Localization of the human urate oxidase gene (UOX) to 1p22

Rationalization design, soluble expression and PEG modification of highly active recombinant human-porcine uricase mutant protein

Uric acid is the end product of purine metabolism in humans due to inactivation of the uricase determined by the mutated uricase gene. Uricase catalyzes the conversion of uric acid into water-soluble allantoin that is easily excreted by the kidneys. Hyperuricemia occurs when the serum concentration of uric acid exceeds its solubility (7 mg/dL). However, modifications to improve the uricase activity is under development for treating the hyperuricemia. Here we designed 7 types of human-porcine chimeric uricase by multiple sequence comparisons and targeted mutagenesis. An optimal human-porcine chimeric uricase mutant (uricase-10) with both high activity (6.33 U/mg) and high homology (91.45 %) was determined by enzyme activity measurement. The engineering uricase was further modified with PEGylation to improve the stability of recombinant protein drugs and reduce immunogenicity, uricase-10 could be more suitable for the treatment of gout and hyperuricemia theoretically.

The Urine Metabolome of Young Autistic Children Correlates with Their Clinical Profile Severity

Autism diagnosis is moving from the identification of common inherited genetic variants to a systems biology approach. The aims of the study were to explore metabolic perturbations in autism, to investigate whether the severity of autism core symptoms may be associated with specific metabolic signatures; and to examine whether the urine metabolome discriminates severe from mild-to-moderate restricted, repetitive, and stereotyped behaviors. We enrolled 57 children aged 2–11 years; thirty-one with idiopathic autism and twenty-six neurotypical (NT), matched for age and ethnicity. The urine metabolome was investigated by gas chromatography-mass spectrometry (GC-MS). The urinary metabolome of autistic children was largely distinguishable from that of NT children; food selectivity induced further significant metabolic differences. Severe autism spectrum disorder core deficits were marked by high levels of metabolites resulting from diet, gut dysbiosis, oxidative stress, tryptophan metabolism, mitochondrial dysfunction. The hierarchical clustering algorithm generated two metabolic clusters in autistic children: 85–90% of children with mild-to-moderate abnormal behaviors fell in cluster II. Our results open up new perspectives for the more general understanding of the correlation between the clinical phenotype of autistic children and their urine metabolome. Adipic acid, palmitic acid, and 3-(3-hydroxyphenyl)-3-hydroxypropanoic acid can be proposed as candidate biomarkers of autism severity.

Serum uric acid increases in patients with systemic autoimmune rheumatic diseases after 3 months of treatment with TNF inhibitors

In patients with gout, the serum uric acid (SUA) is usually lower during acute gouty attacks than during intercritical periods. It has been suggested that systemic inflammatory response can cause this phenomenon. The objective is to determine whether therapy with TNF inhibitors (TNFis) affects SUA levels in patients with systemic autoimmune rheumatic diseases (SARDs) and whether SUA changes correlate with pro-inflammatory cytokines or with the oxidative stress marker allantoin. In this study, SUA, CRP, creatinine, MCP-1, IFN-α2, IFN-γ, Il-1β, IL-6, IL-8, IL-10, IL-12, IL-17a, IL-18, IL-23, IL-33, TNF-α, and allantoin levels were measured prior to and after 3 months of TNFis treatment in patients with SARDs. The values obtained in the biochemical assays were then tested for associations with the patients' demographic and disease-related data. A total of 128 patients (rheumatoid arthritis, n = 44; ankylosing spondylitis, n = 45; psoriatic arthritis, n = 23; and adults with juvenile idiopathic arthritis, n = 16) participated in this study. Among the entire patient population, SUA levels significantly increased 3 months after starting treatment with TNFis (279.5 [84.0] vs. 299.0 [102.0] μmol/l, p < 0.0001), while the levels of CRP, IL-6, IL-8, and MCP-1 significantly decreased. Male sex was the most powerful baseline predictor of ΔSUA in univariate and multivariate models. None of the measured laboratory-based parameters had statistically significant effects on the magnitude of ΔSUA. 3 months of anti-TNF therapy increased the levels of SUA in patients with SARDs, but neither the measured pro-inflammatory cytokines nor the oxidation to allantoin appeared responsible for this effect.

