Lupus-Associated Functional Polymorphism in PNP Causes Cell Cycle Abnormalities and Interferon Pathway Activation in Human Immune Cells.

OBJECTIVE: Systemic lupus erythematosus (SLE) is frequently characterized by activation of the type I interferon (IFN) pathway. We previously observed that a missense single-nucleotide polymorphism (rs1049564) in the purine nucleoside phosphorylase (PNP) gene was associated with high levels of IFN in SLE. PNP is a key enzyme involved in purine metabolism. In this study, we performed functional follow-up of this polymorphism in human cells. METHODS: Type I IFN was measured in patient sera, using a reporter cell assay. Structural modeling of the PNP variant was performed using PyMOL software. PNP messenger RNA (mRNA) and protein levels and type I IFN-induced gene expression were measured in lymphoblastoid cell lines with known PNP rs1049564 genotypes. The cell cycle was assayed using flow cytometry. RESULTS: Structural modeling indicated no major disruption in folding related to rs1049564. We observed that homozygous rs1049564 TT lymphoblastoid cells had decreased PNP mRNA expression and protein levels, and that cells with the TT genotype had reduced PNP enzymatic activity even when the amount of PNP was controlled. Cells with the TT genotype had a 2-fold increase in S-phase block as compared with cells with the homozygous CC phenotype. The S-phase block could be pharmacologically reversed with hypoxanthine and adenosine, supporting the notion that relative PNP deficiency is the cause of the S-phase block. Type I IFN-induced transcripts were increased in a dose-response manner related to the rs1049564 T allele, at both baseline and after type I IFN stimulation. CONCLUSION: The PNP rs1049564 T allele is a loss-of-function variant that induces S-phase block and IFN pathway activation in lymphocytes. The S-phase block could be rescued in our in vitro experiments, suggesting the potential for personalized treatment.

Development of a new HPLC method using fluorescence detection without derivatization for determining purine nucleoside phosphorylase activity in human plasma.

Purine nucleoside phosphorylase (PNP) activity is involved in cell survival and function, since PNP is a key enzyme in the purine metabolic pathway where it catalyzes the phosphorolysis of the nucleosides to the corresponding nucleobases. Its dysfunction has been found in relevant pathological conditions (such as inflammation and cancer), so the detection of PNP activity in plasma could represent an attractive marker for early diagnosis or assessment of disease progression. Thus the aim of this study was to develop a simple, fast and sensitive HPLC method for the determination of PNP activity in plasma. The separation was achieved on a Phenomenex Kinetex PFP column using 0.1% formic acid in water and methanol as mobile phases in gradient elution mode at a flow rate of 1ml/min and purine compounds were detected using UV absorption and fluorescence. The analysis was fast since the run was achieved within 13min. This method improved the separation of the different purines, allowing the UV-based quantification of the natural PNP substrates (inosine and guanosine) or products (hypoxanthine and guanine) and its subsequent metabolic products (xanthine and uric acid) with a good precision and accuracy. The most interesting innovation is the simultaneous use of a fluorescence detector (excitation/emission wavelength of 260/375nm) that allowed the quantification of guanosine and guanine without derivatization. Compared with UV, the fluorescence detection improved the sensitivity for guanine detection by about 10-fold and abolished almost completely the baseline noise due to the presence of plasma in the enzymatic reaction mixture. Thus, the validated method allowed an excellent evaluation of PNP activity in plasma which could be useful as an indicator of several pathological conditions.

[Effect of low-intensity 900 MHz frequency electromagnetic radiation on rat liver and blood serum enzyme activities].

The comparative analysis of the rat liver and blood serum creatine kinase, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and purine nucleoside phosphorylase post-radiation activity levels after a total two-hour long single and fractional exposure of the animals to low-intensity 900 MHz frequency electromagnetic field showed that the most sensitive enzymes to the both schedules of radiation are the liver creatine kinase, as well as the blood serum creatine kinase and alkaline phosphatase. According to the comparative analysis of the dynamics of changes in the activity level of the liver and blood serum creatine kinase, alanine aminotransferase, aspartate aminotransferase and purine nucleoside phosphorylase, both single and fractional radiation schedules do not affect the permeability of a hepatocyte cell membrane, but rather cause changes in their energetic metabolism. The correlation analysis of the post-radiation activity level changes of the investigated enzymes did not reveal a clear relationship between them. The dynamics of post-radiation changes in the activity of investigated enzyme levels following a single and short-term fractional schedules of radiation did not differ essentially.

