishmanial and antiulcer activities.

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The present review with 411 references, in which we focused on the literature data published mainly from 2011 to 2017, aims to update the readers on the recent developments on the synthesis and biological evaluation of pharmacologically relevant 1,2,4,5-tetrasubstituted-1H-imidazole derivatives with an emphasis on their different molecular targets and their potential use as drugs to treat various types of diseases. Reference was also made to substantial literature data acquired before 2011 in this burgeoning research area.

Formation and degradation of lipid droplets in human adipocytes and the expression of aldehyde oxidase (AOX)

Lipid droplet (LD) binding proteins in mammary glands and in adipocytes were previously compared and striking similar sets of these specific proteins demonstrated. Xanthine oxidoreductase (XOR) together with perilipins and the lactating mammary gland protein butyrophilin play an important role in the secretion process of LDs into milk ducts. In contrast, in adipose tissue and in adipocytes, mainly perilipins have been described. Moreover, XOR was reported in mouse adipose tissue and adipocyte culture cells as “novel regulator of adipogenesis”. This obvious coincidence of protein sets prompted us to revisit the formation of LDs in human-cultured adipocytes in more detail with special emphasis on the possibility of a LD association of XOR. We demonstrate by electron and immunoelectron microscopy new structural details on LD formation in adipocytes. Surprisingly, by immunological and proteomic analysis, we identify in contrast to previous data showing the enzyme XOR, predominantly the expression of aldehyde oxidase (AOX). AOX could be detected tightly linked to LDs when adipocytes were treated with starvation medium. In addition, the majority of cells show an enormous interconnected, tubulated mitochondria network. Here, we discuss that (1) XOR is involved—together with perilipins—in the secretion of LDs in alveolar epithelial cells of the lactating mammary gland and is important in the transcytosis pathway of capillary endothelial cells. (2) In cells, where LDs are not secreted, XOR cannot be detected at the protein level, whereas in contrast in these cases, AOX is often present. We detect AOX in adipocytes together with perilipins and find evidence that these proteins might direct LDs to mitochondria. Finally, we here report for the first time the exclusive and complementary localization of XOR and AOX in diverse cell types.

Allopurinol reduces oxidative stress and activates Nrf2/p62 to attenuate diabetic cardiomyopathy in rats

Allopurinol (ALP) attenuates oxidative stress and diabetic cardiomyopathy (DCM), but the mechanism is unclear. Activation of nuclear factor erythroid 2‐related factor 2 (Nrf2) following the disassociation with its repressor Keap1 under oxidative stress can maintain inner redox homeostasis and attenuate DCM with concomitant attenuation of autophagy. We postulated that ALP treatment may activate Nrf2 to mitigate autophagy over‐activation and consequently attenuate DCM. Streptozotocin‐induced type 1 diabetic rats were untreated or treated with ALP (100 mg/kg/d) for 4 weeks and terminated after heart function measurements by echocardiography and pressure‐volume conductance system. Cardiomyocyte H9C2 cells infected with Nrf2 siRNA or not were incubated with high glucose (HG, 25 mmol/L) concomitantly with ALP treatment. Cell viability, lactate dehydrogenase, 15‐F2t‐Isoprostane and superoxide dismutase (SOD) were measured with colorimetric enzyme‐linked immunosorbent assays. ROS, apoptosis, was assessed by dihydroethidium staining and TUNEL, respectively. The Western blot and qRT‐PCR were used to assess protein and mRNA variations. Diabetic rats showed significant reductions in heart rate (HR), left ventricular eject fraction (LVEF), stroke work (SW) and cardiac output (CO), left ventricular end‐systolic volume (LVVs) as compared to non‐diabetic control and ALP improved or normalized HR, LVEF, SW, CO and LVVs in diabetic rats (all P < .05). Hearts of diabetic rats displayed excessive oxidative stress manifested as increased levels of 15‐F2t‐Isoprostane and superoxide anion production, increased apoptotic cell death and cardiomyocytes autophagy that were concomitant with reduced expressions of Nrf2, heme oxygenase‐1 (HO‐1) and Keap1. ALP reverted all the above‐mentioned diabetes‐induced biochemical changes except that it did not affect the levels of Keap1. In vitro, ALP increased Nrf2 and reduced the hyperglycaemia‐induced increases of H9C2 cardiomyocyte hypertrophy, oxidative stress, apoptosis and autophagy, and enhanced cellular viability. Nrf2 gene silence cancelled these protective effects of ALP in H9C2 cells. Activation of Nrf2 subsequent to the suppression of Keap1 and the mitigation of autophagy over‐activation may represent major mechanisms whereby ALP attenuates DCM.