Serum metabolites are associated with all-cause mortality in chronic kidney disease

Chronic kidney disease (CKD) involves significant metabolic abnormalities and has a high mortality rate. Because the levels of serum metabolites in patients with CKD might provide insight into subclinical disease states and risk for future mortality, we determined which serum metabolites reproducibly associate with mortality in CKD using a discovery and replication design. Metabolite levels were quantified via untargeted liquid chromatography and mass spectroscopy from serum samples of 299 patients with CKD in the Modification of Diet in Renal Disease (MDRD) study as a discovery cohort. Six among 622 metabolites were significantly associated with mortality over a median follow-up of 17 years after adjustment for demographic and clinical covariates, including urine protein and measured glomerular filtration rate. We then replicated associations with mortality in 963 patients with CKD from the African American Study of Kidney Disease and Hypertension (AASK) cohort over a median follow-up of ten years. Three of the six metabolites identified in the MDRD cohort replicated in the AASK cohort: fumarate, allantoin, and ribonate, belonging to energy, nucleotide, and carbohydrate pathways, respectively. Point estimates were similar in both studies and in meta-analysis (adjusted hazard ratios 1.63, 1.59, and 1.61, respectively, per doubling of the metabolite). Thus, selected serum metabolites were reproducibly associated with long-term mortality in CKD beyond markers of kidney function in two well characterized cohorts, providing targets for investigation.

Development of Therapeutic Chimeric Uricase by Exon Replacement/Restoration and Site-Directed Mutagenesis

The activity of urate oxidase was lost during hominoid evolution, resulting in high susceptibility to hyperuricemia and gout in humans. In order to develop a more “human-like” uricase for therapeutic use, exon replacement/restoration and site-directed mutagenesis were performed to obtain porcine–human uricase with higher homology to deduced human uricase (dHU) and increased uricolytic activity. In an exon replacement study, substitution of exon 6 in wild porcine uricase (wPU) gene with corresponding exon in dhu totally abolished its activity. Substitutions of exon 5, 3, and 1–2 led to 85%, 60%, and 45% loss of activity, respectively. However, replacement of exon 4 and 7–8 did not significantly change the enzyme activity. When exon 5, 6, and 3 in dhu were replaced by their counterparts in wpu, the resulting chimera H_1-2P₃H₄P_5-6H_7-8 was active, but only about 28% of wPU. Multiple sequence alignment and homology modeling predicted that mutations of E24D and E83G in H_1-2P₃H₄P_5-6H_7-8 were favorable for further increase of its activity. After site-directed mutagenesis, H_1-2P₃H₄P_5-6H_7-8 (E24D & E83G) with increased homology (91.45%) with dHU and higher activity and catalytic efficiency than the FDA-approved porcine–baboon chimera (PBC) was obtained. It showed optimum activity at pH 8.5 and 35 °C and was stable in a pH range of 6.5–11.0 and temperature range of 20–40 °C.

The ratio of oxidized and reduced forms of selected antioxidants as a possible marker of oxidative stress in humans

Oxidative stress is an imbalance between reactive oxygen species exposure and the ability of organisms to detoxify the reactive intermediates and to repair the oxidative damage of biologically important molecules. Many clinical studies of oxidative stress unfortunately provide conflicting and contradictory results. The ability of antioxidant systems to adequately respond to oxidative stress can be used in laboratory diagnostics. In the present review, methods using the ratio of reduced and oxidized forms of uric acid, ascorbic acid, glutathione and coenzyme Q10 as suitable indicators of oxidative stress are discussed. From the mentioned publications it is evident that suitable sample preparation prior to analysis is crucial.

