Noncompetitive Determination of Small Analytes by Sandwich-Type Lateral Flow Assay Based on an Aptamer Kissing Complex

Here, we present the proof-of-concept of a lateral flow assay (LFA) that is capable of detecting small-molecule targets in a noncompetitive manner by deploying a sandwich-type format based on the aptamer kissing complex (AKC) strategy. A fluorescently labeled hairpin aptamer served as the signaling agent, while a specific RNA hairpin grafted onto the strip served as the capture element. The hairpin aptamer switched from an unfolded to a folded form in the presence of the target, resulting in kissing interactions between the loops of the reporter and the capture agents. This design triggered a target-dependent fluorescent signal at the test line. The AKC-based LFA was developed for the detection of adenosine, achieving a detection limit in the micromolar range. The assay revealed the presence of the same analyte in urine. The method also proved effective with another small molecule (theophylline). We believe that the AKC-based LFA approach could overcome many of the shortcomings associated with conventional signal-off methods and competitive processes.

A novel "off-on" ratiometric fluorescent aptasensor for adenosine detection based on FRET between quantum dots and graphene oxide

A novel "off-on" ratiometric fluorescent aptasensor was established for adenosine detection based on fluorescence resonance energy transfer (FRET) between CdS QDs, DNA QDs as donor and graphene oxide (GO) as acceptor. Amino-riched DNA QDs covalently bonded to the carboxyl group on the edge of the GO, and with the absorption of the TGA-modified CdS QDs with aptamer (CdS QDs-apt) onto the GO surface via the π-π stacking interaction. The fluorescence of both CdS QDs and DNA QDs were efficiently quenched due to FRET (turn off). When adenosine was present, the specific binding of the aptamer to the target preferentially that released the CdS QDs-apt from GO. The process would inhibit the FRET which contribute to the fluorescence of CdS QDs-apt recovery again (turn on), while the fluorescence intensity of DNA QDs only slightly altered and acted as the reference signal. Thus, a novel "off-on" ratiometric fluorescent aptasensor for adenosine detection was constructed accordingly. There was a good linearity relationship between the ratio of the FL intensity (F595 nm/F464 nm) and the concentration of adenosine in the range of 20.00-180.0 nmol/L with a detection limit of 1.3 nmol/L (S/N = 3, n = 9). Importantly, the feasibility of the developed aptasensor for selective detection of adenosine in serum and urine samples with satisfactory results. The recoveries were observed to be 97.04-100.2 %.

Understanding Parahydrogen Hyperpolarized Urine Spectra: The Case of Adenosine Derivatives

Parahydrogen hyperpolarization has emerged as a promising tool for sensitivity-enhanced NMR metabolomics. It allows resolution and quantification of NMR signals of certain classes of low-abundance metabolites that would otherwise be undetectable. Applications have been implemented in pharmacokinetics and doping drug detection, demonstrating the versatility of the technique. Yet, in order for the method to be adopted by the analytical community, certain limitations have to be understood and overcome. One such question is NMR signal assignment. At present, the only reliable way to establish the identity of an analyte that gives rise to certain parahydrogen hyperpolarized NMR signals is internal standard addition, which can be laborious. Herein we show that analogously to regular NMR metabolomics, generating libraries of hyperpolarized analyte signals is a viable way to address this limitation. We present hyperpolarized spectral data of adenosines and give an early example of identifying them from a urine sample with the small library. Doing so, we verify the detectability of a class of diagnostically valuable metabolites: adenosine and its derivatives, some of which are cancer biomarkers, and some are central to cellular energy management (e.g., ATP).

Applicability of Supercritical fluid chromatography-Mass spectrometry to metabolomics. II-Assessment of a comprehensive library of metabolites and evaluation of biological matrices

In this work, the impact of biological matrices, such as plasma and urine, was evaluated under SFCHRMS in the field of metabolomics. For this purpose, a representative set of 49 metabolites were selected. The assessment of the matrix effects (ME), the impact of biological fluids on the quality of MS/MS spectra and the robustness of the SFCHRMS method were each taken into consideration. The results have highlighted a limited presence of ME in both plasma and urine, with 30% of the metabolites suffering from ME in plasma and 25% in urine, demonstrating a limited sensitivity loss in the presence of matrices. Subsequently, the MS/MS spectra evaluation was performed for further peak annotation. Their analyses have highlighted three different scenarios: 63% of the tested metabolites did not suffer from any interference regardless of the matrix; 21% were negatively impacted in only one matrix and the remaining 16% showed the presence of matrix-belonging compounds interfering in both urine and plasma. Finally, the assessment of retention times stability in the biological samples, has brought into evidence a remarkable robustness of the SFCHRMS method. Average RSD (%) values of retention times for spiked metabolites were equal or below 0.5%, in the two biological fluids over a period of three weeks. In the second part of the work, the evaluation of the Sigma Mass Spectrometry Metabolite Library of Standards containing 597 metabolites, under SFCHRMS conditions was performed. A total detectability of the commercial library up to 66% was reached. Among the families of detected metabolites, large percentages were met for some of them. Highly polar metabolites such as amino acids (87%), nucleosides (85%) and carbohydrates (71%) have demonstrated important success rates, equally for hydrophobic analytes such as steroids (78%) and lipids (71%). On the negative side, very poor performance was found for phosphorylated metabolites, namely phosphate-containing compounds (14%) and nucleotides (31%).

Optical aptasensor based on silver nanoparticles for the colorimetric detection of adenosine

A new and straightforward optical sensor for the colorimetric determination of adenosine (AD) in human urine samples was developed. The sensor comprised silver nanoparticles (AgNPs) as colorimetric elements and anti-AD aptamer (AP) as a recognition probe. In a solution containing AD and high concentration of NaCl, due to the unique binding of AD with AP, the aggregated metal nanomaterials dispersed in the solution, and the color intensity of the solution was changed accordingly. The absorbance of the solution was monitored for AD quantification. The method was applicable for the determination of AD in the concentration range of 60-280 nM with the detection limit of 21 nM. The relative standard deviation ranged from 4.8 to 8.8% for six replicates. The method showed excellent selectivity toward AD checked over some probable interfering compounds. To investigate the performance of AgNPs, the analytical characteristics of the method including linear range, detection limit, selectivity, and precision were compared with those obtained by a common AuNPs-based aptasensor. The reliability of the method was further ascertained for the detection of AD in urine samples of two lung cancer patients with percentage recoveries in the range of 98-107%.

Adenosine kinase deficiency: expanding the clinical spectrum and evaluating therapeutic options

BACKGROUND

Adenosine kinase deficiency is a recently described defect affecting methionine metabolism with a severe clinical phenotype comprising mainly neurological and hepatic impairment and dysmorphism.

METHODS

Clinical data of 11 additional patients from eight families with adenosine kinase deficiency were gathered through a retrospective questionnaire. Two liver biopsies of one patient were systematically evaluated.

RESULTS

The main clinical symptoms are mild to severe liver dysfunction with neonatal onset, muscular hypotonia, global developmental retardation and dysmorphism (especially frontal bossing). Hepatic involvement is not a constant finding. Most patients have epilepsy and recurrent hypoglycemia due to hyperinsulinism. Major biochemical findings are intermittent hypermethioninemia, increased S-adenosylmethionine and S-adenosylhomocysteine in plasma and increased adenosine in urine. S-adenosylmethionine and S-adenosylhomocysteine are the most reliable biochemical markers. The major histological finding was pronounced microvesicular hepatic steatosis. Therapeutic trials with a methionine restricted diet indicate a potential beneficial effect on biochemical and clinical parameters in four patients and hyperinsulinism was responsive to diazoxide in two patients.

CONCLUSION

Adenosine kinase deficiency is a severe inborn error at the cross-road of methionine and adenosine metabolism that mainly causes dysmorphism, brain and liver symptoms, but also recurrent hypoglycemia. The clinical phenotype varies from an exclusively neurological to a multi-organ manifestation. Methionine-restricted diet should be considered as a therapeutic option.