Metabolites of purine nucleoside phosphorylase (NP) in serum have the potential to delineate pancreatic adenocarcinoma.

Pancreatic Adenocarcinoma (PDAC), the fourth highest cause of cancer related deaths in the United States, has the most aggressive presentation resulting in a very short median survival time for the affected patients. Early detection of PDAC is confounded by lack of specific markers that has motivated the use of high throughput molecular approaches to delineate potential biomarkers. To pursue identification of a distinct marker, this study profiled the secretory proteome in 16 PDAC, 2 carcinoma in situ (CIS) and 7 benign patients using label-free mass spectrometry coupled to 1D-SDS-PAGE and Strong Cation-Exchange Chromatography (SCX). A total of 431 proteins were detected of which 56 were found to be significantly elevated in PDAC. Included in this differential set were Parkinson disease autosomal recessive, early onset 7 (PARK 7) and Alpha Synuclein (aSyn), both of which are known to be pathognomonic to Parkinson's disease as well as metabolic enzymes like Purine Nucleoside Phosphorylase (NP) which has been exploited as therapeutic target in cancers. Tissue Microarray analysis confirmed higher expression of aSyn and NP in ductal epithelia of pancreatic tumors compared to benign ducts. Furthermore, extent of both aSyn and NP staining positively correlated with tumor stage and perineural invasion while their intensity of staining correlated with the existence of metastatic lesions in the PDAC tissues. From the biomarker perspective, NP protein levels were higher in PDAC sera and furthermore serum levels of its downstream metabolites guanosine and adenosine were able to distinguish PDAC from benign in an unsupervised hierarchical classification model. Overall, this study for the first time describes elevated levels of aSyn in PDAC as well as highlights the potential of evaluating NP protein expression and levels of its downstream metabolites to develop a multiplex panel for non-invasive detection of PDAC.

[The clinical diagnostic value of a study of the activity of enzymes of the guanyl branch of purine metabolism in patients with ankylosing spondyloarthritis].

AIM: To assess the diagnosis of the activity of a pathological process in patients with ankylosing spondyloarthritis (AS) and to reveal purine metabolic (PM) changes in relation to the clinical features of AS. MATERIALS AND METHODS: The serum activities of the PM enzymes: xanthine oxidase (XO), guanine deaminase (GDA), guanosine deaminase (GSDA), purine nucleoside phosphorylase (PNP), guanosine phosphorylase (GP), and adenosine deaminase (ADA) were determined in 55 patients (51 males and 4 females) aged 36.0 +/- 1.4 years). A control group comprised 30 apparently age- and gender-matched healthy individuals, as in the study group. RESULTS: On admission, the patients were found to have increased XO, GDA, PNP, and GD activities and decreased GSDA activity. The higher activity of the process was observed, the greater activities of GDA, XO, PNP, GP and the lower activity of GSDA and ADA were. There were the enzymatic activity differences that depended on the degree of pathological process activity, clinical form, the magnitude of X-ray changes, and the degree of joint functional insufficiency. CONCLUSION: The findings suggest that there may be PM disturbances in the immunocompetent cells.

[Purine nucleoside phosphorylase inhibitors and their clinical significance].

PNP catalyzes a reversible phosphorolysis of purine deoxy- and ribonucleosides with formation of (d)Rib-1-P and appropriate bases. PNP plays a leading role in the cell metabolism of nucleosides and nucleotides, as well as in maintaining the immune status of an organism. The major purpose of the majority of studies on the PNP is the detection of high-performance enzyme inhibitors, derivatives of the purine nucleosides, which are used in medicine as immunosuppressors. It is well known that the latter are necessary for creating a selective T-cell immunodeficiency in a human body under organs and tissue transplantation. The review discusses the issues related to deliberate synthesis of effective, metabolically inert, and low-toxic PNP inhibitors. It also analyzes the available studies on substrate and inhibitory properties of the analogues of purine nucleosides, as well as research on the structural factors which reinforce the inhibitor activity of those analogues. The inhibitors which are either used in medical practice or are currently at a stage of preclinical testing are described. The inhibitors which are more efficient in their influence on the PNF from tumorous tissues are of special interest. Using PNP inhibitors in case of a number of pathologies denotes the importance and promise of research on both the enzyme and the compounds affecting its activity.