A Monitoring of Allantoin, Uric Acid, and Malondialdehyde Levels in Plasma and Erythrocytes After Ten Minutes of Running Activity

Uric acid is the final product of human purine metabolism. It was pointed out that this compound acts as an antioxidant and is able to react with reactive oxygen species forming allantoin. Therefore, the measurement of allantoin levels may be used for the determination of oxidative stress in humans. The aim of the study was to clarify the antioxidant effect of uric acid during intense exercise. Whole blood samples were obtained from a group of healthy subjects. Allantoin, uric acid, and malondialdehyde levels in plasma and erythrocytes were measured using a HPLC with UV/Vis detection. Statistical significant differences in allantoin and uric acid levels during short-term intense exercise were found. Immediately after intense exercise, the plasma allantoin levels increased on the average of 200 % in comparison to baseline. Plasma uric acid levels increased slowly, at an average of 20 %. On the other hand, there were no significant changes in plasma malondialdehyde. The results suggest that uric acid, important antioxidant, is probably oxidized by reactive oxygen species to allantoin. Therefore allantoin may be suitable candidate for a marker of acute oxidative stress.

Allantoin as a marker of oxidative stress in human erythrocytes

BACKGROUND

Uric acid is the final product of purine metabolism in humans. It was determined that this compound has important antioxidative properties and it may be oxidized to allantoin by various reactive oxygen species. Therefore, the measurement of allantoin may be useful for the determination of oxidative stress in humans.

METHODS

We measured allantoin and uric acid in human plasma and erythrocytes obtained from patients with chronic renal failure before hemodialysis (n=30) and blood donors (n=30). We used a method based on selective isolation of allantoin from deproteinized plasma and erythrocyte lysate samples on AG 1-X8 resin and its derivatization to glyoxylate-2, 4-dinitrophenylhydrazone. Separation of glyoxylate-2, 4-dinitrophenylhydrazone from interfering substances was achieved on reversed phase HPLC with gradient elution and UV/VIS detection at 360 nm. Uric acid was determined by reversed phase HPLC with UV/VIS detection at 292 nm.

RESULTS

We found significant differences in allantoin and uric acid concentration between the patients with chronic renal failure and the control group both in plasma (20.5+/-6.5 micromol/L and 323.9+/-62.9 micromol/L vs. 2.1+/-1.1 micromol/L and 270.1+/-62.3 micromol/L, p<0.05) and erythrocytes [82.8+/-39.1 nmol/g hemoglobin (Hb) and 110.7+/-28.8 nmol/g Hb vs. 20.1+/-6.1 nmol/g Hb and 82.1+/-23.7 nmol/g Hb, p<0.05].

CONCLUSIONS

Significant higher levels of allantoin in both plasma and erythrocytes of patients with chronic renal failure indicate that allantoin may be used as a good marker of oxidative stress.

Simultaneous determination of allantoin, hypoxanthine, xanthine, and uric acid in serum/plasma by CE

Allantoin (All) is an oxidative end product of purines in mammals. The small amount of All present in human plasma or serum results from free radical action on urate and may provide a stable marker of in vivo free radical activity. Because free radicals have been implicated in the development and progression of atherosclerosis, this study focused on the metabolic compounds of the All pathway. We propose a new fast CE (CE/UV) method for the simultaneous determination of All, uric acid (UA), hypoxanthine (HX), and xanthine (X) in human plasma. These products were quantified in the plasma of patients with chronic renal failure before hemodialysis (n = 6), patients with chronic heart failure (n = 6) and controls (n = 6). The filtered plasma were diluted ten-fold before the direct injection in CE/UV (195 nm), which allows separating the four compounds in less than 13 min. The metabolites were detectable at concentrations of 0.3-0.6 micromol/L. The method was linear over the range 0.5-150 micromol/L for All, HX, and X and 10-1500 micromol/L for UA (r > 0.99). The analytical performance of this method is satisfactory with intra-assay CV < 3.4%, inter-assay CV < 5% (HX and X < 7%), and recovery (93-101%). The proposed CE-UV method appears to be a useful tool for studying physiological and pathological changes of HX, UA, and All levels in plasma samples, the latter being a possible indicator of free radical damage in vivo.