Structure Elucidation of the Metabolites of 2', 3', 5'-Tri-O-Acetyl-N6-(3-Hydroxyphenyl) Adenosine in Rat Urine by HPLC-DAD, ESI-MS and Off-Line Microprobe NMR

2', 3', 5'-Tri-O-acetyl-N6-(3-hydroxyphenyl) adenosine (also known as WS070117) is a new adenosine analog that displays anti-hyperlipidemic activity both in vitro and in vivo experiments as shown in many preliminary studies. Due to its new structure, little is known about the metabolism of WS070117. Hence, the in vivo metabolites of WS070117 in rat urine following oral administration were investigated. Identification of the metabolites was conducted using the combination of high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD), ion trap electrospray ionization-mass spectrometry (ESI-MS), and off-line microprobe nuclear magnetic resonance (NMR) measurements. Seven metabolites were obtained as pure compounds at the sub-milligram to milligram levels. Results of structure elucidation unambiguously revealed that the phase I metabolite, N6-(3-hydroxyphenyl) adenosine (M8), was a hydrolysate of WS070117 by hydrolysis on the three ester groups. N6-(3-hydr-oxyphenyl) adenine (M7), also one of the phase I metabolites, was the derivative of M8 by the loss of ribofuranose. In addition to two phase I metabolites, there were five phase II metabolites of WS070117 found in rat urine. 8-hydroxy-N6-(3-hydroxy-phenyl) adenosine (M6) was the product of M7 by hydrolysis at position 8. The other four were elucidated to be N6-(3-O-β-D-glucuronyphenyl) adenine (M2), N8-hydroxy-N6-(3-O-sulfophenyl) adenine (M3), N6-(3-O-β-D-glucuronyphenyl) adenosine (M4), and N6-(3-O- sulfophenyl) adenosine (M5). Phase II metabolic pathways were proven to consist of hydroxylation, glucuronidation and sulfation. This study provides new and valuable information on the metabolism of WS070117, and also demonstrates the HPLC/MS/off-line microprobe NMR approach as a robust means for rapid identification of metabolites.

Gold-nanoparticle extraction and reversed-electrode-polarity stacking mode combined to enhance capillary electrophoresis sensitivity for conjugated nucleosides and oligonucleotides containing thioether linkers

We present a capillary electrophoresis method for determining two different C8-conjugated deoxyadenosines, and for oligonucleotides containing them, in which a psoralen or an acridine molecule is bonded to the base via a short alkyl chain containing sulfur ethers at both ends. The sensitivity of the micellar electrokinetic chromatography (MEKC) method was increased by using two preconcentration techniques, micro solid-phase extraction (μSPE) followed by reversed-electrode-polarity stacking mode (REPSM). Variables that affect the efficiency of the extraction in μSPE and preconcentration by REPSM, including the type and volume of extraction nanoparticle, concentration, and injection time, were investigated. Under the optimum conditions, enrichment factors obtained were in the range 360-400. The limits of detection (LODs) at a signal-to-noise ratio of 3 ranged from 2 to 5 nmol L(-1). The relative recoveries of labelled adenosines from water samples were 95-103%. The proposed method provided high enrichment factors and good precision and accuracy with a short analysis time. On the basis of the advantages of simplicity, high selectivity, high sensitivity, and good reproducibility, the proposed method may have great potential for biochemical applications.

Facile and label-free detection of lung cancer biomarker in urine by magnetically assisted surface-enhanced Raman scattering

Adenosine plays a crucial role in the regulation of physiological activity in various tissues and organs. As adenosine is a possible biomarker for cancer, the determination of its level presents a demanding task for deeply monitoring progress of diseases. Through the synthesis of Fe3O4/Au/Ag nanocomposites weaved and stabilized by phytic acid and its salt, we develop a magnetically assisted surface-enhanced Raman scattering (SERS) protocol to determine trace level adenosine in urine samples from both lung cancer patients and health human. The magnetic properties of the nanocomposites enable to realize the simple separation of targeted molecules from a complex matrix and the Au/Ag nanoparticles moieties act as the SERS platform. This label-free Fe3O4/Au/Ag-nanocomposites-based SERS protocol shows a good stability, reproducibility, time efficiency (less than 20 min for one sample test), and huge sensitivity down to 1 × 10(-10) M. The protocol also has high selectivity because SERS signal of adenosine provides the molecular fingerprint information as well as an azo coupling pretreatment is performed to remove the interference of urea. Furthermore, a SERS array is designed for on-site screening adenosine in urine samples in a massive way using a portable Raman. Such a magnetically assisted SERS method as a powerful alternative can be expected as a smart and promising tool for effective assessment of healthcare.

The need for vigilance: false-negative screening for adenylosuccinate lyase deficiency caused by deribosylation of urinary biomarkers

OBJECTIVES

Adenylosuccinate lyase deficiency (dADSL) is a rare inherited metabolic disorder. Biochemical diagnosis of the disease is based on the determination of enormously elevated urinary levels of succinylaminoimidazole carboxamide riboside (SAICA-riboside) and succinyladenosine (SAdo). We report a case of false negative screening for dADSL caused by deribosylation of the urinary biomarkers SAICA-riboside and SAdo.

DESIGN AND METHODS

A thin-layer chromatography (TLC) method with Pauly reagent detection of SAICA-riboside was used as a screening method. High-performance liquid chromatography with diode-array detection (HPLC-DAD) and LC-MS/MS methods were used for the identification and quantitative determination of SAICA-riboside, SAdo, succinylaminoimidazole carboxamide (SAICA) and succinyladenine (SA).

RESULTS

Following a negative TLC screening in a known case of dADSL, we analyzed urine using HPLC-DAD. The concentration of SAICA-riboside was 2.7mmol/mol creatinine (below the TLC detection limit), and we detected the two abnormal metabolites identified by LC-MS/MS as SAICA and SA. We showed that SAICA and SA were produced by deribosylation of SAICA-riboside and SAdo in the patient's urine. Studies performed by monitoring the production of SAICA and SA after the addition of SAICA-riboside and SAdo to the patient's urine and to urine samples from patients with urinary tract infections suggested that deribosylation is facilitated by bacterial enzymes.

CONCLUSIONS

Screening methods for the diagnosis of dADSL may be falsely negative due to bacteria-mediated deribosylation of SAICA-riboside and SAdo. HPLC-DAD or LC-MS/MS analyses allowing for simultaneous detection of SAICA-riboside, SAdo and their deribosylation products SAICA and SA should be preferentially used for the diagnosis of dADSL in urine.

Adenylosuccinate lyase deficiency in a Malaysian patient, with novel adenylosuccinate lyase gene mutations

Most cases of adenylosuccinate lyase (ADSL OMIM 103050) deficiency reported to date are confined to the various European ethnic groups. We report on the first Malaysian case of ADSL deficiency, which appears also to be the first reported Asian case. The case was diagnosed among a cohort of 450 patients with clinical features of psychomotor retardation, global developmental delay, seizures, microcephaly and/or autistic behaviour. The patient presented with frequent convulsions and severe myoclonic jerk within the first few days of life and severe psychomotor retardation. The high performance liquid chromatography (HPLC) profile of the urine revealed the characteristic biochemical markers of succinyladenosine (S-Ado) and succinyl-aminoimidazole carboximide riboside (SAICAr). The urinary S-Ado/SAICAr ratio was found to be 1.02 (type I ADSL deficiency). The patient was compound heterozygous for two novel mutations, c.445C > G (p.R149G) and c.774_778insG (p.A260GfsX24).