Antihyperuricemic effect of dietary polyphenol sinapic acid commonly present in various edible food plants

The present study was conducted to evaluate the antihyperuricemic effect of sinapic acid (SA). The results showed that SA potently inhibited xanthine oxidase (XOD) in a dose-dependent manner by entering the enzyme active site and thwarting the entrance of the substrate. These results were further confirmed by the quantum chemical descriptors analysis and ¹ H NMR titration analysis. The in vivo results indicated that SA not only has the potential to inhibit serum and hepatic XOD (p < .05), but also remarkably lowered serum and urine uric acid levels at 50 and 100 mg/kg bw. Furthermore, SA regulated serum creatinine and blood urea nitrogen levels to normal and lowered inflammation in the renal tubules. Thus, the utilization of SA as an antihyperuricemic agent may have considerable potential for the development of functional foods for the possible treatment of hyperuricemia. PRACTICAL APPLICATIONS: Plant-derived bioactive compounds have multiple health benefits. The present study assesses the effects of sinapic acid against hyperuricemia. The results suggested that sinapic acid may have a strong protective effect against uric acid-related complications and may be used for the formulation of functional foods. However, further mechanistic studies are required to verify this hypothesis.

Effect of Eurycoma longifolia Stem Extract on Uric Acid Excretion in Hyperuricemia Mice

Background:Eurycoma longifolia is a tropical medicinal plant belonging to Simaroubaceae distributed in South East Asia. The stems are traditionally used for the treatment of sexual insufficiency, fever, hypertension, and malaria. Furthermore, it has antidiabetic and anticancer activities. Recently, it has been reported to reduce uric acid, but the mechanism is unclear.

Hypothesis/Purpose: The aim of this study is to explore the effect and mechanism of E. longifolia stem 70% ethanol extract (EL) and its active compounds on uric acid excretion.

Study Design and Methods: Potassium oxonate (PO) induced hyperuricemia rats model and adenine-PO induced hyperuricemia mice model were used to evaluate the effects of EL. Ultraperformance liquid chromatography was used to determine the levels of plasma or serum uric acid and creatinine. Hematoxylin-eosin staining was applied to observe kidney pathological changes, and western blot was applied to detect protein expression levels of uric acid transporters. Effects of constituents on urate uptake were tested in hURAT1-expressing HEK293T cells.

Results: EL significantly reduced serum and plasma uric acid levels at dosages of 100, 200, and 400 mg/kg in hyperuricemia rats and mice, increased the clearance rate of uric acid and creatinine, and improved the renal pathological injury. The protein expression levels of urate reabsorption transporter 1 (URAT1) and glucose transporter 9 were down-regulated, while sodium-dependent phosphate transporter 1 and ATP-binding cassette transporter G2 were up-regulated in the kidney after EL treatment. The quassinoids isolated from EL showed inhibitory effects on urate uptake in hURAT1-expressing HEK293T cells, and the effect of eurycomanol was further confirmed in vivo.

Conclusion: Our findings revealed that EL significantly reduced blood uric acid levels, prevented pathological changes of kidney in PO induced hyperuricemia animal model, and improved renal urate transports. We partly clarified the mechanism was related to suppressing effect of URAT1 by quassinoid in EL. This study is the first to demonstrate that EL plays a role in hyperuricemia by promoting renal uric acid excretion.

Oxidative Stress in Cell Death and Cardiovascular Diseases

ROS functions as a second messenger and modulates multiple signaling pathways under the physiological conditions. However, excessive intracellular ROS causes damage to the molecular components of the cell, which promotes the pathogenesis of various human diseases. Cardiovascular diseases are serious threats to human health with extremely high rates of morbidity and mortality. Dysregulation of cell death promotes the pathogenesis of cardiovascular diseases and is the clinical target during the disease treatment. Numerous studies show that ROS production is closely linked to the cell death process and promotes the occurrence and development of the cardiovascular diseases. In this review, we summarize the regulation of intracellular ROS, the roles of ROS played in the development of cardiovascular diseases, and the programmed cell death induced by intracellular ROS. We also focus on anti-ROS system and the potential application of anti-ROS strategy in the treatment of cardiovascular diseases.