Monitoring of antioxidant properties of uric acid in humans for a consideration measuring of levels of allantoin in plasma by liquid chromatography

Uric acid is the end product of purine metabolism in humans. It has been pointed out that uric acid acts as an antioxidant and is capable to react with biologically relevant oxidants to form allantoin. Therefore, measurement of allantoin in humans was proposed as a marker of oxidative stress. We estimated allantoin in human plasma obtained from the patients with chronic renal failure before hemodialysis (n=30), patients with non-insulin dependent diabetes mellitus (n=30) and blood donors (n=30) using a method based on selective isolation of allantoin from deproteinized plasma samples on AG 1-X8 resin and its derivatization to glyoxylate-2,4-dinitrophenylhydrazone. The method is free from urate and glyoxylate interferences. Separation of glyoxylate-2,4-dinitrophenylhydrazone from other hydrazones was achieved on reversed phase HPLC with gradient elution and UV/VIS detection at 360 nm. The analytical performance of this method is satisfactory with intra-assay CV 5.7%, inter-assay CV 8.3% and recovery 94.1%. We have determined other parameters of oxidative stress (malondialdehyde, total antioxidant status, superoxide dismutase and glutathione peroxidase) too. The preliminary reference range of allantoin in a group of blood donors is 4.76+/-2.99 micromol/L. In the patients with chronic renal failure and the patients with non-insulin dependent diabetes mellitus we found allantoin levels in plasma (27.1+/-13.8) micromol/L and (11.08+/-5.90) micromol/L, respectively. It seems that allantoin is a possible indicator of free radical damage in vivo.

Acute renal failure in cancer patients

Acute renal failure (ARF) is defined as a sudden decrease in glomerular filtration rate leading to an acute rise in blood urea nitrogen and serum creatinine levels. It is a serious complication of cancer and constitutes a major source of morbidity and mortality. Current data suggest that ARF has the potential to substantially jeopardize the chances of cancer patients receiving optimal treatment and a potential cure. The pathways leading to ARF in cancer patients are common to the development of ARF in other conditions. However, ARF may also develop due to aetiologies arising from cancer treatment or the disease itself, including: nephrotoxic chemotherapy agents, post-renal obstruction, compression and infiltration by malignancy, tumour lysis syndrome, uric acid, sepsis and contrast agent nephropathy. This review provides a comprehensive overview of the causes of ARF in patients with cancer and guidance on how to prevent and treat this condition. Ultimately, the key to managing ARF in cancer patients is to ensure that a multidisciplinary approach provides adequate assessment, appropriate preventative measures and early intervention.

Rasburicase: a potent uricolytic agent

Rasburicase (Fasurtec, Elitek, Sanofi-Synthelabo) is a new recombinant urate oxidase developed for the prevention and treatment of hyperuricaemia. It has a half-life of 17-21 h and produces rapid (within 4 h) and pronounced reductions in plasma uric acid concentrations. To date, rasburicase has been tested in four clinical trials conducted in patients with cancer (primarily haematological malignancies). It successfully alleviated hyperuricaemia in 98% of patients and prevented this complication in 99.6% of those who were at risk. In a stratified, randomised trial, rasburicase was more effective than allopurinol. Most patients had improved or stabilised renal function during rasburicase treatment, despite ongoing chemotherapy-induced tumour lysis. Except for occasional instances of haemolytic anaemia and methemoglobinaemia in patients with glucose-6-phosphate dehydrogenase deficiency, rasburicase was well-tolerated, with a low frequency of mild adverse events. Rasburicase is a safe and effective agent in the prevention or treatment of hyperuricaemia in cancer patients.