D-ribose therapy in four Polish patients with adenylosuccinate lyase deficiency: absence of positive effect

Deficiency of adenylosuccinate lyase (ADSL) (OMIM 103050) is an autosomal recessive disorder of the purine de novo synthesis pathway and purine nucleotide cycle, diagnosed so far in approximately 50 patients. The clinical presentation is characterized by severe neurological involvement including hypotonia, seizures, developmental delay and autistic features. Epilepsy in ADSL deficiency is frequent and occurs in approximately two-thirds of patients, beginning either early in the neonatal period or after the first year of life. At present there is no treatment of proven clinical efficacy. Despite of the increasing number of ADSL-deficient patients reported, there are only a few communications of therapeutic considerations or efforts. Among them only two showed some beneficial effects in ADSL-deficient patients. D-ribose, a simple and relatively cheap therapy, has been associated with improvement of behaviour and progressive reduction of the seizure frequency in one 13-year-old patient with ADSL deficiency. In this study we have re-examined D-ribose treatment in four ADSL-deficient patients. Assessments consisted of biochemical markers and neurological outcome. The 12-month trial of D-ribose failed to show any clinical benefit in ADSL patients with both milder and severe phenotype. D-ribose administration was accompanied by neither reduction in seizure frequency nor growth enhancement. Additionally, patients with milder type II presented the first seizure after 4 and 8 months of the D-ribose treatment. Therefore, we could not confirm a positive effect of D-ribose as previously reported.

Methotrexate and erythro-9-(2-hydroxynon-3-yl) adenine therapy for rat adjuvant arthritis and the effect of methotrexate on in vivo purine metabolism

The objectives were: (1) to test the association of methotrexate (MTX) efficacy in rat adjuvant arthritis (rat AA) with interference of purine biosynthesis and adenosine metabolism and (2) to test the efficacy of erythro-9-(2-hydroxynon-3-yl) adenine (EHNA), an inhibitor of adenosine deaminase, and the efficacy of aminoimidazolecarboxamide (AICA) riboside plus MTX in rat AA. Radiographic and histologic examinations of the hind limbs were measures of efficacy. Urinary excretions of AICA and adenosine were markers of AICA ribotide transformylase inhibition (i.e., blockage of purine biosynthesis) and interference with adenosine metabolism, respectively. AICA and adenosine excretions increased during the day of MTX dosing (treatment day) compared to the previous baseline day in animals responding well to MTX (i.e., low radiographic and histologic scores). Based on radiographic and histologic scores, adjuvant injected rats were separated into two disease categories (i.e., no/mild and moderate/severe). Only AICA excretion was significantly elevated on the treatment day in rat AA with no/mild disease (i.e., those responding well to MTX therapy). AICA (not adenosine) excretion was significantly correlated with the above scores. EHNA was not efficacious, even at toxic levels, while AICA riboside potentiated the efficacy of MTX. The data suggests that efficacious MTX therapy in rat AA (1) blocks purine biosynthesis; (2) increases in in vivo AICA levels. Also adenosine accumulation and blockage of adenosine deaminase (i.e., by EHNA) appear to be less critical to MTX efficacy. Increased levels of AICA metabolites may suppress the immune response in rat AA.

Effect of gender and cigarette smoking on urinary excretion of etheno DNA adducts in humans measured by isotope dilution gas chromatography/mass spectrometry

Endogenous formation of the promutagenic DNA adducts 1,N(6)-ethenoadenine (epsilon Ade) and 3,N(4)-ethenocytosine (epsilon Cyt) has been considered as biomarkers originated from lipid peroxidation. Elevated levels of epsilon Ade and epsilon Cyt were observed in cancer-prone tissues, suggesting the validity of these adducts in cancer risk assessment. The presence of DNA base adducts in biological fluids is considered to derive primarily from base excision repair (BER) systems. In this study, a modified gas chromatography/mass spectrometry (GC/MS) method is developed for simultaneous analysis of epsilon Ade and epsilon Cyt in human urine. After adjusting for creatinine concentration, urinary excretion of epsilon Ade, as well as epsilon Cyt, is much higher in 18 male smokers than in 10 male nonsmokers (p=0.003 for epsilon Ade and p=0.04 for epsilon Cyt). Furthermore, excretion of epsilon Ade and epsilon Cyt in 14 female nonsmokers is much higher than in 10 male nonsmokers (p=0.002 for epsilon Ade and p=0.005 for epsilon Cyt). These results suggest a statistically significant association between gender, as well as smoking, and excretion of epsilon Ade and epsilon Cyt. Moreover, urinary excretion of epsilon Ade in these 42 subjects correlates with that of epsilon Cyt (R(2)=0.6846, p<0.0001). Measurement of urinary epsilon Ade and epsilon Cyt excretion should provide valid noninvasive biomarkers for carcinogenesis and chemoprevention studies.

The pancreatohepatorenal cAMP-adenosine mechanism

Stimulation of adenylyl cyclase causes cellular efflux of cAMP, and cAMP (unlike adenosine) is stable in blood. Therefore, it is conceivable that cAMP could function as a circulating adenosine prohormone by local target-organ conversion of distally released cAMP to adenosine via the sequential actions of ectophosphodiesterase and ecto-5'-nucleotidase (cAMP==> AMP==> adenosine; called the cAMP-adenosine pathway). A possible specific representation of this general concept is the pancreatohepatorenal cAMP-adenosine mechanism. The pancreas secretes glucagon into the portal circulation, and glucagon is a stimulant of hepatic adenylyl cyclase. Therefore, we hypothesize that the pancreas, via glucagon, stimulates hepatic cAMP production, which provides circulating cAMP for conversion to adenosine in the kidney via the cAMP-adenosine pathway. In normal rats, intravenous cAMP increased urinary and renal interstitial (assessed by renal microdialysis) cAMP and adenosine. Intraportal infusions of glucagon increased plasma cAMP 10-fold, it did not affect plasma adenosine, and it increased urinary and renal interstitial cAMP and adenosine. Local renal interstitial blockade (by adding inhibitors directly to the microdialysis perfusate) of ectophosphodiesterase (using 3-isobutyl-1-methylxanthine or 1,3-dipropyl-8-p-sulfophenylxanthine) or ecto-5'-nucleotidase (using alpha,beta-methyleneadenosine-5'-diphosphate) prevented the cAMP-induced and glucagon-induced increases in renal interstitial adenosine, but not cAMP. In ZSF1 rats with the metabolic syndrome, an oral glucose load increased plasma glucagon and urinary cAMP and adenosine excretion. We conclude that circulating cAMP is a substrate for local conversion to adenosine via the cAMP-adenosine pathway. A specific manifestation of this is the pancreatohepatorenal cAMP-adenosine mechanism (pancreas==> portal glucagon==> liver==> circulating cAMP==> kidney==> local cAMP-adenosine pathway).

A Simple Quantitative Assay for Urinary Adenosine Using Column-Switching High-Performance Liquid Chromatography

Adenosine is a physiologically active molecule produced locally in many sites of the body to regulate various cell functions. Measurement of levels of the factor in organs and biological fluids provides clues to its role and we reported an accurate quantitative high-performance liquid chromatography method for urinary adenosine requiring no preliminary sample preparation, other than filtration. Analyses were performed isocratically with a reversed-phase and a molecular exclusion columns connected by a column switch. Each sample was analyzed automatically in 35 min. Linearity could be verified up to 1,000 micromol/L (r = 0.999) and recovery of adenosine was 94.6-98.0%. The coefficients of variation (CV) were established to be 0.56-1.32%, intra-assay, and 1.61-4.67%, inter-assay. Based on analyses of healthy individuals at different ages, we are here able to provide age-related values, infants (1.51 +/- 0.71 micromol/mmol creatinine) and children (1.06 +/- 0.36 and 0.83 +/- 0.27 micromol/mmol creatinine; aged 1-5 and 6-10 years), excreting significantly higher amounts of adenosine than adults (0.44 +/- 0.08 micromol/mmol creatinine). We also measured urinary adenosine from patients suffering from metabolic disease or severe respiratory failure and found that unfavorable pathophysiologic conditions are associated with appreciable elevation of adenosine.