Plasma purine nucleoside phosphorylase in cancer patients.

BACKGROUND: Purine nucleoside phosphorylase (PNP) is the purine salvage enzyme that converts guanosine to guanine and inosine to hypoxanthine. METHODS: 279 samples from patients with differing cancers were collected during treatment at both pre- and post-dose stages for plasma PNP activity and compared with a normal population. RESULTS: Normal plasma PNP activity was found to be 3.2+/-1.4 U/l (n=55) as compared with the cancer patients (pre-dose 12.3+/-7.4 U/l [n=215] and post-dose 11.2+/-5.9 U/l [n=64]). Levels of plasma PNP did not differ greatly between the different cancer types but were on average four times greater than that found in the reference population.

Capillary electrophoresis in diagnosis and monitoring of adenosine deaminase deficiency.

BACKGROUND: The diagnosis and monitoring of severe combined immunodeficiency disease (SCID) attributable to adenosine deaminase (ADA) deficiency requires measurements of ADA, purine nucleoside phosphorylase (PNP), and S-adenosyl-L-homocysteine-hydrolase (SAHH) activity and of deoxyadenosine metabolites. We developed capillary electrophoresis (CE) methods for the detection of key diagnostic metabolites and evaluation of enzyme activities. METHODS: Deoxyadenosine metabolites were separated in 30 mmol/L sodium borate-10 mmol/L sodium dodecyl sulfate (pH 9.80) at 25 degrees C on a 60-cm uncoated capillary. For determination of enzyme activities, substrate-product separation and measurements were carried out in 20 mmol/L sodium borate (pH 10.00) at 25 degrees C on a 42-cm uncoated capillary. RESULTS: Deoxynucleotides and deoxyadenosine were readily detectable in erythrocytes and urine, respectively. Both methods were linear in the range 2-500 micro mol/L (r >0.99). Intra- and interassay CV were <4%. Enzyme activities were linear with respect to sample amounts in the incubation mixture and to incubation time (r >0.99 for both). In erythrocytes from healthy individuals, mean (SD) ADA activity was 5619 (2584) nmol/s per liter of packed cells. In erythrocytes of SCID patients at diagnosis, ADA activity was 56.9 (48.3) nmol/s per liter of packed cells; SAHH activity was also much reduced. PNP activity was similar in patients and controls. CONCLUSIONS: CE can be used to test ADA deficiency and enables rapid assessment of ADA expression in hematopoietic cells of SCID patients during therapy.

Purine metabolism in leukocytes and erythrocytes in Graves' or Hashimoto's disease.

INTRODUCTION: Adenosine deaminase (ADA), purine nucleoside phosphorylase (PNPase), S-adenosylhomocysteine hydrolase (SAHH), 5'-nucleotidase (5N), and deoxycytidine kinase (dCK) are involved in purine salvage metabolism. Changes of the activities of the above enzymes have been observed in blood cells in patients with immunological disorders. MATERIALS AND METHODS: The activities of ADA, PNPase, SAHH, 5'N, and dCK in lysates of leukocytes and erythrocytes, obtained from patients with Graves' or Hashimoto's disease, were measured, using chromatographic analysis. Serum concentrations of antithyroglobulin (Tg Ab) and antithyroperoxidase (TPO Ab) antibodies were measured by an immunoenzymatic method. RESULTS: (1) ADA activity in leukocytes, obtained from patients with Hashimoto's disease, was significantly higher than in control leukocytes, as well as in leukocytes from patients with Graves' disease; (2) dCK activities in leukocytes from patients with both Graves' and Hashimoto's diseases were approximately four and five times higher, respectively, than in leukocytes of control subjects; (3) a positive correlation was observed between dCK activity in leukocytes and serum Tg Ab concentration in patients with Graves' disease. In conclusion, the increased ADA and dCK activities in leukocytes from patients with Graves' and Hashimoto's diseases may be regarded as indicators of autoimmunological thyroid diseases.

Blood transfusion causes deterioration in liver regeneration after partial hepatectomy in rats.