Flavones scaffold of Chromolaena odorata as a potential xanthine oxidase inhibitor: Induced Fit Docking and ADME studies

Introduction: Gout is a type of painful inflammation initiated by the interactions between monosodium urate crystals and connective tissue. Xanthine oxidase (XO) catalyzes the oxidation of hypoxanthine to xanthine, then to uric acid. The primary treatments for gout include XO inhibitors. At present, allopurinol is the most used XO inhibitor for the treatment of gout. However, it can cause adverse effects commonly known as allopurinol hypersensitivity syndrome, thereby limiting its usage. Consequently, it is necessary to develop potent and less toxic inhibitors of XO. Chromolaena odorata is one of such plants under investigation for its diverse health benefits. Methods: Phytochemicals of C. odorata were screened against XO receptor, using molecular docking. The top five hit compounds of glide docking yield flavones scaffold which were subjected to induced fit docking (IFD) and absorption, distribution, metabolism, and excretion (ADME) studies. Results: The result showed that flavones scaffold of C. odorata can bind with higher affinity and lower free energy values when compared to that of the standard, allopurinol. The IFD scores of the flavones scaffold range from -1525.25 to -1527.99 kcal/mol. Conclusion: Our results have shown that flavones scaffold might have the potential to act as an effective drug candidate when compared to allopurinol in treating and/or preventing gout and some inflammatory condition.

Antioxidant, Xanthine Oxidase, α-Amylase and α-Glucosidase Inhibitory Activities of Bioactive Compounds from Rumex crispus L. Root

The root of Rumex crispus L. has been shown to possess anti-gout and anti-diabetic properties, but the compounds responsible for these pharmaceutical effects have not yet been reported. In this study, we aimed to isolate and purify active components from the root of R. crispus, and to evaluate their anti-radical, anti-gout and anti-diabetic capacities. From the ethyl acetate (EtOAc) extract, two compounds, chrysophanol (1) and physcion (2), were isolated by column chromatography with an elution of hexane and EtOAc at a 9:1 ratio. Their structures were identified by spectrometric techniques including gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), X-ray diffraction analyses and nuclear magnetic resonance (NMR). The results of bioassays indicated that (1) showed stronger activities than (2). For antioxidant activity, (1) and (2) exhibited remarkable DPPH radical scavenging capacity (IC₅₀ = 9.8 and 12.1 µg/mL), which was about two times stronger than BHT (IC₅₀ = 19.4 µg/mL). The anti-gout property of (1) and (2) were comparable to the positive control allopurinol, these compounds exerted strong inhibition against the activity of xanthine oxidase (IC₅₀ = 36.4 and 45.0 µg/mL, respectively). In the anti-diabetic assay, (1) and (2) displayed considerable inhibitory ability on α-glucosidase, their IC₅₀ values (IC₅₀ = 20.1 and 18.9 µg/mL, respectively) were higher than that of standard acarbose (IC₅₀ = 143.4 µg/mL). Findings of this study highlight that (1) and (2) may be promising agents to treat gout and diabetes, which may greatly contribute to the medicinal properties of Rumex crispus root.

Purine versus non-purine xanthine oxidase inhibitors against cyclophosphamide-induced cardiac and bone marrow toxicity in rats

BACKGROUND AND AIM

Cancer is a fatal and serious disease. Cyclophosphamide (CYC) is a commonly used anticancer drug. Cardiotoxicity and myelotoxicity are life-threatening side effects of CYC treatment. We aimed to evaluate the effect of the xanthine oxidase (XO) inhibitors, allopurinol (ALL) and febuxostat (FEB), on CYC-induced cardio- and hematopoietic toxicity in rats.