Adenylosuccinate lyase deficiency--first British case

A deficiency of adenylosuccinate lyase (ASDL) is characterised by the accumulation of SAICAriboside (SAICAr) and succinyladenosine (S-Ado) in body fluids. The severity of the clinical presentation correlates with a low S-Ado/SAICAr ratio in body fluids. We report the first British case of ADSL deficiency. The patient presented at 14 days with a progressive neonatal encephalopathy and seizures. There was marked axial and peripheral hypotonia. Brain MRI showed widespread white matter changes. She died at 4 weeks of age. Concentrations of SAICAr and SAdo were markedly elevated in urine, plasma and CSF and the SAdo/SAICAr ratio was low, consistent with the severe phenotype. The patient was compound heterozygous for 2 novel ADSL mutations; c.9 G>C (A3P) and c.572 C>T (R190X).

The effect of folic acid and folinic acid supplements on purine metabolism in methotrexate-treated rheumatoid arthritis

OBJECTIVE

To determine if folinic acid supplementation during methotrexate (MTX) therapy for rheumatoid arthritis (RA) reduces both urinary 5-aminoimidazole-4-carboxamide (AICA) and urinary adenosine excretion more than does folic acid supplementation. AICA and adenosine are markers for MTX interference with purine metabolism.

METHODS

Forty patients with RA who received MTX for 6 weeks were randomized to receive either daily folic acid or folinic acid supplements during an additional week of MTX therapy. Colorimetric and radioimmunocompetition assays were used to measure 24-hour urinary AICA and adenosine excretion levels, respectively.

RESULTS

At the end of 6 weeks, 24-hour urinary levels of AICA, but not adenosine, were elevated as compared with baseline levels (i.e., prior to MTX therapy). Folinic acid, but not folic acid, supplementation normalized urinary AICA levels during MTX therapy. Relatively high urinary levels of AICA were correlated with reduced disease activity. No similar correlations were seen with urinary adenosine levels.

CONCLUSION

The blockade of purine nucleotide biosynthesis by MTX at the AICA ribonucleotide transformylase-catalyzed step may be related to the efficacy of MTX, and this blockade is effectively relieved by folinic acid, but not by folic acid, supplementation.

Regulation of renal adenosine excretion in humans--role of sodium and fluid homeostasis

BACKGROUND

Adenosine is a vasoactive metabolite of ATP hydrolysis that is involved in the regulation of renal haemodynamics, tubular reabsorption and renin release. Elevated tissue levels are found under conditions of increased metabolic load, ischaemia or renal injury. Urinary adenosine excretion (EADO) may therefore provide a sensitive marker of renal functional impairment in allograft rejection and kidney disease. To provide a basis for evaluation of EADO in clinical settings, we investigated, in an intra-individual, crossover clinical trial the physiological variability and regulation of EADO in response to altered sodium and fluid balance.

METHODS

Twelve healthy volunteers were randomized to normal (ad libitum), low (<5 g/day) or high (supplementation of 100 mg/kg/day) sodium chloride diets for 8 days prior to assessment of renal haemodynamics and tubular function in standard clearance investigations. Following baseline periods, fluid homeostasis was altered independently by acute oral water load. EADO was determined in 24 h urine collections and during clearance investigations.

RESULTS

Mean EADO in humans was 3.2+/-0.2 micromol/ 24 h during euvolaemia and normal sodium intake. A weak correlation was found between sodium load and EADO. In clearance experiments, variation in EADO was <1.3-fold, despite profound alterations in sodium intake. EADO was independent of urinary flow rate. Renal haemodynamics were not significantly altered by dietary regimen or by acute volume load.

CONCLUSION

In summary, the physiological variability of EADO is remarkably small in humans. We demonstrate that even profound alterations in sodium and fluid homeostasis do not significantly affect EADO. These data provide a basis for evaluation of elevated EADO as a marker of renal injury in various clinical settings.

Diurnal variation in the renal excretion of modified RNA catabolites in humans

Renally excreted modified RNA catabolites [pseudouridine (psi), N (2), N (2)-dimethylguanosine (m(2)(2)G) and N (6)-threoninocarbonyladenosine (t(6)A)] are markers of whole-body rates of degradation of rRNA and tRNA, and are thought to be potential indicators of the resting metabolic rate. To investigate diurnal variations of these RNA catabolites, the amounts of psi, m(2)(2)G and t(6)A excreted were determined by HPLC of the urine from eight healthy male adults collected over 47-h periods, which were subdivided into the morning (06.00 or 09.00 to 12.00 hours), the afternoon (12.00 to 18.00 hours), the evening (18.00 to 24.00 hours) and the night (00.00 to 06.00 or 08.00 hours), under two different nutritional regimens with 100 or 50 g of protein/day. Furthermore, rates of degradation of rRNA and tRNA were calculated using values for these RNA catabolites. For comparison, the corresponding excretion of creatinine, which originates from the energy metabolism of muscle, and of 3-methylhistidine (m(3)His), which is an indicator of muscle protein degradation, was determined. Differences in excretion during the collection periods were tested using the Friedmann test. The excretion of psi, creatinine and m(3)His (micromol x h(-1) x kg(-1)) altered significantly (P <0.001) during the day. Medians were: for psi, 0.21 (morning), 0.19 (afternoon), 0.19 (evening) and 0.18 (night); for creatinine, 8.8, 8.4, 8.0 and 7.3 respectively; for m(3)His, 0.13, 0.11, 0.12 and 0.10 respectively. The excretion rates of m(2)(2)G and t(6)A (nmol x h(-1) x kg(-1)) altered, but not significantly, during the day; corresponding medians were: for m(2)(2)G, 9.0, 8.4, 8.0 and 8.4 respectively; for t(6)A, 4.3, 4.1, 3.9 and 3.9 respectively. From these results it can be concluded that, in order to assess the average daily rates of degradation of tRNA and rRNA using modified RNA catabolites, urine collection should be carried out quantitatively over 24 h periods. Likewise, the catabolites creatinine and m(3)His must be determined using 24 h urine samples when average daily excretion values are required.

Pharmacokinetics and tolerability of intravenous infusion of adenosine (SUNY4001) in healthy volunteers

AIMS

To examine the tolerability and disposition of i.v. adenosine (SUNY4001) in healthy male Japanese volunteers.

METHODS

SUNY4001 was infused i.v. for 6 min at 0 (placebo), 60, 100, 120 and 140 microg kg-1 min-1 in a dose-escalating manner in 30 healthy subjects. Adenosine and its metabolites were determined in the plasma and urine.

RESULTS

Only plasma hypoxanthine was increased from 3 min during until 5-10 min after SUNY4001 infusion at the higher rates without any significant dose-related changes in plasma adenosine, inosine, xanthine or uric acid, or in urinary adenosine and all metabolites compared with the placebo. There was a dose-related increase in the incidence of subjective symptoms such as heat sensation, flushed face, dyspnoea, chest discomfort, etc. Transient and self-subsiding episodes of second-degree atrioventricular block were found in two subjects each at the higher doses.

CONCLUSIONS

Adenosine infusion at < or = 140 microg kg-1 min-1 was concluded to be generally well tolerated.

Simple and sensitive binding assay for measurement of adenosine using reduced S-adenosylhomocysteine hydrolase

BACKGROUND

Adenosine has been suggested to play an important role in the regulation of renal function. We developed a simple and sensitive binding assay for the detection of adenosine based on the displacement of [(3)H]adenosine from S-adenosylhomocysteine (SAH) hydrolase in its reduced form.