The cloning, genomic structure, localization, and expression of human deoxyribonuclease IIβ

Acidic endonuclease activity is present in all cells in the body and much of this can be attributed to the previously cloned and ubiquitously expressed deoxyribonuclease II (DNase II). Database analysis revealed the existence of expressed sequence tags and genomic segments coding for a protein with considerable homology to DNase II. This report describes the cloning of this cDNA, which we term deoxyribonuclease IIbeta (DNase IIbeta) and comparison of its expression to that of the originally cloned DNase II (now termed DNase IIalpha). The cDNA encodes a 357 amino acid protein. This protein exhibits extensive homology to DNase IIalpha including an amino-terminal signal peptide and a conserved active site, and has many of the regions of identity that are conserved in homologs in other mammals as well as C. elegans and Drosophila. The gene encoding DNase IIbeta has identical splice sites to DNase IIalpha. Human DNase IIbeta is highly expressed in the salivary gland, and at low levels in trachea, lung, prostate, lymph node, and testis, whereas DNase IIalpha is ubiquitously expressed in all tissues. The expression pattern of human DNase IIbeta suggests that it may function primarily as a secreted enzyme. Human saliva was found to contain DNase IIalpha, but after immunodepletion, considerable acid-active endonuclease remained which we presume is DNase IIbeta. We have localized the gene for human DNase IIbeta to chromosome 1p22.3 adjacent (and in opposing orientation) to the human uricase pseudogene. Interestingly, murine DNase IIbeta is highly expressed in the liver. Uricase is also highly expressed in mouse but not human liver and this may explain the difference in expression patterns between human and mouse DNase IIbeta.

Assignment of 19 porcine type I loci by somatic cell hybrid analysis detects new regions of conserved synteny between human and pig

Nineteen so-called type I-loci, including ACO2, ADRA2, CAST, CCK, CHAT, IGKC, IGLV, IL4, IL6, INHA, LIF, MX1, PTH, RBP2, TCRA, TCRB, TGFB2, TGFB3, and UOX have been mapped in the pig with an informative somatic cell hybrid panel. By analyzing these new assignments in the knowledge of heterologous chromosome painting (Zoo-FISH) data for the porcine genome, it is possible to predict subchromosomal locations for most of these loci. Previously defined regions of conserved synteny were confirmed, and the extent of six of these regions was refined. These improvements in the porcine gene map facilitate the transfer of gene mapping data from "map-rich" species such as humans and mice.

Mapping of the porcine urate oxidase and transforming growth factor beta 2 genes by fluorescence in situ hybridization

We have mapped two genes from human chromosome 1, urate oxidase (UOX) and transforming growth factor beta 2 (TGFB2), by fluorescence in situ hybridization (FISH) in the pig genome. Porcine-specific polymerase chain reaction (PCR) primers for both genes were designed from the porcine cDNA sequence. With the help of these primers yeast artificial chromosome (YAC) clones for UOX and TGFB2 were isolated from a pig YAC library. These DNA probes were used for FISH analysis. TGFB2 was localized to SSC 10p16. With the YAC probe for UOX two porcine chromosome regions 6q26 and 6q32, revealed specific signals. These results, help to refine the comparative mapping data between human and pig.

Towards the physiological function of uric acid

Uric acid, or more correctly (at physiological pH values), its monoanion urate, is traditionally considered to be a metabolically inert end-product of purine metabolism in man, without any physiological value. However, this ubiquitous compound has proven to be a selective antioxidant, capable especially of reaction with hydroxyl radicals and hypochlorous acid, itself being converted to innocuous products (allantoin, allantoate, glyoxylate, urea, oxalate). There is now evidence for such processes not only in vitro and in isolated organs, but also in the human lung in vivo. Urate may also serve as an oxidisable cosubstrate for the enzyme cyclooxygenase. As shown for the coronary system, a major site of production of urate is the microvascular endothelium, and there is generally a net release of urate from the human myocardium in vivo. In isolated organ preparations, urate protects against reperfusion damage induced by activated granulocytes, cells known to produce a variety of radicals and oxidants. Intriguingly, urate prevents oxidative inactivation of endothelial enzymes (cyclooxygenase, angiotensin converting enzyme) and preserves the ability of the endothelium to mediate vascular dilatation in the face of oxidative stress, suggesting a particular relationship between the site of urate formation and the need for a biologically potent radical scavenger and antioxidant.