METHODS

ALL (100 mg/kg/day) or FEB (10 mg/kg/day) were administered orally to rats in the presence and absence of CYC (200 mg/kg kg i.p. single dose) treatment. Serum creatine kinase-MB creatine kinase myocardial band (CK-MB) and lactate dehydrogenase (LDH) activities were estimated. Complete blood counting (CBC), cardiac and bone marrow XO activity, malondialdehyde level, and superoxide dismutase activity were determined. Cardiac and bone marrow histopathological changes were also evaluated.

RESULTS

ALL and FEB significantly decreased CK-MB and LDH induced by CYC. Disturbed levels of XO, oxidative stress parameters, and CBC were also corrected by both XO inhibitors tested, with amelioration of cardiac histopathological changes caused by CYC. Treatment with FEB, but not ALL, prior to CYC challenges normalized bone marrow histopathological changes.

CONCLUSION

These results suggest that both XO inhibitors tested; ALL and FEB can ameliorate CYC-induced cardiotoxicity. However, only FEB can protect against CYC-induced myelotoxicity, whereas ALL, to the contrary, might aggravate it.

Bioluminescence Detection of Superoxide Anion Using Aequorin

Although the superoxide anion (O2-·) is generated during normal cellular respiration and has fundamental roles in a wide range of cellular processes, such as cell proliferation, migration, apoptosis, and homeostasis, its dysregulation is associated with a variety of diseases. Regarding these prominent roles in biological systems, the development of accurate methods for quantification of superoxide anion has attracted tremendous research attention. Here, we evaluated aequorin, a calcium-dependent photoprotein, as a potential bioluminescent reporter protein of superoxide anion. The mechanism is based on the measurement of aequorin bioluminescence, where the lower the concentration of coelenterazine under the oxidation of superoxide anion, the lower the amount aequorin regeneration, leading to a decrease in bioluminescence. The bioluminescence intensity of aequorin was proportional to the concentration of superoxide anion in the range from 4 to 40 000 pM with a detection limit (S/N = 3) of 1.2 pM, which was 5000-fold lower than those of the chemiluminescence methods. The proposed method exhibited high sensitivity and has been successfully applied to the determination of superoxide anion in the plant cell samples. The results could suggest a photoprotein-based bioluminescence system as a highly sensitive, specific, and simple bioluminescent probe for in vitro detection of superoxide anion.

Pseudomonas aeruginosa Quorum Sensing Molecule Alters Skeletal Muscle Protein Homeostasis by Perturbing the Antioxidant Defense System

Skeletal muscle function is compromised in many illnesses, including chronic infections. The Pseudomonas aeruginosa quorum sensing (QS) signal, 2-amino acetophenone (2-AA), is produced during acute and chronic infections and excreted in human tissues, including the lungs of cystic fibrosis patients. We have shown that 2-AA facilitates pathogen persistence, likely via its ability to promote the formation of bacterial persister cells, and that it acts as an interkingdom immunomodulatory signal that epigenetically reprograms innate immune functions. Moreover, 2-AA compromises muscle contractility and impacts the expression of genes involved in reactive oxygen species (ROS) homeostasis in skeletal muscle and in mitochondrial functions. Here, we elucidate the molecular mechanisms of 2-AA's impairment of skeletal muscle function and ROS homeostasis. Murine in vivo and differentiated C2C12 myotube cell studies showed that 2-AA promotes ROS generation in skeletal muscle via the modulation of xanthine oxidase (XO) activity, NAD(P)H oxidase2 (NOX2) protein level, and the activity of antioxidant enzymes. ROS accumulation triggers the activity of AMP-activated protein kinase (AMPK), likely upstream of the observed locations of induction of ubiquitin ligases Muscle RING Finger 1 (MuRF1) and Muscle Atrophy F-box (MAFbx), and induces autophagy-related proteins. The protein-level perturbation in skeletal muscle of silent mating type information regulation 2 homolog 1 (SIRT1), peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1), and uncoupling protein 3 (UCP3) is rescued by the antioxidant N-acetyl-l-cysteine (NAC). Together, these results unveil a novel form of action of a QS bacterial molecule and provide molecular insights into the 2-AA-mediated skeletal muscle dysfunction caused by P. aeruginosa IMPORTANCE Pseudomonas aeruginosa, a bacterium that is resistant to treatment, causes serious acute, persistent, and relapsing infections in humans. There is increasing evidence that bacterial excreted small molecules play a critical role during infection. We have shown that a quorum sensing (QS)-regulated excreted small molecule, 2-AA, which is abundantly produced by P. aeruginosa, promotes persistent infections, dampens host inflammation, and triggers mitochondrial dysfunction in skeletal muscle. QS is a cell-to-cell communication system utilized by bacteria to promote collective behaviors. The significance of our study in identifying a mechanism that leads to skeletal muscle dysfunction, via the action of a QS molecule, is that it may open new avenues in the control of muscle loss as a result of infection and sepsis. Given that QS is a common characteristic of prokaryotes, it is possible that 2-AA-like molecules promoting similar effects may exist in other pathogens.