METHODS

SAH hydrolase was purified to apparent homogeneity from bovine kidney by standard chromatographic methods. SAH hydrolase was converted in its reduced form, which had the advantage that the SAH hydrolase is enzymatically inactive. This reduced enzyme retains its ability to bind adenosine with high affinity. To determine adenosine in urine or tissues, samples must be deproteinized (e.g., with 10 g/L sulfosalicylic acid or 0.6 mol/L perchloric acid).

RESULTS

The reduced SAH hydrolase bound adenosine with a dissociation constant of 33.0 +/- 2 nmol/L. Displacement of adenosine binding by the adenine 5'-nucleotides, adenine and hypoxanthine, required >1000-fold higher concentrations than adenosine itself. The intra- and interassay imprecision (CV) was <3.9% and 7.8%, respectively, and the values obtained showed acceptable correlation with those by HPLC.

CONCLUSIONS

The highly sensitive adenosine-binding protein assay is a simple test that allows detection of adenosine in samples with small volumes without purification, and is in this respect superior to HPLC.

Urinary adenosine and aminoimidazolecarboxamide excretion in methotrexate-treated patients with psoriasis

BACKGROUND

We hypothesized that low-dose methotrexate treatment for patients with psoriasis would block purine biosynthesis at the step catalyzed by aminoimidazolecarboxamide (AICA) ribotide transformylase and would inhibit adenosine metabolism as evidenced by increased urinary levels of AICA and adenosine, respectively. Eight patients collected a 24-hour urine specimen on the day before their methotrexate dose and the next day during their methotrexate dose. Eight age- and sex-matched controls also collected a 24-hour urine sample. Urinary AICA and adenosine were assayed by spectrophotometric and radioimmune assays, respectively; means are reported as micromole per millimole of creatinine and were compared by the paired t test (1-tailed).

OBSERVATIONS

Mean AICA excretion increased from 1.30 micromol/mmol on the day before to 1.85 micromol/mmol on the day during methotrexate dosing (P<.01). Mean adenosine values increased from 0.68 to 1.07 micromol/mmol, (P<.03). Controls had mean AICA and adenosine levels of 1.29 and 0.50 micromol/mmol, respectively. During the day of methotrexate dosing, patients had higher mean AICA and adenosine levels when compared with controls (P<.01). Mean AICA levels increased from 1.36 to 2.06 micromol/mmol (P<.025), and mean adenosine levels increased from 0.72 to 1.25 micromol/mmol (P<.025) in 5 patients showing improvement in clinical disease activity. In contrast, 3 patients with no change or worsening in clinical disease activity had smaller increases.

CONCLUSIONS

Methotrexate treatment of patients with psoriasis inhibits AICA ribotide transformylase and adenosine metabolism. Since adenosine is a T-lymphocyte toxin, it may be partially responsible for the immunosuppressive effect.

Creatinine at the evaluation of urinary 1-methyladenosine and pseudouridine excretion

The elevation of urinary modified nucleosides levels in urine is found in patients with cancers. In the present study, we have tested 616 urine samples randomly collected from non-malignant cases. Thirty-two percent (194/616) and 11% (68/616) had elevated levels of 1-methyladenosine and pseudouridine, respectively (They are designated as false-positive cases). To elucidate the cause on non-specific elevation of the nucleosides, the correlation between creatinine excretion level and urinary nucleosides levels were determined. The result revealed that false-positive cases were frequently detected in patients with lower creatinine excretion levels. The mean creatinine levels of false-positive cases were significantly lower than those of negative cases. From these results, the false-positive of urinary 1-methyladenosine and pseudouridine might be due to the low creatinine excretion mainly caused by the renal dysfunction. Creatinine excretion in each individual should be taken into consideration in case of determining urinary modified nucleosides.

Effects of fructose and xylitol on the urinary excretion of adenosine, uridine, and purine bases

To examine whether fructose and xylitol increase the plasma concentration and urinary excretion of adenosine, as well as uridine and purine bases (hypoxanthine, xanthine, and uric acid), we intravenously administered xylitol and, 2 weeks later, fructose, to five healthy subjects. Analyses of blood and urine samples obtained during these infusion studies demonstrated that fructose increased the urinary excretion of adenosine and uridine 11.9- and 105.5-fold, respectively, and caused only a small increase in the plasma concentrations of uridine and purine bases. It was further demonstrated that xylitol increased the urinary excretion of uridine 58.4-fold, with a marked increase in the plasma concentrations of purine bases and uridine but without an increase in the urinary excretion of adenosine. However, neither infusion increased the plasma concentration of adenosine. These results suggest that in addition to many organs, including the liver, fructose is significantly metabolized by an abrupt adenosine triphosphate (ATP) consumption in the kidney, leading to an increase in the urinary excretion of adenosine and uridine. They also suggest that xylitol is not significantly metabolized in the kidney.

Simultaneous determination of adenosine, S-adenosylhomocysteine and S-adenosylmethionine in biological samples using solid-phase extraction and high-performance liquid chromatography

A sensitive and rapid method for measuring simultaneously adenosine, S-adenosylhomocysteine and S-adenosylmethionine in renal tissue, and for the analysis of adenosine and S-adenosylhomocysteine concentrations in the urine is presented. Separation and quantification of the nucleosides are performed following solid-phase extraction by reversed-phase ion-pair high-performance liquid chromatography with a binary gradient system. N6-Methyladenosine is used as the internal standard. This method is characterized by an absolute recovery of over 90% of the nucleosides plus the following limits of quantification: 0.25-1.0 nmol/g wet weight for renal tissue and 0.25-0.5 microM for urine. The relative recovery (corrected for internal standard) of the three nucleosides ranges between 98.1 +/- 2.6% and 102.5 +/- 4.0% for renal tissue and urine, respectively (mean +/- S.D., n = 3). Since the adenosine content in kidney tissue increases instantly after the onset of ischemia, a stop freezing technique is mandatory to observe the tissue levels of the nucleosides under normoxic conditions. The resulting tissue contents of adenosine, S-adenosylhomocysteine and S-adenosylmethionine in normoxic rat kidney are 5.64 +/- 2.2, 0.67 +/- 0.18 and 46.2 +/- 1.9 nmol/g wet weight, respectively (mean +/- S.D., n = 6). Urine concentrations of adenosine and S-adenosylhomocysteine of man and rat are in the low microM range and are negatively correlated with urine flow-rate.

Determination of adenosine and deoxyadenosine in urine by high-performance liquid chromatography with column switching

The means of measurement of adenosine and deoxyadenosine in urine was developed by separating adenosine and deoxyadenosine from other compounds using high-performance liquid chromatography with column switchings. This method is simple and convenient since no pretreatment of the urine is needed. Using this method, it could be demonstrated that urinary adenosine was higher in an adenosine deaminase (ADA) deficient patient who had a bone marrow transplant treatment (1.97 micromol/mmol creatinine) and in a heterozygote who had a markedly low erythrocyte ADA activity (1% of control ADA activity) (1.33 micromol/mmol creatinine) as compared to normal subjects (0.22+/-0.09 micromol/mmol creatinine, n=11). It was also noted that urinary deoxyadenosine was below the detection limits in the ADA-deficient bone marrow transplant patient, but it was detected in the heterozygote (3.7 micromol/mmol creatinine). Furthermore, it was also demonstrated that a fructose infusion increased the urinary concentration of adenosine from 0.21+/-0.03 to 2.66+/-1.21 micromol/mmol creatinine in five normal subjects.

Low-dose theophylline increases urine output in diuretic-dependent critically ill children

OBJECTIVE

Determine the effect of low-dose theophylline on urine output and the urinary adenosine: cAMP (cyclic adenosine monophosphate) excretion ratio (a measure of phosphodiesterase inhibition) in diuretic-dependent critically ill children.

DESIGN

Observational clinical case series and animal laboratory experiment.

SETTING

A university pediatric intensive care unit and a pharmacology research laboratory.

PATIENTS

10 consecutive oliguric patients treated with theophylline for diuresis.