BACKGROUND: This study investigated the effects of blood transfusion on liver regeneration and function after hepatectomy in rats. METHODS: Inbred male Sprague-Dawley rats underwent a sham operation or a 70% hepatectomy (PHx) and were randomly divided into seven groups according to transfusion type: groups I and II underwent a sham operation and received saline (I) or whole blood (II). Groups III to VII underwent PHx with saline (III), whole blood (IV), irradiated/leukocyte-depleted whole blood (V), plasma (VI), or autologous blood (VII). The liver regeneration rate, proliferating cell nuclear antigen (PCNA) labeling index, serum aspartate aminotransferase, alanine aminotransferase, purine nucleoside phosphorylase (PNP) activity, hepatocyte growth factor (HGF), and activated transforming growth factor beta1 (TGF-beta(1)) were measured 6 and 24 h and 5 days after PHx. RESULTS: The liver regeneration rate and PCNA labeling index were lower in groups IV and V than in the other groups. Serum liver enzymes 6 h after PHx were worst in groups IV and V. PNP activity increased most in group IV, 6 and 24 h after PHx. The HGF values 6 h after PHx in all the transfused groups were lower than in group III. The activated TGF-beta(1) level 6 h after surgery was highest in group IV. CONCLUSION: Whole blood or irradiated/leukocyte-depleted whole blood impaired liver regeneration after PHx, probably through the production of activated TGF-beta(1) and HGF outside the liver, and plasma or autologous blood reduced the deleterious effects.

Successful HLA-identical bone marrow transplantation in a patient with PNP deficiency using busulfan and fludarabine for conditioning.

PNP deficiency is an autosomal recessive metabolic disorder characterized by severe combined immunodeficiency and by complex neurological symptomatology including ataxia, developmental delay and spasticity. Patients usually die in the first or second decade of life due to recurrent infections. The only curative treatment is bone marrow transplantation (BMT). We describe a 22-month-old girl who underwent BMT from her HLA-identical brother. Conditioning consisted of busulfan and fludarabine only, resulting in low toxicity and prompt engraftment. At 18 months after BMT, the girl has developed normal immunological functions, and her neurological status has improved.

Obstructive jaundice impairs hepatic sinusoidal endothelial cell function and renders liver susceptible to hepatic ischemia/reperfusion.

BACKGROUND/AIMS: Obstructive jaundice is associated with increased surgical morbidity and mortality. While parenchymal injury has been defined in obstructive jaundice, the pathogenesis of hepatic sinusoidal endothelial cell injury in obstructive jaundice is unclear. The aims of this study were to investigate hepatic sinusoidal endothelial cell injury in obstructive jaundice by determining serum hyaluronic acid levels, purine nucleoside phosphorylase/alanine aminotransferase ratios, and hyaluronic acid elimination rate, and also to determine whether hepatic parenchymal cell injury in obstructive jaundice is induced more than in normal liver after hepatic ischemia/reperfusion. METHODS: Male Wistar rats underwent ligation and division of the common bile duct (obstructive jaundice group) or sham operation (Sham group). Serum hyaluronic acid levels and purine nucleoside phosphorylase/alanine aminotransferase ratios in both groups were examined at intervals up to 21 days after surgery. Hepatic blood flow, permeability, neutrophil accumulation, and hyaluronic acid elimination rates in both groups were measured 14 days after surgery. Changes in serum hyaluronic acid and alanine aminotransferase concentrations were determined after 15 min of hepatic ischemia followed by reperfusion. RESULTS: Serum hyaluronic acid levels remained elevated after bile duct ligation. Hepatic sinusoidal endothelial cell swelling was observed by electron microscopy, and hepatic permeability was increased 14 days after bile duct ligation in association with neutrophil accumulation. Hepatic blood flow in obstructive jaundice remained unchanged, but hyaluronic acid elimination capacity was less than that in the Sham group. After hepatic reperfusion, the disappearance rate of serum hyaluronic acid in obstructive jaundice was lower, and serum alanine aminotransferase levels were higher than those in the Sham group. CONCLUSIONS: Our findings suggest that obstructive jaundice impairs sinusoidal endothelial cells and that sinusoidal endothelial cell damage in association with sinusoidal deterioration during obstructive jaundice renders liver susceptible to ischemia/reperfusion relative to normal liver.

Purine metabolism in Echinococcus multilocularis.