Alkaloids isolated from Tabernaemontana bufalina display xanthine oxidase inhibitory activity

Continued interest in bioactive alkaloids led to the isolation of four undescribed alkaloids along with 74 known ones from the aerial parts of Tabernaemontana bufalina Lour. The structures of the yet undescribed alkaloids were elucidated based on NMR, IR, UV, MS and CD spectroscopic data and X-ray crystal diffraction and, according to the plant source, named as taberhaines A-D (1-4). The known compounds comprised of 66 monoterpenoid indole, three carboline and five isoquinoline alkaloids. Among them, the known apparicine inhibited significantly the activity of xanthine oxidase, which plays an important role for gout, with an IC₅₀ value of 0.65 μM, compared to the standard drug allopurinol (IC₅₀ = 0.60 μM).

Annual change in plasma xanthine oxidoreductase activity is associated with changes in liver enzymes and body weight

Xanthine oxidoreductase (XOR), an enzyme of uric acid formation from hypoxanthine and xanthine, is recognized as a source of oxidative stress. Plasma activity of XOR has been reported to be a biomarker of metabolic disorders associated with obesity, liver dysfunction, insulin resistance, hyperuricemia and adipokines. We investigated longitudinal change in plasma XOR activity, which was determined by using mass spectrometry and liquid chromatography to detect [¹³C₂, ¹⁵N₂]-uric acid using [¹³C₂, ¹⁵N₂]-xanthine as a substrate, in 511 subjects (male/female: 244/267) of the Tanno-Sobetsu Study in the years 2016 and 2017. Plasma XOR activity in a basal state was significantly higher in men than in women, but no significant sex difference was observed in annual change in plasma XOR activity. Annual change in plasma activity of XOR was positively correlated with changes in each parameter, including body weight (r = 0.203, p < 0.001), body mass index, diastolic blood pressure, aspartate transaminase (AST) (r = 0.772, p < 0.001), alanine transaminase (r = 0.647, p < 0.001), γ-glutamyl transpeptidase, total cholesterol, triglycerides, uric acid, fasting glucose and HbA1c. Multivariate regression analysis demonstrated that change in AST and that in body weight were independent predictors of change in plasma XOR activity after adjustment of age, sex and changes in each variable with a significant correlation without multicollinearity. In conclusion, annual change in plasma XOR activity is independently associated with changes in liver enzymes and body weight in a general population. Improvement of liver function and reduction of body weight would decrease plasma XOR activity and its related oxidative stress as a therapeutic strategy.

Synthesis and pharmacological properties of polysubstituted 2-amino-4H-pyran-3-carbonitrile derivatives

2-Amino-3-cyano-4H-chromenes are structural core motifs that received increasing attention in the last years due to their interesting potential pharmacological properties. In this review, the synthetic methods for these compounds are classified based on the type of catalyst in the pertinent reactions. In addition, the wide range of pharmacological properties of these compounds is covered in a separate section.