INTERVENTIONS

Urine output, fluid intake, diuretic dosages, and number of pressors (including dopamine) were monitored over the 24-h period prior to and the 24-h period immediately after theophylline was started. Hourly collections of urine were obtained at baseline and 1 and 3 h after theophylline was started and urinary excretion rates of adenosine and cAMP were measured and calculated.

MEASUREMENTS AND RESULTS

Mean theophylline level in the children was 5.0 microg/ml. Urine output increased from 1.58 +/- 0.46 to 3.75 +/- 0.77 ml/kg per h (p = 0.008, paired t-test) after theophylline administration. There was no significant change in fluid intake, vasoactive agents, or dosages of other diuretics during the study periods. Intrarenal infusion of the IC50 concentration of isobutylmethylxanthine for phosphodiesterase activity resulted in a reduction of the adenosine: cAMP urinary excretion ratio in rats (p < 0.05). Low-dose theophylline had no effect on the adenosine: cAMP urinary excretion ratio in children. Concurrent therapy with dopamine was associated with an enhanced diuretic effect of theophylline (with dopamine, 1.30 +/- 0.30 to 5.07 +/- 0.77 ml/kg per h vs without dopamine, 1.77 +/- 0.76 to 2.86 +/- 1.08 ml/kg per h; p = 0.03, two-way ANOVA). There was no interaction between dopamine and low-dose theophylline on the urinary adenosine: cAMP excretion ratio (p = 0.56, two-way ANOVA).

CONCLUSIONS

Theophylline increased urine output in diuretic-dependent critically ill children and the diuretic effect may have been potentiated by concurrent use of dopamine. Adenosine receptor antagonism may be a more likely mechanism for the diuretic effect of theophylline than phosphodiesterase inhibition.

Adenylosuccinase deficiency with neonatal onset severe epileptic seizures and sudden death

We report a male infant with adenylosuccinase deficiency who developed epileptic seizures on the second day of life. Growth was normal and seizures were well controlled with anti-epileptic drugs. Despite axial hypotonia associated with peripheral hypertonicity he presented some development until seven months of age, when he developed high fever and died within a few hours. Although clinical heterogeneity in this disorder of purine synthesis and interconversion is well-known, in 14 out of 17 cases who experienced epilepsy seizures started after the first year of life. The early presentation in our index patient followed by his sudden death at the age of 7 months has not been described before. A search for disorders of purine metabolism should be included in the screening programme for every child with severe neonatal convulsions.

Relationship between urinary excretion of modified nucleosides and rheumatoid arthritis process

The levels of the five methylated nucleosides pseudouridine (psi-Urd), 1-methyladenosine (1-MeAdo), 4 acetylcytidine (4-AcCyd), 1 methylinosine (1-Melno) and 7 methylguanosine (7-MeGuo) resulting from RNA degradation were examined in the urine of rheumatoid arthritis (RA) patients. Of these five, 1-MeAdo and psi-Urd were correlated with the active phase of the disease, while two others (4-AcCyd and 1-Melno), which require further evaluation, appeared to be linked to the prognosis of the disease. As RNA turnover is closely associated with cell proliferation, including that of lymphocytes in RA, there may be a hitherto unsuspected benefit in measuring 1-MeAdo and psi-Urd as biochemical markers of RA disease activity.

Two newly identified mutations (Thr233Ile and Leu152Met) in partially adenosine deaminase-deficient (ADA-) individuals that result in differing biochemical and metabolic phenotypes

Deficiency of adenosine deaminase (ADA-) results in autosomal recessive immunodeficiency disease of varying severity. Partial ADA- [ADA deficiency in erythrocytes (RBCs) but substantial ADA in non-RBCs] has also been identified, primarily by population screening of healthy adults in Africa and newborns in New York State. Normal immune function and/or minimal elevations of toxic metabolites in childhood suggested that partial ADA deficiency was benign and therefore that six mutations identified in partially ADA-deficient newborns and expressing 8-80% of normal ADA in non-RBCs were not pathogenic. However, the lowest activity mutation (Arg211Cys) has now been reported in patients with adult-onset immunodeficiency. We have now molecularly and biochemically studied two additional individuals whom we found to represent opposite ends of the spectrum of partial ADA deficiency as to biochemical abnormalities and age of ascertainment. Homozygosity for a newly identified Leu152Met mutation expressing considerably less activity than the pathogenic Arg211Cys mutation was found in a currently healthy 10-year-old Afghanistani child (ascertained at birth). He had the highest accumulation of the metabolite dATP among 13 partially ADA-deficient patients studied, but considerably lower than in those with immunodeficiency. Homozygosity for a newly identified Thr233Ile mutation expressing somewhat greater ADA activity than Arg211Cys was found in a healthy young adult Kung individual, associated with very low metabolite concentrations. Biochemical findings and a family history suggestive of immunodeficiency in prior offspring support the idea that the Leu152Met mutation could result in disease in homozygous individuals challenged by severe environmental insult or in heterozygosity with a null mutation. The pathogenicity of the Thr233Ile mutation, as well as a previously described Ala215Thr mutation with relatively lower activity is less likely but will only be determined by long-term observation of individuals carrying these mutations. Although, in contrast to other partial mutations, neither of these two mutations are at CpG hot spots, the frequency of CpG mutations remains high for partial mutations but is also similarly high in ADA- immunodeficient patients (5/8 vs 12/21).

Quantitation of urinary nucleosides by high-performance liquid chromatography

It is known that some modified, especially methylated, nucleosides originating from RNA degradation are excreted in abnormal levels in the urine of patients with malignant tumours and they have been proposed as tumour markers. Their measurement could provide a non-invasive diagnostic method, be helpful in the identification of different cancers and in the monitoring of therapeutic effects. In this study, we developed and optimized an analytical procedure to isolate and quantify normal and modified ribonucleosides. The extraction of urinary nucleosides was performed by affinity chromatography on a phenylboronic acid column prior to separation. The reversed-phase high-performance liquid chromatography method allowed a complete separation of sixteen urinary ribonucleosides. The recoveries for the different nucleosides ranged from 83 to 100%, except for xanthosine (66%) and pseudouridine (74%). In normal 24 h urine, the mean levels of thirteen nucleosides (in nmol of nucleoside/mumol of creatinine) were found to be as follows: dihydrouridine (6.37), pseudouridine (25.52), cytidine (0.07), uridine (0.21), 1-methyladenosine (2.19), inosine (0.30), guanosine (0.06), xanthosine (0.59), 3-methyluridine (0.11), 1-methylinosine (1.13). 1-methylguanosine (0.74), adenosine (0.21) and 5'-deoxy-5'-methylthioadenosine (0.12). The first results concerning two kinds of tumours, i.e. breast and floor of mouth tumours, showed some abnormal levels of ribonucleosides. Further experiments are now in progress to measure the modified nucleosides in urine of patients with different forms of cancer.

Urinary adenosine excretion in patients receiving amphotericin B

BACKGROUND

Intravenous amphotericin B (AMB) administration in animals causes renal vasoconstriction, ischemia, and oliguria that may result in irreversible renal injury; the mechanism of AMB nephrotoxicity may be similar in human beings. Adenosine is excreted in urine by the ischemic kidney. We hypothesized that adenosine excretion and oliguria would be a marker for patients who later would manifest AMB-associated renal insufficiency and that pre-AMB saline administration (which ameliorates AMB nephrotoxicity) would negate the change in adenosine excretion and urine output.

METHODS

Twenty hospitalized patients being treated at the direction of their attending physician and who were receiving AMB (15 to 75 mg intravenously) had urine collected for 1 hour before and for 2 hours during AMB infusion. Eleven patients received normal saline solution (500 ml intravenously) before the AMB infusion; the other nine formed the comparator group. An aliquot of each urine collection was precipitated with perchloric acid to remove protein and cellular elements and centrifuged, and the supernatant was assayed for adenosine by using high-pressure liquid chromatography.

