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Quantitative UPLC-MS/MS assay of urinary 2,8-dihydroxyadenine for diagnosis and management of adenine phosphoribosyltransferase deficiency.

ABSTRACT: Adenine phosphoribosyltransferase (APRT) deficiency is a hereditary disorder that leads to excessive urinary excretion of 2,8-dihydroxyadenine (DHA), causing nephrolithiasis and chronic kidney disease. Treatment with allopurinol or febuxostat reduces DHA production and attenuates the renal manifestations. Assessment of DHA crystalluria by urine microscopy is used for therapeutic monitoring, but lacks sensitivity. We report a high-throughput assay based on ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) for quantification of urinary DHA. The UPLC-MS/MS assay was optimized by a chemometric approach for absolute quantification of DHA, utilizing isotopically labeled DHA as an internal standard. Experimental screening was conducted with D-optimal design and optimization of the DHA response was performed with central composite face design and related to the peak area of DHA using partial least square regression. Acceptable precision and accuracy of the DHA concentration were obtained over a calibration range of 100 to 5000ng/mL on three different days. The intra- and inter-day accuracy and precision coefficients of variation were well within ±15% for quality control samples analyzed in replicates of six at three concentration levels. Absolute quantification of DHA in urine samples from patients with APRT deficiency was achieved wihtin 6.5min. Measurement of DHA in 24h urine samples from three patients with APRT deficiency, diluted 1:15 (v/v) with 10mM ammonium hydroxide (NH4OH), yielded a concentration of 3021, 5860 and 10563ng/mL and 24h excretion of 816, 1327 and 1649mg, respectively. A rapid and robust UPLC-MS/MS assay for absolute quantification of DHA in urine was successfully developed. We believe this method will greatly facilitate diagnosis and management of patients with APRT deficiency.

SUBMITTER: Thorsteinsdottir M

PROVIDER: S-EPMC5445224 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Quantitative UPLC-MS/MS assay of urinary 2,8-dihydroxyadenine for diagnosis and management of adenine phosphoribosyltransferase deficiency.

Thorsteinsdottir Margret M Thorsteinsdottir Unnur A UA Eiriksson Finnur F FF Runolfsdottir Hrafnhildur L HL Agustsdottir Inger M Sch IM Oddsdottir Steinunn S Sigurdsson Baldur B BB Hardarson Hordur K HK Kamble Nilesh R NR Sigurdsson Snorri Th ST Edvardsson Vidar O VO Palsson Runolfur R

Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 20160914

Adenine phosphoribosyltransferase (APRT) deficiency is a hereditary disorder that leads to excessive urinary excretion of 2,8-dihydroxyadenine (DHA), causing nephrolithiasis and chronic kidney disease. Treatment with allopurinol or febuxostat reduces DHA production and attenuates the renal manifestations. Assessment of DHA crystalluria by urine microscopy is used for therapeutic monitoring, but lacks sensitivity. We report a high-throughput assay based on ultra-performance liquid chromatography ...[more]

PMID: 27770717

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Project description:BACKGROUND:Hereditary deficiency of adenine phosphoribosyltransferase causes 2,8-dihydroxyadenine (2,8-DHA) nephropathy, a rare condition characterized by formation of 2,8-DHA crystals within renal tubules. Clinical relevance of rodent models of 2,8-DHA crystal nephropathy induced by excessive adenine intake is unknown. METHODS:Using animal models and patient kidney biopsies, we assessed the pathogenic sequelae of 2,8-DHA crystal-induced kidney damage. We also used knockout mice to investigate the role of TNF receptors 1 and 2 (TNFR1 and TNFR2), CD44, or alpha2-HS glycoprotein (AHSG), all of which are involved in the pathogenesis of other types of crystal-induced nephropathies. RESULTS:Adenine-enriched diet in mice induced 2,8-DHA nephropathy, leading to progressive kidney disease, characterized by crystal deposits, tubular injury, inflammation, and fibrosis. Kidney injury depended on crystal size. The smallest crystals were endocytosed by tubular epithelial cells. Crystals of variable size were excreted in urine. Large crystals obstructed whole tubules. Medium-sized crystals induced a particular reparative process that we term extratubulation. In this process, tubular cells, in coordination with macrophages, overgrew and translocated crystals into the interstitium, restoring the tubular luminal patency; this was followed by degradation of interstitial crystals by granulomatous inflammation. Patients with adenine phosphoribosyltransferase deficiency showed similar histopathological findings regarding crystal morphology, crystal clearance, and renal injury. In mice, deletion of Tnfr1 significantly reduced tubular CD44 and annexin two expression, as well as inflammation, thereby ameliorating the disease course. In contrast, genetic deletion of Tnfr2, Cd44, or Ahsg had no effect on the manifestations of 2,8-DHA nephropathy. CONCLUSIONS:Rodent models of the cellular and molecular mechanisms of 2,8-DHA nephropathy and crystal clearance have clinical relevance and offer insight into potential future targets for therapeutic interventions.

Project description:Diacyl glycerophospholipids (GPs) belong to the most abundant lipid species in living organisms and consist of a glycerol backbone with fatty acyl groups in sn-1 and sn-2 and a polar head group in the sn-3 position. Regioisomeric mixed diacyl GPs have the same fatty acyl composition but differ in their allocation to sn-1 or sn-2 of the glycerol unit. In-depth analysis of regioisomeric mixed diacyl GP species composed of fatty acyl moieties that are similar in length and degree of saturation typically requires either chemical derivatization or sophisticated analytical instrumentation, since these types of regioisomers are not well resolved under standard ultra-performance liquid chromatography (UPLC) conditions. Here, we introduce a simple and fast method for diacyl GP regioisomer analysis employing UPLC tandem mass spectrometry (MS/MS). This GP regioisomer analysis is based both on minor chromatographic retention time shifts and on major differences in relative abundances of the two fatty acyl anion fragments observed in MS/MS. To monitor these differences with optimal precision, MS/MS spectra are recorded continuously over the UPLC elution profile of the lipid species of interest. Quantification of relative abundances of the regioisomers was performed by algorithms that we have developed for this purpose. The method was applied to commercially available mixed diacyl GP standards and to total lipid extracts of Escherichia coli (E. coli) and bovine liver. To validate our results, we determined regioisomeric ratios of phosphatidylcholine (PC) standards using phospholipase A2-specific release of fatty acids from the sn-2 position of the glycerol backbone. Our results show that most analyzed mixed diacyl GPs of biological origin exhibit significantly higher regioisomeric purity than synthetic lipid standards. In summary, this method can be implemented in routine LC-MS/MS-based lipidomics workflows without the necessity for additional chemical additives, derivatizations, or instrumentation.

Dataset Information

Quantitative UPLC-MS/MS assay of urinary 2,8-dihydroxyadenine for diagnosis and management of adenine phosphoribosyltransferase deficiency.

Publications

Quantitative UPLC-MS/MS assay of urinary 2,8-dihydroxyadenine for diagnosis and management of adenine phosphoribosyltransferase deficiency.

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