The activities of the enzymes in Echinococcus multilocularis metacestodes involved in purine salvage were studied by HPLC. As in most parasites, this cestode relies entirely on salvage of preformed bases and nucleosides for its purine requirement. Therefore, these enzymes may be targets for drugs in the chemotherapeutic treatment of diseases caused by this parasite. The animals used in this study were gerbils (Meriones unguiculatus). Enzyme activities from sera and hepatic tissue in control and infected animals were similar with the exception of adenine phosphoribosyltransferase which showed an activity 4-fold greater in the serum from control than in serum from infected animals. In the parasite, adenine and hypoxanthine-guanine phosphoribosyltransferases and adenosine deaminase had the highest activities. Therefore, in E. multilocularis metacestodes, this pathway seems to be important for the parasite's metabolism.

[Certain biochemical features of leukocytes in blast crisis of chronic myelogenous leukemia]. / Nekotorye biokhimicheskie osobennosti leikotsitov pri blastnom krize khronicheskogo mieloleikoza.

The content of nuclear high mobility group (HMG) proteins, activities of ornithine decarboxylase (ODC), adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) and also glycosaminoglycan (GAG) content and composition were studied in leukocytes of patients with chronic myelogenous leukemia in the phase of blast crisis (BC CML). Myeloid and lymphoid cytochemical variants of BC CML differ by biochemical parameters. It is suggested, that the content of HMG-proteins, activities of ODC and PNP, and electrophoretic patterns of GAGs could be used in diagnostics of two main variants of BC CML.

The effects of FR167653 in extended liver resection with ischemia in dogs.

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) are cytokines commonly associated with inflammatory conditions such as hepatic injury after ischemia-reperfusion. FR167653 has been characterized as a potent suppressant of IL-1beta and TNF-alpha production. In this study, we evaluated the effect of FR167653 in an extended liver resection with ischemia in a dog model. The right portal pedicle was clamped for 60 minutes, while the left portal branch was patent to avoid portal congestion. Following reperfusion, 75% of the liver (including the right central, quadrate, left central, left lateral, and papillary lobes) were resected. Animals were divided into two groups: a control group (n = 10), and a FR-treated group (n = 6) in which FR167653 was administered via the portal vein. Hepatic venous blood was collected to measure alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), purine nucleoside phosphorylase (PNP), and hyaluronic acid (HA) levels, and IL-1beta expression was also measured by reverse-transcriptase polymerase chain reaction (RT-PCR). ALT, AST, LDH, PNP, and HA levels after reperfusion were significantly lower (P < .05) in the FR-treated group than in the control group, and the FR-treated group showed inhibited IL-1beta expression. Liver tissue blood flow, measured by a laser Doppler flow meter, was kept higher in the FR-treated group than in the control group. Histologically, tissue damage was mild in the FR-treated group. The 2-day survival rate was statistically better (P < .05) in the FR-treated group than in the control group. We conclude that FR167653 provides a protective effect for liver parenchyma and sinusoidal endothelial cells in extended liver resection with ischemia.

[Metabolism of purine compounds in psoriasis]. / Metabolizm purinovykh soedinenii pri psoriaze.

The pool of free purine derivatives and activities of the key enzymes of purine metabolism (adenosine deaminase, purine nucleoside phosphorylase, and 5'-nucleotidase) in lymphocytes, erythrocytes, and epidermis homogenates were measured in 20 normal subjects and 15 patients with psoriasis by high-performance liquid chromatography. The levels of AMP, GMP, and IMP purine monophosphates are decreased in the epidermis and red cells of psoriasis patients, whereas the final products of hypoxanthine, xanthine, and uric acid metabolism are accumulating, and the activities of ADA and PNP are increased double in the skin, all this indicating purine derivatives catabolism.

Development of an assay method for purine catabolic enzymes in the mouse and its adaptation for use on an autoanalyzer.

An assay method has been developed for the purine catabolic enzymes adenosylhomocysteinase, adenosine deaminase (ADA), purine-nucleoside phosphorylase (PNP), and urate oxidase in mice. The assay links H2O2 produced during purine catabolism to the production of a dye complex. The assay method has been developed for ADA and PNP in erythrocytes and for all four enzymes in liver. The assay is cheap, sensitive, and easy to perform. The dye complex absorbs in the visible range, negating the need for an expensive ultraviolet spectrophotometer and allowing the use of an autoanalyzer.