RESULTS

Infusion of AMB was associated with a decrease in mean urine output both in patients who received saline solution (245 before versus 149 ml/hr during AMB infusion, p = 0.04) and in patients in comparator group (139 versus 89 ml/hr, p = 0.027). The mean urinary adenosine excretion was unchanged in the saline-loaded group (0.1354 before versus 0.1255 mmol/hr during drug infusion, p = 0.25) and was decreased in the comparator group (0.2276 versus 0.1127 mmol/hr, p = 0.01). Development of renal insufficiency did not correlate with the change in urine output or adenosine excretion.

CONCLUSIONS

AMB infusion in human beings results in decreased urine output and decreased adenosine excretion. The latter effect is prevented by a pre-AMB saline load. The changes in urine output and adenosine excretion are not predictive of the development of renal insufficiency.

Injured erythrocytes release adenosine deaminase into the circulation

The purpose of this study was to test the hypothesis that circulating red blood cells (RBCs) release adenosine deaminase (ADA) when injured. This hypothesis was evaluated in rats using dimethyl sulfoxide (DMSO) to damage RBCs. Boluses and infusions of DMSO caused a reduction in urinary adenosine and a concomitant hemoglobinuria, and the ability of DMSO to reduce urinary adenosine was blocked by pretreatment with the ADA inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine. Infusions of DMSO also significantly enhanced ADA activity in urine and plasma. Dimethylsulfone, an analog of DMSO that does not affect RBCs, did not cause hemoglobinuria and did not affect urinary adenosine. High concentrations of DMSO did not affect adenosine metabolism in rat kidneys perfused without RBCs, and DMSO did not decrease urinary adenosine in rats rendered severely anemic (hematocrit < 15%) by replacing whole blood with plasma. However, DMSO did decrease urinary adenosine in rats without a spleen, a major source of adenosine deaminase apart from circulating RBCs. DMSO reduced renal interstitial levels of adenosine and attenuated bradycardic responses to exogenous adenosine, and these effects were prevented by erythro-9-(2-hydroxy-3-nonyl)adenine. These results indicate that circulating damaged RBCs release significant amounts of ADA, a process that may predispose to vasoocclusive events.

Measurement of adenosine by capillary zone electrophoresis with on-column isotachophoretic preconcentration

An on-column isotachophoretic (ITP)-capillary electrophoresis (CE) system capable of preconcentrating polyhydroxyl species is reported. The ITP-CE system utilizes borate complexation of the neutral diol species to form anionic compounds that can be directly separated by CE. Borate buffer functions as both the terminating electrolyte for the ITP preconcentration and the operating buffer for the subsequent CE separation. Isotachophoretic preconcentration allows injection volumes as large as 50% of the column volume, without compromising separation integrity, to yield detection limits about 70-fold lower than direct CE separation (with borate operating buffer). In this paper we also present an application of the ITP-CE system, with laser-induced fluorescence (LIF) detection, to the quantitative analysis of adenosine from urine. Nanomolar concentration levels of adenosine are successfully derivatized with chloroacetaldehyde (CAA) to form a fluorescent derivative whose spectral characteristics match the He-Cd laser. The technique is shown to be capable of quantitative measurement of adenosine as low as 10(-9) M, the levels expected in plasma and urine.

Automated screening system for purine and pyrimidine metabolism disorders using high-performance liquid chromatography

An automated screening system for purine and pyrimidine metabolism disorders using high-performance liquid chromatography (HPLC) with column switching is described. The system consists of a reversed-phase column, a cation-exchange column, a column switch, four sets of ultraviolet absorbance detectors, a microcomputer and other conventional equipment. As this system permits the simultaneous determination of urinary orotic acid, uracil, dihydrouracil, pseudouridine, xanthine, 2,8-dihydroxyadenine and succinyladenosine, it offers a useful method for the detection of orotic aciduria, dihydropyrimidine dehydrogenase deficiency, dihydropyrimidinuria, xanthinuria, adenine phosphoribosyltransferase deficiency and adenylosuccinase deficiency.

Capillary electrophoresis for screening of adenylosuccinate lyase deficiency

We report a new screening method for adenylosuccinate lyase (ASase) deficiency using capillary electrophoresis (CE). This enzyme defect causes secondary autism and psychomotor retardation in early childhood. In all body fluids of these patients, two succinylpurine metabolites can be found that are normally not detectable: succinyladenosine and succinylaminoimidazole carboxamide (SAICA) riboside. A Beckman P/ACE 2050 capillary electrophoresis system was used with a 47.1 cm capillary, 75 microns ID, and the P/ACE Beckman UV absorbance detector. Untreated urine, injected for 1 s, was separated in a pH 8.63 borate buffer at 20 kV. The two succinylpurines (migration times 13.36 and 13.60 min) were detected at 254 nm only in urine of patients with ASase deficiency but not in control samples.

Comparison of serum and urinary levels of modified nucleoside, 1-methyladenosine, in cancer patients using a monoclonal antibody-based inhibition ELISA

To evaluate the clinical usefulness of serum 1-methyladenosine, several modifications have been made in our previously established inhibition ELISA system. Horseradish peroxidase (HRP) labeled anti-mouse IgG and 3,3',5,5'-tetramethylbenzidine (TMBZ) were used as a secondary antibody and a substrate, respectively. The second blocking was done just before the addition of the secondary antibody. The standard curve of the modified ELISA system showed good linearity between 1 and 1,000 ng/ml, and the detection limit was 50 pg/well. Using the ultrafiltrated-serum samples, serum 1-methyladenosine levels in healthy individuals and cancer patients were determined. The mean level of 1-methyladenosine in 31 healthy individuals was 28.3 +/- 7.9 ng/ml, and cut off value was set at 44.1 ng/ml (Mean+ 2SD). In cancer patients, elevated levels of serum 1-methyladenosine above the cut off value were detected in 4 out of 25 cases tested, though 11 cases had elevated urinary 1-methyladenosine levels above the cut off value (3.23 nmol/mumol creatinine). Since 1-methyladenosine has no interaction with serum proteins and its molecular weight is quite low, it might be rapidly excreted into the urine.

Nephrotoxicity from contrast media: attenuation with theophylline

PURPOSE

To determine if depression of creatinine clearance after administration of contrast medium may be prevented with theophylline.

MATERIALS AND METHODS

A nonionic, low-osmolality contrast medium (iopamidol) or an ionic, high-osmolality contrast medium (sodium diatrizoate) was administered to 93 patients. Before the examination, these patients were given theophylline or a placebo orally. There were also 30 patients who received an adenosine-uptake inhibitor (dipyridamole). Creatinine clearance and urinary adenosine levels were measured before and after angiography.

RESULTS

Creatinine clearance decreased 18% +/- 4 in the placebo-iopamidol group but did not decrease in the theophylline group; urinary adenosine increased 67% +/- 7. Creatinine clearance decreased 42% +/- 5 in the placebo-sodium diatrizoate group and decreased 24% +/- 3 in the theophylline group; urinary adenosine increased 119% +/- 8. In the dipyridamole group in which iopamidol was given, urinary adenosine increased 96% +/- 7 and creatinine clearance decreased 37% +/- 5.

CONCLUSION

Intrarenal adenosine can be implicated in the pathogenesis of hypertonic contrast medium nephrotoxicity.

An immunohistochemical analysis for cancer of the esophagus using monoclonal antibodies specific for modified nucleosides

BACKGROUND

Modified nucleosides such as 1-methyl-adenosine and pseudouridine exist as minute components of transfer ribonucleic acid (tRNA) and are excreted in the urine in large amounts in the presence of malignancy. Although use of these modified nucleosides as tumor markers has long been studied and many reports have detailed their relationship with malignant tumors and the urinary excretion of various modified nucleosides, there have been no reports on modified nucleosides in esophageal carcinoma.

