Urinary excretion patterns of modified nucleosides, pseudouridine and 1-methyladenosine, in healthy individuals

Cellular protein breakdown and systemic inflammation are unaffected by pulmonary rehabilitation in COPD

BACKGROUND

Pulmonary rehabilitation can improve the functional capacity, but has a variable effect on the low fat-free mass (FFM) in patients with chronic obstructive pulmonary disease.

HYPOTHESIS

Pulmonary rehabilitation would not affect catabolic drives such as systemic inflammation and also protein breakdown.

METHODS

Patients (n = 40) were studied at the start of an 8-week in-patient pulmonary rehabilitation programme, at the end of the programme and 4 weeks later. FFM and functional capacity (quadriceps strength, handgrip strength and peak workload) were assessed. Pseudouridine (PSU) urinary excretion (cellular protein breakdown) and inflammatory status were determined. Healthy participants had a single baseline assessment (n = 18).

RESULTS

PSU, (IL)-6 and soluble tumour necrosis factor (sTNF)alpha R75 were increased in patients compared with healthy participants, whereas FFM and functional capacity were reduced (all p < 0.01). PSU was inversely related to both FFM and skeletal muscle function. FFM and functional parameters increased with rehabilitation, but PSU and inflammatory status were unaffected. The gain in FFM was lost 4 weeks after the completion of rehabilitation (p < 0.01).

CONCLUSION

The anabolic effect of pulmonary rehabilitation improved FFM, but it did not reverse the increased protein breakdown or systemic inflammation. Thus, on cessation of pulmonary rehabilitation the FFM gains were lost owing to a loss of anabolic drive.

Determination of urinary nucleosides by direct injection and coupled-column high-performance liquid chromatography

A coupled-column liquid chromatographic method for the direct analysis of 14 urinary nucleosides is described. Efficient on-line clean-up and concentration of 14 nucleosides from urine samples were obtained by using a boronic acid-substituted silica column (40 mm x 4.0 mm I.D.) as the first column (Col-1) and a Hypersil ODS2 column (250 mm x 4.6 mm I.D.) as the second column (Col-2). The mobile phases applied consisted of 0.25 mol/L ammonium acetate (pH 8.5) on Col-1, and of 25 mmol/L potassium dihydrogen phosphate (pH 4.5) on Col-2, respectively. Determination of urinary nucleosides was performed on Col-2 column by using a linear gradient elution comprising 25 mmol/L potassium dihydrogen phosphate (pH 4.5) and methanol-water (60:40, v/v) with UV detection at 260 nm. Urinary nucleosides analysis can be carried out by this procedure in 50 min requiring only pH adjustment and the protein precipitation by centrifugation of urine samples. Calibration plots of 14 standard nucleosides showed excellent linearity (r > 0.995) and the limits of detection were at micromolar levels. Both of intra- and inter-day precisions of the method were better than 6.6% for direct determination of 14 nucleosides. The validated method was applied to quantify 14 nucleosides in 20 normal urines to establish reference ranges.

Chromatographic, capillary electrophoretic and matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of urinary modified nucleosides as tumor markers

Modified nucleosides are formed posttranscriptionally in RNA. During RNA turnover free modified nucleosides are formed which circulate in the blood stream and are excreted in the urine. Their levels are increased in a number of malignant diseases, and they can be used in clinical chemistry as tumor markers. The analysis includes the isolation of the nucleosides from urine with phenylboronate gel and their separation and quantitation by HPLC on C18 columns or by capillary electrophoresis on uncoated columns applying a sodium dodecyl sulfate-borate-phosphate buffer. Identification of the nucleosides is performed with matrix-assisted laser desorption ionization time-of-flight mass spectrometry including post source decay spectra. In two clinical studies the diagnostic value of urinary modified nucleosides is investigated, in a study on children with leukemia and other malignant diseases and a study on women with breast cancer. Candidate markers are pseudouridine, 1-methylguanosine, N2-methylguanosine, 3-methyluridine and 1-methyl-inosine.

Cellular proteolysis and systemic inflammation during exacerbation in cystic fibrosis

BACKGROUND

Weight loss indicates a poor prognosis in cystic fibrosis (CF). We hypothesised that fat-free mass (FFM) depletion and increased systemic inflammation would be associated with increased cellular proteolysis during an exacerbation of the respiratory symptoms. Patients were studied prospectively from the beginning of treatment with antibiotics when admitted to the Adults CF Centre.