Design, synthesis and biological evaluation of N-(3-(1H-tetrazol-1-yl)phenyl)isonicotinamide derivatives as novel xanthine oxidase inhibitors

In our previous study, we reported a series of N-phenylisonicotinamide derivatives as novel xanthine oxidase (XO) inhibitors and identified N-(3-cyano-4-((2-cyanobenzyl)oxy)phenyl)isonicotinamide (compound 1) as the most potent one with an IC₅₀ value of 0.312 μM. To further optimize the structure and improve the potency, a structure-based drug design (SBDD) strategy was performed to construct the missing H-bond between the small molecule and the Asn768 residue of XO. We introduced a tetrazole moiety at the 3'-position of the phenyl to serve as an H-bond acceptor and obtained a series of N-(3-(1H-tetrazol-1-yl)phenyl)isonicotinamide derivatives (2a-t and 6-8). Besides, to investigate the influence of the amide-reversal, some N-(pyridin-4-yl)-3-(1H-tetrazol-1-yl)benzamide derivatives (3c, 3e, 3i, 3k and 3u) were also synthesized and evaluated. Biological evaluation and structure-activity relationship analysis demonstrated that the 3'-(1H-tetrazol-1-yl) moiety was an excellent fragment for the N-phenylisonicotinamide scaffold; a substituted benzyloxy, especially, an m-cyanobenzyloxy (e.g., 2s), linking at the 4'-position was welcome for the potency; and the amide-reversal could damage the potency, so maintenance of the N-phenylisonicotinamide scaffold was essential. In summary, starting from compound 1, the SBDD effort successfully identified a promising XO inhibitor 2s (IC₅₀ = 0.031 μM), with a 10-fold gain in potency. Its potency was very close to the positive control topiroxostat (IC₅₀ = 0.021 μM). A Lineweaver-Burk plot indicated that compound 2s acted as a mixed-type XO inhibitor. Molecular docking and molecular dynamics simulations revealed that the tetrazole moiety could occupy the Asn768-sub-pocket with N-4 atom accepting an H-bond from the Asn768 residue, as expected.

Oxidative Stress and Renal Fibrosis: Mechanisms and Therapies

Oxidative stress results from the disruption of the redox system marked by a notable overproduction of reactive oxygen species. There are four major sources of reactive oxygen species, including NADPH oxidases, mitochondria, nitric oxide synthases, and xanthine oxidases. It is well known that renal abnormalities trigger the production of reactive oxygen species by diverse mechanisms under various pathologic stimuli, such as acute kidney injury, chronic kidney disease, nephrotic syndrome, and metabolic disturbances. Mutually, accumulating evidences have identified that oxidative stress plays an essential role in tubulointerstitial fibrosis by myofibroblast activation as well as in glomerulosclerosis by mesangial sclerosis, podocyte abnormality, and parietal epithelial cell injury. Given the involvement of oxidative stress in renal fibrosis, therapies targeting oxidative stress seem promising in renal fibrosis management. In this review, we sketch the updated knowledge of the mechanisms of oxidative stress generation during renal diseases, the pathogenic processes of oxidative stress elicited renal fibrosis and treatments targeting oxidative stress during tubulointerstitial fibrosis and glomerulosclerosis.

Effects of allopurinol and febuxostat on cardiovascular mortality in elderly heart failure patients

Hyperuricemia is an emerging risk factor for the development of heart failure (HF) and is associated with a worsen prognosis of the disease. The effect of urate lowering drugs (ULT) and, in particular, the xanthine oxidase inhibitor in patients with HF is controversial. The aim of the study is to compare the effects of treatment with two different xanthine oxidase inhibitors (allopurinol or febuxostat) on cardiovascular mortality in elderly patients with chronic HF in a setting of clinical practice. In this observational trial, 255 elderly patients affected by chronic HF and treated with ULT on top of optimal medical treatment for HF. The sample included only outpatients with mild-to-moderate HF mainly secondary to chronic arterial hypertension or coronary artery disease and not previously hospitalized for HF. Patient treated with febuxostat (N. 120) and allopurinol (N. 135) were balanced for most of the baseline variables. In particular age, NYHA class distribution, drug treatment and renal function were comparable at the baseline and during the observation in both groups (p > 0.05). After a mean follow-up period of 5.1 years, the cumulative cardiovascular survival was 0.96 (95% CI 0.93-0.99) in febuxostat-treated patients and 0.89 (95% CI 0.84-0.93) in those treated with allopurinol. The between group difference, adjusted for the main confounding risk factors, was statistically significant (p = 0.04). Our study results suggest that possibility that febuxostat, a selective XO inhibitor, may favorably affect cardiovascular mortality in comparison with allopurinol in elderly patients with mild-to-moderate HF. This preliminary observation deserves further evaluation in the next future.