METHODS

Monoclonal antibody patterns against 1-methyladenosine and pseudouridine were studied in esophageal carcinoma, freshly resected esophageal carcinoma tissue specimens fixed in 10% neutral formaldehyde solution, embedded in paraffin, and sectioned for immunohistochemical study. Inhibition enzyme-linked immunosorbent assay (ELISA) was used to examine urinary excretion of these modified nucleosides in patients with esophageal carcinoma.

RESULTS

Although rare in normal esophageal epithelium, these modified nucleosides were strongly stained in esophageal carcinoma cells. Most carcinoma cells exhibited a cytoplasmic pattern, although some cells at the infiltrating edge displayed a nuclear pattern. These modified nucleosides were intensely imaged in 11 of 12 cultured esophageal cell lines, the exception being one line that had a much longer doubling time. Using ELISA, urinary excretion of these modified nucleosides was found to be significantly higher in patients with esophageal carcinoma than in healthy subjects; such excretion correlated with carcinoma size and stage and tended to decrease after treatment.

CONCLUSIONS

These findings indicate that the modified nucleosides 1-methyladenosine and pseudouridine may be useful as tumor markers for esophageal carcinoma.

5,6-Dihydrouridine: a marker ribonucleoside for determining whole body degradation rates of transfer RNA in man and rats

It has previously been demonstrated that N6-threoninocarbonyladenosine is virtually quantitatively excreted in urine. From the similarity of the average molar ratio of 5,6-dihydrouridine to N6-threoninocarbonyladenosine in the urine of human adults (12.6), newborns (12.6) and rats (13.6) with the respective ratio in cytoplasmic tRNA (11.8) we conclude that 5,6-dihydrouridine is also virtually quantitatively excreted in urine. Therefore, excreted 5,6-dihydrouridine is suitable as a marker to assess the whole body degradation rate of tRNA. Relative degradation rates of tRNA determined via excreted 5,6-dihydrouridine in urine are 4.7 times higher in rats (2.2 +/- 0.33 mumol/kg per day) than in human adults (0.48 +/- 0.05 mumol/kg per day) which is similar to the respective difference in the resting metabolic rate per weight unit.

Gas chromatography/mass spectrometric analysis of urinary nucleosides in cancer patients; potential of modified nucleosides as tumour markers

Analysis of urine from cancer patients by capillary gas chromatography/mass spectrometry positively identified 14 urinary nucleosides including several modified nucleosides. Levels of the modified nucleosides 1-methyl-adenosine, 2-methylguanosine, N2,N2-dimethylguanosine and 1-methylinosine as well as the total nucleoside level were elevated in the urine when a malignant tumour was present; the levels of N2,N2-dimethylguanosine were found to correlate with the stage of the cancer.

Diagnostic use of anti-modified nucleoside monoclonal antibody

By use of monoclonal antibodies (MoAbs) termed APU-6 and AMA-2, we determined the usefulness of urinary modified nucleosides, pseudouridine and 1-methyladenosine, as markers for malignancy. In patients with leukemia and other forms of cancer, these nucleosides elevated significantly and reflected the disease status of patients. The immunohistochemical analysis showed that cancer cells were specifically stained with the MoAbs. Chemical identification of the cellular components reactive with the MoAbs revealed that APU-6-associated antigens were mainly rRNA and AMA-2-associated antigens were mainly tRNA. These results suggest that APU-6 and AMA-2 would be useful tools for clinical and biological studies of cancer.

Detection and quantitation of dG-AAI and dA-AAI adducts by 32P-postlabeling methods in urothelium and exfoliated cells in urine of rats treated with aristolochic acid I

Analysis of aristolochic acid I (AAI)-DNA adducts in exfoliated cells in urine, urothelium and entire urinary bladder were studied after oral administration of five daily doses (10 mg/kg body wt) AAI for 3 months to rats. The two major adducts excreted in urine are presumably identical to the two main adducts formed in vitro and in vivo in different organs in the rat, which have previously been characterized in vitro as 7(-deoxyguanosin-N2-yl)-aristolactam I and 7(-deoxyadenosin-N6-yl)-aristolactam I. Urine samples were collected on dry-ice, subsequently pooled and purified according to the protocol of Kadlubar and co-workers. DNA was isolated, digested and AAI-DNA adducts of exfoliated cells in urine and urothelium of rats were detected and quantitated by enhancement methods of the 32P-postlabeling assay, namely nuclease P1 enrichment or butanol extraction. Autoradiograms indicated that adduct patterns in DNA derived from exfoliated cells in urine were very similar to those obtained from DNA isolated from tissues. Quantitative analysis of adducts revealed adduct levels declining for both adducts from DNA isolated from urothelium to DNA isolated from the entire urinary bladder to DNA isolated from exfoliated cells in urine. In general, count rates of two predominant AAI adducts were enhanced by butanol extraction approximately 3- to 8-fold when compared with the nuclease P1 digestion technique. The identity of the two major adducts was confirmed by co-chromatography with eluted spots from in vivo adducts by comparing mobilities on poly-(ethyleneimine)-cellulose plates. Microbiological investigations of the urine revealed no gross contamination with bacteria, so that the isolated DNA supposedly originated from exfoliated urothelial cells. This study indicates that 32P-postlabeling analysis can be used to monitor non-invasively the formation of carcinogen-DNA adducts in animals or humans exposed to carcinogens.

Axial heterogeneity of adenosine transport and metabolism in the rabbit proximal tubule

Transport and metabolism of adenosine were studied in the S1, S2, and S3 segments of the rabbit proximal renal tubule. Isolated segments were perfused in vitro with uniformly labelled 14C-adenosine to measure the lumen-to-bath flux of adenosine. This flux rate was measured by the disappearance of 14C from the luminal fluid (JD) and simultaneously by the appearance of 14C in the bathing solution (JA), expressed as femtomoles per minute per millimeter of tubule length (fmol.min-1.mm-1). At a perfused concentration of 83.3 microM adenosine, when corrected for metabolism, the JDs for adenosine in the S1, S2, and S3 segments were 735, 212, and 273, respectively. JAs, corrected for metabolism, were 0, 0, and 4.8 fmol.min-1.mm-1 for the S1, S2, and S3 segments, indicating that very little or no 14C-adenosine moved across the basolateral membrane. To correct for metabolism of 14C-adenosine, the perfusion fluid, collected fluid, tubular extract, and bathing fluid, from three tubules of each segment type, were analyzed by high-performance liquid chromatography to identify 14C-adenosine and its 14C-metabolites. At 83.3 microM, all segments metabolized adenosine extensively. Consequently, adenosine-5'-monophosphate (AMP) and inosine were found in tubule cells of all segments. Inosine also appeared in the collected fluid, but AMP did not. In S1 and S2 segments, none of the 14C in the bathing solutions could be identified and no adenosine was found. Of the small amounts of 14C found in bathing solutions from S3 segments, about 27% appeared to be adenosine, the rest were inosine and hypoxanthine or unidentified metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of urinary pseudouridine and 1-methyladenosine to activity of leukemia and lymphoma

Urinary levels of pseudouridine and 1-methyladenosine in patients with leukemia and lymphoma were measured by the inhibition ELISA using monoclonal antibodies to determine the correlation of nucleosides excretion with disease activity. Significantly elevated levels of these nucleosides were detected in patients with all types of disease tested. Seventy-seven percent (46/60) and 62% (37/62) of patients had elevated levels of pseudouridine and 1-methyladenosine above normal mean + 2S.D., respectively, and combination assay of these nucleosides gave higher positive rate (87%; 52/60) than either single assay. The changes of urinary pseudouridine and 1-methyladenosine reflected the disease status of patients in remission or in relapse and the effect of chemotherapy. These results suggest that urinary pseudouridine and 1-methyladenosine might be clinically useful as complementary markers to the monitoring of the disease status of patients with leukemia and lymphoma by hematological examination.