METHODS

Twenty six patients with CF were studied at the start and end of antibiotic treatment and 2 weeks later. Mean (95% CI) FEV1 when clinically stable was 54.1 (44.5, 62.6)% predicted. Urinary excretion of Pseudouridine (5-ribosyluracil, PSU) was determined as an indicator of cellular protein breakdown. Body composition was assessed by dual energy X-ray absorptiometry (DXA).

RESULTS

Patients had increased concentrations of PSU at all assessments (p<0.01). Those with a low FFM had greater PSU (ratio to FFMI) than those with a normal FFM at all assessments. At the start of treatment, PSU was related to FFM, C-reactive protein (CRP) (p<0.05) and tumour necrosis factor (TNF)alpha soluble receptors (sr) I and II (p<0.01). Circulating inflammatory mediators were greater in patients than in healthy subjects at all assessments.

CONCLUSION

Increased protein breakdown is associated with a low FFM and increased systemic inflammation and it may be a contributory mechanism of poor weight preservation in CF.

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.

Separation of nucleosides using capillary electrochromatography

The analysis of nucleosides and nucleotides have in most cases been performed by HPLC using either reversed-phase HPLC with gradient elution or using reversed-phase ion-pair chromatography. In this paper we have explored the possibility of using capillary electrochromatography (CEC) in order to avoid the use of gradients or ion-pairing reagents. CEC is in many ways comparable to HPLC, but CEC is theoretically able to provide better separations due to the higher efficiency caused by the flowfront being more plug-like as also is the case in CE, which is to be compared to the more parabolic flow observed in HPLC. The separation of six nucleosides (adenosine, cytidine, guanosine, inosine, thymidine and uridine) was investigated with respect to concentration of buffers, pH, amount of acetonitrile, temperature and voltage in order to optimise the separation. Baseline separation was achieved for the six nucleosides in less than 13 min using a background electrolyte consisting of (5 mM acetic acid, 3 mM triethylamine, pH 5.0)-acetonitrile (92:8, v/v).

Urinary nucleosides

The methods of analysis, origins, and clinical significance of urinary nucleosides are reviewed through 1997. Structures, chromatographic and mass spectral data and references to the clinical literature are presented for each of the 57 nucleosides currently identified in normal and pathogenic human urine samples. Data from the HPLC separation and GC/MS analysis of 37 individual HPLC fractions are presented and discussed. Methods, including sample preparation techniques, used for the analysis of urinary nucleosides including GC, HPLC, GC/MS, HPLC/MS and immunoassays are compared and the advantages and limitations of each method described. The conclusion is drawn that the urinary nucleosides do serve as biomarkers of cancer and other diseases, but analytical methods need further improvement if clinical decisions are to be made based on the levels of nucleosides in human urine.

Analysis of urinary pseudouridine by micellar electrokinetic capillary chromatography

We describe a capillary electrophoresis procedure, using uridine as an internal standard, for the analysis of urinary pseudouridine following solid-phase extraction. This method retains the advantages of existing chromatographic techniques but has superior resolving power and is technically less demanding. The standard curves were linear and reproducible with a detection limit of 60 fmol; chromatographic analysis was complete in under 10 min. Injection variability was < 5% and multiple independent analyses of the same urine sample for pseudouridine concentration gave coefficients of variation of < 10%. The mean (SD) urinary pseudouridine level in 18 healthy subjects was 16.1 (2.1) nmol/mumol creatinine. For a limited group of subjects where samples were taken more frequently, intra-individual variation averaged 27.5% reflecting variable excretion.

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.

Immunochemical detection of urinary 5-methyl-2'-deoxycytidine as a potential biologic marker for leukemia

A monoclonal antibody against 5-methylcytidine was prepared and characterized. This antibody, termed AMC, was reactive with compounds that had 5-methylcytosine structure (i.e. 5-methyl-2'-deoxycytidine, 5-methylcytidine and 5-methylcytosine). AMC had the highest reactivity to 5-methyl-2'-deoxycytidine among reactive compounds and had no or very slight cross-reactivity to cytidine-related compounds and any other compounds. Analysis of immunoreactive materials in urine revealed that 5-methyl-2'-deoxycytidine rather than 5-methylcytidine was, contrary to our expectation, the major component. Then the inhibition ELISA system using AMC was established and urinary levels of 5-methyl-2'-deoxycytidine in healthy individuals and cancer patients were determined. The mean excretion levels of healthy individuals was 0.90 +/- 0.43 nmol/mumol creatinine and the cut-off value was set at the mean + 2 S.D. of healthy individuals (1.76 nmol/mumol creatinine). Among various types of cancer tested, elevated levels of 5-methyl-2'-deoxycytidine were detected in leukemia patients. From these results, urinary 5-methyl-2'-deoxycytidine might be applicable as a biologic marker for leukemia.